Background: Locking plates are used frequently in distal tibial fractures. We tested two different types of locking compression plates (LCP): the metaphyseal plate (MP) and the distal tibial plate (DTP). We evaluated the strain imposed on an experimental tibial osteotomy, and the stability of plate-tibia (composite bone) construct using LCP-MP and LCP-DTP.

Materials and methods: Twin strain gauged special composite tibial bones were used to simulate the human tibiae. We tested 5 tibiae: one was used as control, two tibiae were tested using LCP-MP, and two with LCP-DTP. Strain was measured by subjecting each construct to a cyclic load of 700 N at 3 Hz in neutral, flexion, extension and torsion to simulate the normal walking cycle.

Results: When compared with the control tibia, strain during the neutral moment at the proximal and distal strain gauge site in the LCP-MP and LCP-DTP constructs decreased by 6.4%/−41.5% and −39%/−47%, respectively. In flexion, the strain increased consistently in both the proximal and distal strain gauge sites using the LCP-MP by 34% and 109%. Using the LCP-DTP, the strain at the proximal strain gauge site decreased by 0.2% and increased by 18% at the distal strain gauge site. In extension, strain decreased by 25% at the proximal strain gauge site, and by 60% at the distal strain gauge site in the LCP –MP construct. In the LCP-DTP construct, the strain decreased by 13% at the proximal strain gauge site, and by 21% at the distal strain gauge site. There were no statistically significant torsional differences between LCP-MP and LCP-DTP group (P=0.121). In this experimental setup, the LCP-DTPs offer greater control of strain than LCP-MPs. They also confer greater resistance to fracture macro-movements, and improved stiffness consistently in neutral, flexion, and torsion than LCP-MPs.

Conclusion: The strain from osteotomised tibiae stabilised with LCP-MPs and LCP-DTPs were close to the strain of the control tibia. Both these locking plates were equally good and conferred greater stiffness in all loading positions.

While previous studies have highlighted possible aetiological factors for adolescent idiopathic scoliosis (AIS), research employing gait measurements have demonstrated asymmetries in the ground reaction forces, suggesting a relationship between these asymmetries, neurological dysfunction and spinal deformity. Furthermore, investigations have indicated that the kinematic differences in various body segments may be a major contributing factor. This investigation, which formed part of a wider comprehensive study, was aimed at identifying asymmetries in lower limb kinematics and pelvic and back movements during level walking in scoliotic subjects that could be related to the spinal deformity. Additionally, the study examined the time domain parameters of the various components of ground reaction force together with the centre of pressure (CoP) pattern, assessed during level walking, which could be related to the spinal deformity. Although previous studies indicate that force platforms provide good estimation of the static balance of individuals, there remains a paucity of information on dynamic balance during walking. In addition, while research has documented the use of CoP and net joint moments in gait assessment and have assessed centre of mass (CoM)–CoP distance relationships in clinical conditions, there is little information relating to the moments about CoM. Hence, one of the objectives of the present study was to assess and establish the asymmetry in the CoP pattern and moments about CoM during level walking and its relationship to spinal deformity.

The investigation employed a six camera movement analysis system and a strain gauge force platform in order to estimate time domain kinetic parameters and other kinematic parameters in the lower extremities, pelvis and back. 16 patients with varying degrees of deformity, scheduled for surgery within a week took part in the study. The data for the right and left foot was collected from separate trials of normal walking. CoP was then estimated using the force and moment components from the force platform.

Results indicate differences across the subjects depending on the laterality of the major curve. There is an evidence of a relationship between the medio-lateral direction CoP and the laterality of both the main and compensation curves. This is not evident in the anterior-posterior direction. Similar results were recorded for moments about CoM. Subjects with a higher left compensation curve had greater deviation to the left. Furthermore, the results show that the variables identified in this study can be applied to initial screening and surgical evaluation of spinal deformities such as scoliosis. Further studies are being undertaken to validate these findings.

Objective: To establish a relationship between the scoliotic curve and the centre of gravity during level walking in patients diagnosed with adolescent idiopathic scoliosis.

Background data: There is no established aetiology for adolescent idiopathic scoliosis and the reasons for the progression of the curve are still unknown. But there is an agreement regarding multifactorial nature of the aetiology among many authors. One of the interesting factors suggested is asymmetry in the ground reaction forces during walking and their relation to the deformity, indicated by gait analysis studies. Studies have also indicated that the cause and progression of the deformity in idiopathic scoliosis may be due to kinematic differences in the spine, pelvis and lower limb. If a relation could be established between the scoliotic curve and the centre of gravity, it is possible to draw some conclusions regarding the aetiology. There is no method or study till date which looked at the relation of scoliotic curve with the centre of gravity.

Materials and Methods: Patients who were diagnosed with adolescent idiopathic scoliosis were selected. Informed consent was taken for gait analysis. 16 Markers were placed over the lower limb and force plate, using modified Helen Hays set. 5 markers were placed over the surface landmarks of selected spinous processes (C7, T6, T12, L3 and S2). Ground reaction forces and motion data were analysed, using APAS gait system and the lines of vectors were developed and correlated with the marker over the second sacral spinous process.

Results: With the help of this method we were able to establish a relationship between the scoliotic curve and centre of gravity line. These in turn were expressed in terms of changes in the moment in relation to the midline of the coronal plane. The results indicated that the changes were proportional to the severity of the scoliotic curve.

Conclusion: We present a new method of establishing the relation of scoliotic curve with the ground reaction force and the centre of gravity. Initial results obtained from this method indicate the asymmetries in the deviation of the centre of gravity line in relation to the curve, during walking. Ongoing studies based on this method, will help to understand the pathogenesis and aetiology of scoliosis on a biomechanical basis which can help in developing new treatment modalities and efficient management of these patients.

Purpose of study: To study the effect of an additional locking screw on fracture strain and stability in tibias undergoing intramedullary nailing.

Methods: An additional locking hole was drilled into four tibial nails, 185 mm from the proximal end of the 8 mm x 315 mm solid tibial nails. The nails were locked proximally and distally into a triple strain-gauged sawbone. An osteotomy was created distal to the additional hole, and the construct loaded axially, in flexion and extension, and in torsion with and without the extra locking screw. With the additional locking screw in place, strain increased at the proximal strain gauge site during loading in neutral by 17% (139 mϵ, 91–198) (p=0.01) and flexion by 8% (65 mϵ, 60–73) (p< 0.005). Strain decreased on loading in extension by 10% (141 mϵ, 62–243) (p=0.0497). The extra locking screw decreased strain at the gauge closest to the osteotomy site in all loading positions. Strain showed an overall increase with axial loading of 14% (47 mϵ, 4–105) (p=0.16), an increase with loading in flexion of 2% (9 mϵ, −38 to 62) (p=0.75) but a decrease of 47% (254 mϵ, 6–549) (p=0.18) with loading in extension. A significant reduction in angular motion at the osteotomy site occurred with the addition of the extra locking screw (21° at 34.5 Nm without the screw, 13° at 34.5 Nm with the screw, p=0.001). Additional hole in the shaft of the nail lead to increase the stress from 29 – 48 mPa (29 – 48 N/mm2) but did not fail when vertically loaded with 450 Newtons applied at rate of 5Hz sinusoidal waves for 2 million cycles.

Conclusion: Nails with additional locking options, by altering strain and motion at the fracture site, may have the clinical potential to affect fracture healing with relatively low risk of implant failure.

Introduction and Objective: Although the causation and progression of adolescent idiopathic scoliosis (AIS) remains unclear, a recent review has highlighted a series of possible aetiological factors. Additionally, research investigations have indicated that the kinematic differences in various body segments may be a major contributing factor. The value of gait analysis systems employed to measure dynamic back movements in furthering understanding of spinal deformity has also been demonstrated by various studies. Research employing gait measurements have indicated asymmetries in the ground reaction forces and have suggested relationship between these asymmetries, neurological dysfunction and spinal deformity. This investigation, which formed part of a wider comprehensive study, was aimed at identifying asymmetries in lower limb kinematics and pelvic and back movements during level walking in scoliotic subjects that could be related to the spinal deformity.

Design and Methodology: The research employed a movement analysis system and a strain gauge force platform to estimate time domain kinetic parameters and other kinematic parameters in the lower extremities, pelvis and back. 16 patients with varying degrees of deformity, scheduled for surgery within a week took part in the study.

Results and conclusions: The findings have demonstrated the presence of asymmetries in kinetic parameters in the scoliotic subject and have also served to highlight the value of using kinetic and kinematic parameters in developing the understanding of the pathogenesis and aetiology of scoliosis. In addition, the results have also indicated that the variables identified in the study can be applied to initial screening and surgical evaluation of spinal deformities such as scoliosis. Further studies are being undertaken to validate these findings.