Impact of First Metatarsal Hyperpronation on First Ray Alignment: A Study in Cadavers

Abstract

BackgroundThere is increased evidence of first metatarsal hyperpronation in patients with hallux valgus, but its impact on the stability of the first metatarsophalangeal and metatarsosesamoid joints is unknown. A previous biomechanical study showed that an increase in hallucal pronation might lead to medial soft tissue failure of the first metatarsophalangeal joint. Conversely, dynamic studies on hallux valgus have shown that the first tarsometatarsal joint moves in supination during weightbearing, and supination was associated with an increase in the intermetatarsal angle (IMA) and hallux valgus angle (HVA).Questions/purposes(1) Does an increase in first metatarsal pronation cause an increase in hallucal pronation? (2) Can an intrinsic increase in first metatarsal pronation lead to first ray supination during weightbearing? (3) Can a combination of intrinsic first metatarsal hyperpronation and first metatarsophalangeal medial soft tissue failure increase supination of the first ray during weightbearing? (4) Is first ray supination during weightbearing associated with an increase in the IMA and HVA?MethodsTwelve transtibial, nonpaired cadaver specimens without deformities were used. Each specimen underwent six weightbearing CT scans under different conditions. The first three CT examinations were performed without any osteotomy of the first metatarsal. The first was a simulated nonweightbearing condition. The second was a simulated weightbearing condition. The third was a simulated weightbearing condition with medial soft tissue release. Subsequentially, a 30° pronation osteotomy of the first metatarsal was performed, and the same sequence of weightbearing CT images was obtained. On each weightbearing CT image, the HVA, IMA, sesamoid rotation angle, metatarsal pronation angle (MPA), metatarsosesamoid rotation angle, and hallucal pronation (HP) were measured. Motions were calculated based on the differential values of these angular measurements produced by the six different conditions (weightbearing, medial soft tissue release, 30° pronation osteotomy, and combinations of these conditions). We compared means using a t-test for normally distributed variables and the Mann-Whitney U test for nonnormally distributed variables. Correlations were assessed with Pearson product-moment correlation coefficients.ResultsWe found that 30° pronation osteotomy of the first metatarsal increased the MPA and HP by 28° ± 4° and 26° ± 6°, respectively, in the nonweightbearing condition. No differences between the increase in MPA and the increase in HP were noted (mean difference 2° [95% CI -1° to 5°]; p = 0.20). Therefore, an increase in first metatarsal pronation caused an increase in hallucal pronation. When a 30° pronation osteotomy of the first metatarsal was performed, the first ray motion during weightbearing went from pronation to supination (4° ± 2° in pronation without osteotomy versus 4° ± 2° in supination after the osteotomy, mean difference 8° [95% CI 6° to 9°]; p < 0.001). Therefore, an intrinsic increase in prona...

CORR Insights®: Impact of First Metatarsal Hyperpronation on First Ray Alignment: A Study in Cadavers

“…As Lalevée et al [1] noted in the current study in cadavers, the combination of first metatarsal intrinsic hyperpronation and first metatarsophalangeal medial soft tissue failure led to a hallux valgus deformity. The authors indicated that hallux valgus is a dynamic condition, and the deformity could be more correlated with motions during weightbearing than with plain static measurements.…”

“…To further evaluate how medial deviation and/or hyperpronation of the first metatarsal affects the stability of the first metatarsophalangeal and metatarsosesamoid joints, a cadaver model could be tested, similar to what Lalevée et al [1] did in the current study. This also could be tested in a biomechanical model.…”

Recurrence Rates With Longer-Term Follow-up After Hallux Valgus Surgical Treatment With Distal Metatarsal Osteotomies: A Systematic Review and Meta-analysis

“…The high recurrence rates in the long term for all categories of surgical procedures suggest that better understanding of pathogenesis and prognosis of HV is required to prescribe the ideal treatment, before modifying or introducing new surgical techniques. 21,28…”

Ankle syndesmotic instability assessment using a three-dimensional distance mapping algorithm: a cadaveric pilot WBCT study

“…The proximal tibia was then potted in a square block using polymethylmethacrylate bone cement. The cemented block was utilized to fix the specimen vertically and in a plantigrade fashion into an external radiolucent frame that was previously utilized in the literature to allow for simulated weight bearing (17) . Weight bearing was simulated by introducing 36.3 kilograms (356N) of vertical load into the specimen frame construct (Figure 1).…”