Heterotopic ossification of the quadratus lumborum muscle

Abstract

Heterotopic ossification is a benign process of mature laminar bone formation in the soft tissues. A synonymous term used to describe this pathology in muscle is myositis ossificans. The pathogenesis is unclear, but is likely multifactorial. The basic pathology is thought to be ectopic production of osseous tissue as part of a repair process in response to tissue injury. This report describes a case of heterotopic ossification of the quadratus lumborum muscle as an incidental finding. This case highlights that treatment is based on symptoms and conservative management might be appropriate for the asymptomatic patient.

Keywords: Quadratus lumborum muscle; computed tomography; idiopathic ossification; imaging.

Figure 1

A 29 year old male with myositis ossificans of the quadratus lumborum muscle. Protocol: Non-contrast enhanced CT, Siemens Somatom. Images were acquired kVp 120, mAs 51, helical acquisition, pitch 0.8, the original image collimation was 1.2 mm, the final images were reformatted to 5 mm thickness. a) An axial CT scan in the mid-portion of the abnormality reveals a thick cortical type of bone and a central lucency within the region of ossification (arrow). b) An axial CT scan in the caudal aspect of the ossification near the junction with the left iliac bone again reveals dense cortical type bone with more lucent bone centrally (arrow).

Figure 2

A 29 year old male with myositis ossificans of the quadratus lumborum muscle. Protocol: Non-contrast enhanced CT, Siemens Somatom. Images were acquired kVp 120, mAs 51, helical acquisition, pitch 0.8, the original image collimation was 1.2 mm, the final images were reformatted to 5 mm thickness. a) A coronal plane MIP reformat demonstrates the mature bone arising from the left iliac crest projecting toward the upper lumbar spine (arrow). b) An anteriorly oriented 3D volume rendered CT image shows the relationship of the quadratus lumborum lesion with the L3 transverse process (arrow). c) A posteriorly oriented 3D volume rendered CT image shows the relationship of the quadratus lumborum lesion with the L3 transverse process (arrow).

Figure 3

A 29 year old male with myositis ossificans of the quadratus lumborum muscle. a) A magnified view of the L3 pseudoarthrosis is provided (arrow). b) The plain x-ray of the abdomen reveals abnormal ossified mass arising from the left iliac crest forming a pseudoarthrosis with the L3 transverse process (arrow).