Restoration of Thoracic Sagittal Kyphosis Following Operative Treatment for Adolescent Idiopathic Scoliosis: A Comparison of Three Surgical Approaches

• a, b - Medtronic/Sofamor Danek

Introduction: Adolescent idiopathic scoliosis (AIS) is characterized by thoracic hypokyphosis in the sagittal plane. Various surgical approaches and instrumentations may result in different surgical outcomes with respect to restoration of thoracic kyphosis, however, this has not been well studied.

Objective: To evaluate three surgical approaches to determine the modality that has the greatest influence on improving thoracic sagittal deformity.

Methods: A multicenter retrospective AIS database of patients operated between 1992 and 2000 was reviewed to compare postoperative thoracic kyphosis following surgical treatment. Demographic data was retrieved from the medical record. The PA radiograph was used to determine the Lenke classification and measure the main thoracic coronal curve. Lateral radiographs were analyzed to determine sagittal parameters including the Cobb measurement from T2-T5, T5-T12, T2-T12, T10-L2, and L1-S1. Measurements were performed preoperatively and postoperatively at 6-8 weeks, 1 year and 2 years. Student’s t test was used to compare groups and statistical significance was defined as p<0 .05.

Results: S: Lenke curve types 1A, 1B, 3A and 3B were included in this study and only the thoracic spine was instrumented. Three type of surgical approaches were performed: Anterior spinal fusion (ASF): N= 145; Posterior spinal fusion-hybrid (hooks and/or wires and screws) (PSF-Hyb): N=112; PSF with hooks only PSF-H: n=142. The average age, gender, Risser status, height and weight were similar between the three groups. There were no differences in the preoperative coronal main thoracic curve magnitude for the three groups ( ASF: 53.4º, PSF-Hyb: 50.5º, PSF-H: 51.8º degrees). The preoperative sagittal plane parameters including overall sagittal balance were similar between the three groups. Postoperatively the T5-T12 kyphosis was significantly greater in the ASF group (26.3º) when compared to the PSF-H (18.7º) and PSF-Hyb (19.3º) groups (p<0 .05). At one and two years postoperatively, thoracic kyphosis (both T2-T12 T5- T12) remained significantly greater in the ASF groups when compared to PSF-H PSF-Hyb (P<0.05). Kyphosis below instrumented levels was not seen those patients who had pedicle screw fixation at base of construct (PSF-Hyb) but groups. There were no differences lumbar lordosis any time period between

Conclusions: In the treatment of thoracic AIS, anterior instrumentation and fusion results in a greater ability to restore normal thoracic kyphosis when compared to the posterior approach whether hooks alone or a hybrid construct are used. These results require comparison to patients treated with all pedicle screw constructs.

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