Potential significance of facet joint fusion or posteromedial fusion observed on CT imaging following attempted posterolateral or posterior interbody fusion

Comparison of facet fusion rates and clinical outcomes between cortical bone trajectory screw and percutaneous pedicle screw fixation for degenerative lumbar spondylolisthesis

BACKGROUND CONTEXT

Cortical bone trajectory (CBT) screws have been introduced as an alternative technique for pedicle screw (PS) insertion because they have greater contact with the cortex and a greater uniaxial pullout load than traditional PS. CBT screwing can also minimize muscle dissection. However, CBT screws and traditional PSs have not yet been compared in terms of fusion rates and clinical outcomes for particular operative procedures.

PURPOSE

This study aimed to assess the fusion rate and clinical outcomes of facet fusion (FF) fixed with CBT screws (CBT-FF) and to compare them with those of FF fixed with percutaneous PS (PPS-FF).

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

Records of 68 patients who underwent CBT-FF for single-level degenerative lumbar spondylolisthesis (DLS) with at least 1 year of follow-up were retrospectively reviewed. The control group comprised 143 patients who underwent PPS-FF under the same conditions.

OUTCOME MEASURES

Computed tomography was performed to confirm fusion. Therapeutic effectiveness was assessed as a clinical outcome using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), Roland-Morris Disability Questionnaire (RMDQ), and visual analog scale (VAS) preoperatively and 1 year postoperatively. The rate of revision surgery was also calculated. Intraoperative blood loss was measured.

METHODS

Fusion rate, clinical outcomes, revision surgery rate, and intraoperative blood loss of CBT-FF and PPS-FF were compared.

RESULTS

The CBT-FF and PPS-FF fusion rates were 91.2% and 90.1%, respectively. The JOABPEQ category scores demonstrated therapeutic effectiveness in 74.5% and 77.1% of the patients for low back pain; the corresponding proportions for walking ability were 84.7% and 89.3%, respectively. No significant differences in therapeutic effectiveness were observed for any category, including the RMDQ and VAS scores for buttock and lower limb pain. Three patients required revision surgery for adjacent segment disease between 6 months and 3.5 years after CBT-FF (revision surgery rate, 4.4%), whereas the revision surgery rate for PPS-FF was 6.3% (9/143 cases). Average intraoperative blood loss was significantly less in the CBT-FF group than in the PPS-FF group.

CONCLUSIONS

Both procedures were equally useful in terms of fusion rate and clinical outcomes for DLS management.

Pedicle Screw-Associated Violation of the Adjacent Unfused Facet Joint: Clinical Outcomes and Fusion Rates

STUDY DESIGN

Retrospective review of a prospective randomized trial.

OBJECTIVES

To compare outcome scores and fusion rates in patients with and without pedicle screw-associated facet joint violation (FJV) after a single-level lumbar fusion.

METHODS

Clinical outcomes data and computed tomography (CT) imaging were reviewed for 157 patients participating in a multicenter prospective trial. Post-operative CT scans at 12-months follow-up were examined for fusion status and FJV. Patient-reported outcomes (PROs) included Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) for leg and low back pain. Chi-square test of independence was used to compare proportions between groups on categorical measures. Two-sample t-test was used to identify differences in mean patient outcome scores. Logistic regression models were performed to determine association between FJV and fusion rates.

RESULTS

Of the 157 patients included, there were 18 (11.5%) with FJV (Group A) and 139 (88.5%) without FJV (Group B). Patients with FJV experienced less improvement in ODI (P = .004) and VAS back pain scores (P = .04) vs patients without FJV. There was no difference in mean VAS leg pain (P = .4997). The rate of fusion at 12-months for patients with FJV (27.8%) was lower compared to those without FJV (71.2%) (P = .0002). Patients with FJV were 76% less likely to have a successful fusion at 12-months.

CONCLUSION

Pedicle screw-associated violation of the adjacent unfused facet joint during single-level lumbar fusion is associated with less improvement in back pain, back pain-associated disability, and a lower fusion rate at 1-year after surgery.

Modified facet joint fusion for multilevel lumbar spinal stenosis: a retrospective study of 135 consecutive patients

OBJECTIVE

To evaluate the safety and efficacy of modified facet joint fusion (MFF) for the treatment of multilevel (three-level or more) lumbar spinal stenosis (LSS).

PATIENTS AND METHODS

In this retrospective study, 135 consecutive patients who underwent initial MFF for multilevel LSS were included. Clinical outcomes included fusion rate, change of visual analogue scale pain scores for low back pain (VAS-LBP) and leg pain (VAS-LP), Japanese Orthopedic Association scores (JOA), Oswestry Disability Index (ODI) and MacNab classification before and after MFF. The complications were also analyzed.

RESULTS

The fusion rates were 46.7% (63/135) at 6-month and 89.6% (121/135) at 1-year. The mean VAS-LBP, VAS-LP, and ODI significantly decreased from 5.2 ± 0.6, 5.7 ± 0.8 and 65 ± 7.9 to 1.58 ± 0.4, 0.58 ± 0.3 and 20.8 ± 5.8, respectively (all p < 0.001). The mean JOA markedly improved from 10.0 ± 1.3 to 26.1 ± 1.5 (p < 0.001). Excellent/good results of MacNab classification were achieved in 88.9% (120/135) of the patients. The overall rate of complications after MFF was 5.9%, including poor wound healing (2.2%), calf muscular venous thrombosis (0.74%), deep venous thrombosis (0.74%), superficial wound infection (1.48%), transient foot drop (0.74%). All the complications were transient and improved without prolonged hospital stay and sequelae.

CONCLUSION

MFF may be safe and efficient for multilevel LSS with high fusion rate and significant symptom relief, which is worthy of further study.

Assessment of Posterolateral Lumbar Fusion: A Systematic Review of Imaging-Based Fusion Criteria

BACKGROUND

Noninvasive assessment of osseous fusion after spinal fusion surgery is essential for timely diagnosis of patients with symptomatic pseudarthrosis and for evaluation of the performance of spinal fusion procedures. There is, however, no consensus on the definition and assessment of successful posterolateral fusion (PLF) of the lumbar spine. This systematic review aimed to (1) summarize the criteria used for imaging-based fusion assessment after instrumented PLF and (2) evaluate their diagnostic accuracy and reliability.

METHODS

First, a search of the literature was conducted in November 2018 to identify reproducible criteria for imaging-based fusion assessment after primary instrumented PLF between T10 and S1 in adult patients, and to determine their frequency of use. A second search in July 2021 was directed at primary studies on the diagnostic accuracy (with surgical exploration as the reference) and/or reliability (interobserver and intraobserver agreement) of these criteria. Article selection and data extraction were performed by at least 2 reviewers independently. The methodological quality of validation studies was assessed with the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) and QAREL (Quality Appraisal of Reliability Studies).

RESULTS

Of the 187 articles included from the first search, 47% used a classification system and 63% used ≥1 descriptive criterion related to osseous bridging (104 articles), absence of motion (78 articles), and/or absence of static signs of nonunion (39 articles). A great variation in terminology, cutoff values, and assessed anatomical locations was observed. While the use of computed tomography (CT) increased over time, radiographs remained predominant. The second search yielded 11 articles with considerable variation in outcomes and quality concerns. Agreement between imaging-based assessment and surgical exploration with regard to demonstration of fusion ranged between 55% and 80%, while reliability ranged from poor to excellent.

CONCLUSIONS

None of the available criteria for noninvasive assessment of fusion status after instrumented PLF were demonstrated to have both sufficient accuracy and reliability. Further elaboration and validation of a well-defined systematic CT-based assessment method that allows grading of the intertransverse and interfacet fusion mass at each side of each fusion level and includes signs of nonunion is recommended.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

A BMP/Activin A Chimera Induces Posterolateral Spine Fusion in Nonhuman Primates at Lower Concentrations Than BMP-2

BACKGROUND

Supraphysiologic bone morphogenetic protein (BMP)-2 concentrations are required to induce spinal fusion. In this study, a BMP-2/BMP-6/activin A chimera (BV-265), optimized for BMP receptor binding, delivered in a recombinant human collagen:CDHA [calcium-deficient hydroxyapatite] porous composite matrix (CM) or bovine collagen:CDHA granule porous composite matrix (PCM), engineered for optimal BV-265 retention and guided tissue repair, was compared with BMP-2 delivered in a bovine absorbable collagen sponge (ACS) wrapped around a MASTERGRAFT Matrix (MM) ceramic-collagen rod (ACS:MM) in a nonhuman primate noninstrumented posterolateral fusion (PLF) model.

METHODS

In vivo retention of 125I-labeled-BV-265/CM or PCM was compared with 125I-labeled-BMP-2/ACS or BMP-2/buffer in a rat muscle pouch model using scintigraphy. Noninstrumented PLF was performed by implanting CM, BV-265/CM, BV-265/PCM, or BMP-2/ACS:MM across L3-L4 and L5-L6 or L3-L4-L5 decorticated transverse processes in 26 monkeys. Computed tomography (CT) images were acquired at 0, 4, 8, 12, and 24 weeks after surgery, where applicable. Manual palpation, μCT (microcomputed tomography) or nCT (nanocomputed tomography), and histological analysis were performed following euthanasia.

RESULTS

Retention of 125I-labeled-BV-265/CM was greater than BV-265/PCM, followed by BMP-2/ACS and BMP-2/buffer. The CM, 0.43 mg/cm3 BMP-2/ACS:MM, and 0.05 mg/cm3 BV-265/CM failed to generate PLFs. The 0.15-mg/cm3 BV-265/CM or 0.075-mg/cm3 BV-265/PCM combinations were partially effective. The 0.25-mg/cm3 BV-265/CM and 0.15 and 0.3-mg/cm3 BV-265/PCM combinations generated successful 2-level PLFs at 12 and 24 weeks.

CONCLUSIONS

BV-265/CM or PCM can induce fusion in a challenging nonhuman primate noninstrumented PLF model at substantially lower concentrations than BMP-2/ACS:MM.

CLINICAL RELEVANCE

BV-265/CM and PCM represent potential alternatives to induce PLF in humans at substantially lower concentrations than BMP-2/ACS:MM.

Initial Experience With a Full Endoscopic Facet Fusion in Combination With Endoscopic Interbody Fusion

Background Facet fusion has been described in open and minimally invasive approaches to promote fusion. Our objective is to describe the technique of an endoscopic facet decortication and allograft placement as an adjunct to an interbody fusion. Methodology This was a descriptive analysis of patients who underwent endoscopic interbody fusion combined with facet fusion and percutaneous screw placement. General demographics, clinical presentation, length of stay, follow-up, and outcome were gathered. The technique involves endoscopic access to the Kambin's triangle, discectomy/endplate preparation, expandable cage/allograft insertion, and percutaneous pedicle screw placement. A midline incision was performed, and the endoscope was advanced over the facet joints at the desired level. After removing the soft tissue with grasping forceps, cautery was used to disrupt the facet capsule. An articulating high-speed bur was used to drill inside and over the dorsal surface of the joint. Finally, allograft chips were placed through the endoscope cannula. Results From May 2019 to December 2019, four patients underwent endoscopic interbody fusion. All were female, with a mean age of 67.5 years (SD: 12.7). All had chronic low back pain and radiculopathy associated with Grade 1 spondylolisthesis. Two (50%) of the patients underwent two-level fusion. The median hospital stay was two days. Two (50%) reported improvement of both low back and radiculopathy symptoms. None of the patients had a significant complication or required reoperation in eight months' mean follow-up. Conclusions Facet decortication and allograft placement are feasible using an endoscopic approach in conjunction with interbody fusion.

Increasing Fusion Rate Between 1 and 2 Years After Instrumented Posterolateral Spinal Fusion and the Role of Bone Grafting

STUDY DESIGN

Two-year clinical and radiographic follow-up of a double-blind, multicenter, randomized, intra-patient controlled, non-inferiority trial comparing a bone graft substitute (AttraX Putty) with autograft in instrumented posterolateral fusion (PLF) surgery.

OBJECTIVES

The aim of this study was to compare PLF rates between 1 and 2 years of follow-up and between graft types, and to explore the role of bone grafting based on the location of the PLF mass.

SUMMARY OF BACKGROUND DATA

There are indications that bony fusion proceeds over time, but it is unknown to what extent this can be related to bone grafting.

METHODS

A total of 100 adult patients underwent a primary, single- or multilevel, thoracolumbar PLF. After instrumentation and preparation for grafting, the randomized allocation side of AttraX Putty was disclosed. The contralateral posterolateral gutters were grafted with autograft. At 1-year follow-up, and in case of no fusion at 2 years, the fusion status of both sides of each segment was blindly assessed on CT scans. Intertransverse and facet fusion were scored separately. Difference in fusion rates after 1 and 2 years and between grafts were analyzed with a Generalized Estimating Equations (GEE) model (P < 0.05).

RESULTS

The 2-year PLF rate (66 patients) was 70% at the AttraX Putty and 68% at the autograft side, compared to 55% and 52% after 1 year (87 patients). GEE analysis demonstrated a significant increase for both conditions (odds ratio 2.0, 95% confidence interval 1.5-2.7, P < 0.001), but no difference between the grafts (P = 0.595). Ongoing bone formation was only observed between the facet joints.

CONCLUSION

This intra-patient controlled trial demonstrated a significant increase in PLF rate between 1 and 2 years after instrumented thoracolumbar fusion, but no difference between AttraX Putty and autograft. Based on the location of the PLF mass, this increase is most likely the result of immobilization instead of grafting.

LEVEL OF EVIDENCE

1.