Purpose: The purpose of this study was to evaluate the application of the minimum clinically important difference (MCID) concept to postoperative clinical results by using a prospective cohort study in Chinese patients with cervical spondylotic myelopathy (CSM).
Methods: The sample consisted of 113 patients who underwent surgical treatment for CSM in our hospital between February 2008 and November 2012. The preoperative and 1-year postoperative modified Japanese Orthopaedic Association (mJOA) scores, mJOA score recovery rate, physical component summary (PCS) and mental component summary (MCS) of the Short Form 36 were collected. The MCID of each outcome measurement was calculated by four approaches including average change, minimum detectable change, change difference and receiver operating characteristic curve. The responsiveness of each measurement was then analyzed.
Results: The patients presented a statistically significant improvement (p < 0.01) postoperatively in mJOA, PCS, and MCS. The MCID calculated by four approaches varied from 4.09 to 9.62 for the PCS, 3.11 to 7.41 for the MCS, 1.25 to 3.07 for mJOA score, and 31.37 to 44.02% for mJOA recovery rate. In addition, the improvement of the mJOA score owned the highest responsiveness of the four outcome measurements.
Conclusions: The threshold value of the MCID was determined by the choice of the assessment approach. In addition, the recovery rate of the mJOA score appeared to be the most valid and responsive measure of effectiveness of surgery in CSM patients.
Keywords: Cervical spine; Cervical spondylotic myelopathy; Minimum clinically important difference; Modified Japanese Orthopaedic Association score; Short Form 36.