Efficacy of mesenchymal stem cell enriched grafts in an ovine posterolateral lumbar spine model.

STUDY DESIGN: Four groups of 6 animals underwent single-level noninstrumented posterolateral lumbar fusion (PLF) with one of the following grafts: 1) autograft, 2) cell-enriched beta-tricalcium phosphate (TCP), 3) TCP with whole bone marrow, and 4) TCP alone. Plain radiographs were taken after surgery and at death, 6 months after surgery. Explanted spine segments were analyzed by manual palpation, micro-CT, and histology. OBJECTIVE: A sheep spine fusion study was undertaken to evaluate the healing performance of a TCP graft enriched with osteoprogenitor cells using Selective Cell Retention technology (SCR), compared with autograft, TCP with whole bone marrow, and TCP alone. SUMMARY OF BACKGROUND DATA: Improved bone healing with previously demonstrated using grafts enriched in osteoprogenitor cells. METHODS: Cell-enriched grafts were obtained by processing 30 mL of bone marrow through 10 mL of TCP. TCP was also used either saturated with bone marrow or alone. RESULTS: At 6 months, 33% of the SCR-enriched TCP and 25% of the autograft sites were fused, compared with 8% of the TCP plus whole bone marrow and 0% of the TCP alone. Histology of fused samples showed denser bone formation in the SCR-enriched TCP grafts than in the autograft sites. CONCLUSIONS: The use of SCR-enriched TCP and autograft resulted in similar fusion rates in an ovine posterolateral noninstrumented lumbar spine fusion model.

Apical sublaminar wires versus pedicle screws--which provides better results for surgical correction of adolescent idiopathic scoliosis?

STUDY DESIGN: The results of correction for adolescent idiopathic scoliosis (AIS) were compared using apical sublaminar wires versus pedicle screws. OBJECTIVE: To compare comprehensively the 2-year minimum postoperative results of posterior correction and spinal fusion using translational correction through either hybrid hook/sublaminar wire/pedicle screw constructs versus in situ rod-contouring correction with pedicle screw constructs in the treatment of AIS at 2 institutions. SUMMARY OF BACKGROUND DATA: Despite the reports of satisfactory correction of scoliotic curves by both apical (sublaminar wire) instrumentation and apical pedicle screw instrumentation, to our knowledge, no reports on the comprehensive comparison of hybrid (hook/sublaminar wire/pedicle screw) instrumentation versus segmental pedicle screw instrumentation exist. METHODS: A total of 50 patients with AIS at 2 institutions who underwent posterior spinal fusion with sublaminar wire (25 patients) or pedicle screw (25) constructs were sorted and matched according to 4 criteria: (1) similar age at surgery (14.2 years in the sublaminar wire and 14.4 in the pedicle screw group, P = 0.72); (2) similar number of fused vertebrae (11.4 in the sublaminar wire and 11.8 in the pedicle screw group, P = 0.36); (3) similar operative methods; and (4) identical Lenke curve types and similar preoperative major curve measurements (63.5 degrees in the sublaminar wire and 59.5 degrees in the pedicle screw group, P = 0.42). Patients were evaluated preoperatively, immediately postoperatively, and at 2-year follow-up according to radiographic changes in curve correction, operating time, intraoperative blood loss, implant costs, and the Scoliosis Research Society patient questionnaire (SRS-24) scores. RESULTS: After surgery, average major curve correction was 67.4% in the sublaminar wire and 68.1% in the pedicle screw group (P = 0.56). At 2-year follow-up, loss of the major curve correction was 4.6% in the sublaminar wire compared to 5.1% in the pedicle screw group (P = 0.79). Postoperative global coronal and sagittal balance were similar in both groups. No significant difference was found in the average number of levels fused from the distal end vertebra (1.48 in the sublaminar wire and 0.64 in the pedicle screw group, P = 0.21). Operating time averaged 350 minutes in the sublaminar wire and 357 in the pedicle screw group (P = 0.86). Intraoperative blood loss was significantly different in both groups (1791 +/- 816 mL in the sublaminar wire and 824 +/- 440 mL in the pedicle screw group) (P = 0.0003). Average implant cost in the sublaminar wire group (16.0 fixation points; 8,341 US dollars) was significantly lower than that of the pedicle screw group (17.1 fixation points; 13,462 US dollars) (P < 0.0001). Postoperative 2-year SRS-24 scores were similar in both groups (sublaminar wire = 107.3, pedicle screw = 103.5, P = 0.19). There were no neurologic or visceral complications related to sublaminar wire or pedicle screw instrumentation and no reoperations at a minimum 2-year follow-up. CONCLUSIONS: Apical sublaminar wire and pedicle screw instrumentation both offer similar major curve correction with similar fusion lengths without neurologic problems in the operative treatment of AIS. Although more expensive, pedicle screw constructs had significantly less blood loss and slightly shorter fusion lengths than the sublaminar wire constructs.

Estrogen-dependent actions of bone morphogenetic protein-7 on spine fusion in rats.

STUDY DESIGN: Intertransverse process spinal fusion using recombinant human bone morphogenetic protein-7 (rhBMP-7) was performed in intact and ovariectomized female rats. OBJECTIVES: To examine fusion rates in intact and ovariectomized female rats using rhBMP-7 to determine if spine fusion is dependent on estrogen status. SUMMARY OF BACKGROUND DATA: Rat spinal fusion has been established as a consistent, efficient model for posterolateral intertransverse process fusion. Previous experiments have confirmed the efficacy of pellets containing the carrier, insoluble collagen bone matrix (ICBM), and rhBMP-7 to augment intertransverse process single level fusion in a rat model. Studying these implications in an osteoporosis model is of clinical value because there are many patients undergoing spinal fusion surgery that have osteoporotic bone disease, and there is a steady increase in this group of patients. METHODS: A total of 15 ovariectomized and 15 intact Sprague-Dawley female rats were randomly assigned to groups receiving 25 mg ICBM alone, 25 mg ICBM + 10 microg rhBMP-7, and 25 mg ICBM + 30 microg rhBMP-7. Spinal fusion was evaluated by manual motion testing at each lumbar segment, radiographic evaluation using the Lenke grading system, and histology. RESULTS: Ovariectomized and intact rats receiving 25 mg carrier ICBM alone did not show spinal fusion. With 25 mg ICBM + 10 microg rhBMP-7, there was not a significant difference in fusion rates between intact and ovariectomized rats (P = 0.63). Ovariectomized rats receiving 25 mg ICBM + 30 microg rhBMP-7 showed significantly lower fusion rates than intact rats (P = 0.013). CONCLUSION: These data suggest that spinal fusion using rhBMP-7 is estrogen-dependent in rats. At the dosages used, rhBMP-7 was unable to overcome the inhibitory effects of estrogen deficiency on spinal fusion.