Treatment of comminuted intraarticular calcaneal fractures remains controversial and challenging. Anatomic reduction with stable fixation has demonstrated better outcomes than nonoperative treatment of displaced intraarticular fractures involving the posterior facet and anterior calcaneocuboid joint (CCJ) articulating surface of the calcaneus. The aim of this study was to investigate the biomechanical performance of three different methods for fixation of comminuted intraarticular calcaneal fractures. Comminuted calcaneal fractures, including Sanders III-AB fracture of the posterior facet and Kinner II-B fracture of the CCJ articulating calcaneal surface, were simulated in 18 fresh-frozen human cadaveric lower legs by means of osteotomies. The ankle joint, medial soft tissues and midtarsal bones along with the ligaments were preserved. The specimens were randomized according to their bone mineral density to 3 groups for fixation with either (1) 2.7 mm variable-angle locking anterolateral calcaneal plate in combination with one 4.5 mm and one 6.5 mm cannulated screw (Group 1), (2) 2.7 mm variable-angle locking lateral calcaneal plate (Group 2), or (3) interlocking calcaneal nail with 3.5 mm screws in combination with 3 separate 4.0 mm cannulated screws (Group 3). All specimens were biomechanically tested until failure under axial loading with the foot in simulated midstance position. Each test commenced with an initial quasi-static compression ramp from 50 N to 200 N, followed by progressively increasing cyclic loading at 2Hz. Starting from 200 N, the peak load of each cycle increased at a rate of 0.2 N/cycle. Interfragmentary movements were captured by means of optical motion tracking. In addition, mediolateral X-rays were taken every 250 cycles with a triggered C-arm. Varus deformation between the tuber calcanei and lateral calcaneal fragments, plantar gapping between the anterior process and tuber fragments, displacement at the plantar aspect of the CCJ articular calcaneal surface, and Böhler angle were evaluated. Varus deformation of 10° was reached at significantly lower number of cycles in Group 2 compared to Group 1 and Group 3 (P ≤ 0.017). Both cycles to 10° plantar gapping and 2 mm displacement at the CCJ articular calcaneal surface revealed no significant differences between the groups (P ≥ 0.773). Böhler angle after 5000 cycles (1200 N peak load) had significantly bigger decrease in Group 2 compared to both other groups (P ≤ 0.020). From biomechanical perspective, treatment of comminuted intraarticular calcaneal fractures using variable-angle locked plate with additional longitudinal screws or interlocked nail in combination with separate transversal screws seems to provide superior stability as opposed to variable-angle locked plating only

Abstract. Objectives. The fidelity of a 3D model created using image segmentation must be precisely quantified and evaluated for the model to be trusted for use in subsequent biomechanical studies such as finite element analysis. The bones within the ankle joint vary significantly in size and shape. The purpose of this study was to test the hypothesis that the accuracy and reliability of a segmented bone geometry is independent of the particular bone being measured. Methods. Computed tomography (CT) scan data (slice thickness 1 mm, pixel size 808±7 µm) from three anonymous patients was used for the development of the ankle geometries (consisting of the tibia, fibula, talus, calcaneus, and navicular bones) using Simpleware Scan IP software (Synopsys, Exeter, UK). Each CT scan was segmented 4 times by an inexperienced undergraduate, resulting in a total of 12 geometry assemblies. An experienced researcher segmented each scan once, and this was used as the ‘gold standard’ to quantify the accuracy. The solid bone geometries were imported into CAD software (Inventor 2023, Autodesk, CA, USA) for measurement of the surface area and volume of each bone, and the distances between bones (tibia to talus, talus to navicular, talus to calcaneus, and tibia to fibula) were carried out. The intra-class coefficient (ICC) was used to assess intra-observer reliability. Bland Altman plots were employed as a statistical measure for criteria validity (accuracy) [1]. Results. The average ICC score was 0.93, which is regarded as a high reliability score for an inexperienced user. The talus to navicular and talus to tibia separations, which had the smallest distances, showed a slight decrease in reliability and this was observed for all separations shorter than 2 mm. According to the Bland-Altman plots, more than 95% of the data points were inside the borders of agreement, which is an excellent indication of accuracy. The bias percentage (average error percentage) varied between 1% and 4% and was constant across all parameters, with the proportion rising for short distance separations. Conclusions. The current study demonstrates that an inexperienced undergraduate, with access to software manuals, can segment an ankle CT scan with excellent reliability. The present study also concluded that all five bones were segmented with high levels of accuracy, and this was not influenced by bone volume or type. The only factor found to influence the reliability was the magnitude of distance between bones, where if this was smaller than 2 mm it reduced the reliability, indicating the influence of CT scan resolution on the segmentation reliability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. This abstract provides an update on the Open Ankle Models being developed at the University of Bath. The goal of this project is to create three fully open-source finite element (FE) ankle models, including bones, ligaments, and cartilages, appropriate musculoskeletal loading and boundary conditions, and heterogeneous material property distribution for a standardised representation of ankle biomechanics and pre-clinical ankle joint analysis. Methods. A computed tomography (CT) scan data (pixel size of 0.815 mm, and slice thickness of 1 mm) was used to develop the 3D geometry of the bones (tibia, talus, calcaneus, fibula, and navicular). Each bone was given the properties of a heterogeneous elastic material based on the CT greyscale. The density values for each bone element were calculated using a linear empirical relation, ρ= 0.0405 + (0.000918) HU and then power law equations were utilised to get the Young's Modulus value for each bone element [1]. At the bone junction, a thickness of cartilage ranging from 0.5–1 mm, and was modelled as a linear material (E=10 MPa, ν=0.4 [2]). All ligament insertions and positions were represented by four parallel spring elements, and the ligament stiffness and material attributes were applied in accordance with the published literature [2]. The ankle model was subjected to static loading (balance standing position). Four noded tetrahedral elements were used for the discretization of bones and cartilages. All degrees of freedom were restricted at the proximal ends of the tibia and fibula. The ground reaction forces were applied at the underneath of the calcaneus bone. The interaction between the cartilages and bones was modelled using an augmented contact algorithm with a sliding elastic contact between each cartilage. A tied elastic contact was used between the cartilages and the bone. FEbio 2.1.0 (University of Utah, USA) was used to construct the open-source ankle model. Results. When the double-legged stance phase loading condition was taken into consideration, stress at the antero-medial tibial wall (ranged from 1 to 7 MPa) was found to be similar to the prior work [2], indicating bulk of the load transfer was through this region. The maximum principal strain was predicted at the different regions on bones around the ankle joint. The proximal surface of the talus, and tibial distal surface were shown to have the highest maximum principal strains followed by antero-medial walls of the tibia bone, at the proximal location. Conclusions. The present open 3D FE model of the ankle will assist researchers in better understanding ankle biomechanics, precisely predicting load transfer, and examining the ankle to address unmet clinical needs for this joint. The results of the current investigation are realistic in terms of load transfer and stress-strain distribution across the ankle joint and well comparable to those reported in the literature [2]. However, sensitivity and ankle instability simulations will be performed in future work to investigate the model's reliability and robustness. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

The aim of this study was to evaluate the relationship between the location of the insertion point of the AT into the posterior aspect of the calcaneus and the PF. Two hundred and two feet were evaluated from MRI scans. Ninety-seven women and one hundred and five men with a mean age of 40.15±18.58 were included in this study. Two independent investigators measured the horizontal distance from the most anterior point of the calcaneus to the most posterior part of the PF (A), including the horizontal length of the calcaneus (B). Moreover, distance between the most inferior point of the calcaneus and the most inferior part of the AT insertion into the calcaneus (C) and height of the posterior aspect of the calcaneus (D) were measured. Patients were divided into three groups based on age (I - patients younger than 18, II − 18–65, III - older than 65The all obtained mean values showed high sexual dimorphism between genders. However, when standardized ratios were compared, no statistically significant sexual differences were noted (p>0.05). Although previous studies have reported a correlation between the PF, age and gender, this correlation was not found in our study. Based on the obtained results, this study concludes that age and sex do not influence the morphology of the PF. However, aging strongly affects the location of the AT insertion point. Therefore, we believe this is the key factor which influence the relationship between the AT and PF

Background. Surgical management of calcaneus fractures is demanding and has a high risk of wound complications. Traditionally these fractures are managed with splinting until swelling has subsided. We describe a novel protocol for the management of displaced intra-articular calcaneus fractures utilising a temporizing external fixator and staged conversion to plate fixation through a sinus tarsi approach. The goal of this technique is to allow for earlier treatment with open reduction and internal fixation, minimise the amount of manipulation required at the time of definitive fixation and reduce the wound complication rate seen with the extensile approach. Methods. The records of patients with displaced calcaneus fractures from 2010–2014 were retrospectively reviewed. A total of 10 patients with 12 calcaneus fractures were treated with this protocol. All patients underwent ankle-spanning medial external fixation within 48 hours of injury. Patients underwent conversion to open plate fixation through a sinus tarsi approach when skin turgor had returned to normal. Time to surgery, infection rate, wound complications, radiographic alignment, and time to radiographic union were recorded. Results. The average Bohler's angle improved from 13.2 (range −2 to 34) degrees preoperatively to 34.3 (range 26 to 42) degrees postoperatively. The average time from external fixation to conversion to internal fixation was 4.8 (range 3 to 7) days. There were no immediate post-surgical complications. The average time to weight bearing was 8.5 weeks. The average time to radiographic union was 9.5 (range 8 to 12) weeks. There were no infections or wound complications at the time of last follow-up. Conclusions. Early temporizing external fixation for the acute management of displaced calcaneus fractures is a safe and effective method to reduce and stabilise the foot and may decrease the time to definitive fixation. In our series there were no complications related to the use of the external fixator. Level of Evidence. IV Retrospective case series

Background. A calcaneal medial osteotomy (CMO) is a surgical procedure frequently performed to correct a valgus alignment of the hindfoot. However currently little is known on its accurate influence on hindfoot alignment (HA). Aim. To assess the influence of a CMO on HA in both 2D and 3D measurements using weightbearing CT (WBCT). Methods. Twelve patients with a mean age of 49,4 years (range 18–67yrs) were prospectively included. Indications for surgical correction by a CMO with a solitary translation of the calcaneus consisted of an adult acquired flat foot stage II (N=10) and a talocalcaneal coalition (N=2). Fixation of the osteotomy was performed either using a step plate or double screw. A WBCT was obtained pre- and post-operative. HA was assessed by an angle between the anatomical tibia axis and the axis connecting the inferior calcaneus point and the middle of the talus in the coronal plane (HA. 2D. ) using Curvebeam® software. The tibia in the HA was separately assessed by the anatomical tibia axis (TA. X 2D. ). The same method was translated in 3D using 3-Matic® software with a Cartesian coordinate system originating in the inferior point of the calcaneus (HA. 3D. and TA. x 3D. ). Results. Both the mean pre-op HA. 2D. =12.8°± 4.5 and HA. 3D. =21.1°± 8.4 of valgus improved significantly post-operatively to a HA. 2D. =4.2°±4.5 and a HA. 3D. =11,9°± 6.1 (P < 0.001). Additionally, the mean pre-op TA. X 2D. = 4°± 2.6 and TA. X 3D. = 7,2 °± 3.2 showed a significant improvement to a TA. X 2D. = 3.1°± 2.7 and a TA. X 3D. = 6.1 °± 3.4 post-operatively (P < 0.05). The inter-rater reliability of the 2D measurement method with a mean ICC. HA2D. =0.74 and a mean ICC. TA2D. = 0.77 showed to be lower when compared to the 3D measurement method with a mean ICC. HA3D. =0.94 and a mean ICC. TA3D. =0.89. Conclusion. This study shows an effective correction of the valgus position from the calcaneus measured both in 2D and 3D when using a surgical CMO. The novelty is the marked influence on the tibia, which could now be accurately assessed using a weightbearing CT and additional 3D measurements. This resulted in 10% of the achieved HA correction, when analyzed both in 2D and 3D. This information could be of use when performing a pre-operative planning of a hindfoot deformity

The flat foot is a frequent deformity in children and results in various levels of functional alterations. A diagnosis based on foot morphology is not sufficient to define the therapeutic approach. In fact, the degree of severity of the deformity and the effects of treatments require careful functional assessment. In case of functional flatfoot, subtalar arthroereisis is the surgical treatment of choice. The aim of this study is to evaluate and compare the functional outcomes of two different bioabsorbable implants designed for subtalar arthroereisis in childhood severe flat foot by means of thorough gait analysis. Ten children (11.3 ± 1.6 yrs, 19.7 ± 2.8 BMI) were operated for flat foot correction [1,2] in both feet, one with the calcaneo-stop method, i.e. a screw implanted into the calcaneus, the other with an endoprosthesis implanted into the sinus-tarsi. Gait analysis was performed pre- and 24 month post-operatively using a 8-camera motion system (Vicon, UK) and a surface EMG system (Cometa, Italy) to detect muscular activation of the main lower limb muscles. A combination of established protocols, for lower limb [3] and multi-segment foot [4] kinematic analysis, was used to calculate joint rotations and moments during three level walking trials for each patient. At the foot, the tibio-talar, Chopart, Lisfranc, 1. st. metatarso-phalangeal joints were tracked in three-dimensions, together with the medial longitudinal arch. Significant differences in standard X-ray measurements were observed between pre- and post-op, but not between the two treatment groups. Analysis of the kinematic variables revealed functional improvements after surgery. In particular, a reduction of eversion between the shank and calcaneus (about 15° on average) and a reduction of inversion between metatarsus and calcaneus (about 18° on average) were detected between pre- and post-operatively after both treatments. Activation of the main plantar/dorsiflexor muscles was similar at both pre- and post-op assessments with both implants. The combined lower limb and multi-segment foot kinematic analyses were found adequate to provide accurate functional assessment of the feet and of the lower limbs. Both surgical treatments restored nearly normal kinematics of the foot and of the lower limb joints, associated also to a physiologic muscular activation

Objectives. Lengthening osteotomies of the calcaneus in children are in general grafted with bone from the iliac crest. Artificial bone grafts have been introduced, however, their structural and clinical durability has not been documented. Radiostereometric analysis (RSA) is a very accurate and precise method for measurements of rigid body movements including the evaluation of joint implant and fracture stability, however, RSA has not previously been used in clinical studies of calcaneal osteotomies. We assessed the precision of RSA as a measurement tool in a lateral calcaneal lengthening osteotomy (LCLO). Methods. LCLO was performed in six fixed adult cadaver feet. Tantalum markers were inserted on each side of the osteotomy and in the cuboideum. Lengthening was done with a plexiglas wedge. A total of 24 radiological double examinations were obtained. Two feet were excluded due to loose and poorly dispersed markers. Precision was assessed as systematic bias and 95% repeatability limits. Results. Systematic bias was generally below 0.10 mm for translations. Precision of migration measurements was below 0.2 mm for translations in the osteotomy. Conclusion. RSA is a precise tool for the evaluation of stability in LCLO. Cite this article: Bone Joint Res 2015;4:78–83

Osteoporosis (OP) results in a reduction in the mechanical competence of the bone tissue of the sufferers. In skeletal sites such as the proximal femur and the vertebrae, OP manifests itself in low trauma fragility fractures which are debilitating for the patient. The relationships between the compressive strength of cancellous tissue and its apparent density are well established in studies of the past. Recently the authors have presented a method able to assess the fracture toughness properties of cancellous bone (1), a challenging cellular material which can exhibit large elasto-plastic deformations. The in-vitro measurement of fracture toughness alongside the customary compressive strength can provide a comprehensive assessment of the mechanical capacity of cancellous bone, which will reflect closer its ability to resist crack initiation. The aims of the present study were: (1) to examine whether the observed fracture toughness deterioration can also be detected by non-invasive quantitative ultrasound (QUS); and (2) to provide rational evidence for the well proven ability of QUS to predict directly ‘risk of fracture’. 20 femoral heads were obtained from donors undergoing emergency surgery for a fractured neck of femur. QUS investigations of the calcaneus, proximal phalanx and distal radius were undertaken within 72 hours of surgery. 128 fracture toughness samples and 20 compression cores were manufactured and tested. Two clinical QUS systems were used to obtain in-vivo scan data and then directly compared those to the density, porosity and the fracture mechanics of tissue extracted from the same individuals. The results demonstrated not only that there was a significant link between in-vivo determined QUS values for the calcaneus and finger to the density of the density of the femoral head; but that there was also a significant link between the QUS results from the calcaneus and the fracture toughness of the cancellous bone from the femoral head. These results point towards a systemic effect of osteoporosis which affects similarly different parts of the skeleton and supports the use of clinical QUS systems as a diagnostic tool for the prediction of fracture risk

Displaced intraarticular calcaneal fractures are debilitating injuries with significant socioeconomic and psychological effects primarily affecting patients in active age between 30 and 50 years. Recently, minimally and less invasive screw fixation techniques have become popular as alternative to locked plating. The aim of this study was to analyze biomechanically in direct comparison the primary stability of 3 different cannulated screw configurations for fixation of Sanders type II-B intraarticular calcaneal fractures. Fifteen fresh-frozen human cadaveric lower limbs were amputated mid-calf and through the Chopart joint. Following, soft tissues at the lateral foot side were removed, whereas the medial side and Achilles tendon were preserved. Reproducible Sanders type II-B intraarticular fracture patterns were created by means of osteotomies. The proximal tibia end and the anterior-inferior aspect of the calcaneus were then embedded in polymethylmethacrylate. Based on bone mineral density measurements, the specimens were randomized to 3 groups for fixation with 3 different screw configurations using two 6.5 mm and two 4.5 mm cannulated screws. In Group 1, two parallel longitudinal screws entered the tuber calcanei above the Achilles tendon insertion and proceeded to the anterior process, and two transverse screws fixed the posterior facet perpendicular to the fracture line. In Group 2, two parallel screws entered the tuber calcanei below the Achilles tendon insertion, aiming at the anterior process, and two transverse screws fixed the posterior facet. In Group 3, two screws were inserted along the bone axis, entering the tuber calcanei above the Achilles tendon insertion and proceeding to the central-inferior part of the anterior process. In addition, one transverse screw was inserted from lateral to medial for fixation of the posterior facet and one oblique screw – inserted from the posterior-plantar part of the tuber calcanei – supported the posterolateral part of the posterior facet. All specimens were tested in simulated midstance position under progressively increasing cyclic loading at 2 Hz. Starting from 200N, the peak load of each cycle increased at a rate of 0.1 N/cycle. Interfragmentary movements were captured by means of optical motion tracking and triggered mediolateral x-rays. Plantar movement, defined as displacement between the anterior process and the tuber calcanei at the most inferior side was biggest in Group 2 and increased significantly over test cycles in all groups (P = 0.001). Cycles to 2 mm plantar movement were significantly higher in both Group 1 (15847 ± 5250) and Group 3 (13323 ± 4363) compared to Group 2 (4875 ± 3480), P = 0.048. Medial gapping after 2500 cycles was significantly bigger in Group 2 versus Group 3, P = 0.024. No intraarticular displacement was observed in any group during testing. From biomechanical perspective, screw configuration implementing one oblique screw seems to provide sufficient hindfoot stability in Sanders Type II-B intraarticular calcaneal fractures under dynamic loading. Posterior facet support by means of buttress or superiorly inserted longitudinal screws results in less plantar movement between the tuber calcanei and anterior fragments. On the other hand, inferiorly inserted longitudinal screws seem to be associated with bigger interfragmentary movements

Bone loss continues to be a clinical and therapeutic problem. Bone reconstruction of osseous defects is a challenge after fracture and traumatic injuries, infections and tumors. The common objective is to regenerate bone morphology and function. Several techniques have been developed to promote bone formation, but the advent of new biomaterials allows us to take an entirely different approach to the treatment of bone voids. However, the use of bone substitutes should be considered carefully, as not all biomaterials behave the same way in humans. Calcium phosphate ceramics are osteoconductive materials that promote bone regeneration. The aim of this study was to retrospectively evaluate the clinical, radiographic and histological results of bone loss treated with an adjunct injectable biphasic bone substitute (BBS). We analysed the results of patients with fractures and a bone defect that were treated using an injectable BBS (calcium sulfate + hydroxyapatite) and those that were treated using the same bone substitute with antibiotic (gentamicin and/or vancomycin). Patient outcome was evaluated clinically and radiographically. In 9 cases samples for histological analysis were obtained. From July 2009 to May 2015, 126 cases (cs) on 111 patients (pt) (calcaneus: 53 cs, 47 pt; tibia: 32 cs, 30 pt; Femur: 14 cs, 9 pt, Elbow: 5 cs, 5 pz; humerus 2 cs, 2 pz; wrist 7cs, 7pz; forearm 6 cs, 4 pz; foot 2 cs, 2 pz; Phalanx 5 cs, 5 pt) were treated at our hospital with a BBS. The mean follow-up was 15 months, and bone ingrowth was assessed at 1, 2, 3, 6 and 12 months by X-ray. In all cases, the calcium sulphate phase of the BBS dissolved within 4–6 weeks, and new bone formation was observed at 6 months. On six patients large bone was treated with a revision surgery (autologous cancellous bone graft combined with BBS and antibiotic). No complications were reported. The 9 histological samples confirmed gradual remodeling and regeneration of the bone substitute over time. This biomaterial is versatile, offers a good augment for hardware and bone alignment, is biocompatible and osteoconductive, and has allowed us to manage significant bone voids. Histological analysis of samples from the tibia, ulna and calcaneus have confirmed the ability of this bone substitute to remodel into bone

DVC allowed measurements of displacement and strain distribution in bone through the comparison of two, or more, 3D images. Hence, it has a potential as a diagnostic tool in combination with clinical CT. Currently, traditional computed tomography (CT) allows for a detailed 3D analysis of hard tissues, but imaging in a weight-bearing condition is still limited. PedCAT-CT (Curvebeam, USA) emerged as a novel technology allowing, for the first time, 3D imaging under full-weight bearing (Richter, Zech et al. 2015). Specifically, a PedCAT-CT based DVC was employed to establish its reliability through the strain uncertainties produced on bone structure targets, preliminarily to any further clinical studies. In addition, a reverse engineering FE modeling was used to predict possible force associated to displacement errors from DVC. Three porcine thoracic vertebrae were used as bone benchmark for the DVC (Palanca, Tozzi et al. 2016, Tozzi, Dall'Ara et al. 2016). The choice of using porcine vertebrae (in a CT designed for foot/ankle) was driven by availability, as well as similar dimensions to the calcaneus. Each vertebra was immersed in saline solution and scanned twice without any repositioning (zero-strain-test) with a pedCAT-CT (Curvebeam, USA) obtaining an isotropic voxel size of 370 micrometers. Volumes of interest of 35 voxel were cropped inside the vertebrae. Displacement and strains were evaluated using DVC (DaVis-DC, LaVision, Germany), with different spatial resolution. The displacement maps were used to predict the force uncertainties via FE (Ansys Mechanical v.14, Ansys Inc, Canonsburg, PA). Each element was assigned a linear elastic isotropic constitutive law (Young modulus: 8 GPa, Poisson's ratio: 0.3, as in (Follet, Peyrin et al. 2007)). Overall, the precision error of strain measurement was evaluated as the average of the standard deviation of the absolute value of the different component of strain (Liu and Morgan 2007). The force uncertainties obtained with the FE analysis produced magnitudes ranging from 231 to 2376 N. No clear trend on the force was observed in relation to the spatial resolution. Precision errors were smaller than 1000 microstrain in all cases, with the lowest ranging from 83 microstrain for the largest spatial resolution. Full-field strain on the bone tissue did not seem to highlight a preferential distribution of error in the volume. The precision errors showed that the pedCAT-CT based DVC can be sufficient to investigate the bone tissue failure (7000–10000 microstrain) or, physiological deformation if well-optimized. FE analysis produced important force uncertainties up to 2376 N. However, this is a preliminary investigation. Further investigation will give a clearer indication on DVC based PedCAT-CT, as well as force uncertainties predicted. So far, the DVC showed its ability to measure displacement and strain with reasonable reliability with clinical-CT as well

The Dumfries and Galloway Royal Infirmary (DGRI) catchment area encompasses 5 of the “7 Stanes” mountain bike trails which had approximately 165000 visitors in 2010. Using our hospital coding system we identified potential mountain bike injuries in 2010. Patient postcode, injuries, operating theatre time and number of clinic appointments was recorded. We confirmed mountain bike related hospital admissions in 29 patients. 13 patients had local (DG) postcodes and 16 had non-DG post codes. The DG postcode patients required 41 bed days, 8 operations, 400 minutes theatre time, and 35 DGRI clinic appointments. The non-DG postcodes required 50 bed days, 11 operations, 730 minutes theatre time, 3 DGRI clinic appointments and 8 outpatient referrals to other hospitals. Totals for all postcodes were 91 bed days, 19 operations, 1130 minutes theatre time and 38 DGRI clinic appointments. The surgeries comprised: 2 ankle ORIF; 1 subsequent removal of syndesmosis screw; 5 wrist/forearm manipulations (+/−kwires); 2 distal radius ORIF; 1 DHS; 2 shoulder MUA, 1 calcaneus ORIF, 4 wound debridements, 1 facial wound closure. Other noteworthy admissions were 5 head injuries including 2 cervical spine fractures. We anticipate this is an underestimate and suggest a new code is created to specifically identify mountain bike injuries for A&E and inpatient care. This would allow a more accurate assessment of the impact on all healthcare providers in the county

Bony tumours of the foot account for approximately 3% of all osseous tumours. However, literature regarding os calcis tumours comprises individual case reports, short case series or literature reviews, with the last large case series in 1973. We retrospectively reviewed the medical notes and imaging for all patients with calcaneal tumours recorded in the Scottish Bone Tumour Registry since the 1940's. Demographics, presentation, investigation, histology, management and outcome were reviewed. 38 calcaneal tumours were identified. Male to female ratio 2:1, mean age at presentation 30 with heel pain and swelling, average length of symptoms 9 months. 4 cases present with pathological fracture. 24 tumours benign including 6 unicameral bone cysts, 3 chondroblastoma, 3 PVNS with calcaneal erosion, and a wide variety of individual lesions. 13 malignant tumours comprising 6 osteosarcoma, 5 chondrosarcoma and 2 Ewings sarcoma. 1 metastatic carcinoma. Tumours of the calcaneus frequently are delayed in diagnosis due to their rarity and lack of clinician familiarity. They are more common in men and have a 1 in 3 risk of malignancy, covering a wide variety of lesions. Outcome is dependent on early diagnosis, timely surgery and most importantly neo-adjuvant chemotherapy. Diagnosis is often made on plain radiograph but MRI is the gold standard. We present the largest case series of calcaneal tumours, from our experience with the Scottish Bone Tumour Registry. Despite their rarity clinicians should maintain a high index of suspicion as accurate and timely diagnosis is important to management and outcome

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. Introduction. Achilles tendon injuries are common, occurring about 250,000 per year in the US alone, yet the mechanisms of tendinopathy and rupture remain unknown. Most Achilles tendon ruptures occur at 2 to 6 cm above the insertion to the calcaneus bone. Previous angiographic studies have suggested that there is an avascular area in this region. However, it is not understood why that region receives poor blood supply and prone to rupture. The aim of this study is to investigate influence of geometry and material properties on Achilles tendon rupture with mechanical experiment and corresponding subject-specific finite element (FE) analysis. Patients & Methods. Mechanical experiment was performed on 10 fresh human Achilles tendons. High frequency ultrasound images were used to measure cross sectional areas at the midsection of the tendon. Cyclic testing was performed to measure mechanical properties and failure loads. Subject-specific FE models of these tendons were generated with Free Form Deformation (FFD) technique. FE mechanical simulations that mimic the experimental cyclic loading were performed on these subject specific models. Tendon material properties were described as transversely isotropic hyperelastic and the optimum material parameters for the human Achilles tendon were obtained. Linear portion of the cyclic loading data was used as boundary conditions. Measured strains from the experiment were compared with predicted strains from the FE analysis. This process was repeated until optimum parameters were found. The influence of geometry and material properties on the Achilles tendon rupture was then investigated– first with subject-specific geometry with average material properties and then with subject-specific material properties with average geometry. Results. Our results indicate that a significant variation exist in the geometry and material properties in human Achilles tendons. Stress concentrations occurred at the midsection of the tendon, supporting previous studies that reported tendon rupture at the region. In particular the thinning of midsection in geometry is highly correlated with the collagen uncrimpping rate in material properties where thinner midsection leads to faster uncrimpping of collagen fibres. Variations in geometry led to shifts in the location of stress concentration within the midsection while variations in material property led the change in the magnitude of stress concentration. Discussion/Conclusion. Our results indicate that Achilles tendon rupture is highly dependent on subject-specific geometry and material properties. In particular the mid section is the location of stress concentration but depending on the geometrical shape, multiple stress concentrations occur, making the tendon more prone to rupture while the material properties influenced the magnitude of stress concentration. Our results indicate stiffening and thinning of tendon may lead to higher risk for tendon rupture

We have studied the mechanosensitive afferent units in the lateral ligament of the ankle of the cat, with reference to the causes of lateral instability after injury, using electrophysiological recording from the lumbar dorsal rootlets. We identified 30 mechanosensitive units in the lateral ligament; 28 (93%) were located near the attachment to the fibula and calcaneus, which included both low-threshold group-II units and low- and high-threshold group-III units. Our results indicate that there are both proprioceptors and nociceptors in the lateral ligament of the cat ankle, and confirm that afferent fibres from the lateral ligament may contribute to the stability of the joint by regulation of position and movement

To study the effect of ligament injuries and surgical repair we investigated the three-dimensional kinematics of the ankle joint complex and the talocrural and the subtalar joints in seven fresh-frozen lower legs before and after sectioning and reconstruction of the ligaments. A foot movement simulator produced controlled torque in one plane of movement while allowing unconstrained movement in the remainder. After testing the intact joint the measurements were repeated after simulation of ligament injuries by cutting the anterior talofibular and calcaneofibular ligaments. The tests were repeated after the Evans, Watson-Jones and Chrisman-Snook tenodeses. The range of movement (ROM) was measured using two goniometer systems which determined the relative movement between the tibia and talus (talocrural ROM) and between the talus and calcaneus (subtalar ROM). Ligament lesions led to increased inversion and internal rotation, predominantly in the talocrural joint. The reconstruction procedures reduced the movement in the ankle joint complex by reducing subtalar movement to a non-physiological level but did not correct the instability of the talocrural joint

Introduction. Kager's fat pad (KFP) is located in Kager's triangle between the Achilles tendon (AT), the superior cortex of the calcaneus and Flexor Hallucis Longus (FHL) muscle & tendon. Although the biomechanical functions of KFP are not yet fully understood, a number of studies suggested that KFP performs important biomechanical roles including assisting in the dynamic lubrication of the AT subtendinous area, protection of AT vascular supply, and load and stress distribution within the retrocalcaneal bursa space. Similar to the knee meniscus, KFP has become under increasing investigations since strong indications were found that it serves more than just a space filler. Both KFP and the knee meniscus are anchored to their surrounding tissues via fibrous attachments, they can be found in encapsulated (or ‘air tight’) regions, lined by synovial membranes, and they both slide within their motion ranges. The protruding wedge (PW) of KFP was observed to slide in and out of the retrocalcaneal bursal space during ankle plantarflexion and dorsiflexion, respectively. In-vitro studies of KFP suggest that it reduces the load by 39%, which is similar to that of the knee meniscus (30%-70% of the load applied on the knee joint). This study investigated the in-vivo load bearing functionality of KFP. Materials and Methods. The ankles of 5 volunteers (3 males, 2 females, Age 20-28, BMI 21-26) were scanned using a 0.2T MRI scanner at ankle plantarflexion and neutral positions. The ankles of 2 of those volunteers were later scanned using a 3T MRI scanner for higher accuracy. The areas and volumes of KFP were measured using Reconstruct¯ 3D modelling software. The hind foot of the volunteers were scanned using dynamic ultrasound to measure in-vivo real time shape changes of PW. Results. The cross sectional area of KFP in the AT midline saggital plane increased on average by 10% when ankles were changed from neutral to plantarflexion positions. The volume of KFP showed less variation than cross sectional areas (3.9% variation in volume). Previous studies showed the cross sectional area of the knee meniscus changes by 9.8% during loading, or flexing the knee by 90°, and its volume was reduced by 3.5%-5.9% (medial and lateral menisci respectively). Ultrasound imaging showed that PW's thickness decreased during dorsiflexion compared to plantarflexion by an average of 1mm and a hysteresis was found between the location of PW's tip and the insertion angle of AT, suggesting the fibrous tip of PW bears load during dorsiflexion. Discussions and conclusions. The similarities in results between the knee meniscus (literature review) and KFP supports hypotheses that KFP assists in reducing the load applied at the AT enthesis organ. Furthermore, histological studies showed a fibrosis is evident at the tip of PW, which is thought to be developed as a result of resisting external loading. This also supports speculations that KFP removal is likely to reduce lubrication, pressure distribution, load bearing, and consequently, increasing the tear and wear level within AT enthesis

Objectives

The aim of the current study was to assess whether calcaneal broadband ultrasound attenuation (BUA) can predict whole body and regional dual-energy x-ray absorptiometry (DXA)-derived bone mass in healthy, Australian children and adolescents at different stages of maturity.

Different calcaneal plates with locked screws were compared in an experimental model of a calcaneal fracture. Four plate models were tested, three with uniaxially-locked screws (Synthes, Newdeal, Darco), and one with polyaxially-locked screws (90° ± 15°) (Rimbus). Synthetic calcanei were osteotomised to create a fracture model and then fixed with the plates and screws. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1000 cycles at 800 N, 0.75 mm/s), and load to failure (0.75 mm/s).

During cyclic loading, the plate with polyaxially-locked screws (Rimbus) showed significantly lower displacement in the primary loading direction than the plates with uniaxially-locked screws (mean values of maximum displacement during cyclic loading: Rimbus, 3.13 mm (sd 0.68); Synthes, 3.46 mm (sd 1.25); Darco, 4.48 mm (sd 3.17); Newdeal, 5.02 mm (sd 3.79); one-way analysis of variance, p < 0.001).

The increased stability of a plate with polyaxially-locked screws demonstrated during cyclic loading compared with plates with uniaxially-locked screws may be beneficial for clinical use.