The conventional lumbar interbody fusion including the early posterior lumbar interbody fusion (PLIF) is advocated as a main treatment of choice for chronic low back pain and compressive radicular pain due to the advanced disc degenerative disease because 70–90% of the patients were satisfied with the results [1
] and 75–95% returned to work [7
]. Although PLIF with conventional cages has established itself as a surgical approach of choice, its record of major complications has been puzzling. A recent review reported complications in 95% of the cases and re-operation in 25–45% [2
]. Expandable spinal cages have the potential to achieve similar results with less invasive techniques. The biomechanical properties of the B-Twin ESS were designed to provide immediate mechanical constraint in all planes. The constraints of flexion and lateral bending are mediated by the annulus. This is attained by distraction of the disc space from the expansile spinal cages. This is only accomplished by a ‘Jacking up” mechanism. The stability in the axial plane is credited to the limited invasiveness of the surgical procedure which makes it possible to preserve the main stabilizers in the axial plane, namely the facet joints and the annulus fibrosus [10
Percutanous posterior-lateral lumbar interbody fusion (PPLLIF) is a new procedure developed in recent years with the novel B-Twin expandable spinal system emerging. The implant is typically proceeded bilaterally but our 12 cases were performed unilaterally and as a stand alone according to the chinese patients’ figure and economy level. The unilateral procedure of PPLLIF has more advantages compared with the PLIF using the ESS: firstly, the mean blood loss with 35 ± 18 mL (range 20–60 mL) was dramatically decreased compare to it of PLIF with 410 ± 330 ml (range 300–1,500 ml) [3
]; Secondly, the poster-lateral puncture approach of PPLLIF was a minimal invasive procedure, especially the unilateral procedure, it did not interfered the construction of the spinal canal and did not require the sacrifice of the posterior stabilizing structure (such as ligament, lamina and facet joint). Therefore, it could better maintain the stability of the spine than the surgery of PLIF. Thirdly, it shortened the procedure time and reduced the risk of nerve damage. It is an alternative method for PLIF if the selective candidate was chosen wisely. The main concern was in regard to the penetration of the endplate by the fins and the possibility of implant migration. The averaged subsidence in the 12 cases was 0.35 mm per fin (0.7 mm per implant) after 1 year follow-up visit. It is deeper than 0.28 mm per fin (0.56 mm per implant) reported by Folman [4
]. This might be in correlation with one-cage implanted into the spinal space for the 12 patients. This subsidence did not jeopardize the stability of the ESS, and the engagement of the fins into the vertebral endplate provided an element of resistance against migration. However, the quality of the bone is most essential in determining the anchorage of the fins into the endplate. This consideration may be of crucial importance when selecting candidates for PPLLIF using ESS. The 11 patients’ plain X-ray established that fusion was accomplished by 1 year follow-up. This favorable result may be ascribed to the relatively small implant-endplate contact area, and this will leave a large area free so that the bone graft is in contact with the bone; enabling bone to bone contiguity without having to depend on bone growth into and through the cage as in the cases of conventional cages. Moreover, meticulous curettage of the nucleus, rather than installation of the device within a reamed channel, was suggested to promote fusion [9
]. In the 11 patients’ radiolucencies at the implant endplate, interface was not there, which means that fusion is already occurring. Stress views did not show any sign of instability. The length of the implant and its contouring may preclude radiological assessment of fusion. In this study, we found that the stability of one implant insertion into the intervertebral body is the same with that of two implants.
Bone graft for spinal fusion surgeries may either be harvested from the patient (autograft bone) or from a cadaver (allograft bone). In the final result, we did not find any difference of spinal fusion between patients using autograft bone or allograft bone. Wimmer et al. [12
] followed 94 cases with the anterior interbody fusion and found that the resource of bone makes no difference in spinal fusion rate. The patients treated with the technique exhibited satisfactory results with improved neurological function. Eleven patients had good relief 1 month postoperatively. In the final analysis, VAS on movement and ODI (Oswestry disability index) dropped by more than 80 and 67.4%, respectively. The results was similar to the report of Kuslic et al. [13
] who implanted the cage by anterior or posterior approach. Disk space heights averaging 9.0 mm before procedure was increased to 11.5 mm after surgery 1 mouth and stabilized at 10.8 mm (a significant difference compared with preprocedure, P
< 0.01) upon after more than 1 year follow-up.