Over the years, the indications and contraindications for the Oxford Knee used medially have become more clearly defined. The main indication is AMOA although Spontaneous Osteonecrosis of the Knee (SONK) is also a good but rare indication. The key criteria that need to be satisfied to make the diagnosis of AMOA is that there is bone-on-bone medial OA, the ACL is functionally intact, there is full thickness cartilage laterally and the intra-articular deformity is correctable, but not over correctable, indicating that the MCL is functionally normal. If a patient has severe symptoms, if these criteria are satisfied and there are no general contraindications for arthroplasty, then an Oxford Knee is indicated. All the specific contraindications for UKA defined by Kozinn and Scott (1989), and others, do not apply. In particular, patient age, activity level and obesity are not contraindications; nor are site of pain, the state of the PFJ (except for severe lateral OA), chondrocalcinosis or lateral osteophytes. The indications for the Oxford Knee are satisfied in about 50% of knees needing replacement. However, when surgeons start using the Oxford, they are often concerned about ignoring the Kozinn and Scott contraindications, particularly the PFJ, so their usage is lower. With time and development of confidence, usage tends to increase.
In the published or presented series of the Phase 3 Oxford Knee with 10 year results which together include about six thousand patients, the survival is about 95% (Murray et al., 2013). The surgeons involved tended to adhere to the recommended indications and use the Oxford Knee in at least 20% and commonly 50% of their knee replacements. In contrast, the National Registers report a ten-year survival of about 85%. The main reason for the high failure rate in the National Registers is that most surgeons do very small numbers. In the UK, the commonest number of UKA done by surgeons doing this procedure is one per year and the average is about five per year (Liddle et al., 2014). Analysis of NJR data showed that the survival rate was lowest among surgeons doing small numbers and increases as surgeon numbers increased. It is suggested that surgeons should perform more than 12 per year to achieve results comparable to those of the high volume operators. The only way surgeons can easily increase their numbers of UKA is to increase the proportion of their knee replacements that are UKA. Analysis of NJR data would suggest that to get good results, surgeons should do at least 20% and ideally 50% of their knee replacements as OUKA. If surgeons want to use the Oxford Knee, they should therefore adhere to the recommended indications and ignore the unnecessary contraindications. They will then do at least 20% of their knees as Oxfords and should achieve good results.
Purpose of this book
The main aim of this book is to advise surgeons on the choice of patients appropriate for treatment with OUKA (Chapters 4 and 5), and to guide them on the performance of the operation (Chapters 6 and 7) and the management of complications (Chapter 11). In addition we have chapters about the design of the OUKA (Chapter 2), knee kinematics (Chapter 3), post-operative management (Chapter 9), and results (Chapter 10). We also have chapters about the rare medial indications (Chapter 8) and lateral OUKA (Chapter 12).
The reader may wish to view the website for this book, where there are animations of the surgical technique and videos of the operation:
