Bilateral Double-Layered Patella: MRI Findings and Fusion with Multiple Headless Screws: A Case Report.

Abstract

The double-layered patella (DLP) was first described by Buttner in 19251. It is a rare entity that is often associated with an autosomal recessive form of multiple epiphyseal dysplasia (MED) caused by a homozygous diastrophic dysplasia sulfate transporter (DTDST) gene mutation2-5, although COMP6 and COL9A27 deletions have also been reported to cause DLP. DLP is a relatively mild form of MED, and clinical findings are often limited to bilateral recurrent anterior knee pain and early-onset hip osteoarthritis (C653S homozygous DTDST gene)2 as well as mild brachydactyly and clubfoot deformity (R279W homozygous DTDST gene)8. If the soft-tissue interface between the anterior and posterior osseous layers in DLP is stable and allows for little motion, patients may be asymptomatic. In these cases, DLP is often discovered incidentally as part of a broader diagnostic evaluation for MED9. However, if the soft-tissue interface is unstable, considerable motion can occur between the two ossified layers, which can cause symptoms, particularly during knee extension. This can present as a sensation of locking, giving way, or subluxation2, or alternatively as painful clicking or a snapping sensation with flexion near 30° to 40° 10,11. There is very limited information regarding the surgical treatment of symptomatic DLP. In several prior reports, a good clinical outcome was achieved with debridement of the soft-tissue interface and fusion of the osseous layers with screws10-12. In a patient with DLP who had undergone unsuccessful soft-tissue stabilization (Ali-Krogius procedure13), Hinrichs et al. utilized a tibial tuberosity medialization addition to a second soft-tissue stabilization2. We present a case of symptomatic bilateral DLP in an adolescent who was treated with fusion with use of four headless screws. The patient’s parents were …