C1–C2 fusion is a well-established procedure for treating instability at the upper cervical spine. However, its precise impact on cervical range of motion (ROM) and the degree to which thoracolumbar or global compensations can restore functional mobility remain incompletely understood. Moreover, patient-reported outcomes after such surgery are not fully characterized. This study addresses four questions: (1) How does C1–C2 fusion affect cervical ROM compared to healthy controls? (2) Can thoracolumbar and global compensations restore normal mobility? (3) What is the impact on quality of life measured by the Neck Disability Index (NDI) and the Short Form Health Survey 36 (SF-36)? (4) Are these compensations sufficient for activities of daily living?

We hypothesized that while C1–C2 fusion would significantly reduce cervical ROM, compensatory mechanisms would enable patients to preserve sufficient motion for daily activities, albeit with a potential decrease in quality of life.

This retrospective observational study included 19 patients (11 males, 8 females) who underwent Goel–Harms C1–C2 fusion between 2010 and 2021, with a minimum six-month postoperative follow-up. Cervical ROM (flexion-extension, lateral bending, rotation) was measured using the Cervical Range of Motion (CROM) device in three scenarios: no compensation, thoracolumbar compensation, and global compensation. We performed a comparison with the normal values reported in literature. Patient-reported outcomes were evaluated using the NDI and SF-36 questionnaires. Statistical analyses included t-tests, repeated measures ANOVA, and correlation tests.

(1) Cervical ROM was significantly reduced in operated patients compared to controls (p < 0.001). (2) Thoracolumbar and global compensations partially restored mobility, with extension remaining notably limited. (3) Patients reported moderate disability on the NDI and lower SF-36 subscale scores (particularly in physical functioning and pain domains). (4) Despite reduced cervical motion, most activities of daily living were achievable through compensatory mechanisms.

C1–C2 fusion substantially restricts upper cervical mobility, yet thoracolumbar and global compensations help maintain functional ROM for daily tasks. Nevertheless, the observed reduction in quality of life highlights the importance of thorough preoperative counseling. These findings align with existing literature on balancing spinal stability with motion preservation. Larger prospective studies are needed to refine patient selection and optimize postoperative rehabilitation.

IV; retrospective observational study.