Maximum mouth opening and trismus in 143 patients treated for oral cancer: a 1-year prospective study.

Background: Patients with oral cancer can develop restricted mouth opening (trismus) because of the oncologic treatment.

Methods: Maximum mouth opening (MMO) was measured in 143 patients shortly before treatment and 0, 6, and 12 months posttreatment, and the results were analyzed using a linear mixed-effects model.

Results: In every patient, MMO decreased after treatment. The patients who underwent surgery, recovered partially by 6 and 12 months after treatment, whereas the patients who received both surgery and radiotherapy or primary radiotherapy did not recover. Tumor location, tumor size, and alcohol consumption had independent effects on MMO. Having trismus (MMO <35 mm) 1 year after treatment was associated most strongly with pretreatment MMO, receiving both surgery and radiotherapy, and maxillary or mandibular tumor involvement.

Conclusion: Postoperative radiotherapy and maxillary or mandibular tumor involvement are the highest contributing risk factors to decreasing MMO and the subsequent development of trismus after oral cancer treatment.