Fusion in degenerative spondylolisthesis: comparison of osteoconductive and osteoinductive bone graft substitutes.

INTRODUCTION: The emergent widespread options of bone graft substitutes for spinal fusion procedures vary in their osteobiologic activity. A majority of current literature focuses on the comparison of osteoinductive (OI) or osteoconductive (OC) bone graft substitutes individually against ICBG. These studies have demonstrated the legitimacy of bone graft substitutes, but despite the widespread use in spinal fusion procedures there is a dearth in the current literature in the direct comparison of OC and OI substitutes. This retrospective comparative analysis compares the efficacy of OI vs. solely OC agents in producing radiographic fusion on patients with DS. METHODS: Patients, who underwent a lumbar fusion for DS with at least 6 months post-op radiographs, were divided based on whether they received an OC or OI bone graft substitute. The OC groups included allografts, calcium phosphate, ceramics and hydroxyapatite products. The OI group included bone morphogenic protein, demineralized bone matrix, and stem cell-based products. MEASUREMENT CRITERIA: Using a conservative hierarchical approach to determine fusion, fusion criteria included stringent use of multiple measurement methods including flexion/extension x-rays, Lenke and Brantigan CT fusion measurement criteria, and history of revision surgery due to pseudoarthrosis. RESULTS: A total of 126 patients (78 OI, 48 OC) met the studies inclusion criteria for the assessment for fusion. The mean time for flexion-extension radiographic evaluation was 13.1 months for the OI group and 15 months for the OC group. The mean time for CT scan evaluation was 18 months for the OI group and 15.9 months for the OC group. Using the stated hierarchical criteria for fusion stated above, the fusion rate for the OI group was 87.18%, and the fusion rate for the OC group was 93.75%. The difference in OI and OC groups was not statistically significant (P = 0.367). Based on the demographic data collected, there were no statistically significant factors determining fusion. CONCLUSION: With the vastly growing market for OI and OC materials commonly used in lumbar spinal fusions, the options for surgical treatment for degenerative spondylolisthesis are ever expanding. No significant difference was found when comparing fusion rates between the two types of materials in this retrospective analysis. Interestingly, TLIF procedures provided lower fusion rates than posterolateral fusion procedures. This may be due to a small sample size but the association with a minimally invasive technique warrants investigation. Due to the substantial difference in price between the OI and OC materials and the lack of evidence supporting higher fusion rates with more expensive OI agents, it is incumbent on the spine community to consider and reassess the products that are routinely used.

Comparison of body-powered voluntary opening and voluntary closing prehensor for activities of daily life.

Persons with an upper-limb amputation who use a body-powered prosthesis typically control the prehensor through contralateral shoulder movement, which is transmitted through a Bowden cable. Increased cable tension either opens or closes the prehensor; when tension is released, some passive element, such as a spring, returns the prehensor to the default state (closed or open). In this study, we used the Southampton Hand Assessment Procedure to examine functional differences between these two types of prehensors in 29 nondisabled subjects (who used a body-powered bypass prosthesis) and 2 persons with unilateral transradial amputations (who used a conventional body-powered device). We also administered a survey to determine whether subjects preferred one prehensor or the other for specific tasks, with a long-term goal of assessing whether a prehensor that could switch between both modes would be advantageous. We found that using the voluntary closing prehensor was 1.3 s faster (p = 0.02) than using the voluntary opening prehensor, across tasks, and that there was consensus among subjects on which types of tasks they preferred to do with each prehensor type. Twenty-five subjects wanted a device that could switch between the two modes in order to perform particular tasks.