The initial literature search retrieved 9230 relevant articles. After a careful screen of the titles,9071 articles were excluded for not investigating the topic of interest. After reviewing the abstracts, 105 more articles were excluded (73 animal/cell studies, 30 cadaver studies, and 25 reviews), leaving 31 studies for further full publication review. One study was excluded because it only reported the protocol of an RCT . Another four studies were excluded because the articles did not report any useful outcomes. Therefore, a total of 26 papers matched the selection criteria, but only 10 papers were suitable for the meta-analysis as lots of papers were reporting the outcomes of the same study (Fig.1).
A total of 1907 participates (1203 treated and 704 control) were enrolled in the study. The key characteristics of the included studies are summarized in Table 1. Seven of the included studies were prospective cohort studies (3 RCTs) and the remaining three were retrospective. Seven of the studies were from European or American, two from Korea, and the remaining from China. Seven of the studies utilized an annular closure device called Barricaid, and the remaining three studies utilized suture-based techniques including Xclose technique, No. 2 fiberwire sutures and PushLock implant technique, and jetting suture technique. Most studies followed the patients for at least 2 years and only one reported the outcomes at the mean of 15 months. Table 2 listed the basic characteristics of the studies, including population number, gender, age, BMI, and operating level.
Among the included studies, only the VAS scale of leg and back, the ODI scale, the symptomatic re-herniation rate, and the re-operation rate were matched. Table 3 listed the extracted matched outcomes. On review of the data extraction, there was 100% agreement between the 2 reviewers. According to the checklist for measuring study quality, all the studies were considered as medium/high quality of methodology. Thus, the methodological bias of this study was considered low.
In comparison with the control group, the ODI scales of the annular repair group demonstrated no statistical difference (p=0.945, Fig.2). Similar results were found for the VAS-leg and VAS-back scales (p=0.82 and p=0.847, Fig.3 and Fig.4, respectively).
For the comparison of the radiological and symptomatic re-herniation, a significant decrease was found in the annular repair group (treated v.s. control, 4.9% v.s. 14.6%, p=0.004, Fig.5). Similarly, the treated group demonstrated a significantly lower re-operation rate compared with the control group (4.7% vs. 14.3%, p=0.004, Fig.6), when only take the re-herniation related re-operation into consideration.
The adverse problems especially annular repair related complications were also analyzed, including peri-operation complications and device related long term complications. As the additional annular repair procedures, there is no doubt that the surgical time and blood loss are much more in annular repair group. For peri-operation complications, all annular repair techniques seem safe enough as only a few complications (mainly dural tear and perioperative infections) were reported, with no statistically significant difference found (Table 4). However, there were much more device related long term complications such as device failure, loosing, migration, and epidural infection happened in annular repair group, especially for the cases with ACD (Barricaid) technique (p=0.031, Table 3). However, though much more device related complications happened, the overall re-operation rate is still much lower in the annular repair group (7.9% v.s. 16.2%, p=0.006, Fig.7).
The annular repair technique is always recommended for LDH patients with large annulus fibrosus defect, so, subgroup analysis according to the defect size was performed. For patients with large annulus fibrosus defect, namely, high risk patients, only the repair technique based on ACD device was employed. The analysis demonstrated a disc re-herniation rate (radiology and symptomatic) of 4.4%, a re-herniation induced reoperation rate of 4.3%, and an overall re-operation rate of 7.4% (table 5).
No publication bias was found among the studies.