Introduction. Recently various type of spinal instrumentation was applied, and they are essential in modern spinal fusion surgery. Whereas several authors reported increased possibility of complication and degeneration on adjacent segment. We tried PLIF without instrumentation with box type intervertebral cages. Method. Forty-one cases of degenerative lumbar diseases were treated by PLIF with carbon cages without spinal instrumentation. There were 17 males and 24 females, and age averaged 71.4 years. Thirty-two cases were degenerative spondylolisthesis, five were spinal stenosis, and four were disc herniation. Single PLIF was performed on forty cases, and double segment in one, with additional decompression on other segment in twenty. Bilateral facet joint were preserved to avoid lateral instability. Two pieces of cage were inserted with local bone graft. Post-op. follow-up period were 12 to 24 months, 15 months on average. Result. JOA score (29 pts on full mark) averaged 12.7 pts before the operation and was 25.4 pts at the F/U. Recovery ratio averaged 77.9%. Clinical result was excellent in 27 with more than 75% of R/R. One case showed symptomatic non-union, and additional instrumentation was applied after one year. Thirty-three cases (80%) showed solid bone union after one year, and eight cases were classified as non-union. Whereas early cage migration with vertebral collapse was seen on fourteen, and union with collapse was seen in eight. These conditions showed less clinical outcome. Conclusion. Stand alone PLIF resulted in good clinical results with box type cages. Stand alone PLIF is less invasive method and minimize chance of complication. Conflicts of interest. None. Sources of funding. None

Introduction and Objective. Posterior and transforaminal lumbar interbody fusion (PLIF, TLIF) represent the most popular techniques in performing an interbody fusion amongst spine surgeons. Pseudarthrosis, cage migration, subsidence or infection can occur, with subsequent failed surgery, persistent pain and patient’ bad quality of life. The goal of revision fusion surgery is to correct any previous technical errors avoiding surgical complications. The most safe and effective way is to choose a naive approach to the disc. Therefore, the anterior approach represents a suitable technique as a salvage operation. The aim of this study is to underline the technical advantages of the anterior retroperitoneal approach as a salvage procedure in failed PLIF/TLIF analyzing a series of 32 consecutive patients. Materials and Methods. We performed a retrospective analysis of patients’ data in patients who underwent ALIF as a salvage procedure after failed PLIF/TLIF between April 2014 to December 2019. We recorded all peri-operative data. In all patients the index level was exposed with a minimally invasive anterior retroperitoneal approach. Results. Thirty-two patients (average age: 46.4 years, median age 46.5, ranging from 21 to 74 years hold- 16 male and 16 female) underwent salvage ALIF procedure after failed PLIF/TLIF were included in the study. A minimally invasive anterior retroperitoneal approach to the lumbar spine was performed in all patients. In 6 cases (18.7%) (2 infection and 4 pseudarthrosis after stand-alone IF) only anterior revision surgery was performed. A posterior approach was necessary in 26 cases (81.3%). In most of cases (26/32, 81%) the posterior instrumentation was overpowered by the anterior cage without a previous revision. Three (9%) intraoperative minor complications after anterior approach were recorded: 1 dural tear, 1 ALIF cage subsidence and 1 small peritoneal tear. None vascular injuries occurred. Most of patients (90.6%) experienced an improvement of their clinical condition and at the last follow-up no mechanical complication occurred. Conclusions. According to our results, we can suggest that a favourable clinical outcome can firstly depend from technical reasons an then from radiological results. The removal of the mobilized cage, the accurate endplate and disc space preparation and the cage implant eliminate the primary source of pain reducing significantly the axial pain, helping to realise an optimal bony surface for fusion and enhancing primary stability. The powerful disc distraction given by the anterior approach allows inserting large and lordotic cages improving the optimal segmental lordosis restoration

The clinical success of posterior lumbar interbody fusion (PLIF) may be limited by pseudarthrosis, defined as the absence of solid fusion 1 year after surgery. Currently, CT is used to diagnose pseudarthrosis but is not able to be conclusive earlier than 1 year after surgery. No non-invasive technique is available to reliably assess bone graft incorporation in the early phase after PLIF. Positron Emission Tomography (PET) is a nuclear imaging modality that is able to identify changes at the cellular and molecular level in an early stage, well before manifestation of anatomical changes. PET/CT with the bone seeking tracer . 18. F-fluoride allows localization and quantification of bone metabolism. This study investigates whether an . 18. F-fluoride PET/CT scan early after PLIF is able to predict the fusion status at 1 year postoperative on CT. Twenty patients after PLIF were enrolled after written informed consent. At 6 weeks and at 1 year after PLIF, intravenous injection of . 18. F-fluoride was followed by a static scan at 60 minutes (Philips, Gemini TF PET/CT). Processing of images resulted in a bone metabolism parameter i.e. standardized uptake value (SUV). This parameter was determined for 3 regions of interest (ROIs): the intervertebral disc space (IDS) and the upper and lower endplate (UE and LE, respectively) of the operated segment. Interbody fusion was scored on a diagnostic CT scan made 1 year postoperatively and was defined as the amount of complete bony bridges between vertebrae, i.e 0, 1 or 2. Based on these scores, patients were divided in either the pseudarthrosis group (score 0) or the fusion group (scores 1 and 2). Differences between groups were analyzed using the independent samples Mann-Whitney U-test. Ten patients were classified as pseudarthrosis (0 bridges: n=10) and 10 patients as fused (1 bridge: n=5, 2 bridges: n=5). Patients in the pseudarthrosis group showed significantly lower bone metabolism values in the IDS on the 6 weeks PET/CT scan compared to patients in the fusion group (SUV. IDS,6w. 13.3±5.62 for pseudarthrosis and 22.6±6.42 for the fusion group, p=0.003), whereas values at the endplates were similar (SUV. UE,6w. 20.3±5.85 for pseudarthrosis and 21.6±4.24 for the fusion group, p=0.282). Furthermore, only in the pseudarthrosis group, bone metabolism in the IDS was significantly lower than at the endplates (p=0.006). In the fusion group, bone metabolism in the IDS and at the endplates was similar (p=0.470). The PET/CT scan at 1 year postoperative showed that in the pseudarthrosis group, bone metabolism of the IDS remained lower compared to the endplates (SUV. IDS,1y. 13.2±4.37, SUV. UE,1y. 16.4±5.33, p=0.004), while in the fusion group, IDS and endplate bone metabolism was similar (SUV. IDS,1y. 13.6±2.91, SUV. UE,1y. 14.4±3.14, p=0.397). This study shows that low bone metabolism values in the IDS of the operated segment as seen on . 18. F-fluoride PET/CT 6 weeks after PLIF, is related to development of pseudarthrosis 1 year postoperatively. These results suggest that . 18. F-fluoride PET/CT might be an early diagnostic tool to identify patients prone to develop pseudarthrosis after PLIF