Traction X-ray under general anesthesia helps to save motion segment in treatment of Lenke type 3C and 6C curves

In patients with structural lumbar curves, several studies have shown the advantages of stopping fusion at L3 and saving L4. However, fusing the L4 may still be deemed necessary in a significant number of patients with structural lumbar curves (ie, Lenke types 3 and 6) when fusion levels are selected by using traditional flexibility X-ray (TXR) methods such as supine side bends and traction.

The aim of this retrospective study was to evaluate the effectiveness of the traction X-ray under general anesthesia (TrUGA) method in saving the L4 in patients with Lenke types 3C and 6C curves.

This was a retrospective clinical study.

Eighty-nine consecutive patients (77 females and 12 males) with adolescent idiopathic scoliosis Lenke types 3C (46 patients) and 6C (43 patients) curves and who underwent an instrumented posterior spinal fusion by a single surgeon were included. The selection of lower instrumented vertebrae (LIV) was done by using the central sacral vertical line (CSVL). LIV was defined as the uppermost vertebrae of the lumbar curve that was not intersected by CSVL on standing anteroposterior radiograph, but became parallel to the sacrum and was intersected by CSVL at the concave bending or TrUGA. The disc wedging under LIV should be parallel or near parallel and rotation of LIV should be corrected at least one to two (Nash-Moe) grades.

Radiological evaluation included preoperative standing AP, lateral and TXR, and intraoperative supine TrUGA, which was taken after the induction of anesthesia and before positioning the patient. LIV was determined by using TXR and TrUGA. Preoperative, postoperative with ≥2 year follow-up curve magnitudes, LIV tilt, and disc wedging below LIV and CSVL to T1 distance were all measured. A satisfactory radiographic outcome was determined to be the result if CSVL was within 2 cm of the center of T1, the LIV tilt angle was less than 10°, and any increase in thoracic and lumbar curve during follow-up was less than 5°. Clinical outcome was analyzed by using follow-up Scoliosis Research Society-22 (SRS-22) questionnaire and by the global outcome scores (GOS) for improvement and deterioration measured with a 15-point scale ranging from -7 (no improvement) to +7 (significant improvement).

The average follow-up period was 5.4 (range: 2 to 8) years. Average age at surgery was 15.5 (range: 13 to 19) years. Pedicle screw constructs were used in all patients. LIV was L3 in 85 patients, and L4 in the remaining 4 patients. Using the same selection criteria, L3 was LIV according to both the TXR and TrUGA films in 39 cases (44%) and fusion was stopped at L3. In 46 (52%) cases, TXR determined L4 to be the LIV, whereas in all those patients L3 was the LIV according to TrUGA and fusion was stopped at L3 in all. LIV was L4 according to both methods in four (4%) patients and fusion was stopped at L4. All patients had successful radiographic outcomes according to the criteria of CSVL to be within 2 cm of the center of T1, L3 tilt angle of less than 10°, and L3-L4 disc wedging to be less than 10° at the final follow-up. Average follow-up SRS-22 score was 4.3 (range: 3.3-5) and GOS was 6.1 (range: 3-7). None of the patients required additional surgery for decompensation or adding on, and there was no significant correction loss during follow-up.

TrUGA may be an alternative method for selection of fusion levels and may help to save L4 when compared with traditional radiograph methods in surgical treatment of Lenke types 3 and 6 curves.