For proper treatment, it's necessary to be able to recognize it in time. In a child who presents with refractory or atypical LBP suggestive of spondylolysis, lumbosacral X-rays are indicated. Bilateral defects are easily recognized on a lateral radiograph but unilateral lesions are usually better detected on an oblique view (Fig. 1), although recent studies have questioned the value of these oblique films [10]. Lateral lumbosacral views should always be taken in standing posture to assess any associated spondylolisthesis and spinopelvic parameters that are essential in making therapeutic decisions. As lumbar hyperlordosis is a predisposing factor for developing spondylolysis, standing full-length radiographs of the spine are necessary to rule out associated thoracic hyperkyphosis, including Scheuerman's kyphosis.

All spondylotic defects cannot be detected on plain radiographs, especially in patients with normal lumbar radiographs. But persistent pain or disability is suggestive of the disease and single photon emission computed tomography may be the most valuable and sensitive method of identifying spondylolysis [11,12]. Other imaging modalities that can be used to better visualization of integrity and status of the posterior vertebral elements may include a computed tomography (CT) scan, bone scan, or magnetic resonance imaging (MRI) [13,14,15,16]. A technetium bone scan is very helpful in the diagnosis of spondylolysis and during treatment. Increased radioisotope uptake is indicative of the presence of osseous activity and healing potential (Fig. 2), while the lack of uptake is a sign of non-union (chronic disease) and decreased healing potential [17].

In patients with spondylolysis, a CT scan may show that everything is normal, a stress reaction, an acute stress fracture (early stage), progression of the condition, or terminal stage (chronic or pseudoarthrosis) [18,19]. It should be noted that stress reaction is the body's adaptive and reactive response to extraordinary, repeated stresses. In hyperlordosis posture, the inferior articular process of the superior vertebra applies a traction force on the pars interarticularis of the vertebra below and this part eventually fails anteriorly [20]. At first, this reaction results in microfracture of the cancellous bone associated with edema and hemorrhage. This bone bruising stage can be seen more clearly in an MRI while a CT scan may be interpreted as normal [21]. Acute lesions in an MRI show increased signal intensity on T2-weighted images that are indicative of bone marrow edema [21]. When the bony disruption progresses to the cortical bone, a CT scan becomes the most sensitive modality. Chronic stress reaction in CT is presented as increased sclerosis and thickening of trabeculae due to repeated fractures and healings [22]. An acute stress fracture (early stage) has a sharp margin of bone disruption and is defined as a fissure in the pars. In progressive stage, the defect is still narrow but has round edges, while in a chronic or terminal stage, a wide defect is observed with hazy, blunt and sclerotic margins.

It should not be forgotten that in chronic cases, every bony disruption observed in the posterior elements of a vertebra is not always indicative of spondylolysis. If the axial slice was taken at the level of intervertebral disc space, this is not a pseudoarthrosis of the spondylolysis. This is a degenerative joint disease of the facet articulations, because the typical location of pars defect in axial CT scanning is inside the cuts taken at the pedicles of the involved vertebra.

In those patient where no abnormality observed in radiographs, bone scan, and CT scan, spondylolysis is certainly ruled out. If a pre-lysis defect is observed in an MRI or CT scan associated with positive bone scan, the preferred treatment is avoidance of harmful activities that would create hyperlordosis and rotational spinal loading (like weight-lifting, diving, wrestling, rowing, and gymnastics) [23,24]. A brace and surgery are unnecessary.

In those spondylolytic patients with a negative bone scan, non-union of the pars is diagnosed and the recommended initial treatment is conservative and directed at improving clinical disabilities, not healing the pars defect. The pain usually resolves when harmful activities are stopped for 2 to 3 weeks, with aggressive rehabilitation, and analgesic consumption. After this period of time, the patient can gradually resume his/her physical activity even in the championship.

Ultimately, in cases of acute spondylolysis (acute fracture in CT and hot spot in bone scan), the primary treatment is a lumbosacral orthosis in order to decrease lumbar lordosis, even by 15 of degrees flexion [25]. A brace regimen consists of wearing it full time (>20 hr/day) for three months with no sports activities allowed. After that, another three months full-time bracing should be continued, but allowing sport activity. At the end of each phase, the patient should be seen to be evaluated for pain. If the pain persists, surgery is indicated [26]. Bracing for more than six months is not indicated and is useless [27].

It is known that more than 80%-90% of the patients with spondylolysis improve with non-surgical treatment [26,28,29]. The healing rates in acute unilateral, acute bilateral, and chronic lesions are 100%, 50%, and 0%, respectively [21,28]. Stability of a fibrous union is acceptable, therefore, non-healed lesions are frequently asymptomatic throughout life and do not usually progress to spondylolisthesis, especially after skeletal maturity achieved [30].

In growing children with lumbar spondylolysis, repeated clinical examinations every six months are recommended until skeletal maturity is reached in order to detect the possible progression of vertebral slippage, but radiographs are usually reserved for those patients with associated pain or change in clinical posture, although progression to slip is not always associated with pain [31,32]. Because there is not a remarkable relationship between presence of spondylolysis on an X-ray and LBP, careful attention to the proper surgical indications is necessary. These include refractory LBP not related to other sources (it is preferred to prove the pars defect by direct injection of local anesthetic drugs preoperatively and under fluoroscopic control), progressive neurological deficit, and pain or disability that is incompatible with activity of daily living without any associated significant underlying psychological disorders [3,8,22,33,34]. We summarized this as an algorithmic approach to the patient with lumbar spondylolysis (Fig. 3).