Failed Unicompartmental Knee Arthroplasty Research Articles

Early failure of the porous coated anatomic cemented unicompartmental knee arthroplasty: Aids to diagnosis and revision

Unicompartmental knee arthroplasty (UKA) is performed less frequently than total (tricompartmental) knee arthroplasty (TKA). This study examined the range of presenting symptoms and usefulness of diagnostic tests to determine the failure mode; the outcome of surgical revision of failed UKA is also reported. From a consecutive prospective series of 43 Porous Coated Anatomic (Howmedica, Rutherford, NJ) UKAs performed between 1985 and 1992 and followed for an average of 64 months, 12 cases have come to revision surgery (28%). The average time to failure was 37 months. Symptoms preceded revision surgery by an average of 10 months. The most common presenting symptom was pain (100%), followed by swelling (92%), reduced range of motion (42%), instability (42%), and clicking (17%). Failure was caused by polyethylene wear in 50%, loosening of the femoral component in 42%, and progression of patellofemoral arthritis in one patient. The combination of single leg standing anteroposterior radiographs and supine lateral radiographs detected most causes of UKA failure. A bone scan was confirmatory in every case of suspected loosening of the femoral component. Arthroscopy diagnosed polyethylene wear in two cases and progression of joint arthritis in one case and was not helpful in one case. Revision surgery was done with primary TKA components, and follow-up periods averaged 27 months. Bone stock deficiency was found in 58%, but required bone-grafting in only one case. Revision surgery successfully restored pain-free function and range of motion in all cases. Two-year postrevision Hospital for Special Surgery scores are equal to those for primary TKA. Survivorship analysis showed a 33% failure rate at 57 months after Porous Coated Anatomic UKA when revision was the endpoint and a 41% failure rate when unsatisfactory clinical status was the endpoint. Regular follow-up evaluation is suggested for the Porous Coated Anatomic UKA.

Conversion of failed modern unicompartmental arthroplasty to total knee arthroplasty

Between January 1983 and January 1991, 29 patients (31 knees) with a failed Robert Brigham metal-backed knee arthroplasty (Johnson & Johnson, Raynham, MA) underwent revision to a total knee arthroplasty (TKA). Twenty-five patients had osteoarthritis, three avascular necrosis, and one rheumatoid arthritis. The average patient age was 72.3 years (range, 49–88 years), and the average weight was 179 lb. (range, 112–242 lb.). The interval between the primary and secondary index procedures averaged 62 months (range, 7–106 months), and mean postrevision follow-up period was 45 months (range, 24–104 months). The primary mechanism of failure of the UKA was tibial polyethylene wear in 21 knees and opposite compartment progression of arthritis in 10 knees. Sixteen knees had particulate synovitis with dense metallic staining of the synovium. At revision, the posterior cruciate ligament was spared in 30 knees and substituted in 1 knee. Restoration of bony deficiency at revision required cancellous bone—graft for contained defects in seven knees, tibial wedges in four knees, and femoral wedges in two knees. No defects received structural allografts. The data suggest that failed, modern unicompartmental knee arthroplasty can successfully be converted to TKA. In most cases, the posterior cruciate ligament can be spared and bone defects corrected with simple wedges or cancellous grafts. Moreover, the results of revision of failed unicompartmental knee arthroplasty are superior to those of failed TKA and failed high tibial osteotomy and comparable to the authors' results of primary TKA with similar-length follow-up periods. Although these results are encouraging, longer-term follow-up evaluation is required to determine survivorship of these revision arthroplasties.

Prothèses unicompartimentales — Conclusions de la Table Ronde Réponses aux questions posées

Unicompartmental knee arthroplasty (UKA) is an excellent operation provided the technique is properly applied and the indication is well established. Obesity (weight > 100 kg, or BMI > 32) is a contraindication. The shape of the femoral prosthetic condyle is a cause of loosening in the medium and long term. There is an important difference between medial UKA and lateral UKA. Indications are different and they correspond to different types of patients. UKA is not an alternative to osteotomy; it is in competition with both osteotomy and total knee prostheses and has its own indications. UKA without cement is possible provided sufficient primary stability is achieved. This appears difficult to achieve at the femoral level. The patella poses no problems provided the unicompartmental prosthesis is fitted correctly. The absence of anterior cruciate ligament, together with clinical or radiological anteroposterior laxity, is a contraindication to UKA. The average lifetime of a unicompartmental prosthesis is 8–10 years; lateral prostheses have a longer lifetime. Failure of UKA implies reoperation with conversion to the total knee prosthesis. Hypercorrection by lateral UKA is undesirable. In contrast, there is no objection to hypercorrection of less than 5° by medial UKA. After medial UKA, the recurrence of a varus deformity is possible only if lateral laxity has not been controlled or if one of the prosthetic components is displaced. UKA is not indicated if patellar surgery is required. Hypocorrection by lateral UKA is desirable. Medially, the residual varus should not exceed 5°. In medium and long-term failures, most complications affect the tibia (loosening, polyethylene wear).

Revision technique for failed unicompartmental knee arthroplasty

The main objective is to fit a total tricompartmental knee prosthesis. Conserving the ligaments and preserving the healthy bone are therefore the two main requirements. The surgical approach is, in most cases, parapatellar anteriorly and medially except in certain specific cases (lateral UKA). Total synovectomy is always necessary. The condition of the posterior cruciate ligament (PCL) should be evaluated with great precision, as this will indicate the type of revision prosthesis to be used. Bone cuts will be performed with the unicompartmental prosthesis in place. Bone grafts or filling blocks are rarely used; they are most often used in revising cemented unicompartmental knee prostheses.