Acetabular cup positioning in primary routine total hip arthroplasty—a review of current concepts and technologies

Arthroplasty (2023) 5:59 Sai Sathikumar et al. Arthroplasty https://doi.org/10.1186/s42836-023-00213-3 Open Access REVIEW Acetabular cup positioning in primary routine total hip arthroplasty—a review of current concepts and technologies Aravind Sai Sathikumar1* , George Jacob1, Appu Benny Thomas1, Jacob Varghese1 and Venugopal Menon2 Abstract Introduction Total hip arthroplasty (THA) has revolutionized the treatment of hip joint arthritis. With the increased popularity and success of the procedure, research has focused on improving implant survival and reducing surgical complications. Optimal component orientation has been a constant focus with various philosophies proposed. Regardless of the philosophy, achieving an accurate acetabular position for each clinical scenario is crucial. In this paper, we review the recent developments in improving the accuracy and ideal positioning of the acetabular cup in routine primary THA. Methodology A review of the recent scientific literature for acetabular cup placement in primary THA was performed, with available evidence for safe zones, spinopelvic relationship, preoperative planning, patient-specific instrumentation, navigation THA and robotic THA. Conclusion Though the applicability of Lewinnek safe zones has been questioned with an improved understanding of spinopelvic relationships, its role remains in positioning the acetabular cup in a patient with normal spinopelvic alignment and mobility. Evaluation of spinopelvic relationships and accordingly adjusting acetabular anteversion and inclination can significantly reduce the incidence of dislocation in patients with a rigid spine. In using preoperative radiography, the acetabular inclination, anteversion and intraoperative pelvic position should be evaluated. With improving technology and the advent of artificial intelligence, superior and more accurate preoperative planning is possible. Patient-specific instrumentation, navigated and robotic THA have been reported to improve accuracy in acetabular cup positioning as decided preoperatively but any significant clinical advantage over conventional THA is yet to be elucidated. Keywords Acetabular cup positioning, Primary THA, Robotic THA, Patient specific instrumentation, Navigation THA, Spinopelvic relation *Correspondence: Aravind Sai Sathikumar 1 Division of Joint Replacement and Sports Medicine, VPS Lakeshore Hospital: Lakeshore Hospital and Research Centre Ltd, Kochi, Kerala 682040, India 2 Department of Orthopaedics, Bharati Vidyapeeth Deemed University, Pune, Maharashtra 411043, India Introduction Total hip arthroplasty(THA) is known as the “Operation of the century” revolutionizing treatment for people suffering from crippling hip arthritis [1]. Accurate orientation and positioning of the acetabular cup in total hip arthroplasty (THA) is crucial for satisfactory outcomes. Erroneous acetabular cup positioning can result in dislocation, accelerated implant wear, osteolysis leading to aseptic loosening of cup, impingement or limb length discrepancy [2, 3]. Anteversion, inclination, height, and © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Sai Sathikumar et al. Arthroplasty (2023) 5:59 offset are important variables during acetabular cup placement [3]. Lewinnek et al. described a safe zone or safe range for the placement of the acetabular component in 1978 [4]. However, recent literature confers poor predictive values for Lewinnek’s safe zone with regard to hip joint instability [5, 6]. It is suggested to consider a “functional safe zone” for acetabular cup placement rather than a “one size fits all” philosophy [5, 6]. Therefore, each case requires preoperative radiological evaluation and planning to determine each individual patient’s functional safe zone [7]. Acetabular cup orientation is significantly influenced by the intraoperative position of patient’s pelvis during THA [8]. Some studies suggest that the use of mechanical guides are superior to freehand techniques for appropriate acetabular cup placement [9]. Further use of preoperative computed topography and 3D printing of custom acetabular jigs decreases the incidence of acetabular cup malposition during THA [10–12]. Navigated THA (N-THA) has been reported to have more accurate positioning of the acetabular component than freehand placement [13, 14]. However, some studies have reported no significant advantage in using navigation for acetabular cup positioning [15, 16]. Robotic THA (R-THA) has been reported to be effective in acetabular cup positioning within the Lewinnek and Callanan safe zones. However, again significant functional difference between robotic vs. conventional THA (C-THA) remains debatable [17–19]. In this paper we aimed to comprehensively review the recent concepts and technological advances for positioning of an acetabular cup in a routine primary THA and their merits, demerits, practicality in clinical application and their functional outcomes. Methodology The PubMed database was searched for recent scientific literature published in last 5 years (2017 to 2022) regarding acetabular cup placement with specific regard to acetabular cup positioning, safe zones for cup placement, spinopelvic relationship in THA, preoperative planning for cup placement, patient-specific instrumentation, navigated and robotic THA. A total of 1,204 articles appeared in the search, out of which 36 eligible articles were considered for critical analysis. We included randomized controlled trials (RCTs), prospective and retrospective case-control or cohort studies which focused on acetabular cup placement in primary routine THA. We excluded narrative reviews, scoping reviews, newsletters as well as other research articles which focused on femoral component positioning, revision THA and acetabular positioning in complex primary THA, such as those for Page 2 of 13 developmental dysplasia of hip, severe protusio acetabuli, previous acetabular surgery, hip infection, severe acetabular bone loss or severe osteoporosis. Acetabular cup position and safe zones Over the last 44 years, the most popular “safe zones” for acetabular cup placement were descri (...truncated)