Abstract
Introduction
Implantation of total hip replacement (THR) remains a concern in patients with developmental dysplasia of the hip (DDH) because of bone deformities and previous surgeries. In this frequently young population, anatomical reconstruction of the hip rotation centre is particularly challenging in severe, low and high dislocation, DDH. The basic principles of the technique and the implant selection may affect the long-term results.
The aim of the study was to compare surgical difficulties and outcome in patients who underwent THR due to arthritis secondary to moderate or severe DDH.
Material and Methods
We assessed 131 hips in patients with moderate DDH (group 1) and 56 with severe DDH (Group 2) who underwent an alumina-on-alumina THR between 1999 and 2012. The mean follow-up was 11.3 years (range, 5 to 18). Mean age was 51.4 years in group 1 and 42.2 in group 2. There were previous surgery in 5 hips in group 1 and in 20 in group 2 (p<0.001). A dysplastic acetabular shape type C according to Dorr and a radiological cylindrical femur were both more frequent in group 2 (in both cases p<0.001). We always tried to place the acetabular component in the true acetabulum. Smaller cups (p<0.001), screw use for primary fixation (p<0.001) and bone autograft used as segmental reinforcement in cases of roof deficiency (p<0.001) were more frequent in group 2. Radiological analysis of the cup included acetabular abduction, version and Wiberg angles, horizontal, vertical, and hip rotation centre distances, and acetabular head index. Abductor mechanism reconstruction according to the lever arm distance and height of the greater trochanter was also evaluated. Cup placement within or outside Lewinnek´s safe zone was recorded. Two-way ANOVA with repeated measures were used to analyse clinical and radiological changes.
Results
There were 6 cups revised for aseptic loosening, three in each group. Survivorship analysis at 15 years: 97.3% (95% IC 94.4–100) for group 1 and 93.0% (95% IC 85.2–100) for group 2 (p=0.186). Despite a worse preoperative status in group 2, the outcome improved similarly in both groups. Postoperative radiological measurements were better in group 1 except for acetabular acetabular and version angles. The improvement from the pre- to the post-operative situation was greater in group 2 except for the height of the greater trochanter. Acetabular component placement within the Lewinnek´s safe zone was similar in both groups. All revised cups were outside this zone. No osteolysis or complications related to the use of ceramics were found.
Conclusions
The alumina-on-alumina THR provided good results in both groups including pain relief and functional improvement. Placing the acetabular component in the true acetabulum inside the Lewinnek safe zone can ensure a good result in these challenging dysplastic hips.
