Reliability of Range of Movement Measurements in Cerebral Palsy

Scientific question The aim is to investigate the inter-rater reliability of passive range of motion (pROM) measurement with goniometer of knee extension and ankle dorsiflexion for children with unilateral spastic cerebral palsy (USCP) and secondary to explore to what extent spasticity influences the reliability.

Overview of the field Evaluating joint mobility is commonly used and important for physicians and physiotherapists assessing and treating children with cerebral palsy, to early detect occurrence of joint contracture. The primarily used method to measure joint pROM is to use a manual goniometer, even if techniques using a smartphone or other electronic device has been demonstrated (Herrero et al. 2011, Ferriero et al. 2013, Hancock et al. 2018). Previous studies indicate that traditional goniometry is usually reliable both for ankle and knee both in individuals with and without spastic muscles (Brosseau et al. 2001, Allington et al. 2002, McWhirk et al. 2006, Konor et al. 2012) even if some authors indicate that there is a considerable variability among children with spasticity (McDowell et al. 2000).

To our knowledge no earlier study has investigated children with hemiplegic cerebral palsy to evaluate the influence of spasticity on pROM measurements. The idea is to use the child as its own control having both a spastic and a non spastic limb.

Project description

Participants Almost all children with cerebral palsy in Sweden are linked to a local habilitation unit where regular assessments are made by the child's physiotherapist. Information from the national quality registry and follow-up program for individuals with cerebral palsy (CPUP) indicates that there are approximately 140 children with unilateral spastic cerebral palsy (USCP) in Skåne. Families and children (age 2 - 17 years) with USCP linked to habilitation units in Skåne will be asked to participate in the study trough written letter and/or by phone call. When applicable this will be part of the child´s regular and planned assessment. Children with other diagnoses than USCP will be excluded. Children with surgery on the lower extremity within the last year or botox administration to the lower extremity within the last 3 month will also be excluded.

Methods The child will be assessed during one session of around 30-60 min. ROM measurements of knee extension and ankle dorsiflexion will be made on each child's both legs by two investigators with a standard two axis goniometer used in regular practice. The goniometer consists of two 20 cm arms attached in one end by a node and with a grade scale. The CPUP manual describes standardized patient positions and goniometer arm position for ROM in different joints.

For popliteal angle the child is positioned supine with the measured legs hip flexed to 90 degree while the other leg is fixed in extended position. The node of the goniometer is positioned lateral over the knee joint, the fixed arm aligned with femur and pointing towards the greater trochanter, the moving arm is held parallel to the anterior margin of tibia and pointing to the lateral malleolus.

Knee extension is examined with the child in supine position and extended knee, the node of the goniometer is positioned lateral over the knee joint center of rotation, the fixed arm aligned with femur and pointing towards the greater trochanter, the moving arm is held parallel to the anterior margin of tibia and pointing to the lateral malleolus. Knee extension deficit is noted as a negative value.

ROM for the ankle joint is measured with extended knee. The child is positioned in supine position. The subtalar joint is stabilized by the examinator fixating the calcaneus. The intertarsal movement is inhibited by slightly inverting the forefoot. The fixed arm of the goniometer will be parallel to the anterior margin of the tibia and the moving arm parallel to the lateral margin of the foot. 90 degree in the ankle will be noted as 0 degree. Dorsal flexion less than 0 degree will be noted as a negative value.

The two investigators will do measurements separate and blinded from each other. Data including age, sex, spastic side (right/left), Gross Motor Classification System level (GMFCS), use of orthosis and level of spasticity according to Ashworth. Level of spasticity on the spastic side will be a consensus decision by the two investigators.

Statistics Statistical power analyses calculations imply that the planned study need at least 32 children to examine 64 legs. Inter-rater reliability will be evaluated using Intra-class correlation coefficient (ICC). Limits of agreement analysis will also be used. Effect of spasticity on the reliability of pROM measurement will be evaluated comparing the ICC on the spastic leg to the non spastic leg.

Ethics The risk of causing physical harm to the research participants is considered very low. Evaluating pROM is part of regular assessment of these children. The time consumed by participating in the study might be extra compared to normal follow up but is very limited and proportional to valuable information that might be the result of the study. To minimize the pressure on families to participate, families under treatment from the researchers will primarily not be approached. Data collected will be stored in a safe way on encrypted hard drive. Personal numbers will be replaced by serial numbers and only the main researcher will have the code key.

Importance The risk of joint contracture is a major cause for concern in the growing child with cerebral palsy and something that is closely monitored by physicians and physiotherapists. Delayed diagnosis of joint contracture often leads to surgical release, a last option of treatment. The main tool for monitoring is by ROM measurements on a regular basis. Early detection of a decreasing ROM is vital for successful treatment and optimal outcome over time. The current study will add further knowledge on how ROM measurements can be interpreted and so hopefully lead to improved care for this group of children. The results will also be of importance to the research field for planning future studies and interpreting results.