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As a first year orthopaedic surgery resident at New Jersey Medical School in Newark, New Jersey, I first met Michael J. Pappas, PhD, my biomechanics teacher from New Jersey Institute of Technology, (NJIT) (also in Newark, N.J.). It was early in 1974 when my orthopaedic chairman, Anthony F. DePalma, MD (a feisty, world renowned shoulder surgeon and founder of Clinical Orthopaedics and Related Research) decided that his orthopaedic residents needed to have an understanding of engineering principles as they applied to bone and joint surgery. To that end he enlisted two mechanical engineering volunteers from NJIT, Harry Herman, PhD and his junior associate Michael J. Pappas, PhD.

Mobile bearings were originally introduced with the Oxford knee in 1977 which sought to improve articular congruity for improved wear characteristics using a spherical, congruous articulation while diminishing implant constraint with a floating surface p[6]. The Low Contact Stress (LCS) knee prosthesis (Depuy, Warsaw), the subject of this outcome study was a mobile bearing design with modifications of the tibial component to allow for posterior cruciate retention (meniscal bearing) or sacrifice (rotating platform). From the outset, it was recognized that a long term experience would be needed to prove the experiment that mobile bearings would solve the issues of fixation and wear through a favorable, high area of contact, wear surface and nonconstrained moveable bearings [2].

The Low Contact Stress (LCS) knee prosthesis, (Depuy, Warsaw, IN) was originally designed with a tibial component that allowed for posterior cruciate retention (meniscal bearing) or sacrifice (rotating platform) [1]. The femoral component was designed with polycentric radii of curvature which approximated the condylar shape of the normal distal femur. Clinical reports have demonstrated comparable midterm clinical results with either posterior cruciate retention or sacrifice using this implant and osteolysis has been a rare event [2, 8, 11, 20). With longer follow-up beyond ten years, investigators found increasing rates of fracture, wear and dislocation of the original meniscal bearings as compared to the rotating platform tibial insert [31. The rotating platform was originally developed for more difficult cases and early clinical results with this implant may have been biased from that factor [1]. However, the implant gained increasing popularity as long term results have been shown to be durable even in younger patients, and the surgical technique is generally simpler with less technical challenge [13].

The Low Contact Stress (LCS) knee system was introduced in 1977 as an attempt to improve the survivorship and clinical function of total knee replacement. From its outset, the design goals of this mobile bearing knee system were to decrease the prospect of polyethylene material damage, minimize constraint and optimize patient implant kinematics. The gait-congruent LCS design, in its origin, was proposed as a system inclusive of both cruciate-sparing meniscal bearing and PCL-sacrificing rotating platform variants, with the latter gaining the majority of popular usage over time. Both systems employ a dynamic tracking metal-backed rotating patellar component that articulates with the femoral sulcus.

Ankle arthroplasty has previously had a dubious reputation based on the experience with the first-generation two-piece designs. This has given the impression that ankle arthrodesis is the preferable choice in painful and degenerate ankles when conservative treatment has failed. Introducing a sliding meniscus in a prosthetic ankle joint resulted in a better perfor mance* especially by imitating the normal torque and, thereby, decreasing stress at the bone-prosthesis interface.