This paper will outline the development of a method of assessment, the Chailey Levels of Ability, how they fit with current theories of motor development and describe how they are used to prescribe treatment and equipment.

The Chailey Levels of Ability in lying , sitting and standing were developed in response to a clinical need for an assessment method which clearly identifies elements of achievement for children at low levels of physical ability and forms a basis for prescription of postural management programmes including treatment and equipment .

The Chailey Levels of Ability were initially developed during a period of clinical research investigating normal motor development and postural management for children with motor impairment . They have been further confirmed, developed and defined during ongoing clinical research, in particular a detailed study which investigated early motor development from a new perspective . Normal infants were studied in the positions of lying, sitting and standing, up to the onset of walking. Postures were observed and described from a biomechanical as well as neurodevelopmental viewpoint. This resulted in a definition of levels of physical ability. These levels were successfully transferred for use with children with cerebral palsy. Children with cerebral palsy follow the same progression as normal infants although move more slowly through this sequence and exhibit a poorer quality of movement.

Reliability & validity has been established for The Chailey Levels of Ability and are specified for use with individuals with motor impairment as an evaluative measure for motor ability, a prescriptive measure for the provision of postural management programmes and a predictive measure for the development of deformity.

Reliability studies on the lying and standing scales confirmed the appropriateness of the scales for use in cerebral palsy. For standing an inter-rater reliability co-efficient of 0.94 and intra-rater reliability co-efficient of 0.92 was established . In supine lying a Spearman rank order co-efficient of 0.908 was established and a 0.65 Kappa coefficient, in prone lying a Spearman rank order of 0.948 was established and a 0.73 Kappa coefficient .

Content and concurrent criterion validation has been demonstrated. The Chailey Levels of Ability were correlated with the Alberta Infant Motor Scale (correlation co-efficient 0.94) and the Gross Motor Function Measure (correlation co-efficient 0.92) with high Chailey Levels of Ability correlation in all domains.

Achievements in lying, sitting and standing correlated. No child sat independently until they had achieved level 4 lying in prone and supine and no child was able to stand independently until they had reached level 7 sitting and level 6 lying ability.

This method of assessment differs from methods which use neurological signs such as tone, postural reactions and reflexes as an indicator of motor skill as these have been shown to be unreliable and unrepeatable. In the Chailey approach to assessment reliable measures are used to indicate a child’s level of ability: areas of load-bearing, the relationship between different body parts when still and moving , the ability to move within as well as into and out of position and the ability to achieve symmetrical postures. Concomitant change is seen in motor ability and postural biomechanics. Scales of assessment which use the achievement of major milestones as indicators of improving ability are not always appropriate for children with severe motor impairment as the milestones are often unattainable. Other scales measure progress in terms of function alone and do not provide adequate analysis of posture to enable developmentally and bio-mechanically appropriate positioning equipment to be designed and do not consider the quality of movement which if not addressed lead to deformity. The Chailey Levels of Ability enable small changes in a child’s development to be charted where previously this was not possible. Identifiable small steps of progression enable treatment to be goal directed and postural support equipment can be designed to give developmentally and bio-mechanically appropriate postural support and feedback. This approach to appropriate equipment design has been named developmental biomechanics.

The Chailey Levels of Ability chart changes in the following areas:

• Areas of load-bearing
• Position of the pelvis, shoulder girdle, trunk, head, limbs
• Symmetry of position and whether this was voluntary or involuntary
• Ability to move within position
• Ability to move into and out of position
• Support required to be maintain the position
• Fine motor movements

The changes in these components determine the level of ability. All the components that are involved in establishing a level of ability are important, not one in isolation from the others. It is the details of these components that are important rather than the overall level of ability. Implications for treatment and management will arise from this detailed information.

The highest level of ability that a child performs at is his most newly acquired skill and is likely to require maximum effort to perform. It was noted during the study that children move from their highest level of ability to a more practised and stable posture to play. For example a child would move from lying ability level 6 back to level 5 prone to play with a toy.

The Chailey Levels of Ability can also be used to assessment a child’s level of ability once positioned in their equipment and thereby determine the appropriateness of the equipment for different types of functional activity.

This scale of assessment offers a method of assess motor ability in children with severe neurological impairment and can provide a basis for prescription of equipment and expectations regarding a child’s functional ability.

REFERENCES