Purpose of the study: Knee pain can be a problem after unicompartmental arthroplasty, compromising the long-term outcome. Arthroscopy may be useful to treat some of the causes such as cement extrusion, fibrous interposition between prosthetic elements, meniscal regeneration, hypertrophic synovitis, or arthroscopic degeneration. We evaluated the results of these procedures.
Material and methods: Seven patients, mean age of 75 years (range 70-79), underwent knee arthroscopy. These patients were among a series of 214 unicompartmental knee prostheses implanted from 1988 to 2005. Arthroscopy was undertaken because of persistent pain after prosthesis implantation. Repeated physical examinations, X-rays and laboratory work-ups were negative for infection or mechanical anomaly. Medical treatment was attempted. The delay before recourse to arthroscopy was 16.3 months (range 9-36 months). The series was composed of five women and two men.
Results: Arthroscopy after unicompartmental prosthesis enabled the discovery of chondral, meniscal, and synovial lesions which had not been diagnosed with the usual imaging and laboratory tests. Meniscal regeneration, neomeniscus, and fibrous interpositions were observed. Biopsies were obtained. The arthroscopic procedures performed were: regularization of degenerative contralateral menisci, resection of neomenisci, and synovectomy. Arthroscopic treatment by washout shaving of the cartilage lesions and regularization of the meniscal lesions provided good results. Outcome was scored excellent or good in five knees, and insufficient in two due to progressive degeneration. For one of these two knees, the non-prosthesis femorotibial compartment progressed to overt degeneration. The IKS knee score improved 13 points in the seven patients and the function score 20 points at one to five years follow-up.
Discussion: Arthroscopy after unicompartmental prosthesis for knee pain can give good results for unexplained pain, both in terms of diagnosis and in terms of etiological treatment. In certain knees, diagnostic arthroscopy can enable identification of the cause of pain after unicompartmental prosthesis. Therapeutic arthroscopy avoids repeated arthrotomy and shortens recovery time.