Stand-alone cage for posterior lumbar interbody fusion in the treatment of high-degree degenerative disc disease: design of a new device for an "old" technique. A prospective study on a series of 116 patients.

Chronic lumbar pain due to degenerative disc disease affects a large number of people, including those of fully active age. The usual self-repair system observed in nature is a spontaneous attempt at arthrodesis, which in most cases leads to pseudoarthrosis. In recent years, many possible surgical fusion techniques have been introduced; PLIF is one of these. Because of the growing interest in minimally invasive surgery and the unsatisfactory results reported in the literature (mainly due to the high incidence of morbidity and complications), a new titanium lumbar interbody cage (I-FLY) has been developed to achieve solid bone fusion by means of a stand-alone posterior device. The head of the cage is blunt and tapered so that it can be used as a blunt spreader, and the core is small, which facilitates self-positioning. From 2003 to 2007, 119 patients were treated for chronic lumbar discopathy (Modic grade III and Pfirrmann grade V) with I-FLY cages used as stand-alone devices. All patients were clinically evaluated preoperatively and after 1 and 2 years by means of a neurological examination, visual analogue score (VAS) and Prolo Economic and Functional Scale. Radiological results were evaluated by polyaxial computed tomography (CT) scan and flexion-extension radiography. Fusion was defined as the absence of segmental instability on flexion-extension radiography and Bridwell grade I or II on CT scan. Patients were considered clinical "responders" if VAS evaluation showed any improvement over baseline values and a Prolo value >7 was recorded. At the last follow-up examination, clinical success was deemed to have been achieved in 90.5% of patients; the rate of bone fusion was 99.1%, as evaluated by flexion-extension radiography, and 92.2%, as evaluated by CT scan. Morbidity (nerve root injury, dural lesions) and complications (subsidence and pseudoarthrosis) were minimal. PLIF by means of the stand-alone I-FLY cage can be regarded as a possible surgical treatment for chronic low-back pain due to high-degree DDD. This technique is not demanding and can be considered safe and effective, as shown by the excellent clinical and radiological success rates.