The lower limbs of vehicle occupants are vulnerable to severe injuries during under vehicle explosions. Understanding the injury mechanism and causality of injury severity could aid in developing better protection. Therefore, we tested three different knee positions in standing occupants (standing, knee in hyper-extension, knee flexed at 20˚) of a simulated under‐vehicle explosion using cadaveric limbs in a traumatic blast injury simulator; the hypothesis was that occupant posture would affect injury severity.

Skeletal injuries were minimal in the cadaveric limbs with the knees flexed at 20˚. Severe, impairing injuries were observed in the foot of standing and hyper‐extended specimens. Strain gauge measurements taken from the lateral calcaneus in the standing and hyper-extended positions were more than double the strain found in specimens with the knee flexed position. The results in this study demonstrate that a vehicle occupant whose posture incorporates knee flexion at the time of an under‐vehicle explosion is likely to reduce the severity of lower limb injuries, when compared to a knee extended position.

Current military conflicts are characterised by the use of the Improvised Explosive Device (IED). Improvements in personal protection, medical care and evacuation logistics have resulted in increasing numbers of casualties surviving with complex musculoskeletal injuries, often leading to life-long disability. Thus, there exists an urgent requirement to investigate the mechanism of extremity injury caused by these devices in order to develop mitigation strategies. In addition, the wounds of war are no longer restricted to the battlefield; similar injuries can be witnessed in civilian centres following a terrorist attack.

Key to mitigating such injuries is the ability to deconstruct the complexities of an explosive event into a controlled, laboratory-based environment. In this study, an anti-vehicle underbelly injury simulator, capable of recreating in the laboratory the impulse from an anti-vehicle (AV) explosion, is presented and characterised. Tests were then conducted to assess the simulator's ability to interact with human cadaveric legs. Two mounting conditions were assessed, simulating a typical seated and standing vehicle passenger using instrumented cadaveric lower limbs.

This experimental device, will now allow us (a) to gain comprehensive understanding of the load-transfer mechanisms through the lower limb, (b) to characterise the dissipating capacity of mitigation technologies, and (c) to assess the biofidelity of surrogates.

The defining weapon of the conflicts in Iraq and Afghanistan has been the Improvised Explosive Device (IEDs). When detonated under a vehicle, they result in significant axial loading to the lower limbs, resulting in devastating injuries. Due to the absence of clinical blast data, automotive injury data using the Abbreviated Injury Score (AIS) has been extrapolated to define current NATO injury thresholds for Anti-vehicle (AV) mine tests. We hypothesized that AIS, being a marker of fatality rather than disability would be a worse predictor of poor clinical outcome compared to the lower limb specific Foot and Ankle Severity Score (FASS).

Using a prospectively collected trauma database, we identified UK Service Personnel sustaining lower leg injuries from under-vehicle explosions from Jan 2006–Dec 2008. A full review of all medical documentation was performed to determine patient demographics and the severity of lower leg injury, as assessed by AIS and FASS. Clinical endpoints were defined as (i) need for amputation or (ii) poor clinical outcome. Statistical models were developed in order to explore the relationship between the scoring systems and clinical endpoints.

63 UK casualties (89 limbs) were identified with a lower limb injury following under-vehicle explosion. The mean age of the casualty was 26.0 yrs. At 33.6 months follow-up, 29.1% (26/89) required an amputation and a further 74.6% (41/89) having a poor clinical outcome (amputation or ongoing clinical problems). Only 9(14%) casualties were deemed medically fit to return to full military duty. ROC analysis revealed that both AIS=2 and FASS=4 could predict the risk of amputation, with FASS = 4 demonstrating greater specificity (43% vs 20%) and greater positive predictive value (72% vs 32%). In predicting poor clinical outcome, FASS was significantly superior to AIS (p<0.01). Probit analysis revealed that a relationship could not be developed between AIS and the probability of a poor clinical outcome (p=0.25).

Foot and ankle injuries following AV mine blast are associated with significant morbidity. Our study clearly demonstrates that AIS is not a predictor of long-term clinical outcome and that FASS would be a better quantitative measure of lower limb injury severity. There is a requirement to reassess the current injury criteria used to evaluate the potential of mitigation technologies to help reduce long-term disability in military personnel. Our study highlights the critical importance of utilising contemporary battlefield injury data in order to ensure that the evaluation of mitigation measures is appropriate to the injury profile and their long-term effects.

The conflict in Afghanistan has been epitomised by the emergence of the Improvised Explosive Device(IEDs). Improvements in medical treatments have resulted in increasing numbers of casualties surviving with complex lower extremity injuries. To date, there has been no analysis of foot and ankle blast injuries as a result of IEDs. Therefore the aims of this study are to firstly report the pattern of injury and secondly determine which factors were associated with a poor clinical outcome in order to focus future research.

Using a prospective trauma registry, UK Service Personnel who sustained lower leg injuries following an under-vehicle explosion between Jan 2006 and Dec 2008 were identified. Patient demographics, injury severity, the nature of lower limb injury and clinical management was recorded. Clinical endpoints were determined by (i)need for amputation and (ii)need for ongoing clinical output at mean 33.0 months follow-up.

63 UK Service Personnel (89 injured limbs) were identified with lower leg injuries from explosion. 50% of casualties sustained multi-segmental injuries to the foot and ankle complex. 26(29%) limbs required amputation, with six amputated for chronic pain 18 months following injury. Regression analysis revealed that hindfoot injuries, open fractures and vascular injuries were independent predictors of amputation.

Of the 69 limbs initially salvaged, the overall infection rate was 42%, osteomyelitis 11.6% and non-union rates was 21.7%. Symptomatic traumatic osteoarthritis was noted in 33.3% salvaged limbs. At final follow-up, 66(74%) of injured limbs had persisting symptoms related to their injury, with only 9(14%) fit to return to their pre-injury duties.

This study demonstrates that foot and ankle injuries from IEDs are frequently associated with a high amputation rate and poor clinical outcome. Although, not life-threatening, they remain a source of long-term morbidity in an active population. Primary prevention of these injuries remain key in reducing the injury burden.

Anti-vehicle mines (AV) and Improvised Explosive Devices (IEDs) remain the most prevalent threat to Coalition troops operating in Iraq and Afghanistan. Detonation of these devices results in rapid deflection of the vehicle floor resulting in severe injuries to calcaneus. Anecdotally referred to as a ‘deck-slap’ injury, there have been no studies evaluating the pattern of injury or the effect of these potentially devastating injuries since World War II. Therefore the aim of this study is to determine the pattern of injury, medical management and functional outcome of UK Service Personnel sustaining calcaneal injuries from under-vehicle explosions.

From Jan 2006 – Dec 2008, utilising a prospectively collected trauma registry (Joint Theatre Trauma Registry, JTTR), the records of all UK Service Personnel sustaining a fractured calcaneus from a vehicle explosion were identified for in depth review. For each patient, demographic data, New Injury Severity Score (NISS), and associated injuries were recorded. In addition, the pattern of calcaneal fracture, the method of stabilisation, local complications and need for amputation was noted. Functional recovery was related to the ability of the casualty to return to military duties.

Forty calcaneal fractures (30 patients) were identified in this study. Mean follow-up was 33.2 months. The median NISS was 17, with the lower extremity the most severely injured body region in 90% of cases. Nine (30%) had an associated spinal injury. The overall amputation rate was 45% (18/40); 11 limbs (28%) were amputated primarily, with a further 3 amputated on return to the UK. Four (10%) casualties required a delayed amputation for chronic pain (mean 19.5 months). Of the 29 calcaneal fractures salvaged at the field hospital, wound infection developed in 11 (38%). At final follow-up, only 2 (6%) were able to return to full military duty with 23 (76%) only fit for sedentary work or unfit any military duty.

Calcaneal injuries following under-vehicle explosions are commonly associated with significant polytrauma, of which the lower limb injury is the most severe. Spinal injuries were frequently associated with this injury pattern and it is recommended that radiological evaluation of the spine be performed on all patients presenting with calcaneal injuries from this injury mechanism. The severity of the hindfoot injury witnessed is reflected by the high infection rate and amputation rate seen in this cohort of patients. Given the high physical demands of a young, active military population, only a small proportion of casualties were able to return to pre-injury duties. We believe that the key to the reduction in the injury burden to the soldier lies in the primary prevention of this injury. Work is currently on going to develop experimental and numerical models of this injury in order to drive future mitigation strategies.

The aim of this work was to define the tensile material properties of the glenoid labrum. Previous SEM studies of the labrum have observed three definitive layers, with a densely packed circumferentially orientated collagen core layer. The glenoid labrum from ten cadaveric shoulders were dissected out and divided into eight equal sections. Each section was cut to produce specimens from the core layer using a microtome and a specifically designed cryo-clamp resulting in uniform specimens with dimensions of 1mm x 1mm x 8mm. All of the tensile testing was performed within a controlled-environment unit of 38°C and 100% relative humidity. Each specimen was precycled to a quasi-static state to alleviate the effects of deep-freezing, prior to final testing. The elastic modulus was calculated for each specimen before and after a 5-minute period of stress relaxation and before failure initiation. The mean age of the specimens was 61 years (range 47–70). Load to failure was 2.7N (1.0–7.0). The mean modulus was 10.2MPa (3.0–22.3) before stress relaxation, 18.0MPa (5.8–36.7) immediately after stress relaxation and 22.3MPa (8.4–66.4) before failure initiation. The 1 and 2 o’clock specimens had lower moduli than the 4 and 5 o’clock specimens (p=0.01). These results can aid in explaining the differing pathologies encountered around the circumference of the labrum. The high moduli at the 4 and 5 o’clock positions may reflect the ability of this portion of the labrum to accommodate forces and thus resist anteroinferior subluxation. The lower moduli at the 1 and 2 o’clock positions suggest that this portion of the labrum is less apt to accommodate tension; this might explain the higher incidence of labral foramen observed in this area and the anatomical variant of the Buford complex.

Objective: To compare double bundle ACL reconstruction kinematics to single bundle reconstruction, intact knee and ACL deficient knee employing an electromagnetic device in six cadaver knees under different antero-posterior and rotational loading conditions.

Methods: All the tests were performed with an intact ACL, with a deficient ACL and after single and double bundle ACL reconstruction.

In double bundle ACL reconstruction two tibial tunnels were drilled: for the anteromedial the 65 degrees Howell guide was employed; the posterolaetral was drilled through a prototype jig attached to the first guide. Two femoral tunnels were drilled outside-in with the Rear Entry guide. A 6 millimetres bovine tendon graft was employed and fixed to bone with interference screws.

Results: Posterior drawer loading conditions did not show differences between intact knee, single and double ACL reconstruction independently from rotational stresses.

Under an anterior drawer test double bundle ACL reconstruction restored anteroposterior laxity significantly better than single bundle reconstruction at 20 and 40 degrees of flexion. A trend towards a better rotational control of double bundle reconstruction was observed in extension.

The motion of the shoulder complex, the scapulo-humero-thoracic rhythm, is an equilibrium between transmission of loads and positioning of the upper limb. This rhythm, which can be described by 12 spatial variables, is either responsible for, or affected by the genesis of shoulder pathology and trauma. Thus, imaging the articulations of the shoulder through a global range of motion is essential in aiding diagnosis, management decisions and interpreting operative outcome. As such, the objective of this study was to dynamically image the scapulo-humero-thoracic rhythm.

The subjects were seated between the toroid of the scanner and maximally slewn table on a customised tripod which both protects the target rings and provides a degree of comfort. Each subject was asked to carryout 4 movements; adduction to abduction in the scapular plane, internal rotation to external rotation at 0° and 90° abduction and flexion to extension. Each movement was carried out over a period of 5 seconds, enabling the acquisition of 20 volumes per movement.

Electron Beam Computed Tomography (EBCT) enables the scanning of a number of contiguous slices, each taking 50 msec. Previously this has facilitated real-time imaging and rendering of both cardiopulmonary function and colonography. A GE Imatron EBCT C300 scanner was used with a multislice sequence imaging protocol to collect 8 transaxial slices per volume by sweeping an x-ray beam sequentially over 4 tungsten target rings and recording x-ray intensity via two fixed detector rings after the reflected beam passes through the body.

Each slice was post-processed by semi-automatic segmention using Amira software, and reconstructed to produce three-dimensional volumes of the humerus, scapula, clavicle and selected ribs. Anatomical landmarks were then identified and the normal rhythm of the shoulder was described.

In conclusion, EBCT provides a quick and efficient method for direct realtime dynamic imaging of the shoulder girdle under normal conditions, the first time this has been achieved to the best of our knowledge. Not only do these reconstructions provide further input matter for preexisting and future computational shoulder models, but estabilishes an initial baseline for further clinical experience. As such, we hypothesise the ability of this modalitiy to image pathological and traumatic disruption to shoulder rhythm. The potential clinical application of this tool would include imaging of traumatic instability and impingement, facilitated by some minor ergonomic alterations to the apparatus.

Aims: Surgical joint stabilisation can be achieved by capsular plication or thermal shrinkage. We hypothesised that there was no difference in mechanical and morphological properties after reduction of laxity in ligaments treated by either technique.

Methods: 30 skeletally mature female rabbits underwent either ‘thermal’ treatment, or ‘plication’ of their left medial collateral ligament (MCL). After 12 weeks convalescence, MCL complexes were procured from left and contralateral knees to undergo viscoelastic (creep) testing, quantitative transmission electron microscopy (TEM) and immunohistochemistry.

Results: Mean creep strain in both thermal (1.85 +/− 0.32%) and plicated ligaments (1.92 +/− 0.36%) was almost twice that of the control group (1.04 +/− 0.15%), although there was no difference between treatment modalities. However, collagen morphological parameters of all three groups were significantly different (p< 0.001). The thermal ligaments demonstrated predominantly small fibrils, whilst the plicated group displayed an intermediate distribution of heterogeneous fibrils (Fig. I). Immunohistochemistry followed by TEM revealed a random distribution of alpha-smooth muscle actin staining fibroblasts in both thermal and plicated groups.

Conclusion: Susceptibility to creep, and residual deformation after recovery, is similar after thermal shrinkage or plication, although inferior to intact ligaments. However, a different pattern of remodelling was revealed in the treatment groups. The plicated results suggest remodelling on a pre-existing fibrillar scaffold, yet the thermal group demonstrated histomorphometry similar to scar tissue, suggesting de novo synthesis. The absence of contractile myofibroblasts suggests that these cells may play an insignificant role in regulation of matrix tension during healing.

Purpose: Many different rotator cuff repairs have been advocated in previous publications without experimental evidence. Our aim was to mechanically test the static tensile properties and cyclical loading to failure of a single row lateral anchor repair and a double row medial and lateral anchor repair.

Method: Fresh frozen cadaveric shoulders were mounted on a rig and a mini-open deltoid split used to visualise the supraspinatus. A standardised full thickness incision of 2 cms was made with a scalpel across the supraspinatus tendon. After the deltoid was repaired and specimens randomised, an arthroscopic rotator cuff repair was performed by the two senior authors in which the medial border of the tear was apposed to the lateral border using either a double or single row technique with a ‘Twinfix AB’ suture anchor. Once the repair had been performed, the gross specimens were dissected down to the rotator cuff musculature and the repair inspected. Those with associated cuff pathology were excluded from the experiment. Specimens were then mounted on a custom made rig to statically load each tendon simulating physiological loading of a repaired cuff defect in a post-operative 300 abducted position. The increase in tear size was then measured against time for 1 hour or to a point at which the mean tendon gap formation exceeded 5mm. Each specimen was then transferred to an Instron tensile testing machine to cyclically load to failure the supraspinatus musculotendinous unit. Each specimen was freeze clamped proximally in a specially designed clamp, whilst the humeral shaft was mounted at an angle of 300 of abduction.

Results: The two groups had a distinct difference in tensile properties with the single row fixation developing a 5mm gap in under 30 minutes. After 1 hour, the gap formed in the double row specimens was less than 5mm. In cyclical loading, the single row failed at a lower load compared with the double row. In some double row specimens the tendon failed mid substance above 250N, rather than at the anchor-suture or suture-tendon interface.

Conclusions: Our results suggest that the double row mattress technique has superior loading properties when tested with a simulated physiological load comparative to the normal post-operative setting.

Surgical joint stabilisation can be achieved by ligamentous plication or thermal shrinkage, and as such, we hypothesized that there is no difference in mechanical and morphological properties after reduction of laxity in ligaments treated by either technique.

Methods: 30 mature female rabbits underwent either ‘thermal’ treatment of their left medial collateral ligament (MCL) using a bipolar radiofrequency probe, or plication with two 4/O non-absorbable sutures following division along its midsubstance and loaded positioning of the free ends. After 12 weeks convalescence, the animals were euthanised and MCL complexes were procured from left and contralateral knees to undergo viscoelastic (creep) testing, quantitative Transmission Electron Microscopy (TEM) and immunohistochemistry. The TEM data was quantified by two data procurement protocols; computational analysis and manual graticule.

Mean creep strain in both thermal (1.85 +/− 0.32%) and plicated ligaments (1.92+/−0.36%) was almost twice that of the control (1.04+/−0.15%), although there was no difference between treatment modalities. Similar findings were seen in the thermal (1.77+/−0.45%), plication (1.85+/−0.40%) and control groups (0.92+/−0.20%) for viscoplastic deformation. However, collagen morphological parameters of all three groups were significantly different (p< 0.001). The thermal ligaments demonstrated predominantly small fibrils, whilst the plicated group displayed an intermediate distribution of heterogenous fibrils. Immunohistochemistry followed by TEM revealed a sparse random distribution of alpha-smooth muscle actin staining fibroblasyts in both thermal and plicated groups. There was an insignificant difference in computational and manual procurement methods (p=0.84).

Susceptibility to creep, and residual deformation after recovery, is similar after thermal shrinkage or plication, although inferior to intact ligaments. However, the plicated results suggest remodeling on a pre-existing fibrillar scaffold, yet the thermal group demonstrated histomorphometry similar to scar tissue, suggesting de novo synthesis. The absence of contractile myofibroblasts suggests that these cells may have an insignificant role in regulation of matrix tension during healing.

The scapulo-humerothoracic rhythm, which can be described by up to 12 spatial variables, is either responsible for, or affected by the genesis of shoulder pathology and trauma, and therefore, imaging the articulations of the shoulder through a global range of motion is desirable in aiding the diagnosis and management of both movement deficiency and osseous lesions.

4 control volunteers were seated between the toroid of the scanner and maximally slewn table on a customised tripod. The subjects were asked to carryout a sequence of defined movements, each over a period of 5 seconds. These included adduction to abduction in the scapular plane, internal rotation to external rotation at 0° and 90° abduction and flexion to extension. An EBCT C300 scanner was used with a multislice sequence imaging protocol to collect 8 transaxial slices per volume by sweeping an x-ray beam sequentially over 4 tungsten target rings and recording x-ray intensity via two fixed detector rings after the reflected beam passes through the body, enabling the acquisition of 20 volumes per movement with minimal radiation exposure. Each slice was post-processed by semi-automatic segmentation using Amira software, and reconstructed to produce three-dimensional reconstructions. Following this, a kinematic description of the joint complex was developed using SIMM, enabling quantification of up to 5 Degrees of Freedom at the Glenohumeral joint.

EBCT provides a quick and efficient method for direct real-time dynamic imaging of the shoulder girdle, although currently crude. As such, we hypothesis the ability of EBCT to image traumatic disruption to shoulder rhythm, and are currently pursuing this work. These reconstructions promise great potential for further clinical experience and quantitative analysis of small translations aided by achievable limited technological refinement of the modality.

This study aimed to quantify the relationship between passive tension of rotator cuff repair and arm position intraoperatively and to examine the effect of the passive tension on gap formation in cadaveric rotator cuff repairs.

Five patients undergoing open surgical reconstruction of the rotator cuff were recruited. The operations were performed by a single surgeon using a standardised technique, which was acromioplasty, minimal debridement, mobilisation of tissue, bone troughs and transosseous suture tunnels.

A Differential Variable Reluctance Transducer (DVRT) was placed at the apex of the debrided tendon. An in situ calibration was performed to relate the output from the DVRT to actual tension in the tendon. The tension generated was recorded as the supraspinatus tendon was advanced into a bone trough and secured.

The relationship between arm position and repair tension was measured, by simultaneously collecting data from the DVRT and a calibrated goniometer. Particular attention was paid to the three standard positions of post-operative immobilisation; full adduction with internal rotation, neutral rotation with a 30° abduction wedge and ninety degrees of abduction.

Five cadaveric shoulders were used for the creation of standardised rotator cuff tears which were then repaired using the technique described above. The difference in tension measured between full adduction and 30° abduction was statically applied for twenty four hours and the gap formation measured.

Repair tension increased with advancement of the supraspinatus tendon into the bone trough. Abduction reduced the repair load, this was observed mainly in the first 30° of abduction. The mean reduction in load by 30° of abduction was 34 N.

Twenty four hours of 34N static loading caused gap formation in each cadaveric rotator cuff repairs, the mean was 9.2 mm.

Rotator cuff repairs tension can be reduced by postoperative immobilisation in 30° abduction. The change in tension with full adduction was caused gap formation in cadaveric rotator cuff repairs.