Patients with a hindfoot deformity impose a particular challenge when performing a total knee arthroplasty (TKA). This could be attributed to the lack of insights concerning the outcome towards the hindfoot alignment. Our objective was to perform a systematic review of the literature to investigate the influence of TKA on hindfoot alignment and vice-versa. In accordance with the Methodological Index For Non-Randomized Studies (MINORS) statement standards, we performed a systematic review. Electronic databases Pubmed, EMBASE, Web of Science, Google Scholar and Cochrane Library were searched to identify capable studies studying the influence between TKA and hindfoot malalignment. We indentified four prospective cohort studies, seven retrospective cohort studies and one case-control study. All twelve articles addressed the influence of TKA on hindfoot alignment. Seven out of nine studies which noticed an improvement of hindfoot alignment after TKA, found a significant improvement (p<0.05). Aditionally three of these studies reported a significant improvement only in valgus hindfeet (p<0.05). On the topic of hindfoot alignment influencing TKA, we identified two studies. These studies reported an impact of hindfoot alignment on the weightbearing and described that 87% of hindfeet remained in valgus alignment after TKA. Available data suggests that alignment in valgus hindfeet can improve after TKA, though long term results are not present. Contrary to last, improvement of hindfoot alignment is not expected in varus hindfeet. Furthermore hindfoot alignment deformity may cause a reduction of the long term survival of the knee prosthesis and therefore should be taken in to account

Background. There have been multiple techniques described to determine hindfoot alignment radiographically. The 2-dimensional nature of radiographs fails to take into account the contribution of the remainder of the foot to overall alignment. A new radiographic technique has been published in which the hindfoot alignment is calculated using the Ground Reaction Force Calcanea Offset. This technique accounts for the individual forefoot contribution to alignment, but is still limited by it´s 2-dimensional nature. The purpose of this study was to compare the hindfoot moment arm (HMA) described by Saltzman and the hindfoot alignment angle (HAA) described by Williamson, with a technique determining the ground reaction force calcaneal offset (GRF-CT) using 3-dimensional weight bearing CT Scans. Methods. The HMA, HAA, and GRF-CT 3-D weight bearing CT scans were measured by three different investigators. Each of these measurements were calculated twice on separate occasions by each investigator to determine the intra- and inter-observer reliability. Results. 104 patients underwent weight bearing hindfoot alignment radiographs and 3-dimensional weight bearing CT scans including 33 patients with varus and 71 patients with valgus hindfoot deformities. There was excellent intra- and inter-observer reliability with all three measurement techniques (P< 0.01), however the GRF-CT showed the best intra- and inter-observer reliability with the lowest standard deviation (P< 001). Conclusions. The GRF-CT technique is more reliable than traditional radiographic techniques for measuring the hindfoot alignment. While the intra- and inter-observer reliability is good for all three techniques, the GRF-CT technique resulted in the best intra- and inter-observer reliability with the lowest standard deviation. This technique provides the most accurate hindfoot alignment as it takes into account the effect of forefoot on overall alignment, preventing inaccuracies of projection and foot orientation in contrast to traditional radiographic techniques, which may be valuable in surgical decision making

The weight bearing axis of the limb goes from the pelvis to the ground and includes the hindfoot. However, the influence of hindfoot alignment on mechanical axis deviation and overall limb alignment after total knee arthroplasty (TKA) is unknown. This study aimed to assess the change in hindfoot alignment after TKA for knee osteoarthritis, the difference in mechanical axis deviation at the knee when calculated using the ground mechanical axis as compared to the conventional mechanical axis, and the effect of hindfoot alignment on the overall postoperative limb alignment after TKA. We evaluated the pre- and postoperative hip-knee-ankle (HKA) angle, conventional mechanical axis deviation (CMAD), ground mechanical axis deviation (GMAD), and tibiocalcaneal angle (TCA) in 125 patients who underwent 165 consecutive TKAs. Overall, the change in pre- and postoperative mean TCA was not significant (p=0.48) whereas it was significant (p=0.01) in knees with =15° deformity where the hindfoot valgus decreased by approximately 25%. Preoperatively, there was no significant difference between mean CMAD and mean GMAD whereas postoperatively the difference was significant (p=0.0001). Hindfoot valgus alignment of =10° was present in 22.5% of limbs and 29% limbs had a postoperative GMAD of =10 mm in spite of the limb alignment being restored to within 3° of neutral after TKA. Despite accurate restoration of limb alignment after TKA, as a result of persistent hindfoot valgus alignment the ground mechanical axis may pass lateral to the centre of the knee joint - with potential detrimental effects on bone, ligaments and implants

Background. Traditional measurements of hindfoot alignment are based on the tibio-calcaneal angle and do not take the forefoot into account. We have developed an algorithm based on standard radiographs to calculate calcaneal offset using Ground Reaction Force (GRF). Hypothesis. The GRF algorithm measures hindfoot alignment without using the tibial axis. Materials and Methods. Thirty six patients (40 feet) were included (21 female, 15 male). Mean age was 56 (SD:17). Weight bearing orthogonal radiographs were taken. Calcaneal offsets were measured using the tibio-calcaneal angles and the GRF algorithm. The two methods were compared using the Bland-Altman method. Results. Ground Reaction Force Calcaneal Offset was in agreement with traditional measurement (p< 0.05) but individual discrepancies were found. Mean measured offsets were respectively −11.5 mm (SD:10.2) and −8 mm (SD:9.3) valgus. Mean bias between the two methods was −0.88 mm. Discussion. The GRF algorithm successfully measured hindfoot alignment, and took into consideration the influence of forefoot position. The absence of a previous gold standard and variability related to radiographic protocols are a limit. Overall, angular measurements underestimated calcaneal offset. Individual discrepancies showed that including data related to forefoot position provided a more accurate assessment. This could be of particular clinical relevance for surgical planning. Unexplained total ankle replacement failures and diffuse arthritis after ankle fusion might be reduced by using this information preoperatively. Conclusion. Ground Reaction Force could improve assessment of hindfoot alignment and provide useful information for surgical planning

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

Aims. Patients with a deformity of the hindfoot present a particular challenge when performing total knee arthroplasty (TKA). The literature contains little information about the relationship between TKA and hindfoot alignment. This systematic review aimed to determine from both clinical and radiological studies whether TKA would alter a preoperative hindfoot deformity and whether the outcome of TKA is affected by the presence of a postoperative hindfoot deformity. Methods. A systematic literature search was performed in the databases PubMed, EMBASE, Cochrane Library, and Web of Science. Search terms consisted of “total knee arthroplasty/replacement” combined with “hindfoot/ankle alignment”. Inclusion criteria were all English language studies analyzing the association between TKA and the alignment of the hindfoot, including the clinical or radiological outcomes. Exclusion criteria consisted of TKA performed with a concomitant extra-articular osteotomy and case reports or expert opinions. An assessment of quality was conducted using the modified Methodological Index for Non-Randomized Studies (MINORS). The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and registered in the PROSPERO database (CRD42019106980). Results. A total of 17 studies were found to be eligible for review. They included six prospective and ten retrospective studies, and one case-control study. The effects of TKA showed a clinical improvement in the hindfoot deformity in three studies, but did not if there was osteoarthritis (OA) of the ankle (one study) or a persistent deformity of the knee (one study). The radiological alignment of the hindfoot corrected in 11 studies, but did not in the presence of a rigid hindfoot varus deformity (in two studies). The effects of a hindfoot deformity on TKA included a clinical association with instability of the knee in one study, and a shift in the radiological weightbearing axis in two studies. The mean MINORS score was 9.4 out of 16 (7 to 12). Conclusion. TKA improves both the function and alignment of the hindfoot in patients with a preoperative deformity of the hindfoot. This may not apply if there is a persistent deformity of the knee, a rigid hindfoot varus deformity, or OA of the ankle. Moreover, a persistent deformity of the hindfoot may adversely affect the stability and longevity of a TKA. These findings should be interpreted with caution due to the moderate methodological quality of the studies which were included. Therefore, further prospective studies are needed in order to determine at which stage correction of a hindfoot deformity is required to optimize the outcome of a TKA. Cite this article: Bone Joint J 2021;103-B(1):87–97

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

Aims. Total knee arthroplasty (TKA) may provoke ankle symptoms. The aim of this study was to validate the impact of the preoperative mechanical tibiofemoral angle (mTFA), the talar tilt (TT) on ankle symptoms after TKA, and assess changes in the range of motion (ROM) of the subtalar joint, foot posture, and ankle laxity. Methods. Patients who underwent TKA from September 2020 to September 2021 were prospectively included. Inclusion criteria were primary end-stage osteoarthritis (Kellgren-Lawrence stage IV) of the knee. Exclusion criteria were missed follow-up visit, post-traumatic pathologies of the foot, and neurological disorders. Radiological angles measured included the mTFA, hindfoot alignment view angle, and TT. The Foot Function Index (FFI) score was assessed. Gait analyses were conducted to measure mediolateral changes of the gait line and ankle laxity was tested using an ankle arthrometer. All parameters were acquired one week pre- and three months postoperatively. Results. A total of 69 patients (varus n = 45; valgus n = 24) underwent TKA and completed the postoperative follow-up visit. Of these, 16 patients (23.2%) reported the onset or progression of ankle symptoms. Varus patients with increased ankle symptoms after TKA had a significantly higher pre- and postoperative TT. Valgus patients with ankle symptoms after TKA showed a pathologically lateralized gait line which could not be corrected through TKA. Patients who reported increased ankle pain neither had a decreased ROM of the subtalar joint nor increased ankle laxity following TKA. The preoperative mTFA did not correlate with the postoperative FFI (r = 0.037; p = 0.759). Conclusion. Approximately one-quarter of the patients developed ankle pain after TKA. If patients complain about ankle symptoms after TKA, standing radiographs of the ankle and a gait analysis could help in detecting a malaligned TT or a pathological gait. Cite this article: Bone Joint J 2023;105-B(11):1159–1167

3D accurate measurements of the skeletal structures of the foot, in physiological and impaired subjects, are now possible using Cone-Beam CT (CBCT) under real-world loading conditions. In detail, this feature allows a more realistic representation of the relative bone-bone interactions of the foot as they occur under patient-specific body weight conditions. In this context, varus/valgus of the hindfoot under altered conditions or the thinning of plantar tissues that occurs with advancing age are among the most complex and interesting to represent, and numerous measurement proposals have been proposed. This study aims to analyze and compare these measurements from CBCT in weight-bearing scans in a clinical population. Sixteen feet of diabetic patients and ten feet with severe adult flatfoot acquired before/after corrective surgery underwent CBCT scans (Carestream, USA) while standing on the leg of interest. Corresponding 3D shapes of each bone of the shank and hindfoot were reconstructed (Materialise, Belgium). Six different techniques found in the literature were used to calculate the varus/valgus deformity, i.e., the inclination of the hindfoot in the frontal plane of the shank, and the distance between the ground and the metatarsal heads was calculated along with different solutions for the identification of possible calcifications. Starting with an accurate 3D reconstruction of the skeletal structures of the foot, a wide range of measurements representing the same angle of hindfoot alignment were found, some of them very different from each other. Interesting correlations were found between metatarsal height and subject age, significant in diabetic feet for the fourth and fifth metatarsal bones. Finally, CBCT allows 3D assessment of foot deformities under loaded conditions. The observed traditional measurement differences and new measurement solutions suggest that clinicians should consider carefully the anatomical and functional concepts underlying measurement techniques when drawing clinical and surgical conclusions

Introduction. Pes cavovarus is a foot deformity that can be idiopathic (I-PC) or acquired secondary to other pathology. Charcot-Marie-Tooth disease (CMT) is the most common adult cause for acquired pes cavovarus deformity (CMT-PC). The foot morphology of these distinct patient groups has not been previously investigated. The aim of this study was to assess if morphological differences exist between CMT-PC, I-PC and normal feet (controls) using weightbearing computed tomography (WBCT). Methods. A retrospective analysis of WBCT scans performed between May 2013 and June 2017 was undertaken. WBCT scans from 17 CMT-PC, 17 I-PC and 17 healthy normally-aligned control feet (age-, side-, sex- and body mass index-matched) identified from a prospectively collected database, were analysed. Eight 2-dimensional (2D) and three 3-dimensional (3D) measurements were undertaken for each foot and mean values in the three groups were compared using one-way ANOVA with the Bonferroni correction. Results. Significant differences were observed between CMT-PC or I-PC and controls (p< 0.05). Two-dimensional measurements were similar in CMT-PC and I-PC, except for forefoot arch angle (p= 0.04). 3D measurements (foot and ankle offset, calcaneal offset and hindfoot alignment angle) demonstrated that CMT-PC exhibited more severe hindfoot varus malalignment than I-PC (p= 0.03, 0.04 and 0.02 respectively). Discussion. CMT-related cavovarus and idiopathic cavovarus feet are morphologically different from healthy feet, and CMT feet exhibit increased forefoot supination and hindfoot malalignment compared to idiopathic forms. The use of novel three-dimensional analysis may help highlight subtle structural differences in patients with similar foot morphology but aetiologically different pathology

Background. Occasionally, patients experience new or increased ankle pain following total knee arthroplasty (TKA). The aims of this study were to determine (1) how the correction of varus malalignment of the lower limb following TKA affected changes in alignment of the ankle and hindfoot, (2) the difference in changes in alignment of the ankle and hindfoot between patients with and without ankle osteoarthritis (OA), and (3) whether the rate of ankle pain and the clinical outcome following TKA differed between the 2 groups. Methods. We retrospectively reviewed prospectively collected data of 56 patients (99 knees) treated with TKA. Among these cases, concomitant ankle OA was found in 24 ankles. Radiographic parameters of lower-limb, ankle, and hindfoot alignment were measured preoperatively and 2 years postoperatively. In addition, ankle pain and clinical outcome 2 years after TKA were compared between patients with and without ankle OA. Results. The orientation of the ankle joint line relative to the ground improved from varus 9.4° to varus 3.4°, and the valgus compensation of the hindfoot for the varus tilt of the ankle joint showed a 2.2° decrease following TKA. Patients in the group with ankle OA showed decreased flexibility of the hindfoot resulting in less preoperative valgus compensation (p = 0.022) compared with the group without ankle OA. The postoperative hindfoot alignment was similar between the 2 groups because of the smaller amount of change in patients with ankle OA. The group with ankle OA had a higher rate of increased ankle pain (38% compared with 16%) as well as a worse Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (mean of 22.2 compared with 14.2) following TKA. Conclusions. A considerable proportion of patients who underwent TKA had concomitant ankle OA with reduced flexibility of the hindfoot. These patients experienced increased ankle pain following TKA and a worse clinical outcome

Hindfoot disorders are complex 3D deformities. Current literature has assessed their influence on the full leg alignment, but the superposition of the hindfoot on plain radiographs resulted in different measurement errors. Therefore, the aim of this study is to assess the hindfoot alignment on Weight-Bearing CT (WBCT) and its influence on the radiographic Hip-Knee-Ankle (HKA) angle. A retrospective analysis was performed on a study population of 109 patients (mean age of 53 years ± 14,49) with a varus or valgus hindfoot deformity. The hindfoot angle (HA) was measured on the WBCT while the HKA angle, and the anatomical tibia axis angle towards the vertical (TA. X. ) were analysed on the Full Leg radiographs. The mean HA in the valgus hindfoot group was 9,19°±7.94, in the varus hindfoot group −7,29°±6.09. The mean TA. X. was 3,32°±2.17 in the group with a valgus hindfoot and 1,89°±2.63 in the group with a varus hindfoot, which showed to be statistically different (p<0.05). The mean HKA Angle was −1,35°±2.73 in the valgus hindfoot group and 0,4°±2.89 in the varus hindfoot group, which showed to be statistically different (p<0.05). This study demonstrates a higher varus in both the HKA and TA. X. in valgus hindfoot and a higher tibia valgus in varus hindfoot. This contradicts the previous assumption that a varus hindfoot is associated with a varus knee or vice versa. In clinical practice, these findings contribute to a better understanding of deformity corrections of both the hindfoot and the knee

Aims

The aim of this study was to capture 12-month outcomes from a representative multicentre cohort of patients undergoing total ankle arthroplasty (TAA), describe the pattern of patient-reported outcome measures (PROMs) at 12 months, and identify predictors of these outcome measures.

Aims

This scoping review aims to identify patient-related factors associated with a poorer outcome following total ankle arthroplasty (TAA).

Our goal was to evaluate the use of Ponseti’s method, with minor adaptations, in the treatment of idiopathic clubfeet presenting in children between five and ten years of age. A retrospective review was performed in 36 children (55 feet) with a mean age of 7.4 years (5 to 10), supplemented by digital images and video recordings of gait. There were 19 males and 17 females. The mean follow-up was 31.5 months (24 to 40). The mean number of casts was 9.5 (6 to 11), and all children required surgery, including a percutaneous tenotomy or open tendo Achillis lengthening (49%), posterior release (34.5%), posterior medial soft-tissue release (14.5%), or soft-tissue release combined with an osteotomy (2%). The mean dorsiflexion of the ankle was 9° (0° to 15°). Forefoot alignment was neutral in 28 feet (51%) or adducted (< 10°) in 20 feet (36%), > 10° in seven feet (13%). Hindfoot alignment was neutral or mild valgus in 26 feet (47%), mild varus (< 10°) in 19 feet (35%), and varus (> 10°) in ten feet (18%). Heel–toe gait was present in 38 feet (86%), and 12 (28%) exhibited weight-bearing on the lateral border (out of a total of 44 feet with gait videos available for analysis). Overt relapse was identified in nine feet (16%, six children). The parents of 27 children (75%) were completely satisfied. A plantigrade foot was achieved in 46 feet (84%) without an extensive soft-tissue release or bony procedure, although under-correction was common, and longer-term follow-up will be required to assess the outcome. Cite this article: Bone Joint J 2013;95-B:1721–5

Introduction:. Cone Based CT (CBCT) scanning uses a point source and a planar detector with parallel data acquisition and volumetric coverage of the area of interest. The pedCAT (Curvebeam USA) scanner is marketed as a low radiation dose, compact, faster and inexpensive CT scanner that can be used to obtain both non- weightbearing and true 3 dimensional weightbearing views. Method:. A review of the first 100 CBCT scanning in our unit has been performed to assess ease of scanning, imaging time, radiation dose and value of imaging as opposed to conventional imaging. Results:. A pedcat CT scan was available within minutes of the request, similar to plain radiographs but much earlier than a 6 week delay for a patient to attend a new appointment for a conventional CT. All patients returned to see the clinician for a clinical decision in the same NHS clinic and did not require a new clinic visit; illustrative cases include fracture/subluxation detection, surgical planning, extent of arthritis and 3D assessment of union of arthrodeses. All patients were able to transfer to the scanner with ease and the imaging time was 10 times than a conventional CT. The radiation dose to the patients was 9% that of a full gantry system. Weightbearing CT scanning enabled a 3D evaluation of reduction of joint space and ankle/hindfoot alignment. Anterior ankle and sesamoid impingement have been diagnosed in patients with previously obscure pain. Conclusion:. 3D Cone Beam imaging has been found to be easily accessible, rapidly performed and safer to the patient in providing a lower radiation dose. Weightbearing 3D imaging provides additional diagnostic information

The June 2024 Foot & Ankle Roundup³⁶⁰ looks at: First MTPJ fusion in young versus old patients; Minimally invasive calcaneum Zadek osteotomy and the effect of sequential burr passes; Comparison between Achilles tendon reinsertion and dorsal closing wedge calcaneal osteotomy for the treatment of insertional Achilles tendinopathy; Revision ankle arthroplasty – is it worthwhile?; Tibiotalocalcaneal arthrodesis or below-knee amputation – salvage or sacrifice?; Fusion or replacement for hallux rigidus?.

The December 2023 Foot & Ankle Roundup³⁶⁰ looks at: Subchondral bone cysts remodel after correction of varus deformity in ankle arthritis; 3D-printed modular endoprosthesis reconstruction following total calcanectomy; Percutaneous partial bone excision in the management of diabetic toe osteomyelitis; Hemiepiphysiodesis is a viable surgical option for Juvenile hallux valgus; Ankle arthroplasty vs arthrodesis: which comes out on top?; Patient-related risk factors for poorer outcome following total ankle arthroplasty; The Outcomes in Ankle Replacement Study.

The December 2024 Foot & Ankle Roundup³⁶⁰ looks at: Tibiotalar sector and lateral ankle instability; Isolated subtalar fusion and correction of progressive collapsing foot deformity; Diabetic control and postoperative complications following ankle fracture fixation; Are insoles of any benefit for plantar fasciitis?; Postoperative foot shape and patient-reported outcome following surgery for progressing collapsing foot deformity; Calcaneo-stop procedure for symptomatic flexible flatfoot in children.