Impact of deep extensor muscle-preserving approach on clinical outcome of laminoplasty for cervical spondylotic myelopathy: comparative cohort study

This study aimed to compare patients undergoing deep extensor muscle-preserving laminoplasty and conventional open-door laminoplasty for the treatment of cervical spondylotic myelopathy (CSM). We specifically assessed axial pain, cervical spine function, and quality of life (QOL) with a minimum follow-up period of 3 years. Ninety patients were divided into two groups and underwent either conventional open-door laminoplasty (CL group) or laminoplasty using the deep extensor muscle-preserving approach (MP group). The latter approach was undertaken by preserving the multifidus and semispinalis cervicis attachments followed by open-door laminoplasty and resuturing of the bisected spinous processes at each decompression level. The mean follow-up period was 7.7 years (range, 36-128 months). Preoperative and follow-up evaluations included the Japanese Orthopaedic Association (JOA) score, a tentative version of the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) including cervical spine function and QOL, and a visual analog scale (VAS) for axial pain. Radiological analyses included cervical lordosis and flexion-extension range of motion (C2-7), as well as deep extensor muscle areas on axial magnetic resonance imaging (MRI). The mean number of decompressed laminae was 3.9 and 3.3 in CL and MP groups, respectively, which was statistically equivalent. Japanese Orthopaedic Association recovery was statistically equivalent between the two groups. The MP group demonstrated a superior QOL score (57 vs. 46 %) compared with the CL group at final follow-up (p < 0.05). Mean VAS scores at final follow-up were 2.2 and 4.3 in MP and CL groups, respectively (p < 0.05). Cervical lordosis and flexion-extension range of motion were statistically equivalent. The percentage deep muscle area on MRI was significantly lesser in the CL group compared with the MP group (58 vs. 102 %; p < 0.01). We demonstrated the superiority of deep extensor muscle-preserving laminoplasty in terms of postoperative axial pain, QOL, and prevention of atrophy of the deep extensor muscles over conventional open-door laminoplasty for the treatment of CSM.