Pedicle Screw Fixation in Idiopathic Scoliosis: Does it Save Lumbar Motion Segments when Compared to Hooks?

Purpose: The use of pedicle screws in the treatment of idiopathic scoliosis has been demonstrated to improve coronal lumbar curve correction when compared to hook fixation. This improvement in the ability to control the spine may allow the surgeon to fuse less motion segments. The purpose of this study was to determine whether pedicle screw fixation in the lumbar spine has the ability to save motion segments when compared to hooks.

Methods: Patients who had operative treatment for a double major idiopathic curve using posterior segmental spinal instrumentation were identified. Three groups of patients were matched for coronal plane lumbar curve magnitude and flexibility: Group S3: pedicle screw fixation to L3; Group H3: hook fixation to L3, Group H4: hook fixation to L4. Preoperative, initial postoperative and final follow-up radiographs were measured. All data were analyzed using an analysis of variance and statistical significance was defined as a P<0.05.

Results: 36 patients with an average age of 13.4 years were matched into the three groups. There was no difference between Groups S3, H3 and H4 with respect to age, lumbar curve magnitude (59.0, 59.3, 61.0), the lumbar curve flexibility index (62.1%, 62.3%, 58.4%), tilt angle of L3 to the pelvis (19.4, 19.0, 17.8) or other preoperative radiographic measurements in the coronal or sagittal planes. Postoperatively, lumbar curve correction was greater in Group S3 (60.5%) when compared to Group H3 (36.3%) (P=0.002) but no different than group H4 (50.1%). When measuring the angle between L3 and the pelvis postoperatively, there was less tilt of L3 in those patients in Group S3 (4.8) when compared to group H3 (15.0) and group H4 (8.4) (P<0.05). At an average final follow-up of 32.5 months, the final lumbar curve correction was better in group S3 (60.3%) when compared to groups H3 (33.0%) and H4 (42.6%) (P=0.001). The final tilt of L3 was less in group S3 (6.0) when compared to groups H3 (13.8) or H4 (10.5) (P=0.01). Coronal balance was similar in all groups at final follow-up. There were no differences between groups with respect to the sagittal plane parameters measured postoperatively or at final follow-up.

Conclusions: Lumbar pedicle screw fixation to L3 for double major curves offers better initial and final correction in the coronal plane when compared to hook fixation to L3 and better final correction when compared to hook fixation to L4. Pedicle screw fixation in the lumbar spine may offer the ability to save a distal motion segment when compared to hooks. Further study is needed to determine whether fixation to L2 using pedicle screws in these curves is possible.