Efficacy of subtalar arthroereisis and Kidner procedure for adolescent flexible flatfoot with painful accessory navicular: A systematic review and meta-analysis

Abstract

Background:

Flexible flatfoot with painful accessory navicular poses a significant therapeutic challenge in adolescents, with no consensus on optimal surgical management. This meta-analysis evaluates the efficacy of subtalar arthroereisis (STA) combined with the Kidner procedure for this condition.

Methods:

We systematically searched 6 databases (PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang) up to (insert date). Eight studies involving 249 participants met inclusion criteria. Standardized mean differences (SMDs) with 95% confidence intervals were calculated for radiographic parameters (Meary’s angle, talus-first metatarsal angle [T1MT], talonavicular coverage angle [TCA]), pain (visual analog scale), and function (American Orthopaedic Foot & Ankle Society Score [AOFAS]). Heterogeneity and publication bias were assessed using I² statistics and Egger’s test.

Results:

The combined procedure significantly improved all measured outcomes: Meary’s angle (SMD −3.71, 95% confidence interval, −4.90 to −2.51), T1MT (SMD −2.63, −3.69 to −1.57), TCA (SMD −2.65, −4.29 to −1.01), visual analog scale (SMD −4.36, −5.17 to −3.54), and AOFAS (SMD 4.85, 4.25–5.44). Compared to STA alone, the combination showed superior correction of T1MT (SMD −0.35, −0.66 to −0.04) but no significant differences in other parameters (AOFAS: SMD 0.80, −0.45 to 2.05; TCA: SMD −0.68, −1.67 to 0.31).

Conclusion:

STA with Kidner procedure effectively corrects deformity and improves function in adolescent flexible flatfoot with accessory navicular. While superior to STA alone in T1MT correction, most outcomes were comparable between approaches. These findings support the combined technique as a viable surgical option for this challenging condition.

1. Introduction

Flexible flatfoot is a common progressive foot deformity in children, with typical clinical manifestations including collapse of the medial arch, heel valgus, and forefoot abduction.^[1,2] Although most pediatric flexible flatfeet improve spontaneously with age, some children experience persistent pain, gait abnormalities, and motor dysfunction, which may even extend into adulthood.^[3,4] Similarly, the accessory navicular (AN) is one of the most common accessory bones in the foot, and the clinically symptomatic AN often causes persistent medial midfoot pain and tenderness.^[5–7] Recent studies have shown an association between AN and flatfoot. The AN may cause relaxation of the posterior tibial tendon, weakening its support for the medial arch and hindfoot inversion, thereby altering the biomechanics of the arch and promoting the development of flatfoot.^[8,9] At the same time, the flatfoot deformity can further lead to or exacerbate symptoms associated with the AN.^[9] Epidemiological studies indicate that the prevalence of adolescent flexible flatfoot is approximately 20%,^[10] with about 12% of these patients having symptomatic AN.^[11]

Currently, in clinical practice, subtalar arthroereisis (STA) is an effective treatment option for adolescent patients with flexible flatfoot.^[12] This surgery involves placing an implant into the sinus tarsi to restore the medial longitudinal arch, thereby effectively correcting the flatfoot deformity.^[13,14] For painful AN, the Kidner surgery and its modified versions are the current standard treatment options, which can effectively alleviate local symptoms by directly excising the symptomatic AN.^[15,16] However, for adolescent flexible flatfoot with painful AN, there is still no consensus on the choice of surgical method. Fang, K. et al suggested that STA combined with Kidner surgery effectively alleviates pain and improves foot function in children with flexible flatfoot and painful AN.^[9] On the other hand, the study by Gan T.J. et al indicated that STA alone could also achieve good outcomes for these patients, without the need for Kidner surgery.^[17]

In view of this, the present study conducted a systematic review and meta-analysis of relevant literature to comprehensively evaluate the clinical efficacy of STA combined with Kidner surgery for treating flexible flatfoot with painful AN, aiming to provide more reliable evidence for clinical decision-making.

2. Materials and methods

2.1. Standard protocol approvals, registrations, and methodological

This meta-analysis was conducted in strict accordance with the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions, following the reporting standards of the preferred reporting items for systematic reviews and meta-analyses (PRISMA).^[18] Additionally, the methodological quality of this systematic review was assessed using the AMSTAR (A Measurement Tool to Assess systematic Reviews) checklist.^[19,20] The study protocol has been registered on the PROSPERO platform, with the registration URL (https://www.crd.york.ac.uk/prospero/.). The checklist is showed in Table S1, Supplemental Digital Content, https://links.lww.com/MD/Q380.

2.2. Search strategy

Up to October 1, 2024, two independent investigators conducted searches in the following electronic databases: PubMed, Embase, Web of Science, Cochrane Library, CNKI Data, and WanFang Data. The search results were then cross-checked. No language or time restrictions were applied during the search; the search terms were limited only to patient-related and surgical-related terminology to avoid missing potentially relevant studies.

The specific search terms and strategy for PubMed are as follows: (“Flatfoot [Mesh]” or “Accessory navicular bone [Mesh]” or “flexible flatfoot or flat foot or talipes valgus or splayfoot or talipes calcaneovalgus or flat feet or pes plan* or planovalgus or Acquired Adult Flatfoot Deformity or flat footedness or longitudinal arch or fallen arch or pronat* or Flexible Adult Acquired Flatfoot or painful AN or symptomatic AN or AN syndrome or symptomatic navicular [Title/Abstract]”) and (“Subtalar Joint [Mesh]” or “Subtalar Arthroereisis or STA or SA or Subtalar Joint Arthroereisis or Subtalar Joint immobilization or extraosseous talotarsal stabilization [Title/Abstract]” or “kidner surgery or kidner procedure [All fields]”; Table S2, Supplemental Digital Content, https://links.lww.com/MD/Q380).

2.3. Inclusion criteria and exclusion criteria

2.3.1. Inclusion criteria

1. Study population: adolescents with flexible flatfoot and painful AN who underwent STA combined with Kidner procedure.

2. Intervention group: STA combined with Kidner procedure.

3. Control group: baseline treatment involving either only STA or preoperative indicators for combined surgery.

4. Primary outcome measures: the efficacy of STA combined with Kidner procedure was evaluated using standardized mean difference (SMD) and its 95% confidence interval (CI).

5. Study design: prospective or retrospective cohort study.

2.3.2. Exclusion criteria

1. Study population: patients who underwent only STA or only Kidner procedure, as well as those with only painful AN or flexible flatfoot, were excluded. Additionally, duplicate publications or repeated reports on the same regional population were excluded.

2. Study type: reviews, case reports, conference guidelines, commentary articles, animal studies, literature without full-text, and case-control studies were excluded.

3. Study content: studies without original data, without explicit inclusion criteria or surgery-related information, or with unusable data were excluded.

2.4. Study selection and data extraction

2.4.1. Study selection

According to the established systematic search strategy, the relevant studies retrieved from electronic databases were imported into Endnote X9.1 for organization, and duplicate studies were removed. Subsequently, 2 researchers independently and blindly screened the titles and abstracts of the studies. After the initial screening, both researchers cross-checked the results. In case of disagreement during screening, inclusion was determined through discussion or arbitration by a third researcher. To avoid missing any relevant studies, additional searches were manually conducted in Google Scholar by entering keywords, and citations from previous related systematic reviews and meta-analyses were reviewed. If multiple articles were published from the same cohort study, only the one with the largest sample size or the most complete information was included for analysis.

2.4.2. Data extraction

After downloading and thoroughly reviewing the full texts, the research team developed a data extraction form through discussion. This form was used to systematically collect key information from the studies ultimately included in the analysis. The extracted data included the following: first author, publication year, region, observation period, sample size, average age, gender ratio, study design, follow-up period, surgical method, and relevant outcomes. The outcomes measured included the American Orthopaedic Foot & Ankle Society Score (AOFAS), Meary’s angle (MA), visual analog scale (VAS), talus-tirst metatarsal angle (T1MT), talus-second metatarsal angle (T2MT), talonavicular coverage angle (TCA), pitch angle (PA), calcaneal inclination angle (CIA), talar declination angle (TDA), and the continuous data of these outcomes.

2.5. Quality assessment

Two reviewers independently and systematically assessed the methodological quality of the included studies using the Newcastle–Ottawa quality assessment scale (NOS), which is applicable for non-randomized controlled studies.^[21,22] The scale assesses study quality from 3 aspects: selection of study population, comparability between groups, and assessment of exposure/outcome. The total score is 9 points, with a score of ≥8 indicating high-quality (low risk of bias).^[23] If there were disagreements between the 2 reviewers on the score, the final quality of the study was determined through discussion and consultation with a third reviewer.

2.6. Statistical analysis

This study conducted the meta-analysis using Stata 17.0 software. The continuous data were presented as SMD and its 95% CI. Given the small sample size, data integration was performed using Hedges’s g.^[24,25] Heterogeneity was assessed using the I² test, where P < .05 or I² >50% indicated significant heterogeneity.^[26] For high heterogeneity data, Hedges’s g random effects model was used; for low heterogeneity data, the inverse variance fixed effects model was applied.^[27] Publication bias was evaluated using the Egger test and funnel plots; a P-value < .05 in the Egger test suggested potential publication bias.^[28] The robustness of the results was assessed using leave-one-out analysis, which was considered robust if no significant changes were observed.^[29]

3. Result

3.1. Literature search and study characteristics

A total of 3479 records were identified during the systematic literature search. After excluding 509 duplicate records, we screened the titles and abstracts of the remaining 2970 records and identified 91 articles for full-text review. Subsequently, we excluded 2 citations for which the full-text was unavailable, resulting in 89 studies selected for full-text evaluation. During the full-text evaluation, we excluded 81 articles, including those with nonmatching surgical methods, reviews or meta-analyses, and those with insufficient outcome data (Table S3, Supplemental Digital Content, https://links.lww.com/MD/Q380). Finally, a total of 8 studies^{[9,14,17,30–34]}, involving 249 participants, met the inclusion and exclusion criteria for this meta-analysis (Fig. 1).

Figure 1.

Study selection flow diagram based on PRISMA guidelines. PRISMA = preferred reporting items for systematic reviews and meta-analyses.

Table 1 presents the basic characteristics of the included studies. The publication dates of the studies ranged from 2012 to 2023, with 87.5% (7/8) of the studies^{[9,17,30–34]} published after 2018. Among the included studies, 75% (6/8)^[17,30–34] were conducted in China, while 25% (2/8)^[9,14] were conducted in the United States. In this meta-analysis, 87.5% (7/8) of the studies^{[9,14,17,31–34]} reported the outcomes of combined surgery before and after treatment, while 37.5% (3/8) of the studies^[17,30,33] compared the efficacy of combined surgery with STA alone. Additionally, 75% (6/8) of the studies^{[9,17,30–33]} had an NOS score > 8 (Fig. 2), indicating a low risk of bias.

Table 1.

Characteristics of studies included in meta-analysis.

First author	Publication year	Region	Observation period	Sample size		Average age (yr)		Gender (M/FM)		Study design	Follow-up period	Surgical method		Outcomes
				E	C	E	C	E	C			E	C
Wu, Y.*	2021	China	2013.1–2017.1	16 (21 ft.)	24 (33 ft.)	15.25	15.87	11/5	16/8	PS	24 mo	STA + M-KC	STA	AOFAS, CI, T1MT, T2MT, TCA, TDA, VAS, MA
Gan, T.J.	2023	China	2017.8–2021.8	35 (35 ft.)	37 (37 ft.)	11.7	11.9	19/16	17/20	RS	29 mo	STA + Kidner	STA	AOFAS, PA, HAA, KA, MA, OAFQC, TDA, TM1T, TM2T, TCA, VAS
Deng, M.M.*	2023	China	2018.8–2021.8	17 (17 ft.)	16 (16 ft.)	10.23	10.25	11/6	11/5	RS	19.6 mo	STA + Kidner	STA	AOFAS, HV, MA, PA, T1MT, T2MT, TCA, VAS
Garras, D.N.	2012	USA	2003.4–2010.4	20 (23 ft.)		18		6/17		RS	53.9 mo	STA + M-KC		MA, AP, AOFAS, VAS
Zhang, D.X.*	2018	China	2014.12–2016.10	17 (24 ft.)		13.35		6/11		PS	13.6 mo	STA + Kidner		AOFAS, CI, TCA, T1MT, TCA, VAS
Ma, F.Q.*	2020	China	2017.10–2019.1	29 (38 ft.)		13.4		17/12		RS	18.6 mo	STA + Kidner		AOFAS, CI, MA, TCA, T1MT, TM2T, TCA, VAS
Liu, W.Z.*	2022	China	2017.6–2019.10	13 (17 ft.)		11.3		5/8		PS	6–18 mo	STA + M-KC		AOFAS; CE; PA; TCA; TMA; VAS
Fang, K.	2023	USA	2018.1–2022.1	25 (40 ft.)		11.28		23/17		RS	15.2 mo	STA + M-KC		AOFAS, APTMT, MA, PA, TCA, TCA, TMA, VAS

AOFAS = American Orthopaedic Foot & Ankle Society Score, AP = anteroposterior, C = control group, CE = calcaneal eversion angle, CIA = calcaneal inclination angle, E = experimental group, HAA = Hindfoot Alignment Angle, HV = Hallux Valgus, KA = Kite’s Angle, MA = Meary’s angle, M-KC = modified Kidner-Cobb procedure, OAFQC = Oxford ankle foot questionnaire for children, PA = pitch angle, PS = prospective study, RS = retrospective study, STA = subtalar arthroereisis, T1MT = talus-first metatarsal angle, T2MT = talus-second metatarsal angle, TCA = talonavicular coverage angle, TDA = talar declination angle, TMA = talometatarsal angle, USA = United States of America, VAS = visual analog scale.

^*indicates that the literature sources are from Chinese databases.

Figure 2.

Methodological quality scores of the included studies based on the NOS tool. NOS = Newcastle–Ottawa quality assessment scale.

3.2. Outcomes

Figure 3 shows the summary forest plot for all outcomes of this meta-analysis.

Figure 3.

Forest plot of summary of outcomes. LL = lower limit, SMD = standardized mean differences, UL = upper limit.

3.2.1. Preoperative and postoperative indicators for STA combined with Kidner surgery

A total of 7 studies^{[9,14,17,31–34]} summarized the efficacy analysis of STA combined with Kidner surgery for treating flexible flatfoot with painful AN. Meta-analysis results showed significant differences in the comparison before and after combined surgery for PA (SMD, 1.31; 95% CI, 0.86–1.76), AOFAS (SMD, 4.85; 95% CI, 4.25–5.44), MA (SMD, −3.71; 95% CI, −4.90 to −2.51), VAS (SMD, −4.36; 95% CI, −5.17 to −3.54), T1MT (SMD, −2.63; 95% CI, −3.69 to −1.57), T2MT (SMD, −3.46; 95% CI, −5.45 to −1.47), and TCA (SMD, −2.65; 95% CI, −4.29 to −1.01; Figs. S1–S7, Supplemental Digital Content, https://links.lww.com/MD/Q379). However, we found that the differences in CIA (SMD, 2.32; 95% CI, −0.81 to 5.45) and TDA (SMD, −4.91; 95% CI, −9.87 to 0.05) before and after combined surgery were not statistically significant (Figs. S8 and S9, Supplemental Digital Content, https://links.lww.com/MD/Q379).

3.2.2. STA combined with Kidner surgery vs STA alone

Three studies^[17,30,33] compared the efficacy of STA combined with Kidner surgery versus STA alone for treating flexible flatfoot with painful AN. In our results, only Change. (▲) T1MT (SMD, −0.35; 95% CI, −0.66 to −0.04; Fig. 4) showed a significant difference between the 2 surgical techniques, indicating that the combined surgery group had a slight advantage over the STA alone group in correcting MA. However, no significant differences were found between the 2 surgical techniques for other outcomes, including Post. AOFAS (SMD, 0.80; 95% CI, −0.45 to 2.05), ▲PA (SMD, 0.26; 95% CI, −0.12 to 0.64), ▲MA (SMD, 0.80; 95% CI, −2.31 to 0.70), ▲TCA (SMD, −0.68; 95% CI, −1.67 to 0.31), ▲TDA (SMD, −1.11; 95% CI, −3.33 to 1.10), and ▲T2MT (SMD, −0.55; 95% CI, −1.34 to 0.23; Figs. S10–S15, Supplemental Digital Content, https://links.lww.com/MD/Q379).

Figure 4.

Forest plot of ▲T1MT comparing STA combined with Kidner surgery to STA alone using a random effects model. CI = confidence interval, SD = standard deviation, STA = subtalar arthroereisis, T1MT = talus-first metatarsal angle.

3.2.3. Sensitivity analyses and publication bias

To test the robustness of our outcomes, we performed sensitivity analyses for all outcomes using the leave-one-out method (Figs. S16–S31, Supplemental Digital Content, https://links.lww.com/MD/Q379), and most outcomes remained consistent. Additionally, we assessed potential publication bias using funnel plots (Figs. S32–S47, Supplemental Digital Content, https://links.lww.com/MD/Q379) and Egger’s test (Table 2), and adjusted for potential publication bias using Duval’s nonparametric trim-and-fill method (Table S4, Supplemental Digital Content, https://links.lww.com/MD/Q380).

Table 2.

Summary of outcomes.

Outcomes	Number of studies	Sample size	SMD (95% CI) with P-value	Egger’s P-value	I2, % (P-value)
Postoperative vs preoperative
AOFAS	7	183	4.85 (4.25, 5.44) with .00	.0003	51.45 (.01)
MA	5	157	−3.71 (−4.90, −2.51) with .00	0	91.15 (.00)
VAS	7	183	−4.36 (−5.17, −3.54) with .00	.0049	95.7 (.00)
T1MT	5	141	−2.63 (−3.69, −1.57) with .00	.005	90.96 (.00)
T2MT	4	134	−3.46 (−5.45, −1.47) with .05	.0001	96.67 (.00)
TCA	7	192	−2.65 (−4.29, −1.01) with .00	.0001	97.36 (.00)
PA	3	92	1.31 (0.86, 1.76) with .00	.894	47.98 (.08)
CIA	3	83	2.32 (−0.81, 5.45) with .15	0	98.35 (.00)
TDA	2	56	−4.91 (−9.87, 0.05) with .05	–	96.64 (.00)
STA + Kidner vs STA
Post. AOFAS	3	159	0.80 (−0.45, 2.05) with .21	–	90.79 (.00)
▲PA	2	105	0.26 (−0.12, 0.64) with .18	–	0.00 (.37)
▲MA	3	159	0.80 (−2.31, 0.70) with .30	.4287	94.67 (.00)
▲TCA	3	159	−0.68 (−1.67, 0.31) with .18	.9104	88.55 (.00)
▲TDA	2	126	−1.11 (−3.33, 1.10) with .32	–	96.53 (.00)
▲T1MT	3	159	−0.35 (−0.66, −0.04) with .03	.448	49.72 (.14)
▲T2MT	3	159	−0.55 (−1.34, 0.23) with .17	.7581	82.56 (.00)

AOFAS = American Orthopaedic Foot & Ankle Society Score, CI = confidence interval, CIA = calcaneal inclination angle, MA = Meary’s angle, PA = pitch angle, Post. = postoperative, SMD =  standardized mean differences, STA = subtalar arthroereisis, T1MT = talus-first metatarsal angle, T2MT = talus-second metatarsal angle, TCA = talonavicular coverage angle, TDA = talar declination angle, VAS = visual analog scale; ▲ = preoperative and postoperative changes.

3.2.4. Subgroup analyses

In our study, when the heterogeneity test results for the outcomes showed P < .05 or I² > 50%, we considered the outcome to have significant heterogeneity. To further explore the sources of heterogeneity, we conducted subgroup analyses on outcomes that involved ≥5 studies. The subgroup analysis results indicated that in the AOFAS, region [USA (SMD, 5.69; 95% CI, 4.79–6.59; I² = 0.0%); China (SMD, 4.52; 95% CI, 3.93–5.10; I² = 38.0%)] and mean age [≥ 13 years (SMD, 5.51; 95% CI, 4.77–6.24; I² = 0.0%); < 13 years (SMD, 4.43; 95% CI, 3.73–5.14; I² = 48.9%)] were potential sources of heterogeneity.

Moreover, patients from different regions (USA vs China) showed significant differences in the AOFAS (P = .03 < 0.05). Additionally, patients of different mean ages (≥ 13 years vs <13 years) had significant differences in AOFAS (P = .04), VAS (P = .03), T1MT (P = .01), and TCA (P < .01). Furthermore, patients with different follow-up period (≥ 24 months vs < 24 months) also exhibited significant differences in the T1MT outcome (P = .03; Table S5, Supplemental Digital Content, https://links.lww.com/MD/Q380).

4. Discussion

4.1. Principal findings and potential mechanisms

This meta-analysis aimed to explore the efficacy of STA combined with Kidner procedure in treating patients with flexible flatfoot and painful AN. Seven studies provided the results of related indicators before and after combined surgery.^{[9,14,17,31–34]} The results showed that, compared to preoperative levels, postoperative TCA, T1MT, T2MT, MA, and VAS significantly decreased, while PA and AOFAS significantly increased. Gan T.J. et al^[17] and Wu Y. et al^[33] indicated that TDA also significantly decreased postoperatively. Regarding CIA-related indicators, the studies by Wu Y. et al^[33] Zhang D.X. et al,^[34] and Ma F.Q. et al^[32] all demonstrated a significant increase in CIA after combined surgery.

Three studies^[17,30,33] compared the efficacy of STA combined with Kidner procedure versus STA alone. The meta-analysis results showed that T1MT was significantly lower in the combined surgery group, indicating that the combined surgery was superior to STA alone for this indicator. However, no significant differences were found for other integrated indicators. This result differed significantly from Wu Y. et al^[33] who found that in all cases, X-ray measurements showed significant reductions in TCA, T1MT, T2MT, VAS, MA, and TDA (P < .05), while CIA and AOFAS significantly increased (P < .05). In contrast, Gan T.J.^[17] reported no significant differences in VAS, AOFAS, Oxford ankle foot questionnaire for children scores, and radiographic parameters between the 2 groups at preoperative and final follow-up (P > .05). There were no differences in complications between the 2 surgery groups; however, STA alone showed significantly shorter operation time, smaller incision length, less intraoperative blood loss, and fewer fluoroscopic views compared to the combined surgery group (P < .05). Therefore, Gan T.J.^[17] suggested that the Kidner procedure might be unnecessary. Deng, M.M.,^[30] on the other hand, concluded that both procedures were effective for treating flexible flatfoot with painful AN, with STA alone having a minimally invasive advantage, whereas STA combined with Kidner procedure had better clinical efficacy.

Simple STA reduces the burden on the posterior tibial tendon in supporting the arch by controlling the abnormal movement of the talus.^[35] Additionally, AN-induced flexible flatfoot has significant reversibility in the early stages, as structural changes in the foot have not yet become irreversible.^[36] Therefore, at this stage, simple STA can limit talus movement mechanically, providing sufficient time and space for arch reconstruction. This is often sufficient to alleviate symptoms without the need for more complex combined surgery.^[37–39] In contrast, simple STA is relatively straightforward to perform, involves less surgical trauma, and does not require repositioning of the posterior tibial tendon or removal of the AN.^[40,41] This simplified surgical approach reduces surgical trauma and helps patients recover foot function more quickly. Therefore, for patients with relatively mild AN-induced flexible flatfoot, simple STA may be an adequately effective solution.^[38,42,43] This is also an important reason for the lack of significant differences in efficacy between the 2 approaches.

4.2. Strengths

First, this study included 8 cohort studies with a total of 249 participants. To our knowledge, this is the first meta-analysis focusing on the efficacy of STA combined with Kidner procedure for treating flexible flatfoot combined with painful AN. Second, we conducted a detailed analysis of radiographic changes before and after combined surgery and compared the efficacy of combined surgery with that of STA alone. Third, we conducted an extensive literature search and supplemented it through multiple approaches to identify all original studies that met the inclusion criteria, thereby minimizing publication bias and enhancing the reliability of the results. Fourth, the study strictly adhered to PRISMA guidelines and used the NOS scale for evaluation, which improved the quality and transparency of the meta-analysis, enhancing the validity and credibility of the results. Finally, the reliability of the study results was ensured by using the Egger test and applying the trim-and-fill technique for data evaluation and adjustment.

4.3. Limitations

Currently, there are limited studies worldwide on the use of combined surgery for treating flexible flatfoot combined with painful AN. As a result, the studies included in our analysis were from China and the United States, lacking clinical results from other regions. Additionally, only 3 studies compared the efficacy of combined surgery with STA alone, and the small sample sizes prompted us to use Hedges’s g model to combine effect sizes, enabling more accurate results. We also hope that more high-quality, high-evidence level clinical studies will be conducted in more regions in the future to verify our findings.

5. Conclusions

This meta-analysis demonstrates that STA combined with Kidner procedure has favorable surgical outcomes in treating flexible flatfoot and painful AN, particularly in PA, TCA, T1MT, T2MT, VAS, MA, and AOFAS. Compared to STA alone, the combined surgery showed better postoperative results in T1MT, while no statistically significant differences were found in the other meta-analysis results.

Author contributions

Conceptualization: Guanglong Zeng.

Data curation: Qingxiang Xie.

Formal analysis: Limin Cai.

Investigation: Yu Wu.

Methodology: Liu Zhang.

Software: Haiquan Mai.

Visualization: Guanglong Zeng.

Writing – original draft: Guanglong Zeng, Boyuan Su.

Writing – review & editing: Guanglong Zeng, Boyuan Su.