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

Effects of Cervical Paravertebral Extensors in Patients with Cervical Ossification of the Posterior Longitudinal Ligament Grouped According to mK-Line

OBJECTIVES

The objective of this study was to quantify the morphology, composition, and asymmetry of the paravertebral extensor muscles (PSEMs) in patients with cervical ossification of the posterior longitudinal ligament (OPLL) who had different modified K-line (mK-line) and the minimum interval between the mK-line and OPLL (INTmin ) values and to investigate the relationship between PSEMs and symptoms and outcomes following laminoplasty. These original findings elucidated that the atrophy of PSEMs could predict decompression outcomes and provided a theoretical basis for paraspinal muscle rehabilitation.

METHODS

A total of 94 consecutive patients who underwent laminoplasty for OPLL between January 2020 and January 2022 were enrolled in this retrospective study. The relative cross-sectional areas (rCSA), functional cross-sectional areas (rFCSA), and FCSA/CSA ratio of the multifidus (MF), semispinalis cervicalis (SSCe), semispinalis capitis (SSCa), and splenius capitis (SpCa) were measured at the C3-C7 segments on cervical magnetic resonance imaging (MRI). This study compared the differences between the mK-line (+) group and the mK-line (-) group, as well as between the INTmin  <4 mm group and the INTmin  ≥4 mm group, using the independent t-test or Mann-Whitney test for continuous variables and the χ2 -test for categorical variables. The correlations between the PSEMs and symptoms were analyzed using either the Pearson or Spearman correlation coefficient.

RESULTS

The relative total CSA (rTCSA) of the PSEMs, especially the MF, was significantly smaller in the mK-line (-) group. However, the FCSA/CSA of the right deep extensor muscle (DEM) was larger. The asymmetry of the MF TFCSA/TCSA showed a significant difference between the mK-line groups. In the INTmin  <4 mm group, the PSEMs rCSA and rFCSA were significantly smaller, while the bilateral MF TFCSA/TCSA and right SSCe TFCSA/TCSA were larger. The asymmetry of the superficial extensor muscle rCSA was significantly lower in the group with INTmin  <4 mm. The postoperative modified Japanese Orthopedic Association score (mJOA) and mJOA recovery rate were positively correlated with the INTmin and DEM rCSA and negatively correlated with the asymmetry of MF FCSA/CSA.

CONCLUSIONS

In patients with mK-line (-) or INTmin  <4 mm, the PSEMs were smaller, and the DEM atrophy and composition changes were predominant. The MF asymmetry was higher in patients with mK-lines (-), whereas the SEM atrophy and asymmetry were more prevalent in patients with INTmin  <4 mm. The DEM was related to the preoperative and postoperative mJOA scores. DEM-preserving surgery or DEM-specific rehabilitation exercises can improve the recovery of patients with OPLL during the perioperative period. In addition, attention should be paid to the evaluation of the SEM, especially the SpCa at the C3 and C5 levels.

Evaluating Changes to the Modified K-Line Using Kinematic MRIs

STUDY DESIGN

Retrospective cross-sectional review of a large database.

OBJECTIVE

Little is known regarding extension K-lines for treatment of cervical myelopathy. Therefore, this study seeks to examine differences between K-lines drawn in neutral and extension.

SUMMARY OF BACKGROUND DATA

The modified K-line is a radiological tool used in surgical planning of the cervical spine. As posterior cervical decompression and fusion often results in patients being fused in a more lordotic position than the preoperative neutral radiograph, a K-line measured in the extension position may offer better utility for these patients.

MATERIALS AND METHODS

Total of 97 patients were selected with T2-weighted, upright cervical magnetic resonance imaging taken in neutral and extension. For each patient, the K-line was drawn at the mid-sagittal position for both neutral and extension. The distance from the most posterior portion of each disk (between C2 and C7) to the K-line was measured in neutral and extension and the difference was calculated. Paired t test was used to assess significant differences.

RESULTS

Across all levels between C2 and C7 there was an increase in the distance between the dorsal aspect of the disk and K-line when comparing neutral and extension radiographs. The average change in difference (extension minus neutral) at each cervical spinal level was 0.9 mm (C2-C3), 2.5 mm (C3-C4), 2.6 mm (C4-C5), 2.0 mm (C5-C6), and 0.9 mm (C6-C7). A paired t test showed that the K-line increase from neutral to extension was statistically significant across all disk levels ( P <0.001).

CONCLUSION

When positioned in extension, patients experience a significant increase in distance from the dorsal aspect of a disk to the K-line compared to when positioned in neutral, especially between C3 and C6. This is clinically relevant for surgeons considering a posterior cervical decompression and fusion in patients with a negative modified K-line on preoperative magnetic resonance imaging, as these patients may have enough cervical cord drift back when fused in an extended position, maximizing likelihood of improving postoperative DSM functional outcomes.

Assessment of Cervical Myelopathy Risk in Ossification of the Posterior Longitudinal Ligament Patients With Spinal Cord Compression Based on Segmental Dynamic Versus Static Factors

OBJECTIVE

Using segmental dynamic and static factors, we aimed to elucidate the pathogenesis and relationship between ossification of the posterior longitudinal ligament (OPLL) and the severity of cervical myelopathy.

METHODS

Retrospective analysis of 163 OPLL patients' 815 segments. Imaging was used to evaluate each segmental space available for the spinal cord (SAC), OPLL diameter, type, bone space, K-line, the C2-7 Cobb angle, each segmental range of motion (ROM), and total ROM. Magnetic resonance imaging was used to evaluate spinal cord signal intensity. Patients were divided into the myelopathy group (M group) and the without myelopathy group (WM group).

RESULTS

Minimal SAC (p = 0.043), (C2-7) Cobb angle (p = 0.004), total ROM (p = 0.013), and local ROM (p = 0.022) were evaluated as an independent predictor of myelopathy in OPLL. Different from the previous report, the M group had a straighter whole cervical spine (p < 0.001) and poorer cervical mobility (p < 0.001) compared to the WM group. Total ROM was not always a risk factor for myelopathy, as its impact depended on SAC, when SAC > 5 mm, the incidence rate of myelopathy decreased with the increase of total ROM. Lower cervical spine (C5-6, C6-7) showing increased "Bridge-Formation," along with spinal canal stenosis and segmental instability (C2-3, C3-4) in the upper cervical spine, could cause myelopathy in M group (p < 0.05).

CONCLUSION

Cervical myelopathy is linked to the OPLL's narrowest segment and its segmental motion. The hypermobility of the C2-3 and C3-4, contributes significantly to the development of myelopathy in OPLL.

Can the Risk of Postoperative Cerebrospinal Fluid Leakage Be Predicted for Patients Undergoing Cervical Spine Surgery? Development and Evaluation of a New Predictive Nomogram

OBJECTIVE

Previous studies have retrospectively analyzed the likely causes of cerebrospinal fluid leakage (CSFL) during cervical spine surgery and the management of CSFL after its occurrence. In the present study, we aimed to develop and validate a nomogram for the risk of CSFL in Chinese patients who had undergone cervical decompression and internal fixation (CDIF) surgery.

METHODS

We performed a retrospective analysis of patients who had undergone CDIF surgery. Of the 1286 included patients, 54 were in the CSFL group and 1232 were in the normal group. The patients were randomly divided into training and validation tests. The risk assessment for CSFL included 21 characteristics. The feature selection for the CSFL model was optimized using the least absolute shrinkage and selection operator regression model in the training test. Multivariate logistic regression analysis was performed to construct the model according to the selected characteristics. The clinical usefulness of the predictive model was assessed using the C-index, calibration curve, and decision curve analysis with identification and calibration.

RESULTS

The risk prediction nomogram included the diagnosis, revision surgery, ossification of the posterior longitudinal ligament, cervical instability, and a history of malignancy in the training test. The model demonstrated high predictive power, with a C-index of 0.914 (95% confidence interval, 0.876-0.951) and an area under the curve of 0.914. The results of the decision curve analysis demonstrated the clinical usefulness of the CSFL risk nomogram when the probability threshold for CSFL was 1%-62%.

CONCLUSIONS

Our proposed nomogram for CSFL risk includes the diagnosis, revision surgery, ossification of the posterior longitudinal ligament, cervical instability, and a history of malignancy. The nomogram can be used to evaluate the risk of CSFL for patients undergoing CDIF surgery.