Biomechanics, Volume 1, Issue 3 (December 2021) – 8 articles

The identification of homogeneous subgroups of patients with chronic low back pain (CLBP), based on distinct patterns of motor control, could support the tailoring of therapy and improve the effectiveness of rehabilitation. The purpose of this review was (1) to assess if there are differences in motor variability between patients with CLBP and pain-free controls, as well as inter-individually among patients with CLBP, during the performance of functional tasks; and (2) to examine the relationship between motor variability and CLBP across time. A literature search was conducted on the electronic databases Pubmed, EMBASE, and Web of Science, including papers published any time up to September 2021. Two reviewers independently screened the search results, assessed the risk of bias, and extracted the data. Twenty-two cross-sectional and three longitudinal studies investigating motor variability during functional tasks were examined. There are differences in motor variability between patients with CLBP and pain-free controls during the performance of functional tasks, albeit with discrepant results between tasks and among studies. The longitudinal studies revealed the persistence of motor control changes following interventions, but the relationship between changes in motor variability and reduction in pain intensity was inconclusive. Based on the reviewed literature, no stratification of homogeneous subgroups into distinct patterns of motor variability in the CLBP population could be made. Studies diverged in methodologies and theoretical frameworks and in metrics used to assess and interpret motor variability. In the future, more large-sample studies, including longitudinal designs, are needed, with standardized metrics that quantify motor variability to fill the identified evidence gaps. Full article

Background: This study determined whether prolonged load carriage increased the magnitude and velocity of knee adduction biomechanics and whether increases were related to knee varus thrust or alignment. Methods: Seventeen participants (eight varus thrust and nine control) had knee adduction quantified during 60-min of walking (1.3 m/s) with three body-borne loads (0 kg, 15 kg, and 30 kg). Magnitude, average and maximum velocity, and time to peak of knee adduction biomechanics were submitted to a mixed model ANOVA. Results: With the 0 and 15 kg loads, varus thrust participants exhibited greater magnitude (p ≤ 0.037, 1.9–2.3°), and average (p ≤ 0.027, up to 60%) and maximum velocity (p ≤ 0.030, up to 44%) of varus thrust than control, but differences were not observed with the 30 kg load. The 15 and 30 kg loads led to significant increases in magnitude (p ≤ 0.017, 15–25%) and maximum velocity (p ≤ 0.017, 11–20%) of knee adduction moment, while participants increased magnitude (p ≤ 0.043, up to 0.3°) and maximum velocity (p ≤ 0.022, up to 5.9°/s and 6.7°/s) for knee adduction angle and varus thrust at minutes 30 and 60. Static alignment did not differ between groups (p = 0.412). Conclusion: During prolonged load carriage, all participants increased the magnitude and velocity of knee adduction biomechanics and the potential risk of knee OA. Full article

An important health-related problem of obesity is reduced stance stability, leading to increased chance of falling. In the present experiment, we aimed to compare stability in quiet and in dynamic body balance between women with morbid obesity (n = 13, body mass index [BMI] > 40 Kg/m², mean age = 38.85 years) and with healthy body weight (lean) (n = 13; BMI < 25 Kg/m², mean age = 37.62 years), evaluating the extent to which quiet and dynamic balance stability are associated with plantar sensibility. Quiet stance was evaluated in different visual and support base conditions. The dynamic task consisted of rhythmic flexion—extension movements at the hip and shoulder, manipulating vision availability. The plantar sensibility threshold was measured through application of monofilaments on the feet soles. The results showed that the morbidly obese, in comparison with the lean women, had higher plantar sensibility thresholds, and a reduced balance stability in quiet standing. Mediolateral stance stability on the malleable surface was strongly correlated with plantar sensibility in the obese women. Analysis of dynamic balance showed no effect of obesity and weaker correlations with plantar sensibility. Our results suggest that reduced plantar sensibility in morbidly obese women may underlie their diminished stance stability, while dynamic balance control seems to be unaffected by their reduced plantar sensibility. Full article

Open-book fractures are defined as the separation of the pubic symphysis or fractures of the rami and disruption of the anterior sacroiliac, sacrotuberous, and sacrospinal ligaments. They can be stabilized by fixation of the anterior arch. However, indications and advantages of additional placement of iliosacral screws remain unknown. A CT-based model of the healthy pelvis was created and ligaments were modeled as tension springs. Range of motion of the sacroiliac joint and the pubic symphysis, and bone and implant stresses were compared for the physiological model, anterior symphyseal plating alone, and additional posterior fixation using two iliosacral screws. The range of motion of the sacroiliac joint was reduced for anterior symphyseal plating alone and further decrease was noted with additional posterior fixation. Von Mises stresses acting on the symphyseal plate were 819.7 MPa for anterior fixation only and 711.56 MPa for additional posterior fixation equivalent with a safety factor of 1.1 and 1.26, respectively. Implant stresses were highest parasymphyseal. While bone stresses exhibited a more homogeneous distribution in the model of the healthy pelvis and the model with anterior and posterior fixation, pure symphyseal plating resulted in bending at the pelvic rami. The analysis does not indicate the superiority of either anterior plating alone or additional posterior fixation. In both cases, the physiological range of motion of the sacroiliac joint is permanently limited, which should be taken into account with regard to implant removal or more flexible techniques for stabilization of the sacroiliac joint. Full article

Chronic health problems, such as neurological conditions or long-lasting diseases, impair patients’ physical and mental functions with a subsequent reduction in overall quality of life. The purpose of this systematic review was to summarize how ballroom dance is being investigated as a rehabilitative method in individuals with neurological or medical diseases. A systematic literature search was conducted in databases including MEDLINE, SPORTDiscus, and PubMed. Of 728 articles located and titles and abstracts screened, 12 studies were included in this review. Study groups included Parkinson’s disease (4 studies), multiple sclerosis (2), spinal cord injury (1), stroke (1), dementia (1), cancer (2), and diabetes (1). Ballroom dances utilized included a combination of smooth and rhythm dances. Results revealed that ballroom dance is effective in improving gait functions, balance, and quality of life among various populations living with chronic neurological or medical conditions. In addition, ballroom dance is safe and associated with a low attrition rate (7.7%). There is increasing evidence to support ballroom dance as a feasible and effective intervention for adults with chronic neurological disorders or medical diseases. Further large-scale, randomized controlled trials are needed to examine the mechanisms, effectiveness, retention, and safety of ballroom dance as a rehabilitative intervention. Full article

Finite element musculoskeletal (FEMS) approaches using concurrent musculoskeletal and finite element models driven by motion data such as marker-based motion trajectory can provide insight into the interactions between the knee joint secondary kinematics, contact mechanics, and muscle forces in subject-specific biomechanical investigations. However, these data-driven FEMS systems have a major disadvantage that makes them challenging to apply in clinical environments, i.e., they require expensive and inconvenient equipment for data acquisition. In this study, we developed an FEMS model of the lower limb driven solely by inertial measurement unit sensors that include the tissue geometries of the entire knee joint, and that combine modeling of 16 muscles into a single framework. The model requires only the angular velocities and accelerations measured by the sensors as input. The target outputs (knee contact mechanics, secondary kinematics, and muscle forces) are predicted from the convergence results of iterative calculations of muscle force optimization and knee contact mechanics. To evaluate its accuracy, the model was compared with in vivo experimental data during gait. The maximum contact pressure (11.3 MPa) occurred on the medial side of the cartilage at the maximum loading response. The developed framework combines measurement convenience and accurate modeling, and shows promise for clinical applications aimed at understanding subject-specific biomechanics. Full article

It is unclear whether military shoes (combat boots and sports shoes) attenuate loading rate or affect force transfer during walking. Therefore, this study compared ground reaction forces (GRF) related to impact and force transfer between combat boots, military sports shoes, and running shoes. Ten army recruits walked over a walkway with two force plates embedded. GRF were measured when walking barefoot (for data normalisation) and with combat boots, military sports shoes, and running shoes. Loading rate, first and second peak forces, and push-off rate of force were computed along with temporal analysis of waveforms. Reduced loading rate was observed for the running shoe compared to the combat boot (p = 0.02; d = 0.98) and to the military sports shoe (p = 0.04; d = 0.92). The running shoe elicited a smaller second peak force than the combat boot (p < 0.01; d = 0.83). Walking with military shoes and combat boots led to larger force transfer than running shoes, potentially due to harder material used in midsole composition (i.e., styrene-butadiene rubber). Combat boots did not optimise load transmission and may lead, in a long-term perspective, to greater injury risk. Full article