Pedicle Fractures

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Pedicle stress fractures are an uncommon cause of lower back pain [60]. Of increasing interest in the pediatric literature is the development of pedicle stress

Fig. 4. (A) Painful spondylolysis in a 19-year-old volleyball player, unhealed despite 9 months of bracing and physical therapy. (B) Bony union and pain relief was attained after 4 months of electric bone stimulation.

fractures among athletes with spondylolysis [21-23]. Defects of the pedicle of the lumbar spine may be congenital [61]. Pedicle stress fractures also may result as a complication of posterolateral lumbar fusion, laminectomy, and surgery for idiopathic thoracolumbar scoliosis [61,62].

Cause

The cause of pedicle stress fractures remains controversial among clinicians. In mechanical testing of the neural arch, the pedicle has been shown to be the second point of weakness after the pars [61]. Cyron and colleagues [31] have found that the pars interarticularis failed 10 times more than the pedicles did when the lumbar spine was loaded in flexion [23,31]. The two main reasons for this are the pedicle is mechanically stronger than the pars interarticularis [23], and the anatomy and biomechanics of the lumbar spine serve to selectively concentrate shear stress at the pars interarticularis [63-65].

Biomechanics

Pedicle stress fractures result from abnormal forces distributed across the neural arch [66-68]. This condition may be explained partly by the location of the pedicles near the pars and the relatively immature ossification center in the pediatric athlete at each side of the neural arch at the pedicles [4].

Abnormal forces across the neural arch that result in fractures of the pars may also result in a redistribution of forces, leading to a pedicle fracture in the contralateral side [66,67]. In a study by Sairyo and colleagues [66], two of 13 patients (15.4%) with unilateral spondylolysis developed a stress fracture of the contralateral pedicle. This study supports the hypothesis that the stresses in the contralateral pedicle increase in response to axial loads, especially in axial rotation. In another study, Abel [68] has demonstrated that spondylolytic defects begin at the inferior margin of the pedicle, which is under the highest concentration of stress, and are then propagated obliquely across the pars interarticularis as the forces increase [23,68].

Prevalence

The exact prevalence of pedicle stress fractures is unknown, yet there are a number of case reports in the athletic population [21-23]. In addition to their biomechanical findings, Sairyo and colleagues [66] have demonstrated that, with advancing stages of spondylolysis, the stress at the contralateral pedicle side begins to increase, causing the sclerosis-fracture. The present author (LJM) [23] has demonstrated that isolated lesions may occur in the pedicles in dancers who repeatedly flex and extend the spine. Pedicle stress fractures also have been described in Olympic athletes and female athletes [21,22].

Diagnostic Imaging

As in all stress fractures, the early detection of pedicle stress fractures is important for early diagnosis and early return to sport for athletes. Plain radiography may reveal sclerosis of the pedicle [69]. Bone scintigraphy with single photon emission-CT is favored for the initial evaluation [70].

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  • norma
    What is a pedicle fracture?
    4 months ago

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