Management of a pseudarthrosis with sagittal malalignment in a patient with ochronotic spondyloarthropathy

Ochronotic spondyloarthropathy is an uncommon disease, and its association to sagittal malalignment in the context of a pseudarthrosis has never been described.

We present the case of a 56-year-old female, who underwent previously L4L5 laminectomy for central canal stenosis and started later on to complain of progressively severe low back pain with a significant forward imbalance while walking. X-rays showed non-compensated sagittal malalignment due to thoracolumbar kyphosis, CT scan revealed multilevel central intradiscal calcifications with important vacuum disc at L4L5, and MRI showed T1 and T2 hypointensity signal at the same level with bone marrow oedema. Alkaptonuric ochronosis was suspected and confirmed by the presence of homogentisic acid in the urine, and the diagnosis of L4L5 pseudarthrosis with associated severe sagittal malalignment in the context of ochronotic spondyloarthropathy was established.

The patient underwent surgery with a posterior-only approach with a long-segment pedicle screw construct from T10 to the pelvis with a 360° fusion with a cage at L4L5. Samples taken from the disc and ligaments confirmed the diagnosis of ochronotic spondyloarthropathy macroscopically and microscopically. She could walk on day 2 with a satisfactory clinical and radiological result at 2 years.

This is the first case in the literature to describe a post-laminectomy pseudarthrosis leading to a significant sagittal malalignment in a patient with ochronotic spondyloarthropathy. Management of such a case is challenging as the spine is partially ankylosed; therefore, a long construct is advisable to avoid ankylosing disorders related complications.