Ossification of the posterior longitudinal ligament (OPLL) of the spine is common as we get older. Treatment for this problem remains a hot topic in orthopedics. Should everyone be treated conservatively without surgery? If surgery is done early, will it prevent worse problems from happening later?
Ossification means the ligament becomes hardened from bits of bone forming within it. The posterior longitudinal ligament is located inside the spinal canal along the back wall of the canal. It runs down the spine from top (cervical spine) to bottom (sacrum). The spinal canal is the round tube formed by the vertebrae where the spinal cord is located.
When the posterior longitudinal ligament hardens, it takes up space in the spinal canal. With decreased space for the spinal cord, myelopathy can occur. Myelopathy refers to any condition that affects the spinal cord. In this case, pressure on the cord from the ossified ligament can cause neurologic problems. Patients may report numbness, arm weakness, clumsiness of the hands, and trouble walking. Too much pressure can lead to paralysis.
But it’s not clear yet whether or not treating this problem can prevent neurologic damage from occurring. Surgeons don’t want to disturb this area by performing surgery if it’s not really necessary. Studies like this one help determine the results of conservative versus operative treatment.
Two equal-sized groups of patients with OPLL were compared. The first group had no myelopathy or only mild myelopathy. Patients with no myelopathy came to the doctors because of neck pain and/or stiffness. Their pre-treatment range-of-motion was less than those patients in the second (surgical) group. Group one received nonoperative care but the authors did not describe what this included.
The second group with moderate-to-severe myelopathy had surgery. The surgeons entered the spinal canal from the anterior (front of the) spine. The main area of hardened ligament was removed. The vertebrae were fused at that spot using bone taken from the patient’s fibula (lower leg bone) or iliac crest (pelvic bone).
Everyone was followed for three to five years. Special tests were performed before and after treatment to assess the results of treatment. The Japanese Orthopaedic Association (JOA) scale was used to measure the severity of the myelopathy. This same scale used after treatment showed changes (improvement or worsening). X-rays (also taken before and after treatment) were used to show how much of the spinal canal was occupied by the ossified ligament.
In the first group who had nonoperative care, those patients who had no myelopathy remained unchanged. Of the remaining patients with measurable myelopathy, half got better. The rest (except for one person) stayed the same. Neck range-of-motion did not change before and after conservative care.
As might be expected, the amount of residual space for the spinal cord was less in the nonoperative group compared to those who had surgery to increase the diameter of the spinal canal and take pressure off the spinal cord. This finding represents improvement in the surgical group.
In looking back over the results from before and after treatment between the two groups, the authors outline a plan for deciding who should have surgery and when to operate. Conservative care is always the first choice whenever possible. This is most likely when there is no myelopathy or only mild myelopathy in older patients with continuous OPLL. Continuous means the problem affects more than one vertebral segment.
Surgical treatment is advised for patients with excessive neck motion and signs of growth activity of the ossified mass (as seen on MRIs). Surgery is also indicated when the MRIs show high signal intensity indicating an increased risk of myelopathy developing or getting worse if already present. The presence of segmental OPLL (affecting multiple vertebral levels) was another indication that surgery was the best treatment choice. Most of the patients who met these criteria were younger (less than 50 years old).
Surgeons can use these guidelines when deciding on the best timing for surgery to treat myelopathy associated with cervical OPLL. The results of this study showed that conservative care is effective even when the spinal canal is narrowed. Patients in this group did not get worse over time, so there was no theoretical advantage of early surgical treatment to avoid a worsening of the problem.