Abstract
Background Nanoscope, given its smaller size, may be safer when establishing dorsal wrist arthroscopy portals compared with the traditional 2.7 mm arthroscope.
Case Description Ten fresh frozen cadaver specimens were utilized. Dorsal radiocarpal portals were established with the Nanoscope and calipers were used to measure the distance between the portals and the surrounding anatomical structures. The only structure that was pierced during portal placement was the dorsal sensory branch of the ulnar nerve (DSUN) in one specimen when establishing the 6U portal. Our study did not note any tendon injuries.
Literature Review Traditional wrist arthroscopy may be performed with a 2.7 mm arthroscope. With its larger outer sheath cannula, this may place adjacent anatomical structures at risk of injury.
Clinical Relevance During wrist arthroscopy, the Nanoscope may be safer when creating portals to underlying structures.
Level of Evidence This is a Level IV study.
Keywords: wrist arthroscopy, arthroscope, surface anatomy, midcarpal radial, midcarpal ulnar
Dorsal wrist arthroscopy is performed to diagnose and treat wrist pathologies such as ligamentous injuries, triangular fibrocartilage complex tears, distal radius fractures, and carpal bone fractures, among others. 1 2 3 4 5 The standard dorsal wrist portals are the 1-2, 2R, 3-4, 4-5, 6R, 6U, and midcarpal radial and ulnar portals. Complications mostly arise from injury to neurovascular or tendinous structures during portal placement. 1
Cadaveric studies have investigated the distances from the dorsal portals to anatomical structures to better understand their relationships and how best to avoid these structures. 2 3 4 6 7 8 9 10 11 12 13 14 However, most of these studies use the distance from a small needle placed within the portal to these structures when clinically the arthroscope trochar/cannula would be present. The trochar/cannula creates a larger portal than a needle and therefore would be closer to vital structures than quoted in these studies. Abrams et al 6 did use the trochar for the 2.7 mm arthroscope as a marker and therefore these measurements are more clinically relevant.
The Nanoscope (Arthrex, Naples, FL) is a new arthroscopic instrument that is 1.9 mm in diameter with a 2.2-mm outer trochar sheath. This instrument views end on with no angulation and attaches to a small, portable screen. Given the smaller size of its cannula, our hypothesis is that this may be a safer option for portal placement compared with the 2.7-mm arthroscope (outer diameter cannula is 4.0 mm), as it would theoretically be further from surrounding anatomical structures.
Therefore, the purpose of this paper was to describe the standard dorsal wrist portals in relation to the surrounding neurovascular and tendinous structures using the Nanoscope.
Materials and Methods
After institutional review board approval, a sample of convenience 2 6 of 10 fresh frozen mid-humerus to fingertip cadaver specimens devoid of any pre-existing trauma or surgery were placed under 10 pounds of longitudinal traction. Specimens were excluded if they had a history of wrist surgery or injury. 1-2, 2R (radial to the 2nd extensor compartment), 3-4, 4-5, 6R, 6U, midcarpal radial (MCR) and midcarpal ulnar (MCU) portals were created using previously described surface anatomy landmarks. 15 Portals were created by first localizing the joint space with a 22-gauge needle, followed by tenotomy scissors to bluntly spread the soft tissues and create a wider opening in the joint capsule. A 1.9-mm Nanoscope and cannula (total outer diameter of 2.2 mm) was then introduced into each portal to confirm intra-articular placement and assess field of view.
The arm was then removed from the traction with the trochars in place. With the forearm in neutral rotation, skin and soft tissue were dissected under 3.5 mm loupe magnification by fellowship trained hand surgeons, exposing the surrounding nerves, arteries and tendons. Calibrated digital calipers were used to measure the distance between the portals and the surrounding anatomical structures to the nearest 100 th of a millimeter. Measurements were taken by two independent fellowship trained hand surgeons, and the obtained values were averaged. If a structure was abutting but not pierced by the trochar, a value of 0.01 mm was recorded. If a structure was pierced, it was recoded at 0 mm. This methodology was reproduced from the study by Gillis et al. 2
Results
The average distances from the standard dorsal portals and dorsal midcarpal portals to the surrounding neurovascular and tendinous structures are presented in Tables 1 and 2 . The only structure that was pierced during portal placement was the dorsal sensory branch of the ulnar nerve (DSUN) in one specimen when establishing the 6U portal.
Table 1. The average distances to vital structures from the trochar in the radiocarpal 1-2 and 2R, 3-4, 4-5, 6R, and 6U portals.
| Structure | 1-2 Portal distance mm (SD; Range) |
2R Portal distance mm (SD; Range) |
3-4 Portal distance mm (SD; Range) |
4-5 Portal distance mm (SD; Range) |
6R Portal distance mm (SD; Range) |
6U Portal distance mm (SD; Range) |
|---|---|---|---|---|---|---|
| Superficial branch of the radial nerve 1 | 3.04(3.31; 0.01–8.5) | 7.6(4.6; 0.01–14.1) | 18.9(4.9; 14.3–27.0) | a | a | a |
| Superficial branch of the radial nerve 2 | 6.1 (2.9: 2.1-10.8) | 13.67 (5.88; 4.4-20.2) | a | a | a | a |
| Superficial branch of the radial nerve 3 | 10.4(2.5; 5.8–13.6) | 22.6(4.5; 16.6–27.0) | a | a | a | a |
| Radial artery snuffbox | 1.43(0.9; 0.01–2.6) | 14.25(3.1; 10.1–18.6) | a | a | a | a |
| Abductor pollicis longus | 4.48(2.7; 1.4–10.3) | 16.8(2.1; 13.9–19.3) | a | a | a | a |
| Extensor pollicis brevis | 2.17(2.3; 0.01–5.9) | 14.7(2.0; 11.4–17.3) | a | a | a | a |
| Extensor carpi radialis longus | 9.8(3.5; 5.3–15.2) | 0.53(0.8; 0.01–2.2) | 9.9(4.8; 3.4–21.6) | a | a | a |
| Extensor carpi radialis brevis | 15.4(3.1; 12.2–20.0) | 2.63(3.7; 0.01–8.4) | 2.34(3.1; 0.01–9.3) | a | a | a |
| Extensor pollicis longus | 11.9(3.75; 9.0–21.6) | 1.7(3.3; 0.01–8.7) | 2.8(3.5; 0.01–10.0) | a | a | a |
| Extensor indicis proprius | a | a | 6.1(4.1; 0.51–13.6) | a | a | a |
| Extensor digitorum communis index | a | 13.2(3.8; 8.3–18.5) | 5.5(3.6; 0.34–10.7) | a | a | a |
| Extensor digitorum communis long | a | a | 8.9(4.7; 2.9–14.1) | 3.8(1.2; 2.3–5.4) | a | a |
| Extensor digitorum communis ring | a | a | a | 3.5(3.4; 0.01–9.9) | 12.1(2.7; 10.2–16.8) | a |
| Extensor digitorum communis small | a | a | a | 1.0(1.0; 0.01–2.3) | 6.0(2.3; 3.4–8.5) | 16.8(4.9; 10.1–21.5) |
| Extensor digiti minimi | a | a | a | 1.7(1.9; 0.01–4.4) | 2.34(1.7; 0.01–4.9) | 11.6(2.7; 6.8–15.1) |
| Extensor carpi ulnaris | a | a | a | 9.7(2.4; 6.2–13.4) | 1.7(1.3; 0.01–3.6) | 2.54(1.7; 0.1–6.02) |
| Dorsal sensory branch of the ulnar nerve1 | a | a | a | 19.0(4.0; 10.9–23.2) | 14.73(3.5; 10.3–19.5) | 2.0(2.2; 0.0–5.4) Pierced in one specimen |
| Dorsal sensory branch of the ulnar nerve 2 | a | a | a | 16.73(10.0; 9.7–24) | a | 7.9(0.2; 7.7–8.2) |
Not in vicinity and therefore not measured.
Table 2. The average distances to vital structures from the trochar in the midcarpal-radial (MCR) and midcarpal-ulnar (MCU) portals.
| Structure | MCR portal distance mm (SD; Range) |
MCU portal distance mm (SD; Range) |
|---|---|---|
| Superficial Branch of the Radial Nerve | 16.6 (5.2; 8.4–25.2) | a |
| Extensor carpi radialis longus | 10.3 (2.3; 7.1–14.7) | a |
| Extensor carpi radialis brevis | 2.4 (4.0; 0.01–10.3) | a |
| Extensor pollicis longus | 9.8 (3.5; 4.4–14) | a |
| Extensor indicis proprius | 5.1 (2.9; 1.2–9.8) | a |
| Extensor digitorum communis index | 3.3 (2.9; 0.01–7.9) | a |
| Extensor digitorum communis long | 7.1 (4.4; 2.4–13.5) | 7.7 (4.0; 4.6–13.9) |
| Extensor digitorum communis ring | a | 3.4 (3.2; 0.01–8.6) |
| Extensor digitorum communis small | a | 1.3 (2.3; 0.01–5.5) |
| Extensor digiti minimi | a | 5.0 (2.9; 0.01–8.7) |
| Extensor carpi ulnaris | a | 10.7 (3.8; 6.4–19.4) |
| Dorsal sensory branch of the ulnar nerve 1 | a | 13.5 (3.2; 9.8–16.9) |
| Dorsal sensory branch of the ulnar nerve 2 | a | 22.7 (5.2; 15.3–27.4) |
Not in vicinity and therefore not measured.
The 1-2 portal often came very close to the superficial branch of the radial nerve (SBRN) with an average of 3 mm away (0.01–8.45 mm). Additionally, the extensor pollicis brevis tendon and radial artery in the snuffbox were quite close to this portal as well (average 2.1 and 1.4 mm, respectively). The 2R, 3-4, 4-5, 6R, MCR and MCU portals were near surrounding tendinous intervals but never pierced these tendons or neurovascular structures. The 6U portal did pierce the DSUN in one specimen, as stated above, and was at an average of 1.975 mm from this.
The results of the current study were compared with a historical control by Abrams et al 6 and the results are summarized in Tables 3 and 4 .
Table 3. Comparison of current study vs historical control (Abrams et al) of the average distances to vital structures from the trochar in the radiocarpal 1-2 and 2R, 3-4, 4-5, 6R, and 6U portals.
| Structure | 1-2 Portal | 1-2 Portal control |
3-4 Portal | 3-4 Portal control |
4-5 Portal | 4-5 Portal control |
6R Portal | 6R Portal control |
6U Portal | 6U Portal control |
|---|---|---|---|---|---|---|---|---|---|---|
| Superficial Branch of the Radial Nerve 1 | 3.04(3.31; 0.01–8.5) | 3.0(1.5; 1.0–6.0) | 18.9(4.9; 14.3–27.0) | 16(5.8; 5–22) | a | a | a | |||
| Superficial Branch of the Radial Nerve 2 | 6.1(2.9; 2.1–10.8) | 5.0(2.9; 2–12) | a | a | a | a | ||||
| Radial artery snuffbox | 1.43(0.9; 0.01–2.6) | 3.0(1.3; 1–5) | a | a | a | a | ||||
| Dorsal sensory branch of the ulnar nerve 1 | a | a | 19.0(4.0; 10.9–23.2) | 14.73(3.5; 10.3–19.5) | 8.2(3.6; 0–14) | 2.0(2.2; 0.0–5.4) Pierced in one specimen |
1.9(1.5; 0–4) | |||
| Dorsal sensory branch of the ulnar nerve 2 | a | a | 16.73(10.0; 9.7–24) | a | 7.9(0.2; 7.7–8.2) | 4.8 |
Note: Values are distances in mm (SD; Range). Spaces left blank in the control columns were values not recorded in the control paper.
Not in vicinity and therefore not measured.
Source: Modified from Abrams et al 1994. 6
Table 4. Comparison of current study vs. historical control (Abrams et al) of the average distances to vital structures from the trochar in the midcarpal-radial (MCR) and midcarpal-ulnar (MCU) portals.
| Structure | MCR portal | MCR portal control |
MCU portal | MCU portal control |
|---|---|---|---|---|
| Superficial branch of the radial nerve | 16.6(5.2; 8.4–25.2) | 15.8(6.3; 5–26) | a | |
| Dorsal sensory branch of the ulnar nerve 1 | a | 13.5(3.2; 9.8–16.9) | 15.1(4.6; 0–25) | |
| Dorsal sensory branch of the ulnar nerve 2 | a | 22.7(5.2; 15.3–27.4) |
Note: Values are distances in mm (SD; range). Spaces left blank in the control columns were values not recorded in the control paper.
Not in vicinity and therefore not measured.
Source: Modified from Abrams et al 1994. 6
Discussion
Dorsal wrist arthroscopy using a 2.7-mm arthroscope (4.0-mm trochar) has been commonly used to diagnose and treat many pathologies of the wrist. 1 2 3 5 6 14 15 In addition, other smaller arthroscopes have been created (1.9 mm and 2.4 mm arthroscopes with their corresponding trochars) for wrist arthroscopy. The standard dorsal wrist arthroscopy portals include the 1-2, 2R, 3-4, 4-5, 6R, 6U, and MCR and MCU portals. 15 A careful understanding of the surrounding neurovascular and tendinous anatomy is important to avoid iatrogenic injury to these structures during portal placement. In terms of relevant neurovascular anatomy, the 1-2 portal is often very close to branches of the superficial radial nerve, the radial artery, and the extensor pollicis brevis tendon. 1 6 11 14 The 2R, 3-4, 4-5, 6R, MCR and MCU portals utilize intervals between tendons and therefore these are the most commonly injured structures when creating these portals. The 6U portal comes close to the DSUN and postoperative numbness or pain in the DSUN distribution can occur if this structure is injured. 1 6 11 14
Previous cadaveric studies have investigated the distances from the dorsal portals to vital structures to better understand their anatomical relationships and how best to avoid these structures. 2 3 4 6 7 8 9 10 11 12 13 14 However, these studies vary considerably in terms of how measurements were performed to determine the exact distances from vital structures. Most of these studies use the distance from a needle in the portal of interest to neurovascular and tendinous structures when clinically the arthroscope trochar/cannula would be present. The trochar creates a larger portal than a needle and therefore would be closer to vital structures than quoted in these studies. Additionally, most studies only measured the distance to neurovascular structures and did not measure the distance to surrounding tendons. Abrams et al 6 did use the trochar for the 2.7 mm arthroscope as a marker for a majority of their study, and therefore these measurements are more clinically relevant and can be used as a historical control as a comparison to the present study.
The arthroscope we used in this study is 1.9 mm in diameter with a 2.2-mm outer diameter cannula. We therefore utilized this instrument for our cadaveric study to establish accurate distances from adjacent anatomic structures to portals and to compare with the 2.7-mm arthroscope with a 4.0-mm trochar. This study is novel in that it also reported distances to the extensor tendons. Using this smaller Nanoscope, the 1-2 portal was on average 3 mm away from the SBRN. The extensor pollicis brevis tendon and radial artery in the snuffbox were on average 2.1 and 1.4 mm away, respectively. Given these findings, we typically use the 2R portal (radial to the extensor compartment) rather than the 1-2 portal. The results from this study would suggest that this is a safer portal, with a similar field of view, as the SBRN and radial artery are further away from the cannula compared with the 1-2 portal (13.7 mm vs. 6.1 mm for the radial nerve and 14.3 mm vs. 1.4 mm for the radial artery, respectively). The trochars/cannulas within the 3-4, 4-5, 6R, MCR, and MCU portals were near surrounding tendon intervals but never pierced these tendons or neurovascular structures. The 6U portal did pierce the DSUN in one specimen and was an average of 1.98 mm from this.
Abrams et al 6 reported on the distances to anatomical structures using the 2.7-mm arthroscope in 10 specimens. Overall, they measured similar structures that were close to the portals. The authors did not measure distances to tendons but did note nine tendon injuries during portal placement. The injured tendons included the extensor digitorum communis (EDC) once, four, and three times when establishing the 3-4, MCR, and MCU portals, respectively. The extensor digiti quinti was injured once when establishing the 6R portal. In comparison, no tendon injuries were noted in our study.
In terms of the 1-2, 3-4, 4-5, 6R, 6U, and MCR and MCU portals and their distance to neurovascular structures, the values in our study were quite similar to those in the Abrams et al study, as noted in Tables 3 and 4 . Using the results from Abrams et al 6 as a historical control, the “1-2” portal distance for the SBRN was identical at 3 mm and the DSUN to the 6U portal was 2 mm. However, the Nanoscope was further from the SBRN (18.9 vs. 16 mm) in the 3-4 portal, and DSUN (14.7 vs. 8.2 mm) in the 6R portal. The SBRN was slightly further from the MCR in our study compared with historical control (16.6 vs. 15.8). The DSUN was also further in our study to the MCU portal versus the control (12.7 vs. 15.1). However, the authors noted that they averaged the distance to all branches of the DSUN, which we did not do and would skew the results to a larger distance.
Our study did have one injury to the DSUN when creating the 6U portal and the study by Abram's et al did not note any of these injuries but found the closest branch of the DSUN to be 1.9 mm average distance from the portal. However, they did note a range with a lowest value of 0, indicating the portal must have been abutting the nerve.
Injury to surrounding structures can occur during portal placement. 1 In the study by Shyamalan et al, 11 six extensor tendon injuries were noted including the EDC to index finger, EDC to middle finger, extensor carpi ulnaris, and extensor digiti minimi. One study 9 recorded 3/15 cases of transection of the DSUN. Each formed a neuroma which required excision. The authors recommended “diligent spreading with a fine-point hemostat during portal establishment and diligent soft tissue dissection techniques for instrumentation.”
There are several limitations to our study. The study was performed on cadaveric limbs; however, these limbs were fresh frozen specimens that were screened for previous surgery or trauma. Although the portal placement and dissections were completed by fellowship trained hand surgeons, it is possible that portal placement could vary between specimens and dissection could disturb the anatomical relationship of structures. However, we tried to decrease this risk by performing dissection under 3.5-mm loupe magnification and performing measurements prior to complete dissection of all structures. Given the small number of cadaveric specimens, only descriptive statistics were used for this study. Lastly, no direct control group was utilized to compare the distances between the Nanoscope and the 2.7 mm arthroscope trochar and instead a historical control was used for comparison.
Despite these limitations, we noted that the Nanoscope appeared to be safe for dorsal wrist arthroscopy. We found that the 2R portal appeared to be safer than the 1-2 portal in terms of proximity to the dorsal sensory branches of the radial nerve and radial artery. Given the proximity of the DSUN to the 6U portal, we recommend an incision and spread technique when creating this portal. Given the lack of tendon injury in this anatomical study, this data would suggest that these structures are less at-risk during portal placement using the Nanoscope. Further clinical studies are needed to validate these findings.
Acknowledgments
The authors would like to thank Dr. Taghi Ramazanian MD for his help with this project.
Funding Statement
Funding None.
Conflict of Interest S.K. is a consultant for Arthrex. The other author(s) declare no potential conflict of interest with respect to the research, authorship, and/or publication of this article.
Ethical Approval
Cadaver study, there is no IRB but we have biospecimens approval.
Authors' Contribution
All the named authors were actively involved in the planning, enactment, and writing up of the study.
References
- 1.Ahsan Z S, Yao J. Complications of wrist and hand arthroscopy. Hand Clin. 2017;33(04):831–838. doi: 10.1016/j.hcl.2017.07.008. [DOI] [PubMed] [Google Scholar]
- 2.Gillis J A, Kakar S. Volar midcarpal portals in wrist arthroscopy. J Hand Surg Am. 2019;44(12):10940–1.094E9. doi: 10.1016/j.jhsa.2019.02.006. [DOI] [PubMed] [Google Scholar]
- 3.Hofmeister E P, Dao K D, Glowacki K A, Shin A Y. The role of midcarpal arthroscopy in the diagnosis of disorders of the wrist. J Hand Surg Am. 2001;26(03):407–414. doi: 10.1053/jhsu.2001.24973. [DOI] [PubMed] [Google Scholar]
- 4.Slutsky D J. Clinical applications of volar portals in wrist arthroscopy. Tech Hand Up Extrem Surg. 2004;8(04):229–238. doi: 10.1097/00130911-200412000-00006. [DOI] [PubMed] [Google Scholar]
- 5.Slutsky D J, Nagle D J. Wrist arthroscopy: current concepts. J Hand Surg Am. 2008;33(07):1228–1244. doi: 10.1016/j.jhsa.2008.07.015. [DOI] [PubMed] [Google Scholar]
- 6.Abrams R A, Petersen M, Botte M J. Arthroscopic portals of the wrist: an anatomic study. J Hand Surg Am. 1994;19(06):940–944. doi: 10.1016/0363-5023(94)90093-0. [DOI] [PubMed] [Google Scholar]
- 7.Corella F, Ocampos M, Cerro M D, Larrainzar-Garijo R, Vázquez T. Volar central portal in wrist arthroscopy. J Wrist Surg. 2016;5(01):80–90. doi: 10.1055/s-0035-1570741. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Kiliç A, Kale A, Usta A, Bilgili F, Kabukçuoğlu Y, Sökücü S. Anatomic course of the superficial branch of the radial nerve in the wrist and its location in relation to wrist arthroscopy portals: a cadaveric study. Arthroscopy. 2009;25(11):1261–1264. doi: 10.1016/j.arthro.2009.05.015. [DOI] [PubMed] [Google Scholar]
- 9.Lourie G M, King J, Kleinman W B. The transverse radioulnar branch from the dorsal sensory ulnar nerve: its clinical and anatomical significance further defined. J Hand Surg Am. 1994;19(02):241–245. doi: 10.1016/0363-5023(94)90013-2. [DOI] [PubMed] [Google Scholar]
- 10.Naroura I, Zemirline A, Taleb C. Inside-out method to develop volar arthroscopic portals of the wrist in cadaver specimens. Hand Surg Rehabil. 2016;35(03):210–214. doi: 10.1016/j.hansur.2016.02.006. [DOI] [PubMed] [Google Scholar]
- 11.Shyamalan G, Jordan R W, Kimani P K, Liverneaux P A, Mathoulin C. Assessment of the structures at risk during wrist arthroscopy: a cadaveric study and systematic review. J Hand Surg Eur Vol. 2016;41(08):852–858. doi: 10.1177/1753193416641061. [DOI] [PubMed] [Google Scholar]
- 12.Slutsky D J. The use of a volar ulnar portal in wrist arthroscopy. Arthroscopy. 2004;20(02):158–163. doi: 10.1016/j.arthro.2003.11.015. [DOI] [PubMed] [Google Scholar]
- 13.Slutsky D J. Distal radioulnar joint arthroscopy and the volar ulnar portal. Tech Hand Up Extrem Surg. 2007;11(01):38–44. doi: 10.1097/bth.0b013e318031d656. [DOI] [PubMed] [Google Scholar]
- 14.Tryfonidis M, Charalambous C P, Jass G K, Jacob S, Hayton M J, Stanley J K. Anatomic relation of dorsal wrist arthroscopy portals and superficial nerves: a cadaveric study. Arthroscopy. 2009;25(12):1387–1390. doi: 10.1016/j.arthro.2009.06.005. [DOI] [PubMed] [Google Scholar]
- 15.Cooney W P, Dobyns J H, Linscheid R L. Arthroscopy of the wrist: anatomy and classification of carpal instability. Arthroscopy. 1990;6(02):133–140. doi: 10.1016/0749-8063(90)90014-5. [DOI] [PubMed] [Google Scholar]