Pelvic obliquity in adolescent idiopathic scoliosis planned for posterior spinal fusion: A preoperative analysis of 311 lower limb axis films

Abstract

To analyze the incidence, pattern, and contributing factors of pelvic obliquity among Adolescent Idiopathic Scoliosis (AIS) patients who will undergo surgery. Methods: In total, 311 patients underwent erect whole spine anteroposterior, lateral and lower limb axis films. Radiographic measurements included Transilium Pelvic Height Difference (TPHD; mm), Hip Abduction-Adduction angle (H/Abd-Add;), Lower limb Length Discrepancy (LLD; mm), and Pelvic Hypoplasia (PH angle;). The incidence and severity of pelvic obliquity were stratified to Lenke curve subtypes in 311 patients. The causes of pelvic obliquity were analyzed in 57 patients with TPHD !10 mm. Results: The mean Cobb angle was 64.0 + 17.2. Sixty-nine patients had a TPHD of 0 mm (22.2%). The TPHD was <5 mm in 134 (43.0%) patients, 5-9 mm in 104 (33.4%) patients, 10-14 mm in 52 (16.7%) patients, 15-19 mm in 19 (6.1%) patients, and !20 mm in only 2 (0.6%) patients. There was a significant difference between the Lenke curve types in terms of TPHD (p ¼ 0.002). L6 curve types had the highest TPHD of 9.0 + 6.3 mm followed by L5 curves, which had a TPHD of 7.1 + 4.8 mm. In all, 44.2% of L1 curves and 50.0% of L2 curves had positive TPHD compared to 66.7% of L5 curves and 74.1% of L6 curves which had negative TPHD. 33.3% and 24.6% of pelvic obliquity were attributed to PH and LLD, respectively, whereas 10.5% of cases were attributed to H/Abd-Add positioning. Conclusions: 76.4% of AIS cases had pelvic obliquity <10 mm; 44.2% of L1 curves and 50.0% of L2 curves had a lower right hemipelvis compared to 66.7% of L5 curves and 74.1% of L6 curves, which had a higher right hemipelvis. Among patients with pelvic obliquity !10 mm, 33.3% were attributed to PH, whereas 24.6% were attributed to LLD.

Preoperative Leg Length Discrepancy >2 cm in the Supine Decubitus Position May Induce Compensatory Pelvic Obliquity in Patients during Total Hip Arthroplasty

“…In the current study, pelvic obliquity was positively correlated with LLD. Our findings were consistent with the conclusion reached by Young et al 39 Chan et al found that 24.6% of patients with pelvic obliquity ≥10 mm had such cases attributed to LLD 40 . A previous report demonstrated that THA patients with leg length inequalities need to be compensated differently from those patients without THA 30 .…”

“…Our findings were consistent with the conclusion reached by Young et al 39 Chan et al found that 24.6% of patients with pelvic obliquity ≥10 mm had such cases attributed to LLD. 40 A previous report demonstrated that THA patients with leg length inequalities need to be compensated differently from those patients without THA. 30 As shortening of the affected leg might be accommodated by pelvic obliquity and the development of spine scoliosis, it is common to observe compensation of the pelvis‐spine complex.…”

Postoperative improvement in leg length discrepancy in adolescent idiopathic scoliosis differs between right and left legs

“…Postoperative changes in pelvic obliquity were reported by Chen et al [13] . They described how pelvic obliquity could improve following the correction of scoliosis, but did not improve in the presence of structural problems such as pelvic hypoplasia.…”

“…Moreover, LLD did not improve after surgery in almost all patients with shortened right leg and in half of patients with shortened left leg. These results suggest that various factors other than scoliosis are involved in the development of functional LLD, including pelvic/trunk rotation and pelvic asymmetry [13] .…”

A Novel Method for Predicting Ideal Postoperative Upper Instrumented Vertebra Tilt to Prevent Lateral Shoulder Imbalance after Scoliosis Correction Surgery

“…We used the crossbar method reported in the literature [ 18 ] and improved this method in practice. To avoid the influence of leg length discrepancies and pelvic inclination [ 19 , 20 ], the patients were required to try to straighten both lower extremities during preoperative radiography of the entire spine, and the S1 tilt was measured precisely, which should be consistent with the angle between the crossbar and the sacrum intraoperatively. On this basis, the angle between the upper endplate of the UIV and the crossbar should be consistent with the ideal postoperative UIV tilt calculated preoperatively.…”