Yener Temelli

Human spastic Gracilis muscle isometric forces measured intraoperatively as a function of knee angle show no abnormal muscular mechanics

BACKGROUND To show whether mechanics of activated spastic muscle are representative of the functional deficiencies clearly apparent in the joints, our goal was to test the following hypotheses: (1) The muscles joint range of force exertion is narrow, and (2) high muscle forces are available at low muscle length. METHODS During remedial surgery, we measured the forces of the Gracilis muscle of spastic cerebral palsy patients (n=7, 10 limbs tested) as a function of knee joint angle from flexion (120°) to full extension (0°). FINDINGS The spastic Gracilis exerted non-zero forces for the entire knee angles studied. For four limbs, the peak force was exerted at the highest length. For the remainder limbs, the closest knee angle of peak force exertion to 120° was 66°. Maximally 79.1%, and for most limbs only a much lower percentage (minimally 22.4%) of peak Gracilis force (mean 41.59N (SD 41.76N)) was available at 120° knee flexion. Moreover, a clinical metric was obtained showing that the occurrence of a contracture was not correlated significantly with key determinants of knee angle-Gracilis force characteristics. INTERPRETATION Our hypotheses are rejected: the spastic Gracilis has no narrow operational joint range of force exertion and no supreme active resistance capacity to stretch at low length. We conclude that if activated alone, spastic muscle shows no abnormal mechanics representative of joint movement disorder. Simultaneous stimulation of other muscles as in daily activities may change this situation.

Intraoperative experiments show relevance of inter-antagonistic mechanical interaction for spastic muscle's contribution to joint movement disorder

BACKGROUND Recent intra-operative knee angle-muscle force data showed no abnormal muscular mechanics (i.e., a narrow joint range of muscle force exertion and peak muscle force availability at flexed joint positions), if the spastic gracilis muscle was stimulated alone. This can limit inter-muscular mechanical interactions, which have been shown to affect muscular mechanics substantially. We aimed at testing the hypothesis that the knee angle-muscle force curves of the spastic gracilis muscle activated simultaneously with a knee extensor are representative of joint movement disorder. METHODS Experiments were performed during remedial surgery of spastic cerebral palsy patients (n=6, 10 limbs tested). Condition-I: muscle forces were measured in flexed knee positions (120° and 90°) after activating the gracilis exclusively. Condition-II: knee angle-muscle force data were measured from 120° to full extension after activating the vastus medialis, simultaneously. FINDINGS Condition-II vs. I: Inter-antagonistic interaction did not consistently cause a gracilis force increase. Condition-II: Peak muscle force=mean 47.92 N (SD 22.08 N). Seven limbs showed availability of high muscle force in flexed knee positions (with minimally 84.8% of peak force at 120°). Knee angle-muscle force curves of four of them showed a local minimum followed by an increasing force (explained by an increasing passive force, indicating muscle lengths unfavorable for active force exertion). High active gracilis forces measured at flexed knee positions and narrow operational joint range of force exertion do indicate abnormality. The remainder of the limbs showed no such abnormality. INTERPRETATION Our hypothesis is confirmed for most, but not all limbs tested. Therefore, tested inter-antagonistic mechanical interaction can certainly, but not exclusively be a factor for abnormal mechanics of the spastic muscle.

Effects of unilateral backpack carriage on biomechanics of gait in adolescents: a kinematic analysis

OBJECTIVE The aim of this study was to analyze the biomechanical alterations during unilateral backpack carriage in adolescents and to compare the kinematic parameters of the loaded and unloaded sides. METHODS Twenty adolescents (mean age: 13 ± 1.2 years) were assessed during walking with no backpack and with a backpack on one shoulder. The kinematic parameters of a gait at a self-selected speed were analyzed using motion analysis. Specific kinematic peak points were compared between asymmetric walking; unloaded, loaded side and mean of unloaded walking. RESULTS Peak ankle dorsal flexion, mean knee varum angle, peak value of hip extension and range of pelvic rotation decreased; and knee flexion at initial contact, hip adduction angle, mean pelvic anterior tilt and mean pelvic obliquity increased on the loaded side relative to the unloaded side and unloaded walking. Decreased maximum hip extension during late stance, increased hip adduction, elevated pelvis and increased anterior pelvic tilt were seen on the loaded side and the pelvis was lowered, ankle dorsal flexion increased and the hip was abducted on the unloaded side as a counter effect. CONCLUSION Both the unloaded and loaded sides were affected by asymmetrical backpack carriage. The biomechanical alterations seen in asymmetrical backpack carriage may put some extra load on the lumbar vertebral joints and altered frontal knee biomechanics contribute to low back pain and pathologies in the knee joint.

Discrimination of abnormal gait parameters due to increased femoral anteversion from other effects in cerebral palsy

The effects of increased femoral anteversion (IFA) on gait pattern have a complex relationship with other orthopaedic and neurological abnormalities of cerebral palsy (CP). The aim of this study was to differentiate the effects of IFA from other factors in CP. The four groups in this study included: 15 typically developing children (Group: TDC) (age: 9.7 ± 0.5); 14 TDC with IFA (7.5 ± 1.7) (Group: TDC-IFA); 8 CP participants with IFA (age: 6.3 ± 1.7) (Group: CP IFA); and 10 CP participants with nearly normal femoral anteversion (age: 10.3 ± 4.7) (Group: CP-NFA). Altered peak knee-extension angle and stance-time, increased internal hip-rotation, internal foot-progression (p≤0.05) were influenced by IFA in both groups of CP-NFA and TDC-IFA. For the TDC groups; pelvic-rotation increased and peak knee and hip-extension, knee flexion-moment, peak knee-power generation in late-stance decreased among children with IFA (p≤0.05). For CP children; anterior pelvic-tilt, hip-flexion and peak knee-extension, hip power-absorbsion and generation, and peak knee power-absorsion (K3) increased and peak knee-flexion was delayed by IFA (p≤0.05). Therefore, IFA effects are different in CP and TDC. Peak knee-extension angle increased in TDC and decreased in CP with IFA. Besides the well known gait parameters related to IFA which are increased internal hip-rotation and foot-progression angle, it is recognised that peak knee-extension and stance-time are also influenced. Therefore, before muscle lengthening, femoral derotational osteotomy should be considered in the early stages of growth in CP to improve pelvic stability and the knee extensor mechanism.

Treatment approaches to flexion contractures of the knee

The knee is the most affected joint in children with cerebral palsy. Flexion contracture of the knee is the cause of crouch gait pattern, instability in stance phase of gait, and difficulties during standing and sitting, and for daily living activities. It may also cause patella alta, degeneration of the patellofemoral joint, and stress fractures of the patella and tibial tubercle in young adults. Children with cerebral palsy may even give up walking due to its high energy demand in the adult period. The purpose of this article is to review the causes of the knee flexion contractures, clinical and radiological evaluations, and treatment principles in children with cerebral palsy. The biomechanical reasons of knee flexion deformity are discussed in detail in the light of previous studies and gait analysis data.

Effects of inter-synergistic mechanical interactions on the mechanical behaviour of activated spastic semitendinosus muscle of patients with cerebral palsy

Previous physiological experiments and finite element modelling indicate that inter-synergistic epimuscular myofascial force transmission (EMFT) between co-activated muscles has a potential to affect healthy muscles contribution to joint moment and joint range of movement. This is quite relevant for patients with cerebral palsy (CP) since, amplitude of spastic muscles force and the joint range of force exertion are central to the joint movement limitation. Stiffness of activated spastic muscle is also a determinant for pathological joint movement. However, assessments of effects of inter-synergistic EMFT on the mechanical behaviour of spastic muscle are lacking. Those assessments require measurement during surgery of activated spastic muscles forces directly at its tendon and as a function of joint angle. Employing this methodology, the aim was to test the following study hypotheses: added activation of semimembranosus (SM) and gracilis (GRA) muscles of patients with CP changes (1) force, (2) stiffness and (3) joint range of force exertion of activated spastic semitendinosus (ST) due to inter-synergistic EMFT. Isometric spastic ST forces were measured intraoperatively (12 limbs of 7 patients (mean age 8 years 9 months) for knee angles from flexion (120°) to full extension (0°). Conditions I and II: spastic ST was activated alone, and simultaneously with its synergists SM and GRA muscles, respectively. Condition II did increase activated spastic STs forces significantly (by 33.3%), but did not change its stiffness and joint range of force exertion, confirming only study hypothesis 1. Therefore, we conclude that inter-synergistic EMFT affects forces exerted at spastic ST tendon, but not other characteristics of its angle-force relationship.

Effects of antagonistic and synergistic muscles’ co-activation on mechanics of activated spastic semitendinosus in children with cerebral palsy

OBJECTIVES Most activities involve co-activation of several muscles and epimuscular myofascial force transmission (EMFT) can affect their mechanics. This can be relevant for spastic muscles of cerebral palsy (CP) patients. Isometric spastic semitendinosus (ST) forces vs. knee angle (KA-FST) data were collected intra-operatively to test the following hypotheses: (i) Inter-antagonistic EMFT elevates FST, (ii) changes the shape of KA-FST characteristics, (iii) reduces the muscles joint range of force exertion (Range-FST) and (iv) combined inter-antagonistic and synergistic EMFT further changes those effects. METHODS 11 limbs of 6 patients with CP (mean (SD) = 7.7 (4.7) years; GMFCS levels = II-IV) were tested in 3 conditions from 120° to full extension: ST activated (I) exclusively, (II) simultaneously with an antagonist, and (III) with added activation of synergists. RESULTS Condition II increased FST (e.g., peak force = 87.6 N (30.5 N)) significantly (by 33.6%), but condition III caused no further change. No condition changed the muscles wide Range-FST (100.7° (15.9°)) significantly. Therefore, only the first hypothesis was confirmed. CONCLUSIONS Co-activating its antagonist elevates forces of activated spastic ST substantially, but does not change its joint range of force exertion. Added activation of its synergists causes no further effects. Therefore, EMFT effects in CP can be relevant and need to be tested in other knee flexors.

Intra-operatively measured spastic semimembranosus forces of children with cerebral palsy

The knee kept forcibly in a flexed position is typical in cerebral palsy. Using a benchmark, we investigate intra-operatively if peak spastic hamstring force is measured in flexed knee positions. This tests the assumed shift of optimal length due to adaptation of spastic muscle and a decreasing force trend towards extension. Previously we measured spastic gracilis (GRA) and semitendinosus (ST) forces. Presently, we studied spastic semimembranosus (SM) and tested the following hypotheses: spastic SM forces are (1) high in flexed and (2) low in extended positions. We compared the data to those of GRA and ST to test (3) if percentages of peak force produced in flexed positions are different. During muscle lengthening surgery of 8 CP patients (9years, 4months; GMFCS levels=II-IV; limbs tested=13) isometric SM forces were measured from flexion (120°) to full extension (0°). Spastic SM forces were low in flexed knee positions (only 4.2% (3.4%) and 10.7% (9.7%) of peak force at KA=120° and KA=90° respectively, indicating less force production compared to the GRA or ST) and high in extended knee positions (even 100% of peak force at KA=0°). This indicates an absence of strong evidence for a shift of optimal muscle length of SM towards flexion.

Interaction of Ligament Bundles and Articular Contacts for the Simulation of Passive Knee Flexion

The purpose of this study is to investigate the effects of anterior bundle of ACL (aACL), anterior portion of PCL (aPCL), anterior and deep portions of MCL (aMCL, dMCL) and the tibio-femoral articular contacts on to passive knee motion. A three-dimensional simplistic anatomical dynamic model, based on the literature was used as a reference. This reference model attaches the bundles of the ligaments on medial and the lateral spherical condyles of the femur and tibial plateau giving us a representation close enough to a normal natural tibio-femoral joint, but does not allow to study abnormalities of the knee kinematics due to the assumptions of the femur shape. The proposed three-dimensional dynamic tibio-femoral model, however includes the isometric fascicles, aACL, aPCL, aMCL, dMCL, and irregularly shaped medial- lateral contact surfaces. The approach taken in this model is capable of ligament and bone surface modifications that will enable us to analyze bone shape and ligament related abnormalities of knee kinematics.

Weakening iliopsoas muscle in healthy adults may induce stiff knee pattern

Objective The goal of the present study was to investigate the relationship between iliopsoas muscle group weakness and related hip joint velocity reduction and stiff-knee gait (SKG) during walking in healthy individuals. Methods A load of 5% of each individuals body weight was placed on non-dominant thigh of 15 neurologically intact, able-bodied participants (average age: 22.4 ± 0.81 years). For 33 min (135 s × 13 repetitions × 5 s rest), a passive stretch (PS) was applied with the load in place until hip flexor muscle strength dropped from 5/5 to 3+/5 according to manual muscle test. All participants underwent gait analysis before and after PS to compare sagittal plane hip, knee, and ankle kinematics and kinetics and temporo–spatial parameters. Paired t-test was used to compare pre- and post-stretch findings and Pearson correlation coefficient (r) was calculated to determine strength of correlation between SKG parameters and gait parameters of interest (p < 0.05). Results Reduced hip flexion velocity (mean: 21.5%; p = 0.005) was a contributor to SKG, decreasing peak knee flexion (PKF) (−20%; p = 0.0008), total knee range (−18.9%; p = 0.003), and range of knee flexion between toe-off and PKF (−26.7%; p = 0.001), and shortening duration between toe-off to PKF (−16.3%; p = 0.0005). Conclusion These findings verify that any treatment protocol that slows hip flexion during gait by weakening iliopsoas muscle may have great potential to produce SKG pattern combined with reduced gait velocity.