Unexpected Ipsilateral Pedicle Fracture in Nontraumatic Lumbar Spondylolysis: An Uncommon Case

We describe a rare case of unexpected ipsilateral pedicle fracture in nontraumatic lumbar spondylolysis. A 54-year-old male fish market worker (height: 171 cm; weight: 91 kg; body mass index: 31.1 kg/m²) presented with a 30-day history of progressive low back pain following repetitive heavy lifting at work. His occupational duties involved repeatedly handling and loading approximately 20 kg boxes of fish onto trucks at a wholesale fish market. Physical examination revealed a visual analogue scale score of 50 mm, left lower extremity motor weakness in the L5 distribution (Medical Research Council (MRC) grade 4), and sensory disturbance in the same dermatome. The patient was a current smoker. Radiography and computed tomography demonstrated unilateral left-sided lumbar spondylolysis at the fifth lumbar vertebra (L5), accompanied by an ipsilateral pedicle fracture and low-grade spondylolisthesis at the same segment. Dual-energy X-ray absorptiometry demonstrated osteopenia (T-score -2.4 at L2-L4). Pedicle fractures associated with spondylolysis typically occur contralaterally as a compensatory biomechanical response; therefore, ipsilateral occurrence without trauma is exceedingly rare. In the present case, segmental instability related to spondylolisthesis may have altered posterior load transmission, potentially increasing repetitive mechanical stress on the ipsilateral pedicle. Conservative management failed, and the patient subsequently underwent transforaminal lumbar interbody fusion (TLIF) with pedicle screw fixation 115 days after initial presentation. Postoperatively, the low back pain and numbness resolved completely, while the motor weakness remained stable (MRC grade 4). He returned to work 130 days after initial presentation. This case contributes to the existing literature by demonstrating that the interaction of smoking, borderline low bone mineral density, elevated body mass index, repetitive occupational heavy lifting, and segmental instability may create a biomechanical environment that can produce atypical ipsilateral structural failure of the posterior spinal elements. In patients with unilateral spondylolysis and persistent neurological symptoms, clinicians should meticulously evaluate both pedicles rather than focusing solely on the contralateral side.