Cup Alignment Change after Screw Fixation in Total Hip Arthroplasty

Abstract

Background: Cup malalignment increase impingement, dislocation, cup migration, and polyethylene wear. Screw fixation for enhanced stability is the preferred option in cases of doubtful primary cup stability. There have been few studies about alignment changes after screw fixation, which may be another cause of cup malalignment. This study aimed to evaluate cup alignment change after screw fixation. Materials and Methods: Patients undergoing imageless navigation total hip arthroplasty using screws fixation for acetabular cup were corrected. After the press-fit cup was fully seated, the cup orientation was recorded. After screws were inserted, the cup orientation was recorded again to calculate the alignment change. Results: There were 99 cases with a mean age 63.7 years (25–93). Alignment change after screw fixation was found in 73 cases (73.7%). There were 56 cases (56.6%) with inclination angle change and the mean change was 2.21° (0°–8°). The inclination angle increased in 47 cases (47.5%) with 9 cases (9.1%) increased by 5° or more and decreased in 9 cases (9.1%). There was statistically significant difference between patients using one screw and patients using two or more screws in inclination angle change, 1.56° (0°–5°) and 3.4° (0°–8°), respectively ( P = 0.0039). There was statistically significant correlation between inclination angle change and number of screws ( r = 0.5401, P < 0.01). There were 49 cases (49.5%) with anteversion angle change and the mean change was 1.67° (0°–5°). The anteversion angle increased in 31 cases (31.3%), decreased in 18 cases (18.2%) with two cases (2%) decreased by 5° or more. There was significant difference between patients using one screw and patients using two or more screws in anteversion angle change, 1.46° (0°–5°) and 2.21° (0°–5°), respectively ( P = 0.009). There was significant correlation between anteversion angle change and number of screws ( r = 0.284, P = 0.048). Conclusions: Changes in cup alignment after screw fixation were detected in most cases. It is one possible cause of cup malalignment.

Are additional screws required for press-fit fixation of cementless acetabular cups? A systematic review and meta-analysis

“…Then a variety of inflammatory factors are released from macrophages, causing osteoclast activation and osteoblast inhibition [ 35 , 42 ]. It has been suggested that changes in cup alignment after screw fixation might affect the wear of acetabulum components [ 43 ]. Our results showed that there was no difference in wear rate between the acetabular component with and without screws.…”

No linear correlation between pelvic incidence and acetabular orientation

“…All the measurements were based on the anatomical reference coordinate system that was built based on the anterior pelvic plane (APP). [ 15 , 35 , 38 ] The APP comprising both anterior superior iliac spines (ASIS) and both pubic tubercles were defined as the coronal plane. The sagittal plane was normal to the vector passing through the bilateral ASISs.…”

“…[ 11 , 12 ] To emphasize this idea, Dubousset even referred to the pelvis as the “pelvic vertebra.” [ 13 , 14 ] The acetabular orientation is a determinant of both native joint pathology and complications of the artificial joints. [ 15 – 18 ] The acetabular orientation is often described in 2 different coordinate systems. As the functional acetabular coordinate system is described in that of the whole body, the functional acetabular orientation in the native joint or the acetabular cup in the replaced joint is inherently influenced by the pelvic orientation.…”

Can a Nomogram Predict the Failure Risk of Internal Fixation Devices in Chinese Patients Undergoing Hip Arthroplasty?

“…The nomogram revealed that the use of more than 4 screws increased the risk of refurbishment. When the stability of the acetabular cup is compromised, screw xation is recommended [32].…”