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Foot and ankle weightbearing CT (WBCT) imaging has emerged over the past decade. However, a systematic review of diagnostic applications has not been conducted so far. A systematic literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines after Prospective Register of Systematic Reviews (PROSPERO) registration. Studies analyzing diagnostic applications of WBCT were included. Main exclusion criteria were: cadaveric specimens and simulated WBCT. The Methodological Index for Non-Randomized Studies (MINORS) was used for quality assessment. A total of 78 studies were eligible for review. Diagnostic applications were identified in following anatomical area's: ankle (n = 14); hindfoot (n = 41); midfoot (n = 4); forefoot (n = 19). Diagnostic applications that could not be used on weightbearing radiographs (WBRX) were reported in 56/78 studies. The mean MINORS was 9.8/24 (range: 8–12). Diagnostic applications of WBCT were most frequent in the hindfoot, but other areas are on the rise. Post-processing of images was the main benefit compared to WBRX based on a moderate quality of the identified studies. [ABSTRACT FROM AUTHOR]

The aim of the study was to test a novel planning method for simultaneous midfoot and hindfoot deformity correction, based on reference lines and angles (RLA) of the talus, calcaneus and first metatarsal in 64 normal radiographs from 55 patients. Talus Joint Line (TJL), from the border of the articular surface of the talus and the posterior process of talus, and mechanical axis of the first metatarsal form the mechanical Lateral Talometatarsal Angle (mLTMA) = 23.6º (±3.2). The length of the first metatarsal line was measured from its intersections with the TJL and first metatarsal head and it was 4.3 (±0.94) times longer that TJL (k). For hindfoot correction planning, we used an axis of the calcaneus formed by a line starting at the middle of the back of the calcaneal tuberosity and going perpendicular to a line from the top point to the bottom point of the calcaneal tuberosity. The intersection of the calcaneal line and the anterior continuation of TJL form the lateral heel angle (LHA) = 15.2º (±3.4).The following parameters were identified: the length from the intersection point of the lines and anterior point of TJL was 2.56 ± 1.1 longer than TJL (k1). The length from the intersection point and posterior border of the calcaneus was 4.59 ± 1.0 times longer than TJL (k2). Planning using the new method was demonstrated and confirmed on 3 case examples. A novel method for analysis and planning of midfoot and hindfoot sagittal plane deformity correction may be used separately or simultaneously for complex deformity correction. [ABSTRACT FROM AUTHOR]

Category: Hindfoot; Ankle Introduction/Purpose: To date, only a few studies have reported postoperative changes in coronal ankle alignment after valgus knee correction through Medial Closing Wedge Distal Femoral Varization Osteotomy (MCWDFO). This study aimed to measure the changes of MCWDFO on coronal ankle and hindfoot alignment. Methods: We retrospectively reviewed the radiographic findings of 27 consecutive patients (34 cases) with knee valgus malalignment who underwent MCWDFO for either lateral knee joint osteoarthritis (OA) or recurrent patellar subluxation/dislocation (RPD). Several radiographic parameters were measured and compared based on the reason for operation, followed by the status of preoperative hindfoot alignment (hindfoot alignment angle [HAA] > 4°, varus; -4° HAA 4°, neutral; HAA < -4°, valgus) in each group. Results: Overall, pre- and postoperative hindfoot alignments were within the neutral alignment range and were not significantly changed after the operation (P > 0.05). Nineteen cases were for lateral knee OA and 15 were for RPD, respectively. In both groups, preoperative neutral hindfoot alignments accounted for the largest portion (52.6% in the lateral OA group; 80.0% in the RPD group). Postoperatively, regardless of the reason for operation, hindfoot alignments changed toward the neutral range in all subgroups (i.e., no changes in the preoperative neutral group; increased in the valgus group; decreased in the varus group). Conclusion: We recommend that surgeons leave the hindfoot untouched when they plan the MCWDFO to correct knee joint valgus malalignment concomitant with hindfoot valgus or varus deviation as the hindfoot malalignment appears to change towards neutral range postoperatively. [ABSTRACT FROM AUTHOR]

Background. Tibiotalocalcaneal (TTC) arthrodesis is a common treatment option for complex hindfoot pathology. Overall union rates range from 50% to 86% but can be even lower in certain populations. A novel retrograde intramedullary nail has recently been developed. The purpose of this study was to report fusion rates, time to weight-bearing, and complications with the use of the A3 Fusion Nail. Methods. All patients 18 years or older who underwent TTC arthrodesis with an A3 Fusion Nail at a single institution from 2010 to 2015 with a minimum 3-month follow-up were included in this study. Rates of successful fusion, time to union, time to weight-bearing, and complications were evaluated. A total of 20 patients with an average age of 58.1 years and an average follow-up of 12.5 months met inclusion criteria. Results. Successful TTC arthrodesis was achieved in 14 of 20 patients (70%) overall. Average time to union was 8.1 months, and average time to weight-bearing was 6.8 weeks. Of 20 patients, 17 (85%) required femoral head allograft for bulk bone defects, and the union rate in this subset of patients was 76.5%. The rates of revision surgery (10%) and complications were low. Conclusion. The A3 Fusion Nail demonstrated a favorable safety profile and achieved TTC arthrodesis at a rate consistent with historical data despite being used in a patient population at high risk for nonunion. In patients with bulk bone defects at high risk for nonunion, the A3 Fusion Nail demonstrated superior rates of fusion (76.5%) to those reported in the literature (50%).Level of Evidence: Level III: Retrospective cohort study. [ABSTRACT FROM AUTHOR]

Background: Percutaneous osteotomy of calcaneus has been proposed to reduce the complication rate and became more and more popular. The bone cut can be performed as a straight or chevron-like (V) osteotomy using a Shannon burr. Comparative studies of straight or V-osteotomy as like as one or two screws in percutaneous calcaneal osteotomies are missing in the literature. We hypothesize that the V-osteotomy will result in a higher stiffness in biomechanical testing as the straight osteotomy using single screw for fixation.Methods: The straight osteotomy (9 fresh-frozen specimens) and V-osteotomy (9 fresh-frozen specimens) was performed and the calcaneal tuberosity was moved 10mm medially and slightly rotated. One 6,5mm cancellous compression screw was used for osteosynthesis. Specimens were preconditioned with 100N over 100 cycles. The force was increased after every 100N by 100N from 200 to 500N. This was followed by cyclic loading with 600N for 500 cycles.Results: Despite the higher mean values of the group with V-osteotomy, no significant difference was registered between the two groups regarding the stiffness at all force levels. A higher failure rate was observed in the group with straight osteotomy.Conclusion: The moderate correlation of bone density and stiffness in the V-group, and significantly lower failure rate with no secondary dislocation in fluoroscopy indicates the superiority of the V-osteotomy in the present study. Whether the demonstrated advantages can be reflected in clinical practice should be investigated in further studies.Level Of Clinical Evidence: 5. [ABSTRACT FROM AUTHOR]

Background. Tibiotalocalcaneal (TTC) arthrodesis is a common treatment option for hindfoot arthritis and deformity. Loss of compression over time with statically locked nails may contribute to nonunion. A novel retrograde intramedullary nail with an internal pseudoelastic component has recently been used to provide sustained dynamic compression (SDC). The purpose of this study was to compare fusion rates and time to union between the SDC and nondynamized (ND) nails. Methods. All patients who underwent TTC arthrodesis with an intramedullary nail at a single institution from 2013 to 2017 and who had at least 1 year of follow-up were included in this study. Baseline patient and operative characteristics were collected and compared between the sustained SDC and ND nail groups. The rate of successful fusion, time to union, and complications were compared between the groups. Results. The SDC cohort had a significantly faster time to union by 3.9 months (P = .049). The SDC cohort had a higher fusion rate (78.0%) compared with the ND nail cohort (75.0%), although this was not statistically significant (P = .75). The SDC nail was used significantly (P < .05) more often in patients with known risk factors for nonunion, including female sex, smoking, revision surgery, prior trauma, and patients requiring 3D cage implants for significant bone loss. There were no differences between the groups in terms of complications. Conclusion. The SDC nail has been shown to achieve successful arthrodesis in a population at high risk for nonunion, using less hardware, and at a faster rate than ND nails. Level of Evidence: Level III: Retrospective, comparative study. [ABSTRACT FROM AUTHOR]

Background: Subtalar distraction arthrodesis (SDA) was developed as a means of treating the symptoms of subtalar arthritis. Despite almost 30 years of research in this field, many controversies still exist regarding SDA. The objective of this study was to present an overview of outcomes following SDA, focusing on surgical technique as well as clinical and radiographic results. Methods: MEDLINE and EMBASE were queried and data abstraction was performed by 2 independent reviewers. Inclusion criteria for the articles were (1) English language, (2) peer-reviewed clinical studies with evidence levels I to IV, (3) with at least 5 patients, and (4) reporting clinical and/or radiographic outcomes of SDA. Results: Twenty-five studies matched the inclusion criteria (2 Level III and 23 Level IV studies) including 492 feet in 467 patients. The most common indication for SDA was late complications of calcaneus fractures. Many different operative techniques have been described, and there is no proven superiority of one method over the other. The most commonly reported complications were nonunion, hardware prominence, wound complications, and sural neuralgia. All studies showed both radiographic and clinical improvement at the last follow-up visit compared with the preoperative evaluation. Pooled results (12 studies, 237 patients) demonstrated improved American Orthopaedic Foot & Ankle Society ankle-hindfoot scores with a weighted average of 33 points of improvement. Conclusion: SDA provides good clinical results at short-term and midterm follow-up, with improvement in ankle function as well as acceptable complication and failure rates. Higher quality studies are necessary to better assess outcomes between different operative techniques. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

Currently available methods for analysis and planning of post-traumatic or congenital deformity correction of the foot have some limitations. The aim of this retrospective study was to establish reference lines and angles (RLAs), and the resulting ratios, based on reproducible anatomic points on sagittal feet radiographs. The key starting point of our evaluation was the previously undescribed length and position of the talus joint line (TJL), from the border of the articular surface of the talus and the posterior process of talus. First, we calculated the relationships between the TJL and the axes of the foot, particularly the anatomic and mechanical lateral talometatarsal angle axes of the first metatarsal. Then, we assessed the relationships with the calcaneus, particularly the lateral heel angle. Finally, we calculated the parameters (angles and coefficients k) derived from the TJL and the foot-bearing points (foot quadrilateral). A total of 64 normal radiographs from 55 patients were analyzed. The values that resulted are as follows: anatomic lateral talometatarsal angle = 28.5° ± 4.5°, mechanical lateral talometatarsal angle = 23.6° ± 3.2°, lateral heel angle = 15.2° ± 3.4°, foot quadrilateral: abc = 144.6° ± 9.4°, bcd = 31.3° ± 2.6°, cda = 79.2° ± 9.8°, dab = 105.0° ± 8.3°, k 1 = 3.09 ± 0.4, k 2 = 3.77 ± 0.78, and k 3 = 1.56 ± 0.24. Sagittal plane reference lines and angles are proposed, providing quantitative values for reference. These parameters have the potential to be easily implemented in foot deformity analysis and correction planning. [ABSTRACT FROM AUTHOR]

Background: Calcaneal osteotomies are often required in the correction of hindfoot deformities. The traditional open techniques, which include a lateral or oblique incision, are occasionally associated with wound healing problems and neurovascular injury. Methods: A total of 122 consecutive patients who underwent a calcaneal osteotomy for hindfoot realignment treatment were included. Fifty-eight patients were operated using an open incision technique and 64 patients (66 feet) using a percutaneous technique. Clinical and radiologic assessments were performed preoperatively, at 6 weeks, and 1 year postoperatively. Results: The American Orthopaedic Foot & Ankle Society scale scores and visual analog scale pain scores improved in both groups postoperatively. The difference between the groups was not significant. The results of the radiologic measurements pre- and postoperatively were not significantly different. No pseudarthrosis occurred in either group. The comparison of both groups showed a significantly lower risk for wound healing problems in the percutaneous group. The hospitalization time was significantly shorter in the percutaneous group. Conclusion: Because of the excellent results with the percutaneous calcaneal osteotomy, the authors feel encouraged to establish this procedure as a standard technique for calcaneus osteotomy, especially patients at high risk for wound healing problems. Level of Evidence: Level III, comparative series. [ABSTRACT FROM AUTHOR]

Category: Hindfoot; Ankle Arthritis Introduction/Purpose: Subtalar arthrodesis (STA) is a common procedure used to correct rigid, arthritic hindfoot deformity. The deformity is often able to be corrected through the subtalar arthrodesis-site, however in severe deformity, calcaneal osteotomy (CO) may also be required to realign the hindfoot. CO may predispose the patient to additional risk of wound complication due to the proximity of sinus tarsi and open lateral calcaneal osteotomy incisions. Despite the relatively common nature of hindfoot deformity, there is no study to date assessing the complication profile and outcomes of combined STA and CO when compared STA alone. The purpose of this study was to compare STA alone versus STA and CO to examine union rates and complications for a procedure with known nonunion risk. Methods: A retrospective review of all STA performed two institutions between January 2011 and August 2021 was performed. All STA performed during that time period were identified using a CPT code search and chart review. 22 patients were identified with combined STA and CO as part of a simultaneous procedure. We then performed a matched pair analysis for STA only as a control group identifying 22 patients with STA only. Complications including delayed union or nonunion, removal of hardware, wound complications, and the need for revision surgery were recorded. The two groups were matched for age, gender, presence of diabetes, and smoking status. Differences were analyzed using a two-tailed Fisher's exact test. Results: There were 22 patients in the STA and CO group with 22 included matched pairs as our control group. There were no significant statistical differences between the two groups when comparing for age and comorbidities. The STA group had 4 recorded complications, while the STA and CO group had 1 recorded complication in the follow-up period. There was no significant difference in complications between the STA and the combined STA and CO group (p= 0.6361). Radiographic union was identified with CT scan. All but 1 patient achieved union in the STA and CO group (nonunion ST only and not CO). 0 nonunions were identified in the STA control group. Post hoc power analysis demonstrates 81% power regarding union compared to historical controls. Conclusion: There was no statistically significant increase in complications when a calcaneal osteotomy was performed in addition to a subtalar arthrodesis, with no specific concern for wound complication. This data supports that performing a calcaneal osteotomy in combination with a subtalar arthrodesis may be utilized to prevent undercorrection of hindfoot deformity without additional wound complication risk. This study is limited by small study groups due to the severity of deformity required to have an additional calcaneus osteotomy. However it also highlights the importance of deformity correction as no additional risk of revision surgery was added. [ABSTRACT FROM AUTHOR]

Category: Hindfoot; Other Introduction/Purpose: A calcaneal osteotomy is often included as part of the treatment in planovalgus and cavovarus foot deformities. Often this is done through an open approach where complications of wound infection and sural nerve injury are common. More recently, this strategy has been modified using minimally invasive techniques. A percutaneous approach, in comparison to the standard open calcaneal osteotomy, allows for reduced postoperative complication and decreased pain compared to an open procedure. This retrospective chart review aims to evaluate the postoperative outcomes of patients undergoing calcaneal osteotomy via a minimally invasive percutaneous approach in foot reconstructive surgery to assess early functional outcomes, complication rate and revision rates. Methods: One fellowship-trained foot and ankle orthopaedic surgeon at one academic institution performed minimally invasive calcaneal osteotomy on 20 patients. All cases were completed between March 2021 and March 2023. Patient charts were reviewed for outcome data including complication rate, union rate, revision rate, and Patient-Reported Outcomes Measurement Information System (PROMIS) scores. Results: Participants included 15 females and 5 males, 4 of whom were smokers. Average age was 42.2 years. Average BMI was 32.3, and average follow up was 130.4 days. Complications included 1/20 patients had a postoperative wound breakdown of the screw site requiring incision and debridement with closure and 2/20 cases of sural neuritis. One resolved 6 months after treatment and the other was present but became less symptomatic. All participants achieved union, and there were no revisions. All shifts corrected hindfoot deformity either via medializing or lateralizing osteotomy. Average preoperative PROMIS scores in the domains of physical function, pain interference, and mobility were 36.8 (28.6-46), 67.1 (54.3-78), and 34.6 (25-40), respectively. Average postoperative PROMIS scores were 35.7 (21-76), 62.3 (39-76), and 33.4 (16-75), respectively. Conclusion: Minimally invasive calcaneal osteotomy appears to be an efficacious and safe treatment option for the correction of cavovarus and planovalgus hindfoot deformities with the ability to obtain appropriate hindfoot correction with low complication rates and high union rates. Early outcome measures show a favorable pain interference PROMIS score as well as a trend in improvements in PROMIS physical function scores. Longer term data will need to be done to assess long term functional outcome and revision rates. [ABSTRACT FROM AUTHOR]

Category: Hindfoot; Other Introduction/Purpose: Triple arthrodesis of the subtalar, talonavicular, and calcaneocuboid joints is a commonly performed procedure to treat hindfoot deformity. Debate exists regarding the need to include the calcaneocuboid joint in the arthrodesis, leading some surgeons to perform double arthrodesis of the subtalar and talonavicular joints to treat similar pathology. Differences in clinical, radiographic and patient reported outcomes between the two procedures have not been thoroughly reported. The purpose of this study is to evaluate the clinical and radiographic outcomes of double versus triple arthrodesis for the correction of symptomatic hindfoot deformity. Methods: A retrospective cohort study reviewed all patients who underwent double or triple arthrodesis to correct hindfoot pathology between January 2016 and April 2019 at our institution. Patients were identified using CPT codes. Inclusion criteria included patients greater than 18 years old who underwent hindfoot correction by a primary double or triple arthrodesis with a minimum 3 month clinical and radiographic follow up. Exclusion criteria included prior hindfoot arthrodesis and peripheral neuropathy. The primary outcome was union at each arthrodesis site. Secondary outcomes included deformity correction, operative times, re-operation rates, complications, and patient reported outcomes. Chi-squared or Fisher's Exact tests were used as appropriate to compare categorical variables and t-tests were used to compare numerical variables. Results: One hundred fourteen procedures met inclusion criteria. There were 86 double (75%) and 28 triple arthrodeses (25%). Eleven talonavicular non-unions were identified in the double arthrodesis group (12.7%) compared to 5 in the triple arthrodesis group (17.9%, p =0.54). There were 2 (7.1%) calcaneocuboid non-unions in the triple group. Subtalar arthrodesis was achieved 100% in both groups. Operative time was shorter for doubles compared to triples, but this did not reach statistical significance (104 min vs 117 min, p = 0.089). The only deformity correction parameter to reach significance was post operative cuboid height being higher in the double group (19.1mm vs 16.7mm, p = 0.012). Pre-operative deformity, overall union rates, reoperation rate, and post operative complications were not statistically different between the two procedures. Conclusion: In this study double arthrodesis was shown to result in shorter operative times with similar deformity correction, union rates, and post operative complications when compared to triple arthrodesis. The double arthrodesis is a viable alternative to treat hindfoot pathology. More research is warranted to further compare the long term outcomes between the two procedures. [ABSTRACT FROM AUTHOR]

This survey clarified foot pressure patterns and hindfoot deformities in individuals with advanced knee osteoarthritis (OA) and analyzed their associations with foot pain. Sixty-four individuals with unilateral knee OA who underwent total knee arthroplasty (TKA) were divided into the following groups: no foot pain (n=26; men:women, 4:22; mean age, 73.7 years), foot pain resolved after TKA (12; 2:10; 75.8), and foot pain remaining after TKA (26; 4:22; 74.7). Elderly individuals without pain or deformity in either knee (54; 10:44; 74.3) were controls. Navicular height ratio of the medial longitudinal arch, leg-heel angle, and partial foot pressure as the percentage of body weight (%PFP) were calculated.%PFPs of the medial and lateral heel regions before TKA were significantly lower for the no foot pain group than for controls. One year after TKA, %PFP improved significantly. In the foot pain resolved group, before TKA, the leg-heel angle was significantly higher, and%PFPs of the medial and lateral heel regions and navicular height ratio before TKA were significantly lower than those of controls. One year after TKA, all parameters improved significantly. In the foot pain remaining group, similar abnormalities were observed before TKA; however, significant improvement was only observed for%PFP of the medial heel region 1year after TKA. More than half of the patients with advanced knee OA had foot pain. This improved in approximately one-third, 1year after TKA. Hindfoot deformities are probably associated with foot pain in individuals with advanced knee OA. [ABSTRACT FROM AUTHOR]

Objectives: Advances in drug therapy for rheumatoid arthritis (RA) have been encouraging us to preserve the metatarsopharangeal (MTP) joint in correction of forefoot deformities, and original metatarsal shortening offset osteotomy was recommended as one of the conventional surgical options for forefoot deformities in RA cases. The objective of this study was to evaluate short-to mid-term outcomes of modified metatarsal shortening offset osteotomy. Methods: A retrospective observational study was completed for 80 RA cases (mean follow-up period: 3.2 years) who underwent modified metatarsal shortening offset osteotomy. Both lesser toe scales and RA foot ankle scales were administered using the Japanese Society for Surgery of the Foot (JSSF) standard rating system, and a postoperative self-administered foot evaluation questionnaire (SAFE-Q) at final follow-up was also checked to evaluate clinical outcomes. Results: This procedure significantly improved clinical scores of both the JSSF [lesser toes and RA foot and ankle] scales. Of 80 feet, 24 (30%) showed recurrence of MTP joint subluxation/dislocation. Furthermore, the feet in the recurrence group showed significant varus hindfoot. On the other hand, valgus foot in the recurrence group more frequently included midfoot bony ankyloses. All of the affected feet showed the limitation of MTP joints (<70°) after surgery. Conclusions: Modified metatarsal shortening offset osteotomy was recommended for RA forefoot disorders as one of the joint preservation surgeries in short- to mid-term follow-up. However, some modifications to avoid limitation of ROM in the MTP joint are required. It must be borne in mind that varus hindfoot and/or bony ankyloses in the mid-hindfoot can cause recurrence of dorsal dislocation/subluxation of the lesser toe MTP joint. [ABSTRACT FROM AUTHOR]

The article discusses the joint-preserving possibilities to balance the forces in the ankle joint by performing osteotomies around the ankle joint.

Background: Good clinical and radiographic short-term results have been reported for patients who underwent realignment surgery of the hindfoot for treatment of early- and mid-stage ankle osteoarthrosis (OA). However, no mid- to long-term results have been reported. The aim of this study was to gain a better insight into the indications and contraindications for realignment surgery. Methods: Two hundred ninety-four patients (298 ankles) underwent realignment surgery between December 1999 and June 2013. Kaplan-Meier survival analysis was performed with total ankle replacement and arthrodesis of the ankle joint as endpoints. A Cox proportional hazards model was performed to identify risk factors for failure. The mean time to follow-up was 5.0 ± 3.7 years. Results: The overall 5-year survival rate was 88%. Thirty-eight patients (12.9%) underwent either secondary total ankle replacement or ankle arthrodesis (30 total ankle replacements, 8 ankle arthrodesis). Risk factors for failure following realignment surgery were age at the time of surgery and a Takakura score of 3b preoperatively. Conclusion: Realignment surgery of the hindfoot was an excellent treatment option for young and physically active patients with early to mid-stage ankle OA. Level of Evidence: Level IV, prospective observational study. [ABSTRACT FROM AUTHOR]

The article discusses studies which reported successful use of isolated talonavicular fusions for the treatment of posterior tibial tendon dysfunction (PTTD) and deformity correction. It cites the use of biomechanical studies to assess the effect of isolated talonavicular fusion on hindfoot motion and the ability of this procedure to correct angular deformity. It suggests that isolated talonavicular arthrodesis substantially reduces remaining motion at the subtalar and calcaneocuboid joints.

Purpose: Triple arthrodesis is a commonly performed salvage procedure to correct hindfoot deformity. Non-union is considered an undesirable radiographic outcome; however, the clinical ramifications of this are not as well defined. The purpose of this study was to determine the incidence of partial or complete radiographic non-union after triple arthrodesis in children and characterize the clinical consequences. Methods: An IRB-approved retrospective review of triple arthrodesis surgeries in patients less than 16 years of age performed by a single surgeon (DSW) identified 159 cases meeting the inclusion criteria. Plain radiographs were reviewed for bony fusion (defined as over 80 % radiographic bony union of the subtalar, calcaneocuboid, and talonavicular bones) and charts for clinical outcomes (pain, return to activity, and subsequent hindfoot surgeries). Statistics were used to compare the fused and unfused cases, with p < 0.05 considered to be significant. Results: Of the 159 cases included in the study, 9 % did not achieve at least 80 % plain film radiographic union. The fused and unfused groups had similar clinical outcomes. Only one patient required surgery for sequelae of symptoms arising from a pseudoarthrosis related to the triple arthrodesis. The fused and unfused groups were similar in terms of gender and pin removal time, but differed significantly in surgical age and underlying diagnosis. Conclusions: This is one of the largest case series of pediatric triple arthrodesis surgery presented in the literature. This study demonstrated that good clinical outcomes can be achieved despite the lack of radiographic union after triple arthrodesis surgery in children. Level of evidence: IV. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Peritalar subluxation in both the talonavicular and subtalar joints has been described as characteristic markers for adult acquired flatfoot deformity (AAFD). However, no study has reported these changes in in cavovarus deformity, and we postulated that peritalar subluxation would apply to both the AAFD as well as the cavovarus foot deformity but in different directions using the same markers. Furthermore, the use of calcaneocuboid (CC) joint subluxation as an additional marker for peritalar subluxation has never been investigated in either flatfoot or cavovarus deformities. This study used three dimensional images of weightbearing cone beam computed tomography (WBCT) to evaluate the alignment of the peritalar joints in feet with normal, varus and valgus hindfoot alignment. Methods: WBCT scan images and medical charts of 400 patients were retrospectively reviewed. Thirty cavovarus and 15 flexible AAFD feet were chosen as the study groups. Fifteen feet without deformities and arthritis, a history of trauma or surgery in both the hindfoot and ankle were chosen as controls. Hindfoot moment arm (HMA), Foot and ankle offset (FAO) were used to assess hindfoot alignment. Middle facet subluxation (MFS), talonavicular joint coverage angle (TNCA), and calcaneocuboid joint subluxation (CCS) were used as markers of peritalar subluxation. The talocalcaneal (Kite's) angle in the axial plane was used to demonstrate the relative position between the talus and the calcaneus. The arch height index in the sagittal plane was used to assess medial arch height. Positive was used to reflect lateral subluxations while negative for medial ones. Correlations between HMA, FAO and each of the above three peritalar subluxation parameters were assessed by bivariate linear regression. Results: Patients in both the cavovarus and the AAFD groups showed totally different hindfoot alignment, peritalar subluxation and the height of the medial arch compared to the control group. In the order of Cavovarus, AAFD, and Control, the mean HMACR values were -20.43mm, 14.02mm, and 0.03mm, respectively; HMA-WBCT values were -6.34mm, 15.75 mm, and 3.19 mm; FAO values were -11.17%, 7.42%, and 2.63%; TNCA were -16.8 degrees, 22.11, and 6.45; The MFS values were -17%, 42%, and 22%; CCS values were -21% (IQR=-35%,-0.17%), -7% (IQR=-11%, 0) and 0 (IQR=-4%, 5%); The Kite's angles were 22.19 degrees, 34.27 degrees, and 28.06 degrees; The arch height index values were 0.25, 0.71, and 0.44. There was a statistically significant difference among the three groups in all the above parameters. There was a strong positive linear correlation between each parameter of the peritalar subluxation marks with both hindfoot moment arm and FAO. Conclusion: This is the first study to bring the concept of peritalar subluxation to cavovarus deformity assessment, proving that peritalar subluxation is a key characteristic in both flatfoot and cavovarus foot deformities. The two deformities are pathologically completely different, and as expected, markers of peritalar subluxation were in opposite directions. The use of calcaneocuboid joint subluxation as additional marker of perisubtalar subluxation is novel to assess both deformities. The findings of this study will provide useful guidelines for future clinical evaluation and decision making in treating patients with either varus or valgus hindfoot deformities. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Number of fractures of the calcaneus amounts to 1-5.7% of all fractures of skeleton bones according to various authors. Moreover, these figures correspond to 50% of all fractures of feet bones. Consequences of calcaneus malunion leads to early disability, arthrosis, pain syndrome, disorder of the entire low extremity axis of motion alongside cosmetic defects and shoe wearing discomfort. Purpose of the study: classification of calcaneal malunions based on a geometrically normal position and dimensions of hindfoot in order to develop optimal type of treatment for multicomponent calcaneal deformity. Methods: Twelve patients with post traumatic deformed hindfoot after malunited calcaneal fractures and as a result varus and valgus deformity, subtalar arthritis, pain syndrome, shoe wear discomfort at different stages after trauma (from 1 to 10 years) were examined, underwent surgical alignment of calcaneus and were followed up for 24 months. All cases were assessed clinically using the American Orthopaedic Foot & Ankle Society (AOFAS) and visual analog scale (VAS); radiologically by measuring hindfoot varus/valgus, talus tilt, Meary's angle, and hight of calcaneal. Results: It was found a significant improvement in AOFAS (55.2 preoperatively to 78.8 after 24 months) and VAS (65 preoperatively to 30.1). Moreover, our study revealed a significant improvement in the radiographic measurements including hindfoot varus/valgus, the talar inclination, Meary's angle, and hight of calcaneus. Conclusion: The elimination of angular hindfoot varus or valgus deformation, exostectomy of the lateral wall and subtalar fusion, as well as the use of a tricortical autograft for distarction arthrodesis at III-V type Zwipp and Rammelt classification, resulted in reduced pain, improved function, cosmetic results and shoe wearing. [ABSTRACT FROM AUTHOR]

Isolated midfoot and hindfoot Charcot reconstruction using internal fixation is increasingly a common procedure in multidisciplinary diabetic foot units, and the surgical techniques using internal fixation have well been described. However, about a third of Charcot deformities that require surgical limb salvage present with the involvement of midfoot and hindfoot. Surgical reconstruction of a combined hindfoot and midfoot deformity is an evolving technique and technically challenging. We present the surgical technique of deformity correction and stabilisation using internal fixation, developed by the senior author (VK), and present the outcomes. All patients that had undergone combined hindfoot and midfoot reconstruction to address a limb threatening deformity due to Charcot neuroarthropathy, performed by the senior author, with a minimum follow-up of 12 months, have been included in this study. The principles of surgical reconstruction included adequate pre-operative optimisation of the patient, sequential deformity correction and stabilisation of the hindfoot followed by midfoot using the principle of long-segment rigid internal fixation with optimal bone opposition. Standard post-operative regime, including offloading, has been used in all patients. A total of 34 patients (35 feet) had undergone combined midfoot and hindfoot Charcot reconstruction between January 2009 and December 2019. Active ulcers were noted in 13 feet at the time of the procedure. Eleven reconstructions were performed as two-stage procedures due to the presence of active infection. At a mean follow-up of 53 months, 11/13 ulcer healed, and 32 patients (33 feet) were full weightbearing in surgical shoes or a brace at the latest follow-up. Bone fusion was noted in 28 feet in the hindfoot region and 32 feet in the midfoot. Metal work failure was noted in 5 feet requiring removal in 3 feet. Revision procedures were required in 4 patients. Our newly described technique of combined hindfoot and midfoot Charcot has provided functional limb salvage in majority of presentations, with an acceptable level of complications, at a medium-term follow-up of 53 months., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-23/coif). The authors have no conflicts of interest to declare., (2023 Annals of Joint. All rights reserved.)

Background. The calcaneal displacement osteotomy is a procedure frequently used by foot and ankle surgeons for hindfoot angular deformity. Traditional techniques use compression screw fixation that can result in prominent hardware. While the results of the procedure are generally good, a common concern is the development of plantar heel pain related to prominent hardware. The primary purpose of this study is to retrospectively compare clinical outcomes of 2 fixation methods for the osteotomy. Secondarily a cost analysis will compare implant costs to hardware removal costs. Methods. Records were reviewed for patients who had undergone a calcaneal displacement osteotomy fixated with either lag screw or a locked lateral compression plate (LLCP). Neuropathy, previous ipsilateral calcaneus surgery, heel pad trauma, or incomplete radiographic follow-up were exclusionary. Results. Thirty-two patients (19.4%) required hardware removal from the screw fixation group compared to 1 (1.6%) of the LLCP group, which is significant (P < .05). Time to radiographic healing was not significantly different (P = .87). The screw fixation group required more follow-up visits over a longer period of time (P < .05). Implant cost was remarkably different with screw fixation costing on average $247.12, compared to the LLCP costing $1175.59. Although the LLCP cost was significantly higher, cost savings were identified when the cost of removal and removal rates were included. Conclusion. This study demonstrates that this device provides adequate stabilization for healing in equivalent time to screw fixation. The LLCP required decreased rates of hardware removal with fewer postoperative visits over a shorter period of time. Significant savings were demonstrated in the LLCP group despite the higher implant cost.Levels of Evidence: Therapeutic, Level III, Retrospective Comparative Study [ABSTRACT FROM PUBLISHER]

The involvement of valgus hindfoot deformity in hallux valgus deformity was confirmed in a rheumatoid arthritis case with a destructive valgus hindfoot deformity. Correction of severe valgus, calcaneal lateral offset, and pronated foot deformity instantly normalized hallux valgus deformities postoperatively. Thus, careful hindfoot status evaluation is important when assessing forefoot deformity, including hallux valgus, in rheumatoid arthritis cases. [ABSTRACT FROM AUTHOR]

Abstract: Background: Subtalar arthrodesis (SA) is the preferred treatment for painful isolated subtalar disease. Although results are generally favourable, analysis of current operative techniques will help optimizing this treatment. The aim was to give an overview of SA-techniques and their pitfalls. Possible solutions were identified. Materials and methods: A literature search was performed for papers that presented SA operative techniques. The general technique was divided into phases: surgical approach, cartilage removal, bone graft selection, hindfoot deformity correction and fixation. Results: The published series were invariably retrospective reviews of small heterogenous groups of different hindfoot pathologies. The weighted outcome rate for SA was 85% (68–100%) performed in 766 feet and for SA requiring correction of malalignment 65% (36–96%) in 1001 feet. Non-union (weighted percentage 12%), malalignment (18%), and screw removal (17%) were the prevailing late complications. Pitfalls: The following pitfalls were identified: 1) early complications related to the incisions made in open approaches, 2) insufficient cartilage removal, improper bone graft selection and fixation techniques, all possibly leading to non-union, 3) morbidity caused by bone graft harvesting and secondary screw removal, 4) under- or overcorrection of the hindfoot possibly due to improper intraoperative verification and 5) inadequate assessment of bony fusion. Solutions: The review provides solutions to possibly overcome some pitfalls: 1) if applicable use an arthroscopic approach in combination with distraction devices and new burrs, 2) if possible use local bone graft or allografts, 3) use two screws for fixation to prevent rotational micromotion, and 4) improve assessment of operative outcome by application of appropriate assessment of bony fusion and alignment. Conclusion: The review provides practical suggestions to optimize SA-techniques. [Copyright &y& Elsevier]

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The authors present the results of their comparison of intramedullary nail to blade plate fixation in the salvage procedure tibiocalcaneal arthrodesis for complex problems of the ankle and hindfoot. They determined that intramedullary nail fixation was biomechanically preferable to screw fixation and provided greater stiffness for fixation.

Introduction/Purpose: While correction of varus alignment at the level of the ankle joint has been investigated extensively after supramalleolar osteotomy (SMOT), the effect on the hindfoot alignment remains unclear. This can be attributed to the limitations of former 2-dimensional radiographic measurements used to quantify the complex 3-dimensional subtalar joint alignment. Therefore, we aimed to determine both the ankle and subtalar joint alignment before and after SMOT using a weightbearing CT and autogenerated 3-dimensional measurements. Methods: Twenty-seven patients with a mean age of 53 years (SD=10.1; range=25-73) were retrospectively analyzed in a prepost study design using weightbearing CT images. Inclusion criteria were correction of ankle varus deformity by either an opening wedge (N=19) or dome osteotomy (N=8). Exclusion criteria consisted of an additional inframalleolar bony correction, i.e. calcaneal osteotomy or subtalar arthrodesis. Corresponding three-dimensional bone models were reconstructed to compute the autogenerated measurements: tibial anterior surface (TAS) -, tibiotalar surface (TTS)-, talar tilt (TT) - and talocalcaneal (TC) angle. Results: The pre-operative (TAS=86.9°, SD=4.9; TTS=79.8°, SD=5.6; TT=8.8°, SD=4.3) radiographic parameters of the ankle joint alignment improved significantly compared to the post-operative parameters (TAS=92.4°, SD=4.9; TTS=87.1°, SD=6.3; TT=5.1°, SD=2.7; P<0.05). (Fig. 1A) Radiographic parameters to assess the subtalar joint alignment improved significantly from preoperatively (TCax =42.8°, SD=9.3; TCsag=42.3°,SD=10.9; TCcor =29.5°,SD=11.8) to post-operatively (TCax =37.8°, SD=8.8; TCsag=39.1°, SD=10.6; TCcor=24.6°,SD=9.1; P<0.05). (Fig. 1B). Conclusion: A supramalleolar osteotomy is able to correct both the ankle and subtalar joint alignment. However, correction at the level of the subtalar joint accounted for only 3 to 4 degrees, which was less than found for the ankle joint alignment. For cases where a higher correction at the subtalar joint is necessary, we thus suggest adding a calcaneal osteotomy or subtalar arthrodesis to the SMOT. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Painful adult acquired flatfoot is classified into multiple types, with a one category reserved for those that have rigid deformity. However, there is a subset of patients with rigid progressive collapsed foot deformity (PCFD) in which navicular and calcaneus are subluxed from the talus causing sub-fibular impingement and erosion and fixed abduction of the forefoot. This condition is not well described in the literature. The treatment of these patients can be technically difficult given the attenuation and erosion of soft tissue and articular constraints. In this study we sought to identify reduction technique, shared characteristics, treatments, and outcomes in patients with severe hindfoot valgus deformity with subluxation and subfibular impingement who were treated by subtalar reduction and arthrodesis, and talonavicular arthrodesis at a single institution. Methods: A retrospective chart review was done of all patients who underwent flat foot reconstruction by a single surgeon. Patient were included in the study if on preoperative weight-bearing (WB) CT they met the following radiographic criteria: 3 sequential sagittal cuts of the calcaneus without the talus present, 3 sequential sagittal cuts of the talus without the calcaneus present, and the presence of a calcaneofibular articulation on coronal cuts. Patients with neuromuscular disorders or peripheral neuropathy were excluded. This review evaluated demographic data, comorbidities, complications, and the need for reoperation. Plane radiographs and CT findings were compared to identify subluxation on plane images. Patients were treated with a double, triple, or pantalar arthrodesis based on the treating surgeon's discretion. A cohort of 23 patients has already been identified, but additional data review is currently underway. Results: The initial patient cohort consisted of twenty-three patients who met the inclusion criteria with an average age of 64.5 (range, 48-79) years. The initial cohort consisted of patients who were treated from 2009-2014. Seven of the twenty-three patients (30.4%) required reoperation for various reasons ranging from late infection to nonunion and symptomatic hardware (Table 1). We found that the average BMI for patients with this disorder was 34kg/m2. Four patients have fibular stress fractures on presentation, these patients had an average BMI of 41.6kg/m2. Specific techniques for reduction included use of distractors at subtalar and TN joints. Radiographic findings on plane films are linked to findings on CT scan. Recurrence of deformity occurred with tilt of the talus requiring bracing in 2 patients. Incomplete correction was common, particularly early in the study period. Conclusion: PCFD is a very problem seen by foot and ankle surgeons. Physicians should be aware of the challenges presented in treating the subset of patients who have atraumatic dislocation of the subtalar joint. Diagnosis can be made on plane radiographs, though WB CT is useful for treatment planning. Treatment of these patients requires careful physical and radiographic examination. Reduction and arthrodesis is the treatment of choice. Patients should also be counseled about the possible need for reoperation given the high rate of reoperation in this population. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: The hindfoot moment arm was first described by Saltzman and el-Khoury to evaluate hindfoot varus and valgus alignment and has been well described and validated in the literature. It is commonly used by surgeons for preoperative planning of various hindfoot reconstructive procedures. The hindfoot alignment angle (the angle formed by the intersection between the tibial axis and the calcaneal axis) is another metric of measuring hindfoot alignment commonly utilized by surgeons. The purpose of this study was to determine if rotation of the hindfoot alters the hindfoot alignment moment arm and hindfoot alignment angle. We hypothesize that slight changes in internal and external rotation of the foot during x-ray positioning will have a large effect on the hindfoot moment arm and hindfoot alignment angle. Methods: We prospectively enrolled 29 patients, totaling 58 lower extremities, presenting to outpatient clinic for evaluation of a foot and ankle complaint. Patients <18 years of age, unable to perform bilateral weightbearing radiographs, or presenting for postoperative visits from recent foot and ankle surgery were excluded. Bilateral Saltzman hindfoot radiographs in neutral, 10 degrees of internal rotation, and 10 degrees of external rotation were performed. Marking lines were drawn on the standing platform to standardize rotation, with patients aligning their second ray with the lines. A fellowship-trained foot and ankle orthopaedic surgeon and an orthopaedic surgery resident individually measured the hindfoot moment arms and alignment angles. Analysis of variance (ANOVA) testing was used to assess for differences in hindfoot moment arm and hindfoot alignment angle in neutral, internal, and external rotation. Intra- and inter-observer agreement (95% limits) and intra-class correlation coefficients were calculated to assess for intra- and inter-observer reliability. Results: The cohort consisted of 11 (37.9%) males and 18 (62.1%) females, with a mean age of 48.7 (SD=14.7) years and mean body mass index (BMI) of 29.9 (SD=6.6) kg/m2. The mean hindfoot moment arms were 4.6 (SD=6.7) mm, 11.3 (SD=3.4) mm, and -5.4 (SD=6.2) mm in neutral, internal, and external rotation, respectively. The mean hindfoot alignment angles were 4.5 (SD=5.6) degrees, 18.6 (SD=6.8) degrees, and -10.9 (SD=10.6) degrees in neutral, internal, and external rotation, respectively. There was a significant difference in both the hindfoot moment arm (p<0.001) and hindfoot alignment angle (p<0.001) among rotational positions. A strong positive correlation existed between the amount of rotation and both moment arm (r=0.78; p<0.001) and alignment angle (r=0.84; p<0.001). Conclusion: There appears to be significant variability in both the hindfoot moment arm and hindfoot alignment angle with respect to rotation of the patient's lower extremity. Orthopaedic surgeons should carefully scrutinize limb rotation when making clinical decisions based on the hindfoot moment arm or alignment angle. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Semi-automatic three-dimensional (3D) biometric weightbearing CT (WBCT) tools have been shown to accurately demonstrate the relationship between the center of the ankle joint and the tripod of the foot. The measurement of the Foot and Ankle Offset (FAO) represents an optimized biomechanical assessment of foot alignment. The objective of this study was to evaluate the correlation between FAO and traditional adult acquired flatfoot deformity (AAFD) markers, measured in different planes. We hypothesized that the FAO would significantly correlate with other radiographic markers of pronounced AAFD. Methods: In this retrospective comparative study, we included 113 patients with stage II AAFD, 43 men and 70 women, mean age of 53.5 (range, 20 to 86) years. Three-dimensional coordinates (X, Y and Z planes) of the foot tripod (most plantar voxel of the first and fifth metatarsal heads, and calcaneal tuberosity) and the center of the ankle joint (most proximal and central voxel of the talar dome) were harvested by two blinded and independent fellowship-trained orthopedic foot and ankle surgeons. The FAO was automatically calculated using the 3D coordinates by dedicated software. Multiple WBCT parameters related to the severity of the deformity in the coronal, sagittal, and transverse plane were manually measured. Results: We found overall good to excellent intra (range, 0.84-0.99) and interobserver reliability (range, 0.71-0.96) for manual AAFD measurements. FAO semi-automatic measurements demonstrated excellent intra (0.99) and interobserver reliabilities (0.98). Hindfoot moment arm (p<0.00001), subtalar horizontal angle (p<0.00001), talonavicular uncoverage angle (p=0.00004) and forefoot arch angle (p=0.0001) were the only variables found to significantly influence and correlate with FAO measurements, with an R-squared value of 0.79. A value of hindfoot moment arm of 19.8mm was found to be a strong threshold predictor of increased values of FAO, with mean values of FAO of 6.5 when the HMA was lower than 19.8mm and 14.6 when the HMA was equal or higher than 19.8mm. Conclusion: We found that 3D WBCT semi-automatic measurements of Foot and Ankle Offset (FAO) significantly correlated with traditional markers of pronounced AAFD. HMA, subtalar horizontal angle, talonavicular uncoverage angle and forefoot arch angle were found to explain 79% of the variations in FAO measurements. FAO Measurements were also found to be more reliable than the manual measurements. The FAO offers a more complete biomechanical and multiplanar assessment of the AAFD, that that accounts for relative positioning of the foot tripod and the center of the ankle joint, representing in a single measurement the three-dimensional components of the deformity. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Recent literature has established the middle facet of the subtalar joint as a reliable and accurate marker of pronounced peritalar subluxation (PTS) in Adult Acquired Flatfoot Deformity (AAFD) patients. The Foot and Ankle Offset (FAO) has also been accepted as a more complete and three-dimensional (3D) measurement of foot collapse and hindfoot valgus. To date, no assessment has been made regarding the relationship between the severity of the AAFD and the amount PTS measured at the middle facet. The objective of this study was to investigate the correlation between these variables. We hypothesized that direct positive linear correlation would be found, with significantly increased middle facet joint incongruence and subluxation in patients with more pronounced hindfoot valgus and foot collapse. Methods: In this IRB-approved retrospective comparative study, we included 76 feet (42 left, 35 right) with symptomatic AAFD who underwent standing weightbearing CT (WBCT) as standard baseline assessment of their foot deformity. One blinded fellowship-trained foot and ankle surgeon with more than 10 years of experience performed measurements using multiplanar reconstruction (MPR) WBCT images. Manual measurements of subluxation and incongruence of the middle facet were performed at the anteroposterior midpoint of the articular facet. Semiautomatic calculation of the FAO was performed after 3D coordinate harvesting of the weightbearing points of the first, fifth metatarsal and calcaneus as well as the center of the ankle. Correlation of FAO severity and subluxation/incongruence of the middle facet was assessed by Spearman's correlation and bivariate analysis. Paired Wilcoxon was utilized to compare FAO values in congruent (0% subluxation), subluxated (1-99% subluxation) and dislocated middle facets. P-values <0.05 were considered significant. Results: No significant direct correlation was observed between FAO and Middle Facet Incongruence angle (p=0.12). However, positive linear correlation was found between middle facet subluxation and FAO (Spearman's 0.54, R2 0.29, p<0.0001). The subluxation of the middle facet was found to increase by 3.5% for every one-point FAO increase (Middle Facet Subluxation (%) = 6.903202 + 3.5452074*Foot and Ankle Offset). Mean values and confidence intervals (CI) of FAO were significantly different depending on the congruency of the middle facet (p=0.0003): congruent, 5.2 (CI, 3.4 to 7.0), subluxated, 8.7 (CI, 6.8 to 9.0) and dislocated, 12.9 (CI, 9.8 to 15.9). Similarly, middle facet subluxation was also found to progressively and significantly increase when FAO values were staged from zero (normal alignment) to four (FAO>20) (p<0.0001). Conclusion: This study is the first to compare and correlate measurements regarding the amount of subluxation of middle facet with the severity of AAFD, when measured by the foot and ankle offset (FAO). We found a significant, positive and linear correlation between the amount of subluxation of the middle facet and FAO measurements. No correlation was found between the incongruence angle of the facet and FAO. Our results support the concept of using the subluxation of the middle facet of the subtalar joint as a key marker of early and progressive deformity in patients with AAFD. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Sinus tarsi and Subfibular impingement are considered the main causes of lateral foot pain in patients with Adult Acquired Flatfoot Deformity (AAFD). They are considered important markers in the spectrum of progressive peritalar subluxation (PTS) in patients with AAFD. Recent literature has also highlighted the use of the Middle Facet of the subtalar joint as a more accurate indicator of PTS. The objective of this study was to assess the relationship between lateral impingement and middle facet PTS. Our hypotheses were that patients with sinus tarsi and subfibular impingement would demonstrate more severe PTS than patients with no impingement, and that subfibular impingement would represent a better indicator of pronounced deformity when compared to sinus tarsi impingement. Methods: In this retrospective comparative Cohort Study, we included 110 AAFD patients that underwent standing weightbearing CT (WBCT) as a standard baseline assessment of their foot deformity. The presence or absence of sinus tarsi and subfibular impingements, as well as the incongruence angle and percentage of subluxation of the middle facet of the subtalar joint, were manually measured on multiplanar reconstruction (MPR) WBCT images by a blinded fellowship-trained foot and ankle surgeon. Descriptive statistics were used to describe the rate of sinus tarsi and subfibular impingement as well as mean values for middle facet incongruence angle and subluxation. Wilcoxon test was used to compare the values of PTS at the middle facet in patients with or without sins tarsi and subfibular impingement. A partition prediction model was used to assess the values of middle facet PTS that would foresee a higher risk for lateral impingement. P-values <0.05 were considered significant. Results: Seventy-five percent (n=82) of the AAFD patients had sinus tarsi impingement and 64% (n=70) of the AAFD patients had subfibular impingement. The mean value and 95% CI for middle facet incongruence angle and subluxation percentage were respectively 10.5o (CI, 8.7 to 12.2o) and 28.7% (CI, 23.5 to 33.9%). Middle facet subluxation was significantly higher in patients with sinus tarsi and subfibular impingement by respectively 22.6% and 23.9%, both p-values <0.0001. No similar significant differences were observed on incongruence angle measurements. The partition model demonstrated that the middle facet subluxation percentage was the best predictor of both sinus tarsi (R2=0.15) and subfibular impingements (R2=0.17), with 24.9% subluxation representing an important threshold for higher risk of sinus tarsi (90% incidence) and subfibular impingements (84% incidence). Conclusion: Our results showed significantly increased middle facet subluxation in AAFD patients with sinus tarsi and subfibular impingement. Subfibular impingement was less frequent and associated with more pronounced deformity than sinus tarsi impingement. Measurements of the percentage of subluxation of the middle facet were also found to be the best predictor of impingement, with 29.4% representing an important threshold value above which the risks for both sinus tarsi and subfibular impingement were significantly higher. With that in mind, we would recommend close assessment and follow-up of the amount of middle facet subluxation in the decision-making for the treatment of AAFD patients. [ABSTRACT FROM AUTHOR]