Several pathologies cause delayed postoperative paralysis following posterior decompression and spinal fusion for thoracic myelopathy caused by ossification of the posterior longitudinal ligament

Preventing neurological deterioration after ambulation in posterior decompression and fusion for thoracic ossification of the posterior longitudinal ligament

PurposeThe objective of this study was to clarify the characteristics of immediate neurological deterioration (ND) after ambulation and its potential preventative measures using multi-rod reinforcement during posterior decompression and fusion (PDF) with instrumentation for thoracic ossification of the posterior longitudinal ligament (T-OPLL).MethodsStudy 1: Fifteen patients with T-OPLL who underwent PDF before 2020 were included. Demographic, radiographic, intraoperative, and postoperative data were compared between the 6 patients with ND and 9 patients without ND after ambulation. Study 2: The primary (incidence of ND after ambulation) and the secondary (postoperative hospital stay) outcomes were compared between 15 patients with a multi-rod construct since 2020 (multi-rod group) and 15 patients with a dual-rod construct before 2020 (dual-rod group; patients who were indicated in study 1).ResultsStudy 1: ND after ambulation tends to occur only in the upper or middle thoracic spine. The mean maximum OPLL occupation ratio was significantly different between the groups (ND vs non-ND, 67.7% vs 53.4%; p = .021). Study 2: The incidence of ND after ambulation (dual-rod vs multi-rod, 40% vs 6.7%; p = .040) and the mean duration of the postoperative hospital stay (dual-rod vs multi-rod, 51.2 days vs 25.6 days; p = .007) were significantly different between the groups.ConclusionsImmediate ND after ambulation occurs in the upper or middle thoracic spine, and a higher maximum OPLL occupation ratio is a significant risk factor. Multi-rod reinforcement can reduce its incidence, regardless of maximum OPLL occupation ratio, and duration of postoperative hospital stay, which could be a potential preventative measure.

Anterior shift of the ventral dura mater: A novel concept of the posterior surgery for ossification of the posterior longitudinal ligament in thoracic spine

Background

Thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) remains one of the most difficult disorders to treat. The Ohtsuka procedure, extirpation, or anterior floating of the OPLL through a posterior approach, has shown great surgical outcomes after several modifications. However, these procedures are technically demanding and pose a significant risk of neurological deterioration. We have developed a novel modified Ohtsuka procedure in which removal or minimization of the OPLL mass is unnecessary; instead, the ventral dura mater is shifted anteriorly with the posterior part of the vertebral bodies and targeted OPLL.

Surgical Procedure

First, pedicle screws were inserted at more than three spinal levels above and below the spinal level where pediculectomies were performed. After laminectomies and total pediculectomies, partial osteotomy of the posterior vertebra adjacent to the targeted OPLL was performed by using a curved air drill. Then, the PLL is completely resected at the cranial and caudal sites of the OPLL using special rongeurs or a threadwire saw with a diameter of 0.36 mm. The nerve roots were not resected during surgery.

Methods

Eighteen patients (follow-up ≥1 year) treated with our modified Ohtsuka procedure were assessed clinically, including the Japanese Orthopaedic Association (JOA) score for thoracic myelopathy and radiographically.

Results

The average follow-up period was 3.2 years (range, 1.3-6.1 years). The preoperative JOA score was 2.7 ± 1.7, which improved to 8.2 ± 1.8 at 1 year postoperatively; therefore, the recovery rate was 65.8 ± 19.8%. The CT scan at 1 year after surgery revealed the anterior shift of the OPLL averaged 3.1 ± 1.7 mm and the ossification-kyphosis angle of the anterior decompression site decreased at an average of 7.2 ± 6.8 degrees. Three patients demonstrated temporary neurological deterioration, all of whom completely recovered within 4 weeks postoperatively.

Discussion

The concept of our modified Ohtsuka procedure is 1) not OPLL extirpation or minimization but only the creation of space between the OPLL and spinal cord by an anterior shift of the ventral dura mater, which is achieved by complete resection of the PLL at the cranial and caudal sites of the OPLL; and 2) no nerve roots are sacrificed to prevent ischemic spinal cord injury. This procedure is not technically demanding and safe and provides secure decompression for thoracic OPLL. The anterior shift of the OPLL was smaller than expected, but it resulted in a relatively good surgical outcome with a recovery rate ≥65%.

Conclusion

Our modified Ohtsuka procedure is quite secure and is not technically demanding, with a recovery rate of 65.8%.

Retrospective comparison of the surgical results for patients with thoracic myelopathy caused by ossification of the posterior longitudinal ligament: Posterior decompression with instrumented spinal fusion versus modified anterior decompression through a posterior approach

BACKGROUND

In Japan, approximately 75% of patients with thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) are treated by posterior decompression with instrumented spinal fusion (PDF) because of its efficacy and safety. To achieve more effective decompression of the spinal cord using a posterior approach, anterior decompression through a posterior approach was developed. However, this technique has a high risk of postoperative paralysis. We have added a couple of ingenuities to this procedure (modified Ohtsuka procedure). This study was performed to report the surgical results of our modified Ohtsuka procedure and to compare them with the results of PDF.

METHODS

This was a retrospective case series. From 2008 to 2018, we surgically treated 32 patients: 20 patients treated by PDF (PDF group) and 12 patients by our modified Ohtsuka procedure (modified Ohtsuka group) as the initial surgery. All patients were followed up for at least 12 months. The degree of surgical invasion and patients' neurological condition were assessed.

RESULTS

The operative duration and intraoperative blood loss indicated no significant differences (PDF vs. Ohtuska: 507 ± 103 vs. 534 ± 99 min, 1022 ± 675 vs. 1160 ± 685 ml, respectively). The preoperative Japanese Orthopaedic Association (JOA) score was 4.5 ± 2.0 in the PDF group and 3.3 ± 1.4 in the modified Ohtsuka group (p < 0.05). However, the latest JOA score and recovery rate were significantly better in the modified Ohtsuka group than in the PDF group (8.9 ± 1.2 vs. 7.4 ± 2.5 and 70.8 ± 17.6% vs. 44.5 ± 40.2%, respectively). Postoperative paralysis did not occur in the modified Ohtsuka group while four patients had it in the PDF group.

CONCLUSIONS

The present study clearly indicated the modified Ohtsuka group showed significantly better surgical outcomes than the PDF group with the recovery rate ≥70%.