A retrospective cohort analysis conducted at a single facility between 2020 and 2022 initially included 117 patients diagnosed with single-level CLDH at the L5/S1 level and treated with PELD. With comprehensive clinical data at our disposal, we utilized a retrospective methodology to evaluate the outcomes of these surgical procedures. The clinical ethics committee approved this research. Written informed consent was obtained from all participants, and all procedures adhered to the guidelines set by the relevant Chinese authorities and the Helsinki Declaration.
Key end measures (VAS, ODI, JOA, and SF-12 scores), minimum clinically important difference (MCID), and expected to be detected difference for efficacy have been considered to find how many participants should be included in the trial, to detect efficacy between two surgical procedures (PETD and PEID). These estimates are based on the effect sizes and standard deviations estimated from previous research and pilot test studies. It was estimated that the study had 80% statistical power against an alpha error rate of 0.05. Sample size estimation was evaluated using G*Power software. To have sufficient statistical power, not less than 50 patients in each group would be necessary, totaling a minimum of 100 patients for the first sample. In this study, 117 patients were enrolled at the beginning. After all, they have been considered and analyzed as to meet the necessary statistical criteria.
The inclusion criteria were carefully established to create a uniform study population, consisting of: (1) patients who had lower back pain and unilateral lower limb symptoms, such as discomfort, numbness, or weakness; and (2) patients who had CT-confirmed evidence of CLDH. The exclusion criteria were implemented to minimize potential factors that could distort the results. These criteria consisted of: (1) patients displaying indications of lumbar instability; and (2) patients with severe cardiopulmonary dysfunction, determined by an anesthesiologist to be unfit for surgical intervention based on an evaluation of their overall health status.
The PETD procedure is executed via a transforaminal route as described by Yeung8. The surgery begins with the patient lying face down, which allows for the accurate determination of the puncture site using a C-arm X-ray apparatus. The device is usually placed 10–12 cm to the side of the midline at the afflicted level. Once local anesthetic is given, the needle is precisely positioned in the back part of the specific intervertebral disc. An anteroposterior (AP) image is initially obtained to verify the intervertebral level and ensure accurate alignment of the foramen with the intended disc region.The angulation of the C-arm is then made in such a way that a lateral view through which the insertion of the needle and advancement to the foramen's lower safe zone can be easily seen. This procedure minimizes the chances of root injury. This guidewire is then passed through the needle, which is withdrawn in order to facilitate placement of a bone drill over the guidewire, aiming to enlarge the intervertebral foramen carefully by removing bone. This creates a pathway for the insertion of electrocoagulation devices and forceps, clearly defining the surgical area and making it easier to make an incision in the ligamentum flavum to reach the disc space. The operative cannula is skillfully maneuvered to safeguard neighboring nerve structures while the calcified portions of the disc are observed and systematically eliminated using a fast-rotating drill, with a constant flow of saline solution to minimize the possibility of heat-related harm. After removing the calcifications, the primary goal is to fully decompress the disc space, while optimizing the preservation of the good disc tissue. Following decompression, a comprehensive evaluation of the nerve root is conducted to confirm the absence of compression or bleeding, effectively alleviating symptoms. The treatment concludes with the removal of the endoscopic equipment, suturing the skin, and applying a sterile bandage to the incision site (Fig. 1A). The PEID technique is performed through an interlaminar approach according to Ruetten9. This technique is initiated with the patient under general anesthesia, in a prone position to optimize surgical access. A small, 1 cm horizontal incision is made approximately 2 cm lateral to the spinous process at the involved level. The puncture needle is precisely positioned at the specified section, and then a pencil head and working cannula are inserted through a 0.7 cm incision. The placement is confirmed using a C-arm X-ray system. After removing the pencil head, the working cannula is filled with irrigation fluid, preparing for the insertion of the endoscope. The outermost layers of the ligamentum flavum are carefully removed, followed by a precise cut into the ligamentum flavum to reduce the risk of harming the nerves beneath it. When there is stenosis, the surgeon strategically removes the medial facet joint edge and a part of the lamina bone according to the preoperative plan in order to assist decompression. Utilizing specialized instruments, a segment of the ligamentum flavum is excised, revealing the underlying nerve root and dural sac. Care is taken to gently maneuver the working cannula around the nerve retractor, avoiding direct nerve contact, to access and remove the calcified disc material, mirroring the approach employed in the PETD technique. (Fig. 1B).
Following the operation, a standard postoperative care plan was put in place for all these patients in a bid to optimize recovery outcomes. The plan of care entailed an elaborate method of pain management, individualized physical therapy programs, and careful wound care. Individualized pain management plans were made in relation to each patient's pain tolerance and advancement in recovery in order to keep the level of pain to a minimum so that early movement was encouraged. When the patient's condition allowed, early physical therapy was initiated. The program focused on enhancing muscle strength, increasing flexibility, and promoting functional mobility. The enhancement of muscle strength with time, coupled with increased flexibility and easier functional mobility, was noteworthy. The main goals were to teach the patient good body mechanics and offer advice on exercises that would help them avoid having back problems in the future. This included treating wounds with strict aseptic methods to avoid infection and keeping a close eye out for any signs of problems. Patients were advised to initiate ambulation promptly following the surgical procedure, in accordance with the recommendations provided by the healthcare staff. It is highly recommended to include the patient in a rehabilitation program to expedite a full recovery process and ensure a return to the former level of activity and quality of life following the surgery.
The principal outcomes measured in this study included the Oswestry Disability Index (ODI) score, Visual Analog Scale (VAS) score for pain, Japanese Orthopaedic Association (JOA) Score related to functional recovery for low back, and the 12-item Short Form Health Survey Physical Composite Score (SF-12 PCS) for the physical health quality. These all were laboriously collated measured indicators of successful surgical interventions at discrete time points over the follow-up period of 1, 3, and 12 months after the operation, respectively.
In addition to the primary outcomes, a comprehensive set of secondary outcomes were also evaluated to provide a holistic view of the treatment effects. These included detailed patient demographics, the preoperative diagnosis, and the morphology of calcification as classified by the Wu Scoring System. The calcification residual area (CRA) of the intervertebral disc, along with the percentage of CRA (S%), was carefully measured to assess the extent of calcification removal. Other parameters collected included the segment of operation, duration of surgery, volume of blood lost intra-operatively, and time spent in bed after surgery and in overall length of hospital stay. The postoperative complications were carefully documented to determine the security profile of the surgical procedures.
Within 48 hours post-surgery, patients received high-resolution computerized tomography (CT) scans to obtain fine-grain images of the calcified lumbar discs. High-resolution CT is perhaps the most effective way to obtain crisp and accurate images of the bone and its calcifications. The quantification of the remaining calcified area was performed independently by two experienced radiologists using the ImageJ software (National Institutes of Health, USA). The area of calcification was established through a comparison of pre- and post-operative disc imaging, with the estimation of the area of residual calcification represented as a percentage of the whole disc calcification. Pearson Correlation Coefficients were estimated to quantify linear associations between residual calcified area and the functional scores (VAS, ODI, JOA, SF-12). Moreover, the use of statistical analysis has been used to get the need for using a multivariate linear regression model to account for relevant confounding variables such as age, gender, BMI, and surgery parameters. This may have been possible because such confounders had been controlled during the research and might be having an impact on postoperative functional recovery.
The statistical and well-structured analysis guaranteed a solid assessment of the gathered data. When applicable to the paper, the continuous variables, such as the SF-12 PCS, ODI, JOA, and VAS scores, were reported as means ± standard deviations (SD). In respect to patient demographics and complications, mean scores were compared between the groups of patients who were admitted and those who were discharged. The Student t-test, which is pertinent to comparing means in situations when the data are regularly distributed, was employed for this purpose. For categorical variables, descriptive analyses included patient demographics and specific complications represented as percentage frequencies and numbers. Chi-square testing was used as the primary analytical tool for the data, along with all other statistical techniques. The software has incorporated the Fisher-Freeman-Halton test, which is a generalization of Fisher's exact test, to ensure the validity of all results in the event of low predicted frequencies. Using the Pearson correlation coefficient, we examined the linear relationship between the variables in this study—calculated area and functional scores—one at a time.
Statistical analyses were conducted using SPSS 22.0 (IBM Corp., Armonk, NY) for all but the Fisher-Freeman-Halton test, which was used to determine the frequency of postoperative complications in the previous section. With a p-value less than 0.05, the null hypothesis was rejected due to statistically significant differences. This indicates a notable difference between the PETD and PEID groups in the analyzed outcomes.