title: Mid-term equivalent survival of medial and lateral unicondylar knee replacement: an analysis of data from a National Joint Registry.
abstract: Current analysis of unicondylar knee replacements   (UKRs) by national registries is based on the pooled results of medial   and lateral implants. Consequently, little is known about the differential   performance of medial and lateral replacements and the influence   of each implant type within these pooled analyses. Using data from   the National Joint Registry for England and Wales (NJR) we aimed   to determine the proportion of UKRs implanted on the lateral side   of the knee, and their survival and reason for failure compared   with medial UKRs. By combining information on the side of operation   with component details held on the NJR, we were able to determine   implant laterality (medial versus lateral) for   32 847 of the 35 624 unicondylar replacements (92%) registered before   December 2010. Of these, 2052 (6%) were inserted on the lateral   side of the knee. The rates of survival at five years were 93.1%   (95% confidence interval (CI) 92.7 to 93.5) for medial and 93.0%   (95% CI 91.1 to 94.9) for lateral UKRs (p = 0.49). The rates of   failure remained equivalent after adjusting for patient age, gender,   American Society of Anesthesiologists (ASA) grade, indication for   surgery and implant design using Cox's proportional hazards method   (hazard ratio for lateral relative to medial replacement = 0.88   (95% CI 0.69 to 1.13); p = 0.32). Aseptic loosening/lysis and unexplained   pain were the main reasons for revision in both groups, although   the reasons did vary depending on whether a mobile- or a fixed-bearing   design was used. At a maximum of eight years the mid-term survival   rates of medial and lateral UKRs are similar.
authors.affiliation: Institute of Cellular Medicine, University of Newcastle upon Tyne, Newcastle upon Tyne NE3 4XE, UK. drpnbaker@hotmail.com
authors.forename: P N
authors.initials: PN
authors.lastname: Baker
authors.forename: S S
authors.initials: SS
authors.lastname: Jameson
authors.forename: D J
authors.initials: DJ
authors.lastname: Deehan
authors.forename: P J
authors.initials: PJ
authors.lastname: Gregg
authors.forename: M
authors.initials: M
authors.lastname: Porter
authors.forename: K
authors.initials: K
authors.lastname: Tucker
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D004739:England; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure / Q000209:etiology*; D012042:Registries; D012086:Reoperation; D016019:Survival Analysis; D014852:Wales; D055815:Young Adult