Abstract
BackgroundTo study the segmental uncoverage ratio (UCR) of a 44-mm cup model placed in a true acetabulum of Crowe type-IV developmental dysplasia of the hip via 3-Dimensional (3D) implantation simulation.MethodsQualified CT imaging data of 26 patients (involving 30 hips) with Crowe type-IV DDH were imported into Mimics software for reconstruction. Then a 44-mm eggshell cup model was placed in a true acetabulum. First, total uncoverage ratio (TUCR) was measured. Then the virtual cup was divided into 4 segments according to the quadrant setting of the true acetabulum, i.e., anterior-superior (A-S) segment, anterior-inferior (A-I) segment, posterior-superior (P-S) segment and posterior-inferior (P-I) segment. The UCRs of the aforementioned segments were measured, i.e., anterior-superior uncoverage ratio (A-SUCR), anterior-inferior uncoverage ratio (A-IUCR), posterior-superior uncoverage ratio (P-SUCR) and posterior-inferior uncoverage ratio (P-IUCR). The acetabular height and anterior-posterior diameter on the 3-D model were also calculated. Statistic analyses were performed by using SPSS software package.ResultsTUCR was 0.2958 ± 0.1003 (95% [CI], 0.1020 to 0.5400) in this cohort of Crowe Type-IV hips. P-SUCR had the greatest value among all the segmental UCRs (0.1012 ± 0.0435, 95% confidence interval [CI],0.0152 to 0.1914) and the most significant positive correlation with TUCR (Pearson correlation = 0.889, p < 0.01. Linear regression R2 = 0.791). Similarly, P-IUCR and A-SUCR showed a significant positive correlation with TUCR. However, A-IUCR exhibited no correlation with either total or other segmental UCRs. P-SUCR was found to bear significant positive correlation with P-IUCR (pearson correlation = 0.644, p < 0.01. Linear regression R2 = 0.415). Acetabular height and A-P diameter were not correlated with TUCR.ConclusionImplantation of a 44-mm cup into Crowe type IV acetabulum is feasible and could achieve acceptable host bone coverage in most of the cases. P-SUCR contributed most to TUCR. TUCR had no linear relationship with the size of the host acetabulum, suggesting that the pre-operative plan should be individualized.
Highlights
Developmental dysplasia of the hip (DDH) represents the most common cause leading to secondary osteoarthritis of hip
Our research questions are as follows: What are the segmental uncoverage ratios of a 44-mm cup placed in a true acetabulum in Crowe type-IV DDH and what are their influencing factors? We aimed to address these questions via three-dimensional implantation simulation
The relationship between acetabular size and uncoverage ratio (UCR) Pearson correlation and linear regression analysis showed that the acetabular height bore a significant negative correlation with posterior-inferior uncoverage ratio (P-IUCR)
Summary
Developmental dysplasia of the hip (DDH) represents the most common cause leading to secondary osteoarthritis of hip. Different operative principles apply with different classifications, and even within one classification, surgery strategies vary Among those classifications, Crowe type-IV acetabula are often small and shallow, irregular in shape, and may be associated with bone defects. With Crowe type-IV DDH, it is an feasible choice to use a 44-mm cup to achieve a balance between small bone volume in a true acetabulum and adequate cup size for hip stability. Our research questions are as follows: What are the segmental uncoverage ratios of a 44-mm cup placed in a true acetabulum in Crowe type-IV DDH and what are their influencing factors? To study the segmental uncoverage ratio (UCR) of a 44-mm cup model placed in a true acetabulum of Crowe type-IV developmental dysplasia of the hip via 3-Dimensional (3D) implantation simulation
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