Level-specific impairment of the 10-second grip-and-release test and grip strength in degenerative cervical myelopathy: analysis of 39 surgical cases.

PURPOSE: To characterise the relationship between the 10-second grip-and-release test (GRT) and grip strength—simple measures of upper limb function in degenerative cervical myelopathy (DCM)—with the responsible level. METHODS: We retrospectively evaluated patients with DCM who underwent posterior cervical decompression at our institution (2003–2020). Patients with ossification of the posterior longitudinal ligament, disc herniation, or prior cervical surgery were excluded. The responsible level was determined using neurological findings and kinematic magnetic resonance imaging (MRI). Patients were classified into C4/5, C5/6, C4/5 + 5/6, and C5/6 + 6/7 groups. Preoperative GRT and grip strength were compared between the groups using linear mixed models (LMMs) adjusted for age and sex, with patient ID as a random intercept to account for within-patient correlation of bilateral measurements. RESULTS: Thirty-nine patients (25 males, 14 females; mean age 59.7 ± 13.3 years) were analysed. In single-level disease, linear mixed models with patient ID as a random intercept were used to account for within-patient correlation of bilateral measurements. GRT was significantly lower in C5/6 than in C4/5 (p = 0.016), whereas grip strength showed no significant difference (p = 0.936). In two-level disease, neither GRT (p = 0.173) nor grip strength (p = 0.153) showed a statistically significant difference between C4/5 + 5/6 and C5/6 + 6/7 groups. CONCLUSIONS: GRT was specifically and significantly impaired in C5/6 single-level disease, a finding that remained robust after accounting for within-patient correlation using linear mixed models. In two-level disease, similar trends were observed but did not reach statistical significance, warranting further investigation. These findings suggest that GRT may serve as a sensitive indicator of C5/6 involvement in DCM. The exploratory nature of this study necessitates validation in larger, prospective cohorts.