Fixation of trochanteric slide osteotomies: a biomechanical study

Delayed presentation of bilateral central hip protrusio acetabuli: evidence-based management

This is a case of a previously healthy 51-year-old man who sustained bilateral central hip dislocations following a sudden presentation of epileptic seizures. The patient was initially treated conservatively for a period of 9 months. On presentation, he had gross disability due to stiffness in both hips and left peroneal nerve paresis. Through minimally invasive direct anterior approaches, bilateral total hip arthroplasties were performed using tripolar head articulations. These were cemented into a biologic acetabular buttress constructed out of autologous bone graft. The femoral heads and necks were used as plugs and pressed into the acetabular defects, putting the medial acetabular walls under tension. At 24 months' follow-up, there was a good clinical outcome, and the acetabular walls remodelled bilaterally. In conclusion, in traumatic protrusio acetabuli, a functional, biologic reconstruction of the acetabular wall can be facilitated with the application of distraction osteogenesis (tension-stress) principles while using minimally invasive surgical techniques.

Use of auxiliary locking plates for the treatment of unstable pertrochanteric femur fractures

Pertrochanteric femur fractures are successfully treated by orthopedic surgeons worldwide, but maintaining the reduction status or fixation of the greater trochanter is sometimes difficult in unstable cases in elderly patients. Several biomechanical advantages have been reported in locking plates when compared with conventional plates; locking plates provide angular and axial stability, better rigidity, and no toggling, and they preserve periosteal blood supply. The authors describe the use of auxiliary locking plates in unstable pertrochanteric femur fractures in elderly patients. Mini locking plates are simple, straightforward, and versatile enough to be used in elderly patients.

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.

Greater trochanteric fixation using a cable system for partial hip arthroplasty: a clinical and finite element analysis

The aim of the study was to investigate the efficacy of greater trochanteric fixation using a multifilament cable to ensure abductor lever arm continuity in patients with a proximal femoral fracture undergoing partial hip arthroplasty. Mean age of the patients (12 men, 20 women) was 84.12 years. Mean follow-up was 13.06 months. Fixation of the dislocated greater trochanter with or without a cable following load application was assessed by finite element analysis (FEA). Radiological evaluation was based on the distance between the fracture and the union site. Harris hip score was used to evaluate final results: outcomes were excellent in 7 patients (21.8%), good in 17 patients (53.1%), average in 5 patients (15.6%), and poor in 1 patient (9.3%). Mean abduction angle was 20.21°. Union was achieved in 14 patients (43.7%), fibrous union in 12 (37.5%), and no union in 6 (18.7%). FEA showed that the maximum total displacement of the greater trochanter decreased when the fractured bone was fixed with a cable. As the force applied to the cable increased, the displacement of the fractured trochanter decreased. This technique ensures continuity of the abductor lever arm in patients with a proximal femoral fracture who are undergoing partial hip arthroplasty surgery.

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.

[Osteotomy of the greater trochanter]

The increasing number of total hip arthroplasty procedures lead to an increasing number of revision surgeries. The trochanteric osteotomy technique is an established procedure in selected cases with the necessity of extending the usual surgical approach. Trochanteric osteotomy is also successfully performed in other areas, such as trauma surgery and joint-preserving surgery (surgical dislocation). Several techniques for trochanteric osteotomy are availably employing various fixation techniques and implants. This article presents the most common trochanteric osteotomy techniques for extension of the surgical approach (the classical according to Charnley, the trochanter slide, the extended trochanteric, and the stepped osteotomy) as well as clinical results and biomechanical experiences.

Does trochanteric step osteotomy provide greater stability than classic slide osteotomy? A preliminary study

The use of a trochanteric slide osteotomy needs a partial weightbearing period to allow safe healing of the osteotomy. We compared the initial rigidity of fixation of the trochanteric slide osteotomy with that of a newly developed technique, the trochanteric step osteotomy. The slide and step osteotomies were tested on six bilateral pairs of cadaveric femora with cyclic shear load of constant amplitude for 100 cycles in both a superior direction to represent standing and 60 degrees of hip flexion to represent a squat stance. Translational and rotational migration and cyclic amplitude were measured with an optoelectronic camera system. During superior loading, translational migration of the slide osteotomy was greater than for the step osteotomy (slide median, 1.7 mm; step median, 0.3 mm), but rotational migration was not (slide median, 1.9 degrees; step median, 0.2 degrees ). Translational amplitude was greater for the slide osteotomy in the superior direction (median slide, 0.3 mm; median step, 0.16 mm), but not in rotational amplitude. Similar trends in migration and amplitude were observed for the squat loading configuration. The data suggest the trochanteric step osteotomy is a more stable construct than the commonly performed slide osteotomy.