Prevalence and pattern of lateral impingements in the progressive collapsing foot deformity.

INTRODUCTION: The prevalence of lateral bony impingements [i.e., Sinus Tarsi (STI), Talo-Fibular (TFI) and Calcaneo-Fibular (CFI)] and their association with Peritalar Subluxation (PTS) have not been clearly established for progressive collapsing foot deformity (PCFD).This study aims to assess the prevalence of STI, TFI and CFI in PCFD, in addition to their association with PTS. We hypothesized that STI and TFI would be more prevalent than CFI. MATERIALS AND METHODS: Seventy-two continuous symptomatic PCFD cases were retrospectively reviewed. Weightbearing computed tomography (WBCT) was used to assess lateral impingements and classified as STI, TFI and CFI. PTS was assessed by the percent of uncovered and the incongruence angle of the middle facet, and the overall foot deformity was determined by the foot and ankle offset (FAO). Data were collected by two fellowship-trained independent observers. RESULTS: Intra-observer and inter-observer reliabilities for impingement assessment ranged from substantial to almost perfect. STI was present in 84.7%, TFI in 65.2% and CFI in 19.4%. PCFD with STI showed increased middle facet uncoverage (p = 0.0001) and FAO (p = 0.0008) compared to PCFD without STI. There were no differences in FAO and middle facet uncoverage in PCFD with TFI and without TFI. PCFD with CFI was associated with STI in 100% of cases. PCFD with CFI showed decreased middle facet incongruence (p = 0.04) and higher FAO (p = 0.006) compared to PCFD without CFI. CONCLUSIONS: STI and TFI were more prevalent than CFI in PCFD. However, only STI was associated with PTS. Conversely, CFI was associated with less PTS, suggesting a different pathological mechanism which could be a compensatory subtalar behavior caused by deep layer failure of the deltoid ligament and talar tilt.

A comparison between the Bluman et al. and the progressive collapsing foot deformity classifications for flatfeet assessment.

INTRODUCTION: Bluman et al., flatfoot classification is based on posterior tibial tendon (PTT) dysfunction leading to a chronological appearance of several foot deformities. An expert consensus recently proposed a new classification named Progressive Collapsing Foot Deformity (PCFD) in which the focus was shifted to five different independent foot and ankle deformities and their flexibility or rigidity. The aim of this study was to compare Bluman and PCFD classifications. We hypothesize that both classifications will be reliable and that the PCFD classification will allow a larger distribution of the different types of foot deformity. MATERIALS AND METHODS: We performed a retrospective IRB-approved study including 92 flatfeet. Three foot and ankle surgeons reviewed patient files and radiographs to classify each foot using both classifications. Bluman classification was performed one time as initially described and a second time after removing the Angle of Gissane sclerosis sign. Interobserver reliabilities were determined with Fleiss' kappa values. RESULTS: Interobserver reliabilities of Bluman and PCFD classifications were, respectively, substantial 0.67 and moderate 0.55. PCFD Class C and D reliabilities were, respectively, slight 0.07 and fair 0.28. The 276 readings were spread into 10 substages in Bluman and 65 subclasses in PCFD. The progressivity of the Bluman classification prevented the combination of flexible hindfoot valgus (II Bluman, 1A PCFD), midfoot abduction (IIB, 1B) and medial column instability (IIC, 1C) which was frequent in our study (112/276 readings, 40.6%). By removing the Angle of Gissane sclerosis sign from the Bluman classification, the prevalence of stage III decreased from 44.2 to 10.1%. CONCLUSIONS: Bluman and PCFD classifications were reliable. The PCFD classification showed a larger distribution of different types of flatfeet but Classes C and D need better definition. The progressivity of Bluman classification causes inconsistencies and Gissane angle sclerosis sign is inappropriately used and might lead to incorrect surgical indications.

Early results and complication rate of the LapiCotton procedure in the treatment of medial longitudinal arch collapse: a prospective cohort study.

INTRODUCTION: Instability/collapse of the medial column has been associated with many conditions, particularly progressive collapsing foot deformity (PCFD), hallux valgus (HV), and midfoot arthritis (MA). Restoration of first ray length and sagittal plane alignment to restore the foot tripod is essential when treating these deformities. This study aimed to assess early results, healing, and complication rate of a distraction dorsal opening plantarflexion wedge allograft first tarsometatarsal joint fusion (LapiCotton Procedure) in patients with collapse/instability of the medial column. METHODS: In this prospective cohort study, we included PCFD, HV, and MA patients that underwent a LapiCotton procedure. Fusion site healing was defined by > 50% bone bridging in both interfaces between allograft wedge and host bone using weight-bearing computed tomography (WBCT) after 3 months. First ray collapse radiographic correction and minor and major complications (deep dehiscence, deep infection, and reoperation) were assessed. RESULTS: A total of 22 patients (22 feet) were included (11 PCFD, 6 MA, and 5 of HV patients). Mean follow-up was 5.9 months (range 3-12) and median allograft size was 8 mm (range 5-19 mm). Bone healing was observed in 91% of cases. Two minor complications (9%, both superficial dehiscence) and one major complication (4.5%, deep infection) were observed. Statistically significant improvement of the sagittal plane talus-first metatarsal angle was observed, with mean improvement of 9.4° (95% CI 6.7-12.1°; p < 0.0001). CONCLUSION: In this prospective cohort study of 22 patients treated with the LapiCotton procedure for medial longitudinal arch collapse/instability, we observed a low complication rate (9% minor, 4.5% major), high healing rate after 3 months (91%), one clinically stable radiographic non-union (4.5%) and one unstable non-union (4.5%) needing reoperation. Our results demonstrate promising initial results for LapiCotton technique in treating collapse of the medial longitudinal arch in patients with PCFD, MA and HV deformities. Long-term results are needed to confirm these promising results. LEVEL OF EVIDENCE: Level II, prospective cohort study.

Diagnostic accuracy of measurements in progressive collapsing foot deformity using weight bearing computed tomography: A matched case-control study.

BACKGROUND: We aimed to investigate the diagnostic accuracy of known two-dimensional (2D) and three-dimensional (3D) measurements for Progressive Collapsing Foot Deformity (PCFD) in weight-bearing computed tomography (WBCT). We hypothesized that 3D biometrics would have better specificity and sensitivity for PCFD diagnosis than 2D measurements. METHODS: This was a retrospective case-control study, including 28 PCFD feet and 28 controls matched for age, sex and Body Mass Index. Two-dimensional measurements included: axial and sagittal talus-first metatarsal angles (TM1A and TM1S), talonavicular coverage angle (TNCA), forefoot arch angle (FFAA), middle facet incongruence angle (MF°) and uncoverage percentage (MF%). The 3D Foot Ankle Offset (FAO) was obtained using dedicated semi-automatic software. Intra and interobserver reliabilities were assessed. Receiver Operating Characteristic (ROC) curves were calculated to determine diagnostic accuracy (Area Under the Curve (AUC)), sensitivity and specificity. RESULTS: In PCFD, mean MF% and MF° were respectively 47.2% ± 15.4 and 13.3° ± 5.3 compared with 13.5% ± 8.7 and 5.6° ± 2.9 in controls (p < 0.001). The FAO was 8.1% ± 3.8 in PCFD and 1.4% ± 1.7 in controls (p < 0.001). AUCs were 0.99 (95%CI, 0.98-1) for MF%, 0.96 (95%CI, 0.9-1) for FAO, 0.90 (95%CI, 0.81-0.98) for MF°. For MF%, a threshold value equal or greater than 28.7% had a sensitivity of 100% and specificity of 92.8%. Conversely, a FAO value equal or greater than 4.6% had a specificity of 100% and a sensitivity of 89.2%. All other 2D measurements were significantly different in PCFD and controls (p < 0.001). CONCLUSIONS: MF% and FAO were both accurate measurements for PCFD. MF% demonstrated slightly better specificity. FAO better sensitivity. A combination of threshold values of 28.7% for MF% and 4.6% for FAO yielded 100% sensitivity and specificity.

Does tibialis posterior dysfunction correlate with a worse radiographic overall alignment in progressive collapsing foot deformity? A retrospective study.

BACKGROUND: Posterior Tibial Tendon (PTT) dysfunction is considered to have an important role in Progressive Collapsing Foot Deformity (PCFD). The objective of our study was to assess the relationship between PTT status and three-dimensional foot deformity in PCFD. METHODS: Records from 25 patients with PCFD were included for analysis. The PTT was considered deficient in patients with a positive single heel rise test or a deficit in inversion strength. Three-dimensional foot deformity was assessed using the Foot and Ankle Offset (FAO) from Weight-Bearing-CT imaging. Hindfoot valgus, midfoot abduction and medial longitudinal arch collapse were assessed on X-Rays using hindfoot moment arm, talonavicular coverage angle and Meary's angle respectively. Deland and Rosenberg MRI classifications were used to classify PTT degeneration. RESULTS: PCFD with PTT deficit (13/25) had a mean FAO of 7.75 + /- 3.8% whereas PCFD without PTT deficit had a mean FAO of 6.68 + /- 3.9% (p = 0.49). No significant difference was found between these groups on the hindfoot moment arm and the talonavicular coverage angle (respectively p = 0.54 and 0.32), whereas the Meary's angle was significantly higher in case of PCFD with PTT deficit (p = 0.037). No significant association was found between PTT degeneration on MRI and FAO. CONCLUSION: PCFD associated three-dimensional deformity, hindfoot valgus and midfoot abduction were not associated with PTT dysfunction. PTT dysfunction was only associated with a worse medial longitudinal arch collapse in our study. Considering our results, it does not appear that PTT is the main contributor to PCFD. LEVEL OF EVIDENCE: Level III, Retrospective Comparative Study.

Combined weightbearing CT and MRI assessment of flexible progressive collapsing foot deformity.

BACKGROUND: The objective of this study was to evaluate the correlation between Weightbearing CT (WBCT) markers of pronounced peritalar subluxation (PTS) and MRI findings of soft tissue insufficiency in patients with flexible Progressive Collapsing Foot Deformity (PCFD). We hypothesized that significant correlation would be found. METHODS: Retrospective comparative study with 54 flexible PCFD patients. WBCT and MRI variables deformity severity were evaluated, including markers of pronounced PTS, as well as soft tissue degeneration. A multiple regression analysis and partition prediction models were used to evaluate the relationship between bone alignment and soft tissue injury. P-values of less than .05 were considered significant. RESULTS: Degeneration of the posterior tibial tendon was significantly associated with sinus tarsi impingement (p = .04). Spring ligament degeneration correlated to subtalar joint subluxation (p = .04). Talocalcaneal interosseous ligament involvement was the only one to significantly correlate to the presence of subfibular impingement (p = .02). CONCLUSION: Our results demonstrated that WBCT markers of pronounced deformity and PTS were significantly correlated to MRI involvement of the PTT and other important restraints such as the spring and talocalcaneal interosseus ligaments. LEVEL OF EVIDENCE: Level III, Retrospective comparative study.

First Tarsometatarsal Alignment May Self-Correct After Triple Arthrodesis in Progressive Collapsing Foot Deformity.

BACKGROUND: Triple arthrodesis is commonly used to correct rigid progressive collapsing foot deformity (PCFD). These patients often have associated first tarsometatarsal (TMT) instability on lateral weightbearing radiographs. It has not been well established if it is necessary to add first TMT arthrodesis to adequately correct the overall deformity. This study retrospectively examined pre- and postoperative radiographs of PCFD patients with first TMT instability that were managed by triple arthrodesis alone. METHODS: All triple arthrodesis cases were searched for a single surgeon between 2013 and 2021. Inclusion criteria were patients with PCFD who underwent triple arthrodesis without first TMT joint fusion. Preoperative radiographs were examined for first TMT joint instability, demonstrated by plantar gapping of the first metatarsal-medial cuneiform angle or first metatarsal dorsal subluxation at the TMT joint. Measurement of sagittal first metatarsal-medial cuneiform angle and first metatarsal subluxation as described by King and Toolan was performed. RESULTS: Twenty patients satisfied the inclusion criteria. Six patients did not demonstrate at least 30% improvement of one or both measurements of first TMT instability postoperatively and were considered failures. Fourteen patients demonstrated correction of their first TMT joint instability. Average follow-up was 5.0 (range, 1.8-9.4) years. The first metatarsal-medial cuneiform angle improved from 3.8 to 1.1 degrees (P < .05). The first metatarsal subluxation corrected from 4.1 to 1.5 mm (P < .05). One patient showed radiographic evidence of arthritis in the first TMT joint at final follow-up. CONCLUSION: Seventy percent of patients with PCFD with asymptomatic first TMT joint instability demonstrated correction of first TMT radiographic instability with isolated triple arthrodesis. This was maintained at 5-year mean follow-up. In cases of PCFD with medial column instability, triple arthrodesis alone may be adequate to restore overall alignment.

Correlation of progressive collapsing foot deformity with varus knee alignment in young adults - A case control study.

Background: Majority of patients with Progressive Collapsing Foot Deformity(PCFD) have symptoms pertaining to the knee. Malalignment at the foot will have effects on the alignment of the knee. In this case control study, we compare the alignment of the knees between patients with PCFD and controls. Materials: Sixty subjects, 30 PCFD and 30 controls, underwent radiographs in which the tibiofemoral angle and radiological parameters of PCFD were assessed. Parameters of PCFD were correlated with the tibiofemoral angle. Results: Mean tibiofemoral angle was 3.8° among the cases and 4.8° among the controls which was statistically significant(P = 0.001). Varus knee alignment was seen in 41 out of 60 limbs with PCFD which was statistically significant(P < 0.001). The tibiofemoral angle correlated significantly with the Meary angle(P = 0.03) and the talonavicular coverage angle(P = 0.003). Conclusions: PCFD is associated with varus knee malalignment. This varus deformity early in adulthood may lead to deleterious effects like medial compartment osteoarthritis in later life. Early intervention for such patients may help avoid this knee damage. Level of evidence: Level 3-prognostic.

Review of Classification Systems for Adult Acquired Flatfoot Deformity/Progressive Collapsing Foot Deformity and the Novel Development of the Triple Classification Delinking Instability/Deformity/Reactivity and Foot Type.

Background: Classifications of AAFD/PCFD have evolved with an increased understanding of the pathology involved. A review of classification systems helps identify deficiencies and respective contributions to the evolution in understanding the classification of AAFD/PCFD. Methods: Using multiple electronic database searches (Medline, PubMed) and Google search, original papers classifying AAFD/PCFD were identified. Nine original papers were identified that met the inclusion criteria. Results: Johnson's original classification and multiple variants provided a significant leap in understanding and communicating the pathology but remained tibialis posterior tendon-focused. Drawbacks of these classifications include the implication of causality, linearity of progression through stages, an oversimplification of stage 2 deformity, and a failure to understand that multiple tendons react, not just tibialis posterior. Later classifications, such as the PCFD classification, are deformity-centric. Early ligament laxity/instability in normal attitude feet and all stages of cavus feet can present with pain and instability with minor/no deformity. These may not be captured in deformity-based classifications. The authors developed the 'Triple Classification' (TC) understanding that primary pathology is a progressive ligament failure/laxity that presents as tendon reactivity, deformity, and painful impingement, variably manifested depending on starting foot morphology. In this classification, starting foot morphology is typed, ligament laxities are staged, and deformity is zoned. Conclusions: This review has used identified deficiencies within classification systems for AAFD/PCFD to delink ligament laxity, deformity, and foot type and develop the 'Triple classification'. Advantages of the TC may include representing foot types with no deformity, defining complex secondary instabilities, delinking foot types, tendon reactivity/ligament instability, and deformity to represent these independently in a new classification system. Level of Evidence: Level V.

The Role of the Transverse Arch in Progressive Collapsing Foot Deformity.

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.

Influence of Weightbearing Computed Tomography in the Progressive Collapsing Foot Deformity Classification System.

BACKGROUND: The objective of this study was to compare progressive collapsing foot deformity (PCFD) classifications performed using clinical and conventional radiographs (CR) with classifications established using clinical and weightbearing computed tomography (WBCT). METHODS: This retrospective comparative study evaluated 89 consecutive PCFD feet (84 patients). Three readers performed chart reviews and CR evaluations, determining PCFD classifications that were previously published. After a washout period, the sequence was randomized, and a new classification was executed using clinical and WBCT assessment. One of the readers repeated the WBCT evaluation for intrarater reliability. RESULTS: Interrater reliability for the WBCT was found moderate (0.55) and intrarater excellent (0.98). Evaluation using WBCT produced 29.6% of 1ABC (CR: 25.4%, P = .270), 11.6% of 1ABCD (CR: 6.9%, P = .081), and 6.4% of BC (CR: 3.3%, P = .090) as most prevalent. Class A was presented in 83.9% (CR: 89.5%, P = .55), class B in 89.9% (CR: 76.4%, P < .001), class C in 93.6% (CR: 86.2%, P = .004), class D in 46.4% (CR: 34.8%, P = .006), and class E in 27.7% (CR: 22.5%, P = .158) of the classifications performed by WBCT. CONCLUSION: WBCT showed a different rate of deformity recognition, which increased the incidence of all classes, especially B, C, and D. An excellent intrarater agreement was found, which infers assessment reliability combining clinical and WBCT evaluation. The obtained information could enhance disease understanding and supply patients with more precise care. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Effect of Peritalar Subluxation Correction for Progressive Collapsing Foot Deformity on Patient-Reported Outcomes.

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.

Three-Dimensional Distance Mapping to Identify Safe Zones for Lateral Column Lengthening.

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.

Deformities Influencing Different Classes in Progressive Collapsing Foot.

Background: The current classification system of progressive collapsing foot deformity (PCFD) is comprised of 5 possible classes. PCFD is understood to be a complex, three-dimensional deformity occurring in many regions along the foot and ankle. The question remains whether a deformity in one area impacts other areas. The objective of this study is to assess how each one of the classes is influenced by other classes by evaluating each associated angular measurement. We hypothesized that positive and linear correlations would occur for each class with at least one other class and that this influence would be high. Methods: We retrospectively assessed weight bearing CT (WBCT) measurements of 32 feet with PCFD diagnosis. The classes and their associated radiographic measurements were defined as follows: class A (hindfoot valgus) measured by the hindfoot moment arm (HMA), class B (midfoot abduction) measured by the talonavicular coverage angle (TNCA), class C (medial column instability) measured by Meary's angle, class D (peritalar sub-luxation) measured by the medial facet uncoverage (MFU), and class E (ankle valgus) measured using the talar tilt angle (TTA). Multivariate analyses were completed comparing each class measurement to the other classes. A p-value <0.05 was considered significant. Results: Class A showed substantial positive correlation with class C (ρ=0.71; R2=0.576; p=0.001). Class B was substantially correlated with class D (ρ=0.74; R2=0.613; p=0.001). Class C showed a substantial positive correlation with class A (ρ=0.71; R2=0.576; p=0.001) and class D (ρ=0.75; R2=0.559; p=0.001). Class D showed substantial positive correlation with class B and class C (ρ=0.74; R2=0.613; p=0.001), (ρ=0.75; R2=0.559; p=0.001) respectively. Class E did not show correlation with class B, C or D (ρ=0.24; R2=0.074; p=0.059), (ρ=0.17; R2=0.071; p=0.179), and (ρ=0.22; R2=0.022; p=0.082) respectively. Conclusion: This study was able to find relations between components of PCFD deformity with exception of ankle valgus (Class E). Measurements associated with each class were influenced by others, and in some instances with pronounced strength. The presented data may support the notion that PCFD is a three-dimensional complex deformity and suggests a possible relation among its ostensibly independent features. Level of Evidence: III.

Managing Complications of Foot and Ankle Surgery: Reconstruction of the Progressive Collapsing Foot Deformity.

Our understanding of the cause and principles of treatment of progressive collapsing foot deformity (PCFD) has significantly evolved in recent decades. The goals of treatment remain improvement in symptoms, correction of deformity, maintenance of joint motion, and return of function. Although notable advancements in understanding the deformity have been made, complications still occur and typically result from (1) poor decision making, (2) technical errors, and (3) patient-related conditions. In this article, we discuss common surgical modalities used in the treatment of PCFD and further highlight the common complications that occur and the techniques that can be used to prevent them.

Plantar Plating for Medial Naviculocuneiform Arthrodesis in Progressive Collapsing Foot Deformity.

Background: Medial column procedures are commonly used to treat progressive collapsing foot deformity (PCFD) reconstruction. The aim of this research is to present the clinical results of plantar plating for medial naviculocuneiform (NC) arthrodesis when NC joint pathology contributes to medial arch collapse. The authors hypothesized that lag screws with a plantar neutralization plate would result in a satisfactory NC joint fusion rate. Methods: A single-surgeon, retrospective case series was performed on patients with flexible PCFD who underwent NC arthrodesis using lag screws and a contoured neutralization plate applied plantarly across the medial NC joint as part of PCFD reconstruction. Thirteen patients (11 females, 2 males; mean age 53.1 [34-62] years) between 2016 and 2019 were identified for inclusion. Mean follow-up was 25.2 ± 12.7 months. Preoperative and postoperative anteroposterior talo-first metatarsal angle, lateral talo-first metatarsal angle, talonavicular coverage angle, and calcaneal pitch were measured. Union was evaluated radiologically. AOFAS midfoot scores were recorded at final follow-up. Results: All parameters demonstrated a significant improvement. Fusion was confirmed in 11 of 13 patients (85%) at a mean 5.7 ± 2.1 months. One patient required a revision of their NC fusion because of symptomatic nonunion. There were no cases of symptomatic plantar hardware. Conclusion: The results of this small cohort series suggest that lag screw with plantar plate NC arthrodesis yielded generally improved short-term radiographic and clinical outcomes in PCFD patients with medial arch collapse through the NC joint.Level of Evidence: Level IV, retrospective case series.

Intra- and Interobserver Reliability of the New Classification System of Progressive Collapsing Foot Deformity.

BACKGROUND: Historical concept of flatfoot as posterior tibial tendon dysfunction (PTTD) has been questioned. Recently, the consensus group published a new classification system and recommended renaming PTTD to Progressive Collapsing Foot Deformity (PCFD). The new PCFD classification could be effective in providing comprehensive information on the deformity. To date, there has been no study reporting intra- and interobserver reliability and the frequency of each class in PCFD classification. METHODS: This was a single-center, retrospective study conducted from prospectively collected registry data. A consecutive cohort of PCFD patients evaluated from February 2015 to October 2020 was included, consisting of 92 feet in 84 patients. Classification of each patient was made using characteristic clinical and radiographic findings by 3 independent observers. Frequencies of each class and subclass were assessed. Intraobserver and inteobserver reliabilities were analyzed with Cohen kappa and Fleiss kappa, respectively. RESULTS: Mean sample age was 54.4, 38% was male and 62% were female. 1ABC (25.4%) was the most common subclass, followed by 1AC (8.7%) and 1ABCD (6.9%). Only a small percentage of patients had isolated deformity. Class A was the most frequent component (89.5%), followed by C in 86.2% of the cases. Moderate interobserver reliability (Fleiss kappa = 0.561, P < .001, 95% CI 0.528-0.594) was found for overall classification. Very good intraobserver reliability was found (Cohen kappa = 0.851, P < .001, 95% CI 0.777-0.926). CONCLUSION: Almost half (49.3%) of patients had a presentation dominantly involving the hindfoot (A) with various combinations of midfoot and/or forefoot deformity (B), (C) with or without subtalar joint involvement (D). The new system may cover all possible combinations of the PCFD, providing a comprehensive description and guiding treatment in a systematic and individualized manner, but this initial study suggests an opportunity to improve overall interobserver reliability. LEVEL OF EVIDENCE: Level III, retrospective diagnostic study.

Association Between Middle Facet Subluxation and Foot and Ankle Offset in Progressive Collapsing Foot Deformity.

BACKGROUND: Subtalar middle facet (MF) subluxation was recognized as a reliable marker for progressive collapsing foot deformity (PCFD) diagnosis. Foot and Ankle Offset (FAO) is an established measurement, predictive of malalignment severity. The objective of this study was to assess the potential association between MF subluxation and FAO in PCFD patients. METHODS: 56 individuals with flexible PCFD (74 feet) were assessed. Two blinded foot and ankle surgeons calculated MF uncoverage, MF incongruence, and FAO. Agreement was quantified using intraclass correlation coefficient (ICC). A multivariate regression analysis and partition prediction models were applied to assess relationship between values. RESULTS: All ICCs were >0.80. MF subluxation and FAO were found to be correlated (rs = 0.56; P < .0001). Changes in the MF subluxation were noticeably explained by FAO and BMI (R2 = 0.33). MF incongruence was not correlated with the assessed variables (P = .10). In this cohort, an MF subluxation of 27.5% was a threshold for increased FAO (FAO of 3.4%±2.4% when below; FAO of 8.0% ±3.5% when above). CONCLUSION: We found a correlation between MF subluxation and FAO. An MF subluxation of 27.5% was found to be a threshold for higher FAO, which corresponded to a greater malalignment. These data may help surgeons optimize treatment decisions in PCFD patients. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Injuries to the Spring Ligament: Nonoperative Treatment.

The fibrocartilage within the superomedial calcaneonavicular (spring) ligament is part of an interwoven complex of ligaments that span the ankle, subtalar, and talonavicular joints. Acute isolated rupture of the spring ligament has been reported in association with an eversion ankle sprain. Attenuation and failure of the spring ligament causes complex 3D changes called the progressive collapsing foot deformity (PCFD). This deformity is characterized by hindfoot eversion, forefoot supination, collapse of the medial longitudinal arch, and forefoot abduction. Nonoperative treatment of an isolated spring ligament rupture and PCFD using various designs of orthoses have shown promising results.

Diagnostic Accuracy of the Progressive Collapsing Foot Deformity (PCFD) Classification.

BACKGROUND: A consensus group recently proposed the term progressive collapsing foot deformity (PCFD) and a new classification with 2 stages plus 5 classes to describe the complex array of flatfoot deformities. This study aimed to validate different diagnostic accuracy rates of the PCFD classification. METHODS: This was a survey-based study distributed among 13 foot and ankle fellowship programs for 3 groups of participants with varied experience in practice (group 1: fellows in training, group 2: surgeons in practice for 1-4 years, and group 3: surgeons in practice for ≥5 years). Each participant was asked to assign 20 different cases of flatfoot deformity to the appropriate classes and stages using the PCFD classification. The overall diagnostic accuracy, class, and stage diagnostic accuracy rates for the 20 cases were calculated first for the entire cohort and then compared among the 3 groups. The misdiagnosis rate for each class of deformity (the sum of overdiagnosis and underdiagnosis rates) of the entire cohort was calculated and compared with the other classes. Mean and standard evidence were used to describe numerical data. One-way analysis of variance was used to compare values among the 3 groups and the 5 classes. P <.05 was considered statistically significant. RESULTS: For the whole cohort, the overall diagnostic accuracy, class diagnostic accuracy, and stage diagnostic accuracy rates were 71.0%, 78.3%, and 81.7%, respectively There was a statistically significant difference between group 1 and 2, and group 1 and 3, in overall diagnostic accuracy and class diagnostic accuracy, with no significant difference among the 3 groups regarding stage diagnostic accuracy. Class B had a significantly higher overdiagnosis rate than the rest of the classes, whereas class D was significantly underdiagnosed than others. The misdiagnosis rates for classes A to E were 3.3%, 17.5%, 11.1%, 26.0%, and 3.7%, respectively. CONCLUSION: The PCFD classification showed overall fair diagnostic accuracy rates. The highest diagnostic accuracy was for "hindfoot valgus deformity" and "ankle instability." Further content validation of the PCFD classification is needed to examine the terminology and interpretation of those classes with low diagnostic accuracy including "midfoot/forefoot abduction deformity," "forefoot varus deformity/medial column instability," and "peritalar subluxation/dislocation."Level of Evidence: Level II, prospective comparative study.