Data from the Australian Joint Register suggests that the revision rate for cruciate retaining [CR] prosthesis is less than for cruciate sacrificing prosthesis[PS]. We have analysed data from the NZOA joint register to see if this is the case in NZ.

Data for all PS and CR knee replacements in NZ between 1999 and 2004, and any subsequent revisions were analysed and the results compared with the AOA registry data [2008]. There were 3808 PS knees and 7152 CR knees on the AOA register, with a seven year revision rate of 3.3% and 2.1% respectively p=.002. On the NZOA register there were 1869 PS knees and 5749 CR knees, with a five year revision rate of 1.55% and 1.39% respectively p=.608

This aspect of prosthesis design did not influence the revision rate at five years.

Polyethylene wear and osteolysis continue to be associated with failure of total hip arthroplasty. The advent of highly cross linked polyethylene may potentially reduce such wear.

The aim of this study was to compare the rate of wear of acetabular polyethylene using conventional cross linked versus highly cross linked polyethylene.

From June 2001 to September 2003, 119 patients were followed prospectively for up to five years on an annual basis in a double blinded, randomised trial. The mean age of patients was 59 years (range 48 to 75 yrs). The radiographs have been analyzed using previously validated measurement software to assess linear, three dimensional and volumetric wear.

The five year results show significantly reduced wear rates for highly cross linked polyethylene compared to conventional polyethylene. There was no statistically significant difference between groups with respect to age, sex, operative side, surgeon, cup abduction angle, cup anteversion or size of cup.

The reduction in wear shown after five years with the highly cross linked polyethylene is highly encouraging and is consistent with in vitro wear simulator testing. This may reduce failure of total hip arthroplasties due to wear and osteolysis over the medium to long term.

Revision of a failed femoral component in the face of extensive bone loss is a major challenge. When the bone loss extends down below the isthmus it may be difficult to obtain longitudinal stability with a tapered or fully porous coated prosthesis. If subsidence occurs then recurrent dislocation can be an insoluble problem. This study reviews the use of a distally interlocked femoral component designed to address this challenging situation.

We have reviewed 21 cases in which extensive bone loss made the use of an interlocking prosthesis desirable. The average time from surgery was over four years. All patients completed an Oxford hip score and an EO-50. All radiographs were reviewed.

There were 14 males and seven females with an overall average age of 74 years at the time of surgery. Patients had had an average of two previous THR’s, and up to nine previous hip operations. One patient underwent re-revision because of subsidence related to screw cut out. There was one dislocation. Patient satisfaction was high with low Oxford hip scores compared with other revision prostheses, and good EO – 50 ratings.

This type of prosthesis offers a very satisfactory solution to difficult revision situations when bone loss makes the use of regular prostheses difficult. The prosthesis used in this study has a low offset and thus dislocation precautions should be emphasised.

We have performed an RCT of cross-linked versus non cross-linked polyethylene with 125 patients followed for five years. The study showed a dramatic reduction of wear with the cross-linked polyethylene consistent with the in-vitro studies. Because it has been recognised that hard bearings are sensitive to edge loading we were concerned that highly cross-linked polyethylene might exhibit wear properties similar to hard bearings. We have therefore analysed the wear rate as it relates to both anteversion and tilt, to compare non cross-linked polyethylene with cross-linked polyethylene. We found that there was no relationship between tilt and ante-version on any wear indices. These data suggest that, despite having different mechanical properties to non cross-linked polyethylene, cross-linked polyethylene does not exhibit increased wear with conditions that increase edge loading.

The treatment of supracondylar humeral fractures in children continues to evolve. The currently fashionable treatment for displaced fractures is closed reduction and the insertion of at least two K-wires. This usually requires the patient to have a second surgery to remove the K-wires, and may result in significant scarring. The senior author has used the straight arm method to treat displaced supracondylar fractures. We have reviewed the long term results of seven children treated by the straight arm method. No patient had a scar, no patient had a cubitus varus and all children regained a full range of movement. This method offers excellent results with no risk of iatrogenic nerve injury, scarring, or second surgery.

Single stage bilateral total knee replacement is an uncommon and often controversial procedure. Some authors have reported significant complications. We have reviewed our experience with the procedure in 40 cases.

Forty patients undergoing simultaneous bilateral total knee replacement with a minimum follow up of two years were reviewed. Thirty of the patients completed an Oxford Knee score and an EQ-5D. Eight patients were lost to follow up. Two were deceased.

The age at the time of surgery ranged from 25–87 years – mean 68yrs. 8o% were done under general anaesthetic. 50% required blood transfusion in the post operative period, the average volume being 4 units. 50% had physiotherapy following discharge. There were 4 patients with delay in wound healing and 1 patient who had an infection requiring wound debridement. There were no other significant complications. The mean Oxford Knee score was 21.6, the mean score for primary unilateral knee arthroplasty for patients on the National Joint Register is 23.5. The EQ-5D scores were very satisfactory.

This study demonstrates that in our unit this procedure can be performed with minimum complications and the expectation of an excellent outcome.

We analysed factors affecting the rate of recovery from ankle fractures. Delays in return to normal functioning may relate to poorer quality and duration of sleep during recovery.

This prospective study investigates the relationship between the rate of recovery from ankle fracture and sleep disturbance, comparing ankle fractures classified using AO-Danis-Weber Classification – types A, B & C treated at Wellington Hospital, aged between 18 and 55 years. From June 2003 to October 2004 participants completed an ankle fracture questionnaire, and a general health profile at three, six and twelve months post-injury. A randomly selected subgroup was interviewed to identify specific recovery issues.

Six percent were Weber A, 56% B and 39%, C. Mean (and standard deviation) for return to normal functioning was; 5 (2); 8 (3) and 8 (7) weeks respectively, overall range – 2 to 24 weeks. Those who returned in 2 weeks had sedentary jobs, worked from home or were students, all with a high level of support by ACC. Physically demanding occupations delayed return to work. After one year, (93%) scored 85 – 90% satisfaction with their ankle performance. 97% scored highly on the SF 36, indicating positive life attitudes. 98% reported no change from their pre-fracture sleep patterns.

Rate of recovery is less predictable and sometimes more prolonged for Weber C than for A and B ankle fractures. Earlier return to work is a function of practical support in the workplace and positive health attitudes including balanced sleep patterns. Work planning and workplace assessment are significant factors.

The aim was to investigate whether or not the pre-operative injection of cortico-steroids into the knee influences the infection rate of a subsequent total knee replacement.

This was a case controlled study, in which it was calculated that 152 controls and 38 infected cases would give sufficient power to the study. The infection group had to have had a delay in wound healing or have had a revision for infection.

A total of 32.8% had had an injection at some time pre-operatively. The average number of injections was 2.23, with a range of 1–15. 37% were performed by a G.P., 35% by an orthopaedic surgeon, and 22% by a rheumatologist.79% had the injection within 12 months of surgery. The rate of injection was the same in the two groups. There was no significant difference in the infection rate between the two groups (OR 1.38; 95%CI 0.55–3.31)

Despite recent literature indicating that there is a 10% increase in infection in patients having steroid injections into the hip prior to THR this study does not confirm this risk in patients undergoing TKR.

The aim was to determine how periprosthetic hip and knee infection and subsequent revision impact on patient lifestyle and function. While the literature abounds with studies of outcomes of revision surgery for prosthetic infection, few studies address functional outcome and patient-based outcome measures.

This retrospective study examined a consecutive series of revision total knee and hip arthroplasties performed for infection between 1996 and 2002 by surgeons at Wellington Hospital. Eight knees and ten hips were treated with a two-stage exchange using antibiotic spacer and IV antibiotics. Two knee and seven hip patients underwent direct exchange procedures.

In 90% of knees and 65% of hips Infection was successfully eradicated after one revision. One (10%) knee and eight (47%) hips required further intervention of either surgery or antibiotic therapy. Mean Oxford Scores for knees and hips were 29.6 and 29.5 respectively. Oxford scores following revision for infection were slightly higher compared with scores following the primary procedure, indicating poorer functional outcome. EuroQol-5D responses indicated a lower level of function than that of a general population sample, with problems in the areas of mobility, usual activities, and pain/discomfort, most apparent.

While functional outcome is intrinsically related to both the amount of destruction caused by infection and the eradication of infection, absence of re-revision in itself cannot be equated with functional success. Although TKA/THA revision is a technically challenging orthopaedic procedure, patients do attain favourable results. Surgical revision of a prosthetic joint implant for infection can be associated with reasonable function and satisfaction scores.

To assess if highly cross-linked polyethylene is associated with less linear wear than ultra high molecular weight polyethylene in vivo.

To assess whether alteration in biomechanical characteristics of the reconstructed hip influence’s wear patterns.

A randomised prospective trial comparing conventional polyethylene with highly cross-linked polyethylene in an acetabular component was designed. Identical cemented stems were used in all cases, with a metal head. The polyethylene thickness was controlled. The trial design required 124 cases to be entered to give the study sufficient power to determine any difference in wear rates. Polyware Auto was used to assess 2D wear rate and volume.

This paper presents the preliminary results of the early patients entered into the study and looks at both 2D wear or creep at 18 months post operatively, and seeks to establish any relationships between 2D movement and biomechanical characteristics of the reconstructed hip.

There was no significant difference in the 2D wear (or creep) between the two types of polyethylene at 18 months. There was no correlation between femoral offset, cup offset, or centre of rotation offset and 2D wear (or creep).

This preliminary data shows no difference in the early wear rate of the two types of polyethylene. This is in contrast to an in vitro wear simulator study that has shown more creep in highly cross-linked polyethylene. The significance of this observation is unclear. We hope to demonstrate that as the trial progresses any difference in the performance of the two types of polyethylene should be evident.

To review the results of revision THR performed with a modular titanium tapered uncemented stem in two cohorts of patients to assess whether subsidence of this type of stem is avoidable through improved surgical technique.

The first 70 patients undergoing revision THR with this type of stem were compared with 38 patients who had their revision in the last 24 months and had a minium follow up of 12 months., with particular reference to stem subsidence. All patients were also assessed with the Oxford Hip Score. All radiographs were reviewed to measure subsidence. Identical post-operative management was used in both groups.

The mean subsidence in the first group was 11.7 mm and in the most recent group 4mm. The Oxford Hip Score in both groups was similar (20.9) which compares very favourably with the OHS score from the National joint Register for revision arthroplasty (24.3).

This comparison shows that changes in surgical technique can limit the subsidence seen with tapered stems used in revision total hip replacement. No bone grafts were used in either series, only small changes in bone preparation, and prosthesis selection were used .The outcome as determined by the OHS was similar in both groups.

The aim was to review patients that had single stage bilateral total hip joint replacements (SSBTHJR) of two surgeons in the Wellington area, to assess symptomatic relief and overall quality of life before and after surgery. To also review xrays of this population to assess acetabular component orientation.

Fifty patients from two hospitals, with minimum follow up of two years, who had SSBTHJR, were reviewed for duration of stay, time to mobilisation, and complications (eg. wound infections, venous thrombus and embolism (VTE), gastrointestinal ileus, and cardiac events). Patient opinions on hip joint function (Oxford Hip Score) and overall quality of life (EQ-5D Score) were performed (37/50 patients could participate). Patient’s postoperative radiographs were analysed with Polyware Auto Version 6.00 to measure acetabular cup orientation for both sides.

Oxford Hip Score mean was 20.5 (range 12 – 56), compared to the national mean 19.3. The median score was 14. Most patients (65%) had no symptoms of pain, difficulty in mobilising, or performing activities of daily living (ADL). 19% of patients had mild to moderate symptoms/difficulty, and 16% had significant pain/difficulty On average, using a visual analogue scale, patients felt their health was 42% better after having their surgery. Complication rates were minimal, and were primarily superficial wound infections. Hip acetabular cup positioning analysis was performed (statistical analysis pending).

Patients undergoing SSBTHJR have comparable results for Oxford Hip Scores compared to unilateral THJR patients, improved lifestyle, but not increased complications.

Introduction and Aims: Single-stage bilateral total knee arthroplasty is an uncommon and often controversial procedure. Recent reports have refined the data relative to bilateral total knee arthroplasty and complications, which include myocardial infarction, deep vein thrombosis, pulmonary embolus and death.

Method: A retrospective study of the cases of total knee arthroplasty performed by the senior authors in the last 10 years examines details of surgery and anaesthesia, pre- and post-operative management to identify the occurrence of complications. Patients also completed an Oxford Knee Score and a questionnaire relating to their experience of having a bilateral procedure.

Results: While the outcomes and cost benefits of single-stage bilateral replacement are established, the risk of complications remains. This study establishes the low complication rate associated with this procedure in the senior author’s hands and documents the high patient satisfaction from it.

Conclusion: The study demonstrates that, in selected patients, simultaneous bilateral knee replacement surgery can be performed with good outcomes without a definite increase in peri-operative risk.

Single-stage bilateral total knee arthroplasty is an uncommon and often controversial procedure. Recent reports have refined the data relative to bilateral total knee arthroplasty and complications which include myocardial infarction, deep vein thrombosis, pulmonary embolus and death. Less significant complications, including post-operative ileus and pseudo-obstruction are also more common following bilateral replacement.

A retrospective study of the cases of total knee arthroplasty performed by the senior authors in the last ten years, examines details of surgery and anaesthesia, pre and post-operative management to identify the occurrence of complications. Patients also completed an Oxford Knee Score and a questionnaire relating to their experience of having a bilateral procedure.

While the outcomes and cost benefits of single stage bilateral replacement are established, the risk of complications remains. This study establishes the low complication rate associated with this procedure in the senior authors’ hands, and documents the high patient satisfaction from it.

The study demonstrates that, in selected patients, simultaneous bilateral knee replacement surgery can be performed with good outcomes without a definite increase in perioperative risk.