Old age has been proposed as a relative contraindication (Sisto et al., 1993). However, in a study based on NJR data (Liddle et al., 2014), we found that elderly patients had particularly good results with UKA. With increasing age, not only did the implant survival increase but also outcome scores and satisfaction improved. Furthermore, the lower morbidity and mortality and quicker recovery of UKA recommend it in the elderly, particularly the unfit elderly. It is therefore surprising that surgeons tend not to do UKA in the elderly: UKA compromises nearly 20% of knee replacements performed in patients in their 50s, but only 5% in octogenarians. This may be because surgeons believe that TKA is the best solution in the elderly, as it is highly unlikely that a revision will be required. However, the same applies to UKA in the elderly, because of the high UKA survival rates and limited life expectancy in this group. We therefore believe that all elderly patients with AMOA who need knee replacement should be treated with a UKA. Furthermore, in the elderly, particularly the unfit elderly, if the indications are borderline we would still do a UKA.
Youth is a recognised contraindication for fixed-bearing prostheses, some of which have proved susceptible to late failure from polyethylene wear, particularly in young active patients (Witvoet et al., 1993). The linear wear rate of polyethylene in congruent mobile bearings is an order of magnitude lower than in fixed bearings (Argenson & O’Connor, 1992; Psychoyios et al., 1998), and failure from wear-through of an Oxford implant has rarely been reported. So, in theory, youth need not be a contraindication for the OUKA.
Youth relative to the average age for joint replacement has been shown in many studies, including the Swedish Knee Arthroplasty Register and the NJR, to increase the risk for revision for both UKA and TKA (Lidgren et al. 2004). Therefore, it is not a good criterion for deciding between the two treatments. If, because of relative youth, the patient is likely to outlive the prosthesis, UKA may still be preferred because it is easier to revise than TKA.
The detailed analysis in the study based on NJR data found that, with decreasing age, not only did the survival rate decrease markedly but also the outcome scores worsened (Liddle et al., 2014). However, in two large prospective series of the OUKA, this effect was not seen. In a combined study based on series from Goodfellow (Murray et al,. 1998) and Svard (Svard & Price, 2001), there were 564 knees of which 52 were less than 60 years of age at the time of surgery (Price et al., 2005). The survival rates of those below and above 60 were not significantly different (91%, CI 12.4 and 96%, CI 3.2 respectively), whereas the clinical scores were significantly better in those less than 60 (HSS 94% CI 3 compared to 86% CI 2). In a series of 1000 Phase 3 knees (Kozinn & Scott, 1989), of which 245 were aged less than 60, there was no significant difference between the survival rates (10-year survival <60 97.3% [CI 91 to 100%]; >60 95.1% [CI 91 to 99%], p=0.63) and the functional outcome was significantly better in those less than 60 (AKSS Function 87.8 [SD 20.2]) to those older than 60 (AKSS Function 82.1 [SD 18.8]). In contrast, Kuipers et al. (2010) found that young age (<60) had a 2.2-fold increased risk of early revision with the same prosthesis. In order to determine the outcome in patients under 50 at the time of surgery, data from seven series were combined (Price et al. 2010). In 107 patients, with mean age 47, the seven year survival was 98% when there were 24 patients at risk.
It is interesting that in some series reported by experienced surgeons, very good results are achieved in younger patients, whereas in the national registries the results are poor in this group. One reason for this may be that some surgeons, who are relatively inexperienced with UKA, mainly use UKA in young patients with early arthritis who may not have bone-on-bone as they know that these patients tend not to do well with TKA. However these patients often do not do well with UKA (Pandit et al., 2011a; Niinimaki et al., 2011). In contrast, we try to use the OUKA only if there is osteoarthritis with bone-on-bone OA even in young patients. In this condition the results tend to be good.
We therefore believe that age need not be a factor in choosing between OUKA and TKA. If the indications for OUKA are fulfilled, with bone-on-bone arthritis, we prefer it at all ages.