Acute left-hip pain in a 9-year-old boy after a fall at summer camp

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The patient was brought to the hospital when his hip discomfort worsened. A set of x-rays confirmed the diagnosis.

The mother of a 9-year-old boy reported that her son fell off a two-foot-high stage at camp two weeks before. Subsequently, he began to complain of vague left-hip and groin discomfort. The pain became acutely worse over the ensuing couple of days, and his mother brought him to the local emergency department (ED). The hip x-rays taken at that visit were judged normal, and he was discharged home.

After further review of the x-ray by the radiologist, however, the family was contacted and instructed to return to the ED. In the meantime, the boy had noticed an intensification of his left-hip pain while simply walking. Now in severe pain, he became unable to put any weight on the left leg. An ambulance brought him to the ED, where additional x-rays were taken (Figure 1).

Examination

Physical examination revealed stable vital signs, temperature 98.5°F, weight 42 kg, and BMI 20. The boy was unable to tolerate any range of motion or weight-bearing by the left hip. He held the leg in an externally rotated and flexed position and resisted any movement. Evaluation of his neurovascular status revealed that distal sensation and pulses were normal.

Diagnosis

The boy was diagnosed with acute unstable slipped capital femoral epiphysis (SCFE) of the left hip. SCFE is a relatively common affliction of the hip in the actively growing adolescent and pre-adolescent. SCFE is defined as displacement or slippage of the femoral head relative to the femoral neck occurring through the femoral physis or growth plate. This slippage occurs when the shearing stress exerted on the femoral head is greater than the resistance provided by the intrinsic mechanical stability of the growth plate.

The true cause of SCFE is unknown, although there are many theories and some known risk factors. Age of onset is usually between 10 and 16 years, and there is a 2.5-to-1 male-female ratio. Most pediatric orthopedic surgeons agree that a combination of mechanical and constitutional factors contribute to this affliction. A multifactorial etiology, including local trauma, obesity resulting in mechanical overload of the maturing growth plate, inflammatory factors, and endocrinologic factors, appears likely.1

While the majority of cases are believed to be idiopathic, SCFE may also be associated with endocrine disorders (e.g., growth-hormone administration, hypothyroidism), renal osteodystrophy, or previous radiation therapy.2

Obesity seems to be the strongest risk factor for SCFE. Excessive weight combines with retroversion (posteriorly directed femoral head) of the femur to result in mechanical stresses on the growth plate. A recent study revealed that 81% of adolescents with an SCFE had a BMI above the 95th percentile.3 The increased shear stress across the physis caused by obesity in combination with the pre-adolescent and adolescent growth spurt can lead to a disruption through the weakest portion of the growth plate.

Symptoms and diagnosis of SCFE

The diagnosis of SCFE is typically based on symptoms, physical examination, and radiographic studies. Patients with SCFE will often present with complaints of pain in the affected hip, groin, thigh, or knee and will frequently exhibit a limping or antalgic gait. The common classifications of SCFE are listed in Table 1.

It is important to note that hip pain is often referred to the knee because of the sensory distribution of the obturator and femoral nerves.


Figure 2. External rotation and abduction with hip flexion

Increased fluid in the hip joint will result in decreased range of motion compared with the contralateral unaffected hip. Another classic physical exam finding in patients with SCFE is obligatory external rotation and abduction of the hip with attempts at flexion (Figure 2). Patients with acute unstable slips will often be unable to put any weight on the affected leg and will not tolerate any hip motion.

Treatment

Our patient was taken from the ED to the operating room for stabilization and pinning of the acute unstable left SCFE. Because it was a severe unstable slip, two cannulated percutaneous screws were placed across the physis.

The slip was reduced by gentle manipulation and positioning on the operating table. Using fluoroscopic guidance, the screws were placed without difficulty. On postoperative day one, the patient was cleared by physical therapy and discharged. He remained nonweight-bearing on crutches for six weeks. At the two-month postoperative evaluation, anteroposterior and frog lateral x-rays of the pelvis were obtained (Figure 3). The boy was allowed partial weight-bearing (approximately 20-30 lb) at that time, and physical therapy was initiated to improve strength and range of motion.


Figure 3. Percutaneous screws placed across the physis

Potential complications

The vast majority of patients who present with a stable SCFE and undergo percutaneous pinning do not develop any long-term complications. With early recognition and timely intervention, the prognosis is excellent. Severe unstable slips (like the one in this case) increase the risk for early-onset hip arthritis. Because modern surgical techniques and fixation methods are far superior to those used in the available long-term studies, however, the true incidence of precocious arthritis is unknown.

Another potential complication is contralateral SCFE. Approximately 40% of patients who suffer SCFE will experience slippage in the other hip. This is even more common in younger patients (because the growth plate is open longer) and in patients who present with more severe or unstable slips. Many pediatric orthopedic surgeons prefer to prophylactically pin the unaffected hip in younger patients who present with a severe SCFE. Our patient (young male with severe unstable slip) is scheduled to undergo a right-hip prophylactic pinning once he has fully recovered from the left SCFE.

The two most troublesome complications of SCFE are avascular necrosis (AVN) and chondrolysis. AVN, or osteonecrosis, refers to the loss of blood supply to the proximal femoral physis resulting in death of that portion of the bone. It is the most serious complication of SCFE and is more likely to occur if the slip is severe or unstable. Patients with AVN will often develop more rapid arthritic deterioration of the hip, requiring further surgical intervention.4

Chondrolysis represents a loss of articular cartilage and can be seen in both treated and untreated SCFE. It occurs in approximately 5%-7% of all children with an SCFE.5 Similar to AVN and contralateral slips, chondrolysis is also more common in severe and/or unstable SCFE. Clinically, patients with chondrolysis of the hip will usually complain of pain and have decreased range of motion. A loss of articular cartilage width can be seen on x-rays. Treatment generally involves relieving pain and improving motion.

Approximately 50% of patients with chondrolysis related to SCFE will improve regardless of the treatment given. In other children, however, chondrolysis may progress to such severe pain and contracture that hip arthrodesis (fusion) or replacement is necessary.6

Ms. Hart is a pediatric orthopedic nurse practitioner at Massachusetts General Hospital in Boston, where Dr. Grottkau is chief of pediatric orthopedics.

References

1. Eldridge JC. Slipped capital femoral epiphysis. In: Sponseller PD, ed. Orthopaedic Knowledge Update: Pediatrics. Rosemont, Ill. American Academy of Orthopaedic Surgeons; 2002:143-151.

2. Benchot R. The adolescent with slipped capital femoral epiphysis. J Pediatr Nurs. 1996;11:175-182.

3. Manoff EM, Banffy MB, Winell JJ. Relationship between body mass index and slipped capital femoral epiphysis. J Pediatr Orthop. 2005;25:744-746.

4. Krahn TH, Canale ST, Beaty JH, et al. Long-term follow-up of patients with avascular necrosis after treatment of slipped capital femoral epiphysis. J Pediatr Orthop. 1993;13:154-158.

5. Lubicky JP. Chondrolysis and avascular necrosis: complications of slipped capital femoral epiphysis. J Pediatr Orthop B. 1996;5:162-167.

6. Loder RT. Slipped capital femoral epiphysis. Am Fam Physician. 1998;57:2135-2142, 2148-2150.

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