New Mini-Incision Not All It’s Cut Out to Be

How does the new mini-incision method of hip replacement compare with the standard incision? That’s the question doctors at Stanford University Hospital studied. Total hip replacement (THR) can be done now using only a two-and-a-half inch incision. A smaller incision may be better than the usual method of THR.

Three doctors replaced 135 hip joints. Fifty patients had the mini-incision. Eighty-five patients were operated on using the standard incision. Doctors collected information on each patient before the operation. Age, height, weight, type of anesthesia, and time in the operating room were some of the measures taken. Others included amount of blood loss, lab values, and number of days in the hospital.

The authors report very few differences in results between the two groups. If anything, the mini-incision group had more problems after the operation. They had more infections and a poorer fit of the implant than the standard group.

Based on the results of this study, there isn’t enough evidence to support the general use of a mini-incision for THRs. The researchers suggest that more data should be collected about this new way of replacing hip joints.

New Phase of Exercise Advised Four Months after Hip Replacement

Exercises for a total hip replacement (THR) usually start in the hospital right after the operation. Physical therapy may continue at home after the patient leaves the hospital. But how long should patients keep up the exercise program? In this study the benefits of late-phase rehab were measured.

The study included 34 adults with THRs. All had the THR between four months and one year ago. The patients were divided into two groups. Both groups did exercises. One group did a program of exercises usually given right after the surgery. The second group did special weight-bearing exercises. In these exercises, the patient stands on the affected leg and completes a series of slow, controlled motions.

Before this study there was no data on how well either type of exercise worked. These researchers measured muscle strength, stability, and fear of falling before and after eight weeks. Both exercise groups were tested. The researchers also asked patients to rate their pain and difficulty with daily activities.

The authors report that patients showed improvement in all areas after the weight-bearing exercises. Patients doing early rehab exercises showed no change. The authors conclude that patients don’t benefit by doing the early rehab exercises past four months after THR.

A new phase of rehab is advised after THR using weight-bearing exercises. The program can start when tissues are healed and standing no longer causes pain.

True Merit of a Mini-Incision THR

Wouldn’t it be great to have a total hip replacement (THR) with less pain? Faster recovery? Shorter time in the hospital with less blood loss? Smaller scar and fewer problems? These are a few of the claims being made for the mini-incision approach to THR. But how true are these claims?

According to researchers studying this topic, none of these statements has been proven. Improved appearance may be the only real advantage to the mini-approach to THR.

In this study two groups of patients getting a THR were compared. The first group had the mini-incision. The second group had the standard incision. There were 42 patients in each group. The mini-incision was about two inches long. The standard cut to open the hip was five to 10 inches long. The length of the opening was the only difference between the two groups. All other aspects of the operations were the same.

Patients were asked later if they would be happier with a smaller or larger incision. Patients were asked to rate the appearance of the scar. All hips were X-rayed and joint motion was measured. Amount of blood lost and time in the operating room were tracked.

The authors report that 100 percent of both groups had good alignment of the hip implants. No differences were measured in the length of hospital stay or problems afterwards. The group with the smaller scar was very pleased with the results. About two-thirds of the group with the longer scar said they would be happier with a smaller incision.

These researchers conclude that a THR can be done safely and effectively with a mini-incision. However, the only real advantage may be the appearance. They advise doctors to use the mini-incision whenever possible to improve patient satisfaction. But they say that appearance shouldn’t be more important than a good fit or position of the THR. They are less likely to use the mini-incision on large or overweight patients.

Scoping Out Sources of Hip Pain

A doctor at the Nashville Sports Medicine Center reports on the number of patients with damage to the ligamentum teres in the hip. This is the ligament that goes between the head of the femur (the thighbone) and the hip socket. It can be injured during major trauma such as a fall, a twisting injury, a car accident, or an athletic injury.

Arthroscopy has been very helpful in finding damage to this ligament. It doesn’t show up on MRI, X-ray, or CT scan. The authors looked at 271 hips using arthroscopy. They found that 41 had a tear or other damage to the ligamentum teres. Before his study, only a few cases had been reported.

In this study 23 patients had a traumatic cause of damage. The other 18 cases were caused by thickening or aging of the ligament. All patients had constant groin pain that didn’t get better with treatment. About half had catching, popping, locking, or giving way of the hip joint. A few reported pain with activities and loss of motion.

Arthroscopic surgery was used to repair the torn ligament. Almost all of the patients had a good result and good recovery. Only one patient had some symptoms from minor nerve damage that went away in time.

The authors conclude that tears of the ligamentum teres are more common than has been recognized or reported. Arthroscopy can be used to find and repair this type of injury.

Helping Patients Get Back on Their Feet after Hip Fracture

Falls and fractures. These are two of the aging adults’ worst enemies. What’s the best way to rehabilitate these injuries and get patients back on their feet? Researchers in Australia compare a home program of weightbearing exercises (WBE) against non-weightbearing exercises (NWBE) or no exercise (control group).

NWBE is the standard treatment after hip fracture. But some researchers think it’s best to use exercises closely related to the desired task to increase function. So standing up, walking, and climbing stairs are best improved by doing these activities.

The three groups were followed for four months. At the end of one month most of the patients (85 to 89 percent) in exercise groups were doing the exercises at least three times a week. By the end of four months the number had dropped to between 69 and 73 percent.

The authors report no change in strength for either exercise group after four months. Balance and function were both improved in the exercise groups. The WBE group showed the greatest change. No differences were reported by any of the patients at the end of the four months for pain, activity, or sleep.

The authors conclude that a home exercise program after hip fracture can help patients. Weightbearing exercise is better than non-weightbearing exercise. Any exercise is better than none.

What Time Is the Right Time for THR?

Total hip replacement (THR) can effectively relieve pain and restore function in hip joints with osteoarthritis or other diseases. Still, THR is usually postponed for as long as possible. Any major surgery has risks. And artificial joints don’t last forever. So waiting as long as possible before THR surgery makes sense. But how long is too long?

The question of waiting periods for surgery is especially important in countries like the Netherlands, where this study was done. Countries with publicly funded health systems often have long waits for surgery. Studies that pinpoint when a wait for THR becomes too long could help set limits on waiting periods. This could help improve patient outcomes.

This study looked at results for 161 patients who had THR. Most had osteoarthritis of the hip. On average, they waited six months for THR surgery after being put on the waiting list. The authors compared their pain levels, hip function, and general health during the waiting period and for the year after THR. The scores went down significantly during the waiting period. This time was very hard on many of the patients. After THR, the scores went up significantly.

The results showed that waiting time had no direct link to worse outcomes after THR. However, patients who were further along in the disease process did not improve as much as patients who were doing better before surgery. The authors recommend that doctors rethink the policy of waiting as long as possible to for THR, especially in older patients. In this study, too many patients had much worse quality of life for too long.

Locating the Best Approach for Total Hip Replacement Surgery

There are many ways to insert a total hip replacement. Sometimes doctors go in from the front, called an anterior approach. Other times it’s best to enter directly from the side (lateral approach). The posterior approach from behind is the simplest and can often be done with the least trauma to the muscles. But the posterior approach can result in too many hip dislocations later.

In this report doctors from the Brigham and Women’s Hospital in Boston describe a new, simple method for the posterior approach. They insert the new hip implant and then repair the capsule around the joint. First a flap is made in the capsule. It’s moved over and attached to a nearby tendon from the gluteus maximus muscle. Usually the capsule is reattached to the bone itself. Holes have to be drilled into the bone to do this.

This newer, simpler method avoids drilling holes. The risk of bone fracture is much lower when no drilling is done. The repair site is elastic and has some “give” to it during the healing process. The doctor can check the tension during the operation and get it just right.

The authors describe each step of this operation for other doctors interested in trying the new method. They report that dislocations occurred in only 0.4 percent of their 255 patients. The rate of dislocation reported by this same group of doctors before the new technique was four percent.

Cold Treatment Relieves Pain after Total Hip Replacement

This is the first study to show that cold can be used effectively after total hip replacement (THR) for pain relief. They also showed how local cooling of the hip can relieve stress and result in faster rehabilitation.

Two groups of patients were part of this study. Each group had 23 patients who got a cementless THR for osteoarthritis. The first group had a cooling pad wrapped in a waterproof cover applied over the wound area. A layer of gauze protected the wound first. A computer was used to keep the pad at a constant temperature for four days.

The second group had the same exact treatment including the pad. The pad in the control group was kept on for four days, but it was not cooled below room temperature. Blood loss and pain levels were the two measures used to compare treatment methods.

Both groups had about the same amount of blood loss. The big difference was in pain levels. Pain scores for the group with the cooling pad were much lower than for the control group. Pain was gone by day three for more than half of the cold therapy group. It took up to five days to reduce pain to zero in the control group.

The cold therapy didn’t reduce swelling, but it did change the amount of pain pills taken. The cold therapy group used less total amount of the main pain reliever. The authors conclude that using cold the first four days after THR is simple and effective for controlling pain. The patient can start rehab sooner with less risk of blood clots.

Hip Osteoarthritis in Men Reduces Motion and Function

Researchers in Finland compared the range of motion and function of the hip joint for men with and without hip osteoarthritis (OA). It’s the first time range of motion values for the hip have been compared between these two groups. The doctors also looked at which tests are the best to assess function in patients with hip OA.

Men in two groups (men with OA and the control group without OA) carried out a series of tests. They walked 25 meters, marched and jumped, and also walked up and down stairs. Other tests included knee bending and hip range of motion. In the OA group some of the men couldn’t do the knee bending or leg jumping tests because of pain or stiffness.

The authors report that men without hip OA have better motion, especially in abduction (legs apart) and rotation (turning the leg in or out). Control subjects were 13 to 52 percent more flexible than the men with OA. The worse the OA, the less motion was recorded.

In this study several practical and repeatable tests were found to assess the need for rehab for men with hip OA. These tests can be used for adults who are not in the hospital or living in a nursing home. Marching in place and going up or down stairs were the most reliable tests. Knee bending and standing on one leg were impractical tests and not suggested as measures of function.

Scoping Out a Unique Cause of Hip Pain

A surgeon at the Nashville Sports Medicine Center reports on the number of patients with damage to the ligamentum teres in the hip. This is the ligament that goes between the head of the femur (thighbone) and the hip socket. It can be injured during major trauma such as a fall, twisting injury, car accident, or athletic injury.

Arthroscopy has been very helpful in finding damage to this ligament. It doesn’t show up on MRI, X-ray, or CT scan. In this study, 271 hips were examined using the arthroscope. Notably, there was a tear or other damage of the ligamentum teres in 41 of the hips examined. Before this study, only a few cases had been reported.

In this study 23 patients had a traumatic cause of damage. The other 18 cases were caused by thickening or aging of the ligament. All patients had constant groin pain that didn’t get better with treatment. About half had catching, popping, locking, or giving way of the hip joint. A few reported pain with activities and loss of motion.

Arthroscopic surgery was used to repair the torn ligament. Almost all of the patients had a good result and good recovery. Only one patient had some symptoms from minor nerve damage that went away in time.

The authors of this study conclude that tears of the ligamentum teres are more common than has been recognized or reported. Arthroscopy can be used to find and repair this type of injury.

How to Take Away Pain after Total Hip Replacement

Total hip replacement (THR) surgeries have become more and more common. In 1999 surgeons did 168,000 THR surgeries and 30,000 revision THR surgeries in the United States. Most patients get improved function and good pain relief from a THR. However, sometimes a THR can cause new kinds of pain. This is a difficult situation for patients. And surgeons can have a difficult time developing a treatment plan that works.

This article gives surgeons an overview of the causes of painful THRs. The authors stress that the underlying cause of pain must be determined. Potential causes of THR pain include infection, other problems with the bones and hip joint, and problems with the implant itself. The authors say that surgeons should always be sure to rule out infection in cases of a painful THR.

The article details the best ways to diagnose the problem. The authors say that the history and physical exam must be thorough. The article outlines imaging and laboratory tests that can help identify the problem. It also discusses some new diagnostic tests that could help show the cause of a painful THR.

Understanding the Unstable Total Hip Replacement

Total hip replacement (THR) surgeries are usually very successful in relieving pain and restoring function. But from one to three percent of artificial hips end up dislocating. This article discusses the reasons behind THR dislocation. The authors focus on understanding the causes of the instability. An unstable THR can be caused by patient factors or surgical factors.

Patient factors include:

  • Patient age and possibly gender.
  • The medical reason that a THR was needed.
  • Other health problems, especially if they affect the bones or soft tissues of the hip.

    Surgical factors include:

  • Whether the surgeon used an anterior (front) or posterior back approach.
  • Design and positioning of the artificial joint.
  • Whether or not the soft tissues around the joint were repaired.

    The authors stress that surgeons must identify the cause of instability before they can come up with an effective treatment plan. The article gives guidelines for surgeons to use when diagnosing problems with an unstable THR. The authors note that dislocations that happen soon after THR are usually treated much differently than dislocations that happen later.

    The article discusses bracing. It reviews the best types of implants and procedures to use for revision surgeries. The article also discusses newer techniques and technologies that may be useful in successfully treating the unstable THR.

  • Understanding Dislocation after Total Hip Replacement

    Total hip replacement (THR) surgeries have become fairly common and very successful. Still, some patients have problems with the new joint dislocating. Replacement surgeries that enter the hip joint from the back (the posterior approach) seem to have more problems with dislocation than those that enter from the front (the anterior approach).

    These researchers studied different posterior techniques in hip joints taken from cadavers (bodies preserved for study). The researchers tested the range of motion in a hip without a replacement joint. Range of motion was also tested in hips that had THR done through the posterior approach. The researchers tested motion of the THR with different degrees of repair done to the joint capsule and surrounding tendons and muscles. The tests tried to force the joint to dislocate.

    Results showed that the posterior approach with repair of the joint capsule and surrounding tissues was the hardest to dislocate. The repaired tissues held the new joint most securely in position. Even when a dislocation was forced, the artificial joint itself did not fail. The easiest THR hip to dislocate was when the joint had to be opened up during the surgery without repair of the joint capsule.

    Improving Results of Total Hip Replacement in the Under-50 Crowd

    Doctors are reluctant to replace hip and knee joints in patients under 50 years old. There are good reasons for this, but changes are on the way.

    The biggest concern with early joint replacement is failure of the implant. Younger patients tend to be more active and wear the joint out sooner. Implants don’t last as long, and another implant is needed to replace the first worn-out one. With each operation there’s the risk of bone loss and loosening of the implant. Knowing which implant to use is also a challenge. There just aren’t enough studies yet to guide doctors in choosing the type of implant that will last the longest for each patient.

    In this study, 561 total hip replacements (THRs) were done on patients younger than 50. Within that group was a subset of patients who were 40 years old or younger. Different kinds of implants were used and compared. The authors report results after five, 10, and 15 years.

    In general, implant parts coated with a full (rather than partial) porous covering held up the best. When cement isn’t used to hold the implant in place, a press-fit type of implant is used. The press-fit socket (the cup portion) of the implant wore out before the press-fit ball of the joint.

    The authors report that the weak link in this study was the polyethylene (PE) liner inside the cup. The rest of the implant held up well even after 15 years. The PE liners wear out in 10 to 15 years and have to be replaced. A thicker PE may be needed. Studies of other types of materials, such as ceramic and metal, are needed to make this decision.

    If survivor rates of the PE aren’t included, then 90 percent of the THRs lasted 10 years. After 15 years, 80 percent were still working well. It’s likely that more patients will be given the green light for early hip replacement in years ahead. Finding THR materials that won’t wear out is the key.

    Cruisin’ for a Hip Fusion

    Hip fusion may be a good option for patients too young for a hip replacement. It relieves pain and restores function. The leg is a little shorter on that side, and the patient may walk with a limp, but most patients are very happy with the results.

    In this study, doctors from the Joint Replacement Institute in California report on hip fusion as a treatment option. Their target group is patients 40 years old or younger. They point out who might be helped by the operation and who shouldn’t have it. They offer some ideas about the importance of the patient-doctor relationship.

    Technical ideas such as hip position, surgical planning, and methods of surgery are presented. The authors also give guidelines for care after the operation, and they point out when to use antibiotics, drains, and compression boots. Specifics of rehab and limits for the patient during the first six weeks are also covered.

    Dr. Stover and his co-authors take the time to list and discuss various problems that can occur after hip fusion surgery. Some complications are more likely to occur early after the operation. These complications include blood loss, infection, nerve injury, blood clots, fracture, and failure to heal. Later on, problems are more likely to affect other nearby joints. Pain in the opposite hip, spine, or knee on the same side can limit the patient years later.

    Finally, the authors discuss steps to take when changing a fused hip over to a hip replacement. This is called conversion. The benefits and problems with conversion are presented. The doctors conclude that hip fusion surgery is an excellent option for arthritic hips in young adults. The surgeon must take care to place the hip in a good position during the fusion. This will improve function, prevent deformity, and make conversion easier.

    Medicinal Prevention of Heterotopic Ossification after Total Hip Replacement Surgery

    Hip surgery, especially hip joint replacement, is a common operation around the world. Any trauma to the hip can cause bits of bone to form within the soft tissues around the hip. This condition is called heterotopic ossification (HO).

    There are risk factors for HO, but many patients without any risk factors develop it after total hip replacement surgery. For this reason, the authors of this study think prevention of HO is important for all patients, not just those with known risk factors.

    Radiation can be used, but there are many concerns about the costs and side effects of radiation therapy. Drugs, such as COX-1 and COX-2 inhibitors, may work. These are anti-inflammatory drugs used instead of aspirin. They tend to have fewer side effects on the gut. The COX-2 inhibitor is a new class of anti-inflammatory drug. It inhibits the COX-2 enzyme (in the gut), but leaves the COX-1 enzyme alone. In this study researchers in Italy compare the two drugs in patients after a total hip replacement.

    Four hundred patients were divided into two groups. The first group received indomethacin (a COX-1 and COX-2 inhibitor). The second group got celecoxib (a COX-2 inhibitor). All patients started taking the drug the day after the operation. They kept taking it for 20 days.

    The authors report no difference between the two groups when it comes to number of patients who developed HO. There was a difference in how many patients had side effects from the drug. About eight percent of the patients taking indomethacin had enough side effects to stop taking the drug. This compared with only two percent in the celecoxib group.

    In other words, celecoxib was just as good as indomethacin in preventing HO, yet without as many unpleasant side effects. The authors advise that steps should be taken to prevent HO in any patient having major hip surgery. They conclude that celecoxib is an effective COX-2 inhibitor that can be used to prevent HO.

    Bandage Surgery for Total Hip Replacement

    Imagine having a total hip replacement (THR) and going home the same day with just two small bandages on your hip. That’s how Dr. Richard A. Berger at St. Luke’s Medical Center in Chicago treats some of his patients. In this study, he reports on the results of the first 100 minimally invasive two-incision operations done for THR.

    Doctors have been looking for a way to avoid cutting through muscles and tendons during THR. Making such cuts causes pain and slows recovery. Making one cut above and another below the hip to replace the joint is possible now. Specially designed surgical tools and imaging X-rays called fluoroscopy have brought about these changes. New instruments include retractors to pull muscles and tendons away from the area, a special saw to cut away bone, and a special reamer. The reamer is used to make the hole bigger to fit the implant.

    Dr. Berger describes step-by-step how it’s done from start to finish. He points out the benefits of this method. Besides less trauma to the nearby tissues and less pain, the operation takes less time. The result is cost savings. And patients recover faster.

    Very few problems occurred during this 100-patient series. One patient had a broken thighbone during the operation. This was repaired and healed well. At first, patients selected for the operation were thin and had a fairly normal hip shape and size. With practice, the doctor was able to include patients who were obese or who had abnormal hip anatomy. Even patients with hip dislocation or who had surgery before could have this new type of operation.

    The author reports good results with this two-incision THR. Someone with special training must do the operation. The method must be practiced many times on cadavers before doing it on live humans. Going home the same day, having less pain, and a faster recovery time make this a favorable option for patients.

    Long-Term Results of Total Hip Replacement Surgery

    Total hip replacements (THRs) work well to reduce pain and improve function for almost all patients having this surgery. So say researchers in Switzerland. They conducted a large study of more than 25,000 THRs. In this study, the results of first-time THRs are reported. Factors such as age, gender, and body weight are also measured. The effects of these patient-related factors on the final outcome are summarized.

    Patients were followed for up to 15 years. Activities were measured, such as getting up from a chair, stair climbing, and walking. X-rays were reviewed. The patients’ opinions about the results were graded as excellent, good, fair and poor. Patients were asked to rate their satisfaction based on symptoms, limits, and need for drugs.

    The authors report that more than 93 percent of the patients said their results were “excellent” or “good” for the first five years. After that, patient satisfaction declined slowly. In later follow-ups, between 85 and 90 percent of patients were still satisfied with their THRs. This figure dropped to 70 percent at 15 years.

    The researchers also found the greatest improvement in pain and function during the first two years after THA. For some patients walking capacity continues to improve for as many as five years after THA. Later declines in walking and function may be caused by aggravation of symptoms in the other (as yet unreplaced) hip.

    Male patients seem to get better function than females. Doctors think this may be because women have more THRs for rheumatoid arthritis and hip fractures. These two diagnoses are known to have poorer results after THR than for osteoarthritis. Obese patients and patients older than 70 years have the poorest results.

    The authors conclude THR is very effective and reliable. Most patients see gains for up to five years. Even after the first five years, THR is a durable option, and most patients are very satisfied with the results.

    Shallow Hip Socket Linked to Osteoarthritis

    A recent study from the Mayo Clinic has some new information for doctors who operate on hips. The results show the need to look for a bony abnormality called acetabular retroversion. The acetabulum is the hip socket. Retroversion means the back half of the socket is shallow. The socket doesn’t fully cover the round head at the top of the thighbone.

    Any hip operation must take this lack of coverage into account. Retroversion is linked to osteoarthritis (OA) of the hip. In this study researchers looked at X-rays of 82 hips with hip OA of unknown cause. They compared them to 99 X-rays taken for some other problem. Most of the patients in the second group had bladder surgery or a hysterectomy.

    The authors report that 20 percent of the patients with hip OA also had acetabular retroversion. Only five percent of the nonorthopedic cases had this deformity. They think the lack of the back wall of the acetabulum is the simplest way to explain why patients with retroversion get OA. Contact pressures from movement may put extra stress on the cartilage of the hip where the back wall is missing. Every time someone stands up from a chair, reaction forces push up and back into the hip socket. Over time, hip OA occurs where the bone ends, leaving the head of the femur uncovered.

    The authors say it’s important to look for this problem whenever treating the hip. If the doctor is putting in a new hip replacement, the implant must be positioned just right to get the best coverage. The wrong angle in the new socket can lead to pinching of the tissues. Tissue tension and even hip dislocation are also possible.

    X-rays can show acetabular retroversion. The doctor must look at X-rays carefully before a total hip replacement or other hip surgery is done. The presence of this acetabular retroversion will alert the surgeon to possible problems. The operation can be planned with this in mind.

    Rehab on the Treadmill after Hip Replacement Surgery

    The mission after total hip replacement (THR) surgery is to get up and walking. Physical therapists and doctors are always looking for ways to help THR patients get back on their feet as soon as possible. Walking is the best way to build strength in the legs and hips. But walking is difficult after THR. Patients can’t put full weight on their new hip for some time.

    Which is where this study comes in. Treadmill training with body support has helped patients with certain types of hip fractures. These authors tested whether treadmill training would help THR patients.

    The authors looked at pain, strength, and walking ability in 80 THR patients. All of them could walk using two crutches. The patients were divided into two groups. Each person in the control group got 45 minutes of physical therapy every day for 10 days.

    The test group also got 45 minutes of therapy. However, they spent about 30 minutes of that time walking on a treadmill. They wore a special body harness that supported much of their weight. The rest of the session was spent doing physical therapy exercises. Both groups also got 30 minutes of occupational therapy, massage, heat, or ultrasound each day. And both groups spent 25 minutes a day doing exercises in the pool.

    All the patients were followed for one year. They were regularly checked for pain levels, hip and leg strength, and walking ability. Both groups improved over time. But the treadmill group did significantly better than the control group over the whole year. The treadmill group had less pain and stronger hip muscles. They had better range of motion and a more even walking gait. They got off crutches five weeks earlier. The only measurement that wasn’t any different was walking speed.

    And there was even a surprise bonus. No one in the treadmill group had loosening of the hip implant, compared to four patients in the control group. This might not mean anything. But the authors say stronger muscles may have helped prevent loosening.

    Why such a big difference? The authors point out that patients in the treadmill group took between 1,000 and 1,500 steps in each training session. This compares to only 100 to 150 steps for the control group. That means the treadmill group walked 10 times as much in the 10 days of therapy. All this walking helped the hip muscles get stronger much faster. And stronger muscles let the treadmill group walk even more outside of therapy sessions.

    The authors note one potential problem with the program. One of the treadmill patients died of a blood clot. The patient had earlier problems with blood clots. It is possible that the harness or the exercise made blood clots more likely to loosen and travel to the lungs. They now put all patients on blood thinners during the treadmill program after THR.