How do different anterior tibial tendon transfer techniques influence forefoot and hindfoot motion?

BACKGROUND: Idiopathic clubfoot correction is commonly performed using the Ponseti method and is widely reported to provide reliable results. However, a relapsed deformity may occur and often is treated in children older than 2.5 years with repeat casting, followed by an anterior tibial tendon transfer. Several techniques have been described, including a whole tendon transfer using a two-incision technique or a three-incision technique, and a split transfer, but little is known regarding the biomechanical effects of these transfers on forefoot and hindfoot motion. QUESTIONS/
PURPOSE: We used a cadaveric foot model to test the effects of three tibialis anterior tendon transfer techniques on forefoot positioning and production of hindfoot valgus.
METHODS: Ten fresh-frozen cadaveric lower legs were used. We applied 150 N tension to the anterior tibial tendon, causing the ankle to dorsiflex. Three-dimensional motions of the first metatarsal, calcaneus, and talus relative to the tibia were measured in intact specimens, and then repeated after each of the three surgical techniques.
RESULTS: Under maximum dorsiflexion, the intact specimens showed 6° (95% CI, 2.2°-9.4°) forefoot supination and less than 3° (95% CI, 0.4°-5.3°) hindfoot valgus motion. All three transfers provided increased forefoot pronation and hindfoot valgus motion compared with intact specimens: the three-incision whole transfer provided 38° (95% CI, 33°-43°; p < 0.01) forefoot pronation and 10° (95% CI, 8.5°-12°; p < 0.01) hindfoot valgus; the split transfer, 28° (95% CI, 24°-32°; p < 0.01) pronation, 9° (95% CI, 7.5°-11°; p < 0.01) valgus; and the two-incision transfer, 25° (95% CI, 20°-31°; p < 0.01) pronation, 6° (95% CI, 4.2°-7.8°; p < 0.01) valgus.
CONCLUSION: All three techniques may be useful and deliver varying degrees of increased forefoot pronation, with the three-incision whole transfer providing the most forefoot pronation. Changes in hindfoot motion were small. CLINICAL RELEVANCE: Our study results show that the amount of forefoot pronation varied for different transfer methods. Supple dynamic forefoot supination may be treated with a whole transfer using a two-incision technique to avoid overcorrection, while a three-incision technique or a split transfer may be useful for more resistant feet. Confirmation of these findings awaits further clinical trials.