Analgesic efficacy of local versus proximal nerve blocks after hallux valgus surgery: a systematic review

Hallux valgus (HV) or bunion is a progressive deformity of the first ray of the foot that causes lateral displacement of the proximal phalanx on the metatarsal head [1]. The overall prevalence of bunion in the adult population is 23% [2]. In Australia, 82.3% of bunions are found in females and 8.50% are in those ≥ 45 years old [2]. Australians see a GP for bunions 4.2% per 10,000 encounters [3].

Conservative methods can be used to control HV, but they do not repair the deformity. Surgery offers a potentially permanent solution [1]. Corrective surgery for HV is a common elective operation. In 2007, bunion surgery was the second most prevalent performed operation (20.8%) among Australian podiatric surgeon graduates [4].

Different studies have employed bunion surgery and preoperative injections to measure analgesic effectiveness. Most bunionectomy patients are healthy, but they have chronic, severe pain [5]. Bunions require soft tissue and bone surgeries [6]. Due to the good health of patients, studying analgesic effects in bunionectomy may be done with little confounding from participant health, and results can be expanded to many other procedures due to their parallels with bunionectomy [7]. Preoperative injections can block peripheral nerve inputs early after surgery and avoid central hyperexcitability, which can amplify local anaesthetic (LA) effects [8]. Central sensitisation increases the excitability of medullary and spinal dorsal horn neurones through a cascade of events. This phenomenon happens due to the nerve or tissue injury irrespective to the general anaesthesia and causes progressively worsening pain after surgery [8]. Increases in nociceptor activity can lead to long-term hyperexcitability in the nervous system and amplification of pain, hence preoperative regional blocks in surgeries such as bunionectomy can block this activity in peripheral nociceptors and yield better outcomes [8].

This evaluation used local anaesthetics (LAs) to give regional blocks. LAs decrease neuronal excitation and conduction by raising depolarisation thresholds [9]. Lidocaine and levobupivacaine are LAs typically used for regional blocks. Regional blocks for bunion surgeries in this review included popliteal blocks, ankle blocks and local blocks (i.e., Mayo and peri-incisional blocks) [9]. Popliteal blocks target the sciatic nerve prior to its branching into the common peroneal and tibial nerves. An ankle block targets the posterior tibial, saphenous, superficial peroneal, deep peroneal, and sural nerves. Local nerve blocks, such as Mayo and peri-incisional, anaesthetize the nerve branches around the first ray [10].

Regardless of surgical approach, postoperative (bunionectomy) pain is common, hence localised blocks are important. Local anaesthetic (LA), opioids, or N-methyl-D-aspartate (NMDA) receptor antagonists are utilised to block afferent pathways and disrupt pathological pain cycles [11]. In order to prevent opioid dependency and other undesirable consequences, recent focus has shifted from opioid to non-opioid analgesic regimes [11]. Administering a regional LA block is a non-opioid approach to decrease bunionectomy pain.

The current systematic review aimed to compare and assess the analgesic efficacy of the proximal (popliteal and ankle) blocks and local (Mayo and peri-incisional) blocks in patients undergoing HV procedures. The objective was to establish recommendations for the management of acute postoperative pain in patients with HV.

The protocol was registered with PROSPERO (registration number: CRD42022307974). This quantitative systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [12] (Additional file 1:Appendix 1) standards (National Institute for Health and Care Research, n.d.).

The databases were searched from their inceptions till December 29, 2021. Missed studies were found using Google Scholar. Article reference lists were also searched. Search terms were: Analgesic effect, anaesthetic, ankle block, popliteal block, Mayo block, peri-incisional block, bunion, hallux valgus, pain treatment, postoperative pain. These phrases and synonyms were combined using Boolean operators ('AND,' 'OR,' and '*'). When the full text was unavailable or there was missing data, associated authors were contacted to discover another research. Additional file 1: Appendices 2A-F include the database search strategy.

Articles were selected using the following criteria: English-language peer-reviewed observational studies and clinical trials having at least 20 participants. The included trials involved adults over 18 who could describe their discomfort and had a bunionectomy. Entries up to December 2021 was included. In this evaluation, pure LAs were injected preoperatively to reduce pain. Mayo and peri-incisional blocks were local; ankle and popliteal blocks were proximal. Pain treatment strategies that combined analgesics or corticosteroids with LAs, continuous infiltration or recurring bolus infiltration of LAs, and post-surgical anaesthetic injections were eliminated. Measurement techniques were used to categorise experiments for synthesis. The included trials examined pain using a visual analogue scale (VAS) ranging from 0 to 10 cm or 0 to 100 mm, where 0 indicated no pain and 10 or 100 indicated the most severe pain [13]. In the included trials, 0 represented no pain and 10 represented severe pain [14].

EndNote X9 (Thomson Reuters, Carlsbad, CA, USA) was used to filter titles and abstracts [15] and remove duplicates. Each record was examined using the study criteria. This systematic review used full-text publications. Each stage was evaluated by the author.

The reviewer constructed a Microsoft Excel table to gather the following data from the papers: Name, country, patient demographics (mean age and gender), research design, intervention and comparator group features, LA injection techniques, continuous or bolus injection, preoperative or postoperative injection, LA dose, LA injection route, and tourniquet appliers (GA). Patient main characteristics, patterns of LA administration for postoperative pain, mean change in pain scores on VAS or NRS, percentage of pain-free participants, time to first rescue analgesia, time to mobilisation, pethidine consumption, time to first rescue analgesic, tramadol consumption, number of PCA bolus demands, nausea, and vomiting were also studied. If data from a trial was available at multiple times throughout each preceding period, all data was retrieved and compared. WebPlotDigitizer was used to extract data from graphs [16]. Table data was used throughout the review.

The studies were appraised using the revised Cochrane risk of bias 2 methodology [17]. One person assessed quality. RoB 2 includes randomisation bias, intervention variations, missing outcome data, outcome measurement, and outcome selection. The same methodology was applied to each study, separately. Synthesis was carried out using narrative assessment findings. Overall risk of bias was defined as the greatest risk of bias in any of the investigated domains (Table 1 and Fig. 4).

Inferential data analysis was not appropriate given the heterogeneity of treatments, locations, research designs, and outcome measures [23]. The author utilised descriptive analysis with a quantitative methodology to generate tables and graphs. The studies were categorised by their outcome measuring tools and individually assessed.

The primary analysis included continuous variables such as the proportion of patients with no postoperative discomfort or the average VAS or NRS score. The author used the STATA automation tool [24] to build forest plots between intervention and control. Due to study variations, comparing forest plot from different study results was not possible.

Databases produced 476 studies. 37 duplicate studies were eliminated. 365 papers were removed after reading titles and abstracts, and 74 full-text articles were included. 69 papers were excluded due to non-matching interventional groups (3 studies), no demographic matching (43 studies), comparison of different LA medications (11 studies), or non-pain outcomes (12 studies). Finally, five articles fit the review [18‐22, 25] (Additional file 1: Appendices 3A-E) Fig. 1 depicts the PRISMA flow diagram for this systematic review. Additional file 1: Appendix 4 contains citations and reasoning for articles rejected during full-text screening.

All relevant studies were hospital-based randomised trials (Table 2). Two studies administered ankle blocks [21, 22], one article explored local blocks [18], one research compared local blocks to ankle blocks [19], and one study compared the popliteal block to ankle blocks [20]. None of the final publications on local blocks addressed Mayo (Additional file 1: Appendices 3A—B).

The Cochrane library's RoB 2 tool was used to identify bias in each listed study. Figures 2 and 4 summarise the investigations. Although all five articles were randomised, only three showed sufficient randomisation quality. Five studies adequately handled missing outcome data. Other RoB 2 elements, including intervention deviation, outcome measurement, and result selection, showed a high risk.

In total, five studies involving 459 cases ranging in age from 20 to 72 years were studied in this review. Among the cases, at least 80% were female. Only one study had no control [20]. Three studies had a sample size of greater than 90 participants, Su et al. [19], included 75 participants, whereas Migues et al., included 51 participants. Further details regarding these studies are available in Additional file 1: Appendices 2A—E.

Although computing cumulative evidence was not practical in this descriptive analysis, a summary bar chart was created to analyse the overall risk (Fig. 4). The chart indicated that the overall risk level in this study was quite high (Fig. 4).

The current systematic review compared the analgesic efficacy of proximal (popliteal and ankle) to local (Mayo and peri-incisional) blocks in HV surgery patients. This analysis included five trials assessing regional block effectiveness, with 459 individuals aged 25 to 72. Regarding demographic characteristics of the included studies, the study by Su et al. [19] had the smallest sample size (24 participants) in one of its two intervention groups, while Gadek et al. [18] had the largest population size, with 118 participants (59 in each group). There was a higher proportion of females than males in three of the five included studies (Table 2), while the other two studies also reported this higher proportion in their intervention groups (Additional file 1: Appendices 2C—D). The lowest and highest proportions of females to males were 24:6 and 29:1, respectively, both of which belonged to the intervention groups of Turan et al. [21]. This study also included the youngest population (mean age; 47.0 ± 13.3 years old) [21], whereas the Migues et al. [20] study contained the oldest age population (61.0 ± 11.0 years old). The key findings of the present review were that for postoperative pain management blocking peripheral nerves using LA was more effective than not blocking at all. In bunionectomy patients, ankle blocks were equivalent to popliteal blocks and better than peri-incisional blocks. Some of the included trials showed that an ankle block reduced mood problems during the first six POH, the need for rescue analgesics, and postoperative nausea/vomiting. The next paragraphs discuss these findings.

In HV surgical patients, ankle blocks were more effective than local blocks or a control (no blocks) [19, 22]. An ankle block before GA was more effective than a placebo, according to Özhan et al. [22]. In this study, postoperative pain was assessed for 12 POH, and an ankle block decreased pain (WMD: -2.92 VAS, 95% CI: -3.13, -2.71). Su et al. [19] compared ankle nerve blocks to peri-incisional blocks and controls. Activity and rest discomfort NRS ratings were recorded at 6, 12, 24, and 36 POH. The study reported that pre-treatment ankle nerve blocks were better to peri-incisional blocks and control up to six POH. Even though two of the five investigations corroborated this effectiveness [19, 22], Turan et al. [21] showed that an ankle block did not significantly reduce postoperative pain compared to saline (Additional file 1: Appendix 3D). However, the authors still found that an ankle block reduced the requirement for intraoperative GA. A reduction in GA demand intraoperatively tends to be better systemically for the patient in the long run [11], thus although Turan et al. [21] did not conclude that an ankle block played a major influence postoperatively, it did intraoperatively. Consequently, it could be asserted that ankle blocks provide greater postoperative pain management than peri-incisional blocks after bunionectomies.

The only research to explore the popliteal block, found that it was equally effective as an ankle block in treating postoperative pain. Both groups were tracked for 24 POH. The lack of a control group in this study makes it impossible to compare these results with those from other investigations [26]. Small study size (51 individuals), older age cohort [26], and simultaneous foot operations potentially affect the accuracy of this evaluation [13].

Local (peri-incisional) blocks were assessed as an alternate strategy for controlling postoperative pain after HV correction surgery. Su et al. [19] found a local block to be more effective than none. Local (peri-incisional) blocks reduced activity and rest pain up to 12 POH, according to research [2], and at six POH had maximal impact (WMD: -1.90 NRS, 95%, CI: -3.17, -0.63). This research still favoured ankle blocks for postoperative pain management. Gadek et al. [18] only evaluated peri-incisional blocks with the longest follow-up time (72 POH). Their investigation showed peri incisional blocks are better than controls. Local (peri-incisional) block was effective for eight POH (WMD: -4 VAS, 95% CI: -4.51, -3.49). It should be noted that this was the only study that administered a spinal block instead of GA. Therefore, both investigations found peri-incisional blocks useful for pain management following bunionectomy, with Su et al. [19] showing ankle blocks were more effective.

Özhan et al. [22] and Su et al. [19] had less important but still meaningful results. These have been categorised as secondary outcomes in this review (Tables 8 and 9). Özhan et al. [22] found that ankle nerve block combined GA reduced the demand for pethidine and tramadol compared to GA alone. In the intervention group, the time to first rescue analgesic usage and mobility improved. Ankle block reduces nausea and vomiting. Notably, trauma, stress, and postoperative immobilisation can also produce similar symptoms [27]. Su et al. [19] showed considerably less mood disturbance in ankle block patients compared to peri-incisional block patients and control groups after six POH, but no significant changes thereafter. No significant difference in disrupted sleep after surgery was seen between the three groups. Ankle blocks lowered postoperative fentanyl usage and patient demand during the first 36 POH. Overall, both trials supported regional blocks, especially ankle blocks, for controlling postoperative pain following bunionectomy.

Randomization in included trials reduces probable confounders, yet it can still contribute to systematic review heterogeneity and confounding [28]. For instance, people with higher BMIs may feel greater discomfort [29], as well as red-haired patients, as they are harder to anaesthetize [30]. These variables have not been discussed in part of the included studies properly; however, they can still play a confounding role. Other heterogeneities among the research include gender, age, anaesthetic drugs and procedures, procedure choice and applied fixation, follow-up period, and bunion severity before operation. These parameters were sometimes studied, although the findings differed. For example, the studies have different female and age proportions. Generally, bunions are more prevalent among females over the age of 18 [1, 31], and bunionectomy in individuals below 18 is uncommon [32]. However, despite these overall trends being present in the higher proportion of females than males and age ranges in participants across all samples, the proportions varied significantly among the included studies, suggesting that they may still have played a confounding role [28]. Gadek et al. used spinal anaesthesia instead of oral or IV GA [18]. In other research, individuals who had spinal anaesthesia instead of GA reported less discomfort and problems [33]. Gadek et al. [18] reported intrathecally injecting 12.5 mg of bupivacaine 5 mg/ml. Spinal anaesthesia can considerably lessen postoperative pain. The mechanism of action and duration depend on the fat and protein content of the administered medication, which regulates its nervous system penetration [34].

Unlike popliteal block, spinal block inhibits the sciatic nerve and autonomic nervous system more proximally and produces more side effects and patient dissatisfaction [35].

Therefore, in the literature, spinal anaesthesia was utilised largely for anaesthetic purposes and its postoperative analgesic effects were not examined [36].

A spinal block in Gadek et al. 's investigation [18] may have skewed the systematic review's findings [33]. Different experiments employed different analgesics and dosages. For instance, Özhan et al. [22] injected midazolam and fentanyl before an ankle block and Pethidine (0.5 mg/kg) was also given IV as a rescue analgesic. In the trial by Gadek et al. [18], patients received IV ketoprofen (100 mg) and paracetamol (1000 mg) three times after surgery, commencing at four POH, with 7.5 mg of morphine sulphate as a rescue analgesic. Su et al. [19] reported that patients received fentanyl through PCA a few hours postoperatively at 1 g/kg and 0.33 g/kg. Block analgesic effectiveness may have been affected by the analgesic activity and half-life of several medications. This can bias trials with and without analgesics [25]. Follow-up should be appropriate for the half-life of the LAs utilised; otherwise, changes in LA efficacy may confound regional block results [26]. The timing of LAs before or after GA [37] or tourniquet administration [31], expertise level of the surgeon or person providing the block [38], and kind of bunionectomy procedure [39] might also matter. Among the articles included in this study, only Gadek et al. [18] explains the type of bunion surgery utilized (Table 3), which is the chevron osteotomy. However, over a hundred distinct bunionectomy procedures have been recorded [40]. The choice between these operations depends on the degree of the deformity and surgeon's preferences. Most patients will have a corrective osteotomy, with or without an additional soft tissue procedures (Fig. 2). In Australia, both the chevron and scarf osteotomies are regularly performed. Mild to moderate malformations are often treated with a distal metatarsal osteotomy, however severe deformities may necessitate a proximal osteotomy or tarsometatarsal joint fusion. In cases of severe arthritis (hallux rigidus), a fusion of the MTPJ may be recommended. Simple excision of the bony prominence (bunionectomy) is uncommon due to the high likelihood of recurrence and the dissatisfaction of patients with the outcome [40]. Infrequently are soft tissue operations performed alone; they are more often employed as an adjuvant to osteotomy [40]. Additionally, the use of minimally invasive surgical procedures is on the rise, although most studies have found no change in patient function, complication rates, or clinical outcomes when compared to conventional approaches [41].

Among these different surgical procedures, only the percutaneous chevron/Akin osteotomy has debatable reduction in the postoperative pain level [42‐45]. A study of 25 articles on hallux valgus surgery found that the surgical methods had no clinical impact on gait, quality of life, or patient satisfaction [46]. Even the type of internal fixations (bioabsorbable magnesium vs titanium screws) did not make difference in the level of postoperative pain [47, 48].

Additionally, extended tourniquet periods at high pressures result in increased pain, opioid usage, and hospital stay. It is probable that putting tourniquet pressures on limb occlusion pressure (LOP), will increase the safety margin of tourniquets [49].

Overall, different variables may remain hidden in the included studies while skewing the findings of the systematic review [50]. Therefore, included research should address these issues as much as feasible.

This review's results will benefit patients by reducing their postoperative pain. This knowledge will also benefit surgeons, anaesthetists, nurses, and rehabilitation practitioners [11].

This is the first systematic review to investigate the effects of preoperative LA on postoperative pain in HV surgery, however bias and limitations still exist.

In terms of bias, Gadek et al. [18] and Ozhan et al. [22] pose some concerns. The reviewer also believes three other research papers [19‐21] raise high risk. Gadek et al. [18] and Ozhan et al. [22] had intervention discrepancies (where planned patients declined to participate in the study and insufficient information regarding the protocol was available). Also, neither Turan et al. [21] nor Migues et al. [20] were double-blind. This raises the likelihood of measuring errors or intervention deviation [28]. These studies didn't mention their chosen analytic strategy, which might affect outcome selection. Su et al. [19] also faced risks, including deviating from the planned intervention (it is unclear if participants knew about it), outcome measurement (no information on the assessor), and result selection (the person performing the intervention was not blinded to the project). Overall, these hazards affect the review's dependability.

Regarding limitations, it is to be noted that the current review has limitations arising from two sources. Firstly, in this field there is a scarcity of relevant papers to study, with only five deemed to meet the inclusion criteria for the current review. According to the study by Pannucci et al., this is due to the difficulties associated with surgical randomisation, blinding, patient variability or control, and this is a significant drawback [51]. Secondly, there were limitations in the five studies on which the current review is based. There were heterogeneity factors among the included studies which precluded any inferential analysis [52]. In a descriptive analysis, the efficacy was determined by assessing the frequency of supportive interventions, though this frequency cannot be accurately assigned because it may be attributable to factors other than the intervention [28]. Given the relatively small sample size in part of included studies and the high-risk levels, our findings should be interpreted with caution [53].

Nevertheless, the present review is a valuable contribution to bunionectomy pain reduction and has transferability to comparable surgical procedures. It also offers advice for future low-risk investigations.