Varus ankle osteoarthritis (OA) is typically associated with peritalar instability, which may result in altered subtalar joint position. This study aimed to determine the extent to which total ankle replacement (TAR) in varus ankle OA can restore the subtalar position alignment using 3-dimensional semi-automated measurements on WBCT. Fourteen patients (15 ankles, mean age 61) who underwent TAR for varus ankle OA were retrospectively analyzed using semi- automated measurements of the hindfoot based on pre-and postoperative weightbearing WBCT (WBCT) imaging. Eight 3-dimensional angular measurements were obtained to quantify the ankle and subtalar joint alignment. Twenty healthy individuals were served as a control groups and were used for reliability assessments. All ankle and hindfoot angles improved between preoperative and a minimum of 1 year (mean 2.1 years) postoperative and were statistically significant in 6 out of 8 angles (P<0.05). Values The post-op angles were in a similar range to as those of healthy controls were achieved in all measurements and did not demonstrated statistical difference (P>0.05). Our findings indicate that talus repositioning after TAR within the ankle mortise improves restores the subtalar position joint alignment within normal values. These data inform foot and ankle surgeons on the amount of correction at the level of the subtalar joint that can be expected after TAR. This may contribute to improved biomechanics of the hindfoot complex. However, future studies are required to implement these findings in surgical algorithms for TAR in prescence of hindfoot deformity

A medializing calcaneal osteotomy (MCO) is one of the key inframalleolar osteotomies to correct progressive collapsing foot deformity (PCFD). While many studies were able to determine the hind- and midfoot alignment after PCFD correction, the subtalar joint remained obscured by superposition on plain radiography. Therefore, we aimed to perform a 3D measurement assessment of the hind- and subtalar joint alignment pre- compared to post-operatively using weightbearing CT (WBCT) imaging. Fifteen patients with a mean age of 44,3 years (range 17-65yrs) were retrospectively analyzed in a pre-post study design. Inclusion criteria consisted of PCFD deformity correct by MCO and imaged by WBCT. Exclusion criteria were patients who had concomitant midfoot fusions or hindfoot coalitions. Image data were used to generate 3D models and compute the hindfoot - and talocalcaneal angle as well as distance maps. Pre-operative radiographic parameters of the hindfoot and subtalar joint alignment improved significantly relative to the post-operative position (HA, MA. Sa. , and MA. Co. ). The post-operative talus showed significant inversion, abduction, and dorsiflexion of the talus (2.79° ±1.72, 1.32° ±1.98, 2.11°±1.47) compared to the pre-operative position. The talus shifted significantly different from 0 in the posterior and superior direction (0.62mm ±0.52 and 0.35mm ±0.32). The distance between the talus and calcaneum at the sinus tarsi increased significantly (0.64mm ±0.44). This study found pre-dominantly changes in the sagittal, axial and coronal plane alignment of the subtalar joint, which corresponded to a decompression of the sinus tarsi. These findings demonstrate the amount of alternation in the subtalar joint alignment that can be expected after MCO. However, further studies are needed to determine at what stage a calcaneal lengthening osteotomy or corrective arthrodesis is indicated to obtain a higher degree of subtalar joint alignment correction

To be able to assess the biomechanical and functional effects of ankle injury and disease it is necessary to characterise healthy ankle kinematics. Due to the anatomical complexity of the ankle, it is difficult to accurately measure the Tibiotalar and Subtalar joint angles using traditional marker-based motion capture techniques. Biplane Video X-ray (BVX) is an imaging technique that allows direct measurement of individual bones using high-speed, dynamic X-rays. The objective is to develop an in-vivo protocol for the hindfoot looking at the tibiotalar and subtalar joint during different activities of living. A bespoke raised walkway was manufactured to position the foot and ankle inside the field of view of the BVX system. Three healthy volunteers performed three gait and step-down trials while capturing Biplane Video X-Ray (125Hz, 1.25ms, 80kVp and 160 mA) and underwent MR imaging (Magnetom 3T Prisma, Siemens) which were manually segmented into 3D bone models (Simpleware Scan IP, Synopsis). Bone position and orientation for the Talus, Calcaneus and Tibia were calculated by manual matching of 3D Bone models to X-Rays (DSX Suite, C-Motion, Inc.). Kinematics were calculated using MATLAB (MathWorks, Inc. USA). Pilot results showed that for the subtalar joint there was greater range of motion (ROM) for Inversion and Dorsiflexion angles during stance phase of gait and reduced ROM for Internal Rotation compared with step down. For the tibiotalar joint, Gait had greater inversion and internal rotation ROM and reduced dorsiflexion ROM when compared with step down. The developed protocol successfully calculated the in-vivo kinematics of the tibiotalar and subtalar joints for different dynamic activities of daily living. These pilot results show the different kinematic profiles between two different activities of daily living. Future work will investigate translation kinematics of the two joints to fully characterise healthy kinematics

Introduction. Tibiocalcaneal arthrodesis with a retrograde intramedullary nail is an established procedure considered as a salvage in case of severe arthritis and deformity of the ankle and subtalar joints [1]. Recently, a significant development in hindfoot arthrodesis with plates has been indicated. Therefore, the aim of this study was to compare a plate specifically developed for arthrodesis of the hindfoot with an already established nail system [2]. Method. Sixteen paired human cadaveric lower legs with removed forefoot and cut at mid-tibia were assigned to two groups for tibiocalcaneal arthrodesis using either a hindfoot arthrodesis nail or an arthrodesis plate. The specimens were tested under progressively increasing cyclic loading in dorsiflexion and plantar flexion to failure, with monitoring via motion tracking. Initial stiffness was calculated together with range of motion in dorsiflexion and plantar flexion after 200, 400, 600, 800, and 1000 cycles. Cycles to failure were evaluated based on 5° dorsiflexion failure criterion. Result. Initial stiffness in dorsiflexion, plantar flexion, varus, valgus, internal rotation and external rotation did not differ significantly between the two arthrodesis techniques (p ≥ 0.118). Range of motion in dorsiflexion and plantar flexion increased significantly between 200 and 1000 cycles (p < 0.001) and remained not significantly different between the groups (p ≥ 0.120). Cycles to failure did not differ significantly between the two techniques (p = 0.764). Conclusion. From biomechanical point of view, both tested techniques for tibiocalcaneal arthrodesis appear to be applicable. However, clinical trials and other factors, such as extent of the deformity, choice of the approach and preference of the surgeon play the main role for implant choice. Acknowledgements. This study was performed with the assistance of the AO Foundation

Several emerging reports suggest an important involvement of the hindfoot alignment in the outcome of knee osteotomy. At present, studies lack a comprehensive overview. Therefore, we aimed to systematically review all biomechanical and clinical studies investigating the role of the hindfoot alignment in the setting of osteotomies around the knee. A systematic literature search was conducted on multiple databases combining “knee osteotomy” and “hindfoot/ankle alignment” search terms. Articles were screened and included according to the PRISMA guidelines. A quality assessment was conducted using the Quality Appraisal for Cadaveric Studies (QUACS) - and modified methodologic index for non-randomized studies (MINORS) scales. Three cadaveric, fourteen retrospective cohort and two case-control studies were eligible for review. Biomechanical hindfoot characteristics were positively affected (n=4), except in rigid subtalar joint (n=1) or talar tilt (n=1) deformity. Patient symptoms and/or radiographic alignment at the level of the hindfoot did also improve after knee osteotomy (n=13), except in case of a small pre-operative lateral distal tibia- and hip knee ankle (HKA) angulation or in case of a large HKA correction (>14.5°). Additionally, a pre-existent hindfoot deformity (>15.9°) was associated with undercorrection of lower limb alignment following knee osteotomy. The mean QUACS score was 61.3% (range: 46–69%) and mean MINORS score was 9.2 out of 16 (range 6–12) for non-comparative and 16.5 out of 24 (range 15–18) for comparative studies. Osteotomies performed to correct knee deformity have also an impact on biomechanical and clinical outcomes of the hindfoot. In general, these are reported to be beneficial, but several parameters were identified that are associated with newly onset – or deterioration of hindfoot symptoms following knee osteotomy. Further prospective studies are warranted to assess how diagnostic and therapeutic algorithms based on the identified criteria could be implemented to optimize the overall outcome of knee osteotomy. Remark: Aline Van Oevelen and Arne Burssens contributed equally to this work

Subtalar arthrodesis known as talocalcaneal fusion is an end-stage treatment for adult hind foot pathologies. The goal of the arthrodesis is to restrict the relative motion between bones of the subtalar joints, aiming to reduce pain and improve function for the patient. However, the change of the subtalar structures through the fusion is considered a disturbance to the joint biomechanics, which have been suggested to affect the biomechanics of the adjacent joints. However, no quantitative data are available to document this phenomenon. The purpose of the current study was to quantify the effects of subtalar arthrodesis on the laxity and stiffness of the talocrural joint in vitro using a robot-based joint testing system (RJTS) during anterioposterior (A/P) drawer test. Six fresh frozen ankle specimens were used in this study. The lateral tissues of the specimens were removed but the anterior and posterior talofibular ligaments and calcaneofibular ligament were kept intact. A/P drawer tests were performed on each of the specimens at neutral position, 5° and 10° of dorsiflexion, and 5?and 10?of plantarflexion using a robot-based joint testing system (RJTS), before and after subtalar arthrodesis. The RJTS enabled unconstrained A/P drawer testing at the prescribed ankle position while keeping the proximal/distal and lateral/medial forces, and varus/valgus and internal/external moments to be zero. This was achieved via a force-position hybrid control method with force and moment control, which has been shown to be more accurate than other existing force-position hybrid control methods. The target A/P force applied during the A/P drawer test was 100N in both anterior and posterior directions. The stiffness and laxity were calculated from the measured force and displacement data. The anterior and posterior stiffness of the talocrural joint were defined as the slope beyond 30% of the target A/P force, and the peak displacements quantified the laxity of the joint. Comparisons of laxity and stiffness between the intact and fusion ankle specimens were performed using Wilcoxon signed rank test (SPSS 19.0, IBM, USA) and a significance level of 0.05 was set. Subtalar arthrodesis did not lead to significant changes in the stiffness and laxity in both anterior and posterior directions (P>0.05). The mean anterior stiffness before arthrodesis was 9.54±1.17 N/mm and was 10.35±2.40 N/mm after arthrodesis. The mean anterior displacements before and after arthrodesis were 9.68±0.94 mm and 8.97±1.42 mm, respectively. Subtalar arthrodesis did not show significant effects on the A/P laxity and stiffness of the talocrural joint in both anterior and posterior directions. This may imply that the motion of the subtalar joints do not have significant effects on the A/P stability of the talocrural joint, which is the main joint of the ankle complex. This agrees with the anatomical roles of the subtalar joints which provide mainly the varus/valgus motions for the ankle complex. The current study provides a basis for further studies needed to evaluate the effects subtalar arthrodesis on the varus/valgus stability

Abstract. Skeletal kinematics are traditionally measured by motion analysis methods such as optical motion capture (OMC). While easy to carry out and clinically relevant for certain applications, it is not suitable for analysing the ankle joint due to its anatomical complexity. A greater understanding of the function of healthy ankle joints could lead to an improvement in the success of ankle-replacement surgeries. Biplane video X-ray (BVX) is a technique that allows direct measurement of individual bones using highspeed, dynamic X-Rays. Objective. To develop a protocol to quantify in-vivo foot and ankle kinematics using a bespoke High-speed Dynamic Biplane X-ray system combined with OMC. Methods. Two healthy volunteers performed five level walks and step-down trials while simultaneous capturing BVX and synchronised OMC. participants undertook MR imaging (Magnetom 3T Prisma, Siemens) which was manually segmented into 3D bone models (Simpleware Scan IP, Synopsis). Bone position and orientation for the Talus, Tibia and Calcaneus were calculated by manual matching of 3D Bone models to X-Rays (DSX Suite, C-Motion, Inc.). OMC markers were tracked (QTM, Qualisys) and processed using Visual 3D (C-motion, Inc.). Results. Initial results for level walking showed that OMC overestimated the rotational range of motion (ROM) in all three planes for the tibiotalar joint compared with BVX (Sagittal: OMC 30°/BVX 20°, Frontal: OMC 16°/BVX 15° and Transverse: OMC 20°/BVX 17°). For the subtalar joint, OMC (22°) over-estimated sagittal ROM compared with BVX (14°) and underestimated the ROM in the other planes (Frontal: OMC 8°/BVX 15° and Transverse: OMC 18°/BVX 20°). Conclusions. The results highlight the discrepancy between OMC and BVX methods. However, the BVX results are consistent with previous literature. The protocol developed here will form the foundation of future patient-based studies to investigate in-vivo ankle kinematics. 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

Purpose. Flat feet are an important cause of foot problems in children. The flexible flat foot is the most common form and is normally physiological and asymptomatic. Further assessment is necessary when a symptomatic flat foot persists. Surgical interventions are indicated when conservative therapies have failed. The Kalix arthroereisis is a surgical option and is placed in the subtalar joint of the foot, thereby preventing hyperpronation, and stabilizes the foot against excessive movements. The purpose of this study was to evaluate the functional and radiological outcomes of pediatric patients who had undergone a Kalix implantation for the treatment of a symptomatic flexible flat foot. Methods. Patient files of our institution were searched for patients who underwent a Kalix implantation between 2009 and 2014. Sixteen patients (26 feet) with symptomatic flexible flat feet were clinically and radiographically evaluated in this retrospective study. The calcaneal pitch and Meary”s angle were measured on the pre-, and postoperative follow-up radiographs and patient satisfaction survey was performed at follow-up to gain insight into functional outcome and satisfaction after the intervention. Results. Surgery was performed on an average age at 12.5 (range:10–15) years with a mean time from surgery to follow-up of 45.1±3.16 (range:18–78) months. There was a statistically significant increase in calcaneal pitch of 2.9° (11.7°to14.6°) and decrease in Meary”s angle of 15.8° (23.2° to7.85°) after surgery. The postoperative angles were maintained during follow-up, for both the calcaneal pitch (13.89°) and Meary”s angle (8.67°) in patients with the Kalix in situ (n=9/26) and in patients with the Kalix removed (15.4° and 7.8° respectively, n=17/26). The patient satisfaction survey shows that the majority of patients were satisfied regarding the state (81%) and appearance (75%) of their feet at follow-up. The majority never complained about their feet (81%) and heavy exercise was the major cause of complaints (23%). Limitations during walking were usually not the case (81%), though some patient experienced limitations during running (57%). Most reported preoperative complaints were pain, walking problems or a combination of both. The majority of these are relieved after surgery and patients were still asymptomatic at follow up. Conclusion. Kalix implantation improves the calcaneal pitch and Meary”s angle, thereby restoring foot anatomy towards a normal anatomy. These improvements were observed directly postoperatively and remained at follow-up. In addition, relieve of symptoms was observed postoperatively and the majority of patients were even satisfied at follow-up. We therefore suggest that Kalix arthroereisis is an appropriate treatment option for pediatric patients with symptomatic flexible flat feet. Significance. This was the first study evaluating functional and radiological outcomes of the Kalix arthroereisis in patients with symptomatic flexible flat feet

Background. Surgical resection of middle facet tarsal coalition is a well documented treatment option in symptomatic individuals that do not respond to conservative treatment. The ability to return to full recreational activity post resection may have implications on foot biomechanics and possibly degenerative changes in the subtalar and adjacent joints. Hypothesis. Open resection of middle facet tarsal coalitions should improve subtalar joint motion and biomechanical function and facilitate return to sports. Aim. The aim of this study was to assess the outcomes of open resection of middle facet tarsal coalitions (MFTCs) with particular emphasis on return to sports. Methods. Retrospective review of clinical and radiographic records of paediatric and adolescent patients who had open resection of middle facet tarsal coalitions. The ankle and hind foot were evaluated according to the American Orthopaedic Foot and Ankle Society Ankle-Hind foot Scale (AOFAS). We also quantified the return-to-activity time after tarsal coalition surgery. Results. We identified thirteen patients (Mean age; 13.7years Range; 7–21 years) with eighteen middle facet tarsal coalitions operated over a seven year period. Ten patients (12 feet) who underwent resection had an average return to recreational activity time of approximately twelve weeks and reported better exercise tolerance post resection. Conclusion. Surgical excision of middle facet tarsal coalitions has a favourable outcome with respect to return to sports

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

Objectives

To review the systemic impact of smoking on bone healing as evidenced within the orthopaedic literature.

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load.

The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure.

These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability.

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.

External fixation of distal tibial fractures is often associated with delayed union. We have investigated whether union can be enhanced by using recombinant bone morphogenetic protein-7 (rhBMP-7).

Osteoinduction with rhBMP-7 and bovine collagen was used in 20 patients with distal tibial fractures which had been treated by external fixation (BMP group). Healing of the fracture was compared with that of 20 matched patients in whom treatment was similar except that rhBMP-7 was not used.

Significantly more fractures had healed by 16 (p = 0.039) and 20 weeks (p = 0.022) in the BMP group compared with the matched group. The mean time to union (p = 0.002), the duration of absence from work (p = 0.018) and the time for which external fixation was required (p = 0.037) were significantly shorter in the BMP group than in the matched group. Secondary intervention due to delayed healing was required in two patients in the BMP group and seven in the matched group.

RhBMP-7 can enhance the union of distal tibial fractures treated by external fixation.