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Paul M. Arnold, Philip L. Johnson and Karen K. Anderson

Object

Symptomatic thoracic disc herniations (TDHs) are rare, and multiple TDHs account for an even smaller percentage of symptomatic herniated discs. Most TDHs are found in the lower thoracic spine, with more than 75% occurring below T-8. The authors report a series of 15 patients with multiple symptomatic TDHs treated with a modified transfacet approach.

Methods

Fifteen patients (9 women and 6 men) with a total of 32 symptomatic TDHs were treated surgically at the authors' institution between 1994 and 2010. The average patient age was 51.1 years. Thirteen patients had 2-level herniation and 2 patients had 3-level disease. The most commonly involved level was T7–8 (10 herniations), followed by T6–7 and T8–9 (6 herniations each). All patients had long-standing myelopathic and/or radicular complaints at the time of presentation. Each disc that exhibited radiographically confirmed compression of the spinal cord or nerve root was considered for resection. Only patients with lateral disc herniations were considered for the modified transfacet approach; patients with a centrally herniated disc underwent ventral or ventral-lateral procedures. The average follow-up time was 30 months.

Results

All patients had successful resection of their herniated discs. All patients with preoperative weakness demonstrated improved strength, and 11 of 12 patients with preoperative pain showed improvement in pain. Sensory loss was less consistently improved. The 2 patients who underwent posterior fixation and fusion achieved radiographically confirmed fusion by the 1-year follow-up. Nine of 10 patients who were working returned to their jobs. Eleven of 12 patients with preoperative back or radicular pain had drastic or complete pain resolution; 1 patient had no change in pain. All 7 patients with preoperative ambulatory difficulty had postoperative gait improvement. Complications were minimal.

Conclusions

Multiple symptomatic herniated thoracic discs are rare causes of pain and disability, but should be treated surgically because good outcomes can be achieved with acceptably low morbidity.

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Paul M. Arnold, Karen K. Anderson, Abdulhafez Selim, Randall F. Dryer and J. Kenneth Burkus

OBJECTIVE

Heterotopic ossification (HO) has been reported following total hip, knee, cervical, and lumbar arthroplasty, as well as following posterolateral lumbar fusion using recombinant human bone morphogenetic protein–2 (rhBMP-2). Data regarding HO following anterior cervical discectomy and fusion (ACDF) with rhBMP-2 are sparse. A subanalysis was done of the prospective, multicenter, investigational device exemption trial that compared rhBMP-2 on an absorbable collagen sponge (ACS) versus allograft in ACDF for patients with symptomatic single-level cervical degenerative disc disease.

METHODS

To assess differences in types of HO observed in the treatment groups and effects of HO on functional and efficacy outcomes, clinical outcomes from previous disc replacement studies were compared between patients who received rhBMP-2/ACS versus allograft. Rate, location, grade, and size of ossifications were assessed preoperatively and at 24 months, and correlated with clinical outcomes.

RESULTS

Heterotopic ossification was primarily anterior in both groups. Preoperatively in both groups, and including osteophytes in the target regions, HO rates were high at 40.9% and 36.9% for the rhBMP-2/ACS and allograft groups, respectively (p = 0.350). At 24 months, the rate of HO in the rhBMP-2/ACS group was higher than in the allograft group (78.6% vs 59.2%, respectively; p < 0.001). At 24 months, the rate of superior-anterior adjacent-level Park Grade 3 HO was 4.2% in both groups, whereas the rate of Park Grade 2 HO was 19.0% in the rhBMP-2/ACS group compared with 9.8% in the allograft group. At 24 months, the rate of inferior-anterior adjacent-level Park Grade 2/3 HO was 11.9% in the rhBMP-2/ACS group compared with 5.9% in the allograft group. At 24 months, HO rates at the target implant level were similar (p = 0.963). At 24 months, the mean length and anteroposterior diameter of HO were significantly greater in the rhBMP-2/ACS group compared with the allograft group (p = 0.033 and 0.012, respectively). Regarding clinical correlation, at 24 months in both groups, Park Grade 3 HO at superior adjacent-level disc spaces significantly reduced range of motion, more so in the rhBMP-2/ACS group. At 24 months, HO negatively affected Neck Disability Index scores (excluding neck/arm pain scores), neurological status, and overall success in patients in the rhBMP-2/ACS group, but not in patients in the allograft group.

CONCLUSIONS

Implantation of rhBMP-2/ACS at 1.5 mg/ml with polyetheretherketone spacer and titanium plate is effective in inducing fusion and improving pain and function in patients undergoing ACDF for symptomatic single-level cervical degenerative disc disease. At 24 months, the rate and dimensions (length and anteroposterior diameter) of HO were higher in the rhBMP-2/ACS group. At 24 months, range of motion was reduced, with Park Grade 3 HO in both treatment groups. The impact of Park Grades 2 and 3 HO on Neck Disability Index success, neurological status, and overall success was not consistent among the treatment groups. The study data may offer a deeper understanding of HO after ACDF and may pave the way for improved device designs.

Clinical trial registration no.: IDE# G060021; data compared with pooled data from control arms of IDE# G010188/NCT00642876 and IDE# G000123/NCT00437190 (www.clinicaltrials.gov).