[Type AO/ASIF B3 fractures of the thoracic and lumbar spine].

PURPOSE OF THE STUDY

Type B3 thoracic and lumbar fractures are often found in spines with previous hyperossification processes such as ankylosing spondylarthritis (AS) or diffuse idiopathic skeletal hyperostosis (DISH). They occur most frequently due to high-energy trauma in a healthy spine and as fall-related domestic injury in a spine affected by hyperossification. Generally, they are less frequent than type B3 cervical spine fractures. In this retrospective study involving two centres, the incidence of these fractures, their characterisation, therapy and complications associated with them were investigated.

MATERIAL AND METHODS

Between March 2003 and March 2012, 21 patients with type B3 injuries (Magerl classification) were treated in our centres. The thoracic spine was involved in 14 and the lumbar spine in seven patients. The patients' average age was 61.8 years, with a range of 33 to 87 years. There were three women and 18 men. Six fractures occurred in previously healthy spines, five and 10 were in AS- and DISH-affected spines, respectively. The evaluation included the mechanism of injury, patient's weight and height, neurological findings, type of treatment and its result, outcome after treatment termination, complications and associated diseases and injuries.

RESULTS

The mechanism of injury differed between the healthy and disease-affected spines. All five AS patients suffered low-energy fractures while patients with previously healthy spines had high-energy injuries. The DISH patients had both low- and high-energy fractures. Type B3.1.1 fractures were diagnosed in two AS patients and six DISH patients, and in no previously healthy patient. Type B3.1.2 fractures were found in one AS patient, two DISH patients and one previously healthy patient. Type B3.2 fracture occurred in one patient with a previously healthy spine, in two AS and two DISH patients. Type B3.3 fractures were in four patients with previously healthy spines. Neurological deficit was found in five injured patients, four of whom had complete paraplegia (Frankel grade A) which did not improve. One AS patient in whom the spinal fracture was associated with Frankel grade C injury improved to Frankel D after surgery. All patients had an elevated BMI, ranging from 25.1 to 41.9; the average value was 32.2, which is within grade 1 obesity. Associated injuries were found in 11 patients, mostly in those with high-energy trauma. Seventeen patients were treated surgically, four conservatively. Posterior stabilisation was carried out in 10 patients who had either AS or DISH conditions; seven patients had a short spinal stabilisation. Complications included early infection in two patients, cerebrospinal fluid fistula in one, urinary tract infection in one and confused state of mind in two patients. All patients healed well but for one patient who died at 4 months after injury due to multiple complications.

DISCUSSION

In the majority of relevant publications these injuries are reported in patients suffering from hyperossification disorders such as AS or DISH. In patients with healthy spines they occur less frequently and the traumatic hyperextension mechanism must have great intensity. Fractures of a hyperossified spine are related to obesity and this was also confirmed by our study in which all patients were overweight or obese. This factor plays an important role in the hyperextension mechanism that produces a sudden overcoming of the resistance of a spinal segment to force, resulting in a type B3 fracture.

CONCLUSION

A different approach to these fractures is required in comparison with other spinal fractures. Type B3 fractures have some features common with type C fractures and are frequent in spines affected by spinal disease. In hyperossification disorders, paradoxically associated with advanced osteoporosis, fracture treatment requires long instrumentation. In healthy spines, fractures are treated with short instrumentation. In AS and DISH patients, the diagnosis may be delayed because these patients suffer from chronic spine pain and the pain due to fracture may be attributed to an accelerated chronic condition.