Immediate weight bearing of comminuted supracondylar femur fractures using locked plate fixation.

Full article available online at Healio.com/Orthopedics. Search: 20120725-21 Comminuted supracondylar femur fractures (AO-OTA 33A3) are commonly treated with locked plates. Weight bearing is generally restricted for 6 to 12 weeks until radiologic evidence exists of sufficient callous to support weight bearing. Recent clinical studies have reported high nonunion rates with distal femur locked plates. In an attempt to induce beneficial motion across the fracture site, some studies have recommended earlier weight bearing. The purpose of the current study was to determine the biomechanical feasibility of an immediate weight-bearing rehabilitation protocol to encourage healing of distal femur fractures treated with lateral locked plate fixation. Sixteen fresh-frozen cadaveric femora were used for this study. A 2.5-cm supracondylar gap osteotomy was made. Ten-hole, 4.5-mm distal femur locking plates were used with a standardized screw configuration that maximized the working length. The specimens were placed in a servohydraulic testing machine and axially loaded (unidirectional) at 1 Hz for up to 200,000 cycles. Failure was defined as 1 cm of deformation of the construct. The staircase method was used to determine the fatigue limit of the construct. The fatigue limit was calculated to be 13296106 N. No specimen failed through the non-locking diaphyseal screws. Plastic deformation, when present, occurred at the metaphyseal flare of the plate. The fatigue limit of the locked plate constructs equaled 1.9 times body weight for an average 70-kg patient over a simulated 10-week postoperative course. Given that distal femoral loads during gait have been estimated to be more than 2 times body weight, the data from this study do not support immediate full weight bearing. Drs Granata, Litsky, Lustenberger, and Ellis are from the Department of Orthopaedics, The Ohio State University, Columbus, Ohio; and Dr Probe is from Scott & White Memorial Hospital, Temple, Texas. Drs Granata, Litsky, Lustenberger, Probe, and Ellis have no relevant financial relationships to disclose. Funding was obtained through a research grant from the Orthopedic Trauma Association. The Musculoskeletal Transplant Foundation donated all cadaveric specimens. The implants were provided through a materials grant from Smith & Nephew. The research was conducted independently without input from the funding sources. Correspondence should be addressed to: Thomas J. Ellis, MD, Department of Orthopaedics, The Ohio State University, 735 Prior Hall, 376 W 10th Ave, Columbus, OH 43205 (thomas.ellis@osumc.edu). doi: 10.3928/01477447-20120725-21 Immediate Weight Bearing of Comminuted Supracondylar Femur Fractures Using Locked Plate Fixation Jaymes D. Granata, mD; alan s. litsky, mD, scD; DaviD P. lustenberGer, mD; robert a. Probe, mD; thomas J. ellis, mD Figure 1: Photograph of gap osteotomy with implants in place. 1 Figure 2: Photograph of specimen mounted in Bionix 858 materials test frame (MTS Systems Corporation, Eden Prairie, Minnesota). 2