Introduction Periprosthetic bone loss is a major cause of concern in patients undergoing total hip arthroplasty (THA). In this study we monitored the periprosthetic bone loss around two different types of femoral implant to evaluate their design and investigate the relationship with the preoperative bone mineral density (BMD).
Materials and Methods Sixty patients (35 female, 25 male, mean age 63 (range, 46–75) years) undergoing THA were randomised to either the ABG or Mallory Head femoral stem. Preoperative DEXA scans were acquired of the posteroanterior (PA) and lateral lumbar spine, the contra-lateral hip and the non-dominant forearm. Postoperative DEXA scans were performed at 10 days (treated as baseline), six weeks, and 3, 6, 12, 24 and 36 months after THA.
Results A total of 50 patients (24 ABG, 26 MH) completed the study. Three months after THA there was a statistically significant BMD decrease in every Gruen zone that varied between 5.6% and 13.8% for the ABG pros-thesis and between 3.8% and 8.7% for the MH prosthesis. Subsequently, in most zones BMD reached a plateau or showed a small recovery. However, BMD continued to fall in Gruen zones 1 and 7 in ABG patients and Gruen zone 1 in MH patients. Bone loss was less in every Gruen zone in MH patients compared with ABG with the largest difference (10%, P = 0.018) in Gruen zone 7. After adjustment for multiple comparisons the relationship between peri-prosthetic bone loss and preoperative BMD was highly statistically significant for spine, hip and radius BMD.
Discussion The present study showed that statistically significant bone loss occurred with both stems during the first three months following implantation, and confirmed that prosthesis design influences peri-prosthetic bone loss. Although the greater bone loss in patients with lower spine, hip or forearm BMD may not adversely affect the outcome for patients in the short and mid-term, preservation of femoral bone stock may be important in the longer term because a low femoral BMD can adversely affect the results of a subsequent revision. Greater femoral bone stock may be particularly advantageous in younger patients in whom a future revision is more likely.
