2.1 Study design

This systematic review and meta-analysis adhered to the 2020 updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.¹⁶

2.2 Literature search

A thorough search was performed across several electronic databases including PubMed, Scopus, Web of Science, the Cochrane Library of Randomized Trials (CENTRAL), and Google Scholar, spanning their inception to February 22nd, 2024. In line with recent guidelines,¹⁷ we limited our Google Scholar results to the first 200 entries for screening. Our search strategy targeted studies that contrast arthroscopic with open surgery techniques in treating lateral epicondylitis, using terms and Medical Subject Headings (MeSH) such as “lateral epicondylitis,” “tennis elbow,” “arthroscopy,” “open surgery,” and “comparative studies.” For a comprehensive search strategy, refer to Table S1. No language limitations were imposed. Further accuracy in our search was ensured by manually reviewing references in selected studies, checking PubMed's related articles, and performing a manual Google search using the study keywords.¹⁸ Exclusions were made for non-original studies (e.g., reviews, commentaries), studies on conditions other than lateral epicondylitis, studies lacking a comparison group, duplicates, and those with overlapping patient data.

2.3 Selection strategy

We used a detailed PICOS (Population, Intervention, Comparison, Outcomes, and Study Design) framework to define eligibility criteria.¹⁹ We included observational and experimental comparative studies, both randomized and non-randomized, involving patients with lateral epicondylitis requiring surgical intervention, comparing arthroscopic to open surgical methods, and documenting any post-surgical clinical outcomes. We verified the absence of overlap by reviewing the period of patient recruitment, country, and demographic details such as age and gender.

2.4 Data collection and outcome measures

The data collection form, created in Microsoft Excel by the lead author, was divided into three sections: the first recorded details about the studies and participants, the second focused on outcomes like functional elbow recovery measured via DASH, QuickDASH, and Mayo Elbow Performance Score (MEPS), and the third section evaluated the risk of bias in the studies.

The primary outcome focused on various aspects of elbow function recovery. This encompassed ratings from good to excellent, as well as instances of poor recovery, failure, and instances necessitating further surgeries or revisions. The evaluation of functional recovery utilized the DASH, QuickDASH, and MEPS scales. A good recovery was classified by scores of 20–39 on the DASH, 6–15 on the QuickDASH, and 75–89 on the MEPS.^20,21 An excellent recovery was indicated by a DASH score below 20, a QuickDASH score between 0 and 5, and a MEPS score ranging from 90 to 100 ^{20, 21}. Secondary outcomes were comprised of recurring pain, defined as pain resurfacing after at least one month of being pain-free, elbow motion range during flexion and extension, grip strength, postoperative pain measured via the visual analogue scale (VAS), arthroscopic observations of intra-articular loose bodies and noticeable synovitis, times related to returning to work and staying off work, duration of the operation, and the rate of complications. The final section addressed the risk of bias evaluation for the included studies.

2.5 Risk of bias assessment

Bias in randomized controlled trials was evaluated using the Cochrane Collaboration's Risk of Bias tool (RoB-2), while non-randomized studies were assessed through the ROBINS-I tool. Discrepancies were resolved by consensus or third-party adjudication.

2.6 Data synthesis and analysis

All statistical evaluations were conducted using STATA Software (Version 18, Stata Corp, USA). Prior to the meta-analysis, necessary data transformations were applied to standardize the reporting by converting median/range or interquartile range data into mean and standard deviation, employing validated equations.^22,23

For aggregating outcomes, the last observation carried forward (LOCF) method was used to address data heterogeneity across different follow-up periods and to reduce the risk of data omission.²⁴ Both the log odds ratio (logOR) for binary outcomes and the mean difference (MD) for continuous outcomes were calculated, and analyzed using a random-effects model applying the restricted maximum likelihood (REML) method. We examined Galbraith plots to detect any outliers, discarding data confirmed as inaccurate.

The random-effects model was chosen due to expected clinical variability across the studies. We assessed heterogeneity using the I² statistic, categorizing 25 %, 50 %, and 75 % as low, moderate, and high heterogeneity, respectively.²⁵ Further analysis included subgroup examinations based on follow-up duration to probe potential heterogeneity sources and to observe variations in treatment effects over time.

Robustness of the results was tested through sensitivity analyses that involved sequentially excluding studies to observe the effects on overall results, particularly under conditions of notable heterogeneity. Due to the limited number of studies in each outcome analysis (<10), conducting publication bias assessment using funnel plots and Egger's test for asymmetry was impractical.

3.1 Literature search and screening results

The search yielded 424 citations, with 165 identified as duplicates. Of the remaining 259, 235 were excluded at the title/abstract screening stage (Fig. 1). Full-text screening was conducted for the remainder, with one article inaccessible and five excluded for lacking original data. A manual search added one more study, bringing the total to 19 studies included in the analysis.^{11–14,26–40}

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Fig. 1 PRISMA diagram showing the results of the literature search and screening processes.

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3.2 Baseline characteristics of included studies

Table 1 offers an exhaustive breakdown of the attributes of the studies included. The majority of these studies were conducted in the Republic of Korea and the United States, each hosting four studies, followed by two studies each in Canada, Norway, and Spain. Most of the studies (11) were retrospective cohorts, with the remainder comprising six randomized controlled trials, one prospective cohort, and one case-control study. Detailed information on the study populations, including age and gender distribution, is also provided in Table 1. A total of 20,409 patients diagnosed with lateral epicondylitis were part of these studies, with 2770 receiving arthroscopic release treatment and 17,639 undergoing open surgery. The duration of follow-up varied widely, ranging from 2 weeks to nearly 94 months.

3.3 Risk of bias

The risk of bias evaluation is summarized in Figs. 2 and 3. Six randomized controlled trials (RCTs) were assessed using Cochrane's RoB-2 tool. This assessment revealed that three RCTs exhibited a high risk of bias, two RCTs presented some concerns, and only one RCT was found to have a low risk of bias. For non-randomized studies, three were determined to have a low risk of bias, whereas the other ten exhibited a moderate risk, largely due to confounding factors and reporting biases.

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Fig. 2 The risk of bias assessment of randomized controlled trials using Cochrane's RoB-2 tool.

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Fig. 3 The risk of bias assessment of non-randomized trials using ROBINS-I tool.

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3.4 Functional recovery

3.4.1

3.4.1 DASH score

No significant change the postoperative DASH score was observed between the arthroscopic and open approaches [7 studies, MD = 0.06; 95%CI: 0.81: 0.94] (Fig. 4). Although moderate heterogeneity was observed, it was statistically insignificant [I² = 51.52 %, P = 0.05].

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Fig. 4 Forest plot showing the difference in postoperative DASH score between arthroscopic and open lateral release in patients with lateral epicondylitis.

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The subgroup analysis based on time showed a significant reduction in the DASH score in favor of the arthroscopic approach compared to the open one during the first postoperative month [MD = −4.47; 95%CI: 7.24: 1.70]; however, this difference was deemed insignificant over the short- and long-terms (Fig. S1).

Excellent recovery, defined as DASH score <20, was similar between both arthroscopic and open methods [4 studies, logOR = 0.33; 95%CI: 0.09: 0.75] (Fig. S2).

3.5 Elbow parameters

3.5.2

3.5.2 Grip strength (kg)

Six studies examined the grip strength following the management of lateral epicondylitis. The meta-analysis; however, showed no significant difference in grip strength between the arthroscopic and open methods [logOR = 0.49; 95%CI: 0.43: 1.41] (Fig. 5). This finding was supported by the insignificantly low heterogeneity level [I² = 23.99 %; P = 0.25].

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Fig. 5 Forest plot showing the difference in grip strength between arthroscopic and open lateral release in patients with lateral epicondylitis.

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The subgroup analysis based on time showed only a significant reduction in grip strength in favor of the arthroscopic group compared to the open group at 6 months of follow-up [MD = −1.50; 95%CI: 2.67: 0.33] (Fig. S9). However, no significant change was observed beyond that timepoint until 60 months of follow-up.

3.6 Associated radiographic findings

3.7 Postoperative pain

3.7.1

3.7.1 VAS measures

The overall VAS score was reported by 10 studies. The meta-analysis; however, showed no significant difference in the total VAS score between the arthroscopic and open methods [MD = −0.14; 95 % CI: 0.34: 0.06]. This finding was supported by the lack of statistical heterogeneity [I² = 0 %; P = 0.85] (Fig. 6). This was consistent with VAS measurement during rest [2 studies, MD = 0.18; 95%CI: 0.11: 0.47] (Fig. S12) and during work [2 studies, MD = 0.14; 95%CI: 0.12: 0.41] (Fig. S13), where no significant difference was observed between both methods.

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Fig. 6 Forest plot showing the difference in pain score (measured by visual analogue scale) between arthroscopic and open lateral release in patients with lateral epicondylitis.

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The subgroup analysis of the main VAS analysis showed a significant reduction in VAS score in favor of the arthroscopic method only by the 1st month [2 studies, MD = −1.13; 95 % CI: 1.77: 0.50] (Fig. S14). However, beyond this timepoint, both methods had similar scores.

3.8 Work-related outcomes

3.9 Other clinical outcomes

4.1 Comparison of functional recovery outcomes

Our meta-analysis provides a comprehensive comparison of arthroscopic versus open release for lateral epicondylitis, particularly focusing on functional recovery as measured by the DASH and MEPS scores. Consistent with prior reviews,^6,8 we found no significant difference in overall postoperative DASH and MEPS scores between the two methods. These findings suggest that both surgical approaches are effective in restoring function without any marked superiority of one over the other.⁶ Determinants of functional recovery are diverse, including a wide variety of factors. For instance, patients with severe preoperative limitations typically show more significant improvements post-treatment but may still have suboptimal DASH scores compared to those with milder baseline symptoms. Additionally, compliance with structured, patient-specific rehabilitation protocols leads to better functional recovery and higher DASH scores. Furthermore, recovery can vary due to age, gender, and occupation, with older adults typically experiencing slower recovery and physically demanding jobs requiring additional rehabilitation for work-specific activities. Coexisting musculoskeletal or systemic conditions can complicate postoperative rehabilitation, potentially resulting in reduced DASH scores. Finally, the surgeon's proficiency with the chosen technique and the occurrence of complications like infections or nerve injuries can prolong recovery and impact DASH scores. Unfortunately, the impact of these factors on functional recovery could not be investigated due to the nature of reported data. Therefore, future studies should address these points.

Interestingly, the subgroup analysis revealed a significant reduction in DASH scores favoring the arthroscopic approach during the first postoperative month, indicating a potentially quicker initial recovery. This aspect might be particularly appealing to patients and surgeons aiming for a faster return to daily activities, a finding that aligns with some studies highlighted in the review articles which emphasized the importance of early functional recovery in determining surgical success.

4.2 Surgical outcomes and complications

Both procedures risk damaging nearby nerves, particularly the radial nerve. This can result in transient or persistent sensory deficits and, occasionally, motor weakness. Arthroscopic techniques tend to carry a lower risk due to smaller incisions, but the risk remains due to the proximity of nerves in the operative field. Our analysis found no significant differences in the rates of surgical failures and revisions between the two methods, highlighting the comparable long-term dependability of both techniques. Synovitis and intra-articular loose bodies can develop or persist post-surgery, potentially requiring further arthroscopic debridement, and this was evident in our analysis. The comparable rates of postoperative complications, as we observed, also support the assertion made in earlier studies that the choice of technique should be tailored to the surgeon's expertise and patient-specific factors rather than inherent risks associated with either method.^6,15

4.3 Elbow motion and grip strength

Grip strength is another key metric in assessing functional recovery, reflecting the forearm muscle's ability to generate force. In the short term, arthroscopic surgery may confer a temporary advantage in grip strength at six months postoperatively. This could be due to the less invasive nature of the procedure, which minimizes soft tissue disruption and allows for quicker initial recovery. The equivalence in elbow range of motion (ROM) and grip strength outcomes further supports the parity between arthroscopic and open releases. Although arthroscopic release showed a temporary advantage in grip strength at the 6-month follow-up, this did not persist into longer-term follow-ups, suggesting that any early benefits may diminish over time. This transient benefit might be related to less invasive nature of the arthroscopic approach, which potentially allows for lesser tissue disruption.^6,41

4.4 Radiographic and pain assessment outcomes

Our findings regarding intra-articular loose bodies and evident synovitis did not show significant differences, pointing to a negligible impact of surgical choice on these specific radiographic outcomes.

During the immediate postoperative period, patients who undergo arthroscopic lateral release tend to report reduced immediate postoperative pain compared to open surgery. This may be due to the minimally invasive nature of the procedure, leading to less disruption of surrounding tissues. Smaller incisions and less soft tissue dissection reduce the trauma and inflammation that contribute to early postoperative pain.¹⁵ On the other hand, open surgery requires a larger incision and more extensive dissection of soft tissue to access the affected area. This often results in greater immediate postoperative pain due to increased tissue damage and inflammation. Proper pain management and early mobilization can help alleviate this pain, but it generally remains higher than with arthroscopic techniques.

In the medium- and long-term, arthroscopic surgery can lead to faster pain resolution, as demonstrated by significantly lower VAS pain scores within the first postoperative month. However, beyond this period, pain differences between arthroscopic and open approaches diminish. Both techniques achieve comparable long-term pain control, indicating that the initial arthroscopic benefits may not persist. On the other hand, open surgery also provides effective long-term pain relief, although it may take longer for pain to subside compared to arthroscopic surgery. Over time, with consistent rehabilitation, patients achieve similar pain reduction, highlighting the importance of proper postoperative care.¹⁵

In terms of recurrent of pain, both methods are associated with a low recurrence rate of pain following lateral release. The risk of recurrence is linked to surgical failures or incomplete resolution of the tendinosis, which is uncommon with either method. Proper patient selection and adherence to postoperative rehabilitation protocols are crucial to minimizing this risk.¹⁵

4.5 Work-related outcomes

The significant reduction in the time taken to return to work with the arthroscopic approach is a critical finding, considering the economic implications and patient satisfaction. The significant reduction in the time taken to return to work following the arthroscopic approach is a noteworthy finding with broader implications, especially in terms of economic considerations and patient satisfaction. A shorter recovery period allows patients to resume their professional activities sooner, which is crucial for maintaining economic stability and minimizing the financial impact of extended medical leave. This is particularly important for individuals employed in physically demanding professions where time away from work can lead to substantial income loss.

Faster return to work not only benefits the patients but also their employers, who face reduced costs associated with temporary staffing and productivity losses. Moreover, a quicker recovery and resumption of professional activities contribute to improved morale and consistent work quality within the workplace. From the healthcare perspective, shorter recovery times reduce the economic burden on healthcare systems through shorter hospital stays and decreased need for extended rehabilitation, leading to overall cost savings.

The advantages observed with the arthroscopic approach support the hypothesis that less invasive procedures facilitate quicker rehabilitation. Although arthroscopic surgery may involve marginally longer operative times, its benefits in reducing postoperative recovery time are significant. This approach leads to early functional recovery, allowing patients to regain full productivity swiftly, which is a crucial factor in the overall evaluation of surgical success.⁶

4.6 Strengths and limitations

Our systematic review and meta-analysis is strengthened by several factors. Firstly, the comprehensive literature search and rigorous selection criteria ensured a thorough exploration of available studies, enhancing the generalizability of our findings. Additionally, the inclusion of multiple study designs, such as RCTs, prospective cohorts, and retrospective cohorts, provides a broad perspective on the outcomes of interest. Furthermore, we included non-English studies to ensure adequate reporting while minimizing the risk of selection and publication bias considerably.

However, our study is not without limitations. The heterogeneity observed in some outcomes, particularly in subgroup analyses, suggests variability in study design, participant characteristics, or surgical techniques that could affect the results. The presence of moderate-to-high risk of bias in some included studies also tempers the strength of our conclusions. Furthermore, the limited number of studies reporting long-term follow-up data restricts our understanding of the durability of surgical outcomes over time.

4.7 Literature gaps and future research directions

Our review has identified several critical outcomes, yet there are notable deficiencies in the existing research. Specifically, there is a scarcity of information on patient-reported outcomes like quality of life and satisfaction after surgery. Moreover, the majority of studies we analyzed originated from higher-income nations, which may restrict the relevance of our findings to contexts with fewer resources. Additionally, we did not restrict the search to publications in the past two decades, as recommended in recent guidelines.¹⁷ This could account, to some extent, to the observed heterogeneity given the progressive advancement of the surgical management of lateral epicondylitis. Moreover, only a few studies investigated revision rate between both procedures; this needs to be addressed thoroughly in future research to determine long-term efficacy.

Future research should aim to address these gaps by including more diverse populations and incorporating patient-centered outcomes. Long-term follow-up studies are also needed to better understand the durability of both surgical techniques. Moreover, further investigation into the cost-effectiveness of arthroscopic versus open release could inform healthcare policy and surgical practice, ensuring that resource allocation aligns with patient benefits.