gms | German Medical Science

Problem: The principle of Neer prosthesis was to restore normal anatomy. Studies demonstrated that normal anatomy was highly variable. Experimental studies have shown that better anatomical reconstruction gives a better biomechanics. The aim of this study is to verify if better anatomical reconstruction achieves a better clinical result.

Method: 50 prostheses implanted for primary arthritis were reviewed with a clinical and an anatomic assessment based on the X-rays. The quality of the anatomical reconstruction has been quantified by the comparison between 5 parameters (head height, centering, medial offset, diameter and inclination angle) measured respectively on the pre-operative and post-operative x-rays. Each parameter was assigned a rating out of 2 based upon its correspondence of pre- and postoperative measurements. The assigned values were summed to create an anatomic reconstruction index out of 10. A statistical analysis of the correlation between anatomical and clinical result was done.

Results and conclusions: Mobility correlated with all anatomic factors. Pain correlated with head height (p=0.02). Strength correlated with head diameter (p=0.02). The global clinical score correlated with the quality of the head height (p=0.025) and medial offset (p=0.014) reconstruction.

The anatomic reconstruction index correlated very specifically with mobility (R2=0.8).

These results seem to concur with the experimental studies and the clinical outcome also depends on the quality of anatomical reconstruction. It also introduces an anatomic reconstruction index to appreciate the quality of the reconstruction. The ability of prosthesis to reproduce the anatomy appears to be a major prognostic factor if the cuff is intact.