The purpose of this study was to evaluate the success of functional free muscle transfer in patients with chronic facial paralysis using a recently developed quantitative method known as the maximum static response assay of facial motion. A retrospective review of a single surgeon series of six patients with longstanding facial paralysis was performed. The maximum static response assay was performed on all patients preoperatively and serially during the postoperative period. Twenty-seven patients (54 sides) with normal facial function were also evaluated and served as controls. The contralateral normal side in those patients with unilateral facial paralysis (n = 4) also served as a control. Movement of the modiolus during smile was recorded in the x axis and y axis. To determine net smile movement, the vector of movement was calculated by means of the Pythagorean theorem. Vectors were then defined mathematically by calculating direction and magnitude. The average direction of the vector during smile for the normal control population was 58.3°(range 32.5 to 83.1°) from the horizontal through the modioli, and the average magnitude was 10.6 mm (range 4.2 to 20.1 mm). The average preoperative direction for the reanimated sides was 176.8°with a range of 83.3 to 225°. Patients with bilateral paralysis (n = 2) were excluded for calculation of the vectors on the normal contralateral side. The average preoperative direction for the normal contralateral side in patients with facial paralysis was 58.3°with a range of 48.2 to 68.4°. Postoperatively, the average direction of the vector during smile for the reanimated sides improved to a value of 77.6°with a range of 45.7 to 113.8°. The average change in direction of the preoperative reanimated side compared with the postoperative reanimated side was significant (p = 0.01). Postoperatively, the average direction of the vector for the contralateral normal sides was 43°with a range of 11 to 57.2°. The change in direction for the contralateral normal side was not significant (p = 0.18). The average magnitude of the reanimated side improved from a non-anatomic 2.8 mm preoperatively (range 0.8 to 6.8 mm) to an anatomic 4.9 mm postoperatively (p = 0.02). The contralateral normal side magnitude decreased from 9.4 mm (range 7.3 to 11.6 mm) preoperatively to 5.7 mm (range 3.8 to 7.7 mm) postoperatively (p = 0.006). More specifically, the absolute change in movement on the reanimated side during smile for the x axis and y axis was 2.3 mm (p = 0.05) and 4.0 mm (p = 0.002), respectively. This corresponded to an absolute change in the magnitude of the vector of 4.6 mm in an anatomic direction, on the contralateral side the absolute change in magnitude during smile from preoperative to postoperative for the x axis and y axis decreased by 1.5 mm (p = 0.13) and 5.3 mm (p = 0.05), respectively. This reflected an absolute change in the magnitude of the vector of 5.5 mm. Functional free muscle transfer in patients with chronic facial paralysis resulted in anatomic recovery of motion in the majority of patients in this series. The maximum static response assay can be used to objectively assess the results of facial reanimation.
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