• Jean-Marc Mac-Thiong, Stefan Parent, Julie Joncas, Soraya Barchi, and Hubert Labelle.
• University of Montreal, Montreal, Canada. macthiong@gmail.com.
• Eur Spine J. 2018 Aug 1; 27 (8): 2038-2043.

PurposePrevious studies did not specifically assess the influence of proximal femoral angle (PFA) on sagittal balance in high-grade spondylolisthesis (HGS). In addition, the relationship between PFA and quality of life (QOL) remains unknown. This study determines if increased PFA is associated with decreased QOL and sagittal balance in lumbosacral HGS.MethodsThis retrospective case-control study was performed on a cohort of 56 normal subjects and 42 patients with HGS. Initially, PFA was measured twice by 3 raters in a random subset of 30 subjects (15 normal and 15 HGS) to determine the intrarater and interrater reliability of the measurement technique. PFA was then measured for all subjects. For the 42 patients with HGS, QOL was assessed from the SRS-22 questionnaire, in addition to the evaluation of the spino-pelvic balance.ResultsThe intrarater and interrater intraclass correlation coefficients for the measurement of PFA were, respectively, 0.951 and 0.958, suggesting excellent reliability. PFA was significantly higher in HGS patients (8.3° ± 6.7°; range - 5° to 24°) when compared to normal subjects (3.0° ± 3.1°; range - 6° to 10°). The PFA in HGS was 5.6° ± 5.6° (range - 5° to 18°), 8.9° ± 6.7° (range - 2° to 24°), and 14.0° ± 6.0° (range 7°-23°) in type 4 (balanced pelvis), type 5 (unbalanced pelvis/balanced spine), and type 6 (unbalanced pelvis and spine) subjects, respectively. There were, respectively, 23.5% (4/17), 26.3% (5/19), and 83.3% (5/6) of HGS patients with abnormal PFA ≥ 10° in type 4, type 5, and type 6 subgroups. Increased PFA in HGS patients was related with deteriorating self-image, pain, function and total SRS-22 score, as well as with increasing pelvic tilt and decreasing sacral slope.ConclusionA PFA ≥ 10° is proposed as a criterion to define abnormal PFA. PFA was increased in HGS and increased along with deteriorating sagittal balance and QOL. PFA is a clinically relevant parameter of sagittal balance, and can be useful in the evaluation and management of patients with HGS.

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