Abstract
Introduction
Unicompartmental knee arthroplasty (UKA) is becoming an increasingly popular option in single compartment osteoarthritis. As a result, diverse re-operations including revisions to total knee arthroplasty (TKA) has also increase. The objective of this study is to investigate the distribution of causes of re-operations after UKA and to analyze the types of re-operations.
Method
We retrospectively reviewed 691 UKAs performed on 595 patients between January 2003 and December 2011. Except in one case, all UKAs were performed for medial compartment osteoarthritis of the knee. The UKAs were performed in 487 (81.8%) women and 108 (18.2%) men. The mean age at the time of UKA was 61.5 years (47 to 88 years). Mobile-bearing designs were implanted in 627 (90.7%) knees (626- Oxford knee and 1- Scorpio knee) and fixed designs were implanted in 64 (9.3%) knees (42- Tornier and 18- Zimmer). The mean interval between UKA and second operation was 15.4 months (10 days to 10 years) and between second and third operation was 7.7 months (5 weeks to 17 months). In the re-operation group, there were 50 knees (48 patients) with 38 female and 10 male patients.
Results
In our study, the burden of a re-operation after the initial UKA was 8.7%with, the total number of re-operation of 60. There was 50 cases of second operations (n = 45 mobile, n = 5 fixed), and 10 cases of second re-operation. The most common cause of a second re- operation after a mobile-bearing UKA was the dislocation of the meniscal bearing (32%), followed by component loosening (20%), the formation of a cement loose body (14%), unexplained pain (12%), infection (6%), periprosthetic fracture (4%), and others (2%). For the fixed-bearing UKA, the causes of a second operation were loosening (4%), unexplained pain (4%), and bearing wear (2%). 10 cases required a 3rd operation at mean time interval of 7.7 months, of them 7 cases (70%) had liner exchange at their 2nd operation.
Discussion and conclusion
The most common cause of a second re-operation after a mobile-bearing UKA was the dislocation of the bearing, followed by component loosening and the formation of a cement loose body. After a fixed-bearing UKA, component loosening and unexplained pain were the most common causes of re-operation. In cases which underwent a third operation, 70 percent had liner exchange with or without some minor procedure at the time of the 2ndoperation. All were converted to TKA at their 3rd operation at a mean time interval of only 7.7 months. Based on our observations, we recommend a cause-based approach to the management of primary and failed UKA to help minimize the possibility of second and third operations. Furthermore caution should be undertaken when contemplating liner exchange as treatment option in cases involving mobile-bearing UKA.
