A1098. RADIOLOGIC ASSESSMENT OF THE SHORT HIP STEM USING A NOVEL SCORING SYSTEM

Abstract

Background: The purpose of this study was to assess the stability of short hip stem postoperatively using the radiographic parameters and a novel scoring system based on the unique fixation mechanism of the short hip stem system.

Materials and Methods: Postoperative radiographic analysis was done for 31 total hip arthroplasties performed using Metha^® short hip stem prosthesis. The Metha^® short hip stem system (B. Braun Aesculap; Tuttlingen, Germany) design provides a unique fixation mechanism, with support at the medial calcar region, lateral neck, and dorso-lateral cortical contact distally.

Additionally the modular design offers increased options and variations. We assessed the stability of stem by using a novel scoring system conceptually based on the unique fixation characteristics of the short stem design and included surgeon controlled variables like position and sitting of stem, dorso-lateral cortical contact and filling ratio of stem. The system also incorporated unmodifiable patient specific variables that ultimately render additional stability to the cementless stems in long run.

Results: The positioning of stem was within normal range in all cases in terms of anteroposterior and lateral CCD angles and horizontal offset. The mean filling ratio of stem were 93.48%±4.38% (range 82–100%). 82.75% hips had acceptable sitting of the short stem at the osteotomy site at proximal end of femur. None of the hips showed any amount of subsidence, except one with a static first follow-up subsidence of 2mm. Using our scoring system all hips showed good to excellent results, with mean score of 44.29±3.83 (range 38–50, maximum score 50).

Conclusion: Our scoring system acts as valuable tool for radiological assessment of Metha^® short stem postoperatively. Furthermore, in future longer follow-up studies are required to correlate the scoring system with the longevity and stability of the endoprosthesis.