Visibility During Elbow Arthroscopy Using Needle Arthroscope: A Cadaveric Study

Abstract

Background:

The visibility of the elbow joint during needle arthroscopy with 0° viewing is unknown. Moreover, the surgeon's level of experience required to perform needle arthroscopy with adequate proficiency has not been established.

Purpose:

To clarify visibility during elbow needle arthroscopy and investigate how the surgeon’s experience affects it.

Study Design:

Descriptive laboratory study.

Methods:

Twenty elbow specimens from 11 cadavers were used. A 1.9-mm needle arthroscope with a 0º viewing angle was inserted into 4 standard portals (anterolateral [ALP], anteromedial [AMP], lateral [LP], and posterior [PP]) to observe 18 different anatomic landmarks. The procedure was performed by 3 surgeons with >15 years of experience (ME) and 3 surgeons with lesser experience (LE) in elbow arthroscopy, defined as having performed ≤5 procedures. Each examiner evaluated 10 elbows. The observation times of all checkpoints from each portal were recorded and the mean durations compared.

Results:

The percentage of each structure that was adequately visualized using the ALP and AMP were 100% for each group. Successful visualization of structures through the LP was 100% in the ME group and ranged from 86.7% to 100% in the LE group. Visualization through the PP ranged from 56.7% to 86.7% in the ME group and from 53.3% to 83.3% in the LE group. The percentage of visibility for the posterior aspect of the lateral epicondyle was significantly lower in the ME group (56.7%; P = .008), and that for the border between the trochlear cartilage (56.7%; P = .008) and olecranon fossa (53.3%; P = .003) was significantly lower in the LE group. No significant differences in visibility rates were observed between the ME and LE groups across all 18 checkpoints. The mean observation times were not significantly different between groups for all portals.

Conclusion:

The needle arthroscope is a valuable tool for the arthroscopic examination of the anterior joint space and humeroulnar joints; however, visualizing the posterior joint space can be challenging, regardless of the surgeon's experience level. No significant difference was observed in the visibility probability based on experience.

Clinical Relevance:

The needle arthroscope can be beneficial for the management of elbow diseases in the anterior joint space and humeroulnar joints, regardless of the surgeon's experience level, and enables more precise diagnosis and treatment planning.

Initially introduced in 1931, elbow arthroscopy was not widely adopted due to the anatomic challenges posed by the narrow joint space. ³ In the 1980s and 1990s, reports and studies on elbow arthroscopy improved substantially, marking its global acceptance and adoption.^2,3,17,39 Over the past 4 decades, considerable progress has been made, and as experience accumulates, the technique has been further refined.^5-7 Several recent studies on elbow arthroscopy have been published, indicating its emergence as a standard surgical procedure.^7,22

Compared with conventional arthroscopy, needle arthroscope offers several distinct advantages. It requires less equipment and involves the creation of only small, approximately 2-mm portals, which are more comfortable for patients and is more for procedures performed under local anesthesia.^35,41,49 The development of needle arthroscopy in the 1990s marked a shift toward less invasive diagnostic techniques^35,41; however, its initial adoption was hindered by poor imaging quality. Recent improvements in image quality have renewed interest. ⁴² The ongoing advancements in needle arthroscopy may significantly increase its utilization, offering a new modality that is less invasive compared with traditional 30° oblique arthroscopy. ⁴² The use of needle arthroscopy has been reported as a treatment for various musculoskeletal conditions, such as anterior ankle impingement, biceps tenotomy, anterior labral repair, rotator cuff repair, meniscectomy, and meniscal repair,^{10,15,27,30,31,43,47} and has been suggested to have the potential for diagnostic capabilities equal to or superior to that of magnetic resonance imaging (MRI) for knee and shoulder pathologies, while also potentially offering cost-saving benefits.^16,34,48 However, its efficacy in the elbow is yet to be thoroughly investigated.

The introduction of needle arthroscopy for the elbow in 2020 marked a significant advancement in minimally invasive surgery, ⁴² particularly due to the proximity of critical neurovascular structures in this area. Elbow arthroscopy poses a risk of nerve injury, with reported incidence rates ranging from 0.5% to 5.3%.^{14,24,25,28,38,44}

While most nerve injuries are transient palsies,^{24,29,32,38,40} cases of complete transection of the radial and median nerves have been reported.^{18,20,26,36,45} Nerves and the brachial artery are particularly vulnerable during portal placement, anterior capsular release, and synovectomy procedures. ²¹ The small size of the device camera (1.9 mm) facilitates a percutaneous approach, potentially reducing the risk of iatrogenic injury near vital neurovascular structures.^1,7,9,21

In addition to the elbow joint, needle arthroscopes have been effectively utilized in small joints such as the ankle.^10,23,41,46 Given the narrow joint cavity of the elbow, employing a thin arthroscope offers significant advantages, enhancing visualization and facilitating minimally invasive procedures.

However, the 0° viewing angle of this device may be unfamiliar to surgeons who are accustomed to the 30° angle commonly used in standard arthroscopy. Despite its potential, the evidence on the level of experience required for surgeons to utilize this needle effectively is limited. Therefore, this study aimed to clarify the visibility during elbow needle arthroscopy and investigate the extent to which the surgeon's experience affected visibility. The hypothesis was that more experienced surgeons would be better able to observe the inside of the elbow joint and would be able to adequately visualize all important intra-articular structures.

Methods

Specimens

This cadaveric study was approved by the institutional review board (IRB) of the ethics committee of our institution. The specimens were obtained through the Science Care donation program and donated with consent for use in medical science. A total of 11 specimens with 22 elbows (mean age, 88.1 ± 7.5 years; range, 79-97 years; 5 male and 6 female) were included in the present study. Two elbows were excluded due to contractures. The cadavers were accepted within 3 days postmortem, fixed using the Thiel method, and appropriately preserved. Only cadavers ≤6 months postmortem were used. Thiel-embalmed cadavers with whole bodies and bilateral elbows were examined. Specimens with a history of surgery or elbow contracture were excluded. Fluoroscopy was used to confirm the absence of severe arthritis or elbow fractures. All assessments were conducted by an examiner (S.Y.) who was not involved in performing the arthroscopy.

Arthroscopy and Assessment

The procedure was performed by 3 surgeons with >15 years of arthroscopy experience (ME) and 3 surgeons with lesser elbow arthroscopy experience (LE) who had performed ≤5 elbow arthroscopy procedures. None of the surgeons had experience using the needle arthroscope (NanoScope; Arthrex). The study was conducted using the ME group with 6 specimens (mean age, 89.2 ± 8.5 years; 2 male, 4 female), 10 elbows, and the LE group with 5 specimens (mean age: 87.0 ± 6.4 years; 3 male, 2 female), 10 elbows. Each surgeon performed 10 elbow arthroscopy procedures using the device. Specimens were placed in the supine position, which was chosen to minimize invasiveness as much as possible, assuming an outpatient surgery setting; and a 1.9-mm needle arthroscope (Figure 1) with a 0° viewing angle was inserted into 4 standard portals (anterolateral portal [ALP], anteromedial portal [AMP], lateral portal [LP], and posterior portal [PP]) ¹ to observe 18 checkpoints.^2-4,22 The ALP was created 2 cm proximal and 2 cm anterior to the lateral humeral epicondyle and used to observe the coronoid fossa, humeral trochlea, anterior medial capsule, coronoid process, and proximal radioulnar joint (Figure 2A and Figure 3, A and B). The AMP was created 2 cm proximal to the medial humeral epicondyle and anterior to the intermuscular septum, and the radial head, humeral capitellum, anterior lateral capsule, and radial fossa (Figure 2A) were observed. The LP (soft spot portal) was created in the center of the triangle formed by the lateral humeral epicondyle, olecranon, and the radial head, and the articular surface of the radial head, humeral capitellum, proximal radioulnar joint, and humeroulnar joint (Figure 2B) were observed. The PP was created 3 cm proximal in the midline to the olecranon tip, and the olecranon tip, border between the trochlear cartilage and olecranon fossa, lateral edge of the olecranon, medial edge of the olecranon, and posterior aspect of the lateral epicondyle (Figure 2C) were observed. A 0.9% saline solution was used to irrigate joints with 20 mL of the solution administered. A total of 18 checkpoints were established for arthroscopic examination through the 4 portals, with photographs recorded at each checkpoint. If everything was observable, then once the arthroscope was inserted, the time required to examine each portal was measured. The 18 images were evaluated by 2 orthopaedists, referred to as testers (T.O. and K.K.), with sufficient experience in elbow arthroscopy. Neither assessor had previous access to the images or information pertaining to this study, ensuring an unbiased review process. If the testers was able to observe even a portion of a structure, it was considered observable, provided that approximately 50% or more of the structure was visible.

Figure 1.

Supine position setup with 1.9-mm needle arthroscope and 0° viewing angle.

Figure 2.

Checkpoints with the needle arthroscope. (A) Checkpoints via the anterolateral portal and anteromedial portal: coronoid fossa (1), humeral trochlea (2), anterior medial capsule (3), coronoid process (4), and proximal radioulnar joint (5) observed from the anterolateral portal; and the radial head (6), humeral capitellum (7), anterior lateral capsule (8), and radial fossa (9) observed from the anteromedial portal. (B) Checkpoints via the lateral portal: articular surface of the radial head (10), humeral capitellum (11), proximal radioulnar joint (12), and humeroulnar joint (13) observed via the lateral portal. (C) Checkpoints via the posterior portal: olecranon tip (14), border between the trochlear cartilage and olecranon fossa (15), lateral edge of the olecranon (16), medial edge of the olecranon (17), and posterior aspect of the lateral epicondyle (18) observed via the posterior portal.

Figure 3.

(A) Needle arthroscopy of the elbow through the anterolateral portal. The yellow arrow indicates the insertion site of the 1.9-mm needle arthroscope. (B) Arthroscopic view showing the humeral trochlea (▲) and coronoid process (*). R, radius; H, humerus.

Statistical Analysis

The points to be visualized were reported as frequency with percentage according to the numbers visible, which were compared among the portals between the ME and LE groups using Fisher exact test. In case of a significant difference, post hoc pairwise comparisons were performed using Bonferroni correction. The interrater agreement of visualization was assessed by calculating Cohen kappa (κ) coefficient. We also performed binary logistic regression analysis using visibility as the dependent variable, with the surgeon’s experience and viewing point as predictor variables. The mean times in the ME and LE groups were compared using unpaired t test.

Statistical significance was set at P < .05. All statistical analyses were performed using the open-source statistical computing software package R (R Foundation for Statistical Computing; http://www.r-project.org). This software was used to calculate the sample size, effect size, and statistical power. The minimal significance (α) and statistical power (1–β) were set at .05 and 0.80, respectively. The necessary sample size was observation of 22 elbows. Three examiners evaluated 10 elbows each in both the ME and LE groups, resulting in 30 assessments per observation point in each group, which satisfies this requirement.

Results

Visibility Using the Needle Arthroscope

In the ME group, the percentage of all visualizations through the ALP, AMP, and LP was 100% (checkpoints 1-13: 100%). The proportion visualized through the PP was relatively low, and the visibility for checkpoint 18 was 56.7% (checkpoint 14, 86.7%; 15, 73.3%; 16, 83.3%; and 17, 83.3%), significantly lower than those for checkpoints 1 to 13 (P = .008) (Table 1).

Table 1.

Visibility of the 18 Checkpoints From 4 Different Portals in ME Group During Arthroscopic Elbow Surgery Using Needle Arthroscope ^a

Checkpoint	Portal	Visualization of Each Checkpoint in ME Group, the number of successful visualizationsn (%)
1	ALP	30 (100)
2		30 (100)
3		30 (100)
4		30 (100)
5		30 (100)
6	AMP	30 (100)
7		30 (100)
8		30 (100)
9		30 (100)
10	LP	30 (100)
11		30 (100)
12		30 (100)
13		30 (100)
14	PP	26 (86.7)
15		22 (73.3)
16		25 (83.3)
17		25 (83.3)
18		17 (56.7) b

^aALP, anterolateral portal; AMP, anteromedial portal; LP, lateral poral; PP, posterior portal; ME, >15 years of experience in arthroscopic elbow surgery.

^bSignificantly lower than checkpoints 1-13 (P < .05).

For the LE group (Table 2), the proportion visualized through the ALP and AMP was 100% (checkpoints 1-9). The proportion visualized through the LP was slightly lower for the LE than for the ME group (checkpoints 10 and 11, 100%; 12, 96.7%; 13, 86.7%), and the percentage of visualization through the PP was relatively low (checkpoint 14, 83.3%; 15, 56.7%; 16, 76.7%; 17, 73.3%; 18, 53.3%). The percentage visibility for checkpoint 18 was significantly lower than those for checkpoints 1 to 12 (checkpoints 1-11, P = .003; 12, P = .03), and the percentage visibility for checkpoint 16 was significantly lower than those for checkpoints 1 to 11 (P = .008) (Table 2). No statistically significant differences in the percentage visibility for each checkpoint were observed between the ME and LE groups.

Table 2.

Visibility of the 18 Checkpoints From 4 Different Portals in LE Group Using Needle Arthroscope ^a

Checkpoint	Portal	Visualization of Each Checkpoint in LE Group, the number of successful visualizations
1	ALP	30 (100)
2		30 (100)
3		30 (100)
4		30 (100)
5		30 (100)
6	AMP	30 (100)
7		30 (100)
8		30 (100)
9		30 (100)
10	LP	30 (100)
11		30 (100)
12		29 (96.7)
13		26 (86.7)
14	PP	25 (83.3)
15		17 (56.7) b
16		23 (76.7)
17		22 (73.3)
18		16 (53.3) c

^aALP, anterolateral portal; AMP, anteromedial portal; LP, lateral portal; PP, posterior portal; LE, lesser experience in arthroscopic elbow surgery (≤5 procedures).

^bSignificantly lower than checkpoints 1-11 (P < .05).

^cSignificantly lower than checkpoints 1-12 (P < .05).

The interrater agreement for testers A and B was assessed using Cohen kappa coefficient. The agreement rate was 100% for checkpoints 1 to 14, 93.3% for checkpoint 15, and 98.3% for checkpoints 16 to 18. The coefficients were substantial to almost perfect: 1.0 for checkpoint 14; 0.93 for checkpoint 15; 0.95 for both checkpoints 16 and 17; and 0.97 for checkpoint 18, indicating a high level of agreement between the 2 testers. The discrepancy can be attributed to the obstruction of the field of view by the fat pad, as well as the difficulty in distinguishing cartilage boundary surfaces, which was often the case due to the advanced age of the cadavers.

Mean Duration Using the Needle Arthroscope

The mean duration for visualization was slightly lower in the ME group than the LE group: ME vs LE group: ALP, 22.8 ± 10.3 seconds vs 24.9 ± 14.1 seconds (Figure 4A); AMP group: 12.5 ± 3.3 seconds vs 12.7 ± 6.2 seconds (Figure 4B); LP group: 28.4 ± 11.3 seconds vs 33.7 ± 11.4 seconds (Figure 4C); and PP group: 41.6 ± 15.7 seconds vs 44.5 ± 26.5 seconds (Figure 4D). However, the difference was not statistically significant.

Figure 4.

(A) Mean time to observation of 5 checkpoints via the anterolateral portal by 3 surgeons with >15 years of experience in arthroscopic elbow surgery (ME) and 3 surgeons with lesser experience in arthroscopic elbow surgery (≤5 procedures) (LE). (B) Mean time to observation of 4 checkpoints via the anteromedial portal by 3 surgeons in the ME group and 3 surgeons in the LE group. (C) Mean time to observation of 5 checkpoints via the lateral portal by 3 surgeons in the ME group and 3 surgeons in the LE group. (D) Mean time to observation of 5 checkpoints via the posterior portal by 3 surgeons in the ME group and 3 surgeons in the LE group.

Discussion

In the present study, the needle arthroscope provided good visibility through the ALP and AMP, allowing for the observation of all anterior checkpoints; nearly all checkpoints were observed through the LP, although visualizing the posterior joint space can be challenging. Furthermore, the surgeon's experience with elbow arthroscopy did not demonstrate any difference regarding the percentage of visualizations or observation time.

In this study, we noted that the visibility was generally good for most checkpoints; however, observing the posterior joint structures to achieve consistent and clear visibility is often more challenging than observing the anterior or lateral joint structures, regardless of experience in elbow arthroscopy. This could be the case for 2 main reasons: first, the soft tissue in the posterior joint space hinders visualization. The posterior fat pad is located outside the synovial membrane and is enveloped by the capsular leaflets. The outermost leaflet covering the fat pad is merely a thin membranous outgrowth of the fibrous capsule, strongly interweaving with the periosteum at the edges of the olecranon fossa. ³⁷ In conventional elbow arthroscopy literature and studies on needle arthroscopy, the posterolateral portal is frequently referenced as a working portal. These studies highlight the importance of debriding soft tissue, such as fat pads, through the working portal to ensure adequate access to the posterior joint cavity.^3,22,42 Establishing a working portal is regarded as critical for achieving optimal visualization of the posterior joint cavity. However, the use of instruments such as a shaver through the working portal may result in a level of invasiveness comparable with that of standard arthroscopy, necessitating careful consideration. Second, using a 0° scope presents challenges in observing peripheral areas. PPs are standard in elbow arthroscopy, where a 4.0-mm, 30° oblique arthroscope is commonly used.^3,39 With conventional arthroscopy using a 30° oblique view, key landmarks such as the border between the trochlear cartilage and olecranon fossa, as well as the olecranon tip and edge, can be effectively visualized from the PP. The constrained intra-articular space of the elbow joint further underscores the benefits of the 30° oblique scope for detailed observation.

Additionally, a report suggested that the portal position may need to be adjusted when using a 0° needle arthroscope. ⁴² It has been suggested that placing the portal slightly more proximally may improve visualization for PP. Modifying portal positions compared with conventional placements could potentially enhance the field of view. The current study found that a mean of 76.6% (56.7%-86.7%) and 68.7% (53.3%-83.3%) of checkpoints in this region could be effectively visualized via the PP in the ME and LE groups, respectively. However, the study was conducted without the use of a working portal and relied on conventional arthroscopy portal positions, which may have limited visualization.

Contrary to previous limitations, the LP afforded high accessibility for the observation of the humeroulnar joint using the needle arthroscope. Previous studies have consistently highlighted the utility of such approaches in examining narrow joints, including those of the ankle, foot, and wrist.^{10,13,23,27,41} Specifically, arthroscopy via the LP has been traditionally emphasized for the olecranon, radial head, and lateral epicondyle.^3,22,39 However, earlier reports have omitted detailed discussions on the observation of the humeroulnar joint. Nonetheless, contemporary clinical practice has revealed significant benefits in observing the humeroulnar joint, underscoring the inherent advantages offered by the innovative use of the needle arthroscope system (Figure 5).

Figure 5.

(A) Arthroscopic view of the humeroulnar joint via the lateral portal using the needle arthroscope. (B) Arthroscopic view of the humeroulnar joint via the lateral portal using a conventional arthroscope. H, humerus; U, ulnar.

The needle arthroscopy offers distinct advantages over traditional arthroscopy techniques, combining a minimally invasive design with exceptional portability and flexibility. Its smaller size reduces tissue trauma, which can lead to faster recovery times and potentially less postoperative pain, making it particularly suitable for diagnostic procedures and therapeutic interventions in tight joint spaces or delicate anatomic regions.^12,42,46,49 Furthermore, its diagnostic capability for detecting cartilage lesions is equivalent or even superior to that of MRI.^8,16,34,48 In this study, needle arthroscopy demonstrated its suitability for the elbow joint, particularly in observing cartilage lesions and loose bodies within the humeroulnar joint and anterior joint cavity, as well as in performing second-look evaluations after surgery. Additionally, its adaptability for use in outpatient or bedside settings, without requiring full operating room setups, streamlines procedures and improves patient accessibility to minimally invasive treatments.

In the present study, the surgeons could visualize almost all checkpoints of the elbow joint using needle arthroscopy without previous experience with this technique, regardless of experience in conventional elbow arthroscopy. The learning curve of arthroscopic procedures in other joints has been reported, with studies stating that increasing experience of the procedure decreases the operating time and leads to better clinical outcomes.^11,19,33 However, the observation duration or visualization probability for the elbow joint did not differ significantly with elbow arthroscopy experience in this study. This suggests that good visibility of the elbow joint can be achieved for observation purposes even without previous extensive experience with elbow arthroscopy.

Future research directions include investigating the differences in visualization probability within the posterior joint space when using working portals, and a 30°oblique needle arthroscope has been released in recent years, though it remains unclear how its use would affect visualization probability. Additionally, studies should assess the in vivo visualization capabilities of needle arthroscopy of the elbow to better understand its potential applications and limitations. Comparative research on the risk of neurovascular injury between needle arthroscopy and conventional elbow arthroscopy is also necessary to establish safety profiles. Finally, exploring the use of needle arthroscopy in surgical procedures, such as the removal of loose bodies, could provide valuable insights into its efficacy and clinical utility.

Limitations

The present study has some limitations; first, it included a small sample of 10 elbows in each group. Second, no bleeding occurred, as this was a cadaveric study; intraoperative bleeding may affect the visibility in a clinical setting, and use of a tourniquet may not allow this to be performed under local anesthesia. Third, as our research facility only had access to younger cadaveric donors, the age distribution in this cadaveric study was high, even though elbow arthroscopy is generally indicated for younger patients. Unlike younger elbows, synovial changes can lead to poor visualization in adult elbows. Fourth, we only examined the differences based on the surgeon’s experience in conventional elbow arthroscopy and did not investigate the learning curve associated with the needle arthroscope. Fifth, this study focused solely on imaging evaluation within the elbow joint and did not assess surgical techniques. Considering surgical procedures, there is a possibility that differences in operative time and other factors may arise between the ME and LE groups. Sixth, we only determined whether the structures within the elbow joint were visible and did not assess the quality of visualization. Seventh, we did not evaluate neurovascular injury during the procedure.

Conclusion

The needle arthroscope is a valuable tool for the arthroscopic examination of the anterior joint space and humeroulnar joints; however, visualizing the posterior joint space can be challenging, regardless of the surgeon's experience level. No significant difference was observed in the visibility probability based on experience.