|
Year |
2002 |
|---|---|
|
Question Number |
258(2) |
|
Category |
Pediatric Orthopaedics |
Question
Figure 72 shows the planar technetium Tc 99m bone scan of a 14-year-old boy who has had localized back pain for the past 6 weeks. Pain is reported with hyperextension of the lumbar spine. The neurologic examination and radiographs of the lumbar spine are normal. What is the most likely diagnosis?
1- Herniated nucleus pulposus at L4-L5
2- Herniated nucleus pulposus at L5-S1
3- Spondylolysis at L5
4- Hemangioma
5- Tuberous sclerosis
Figures
Answer (click for answer)
Preferred answer: 3
You don’t really even need the bone scan to answer this question, but it is good confirmation. The cited paper states that spondylolysis is the most common cause of low back pain in childhood according to multiple studies. Spondylolysis, or bony deficiency of the pars interarticularis, is present in 5-8% of the American population. It can be degenerative, congenital, traumatic, pathologic, or isthmic. It is the isthmic variety, thought to be caused by stress fracture of the pars from repetitive microtrauma, that is most common in children and adolescents. It can be seen as early as age 5-7, but is most common in teenagers, which this patient is. Furthermore, pain with hyperextension of the spine also points to spondylolysis, as this position puts the most stress on the pars. In fact, patients who participate in activities requiring repetitive hyperextension, such as gymnasts and football linemen, have been shown to be at increased risk for the condition. The lack of a neuro deficit is also consistent with the diagnosis, as this is seen only on rare occasions (and is more likely with the other conditions listed as answered).
The identification of pars lesions is often unable to be done with plain radiographs, although this should always be the first imaging step. Bone scanning techniques have been shown to be more sensitive in demonstrating spondylolysis, and both planar bone scanning (PBS-as demonstrated in the figure) and SPECT (single photon emission computed tomography) have been used with success. The cited study of 34 patients found that 53% of plain radiographs were falsely negative when compared with SPECT results. Thus, the fact that our patient had negative X-rays is not a surprise. Additionally, PBS was shown to have a 20% false-negative rate when compared to SPECT, suggesting the superiority of the latter. The bone scan shown, however, is markedly positive for unilateral uptake in the region of the L5 pars. With the given history and this positive test, the diagnosis of spondylolysis can be made. The other answers are far less common in this age group and do not fit with the clinical and radiographic data.
Reference: Anderson K, Sarwark JF, Conway JJ, Logue ES, Schafer MF: Quantitative assessment with SPECT imaging of stress injuries of the par interarticularis and response to bracing. J Pediatr Orthop 2000; 20:28-33.
Lonstein J: Spondylolysis and spondylolithesis, in Morrissey RT, Weinstein SL (eds): Lovell and Winter’s Pediatric Orthopaedics, ed. 5. Philadelphia, PA, Lippincott Williams and Wilkins, 2001, pp. 777-798.
Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 155-156 and 179.