PURPOSE Many anecdotes linking w-sitting to hip dysplasia and other musculoskeletal issues seem to be common place; however, there is a paucity of systematic investigation into the relationship between w-sitting and hip dysplasia. This discrepancy may lead to misconceptions and attempts to solve a problem that is not even an issue. The purpose of this study was to investigate the relationship between w-sitting and the incidence of abnormal hip morphology in normal hips. METHODS Parents of children who were of sitting age or older, and who underwent hip/pelvis radiographs for non-orthopaedic problems between 2014 and 2015 were asked to complete a questionnaire regarding their child’s sitting habits. Patients with a history of hip surgery, prior hip fracture or hip pathology were excluded. Radiographic measures were taken including femoral head migration percentage, acetabular index and center edge angle. Hip dysplasia was defined as a center edge angle <20° or an acetabular index >25°. RESULTS 27 patients were included (mean age at time of hip radiograph: 11.1 ± 5.4 years, 63% female). 11 patients (41%) reported a history of current or past w-sitting (W-sit) and 16 patients (59%) did not (no W-sit). No significant differences in average acetabular index were seen between W-sit and no W-sit groups (W-sit: 12.9±9.4°, no W-sit: 17.9±6.0°, p=0.11) in the skeletally immature (Figure 1). Similar average center edge angles were found in the W-sit and no W-sit groups (W-sit: 38.0±1.4°, no W-sit: 35.8±15.6°, p=0.86) in the skeletally mature. Migration percentage was similar for the two groups (W-sit: 8.4+9.3%, no W-sit: 15.2±13.3%, p=0.15). No significant difference in incidence of hip dysplasia was found between groups (W-sit: 2/11, no W-sit: 3/16, p=0.97). CONCLUSION Regardless of sitting position, similar mean acetabular index, center edge angles and incidences of hip dysplasia were observed. This suggests that w-sitting does not affect risk for developmental dysplasia of the hip in healthy children. We hope data from this study will allow clinicians to validly re-assure families with children whom w-sit that there is no evidence to suggest a relationship between w-sitting and hip dysplasia.

Radiographic Measures of Femoral Head Migration Percentage and Acetabular Index in W-sit and No W-sit groups.

Radiographic Measures of Femoral Head Migration Percentage and Acetabular Index in W-sit and No W-sit groups.

Close modal