Association of complete uncinate process removal on 2-year assessment of radiologic outcomes: subsidence and sagittal balance in patients receiving one-level anterior cervical discectomy and fusion

Anatomic Research of the Safe Space Between the Cervical Uncinate Process and the V2 Vertebral Artery

OBJECTIVE

A retrospective study was performed to observe and measure the safe distance between the uncinate process (UP) and the V2 vertebral artery (VA).

METHODS

Two hundred and sixteen patients who underwent head and neck computed tomography angiography were selected and measured. The upper tip (UT) of the UP, the posterior tip of the UP (PT), and the center of the VA (CA) were identified. Then, the width between the UT and the CA, the depth between the UT and the CA, and the distance between the UT and the CA were measured. The width between the PT and the CA, the depth between the PT and the CA, and the length between the PT and the CA were measured. These values were compared between the left and right sides of the same vertebral body and also the results of the same side from C3 to C6 were compared.

RESULTS

The width between the UT and the CA fluctuates between 6.1 and 4.4 mm on the left side with the narrowest at C5 and C6 (4.4 mm) and between 6.5 and 4.6 mm on the right side with the narrowest at C5 (4.6 mm). It could be concluded that the safe space for operation outside UP is about 4 mm and more care should be taken when operating on the caudal spine. The width between the PT and the CA fluctuates between 10.6 and 10.0 mm on the left side with the narrowest at C3 (10 mm) and between 11.0 and 9.9 mm on the right side with the narrowest at C4 (9.9 mm). The safe space for operation outside the PT is about 10 mm and more care should be taken when operating on the cephalad spine. Depth between the PT and the CA fluctuates between 6.5 and 4.6 mm on the left and is narrowest at C3 (4.6 mm) and between 6.5 and 4.7 mm on the right and narrowest at C3 (4.7 mm). The safe space for operation from the PT to the ventral side is about 4.5 mm, and more care should be taken when operating on the cephalad side of the cervical spine.

CONCLUSIONS

UP and PT could be seen as landmarks in the operations of anterior cervical discectomy and fusion. The safe space outside UP is about 4 mm and more care should be taken when operating on the caudal spine. The safe space outside PT is about 10 mm and more care should be taken when operating on the cephalad spine. The safe space for operation from the PT to the ventral side is about 4.5 mm, and more care should be taken when operating on the cephalad side of the cervical spine.

Comparison of the effectiveness of zero-profile device and plate cage construct in the treatment of one-level cervical disc degenerative disease combined with moderate to severe paraspinal muscle degeneration

Objective

Recent evidence indicates that cervical paraspinal muscle degeneration (PMD) is a prevalent and age-related condition in patients with cervical disc degenerative disease (CDDD). However, the relationship between surgery selection and post-operative outcomes in this population remains unclear. Consequently, this study aims to investigate the disparities in clinical outcomes, radiological findings, and complications between two frequently utilized anterior cervical surgical procedures. The objective is to offer guidance for the management of PMD in conjunction with CDDD.

Methods

A total of 140 patients who underwent single-level anterior cervical discectomy and fusion (ACDF) at our department were included in this study. The patients were divided into three groups based on the severity of PMD: mild (n=40), moderate (n=54), and severe (n=46), as determined by Goutalier fat infiltration grade. The subjects of interest were those with moderate-severe PMD, and their clinical outcomes, radiological parameters, and complications were compared between those who received a stand-alone zero-profile anchored cage (PREVAIL) and those who received a plate-cage construct (PCC).

Results

The JOA, NDI, and VAS scores exhibited significant improvement at all postoperative intervals when compared to baseline, and there were no discernible differences in clinical outcomes between the two groups. While the PCC group demonstrated more pronounced enhancements and maintenance of several sagittal alignment parameters, such as the C2-7 angle, FSU angle, C2-7 SVA, and T1 slope, there were no statistically significant differences between the two groups. The incidence of dysphagia in the zero-profile group was 22.41% at one week, which subsequently decreased to 13.79% at three months and 3.45% at the final follow-up. In contrast, the plate cage group exhibited a higher incidence of dysphagia, with rates of 47.62% at one week, 33.33% at three months, and 11.90% at the final follow-up. Notably, there were significant differences in the incidence of dysphagia between the two groups within the first three months. However, the fusion rate, occurrence of implant subsidence, and adjacent segment degeneration (ASD) were comparable at the final follow-up.

Conclusion

For patients with one-level cervical disc degenerative disease combined with paraspinal muscle degeneration, both the zero-profile technique and PCC have demonstrated efficacy in ameliorating clinical symptoms and maintaining the postoperative sagittal balance. Although no significant disparities were observed between these two technologies in terms of complications such as adjacent segment degeneration and implant subsidence, the zero-profile technique exhibited superior performance over PCC in relation to dysphagia during the early stages of postoperative recovery. To validate these findings, studies with longer follow-up periods and evaluations of multilevel cervical muscles are warranted.

Preoperative Radiographic Simulation for Partial Uncinate Process Resection during Anterior Cervical Discectomy and Fusion to Achieve Adequate Foraminal Decompression and Prevention of Vertebral Artery Injury

STUDY DESIGN

Retrospective radiographic study.

PURPOSE

This study aims to demonstrate the proper resection trajectory of a partial posterior uncinate process resection combined with anterior cervical discectomy and fusion (ACDF) and evaluate whether foraminal stenosis or uncinate process degeneration increases the risk of vertebral artery (VA) injury.

OVERVIEW OF LITERATURE

Appropriate resection trajectory that could result in sufficient decompression and avoid vertebral artery injury is yet unknown.

METHODS

We retrospectively reviewed patients who underwent cervical magnetic resonance imaging and computed tomography angiography for preoperative ACDF evaluation. The segments were classified according to the presence of foraminal stenosis. The height, thickness, anteroposterior length, horizontal distance from the uncinate process to the VA, and vertical distance from the uncinate process baseline to the VA of the uncinate process were measured. The distance between the uncinate anterior margin and the resection trajectory (UAM-to-RT) was measured.

RESULTS

There were no VA injuries or root injuries among the 101 patients who underwent ACDF (163 segments, mean age of 56.3±12.2). Uncinate anteroposterior length was considerably longer in foramens with foraminal stenosis, whereas uncinate process height, thickness, and distance between the uncinate process and VA were not significantly associated with foraminal stenosis. There were no significant differences in radiographic parameters based on uncinate degeneration. The UAM-to-RT distances for adequate decompression were 1.6±1.4 mm (range, 0-4.8 mm), 3.4±1.7 mm (range, 0-7.1 mm), 4.0±1.7 mm (range, 0-9.0 mm), and 4.5±1.2 mm (range, 2.5-7.5 mm) for C3-C4, C4-C5, C5-C6, and C6-C7, respectively.

CONCLUSIONS

More than half of the uncinate process in the anteroposterior plane should be removed for adequate neural foramen decompression. Foraminal stenosis or uncinate degeneration did not alter the relative anatomy of the uncinate process and the VA and did not impact VA injury risk.

Follow-up of a new titanium cervical plate for fusion of the cervical spine

Cervical plates are in use since the 1990ies for anterior cervical discectomy and fusion (ACDF). The latest step in development was a dynamic plate that allows sliding of the screws facilitating the natural settling of the bone after surgery. We investigated the clinical and radiological results of such a dynamic plate in a patient cohort that underwent single or multi-level ACDF for various cervical degenerative indications, including revision cases, from 2014 to 2019. Clinical and radiological outcome were assessed in 60 eligible patients after a mean of 2.9 years. The assessed neck disability index (NDI), and the visual analogue scale (VAS) of neck and arm pain show comparable results to the literature of ACDF, and specifically other plate designs. Forty-eight Adverse and Serious Adverse Events do not show a link to the product used. Clinical and radiological outcomes of ACDF with dynamic, third generation cervical plates show comparable results to the literature. Careful reporting of all Adverse Events revealed a variety of concomitant diseases, but could not be correlated to the implant used.

Predicting surgical outcome and sagittal alignment change in patients with cervical spondylosis and degenerative kyphosis after anterior cervical discectomy and fusion

The aim of this study was to forecast the risk factors of poor outcomes and postoperative loss of lordosis or recurrence of kyphosis. In this retrospective study, 101 patients with cervical spondylosis and preoperative kyphosis who underwent anterior cervical discectomy and fusion (ACDF) were enrolled, between June 2015 and June 2019. Patients were grouped according to the recovery rate of Japanese Orthopaedic Association (JOA) score whether more than 50%, and the change of postoperative cervical Cobb angle. There were 22 cases with less than 50% of recovery rate and 35 cases with the worsening of postoperative sagittal alignment (WPSA). Multivariate linear-regression analysis was conducted with the data. Advanced age (p = 0.019), longer duration of symptoms (p = 0.003) and loss of local Cobb angle (LCA) after surgery (p = 0.031) was significantly associated with a poor clinical outcome. A whole kyphosis (p = 0.009), aggravated neck pain after surgery (p = 0.012), preoperative lower thoracic 1 (T1) (p < 0.001), bigger change of C2-7 sagittal vertical axis (SVA) (p = 0.008) and adjacent segment degeneration (ASD) (p = 0.024) was significantly associated with the WPSA. Preoperative health education, nutritional support and early postoperative rehabilitation intervention, in perioperative period, were recommended for patients with advance age, longer duration of symptoms, whole cervical kyphosis and lower T1. Postoperative sagittal malalignment was related to neck pain and ASD after surgery.

Effect of Anterior Cervical Decompression Fusion and Partial Resection of Uncinate Vertebra Joint on Cervical Sagittal Sequence in Patients with Non-Single-Segment Radiculopathy and its Correlation with Curative Effect: A Retrospective Analysis

OBJECTIVE

Analyze the effect of preservation or resection of the partial uncinate joint on the sagittal sequence of the cervical vertebrae in patients with non-single-segment radiculopathy and the correlation between the sagittal sequence of the cervical vertebrae and the long-term effect after surgery, we explored whether it is necessary to perform partial resection of the uncinate joint in patients with cervical spondylotic radiculopathy undergoing anterior cervical decompression and fusion (ACDF).

METHODS

The study retrospectively analyzed 96 patients with cervical spondylotic radiculopathy with more than two segments from August 2016 to January 2021, who underwent ACDF (ACDF group, 45 patients) or ACDF combined with partial uncinate joint resection (ACDF + UT group, 51 patients). Partial resection of the uncinate joint indicated removal of part of the uncinate joint and osteophyte based on the compression of the nerve root during surgery, whereas the uncinate joints in the ACDF group were retained completely. The imaging data and functional scores of the two groups were recorded before surgery, 1 month after surgery, and at the last follow-up. A paired t-test or rank sum test was applied to analyze the data. In addition, the correlation between the imaging parameters and functional scores was validated using the Pearson's test.

RESULTS

All 96 patients successfully completed the surgery and were followed up for at least 12 months, with an average follow-up time of 14 months. At the last follow-up, the pain visual analog scale (VAS), neck disability index (NDI), and neck pain and disability scale (NPAD) scores of the two groups were significantly lower than those before surgery, and the Japanese Orthopaedic Association (JOA) score was significantly higher than that before surgery. At the last follow-up, compared with the ACDF+UT group, the NDI and NPAD scores in the ACDF group decreased more significantly (p < 0.05), and C2-7SVA, △C2-7SVA (the difference between C2-7 SVA at last follow-up and before operation), and T1S values decreased significantly (p < 0.05). The C2-7 Cobb angle was positively correlated with the JOA score and T1S (p < 0.05) and negatively correlated with the VAS, NDI, and NPAD scores and CGH-C7SVA (p < 0.05). C2-7SVA was positively correlated with CGH-C7SVA and T1S (p < 0.05).

CONCLUSION

Patients with non-single-segmental cervical spondylotic radiculopathy and ACDF with or without uncinate joint resection can have effective improvement in the clinical effect and sagittal balance; however, partial uncinate joint resection has a certain negative impact on the long-term reconstruction of sagittal balance and long-term effects in patients after surgery.

Posterior cervical full-endoscopic technique for the treatment of cervical spondylotic radiculopathy with foraminal bony stenosis: A retrospective study

Objective

In the treatment of cervical spondylotic radiculopathy (CSR), spinal endoscopy has been developed vigorously in the past 30 years. However, its effectiveness and subsequent problem of cervical spine stability have always been the controversial hotspots. This study aims to conduct a retrospective study using posterior cervical full-endoscopic technique for the treatment of CSR with foraminal bony stenosis, and evaluate its clinical effect and application value.

Methods

All 22 patients treated for CSR with foraminal bony stenosis using posterior cervical full-endoscopic technique were analyzed since Dec 1, 2016, to Apr 30, 2020. The data collection included operation time, length of stay, wound healing, surgical complications, visual analog scale (VAS), Japanese Orthopaedic Association (JOA) scores, intervertebral foramen diameter, intervertebral foramen area and cervical instability. The relevant indicators were observed on admission, at postoperative 1 week and 3 months, and at the last follow-up.

Results

The operation time was 141.6 ± 13.7 min. The length of stay was 6.0 ± 2.5 days. VAS and JOA at different time points after operation were decreased compared with before operation (p < 0.05). There were no statistical differences between VAS or JOA at different postoperative time points (p > 0.05). The height, anteroposterior diameter and area of intervertebral foramen after operation were significantly increased compared with before operation (p < 0.05).

Conclusion

Posterior cervical full-endoscopic technique shows the advantages of smaller invasion, faster recovery, significant effectiveness and fewer complications in our study. Meanwhile, it has little influence on the ROM and stability of the cervical spine. Therefore, it is a minimally invasive, safe and effective surgical method for the treatment of CSR with foraminal bony stenosis.

Effect of ACDF combined with different degrees of partial resection of uncovertebral joints on cervical stability and degeneration: a three-dimensional finite element analysis

BACKGROUND

To evaluate the influence of the resection of different amounts of the uncovertebral joints on the stability of the cervical spine by comparing and analyzing the stress distribution and peak displacement characteristics of the internal fixation structures and endplates.

METHODS

After obtaining the CT data of a 34-year-old male healthy cervical spine, a three-dimensional finite element model was established and verified. The three-dimensional finite element method was used to establish the models of anterior cervical compression fusion and internal fixation surgical implants and anterior cervical compression fusion and internal fixation combined with the partial resection of different amounts of the unilateral or bilateral uncovertebral joints. The models were tested under six working conditions: flexion, extension, left bending, right bending, left rotation, and right rotation. The surgical models were compared regarding the stress distribution of the titanium mesh, titanium plate and screw, and endplate, and the peak displacement of the vertebral body.

RESULTS

There were no significant differences in the stress distribution and peak displacement of the vertebral body of ACDF combined with different amounts of uncovertebral joint resection in the states of flexion and extension. However, there were significant increases in the stress distribution and peak displacement of the vertebral body in the states of left and right bending and rotation. In the states of left and right bending and rotation, the stress distribution and peak displacement of the vertebral body were significantly greater in the models with bilateral partial resection of the uncovertebral joints than in the models with unilateral partial resection of the uncovertebral joints. Bilateral resection of the uncovertebral joints by 30-40% and unilateral resection of the uncovertebral joints by 40-50% resulted in the greatest increases in the maximum stress distribution of the titanium plate and screw and the peak displacement of the vertebral body.

CONCLUSION

Finite element analysis of the biomechanical changes in the cervical spine showed that anterior cervical compression fusion and internal fixation combined with bilateral resection of less than 30% of the uncovertebral joints or unilateral resection of less than 40% of the uncovertebral joints had little effect on the stability of the cervical spine.

The Échancrure of the Uncovertebral Joint: A Forgotten Structure of the C3-C7 Cervical Vertebral Bodies

Introduction The échancrure (a French term meaning "indentation") of the cervical vertebrae is the poorly defined articular part on the inferolateral aspect of the cervical spine body, which, with the uncinate processes of the associated caudal vertebra, makes up the joints of Luschka (uncovertebral joint). With no known previous studies on the échancrure, the present anatomical study aimed to better elucidate this structure, its prevalence, and its relationships to the adjacent intervertebral foramen and uncinate process. Methods We observed 50 adult cervical spines (100 sides) for the presence of an énchancrure. When an énchancrure was identified, its morphometry was documented and photographed. Measurements included the width and height of the énchancrure. The relationship with the adjacent uncinate process was also studied. Any correlation between the size and shape of the adjacent uncinate process and the énchancrure was recorded. Results Anénchancrure was found at all levels of the cervical vertebrae except at C1 and C7 and was clearly visible on 88% of the sides. The énchancrure, more or less, conformed to the reciprocal shape of the uncinate process, which was found on all sides. The shapes were roughly arched, ovoid, or linear. These structures were always in an anterolateral position on the body of the vertebra and just outside the apophyseal ring. The mean height of the énchancrure was 2.1 mm. The length of the uncinate process correlated positively (r=0.8) to the size of the adjacent énchancrure. The height of the énchancrure was inversely related to the diameter of the adjacent intervertebral foramen. The mean width was 8.3 mm. These structures tended to be largest at C3 and C4 vertebral levels and were smallest at C5 and C6 levels. The énchancrure was most in contact with the uncinate process with lateral flexion of the cervical spine and in specimens with a longer uncinate process, e.g., C6. The énchancrure was also found to be wider in cases of cervical spine degeneration involving the body of the cervical vertebrae. Degeneration of the uncovertebral joint was most often seen at the énchancrure and not at the adjacent uncinate process. Conclusions We found that the énchancrure is found in the majority of cervical spines. These structures tended to be largest at C3 and C4 vertebral levels and were smallest at C5 and C6 levels, and they had more prominence when the adjacent uncinate process was enlarged. The énchancrure should be considered a normal feature of the inferolateral aspect of the cervical vertebrae. Future clinical studies are necessary to better elucidate their functional significance.

Safety and Efficacy of Anterior Cervical Discectomy and Fusion with Uncinate Process Resection: A Systematic Review and Meta-Analysis

STUDY DESIGN

This is a meta-analysis and systematic review of the available literature.

OBJECTIVE

In the case of severe foraminal stenosis, conducting uncinate process resection (UPR) during ACDF could achieve complete nerve root decompression and significant relief of neurological symptoms for CR. However, there is some controversy regarding its necessity and safety. This study aims to compare the safety and efficacy of ACDF with UPR and ACDF.

METHODS

The following electronic databases were searched: Medline, PubMed, Embase, the Cochrane Central Register of Controlled Trials, Evidence Based Medicine Reviews, VIP, and CNKI. And the following data items were considered: baseline demographics, efficacy evaluation indicators, radiographic outcome, and surgical details.

RESULTS

10 studies were finally identified, including 746 patients who underwent ACDF with UPR compared to 729 patients who underwent ACDF. The group of ACDF with UPR had statistically longer intraoperative time (95% CI: 4.83, 19.77, P = .001) and more intraoperative blood loss (95% CI: 12.23, 17.76, P < .001). ACDF with UPR obtained a significantly better improvement of Arm VAS at postoperative first follow-up (95% CI: -1.85, -.14 P = .02). There was no significant difference found in improvement of Neck VAS at postoperative latest follow-up (95% CI: -.88, .27, P = .30), improvement of Arm VAS at postoperative latest follow-up (95% CI: -.59, -.01, P = .05), improvement of NDI (95% CI: -2.34, .33, P = .14), JOA (95% CI: -.24, .43, P = .56), change of C2-C7 lordosis (95% CI: -.87, 1.33, P = .68), C2-C7 SVA (95% CI: -.73, 5.08, P = .14), T1 slope (95% CI: -2.25, 1.51, P = .70), and fusion rate (95% CI: .83, 1.90 P = .29).

CONCLUSION

ACDF with UPR is an effective and necessary surgical method for CR patients with severe foraminal stenosis.

Comparative Analysis of the Biomechanical Characteristics After Different Minimally Invasive Surgeries for Cervical Spondylopathy: A Finite Element Analysis

Minimally invasive surgeries, including posterior endoscopic cervical foraminotomy (PECF), microsurgical anterior cervical foraminotomy (MACF), anterior transdiscal approach of endoscopic cervical discectomy (ATd-ECD), and anterior transcorporeal approach of endoscopic cervical discectomy (ATc-ECD), have obtained positive results for cervical spondylotic radiculopathy. Nonetheless, there is a lack of comparison among them regarding their biomechanical performance. The purpose of this study is to investigate the biomechanical changes of operated and adjacent segments after minimally invasive surgeries compared to a normal cervical spine. A three-dimensional model of normal cervical vertebrae C3–C7 was established using finite element analysis. Afterwards, four surgical models (PECF, MACF, ATd-ECD, and ATc-ECD) were constructed on the basis of the normal model. Identical load conditions were applied to simulate flexion, extension, lateral bending, and axial rotation of the cervical spine. We calculated the range of motion (ROM), intradiscal pressure (IDP), annulus fibrosus pressure (AFP), uncovertebral joints contact pressure (CPRESS), and facet joints CPRESS under different motions. For all circumstances, ATc-ECD was close to the normal cervical spine model, whereas ATd-ECD significantly increased ROM and joints CPRESS and decreased IDP in the operated segment. PECF increased more the operated segment ROM than did the MACF, but the MACF obtained maximum IDP and AFP. Except for ATc-ECD, the other models increased joints CPRESS of the operated segment. For adjacent segments, ROM, IDP, and joints CPRESS showed a downward trend in all models. All models showed good biomechanical stability. With their combination biomechanics, safety, and conditions of application, PECF and ATc-ECD could be appropriate choices for cervical spondylotic radiculopathy.

The CT assessment of uncovertebral joints degeneration in a healthy population

Background

A retrospective study investigated the degeneration trend of uncovertebral joints in a healthy population based on CT assessment.

Methods

A total of 200 males and 160 females, aged 21–79 years old (50.82 ± 17.06), who underwent CT examination in our hospital from September 2020 to March 2021 were enrolled. Sixty patients were included in each age group. According to the Kellgren and Lawrence classification and CT was used to evaluate the uncovertebral joints degeneration in different groups.

Results

With the increase of age, the degeneration of each segment was gradually aggravated. The uncovertebral joints started degenerating in the 20 s, and the C5–6 is the most degenerative segment, followed by the C4–5 and C6–7. Significant degeneration occurred in each segment between the 40 s and 60 s and became more severe after the 70 s.

Conclusions

The modified Kellgren and Lawrence classification based on CT scan could provide a quantitative assessment of uncovertebral joints degeneration in a healthy population and could provide more details for artificial cervical arthroplasty.

Partial uncinatectomy combined with anterior cervical discectomy and fusion for the treatment of one-level cervical radiculopathy: analysis of clinical efficacy and sagittal alignment

BACKGROUND

Biomechanical studies have demonstrated that uncovertebral joint contributes to segment mobility and stability to a certain extent. Simultaneously, osteophytes arising from the uncinate process are a common cause of cervical spondylotic radiculopathy (CSR). For such patients, partial uncinatectomy (UT) may be required. However, the clinical efficacy and sagittal alignment of partial UT during anterior cervical discectomy and fusion (ACDF) have not been fully elucidated.

METHODS

A total of 87 patients who had undergone single level ACDF using a zero-profile device from July 2014 to December 2018 were included. Based on whether the foraminal part of the uncovertebral joint was resected or preserved, the patients were divided into the ACDF with UT group (n = 37) and the ACDF without UT group (n = 50). Perioperative data, radiographic parameters, clinical outcomes, and complications were compared between the two groups.

RESULTS

The mean follow-up was 16.86 ± 5.63 and 18.36 ± 7.51 months in the ACDF with UT group and ACDF without UT group, respectively (p > 0.05). The average preoperative VAS arm score was 5.89 ± 1.00 in the ACDF with UT group and 5.18 ± 1.21 in the ACDF without UT group (p = 0.038). However, the average VAS arm score was 4.22 ± 0.64, 4.06 ± 1.13 and 1.68 ± 0.71, 1.60 ± 0.70 at 1 week post operation and at final follow up, respectively, (p > 0.05). We also found that the C2-7 SVA and St-SVA at the last follow-up and their change (last follow-up value - preoperative value) in the ACDF with UT group were significantly higher than ACDF without UT group (p < 0.05). No marked differences in the other cervical sagittal parameters, fusion rate or complications, including dysphagia, ASD, and subsidence, were observed.

CONCLUSIONS

Our result indicates that ACDF using a zero-p implant with or without partial UT both provide satisfactory clinical efficacy and acceptable safety. However, additional partial UT may has a negative effect on cervical sagittal alignment.

Spino cranial angle as a predictor of loss of cervical lordosis after laminoplasty in patients with cervical myelopathy

Background

To explore the relationship between spino cranial angle (SCA) and loss of cervical lordosis (LOCL), and to determine whether SCA has the ability to predict LOCL for patients with cervical myelopathy.

Methods

A total of 68 consecutive patients with cervical myelopathy who received laminoplasty (LAMP) were selected to the current study. C2–C7 lordosis was defined as a representation of the cervical alignment. Alignment change > 0° was considered LOCL. Multiple linear regression analysis was applied to evaluate the association between LOCL and various sagittal parameters at preoperative, such as SCA, CL, T1s and cSVA. Linear regression analysis was applied to evaluate the relationships between LOCL and preoperative SCA in each subgroup.

Results

Patients were assigned to three groups depending on the quartile of preoperative SCA. The first quarter of patients were defined as the low SCA group, the last quarter were defined as the high SCA group and the middle half were defined as the middle SCA group. There was no statistically significant difference in age, sex and the type of OPLL among the three groups. Patients in the low SCA group showed more cervical lordosis before surgery and more LOCL after LAMP (p < 0.001). After linear regression analysis for SCA and LOCL, preoperative SCA was negatively correlated with LOCL in the low SCA group (r = − 0.857, p < 0.001) and high SCA group (r = − 0.515, p = 0.034). However, there was no significant correlation between preoperative SCA and LOCL in the middle SCA group (r = 0.027, p = 0.881).

Conclusions

Patients with lower SCA had more lordosis preoperatively and performed more LOCL after LAMP at 2 years of follow-up. Both too high or low preoperative SCA were negatively correlated with the degree of LOCL, while when the SCA fluctuates in a suitable range, it is easier to compensate for the changes of cervical sagittal alignment.