Plantar Plating in the Modified Lapidus Procedure: Evaluation of Function and Impairment of the Tibialis Anterior Tendon

CATEGORY: Bunion; Midfoot/Forefoot INTRODUCTION/PURPOSE: Plantar Plating in the Modified Lapidus Procedure (MLP) to treat severe Hallux Valgus deformities (HVD) or hypermobility of the first ray has become more popular. Due to biomechanical considerations, early weightbearing can be achieved. The surgical procedure and some plate designs make a release of the Tibialis Anterior tendon (TAT) necessary and screws have to be placed through or close to its insertion. We investigate if there are detectable changes of the tibialis anterior tendon or the function of the tibialis anterior muscle (TAM). METHODS: We retrospectively reviewed 22 Feet (17 patients) after plantar plating for a modified Lapidus procedure. All patients underwent a MRI at an average of 27 months (range 12-49 months) postoperatively for evaluation of the tendon. Clinical outcome was evaluated using the EFAS score. Dorsiflexion strength was measured and compared to the healthy contralateral extremity. Complications and union rates were assessed. RESULTS: The subjective satisfaction was rated at a mean of 8.2 (range, 5 - 10; SD +-1.5) on a scale from 0 to 10. Fourteen (82%) patients would undergo the same surgical treatment again. MRI images showed signs of tendinopathy of the TAT in 13 feet (59%). There were no ruptures, signs of thinning of the tendon or fatty infiltration detected. Complication rate was low with only on case with performed revision surgery. Regarding the Range of Motion, the force data comparing both feet of the patients is statistically close in comparison to the other side without any statistical differences. CONCLUSION: The MLP using a plantar-positioned locking plate leads to high patient satisfaction rates and provides significant improvement of preoperative deformity in severe HVD at midterm follow-up. Inversion strength was reduced, and MRI showed signs of tendinopathy in more than half of the cases. However, these findings did not seem to have any effect on the clinical outcome. None of the present patients had a high degree of fatty infiltration of the TAM in accordance with the Goutallier grading. Plantar-positioned locking plates do not seem to impair the TAM or the TAT.