Can intraoperative radiation dose in percutaneous posterior thoracolumbar internal fixation be reduced by impedancemetry-guided pedicle sighting? A prospective randomized study.

INTRODUCTION: Percutaneous spine surgery is on the rise; the main drawback is iterative irradiation of the care team in theater. The aim of the present study was to compare intraoperative radiation dose in percutaneous posterior thoracolumbar internal fixation (PPTLIF) using impedancemetry-guided pedicle sighting by the PediGuard device (SpineGuard®) versus gold-standard free-hand sighting. MATERIAL AND METHODS: A single-center, single-surgeon continuous prospective randomized study was conducted from September 2017 to April 2018. Dose-area product (DAP, in cGy.cm2) was recorded at the end of pedicle sighting and end of surgery in the free-hand control group and the impedancemetry group. Pedicle screw position was studied on postoperative CT scan. RESULTS: Sixteen patients were included in either group after 2 had been excluded. The groups were comparable for age, gender, body-mass index (BMI), indication and number of instrumented levels. Mean DPA at end of sighting and end of procedure was respectively 147.4 cGy.cm2 and 230.9 cGy.cm2 in the control group and 171.1 cGy.cm2 and 280.7 cGy.cm2 in the PediGuard group (p> 0.05). Screw positioning on CT was comparable in the 2 groups. CONCLUSION: In the present study, the PediGuard device did not reduce intraoperative radiation dose. The correlation between radiation dose and BMI was confirmed. LEVEL OF EVIDENCE: II; prospective randomized study.

Morbidity and clinicoradiological outcomes of anterior lumbar arthrodesis using tantalum intervertebral implants.

PURPOSE: The objective of this study was to assess the morbidity of Anterior Lumbar Interbody Fusion (ALIF) using an intervertebral tantalum implant. Tantulum is an extremely porous metallic material which possesses properties of osseointegration, osteoinduction and osteoconduction while offering superior primary stability, compared to other materials more commonly used (polyether ether ketone or PEEK, titanium). Perioperative morbidity, short-term functional outcomes (2 years) and radiographic impaction of implants were also analysed. METHODS: This retrospective monocentric study involved 94 patients operated on between 2014 and 2017 for degenerative disc disease (75%), degenerative spondylolisthesis (3%) or isthmic lytic spondylolisthesis (22%). Sixty-five patients (69%) had isolated ("stand-alone") ALIF procedures, 24 (26%) with associated anterior osteosynthesis and 5 (5%) with associated posterior osteosynthesis. A Kaplan-Meier survival curve was established with surgical revision listed as the main criterion for failure. Perioperative complications were identified. The clinical evaluation at the last follow-up used a Visual Analogue Scale for radicular pain (VAS-R), for lumbar pain (VAS-L) and the Oswestry Disability Index (ODI) score. The impactions, assessed on x-rays, were divided into 2 groups according to severity in order to establish risk factors (RF). RESULTS: The primary objective showed a 2-year survival rate of 94% (95% CI [0.88; 0.99]). Two patients had early surgical revision for impaction and 4 patients had late surgical revision for pseudarthrosis. The rate of perioperative complications was 8.5%, mostly due to vascular causes. At the average follow-up of 33 months (24-59), the clinical results were significantly improved and the impaction rate was 36% in the immediate postoperative period (IPO) and 47% at one year. CONCLUSION: ALIF using an intervertebral tantalum implant is a reliable, reproducible and low morbidity technique. However, it is accompanied by a significant rate of immediate and secondary impaction but without any resounding influence on short-term clinical outcomes. LEVEL OF EVIDENCE: IV.

Tantalum implants for posterior lumbar interbody fusion: A safe method at medium-term follow-up?

INTRODUCTION: Intervertebral implants increase stability and improve results in lumbar interbody fusion (LIF). The aim of the present study was to assess clinical and radiological results of posterior lumbar interbody fusion (PLIF) using a tantalum intervertebral implant without associated interbody bone graft. MATERIEL AND METHODS: A single-center retrospective study included 52 cases of single-level PLIF, using 2 tantalum intervertebral cages, without interbody bone graft: 42 for degenerative disc disease, 10 for isthmic spondylolisthesis. Minimum follow-up was 2 years. Clinical assessment used a visual analog (pain) scale (VAS), the Oswestry Disability Index (ODI) and the Roland Morris (RM) scale. Tantalum osseointegration and intersegment mobility were assessed on static and dynamic X-ray. RESULTS: Forty-nine patients were included, with a mean 55months' follow-up (range, 25-74months). VAS, ODI and RM scores showed significant improvement at last-follow-up, at 4, 30 and 28 points respectively. There was no mechanical failure on static X-ray; all patients had less than 5° mobility on dynamic X-ray at last follow-up. DISCUSSION: PLIF with tantalum intervertebral implant without interbody bone graft provided satisfactory clinical and radiological results at medium-term follow-up. The present findings showed reliable primary stability and osseointegration of the tantalum implant. LEVEL OF EVIDENCE: IV.

Role of MRI in the assessment of interbody fusion with tantalum intervertebral implant.

INTRODUCTION: Radiologic assessment of interbody fusion (IF) is controversial; thin-slice CT is the present gold standard despite artifacts due to the metal implant that hinder interpretation. The present study aimed to assess the contribution of MRI in IF assessment after instrumented posterior lumbar interbody fusion (PLIF) using tantalum intervertebral implants. The study hypothesis was that fusion following PLIF can be assessed on MRI. MATERIALS AND METHOD: A single-center retrospective study included 52 single-level PLIF procedures (42 for degenerative disc disease and 10 for isthmic spondylolisthesis) using 2 tantalum intervertebral cages without interbody bone graft. Fusion was assessed at 1 year on static and dynamic X-ray and on MRI with a dedicated protocol. Two senior osteoarticular radiologists screened frontal and sagittal MRI slices for continuous cancellous interbody bridges. Consolidation was considered acquired (grade I) in case of continuous bridges on at least 2 successive frontal or sagittal slices, possible (grade II) in case of continuous bridge on just 1 slice, or absent (grade III) in case of no or discontinuous bridge. RESULTS: Forty-eight patients were included, with a mean 55 months' follow-up (range, 25-74 months). There were no hardware failures. Intervertebral mobility on dynamic X-ray was systematically less than 5°. Fusion on MRI was grade I in 71% of cases, grade II in 8% and grade III in 21%. Interobserver agreement was 100% on X-ray and 81% on MRI, with kappa coefficient=0.56 (range, 0.35-0.77). DISCUSSION: Tantalum implants without bone autograft enabled satisfactory standard radiographic study. MRI provided imperfect assessment of fusion, being contributive only in case of positive findings (71% in the present study); when no bridge is detected on MRI, no conclusion can be drawn. Progress in CT to reduce artifacts may improve fusion assessment, unless bone integration on both sides of the implant is considered to be sufficient for interbody continuity, without a continuous bone bridge between endplates being a requirement. LEVEL OF EVIDENCE: IV.