MEASUREMENT OF THE FORCES AND MOVEMENTS INVOLVED IN NEONATAL HIP TESTING

The screening for Developmental Dysplasia of the Hip in infants relies on the two manipulative tests developed by Ortolani(6) and Barlow(7) which are often poorly performed. This study investigated the forces a pplied and the sequences of physical manoeuvres underlying the tests i n order to define a standard of safe practice. Eight subjects examined the hips of two training models that closely simulated the behaviour of a range of infant hip pathologies. The forces applied and transduce r system. The analysis concentrated on the peak forces and the biomech anical conditions necessary to detect an abnormality. The models' legs had to be abducted beyond certain critical angles in order to disloca te and relocate an unstable femoral head and the magnitude of the forc e required to dislocate the femoral head was significantly less than t he peak force applied (72 N vs 33 N, p < 0.001). Also, the Palmen(8) t est, a less well known technique, provided the same level of diagnosti c performance as the Barlow test but with a lower peak applied force ( 28 N vs 47 N, p < 0.001). Changes are therefore necessary to the train ing programmes for medical staff to ensure that the range of abduction during the manoeuvres is large enough to encompass the likely range o f critical angles and that the forces applied are just sufficient so a s not to overstress the joints.