Patients with severe joint pain and disability may undergo joint replacement. Conditions contributing to joint degeneration in-clude osteoarthritis (degenerative joint disease), rheumatoid arthritis, trauma, and congenital deformity. Some fractures (eg, femoral neck fracture) may cause disruption of the blood supply and subsequent avascular necrosis; management with joint re-placement may be elected over ORIF. Joints frequently replaced include the hip, knee (Fig. 67-6), and finger joints. Less frequently, more complex joints (shoulder, elbow, wrist, ankle) are replaced. The procedure is usually an elective one.
Most joint replacements consist of metal and high-density polyethylene components. Finger prostheses are usually Silastic. The joint implants may be cemented in the prepared bone with polymethyl methacrylate (PMMA), a bone-bonding agent that has properties similar to bone. Loosening of the prosthesis due to cement–bone interface failure is a common reason for prosthesis failure. Press-fit, ingrowth prostheses (porous-coated, cementless artificial joint components) that allow the patient’s bone to grow into and securely fix the prosthesis in the bone are alternatives to cemented prostheses. Accurate fitting and the presence of healthy bone with adequate blood supply are important in the use of ce-mentless components. Much progress has been made in reducing prosthesis failure rate through improved techniques, improved materials, and use of bone grafts.
With joint replacement, excellent pain relief is obtained in most patients. Return of motion and function depends on pre-operative soft tissue condition, soft tissue reactions, and general muscle strength. Early failure of joint replacement is associated with excessive activity and preoperative joint and bone pathology.
Assessment of the patient and preoperative management are aimed at having the patient in optimal health at the time of surgery. Pre-operatively, it is important to evaluate cardiovascular, respiratory, renal, and hepatic functions. Age, obesity, preoperative leg edema, history of DVT, and varicose veins increase the risk of post-operative DVT and pulmonary embolism. These are the most com-mon causes of postoperative mortality for patients older than 60 years of age undergoing total hip replacement. Every effort is made to prevent these complications.
Preoperatively, it is important to assess the neurovascular sta-tus of the extremity undergoing joint replacement. Postoperative assessment data are compared with preoperative assessment data to identify changes and deficits. For example, an absent pulse postoperatively is of concern unless the pulse was also absent pre-operatively. Nerve palsy could occur as a result of surgery.
Preoperative assessment of the patient for infections, including urinary tract infection, is necessary because of the risk of post-operative infection. Any infection 2 to 4 weeks before planned surgery may result in postponement of surgery. Preoperative skin preparation frequently begins 1 or 2 days before the surgery. Air-borne bacteria that contaminate the wound at the time of surgery cause most deep infections. Therefore, as with any surgery, there is strict adherence to aseptic principles and the operating area is controlled and made as bacteria free as possible.
Prophylactic antibiotics are administered perioperatively as a single preoperative or short perioperative course (Rosen et al., 1999). Culture of the joint during surgery, before intraoperative antibiotic therapy is begun, may be important in identifying and treating subsequent infections.
If osteomyelitis develops, it is difficult to treat. Persistent in-fection at the site of the prosthesis usually requires removal of the implant and joint revision, which is a complex procedure. Also, it is not always possible to achieve a functional joint when the re-construction procedure has to be repeated.
Patients with total hip or total knee replacement begin ambu-lation with a walker or crutches within a day after surgery. The nurse and the physical therapist assist the patient in achieving the goal of independent ambulation. At first, the patient may only be able to stand for a brief period because of orthostatic hypoten-sion. Specific weight-bearing limits on the prosthesis are deter-mined by the physician and are based on the patient’s condition, the procedure, and the fixation method. Usually, patients with cemented prostheses can proceed to weight bearing as tolerated. If the patient has a press-fit, cementless, ingrowth prosthesis, weight bearing immediately after surgery may be limited to min-imize micromotion of the prosthesis in the bone. As the patient is able tolerate more activity, the nurse encourages transferring to a chair several times a day for short periods and walking for pro-gressively greater distances.