INTRODUCTION:

Adolescent sporting activity predisposes to lumbar bone stress injury of the vertebral pars interarticularis or pedicle (pars bone stress injury) and is the primary cause of significant adolescent low back pain. These injuries are at relatively high risk of non-union and potential progression to isthmic spondylolisthesis. Rigid bracing has been proposed as a treatment method for acute lesions. Bracing not only relieves pain, but increases the likelihood of bony healing, thereby reducing the risk of delayed bony union or non-union and progression to isthmic spondylolisthesis. The objective of this study was to evaluate bony healing rates after twelve weeks of rigid lumbo-sacral orthosis in individuals with pars bone stress injury.

METHODS:

We performed a retrospective analysis of 46 male and female athletes (age mean +/- SD) with acute pars bone stress injuries (as defined by a bone marrow oedema ratio > 2) who wore a lumbosacral orthosis for twelve weeks. All participants underwent a Magnetic Resonance Imaging (MRI) scan for both the symptomatic pars and the contralateral pars at the same level. Participants underwent the MRI scan prior to immobilisation (baseline), 6-weeks and 12-weeks after the commencement of bracing. The main outcomes evaluated were fracture grade (stress reaction/incomplete fracture/complete fracture) and healing outcome on 6-week and 12-week scans (unchanged/ progressed/ healed).

RESULTS:

The presence of a chronic (“cold”) contralateral pars stress fracture influenced outcome. (Table 1). The majority of patients presented with a unilateral incomplete fracture (n=18). All of these patients achieved complete healing. In contrast, those with bilateral complete fractures (n=10) showed no healing. A combination of complete and incomplete lesions showed mixed results.

DISCUSSION:

Early detection and immobilisation optimises healing in individuals with unilateral pars bone stress injury. This study raises questions as to the role of bracing for acute pars injury if a contralateral chronic lesion is present. A larger study is currently in progress to explore the influence of contralateral pars bone stress injury on bony healing.