Activités scientifiques

ABSTRACT

Background: Progressive Collapsing Foot Deformity (PCFD) is a complex multiplanar deformity commonly treated with osteotomy-based reconstruction in flexible cases. Although weight-bearing CT (WBCT) has improved assessment of PCFD, WBCT-based predictive planning models remain unexplored.

Purpose: To evaluate the accuracy of a WBCT-based predictive surgical planning model in estimating postoperative alignment following reconstruction for flexible PCFD.

Study design: Retrospective cohort study.

Methods: Thirty-four patients with PCFD who underwent reconstruction with medial displacement calcaneal osteotomy, lateral column lengthening, and/or first-ray plantarflexion osteotomy and had preoperative and 3-month postoperative WBCT were included. The model estimated postoperative hindfoot moment arm (HMA), axial talus−first metatarsal angle (TFMA-A), talonavicular coverage angle (TNCA), and sagittal talus−first metatarsal angle (TFMA-S) using correction magnitudes. Predicted alignment was compared with postoperative WBCT measurements using Bland−Altman analysis, mean absolute error (MAE), root-mean-square error (RMSE), and paired t-tests.

Results: Predictive accuracy was highest for HMA, with a mean bias of +2.73 mm (p = 0.005), narrowest limits of agreement (−7.66 mm to +13.12 mm), and lowest MAE and RMSE values (approximately 2.9 mm and 3.7 mm). TFMA-A, TNCA, and TFMA-S demonstrated wider limits of agreement (approximately −17° to +21°) and greater case-level variability, although no significant systematic differences between predicted and postoperative values were observed (p = 0.21–0.90).

Conclusions: A WBCT-based predictive surgical planning model estimated postoperative alignment accurately for hindfoot valgus correction, while predictions of midfoot/forefoot abduction and arch collapse demonstrated greater individual variability. Despite this variability, the model accurately reproduced mean multiplanar correction, supporting patient-specific surgical planning in PCFD.

Abstract

First ray hypermobility is implicated in many forefoot pathologies, yet its quantitative assessment remains challenging. Instrumented methods have traditionally focused on isolated dorsal displacement of the first metatarsal, which may not reflect physiological load sharing within the forefoot. This cadaveric biomechanical study evaluated the reliability and construct validity of two arthrometer-based measures: the first ray absolute (FRAM) and relative (FRRM) mobility, respectively assessed under isolated loading of the first metatarsal and symmetrical loading of the first metatarsal and lesser metatarsals. Ten fresh-frozen cadaveric lower limb segments were tested using an automated forefoot arthrometer. Within-session reliability was quantified using intraclass correlation coefficients, standard error of measurement, and minimal detectable change. Construct validity was assessed by correlating FRAM and FRRM with a biomechanical reference construct defined as the sum of superior-inferior translations at the first tarsometatarsal and medial naviculo-cuneiform joints measured using optical motion capture. Linear mixed-effects models were used to characterise joint-level kinematic behaviour under each loading mode. FRRM demonstrated excellent within-session reliability (ICC = 1.00) and a high positive correlation with the reference construct (R = 0.70, p < 0.001). FRAM also showed excellent reliability (ICC = 0.97) but higher absolute measurement error and a moderate positive correlation with the reference construct (R = 0.63, p < 0.001). Symmetric loading engaged proximal first ray joints more effectively than isolated loading, which predominantly mobilised the first tarsometatarsal joint. These findings indicate that arthrometer-based assessment of the first ray mobility is sensitive to the loading mode and that symmetric loading provides a more biomechanically representative evaluation of the first ray mobility than traditional isolated approaches.

Abstract

Introduction

The Lapidus procedure treats hallux valgus with first-ray hypermobility. It can be performed as a single first tarsometatarsal (TMT) arthrodesis or a three-corner TMT construct with additional intermetatarsal fusion. Early loss of correction remains a concern. This study compared early radiographic stability between techniques.

Methods

Fifty patients (15 three-corner TMT arthrodesis, 35 single first TMT arthrodesis) treated between 2014 and 2023 were retrospectively reviewed. Hallux valgus angle (HVA), intermetatarsal angle (IMA), Méary’s angle, and tibial sesamoid position were measured on weight-bearing radiographs at 6 weeks and 6 months postoperatively.

Results

Both techniques achieved significant correction. The three-corner TMT arthrodesis group showed greater initial IMA correction at 6 weeks (p = 0.020) and maintained a lower IMA at 6 months (p = 0.001). Early IMA loss was greater after single first TMT arthrodesis (1.5°±1.7° vs 0.6°±0.8°, p = 0.013).

Conclusion

Three-corner TMT arthrodesis was associated with greater early intermetatarsal stability than single first TMT arthrodesis.

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