Outcome of Ceramic-on-Ceramic Total Hip Arthroplasty with 4th Generation 36 mm Head Compared to that with 3rd Generation 28 mm Head by Propensity Score Matching.

Background: With the development of 4th generation ceramic bearing, the large ceramic head is available for ceramic-on-ceramic total hip arthroplasty (THA). This retrospective study aimed to compare the outcomes of ceramic-on-ceramic THA with 4th generation 36 mm head to those with 3rd generation 28 mm head using propensity score matching.

Methods: We retrospectively reviewed the results of 133 ceramic-on-ceramic THAs with 4th generation 36 mm ceramic head in 129 patients and 133 ceramic-on-ceramic THAs identified from 405 ceramic-on-ceramic THAs with 3rd generation 28 mm head by propensity score matching. There were 83 males and 50 females in both groups with a mean age of 55 years. There was no significant difference in other demographic features except for follow-up period (4.2 years in the 36 mm group and 6.4 years in the 28 mm group,  < 0.001). Clinical and radiological results and occurrence of complication were compared between the two groups.

Results: Harris Hip Score was increased significantly from 46.4 to 92.1 in the 36 mm group and from 46.7 to 93.6 in the 28 mm group. No loosening or osteolysis was observed in the 36 mm group. However, one hip showed radiologic sign of loosening in the 28 mm group. As for complication, postoperative dislocation was more frequent in the 28 mm group (6 in the 28 mm group vs. 0 in the 36 mm group,  = 0.03). Otherwise, there was no significant difference in other results including inguinal pain, squeaking or ceramic fracture.

Conclusion: Ceramic-on-ceramic THA with 4th generation 36 mm head significantly reduced postoperative dislocation rate without increasing the rate of inguinal pain, squeaking, or ceramic fracture compared to that with 3rd generation 28 mm head.