No abstract

Background:Orthopaedic hardware pull-out studies frequently utilize various animal models to assess axial and multiplanar loading of bone. Biomechanical models and techniques for testing are common; however, bone quality measures frequently are not provided in published studies. Bone mineral density (BMD) and bone mineral content (BMC) are used for assessment of bone quality. The authors sought to determine whether immature porcine knees would be an appropriate model for human graft and hardware pull-out studies. Our hypothesis was that immature cadaver porcine knees (ICPK) would be less dense than those of healthy adult human distal femurs and proximal tibias and thus an inadequate model for human graft and hardware pull-out studies. Methods:This was an in vivo and in vitro comparative laboratory study of BMD and BMC between two human knee groups and ICPK. Eleven ICPK 3 mo in age (body mass 25.0 ± 3.3 kg) were used. Human Group 1 consisted of 18 collegiate athletes with a mean age of 19.2 ± 0.86 yr (body mass 76.1 ± 14.4 kg). Human group 2 included 10 people with a mean age of 34.4 ± 9.3 yr (body mass 79.3 ± 5.9 kg). BMD and BMC were measured using a Lunar 10655/Prodigy DEXA Scanner and software. ANOVA tested differences among the three groups, and post hoc testing assessed differences between the groups. Results:Differences in BMD were shown among the three groups for distal femur (ICPK-0.91 ± 0.11 g/cm 2 ; HG1-1.17 ± 0.34 g/cm 2 ; HG2-1.2 ± 0.32 g/cm 2 [P ¼ 0.037]), and proximal tibia (ICPK-0.94 ± 0.12 g/cm 2 ; HG1-1.41 ± 0.22 g/cm 2 ; HG2-1.26 ± 0.17 g/ cm 2 [P ¼ 0.001]). Statistical differences were found among the three groups for femoral BMC (ICPK-3.51 ± 1.25 g; HG1-7.5 ± 3.06 g; HG 2-11.59 ± 5.40 g [P ¼ 0.001]) and tibial BMC (ICPK-4.58 ± 2.00 g; HG1-9.64 ± 3.92 g; HG2-13.07 ± 5.37 g [P ¼ 0.001]). Conclusions:BMD and BMC in the distal femur and proximal tibia of an immature pig are significantly less than that of an adult human. Testing of graft pull-out using an immature porcine model involving the bones about the knee may not be accurately extrapolated to humans. We believe our work illuminates the need for bone quality assessment and documentation with BMD and BMC when performing or comparing pull-out studies.

The scaphoid is the most commonly fractured carpal bone. The fracture pattern and its relationship to the blood supply have significant implications regarding treatment and prognosis. Prompt recognition and treatment are fundamental to successful management.