Crowe Classification of Developmental Hip Dysplasia

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The Crowe classification quantifies the severity of developmental dysplasia of the hip by measuring how far the femoral head has migrated superiorly out of the true acetabulum. It was described in 1979 for planning total hip replacement in congenital dislocation of the hip and remains the reference grading system worldwide.

Accurate measurement requires a well-positioned standing AP pelvis radiograph with adequate exposure of both hips. The technique is reproducible but requires attention to landmarks.

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The Crowe grade is the single most important pre-operative classification for planning THA in the dysplastic hip because it predicts acetabular deficiency, femoral anatomy, leg length discrepancy, and the need for femoral shortening.

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• Measurement variability. The interteardrop line is not always clearly visible, and the femoral head-neck junction can be difficult to identify in severely deformed or previously operated hips. CT-based measurements improve reproducibility but are not required for routine clinical use.
• It does not classify acetabular deficiency directly. The Crowe system grades femoral migration but not the shape or bone stock of the acetabulum itself. For acetabular planning, supplement Crowe with the Hartofilakidis classification (low dislocation, high dislocation, true dislocation) or the AAOS acetabular bone deficiency classification (type I to VII) for bone stock quantification.
• Leg length discrepancy is not captured. A Crowe III hip with a moderate leg length discrepancy may be easier to manage than a Crowe II hip with a severe discrepancy that requires lengthening of the contralateral limb. Clinical leg length measurement complements the radiographic grade.
• It does not account for previous surgery. Patients who had open reduction, Salter osteotomy, or pelvic osteotomy in childhood have scarring and distorted anatomy that increase surgical difficulty regardless of Crowe grade. Previous surgery should be noted separately.
• Bilateral disease doubles the planning burden. When both hips are affected, staging, leg length balance, and acetabular bone stock become more complex than the Crowe grade alone predicts.
• The Hartofilakidis classification (dysplastic, low dislocation, high dislocation) is more commonly used by European surgeons and focuses on the relationship between the femoral head and the true acetabulum rather than a percentage measurement.
• The Eftekhar classification describes three types (A, B, C) based on the degree of subluxation and the adequacy of the acetabular roof, offering a simpler system for quick clinical use.