What is the force required to treat trismus in patients undergoing oral cavity free flap reconstruction?

Trismus therapy is often delayed after jaw reconstruction to avoid hardware failure or non-union. The aim of this study is to document the forces that have been applied to patients undergoing free flap reconstruction of the oral cavity in the 12 months following oral cavity reconstruction, and to analyze the associations between force and maximal interincisal opening (MIO) over time.

Participants with trismus after free flap reconstruction of the oral cavity completed a 10-week jaw stretching program using Restorabite™. Primary outcome measures included the minimum and maximal force applied by a trismus device during rehabilitation, MIO, bone union, and health-related quality of life outcomes up to 12 months postoperatively.

A mean of 20.6 Newtons (N) was used during passive exercises and 38.9 N during active exercises was used during trismus therapy. The mean increase in MIO for the 45 participants after 10 weeks, 6 months, and 12 months of therapy was 8.4 mm (p < 0.001), 12.6 mm (p < 0.001), 12.7 mm (p < 0.001), respectively. There was no significant difference in the mean minimal (p = 0.37) or mean maximal (p = 0.08) force applied between those who underwent osseous free flap reconstruction compared to fasciocutaneous only, respectively. In patients who underwent osseous reconstruction, 25 (67.6%) had complete bone union and 12 (32.4%) had partial union at 12 months postsurgery.

In participants undergoing osseous free flap reconstruction, there was no association between the force applied to the rates of bone union. Further research to define safe and optimal loading may benefit patients undergoing jaw reconstruction.