Luc P Cloutier1, G Yves Laflamme2, Jeremie Menard2, Yvan Petit3. 1. Mechanical Engineering Department, École de technologie supérieure, Montreal, Quebec, Canada; Laboratoire d'imagerie et d'orthopédie, Hôpital du Sacré-Cœur, Research Center, Montreal, Quebec, Canada. 2. Laboratoire d'imagerie et d'orthopédie, Hôpital du Sacré-Cœur, Research Center, Montreal, Quebec, Canada. 3. Mechanical Engineering Department, École de technologie supérieure, Montreal, Quebec, Canada; Laboratoire d'imagerie et d'orthopédie, Hôpital du Sacré-Cœur, Research Center, Montreal, Quebec, Canada. Electronic address: yvan.petit@etsmtl.ca.
Abstract
BACKGROUND: Greater trochanter fractures or osteotomies fixed with lateral plates still present high rates of complications. Unblocked greater trochanter anterior movement during hip extension might be a possible cause of failure. This study aimed to determine, under stair climbing conditions, the biomechanical behaviour of a greater trochanter fragment and the impact of an anterior locking plate on its migration. METHODS: Eighteen femurs paired from nine fresh frozen cadaveric specimens were tested on a quasi-dynamic stair climbing cycling test bench. Left and right sides with greater trochanter fractures were randomly fixed either with an antero-lateral locking plate or with a lateral locking plate. Migrations, defined as the remaining movements of the unloaded greater trochanter fragment, were measured for all 18 femurs. FINDINGS: During hip extension, multi-directional greater trochanter fragment movements occurred and showed a back-and-forth anterior rotation. The lateral locking plate failed due to greater trochanter fragment rotation around the superior axis and anterior translation. The antero-lateral locking plate significantly reduced greater trochanter anterior migration (-0.9 mm ± 1.6) compared to the lateral locking plate (9.6 mm ± 9.5). INTERPRETATION: Hip extension provides a plausible explanation for the high rate of post-operative failures of greater trochanter fixations. An antero-lateral locking plate represents an efficient surgical alternative counteracting the multi-directional greater trochanter movements occurring during hip extension.
BACKGROUND: Greater trochanter fractures or osteotomies fixed with lateral plates still present high rates of complications. Unblocked greater trochanter anterior movement during hip extension might be a possible cause of failure. This study aimed to determine, under stair climbing conditions, the biomechanical behaviour of a greater trochanter fragment and the impact of an anterior locking plate on its migration. METHODS: Eighteen femurs paired from nine fresh frozen cadaveric specimens were tested on a quasi-dynamic stair climbing cycling test bench. Left and right sides with greater trochanter fractures were randomly fixed either with an antero-lateral locking plate or with a lateral locking plate. Migrations, defined as the remaining movements of the unloaded greater trochanter fragment, were measured for all 18 femurs. FINDINGS: During hip extension, multi-directional greater trochanter fragment movements occurred and showed a back-and-forth anterior rotation. The lateral locking plate failed due to greater trochanter fragment rotation around the superior axis and anterior translation. The antero-lateral locking plate significantly reduced greater trochanter anterior migration (-0.9 mm ± 1.6) compared to the lateral locking plate (9.6 mm ± 9.5). INTERPRETATION: Hip extension provides a plausible explanation for the high rate of post-operative failures of greater trochanter fixations. An antero-lateral locking plate represents an efficient surgical alternative counteracting the multi-directional greater trochanter movements occurring during hip extension.