A Rare Diagnosis And Repeated Knee Injury In A Young Athlete - Page #4
 

Working Diagnosis:
Stress fracture of the right patella

Treatment:
The patient was braced in extension and remained non-weight bearing for 4 weeks. Through the following 2 weeks, he was limited to walking/ADLs while wearing his protective brace. After 6 weeks of rest, the patient was pain-free and resumed activities/PT as tolerated without bracing.

Outcome:
6 weeks after resuming activities, the patient returned to clinic with recurrent right knee pain. Symptoms occurred suddenly with a sprint out of the batterís box during a baseball game. X-ray found a new complete, undisplaced fracture of the right inferior patella. Case Photo #6

The patient was once again placed in a protective brace and removed from activities until pain-free. After 4 weeks of rest, x-ray of the right knee displayed healing of the repeat patellar fracture and he gradually weaned off the knee brace, returning to activities as tolerated while completing physical therapy. He has since returned to play without restriction or exacerbation for 7 months. Case Photo #7

Author's Comments:
Stress fractures of the patella are uncommon in athletes. They typically arise in normal bone that has been exposed to repetitive, excessive stress (fatigue). Less commonly, they can result from abnormal bone structure or density exposed to relatively normal loading (insufficiency), often secondary to iatrogenic insult rather than bone pathology.(1-4)
Patients generally present with anterior knee pain in the setting of increased activity with limited time for recovery. Symptoms may resolve with rest and immobilization, then come back with resumption of activity.(1,5)
Radiography is the initial study of choice, but MRI may be required in patients with a high index of suspicion for fracture.(1,6,7)
Complete undisplaced fractures typically heal with non-operative treatment. This consists of bracing in extension for 4-6 weeks, followed by rehab and gradual return to activities. Generally, patients can be expected to make a full recovery and return to pre-injury levels of activity.(1)
This patient deviates from the normal course by experiencing a repeat injury. The patientís right leg sequelae secondary to PVL could be a source of bone insufficiency, and his 7-day-a-week activity level in multiple sports could fatigue the patella. Both of these factors may have predisposed him to further injury. If he were to have failed conservative management, or if the fracture was displaced, he may have required operative treatment.(1)

A pediatric neurologist diagnosed this patientís condition at age 6 when right leg weakness/foot drop, decreased right leg length, right toenail hypoplasia, and left-handedness prompted imaging.
PVL is the predominant form of ischemic brain injury in premature infants. Unlike preterm newborns, the most common pattern of injury in term infants predominantly affects watershed areas of the cerebral cortex.(8-10) Since this patient was born full term without complication, the periventricular insult likely occurred early in the third trimester as in other cases of term infants with PVL.(11-13)
Preterm infants with PVL are at high risk for spastic diplegia, developmental delay, visual impairment, and epilepsy.(11,12,14) PVL in term children represents a distinct clinical entity with developmental delay and heterogeneous motor findings beyond the classic spastic diplegia/cerebral palsy. This diagnosis should be considered in patients with developmental or motor abnormalities even in the absence of perinatal complications.(11)

Editor's Comments:
Patella stress fractures are considered high risk stress fractures. Risk factors include bipartite patella and cerebral palsy. Given this patient's previous neurological condition, it is reasonable to suggest that his decreased VMO size places him at more risk for patella stress fractures. Since the VMO absorbs the majority of the force in the lower extremity and given his slight in-toeing during his gait, the force distribution across the lower extremity may prove to be too much to handle for his smaller patella. Treatment for patella stress fractures are individualized. For displaced fractures or with non-union, ORIF often is required. If the stress fracture is not displaced, conservative therapy including restriction of activity. Bracing may be indicated as well.

References:
1. Crane TP, Spalding JW. The Management of Patella Stress Fractures and the Symptomatic Bipartite Patella. Operative techniques in Sports Medicine 2009;17:100-105.
2. Matheson GO, Clement DB, McKenzie DC, et al. Stress fractures in athletes. A study of 320 cases. Am J Sports Med 15:46-58, 1987.
3. Rosenthal RK, Levine DB. Fragmentation of the distal pole of the patella in spastic cerebral palsy. J Bone Joint Surg 59A:934-939, 1977.
4. Grace JN, Sim FH. Fracture of the patella after total knee arthroplasty. Clin Orthop Relat Res 230:168-175, 1988.
5. Drabicki RR, Greer WJ, DeMeo PJ. Stress fractures around the knee. Clin Sports Med 25:105-115, 2006.
6. Rockett JF, Freeman BL. Stress fracture of the patella. Confirmation by triple-phase bone imaging. Clin Nucl Med 15:873-875, 1990.
7. Orava S, Taimela S, Kvist M, et al. Diagnosis and treatment of stress fracture of the patella in athletes. Knee Surg Sports Traumatol Arthrosc 4:206-211, 1996.
8. Deng W, Pleasure J, Pleasure D. Progress in Periventricular Leukomalacia. Arch Neurol. 2008;65(10):1291-1295.
9. Back SA, Riddle A, McClure MM. Maturation-dependent vulnerability of perinatal white matter in premature birth. Stroke. 2007;38(2)(suppl):724-730.
10. McQuillen PS, Ferreiro DM. Perinatal subplate neuron injury: implications for cortical development and plasticity. Brain Pathol. 2005;15(3):250-260.
11. Miller s, Shevell M, Patenaude Y, et al. Neuromotor Spectrum of Periventricular Leukomalacia in Children Born at Term. Pediatr Neurol. 2000;23:155-159.
12. Volpe JJ. Hypoxic-ischemic encephalopathy: Neuropathology and pathogenesis. In: Neurology of the newborn, 3rd ed. Philadelphia: WB Saunders, 1995:279-313.
13. Okumura A, Hayakawa F, Kato T, et al. MRI findings in patients with spastic cerebral palsy. I: Correlation with gestational age at birth. Dev Med Child Neurol 1997;39:363-8.
14. Aicardi J, Bax M. Cerebral palsy. In: Aicardi J, ed. Diseases of the nervous system in childhood. London: MacKeith Press, 1992:330-74.
15. Boden BP and Osbahr DC. High Risk Stress Fractures: Evaluation and Treatment. J Am Acad Orthop Surg 2000; 8:344-353.

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