Pigmented villonodular synovitis of the zygoapophyseal joint: a case report

Case report of Pigmented Villonodular Synovitis (PVNS) of a lumbar facet joint which presented as an incidental finding of an expansile lytic lesion of the L5 lamina.

Exceedingly rare is the case of PVNS affecting the zygoapophyseal (facet) joints of the spine. To our knowledge only 30 cases have to this point been reported. We will discuss clinical presentation, diagnostic workup, treatment, and follow-up of this rare case that was treated at our institution.

First described by Jaffe et al in 1941, PVNS is a relatively uncommon benign disorder of unknown etiology that is characterized by progressive synovial proliferation. Benign, but locally aggressive, it is found most commonly in the knee and other large joints. PVNS affecting the zygoapophyseal (facet) joints of the spine is extremely rare, and in our opinion suitable for reporting.

The physical examination of this patient showed signs and symptoms that prompted the need for a plain radiographs and subsequently magnetic resonance imaging (MRI). MRI showed evidence of a lesion in the right lamina of L5. After follow-up MRI showed an expanding lesion, and CT scan confirmed the lytic nature of the lesion, it was decided that an excisional biopsy was warranted. RESULTS.: Postoperative clinical course was unremarkable. The patient was ambulating the next day and was discharged home 2 days later without neurologic deficit or local wound problems. On office follow-up, the patient continued to have diffuse, vague low back pain. Repeat radiograph examination shows no further boney destruction. Repeat MRI shows no residual lesion.

We have learned from this case that PVNS of the facet joint, although exceedingly rare must be considered as a possible cause of expanding lytic lesions of the spine.