FEMORAL PERIPROSTHETIC STRESSSHIELDING FOLLOWING CEMENTLESS TOTAL HIP REPLACEMENT

Background: Joint replacements are being performed on ever younger patients at a time when average expectancy of life is continuing to rise. Any reduction in the strength and mass of periprosthetic bone could threaten the longevity of implant by predisposing to loosening and migration of prosthesis, periprosthetic fracture and problems in revision arthroplasty. Aims & Objectives: This study aims to analyse the femoral periprosthetic stress-shielding following unilateral cementless total hip replacement using DEXA scan by quantifying the changes in bone mineral density around femoral component. Materials and Methods: Femoral periprosthetic bone mineral density was measured in the seven Gruen Zones with DEXA scan at 2 weeks, 1 year and 2 year after surgery in 60 patients who had undergone unilateral cementless total hip replacement, of which 30 patients had been implanted with 4/5th porous coated CoCr stems and other 30 patients with 1/3rd porous coated titanium alloy stems. Results: At both one and two years postoperatively, bone loss due to stress-shielding was seen in both stems with maximum loss in zone VII and minimum in zone III, IV, V. The maximum mean percentage bone mineral density loss in 4/5th porous coated CoCr stems in zone VII was 16.03% at one year and 22.42% at 2 years as compared to loss of 10.07% and 16.01% in 1/3rd porous coated Ti alloy stems. Increased bone loss was seen in patients who had larger diameter stem (> 13.0 mm) and in patients with low bone mineral density in the unoperated hip. Conclusion: Bone loss as a result of stress-shielding is more pronounced in 4/5th porous coated CoCr stems as compared to 1/3rd porous coated titanium alloy stems.