Prosthetic Joint Replacement
Harry E. Figgie III
Total joint arthroplasty consists of resecting a damaged joint and replacing the articulating surfaces with prosthetic components. The convex side is usually a titanium alloy or a chrome–cobalt alloy that articulates with a concave surface made of high-density polyethylene. The polyethylene component is usually reinforced by a metal tray, which consists of titanium or chrome cobalt alloy. Traditionally, polymethylmethacrylate bone cement has been used as a grout between the implant and the bone. This material provides fixation by filling the irregular interstices of the bone and closely contacting the prosthetic surfaces. Recent prosthetic designs and technology have allowed the prosthesis to be attached to the bone without cement.
Resection arthroplasty consists of excision of the damaged joint for pain relief or control of infection. Stability and motion are achieved by the scar tissue that grows between the bone ends.
Interposition arthroplasty consists of excision of the damaged joint and interposition of a biologic or foreign nonarticular material between two bones. Commonly interposed materials include fascia, muscle, or silicone spacers. Relief of pain is the primary goal. Motion and stability are variable, depending on the joint involved and the material used.
Arthrodesis or fusion is obtained by denuding the articular cartilage and shaping the subchondral bone to maximize bone-to-bone contact. The process of fusion is similar to the healing of a fracture. When solid bony fusion is achieved, no motion is possible.
The optimal artificial joint must allow for a stable, painfree, functional arc of motion. Additionally, its expected longevity should be adequate with regard to material properties and security of fixation. In general, the performance of the more common types of joint replacement is superior to that of resection arthroplasty, interposition arthroplasty, or arthrodesis.
ARTHRODESIS. In arthrodesis, the elimination of joint motion places abnormal stress on the joint above and below the fusion and on the contralateral extremity. In addition, arthrodesis may be difficult to achieve when metaphyseal bone loss is present. Fusion is used predominantly in the ankle, wrist, and hip and as salvage for a failed arthroplasty of the knee.
Resection arthroplasty or interpositional arthroplasty provides unpredictable pain relief, motion, and stability. It has been virtually abandoned in the knee and hip, except in salvage procedures, and is used most commonly in the wrist, carpometacarpal joint of the thumb, metacarpophalangeal joints of the hands, and metatarsophalangeal joints of the feet.
Total joint replacement usually provides a stable, painfree, functional arc of motion. Joint replacements of the hip and knee provide the most predictable results and have demonstrated adequate performance for more than 10 years. A small percentage of patients will require reoperation after 10 years, usually for loosening of prosthetic fixation.
INDICATIONS FOR TOTAL JOINT REPLACEMENT
Indications for total joint replacement are severe, unremitting pain with loss of joint function and radiographic evidence of articular damage. The degree of joint dysfunction is evaluated by using one of the several quantitative scoring systems with numeric grades for preoperative pain, motion, stability, and activity levels. Postoperatively, the same system can be used to evaluate the degree and the durability of improvement.
CONTRAINDICATIONS TO TOTAL JOINT REPLACEMENT
I. ABSOLUTE CONTRAINDICATIONS
Active local or remote sepsis.
II. RELATIVE CONTRAINDICATIONS
Neurologic disorders, including hemiparesis, parkinsonism, and Charcot joint.
Severe loss of bone stock.
Poor soft-tissue coverage.
Multiple revision procedures.
Systemic illness precluding elective surgery.