To ascertain whether there is any relationship between the Oxford 12 scores gained six months post surgery and early revision for primary hip and knee arthroplasty.

The six month post surgery Oxford 12 scores were retrieved from the National Joint Registry (NJR) for the seven year period ending 31^st December 2006. These were analysed in relation to revision of primary hip and knee procedures using three methods of statistical analysis; logistic regression, receiver operating characteristic (ROC) curve and direct plotting of groups of scores against the proportion of hips revised for that same group.

Logistic regression: For every one unit increase in the Oxford score there was an 11% increased risk of revision (hips) and 12% (knees) within the first two years of surgery, 5 and 6% respectively between two and four years and 3 and 4% risk respectively between four and six years (p> 0.001).

The ROC Curve Analysis: demonstrated that a patient with a score greater than 20 (hips) or 28.5 (knees) or 24 (uni knees) has eight times the risk of needing a revision within two years compared to a person with a score equal or less than the above numbers. Alternatively the ROC analysis predicted 73% of the revisions within three years for all three arthroplasty groups.

Plotting Scores Against Revisions: Plotting scores in groups of five demonstrated an incremental increase in the risk during the first two years. A person with a score greater than 40 has; for hips 24 times, knees 27 times and uni knees 69 times the risk of a revision within two years compared to a person with a score between 16 and 20.

Monitoring of the six month post surgical Oxford 12 score is another tool in the surgeon’s armamentarium for deciding which patients need closer monitoring following arthroplasty 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.

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 purpose of this study was to evaluate the results of simultaneous bilateral total hip and total knee arthroplasty performed in New Zealand during the first five years of the New Zealand National Joint Register and to determine whether this was an acceptable practice.

All total knee and total hip arthroplasties collected on the National Joint Register between 1999 and 2003 were divided into three groups – unilateral joint arthroplasty, staged bilateral joint arthroplasty and simultaneous joint arthroplasty. The Oxford 12 questionnaire results at six months were assessed as well as the patients self reported complications. All deaths that occurred within 6 months of the surgery were also recorded.

Analysis between the three groups was then performed using ANOVA tables comparing age, the Oxford scores and complications.

There was generally a significant difference (p< .001) in age between unilateral hip and knee replacement and staged or simultaneous bilateral replacement, with patients undergoing bilateral simultaneous replacement being younger.

There was a significant difference (p< .001) in the Oxford 12 scores between unilateral hip and knee replacement and both staged and simultaneous bilateral hip and knee replacement, with the bilateral simultaneous replacements scoring the best.

The death rate within the first 6 months was low in all groups with only 1 patient dying within 3 months of the surgery from an unrelated cause. The complication rate was low in all groups, in particular the DVT and pulmonary embolus rate, as reported by the patients, was not increased in either the sequential staged group or the simultaneous bilateral group.

The New Zealand National Joint Register has proven to be a valuable tool in gaining early information regarding the outcome following bilateral and staged lower limb total joint arthroplasty. The results clearly show that in the appropriate clinical situation performing simultaneous bilateral total knee or total hip arthroplasty is a safe and effective procedure.

Aim: To measure the percentage increase in length of the donor graft during rehabilitation from 0 degrees to 120 degrees of elbow flexion and to compare this with the end range strength.

Method: During the troids procedure four metal skin-clips were inserted at the proximal and distal margins of the proximal and distal tibialis posterior tendon weaves creating three intervals for measurement. Lateral x-rays of the humerus with the tube distance at 100cms were taken after five weeks of plaster immobilisation before elbow flexion commenced at a maximum rate of 15 degrees per week. X-rays were repeated when 60 degrees and 120 degrees of flexion obtained and when possible six months post surgery. Elbow torque was measured by the Troidometer throughout the range of motion at similar time intervals. Interval measurement was by a Vidar VRX 12 digital scanner. The Paired T test was used for statistical analysis.

Results: Sixteen arms (nine patients) were entered into the study but complete rehabilitation data were available from only 12 arms and late data from only four. There was a 12.3% average increase between 0 degrees and 60 degrees (range six to 20.6 degrees) and a further 3% increase from 60 degrees to 120 degrees (range −6 degrees to 21 degrees). The most stretch occurred in the distal segment and in bilateral arms the percentage of stretch was similar for each arm. There was no correlation between the percentage of stretch and end range torque or lag.

Conclusions: The Troids transfer restores elbow extension for tetraplegics but an extensor lag often develops which is thought to be from stretching of the donor tendon graft. This study confirmed that tendon stretch occurs but there was wide variation among individuals although similar for each arm in bilateral procedures. An average of 75% of stretch occurred during the 0 degrees to 60 degrees mobilisation. We concluded that tendon stretch is inevitable but is not a major contributor to end range weakness or lag.

Aim: To develop a database of the force generated by brachioradialis muscle (BR) using IEMG.

Methods: The 32 BR muscles of 12 young male and four young female adults were studied using the MedTronic functional diagnostics key point EMG machine. Two self adhesive surface electrodes were placed 3mm apart over the BR belly and a third earth electrode over the radial styloid process. The subject’s arm was at the side of the trunk, the elbow flexed to 90 degrees and the forearm strapped in neutral rotation. Recordings were taken over a five-second voluntary maximum isometric elbow flexion and the force of the contraction measured from the rectified and integrated tracing (mv.ms). Four recordings were taken for each arm; wrist in neutral and at maximum passive flexion, with a two-minute rest between recordings. Recordings were repeated after minimum of 24 hours later.

Results: There was large inter-subject variability with a range of values recorded between 14 685 and 278 533 mv.ms with an average of 99 472 for the wrist in neutral and 93 038 with the wrist flexed in males and 53 292 and 57 224 respectively for females. However, intra-subject variability was low (co-efficient of variation, CV 8 to 11%) and good repeatability (CV 6 to13%). There was no significant statistical difference with the wrist either in neutral or fully flexed.

Conclusions: BR is the key muscle for hand reconstruction in tetraplegia but it has not been possible until now to test its force objectively in isolation from other elbow flexors. Although the results from the study demonstrated a wide range of values for the BR muscle the consistent repeatability probably reflected different involvement of the BR muscle in elbow flexion. If verified, it would indicate that tetraplegics who have low IEMG values should benefit from specific strengthening exercises prior to transfer surgery.