Iatrogenic spinal instability: Cervical and thoracic spine

Iatrogenic spinal instability is defined as an instability resulting from direct surgical and/or medical intervention. Spinal instability of this variety was originally described in the early to mid-20th century and many of the treatments that produce instability have been known and studied for decades. More importantly, patients with iatrogenic instability are now recognized to have decreased functional outcomes and are at increased risk of requiring revision surgery. The most common clinical presentation is seen in an at-risk patient who fails to meet expected post-operative gains, functionally declines, or presents with new symptoms. Arriving at the correct diagnosis requires a high degree of suspicion and detailed history. While improvements in the understanding of spinal stability and advances in surgical technique have altered the incidence of iatrogenic instability, it continues to remain a relatively common clinical problem. A thorough comprehension of the etiologies, prevention strategies, and subsequent management of iatrogenic instability is imperative to the practicing spine surgeon. This review will outline four of the most common clinical scenarios that result from treatment-induced spinal instability: post-laminectomy kyphosis, posterior foraminotomy-induced kyphosis, adjacent segment disease, and radiation-induced instability. The goal will be to detail the proposed mechanisms of the induced instability, allowing for potential prevention strategies, and to provide an approach to treatment for patients with each of these iatrogenic instability conditions.