Use of the Universal Clamp in adolescent idiopathic scoliosis for deformity correction and as an adjunct to fusion: 2-year follow-up

Abstract

Purpose: Among posterior surgical techniques for treating adolescent idiopathic scoliosis (AIS), hybrid constructs with pedicle-screw fixation in the lumbar spine and other anchors in the thoracic spine have been reported to provide to be of more physiological value in postoperative thoracic kyphosis than all-screw constructs. The Universial Clamp (UC) equipped with a soft sublaminar band is a relatively new thoracic anchor that can be used in hybrid constructs. A dedicated reduction tool that applies traction to the sublaminar band permits gentle translation of the thoracic curve to the precontoured fusion rods, which have been previously anchored distally by pedicle screws and proximally by hooks in a claw configuration. The aim of this study was to evaluate radiographic results of AIS treatment using UC hybrid constructs.

Methods: This was a prospective case series in which 29 consecutive patients with Lenke type 1, 2 or 3 AIS operated on by two surgeons in two centers were followed for 24 months. Necessity for anterior release was an exclusion criterion.

Results: A total of 5.4 ± 1.4 UCs were used per patient. The major thoracic curve was reduced from 55 ± 7° to 14 ± 6° at 1 month and 17 ± 6° at 24 months (correction 70%) without complications. In the patients who had less than 20° of T5-T12 kyphosis preoperatively, thoracic kyphosis improved from 14 ± 4° to 20 ± 3° at 3 months and 24 ± 9° at 24 months. In the other patients, preoperative thoracic kyphosis (27° ± 6°) was unchanged by the operation.

Conclusion: UC hybrid constructs appear to safely provide satisfying coronal correction while consistently improving thoracic kyphosis in patients who also have preoperative hypokyphosis. We hypothesize that diminution in thoracic kyphosis was consistently avoided due to the straightforward traction of the spine to the fusion rods into which the chosen kyphosis was contoured by the surgeon before applying the reduction tool to the sublaminar bands.

Keywords: Adolescent idiopathic scoliosis; Rod precontouring; Thoracic kyphosis; Universal Clamp.

Fig. 1

Curve of major thoracic curve Cobb angle. The bars around the mean values (circles) represent ±1 standard deviation (SD)

Fig. 2

Correlation between preoperative flexibility and major thoracic curve Cobb angle correction at 24 months

Fig. 3

Course of lumbar curve Cobb angle. The bars around the mean values (circles) represent ±1 SD

Fig. 4

Course of lumbar lordosis and of thoracic kyphosis. The bars around the mean values (circles) represent ±1 SD

Fig. 5

Preoperative view of one of the patients treated for Lenke type 3 adolescent idiopathic scoliosis (AIS)

Fig. 6

Lateral view of the same patient showing T5–T12 hypokyphosis (7°)

Fig. 7

Two-year follow-up view showing the 60% correction achieved

Fig. 8

The T5–T12 kyphosis had improved by 13–20° at the 2-year follow-up