Large volume inside the cage leading incomplete interbody bone fusion and residual back pain after posterior lumbar interbody fusion

Validation of Impaction Grafting for Single-Level Transforaminal Lumbar Interbody Fusion-Technical Pearls and MicroCT Analysis

STUDY DESIGN

Cadaveric study.

BACKGROUND CONTEXT

Transforaminal lumbar interbody fusion (TLIF) represents a well-documented operative surgical technique utilized in the management of lumbar pathology requiring interbody arthrodesis. The microstructural properties of impaction grafting (IG) after TLIF has yet to be reported.

PURPOSE

The current study was designed first, to quantify the degree, to which IG augmentation would increase intrabody final bone volume and bone graft surface contact area with the endplates; secondly to quantify the volumes of locally harvested bone and bone needed for maximal impaction.

MATERIALS AND METHODS

Three cadaveric lumbosacral spine specimens were dissected into L1-L2, L3-L4, and L5-S1 motion segments for a total of 9 functional spinal units. Each interbody unit underwent a TLIF procedure with the implantation of an interbody spacer containing autogenous morselized bone. Microcomputed tomography scans were then performed to evaluate the final bone volume and bone surface contact area (BSCA). Subsequently, IG augmented TLIF procedure was carried and microcomputed tomography scans were repeated.

RESULTS

IG augmentation of TLIF exhibited a 346% increase in final bone volume (TLIF: 0.30 ± 0.07 cm 3 ; IG-TLIF: 1.34 ± 0.42 cm 3 ; P < 0.05) and a 152% increase in BSCA (TLIF: 45.06 ± 15.47%; IG-TLIF: 68.28 ± 6.85%; P < 0.05) when compared with the nonimpacted TLIF treatment. In addition, the average amount of autogenous bone collected was 8.21±2.08 cm 3 , which sufficiently fulfilled the requirements for bone grafting (TLIF: 1.23 ± 0.40 cm 3 ; IG-TLIF 6.42 ± 1.20 cm 3 ).

CONCLUSIONS

IG augmentation of TLIF significantly improved final bone volume in the disc space and BSCA with vertebral endplates in vitro.

CLINICAL SIGNIFICANCE

Greater BSCA and final volume of bone graft reflect promisingly on their potential to increase fusion rates. Clinical studies will be needed to corroborate these findings.

Cortical bone trajectory fixation cause low compression force in anterior vertebral column

Background

The cortical bone trajectory (CBT) screws follow a caudocephalad and lateral path from the pedicle to the vertebral body. The bone fusion rate of CBT fixation is equal to or lower than conventional pedicle screw fixation. It remains unclear whether or not CVT screws exert equally compressive forces across the vertebral column. In this study, we intraoperatively examined the insertional torque of CBT screws, and investigated the compression loading and pressure distribution in conventional and CBT fixation using pig bones.

Methods

The insertional torque was measured for a total of 115 CBT screws. Detailed positions of these screws were retrospectively confirmed using CT scans. Screw loosening and interbody fusion were examined 1 year after surgery. In the experiment using pig bones, we inserted screws by conventional trajectory (n = 3) and CBT (n = 4).

Results

Multiple regression analysis showed that the total screw length, the distance from the screw to the medial border of the pedicle and the distance from the superior endplate of the vertebrae were significant independent factors affecting the insertional torque. There was no significant association between the insertional torque and the radiographic bone fusion rate 12 months after surgery. The average pressure and the compression loading in the anterior column were significantly lower in CBT group.

Conclusion

These results suggested that the long CBT screws as close to the endplate had high insertional torque, but the anterior column in CBT fixation showed low compression force leading to the insufficient holding intervertebral cage. CBT screws may cause the micromotion of cages, which lowers the bone fusion rate.

A double-blind randomized controlled trial of the local application of vancomycin versus ampicillin powder into the operative field for thoracic and/or lumbar fusions

OBJECTIVERetrospective studies have reported that the local application of vancomycin (VCM) powder into the operative field decreases the incidence of surgical site infection (SSI) in thoracic and/or lumbar fusion. Authors of the present study prospectively evaluated the effects of VCM in patients undergoing thoracic and/or lumbar fusion.METHODSIn this randomized double-blind trial, 230 patients undergoing thoracic and/or lumbar fusion were randomly assigned to the local administration of VCM (interventional group, 1 g) or ampicillin (AMP; control group, 1 g) into the surgical field. The primary outcome was SSI results within 1 year of surgery.RESULTSThe trial was prematurely stopped according to predetermined rules. The results showed one superficial infection (0.9%, Staphylococcus aureus) and one deep infection (0.9%, S. aureus) in the VCM group and two superficial infections (1.8%, Staphylococcus epidermidis and culture negative) and one deep infection (0.9%, methicillin-resistant S. aureus) in the AMP group. No significant differences in infection rates were observed between the groups (p = 0.8).CONCLUSIONSThis double-blind randomized controlled trial demonstrated that the local application of VCM or AMP powder into the operative field in short thoracic and/or lumbar fusion procedures resulted in a similar incidence of SSI.■ CLASSIFICATION OF EVIDENCE Type of question: therapeutic; study design: randomized controlled trial; evidence: class III.Clinical trial registration no.: UMIN000009377 (umin.ac.jp/ctr).

Reliability of an Intraoperative Radiographic Anteroposterior View of the Spinal Midline for Detection of Pedicle Screws Breaching the Medial Pedicle Wall in the Thoracic, Lumbar, and Sacral Spine

OBJECTIVE

The purpose of this study was to determine the sensitivity and specificity of using the spinal midline (M line) on a radiographic anteroposterior (AP) view for detecting pedicle screws (PSs) breaching the medial pedicle wall.

METHODS

We retrospectively reviewed 145 patients who underwent fusion surgery using PSs between January 2006 and May 2017. We defined the M line as a line that connected the upper and lower spinous processes through the fixed vertebrae. The M line was positive if the tip of the PS crossed the M line. The reference standard was a computed tomography scan. The reliability of the M line was examined.

RESULTS

The subjects included 145 patients (70 men and 75 women; mean age, 63.4 years). A total of 599 PSs were examined. Most cases were because of spondylolisthesis (66.9%). Most screws were inserted at a lower lumber level (77.6%). Analysis of the diagnostic accuracy of the M line yielded a sensitivity of 74.1% and a specificity of 95.3%. In addition, the positive predictive value of the M line was 42.6%, and the negative predictive value of the M line was 98.7%.

CONCLUSIONS

Assessment of the M line via an intraoperative radiographic AP view is a simple, readily available, complementary method for detecting PSs that have breached the medial pedicle wall in the thoracic, lumbar, and sacral spine. In particular, the M line has a strong negative predictive value, which is much more meaningful.

Unidirectional porous β-tricalcium phosphate induces bony fusion in lateral lumbar interbody fusion

Lateral lumbar interbody fusion (LLIF) often requires the use of allograft or artificial bone. We used β-tricalcium phosphate artificial bone with a porosity of 57% consisting of a novel unidirectional porous structure (Affinos®) in patients (5 male and 9 female) who underwent LLIF from August 2015 as a substitute for autologous bone. We evaluated 60 graft windows in the cages at 30 intervertebral levels. To evaluate interbody bony fusion, CT multi-planar reconstruction coronal and sagittal images obtained 1 year after surgery were assessed. Intra-cage bony fusion was observed in 39 of 60 graft windows and so total bony fusion rate was 65%. Intra-cage bony fusion was confirmed in 17 of 29 (58.6%) graft windows with autologous bone and 22 of 31 (70.9%) graft windows with Affinos®. There was no significant difference in the rate of bony fusion between autologous bone and Affinos® (p = 0.418). In conclusion, the rate of bony fusion using Affinos® in LLIF cages was not inferior to that using autologous bone graft. Affinos® is a candidate for graft material in LLIF surgery and further exploration is warranted.

The Impact of L5 Sacralization on Fusion Rates and Clinical Outcomes After Single-level Posterior Lumbar Interbody Fusion (PLIF) at L4-L5 Level

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

To determine the impact of L5 sacralization on fusion rates and clinical outcomes after single-level posterior lumbar interbody fusion (PLIF) surgery at the L4-L5 level.

SUMMARY OF BACKGROUND DATA

L5 sacralization can produce greater stress concentration at the adjacent segment (L4-L5); therefore, L4-L5 PLIF surgery in patients with L5 sacralization may negatively affect fusion rate and be associated with poor clinical outcomes. However, no study has examined the impact of L5 sacralization on fusion rates and clinical outcomes of patients who undergo L4-L5 PLIF surgery.

MATERIALS AND METHODS

Of 153 patients who underwent L4-L5 PLIF, data of 145 who met the study criteria were retrospectively reviewed. Among them, 31 patients had L5 sacralization (group A), whereas the remaining 114 patients did not (group B). The primary study endpoint was fusion rate evaluated using dynamic radiographs and computed tomographic scans. Secondary endpoints included (1) pain intensity in the lower back and radiating to the lower extremities on the visual analog scale; (2) clinical outcomes assessed using the Oswestry Disability Index and 12-item Short Form Health Survey; (3) surgical outcomes; and (4) complications.

RESULTS

Fusion rate evaluated using dynamic radiographs and computed tomographic scans at 6 months after surgery did not differ significantly between patients with and without sacralization (P=0.70 and 0.81, respectively), whereas fusion rate at 1 year after surgery did (P=0.04 and 0.04, respectively). In particular, patients with type II or III L5 sacralization had significantly lower fusion rates than those with other types of or no L5 sacralization. Pain intensity, clinical and surgical outcomes, and complications did not differ significantly between groups.

CONCLUSIONS

Patients with type II or III L5 sacralization may have worse fusion rates after L4-L5 PLIF surgery than those with type I or no sacralization.

A Compaction Bone Grafting Technique Leads to Early Bone Fusion in Cases of Posterior Lumbar Interbody Fusion

BACKGROUND

The impaction bone grafting technique is a popular approach for achieving complete bone fusion during hip surgery or total knee arthroplasty. We hypothesized that compaction bone grafting (CBG), a modified version of impaction bone grafting, could be applied to lumbar fusion surgery.

OBJECTIVE

To compare the bone fusion rates and durations achieved using the CBG technique and a conventional loose bone grafting technique.

METHODS

We retrospectively reviewed 89 patients who underwent single-level posterior lumbar interbody fusion at the university hospital; 35 other posterior lumbar interbody fusion recipients were excluded due to undergoing multilevel fusion, prior lumbar surgery, trauma, infection, or inadequate computed tomographic data. Computed tomographic-based bone fusion assessments were obtained using the Brantigan, Steffee, and Fraser criteria at 1 and 2 years after surgery.

RESULTS

The baseline characteristics of the CBG (n = 42) and loose bone grafting (n = 47) groups did not significantly differ. Fusion assessments indicated that significantly superior bone fusion rates were achieved at 1 year after surgery in the CBG group than in the loose bone grafting group (P = .04, χ2 test). However, the bone fusion rates of the 2 groups at 2 years after surgery did not significantly differ (P = .3). A nonsymptomatic surgical complication occurred in the CBG group when a spacer was inserted into the intervertebral space; specifically, the spacer slipped out of the right psoas muscle because a large quantity of compaction bone grafts disrupted the cage's pathway.

CONCLUSION

In posterior lumbar interbody fusion surgeries, bone fusion was achieved more quickly with the CBG technique than with the conventional technique.