Purpose. The goal of Total Ankle Arthroplasty (TAA) is to relieve pain and restore healthy function of the intact ankle. Restoring intact ankle kinematics is an important step in restoring normal function to the joint. Previous robotic laxity testing and functional activity simulation showed the intact and implanted motion of the tibia relative to the calcaneus is similar. However there is limited data on the tibiotalar joint in either the intact or implanted state. This current study compares modern anatomically designed TAA to intact tibiotalar motion. Method. A robotic testing system including a 6 DOF load cell (AMTI, Waltham, MA) was used to evaluate a simulated functional activity before and after implantation of a modern anatomically designed TAA (Figure 1). An experienced foot and ankle surgeon performed TAA on five fresh-frozen cadaveric specimens. The specimen tibia and fibula were potted and affixed to the robot arm (KUKA Robotics Inc., Augsburg, Germany) while the calcaneus was secured to a fixed pedestal (Figure 1). Passive reflective motion capture arrays were fixed to the tibia and talus and a portable coordinate measuring machine (Hexagon Metrology Group, Stockholm, Sweden) established the location of the markers relative to anatomical landmarks palpated on the tibia. A four camera motion capture system (The Motion Monitor, Innovative Sports Training, Chicago, IL) recorded the movement of the tibia and talus. The tibia was rotated from 30 degrees plantar flexion to 15 degrees dorsiflexion to simulate motions during the stance phase of gait. At each flexion angle the robot found the orientation which zeroed all forces and torques except compressive force, which was either 44N or 200N. Results. Preliminary data indicates the tibiotalar motion of the TAA is similar to the intact ankle. The pattern and magnitude of tibiotalar translations and rotations are similar between the intact and implanted states for both 44N and 200N compressive loads (Figure 2). The most variation occurs with internal-external rotation. Increased translation especially in the anterior-posterior directions was observed in plantarflexion while the mediolateral translation remained relatively centered moving less than a millimeter. The intact talus with respect to the calcaneus had less than 3 degrees of rotation over the whole arc of ankle flexion (Figure 3). The angular motion of the implanted talus was similar in pattern to the intact talus, however there were offsets in all three angular directions which changed depending on the loading (Figure 3). This indicates that most of the motion that occurs between the intact tibial calcaneal complex occurs in the tibiotalar joint. Conclusion. Although more investigation is required, this study adds to the limited available tibiotalar kinematic data. This current study suggests the anatomical TAA design allows the tibiotalar joint to behave in similar way to the intact tibiotalar joint. Restoring intact kinematics is an important step in restoring normal function to the joint. For figures/tables, please contact authors directly.

Ankle arthrodesis is the gold standard for treatment of end stage ankle arthritis. We analysed the data of 124 Ankle Arthrodesis (Open Ankle Arthrodesis (OAA) −27; Arthroscopic Ankle Arthrodesis (AAA)- 97) performed between January 2005 and December 2015 by fellowship trained foot and ankle surgeons in a single institution. Based on preoperative deformity (AAA- 28 degree valgus to 26 degrees varus; OAA- 41 degree valgus to 28 degree varus), they were subdivided into 2 groups based upon deformity more than 15 degrees. Union rates, time to union, length of hospital stay and patient related factors like smoking, alcoholism, diabetes, BMI were assessed. Mean age of patients was 60 years (Range 20 to 82 years)(Male:Female-87:32). Overall fusion rate was 93% in AAA and 89% in OAA (p=0.4). On sub group analysis of influence of preoperative deformity, there was no difference in union rates of AAA versus OAA. 7 patients in AAA and 3 in OAA required further procedures. Average time to union was 13.7 in AAA and 12.5 weeks in OAA (p=0.3). Average hospital stay was 2.6 days in AAA and 3.8 days in OAA (p=0.003). Smoking, alcoholism, Diabetes, BMI did not have any correlation with union rates. Although both AAA and OAA showed good union rates, hospital stay was significantly shorter in AAA. A larger deformity did not adversely affect union rates in AAA. Time to union was higher in AAA though it was statistically insignificant. Lifestyle risk factors did not have cumulative effect on union. We conclude that AAA is a reproducible method of treating end stage tibiotalar arthritis irrespective of preoperative deformity and patient related factors

Aim

Post traumatic distal tibia osteomyelitis (DTOM) with an upper ankle joint involvement is a serious complication after primary osteosynthesis and can be a nightmare for the patient and the surgeon as well. Our aim was to identify mayor complications during treatment and to find the way to prevent or treat them.

Preoperative talar valgus deformity increases the technical difficulty of total ankle replacement (TAR) and is associated with an increased failure rate. Deformity of ≥15° has been reported to be a contraindication to arthroplasty. The goal of the present study was to determine whether the operative procedures and clinical outcomes of TAR for treatment of end-stage ankle arthritis were comparable for patients with preoperative talar valgus deformity of ≥15° as compared to those with <15°. We will describe the evolving surgical technique being utilized to tackle these challenging cases. Fifty ankles with preoperative coronal-plane tibiotalar valgus deformity of ≥15° “valgus” group) and 50 ankles with valgus deformity of <15° (“control” group) underwent TAR. The cohorts were similar with respect to demographics and components used. All TARs were performed by a single surgeon. The mean duration of clinical follow-up was 5.5 years (minimum two years). Preoperative and postoperative radiographic measurements of coronal-plane deformity, Ankle Osteoarthritis Scale (AOS) scores and Short Form (SF)-36 scores were prospectively recorded. All ancillary (intraoperative) and secondary procedures, complications and measurements were collected. The AOS pain and disability subscale scores decreased significantly in both groups. The improvement in AOS and SF-36 scores did not differ significantly between the groups at the time of the final follow-up. The valgus group underwent more ancillary procedures during the index surgery (80% vs 26%). Tibio-talar deformity improved significantly toward a normal weight-bearing axis in the valgus group. Secondary postoperative procedures were more common in the valgus group (36%) than the controls (20%). Overall, re-operation was not associated with poorer patient outcome scores. Metal component revision surgery occurred in seven patients (three valgus and four controls). These revisions included two deep infections (2%), one in each group, which were converted to hindfoot fusions. Therefore, 94% of the valgus group retained their original components at final follow-up. Thus far, this is the largest reported study that specifically evaluates TAR with significant preoperative valgus alignment, in addition to having the longest follow-up. Satisfactory midterm results were achieved in patients with valgus mal-alignment of ≥15°. The valgus cohort required more procedures during and after their TAR, as well as receiving more novel techniques to balance their TAR. Whilst longer term studies are needed, valgus coronal-plane alignment of ≥15° should not be considered an absolute contraindication to TAR if the associated deformities are addressed

Purpose. Coronal plane malalignment at the level of the tibiotalar joint is not uncommon in advanced ankle joint arthritis. It has been stated that preoperative varus or valgus deformity beyond 15 degrees is a relative contraindication and deformity beyond 20 degrees is an absolute contraindication to ankle joint replacement. There is limited evidence in the current literature to support these figures. The current study is a prospective clinical and radiographic comparative study between patients who underwent total ankle arthroplasty with coronal plane varus tibiotalar deformities greater than 10 degrees and patients with neutral alignment, less than 10 degrees of deformity. Method. Thirty-six ankles with greater than 10 degrees of varus alignment were compared to thirty-six ankles which were matched for implant type, age, gender, and year of surgery. Patients completed preoperative and yearly postoperative functional outcome scores including the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scores, the Ankle Osteoarthritis Scale (AOS) and the Short Form-36 Standard Version 2.0 Health Survey. Weightbearing preoperative and postoperative radiographs were obtained and reviewed by four examiners (AC, AQ, TD, TT) and measurements were taken of the degree of coronal plane deformity. Results. After a mean follow-up of 27 months (9–54), the varus ankles improved significantly on the AOFAS (P<0.0001), AOS-Pain Score (P<0.0001), AOS-Disability Score (P<0.0001), and SF-36 Physical Component Score (P<0.0001). There was no improvement in SF-36-Mental Component Score. (P=0.722). There was no statistically significant differences between the two groups when comparing AOFAS (P=0.155), AOS-Pain Score (P=0.854), AOSDisability Score (P=0.593), SF-36-Physical Component Score (P=0.433), SF-36 Mental Component Score (P=0.633). Sixteen of Thirty-Six ankles in the varus group needed a secondary procedure (implant failure, infection, malalignment) which was approaching significance in comparison to eight ankles in the neutral group. (P = 0.079). Secondary procedures in the varus group included: tendon transfers, calcaneal / metatarsal / malleolar ostoetomies and ligament reconstructions. Radiographically, the pre-operative coronal plane varus tibiotalar deformity averaged 19.4 6.4 and postoperatively 1.44 2.6 (P< 0.0001). There was no statistical difference in post operative tibiotalar alignment between the varus and neutral groups (P<0.05). Conclusion. The clinical outcome of TAR performed in ankles with pre-operative varus alignment >10 degrees is comparable with that of neutrally aligned ankles. The increased number of secondary procedures in the varus group was attributed to the complexity of the deformity and the steep learning curve. Outcomes as measured radiographically and through validate scores were similar to patients without deformity suggesting that varus coronal plane deformity of the talus is not a contraindication to total ankle replacement

Autologous bone has been the gold standard for grafting material in foot and ankle arthrodesis. While autograft use has been effective, the harvest procedure does present risks to the patient including readmission, infection, and persistent graft harvest site pain. Previous studies have examined graft harvest site pain, but most have focused on the iliac crest and none have long term follow-up. The purpose of this study was to examine long-term (7–10 year) harvest site pain in subjects undergoing autograft harvest from multiple sites for hindfoot and/or ankle arthrodesis. Sixty (60) subjects underwent hindfoot or ankle arthrodesis supplemented with autograft as part of the control arm of a prospective, randomized trial. The mean subject age was 59.4 years (range, 24.7–76.8) and mean body mass index was 30.6 kg/m2 (range, 22.0–44.0). There were 29 males and 31 female subjects. Subjects had the tibiotalar (37.9%), subtalar (24.1%), talonavicular (10.3%), subtalar/talonavicular (5.1%), or subtalar/calcaneocuboid/talonavicular (22.4%) joints arthrodesed. Autograft was harvested from either the proximal tibia (51.7%), iliac crest (17.2%), calcaneous (15.5%), distal tibia (6.8%), or other location (8.6%). Graft harvest site pain was evaluated using a 100-point visual analog score (VAS), with clinically significant pain being any score greater than 20. Subjects were followed a mean of 9.0 years (range, 7.8–10.5). The percentage of subjects who reported clinically significant pain was 35.7%, 21.4%, 18.2%, 10.5%, 8.9%, and 5.2% at 2, 6, 12, 24, 52 weeks, and final follow-up (7.8–10.5 years), respectively. The mean VAS autograft harvest site pain at final follow-up was 4.4 (range, 0.0–97.0), with 37.9% of subjects reporting at least some pain. For three subjects (5%) with clinically significant pain (VAS >20) at final follow-up, two had proximal tibial harvest sites and one had an iliac crest harvest site. There was no correlation between graft volume and harvest site pain. This study is the first to examine long-term pain following autologous bone graft harvest for hindfoot and/or ankle arthrodesis. Over a third of patients reported having some pain at an average follow-up of nine years, with 5% experiencing clinically significant pain. The results of this study suggest that harvesting autograft bone carries a risk of persistent, long-term pain regardless of the volume of graft that is harvested. This potential for persistent pain should be considered when informing patients of procedure risks and when deciding to use autograft or a bone graft substitute material

Traditional screw fixation of the syndesmosis can be prone to malreduction. Suture button fixation however, has recently shown potential in securing the fibula back into the incisura even with intentional malreduction. Yet, if there is sufficient motion to aid reduction, the question arises of whether or not this construct is stable enough to maintain reduction under loaded conditions. To date, there have been no studies assessing the optimal biomechanical tension of these constructs. The purpose of this study was to assess optimal tensioning of suture button fixation and its ability to maintain reduction under loaded conditions using a novel stress CT model. Ten cadaveric lower limbs disarticulated at the knee were used. The limbs were placed in a modified external fixator frame that allows for the application of sustained torsional (5 Nm), axial (500 N) and combined torsional/axial (5Nm/500N) loads. Baseline CT scans of the intact ankle under unloaded and loaded conditions were obtaining. The syndesmosis and the deltoid ligament complex were then sectioned. The limbs were then randomised to receive a suture button construct tightened at 4 kg force (loose), 8 kg (standard), or 12 kg (maximal) of tension and CT scans under loaded and unloaded conditions were again obtained. Eight previously described measurements were taken from axial slices 10 mm above the tibiotalar joint to assess the joint morphology under the intact and repair states, and the three loading conditions: a measure of posterolateral translation (a, b), medial/lateral translation (c, g), a measure of anterior-posterior translation (f), a ratio of anterior-posterior translation (d/e), an angle (Angle 1) created by a line parallel to the incisura and the axis of the fibula, and an angle (Angle 2) created between the medial surfaces of two malleoli. These measurements have all been previously described. Each measurement was taken at baseline and compared with the three loading scenarios. A repeated measures ANOVA with a Bonferroni correction for multiple comparisons was used to test for significance. Significant lateral (g, maximum 5.26 mm), posterior (f, maximum 6.42 mm), and external rotation (angle 2, maximum 11.71°) was noted with the 4 kg repair when compared to the intact, loaded state. Significant posterior translation was also seen with the both the 8 kg and 12 kg repairs, however the incidence and magnitude was less than with the 4 kg repair. Significant overcompression (g, 1.69 mm) was noted with the 12 kg repair. Suture button constructs must be appropriately tensioned to maintain reduction and re-approximate the degree of physiological motion at the distal tibiofibular joint. If inserted too loosely, these constructs allow for supraphysiologic motion which may have negative implications on ligament healing. These constructs also demonstrate overcompression of the syndesmosis when inserted at maximal tension however the clinical effect of this remains to be determined

The purpose of this study is to assess the improvement in pain and function of the ankle when arthrodiastasis is used for end stage juvenile idiopathic arthritis [JIA] in the paediatric population. All patients treated with ankle arthrodiastasis, 2009–2013 were studied. Clinical, radiological and survivorship data were examined. The Oxford Ankle Foot Questionnaire for Children (OxAFQ-C) and Parents (OxAFQ-P), along with the American Orthopaedic Foot and Ankle Society (AOFAS) Clinical rating system for Ankle-Hindfoot were recorded pre-operatively and at 6 months. Eight patients (9 ankles) with severe tibiotalar JIA, refractory to medical management were treated. Average age at surgery was 14.5 years (range 8–19). Average length of arthrodiastasis was 3.5 months. Length of follow-up averaged 13 months (range 5–28 months). All scores showed an improvement at 6 months. OxAFQ-C scores (out of 60) improved on average from 23 to 43. OxAFQ-P scores also improved from19 to 39. The largest improvement was found for the physical subsection. AOFAS Ankle-Hindfoot score (out of 100) averaged 34 pre-op and 74 at 6 months. Pain scored out of 10 decreased from an average of 7.4 to 4.3 at 6 months. All patients and parents were satisfied with the surgery and would have the procedure performed again. Radiological studies demonstrated cartilage regeneration, joint restoration and deformity correction with arthrodiastasis. Survivorship was good (75%) at 36 months, but 2 patients (3 ankles) had subsequent surgery in the adult sector for progression of disease despite initial improvement following arthrodiastasis. This case series demonstrates the efficacy of ankle arthrodiastasis as a surgical option in severe end-stage ankle inflammatory arthritis in paediatric patients in the short to midterm. It improved functional scores and pain scores which should delay the need for more radical joint fusion or replacement procedures in this challenging surgical condition

Introduction. The incidence of osteochondral lesions following ankle fractures varies in the literature between 17-70%. They are commonly associated with chronic pain and swelling in patients diagnosed with such pathology. There is less evidence about the relationship between OCL and the development of post-traumatic osteoarthritis, the most common type of ankle arthritis. Methods. Through the use of MRI 8 weeks following ankle fractures, we investigated the incidence of OCL in patients treated both surgically and conservatively for ankle fractures of all AO subtypes. Results. 29 patients met our inclusion criteria, 16 females: 13 males with a mean age of 36 (range 16-64). Twelve patients required surgery with seventeen treated conservatively. The majority of patients (11) were classified as 44B1 fractures with the 44C1 and 44B2 the next most common. We did not detect any OCL in any patient but 65% of patients had both a tibiotalar effusion and associated bone bruising. Conclusion. Contrary to the current literature, we did not associate ankle fractures of any subtype with the development of OCL. Future evaluation of this same cohort will be necessary to evaluate the incidence of post traumatic ankle osteoarthritis

Few previous studies showed that the conventional total knee replacement (TKR) has affection to the same side of talar tilt (TT). We expected to prevent this problem by the computer-assisted (CAS) TKR. The purpose of this study was to compare between pre and post-operative talar tilt and ankle clinical assessment on the CAS TKR and the Conventional TKR in 28 patients (56 knees) whom underwent bilateral TKR. 28 patients, 56 knees, whom underwent both CAS total knee replacement (TKR) and conventional total knee replacement (TKR), in both knees, with the combination of Gap Balance and Measurement Resection techniques performed by one surgeon (P. Sriphirom) at Rajavithi Hospital, Bangkok. The post-operative has a 12 months follow-up for ankle radiographic finding by tibiotalar angle (TTA), tibial articular surface angle (TAS), and talar tilt (TT) = (TAS-TTA) and for ankle clinical assessment by foot functional index (FFI) from pre-operation and post-operation from both groups. The study also compares the CAS TKR with the Conventional TKR for pre-operation and post-operation. 56 knees, 28 patients, mean age = 67.79 years whom underwent bilateral TKR by the Conventional group and the CAS group had pre-operative TT (TT = TAS − TTA). The Conventional group = 1.5 (−5, 8), the CAS group = 0.5 (−5, 8), P value = 0.65. On post-operative TT the Conventional group = 0.0 (−5, 3), the CAS group = 1.0 (−3, 8), the P value = 0.4. The comparison of pre-operative TT and post-operative TT in the Conventional group, the P value = 0.01. On pre-operative TT and post-operative TT in the CAS group, the P value = 0.65. TT was significantly different in the Conventional group but was not significantly different in the CAS group. The ankle clinical assessment by foot functional index (FFI), which are (1) Pain, (2) Difficulty living, and (3) Daily life activity limitation. The pre-operative FFI in the Conventional group = 1.85 (0.81, 6.88) and pre-operative FFI in the CAS group = 1.91 (0.24, 66.5), the P value = 0.57. The post-operative FFI in the Conventional group = 1.68 (0.24, 7.0) and post-operative FFI in the CAS group = 1.65 (0.24, 6.76), the P value = 0.04, which showed a significantly different between the post-operative FFI from both groups. In the Conventional group the post-operative FFI was not significantly different from pre-operative FFI, the P value = 0.2 but for the CAS group the post-operative FFI was not significantly different from pre-operative FFI, the P value = 0.04. This study showed that the conventional TKR effected to post-operative talar, tilt but CAS TKR has less effect and was not significantly different to ankle joint. Finally, the study needs to be conducted on more patients and to be observed on a longer term follow-up

Ankle sprains have been shown to be the most common sports related injury. Ankle sprain may be classified into low ankle sprain or high ankle sprain. Low ankle sprain is a result of lateral ligament disruption. It accounts for approximately 25% of all sports related injuries. The ankle lateral ligament complex consists of three important structures, namely the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL) and posterior talofibular ligament (PTFL). The ATFL is the weakest and most easily injured of these ligaments. It is often described as a thickening of the anterolateral ankle capsule. The ATFL sits in a vertical alignment when the ankle is plantarflexed and thus is the main stabiliser against an inversion stress. T he CFL is extracapsular and spans both the tibiotalar and talocalcaneal joints. The CFL is vertical when the ankle is dorsiflexed. An isolated injury to the CFL is uncommon. Early diagnosis, functional management and rehabilitation are the keys to preventing chronic ankle instability following a lateral ligament injury. Surgery does not play a major role in the management of acute ligament ruptures. Despite this up to 20% of patients will develop chronic instability and pain with activities of daily living and sport especially on uneven terrain. Anatomic reconstruction for this group of patients is associated with 90% good to excellent results. It is important that surgery is followed by functional rehabilitation. One of the aims of surgery in patients with recurrent instability is to prevent the development of ankle arthritis. It should be noted that the results of surgical reconstruction are less predictable in patients with greater than 10 year history of instability. Careful assessment of the patient with chronic instability is required to exclude other associated conditions such as cavovarus deformity or generalised ligamentous laxity as these conditions would need to be addressed in order to obtain a successful outcome. High ankle sprain is the result of injury to the syndesmotic ligaments. The distal tibiofibular joint is comprised of the tibia and fibula, which are connected by anterior inferior tibiofibular ligament, interosseous ligament and the posterior inferior tibiofibular ligament (superficial and deep components). The mechanism of injury is external rotation and hyperdorsiflexion. High index of suspicion is required as syndesmotic injuries can occur in association of low ankle sprains. The clinical tests used in diagnosing syndesmotic injuries (external rotation, squeeze, fibular translation and cotton) do not have a high predictive value. It is important to exclude a high fibular fracture. Plain radiographs are required. If the radiograph is normal then MRI scan is highly accurate in detecting the syndesmotic disruption. Functional rehabilitation is required in patients with stable injuries. Syndesmotic injuries are often associated with a prolonged recovery time. Accurate reduction and operative stabilisation is associated with the best functional outcome in patients with an unstable syndesmotic injury. Stabilisation has traditionally been with screw fixation. Suture button syndesmosis fixation is an alternative. Early short-term reviews show this alternate technique has improved patient outcomes and faster rehabilitation without the need for implant removal

Restoration of natural range and pattern of motion is the primary goal of joint replacement. In total ankle replacement, proper implant positioning is a major requirement to achieve good clinical results and to prevent instability, aseptic loosening, meniscal bearing premature wear and dislocation at the replaced ankle. The current operative techniques support limitedly the surgeon in achieving a best possible prosthetic component alignment and in assessing proper restoration of ligament natural tensioning, which could be well aided by computer-assisted surgical systems. Therefore the outcome of this replacement is, at present, mainly associated to surgeon's experience and visual inspection. In some of the current ankle prosthetic designs, tibial component positioning along the anterior/posterior (A/P) and medio/lateral axes is critical, particularly in those designs not with a flat articulation between the tibial and the meniscal or talar components. The general aim of this study was assessing in-vitro the effects of the A/P malpositioning of the tibial component on three-dimensional kinematics of the replaced joint and on tensioning of the calcaneofibular (CaFiL) and tibiocalcaneal (TiCaL) ligaments, during passive flexion. Particularly, the specific objective is to compare the intact ankle kinematics with that measured after prosthesis component implantation over a series of different positions of the tibial component. Four fresh-frozen specimens from amputation were analysed before and after implantation of an original convex-tibia fully-congruent three-component design of ankle replacement (Box Ankle, Finsbury Orthopaedics, UK). Each specimen included the intact tibia, fibula and ankle joint complex, completed with entire joint capsule, ligaments, muscular structures and skin. The subtalar joint was fixed with a pin protruding from the calcaneus for isolating tibiotalar joint motion. A rig was used to move the ankle joint complex along its full range of flexion while applying minimum load, i.e. passive motion. In these conditions, motion at the ankle was constrained only by the articular surfaces and the ligaments. A stereofotogrammetric system for surgical navigation (Stryker-Leibinger, Freiburg, Germany) was used to track the movement of the talus/calcaneus and tibial segments, by using trackers instrumented with five active markers. Anatomical based kinematics was obtained after digitization by an instrumented pointer of a number of anatomical landmarks and by a standard joint convention. The central point of the attachment areas of CaFiL e TiCaL was also digitised. Passive motion and ankle joint neutral position were acquired, and the standard operative technique was performed to prepare the bones for prosthesis component implantation. The final component for the talus was implanted, the tibial component was initially positioned well in front of the nominal right (NR) position, the meniscal bearing was instrumented with an additional special tracker, and passive motion was collected again in passive flexion. Data collection was repeated for progressively more posterior locations for the tibial component, for a total of six different locations along the tibial A/P axis: three anterior (PA), the NR, and two more posterior (PP), approximately 3 to 5 mm far apart each. The following three-dimensional kinematics variables were analyzed: the three anatomical components of the ankle joint (talus-to-tibial) rotation (dorsi/plantar flexion, prono/supination and internal/external rotation respectively in the sagittal, frontal and transverse planes), the meniscal bearing pose with respect to the talar and tibial components, the ‘ligament effective length fraction’ as the ratio between the instantaneous distance between the ligament attachment points and the corresponding maximum distance, and the instantaneous and mean helical axes in the tibial anatomical reference frame. In all specimens and in all conditions, physiological ranges of flexion, prono/supination and internal/external rotation were observed at the ankle joint. A good restoration of motion was observed at the replaced joint, demonstrated also by the coupling between axial rotation and flexion and the physiological location of the mean helical axis, in all specimens and in most of the component positions. Larger plantar- and smaller dorsi-flexion were observed when the tibial component was positioned more anteriorly than NR, and the opposite occurred for more posterior positions. In regards to the meniscal bearing, rotations were small and followed approximately the same patterns of the ankle rotations, accounted for the full conformity of the articulating surfaces. Translations in A/P were larger than in other directions, the bearing moving backward in plantarflexion and forward in dorsiflexion with respect to both components. It was observed that the closer to NR the position of the tibial component is, the larger this A/P motion is, accounted mainly to the associated larger range of flexion. The change of CaFiL and TiCaL effective length fraction over the flexion arc was found smaller than 0.1 in three specimens, smaller than 0.2 in the fourth, larger both in more anterior and more posterior locations of the tibial component. The simulated malpositioning did not affect much position and orientation of the mean helical axis in both the transversal and frontal planes. The experimental protocol and measurements were appropriate to achieve the proposed goals. All kinematics variables support the conclusion that the ankle replaced with this original prosthesis behaves as predicted by the relevant computer models, i.e. physiological joint motion and ligament tension is experienced resulting in a considerable A/P motion of the meniscal bearing. These observations are particularly true in the NR postion for the prosthesis, but are somehow correct also in most of the tibial malpositions analysed, in particular those on the back

The use of robots in orthopaedic surgery is an emerging field that is gaining momentum. It has the potential for significant improvements in surgical planning, accuracy of component implantation and patient safety. Advocates of robot-assisted systems describe better patient outcomes through improved pre-operative planning and enhanced execution of surgery. However, costs, limited availability, a lack of evidence regarding the efficiency and safety of such systems and an absence of long-term high-impact studies have restricted the widespread implementation of these systems. We have reviewed the literature on the efficacy, safety and current understanding of the use of robotics in orthopaedics.

Cite this article: Bone Joint J 2015; 97-B:292–9.

Surgeons need to be able to measure angles and distances in three dimensions in the planning and assessment of knee replacement. Computed tomography (CT) offers the accuracy needed but involves greater radiation exposure to patients than traditional long-leg standing radiographs, which give very little information outside the plane of the image.

There is considerable variation in CT radiation doses between research centres, scanning protocols and individual scanners, and ethics committees are rightly demanding more consistency in this area.

By refining the CT scanning protocol we have reduced the effective radiation dose received by the patient down to the equivalent of one long-leg standing radiograph. Because of this, it will be more acceptable to obtain the three-dimensional data set produced by CT scanning. Surgeons will be able to document the impact of implant position on outcome with greater precision.