T1 Pelvic Angle Is a Useful Parameter for Postoperative Evaluation in Adult Spinal Deformity Patients.

STUDY DESIGN

Retrospective review.

OBJECTIVE

We investigated validity of T1 pelvic angle (TPA) for postoperative assessment and determined its target value for corrective scoliosis surgery.

SUMMARY OF BACKGROUND DATA

TPA is a novel spinopelvic parameter accounting for both pelvic retroversion and trunk anteversion. As an angle, it is less affected by posture and correlates well with health-related quality of life in adult spinal deformity patients. According to our study in elderly volunteers, the threshold TPA value for disability (Oswestry Disability Index [ODI] score >20) was approximately 20°.

METHODS

Seventy adult scoliosis patients (5 men and 65 women; mean age, 67.8 yr) who underwent spinal deformity surgeries and were followed up for at least 2 years postoperatively were studied. The following parameters based on whole-spine and pelvic radiography were assessed preoperatively, soon after operation, and 2 years postoperatively: C7-central sacral vertical line, TPA, sagittal vertical axis (SVA), pelvic tilt, and pelvic incidence minus lumbar lordosis. ODI and Scoliosis Research Society-22 scores were obtained preoperatively and 2 years postoperatively. Based on postoperative TPA, patients were divided into two groups: ≤20° (group G) and greater than 20° (group P).

RESULTS

TPA and SVA correlated with health-related quality of life. Two years postoperatively, TPA best correlated with ODI and Scoliosis Research Society-22 scores, although all parameters correlated with them, and TPA soon after operation best correlated with ODI scores 2 years postoperatively. Two years postoperatively, each parameter and ODI scores in group G were better than those in group P.

CONCLUSION

The correlation results showed that TPA appropriately assessed clinical outcomes following spinal deformity surgery. TPA assessed soon after operation correlated with ODI score 2 years postoperatively, and thus predicted prognosis. Because patients whose postoperative corrected TPA was 20° or lesser had better spinopelvic parameters and ODI scores 2 years postoperatively, TPA 20° or lesser was the proper target value for corrective surgery.

LEVEL OF EVIDENCE