PEDICLE SCREWS VERSUS PEDICLE HOOKS FOR CORRECTION OF THORACIC SCOLIOSIS USING THE UNIVERSAL SPINAL SYSTEM II – A MODIFICATION OF THE ORIGINAL TECHNIQUE

Abstract

Introduction: Pedicle screws are now commonly used to instrument the thoracic spine and offers improved three point fixation and therefore theoretically offers better derotation of the spine during corrective manoeuvres in scoliosis surgery.

Aim: To compare thoracic scoliosis correction using either pedicle hooks or pedicle screws.

Methods: Two patient groups were studied. Data was collected prospectively and this is a review of the radiological data. All patients had structural thoracic scoliosis. Group 1, 14 patients (9 female and 5 male) mean age 14.6, were treated with posterior correction of scoliosis using the standard USS II technique using pedicle hooks and screws. Group 2, 14 patients (11 female and 3 male) mean age 15.3 were treated using pedicle screws alone to correct the apical deformity, using a variation of the original USS technique. Pre and postoperative Cobb angle, apical vertebral rotation (AVR, Perdriolle method) and apical vertebral translation (AVT) were measured. Unpaired “t” test was used to compare the magnitude of correction in both groups. The mean follow up period was 30 months (range: 27–42).

Results: The mean corrections of Cobb angle, AVR and AVT, in group I were 61.1% (range: 48.5–83.9), 33.3% (range: 8.6–100) and 62.9% (range: 43.2–91.4), respectively. In Group 2 the corrections were: 57.4% (range: 21.4–81.7), 57.2% (range:16.7–100) and 58.7% (range: 34–80.9). There were no statistically significant differences between the correction of Cobb angle or AVT in both groups (P=0.479 and 0.443 respectively). However, the pedicle screws proved to be more effective at correcting the AVR (P= 0.017). No complications occurred and correction has been well maintained with a minimum of 2 year follow-up.

Conclusion: Pedicle screws can safely and effectively replace the pedicle hooks in the classical USS technique. They are more effective at correcting the rotational deformity, although do not provide a better correction of Cobb angle. These technical results now need to be correlated with relevant clinical outcomes.