Correlation between femoral version and severity of hip dysplasia in patients with advanced osteoarthritis prior to total hip arthroplasty.

INTRODUCTION

Developmental dysplasia of the hip (DDH) is a condition which comprises a number of joint abnormalities, including modifications in femoral version and neck-shaft angle (CCD), as well as a probable progression to osteoarthritis in certain cases. The main objective of this research was to find a correlation between femoral version and severity of DDH in patients with advanced osteoarthritis prior to joint replacement, which has not been previously reported. A secondary aim was to describe the modification of CCD as the severity of DDH increases.

MATERIALS AND METHOD

Patients over the age of 15 with dysplastic hips and severe osteoarthritis prior to total hip arthroplasty were assessed between March 2018 and February 2019. Cases with any previous hip surgery were excluded. Anteroposterior pelvis X rays and femoral computed tomography (CT) were performed; femoral version was measured in CT and CCD was evaluated both in X rays (2 observers: A and B) and CT (one observer: musculoskeletal radiologist). Severity of DDH was defined by observers A and B according to Crowe classification in X rays. Statistical analysis was performed on SPSS v.21. Shapiro-Wilk test was used to confirm a normal data distribution. Intraclass correlation coefficient (ICC) determined the level of agreement between observers A and B. Pearson test assessed the correlation between femoral version and Crowe classification (positive if >0.5). Student's t test evaluated the statistical significance, which was defined as P<0.05.

RESULTS

One-year assessment; 42 patients (54 hips), 76% women. Mean age 52.7 years. 45 hips completed the imaging set, 9 hips were assessed only with X rays. 48%, 16%, 7% and 28% were classified as Crowe I, II, III and IV (100% interobserver agreement). Crowe classes were grouped as I, II/III and IV due to a low number of cases classified as II and III. Mean femoral version was 21.73°, 26.8° and 43.58°, respectively. ICC between observers A and B for CCD measured in X rays was 0.96. Mean CCD measured in X rays for each group (I, II/III and IV) was 148.11°, 147.7° and 147°, and in CT was 131.21°, 127.9° and 122.14°, respectively. A significant difference was found in femoral version between groups I and IV (P=0.0002) and II/III and IV (P=0.042). Pearson correlation between femoral version and severity of DDH was positive (r=0.52; P=0.0002). A significant difference between CCD measured in CT was found between groups I and IV (P=0.003).

CONCLUSIONS

A significant increase in femoral version related to severity of DDH and a positive correlation between these 2features were found. Furthermore, a significant decrease in CCD between groups I and IV measured in CT was revealed. These findings would be helpful for preoperative planning of total hip replacement in osteoarthritis secondary to DDH, because once the surgeon has assessed the severity of DDH on X rays or CT, an increased femoral version could be expected. Therefore, availability of specific implants such as conic, modular or cemented stems is critical, in order to modify the femoral anteversion to normal values in the most severe cases.