The minimally invasive technique recommended by the designers in the implantation of the OXF UKA make for a demanding procedure: most recorded failures are of a technical nature and occur within the first 2-years of implantation. Also, data from the Swedish and NZ National Joint Registries (NJR) show clearly that revision rates and surgeon experience are inversely related. To present some technical points, using illustrative cases, where implantation has been associated with suboptimal outcome, or has lead to re-operation. To offer solutions for these potential problems In 2004, data from the NZ NJR allowed analysis of all failures of OXF UKA leading to revision. The case notes and x-rays (where available) were studied (Hartnett et al, NZOA ASM, 2004). Clinical records of personal cases performed over 8 years up till July 2008 have also been studied and provide the illustrative cases. On the tibial side, mismatch between the length of the keel on the tibial component and the bony slot created for it can cause the tibial component to be too posteriorally-sited. Also, if too much cement is used, posterior protrusion of cement may be difficult to detect at operation. The combination of these two may cause symptoms postero-medially. Ways of preventing these problems are outlined. On the femoral side, NZJR records that aseptic loosening of the femoral component is a prominent cause of failure of OXF UKA. A number of techniques to improve cement intrusion can be implemented and are outlined. A case study of the only such encountered describes the possibility that the femoral intramedullary guide rod can inadvertently be driven into the femoral canal by knee motion during operation: this remained undetected until shown on the x-ray taken after operation. Simple modifications of technique can minimise the chance of suboptimal outcome after OXF UKA surgery.
A previous audit of New Zealand Joint Registry data showed that, overall, OXF UKA had over three times the seven–year revision rate (RR) compared with TKA. Where the RR was calculated for surgeons performing one or more OXF UKA per month, however, the RR was comparable to that for all–surgeon TKA (Hartnett et al, NZOA ASM, 2007). To audit and compare revisions of OXF UKA and TKA performed by one surgeon, as recorded in the New Zealand National Joint Registry, and to highlight a complication of OKF UKA unreported in the literature. The data from a personal series of 177 consecutive medial Oxford (Phase three) cemented UKAs entered in the Registry from January 2000 to December 2007 was analysed. The number and reasons for revision of the cohort was compared with a similar personal cohort of 229 consecutive cemented TKAs performed over the same period. Comparison was also made between this personal data with that for all surgeons recorded in the Registry. OXF UKAs were performed at a mean rate of 1.8 procedures per month. The prime indication was antero-medial osteoarthritis: valgus stress x-rays performed routinely had to establish adequate thickness of lateral articular cartilage and ACL had to be competent before the UKA was preferred to TKA. Fifty six (31.6%) of the 177 operations were performed as part of bilateral procedures under the one anaesthetic. Two OXF UKAs were revised to TKA. In neither was there failure of fixation or integrity of the prosthesis: one case was revised for unexplained pain where OXF UKA was for post–traumatic medial OA. The 2nd revision followed recurrent haemarthrosis and subsequent joint destruction: arteriography found no arterial injury. The RR for personal OXF UKA was therefore 1.1%, which compares with personal TKA RR of 2.2% (difference not significant p=0.42). The RR for all OXF UKAs in NZ was 5.6%, and that for TKA was 1.8%. The difference between personal and national RR for OXF UKA is significant (p=0.010), and that for TKA is not (p=0.63). Since 2000, two other revisions of OXF UKA outside the studied cohort both followed recurrent haemarthrosis causing joint destruction. The results of OXF UKA reported here confirm that an early revision rate comparable to TKA is achievable when this surgery is performed relatively frequently by the surgeon. Recurrent haemarthrosis occurring later after early successful OXF UKA surgery is not recorded in the English literature. It has been the most frequent reason for revision (three of four revisions).
To identify frequency and patterns of Oxford Phase 3 Unicompartmental Knee Arthroplasty (UKA) failure in New Zealand through analysis of national primary and revision data. Compare the results of this data with that of total knee arthroplasty and other international joint registers. Retrospective audit examining all Oxford Phase 3 UKAs recorded in the New Zealand National Joint Register from January 2000 to December 2007 were analysed and then statistic al analysis performed to identify patterns of failure and reasons for revision. Two thousand six hundred and twenty Oxford UKAs were performed by 99 Orthopædic Surgeons. The average age was 66.1 years (range 35–94). Osteoarthritis was the primary diagnosis. Mean time to revision 839 days (2.3 years). Revision rate was 5.6% (n=148). The most common reasons for revision were pain (n=61, 41%), aseptic loosening (n=53, 36%), and bearing dislocation (n=16, 11%). Deep infection rate was 0.26% (7/2620) compared with 1.76% of total knee arthroplasties (564/32029). Six surgeons (high use &
#8805;10 UKAs/year) performed 699 (26.7%) operations, revision rate 2.6%. Fifty-five surgeons (low use &
#8804; two UKA/year) performed 283 (10.8%) operations, revision rate 10.6%. There was a statistically significant difference seen with an inverse relationship between surgeon experience and revision. The revision rate for the Oxford is three, two times greater than TKA. UKA is now decreasing in New Zealand whilst Total Knee Arthroplasty (TKA) continues to increase. The number of is now decreasing in New Zealand whilst Total Knee Arthroplasty (TKA) continues to increase. The number of surgeons using Oxford UKA has increased by 19% but the number of Oxfords being done has fallen by 13%. High use surgeons’ revision rate is now higher than TKA. An inverse relationship between failure and surgeon experience exists which confirms Swedish Knee Arthroplasty register reports. The deep infection rate is less than TKA. Revisions were performed early for unexplained pain in the absence of obvious mechanical failure. This is against generally held wisdom for TKA and may reflect the perception that UKA is easily revised to TKA.
The purpose of this study was to identify causes of failure and rates of revision of the Oxford prosthesis (OXF) in New Zealand, by reviewing and comparing the uni-compartmental (UKA) and total knee arthroplasty (TKA) data from January 2000 to December 2005, as recorded in the New Zealand National Joint Registry. Eighty one orthopaedic surgeons performed 2006 Oxford UKAs (64% of all UKAs). The revision rate was 4.7%. This compared with a revision rate of 4.8% for all UKAs combined, and 1.6% for TKA. UKA (3122) made up 13% of all knee arthroplasties (24 260). The most common reasons for revision of the OXF were aseptic loosening (45%), unexplained pain (33%) and bearing dislocation (12%). Unexplained pain as the only reason for revision (33%) was significantly different (p = 0.001) from the TKA rate (23%). Deep infection as a cause for revision was 0.20% for the OXF compared with 0.48% for TKA (p=0.07). The patient- generated Oxford scores at six months after operation were rated excellent or very good (Field et al, 2004) in 68% of OXF compared with 62% TKA patients (p = 0.001). Five higher-use OXF surgeons (12 or more/year) performed 25.1% of the operations with a revision rate of 0.99%. Ten high- use surgeons (eight to 11/year) performed 28.1 % of operations with a revision rate 4.6%. Thirty medium-use surgeons (two to seven/year) performed 39.0% of the operations with a revision rate of 6.4%. Thirty-six low-use surgeons (one or less/ year) performed 7.8% of the operations with a revision rate of 8.3%. The difference in revision rate between the higher-use surgeons (one operation/month) and all the other three lower use groups was significant (e.g. p=0.0006 higher/low) The early revision rate for the OXF was 2.9 times greater than that for TKA. However, higher-use surgeons (i.e. those performing one/month or more) had a revision rate comparable to TKA. Deep infection was lower and six month function scores were higher for OXF compared with TKA. Unexplained pain as the only reason for revision was significantly higher for OXF compared with TKA.
The aim was to identify frequency and pattern of early UKR failure in New Zealand. We analysed data from the New Zealand National Joint Register in a 44 month period of 2000–2003. Thirty-five percent of the 1790 registered UKRs were performed in the last 8 months [ie. in 18% of the total time period]. The ratio of UKRs to TKRs performed was 1:6.25. Fifty two revisions meant a failure rate of 2.9% for UKR (n=1790) compared with 1.6% for TKR (n=11243). The most commonly used implants were the Oxford P3 (68% of total with 2.2% revision rate), MG uni (14.6% with 4.6% revision rate) and Preservation (7% with 5.6 revision rate). The most common reasons for revision (n=52) were aseptic loosening (28%), bearing dislocation or impingement (19%), and unexplained pain (13%). The deep sepsis rate for UKR was 0.33% compared to 0.43% for TKR. UKR usage is rapidly increasing in NZ. The revision rate for UKR was 1.8 x that for TKR. The revision rate for deep sepsis was 77% that for TKR. Unexplained pain in apparently technically normal UKR was the 3rd most common reason for revision. Bearing impingement was as common as bearing dislocation as a cause for failure in the Oxford P3 UKR. Early polythene wear was the reason for revision only in the 8mm MG prosthesis.
To identify frequency and patterns of Oxford Phase 3 UKA failure in New Zealand through analysis of national primary and revision data. Retrospective audit examining all revision Oxford Phase 3 UKAs recorded in the New Zealand National Joint Register from January 2000 to October 2003 were analysed along with surgeons’ clinical notes and patient x-rays. Seventy-three Orthopædic Surgeons performed 1216 Oxford UKAs. The average age was 66.4 years (range 35–94). Osteoarthritis was the primary diagnosis for 1163 (96%) patients. Mean time to revision was 437 days (14.4 months). The early revision rate was 2.2% (n=27). The most common reasons for revision were aseptic loosening (n=7, 26%), bearing dislocation (n=5, 19%) and pain (n=4, 15%). The deep infection rate was 0.16% (2/1216). Eighteen surgeons (high use >
8 UKAs/year) performed 787 (64%) operations, with a revision rate of 1.5%. Twenty-two surgeons (low use ≤ 1 UKA/year) performed 38 (3%) operations, with a revision rate of 8%. This was statistically significant, p= 0.03 (odds ratio 5.7). The early revision rate for the Oxford UKA is 1.4 times greater than TKA. High use surgeons revision rate is lower than TKA. An inverse relationship between failure and surgeon experience exists. This confirms Swedish Knee Arthroplasty Register findings.
The aim was to compare anterior knee pain (AKP) felt before, and after hamstrings (HS, n = 65) and bone-patellar tendon- bone [B-PT-B, n = 94] ACL reconstructions. The same questionnaire (modified from Shelbourne et al 1997) was answered by patients before, and at least 12 months after surgery. Questions covered five main categories of pain ie. during prolonged sitting, stair climbing, kneeling, sport or vigorous activity, and ADL. There was no statistical difference in the two groups in overall AKP scores before surgery. After surgery, there were improvements in this overall score in both groups, but the improvement was statistically greater in the HS group (p = 0.02). Analysis of the five different pain categories showed no significant difference in the improvements in sitting, sport or ADL. In both climbing stairs (p = 0.009), and kneeling (p = 0.02) there were significantly greater improvements in the HS group. The majority of patients had AKP before surgery. Surgery improved pain levels in both HS and B-PT-B groups, but there was statistically significant greater improvements in overall AKP scores, and the scores for climbing stairs and kneeling in the HS group.
