Isolated Polyethylene Wear and Elbow Replacement

Introduction

With the increasingly established reliability and success of total elbow arthroplasty (TEA) over the last 2 decades, indications for the procedure have expanded from rheumatoid arthritis to include the full spectrum of traumatic conditions, including posttraumatic arthritis, distal humeral nonunion, chronic fracture–dislocations, instability, ankylosis, and acute, comminuted, intraarticular fractures in the elderly. TEA for the latter is the most common indication for total elbow replacement today.

Wear of the polyethylene articulating bushings has become increasingly recognized as a cause of failure, especially since the most common indication is for a traumatic condition and since stem loosening is now less of a problem. Hence, increasing longevity, improved function, and expanded indications have resulted in increased use and loading of the involved limb. The presence of severe preexisting deformity in the joint has also been seen as a risk factor for increased wear. Hence, the problem is more likely to occur in younger, more active individuals with significant preexisting deformity.

Because there has been little reported in the literature regarding this problem in other designs, this chapter will focus on our experience with wear in the linked semiconstrained Coonrad-Morrey implant. Our comments in this chapter are primarily based on our study of wear associated with 919 Coonrad-Morrey TEAs performed at the Mayo Clinic.

Clinical and Radiological Features

Pain, crepitus, swelling, and squeaking sounds are the most common presenting features of articular bushing wear. Loss of range of motion is not marked, and symptoms of functional instability are uncommon. In our experience, the patients with posttraumatic arthritis are at greater risk of bushing wear (7 of 294; 2.4%) compared to those with rheumatoid arthritis (5 of 377; 1.4%).

Radiographic assessment before the total elbow replacement is helpful to identify deformity that places the patient at risk. After replacement, plain radiographs are adequate to identify signs of bushing wear, osteolysis, and status of the implant. The criteria for the assessment of wear were described by Ramsey et al. Anteroposterior plain radiographs of the elbow in full extension made following the index arthroplasty and at the time of bushing exchange are compared. The prosthesis was designed with 7 to 10 degrees of varus-valgus laxity. A line is drawn parallel to the yoke of the humeral component, and another line is drawn parallel to the medial or lateral surface of the articular surface of the ulnar component. An angle of intersection of more than 7 degrees between these two lines indicates alteration of the bushing due to wear or plastic deformation. An angle of more than 10 degrees is considered to indicate mild to moderate bushing wear ( Fig. 104.1 ). However, for these criteria to be useful the films should be fluoroscopically centered varus and valgus stress radiographs.