Insall and colleagues compared four early knee replacement designs — unicondylar, duocondylar, geometric, and Guepar hinge — in 193 consecutive arthroplasties at HSS. The central question: should prosthetic design be matched to the severity of joint pathology and deformity? Follow-up ranged from 2 to 3.5 years, using the HSS knee rating scale for pre- and postoperative evaluation.
In 1976, TKA was in its infancy and surgeons were implanting whatever design was available regardless of the knee's degree of destruction or deformity. This paper from Insall's group at HSS was the first systematic attempt to ask whether prosthesis selection should be matched to pathology — and the data answered yes.
The practical rule that emerged: use unconstrained condylar designs for mild-to-moderate disease, reserve constrained or hinge designs for extreme deformity and instability. When you see a knee with >25° flexion contracture or lateral tibial subluxation, a condylar design will fail. This paper is why those remain contraindications today.
The near-universal tibial radiolucency in flat-surface condylar components told Insall the tibial interface needed to be redesigned. That insight drove the development of the Total Condylar prosthesis. The first modern TKA. Introduced just after this paper was published.
The patellofemoral findings are equally durable: none of the four designs addressed the patella adequately, and patellectomy made things worse by weakening the extensor mechanism. This is why patellar resurfacing became a standard component of modern TKA design.
Insall and colleagues compared four early knee replacement designs — unicondylar, duocondylar, geometric, and Guepar hinge — in 193 consecutive arthroplasties at HSS. The central question: should prosthetic design be matched to the severity of joint pathology and deformity? Follow-up ranged from 2 to 3.5 years, using the HSS knee rating scale for pre- and postoperative evaluation.
In 1976, TKA was in its infancy and surgeons were implanting whatever design was available regardless of the knee's degree of destruction or deformity. This paper from Insall's group at HSS was the first systematic attempt to ask whether prosthesis selection should be matched to pathology — and the data answered yes.
The practical rule that emerged: use unconstrained condylar designs for mild-to-moderate disease, reserve constrained or hinge designs for extreme deformity and instability. When you see a knee with >25° flexion contracture or lateral tibial subluxation, a condylar design will fail. This paper is why those remain contraindications today.
The near-universal tibial radiolucency in flat-surface condylar components told Insall the tibial interface needed to be redesigned. That insight drove the development of the Total Condylar prosthesis. The first modern TKA. Introduced just after this paper was published.
The patellofemoral findings are equally durable: none of the four designs addressed the patella adequately, and patellectomy made things worse by weakening the extensor mechanism. This is why patellar resurfacing became a standard component of modern TKA design.