Current concepts: approach to spondylolysis

Abstract

Lumbar spondylolysis is an acquired defect of the pars interarticular process (‘isthmus’) due to the human species’ erect posture. Anatomical and load factors play a role. With lumbar extension, the superior vertebra’s inferior articular process drives down dorsally on the inferior pars, causing a ventral tensile stress, bone oedema, fracture, and ultimately nonunion in some. The population incidence is around 6%, where most are inconsequential as they are asymptomatic and have a favourable natural history.

In the physically highly active group, especially athletes, back and radicular pain is more common, leading to a three to four times higher incidence of lysis in this group.

Although X-rays are typically the first imaging modality used, computed tomography (CT) is far more sensitive and, with staging, more predictive of fusion with comparable radiation dose. Magnetic resonance imaging (MRI) allows identification of bone oedema, a precursor of fracture, and assessment of the disc status. This has replaced previously used isotope bone scans and single-photon emission computed tomography (SPECT).

Management involves cessation of physical activity and bracing to block extension for three to six months, with around 90% resolution of symptoms. Union rate is negatively related to bilaterality and terminal stage (nonunion), but not necessarily correlated to symptom/functional status.

Surgical intervention in those that fail nonoperative care includes pars repair or fusion, with a high fusion and return to activity rate. The young athlete poses a particular challenge due to return to play pressure, but still does well with nonoperative care and subsequent activity modification. Counselling of the family and sports staff is extremely important when planning treatment in this high-demand group.

Level of evidence: Level 5