Spinopelvic alignment and precise cup placement in total hip arthroplasty - A systematic review.

Study Design: A systematic literature review and meta- analysis.

Objective: To extract and combine the available literature focused on normal and abnormal biomechanical principles of spine-pelvis-hip complex and to sum up the data in the application of THA both in the setting with and without spinal disorders.

Methods: An extensive search and analysis of the articles was done by 3 authors independently in 7 platforms based on PRISMA and MOOSE guidelines. Selection criteria 1. Articles that assessed spinopelvic parameters (SS, SPT, PI, and acetabular cup orientation) in patients undergoing THA, Articles that assessed balance in spinopelvic complex after THA, Randomized control studies, Systematic literature reviews, Meta-analyses, Clinical trials / original research studies, Review articles and Articles after 2015 were included. Cochrane's GRADE method was used to define the level of evidence. 2.Participants: Patients who underwent THA only (in asymptomatic spine), those who had ankylosing spondylitis and underwent THA and those who underwent THA with prior spinal arthrodesis. 3.Study parameters: Ante Inclination (AI), sacral slope (SS), pelvic Incidence (PI) and spinopelvic tilt (SPT) in both positions of standing and sitting. ΔAI, ΔSS and ΔSPT. Data were collected and analyzed, the means of the study parameters with SD were calculated and a meta-analysis is performed to evaluate the pooled means with optimal value range.

Results: From 218 abstracts extracted and after eligibility assessment and exclusion, 4 articles involving 439 patients were enrolled. The mean SS in standing and sitting calculated were 35.53±10.52 and 33.13±12.38. The mean of AI and SPT in standing /sitting positions are 29.7±12.29/34.69±12.96 (n = 242) and 19.56±8.9/21.22±12.53 (n=439) respectively. The ΔAI, ΔSS, and ΔSPT were 4.99,2.4 and 1.66 respectively.

Conclusion: There is a proportionate change between the spinopelvic tilt and the acetabular orientation in postural variations. Evaluation of spine, pelvis and hip becomes more critical in identifying these changes and thereby prompting the acetabular cup position in the functional safe zone.