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Background: The talus is more internally rotated within the ankle mortise in progressive collapsing foot deformity (PCFD) patients. However, no studies have investigated the change in talar axial rotation (AR) in PCFD postoperatively. The primary aim was to investigate the change in talar AR following PCFD reconstruction. Secondary aims were to determine whether talar AR changes were associated with other radiographic measurements or specific procedures, and whether postoperative talar AR was associated with 2-year patient-reported outcome scores., Methods: Twenty-seven patients older than 18 years who underwent flexible PCFD reconstruction with preoperative and at least 5-month postoperative weightbearing computed tomographic (WBCT) scans and radiographs and had preoperative and at least 2-year postoperative PROMIS scores were included. Patients with talonavicular fusions were excluded. Talar AR was the angle between the transmalleolar axis and talar axis on WBCT scans, with smaller angles representing more internal rotation as described by Kim et al. Hindfoot moment arm, Meary angle, fibulocalcaneal and talocalcaneal distance, subtalar middle facet uncoverage, and talonavicular angle were measured on radiographs., Results: Postoperative talar AR was 49.7 degrees (IQR, 45.9, 57.3), which was more externally rotated than preoperative AR by a median of 8.3 degrees (IQR, 2.2, 15.7) ( P  > .001). The change in talar AR was not associated with changes in any radiographic parameter. Increasing external talar AR was associated with an increase in postoperative PROMIS pain intensity ( r s  = 0.38, 95% CI 0.00, 0.67). Lateral column lengthening and subtalar fusion procedures were not associated with changes in talar AR ( P  > .10)., Conclusion: PCFD reconstruction results in external rotation of the talus within the ankle mortise. Kim et al found that control patients had approximately 40 to 60 degrees of talar AR, which is similar to this study's corrected position of the talus. However, increasing talar external rotation resulted in worse postoperative PROMIS pain intensity, suggesting the possibility of overcorrecting the internal AR deformity., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Background: There are various deformities described in the spectrum of Progressive Collapsing Foot Deformity (PCFD) which not only have adverse effects on the foot but also on the entire lower limb. Early lower limb muscular fatigue and pain during exertion is the most common complaint of patients with PCFD. Surface electromyography (sEMG) provides an accurate assessment of muscle activity. In this study, we aim to compare the activities of quadriceps, hamstrings, and gastrosoleus muscle groups of adult patients with PCFD with normal lower limbs and correlate the radiological parameters and functional effects of PCFD with the activities., Methods: Thirty patients with bilateral PCFD and 30 controls underwent weight-bearing anteroposterior (AP), lateral, and hindfoot alignment radiographs of the foot. Radiographic parameters of PCFD were assessed. Surface electromyography was used to assess the quadriceps, hamstrings, and gastrosoleus activities, and this was compared between the 2 groups and correlated with radiological measurements of PCFD. Tegner activity questionnaire was used to assess the functional effects of collapsed arch., Results: Electrical activities of all muscle groups were significantly higher in cases than controls. Meary's angle and hindfoot moment arm had significant correlations with hamstring activity (P = .013) and gastrosoleus activity (P = .027), respectively. Tegner scores of cases were significantly lower than those of controls (P = .041)., Conclusions: The PCFD causes an increase in activity of large muscles of the affected lower limb which act on joints other than those in the foot. This finding may be due to several compensatory mechanisms that counteract the deforming forces. This may be a cause for the frequent complaint, early fatigue, and hence functional impairment. However, most radiological parameters did not correlate with muscle activities and larger study size may be required for further association., Levels of Evidence: Diagnostic: Level 3., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Although operative treatment of the flexible progressive collapsing foot deformity (PCFD) remains controversial, correction of residual forefoot varus and stabilization of the medial column are important components of reconstruction. A peroneus brevis (PB) to peroneus longus (PL) tendon transfer has been proposed to address these deformities. The aim of our study was to determine the effect of an isolated PB-to-PL transfer on medial column kinematics and plantar pressures in a simulated PCFD (sPCFD) cadaveric model., Methods: The stance phase of level walking was simulated in 10 midtibia cadaveric specimens using a validated 6-degree of freedom robot. Bone motions and plantar pressure were collected in 3 conditions: intact, sPCFD, and after PB-to-PL transfer. The PB-to-PL transfer was performed by transecting the PB and advancing the proximal stump 1 cm into the PL. Outcome measures included the change in joint rotation of the talonavicular, first naviculocuneiform, and first tarsometatarsal joints between conditions. Plantar pressure outcome measures included the maximum force, peak pressure under the first metatarsal, and the lateral-to-medial forefoot average pressure ratio., Results: Compared to the sPCFD condition, the PB-to-PL transfer resulted in significant increases in talonavicular plantarflexion and adduction of 68% and 72%, respectively, during simulated late stance phase. Talonavicular eversion also decreased in simulated late stance by 53%. Relative to the sPCFD condition, the PB-to-PL transfer also resulted in a 17% increase ( P  = .045) in maximum force and a 45-kPa increase ( P  = .038) in peak pressure under the first metatarsal, along with a medial shift in forefoot pressure., Conclusion: The results from this cadaver-based simulation suggest that the addition of a PB-to-PL transfer as part of the surgical management of the flexible PCFD may aid in correction of deformity and increase the plantarflexion force under the first metatarsal., Clinical Relevance: This study provides biomechanical evidence to support the addition of a PB-to-PL tendon transfer in the surgical treatment of flexible PCFD., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Background: Establishing a surgical plan for ankle deformities necessitates a comprehensive understanding of the deforming forces involved, and the morphology of the ankle deformity plays an important role as well. Valgus tibiotalar tilt development has mostly been described in patients with a low medial longitudinal arch, as seen in progressive collapsing foot deformity (PCFD). However, some valgus ankles demonstrate no radiographic evidence of a collapsed medial arch. This study aims to investigate whether there are differences in the radiographic morphology of valgus ankle deformities between patients with and without a low medial longitudinal arch to explore if they have different etiologies., Methods: We retrospectively reviewed patients who underwent surgical treatment for asymmetric valgus ankle deformity at our institution between 2017 and 2021. Patients with a valgus tibiotalar tilt (TT) greater than 4 degrees and Meary angle greater than 30 degrees (mean: 38.9) were included in the PCFD group (n = 29). The non-PCFD group (n = 24) with TT greater than 4 degrees and Meary angle less than 4 degrees (mean: 0.3) was also established. In the weightbearing ankle anteroposterior view, the TT and medial distal tibial angle were measured. Additionally, to assess the mediolateral position of the talus, the talar center migration (TCM) and lateral talar dome-plafond distance (LTD-P) ratio in the coronal plane were measured. In weightbearing computed tomography (WBCT), the degree of axial plane talocalcaneal subluxation and the prevalence of sinus tarsi bony impingement were assessed. Intergroup comparison was conducted., Results: Both groups demonstrated a similar degree of TT, with a mean of 11.6 degrees in the PCFD group and 13.7 degrees in the non-PCFD group ( P  = .2330). However, the PCFD group showed a significantly greater TCM and LTD-P ratio compared with those of the non-PCFD group ( P  < .0001), indicating that PCFD patients have a more medially translated talus in ankle anteroposterior radiographs. WBCT showed that the PCFD group on average had 18 degrees greater axial plane talocalcaneal subluxation ( P  < .0001) and 52% higher prevalence of sinus tarsi bony impingement ( P  = .0002) compared with the non-PCFD group., Conclusion: This study suggests that valgus ankles may exhibit different radiographic morphologies depending on the status of the longitudinal arch. Valgus ankles in PCFD patients tend to have a more medially translated talus. This finding may suggest the presence of different deforming forces between the 2 groups and may indicate the need for different treatment strategies to address talar tilt., Level of Evidence: Level III, case-control., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Background: Weightbearing computed tomography (WBCT) scans allow for a better understanding of foot alignment in patients suffering from progressive collapsing foot deformity (PCFD). However, soft tissue integrity (eg, spring ligament complex or tibialis posterior tendon) cannot be easily assessed via WBCT. As performing both WBCT and magnetic resonance imaging (MRI) might not be cost effective, we aimed to assess whether there is an association between osseous and soft tissue findings in WBCT and MRI., Methods: In this observational study, a consecutive cohort of 24 patients of various stages of PCFD (mean age 51 ± 18 years) underwent WBCT scans and MRI. Twenty-four healthy individuals of similar age, body mass index (BMI), and sex with WBCT scans were used as a control group. In addition to of osseous sinus tarsi impingement, 4 commonly used 3-dimensional (3D) measurements (talocalcaneal overlap [TCO], talonavicular coverage [TNC], Meary angle [MA], axial/lateral) were obtained using a dedicated postprocessing software (DISIOR 2.1, Finland) on the WBCT data sets. Sinus tarsi obliteration, spring ligament complex, tibiospring ligament integrity, as well as tibialis posterior tendon degeneration were evaluated with MRI. Statistical analysis was performed for significant ( P  < .05) correlation between findings., Results: None of the assessed 3D measurements correlated with either spring ligament complex or tibiospring ligament tears. BMI and TCO were found to be associated with tibialis posterior tendon tears. Seventy-five percent of patients with osseous sinus tarsi impingement on WBCT also showed signs of sinus tarsi obliteration on MRI., Conclusion: Although WBCT reflects foot alignment and can reveal osseous sinus tarsi impingement in PCFD patients, the association between WBCT-based 3D measurements and ligament or tendon tears assessed via MRI is limited. WBCT appears complimentary to MRI regarding its diagnostic value. Both imaging options add important information and may impact decision making in the treatment of PCFD patients., Level of Evidence: Level IV, observational study., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Background: For the younger, more active patient with flexible symptomatic progressive collapsing foot deformity (PCFD), joint-sparing procedures may be preferred to preserve functional motion. Isolated talonavicular (TN) arthrodesis has been described for treatment of rigid and flexible PCFD for patients that are older and less active whose deformity is still correctable through the TN joint. The purpose of this study was to evaluate radiographic and clinical outcomes in patients with PCFD treated with isolated triplanar correction with a TN joint arthrodesis., Methods: Forty-nine patients (53 feet) with flexible PCFD underwent isolated TN arthrodesis. Weightbearing radiographs were performed pre- and postoperatively, and measurements included lateral talar-first metatarsal angle, calcaneal pitch, TN coverage angle, and the anteroposterior (AP) talar-first metatarsal angle. The Foot and Ankle Ability Measure (FAAM) and Veterans-Rand 12-Item Health Survey (VR-12) scores were also collected., Results: Thirty-five females and 14 males were evaluated with a mean age of 63 years, at an average follow-up of 41.3 months. Significant improvements were found radiographically. Lateral radiographs demonstrated improvements in lateral talar-first metatarsal angle from 25.2 degrees preoperatively to 9.5 degrees postoperatively ( P  < .001) and calcaneal pitch from 14.9 degrees preoperatively to 17.5 degrees postoperatively ( P  < .001). AP radiographs showed the TN coverage angle improving from 35.0 degrees to 4.9 degrees postoperatively ( P  < .001) and AP talar-first metatarsal angle improving from 17.3 degrees to 5.9 degrees postoperatively ( P  < .001). Clinical outcomes were improved in the FAAM pain score (48.6 to 39.2, P  = .130), FAAM ADL score (53.8 to 69.2, P  = .002), FAAM Sport score (29.5 to 40.7, P  = .099), and the overall FAAM score (47.7 to 63.1, P  = .006). Patient satisfaction with medical care was 85.2/100 postoperatively., Conclusion: Isolated TN arthrodesis is a viable surgical option for older, lower-demand patients with flexible PCFD. This study demonstrated significant improvements in radiographic alignment and FAAM scores. Comparative studies with other surgical procedures should be performed to determine which is the best technique for older, lower-demand patients with flexible PCFD., Level of Evidence: Level III, retrospective cohort study., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online., (© The Author(s) 2024.)

Background: The purpose of this study is to investigate the biomechanical effect of medial displacement calcaneal osteotomy (MDCO), subtalar joint fusion (SF), and medial ligament reconstruction (MLR: deltoid-spring ligament) in a severe flatfoot model. We hypothesized that (1) combination of MDCO and SF improves the tibiotalar and foot alignment in severe progressive collapsing foot deformity (PCFD) cadaver model. (2) However, if a residual valgus heel alignment remains after MCDO and SF, it can lead to increased medial ligament strain, foot malalignment, and tibiotalar valgus tilt, which will be mitigated by the addition of MLR., Methods: Ten fresh-frozen cadaveric foot specimens were used to create a severe flatfoot model. The foot alignment changes, including the talo-first metatarsal angle in the axial and sagittal planes, subtalar angle, and tibiotalar angle in the coronal plane, were measured. The angles were measured at the initial condition, after creating the severe flatfoot model, and after each successive reconstructive procedure in the following order: (1) MDCO, (2) SF, and (3) MLR., Results: Tibiotalar valgus tilt was decreased with the MDCO procedure: 4.4 vs 1.0 degrees ( P  = .04). Adding in situ SF to the MDCO led to increased tibiotalar tilt to 2.5 degrees was different from the initial condition ( P  = .01). Although the tibiotalar valgus tilt was significantly decreased after adding the MLR to the MDCO/SF procedure compared with the severe flatfoot model (0.8 vs 4.4 degrees, P  = .03), no significant difference in the tibiotalar valgus tilt was observed between MDCO/SF and MDCO/SF with MLR., Conclusion: Our results demonstrated that MDCO significantly improved forefoot abduction and medial arch alignment, with no significant additional improvement observed with addition of SF. Following SF, a residual valgus heel alignment can contribute to subsequent tibiotalar valgus tilt. The addition of MLR did not show significantly decreased tibiotalar valgus tilt following SF., Clinical Relevance: Residual valgus heel alignment after subtalar joint fusion in the surgical treatment of PCFD can lead to increased medial ligament strain. Although MLR might be considered for providing medial stability, it may not necessarily prevent the development of tibiotalar valgus tilt., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

Background: In progressive collapsing foot deformity (PCFD), an internal and plantar rotation of the talus relative to the calcaneus may result in painful peritalar subluxation. Medial soft tissue procedures (eg, spring ligament repair) aim to correct the talar position via the navicular bone if bony correction alone is not sufficient. The effect of the medial soft tissue reconstruction on the talar reposition remains unclear. We hypothesized that a subtalar talocalcaneal ligament reconstruction might be favorable in PCFD to correct talar internal malposition directly. This pilot study aims to evaluate the anatomical feasibility and kinematic behavior of a subtalar ligament reconstruction in PCFD., Methods: Three-dimensional surface model from 10 healthy ankles were produced. A total of 1089 different potential ligament courses were evaluated in a standardized manner. A motion of inversion/eversion and talar internal/external in relation to the calcaneus were simulated and the ligament strain, expressed as a positive length variation, for each ligament was analyzed. The optimal combination for the ligament reconstruction with increased length in internal rotation of the talus, isometric kinematic behavior in inversion/eversion, and extraarticular insertion on talus and calcaneus was selected., Results: A laterodistal orientation of the talar insertion point in respect to the subtalar joint axis and laterodistal deviation of the calcaneal insertion point presents the highest ligament lengthening in internal talar rotation (+0.56 mm [3.8% of total length]) and presented a near-isometric performance in inversion/eversion (+0.01 to -0.01 mm [0.1% of total length])., Conclusion: This kinematic model shows that a ligament reconstruction in the subtalar space presents a pattern of length variation that may stabilize the internal talar rotation without impeding the physiological subtalar motion., Clinical Relevance: This study investigates the optimal location, feasibility, and kinematic behavior of a ligament reconstruction that could help stabilize peritalar subluxation in progressive collapsing foot deformity., [Formula: see text]., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

Background: The transverse arch (TA) has recently been shown to significantly increase the intrinsic stiffness of the midfoot when coupled with the medial longitudinal arch (MLA). Progressive collapsing foot deformity (PCFD) is a complex deformity that ultimately results in a loss of stiffness and collapse of the MLA. The role of the TA has not been investigated in patients diagnosed with this disorder using weightbearing CT (WBCT). Therefore, this study aims to answer the following questions: (1) Is the curvature of the TA decreased in PCFD? (2) Where within the midfoot does TA curvature flattening happen in PCFD?, Methods: A retrospective review of weightbearing CT images was conducted for 32 PCFD and 32 control feet. The TA curvature was assessed both indirectly using previously described methods and directly using a novel measurement termed the transverse arch plantar (TAP) angle that assesses the angle formed between the first, second, and fifth metatarsals in the coronal plane. Location of TA collapse was also assessed in the coronal plane., Results: The TAP angle was significantly higher in PCFD (mean 115.2 degrees, SD 10.7) than in the control group (mean 100.8 degrees, SD 7.9) ( P  < .001). No difference was found using the calculated normalized TA curvature between PCFD (mean 17.1, SD 4.8) and controls (mean 18.3, SD 4.0) ( P  = .266). Location of collapse along the TA in PCFD was most significant at the second metatarsal and medial cuneiform., Conclusion: The TA is more collapsed in PCFD compared to controls. This collapse was most substantial between the plantar medial cuneiform and the plantar second metatarsal. This may represent a location of uncoupling of the TA and MLA., Level of Evidence: Level III, retrospective case control., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Francois Lintz, MD, MS, reports grants or contracts; consulting fees; payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events; support for attending meetings and/or travel; and stock or stock options from CurveBeam LLC. Cesar de Cesar Netto, MD, PhD, reports payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events; and stock or stock options from CurveBeam LLC. ICMJE forms for all authors are available online.

Background: Peritalar subluxation (PTS) is part of progressive collapsing foot deformity (PCFD). This study aimed to evaluate initial deformity correction and PTS optimization in PCFD patients with flexible hindfoot deformity undergoing hindfoot joint-sparing surgical procedures and its relationship with improvements in patient-reported outcome measures (PROMs) at latest follow-up. We hypothesized that significant deformity/PTS correction would be observed postoperatively, positively correlating with improved PROMs., Methods: A prospective comparative study was performed with 26 flexible PCFD patients undergoing hindfoot joint-sparing reconstructive procedures, mean age 47.1 years (range, 18-77). We assessed weightbearing computed tomography (WBCT) overall deformity (foot and ankle offset [FAO]) and PTS markers (distance and coverage maps) at 3 months, as well as PROMs at final follow-up. A multivariate regression model assessed the influence of initial deformity correction and PTS optimization in patient-reported outcomes., Results: Mean follow-up was 19.9 months (6-39), and the average number of procedures performed was 4.8 (2-8). FAO improved from 9.4% (8.4-10.9) to 1.9% (1.1-3.6) postoperatively ( P  < .0001). Mean coverage improved by 69.6% ( P  = .012), 12.1% ( P  = .0343) and 5.2% ( P  = .0074) in, respectively, the anterior, middle, and posterior facets, whereas the sinus tarsi coverage decreased by an average 57.1% ( P  < .0001) postoperatively. Improvements in patient-reported outcomes were noted for all scores assessed ( P  < .03). The multivariate regression analysis demonstrated that improvement in both FAO and PTS measurements significantly influenced the assessed PROMs., Conclusion: This study demonstrated significant improvements in the overall 3D deformity, PTS markers, and PROMs following hindfoot joint-sparing surgical treatment in patients with flexible PCFD. More importantly, initial 3D deformity correction and improvement in subtalar joint coverage and extraarticular impingement have been shown to influence PROMs significantly and positively. Addressing these variables should be considered as goals when treating PCFD., Level of Evidence: Level II, prospective cohort study., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

Background: Subluxation at the subtalar joint is one of the major radiographic features that characterize progressive collapsing foot deformity (PCFD). Although it is recognized that the cervical ligament plays an important function in maintaining the subtalar joint's stability, its role and involvement in PCFD is largely unknown. The purpose of this study was to assess the prevalence of cervical ligament insufficiency in patients with PCFD and to establish if the degree of its pathology changes with increasing axial plane deformity., Methods: This study retrospectively reviewed magnetic resonance imaging (MRI) of 78 PCFD patients and age- and gender-matched controls. The structures evaluated were the cervical, spring, and talocalcaneal interosseous ligaments. Structural derangement was graded on a 5-part scale (0-4), with grade 0 being normal and grade 4 indicating a tear of greater than 50% of the cross-sectional area. Plain radiographic parameters (talonavicular coverage angle [TNC], lateral talo-first metatarsal [Meary] angle, calcaneal pitch, and hindfoot moment arm) as well as axial plane orientation of the talus (TM-Tal) and calcaneus (TM-Calc) relative to the transmalleolar axis and talocalcaneal subluxation (Diff Calc-Tal) were correlated with the cervical ligament MRI grading system., Results: The overall distribution of the degree of cervical ligament involvement was significantly different between the PCFD and control groups ( P  < .001). MRI evidence of a tear in the cervical ligament was identified in 47 of 78 (60.3%) feet in the PCFD group, which was significantly higher than the control group (10.9%) and comparable to that of superomedial spring (43.6%) and talocalcaneal interosseous (44.9%) ligaments. Univariate ordinal logistic regression modeling demonstrated a predictive ability of TM-Calc (odds ratio [OR] 1.17, 95% CI 1.06-1.30, P  = .004), Diff Calc-Tal (OR 1.15, 95% CI 1.06-1.26, P  = .002), TNC (OR 1.08, 95% CI 1.03-1.13, P  = .003), and Meary angle (OR 1.05, 95% CI 1.02-1.10, P  = .006) in determining higher cervical ligament grade on MRI., Conclusion: This study found that cervical ligament insufficiency is more often than not associated with PCFD, and that an increasing axial plane deformity appears to be associated with a greater degree of insufficiency., Level of Evidence: Level III, case-control study., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

Background: Evans (E-LCL) and Hintermann LCL (H-LCL) lateral column lengthening osteotomies are standard surgical solutions for flexible, progressive collapsing feet. E-LCL is performed between the anterior and middle facets and endangers specific os calcis subtalar joint (OCST) subtypes without distinct facets. H-LCL is oriented between the posterior and middle facets and should be suitable for all OCSTs. Both osteotomies are associated with increased subtalar osteoarthritis, indicating iatrogenic damage. Distance mapping (DM) enables visualization of the relative distance between 2 articular surfaces represented by color patterns. This study aims to measure the safe zones for LCL using 3-dimensional (3D) models and DM; we hypothesize that it could be measured with high reproducibility., Methods: Two raters categorized 200 feet across 134 patients into OCSTs based on the Bruckner classification. Four angles were measured independently. The proximal and distal extents of the posterior safe zone (PSZ) angles were determined for H-LCL osteotomies; similarly, the proximal and distal extents of the anterior safe zone (ASZ) angles were identified for E-LCL osteotomies. Consequently, the surface available for safe osteotomies were calculated. An interclass correlation was used to assess the agreement between the 2 raters. Additionally, analysis of variance and Mann-Whitney U test were used to compare the safe zones between OCSTs., Results: The mean proximal and distal extents of the PSZ angles were 68 ± 7 and 75 ± 5 degrees from a line parallel to the lateral border of the calcaneus, respectively, and the proximal and distal extent of the ASZ angles were 89 ± 6 and 95 ± 5 degrees, respectively. There were no statistically significant differences between the OCSTs. Two raters measured the angles with good to excellent interrater and intrarater agreement. In 18 cases, we were unable to plan for H-LCL or E-LCL osteotomies., Conclusion: Distance mapping could be used to measure the safe zone, tailor a preoperative plan, and potentially reduce the risk for iatrogenic damage in LCL. 3D models and DM can increase the reliability of preoperative plans in bones with complex 3D structures., Level of Evidence: Level III, retrospective comparative study., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.

The spring ligament is one of the main stabilizers of the medial arch of the foot and the primary static supporter of the talonavicular joint. Attenuation or rupture of this ligament is thought to play a central role in the pathophysiology of progressive collapsing foot deformity. Traditional correction of flexible flatfoot consists of posterior tibial tendon augmentation along with various osteotomies or hindfoot fusions. Repair or reconstruction of the spring ligament has not been as widely pursued. In recent years, newer techniques have been explored and may improve outcomes of traditional procedures, or possibly entirely replace some osteotomies. Combined spring-deltoid ligament reconstruction is also gaining traction as a viable technique, particularly as the ankle begins to deform into valgus. This review summarizes the variety of nonanatomic and anatomic reconstruction techniques that have been described, including autologous tendon transfers, allografts, and synthetic augmentation. Although many have only been characterized in biomechanical cadaver studies, this article reviews preliminary clinical studies that have shown promising results. There is a need for more high-quality studies evaluating the clinical, radiographic, and patient-reported outcomes following spring ligament reconstruction.

Background: Spring ligament reconstruction (SLR) has been suggested as an adjunct to other reconstructive procedures to potentially avoid talonavicular joint fusion in progressive collapsing foot deformity (PCFD) with severe abduction deformity. Most clinical reports present short-term follow-up data and a small number of patients. The purpose of this study was to examine the medium- to long-term outcomes of an SLR using allograft tendon augmentation as part of PCFD surgical reconstruction. This study to our knowledge represents the largest number of patients and the longest follow-up to date., Methods: This study retrospectively reviewed 26 patients (27 feet, mean age of 61.4 years) who underwent SLR with allograft tendon as part of PCFD reconstruction. The mean follow-up of the cohort was 8 years (range, 5-13.4). Radiographic evaluation consisted of 5 parameters including talonavicular coverage angle (TNC), with the maintenance of correction being evaluated by comparing parameters from the early postoperative period (mean: 11.6 months, range, 8-17) to final follow-up. Foot and Ankle Outcome Score (FAOS) and patient satisfaction questionnaires were collected at final follow-up. Conversion to talonavicular or subtalar fusion was considered as a failure., Results: Final radiographs demonstrated successful abduction correction, with the mean TNC improving from 43.7 degrees preoperatively to 14.1 degrees postoperatively (P < .0001). All other radiographic parameters improved significantly and exhibited maintenance of the correction. All FAOS subscales showed significant improvement. Responses to the satisfaction questionnaire were received from all except 1 patient, of whom 88.5% (23/26) were satisfied with the results, 96.2% (25/26) would undergo the surgery again, and 88.5% (23/26) would recommend the surgery. Eight feet (29.6%) required painful hardware removal and 1 (3.7%) developed nonunion of the lateral column lengthening osteotomy. No patient required conversion to talonavicular or subtalar fusion., Conclusion: This study demonstrates favorable medium- to long-term outcomes following PCFD reconstruction including an SLR with allograft tendon augmentation., Level of Evidence: Level IV, case series.

Background: Progressive collapsing foot deformity (PCFD) is recognized as a 3-dimensional deformity centered around the talus. Previous studies have described some features of talar motion in the ankle mortise in PCFD, such as sagging in the sagittal plane or valgus tilt in the coronal plane. However, axial plane alignment of the talus in the ankle mortise in PCFD has not been investigated extensively. The purpose of this study was to examine this axial plane alignment of PCFD vs controls using weightbearing computed tomography (WBCT) images and to determine if talar rotation in the axial plane is associated with increased abduction deformity, as well as to assess the medial ankle joint space narrowing in PCFD that may be associated with axial plane talar rotation., Methods: Multiplanar reconstructed WBCT images of 79 patients with PCFD and 35 control patients (39 scans) were retrospectively analyzed. The PCFD group was divided into 2 subgroups depending on preoperative talonavicular coverage angle (TNC): moderate abduction (TNC 20-40 degrees, n=57) and severe abduction (TNC >40 degrees, n=22). Using the transmalleolar (TM) axis as a reference, the axial alignment of the talus (TM-Tal), calcaneus (TM-Calc), and second metatarsal (TM-2MT) were calculated. Difference between TM-Tal and TM-Calc was calculated to examine talocalcaneal subluxation. A second method to assess talar rotation within the mortise utilized an angle between the lateral malleolus and the talus (LM-Tal) in the axial slices of WBCT. In addition, the prevalence of medial tibiotalar joint space narrowing was assessed. These parameters were compared between the control and PCFD groups, and between moderate and severe abduction groups., Results: The talus was significantly more internally rotated with respect to the ankle TM axis and the lateral malleolus in PCFD patients compared to controls, and in the severe abduction group compared with the moderate abduction group, using both measurement methods. Axial calcaneal orientation did not differ between groups. There was significantly greater axial talocalcaneal subluxation in the PCFD group, and this was also greater in the severe abduction group. The prevalence of medial joint space narrowing was higher in PCFD patients., Conclusion: Our findings suggest that talar malrotation in the axial plane should be considered an underlying feature of abduction deformity in PCFD. The malrotation occurs in both the talonavicular and ankle joints. This rotational deformity should be corrected at the time of reconstructive surgery, especially in cases of severe abduction deformity. In addition, medial ankle joint narrowing was observed in PCFD patients, with a higher prevalence of medial ankle joint narrowing in those with severe abduction., Level of Evidence: Level III, case-control study.

Background: Progressive collapsing foot deformity (PCFD) is a complex pathology associated with tendon insufficiency, ligamentous failure, joint malalignment, and aberrant plantar force distribution. Existing knowledge of PCFD consists of static measurements, which provide information about structure but little about foot and ankle kinematics during gait. A model of PCFD was simulated in cadavers (sPCFD) to quantify the difference in joint kinematics and plantar pressure between the intact and sPCFD conditions during simulated stance phase of gait., Methods: In 12 cadaveric foot and ankle specimens, the sPCFD condition was created via sectioning of the spring ligament and the medial talonavicular joint capsule followed by cyclic axial compression. Specimens were then analyzed in intact and sPCFD conditions via a robotic gait simulator, using actuators to control the extrinsic tendons and a rotating force plate underneath the specimen to mimic the stance phase of walking. Force plate position and muscle forces were optimized using a fuzzy logic iterative process to converge and simulate in vivo ground reaction forces. An 8-camera motion capture system recorded the positions of markers fixed to bones, which were then used to calculate joint kinematics, and a plantar pressure mat collected pressure distribution data. Joint kinematics and plantar pressures were compared between intact and sPCFD conditions., Results: The sPCFD condition increased subtalar eversion in early, mid-, and late stance ( P < .05), increased talonavicular abduction in mid- and late stance ( P < .05), and increased ankle plantarflexion ( P < .05), adduction ( P < .05), and inversion ( P < .05). The center of plantar pressure was significantly ( P < .01) medialized in this model of sPCFD and simulated stance phase of gait., Discussion: Subtalar and talonavicular joint kinematics and plantar pressure distribution significantly changed with the sPCFD and in the directions expected from a PCFD foot. We also found that ankle joint kinematics changed with medial and plantar drift of the talar head, indicating abnormal talar rotation. Although comparison to an in vivo PCFD foot was not performed, this sPCFD model produced changes in foot kinematics and indicates that concomitant abnormal changes may occur at the ankle joint with PCFD., Clinical Relevance: This study describes the dynamic kinematic and plantar pressure changes in a cadaveric model of simulated progressive collapsing foot deformity during simulated stance phase.

Background: There has been concern about lateral prominence pain at the osteotomy site following medial displacement calcaneal osteotomy (MDCO). However, no study has investigated this complication. This study aimed to investigate the incidence of lateral prominence pain following MDCO and examine the efficacy of crushplasty as a surgical technique to minimize this complication., Methods: This was a retrospective cohort study in which 137 patients (148 feet) who underwent MDCO were divided into 2 groups by whether they had concurrent crushplasty at the time of MDCO (crushplasty [n = 81] vs noncrushplasty group [n = 67]). Crushplasty was performed by flattening the bony step-off using a rongeur and bone impactor. Lateral prominence pain was defined as pain or irritating symptoms over the osteotomy site that persisted over 12 months after MDCO. The overall incidence of lateral prominence pain after MDCO and within each group was investigated. Multiple logistic regression analysis was used to determine the influence of possible risk factors on the development of postoperative lateral prominence pain., Results: The overall incidence of lateral prominence pain was 9.5% (14 of 148): 3.4% (3 of 87) in the crushplasty group, and 18% (11 of 61) in the noncrushplasty group, and χ 2 analysis showed a statistically significant relationship between crushplasty and lateral prominence pain ( P < .05). A relationship between the amount of medial displacement and the development of lateral prominence pain was observed in the noncrushplasty group (OR = 5.31, 95% CI 2.35-16.4, P < .05), but this was not observed in the crushplasty group ( P = .641). The amount of medial displacement was an independent risk factor for the development of lateral prominence pain (OR = 2.72, 95% CI 1.54-4.79, P < .05), and concurrent crushplasty had a negative relationship with lateral prominence pain development (OR = 0.12, 95% CI 0.03-0.57, P < .05)., Conclusion: This study revealed that lateral prominence pain is a significant complication of MDCO, especially in the setting of a larger displacement. The crushplasty following MDCO may minimize this complication, particularly when a greater degree of hindfoot correction is attempted.

Background: Lateral bony impingement is a major cause of lateral foot pain in progressive collapsing foot deformity (PCFD). Weightbearing computed tomography (WBCT) provides better sensitivity than standard radiographs for detecting impingement. However, many orthopaedic centers have not yet acquired WBCT imaging. This study aimed to (1) investigate the correlation of common radiographic parameters measured on standard weightbearing radiographs with talocalcaneal and calcaneofibular distance assessed with WBCT and (2) establish radiographic cutoff values to detect bony impingement as identified on WBCT., Methods: Ninety-one patients treated for PCFD with standard preoperative radiographs and WBCT were identified. Patients with asymmetric ankle arthritis (talar tilt >2 degrees) were excluded. The talocalcaneal distance at the sinus tarsi and calcaneofibular distance were measured in multiplanar reconstructed WBCT images. Impingement was defined as direct abutment between bones. The relationships between WBCT measurements and 4 common parameters (talonavicular coverage angle [TNC], talo-first metatarsal angle, calcaneal pitch, and hindfoot moment arm [HMA]) in standard radiographs were assessed with Pearson correlations. Receiver operating characteristic curve analysis evaluated the ability of radiographic cutoffs to detect sinus tarsi or calcaneofibular bony impingement, and the area under curve (AUC), sensitivity, specificity, negative and positive predictive value (PPV) were calculated., Results: Talocalcaneal distance narrowing at the sinus tarsi strongly correlated with TNC ( r = 0.64, P < .001), and the calcaneofibular distance narrowing correlated with the HMA moderately yet best among the parameters ( r = 0.55, P < .001). TNC (AUC = 0.837, 95% CI 0.745-0.906) and HMA (AUC=0.959, 95% CI 0.895-0.989) provided the best predictive ability for sinus tarsi and calcaneofibular bony impingement, respectively. A TNC threshold of 41.2 degrees had a 100% PPV for predicting sinus tarsi impingement, whereas an HMA threshold of 38.1 mm had a 100% PPV for calcaneofibular impingement., Conclusion: This study provides evidence that TNC and HMA measurements made on standing radiographs could be used to indicate potential lateral bony impingement in PCFD. Narrowing of talocalcaneal distance best correlated with abduction deformity of the foot, and the narrowing of calcaneofibular distance was best correlated with valgus hindfoot deformity., Level of Evidence: Level III, case control study.

Background: Reconstruction of progressive collapsing foot deformity (PCFD) with ankle instability (PCFD class E) remains a substantial challenge to orthopaedic surgeons. We report the outcomes of PCFD class E treated by means of a relatively standard PCFD foot reconstruction approach with the addition of a supramalleolar lateral opening-wedge osteotomy., Methods: We conducted a retrospective study of 13 patients (15 ankles) who underwent this procedure for PCFD class E between 2010 and 2021. Mean follow-up time was 3.8 (range, 2-6.3) years. Clinical assessment was based on the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale as well as a Self-Administered Foot Evaluation Questionnaire (SAFE-Q). Radiographic assessments, including identification of the mechanical ankle joint axis point and a modified valgus Takakura-Tanaka osteoarthritis grade, were recorded., Results: The mean JSSF score improved significantly from 45.2 preoperatively to 83.9 postoperatively ( P < .001). SAFE-Q scores at the final follow-up were 70.1 for the pain and pain-related subscale, 75.4 for the physical functioning and daily living subscale, 83.0 for the social functioning subscale, 74.4 for the shoe-related subscale, and 78.1 for the general health and well-being subscale. Radiographic measurements showed improvement in the tibiotalar tilt angle (average improvement: 5.4 degrees); orientation of the talus joint line relative to the ground (average improvement: 14.0 degrees); anteroposterior talus-first metatarsal angle (average improvement: 11.2 degrees), talonavicular coverage angle (average improvement: 21.6 degrees), and lateral talus-first metatarsal angle (average improvement: 17.0 degrees). Postoperatively, the mechanical ankle joint axis point moved medially for all patients and into the medial half of the ankle joint for 7 patients. The modified osteoarthritis stage improved postoperatively in most cases., Conclusion: In this select and relatively small group of patients who had a supramalleolar lateral opening-wedge osteotomy combined with PCFD reconstruction, we measured general improvement in JSSF scores and radiographic variables. Long-term durability of the procedure remains unknown. This procedure may be an option for preserving the ankle joint in treatment of PCFD class E with osteoarthritis of the ankle., Level of Evidence: Level IV, therapeutic.

Background: Digitally reconstructed radiographs (DRRs) generated from weightbearing computed tomography (WBCT) may potentially substitute for weightbearing plain radiographs (XRs) but have not been clinically validated. This study aims to test the reliability of 6 radiographic parameters of progressive collapsing foot deformity (PCFD) as measured on DRR, to investigate whether DRR represents comparably to XR through the same measurements, and to compare agreement of DRR and XR measurements of a standardized arch height parameter with reference measurements made on WBCT., Methods: DRR generated from preoperative WBCT of 71 patients (72 feet) treated surgically for PCFD were retrospectively compared with preoperative weight-bearing XR after exclusion criteria were applied. Six radiographic measurements were performed, including Meary angle, calcaneal pitch (CPA), medial cuneiform height (MCH), AP talar-first metatarsal angle (T-1MT), talonavicular coverage (TNCA), and talar incongruency (TIA). Arch height was measured on XR, DRR, and WBCT using a validated, standardized, navicular-based index. Intraclass correlation coefficients assessed DRR intraobserver and interobserver reliability. Paired samples t tests tested differences between XR and DRR. Bland-Altman limits of agreement analysis compared DRR and XR agreement with WBCT measurements., Results: Measurements were within standard PCFD ranges on XR and DRR. All measurements demonstrated excellent intrarater reliability and good to excellent interrater agreement, consistent with previous literature on XR. No differences were found for Meary, CPA, or TNCA. Minor differences were observed for MCH, T-1MT, and TIA. DRR measurements demonstrated greater agreement with WBCT than XR measurements., Conclusion: DRR from WBCT may be a promising substitute for XR in the clinical evaluation of PCFD. Radiographic measurements made on DRR demonstrated good to excellent reliability. Although small differences were found between XR and DRR for certain measurements, DRR more accurately represented medial arch anatomy compared to gold standard WBCT data than XR. If validated as a clinical substitute, DRR could eventually obviate XR where WBCT is available., Level of Evidence: Level III, retrospective cohort study.

Background: Progressive collapsing foot deformity (PCFD) is a debilitating condition encompassing several interrelated, progressive deformities requiring a combination of reconstructive procedures. Few studies investigate returns to activity following flatfoot reconstruction, and existing studies only examine 1 or 2 of the numerous procedures employed. This study aims to provide the first generalizable assessment of returns to sports and physical activity following reconstruction surgery in patients with flexible flatfoot deformity., Methods: Patients aged 18-60 years who underwent reconstructive surgery between February 16 and May 19 for symptomatic flexible-stage flatfoot deformity were identified by registry review. Eighty-two of 113 eligible patients (73%) were reached at a mean 2.9 years (range, 2.0-5.4) of follow-up with mean age at surgery of 48.9 years (range, 18-59). Returns to physical activity were evaluated with a sports-specific survey. Clinical outcomes were evaluated with Patient-Reported Outcomes Measurement Information System (PROMIS) scores., Results: Patients reported participation in 21 specific sports and activities. One-fourth (25.6%) of patients (21/82) reported increased difficulty with physical activities postoperatively, 15.9% reported equal difficulty, and 58.5% (48/82) reported decreased difficulty. Median return times were 9-12 months for participation and 12-18 months to reach maximum preoperative participation levels. Improvements in Physical Function ( P = .001), Pain Interference ( P < .001), Pain Intensity ( P <.001), and Global Physical Health ( P = .004) were associated with increased satisfaction with respect to sports and physical activities., Discussion: This study investigated participation in specific sports and physical activities following flatfoot reconstruction. Our findings suggest mixed outcomes, where many patients reported life-changing improvements but many also experienced prolonged pain and difficulty after surgery. Some patients reported increased difficulty or inability to return to their preoperative maximum level of participation, indicating that flatfoot reconstructions can lead to athletic limitations., Conclusion: Although flatfoot reconstruction can be a powerful tool to increase patients' capacity to engage in physical activity, in our cohort many patients had reduced physical activity outcomes., Level of Evidence: Level IV, retrospective case series.

Background: In progressive collapsing foot deformity (PCFD), hind- and midfoot deformities can be hard to characterize based on weightbearing plain radiography. Semiautomated 3-dimensional (3D) measurements derived from weightbearing computed tomography (WBCT) scans may provide a more accurate deformity assessment. In the present study, automated 3D measurements based on WBCT were used to compare hindfoot alignment of healthy individuals to patients with PCFD., Methods: The WBCT scans of 20 patients treated at our institution with either a flexible (N = 10) or rigid (N = 10) PCFD were compared with the WBCT scans of a control group of 30 healthy individuals. Using semiautomated image analysis software, from each set of 3D voxel images, we measured the talar tilt (TT), hindfoot moment arm (HMA), talocalcaneal angle (TCA; axial/lateral), talonavicular coverage (TNC), and talocalcaneal overlap (TCO). The presence of medial facet subluxation as well as sinus tarsi/subfibular impingement was additionally assessed., Results: With the exception of the TCA (axial/lateral), the analyzed measurements differed between healthy individuals and patients with PCFD. The TCA axial correlated with the TNC in patients with PCFD. An increased TCO combined with sinus tarsi impingement raised the probability of predicting a deformity as rigid., Conclusion: Using 3D measurements, in this relatively small cohort of patients, we identified relevant variables associated with a clinical presentation of flexible or rigid PCFD. An increased TCO combined with sinus tarsi impingement raised the probability of predicting a deformity as rigid. Such WBCT-based markers possibly can help the surgeon in decision-making regarding the appropriate surgical strategy (eg, osteotomies vs realignment arthrodesis). However, prospective studies are necessary to confirm the utility of the proposed parameters in the treatment of PCFD., Level of Evidence: Level III, case-control study.

Background: The Evans calcaneal lengthening osteotomy procedure is widely used for correcting progressive collapsing foot deformity. However, it can result in overcorrection and degenerations of the calcaneocuboid joint. Different shapes of graft have been used in the Evans calcaneal osteotomy, but potential differences in their biomechanical effects is still unclear. The present study was designed to explore the biomechanical effects of graft shape and improve the Evans procedure to avoid or minimize detrimental effects., Methods: Twelve patient-specific finite element models were established and validated. A triangular or rectangular wedge of varying size was inserted at the lateral edge of calcaneus, and the degree of correction was quantified. The stress in spring ligaments and plantar fascia and the contact characteristics of the talonavicular and calcaneocuboid joints were calculated and compared accordingly., Results: The rectangular graft provided a much higher degree of correction than triangular grafts did. However, the contact characteristics of the calcaneocuboid joint and talonavicular joint were abnormal, with clear sensitivity to increased graft size, and the modeled strain of the spring ligament increased., Conclusion: The finite element analysis predicts that the rectangular grafts provide a higher degree of correction, but risks overcorrection compared with triangular grafts. The triangular graft may have a lower degree of disturbance to the biomechanical behaviors of the midtarsal joint., Clinical Relevance: The model shows that both the shape and size of an Evans osteotomy bone wedge can have effects on the contiguous joints and ligamentous structures. Those effects should be considered when selecting a bone wedge for an Evans calcaneal osteotomy., Level of Evidence: Level III, case-control study.

Background: Progressive collapsing foot deformity (PCFD), formerly termed adult-acquired flatfoot deformity , is a complex 3-dimensional (3D) deformity of the foot characterized by peritalar subluxation (PTS). PTS is typically measured at the posterior facet, but recent studies have called this into question. The objective of this study was to use 3D distance mapping (DM) from weightbearing computed tomography (WBCT) to assess PTS in patients with PCFD and controls. We hypothesized that DMs would identify the middle facet as a superior marker for PTS., Methods: We analyzed WBCT data of 20 consecutive stage I patients with PCFD and 10 control patients with a novel DM technique to objectively characterize joint coverage across the entire peritalar surface, including both articular and nonarticular regions. Joint coverage was defined as the percentage of articular area with DMs <4 mm and impingement when distances were <0.5 mm. Comparisons were performed with independent t tests or Wilcoxon tests. P values <.05 were considered significant., Results: Overall, coverage was decreased in articular regions and impingement was increased in nonarticular regions of patients with PCFD with a significant increase in uncoverage in the middle (46.6%, P < .001) but not anterior or posterior facets. Significant increases in sinus tarsi coverage were identified (98.0%, P < .007) with impingement in 6 of 20 patients with PCFD. Impingement of the subfibular region was noted in only 1 of 20 cases but narrowing greater than 2 standard deviations was noted in 17 of 20 patients., Conclusion: Objective DMs identified significant markers of PTS in the middle but not posterior or anterior facets. We confirmed prior 2-dimensional data that suggested uncoverage of the middle facet provided a more robust and consistent measure of PTS than measures in the posterior facet., Level of Evidence: Level III, case-control study.

Background: Previous studies have demonstrated that procedure-specific thresholds using preoperative patient-reported outcome scores may be used to predict postoperative outcomes. The primary purpose of this study was to determine if preoperative Patient-Reported Outcomes Measurement Information System (PROMIS) thresholds could be used to predict which patients would clinically improve at 2 years postoperatively following reconstruction of their flexible adult-acquired flatfoot deformity (AAFD)., Methods: PROMIS physical function, pain interference, and depression scores were prospectively collected preoperatively and at a minimum of 2 years postoperatively for 75 feet with flexible AAFD. Minimal clinically important differences (MCIDs) were calculated to establish significant postoperative improvement. Receiver operating characteristic curves and area under the curve analyses were employed to determine whether preoperative PROMIS scores could be used to predict postoperative outcomes., Results: The PROMIS physical function receiver operating characteristic curve analysis (area under the curve = 0.913, P < .001) found that a preoperative PROMIS physical function score greater than 45.7 resulted in a 14.3% probability of achieving the MCID, whereas a preoperative score of less than 40.8 had a 97.7% probability of achieving the MCID. A preoperative PROMIS pain interference score (area under the curve = 0.799, P < .001) less than 54.1 had only a 23.1% probability of achieving the MCID at 2 years postoperatively., Conclusions: Preoperative PROMIS physical function and pain interference scores could be used to predict postoperative improvement in patients with flexible AAFD. These results may help surgeons counsel patients regarding the anticipated benefit of surgery., Level of Evidence: Level III, retrospective comparative series.

Background: Progressive collapsing foot deformity (PCFD) is a progressive hindfoot and midfoot deformity causing pain and disability. Although operative treatment is stage dependent, few studies have looked at patient-reported and radiographic outcomes stratified by primary vs revision stage II, III, and IV reconstruction surgery. Our goal was to assess operative improvement using Patient-Reported Outcomes Measurement Information System (PROMIS) and to determine whether radiographic parameter improvement correlates with patient-reported outcomes., Methods: PROMIS Physical Function (PF) and Pain Interference (PI) scores were prospectively obtained on 46 consecutive patients who underwent PCFD reconstruction between November 2013 and January 2019. Thirty-six patients completed pre- and postoperative PROMIS surveys, 6 patients completed only preoperative PROMIS surveys, and 4 patients completed 12-month postoperative PROMIS surveys but did not complete preoperative PROMIS surveys. Minimum follow-up was 12 (average, 23) months. Radiographic correction was measured with pre- and postoperative weightbearing radiographs and correlated with PROMIS scores. Measurements included the talonavicular uncoverage angle, talonavicular uncoverage percentage, anteroposterior talo-first metatarsal angle, Meary angle, medial cuneiform height (MCH), and medial cuneiform-fifth metatarsal height., Results: For the overall cohort, PROMIS PF increased significantly from 37.5±5.6 to 42.3±7.1 ( P = .0014). PROMIS PI improved significantly from 64.5±6.0 to 55.1±9.8 ( P < .0001). Preoperative, postoperative, and change in PROMIS scores were not statistically different between PCFD stages. Change in PROMIS PI was significantly greater in primary (-12.3) vs revision (-3.7) surgery ( P = .0157). Change in PROMIS PF was greater in primary (+6.0) vs revision surgery (+2.3) but did not reach statistical significance. All radiographic measurements improved significantly ( P < .05). In primary stage II PCFD, postoperative PROMIS scores correlated with postoperative MCH (PF: r = 0.7725, P = .0020; PI: r = -0.5692, P = .0446)., Conclusion: Patient-reported and radiographic outcomes improved significantly after PCFD reconstruction. We found no significant difference in preoperative, postoperative, or change in PROMIS scores between PCFD stages. However, stage III patients had smaller improvements in PROMIS PF, which we feel may be secondary to change in function after arthrodesis. Primary operations had better patient-reported outcomes compared to revision operations. In primary stage II PCFD, reconstructing the medial arch height correlated significantly with improvement in pain and functionality., Level of Evidence: Level II, prospective cohort study., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2021.)

Recommendation: Forefoot varus is a physical and radiographic examination finding associated with the Progressive Collapsing Foot Deformity (PCFD). Varus position of the forefoot relative to the hindfoot is caused by medial midfoot collapse with apex plantar angulation of the medial column. Some surgeons use the term forefoot supination to describe this same deformity (see Introduction section with nomenclature). Correction of this deformity is important to restore the weightbearing tripod of the foot and help resist a recurrence of foot collapse. When the forefoot varus deformity is isolated to the medial metatarsal and medial cuneiform, correction is indicated with an opening wedge medial cuneiform (Cotton) osteotomy, typically with interposition of an allograft bone wedge from 5 to 11 mm in width at the base. When the forefoot varus is global, involving varus angulation of the entire forefoot and midfoot relative to the hindfoot, other procedures are needed to adequately correct the deformity., Level of Evidence: Level V, consensus, expert opinion.

Recommendation: There is evidence indicating that the amount of bony correction performed in the setting of progressive collapsing foot deformity reconstructive surgery can be titrated within a recommended range for a variety of procedures. The typical range when performing a medial displacement calcaneal osteotomy should be 7 to 15 mm of medialization of the tuberosity. The typical range when performing an Evans lateral column lengthening should be 5 to 10 mm of a laterally based wedge in the anterior calcaneus. The typical range when performing a plantarflexion opening wedge osteotomy of the medial cuneiform (Cotton) osteotomy should be 5 to 10 mm of a dorsal wedge., Level of Evidence: Level V, consensus, expert opinion.

Recommendation: The historical nomenclature for the adult acquired flatfoot deformity (AAFD) is confusing, at times called posterior tibial tendon dysfunction (PTTD), the adult flexible flatfoot deformity, posterior tibial tendon rupture, peritalar instability and peritalar subluxation (PTS), and progressive talipes equinovalgus. Many but not all of these deformities are associated with a rupture of the posterior tibial tendon (PTT), and some of these are associated with deformities either primarily or secondarily in the midfoot or ankle. There is similar inconsistency with the use of classification schemata for these deformities, and from the first introduced by Johnson and Strom (1989), and then modified by Myerson (1997), there have been many attempts to provide a more comprehensive classification system. However, although these newer more complete classification systems have addressed some of the anatomic variations of deformities encountered, none of the above have ever been validated. The proposed system better incorporates the most recent data and understanding of the condition and better allows for standardization of reporting. In light of this information, the consensus group proposes the adoption of the nomenclature "Progressive Collapsing Foot Deformity" (PCFD) and a new classification system aiming at summarizing recent data published on the subject and to standardize data reporting regarding this complex 3-dimensional deformity., Level of Evidence: Level V, consensus, expert opinion., Consensus Statements Voted: CONSENSUS STATEMENT ONE: We will rename the condition to Progressive Collapsing Foot Deformity (PCFD), a complex 3-dimensional deformity with varying degrees of hindfoot valgus, forefoot abduction, and midfoot varus.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus) CONSENSUS STATEMENT TWO: Our current classification systems are incomplete or outdated.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus) CONSENSUS STATEMENT THREE: MRI findings should be part of a new classification system.Delegate vote: agree, 33% (3/9); disagree, 67% (6/9); abstain, 0%.(Weak negative consensus) CONSENSUS STATEMENT FOUR: Weightbearing CT (WBCT) findings should be part of a new classification system.Delegate vote: agree, 56% (5/9); disagree, 44% (4/9); abstain, 0%.(Weak consensus) CONSENSUS STATEMENT FIVE: A new classification system is proposed and should be used to stage the deformity clinically and to define treatment.Delegate vote: agree, 89% (8/9); abstain, 11% (1/9).(Strong consensus).

Recommendation: Progressive collapsing foot deformity (PCFD) is a complex 3D deformity with varying degrees of hindfoot valgus, forefoot abduction, and midfoot supination. Although a medial displacement calcaneal osteotomy can correct heel valgus, it has far less ability to correct forefoot abduction. More severe forefoot abduction, most frequently measured preoperatively by assessing talonavicular coverage on an anteroposterior (AP) weightbearing conventional radiographic view of the foot, can be more effectively corrected with a lateral column lengthening procedure than by other osteotomies in the foot. Care must be taken intraoperatively to not overcorrect the deformity by restricting passive eversion of the subtalar joint or causing adduction at the talonavicular joint on simulated AP weightbearing fluoroscopic imaging. Overcorrection can lead to lateral column overload with persistent lateral midfoot pain. The typical amount of lengthening of the lateral column is between 5 and 10 mm., Level of Evidence: Level V, consensus, expert opinion., Consensus Statement One: Lateral column lengthening (LCL) procedure is recommended when the amount of talonavicular joint uncoverage is above 40%. The amount of lengthening needed in the lateral column should be judged intraoperatively by the amount of correction of the uncoverage and by adequate residual passive eversion range of motion of the subtalar joint.Delegate vote: agree, 78% (7/9); disagree, 11% (1/9); abstain, 11% (1/9).(Strong consensus)., Consensus Statement Two: When titrating the amount of correction of abduction deformity intraoperatively, the presence of adduction at the talonavicular joint on simulated weightbearing fluoroscopic imaging is an important sign of hypercorrection and higher risk for lateral column overload.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus)., Consensus Statement Three: The typical range for performing a lateral column lengthening is between 5 and 10 mm to achieve an adequate amount of talonavicular coverage.Delegate vote: agree, 100% (9/9); disagree, 0%; abstain, 0%.(Unanimous, strongest consensus).

Recommendation: In the treatment of progressive collapsing foot deformity (PCFD), the combination of bone shape, soft tissue failure, and host factors create a complex algorithm that may confound choices for operative treatment. Realignment and balancing are primary goals. There was consensus that preservation of joint motion is preferred when possible. This choice needs to be balanced with the need for performing joint-sacrificing procedures such as fusions to obtain and maintain correction. In addition, a patient's age and health status such as body mass index is important to consider. Although preservation of motion is important, it is secondary to a stable and properly aligned foot., Level of Evidence: Level V, consensus, expert opinion.

Recommendation: There is evidence that the use of WEIGHTBEARING imaging aids in the assessment of progressive collapsing foot deformity (PCFD). The following WEIGHTBEARING conventional radiographs (CRs) are necessary in the assessment of PCFD patients: anteroposterior (AP) foot, AP or mortise ankle, and lateral foot. If available, a hindfoot alignment view is strongly recommended. If available, WEIGHTBEARING computed tomography (CT) is strongly recommended for surgical planning. When WEIGHTBEARING CT is obtained, important findings to be assessed are sinus tarsi impingement, subfibular impingement, increased valgus inclination of the posterior facet of the subtalar joint, and subluxation of the subtalar joint at the posterior and/or middle facet., Level of Evidence: Level V, consensus, expert opinion.

Recommendation: Peritalar subluxation represents an important hindfoot component of progressive collapsing foot deformity, which can be associated with a breakdown of the medial longitudinal arch. It results in a complex 3-dimensional deformity with varying degrees of hindfoot valgus, forefoot abduction, and pronation. Loss of peritalar stability allows the talus to rotate and translate on the calcaneal and navicular bone surfaces, typically moving medially and anteriorly, which may result in sinus tarsi and subfibular impingement. The onset of degenerative disease can manifest with stiffening of the subtalar (ST) joint and subsequent fixed and possibly arthritic deformity. While ST joint fusion may permit repositioning and stabilization of the talus on top of the calcaneus, it may not fully correct forefoot abduction and it does not correct forefoot varus. Such varus may be addressed by a talonavicular (TN) fusion or a plantar flexion osteotomy of the first ray, but, if too pronounced, it may be more effectively corrected with a naviculocuneiform (NC) fusion. The NC joint has a curvature in the sagittal plane. Thus, preserving the shape of the joint is the key to permitting plantarflexion correction by rotating the midfoot along the debrided surfaces and to fix it. Intraoperatively, care must be also taken to not overcorrect the talocalcaneal angle in the horizontal plane during the ST fusion (eg, to exceed the external rotation of the talus and inadvertently put the midfoot in a supinated position). Such overcorrection can lead to lateral column overload with persistent lateral midfoot pain and discomfort. A contraindication for an isolated ST fusion may be a rupture of posterior tibial tendon because of the resultant loss of the internal rotation force at the TN joint. In these cases, a flexor digitorum longus tendon transfer is added to the procedure., Level of Evidence: Level V, consensus, expert opinion.

Recommendation: There is evidence that the medial displacement calcaneal osteotomy (MDCO) can be effective in treating the progressive collapsing foot deformity (PCFD). This juxta-articular osteotomy of the tuberosity shifts the mechanical axis of the calcaneus from a more lateral position to a more medial position, which provides mechanical advantage in the reconstruction for this condition. This also shifts the action of the Achilles tendon medially, which minimizes the everting deforming effect and improves the inversion forces. When isolated hindfoot valgus exists with adequate talonavicular joint coverage (less than 35%-40% uncoverage) and a lack of significant forefoot supination, varus, or abduction, we recommend performing this osteotomy as an isolated bony procedure, with or without additional soft tissue procedures. The clinical goal of the hindfoot valgus correction is to achieve a clinically neutral heel, as defined by a vertical axis from the heel up the longitudinal axis of the Achilles tendon and distal aspect of the leg. The typical range when performing a MDCO, while considering the location and rotation of the osteotomy, is 7 to 15 mm of correction., Level of Evidence: Level V, consensus, expert opinion.