Medial displacement calcaneal osteotomy (MDCO) is the standard procedure for flatfoot. We investigated the effect of MDCO on the foot using a finite element analysis. Foot models were created from computed tomography data of 8 patients with flat feet. MDCO was performed on each model with bone translation distance of 4, 8, and 12 mm. The morphological changes, plantar pressures, and stress percentage on the talocrural and subtalar joints were evaluated before and after surgery. Morphological evaluation showed improvement in the medial longitudinal arch. The stress percentage of plantar pressure in the medial area decreased, and the stress percentage of plantar pressure in the mid- and lateral forefoot area increased. At the talocrural joint, the medial and middle stress percentage increased, while the lateral and posterior stress percentage decreased. In the subtalar joint, the stress percentage in the middle subtalar joint increased and that in the posterior subtalar joint decreased. Within the posterior subtalar joint, the anterior and medial stress percentage increased, while the posterior and lateral stress percentage decreased. Preoperative simulation using the finite element analysis may be useful in understanding postoperative morphological changes and loading conditions to perform patient-specific surgery.

The adult-acquired flatfoot is a complex multiplanar deformity that requires the foot and ankle surgeon to balance soft tissue, correct hindfoot valgus, and address instability of the medial column. The naviculocuneiform joint is historically underappreciated in regard to its involvement in medial column instability relative to the talonavicular and tarsometatarsal joints. Proper clinical and radiographic evaluation of the medial column, specifically evaluating for deformity at each medial column joint, will allow the surgeon to ensure correction of deformity and decrease the recurrence of instability or failure of the reconstruction.

The correction of the flexible pes planovalgus foot and ankle is a complicated and somewhat controversial topic. After conservative methods fail, there is a wide range of possible soft tissue and bony procedures. The appropriate work up and understanding of the pathomechanics are vital to the correct choice of procedures to correct these deformities. Once the work up and procedure selection are done, the operation must also be technically performed well and with efficiency, as most often the condition is corrected with a variety of procedures. This article discusses some of the most common procedures necessary to fully correct the pes planovalgus foot and discusses the authors\' technique and pearls.

Utilization of the talonavicular joint (TN) arthrodesis as an isolated procedure or in combination with hindfoot arthrodesis has been described in the literature for treatment of numerous hindfoot conditions. When used in isolation or with concomitant hindfoot arthrodesis, the TN joint has demonstrated nonunion rates reported as high as 37% in the literature. Despite previous research, there remains a lack of agreement upon the ideal fixation technique for TN joint arthrodesis with and without concomitant subtalar joint arthrodesis. The purpose of this study was to retrospectively compare the radiographic and clinical results of TN joint arthrodesis as part of double arthrodesis procedure utilizing 4 separate fixation constructs in the treatment of advanced hindfoot malalignment in stage III adult-acquired flatfoot deformity. We retrospectively reviewed 105 patients who underwent TN joint arthrodesis as part of double arthrodesis procedure utilizing 4 separate fixation constructs. Our results demonstrated a nonunion rate of 16.2%, with 17 nonunions identified within our patient population. One (2.4%) nonunion was observed in the 3-screw cohort, 7 (33.3%) nonunions were observed in the 2-screw cohort, 4 (16.0%) nonunions were observed in the 2-screw plus plate cohort, and 5 (29.4%) nonunions were observed in the 1-screw plus plate cohort. The difference in nonunion rate between the 4 cohorts was statistically significant. Based on these results, we conclude that the use of a 3-screw construct for TN joint arthrodesis as part of double arthrodesis procedure demonstrates a statistically significant reduction in nonunion rate and should be considered a superior fixation construct for this procedure.

BACKGROUND: Our aims were (a) to determine whether subtalar arthroereisis (STA) as adjunct procedure improved radiographic correction of stage IIb adult-acquired flexible flatfoot deformity (AAFD); (b) to assess the STA-related complication rate.
METHODS: A retrospective analysis of 22 feet (21 patients) diagnosed with stage IIb AAFD treated by medializing calcaneal osteotomy (MCO), flexor digitorum longus (FDL) transfer, spring ligament (SL) repair with or without Cotton osteotomy and with or without STA in a single institution was carried out. Seven measurements were recorded on pre- and postoperative (minimum 24 weeks) radiographs by 2 observers and repeated twice by 1 observer. Inter- and intraobserver reliabilities were assessed. The association of demographic (gender, side, age, body mass index) and surgical variables (Cotton, STA) with radiographic change was tested with univariate analysis followed by a multivariable regression model.
RESULTS: Excellent inter- and intraobserver reliabilities were demonstrated for all measurements (intraclass correlation coefficient range, 0.75-0.99). Gender, side, Cotton osteotomy, and STA were included in the multivariable analysis. Regression showed that STA was the only predictor of change in talonavicular coverage angle (TNCA) (R2 = 0.31; P = .03) and in calcaneo-fifth metatarsal angle (CFMA) (R2 = 0.40; P = .02) on dorsoplantar view. STA was associated to a greater change in TNCA by 10.1° and in CFMA by 5°. Four patients out of 12 STA complained of sinus tarsi pain after STA, and removal of the implant resolved symptoms in 3 of them.
CONCLUSIONS: In this series, STA as an adjunct procedure to MCO, FDL transfer, SL repair in the treatment of stage IIb AAFD led to improvement in correction of forefoot abduction. STA-related complication and removal rates were 33%.
UNASSIGNED: Level IV: Retrospective cohort study.

Lateral hindfoot pain associated with stage 2 to 3 adult-acquired flatfoot is often attributed to subfibular impingement. Preoperative magnetic resonance imaging (MRI) is generally performed to assess the extent of degeneration within the posterior tibial tendon, attenuation of medial soft tissue constraints, and degeneration of hindfoot and/or ankle articulations. The purpose of this study is to determine the incidence of lateral collateral ligament disease/injury associated with stages 2 and 3 adult-acquired flatfoot. The subjects were identified using a searchable computerized hospital database between 2015 and 2017. Stage 2 or 3 adult-acquired flatfoot deformity was confirmed in patients via chart review and MRI analysis. Lateral ankle ligament injury was confirmed using patient MRI results per the hospital radiologist and documented within the patients\' chart. Inclusion criteria required that patients be diagnosed with Johnson and Strom stage 2 or 3 flatfoot deformity with documented lateral ankle pain and that preoperative MRI scans be available with the radiologist\'s report. Patient exclusion criteria included patients <18 years of age, patients with flatfoot deformity caused by previous trauma, tarsal coalition, neuropathic arthritis, patients with previous surgery, or patients with incomplete medical records. In total, 118 patients were identified with these parameters. Of the 118 patients, 74 patients (62.7%) had documented lateral ankle ligament injury on MRI. Of the 77 patients with stage 2 adult-acquired flatfoot, 55 (71.4%) had confirmed lateral ankle ligament injury on MRI. Of the 41 patients with stage 3 adult-acquired flatfoot, 19 (46.3%) had confirmed lateral ankle ligament injury on MRI. This study demonstrates a relatively high incidence of lateral ligament disease associated with adult-acquired flatfoot deformity. These findings might have long-term implications regarding ankle arthritis after surgical management of adult-acquired flatfoot.