UNASSIGNED: Although operative treatment of the flexible progressive collapsing foot deformity (PCFD) remains controversial, correction of residual forefoot varus and stabilization of the medial column are important components of reconstruction. A peroneus brevis (PB) to peroneus longus (PL) tendon transfer has been proposed to address these deformities. The aim of our study was to determine the effect of an isolated PB-to-PL transfer on medial column kinematics and plantar pressures in a simulated PCFD (sPCFD) cadaveric model.
UNASSIGNED: The stance phase of level walking was simulated in 10 midtibia cadaveric specimens using a validated 6-degree of freedom robot. Bone motions and plantar pressure were collected in 3 conditions: intact, sPCFD, and after PB-to-PL transfer. The PB-to-PL transfer was performed by transecting the PB and advancing the proximal stump 1 cm into the PL. Outcome measures included the change in joint rotation of the talonavicular, first naviculocuneiform, and first tarsometatarsal joints between conditions. Plantar pressure outcome measures included the maximum force, peak pressure under the first metatarsal, and the lateral-to-medial forefoot average pressure ratio.
UNASSIGNED: Compared to the sPCFD condition, the PB-to-PL transfer resulted in significant increases in talonavicular plantarflexion and adduction of 68% and 72%, respectively, during simulated late stance phase. Talonavicular eversion also decreased in simulated late stance by 53%. Relative to the sPCFD condition, the PB-to-PL transfer also resulted in a 17% increase (P = .045) in maximum force and a 45-kPa increase (P = .038) in peak pressure under the first metatarsal, along with a medial shift in forefoot pressure.
UNASSIGNED: The results from this cadaver-based simulation suggest that the addition of a PB-to-PL transfer as part of the surgical management of the flexible PCFD may aid in correction of deformity and increase the plantarflexion force under the first metatarsal.
UNASSIGNED: This study provides biomechanical evidence to support the addition of a PB-to-PL tendon transfer in the surgical treatment of flexible PCFD.

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

BACKGROUND: 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.
CONCLUSIONS: 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.
METHODS: Level III, Retrospective Comparative 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.

The contribution of each of the ligaments in preventing the arch loss, hindfoot valgus, and forefoot abduction seen in progressive collapsing foot deformity (PCFD) has not been well characterized. An improved understanding of the individual ligament contributions to the deformity would aid in selecting among available treatments, optimizing current surgical techniques, and developing new ones. In this study, we evaluated the contribution of each ligament to the maintenance of foot alignment using a finite element model of the foot reconstructed from computed tomography scan images. The collapsed foot was modeled by simulating the failure of all the ligaments involved in PCFD. The ligaments were removed one at a time to determine the impact of each ligament on foot alignment, and then restored one at a time to simulate isolated reconstruction. Our findings show that the failure of any one ligament did not immediately lead to deformity, but that combined failure of only a few (the plantar fascia, long plantar, short plantar, deltoid, and spring ligaments) could lead to significant deformity. The plantar fascia, deltoid, and spring ligaments were primarily responsible for the prevention of arch collapse, hindfoot valgus, and forefoot abduction, respectively. Moreover, to produce deformity, a considerable amount of attenuation in the spring, tibiocalcaneal, interosseous talocalcaneal, plantar naviculocuneiform, and first plantar tarsometatarsal ligaments, but only a small amount in the plantar fascia, long plantar, and short plantar ligaments was needed. The results of this study suggest that the ability of a ligament to prevent deformity may not correlate with its attenuation in a collapsed foot.

OBJECTIVE: Adult-acquired flatfoot deformity (AAFD) requires optimum planning that often requires several procedures for deformity correction. The objective of this study was to detect the difference between MDCO versus LCL in the management of AAFD with stage II tibialis posterior tendon dysfunction regarding functional, radiographic outcomes, efficacy in correction maintenance, and the incidence of complications.
METHODS: 42 Patients (21 males and 21 females) with a mean age of 49.6 years (range 43-55), 22 patients had MDCO while 20 had LCL. Strayer procedure, spring ligament plication, and FDL transfer were done in all patients. Pre- and Postoperative (at 3 and 12 months) clinical assessment was done using AOFAS and FFI questionnaire. Six radiographic parameters were analyzed, Talo-navicular coverage and Talo-calcaneal angle in the AP view, Talo- first metatarsus angle, Talo-calcaneal angle and calcaneal inclination angle in lateral view and tibio-calcaneal angle in the axial view, complications were reported.
RESULTS: At 12 months, significant improvement in AOFAS and FFI scores from preoperative values with no significant difference between both groups. Postoperative significant improvements in all radiographic measurements in both groups were maintained at 12 months. However, the calcaneal pitch angle and the TNCA were better in the LCL at 12 months than MDCO, 17̊±2.8 versus 13.95̊±2.2 (p=0.001) and 13.70̊±2.2 versus 19.05̊±3.2 (p<0.001) respectively. 11 patients (26.2%) had metal removal, seven (16.6%) in the MDCO, and four (9.6%) in the LCL. Three (7.1%) in the LCL group had subtalar arthritis, only one required subtalar fusion.
CONCLUSIONS: LCL produced a greater change in the realignment of AAFD, maintained more of their initial correction, and were associated with a lower incidence of additional surgery than MDCO, however, a higher incidence of degenerative change in the hindfoot was observed with LCL.

The study aims to prospectively compare double and triple arthrodesis in terms of functional outcomes and deformity correction. To the best of our knowledge, this is the first prospective comparative study in the literature to date.
This is a prospective comparative cohort study carried out between May 2017 and May 2019. The study was approved by the IRB at Assiut University and done according to the Helsinki declaration. Patients with AAFD stage III aged between 15 and 40 years old were assigned to double arthrodesis or triple arthrodesis. The groups were prospectively followed for one year. Primary outcomes were union rates, AOFAS scores, and radiological parameters of deformity correction on AP and lateral plain radiographs. Secondary outcomes were operative time, time to union, and complications. The double arthrodesis was done through the medial approach, while the triple arthrodesis was done through dual medial and lateral approaches. The post-operative protocol was standardized for both groups.
A total of twenty-three patients matched the inclusion criteria and provided their consent to participate in the study. Thirteen (all males) patients underwent double arthrodesis, while ten (nine males and one female) patients underwent triple arthrodesis. The mean age for double and triple arthrodesis was 20.15 ± 5.63 and 25.10 ± 8.36 years, respectively, and the mean follow-up lengths were 12.46 and 12.9 months, respectively. There were no statistically significant differences between both groups in age, gender, laterality, or duration of follow-up. There were no statistically significant differences between both groups in AOFAS hindfoot scores or radiographic parameters. All patients were available for the final follow-up evaluation. All patients in both groups achieved union by four months post-operatively. The mean time to union in the double and triple arthrodesis groups was 3.39 ± 0.65 vs. 3.31 ± 0.6 months, respectively, with no statistically significant differences (p = 0.77). The mean operative time was significantly shorter in the double arthrodesis group than the triple arthrodesis group, 55.77 ± 15.18 vs. 91.6 ± 24.14 min (p < 0.001), respectively. Both double and triple arthrodesis groups had a statistically significant improvement of the mean AOFAS hindfoot score post-operatively (71.46 ± 7.77 vs. 88.38 ± 3.66, p < 0.001) and (66.9 ± 7.69 vs. 85 ± 5.83, p < 0.001), respectively. In the double arthrodesis group, the mean calcaneal pitch angle increased from 11.46° pre-operatively to 19.34° (MD = 8.45°, p < 0.001). The mean Meary\'s angle improved from - 4.19 to 2.9° (MD = 7.32°, p < 0.001). Hibbs angle had a mean reduction of 6.45° post-operatively (p = 0.069). In the triple arthrodesis group, the mean calcaneal pitch angle improved from 10.06° pre-operatively to 17.49° post-operatively (MD = 7.12°, p < 0.001). The mean Meary\'s angle improved from - 4.72 to 2.29° (MD = 7.09°, p < 0.001). The mean Hibbs angle decreased from 153.07 to 142.32° (MD = 10.54°, p < 0.001). The double vs. triple arthrodesis groups had no statistically significant differences in AOFAS hindfoot score improvement (16.92 vs. 19.1, p = 0.44), respectively. The two groups had no statistically significant differences in the magnitude of correction of all the radiographic parameters.
Double arthrodesis is an equally reliable surgical option for AAFD stage III for achieving union, improving the functional outcomes, and deformity correction as triple arthrodesis with a significantly shorter operative time in the former. The authors recommend double arthrodesis if the calcaneocuboid joint is unaffected.