Following anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft measures such as length, cross-sectional area, and volume may not fully describe the effects of tendon harvest on muscle morphology as these discrete measures cannot characterize three-dimensional muscle shape. This study aimed to determine between-limb ST shape similarity and regional morphology in individuals with a unilateral history of ACLR using a ST graft, and healthy controls.

A secondary analysis of magnetic resonance imaging was undertaken from 18 individuals with unilateral history of ST ACLR and 18 healthy controls. ST muscles were manually segmented, and shape similarity were assessed between limbs and groups using Jaccard index (0-1) and Hausdorff distance (mm). ST length (cm), peak cross-sectional area (CSA) (cm²), and volume (cm³) was compared between surgically reconstructed and uninjured contralateral limbs, and between the left and right limbs of control participants with no history of injury. Cohen's d was reported as a measure of effect size.

Compared to healthy controls, the ACLR group had significantly (p<0.001, d= −2.33) lower bilateral ST shape similarity. Furthermore, the deviation in muscle shape was significantly (p<0.001, d= 2.12) greater in the ACLR group. Within the ACLR group, maximum Hausdorff distance indicated ST from the ACLR limb deviated (23.1±8.68 mm) from the shape of the healthy contralateral ST, this was observed particularly within the distal region of the muscle. Compared to the uninjured contralateral limb and healthy controls, deficits in peak cross-sectional area and volume in ACLR group were largest in proximal (p<0.001, d= −2.52 to −1.28) and middle (p<0.001, d= −1.81 to −1.04) regions.

Findings highlight morphological features in distal ST not identified by traditional discrete morphology measures. ST shape was most different in the distal region of the muscle, despite deficits in CSA and volume being most pronounced in proximal and middle regions. ST shape following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength.

Anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft, with or without gracilis (GR), results in donor muscle atrophy and varied tendon regeneration. The effects of harvesting these muscles on muscle moment arm and torque generating capacity have not been well described. This study aimed to determine between-limb differences (ACLR vs uninjured contralateral) in muscle moment arm and torque generating capacity across a full range of hip and knee motions.

A secondary analysis of magnetic resonance imaging was undertaken from 8 individuals with unilateral history of ST-GR ACLR with complete ST tendon regeneration. All hamstring muscles and ST tendons were manually segmented. Muscle length (cm), peak cross-sectional area (CSA) (cm²), and volume (cm³) were measured in ACLR and uninjured contralateral limbs. OpenSim was used to simulate and evaluate the mechanical consequences of changes in normalised moment arm (m) and torque generating capacity (N.m) between ACLR and uninjured contralateral limbs.

Compared to uninjured contralateral limbs, regenerated ST tendon re-insertion varied proximal (+) (mean = 0.66cm, maximum = 3.44cm, minimum = −2.17cm, range = 5.61cm) and posterior (+) (mean = 0.38cm maximum = 0.71cm, minimum = 0.02cm, range = 0.69cm) locations relative to native anatomical positions. Compared to uninjured contralateral limbs, change in ST tendon insertion point in ACLR limbs resulted in 2.5% loss in peak moment arm and a 3.4% loss in peak torque generating capacity. Accounting for changes to both max isometric force and ST moment arm, the ST had a 14.8% loss in peak torque generating capacity.

There are significant deficits in ST muscle morphology and insertion points following ST-GR ACLR. The ST atrophy and insertion point migration following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength.

There is currently no commercially available and clinically successful treatment for scapholunate interosseous ligament rupture, the latter leading to the development of hand-wrist osteoarthritis. We have created a novel biodegradable implant which fixed the dissociated scaphoid and lunate bones and encourages regeneration of the ruptured native ligament. To determine if scaphoid and lunate kinematics in cadaveric specimens were maintained during robotic manipulation, when comparing the native wrist with intact ligament and when the implant was installed.

Ten cadaveric experiments were performed with identical conditions, except for implant geometry that was personalised to the anatomy of each cadaveric specimen. Each cadaveric arm was mounted upright in a six degrees of freedom robot using k-wires drilled through the radius, ulna, and metacarpals. Infrared markers were attached to scaphoid, lunate, radius, and 3rd metacarpal. Cadaveric specimens were robotically manipulated through flexion-extension and ulnar-radial deviation by ±40° and ±30°, respectively.

The cadaveric scaphoid and lunate kinematics were examined with 1) intact native ligament, 2) severed ligament, 3) and installed implant.

Digital wrist models were generated from computed tomography scans and included implant geometry, orientation, and location. Motion data were filtered and aligned relative to neutral wrist in the digital models of each specimen using anatomical landmarks. Implant insertion points in the scaphoid and lunate over time were then calculated using digital models, marker data, and inverse kinematics. Root mean squared distance was compared between severed and implant configurations, relative to intact.

Preliminary data from five cadaveric specimens indicate that the implant reduced distance between scaphoid and lunate compared to severed configuration for all but three trials.

Preliminary results indicate our novel implant reduced scapho-lunate gap caused by ligament transection. Future analysis will reveal if the implant can achieve wrist kinematics similar to the native intact wrist.

Summary Statement

Subject specific FE models of human Achilles tendon were developed and optimum material properties were found. Stress concentration occurred at the midsection but dependent on stiffening and thinning of tendon, indicating that they are two major factors for tendon rupture.

Background: Prophylactic taping is commonly used to prevent ankle injuries during sports. However unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. Any association between the use of ankle tape and knee joint loading has not previously been investigated. Purpose: To determine changes in ankle and knee kinetics and kinematics associated with use of ankle taping during athletic activities. Thereby, both the prophylactic benefits and the potential of taping to be an isolated mechanism for a ligamentous injury of the knee will be examined.

Methods: A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions, and undertaken with and without the use of ankle tape.

Results: Taping reduced the range of motion at the ankle in all three planes (p< 0.05), as well as peak inversion (p=0.017) and average eversion moments (p=0.013). At the knee, internal rotation moments (p=0.049), internal rotation impulse (0.034), varus moment (p=0.015) and varus impulse (p=0.050) were reduced with the use of ankle tape. There was a trend toward increased valgus impulse for sidestepping trials undertaken with ankle tape (p=0.056).

Conclusion: By limiting motion at the ankle, taping increased the mechanical stability of this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses, although the effects were task-specific. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Introduction: Treatment of dual compartment osteoarthritis remains controversial, with conjecture over whether Uni-Compartmental (‘UKA’) or Total Knee Arthroplasty (‘TKA’) is more appropriate for patients with patello-femoral disease. The ‘Journey Deuce’ 2/3 Knee Arthroplasty (‘2/3 Knee’) (Smith & Nephew) is a bi-cruciate retaining prosthesis designed to treat this subgroup of patients with both antero-medial and patello-femoral disease.

We have conducted a prospective, observational clinical trial of 34 patients with dual compartment osteoarthritis of the knee treated with a 2/3 Knee.

Aims: To assess the safety and clinical efficacy outcomes of the 2/3 Knee.

Method: All patients pre-op leg alignment films, as well as MRI or arthroscopy to confirm the inclusion criteria of dual compartment osteoarthritis with a preserved lateral compartment and intact cruciate ligaments. All operations were performed by a single surgeon (DW) using computer assisted surgery (CAS) and a minimally invasive technique (MIS) at a local university affiliated private hospital (HPH).

Exclusion criteria included obesity, inflammatory arthritis and a fixed flexion deformity > 10 degrees.

Subjective outcome measures included Oxford Knee Scores (OKS) and EQ-5D Scores. RSA beads were implanted at surgery to detect loosening, micro-motion and prosthesis wear. Gait analysis was conducted at 1 year post op in a subgroup of patients.

Results: Follow up ranged from 6 months to 2 years. There have been no early failures requiring complete revision. The first 23 knees (18 patients) did not have primary resurfacing of the patella. Some of these patients suffered palpable and audible patello-femoral crepitus, with a subgroup (17%, 4 knees-3 patients) having associated anterior knee pain. This subgroup had revision procedures to resurface their patellae with resolution of their symptoms. All subsequent patients have had primary patella resurfacing with no incidence of Significant crepitus or anterior knee pain.

The patients have recorded Significant improvement in their Oxford Knee Scores at 6 months (mean reduction all patients: 17.3, resurfaced 20).

Early RSA results have not detected Significant migration to indicate early loosening. Gait analysis has shown that patients return to approximate normal rather than pre-operative gait.

Conclusions: Although longer follow up is required the 2/3 Knee appears a safe and effective treatment option for patients with dual-compartment osteoarthritis; with rehabilitation, function and gait tending towards that seen in UKA rather than TKA.

It is essential that patients undergo primary patella resurfacing to prevent crepitus and associated anterior knee pain.

A study comparing clinical outcomes of 2/3 Knee vs TKA is underway at our institution.

The purpose of the study is to assess changes in cortical activity in chronic low back pain patients with and without illness behaviour.

Introduction: It is well recognised that patients with chronic low back pain (CLBP) may have major psychological factors which affect their level of disability. Abnormal patterns of illness behaviour have been described ¹.

Methodology: 30 patients with CLBP of more than six months duration were recruited. Patients with radicular pain or previous surgery were excluded. Two groups were created dependant on the presence of Waddell signs. “Copers” (n=16) showed 0 or 1 Waddell signs. “Non-copers” (n=14) showed 4 or 5 Waddell signs.

After informed consent, all subjects underwent fMRI scanning. Experimental pain was induced by thermal stimulation of the right hand. Straight leg raising (SLR) was performed following visual clues indicating that a leg raise was either definitely, possibly or not going to occur. Finally, clinical LBP was simulated by direct vibrotactile stimulation of the lumbar spine to a VAS threshold of 7/10.

The individual fMRI scans were independently referenced to anatomical markers and corrected for motion. Inter group analysis was performed using cluster-corrected thresholds of p< 0.05.

Results: During experimental pain stimulation, Non-copers showed significantly increased cortical activity as compared to Copers. Similar findings were evident when SLR was anticipated. The areas of increased cortical activity were primarily regions known to be involved in affective pain interpretation suggesting heightened activity.

When clinical LBP was simulated, the outcome was strikingly different with the Copers showing increased cortical activity particularly in the dorsolateral prefron-tal cortex and regions associated with cognitive pain processing and inhibition of subcortical pain pathways.

Discussion: This study shows that in patients with CLBP and illness behaviour cortical pain processing is abnormal. The findings suggest that possibly the abnormal behaviour shown by such patients may be due to failure of cognitive inhibitory pain pathways. It is possible that these abnormalities might respond to either pharmacological or psychological treatment.

Introduction and Aims: Stability training on a wobble board is a common method of rehabilitation from lower limb injuries. Injury prevention represents a relatively new application of this exercise but the neural mechanisms underlying its success remain unknown. We hypothesised that a three-week period of wobble board training will result in a decrease in the reflex response in the muscles crossing the left ankle joint.

Method: Fourteen moderately trained university students were randomly assigned to a control and training group. The training group underwent 10-, 20-minute sessions of wobble board training over three weeks. Pre- and post-testing was conducted on an ankle perturbation rig and involved applying various levels of plantar torque to a stable (1DOF) and unstable (3 DOF) footplate. Nine potentiometers measured the position of the footplate, a force transducer measured the applied torque and a dorsiflexing perturbation could be given. Electromyographic data was recorded from four superficial muscles crossing the ankle joint to determine stretch reflex profiles for each muscle. Data was displayed in bar graphs and a two-way ANOVA was used.

Results: No significant difference in the stretch reflex amplitude was noted between the training and control groups in medial gastrocnemius, lateral gastrocnemius, soleus or peroneus longus. A reduction in the amplitude of the stretch reflex in the experimental group was recorded after wobble board training in medial gastrocnemius (35% reduction), lateral gastrocnemius (25% reduction), soleus (15% reduction), and peroneus longus (40% reduction) during post-testing (significant at p < 0.05). There was no significant change in the amplitude of the stretch reflex in any of the four superficial muscles of the ankle joint in the control group between pre- and post-testing sessions.

Conclusion: Presynaptic inhibition represents the most likely neural mechanism responsible for the observed reduction in the stretch reflex amplitude after a brief period of wobble board training. This neuromuscular adaptation may offer dynamic protection prior to and during heel contact, helping to prevent inversion sprains.

Introduction and Aims: It is probable that the success of total knee arthroplasty without patellar resurfacing is influenced by the design of the femoral trochlea. The aim of this study was to compare measures of clinical outcome including gait analysis between total knee arthroplasty with and without patellar resurfacing using a prosthesis compatible with the native patella.

Method: A prospective trial of 78 patients was performed, with 43 total knee arthroplasty randomised to receive patellar resurfacing and 48 to receive patellar retention. The mean duration of follow-up was 3.2 years (range 2.0–4.7 years). Patients were assessed pre- and post-surgery using the Knee Society Clinical Rating System, the Knee Pain Scale, and a Patellar Function Score. A subset of 34 patients also underwent pre- and post-surgery analysis of knee kinematics and kinetics during walking.

Results: At a minimum two-year follow-up, total knee arthroplasty with patellar resurfacing had significantly lower Knee Society knee scores (Mann Whitney U test; p = 0.036). Total knee arthroplasty with patellar resurfacing exhibited a greater degree of knee flexion contracture (Mann-Whitney U test; p = 0.020) and significantly less knee extension at heelstrike during walking in those subjects undergoing gait analysis (Independent t-test; p = 0.013). The presence of a knee flexion contracture was a significant predictor of post-surgery anterior knee pain (Exp β = 4.1, CI: 1.1 to 14.9, p = 0.033). Post-surgery Knee Society function scores and Patellar Function Scores were significantly better in those patients with total knee arthroplasty without patellar resurfacing (Mann-Whitney test; p = 0.031 and 0.017 respectively).

Conclusion: In this study using an anatomically designed femoral component with a domed patellar prosthesis, total knee arthroplasty with patellar resurfacing exhibited inferior clinical results as compared to total knee arthroplasty with patellar retention. Total knee arthroplasty with patellar resurfacing exhibited significant limitation of knee extension, which was significantly associated with the presence of post-surgery anterior knee pain (p = 0.033).