Image-guided spine surgery requires registration between the patient anatomy and the preoperative computed tomography (CT) image. We have previously developed an accurate and robust registration technique for this application by using intraoperative ultrasound to acquire patient anatomy and then registering the ultrasound images to the CT images by aligning the posterior vertebral surfaces extracted from both modalities. In this study, we validate our registration technique across 18 vertebrae on three porcine cadavers.

We applied the ultrasound-registration technique on the thoracic and lumbar vertebrae of the porcine cadavers using both single sweeps and double orthogonal sweeps. For each sweep pattern at each vertebra, we also randomly simulated 100 different initial misalignments and registered each misalignment. The resulting registration transformations are compared to gold standard registrations to assess the accuracy and the robustness of the technique.

Orthogonal-sweep acquisition was found to be the sweep-pattern that performed the best and yielded a registration accuracy of 1.65 mm across all vertebrae on all porcine cadavers. It was found that the target registration errors (TRE) stay relatively constant with increasing initial misalignment and that the majority (82.7%) of the registrations resulted in TREs below the clinically recommended 2 mm threshold. In addition, it was found that the registration accuracy varies by the sweep pattern and the vertebral level, but neighbouring vertebrae tend to result in statistically similar accuracy.

We found that our ultrasound-CT registration technique yields clinically acceptable accuracy and robustness on multiple vertebrae across multiple porcine cadavers.

Introduction

Uncemented components necessitate accurate intraoperative assessment of size to avoid complications such as calcar fracture and subsidence whilst maintaining bone stock on the acetabular side. Potential problems can be anticipated pre-operatively with the use of a templating system. We proposed that pre-operative digital templating could accurately assess femoral and acetabular component size.

Introduction: Recent data from the UK suggests that the incidence of osteomyelitis in the paediatric population is declining. However, the incidence in the Scandic countries has risen in the late eighties and nineties. We undertook to examine the epidemiology of osteomyelitis presenting to a paediatric teaching hospital in an Irish urban setting.

Patients and Methods: We undertook a retrospective review to identify patients admitted over a twenty-five year period with a diagnosis of osteomyelitis. Patients were identified from hospital records, theatre log-books and a departmental database. Demographic data was collected, as were details of the infected bony structure, treatment required and organism cultured.

Results: A total of 291 patients were admitted over a twenty-four year period, from 1977 to 2000.

A marked reduction in osteomyelitis was noted over the twenty-four year incidence of the study. In addition, a shift in the causative organism was noted from an incidence of H Influenzae in the 70’s of up to 30%, to less than 5% in the 90’s. The treatment regime changed markedly over the course of the study period, with a significantly reduced duration of hospital stay reflecting the move away from protracted periods of hospitalisation.

Conclusion: A marked fall in osteomyelitis has occurred in the paediatric population. This may be due to improved living conditions and the introduction of H Influenzae vaccinations. The duration of hospital stay has declined markedly and the introduction of newer imaging modalities has aided diagnosis, allowing early aggressive intervention. However, as osteomyelitis is becoming increasingly rare, a higher index of suspicion is required, particularly from non-specialists who are more likely to be the first to encounter these patients.

Introduction and Aims: Hip arthroplasty alters stress patterns in the proximal femur, thereby influencing femoral bone remodelling. The purpose of our study was to determine long-term skeletal response to wellfixed total hip arthroplasty.

Method: Seventy-two hips in 66 patients (mean age 57, range 25–72; 29 male, 37 female) were evaluated with standardised measurement protocol after arthroplasty with cemented Charnley (32 hips) or uncemented 5/8 coated AML stem (40 hips). Inclusion criteria: stable implants and complete radiographic record with minimum follow-up 15–20 years. 3159 measurements were made with power calipers and normalised for magnification.

Results: There was time dependent loss of proximal cortical thickness around both stems (AML greater than Charnley; proximal medial greater than proximal lateral cortex, (p< 0.05, all parameters). At 15–20 years, median proximal medial cortical thickness decreased by 12% for Charnley and 70% for AML stems. Median proximal lateral cortical thickness decreased by 9% for Charnley and 21% for AML stems. Median cortical thickness changes around the mid and distal prosthesis for both stems was mild, with a non-statistically significant trend (p> 0.05) towards more cortical loss (2–9%) around Charnley than AML stems (0–8%). The median intramedullary width increased by 1–10%, depending on level (no difference by prosthesis type, p> 0.05). Changes continued progressively over the entire observation period.

Conclusion: This paper provides the first detailed long-term information on the effect of well-functioning hip arthroplasty on femoral morphology in a large patient group. Morphologic changes are most pronounced in the proximal medial femur and vary by implant type. Also, the medullary canal widens around a replaced hip as the patient ages.

The number of skate related injuries has seen a resurgence in the western world with almost 51000 patients in 1999 presenting to US hospitals with a skateboard related injury, almost 90% of these being male and almost 70% of these are orthopaedic related injuries. Protection , particularly wrist guards, elbow pads, knee pads and recognized helmets are all necessary in protecting the young child against orthopaedic injuries. However despite these physical barriers little training or supervision exists in adequately educating children as to the dangers of these devices. Having observed an increased number of referrals to our Accident and Emergency Dept with fractures sustained whilst roller-blading and skateboarding we set about prospectively evaluating the epidemiology and nature of such injuries. 100 successive referrals to the orthopaedic service as a result of roller/skate injuries were evaluated. Childs age, sex, time using apparatus, mechanism of injury, and whether the injury occurred in a dedicated skatepark or on the street was recorded. Whether the child was wearing any form of protective gear and what type was also recorded. The type of fracture and its treatment and follow up was evaluated. All results were recorded on standard excel spreadsheets and statistical analysis was performed using Instat statistics (Graphpad USA 2002). The Male to female ratio in street injuries was 1:1, whereas in ramp injuries 4:1. 60 injuries occurred on the street whereas 40 occurred whilst using the ramps. The mean age was 11.4yrs. The mean length of time using rollerblades/skateboards was 20 and 19 months for street and ramps respectively. The number of children wearing some form of protective gear shows only 20 children out of the 100 studied wore gear, of these 15 wore helmets only. The treatment initiated shows almost 80% of ramp related injuries required formal manipulation under general anaesthesia or open reduction and internal fixation, where as only 25% of street fractures required this form of treatment, The usage of ramps demonstrates an increased relative risk of 4.26 (95% CI 3.5–5.1) This study shows that skateboards and rollerblades still constitute a major component of childhood fracture admissions. Only 20% of children use some form of protective gear whilst skating, this needs to be addressed on a national level. The wearing of helmets whilst protecting the child against head injury do not prevent serious orthopaedic injuries. Wrist guards should be worn by all children skating as the fall onto outstretched hand still remains a childs defensive mechanism when thrown off balance. Almost 75% of all fractures involve the wrist or the forearm. We urge better education and a tighter supervision of children whilst skating. Dedicated skateparks should only be used by experienced and older children and they should at least be supervised during their first attempts at using the parks, 85% of ramp injuries occurred during first or second time users. A child using a skatepark particularily for the first time is three times more likely to sustain a fracture, and almost 4 and a half times more likely to require definitive surgical treatment of this fracture. This constitutes a huge orthopaedic burden as well as it’s associated morbidity and financial costs to the health service. Children should be encouraged to use limb protectors as well as helmets whilst skating and should be supervised more closely during their initial attempts.

A retrospective study was undertaken in our unit to investigate any change in osteomyelitis trends in the last ten years (1991-2001). These results were then compared to 3 previous studies conducted by our unit on childhood osteomyelitis, 1977-1979 45 cases(O’Brien et al)1, 1980-87 (84 cases) and 1988-1991 (54 cases).

149 patients were identified from hospital discharge database with a diagnosis of osteomyelitis between 1991 and 2001. 136 fully completed charts were discovered and included in the study. 22 children did not fulfil the criterion for the diagnosis of acute or subacute osteomyelitis and were excluded. Cellulitis was the actual diagnosis 18/22 cases, leukaemia or other neoplasm in 4/22 cases. 28% of the children 32/114 had acute haematog-enous osteomyelitis with classical signs and symptoms the remaining 72% fell into the subacute osteomyelitis category as described by Gledhill. Table 1 shows the comparison between the 4 studies.

89% of patients underwent 3 phase bone scanning, and 90% of these were positive. Blood cultures were performed in 87% of patients and were positive in 8.5%, 2 patients being positive and symptomatic of Nesseria meningitis, 4 Staph aureus, 2 Strep Pneumonia, 1 staph epidermidis and 1 E.Coli. As compared to previous 3 studies no case of haemophilus influenza type B was encountered. Aspiration was performed in 22 patients and 18 demonstrated bacteria, the two commonest pathogens were Staphylococcus aureus 66% and epider-midis 16%. 8 patients underwent surgical debridement or drilling if clinically septic or because of failure to improve despite medical treatment.

Initial antibiotic treatment comprised of i.v. penicillins and oral fucidin in 92% of patients, the remainder receiving cephalosporins as favoured by physicians or erythromycin if history of hypersensitivity. Antibiotics arethen tailored to clinical picture or culture results. Table 2 shows the changing duration pattern of antibiotic administration.

There were four cases of complications, 2 cases of chronic osteomyelitis and 2 cases of limb shortening both around the knee joint.

Our results correlate well with other authors. Surgery has an ever-decreasing role in the management of osteomyelitis, with conservative antibiotic management and splintage being the treatment of choice. Subacute osteomyelitis is an ever-increasing entity as reflected in other studies. The incidence of osteomyelitis presenting to our unit has fallen to 2.34 per 10000 per yea. A possible explanation may lie in altered host pathogen interactions, increased host resistance, the frequent administration of broad-spectrum antibiotics in general practice. Increased population wealth as experienced in Ireland in the last 8 years may also have a role.

Introduction: Subject to recent literature citing a reduction in ankle range of motion predisposing to ankle fractures in children, we decided prospectively to analyse the passive range of motion in children presenting to our fracture clinic with simple distal radial metaphyseal fractures treated conservatively in cast.

The range of motion was assessed by two observers, and measured using a goniometer in 80 patients. (42 radial fractures and 38 controls) The controls were recruited from children presenting with lower limb injuries and with no prior history of an upper limb injury or neuromuscular condition. The fractures were as a result of simple falls onto the outstretched hand with definite radiological and clinical findings. The range of motion in the contralateral limb was assessed. Both groups showed an equal distribution of dominant and non-dominant limbs.

Results: Both groups were well matched with an average age of 10 and 10.3 years fracture group and control group respectively, and gender 55% male fracture group and 52.5% control group. The m injured group showed a passive range of motion of 1680, whereas the control group showed a higher range of motion of 1820, a difference of 140 (p< . 005 student t-test). A third blinded independent observer of 20 children assessed Intra and interobserver error, and no observer was noted to have higher or lower readings.

Conclusion: Children with radial fractures have a lower passive range of motion of their wrists than Controls. This may contribute to the aetiology of wrist fractures in a paediatric population. An possible explanation may be as cited in original work that children who sustain fractures have less mobility around their joints due to reduced elasticity in their musculoskeletal framework. Simple passive stretching of fracture prone joints should therefore be advised.