Where Are We Now?
Slipped capital femoral epiphysis (SCFE) is common and has been associated with frequent long-term morbidity extending far beyond childhood ; many questions remain regarding its best treatment. The deformity varies widely and is incompletely characterized by simple radiographs . The standard primary treatment of stable SCFE in most centers remains in situ fixation with a single screw. Although controversy remains regarding the best screw position, placement in the central portion of the head is generally favored, but progression of a stable slip may occur even with central screw placement. Another important issue is understanding the nature of the SCFE deformity; realignment of the epiphysis may be considered to correct the deformity.
Recent research has suggested that SCFE may involve a rotational mechanism [8, 9, 13]. The size of the epiphyseal tubercle, which seems to act as a stabilizer in the epiphysis of preadolescent children, seems to be related to the risk of SCFE, which may occur as the tubercle rotates around and potentially out of the fossa.
Here, Novais et al.  used a CT analysis in 57 hips with clinically stable SCFE to determine the relative contributions of translation and rotation to the deformity and noted the relationship between epiphyseal rotation and the size of the epiphyseal tubercle, the metaphyseal fossa, and cupping of the epiphysis. Their findings in their series suggest that rotation does occur, occurs more often with larger slips, and is associated with posterior translation of the epiphysis. They noted that increased epiphyseal rotation was associated with an increased size and depth of the metaphyseal fossa, with inferior cupping of the epiphysis.
The existence of true rotational displacement in SCFE may also contribute to an external rotation deformity that is common even in extension and in mild cases of SCFE . This study  confirms and builds on a body of work that has established the epiphyseal tubercle, metaphyseal fossa, and epiphyseal cupping as “parties of interest” in the evolution of capital femoral epiphyseal displacement [9, 10, 13].
Although this study  did not evaluate the placement of stabilizing screws in relation to the epiphyseal tubercle, its discussion suggests increased stability of fixation constructs for which screws are not placed through the tubercle . That said, many questions remain regarding how to use this information in clinical practice.
The most frequently cited North American long-term outcome study of SCFE documented progression to osteoarthritis in most patients, independent of severity or treatment method . An epiphyseal rotational deformity, even if seemingly minor, may potentiate impingement, which is felt to be a major factor in causing arthrosis after SCFE [5, 7].
Where Do We Need To Go?
It seems clear that a rotational deformity exists in many hips with SCFE. The degree of residual deformity seems to be related to the long-term risk of symptomatic osteoarthritis after SCFE , although previously, simplistic measurement of slip angles and the percentage of epiphyseal displacement on radiographs were standard . It is unknown how an epiphyseal rotational deformity might mechanically affect the hip, nor do we know how much of a deformity would be “big enough to matter” in terms of the risk of a patient developing painful arthrosis.
An important related question is knowing when advanced imaging should be used in patients with SCFE . If CT or MRI is used, then user-friendly software must be available to assist in characterizing the deformity.
Finally, we need to better understand the short-term and long-term effects of three-dimensional SCFE-related deformities on hip function.
How Do We Get There?
The intriguing study in this month’s Clinical Orthopaedics and Related Research®  invites large, carefully designed prospective studies of patients with SCFE to determine the importance of specific deformities, including epiphyseal malrotation, on outcomes, combined with studies evaluating the effect of rotationally sensitive deformity correction. Large numbers of patients should be evaluated using contemporary imaging beyond simple biplanar radiographs to clearly determine a three-dimensional deformity. Ideally, cartilage-sensitive imaging will allow an assessment of articular health at the time of the primary treatment and at intervals thereafter. Treatment arms must be carefully chosen, and decades of follow-up will yield the best information. Although long-term prospective studies of patients with SCFE will be challenging to perform, their high value in answering important clinical questions makes them attractive. Large groups such as the Academic Network of Conservational Hip Outcomes Research group  and the SCFE Longitudinal International Prospective Registry [3, 11] may be able to deliver the types of answers we need in this regard.
However, even today, without waiting decades, a surgeon treating a patient with SCFE can both practice evidence-based medicine and contribute to orthopaedic science. A study of the clinical importance of the epiphyseal tubercle and metaphyseal fossa in transphyseal stability suggests placing screws into the epiphysis and not through the epiphyseal tubercle . In performing open reductions or realignment osteotomies, surgeons should consider epiphyseal malrotation. An analysis of rotational alignment across the proximal femoral physis offers another parameter of potential importance for study.
Low-dose CT scanning and dedicated MRI are at present not done universally before SCFE treatment owing to issues with cost and time. It is, however, through careful documentation of both the three-dimensional deformity and cartilage health before treatment and over time that we will achieve the highest numbers of patients with long-term freedom from hip pain and stiffness. Careful prospective documentation is necessary, but it is not sufficient without longitudinal information. We must therefore also strive to maintain long-term follow-up of as many patients with SCFE as possible.
1. Academic Network of Conservational Hip Outcomes Research. Welcome to the ANCHOR group. Available at: https://www.anchorhipsurgeons.com/anchor-history-adolescent-adult-hip-disorders.html
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9. Maranho DA, Bixby S, Miller PE, Novais EN. A novel classification system for slipped capital femoral epiphysis based on the radiographic relationship of the epiphyseal tubercle and the metaphyseal socket. JBJS Open Access. 2019;4:e0033.
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11. Nemours Children’s Health System. SCFE registry (slipped capital femoral epiphysis). Available at: https://www.nemours.org/pediatric-research/clinicaltrials/ortho-1288281.html
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12. Novais EN, Hosseinzadeh S, Emami SA, Maranho DA, Kim Y-J, Kiapour AM. What is the association among epiphyseal rotation, translation, and the morphology of the epiphysis and metaphysis in slipped capital femoral epiphysis? Clin Orthop Relat Res
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