<p><strong>Objective</strong>: To perform an environmental survey of clinical practice amongst surgeons and physiotherapists in making return to sport (RTS) decisions following ACL reconstruction (ACLR); to gain a better understanding of how clinicians and patients define successful return to sport; and to compare patients’ level of satisfaction with their current level of activity following ACLR.</p> <p><strong>Design: </strong>Multidisciplinary cross sectional study.</p> <p><strong>Setting</strong>: Online</p> <p><strong>Participants:</strong> Orthopaedic surgeons and registered physiotherapists; and patients who had undergone ACLR within the previous 6-18 months.</p> <p><strong>Interventions: </strong>Surgeons and physiotherapists completed separate web surveys, each consisting of 10 closed format questions that included sections on demographics, outcome measures, treatment procedures, and RTS decisions. Patients completed a web survey consisting of 19 questions about their activity level, their experience surrounding the process of rehabilitation after ACLR, and their decisions surrounding RTS.</p> <p><strong>Main Outcome Measures</strong><strong>: </strong>Descriptive and subjective data were collected for all groups. Clinician responses were compared for differences in frequencies of clinical outcome measures used to decide RTS readiness. Frequency data were collected for all groups for the definition of successful RTS following ACLR using a self-report form. The relationship between patient satisfaction and current level of activity following ACLR was compared using the Tegner Activity Scale and Single Assessment Numeric Evaluation (SANE).</p> <p><strong>Results:</strong> All patients were unanimous in their definition of successful RTS post ACLR as the ability to fully participate in pre-injury level of sport with no limitations or deficits (100%), and restoring functional stability (100%). Mean Tegner activity level scores of respondents decreased a mean of 3.4 (SD ± 2.5) from pre-injury to current level of activity (p < 0.011). However, no significant decrease from pre-injury level of activity to expected level of activity post surgery was seen. A statistically significant correlation was demonstrated between patients’ level of satisfaction and current level of activity (r = 0.84, p = 0.02), with higher levels of activity associated with increased levels of satisfaction. Overall, the majority of clinician respondents reported that jump tests, range of motion (ROM), Lachman clinical test of stability, pain, swelling, functional movement and giving way contributed to their RTS decisions. Unanimous consensus existed between clinicians for the ability to participate in any level of sport, with or without limitations, as the definition of successful RTS following ACLR.</p> <p><strong>Conclusions:</strong> Following ACLR, medically cleared patients had not met their high expectations of functional stability and ability to return to their pre-injury level of sport. The discordance between unmet expectations and current level of sporting activity was reflected in lower rates of patient satisfaction. Most clinicians reported using primarily impairment based not self-report measures to contribute to their RTS decisions. Clinicians and patients expressed subtle differences in their definition of successful RTS.</p> <p><strong>Clinical Relevance: </strong>Establishing an operational definition of success, and professional consensus on measures which include patient reported outcomes is an important next step in the development of goal oriented RTS guidelines.</p> / Master of Science Rehabilitation Science (MSc)

Osteoarthritis (OA) of the knee is common in Western society. OA of the patellofemoral (PF) compartment of the knee is prevalent in adults greater than 55 years of age. Isolated radiographic PFOA is present in 13.6-24% of females and 11-15.4% of males with knee pain. Biomechanical factors such as tibiofemoral alignment and high joint stress are associated with the development and progression of PFOA. PF joint stress is high when the quadriceps contracts with the knee in a position of extreme flexion, such as rising from sitting. The purposes of this study were to determine 1) the triplanar biomechanics of the hips and knees during sit-to-stand (STS) for persons with PFOA versus age- and gender-matched control subjects, 2) the impact of PFOA on physical performance, perceived functional status, and pain, and 3) the relationship between knee kinematics during STS and physical performance. The biomechanics of STS was examined using a video-based motion analysis system and two force plates. Physical performance was measured with the Timed Up and Go (TUG) and Fifty-Foot Walk (FFW) tests. Perceived functional status, pain, and stiffness were measured using the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaire. Knee pain was measured with a Visual Analog Scale (VAS) following STS, TUG, and FFW. Persons with PFOA required a significantly longer time to perform STS and the TUG as compared to healthy controls. The PFOA group demonstrated greater hip flexion and knee abduction versus the control group. The hip and knee moments were significantly different with the PFOA group demonstrating greater hip extension, hip abduction, hip external rotation, knee extension, and knee adduction moments. Persons with PFOA were found to have significantly less perceived physical function, greater stiffness, and greater pain. Pain following STS, TUG, and FFW were all greater in the PFOA group. No significant association was found between any knee angle and time to perform the TUG or the FFW. These results indicate that dynamic malalignment of the TF joint is present during STS in persons with PFOA. This may contribute to the increased pain and decreased function in persons with PFOA. / Physical Therapy

Osteoarthritis and cartilage deterioration are favored by meniscetomy, which is the ablation of the meniscus from the knee joint. Meniscectomy can be partial or total. This procedure is performed when meniscus lesions and tears or the degeneration of the meniscus caused by its natural dehydration occur. There is a peak of meniscal lesions observed between 20 and 29 years old. Alternative methods such as sutures fail in that they present a short term solution which is ideal for a less active, older generation. A long term solution is needed for a younger population to reduce the number of surgical procedures over the lifetime of this active group. There is a crucial need for a functional implant designed in the image of the native meniscus. Blends of poly (vinyl alcohol) PVA and poly (vinyl pyrrolidone) (PVP) present a potential solution. PVA has shown similar characteristics to soft tissues. PVP further stabilizes the hydrogel network. This work is the mechanical characterization of PVA/PVP (99:1) hydrogels under physiological conditions. Equilibrium swelling in a medium replicating the ionic and the osmotic content of the synovial fluid was investigated during 35 days. The mass retention of hydrogels was characterized using data obtained from the swelling study and was examined as a function of the cross link density and the polymer content. The modulus of hydrogels was obtained in unconfined compression, first at a strain rate slow enough to ignore fluid flow in and out of the gels, and subsequently at a physiological strain rate of walking. Results indicate that PVA/PVP hydrogels volume swelling ratio and weight swelling ratio show no significant difference for most formulations by the 14th day of immersion. A few hydrogels would reach equilibrium by day 21. Additionally, percentage polymer mass retention increases with the cross link density. However, there is no consistent trend with the polymer content. All formulations with 10% wt of polymer show the highest mass retention while 15% wt show the lowest. Interestingly, the mechanical characterization of hydrogels at 100%/min strain rate shows that 15% wt is the only formulation whose compressive modulus falls within the targeted range whereas 10% wt proves to not be stiff enough. 20% wt and 25% wt are always too stiff. Results obtained from unconfined compression at the physiological strain rate, that is 1920%/min, are rather inconclusive. There is not enough consistency in the literature to narrow the results down to one successful candidate formulation. The modulus range obtained at physiological strain rate encompasses the range obtained at 100%/min strain rate. The highest modulus value obtained is 10 times higher at physiological strain rate than the modulus of a real human meniscus obtained at 100%/min strain rate. It is not reasonable at this time to make a choice of a formulation at physiological strain rate due to high variability of the modulus of a human meniscus as a result of its intrinsic anisotropy. All formulations tested would be considered successful candidates, which is irrational considering the difference in their stiffness. / Mechanical Engineering

<p> We aimed to determine the effectiveness of a low volume of high-intensity resistance exercise, alone (EX) or in combination with a whey protein supplement (WHY +EX), on prevention of muscle mass and strength loss following 14 days of knee immobilization in humans. Seventeen recreationally active (i.e., exercise ≤ 2-3 d·wk^-1) participants (23.9±5.0 yr; BMI = 25.4±3.6 kg·m^-2) were divided into three groups: exercise (EX; n=6), whey protein supplementation with exercise (WHY+EX; n=6), and control (CON; n=5). All subjects wore a knee-immobilization brace such that one leg was completely non-weight bearing for 14d. The resistance exercise (RE) were performed unilaterally and consisted of one set of ten repetitions of leg press (with plantar flexion at full extension), knee extension, and seated calf raises every other day during the 14d immobilization period, at 80% of one repetition maximum. Subjects in the WHY+EX group consumed two 30g boluses of whey protein daily while EX and CON consumed isocaloric carbohydrate beverages. Immobilization induced a significant reduction (p<0.05) in thigh cross-sectional area (CSA), isometric knee extensor strength, and isometric plantar flexion strength in CON but not in EX and WHY+EX. There were significant losses in lower leg CSA for all three groups, with a tendency for losses to be mitigated in both the EX and WHY+EX groups versus CON (p=0.065). The two constituent muscles of the triceps surae muscle group showed a differential response to the RE training with the gastrocnemius showing reductions in CSA almost uniformly across the three groups whereas soleus CSA was significantly reduced in the CON (p<0.05) but not in the EX and WHY+EX groups. We conclude that a relatively low volume of high-intensity resistance exercise is an effective countermeasure against atrophy of the thigh and the soleus muscle, as well as against knee extension and plantar flexion strength loss during 14d of leg immobilization. As a countermeasure to immobilization, there is no additional benefit of consumption of a daily whey protein supplement in combination with resistance exercise in maintaining muscle mass or strength.</p> / Thesis / Master of Science (MSc)

INTRODUCTION: Altered walking patterns in individuals with knee osteoarthritis (OA) are a key driver of disease; however, mechanisms underlying this relationship are not clear. Central sensitization is now recognized as an important contributor to pain experience in people with knee OA. In the presence of chronic pain and central sensitization, there are alterations in activity and connectivity across multiple brain regions (e.g., prefrontal cortex, primary motor cortex) that could influence dynamic control of gait. However, the association of central sensitization with gait patterns in knee OA has not been studied. Our objective was to investigate whether central sensitization in individuals with knee OA is associated with dynamic control of gait as assessed using wearable sensor-derived measures of gait complexity and dynamic stability. We hypothesized that a greater degree of sensitization would be associated with lower gait complexity and stability. METHODS: We used data from the 12th-year visit of the Multicenter Osteoarthritis Study, a longitudinal cohort study of individuals with and without knee OA. This was the first visit at which the relevant gait parameters were collected using wearable sensors. Individuals from this visit with valid data available for all measures contained in this analysis were included. Mechanical temporal summation (TS), an augmented response to repetitive mechanical stimulation, is a reliable and valid measure of central sensitization. To assess TS, participants’ pain ratings were assessed after a single wrist stimulus was applied with successively weighted probes until a pain rating of at least 4/10 was achieved (the highest weighted probe was used if that pain rating was not obtained), then was assessed again after 10 repeated stimuli at a rate of 1 Hz was applied with the same probe. A post-stimulation pain rating larger than the initial pain rating reflected facilitated TS. For gait analyses, participants completed 2 trials of a 20m walking test at their usual walking pace while wearing inertial sensors on their lower back and both feet. The lower back sensor was used to calculate sample entropy and Lyapunov exponent, both of which may provide a window into how dynamic control of gait is altered in disease. Sample entropy measures the inter-stride predictability or regularity of gait kinematics. Lower sample entropy represents a more regular or predictable (i.e., less complex) gait pattern and may reflect a reduced ability of the neuromotor system to adapt to ongoing changes experienced in daily walking. LE measures the inter-stride stability of gait kinematics. Large LE values represent more gait instability and may reflect a reduced ability of the motor system to recover from small perturbations. We averaged the gait outcomes across the two trials. Exposure variables were standardized. We determined the association between TS and gait parameters using linear regression while adjusting for age, sex, race, body mass index (BMI), depressive symptoms, education, and presence of radiographic knee OA. Analyses were not adjusted for pain or gait speed because we hypothesized that these impairments were on the causal pathway between our exposure and outcomes. RESULTS: Data from 2,179 participants (age = 62.4 ± 10.0 years, BMI = 29.1 ± 5.5 kg/m2, 56.3% female) were included in the analysis. One standard deviation (SD) increase in TS was associated with a -0.024 [95% Confidence intervals -0.038, -0.010] change in sample entropy (i.e., more regular gait) but not with a change in LE (-0.002 [95% Confidence intervals -0.008, 0.004]). CONCLUSION: Individuals with knee OA and central sensitization display a less complex or more predictable gait pattern, evidenced by lower sample entropy, likely reflecting a deterioration in dynamic control of gait. However, central sensitization was not associated with an individual’s ability to respond to natural fluctuations that occur in walking, as evidenced by a lack of association with LE. We propose a plausible mechanism in which central sensitization may cause a reduction in gait complexity via continuous nociceptor release of glutamate, NMDAR activation, and changes in motoneuron excitability and inhibition at multiple sites along the motor pathway. Although causality cannot be determined from this cross-sectional study, these findings provide support for an association between central sensitization and specific aspects of the walking pattern in people with knee OA. Interventions to mitigate central sensitization may be useful to improve gait quality in people with knee OA.

The knee joint is a diarthrodial joint that rotates in the flexion-extension axis to provide individuals mobility. A limitation in the passive range of motion (ROM) is detrimental for function and this limitation is termed a joint contracture. A commonly shared characteristic between conditions that lead to contracture formation is prolonged periods of immobilization. However, the etiology of immobility-induced joint contractures is not well described and requires quantitative data on anatomical structures limiting knee mobility to design new interventions aimed at restoring function. In turn, our research group has developed an experimental animal model to study the temporal pathophysiology of knee immobilization and reversibility through unassisted remobilization. With durations of immobilization ranging from 1 to 32 weeks and remobilization up to 48 weeks, our experimental design provides a comprehensive temporal overview on the various stages of contracture formation: initiation, progression, and severity. A combination of muscles and articular structures are involved in the pathophysiology of knee flexion contractures, but the posterior joint capsule is of particular interest. Through histomorphological analysis, we provided quantitative data on the contribution of the reduced posterior capsule length in the limitation of knee extension and increased joint stiffness. Moreover, elucidation of synoviocyte profiles within the synovium of the capsule provided insights to potential mechanisms of capsule shortening. Our novel measurable outcome of mechanical joint stiffness revealed distinct temporal differences with ROM measurements after joint immobilization and remobilization, suggesting that alterations in the biomechanical properties of articular tissue structures are also contributing to the limitation in function. Malleability of the dynamic reciprocal relationship between trabecular bone loss and accumulation of marrow adipose tissue (predominately through adipocyte hyperplasia) after knee immobilization underscores the sensitivity of the bone marrow microenvironment in response to mechanical stimuli and lack thereof. Remobilization of the knee joint is limited in its capacity to reverse detriments induced by extended periods of joint immobilization. Findings from this work point to the temporal changes detected in different musculoskeletal tissues during knee immobilization and emphasizes the contribution of the joint capsule in limiting joint mobility.

A novel exoskeleton robotic system was developed to assist stair climbing. This active demonstrator consists of a motor with a cable system, various sensors, and a control system with a power supply. The objective of this preliminary study is a biomechanical evaluation of the novel system to determine its effectiveness in use. For this purpose, three test persons were biomechan- ically investigated, who performed stair ascents and descents with and without the exoskeleton. Kinematics, kinetics, and muscle activity of the knee extensors were measured. The measured data were biomechanically simulated in order to evaluate the characteristics of joint angles, moments, and reaction forces. The results show that the new exoskeleton assists both the ascent and the descent according to the measured surface electromyography (sEMG) signals, as the knee extensors are relieved by an average of 19.3%. In addition, differences in the interaction between the test persons and the system were found. This could be due to a slightly different operation of the assisting force or to the different influence of the system on the kinematics of the users.

Knee osteoarthritis (OA) is a debilitating disease affecting the entire knee joint by inducing pathological changes to the cartilage and menisci. Currently, the etiology of OA is not completely understood. However, altered gait mechanics, specifically increased joint loading, of OA patients have a clear association with both symptomatic and structural OA progression. Non-surgical intervention tools, such as variable stiffness shoes (VSS), have been developed as a way to decrease loading within the knee joint. However, with external moments being surrogate measures for knee loading, it is unclear if changes in knee moments with the footwear are sufficient to result in a clinical benefit. Therefore, this project’s purpose was to investigate whether a VSS intervention can alter knee joint loading and menisci function in a knee OA population. We used gait analysis, musculoskeletal modeling, and finite element (FE) analysis to determine the effect of VSS on gait mechanics, knee joint contact force, and menisci stress and strain, compared to a control shoe. We found knee moments did not decrease with the VSS intervention. Furthermore, participants who did experience a decrease in knee adduction moment did not always experience a decrease in medial compartment contact force. However, results from our FE modeling of the tibiofemoral joint indicate significant changes in knee joint contact force can influence stress placed on the menisci. Results from this study suggest knee contact forces and tissue stress, not only external moments, should be considered when investigating if VSS can positively impact an OA population.

The purpose of this dissertation was to study the effects of graft pretension in anterior cruciate ligament (ACL) reconstruction through a series of experiments. First, an in vitro study of 5 human knees was conducted to determine if intact joint kinematics could be restored when using the ideal graft - the intrinsic ACL. The ACL tibial insertion site was freed, and pretensions of 0, 10, 20, 30, and 40 N were applied to the ligament using a custom designed load cell connection. Kinematics during a simulated active extension were compared to those of the intact knee. Intact knee kinematics were not restored. Pretensions that best restored tibial anterior/posterior translation and internal/external rotation ranged from 0-40 N. Furthermore, the pretensions that best restored these kinematic variables were widely disparate in two specimens. Second, the in vitro kinematics during a simulated active extension of human and porcine knees were compared and contrasted both prior to and following transection of the ACL. The ACL limited: (1) tibial anterior translation in both species, (2) tibial internal rotation in humans, and (3) tibial external rotation in pigs. Differences in kinematic patterns for tibial internal/external rotation and abduction/adduction between the species was explained by requirements for biped and quadruped stances. Third, the mechanical characteristics of porcine patellar tendon (PT) were investigated by uniaxial tensile testing at two strain rates. Patella-PT-tibia complexes from freshly sacrificed skeletally immature and mature animals were loaded to failure at elongation rates of 20 and 200 mm/min. Both strain rate and skeletal maturity significantly affected failure mode, tangent modulus, and ultimate stress of the tendons, and hence are important considerations in the mechanical evaluation of porcine PT. Fourth, ACL reconstructions were performed using pretensions of 10 or 20 N in an in vivo porcine model with a specially designed load cell/telemetry system to monitor graft load. Graft pretension was seen to increase during fixation with interference screws. Following sacrifice at 4 weeks, tissues were mechanically, histologically, and biochemically analyzed. A pretension of 20 N resulted in a tissue more similar to the intrinsic ACL. / Ph. D.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第25186号 / 医博第5072号 / 新制||医||1072(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 安達 泰治, 教授 森本 尚樹, 教授 羽賀 博典 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM