Outcomes of extended transforaminal lumbar interbody fusion for lumbar spondylosis

Surgical techniques in restoration lumbar lordosis: a biomechanical human cadaveric study

PURPOSE

Degenerative changes of the lumbar spine lead in general to decrease of lumbar lordosis (LL). This change affects the overall balance of the spine, and when surgery is deemed, necessary restoration of the LL is considered. How this restoration can be achieved is a matter of controversy. The main purpose of this cadaveric study was to investigate the different steps of common posterior surgical techniques to understand the contribution of each successive step in restoring LL.

METHODS

Ten fresh-frozen human lumbar spine specimens were used to perform a sequential correction and instrumentation with a pedicle screw construct.

RESULTS

The mean LL angle measured at L3-L4 in intact condition was 12.9°; after screw insertion and compression, this increased to 13.8° (+ 7%, p = 0.04), after bilateral facetectomy to 16.3° (+ 20%, p = 0.005), after discectomy and insertion of interbody cage to 18.0º (+ 9%, p = 0.012), after resection of the lamina and the processes spinosus to 19.8° (+ 10%, p = 0.017), and after resection of the anterior longitudinal ligament to 25.4° (+ 22%, p = 0.005).

CONCLUSIONS

Each step contributed statistically significant to restoration of segmental lordosis with bilateral facetectomy contributing the most in terms of percentage.

LEVEL OF EVIDENCE

IV.

Myocardial Infarction After Lumbar Surgery: A Critical Meta-Analysis of Cohort versus Database Studies for a Rare Complication

BACKGROUND

One potentially fatal complication of spine surgery is myocardial infarction (MI). There is still uncertainty of the true incidence of MI within subsets of spine surgeries. The aim of this study was to survey the contemporary spine literature and ascertain the true incidence of MI after lumbar spine surgery, as well as to provide commentary on the inherent assumptions made when interpreting cohort versus database studies on this topic.

METHODS

A systematic search of 4 electronic databases from inception to November 2020 was conducted following PRISMA guidelines. Articles were screened against prespecified criteria. MI incidence was then estimated by random-effects meta-analyses of proportions based on cohort versus database studies.

RESULTS

A total of 34 cohort studies and 32 database studies describing 767,326 lumbar procedures satisfied all criteria for selection. There were 12,170 (2%) cases from cohort studies and 755,156 (98%) cases from database studies. Cohort studies reported a significantly older patient cohort (P < 0.01) and longer follow-up period than did database studies (P < 0.03). Using cohort studies only, the incidence of MI was 0.44% (P heterogeneity < 0.01), whereas using database studies only, the incidence of MI was 0.41% (P heterogeneity < 0.01). These 2 incidences were statistically different (P interaction = 0.01). Bias analysis indicated that cohort studies were more vulnerable to small-study biases than were database studies.

CONCLUSIONS

Although infrequent, the incidence of MI after lumbar spine surgery is unequivocally nonzero. Furthermore, the literature on this topic remains skewed based on study type, and translation of academic findings into practice should be wary of this.

Biomechanical Evaluation of Oblique Lumbar Interbody Fusion with Various Fixation Options: A Finite Element Analysis

Objective

The aim of the present study was to clarify the biomechanical properties of oblique lumbar interbody fusion (OLIF) using different fixation methods in normal and osteoporosis spines.

Methods

Normal and osteoporosis intact finite element models of L₁–S₁ were established based on CT images of a healthy male volunteer. Group A was the normal models and group B was the osteoporosis model. Each group included four subgroups: (i) intact; (ii) stand‐alone cage (Cage); (iii) cage with lateral plate and two lateral screws (LP); and (iv) cage with bilateral pedicle screws and rods (BPSR). The L₃–L₄ level was defined as the surgical segment. After validating the normal intact model, compressive load of 400 N and torsional moment of 10 Nm were applied to the superior surface of L₂ to simulate flexion, extension, left bending, right bending, left rotation, and right rotation motions. Surgical segmental range of motion (ROM), cage stress, endplate stress, supplemental fixation stress, and stress distribution were analyzed in each group.

Results

Cage provided the minimal reduction of ROM among all motions (normal, 82.30%–98.81%; osteoporosis, 92.04%–97.29% of intact model). BPSR demonstrated the maximum reduction of ROM (normal, 43.94%–61.13%; osteoporosis, 45.61%–62.27% of intact model). The ROM of LP was between that of Cage and BPSR (normal, 63.25%–79.72%; osteoporosis, 70%–87.15% of intact model). Cage had the minimal cage stress and endplate stress. With the help of LP and BPSR fixation, cage stress and endplate stress were significantly reduced in all motions, both in normal and osteoporosis finite element models. However, BPSR had more advantages. For cage stress, BPSR was at least 75.73% less than that of Cage in the normal model, and it was at least 80.10% less than that of Cage in the osteoporosis model. For endplate stress, BPSR was at least 75.98% less than that of Cage in the normal model, and it was at least 78.06% less than that of Cage in the osteoporosis model. For supplemental fixation stress, BPSR and LP were much less than the yield strength in all motions in the two groups. In addition, the comparison between the two groups showed that the ROM, cage stress, endplate stress, and supplemental fixation stress in the normal model were less than in the osteoporosis model when using the same fixation option of OLIF.

Conclusion

Oblique lumbar interbody fusion with BPSR provided the best biomechanical stability both in normal and osteoporosis spines. The biomechanical properties of the normal spine were better than those of the osteoporosis spine when using the same fixation option of OLIF.

Biomechanical comparison of multilevel lateral interbody fusion with and without supplementary instrumentation: a three-dimensional finite element study

BACKGROUND

Lateral lumbar interbody fusion (LLIF) is a popular, minimally invasive technique that is used to address challenging multilevel degenerative spinal diseases. It remains controversial whether supplemental instrumentation should be added for multilevel LLIF. In this study, we compared the kinematic stability afforded by stand-alone lateral cages with those supplemented by bilateral pedicle screws and rods (PSR), unilateral PSR, or lateral plate (LP) fixation using a finite-element (FE) model of a multi-level LLIF construct with simulated osteoporosis. Additionally, to evaluate the prospect of cage subsidence, the stress change characteristics were surveyed at cage-endplate interfaces.

METHODS

A nonlinear 3-dimensional FE model of the lumbar spine (L2 to sacrum) was used. After validation, four patterns of instrumented 3-level LLIF (L2-L5) were constructed for this analysis: (a) 3 stand-alone lateral cages (SLC), (b) 3 lateral cages with lateral plate and two screws (parallel to endplate) fixated separately (LPC), (c) 3 lateral cages with bilateral pedicle screw and rod fixation (LC + BPSR), and (d) 3 lateral cages with unilateral pedicle and rod fixation (LC + UPSR). The segmental and overall range of motion (ROM) of each implanted condition were investigated and compared with the intact model. The peak von Mises stresses upon each (superior) endplate and the stress distribution were used for analysis.

RESULTS

BPSR provided the maximum reduction of ROM among the configurations at every plane of motion (66.7-90.9% of intact spine). UPSR also provided significant segmental ROM reduction (45.0-88.3%). SLC provided a minimal restriction of ROM (10.0-75.1%), and LPC was found to be less stable than both posterior fixation (23.9-86.2%) constructs. The construct with stand-alone lateral cages generated greater endplate stresses than did any of the other multilevel LLIF models. For the L3, L4 and L5 endplates, peak endplate stresses caused by the SLC construct exceeded the BPSR group by 52.7, 63.8, and 54.2% in flexion, 22.3, 40.1, and 31.4% in extension, 170.2, 175.1, and 134.0% in lateral bending, and 90.7, 45.5, and 30.0% in axial rotation, respectively. The stresses tended to be more concentrated at the periphery of the endplates.

CONCLUSIONS

SLC and LPC provided inadequate ROM restriction for the multilevel LLIF constructs, whereas lateral cages with BPSR or UPSR fixation provided favorable biomechanical stability. Moreover, SLC generated significantly higher endplate stress compared with supplemental instrumentation, which may have increased the risk of cage subsidence. Further biomechanical and clinical studies are required to validate our FEA findings.

Comparison of Clinical and Radiographic Outcomes in Patients Receiving Single-Level Transforaminal Lumbar Interbody Fusion With Removal of Unilateral or Bilateral Facet Joints

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The objective of this study is to compare the radiographic and clinical outcomes of transforaminal lumbar interbody fusion (TLIF) with bilateral facetectomy (BF) versus unilateral facetectomy (UF).

SUMMARY OF BACKGROUND DATA

BF is a surgical technique utilized with the intent of creating a greater degree of segmental lordosis than UF alone. However, the clinical benefits of this technique have not been defined. We seek to determine whether a difference exists between bilateral versus UF during TLIF by utilizing both clinical and radiographic outcome measures.

METHODS

The electronic medical records of 57 patients who underwent single-level TLIF with either a UF (n = 28) or BF (n = 29) were reviewed. Clinical outcomes were measured through Patient Health Questionnaire-9 (PHQ-9), Pain Disability Questionnaire (PDQ), EuroQol 5 Dimensions (EQ-5D) Health State, and Quality Adjusted Life Year (QALY). Radiographic parameters including disc height and sagittal balance were measured on plain radiographs at 1 year following operation.

RESULTS

All radiographic parameters showed no significant differences between the UF and BF cohorts. Segmental lordosis increased significantly in both cohorts. However, there was no significant difference in the increase of segmental lordosis between cohorts. Overall lumbar lordosis did not increase significantly in either cohort. Perioperative complications were also similar between cohorts. PDQ and EQ-5D scores improved significantly in both cohorts at 1 year postoperatively. The BF cohort showed a significantly greater improvement in both EQ-5D (0.1 ± 0.2 vs. 0.3 ± 0.2, P = 0.01) and PHQ-9 scores (-0.8 ± 4.6 vs. 4.6 ± 5.2, P = 0.03) than the UF cohort. The PDQ score improved over the minimally clinical important difference (MCID) of 26 in only the BF cohort.

CONCLUSION

The findings in the present study demonstrate that BF during single-level TLIF improves clinical outcomes to a greater degree than UF without any notable differences in perioperative complications or radiographic measurements.

LEVEL OF EVIDENCE

3.