Introduction: Vertebroplasty (VP) is a relatively new procedure to treat osteoporotic compression fractures of vertebral bodies. During this procedure polymethyl-methacrylate (PMMA) is injected into vertebral bodies. However there is the concern, that fat embolism (FE) and acute hypotension could occur as in a variety of other orthopaedic procedures.

Aim: To investigate whether FE and acute hypotension are potential complications of VP using an animal model.

Methods: In six sheep, 6.0 ml PMMA were injected unilaterally into the L1 vertebral body. Transœsophageal echocardiography was used to monitor the pulmonary artery for bone marrow and fat particles until 30 minutes post-operatively. Pulse, arterial and venous pressures were also recorded. The lumbar spine and the lungs were harvested post mortem. The histopathologic score, (percentage of lung fields occupied by intravascular fat globules as seen through the microscope), was calculated.

Results: The first showers of echogenic material were visible approximately seven seconds after the beginning of the cement injection and lasted for about 2.5 minutes. The injection of bone cement caused a very rapid decrease in the heart rate after two seconds followed by a fall in the mean arterial pressure after 6.0 seconds. A maximum fall in heart rate was accompanied by a delayed fall in mean arterial pressure of 33.0 mmHg (P=0.0003) at 36seconds. The heat rate had returned to the baseline by 89 seconds and had increased by 10 beats/min (P=0.02) at 25 minutes. Mean arterial pressure had recovered by 209 seconds and was not different from the baseline at 25 minutes. Post mortem examination showed that no leakage of cement into the spinal cord had occurred. The histology revealed fat globules and bone marrow cells in the smaller and larger vessels throughout the lungs. The histopathologic score was 5.2 ± 0.9%.

Conclusions: This study clearly showed that VP resulted in FE with a two-phase decrease in heart rate and arterial blood pressure. The first phase was probably due to an autonomic reflex and the second phase was due to the passage of fat emboli through the right heart and obstructing the lungs.

Introduction: After more than 10 years of clinical experience, hydroxyapatite (HA) coated orthopaedic implants are now an established, viable alternative to porous coatings for achieving good implant fixation. However, developments are continuing to improve the nature and adhesion of the HA coating.

Aim: To investigate the biological attachment characteristics of titanium and highly crystalline HA implant coatings in the metaphysis of an animal model.

Method: Titanium alloy implants with a coating of commercially pure titanium (Ti) or highly crystalline HA were evaluated by light microscopy and pullout tests after one, two and four weeks of unloaded implantation in the tibial and femoral metaphyses of 18 sheep.

Results: The interface shear strength pullout increased from approximately 29N/cm2 at one week to approximately 326N/cm² at two weeks. At four weeks the pull-out strength for Ti and HA coated implants was 1,004.87 ± 189.82N/cm2 and 1,043.26 ± 260.61N/cm2 respectively. The pullout strength increased significantly over time up to four weeks, but the difference between the coatings was not statistically significant at any time interval.

Histomorphometric analysis showed an increase of bone-implant contact between one and two weeks from 0 to 15% for Ti and 0 to 20% for HA coated implants. At four weeks Ti and HA implants showed 44% and 60% bone-implant contact respectively. There was a significant increase in bone-implant contact over time for both coatings. HA implants had significantly higher bone-implant contact at two and four weeks. Light microscopy revealed that bone grew into HA coated surfaces in the form of feet, spreading over the surface. Whereas for Ti the newly formed bone looked like a bridge linking the original bone with the implant surface.

Conclusion: The different growth patterns of bone into Ti and HA surfaces resulted in different bone-implant contact areas. Highly crystalline hydroxyapatite coatings enhanced the osseointegration in the early stages of bone healing. However there was a discrepancy between the mechanical and histological results. This may suggest that the mechanical failure does not occur at the implant-bone interface.

Purpose: The ABG Total Hip Joint Replacement is a cementless, hydroxyapatite coated prosthesis designed to be metaphyseal loading. The aim of our study was to analyze the changes in proximal femoral bone mineral density (BMD) following implantation of this prosthesis.

Method: Dual energy x-ray absorptiometry (DEXA) scanning has been shown to be an accurate and reliable method of assessing BMD following total hip arthroplasty. 14 patients undergoing primary ABG Total Hip Joint Replacement were recruited into the study following informed consent. BMD was determined for each of the seven periprosthetic zones of Gruen from DEXA scans, which were performed serially at preoperative,, 3 months, 6 months, 1 year and 2 years.

Results: 8 patients have now completed their scans. The most dramatic change in BMD was found in zone 7 which is the femoral calcar. In this region there was a progressive decrease in average BMD to 75% of the preoperative value at 2 years. In zones 2 and 3 representing the femoral cortex lateral to the prosthesis there was an increase in BMD to approximately 114.5% at 3 months and this was maintained at 2 years. In the remaining zones BMD was reasonably stable between 97.5 and 101%.

Conclusion: We have found that in the 2 years following ABG hip arthroplasty there is a dramatic decrease in BMD to 75% within the region of the femoral calcar. Further scans are required to determine if this is progressive. In the remaining regions BMD is either increased or relatively well preserved.

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 it does in a variety of other orthopaedic procedures (e.g. knee and hip replacements).

Aim: To investigate the cardiovascular changes during FE caused by multiple VP using an animal model.

Method: PMMA was injected unilaterally, into L1 – L6 in six sheep, with 10 minutes between injections. Arterial, venous and pulmonary arterial pressure, cardiac output and blood gas values were recorded before injection and again after the injection at one, three, five and 10 minutes. The lungs were harvested post mortem and the histopathologic score (percentage of lung fields occupied by intravascular fat globules as the field of the microscope) was calculated.

Results: The sequential injection of bone cement into six vertebral bodies from values before injection of L1 to 10 minutes after injection of L6 resulted in significant falls in arterial blood pressure (P< 0.0001), cardiac output (P=0.0049), pO² (P< 0.0001) and pH (P< 0.0001). There were also 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%,

Conclusions: This study clearly showed 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 that in human patients, particular attention should be paid to falls in arterial blood pressure during multiple VP.

Aim: To demonstrate the pattern and mechanism of injury of alpine skiing and snowboarding, and to evaluate the potential risk factors.

Methods: We analysed prospectively all cases of orthopaedic injuries requiring hospital admission that were the result of snowboarding or skiing accidents in the winter of 2000. This included four popular skiing facilities in the South Island of New Zealand.

Results: Seventy-six patients were reviewed. Of those, 30 cases were the results of accidents from snowboarding and 44 cases were from skiing. In addition to appropriate medical evaluations and medical care, a detailed examination was performed on every patient to determine various factors, including demographics, their level of experience and the cause and mechanism of the accident. There were 47 males and 29 females, with an average age of 28 (range: seven to 62)years. Snowboarders tended to be younger men with an average age of 23 years compared with 31 years in skiers. Males constituted 77% of snowboarders and 54% of skiers.

There were 14 patients in the beginners’ group, 32 intermediate, 20 advanced and nine at an extreme-skill level. Thirty-eight patients sustained injuries of the lower extremities, 24 of the upper extremities, 13 of the spine, and one of the pelvis. Lower extremity injuries were more common in skiers (59% of lower limbs, versus 25% of upper limbs), while in snow boarding upper extremity injuries were more common (43% upper limbs versus 36% lower limbs). Ulnar collateral ligament injuries of the metacarpophalangeal joint of the thumb, were far more common in skiers (six in skiers versus one on snowboard). Sixteen patients (nine skiers and six snow-boarders) sustained diaphyseal fractures of their tibiae. In all nine patients in the skiing group, the mechanism of injury was failure of the binding to release resulting in a twisting force to the leg, while in the snowboarding group, three patients (50%) fractured their tibiae on landing badly from a jump and in the other three on colliding with another person or a fixed object.

Conclusions: Lower extremity, equipment-related injuries are common in alpine skiing. The data suggested that currently used bindings are insufficient. Research, technical developments and optimal adjustment of binding are required.

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. However, there is the concern, that fat embolism (FE) and acute hypotension could occur as in a variety of other orthopaedic procedures.

This study was undertaken to investigate whether FE and acute hypotension are potential complications of VP using an animal model.

In six sheep 6.0 ml PMMA were injected unilaterally into L1. Transesophageal echocardiography was used to monitor the pulmonary artery for bone marrow and fat particles until 30 minutes postoperatively. Pulse, arterial and venous pressure were also recorded. Post mortem the lumbar spine and the lungs were harvested. The lungs were subjected to histological evaluation.

The first showers of echogenic material were visible approximately 7.0 seconds after the beginning of the cement injection and lasted for about 2.5 minutes.

Injection of bone cement elicited a very rapid decrease in heart rate after 2.0 seconds followed by a fall in mean arterial pressure after 6.0 seconds. A maximum fall in heart rate was accompanied by a delayed fall in mean arterial pressure of 33.0 mmHg (P=0.0003) at 36.0 seconds. Heat rate had returned to baseline by 89.0 seconds and had increased by 10.0 beats/min (P=0.02) at 25 minutes. Mean arterial pressure had recovered by 209.0 seconds and was not different to the baseline at 25 minutes.

The post mortem inspection revealed disseminated haemorrhages on the lung surface and throughout the parenchyma mainly in the caudal lobes of all six animals. No leakage of cement into the spinal cord was detected. In histology fat globules and bone marrow cells were observed in both the smaller and larger vessels throughout the lung.

This study clearly shows that VP resulted in a two-phase decrease in heart rate and arterial blood pressure. The first phase was probably due to an autonomic reflex and the second phase was due to the passage of fat emboli through the right heart and obstructing the lungs.

Aim: To analyse the Dunedin residual orthopaedic waiting list based on a simple patient questionnaire and a quality of life assessment using EuroQol and SF12.

Method: All patients on the residual waiting list were sent a postal questionnaire enquiring about their need for surgery and their quality of life. Based on their answers, patients were entered into three action groups: 1. back to GP care 2. clinical review 3. booked for surgery. Those patients requiring a clinical review were seen in a special clinic and reassessed in relation to their need for surgery.

Results: Two hundred and sixty-one patients were surveyed. One hundred and fifty-eight had complete data available for analysis and of the remaining 103 patients, 88 were taken off the waiting list for various reasons. Fifteen did not reply. The average time on the waiting list was 19 months (range: < six months to eight years). Sixty percent of the patients felt that their condition had changed and 99% felt that they still required the surgery. The results of the EuroQol and DF12 questionnaire revealed three groups of patients. 1. normal (9 patients). 2. slight impairment (115 patients) 3. moderate impairment (34 patients). Most of these patients had stable conditions except the sub group with deteriorating osteoarthritis of the hip/knee. Group 1 patients were all referred back to their GP. Thirty percent of group 2 patients were referred back to their GP, 60% were booked for a review and 10% were booked for surgery. None of Group 3 patients were referred back to their GP. Seventy percent required a clinical review and 30% were booked for surgery. Our clinical review is continuing but it is anticipated that those who still require surgery and score above the financial threshold will probably be less than one third of the cases.

Conclusion: This paper describes a decision making rationale in relation to assessment of continuing need for surgery in patients on the residual orthopaedic waiting list. Eighty percent of patients had stable conditions, which were not interfering significantly with their activities of daily living and could be managed safely by the GP. Further work is required to identify those patients who are at risk of deteriorating and to work out a practical and cost effective monitoring programme.