Spinal Balance in Lenke 1A-C Curves

Methods: Using a multicenter database, preoperative and postoperative digital radiographic trunk balance measurements were compared in patients with Lenke 1A, 1B, and 1C curves. The percentage of patients whose imbalance (deviation away from the midline) exceeded magnitudes of 1 cm and 2 cm were recorded. Comparisons were made between the three subgroups.

Results: Preoperative: 88% of 137 patients with Lenke 1A curves had thoracic trunk shift >1 cm, compared to 88% of 32 patients with 1B curves, and 44% of 64 patients with 1C curves. The difference between 1A/1B curves and 1C curves was significant (p2 cm, compared to 31% for Lenke 1B curves, and 14% for Lenke 1C curves. All three groups were significantly different (p<.05).

Postoperative: 32% of 124 patients with Lenke 1A curves had thoracic trunk shift >1 cm, compared to 53% of 32 patients with 1B curves, and 62% of 58 patients with 1C curves. The difference between 1A and 1B was significant (p=.03), as was the difference between 1A and 1C (p1 cm was significantly lower than 1C (p2 cm, compared 16% for Lenke 1B curves, and 31% for Lenke 1C curves. The difference beteen group 1A and 1C was significant (p<.001).

Conclusions: Patients with Lenke 1A curves improve significantly in their trunk balance following surgery when compared to those with Lenke 1B and 1C curves. Patients with Lenke 1C curves have a compensatory flexible lumbar component which allows for better trunk balance preoperatively but leads to a greater measurable decompensation postoperatively.