The Ring uncemented polyethylene cup in the abnormal acetabulum

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Protrusio acetabuli and hip dysplasia present challenges in total hip arthroplasty due to acetabular deformities and lack of bone support.
• Uncemented prostheses offer potential for bone ingrowth and biological fixation, which may address structural deficiencies in these challenging cases.

Purpose of the Study:

• To evaluate the efficacy of the Ring uncemented polyethylene-to-metal (UPM) prosthesis in patients with protrusio acetabuli.
• To assess the impact of the uncemented prosthesis on lateral support in dysplastic acetabula.
• To investigate the potential biomechanical remodeling effects of the UPM prosthesis.

Main Methods:

• Retrospective analysis of 54 cases of protrusio acetabuli treated with the Ring UPM prosthesis.
• Development and application of a modified measurement technique for acetabular deformity.
• Radiographic evaluation of 38 hips with dysplastic acetabula treated with the Ring UPM prosthesis, with an average follow-up of 31 months.

Main Results:

• Significant improvement in medial wall remodeling observed in protrusio acetabuli cases, averaging 29.6% post-operation.
• Average increase in lateral support of 21% in dysplastic acetabula, supporting the hypothesis of improved stability with uncemented fixation.
• Observed remodeling effects are potentially attributable to the biomechanical design of the Ring UPM prosthesis.

Conclusions:

• The Ring UPM prosthesis is effective in addressing medial wall deformities in protrusio acetabuli.
• The uncemented design of the Ring UPM prosthesis enhances lateral support in dysplastic acetabula.
• The biomechanical characteristics of the prosthesis likely contribute to observed bone remodeling and improved hip stability.