Rotational abnormalities in dysplastic hips and how to predict acetabular torsion.

OBJECTIVES: The aim of this study was to investigate the degree to which conventional radiography can represent the acetabular and femoral rotational alignment profile between dysplastic and borderline-dysplastic hips. METHODS: A retrospective trial was conducted including 56 borderline-dysplastic and dysplastic hips at a mean age of 28.9 years (range from 18 to 46). Inclusion criteria consisted of symptomatic patients with hip dysplasia undergoing 2-dimensional radiography as well as computed tomography. On radiography, the lateral center edge angle, acetabular hip index, hip lateralization index, acetabular index angle, and the Sharp angle were measured, and the presence of a crossover sign was noted. In computed tomography, the full rotational profile of the lower limb was measured. RESULTS: Significant correlations were observed in the overall analysis between the anteversion of the acetabulum and the hip lateralization index (mean 0.56, coefficient of regression (CoR) -32.35, p = 0.011) as well as the acetabular index angle with a mean of 11.50 (CoR 0.544, p = 0.018). Similar results were found in the subgroup of dysplastic hips with an acetabular index angle of 13.9 (p = 0.013, CoR 0.74). For the borderline-dysplastic group, no significant correlations between the pelvis radiography and rotational CT were seen. CONCLUSION: Although the femoral and acetabular torsion cannot be predicted from x-rays, the anteversion of the acetabulum correlates with the acetabular index angle, the hip lateralization index, and eventually the beta angle in dysplastic hips. For borderline-dysplastic hips, such results did not show up, which strongly illustrates the need for computed tomography in these cases. KEY POINTS: • Much of the current literature focuses on rotational alignment especially with respect to the femur and tibia in healthy patients, although little is known about the acetabular, femoral, and tibial torsion in dysplastic hips. • This is the first study showing significant correlations between the anteversion of the acetabulum and the hip lateralization index as well as the acetabular inclination angle. Also, it is the first study to provide a mechanism for estimation of the torsion of the acetabulum with plain radiography in dysplastic hips. • In borderline-dysplastic hips, no significant correlation was found, which raises the question if a simple x-ray has enough validity to address the acetabular deformity with surgery.

The Impact of the Laterality on Radiographic Outcomes of the Bernese Periacetabular Osteotomy.

The purpose of this study was to compare the pre and postoperative radiographic findings and analyze the complication rate with respect to the laterality in periacetabular osteotomy in right-handed surgeons. Satisfaction rate and radiographic findings were prospectively collected between 2017 and 2019 and retrospectively reviewed. For analysis, all measurements of the CT scans were performed by a musculoskeletal fellowship-trained radiologist. Complications were classified into two categories: perioperative or postoperative. All surgeries were performed by three right-hand dominant hip surgeons. A total of 41 dysplastic hips (25 right and 16 left hips) in 33 patients were included. Postoperatively, a significantly lower acetabular index angle on the left side was observed at −2.6 ± 4.3 as compared to the right side at 1.6 ± 6.5 (p < 0.05). The change in Center edge (CE) angle was significantly lower for the left side 13.7 ± 5.5° than on the right side, measured at 18.4 ± 7.3 (p < 0.001); however, the overall CE angle was comparable at 38.5 ± 8.9° without any significant difference between the operated hips (left side at 37.8 ± 6.1° versus right side at 39.0 ± 10.3; p = 0.340). No significant differences in other radiographic measurements or surgical time were observed. For complications, the right side was more commonly affected, which may also explain a higher satisfaction rate in patients who were operated on the left hip with 92.3%. The change in lateral CE angle was significantly lower for the left side and the right hip seems to be predisposed to complications, which correlate with a lower satisfaction rate in right-handed surgeons.

The Impact of Hip Dysplasia on CAM Impingement.

Predisposing factors for CAM-type femoroacetabular impingement (FAI) include acetabular protrusion and retroversion; however, nothing is known regarding development in dysplastic hips. The purpose of this study was to determine the correlation between CAM-type FAI and developmental dysplastic hips diagnosed using X-ray and rotational computed tomography. In this retrospective study, 52 symptomatic hips were included, with a mean age of 28.8 ± 7.6 years. The inclusion criteria consisted of consecutive patients who suffered from symptomatic dysplastic or borderline dysplastic hips and underwent a clinical examination, conventional radiographs and rotational computed tomography. Demographics, standard measurements and the rotational alignments were recorded and analyzed between the CAM and nonCAM groups. Among the 52 patients, 19 presented with CAM impingement, whereas, in 33 patients, no signs of CAM impingement were noticed. For demographics, no significant differences between the two groups were identified. On conventional radiography, the acetabular hip index as well as the CE angle for the development of CAM impingement were significantly different compared to the nonCAM group with a CE angle of 21.0° ± 5.4° vs. 23.7° ± 5.8° (p = 0.050) and an acetabular hip index of 25.6 ± 5.7 vs. 21.9 ± 7.3 (p = 0.031), respectively. Furthermore, a crossing over sign was observed to be more common in the nonCAM group, which is contradictory to the current literature. For rotational alignment, no significant differences were observed. In dysplastic hips, the CAM-type FAI correlated to a lower CE angle and a higher acetabular hip index. In contrast to the current literature, no significant correlations to the torsional alignment or to crossing over signs were observed.