This work examines the Upper limb (UL) blast-mediated traumatic amputation (TA) significance from recent operations in Afghanistan. It is hypothesized that the presence of an UL amputation at any level is an independent predictor of torso injury.

A joint theatre trauma registry search was performed to determine the number of British casualties with TA and their associated injuries.

UL TA accounted for 15.7% of all amputations; distributed: shoulder disarticulation 2.5%, trans-humeral 30%, elbow disarticulation 10%, trans-radial 20% and hand 37.5%. The presence of an UL amputation was more likely in dismounted casualties (P=0.015) and is a predictor of an increased number of total body regions injured and thoracic injuries (P 0.001 and P 0.026 respectively). An increased Injury Severity Score (ISS) was seen in patients with multiple amputations involving the UL (UL TA present ISS=30, no UL TA ISS=21; P=0.000) and the ISS was not significantly different whether mounted or dismounted (P=0.806).

The presence of an upper limb amputation at any level should insight in the receiving clinician a high index of suspicion of concomitant internal injury; especially thoracic injury. Therefore with regards to blast mediated TA the injury patterns observed reflect a primary and tertiary blast mechanism of injury.

Electron Microscopy and Synchrotron analysis of Heterotopic Ossification (HO) from blast-related amputees' has shown that HO is bone with a disorganised structure and altered remodelling. This research performs mechanical testing of HO to understand its biomechanical properties in an attempt to create an accurate model to predict its morphological appearance. The hypothesis of this work is that HO is mechanically mediated in its formation.

Synchrotron mechanical analysis of HO samples was performed to measure Young's modulus, ultimate strength and density distribution. A novel algorithm based on Wolf's law was implemented in a Finite Element (FE) analysis model of HO to take into account the differing mechanical and biological properties measured and the presence of HO outside the skeletal system.

An HO modeling factor, which considers boundary conditions, and regulates recruitment of the soft tissue into bone formation, results in a re-creatable formation of HO within the soft tissues, comparable to the appearance of HO seen in military amputees. The results and model demonstrates that certain types of HO are under the control of endogenous and exogenous mechanical stimulus. HO can thus be mechanically exploited in the casualty management and rehabilitation process to achieve better clinical outcomes.

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.

The explosive device has successfully been used by terrorists globally, with their effects extending beyond the resulting injuries. Suicide bombings, in particular, are being increasingly deployed due to the devastating effect of a combination of, high lethality and target accuracy. This aim of this study was to analyse the demographics and casualty figures of terrorist bombings worldwide. Analysis of the Global Terrorism Database and a PubMed search (keywords “terrorist”, and/or “suicide”, and/or “bombing”) from 1970 to date was performed. Of 58,095 reported terrorist explosions worldwide, 5.08% were suicide bombings. Incidents per year is increasing (P<0.01). PubMed identified 41 publications reporting 167 incidents. Mean casualty statistics per incidents was 1.14 deaths and 3.45 wounded from non-suicide incidents, and 10.16 and 24.16 from suicide bombings (p<0.05). The Middle East witnessed the most incidents (26.9%), with Europe ranked 4^th in the number of terrorist related explosion (13.2%). Differing injury patterns were seen in open, confined and building collapse incidents. Terrorist bombings continue to be a threat and are increasing in the Middle East and Europe. Suicide bombings are becoming an increased threat with greater casualty figures per incident seen. This data assists in the planning of security, logistics, casualty evacuation and care.

Heterotopic ossification (HO) is the formation of lamellar bone in extra-skeletal soft tissues. Its exact pathogenic mechanism remains elusive. Previous studies demonstrate observation only of HO at the microscopic scale. This study uses scanning electron microscopy (SEM), Back-scatter electron (BSE) imaging and mechanical testing to detail the organic and non-organic elements of HO, compared to normal bone, to guide stem cell and bio-modelling research into HO. Samples analysed were 5 military blast related HO patients, 5 control cadaveric samples (age and sex matched). Samples were imaged using SEM, BSE and the I13 beam Synchrotron x-ray diffraction scanner using validated quantitative and qualitative techniques of measurement. Appearances seen in HO compared to normal bone were characterised by the presence of a hyper-vascular network and high lacunae (osteocyte) counts, two distinct zones of bone mineral density distribution, with a tendency for hypermineralisation with kurtosis of the grey scale plots (mineral content as a weight percentage of Ca²⁺ was calibrated to atomic weight of C, Al and HA). Direction of dependence and collagen orientation in HO suggest isotropic properties. This research demonstrates that HO is bone, however its characteristics suggest a high metabolic turnover and disorganised ultra-structure consistent with an inflammatory origin.

Previous reports of the prevalence of Heterotopic Ossification (HO) in limbs from UK blast-related amputees from Afghanistan, is demonstrated to be 57.1%. With the end of UK military operations in Afghanistan in 2014 the aim of this study is establish the rate of HO, assess causality demographics and ascertain risk factors for the formation of HO during the entire period of operations in Afghanistan. Military databases, case notes and radiographs were scrutinised to quantify and qualify the prevalence and risk factors for the formation of HO. 256 servicemen sustained 398 military trauma related amputations. The overall prevalence of HO was 65.9%. Significant (p<0.05) risks identified for the formation of HO included a blast mechanism of injury, a zone of injury the same as the subsequent amputation, and an increased number of debridements prior to closure. Positive correlation existed between the number of amputations and the presence and grade of HO (p=0.04). HO presents clinical problems to military blast injury patient populations. This study demonstrates that both a blast mechanism of injury and an increased injury load are key factors in the increased prevalence of HO seen in military trauma.

Recent evidence suggests that both the accepted mechanism of blast-mediated traumatic amputation (TA) (shockwave then blast wind exposure) and the link with fatal shockwave exposure merit review. Searching UK military prospectively gathered trauma registry data and post mortem CT (PM-CT) records identified casualties from August 2008 to August 2010 with blast-mediated TAs. TA level and associated injuries were recorded. Data on pre-debridement osseous and soft tissue injuries were only consistently available for fatalities through PM-CT imaging. 146 Cases (75 survivors and 71 fatalities) with 271 TAs (130 in survivors and 141 in fatalities) were identified. Through-joint TA rate in fatalities was 34/141 (24.1%). PM-CT analysis demonstrated only 9/34 through joint TAs with contiguous fractures in the immediately proximal long bone/limb girdle. 18/34 had no fracture, and 7/34 had a non-contiguous fracture. The previously reported link between TA and blast lung injury was not present, calling into question the significance of shockwaves in generating blast-mediated TAs. Furthermore, contemporary blast injury theory cannot account for the high prevalence of through joint TAs (previously published rate 1.3%). The proportion of through joint TAs with no associated fracture or a non-contiguous fracture (74%) is supportive of pure flail as a mechanism for blast-mediated TA.

Traumatic amputations (TAs) are amongst the most significant orthopaedic sequelae following IED strikes. Biomechanically, longer residual limb length confers better function. However, post-trauma definitive through knee amputation (TKA) remains controversial.

UK military casualties sustaining ≥1 major TA, 01/08/2008–01/08/2010 were identified using the UK JTTR and post mortem CT databases. All through- and below-knee TAs were termed ‘potential TKAs’ (p-TKAs); hypothetical candidates for definitive TKA. We hypothesised that traumatic TKAs were more common than previously reported (4.5% of lower limb TAs) and a significant cohort of blast injuries exist suitable for definitive TKA.

146 cases (75 survivors, 71 fatalities) sustained 271 TAs (235 lower limb). TKA rate was 34/235 (14.2%). 63/130 survivor TAs and 66/140 fatality TAs merited analysis as p-TKAs. Detailed pathoanatomy was only available for fatality p-TKAs, for whom definitive TKA would have been proximal to the zone of injury (ZOI) in only 3/66 cases.

Blast-mediated traumatic TKAs are significantly more common than previously reported (p=0.0118). Most lower limb TAs are skeletally amenable to definitive TKA. Maximising stump length for function incurs the risks of definitive amputation within the original ZOI (including infection and heterotopic ossification) but proximal extent of blast soft tissue injury commonly makes this unavoidable.

Characterising material properties of ligaments is essential in the analysis of human morbidity and mortality of low-speed sporting accidents, high-speed road traffic accidents, and very high-speed battlefield injuries. At lower strain rates the elastic modulus and ultimate stress increase relative to strain rate, although very high strain rate testing has not been performed to date.

A porcine stifle joint lateral collateral ligament experiment was conducted that simulated the strain rates that occur during across a full range of different human knee ligament injuries. Tensile testing was performed at five strain rates, each an order of magnitude apart, in the range 10⁰–10⁴%/s. Seven specimens were tested at each rate. Three loading techniques were used: 1) screw-driven, 2) servo-hydraulic, 3) drop weight rig with tensile impact adaptor. Cross sectional area was measured by counting pixels on a standardized digital photograph of an alginate-paste cast of the mid-substance of each sample. Strain was measured directly from the mid-substance of each ligament by high-speed video extensometry. Stress-strain curves were produced and used to quantify the elastic modulus, failure strain and ultimate stress at each strain rate.

Across the range of strain rates, elastic modulus increased from 288 to 905 MPa (p< 0.05), and ultimate stress increased from 39.9 to 77.3 MPa (p< 0.05). A relationship between strain rate and both, elastic modulus and ultimate stress was identified. Strain rate sensitivity was not observed at very fast strain rates.

Ligament strength increases when strain rates are high. These data provide an explanation for very high strain rate failure of ligaments under extreme loading conditions, that can be considered protective of bone fracture, such as can be seen in traumatic through knee amputations in blast injuries.

The accepted mechanism of traumatic limb amputation following blast is initial bone disruption due to the shock wave, with amputation completed by the blast wind; survival is considered unlikely. The high survival rate of traumatic amputees following explosion, from the current conflict in Afghanistan, is at odds with previous work.

We reviewed extremity injuries, sustained in Afghanistan by UK military personnel, over a 2 year period. 774 British servicemen and women sustained AIS >1 injuries, 72.6% of whom survived. No significant difference was found in the survival rates following explosive blast or gunshot (p>0.05).

169 casualties (21.8%) sustained 263 lower limb and 74 upper limb traumatic amputations. Amputations were more common in the lower than the upper limbs and more common in the extremity proximal bone. Bilateral lower limb amputations were more common than a unilateral lower limb amputation. The majority (99%) of major amputations were sustained as a result of explosion. 46.3% (74) of those who sustained a major amputation following explosion survived.

Rates of fatalities caused by explosion, or by small arms are not statistically different. Blast-mediated amputations are not universally fatal, and a significant number were through joint, calling into question previously proposed mechanisms.

Background

The conflict in Afghanistan has been epitomised by the emergence of the Improvised Explosive Device (IEDs). Improvements in protection and 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 report the pattern of injury and determine which factors were associated with a poor clinical outcome.

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.

Recent advances in combat casualty care have enabled survival following battlefield injuries that would have been lethal in past conflicts. While some injuries remain beyond our current capability to treat, they have the potential to be future ‘unexpected’ survivors. The greatest threat to deployed coalition troops currently and for the foreseeable future is the improvised explosive device (IED) Therefore, the aim of this study was to conduct an analysis of causes of death and injury patterns in recent explosive blast fatalities in order to focus research and mitigation strategies, to further improve survival rates.

Since November 2007, UK Armed Forces personnel killed whilst deployed on combat operations undergo both a post mortem computed tomography (PMCT) scan and an autopsy. With the permission of the coroners, we analysed casualties with PMCTs between November 2007 and July 2010. Injury data were analysed by a pathology-forensic radiology-orthopaedic multidisciplinary team. Cause of death was attributed to the injuries with the highest AIS scores contributing to the NISS score. Injuries with an AIS < 4 were excluded. During the study period 227 PMCT scans were performed; 211 were suitable for inclusion, containing 145 fatalities due to explosive blast from IEDs. These formed the study group. 24 cases had such severe injuries (disruptions) that further study was inappropriate. Of the remaining 121, 79 were dismounted, and 42 were mounted (in vehicles).

Leading causes of death were head CNS injury (47.6%), followed by intra-cavity haemorrhage (21.7%) in the mounted group, and extremity haemorrhage (42.6%), junctional haemorrhage (22.2%) and head CNS injury (18.7%) in the dismounted group.

The severity of head trauma in both mounted and dismounted IED fatalites would indicate that prevention and mitigation of these injuries is likely to be the most effective strategy to decrease their resultant mortality. Two thirds of dismounted fatalities have haemorrhage implicated as a cause of death that may have been amenable to prehospital treatment strategies. One fifth of mounted fatalites have haemorrhagic trauma which currently could only be addressed surgically. Maintaining the drive to improve all haemostatic techniques for combat casualties from point of wounding to definitive surgical proximal control alongside development and application of novel haemostatics could yield a significant survival benefit.

The mechanism of traumatic amputation (TA) from explosive blast has traditionally been considered to be a combination of blast wave induced bone injury – primary blast - followed by limb avulsion from the blast wind – tertiary blast. This results in a transosseous TA, with through joint amputations considered to be extremely rare. Data from previous conflicts has also suggested that this injury is frequently associated with a non-survivable primary blast lung injury (PBLI), further linking the extremity injury to the primary blast wave. However, our current experience in the Middle East would suggest that both the mechanism of TA and the link with fatal primary blast exposure need to be reconsidered. The aim of this study was to analyse the injury profile of the current cohort of TA fatalities to further investigate the underlying blast injury mechanism and to allow hypotheses on injury mechanisms to be developed for further analysis.

With the permission of the coroners, 121 post-mortem CT (PMCT) scans of UK Armed Forces personnel who died following an IED blast were analysed. All orthopaedic injuries were identified, classified and the anatomical level of any associated soft tissue injury noted. PMCT evidence of PBLI was used as a marker of significant primary blast exposure.

75/121 (62%) sustained at least 1 TA, with 138 TAs seen in total. 31/138 (22%) were through joints, with through knee amputations most common (23/31, 74%). Only 7/31(23%) through joint amputations had an associated fracture proximal to and contiguous with the amputation site. The soft tissue injury profile of through joint and transosseous TAs were not significantly different (p=0.569). When fatality location was considered (i.e. mounted or dismounted), no overall relationship between PBLI and TA was evident. The two pathologies were not seen to consistently occur concurrently, as has been previously reported.

The accepted mechanism for traumatic amputation following explosive blast does not adequately explain the significant number of through joint TAs presented here. The previously reported link between TA and PBLI in fatalities was not supported by this analysis of modern combat blast fatalities. Lack of an associated fracture with the majority of through joint TAs in conjunction with a lesser contribution of primary blast may implicate flail and periarticular soft tissue failure as a potential injury mechanism. Analysis of through joint TA incidence and associated injuries in survivors is now indicated. Case studies within the fatality dataset may facilitate generation of injury mechanism hypotheses. To further investigate the injury mechanism, work is required to understand osseous, ligamentous and other soft tissue behaviour and failure at high strain rates. This should allow characterisation and modeling of these injuries and inform mitigation strategies.

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.

Background

The measurement of pelvic kinematics is key to the analysis of aberrant movement patterns of lower back, yet to date technical issues of skin artefacts, body composition and optical motion tracking sensor occlusion [1] are unresolved.

Introduction

The reliability of currently available proximal humeral fracture classi?cation systems has been shown to be poor, giving rise to the question whether a more objective measure entails improved predictability of surgical outcome. This study aims to apply a novel software system to predict the functional range of motion of the glenohumeral joint after proximal humeral fracture.

Background

Tears of the rotator cuff are a common pathology and poorly understood. Achieving a good functional outcome for patients may be difficult, and the degree of fat infiltration into the muscle is known to be a major determining factor to surgical repair and post operative function. It is the hypothesis of this study that the degree of retraction of the common central tendon as seen on MRI corresponds to the amount of fat infiltration classified according to the Goutallier grading System.

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.

This paper reports a series of comparative tests in-vitro that examined how lateral meniscectomy and meniscal allografting affected tibio-femoral joint contact pressures. 8 Cadaver knees (age range 81 – 98 years) were loaded in axial compression in an Instron materials testing machine up to 700N for 10 seconds and pressure maps obtained from the lateral compartment using Fuji Prescale film inserted below the meniscus. This was repeated after meniscectomy, then after meniscal allografting with fixation by a bone plug for the insertional ligaments, plus peripheral sutures. Finally, the pressure when the allograft was secured by peripheral sutures alone was measured.

Meniscectomy caused a significant increase in peak contact pressures (p=0.0002). Both of the reconstructive methods reduced the peak contact pressures significantly below that of the meniscectomised knee (p=0.0029 with bone block; p=0.0199 with sutures alone). A significant difference was not found between the peak contact pressures after the reconstructions and that of the intact knee (p=0.1721 with bone block; p=0.0910 with sutures alone). The peak pressures increased slightly when the allografts were converted from bone block to suture-only fixation (p=0.0349).

The principal finding was that both of the meniscal allograft insertion techniques reduced the peak contact pressure significantly below that of the meniscectomised knee, so that it did not then differ significantly from the peak contact pressure in the intact knee. When the two fixation methods were compared, the loss of the bone plug attachment caused a small increase in peak pressure.

This study suggests that meniscal allografting should have a chondroprotective effect and that there is a small advantage from adding bony fixation to suture fixation.

The posterior drawer is a commonly used test to diagnose an isolated PCL injury and combined PCL and PLC injury. Our aim was to analyse the effect of tibial internal and external rotation during the posterior drawer in isolated PCL and combined PCL and PLC deficient cadaver knee.

Ten fresh frozen and overnight-thawed cadaver knees with an average age of 76 years and without any signs of previous knee injury were used. A custom made wooden rig with electromagnetic tracking system was used to measure the knee kinematics. Each knee was tested with posterior and anterior drawer forces of 80N and posterior drawer with simultaneous external or internal rotational torque of 5Nm. Each knee was tested in intact condition, after PCL resection and after PLC (lateral collateral ligament and popliteus tendon) resection. Intact condition of each knees served as its own control. One-tailed paired student's t test with Bonferroni correction was used.

The posterior tibial displacement in a PCL deficient knee when a simultaneous external rotation torque was applied during posterior drawer at 90° flexion was not significantly different from the posterior tibial displacement with 80N posterior drawer in intact knee (p=0.22). In a PCL deficient knee posterior tibial displacement with simultaneous internal rotation torque and posterior drawer at 90° flexion was not significantly different from tibial displacement with isolated posterior drawer. In PCL and PLC deficient knee at extension with simultaneous internal rotational torque and posterior drawer force the posterior tibial displacement was not significantly different from an isolated PCL deficient condition (p=0.54).

We conclude that posterior drawer in an isolated PCL deficient knee could result in negative test if tibia is held in external rotation. During a recurvatum test for PCL and PLC deficient knee, tibial internal rotation in extension results in reduced posterior laxity.

Our aim was to determine the effects of tibial component malrotation and posterior slope on knee kinematics following Scorpio cruciate retaining total knee replacement in cadaver specimens.

The movements of the hip, thigh and lower leg were monitored in 3D using a validated infra-red Computer Navigation System via bone implanted trackers. Ten normal comparable cadaver specimens were mounted in a custom rig allowing 3D assessment of kinematics under various loading conditions. The specimens then underwent Navigated TKR as per normal operating surgical protocols however an augmented tibial component was implanted. This allowed the researchers to precisely modify the rotation of the tibial component around its predetermined central axis, as well as to alter the posterior slope of the component. A pneumatic cylinder was used to provide a simulated quadriceps extension force while the knee was tested with a variety of applied loads including anterior and posterior draw, abduction and adduction, internal and external rotation.

TKR kinematics are significantly different from those of the native knee (p< 0.05). Increasing tibial posterior slope resulted in an incremental posterior position of the femur (p< 0.05), deviation of the neutral path of motion (p< 0.05) and alteration of the normal AP envelope of laxity (p< 0.05). Tibial component malrotations over 10 degrees resulted in increasing deviations of the neutral movement path of motion (p< 0.05) without significantly affecting the envelope of laxity. Tibial component malrotations of more than 10 degrees, when combined with a posterior slope of six degrees or more, resulted in prosthetic subluxation under certain loading conditions.

This study has demonstrated significant differences in knee kinematics before and after total knee implantation. Increasing values of internal and external rotation, as well as posterior slope of the tibial tray resulted in further deviations of total knee kinematics from normal by altering the neutral path of motion and the soft tissue envelope, with combined misalignments resulting in the greatest deviations from normal with prosthetic subluxation in some cases. Deviations from normal kinematics may result in increased ligament tension and incongruence or dysfunction of the component articulations, with the generation of sheer forces in the gait cycle. These may contribute to premature wear and loosening. Surgeons should be aware of this when considering the addition of posterior slope or assessing tibial component positioning in TKR.

Aims: To determine the effects of tibial component rotation and posterior slope on kinematics following Scor-pio navigated TKR in cadaver specimens.

Methods: Knee kinematics were monitored using a validated Infra Red Navigation System. Ten normal comparable cadaver specimens were mounted in a custom rig allowing assessment of kinematics under various loading conditions. The specimens then underwent Navigated TKR. The surgery was performed as per normal operating surgical protocols by an expert knee surgeon. However an augmented tibial component was implanted allowing the researchers to precisely modify its rotation and posterior slope. A pneumatic cylinder attached to the quadriceps tendon was then used to repetitively flex and extend the knee with a variety of applied loads.

Results: Kinematics were different after TKR. Increasing posterior slope resulted in increasing posterior position of the femur, particularly at maximum flexion. Posterior slope also resulted in a deviation of the neutral path of motion and alteration of the normal envelope of laxity. Tibial component malrotations over 5 degrees resulted in deviations of the neutral path of motion without affecting the envelope of laxity. A combined malrotations over 10 degrees with posterior slopes over 6 degrees resulted in prosthetic subluxation under certain loading conditions.

Discussion: Knee kinematics are different after TKR. Increasing internal and external malrotation as well as the addition of posterior slope resulted in deviations of TKR kinematics through alteration of the neutral path of movement and or the envelope of laxity. Combined misalignments of slope and rotation resulted in the greatest deviations from normal kinematics and in some cases, prosthetic subluxation. Incompatibilities of alignment may result in increased ligament tension and component articulation dysfunction that may contribute to premature wear and loosening. Surgeons should be aware of this when considering the addition of posterior slope or assessing tibial component positioning in TKR.

AIMS: To determine the effects of tibial component rotation and posterior slope on kinematics following Scorpio CR navigated TKR in cadaver specimens.

METHODS AND RESULTS: Knee kinematics were monitored using a validated IR Navigation System. Ten normal comparable cadaver specimens were mounted in a custom rig allowing assessment of kinematics under various loading conditions. The specimens then underwent Navigated TKR. The surgery was performed as per normal operating surgical protocols by an expert knee surgeon. However an augmented tibial component was implanted allowing the researchers to precisely modify its rotation and posterior slope. A pneumatic cylinder attached to the quadriceps tendon was then used to repetitively flex and extend the knee with a variety of applied loads.

Kinematics were different after TKR. Increasing posterior slope resulted in increasing posterior position of the femur, particularly at maximum flexion. Posterior slope also resulted in a deviation of the neutral path of motion and alteration of the normal envelope of laxity. Tibial component malrotations over 5 degrees resulted in deviations of the neutral path of motion without affecting the envelope of laxity. Combined malrotations over 10 degrees with posterior slopes over 6 degrees resulting in prosthetic subluxation under certain loading conditions.

Discussion: Knee kinematics are different after TKR. Increasing internal and external tibial component malrotation as well as the addition of posterior slope resulted in deviations of TKR kinematics through alteration of the neutral path of movement and or the envelope of laxity. Combined misalignments of slope and rotation resulted in the greatest deviations from normal kinematics and in some cases, prosthetic subluxation. Incompatibilities of alignment may result in increased ligament tension and component articulation dysfunction that may contribute to premature wear and loosening. Surgeons should be aware of this when considering the addition of posterior slope or assessing tibial component positioning in TKR.

Purpose: To correlate arthroscopic appearances of the anterior and posterior meniscofemoral ligaments (aMFL and pMFL respectively) with their appearances on magnetic resonance imaging.

Methods: 50 patients underwent MRI scanning of their knees for a variety of suspected pathologies. The radiological presence or absence of the MFLs was assessed by examination of sequential coronal and sagittal T2 weighted MRI scans. Arthroscopic examination of the knees was subsequently performed, during which the MFLs were identified using several anatomical cues. These included their femoral and meniscal attachments, their obliquity relative to the PCL, and the meniscal “tug test”. Identification was classed as “easy” or “hard” by the operating surgeon.

Results: From 50 knees 44 (88%) aMFLs and 30 (60%) pMFLs were identified on MRI scanning, whilst 47 (94%) aMFLs and 5 (10%) pMFLs were identified arthroscopically. Identification of the presence or absence of the aMFL was classed as easy in 47 (94%), whilst the pMFL was easy to identify in only 5 (10%) of knees, of which 3 (6%) had a ruptured PCL. Using arthroscopy of the aMFL as the gold standard, the sensitivity and specificity of MRI in detecting the aMFL were 94% and 75% respectively. Equivalent values for the pMFL were not calculated due to the difficulty of identifying the pMFL arthroscopically. Thus, with the exception of PCL-deficient knees, it was felt that many pMFLs were missed due to difficulties in identification through anterior portals.

Conclusions: This is the first study correlating the MRI appearances of the MFLs with arthroscopic findings. MRI is relatively sensitive in identifying the aMFL, but its accuracy in identifying the pMFL remains undetermined. Accurate identification of the MFLs at MRI is of value when assessing the status of the PCL, as these ligaments may contribute to stabilising the PCL-deficient knee.

Background and purpose of the study: the anterior cruciate ligament (ACL) is a continuum of fibres which are differently recruited through range of motion. Two main functional bundles can be identified: the postero-lateral bundle (PLB) which is taut exclusively towards extension and the anteromedial bundle (AMB) which is taut through full range of motion. The purpose of this investigation was to assess the relative contribution of the bundles to intact knee kinematics.

Material and methods: fourteen intact cadaver knees were instrumented in a non-ferromagnetic rig and six degrees of freedom kinematics through flexion-extension was recorded with an electromagnetic device under the application of a 90N anterior force or a 5Nm internal rotation torque. The AMB and PLB were alternatively cut first in each knee and knee kinematics was recorded. The other bundle was then dissected and ACL deficient knee kinematics tested.

Results: when the AMB was cut anterior tibial translation increased and no effects on rotations were recorded. When the PLB was first cut no significant effects on anterior laxity were observed. Different rotational responses were observed in different knees. After the section of both bundles a larger increase in anterior laxity was observed. The changes in rotation differed from knee to knee.

Discussion: The AMB is a primary restraint against anterior tibial translation and has a small and variable effect on rotations. The PLB is a secondary restraint against anterior tibial translation in extension and maintains normal rotational laxity in AMB deficient knees. Therefore, reconstruction of both bundles is theoretically advantageous to restore both intact knee anteroposte-rior and rotational laxity.

Aim: To analyse the posterior and external rotational laxities in single bundle PCL (sPCL) and double bundle PCL reconstruction (dPCL) in a PCL and PLC deficient knee.

Methods: Ten fresh frozen were used. A custom made wooden rig with electromagnetic tracking was used to measured knee kinematics. Each knee was tested with posterior and anterior drawer forces of 80N and an external rotation moment of 5Nm when intact, after PCL resection, after dividing the PLC and after performing dPCL and sPCL reconstructions with a bone patellar tendon bone allograft and tibial inlay technique.

Results: The one-tailed paired Student’s t test with Bon-ferroni correction was used. There was a significant difference between the ability of the dPCL and sPCL reconstruction to correct the posterior drawer in extension (p=0.002). There was no difference between the dPCL reconstruction and the intact condition of the knee near extension (p=0.142, Fig 1). There was no significant difference between the intact condition and both sPCL (p=0.26) and dPCL (p=0.20) reconstructions in flexion in restoring posterior laxity. Neither of the reconstructions could restore the rotational laxity (Fig 3).

Conclusion: In a combined PCL and PLC deficient knee the posterior laxity can be controlled by both the sPCL as well as the dPCL reconstructions except near extension where the dPCL reconstruction was better.

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.

Aim: To compare the ability of two different PLC reconstruction techniques to restore the kinematics of a PCL & PLC deficient knee to PCL deficient condition.

Methods: 8 fresh frozen cadaver knees were used. A custom rig with electromagnetic tracking system measured knee kinematics. Each knee was tested with posterior & anterior drawer forces of 80N, external rotation moment of 5Nm & varus moment of 5Nm when intact, after dividing PCL, PLC (lateral collateral ligament & popliteus tendon), after PLC reconstruction type1 (1PLC) & PLC reconstruction type 2 (2PLC). 1PLC was modification of Larson’s technique with semitendinosus graft. 2PLC was performed with semitendinosus graft to reconstruct the lateral collateral ligament & the pop-liteofibular ligament, gracillis used to reconstruct pop-liteus tendon.

Results: The one-tailed paired student’s t test with Bon-ferroni correction was used to analyse the data. Only in deep flexion 2PLC reconstruction was significantly better than the 1PLC reconstruction in restoring the posterior laxity to PCL deficient condition (p=0.02). (Figure1) In deep flexion 1PLC could not restore the rotational laxity to PCL deficient condition (p=0.02). In mid flexion the 2PLC was unable to restore the rotational laxity to PCL deficient condition (p=0.048) (Figure 2).

Conclusion: The 2PLC reconstruction was better than the 1PCL in controlling the posterior drawer. The 1PLC technique though not significant tended to over constrain the external & varus rotations.

Although total knee replacement (TKR) has good long term reliability, some patients remain unhappy; this may relate to abnormal motion causing pain or instability. This study measured the effect of TKR femoral component internal-external rotation position upon knee kinematics.

The kinematics of eight fresh-frozen cadaveric legs were measured, with a range of loading and states of preparation. The stages of preparation included intact; TKR in standard navigated position aligned to mechanical and epicondylar axes, TKR with three and six degree internal and then external rotation of femoral component. The loads applied were 70N anterior and posterior draw; Five Nm internal and external rotation; Five Nm valgus and varus. All these were applied in every state of preparation with the knee moved passively in 0–120deg flexion-extension, then repeated with the quadriceps tensed to 400N by a pneumatic cylinder and cable. The TKR used was a Stryker Scorpio posterior cruciate retaining. The implant positions and tibio-femoral kinematics were measured continuously using a modified software Stryker knee navigation system, leading to ′envelopes of laxity′ for each degree of freedom across the range of flexion-extension. In order to vary the implant rotation, the ‘standard’ TKR was removed and then remounted on an adjustable intra-medullary rod-intube mechanism that was also linked to the navigation system. Adjustments in 6 degrees of freedom allowed the datum position to be regained within 1mm and 1deg, using a custom software module and a sensor located on the implant.

Internal rotation of the femoral component caused increasing tibial valgus with knee flexion, with the increase in valgus at 90deg matching the changed rotation. Similarly, external component rotation caused matching tibial varus with knee flexion. Varus and valgus laxities were not altered significantly from those in the datum condition by femoral component internal rotation, across the whole range of flexion. However, external rotation caused increased valgus laxity in flexion. Tibial rotational effects were complex. In the extended knee, femoral component rotation caused a matching tibial rotation. Thus, an externally rotated femoral implant magnified tibial external rotation (the screw-home) with terminal knee extension. The tibial internal rotation with knee flexion was then increased above normal, so that the tibia was internally rotated at 90deg flexion. Internal rotation of the component caused increased internal rotation laxity and decreased external rotation laxity; the opposite occurred after femoral component external rotation.

Changes in femoral component position had complex effects on the movement and posture of the tibia across the range of knee flexion. Some have easily-understood consequences, such as component internal rotation caused tibial valgus in flexion, thus increasing the lateral force vector acting on the patella. The changes in rotational laxity patterns are related to the differing structures of the medial and lateral collateral ligament complexes, the lateral collateral ligament allowing greater freedom of movement in response to the altered height of the ligament attachment above the joint line at that side of the knee, whereas the medial collateral ligament maintained greater control of rotational laxity. These effects explain loss of stability in flexion and the tendency of the knee to pivot about a medial axis.

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.

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.

Aims: To evaluate different surgical techniques of lateral meniscal allograft transplantation in cadaver knees, and to assess how these techniques affect tibial contact pressures.

Methods: The femoral and tibial shafts of five human cadaver knees were cemented into steel pots. Fresh-frozen irradiated human meniscal allografts were supplied by the East Anglia Tissue Services Department of the National Blood Service.

The knees were mounted into an Instron materials testing machine. Paddles of pressure-sensitive Fuji Prescale Film were inserted into the lateral compartment of the knee, underneath the lateral meniscus. Each knee was then loaded to 700N for 10 seconds. The Fuji Film paddles were digitally scanned and then analysed using Scion Image Analysis software to determine the intra-articular contact pressures.

Contact pressures were then determined after (i) total lateral meniscectomy, (ii) lateral meniscal allograft transplantation using a bone plug-keyhole technique to secure the horn attachments, and (iii) after insertion of the graft by suturing only.

Results: Total lateral meniscectomy led to a mean increase in maximum contact pressures of 103% (s.d. 63). Mean maximum contact pressures after lateral meniscal transplantation with a bone cylinder were 59% (s.d. 60) greater than the intact state, and after suturing only of the graft, were 85% (s.d. 74) greater than the intact knees.

Conclusions: Overall, lateral meniscal transplantation did partially restore contact pressures within the knees, and the use of a graft attached to a bone cylinder appeared to be more effective than just simple suturing of the graft. However, the results varied greatly between the different knees. In two knees, the results of meniscal transplantation were excellent. However, results were poor in knees with inaccurate graft-to-host size matching or where there was significant articular degeneration.

Aim: To test the hypothesis that the meniscofemoral ligaments (MFLs) make a significant contribution to resisting anteroposterior and rotatory laxity of the posterior cruciate ligament (PCL) deficient knee.

Methods: The anterior and posterior MFLs of eight cadaveric knees were identified using previously described dissection techniques [1], which were shown not to affect overall knee stability in control studies. These specimens were tested for anteroposterior and rotatory laxity in a materials testing machine. The posterior cruciate ligament was then divided, followed by division of the MFLs. Laxity results were obtained for intact, PCL-deficient and PCL/MFL-deficient knees. Results were analysed using repeated measures analysis of variance and paired t tests.

Results: Division of the MFLs in the PCL-deficient knee significantly increased posterior laxity between 15o and 90o of flexion (p< 0.01). Force/displacement measurements revealed that, at 90° flexion, the MFLs contributed to 28% of total resistance to posterior drawer in the intact knee and 70% in the PCL-deficient knee (p< 0.01). There was no effect on rotatory laxity (p> 0.2).

Discussion: Previous studies have demonstrated a high prevalence of the MFLs in knees1 and that these ligaments have a strength similar to the posterior fibre bundle of the PCL [2]. The current in vitro study suggests that they contribute to overall resistance to posterior drawer, especially in the PCL-deficient knee. If this is confirmed in vivo, patients with PCL injuries may have a reduced posterior drawer sign if their MFLs are intact, and this may result in a more stable knee. Thus the MFLs should be accurately identified and assessed during MRI scanning and arthroscopy [3].

Conclusion: This is the first study demonstrating a function for the MFLs as secondary restraints to posterior drawer in the PCL-deficient knee. The integrity of these structures should be assessed during both MRI scanning and arthroscopy of PCL-injured patients, as this may affect the diagnosis and management of such injuries.

Introduction: Accurate size-matching of meniscal allografts is essential to maintain tibiofemoral congruity, and therefore function, especially when the surgical technique of using a bony bridge is employed.

Methods of accurately assessing the required dimensions of an ideal meniscal allograft for each patient are limited. One popular method used is to choose the appropriate graft according to the bony tibial plateau dimensions of the patient, as determined from plain radiographs.

Aims: To correlate meniscal dimensions with the bony dimensions of donor tibial plateaus.

Methods: 22 left and right pairs of donor tibial plateaus with intact meniscal allografts were obtained, giving a total of 88 individual meniscal allografts. Using a digital micrometer, the following meniscal dimensions were measured: anteroposterior length, medial-lateral width, and the radial width at the mid-point of the meniscal body. Peripheral circumference was measured using flexible steel wire. Medial and lateral bony tibial plateau width and length, and total plateau width were also recorded.

Linear regression analysis was used to obtain a formula, relating each meniscal dimension to the various bony plateau measurements. The resulting equations were used to calculate an expected meniscal dimension from the measured plateau dimensions, and this was compared to the size of the actual dimension measured.

Results: The magnitude of the meniscal dimensions measured approximately fitted a normal distribution amongst all the specimens studied. The tibial plateau widths ranged from 69.2mm to 88.4mm (mean 78.5mm, s.d. 5.4mm), a 28% difference. The mean difference between meniscal measurements between the left and right knee of each pair was 7.3%. However, the greatest individual difference observed was 41.8%.

The mean percentage error between meniscal dimensions calculated from specific compartmental tibial plateau dimensions, and the actual measured meniscal dimensions was 5.3% (s.d. 4.1%). When using just total bony tibial plateau width to calculate meniscal dimensions, the percentage error was 6.2% (s.d. 4.9%). This difference was not statistically significant. The maximum error between calculated and actual meniscal dimensions was 32%.

Conclusions: This anatomical study shows that the use of plateau dimensions as a determinant for the sizing of meniscal allografts can be used to predict meniscal dimensions. However, mean errors are in the region of 5% – 6%, and can be as high as 32%. The potential mechanical effects of such graft to host size mismatching must be carefully borne in mind.

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.

In vivo loading data for the rotator cuff would be of value to scientists and clinicians interested in the shoulder in the testing of surgical repairs, design of rehabilitation programs and for finite element models.

A technique for insertion and retrieval of the Arthroscopically Insertable Force Probe (AIFP - Microstrain Inc. Burlington, Vermont, USA) from the subscapularis is described was initially established in a cadaveric model. Ethical approval was obtained for AIFP insertion into the subscapularis tendon of volunteers during diagnostic shoulder arthroscopy. An in situ calibration was carried out using a modified arthroscopic grasper ( Smith and Nephew, Huntingdon, UK). After motor effects of interscalene block had worn off dynamic data relating to subscapularis tendon loading was collected. The AIFPs were removed through a port site by traction on an O (3.5 metric) nylon suture without complication.

Maximum loading of the subscapularis tendon was measured during internal rotation from neutral with the arm fully adducted. Forces measured exceeded 200N.

This paper describes a novel technique for the insertion, calibration and retrieval of AIFPs from the rotator cuff. In vivo tendon loading data was obtained. The techniques described may be applied to other structures of interest to orthopaedic surgeons.

Objective: This study challenges the assumption that pivot shift is abolished once anterior stability is restored in the ACL reconstructed knee. Method: The kinematics of 7 cadaver knees were studied with the Flock-of-Birds, as pivot shift was repeated in intact, ACL deficient, then ACL reconstructed specimens with grafts tensioned at 0, 10, 20, 40 and 60N. All were BPTB grafts in similar positions. Results: Pivot shift is described as a sudden reduction from internal rotation of 8.57 +/− 2.3° at knee flexion of 24.2 +/− 11°; achieved with iliotibial loading of 56.2 +/− 11.5N, 2.26 +/− 0.6Nm valgus load and 1.5 +/− 0.4Nm internal torque. Internal rotation was significantly reduced at 40N (3.2°, p< 0.005) and 60N (2.9°, p=0.001). At maximum tension, all specimens felt stable and pivoted less. This reduction of internal rotation averaged 62%; ranging from 42% (subtle pivot) to 100% (complete abolition). At 90° knee flexion external rotation was reduced with graft tension of 60N, but not significantly (p=0.03). The range of knee flexion during reduction of the pivot shift was not significantly altered. Conclusions: Tensions of grafts that restored anterior stability (40N & 60N) did not always abolish the pivot shift, but significantly reduced it. This may account for complaints of subtle instability despite surgical reconstruction. Grants: DTT Lie was supported by a grant from the Singapore National Medical Research Council.

Low back pain (LBP) is a common problem in rowers of all levels. Few studies have looked at the relationship between rowing technique, the forces generated during the rowing stroke and the kinematics of spinal motion. Of particular concern with respect to spinal injury and damage are the effects of fatigue during long rowing sessions.

A technique has been developed using an electromagnetic motion system and strain gauge instrumented load cell to measure spinal and pelvic motion and force generated at the oar during rowing on an exercise rowing ergometer. Using this technique 13 elite national and international oarsmen (mean age 22.43 ± 0.02 years) from local top squad rowing teams were investigated. The test protocol comprised of a one hour rowing piece. During this session rowing stroke profiles were quantified in terms of lumbopelvic kinematics and stroke force profiles. These profiles were sampled at the start of the session and quarterly intervals during the hour piece.

From this data we were able to quantify the motion of the lumbar spine and pelvis during rowing and relate this to the stroke force profile. The stroke profiles over the one hour piece were then compared to examine the effects of fatigue. This revealed marked changes and increases in the amount of spinal motion during the hour piece suggesting that to maintain stroke force profiles athletes were utilising greater ranges of spinal motion. The relevance of this with regard to low back pain however, requires further investigation.