Nicky Thompson

Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis.

An unbiased understanding of foot kinematics has been difficult to achieve due to the complexity of foot structure and motion. We have developed a protocol for evaluation of foot kinematics during barefoot walking based on a multi-segment foot model. Stereophotogrammetry was used to measure retroreflective markers on three segments of the foot plus the tibia. Repeatability was evaluated between-trial, between-day and between-tester using two subjects and two testers. Subtle patterns and ranges of motion between segments of the foot were consistently detected. We found that repeatability between different days or different testers is primarily subject to variability of marker placement more than inter-tester variability or skin movement. Differences between inter-segment angle curves primarily represent a shift in the absolute value of joint angles from one set of trials to another. In the hallux, variability was greater than desired due to vibration of the marker array used. The method permits objective foot measurement in gait analysis using skin-mounted markers. Quantitative and objective characterisation of the kinematics of the foot during activity is an important area of clinical and research evaluation. With this work we hope to have provided a firm basis for a common protocol for in vivo foot study.

Dynamic foot movement in children treated for congenital talipes equinovarus.

The aim of this study was to define objectively gait function in children with treated congenital talipes equinovarus (CTEV) and a good clinical result. The study also attempted an analysis of movement within the foot during gait. We compared 20 children with treated CTEV with 15 control subjects. Clinical assessment demonstrated good results from treatment. Three-dimensional gait analysis provided kinematic and kinetic data describing movement and moments at the joints of the lower limb during gait. A new method was used to study movement within the foot during gait. The data on gait showed significantly increased internal rotation of the foot during walking which was partially compensated for by external rotation at the hip. A mild foot drop and reduced plantar flexor power were also observed. Dorsiflexion at the midfoot was significantly increased, which probably compensated for reduced mobility at the hindfoot. Patients treated for CTEV with a good clinical result should be expected to have nearly normal gait and dynamic foot movement, but there may be residual intoeing, mild foot drop, loss of plantar flexor power with compensatory increased midfoot dorsiflexion and external hip rotation.

Muscle strength and walking ability in Diplegic Cerebral Palsy: Implications for assessment and management

Muscle weakness is a recognised problem in children with Cerebral Palsy (CP). Changes in the understanding of motor control, and progress in the treatment of spasticity, have led to a greater appreciation that spastic muscles are also weak. In recent years weakness has been identified in isolated muscle groups, but studies quantifying the degree and distribution of weakness in multiple muscles remain limited. This study evaluated isometric lower limb muscle strength in 50 ambulant children with CP/Spastic Diplegia (mean age 11 years 7 months) at GMFCS levels I (n=14), II (n=26) and III (n=10). Muscle strength was compared with 15 control children (mean age 11 years 1 month) using the same protocol. Six muscle groups in both lower limbs were measured using a digital dynamometer. All lower limb muscles were significantly weaker in the CP children than in healthy children (p<0.05) except for the hip extensors. Muscle strength ranged from 43% to 90% of control values depending on the muscle group, with the knee extensors measured at 30° being the relatively weakest group. There was a significant difference in strength between GMFCS levels in 4/6 muscle groups with a progressive reduction in strength in all muscle groups with increasing walking difficulty from GMFCS levels I to III. The greatest difference in strength between independent walkers and those dependent on walking aids was in the hip abductors and knee extensors at 30°, which are key muscle groups in sagittal and coronal plane walking stability. This has implications in targetting strength training to maximise functional outcomes.

Gait compensations caused by foot deformity in cerebral palsy

Cerebral palsy (CP) is a complex syndrome, with multiple interactions between joints and muscles. Abnormalities in movement patterns can be measured using motion capture techniques, however determining which abnormalities are primary, and which are secondary, is a difficult task. Deformity of the foot has anecdotally been reported to produce compensatory abnormalities in more proximal lower limb joints, as well as in the contralateral limb. However, the exact nature of these compensations is unclear. The aim of this paper was to provide clear and objective criteria for identifying compensatory mechanisms in children with spastic hemiplegic CP, in order to improve the prediction of the outcome of foot surgery, and to enhance treatment planning. Twelve children with CP were assessed using conventional gait analysis along with the Oxford Foot Model prior to and following surgery to correct foot deformity. Only those variables not directly influenced by foot surgery were assessed. Any that spontaneously corrected following foot surgery were identified as compensations. Pelvic rotation, internal rotation of the affected hip and external rotation of the non-affected hip tended to spontaneously correct. Increased hip flexion on the affected side, along with reduced hip extension on the non-affected side also appeared to be compensations. It is likely that forefoot supination occurs secondary to deviations of the hindfoot in the coronal plane. Abnormal activity in the tibialis anterior muscle may be consequent to tightness and overactivity of the plantarflexors. On the non-affected side, increased plantarflexion during stance also resolved following surgery to the affected side.

The use of minimally invasive techniques in multi-level surgery for children with cerebral palsy: PRELIMINARY RESULTS

This study compares the initial outcomes of minimally invasive techniques for single-event multi-level surgery with conventional single-event multi-level surgery. The minimally invasive techniques included derotation osteotomies using closed corticotomy and fixation with titanium elastic nails and percutaneous lengthening of muscles where possible. A prospective cohort study of two matched groups was undertaken. Ten children with diplegic cerebral palsy with a mean age of ten years six months (7.11 to 13.9) had multi-level minimally invasive surgery and were matched for ambulatory level and compared with ten children with a mean age of 11 years four months (7.9 to 14.4) who had conventional single-event multi-level surgery. Gait kinematics, the Gillette Gait Index, isometric muscle strength and gross motor function were assessed before and 12 months after operation. The minimally invasive group had significantly reduced operation time and blood loss with a significantly improved time to mobilisation. There were no complications intra-operatively or during hospitalisation in either group. There was significant improvement in gait kinematics and the Gillette Gait Index in both groups with no difference between them. There was a trend to improved muscle strength in the multi-level group. There was no significant difference in gross motor function between the groups. We consider that minimally invasive single-event multi-level surgery can be achieved safely and effectively with significant advantages over conventional techniques in children with diplegic cerebral palsy.