Endoscopic Versus Open Cubital Tunnel Release

Abstract

Background: Several surgical techniques exist for treatment of cubital tunnel syndrome. Endoscopic cubital tunnel release (ECTuR) has been recently reported as a promising minimally invasive technique. This study aims to compare outcomes and complications of open cubital tunnel release (OCTuR) and ECTuR in the treatment of idiopathic cubital tunnel syndrome. Methods: A systematic review of the literature (1980-2014) identified 118 citations. Studies including adults with idiopathic cubital tunnel treated exclusively by ECTuR or OCTuR were included. Outcomes of interest were postoperative grading, complications, number of reoperations, and the need for intraoperative conversion to another technique. Postoperative outcomes were combined into a uniform scale with 4 categories: “excellent,” “good,” “fair,” and “poor.” Results: Twenty studies met the inclusion criteria (17 observational and 3 comparative), representing 425 open and 556 endoscopic decompressions. In the open group, 79.8% experienced “good” or “excellent” results with 12% complication rate and 2.8% reoperation rate. In the endoscopic group, 81.8% experienced “good” or “excellent” results with 9% complication rate and 1.6% reoperation rate. Meta-analysis of 3 comparative studies demonstrated a significantly lower overall complication rate with ECTuR. Subgroup analysis of complications revealed a significantly higher incidence of scar tenderness and elbow pain with OCTuR. Conclusions: The current study demonstrates similar effectiveness between the endoscopic (ECTuR) and open (OCTuR) techniques for treatment of idiopathic cubital tunnel syndrome with similar outcomes, complication profiles, and reoperation rates.

Introduction

Ulnar nerve entrapment at elbow represents the second most common entrapment syndrome in upper extremity after carpal tunnel syndrome with an annual incidence of 20.9/100 000.¹⁷ Various surgical techniques have been proposed to release ulnar nerve from the confines of cubital tunnel; however, no gold standard exists. Traditionally, surgical options ranged from simple open decompression with or without nerve transposition to open decompression with medial epicondylectomy. Several studies, including a recent Cochrane meta-analysis,⁴ showed comparable outcomes between simple decompression and transposition with a higher complication rate with ulnar nerve transposition.^2,10,15 However, the evidence is still insufficient and the choice is largely left to the surgeon’s discretion.

In recent years, a minimally invasive technique has been introduced. First described by Tsai et al in 1995,²⁹ endoscopically assisted release of cubital tunnel has shown promising results similar to those reported for open decompression. Furthermore, several authors have claimed that endoscopic approach has the additional benefits of smaller scar, reduced postoperative pain, and faster return to activities of daily living.^1,8,9,11,25 To examine whether endoscopic cubital tunnel release (ECTuR) or open cubital tunnel release (OCTuR) would have superior outcomes with lower morbidity in patients with idiopathic cubital tunnel syndrome, we reviewed all studies that examined either endoscopic or open cubital tunnel release or compared both with regard to postoperative outcomes and complication profile in a systematic review design with meta-analysis.

Materials and Methods

Study Selection

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All articles describing open simple decompression or endoscopic simple decompression for idiopathic cubital tunnel syndrome between 1980 and 2014 were retrieved. Electronic databases of PubMed, Ovid MEDLINE, EMBASE, and SCOPUS were searched with medical subject headings and key words, including “cubital tunnel,” “ulnar neuropathy,” ulnar neuritis,” “ulnar nerve entrapment,” “open decompression,” “simple decompression,” “in situ decompression,” “endoscopic decompression,” and “arthroscopic decompression.” Furthermore, abstracts were searched from the archives of the American Society of Plastic Surgeons (2002-2014), Canadian Society of Plastic Surgeons (2007-2014), American Association of Plastic Surgeons (2006-2014), American Association of Hand Surgeons (2007-2014), American Society for Surgery of the Hand (2000-2014), American Association of Neurological Surgeons (2009-2014), and Canadian Orthopedic Association (2003-2014).

Inclusion/Exclusion Criteria

The following inclusion criteria were applied: (1) study population of adult patients (>18 years), (2) idiopathic ulnar nerve entrapment at elbow confirmed clinically and/or electrophysiologically, (3) surgical intervention either open simple decompression or endoscopic decompression, (4) study including objective and well-described outcomes, (5) study published in English or French, (6) year of publication between 1980 and 2014, and (7) sample size >10 patients. Exclusion criteria included any study that included surgical techniques other than open or endoscopic cubital tunnel release (eg, transposition, epicondylectomy, etc). Articles that met inclusion/exclusion criteria following title and abstract review were selected for full-text review. Inclusion criteria were applied once again and all remaining papers were reference checked to identify additional relevant studies. The review process was done by 2 reviewers independently, and any discrepancies were resolved by consensus.

Data Extraction/Collection Process

Data were collected from all selected studies using a standard data extraction sheet developed for this review. The following study characteristics were recorded: type of intervention, number of patients, number of arms operated, age, diagnostic criteria, inclusion/exclusion criteria, preoperative evaluation of severity of symptoms, postoperative complications, type and number of reoperations, postoperative evaluation of outcomes, and follow-up period. The level of evidence from the Oxford Centre for Evidence-Based Medicine was used to grade all articles (Table 1).²³

Table 1.

Level of Evidence for Primary Research Question: Therapeutic Studies.

Level of evidence	Qualifying studies
I	High-quality randomized controlled trial with statistically significant difference or no statistically significant difference but narrow confidence intervals, or systematic review of these studies
II	Lesser quality randomized controlled trial, prospective comparative study, or systematic review of these studies
III	Retrospective comparative study, case-control study, or systematic review of these studies
IV	Case series
V	Expert opinion

Source. Based on data from Oxford Centre for Evidence-Based Medicine—Levels of Evidence (March 2009).

Specific attention was given to the evaluation of preoperative clinical status and grading of postoperative outcomes. For each article, we recorded disease-specific instruments used by authors to classify disease severity prior to surgery and instruments used to evaluate surgical success. For preoperative severity assessment, McGowan’s and Dellon’s scales were used in nearly all studies. To simplify the analysis process, definitions of each scale were carefully examined and McGowan’s scale was transformed into Dellon’s scale in the following manner: Grade I McGowan is equivalent to “Mild,” Grade II is equivalent to “Moderate,” and Grade III is equivalent to “Severe” on Dellon’s scale. For postoperative outcome assessment, several rating systems were used across all studies (see Table 3). Also, several studies used author-generated instruments to assess postoperative outcomes, which needed to be converted manually into the Wilson and Krout scale as it contains a broad definition for each category. Similarly, all scales used in postoperative assessment were analyzed individually. Despite their slight differences, they shared sufficient similarities with respect to postoperative results and status of clinical improvement and were unified for the purpose of statistical analysis. Therefore, they were combined into a single, uniform unit of measurement comprised of 4 categories as shown in Table 2.

Table 3.

Study Characteristics.

Author	Year	Study design	Level of evidence	Type of decompression	Patients operated	Arms operated	Preoperative severity scale	Postoperative severity scale
Tsai et al29	1999	Case series	IV	ECTuR	76	85	Dellon	Bishop
Hoffmann and Siemionow10	2006	Case series	IV	ECTuR	75	76	Dellon	Bishop
Ahcan and Zorman1	2007	Case series	IV	ECTuR	36	36	McGowan	W & K
Yoshida et al31	2009	Case series	IV	ECTuR	35	35	McGowan	McGowan
Oertel et al22	2010	Case series	IV	ECTuR	24	26	McGowan	McGowan
Stadie et al25	2010	Case series	IV	ECTuR	27	32	McGowan	McGowan
Cobb et al6	2010	Case series	IV	ECTuR	94	104	Dellon	Bishop
Flores9	2010	Case series	IV	ECTuR	13	13	Dellon	Bishop
Leclere et al13	2011	Case series	IV	ECTuR	55	55	Dellon	Bishop
Miller and Hummel16	1980	Case series	IV	OCTuR	12	12	N/A	Author-generated
Nathan et al21	1995	Case series	IV	OCTuR	131	164	McGowan	Author-generated
Taniguchi et al26	2002	Case series	IV	OCTuR	17	18	McGowan	Messina
Pavelka et al24	2004	Case series	IV	OCTuR	52	55	Dellon	Author-generated
Mondelli et al18	2004	Case series	IV	OCTuR	18	19	McGowan	A & F
Cho et al5	2007	Case series	IV	OCTuR	15	15	Dellon	Bishop
Karthik et al12	2012	Case series	IV	OCTuR	30	30	Dellon	Bishop
Nagle et al20	2012	Case series	IV	OCTuR	12	16	McGowan	G & A
Bolster et al3	2013	Prospective comparative study	III	ECTuR vs OCTuR	42	42	Dellon	Bishop
Dutzmann et al8	2013	Retrospective comparative study	III	ECTuR vs OCTuR	114	114	McGowan	Bishop
Watts and Bain30	2009	Retrospective comparative study	III	ECTuR vs OCTuR	34	34	McGowan	Author-generated

Note. ECTuR, endoscopic cubital tunnel release; W & K, Wilson and Krout; OCTuR, open cubital tunnel release; A & F, Alnot and Frajman; G & A, Gabel and Amadio.

Table 2.

Definition of the Combined Postoperative Outcome Assessment System and Equivalence of Original Scales to the Combined System.

Combined system	Definition	Bishop	Messina	W & K	G & A	A & F	McGowan
Excellent	Complete resolution of symptoms	Excellent	Excellent	Excellent	Excellent	Excellent	0
Good	General resolution with mild residual intermittent symptoms	Good	Good	Good	Good	Good	I
Fair	Mild improvement with significant residual persistent symptoms	Fair	Fair	Fair	Fair	Poor	II
Poor	Lack of improvement or worsening of initial symptoms	Poor	Poor	Poor	Poor	Worse	III

Note. W & K, Wilson and Krout; G & A, Gabel and Amadio; A & F, Alnot and Frajman.

Meta-Analysis

Data from 3 studies^3,8,30 that compared ECTuR with OCTuR were pooled for meta-analysis. Analysis was done for 2 outcomes: (1) clinical improvement and (2) complications. (1) Clinical improvement was defined as either an “excellent” or “good” outcome on postoperative Bishop score^3,8 or as subjective patient satisfaction measured on the Visual Analog Scale (VAS),³⁰ as those were the primary outcomes in those studies. (2) Overall complication rate was determined and a subgroup analysis was performed for each of the most frequently observed complications in each group: (1) scar tenderness/elbow pain, (2) hematoma, (3) ulnar nerve subluxation, and (4) reoperation. Data were dichotomized into “improved or not improved” for the clinical improvement outcome and into “present or absent” for the complications outcome. For each outcome, risk ratio (RR) was calculated with 95% confidence interval (CI), and effect sizes were weighted by the sample size of each study. Data were pooled and analyzed using random effect model based on the assumption that different studies are estimating different, yet related, intervention effects, and hence it is a more conservative approach to address intra- and interstudy differences as opposed to fixed effect. Random effect model was performed using inverse-variance statistical method. As clinical improvement is a desired outcome, RR of more than 1 is in favor of experimental group (ECTuR). In contrast, complications are undesired and therefore RR of less than 1 would favor the experimental group (ECTuR). A P value < .05 was considered statistically significant.

Heterogeneity was explored using the I-square test (I²) and any sources of heterogeneity, if present, were examined. I² < 30% indicates no heterogeneity. We hypothesized sources of potential heterogeneity a priori, which include differences in surgical techniques, outcome measures reporting, and duration of postoperative assessment. Statistical analysis was performed using Review Manager (RevMan) software, Version 5.2 (Nordic Cochrane Centre, Cochrane Collaboration, Copenhagen).

Results

Study Selection

After eliminating nonrelevant and duplicate studies, the primary literature search identified 118 citations. A multistep reviewing process is shown in Figure 1. A total of 17 studies were included. Cross-referencing added 3 more studies for a total of 20 studies included.

Figure 1.

Study selection flowchart.

Study Characteristics

Among the studies selected, 17 were observational and 3 were comparative. Studies were grouped according to type of intervention into 2 groups; the OCTuR group was comprised of 11 studies, representing a total of 383 patients with 425 arms, and the ECTuR group was made up of 12 studies representing 529 patients with 556 arms (Table 3). The follow-up ranged from 5 to 51 months (average 15.1 months) in the OCTuR group and 6 to 37 months (average 18.8 months) in the ECTuR group. The mean age of patients was comparable in both groups, 48.1 years in the OCTuR group versus 48.9 years in the ECTuR group.

Open Cubital Tunnel Release

Of the 425 open decompressions, 243 were graded preoperatively (Table 4); 43 (17.7%) were graded as Grade I, 70 (28.8%) as Grade II, and 130 (53.5%) as Grade III. Postoperative outcomes were evaluated in 403 of the open cases; 257 (60.5%) were reported as “excellent,” 82 (19.3%) as “good,” 46 (10.8%) as “fair,” and 18 (4.2%) as “poor.” Watts et al³⁰ reported their 15 cases using patient satisfaction (9 patients satisfied; 60%) and median VAS for ongoing hand symptoms, which was 60% for OCTuR group.

Table 4.

Summary of Grading and Complications by Group.

Group	Combined preoperative grading	Combined postoperative grading	Complications	Reoperations	Converted to open
OCTuR (n = 425)	Grade I: 43 (17.7%) Grade II: 70 (28.8%) Grade III: 130 (53.5%)	Excellent: 257 (60.5%) Good: 82 (19.3%) Fair: 46 (10.8%) Poor: 18 (4.2%) Ungraded: 22	Hematoma: 2 MABC nerve lesion: 20 Scar sensitivity: 10 Diffuse elbow pain: 1 Subluxation: 4 Infection: 1 Reoperation: 13 Conversion: 0 Total: 51 (12%)	Recurrence: 1 Failure: 7 (AT) Subluxation: 4 (2 AT, 2 medial epicondylectomy) Total: 12 (2.8%)	None
ECTuR (n = 556)	Grade I: 95 (17.4%) Grade II: 257 (47%) Grade III: 195 (35.6%)	Excellent: 302 (54.3%) Good: 153 (27.5%) Fair: 51 (9.2%) Poor: 13 (2.3%) Missing/Converted: 9 (1.6%) Ungraded: 28	Hematoma: 17 (4 operative) MABC nerve lesion: 10 (8 resolved by 3 months) Diffuse elbow pain: 1 Subluxation of nerve: 4 Infection: 2 CRPS: 2 Thrombophlebitis: 1 Partial ulnar nerve injury: 1 Reoperation: 9 Conversion: 3 Total: 50 (9%)	Recurrence: 4 (MT) Failure: 3 (OCTuR) Subluxation of nerve: 2 (endoscopic AT) Total: 9 (1.6%)	Ganglion: 1 Subluxation: 1 Nerve adhesions: 1 Total: 3 (0.5%)

Note. OCTuR, open cubital tunnel release; MABC, medial antebrachial cutaneous; ECTuR, endoscopic cubital tunnel release; AT, anterior transposition; MT, submuscular transposition; CRPS, complex regional pain syndrome.

The overall complication rate was 12% (51 cases), the most frequent being numbness due to medial antebrachial cutaneous (MABC) nerve injury (n = 20) and scar sensitivity (n = 10). Resolution of numbness along the MABC nerve distribution was not described. Twelve patients needed reoperations with either anterior transposition of the ulnar nerve (n = 9), medial epicondylectomy (n = 2), or redo open release (n = 1). No cases were converted to other techniques intraoperatively.

Endoscopic Cubital Tunnel Release

Of 556 endoscopic decompressions, 547 were graded preoperatively; 95 (17.4%) were graded as Grade I, 257 (47%) as Grade II, and 195 (35.6%) as Grade III. Postoperative outcomes were evaluated in 519 cases; 302 (54.3%) were reported as “excellent,” 153 (27.5%) as “good,” 51 (9.2%) as “fair,” and 13 (2.3%) as “poor.” Eight cases (1.5%) were lost to follow up and were excluded from the original results,^22,25 and 1 case (0.2%) was converted to submuscular transposition and excluded as well.²² However, we included all missing and converted cases in our analysis in an intention to treat analysis. Watts et al did not use any of the outcome scales, rather they used patient satisfaction as their primary outcome (15 out of 19 patients were satisfied; 79%) and median VAS for ongoing hand symptoms which was 90% for the ECTuR group.³⁰

There were a total of 50 reported complications with an overall complication rate of 9%. The most frequent complication was hematoma (n = 17) that needed operative evacuation in 4 cases, the rest resolved spontaneously. Numbness along the MABC nerve distribution was the second common complication (n = 10), the majority of which resolved completely by 3 months (8 out of 10 cases). Nine cases (1.6%) required reoperation, 4 of which due to symptoms recurrence, 3 due to treatment failure, and 2 for subluxation of ulnar nerve. Three cases (0.5%) required intraoperative conversion to open decompression; 2 cases were converted to OCTuR due to a ganglion surrounding the ulnar nerve in the forearm in 1 case and the need for neurolysis in another. The third case was converted to anterior submuscular transposition due to ulnar nerve subluxation. There was 1 reported case (0.18%) of partial ulnar nerve injury (laceration of less than 5% of the nerve’s cross-sectional area) during endoscopic release¹³ that was repaired intraoperatively with complete recovery. Table 4 summarizes severity, outcomes, and complications of both groups.

Meta-Analysis

Three studies that compared ECTuR with OCTuR were included in meta-analysis with a total of 190 patients.^3,8,30 Figures 2, 3, and 4 summarize results of the analysis. Although there was a trend in favor of ECTuR with regard to clinical improvement (RR 1.1), the results were not statistically significant (P = .15). Regarding overall complications, there was a significantly lower complication profile (hematoma, scar tenderness/elbow pain, ulnar nerve subluxation, reoperation) in ECTuR compared with OCTuR (P = .01). In a subgroup analysis of individual complications, there was a significantly higher incidence of scar tenderness/elbow pain in OCTuR group (P = .002; Figures 3 and 4), whereas there were no significant differences in the other complications such as hematoma (RR 3.64 [95% CI, 0.4-31.9]; P = .24), ulnar nerve subluxation (RR 9.64 [95% CI, 0.53-175.07], P = .13), and reoperation (RR 5.36 [95% CI, 0.26-109.17]; P = .28).

Figure 2.

Forest plot of Comparison 1: Clinical improvement.

Note. ECTuR, endoscopic cubital tunnel release; OCTuR, open cubital tunnel release; CI, confidence interval.

Figure 3.

Forest plot of Comparison 2: Complications, outcome: 2.1 overall complications.

Note. ECTuR, endoscopic cubital tunnel release; OCTuR, open cubital tunnel release; CI, confidence interval.

Figure 4.

Forest plot of Comparison 2: Complications, outcome: 2.2 scar tenderness/elbow pain.

Note. ECTuR, endoscopic cubital tunnel release; OCTuR, open cubital tunnel release; CI, confidence interval.

Discussion

ECTuR has been introduced as an alternative treatment modality for cubital tunnel syndrome since the 1990s. In theory, it offers outcomes similar to open cubital tunnel release (OCTR) while providing the additional benefits of a minimally invasive approach. It aims to minimize incision size, reduce potential risk of MABC nerve injury, and provide better visualization of the entire course of ulnar nerve both proximal and distal to the elbow.

Our systematic review demonstrated an overall weighted average of excellent outcomes of 54.3% and 60.5% in ECTuR and OCTuR, respectively. Good outcomes were observed in 27.5% and 19.3% of ECTuR and OCTuR cases, respectively. Together, good and excellent results were achieved in 81.8% of patients in the OCTuR group and 79.8% in the ECTuR group. Statistical comparison was not performed due to significant heterogeneity in outcome measures across included studies. Similarly, inconsistency in data reporting including details of preoperative severity scales further complicated any attempt at data pooling and determining if a correlation exists between the severity of nerve compression and the treatment outcomes. Although more severe preoperative grading (Grade III) was reported in the OCTuR group (57.2% vs 35.6%), which may mitigate the higher complication rate observed with this technique, only 57.2% of patients (243/425) had the severity of their symptoms graded compared with 98.4% of patients (547/556) in the endoscopic group.

Nevertheless, we were able to combine the only 3 comparative studies in a meta-analysis, which showed no difference in clinical improvement outcome among both groups (RR 1.10 [95% CI, 0.97-1.25]), but demonstrated a significant reduction in the overall complication rate (RR 0.44 [95% CI, 0.23-0.85]), particularly in scar tenderness and elbow pain (RR 0.08 [95% CI, 0.02-0.40]) in favor of ECTuR. However, given the small sample size and scarcity of comparative studies included, a meta-analysis on this subject does not provide sufficient evidence to draw concrete conclusions and does not show superiority of one procedure versus another.

Advantages of OCTuR over other types of surgical releases (transposition, epicondylectomy) have been well documented in the literature as evidenced by its comparable outcomes with lower complication profile.^15,19,32 Yet, no comparisons were made to endoscopic release, which in theory achieves the same goals of simple in situ decompression but using a minimally invasive approach. Reported advantages of ECTuR include smaller incision, minimal soft tissue dissection with reduced injury of MABC nerve, and complete release of distant potential compression sites. Furthermore, it requires no special instrumentation apart from the endoscope and has a relatively short learning curve.¹¹ Hoffmann and Siemionow demonstrated multiple compression sites of the ulnar nerve up to 9 cm distal to the midpoint of the retrocondylar groove.¹¹ He believes that the release of those bands would otherwise require a radical in situ decompression or a complex transposition, and hence an endoscopic release would offer a greater advantage of releasing those bands without complex soft tissue dissection. Drawbacks of ECTuR include higher risk of hematoma, resulting ulnar nerve subluxation, and theoretical risk of iatrogenic ulnar nerve injury with blind introduction of the endoscope.

Our systematic review showed an overall complication rate of 9% and 12% in ECTuR and OCTuR, respectively. The slightly lower trend in complication rate in the ECTuR group is supported by the meta-analysis that showed RR of 0.44 in favor of ECTuR. Hematoma was the most common complication in the ECTuR group (34% of overall complications) compared with 4% in the OCTuR; however, less than 25% of those required surgical evacuation. Despite the fact that almost all studies in the ECTuR group (9 out of 12) have reported some form of preventive steps to reduce hematoma formation (tourniquet release, bipolar cauterization, closed suction drains, compressive dressing), the incidence of hematoma persisted to be higher in this group. The only explanation of such a finding is the inherent narrow surgical field in ECTuR with resulting limited hemostasis. On the contrary, numbness around elbow and medial forearm likely related to MABC nerve injury was the most common complication in the OCTuR group (39%) compared with 20% in the ECTuR (only 4% were permanent). MABC nerve injury is undoubtedly more common in OCTuR, as demonstrated in our meta-analysis and in the rest of literature.^7,14 Furthermore, better postoperative scar tenderness was noticed in the ECTuR group that goes along with similar findings in endoscopic carpal tunnel release.²⁷

For purposes of this review, we defined recurrence as worsening symptoms following an initial period of improvement after original cubital tunnel release that necessitated a reoperation whereas failure was defined as the persistence of original symptoms despite surgical intervention. Reasons for reoperation were either recurrence of symptoms, failure of treatment, or resulting ulnar nerve subluxation following decompression. The reoperation rate was slightly higher in OCTuR (2.8% vs 1.6%). Generally, reoperated cases among the ECTuR group were done using OCTuR for failures, endoscopic subcutaneous transposition for subluxation, or open submuscular transposition for recurrences. In contrast, reoperations in the OCTuR group were mostly done using subcutaneous transposition for failures/subluxation or epicondylectomy for subluxation (Table 4). The intraoperative conversion from ECTuR to OCTuR was needed due either to a ganglion compressing ulnar nerve, an intraoperative ulnar nerve subluxation necessitating a transposition, or ulnar nerve adhesions necessitating a safe open neurolysis. However, conversion rate is probably underestimated as many studies had excluded converted cases in their exclusion criteria. Similarly, studies in OCTuR did not include any cases that were converted to transposition due to ulnar nerve subluxation. Hence, careful interpretation of the conversion rate should not overlook an inherent selection bias in those studies.

Limitations of our study include the absence of randomized controlled trials, inclusion of predominantly observational studies (Level IV evidence), paucity of articles directly comparing OCTuR and ECTuR included in the meta-analysis, and inconsistency in outcome measures reporting, making an objective conclusion more difficult to make. Diversity in postoperative outcome scales makes data pooling and subgroup analysis a statistically impossible task to perform and therefore calls for a more unified classification system to be used in all future studies. Attempt at combining those systems was done for purposes of combining crude results using weighted averages but not to contemplate statistical analysis. In addition, data on return to work and grip strength were insufficient to draw any useful inferences if any difference exists. One should be cautious in interpreting the results of unified postoperative scale, as it does not address those objective outcomes (grip strength, postoperative nerve conduction studies, etc). Another limitation is selection bias in those studies inherent to their nonrandomized, uncontrolled designs. Majority of studies excluded patients who had an intraoperative subluxation and therefore needed epicondylectomy or an anterior transposition. Furthermore, patients who were expected to have subluxation (on preoperative evaluation) were not included at first intention. We tried to include those patients in data pooling in an intention to treat analysis; however, this was not possible in most studies in systematic review due to unreported data. Such a bias could have a significant impact on overall conversion rates, and hence it should be interpreted cautiously. With regard to surgical techniques, several ones have been used by different studies, but conducting a subgroup analysis was not feasible due to lack of standardized outcome measures as previously discussed. Techniques can be broadly categorized as those involving passing endoscope below the cubital tunnel roof: Agee system,^25,30 Universal Subcutaneous Endoscope,³¹ cannula or glass tube-assisted,^6,28 or in a plane between the cubital tunnel roof^1,8,9,11 and subcutaneous tissue.^3,13,22

The current study demonstrates similar effectiveness between the endoscopic (ECTuR) and open (OCTuR) techniques for treatment of idiopathic cubital tunnel syndrome with similar outcomes, complication profiles, and reoperation rates. However, it should be applied in selected patients who do not have preoperative evidence of nerve subluxation, previous traumatic injuries to elbow, or obvious anatomical pathology. Current evidence lacks data to draw rigorous conclusion on objective outcome measures, return to work, and cost-benefit analyses. Further randomized controlled studies implementing standardized classification systems and objective outcome measures are required.