INTRODUCTION: Cotyloplasty is a technique that involves making a perforation of the medial wall of a dysplastic acetabulum and then inserting an acetabular cup with the medial aspect of it’s dome beyond the Kohler’s line. Although this method is in use since 1976., so far no one has not defined how much cotyloplasty can be performed to remain acetabular component stablity. In this study we measured acetabular component stability depending on the diameter of cotyloplasty. MATERIALS AND METHODS: On the 24 pigs pelvis models iatrogenic medial wall defect in different diameters (10, 20, 25, 30mm) was made followed with acetabular component placement (size 44). Acetabulum was loaded for determining to which diameter of cotyloplasty acetabular component remains stable, or at which point the remaining medial wall of the acetabulum can´t withstand the load and acetabular cup moves through the pelvis for more than 2 mm or breaks through acetabulum. RESULTS: In our study we found that in the average person (weighing 70 kg), we can make acetabular defect that is between 25 and 30 mm if we use the acetabular component size 44. If it is a person with higher body weight, up to 100 kg, this defect should not exceed the diameter of 25 mm. CONCLUSION: For the first time maximal diameter of cotyloplasty which ensures the primary stability of acetabular component is determed. We confirmed our hypothesis that THA will have sufficient stability to ensure secondary bone ingrowth around it, if amount of cotyloplasty does not exceed half of the acetabular component diameter. This information will help orthopedic surgeons in preoperative planning of total hip arthroplasty and postoperative rehabilitation patients with hip dysplasia.
