Introduction
Spinal corrective fusion surgery for adult spinal deformities is performed at an increasing rate because of the aging population. The use of spinopelvic fusion surgery has induced a new problem at the hip joint because spinopelvic fixation can cause the progression of hip joint osteoarthritis (OA). The aim of this study was to investigate the prevalence of and risk factors for hip OA at 5 years after spinal fusion surgery.
Methods
This study enrolled the 267 patients. A digital standing anteroposterior whole-spine radiograph including the hip joint was obtained by the same skilled technician using a standard protocol at preoperatively, 1 month and 5 years postoperatively. We measured lateral center edge (LCE) angle at 1month after surgery, and Kellgren-Lawrence (KL) grade at 1 month and five years postoperatively using the anteroposterior radiographic images. We defined a LCE angle of <20° as DDH. This study also measured spinopelvic sagittal alignment parameters at preoperatively, 1 month and 5 years postoperatively,
Results
The 267 patients included 72 men and 195 women. The progression of KL grade was identified in 80 hips (15.0 %, Group P) and no progression was 454 hips (85.0 %, Group N). Group P had a significantly higher percentage of women than Group N (90.0% and 69.6%, respectively). Group P was significantly older than Group N (69.3 ± 9.8 and 66.4 ± 11.0 years, respectively). The LL at preoperation was significantly lower in Group P (14.5±23.1) than Group N (21.3±22.1). The SS at preoperation was also significantly lower in Group P (18.2±16.6) than Group N (22.6±13.0). The correction of LL was significantly greater in Group P (17.8±22.7) than Group N (9.4±24.2). The correction of SS was also significantly greater in Group P (6.3±17.1) than Group N (1.0±14.2). The number of the fusion segments was significantly higher in Group P (7.7 ± 4.2) than in Group N (6.2 ± 3.9). The percentage of pelvic fixation was higher in Group P (47 hips, 58.8%) than in Group N (153 hips, 33.7%), but the percentage of sacral fusion was lower in Group P (8 hips, 10.0%) than in Group N (92 hips, 20.3%). A higher percentage of DDH in Group P (10 hips, 12.5%) than in Group N (26 hips, 5.7%). The KL grade at 1 month was significantly higher in Group P than in Group N. The multiple logistic regression analysis showed that the risk factors for the progression of KL grade were female, having undergone pelvic fixation, the presence of DDH, and having a higher KL grade at 1 month postoperatively
Conclusions
This five years follow-up study identified the rate of progression of the KL grade was 15.0%. The risk factors for the progression of KL grade included being female, comorbidities such as hip OA or DDH, and undergoing pelvic fixation. These findings suggest that surgeons should be aware of the risk of the progression of hip OA after spinopelvic fusion surgery.