Abstract
Introduction and Objective
In multiple trauma patients, as well as in the healing of isolated fractures (Fx) with heavy bleeding (trauma haemorrhage, TH), complications occur very often. This is particularly evident in elderly patients over 65 years of age. Since these accompanying circumstances strongly influence the clinical course of treatment, the influence of age on bone regeneration after femoral fracture and severe blood loss was investigated in this study.
Materials and Methods
12 young (17–26 weeks) and 12 old (64–72 weeks) male C57BL / 6J mice per group were examined. The fracture group Fx underwent an osteotomy after applying an external fixator. The THFx group also received blood pressure-controlled trauma hemorrhage (35 mmHg for 90 minutes) and reperfusion with Ringer's solution for 30 minutes. The Sham group received only the catheter and one external fixator. μCT scans of the femora were performed in vivo after 2 weeks and ex vivo after 3 weeks. Histological and biomechanical examinations were also carried out. The statistical significance was set at p ≤ 0.05. The non-normally distributed data were analyzed using the Mann-Whitney-U or Kruskal-Wallis test.
Results
The histology showed less mineralized bone in the fracture gap in old animals of the Fx (25.41% [1.68%]) and THFx groups (25.50% [4.07%]) compared with the young ones (34.20% [6.36%], p = 0.003; 34.31% [5.12%], p=0.009). Moreover, a severe blood loss lead to more cartilage in both young (6.91% [5.08%]) and old animals (4.17% [1.42%]) compared to animals with only a fracture (2, 45% [1.04%], p=0.004; 2.95% [1.12%], p=0.032). In old animals (11.37 / nm2 [17.17 / nm2]) in contrast the young mice with an isolated fracture (33.6/nm2 [8.83/nm2]) fewer osteoclasts were present (p=0.009). Therefore, the severe blood loss further reduced the number of osteoclasts only in young animals (16.83/nm2 [6.07/nm2]) (p=0.004). In the in vivo μCT, after 2 weeks, a lower volume of bone, cortex and callus was found in old THFx animals (3.14 mm3 [0.64 mm3]); 1.01 mm3 [0.04 mm3]; 2.07 mm3 [0.57 mm3]) compared with the Fx animals (4.29 mm3 [0.74 mm3], p=0.008; 1.18 mm3 [0, 25 mm3], p=0.004; 3.02 mm3 [0.77 mm3], p=0.008) After 3 weeks, the ex vivo μCT scans also showed a reduced callus percentage in old THFx animals (61.18% [13.9 9%]), as well as a low number of trabeculae (1.81 mm-1 [0.23 mm-1]) compared to animals without blood loss (68.72% [15.71%], p = 0.030; 2.06mm-1 [0.37mm-1], p=0.041). In the biomechanical test, a reduced elasticity limit of the old THFx mice (7.75 N [3.33 N]) in contrast to the old Fx (10.24 N [3.32 N]) animals was shown (p=0.022).
Conclusions
A severe blood loss has a higher negative effect on the healing, morphometry, and biomechanical properties of previously fractured femora in old compared to young individuals.
