Total hip replacement and the law of diminishing returns

This paper explores the current developments in total hip replacement and considers the justification for the escalating costs of what has already been shown to be a very successful procedure. Total hip replacement was introduced primarily to relieve pain and restore function in patients crippled with arthritis of the hip. Secondary objectives included optimized durability of implant fixation and the bearing surfaces, as well as a combination of optimized mobility and stability of the articular couple. Early attempts at replacement of the hip joint were condemned as a result of poor materials and poor design. Charnley made three major contributions to the evolution of contemporary hip replacement: the concept of low-friction torque arthroplasty, the introduction of high-density polyethylene, and the use of acrylic bone cement to secure implant fixation to bone. In studies of total hip arthroplasty with use of the first-generation Charnley stem, Berry et al and Callaghan et al reported a twenty-five-year survival rate of 81% and 77%, respectively, with revision of any component as the end point. Similar results have been reported by other authors. Initially, the indications for total hip replacement were largely limited to the elderly and infirm, or to patients who had other locomotor limitations (e.g., rheumatoid arthritis with polyarticular involvement). Today, indications for total hip replacement are often influenced by quality-of-life issues, and patients seek "high-performance hips" to deliver their aspirations and expectations. Components must therefore provide durable fixation despite high activity levels, and the bearing surfaces need to be resilient and exhibit low wear to provide a durable articulation. The wear debris should excite a limited biological response or none at all. Surgical practice is changing to accommodate the philosophy of the preservation of bone and soft tissue and to deliver the accelerated rehabilitation regimes expected by the patient. Computer-aided surgery may assist with component orientation, particularly when exposure is reduced by soft-tissue-sparing minimally invasive surgery.