Surgical Management of Unstable Superior Femoral Epiphysiolysis with Great Displacement

Introduction: Superior femoral epiphysiolysis (SFE) is a most progressive but sometimes abrupt displacement of the femoral head relative to the superior femoral metaphysis through the cervicocerebral growth plate of the femur. The displacement of the femoral head is most often downward and backward. It is a typical pathology of the pubescent adolescent, most often overweight. It occurs on average at the age of 12 years in girls and 14 years in boys. Unstable forms with large displacements have a high risk of femoral head necrosis and chondrolysis. Although in situ fixation is the generally accepted treatment for minor SFE, the treatment of more severe cases remains controversial. When the extent of the displacement makes it impossible to pass a screw between the femoral neck and the femoral head, the only option is to reduce the displacement. This reduction must be gentle, progressive and limited to the minimum necessary for osteosynthesis. Objective: The aim of the work was to evaluate the results of the technique of progressive reduction of epiphyseal displacement by transtibial traction followed by percutaneous fixation of the femoral head by screw. Patients and Method: This was a retrospective descriptive study over a 10-years period from January 1, 2013 to December 31, 2022. It focused on the surgical treatment of unstable upper femoral epiphysiolysis with large displacement in the orthopaedic trauma department of the University Hospital of Kati. All patients operated on in our department for large displacement SFE were included in this study. Cases of secondary large displacement upper femoral epiphysiolysis and patients who had already undergone surgery on the proximal femur were excluded. Continuous progressive traction on the Boppe splint through a pin under the anterior tibial tuberosity was performed for 15 days in all patients. The hip was flexed to 45° and the knee to 35°. Fixation was performed with one or two screws. No contralateral preventive fixation was performed. Minimum follow-up was one year. Functional outcome was assessed by the Postel Merle d’Aubigné score. Anatomical outcome was assessed by the quality of reduction, the occurrence or non-occurrence of femoral head necrosis, and chondrolysis. Results: We identified nine patients with a mean age of 12.8 years and extremes of 9 and 17 years. There were three boys and six girls. Trauma was mentioned in four cases. The cause was idiopathic in five cases. Functional impotence was complete in all patients. The slippage was acute on a chronic background in all patients. The left side was affected in 7 cases and the right side in 2 cases. The patients were overweight in 7 cases. The patient’s weight was within the normal range in two cases. At final follow-up, all nine patients were asymptomatic. Anatomically, all nine patients had a femoral head free of avascular necrosis. In eight patients, the posterior tilt was absent, identical to that obtained after the traction period. Only one patient had a moderate posterior tilt with a neck uncovering of less than 25%. Functionally, the PMA score was very good in eight cases and good in one case. Conclusion: This study shows that the treatment of acute and unstable forms of upper femoral epiphysiolysis by progressive reduction with transtibial traction can lead to satisfactory results. Reduction in large displacement forms should be gentle, progressive and limited to the minimum necessary for osteosynthesis. Magnetic resonance imaging examination is an essential and indispensable prognostic element. Indications for preventive fixation should be selectively reserved for specific cases.

Theoretical aspects of selecting repeated unit cell model in micromechanical analysis using displacement-based finite element method

Repeated Unit Cell（RUC）is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element（DFE）method,and merely applying Periodic Displacement Boundary Conditions（PDBCs）to RUC is almost a standard practice to conduct such analysis.Two basic questions arising from this practice are whether Periodic Traction Boundary Conditions（PTBCs,also known as traction continuity conditions）are guaranteed and whether the solution is independent of selection of RUCs.This paper presents the theoretical aspects to tackle these questions,which unify the strong form,weak form and DFE method of the micromechanical problem together.Specifically,the solution’s independence of selection of RUCs is dealt with on the strong form side,PTBCs are derived from the weak form as natural boundary conditions,and the validity of merely applying PDBCs in micromechanical Finite Element（FE）analysis is proved by referring to its intrinsic connection to the strong form and weak form.Key points in the theoretical aspects are demonstrated by illustrative examples,and the merits of setting micromechanical FE analysis under the background of a clear theoretical framework are highlighted in the efficient selection of RUCs for Uni Directional（UD）fiber-reinforced composites.