M93.03 Acute on chronic slipped upper femoral epiphysis (nontraumatic)

Name of the Condition

• Acute on chronic slipped upper femoral epiphysis (nontraumatic)

Summary

Acute on chronic slipped upper femoral epiphysis (SUFE) is a condition where the femoral head (ball of the hip joint) shifts from its normal position on the femoral neck due to a fracture through the growth plate. This nontraumatic form combines acute symptoms with a chronic underlying process, meaning the displacement develops gradually but presents with sudden worsening. The condition primarily affects adolescents during growth spurts and can lead to hip pain, stiffness, or gait changes. Prompt evaluation is important to prevent complications.

Causes

The exact cause of acute on chronic SUFE is not fully understood, but it is thought to result from mechanical stress on the growth plate combined with hormonal influences during puberty. Reduced blood flow to the growth plate may weaken the bone, allowing the femoral head to slip. Obesity is also considered a contributing factor due to increased mechanical load on the hip. The acute presentation suggests a sudden displacement, possibly due to cumulative stress or a minor, unrecognized event, superimposed on a chronic, slowly progressive slip.

Risk Factors

• Age: Most common in adolescents aged 10-16 years, particularly during rapid growth spurts.
• Gender: Males are more frequently affected than females.
• Obesity: Higher body weight increases stress on the hip joint.
• Endocrine disorders: Conditions like hypothyroidism or growth hormone abnormalities may elevate risk.
• Prior chronic slip: A history of undiagnosed or untreated chronic SUFE increases the risk of acute progression.

Symptoms

• Hip, thigh, or knee pain (pain may be referred to the knee).
• Limp or altered gait (e.g., walking with a limp or toe-out stance).
• Reduced range of motion in the hip, especially internal rotation.
• Sudden worsening of pain or gait changes in a patient with a known or suspected chronic slip.
• Pain worsened by activity or weight-bearing.

Diagnosis

Diagnosis involves a physical exam to assess hip range of motion, gait, and pain patterns, followed by imaging. X-rays of the pelvis and hips are standard, showing displacement of the femoral head relative to the femoral neck. In some cases, MRI or CT may be used to evaluate the growth plate and surrounding structures. The acute-on-chronic nature is identified by comparing current imaging with prior studies (if available) or by noting signs of chronic changes (e.g., remodeling) alongside acute displacement.

Treatment Options

Treatment depends on the severity of the slip and stability. Stable slips may be managed with in situ pinning (surgical fixation) to prevent further displacement. Unstable slips often require urgent surgical reduction and fixation. Postoperative care includes activity modification and follow-up imaging to monitor healing. Physical therapy may be recommended to restore range of motion and strength.

Prognosis and Follow-Up

Prognosis is generally good with timely treatment, but complications like avascular necrosis (loss of blood supply to the femoral head) or chondrolysis (cartilage damage) can occur, especially with unstable slips. Follow-up includes regular imaging to assess healing and monitor for long-term hip function. Adolescents may need ongoing orthopedic care until growth is complete.

Complications

• Avascular necrosis of the femoral head.
• Chondrolysis (cartilage degeneration).
• Premature physeal closure (growth plate fusion) leading to leg length discrepancy.
• Chronic hip pain or arthritis.
• Gait abnormalities.

Lifestyle & Prevention

• Maintain a healthy weight to reduce hip stress.
• Avoid high-impact activities that strain the hip during growth spurts.
• Ensure regular orthopedic evaluations for adolescents with hip pain or gait changes.
• Follow post-treatment activity restrictions and rehabilitation guidelines.

When to Seek Professional Help

Seek immediate medical attention if there is sudden, severe hip pain, inability to bear weight, or a noticeable change in gait, especially in an adolescent. Early evaluation can prevent progression to an unstable slip and reduce complication risk.

Tips for Medical Coders

Document the acute-on-chronic nature of the slip, including any prior history of chronic SUFE or imaging showing chronic changes. Note the stability of the slip (stable vs. unstable) and any surgical interventions. Ensure documentation supports the nontraumatic etiology, as this distinguishes it from traumatic slips. Code M93.03 is specific to acute on chronic nontraumatic SUFE; avoid using it for acute or chronic slips alone.