Abstract
BackgroundReduction of femoral shaft fractures remains a challenging problem in orthopaedic surgery. Robot-assisted reduction might ease reduction and fracture treatment. However, the influence of different reduction pathways on patients’ physiology is not fully known yet. Therefore, the aim of this study was to examine the biomechanics and histology of fracture healing after direct and prolonged robot-assisted reduction in an in vivo rat model.Methods144 male CD® rats were randomly assigned to 12 groups. Each animal received an external fixator and an osteotomy on the left femoral shaft. On the fourth postoperative day, the 1× reduction groups received a single reduction maneuver, whereas the 10× reduction groups received the same reduction pathway with ten repetitions. The control groups did not undergo any reduction maneuvers. Animals were killed after 1, 2, 3 and 4 weeks, respectively, and the composition of the fracture gap was analyzed by µCT and non-decalcified histology. Biomechanical properties were investigated by a three-point bending test, and the bone turnover markers PINP, bCTx, OPG, sRANKL, TRACP-5b, BALP, and OT/BGP were measured.ResultsOne week after the reduction maneuver, µCT analysis showed a higher cortical bone volume in the 1× reduction group compared to the 10× reduction group. Biomechanically, the control group showed higher maximum force values measured by three-point bending test compared to both reduction groups. Furthermore, less collagen I formation was examined in the 10× reduction group compared to the control group after 1 week of fracture healing. PINP concentration was decreased in 10× reduction group after 1 week compared to control group. The same trend was seen after 3 weeks.ConclusionA single reduction maneuver has a beneficial effect in the early phase of the fracture healing process compared to repeated reduction maneuvers. In the later phase of fracture healing, no differences were found between the groups.
Highlights
Reduction of femoral shaft fractures remains a challenging problem in orthopaedic surgery
We examined the fracture healing process by non-decalcified histology and measured the bone turnover markers type-I collagen N-terminal propeptide “PINP”, bone C-telopeptide of type-I collagen “bCTx”, osteoprotegerin “OPG”, soluble receptor activator of nuclear factor NF-kB ligand “soluble receptor activator of NF-kB ligand (sRANKL)”, tartrate-resistant acid phosphatase “TRACP-5b”, human bone alkaline phosphatase “bone-specific alkaline phosphatase (BALP)” and osteocalcin/bone Gla protein “OT/BGP” after the reduction process at the same points in time
Bone turnover marker Analysis of the concentration of soluble receptor activator of NF-kB ligand, osteocalcin (OT/ BGP), osteoprotegerin (OPG), beta-crossLAPS, bone-specific alkaline phosphatase (BALP) and tartrateresistant acid phosphatase 5b (TRACP-5b) showed no significant differences between the reduction groups at any point in time
Summary
Reduction of femoral shaft fractures remains a challenging problem in orthopaedic surgery. The aim of this study was to examine the biomechanics and histology of fracture healing after direct and prolonged robot-assisted reduction in an in vivo rat model. As robot-assisted devices aim to reach anatomical bone alignment, while X-ray exposure, soft tissue damage and surgical time are reduced, they could be a good tool to help physicians in the future. Such an in vitro robot-assisted fracture reduction model has been described by Fuchtmeier [6], Koo [7] and Oszwald et al [8]. Our study aimed to explore in a rat model the difference between direct reduction path and a reduction path with a prolonged reduction performed by a robot, to standardize the reduction pathway
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