AO Foundation, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland.
Foot Ankle Int. 2009 Dec;30(12):1183-9. doi: 10.3113/FAI.2009.1183.
Bone strength is currently measured with indirect techniques. We investigated the use of an intraoperative mechanical measurement for local bone strength determination and prediction of intramedullary-nail fusion failure. We investigated whether intraoperative local bone strength determination may be useful to the surgeon in predicting intramedullary nail hindfoot fusion performance.
In seven human specimens, bone mineral density (BMD) was determined with qCT. A device (DensiProbe) specially devised for nailed tibiotalocalcaneal arthrodesis (TTCA) was inserted at the intended calcaneal screw sites of an intramedullary nail, and the cancellous break-away torque was measured. The constructs were then cyclically loaded to failure in dorsiflexion-plantarfexion.
The BMD range was wide (42.8 to 185.9 mg HA/cm(3)). The proximal-screw site peak torque was 0.47 to 1.61 Nm; distal-screw site peak torque was 0.24 to 1.06 Nm. The number of cycles to failure correlated with peak torque both proximally (p = 0.021; r(2) = 0.69) and distally (p = 0.001; r(2) = 0.92). Proximally, peak torque did not correlate with BMD (p = 0.060; r(2) = 0.54); distally, it correlated significantly (p = 0.003; r(2) = 0.86).
DensiProbe measurements can be used in the hindfoot to assess bone strength. In this study, specimens that failed early could be identified. However, in clinical practice fusion failure is multifactorial in origin, and failure prediction cannot be based upon peak torque measurements alone.
The technique described here may be of use to give an intraoperative decision aid to predict intramedullary nail hindfoot fusion performance.
目前，骨骼强度是通过间接技术进行测量的。我们研究了术中机械测量在局部骨骼强度测定和髓内钉融合失败预测中的应用。我们研究了术中局部骨骼强度测定是否可以帮助外科医生预测髓内钉后足融合性能。
在七个人体标本中，使用 qCT 测定骨密度（BMD）。专门为髓内钉固定的距跟骨节段融合术（TTCA）设计的设备（DensiProbe）插入髓内钉的预期跟骨螺钉部位，并测量松质骨分离扭矩。然后，构建物在背屈-跖屈方向进行循环加载直至失效。
BMD 范围较宽（42.8 至 185.9 mg HA/cm³）。近侧螺钉部位峰值扭矩为 0.47 至 1.61 Nm；远侧螺钉部位峰值扭矩为 0.24 至 1.06 Nm。失效时的循环次数与近侧（p = 0.021；r² = 0.69）和远侧（p = 0.001；r² = 0.92）的峰值扭矩相关。近侧，峰值扭矩与 BMD 不相关（p = 0.060；r² = 0.54）；远侧，相关性显著（p = 0.003；r² = 0.86）。
DensiProbe 测量可用于后足评估骨骼强度。在本研究中，可以识别早期失效的标本。然而，在临床实践中，融合失败是多因素引起的，不能仅基于峰值扭矩测量来进行失效预测。
这里描述的技术可能有助于提供术中决策辅助，以预测髓内钉后足融合性能。
