In-vitro comparison of LC-DCP- and LCP-constructs in the femur of newborn calves – a pilot study

The bone-thread interface was stripped in 21 of 80 cortical screws (26.3%) before a pre-set insertion torque of 3 Nm was achieved. Only 3 corresponding intact pairs of constructs could be statistically compared for relative structural stiffness, actuator excursion and width of the osteotomy gap. Relative structural stiffness was significantly greater, actuator excursion and width of the osteotomy gap were significantly smaller in the LCP constructs. While failure occurred by loosening of the screws in the LC-DCP constructs, locking constructs failed by cutting large holes in the soft distal metaphyseal bone.An insertion torque sufficient to provide adequate stability in femurs of newborn calves could not be achieved reliably with 4.5 mm cortical screws. Another limiting factor for both constructs was the weak cancellous bone of the distal fracture fragment. LCP constructs were significantly more resistant to compression than LC-DCP constructs.Fractures of the os femoris are common in newborn calves [1-5]. Femoral and tibial fractures rank second to metacarpal and metatarsal fractures in order of frequency of long bone fractures in cattle [6,7]. The most common cause of femoral fractures in calves is excessive traction during delivery, but trauma, such as the dam standing on the calf, and bovine viral diarrhoea (BVD) virus infection are other causes [8,9].In calves, femoral fractures occur most often in the proximal epiphysis and distal metaphysis [1,2,10,11]. In a study of newborn calves, 28 of 50 femoral fractures (56%) were located in the distal metaphysis [2]. Because the cortex becomes considerably thinner at the transition from the diaphysis to the metaphysis, this part of the femur has only limited axial strength [12]. If a “stifle lock” occurs during delivery of a calf in anterior presentation and dorsopubic position, forced extraction can lead to wedging of the femur, which increases axial loading, thus leading to femoral fracture [12]. Excessive traction on