CORONAL AND SAGITTAL BALANCE IN SURGICALLY TREATED ADOLESCENT IDIOPATHIC SCOLIOSIS WITH THE KING-II CURVE PATTERN - A REVIEW OF 67 CONSECUTIVE CASES HAVING SELECTIVE THORACIC ARTHRODESIS

Study Design. A retrospective study by an independent observer of a co nsecutive series of 67 cases of adolescent idiopathic scoliosis presen ting with a King II curve pattern. Objectives. To demonstrate the vali dity of a selective thoracic fusion as a treatment of King II curves w ith special attention to immediate postoperative and longterm trunk ba lance in the coronal and sagittal planes. Summary of the Background Da ta. The literature has been fairly controversial in terms of the recom mended treatment of King II curve patterns in adolescent idiopathic sc oliosis. The main confusion appears to be whether the thoracic curve a lone or both curves should be instrumented and fused. Methods. Sixty-s even patients were identified as having had a selective posterior thor acic spine fusion with instrumentation between 1961 and 1994. None of these cases had a fusion of the lumbar spine. Preoperative radiographs were analyzed for determination of the appropriate fusion level using the criteria of the stable and neutral vertebra. Follow-up radiograph s were evaluated for balance in the coronal and sagittal planes using the central sacral line on posteroanterior radiograph and the C7 sacra l promontory line on lateral film. Results. At 2-year or greater follo w-up, the unfused lumbar curve remained equal to or less than the corr ected thoracic curve in 63 patients (94%). No patient required extensi on of fusion. Frontal plane balance analysis showed that 47 of the 67 patients had the T1 plumb line within 2 cm of the midline for an avera ge decompensation of 8.7 mm. In no patient was the loss of balance gre ater than 3.8 cm. Sagittal plane balance analysis showed that only one patient had inferior junctional kyphosis greater than 10 degrees. Thi s did not require extension of fusion. There were no cases of superior junctional kyphosis. Conclusions. The concept of selective thoracic f usion in the King II curve pattern appears to be valid. These findings suggest that arthrodesis of the lumbar spine can be avoided when this pattern is properly diagnosed and appropriately treated. Proper ident ification of the stable and neutral vertebra and of the appropriate le vel of fusion are important to achieve good postoperative balance. Suc cessful preservation of lumbar motion segments is important to long-te rm satisfactory outcome in adolescent idiopathic scoliosis.