Background
Total knee arthroplasty (TKA) is a common procedure for improving mobility and quality of life in patients with osteoarthritis or rheumatoid arthritis. However, TKA itself is always associated with moderate to severe pain after surgery. It is reported that 60 and 30% of TKA patients experience severe and moderate pain, respectively [
1]. Currently, both femoral nerve block (FNB) and local infiltration anesthesia (LIA) can provide effective analgesia, facilitate early mobilization, and reduce the length of hospital stay [
2,
3]. Chan et al. [
4] conducted a meta-analysis to compare FNB with other analgesic techniques, and the results indicated that there was insufficient data to draw a definitive conclusion regarding FNB with LIA. Although FNB is a well-accepted and commonly used technique for regional anesthesia after TKA, previous studies indicate that some patients experience significant postoperative pain despite the administration of FNB [
5,
6]. Compared with peripheral nerve block, LIA is an alternative, convenient anesthetic technique that is usually performed by orthopedic surgeons. Meanwhile, the efficacy and safety of LIA is comparable to that of epidural anesthesia, FNB, and intrathecal morphine [
7]. Therefore, anesthesia via sciatic nerve block (SNB) and LIA are two major options for supplementing FNB to relieve pain after TKA [
8‐
10]. However, there is no consensus regarding which anesthesia method is preferable to relieve pain as an adjunct to FNB. Thus, a meta-analysis of randomized controlled trials (RCTs) was conducted to compare the efficacy and safety of pain control with SNB versus LIA when combined with FNB after TKA.
Methods
This review is registered in Protocol registration: PROSPERO 2016 CRD42016050735.
Search strategy
The electronic databases PubMed, Embase, Cochrane Library, and Web of Science were searched from their inception to 15 June 2016. The search terms included local infiltration anesthesia, femoral nerve block, sciatic nerve block, and total knee arthroplasty. The Boolean operators “AND” and “OR” were used to couple these terms. The details of the search strategy are displayed in Additional file
1. There were no restrictions regarding language and publication date. We also manually retrieved reference lists from the identified studies and relevant review studies to identify additional relevant studies. Two investigators independently assessed the titles and abstracts of the studies identified by the retrieval. The full text of the remaining studies was then reviewed to ensure that they met the eligibility criteria. Disagreements were settled by consulting a third reviewer.
Inclusion criteria and study selection
All RCTs comparing combined femoral and SNB versus femoral and LIA for pain control were eligible for this meta-analysis. If there were more than one eligible trials from one team, the study with most recent publication data were enrolled for analysis. Studies that included bilateral TKA, revision of TKA, or other anesthetic methods were excluded. All non-randomized trials were also excluded.
Data abstraction
Two reviewers extracted the data independently using a predefined data extraction form. Disagreements were resolved through discussion or consensus with a third reviewer. The data extracted included the first author, publication year, study characteristics (number of patients and percent of female patients), participant characteristics (i.e., mean age, type of anesthesia, operative approach, and type of prosthesis), and the length of follow-up. For studies with insufficient information, the reviewers tried to contact the first author via e-mail or telephone to obtain the original data. After duplicates were excluded, two reviewers independently read the titles and abstracts of the selected literature. Most of the articles were excluded based on the topic of the article provided in the title or abstract, and disagreements regarding whether an article should be included were resolved via discussion or consultation with a senior reviewer. Postoperative pain intensity was measured using a 100-point visual analogue scale (VAS). The 10-point VAS score was converted to a 100-point VAS score. Data in other forms (i.e., median, interquartile range, and mean ± 95% confidence interval (CI)) were converted to mean ± SD as described in the Cochrane handbook [
11]. If the data were not reported numerically, we extracted them from the published figures using the “GetData Graph Digitizer” software [
12].
Quality assessment
Two independent reviewers assessed the methodological quality of the included trials according to the Cochrane Collaboration recommendations [
11]. The following information was evaluated: random sequence generation, allocation concealment, blinding of outcome assessments, incomplete outcome data, selective reporting, and other biases. An independent arbiter was consulted to reconcile any disagreement.
Statistical analysis
Continuous outcomes, such as the VAS at 12, 24, and 48 h, morphine consumption at 24 and 48 h, active knee flexion, the length of hospital stay, and anesthesia time, were expressed as the mean difference (MD) with the respective 95% CIs. Discontinuous outcomes (the rate of postoperative nausea and vomiting (PONV) and fall) were expressed as the relative risk (RR) with 95% CIs. Statistical significance was set at P < 0.05 to summarize the findings across the trials. Stata 12.0 software (Stata Corp., College Station, TX) was used for the meta-analysis. Statistical heterogeneity was tested using the I2 statistic. A value of I2 > 50% was considered to indicate statistical heterogeneity, and a random effects model was applied. Then, sensitivity analysis was conducted to identify potential sources of heterogeneity. When there was no statistical evidence of heterogeneity, a fixed-effects model was adopted. A subgroup analysis was conducted to identify whether the type of FNB (continuous FNB versus single-shot FNB) and anesthesia (general anesthesia versus spinal anesthesia) affected the VAS at 12, 24, and 48 h.
Trial sequential analysis
Because cumulative meta-analyses carry a risk of producing random errors, mainly because of sparse data and repetitive testing of cumulative data [
13‐
15], trial sequential analysis was performed in case the data were too sparse to draw firm conclusions. Trial sequential analysis is comparable to interim analysis in a single trial, and the trial sequential monitoring boundary can be applied to meta-analysis to determine whether the
P value is small enough to show the anticipated effect and whether the trial should be terminated early [
16]. If the trial sequential analysis boundary or the futility zone is crossed, more trials are unnecessary.
Discussion
This is the first systematic review and meta-analysis to compare combined femoral and SNB versus combined femoral with LIA for pain control after TKA. On the basis of the pooled estimates, combined femoral and SNB, compared with combined femoral with LIA, was associated with a reduction in pain scores, equivalent on an 110-point VAS to 6.96 point (95% CI, −8.36 to −5.56 point) at 12 h and 2.41 point (95% CI, −3.90 to −0.91) at 48 h. However, this reduction is not of clinical importance. There was no significant difference between active knee flexion, morphine consumption at 24 and 48 h, length of hospital stay, and the occurrence of PONV. And combined femoral and LIA, compared with combined femoral with SNB, are associated with less anesthesia time.
The only positive result is that SNB can decrease the VAS score at 12 and 48 h compared with LIA, and the difference is statistically significant. These outcomes concur with the morphine consumption at 24 and 48 h. Peripheral nerve block was induced before surgery and can decrease the morphine consumption during the early period. Morphine consumption was also used as a marker to test the efficacy of adjunctive analgesia [
25‐
27]. Abdallah et al. [
12] conducted a systematic review, and the results indicated that there was insufficient evidence to support the effect of adding SNB to FNB for anesthesia following TKA. Meanwhile, there was no statistically significant difference between the morphine-related complications of PONV.
Regarding active knee flexion, there was no significant difference between the two groups on day 3 and month 3 after TKA. The present results did not find any significant difference in the progress of rehabilitation, knee mobilization, and length of hospital stay. These results also indicated that improved early anesthesia cannot facilitate early rehabilitation. The results are consistent with past reports that concluded that SNB or LIA had no benefit in terms of knee function or length of hospital stay [
23,
28,
29].
It has been reported that the rate of peripheral nerve injury is 2.9/10,000 for FNB and 2.4/10,000 for SNB, and the incidence of permanent nerve damage is 1.5/10,000 [
30]. Sciatic nerve injury is also a generally known complication after TKA, with an incidence of 1.3 to 2.2% [
31,
32]. Thus, LIA is a relatively safe anesthetic technique for pain control after TKA. The occurrence of falls did not differ significantly between the two groups after TKA. Spanghel et al. [
22] found that four patients in the SNB group and no patients in the LIA group fell after TKA, and one patient suffered from a lumbar vertebral fracture after a fall. Tanikawa et al. [
18] reported that one patient in the LIA group and one in the SNB group fell after TKA. The patients in each group were not permitted to ambulate without assistance from nurses or physiotherapists to prevent falls. Furthermore, the duration of the motor block of toe motion in the LIA group was less than that in the SNB group, and the difference was statistically significant. Nagafuchi et al. [
20] found that one patient in the LIA group fell after surgery. Although the results of this meta-analysis indicated that there was no significant difference between SNB and LIA in terms of fall, a larger sample may have shown a trend toward more falls among patients who underwent FNB combined with SNB.
There were several limitations to this meta-analysis: (1) only seven RCTs were included, and the sample sizes in each trial were not large, which could affect the final results; (2) the duration of follow-up in some studies was unclear, and long-term follow-up was necessary for this analysis; (3) the publication bias that existed in the meta-analysis also influenced the results; (4) variations in the methods for obtaining, preparing, and applying the perioperative anesthetic protocol currently constitute a limitation to performing any comparisons between studies; (5) there is gross variability in SNB and FNB techniques (single-shot or continuous), location and needle approach and in the concentration, and volume and frequency of local anesthetic administered; (6) no studies applied the postoperative recovery scale, and high-quality studies that include a multi-domain quality of recovery assessment tool are preferred.
Conclusions
In conclusion, there were no differences in pain scores with rest at 24 h, morphine consumption, active knee flexion, the occurrence of fall, and PONV between the groups. Although some analgesic efficacy at 12 and 48 h were seen with the use of combined femoral and SNB, these were unlikely to be of clinical importance. LIA may offer a practical and potentially safer alternative to SNB. Further high-quality RCTs are needed to identify the optimal dose of LIA for reducing pain after TKA.
Acknowledgements
No funding was required for this retrospective study.