Polyethylene Failure and Aseptic Loosening

Revision should be performed for symptomatic patients with synovitis and radiographic evidence of loosening or osteolysis, assuming they are medically fit for surgery. Aseptic loosening typically is a mid- to late-term complication of total elbow arthroplasty. Loosening of the implants usually causes pain. Some patients do not experience pain, however, until late in the process. Progression to the point where revision becomes more difficult may be prevented by routine annual followup, including clinical examination and radiographs, for the life of the prosthesis. Synovitis and grossly abnormal articulation are detectable by physical examination. Range of motion at the elbow may not be affected. Patients who are at greatest risk for aseptic loosening include males; young patients (<60 years); those with a high activity level; patients with posttraumatic arthritis; and those with component malpositioning, missing condyles, and severe deformity. Radiographic evidence of loosening includes a localized area of osteolysis, commonly observed at the distal end of a failed precoated ulnar component. Anterior impingement of the anterior flange of the humeral component on a prominent coronoid process has also resulted in loosening from ulnar component pistoning ( Fig. 22-1 ).

A 49-year-old female with aseptic loosening of her TEA that was placed for posttraumatic arthritis. A: Lateral radiograph demonstrating loosening of the ulnar component associated with an uncontained bone deficiency. B: Anteroposterior preoperative radiograph. Lateral (C) and anteroposterior (D) postoperative radiographs. The ulnar prosthesis was revised to a longer implant and the bone defect was addressed with an allograft strut.

Aseptic loosening may result from primary failure at the bone–cement interface or secondary to osteolysis from particulate debris. Particulate debris is most commonly generated by polyethylene wear but also by a loose cement mantle. Linked prostheses with bearing surfaces coated with a thin layer of polyethylene have been associated more frequently with particulate debris. Most linked prostheses are designed with a “sloppy hinge,” which subjects the polyethylene to shear forces. This is typically a progressive process and the increased movement causes acceleration of wear. Eventually, with significant wear, metal-on-metal wear occurs and can lead to catastrophic failure. Appropriate clinical and radiographic monitoring may allow early detection of bushing wear. Bushing exchange for patients with polyethylene wear but stable implants may prevent future osteolysis and loosening.

Asymptomatic patients with radiographic evidence of loosening should be monitored closely. Although these patients may not report any pain, early revision is recommended to preserve remaining bone stock. Progressive resorption may weaken the bone and predispose the patient to fracture.

A symptomatic TEA that is loose or has significant or progressive osteolysis has no good alternative to revision. An asymptomatic patient with a loose implant and no detectable osteolysis is rare and may be treated with close observation. Excision arthroplasty is the last resort for a young patient with a high activity level or for one with associated severe bone loss or inadequate soft tissue coverage.

Cancellous impaction grafting is indicated when simple reimplantation is precluded by expanded cortical bone with smooth endosteal surfaces. This technique relies on dense impaction of a fine mush of cancellous bone into the lytic segment. The prosthesis is then cemented within the cancellous bone. For the procedure to be successful, the terminal end of the implant must also have solid fixation in adequate (3 cm) undamaged cortical bone ( Fig. 22-2 ).

A patient with loosening of the ulnar component and a large contained defect of the proximal ulna. A preoperative anteroposterior (A) and lateral (B) radiographs demonstrating the loosening and subsidence of the ulnar prosthesis. Anteroposterior (C) and lateral (D) postoperative radiographs after revision to a longer stem using an impaction bone grafting technique for fixation.

Cortical strut grafting is used to reinforce thin osteolytic cortices, impending or actual periprosthetic fractures, deficiency of the triceps attachment, and augmentation of expanded segments filled with impaction graft. This is particularly useful in reconstruction of the olecranon.

Gross Instability of the Articulation

Patients who have instability with an unlinked prosthesis may be functionally impaired. Soft tissue reconstruction of an unstable TEA is associated with a high rate of failure. Revision of the malpositioned components or conversion to a linked prosthesis is often indicated. Instability may also occur with linked designs in the context of early polyethylene wear and loosening. Semi-constrained prostheses have some built-in laxity and stress radiographs may be necessary to quantify the degree of movement as the bushing may be entirely worn.

Late failure of the locking mechanism in semi-constrained total elbow prosthesis has also been described. This condition is considered a catastrophic failure and necessitates revision ( Figs. 22-3 and 22-4 ).

Lateral radiograph of an elbow with a Coonrad-Morrey total elbow prosthesis (Zimmer, Warsaw, IN) with failed linking mechanism as a result of polyethylene wear and subsequent C-ring failure. In the version of this prosthesis currently in use, the C-ring has been updated to a snap pin, which appears to have decreased this type of catastrophic failure.

(From Wright TW, Hastings H II: Total elbow arthroplasty failure due to overuse, C-ring failure, and/or bushing wear. J Shoulder Elbow Surg 14:65–72, 2005.)

A: Schematic drawing of a Coonrad-Morrey TEA. B: Schematic drawing showing the initiation of wear associated with varus–valgus and probably rotatory loading. C: Schematic drawing showing progression of wear. D: Schematic drawing showing progression of wear to the point where there is now metal contact and the creation of metal debris is initiated. E: Schematic drawing showing C-ring failure. This occurs as bushing wear allows the prosthesis to move in a greater varus–valgus arc, resulting in medial and lateral displacement of the pin that overloads the C-ring and causes it to pop off. Metal contact may or may not occur before the C-ring failure.

(Adapted from Wright TW, Hastings H II: Total elbow arthroplasty failure due to overuse, C-ring failure, and/or bushing wear. J Shoulder Elbow Surg 14:65–72, 2005.)

Periprosthetic Fracture with a Loose Prosthesis

The rate of periprosthetic fracture in the literature ranges from 5% to 22% and may increase as more TEAs are performed. Management is dependent on the type of implant, location of the fracture, stability of the implants, and timing of the fracture.

Intraoperative fractures may occur during bone preparation, implant insertion, or extremity positioning and typically involve the condyles or epicondyles of the humerus or olecranon process of the ulna. Management depends on the stability of the implant. If a linked prosthesis is used, then excision of displaced fractures of the condyles with soft tissue reconstruction to the triceps may be performed. Fractures involving an unlinked implant should be fixed because the collateral ligaments are required for joint stability. Internal fixation should be performed on all olecranon fractures, even if nondisplaced, to preserve the extensor mechanism.

Fractures of the humeral shaft that occur during positioning are often spiral in nature. Ulna fractures can occur during preparation or implant insertion. Both of these fractures compromise implant stability and should be treated with a longer stem that extends the distance of two cortical diameters beyond the fracture and cerclage wires to stabilize the bone. If bone quality is marginal, then strut allograft augmentation should be used. If there is significant intramedullary bone loss, then cancellous impaction bone grafting should be considered.

Periprosthetic fractures that occur postoperatively are typically traumatic in mechanism and often associated with implant loosening. Fractures of the humeral condyles are usually well tolerated and can be managed nonoperatively, except with an unlinked prosthesis where stability is more dependent on the collateral ligaments. In this case, internal fixation or revision to a linked prosthesis is indicated. Fractures proximal to the humeral prosthesis and distal to the end of the ulnar prosthesis are often treated nonoperatively if the implants remain stable; however, some recommend fixation to avoid deformity that may complicate future revision.

Surgery is not required for periprosthetic fractures if neither the implant stability nor the extremity is compromised. In this situation, closed treatment and activity modification may suffice and are tailored to the location and extent of the fracture.

Implant fractures in total elbow arthroplasty are uncommon. They occur as a result of component design, notch sensitivity, or high stresses as a result of bone deficiency. Techniques such as cement-within-cement reimplantation have shown to be reliable in relieving pain and restoring function; however, the rate of complications is a cause for concern.

Joint Sepsis

Infection of a TEA is a catastrophic complication that has reported rates of 1.5% to 11%. Treatment options include the following: (1) irrigation and debridement with staged reimplantation (most common); (2) irrigation and debridement with retention of the prosthesis; (3) single-stage revision arthroplasty; and (4) resection arthroplasty.

Primary considerations when deliberating treatment options for an infected TEA must include the functional capacity, health status, and expectations of the patient. In a younger patient the maintenance of function is important. Such an individual will also be more likely to have the reserve to withstand multiple operations. If consideration is given to preservation of the original implants, then several surgeries typically will be required and there is a high risk of failure and complications. Patients may have medical comorbidities that preclude such a treatment plan. Particular attention must be paid to patients taking immunosuppressive medications and patients who have poor nutrition or anemia of chronic disease. With these patients the goal of surgery may only be to clear infection and provide pain relief. This can often be achieved with a resection arthroplasty.

The likelihood of eradication of the infection varies with the organism. Coagulase-negative (staphylococcus epidermidis) and Coagulase-positive staphylococci (S. aureus) are particularly problematic. S. epidermidis produces a biofilm, a polysaccharide glycocalyx that envelopes the bacteria, and thereby facilitates adherence and colonization of these bacteria by protecting them from the host immune system. Implant retention with S. epidermidis is challenging and may not be recommended. Similarly, infection with any antibiotic-resistant organism precludes prosthetic retention. S. aureus is virulent, with the capacity to invade healthy tissue, but is less likely to form a biofilm.

Assessment of both component fixation and bone quality is critical in planning a revision for a septic TEA. High-quality radiographs must be obtained and compared to previous studies. Poor fixation is evident by radiolucent lines, osteolysis, and cortical erosions. A patient with a well-fixed prosthesis may be a candidate for retention with irrigation and debridement, depending on the infecting organism. Poorly fixed prostheses must be removed, typically followed by attempted staged reimplantation. Severe bone loss may preclude reconstruction, and a resection arthroplasty may be required.

The duration of symptoms must be clarified. If symptoms have been present for less than 30 days, then retention of the implant may be considered for infection with antibiotic-sensitive organisms. Multiple debridements may be required to achieve success in this setting.

Revision of an infected TEA requiring multiple debridements may compromise an already-fragile soft tissue envelope. If primary closure is not going to be possible, then a coverage procedure must be performed. Alternatively, the shortening of bone in a resection arthroplasty may be sufficient to allow for coverage.