Revision Hip Arthroplasty with Initially High Position of the Acetabular Component: What's Special?

Relevance. Total hip arthroplasty with a severe dysplasia refers to complex cases of joint replacement. One of the options for fixation of the acetabular component in this situation is to place the cup in the false acetabulum. Revisions in case of the acetabular component initial placement into the false acetabulum are highly complex. The purpose - to study the features of revision hip arthroplasty in the patients with dysplastic arthritis and loosening of the acetabular component initially placed in the false acetabulum. Materials and Methods. The clinical and functional results and complications were evaluated after 44 revisions performed by one surgical team from 2001 to 2019. How the position of vertical and horizontal centers of rotation of acetabular component after primary arthroplasty influenced the long-term survival of implants was analyzed. The degree of impact of the preoperative cranial displacement from the anatomical position of the femoral component center of rotation impact on surgical tactics was also investigated. Results. A combination of a highly porous cup with augment was used most frequently for acetabular component replacement (24 cases; 54.5%). Complications after the revision were detected in 6 (13.6%) patients. The values of the Oxford Hip Score, EQ-5D, VAS general health, and VAS pain depended on the postoperative position of the hip prosthesis center of rotation within 10 mm from the anatomical center. The odds ratio for the revision performed less than 10 years after the primary arthroplasty in the patients with a horizontal position of the center of rotation of 40 mm or more was equal to 14.571 (95% CI from 1.682 to 126.249; p = 0.011). The average value of the distal displacement of the center of rotation after the surgery was 32.0 mm (min-max 4.7 to 90.3 mm; Me 23.9 mm), the average residual displacement of the center of rotation after the surgery was 6.2 mm (min-max 10.8 to 32.1 mm; Me 4.75 mm). The standard approach was characterized by a lesser distal displacement of the center of rotation than various osteotomy options: 26.1 mm (min-max 4.7 to 77.2; Me 19.1 mm) vs 41.2 mm (min-max 10.8 to 90.3 mm; Me 36 mm), respectively (p = 0.021). A well-fixed stem preservation resulted in the mean distal displacement of the femur of 23.8 mm, the stem removed - of 35.0 mm. Conclusion. A horizontal center of rotation displacement of 40 mm or more affects the long-term survival of the implant. When the significant lowering of the femur is required (more than 30 mm) and a well-fixed femoral component is preserved, it is advisable to use the approach with extended trochanteric osteotomy or shortening femoral osteotomy. The acetabular component placement into the true acetabulum with weakened bone requires extended screw fixation. In this situation the use of individual 3D-printed implants has potential benefits.