Caroline Stewart

The complementary role of the plantarflexors, hamstrings and gluteus maximus in the control of stance limb stability during gait

This paper focuses on the contributions of the gluteus maximus, biceps femoris, gastrocnemius and soleus in maintaining the stability of the stance limb in the sagittal plane during the mid-stance phase of gait. In the absence of any one of these muscles, the potential compensatory changes in muscle activation are explored, the aim being to restore stability to the stance limb. The investigation was carried out by integrating musculoskeletal modelling, forward simulation and optimization techniques. We concluded that maintenance of stance limb stability requires a subtle interplay of muscle activations. Weakness in a single muscle is unlikely to be adequately compensated for by increasing or decreasing the activation of one muscle alone.

The study of muscle action during single support and swing phase of gait: clinical relevance of forward simulation techniques

Individual muscle function during single stance and swing phase of gait were analyzed using muscle driven forward simulation. The activation of each of 22 muscles in a musculoskeletal model with seven degrees of freedom were excluded from the forward simulation and the resulting changes in joint angles studied. A classification of muscle function during single support and swing phase of gait is presented. Altered joint kinematics due to the absence of individual muscle action is discussed in the light of pathological gait kinematics and clinical decision-making.

Selective dorsal rhizotomy for children with cerebral palsy: the Oswestry experience.

Background: Although three randomised control trials have shown that selective dorsal rhizotomy (SDR) reduces spasticity in children with cerebral palsy, a meta-analysis of the results demonstrated that the procedure conferred only small functional benefit on the patient. Aim: To determine whether applying strict criteria for patient selection as practised in Oswestry leads to improved outcomes, using gait analysis as an outcome measure. Methods: Ambulant children with cerebral palsy were selected for SDR using very strict clinical criteria. Instrumented gait analysis was used as the main outcome measure. Results: Of 53 children referred for the procedure, only 19 (35%) fulfilled our strict criteria for selection. These children underwent surgery and when pre- and post-SDR data were compared, they showed improvement in cosmesis of gait, clinical examination and temporal, kinetic and kinematic parameters of gait. After SDR the children walked, on average, 0.15 m/s faster, with a step length improvement of 0.11 m. Changes were seen at hip, knee and ankle, with those at the knee being most marked. A 0.3 grade improvement in knee extensor power on clinical examination led to a 13° improvement in stance phase knee extension. Knees also became less stiff, with an 82°/s improvement in the rate of flexion into swing phase. A functional tool (the GMFCS) applied retrospectively also confirmed post-operative improvement, with 15 of the 19 children improving by at least one level. Conclusion: Application of strict selection criteria when considering children for SDR leads to encouraging results as demonstrated by gait analysis and other measures.

The effect of osteoarthritis of the knee on the biomechanics of other joints in the lower limbs

The aim of this study was to examine the loading of the other joints of the lower limb in patients with unilateral osteoarthritis (OA) of the knee. We recruited 20 patients with no other symptoms or deformity in the lower limbs from a consecutive cohort of patients awaiting knee replacement. Gait analysis and electromyographic recordings were performed to determine moments at both knees and hips, and contraction patterns in the medial and lateral quadriceps and hamstrings bilaterally. The speed of gait was reduced in the group with OA compared with the controls, but there were only minor differences in stance times between the limbs. Patients with OA of the knee had significant increases in adduction moment impulse at both knees and the contralateral hip (adjusted p-values: affected knee: p < 0.01, unaffected knee p = 0.048, contralateral hip p = 0.03), and significantly increased muscular co-contraction bilaterally compared with controls (all comparisons for co-contraction, p < 0.01). The other major weight-bearing joints are at risk from abnormal biomechanics in patients with unilateral OA of the knee.

An investigation of the action of the hamstring muscles during standing in crouch using functional electrical stimulation (FES)

The hamstring muscle moment arms indicate that they act as hip extensors and knee flexors. Previous work using induced acceleration (IA) analysis and functional electrical stimulation (FES) has, however, revealed counter-intuitive muscle actions, particularly for biarticular muscles during the stance phase of normal gait. In conditions such as cerebral palsy the hamstrings have been associated with the development of pathological gait patterns, particularly crouch gait. This study examines the role of these muscles in the control of crouched standing postures. Five unimpaired adult subjects had their muscles stimulated during quiet standing in different degrees of crouch. Kinematic and kinetic changes were observed and measured using a 3D motion analysis system. The hamstring muscles were shown to act strongly to retrovert the pelvis and extend the hip. The action at the knee changes as crouch increases, moving from flexing to extending.

The effects of surgical lengthening of hamstring muscles in children with cerebral palsy – The consequences of pre-operative muscle length measurement

Children with cerebral palsy often undergo multiple orthopaedic surgical procedures in a single episode. Evidence of the effectiveness of individual components within the overall package is sparse. The introduction of musculoskeletal modelling in Oswestry has led to a more conservative management approach being taken with hamstring muscles for children walking in a degree of crouch. Muscles which were shown to be of at least normal length at initial contact were not surgically lengthened, as would have been the case previously. A retrospective review of 30 such patients was therefore possible, comparing 15 patients treated before the policy change who had their hamstrings lengthened with 15 treated after who did not. All patients had pre and post operative gait assessments and significant changes were observed for each group separately and for the two groups when compared. The comparison revealed that preserving the hamstrings does tend to reduce, and therefore normalize, the dynamic muscle length. Examination of the two patient groups separately, however, reveals a more complex picture with more global gait improvements seen when the hamstrings were lengthened. No absolute recommendation can be made to inform the clinical management of all children with normal to long hamstring muscles during gait. The final decision of whether to include a hamstring lengthening will need to take into account the characteristics of the individual child.

Gait analysis to guide a selective dorsal rhizotomy program.

Selective dorsal rhizotomy is a valuable surgical option to manage spasticity in children with bilateral cerebral palsy with the objective of improving function. Choosing the correct patient for rhizotomy requires considerable effort and a comprehensive evaluation. Instrumented three-dimensional gait analysis provides supporting evidence in the selection of the ideal child for SDR as well as enabling quantitative monitoring of outcome and post-operative management up to skeletal maturity.

Developing a technique to measure intra-limb coordination in gait : Applicable to children with cerebral palsy

Lower limb intra-limb coordination was investigated using sagittal plane kinematic data extracted from gait data recorded using a Vicon system (Vicon Motion Systems Ltd., Oxford, UK) of 20 normal (N) and 20 children with cerebral palsy (CP). Walking speed, maximum and minimum flexion and range of motion (ROM) were calculated. The repeatability of the data was checked by calculating the coefficient of multiple correlation. Data were also processed to determine angular velocity of hip and knee joints. A logical spreadsheet was devised to determine when both joints moved in the same direction (in-phase), in different directions (antiphase, AP) or if either joint was immobile (JS). In-phase joint motion was further subdivided into in-phase flexion (IPF) and in-phase extension (IPE), which comprises in-phase during stance phase (IPEst) and in-phase during swing phase (IPEsw). Data were processed using two threshold values for angular velocity below which the joint was considered to be immobile. The threshold values used were 0.05 degrees /% of gait cycle and 0.025 degrees /% of gait cycle. Children with cerebral palsy had reduced ROM and walked more slowly than normal children. There are significant differences between N and cerebral palsy coordination phases with marginally greater significance at the 0.05 degrees /% threshold for most component parameters; the exception being in-phase flexion. It is therefore suggested that this threshold value (0.05 degrees /%) is used for future work.

Changes in gait which occur before and during the adolescent growth spurt in children treated by selective dorsal rhizotomy

This paper presents long term follow up results from 17 children (6 girls, 11 boys, GMFCS levels II-IV), treated by means of selective dorsal rhizotomy (SDR). The particular focus is on the effect of the adolescent growth spurt on patients who had previously undergone SDR. The children were all assessed using 3D gait analysis, in combination with clinical examination at three time points-before SDR surgery (PRE), after SDR surgery when pre-adolescent (POST1) and post-adolescence (POST2). The total follow up period to POST2 was 8 years 6 months for girls and 9 years 5 months for boys. All children maintained or improved their GMFCS level. Positive changes in ranges of motion and gait were observed at POST1 and these were generally maintained over adolescence to POST2. The mean Gait Profile Score (GPS) had improved by 3.2 points (14.7-11.5) at POST1, with a non-significant deterioration of 0.3 over the adolescent growth spurt. These positive results reflect the total package of care for the children, involving careful pre-operative selection by a multidisciplinary team and post-operative management including intensive physiotherapy and maintenance in tuned ankle foot orthoses. Fifty-nine per cent of children had some additional orthopaedic surgery, mostly bony procedures. The overall benefits arising from their management need to be considered in the light of the likely deterioration experienced by this patient group. The results of this study support the use of SDR as part of a management strategy for carefully selected children with cerebral palsy with the aim of optimizing gait at skeletal maturity.

Abnormal loading and functional deficits are present in both limbs before and after unilateral knee arthroplasty

Highlights • Joint loading and function was assessed bilaterally in unilateral knee OA.• Gait data can be summarised using a functional classification approach.• Gait abnormailities in knee OA and following arthroplasty are relatively symmetrical.• Joint loading and function frequently remains abnormal following arthroplasty.• Pre-operative function (the Cardiff Classifier) can predict post-operative function.