Increasing Cervical Kyphosis Correlates With Cervical Degenerative Disk Disease in Patients With Adolescent Idiopathic Scoliosis

Study Design. Retrospective review. Objective. Our goal was to investigate the incidence of cervical degenerative disk disease (DDD) in patients with adolescent idiopathic scoliosis (AIS), before surgical intervention. Summary of Background Data. AIS is often associated with thoracic hypokyphosis and compensatory cervical kyphosis. In adults, cervical kyphosis is associated with DDD. Although cervical kyphosis has been reported in up to 60% AIS patients, the association with cervical DDD has not been reported. Materials and Methods. A retrospective review was conducted from January 2014 to December 2019 of all consecutive AIS patients. Inclusion criteria were AIS patients over 10 years of age with cervical magnetic resonance imaging and anterior-posterior and lateral spine radiographs within 1 year of each other. Magnetic resonance imaging were reviewed for evidence of cervical DDD. Severity of cervical changes were graded using the Pfirrmann classification and by a quantitative measure of disk degeneration, the magnetic resonance signal intensity ratio. Results. Eighty consecutive patients were included (mean age: 14.1 years, SD=2.5 years). Increasing cervical kyphosis was significantly correlated to decreasing thoracic kyphosis ( r =0.49, P <0.01) and increasing major curve magnitude ( r =0.22, P =0.04). Forty-five patients (56%) had the presence of DDD (grades 2–4) with a mean cervical kyphosis of 11.1° (SD=9.5°, P <0.01). More cervical kyphosis was associated with more severe cervical DDD as graded by Pfirrmann classification level ( P <0.01). Increasing cervical kyphosis was also positively associated with increasing magnetic resonance signal intensity ratio ( P <0.01). Nine patients had ventral cord effacement secondary to DDD with a mean cervical kyphosis of 22.8° (SD=8.6°) compared with 2.6° (SD=11.2°) in those who did not ( P <0.01). Conclusions. Cervical kyphosis was significantly associated with increasing severity of cervical DDD in patients with AIS. Patients with evidence of ventral cord effacement had the largest degree of cervical kyphosis with a mean of 22.8±8.6°. This is the first study to evaluate the association between cervical kyphosis in AIS with cervical DDD.