Over a nine-year period, 20 feet with persistently symptomatic talocalcaneal coalition were treated by resection of the bar. The 17 patients were all under 16 years of age. Excellent or good long-term results were achieved in the ten feet in which preoperative coronal CT had shown that the area of coalition measured 50% or less of the area of the posterior facet of the calcaneum. In these feet heel valgus was less than 16 degrees and there were no radiographic signs of arthritis of the posterior talocalcaneal joint. Talar beaking was present in 70% of these feet but it did not impair the clinical result. Fair or poor results were observed in the ten feet in which preoperative CT had shown the area of relative coalition to be greater than 50%. In these feet, heel valgus was greater than 16 degrees and most had narrowing of the posterior talocalcaneal joint and impingement of the lateral process of the talus on the calcaneum

Surgical resection of the persistently painful talocalcaneal tarsal coalition has not been shown to reliably relieve symptoms in patients with coalitions that are large and have associated hindfoot valgus and subtalar arthrosis. It has been recommended that these patients undergo triple arthrodesis, a procedure that is known to lead to premature arthrosis of the ankle joint. To avoid additional stress on this important joint, treatment of this patient group using calcaneal lengthening osteotomy (CLO), with or without resection of the coalition, has been performed at our institution for the last 15 years. A retrospective review of all patients with talocalcaneal coalitions who had undergone CLO was performed. Clinical and radiographic records were reviewed. Demographic data, and pre- and post-operative pain and function were recorded. Pre- and post-operative radiographs and computed tomography (CT) scans were reviewed and measurements recorded. CT scans were used to calculate the degree of hindfoot valgus and the size of the coalition. Patients were invited to return for clinical examination and follow-up x-rays if two years had passed since their operation. They completed American foot and ankle hindfoot scores, VAS pain scores and were asked satisfaction questionnaires. Radiographic measurements were performed. There were 13 patients who underwent 19 CLOs. Of these 13 patients, eight patients with 13 CLO’s returned for clinical examination and radiographs. Five patients had nine CLO’s to correct deformity without resection of a large middle facet talocalcaneal coalition with severe hindfoot deformity. All patients had restoration of normal foot shape with improvement in comfort and function. One patient had improvement in comfort and function following bilateral simultaneous coalition resection of cartilaginous coalition and CLO to correct significant hindfoot deformity. Two patients had improvement in pain and function in a foot that had residual pain and deformity following prior talocalcaneal coalition resection. CLO, usually accompanied by a heel cord lengthening, is a useful operation both in the failed middle facet resection where there is persistent pain and deformity, and also in the very large coalition with associated deformity and/or arthrosis that is not appropriate for resection. It corrects the foot deformity, improves comfort and function, maintains motion in Chopart’s joints and therefore, unlike triple arthrodesis, avoids additional stresses in the ankle joint

We analysed 42 weight-bearing lateral radiographs of the ankle, 20 of which were from patients with a clinical and plain radiological diagnosis of talocalcaneal coalition (TCC) who subsequently had CT. The remainder were from 22 healthy volunteers with no clinical findings suggestive of hindfoot pathology. Four observers, blinded to the CT findings, independently evaluated the radiographs on two separate occasions. With the 95% confidence interval and using the CT findings as the comparison we calculated the sensitivity, specificity, accuracy, and positive and negative predictive values for the C-sign, and for other signs known to be associated with TCC. Similarly, we also calculated the interobserver and intraobserver reliability for these signs using the kappa statistic. Our results suggest that the C-sign is highly sensitive and specific for TCC. It is an accurate indicator and significantly more reliable than other previously recognised radiological signs of TCC. Features of the C-sign, however, cannot be relied upon to indicate whether the TCC is fibrous or bony

Introduction:. Symptomatic tarsal coalitions failing conservative treatment are traditionally managed by open resection. Arthroscopic excision of calcaneonavicular bars have previously been described as has a technique for excising talocalcaneal bars using an arthroscope to guide an open resection. We describe a purely arthroscopic technique for excising talocalcaneal coalitions. We present a retrospective two-surgeon case series of the first eight patients (nine feet). Methods:. Subtalar arthroscopy is performed from two standard sinus tarsi portals with the patient in a saggy lateral position. Coalitions are resected with a barrel burr after soft tissue clearance with arthroscopic shavers. Early postoperative mobilisation and non-steroidal anti-inflammatory drugs prevent recurrence of coalition. Outcome measures include restoration of subtalar movements, return to work and sports, visual analogue pain scales and Sports Athlete Foot and Ankle Scores (SAFAS). Follow-up ranges from 1 to 5.5 years. Results:. Pain and SAFAS scores improved in 7 patients. Subtalar movements were improved in all feet and were sustained to final follow-up. All patients achieved early good function and returned to sports and demanding jobs. One patient's pain recurred requiring subsequent fusions. One posterior tibial nerve was damaged. Both of these patients had coalitions extending across more than one quarter of the posterior facet. Conclusion:. Minimal destruction of bone and soft tissues with an arthroscopic technique allows early mobilization and minimizes pain. We acknowledge the risk of neurological damage from both open and arthroscopic excision of tarsal coalitions. Patient selection and preoperative planning are crucial to avoid relapse and complication. If significant degenerative changes are present at surgery or resections are too extensive onto the posterior facet early recurrence of pain may occur. This series from two independent surgeons supports the feasibility and effectiveness of this technique

Aim

Historically, surgeons have focused on isolated simple coalition resection in symptomatic tarsal coalition with concomitant rigid flat foot. However, recent evidence suggests that coalitions with severe preoperative planovalgus malposition treated with resection alone are associated with continued disability and deformity. We believe that concomitant severe flatfoot should be considered as much as a pathological component and pain generator as the coalition itself. Our primary hypothesis is that simple resection of middle facet tarsal coalitions and simultaneous flat foot reconstruction can improve clinical outcomes.

Distraction bone-block arthrodesis has been advocated for the treatment of the late sequelae of fracture of the os calcis. Between 1997 and 2003 we studied a consecutive series of 17 patients who had in situ arthrodesis for subtalar arthritis after fracture of the os calcis with marked loss of talocalcaneal height. None had undergone any previous attempts at reconstruction. We assessed the range of dorsiflexion and plantar flexion and measured the talocalcaneal height, talocalcaneal angle and talar declination angle on standing lateral radiographs, comparing them with the normal foot. The mean follow-up was for 78.7 months (48 to 94). The mean American Orthopaedic Foot and Ankle Society hindfoot score improved from 29.8 (13 to 48) to 77.8 (48 to 94) (Student’s t-test, p < 0.001). The mean loss of talocalcaneal height was 10.3 mm (2 to 17) and the mean talar declination angle was 6.7° (0° to 16°) which was 36% of the normal side. One patient suffered anterior ankle pain but none had anterior impingement. Two patients complained of difficulty in ascending slopes and stairs and four in descending. The mean ankle dorsiflexion on the arthrodesed side was 11.6° (0° to 24°) compared with 14.7° (0° to 24°) on the normal side, representing a reduction of 21.1%. The mean plantar flexion on the arthrodesed side was 35.5° (24° to 60°) compared with 44.6° (30° to 60°) on the normal side, a reduction of 20.4%. These results suggest that anterior impingement need not to be a significant problem after subtalar arthrodesis for fracture of the os calcis, even when the loss of talocalcaneal height is marked. We recommend in situ arthrodesis combined with lateral-wall ostectomy for all cases of subtalar arthritis following a fracture of the os calcis, without marked coronal deformity, regardless of the degree of talocalcaneal height loss

We investigated 60 patients (89 feet) with a mean age of 64 years (61 to 67) treated for congenital clubfoot deformity, using standardised weight-bearing radiographs of both feet and ankles together with a functional evaluation. Talocalcaneal and talonavicular relationships were measured and the degree of osteo-arthritic change in the ankle and talonavicular joints was assessed. The functional results were evaluated using a modified Laaveg-Ponseti score. The talocalcaneal (TC) angles in the clubfeet were significantly lower in both anteroposterior (AP) and lateral projections than in the unaffected feet (p < 0.001 for both views). There was significant medial subluxation of the navicular in the clubfeet compared with the unaffected feet (p < 0.001). Severe osteoarthritis in the ankle joint was seen in seven feet (8%) and in the talonavicular joint in 11 feet (12%). The functional result was excellent or good (≥ 80 points) in 29 patients (48%), and fair or poor (< 80 points) in 31 patients (52%). Patients who had undergone few (0 to 1) surgical procedures had better functional outcomes than those who had undergone two or more procedures (p < 0.001). There was a significant correlation between the functional result and the degree of medial subluxation of the navicular (p < 0.001, r. 2 . = 0.164), the talocalcaneal angle on AP projection (p < 0.02, r2 = 0.025) and extent of osteoarthritis in the ankle joint (p < 0.001). We conclude that poor functional outcome in patients with congenital clubfoot occurs more frequently in those with medial displacement of the navicular, osteoarthritis of the talonavicular and ankle joints, and a low talocalcaneal angle on the AP projection, and in patients who have undergone two or more surgical procedures. However, the ankle joint in these patients appeared relatively resistant to the development of osteoarthritis

Introduction. The arch of the foot has been described as a truss where the plantar fascia (PF) acts as the tensile element. Its role in maintaining the arch has likely been underestimated because it only rarely torn in patients with progressive collapsing foot deformity (PCFD). We hypothesized that elongation of the plantar fascia would be a necessary and sufficient precursor of arch collapse. Method. We used a validated finite element model of the foot reconstructed from CT scan of a female cadaver. Isolated and combined simulated ligament transection models were created for each combination of the ligaments. A collapsed foot model was created by simulated transection of all the arch supporting ligaments and unloading of the posterior tibial tendon. Foot alignment angles, changes in force and displacement within each of the ligaments were compared between the intact, isolated ligament transection, and complete collapse conditions. Result. Isolated release of the PF did not cause deformity, but lead to increased force in the long (142%) and short plantar (156%), deltoid (45%), and spring ligaments (60%). The PF was the structure most able to prevent arch collapse and played a secondary role in preventing hindfoot valgus and forefoot abduction deformities. Arch collapse was associated with substantial attenuation of the spring (strain= 41%) and interosseous talocalcaneal ligaments (strain= 27%), but only a small amount in the plantar fascia (strain= 10%). Conclusion. Isolated PF release did not cause arch collapse, but arch collapse could not occur without at least 10% elongation of the PF. Simulated transection of the PF led to substantial increase in the force in the other arch supporting ligaments, putting the foot at risk of arch collapse over time. Chronic degeneration of the PF leading to plantar fasciitis may be an early sign of impending PCFD

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

Aims. We hypothesized that there is no difference in the clinical and radiological outcomes using local bone graft versus iliac graft for subtalar distraction arthrodesis in patients with calcaneal malunion. In addition, using local bone graft negates the donor site morbidity. Patients and Methods. We prospectively studied 28 calcaneal malunion patients (the study group) who were managed by subtalar distraction arthrodesis using local calcaneal bone graft. The study group included 16 male and 12 female patients. The median age was 37.5 years (interquartile range (IQR) 29 to 43). The outcome of the study group was compared with a control group of ten patients previously managed by subtalar distraction arthrodesis using iliac bone graft. The control group included six male and four female patients. The median age was 41.5 years (IQR 36 to 44). Results. The mean American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score improved significantly in the study and the control groups (p < 0.001). Fusion was achieved in 27 patients in the study group at a median time of 13 weeks (IQR 12 to 14), while all the patients in the control group achieved fusion at a mean time of 13.2 weeks (11 to 15). The mean talocalcaneal height and talar declination angle improved significantly in both the study and the control groups (p < 0.001). There was no significant difference between both groups concerning the preoperative or the postoperative clinical and radiological measurements. Donor site morbidity was reported in four out of ten patients in the control group. Conclusion. Local calcaneal bone graft can successfully be used to achieve subtalar distraction arthrodesis with appropriate correction of alignment and calcaneal malunion. We recommend using local instead of iliac bone graft as it gave comparable results and avoids the possibility of donor site morbidity. Cite this article: Bone Joint J 2019;101-B:596–602

Aims. Various radiological parameters are used to evaluate a flatfoot deformity and their measurements may differ. The aims of this study were to answer the following questions: 1) Which of the 11 parameters have the best inter- and intraobserver reliability in a standardized radiological setting? 2) Are pre- and postoperative assessments equally reliable? 3) What are the identifiable sources of variation?. Patients and Methods. Measurements of the 11 parameters were recorded on anteroposterior and lateral weight-bearing radiographs of 38 feet before and after surgery for flatfoot, by three observers with different experience in foot surgery (A, ten years; B, three years; C, third-year orthopaedic resident). The inter- and intraobserver reliability was calculated. Results. Preoperative interobserver reliability was high for four, moderate for five, and low for two parameters. Postoperative interobserver reliability was high for four, moderate for five, and low for two parameters. Intraobserver reliability was excellent for all parameters preoperatively as recorded by observer A (PB) and B (MP), and for eight parameters as recorded by observer C (SR). Intraobserver reliability was excellent for ten parameters postoperatively as recorded by observer A and B, and for eight parameters as recorded by observer C. Conclusion. The following parameters can be recommended. For preoperative and postoperative evaluation of flatfoot: anteroposterior, talonavicular coverage angle; lateral, talometatarsal I angle, calcaneal pitch angle, and cuneiform-medial height (high interobserver reliability); and anteroposterior, talometatarsal II angle; lateral, talocalcaneal angle,tibiocalcaneal angle (moderate interobserver reliability). For more experienced observers, we also recommend the anteroposterior talometatarsal I angle (moderate reliability). The inter- and intraobserver reliability for most parameters were similar pre- and postoperatively. The experience of the observer and the definition and ability to measure the parameters themselves were sources of variation. Cite this article: Bone Joint J 2018;100-B:596–602

Tarsal coalition has been well recognized as the commonest cause of peroneal spastic flat feet in children and adolescents (Mosier and Asher 1984). Other rare causes are tuberculosis and rheumatoid arthritis. If no etiology can be found the term idiopathic peroneal spastic flat foot has been coined by Schoenecker (2000). We prospectively assessed all children and adolescents with peroneal spastic flat feet seen at our clinic in the period 2002 to 2004. Twelve patients (17 feet) were assessed. The average age was 11,9 years (range10 to15years). Seventy five percent of the patients were above the 95th percentile weight for age. Screening for tuberculosis (ESR, Mantoux and chest radiograph) was negative in all patients. Rheumatoid factor was positive in one patient with juvenile idiopathic arthritis (JIA). Radiology was standardized. Plain radiographs were standing lateral and 45 degree oblique views. CT and MRI:. axial: parallel to plantar surface;. coronal oblique: gantry perpendicular to the plane of the subtalar joint. This latter view best illustrates a talocalcaneal coalition (Newman 2000). Two patients (four feet) had a calcaneonavicular coalition on the 45 degree oblique plane radiographs. This was also shown on the axial CT and MRI views. No talocalcaneal coalition was visualized on the coronal oblique CT and MRI views. In order to find a diagnosis and to confirm the accuracy of the MRI and CT, the middle facet of the talocalcaneal joint was explored in eight feet and a synovial biopsy done. No talocalcaneal coalition was found. JIA was histologically confirmed in one patient. The authors concluded that the idiopathic type is by far the commonest peroneal spastic flat foot seen in our clinic. The 45 degree oblique plain radiograph is as accurate as axial CT and MRI to diagnose calcaneonavicular coalition. The coronal oblique CT and MRI views are equally accurate to exclude a talocalcaneal coalition

Introduction: Congenital tarsal coalition is one of the most prevalent (1–6%) anomalies of the hindfoot and midfoot. Its etiology is unknown. By definition there are boney, cartilaginous or fibrous brigdes between 2 bones of the hindfoot and midfoot, which are classified by their localization; the most common coalitions are calcaneonavicular (53%) and talocalcaneal (37%). Patients and Methods: From 2001 to 2007 28 patients with 37 coalitions had surgery at the Orthopedic Hospital Vienna-Speising. 32 calcaneonavicular coalitions were surgically excised and an autogenous free fat graft was interponed to prevent a relapse. 1 calcaneonavicluar coalition also had an interposition of the extensor digitorum brevis after resection, while 1 calcaneonavicular coalition had lengthening of the short peroneal tendon in addition to excision and autogenous free fat graft. 1 calcaneonavicular coalition had to have an arthrodesis of the talocalcaneal joint. From 2 talocalcaneal coalitions 1 had excision the other 1 talocalcaneal arthrodesis. Both of the coalitions that had arthrodesis had short-leg plastercasts for 12 to 13 weeks. For patients with bilateral coalition pedobarography was performed and the foot that had been treated compared to the untreated contralateral side. For these patients the AOFAS ankle and hind foot score and pain according to the VAS were evaluated. Results: 22 coalitions that had had surgery were uncomplaining after intervention, including 1 patient who had had arthrodesis. 3 calcaneonavicular coalitions that had had excision and autogenous free fat graft had a relapse within 2 to 3 years. 2 of them had a revision and second-look excision of the bridge. 1 patient showed a suspicious relapse in MRI after excision of a calcaneonavicular coalition. 1 talocalcaneal coaltion that had had excision continued to have pain after surgery. Both patients did not want a revision. 1 patient who was treated by an arthrodesis of the subtalar joint had a fracture of the tibial head, where autogenous bone graft had been taken. Osteosynthesis of the tibia was performed. 4 patients had pain after excision of a calcaneonavicular coalition but could be relieved by conservative treatment. For 5 patients adequate follow up is still pending due to short interval to surgery. Pedobarography showed tendecies of improved pressure distribution of the treated feet that were not significant. Conclusion: Excision and autogenous free fat graft should be first approach to surgery of symptomatical congenital tarsal coalitions for whom conservative treatment was not satisfying. When resected sufficiently the rate of relapse of the boney, cartilaginous or fibrous bridge is 7%. Depending on the patients age, the size of the affected area of the joint (50%) and secondary arthrotic changes of the joint an arthrodesis of the talo-calcaneal joint should be performed

Introduction: Distraction bone block arthrodesis has been advocated in the literature to treat the late sequelae of os calcis fracture with loss of heel height including the prevention of anterior impingement. We have studied a consecutive series of subjects who have had in situ arthrodesis for subtalar arthrosis as a consequence of os calcis fracture with marked loss of talocalcaneal height paying particular attention to range of movement and anterior impingement. Materials and Methods: Between 1997 and 2003 31 consecutive subjects underwent subtalar arthrodesis. Five subjects who had undergone ORIF, two non-unions and three subjects with bilateral injuries were excluded. Two subjects who had marked coronal displacement that required additional surgery at the time of arthrodesis were also excluded. Two subjects were lost to follow up leaving 17 for assessment. AOFAS hind foot scores improved from 29.8 (range 13–48) preoperatively to 77.8 (range 48–94) postoperatively. Mean loss of talocalcaneal height was 10.3mm and the mean talar declination angle was 6.7 degrees which was 35% of the normal side. One subject suffered anterior ankle pain but none had anterior impingement. Two subjects complained of difficulty ascending slopes and stairs and four of difficulty descending. Mean ankle dorsiflexion was 11.6 degrees (range 0–24) compared to 14.7 degrees on the normal side: A reduction of 21.1%. Mean plantarflexion was 35.5 degrees (range 24–60) compared to 44.6 degrees on the normal side: A reduction of 20.4%. Discussion: Our results suggest that anterior impingement is not a significant problem in os calcis fracture, even when loss of talocalcaneal height is marked. We recommend ISA combined with lateral wall ostectomy for all cases of subtalar arthrosis as a result of os calcis fracture, without marked coronal deformity, regardless of the degree of talocalcaneal height loss

The purpose of this study was to evaluate the longterm results of 736 cases of operatively treated clubfeet, and to examine if there is any difference in the results between our patients and referred patients. A follow-up examination was carried out in 736 cases of clubfeet operated on between 1966 and 1990. The average follow-up period was 14.7 years. Treatment was based on three pillars: well-organized care, conservative treatment and early operative treatment. In all of the reviewed cases, posteromedial soft tissue release was performed. Surgical intervention was indicated in cases of residual deformity after conservative treatment, cases of recurrent deformity, and cases of untreated clubfeet. Clinical evaluation contained the examination of residual deformities and the passive and active motions of the foot. In the radiological assessment, the anteroposterior talocalcaneal angle, the lateral talocalcaneal angle and the talometatarsal angle was measured. In the clinical evaluations equinus deformity was found in 3.35%, varus in 7.23%, valgus in 8.55%, adducted forefoot in 30.8%, inflexion of the forefoot in 7.14%, and overcorrection to the vertical talus in 3.35%. Range of motion was normal in only 36% of the cases. Average anteroposterior talocalcaneal angle was 13.05 preoperatively and 22.13 postoperatively. Average lateral talocalcaneal angle was 10.78 preoperatively and 27.66 postoperatively. Average talometatarsal angle changed from 26 to 5.5 after the operation. The overall success rate of the operated cases was 65%. After long-term follow-up, 65% of the cases were classified as successful. When comparing our patients with referred patients, there were considerable differences found in the rate of reoperation, age at the time of the first operation, and also in the results. These differences point out the importance of the early beginning of operative treatment, with regular follow-up and care

The purpose of this study was to evaluate the longterm results of 736 cases of operatively treated clubfeet, and to examine if there is any difference in the results between our patients and referred patients. A follow-up examination was carried out in 736 cases of clubfeet operated on between 1966 and 1990. The average follow-up period was 14.7 years. Treatment was based on three pillars: well-organized care, conservative treatment and early operative treatment. In all of the reviewed cases, posteromedial soft tissue release was performed. Surgical intervention was indicated in cases of residual deformity after conservative treatment, cases of recurrent deformity, and cases of untreated clubfeet. Clinical evaluation contained the examination of residual deformities and the passive and active motions of the foot. In the radiological assessment, the anteroposterior talocalcaneal angle, the lateral talocalcaneal angle and the talometatarsal angle was measured. In the clinical evaluations equinus deformity was found in 3.35%, varus in 7.23%, valgus in 8.55%, adducted forefoot in 30.8%, inflexion of the forefoot in 7.14%, and overcorrection to the vertical talus in 3.35%. Range of motion was normal in only 36% of the cases. Average anteroposterior talocalcaneal angle was 13.05 preoperatively and 22.13 postoperatively. Average lateral talocalcaneal angle was 10.78 preoperatively and 27.66 postoperatively. Average talometatarsal angle changed from 26 to 5.5 after the operation. The overall success rate of the operated cases was 65%. After long-term follow-up, 65% of the cases were classified as successful. When comparing our patients with referred patients, there were considerable differences found in the rate of reoperation, age at the time of the first operation, and also in the results. These differences point out the importance of the early beginning of operative treatment, with regular follow-up and care

Objective. The objective of this study was to evaluate the rotation and translation of each joint in the hindfoot and compare the load response in healthy feet with that in stage II posterior tibial tendon dysfunction (PTTD) flatfoot by analysing the reconstructive three-dimensional (3D) computed tomography (CT) image data during simulated weight-bearing. . Methods. CT scans of 15 healthy feet and 15 feet with stage II PTTD flatfoot were taken first in a non-weight-bearing condition, followed by a simulated full-body weight-bearing condition. The images of the hindfoot bones were reconstructed into 3D models. The ‘twice registration’ method in three planes was used to calculate the position of the talus relative to the calcaneus in the talocalcaneal joint, the navicular relative to the talus in talonavicular joint, and the cuboid relative to the calcaneus in the calcaneocuboid joint. Results. From non- to full-body-weight-bearing condition, the difference in the talus position relative to the calcaneus in the talocalcaneal joint was 0.6° more dorsiflexed (p = 0.032), 1.4° more everted (p = 0.026), 0.9 mm more anterior (p = 0.031) and 1.0 mm more proximal (p = 0.004) in stage II PTTD flatfoot compared with that in a healthy foot. The navicular position difference relative to the talus in the talonavicular joint was 3° more everted (p = 0.012), 1.3 mm more lateral (p = 0.024), 0.8 mm more anterior (p = 0.037) and 2.1 mm more proximal (p = 0.017). The cuboid position difference relative to the calcaneus in the calcaneocuboid joint did not change significantly in rotation and translation (all p ≥ 0.08). . Conclusion. Referring to a previous study regarding both the cadaveric foot and the live foot, joint instability occurred in the hindfoot in simulated weight-bearing condition in patients with stage II PTTD flatfoot. The method used in this study might be applied to clinical analysis of the aetiology and evolution of PTTD flatfoot, and may inform biomechanical analyses of the effects of foot surgery in the future. Cite this article: Bone Joint Res 2013;2:255–63