X-Ray-based Kinematic Analysis of Cervical Spine According to Prosthesis Designs: Analysis of the Mobi C, Bryan, PCM, and Prestige LP.

STUDY DESIGN: A retrospective study. OBJECTIVE: To identify significant kinematic changes in the cervical spine after cervical artificial disk replacement (ADR) using prostheses with diverse designs. SUMMARY OF BACKGROUND DATA: Various types of artificial disks are used for cervical ADR. However, few clinical studies with a follow-up of 2 or more years have reported on the change in the curvatures and range of motion (ROM) of the cervical spine after cervical ADR in relation to different designs. METHODS: The cohort comprised 58 patients who underwent single-level cervical ADR for radiculopathy. The patients were divided into 4 groups according to the device they received: Mobi-C, Bryan, PCM, and Prestige LP. The radiographs of the cervical spine were obtained preoperatively and at 12, 24, and 36 months after surgery. Several kinematic parameters, including lordotic angles and ROM of the cervical spine, index level, and superior and inferior adjacent disk levels, were assessed preoperatively and at predefined follow-up time points. RESULTS: Cervical sagittal lordosis in patients who received Bryan and PCM prostheses increased at the last follow-up period. The 4 patient groups showed a trend toward an increase of lordosis in the superior adjacent segment with time. The patients who received the Bryan device lost their preoperative lordotic angle at the inferior adjacent level. The ROM of the cervical spine in patients who received Bryan and PCM prostheses increased at the last follow-up compared with preoperative values. The incidence of adjacent segment degeneration in the Mobi-C, Bryan, Prestige LP, and PCM groups were 14.2%, 25%, 9.0%, and 7.6%, respectively. CONCLUSIONS: These results suggest preservation of sagittal ROM and increased superior adjacent segment kinematics, regardless of prosthesis design. Devices with an unconstrained design may not be beneficial to adjacent segment kinematics compared with semiconstrained prostheses.

Evaluation of HealosMP52 osteoinductive bone graft for instrumented lumbar intertransverse process fusion in sheep.

STUDY DESIGN: HealosMP52 was evaluated in a sheep model of instrumented lumbar intertransverse process spine fusion and compared to autogenous bone graft. OBJECTIVES: To determine the long-term efficacy and safety of HealosMP52 as a bone graft substitute in posterolateral instrumented spinal fusion. SUMMARY OF BACKGROUND DATA: Although the standard intertransverse fusion method employs autogenous iliac crest bone, autograft has certain limitations. HealosMP52, an osteoinductive bone graft material, can facilitate noninstrumented posterolateral spine fusion in rabbits and nonhuman primates, but the long-term outcome of such fusions has not been evaluated. METHODS: Eleven skeletally mature, female sheep were instrumented with pedicle screws and rods at L2-L3 and L5-L6. Each animal was treated with autograft bone at one fusion level and HealosMP52 at the other. At 6 and 12 months after surgery, bone formation was measured on contact microradiographs and by backscattered electron imaging. Bone core biopsies taken from 6-month and 12-month specimens were evaluated histologically for pathology indicative of osteosarcoma. RESULTS: Grossly, all autograft- and HealosMP52-treated levels showed stable fusions at 6 and 12 months. HealosMP52 and autograft treatments resulted in equivalent mean percent bone volumes within fusion bodies; similar values were observed at 6 and 12 months. Fusion bodies contained cortical and trabecular bone with osteoid seams and fatty marrow, and fusion masses showed maturation from 6 to 12 months. HealosMP52 treatment was not associated with implant migration, ectopic bone formation, or pathologic abnormality. No histologic evidence of osteosarcoma was seen on bone core biopsies. CONCLUSIONS: This long-term assessment of the use of HealosMP52 in posterolateral instrumented spine fusion indicates that HealosMP52 possesses safe and efficacious bone grafting properties and can potentially serve as anosteoinductive alternative to autograft bone.

Thoracoscopic transdiaphragmatic approach to thoracolumbar junction fractures.

BACKGROUND CONTEXT: Anterior approaches to the thoracocolmbar junction (TLJ) are often required to restore anterior column deficiency after spinal trauma. Conventional open approaches are often associated with significant morbidity, and hence there is a need for a minimally invasive approach to TLJ fractures. PURPOSE: To report the feasibility and effectiveness of the thoracoscopic transdiaphragmatic approach (TTA) in the management of TLJ fractures. STUDY DESIGN: A retrospective analysis of 212 patients undergoing surgery at two institutions by the TTA with neurological outcomes, fusion rates and complications. PATIENT SAMPLE: This is a two-institution study of 212 patients managed by TTA, from Berufsgenossenschaftliche Unfallklinik Marnau, a regional trauma facility located in Murnau, Bavaria, Germany, and from Stanford University, Stanford, California from May 1996 to June 2002. Patient ages ranged from 16 to 75 years (mean, 36 years) and included 158 males and 62 females. OUTCOME MEASURES: The neurological status was assessed by the Frankel Neurological Performance scale pre- and postoperatively. Plain radiographs obtained 1 year postoperatively assessed fusion radiologically. METHODS: All patients underwent spinal decompression, reconstruction and instrumentation by the TTA. Seventy-five patients had anterior instrumentation alone, whereas the remaining 137 had combined anterior and posterior instrumentation. A Z-Plate was used for spinal instrumentation from May 1996 to October 1999 and the MACS-TL system from November 1999 to June 2002. RESULTS: Monosegmental, bisegmental and multisegmental fixations were used in 46%, 48% and 6% of cases, respectively. Follow-up ranged from 12 months to 6 years (mean, 3.9 years). Surgical durations ranged between 70 minutes and 7 hours (mean, 3.5 hours). Successful bony fusion with maintenance of satisfactory spinal alignment was observed in approximately 90% of our patients. Anterior screw loosening was seen in five cases (2.4%), four involving the Z-Plate system and the other involving the MACS-TL system. Three patients (1.4%) required conversion to an open procedure. Access-related complications, such as pleural effusion, pneumothorax and intercostal neuralgia, were seen in 12 patients (5.7%). Three patients (1.4%) had superficial portal infections. We encountered no diaphragmatic herniations. CONCLUSIONS: TTA provides excellent access to the entire TLJ, permitting satisfactory spinal decompression, reconstruction and instrumentation. Diaphragmatic opening and repair can be accomplished safely and effectively without special endoscopic instrumentation. It also precludes the need for retroperitoneoscopic or open thoracoabdominal approaches and thus avoids the associated significant morbidity.