DDH Treatment Options

The topic repeatedly refers to the spica cast, the "human position", and an "immediate MRI in spica to confirm reduction", but never develops why post-reduction imaging is mandatory or the cast-specific complications - both are examinable, and getting the cast wrong is a direct cause of the AVN the whole topic warns against.

• Why image inside the cast - you must PROVE a concentric reduction. After a closed reduction the femoral head is hidden by plaster, and a hip that looks reduced on the table can be non-concentrically reduced or frankly re-dislocated once cast. Post-reduction cross-sectional imaging - CT (fast, low-dose limited slices) or MRI (no radiation, also shows the cartilaginous head and soft-tissue obstacles) - confirms the head is concentrically seated in the acetabulum. A non-concentric reduction (persistent medial gap/pooling) must not be accepted - it will fail and predisposes to dysplasia and AVN, so it mandates re-casting or open reduction rather than "waiting and hoping".
• Apply the cast in the safe "human position", never forced abduction. The spica is moulded in ~100° hip flexion, 40-50° abduction and neutral rotation - the same AVN-avoiding position emphasised throughout. Forced/extreme abduction to "hold" a borderline reduction is the classic error that occludes the posterosuperior head vessels and causes AVN (the Gardner review specifically linked ≥60° abduction immobilisation to AVN).
• Cast-specific complications to counsel and watch for. Vascular/neurological compromise of the limb (over-tight or over-abducted cast - check perfusion and the femoral nerve), pressure sores (bony prominences, cast edges - especially in the non-verbal infant), cast (superior mesenteric artery) syndrome with vomiting in body casts, skin maceration/soiling at the perineum, and loss of position/re-dislocation inside the cast. Cast changes are done under anaesthesia (typically at ~6 weeks) with re-check of position.

The topic notes that "residual dysplasia may occur despite successful reduction", that the "acetabular index should normalize by age 2-3 years", and that a persistently high index "may need later osteotomy" - but never develops the actual decision: how long to allow remodelling before intervening, and how to choose the operation. This is a classic paediatric-hip viva progression.

• A concentric reduction is itself the main treatment for the acetabulum. Acetabular development depends on a concentrically reduced femoral head providing the growth stimulus - so achieving and holding a concentric reduction lets the majority of acetabular dysplasia remodel spontaneously. The evolution (trajectory) of the acetabular index over serial radiographs is the best predictor of persistent dysplasia - an index that is steadily falling toward normal can be observed, whereas one that plateaus or stays high will not correct on its own.
• How long to wait - the remodelling window. Most acetabular improvement occurs in the first 18-24 months after reduction, with useful remodelling potential continuing to about 4-5 years. A reasonable rule is to observe with serial films while the index is improving, and to consider a pelvic (acetabular) procedure once it is clear that spontaneous correction has stalled (persistently elevated acetabular index / low centre-edge angle beyond the expected window, typically after ~age 3-5), rather than operating on every high index early.
• Choose the osteotomy by triradiate status and the deformity. With an open triradiate cartilage in a young child, a reshaping acetabuloplasty (Pemberton, hinging on the triradiate; Dega for posterior deficiency, e.g. neuromuscular) or a redirectional Salter innominate osteotomy (hinging on the pubic symphysis) is used; once the triradiate closes (adolescent/adult), a redirectional periacetabular [Ganz] osteotomy is required (developed in the periacetabular-osteotomy topic). A coexisting femoral deformity (excess anteversion/valgus) may need a varus derotation femoral osteotomy alongside.
• The reduction must be concentric and AVN-free first. As the long-term Salter data show, durability depends on a concentric, avascular-necrosis-free reduction - a pelvic osteotomy cannot rescue a non-concentric or AVN-damaged hip, so fix the reduction before, or reserve/stage, the osteotomy.