The aim of this study was to evaluate a new joint arthroplasty clinical priority scoring tool.

A new arthroplasty scoring tool based on pain, function, social limitation, potential of benefit from surgery and consequence of more than 6 months delay was developed and evaluated using 16 patient scenarios (vignettes) related to hip and knee osteoarthritis. Sixteen orthopaedic surgeons were asked to score the vignettes using clinical ranking, ISS tool and the new tool.

Significant variation in ranks allocated by surgeons was recorded for all three tools. Vignettes at either end of the scale ie. those who are severely or minimally disabled had less variability compared to a large group in the middle range. Comparing the three tools there did not appear to by any advantage of one over the other. Most of the variations occurred in the interpretation of benefit from the operation and consequence of delay.

Scoring tools rely heavily on judgement based decisions. More work is required to understand judgement processes used by surgeons and audit/feedback mechanisms may help in reducing the variations in priority assignment.

We analysed the clinical outcome of infected hip and knee replacements treated in Dunedin over a 10 year period.

Using the departmental audit data base all infected arthroplasties treated between 1990 and 2000 and the clinical notes reviewed.

Fifty-three hips and 20 knees were identified. 69% of patients had debridement and antibiotics as the primary treatment. In terms of prosthesis retention 41% of patients had retained the original prosthesis, 30% had implants in place following revision and 29% had a resection arthroplasty or arthrodesis. Retention of the original prosthesis was significantly higher in early as compared to late infections and knees did better than hips. The most common organisms identified were staphylococci (47%) and streptococci (29%). We did not see any difference in outcome of streptococcal infections.

The treatment of infected arthroplasties remains controversial. We propose management guidelines based on outcomes of a series of 73 cases.

Purpose: There are numerous papers from specialist arthroplasty centres outlining results of total knee arthroplasties but little information from outside these major centres. We carried out a review of a fixed bearing total condylar knee replacement used in Dunedin by a variety of surgeons for over 10 years.

Method: All patients who received a Duracon/PCA fixed bearing total knee replacement between 1992 and 1996 were assessed clinically, fluoroscopically and completed an SF12, WOMAC and IKSS questionnaire.

Results: At a mean 9.7 (8–12) years follow up, 126 (69.6%) patients were available for review and 46 (25%) were deceased. The average age was 72 years (52–88) and the primary diagnosis was osteoarthritis in 95% of the cases. There were 34% Charnley Grade A, 37% Grade B and 29% Grade C respectively.

The average IKS Knee score was 72 (23–97) and the functional score was 68 (0–100) with 74% experiencing none or only mild pain. The SF12 assessment revealed a mean physical score of 55 (14–99). Ninety per cent of patients were satisfied with their knee and 89% would have the operation again if required.

There was one operative death (PE), one deep infection, 3 PE’s, 3 DVT’s and 5 superficial infections. An MUA was required in 9 cases.

Eight knees were revised. Using ‘all revisions’ as an end point. The survival rate was 95.3% at 10 years.

Conclusion: These results suggest that knee replacements carried out outside specialist arthroplasty centres perform very well with a survival rate of the implant of 95% at 10 years.

Purpose: To investigate the effect of pressurizing vertebral bodies during vertebroplasty using different materials in the development of fat embolism (FE) and any associated cardiovascular changes.

Polymethylmethacrylate (PMMA) is the material of choice for vertebroplasty (VP). However, PMMA has several disadvantages such as exothermic curing, uncertain long-term biomechanical effects and biocompatibility. As a result alternative materials are being developed to overcome these problems.

In order to determine the role of PMMA in the generation of cardiovascular changes following vertebroplasty we compared injection of cement with wax in an animal model.

Method: In twenty sheep, four vertebral bodies were augmented either with PMMA or bone wax. Heart rate, arterial, central venous and pulmonary artery pressure, cardiac output and blood gas values were recorded. At postmortem the lungs were subjected to histological evaluation.

Results: The consecutive augmentation of four vertebral bodies with PMMA induced cumulative fat embolism causing significant deterioration of baseline mean arterial blood pressure (MABP) and blood gas values. Injection of bone wax resulted in similar cardiovascular changes and amount of intravascular fat in the lungs.

Conclusion: In this animal model cardiovascular complications during multiple VP happen regardless of the augmentation material used. The deteriorating baseline MABP during VP is associated with the pressurization and displacement of bone marrow/fat into the circulation rather than caused by polymethylmethacrylate.

Current research efforts aim at enhancing osseointegration of cementless implants to improve early bone fixation.

Purpose: The aim of the present study was to investigate whether bone morphogenic protein (BMP) 2 had a positive effect on the osseointegration of hydroxyapatite coated implants.

Method: Hydroxyapatite (HA) implants were coated with BMP-2 and hyaluronic acid (HY) as the carrier or with HY alone. Uncoated HA-implants served as controls. The osseointegration of the implants was evaluated either by light microscopy or by pullout tests after 1, 2 and 4 weeks of unloaded implantation in the cancellous bone of 18 sheep.

Results: The BMP-2 coating significantly increased bone growth into the perforations of HA-implants. The proportion of bone-ingrowth at 4 weeks was 32% for the BMP-implants compared to 12% for HA implants. However, BMP-2 did not enhance the percentage of bone implant contact and interface shear strength values.

Conclusion: This study indicates that BMP-2 may help to increase bone growth across gaps of cementless implants in the early stages of bone healing improving fixation and decreasing the risk of loosening.

Introduction Polymethylmethacrylate (PMMA) has been widely used in orthopaedic procedures for fixation of joint replacements or enhancing the fixation of implants. However, the use of PMMA has been associated with cardiovascular deterioration and even death. More recently, PMMA has also been used for augmenting osteoporotic vertebral bodies which have fractured or are at risk of fracture. The main complication is PMMA leakage into adjacent structures. Transient hypotension and fatal fat embolism (FE) have also been reported.

The pathomechanism of cardiovascular deterioration after the injection of PMMA (i.e. FE) remains a highly controversial subject. The exact role of PMMA in the development of FE remains unclear. The aim of the present study was to elucidate the acute effects of injecting PMMA compared with bone wax into vertebral bodies on the cardiovascular system using an established animal model for vertebroplasty (VP) (Aebli, N, et al. Spine. 2002).

Methods In 8 skeletally mature mixed-bred ewes (2–4 years) 6.0ml PMMA (CMW3-Depuy) or bone wax (Bone Wax, Ethicon) were injected unilaterally, through an open approach into the L1 & L2 pedicles. Blood pressure, heart rate, and cardiac output were measured.

Results The major difference between the cardiovascular response of the PMMA and that of the bone wax group was the recovery in Pulmonary Artery Pressure (PAP) and Pulmonary Vascular Resistance (PVR). Three minutes post-injection, PAP had fully recovered to baseline values in the wax group. However in the PMMA group, PAP had only recovered by 52% after 3 min and fully recovered after 10 min.

Discussion The augmentation of vertebral bodies resulted in transient cardiovascular changes regardless of the material used. However, the recovery of PAP and PVR values took significantly longer with the PMMA group. The peak response was a result of pulmonary vasoconstriction triggered by a reflex reaction to the embolisation of bone marrow particles or by vasoactive cytokines. The peak response was therefore mainly associated with the increase in intraosseous pressure during the augmentation causing release of bone marrow contents into the and not the cement monomer. The cement monomer however plays a role in the cardiovascular complications during FE. The delayed recovery of PAP and PVR in the PMMA group may be due to a vasoconstriction effect of the cement monomer on the pulmonary vascular system.

Potentially serious cardiovascular complications may occur during VP regardless of the material used. The injection of PMMA may cause prolonged pulmonary hypertension during vertebro- and also arthroplasty. Continuous invasive cardiovascular monitoring may be required in patients with impaired cardiovascular and pulmonary function

Introduction and Aims: To determine whether sagittal laxity has an effect on functional outcome following posterior cruciate retaining total knee replacement using two differing tibial insert designs.

Method: Ninety-seven knees in 83 patients were reviewed clinically, radiologically and underwent KT1000 testing at minimum five-year follow-up post-TKA. Knee society, WOMAC and SF12 scores were calculated. The same femoral component (Duracon, Stryker) was used in all patients. Two differing tibial inserts were used (51 Condylar and 46 AP lipped).

Results: The two groups were comparable for age, sex, Charnley category and Body mass index. There was no significant difference in knee society score, WOMAC scores, SF12 scores, knee flexion, posterior tibial slope or KT1000 laxity measurements between the two groups. Total laxity measured by KT1000 was 5mm in the AP lipped group and 4mm in the condylar group. There was no correlation between anterior, posterior or total laxity and functional outcome as measured by WOMAC, KSS, SF12 or knee flexion.

Conclusion: Increased sagittal laxity does not have a strong influence on functional outcome following TKA. The differing tibial insert designs had no significant influence on laxity or function.

Introduction and Aims: Current research efforts aim at enhancing osseointegration of cementless implants to improve early bone fixation. The aim of the present study was to investigate whether bone morphogenic protein (BMP) 2 had a positive effect on the osseointegration of hydroxyapatite-coated implants in an animal model.

Method: Hydroxyapatite (HA) implants were coated with BMP-2 and hyaluronic acid (HY) as the carrier or with HY alone. Uncoated HA-implants served as controls. The osseointegration of the implants was evaluated by light microscopy and pullout tests after one, two and four weeks of unloaded implantation in the cancellous bone of 18 sheep.

Results: The BMP-2 coating significantly increased bone growth into the perforations of HA-implants. The proportion of bone-ingrowth at four weeks was 32% for the BMP-implants compared to 12% for HA implants. However, BMP-2 did not enhance the percentage of bone implant contact and interface shear strength values.

Conclusion: This study indicates that BMP-2 may help to increase bone growth across gaps of cementless implants in the early stages of bone healing improving fixation and decreasing the risk of loosening.

Introduction and Aims: Polymethylmethacrylate (PMMA) has been widely used in orthopaedic surgery including more recently vertebroplasty. The reported rate of complications following vertebroplasty is low and mainly related to PMMA leakage.

The aim of this study was to elucidate the acute cardiovascular effects of PMMA or bone wax in a vertebroplasty animal model.

Method: Eight skeletally mature sheep were used and PMMA or bone wax were injected unilaterally into L1 and L2 at 10-minute intervals. Arterial, central venous, pulmonary artery and left ventricular pressures were recorded using Statham pressure transducers and Swan Ganz catheters were used for monitoring cardiac output.

Results: Augmentation resulted in a two-phase response regardless of which material was used. First the mean arterial blood pressures started to drop after approximately two seconds. Secondly the pulmonary artery pressure and central venous pressure increased after approximately 11 seconds, whereas cardiac output and left ventricular pressure decreased. There was no significant change in heart rate for both groups. There was a significant difference (p< 0.05) in the pulmonary artery pressure values in the PMMA group compared to the basal values at one, three and five minutes, whereas in the wax group the pulmonary artery pressure recovered within three minutes.

Conclusion: Augmentation resulted in a two-phase cardiovascular response regardless of which material was used. Peak responses were similar for both groups, but pulmonary artery pressure and cardiac output recovered quicker in the wax group. The late recovery of pulmonary artery pressure and cardiac output in the PMMA group may be due to a vasoconstriction effect of the cement monomer.

We report early major complications encountered following TEN fixation of femoral fractures in children.

A case series of four children aged 8– 16 years who had primary TEN fixation of isolated femoral diaphyseal fractures.

Three of the four patients had major complications. These were: significant knee stiffness requiring manipulation, haemarthrosis requiring washout and nail removal, loss of position and refracture. Two required revision to locked intramedullary nails without early complication.

In the skeletally immature child TEN fixation of femoral fractures has a significant major complication rate. This needs to be recognised when comparing TEN fixation with other treatment options.

To investigate the effect of pressurizing vertebral bodies during vertebroplasty using different materials in the development of fat embolism (FE) and any associated cardiovascular changes.

Polymethylmethacrylate (PMMA) is the material of choice for vertebroplasty (VP). However, PMMA has several disadvantages such as exothermic curing, uncertain long-term biomechanical effects and biocompatibility. As a result alternative materials are being developed to overcome these problems.

In order to determine the role of PMMA in the generation of cardiovascular changes following vertebroplasty we compared injection of cement with wax in an animal model.

In twenty sheep, four vertebral bodies were augmented either with PMMA or bone wax. Heart rate, arterial, central venous and pulmonary artery pressure, cardiac output and blood gas values were recorded. At postmortem the lungs were subjected to histological evaluation.

The consecutive augmentation of four vertebral bodies with PMMA induced cumulative fat embolism causing significant deterioration of baseline mean arterial blood pressure (MABP) and blood gas values. Injection of bone wax resulted in similar cardiovascular changes and amount of intravascular fat in the lungs.

Conclusion: In this animal model cardiovascular complications during multiple VP happen regardless of the augmentation material used. The deteriorating baseline MABP during VP is associated with the pressurization and displacement of bone marrow/fat into the circulation rather than caused by polymethylmethacrylate.

The ability to assess the blood flow to a bone (IBF) is important for orthopaedic surgeons when deciding the fate of an injured or diseased bone. Currently there is no easy and effective method for quickly assessing the blood flow status of a bone. There is accumulating evidence that suggests that IBF may be correlated to intraosseous pressure (IOP).

Therefore, we aimed to investigate whether the two variables are correlated so that the orthopaedic surgeon could confidently use IOP as an indicator of IBF.

Using 8 mature female ewes (B.W. ~56 kg) we measured cardiovascular (eg. arterial blood pressure – ABP), and intraosseous (ie. IOP and IBF) responses to nor-adrenaline (0–1.5 μg/kg/min. i.v.) and nitroglycerine (0–80 μg/kg. i.v.) IBF was measured using semi-quantitative technique of laser Doppler flowmetry (LDF).

Our results revealed that changes in ABP were directly correlated to changes in IOP (p < 0.001). Due to technical difficulties that were encountered when using LDF, the collected IBF data were limited. However, there was compelling evidence that there is a positive and direct correlation between IBF and IOP.

This opens an exciting possibility of using IOP for quickly and accurately assessing IBF as well as providing insight into the pathological mechanisms responsible for bone and joint disorders.

Current research efforts aim at enhancing osseointegration of cementless implants to improve early bone fixation.

The aim of the present study was to investigate whether bone morphogenic protein (BMP) 2 had a positive effect on the osseointegration of hydroxyapatite coated implants.

Hydroxyapatite (HA) implants were coated with BMP-2 and hyaluronic acid (HY) as the carrier or with HY alone. Uncoated HA-implants served as controls. The osseointegration of the implants was evaluated either by light microscopy and pullout tests after 1, 2 and 4 weeks of unloaded implantation in the cancellous bone of 18 sheep.

The BMP-2 coating significantly increased bone growth into the perforations of HA-implants. The proportion of bone-ingrowth at 4 weeks was 32% for the BMP-implants compared to 12% for HA implants. However, BMP-2 did not enhance the percentage of bone implant contact and interface shear strength values.

Conclusion: This study indicates that BMP-2 may help to increase bone growth across gaps of cementless implants in the early stages of bone healing improving fixation and decreasing the risk of loosening.

This study explores the outcomes of a pilot project involving five Orthopaedic services in developing approaches to improve the consistency and equity of clinical decision-making for access to treatment.

The pilot was conducted in two phases; the first involved development of retrospective and prospective data collection and analysis tools including use of:

The Orthopaedic Integrated CPAC tool:

Large variations in internal equity were found within most services. Additionally a significant, systemic equity issue is apparent between patients prioritised for major joints versus other conditions. The pilot has made useful progress in developing improvement tools and processes targeting electives service management, improvements in prioritisation and clinical decision making, and funding and planning decisions. The pilot has also raised issues for further CPAC development and national service policy.

To determine whether increased sagittal laxity has an effect on functional outcome following posterior cruciate retaining total knee replacement using two differing tibial insert designs.

Ninety-seven patients were reviewed clinically, radiologically and underwent KT1000 testing of their TKR at a minimum follow up of 5 years (mean 6.5 yrs). The femoral component design was the same in all patients (Duracon/PCA). Fifty two patients had a relatively flat tibial insert design (group 1), while 45 patients had an AP lipped insert (group 2) following a change in design in 1995.

The 2 groups were comparable for age, sex, Charnley category, BMI, tibial slope and follow up. There was no significant difference in laxity measurements, IKS or WOMAC scores between the groups. There was no significant correlation between laxity and outcome score or flexion range.

Increased sagittal laxity in a knee replacement does not have a strong influence on functional outcome. The differing tibial insert designs had no significant effect on either laxity or function.

Surgical waiting lists have led to development of clinical priority access criteria (CPAC) for prioritisation of patients selected for surgery. Although introduced widely into clinical practice in New Zealand CPAC tools have not been validated. Reliability studies were therefore undertaken by the CPAC Evaluation Consortium.

Methodology Thirty eight orthopaedic surgeons practising in public hospitals were randomly selected to participate in a prioritisation exercise using computer administered clinical vignettes. Fifty vignettes were developed from the clinical histories of patients selected for total knee arthroplasty (15), carpal tunnel decompression (15) and miscellaneous orthopaedic procedures (20). These were prioritised using each of 3 priority tools producing scores between 0 and 100: visual analogue scale reflecting global clinical opinion (VAS), a generic point scoring system based on points assigned to 5 clinical domains (GOPC), and diagnosis-specific 5 point Likert scale of priority combined with a predetermined table of a range of scores for each diagnosis (ISS).

The extent of inter-surgeon variability was striking but significantly less for ISS than GOPC or VAS. This was entirely explained by the complication of a predetermined table. The other two tools were similar except that the inter centile gap was larger for the clinical opinion based tool (VAS).

As access to elective surgery is determined by a fixed financial threshold a reliable scoring system will ensure equity of access. This seems to be best achieved by using the Integrated Scoring System.

Introduction: Vertebroplasty (VP) is a new prophylactic treatment for preventing osteoporotic compression fractures of vertebral bodies. During this procedure polymethylmethacrylate (PMMA) is injected into several vertebral bodies. It has been shown that fat embolism (FE) with acute cardiopulmonary deterioration occurs during VP as in a variety of other orthopaedic procedures (e.g. knee and hip replacements). The aim of the study is to investigate cardiovascular changes during FE caused by multiple VP using an animal model.

Method: In six sheep, PMMA was injected unilaterally, into L1 – L6, with ten minutes in-between injections. Arterial, venous and pulmonary artery pressure, cardiac output and blood gas values were recorded pre injection and 1, 3, 5 and 10 minutes post injection. Post mortem lungs were harvested and the histopathologic score (percentage of lung fields occupied by intravascular fat globules as seen in the microscope) was calculated.

Results: The sequential injection of bone cement into six vertebral bodies from values pre injection of L1 to 10 minutes post injection of L6 resulted in: significant falls in arterial blood pressure (P< 0.0001), cardiac output (P< 0.0001) (P=0.0049), pO₂ and pH (P< 0.0001) and significant rises in pulmonary arterial pressure (P=0.0005) and pCO₂ (P< 0.0001),but no significant change in central venous pressure. The histopathological score was 19.1±1.94%.

Conclusion: This study clearly shows that multiple VP in sheep leads to FE with major cardiovascular reactions. Arterial blood pressure showed a stepwise, cumulative fall and was clearly the best parameter to demonstrate these reactions. This suggests, in human patients, particular attention should be paid to falls in arterial blood pressure during multiple VP.

We carried out a histological study of a proximally hydroxyapatite (HA)-coated femoral component, retrieved after 9.5 years of good function. The HA coating had completely degraded. Bone was in direct contact with the titanium surface in all the areas which had been coated, with no interposing fibrous tissue. There were no signs of particles, third-body wear, adverse tissue reactions or osteolysis. Bone remodelling was evident by the presence of resorption lacunae; tetracycline labelling showed bone laid down six years after implantation.

The loss of the HA-coating had no negative effect on the osseo-integration of the stem. We conclude that the HA coating contributes to the fixation of the implant and that its degradation does not adversely affect the long-term fixation.

There are numerous papers from specialist arthroplasty centres outlining results of total knee replacement. This review was performed as there is little information on results in general orthopaedic centres. All patients received a Duracon/PCA replacement between 1992 and 1996. Patients were assessed clinically, fluoroscopically and completed SF12, WOMAC and IKSS questionnaires. At a mean of 6.7 (5–9) years follow up 93 (78%) were available for review. The average age was 70 years (52–88) with 58% being male. The primary diagnosis was osteoarthritis in 94.3%, with 41 %, 38% and 21 % being Charnley grades A, B and C respectively.

The average IKS knee score was 71.4 (23–96) and functional score 70 (0–100), with 72.7% experiencing none or only mild pain. The SF12 assessment revealed a mean physical score of 38 (14–63) and mental score of 53 (25–67). There were 88.6% of patients satisfied with their knee and 92% would have the operation again if required. There were no deep infections or PE’s but there were 7 superficial infections and 2 DVT’s. A MUA was required in 8 patients. One patient retains a radiologically loose prosthesis at 8 years but had mild pain with stairs only, a WOMAC functional score of 85 and was happy. There was a best-case survival of 94.4% at 5 years. There were 5 knees revised in 5 patients and no revisions of the deceased patients, all surviving greater than 5 years from surgery. These results suggest that those in general orthopaedic centres are a little less reliable than those in specialist centres. However they are acceptable and patient satisfaction remains high.

Magnetic Resonance Imaging is increasingly utilised for the assessment of knee pathology. The aim of this study was to review our entire knee MRI scans and to assess the accuracy of diagnosis when compared with operative diagnosis. Using data from the radiology department and medical records (public and private) all patients having knee MRI scans in a 6-year period were identified.

There were 956 scans performed on 930 patients. Scan diagnosis, operative diagnosis and diagnostic accuracy were assessed. Of the scanned patients 181 (19.5%) had normal scans and of these 168 (92.8%) were accurately diagnosed as normal. The remaining 749 (80.5%) had an abnormality noted on scan and of these 298 (39.8%) proceeded on to surgery. Of those patients having surgery, diagnosis at surgery was found to exactly match the results of the scan in 163 (57.0%) patients. Furthermore 51.5% of patients with a diagnosis of meniscal degeneration by scan actually had a meniscal tear at operation. However the sensitivity for diagnosis of ACL tears was 89.0% and that of medial meniscal tears was 90.6%.

MRI diagnosis is far from infallible and clinicians should be conscious of its limitations. However it is particularly reliable in confirming the lack of pathology within a knee with an accuracy of 93%. It also has high sensitivity for diagnosis of ACL and meniscal tears.