Summary of Congenital Malformations of Pediatric Wrist and Forearm

## Introduction The pediatric forearm can be affected by several congenital conditions that alter bone growth, joint relationships, and function. This material focuses on common congenital forearm deformities and conditions described in the provided text: proximal radioulnar synostosis (PRUS), congenital pseudarthrosis of the ulna or radius (often associated with neurofibromatosis), and Madelung’s deformity. The goal is to explain pathology, evaluation, treatment principles, and expected outcomes in clear, study-friendly sections. > Definition: Proximal radioulnar synostosis (PRUS) is a congenital fusion of the proximal radius and ulna that limits or eliminates forearm rotation. > Definition: Congenital pseudarthrosis is a segment of bone replaced by fibrous tissue producing a false joint; in the forearm it most commonly affects the ulna and is often associated with neurofibromatosis. > Definition: Madelung’s deformity is a growth disturbance of the distal radius causing radial and palmar angulation, often related to an abnormal palmar ligament (Vickers’ ligament) and localized physeal arrest. ## Proximal Radioulnar Synostosis (PRUS) ### Key features - Forearm rotation (supination/pronation) is absent or markedly limited; often fixed in pronation. - Children usually noticed between ages 2 and 6 because infants compensate with shoulder/wrist motion. - The synostosis often begins as cartilage and ossifies over time; it is typically proximal and variable in length. - Radial head dislocation may coexist. ### Clinical presentation and examination - Observe the resting position; note degree of fixed pronation (measure at radial styloid and ulnar head to avoid wrist or shoulder compensation). - Bilateral in ~60% of children; ~40% have >60° pronation and more functional limitation. - Occupational therapy assessment is useful to determine functional deficits and ideal forearm position. ### Imaging - Radiographs show the synostosis once ossified and reveal radial head position and synostosis length. ### Treatment principles - Resection of the synostosis to restore rotation has historically failed in most cases (literature shows failure in 22 of 23 forearms for simple resection). - Interposition of vascularized fascial flaps may reduce recurrence but gains in rotation are small. - Corrective rotational osteotomy through the fusion mass (derotation osteotomy) is the preferred surgical option when severe fixed pronation (>60°) impairs function. - Timing of surgery is individualized: options range from before school age to waiting until the child chooses intended occupation. ### Operative technique highlights - Approach: dorsal longitudinal incision along subcutaneous ulnar border; subperiosteal dissection around synostosis. - Fixation: Derotation osteotomy through synostosis with small Steinmann pins or plate/screws; Steinmann pin via olecranon apophysis may be used for intramedullary support. - Target rotational alignment: for unilateral cases, 0–15° pronation is common; recommended dominant forearm position often ~10–20° pronation. - Other options for severe deformity: two-stage osteoclasis, gradual correction with Ilizarov external fixation, or osteotomy distal to synostosis. ### Complications and outcomes - Frequent complications: compartment syndrome, vascular compromise, radial (posterior interosseous) nerve palsy, loss of correction, and need for repeat osteotomy. - Nerve palsies reported often recover within weeks (examples: radial nerve palsies resolving at 4–8 weeks). - Rotational osteotomy reliably realigns the forearm; improvements in hand positioning and daily activities are common and malalignment does not recur. Fun fact: Children with PRUS often compensate remarkably well using shoulder abduction/adduction and wrist motion, which is why diagnosis can be delayed until preschool age. ## Congenital Pseudarthrosis of the Ulna or Radius ### Epidemiology and etiology - Rare condition; commonly associated with neurofibr