A randomized prospective study comparing migration of hydroxyapatite and non-hydroxyapatite coated glenoid components using radiostereometric analysis

Background: Primary shoulder arthroplasty can significantly improve quality of life; however, the glenoid baseplate remains the most common component to loosen, which may result in implant failure and subsequent revision surgery. Radiostereometric analysis (RSA) is considered the gold standard for accurate measurement of micro-motion between implant and bone. The aims of this study were to compare migration of the Lima SMR porous titanium hydroxyapatite (HA) coated and non-hydroxyapatite (non-HA) coated glenoid components through a prospective, randomized 2-arm trial using RSA, whilst also comparing clinical and functional outcomes. Methods: Twenty patients were randomized into 2 equal (HA and non-HA coated) groups with all patients undergoing primary anatomic shoulder arthroplasty, at which time tantalum beads were also inserted. RSA imaging was performed immediately postoperatively, then at 3, 6, 12, and 24 months postprocedure. These images were digitized and analyzed using model-based RSA software. All patients completed Oxford Shoulder Score (OSS), American Shoulder and Elbow Surgeons (ASES) score, Constant Score (CS) and Visual Analogue Scale (VAS) pain scores pre-and postoperatively at the aforementioned time points. Unpaired t-tests were used for clinical outcome data; Mann-Whitney U tests were used for RSA data. Significance levels were set at P <.05. Results: Mean age for the HA group was 72.3 years; 69.5 years for the non-HA group. Mean follow-up for both groups was above 36 months. No significant differences in glenoid migration were observed at each of the postoperative time points; the only exception being at 12 months (non-HA group displaying significantly greater rotation in the z-axis). The HA group displayed fractionally more translation in the x- and z-axes at all time points (not significant). Rotation in the z-axis was marginally greater at all postoperative time points in the non-HA group. Median total migration values revealed greater motion for the non-HA group at 3, 6, and 12 months (not significant). All clinical outcome measures improved significantly within each group; no statistical differences were observed between the groups for any outcome measure. One patient in each group underwent revision surgery to reverse shoulder arthroplasty due to unexplained pain (HA group) and cuff failure (non-HA group) only. Radiolucent lines were noted in 2 patients who are still under follow-up. Conclusion: This study has revealed promising early results of both HA coated and non-HA coated implants, however, hydroxyapatite coating of glenoid components does not significantly improve outcome scores nor provide extra stability compared to non-hydroxyapatite coated implants at 2 years postprocedure. Level of evidence: Level II; Randomized Controlled Trial