At present, the treatment of cervical spine abnormalities, such as degeneration of cervical intervertebral discs, ossification of the posterior longitudinal ligament (PLL), cervical fractures, and herniated discs, is commonly performed through anterior cervical decompression surgery. This involves removing the cervical intervertebral disc and addressing abnormalities in the cervical spine or herniated discs compressing nerves or the spinal cord. This approach is favored due to reduced blood loss during surgery, shorter hospital stays, and greater relief from neck pain compared to posterior cervical decompression surgery. Additionally, it allows for spinal fusion to be performed during the same procedure. Although this surgical method has been used since 1958 and is considered safe and highly effective [1–4], there is still ongoing debate regarding the necessity of removing the PLL that attaches to the back of the cervical vertebrae. The PLL is a long ligament that extends from the back of the skull to the sacral vertebrae, providing stability to the spine and protecting nerves and the spinal cord [5,6]. However, its width is almost equivalent to that of the corresponding vertebrae, and it is broadly attached to the covering of the spinal cord making it easy to separate during surgery [5]. The decision to perform PLL resection surgery is often based on the surgeon’s discretion, and currently there is limited, high-level, medical evidence supporting whether removing or preserving the PLL is beneficial or carries certain risks. Complications associated with PLL removal and increased surgery duration are crucial considerations. The risk of complications, such as cerebrospinal fluid leakage, may increase when the PLL is removed with an incidental dural tear. Additionally, when considering the biomechanics of the cervical spine, PLL presence plays a crucial role in preventing excessive movement of the cervical vertebrae in multiple directions, and its removal may lead to a loss of stability in the cervical spine [7]. This research aimed to conduct a comparative study of both clinical symptoms and radiographic findings before and after anterior cervical decompression surgery with and without removal of the PLL.

From October 2018 to December 2023 a total of 102 consecutive patients with cervical spine disorders who underwent anterior cervical decompression surgery at the Vajira center of excellence in Neurosurgery and Chulabhorn Hospital were included in this multicenter study. These operations were performed by two experienced spine neurosurgeons. The indications for anterior cervical decompression included cervical spondylosis, cervical spine injuries, ossification of the posterior longitudinal ligament of the cervical spine (OPLL), and cervical spine tumors. Patients lacking operative details, pre- or postoperative imaging records, or complete follow-up data were excluded from the analysis.

A review of the operating room reports, hospital charts, office charts, and radiographic studies was performed. Data collected included demographic data such as patient age, gender, diagnosis, body mass index (BMI), length of hospital stay, and medical comorbidities. We recorded operative data including operative time, retractor time, operative blood loss, status of PLL (resected or non-resected), and postoperative complications. A comparison between preoperative and postoperative radiological and clinical outcomes was conducted. Clinical assessment utilized the following scales: a Visual Analog Scale (VAS) for neck pain and a modified Japanese Orthopedic Association (mJOA) score [8,9]. A cervical X-ray and magnetic resonance imaging (MRI) of the cervical spine were performed. This study was approved by the Institutional Review Board (IRB) of Faculty of Medicine Vajira Hospital, Navamindradhiraj University (194/64E) before study initiation. All patient profiles were concealed by using their case number. Informed consent was waived by the IRB due to the retrospective nature of the study. All methods were performed following relevant guidelines and regulations.

During anterior cervical decompression surgery, in both ACDF and ACCF procedures, it has been proposed that resection of the PLL enhances distraction, thereby enabling more thorough neural decompression and greater disc space height. This can result in an increased lordosis of the cervical spine postoperatively [11,12]. Many surgeons prefer removing the PLL during decompression procedures, while others advocate for its removal only in specific circumstances and typically recommend resecting the PLL only when it directly contributes to neurological compression or when disc fragments are situated behind the PLL. Excision of the PLL during surgery is associated with 3.8 times greater odds of improvement from preoperative radiculopathy, with no significant difference in the complication rate [7,13]. Furthermore, Elayouty et al. [14] studied the effect of PLL resection in ACDF surgery and stated that despite there being additional surgical procedures, resection of the PLL does not seem to add significant surgical risk. Lin et al. [15] investigated the impact of PLL resection on disc-associated axial pain. They observed improvements in postoperative VAS scores for axial neck pain, leading them to conclude that the intervertebral PLL could potentially serve as the source of such pain. This finding suggests that removing the PLL during surgical procedures may alleviate axial neck pain in patients suffering from disc-related issues. Another study conducted by Avila et al. [16] found that excision of the PLL leads to 3.8 times greater odds of improvement in radiculopathy. In a study investigating the effect of PLL resection on anterior decompression for cervical spondylotic myelopathy, Wang et al. [17] demonstrated a significant increase in spinal cord diameter, and the mean JOA score in the PLL removed group was greater than that in the PLL reserved group. This suggests that the benefits of PLL resection, such as enhanced neural decompression and increased disc space height leading to improved cervical spine alignment, may outweigh any potential risks associated with the additional surgical steps. In our cohort, we found no difference in clinical outcomes between the two groups. This may be due to patient selection bias and the small number of patients, both of which are limitations of this cohort. We preserved the PLL in patients with cervical spondylosis with only axial neck pain, cervical spine injuries with an intact PLL and intervertebral disc, and cervical spine tumors that required ACCF because we felt that PLL resection was not needed in this group. The primary pathology is located only at the intervertebral disc or vertebral body. We removed the main source of pathology and preserved the PLL to maintain the biomechanics of this ligament and decrease the perioperative complication of removing the PLL. Since patients with a diagnosis of OPLL with double layer signs on preoperative imaging have a high risk for complications with PLL removal, we preserved it for improved patient safety. There are studies showing that longer operative and retractor times were related to postoperative complications such as recurrent laryngeal nerve (RLN) injuries, including hoarseness, dysphagia, and RLN palsy [18,19]. In our cohort, we found that the preserved PLL group had decreased operative and retractor times when compared to the resected PLL group, because time was not spent cutting the PLL. Therefore, this group had slightly fewer postoperative complications from RLN injuries. Based on this result, we suggest that surgeons should preserve the PLL in cases of cervical spondylosis with only axial neck pain, cervical spine injuries with an intact PLL and intervertebral disc, and cervical spine tumors that need ACCF to decrease postoperative complications from PLL resection.

In a meta-analysis of the prevalence of complications after surgery for the treatment of cervical compressive myelopathy, Wang et al. [20] reported incidence rates of various complications. These included C5 nerve root injury (5.3% incidence), cerebrospinal fluid leak (1.9%), infection (2.8%), and a 1.1% incidence for the development of an epidural hematoma. In our current study, significant improvements were observed in both VAS and mJOA scores. Importantly, the incidence of complications was notably lower compared to the rates reported in the meta-analysis by Wang et al. [20]. Specifically, the current study noted only a 0.96% incidence of nerve root injury, with no infection, cerebrospinal fluid leakage, or epidural hematoma observed. These findings suggest that the surgical approach and techniques employed in the current study may have contributed to reduced rates of complications compared to the aggregated data from the meta-analysis. In our cohort, there are no patients with perioperative CSF leakage. We believe that our technique and patient selection process for resection of the PLL were safe. We removed the PLL using the optimal illumination and visualization provided by a surgical microscope. The PLL is opened with a right-angle blunt microhook and micro instruments as described above. However, in the group with a preserved PLL, we did not remove this ligament in cases with a high risk for perioperative CSF leakage, such as OPLL with double layer signs on preoperative imaging.

There are cadaver studies that investigate the biomechanics and significance of individual ligaments in the cervical spine [21,22]. Their findings suggested that the PLL plays a crucial role in maintaining the biomechanical stability of the cervical spine. Specifically, they noted that removing the PLL could lead to instability. In our study, a comparative radiological evaluation was conducted measuring various parameters, including DLCA, SCA, GCA, C2–7 SVA, and SA between the PLL resected and non-resected groups. Both groups showed improvement in radiographic outcome measurements. However, none of these parameters demonstrated statistically significant differences between the two groups. Furthermore, no patients in the PLL resected group had postoperative instability or adjacent segment disease during the 1-year follow-up period. We feel that PLL resection does not produce postoperative instability and results in identical radiographic outcomes when compared to preserving the PLL. Although the PLL could prevent hyperflexion and over-distraction as noted in biomechanical studies, there are still many ligaments and muscles that prevent cervical motion. The PLL is comparatively thinner and weaker than the anterior longitudinal ligament. Proponents of PLL resection argue that it has a minor role in stabilizing segmental motion relative to other ligamentous structures. Additionally, following PLL resection, stability is enhanced by placing a longer graft. This approach helps counteract the destabilizing effects of PLL resection by utilizing ligamentous tension through segment distraction. While the findings of this cadaver study provide valuable insights into the biomechanics of the cervical spine, it is important to recognize the limitations of extrapolating these results directly to live patients who have undergone cervical fusion procedures. Cadaver studies may not fully replicate the dynamic and physiological conditions present in live patients.

The current study is subject to certain limitations. First, this is a retrospective study, and selection bias as well as incomplete data may have existed. Second, it did not compare preoperative and postoperative radiological outcomes using dynamic techniques or under normal living conditions, such as standing or walking. These comparisons could provide valuable insights into the functional implications of the surgical intervention. Additionally, the study did not assess the long-term effects of resecting the PLL on subsequent cervical alignment. Finally, the follow-up period was only 1 year. Further studies with larger sample sizes and longer follow-up periods are necessary to confirm our findings. Further investigation into the extended outcomes following PLL resection would offer a more comprehensive understanding of its impact on cervical spine stability and alignment over time.

Resecting the PLL in patients undergoing anterior cervical spine surgery may prolong operative and retractor times and could potentially result in postoperative complications. However, it does not significantly affect the outcome of radiographic cervical spine alignment when compared to the group where the PLL was not cut. Preserving the PLL may be beneficial in patients with cervical spondylosis with only axial neck pain, cervical spine injuries with intact PLL and intervertebral disc, and OPLL with double layer signs on MRI studies.