Tendon lengthening after achilles tendon rupture-passive effects on the ankle joint in a cadaveric pilot study simulating weight bearing

Workflow assessing the effect of Achilles tendon rupture on gait function and metatarsal stress: Combined musculoskeletal modeling and finite element analysis

Achilles tendon rupture (ATR) incidence has increased among badminton players in recent years. The foot internal stress was hard to obtain through experimental testing. The purpose of the current research is to develop a methodology that could improve the finite element model derived foot internal stress prediction for ATR clinical and rehabilitation applications. A subject-specific musculoskeletal model was combined with a 3D finite element model to predict the metatarsal stress. The 80% point during the push-off phase of walking was selected for the comparing between injured and uninjured sides. The surgical repaired Achilles tendon (AT) after 12 months was elongated by 5.5% than the uninjured tendon. At 80% point of stance phase, the ankle plantarflexion angle and AT force decreased by 39.6% and 21.9% on the injured side, respectively. The foot inversion degree increased by 22.9% and was accompanied by the redistribution of metatarsals von Mises stress. The stresses on the fourth and fifth metatarsals were increased by 59.5% and 85.9% on the injured side. The workflow is available to assess musculoskeletal disorders and obtain foot internal stress after ATR. The decreased ankle plantar flexor force may be affected by triceps surae muscle atrophy and weakened force transmission ability of elongated AT. The increased von Mises stress on fourth and fifth metatarsals accompanied by higher foot inversion may increase the ankle lateral sprain injury risk.

First Tarsometatarsal Joint Loading After Sequential Correction of Hallux Valgus Using a Proximal Opening Wedge Metatarsal Osteotomy and Distal Soft Tissue Procedure

Background:

The proximal opening wedge osteotomy (POWO) of the first metatarsal (TMT-1) is commonly performed in the operative treatment of hallux valgus. Limited work has been dedicated to study POWO’s effect on the TMT-1 joint, however. The purpose of this study is to evaluate the changes in TMT-1 joint contact stress following POWO of the first metatarsal.

Methods:

Five fresh-frozen cadaveric below-knee specimens (mean age: 73 years) with hallux valgus deformities (mean hallux valgus angle [HVA]: 37.4 ± 8.5 degrees) were studied. The specimens were loaded to 400 N on an MTS servohydraulic load frame. Joint contact characteristics at TMT-1 joint were measured with a Tekscan pressure sensor (Model 6900, 1100 psi; Tekscan Inc, Boston, MA) with various opening wedge sizes of 3, 5, and 7 mm both without and with a distal soft tissue release (DSTR). The contact force, area, and peak contact stress were compared among groups using analysis of variance and post hoc multiple comparisons over the untreated (Dunnett test, P < .05).

Results:

The mean contact force was 47.7 ± 33.5 N for untreated specimens. This increased sequentially with opening wedge size and reached statistical significance for 7-mm opening wedge (129.7 ± 62.3 N, P = .01) and 7-mm wedge + DSTR (134.8 ± 60.5 N, P = .008). The mean peak contact stress was 2.8 ± 1.3 MPa for the untreated specimens and increased incrementally with wedge size to 5.7 ± 3.0 MPa for 7-mm wedge only (P = .03) and 5.6 ± 2.5 MPa for 7-mm wedge + DSTR (P = .05). The contact area increased with corrections, but none reached significance.

Conclusion:

With increasing opening wedge size, loading of the TMT-1 joint increases. Joint stresses higher than 4.7 MPa have been shown to be chondrotoxic, potentially predisposing patients to arthritic joint changes following POWO.

Level of Evidence:

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