MO567PILOT STUDY OF BONE RESISTANCE MEASURED IN VIVO BY IMPACT MICROINDENTATION IN KIDNEY TRANSPLANTATION
Authors: Lloret Maria Jesus , Canal Cristina , Di Gregorio Silvana , Facundo Molas Carmen , Vila Santandreu Ana , Serra Cabanas Nuria , Gelpi Rosana , Fayos De Arizon Leonor , Arana Carolt , Montolio Daniel , Bardaji Beatriz , Guirado Lluis , Bover Jordi 
Published: May 2021

Abstract

Background and Aims
Impact microindentation (IMI) is a new technique that measures bone material strength (BMS). Results are expressed as a BMS index (BMSi) which represents the ratio between the IMI distance [penetration of the needle-probe in patient’s bone (mid-shaft tibia)] versus a reference material (polimethylmethacrylate).

Method
Observational, prospective, single-center study. Baseline IMI (Osteoprobe®, Active Life Scientific, USA) and bone densitometry (iDXA, Lunar Health Care GE) were performed and data collected in the peritransplantation period of kidney transplant (KT) patients from May 2019 to May 2020, following our current clinical bone and transplant protocols. Based on the individual risk of fracture and current Spanish Society of Rheumathology/Nephrology guidelines, antirresorptive treatment (bisphosphonates or denosumab) was added on top of calcium and vitamin D supplements. We hereby present preliminary results of the control IMI performed 6 months after KT.

Results
Baseline IMI was performed in 45 patients, 62% men, 56±14 y/o, and a BMI of 24.9±3.5 kg/m2, reasonably controlled for classical serum bone mineral parameters. 70% were on dialysis prior to KT, 20% were diabetic, and 33.3% of women suffered from early menopause. 15.9% had a history of previous fragility fracture, 13% had a parent history of hip fracture, and 14% fell more than twice during the last year. Mean baseline FRAX® (https://www.sheffield.ac.uk/FRAX/tool.aspx?lang=sp) for a major osteoporotic fracture and hip were 4.3% and 2.3%, respectively. Baseline lumbar, femoral neck, hip and ultradistal radius DXA T-score were respectively -0.9, -1.7, -1.5, -2.0 SD. Mean BMSi was 78.5±7.6. Osteopenic/osteoporotic patients had a significantly lower BMSi than those who were not (76.3 vs 83; r = 0.37; p = 0.012). A statistically significant positive correlation was observed between BMSi and the trabecular bone score [(TBS), r = 0.346 ; p = 0.036). On a visual-analogic scale of pain, puncture was rated on average 1.1±1.6 over 10 (82% 0-2). 37.2% of patients began bisphosphonates (alendronic acid) and 9.3% denosumab. Control IMI was performed at 6 months in 24 patients, with a mean BMSi of 76.9±10.5. Mean difference between baseline and 6 months BMSi in this subgroup was 1.18±11.5. The group of patients treated with antiresorptives showed on average an increase in BMSi at 6 months, compared with a decrease in the control group (+5.2 vs -5.3; p = 0.054).

Conclusion
IMI is a technique with excellent tolerance that may offer complementary information on bone quality in the global assessment of bone resistance. IMI may allow the detection of EARLY changes in bone resistance in corticosteroid-treated KT patients with/without antiresorptives added to prophylactic treatment with calcium and vitamin D.