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Abstract & Commentary
By Matt Shores, MD, St. Joe's Hospital and Medical Center, Family Medicine Residency, Phoenix, AZ, is Associate Editor for Urgent Care Alert.
Dr. Shores reports no financial relationships relevant to this field of study.
Synopsis: The one-legged hyperextension test is not accurate in screening for spondylolysis and bone scintigraphy (with SPECT) should remain the gold standard in diagnosing spondylolysis.
Source: Masci L, et al. Use of the one-legged hyperextension test and magnetic resonance imaging in the diagnosis of active spondylolysis. Br J Sports Med. 2006;40:940-946.
Low back pain is a common presentation in primary care offices, urgent care facilities, and emergency departments across the nation. However, low back pain in an adolescent, or an otherwise young healthy adult, is a bit curious, particularly when occurring in an active individual. The most common cause of low back pain in the active, athletic population is spondylolysis, an acquired defect in the pars interarticularis. Spondylolysis may be seen in a wide spectrum of patients; however, it is most commonly seen in individuals whose activities require repetitive lumbar extension and rotation. For example, spondylolysis is more common in football offensive lineman, gymnasts, and divers. It is important to recognize active spondylolysis, given that early recognition has been associated with improved fracture healing. In the past, reproduction of pain with the one-legged hyperextension test has been pathognomonic for spondylolysis. Given a positive one-legged hyperextension test, patients are often then referred for bone scintigraphy with SPECT, the gold standard in diagnosing spondylolysis. If bone scintigraphy (with SPECT) is positive, a follow-up CT scan is done to look for a fracture.
The purpose of this study in the November 2006 British Journal of Sports Medicine is to determine the efficacy of the one-legged hyperextension test in screening for spondylolysis and to compare the use of MRI vs the gold standard, bone scintigraphy (with SPECT), with follow-up CT when positive. Patients were chosen if they were between the ages of 10 and 30 and participated in regular activity. Patients must have had back pain for 6 months or less, with a tentative diagnosis of spondylolysis. Finally, the patients needed to have been referred for bone scintigraphy (with SPECT) as the initial evaluation. Also, patients were excluded if they had a contraindication to MRI or if they had a diagnosis of spondylolysis confirmed by bone scintigraphy (with SPECT) within the last 12 months. The patients chosen proceeded to complete a study questionnaire under the supervision of the main investigator. In addition, the main investigator had the patients perform the one-legged hyperextension test. Finally, each patient had both bone scintigraphy (with SPECT) and an MRI; CT scan was only done on those patients with a positive bone scintigraphy (with SPECT).
The results of this study did not bode well for the one-legged hyperextension test. One main investigator examined 71 patients using the one-legged hyperextension test (the patient stands on one leg as the opposite leg is raised with its knee in flexion and the hip slightly flexed, while the patient actively extends their lumbar spine). When the left leg was tested, 42 of the 71 patients had a positive test (reproduced pain); however, only 17 of those 42 actually had an active spondylolysis confirmed by bone scintigraphy (with SPECT). The results were equally poor when examining the right side; 39 of those patients had a positive one-legged hyperextension test, while only 21 truly had an active spondylolysis. These results rendered the one-legged hyperextension test, with a sensitivity of 50% and 55.2% on the left side and right side, respectively. The tests specificity was equally poor; 67.6% and 45.5% on the left side and right side, respectively.
The study also took a look at the use of imaging in diagnosing spondylolysis. Bone scintigraphy (with SPECT) is currently the gold standard in diagnosis; however, MRI has been thought of as a possible alternative. The study performed both bone scintigraphy (with SPECT) and MRI on all subjects. In the 71 subjects, a total of 50 pars interarticularis were found (11 patients had bilateral uptake and 28 patients had unilateral uptake). When MRI was performed, only 40 pars interarticularis were found. Therefore, MRI only detected 80% of the pars interarticularis that bone scintigraphy picked up. When bone scintigraphy (with SPECT) is positive, a follow-up CT scan is performed to look for fractures. In the 50 pars interarticularis, follow-up CT scan found 19 fractures; MRI detected 18 fractures.
The conclusions of this study are fairly straightforward. The one-legged hyperextension test has a very poor sensitivity and specificity when looking for spondylolysis. It may, therefore, be determined that it alone is a sub-par screening tool and can neither rule-in nor rule-out spondylolysis. A positive test should no longer be pathognomonic for spondylolysis. In addition, it would be nice if MRI was as efficient in picking up pars interarticularis as bone scintigraphy (with SPECT); however, MRI only picked up 80% of those pars interarticularis that bone scintigraphy (with SPECT) detected, and frankly that's just not good enough. MRI did have comparable results to CT in detecting fractures; however, MRI cannot differentiate between acute and chronic fractures, a feature attributed to the CT scan. So, in the end, bone scintigraphy (with SPECT) should remain the gold standard in diagnosing spondylolysis, and it should be ordered on clinical suspicion, not on whether or not a one-legged hyperextension test was positive or negative.
Spondylolysis is the most common cause of low back pain in the young athlete or any young active individual. Simply put, spondylolysis is a stress reaction of the pars interarticularis. It is most commonly seen at the levels of the fourth and fifth lumbar vertebrae. As mentioned previously, the mechanism of injury is repeated hyperextension of the lumbar spine, and is most common in young athletes whose sports require such repetitive motion, such as divers, gymnasts, or offensive lineman. The injury occurs as a continuum, in that the stress reaction may progress to a true stress fracture given repeated hyperextension activity in the face of low back pain. As this study has shown, the one-legged hyperextension test is not proficient in screening for spondylolysis. Referral for imaging should be approached on a strong clinical suspicion. A referral for bone scintigraphy (with SPECT) would be prudent to evaluate any young active individual that presents with low back pain that does not improve after 2 weeks of conservative treatment. Treatment of spondylolysis includes the use of a lumbosacral orthosis in a position of slight flexion. Bracing and inactivity should occur for a time period of at least 6 weeks and/or until the patient is pain free, which may take up to 6 months. Once the patient is pain free, a rehab program may be started and the patient may return to activity if rehab is tolerated well.5
In an urgent care setting, low back pain is often briefly evaluated. The pain is treated with a short course of medication, and the patient is advised to follow up with their PCP for further evaluation and pain management. Of course, this is appropriate care in the urgent care setting. However, it can never hurt to have more knowledge as to what we are treating as physicians, as well as equipping our patients and their PCPs with this knowledge so that we steer them in the right direction.