News Category: Lumbar Spine

Today’s physicians depend on evidence from clinical studies and what are considered “best practice” approaches by experts whenever possible. When evaluating patients with degenerative lumbar spinal stenosis (DLSS or sometimes referred to as just LSS), the clinical practice guidelines of 2006 have been the “go to” document for guidance. This saves physicians from sorting through the hundreds of studies published each year in many different journals.

But now, the 2006 guidelines have been reviewed (based on published studies up to and including July 2010) and revised. In this document, members from the Degenerative Lumbar Spinal Stenosis Work Group of the North American Spine Society (NASS) provide a summary of the new guidelines. This update is now considered the most recent evidence-based clinical practice guideline (CPG) on LSS.

Sixteen questions were posed and answered in the 2006 Clinical Practice Guidelines. The questions covered topics ranging from natural history of LSS to diagnosis and treatment of this condition. All questions were reviewed and responses provided in this 2013 update. The levels of evidence were indicated for each response using grades labeled A (recommended), B (suggested), C (an option), and I (insufficient evidence to recommend for or against).

The working group also provided a consensus statement when there wasn’t enough reliable evidence to provide a guideline. This consensus statement is the opinion of the group based on all currently available evidence and expert opinion. Here is a sampling of the questions and some of the updated responses:

Patients in need of surgery for severe, chronic back pain can benefit by today’s modern surgical techniques, especially minimally invasive surgery (MIS) for spinal fusion. But this MIS technique exposes the surgeon (and operating room staff) to greater levels of radiation. The increased radiation exposure occurs because of the need for more intraoperative imaging to guide the surgeon (usually with real-time X-ray called fluoroscopy).

In this study, two groups of patients having spinal fusion were compared. All 162 patients had an anterior lumbar interbody fusion (ALIF) first and then a second procedure. The second procedure was a posterior fusion with either an open incision (group one) or a minimally invasive approach (group two). Some patients (but not all) had a decompression of the nerve tissue as part of the second procedure.

A little information about the advantages of the minimally invasive surgery (MIS) gives a greater appreciation for why this approach is being studied so closely. The traditional open incision involves cutting through the many layers of spinal muscles and other soft tissue structures to gain access to the vertebral bones.

With MIS, a tube-shaped instrument is passed down through the soft tissues between muscle groups. The soft tissue structures are pushed aside without cutting them. This technique reduces the risk instability from damage to muscles, tendons, ligaments, and bone. MIS also makes it possible for patients to get up and moving again sooner, allowing for faster recovery.

Fiber optic lighting and advanced imaging technology aid the surgeon in seeing inside the body to perform the necessary steps. After removal of the disc from an anterior (front of the body/spine), bone graft was placed inside the disc space to maintain normal disc height. Then the patients were turned over and operated on from the back. This was when the spinal fusion was done using either the open or minimally invasive approach.

Results were compared using a variety of measures including amount of blood lost during surgery (and need for blood transfusion), length of surgery and minutes of time exposed to fluoroscopy, length of hospital stay after surgery, and complications (type and severity).

As it turns out, blood loss and the corresponding transfusion rates were greater in the open group. But a second look at this difference showed that it was the patients who had an additional surgical procedure (neural decompression) who experienced these complications. And as expected, the MIS group was exposed to longer periods of radiation exposure due to the increased need for fluoroscopy during the procedure.

The unique aspect of this study was the fact that patients had an open anterior spinal fusion followed by a posterior spinal fusion (either by open or a minimally invasive approach). The authors concluded that minimally invasive posterior fusion following open anterior spinal fusion does have the advantages of less blood loss and therefore less need for a blood transfusion. MIS was also associated with a shorter hospital stay (and lower costs). Blood loss was greater in the patients who had open neural decompression.

However, rates of major complications such as blood clots, infection, or need for revision surgery due to problems with hardware were similar between the open and MIS group. The benefit or value of a minimally invasive procedure when performing a posterior spinal fusion with decompression may be compromised. And with the increased exposure to radiation required by the added decompression procedure, it may be that the open incision approach is best when decompression is needed.

SPORT stands for Spine Patient Outcomes Research Trial. It is an ongoing long-term study conducted at 13 medical centers across 11 states in the United States. These medical centers provide multidisciplinary treatment to patients with spinal disorders. Patients are followed at regular intervals and outcomes are measured in terms of pain, function, and disability.

Patients enrolled in this study had leg pain or discomfort and other neurologic symptoms for at least three months. Imaging studies showed both single-level degenerative spondylolisthesis and single or multi-level lumbar stenosis.

Degenerative spondylolisthesis occurs with aging most often affecting the L4-L5 level in people over 50 years old. Women are affected six times more often than men. Spondylolisthesis alters the alignment of the spine. In this condition, degeneration of the disc and facet (spinal) joints can lead to one of the vertebral bones to slip forward over the one below it. As the bone slips forward, the nearby tissues and nerves may become irritated and painful. The spinal canal narrows (a condition called stenosis) putting pressure on the spinal nerves.

This is the first study to compare the results of surgery for single-level degenerative spondylolisthesis accompanied by multilevel stenosis. The patients were divided into two groups. One group (130 patients) had a decompression procedure at more than one level (for the stenosis) and a fusion at one level (for the spondylolisthesis). The second group (77 patients) had the same multilevel decompression but only a single-level fusion.

Because SPORT is an ongoing data collecting type of study, many different pieces of information are collected about the patient, symptoms, insurance, clinical observations and test results, levels and severity of dysfunction, operative problems and results, and so on. This makes it possible to present tables of comparisons for patient demographics, comorbidities, fusion levels, and outcomes.

Although the multilevel fusion procedures took longer and the patients had more blood loss, there were no differences between the two groups in terms of blood replacement, complications during or after the surgeries, or number of reoperations required. Most other comparisons were similar between the two groups.

The only real trend was for greater improvement of physical function in the single-level fusion group compared with the patients who had multilevel fusion. But that was only seen after the third year and the benefit evened out between the two groups after the fourth year of follow-up.

Previous SPORT studies have shown that patients have more improvement with surgery compared with a conservative (nonoperative) approach for the problem of degenerative spondylolisthesis with multilevel stenosis.

This study offers the additional information that surgical results are very similar when treating patients who have single-level degenerative spondylolisthesis and multilevel lumbar stenosis using different surgical approaches. Whether performing a single-level fusion procedure or a multiple-level fusion, the outcomes (measured as bodily pain and function) are about the same (i.e., not significantly different).

Therefore, surgeons may want to limit fusion to just the spinal level where instability from the degenerative spondylolisthesis is present. In this way, patients are not exposed to longer operative times. And they are saved from higher levels of blood loss. This is an important consideration for older adults with multiple medical problems. It may be argued that fusing additional levels prevents future adjacent-segment disease but this remains under investigation.

Sports athletes are not immune to low back pain. Bony defects such as spondylolysis and spondylolisthesis present from birth or as a result of stress fractures from overuse can be a common cause of lumbar instability. In the case of spondylolysis, the supporting bony column (called the pars interarticularis) fractures. If the fracture displaces (separates) and the vertebral body shifts forward, the condition is referred to as spondylolisthesis.

It is estimated that nearly half of all low back pain in athletes comes from spondylolysis/spondylolisthesis. And there isn’t one main sport or activity where these injuries occur most often. Anyone who participates in a sport that includes extension of the spine with rotation (and especially rotation with compression or load) is at risk. For example, this condition has been reported in dancers, gymnasts, figure skaters, weight lifters, and football players.

As you might imagine, most athletes would prefer a nonoperative approach to treatment — but preferably one that gets them back on their feet and returns them to full participation quickly. In an effort to identify the most helpful conservative (nonoperative) care for these patients, a group of physical therapists conducted this systematic review and reported their findings.

They conducted a computer-assisted search of articles published in English over a span of 46 years (from 1966 to 2012). After gathering all the acceptable articles and compiling all the information, the authors organized the data into five tables. Information in these tables included:

1) Description of each study (design, patient demographics, training type and duration)

2) Type of injury (acute versus chronic, severity) and type of surgery (decompression, fusion, fusion with or without instrumentation)

3) Comparison of outcomes for nonoperative treatments (bracing versus activity restriction)

4) Comparison of outcomes for nonoperative treatments (bracing and physical therapy versus placebo/control)

5) Results for exercise interventions (core training, back strengthening, postural exercises, general exercise)

Although the information was carefully organized, as it turned out, many of the studies collected (and reported on) different things. There wasn’t enough consistency across studies to make comparisons with meaning. The authors report “limited investigation” and “lack of homogeneity” as the two main reasons there was no consensus on the role of conservative care or on outcomes of nonoperative care versus surgery for this condition.

There was one other major stumbling block in studying the effects of exercise: poor patient compliance. In other words, the patients didn’t do the exercises as prescribed (or didn’t do them at all)! With the limited evidence available, the best that can be said is that surgery (over conservative care) seems to be most effective for higher grades of vertebral slippage. And exercise to strengthen the core muscles (abdominals and trunk stabilizers) decreases pain and improves function.

No evidence but clear consensus (based on expert opinion or case studies suggest) suggested that bracing works better for healing the fracture when compared with restricted activity for children and teens with spondylolysis (fracture without separation). In adults, lumbar exercises helped some people recover and return to work. But there was inconsistency in the most effective type of lumbar exercises. For example, some people responded to extension exercises better than flexion exercises and vice versa.

This very carefully constructed systematic review of the results of conservative (nonoperative care) for low back pain in athletes caused by spondylolysis or spondylolisthesis faced some challenges because of limitations in how studies are conducted. The lack of consensus or evidence-based agreement on the best way to treat these patients must be addressed in future high-quality research.

Patients with chronic, persistent, and disabling low back pain from degenerative disc disease (DDD) will be interested in the results of this study. The authors (surgeons from four well-known Spine Centers in the U.S.) collected, reviewed, and summarized data from studies comparing surgical fusion with nonoperative (conservative) care.

They used careful selection criteria to get the best evidence possible. Studies included had to use validated patient assessment tools to measure outcomes (e.g., the Oswestry Disability Index, Short Form Health Survey). Patient satisfaction and X-ray results were also acceptable measures of clinical outcomes.

Articles considered unacceptable for review (inclusion) and therefore excluded were: 1) based on opinion, 2) only reporting on surgical technique, or 3) included patients receiving a fusion at more than two spinal levels. In addition, studies that were too small (less than 20 patients) or too short (follow-up was less than one year) were not included.

Twenty-six (26) studies with a total of over 3,000 patients met the necessary standards to be included. All patients had pain and loss of function as a result of degenerative disc disease in the lumbar spine (low back). Spinal surgery done was fusion at one or two levels.

The authors provided several summaries of data (in table form) from studies that compared results of surgery versus nonoperative care for this condition. The tables showed specific information compiled for randomized and nonrandomized controlled trials. They included length of follow-up time, patient age, baseline back pain information, change in outcome scores, fusion rates, reoperation rates, and level of patient satisfaction.

Overall patient satisfaction was 75 per cent for patients who had the fusion procedure, while patients in the nonoperative group reported a much lower rate (55.6 per cent) of satisfaction. The percentage of patients who had a successful fusion was 84 per cent. Seven per cent (7%) of the total group had a second surgery due to a failed first surgery.

Pain relief and improved function were reported for the fusion patients in the majority of cases. Type of fusion technique and age of the patient (young versus old) did not seem to affect success of the fusion procedure.

Patients evaluating results of surgery versus nonoperative care for degenerative disc disease should keep in mind that these two treatments are not really competing with one another. Patients aren’t usually given the opportunity to choose between them.

Instead, treatment is offered in a series: first conservative care with medications, physical therapy, and rest. Then, if the treatment fails, follow-up surgery (spinal fusion) is advised. Surgeons who seek the best evidence available to support their clinical decisions may rely on systematic reviews like this one to direct and guide them.

Summary: Collecting information on treatment results like in this review (especially success and failure risks and rates) is important today because of the large number of people missing work or seeking medical care for chronic low back pain. The high cost of fusion surgery also warrants knowing if surgical care is the best way to go.

As this systematic review showed, patients who do not get relief from their painful, disabling symptoms with nonsurgical treatment may find surgical fusion is a very good next step in the treatment algorithm (clinical decision pathway).

Patients who have spine surgery (laminectomy and/or fusion) have different results depending on where the surgery was done. Those are the findings of a recent review of data collected from 13 spine centers in 11 different cities across the United States. Naturally, the reasons for these differences in outcomes are of interest but will have to wait for another study.

For now, this study shows that patients with stenosis (narrowing of the spinal canal) or degenerative spondylolisthesis (age-related fracture and slippage of the vertebra) who have the same surgery may not get the same results. And that is a significant finding. Let’s take a closer look at the details of this study.

The background information about these patients may be helpful. All had severe low back, buttock, and/or leg pain and were unable to walk very far. Conservative (nonoperative) care was unable to change their symptoms. The purpose of the surgery was to remove the bone putting pressure on the nerve tissue (laminectomy) and to stabilize the spine (fusion).

Most of the time this type of surgery is successful with good postoperative outcomes. But there are cases where there is no change in painful, limiting symptoms, and the patient ends up having another surgery.

There are many different reasons why some patients don’t fare well after these procedures. Sometimes the patient was misdiagnosed or the surgical technique failed. In other cases, the spine was unstable and this problem wasn’t addressed during the surgery. Many studies have shown that over time, adjacent segment disease (breakdown of the spinal segment next to the fusion site) is a problem.

Most of the studies reporting results of surgery for lumbar stenosis and degenerative spondylolisthesis are done at one single center. Often, there is only one surgeon performing all of the procedures being studied. This review is different because it reports on both short- and long-term outcomes across multiple centers with many surgeons.

In each of the nearly 800 similar cases, surgery performed varied slightly and the number of levels operated on was anywhere from one to three or more. Events associated with the procedures (e.g., length of time in the operating room, amount of blood lost, number of dural tears) varied from center to center. And there were significantly different reports on how long patients stayed in the hospital and the number of wound infections.

Long-term results (measured at one, two, three, and four years after surgery) were also significantly different across the spinal centers involved. For example, the number of patients who required another surgery ranged from five to 21 per cent. The level of pain and physical function reported by patients was also different.

The data was collected and analyzed in such a way as to make sure that these differences were directly linked with the effect of the center rather than being due to patient factors such as age, size, smoking history, socioeconomic status, or level of preoperative exercise. Factors that may be important (but as yet unproven) include: surgeon preference for certain techniques, patient genetics, neurobiological responses to the underlying condition, and differences in patient response to pain.

In summary, this study cannot answer the “why” of differences in response to surgery for these two conditions. But it does bring to our attention the fact that there are broad ranges of patient outcomes across centers for the same conditions using similar surgical approaches. This new information should be a springboard for the next study: to answer the “why” question. What characteristics of patient, surgeon, or center make for better patient results following surgery for spinal stenosis and degenerative spondylolisthesis?

Studying the causes and ways to avoid adjacent segment disease (ASD) of the cervical (neck) and lumbar (low back) spine has become a major focus of research these days. But with the ever changing surgical tools and techniques, it is difficult to compare studies from 10 years ago with current studies. And that dilemma will continue into the future as treatment strategies change with evolving technology.

Even so, efforts are being made to study the problem of adjacent segment disease (ASD) and ways to avoid it. Adjacent segment disease refers to breakdown of the vertebrae next to a spinal fusion or disc replacement implant. Focusing on the causes of the problem may help surgeons identify avoidance strategies.

Currently, there are three known causes of adjacent segment disease. They are: 1) the natural history (what normally happens) in the disc at the next level, 2) the biomechanical stress and increased motion placed on the next level because of the fusion, and 3) anatomical disruption of the vertebral segment at the next level from the surgery.

In this review article, surgeons from Walter Reed Military Medical Center and Thomas Jefferson University team up together to present the latest evidence on adjacent segment disease (ASD) and how to avoid it. They say that strategies to avoid ASD seem to be working better for the cervical spine than for the lumbar spine. And ASD may be less likely to develop after disc replacement compared with spinal fusion.

Matching strategies with causes isn’t easy. For example, to know for sure if natural history (the natural tendency for the spine to degenerate over time without surgery) is the real problem is difficult to study. Providing needed surgery for one group of patients while comparing them to a control group (those who don’t have the surgery) isn’t ethical. So the true incidence of ASD linked with natural progression of disc degeneration is likely to remain unknown.

Studying the biomechanical changes at the adjacent levels is a bit easier. Researchers can measure the increased motion at the next vertebral levels and measure the increased pressure on the disc in between the vertebrae.

These kinds of changes are more likely after fusion (because of loss of motion) than with disc replacement where motion is preserved. Determining the exact biomechanical changes that contribute to ASD and finding ways to change that relationship are the focus of many current studies. To date, there has been a wide range of conclusions about this variable. Some studies show that the natural tendency for discs to degenerate over time is the main cause of the problem while others point to the change in biomechanics as the most important factor.

But there’s no mistaking the fact that the surgery has an effect as well. Whether fusion or disc replacement, the structures are changed, the normal anatomy is altered, and the result could be aggravation of the adjacent levels. Studies are needed to show what anatomic parts must be preserved and not disrupted during surgery to prevent adjacent segment disease. Likewise, determining technical strategies during the procedure that might help avoid adjacent segmental disease will be important.

In summary, studies of adjacent segment disease (ASD) for the cervical and lumbar spines continue to report a wide range of variable results. Working to find avoidance strategies based on known causes of ASD will remain the focus of ongoing research. Long-term results will be difficult to judge given the ongoing changes in technology and surgical techniques used in these procedures. But this should not deter surgeons from trying to develop effective avoidance strategies.

When all nonsurgical, noninvasive treatments have been tried without success for lumbar spinal stenosis, surgeons often try epidural steroid injections (ESI). But based on the results of a new study, it may be time to rethink that step.

Lumbar spinal stenosis (stenosis of the low back) is a common cause of back problems in adults over 55 years old. Symptoms of buttock or leg pain occur with or without back pain when the nerves in the spinal canal are compressed or pinched.

The spinal canal is the hollow tube formed by the bones of the spinal column. Anything that causes this bony tube to shrink can squeeze the nerves inside. As a result of many years of wear and tear on the parts of the spine, bone spurs may form and ligaments thicken closing around the spinal canal. Anything that narrows the spinal canal opening for the spinal cord and spinal nerves can put pressure against the nerves.

Many older adults never know they have this condition. They are said to be asymptomatic (without symptoms). But for those who do experience the back, buttock, and/or leg pain (and sometimes tingling/numbness), treatment is important. Most people want to avoid surgery, which is why they run the gamut of all conservative approaches ending with steroid injections.

But the question comes up: do epidural steroid injections (ESIs) really make a significant difference? Are patients improved enough to go this step? In this study, results for patients who received ESI for their symptomatic (with symptoms) lumbar stenosis were compared with outcomes of patients who did NOT receive the injection.

Everyone in both groups did have painful neurologic symptoms and had tried at least three months of nonoperative care without success. The type of conservative care they received included home exercise, nonsteroidal antiinflammatory drugs, education and counseling, and active physical therapy. All patients were enrolled in a larger (special) study known as SPORT (The Spine Patient Outcome Research Trial).

The researchers were very thorough in examining characteristics of patients and any factors that might affect the results. They looked at age, smoking status, general health, presence and types of other health problems, marital status, work or employment, income, education, race, body mass index, and many other variables.

Details of the symptoms and stenosis (location in the spine, severity, duration, affect on activities) were also recorded and analyzed. Anyone who ended up having surgery (from either group — those who had the steroid injection and those who didn’t) were also examined carefully. Information was collected on type of surgery, length of stay in the hospital, postoperative complications, additional surgeries, blood loss, and number of minutes in surgery.

In the end, they found that patients who had the epidural steroid injections (ESI) during their four year study period had significantly less improvement in symptoms over anyone else. That included patients who had surgery (and those who didn’t have surgery). The main conclusion of this study was that patients with lumbar spinal stenosis who have ESI have worse results than those who don’t have ESI.

A second observation from the study was related to patient crossover. Crossover refers to patients who start in one group (e.g., injection group) and end up going (crossing over) to the surgical group (or vice versa). In this study, the surgical group had better results than the injection group. So the patients who crossed over from originally being in the surgical group to the injection group may have had worse results than if they had stayed in the surgical group.

Patients in the ESI group who had the injection and then crossed over to have surgery also had worse results than the surgical group who did not have any injections. The surgery took longer for the ESI-crossover-to-surgery group. They were also in the hospital longer without any measurable benefit from the procedure.

Of course, with all that data collected, the authors went digging for an explanation. Other studies have suggested that earlier treatment with ESI might make a difference. Obesity and emotional instability have been linked with poorer results using ESI. Sometimes outcomes are significantly worse when patients have both stenosis AND lumbar disc degeneration.

The possible explanations they offered included: 1) adding fluid from the injection to an already narrow spinal canal may make the symptoms worse instead of better, 2) the steroid drug may damage nerve roots, and 3) the injected substances (numbing agent and steroid) may be viewed by the body as “toxic” and cause direct injury to nerve cells and/or scar tissue to form around the nerve tissue.

In the end, from this study it looks like epidural steroid injection for lumbar spinal stenosis may not be the best way to avoid surgery. Future studies may be able to determine who would be a good candidate for ESI before surgery (and who should go from conservative care to surgical care without ESI). Until patient selection for ESI versus surgery is clearly determined, patients should be advised that choosing ESI to avoid surgery isn’t always the best option.

Mechanical low back pain continues to confound health care professionals and researchers alike. Efforts to understand causes, effects, and find the best treatment are ongoing. In this study from Sweden, physical therapists compare the usefulness of two specific tests of disability: fingertip-to-floor and straight leg raise tests.

Both tests have been shown to measure a specific physical disability. But is either test a better measure of treatment outcomes? Can physical therapists use these tests to predict who will get better and by how much? That is a broad question when dealing with all low back pain patients. So they narrowed their focus to a subgroup of just patients with radicular pain (back pain with pain down the leg).

Each of the 65 patients in the study was diagnosed with acute or subacute low back pain (meaning their painful symptoms were fairly new: less than 13 weeks). Disability was measured using a well-known self-reported survey (the Roland Morris Disability Questionnaire or RMDQ).

The RMDQ assesses daily activities on a scale from no disability to severe disability. Everyone filled out the questionnaire at the beginning (baseline), after one month, and after one-year. Each patient also had a positive slump test to verify the presence of radicular pain. And a measure of fingers-to-floor was taken for each one.

As the name suggests, the fingers-to-floor test is done in the standing position. The person bends as far forward as possible reaching toward the floor with the fingers. The number of inches or centimeters from the tip of the index finger to the floor is the test result.

The slump test involves assuming a “slumped” position: sitting with spine flexed forward (bent over) and head and neck forward flexed (chin to chest). Once in this position, the therapist directs the patient to lift and straighten the leg with ankle dorsiflexion (toes pulled toward face). Reproducing pain down the leg is a positive slump test. It is an indication that the sciatic nerve is being stretched or compressed (though it does not reveal the cause of the nerve tension).

In the meantime, everyone was treated by one physical therapist for an average of six sessions. Some patients had as few visits as two while others had as many as 16. The therapist described the techniques used as including the McKenzie method (specific movements and exercises), manual (hands on) therapy, and stabilizing (core training) exercises.

There were two major findings from this study. First, change in fingers-to-floor was associated with improvements in daily function (as measured by the Roland Morris Disability Questionnaire). Second, patients who had improvements in the fingers-to-floor measurement in the first 30-days of treatment had the best long-term results.

The authors of this study direct their final thoughts to physical therapists evaluating and treating patients with acute or subacute mechanical low back pain. They suggest using the slump test to find the subgroup of patients with radicular pain. They suggest using the fingers-to-floor as a measure of change and a predictor of who will improve with treatment. The fingers-to-floor is a more valid test to predict change in disability over time than the straight leg raise test.

Adults suffering from pain, loss of function, and poor quality of life have three basic treatment options: conservative care and rehabilitation, spinal fusion, or the newer option of disc replacement. In order to find out how to advise their patients, surgeons from The Netherlands conducted an extensive survey of the published studies comparing these three approaches.

Current clinical practice seems to be moving away from spinal fusion and more toward lumbar disc replacement for symptomatic degenerative disc disease. The implants were first invented and designed to help with the problem of adjacent spinal disease that often occurs at the level above or below a fused segment.

But do they really protect the spine as intended? That’s one question that needs to be answered. They are expensive and long-term results are limited. So before surgeons shift completely from fusion to disc replacement, it’s a good idea to take a look at the current evidence.

After an extensive search on-line, the authors found seven studies that compared results of disc replacement, fusion, or rehabilitation. Combining all the patients in all seven studies, there was a total of 1301 people included. Only one of those studies really looked at rehabilitation.

Analysis of findings showed that patients improved no matter what type of treatment was applied. Patient satisfaction was greater in the group who had a total disc replacement. As intended, these implants did allow patients more natural motion.

But using a five-point criteria for assessing these studies, they found all had low quality evidence. None of the studies looked at subsequent adjacent segment disease, which is the main reason the implants were developed in the first place. The follow-up was two years or less, so long-term results aren’t really available. And many of the studies are funded by disc manufacturers, so there is a need for unbiased research without conflicts of interest.

The authors suggest strongly to orthopedic surgeons: be prudent in your use of disc replacements. Watch the reported results with a critical eye. Until high-quality studies with long-term results are available, it should not be assumed that “newer is better.” In other words, this new direction away from spinal fusion toward disc replacement hasn’t been adequately proven as the best approach.

Aches and pains seem to be part of the aging process for many people. Hip pain is especially common but doesn’t always come from the hip so diagnosis can be tricky. Likewise, knee and lower leg pain must be evaluated carefully because the origin can be the lumbar spine or hip. Pain that begins in one body part or region but is felt somewhere else is called referred pain.

In this study from Chiba University, Graduate School of Medicine in Japan, orthopedic surgeons review 420 patient records looking for clues to sort out lower leg pain. With patients who have both lumbar spinal stenosis (narrowing of the spinal canal or openings for the spinal nerves) and hip joint osteoarthritis — finding the origin of the pain can be a challenge.

They start by knowing that referred pain is always a possibility. So the patient’s evaluation must include clinical tests that focus on the low back, hip, and knee. The surgeon knows the typical pain patterns but when there is pain along the lateral (outside away from the other leg) side of the lower leg requires some additional testing.

The surgeon has at his or her disposal imaging studies such as X-rays, myelograms, CT scans, and MRIs. These are helpful but when someone has both stenosis and hip osteoarthritis, it might be necessary to perform some nerve injections. In this study, of the 420 patients who had lower leg pain from lumbar spinal stenosis, only four had back or hip pain with lateral leg pain.

Those four patients received a lidocaine (a type of novocaine) injection around the spinal nerve at the L5 level. In all four cases, the pain went away. That might confirm the problem was coming from pressure on the L5 nerve root from the stenosis. Especially because they also received an injection of lidocaine into the hip joint without a change in their pain.

But surgery to remove bone from around the nerve and fuse the lumbar spine did NOT relieve their pain. These four patients did have hip pain but they also had low back and severe leg pain. Clinical tests of the hip (e.g., Patrick and Friberg tests) were negative. Tests for sciatica and vascular compromise (loss of blood supply to the lower leg) were also negative.

Six to 12 months later (without knowing for sure if the origin of the lower leg pain was coming from the hip), surgery was done to replace the diseased hip joint. And guess what? All four patients experienced complete and long-lasting pain relief. How do the surgeons explain these results?

Anatomic studies in animals have shown that messages via the L4 to S1 level nerves do go to the posterior area of the hip capsule. In other words, it is possible that hip joint pain is transmitted along the L5 spinal nerve. This may be why the spinal nerve injection at L5 relieved the pain.

But if the pain was really coming from the degenerated hip, then why didn’t the lidocaine injection into the hip joint provide pain relief? The authors do not know but suspect perhaps there are central mechanisms, a term used to describe pain messages that are transferred via the spinal cord to the brain. Once the pain message is sent along this pathway, the body doesn’t seem to know how to turn the message off — even when pressure is
removed from the nerve.

The authors conclude by suggesting that lower leg pain can be a challenge to diagnose and treat effectively in older adults who have both lumbar spinal stenosis and hip osteoarthritic degenerative changes. Either or both problems can cause referred pain to the lateral lower leg area. Step-by-step evaluation is recommended with conservative care first before considering surgery. The decision to do surgery (lumbar spine decompression versus hip replacement) remains a challenge without clear guidelines to follow.

What are the chances a professional athlete having a diskectomy will be able to get back on the playing field (or court) and how long does it take? These are the two important questions this study answers. The authors (orthopedic surgeons at a spine center) looked back at the medical records of 85 players who had this type of surgery for a herniated disc. This group of patients included football players, basketball players, baseball players, and hockey players.

It is understandable that a professional athlete facing this type of surgery wants to know up front, “How long is it going to take to heal and get back to the game?” No surgeon has a crystal ball to predict the exact answer. But the results of this study might help provide some guidance in at least giving estimates of average return time.

For all of the players in this study, diagnosis was made with MRIs. The surgery was performed using a microscopic technique after they failed to get relief or improvement with a nonsurgical approach. Each player had the disc removed from a single spinal level. The most common area injured was in the lumbar spine: either L45 or L5S1. L5S1 refers to where the last lumbar vertebra joins the sacrum.

As it turns out, return to sports is a progressive phenomenon. At the end of a year, there are many more back in action compared with the first three months. On average, it took the players in this study about six months to return to their preinjury level of participation.

To be more specific: half of the group returned to play after three months, 72 per cent at six months, 77 per cent at nine months, and 84 per cent at the end of one year (12 months). The authors report that from their study, the average chance of returning to sports after microdiskectomy in the lumbar spine was 89 per cent.

The researchers did take a look to see if the spinal level affected made a difference in return to sport rates: it didn’t. They compared sports to see if one type of ball player was likely to return sooner than another. Although more baseball players returned faster and more basketball players returned than in any other sport, there wasn’t a statistically significant difference.

The conclusion of this study was that surgeons counseling professional athletes about disc surgery can offer this information:

According to this new study from the University of Utah, early referral to physical therapy for mechanical low back pain is linked with: 1) lower overall health care costs, 2) fewer doctor visits, 3) less use of advanced imaging (CT scans, MRIs), 4) reduced risk of surgery and injections, and 5) decreased use of narcotic (opioid) medications.

The study was done by reviewing patient records from a national database of employer-sponsored health plans. Although the study was conducted by physical therapists, they had no influence on who among the 32,070 patients studied was sent to physical therapy (PT). They were just reporting trends observed from analyzing the data.

Of the 32,070 patients who were diagnosed with low back pain as the main complaint, seven per cent were referred to PT. About 1100 patients received early PT (within 14 days of their doctor visit). The remaining 975 patients were categorized as delayed PT. They were sent to PT between 15 and 90 days after the primary care index (first) visit.

To get a better sense of national trends, the researchers analyzed characteristics of the individual patients. They looked at age, sex (male or female), and copayment for the first medical visit for low back pain. They also compared insurance plans (PPO, HMO, POS, HDHP, other), employment status, and geographic area where the patients lived. PPO stands for preferred provider organization. HMO is a health maintenance organization. POS is point-of-service and HDHP refers to high-deductible health plan.

What they found was if you live in the Northeast or West (United States), are covered by a preferred provider plan, and not taking narcotic medications, then you would be more likely to see a physical therapist early in the episode of your back pain. With early PT, you would be less likely to have surgery or injections and the cost savings would be nearly $3,000.00.

A second feature of the study was to compare cost savings for patients depending on how they were treated. There are Clinical Practice Guidelines (CPGs) based on research evidence that dictate how patients with mechanical low back pain should be treated. Health care providers who follow those guidelines (guided exercise and self-management) were referred to as adherent.

The second category (nonadherent) described patients who received care outside the guidelines such as hot packs, cold therapy, ultrasound. Costs associated with care according to the Guidelines were lower than nonadherent care. Each patient in the adherent group (treated according to the Guidelines) saved (on average) $1,374.00.

In summary, patients receiving early physical therapy for low back pain (within two-weeks of the episode) are less likely to need more invasive treatment with injections or surgery. Costs are less compared with patients referred later, especially if treatment follows the current published Clinical Practice Guidelines. Type of health care provider/coverage is also a factor in who is referred to physical therapy for this problem (PPO referrals were greater than HMO).

The value of physical therapy in the treatment of low back pain remains an area of debate and study. This study did not examine which patients should be referred to physical therapy or the patient outcomes for those who were referred early versus late. Further studies are needed to help determine who should be referred and how soon after diagnosis.

Events that occur before, during, and after surgery can cause problems for patients. These factors are referred to as preoperative, intraoperative, and postoperative variables. Identifying such risk factors can help reduce the number of days patients are hospitalized with complications. And that translates into less pain and suffering and lower costs.

In this study, predictive factors are investigated for patients having a single-level spinal fusion of the lumbar spine. Just over 100 patients had a minimally invasive procedure using the transforaminal lumbar interbody fusion (TLIF) approach. One surgeon performed all of the fusions.

By looking back at the patients’ medical records, the surgeon and his team could see the patients naturally fell into two groups: those patients who were hospitalized for less than 24 hours (group one) and those who were in the hospital for more than a day (group two). But what made the difference between these two groups? That was the important question.

There are many, many possible reasons why someone might develop problems and need longer hospitalization. Age, sex (male or female), body size, use of narcotic medications to control pain, and general health are preoperative factors to consider. Type of anesthesia used, number of minutes under anesthesia, blood loss, blood pressure, and administration of fluids (e.g., crystalloids, colloids) are intraoperative factors. And pain, blood values (e.g., hemoglobin, hematocrit, creatinine), use of narcotics, and formation of problems such as blood clots, kidney failure, heart attacks, or breathing problems were the types of postoperative factors examined.

After analyzing all the data on each patient in both groups, there were a few helpful findings. Patients requiring more than 24 hours to recover had longer surgical times and higher use of narcotic pain killers before surgery. The longer operative time is important because the patient’s body temperature drops as a result of the anesthesia. Decreased body temperature has been linked with heart attacks, death, infection, and problems stabilizing blood.

This factor (longer operative time) is important for the surgeon to keep in mind. And also for the surgeon, another significant predictive factor of a longer hospital stay was the use of crystalloids and colloids and the ratio between them. These fluids are used to help keep the patient hydrated and replace fluids lost due to bleeding.

The longer the operative time, the more fluids are “pushed” so-to-speak. This finding suggests that a more “restrictive” use of fluids may be better than a “liberal” amount. And other studies have shown better postoperative results with fewer lung problems when lower amounts of fluids are given during the surgery.

Another finding from this study was labeled as “surprising” by the surgeon. Patients who used more (not less) narcotic medications before surgery had faster postoperative recovery and thus shorter hospital stays. This led to the thought that perhaps preoperative pain control is protective — keeping the nervous system from setting up a pain response to the surgery. If that is the case, surgeons can administer oral narcotics as more of a pre-emptive strike to lower the overall pain experience before and after surgery. The end result is a happier, healthier patient. A small financial investment before surgery (i.e., the cost of the drug) can mean a large (thousands of dollars) post-operative savings.

In summary, the surgical team can take some steps to improve results for patients undergoing a transforaminal interbody fusion of the lumbar spine. Narcotic use before surgery for better pain control, fluid balance during and after surgery, and careful attention to blood values after surgery (e.g., hemoglobin, creatinine) can help keep the hospital stay under 24 hours.

Physicians and physical therapists often work together to aid patients with low back pain (LBP). The optimal timing and pathway from physician to physical therapist remains to be determined.

In this study, therapists examine the type of physicians sending patients with low back pain to therapists and the outcomes of treatment. Type of physician refers to the type of medicine practiced such as the primary care physician, an occupational medicine physician, or specialist (e.g., orthopedic surgeon, neurologist, neurosurgeon, internal medicine).

The authors explored three things: 1) patient characteristics based on physician specialty, 2) link between physician type and patients’ final function, and 3) number of physical therapy visits (represents cost analysis). Patient characteristics included age, sex (male or female), level of activity and exercise, medications, and payer source. Other areas of interest also included how long the patients had their symptoms and length of time between physician examination and physical therapy referral.

After collecting and analyzing data on 7,971 patients, they found that physician referral does make a difference. Patients coming from primary care physicians and occupational medicine physicians had the best results. They finished therapy with more function, less pain, and in fewer visits compared with patients referred by other physician types.

A little closer look at the findings showed that patients who have higher function, who exercise at least three times a week, and who are covered by a health maintenance organization (HMO) or preferred provider organization (PPO) had better results at discharge. Patients with the poorest function were older, on Medicaid, and had a longer duration of symptoms.

Other studies have looked at outcomes based on patient work/employment status, type of insurance coverage (including worker’s compensation), and acute versus chronic low back pain. This is one of the first studies starting to look at patterns and sources of referral to physical therapy for this condition.

This study showed that referral source was associated with functional outcome and that patients referred by a specialist tended to have more chronic pain or a more complex clinical picture. Patients are referred sooner (during acute phase of pain) by occupational medicine physicians. That may explain why they respond better and faster compared with patients with chronic pain most often referred by specialist physicians.

The hope from studies like this is to facilitate patient referral from physician to therapist in order to improve patient outcomes. Earlier referral has been shown to reduce overall costs while helping patients reduce pain and improve function. Delays in referral with longer duration of symptoms and shift from acute to chronic status are linked with worse final outcomes.

Spinal stenosis is an unfortunate condition associated with aging. Various factors combined together result in a narrowing of the spinal canal and openings for the spinal nerves to exit. Pressure on these sensitive nerve tissues causes low back (and often leg) pain and impaired quality of life. The personal and economic cost of this condition and what can be done about it are the focus of this review article.

Fortunately, many studies have been done to help surgeons identify the best way to treat this problem in older adults. The Spine Patient Outcomes Research Trial (called SPORT) has provided much of the evidence needed to provide effective treatment. And by effective, we mean both in terms of reducing pain and improving function as well as providing a cost effective treatment.

Let’s take a closer look at what is now known in terms of the management of this condition. The first step to managing this condition is usually conservative (nonoperative) care. Medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) are used to control pain and swelling.

NSAIDs combined with physical therapy may be all that some patients need. The physical therapist addresses posture, strength (especially core strength), and modification of activities. The therapist can teach patients positions and exercises to ease the symptoms. The therapist may use lumbar traction to gently stretch and lengthen the low back, taking pressure off the spinal nerves.

Some patients are given an epidural steroid injection (ESI). The spinal cord is covered by a material called dura. The space between the dura and the spinal column is called the epidural space. It is thought that injecting steroid medication into this space fights inflammation around the nerves, the discs, and the facet joints. This can reduce swelling and give the nerves more room inside the spinal canal.

When conservative care doesn’t work, then surgery may be advised. In fact, the results of the SPORT studies supports the use of surgery in such cases. When there is pain that doesn’t go away with nonoperative care, decreased quality of life, or loss of function, surgery may be the only answer. There are several different ways to approach the problem surgically. The most common technique is called decompression.

The surgeon performs either a laminotomy (shaving some of the bone away from the nerve tissue or removing a small amount of bone on one side of the lamina) or laminectomy (removing the bone from around the nerve tissue). The lamina is the covering layer of the bony ring of the spinal column. It forms a roof-like structure over the back of the spinal canal. Decompressive surgery takes the pressure off the spinal nerves.

Although surgery of this type is expensive (estimated in the SPORT study to be $77,600 per quality of life year), the gains made in pain control and improved health were worth it to the patients. Two years later, patients who had the surgery were still reporting positive results from the procedure. When the cost is spread out over the long-term, the economic benefit becomes clear.

There is one other minimally invasive surgical procedure for lumbar spinal stenosis still under investigation. A device called the X-STOP®. The X-STOP® is a metal implant made of titanium. The implant is inserted through a small incision in the skin of your back. It is designed to fit between the spinous processes of the vertebrae in the lower spine. It stays in place permanently without attaching to the spinal bone or ligaments.

There are several advantages of the X-STOP®. It can be inserted using local anesthesia on an outpatient basis. A small incision is made so the procedure is minimally invasive and no bone or soft tissue is removed. The implant is not close to nerves or the spinal cord. With the implant in place, the patient doesn’t have to bend forward to relieve painful symptoms. The X-STOP® keeps the space between the spinous processes open. With the implant in place, it is possible to stand upright without pinching the spinal nerves.

Research shows that these implants don’t work well for patients with severe stenosis. No improvement and a high revision rate have been reported for patients with severe stenosis. A 73 per cent satisfaction rate has been reported in patients with mild stenosis. And comparing use of the X-STOP® with no treatment has also been shown effective for the patients with the implant.

The problem of a degenerative spine resulting in stenosis is not one that is going to go away anytime soon. With the aging of our Baby Boom generation, surgeons can expect to see more (not less) of this condition.

Studies like the SPORT study will help guide treatment by showing the effectiveness of surgical management. Whereas the high cost of surgery may put some people off, the positive long-term results are very convincing. Nonsurgical care is the first line of treatment but patients should be told that it is not the end-of-the line, so-to-speak. Minimally invasive, surgical approaches are effective for many people at a cost that becomes “affordable” when pain is relieved, function is improved, and quality of life is restored.

In this study, surgeons at Tufts University School of Medicine discover an important reason why half of their patients receiving an X-STOP® device end up with a fracture of the spinous process.

The X-STOP® is a metal implant made of titanium. It is a minimally invasive procedure for the treatment of mild lumbar spinal stenosis (LSS). The implant is inserted through a small incision in the skin of the low back. It is designed to fit between the spinous processes of the vertebrae in the lower back. It stays in place permanently without attaching to the bone or ligaments in the back.

Spinal stenosis describes a clinical syndrome of buttock or leg pain. These symptoms may occur with or without back pain. It is a condition in which the nerves in the spinal canal are closed in, or compressed. The spinous process is the piece of bone that sticks out behind the vertebra. It is the bump you feel down the back of your spine.

The spinal canal is the hollow tube formed by the bones of the spinal column. Anything that causes this bony tube to shrink can squeeze the nerves inside. As a result of many years of wear and tear on the parts of the spine, the tissues nearest the spinal canal sometimes press against the nerves. This helps explain why lumbar spinal stenosis (LSS) is a common cause of back problems in adults over 55 years old.

The X-STOP® procedure has been very successful for carefully selected patients with LSS. And now, thanks to this study, surgeons may be able to screen patients for a specific risk factor that is associated with spinous process fractures after X-STOP® surgery. The single factor predictive they discovered for spinous process fracture was the presence of lumbar spondylolisthesis.

Spondylolisthesis describes a condition in which one lumbar vertebra has slipped forward over the vertebra below. This slippage causes a narrowing of the spinal canal and traction (pulling) on the nerve tissue. Although their study was small (only 39 patients), the high rate (52 per cent) of spinous process fractures after X-STOP® implantation was significant.

The surgeons aren’t exactly sure why spondylolisthesis would increase the risk of fracture. They suspect that the change in alignment with the vertebra shifted forward may have something to do with it. The contact points (where the implant rests against the spinous process) may be further back in patients with spondylolisthesis. This placement is against a weaker part of the spinous process contributing to fracture.

Other factors explored for potential cause of fractures included patient age, gender (male or female), body mass index (BMI), and bone density. The researchers did not find any difference in these risk factors between patients with fractures and those without. Surgical level and number of levels treated were also evaluated for possible links to fracture risk. There weren’t enough patients in the study to make any firm conclusions about these two possible risk factors.

In summary, stenosis and spondylolisthesis in the same patient may be a reason NOT to use the X-STOP® device. The high rate of spinous process fractures as a complication of the X-STOP® procedure may be a reason to try a different surgical approach. In fact, the presence of spondylolisthesis in anyone with lumbar spinal stenosis may be considered a contraindication for this device. Contraindication means a reason not to use these implants.

The authors suggest future studies address the following concerns: 1) this was a small study; results may be different with a larger group, 2) the fracture rate was consistent no matter which type of X-STOP® was used. So it’s not likely to be caused by the implant itself but may be the way it is inserted; this should be further investigated, and 3) perhaps there are other biomechanical or patient factors responsible for these results. More study is needed to explore these concerns.

One final note of importance: fractures of the spinous process did not show up on X-rays for any of the patients who did, in fact, have a spinous process fracture. CT imaging was needed to truly see fractures of this type.

Workers who have an acute low back injury with pain while on the job are often anxious to get back to work. Current Clinical Practice Guidelines (CPGs) recommend that only certain patients require X-rays. This is also true for other imaging studies such as MRIs in the first six weeks after injury. Even so, research shows a high rate of early MRI among Workers’ Compensation patients.

This is the first study to look at factors that might account for the early use of imaging for injured workers. Over 1,800 working adults who filed a claim for a back injury were included. All kinds of data about the workers was collected and analyzed. For example, age, race/ethnicity, level of education and income, and marital status were some factors considered.

Other characteristics that might influence the decision for early imaging were also considered. These included general health, job satisfaction, previous Worker Compensation claims, and type of employment. And finally, information on injury severity, level of pain, and patient-reported disability were also evaluated.

As it turns out, the authors of this study were able to identify what they called red flags for serious back pain. These are patients who are more likely to need early imaging studies. Age (younger than 20 and older than 50) was one important clinical characteristic. Spinal tumor, bone fracture, or infection were the main concerns. Any other signs or symptoms common with these three conditions were also considered red flags.

A second important finding from this study was more specific to the question of: Who is getting an early MRI for acute low back pain? The answer: men, workers with high levels of fear of reinjury, and greater injury severity and disability. Workers who had the lowest rate of early MRIs were first seen for their low back pain by a chiropractor. In contrast, workers who went to a medical doctor (general practitioner, neurologist, or orthopedic surgeon) were the most likely to receive an early MRI.

How did the authors explain their findings? First, some medical doctors routinely order MRIs right away — even though current evidence doesn’t support this practice. Second, chiropractors rely on X-rays taken in their offices rather than on MRIs provided somewhere else. And third, workers who are afraid to go back to work for fear of reinjury make up a large percentage of patients who have an MRI for an acute episode of injury-related back pain.

The results of this study point out again that medical costs can be lowered by following evidence-based recommendations. All physicians have access to the Clinical Practice Guidelines (CPGs) on Low Back Disorders published by the American College of Occupational and Environmental Medicine. In the case of mechanical low back pain from acute injury, conservative care is recommended. Early imaging is not advised unless there are red flags or neurologic signs and/or symptoms.

Is there a link between metabolic syndrome and low back pain? Any condition that can reduce or restrict physical activity has the potential to contribute to weight gain, diabetes, and low back pain. In this study from Japan, researchers investigate the relationship and prevalence between metabolic syndrome and low back pain.

Metabolic syndrome is a combination of medical disorders that, when occurring together, increase the risk of developing cardiovascular disease and diabetes. Different groups (e.g., American Heart Association, International Diabetes Federation, National Cholesterol Education Program) have varied criteria to define metabolic syndrome. Most at least include these three: 1) raised blood pressure, 2) central obesity (increased waist circumference), and 3) abnormal cholesterol levels.

Residents from two cities in Japan between the ages of 40 and 74 were included in the study. Anyone in the group of 2,650 people who reported low back pain lasting more than 24 hours or severe enough to seek medical help were placed in a group for analysis. The low back pain group was then compared to the group of individuals who did not report any low back pain.

The researchers collected many pieces of information about each person in the study to use when analyzing risk factors for low back pain. Body mass index, smoking status, alcohol use, general health, and level of physical activity were included. Sex (male or female), occupation, and a test for depression were additional bits of data collected.

Statistical analysis showed that obese women with metabolic syndrome were more likely to develop low back pain compared with obese men with metabolic syndrome. This difference looked more like a tendency toward low back pain among women than a significant trend.

Why the difference between men and women? Scientists suspect female-specific hormones and menopausal status have something to do with it. Women who are postmenopausal are also older, have reduced estrogen levels, and elevated blood pressure. Lower estrogen levels also contribute to decreased bone density, which in turn, can lead to low back pain.

The authors couldn’t say for sure that low back pain is a factor that leads to the development of metabolic syndrome. Nor could they prove the opposite: that metabolic syndrome leads to low back pain. Their study does show that metabolic syndrome occurred more often in the women in their study who did have low back pain.

They conclude that women who have low back pain should be evaluated for the presence of metabolic syndrome. Treatment to address the metabolic problems may contribute to protecting and restoring normal musculoskeletal function among Japanese adult women.

In this article, surgeons from several large U.S. orthopedic departments take a look back over the last 60 years of spinal surgery for lumbar fusion. What started out as a simple posterior fusion of the vertebrae bones for a wide variety of problems has been streamlined to a procedure called interbody fusion used for lumbar instability.

Techniques and surgical approaches (anterior, posterior, transforaminal, or combination) have changed over the years. Interbody (circumferential) fusion has become mainstream. The introduction of a minimally invasive method has minimized surgical trauma and reduced hospital time, blood loss, and complications.

The authors provide a historical review of each type of fusion (e.g., open versus minimally invasive, different ways to do an interbody fusion) and type of complications with each. Technical challenges and effectiveness of each procedure are also reviewed.

Newer approaches to fusion such as the XLIF, ALIF, and AxiaLIF are discussed. XLIF is actually a trade name that refers to a direct lateral lumbar interbody fusion. ALIF stands for anterior lumbar interbody fusion. In this operation, the surgeon reaches the spine through the abdomen. The axial lumbar interbody fusion (AxiaLIF) is used to fuse the last lumbar vertebra (L5) to the sacrum (S1).

A very helpful table is included that summarizes the methods of interbody fusion and compares the advantages and disadvantages of each one. Some of the techniques developed more recently don’t have enough studies done yet to come to any conclusions. What they have been able to tell so far can be summed up as follows: