The correlation between facet tropism and motor dysfunction of the upper limbs in patients with cervical spondylotic amyotrophy: an observational study.

PURPOSE

To identify the frequency of facet tropism (FT) in patients with cervical spondylotic amyotrophy (CSA) and to analyze the correlation between FT and motor dysfunction in CSA.

METHODS

The side-to-side differences in facet orientation (FO) (≥ 7°) were measured from C3-4 to C7-T1 levels via 3D computed tomography to diagnose FT in 84 CSA patients (proximal- vs. distal-type: 36 vs. 48) and 363 patients with cervical spondylosis (CS). Both the motor unit number index (MUNIX) and Medical Research Council scores were assessed in CSA patients.

RESULTS

Compared with CS patients, both CSA patient groups presented a greater frequency of FT at any cervical level in all different planes (axial, sagittal and coronal) (P < 0.05). Furthermore, more proximal-type CSA patients with FT presented axial FT (smaller FO on the symptomatic side) at C4-5 level, and more distal-type CSA patients with FT exhibited both axial and sagittal FT at C6-7 and C7-T1 levels. In addition, both compound muscle action potential (CMAP) and MUNIX values in proximal-type CSA patients with C4-5 axial FT were lower than those in patients without FT (P < 0.05), and both CMAP and MUNIX values were negatively associated with the side-to-side differences in axial FO at C4-5 and/or C5-6 levels in these patients (P < 0.05).

CONCLUSION

The frequency of FT in CSA patients is greater than that in CS patients. Importantly, axial/sagittal FT may be positively associated with motor dysfunction of upper limbs in CSA patients. Thus, a cautious approach should be taken when treating CSA due to possible comorbid FT.