A short history of joint and spinal disc replacement

Before modern components

The arthroplasty reference distinguishes putting tissue between joint surfaces from removing damaged surfaces. It also describes resurfacing, in which bone surfaces are trimmed and covered. These are different mechanical approaches to a joint that no longer works comfortably. Their inclusion under the same broad term shows why arthroplasty cannot always be understood as a simple synonym for replacing an entire joint (Forms of arthroplasty).

The hip replacement reference describes attempts using ivory, followed by glass and metal. It notes that glass components were fragile despite favorable compatibility with the body. A material could therefore be acceptable to tissue while still failing to withstand the mechanical demands placed on it. Those separate requirements remain useful ideas for understanding the development of an artificial joint (Development of hip replacement).

The development of modern hip replacement

For the hip, the development described in the reference brought together an artificial ball, a socket surface and methods for securing the components to bone. Metal was paired with polyethylene, a plastic used at joint bearing surfaces, while ceramic became another bearing material. The bearing is the surface that moves against its partner. Fixation is how a component is held in the body; it is a different part of the design (Hip materials and fixation).

A 2007 Lancet review was titled The operation of the century: total hip replacement; its abstract described a major change in the management of arthritis and the contribution of bioengineering to prosthesis development (Lancet hip replacement review).

The review also stressed that immediate goals must not compromise longer-term performance. It described both cemented and uncemented fixation, rather than presenting a single design as the whole story. That combination of material, fixation and follow-up is a more informative historical theme than the idea of an operation reaching a final, perfect form. The guide’s explanation of implants and registries develops those distinctions (Hip replacement review).

The knee and the problem of natural movement

The knee replacement reference describes early hinged designs that did not accommodate the knee’s natural rotation well. Later developments included metal surfaces working with polyethylene components. This illustrates a different aspect of replacement design: the knee has to permit movement while retaining stability. The presence of an artificial bearing alone does not explain how a design behaves through that movement (Knee replacement development).

A Lancet seminar on knee replacement discusses how attention expanded beyond the implant’s shape. It describes implantation methods, avoiding complications and care around the operation as additional areas for improvement. Its argument is that changes in technology need careful regulation and monitoring. This is a discussion of how the field develops, rather than a prediction that a particular technical change will improve any individual person’s result (Knee replacement seminar).

Materials and their limits

Ultra-high-molecular-weight polyethylene is a form of plastic with long molecular chains and resistance to wear. The materials reference describes its use in orthopedic and spinal implants. In the history of joint replacement, plastic is therefore a technical material category, not a description of an implant being insubstantial. Metal, ceramic and plastic can serve different roles within the same kind of operation (Polyethylene materials reference).

The U.S. Food and Drug Administration, or FDA, describes metal-on-metal hip systems as designs in which the ball and socket bearing surfaces are both metal. Its page explains the move to the more stringent premarket approval process for those total hip implants. This is an example of regulatory oversight changing in response to questions about a class of implant, rather than approval ending the need for scrutiny (FDA metal-on-metal hip information).

Stability and motion in the spine

Spinal fusion joins spinal bones so that the fused segment no longer moves. The fusion reference describes bone grafting and, in many techniques, supporting hardware while the bones join. That approach provides the mechanical background for understanding disc replacement: stabilizing a segment and retaining movement at a segment are different aims (Spinal fusion reference).

The disc replacement reference describes early experiments with a metal ball in the disc space and later concepts using moving surfaces within a more complex implant. It also describes the difficulties of settling into the nearby bone and of materials enduring repeated loading. These are historical design problems, not reasons to infer how an unnamed implant in current use will perform (Disc replacement development).

What the approval records establish

The FDA database records the approval decision for the first lumbar artificial disc as October 26, 2004, with its original indication limited to one level from L4–S1 in skeletally mature patients with degenerative disc disease (FDA lumbar approval record; Disc replacement approval history).

The disc replacement reference identifies that lumbar approval as the first in the United States; the database record supplies the original decision and indication rather than a general description of all disc replacements (Disc replacement regulation reference).

The FDA’s cervical artificial disc record gives an approval decision dated July 16, 2007 (FDA cervical approval record).

Both database pages warn that supplements may change a device’s description or indication. An original approval record is therefore a record of a particular decision, not an instruction about treatment. The operation itself is explained in Spinal disc replacement, step by step (FDA explanation of its records).

Learning from use

The American Academy of Orthopaedic Surgeons describes its American Joint Replacement Registry as a collection of hip and knee replacement data used to inform quality and safety work. The National Joint Registry describes monitoring the performance of implants and procedures, supporting research and improving data quality (National Joint Registry purposes). These sources explain why the history continues after a component enters use: performance has to be studied across care settings (American Joint Replacement Registry).

The National Joint Registry’s account emphasizes recording, monitoring, analysis and reporting. These activities add a different kind of evidence to the original approval decision. They are concerned with patterns in joint replacement practice and performance. The About page explains the scope of this guide, while the implant and registry page describes what these sources can and cannot tell a reader (National Joint Registry).