Hip joint pain in children with cerebral palsy and developmental dysplasia of the hip: why are the differences so huge?

BACKGROUNDS Non-traumatic hip dislocation in children is most often observed in the course of developmental dysplasia of the hip (DDH) and infantile cerebral palsy. The risk of pain sensations from dislocated hip joint differentiates the discussed groups of patients. Will every painless hip joint in children with cerebral palsy painful in the future? METHODS Material included 34 samples of joint capsule and 34 femoral head ligaments, collected during open hip joint reduction from 19 children with CP, GMFCS level V and from 15 children with DDH and unilateral hip dislocation. All the children were surgically treated.The density of nociceptive fibres was compared between the children with CP and DDH, using S-100 and substance P monoclonal antibodies. RESULTS More frequent positive immunohistochemical reaction to S-100 protein concerned structures of the femoral head ligaments in children with CP and cartilage losses on the femoral head, when compared to the same structures in children with DDH (p = 0.010). More frequent were found positive immunohistochemical reactions for S-100 protein in the joint capsules of children with cartilage losses (p = 0.031) and pain ailments vs. the children with DDH (p = 0.027). More frequent positive reaction to substance P concerned in femoral head ligaments in CP children and cartilage lesions (p = 0.002) or with pain ailments (p = 0.001) vs. the DDH children. CONCLUSIONS Surgical treatment of hip joint dislocation should be regarded as a prophylactics of pain sensations, induced by tissue sensitisation, inflammatory process development or articular cartilage defects.