A Commentary on “Flexion K-Line Status Predicts Surgical Strategy in Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Multicenter Comparison of Laminoplasty and Laminectomy With Fusion”

John H. Chi

doi:10.14245/ns.2551840.920

Ossification of the posterior longitudinal ligament (OPLL) is a frequently encountered condition with controversial treatment options including anterior and posterior surgical approaches both with its own advantages and disadvantages. OPLL causes spinal cord compression that then results in cervical myelopathy leading to neurologic deficits. The calcified ligament that is the hallmark of OPLL is unlike a typical disc osteophyte and can be very adherent or even incorporated into the dura, thereby making decompression more challenging and higher risk. The decision between whether anterior, posterior or combination approaches is best for OPLL depends on what clinical outcome to prioritize while still minimizing complications and adverse events.

The authors in this article [1] present a multicenter, retrospective series of 349 patients undergoing posterior surgery for OPLL with minimum 2-year follow-up and report clinical outcomes in the context of flexion K-line status. The posterior surgery was either laminoplasty or laminectomy with fusion. The authors report that patients with flexion K-line that intersects with the OPLL (FK-line [-]) had more kyphotic alignment and lower recovery ratios compared to patients with flexion K-line that did not intersect with the OPLL (FK-line [+]). Additionally, in FK-line (-) patients, laminectomy and fusion achieved greater increase in FK-line distance, better correction of kyphosis, and increased neurological recovery compared to laminoplasty.

The strengths of this study include the multicenter design and the relatively high number of patients for the condition treated. The focus on just posterior surgery also allows for a more homogeneous surgical comparison on similar surgeries and having a single radiographic measurement in the flexion K-line simplifies the analysis. However, the multicenter design only included 3 centers and being retrospective, there is always the potential for selection bias in deciding which surgery to perform. Additionally, the negative impact of multilevel fusion is not really captured or described in this manuscript and adjacent segment failures may occur later than the 2-year follow-up included here.

The overall results of this study support the well-recognized notion that appropriate cervical lordosis is critical for success in cervical surgery and that laminoplasty is best in patients with preserved cervical lordosis. Though K-line measurements have been well established, this paper highlights the importance of a flexion K-line when considering surgery for OPLL. The authors are commended for presenting this work which will help surgeons evaluate patients with OPLL with relevant and meaningful tests to help decide on the best surgical treatment to offer. Similar to the paper by Ghogawala et al. [2] in 2021, the results of this study may be extrapolated to other conditions beyond OPLL including other causes of cervical spondylotic myelopathy.

A Commentary on “Flexion K-Line Status Predicts Surgical Strategy in Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Multicenter Comparison of Laminoplasty and Laminectomy With Fusion”

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