Pterygium Syndromes / Congenital Popliteal Webbing

A congenital web across the flexor, popliteal, aspect of the knee holding it in fixed flexion, together with orofacial clefting, is popliteal pterygium syndrome. This is a rare autosomal-dominant condition caused by IRF6 mutations, allelic with Van der Woude syndrome, and it is a multisystem disorder: besides the popliteal web and fixed knee flexion, there are commonly orofacial clefts and lower-lip pits, genital anomalies, syndactyly and foot deformity such as equinovarus. So I would assess the whole child and make the genetic diagnosis. The key surgical consideration is the neurovascular anatomy within the web: the sciatic nerve and the popliteal vessels are frequently shortened and lie abnormally superficially, often along the free edge of the web, so the structure that limits straightening the knee is usually the shortened nerve rather than the skin or fascia. This means I cannot simply straighten the knee in one stage, because forcing extension risks a traction injury to the nerve and vascular compromise. Correction must be staged, with careful identification and protection of the neurovascular bundle, skin lengthening by multiple Z-plasty or local flaps, excision of the fibrotic band and graded release of the contracted soft tissues, sometimes accepting a degree of residual flexion to preserve nerve function; nerve-lengthening techniques have been described. I would also correct the associated foot deformity and manage the cleft and genital anomalies in a multidisciplinary team, with genetic counselling. The contrast is the multiple pterygium, or Escobar, syndrome, which has webs across multiple joints with scoliosis.