Tomoyuki Nakasa

➢ Ankle cartilage damage ranges from osteochondral lesions of the talus to end-stage osteoarthritis. End-stage ankle osteoarthritis has been associated with a health burden comparable with that of major chronic diseases such as congestive heart failure and kidney disease, while predominantly affecting young and active patients. ➢ Ankle osteoarthritis often has a posttraumatic nature, making it possible to study the long-term results of traumatic articular injuries and identify potential targets for early therapeutic interventions. ➢ The scientific literature has been predominantly focused on outcomes after surgical treatment of osteochondral lesions of the talus or osteoarthritis. However, evidence on nonoperative treatment has been limited and methodologically weak, with evidence for early interventions (e.g., lifestyle or biologicals) even more scarce. ➢ The greatest opportunity to improve long-term outcomes in ankle cartilage damage may be early recognition and early initiation of treatment.

Background: Although arthroscopic lateral ankle ligament repair for chronic lateral ankle instability (CLAI) is widely performed, the association between patient age and postoperative outcomes remains unclear. This study aimed to investigate the clinical outcomes of arthroscopic lateral ankle ligament repair across a broad age spectrum. Methods: We retrospectively reviewed 934 patients who underwent arthroscopic lateral ankle ligament repair for CLAI with a modified lasso-loop stitch using a suture anchor; all procedures were performed by a single surgeon. Patients were classified into 5 age groups: skeletally immature (SI; P < .001). Time to free gait ( P = .004), jogging ( P < .001), and return to full sports activities ( P < .001) differed significantly among groups; older patients tended to require longer recovery times. SI, AD, and YA groups demonstrated higher postoperative SAFE-Q scores than the EP group in several subscales, particularly in physical and social functioning. In contrast, no age-related differences were observed in the sports activity subscale. Conclusion: The association between age and postoperative outcomes after arthroscopic lateral ankle ligament repair varied across outcome domains. Younger patients demonstrated better outcomes in several functional subscales and achieved faster recovery milestones; however, advanced age alone should not be considered a contraindication to arthroscopic lateral ankle ligament repair. Level of Evidence: Level III, retrospective cohort study.

Early functional rehabilitation after acute Achilles tendon rupture is increasingly used in nonoperative protocols, but the definition of “early” remains highly heterogeneous across the literature and no standardized timing threshold has been established. This narrative review clarifies the conceptual and operational definitions of early rehabilitation and examines the unresolved timing-threshold problem. Existing evidence supports early functional rehabilitation without a demonstrated increase in rerupture risk compared with delayed immobilization. Early rehabilitation may improve short-term functional recovery; however, clear long-term superiority over more delayed strategies has not been demonstrated. Substantial heterogeneity persists in the initiation of weightbearing and range of motion and in orthosis duration. Although weightbearing within four weeks is commonly used as an operational definition of early rehabilitation for evidence synthesis, it is not a biologically or clinically validated threshold. The literature also lacks granular evidence defining a timing–response relationship or an optimal initiation window. Current evidence therefore supports early functional rehabilitation as a reasonable strategy, but future research should identify validated timing–response relationships and patient-specific strategies.

Background/Objectives: Although proximal first metatarsal osteotomy is a common treatment for hallux valgus (HV), its effect on dynamic first tarsometatarsal (TMT) joint mobility remains unclear. Previous assessments have largely relied on static radiographic parameters, which may not capture functional joint kinematics. The aim of this study was to evaluate changes in first TMT joint mobility during the stance phase of gait using a synchronized ultrasound and three-dimensional motion capture system after combined hallux valgus surgery incorporating proximal first metatarsal osteotomy. Methods: We prospectively studied 23 feet of 21 female patients with symptomatic HV undergoing combined hallux valgus surgery incorporating proximal closing-wedge osteotomy. We also evaluated 11 feet of 11 healthy female volunteers as controls. Per clinical indications, additional concomitant procedures were performed for 21 of the 23 feet. Vertical displacement of the first metatarsal and medial cuneiform as well as the first TMT joint gap was measured throughout the stance phase of gait using a synchronized ultrasound and motion capture system. Pre- and postoperative kinematics (>1 year follow-up) were compared with those in the control group using one-dimensional statistical parametric mapping (SPM). Results: Radiographically, the HV and intermetatarsal angles significantly improved, while sagittal plane parameters showed no significant changes. SPM analysis revealed no significant differences in the first TMT joint gap or first metatarsal displacement among groups. Preoperatively, compared with the controls, HV feet exhibited significantly greater plantar displacement of the medial cuneiform during late terminal stance. Postoperatively, this abnormal displacement was significantly decreased, with no significant difference between groups. Conclusions: Combined hallux valgus surgery incorporating proximal first metatarsal osteotomy was associated with reduced dynamic medial column hypermobility, specifically shifting vertical displacement of the medial cuneiform towards patterns observed in healthy controls during the terminal stance phase. These functional improvements occurred despite minimal changes in static sagittal radiographic alignment. The findings highlight the importance of dynamic assessment for evaluation of postoperative medial column biomechanics.

To investigate whether pre-exercise photobiomodulation (PBM) attenuates fatigue-induced decline in ankle joint position reproduction (JPR) and determine whether perceived ankle instability modifies this response. In this randomized, placebo-controlled trial with participant blinding and blinded outcome assessment, 30 healthy young adults (age: 24.3 ± 3.7 years; 15 male, 15 female) received either PBM or placebo treatment applied to the lower-leg musculature before a fatiguing protocol. PBM parameters included a wavelength of 830 nm, average power of 1 W, and total energy of 300 J per limb. Ankle JPR was assessed before and after fatigue. Participants were stratified by Cumberland Ankle Instability Tool (CAIT) scores. All physical assessments were performed by independent outcome assessors blinded to group allocation, with each participant evaluated by the same designated assessor throughout the study. The primary analysis revealed no overall between-group difference in fatigue-related changes in ankle JPR. A secondary exploratory group × CAIT interaction was observed, suggesting potential effect modification by perceived ankle instability. In the higher perceived instability subgroup, the estimated between-group difference was consistent with less post-fatigue worsening of JPR error following PBM; however, this estimate was based on small subgroup sizes and was not adjusted for multiple comparisons. The primary hypothesis was not supported; pre-exercise PBM showed no overall effect on fatigue-induced changes in ankle JPR. The exploratory group × CAIT interaction suggests that perceived ankle instability may be an effect modifier the response to PBM. However, this hypothesis requires confirmation in a larger, preregistered trial prospectively powered for interaction testing and incorporating functional outcomes in populations with clinically diagnosed chronic ankle instability.

Background: Nitinol staples (NSs) are increasingly used in foot and ankle surgery; nonetheless, staple breakage incidence and determinants remain incompletely defined. This study examined NS breakage in a large consecutive series, focusing on anatomical site, implant geometry, and fixation strategy. Methods: We retrospectively reviewed 333 patients (379 feet) who underwent foot and ankle surgery with 2-legged NS between 2021 and 2025. Overall, 702 staples were analyzed. Staple breakage was assessed on plain radiographs at a minimum follow-up of 6 months to evaluate implant integrity during the critical phase of bone union. Anatomical location, implant geometry (symmetric vs asymmetric), and fixation type (isolated vs combined) were analyzed. Multivariable logistic regression was performed to explore factors associated with breakage in the hindfoot. Results: The overall breakage rate was 4.0% (28/702). Breakage rates varied by anatomical site, with higher rates in the calcaneocuboid (22.2%), talonavicular (12.5%), tibiotalar (8.9%), and other joints than in the first ray (0.37%). In the calcaneocuboid joint, isolated staple fixation showed a higher breakage rate (33.3%) than staple fixation with an adjunct screw (6.7%). In second metatarsal shortening osteotomies, asymmetric staples demonstrated a higher breakage rate (35.7%) than symmetric staples (1.0%). Although most breakages were asymptomatic, 2 patients required revision surgery for symptomatic nonunion. In the hindfoot cohort, procedure category (Chopart arthrodesis) showed an association with breakage; however, with the numbers available, no significant association could be detected for body mass index or sex. Conclusion: The overall breakage rate for 2-legged NS was 4.0%. Breakage was more frequent in several high-demand hindfoot joints, and in second metatarsal osteotomies using asymmetric staples. Hybrid fixation showed a lower breakage rate in the first ray and calcaneocuboid joint. These exploratory findings suggest that anatomical site, staple geometry, and fixation strategy may contribute to the risk of radiographic staple breakage.

Background: Modified Lapidus procedure is well established for severe hallux valgus (HV). Nonetheless, postoperative recurrence remains a clinical concern. Peroneus longus (PL) functions as a dynamic stabilizer of the first ray, and its insertion at the base of the first metatarsal may be partially resected during osteotomy. Notably, PL dysfunction may contribute to recurrence by contributing to postoperative first ray instability. Nevertheless, extent of PL insertion resection during modified Lapidus procedure has not been quantified. This study aimed to evaluate the extent of resected PL insertion during modified Lapidus procedure. Methods: We retrospectively reviewed 80 feet from 74 patients with severe HV. We simulated 2 osteotomy methods: lateral wedge osteotomy at the base of the first metatarsal (M-method) and lateral wedge osteotomy at the distal medial cuneiform (C-method). On radiographs, resected lateral edge length of the first metatarsal (rM1-length) to correct intermetatarsal angle (IMA) to 0° was measured. Based on the rM1-length, 3-dimensional computed tomography models were used to measure whole PL insertion length, resected PL insertion length (rPL-length), and percentage of resected PL insertion (%-rPL). These parameters between the M-method and the C-method were compared. Cutoff value of the IMA for diagnosing feet with %-rPL greater than 50% using the M-method was evaluated. Results: rM1-length, rPL-length, and %-rPL were significantly greater with the M-method than with the C-method (all P < .001). Notably, the mean %-rPL with the M-method exceeded 50%. The IMA cutoff value was 21.4°; however, with the numbers available, no statistically significant difference was detected in the rPL-length and %-rPL with the C-method above and below this cutoff. Conclusion: Lateral wedge osteotomy at the first metatarsal may result in substantial PL insertion resection during the modified Lapidus procedure. Lateral wedge osteotomy of the medial cuneiform bone may better preserve PL insertion and potentially have implications for first ray stability.

Pain in hallux valgus (HV) often arises from the medial aspect of the first metatarsophalangeal (MTP) joint, but its mechanisms remain unclear. This study investigated the histological and molecular features of the medial capsule (MC) and their association with pain. Fifty feet from 49 HV patients undergoing corrective surgery were analyzed histologically and immunohistochemically for calcitonin gene-related peptide (CGRP), matrix metalloproteinase-3 (MMP3), and collagen type I/III. The severity of capsular degeneration was scored, and pain was evaluated using the Self-Administered Foot Evaluation Questionnaire (SAFE-Q). MC degeneration correlated with deformity severity (rs = 0.63, P < 0.0001). CGRP was strongly expressed around vessels and chondrocyte-like cells, with sparse expression in fibroblasts, irrespective of deformity degree. CGRP levels correlated positively with MMP3 (rs = 0.35, P < 0.05) and inversely with pain-related SAFE-Q scores (rs = − 0.52, P < 0.0001). Feet with bunion tenderness showed higher CGRP expression and worse pain scores. These findings suggest that bunion pain in HV is more closely associated with CGRP expression than with deformity severity, highlighting CGRP as a potential therapeutic target.

Background: Arthroscopic anterior talofibular ligament (ATFL) repair for chronic lateral ankle instability (CLAI) has shown favorable outcomes; however, instability recurrence has been reported. CLAI is frequently associated with concomitant calcaneofibular ligament (CFL) injury; its effects on postoperative outcomes remain unclear. This study aimed to investigate the association between preoperative magnetic resonance imaging (MRI) findings of the CFL and postoperative recurrence. Methods: This hypothesis-testing retrospective cohort study included 65 ankles in 60 patients (mean age, 34.0 ± 16.0 years) who underwent arthroscopic ATFL repair between November 2019 and June 2024. Preoperative oblique coronal MRI was used to classify the CFL morphology as intact, wavy, or thin. Clinical outcomes were assessed using the Japanese Society for Surgery of the Foot (JSSF) hindfoot-ankle scale, Karlsson- Peterson (K-P) score, and the Self-Administered Foot Evaluation Questionnaire (SAFE-Q). Recurrent ankle instability, defined as any postoperative ankle sprain during follow-up, was recorded. Multivariable analysis was performed to identify independent recurrent instability predictors. Results: Postoperative JSSF, K-P, and SAFE-Q scores improved significantly in all patients. Recurrent instability occurred in 13 of the 65 ankles (20.0%). Preoperative MRI revealed CFL injury in 38 ankles (58.5%). Additional CFL repair was performed in 24 ankles. Recurrence rates were higher in ankles with CFL injuries, particularly in those with thin (31.5%) and wavy (26.3%) morphologies. In the Firth model, CFL injury was independently associated with recurrence (OR 9.00, 95% CI 1.95-56.22, P = .004), whereas CFL repair showed a protective trend. Bootstrap analysis confirmed the significance of CFL injury. Conclusion: Preoperative MRI evaluation of CFL morphology is a significant predictor for identifying risk of postoperative recurrence after arthroscopic ATFL repair. CFL injury, particularly thin-type morphology, is associated with higher recurrence rates, suggesting the need for additional reconstructive or augmentative procedures to optimize clinical outcomes.