QCT Analysis Demonstrates Trabecular Density Increases in Osteoporotic Women Treated with a Triphasic Calcium-Based Implant Material Using a Minimally Invasive Local Osteo-Enhancement Procedure

Introduction:

Fragility hip fractures are associated with high mortality rates and significantly impact patient quality of life. Osteoporosis reduces the trabecular density in the proximal femur which in turn reduces structural integrity and bone strength and ultimately will lead to hip fracture

Methods:

In an IRB-approved clinical study of 12 postmenopausal osteoporotic women a minimally-invasive local osteo-enhancement procedure (LOEP) was performed to inject a resorbable triphasic calcium sulfate/calcium phosphate implant material (AGN1) into one proximal femur. The contralateral femur served as the untreated control. The patient age range was 56 – 89 and their T-score (mean ± sd) for the left (right) hip was -3.1 ± 0.5 (-3.0 ± 0.7). Total hip integral BMD (intBMD), trabecular (trBMD) and implant volume were measured by QCT (MIAF, U. of Erlangen) pre-LOEP, 12 and 24 weeks in all 12 patients and in 10 patients at 5 – 7 years (average 315 weeks) post LOEP treatment

Results:

The average injection volume was 15.3 ± 4.9 cm3 which was 78%, resorbed at 12 weeks, 95% resorbed at 24 weeks and 100% resorbed at 315 weeks. Before AGN1 LOEP was performed all femurs had low trBMD (Control: 21 ± 20; Treated: 22 ± 21) and was lowest in the implant area (7 ± 38). IntBMD increased significantly in treated femurs at all time points as did trBMD (see Table). trBMD surrounding the implant area was not increased at 315 weeks compared to control (data not shown) indicating that increases observed in trBMD were due to changes within the implant area. Animal models had shown an excellent integration of bone formed in the implant area into surrounding trabecular bone.

Discussion:

trBMD increased significantly after AGN1 LOEP treatment where implanted which resulted in a rapid and durable increase in proximal femur BMD. This increase in proximal femur BMD in osteoporotic femurs would be expected to improve bone strength and reduce fracture risk.

Tab. 1:

Total Hip (TH) BMD: Integral (int) and Trabecular (tr) Density^* (mg/cm³)

Week	N	Control intBMD	Treated intBMD	Control trBMD	Treated trBMD	BMD Implant Area
0	10	177 ± 35	176 ± 32	21 ± 20	22 ± 21	7 ± 38
12	10	172 ± 28	290 ± 35*	21 ± 18	217 ± 56***	525 ± 79
24	8**	174 ± 33	257 ± 21*	22 ± 20	161 ± 18***	418 ± 50
315	10	169 ± 28	235 ± 33*	17 ± 15	121 ± 37***	536 ± 78
*excludes femoral head; **2 patients missing axial reconstructions; ***p < 0.001 by paired t-test vs. control