Commentary & Perspective

Commentary & Perspective on
"Mechanical Effects of the Extended Trochanteric Osteotomy"
by Andrew R. Noble, MD, et al.

Commentary & Perspective by
Wayne G. Paprosky, MD, and Kevin Hilton, MD*,
Rush University Medical Center, Chicago, Illinois

The extended trochanteric osteotomy was first described by Wagner¹ and then popularized by Younger et al.² as a valuable technique to facilitate revision total hip arthroplasty. The extended trochanteric osteotomy allows safe and efficient removal of well-fixed cemented and cementless implants and provides an extensile exposure for the removal of femoral components without compromising the distal diaphyseal canal. Proximal femoral varus and torsional deformities associated with loose femoral stems can be bypassed. Risks of femoral perforation, trochanteric fracture, eccentric reaming, and cement retention can be minimized. By providing direct access and visualization of the distal femoral canal, this technique ideally minimizes the risk of distal femoral fracture and the resultant loss of component fixation and stability.

In 2001, Miner et al.³ reviewed the results of 166 consecutive extended trochanteric osteotomies performed as part of revision hip arthroplasty with reimplantation of extensively porous-coated, cementless femoral stems. At a minimum two-year follow-up, fixation of the stem with bone in-growth was found in 153 hips (92%), stable fibrous fixation was found in 12 hips (7%), and the stem in one hip (1%) was unstable and subsequently needed revision. Most of the hips that had stable fibrous fixation had Paprosky Type-IIIB femoral defects, and the hip with the unstable stem had a Paprosky Type-IV femoral defect.

The overall complication rate was 24%, with eighteen femora (10.8%) sustaining small, nondisplaced cracks that extended distally from the osteotomy site and with four femora (2.4%) sustaining fractures that occurred through the osteotomized fragment. The fractures that extended from the osteotomy site occurred at the time of placement of the trial or final femoral component. These fractures were treated with a cerclage wire that was placed just distal to the transverse osteotomy site to halt the fracture propagation. In the fractures that occurred through the extended osteotomy fragment, two occurred intraoperatively and two occurred postoperatively. The two intraoperative fractures were treated with allograft struts, while the two postoperative fractures were treated with protected weight-bearing. In all instances, the fractures healed uneventfully and no femoral stems needed to be revised as a result of loosening.

In the current study, Noble et al. found a significant reduction (p < 0.0001) in the torque to failure for femoral specimens in the osteotomy group and the implant-repaired osteotomy group compared with the intact femoral specimen group. Even in the implant-repaired specimens, torque to failure was reduced by 23% compared with that of the implant group. In all specimens in the implant-repaired osteotomy group, the fracture propagated through the distal tip of the prosthesis with different proximal fracture patterns. The location of the fracture propagation through the distal limb of the osteotomy fragment was similar to our clinical results³, although clinically the fractures are likely due to a combination of hoop stresses and shear stress, rather than pure stress as a result of the applied torque. Clinically, the integrity of the proximal aspect of the femur is often compromised because of massive osteolytic defects or cortical thinning abrasion secondary to abrasion from loose components or fractured cement. In these scenarios, proximal femoral fracture is much more likely during dislocation, canal preparation, instrumentation, or osteotomy closure.

On the basis of the findings from their experiment, the authors of the current paper advocate a practice of more restrictive weight-bearing and the use of abduction braces when an extended trochanteric osteotomy is performed. In our clinical practice, a hip abduction orthosis is fit on postoperative day 1 and is worn for eight weeks. Physical therapy is begun on postoperative day 1. Immediate 30% weight-bearing is allowed, and the patient's progress is observed for the first four weeks, followed by 60% weight-bearing for the second four weeks unless acetabular grafting dictates touch-down weight-bearing only. We believe the protection with the hip abduction orthosis is necessary due to soft-tissue insufficiency and the increased risk of postoperative dislocation rather than for prevention of postoperative femoral fracture. Our clinical experience has shown that only two of 166 patients required extended osteotomy in the revision setting to treat a postoperative femoral fracture³. In addition to postoperative bracing, most revisions are routinely treated with larger femoral head sizes such as 32-mm heads or 40, 42 or 44-mm bipolar heads, depending on the size of the acetabular shell, which further lowers the risk of postoperative dislocation.

*The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. A commercial entity (Zimmer) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

References

1. Wagner H. [A revision prosthesis for the hip joint]. Orthopade. 1989;18:438-53. German.
2. Younger TI, Bradford MS, Magnus RE, Paprosky WG. Extended proximal femoral osteotomy. J Arthroplasty. 1995;10:329-38.
3. Miner TM, Momberger NG, Chong D, Paprosky WL. The extended trochanteric osteotomy in revision hip arthroplasty: a critical review of 166 cases at mean 3-year, 9-month follow-up. J Arthroplasty. 2001;16(8 Suppl 1):188-94.

Copyright © 2005 by the The Journal of Bone and Joint Surgery, Inc.