Lower limb joint loading in patients with unilateral hip osteoarthritis during bipedal stance and the effect of total hip replacement.

Osteoarthritis of the hip is a common condition that affects older adults. Total hip replacement is the end-stage treatment to relief pain and improve joint function. Little is known about the mechanical load distribution during the activity of bipedal stance, which is an important daily activity for older adults who need to rest more frequently. This study investigated the distribution of the hip and knee joint moments during bipedal stance in patients with unilateral hip osteoarthritis and how the distribution changed 1 year after total hip replacement. Kinematic and kinetic data from bipedal stance were recorded. External hip and knee adduction moments were calculated and load distribution over both limbs was calculated using the symmetry angle. Preoperatively, the non-affected limb carried 10% more body weight than the affected limb when standing on two legs. Moreover, the mean external hip and knee adduction moments of the non-affected limb were increased compared to the affected limb. At follow-up no significant differences were observed between the patients' limbs. Preoperative and postoperative changes in hip adduction moment were mainly explained by the combination of the vertical ground reaction force and the hip adduction angle. Stance width also explained changes in the hip and knee adduction moments of the affected leg. Furthermore, as with walking, bipedal standing also showed an asymmetric mechanical load distribution in patients with unilateral hip osteoarthritis. Overall, the findings suggest the need for preventive therapy concepts that focus not only on walking but also on optimizing stance towards a balanced load distribution of both legs.

Comparison of Gait Symmetry and Joint Moments in Unilateral and Bilateral Hip Osteoarthritis Patients and Healthy Controls.

Patients with unilateral hip osteoarthritis show a characteristic gait pattern in which they unload the affected leg and overload the unaffected leg. Information on the gait characteristics of patients with bilateral hip osteoarthritis is very limited. The main purposes of this study were to investigate whether the gait pattern of both legs of patients with bilateral hip osteoarthritis deviates from healthy controls and whether bilateral hip osteoarthritis patients show a more symmetrical joint load compared to unilateral hip osteoarthritis patients. In this prospective study, 26 patients with bilateral hip osteoarthritis, 26 patients with unilateral hip osteoarthritis and 26 healthy controls were included. The three groups were matched for gender, age and walking speed. Patients were scheduled for a unilateral total hip arthroplasty on the more affected/more painful side. All participants underwent a three-dimensional gait analysis. Gait kinematics and gait kinetics of patients and controls were compared using Statistical Parametric Mapping. Corrected for speed, the gait kinematics and kinetics of both legs of patients with bilateral hip osteoarthritis differed from healthy controls. Bilateral patients had symmetrical knee joint loading, in contrast to the asymmetrical knee joint loading in unilateral hip osteoarthritis patients. The ipsilateral leg of the bilateral patients could be included in studies in addition to unilateral hip osteoarthritis patients as no differences were found. Although patients with bilateral hip osteoarthritis show more symmetrical frontal plane knee joint moments, a pathological external knee adduction moment in the second half of stance was present in the ipsilateral leg in patients with unilateral and bilateral hip osteoarthritis. The lateral adjustment of the knee adduction moment may initiate or accelerate progression of degenerative changes in the lateral compartment of the knee.

Muscle load in reaching movements performed by a wheelchair user: a case study.

PURPOSE: The aim of this study was to analyse the load on the shoulder muscles during reaching movements that are specific to wheelchair users in relation to the risk of impingement. METHOD: Three activities of daily living were performed: putting a book on a shelf in front and at the side and putting a pack of water bottles on a table. The AnyBody shoulder model was used to calculate the activity and forces of the shoulder muscles. RESULTS: Handling the pack of bottles caused the highest forces in the deltoideus, trapezius, serratus anterior and rotator cuff muscles. For handling the book, the highest forces were found in the deltoideus (scapular part) and the serratus anterior, especially during the put phase. CONCLUSIONS: Handling heavy objects such as a pack of bottles or a wheelchair produces high forces on the rotator cuff muscles and can lead to early fatigue. Therefore, these activities seem to be associated with a high risk of developing impingement syndrome. Implications for Rehabilitation In a single patient, this study demonstrates that the load on the rotator cuff is high during reaching movements. Handling a pack of water bottles, which resembles wheelchair handling, represents an activity associated with a high risk of developing impingement syndrome. Shoulder muscles must be trained in a balanced way to provide stabilization at the shoulder joint and prevent fatigue.

The effect of crank position and backrest inclination on shoulder load and mechanical efficiency during handcycling.

Handbikes come in different models and setups, but only limited knowledge is available on the handbike-user interface. The aim of this study was to identify optimal handbike setups, assuming that in such a setup mechanical efficiency is high, while shoulder load is low. Thirteen subjects with a spinal cord injury (paraplegia) performed handcycling with different handbike setups at constant power output: four crank positions (two distances, two heights) and four backrest inclinations. The O2-consumption, kinetics, and kinematics were measured to calculate mechanical efficiency and shoulder load (glenohumeral contact force, net shoulder moments, and rotator cuff force). The analysis showed that more upright backrest positions resulted in lower shoulder load compared with the most reclined position [glenohumeral contact force (260 vs 335 N), supraspinatus (14.4% vs 18.2%), and infraspinatus force (5.4% vs 9.8%)], while there was no difference in efficiency. Except for a reduction in subscapularis force at the distant position, no differences in shoulder load or efficiency were found between crank positions. Recreational handbike users, who want to improve their physical capacity in a shoulder-friendly way, should set up their handbike with a more upright backrest position and a distant crank placement.

Acromioclavicular joint arthrosis in persons with spinal cord injury and able-bodied persons.

OBJECTIVE: To compare the prevalence, severity and risk of acromioclavicular (AC) joint arthrosis in persons presenting with shoulder pain between a spinal cord injury (SCI) and able-bodied population. In the SCI population, prevalence and severity of AC joint arthrosis were examined with respect to age, gender and lesion characteristics. METHODS: Retrospective analysis of medical records and magnetic resonance images (MRI) collected in an outpatient orthopaedics clinic. RESULTS: Sixty-eight persons with SCI and 105 able-bodied persons were included in the study. The overall MRI prevalence of AC joint arthrosis was 98% and 92%, respectively. In both groups AC joint arthrosis was frequently accompanied by MRI diagnosis of rotator cuff tears and biceps tendon ruptures. Sensitivity of clinical testing was found to be low in SCI (0.31) and in able-bodied persons (0.24). The odds of increasingly severe arthrosis were nearly four times higher in persons with SCI as compared with able-bodied persons (P<0.0001), about 72% lower in females as compared with males (P=0.0001), and 10% higher per additional year of age (P<0.0001). Arthrosis severity in the SCI-group was weakly associated with time since injury, not with neurological classification of SCI or level of injury (paraplegia vs tetraplegia). CONCLUSION: SCI patients presenting with shoulder pain showed similar prevalence, yet more advanced, AC joint arthrosis than able-bodied patients. As early diagnosis of arthrosis is a prerequisite for the initiation of successful conservative interventions of shoulder deterioration, we recommend routine assessment of shoulder status including diagnostic imaging during check-ups.

Load on the shoulder complex during wheelchair propulsion and weight relief lifting.

BACKGROUND: This study focuses on the relationship between overuse in association with wheelchair activities of daily living and risks for osteoarthrosis in the acromioclavicular and sternoclavicular joints. The aim is to quantify the joint moments and joint reaction forces in all three joints of the shoulder complex during wheelchair-related activities of daily living. METHODS: A convenience sample of 17 subjects performed two tasks (wheelchair propulsion and weight relief lifting). Three-dimensional kinematics and kinetics were measured and position and force data were used as input for a musculoskeletal model of the arm and shoulder. Output variables of the model were the moments and the joint reaction forces on the sternoclavicular, acromioclavicular and glenohumeral joints. FINDINGS: Moments on the sternoclavicular joint were higher than on the acromioclavicular and glenohumeral joint, but the joint reaction forces on the sternoclavicular and acromioclavicular joints were only one third of those on the glenohumeral joint (peak forces around 96N compared to 315N for wheelchair propulsion and around 330N compared to 1288N for weight relief lifting). INTERPRETATION: Based on the results found in this study, net joint moments are likely a better measure to describe the load on the acromioclavicular and sternoclavicular joints due to the passive stabilization. Prospective studies on wheelchair overuse injuries should also look at the acromioclavicular and sternoclavicular joints since the load of wheelchair tasks might be a risk factor for osteoarthrosis in these joints.

Hand-cycling: an active form of wheeled mobility, recreation, and sports.

By studying exercise and performance in hand-cycling in both activities of daily living and in Paralympic sport settings, new insights can be gained for rehabilitation practice, adapted physical activity, and sports. This review looks into the pros and cons of hand-cycling in both rehabilitation and optimal sports performance settings as suggested from the current-but still limited-scientific literature and experimentation. Despite the limited evidence-base and the diversity of study approaches and methodologies, this study suggests an important role for hand-cycling during and after rehabilitation, and in wheeled mobility recreation and sports. An approach that combines biomechanical, physiological, and psychosocial elements may lead to a better understanding of the benefits of hand-cycling and of the fundamentals of exercise in rehabilitation, activities of daily living, and sports.

Submaximal arm crank ergometry: Effects of crank axis positioning on mechanical efficiency, physiological strain and perceived discomfort.

PURPOSE: To evaluate the effect of the spatial orientation of the crank axis on mechanical efficiency, physiological strain and perceived discomfort in submaximal synchronous arm crank ergometry. METHODS: Twelve able-bodied individuals performed 12 submaximal exercise bouts of 3 minutes (women: 20 W/25 W; men: 25 W/35 W). The crank axis position was defined by elbow and shoulder angle. RESULTS: The results showed that a crank set-up with an elbow angle of 30 degrees was more efficient than 15 degrees ; oxygen consumption and minute ventilation were significantly lower. No significant effects were seen for shoulder angle. Power output and gender showed obvious effects. DISCUSSION AND CONCLUSION: The magnitude of this effect and the absence of any significant shoulder angle effects may be due to the relative low exertion levels that were evaluated. An elbow angle of 30 degrees flexion in arm crank exercise is favourable compared to an elbow angle of 15 degrees in able-bodied untrained subjects.

Is effective force application in handrim wheelchair propulsion also efficient?

BACKGROUND: Efficiency in manual wheelchair propulsion is low, as is the fraction of the propulsion force that is attributed to the moment of propulsion of the wheelchair. In this study we tested the hypothesis that a tangential propulsion force direction leads to an increase in physiological cost, due to (1) the sub-optimal use of elbow flexors and extensors, and/or (2) the necessity of preventing of glenohumeral subluxation. METHODS: Five able-bodied and 11 individuals with a spinal cord injury propelled a wheelchair while kinematics and kinetics were collected. The results were used to perform inverse dynamical simulations with input of (1) the experimentally obtained propulsion force, and (2) only the tangential component of that force. FINDINGS: In the tangential force condition the physiological cost was over 30% higher, while the tangential propulsion force was only 75% of the total experimental force. According to model estimations, the tangential force condition led to more co-contraction around the elbow, and a higher power production around the shoulder joint. The tangential propulsion force led to a significant, but small 4% increase in necessity for the model to compensate for glenohumeral subluxation, which indicates that this is not a likely cause of the decrease in efficiency. INTERPRETATION: The present findings support the hypothesis that the observed force direction in wheelchair propulsion is a compromise between efficiency and the constraints imposed by the wheelchair-user system. This implies that training should not be aimed at optimization of the propulsion force, because this may be less efficient and more straining for the musculoskeletal system.

Upper extremity musculoskeletal pain during and after rehabilitation in wheelchair-using persons with a spinal cord injury.

STUDY DESIGN: Prospective cohort study. OBJECTIVES: To study upper extremity musculoskeletal pain during and after rehabilitation in wheelchair-using subjects with a spinal cord injury (SCI) and its relation with lesion characteristics, muscle strength and functional outcome. SETTING: Eight rehabilitation centers with an SCI unit in the Netherlands. METHODS: Using a questionnaire, number, frequency and seriousness of musculoskeletal pain complaints of the upper extremity were measured. A pain score for the wrist, elbow and shoulder joints was calculated by multiplying the seriousness by the frequency of pain complaints. An overall score was obtained by adding the scores of the three joints of both upper extremities. Muscle strength was determined by manual muscle testing. The motor score of the functional independence measure provided a functional outcome. All outcomes were obtained at four test occasions during and 1 year after rehabilitation. RESULTS: Upper extremity pain and shoulder pain decreased over time (30%) during the latter part of in-patient rehabilitation (P<0.001). Subjects with tetraplegia (TP) showed more musculoskeletal pain than subjects with paraplegia (PP) (P<0.001). Upper extremity pain and shoulder pain were significantly inversely related to functional outcome (P<0.001). Muscle strength was significantly inversely related to shoulder pain (P<0.001). Musculoskeletal pain at the beginning of rehabilitation and BMI were strong predictors for pain 1 year after in-patient rehabilitation (P<0.001). CONCLUSIONS: Subjects with TP are at a higher risk for upper extremity musculoskeletal pain and for shoulder pain than subjects with PP. Higher muscle strength and higher functional outcome are related to fewer upper extremity complaints.

Glenohumeral joint loading in tetraplegia during weight relief lifting: a simulation study.

BACKGROUND: The incidence of shoulder complaints in wheelchair users is high and the etiology is poorly understood. The goal of this study was to examine the effect of lesion level and isolated triceps muscle paresis on the internal load on the shoulder by simulation. METHODS: Kinematic and kinetic profiles from four able-bodied subjects and four subjects with tetraplegia were used as input for an inverse dynamics biomechanical model. The model was modified to simulate lesion level and triceps muscle paresis. FINDINGS: The simulations resulted in a significantly higher (+56%) glenohumeral contact force (P=0.037) for tetraplegic profiles than for able-bodied profiles. The model modifications to simulate lesion level only had a minor effect (+7%) on the calculated glenohumeral contact force. More simulations were successful at lower triceps force levels for tetraplegic profiles compared to able-bodied profiles (P=0.012). The muscle forces at the simulated T1 lesion were not significantly higher in tetraplegic profiles compared to able-bodied profiles. INTERPRETATION: The glenohumeral contact force for the tetraplegic profiles is mainly higher due to different task performance. Model modifications only have a minor effect on the calculated glenohumeral contact force. For able-bodied profiles the triceps force seems to be an important factor. The high internal load at the shoulder recommends new techniques of weight relief lifting and proper training of the arm-shoulder muscles in rehabilitation.