Outcomes of fusion surgery for ossification of the posterior longitudinal ligament of the thoracic spine: a multicenter retrospective survey

Risk factors for residual neuropathic pain using specific screening tools in postoperative patients with ossification of the posterior longitudinal ligament of the cervical spine

PURPOSE

Ageing, long illness duration, and poor preoperative Japanese Orthopaedic Association (JOA) score were reported to be risk factors for residual pain after cervical ossification of the posterior longitudinal ligament (cOPLL). In this study, we focused on residual neuropathic pain (NeP) and aimed to elucidate risk factors for residual NeP after cOPLL.

METHODS

Total of 234 patients who underwent cOPLL surgery were included. NeP was evaluated using painDETECT (PDQ) and Spine painDETECT (SPDQ) questionnaires. Score of ≥ 13 / ≥ 0 was defined as NeP for PDQ/SPDQ. Patient backgrounds factors, preoperative radiographic factors and surgical factors were reviewed, and comparisons between the NeP(+) and NeP(-) groups were made. Independent risk factors for residual NeP were evaluated using multiple logistic regression analysis.

RESULTS

Prevalence of residual NeP after cOPLL was 22.6% on PDQ and 55.1% on SPDQ. Preoperative JOA score was significantly lower in the NeP(+) group for PDQ compared with that in the NeP(-) group. Additionally, cervical lordosis angle was significantly lower in the NeP(+) group for SPDQ compared with that in the NeP(-) group. Following multiple logistic regression analysis, poor preoperative JOA score was identified as a risk factor for NeP on the PDQ. Poor preoperative JOA score and low cervical lordosis angle were identified as risk factors using the SPDQ.

CONCLUSIONS

We found high prevalence of residual NeP after cOPLL. Patients with a poor preoperative JOA score and low cervical lordosis angle might be at risk for residual NeP after surgery evaluated by PDQ or SPDQ and should be monitored with greater care after surgery.

Investigation of the Shared Biomarkers in Heterotopic Ossification Between Ossification of the Ligamentum Flavum and Ankylosing Spondylitis

STUDY DESIGN

Bioinformatics analysis of Gene Expression Omnibus (GEO).

OBJECTIVE

Ossification of the ligamentum flavum (OLF) and ankylosing spondylitis (AS) represent intricate conditions marked by the gradual progression of endochondral ossification. This investigation endeavors to unveil common biomarkers associated with heterotopic ossification and explore the potential molecular regulatory mechanisms.

METHODS

Microarray and RNA-sequencing datasets retrieved from the Gene Expression Omnibus (GEO) repository were harnessed to discern differentially expressed genes (DEGs) within the OLF and AS datasets. Subsequently, Weighted Gene Co-expression Network Analysis (WGCNA) was implemented to pinpoint co-expression modules linked to OLF and AS. Common genes were further subjected to an examination of functional pathway enrichment. Moreover, hub intersection genes were identified using the Least Absolute Shrinkage and Selection Operator (LASSO) regression, followed by an evaluation of diagnostic performance in external OLF and AS cohorts. Lastly, an analysis of immune cell infiltration was conducted to scrutinize the correlation of immune cell presence with shared biomarkers in OLF and AS.

RESULTS

A total of 1353 and 91 Differentially Expressed Genes (DEGs) were identified in OLF and AS, respectively. Using the Weighted Gene Co-expression Network Analysis (WGCNA), 2 modules were found to be notably significant for OLF and AS. The integrative bioinformatic analysis revealed 3 hub genes (MAB21L2, MEGF10, ISLR) as shared risk biomarkers, with MAB21L2 being the central focus. Receiver Operating Characteristic (ROC) analysis exhibited a strong diagnostic potential for these hub genes. Gene Ontology (GO) analysis indicated their involvement in the positive regulation of myoblast proliferation. Notably, MAB21L2 was singled out as the optimal common biomarker for OLF and AS. Furthermore, an analysis of immune infiltration demonstrated a correlation between MAB21L2 expression and changes in immune cells. Activated CD8 T cells were identified as shared differential immune infiltrating cells significantly linked to MAB21L2 in both OLF and AS.

CONCLUSION

This study represents the first instance of identifying MAB21L2 as a prospective diagnostic marker for patients contending with OLF associated with AS. The research results indicate that the ECM-receptor interaction and the cell-cell adhesion may play a role in both disease processes. This newfound knowledge not only enhances our understanding of the pathogenesis behind spinal ligament ossification but also uncovers potential targets for therapeutic interventions.

Ten-Year Follow-up of Posterior Decompression and Fusion Surgery for Thoracic Ossification of the Posterior Longitudinal Ligament

BACKGROUND

We evaluated the clinical, functional, and quality of life (QoL) outcomes of surgical treatment of thoracic ossification of the posterior longitudinal ligament (T-OPLL).

METHODS

We retrospectively evaluated 51 patients followed for ≥10 years after posterior decompression and corrective fusion surgery for T-OPLL. The data collected included demographics, comorbidities, and pre- and postoperative symptoms. The Japanese Orthopaedic Association (JOA) score, numerical rating scale (NRS) for back and leg pain, and EuroQol-5 Dimension-5 Level (EQ-5D-5L) were used to assess neurological function, pain, and QoL. Imaging evaluations were conducted to assess changes in kyphotic angles and ossification progression.

RESULTS

A significant improvement was observed in the JOA score from preoperatively (3.7) to 2 years postoperatively (7.9) (p < 0.05); the score remained stable thereafter. The mean EQ-5D-5L score improved from 0.53 preoperatively to 0.68 at 10 years postoperatively (p < 0.001). NRS scores for back and leg pain decreased from 5.4 to 3.5 and 4.0 to 3.0, respectively, from preoperatively to 10 years (p < 0.001 for both). Radiographic outcomes showed changes in kyphotic angles and ossification areas, with no significant progression after 2 years. Fourteen (27.5%) of the patients experienced postoperative complications. Of these, 8 (15.7%) required reoperation, 6 (11.8%) in the perioperative period and 2 (3.9%) later. Four (7.8%) of the patients underwent additional surgeries for conditions including lumbar spinal canal stenosis and cervical OPLL. Nonetheless, physical function in all cases with postoperative complications or additional surgery remained stable over the decade.

CONCLUSIONS

Surgical treatment of T-OPLL is effective in improving neurological function, QoL, and pain management over an extended period. The long-term outcomes of T-OPLL surgery revealed that, although cervical and lumbar spinal lesions led to reoperations, they did not affect QoL, and relative improvement was maintained even after 10 years.

LEVEL OF EVIDENCE

Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Posterior Thoracic Antidisplacement and Fusion Surgery for a Special Type of Ossification of the Posterior Longitudinal Ligament in the Thoracic Spine: Indications and Preliminary Clinical Results of 2-Year Follow-Up

OBJECTIVE

To describe a novel technique, posterior thoracic antidisplacement and fusion (PTAF), for a special type of ossification of the posterior longitudinal ligament in the thoracic spine (T-OPLL), and to evaluate its safety and efficacy.

METHODS

From July to December 2020, 5 consecutive patients with beak-type T-OPLL located at the thoracic vertebral body level underwent PTAF surgery. Their demographic data, radiological parameters, perioperative complications, and surgery-related findings were recorded and analyzed. The surgical outcomes were assessed using a modified Japanese Orthopedic Association scale, and the recovery rate was calculated using the Hirabayashi's method.

RESULTS

All patients were followed up for at least two years. The mean thickness of OPLL was 9.4 ± 1.0 mm, and the OPLL spinal canal occupying ratio was 67.7% ± 8.5%. Postoperatively, the mean antidisplacement distance of OPLL was 8.1 ± 1.8 mm, and the average shortened distance of the spinal column was 6.0 ± 1.13 mm. The mean operation time and blood loss were 158.2 ± 26.3 minutes and 460 ± 89.4 mL, respectively. Perioperative complications were cerebrospinal fluid leakage and instrument failure, 2 cases each. The mean modified Japanese Orthopedic Association score was increased from 3.6 ± 2.9 before surgery to 9.4 ± 3.0 at the last follow-up, and the average recovery rate was 84.2 ± 30.5%.

CONCLUSIONS

The preliminary clinical outcomes indicate that PTAF is a safe and effective method for the treatment of beak-type T-OPLL, which has its apex located at the vertebral body level and has a high spinal canal occupation ratio.

Efficacy of D-Wave Monitoring Combined With the Transcranial Motor-Evoked Potentials in High-Risk Spinal Surgery: A Retrospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research

STUDY DESIGN

Retrospective multicenter cohort study.

OBJECTIVES

We aimed to clarify the efficacy of multimodal intraoperative neuromonitoring (IONM), especially in transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) with spinal cord-evoked potentials after transcranial stimulation of the brain (D-wave) in the detection of reversible spinal cord injury in high-risk spinal surgery.

METHODS

We reviewed 1310 patients who underwent TES-MEPs during spinal surgery at 14 spine centers. We compared the monitoring results of TES-MEPs with D-wave vs TES-MEPs without D-wave in high-risk spinal surgery.

RESULTS

There were 40 cases that used TES-MEPs with D-wave and 1270 cases that used TES-MEPs without D-wave. Before patients were matched, there were significant differences between groups in terms of sex and spinal disease category. Although there was no significant difference in the rescue rate between TES-MEPs with D-wave (2.0%) and TES-MEPs (2.5%), the false-positivity rate was significantly lower (0%) in the TES-MEPs-with-D-wave group. Using a one-to-one propensity score-matched analysis, 40 pairs of patients from the two groups were selected. Baseline characteristics did not significantly differ between the matched groups. In the score-matched analysis, one case (2.5%) in both groups was a case of rescue (P = 1), five (12.5%) cases in the TES-MEPs group were false positives, and there were no false positives in the TES-MEPs-with-D-wave group (P = .02).

CONCLUSIONS

TES-MEPs with D-wave in high-risk spine surgeries did not affect rescue case rates. However, it helped reduce the false-positivity rate.

Posterior Decompression and Fixation for Thoracic Spine Ossification: A 10-Year Follow-Up Study

Ossification of the posterior longitudinal ligament of the thoracic spine (T-OPLL) causes symptoms including leg and back pain, and motor and sensory deficits. This study retrospectively reviewed 32 patients who initially underwent posterior decompression with instrumented fusion (PDF) for T-OPLL between 2001 and 2012, with 20 qualifying for the final analysis after applying exclusion criteria. Exclusions included unknown preoperative neurological findings, follow-up less than 10 years, or prior spinal surgeries at other levels. Outcomes were assessed using the Japanese Orthopedic Association (JOA) score, recovery rate, and kyphotic angle. The average preoperative JOA score of 3.6 improved to 7.4 at 1 year post-surgery and remained at 7.4 at 10 years, with a recovery rate of 52%. The kyphotic angle at T4-12 increased from 26 degrees preoperatively to 29 degrees postoperatively and to 37 degrees at 10 years. At the fused levels, the angle remained at 26 degrees immediately post-operation and increased to 32 degrees at 10 years. Forty percent of patients required additional surgery, primarily for conditions related to cervical OPLL, such as myelopathy, or lumbar OPLL, such as radiculopathy, or cauda equina syndrome. In conclusion, PDF effectively reduces T-OPLL symptoms over the long term, but the high rate of additional surgeries calls for careful patient follow-up.

Thoracic Anterior Spinal Cord Herniation: Treatment and Prognosis Outcome of Seven Patients

BACKGROUND

This study aimed to investigate the diagnosis and treatment of thoracic anterior spinal cord herniation, a rare condition.

METHODS

Clinical data of 7 patients diagnosed with thoracic anterior spinal cord herniation were analyzed. All patients were diagnosed with a complete preoperative examination and scheduled for surgical treatment. In addition, regular follow-up was performed after the surgery, and the operation's efficacy was evaluated according to clinical symptoms, imaging findings, and improvement in neurologic function.

RESULTS

All patients underwent spinal cord release with an anterior dural patch. Notably, no severe postoperative surgical complications were observed. All patients were followed up for 12-75 months, with an average duration of approximately 46.5 months. Post-operative pain symptoms were controlled, neurological dysfunction and related symptoms improved to varying degrees, and anterior spinal cord herniation did not recur. The modified Japanese Orthopedic Association score at the last follow-up was significantly higher than the preoperative score.

CONCLUSIONS

Clinicians should avoid misdiagnosing patients with thoracic anterior spinal cord herniation with intervertebral disc herniation, arachnoid cysts, and other related diseases, and patients should undergo surgical treatment as early as possible. In addition, surgical treatment can protect the neurologic function of patients and effectively prevent the aggravation of clinical symptoms.

Residual Neuropathic Pain in Postoperative Patients With Cervical Ossification of Posterior Longitudinal Ligament

STUDY DESIGN

A prospective multi-institutional observational study.

OBJECTIVE

To investigate and identify risk factors for residual neuropathic pain after surgery in patients with cervical ossification of posterior longitudinal ligament (c-OPLL).

SUMMARY OF BACKGROUND DATA

Patients with c-OPLL often require surgery for numbness and paralysis of the extremities; however, postoperative neuropathic pain can considerably deteriorate their quality of life.

METHODS

Out of 479 patients identified from multicenter c-OPLL registries between 2014 and 2017, 292 patients who could be followed up for 2 years postoperatively were reviewed, after excluding patients with nervous system comorbidities. Demographic details; medical history; radiographic factors including the K-line, spinal canal occupancy rate of OPLL, cervical kyphosis angle, and presence of spinal cord myelomalacia; preoperative Japanese Orthopaedic Association (JOA) score; surgical procedure (fusion or decompression surgery); postoperative neurological deterioration; and the visual analogue scale for pain and numbness in the upper extremities (U/E) or trunk/lower extremities (L/E) at baseline and at 2 years postoperatively were assessed. Patients were grouped into residual and non-residual groups based on a postoperative visual analogue scale ≥40 mm. Risk factors for residual neuropathic pain were evaluated by multiple logistic regression analysis.

RESULTS

The prevalence of U/E and L/E residual pain in postoperative c-OPLL patients was 51.7% and 40.4%, respectively. The U/E residual group had a poor preoperative JOA score and longer illness duration, and fusion surgery was more common in the residual group than in non-residual group. The L/E residual group was older with a poorer preoperative JOA score. On multivariate analysis, risk factors for U/E residual pain were long illness duration and poor preoperative JOA score, whereas those for L/E residual pain were age and poor preoperative JOA score.

CONCLUSIONS

The risk factors for residual spinal neuropathic pain after c-OPLL surgery were age, long duration of illness, and poor preoperative JOA score.

LEVEL OF EVIDENCE

IV.

Failure to Obtain Baseline Signals of Transcranial Motor-Evoked Potentials in Spine Surgery: Analysis of the Reasons

OBJECTIVE

Among the various intraoperative neurophysiologic monitoring (IONM) techniques, transcranial motor-evoked potential (Tc-MEP) has recently become the most widely used method to monitor motor function. However, we often find that Tc-MEP is not sufficiently detected at the start of surgery. Therefore, we aimed to analyze the reasons and risk factors for not detecting sufficient baseline signal of Tc-MEP from the beginning of spinal surgery.

METHODS

We categorized IONM data from 1058 patients who underwent spine surgeries at a single institution from 2014 to 2020 and categorized them into 2 groups: 1) "poor MEP" if Tc-MEP could not be sufficiently obtained and 2) "normal MEP" if Tc-MEP could be sufficiently obtained from the surgery. We analyzed the patient's age, gender, underlying disease, operation type, level numbers, baseline motor function, existence of pathologic reflex, myelopathy, and duration from the onset and clinical diagnosis.

RESULTS

The rate of failure to obtain sufficient baseline Tc-MEP signals in spine surgery was 21.8% (231/1058). Multivariate analysis showed significant associations of existence of diabetes mellitus, myelopathy, thoracic spine surgery, baseline motor deficit and tumor, and trauma disease with loss of meaningful and interpretable signals in baseline Tc-MEP (P < 0.05). Only 15 of 231 patients (6.4%) showed a trend of signal recovery after decompression procedures.

CONCLUSIONS

Various factors (myelopathy, diabetes mellitus, thoracic surgery, baseline motor deficit, tumor, and trauma) were closely related to not obtaining sufficient baseline signals for Tc-MEP. When operating on patients with these considerations, we need to consider the efficacy and usefulness of Tc- MEP.

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%.

Predictors of good outcome after anterior decompression and fusion in patients with ossification of the posterior longitudinal ligament of the thoracic spine

BACKGROUND

There are few reports concerning determinants of the surgical outcome of anterior decompression and fusion (ADF) when performed for ossification of the posterior longitudinal ligament of the thoracic spine (T-OPLL). We investigated prognostic factors associated with neurological recovery in the patients with T-OPLL.

METHODS

This retrospective study included consecutive cases of T-OPLL patients from January 2002 to January 2020 and minimum one-year follow-up. Data were collected for sex, age, body mass index, preoperative manual muscle test score for the weakest muscle, surgical data, and preoperative and postoperative findings on radiographs, magnetic resonance images, and computed tomography scans. Imaging data were also collected, including preoperative kyphotic angles, canal occupancy ratio, type of OPLL, and high-intensity areas on T2-weighted images. The Japanese Orthopaedic Association score for thoracic myelopathy (T-JOA) was used to evaluate the recovery of the thoracic myelopathy. The patients were categorized according to whether the improvement in T-JOA score was >50% or ≤50%.

RESULTS

Forty-six patients who underwent anterior procedures for T-OPLL were included in the study. Preoperative and postoperative T-JOA scores were 4.2 ± 2.3 and 7.9 ± 2.1, respectively. The improvement in the T-JOA score was 54.5 ± 25.6%. The proportion of patients with beak-type OPLL was significantly higher in the >50% JOA improvement group (23/27) than in the ≤50% group (9/19) (p = 0.009) and the canal occupancy ratio was significantly lower in the >50% group (56.3 ± 12.2% vs 64.4 ± 8.73%; p = 0.0163). There were no significant between-group differences in other factors.

CONCLUSIONS

Beak-type ossification and a low canal occupancy ratio are predictors of good outcome after ADF in patients with T-OPLL. ADF should be considered in patients with either or both of these features.

Anterior decompression through a posterior approach for thoracic myelopathy caused by ossification of the posterior longitudinal ligament: a novel concept in anterior decompression and technical notes with the preliminary outcomes

OBJECTIVE

Various surgical procedures are used to manage thoracic myelopathy due to ossification of the posterior longitudinal ligament (OPLL). However, the outcomes of surgery for thoracic OPLL are generally unfavorable in comparison to surgery for cervical OPLL. Previous studies have shown a significant risk of perioperative complications in surgery for thoracic OPLL. Thus, a safe and secure surgical method to ensure better neurological recovery with less perioperative complications is needed. The authors report a novel concept of anterior decompression through a posterior approach aimed at anterior shift of the OPLL during surgery rather than extirpation or size reduction of the OPLL. This surgical technique can securely achieve anterior shift of the OPLL using a curved drill, threadwire saw, and curved rongeur. The preliminary outcomes were investigated to evaluate the safety and efficacy of this technique.

METHODS

This study included 10 consecutive patients who underwent surgery for thoracic OPLL. Surgical outcomes, including the ambulatory status, Japanese Orthopaedic Association (JOA) score, and perioperative complications, were investigated retrospectively. In this surgery, pedicle screws are introduced at least three levels above and below the corresponding levels. The laminae, facet joints, transverse processes, and pedicles are then removed bilaterally at levels wherein subsequent anterior decompression is performed. For anterior decompression, the OPLL and posterior portion of the vertebral bodies are partially resected using a high-speed drill with a curved burr, enabling the removal of osseous tissues just ventral to the spinal cord without retracting the dural sac. To securely shift the OPLL anteriorly, the intact PLL and posterior portion of the vertebral bodies cranial and caudal to the lesion are completely resected using a threadwire saw and/or curved rongeur. Rods are connected to the screws, and bone grafting is performed for posterolateral fusion.

RESULTS

Five patients were nonambulatory before surgery, but all were able to walk at the final follow-up. The average JOA score before surgery and at the final follow-up was 3.2 and 8.8 points, respectively. Notably, the mean recovery rate of JOA score was 72%. Furthermore, no patients showed neurological deterioration postoperatively.

CONCLUSIONS

The surgical technique is a useful alternative for safely achieving sufficient anterior decompression through a posterior approach and may consequently reduce the risk of postoperative neurological deterioration and improve surgical outcomes in patients with thoracic OPLL.

Characteristics of Cases with Poor Transcranial Motor-evoked Potentials Baseline Waveform Derivation in Spine Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research

STUDY DESIGN

Prospective multicenter study.

OBJECTIVE

The purpose of the study is to examine cases with poor baseline waveform derivation for all muscles in multichannel monitoring of transcranial motor-evoked potentials (Tc-MEPs) in spine surgery.

SUMMARY OF BACKGROUND DATA

Intraoperative neuromonitoring (IONM) is useful for identifying neurologic deterioration during spinal surgery. Tc-MEPs are widely used for IONM, but some cases have poor waveform derivation, even in multichannel Tc-MEP monitoring.

METHODS

The subjects were 3625 patients (mean age 60.1 years, range 4-95; 1886 females, 1739 males) who underwent Tc-MEP monitoring during spinal surgery at 16 spine centers between April 2017 and March 2020. Baseline Tc-MEPs were recorded from the deltoid, abductor pollicis brevis, adductor longus, quadriceps femoris, hamstrings, tibialis anterior, gastrocnemius, and abductor hallucis (AH) muscles after surgical exposure of the spine.

RESULTS

The 3625 cases included cervical, thoracic, and lumbar lesions (50%, 33% and 17%, respectively) and had preoperative motor status of no motor deficit, and motor deficit with manual muscle testing (MMT) ≥3 and MMT <3 (70%, 24% and 6%, respectively). High-risk surgery was performed in 1540 cases (43%). There were 73 cases with poor baseline waveform derivation (2%), and this was significantly associated with higher body weight, body mass index, thoracic lesions, motor deficit of MMT <3, high-risk surgery (42/1540 [2.7%] vs. 31/2085 [1.5%], P < 0.05), and surgery for ossification of the posterior longitudinal ligament (OPLL). Intraoperative waveform derivation occurred in 25 poor derivation cases (34%) and the AH had the highest rate.

CONCLUSION

The rate of poor baseline waveform derivation in spine surgery was 2% in our series. This was significantly more likely in high-risk surgery for thoracic lesions and OPLL, and in cases with preoperative severe motor deficit. In such cases, it may be preferable to use multiple modalities for IONM to derive multichannel waveforms from distal limb muscles, including the AH.Level of Evidence: 3.

The muscle evoked potential after epidural electrical stimulation of the spinal cord as a monitor for the corticospinal tract: studies by collision technique and double train stimulation

To study if spinal motor evoked potentials (SpMEPs), muscle responses after electrical stimulation of the spinal cord, can monitor the corticospinal tract. Study 1 comprised 10 consecutive cervical or thoracic myelopathic patients. We recorded three types of muscle responses intraoperatively: (1) transcranial motor evoked potentials (TcMEPs), (2) SpMEPs and (3) SpMEPs + TcMEPs from the abductor hallucis (AH) using train stimulation. Study 2 dealt with 5 patients, who underwent paired train stimulation to the spinal cord with intertrain interval of 50-60 ms for recording AH SpMEPs. We will also describe two illustrative cases to demonstrate the clinical value of AH SpMEPs for monitoring the motor pathway. In Study 1, SpMEPs and SpMEPs + TcMEPs recorded from AH measured nearly the same, suggesting the collision of the cranially evoked volleys with the antidromic signals induced by spinal cord stimulation via the corticospinal tracts. In Study 2, the first and second train stimuli elicited almost identical SpMEPs, indicating a quick return of transmission after 50-60 ms considered characteristic of the corticospinal tract rather than the dorsal column, which would have recovered much more slowly. Of the two patients presented, one had no post-operative neurological deteriorations as anticipated by stable SpMEPs, despite otherwise insufficient IONM, and the other developed post-operative motor deficits as predicted by simultaneous reduction of TcMEPs and SpMEPs in the face of normal SEPs. Electrical stimulation of the spinal cord primarily activates the corticospinal tract to mediate SpMEPs.

New Classification Algorithm Guiding Surgical Decision-making for Posterior Longitudinal Ligament Ossification of the Thoracic Spine: A Study of 108 Patients With Mid-term to Long-term Follow-up

STUDY DESIGN

This is a single-center, retrospective, cohort study.

OBJECTIVE

The objective of this study was to propose a surgical classification algorithm guiding the choice of surgical approaches for ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine based on the characteristics of each patient's specific pathology.

SUMMARY OF BACKGROUND DATA

Surgical decision-making in this OPLL patient population requires balancing a more definitive decompression of the thoracic spinal cord through direct decompression against a higher risk of significant complications.

MATERIALS AND METHODS

Patients with a primary diagnosis of thoracic OPLL who received surgical decompression in a tertiary spine center between May 2009 and June 2015 were included. Surgical planning was guided by our classification algorithm according to the location and the extent of OPLL in each patient. Patient demographics, neurological function using the 11-point Japanese Orthopaedic Association scale, length of procedure, estimated blood loss, the occurrence of major complications, etc., were extracted from the database of electronic medical record system. The Kruskal-Wallis test and Fisher exact test were used when data were not normally distributed.

RESULTS

A total of 115 patients (33 men and 82 women) were included in this study, among whom 108 had a follow-up of at least 12 months (average: 51.7±22.2 mo, range: 12-100 mo). On the basis of our classification algorithm, 11 patients were type I, 26 were type II, 60 were type III, 11 were type IV, and the choice of surgical decompression techniques used in each patient followed that recommended by the algorithm in all cases. On average, the Japanese Orthopaedic Association score improved from 5.0±1.8 preoperatively to 8.7±1.7 postoperatively, with a Hirabayashi improvement rate of 63.6%.

CONCLUSION

A new surgical classification algorithm guiding the choice of approach for decompression of OPLL in the thoracic spine was validated in a series of 108 patients through an analysis of their clinical outcomes and surgical complications.

LEVEL OF EVIDENCE

Level III.

Efficacy of Intraoperative Intervention Following Transcranial Motor-evoked Potentials Alert During Posterior Decompression and Fusion Surgery for Thoracic Ossification of the Posterior Longitudinal Ligament: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research

STUDY DESIGN

Prospective, multicenter, observational study.

OBJECTIVE

The aim of this study was to investigate the efficacy of intervention after an alert in intraoperative neurophysiological monitoring (IONM) using transcranial motor-evoked potentials (Tc-MEPs) during surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL).

SUMMARY OF BACKGROUND DATA

T-OPLL is commonly treated with posterior decompression and fusion with instrumentation. IONM using Tc-MEPs during surgery reduces the risk of neurological complications.

METHODS

The subjects were 79 patients with a Tc-MEP alert during posterior decompression and fusion surgery for T-OPLL. Preoperative muscle strength (manual muscle testing [MMT]), waveform derivation rate at the start of surgery (baseline), intraoperative waveform changes; and postoperative motor paralysis were examined. A reduction in MMT score of ≥1 on the day after surgery was classified as worsened postoperative motor deficit. An alert was defined as a decrease in Tc-MEP waveform amplitude of ≥70% from baseline. Alerts were recorded at key times during surgery.

RESULTS

The patients (35 males, 44 females; age 54.6 years) had OPLL at T1-4 (n = 27, 34%), T5-8 (n = 50, 63%), and T9-12 (n = 16, 20%). The preoperative status included sensory deficit (n = 67, 85%), motor deficit (MMT ≤4) (n = 59, 75%), and nonambulatory (n = 26, 33%). At baseline, 76 cases (96%) had a detectable Tc-MEP waveform for at least one muscle, and the abductor hallucis had the highest rate of baseline waveform detection (n = 66, 84%). Tc-MEP alerts occurred during decompression (n = 47, 60%), exposure (n = 13, 16%), rodding (n = 5, 6%), pedicle screw insertion (n = 4, 5%), posture change (n = 4, 5%), dekyphosis (n = 2, 3%), and other procedures (n = 4, 5%). After intraoperative intervention, the rescue rate (no postoperative neurological deficit) was 57% (45/79), and rescue cases had a significantly better preoperative ambulatory status and a significantly higher baseline waveform derivation rate.

CONCLUSION

These results show the efficacy of intraoperative intervention following a Tc-MEP alert for prevention of neurological deficit postoperatively.Level of Evidence: 2.

Neurophysiological monitoring during anterior cervical discectomy and fusion for ossification of the posterior longitudinal ligament

OBJECTIVE

This study aimed to investigate the value of intraoperative neurophysiological monitoring (IONM) in anterior cervical spine discectomy with fusion (ACDF) for ossification of the posterior longitudinal ligament (OPLL).

METHODS

Patients who underwent multimodal IONM (transcranial electrical motor-evoked potentials [tcMEP], somatosensory-evoked potentials, and continuous electromyography) for ACDF from 2009 to 2019 were compared to historical controls from 2003 to 2009. The rates of postoperative neurological deficits, neurophysiological warnings, and their characteristics were analyzed.

RESULTS

Among 196 patients, postoperative neurological deficit rates were 3.79% and 14.06% in the IONM and historical control (non-IONM) groups, respectively (p < 0.05). The use of IONM (OR: 0.139, p = 0.003) and presence of myelopathy (OR: 8.240, p = 0.013) were associated with postoperative neurological complications on multivariate regression. In total, 23 warnings were observed during IONM (17 tcMEP and/or electromyography; six electromyography). Sensitivity and specificity of IONM warnings for detecting neurological complications were 84.2% and 93.7%, respectively.

CONCLUSIONS

IONM, especially multimodal IONM, may be a useful tool to detect neurological damage in ACDF for high-risk conditions such as OPLL with pre-existing myelopathy.

SIGNIFICANCE

The utility of IONM in ACDF for OPLL has not been evaluated due to its rarity. This study supports the use of IONM in cervical OPLL with myelopathy.

Surgical strategy for non-continuous thoracic spinal stenosis: one- or two-stage surgery?

PURPOSE

Non-continuous thoracic spinal stenosis (NTSS) is a rare disease, but it is a challenging clinical entity for spine surgeons. However, few studies have focused on its treatment. Therefore, the purpose of this study was to provide surgical treatment guidelines for it by comparing the clinical outcomes of different surgical approaches.

METHODS

Patients who underwent thoracic decompression surgery for two diseased segments with two incisions (normal segments ≥ 3) between January 2010 and December 2018 were included. Among these patients, nine were treated with posterior decompression (PD) and circumferential decompression (CD) procedures in one-stage surgery (group A), 14 with PD and CD procedures in two-stage surgery (group B), 36 patients with PD procedures in one-stage surgery and 15 with PD procedures in two-stage surgery (group D). Medical records, operative time, blood loss and complications were reviewed. Neurologic status was assessed by the modified Japanese Orthopaedic Association scale for thoracic myelopathy.

RESULTS

Groups A, B, C and D were followed for 54.11 ± 20.51 months, 49.36 ± 29.30 months, 49.94 ± 31.94 months and 39.93 ± 26.18 months, respectively. When comparing groups A and B, operative time, blood loss and length of stay in hospital were significantly less in group A. However, the average recovery rate in group B was significantly higher than that in group A. In regard to groups C and D, group C showed a significantly shorter length of stay in hospital and lower rate of post-operative neurological deterioration. At final follow-up, groups C and D showed similar average recovery rates.

CONCLUSION

Different surgical procedures are suitable for different types of NTSS. For patients with NTSS mainly caused by posterior compression, PD via laminectomy in one-stage with two incisions can achieve satisfying clinical outcomes. Staged surgery, including CD and PD procedures, is recommended for patients with NTSS mainly caused by anterior compression.

Clinical characteristics in patients with ossification of the posterior longitudinal ligament: A prospective multi-institutional cross-sectional study

Ossification of the posterior longitudinal ligament (OPLL) can occur throughout the entire spine and can sometimes lead to spinal disorder. Although patients with OPLL sometimes develop physical limitations because of pain, the characteristics of pain and effects on activities of daily living (ADL) have not been precisely evaluated in OPLL patients. Therefore, we conducted a multi-center prospective study to assess whether the symptoms of cervical OPLL are different from those of cervical spondylosis (CS). A total of 263 patients with a diagnosis of cervical OPLL and 50 patients with a diagnosis of CS were enrolled and provided self-reported outcomes, including responses to the Japanese Orthopaedic Association (JOA) Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), JOA Back Pain Evaluation Questionnaire (JOABPEQ), visual analog scale (VAS), and SF-36 scores. The severity of myelopathy was significantly correlated with each domain of the JOACMEQ and JOABPEQ. There was a negative correlation between the VAS score for each domain and the JOA score. There were significantly positive correlations between the JOA score and the Mental Health, Bodily Pain, Physical Functioning, Role Emotional, and Role Physical domains of the SF-36. One-to-one matching resulted in 50 pairs of patients with OPLL and CS. Although there was no significant between-group difference in scores in any of the domains of the JOACMEQ or JOABPEQ, the VAS scores for pain or numbness in the buttocks or limbs were significantly higher in the CS group; however, there was no marked difference in low back pain, chest tightness, or numbness below the chest between the two study groups. The scores for the Role Physical and Body Pain domains of the SF-36 were significantly higher in the OPLL group than in the CS group, and the mean scores for the other domains was similar between the two groups. The results of this study revealed that patients with OPLL were likely to have neck and low back pain and restriction in ADL. No specific type of pain was found in patients with OPLL when compared with those who had CS.

Three-Dimensional Analysis of the Radiological Risk Factors for Progression of the Thoracic Ossification of the Posterior Longitudinal Ligament After Posterior Decompression and Stabilization

BACKGROUND

Although research shows that the ossified masses of ossification of the posterior longitudinal ligament (OPLL) continue to grow postoperatively, information regarding thoracic OPLL (T-OPLL) is lacking. To date, no study has investigated the progression of T-OPLL within each motion segment. The purpose of this study was to analyze the progression of T-OPLL in each motion segment using a 3-dimensional measurement and evaluate whether the type of T-OPLL and surgical methods affect its progression postoperatively.

METHODS

Clinical data from 20 patients (101 segments) with thoracic myelopathy secondary to OPLL were evaluated retrospectively. All patients underwent posterior decompression (laminectomy and stabilization or circumferential decompression [CD] and stabilization) at a single center. The 3-dimensional measurement of OPLL volume was performed using computed tomography scans. The ossified masses were classified into 2 types based on the fusion of each segment at the intervertebral space: type 1 = complete bridging (fused); type 2 = not fused. Statistical analyses were performed to determine the degree of T-OPLL progression according to the types and surgical methods.

RESULTS

Mean OPLL progression was significantly higher in type 2. The mean annual growth rates of OPLL (AGRO) for groups 1 and 2 were 6.21% ± 6.11% per year and 23.50% ± 11.34% per year, respectively (P < 0.01). Further, no statistically significant differences were seen between the fixed and non-fixed groups (P = 0.23), and CD and non-CD segments (P = 0.56).

CONCLUSIONS

The mean AGRO does not decrease even after stabilization and CD. Type 2 intervertebral space was a risk factor for T-OPLL progression. Cases of type 2 without CD need close follow-up.

Microsurgical resection of ossification of the posterior longitudinal ligament in the thoracic spine via the transthoracic approach without spinal fusion: case series and technical note

OBJECTIVE

Surgical management of thoracic ossification of the posterior longitudinal ligament (OPLL) remains challenging because of the anatomical complexity of the thoracic spine and the fragility of the thoracic spinal cord. Several surgical approaches have been described, but it remains unclear which of these is the most effective. The present study describes the microsurgical removal of OPLL in the middle thoracic level via the transthoracic anterolateral approach without spinal fusion, including the surgical outcome and operative tips.

METHODS

Between 2002 and 2017, a total of 8 patients with thoracic myelopathy due to OPLL were surgically treated via the transthoracic anterolateral approach without spinal fusion. The surgical techniques are described in detail. Clinical outcome, surgical complications, and the pre- and postoperative thoracic kyphotic angle were assessed.

RESULTS

The mean patient age at the time of surgery was 55 years (range 47-77 years). There were 5 women and 3 men. The surgically treated levels were within T3-9. The clinical symptoms and Japanese Orthopaedic Association (JOA) score improved postoperatively in 7 cases, but did not change in 1 case. The mean JOA score increased from 6.4 preoperatively to 7.5 postoperatively (recovery rate 26%). Intraoperative CSF leakage occurred in 4 cases, and was successfully treated with fibrin glue sealing and spinal drainage. The mean follow-up period was 82.6 months (range 15.3-169 months). None of the patients had deterioration of the thoracic kyphotic angle.

CONCLUSIONS

Anterior decompression is the logical and ideal procedure to treat thoracic myelopathy caused by OPLL on the concave side of the spinal cord; however, this procedure is technically demanding. Microsurgery via the transthoracic anterolateral approach enables direct visualization of the thoracic ventral ossified lesion. The use of microscopic procedures might negate the need for bone grafting or spinal instrumentation.

Indication for anterior spinal cord decompression via a posterolateral approach for the treatment of ossification of the posterior longitudinal ligament in the thoracic spine: a prospective cohort study

PURPOSE

For ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine, anterior decompression is the most effective method for relieving spinal cord compression. The purpose of this study was to prospectively analyze the surgical outcomes based on our strategy in the treatment of thoracic OPLL.

METHODS

This study included 23 patients who underwent surgery for thoracic OPLL based on the following strategy between 2011 and 2017. For patients with a beak-type OPLL in the kyphotic curve with a ≥ 50% canal occupying ratio, circumferential decompression via a posterolateral approach and fusion (CDF) was indicated. For other types of OPLL, posterior decompression and fusion (PDF) was commonly indicated. Posterior fusion without decompression (PF) was applied when the spinal cord was separated from the posterior spinal elements. Clinical and radiological outcomes were compared among the CDF, PDF, and PF groups with a minimum of 20-month follow-up.

RESULTS

Ten, eleven, and two patients underwent CDF, PDF, and PF, respectively. The preoperative Japanese Orthopedic Association (JOA) score in the CDF group was significantly lower than that in the PDF group. The average recovery rate, according to JOA score, was 63%, 56%, and 25% in the CDF, PDF, and PF groups, respectively. The result in the CDF group was better than that in the PF group.

CONCLUSIONS

Anterior decompression was appropriate for patients with localized spinal cord compression by a large OPLL in the kyphotic curve, and CDF via a posterolateral approach appears to be safe and effective. These slides can be retrieved under Electronic Supplementary Material.

Surgical Outcomes According to Dekyphosis in Patients with Ossification of the Posterior Longitudinal Ligament in the Thoracic Spine

Objective

Ossification of posterior longitudinal ligament (OPLL) in the thoracic spine may cause chronic compressive myelopathy that is usually progressive, and unfavorable by conservative treatment. Although surgical intervention is often needed, the standard surgical method has not been established. Recently, it has been reported that posterior decompression with dekyphosis is effective surgical technique for favorable clinical outcome. The purpose of this study was to evaluate the surgical outcomes in patients with thoracic OPLL according to dekyphosis procedure and to identify predictive factors for the surgical results.

Methods

A total of 25 patients with thoracic OPLL who underwent surgery for myelopathy from May 2004 to March 2017, were retrospectively reviewed. Patients with cervical myelopathy were excluded. We assessed the clinical outcomes according to various surgical approaches. The modified Japanese orthopedic association (JOA) scores for the thoracic spine (total, 11 points) and JOA recovery rates were used for investigating surgical outcomes.

Results

Of the 25 patients, 10 patients were male and the others were female. The mean JOA score was 6.7±2.3 points preoperatively and 8.8±1.8 points postoperatively, yielding a mean recovery rate of 53.8±31.0%. The mean patients’ age at surgery was 52.4 years and mean follow-up period was 40.2 months. According to surgical approaches, seven patients underwent anterior approaches, 13 patients underwent posterior approaches, five patients underwent combined approaches. There was no significant difference of the surgical outcomes related with different surgical approaches. Age (≥55 years) and high signal intensity on preoperative magnetic resonance (MR) image in the thoracic spine were significant predictors of the lower recovery rate after surgery (p<0.05). Posterior decompression with dekyphosis procedure was related to the excellent surgical outcomes (p=0.047). Dekyphosis did not affect the complication rates.

Conclusion

In this study, our result elucidated that old age (≥55 years) and presence of intramedullary high signal intensity on preoperative MR images were risk factors related to poor surgical outcomes. In the meanwhile, posterior decompression with dekyphosis affected favorable clinical outcome. Posterior approach with dekyphosis procedure can be a recommendable surgical option for favorable results.

The effect of multiple lesions in patients with ossification of the posterior longitudinal ligament of the cervical spine

PURPOSE

Ossification of the posterior longitudinal ligament of the cervical spine (cervical OPLL) is associated with the lesions at the thoracic and/or lumbar spine. Multiple spinal lesions cause additional neurological deficit, affecting the outcomes of cervical laminoplasty. This study aimed to clarify the effect of multiple lesions on the outcomes of cervical laminoplasty and to compare the results with data from patients without them.

METHODS

From April 1981 to October 2015, 201 patients underwent laminoplasty for cervical OPLL; however, 167 patients were followed for >2 years. Twenty-four patients underwent additional surgery for multiple lesions due to spinal stenosis. The pathologies of the lesions were assessed. The patients were divided into two groups: the thoracic and thoraco-lumbar group (T-group: 8 patients) and the lumbar group (L-group: 16 patients). One-hundred patients without an additional surgery served as the control group. The maximum Japanese Orthopaedic Association (JOA) score and the most recent score for recovery was compared between the multiple and control groups.

RESULTS

The maximum score and recovery rate and the score and recovery rate at the last follow-up in the multiple group were lower than those in the control group. There was no significant difference in the postoperative JOA score and recovery rate between the T-group and the L-group.

CONCLUSIONS

Neurological recovery in patients with multiple lesions was poorer than in those without lesions. Therefore, special attention should be paid to cervical OPLL with multiple spinal lesions.

Alert Timing and Corresponding Intervention With Intraoperative Spinal Cord Monitoring for High-Risk Spinal Surgery

STUDY DESIGN

Prospective multicenter study.

OBJECTIVE

To analyze the incidence of intraoperative spinal neuromonitoring (IONM) alerts and neurological complications, as well as to determine which interventions are most effective at preventing postoperative neurological complications following IONM alerts in high risk spinal surgeries.

SUMMARY OF BACKGROUND DATA

IONM may play a role in identifying and preventing neural damage; however, few studies have clarified the outcomes of intervention after IONM alerts.

METHODS

We analyzed 2867 patients who underwent surgery for high risk spinal pathology using transcranial electrical motor-evoked potentials from 2010 to 2016. The high-risk spinal surgery cases consisted of 1009 spinal deformity cases, 622 cervical ossification of posterior longitudinal ligament (OPLL) cases, 249 thoracic-OPLL cases, 771 extramedullary spinal cord tumor cases, and 216 intramedullary spinal cord tumor (IMSCT) cases. We set a 70% amplitude reduction as the alarm threshold for transcranial electrical motor-evoked potentials and analyzed the outcomes of the interventions following monitoring alerts and postoperative neurological deficits.

RESULTS

The true positive, false positive, true negative, false negative, and rescue cases of IONM comprised 126, 234, 2362, 9, and 136 cases, respectively. Most alerts and interventions occurred during correction and release in deformity cases, posterior decompression and dekyphosis in OPLL cases, and tumor resection and surgery suspension with steroid injection in spinal cord tumor cases; however, individual interventions varied. The rescue rates (number of patients rescued with intervention after IONM alert/number of true positive cases plus rescue cases) for deformity, cervical-OPLL, thoracic--OPLL, extramedullary spinal cord tumor, and IMSCT cases were 61.4% (35/57), 82.1% (32/39), 40% (20/50), 52.5% (31/59), and 31.6% (18/57), respectively.

CONCLUSION

Our prospective multicenter study identified potential neural damage in 9.5% of cases and 52% rescue cases using IONM. Although the rescue ratios for t-OPLL and IMSCT were relatively low, appropriate intervention immediately after an IONM alert may prevent neural damage even in high-risk spinal surgeries.

LEVEL OF EVIDENCE

3.

Perioperative Complications After Surgery for Thoracic Ossification of Posterior Longitudinal Ligament: A Nationwide Multicenter Prospective Study

STUDY DESIGN

Prospective, multicenter, nationwide study.

OBJECTIVE

To investigate perioperative complications and risk factors in surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL) using data from the registry of the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament.

SUMMARY OF BACKGROUND DATA

There is no prospective multicenter study of surgical complications and risk factors for T-OPLL, and previous multicenter retrospective studies have lacked details.

METHODS

Surgical methods, preoperative radiographic findings, pre- and postoperative thoracic myelopathy (Japanese Orthopaedic Association [JOA] score), prone and supine position test (PST), intraoperative ultrasonography, and intraoperative neurophysiological monitoring (IONM) were investigated prospectively in 115 cases (males: 55, females: 60, average age 53.1 y). Factors related to perioperative complications and risk factors for postoperative motor palsy were identified.

RESULTS

Posterior decompression and fusion with instrumentation with or without dekyphosis was performed in 85 cases (74%). The JOA recovery rate at 1 year after surgery in all cases was 55%. Motor palsy occurred postoperatively in 37 cases (32.2%), with a mean recovery period of 2.7 months. A long recovery period for postoperative motor palsy was significantly associated with a high number of T-OPLL levels (P < 0.0001), lower preoperative JOA score (P < 0.05), and greater estimated blood loss (P < 0.05). Perioperative complications or postoperative motor palsy were significantly related to a higher number of T-OPLL levels, comorbid ossification of ligamentum flavum rate, lower preoperative JOA score, higher preoperative positive PST rate, more surgical invasiveness, a lower rate of intraoperative spinal cord floating in ultrasonography, and higher rate of deterioration of IONM.

CONCLUSION

This study firstly demonstrated the perioperative complications with high postoperative motor palsy rate in a nationwide multicenter prospective study. Surgical outcomes for T-OPLL should be improved by identifying and preventing perioperative complications with significant risk factors.

LEVEL OF EVIDENCE

3.

Efficacy of posterior decompression and fixation based on ossification-kyphosis angle criteria for multilevel ossification of the posterior longitudinal ligament in the thoracic spine

OBJECTIVE The range of decompression in posterior decompression and fixation for ossification of the posterior longitudinal ligament in the thoracic spine (T-OPLL) can be established using an index of spinal cord decompression based on the ossification-kyphosis angle (OKA) measured in the sagittal view on MRI. However, an appropriate OKA cannot be achieved in some cases, and posterior fixation is applied in cases with insufficient decompression. Moreover, it is unclear whether spinal cord decompression of the ventral side is essential for the treatment of OPLL. In this retrospective analysis, the efficacy of posterior decompression and fixation performed for T-OPLL was investigated after the range of posterior decompression had been set using the OKA. METHODS The MRI-based OKA is the angle from the superior margin at the cranial vertebral body of the decompression site and from the lower posterior margin at the caudal vertebral body of the decompression site to the prominence of the maximum OPLL. Posterior decompression and fixation were performed in 20 patients. The decompression range was set so that the OKA was ≤ 23° or the minimum if this value could not be achieved. Cases in which an OKA ≤ 23° could and could not be achieved were designated as groups U (13 patients) and O (7 patients), respectively. The mean patient ages were 50.5 and 62.1 years (p = 0.03) and the mean preoperative Japanese Orthopaedic Association (JOA) scores were 5.9 and 6.0 (p = 0.9) in groups U and O, respectively. The postoperative JOA score, rate of improvement of the JOA score, number of levels fused, number of decompression levels, presence of an echo-free space during surgery, operative time, intraoperative blood loss, and perioperative complications were examined. RESULTS In groups U and O, the mean rates of improvement in the JOA score were 50.0% and 45.6% (p = 0.3), the numbers of levels fused were 6.7 and 6.4 (p = 0.8), the numbers of decompression levels were 5.9 and 7.4 (p = 0.3), an echo-free space was noted during surgery in 92.3% and 42.9% of cases (p = 0.03), the operative times were 292 and 238 minutes (p = 0.3), and the intraoperative blood losses were 422 and 649 ml (p = 0.7), and transient aggravation of paralysis occurred as a perioperative complication in 2 and 1 patient, respectively. CONCLUSIONS There was no significant difference with regard to the recovery rate of the JOA score between patients with (group U) and without (group O) sufficient spinal cord decompression. The first-line surgical procedure of posterior decompression and fixation with the range of posterior decompression set as an OKA ≤ 23° before surgery involves less risk of postoperative aggravation of paralysis and may result in a better outcome.

Distribution of ossified spinal lesions in patients with severe ossification of the posterior longitudinal ligament and prediction of ossification at each segment based on the cervical OP index classification: a multicenter study (JOSL CT study)

BACKGROUND

In patients with ossification of the posterior longitudinal ligament (OPLL) in the cervical spine, it is well known that the thoracic ossified lesions often coexist with the cervical lesions and can cause severe myelopathy. However, the prevalence of OPLL at each level of the thoracic and lumbar spinal segments is unknown. The aims of this study were to investigate how often OPLL occurs at each level in the thoracolumbar spine in patients with a radiological diagnosis of cervical OPLL and to identify the spinal levels most likely to develop ossification.

METHODS

Data were collected from 20 institutions in Japan. Three hundred and twenty-two patients with a diagnosis of cervical OPLL were included. The OPLL index (OP index), defined as the sum of the vertebral body and intervertebral disc levels where OPLL is present, was used to determine disease severity. An OP index ≥20 was defined as severe OPLL. The prevalence of OPLL at each level of the thoracic and lumbar spinal segments was calculated.

RESULTS

Women were more likely to have ossified lesions in the thoracolumbar spine than men. Severe OPLL was significantly more common in women than in men (20% vs. 4.5%). For thoracic vertebral OPLL, the most frequently affected was the T1 segment in both men and women, followed by the T1/2 and T3/4 intervertebral levels in men and women, respectively. Ossified lesions were frequently seen at the intervertebral and vertebral levels around the cervicothoracic and thoracolumbar junctions in men with severe OPLL, whereas OPLL was more diffusely distributed in the thoracic spine in women with severe OPLL.

CONCLUSION

Thoracolumbar OPLL occurred most often at T1 in men and at T3/4 in women. In severe OPLL cases, although ossified lesions were frequently seen at the intervertebral and vertebral levels around the cervicothoracic and thoracolumbar junctions in men, OPLL could be observed more diffusely in the thoracic spine in women.

Local Spinal Cord Decompression Through a Full Endoscopic Percutaneous Transcorporeal Approach for Cervicothoracic Ossification of the Posterior Longitudinal Ligament at the T1-T2 Level

OBJECTIVE

To describe a percutaneous full endoscopic transcorporeal procedure to excise local ossification of the posterior longitudinal ligament (OPLL) lesions and decompress the spinal cord at the cervicothoracic transitional segment is safe and effective with respect to surgical complications.

METHODS

A 67-year-old woman presented with nuchal pain and numbness below the T2 dermatome for 3 months and a 2-week history of paraplegia. T1-T2 myelopathy and paraplegia caused by OPLL was diagnosed based on clinical presentation, computed tomography, and magnetic resonance imaging. An anterior percutaneous full endoscopic transcorporeal procedure addressed local OPLL and achieved local spinal cord decompression at T1-T2. After surgery, magnetic resonance imaging was repeated to evaluate degree of spinal cord decompression. Visual analog scale, Neck Disability Index, and Japanese Orthopaedic Association scores were evaluated at each follow-up.

RESULTS

The patient tolerated the full endoscopic operation successfully. Operative time was 225 minutes. On postoperative day 6, muscle strength of the bilateral lower extremities had progressed from grade 0/5 preoperatively to grade 2-/5 on the right and grade 2+/5 on the left. No surgery-related complications were discovered.

CONCLUSIONS

The percutaneous full endoscopic transcorporeal procedure is an alternative to previously described surgical methods of local spinal cord decompression for T1-T2 OPLL with fewer complications, effective spinal cord decompression, and a satisfactory cosmetic result. Successful cases confirm that treatment of spinal cord-limited compression by endoscopic technology is feasible.

Treatment for Thoracic Ossification of Posterior Longitudinal Ligament with Posterior Circumferential Decompression

OBJECTIVE

To report the results of the posterior approach for thoracic ossification of posterior longitudinal ligament (TOPLL) by using a special "L" osteotome.

METHODS

The present study enrolled 16 consecutive patients (9 men and 7 women) between May 2009 and September 2013. All patients underwent a posterior circumferential decompression osteotomy and segmental instrumentation with interbody fusion. The mean age at surgery was 57.3 years (range, 37-68 years). Patients' data, clinical manifestation, blood loss, length of surgery, complications, visual analog scale (VAS), Japanese Orthopedic Association (JOA), and Frankel grading system before and after surgery were collected and evaluated, retrospectively.

RESULTS

The average follow-up period was 30 ± 19 months (range, 12-50 months). All patients were successfully treated with posterior compression and segmental instrumentation with interbody fusion. The average operation time was 261.6 ± 51.3 min (range, 190-310 min). The mean blood loss was 980.3 ± 370.5 mL (range, 600-2100 mL). All patients had subjective improvement of motor power and gait. Average preoperative and postoperative JOA scores were 4.2 ± 1.7 and 7.8 ± 2.5 points, respectively. Differences in the overall JOA scores showed significant postoperative improvement. At the last follow-up, all patients improved either by one or two Frankel grades. There was a significant difference between preoperative VAS scores and those 3 months after surgery (P < 0.05). No significant difference was observed between the 3-month and 12-month results (P > 0.05). Cerebrospinal fluid (CSF) leakage occurred in 3 patients. Acute neurological deterioration was encountered postoperatively in 1 patient.

CONCLUSION

Treatment with posterior transpedicular osteotomy and circumferential decompression was found to be safe, effective, reliable, and technically feasible, and keeping the thoracic cavity intact avoids many shortcomings of anterior surgery and results in a satisfactory spinal decompression.

Ponte Osteotomy During Dekyphosis for Indirect Posterior Decompression With Ossification of the Posterior Longitudinal Ligament of the Thoracic Spine

STUDY DESIGN

Retrospective clinical study.

PURPOSE

To investigate the outcomes after indirect posterior decompression and dekyphosis using multilevel Ponte osteotomies for ossification of the posterior longitudinal ligament (OPLL) of the thoracic spine.

SUMMARY OF BACKGROUND DATA

There are no previous reports on the use of Ponte osteotomy to treat thoracic OPLL.

METHODS

The subjects were 10 patients with an average age at surgery of 47 years, who underwent indirect posterior decompression and dekyphosis using multilevel Ponte osteotomies at our institute. Minimum follow-up period was 2 years, and averaged 2 year 6 months. Using radiographs and CT images, we investigated fusion range, preoperative and postoperative Cobb angles of thoracic fusion levels, intraoperative ultrasonography, and clinical results.

RESULTS

The mean fusion area was 9.8 vertebraes, with average laminectomy of 7.3 laminas. The mean preoperative thoracic kyphosis of fusion levels on standing radiograph measured 35 degrees and was changed to 21 degrees after surgery. The mean number of Ponte osteotomies was 3 levels. The mean preoperative and postoperative (at the 1 y follow-up) JOA scores were 3.5 and 7.5 points, respectively, and the recovery rate was 56%. On intraoperative ultrasonography, 7 of the cases were included in the floating (+) and 3 in the floating (-) groups, and the recovery rates were 66.0% and 33.4%, respectively.

CONCLUSIONS

"The Ponte procedure for indirect spinal cord decompression" is a novel concept used for the first time with thoracic OPLL in our study, and we consider it a useful method to achieve more effectively dekyphosis and indirect spinal cord decompression if there is not the spinal cord free from OPLL on intraoperative ultrasonography after only laminectomies.

Factors for a Good Surgical Outcome in Posterior Decompression and Dekyphotic Corrective Fusion with Instrumentation for Thoracic Ossification of the Posterior Longitudinal Ligament: Prospective Single-Center Study

BACKGROUND

Surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL) is still challenging, and factors for good surgical outcomes are unknown.

OBJECTIVE

To identify factors for good surgical outcomes with prospective and comparative study.

METHODS

Seventy-one consecutive patients who underwent posterior decompression and instrumented fusion were divided into good or poor outcome groups based on ≥50% and &lt;50% recovery rates for the Japanese Orthopaedic Association score. Preoperative, intraoperative, and postoperative findings were compared in the 2 groups, and significant factors for a good outcome were analyzed.

RESULTS

Patients with a good outcome (76%) had significantly lower nonambulatory rate and positive prone and supine position tests preoperatively; lower rates of T-OPLL, ossification of the ligamentum flavum, high-intensity area at the same level, thoracic spinal cord alignment difference, and spinal canal stenosis on preoperative magnetic resonance imaging; lower estimated blood loss; higher rates of intraoperative spinal cord floating and absence of deterioration of intraoperative neurophysiological monitoring; and lower rates of postoperative complications (P &lt; .0005). In multivariate logistic regression analysis, negative prone and supine position test (odds ratio [OR]: 17.00), preoperative ambulatory status (OR: 6.05), absence of T-OPLL, ossification of the ligamentum flavum, high-intensity area at the same level (OR: 5.84), intraoperative spinal cord floating (OR: 4.98), and lower estimated blood loss (OR: 1.01) were significant factors for a good surgical outcome.

CONCLUSION

This study demonstrated that early surgery is recommended during these positive factors. Appropriate surgical planning based on preoperative thoracic spinal cord alignment difference, as well as sufficient spinal cord decompression and reduction of complications using intraoperative ultrasonography and intraoperative neurophysiological monitoring, may improve surgical outcomes.

The incidence and risk factors of postoperative neurological deterioration after posterior decompression with or without instrumented fusion for thoracic myelopathy

The aim of this study was to explore the incidence and risk factors of postoperative neurological deterioration after posterior decompression with or without instrumented fusion for thoracic myelopathy, and hope to provide references in decision-making and surgical planning for both spinal surgeon and thoracic stenosis patients.By retrieving the medical records from January 2001 to November 2015, 168 patients were retrospectively reviewed. According to the occurrence of postoperative neurological deterioration, patients were divided into 2 groups: neurological deterioration (ND) group and non-ND group. To investigate risk values for the occurrence of ND, 3 categorized factors were analyzed statistically: patient characteristics-preoperative data of age, sex, body mass index, bone mineral density, the duration of disease (from first symptoms to operation), the preoperative neurological function (Frankel grade), and diagnosis; surgical variables-surgery time, the amount of bleeding, mean arterial pressure, intervertebral fusion or not, and instrumentation or not; radiographic parameters-the spinal canal occupancy ratio, location of the lesion, thoracic kyphosis, and kyphosis correction.Postoperative neurological deterioration was developed in 23 of 168 patients (13.7%), and were enrolled as ND group. There was no statistically significant difference between the 2 groups in age at operation, sex composition, body mass index, and bone mineral density. The preoperative diagnosis presented significant difference between the 2 groups, because ossification of posterior longitudinal ligament combined with ossification of the ligamentum flavum was more common in ND group, whereas ossification of the ligamentum flavum alone was more common in non-ND group. There was no difference between the 2 groups in mean surgery time, the incidence of intraoperative direct trauma, and the number of patients that received instrumentation. The mean bleeding was much more in ND group than that in non-ND group, and the mean arterial pressure was lower in ND group than that in non-ND group. Also, the mean spinal canal occupancy ratio was more severe in ND group than that in non-ND group. There were no statistically significant difference between the 2 groups in stenosis location and preoperative thoracic kyphosis. The mean kyphosis correction was more significant in ND group. When included in a multivariate logistic regression model, thoracic disc herniation + ossification of posterior longitudinal ligament, spinal canal occupancy ratio more than 70%, bleeding more than 800 mL, and mean arterial pressure less than 81 mm Hg were independently associated with the postoperative neurological deterioration.In conclusion, ossification of posterior longitudinal ligament combined with ossification of the ligamentum flavum, spinal canal occupancy ratio more than 70%, intraoperative bleeding more than 800 mL, and mean arterial pressure less than 81 mm Hg are risk factors for the occurrence of postoperative neurologic deterioration. Improving surgical technique, shortening operation time, and paying more attention to hemostasis could provide opportunities to reduce the incidence of neurologic deterioration and to improve therapeutic outcomes.

Resection of Beak-Type Thoracic Ossification of the Posterior Longitudinal Ligament from a Posterior Approach under Intraoperative Neurophysiological Monitoring for Paralysis after Posterior Decompression and Fusion Surgery

Study Design Prospective clinical study. Objective Posterior decompression and fusion surgery for beak-type thoracic ossification of the posterior longitudinal ligament (T-OPLL) generally has a favorable outcome. However, some patients require additional surgery for postoperative severe paralysis, a condition that is inadequately discussed in the literature. The objective of this study was to describe the efficacy of a procedure we refer to as "resection at an anterior site of the spinal cord from a posterior approach" (RASPA) for severely paralyzed patients after posterior decompression and fusion surgery for beak-type T-OPLL. Methods Among 58 consecutive patients who underwent posterior decompression and fusion surgery for beak-type T-OPLL since 1999, 3 with postoperative paralysis (5%) underwent RASPA in our institute. Clinical records, the Japanese Orthopaedic Association score, gait status, intraoperative neurophysiological monitoring (IONM) findings, and complications were evaluated in these cases. Results All three patients experienced a postoperative decline in Manual Muscle Test (MMT) scores of 0 to 2 after the first surgery. RASPA was performed 3 weeks after the first surgery. All patients showed gradual improvements in MMT scores for the lower extremity and in ambulatory status; all could walk with a cane at an average of 4 months following RASPA surgery. There were no postoperative complications. Conclusions RASPA surgery for beak-type T-OPLL after posterior decompression and fusion surgery resulted in good functional outcomes as a salvage surgery for patients with severe paralysis. Advantages of RASPA include a wide working space, no spinal cord retraction, and additional decompression at levels without T-OPLL resection and spinal cord shortening after additional dekyphosis and compression maneuvers. When used with IONM, this procedure may help avoid permanent postoperative paralysis.

Treatment for thoracic ossification of posterior longitudinal ligament with posterior circumferential decompression: complications and managements

Background

The complications and corresponding managements for patients with thoracic ossification of posterior longitudinal ligament (TOPLL) who were treated with posterior circumferential decompression have not been systematically summarized yet.

Methods

Twenty-one patients with TOPLL who received posterior circumferential decompression between February 2010 and December 2014 were retrospectively reviewed. The patients’ basic characteristics, surgical duration, intraoperative blood loss, Japanese Orthopaedic Association (JOA) scores, and intraoperative and postoperative complications, and the adopted managements were summarized.

Results

The patients were averagely aged 52.1 ± 8.3 (range 32–67) years and included 10 males and 11 females. The mean operation time was 4.0 ± 0.9 (range 2.5–6) h and blood loss was 1619 ± 704 (range 800–4000) ml. Patients were followed up for 24.5 ± 1.2 (range 12–36) months. The average JOA score of patients was significantly elevated from 4.5 ± 1.4 (preoperative) to 7.4 ± 2.4 (P < 0.001, mean recovery rate 57.73%) on the second postoperative day and 7.8 ± 2.2 (P < 0.001, mean recovery rate 60.36%) at the final follow-up visit, respectively. There were 23 cases of complications that occurred in 12 patients, including 10 cases of intraoperative hemorrhage, 5 of cerebrospinal fluid leakage, 4 of intercostal nerve palsy, 3 of neurological deterioration, and 1 of superficial infection. After the corresponding treatment, these complications were recovered during the follow-up except 1 case of postoperative neurological deterioration did not exhibit improvement.

Conclusions

Posterior circumferential decompression is effective for TOPLL but causes complications which need to be proactively prevented and treated. If treated properly, most complications can be recovered with satisfactory outcomes.

Outcomes of Surgical Treatment for Thoracic Myelopathy: A Single-institutional Study of 73 Patients

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim was to investigate the clinical outcomes in patients with thoracic myelopathy in a single institution and to identify prognostic factors for poor outcomes.

SUMMARY OF BACKGROUND DATA

Because of the rarity of thoracic myelopathy, a few studies have analyzed a large number of clinical results for patients with thoracic myelopathy treated in a single institution.

METHODS

Seventy-one patients who underwent surgical treatment for thoracic myelopathy between 2000 and 2011 in a single institution were included in this analysis. We investigated the patients' characteristics, surgical outcomes, and prognostic factors for poor outcomes.

RESULTS

Of the 73 patients, eight patients had disc herniation (DH) or spinal stenosis (SS), 10 patients had ossification of the posterior longitudinal ligament (OPLL), 40 patients had ossification of the ligamentum flavum (OLF), and 15 patients had OPLL + OLF. The mean patient age at the time of surgery was 61.9 years. Thoracic myelopathy was caused by OPLL and/or OLF in 65 patients (89%). Fifty-eight patients underwent laminectomy, eight patients underwent laminectomy and posterior fusion, four patients underwent OPLL extirpation and posterior fusion, and three patients underwent OPLL extirpation. The mean Japanese Orthopedic Association Scoring System scores before surgery and at the final follow-up examination were 6.0 ± 1.8 and 7.7 ± 2.0 points, respectively, yielding a mean recovery rate of 30% ± 43%. The JOA score improved significantly postoperatively (P < 0.05). Risk factors for poor outcomes were longer preoperative symptom duration, preoperative JOA score < 7, and OPLL and/or OLF. Large blood loss volume was significantly associated with a worse postoperative JOA score.

CONCLUSION

A considerable degree of neurological recovery was observed after surgical treatment in patients with thoracic myelopathy. Prognostic factors for poor outcomes were longer preoperative duration of symptoms, worse preoperative symptoms, OPLL and/or OLF, and large volume of intraoperative bleeding.

LEVEL OF EVIDENCE

4.

Surgical Treatment for Thoracic Myelopathy Due to Simultaneous Ossification of the Posterior Longitudinal Ligament and Ligamentum Flavum at the Same Level

STUDY DESIGN

Retrospective review.

OBJECTIVE

The aim of this study was to assess the clinical outcomes of surgery in patients with simultaneous ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) at the same thoracic spine level and identify the risk factors for poor outcomes.

SUMMARY OF BACKGROUND DATA

OPLL complicated with OLF in the thoracic spine is a rare condition. The optimal treatment option for thoracic myelopathy due to OPLL and OLF remains controversial, and high risk of postoperative paralysis remains a major complication.

METHODS

We conducted a retrospective review of clinical and radiographic records of 15 patients who underwent surgery for simultaneous OPLL and OLF at the same level.

RESULTS

Simultaneous OPLL and OLF occurred in the upper thoracic spine in 3 patients (20%), mid-thoracic spine in 10 patients (67%), and lower thoracic spine in 2 patients (13%). Six, 4, 2, and 3 patients underwent posterior decompression, posterior decompression and fusion, posterior decompression and circumferential decompression through a posterior approach, and circumferential decompression and posterior fusion, respectively. The mean Japanese Orthopaedic Association score before surgery and at the final follow-up was 5.7±1.9 and 7.0±2.1 points, respectively, yielding a mean recovery rate of 16.5%. However, no significant difference was observed between preoperative and postoperative Japanese Orthopaedic Association scores. Two patients with mid-thoracic lesions reported postoperative lower extremity weakness. Mid-thoracic lesions and considerable blood loss were risk factors for poor surgical outcome.

CONCLUSIONS

Simultaneous OPLL and OLF in the mid-thoracic spine was observed in two thirds of the patients. We suggest that simultaneous OPLL and OLF in this area has a relatively poor recovery and may be very challenging and risky to treat, regardless of the surgical method selected, and recommend early surgery for OPLL and OLF in the mid-thoracic spine.

Postoperative Paralysis From Thoracic Ossification of Posterior Longitudinal Ligament Surgery Risk Factor of Neurologic Injury: Nationwide Multiinstitution Survey

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

The purpose of this study was to examine the factors of postoperative paralysis in patients who have undergone thoracic ossification of posterior longitudinal ligament (OPLL) surgery.

SUMMARY OF BACKGROUND DATA

A higher percentage of thoracic OPLL patients experience postoperative aggravation of paralysis than cervical OPLL patients, including patients that presented great difficulties in treatment. However, there were a few reports to prevent paralysis thoracic OPLL.

METHODS

The 156 patients who had received thoracic OPLL surgery were selected as the subjects of this study. The items for review were the duration of disease; the preoperative muscle strength (Muscle Manual Testing); OPLL levels (T1/2-4/5: high, T5/6-8/9: middle, and T9/10-11/12: low); the spinal canal occupancy ratio; the ratio of yellow ligament ossification as a complication; the ratio of transcranial-motor evoked potential (Tc-MEP) derivation; the preoperative/postoperative kyphotic angles in the thoracic vertebrae; the correction angle of kyphosis; the duration of surgery; and the amount of bleeding. The subjects were divided into two groups based on the absence or presence of postoperative paralysis to determine the factors of postoperative paralysis.

RESULTS

Twenty-three patients (14.7%) exhibited postoperative paralysis. Multivariate analysis identified factors associated with postoperative paralysis: the duration of disease (odds ratio, OR = 3.3); the correction angle of kyphosis (OR = 2.4); and the ratio of Tc-MEP derivation (OR = 2.2).

CONCLUSION

The risk factors of postoperative paralysis are a short duration of disease and a small correction angle of kyphosis. In addition, ratios of Tc-MEP derivation below 50% may anticipate paralysis.

LEVEL OF EVIDENCE

4.

Prevalence and Distribution of Ossified Lesions in the Whole Spine of Patients with Cervical Ossification of the Posterior Longitudinal Ligament A Multicenter Study (JOSL CT study)

Ossification of the posterior longitudinal ligament (OPLL) can cause severe and irreversible paralysis in not only the cervical spine but also the thoracolumbar spine. To date, however, the prevalence and distribution of OPLL in the whole spine has not been precisely evaluated in patients with cervical OPLL. Therefore, we conducted a multi-center study to comprehensively evaluate the prevalence and distribution of OPLL using multi-detector computed tomography (CT) images in the whole spine and to analyze what factors predict the presence of ossified lesions in the thoracolumbar spine in patients who were diagnosed with cervical OPLL by plain X-ray. Three hundred and twenty-two patients with a diagnosis of cervical OPLL underwent CT imaging of the whole spine. The sum of the levels in which OPLL was present in the whole spine was defined as the OP-index and used to evaluate the extent of ossification. The distribution of OPLL in the whole spine was compared between male and female subjects. In addition, a multiple regression model was used to ascertain related factors that affected the OP-index. Among patients with cervical OPLL, women tended to have more ossified lesions in the thoracolumbar spine than did men. A multiple regression model revealed that the OP-index was significantly correlated with the cervical OP-index, sex (female), and body mass index. Furthermore, the prevalence of thoracolumbar OPLL in patients with a cervical OP-index ≥ 10 was 7.8 times greater than that in patients with a cervical OP-index ≤ 5. The results of this study reveal that the extent of OPLL in the whole spine is significantly associated with the extent of cervical OPLL, female sex, and obesity.

Posterior Trans-Dural Repair of Iatrogenic Spinal Cord Herniation after Resection of Ossification of Posterior Longitudinal Ligament

Iatrogenic spinal cord herniation is a rare complication following spinal surgery. We introduce a posterior trans-dural repair technique used in a case of thoracic spinal cord herniation through a ventral dural defect following resection of ossification of the posterior longitudinal ligament (OPLL) in the cervicothoracic spine. A 51-year-old female was suffering from paraplegia after laminectomy alone for cervicothoracic OPLL. Magnetic resonance imaging revealed a severely compressed spinal cord with pseudomeningocele identified postoperatively. Cerebrospinal fluid leak and iatrogenic spinal cord herniation persisted despite several operations with duroplasty and sealing agent. Finally, the problems were treated by repair of the ventral dural defect with posterior trans-dural duroplasty. Several months after surgery, the patient could walk independently. This surgical technique can be applied to treat ventral dural defect and spinal cord herniation.

Clinical Features of Thoracic Spinal Stenosis-associated Myelopathy: A Retrospective Analysis of 427 Cases

STUDY DESIGN

This was a retrospective review.

OBJECTIVE

The aim of this study was to examine the epidemiological characteristics and causes of spinal cord compression in thoracic spinal stenosis (TSS).

SUMMARY OF BACKGROUND DATA

As the thoracic spinal canal is relatively narrow and the thoracic cord has a poor blood supply, severe neurological symptoms may develop if TSS is not treated promptly. However, as it is rare, TSS is less often studied and its clinical features are often not recognized.

METHODS

Between 2005 and 2012, 427 patients diagnosed with TSS underwent surgery in our department. The male to female ratio was 1.4:1. The mean age was 53 years. The most reported symptom was motor deficit in the lower extremities (347 cases, 81%), followed by sensory deficit in the lower limbs (271 cases, 64%). Falls were the most common trigger of acute symptoms (29 cases, 7%). Preoperative imaging results of each case were reviewed to summarize the causes and site of cord compression and coexisting spinal diseases.

RESULTS

The most reported compressive factor was ossification of the ligamentum flavum (OLF), which implicated in 309 cases, followed by thoracic disk herniation (TDH) and ossification of the posterior longitudinal ligament (OPLL). The most common site of OLF and TDH was T9-L1 (56% and 89%, respectively), whereas OPLL was mainly found at T1-8 (90%). Forty-seven patients (11%) had coexisting lumbar spinal disease and 64 (15%) had cervical disease.

CONCLUSIONS

Onset of TSS was generally insidious but may be triggered acutely by apparently trivial events. Myelopathy mainly affected the lower limbs. The most common cause was OLF in the lower thoracic spine. Cervical or lumbar spinal disease was often also evident; therefore, comprehensive clinical assessment is required to avoid delays in diagnosis and treatment.

Mid- to long-term outcomes of posterior decompression with instrumented fusion for thoracic ossification of the posterior longitudinal ligament

Posterior decompression with instrumented fusion (PDF) surgery has been previously reported as a relatively safe surgical procedure for any type of thoracic ossification of the longitudinal ligament (OPLL). However, mid- to long-term outcomes are still unclear. The aim of the present study was to elucidate the mid- to long-term clinical outcome of PDF surgery for thoracic OPLL patients. The present study included 20 patients who had undergone PDF for thoracic OPLL and were followed for at least 5years. Increment change and recovery rate of the Japanese Orthopaedic Association (JOA) score were assessed. Revision surgery during the follow-up period was also recorded. Average JOA scores were 3.5 preoperatively and 7.1 at final follow-up. The average improvement in JOA score was 3.8 points and the average recovery rate was 47.0%. The JOA score showed gradual increase after surgery, and took 9months to reach peak recovery. As for neurological complications, two patients suffered postoperative paralysis, but both recovered without intervention. Six revision surgeries in four patients were related to OPLL. Additional anterior thoracic decompression for remaining ossification at the same level of PDF surgery was performed in one patient. Decompression surgery for deterioration of symptoms of pre-existing cervical OPLL was performed in three patients. One patient had undergone lumbar and cervical PDF surgery for de novo ossification foci of the lumbar and cervical spine. PDF surgery for thoracic OPLL is thus considered a relatively safe and stable surgical procedure considering the mid- to long-term outcomes.

Use of an Ultrasonic Osteotome for Direct Removal of Beak-Type Ossification of Posterior Longitudinal Ligament in the Thoracic Spine

Direct removal of beak-type ossification of posterior longitudinal ligament at thoracic spine (T-OPLL) is a challenging surgical technique due to the potential risk of neural injury. Slipping off the cutting surface of a high-speed drill may result in entrapment in neural structures, leading to serious complications. Removal of T-OPLL with an ultrasonic osteotome, utilizing back and forth micro-motion of a blade rather than rotatory-motion of drill, may reduce such complications. We have applied the ultrasonic osteotome for posterior circumferential decompression of T-OPLL for three consecutive patients with beak-type OPLL and have described the surgical techniques and patient outcomes. The preoperative chief complaint was gait disturbance in all patients. Japanese orthopedic association scores (JOA) was used for functional assessment. Scores measured 2/11, 5/11, 2/11, and 4/11 for each patient. The ventral T-OPLL mass was exposed after posterior midline approach, laminotomy and transeversectomy. The T-OPLL mass was directly removed with an ultrasonic osteotome and instrumented segmental fixation was performed. The surgeries were uneventful. Detailed surgical techniques were presented. Gait disturbance was improved in all patients. Dural tear occurred in one patient without squeal. Postoperative JOA was 6/11, 10/11, 8/11, and 8/11 (recovery rate; 44%, 83%, 67%, and 43%) respectively at 18, 18, 10, and 1 months postoperative. T-OPLL was completely removed in all patients as confirmed with computed tomography scan. We hope that surgical difficulties in direct removal of T-OPLL might be reduced by utilizing ultrasonic osteotome.

A systematic review of complications in thoracic spine surgery for ossification of the posterior longitudinal ligament

PURPOSE

To answer two questions: (1) what are the common complications associated with surgery for thoracic myelopathy caused by ossification of the posterior longitudinal ligament, and (2) which surgical approach is safer with regard to the incidence of post-operative complications.

METHODS

Relevant literature searches were performed using the Cochrane Central Register of Controlled Trials, PubMed, EMBASE, the Chinese Biomedical Literature Database, the China National Knowledge Infrastructure, KoreaMed, and the Japan CentraRevuoMedicina.

RESULTS

15 studies met the inclusion criteria and were retrieved. They included a total of 595 patients, 39 % of whom were male and 61 % female. The mean patient age ranged from 52.6 to 60.9 years. The mean recovery rate from each individual study varied between 24.7 and 77.6 % and the pooled neurologic function recovery rate was 50.4 %. From these 15 studies, the mean complication rate was 39.4 %. By far, two complications were more common than the others: cerebrospinal fluid leakage (incidence rate 22.5 %) and post-operative neurologic deficit (incidence rate 13.9 %). 7.7 % of patients from the indirect decompression group experienced cerebrospinal fluid leakage, while it was reported in 25.6 % of those in the direct decompression group. Neurologic deficit was reported in 8.4 % of patients undergoing indirect decompression and 19.8 % of those undergoing direct decompression.

CONCLUSIONS

Cerebrospinal fluid leakage and neurologic deficit were the two most common complications following surgical decompression of the thoracic spine with ossification of the posterior longitudinal ligament. Patients undergoing indirect decompression surgeries had significantly lower complication rates compared with those undergoing direct decompression surgeries.