Faculty Bibliography

STUDY DESIGN/METHODS:Retrospective radiographic review. OBJECTIVE:To assess the utility of lateral dynamic flexion-extension radiographs in the initial evaluation of the degenerative lumbar spine. SUMMARY OF BACKGROUND DATA/BACKGROUND:Most surgeons obtain standing anteroposterior (AP) and lateral radiographs in the initial evaluation of patients presenting with lumbar complaints. The potential role of dynamic films in this population has not been established. METHODS:Of a 390 radiograph series, 342 met inclusion criteria and were reviewed. After assessment of the AP and lateral radiographs, dynamic films were evaluated to determine if additional information was obtained. RESULTS:Only 2 of the 342 radiographic series had new findings seen on dynamic films not appreciated on the AP and lateral films (a L3-L4 anterolisthesis of 3 mm with flexion and a L5-S1 retrolisthesis of 4 mm with extension). Fifteen additional radiographic series were noted to have a change in the amount of anterolisthesis or retrolisthesis on the dynamic films (changes ranged from 2 to 5 mm). CONCLUSION/CONCLUSIONS:In the population studied, dynamic radiographs did not significantly alter the initial course of clinical management beyond standing AP and lateral lumbar images.

STUDY DESIGN/METHODS:Posterolateral lumbar spine fusions in New Zealand white rabbits. OBJECTIVE:To evaluate the efficacy of recombinant human growth and differentiation factor-5 (rhGDF-5) lyophilized to a Healos carrier (cross-linked type I collagen with hydroxyapatite coating; DePuy Spine, Inc., Raynham, MA) in inducing fusion. SUMMARY OF BACKGROUND DATA/BACKGROUND:Bone graft substitutes have become an area of considerable interest. rhGDF-5 is one such product. Limited lumbar preclinical studies have been performed with this product. METHODS:Single-level, intertransverse process fusions were performed in 67 rabbits using iliac crest autograft (n = 13), Healos alone (n = 13), or 0.5, 1.0, or 1.5 mg/cc rhGDF-5 lyophilized to Healos (n = 13 per group). At 8 weeks, the rabbits were euthanized. Fusion masses were assessed. RESULTS:There were 2 animals (3%) lost to complication. Manual palpation revealed fusion rates for autograft of 38% (5/13), Healos alone of 0% (0/13), and each of the Healos/rhGDF-5 groups of 100% (13/13). Histologic analyses were 95% sensitive and 95% specific for confirming fusion. Histologic differences were found among the treatment groups. CONCLUSIONS:In this rabbit fusion model, Healos/rhGDF-5 induced fusion in 100% of the rabbits studied. This rate was significantly higher than the fusion rate induced by autograft (38%). Overall, these results support continued research of Healos/rhGDF-5 as a potential bone graft alternative.