Cannulated hip screws are frequently used in the management of hip fractures. There have been concerns over the failure rate of the technique and the outcomes of those that subsequently require conversion to total hip replacement (THR). This study utilised a database of over 600 cannulated hip screw (CHS) fixations performed over a 14-year period and followed up for a minimum of one year (1-14). We identified 57 cases where a conversion to THR took place (40 females, 17 males, mean age: 71.2 years). Patient demographics, original mechanism of injury, fracture classification, reason for fixation failure, time until arthroplasty, implant type and post-arthroplasty complications were recorded. Clinical outcomes were measured using the Oxford Hip Score. The failure rate of cannulated screw treatment was 9.4% and the mean time from initial fixation to arthroplasty was 15.4 (16.5) months. Thirty six fractures were initially undisplaced and 21 were displaced. As one might expect the displaced cases tended to be younger but this didn't reach statistical significance [66.5(14.3) vs 72.7(13.1), p=0.1]. The commonest causes of failure were non-union (25 cases, 44%) and avascular necrosis (17 cases, 30%). Complications after THR consisted of one leg length discrepancy and one peri-prosthetic fracture. The mean Oxford score pre-arthroplasty was 12.2 (8.4), improving to 38.4 (11.1) at one-year. Although the pre op Oxford scores tended to be lower in patients with undisplaced fractures and higher ASA scores, the improvement was the same whatever the pre-op situation. The one-year Oxford score and the improvement in score are comparable to those seen in the literature for THR in general. In conclusion, CHS has a high success rate and where salvage arthroplasty is required it can provide good clinical outcomes with low complication rates

Introduction. Civilian fractures have been extensively studied with in an attempt to develop classification systems, which guide optimal fracture management, predict outcome or facilitate communication. More recently, biomechanical analyses have been applied in order to suggest mechanism of injury after the traumatic insult, and predict injuries as a result of a mechanism of injury, with particular application to the field so forensics. However, little work has been carried out on military fractures, and the application of civilian fracture classification systems are fraught with error. Explosive injuries have been sub-divided into primary, secondary and tertiary effects. The aim of this study was to 1. determine which effects of the explosion are responsible for combat casualty extremity bone injury in 2 distinct environments; a) in the open and b) enclosed space (either in vehicle or in cover) 2. determine whether patterns of combat casualty bone injury differed between environments Invariably, this has implications for injury classification and the development of appropriate mitigation strategies. Method. All ED records, case notes, and radiographs of patients admitted to the British military hospital in Afghanistan were reviewed over a 6 month period Apr 08-Sept 08 to identify any fracture caused by an explosive mechanism. Paediatric cases were excluded from the analysis. All radiographs were independently reviewed by a Radiologist, a team of Military Orthopaedic Surgeons and a team of academic Biomechanists, in order to determine the fracture classification and predict the mechanism of injury. Early in the study it became clear that due to the complexity of some of the injuries it was inappropriate to consider bones separately and the term ‘Zone of Insult’ (ZoI) was developed to identify separate areas of injury. Results. 62 combat casualties with 115 ZoIs (mean 1.82 zones) were identified in this study. 34 casualties in the open sustained 56 ZoIs (mean 1.65); 28 casualties in the enclosed group sustained 59 ZoIs (mean 2.10). There was no statistical difference in the mean ZoIs per casualty in the open vs enclosed group (Student t-test, p=0.24). Open fractures were more prevalent in the open group compared to the enclosed group (48/59 vs 20/49, Chi-squared test p<0.001). Of the casualties in the open, 1 zone of injury was due to the primary effects of blast, 10 a combination of primary and secondary blast zones, 23 due to secondary effects and 24 from the tertiary effects of blast. In contrast, there were no primary or combined primary and secondary blast zones and only 2 secondary blast zones in the enclosed group. Tertiary blast effects predominated in the enclosed group, accounting for 96% of injury zones (57/59). Analysis of the pattern of injury revealed that there were a higher proportion of lower limb injuries in the Enclosed group (54/59) compared to the Open group (40/58, Chi-squared p<0.05). In the Open group the mechanism of lower limb injury was more evenly distributed amongst mixed primary and secondary blast effects (10), secondary (10) and tertiary (20). In the enclosed group, lower limb injuries were almost exclusively caused by tertiary blast effects (47/48). A similar pattern was also seen in the Upper limb with 4/5 in the enclosed group was injured by tertiary effects compared to 4/18 in the Open Group. In the open group fragmentation injury was the predominant cause of injury (13/18). Conclusions. This data clearly demonstrates two distinct injury groups based upon the casualties' environment. The enclosed environment afforded by buildings and vehicles appears to mitigate the primary and secondary effects of the explosion. However, tertiary blast effects were the predominant mechanism of injury, with severe axial loading to the lower extremity being a characteristic of the fractures seen. In contrast, secondary fragments from the explosion were more likely to result in fractures of casualties caught in the open. The development of future mitigation strategies must be focused on reducing all the different mechanisms of injury caused by an explosion. This will require a better understanding on the effects of bone in high strain environments. This method of forensic biomechanics involving clinicians and engineers, combined with accurate physical and numerical simulations can form the basis in reducing the injury burden to the combat soldier

Perilesional changes of chronic focal osteochondral defects were assessed in the knees of 23 sheep. An osteochondral defect was created in the main load-bearing region of the medial condyle of the knees in a controlled, standardised manner. The perilesional cartilage was evaluated macroscopically and biopsies were taken at the time of production of the defect (T0), during a second operation one month later (T1), and after killing animals at three (T3; n = 8), four (T4; n = 8), and seven (T7; n = 8) months. All the samples were histologically assessed by the International Cartilage Repair Society grading system and Mankin histological scores. Biopsies were taken from human patients (n = 10) with chronic articular cartilage lesions and compared with the ovine specimens. The ovine perilesional cartilage presented with macroscopic and histological signs of degeneration. At T1 the International Cartilage Repair Society ‘Subchondral Bone’ score decreased from a mean of 3.0 (sd 0) to a mean of 1.9 (sd 0.3) and the ‘Matrix’ score from a mean of 3.0 (sd 0) to a mean of 2.5 (sd 0.5). This progressed further at T3, with the International Cartilage Repair Society ‘Surface’ grading, the ‘Matrix’ grading, ‘Cell Distribution’ and ‘Cell Viability’ grading further decreasing and the Mankin score rising from a mean of 1.3 (sd 1.4) to a mean of 5.1 (sd 1.6). Human biopsies achieved Mankin grading of a mean of 4.2 (sd 1.6) and were comparable with the ovine histology at T1 and T3.

The perilesional cartilage in the animal model became chronic at one month and its histological appearance may be considered comparable with that seen in human osteochondral defects after trauma.