A Dynamic Model of Hip Joint Biomechanics: The Contribution of Soft Tissues.

Before recent advances in computer modeling technology, it has been nearly impossible to define the contribution of soft tissue structures when constructing models of the body, and in particular the lower extremity. For almost 100 years, the design and fixation of femoral components for total hip arthroplasty (THA), whether cemented or press fit, have been predicated on the Koch model of hip biomechanics. A more comprehensive model, which includes the dynamic contribution of soft tissues, has expanded the Koch's static model.

Permanent Motor Function Loss by Delayed Treatment of Peroneal Intraneural Ganglion.

The low incidence of intraneural ganglion makes it difficult to diagnose and treat before it becomes serious nerve damage. This case describes a 69-year-old female, who suffered from the right drop foot and was diagnosed as a peroneal intraneural ganglion. Resection of the mass relieved the pain; however, motor function was not recovered.

Mechanical failure of metal-polyethylene sandwich liner in metal-on-metal total hip replacement.

Metal-on-metal had been proposed as an optimal articulation in THRs, however, many monoblock prostheses have been recalled in the USA because of significant high rates of early failure. Metal-on-metal prostheses had been implanted in our institution, and this is a case history of a single patient, in whom metal-on-metal THRs with different femoral sizes of heads were implanted. A 57-year-old female patient underwent bilateral total hip replacements with metal-on-metal prostheses using metal-polyethylene "sandwich" liners 9 years ago on the right side and 7 years ago on the left side respectively.

Finite element analysis of femoral neck stress in relation to pelvic width.

Hip resurfacing arthroplasty has been developed as an alternative to traditional total hip arthroplasty, in an effort to minimize the loss of native bone in young patients with symptomatic hip osteoarthritis. Femoral neck fracture following hip resurfacing is a unique complication; several risk factors are associated with this complication, including female gender. In the present study, we used finite element models of the proximal femur to simulate stresses across the femoral neck in pelvis models with varying widths.

Electronic measurement of soft-tissue balancing reduces lateral releases in total knee arthroplasty.

Soft tissue balancing during total knee arthroplasty (TKA) has a direct affect on patello-femoral tracking and knee range of motion, which are necessary for a well functioning TKA postoperatively. We report on the use of an electronic pressure sensing instrument for soft tissue balancing of the knee before completion of all intraoperative bone cuts, as a way to improve patellar tracking. In a retrospective study of 99 consecutive TKAs, with intraoperative electronic instrument guided soft tissue balancing performed, a reduction in the incidence of lateral patellar retinacular release was found, as compared with the 100 consecutive TKAs prior to its use (5.

Regional variations of bone quantity and quality impact femoral head collapse.

Osteonecrosis (ON) of the femoral head causes the bone to deteriorate, buckle, and collapse. As the vasculature is reportedly uniform in the femoral head, one would expect uniform susceptibility to ON; however, collapse typically occurs in the anterior region. We asked whether regional variations in bone quantity and/or quality could explain the bone's anterior susceptibility despite uniform vascularity.

Preservation of femoral bone mass after total hip replacements with a lateral flare stem.

Uncemented, porous-coated femoral stems rely on bone in-growth to achieve stable, long-lasting fixation. The loss of proximal femoral bone mass around hip stems has been traditionally termed "stress shielding" and has been linked to the transfer of loads to the diaphysis and the relative unloading of the proximal femur. A total of 10 total hip arthroplasties with a proximally coated lateral flare device designed to engage both cortices at the metaphyseal level were evaluated with dual-energy X-ray (DEXA) absorptiometry and qualitative radiographic changes 3 weeks after surgery and at 12, 24 and 52 weeks thereafter.