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Abstract BACKGROUND: Pseudoarthrosis after pedicle subtraction osteotomy (PSO) can require revision surgery due to posterior rod failure, and the stiffness of these revision constructs has not been quantified. OBJECTIVE: To compare the multidirectional bending stiffness of 7 revision strategies following rod failure. METHODS: Seven fresh-frozen human spines (T11-pelvis) were tested as follows: (1) posterior instrumentation from T12-S1 (excluding L3) with iliac fixation and L3 PSO; (2) inline connectors after rod breakage at L3 (L2 screws removed for access); (3) cross-links connecting rods above and below inline connectors; satellite rods (4) parallel, (5) 45° anterior, and (6) 45° posterior to original rods; 45°posterior with cross-links connecting (7) original and (8) satellite rods. Groups 3 to 8 were tested in random order. Nondestructive pure moment flexion-extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted to 7.5 Nm; 3D motion tracking monitored the primary range of motion. RESULTS: Addition of inline connectors alone restored stiffness in FE and LB (P > .05), but not in AR (P < .05). Satellite rods (groups 4 to 6) restored stiffness in FE and LB (P > .05), but not in AR (P < .05) and were not significantly different from one another (P > .05). The addition of cross-links (groups 3, 7, and 8) restored stiffness in all bending modes (P > .05) and were significantly greater than inline connectors alone in AR (P < .05). CONCLUSION: The results suggest that these revision strategies can restore stiffness without entire rod replacement. Failure of AR stiffness restoration can be mitigated with cross-links. The positioning of the satellite rods is not an important factor in strengthening the revision.

Ten percent of the 250,000 proximal femur fractures that occur in the United States each year are malreduced into a varus position after treatment. Currently, there is no cephalomedullary nail available that allows the physician to dynamically change the lag-screw-to-nail angle. The Variable Angle Nail (VAN) was designed to allow movement of the lag screw relative to the shaft of the nail. This study compared the characteristics of the VAN to the Gamma 3 nail via finite element analysis (FEA) in stiffness and fatigue. The results of the FEA model with the same loading parameters showed the Gamma 3 and the VAN with lag-screw-to-nail angle of 120° to have essentially the same stiffness values ranging from 350 to 382 N/mm. The VAN with lag-screw-to-nail angles of 120°, 130°, and 140° should be able to withstand more than 1,000,000 cycles from 1,400 N to 1,500 N loading of the tip of the lag screw. The Gamma 3 should be able to last more than 1,000,000 cycles at 1,400 N. In summary, the VAN is superior or equivalent in stiffness and fatigue when compared to the Gamma 3 using FEA.

Background Since the introduction of rhBMP-2 (Infuse®) in 2002, surgeons have had an alternative substitute to autograft and its related donor site morbidity. Recently, the prevalence of reported adverse events and complications related to the use of rhBMP-2 has raised many ethical and legal concerns for surgeons. Additionally, the cost and decreasing reimbursement landscape of rhBMP-2 use have required identification of a viable alternative. Osteo allogeneic morphogenetic protein (OsteoAMP®) is a commercially available allograft-derived growth factor rich in osteoinductive, angiogenic, and mitogenic proteins. This study compares the radiographic fusion outcomes between rhBMP-2 and OsteoAMP allogeneic morphogenetic protein in lumbar interbody fusion spine procedures. Methods Three hundred twenty-one (321) patients from three centers underwent a transforaminal lumbar interbody fusion (TLIF) or lateral lumbar interbody fusion (LLIF) procedure and were assessed by an independent radiologist for fusion and radiographically evident complications. The independent radiologist was blinded to the intervention, product, and surgeon information. Two hundred and twenty-six (226) patients received OsteoAMP with autologous local bone, while ninety-five (95) patients received Infuse with autologous local bone. Patients underwent radiographs (x-ray and/or CT) at standard postoperative follow-up intervals of approximately 1, 3, 6, 12, and 18 months. Fusion was defined as radiographic evidence of bridging across endplates, or bridging from endplates to interspace disc plugs. Osteobiologic surgical supply costs were also analyzed to ascertain cost differences between OsteoAMP and rhBMP-2. Results OsteoAMP produced higher rates of fusion at 6, 12, and 18 months ( p  ≤ 0.01). The time required for OsteoAMP to achieve fusion was approximately 40% less than rhBMP-2 with approximately 70% fewer complications. Osteobiologic supply costs were 80.5% lower for OsteoAMP patients (73.7% lower per level) than for rhBMP-2. Conclusions Results of this study indicate that OsteoAMP is a viable alternative to rhBMP-2 both clinically and economically when used in TLIF and LLIF spine procedures.