Trabecular bone structure in lumbosacral transitional vertebrae: distribution and densities across sagittal vertebral body segments

Mid-Term Outcomes of Screw Loosening in Lumbar Dynamic Stabilization with Polyetheretherketone Rods versus Titanium Rods: A Minimum 4-Year Follow-Up

OBJECTIVE

To retrospectively analyze screw loosening rates following dynamic fixation with polyetheretherketone (PEEK) rods and rigid fixation with titanium rods and assess mid-term outcomes of loosened screws.

METHODS

This retrospective analysis included 203 patients who underwent lumbar pedicle screw fixation between March 2017 and June 2020 (57 with PEEK rods, 146 with titanium rods). Patients were followed for at least 48 months to evaluate screw loosening postoperatively and investigate outcomes of loosened screws. Multivariate logistic regression identified factors influencing screw restabilization.

RESULTS

Both PEEK rod and titanium rod groups exhibited peak screw loosening rates approximately 1 year after surgery, decreasing with longer follow-up. At 48 months, screw loosening rates were 5.3% and 15.8% for PEEK and titanium rods, respectively (P < 0.05). Among patients experiencing early loosening (within 12 months), the proportion of stabilized screws was significantly higher with PEEK rods (84% vs. 34%, P < 0.001). Regression analysis revealed dynamic fixation (odds ratio 4.579; 95% confidence interval 1.611-12.519), lowest fixed vertebra S1 (odds ratio 3.151; 95% confidence interval 1.352-9.233), and L1-L4 average computed tomography value (odds ratio 1.132; 95% confidence interval 1.015-1.263) as independent risk factors for screw restabilization. The area under the receiver operating characteristic curve for L1-L4 average computed tomography value predicting restabilization was 0.713 (P < 0.05), with an optimal threshold of 106 Hounsfield units (sensitivity 0.771, specificity 0.803).

CONCLUSIONS

Following PEEK rod dynamic fixation surgery, a certain proportion of screw loosening may occur in the short term. With prolonged follow-up, screws gradually restabilize at the bone interface, with most loosened screws returning to a stable state.

Clinical study on freehand of bicortical sacral screw fixation with the assistance of torque measurement device

BACKGROUND

Sacral screw loosening is a typical complication after internal fixation surgery through the vertebral arch system. Bicortical fixation can successfully prevent screw loosening, and how improving the rate of bicortical fixation is a challenging clinical investigation.

OBJECTIVE

To investigate the feasibility of improving the double corticality of sacral screws and the optimal fixation depth to achieve double cortical fixation by combining the torque measurement method with bare hands.

METHODS

Ninety-seven cases of posterior lumbar internal fixation with pedicle root system were included in this study. Based on the tactile feedback of the surgeon indicating the expected penetration of the screw into the contralateral cortex of the sacrum, the screws were further rotated by 180°, 360°, or 720°, categorized into the bicortical 180° group, bicortical 360° group, and bicortical 720° group, respectively. Intraoperatively, the torque during screw insertion was recorded. Postoperatively, the rate of double-cortex engagement was evaluated at 7 days, and screw loosening was assessed at 1 year follow-up.

RESULTS

The bicortical rates of the 180° group, 360° group, and 720° group were 66.13%, 91.18% and 93.75%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05).The rates of loosening of sacral screws in the 180° group, 360° group, and 720° group were 20.97%, 7.35% and 7.81%, respectively. There were statistically significant differences between the 180° group and both the 360° and 720° groups (P < 0.05). However, there was no statistically significant difference between the 360° group and the 720° group (P > 0.05). The bicortical 360° group achieved a relatively satisfactory rate of dual cortical purchase while maintaining a lower rate of screw loosening.

CONCLUSION

Manual insertion of sacral screws with the assistance of a torque measurement device can achieve a relatively satisfactory dual cortical purchase rate while reducing patient hospitalization costs.

Prediction of Screw Loosening After Dynamic Pedicle Screw Fixation With Lumbar Polyetheretherketone Rods Using Magnetic Resonance Imaging-Based Vertebral Bone Quality Score

OBJECTIVE

To investigate the correlation between magnetic resonance imaging-based vertebral bone quality (VBQ) score and screw loosening after dynamic pedicle screw fixation with polyetheretherketone (PEEK) rods, and evaluate its predictive value.

METHODS

A retrospective analysis was conducted on the patients who underwent dynamic pedicle screw fixation with PEEK rods from March 2017 to June 2022. Data on age, sex, body mass index, hypertension, diabetes, hyperlipidemia history, long-term smoking, alcohol consumption, VBQ score, L1-4 average Hounsfield unit (HU) value, surgical fixation length, and the lowest instrumented vertebra were collected. Logistic regression analysis was employed to assess the relationship between VBQ score and pedicle screw loosening (PSL).

RESULTS

A total of 24 patients experienced PSL after surgery (20.5%). PSL group and non-PSL group showed statistical differences in age, number of fixed segments, fixation to the sacrum, L1-4 average HU value, and VBQ score (p < 0.05). The VBQ score in the PSL group was higher than that in the non-PSL group (3.56 ± 0.45 vs. 2.77 ± 0.31, p < 0.001). In logistic regression analysis, VBQ score (odds ratio, 3.425; 95% confidence interval, 1.552-8.279) were identified as independent risk factors for screw loosening. The area under the receiver operating characteristic curve for VBQ score predicting PSL was 0.819 (p < 0.05), with the optimal threshold of 3.15 (sensitivity, 83.1%; specificity, 80.5%).

CONCLUSION

The VBQ score can independently predict postoperative screw loosening in patients undergoing lumbar dynamic pedicle screw fixation with PEEK rods, and its predictive value is comparable to HU value.

Is Lumbosacral Transitional Vertebra Associated with Degenerative Lumbar Spinal Stenosis?

The aim of this study was to shed light on the association between lumbosacral transitional vertebra (LSTV) and degenerative lumbar spinal stenosis (DLSS). A cross-sectional retrospective study was performed on 165 individuals that were diagnosed with clinical picture of DLSS (age range: 40-88 years; sex ratio: 80M/85F) and 180 individuals without DLSS related symptoms (age range: 40-99 years; sex ratio: 90M/90F). All participants had undergone high-resolution CT scan for the lumbar region in the same position. We also used the volume rendering method to obtain three-dimensional CT images of the lumbosacral area. Both males and females in the stenosis group manifest greater prevalence of LSTV than their counterparts in the control group (P<0.001). Furthermore, the presence of LSTV increases the likelihood of degenerative spinal stenosis (odds ratio= 3.741, P<0.001). In the control group, LSTV was more common in males, and sacral slope angle of males was significantly greater in LSTV group compared to non-LSTV. This study indicates that LSTV was significantly associated with symptomatic DLSS.

Normative values for CT-based texture analysis of vertebral bodies in dual X-ray absorptiometry-confirmed, normally mineralized subjects

OBJECTIVES

To develop age-, gender-, and regional-specific normative values for texture analysis (TA) of spinal computed tomography (CT) in subjects with normal bone mineral density (BMD), as defined by dual X-ray absorptiometry (DXA), and to determine age-, gender-, and regional-specific differences.

MATERIALS AND METHODS

In this retrospective, IRB-approved study, TA was performed on sagittal CT bone images of the thoracic and lumbar spine using dedicated software (MaZda) in 141 individuals with normal DXA BMD findings. Numbers of female and male subjects were balanced in each of six age decades. Three hundred and five TA features were analyzed in thoracic and lumbar vertebrae using free-hand regions-of-interest. Intraclass correlation (ICC) coefficients were calculated for determining intra- and inter-observer agreement of each feature. Further dimension reduction was performed with correlation analyses.

RESULTS

The TA features with an ICC < 0.81 indicating compromised intra- and inter-observer agreement and with Pearson correlation scores r > 0.8 with other features were excluded from further analysis for dimension reduction. From the remaining 31 texture features, a significant correlation with age was found for the features mean (r = -0.489, p < 0.001), variance (r = -0.681, p < 0.001), kurtosis (r = 0.273, p < 0.001), and WavEnLL_s4 (r = 0.273, p < 0.001). Significant differences were found between genders for various higher-level texture features (p < 0.001). Regional differences among the thoracic spine, thoracic-lumbar junction, and lumbar spine were found for most TA features (p < 0.021).

CONCLUSION

This study established normative values of TA features on CT images of the spine and showed age-, gender-, and regional-specific differences in individuals with normal BMD as defined by DXA.

Potential risks of using cement-augmented screws for spinal fusion in patients with low bone quality

BACKGROUND CONTEXT

Dramatic increases in the average life expectancy have led to increases in the variety of degenerative changes and deformities observed in the aging spine. The elderly population can present challenges for spine surgeons, not only because of increased comorbidities, but also because of the quality of their bones. Pedicle screws are the implants used most commonly in spinal surgery for fixation, but their efficacy depends directly on bone quality. Although polymethyl methacrylate (PMMA)-augmented screws represent an alternative for patients with osteoporotic vertebrae, their use has raised some concerns because of the possible association between cement leakages (CLs) and other morbidities.

PURPOSE

To analyze potential complications related to the use of cement-augmented screws for spinal fusion and to investigate the effectiveness of using these screws in the treatment of patients with low bone quality.

STUDY DESIGN

A retrospective single-center study.

PATIENT SAMPLE

This study included 313 consecutive patients who underwent spinal fusion using a total of 1,780 cement-augmented screws.

METHODS AND OUTCOME MEASURES

We analyzed potential complications related to the use of cement-augmented screws, including CL, vascular injury, infection, screw extraction problems, revision surgery, and instrument failure. There are no financial conflicts of interest to report.

RESULTS

A total of 1,043 vertebrae were instrumented. Cement leakage was observed in 650 vertebrae (62.3%). There were no major clinical complications related to CL, but two patients (0.6%) had radicular pain related to CL at the S1 foramina. Of the 13 patients (4.1%) who developed deep infections requiring surgical debridement, two with chronic infections had possible spondylitis that required instrument removal. All patients responded well to antibiotic therapy. Revision surgery was performed in 56 patients (17.9%), most of whom had long construction. A total of 180 screws were removed as a result of revision. There were no problems with screw extraction.

CONCLUSIONS

These results demonstrate the efficacy and safety of cement-augmented screws for the treatment of patients with low bone mineral density.

Lumbosacral Transitional Vertebra: Possible Role in the Pathogenesis of Adolescent Lumbar Disc Herniation

OBJECTIVE

To investigate the role of lumbosacral transitional vertebra (LSTV) in the pathogenesis of adolescent lumbar disc herniation (ALDH) and the association between LSTV type and the herniation level of ALDH.

METHODS

This study was a retrospective case-control analysis of roentgenographic images. All adolescent patients who received surgical treatment for L4/5 or L5/S1 single level lumbar disc herniation in our department from 2010 to 2015 were eligible for the ALDH group. All adolescent patients admitted to our hospital during the same period and who had ever undergone a plain anteroposterior radiologic examination of the abdomen and met the inclusion criteria that ensured the absence of any spinal disorders were selected into the control group. The anteroposterior lumbar or abdomen roentgenograms were collected to identify the LSTV. The incidence of LSTV in the ALDH group and the control group were compared. Among the ALDH group, the association between LSTV type (sacralization or lumbarization) and the herniation level of ALDH were evaluated.

RESULTS

A total of 80 adolescent patients were included in the ALDH group and 92 asymptomatic adolescents were included in the control group. LSTV was found in 24 patients (30%) in ALDH group compared with 7 patients (7.6%) in the control group (P < 0.001; odds ratio, 5.2; 95% confidence interval 2.1, 12.9). Among the adolescent patients with sacralization, the L4/5 disc herniation was significantly more common than L5/S1 (81.3% vs. 18.7%; P = 0.019).

CONCLUSIONS

The LSTV is associated with LDH in adolescents and the sacralization of L5 may contribute to the L4/5 disc herniation in adolescent patients.

A Review of Symptomatic Lumbosacral Transitional Vertebrae: Bertolotti's Syndrome

BACKGROUND

Lumbosacral transitional vertebrae (LSTV) are increasingly recognized as a common anatomical variant associated with altered patterns of degenerative spine changes. This review will focus on the clinical significance of LSTV, disruptions in normal spine biomechanics, imaging techniques, diagnosis, and treatment.

METHODS

A Pubmed search using the specific key words "LSTV," "lumbosacral transitional vertebrae," and "Bertolotti's Syndrome" was performed. The resulting group of manuscripts from our search was evaluated.

RESULTS

LSTV are associated with alterations in biomechanics and anatomy of spinal and paraspinal structures, which have important implications on surgical approaches and techniques. LSTV are often inaccurately detected and classified on standard AP radiographs and MRI. The use of whole-spine images as well as geometric relationships between the sacrum and lumbar vertebra increase accuracy. Uncertainty regarding the cause, clinical significance, and treatment of LSTV persists. Some authors suggest an association between LSTV types II and IV and low back pain. Pseudoarticulation between the transverse process and the sacrum creates a "false joint" susceptible to arthritic changes and osteophyte formation potentially leading to nerve root entrapment. The diagnosis of symptomatic LSTV is considered with appropriate patient history, imaging studies, and diagnostic injections. A positive radionuclide study along with a positive effect from a local injection helps distinguish the transitional vertebra as a significant pain source. Surgical resection is reserved for a subgroup of LSTV patients who fail conservative treatment and whose pain is definitively attributed to the anomalous pseudoarticulation.

CONCLUSIONS

Due to the common finding of low back pain and the wide prevalence of LSTV in the general population, it is essential to differentiate between symptoms originating from an anomalous psuedoarticulation from other potential sources of low back pain. Further studies with larger sample sizes and longer follow-up time would better demonstrate the effectiveness of surgical resection and help guide treatment.