Comparative Effectiveness of Expandable Versus Static Interbody Spacers via MIS LLIF: A 2-Year Radiographic and Clinical Outcomes Study.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The purpose of this study is to compare the radiographic and clinical outcomes of expandable interbody spacers to static interbody spacers. METHODS: This is a retrospective, institutional review board-exempt chart review of 62 consecutive patients diagnosed with degenerative disc disease who underwent minimally invasive spine surgery lateral lumbar interbody fusion (MIS LLIF) using static or expandable spacers. There were 27 patients treated with static spacers, and 35 with expandable spacers. Radiographic and clinical functional outcomes were collected. Statistical results were significant if P < .05. RESULTS: Mean improvement in visual analogue scale back and leg pain scores was significantly greater in the expandable group compared to the static group at 6 and 24 months by 42.3% and 63.8%, respectively (P < .05). Average improvement in Oswestry Disability Index scores was significantly greater in the expandable group than the static group at 3, 6, 12, and 24 months by 28%, 44%, 59%, 53%, and 89%, respectively (P < .05). For disc height, the mean improvement from baseline to 24 months was greater in the static group compared to the expandable group (P < .05). Implant subsidence was significantly greater in the static group (16.1%, 5/31 levels) compared with the expandable group (6.7%, 3/45 levels; P < .05). CONCLUSIONS: This study showed positive clinical and radiographic outcomes for patients who underwent MIS LLIF with expandable spacers compared to those with static spacers. Sagittal correction and pain relief was achieved and maintained through 24-month follow-up. The expandable group had a lower subsidence rate than the static group.

Clinical and radiographic analysis of expandable versus static lateral lumbar interbody fusion devices with two-year follow-up.

BACKGROUND: Utilization of static and expandable interbody spacers for minimally invasive lateral lumbar interbody fusion (LLIF) offers favorable clinical results. However, complications such as implant migration and/or subsidence may occur with a static implant. Expandable devices allow for in situ expansion to optimize fit and mitigate iatrogenic endplate damage during trialing and impaction. This study sought to compare clinical and radiographic outcomes of static and expandable spacers following LLIF and report device-related complications. METHODS: This study included 29 patients who underwent LLIF with a static spacer and 27 with an expandable spacer; all procedures were combined with supplemental transpedicular posterior fixation. Patient self-assessment forms and radiographic records were used to assess clinical and radiologic outcomes. RESULTS: Mean patient age was 62.3±10.3 years (64% female). One-level surgery was performed in 87.5% of patients, and 12.5% underwent two-level surgery. Results showed no significant differences in blood loss or length of hospital stay (P>0.05). However, operative times differed statistically between static (63.3±37.8 min) and expandable (120.2±59.6 min) groups (P=0.000). Mean visual analog scale (VAS) and Oswestry Disability Index (ODI) scores improved significantly from preoperative to 24-month follow-up in both groups (P<0.05). Preoperative intervertebral and neuroforaminal height increased significantly in both groups (P<0.01). Fusion was observed in all operative levels in the static and expandable spacer groups by 24-month follow-up. Implant subsidence was reported in 16.1% of static levels and none of the expandable levels (P<0.01). Postoperative radiographs showed no evidence of implant migration, and no cases required surgical revision at the index or adjacent levels. CONCLUSIONS: LLIF using expandable spacers resulted in similar clinical and radiographic outcomes when compared with using static spacers, and led to a lower subsidence rate.

Adjacent segment motion after anterior cervical discectomy and fusion versus Prodisc-c cervical total disk arthroplasty: analysis from a randomized, controlled trial.

STUDY DESIGN: Post hoc analysis of data acquired in a prospective, randomized, controlled trial. OBJECTIVE: To compare adjacent segment motion after anterior cervical discectomy and fusion (ACDF) versus cervical total disc arthroplasty (TDA). SUMMARY OF BACKGROUND DATA: TDA has been designed to be a motion-preserving device, thus theoretically normalizing adjacent segment kinematics. Clinical studies with short-term follow-up have yet to demonstrate a consistent significant difference in the incidence of adjacent segment disease. METHODS: Two hundred nine patients at 13 sites were treated in a prospective, randomized, controlled trial of ACDF versus TDA for single-level symptomatic cervical degenerative disc disease (SCDD). Flexion and extension radiographs were obtained at all follow-up visits. Changes in ROM were compared using the Wilcoxon signed-rank test and the Mann-Whitney U test. Predictors of postoperative ROM were determined by multivariate analysis using mixed effects linear regression. RESULTS: Data for 199 patients were available with 24-month follow-up. The groups were similar with respect to baseline demographics. A significant increase in motion at the cranial and caudal adjacent segments after surgery was observed in the ACDF group only (cranial: ACDF: +1.4° (0.4, 2.4), P = 0.01; TDA: +0.8°, (-0.1, +1.7), P = 0.166; caudal: ACDF: +2.6° (1.3, 3.9), P < 0.0001; TDA: +1.3, (-0.2, +2.8), P = 0.359). No significant difference in adjacent segment ROM was observed between ACDF and TDA. Only time was a significant predictor of postoperative ROM at both the cranial and caudal adjacent segments. CONCLUSION: Adjacent segment kinematics may be altered after ACDF and TDA. Multivariate analysis showed time to be a significant predictor of changes in adjacent segment ROM. No association between the treatment chosen (ACDF vs. TDA) and ROM was observed. Furthermore clinical follow-up is needed to determine whether possible differences in adjacent segment motion affect the prevalence of adjacent segment disease in the two groups.

Clinical efficacy of the vertebral wedge osteotomy for the fusionless treatment of paralytic scoliosis.

STUDY DESIGN: Pre-post intervention study using outcome measure design. OBJECTIVE: To evaluate the clinical efficacy and functional impact of a fusionless treatment for paralytic scoliosis at 2-year follow-up. SUMMARY OF BACKGROUND DATA: It has been shown that 67% of pediatric patients with progressive paralytic scoliosis require spinal fusion to correct the curve. However, maintenance of spinal flexibility, motion, and potential growth is desirable. METHODS: Fourteen patients with scoliosis secondary to spinal cord injury or myelodysplasia underwent a fusionless vertebral wedge osteotomy. Thirteen patients were available for minimum 2-year follow-up, using standard scoliosis radiographs. The functional impact of the procedure was evaluated using the Pediatric Outcomes Data Collection Instrument (PODCI), the Functional Independence Measure (FIM), and the Canadian Occupational Performance Measure (COPM). RESULTS: At a minimum 2-year follow-up, 10 patients of 13 (77%) had improvement of greater than 5 degrees in their coronal Cobb angle. Two (15%) patients' curves measured the same (+/-5 degrees). One patient's curve had worsened by 12 degrees as compared to the preoperative Cobb angle. The overall average correction of the 13 patients was 56.1%. Two patients required fusion with an average delay to fusion of 30 months. At current follow-up, range of motion across the treated levels averaged 43 degrees (range 8 degrees to 103 degrees). The FIM showed no changes pre to post, and the PODCI scores showed some increases at 2-year follow-up. Clinical and statistical improvement in performance and satisfaction scores was seen pre to post on the Canadian Occupational Performance Measure. CONCLUSION: Vertebral wedge osteotomy is potentially an effective treatment option for paralytic scoliosis. At 2-year follow-up, there was no loss of function as measured by the PODCI and FIM, and there was improvement in the COPM. Cobb angle measurements were either improved or maintained in 12 of 13 patients. Although 2 patients required fusion, they had an average of 2.5 years of subsequent growth before surgery.

Method for the physical analysis of drug-bone cement composite.

Skeletal metastases are often complicated by progression to impending or pathologic fracture and fixation with polymethylmethacrylate (PMMA) bone cement is used for stabilization and pain relief. Adjuvant therapy involving the delivery of PMMA composites mixed with antibiotic or chemotherapeutic agents requires an understanding of the rate of drug diffusion from the cement in addition to measurement of its mechanical properties pre- and postelution of drug. We have developed a method for the analysis of drug diffusion rate and mechanical properties of drug-cement composites using PMMA/methotrexate as a model system. The analysis method revealed the addition of methotrexate to PMMA in concentrations of 1.8 g methotrexate per 40 g PMMA did not change the compression modulus of the cement pre- or postelution of drug. The PMMA/methotrexate composites displayed an average diffusion rate of 50 ng/(mm2)(hour) during the first 6 hours, which decreased to 10 ng/(mm2)(hour) by 36 hours. Diffusion modeling predicts the 20 x 13-mm cylindrical PMMA/methotrexate samples used by the method deliver 10% of the total methotrexate content within 80 hours and 25% of the total within 133 days.