Bilateral Lumbar L3 Pars Defect Secured with Pedicle Screw Fixation and Interbody Fusion: A Case Report with Literature Review

Abstract

Background: Spondylolysis is a defect of the pars interarticularis, which most often affects the 5th lumbar vertebra and less frequently the 4th lumbar vertebra. The involvement of L3 is rare and bilateral traumatic pars defects at this level is even less reported. We report a case of acute bilateral L3 pars defect subsequent to trauma associated with left L3 radiculopathy which was successfully treated with pedicle screw fixation and interbody fusion.   Case Presentation: A 34-year-old woman fell off of a ladder and complained of low back pain that spread down her left leg, and over the front of her thigh and inside of her leg. This finding was confirmed by computed tomography (CT) which revealed a bilateral pars defect at L3, but not at L4 or L5; most pars defects are found lower in the spine. The MRI revealed mild bone marrow edema over the defect with irritation of the nerve root of L3 and no significant disc herniation or canal stenosis. Neurological examination found that there was sensory loss in the left L3 dermatome and positive straight leg raise, but there was no motor weakness or abnormal reflexes. She then did not get any relief from her pain with conservative treatment and had to have bilateral pedicle screw fixation with interbody fusion performed at L3. She had marked resolution of back and leg pain post surgery, with progressive improvement in the sensory deficit and follow up imaging revealed a good hardware position with early signs of fusion. Conclusion: Bilateral L3 pars defects, though rare, should be taken into consideration in patients with low back pain following trauma especially if imaging does not conform with the typical appearance of lower lumbar spondylolysis. A complete neurological examination is still necessary as it may be possible to identify a radicular cause of instability despite the fact that the bony defect is the most important. In patients who have failed conservative therapy, pedicle screw fixation with interbody fusion can be an effective procedure