Validation of the thigh stabilization system for a novel multi-planar instrumented knee arthrometer

Knee joint laxity characterizes the structural proprieties of the connective tissues and supporting structures within the knee joint. In the past, knee joint laxity has been measured subjectively by clinicians who assess joint integrity through manual manipulation of the joint. More recently however, instrumented knee arthrometers have provided clinicians and researchers alike with objective measures of knee joint laxity. To this end, arthrometry has become an important tool for use in to characterizing knee joint laxity and how it differs across broad populations. Despite the many technological advances in instrumented knee arthrometry over the past three decades, there are still significant issues with the reliability, and generalizability of these measurements. These issues inhibit our understanding of how knee joint integrity changes in response to joint insult and hormonal fluctuations. Therefore, a novel instrumented arthrometer must be developed to specifically address these deficiencies. To this end, this thesis examines and discusses the gaps in current instrumented arthrometry. Furthermore, it proposes a solution to address a key measurement issue associated with thigh segment stabilization and attempts to validate this solution via a stabilization study utilizing cadaveric specimens. The evidence presented herein suggests that, while the a priori benchmarks for this study were not completely met, the stabilization system was clearly able to provide sufficient stability such that an arthrometric assessment of the joint could be repeatedly administered. Moreover, with minor changes to the current stabilization system it may be entirely possible to obtain truly generalizable and highly repeatable arthrometric evaluations

Associations Between Lower Extremity Muscle Mass and Multiplanar Knee Laxity and Stiffness: A Potential Explanation for Sex Differences in Frontal and Transverse Plane Knee Laxity

Background: Compared with men, women have disproportionally greater frontal (varus-valgus) and transverse (internal-external) plane laxity and lower stiffness, despite having similar sagittal (anterior-posterior) plane laxity and stiffness. While the underlying cause is unclear, the amount of lower extremity lean mass (LELM) may be a contributing factor.Hypothesis: Lower extremity lean mass would be a stronger predictor of frontal and transverse plane laxity and incremental stiffness than the sagittal plane. Associations between LELM and stiffness would be stronger at lower force increments.Study Design: Descriptive laboratory study.Methods: Sixty-three women and 30 men with no history of ligament injury were measured for knee laxity and incremental stiffness in the sagittal (-90- to 130-N posterior-to-anterior directed loads), frontal (±10-N·m varus-valgus torques), and transverse (±5-N·m internal-external rotation torques) planes and underwent dual-energy X-ray absorptiometry scans to measure LELM. Linear regressions examined the extent to which LELM predicted each laxity and stiffness value, while also accounting for a person’s sex.Results: Females (vs males) had greater laxity and less stiffness in the frontal and transverse planes but not the sagittal plane. Lower extremity lean mass was a poor predictor of sagittal laxity and stiffness (R2 range = .021-.081; P > .06) but was a stronger predictor of frontal (R2 range = .215-.567; P < .01) and transverse (R2range = .224-.356; P < .01) plane laxity and stiffness. Associations were stronger for low (R 2 = .495-.504) versus high (R2 = .215-.435) frontal plane stiffness but were similar for low (R2 = .233-.293) versus high (R2 = .224-.356) transverse plane stiffness. Once we accounted for a person’s LELM, sex had little effect on laxity and stiffness (change in R2 after removal = .01-.08; P = .027-.797).Conclusion: Less LELM was associated with greater laxity and less stiffness in frontal and transverse planes, which may contribute to the disproportionally higher laxities and reduced stiffnesses observed in females in these planes.Clinical Relevance: Frontal and transverse plane laxity and stiffness may be modifiable through strength training interventions that promote changes in muscle characteristics (eg, muscle cross-sectional area, stiffness) that may contribute to static knee joint stability, thus dynamic joint stability during sport activity

In vivo mechanical assessment of human elbow kinematics using a six axis parallel mechanism developed in house

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityElbow joint laxity is a problem that normally comes with age; it increases up to critical levels due to rupture or damage to the ligaments of the elbow and affects the stability and capacities of the joint, interfering even with daily activities. This work investigates the kinematics of the elbow through in-vivo experimental measurement. To this end, a platform based on Stewart Platform mechanism was built and used at the bioengineering labs of Brunel University in West London, the UK, to measure the six degrees of freedom of the joint. This thesis aims to develop a method to simulate such motion which could be used for elbow implant design and manufacture. This work contributes to both the basic science of joint movement measurement and to the clinical applications of diagnosing elbow illness. In addition this research presents the preliminary results for a design for elbow implants. Tracking system developed in house was used to measure the degrees of freedom in healthy elbow motion. A pilot study was performed to assess the joint motion and its repeatability. A group of volunteers with normal elbow movement was used to carry out this study. A Stewart Platform mechanism based on the tracking system was used in this study as a non-invasive tool to capture elbow joint motion and track the trajectory and pattern of the motion in three-dimensional space. This thesis aimed to develop a method to simulate the elbow joint motion that could potentially be used for the elbow implants design and there manufacture. The goal of this study was achieved by in vivo measurement of the elbow movement. It was found that the results vary from person to person, but a healthy pattern of motion can be distinguished from an abnormal pattern. To ensure the result, the motion of the right and left hand of each person was compared,allowing the behaviour of the elbow motion to be judged and the results can help surgeons to analyze the motion of the elbow joint and follow up suspicions of abnormal behaviour in the joint or trace any possible joint laxity. Furthermore, the errors involved with the mechanism were calculated and appropriate factors were applied to correct them. As part of this study the manufacturing of medical implants was reviewed and discussed.Public Authority for Applied Education and Training (PAAET) in the State of Kuwait

Methods for improved kinematic measurements of the lower extremities

An understanding of knee dynamics is vital to treat neurological and musculoskeletal conditions that affect the lower extremities and achieve peak performance from athletes. To obtain and analyze kinematics and kinetics of the knee, clinicians and athletic trainers require accurate, accessible measurement devices. To assess the functionality of one such device, the Mizzou Knee Arthrometer Testing System (MKATS), dynamic motion studies were carried out on healthy, ACL deficient, and patellofemoral pain populations. To assess the validity of the MKATS, the device output was compared to data collected using a SimVitro robotic manipulator. Through this process, discussions with clinicians, technicians, and participants resulted in modifications to both the software and hardware of the device to improve fit and usability. The following thesis summarizes the findings of the dynamic and cadaver motion studies, and the modifications to the device. We found decreased flexion and internal rotation at specific points (p [less than] 0.05) of the cycle for all dynamic activities for both clinical groups compared to the healthy control group. Due to unperceived amounts of skin artifact and joint laxity, the results of the cadaver study were inconclusive. The MKATS was able to accurately detect kinematic differences in the live study groups and has promise as a useful tool for orthopedic surgeons, physical therapists, and athletic trainers to screen for abnormal dynamics and track treatment success. Further studies utilizing computed tomography on live participants will be needed to further validate the MKATS. The development of such devices is crucial to improve the quality of advice from healthcare and athletic performance specialists.Includes bibliographical references

Posterior stability in posterior-stabilized vs medially congruent total knee replacement: A radiological comparison of two polyethylene designs in a single model:

Objective:The purpose of this radiological study was to assess the posterior laxity of a single model of a total knee arthroplasty design (TKA) having a medially constrained (MC) or a Posterior-Stabilized (PS) polyethylene insert using a well-documented stress x-ray. To the authors knowledge, this is the first report evaluating MC TKA outcomes according to the "kneeling view."Materials and Methods:Sixty patients with non-traumatic primary knee osteoarthritis undergoing TKA were first matched by age, sex, BMI and diagnosis and then divided in two groups: group A (37 knees) received a MC TKA and group B (23 knees) a PS implant made by the same manufacturer. In all cases the posterior cruciate ligament (PCL) was resected. All patients underwent the same postoperative "kneeling view" and were also clinically evaluated according to the Knee Society Score (KSS) and Oxford Knee Score (OKS). Radiographic measurements were taken by tracing a line along the posterior cortex of the tibia and then measuring the perpendicular distance to a point marked at the posterior corner of Blumensaat's line.Results:At 12 months minimum FU, no statistically significant differences were found between the two groups in all the clinical scores. There was a statistically significant difference on kneeling view values between the two groups (P = 0.0002): the mean value in the MC group was −1.97 ± 3.8 mm while was −5.6 ± 3.1 mm in the PS group. In both groups, the average position of the posterior cortex of the tibia was anterior to the posterior corner of Blumensaat's line, showing absence of instability in flexion.Conclusion:This study highlighted that the PCL removal, accompanied by a precise surgical technique, did not increase the instability in flexion in two groups of patients having the same TKA design but polyethylene inserts characterized by different levels of constraint

Comparing knee joint mechanics across phases of the menstrual cycle

Anterior cruciate ligament (ACL) injuries are among the most commonly occurring knee injury. Compared to men in the same sports, females are two to eight times at higher risk for ACL injury. Research suggests that hormone fluctuations across the menstrual cycle (MC) play a crucial role in ACL injuries due to their effect on tendons and ligament\u27s mechanical properties. PURPOSE: To examine knee joint laxity during dynamic movements across three-time points of the MC. METHODS: Seven young, healthy females with regular MCs performed three jump-landing tasks (double leg depth jump, single-leg lateral jump, and single-leg forward jump) across the early-follicular, ovulatory, and mid-luteal phases of the MC. Peak frontal and sagittal plane knee joint angles and moments were measured to assess joint stability during dynamic movements in each jump trial were analyzed. The researchers used an analysis of variance (ANOVA) to determine the effects of the menstrual cycle\u27s phases on joint mechanics during each jump task. RESULTS: No significant change occurred in knee joint frontal or sagittal plane angles or moments across MC time points. CONCLUSION: In support of finding from prior studies, the researchers did not observe any changes in knee joint mechanics across the menstrual cycle phases, suggesting that MC hormonal fluctuations do not affect the knee joint\u27s mechanical properties tendons and ligaments enough to cause changes in joint laxity. Future research should examine the specific relationships between measured hormone levels and knee joint mechanics during dynamic movements across the MC phases to assess these relations more accurately

The effects of limited ankle dorsiflexion range of motion on knee and ankle kinematics

Ankle dorsiflexion (DF) range of motion (ROM) may influence movement variables that are known to impact ACL loading, such as knee valgus and knee flexion. Research has not identified individuals with limited and normal DF to investigate the relationship between DF assessments and movement patterns. DF ROM (knee straight, knee bent), weight bearing lunge technique (WBLT), and anterior/posterior (A/P) talar glide were assessed. Participants were grouped into limited and normal groups based on knee straight DF ROM. Knee and ankle kinematics were assessed during three dynamic movements (OHS, SLS, JL). Three separate ANOVA's for task and Pearson correlations between ROM and ankle kinematics were performed. There were no kinematic differences between the limited and normal groups during any of the tasks. The WBLT strongly correlated with ankle DF displacement during the OHS and SLS. Therefore, the WBLT may be more representative of the amount of DF range of motion during movement

Predictors of Knee Functional Joint Stability in Uninjured Physically Active Adults

Noncontact knee injuries are a major problem for male and female agility sports athletes. These injuries commonly manifest with a valgus collapse that implicates failure of mechanical and/or sensorimotor mechanisms in maintaining knee functional joint stability (FJS). Previous studies have elucidated the role of some mechanical and sensorimotor characteristics in knee FJS. The contributions of active joint position sense (AJPS) and time-to-peak torque (TTPT) have not been investigated. Therefore, the current evidence-base is incomplete and noncontact knee injury control programs may not be as effective as could be. Identifying the role of AJPS and TTPT in knee FJS will deliver new data that potentially assists design of more effective noncontact knee injury control programs. The purpose of this study was to determine how gender, mechanical joint stability, and selected sensorimotor characteristics predict knee FJS. Two analyses were performed, each with a specific operational definition of knee FJS: 1. adapted crossover hop for distance (ACHD); 2. single-leg stop-jump (SLSJ) total knee valgus displacement. Thirty-four subjects participated (male (M) 18; female (F) 16; age 24.1 ± 3.5 years; height 171.8 ± 9.6cm; mass 70.6 ± 12.2kg). The dominant leg was tested. The ACHD analysis included: ACHD (cm), gender (M/F), prone knee extension AJPS (motion analysis system; °), anterior tibial displacement (ATD; mm), and isokinetic hamstrings TTPT (240°•sec–1; msec). The SLSJ analysis included: SLSJ valgus/varus displacement (motion analysis system; °), gender, AJPS, ATD, SLSJ medial hamstrings feedforward and feedback muscle activation (surface electromyography; % maximum voluntary isometric contraction × sec), and TTPT. Multiple linear regression was performed. For the ACHD analysis, gender and TTPT contributed to a model that predicted ACHD performance (R2 = 0.60, P = 0.00). For the SLSJ analysis, 56% of subjects demonstrated varus displacement and valgus/varus raw data and final equation residuals demonstrated a non-normal distribution. Gender and hamstrings TTPT should be considered in noncontact knee injury control programs evaluated by single-leg hop tests. Future multivariate studies should consider new knee proprioception tests and employ additional functional tasks to identify clinically important knee valgus displacement

Multiplanar Knee Laxity and Perceived Function During Activities of Daily Living and Sport

Context: Greater knee-joint laxity may lead to a higher risk of knee injury, yet it is unknown whether results of self-reported outcome measures are associated with distinct knee-laxity profiles.Objective: To identify the extent to which multiplanar knee laxity is associated with patient-reported outcomes of knee function in healthy individuals during activities of daily living and sport.Design: Descriptive laboratory study.Setting: University research laboratory.Patients or Other Participants: Forty healthy individuals (20 men, 20 women; age=18–31 years).Main Outcome Measure(s): All participants were given the Knee Outcome Survey Activities of Daily Living Scale (KOS-ADL) and Sports Activities Scale (KOS-SAS) and subsequently measured for knee laxity in the sagittal, frontal, and transverse planes. Separate backward stepwise regression analyses were performed to determine the extent to which multiplanar knee-laxity values predicted KOS-ADL and KOS-SAS scores within each sex.Results: Women had higher magnitudes of anterior, posterior (POSTLAX), varus (VARLAX), valgus (VALLAX), and internal-rotation laxity than men and trended toward greater external rotation (ERLAX) laxity. Greater POSTLAX, less VALLAX, and greater VARLAX was associated with lower KOS-ADL scores (KOS-ADL=-4.8 [POSTLAX], + 3.3 [VALLAX] - 2.2 [VARLAX] + 100.4, R2=0.74, P Conclusions: The combination of POSTLAX with less relative VALLAX (women) or less relative ERLAX (men) was a strong predictor of KOS scores, suggesting that a self-reported outcome measure may be beneficial as part of a preparticipation screening battery to identify those with perceived functional deficits associated with their knee laxity