The Influence of “loss of Attachment” on the Outcome of Anterior Cervical Fusion Procedures in Patients with Hirayama Disease

The objective of this study was to identify the influence of the measurements of "loss of attachment" on the surgical outcome in Hirayama disease (HD). Forty-two patients with HD underwent neutral and cervical-flexion magnetic resonance imaging (MRI) before surgery, and the cervical-flexion MRI was repeated at the 3-month postoperative visit. The longitudinal separation range (LSR) of loss of attachment, the maximum forward-shifting (MFS) degree in the cervical cord, and the relative morphological changes of the cervical cord were measured on MRI. Additionally, all patients underwent handgrip strength (FIGS) testing, the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, and Medical Research Council scales at the 1-year postoperative visit. Postoperatively, the cervical-flexion X/Y and the LSR decreased significantly at a mean of 94.17 +/- 8.65 days (range, 75-110 days) (P<.01), while the cervical-flexion A/B increased (P<.01). Loss of attachment was resolved in fused segments in all 42 patients, but there were 7 instances of residual loss of attachment at adjacent segments. Twenty (47.6%) of the 42 patients' DASH scores decreased at the 1-year postoperative visit. According to the logistic regression analysis, both LSR and MFS were related to the surgical outcomes. Receiver operating characteristic curve analysis found that area under the curve and cutoff values were 0.959 and 4.5, respectively (P<.05) for LSR and 0.782 and 0.215, respectively (P<.05) for MFS. Anterior cervical fusion procedures can effectively improve the abnormal loss of attachment and prevent further progression of HD. The LSR is an important risk factor for the prognosis, and longer fused segments may be required when the LSR is 5 segments or more.