Hop tests are used to determine return to sports after ACL reconstruction. They mostly measure distance and symmetry but do not assess kinematics and kinetics. Recently, biomechanical evaluations have been incorporated into these functional jump tests for the better assessment of return to sport. We assessed the sagittal plane range of motion (ROM) of the knee, the deviation axis of rotation (DAOR), and the vertical ground reaction force (vGRF) normalized to body weight in nine healthy participants during the single leg (SLH) and crossover hop tests (COHT). Participants' leg lengths were measured. Jumping distances were marked in the test area as being 4/5 of the leg length. Four sensors were placed on the thighs, the legs and the feet. These body parts were handled as a single rigid body. Eight 480 Hz cameras were used to capture the movements of these rigid bodies. vGRF at landing were measured using a force plate (Bertec, Inc, USA). The ROM of the knee joint and the DAOR were obtained from kinematic data. Participants' joint kinematics metrics were similar in within-subjects statistical tests for SLH and COHT. We therefore asked whether the repeated vGRF normalized to body weight will be similar in both legs during these jumps. Joint kinematics metrics however were different in between subjects indicating the existence of a personalized jumping strategy. These hop tests can be recorded at the beginning of the training season for each individual, which can establish a comparative evaluation database for prospective lower extremity injury recovery and return to sport after ACL injury

To investigate differences in the drop vertical jump height in female adolescents with an ACL injury and healthy controls and the contribution of each limb in this task. Forty female adolescents with an ACL injury (ACLi, 15.2 ± 1.4 yrs, 164.6 ± 6.0 cm, 63.1 ± 10.0 kg) and thirty-nine uninjured (CON, 13.2 ± 1.7 yrs, 161.7 ± 8.0 cm, 50.6 ± 11.0 kg) were included in this study. A 10-camera infrared motion analysis system (Vicon, Nexus, Oxford, UK) tracked pelvis, thigh, shank, and foot kinematics at 200Hz, while the participants performed 3 trials of double-legged drop vertical jumps (DVJ) on two force plates (Bertec Corp., Columbus, USA) sampled at 2000Hz.The maximum jump height normalised by dominant leg length was compared between groups using independent samples t-test. The maximum vertical ground reaction force (GRFz) and sagittal ankle, knee and hip velocities before take-off were compared between limbs in both groups, using paired samples t-test. The normalised jump height was 11% lower in the ACLi than in the CON (MD=0.04 cm, p=0.020). In the ACLi, the maximum GRFz (MD=46.17N) and the maximum velocities of ankle plantar flexion (MD=79.83°/s), knee extension (MD=85.80°/s), and hip extension (MD=36.08°/s) were greater in the non-injured limb, compared to the injured limb. No differences between limbs were found in the CON. ACL injured female adolescents jump lower than the healthy controls and have greater contribution of their non-injured limb, compared to their injured limb, in the DVJ task. Clinicians should investigate differences in the contribution between limbs during double-legged drop vertical jump when assessing patients with an ACL injury, as this could help identify asymmetries, and potentially improve treatment, criteria used to clear athletes to sport, and re-injury prevention

Introduction. Weight is a modifiable risk factor for osteoarthritis (OA) progression. Despite the emphasis on weight loss, data quantifying the changes seen in joint biomechanics are limited. Bariatric surgery patients experience rapid weight loss. This provides a suitable population to study changes in joint forces and function as weight changes. Method. 10 female patients undergoing gastric bypass or sleeve gastrectomy completed 3D walking gait analysis at a self-selected pace, pre- and 6 months post-surgery. Lower limb and torso kinematic data for 10 walking trials were collected using a Vicon motion capture system and kinetics using a Kistler force plate. An inverse kinematic model in Visual 3D allowed for no translation of the hip joint centre. 6 degrees of freedom were allowed at other joints. Data were analysed using JASP with a paired samples t-test. Result. On average participants lost 28.8±7.60kg. No significant changes were observed in standing knee and hip joint angles. Walking velocity increased from 1.10±0.11 ms. -1. to 1.23±0.17 ms. -1. (t(9)=-3.060, p = 0.014) with no change in step time but a mean increase in stride length of 0.12m (SE: 0.026m; t(9)=-4.476, p = 0.002). A significant decrease of 21.5±4.2% in peak vertical ground reaction forces was observed (t(9)=12.863, p <0.001). Stride width significantly decreased by 0.04m (SE: 0.010m; t(9)=4.316, p = 0.002) along with a decrease in lateral impulse of 21.2Ns (SE: 6.977Ns; t(7), p = 0.019), but no significant difference in knee joint angles were observed. Double limb support time also significantly reduced by 0.02s (SE: 0.006s; t(9) = 3.639, p=0.005). Conclusion. The reduction in stance width and lateral impulse suggests a more sagittal compass-gait walk is being achieved. This would reduce valgus moments on the knee reducing loading in the medial compartment. The reduction in peak ground reaction force would reduce knee contact forces and again potentially slow OA progression

It has been recently being investigated how the pressure distribution beneath the foot points to the active usage of the foot in standing adults. Nevertheless, it offers new perspectives in postural research by introducing foot-triggered sensory-motor control strategies in quiet standing dynamics. Furthermore, the spatiotemporal evolution of physiological postural control strategies has not clearly been identified yet. Thus, we have chosen developmental aspects of the infant's postural adjustments as a media to explore learning of biped standing. This study investigates developmental changes in active usage of a contact surface and pressure distribution beneath infants’ foot during learning of upright posture. We started studying longitudinally on 22 female and 22 male infants at their 12.5. th. months (1. st. trimester, T1) and kept on screening the same subjects at every three months (19 females and 12 males at 15.5. th. months (T2), 17 females and 7 males at 18.4. th. months (T3)), during their normal checkup appointments in Gazi University Hospital, Social Pediatrics Department-Ankara/Turkey. Each trial was fulfilled by an infant standing on a pressure pad placed on top of a force plate to collect the pressure distribution data beneath the feet for 15 sec at T1, and 25-sec long duration at T2 and T3 and was repeated at least three times. During the data collection, infants’ parents were beside them trying to get infants’ attention towards themselves preventing them from being distracted and/or moving and walking around. The data collection setup additionally contained one camera for videotaping the infants’ reactions. Our main research interest in this study was to explore the spatiotemporal evolution of the behavioral characteristics of human postural sway. We expected to monitor the developmental changes at an infant's standing experience during their 2. nd. -year epoch through time-frequency domain analyses and explorative/exploitative informatics’ metrics. We computed Center of Pressure (CoP) time signal from the data collected by the force plate and the pressure pad. In time domain, mean and the variance at the CoP time signal were estimated in both antero-posterior (CoPx) and medio-lateral (CoPy) directions. In the frequency domain, 50% and 95% power frequency, centroidal frequency (CF), and frequency dispersion were calculated. We observed substantial developmental changes in every trimester, each being comparable with the previous one, which points to infants experiencing a major developmental milestone that can be noticed considerably even in the shorter time intervals. The phase plane analysis performed through the time signals and their time derivatives (estimated velocity of CoPx and CoPy) revealed a shrinkage in the characteristic pattern observed through the following epochs. One-Way ANOVA analysis demonstrated significant differences in 50% and 95% power and centroidal frequency of CoPx (p=0.001, p=0.000, p=0.000) and CoPy (p=0.002, p=0.000, p=0.000) respectively. Further, post hoc analyses demonstrated a significant difference at T1 compared against T2 and T3 for all three frequency domain metrics. Particularly speaking, CF dropped from 2.39 to 1.65 Hz, and from 2.86 to 1.70 Hz for CoPx and CoPy respectively, while passing from T1 to T2. The current status of this research managed to grasp the developmental aspects of infant standing through frequency domain metrics and reconstructed phase space analysis up to their 18 months old

Differences at motor control strategies to provide dynamic balance in various tasks in diabetic polyneuropatic (DPN) patients due to losing the lower extremity somatosensory information were reported in the literature. It has been stated that dynamics of center of mass (CoM) is controlled by center of pressure (CoP) during human upright standing and active daily movements. Indeed analyzing kinematic trajectories of joints unveil motor control strategies stabilizing CoM. Nevertheless, we hypothesized that imbalance disorders/CoM destabilization observed at DPN patients due to lack of tactile information about the base of support cannot be explained only by looking at joint kinematics, rather functional foot usage is proposed to be an important counterpart at controlling CoM. In this study, we included 14 DPN patients, who are diagnosed through clinical examination and electroneuromyography, and age matched 14 healthy subjects (HS) to identify control strategies in functional reach test (FRT). After measuring participants’ foot arch index (FAI) by a custom-made archmeter, they were tested by using a force plate, motion analysis system, surface electromyography and pressure pad, all working in synchronous during FRT. We analyzed data to determine effect of structural and functional foot pathologies due to neuropathy on patient performance and postural control estimating FAI, reach length (FR), FR to height (H) ratio (FR/H; normalized FR with respect to height), displacement of CoM and CoP in anteroposterior direction only, moment arm (MA, defined as the difference between CoP and CoM at the end of FRT), ankle, knee and hip joint angles computed at the sagittal plane for both extremities. Kinematic metrics included initial and final joint angles, defined with respect to start and end of reaching respectively. Further difference in the final and initial joint angles was defined as Δ. FAI was founded significantly lower in DPN patients (DPN: 0.3404; HS: 0.3643, p= <0.05). The patients’ FR, FR/H and absolute MA and displacement of CoM were significantly shorter than the control group (p= <0.05). Displacement of CoP between the two groups were not significant. Further we observed that CoM was lacking CoP in DPN patients (mean MA: +0.88 cm), while leading CoP in HS (mean MA: −1.59 cm) at the end of FRT. All initial angles were similar in two groups, however in DPN patients final right and left hip flexion angle (p=0.016 and p=0.028 respectively) and left ankle plantar flexion angle (p=0.04) were smaller than HS significantly. DPN patients had significantly less (p=0.029) hip flexion (mean at right hip angle, Δ=25.0°) compared to HS (Δ=33.53°) and ankle plantar flexion (DPN mean at right ankle angle, Δ=6.42°, HS mean Δ=9.07°; p=0.05). The results suggest that movement of both hip and ankle joints was limited simultaneously in DPN patients causing lack of CoM with respect to CoP at the end of reaching with significantly lower FAI. These results lead to the fact that cutaneous and joint somatosensory information from foot and ankle along with the structure of foot arch may play an important role in maintaining dynamic balance and performance of environmental context. In further studies, we expect to show that difference at control strategies in DPN patients due to restricted functional foot usage might be a good predictor of how neuropathy evolves to change biomechanical aspects of biped erect posture

Background. Subjects with Low Back Pain (LBP) often have altered trunk muscle activity and postural sway during perturbations. Research suggests different perturbations have differing results on abdominal muscle activity and postural sway, however, the majority of perturbations investigated are not realistic daily tasks and little evidence exists if the changes are still present following resolution of symptoms. Aim: to determine trunk muscle activity, Lumbar multifidus (M), iliocostalis lumborum (IL), external oblique (EO), transversus abdominus/internal oblique TrA/IO and postural sway during two reaching tasks between subjects with history of LBP (HLBP) and those without. Method. 20 volunteers, 8 HLBP (22±2yrs, 174.9±6.0cm, 68.3±6.22kgs,) and 12 without HLBP (20.58±2.23 yrs, 174.5±9.8cm, 68.6±13.9kgs) gave informed consent. Surface Electromyography (sEMG) measured muscle activity of M, IL, TrA/IO, EO and VICON force plate measured postural sway (anterior posterior (AP)centre of pressure (CoP), medial lateral(ML)CoP during high (HRT) and low reaching tasks (LRT). sEMG data was normalized to maximum voluntary contractions. Force plate data was processed using Matlab R2009b. Results: Mann-Whitney U tests noted a significant increase in EO sEMG activity in HLBP group for HRT (p=0.03). Results were insignificant for HRT: M(p=0.64), IL(0.19), TrA/IO,(p=0.14), AP CoP(p=0.44), ML CoP(p=0.69), LRT: M(p=0.58), IL(0.35) TrA/IO(p=0.58), EO(p=0.28), AP CoP (p=0.39), ML CoP (p=0.24). Conclusion. Increased activity of EO in HLBP during HRT may be indicative of a protective mechanism. However, predominantly insignificant results may be due to low subject numbers or the perturbation tasks not being challenging enough. Further research with larger subject numbers is needed to confirm these results. No conflicts of interest. No funding obtained. This abstract has not been previously published in whole or substantial part nor has been presented previously at a national meeting

Summary. Our results prove that Demineralised Cortical Bone (DCB) can be used as biological tendon graft substitute, combined with correct surgical technique and the use of suture bone anchor early mobilisation can be achieved. Introduction. Surgical repair of tendon injuries aims to restore length, mechanical strength and function. In severe injuries with loss of tendon substance a tendon graft or a substitute is usually used to restore functional length. This is usually associated with donor site morbidity, host tissue reactions and lack of remodelling of the synthetic substitutes which may result in suboptimal outcome. In this study we hypothesise that DCB present in biological tendon environment with early mobilisation and appropriate tension will result in remodelling of the DCB into ligament tissue rather that ossification of the DCB at traditional expected. Our preparatory cadaveric study (abstract submitted to CORS 2013) showed that the repair model used in this animal study has sufficient mechanical strength needed for this animal study. Methods. 6 mature female sheep undergone surgical resection of the distal 1 cm of the right patellar tendon and osteotomy of patellar tendon attachment at the tibial tuberosity under general anaesthesia. Repair was done using DCB with 2 suture bone anchor. Animals were allowed immediate mobilisation after surgery and were sacrificed at 12 weeks. The force passing through the operated and non-operated legs was assessed preoperatively and at week 3, week 6, week 9 and week 12 bay walking the animals over a force plate. Radiographs were taken immediately after euthanasia, the Patella-Tendon-tibia constructs were retrieved and pQCT scan was done. Histological analysis included tenocytes and chondrocytes cell counts, semi-quantitative scoring of the neo-enthesis and polarised microscopy. Result. In this study, none of the retrieved specimens showed any evidence of ossification of the DCB as proved by the pQCT analysis. One animal failed to show satisfactory progress after week 3, X-rays showed patella alta, on specimen retrieval no damage to the DCB was found, sutures and stitches were intact and no evidence of anchor pullout was found. Force plate analysis of the other 5 animals showed satisfactory progression over time with 44% functional weight bearing at week 3 progressing to 79% at week 12. There was full range of movement of the stifle joint after 12 weeks. Histological analysis proved formation of neo-enthesis with evidence of cellulisation, vascularisation and remodelling of the collagen leading to ligamentisation of the DCB. Discussion. Surgical reconstruction of damaged tendons is technically challenging, patellar tendon injuries presents even more challenging situation as it involves weight bearing joint. It is generally accepted that a period of immobilisation with passive range of movement exercises and protected weight bearing for up to 6 weeks post operatively is usually advised. Some surgeons use offloading metal wire to protect the repair for 6 weeks involving second surgical procedure to remove the wire. Demineralised bone is usually used in orthopaedics to utilise its osteogenic properties as bone graft substitute and to enhance osteogenesis in load bearing situations. In our study we explored a potential new use of the demineralised bone as tendon graft substitute, it acts as collagen scaffold allowing host cells to remodel its fibres into ligament like structure

Anterior cruciate ligament deficiency (ACLD) affects the performance of walking in some patients (non-copers) while copers are able to minimize the effects via proper musculoskeletal compensations. Since many daily activities are more challenging than level walking, e.g., obstacle-crossing, it is not clear whether copers are able to cope with such a challenging task. A successful and safe obstacle-crossing requires not only sufficient foot clearance of the swing limb, but also the stability of the body provided mainly by the stance limb. Failure to meet these demands may lead to falls owing to loss of balance or tripping over obstacles. The purpose of the current study was to identify the motor deficits and/or biomechanical strategies in coper and non-coper ACLD patients when crossing obstacles of different heights for a better function assessment. Ten coper and ten non-coper ACLD patients were recruited in the current study. The non-coper ACLD subjects were those who had not been able to return to their pre-injury level activities, had at least once giving way during the last six months and their Lysholm knee scale was less than 70 [1]. Each subject walked and crossed obstacles of heights of 10%, 20% and 30% of their leg lengths at a self-selected pace. Kinematic and kinetic data were measured with a 7-camera motion analysis system (Vicon, Oxford Metrics, U.K.) and two force plates (AMTI, U.S.A.). The leading and trailing toe clearances were calculated as the vertical distances between the toe markers and the obstacle when the toe was directly above the obstacle. Joint angles of both limbs, and joint moments of the stance limb, were calculated. Peak extensor moments at the knee during stance phase and the corresponding joint angles were extracted for statistical analysis. A 3 by 2, 2-way mixed-model analysis of variance with one between-subject factor (group) and one within-subject factor (obstacle height) was performed (α=0.05). SAS version 9.2 was used for all statistical analysis. Compared with the copers, significantly reduced leading and trailing toe clearances were found in the non-coper group (P<0.05). The non-copers showed significantly decreased peak extensor moments (P<0.05) and flexion angle at the affected knee during the stance phase before leading limb crossing (P<0.05). Distinctive gait patterns were identified in coper and non-coper patients with unilateral anterior cruciate ligament deficiency during obstacle crossing. During the stance phase before the un-affected leading limb crossing, the non-copers showed significantly reduced flexion and peak extensor moments at the affected knee (i.e., quadriceps avoidance), primarily owing to the impaired stability at the affected knee. The significantly reduced leading and trailing toe clearances in the non-coper group indicate that the non-coper ACLD patients are at a higher risk of tripping over the obstacle, and may have difficulty in regaining balance owing to the unstable ACLD knee. Advanced rehabilitation program or reconstruction of the ACL is suggested for the non-coper group

Identification of gait deviations and compensations in patients with total hip arthroplasty (THA) is important for the management of their fall risks. To prevent collapse of the lower limbs while balancing and supporting the body, proper combinations of joint moments are necessary. However, hip muscles affected by THA may compromise the sharing of load and thus the whole body balance. The current study aimed to quantify the control of body support in patients with THA in terms of the total support moment (Ms) and contributions of individual joint moments to Ms during walking. Six patients who underwent unilateral THA via an anterolateral approach for at least six months at the time of the gait experiment, and six age- and gender-matched healthy controls were recruited. Twenty-eight infrared retro-reflected markers were placed on specific landmarks of the pelvis-leg apparatus to track the motion of the segments during walking. Kinematic and kinetic data were measured using an 8-camera motion analysis system (Vicon, Oxford Metrics, U.K.) and two force plates (AMTI, U.S.A.). The Ms of a limb was calculated as the sum of the net extensor moments at the hip, knee and ankle during stance phase. The contributions of the hip, knee and ankle to the first and second peaks of Ms (Ms1 and Ms2) were calculated by dividing the joint moment value by the corresponding peak values of Ms. Independent t-tests were performed to compare between groups at a significance level set at α=0.05 using SAS version 9.2 (SAS Institute Inc., NC, USA). No significant differences in Ms1 and Ms2 were found between the THA group and normal controls (P >0.05). However, compared to the healthy controls, significantly increased hip and ankle contributions but decreased knee contributions to Ms1, and significantly increased hip contributions but decreased ankle contributions to Ms2 were found in the THA group. Similar Ms1 and Ms2 between groups indicates that the lower limbs in the THA group were able to provide normal body supports. However, this was achieved via an altered contributions of the hip, knee and ankle. Hip and knee extensors play important roles in supporting the body when the Ms1 occurs during early stance of walking. In the THA group, greater hip and ankle contributions but lesser knee contributions for the Ms1 indicates that the function of hip extensors were not affected but compensatory mechanisms of the knee and ankle were found. For the Ms2, hip flexor and ankle plantarflexors are important for supporting the body during late stance. Decreased hip flexor (i.e., greater hip extensor contributions) and ankle plantarflexor moments in the THA patients suggests that the hip flexors and ankle plantarflexor muscles were affected by THA surgery. Hip muscles affected by the THA may compromise the sharing of load at the hip and thus the whole body balance. Further postoperative rehabilitation is suggested for the patients following THA. Further studies on the effects of different surgical approaches on the support moments is needed for improving treatment plans

Posterior cruciate ligament deficiency (PCLD) leads to structural and proprioceptive impairments of the knee, affecting the performance of daily activities including obstacle-crossing. Therefore, identifying the biomechanical deficits and/or strategies during this motor task would be helpful for rehabilitative and clinical management of such patients. A safe and successful obstacle-crossing requires stability of the body and sufficient foot clearance of the swing limb. Patients with PCLD may face demands different from normal when negotiating obstacles of different heights. The objective of this study was thus to identify the biomechanical deviations/strategies of the lower limbs in unilateral PCLD during obstacle-crossing using motion analysis techniques. Twelve patients with unilateral PCLD and twelve healthy controls participated in the current study with informed written consent. They were asked to walk and cross obstacles of heights of 10%, 20% and 30% of their leg lengths at self-selected speeds. The PCLD group was asked to cross the obstacles with each of the affected and unaffected limb as the leading limb, denoted as PCLD-A and PCLD-U, respectively. The kinematic and kinetic data were measured with a 7-camera motion analysis system (Vicon, Oxford Metrics, U.K.) and two force plates (AMTI, U.S.A.). The angles of the stance and swing limbs (crossing angles) and the moments of the stance limbs (crossing moments) for each joint in the sagittal plane when the leading limb was above the obstacle were calculated for statistical analysis. A 3 by 2, 2-way mixed-model analysis of variance with one between-subject factor (PCLD-A vs. Control, and PCLD-U vs. Control) and one within-subject factor (obstacle height) was performed (α=0.05). Paired t-test was used to compare the variables between PCLD-A and PCLD-U (α=0.05). SAS version 9.2 was used for all statistical analysis. When the leading toe was above the obstacle, the PCLD group showed significantly greater hip flexion in the swing limb but decreased dorsiflexion in the stance limb, both in PCLD-A and PCLD-U (P<0.05). Greater knee flexion and greater ankle dorsiflexion were found in the leading limb in PCLD-A (P<0.05). Meanwhile, the PCLD group showed significantly decreased ankle plantarflexor but increased knee extensor crossing moments in the stance limb compared with the Control (P<0.05). None of the calculated variables were found to be significantly different between PCLD-A and PCLD-U (P>0.05). When crossing the obstacle, patients with PCLD reduced ankle plantarflexor moments that were mainly produced by the gastrocnemius. This may help reduce the posterior instability of the affected knee. Greater knee extensor crossing moments may also help reduce the posterior instability of the standing knee when the leading toe was above the obstacle. The changed joint kinetics as a result of PCLD were not only seen on the affected side but also on the unaffected side during obstacle-crossing. This symmetrical pattern may be necessary in performing functional activities that may require either the affected side or the unaffected side leading. These results suggest that rehabilitative intervention, including muscular strengthening, on both affected and unaffected sides are necessary in patients with unilateral PCLD

We have studied patients with Joint Hypermobility Syndrome (JHS) admitted to the Royal National Orthopaedic Hospital (RNOH) for a three-week in-patient rehabilitation programme. Ten patients were investigated at the start and end of this programme, and so far eight patients have been followed up at three months review. Postural stability was measured using a force plate, and the path of the centre of force (CoF) was tracked while patients were asked to attempt a series of more challenging tasks: double leg stance with eyes open and then with eyes closed, followed by single leg stance with eyes open and closed. Patients also completed a number of questionnaires at the same time points. We found the results of the double stance eyes closed test of postural stability to be the most informative. The ellipse area (EA) containing 95% of the points of the path of the CoF decreased from 21.5 + 14.8 cm2 to 9.0 + 11.5 cm2 over the course of the in-patient programme. In the eight patients followed up at three months, EA has remained the same (9.6 + 14.6 cm2). We conclude that the effects of the exercise programme and advice on subsequent exercise can be maintained over three months

Repair of tendon injuries aims to restore length, mechanical strength and function. We hypothesise that Demineralised Cortical Bone (DCB) present in biological tendon environment will result in remodelling of the DCB into ligament tissue. A cadaveric study was carried out to optimize the technique. The distal 1cm of the patellar tendon was excised and DCB was used to bridge the defect. 4 models were examined, Model-1: one anchor, Model-2: 2 anchors, Model-3: 2 anchors with double looped off-loading thread, Model-4: 2 anchors with 3 threads off-loading loop. 6 mature sheep undergone surgical resection of the distal 1cm of the right patellar tendon. Repair was done using DCB with 2 anchors. Immediate mobilisation was allowed, animals were sacrificed at 12 weeks. Force plate assessments were done at weeks 3, 6, 9 and 12. Radiographs were taken and pQCT scan was done prior to histological analysis. In the cadaveric study, the median failure force for the 4 models; 250N, 290N, 767N and 934N respectively. In the animal study, none of the specimens showed evidence of ossification of the DCB. One animal failed to show satisfactory progress, X-rays showed patella alta, on specimen retrieval there was no damage to the DCB and sutures and no evidence of anchor pullout. Functional weight bearing was 79% at week12. Histological analysis proved remodelling of the collagen leading to ligamentisation of the DCB. Results prove that DCB can be used as biological tendon substitute, combined with the use of suture bone anchor early mobilisation can be achieved

ACL injured patients show variability in the ability to perform functional activities (Button et al., 2006). It is unknown whether this is due to differences in physical capability or whether fear of re-injury plays a role. Fear of re-injury is not commonly addressed in rehabilitation. This study aimed to investigate whether fear of re-injury impacts rehabilitation of ACL injured patients. An initial group of five ACL reconstructed participants (ACLR, age: 30±11 years, weight: 815±115 N, height: 1.74±0.07 m, all male), five ACL deficient participants (ACLD, age: 31±12 years, weight: 833±227 N, height: 1.80±0.11 m, four male and one female), and five healthy controls (age: 30±3 years, weight: 704±126 N, height: 1.70±0.09 m, three male and two female) were compared. Fear of re-injury was assessed using the Tampa Scale for Kinesiophobia (Kvist, 2004). Quadriceps strength was measured on a Biodex dynamometer. Functional activity was assessed by a single legged maximum distance hop (on the injured leg for ACL patients). Motion analysis was performed with a VICON system, and a Kistler force plate. Hop distance was calculated using the ankle position. The peak knee extension moment during landing, and the knee angle at this peak moment were calculated in VICON Nexus. The ACLD group scored worse on the Tampa scale for Kinesiophobia than the ACLR group (32±4 and 26±4). The ACLD patients did not hop as far as the ACLR and control groups (1.0±0.3, 1.3±0.1 and 1.4±0.3 m). The peak knee extension moments during landing were lowest in the ACLD group (263±159 Nm), slightly higher in the control group (354±122 Nm) and highest in the ACLR group (490±222 Nm), while knee flexion angles at these moments were similar (ACLD: 28±11, ACLR: 33±7 and control: 36±13 degrees). The ACLD group had weaker quadriceps than the control group, while the ACLR group was stronger (143±44 Nm, 152±42, and 167±50 Nm respectively). Fear of re-injury and decreased quadriceps strength potentially both impact on the functional performance of ACL injured patients. Rehabilitation of ACL injured patients could therefore be improved by addressing strength and fear of re-injury. Future research with more participants will further clarify this

Summary Statement. A porcine model using Yucatan minipigs was found to be very promising for the investigation of healing around transcutaneous osseointegrated implants. Pigs demonstrated surprising agility and adaptability including the ability to ambulate on three legs during the immediate postoperative period. Introduction. Previous non weight-bearing and weight-bearing caprine, canine and ovine models have evaluated design, material, and biological coating variations in an attempt to improve the wound healing and skin-implant seal around transcutaneous osseointegrated implants. Although these models have primarily been used as a window into the application of transcutaneous osseointegrated implants in humans, some important model characteristics affecting wound healing and infection have been missing including: 1) replication of the physiological tissue response, and 2) availability of a transcutaneous site with sufficient soft tissue coverage. Pig skin, like human, is relatively hairless, tightly attached to the subcutaneous tissue, vascularised by a cutaneous blood supply, and healed by means of epithelialization. Swine have been extensively utilised for superficial and deep wound healing studies and can offer ample soft tissue coverage following a lower limb amputation. Development of a porcine model is important for continued understanding and improvement of weight-bearing transcutaneous osseointegration. Methods. Two male Yucatan mini-pigs (9 months, 36kg) were fit with transcutaneous osseointegrated prostheses using a single-stage transtibial amputation and prosthesis implantation procedure. The endo-prosthesis consisted of a cylindrical intraosseous threaded section and a smooth transcutaneous section. The transcutaneous sections were smooth to promote epithelialization and deter direct skin-implant adhesion. The implants were custom manufactured from medical grade Ti-6Al-4V alloy. The exo-prosthesis, consisting of an adjustable length leg and foot, was attached by clamp to the supercutaneous portion of the implant following either one or two days of sling constraint to limit initial weight-bearing. Various exo-prosthesis designs and configurations were trialed. The animals’ behavior and gait were closely observed. Weight-bearing was monitored using a force plate. At 5 and 8 weeks, clinical, microbiological, and histological data were examined to assess wound healing and infection at the skin-bone-implant interface. Results. The pigs demonstrated surprising agility and adaptability. They were able to successfully ambulate on three legs during the post-op period before weight-bearing was permitted. They adapted quickly to changes in exo-prosthesis design, position, and length. Although bacterial colonization was verified, neither of the animals exhibited clinical signs of infection over the respective eight and five week studies. Histological results indicated that there was no skin to implant adhesion but that epithelial growth was progressing towards the implant in one animal. Healing of the transcutaneous wound site showed substantial progress but a definitive skin seal was non-existent at the eight week time point. Discussion/Conclusion. This is likely the first animal model developed, having soft tissue characteristics similar to those found in humans, in which an axially-loaded, weight-bearing implant was successfully used. Results indicated that this porcine model offers many advantages over previous models for the development, evaluation, and comparison of the various techniques being advocated to achieve successful transcutaneous osseointegration in humans. The Yucatan miniature pig's ability to ambulate on three legs during the immediate post-operative period and quickly adjust to changes in the exo-prosthesis design, coupled with their physiological similarity to humans, makes them a valuable model for future studies

INTRODUCTION. Motion analysis is routinely used in the clinical and research sectors to quantify joint biomechanics. It plays an important role in clinical assessments by aiding the physician to distinguish between primary movement abnormalities and any secondary compensatory mechanisms that may overshadow the cause of the problem. During a data collection session, a wealth of biomechanical data regarding joint and segment kinematics and kinetics are collected from patients performing daily activities. Objective classification can be used to automate a diagnosis from this data and has been used previously to analyse measurements of level gait [1]. It is of interest to assess the knee during stair-gait as this activity involves greater range of motion (ROM) of the lower limbs, larger forces and moments acting at the knee. AIM. The aim of the current study is to explore the use of an objective classifier [1] to characterise knee osteoarthritis (OA) and monitor functional recovery following a total knee replacement (TKR) using measurements from stair-gait. METHODS. Motion analysis techniques were used to quantify knee OA kinematics and kinetics during stair-gait for six patients with knee osteoarthritis (OA) and nine subjects without pathology (NP). One OA subject, forming a TKR sample, was also assessed at 4, 8 and 12 post-operatively. Each subject performed three trials of stair ascent and descent. 3D motion capture was performed using 8 Qualisys MCUs, capturing at 60Hz and a 1000Hz force plate (Bertec Corporation). Forces were measured from the first step of the staircase [2]. Independent t-tests were performed on biomechanical measures to compare the NP and OA cohorts (p<0.05). This identified the adaptations associated with knee OA. Principal components of salient kinematic and kinetic waveforms were used as inputs to train the classifier and subsequently characterise recovery of the TKR sample. RESULTS. The OA cohort adapted their stair-gait by reducing their peak: (i) external flexion moment in stance during both stair ascent and descent; (ii) medial ground reaction force (GRF) (iii) vertical GRF during stair descent and increasing their external adduction moment during stair ascent. The classifier was used to characterise knee function of the OA and NP subjects with 100% classification accuracy, defined using a Leave-one-out cross-validation. The TKR sample was classified as having dominant OA functional characteristics pre-operatively. At all subsequent measurements the subject was classified as having NP stair-gait characteristics. These changes correlated significantly with Knee Outcome Survey and Oxford Knee scores. CONCLUSION. Classification is a powerful tool for characterising data into two groups where a simplex plot provides a simple clinical interpretation of the results from a motion analysis assessment. This study demonstrates the use of objective classification to quantify NP, OA and TKR function from stair-gait. It also demonstrates its capability to monitor functional changes during a subject's recovery

Introduction. Patients with knee osteoarthritis (OA) often tell us that they put extra load on the joints of the opposite leg as they walk. Multiple joint OA is common and has previously been related to gait changes due to hip OA (Shakoor et al 2002). The aim of this study was to determine whether patients with medial compartment knee OA have abnormal biomechanics of the unaffected knee and both hips during normal level gait. Methods. Twenty patients (11 male, 9 female), with severe medial compartment knee OA and no other joint pain were recruited. The control group comprised 20 adults without musculoskeletal pain. Patients were reviewed, x-rays were examined and WOMAC and Oxford knee scores were completed. A 12 camera Vicon (Vicon, Oxford) system was used to collect kinematic data (100Hz) on level walking and the ground reaction force was recorded using three AMTI force plates (1000Hz). Surface electrodes were placed over medial and lateral quadriceps and hamstrings bilaterally to record EMG data (1000Hz). Kinematics and kinetics were calculated using the Vicon ‘plug-in-gait’ model. A co-contraction index was calculated for the EMG signals on each side of the knee, representing the magnitude of the combined readings relative to their maximum contraction during the gait cycle. Statistical comparisons were performed using t-tests with Bonferroni's correction for two variables and ANOVA for more than two variables (SPSS v16). Results. The mean age of the patients was 69 (SD 8.8). Mean gait speed was 0.95m/s (study group) and 1.44m/s (control group). Peak adduction moments for the OA group [OA Knee; Unaffected Knee; Ipsilateral Hip; Contralateral Hip; in Nm/Kg(±95% CI)] were: 0.55(0.06); 0.47(0.06); 0.73(0.09); 0.73(0.08). Control values for peak moments were 0.64 (0.06) for the knee and 0.81(0.07) at the hip. Mid-stance adduction moments for the OA group (listed as before) were: 0.44(0.08); 0.33(0.06); 0.64(0.06); 0.61(0.08). Control values for mid-stance moments were 0.14(0.03) and 0.40(0.04). [OA group vs. Controls: p=NS for peak moments at all 4 joints; p<0.01 for mid-stance moments at all joints]. Co-contraction indices for hamstrings and quads, [OA knee medial; and lateral; unaffected knee medial; and lateral; control medial; and lateral; 0<X. Discussion. Although the affected subjects all had only single joint OA, abnormal moments were present in the hips and knees of both legs during normal level gait, despite the reduced gait speed of the OA cohort. Abnormal hamstring and quadriceps co-contraction occurs bilaterally in patient with single joint OA. Increased trunk sway is a recognised compensation in knee OA and may be the cause of the abnormal hip and contra-lateral knee loading found in this study. Further investigation is warranted and may lead to improvements in the long term outcome for these patients. Acknowledgement. The study was funded by the North Wales NHS Trust

Objectives

Whilst gait speed is variable between healthy and injured adults, the extent to which speed alone alters the 3D in vivo knee kinematics has not been fully described. The purpose of this prospective study was to understand better the spatiotemporal and 3D knee kinematic changes induced by slow compared with normal self-selected walking speeds within young healthy adults.

We used demineralised bone matrix (DBM) to augment re-attachment of tendon to a metal prosthesis in an in vivo ovine model of reconstruction of the extensor mechanism at the knee. We hypothesised that augmentation of the tendon-implant interface with DBM would enhance the functional and histological outcomes as compared with previously reported control reconstructions without DBM. Function was assessed at six and 12 weeks postoperatively, and histological examination was undertaken at 12 weeks.

A significant increase of 23.5% was observed in functional weight-bearing at six weeks in the DBM-augmented group compared with non-augmented controls (p = 0.004). By 12 weeks augmentation with DBM resulted in regeneration of a more direct-type enthesis, with regions of fibrocartilage, mineralised fibrocartilage and bone. In the controls the interface was predominantly indirect, with the tendon attached to the bone graft-hydroxyapatite base plate by perforating collagen fibres.

We examined the mechanical properties of Vicryl (polyglactin 910) mesh in vitro and assessed its use in vivo as a novel biomaterial to attach tendon to a hydroxyapatite-coated metal implant, the interface of which was augmented with autogenous bone and marrow graft. This was compared with tendon re-attachment using a compressive clamp device in an identical animal model. Two- and four-ply sleeves of Vicryl mesh tested to failure under tension reached 5.13% and 28.35% of the normal ovine patellar tendon, respectively. Four-ply sleeves supported gait in an ovine model with 67.05% weight-bearing through the operated limb at 12 weeks, without evidence of mechanical failure.

Mesh fibres were visible at six weeks but had been completely resorbed by 12 weeks, with no evidence of chronic inflammation. The tendon-implant neoenthesis was predominantly an indirect type, with tendon attached to the bone-hydroxyapatite surface by perforating collagen fibres.

This study investigates the use of porous biphasic ceramics as graft extenders in impaction grafting of the femur during revision hip surgery.

Impaction grafting of the femur was performed in four groups of sheep. Group one received pure allograft, group two 50% allograft and 50% BoneSave, group three 50% allograft and 50% BoneSave type 2 and group four 10% allograft and 90% BoneSave as the graft material. Function was assessed using an index of pre- and post-operative peak vertical ground reaction force ratios. Changes in bone mineral density were measured by dual energy X ray absorptiometry (DEXA) scanning. Loosening and subsidence were assessed radiographically and by histological examination of the explanted specimens.

There was no statistically significant difference between the four groups after 18 months of unrestricted functional loading for all outcome measures.