Abstract
Objectives. To determine the minimum lateral bone coverage required for securing stable fixation of the porous-coated acetabular components (cups) in hip dysplasia. Methods. In total, 215 primary total hip arthroplasties in 199 patients were reviewed. The average follow-up period was 49 months (range: 24–77 months). The lateral bone coverage of the cups was assessed by determining the cup center-edge (cup-CE) angle and the bone coverage index (BCI) from anteroposterior pelvic radiographs. Further, cup fixation was determined using the modified DeLee and Charnley classification system. Results. All cups were judged to show stable fixation by bone ingrowth. The cup-CE angle was less than 0° in 7 hips (3.3%) and the minimum cup-CE angle was −9.2° (BCI: 48.8%). Thin radiolucent lines were observed in 5 hips (2.3%), which were not associated with decreased lateral bone coverage. Loosening, osteolysis, dislocation, or revision was not observed in any of the cases during the follow-up period. Conclusion. A cup-CE angle greater than −10° (BCI > 50%) was acceptable for stable bony fixation of the cup. Considering possible errors in manual implantation, we recommend that the cup position be planned such that the cup-CE angle is greater than 0° (BCI > 60%).
Highlights
Developmental dysplasia of the hip (DDH) is a common cause of hip osteoarthritis [1], characterized by insufficient acetabular coverage on the femoral head and shallow acetabular concavity [2]
We reviewed the clinical and radiographic data of 260 consecutive patients (281 hips) with hip osteoarthritis who underwent primary total hip arthroplasty (THA) using cementless components between April 2010 and March 2013
Thin radiolucent lines were observed for 5 hips (2.3%), and these hips were associated with older age but not with decreased lateral bone coverage
Summary
Developmental dysplasia of the hip (DDH) is a common cause of hip osteoarthritis [1], characterized by insufficient acetabular coverage on the femoral head and shallow acetabular concavity [2]. Several techniques have been reported to manage insufficient bone coverage, including structural autograft [4], superior placement of the cup [5], and medialization of the cup [6]. The minimum bone coverage required on the porous-coated cup for securing stable fixation without these special techniques remains unclear, since the previously reported values vary greatly among studies, ranging from. The purpose of the present study was to determine the effect of lateral bone uncoverage on the fixation of the porous-coated cups and the minimum requirement for lateral bone coverage on the cup 50% to 80% [7,8,9,10,11,12,13,14], and adequate evidence is not available to determine the absolute value.
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