An Analysis of Anterior versus Posterior Instrumented Fusion for Thoracic Adolescent Idiopathic (AIS)Curves 70-80 Degrees: Are There Advantages of One Over the Other?

• a - DePuy Spine

Purpose: To analyze radiographic and perioperative data in patients undergoing single-stage anterior versus posterior thoracic instrumented fusion for high magnitude thoracic curves.

Objectives: Determine advantages of one approach over the other for treatment of 70°-80° thoracic curves related to major and minor curve correction, preoperative hypo and hyperkyphosis, spinal balance, fusion levels, and several perioperative outcomes measures. Summary of Background Data: The relative success of anterior versus posterior instrumentation and fusion for high magnitude thoracic AIS curves has yet to be analyzed.

Methods: A retrospective analysis of a subset of patients from a multicenter population with major thoracic curves between 70°-80° treated by selective anterior versus posterior instrumented fusion. Measurements were obtained from preoperative, early, and two-year postoperative standing 36in. radiographs of 41 adolescent idiopathic patients with Lenke type 1-3, A-C curve patterns. Measurements included pre and postoperative Cobb and instrumented levels of all curves, regional sagittal measurements, apical and end instrumented vertebra (EIV) translation and angulation, EIV disc angulation, and coronal and sagittal C7 plumblines. Hospital stay, estimated blood loss (EBL), operative time, and pre and two-year postoperative PFTs were also analyzed. Results: Seventeen patients underwent instrumented anterior fusion, and 24 patients posterior fusion with similar preoperative data, see Table 1. The mean distal EIV was the lower Cobb level in the anterior group and Cobb + 1.5 in the posterior group. The posterior group fared better for correction of hyperkyphosis and the anterior group for hypokyphosis. In patients with “C” lumbar modifiers, the distal EIV was the Cobb level in the anterior group whereas the mean distal EIV in the posterior group was Cobb +2 (p=0.007). Hospital stay and operative time were similar. The anterior group demonstrated better correction of EIV angulation and translation. Postoperative distal junctional kyphosis greater than 9° was noted in three anterior patients and six posterior patients. Mean EBL was 500 cc in the anterior group and 1000 cc in the posterior group. At two-year follow-up PFTs were slightly decreased in the open anterior group and slightly increased in the posterior group.

Conclusions: The analysis demonstrated comparable postoperative radiographic results at two-years. Posterior instrumented levels were always longer than anterior, especially in curves with “C” lumbar modifiers. In the sagittal plane, posterior instrumentation was better at reducing hyperkyphosis, and anterior instrumentation was better at improving hypokyphosis. The two-year data demonstrates a slight decrease in PFTs in the anterior group.

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