Percutaneous endoscopic lumbar discectomy for calcified lumbar disc herniation: A retrospective study

Abstract

Background: Percutaneous endoscopic discectomy (PELD), which includes percutaneous endoscopic interlaminar discectomy (PEID) and percutaneous endoscopic transforaminal discectomy (PETD), is a minimally invasive procedure for the treatment of lumbar disc herniation (LDH) . However, studies on PELD for calcified lumbar disc herniation (CLDH) have rarely been recorded. The purpose of this study was to evaluate the PELD's clinical effectiveness for CLDH.

Methods: A retrospective analysis of 45 CLDH patients who got PELD in our department from June 2018 to April 2021 was conducted. Patients were divided into two groups: the PEID group (n = 24) and the PETD group (n = 21) based on the surgical methods. The demographic characteristics and surgical results of the two groups were compared. Utilizing the visual analog scale (VAS) for leg pain, the Oswestry disability index (ODI), and the modified MacNab criteria, clinical results were examined.

Results: PEID or PETD procedures were effective for every patient. There were no discernible changes in the demographics, postoperative hospital stay, operating time, intraoperative blood loss, or complication rate between the PEID and PETD group (p>0.05). When compared to the preoperative period following PELD, the leg pain VAS ratings and ODI scores were considerably lower at each follow-up time (p> 0.05), respectively. After surgery, however, there were no appreciable variations in the VAS and ODI ratings between the PEID and PETD groups (p>0.05). The PEID group outperformed the PETD group in terms of fluoroscopy times, although the modified MacNab criteria were equal in both groups (p>0.05).

Conclusions: While PEID has a shorter fluoroscopy duration, both PEID and PETD are minimally invasive treatments for CLDH.

Introduction

One of the ventral ossifications of the spinal canal [1.2], calcified lumbar disc herniation has an unclear etiology but may be linked to degenerative intervertebral discs, trauma, infection, autoimmunity, excessive vitamin D intake, and calcium deposition in cartilage[3.4.5.6.7]. By compressing nerve roots or the dural sac and narrowing the spinal canal, they may produce pain in the lower back and lower limbs[1.6.7]. The CLDH patients should have surgery when less invasive therapies including medication, bed rest, and physical therapy have failed.

Open lumbar discectomy (OLD) is the gold standard for surgically treating lumbar disc herniation[8]. A few common open surgical side effects that still require major care include dural rips, cerebrospinal fluid leaks, incisional infections, persistent chronic lower back pain, and spinal instability[1.6.9].

A minimally invasive approach for the treatment of LDH is called percutaneous endoscopic lumbar discectomy (PELD), which also comprises percutaneous endoscopic interlaminar discectomy (PEID) and percutaneous endoscopic transverse discectomy (PETD) [10]. When this procedure was used to treat calcified disc herniation in the past, a significant prevalence of postoperative problems was documented in the literature [5]. As a result, the study's objectives are to assess the efficacy of percutaneous endoscopic lumbar discectomy (PELD) in the treatment of CLHD and to provide CLHD patients with expert guidance.

Materials And Methods

General Information

All patients gave their informed consent to participate in this study, which was endorsed by our hospital's ethics committee. Between June 2018 and April 2021, we used PEID and PETD to treat 45 consecutive patients with L4-L5 and L5-S1 CLDH at our facility. These patients were divided into two groups based on the surgical methods: PEID (n = 24) and PETD (n = 21). Each patient came in with a leg-lengthening low back discomfort. Despite taking conservative therapies for at least three months, such as acupuncture, physiotherapy, and medication, the discomfort persisted or recurred and interfered with everyday activities. The preoperative diagnosis of CLDH was validated using computed tomography and/or magnetic resonance imaging. The study did not include any participants with multi-segmented CLDH or lacking CLDH. Surgeons with at least five years of experience performed every operation. We retrieved and reviewed follow-up results, clinical data, and demographic information.

Surgical Procedure

All had general anesthesia and either PETD or PEID neurophysiological monitoring. On a radiolucent table, the patient was positioned prone. Under the supervision of a C-arm fluoroscope, the endoscopy is carried out.

PEID

A guide rod is placed medially into the inferior articular eminence after using fluoroscopy to identify the operative disc space. The working trocar is then inserted through the guide rod adjacent to the inferior articular eminence with an oblique surface facing the ligamentum flavum. A medial osteotomy of the inferior vertebral plate and articular eminence is carried out after inserting the endoscope into the trocar. After cutting a hole in the ligamentum flavum, the working trocar is moved into the epidural space. The region around the nerves and calcified foci is freed once the soft tissue around them has been removed. Following the removal of the soft disc, the nerve is dragged medially, the calcification is removed by grinding the drill, the nerve is tested for relaxation, and finally, the working channel is pushed out and the incision is sutured. All patients underwent CT and MRI scans before (Fig. 1A-D) and after (Fig. 1E-H) operation.

PETD

Once the surgical disc space has been located by fluoroscopy, an 18G puncture needle is inserted into the lateral side of the superior articular process. Cephalad to caudal should be the needle's route. The guide wire, guide rod, and soft tissue dilator are implanted one after the other along the route of the penetration needle. The guide wire, guide rod, and soft tissue dilator are implanted one after the other along the route of the penetration needle. A working cannula is introduced into the spinal canal through each dilator and guide rod. An articular eminence osteotomy was performed while under visualization to show the calcified lesion. After allowing the nerve to pulse, the working channel is removed, the disc and calcified foci are eliminated, and the incision is sutured. Prior to (Fig. 2A-D) and following (Fig. 2E-H) surgery, all patients obtained CT and MRI scans.

Outcome assessment

The demographic variables that were examined between the PEID and PETD groups were age, sex, body mass index (BMI), and follow-up time. In terms of surgical outcomes, including operation time, intraoperative blood loss, intraoperative fluoroscopy times, postoperative hospital stay, and complications, the two groups were compared. Clinical outcome indicators such the Oswestry Disability Index (ODI), the Visual Analog Scale (VAS) for Leg Pain, and modified MacNab criteria at the last follow-up were compared between the two groups. In the meantime, VAS and ODI scores were gathered at each follow-up appointment following PELD in comparison to the preoperative period.

Postoperative Treatment and Follow-Up

Straight leg raising exercises were advised at least on the first postoperative day, and mannitol and dexamethasone were administered for one day after surgery. It is advised to stay in bed for a week. Patients were evaluated one week, one month, three months, and twelve months after surgery. The VAS score and ODI were collected at each follow-up, however only the last follow-up included a Macnab criteria outcome evaluation.

Statistical analysis

All data were statistically analyzed using the SPSS 23.0 software (IBM Corporation, USA). The data's normality was evaluated using the Shapiro-Wilk test. Mean±standard deviation are used to represent parametric data, while median is used to show nonparametric data (interquartile range). Wilcoxon test was used for intragroup comparisons while Mann-Whitney test was utilized to compare the two groups. Chi-square tests were used to compare the modified MacNab criteria, sex and comorbidities. P<0.05 indicates a statistically signifcant diference.

Results

Each patient had successful surgery at our hospital by a skilled spine surgeon. None of the 45 patients, of whom 24 were in the PEID group and 21 were in the PETD group, were lost to follow-up. The demographics of the two groups (age, sex, segment, BMI, and follow-up period) were signifcantly similar as shown in Table 1. In the PEID group , the median operative time, intraoperative fluoroscopy times, median postoperative hospital stay, intraoperative blood loss and complication rate were all 70 min, 4.71±1.23 times, 3days, 19.90±8.42 ml, and 8.33%, respectively. The PETD group's median operative duration, intraoperative fluoroscopy durations, the median postoperative hospitalization, intraoperative blood loss and complication rate were 70min, 9.67±1.93 times, 3 days, 19.25±7.32ml and 4.76%, respectively. Although PEID beat PETD in terms of intraoperative fluoroscopy times, there was no appreciable difference in operating time, intraoperative blood loss, postoperative hospital stays, or incidence of complications, as indicated in Table 2. In the PETD group, there was one case of postoperative hip pain. One patient in the PEID group had persistent postoperative dysesthesia, while another had foot drop. After receiving conservative therapy, all of these patients made a full recovery, with the exception of the patient with foot drop.

 Prior to surgery as well as one day, one month, three months, six months, and a year afterwards, we computed the VAS and ODI values for each patient. The approach significantly improved the patients' leg discomfort（Tab.3,Tab.5,Fig.3）. 

The median VAS score was 7.0 prior to surgery and sharply dropped to 4.0 on postoperative 1 week (P=0.00). At the 1-month, 3-month, 6-month, and 12-month follow-ups, the mean VAS scores were 2, 2, and 1, respectively. However, there was no statistically significant distinction between the PEID and PETD groups. (Tab.4,Fig.4).Within the PEID and PETD groups, there were no differences in the leg pain VAS values in the L4-5 and L5-S1 segment(Tab.6).

 The ODI data are shown in Table 5. The median ODI was significantly lower (32.00%) at the 1-week follow-up than it had been prior to surgery (64%) (P <0.05). The median ODI at the 1-year follow-up was 22.00%. Nevertheless, there was no statistically significant difference between the PEID and PETD groups (Tab.4,Fig.1). In comparison to patients who underwent PEID surgery at the L4-5 segment, patients who underwent PETD surgery had considerably lower ODI at 12 months after surgery（Tab.7）.

 According to surgical outcomes evaluated using the modified Macnab criteria, 90.5% of patients in the PETD group and 83.3% of patients in the PEID group reported excellent, 4.8% good, 8.3% fair, and 4.2% poor results at the most recent follow-up following surgery, respectively.

Discussion

Calcified lumbar disc herniation is a specific type of lumbar disc herniation. shao et al.[11] noted that lumbar disc calcification was related to the degree of degeneration. Treatment options for calcified lumbar disc herniation are debatable. A thorough long-term follow-up should be performed on patients with asymptomatic CLDH. Wan et al.[12] concluded that conservative treatment is the most recommended measure to achieve the same clinical outcome and avoid the various discomforts caused by surgery, because even in large calcified lumbar disc herniations, the calcification could be absorbed thus improving the clinical symptoms. However, the majority concur that surgery is advised if conservative therapy fails[5.13.14].

Percutaneous endoscopic lumbar discectomy (PELD) is a minimally invasive procedure with a short incision, minimal trauma, low intraoperative bleeding and rapid postoperative recovery. PELD is safe and effective and has been shown to have comparable clinical efficacy to traditional open surgery in the treatment of soft LDH[6.7.10]. In recent years, more and more spine surgeons are applying spinal endoscopic techniques to calcified lumbar disc herniation. The clinical results are encouraging, but the complications are equally serious, such as decreased muscle strength, sensory numbness, nerve injury, and dural tears.[4.8.9.14.15]. 

At present, the most extensively applied endoscopic treatment of calcified lumbar disc herniation are the percutaneous endoscopic interlaminar discectomy (PEID) and percutaneous endoscopic transforaminal discectomy (PETD). Kim et al.[16] treated 78 cases of CLDH for PEID and had 2 cases of transient motor weakness after surgery, while no surgical complications in 26 cases for PETD. Zhu et al.[1] applied the cave-in technique to treat 23 cases of CLDH for PETD, and one patient had sensory dullness and one patient had decreased muscle strength after the procedure. Some authors suggest that this is due to adhesions of the calcified foci to the nerve dura, intraoperative nerve traction, and increased surgical difficulty due to the calcified foci restricting the surgical space for PETD [5.17]. In our study, 1 patient had postoperative hip pain in the PETD group.Although this occurred in our experience due to inadequate surgical decompression, it is believed that it may also have been caused by dorsal rami damage during surgery[18]. Meanwhile, creating a surgical channel and exposing calcified foci was crucial to the success of PETD. The superior articular process's medial and lateral saphenous fossa are made of thick, hard bone, making them vulnerable to injury during foraminoplasty when the superior articular process is osteotomized under fluoroscopy. Due to inadequate dorsal decompression of the nerve, the nerve is also injuried during channel rotation. Therefore, foraminal decapitation is necessary in order to expose the ligamentum flavum; it is insufficient to only remove the lateral section of the superior articular eminence[19]. In addition, exposing the nerve root by removing the calcification runs the risk of injuring the nerve. According to several studies, ultrasonic osteotomies are used during PELD. With this ultrasonic bone knife, PELD patients can efficiently remove herniated calcified discs, lessen nerve compression, and safeguard nearby neurovascular tissue. In some CLDH patients, this device may assist to increase the indications for endoscopic surgery and prevent open surgery, but heat radiation may also harm nerves[6.16].

 DABAO et al.[5] treated 30 cases of CLDH by PEID and showed a higher incidence of surgical complications of sensory abnormalities in the early postoperative period. They suggest that this may be related to adhesions of calcified tissue to nerve roots or dural sacs. Cheng et al.[9]treated 28 cases of L5-S1 segment using ultrasound osteotomies with one case of dural tear and one case of sensory abnormality. They concluded that there was no difference in the incidence of surgical complications between PEID and PETD in the treatment of L5-S1 level for CLHD. When treating L4-5 and L5-S1 segments, there was no difference in surgical results or surgical complication rates between the PEID and PETD groups in our research. In the L4-5 segment, however, the PETD group outperformed the PEID group in terms of long-term functional recovery (Table 7). We also accept that the superior articular processes' obstructive impact worsens when the lower lumbar intervertebral foramina gradually shrink. Due to the occlusion of the iliac spine and the size of the L5 transverse process, access is more challenging to achieve, particularly at the L5-S1 level. Therefore, we were forced to select PEID over PETD. PEID better satisfies the surgical preferences of surgeons. The inferior lamina, superior articular process, and lateral saphenous fossa may need to be partially removed, however, if the lamina space is too short, in order to expose the nerve roots. The dura, nerve, and calcified foci should be carefully separated after entering the spinal canal in order to prevent damage to the nerve in patients with CLHD. At this point, bleeding frequently impedes surgery and may unintentionally damage the nerve. In order to effectively treat CLDH, we propose removing the soft disc, relaxing the nerve, widening the dura mater and nerve, and then partially eliminating the head and tail of the calcified foci by grinding them off. There were no dural tears during our PEID operation, however there were one postoperative occurrences of dysesthesia and one postoperative foot drop. According to the research, CLDH with more than 50% intradural occupancy is a significant risk factor for foot drop following lumbar intervertebral disc surgery like this case [20].

 Limitations associated with our study include retrospective clinical outcome assessments and small sample size. Further studies with large sample，multicenter, and long-term follow-up will be conducted in the future.

Conclusion

According to the results, we obtained good long-term clinical results using percutaneous endoscopic discectomy for calcified lumbar disc herniation. This technique is safe and allows complete decompression of the nerve structures, while there is no difference between the PETD and PEID approaches in terms of surgical benefit and surgical complications.

Abbreviations

PELD: Percutaneous endoscopic discectomy;

PEID: Percutaneous endoscopic interlaminar discectomy;

PETD: percutaneous endoscopic transforaminal discectomy;

CLDH : Calcified lumbar disc herniation;

VAS: Visual Analog Scale; ODI: Oswestry Disability Index.

Declarations

Authors’ contributions 

All authors participated in the interpretation of study results, and in the drafting, critical revision, and approval of the fnal version of the manuscript, and all authors agree to be accountable for all aspects of the work. XJF was in charge and contributed to all stages of the present study; SHY was responsible for participated in the design of the study, made revisions of the manuscript and approved the fnal version. HMC contributed to interpreting the data and writing the fnal manuscript; XJF was contributors in writing and editing the manuscript.

Availability of data and materials 

The authors will allow the sharing of participant data. The data will be avail‑ able to anyone who wishes to access them for any purpose. The data will be accessible from immediately the following publication to 6 months after publication, and contact should be made via the frst author by email.

Ethics approval and consent to participate

This retrospective research was approved by the Yueyang Hospital of Traditional Chinese Medicine. Written informed consent was obtained from all participants. All methods were carried out in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable.

Competing interests

The authors report no conficts of interest in this work.

Acknowledgments 

The authors would like to thank all the study participants.

Author details 

¹ Neurospinal Surgery, Luzhou People's Hospital, 646000, Luzhou, China,

²Spinal Orthopedics, Yueyang Hospital of Traditional Chinese Medicine, 414000,Yueyang, China,

³Orthopaedic Surgery, Yueyang Hospital of Traditional Chinese Medicine, 414000,Yueyang, China.

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Tables

Table 1 Demographic characteristics of both the PEID group and PETD group

Values are mean±SD, number, or as otherwise indicated. BMI :body mass index. p<0.05 was statistically significant.

Table 2 Surgical outcomes of both the PEID group and PETD group

Data are presented as mean±SD, or median (interquartile range). a:Mann-Whitney test .b:independent-samples Test .c: Chi-square test, test. p< 0.05 was considered significant.

Table 3. Visual analog scale score for leg pain before and after surgury.

Data are presented as median (interquartile range).* versus previous 

follow-up, respectively. Wilcoxon rank sum test was used for statistical analysis.

p<0.05 was statistically significant.

Table 4 VAS and ODI scores of both the PEID group and PETD group

Data are presented as median (interquartile range).* versus previous 

follow-up, respectively. Mann-Whitney test was used for statistical analysis.

p<0.05 was statistically significant.

Table 5 Oswestry Disability Index before and after surgury.

Data are presented as median (interquartile range).* versus previous 

follow-up, respectively. Wilcoxon rank sum test was used for statistical analysis.

p<0.05 was statistically significant.

 Table 6 VAS scores of L4-5 and L5-S1 CLHD 

Data are presented as median (interquartile range).* versus previous 

follow-up, respectively. Mann-Whitney test was used for statistical analysis.

p<0.05 was statistically significant.

Table 7  ODI scores of L4-5 and L5-S1 CLHD 

Data are presented as median (interquartile range).* versus previous 

follow-up, respectively. Mann-Whitney test was used for statistical analysis.

p<0.05 was statistically significant.