There remains confusion in the literature with regard to the spinopelvic relationship, and its contribution to ideal acetabular component position. Critical assessment of the literature has been limited by use of conflicting terminology and definitions of new concepts that further confuse the topic. In 2017, the concept of a Hip-Spine Workgroup was created with the first meeting held at the American Academy of Orthopedic Surgeons Annual Meeting in 2018. The goal of this workgroup was to first help standardize terminology across the literature so that as a topic, multiple groups could produce literature that is immediately understandable and applicable. This consensus review from the Hip-Spine Workgroup aims to simplify the spinopelvic relationship, offer hip surgeons a concise summary of available literature, and select common terminology approved by both hip surgeons and spine surgeons for future research. Cite this article:
Posterior tilt of the pelvis with sitting provides biological
acetabular opening. Our goal was to study the post-operative interaction
of skeletal mobility and sagittal acetabular component position. This was a radiographic study of 160 hips (151 patients) who
prospectively had lateral spinopelvic hip radiographs for skeletal
and implant measurements. Intra-operative acetabular component position
was determined according to the pre-operative spinal mobility. Sagittal
implant measurements of ante-inclination and sacral acetabular angle were
used as surrogate measurements for the risk of impingement, and
intra-operative acetabular component angles were compared with these.Aims
Materials and Methods
There is great interest in technologies to improve the accuracy and precision in placing implants for total hip arthroplasty (THA). Malik et al. (J Arthroplasty, 2010) showed that an imageless navigation system could be used to produce accurate measures of acetabular cup alignment compared to a CT-based alignment method using an imaging phantom. In this study we sought to compare the precision of an image-based navigation system with post-operative CT scans in a clinical patient cohort who received navigation-assisted THA. Eighteen patients with 20 hips consented to this IRB-approved analysis of intra- and post-operative THA cup alignment. All patients received THA with image-assisted alignment (MAKO Surgical, Fort Lauderdale). Nominal cup placement, subject to intraoperative surgeon adjustment and approval, was 40° radiographic inclination (RI) and 20° radiographic anteversion (RA) according to the definitions of Murray (JBJS-Br, 1993). Intraoperative cup alignment was measured by collecting five points on the cup rim with an optically tracked stylus. Postoperative cup alignment was measured by registering pre- and post-operative pelvic models generated from CT scans, and determining the postoperative cup orientation relative to the pre-operative pelvis coordinate system (Figure 1). Repeated measures testing of the CT-based measurements on 10 patient scans showed precision and bias of 0.7° and 0° for radiographic inclination, and 0.6° and 0.1° for radiographic anteversion.Introduction
Methods
