Introduction

Spondylolysis, which is a stress fracture of the pars interarticularis of the lumbar vertebrae is a form of specific low back pain commonly seen in young active adolescents participating in sports involving many (hyper)extension and rotational movements. Diagnosis is made based upon MRI images, but as this is relatively costly, it would be interesting to have a screening test which may raise the suspicion of a spondylolytic stress fracture being present before referring someone to MRI. The authors therefore wanted to investigate if there exists a motion that accentuates the specific complaints of those with spondylolysis, in order to better differentiate between this form of specific low back pain from low back pain from a nonspecific origin.

Methods

Using a retrospective cohort design, the authors tried to find the most common characteristic motion provoking the adolescents’ low back pain. Therefore, adolescents aged 18 years or younger were included within 1 month of the onset of their acute low back pain. All patients got an MRI scan to evaluate the presence or absence of a spondylolytic stress fracture and were then classified into 2 groups: a group with patients showing no abnormalities (and thus having nonspecific low back pain) or into the spondylolysis group.

Using the Oswestry Disability Index and the Visual Analogue Scale, patients were asked about their low back pain complaints before the clinical examination. Then they were asked to perform active flexion and extension, and lateral flexion and rotation to both the left and right side. The VAS was used to rate the intensity of the lower back pain with every movement. The authors then looked at the differences in VAS during these active movements between those with spondylolysis and those with nonspecific low back pain.

Results

In total, 112 patients were included into this study. Of them, 71 had a spondylolytic stress fracture and 41 had a form of nonspecific low back pain. There was no difference in VAS and ODI before the active movements were performed. After each active movement, pain was reassessed and this revealed that with lateral bending, the level of pain experienced by those with spondylolysis was significantly different from the pain level experienced by those with nonspecific low back pain. In the spondylolysis group, a mean pain level of 2.9/10 was reached while those with nonspecific low back pain had a VAS score of 2.2/10 with lateral bending.

Through the ROC-analysis, the authors tried to determine the optimal VAS cut-off score of the provoked low back pain corresponding to spondylolysis and found it at 3.5 which showed a sensitivity of 43.7% and a specificity of 73.2%

Questions and thoughts

A significant difference in the VAS score was seen between the ones with spondylolysis and those having nonspecific pain in the low back. Lateral bending provoked significantly more pain in those with a spondylolytic stress fracture than in those with nonspecific low back pain. However, this difference of 0.7 points was small and therefore it may be questioned if it is clinically relevant and noticeable.

The active tests that were chosen to perform were relatively easy to explain to the patient and quick to perform. Another good aspect was that the test was only repeated once in each direction and the next movement was only examined when the pain from the previous movement had resided. This is interesting, as it is likely that in this way the wind-up phenomenon (temporal summation) did not have influenced the results.

Talk nerdy to me

The ROC-analysis found a sensitivity of 43.7% and a specificity of 73.2% at a VAS score of 3.5/10 with lateral bending. Therefore the test doesn’t have a strong diagnostic value to exclude or include the presence of a spondylolytic lesion when the VAS score with lateral bending exceeds 3.5. Furthermore, this can also be seen when looking at the ROC-curve. When a test has a strong diagnostic value, the curve goes up all the way, parallel to the Y-axis and then bends to run horizontally at the top of the frame. The more centrally the curve (like the grey line), the worse the diagnostic value of the test as this grey line displays the random intercept. Also, in this study, both the optimal cut-off point and the sensitivity and specificity were determined and this may have introduced bias into the results. First a study should be conducted to determine the cut-off point and this cut-off score should then be tested in another sample to determine the corresponding diagnostic value (sensitivity and specificity).

Adding the fact that this was a retrospective study, the findings of this study should be interpreted cautiously. Indeed, lateral bending was a specific movement provoking a significant difference between those with and without spondylolysis, as stated by the authors. But the diagnostic value was low, and the difference on the provoked VAS pain is likely not to be clinically relevant and noticeable.

Take home messages

The results from this study show that, regardless of what is claimed by the authors, active lateral bending does not have a strong diagnostic value to discriminate between low back pain coming from a nonspecific or from a spondylolytic origin. Therefore the test can be used next to other common tests with low diagnostic value like the 1-legged hyperextension test, the hyperextension and -flexion tests, Kemp test and the vertebral percussion test to establish a suspicion of spondylolysis being present, without being able to diagnose it based on the cut-off of 3.5 out of 10 on the VAS.

If you are interested in rehabilitation ideas for patients with spondylolysis, I refer you to the following video where I discuss functional progression exercises that can be used to avoid the typical “relative rest” that is frequently prescribed in this population. https://www.youtube.com/watch?v=xFy9euq6_aU&t=250s

Reference

Sugiura S, Aoki Y, Toyooka T, Shiga T, Takato O, Ishizaki T, Omori Y, Takata A, Kiguchi Y, Tsukioka A, Okamoto Y, Matsushita Y, Inage K, Ohtori S, Nishikawa S. Lateral bending differentiates early-stage spondylolysis from nonspecific low back pain in adolescents. Musculoskelet Sci Pract. 2022 Feb 1;58:102526. doi: 10.1016/j.msksp.2022.102526. Epub ahead of print. PMID: 35149279. https://pubmed.ncbi.nlm.nih.gov/35149279/