The influence of spine-hip relations on total hip replacement: A systematic review.

Sagittal pelvic kinematics along with spino-pelvic angular parameters have recently been studied by numerous investigators for their effect on total hip replacement (THR) clinical outcomes, but many issue of spine-hip relations (SHR) are currently unexplored. Therefore, our review aims at clarifying the following questions: is there any evidence of a relationship between articular impingement/dislocation risk in primary THR and (1) certain sagittal pelvic kinematics patterns, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilising PubMed and Google search engines was performed in January 2017. Only clinical or computational studies published in peer-reviewed journals over the last five years in either English or French were reviewed. We identified 769 reports, of which 12 met our eligibility criteria. A review of literature shows that sagittal pelvic kinematics, but not the pelvic incidence, influences the risk of prosthetic impingement/dislocation. We found no study having assessed the relationship between this risk and the types of SHRs. Sagittal pelvic kinematics is highly variable among individuals and certain kinematic patterns substantially influences the risk of prosthetic impingement/dislocation. Recommendations for cup positioning are therefore switching from a systematic to a patient-specific approach, with the standing cup orientation Lewinneck safe zone progressively giving way to a new parameter of interest: the functional orientation of the cup. Based on a recently published classification for SHRs, We propose a new concept of "kinematically aligned THR" for the purposes of THR planning. Further studies are needed to investigate the relevance of such a classification towards the assumptions and hypothesis we have made. Level of evidence,- Level IV, systematic review of level III and IV studies.