Introduction

Obesity is known to influence surgical risk in total hip replacement (THR), with increased Body Mass Index (BMI) leading to elevated risk of complications and poorer outcome scores. Using a multinational trial data of a single implant, we assess the impact of BMI and regional variations on Harris Hip scores (HHS).

The introduction of a new implant material is not without risk. A series of worst-case scenarios were developed and tested accordingly to answer questions such as: what will happen if the implant is not placed in a good orientation? What will happen to the material after a long implantation time, e.g. 20 or more years?

To reach a higher level of safety, a new approach for the preclinical testing has been taken. The vitamys® material (a novel vitamin-doped HXLPE) followed a severe pre-clinical testing protocol, including mechanical, tribological and biocompatibility testing. The testing includes a comparison of vitamys® vs. standard-UHMWPE and other HXLPE after accelerated ageing for periods equivalent to 20 and 40 years in-vivo. Hip simulator testing was done at inclination angles from 35° to 65° to assess the “forgiveness” of the material for mal-orientation.

Comparing the test results to published data, it becomes evident that the vitamin addition and the sequence of the manufacturing steps both have a significant effect of the resulting mechanical, ageing and wear properties. In contrast to UHMWPE or HXLPE without antioxidant, the vitamys material behaves in a very “forgiving” manner: Hip simulator testing of vitamys at high inclination angles and even with severely aged material revealed no increase of wear rates. The vitamys material was first introduced in a monoblock polyethylene cup with a thin Ti-particle coating, the RM-Pressfit vitamys® acetabular cup (Mathys Ltd Bettlach, Switzerland). Its first implantation occurred in Sept. 2009. Since then, a total of nearly 500 implantations have been documented in a prospective multi-centre clinical study involving 11 clinics in 5 countries (CH, DE, FR, NL and NZ).

Based on the pre-clinical testing and its first clinical experience, we have reason to believe that the RM-Pressfit vitamys® possesses interesting and unique features such as high elasticity (no stress-shielding), high ageing and wear resistance combined with clinically proven biological anchorage – making it theoretically suitable for a whole range of patients, including the young and active.

The use of peritumoral oedema on magnetic resonance (MR) imaging to predict soft tissue tumour grade is controversial. The clinical significance of oedema visualised on MR scans is poorly defined in the literature. We undertook this study to ascertain a diagnostic relationship between peritumoral oedema surrounding soft tissue sarcomas and the histological grade of the tumour.

One hundred and ten consecutive soft tissue tumours were extracted from the New Zealand Bone and Soft Tissue Tumour Registry. Key inclusion criteria were tumours deep to fascia, measuring more than 5cm in any dimension. Both benign and malignant sarcomas were included. MR scans and histology were reviewed, separately and in random order by a single author. Histology was graded as benign, low or high grade (based on the American Joint Committee on Cancer grading system).

Peritumoral oedema was defined as the increased signal intensity, on T2 or STIR images, immediately surrounding a discrete lesion. It was measured on two or more planes with the largest value used in diagnostic calculations. Oedema greater than or equal to 20mm was defined as a positive test result. Twenty five random scans were double read to ensure inter-observer reliability

Data was obtained for 83 tumours, 36 benign and 47 malignant (34 high grade and 13 low grade). The tumours in all groups were matched for size. The mean peritumoral oedema was 10.5mm for benign tumours, 20.6mm for low grade sarcomas (p<0.1), 28.1mm for high grade tumours (p<0.01) and 26.1mm if all malignant tumours were included as a single group (p<0.01). Using peritumoral oedema as a diagnostic test for tumour grade resulted in a specificity of 72%. The highest diagnostic ability was found when comparing benign to high grade tumours which yielded sensitivity of 59% and a positive likelihood ratio of 2.1. This data suggests a high false negative rate and that the test adds little to the diagnostic process.

To our knowledge this is the first study which assesses the diagnostic accuracy of peritumoral oedema to predict the histological grade of soft tissue sarcomas. Our results show a statistically significant difference, in surrounding peritumoral oedema, exists when comparing benign to high grade sarcomas and to all malignant tumours. This relationship is not apparent for low grade tumours. As a diagnostic test, using only peritumoral oedema to predict histological grade is unreliable.

Objective: Appendicular soft tissue tumours are rare. They represent less than 1% of all malignancy. Failure to appropriately investigate a malignant mass can result in unnecessary loss of limb or life. New Zealand is a sparsely populated country and has four orthopaedic tumour surgeons which is in keeping with the recommended ratio of 1/1,000,000. Consequently some patients find themselves long distances from Tertiary tumour centres. We looked at the investigation and referrals of patients to the Bone and Soft tissue tumour service at our institution.

We reviewed the charts of all patients (126) with a soft tissue tumour referred to the senior authors in 2006 and 2007. The information was stored in a prospective Tumour Registry Database. Where information was not available in records kept at our institution, the referring institution was contacted.

There were 92 tertiary referrals and 34 GP referrals. The majority of the tertiary referrals came from orthopaedic surgeons (55), and general surgeons (28). The mean duration between referral and review was 16 days (0–215 days). There was a of 13 days wait for tertiary referral review. Tissue samples and histology reports accompanied 33 patients which had resulted from 35 invasive Pre Referral Procedures (PRP). This group suffered 21 complications affecting 18 patients. The remainder (91) were Pre Biopsy Referrals (PBR). Biospy was deemed necessary in 47 cases. The PBR group suffered 4 complications. Only one complication occurred to a patient with benign histology in each group. There was an extremely significant relationship between Pre Referral Procedures and suffering a complication (P< 0.0001). The relative risk of complication was 6.2 (C.I. 2.0–18.4) if an invasive procedure was performed prior to referral. There were 3 amputations (plus one recommended but refused by patient) in the PRP group and 1 amputation in the PBR group. This was not statistically significant. The median interval between referral and senior author review was 8 days for the PRP group and 10 days for the PBR group (P=0.2574). Sixty six percent of tertiary referrals were PBR (74% when including GP referrals).

Biopsy of suspected appendicular Soft Tissue Sarcoma should be done by a tumour specialist or in prior consultation with one. There is virtually no delay to see an orthopaedic tumour specialist in New Zealand and achieving a tissue diagnosis does not expedite this.

We report a case of septic arthritis of the hip caused by toxigenic Corynebacterium diphtheria in a healthy, immunized child.

A four-year-old boy was admitted to our hospital with a four-day history of right thigh pain, inability to bear weight on the right leg and sore throat of one-day duration.

He was born in New Zealand and had been immunized against diphtheria. On admission he was febrile (37.3°C) with a congested throat. The right hip was flexed and externally rotated. His inflammatory markers were elevated. Aspiration of the hip yielded 8ml of yellow turbid fluid. Gram stain showed gram-positive bacilli. An arthrotomy was performed and the hip drained

Cultures of the aspirate grew Corynebacterium diphtheriae, the toxigenicity confirmed by the national reference laboratory.

The patient was treated with intravenous and oral antibiotics for 6 weeks and he made a full recovery.

Our patient had a history of immunization to diphtheria and this induces a protective level of antibodies against the toxin but does not prevent the bacteria from invading the blood stream and causing infection.

This is to our knowledge the first reported case of septic arthritis caused by toxigenic strain of Corynebacterium diphtheria.

Treatment of displaced intracapsular fracture of the hip by hemiarthroplasty in old patients is generally satisfactory.

Middlemore Hospital’s agreed criteria for hemiarthroplasty were reviewed and tested.

Two hundred and thirty three patients who had hemiarthroplasty for displaced intracapsular fracture neck of femur between June 199- June 2001. All the patients’ data collected from the hospital computer system and then a search started for these patients to review their current status regarding pain and mobility.

Ninety nine patients (42%) were still alive, of them 13 demented, 13 moved or lost and 7 in a wheel chair.

Sixty six patients reviewed for pain and mobility using Sikorski and Barrington scoring criteria for pain and mobility.

Thirteen patients had painful hemiarthroplasty. Clinical notes of the most active group of these patients (7 patients) reviewed individually to identify the causes.

Two patients had revision to total hip joint replacement within 3 months because of technical errors and two patients placed on the waiting list for revision. The rest had deterioration in their general health that made total hip arthroplasty a risky operation for them.

The revision rate was 1.7 %. We concluded that hemiarthroplasty was an acceptable option for these patients. The selection criteria were correct in 98.2% of the cases. Patients who live in their own home will need a careful assessment before deciding on a hemiarthroplasty for them.