762 FOR OLDER PATIENTS WITH FRAILTY, SIX WEEKS OF ENFORCED IMMOBILITY HAS NO DETRIMENTAL IMPACT ON MUSCLE STRENGTH OR THICKNESS

Abstract

Abstract Introduction Immobility can lead to rapid reductions in muscle size, strength and function. Understanding these changes could inform interventions to prevent or slow decline. This longitudinal study aimed to assess the extent of muscle changes in older patients admitted with fragility fractures where clinical management was immobilisation (non-weight bearing) of the affected limb for at least 6 weeks. Method Handgrip strength (HGS); knee extensor strength(KES); Vastus Lateralis thickness and cross-sectional area at ultrasound (VLMT, VLCSA); and skeletal mass index (SMI; bioimpedance analysis) were measured in the non-injured limb of 50 patients (88% female) aged ≥70. Pre-existing physical frailty meant patients were limited to transfers only while non-weight bearing. Measurements were performed at hospital admission, 1, 3 and 6 weeks. One-way repeated measures ANOVA was used to assess changes in measurements over time. Additionally, baseline measurements in female patients (n = 36) were compared to 11 healthy, non-frail, non-hospitalised females with comparable BMI, aged ≥70, using independent t-tests. Data are mean + SD. Results Patient Clinical Frailty Score (median, IQR) was 5 (4–6). At hospital admission, female patients were older (84 ± 7 years vs. 77 ± 6 years, p < 0.05), weaker (HGS of 9.2 ± 4.7 kg vs. 19.9 ± 5.8 kg, p < 0.001; KES 4.5 ± 1.5 kg vs. 7.8 ± 1.3 kg, p < 0.001) and had lower VLMT (1.38 ± 0.47 cm vs. 1.75 ± 0.30 cm, p = 0.02) than non-frail female controls. Six weeks immobility had no temporal effect on any variable: HGS (F(2,51) = 1.04,p = 0.38,n = 27), KES (F(3,45) = 3.22,p = 0.81,n = 16), VLMT (F(3,54) = 2.52,p = 0.07,n = 19), VLCSA (F(3,42) = 0.74,p = 0.53,n = 15) and SMI (F(2,59) = 0.09,p = 0.94,n = 26). Conclusion Older patients admitted with fragility fractures were weaker and had lower VLMT compared to healthy, non-frail older people. This, together with the lack of decline in muscle strength and thickness with 6 weeks immobility strongly suggests muscle resilience was attenuated pre-admission, such that immobility had no further detrimental effect. These results differ from muscle changes seen in younger and non-frail cohorts, and warrants assessment of clinical interventions aimed at increasing muscle mass and function specifically in older people with frailty.