At the end of 2018, the NZ Joint Registry introduced a “Surgeon Outlier” policy, whereby each year, if an individual surgeons’ lower 95% confidence interval of their revision rate, measured in revision/100 component years(r/ocys), was above the NZ mean (0.71 r/ocys), that surgeon was required to audit their results with a nominated peer. This study investigates whether outlier surgeons also have high early (1 month and 1 year) revision rates.

In 2018, 236 surgeons performed 9,186 total hip arthroplasties in NZ. At the end of 2018, 11 surgeons received notification they were outliers. Results from all surgeons for years 2016, 2017 and 2018 were combined to form the first (pre-notification) time interval, and results from years 2019, 2020 and 2021 were combined to form the second time interval (post-notification). Outlier surgeons performed 2001 total hip replacements in the first time interval and 1947 hips in the second. Early revision rates (1 month and 1 year) of both outlier and nonoutlier surgeons for both time intervals were analysed.

Non-outlier surgeons had a consistent mean early revision rate of 0.75% at one month and 1.6% at one year for both time intervals. The 11 outlier surgeons had a higher earlier revision rate of 1.35% at one month and 2.45% at one year for the pre-notification time interval. These values reduced for the post-notification time interval to a revision rate of 1.23% for one month and 2.36% for one year.

Poor joint registry results of individual surgeons are often attributed to a poor choice of prosthesis. This study shows early revision rates of outlier surgeons, where prosthesis selection has minimal influence, are also high.

A slight improvement in early revision rates of outlier surgeons since introduction of the policy shows it is working.

The Oxford hip score (OHS) at 6 months and five years of less than 27 has previously been reported as having a 5.2% chance of requiring revision of their total hip arthroplasty (THA) within 2 years. We determined whether the OHS obtained at 10 years after surgery would be a suitable screening tool in lieu of clinic visits to detect patients requiring closer monitoring.

We reviewed data from the NZ Joint Registry between January 1999 and December 2016. OHS at 10 years was available for 5,165 non-revised THA patients. Patients were separated into four categories based on their OHS: 3,483 (67%) scored 42–48, 1,023 (20%) scored 34–41, 373 (7%) scored 27–33, and 286 (5%) scored 0–26.

For patients with a 6-month OHS, revision risk within 2 years was 1.3% in the 42–48 group, 2.5% in the 34–41 group, 4.6% in the 27–33 group, and 10.2 % in the 0–27 group. If only patients with a grading of 33 or less were offered clinical follow-up, 659/5165 patients (12.7%) would require evaluation and of these, 46/659 (7%) could be expected to require revision within two years. Of those patients with an OHS > 34 not evaluated, only a small number, 72/4506 (1.6%), might require a revision.

The OHS at 10 years of patients with a THA who have a grading less than 27 is a much stronger predictor of revision than OHS at 6 months or 5 years. Use of the 10 year OHS as a screening tool for THA requires evaluation of only one in eight patients, with the chance of missing 1 in 63 patients not followed up who might require a revision.

Total hip joint replacement (THJR) for high riding congenital hip dislocation (CDH) is often performed in young patients, and presents unique problems with acetabular cup placement and leg length inequality.

A database and the NZ Joint Registry were used to identify 76 hips in 57 patients with a diagnosis of CDH who underwent THJR in the Wellington region between 1994 and 2015. Records and radiographs of 46 hips in 36 patients classified pre-operatively as Crowe II, III or IV were reviewed. Surgical technique used a direct lateral approach, the uncemented acetabular component was located in the anatomic hip center and a primary femoral stem was used in all but one hip. Whether a step-cut sub-trochanteric femoral osteotomy was performed depended on degree of correction, tension on the sciatic nerve, and restoration of leg length.

For the 36 patients classified as Crowe II or higher, the average age at operation was 44 years (26 – 66), female:male ratio was 4.5:1 and follow-up averaged 10 years (2 – 22.3). Of the 15 hips classified as Crowe IV, 10 required a step-cut sub-trochanteric femoral osteotomy to shorten the femur, but 5 were lengthened without undo tension on the sciatic nerve. Nine Crowe IV hips received a conventional proximally coated tapered primary femoral component. Oxford hip scores for 76% of patients was excellent (> 41/48), and 24% had good scores (34 – 41). All femoral osteotomies healed. Five hips have been revised, one at 2 years for femoral loosening, one at 5 years for dislocation, two at 12 years for liner exchanges, and one at 21 years for femoral loosening.

THJR using primary prostheses for CDH can provide durable long-term results.

Objectives

Our study aimed to examine not only the incidence but also the impact of noise from two types of total hip replacement articulations: ceramic-on-ceramic and ceramic-on-polyethylene.

Objectives

Our study aimed to examine if a mobile-bearing total knee replacement (TKR) offered an advantage over fixed-bearing designs with respect to rates of secondary resurfacing of the patella in knees in which it was initially left unresurfaced.

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.

The aim was to assess the wear rate of highly Cross Linked (X3) polyethylene with the use of 36mm femoral heads in total hip arthroplasty (THA). We have previously reported our early results and raised some concern regarding the potential excessive femoral head penetration rates. These results give the 2 year wear rates following this initial bedding-in phase.

There were 100 consecutive patients who had a THA with the same femoral and acetabular components using a 36mm femoral head and X3 polyethylene that were assessed prospectively. Validated computer software (Polyware) was used to assess linear and 3 dimensional wear using standardised x-rays. Examinations were performed at 2,12,18 and 24 months.

There were 40 hips that had completed the 2 year x-ray examination (average 2.4 years). The mean 2-dimensional linear wear rate was 0.17 mm/yr and the mean volumetric wear rate was 113.73 mm3/yr. Steady state wear was achieved after the 2 month and before the 1 year examination. The steady state wear rate was 0.001mm/yr. There was no difference in wear rate with the different sized cups used and wear rate was independent of liner thickness.

The early high wear rates reported have now settled into a more expected pattern of steady state wear similar to other results presented in literature with the use of smaller femoral heads. Using a 36 mm femoral head has not adversely increased the wear rates compared to smaller head sizes when used in conjunction with X3 polyethylene in the short term for THA. These results suggest that the wear rate of X3 is not compromised even with thinner liners and raise the possibility of safely using even larger head sizes with this polyethylene.

Acoustic emission is an uncommon but well-recognised phenomenon following total-hip arthroplasty using hard-on-hard bearing surfaces. The incidence of squeak has been reported between 1% – 10%. The squeak can be problematic enough to warrant revision surgery. Several theories have been proposed, but the cause of squeak remains unknown. Acoustic analysis shows squeak results from forced vibrations that may come from movement between the liner and shell. A potential cause for this movement is deformation of the shell during insertion.

6 cadaver hemipelvises were prepared to accept ace-tabular components. A shell was selected and pre-insertion the inner shape was measured using a profilometer. The shell was implanted and re-measured. 2x screws were then placed and the shells re-measured. The results were assessed for deformation.

Deformation of the shells occurred in 5 of the 6 hemi-pelvises following insertion. The hemipelvis of the non-deformed shell fractured during insertion. Following screw insertion no further shell deformation occurred.

The deformation was beyond the acceptable standards of a morse taper which may allow movement between components, and this may produce an acoustic emission. Further in-vitro testing is being conducted to see whether shell deformation allows movement producing an acoustic emission.

Introduction: We aimed to assess a simple radiological method of predicting redisplacement of paediatric forearm fractures. The Cast Index (CI) is the ratio of sagittal to coronal width from the inside edges of the cast at the fracture site. A CI of > 0.7 was used as the standard in predicting fracture redisplacement. The cast index has previously been validated in an experimental study.

Methods: Case records and radiographs of 1001 children who underwent a manipulation under general anaesthesia for a displaced fracture of the distal forearm were studied. Redisplacement was defined as more than 15 degrees of angulation and/or more than 80 percent of translational displacement on check radiographs at 2 weeks. Angulation (in degrees) and translation displacement (in percentage) were measured on the initial and check radiographs. The CI was measured on postoperative radiographs.

Results: Fracture redisplacement was seen in 107 cases at 2 week follow up. Of the 752 patients (75%) with a CI of less than 0.7 the displacement rate was 5.58%. Of the 249 patients (25%) with a CI greater than 0.7 the redisplacement rate was 26%. The CI was significantly higher in the redisplacement group. No statistically significant difference was seen for age, sex or ethnicity. Nor were statistical differences noted in initial angular deformity, initial displacement and seniority of the surgeon. Good intra and inter observer reproducibility was observed. There was no statistical difference in patients with a cast index between 0.7 and 0.8.

Conclusion: The cast index is a simple and reliable radiographic measurement to predict the redisplacement of forearm fractures in children. Previous studies have used a CI of > 0.7 as the predictor of redisplacement although this study suggests a plaster with a CI of < 0.81 is acceptable. A high cast index is associated with redisplacement of fractures and should therefore be considered when moulding casts in distal forearm fractures.

Measurement of polyethylene (PE) wear in total hip joint replacement (THJR) is performed by measuring change in the position of the femoral head on post-operative radiographs. Early methods used manual measurement with calipers and concentric circles, while more recent techniques involve the use of computer assisted technology. RSA, while mainly used for measuring component migration, can also be used for measurement of PE wear. The aim of this paper is to describe two new methods for measuring PE wear;

A completely automated measurement (which eliminates user error and is 100% reproducible).

For the Automated Measurement Technique (AMT), software has been developed which locates the centre of the acetabular cup and femoral head on both the anteroposterior and lateral radiographs. No user input is required. Accuracy is ± 0.16 mm. Clinically, it has been used in a double-blinded randomized controlled trial (RCT) comparing conventional with cross-linked PE. For the Model Matching Technique (MMT), two pieces of software are combined, Ray-Tracing technology (used in the generation of animated movies), and the Genetic Algorithm (a branch of Artificial Intelligence). CAD models of an acetabular cup and femoral head are matched to post-operative films to position them in 3D space. Change in position of these models over time represents PE wear. CAD models of the patients’ pelvis and femur (built from CT scans) can be similarly used to measure femoral and acetabular component migration.

The AMT was used to measure the PE wear of 116 patients enrolled in a prospective RCT comparing conventional and cross-linked PE. At a follow-up of two to four years, cross-linked PE showed statistic ally significant lower PE wear than the conventional material. A cadaver pelvis and femur has been used to analyse accuracy of the MMT for measurement of component migration. Preliminary results show an accuracy of ± 0.22mm for component migration. The accuracy of PE wear measurement appears to be significantly less than this.

The development of new bearing surfaces to reduce wear in THJR requires new techniques of in-vivo wear measurement. These two new techniques should give important information on the performance of new bearings, and possibly allow measurement of clinical component migration without the need for bead implantation.

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.

The early results with highly cross-linked polyethylene have been encouraging and have increased the ability to use larger head diameters to improve the range of motion and decrease the dislocation rate, the commonest cause of early complications following total hip arthroplasty (THA). Wear rates with 32 mls heads have been satisfactory however there have been very few independent studies looking at early polyethylene wear in 36 mm heads. This study assessed the rate of polyethylene wear of a 36mm ceramic femoral head and a highly cross-linked polyethylene (X3 Stryker) liner in THA.

This prospective study reviewed 100 consecutive THAs in young patients (mean age 58 years) who had undergone THA with the same 36mm ceramic femoral head and highly cross linked polyethylene liner. All patients received the same femoral stem (ABG, Stryker) and acetabular cup (Trident, Stryker). Two surgeons performed all procedures. Patients were assessed radiologically immediately postoperatively, at 10 weeks and at one year. Validated computer software (Polyware) was used to assess both volumetric and linear wear.

At one year the mean two-dimensional linear wear rate was 0.51 mm/yr. Mean three-dimensional linear vector wear rate was 0.59 mls per year with a mean volumetric wear rate of 322.6 mms per three years. Cup size ranged from 52–62 mms and the correlation coefficient between cup size and three-dimensional linear wear rate was −0.100. The correlation coefficient between cup size and volumetric wear rate was −0.009 confirming no significant correlation between cup size and wear.

Larger size femoral heads are associated with a higher volumetric wear compared to linear wear rate when using conventional polyethylene. This study demonstrated much higher early linear wear rates compared to other studies using 28 and 32 mms heads. This higher rate may be associated with the creep phenomenon and early bedding-in in the early stages after a THA and although this is of concern these results should be interpreted with caution.

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.

Early migration of the acetabular and femoral component after total hip replacement has shown to be a good predictor of implant failure. The only current technique available for this measurement is RSA. An entirely new technique for the measurement of component migration and polyethylene wear has been developed. Required are a single CT of the patients’ pelvis and femur, and routine serial postoperative antero-posterior (AP) and lateral radiographs.

A CT scan of the patients pelvis and proximal femur is performed either pre or post-operatively. This CT is used to build a solid model of the patients’ bony anatomy. CAD models of the femoral and acetabular component are obtained from the manufacturer and all four solid models are imported into custom software. Ray tracer (RT) technology is the computer generation of images of a solid model placed between a camera and a screen. It has been adapted to reproduce the radiological setup used to take clinical AP and lateral radiographs. The four solid models (pelvis, acetabular component, femoral component, femoral shaft) are each placed in the RT. Manipulation of each solid model is performed (6 degrees of freedom, x, y, z translation, and rotation about the x, y, z axis) using Artificial Intelligence, until an outline of the solid model generated by the ray tracer is identical to the outline of the AP and lateral radiograph of that patient. Change in relative positions of each solid model over time (pelvis acetabular component represents acetabular migration, acetabular component femoral stem represents polyethylene wear, and femoral stem femur represents femoral migration) are recorded. Validation to measure accuracy of the technique has been performed using computer models, and femoral and acetabular prostheses implanted into a cadaver.

Despite significant variations in the position of the pelvis and leg during the obtaining of post-operative radiographs, this new technique was able to measure polyethylene wear and component migration with accuracy similar to that of RSA (0.25 mm in the AP plane).

Further testing and validation is required, but this technique offers promise for the future in being able to retrospectively measure component migration and poly-ethylene wear, using a single CT scan and routine clinical postoperative radiographs.

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.

Cement-less femoral fixation in revision hip arthroplasty offers advantages over cemented femoral revision with evidence of lower rates of both revision and impending prosthesis failure. Intermediate-term data suggests that extensively-coated stems provide reliable fixation by obtaining in-growth and stability in the healthier bone located more distally in the femoral shaft. We report the results of femoral stem revisions performed by a single surgeon at our institution using an extensively-coated, cement-less femoral component.

A retrospective review of notes and radiology was performed on all patients who underwent femoral revision by a single surgeon between January 1994 and March 2004, with a minimum follow up of 24 months. Patients were identified using a dedicated database and the New Zealand National Joint Registry. All patients were operated on using the same technique and received a Solution femoral stem (De Puy, USA). Each patient’s level of function was assessed using the Oxford Hip Score. Radiographic assessment was performed using Engh criteria for fixation and stability of porous coated implants.

67 Solution stems were inserted into 64 patients. Thirty-six patients (52%) were male. Mean age was 70.5 years (47–86). Mean follow up was 57 months (24–145). The most common indication for revision was osteolysis and/or polyethylene wear (75%). There were no failures of the femoral component requiring re-revision. 65 stems (97%) showed definite or suspected bony in-growth on radiographic review. The mean Oxford Hip Score was 27.3 (12–44).

Five cases (7.5%) developed significant complications requiring return to the operating theatre: one deep wound infection, two recurrent dislocations and two loose or mal-positioned acetabular components. The latter four cases required acetabular revision.

Previous reports have shown good results from the use of extensively porous coated cylindrical stems in revision hip arthroplasty. Our results show the Solution stem to be a reliable femoral revision stem with good medium-term results and a low rate of complications.

The purpose of this paper was to assess the incidence of pelvic osteolysis following the use of a one piece all polyethylene titanium plasma spray backed acetabular component a mean of 9.6 years following implantation.

The radiographs of 86 hips followed for a mean of 9.6 years were reviewed. All had primary total hips using a titanium plasma spray backed all polyethylene uncemented acetabular component. Radiographs were assessed for osteolysis in the three zones described by DeLee and Charnley.

There was no osteolysis seen in any cup in any of the zones. There were no loose cups and no obvious cup migration.

This acetabular component shows superior performance compared with all two piece cups in terms of the development of periacetabular osteolysis. The use of two piece cups should be reconsidered.

The management of periprosthetic femoral fractures associated with a total hip arthroplasty remains controversial. The 2003 AAOS Instructional Course Lecture states “Regardless of the method of fixation, the fracture site should be bone grafted with morcellised allograft.” We do not believe bone grafting is necessary to obtain union .

Forty six periprosthetic femoral fractures associated with a total hip were reviewed retrospectively. Follow up included chart and radiographic review, Oxford Hip Score, and SF-12. All fractures were classified acording to the Vancouver classification.

There were 31 type B fractures and 15 type C fractures. All fractures healed. The mean healing time was 15 weeks. No allograft was used. The mean Oxford Hip Score was 26, and the SF-12 33. There were a number of complications, primarily dislocation in the more severe fractures.

The results of this series indicate that bone graft is not necessary to obtain union in periprosthetic femoral fractures. The use of allograft is associated with possible disease and infection transmission and increased cost, risks that we do not believe are justified.

To document the medium term results of the use of a fluted tapered titanium femoral stem in revision total hip arthroplasty.

70 patients undergoing total hip revision using a tapered grit blasted titanium modular stem were reviewed at a mean follow up time of 47 months. No bone graqfts were used. Femoral defects were classified according to Pak and Paprosky and the femoral bone quality was assessed with the Bohm and Bischel system. Clinical function was assessed by the Oxford Hip Score. Radiographic analysis was performed in all cases.

The results of the use of this prosthesis compares favourably with other revision stems. The Oxford Hip Scores compare favourably with the results for revisions recorded in the New Zealand National Joint Register (24.3) Although technically demanding this stem offers a very satisfactory solution for revision of total hips in most circumstances.

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.

This study examined the effect of completely disregarding dislocation precautions on the incidence of dislocation, as well as the speed of patient rehabilitation after THJR

Since 1^st March 2005, all uncomplicated primary THJR’s performed by one of the senior authors for OA have been told by their physiotherapist to do what they like, when they like, during the post-operative period. All patients were operated on through a modified direct lateral approach A representative sample of 30 patients were administered a questionnaire at their 6 week postoperative visit.

There were no dislocations. Of those patients in full-time employment, the majority had returned to work by 6 weeks. Most were able to drive between 3 and 4 weeks. Nearly all had regained their pre-operative range of movement and could put on their own shoes and socks. All claimed that being told to disregard dislocation precautions gave them more confidence in their THJR and helped with their achieving a speedy recovery from surgery.

Patients who are judged at the time of surgery to have a stable THJR articulation, benefit form being told to disregard the usual dislocation precautions, and are able to return to work and driving in a more timely manner.

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.

The aim was to evaluate the polyethylene wear in an uncemented all polyethylene titanium coated acetabular cup a minimium of ten years post-operatively, and to determine the effect of supine “stress” radiographs on 3-dimensional polyethylene wear, compared with “non-stress” radiographs.

Twenty seven hips in twenty five patients were examined, and standard and stress radiographs were performed. All radiographs were analysed using Polywear 5 auto, to measure 2d, 3d, and volumetric wear. Wear measurements were performed three times to minimise error. Radiographs were analysed for osteolysis.

There were 12 males and 13 females. Eighteen patients had a diagnosis of osteoarthritis.20 patients had a ceramic head and 7 a metal head. There was no association between wear rates and age, weight, diagnosis, Harris hip score or femoral head type. There was no acetabular osteolysis. The average linear wear was 0.11 +/− 0.08 mm/yr. The stress radiographs did not influence the 2D or 3D wear measurements.

This sudy shows a similar wear rate to most published series. The stress radiographs did not influence the wear measurements. The absence of osteolysis is of interest as other uncemented cups have significant osteolysis at ten years.

In the past measurement of deformity correction in spinal surgery has been done using measurements made directly from radiographs using a pencil, ruler and goniometer The aim of this paper is to describe a reproducible, accurate and partially automated system that has been developed for measuring x-rays of patients with spinal disorders.

Computer assisted measurement of polyethylene wear in patients with THJR is now well established. Many of the image processing algorithms have been modified to allow identification of the outline of both thoracic and lumbar vertebral bodies on digital images of radiographs made from patients with spinal disorders. The Genetic Algorithm (GA), a branch of Artificial Intelligence, has been adapted to allow the modelling of a four sided figure to each vertebral body, with minimal user input.

The accurate identification of each vertebral body within a spinal radiograph allows measurement of multiple parameters, including Cobb angles, vertebral width, vertebral height and cross sectional area, as well as measurement of average disc height and cross sectional area. The method is 100% reproducible for each digital image. An attempt to measure accuracy has not been made because these are two dimensional measurements of a three-dimensional structure.

Comparison of these measurements between pre and post-operative radiographs for a patient allows accurate and reproducible measurement of reconstructive surgery for scoliosis and other spinal disorders. It may aid in development of a classification system for scoliosis.

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.

Introduction and Aims: To define the economic and health costs of waiting for THJR surgery.

Method: A prospective cohort of 122 patients requiring primary total hip arthroplasty (HA) was recruited from four hospitals. Health-related quality of life (HRQL) using self-completed WOMAC questionnaires was assessed monthly from enrolment pre-operatively to six months post-surgery. Monthly cost diaries were used to record medical, personal and other costs. Data was analysed using PC-SAS to test the strength of associations between costs and waiting times, and changes in HRQL pre- and post-surgery.

Results: The mean waiting time was 5.2 months, and the mean cost of waiting for surgery was NZ$1376 per person per month, with medical, personal, and social costs contributing NZ$404, NZ$399, NZ$573, respectively. Waiting for more than six months was associated with an increased cost of NZ$730 per patient per month for a total cost of NZ$2177 per patient per month. Age was correlated with greater loss of income and higher medical costs. An incremental improvement over time in WOMAC scores post-operatively was identified. Older age, community services card use and a greater number of months waiting were negatively correlated with post-surgical improvement.

Conclusion: Longer waits for HA incur greater economic costs and impact on patient recovery. This shows that shorter waiting time for HA significantly reduces costs to individuals and society and improves health outcomes.

Introduction and Aims: The aim of this study is to identify specific risk factors for developing haemophilia-related orthopaedic complications and to provide a qualitative and quantitative analysis of the orthopaedic management of haemophilia complications.

Method: A postal survey was sent to 48 patients on the Wellington region haemophilia database. The questionnaire covered both qualitative and quantitative questions covering the participants’ current condition and treatment, past and present orthopaedic and non-orthopaedic management, support, education, employment and leisure activities.

Results: Twenty-five patients returned the questionnaire, a response rate of 52%. Most of the participants (68%; 17/25) felt that their education had been compromised as a result of haemophilia complications. Of those participants that were 16 years or older, 68.4% (13/19) felt that their working opportunities had been compromised as a result of haemophilia complications. Despite patients less than 18 years of age receiving prophylactic Factor VIII replacement (n=7) and all patients having Factor VIII available on demand, 18 patients had significant bleeds in the previous six months. Most bleeds were into joints, 13 knees, 13 ankles, 12 elbows, six shoulders and three hips, but a significant number of intra-muscular bleeds (n=22) also occurred. There were 62 painful joints reported by 19 patients, the ankle being most common (n=21), followed by hip (n=13), elbow (n=12), and knee (n=8). Twenty-five orthopaedic operations were described by eight patients, mainly knee (n=11) and hip (n=5) replacements, and synovectomies (n=9). In the last year, two patients who have factor VIII inhibitor had been successfully operated on, one for a large pseudotumor of the thigh, and the other for contralateral hip and knee joint replacement.

Conclusion: Despite good medical management, recurrent joint bleeds are a major problem in haemophilia. Many study patients commented that orthopaedic procedures were not performed readily enough, and that by the time they received their operation, their function had deteriorated significantly.

Introduction and Aims: Polyethylene wear after total hip arthroplasty with an uncemented titanium coated non-modular acetabular component was measured using a computer-assisted technique and correlated with clinical outcomes. Polyethylene wear measurements using post-operative radiographs and recent supine and standing radiographs were compared to see if there was a difference. To date, there is no definitive evidence in the literature that indicates a difference.

Method: Fifty-five patients who had total hip arthroplasties using a non-modular titanium-backed Mathys (Protec, Switzerland) press-fit acetabular component in 1992–1993 were included in this study. Patients who had a revision were excluded. The patients were contacted and reviewed in clinic. Each patient completed an Oxford Hip Score. They also had a cross-table lateral, supine and standing AP radiographs. The radiographs were digitised and analysed using a computer-assisted method (PolyWare) of measuring polyethylene wear. Correlations were sought between the rate of polyethylene wear and clinical outcome using the Oxford Hip Score. Polyethylene wear measurements using supine and standing radiographs were also compared to determine if there was a significant difference.

Results: Early results showed a trend indicating a difference in measured polyethylene wear rates comparing supine and standing radiographs. Previous experience at this institution measuring polyethylene wear using the same computer-assisted technique has shown that leg position has an effect on polyethylene wear measurements; weightbearing radiographs with the leg maximally internally and externally rotated resulted in an increase in polyethylene wear calculation of volumetric wear by 35% as compared to calculations with supine radiographs. A non-cylindrical wear tract was proposed to be the reason for the difference. There is no definitive answer in the literature as to the significance of the effect of supine versus standing radiographs on the measurement of polyethylene wear. Polyethylene wear rate did not seem to be related to clinical outcome as detected by the Oxford hip score.

Conclusion: Early results indicate a difference in polyethylene wear measurement comparing standing and supine radiographs. Polyethylene wear rates using the Mathys acetabular component do not seem to be related to clinical symptoms as detected by the Oxford Hip Score.

Introduction and Aims: In 1999, the serial polyethylene wear of a group of patients with a porous coated anatomic hip (PCA) replacement were reported by Devane et al. Wear was measured using a computer assisted technique where the points were selected manually from a digitised image displayed on a computer screen (method 1). The purpose of this study is to use a new automated method of polyethylene wear measurement (method 2), for analysis of the same serial radiographs of patients which have since been digitised. Results of the two methods are compared.

Method: Twenty-three porous coated anatomic hips (PCA, Howmedica) in 23 patients had serial radiographs performed with a minimum 8.5-year follow-up. A total of 494 anteroposterior (AP) and lateral radiographs were analysed. Assessment of the presence of osteolysis on the longest-term follow-up AP image was made by an independent observer. Correlation of polyethylene wear rate measured by the two different methods, and osteolysis was made.

Results: Using method 1, if a poor quality AP or lateral image was analysed multiple times by the same observer, a poor reproducibility (±0.4 mm) was obtained. Discarding of poor quality radiographs by the user resulted in 74% of the AP images and 68% of the lateral images being measured. It is very likely that a different user would discard different images. Method 2, however, automatically eliminates poor quality images. Method 2 was able to measure 89% of the AP radiographs and 78% of the lateral radiographs. More importantly, if a different user performed the same analysis using the new automated software, the exact same images would be analysed. Results of wear measurements made using method 1 were statistically similar to measurements made using method 2 in 19/24 hips (83%).

7/23 patients demonstrated osteolysis on their images. Wear measurement using method 2 showed statistically greater wear in these patients (69mm/yr vs 35mm/yr, p = 0.003). Wear measurement using method 1 showed only a weak association.

Perhaps most importantly, wear analysis of these patients using method 2, by two separate observers, independent of each other, gave identical results.

Conclusion: With improved accuracy and elimination of user error, measurement of PE wear may now have the ability to make predictions about the long-term survival of a THJR. Clinical decisions may be able to be made based on individual patient measurements.

Our aim was to assess the impact of the increasing number of patients on orthopaedic waiting lists on general practitioners in New Zealand.

A 10-point questionnaire was developed in association with the General Practice Department at the Wellington School of Medicine, and mailed to 250 randomly chosen general practitioners around New Zealand. One hundred and fifty general practitioners returned the survey.

Sixty three per cent of general practitioners reported having between eleven and thirty patients on an orthopaedic waiting list in their practice. 85% of general practitioners reported spending up to an extra 6 hours per month looking after problems caused by having to provide extra care for the patients. In 90% of cases general practitioners reported that their patients required considerably greater community support in the form of extra physiotherapy, meals-on-wheels and occupational therapy. In 138 cases, general practitioners reported greater levels of stress in the families of patients on waiting lists. The majority of general practitioners reported an increased need for analgesia and night sedation during the period on a waiting list. They also reported substantial increases in paperwork necessary to access social supports.

This study documents the burden on general practitioners produced by the increasing waiting lists, and the re-alignment of waiting lists. This burden is reducing the general practitioner’s ability to deal with routine general practice problems, and likely adversely affects the health of other New Zealanders. There is a need for a study of patients on waiting lists to further assess their needs.

We have developed and tested the accuracy of a completely automated method for polyethylene (PE) wear measurement of digitised antero-posterior and lateral radiographs.

New computer algorithms have been developed to measure PE wear on digitised hip radiographs. The only user input required is the file name of the x-ray. Validation was performed by simulation of PE wear in an acrylic phantom. Radiographs were analysed with the new software and results were compared to know penetration of the femoral head.

Accuracy using 10 antero posterior and lateral phantom radiographs was within ±0.08mm (95% CI) of the real femoral head penetration. There was no inter or intra-observer error (identical results with all measurements). Perhaps most importantly, this system gave accurate results in 94% of 600 clinical radiographs of variable quality. Only 74% of this same group of radiographs were considered of sufficient quality to allow reliable manual measurement.

This new method of PE wear measurements eliminated inter and intra-observer error, allowing comparison of wear results between different institutions. Accuracy is improved, but still limited by resolution of the scanned image.

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.

A new method of polyethylene wear measurement for analysis of serial radiographs of the same patients over a 10 year period is described.

Eighteen patients with a PCA THJR had serial radiographs performed with a minimum of 8.5 year follow up. A total of 560 A-P and lateral radiographs were analysed.

The graphs of PE wear v time fell into two groups: Group 1 – (7 patients) had accelerated PE wear with eventual development of osteolysis. Group 2 – (11 patients) had PE wear of less than 0.16mm/year and their latest radiograph showed no evidence of osteolysis.

With improved accuracy and elimination of user error, measurement of PE wear may now have the ability to make predictions about the longterm survival of a THJR. Clinical decisions may be able to be made based on individual patient measurements.

We assessed the functional and health outcomes of patients treated for a hip fracture ,6–12 months following the injury.

One hundred and ninety six patients over 60 years of age ,admitted with a subcapital or intertrochanteric fracture were sent two questionnaires, an EQ-5D, and a Hip specific outcome questionnaire based on the WOMAC .Patients with pre-existing dementia were excluded.108 (55%) returned completed questionnaires.

There were 36 males and 72 females with an average age of 81. The average time since fracture was 8.44 months. There were 46 intertrochanteric and 62 sub-capital fractures.WOMAC scores averaged 35 for intertrochanteric fractures and 25 for subcapital fractures. Males scored higher than females (31 v’s 24)Age had no influence on WOMAC scores.EQ 5D results were compared with the general population, and showed significant problems with mobility, pain, performance of usual activities, and self care.

This study shows that despite seemingly successful treatment of the fracture, patients suffer very significant reductions in function and quality of life. Greater effort needs to be made to address these issues rather than concentrating on the development of new fixation devices, if we are to improve the results of treatment of these increasingly common fractures.

The purpose of this study was to document difficulties encountered by orthopaedic surgeons with the removal of titanium implants.

A postal questionnaire was sent to all members of the New Zealand Orthopaedic Association seeking to document difficulties with the removal of titanium implants: screws, plates or intramedullary nails. The questionnaire included length of device implantation, estimated increase in theatre operating time over the expected time for the procedure, and complications encountered during the device removal.

Twenty six surgeons responded to the study. Six reported no difficulties in removing implants, 18 reported significant difficulties, and 2 had not had to remove titanium implants. Of the 18 surgeons reporting difficulties, 10 had problems with intramedullary nails, 4 with plates, 6 with screws and 1 with another device. The estimated increase in operating time varied between 20 and 140 minutes. Major complications reported included breaking intramedullary nails, screw heads shearing off, and damage to the underlying bone.

This survey demonstrates significant problems in removing titanium implants. Surgeons need to be aware that when using these devices difficulties with their removal can be encountered and patients should be warned that further injury may be sustained during device removal.

Forty six periprosthetic femoral fractures adjacent to a hip prosthesis have been retrospectively reviewed. Follow up included chart and radiograph review, Oxford Hip Score and SF-12 Global Function Score. Fractures were treated with internal fixation or revision arthroplasty without the use of allograft.

All the fractures united and functional outcome was good. The mean Oxford Hip Score was 26 and the SF-12 was 33. Complications were related to the severity of the fracture according to the Vancouver classification.

These results and a review of the literature support the ongoing management of periprosthetic femoral fractures without allograft.

The aim of this study was to document the medium-term results of the use of fluted, tapered, titanium femoral stem in revision total hip arthroplasty.

Seventy patients undergoing total hip revision using a tapered, grid-blasted titanium modular femoral stem were reviewed at a mean follow-up time of 47 months. Femoral defects were classified according to the Pak and Paprosky system, and femoral bone quality was assessed with the Bohm and Bischel system. Clinical function was measured by the Oxford Hip Score. Radiograpic analysis was performed in all cases.

Stems were classified as a failure or re-revision in 4.3% of the cases. Three required reoperation for recurrent dislocation, in each case the femoral component alone had been revised during the most recent revision. The postoperative mean Oxford Hip Score was 20.9. Subsidence of the component was noted in 84% of hips but did not cause a significant problem. Final leg length discrepancy was 5.4mm.

The results of this titanium, tapered, grid-blasted modular stem compares favourably with other revision stems including the Oxford Hip Score compared to the results for revisions recorded in the National Joint Register (Oxford Score 24.3). Although technically demanding this stem offers a very satisfactory solution for revision of total hips in almost all circumstances.

We have correlated the ‘bedding-in’ response (the high femoral head penetration seen in the first two years after operation) with changes in offset and leg length from opposite normal hip.

Fifteen patients with serial x-rays taken in the first 5 years after operation had measurement of PE wear, femoral offset and leg length change from the opposite normal hip.

There was a weak correlation between increasing the leg length and increasing the offset during operation and increased femoral head penetration (‘bedding-in’) seen during the first two years after the operation. There was no correlation between offset and PE wear after two years in the PCA prosthesis.

Increased tissue tension in the first two years caused an increase in femoral head penetration. This effect is not continued beyond two years.

We assessed the functional outcome of fractures of the os calcis a minimum of twenty- four months following injury.

Eighty-three patients with 85 fractures were assessed a minimum of two years following fracture of the os calcis, using a validated functional outcome measure designed specifically for fractures of the os calcis, and an EQ5D. Radiographic analysis of all fractures was performed to attempt to correlate outcome scores with the fracture pattern.

Sixty per cent of the questionnaires were returned completed. Forty percent of the fractures were treated surgically, the remainder with a period of weight relief, followed by physiotherapy and graded weight-bearing. The majority of patients reported a mild hind foot pain (8/10 on a VAS), and all reported some difficulties with walking on uneven terrain. There was no appreciable difference in the outcomes comparing patients treated by open reduction and internal fixation and those treated non-operatively.

This study demonstrates a surprisingly high patient satisfaction rate following fractures of the os calcis whether they are treated operatively or non-operatively. Patients seemed to have compensated for any altered function very well. We were not able to identify specific fracture patterns that were associated with poorer outcomes.

The purpose of this study was to assess the regional variation in the incidence of hip fractures in patients over 65 years. in New Zealand. Data from the National Minimum Data Set (NMDS) for hip fractures from 1 July 1998 to 31 June 2000 was obtained. The data was divided into 21 District Health Board (DHB) regions by mapping from domicile code to DHB. Population of interest as at 30 June 1999 was estimated on the basis of previous census in 1996. The incidence of hip fracture per 100,000 for each region was calculated and divided into age and sex cohorts.

There is a significant difference between DHBs in the sex and age adjusted incidence of hip fractures. The rates ranged from 556 per 100,000 to 838 per 100,00. As expected there was a higher fracture rate in women and the fracture rate increased with age. There was a weak correlation with sunshine hours (p=0.029) with increasing fracture incidence as sunshine hours decrease.

This study demonstrates a large variation in the incidence of hip fractures per DHB region. The cause for this is unclear, but the cost implications are significant. DHB’s with a high incidence of hip fractures in their region may wish to investigate strategies for reducing the incidence.

The aim of this study is to identify specific risk factors for developing haemophilia related orthopaedic complications and to provide a qualitative and quantitative analysis of the orthopaedic management of haemophilia complications.

A postal survey was sent to 48 patients on the Wellington region haemophilia database. The questionnaire covered both qualitative and quantitative questions covering the participants’ current condition and treatment, past and present orthopaedic and non-orthopaedic management, support, education, employment and leisure activities.

Twenty-five patients returned the questionnaire, a response rate of 52%, Most of the participants (68%; 17/25) felt that their education had been compromised as a result of haemophilia complications. Of those participants that were 16 years or older, 68.4% (13/19) felt that their working opportunities had been compromised as a result of haemophilia complications. Despite patients less than 18 years of age receiving prophylactic Factor VIII replacement (n=7) and all patients having Factor VIII available on demand, 18 patients had significant bleeds in the previous 6 months. Most bleeds were into joints, 13 knees, 13 ankles, 12 elbows, 6 shoulders and 3 hips, but a significant number of intra-muscular bleeds (n=22) also occurred. There were 62 painful joints reported by 19 patients, the ankle being most common (n=21), followed by hip (n=13), elbow (n=12), and knee (n=8). Twenty orthopaedic operations were described by 8 patients, mainly knee (n=6) and hip (n=3) replacements, and synovectomies (n=6). Discussion.

Despite good medical management, recurrent joint bleeds are a major problem in haemophilia. Many study patients commented that orthopaedic procedures were not performed readily enough, and that by the time they received their operation, their function had deteriorated significantly.

The purpose of this study was to assess the incidence of pelvic osteolysis following the use of a one piece all polyethylene acetabular component a mean of 9.6 years following implantation. The radiographs of 86 hips followed for a mean of 9.6 years were reviewed. All had had primary total hip arthroplasty using a titanium plasma spray backed all polyethylene acetabular component. Radiographs were assessed for pelvic osteolysis in the three zones described by Charnley and Delee. There was no osteolysis seen in any cup in any of the three zones. There were no loose cups and no obvious cup migration. This acetabular component shows superior performance compared with all two pieced components in terms of the development of pelvic osteolysis. The use of two-piece cups should be reviewed.

The purpose of this study was to compare the 2D and 3D linear and volume wear readings of the three most commonly used methods for measuring polyethylene wear: the Livermore, Devane and Martell techniques. Inter-observer variation of measurements using the techniques of Devane and of Martell on conventional radiographs was also performed. The radiographs of 80 patients (mean age 60+/−10 yrs) who had a Harris-Galante I total hip arthroplasty were measured. Nine different reviewers for the Devane technique readings including Dr Devane and eight reviewers for the Martell technique readings including Dr Martell made blinded independent wear observations for each radiograph set. One reviewer measured the 20 annual linear wear rate for all radiograph sets using the 2D Livermore technique. Inter-observer variation as a function of patient, reviewer, and total variation was statistically assessed using variance component analysis. Mean wear measured using the Livermore technique was the same as with the Devane and Martell method, but with a greater variation. Comparison of the Devane and Martell method for patient STD, reviewer STD, error STD (multiple reviews of same radiographs), total STD (randomly picked reviewer), mostly show a mean 50% lower STD with the Devane technique. Correlation (correlation coefficient of two randomly selected reviewers) is significantly better with the Devane technique.

The purpose of this study was to determine if the incidence of heterotopic ossification following total hip replacement decreases with increasing experience of the surgeon. A comparison of the incidence of heterotopic ossification between 196 patients having primary total hip replacement in 1989–1990 and a second group of 180 patients between 1999–2000 was performed. The surgery was done by one surgeon. Radiographs taken at least six months post operatively were assessed, and graded using both the Hamblen and Brooker classification systems. No patients were given specific prophylaxis. The groups were well matched. There was a statistically significant reduction in the incidence of Grade 2 and 3 heterotopic ossification in the 1999–2000 patient group.

There did not appear to be any identifiable reason for this except increased surgeon experience. The incidence in the 1999–2000 group was well below reported figures from other studies. The incidence of heterotopic ossification following total hip replacement is falling and the fall may be related to improved surgical technique.

The purpose was to define the economic and health costs of waiting for total hip joint replacement surgery. A prospective cohort of 122 patients requiring primary hip arthroplasty (HA) was recruited from four hospitals in the lower North Island. Health related quality of life (HRQL), using self-completed WOMAC questionnaires, was assessed monthly from enrolment pre-operatively to six months post surgery. Monthly cost diaries were used to record medical, personal and other costs. Data was analysed using PC-SAS to test the strength of associations between costs and waiting times, and changes in HRQL pre- and post-surgery.

The mean waiting time was 5.2 months and mean cost of waiting for surgery was $1,376 per person per month (pp pm) with medical, personal and social costs contributing $404, $399, and $573, respectively. Waiting more than 6 months was associated with an increased cost of $730 pp pm for a total cost of $2177 pp pm (p< 0.003). Age was correlated with greater loss of income (< 65 years) (p=0.001) and higher medical costs (< 65 years) (p=0.08). An incremental improvement over time in WOMAC scores post-operatively was identified (p=0.0001). Older age (p=0.01), community services card use (p=0.003) and a greater number of months waiting (p=0.1) were negatively correlated with post-surgical improvement after adjusting for other variables. Longer waits for HA incur greater economic costs and impact on patient recovery. This lends weight to the view that a shorter waiting time for HA significantly reduces costs to individuals and society and improves health outcomes.

The purpose of the study was to assess the incorporation of defatted, and deproteinated bovine cancellous bone in a sheep bone graft model. Cylindrical defects were created in the femoral condyles of 12 sheep using custom-made trephines. The defect was filled with a cylinder of prepared bovine bone. The removed cylinder of bone was implanted into a defect created in the opposite femoral condlyle. Fluorochrome bone labels were administered over an 8-week period and the sheep sacrificed at 10 weeks. Undecalcified thin bone sections were viewed with a fluorescent microscope.

ln one sheep there was a technical problem leading to unsatisfactory histology. All other sheep showed similar histology. The autograft incorporated rapidly with the graft showing a rim of reactive bone and the graft itself showing rapid laying down of new bone on its surface. The xenograft showed a similar reactive rim of new bone with deposition of new bone throughout the graft and resorption of the graft material.

This study demonstrates that specially prepared bovine cancellous bone can act as a scaffold for the depostion of new bone in a sheep model. The role of this material in humans is to be evaluated.

The aim of the study was to investigate functional outcomes and perceptions of quality of life in a series of elderly patients who have sustained tibial plateau fractures. A retrospective survey of all patients aged over 60 years who were admitted to Wellington and Hutt hospitals for treatment of a tibial plateau fracture between July 1996 and December 2000 was carried out. Patients were sent the Oxford 12 knee score and the Nottingham Health profile (NHP) by mail. Radiographs were reviewed to confirm fracture type and medical notes reviewed to ascertain treatment. Patients were divided into non-operative (plaster cast or brace; n=8) and operative treatment (open reduction and internal fixation (ORIF) or total knee replacement; n=15) groups.

Of 42 eligible patients, 23 returned completed questionnaires (rr=55%). The mean age of patients was 73.6 years with 16 (69.6%) females and 7 (30.4%) males. Mean time to follow up was 38.7 +/−14.5 months. The mean Oxford 12 knee score was 39.3. The mean NHP-part I scores were 17.6, 8.4, 3.3, 14.4, 2.9, 9.3 for energy level, pain, emotional reaction, sleep, social isolation and physical mobility respectively. 73% of the patients felt that their present state of health was not causing problems with any of the activities mentioned in the NHP-part II.

The perceptions of outcomes of tibial plateau fractures in the elderly after conservative treatment is comparable with operative treatment. The results show Oxford 12 Knee and NHP scores similar to other studies and indicate satisfactory knee function.

There is controversy regarding the best way to manage fit, independent patients with acute hip fractures. The aim of this study was to compare, nationally, the early complication rates of total hip arthroplasty (THA) in those patients with an acute fractured neck of femur (NOF) with a similar group of THA’s performed in patients with a diagnosis of osteoarthritis.

Using the National Hip Joint Register and the New Zealand Health Information Service Database, 200 patients with acute hip fractures undergoing THA were identified and compared to 1102 THA’s performed on osteoarthritis patients. The mortality, revision, dislocation and infection rates were analysed at a minimum of one year.

Acute THA had a 7.5% one-year mortality rate compared with 2.5% in the OA group (p < 0.01). The revision rate was 2.5% vs 1.8% in the acute and OA groups respectively. The dislocation rate was 4.3% for the whole group with a 8.5% for the acute group and 3.5% for the OA group (p< 0.01). In the acute group the dislocation rate using the posterior approach was 17.1 % compared to 3.1% for the lateral approach (p< 0.01).

We conclude that acute THA is a useful procedure in fit patients with a fracture of the neck of the femur but that a posterior approach should be avoided.

Early discharge from hospital has the potential to reduce direct costs, but may result in patients being discharged without adequate preparation for a return to the community. This qualitative study aimed to investigate patient expectations of and satisfaction with in-hospital discharge planning after hip arthroplasty in early and late discharge patient groups. A prospective study of 33 consecutive patients requiring hip arthroplasty were recruited from two tertiary hospitals in the lower North Island. Participants were interviewed using in-depth, semi-structured interviews on the day of discharge from hospital and again four-eight weeks later. Comparative analysis of the interviews from patients in early and late discharge groups was made.

Findings reveal good levels of satisfaction with discharge planning for patients in both early and late discharge groups, facilitated by the opportunity to attend a pre-assessment clinic. Discharge planning was viewed as a partnership between patients and key members of the multi-disciplinary team. While written information provided was timely, restricted opportunity for dialogue with health professionals limited patient knowledge and understanding of recovery. Different needs of participants indicate that discharge planning needs to be tailored and more responsive to individuals. The role of health professionals as a mentor-coach is pivotal. Further interaction from health professionals, as a follow-up to written information provided may be a way to improve the discharge process and lead to more consistent outcomes.

Aim: To examine the effect that a modular, uncemented, fully coated titanium stem (PFM-R, Protek) has on the bone stock of revised femora.

Methods: Forty revision hip arthroplasties between 1997–2000 were performed by one surgeon using the PFM-R revision stem. The patients were assessed radiographically over a two-year follow-up period. The pre-operative radiographs were examined for bone defects according to Paprosky et al., 1987. Serial radiographs taken post-operatively after two days, six weeks, three months, six months, 12 months and 24 months were used to assess signs of fixation, stability and change in the cortices of 16 femoral zones according to criteria set out by Engh et al., 1987. The change in the density of the bone defects identified at the time of surgery was also examined.

Results: The average age of the patients was 65 years. Thirteen revision stems were followed for one year and 13 were followed for two years. Fourteen patients had an incomplete radiographic follow-up. Two type I defects, 23 type II defects and one type III defect were identified. Twenty-one of the 23 type II defects showed evidence of regeneration in the subtrochanteric metaphysis. One revision stem had radiographic evidence of bone resorption proximally though three stems subsided. No stress shielding was seen distally.

Conclusion: At early follow-up the PFM-R appears to be a viable revision femoral implant which facilitates the regeneration of metaphyseal bone stock.

Purpose: To examine the histology of the bone cement interface in a canine total hip model comparing two different cementing techniques.

Methods: Seven adult mongrel dogs underwent staged bilateral total hip replacement, on one side cement was finger packed into the femur, on the opposite side the femoral canal was washed, brushed, distally plugged and pressure injected with cement prior to inserting the femoral component. Sequential flurochrome bone labelling was performed. The dogs were sacrificed up to six months post surgery. Under-calcified sections of the femur were examined by fluorescent microscopy.

Results: Post-operative radiographs showed complete filling of the proximal femur with cement in the pressure injected group, and a relatively thin mantle in the finger packed group. Histology of the finger packed group showed minimal intrusion of cement into the cancellous bed, direct opposition of cement and bone with small areas of fibrous tissue interposition. In the pressure injected group the cement extended to the endosteal cortex, there was no bone necrosis, and the intruded bone underwent remodelling similar to that at the margins.

Conclusions: This study suggests that “third generation” cementing techniques result in greater contact between bone and cement, and may explain the claim that femoral stems in humans inserted using third generation techniques are more durable than those inserted using “first generation” techniques.

Introduction: Ankle fractures are the third most common fracture presenting at public hospitals in New Zealand. There have been few outcome studies following treatment of ankle fractures.

Aim: To identify the relationship between three types of ankle fractures and the functional and quality of life outcomes for patients two years after the injuries.

Methods: Seventy-four patients seen at Wellington Hospital with ankle fractures during 1998 were contacted for the study. Patients had been treated by open reduction and internal fixation, or by the application of a plaster cast with manipulation of the fracture being performed where necessary. Each patient completed an ankle specific Olerud and Molander questionnaire and an EQ5D Quality of Life Outcome measure. All x-rays were analysed and the fractures were classified using the Weber classification.

Results: There were 22 males and 52 females, 11% had Weber type A fractures, 67% had Weber type B, 18% Weber type C and 4% an isolated posterior malleolar fracture. Fifty-one patients underwent surgery. Patients who sustained Weber type A fractures generally recorded good to excellent OMA scores, while those with Weber Band C fractures produced significantly poor results. An analysis of the ankle visual analogue score versus the method of treatment showed that patients who underwent surgery judged their ankle to be less functional than the patients who had non-surgical interventions. The mechanism of injury also correlated with the end result, patients who had injured their ankles during sporting activities scored lower scores than those who had injured their ankles in simple falls. Patients requiring removal of an internal fixation device had a lower OMA score when compared with those who retained their fixation devices in situ.

Conclusions: This long-term out come study indicated that there was significant dysfunction following ankle fractures, with a surprising level of disability following Weber B and C fractures. The results of this study do not indicate better results in those patients who underwent surgery.

Introduction: It is well documented that surgery following hip fractures (#NOF) has accepted failure rates of between four and 33%. An average of 120 patients are admitted to Wellington hospital for #NOF each year.

Aim: We aimed to identify the rate of and reasons for readmission for further surgery within a year of #NOF in patients admitted to Wellington hospital.

Methods: A list of all patients admitted for surgical treatment of hip fractures during 1998 and 1999 was obtained from the hospital database. Demographic data, type of fracture, surgical intervention, readmission for surgery on the same hip and subsequent surgical intervention for each patient were noted.

Results: Of the 209 patients who underwent surgery for 215 fractures, 55% (n=119) sustained subcapital, 43% (n=92) intertrochanteric and 2% (n=4) other fractures. Seven percent (n=15) were readmitted for a second hip operation within twelve months. Eighty percent (n=12) of those who were readmitted had sustained sub-capital fractures. Of those in the readmission group primary surgery comprised ORIF with cannulated screws (40%), compression screw with or without one cannulated screw and plate (40%), hemiarthroplasty (HA) (13%) and total hip arthroplasty (THA) (7%).

For patients who had sustained a subcapital fracture (n=117), 21% (P< 0.05) of those who had been treated with cannulated screws required further surgery compared with 2–14% who had the other types of surgery.

Conclusions: Rates of readmission for further hip surgery following hip fracture in Wellington hospital appear to be in the lower range of those reported elsewhere.

Purpose: To measure quality and quantity of sleep in patients before and after hip arthroplasty.

Methods: A prospective survey where 50 participants were sent a sleep diary, an acti-watch motion-logger, and a 32 item sleep questionnaire. These data were collected at least four weeks prior to and three months after surgery. Data analyses included descriptive statistics and within-subject pre and post surgery comparisons. For the subjective data, comparison was by the McNamar Test for the significance of changes. For the acti-graphy variables, comparison was by mixed model analysis of variance.

Results: Preliminary results indicate that subjective measures of sleep quality improve significantly three months after hip arthroplasty, e.g. patients rated their sleep disturbance due to hip-pain on a scale from 1=never to 4=always. 75% of patients reported an improvement, and 25% reported no change in this variable, post surgery. Acti-graphy measures confirm the overall improvement in sleep quality (for sleep efficiency, (p(f)=0.05) and fragmentation index, (p(f)=0.05), and a reduction in mean activity during sleep (p(f)=0.04). Ongoing analyses are addressing the reliability of subjective measures compared to acti-graphy and why some patients show greater improvement in sleep than others, after hip arthroplasty.

Conclusions: Findings suggest that sleep disturbance occurs as a result of painful osteoarthritis in the hip, and that this can be significantly ameliorated by hip arthroplasty surgery. The expected improvement in quality of life and level of day to day functioning that accompany improved sleep are perhaps an under-rated benefit of this procedure.

Aim: To determine the incidence of periacetabular osteolysis in an uncemented, press-fit, one-piece, titanium plasma spray backed acetabular cup used in conjunction with a cemented or uncemented femoral component followed for 10 years.

Method: Patients undergoing primary total hip arthroplasty in 1989 were reviewed and new radiographs obtained. These were compared with the initial post-operative radiographs and the presence of osteolysis in the three zones of Delee and Charnley were recorded.

Results: Of 57 patients, 14 were deceased at the time of follow-up and nine were lost to follow-up. Ten patients had undergone revision for problems related to the femoral stem. There was only one possible case of periacetabular osteolysis seen in this series. In this case the lytic lesion was seen on the early post-operative radiograph and did not change in 10 years, and thus may not have been osteolysis.

Conclusions: The reported incidence of periacetabular osteolysis with two-piece cups varies between 30 and 50%. Thus, this cup has an extremely low possible osteolysis incidence. This study raises the wisdom of the continued use of two piece cups of any design.

Aim: To ascertain whether there is a relationship between time to surgery and mortality in hip fracture patients.

Method: The records of 120 patients admitted with hip fractures were examined. The approximate time of injury, the time of admission to hospital, the time of surgery, the number of medical co-morbidities, the A.S.A. grade, age, and length of hospital stay, were recorded. Death statistics were obtained from the Registrar of Births Deaths and Marriages. An analysis was then performed to assess the presence of correlation between time from injury to surgery, time from admission to surgery and three and six-month mortality in patients who were A.S.A. grades two or three.

Results: Preliminary analysis of the data showed a strong correlation between time from injury and the time from admission, to surgery and subsequent death. When these times exceeded 24 hours the mortality increased.

Conclusion: This study suggested that every effort should be made to operate on patients with hip fractures within 24 hours of admission to minimise mortality resulting from this injury.

Aim: To examine the histology of the bone-cement interface in a canine total hip model comparing two different cementing techniques.

Method: Seven adult mongrel dogs underwent staged bilateral total hip replacement. On one side the cement was packed into the femur with a finger while on the opposite side the femoral canal was washed, brushed, distally plugged and injected with cement under pressure before inserting the femoral component. Sequential fluorochrome bone labelling was performed. The dogs were sacrificed up to six months after the surgery. Undecalcified sections of the femur were examined by fluorescent microscopy.

Results: Post-operative radiographs showed complete filling of the proximal femur with cement in the pressure injected group, and a relatively thin mantle in the finger-packed group. Histology of the finger-packed group showed minimal intrusion of cement into the cancellous bed, direct apposition of cement and bone with small areas of fibrous tissue interposition. In the pressure- injected group the cement extended to the endosteal cortex, there was no bone necrosis, and the intruded bone underwent remodelling similar to that at the margins.

Conclusions: This study suggested that ‘third generation’ cementing techniques result in greater contact between bone and cement, and may explain the claim that femoral stems in humans inserted using third generation techniques are more durable than those inserted using ‘first generation’ techniques.

Introduction: Ultra high molecular weight polyethylene (UHMWPE) wear debris generated at the articulating interface of total hip arthroplasties continues to be the major cause of early failure of these implants.

Aim: To validate the accuracy and reproducibility of the three-dimensional technique (3D) of in vivo measurement of UHMWPE wear using PolyWare ™ when applied to digitised radiographs. The aim was to keep the cumulative errors below the accepted annual linear wear rate of 0.15 mm.

Method: Using precision phantoms with known cup and head sizes and known deviation simulating wear, series of x-rays were taken simulating a number of variables. These variables were grouped into: patient variables (centering, exposure, motion artefact, prosthesis orientation), image acquisition variables (film and cassette type, x-ray exposure, non-circularity of the projected image, magnification, image sharpness), digitisation variables (input resolution, sharpness), and errors inherent to the PolyWare™ software analytical process.

Results: Patient factors contributed the largest errors to the process – these were highly variable. Exposure and input resolution also contributed errors to a lesser extent. No significant error introduction was found with regard to any of the other above-mentioned factors, in particular the PolyWare™ analysis.

Conclusions: The three dimensional method (PolyWare™) is accurate and highly reproducible. Apart from patient factors, which directly and indirectly introduce errors, this method is a satisfactory means of estimating the in vivo wear of UHMWPE.

Aim: The direct lateral approach, as described by Hardinge et al, may have the advantage of reducing the incidence of dislocation after total hip arthroplasty. The purpose of this paper is to describe a modification of the direct lateral approach used by the author on consecutive total hip arthroplasty for all patients; including primary arthritis, fractures and revisions over a period of five years. The incidence and causes of complications, specifically dislocation, is discussed.

Method: A modification of the direct lateral approach, where gluteus minimus is split anteriorly rather than being detached from the greater trochanter, is described. This approach allowed its primary repair during wound closure, reducing surgical dead-space and theoretically reducing the incidence of dislocation. The records of all patients in whom the author performed this approach for total hip arthroplasty between 1 February 1994 and 1 February 1999 were examined. Patients were routinely seen at one year after operation and any early complications of surgery recorded. Minimum follow-up for this series was one year.

Conclusion: This modification of the direct lateral approach which preserves the integrity of gluteus minimus while still allowing adequate exposure and is extensile, gave a very acceptable incidence of dislocation in total hip arthroplasty for degenerative disease, fracture, and revision cases.