Prediction of incomplete decompression after cervical laminoplasty on magnetic resonance imaging: The modified K-line

Evaluating the Predictive Value of K-Line Conversion in Surgical Outcomes for K-Line Negative Cervical Ossification of the Posterior Longitudinal Ligament (OPLL): Laminectomy with Fusion versus Laminoplasty

BACKGROUND CONTEXT

Laminectomy with fusion (LF) and laminoplasty are common treatments for K-line negative cervical ossification of the posterior longitudinal ligament (OPLL). However, the clinical significance of postoperative K-line conversion from negative to positive remains unclear.

PURPOSE

To determine whether converting a K-line from negative to positive improves surgical outcomes in patients with cervical OPLL by comparing LF and laminoplasty.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Patients with cervical myelopathy due to K-line negative OPLL who underwent LF or laminoplasty, with ≥1 year of follow-up.

OUTCOME MEASURES

Primary outcomes included neck and arm pain visual analog scale (VAS) scores, neck disability index (NDI), Japanese Orthopedic Association (JOA) score, JOA recovery rate, and radiographic parameters (C2-C7 lordosis, modified K-line interval).

METHODS

We compared radiographic and clinical outcomes between the two groups.

RESULTS

Among 85 patients with K-line-negative OPLL (39 LF, 46 laminoplasty), postoperative K-line conversion occurred significantly more frequently in the LF group (56.4% vs. 16.8%; p <0.001). Although laminoplasty better preserved cervical range of motion and reduced neck pain, LF provided superior neurologic outcomes, as indicated by higher final JOA scores and recovery rates. Patients who achieved K-line conversion had significantly higher rates of favorable clinical outcomes compared to those who did not (58.1% vs. 27.7%; p=0.019). Multivariate regression analyses further demonstrated that K-line conversion independently predicted favorable clinical outcomes (odds ratio [OR]: 3.900; p = 0.023), and LF was significantly associated with a higher likelihood of K-line conversion compared to laminoplasty (OR: 3.683; p = 0.033).

CONCLUSION

In patients with K-line-negative cervical OPLL, postoperative conversion to K-line-positive status is significantly associated with improved neurological outcomes. Although laminoplasty provides advantages regarding neck pain relief and motion preservation, LF more reliably facilitates K-line conversion and suppresses kyphosis, leading to superior clinical outcomes. Careful preoperative evaluation of cervical alignment, combined with surgical strategies aimed at promoting K-line conversion, may optimize surgical results.

LEVEL OF EVIDENCE

III.

Accuracy of Realigned K-line for Predicting Surgical Outcomes After Laminoplasty in Patients With Degenerative Cervical Myelopathy

STUDY DESIGN

A prospective cohort study.

OBJECTIVES

To report a new index, the realigned K-line, for predicting surgical outcomes after laminoplasty in patients with degenerative cervical myelopathy (DCM).

METHODS

One hundred twenty-eight patients with DCM undergoing laminoplasty were enrolled from January 2018 to April 2021 in our department. A realigned K-line was defined as the line connecting the midpoints of the spinal cord between C2 and C7 on realigned T1-weighted magnetic resonance imaging. The minimum interval between the anterior compression factors of the spinal cord and the realigned K-line (INTrea), and the modified K-line (INTmod) were measured. A logistic regression analysis was performed to identify factors associated with unsatisfactory surgical outcomes. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) was applied to evaluate the reliability of the multivariate logistic regression model.

RESULTS

Univariate analysis showed that the score for the bladder function section of the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire, numeric rating scale scores for arm pain, and INTrea might be related to the Japanese Orthopaedic Association (JOA) recovery rate (RR) not achieving the minimal clinically important difference (MCID) (P < .05). Only INTrea (odds ratio = .744, P < .05) was an independent preoperative factor related to the JOA RR not achieving the MCID (area under the curve, .743). A cutoff of 5.0 mm for INTrea had an accuracy of 71.9% and specificity of 80.3% for predicting the JOA RR not achieving the MCID.

CONCLUSIONS

INTrea is an independent preoperative risk factor related to the JOA RR not achieving the MCID in patients with DCM. A cutoff point of 5.0 mm is most appropriate for alerting spine surgeons to a high likelihood of the JOA RR not achieving the MCID.

Cervical Laminoplasty Versus Posterior Laminectomy and Fusion: Trends in Utilization and Evaluation of Complication and Revision Surgery Rates

INTRODUCTION

Cervical laminoplasty (LP) and laminectomy with fusion (LF) are common operations used to treat cervical spondylotic myelopathy. Conflicting data exist regarding which operation provides superior patient outcomes while minimizing the risk of complications. This study evaluates the trends of LP compared with LF over the past decade in patients with cervical myelopathy and examines long-term revision rates and complications between the two procedures.

METHODS

Patients aged 18 years or older who underwent LP or LF for cervical myelopathy from 2010 to 2019 were identified in the PearlDiver Mariner Database. Patients were grouped independently (LP versus fusion) and assessed for association with common medical and surgical complications. The primary outcome was the incidence of LP versus LF for cervical myelopathy over time. Secondary outcomes were revision rates up to 5 years postoperatively and the development of complications attributable to either surgery.

RESULTS

In total, 1,420 patients underwent LP and 10,440 patients underwent LF. Rates of LP (10.5% to 13.7%) and LF (86.3% to 89.5%) remained stable, although the number of procedures nearly doubled from 865 in 2010 to 1,525 in 2019. On matched analysis, LP exhibited lower rates of wound complications, surgical site infections, spinal cord injury, dysphagia, cervical kyphosis, limb paralysis, incision and drainage/exploration, implant removal, respiratory failure, renal failure, and sepsis. Revision rates for both procedures at were not different at any time point.

CONCLUSION

From 2010 to 2019, rates of LP have not increased and represent less than 15% of posterior-based myelopathy operations. Up to 5 years of follow-up, there were no differences in revision rates for LP compared with LF; however, LP was associated with fewer postoperative complications than LF.

LEVEL OF EVIDENCE

Level III retrospective cohort study.

Modified K-Line in Neck Extension Is a Prognostic Indicator of the Surgical Outcome at 5 Years After Cervical Laminoplasty for Cervical Spondylotic Myelopathy

STUDY DESIGN

A retrospective comparison of the surgical outcome after cervical laminoplasty for cervical spondylotic myelopathy (CSM) using a modified K-line based on lordosis in neck extension as a predictor: in K-line Back CSM (KB group), the K-line crosses the ventral edge of any of the spinous processes, whereas in K-line Front CSM (KF group), the K-line does not.

OBJECTIVE

To investigate the neurological and radiological outcomes 5 years after surgery and the contact between the spinal cord and posterior elements after laminoplasty for CSM using the modified K-line.

SUMMARY OF BACKGROUND DATA

No indicators on a lateral radiograph can predict the neurological outcome after laminoplasty for CSM.

METHODS

Patients with CSM were divided into KB (n = 20) and KF groups (n = 13). We compared the postoperative Japanese Orthopedic Association (JOA) score, recovery rate, grip-and-release and foot-tapping test results, alignment, and contact between the spinal cord and posterior elements between the two groups.

RESULTS

The postoperative JOA score and its recovery rate were significantly lower in the KB group (12.4 points and 34.1%, respectively) than in the KF group (14.1 points and 59.0%, respectively) at final follow-up (P = 0.0415 and 0.0458). The grip-and-release and foot-tapping test results improved significantly in the KF group but not in the KB group. In the KB group, a larger lordotic angle in extension at 1 year postoperatively continued until final follow-up. The rate of recovery of the JOA score in patients with contacts at both C4/5 and C5/6 and any contact in the KB group (-1.5% and 31.9%, respectively) were lower (P = 0.0013 and 0.0534, respectively) than those in the KF group (58.6% and 60.7%, respectively).

CONCLUSION

The K-line Back predicts a poor neurological outcome after laminoplasty for CSM. Decompression with fusion may be recommended for these patients.Level of Evidence: 4.

Preoperative Radiological Parameters to Predict Clinical and Radiological Outcomes after Laminoplasty

Many studies have focused on pre-operative sagittal alignment parameters which could predict poor clinical or radiological outcomes after laminoplasty. However, the influx of too many new factors causes confusion. This study reviewed sagittal alignment parameters, predictive of clinical or radiological outcomes, in the literature. Preoperative kyphotic alignment was initially proposed as a predictor of clinical outcomes. The clinical significance of the K-line and K-line variants also has been studied. Sagittal vertical axis, T1 slope (T1s), T1s-cervical lordosis (CL), anterolisthesis, local kyphosis, the longitudinal distance index, and range of motion were proposed to have relationships with clinical outcomes. The relationship between loss of cervical lordosis (LCL) and T1s has been widely studied, but controversy remains. Extension function, the ratio of CL to T1s (CL/T1s), and Sharma classification were recently proposed as LCL predictors. In predicting postoperative kyphosis, T1s cannot predict postoperative kyphosis, but a low CL/T1s ratio was associated with postoperative kyphosis.

Modified K-line for Making Decisions Regarding the Surgical Approach in Patients with K-line (-) OPLL

Objective

To investigate whether the modified K‐line can be used to predict the clinical outcome and to determine the surgical approach for K‐line (−) patients with cervical ossification of the posterior longitudinal ligament (OPLL).

Methods

A new modified K‐line was defined as the line connecting the midpoints of the spinal cord at C₄ and C₆ on the lateral cervical radiographs. A total of four consecutive patients (three men and one woman) with cervical myelopathy due to OPLL were included in this research. The patients were diagnosed with OPLL with K‐line (−) while they were also classified as modified K‐line (+). Preoperative modified K‐line was used to predict the surgical outcome in K‐line (−) patients with OPLL according to the original K‐line. And a modified laminoplasty with C₃ laminectomy and C_4‐6 bilateral open‐door laminoplasty was adopted to perform on all the patients. The Japanese Orthopaedic Association scores before surgery and at 1‐year follow‐up after surgery were evaluated and the recovery rate was calculated. The visual analogue scale (VAS) scores were also evaluated before surgery and after surgery. Furthermore, cervical plain radiographs in neutral position before surgery and after surgery were obtained to measure C₂–C₇ angles for assessing the cervical sagittal alignment.

Results

The results showed that good neurological improvement could be achieved in all K‐line (−) patients who underwent C₃ laminectomy with C₄–C₆ bilateral open‐door laminoplasty. The Postoperative JOA scores improved from 13.5 to 16.5, from 11 to 16.5, from 13 to 16, and from 12.5 to 13, respectively. The mean recovery rate was 65.4% in the K‐line (−) patients. And the VAS scores dropped from 3 to 1, 5 to 2, 5 to 3, and 4 to 2, respectively. The JOA and VAS scores showed satisfaction in all patients at the 1‐year follow‐up. Relatively satisfactory and stable cervical sagittal alignment was observed on postoperative lateral radiography in all patients at the 3‐month follow‐up period. There were no postoperative complications associated with this technique found in all the patients.

Conclusions

Modified K‐line may predict the clinical outcome of this modified laminoplasty and offer guidance regarding the choice of surgical method for K‐line (−) patients with OPLL. Additionally, C₃ laminectomy with C₄–C₆ bilateral open‐door laminoplasty should be recommended for the use in patients with K‐line (−) OPLL, who were also classified as modified K‐line (+). However, further studies with more cases will be required to reveal its generalizability and availability.

Photogrammetric analysis: An objective measure to assess the craniocervical range of motion after cervical laminoplasty surgeries

Surgical decompression using laminoplasty is commonly performed for multilevel stenosis with cervical spondylotic myelopathy. However, the long-term effects on the craniocervical range of motion (ROM) after surgery are not well understood. This study represents the first entry into the literature of photogrammetric analysis for clinical measurement of craniocervical ROM. All patients underwent a French-door laminoplasty from 1995 to 2016 and were evaluated radiologically and with postoperative photographs (photogrammetric analysis) to measure craniocervical ROM and axial rotation. Radiographic parameters were occiput to C2 angle, C1-2 angle, C2-7 angle/cervical lordosis (CL), T1-slope (T1S), and TS-CL were measured. Chin-brow vertical angle (CBVA) was utilized for flexion and extension, while nose-turn angle (NTA) was used to assess axial rotation. Forty-four patients (mean age: 65.7 years, 50% female) had a mean follow-up of 37.9 months. Mean values in neutral, flexion, and extension were occiput to C2 = 30°, 15°, and 43°; C1-C2 = -32°, -25°, -32°; and C2-C7 = -4°, 11°, -20°, respectively. Mean CL was within 1 SD of the established -17° (±13.86°). Mean T1S and TS-CL were 33° and 30° in the neutral position, respectively. Mean radiographic full range of motion from flexion to extension was 53°. NTA towards patients' left was 48° and the right side was 45°. Mean CBVA, was -4°, mean flexion 37°, and extension -45°; full range was 81°. Global craniocervical ROM has proven to be well preserved for many years following cervical laminoplasty. Photogrammetric analysis is a cost-effective and radiation-free method, accurate for quantitative assessment of craniocervical and cervical ROM.

Development and Achievement of Cervical Laminoplasty and Related Studies on Cervical Myelopathy

Cervical laminoplasty (CL) is one of the surgical methods via the posterior approach for treating patients with multilevel affected cervical myelopathy (CM). The main purpose of CL is to decompress the cervical spinal cord by widening the narrowed spinal canal, combined with preserving the posterior anatomical structures to the degree possible and preserving the widened space stably. During the development and improvement of spine surgeries including CL, various studies on CM have progressed and useful achievements have been obtained: (1) posterior cervical spine fixation systems that can be used in combination with CL simultaneously have been developed; (2) various materials to stably maintain the enlarged spinal canal have been developed; (3) the main influential factors on the surgical results are the inner factors of the patients, such as the patient's age and the disease duration; (4) various surgical methods to preserve the function of the posterior cervical muscles have been tried to avoid postoperative kyphotic changes of the cervical spine; (5) postoperative complications, such as C5 palsy and axial pain, have been examined, and the countermeasures have been tried; (6) K-line on lateral X-ray films has been applied to evaluate the indication of CL in patients with CM due to ossification of the posterior longitudinal ligament (OPLL) preoperatively; and (7) the method and idea of CL have been adapted to surgeries at the thoracic and lumbar spine. However, some issues remain to be resolved, such as the deterioration of neurological findings, especially in patients with continuous or mixed-type OPLL, the postoperative kyphotic-directional alignment change of the cervical spine, C5 palsy, and axial pain.

Comparison of Anterior and Posterior Surgery for Degenerative Cervical Myelopathy: An MRI-Based Propensity-Score-Matched Analysis Using Data from the Prospective Multicenter AOSpine CSM North America and International Studies

BACKGROUND

Surgeons often choose between 2 different approaches (anterior and posterior) for surgical treatment of degenerative cervical myelopathy on the basis of imaging features of spinal cord compression, the number of levels affected, and the spinal alignment. However, there is a lack of consensus on which approach is preferable. The objective of the present study was to use magnetic resonance imaging (MRI)-based propensity-score-matched analysis to compare postoperative outcomes between the anterior and posterior surgical approaches for degenerative cervical myelopathy.

METHODS

A total of 757 patients were enrolled in 2 prospective multicenter AOSpine studies, which involved 26 international sites. Preoperative MRIs were reviewed to characterize the causes of the cord compression, including single-level disc disease, multilevel disc disease, ossification of the posterior longitudinal ligament, enlargement of the ligamentum flavum, vertebral subluxation/spondylolisthesis, congenital fusion, number of compressed levels, or kyphosis. The propensity to choose anterior decompression was calculated using demographic data, preoperative MRI findings, and the modified Japanese Orthopaedic Association (mJOA) scores in a logistic regression model. We then performed 1-to-1 matching of patients who had received anterior decompression with those who had the same propensity score but had received posterior decompression to compare 2-year postoperative outcomes and 30-day perioperative complication rates between the 2 groups after adjustment for background characteristics.

RESULTS

A total of 435 cases were included in the propensity score calculation, and 1-to-1 matching resulted in 80 pairs of anterior and posterior surgical cases; 99% of these matched patients had multilevel compression. The anterior and posterior groups did not differ significantly in terms of the postoperative mJOA score (15.1 versus 15.3, p = 0.53), Neck Disability Index (20.5 versus 24.1, p = 0.44), or Short Form-36 (SF-36) Physical Component Summary (PCS) score (41.9 versus 40.9, p = 0.30). The overall rates of perioperative complications were similar between the 2 groups (16% versus 11%, p = 0.48); however, dysphagia/dysphonia was reported only in the anterior group whereas surgical site infection and C5 radiculopathy were reported only in the posterior group.

CONCLUSIONS

Anterior and posterior decompression for degenerative cervical myelopathy resulted in similar postoperative outcomes and rates of complications.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Clinical outcome of laminoplasty for cervical ossification of the posterior longitudinal ligament with K-line (-) in the neck neutral position but K-line (+) in the neck extension position: A retrospective observational study

Patients with cervical ossification of the posterior longitudinal ligament (OPLL) who are K-line (-) are thought to have poor clinical outcomes after laminoplasty. The aim of this study is to compare the clinical results of patients with OPLL who were K-line (-) in the neck neutral position but K-line (+) in the neck extension position (NEP group) with patients with OPLL who were K-line (+) in the neck neutral position (NNP group).Retrospectively, 42 patients who underwent cervical laminoplasty for OPLL by our surgical group during 2012 and 2013 were reviewed and were followed for at least 2 years. The patients were divided into 2 groups according to K-line status. Standing plain radiographs of the cervical spine were obtained pre- and postoperatively. Cervical spine alignment parameters included the C2-7 Cobb angle and range of motion (ROM) measured on lateral radiographs. Clinical evaluation included pre- and postoperative JOA, NDI, and VAS scores.Ten patients were classified in the NEP group, and 32 patients were classified in the NNP group. Preoperatively, the OPLL involved segments were 4.10 ± 1.66 in the NEP group and 2.53 ± 1.16 in the NNP group (P = .005). The canal-occupying ratios were 58.40 ± 11.11% in the NEP group and 29.08 ± 11.38% in the NNP group (P < .001). The mean Cobb angle of both the groups had not changed significantly at the last follow-up. The mean cervical ROM of both the groups had decreased at the last follow-up. The mean JOA score of the NEP group improved significantly from 9.70 ± 2.16 to 12.50 ± 2.27 (P = .014). The mean JOA score of the NNP group improved significantly from 11.91 ± 1.69 to 14.93 ± 1.58 (P < .001). The mean JOA recovery rate was 32.71 ± 40.45% in the NEP group and 59.00 ± 33.80% in the NNP group (P = .036). The NDI scores of both groups were significantly decreased, and the VAS scores of both groups had not changed significantly at the last follow-up.Laminoplasty is a relatively effective and safe procedure for patients with K-line (-) in the neck neutral position but K-line (+) in the neck extension position. Instead of anterior surgery, we recommend laminoplasty for those patients with OPLL extending to 3 or more segments.