Digital Multi-channel Tibial Implants in Orthopedic Medicine

使用有效和可靠的骨折愈合措施将极大地促进临床和转化性研究，以开发骨折的强化治疗方法。在临床前研究中，金标准是弯曲或扭转刚度的测量；这些是恢复骨骼关键特性的直接测量。只有在对骨折进行保守治疗(不固定)或使用外固定器的情况下，才能在人类身上进行这项手术。然而，胫骨骨干骨折(临床上最有可能出现问题的骨折)最常采用髓内钉治疗。对于原位IM钉，硬度测量被认为是浪费时间，因为它在未知的程度上反映了钉子和骨骼的硬度。这个项目旨在克服这个问题，通过直接测量钉子中的应变来响应骨钉结构的良好特性负载，从而减少骨骼本身的硬度。监测骨折愈合的另一种方法是通过放射成像。对于传统的X光照片，这很容易产生误导，尽管这是临床医生日常使用的。在这项研究中，螺旋CT的三维图像将被有限元分析(FEA)处理，以计算愈合骨折的强度和刚度，这项技术(这在常规使用中不现实)将被用于验证新的遥测方法所获得的结果。我们将从我们的工业合作伙伴那里提供直径11 mm的改良型胫骨钉，并用分布在三个水平的三个圆周位置的36个应变计来测量它们，以及读取应变并以无线电波的形式传输的电路。电子产品将通过钉子末端的陶瓷环中的线圈感应供电，保留整个钉子的插管，使其能够插入导丝。每个器械钉将被校准，以允许测量六个自由度的力和弯曲挠度。几个适当长度的钉将被器械插入正在接受胫骨骨折延迟愈合手术的9名患者，这些患者在不同的胫骨水平上有不同的骨折形态。钉子的顶部和底部将用螺丝双重锁定，使钉子和骨骼之间的机械连接将是刚性的。手术后每隔一段时间，我们将对患者进行步态分析，同时遥测指甲的应变读数。考虑到患者肌肉在胫骨钉结构中产生的力，将开发一个3D腿部生物力学模型，以确定作用在胫骨钉结构上的力。钉子所受的力和挠度将被处理，以产生骨骼对整个结构的贡献。还将探索更简单的静态加载协议。同时，采集0.3 mm层厚的螺旋CT图像，将骨和骨折骨痂的材料特性数据集输入有限元软件，计算出愈合骨的结构刚度。我们还将应用验证的下肢功能等级。使用有限元分析得出的骨骼结构属性作为我们的比较器，我们将基于钉子读数和载荷的分析来验证僵硬测量。然后，我们将使用主成分分析来确定产生足够信息的最小应变计配置和最简单的加载方案，以便改进系统以用于商业化和临床使用。除了为临床试验提供结果衡量标准外，该系统还将用于常规治疗，以指导康复并更早地收到需要进行二次干预的警告，如植骨。

Clinical and translational research to develop enhanced treatments for fractures would be greatly facilitated by the use of a valid and reliable measure of fracture healing. In preclinical studies, the gold standard is the measurement of bending or torsional stiffness; these are direct measures of the restitution of the key property of bone. This can only be performed in humans if the fracture is treated conservatively (without fixation) or by means of an external fixator. However the tibial shaft fracture (the fracture most likely to give problems clinically) is most often treated by intramedullary nailing. With an IM nail in situ, stiffness measurement is considered a waste of time, since it reflects the stiffness of the nail, as well as the bone, to an unknown extent. This project aims to overcome that problem by directly measuring strains in the nail in response to well-characterised loading of the bone-nail construct, thus allowing the stiffness of the bone itself to be deduced.The alternative approach to the monitoring of fracture healing is by radiographic imaging. With conventional radiographs this is apt to be misleading, though that is what clinicians use on a day-to-day basis. In this study, 3-D images from spiral CT will be processed by finite element analysis (FEA) to calculate the strength and stiffness of the healing fracture and this technique (which would not be realistic for routine use) will be used to validate the results obtained by the new telemetric method.We will take modified tibial nails, 11mm in diameter, supplied by our industrial partner and instrument them with 36 strain gauges distributed at three circumferential sites at three levels, together with the circuitry to read the strains and transmit them as radio waves. The electronics will be powered inductively through a coil enclosed in a ceramic ring on the end of the nail, preserving the cannulation of the whole nail which allows its insertion over a guide wire. Each instrumented nail will be calibrated to allow measurement of force with six degrees of freedom, and also bending deflection.Nails of several appropriate lengths will be instrumented for insertion into nine patients who are having surgery for delayed union of tibial shaft fractures, with a variety of fracture configurations at different levels in the tibia. The nails will be double-locked top and bottom with threaded screws so that the mechanical link between nail and bone will be rigid. At intervals following surgery we will examine the patients by gait analysis with simultaneous telemetric readings of strain from the nail. A 3D lower limb biomechanical model will be developed to allow the determination of forces acting on the tibia-nail construct, taking into account the forces generated in the construct by the patient's muscles. The forces and deflections experienced by the nail will be processed to yield the contribution of the bone to the whole construct. Simpler static loading protocols will also be explored. At the same time points, spiral CT images of 0.3mm slice thickness will be acquired and the datasets used to feed material properties of the bone and fracture callus into FEA software, excluding the nail, from which structural stiffness of the healing bone will be calculated. We will also apply validated scales of lower limb function.Using the FEA-derived structural properties of the bone as our comparator, we will validate the stiffness measurement based on analysis of the nail readout and loads. We will then use principal component analysis to determine the minimal strain gauge configuration and simplest loading protocols that yield sufficient information, in order to refine the system for commercialisation and clinical use. As well as providing an outcome measure for clinical trials, the system will be useful in routine treatment to guide rehabilitation and receive earlier warning of the need for secondary interventions such as bone graft.