Congenital Posterior Spinal Agenesis Leads to L2-L3 Instability: a Case Report and Review of the Literature

Congenital absence of posterior elements of the lumbar column is an extremely uncommon anomaly and we found no any reported cases of incomplete congenital absence of the posterior elements of lumbar vertebra in the literature. Here, we present a case with congenital absence of posterior elements of lumbar vertebra. The patient was a 51-year-old man with a history of 20 years of back pain. Imaging of the lumbar spine revealed instability in L2 and L3 and there was evidence of retrolisthesis, agenesis of pars interarticularis, spinous processes, lamina, transverse processes and facets at L2 and L3. The patient underwent lumbar discectomy and posterior spinal fixation and instrumentation was then done using pedicle screw fixation. Four pedicle screws, two rods, and one cross link were employed to bilaterally fix the L2 and L3 and then we used autograft and allograft bone for interbody fusion, substitutes from iliac crest for posterior fusion. There were no postoperative complications, and at 6, 12 and 24 months of follow-up, his leg and back pain had improved, and the patient did not need any analgesic for pain relief. Complete congenital absence of the lumbar posterior element has been rarely reported in the literature. Patients whose congenital anomalies lead to segmental instability are surgical fusion candidates, but if these anomalies occur in pars interarticularis such as spondylolysis isthmus, fixation and inter segmental fusion techniques are useful.