Impact of Ulnar Collateral Ligament Tear on Posteromedial Elbow Biomechanics.

Ulnar collateral ligament insufficiency has been shown to result in changes in contact pressure and contact area in the posteromedial elbow. This study used new digital technology to assess the effect of a complete ulnar collateral ligament tear on ulnohumeral contact area, contact pressure, and valgus laxity throughout the throwing motion. Nine elbow cadaveric specimens were tested at 90° and 30° of elbow flexion to simulate the late cocking/early acceleration and deceleration phases of throwing, respectively. A digital sensor was placed in the posteromedial elbow. Each specimen was tested with valgus torque of 2.5 Nm with the anterior band of the ulnar collateral ligament intact and transected. A camera-based motion analysis system was used to measure valgus inclination of the forearm with the applied torque. At 90° of elbow flexion, mean contact area decreased significantly (107.9 mm(2) intact vs 84.9 mm(2) transected, P=.05) and average maximum contact pressure increased significantly (457.6 kPa intact vs 548.6 kPa transected, P<.001). At 30° of elbow flexion, mean contact area decreased significantly (83.9 mm(2) intact vs 65.8 mm(2) transected, P=.01) and average maximum contact pressure increased nonsignificantly (365.9 kPa intact vs 450.7 kPa transected, P=.08). Valgus laxity increased significantly at elbow flexion of 90° (1.1° intact vs 3.3° transected, P=.01) and 30° (1.0° intact vs 1.7° transected, P=.05). Ulnar collateral ligament insufficiency was associated with significant changes in contact area, contact pressure, and valgus laxity during both relative flexion (late cocking/early acceleration phase) and relative extension (deceleration phase) moments during the throwing motion arc.

Biomechanical comparison of 4 different lateral plate constructs for distal fibula fractures.

BACKGROUND: Displaced lateral malleolar fractures are often treated with reduction and surgical stabilization. However, there has not been a comprehensive laboratory comparison to determine the most appropriate device for treating these patients. This study subjected a range of contemporary lateral fibular plates to a series of mechanical tests designed to reveal performance differences. METHODS: Forty fresh frozen lower extremities were divided into 4 groups. A Weber B distal fibula fracture was simulated with an osteotomy and stabilized using 1 of 4 plate systems: a standard Synthes one-third tubular plate with interfragmentary lag screw, a Synthes LCP locking plate with lag screw, an Orthohelix MaxLock Extreme low-profile locking plate with lag screw, or a TriMed Sidewinder nonlocking plate. Controlled monotonic bending and cyclic torsional loading were applied and bending stiffness, torsional stiffness, and fracture site motion were quantified. Resistance to cyclic torsional loading was determined by quantifying the number of loads withstood before excessive rotation occurred. Correlation between bone mineral density and each of the mechanical measures was determined. RESULTS: There was no difference in angulation or bending stiffness between plates. All plates except the LCP showed greater lateral deflection than in the other bending directions. Bending stiffness was lowest in lateral distal fragment deflection for all 4 plates. There was a positive correlation between bone mineral density and bending stiffness for all plate types. There was no difference in fracture site rotation between plate types in internal or external torsion, but internal rotation of the distal fragment consistently exceeded external rotation. Torsional stiffness in external rotation exceeded stiffness in internal rotation in nearly all specimens. LCP plates performed relatively poorly under cyclic torsion. CONCLUSIONS: Significant differences in plate performance were not demonstrated. The effects of bone quality variability and differences in interfragmentary screw purchase resulted in data dispersion that confounded absolute ranking of plate performance. CLINICAL RELEVANCE: Identification of an optimal lateral fibular plating system has the potential to improve the clinical outcome of malleolar fracture fixation, particularly when patient conditions are unfavorable.

Single-incision medial approach for double arthrodesis of hindfoot in posterior tibialis tendon dysfunction.

BACKGROUND: Triple arthrodesis through a 2-incision approach has been the primary salvage procedure for rigid hindfoot malalignment resulting from posterior tibialis dysfunction. However, complications like calcaneocuboid joint nonunion, lateral wound dehiscence, and adjacent joint arthritis have been reported after triple arthrodesis. Hence we adopted single-incision medial approach arthrodesis of subtalar and talonavicular joints, sparing the uninvolved calcaneocuboid joint and lateral skin. METHOD: We report the results of a series of 18 feet with posterior tibialis dysfunction that had correction of malalignment by this approach. Mean age at surgery was 65 years. The mean follow-up was 24 months. RESULTS: There was statistically significant improvement in all the radiological parameters measured. There were no wound-related complications. The union rate was 89%. There were 2 malunions, and 2 feet developed valgus ankle deformity. The overall satisfaction rate among patients was 78%. CONCLUSION: We present a case series of treatment of posterior tibialis tendon dysfunction by arthrodesis of the subtalar and talonavicular joints through an isolated medial approach. The results were not encouraging enough to recommend adopting this approach as an alternative to triple arthrodesis. LEVEL OF EVIDENCE: Level IV, retrospective case series.