Slipped Capital Femoral Epiphysis (SUFE): Causes, Risk Factors, and Clinical Implications

What is the Cause of SUFE?

Slipped Capital Femoral Epiphysis (SUFE) is primarily caused by a weakening of the growth plate (physis) in the upper thigh bone (femur) during rapid adolescent growth, leading to a posterior and inferior slippage of the femoral head. It is a multifactorial condition, with obesity being the most significant and consistent risk factor.

Understanding Slipped Capital Femoral Epiphysis (SUFE)

Slipped Capital Femoral Epiphysis (SUFE), also known as Slipped Upper Femoral Epiphysis, is an orthopedic condition characterized by the displacement of the femoral head (the ball of the hip joint) from the femoral neck at the epiphyseal plate (growth plate). This slippage typically occurs gradually, but can also be acute. SUFE predominantly affects adolescents during periods of rapid growth, typically between the ages of 10 and 16, and is more common in boys than girls. It is considered an orthopedic emergency requiring prompt diagnosis and treatment to prevent long-term complications.

The Primary Causes of SUFE

SUFE is not attributed to a single cause but rather a complex interplay of mechanical, hormonal, and structural factors that converge to weaken the growth plate of the proximal femur. The underlying vulnerability of the growth plate, combined with increased stress across it, leads to the characteristic slippage.

Key Risk Factors and Contributing Elements

Several factors significantly increase an individual's risk of developing SUFE:

• Adolescent Growth Spurt: This is a crucial predisposing factor. During periods of rapid growth, the cartilaginous growth plate thickens and becomes less resistant to shear forces. The orientation of the growth plate also changes, becoming more horizontal, which makes it more susceptible to slippage under stress.
• Obesity: This is the most consistent and significant risk factor for SUFE. Excess body weight dramatically increases the mechanical stress and shear forces across the hip joint's growth plate. The increased load, particularly during weight-bearing activities, overpowers the weakened physis, leading to displacement.
• Hormonal Factors: Endocrine changes associated with puberty play a role in weakening the growth plate. Certain hormonal imbalances or disorders can further compromise the physis.
  • Hypothyroidism: An underactive thyroid can lead to delayed skeletal maturation and a weaker growth plate.
  • Growth Hormone Deficiency: While less common, certain growth hormone abnormalities can also contribute.
• Mechanical Stress and Biomechanics: Normal daily activities, especially those involving weight-bearing or internal rotation of the hip, generate shear forces across the growth plate. When the physis is inherently weak due to other factors, these normal stresses can become pathological, causing the femoral head to slip posteriorly and inferiorly relative to the femoral neck.
• Anatomical Predisposition: Subtle variations in hip anatomy, such as femoral retroversion (where the femoral neck is rotated backward relative to the femoral condyles), may alter the distribution of stress across the growth plate, potentially increasing vulnerability.
• Genetics: While not a primary cause, there appears to be a genetic predisposition, with a higher incidence in certain families and ethnic groups, suggesting a possible inherited component to growth plate vulnerability.
• Minor Trauma: Although SUFE is often considered an atraumatic condition, a minor fall or injury can sometimes be the precipitating event that causes a slip in an already vulnerable growth plate. It typically acts as a trigger rather than the sole cause.
• Underlying Medical Conditions: Rarely, systemic diseases can weaken the growth plate, making it more susceptible to SUFE. Examples include:
  • Renal Osteodystrophy: Bone disease associated with chronic kidney failure.
  • Radiation Therapy: Exposure to radiation can affect bone and growth plate integrity.

Why These Factors Lead to SUFE

The convergence of these factors creates a critical window of vulnerability. During the adolescent growth spurt, the growth plate is rapidly expanding and is inherently weaker due to its cartilaginous nature. When this physiological weakness is compounded by significant mechanical overload, primarily from excessive body weight (obesity), the shear forces exerted on the hip joint become too great for the weakened physis to withstand. The result is a gradual or acute separation and displacement of the femoral head from the femoral neck at this vulnerable junction. Hormonal influences further modulate the strength and integrity of this critical growth zone.

Clinical Implications and Importance of Early Diagnosis

Recognizing the causes and risk factors for SUFE is crucial for early diagnosis. Common symptoms include pain in the hip, groin, thigh, or even the knee, often accompanied by a limp and limited range of motion in the hip, particularly internal rotation. Prompt diagnosis and surgical stabilization are essential to prevent further slippage, minimize the risk of serious complications such as avascular necrosis (death of bone tissue due to lack of blood supply), and reduce the likelihood of long-term problems like femoroacetabular impingement and early-onset osteoarthritis.

Conclusion

SUFE is a complex orthopedic condition rooted in the delicate balance between the strength of the adolescent growth plate and the mechanical stresses placed upon it. While multifactorial, the primary drivers are the transient weakness of the physis during rapid growth and, most significantly, the increased biomechanical load imposed by obesity. Understanding these underlying causes is paramount for healthcare professionals, fitness educators, and parents to identify at-risk individuals and ensure timely intervention.