The first 101 posterior cruciate retaining modular tibial components of a single design performed by a single surgeon in 75 patients were evaluated at a minimum 20-year follow-up. All components were fixed with cement. These patients had been prospectively followed at five-year intervals and evaluated clinically using Knee Society ratings and documenting any need for reoperation. Serial radiographs were evaluated for radiolucencies, osteolysis or component migration until the time of patient death or at minimum 20-year follow-up.

At minimum 20-year follow-up, five knees (5%) had required a revision operation. All revisions occurred greater than 10 years following the index procedures. Benefits of modularity (i.e. retention of the tibial tray) were utilized in three of five cases in this closely followed cohort. Survivorship from any revision was 90.8% at 20 years. For the 16 living patients with 22 knees, the average Knee Society Clinical and Functional scores were 91 and 59, respectively, and the average range of motion was 115 degrees.

When considering gamma irradiated in air polyethylene and a first generation locking mechanism were utilized, these results encourage the authors to continue to use modular tibial trays.

Over the last two decades, design modifications in cementless total hip arthoplasty have led to longer lasting implants and an increased success rate. However, there remains limitations to the cementless femoral stem implant. Traditional cementless femoral components require large amounts of bone to be broached prior to stem insertion (1). This leads to a decrease in host bone stock, which can become problematic in a young patient who may eventually require a revision operation during his or her lifetime. Osteopenia, only second to distal stress shielding can lead to aseptic loosening of the implant and stem subsidence, which also accelerates the need for a revision operation (2–4). Recent literature suggests that thigh pain due to distal canal fixation, micro-motion, uneven stress patterns or cortex impingement by the femoral stem is directly correlated to increased stem sizes and often very disabling to a patient (5–8). In this study, we sought to determine whether reducing stem length in the femoral implant would produce more physiologic loading characteristics in the proximal femur and thus eliminate any remaining stress shielding that is present in the current design. We analyzed the surface strains in 13 femurs implanted with

no implants,

Analysis of the resulting surface strains was performed using the photoelastic method. For each femur, intact and with the different stem length components in place, the fringe patterns were compared at the same applied loads. The highest fringe orders observed for all tests were located on the lateral proximal femur and medial proximal femur. The fringes decreased as they approached the neutral axis of bending (posterior and anterior). Distal fringe patterns were more prominent as the stem length increased. The results demonstrate that the stemless design most closely replicated normal strain patterns seen in a native femur during simulated gait. The presence of a stemless, ultra short and short stem reduced proximal strain and increased distal strain linearly, thereby increasing the potential for stress shielding. The stemless design most closely replicated normal strain patterns observed in a native femur and for this reason has the potential to address the shortcomings of the traditional cementless femoral implant.

Purpose: The original AML prosthesis was fully coated and later the manufacturer switched it to 5/8ths coating. The second generation Prodigy femoral component was developed to return to full coating of the prosthesis and to provide a medial relief to decrease bone stress shielding. The purpose of this study was to evaluate the minimum ten year results using this device and to compare the results to the same surgeon’s results at 10 years using a first generation proximally coated device.

Method: 100 consecutive primary total hip replacements were performed by a single surgeon in 86 patients using the Prodigy (DePuy, Warsaw, Indiana) femoral component between 1994 and 1997. The components were mated with 80 HGI and 20 Duraloc acetabular components. Patients were evaluated with WOMAC ratings, need for revision and radiographic loosening. The same parameters had been evaluated at minimum 10-year follow-up for the same surgeon’s initial 100 consecutive PCA (Stryker, New Jersey) primary THR’s and were compared to the present series.

Results: At minimum 10 year follow-up, 71 patients with 83 hips were living. The average clinical follow-up for the living patients was 11 years (range 10 to 12 years) and the average radiographic follow-up was 9.2 years for this group (range 7–12 years). No femoral component was revised for loosening and all femoral components were bone ingrown on radiographs. 7 acetabular components required a liner exchange or revision for polyethylene wear. This compares favorably to the same surgeon’s 10 year results with the PCA where 6 femoral components were revised for wear or loosening and an additional 2 were radiographically loose.

Conclusion: The Prodigy femoral component demonstrated excellent durability at 10 years. With the newer cementless stems with a wide variety of sizes, femoral loosening is rarely a clinical problem.