Background: Spasticity is a common complication following spinal cord injury (SCI) and may impede rehabilitation by restricting joint range of motion (ROM) and reducing the effectiveness of strength training. However, the relationship between severe spasticity and functional independence, as assessed by the Spinal Cord Independence Measure (SCIM), after cervical SCI remains unclear.

Objective: To examine the relationship between severe spasticity and functional independence assessed using the SCIM in patients with cervical SCI.

Methods: This retrospective cohort study included 211 patients with cervical SCI treated at our center between 2012 and 2025 who were followed for at least 6 months after injury. Data on demographics, neurological status (ASIA Impairment Scale [AIS]), spasticity severity (Modified Ashworth Scale [MAS]), and functional independence (SCIM) were collected. Patients who developed severe spasticity (MAS ≥ 3 in any ROM) during follow-up were classified as the severe spasticity group, while those with MAS consistently < 3 in any ROM were classified as the control group. SCIM total and subdomain scores were compared between groups.

Results: In patients with motor complete injuries (AIS A/B), no significant differences in SCIM scores were observed between the severe spasticity and control groups. In contrast, severe spasticity was associated with impaired functional independence in patients with motor incomplete injuries. In the AIS C subgroup, patients with severe spasticity showed significantly lower total SCIM scores, as well as reduced performance in eating, grooming, and mobility over moderate and long distances compared with the control group. In the AIS D subgroup, severe spasticity was associated with additional impairments, including bladder management, indoor mobility, and transfers from floor to wheelchair, in addition to deficits in self-care and mobility.

Conclusion: Severe spasticity impairs functional independence after cervical SCI, particularly in patients with motor incomplete injuries. These findings highlight the clinical importance of spasticity management to preserve and improve functional recovery.