Satoshi Nori1, Ryoma Aoyama2, Ken Ninomiya2, Satoshi Suzuki3, Ukei Anazawa2, Tateru Shiraishi4. 1. Department of Orthopaedic Surgery, Tokyo Dental College Ichikawa General Hospital, 5-11-13 Sugano, Ichikawa, Chiba, 272-8513, Japan. Electronic address: satoshi_nori@2003.jukuin.keio.ac.jp. 2. Department of Orthopaedic Surgery, Tokyo Dental College Ichikawa General Hospital, 5-11-13 Sugano, Ichikawa, Chiba, 272-8513, Japan. 3. Department of Orthopaedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo, 160-8582, Japan. 4. Shiraishi Spine Clinic, 1-5-1-1220 Marunouchi, Chiyoda, Tokyo, 100-6512, Japan.
Abstract
BACKGROUND: Posterior cervical decompression results in favorable outcomes for K-line (+) ossification of the posterior longitudinal ligament (OPLL) patients. However, even for patients with K-line (+) in the neck neutral position, K-line (-) in the neck-flexed position (flexion K-line (-)) may affect surgical outcomes. We investigated the influence of flexion K-line (-) on surgical outcomes after muscle-preserving selective laminectomy using multivariate analysis. METHODS: This study involved 113 OPLL patients with K-line (+) in the neck neutral position who underwent muscle-preserving selective laminectomy. Patients were divided into flexion K-line (+) (n = 90) and flexion K-line (-) (n = 23) groups. We analyzed the influence of a flexion K-line (-) on radiological and surgical outcomes. We conducted a multivariate analysis to analyze the factors affecting surgical outcomes. RESULTS: The patients with a flexion K-line (-) had a larger C2-C7 sagittal vertical axis (preoperatively, P = 0.042; postoperatively, P = 0.021), narrower postoperative clearance of the spinal cord (P = 0.003), a smaller proportion of segmental-type OPLL (P < 0.001), and a greater OPLL occupancy ratio (P < 0.001). The recovery rate measured by the Japanese Orthopedic Association (JOA) score was poorer in patients with a flexion K-line (-) (17.6 ± 32.2%) than in those with a flexion K-line (+) (35.3 ± 29.5%) (P = 0.013). Multiple linear regression analysis revealed that the flexion K-line (-) affected the recovery rate of the JOA score (β = -0.233, P = 0.013). CONCLUSIONS: Even for patients with K-line (+) OPLL, the flexion K-line (-) affects surgical outcomes. The flexion K-line (-) is a useful predictor of poor surgical outcomes after posterior decompression surgery.
BACKGROUND: Posterior cervical decompression results in favorable outcomes for K-line (+) ossification of the posterior longitudinal ligament (OPLL) patients. However, even for patients with K-line (+) in the neck neutral position, K-line (-) in the neck-flexed position (flexion K-line (-)) may affect surgical outcomes. We investigated the influence of flexion K-line (-) on surgical outcomes after muscle-preserving selective laminectomy using multivariate analysis. METHODS: This study involved 113 OPLLpatients with K-line (+) in the neck neutral position who underwent muscle-preserving selective laminectomy. Patients were divided into flexion K-line (+) (n = 90) and flexion K-line (-) (n = 23) groups. We analyzed the influence of a flexion K-line (-) on radiological and surgical outcomes. We conducted a multivariate analysis to analyze the factors affecting surgical outcomes. RESULTS: The patients with a flexion K-line (-) had a larger C2-C7 sagittal vertical axis (preoperatively, P = 0.042; postoperatively, P = 0.021), narrower postoperative clearance of the spinal cord (P = 0.003), a smaller proportion of segmental-type OPLL (P < 0.001), and a greater OPLL occupancy ratio (P < 0.001). The recovery rate measured by the Japanese Orthopedic Association (JOA) score was poorer in patients with a flexion K-line (-) (17.6 ± 32.2%) than in those with a flexion K-line (+) (35.3 ± 29.5%) (P = 0.013). Multiple linear regression analysis revealed that the flexion K-line (-) affected the recovery rate of the JOA score (β = -0.233, P = 0.013). CONCLUSIONS: Even for patients with K-line (+) OPLL, the flexion K-line (-) affects surgical outcomes. The flexion K-line (-) is a useful predictor of poor surgical outcomes after posterior decompression surgery.