Study design and patient population.
We retrospectively analyzed 96 patients with single-level LDH who underwent PELD at Shenzhen Traditional Chinese Medicine Hospital from October 2013 to May 2021. Based on whether rehydration occurred at the last follow-up, patients were divided into rehydration group (41 cases) and non-rehydration group (55 cases). Inclusion criteria were: (1) single segment LDH as confirmed by preoperative imaging examination; (2) no improvement in symptoms even after more than half a year of non-surgical treatment; (3) underwent PELD; and (4) a follow-up period of at least 1 year. Exclusion criteria were: (1) significant instability of the responsible segment as revealed by preoperative imaging; (2) spondylolysis of the responsible segment; (3) history of other lumbar surgery; and (4) infection, trauma, or spondylolisthesis. The study involving human participants was reviewed and approved by the Ethics Committee of Shenzhen Traditional Chinese Medicine Hospital. This study also complied with the Declaration of Helsinki for investigation in humans. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.
Surgical Procedure
Epidural anesthesia was used in all patients. After successful anesthesia, the patients were made to lie in the prone position on the operating table, and their hips and knees were disinfected and covered with towels.
Translaminar approach: Percutaneous puncture was performed with a 10-ml syringe needle 2 cm from the posterior median of the body surface of the responsible intervertebral space, and C-arm fluoroscopy was used to confirm the responsible intervertebral disc. Then, the skin was incised using an intervertebral disc puncture needle and using a 0.7-cm pencil, the incision was expanded such that the intervertebral foramen is seen and the degenerated intervertebral disc nucleus pulposus tissue was removed. Ultrasound-guided vertebral canal decompression was used when necessary. Radiofrequency ablation followed by percutaneous adhesiolysis was performed after thorough decompression. The floating disc was checked. Methylprednisolone sodium succinate 40 mg was injected through the foraminal endoscopic channel to prevent postoperative nerve root edema.
Transforaminal approach: An 18-gauge puncture needle was used to enter the posterior third of the intervertebral space through the foraminal area 8–10 cm adjacent to the intervertebral space under the guidance of the C-arm machine, and ioparol contrast agent was injected. The C-arm machine showed the rupture of the annulus fibrosus and herniation of the intervertebral disc. The rest of the procedure is the same as that used in the translaminar approach, except that betamethasone injection (0.5 ml) was used to prevent postoperative edema of the nerve root before suturing off the skin incision.
Postoperative treatment: Bed rest for 1 month after the operation, a waist belt to get out of bed, and oral neurotrophic drugs.
Data Collection
Differences in sex, job type, age, BMI, surgical approach, hypertension, diabetes, duration of disease, smoking status, and other baseline conditions were compared between the two groups. In addition, preoperative peripheral blood-related indicators including count of leukocytes, neutrophils, lymphocytes, monocytes, and platelets, hemoglobin level, ESR, C-reactive protein level, and Th1/Th2 subgroup analysis, including levels of IL-2, IL-4, IL-6, IL-10, TNF-α, interferon (INF)-γ, were compared between the two groups.
Lumbar MRI was performed with a superconducting 1.5T magnetic resonance imager (Siemens, Germany) to detect the signals of lumbar intervertebral discs before and after surgery. Detection conditions: Magnetic acoustic intensity was 0.35 Tes/a, and 11 layers were scanned in sagittal position (interlayer distance was 1.25 mm; layer thickness was 5 mm).
Evaluation of intervertebral disc rehydration: Intervertebral disc water content can be reflected by the intensity of intervertebral disc signal on MRI T2-weighted images (T2WI). Ideally, MRI should be performed using the same MRI device before and at the last follow-up, but not every patient can meet this requirement. To solve this problem, average calibrated disc signal (CDS) proposed by Fay6 was used. On the cross-sectional T2WI of the center of the intervertebral disc, the gray value of the central area of the L2/3 intervertebral disc (the circular area with a radius of 1 cm) was selected as a reference and compared with the gray value of the central area of the surgical segment. This ratio eliminates the influence of other MRI device parameters and reflects the intervertebral disc signal intensity; therefore, it can be used to compare patient data between two MRI examinations.
In addition, IDD grades were assigned at the implanted segment according to the Pfirrmann classification of lumbar IDD. Grade I: the structure of the vertebral disc shows uniform white hyperintensity, and the height of the disc is normal; Grade II: the structure of the bay disk is characterized by uneven white high signal. The annulus fibrosus and nucleus pulposus were distinct, with or without horizontal gray bands; Grade III: intervertebral disc structure with uneven signal intensity and gray signal intensity; the difference between annulus fibrosus and nucleus pulposus is unknown. The disc height is normal or slightly decreased; Grade IV: the signal of intervertebral disc structure is not uniform, showing a black low signal. The difference between the nucleus pulposus and annulus fibrosus disappeared, and the disc height was normal or moderately decreased; Grade V: the signal of intervertebral disc structure is not uniform, showing a black low signal. The difference between the nucleus pulposus and annulus fibrosus disappeared, and the intervertebral space collapsed.
Based on the degree of displacement of the protrusion, LDH was divided into three types by the Komori typing method. Type A: the displacement of the protrusion did not exceed 1/3 of the adjacent vertebral body; Type B: the protrusion displacement does not exceed 2/3 of the adjacent vertebral body; Type C: the protrusion is displaced by more than 2/3 of the adjacent vertebral body or accompanied by distance.
Modic changes in the adjacent vertebrae of the operative segment: whether there are Modic changes in the vertebrae can be determined based on preoperative MRI results. Type 1: T1 low signal, T2 high signal; Type 2: T1 high signal, T2 medium signal; Type 3: T1 low signal, T2 low signal.
Spinal canal morphology: Based on transverse MRI images, spinal canal morphology was divided into three types: elliptic, triangular, and trilobated.
Statistical Analyses
SPSS 24.0 software was used for statistical analysis. The measurement data conformed to normal distribution. All variables were analyzed to screen for factors that may affect reabsorption. The measurement data were analyzed by independent t-test and further analyzed by Chi-square test. Variables with statistical significance were further analyzed using binary logistic regression to identify the factors affecting LDH rehydration. P < 0.05 was considered statistically significant.