All of the joints are prone to similar complications such as dislocation, prosthetic breakage, periprosthetic fractures, infection, and loosening. It is possible for any nonconstrained implant to dislocate. The diagnosis is usually obvious, but should be confirmed by biplane radiographs, because one view may not clearly show the dislocation (Fig 2.7.2-2.2.). Because many of today's implants are modular (snap together in the operating room), relocation should not be attempted without discussion with an orthopedic surgeon. Disassembly of the prosthesis during attempted closed reduction has been reported. Consent for reduction under anesthesia should be obtained prior to any heavy sedation. It is safest to relocate modular implants under fluoroscopy.
FIG. 272-22. A. and B. This patient's total hip arthroplasty is dislocated. The slight asymmetry on the first view was not detected, and further radiographs were needed to diagnose the dislocation.
Modern alloys have greatly reduced the incidence of prosthetic breakage. More commonly the bone around the prosthesis fractures ( Fig.^.Z.?,-^). Other than making the diagnosis of a periprosthetic or prosthetic fracture the emergency medicine physician will generally not be involved in the treatment of these problems.
Total joint arthroplasty should not be painful. Any time a patient presents with new onset of pain around a prosthesis, loosening of the prosthesis must be suspected. Loosening occurs in two ways: from infection or from the loss of implant fixation. Late loosening is usually characterized by insidious onset of pain and rarely presents to the emergency department. Many criteria for radiographic evidence of loosening have been presented in the orthopedic literature. Radiographic loosening is usually detected as migration of the implant over time with lytic destruction of bone around the prosthesis ( ng.JZi-id).
FIG. 272-24. This right cemented total hip arthroplasty is obviously loose, with associated proximal femoral bone loss.
Infection of a total joint arthroplasty is a catastrophic event. In the first few weeks postoperatively the prosthesis may sometimes be salvaged by immediate surgical debridement and intravenous antibiotics. The most sensitive emergency screening tests are an erythrocyte sedimentation rate or C-reactive protein. Aspiration of any joint should be performed prior to administration of any antibiotics but should never be performed without a surgeon's approval. It is possible for an uninfected implant to be infected by a needle aspiration. Late infections of a prosthesis require removal of a prosthesis to clear the infection.
Some of the most serious complications involving total joint arthroplasties involve the soft tissue structures around the joint. Ligaments holding the joint together can disrupt causing instability of the joint. Tendons that pass around the joint can rupture leading to loss of function of the joint. If diagnosed early they can often be repaired with an excellent result.
COMPLICATIONS OF UPPER EXTREMITY ARTHROPLASTIES The silicone interpositional arthroplasties may fail and create particles that cause an inflammatory response. This is differentiated from an infection by radiographs showing the radiolucent silicone "spacers" and aspiration of fluid for cell count, Gram stain, and culture.
The elbow joint has greater complications than any other commonly replaced joint. Even in the best centers infection rates of 10 percent or greater are not uncommon. This may be due to the thin soft tissue over the posterior elbow. Loosening rates at the elbow are also high due to the need for a constrained prosthesis and limited bone for fixation.
The shoulder's humeral component is extremely durable (Fig 2.7.2.-2.5). The glenoid component with its small bone surface area for fixation is prone to failure.
Dislocation of the shoulder can only be diagnosed with a true anteroposterior and either axillary or transcapular lateral radiograph. Acute loss of motor power may be the result of a rotator cuff tear.
COMPLICATIONS OF LOWER EXTREMITY ARTHROPLASTY Silicone interpositional arthroplasty is also used in the feet, but the failure rates are much higher due to the higher forces. Ankle arthroplasty has had limited success because the small bones of the hind foot do not allow adequate fixation to withstand the high forces placed across the ankle joint.
The knee has excellent inherent ligamentous stability and therefore unconstrained implants ( Fig 2.7.2.-2.6) are usually used today. It is possible for these implants to dislocate; however, it is not as common as in the shoulder or hip. Instability can develop in knee arthroplasties if a ligament is disrupted such as the medial collateral ligament or the posterior cruciate ligament. Diagnosis is by the same examination methods used on nonreplaced knees. Disruption of the quadriceps mechanism is a disastrous complication and must be considered if the patient is unable to straight leg raise. When the patella tendon ruptures, repair rates are extremely poor if not diagnosed and treated early.
FIG. 272-26. A. and B. This patient with osteoarthritis underwent a total knee arthroplasty, with all components cemented.
The hip, like the shoulder, may be addressed by hemi- or total arthroplasty. The acetabulum is usually not replaced in fracture management, but almost always replaced for arthritis. The acetabulum is replaced by a plastic shell that accepts the head of the femoral component. This plastic liner may also be metal backed which allows for bone ingrowth or more even stress transfer when cemented (Fig.272-27). The hip is the most common joint to dislocate. This is confirmed by biplane radiographs and because these prostheses are often modular, great care and often fluoroscopy should be used during relocation. Reattachment of the trochanter after the transtrochanteric approach is usually performed with wire. These wires commonly break during the healing process but are not usually a problem.
FIG. 272-27. This "hybrid" total hip arthroplasty has a cemented femoral component and a noncemented acetabular component that is additionally fixed with screws. BIBLIOGRAPHY
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