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Equalisation of leg lengths in total hip arthroplasty for patients with Crowe type‐IV developmental dysplasia of the hip: CLASSIFICATION AND MANAGEMENT

Aims There is no consensus about the best method of achieving equal leg lengths at total hip arthroplasty (THA) in patients with Crowe type‐IV developmental dysplasia of the hip (DDH). We reviewed our experience of a consecutive series of patients who underwent THA for this indication. Patients and Methods We retrospectively reviewed 78 patients (86 THAs) with Crowe type‐IV DDH, including 64 women and 14 men, with a minimum follow‐up of two years. The mean age at the time of surgery was 52.2 years (34 to 82). We subdivided Crowe type‐IV DDH into two major types according to the number of dislocated hips, and further categorised them into three groups according to the occurrence of pelvic obliquity or spinal curvature. Leg length discrepancy (LLD) and functional scores were analysed. Results Type‐I included 53 patients with unilateral dislocation, in which 25 (category A) had no pelvic obliquity or spinal deformity, 19 (category B) had pelvic obliquity with a compensated spinal curvature and nine (category C) had pelvic obliquity and decompensated spinal degenerative changes. Type‐II included 25 patients with one dislocated and one dysplastic hip, in which there were eight of category A, 15 of category B and two of category C. Pre‐operatively, there were significant differences between the anatomical and functional LLD in type‐IB (p = 0.005) and ‐IC (p < 0.001), but not in type‐IA, ‐IIA or ‐IIB. Post‐operatively, bony LLD increased significantly in types‐IB, ‐IC and ‐IIB, whereas functional LLD decreased significantly in each type except for IIA. The mean functional LLD decreased from 30.7 mm (standard deviation (SD) 18.5) pre‐operatively to 6.2 mm (SD 4.4) post‐operatively and the mean anatomical LLD improved from 35.8 mm (SD 19.7) pre‐operatively to 12.4 mm (SD 8.3) post‐operatively. Conclusion Pelvic and spinal changes are common in patients with Crowe type‐IV DDH and need to be taken into consideration when planning THA, in order to obtain equal leg lengths post‐operatively. The principal subdivisions of Crowe type‐IV DDH which we describe proved effective in achieving equal leg lengths and satisfactory outcomes.