A 9-year Old Girl With A - Page #4

Working Diagnosis:
Femoral neck stress fracture, compression side

K.M. was initially placed strict non-weight bearing status with crutches and referred urgently to pediatric orthopedic surgery. She underwent percutaneous pinning of her left femoral neck the following day.Case Photo #1Case Photo #3 She was also evaluated by pediatric endocrinology and was found to have no metabolic or endocrine abnormalities. Given her initial low Vitamin D levels, she was started on Vitamin D 800 IU (international units) daily and Calcium at the time of surgery.

K.M. recovered well from surgery and pain free within 1.5 weeks following surgery. She was cleared for weight bearing as tolerated 2 months following surgery, and was cleared for gymnastics approximately 2 months later.

She was last seen by Orthopedic surgery in Nov 2014. Imaging revealed stable screw placement and alignment. She denied pain and was not bothered by her hardware. The decision was made to leave the hardware in place and follow-up was scheduled to take place in 1 year.

Author's Comments:
Femoral neck stress fractures (FNSF) in skeletally immature individuals are extremely rare. They occur in approximately 12 in 10,000 military recruits per year, yet less than 20 case reports exist in children. In adults, FNSF comprise between 5-8% of all stress fractures, most commonly among long-distance runners, military recruits and those with metabolic bone disease. If undetected, FNSF may have devastating results and lead to severe disability including displacement, avascular necrosis and severe early osteoarthritis. The differential for a child presenting with a limp is large and includes developmental dysplasia of the hip, slipped capital femoral epiphysis (SCFE), Legg-Calve-Perthes disease, joint infection, pelvic muscle sprain, malignancy, transient synovitis, or fracture.

Cases among children typically present with vague hip pain and limping, usually beginning weeks to months prior to presentation. Most cases have known underlying risk factors such as increased activity or repetitive trauma. Some cases, however, have no recognized risk factors. FNSF typically occur in the compression side, though tension side stress fracture have been reported. In general, compression-type fractures have a good prognosis, with most patients returning to previous level of activity with in several months.

Our case did have mild Vitamin D deficiency, otherwise no additional laboratory abnormalities were noted. Calcium and Vitamin D are essential for bone health. A prospective, randomized-control trial of U.S. Navy recruits found that women treated with 2000 mg Calcium and Vitamin D 800 IU had a 21% lower incidence of stress fractures. A different case-control study among female navy recruits found that those with a Vitamin D level < 20ng/ml had twice the risk of a stress fracture of the tibia or fibula compared to those with a Vitamin D of >40 ng/ml or more. No other case reports of FNSF in children with metabolic bone disease have been reported.

Mehmet et al developed a diagnostic and treatment algorithm as follows:
- In children presenting with hip pain or a limp, it is recommended starting the workup with standard AP pelvis and lateral hip radiographs. Xrays are typically negative for the first 3 - 4 weeks.
- Serial radiographs or MRI should be considered if the diagnosis is not clear or there exists a high suspicion for FNSF.
- Radiological findings can be confused with sarcomas or osteomyelitis.
- Bone biopsy should be avoided unless there are clear signs or symptoms of malignancy or infection, as this can potentially further compromise the bone integrity near the site of stress fracture.
- MRI is the imaging modality of choice if X-rays are not definitive. They have superior specificity, equal or better sensitivity, and no radiation exposure. Additionally, an MRI can better describe soft tissue abnormalities compared to bone scans.

Typically, non-displaced compression-sided stress fractures are stable and require only non-weight bearing treatment. On the other hand, urgent internal fixation is recommended for displaced fractures or tension-sided stress fractures, as these may progress to complete fracture.

K.M.'s only clear risk factor was Vitamin D deficiency, which has not been reported in other case studies, but is known to increase the incidence of stress fractures albeit in adults. Though she was an active child, K.M. did not display increasing levels of activity recently. Currently, she remains asymptomatic and will follow-up with Pediatric Orthopedics in one year to determine if her internal fixation can be taken out.

Editor's Comments:
This is an excellent case addressing femoral neck stress fractures even though this case is unique in that the athlete is a child. As discussed, these are commonly-seen injuries in adult (endurance) athletes and action to further characterize the fracture is imperative to prevent further complications with weight-bearing activities. Laying out a well delineated plan detailing weight bearing status, advancement to ambulation, and progression back into athletic activity is essential. While understanding the risk factors for femoral neck stress fractures, it is important to question the patient about dietary preferences, caloric intake, vitamin supplementation, and menstrual cycle history and frequency in females will assist to uncover additional potential contributing factors.

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