SELECTIVE ANTERIOR FUSION OF THORACIC SCOLIOSIS: SPONTANEOUS CORRECTION OF UNFUSED LUMBAR CURVE AND SPINAL BALANCE

Yasuhiro Shono, MD,
Kiyoshi Kaneda, MD;
Kuniyoshi Abumi, MD
* (b– AcroMed)
Hokkaido University School of Medicine, Sapporo, Japan

PURPOSE:
The clinical results of thoracic scoliosis patients treated by selective anterior fusion were analyzed to investigate spontaneous correction of the unfused lumbar curve and spinal balance with respect to preoperative curve pattern and positioning of the lumbar curve.

MATERIALS AND METHODS:
Twenty–nine idiopathic thoracic scoliosis patients were treated by selective anterior correction surgery using Kaneda anterior scoliosis system (KASS). In all patients, fusion range did not extend range of the major thoracic curve. There were 15 patients with King Type II and 14 patients with Type III. All curves were divided into three types according to curve pattern of the secondary lumbar curve (Lenke et al.); Type A (n=14, no apical deviation, all patients with Type III curve were included in this category), Type B (n=7, moderate apical deviation with the apex touching the midline), and Type C (n=8, marked apical deviation with apex completely crossing the midline). The average follow–up period was 4 years, 3 months (2 y ~ 6 y9 m).

RESULTS:
Preoperative curve magnitude ranged between 52° ~ 79°. Correction rates of the major thoracic curve were 66%. Spontaneous correction rates of the lumbar curve were Type A; 75%, Type B; 53%, and Type C; 43%. Spinal balance was well corrected in all patients at the final follow–up, however, five patients showed postoperative imbalance (one patient in Type A, three in Type B, and one in Type C). Rotational deformity in transverse plane measured by CT showed decreased rotational deformity in the major thoracic curve area after surgery, however, unfused lumbar curve showed no marked change in rotational deformity and, in most cases, remained same after surgery.

CONCLUSION:
Anterior surgery is effective to obtain high correction of the deformity by the direct anterior release of the deformed spine which allows selective thoracic scoliosis correction in short fusion area. Effective anterior correction of the three dimensional deformities of the major curve induces spontaneous correction of the unfused lumbar curve, most effectively in patients with non–structural lumbar curve (Type A). However, rotational deformity of the lumbar curve frequently remains uncorrected and postoperative imbalance and decompensation of the unfused lumbar curve may occur, especially in patients with structural lumbar curve patterns such as Type B and C.

* · If noted, the author indicates something of value received. The codes are identified as: a–research or institutional support, b–miscellaneous funding, c–royalties, d–stock options, e–consultant or employee.