Early failure of articular surface replacement XL total hip arthroplasty.

The ASR (articular surface replacement) XL (DePuy, Warsaw, Ind) metal-on-metal hip arthroplasty offers the advantage of stability and increased motion. However, an alarming number of early failures prompted the evaluation of patients treated with this system. A prospective study of patients who underwent arthroplasty with the ASR XL system was performed. Patients with 2-year follow-up or any revision were included. Failure rates, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, and radiographs were evaluated. Ninety-five patients (105 hips) were included. There were 16 revisions. Thirteen (12%) were aseptic acetabular failures. Eight were revised for aseptic loosening; 4, for metallosis; 1, for malposition; 2, for infection; and 1, for periprosthetic fracture. Mean time to revision was 1.6 years (0.18-3.4 years). The ASR XL with a revision rate of 12% is the second reported 1 piece metal-on-metal system with a significant failure rate at early follow-up. This particular class of implants has inherent design flaws that lead to early failure.

In vivo kinematics after a cruciate-substituting TKA.

UNLABELLED: Patterns of motion in the native knee show substantial variability. Guided motion prosthetic designs offer stability but may limit natural variability. To assess these limits, we therefore determined the in vivo kinematic patterns for patients having a cruciate-substituting TKA of one design and determined the intersurgeon variability associated with a guided-motion prosthetic design. Three-dimensional femorotibial contact positions were evaluated for 86 TKAs in 80 subjects from three different surgeons using fluoroscopy during a weightbearing deep knee bend. The average posterior femoral rollback of the medial and lateral condyles for all TKAs from full extension to maximum flexion was -14.0 mm and -23.0 mm, respectively. The average axial tibiofemoral rotation from full extension to maximum flexion for all TKAs was 10.8 degrees. The average weightbearing range of motion (ROM) was 109 degrees (range, 60 degrees-150 degrees; standard deviation, 18.7 degrees). Overall, the TKA showed axial rotation patterns similar to those of the normal knee, although less in magnitude. Surgeon-to-surgeon comparison revealed dissimilarities, showing the surgical technique and soft tissue handling influence kinematics in a guided-motion prosthetic design. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Evaluation of off-loading braces for treatment of unicompartmental knee arthrosis.

Two analyses were performed to assess the effectiveness of off-loading knee braces in producing condylar separation of degenerative compartments in patients with unicompartmental knee osteoarthritis. All patients were analyzed using video fluoroscopy under weight-bearing conditions. In the initial study, a single brace was analyzed in 2 dimensions and demonstrated that medial condylar separation was obtained, with corresponding pain relief, in 78% of patients. The brace was least effective in obese patients. The second study consisted of a 3-dimensional analysis of 5 subjects fitted with 5 different off-loading braces. Condylar separation in most patients was similarly observed with certain braces, whereas others demonstrated little to no condylar separation, suggesting that off-loading knee braces are not equally effective in treatment of unicompartmental knee arthritis.

Cementless revision total hip arthroplasty without allograft in severe proximal femoral defects.

This study evaluates the difficult reconstructive challenge of severe proximal femoral bone loss. We present intermediate-term results of 46 hips with extensive proximal femoral bone loss that underwent revision total hip arthroplasty using cementless distal fixation without supplemental allograft. All were evaluated with the Harris hip score at a minimum of 2 years. Radiographs were assessed using the Engh fixation scale. At a mean of 6.4 (range 2-12) years, 43 of the 46 prostheses were functioning well. Two patients required revision for symptomatic loosening, and 1 prosthesis remains radiographically loose with a fair clinical score. Mean Harris hip score was 77 at last follow-up. There were 6 intraoperative femur fractures, 9 dislocations, 10 cases of severe stress shielding, and no infections.

Bipolar reconstruction for recurrent instability of the hip.

Between 1986 and 1998, 81 total hip revisions were performed for recurrent instability. Twenty-three revisions were fixed cups to bipolars. Average follow-up was 50 months. Radiographic evaluation showed no significant osteolysis and average migration of 1.7 mm. The average postoperative Harris hip score was 74. All patients who underwent revision to a bipolar prosthesis had no further instability. Acetabular revision to a bipolar prosthesis provides stability in recurrent prosthetic hip instability.

Underestimation of osteolysis in posterior stabilized total knee arthroplasty.

Periprosthetic osteolysis in total knee arthroplasty (TKA) has become a significant problem. Routine surveillance is warranted to detect problems that may not be symptomatic. The goal of these radiographs is to detect arthroplasty-related bone loss at an early stage to implement strategies to limit its extension. The purpose of this study was to show the extent to which condylar osteolysis can be underestimated on routine radiographs. Two cadaveric femurs were prepared to receive a posterior stabilized (PS) femoral component. A simulated osteolytic lesion was created using acetabular reamers. Lesions of 36 mm not easily discernible on standard anteroposterior and lateral images were easily recognized on oblique films. The oblique radiographs described can help with the early recognition of retrofemoral osteolysis about a posterior-stabilized implant.