Evaluation of the Three‐Dimensional Translational and Angular Deformity in Slipped Capital Femoral Epiphysis

Abstract

The purpose of this study was to quantify three-dimensional translational and angular deformity (defined as theta) present at the proximal femoral physis in slipped capital femoral epiphysis (SCFE), and to use theta to differentiate between SCFE hips, contralateral unaffected hips, and normal hips by comparing to the current gold standard measure of the Southwick slip angle (SSA). 3DCT reconstructions of the pelvis and femur in SCFE patients and normal adolescents were obtained and pelvic position was standardized. The center point and direction vector of the femoral epiphysis was determined. The femoral neck axis was defined. The angle between the femoral neck axis and epiphysis vector defined the 3D angle of deformity (theta). The 3D translation of the femoral epiphysis, measured as a percentage of femoral neck diameter, was measured in three planes. The average theta angle was significantly greater in SCFE hips (46.5 ± 24.3°) compared with control (13.7 ± 6.4°) or normal (11.7 ± 3.7°) hips (p < 0.001). There was no significant difference in theta angle between control and normal hips (p = 0.468). Theta angle correlated strongly with SSA (r s = 0.737, p < 0.001). Statement of clinical significance: The proximal femoral deformity in patients with slipped capital femoral epiphysis can be defined by measuring displacement of the epiphysis in all three dimensions in relation to the femoral neck axis. This information can be used in epiphyseal reorientation surgery to ensure anatomic reduction. The similarity between control and normal hips may argue against the thought that there is pre-existing deformity in a pre-slip condition of unaffected contralateral hips in SCFE patients.

Femoral Head-Neck Translation Ratio Is a Measurement of the True Deformity of Slipped Capital Femoral Epiphysis

“…FHNTR measurement complies with the results of the study of Bland et al [29]. Both methods describe the posteroinferior translation of the capital femoral epiphysis relative to the femoral neck, which is observed in the typical SCFE cases.…”

“…There was no significant difference of the theta angle between control and normal hips. The authors support that the theta angle is the true angle of deformity in SCFE hips [29].…”

“…They recommend the modified Dunn procedure if OPDA is greater than 50 degrees regardless of slip stability [28]. Bland et al (2019) measured 3D translational and angular deformity in SCFE using CT scans [29]. The authors presented the theta angle, which is the angle formed between the femoral neck axis and the epiphysis vector.…”

“…Splinting of the hip secondary to pain does not affect the CT scans. However, the authors admit that their method is complicated, and it is not expected to be adopted in clinical practice [29].…”

Limited Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling

“…This means that 17 degrees of ER was needed for impingement-free 90 degrees flexion (Table 3), similar to the Drehmann’s sign 31. More recent studies evaluated patient-specific 3D models for 3D printing32 or for detailed analysis of the direction of slip 33. No other study was found that assessed patient-specific location of bony hip impingement in flexion for patients with SCFE.…”