David A. May

Biomechanical comparison of ankle arthrodesis techniques: crossed screws vs. blade plate.

Many different techniques for ankle arthrodesis have been described. Experience at our institution with crossed screws internal fixation has not met the 90+% union rate reported in the literature. A compression blade plate is one technique for ankle arthrodesis which has not been evaluated biomechanically. A biomechanical study comparing two groups of sawbone ankle fusion constructs fixed with crossed screws and compression blade plates was performed in order to evaluate the stiffness and rigidity of these two arthrodesis techniques. The crossed screws construct demonstrated superior stiffness during dorsiflexion (p < 0.001) and valgus (p < 0.001) loading. The two constructs were found to have equal strength in resisting plantarflexion, varus and torsional loads although there was a trend for greater resistance by the crossed screws construct. These findings lend biomechanical support to the use of crossed screws for tibiotalar arthrodesis.

Screening for avascular necrosis of the hip with rapid MRI: preliminary experience.

PURPOSE The purpose of this work was to compare rapidly acquired MR images with routinely employed SE and turbo SE (TSE) images in screening for hip avascular necrosis (AVN). METHOD Twelve patients with findings suspicious for radiographically occult AVN of one or both hips were studied with our routine screening protocol (imaging time >7 min) and similarly weighted, rapidly acquired MR sequences (imaging time <1 min). RESULTS The rapidly acquired MR images were judged to be similar to the routine protocol in demonstrating marrow edema, irregular lines within the femoral head characteristic of AVN, and osteoarthritis. CONCLUSION The rapidly acquired MR sequences that we studied reliably revealed the presence or absence of AVN, marrow edema, and osteoarthritis of the hip in our sample population when compared with SE and TSE sequences that we routinely perform. Further investigation of rapidly acquired MR sequences is warranted, as imaging time may be dramatically reduced and patient throughput increased.