Background: In shoulder arthroplasty, mismatch is defined as the difference in the radius or diameter of curvature between the humeral head and glenoid components. Recommendations for mismatch have not been substantiated scientifically. The purpose of this study was to evaluate the effect of mismatch on glenoid radiolucent lines.
Methods: The results of 319 total shoulder arthroplasties performed for the treatment of primary osteoarthritis were evaluated. All of the arthroplasties were performed with a single type of prosthesis (Aequalis; Tornier, Montbonnot, France) that included a cemented, all-polyethylene glenoid component. Three sizes of glenoid components and seven humeral head diameters were utilized. Radial mismatch was categorized as ≤4 mm, 4.5 to 5.5 mm, 6 to 7 mm, or >7 to 10 mm. Radiographs were evaluated at a mean of 53.5 months (range, twenty-four to 110 months) postoperatively. Glenoid radiolucent lines were scored with a scale ranging from 0 points for no radiolucency to 18 points for radiolucent lines exceeding 2 mm in six zones. Variance, linear contrasts polynomial, quadratic polynomial contrast statistical, and linear regression analyses were performed to evaluate the relationship between radial mismatch and glenoid radiolucent lines.
Results: A significant linear relationship was found between mismatch and the glenoid radiolucency score (p < 0.0001), with significantly lower (better) radiolucency scores associated with radial mismatches of >5.5 mm.
Conclusions: In this study of glenohumeral prosthetic mismatch ranging from 0 to 10 mm, the mismatch had a significant influence on the scores for the glenoid radiolucent lines, which were best when the radial mismatch was between 6 and 10 mm. The theoretical risk of prosthetic instability with larger mismatch values was not demonstrated within the range of mismatch values evaluated in this series.
Gilles Walch, MD; Aziz Boulahia, MD; Department of Orthopaedic Surgery, Clinique Sainte Anne Lumière, 85 Cours Albert Thomas, 69003 Lyon, France. E-mail address for G. Walch: email@example.com
T. Bradley Edwards, MD; Minneapolis Sports Medicine Center, 7201 Washington Avenue South, Edina, MN 55439
Pascal Boileau, MD; Department of Orthopaedic Surgery, Hôpital de l'Archet, 151 Route de Saint Antoine de Ginestière BP 79, 06202 Nice CEDEX, France
Daniel Molé, MD; Clinique Traumatologique et Orthopédique, 49 Rue Hermine, SC 5211, F-54052 Nancy CEDEX, France
Patrice Adeleine, PhD; Department of Biostatistics, Hôpitaux de Lyon, 162 Avenue Lacassagne, 69424 Lyon CEDEX 03, France