Comparison of Femoral Bone Mineral Density Changes around 3 Common Designs of Cementless Stems after Total Hip Arthroplasty—A Retrospective Cohort Study

OBJECTIVE: The aim of this study was to compare the periprosthetic BMD changes around Tri‐Lock “Bone Preserving Stem” with the other two common and longer stems (Corail and Summit) after THA. METHODS: It was a retrospective cohort study followed patients underwent the total hip arthroplasty from January 2013 to December 2015. They were selected and followed from January 2013 to Janaury 2020. Patients without osteoporosis underwent hip replacements with three aimed stems were included. Among the 138 patients included, 49 patients received the Tri‐Lock stem, 44 patients received the Corail stem, and 45 patients received the Summit stem. The periprosthetic BMD changes evaluated by the Dual energy X‐ray absorptiometry (iDXA) measurement according to the seven Gruen zones was the primary outcome. The Radiographic changes including spot welds, pedestal sign and grade of stress shielding was evaluated by the consecutive hip images. Einzel‐Bild‐Roentgen‐Analyze‐femoral component analysis (EBRA‐FCA) was used to measure the stem migration at 5 years postoperatively. Patient‐reported outcomes (PROMs) and adverse events were assessed and compared in three groups. Finally, the subgroups for the periprosthetic BMD changes, radiological and clinical outcomes were made based on the age, gender and length of follow‐up. RESULTS: A total of 138 patients were retrospectively followed for an average of 4.66 years. Excepting the different stems used in three groups, the age, gender and other characteristics of patients included were similar between groups. There was no significant difference between the three groups in periprosthetic BMD changes over postoperative 5 years. The Summit stem shown more BMD loss in Gruen zone 1 compared with the Tri‐Lock and Corail stems without significant difference (7.49%, −1.89% and −2.62%, respectively, P = 0.42). And the most prominent BMD loss was found in Gruen zone 7 for all three stems (−12.60%, −11.84%, and −9.56%, respectively, P = 0.91). The spot weld was significantly more common around the Corail stem, while there was no difference in the stem migration between three groups. Patient reported outcomes (PROMs) were significantly improved compared with the preoperative values. Regarding the rate of postoperative complications, two patients underwent the dislocation and 25 patients sometimes felt mild to moderate thigh pain. Subgroup analysis showed that female patients older than 50 years lost more BMD and had lower clinical scores, while the stem stability was not good enough in male patients. CONCLUSIONS: The Tri‐Lock Bone Preserving Stem did not show significant difference in periprosthetic BMD changes compared with the other two conventional longer stems at 5 years after THA.