Sacral fractures following instrumented spinal fusion are a relatively uncommon yet significant complication in patients undergoing these procedures. With only a limited number of cases documented prior to recent studies, the understanding and recognition of these fractures are crucial for effective patient management. Often subtle in presentation, particularly in initial radiographic assessments, accurate sacral fracture diagnosis relies on a high index of suspicion and advanced imaging techniques. This article delves into the incidence, risk factors, diagnostic approaches, and treatment strategies for sacral fractures occurring caudal to instrumented spinal fusion.
Research indicates that the incidence of sacral fractures subsequent to spinal fusion is approximately 6.1% overall, with a notably elevated risk of 14.5% in cases involving fusions spanning more than four vertebral levels. This highlights the extent of spinal instrumentation as a significant factor contributing to fracture risk. Furthermore, the average time from the initial spinal surgery to the occurrence of a sacral fracture is around 4.3 months, suggesting a relatively early post-operative timeframe for heightened vigilance. Patient characteristics also play a crucial role, with osteoporosis identified as a key predisposing factor, underscoring the importance of pre-operative bone health assessment and optimization strategies in patients considered for extensive spinal fusions.
One of the primary challenges in managing these fractures is the difficulty in initial sacral fracture diagnosis using standard plain radiography. Studies reveal that in many cases, the fracture is not readily apparent on initial X-rays taken at the onset of symptoms. This diagnostic ambiguity necessitates the use of more sensitive imaging modalities. Computed tomography (CT) scans, magnetic resonance imaging (MRI), and nuclear scintigraphy have all proven valuable in establishing a definitive diagnosis when plain radiographs are inconclusive. These advanced imaging techniques offer superior visualization of sacral bone structures and can detect subtle fracture lines or stress reactions that may be missed on conventional radiography, thus playing a critical role in timely and accurate Sacral Diagnosis.
Treatment strategies for sacral fractures post-spinal fusion range from conservative management to surgical intervention, depending on the fracture characteristics and patient presentation. Conservative treatment, typically involving non-operative measures such as bracing and pain management, has been successfully employed in approximately one-third of cases. The average time to fracture union with conservative treatment is around 21 weeks. However, certain fracture patterns are associated with a higher likelihood of conservative management failure. Specifically, fractures exhibiting anterolisthesis (forward slippage) greater than 2 mm and kyphotic angulation are significantly more prone to non-union or symptomatic malunion, necessitating surgical correction.
Surgical intervention becomes necessary when conservative management fails or in cases presenting with fracture instability, significant deformity, or neurological compromise. Surgical strategies primarily involve extending the posterior spinal fusion construct caudally to the S2 vertebra and incorporating the iliac wings with sacroiliac joint fusion. This posterior approach aims to stabilize the sacrum and promote fracture healing. In more complex scenarios, a combined anterior and posterior surgical approach may be required. This combined approach often entails either revision anterior lumbar interbody fusion (ALIF) or transsacral posterior lumbar interbody fusion (TLIF) to achieve comprehensive stabilization and fusion, particularly in cases with significant anterior column involvement or deformity.
In conclusion, sacral fractures following instrumented posterior spinal fusion, while not common, represent a clinically relevant complication that can be easily overlooked if reliance is placed solely on initial plain radiographs. Risk factors such as osteoporosis and the extent of spinal fusion significantly increase the likelihood of these fractures. Accurate and timely sacral fracture diagnosis, often requiring CT, MRI, or nuclear scintigraphy, is paramount for guiding appropriate management. While conservative treatment can be effective in select cases, fractures with anterolisthesis or kyphosis often require surgical stabilization to achieve fracture union and optimal clinical outcomes. Therefore, a heightened awareness of this complication, coupled with a systematic approach to sacral diagnosis and management, is essential for spine surgeons performing instrumented spinal fusions.
