Clinical and statistical correlation of various lumbar pathological conditions

AbstractCurrent clinical evaluations often rely on static anatomic imaging modalities for diagnosis of mechanical low back pain, which provide anatomic snapshots and a surrogate analysis of a functional disease. Three dimensional in vivo motion is available with the use of digital fluoroscopy, which was used to capture kinematic data of the lumbar spine in order to identify coefficients of motion that may assist the physician in differentiating patient pathology. Forty patients distributed among 4 classes of lumbar degeneration, from healthy to degenerative, underwent CT, MRI, and digital x-ray fluoroscopy. Each patient underwent diagnosis by a neurosurgeon. Fluoroscopy was taken as the patient performed lateral bending (LB), axial rotation (AR) and flexion-extension (FE). Patient specific models were registered with the fluoroscopy images to obtain in vivo kinematic data. Motion coefficients, CLB, CAR, CFE, were calculated as the ratio of in-plane motion to total out-of-plane motion. Range of motion (ROM) was calculated about the axis of motion for each exercise. Inter- and Intra- group statistics were examined for each coefficient and a flexible Bayesian classifier was used to differentiate patients with degeneration. The motion coefficients CLB and CFE were significantly different (p<0.05) in 4 of 6 group comparisons. In plane motion, ROMLB, was significantly different in only 1 of 6 group comparisons. The classifier achieved 95% sensitivity and specificity using (CFE, CLB, ROMLB) as input features, and 40% specificity and 80% sensitivity using ROM variables. The new coefficients were better correlated with patient pathology than ROM measures. The coefficients suggest a relationship between pathology and measured motion which has not been reported previously

Investigation of first ray mobility during gait by kinematic fluoroscopic imaging-a novel method

<p>Abstract</p> <p>Background</p> <p>It is often suggested that sagittal instability at the first tarso-metatarsal joint level is a primary factor for hallux valgus and that sagittal instability increases with the progression of the deformity. The assessment of the degree of vertical instability is usually made by clinical evaluation while any measurements mostly refer to a static assessment of medial ray mobility (i.e. the plantar/dorsal flexion in the sagittal plane). Testing methods currently available cannot attribute the degree of mobility to the corresponding anatomical joints making up the medial column of the foot. The aim of this study was to develop a technique which allows for a quantification of the in-vivo sagittal mobility of the joints of the medial foot column during the roll-over process under full weight bearing.</p> <p>Methods</p> <p>Mobility of first ray bones was investigated by dynamic distortion-free fluoroscopy (25 frames/s) of 14 healthy volunteers and 8 patients with manifested clinical instability of the first ray. A CAD-based evaluation method allowed the determination of mobility and relative displacements and rotations of the first ray bones within the sagittal plane during the stance phase of gait.</p> <p>Results</p> <p>Total flexion of the first ray was found to be 13.63 (SD 6.14) mm with the healthy volunteers and 13.06 (SD 8.01) mm with the patients (resolution: 0.245 mm/pixel). The dorsiflexion angle was 5.27 (SD 2.34) degrees in the healthy volunteers and increased to 5.56 (SD 3.37) degrees in the patients. Maximum rotations were found at the naviculo-cuneiform joints and least at the first tarso-metatarsal joint level in both groups.</p> <p>Conclusions</p> <p>Dynamic fluoroscopic assessment has been shown to be a valuable tool for characterisation of the kinematics of the joints of the medial foot column during gait.</p> <p>A significant difference in first ray flexion and angular rotation between the patients and healthy volunteers however could not be found.</p

Computational Modelling of Patella Femoral Kinematics During Gait Cycle and Experimental Validation

The effect of loading and boundary conditions on patellar mechanics is significant due to the complications arising in patella femoral joints during total knee replacements. To understand the patellar mechanics with respect to loading and motion, a computational model representing the patella femoral joint was developed and validated against experimental results. The computational model was created in IDEAS NX and simulated in MSC ADAMS/VIEW software. The results obtained in the form of internal external rotations and anterior posterior displacements for a new and experimentally simulated specimen for patella femoral joint under standard gait condition were compared with experimental measurements performed on the Leeds ProSim knee simulator. A good overall agreement between the computational prediction and the experimental data was obtained for patella femoral kinematics. Good agreement between the model and the past studies was observed when the ligament load was removed and the medial lateral displacement was constrained. The model is sensitive to ±5 % change in kinematics, frictional, force and stiffness coefficients and insensitive to time step

Contact mechanics of modular metal-on-polyethylene total hip replacement under adverse edge loading conditions

Edge loading can negatively impact the biomechanics and long-term performance of hip replacements. Although edge loading has been widely investigated for hard-on-hard articulations, limited work has been conducted for hard-on-soft combinations. The aim of the present study was to investigate edge loading and its effect on the contact mechanics of a modular metal-on-polyethylene (MoP) total hip replacement (THR). A three-dimensional finite element model was developed based on a modular MoP bearing. Different cup inclination angles and head lateral microseparation were modelled and their effect on the contact mechanics of the modular MoP hip replacement were examined. The results showed that lateral microseparation caused loading of the head on the rim of the cup, which produced substantial increases in the maximum von Mises stress in the polyethylene liner and the maximum contact pressure on both the articulating surface and backside surface of the liner. Plastic deformation of the liner was observed under both standard conditions and microseparation conditions, however, the maximum equivalent plastic strain in the liner under microseparation conditions of 2000 µm was predicted to be approximately six times that under standard conditions. The study has indicated that correct positioning the components to avoid edge loading is likely to be important clinically even for hard-on-soft bearings for THR

Does ligament balancing technique affect kinematics in rotating platform, PCL retaining knee arthroplasties?: A prospective randomized study

The goal of this prospective, randomized, blinded trial was to determine if ligament balancing techniques for rotating platform TKA affect postoperative knee kinematics. Sixteen patients with unilateral rotating platform TKA consented to participate in this institutional review board approved study. Eight patients were randomly selected to receive ligament balancing with an instrumented joint spreader device and eight patients received ligament balancing using fixed thickness spacer blocks. A single plane shape matching technique was used for kinematic analysis of static deep knee flexion and dynamic stair activities. There were no differences in knee kinematics between groups during static deep flexion activities. The spreader group demonstrated kinematics more similar to the normal knee during the ascending phase of the dynamic stair activity. Knee kinematics in static knee flexion were unaffected by ligament balancing technique, while knees balanced with the spreader demonstrated a medial pivot motion pattern during stair ascent. This medial pivot motion pattern may improve long-term results by more closely replicating normal knee kinematics

In vivo measures of cartilage deformation: patterns in healthy and osteoarthritic female knees using 3T MR imaging

ObjectiveTo explore and to compare the magnitude and spatial pattern of in vivo femorotibial cartilage deformation in healthy and in osteoarthritic (OA) knees.MethodsOne knee each in 30 women (age: 55 ± 6 years; BMI: 28 ± 2.4 kg/m(2); 11 healthy and 19 with radiographic femorotibial OA) was examined at 3Tesla using a coronal fat-suppressed gradient echo SPGR sequence. Regional and subregional femorotibial cartilage thickness was determined under unloaded and loaded conditions, with 50% body weight being applied to the knee in 20° knee flexion during imaging.ResultsCartilage became significantly (p &lt; 0.05) thinner during loading in the medial tibia (-2.7%), the weight-bearing medial femur (-4.1%) and in the lateral tibia (-1.8%), but not in the lateral femur (+0.1%). The magnitude of deformation in the medial tibia and femur tended to be greater in osteoarthritic knees than in healthy knees. The subregional pattern of cartilage deformation was similar for the different stages of radiographic OA.ConclusionOsteoarthritic cartilage tended to display greater deformation upon loading than healthy cartilage, suggesting that knee OA affects the mechanical properties of cartilage. The pattern of in vivo deformation indicated that cartilage loss in OA progression is mechanically driven

A review of squeaking in ceramic total hip prostheses

The occurrence of audible squeaking in some patients with ceramic-on-ceramic (CoC) hip prostheses is a cause for concern. Considering multifactor contributing to this phenomenon, many studies have been conducted over the last decade. Great efforts have been put on understanding the mechanics of the hip squeaking to gain a deep insight into factors resulting in sound emission from hip articulation. Disruption of fluid-film lubrication and friction were reported as main potential causes of hip squeaking, while patient and surgical factors as well as design and material of hip implants were identified as affecting factors. This review article therefore summarised the recent available literature on this subject to provide a platform for future developments. Moreover, high wear rates and ceramic liner fracture as viable consequences of hip squeaking were discussed.The first author gratefully acknowledges Macquarie University for International Macquarie University Research Excellence Scholarship (iMQRES)-No. 2010017. The second author would like to thank to the Portuguese Foundation for Science and Technology through the project UID/EEA/04436/2013