Lower Hounsfield units on CT are associated with cage subsidence after anterior cervical discectomy and fusion

Is it necessary to use a cervical brace after single- or double-level ACDF?

Although anterior cervical discectomy and fusion (ACDF) is one of the most frequently performed spinal surgeries, there is no consensus regarding the necessity of prescribing a cervical brace after surgery. This study aimed to investigate any difference in radiological and clinical outcomes when wearing or not wearing cervical braces after single- or double-level ACDF. We examined 2 cohorts of patients who underwent single- or double-level ACDF surgery with and without a cervical brace: patients who underwent ACDF between March 2018 and December 2019 received a cervical brace, while patients who underwent ACDF between January 2020 and May 2021 did not. Each patient was evaluated radiologically and functionally using plain X-ray, modified Japanese Orthopedic Association score, and visual analog scale for neck and arm until 12 months after surgery. Fusion rate, subsidence, and postoperative complications were also evaluated. Eighty-three patients were included in the analysis: 38 were braced and 45 were not. The demographic characteristics and baseline outcome measures of both groups were similar. There was no statistically significant difference in any of the clinical measures at baseline. The modified Japanese Orthopedic Association score and visual analog scale for neck and arm were similar in both groups at all time intervals and showed statistically significant improvement when compared with preoperative scores. In addition, fusion rate, subsidence, and postoperative complications were similar in both groups. Our results suggest that the use of cervical braces does not improve the clinical outcomes of individuals undergoing single- or double-level ACDF.

The Effect of Intraoperative Overdistraction on Subsidence Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

The purpose of this study was to evaluate the effect of overdistraction on interbody cage subsidence.

BACKGROUND

Vertebral overdistraction due to the use of large intervertebral cage sizes may increase the risk of postoperative subsidence.

METHODS

Patients who underwent anterior cervical discectomy and fusion between 2016 and 2021 were included. All measurements were performed using lateral cervical radiographs at 3 time points - preoperative, immediate postoperative, and final follow-up >6 months postoperatively. Anterior and posterior distraction were calculated by subtracting the preoperative disc height from the immediate postoperative disc height. Cage subsidence was calculated by subtracting the final follow-up postoperative disc height from the immediate postoperative disc height. Associations between anterior and posterior subsidence and distraction were determined using multivariable linear regression models. The analyses controlled for cage type, cervical level, sex, age, smoking status, and osteopenia.

RESULTS

Sixty-eight patients and 125 fused levels were included in the study. Of the 68 fusions, 22 were single-level fusions, 35 were 2-level, and 11 were 3-level. The median final follow-up interval was 368 days (range: 181-1257 d). Anterior disc space subsidence was positively associated with anterior distraction (beta = 0.23; 95% CI: 0.08, 0.38; P = 0.004), and posterior disc space subsidence was positively associated with posterior distraction (beta = 0.29; 95% CI: 0.13, 0.45; P < 0.001). No significant associations between anterior distraction and posterior subsidence (beta = 0.07; 95% CI: -0.06, 0.20; P = 0.270) or posterior distraction and anterior subsidence (beta = 0.06; 95% CI: -0.14, 0.27; P = 0.541) were observed.

CONCLUSIONS

We found that overdistraction of the disc space was associated with increased postoperative subsidence after anterior cervical discectomy and fusion. Surgeons should consider choosing a smaller cage size to avoid overdistraction and minimize postoperative subsidence.

A novel MRI-based Cervical-Endplate Bone Quality score independently predicts cage subsidence after Anterior Cervical Discectomy and Fusion

INTRODUCTION

Postoperative cage subsidence after Anterior Cervical Discectomy and Fusion (ACDF) often has adverse clinical consequences and is closely related to Bone Mineral Density (BMD). Previous studies have shown that cage subsidence can be better predicted by measuring site-specific bone density. MRI-based Endplate Bone Quality (EBQ) scoring effectively predicts cage subsidence after lumbar interbody fusion. However, there is still a lack of studies on the practical application of EBQ scoring in the cervical spine.

PURPOSE

To create a similar MRI-based scoring system for Cervical-EBQ (C-EBQ) and to assess the correlation of the C-EBQ with endplate Computed Tomography (CT)-Hounsfield Units (HU) and the ability of this scoring system to independently predict cage subsidence after ACDF, comparing the predictive ability of the C-EBQ with the Cervical-Vertebral Bone Quality (C-VBQ) score.

METHODS

A total of 161 patients who underwent single-level ACDF for degenerative cervical spondylosis at our institution from 2012 to 2022 were included. Demographics, procedure-related data, and radiological data were collected, and Pearson correlation test was used to determine the correlation between C-EBQ and endplate HU values. Cage subsidence was defined as fusion segment height loss of ≥ 3 mm. Receiver operating characteristic analysis and area-under-the-curve values were used to assess the predictive ability of C-EBQ and C-VBQ. A multivariate logistic regression model was developed to identify potential risk factors associated with subsidence.

RESULTS

Cage subsidence was present in 65 (40.4%) of 161 patients. The mean C-EBQ score was 1.81 ± 0.35 in the group without subsidence and 2.59 ± 0.58 in the group with subsidence (P < 0.001). Multivariate analysis showed that a higher C-EBQ score was significantly associated with subsidence (OR = 5.700; 95%CI = 3.435-8.193; P < 0.001), was the only independent predictor of cage subsidence after ACDF, had a predictive accuracy of 93.7%, which was superior to the C-VBQ score (89.2%), and was significantly negatively correlated with the endplate HU value (r = -0.58, P < 0.001).

CONCLUSIONS

Higher C-EBQ scores were significantly associated with postoperative cage subsidence after ACDF. There was a significant negative correlation between C-EBQ and endplate HU values. The C-EBQ score may be a promising tool for assessing preoperative bone quality and postoperative cage subsidence and is superior to the C-VBQ.

Lower Hounsfield Units at the Planned Lowest Instrumented Vertebra is an Independent Risk Factor for Complications Following Adult Cervical Deformity Surgery

BACKGROUND

The association of Hounsfield units (HU) and junctional pathologies in adult cervical deformity (ACD) surgery has not been elucidated.

OBJECTIVE

Assess if the bone mineral density of the LIV, as assessed by HUs, is prognostic for the risk of complications after ACD surgery.

STUDY DESIGN/SETTING

Retrospective cohort study.

METHODS

HUs were measured on preoperative CT scans. Means comparison test assessed differences in HUs based on the occurrence of complications, linear regression assessed the correlation of HUs with risk factors, and multivariable logistic regression followed by a conditional inference tree derived a threshold for HUs based on the increased likelihood of developing a complication.

RESULTS

In all, 107 ACD patients were included. Thirty-one patients (29.0%) developed a complication (18.7% perioperative), with 20.6% developing DJK and 11.2% developing DJF. There was a significant correlation between lower LIVs and lower HUs (r=0.351, P=0.01), as well as age and HUs at the LIV. Age did not correlate with change in the DJK angle (P>0.2). HUs were lower at the LIV for patients who developed a complication and an LIV threshold of 190 HUs was predictive of complications (OR: 4.2, [1.2-7.6]; P=0.009).

CONCLUSIONS

Low bone mineral density at the lowest instrumented vertebra, as assessed by a threshold lower than 190 Hounsfield units, may be a crucial risk factor for the development of complications after cervical deformity surgery. Preoperative CT scans should be routinely considered in at-risk patients to mitigate this modifiable risk factor during surgical planning.

LEVEL OF EVIDENCE

Level-III.

Novel Risk Factors for Cervical Facet Joint Degeneration in the Subaxial Cervical Spine: Correlation with Cervical Sagittal Alignment and Bone Mineral Density

OBJECTIVE

The impact of cervical sagittal alignment on cervical facet joint degeneration (CFD) and the risk factors for CFD in patients with degenerative cervical myelopathy (DCM) were investigated in the current study.

METHODS

A total of 250 surgical patients with DCM were recruited. The clinical data and radiographical characteristics, including CFD, cervical sagittal balance parameters, Hounsfield unit (HU) values, disc degeneration (DD), and modic change, were collected. The detailed correlation between these characteristics and CFD was analyzed. Characteristics, including CFD, were compared among the various cervical alignment types and different CFD groups. Finally, the risk factors for CFD were revealed via logistic regression.

RESULTS

CFD was prevalent in DCM patients. Age, cervical sagittal vertical axis (cSVA), range of motion, T1 slope, thoracic inlet angle, DD, HU value, and modic change correlated with CFD segmentally and globally (P < 0.05). The lordosis and sigmoid types had a significantly higher CFD prevalence (P < 0.05). Furthermore, the average CFD threshold for the severe CFD group was 1.625 (area under the curve, 0.958). Additionally, 167 patients with average CFD <1.625 and 83 patients with CFD of ≥1.625 were classified into the mild CFD group and severe CFD group, respectively. Finally, multivariate analysis was performed, and age, cSVA, HU value, modic change, and DD were determined to be independent risk factors for CFD.

CONCLUSIONS

The load distribution tends to shift to a more shear-like pattern in the sigmoid and kyphosis types and in those with a higher cSVA, thereby promoting CFD. Aging, cervical malalignment, low bone mineral density, DD, and modic change were revealed to result in high risks of CFD.

Preoperative MRI-based endplate quality: a novel tool for predicting cage subsidence after anterior cervical spine surgery

PURPOSE

The objective of this study was to examine the predictive value of a newly developed MRI-based Endplate Bone Quality (EBQ) in relation to the development of cage subsidence following anterior cervical discectomy and fusion (ACDF).

METHODS

Patients undergoing ACDF for degenerative cervical diseases between January 2017 and June 2022 were included. Correlation between EBQ scores and segmental height loss was analyzed using Pearson's correlation. ROC analyses were employed to ascertain the EBQ cut-off values that predict the occurrence of cage subsidence. Multivariate logistic regression analyses were conducted to identify the risk factors associated with postoperative cage subsidence.

RESULTS

23 individuals (14.56%) exhibited the cage subsidence after ACDF. In the nonsubsidence group, the average EBQ and lowest T-score were determined to be 4.13 ± 1.14 and - 0.84 ± 1.38 g/cm2 respectively. In contrast, the subsidence group exhibited a mean EBQ and lowest T-score of 5.38 ± 0.47 (p < 0.001) and - 1.62 ± 1.34 g/cm2 (p = 0.014), respectively. There was a significant positive correlation (r = 0.798**) between EBQ and the segmental height loss. The EBQ threshold of 4.70 yielded optimal sensitivity (73.9%) and specificity (93.3%) with AUC of 0.806. Furthermore, the lowest T-score (p = 0.045, OR 0.667) and an elevated cervical EBQ score (p < 0.001, OR 8.385) were identified as significant risk factors for cage subsidence after ACDF.

CONCLUSIONS

The EBQ method presents itself as a promising and efficient tool for surgeons to assess patients at risk of cage subsidence and osteoporosis prior to cervical spine surgery, utilizing readily accessible patient data.

Cervical Vertebral Bone Quality Score Independently Predicts Zero-Profile Cage Subsidence After Single-Level Anterior Cervical Discectomy and Fusion

OBJECTIVE

This is the first study to evaluate the predictive value of the cervical vertebral bone quality (VBQ) score on zero-profile cage (ZPC)subsidence after anterior cervical discectomy and fusion (ACDF) using the Hounsfield units (HU) value of computed tomography as the reference.

METHODS

A total of 89 patients with at least 1 year of follow-up who underwent single-level ACDF with ZPC were retrospectively and consecutively included. VBQ and HU value were determined from preoperative T1-weighted magnetic resonance imaging and computed tomography. Subsidence was defined as ≥2 mm of migration of the cage into the superior or inferior endplate or both using lateral cervical spine radiography. The results were subjected to statistical analysis.

RESULTS

Subsidence was observed among 16 of the 89 study patients (Subsidence rate: 18.0%). The mean VBQ score was 2.94 ± 0.820 for patients with subsidence and 2.33 ± 0.814 for patients without subsidence. The multivariable analysis demonstrated that only an increased VBQ score (odds ratio: 1.823, 95% confidence interval : 0.918,3.620, P = 0.001) was associated with an increased rate of cage subsidence. There was a significant and moderate correlation between HU and VBQ (r = -0.507, P < 0.001). Using receiver operating characteristic curves, the area under the curve was 0.785, and the most appropriate threshold of VBQ was 2.68 (sensitivity 72.7%, specificity 82.1%).

CONCLUSIONS

The VBQ score may be a valuable tool for independently predicting ZPC subsidence after single-level ACDF.

Bone Density Distribution in the Cervical Spine

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Given changes in bone density induced by degenerative disease, general measures of bone health (ie DEXA) are inadequate to evaluate bone density in surgical areas of interest. Regional differences in HU in the cervical spine may influence surgical strategies. The purposes of our study were to determine whether cervical Hounsfield units (HU) vary by level, examine their relationship with age, comorbidities, and alignment, and propose a technique to measure HU in the lateral masses.

METHODS

Two hundred twenty-four patients with degenerative spine pathology with a cervical computed tomography were included (2015-2019). Measurements were performed in each vertebral body (C2-T1; mid-axial, anterior-axial, posterior-axial, mid-coronal, and mid-sagittal) and 2 regions of the lateral masses (C3-C6; mid-cor, mid-sag). To evaluate reliability, 6 observers each measured 355 HU values, inter-relater reliability assessed with intraclass correlation coefficients Correlations of HU with age, BMI, comorbidities, and cervical alignment were evaluated.

RESULTS

Bone density differed by level, with the lowest HU scores in the lower cervical spine (C6-T1) (P < .001). No correlations were found between LM HU and age, BMI, CCI, or alignment (P > .05). Increased kyphosis was weakly correlated with VB HU, while age and CCI showed moderate correlations with VB HU at all levels (P<.001). ICC for HU measurements were good to excellent for the VBs, but poor to moderate for the LMs.

CONCLUSION

Bone is least dense in the lower cervical spine. HU scoring is not reliable in the lateral masses. We recommend that a level-specific approach to bone density is considered in surgical planning.

Different cervical vertebral bone quality scores for bone mineral density assessment for the patients with cervical degenerative disease undergoing ACCF/ACDF: computed tomography and magnetic resonance imaging-based study

BACKGROUND

Bone mineral density (BMD) is important for the outcome of cervical spine surgery. As the gold standard of assessing BMD, dual-energy X-ray absorptiometry scans are often not ordered or go unreviewed in patients' charts. As the supplement, MRI-based vertebral bone quality (VBQ) was found to accurately predict osteopenia/osteoporosis and postoperative complications in lumbar spine. However, discussion of the efficiency of VBQ in cervical spine is lacking. And measurement methods of VBQ in cervical spine are diverse and not universally acknowledged like lumbar spine. We aimed to compare the predictive performance of three kinds of different Cervical-VBQ (C-VBQ) scores for bone mineral density assessment in patients undergoing cervical spine surgery. HU value of cervical spine was set as a reference.

METHODS

Adult patients receiving cervical spine surgery for degenerative diseases were retrospectively included between Jan 2015 and Dec 2022 in our hospital. The VBQ scores and HU value were measured from preoperative MRI and CT. The correlation between HU value/C-VBQs (named C-VBQ1/2/3 according to different calculating methods) and DEXA T-score was analyzed using univariate linear correlation and Pearson's correlation. We evaluated the predictive performance of those two parameters and achieved the most appropriate cutoff value by comparing the receiver operating characteristic (ROC) curves.

RESULTS

106 patients (34 patients with T ≥ - 1.0 vs 72 patients with T < - 1.0) were included (mean age: 51.95 ± 10.94, 48 men). According to Pearson correlation analysis, C-VBQ1/2/3 and HU value were all significantly correlated to DEXA T-score (Correlation Coefficient (r): C-VBQ1: - 0.393, C-VBQ2: - 0.368, C-VBQ3: - 0.395, HU value: 0.417, p < 0.001). The area under the ROC curve (AUC) was calculated (C-VBQ1: 0.717, C-VBQ2: 0.717, C-VBQ3: 0.727, HU value: 0.746). The AUC of the combination of C-VBQ3 and HU value was 0.786. At last, the most appropriate cutoff value was determined (C-VBQ1: 3.175, C-VBQ2: 3.005, C-VBQ3: 2.99, HU value: 299.85 HU).

CONCLUSIONS

Different MRI-based C-VBQ scores could all be potential and alternative tools for opportunistically screening patients with osteopenia and osteoporosis before cervical spine surgery. Among them, C-VBQ calculated in ASIC2-C7/SIT1-CSF performed better. We advised patients with C-VBQ higher than cutoff value to accept further BMD examination.

Advances in Hounsfield units value for predicting cage subsidence on spinal interbody fusion surgery

PURPOSE

A growing number of studies have demonstrated that Hounsfield units (HU) value can effectively assess bone quality and predict cage subsidence (CS) after spinal surgery. The purpose of this review is to provide an overview of the utility of the HU value for predicting CS after spinal surgery and to raise some of the unresolved questions in this field.

METHODS

We searched on PubMed, EMBASE, MEDLINE, and Cochrane Library for studies correlating HU value to CS.

RESULTS

Thirty-seven studies were included in this review. We found that HU value can predicted the risk of CS effectively after spinal surgery. Moreover, the HU value of the cancellous vertebral body and the cortical endplate were used for predicting CS, in comparison, the measurement method of HU value in the cancellous vertebral body was more standardized, but which region is more important to CS remains unknown. Different cutoff thresholds of HU value have been established in different surgical procedures for predicting CS. The HU value may be superior to dual-energy X-ray absorptiometry (DEXA) for CS prediction; however, the usage standard of HU value has not been well established.

CONCLUSIONS

The HU value shows great potential for predicting CS and constitutes an advantage over DEXA. However, general consensuses about how CS is defined and HU is measured, which part of HU value is more important, and the appropriate cutoff threshold of the HU value for osteoporosis and CS still require exploration.

A Novel Cervical Vertebral Bone Quality Score Independently Predicts Cage Subsidence After Anterior Cervical Diskectomy and Fusion

BACKGROUND

Surgeons can preoperatively assess bone quality using dual-energy X-ray absorptiometry or computed tomography; however, this is not feasible for all patients. Recently, a MRI-based scoring system was used to evaluate the lumbar spine's vertebral bone quality.

OBJECTIVE

To create a similar MRI-based scoring system for the cervical spine (C-VBQ), correlate C-VBQ scores with computed tomography-Hounsfield units (HU), and evaluate the utility of this scoring system to independently predict cage subsidence after single-level anterior cervical diskectomy and fusion (ACDF).

METHODS

Demographic, procedure-related, and radiographic data were collected for patients. Pearson correlation test was used to determine the correlation between C-VBQ and HU. Cage subsidence was defined as ≥3 mm loss of fusion segmental height. A multivariate logistic regression model was built to determine the correlation between potential risk factors for subsidence.

RESULTS

Of 59 patients who underwent single-level ACDF, subsidence was found in 17 (28.8%). Mean C-VBQ scores were 2.22 ± 0.36 for no subsidence levels and 2.83 ± 0.38 ( P < .001) for subsidence levels. On multivariate analysis, a higher C-VBQ score was significantly associated with subsidence (odds ratio = 1.85, 95% CI = 1.39-2.46, P < .001) and was the only significant independent predictor of subsidence after ACDF. There was a significant negative correlation between HU and C-VBQ (r 2 = -0.49, P < .001).

CONCLUSION

We found that a higher C-VBQ score was significantly associated with cage subsidence after ACDF. Furthermore, there was a significant negative correlation between C-VBQ and HU. The C-VBQ score may be a valuable tool for assessing preoperative bone quality and independently predicting cage subsidence after ACDF.

The value of Hounsfield units in predicting cage subsidence after transforaminal lumbar interbody fusion

BACKGROUND

Cage subsidence may occur following transforaminal lumbar interbody fusion (TLIF) and lead to nonunion, foraminal height loss and other complications. Low bone quality may be a risk factor for cage subsidence. Assessing bone quality through Hounsfield units (HU) from computed tomography has been proposed in recent years. However, there is a lack of literature evaluating the correlation between HU and cage subsidence after TLIF.

METHODS

Two hundred and seventy-nine patients suffering from lumbar degenerative diseases from April, 2016 to August, 2018 were enrolled. All underwent one-level TLIF with a minimum of 1-year follow-up. Cage subsidence was defined as > 2 mm loss of disc height at the fusion level. The participants were divided into 2 groups: cage subsidence group (CS) and non-cage subsidence group (non-CS). Bone quality was determined by HU, bone mineral density of lumbar (BMD-l) and femoral (BMD-f) from dual-emission X-ray absorptiometry (DXA). HU of each vertebra from L1 to L4 (e.g., HU1 for HU of L1) and mean value of the four vertebrae (HUm) were calculated. Visual analog scale (VAS) of back/leg pain and Oswestry disability index (ODI) were used to report clinical outcomes.

RESULTS

Cage subsidence occurred in 82 (29.4%) cases at follow-ups. Mean age was 50.8 ± 9.0 years with a median follow-up of 18 months (range from 12 to 40 months). A total of 90.3% patients presented fusion with similar fusion rate between the two groups. ODI and VAS in leg were better in non-CS group at last follow-ups. Using receiver operating characteristic curves (ROCs) to predict cage subsidence, HUm provided a larger area under the curve (AUC) than BMD-l (Z = 3.83, P <  0.01) and BMD-f (Z = 2.01, P = 0.02). AUC for HU4 was larger than BMD-f and close to HUm (Z = 0.22, P = 0.481).

CONCLUSIONS

Cage subsidence may indicate worse clinical outcomes. HU value could be a more effective predictor of lumbar cage subsidence compared with T-score of DXA after TLIF.

Low cervical vertebral CT value increased early subsidence of titanium mesh cage after anterior cervical corpectomy and fusion

Study design

This study was a retrospective review.

Objective

To study the predictive effect of Hounsfield units (HU) value in the cervical vertebral body derived from computed tomography (CT) on the early titanium mesh cage (TMC) subsidence after anterior cervical corpectomy and fusion (ACCF).

Methods

This retrospective study was conducted on patients who underwent ACCF at one institution between January 2014 and December 2018. We collected date included age, gender, body mass index (BMI), disease type, surgical segment, whether merge ACDF, HU value of the vertebral body and endplate, vertebral body height loss, cervical lordosis angle, and cervical sagittal alignment. VAS, JOA, and NDI were used to assess clinical efficacy. Univariate analysis was performed to screen the influencing factors of TMC subsidence, and then logistic regression was used to find out the independent risk factors. The ROC curve and area under curve (AUC) were used to analyze the HU value to predict the TMC subsidence.

Results

A total of 85 patients who accepted ACCF were included in this study, and early titanium mesh cage subsidence was demonstrated in 29 patients. The subsidence rate was 34.1%. The JOA, VAS, and NDI scores significantly improved in both groups after the operation. Between the subsidence and non-subsidence groups, there were significant differences in age, intervertebral distraction height, and HU value in both upper and lower vertebral body and endplate. The logistic regression analysis proved that the HU value of the lower vertebral body was an independent risk of TMC subsidence, the AUC was 0.866, and the most appropriate threshold of the HU value was 275 (sensitivity: 87.5%, specificity: 79.3%).

Conclusion

Preoperative cervical CT value is an independent correlative factor for early TMC subsidence after ACCF, and patients with a low CT value of the inferior vertebral body of the operative segment have a higher risk of TMC subsidence in the early postoperative period.

Trial registration: This study is undergoing retrospective registration.

Low Hounsfield units on computed tomography are associated with cage subsidence following oblique lumbar interbody fusion (OLIF)

BACKGROUND CONTEXT

Cage subsidence is one of the most common complications following lumbar interbody fusion surgery. Low bone mineral density (BMD) is an important risk factor that contributes to cage subsidence. Hounsfield units (HU) obtained from clinical computed tomography (CT) scans provided a reliable method for determining regional BMD. The association between HU and cage subsidence following oblique lumbar interbody fusion (OLIF) remains unclear.

PURPOSE

The objective of this study is to evaluate the association between vertebral HU value and cage subsidence following OLIF.

STUDY DESIGN/SETTING

A retrospective study.

PATIENT SAMPLE

Adults with degenerative spinal conditions underwent single-level OLIF at our institution from October 2017 and August 2020 OUTCOME MEASURES: Cage subsidence, disc height, vertebral body global HU value, upper and lower instrumented vertebrae HU value, endplate HU value, fusion rate.

METHODS

This retrospective study was conducted on patients who underwent single-level OLIF at one institution between October 2017 and August 2020. Cage subsidence was measured using the CT scan postoperatively based on the cage protrusion through the vertebral endplates. The HU values were measured from preoperative CT according to previously reported methods.

RESULTS

A total of 70 patients with a mean follow-up of 15.4 months were included in the analysis. The subsidence rate was 25.7% (n=18/70). The average cage subsidence was 2.2 mm, with a range of 0-7.7 mm. No significant difference was found in age, sex, or body mass index (BMI) between the two groups. The mean global HU value of the lumbar vertebral body (L1-5) was 142.7±30.1 in nonsubsidence and 103.7±11.5 in subsidence (p=.004). The upper instrumented vertebrae (UIV) HU value was 141.4±29.7 in the nonsubsidence and 101.1±10.2 in subsidence, (p=.005). The lower instrumented vertebrae (LIV) HU value was 147.4±34.9 in nonsubsidence and 108.1±13.7 in subsidence, (p<.001). The AUC of the UIV HU value was 0.917 (95% CI: 0.853-0.981), and the most appropriate threshold of the HU value was 115 (sensitivity: 84.6%, specificity: 100%). The AUC of the LIV HU value was 0.893 (95%CI: 0.819-0.966), and the most appropriate threshold of the HU value was 125 (sensitivity: 76.9%, specificity: 100%). The mean upper endplate HU value was 235.4±50.9, and the mean lower endplate HU value was 193.4±40.3. No significant difference (upper endplate p=.314, lower endplate p=.189) was observed between the two groups.

CONSLUSIONS

Lower preoperative vertebral body HU values were associated with cage subsidence after single-level OLIF. However, the endplate HU values were not associated with cage subsidence. Preoperative HU measurement is useful in the prediction of the cage subsidence.

The Effect of Hounsfield Unit Value with Conventional Computed Tomography and Intraoperative Distraction on Postoperative Intervertebral Height Reduction in Patients Following Stand-Alone Anterior Cervical Discectomy and Fusion

Objective

The most common complication of anterior cervical discectomy and fusion (ACDF) is cage subsidence and maintenance of disc height affects postoperative clinical outcomes. We considered cage subsidence as an inappropriate indicator for evaluating preservation of disc height. Thus, this study aimed to consider patients with complications such as reduced total disc height compared to that before surgery and evaluate the relevance of several factors before ACDF.

Methods

We retrospectively reviewed the medical records of 40 patients who underwent stand-alone single-level ACDF using a polyetheretherketone (PEEK) cage at our institution between January 2012 and December 2018. Our study population comprised 19 male and 21 female patients aged 24–70 years. The minimum follow-up period was 1 year. Twenty-seven patients had preoperative bone mineral density (BMD) data on dual-energy X-ray absorptiometry. Clinical parameters included sex, age, body mass index, smoking history, and prior medical history. Radiologic parameters included the C2-7 cobb angle, segmental angle, sagittal vertical axis, disc height, and total intervertebral height (TIH) at the preoperative and postoperative periods. Cage decrement was defined as the reduction in TIH at the 6-month follow-up compared to preoperative TIH. To evaluate the bone quality, Hounsfield unit (HU) value was calculated in the axial and sagittal images of conventional computed tomography.

Results

Lumbar BMD values and cervical HU values were significantly correlated (r=0.733, p<0.001). We divided the patients into two groups based on cage decrement, and 47.5% of the total patients were regarded as cage decrement. There were statistically significant differences in the parameters of measuring the HU value of the vertebra and intraoperative distraction between the two groups. Using these identified factors, we performed a receiver operating characteristic (ROC) curve analysis. Based on the ROC curve, the cut-off point was 530 at the HU value of the upper cortical and cancellous vertebrae (p=0.014; area under the curve [AUC], 0.727; sensitivity, 94.7%; specificity, 42.9%) and 22.41 at intraoperative distraction (p=0.017; AUC, 0.722; sensitivity, 85.7%; specificity, 57.9%). Using this value, we converted these parameters into a bifurcated variable and assessed the multinomial regression analysis to evaluate the risk factors for cage decrement in ACDF. Intraoperative distraction and HU value of the upper vertebral body were independent factors of postoperative subsidence.

Conclusion

Insufficient intraoperative distraction and low HU value showed a strong relationship with postoperative intervertebral height reduction following single stand-alone PEEK cage ACDF.

Is there a difference in the outcomes of anterior cervical discectomy and fusion among female patients with different menopausal statuses?

BACKGROUND

The surgical outcomes of anterior cervical discectomy and fusion (ACDF) in female patients according to menopausal status remain unclear. The objective of this study was to investigate the differences in these outcomes among female patients with different menopausal statuses.

METHODS

Ninety-one patients undergoing single-level or consecutive two-level ACDF with a minimum 12-month postoperative follow-up were included in this study. There were 38 patients in the premenopausal group, 28 patients in the early postmenopausal group, and 25 patients in the late postmenopausal group. The clinical outcomes were evaluated by means of the neck disability index (NDI) scores, Japanese Orthopedic Association (JOA) scores, and visual analog scale (VAS) scores. Radiological parameters included cervical lordosis (CL), the functional spinal unit (FSU) angle, range of motion (ROM) of the total cervical spine, ROM of the FSU, anterior and posterior FSU height, implant subsidence, adjacent segment degeneration (ASD), and Hounsfield unit (HU) values.

RESULTS

All groups showed significant improvements in their JOA, VAS, and NDI scores (P < 0.05). The differences in preoperative and final follow-up CL, ROM of C2-7, FSU angle, and ROM of FSU were not statistically significant among the three groups (P > 0.05). The anterior FSU height loss rate showed a significant difference (P = 0.043), while there was no difference in the posterior FSU height loss rate (P = 0.072). The fusion rates in the early and late postmenopausal groups were consistently lower than those in the premenopausal group during the follow-up period. All patients had satisfactory outcomes at the final follow-up.

CONCLUSION

There were no significant differences in clinical or other related outcomes of single-level or consecutive two-level ACDF in the long term among female patients with different menopausal statuses. However, the early bony fusion rates and anterior FSU height loss rates were poorer in late postmenopausal patients than in premenopausal or early postmenopausal patients. Hence, importance should be attached to the protection of late postmenopausal patients in the early postoperative period to guarantee solid bony fusion.