Greater trochanter displacements after Charnley’s trochanterotomy, during passive hip movements: a real-time 3D cadaveric approach

Anterior locking plate reduces trochanteric fracture migrations 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.

Biomechanical analysis of trochanteric fracture fixations using a Y-shaped locking plate

OBJECTIVES

Clinical evidence suggests that the use of Y-shaped locking plates with anterior and lateral locking screws provide improved primary fixation stability over the use of straight locking plates in the treatment of greater trochanter (GT) fractures. However, it remains unclear how the use of cable cerclages, in replacement or addition to the locking screws, would impact the primary fixation stability.

METHODS

Nine surgical fixations were tested on a dynamic test bench through 27 sawbones experiments. These fixations on the GT and bone shaft (BS) included locking screws alone, cable cerclages alone, or 7 combinations of both. Migrations, defined as the remaining movements of the unloaded GT fragment, were measured for all 9 fixations submitted to dynamic stair climbing cycling after an experimental plan.

RESULTS

Under dynamic stair climbing conditions: (1) Y-shaped locking plates fixed by locking screws alone (vs cable cerclages alone) significantly reduced GT migrations, (2) adding cable cerclages to screws provided no significant reduction of migrations, and (3) cable cerclages alone can be used on the BS but is not recommended on the GT.

CONCLUSIONS

Y-shaped locking plates with anterior and lateral locking screws improved primary stability of GT fractures over fixation with cable cerclages. Cable cerclages provided acceptable primary stability when screw fixations were unachievable but on the BS only.