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Modified Anterolateral Portals in Elbow Arthroscopy: A Cadaveric Study on Safety
Modified Anterolateral Portals in Elbow Arthroscopy: A Cadaveric Study on Safety Stephen Thon, M.D., Peter Gold, M.D., Lane Rush, M.D., Michael J. O’Brien, M.D., and Felix H. Savoie III, M.D.
Purpose: To evaluate the proximity to the radial nerve on cadaveric specimens of 2 modified anterolateral portals used for elbow arthroscopy. Methods: Ten fresh cadaveric elbow specimens were prepared. Four-millimeter Steinman pins were inserted into 3 anterolateral portal sites in relation to the lateral epicondyle: (1) the standard distal anterolateral portal, (2) a modified direct anterolateral portal, and (3) a modified proximal anterolateral portal. These were defined as follows: direct portals 2 cm directly anterior to the lateral epicondyle, and proximal portals 2 cm proximal and 2 cm directly anterior to the lateral epicondyle. Each elbow was then dissected to reveal the course of the radial nerve. Digital photographs were taken of each specimen, and the distance from the Steinman pin to the radial nerve was measured. Results: The modified proximal anterolateral and direct anterolateral portals were found to be a statistically significant distance from the radial nerve compare to the distal portal site (P ¼ .011 and P ¼ .0011, respectively). No significant difference was found in the proximity of the radial nerve between the modified proximal and direct anterolateral portals (P ¼ .25). Inadequate imaging was found at a single portal site for the proximal site; 9 specimens were used for analysis of this portal with 10 complete specimens for the other 2 sites. Conclusions: In cadaveric analysis, both the modified proximal and direct lateral portals provide adequate distance from the radial nerve and may be safe for clinical use. In this study, the distal anterolateral portal was in close proximity of the radial nerve and may result in iatrogenic injury in the clinical setting. Clinical Relevance: This is a cadaveric analysis of 2 modified portal locations at the anterolateral elbow for use in elbow arthroscopy. Further clinical studies are needed prior to determining their absolute safety in comparison to previously identified portal sites.
From the Northwell Health Orthopaedic Institute (P.G.), New Hyde Park, New York; and Department of Orthopaedics, Tulane University (S.T., P.G., L.R., M.J.O., F.H.S.), New Orleans, Los Angeles, U.S.A. The authors report the following potential conflicts of interest or sources of funding: M.J.O. is a consultant for Smith & Nephew and DePuy Mitek and has received institutional grants from DePuy Mitek. F.H.S. has board membership (unpaid) in American Shoulder and Elbow Surgeons and the Arthroscopy Association of North America; is a consultant (unpaid) for Biomet, Exactech, Mitek, Rotation Medical, and Smith & Nephew; has received institutional grants from Tulane University, Mitek ($13,500); receives payment for lectures including service on speakers bureaus from Mitek ($2,000, 4 presentations) and Smith & Nephew ($3,500, 6 presentations); royalties from Exactech ($760); and other: unpaid publications, editorial/governing boardsdArthroscopy board of trustees and Wrist Surgery editorial board. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received November 30, 2016; accepted June 19, 2017. Address correspondence to Felix H. Savoie III, M.D., Tulane University Department of Orthopaedics, 1430 Tulane Ave., #8632, New Orleans, LA 70112, U.S.A. E-mail: [email protected] Ó 2017 by the Arthroscopy Association of North America 0749-8063/161143/$36.00 http://dx.doi.org/10.1016/j.arthro.2017.06.012
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ince its inception, advances in techniques have expanded the use of arthroscopy and its indications for use in the elbow.1-13 Prior cadaveric studies have examined the proximity of arthroscopic portal placement in relation to neurovascular anatomy,13-24 but few studies have deviated from the originally described portal locations as first described by Andrews and Carsons13 in 1985. The anterolateral portals have since been described as 3 separate and distinct portals: the distal, direct, and proximal. Their locations are as follows: distal portals are 3 cm distal and 1 cm anterior to the lateral epicondyle, direct portals are 1 cm directly anterior to the lateral epicondyle, and proximal portals are 2 cm proximal and 1 cm anterior to the lateral epicondyle.13,17,18,22,24 We have modified the 2 more proximal portal sites an additional 1 cm anterior compared with the traditional definitions, as we feel this may provide superior access to the elbow joint during advanced arthroscopic procedures. The
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Fig 1. Comparison of the traditional portal sites to our modified anterior portal sites with the elbow flexed in prone position for arthroscopy. The traditional portals are marked in red. Blue markings represent the modified portals presented as an additional 1 cm anterior. The asterisk signifies the proximal portal sites and the caret ( ) signifies the direct portal sites. ˇ
procedures we find the more anterior portal to be useful for include advanced arthritis with deformity, post-traumatic ankyloses with and without anterior heterotopic ossification, acute fracture dislocations (terrible triad injuries), and complex elbow instability cases. Following the same model as previous studies, we set out to demonstrate the safety of these portals with regard to radial nerve proximity and evaluate the safety of their use in both routine and advanced elbow arthroscopy. The purpose of this study was to evaluate the proximity to the radial nerve on cadaveric specimens of 2 modified anterolateral portals used for elbow arthroscopy. Our hypothesis was that there would be no significant difference in safety margin to the radial nerve from the traditional distal portal site compared with our modified portal sites.
osteoarthrosis. The elbows were held at 90 of flexion to mimic intraoperative positioning of an elbow placed into the lateral decubitus or prone positions. As befitting our usual practice, we establish a proximal anterior medial portal for visualization and then established all lateral portals. The distal lateral humerus, the radial head, the proximal radius, and the lateral epicondyle were identified and marked with a surgical marking pen. Three anterolateral portal sites were established in all specimens starting with the distal anterolateral and progressing proximal. Stab incisions via scalpel were made at each mark prior to Steinmann pin insertion at each portal site. The most studied and well-defined portal is that originally used by Andrews and Carson, which has since been termed a distal anterolateral portal. Across the vast majority of the prior cadaveric studies, this portal was used for comparison and study.13-15,17-23 It is defined as 3 cm distal and 1 cm anterior to the lateral epicondyle and was labeled the “distal” portal. After placement of the distal portal, our modified direct and modified proximal portals were placed. The direct portal was placed 2 cm directly anterior to the tip of the lateral epicondyle, and the proximal was placed 2 cm proximal to the lateral epicondyle and 2 cm anterior to the lateral intermuscular septum. Both of these portals were placed more anterior than the prior portals and have not previously been described in the literature (see Fig 1). A 4-mm-diameter Steinmann pin was introduced at each of the identified portal sites after piercing the skin with a scalpel and aiming directly at the midpoint of the elbow joint. The joint was not distended during portal placement to preserve accurate measurements after dissection and to measure the worst-case scenario in distance to the radial nerve. As noted in previous works,13,14,19 this prevents fluid accumulation in the surrounding soft tissues, which can distort the final measurements. Each specimen was then dissected to maintain the placement and position of the Steinmann
Methods Ten fresh cadaveric elbow joints devoid of remaining forearms and hands were dissected and evaluated for final data collection. Prior to dissection, each elbow was screened for signs of trauma, previous surgery, or
Fig 2. Marked elbow prior to dissection with 3 Steinmann pins inserted at each portal site relative to the lateral epicondyle that is marked.
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MODIFIED PORTALS: A STUDY ON SAFETY
Table 1. Distance From the Steinman Pin to the Radial Nerve Specimen 1 2 3 4 5 6 7 8 9 10
Proximal, mm 5 7 10 18 10 17 d* 9 15 9
Direct, mm 12 14 6 16 21 17 12 9 22 9
Distal, mm 3 1 0 (contact) 0 (contact) 9 14 0 (contact) 0 (contact) 12 6
*Considered inadequate image to use for measurement.
Fig 3. Dissected elbow with 3 portal sites. A line of closest fit from each portal site to the radial nerve was then established and measured digitally.
Data and measurements were pooled and organized into Table 1. An inadequate image was obtained in specimen 7 for the proximal anterolateral portal. Therefore, data were collected for 9 cadavers at the proximal anterolateral portal and for all 10 cadavers for
both the direct anterolateral and distal anterolateral portals. The traditional distal portal was an average of 4.5 mm (standard deviation 5.42 mm) away from the radial nerve, with a range of 0 to 14 mm. At the distal portal, the radial nerve came in contact with the Steinman pin in 4 of the cadavers. The direct anterolateral portal was an average of 13.8 mm (standard deviation 5.25 mm) from the radial nerve, with a range of 6 to 21 mm. The proximal anterolateral portal was an average of 11.1 mm (standard deviation 4.51 mm) away from the radial nerve, with a range of 5 to 18 mm. Summary of these data can be found in Table 2. Unpaired t tests comparing the difference in proximity to the radial nerve at both modified sites were then performed. Comparison of the proximity to the radial nerve between the traditional distal portal to both our modified proximal portals revealed a significant difference found in distance to the radial nerve at both sites in our cadaveric model (P ¼ .011 and P ¼ .001, respectively). Comparison of the safety profiles between our 2 modified proximal and direct portals revealed no statistically significant difference in safety margin (P ¼ .25). See Table 3 for comparison data between the different portals.
Fig 4. The Steinmann pin at the distal portal site is in contact with the radial nerve in this specimen. This finding occurred in 4 specimens.
The cadaveric investigation presented here shows no increased risk of iatrogenic injury with the use of more anterior anterolateral portals. In our cadaveric dissections the distal anterolateral portal was found to be the nearest in proximity to the radial nerve, which may place it at risk for iatrogenic injury compared with other portal sites. As indications for elbow arthroscopy continue to grow, knowledge of 3-dimensional neurovascular anatomy is imperative for patient safety. We have modified our portals to allow more advanced surgery to be performed arthroscopically. These more advanced cases include the arthroscopic management of severely arthritic elbows with large anterior spurs and deformity, severe post-traumatic ankyloses with and without heterotopic
pins. The skin and subcutaneous tissue were removed. The radial nerve was then identified at the interval between the brachialis and the brachioradialis muscles and traced distally. Dissection was stopped on visualization of the radial nerve overlying the supinator muscle. Digital photographs were then taken with a ruler in order to provide a digital scale and measurement. A “line of closest fit” was established digitally and measured between the Steinmann pins and the radial nerve at each portal site. The digital photographs were considered adequate when the entire Steinman pin, radial nerve, and line of closest fit were unobstructed. Figures 2 to 4 visually depict the portal entry, dissection, and measurement process.
Results
Discussion
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Table 2. Average Distances Between Each Portal Site Portal Distal Direct Proximal
Distance to Radial Nerve, mm 4.5 5.42 (0-14) 13.8 5.25 (6-21) 11.1 4.51 (5-18)
NOTE. Values are mean standard deviation (range).
bone, fracture dislocations, and complex elbow instability, which require the use of more anterior portals to access the pathology safely. As our indications have increased, the location, safety, and proximity of these portals needed to be evaluated. The goal is to minimize the risk of severe iatrogenic injury to the neurovascular structures that may arise from improper portal placement and from misdirected operative instruments.21,25,26 This study shows that both portal placement and choice of location plays a major role in the risk associated with iatrogenic nerve injury during elbow arthroscopy. The proximal anterolateral and direct anterolateral portals used in our study were found to be at an increased distance from the radial nerve than the traditional distal portal. Comparison of these portals to the cadaveric work of Field et al.18 displayed a similar distance to the radial nerve. Field et al. placed their proximal anterolateral portal 2 cm proximal and 1 cm anterior to the lateral epicondyle. They found the distance between their proximal portal and the radial nerve to be 14.2 mm without joint distention, compared with 11.1 mm in our study. Field et al. obtained their direct anterolateral portal at 1 cm directly anterior to the lateral epicondyle and found the distance between this portal and the radial nerve to be 9.8 mm without joint distention, compared with 13.8 mm in our study. Like the previous cadaveric works that compared different portal sites,17,18,22 we found a statistically significant increase in distance to the nerve from both the proximal and direct anterolateral portals compared with the traditional distal anterolateral portal. In evaluating our cadavers as well as the data from prior works,17-19,22,24 the original distal anterolateral portal appears to be in closer proximity to the radial nerve than previously thought. Andrews and Carson1 described this portal as 3 cm distal and 1 cm anterior to the lateral epicondyle, and since then it has been investigated in 10 cadaveric studies.13-15,17-23 The mean distance to this portal site was found to range from 3 to 16.13 mm across these studies. Our average distance of 4.5 mm compared similarly to these measurements, and in our analysis the use of the distal anterolateral portal was actually found to be in particularly close proximity to the radial nerve. This conclusion is similar to prior studies that have directly compared the distal site to a more proximal site. Independently, they each found that the distal portal was the least safe in
comparison to more proximal portals.17,18,22 The results of those studies, coupled with the data collected here, show that this distance may not be safe for the patient. Our discovery of 4 Steinmann pins coming in contact with the nerve suggest that this danger may be more alarming than previously discussed. In line with prior works,18,22 use of the traditional distal anterolateral portal may be taking on unnecessary risk for entry in elbow arthroscopy, especially when other portal sites are readily available and proven to be in less proximity to the radial nerve. At our institution, we have used a more anterior portal placement for the past 9 years. Compared with the previously described proximal anterolateral and direct anterolateral portals by Field et al.,15 our portals are placed 1 cm more anterior. The more anterior portal locations were developed as more complicated procedures became more common. A more anterior portal entry location does require the surgeon to aim more posteriorly while inserting the arthroscope toward the joint, thereby entering more laterally. This more anterior placement has the additional benefit of providing the surgeon a safer trajectory in relation to the radial nerve. We investigated 2 modified anterolateral portals more anterior to the previously described sites and found that they are a safe distance from the radial nerve. Direct comparisons to the distal anterolateral portal, which is the most commonly used and cited in the literature,13-15,17-23 revealed a statistically significant increase in safety margin to the radial nerve for both our modified portals. The use of the distal anterolateral portal was associated with increased risk of radial nerve injury in our study as well as in previous works.17,18,22 Future study may focus on comparing the safety profile of our modified portals to the original portals, but it is unlikely that a significant difference will be found with both such small distances and limits on cadaver sample sizes. Performing a cadaveric study of necessary size is likely to not be cost-effective. Limitations A possible limitation in our study was the lack of joint distention. Although it has been established in clinical practice that joint distention improves the distance to the radial nerve at the anterolateral portal site,13,14,18-21 multiple studies have noted the difficulty in maintaining distention in the cadaveric model. It was also shown that continued distention may distort the Table 3. Comparison of Safety Margin to Radial Nerve Portals Distal to direct Distal to proximal Direct to proximal
P Value .0011 .011 .248
P < .5? Yes Yes No
MODIFIED PORTALS: A STUDY ON SAFETY
measurements as a result of saline extravasation into the surrounding tissues as the procedure progresses.13,14,19 Marshall et al.17 noted a reduced elasticity in the cadaveric model that limited the effect of joint distention. Similarly, Stothers et al.22 did not feel that the relationship of the radial nerve to the sheath was significantly changed without the presence of joint distention once the procedure had started. Another limitation is that the insertion of 3 steinmann pins in the same specimen may have distorted the overall soft tissue anatomy in the specimens. Although we acknowledge this may alter measurements, we believe the use of a sharp, rigid pin minimizes any distortion. Gravity may also play a role in the soft tissue anatomy. Our specimens were devoid of the remaining forearm and hands and as such there was minimal pull due to gravity at the elbow joint. The work in this study is also not applicable to elbow arthroscopy performed in the supine position, as the position of the elbow during these procedures was not evaluated.
Conclusions In cadaveric analysis, both the modified proximal and direct lateral portals provide adequate distance from the radial nerve and may be safe for clinical use. In this study, the distal anterolateral portal was in close proximity to the radial nerve and may result in iatrogenic injury in the clinical setting.
References 1. Burman MS. Arthroscopy or the direct visualization of joints: An experimental cadaver study, 1931. Clin Orthop Relat Res 2001;390:5-9. 2. Burman MS. Arthroscopy of the elbow joint: A cadaver study. J Bone Joint Surg 1932;14:349-350. 3. Poehling GC, Whipple TL, Sisco L, Goldman B. Elbow arthroscopy: A new technique. Arthroscopy 1989;5:222-224. 4. Ahmad C, Vitale M. Elbow arthroscopy: Setup, portal placement, and simple procedures. Instr Course Lect 2011;60:171-180. 5. Noonburg G, Baker C. Elbow arthroscopy. Instr Course Lect 2006;55:87-93. 6. Bennett J. Elbow arthroscopy: The basics. J Hand Surg 2013;38A:164-167. 7. Carson W. Arthroscopy of the elbow. Instr Course Lect 1988;37:195-201. 8. Baker C, Jones G. Arthroscopy of the elbow. Am J Sports Med 1999;27:251-264.
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9. Abboud J, Ricchetti E, Tjoumakaris F, Ramsey M. Elbow arthroscopy: Basic setup and portal placement. J Am Acad Orthop Surg 2006;14:312-318. 10. Adams J, King G, Steinmann S, Cohen M. Elbow arthroscopy: Indications, techniques, outcomes and complications. Instr Course Lect 2015;64:215-224. 11. Lyons TR, Field LD, Savoie FH. Basics of elbow arthroscopy. Instr Course Lect 2000;49:239-246. 12. Guhl JF. Arthroscopy and arthroscopic surgery of the elbow. Orthopedics 1985;8:1290-1296. 13. Andrews JR, Carson WG. Arthroscopy of the elbow. Arthroscopy 1985;2:97-107. 14. Lynch GJ, Meyers JF, Whipple TL, Caspari RB. Neurovascular anatomy and elbow arthroscopy: Inherent risks. Arthroscopy 1986;2:190-197. 15. Lindenfeld TN. Medial approach in elbow arthroscopy. Am J Sports Med 1990;18:413-417. 16. Verhaar J, Mameren HV, Brandsma A. Risks of neurovascular injury in elbow arthroscopy: Starting anteromedially or anterolaterally? Arthroscopy 1991;7:287-290. 17. Marshall PD, Fairclough JA, Johnson SR, Evans EJ. Avoiding nerve damage during elbow arthroscopy. J Bone Joint Surg 1992;75:129-131. 18. Field L, Altchek D, Warren R, O’Brien S, Skyhar M, Wickiewicz T. Arthroscopic anatomy of the lateral elbow: A comparison of three portals. Arthroscopy 1994;10: 602-607. 19. Adolfsson L. Arthroscopy of the elbow joint: A cadaveric study of portal placement. J Shoulder Elbow Surg 1994;3: 53-61. 20. Drescher H, Schwering L, Jerosch J, Herzig M. The risk of neurovascular damage in the elbow joint arthroscopy. Z Orthop Ihre Grenzgeb 1994;132:120-125. 21. Miller CD, Jobe CM, Wright MH. Neuroanatomy in elbow arthroscopy. J Shoulder Elbow Surg 1995;4:168-174. 22. Stothers K, Day B, Regan W. Arthroscopy of the elbow: Anatomy, portal sites, and a description of the proximal lateral portal. Arthroscopy 1995;11:449-457. 23. Unlu M, Kesmezacar H, Akgun I, Ogut T, Uzun I. Anatomic relationship between elbow arthroscopy portals and neurovascular structures in different elbow and forearm positions. J Shoulder Elbow Surg 2006;15:457-462. 24. Chaware PN, Santoshi JA, Pakhare AP, Rathinam BA. Risk of nerve injury during arthroscopy portal placement in the elbow joint: A cadaveric study. Indian J Orthop 2016;50:74-79. 25. Papilion JD, Neff RS, Shall LM. Compression neuropathy of the radial nerve as complication of elbow arthroscopy: A case report and review of the literature. Arthroscopy 1988;4:284-286. 26. Thomas MA, Fast A, Shapiro D. Radial nerve damage as a complication of elbow arthroscopy. Clin Orthop Relat Res 1987;215:130-131.
Purpose: To evaluate the proximity to the radial nerve on cadaveric specimens of 2 modified anterolateral portals used for elbow arthroscopy. Methods: Ten fresh cadaveric elbow specimens were prepared. Four-millimeter Steinman pins were inserted into 3 anterolateral portal sites in relation to the lateral epicondyle: (1) the standard distal anterolateral portal, (2) a modified direct anterolateral portal, and (3) a modified proximal anterolateral portal. These were defined as follows: direct portals 2 cm directly anterior to the lateral epicondyle, and proximal portals 2 cm proximal and 2 cm directly anterior to the lateral epicondyle. Each elbow was then dissected to reveal the course of the radial nerve. Digital photographs were taken of each specimen, and the distance from the Steinman pin to the radial nerve was measured. Results: The modified proximal anterolateral and direct anterolateral portals were found to be a statistically significant distance from the radial nerve compare to the distal portal site (P ¼ .011 and P ¼ .0011, respectively). No significant difference was found in the proximity of the radial nerve between the modified proximal and direct anterolateral portals (P ¼ .25). Inadequate imaging was found at a single portal site for the proximal site; 9 specimens were used for analysis of this portal with 10 complete specimens for the other 2 sites. Conclusions: In cadaveric analysis, both the modified proximal and direct lateral portals provide adequate distance from the radial nerve and may be safe for clinical use. In this study, the distal anterolateral portal was in close proximity of the radial nerve and may result in iatrogenic injury in the clinical setting. Clinical Relevance: This is a cadaveric analysis of 2 modified portal locations at the anterolateral elbow for use in elbow arthroscopy. Further clinical studies are needed prior to determining their absolute safety in comparison to previously identified portal sites.
From the Northwell Health Orthopaedic Institute (P.G.), New Hyde Park, New York; and Department of Orthopaedics, Tulane University (S.T., P.G., L.R., M.J.O., F.H.S.), New Orleans, Los Angeles, U.S.A. The authors report the following potential conflicts of interest or sources of funding: M.J.O. is a consultant for Smith & Nephew and DePuy Mitek and has received institutional grants from DePuy Mitek. F.H.S. has board membership (unpaid) in American Shoulder and Elbow Surgeons and the Arthroscopy Association of North America; is a consultant (unpaid) for Biomet, Exactech, Mitek, Rotation Medical, and Smith & Nephew; has received institutional grants from Tulane University, Mitek ($13,500); receives payment for lectures including service on speakers bureaus from Mitek ($2,000, 4 presentations) and Smith & Nephew ($3,500, 6 presentations); royalties from Exactech ($760); and other: unpaid publications, editorial/governing boardsdArthroscopy board of trustees and Wrist Surgery editorial board. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received November 30, 2016; accepted June 19, 2017. Address correspondence to Felix H. Savoie III, M.D., Tulane University Department of Orthopaedics, 1430 Tulane Ave., #8632, New Orleans, LA 70112, U.S.A. E-mail: [email protected] Ó 2017 by the Arthroscopy Association of North America 0749-8063/161143/$36.00 http://dx.doi.org/10.1016/j.arthro.2017.06.012
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ince its inception, advances in techniques have expanded the use of arthroscopy and its indications for use in the elbow.1-13 Prior cadaveric studies have examined the proximity of arthroscopic portal placement in relation to neurovascular anatomy,13-24 but few studies have deviated from the originally described portal locations as first described by Andrews and Carsons13 in 1985. The anterolateral portals have since been described as 3 separate and distinct portals: the distal, direct, and proximal. Their locations are as follows: distal portals are 3 cm distal and 1 cm anterior to the lateral epicondyle, direct portals are 1 cm directly anterior to the lateral epicondyle, and proximal portals are 2 cm proximal and 1 cm anterior to the lateral epicondyle.13,17,18,22,24 We have modified the 2 more proximal portal sites an additional 1 cm anterior compared with the traditional definitions, as we feel this may provide superior access to the elbow joint during advanced arthroscopic procedures. The
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Fig 1. Comparison of the traditional portal sites to our modified anterior portal sites with the elbow flexed in prone position for arthroscopy. The traditional portals are marked in red. Blue markings represent the modified portals presented as an additional 1 cm anterior. The asterisk signifies the proximal portal sites and the caret ( ) signifies the direct portal sites. ˇ
procedures we find the more anterior portal to be useful for include advanced arthritis with deformity, post-traumatic ankyloses with and without anterior heterotopic ossification, acute fracture dislocations (terrible triad injuries), and complex elbow instability cases. Following the same model as previous studies, we set out to demonstrate the safety of these portals with regard to radial nerve proximity and evaluate the safety of their use in both routine and advanced elbow arthroscopy. The purpose of this study was to evaluate the proximity to the radial nerve on cadaveric specimens of 2 modified anterolateral portals used for elbow arthroscopy. Our hypothesis was that there would be no significant difference in safety margin to the radial nerve from the traditional distal portal site compared with our modified portal sites.
osteoarthrosis. The elbows were held at 90 of flexion to mimic intraoperative positioning of an elbow placed into the lateral decubitus or prone positions. As befitting our usual practice, we establish a proximal anterior medial portal for visualization and then established all lateral portals. The distal lateral humerus, the radial head, the proximal radius, and the lateral epicondyle were identified and marked with a surgical marking pen. Three anterolateral portal sites were established in all specimens starting with the distal anterolateral and progressing proximal. Stab incisions via scalpel were made at each mark prior to Steinmann pin insertion at each portal site. The most studied and well-defined portal is that originally used by Andrews and Carson, which has since been termed a distal anterolateral portal. Across the vast majority of the prior cadaveric studies, this portal was used for comparison and study.13-15,17-23 It is defined as 3 cm distal and 1 cm anterior to the lateral epicondyle and was labeled the “distal” portal. After placement of the distal portal, our modified direct and modified proximal portals were placed. The direct portal was placed 2 cm directly anterior to the tip of the lateral epicondyle, and the proximal was placed 2 cm proximal to the lateral epicondyle and 2 cm anterior to the lateral intermuscular septum. Both of these portals were placed more anterior than the prior portals and have not previously been described in the literature (see Fig 1). A 4-mm-diameter Steinmann pin was introduced at each of the identified portal sites after piercing the skin with a scalpel and aiming directly at the midpoint of the elbow joint. The joint was not distended during portal placement to preserve accurate measurements after dissection and to measure the worst-case scenario in distance to the radial nerve. As noted in previous works,13,14,19 this prevents fluid accumulation in the surrounding soft tissues, which can distort the final measurements. Each specimen was then dissected to maintain the placement and position of the Steinmann
Methods Ten fresh cadaveric elbow joints devoid of remaining forearms and hands were dissected and evaluated for final data collection. Prior to dissection, each elbow was screened for signs of trauma, previous surgery, or
Fig 2. Marked elbow prior to dissection with 3 Steinmann pins inserted at each portal site relative to the lateral epicondyle that is marked.
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Table 1. Distance From the Steinman Pin to the Radial Nerve Specimen 1 2 3 4 5 6 7 8 9 10
Proximal, mm 5 7 10 18 10 17 d* 9 15 9
Direct, mm 12 14 6 16 21 17 12 9 22 9
Distal, mm 3 1 0 (contact) 0 (contact) 9 14 0 (contact) 0 (contact) 12 6
*Considered inadequate image to use for measurement.
Fig 3. Dissected elbow with 3 portal sites. A line of closest fit from each portal site to the radial nerve was then established and measured digitally.
Data and measurements were pooled and organized into Table 1. An inadequate image was obtained in specimen 7 for the proximal anterolateral portal. Therefore, data were collected for 9 cadavers at the proximal anterolateral portal and for all 10 cadavers for
both the direct anterolateral and distal anterolateral portals. The traditional distal portal was an average of 4.5 mm (standard deviation 5.42 mm) away from the radial nerve, with a range of 0 to 14 mm. At the distal portal, the radial nerve came in contact with the Steinman pin in 4 of the cadavers. The direct anterolateral portal was an average of 13.8 mm (standard deviation 5.25 mm) from the radial nerve, with a range of 6 to 21 mm. The proximal anterolateral portal was an average of 11.1 mm (standard deviation 4.51 mm) away from the radial nerve, with a range of 5 to 18 mm. Summary of these data can be found in Table 2. Unpaired t tests comparing the difference in proximity to the radial nerve at both modified sites were then performed. Comparison of the proximity to the radial nerve between the traditional distal portal to both our modified proximal portals revealed a significant difference found in distance to the radial nerve at both sites in our cadaveric model (P ¼ .011 and P ¼ .001, respectively). Comparison of the safety profiles between our 2 modified proximal and direct portals revealed no statistically significant difference in safety margin (P ¼ .25). See Table 3 for comparison data between the different portals.
Fig 4. The Steinmann pin at the distal portal site is in contact with the radial nerve in this specimen. This finding occurred in 4 specimens.
The cadaveric investigation presented here shows no increased risk of iatrogenic injury with the use of more anterior anterolateral portals. In our cadaveric dissections the distal anterolateral portal was found to be the nearest in proximity to the radial nerve, which may place it at risk for iatrogenic injury compared with other portal sites. As indications for elbow arthroscopy continue to grow, knowledge of 3-dimensional neurovascular anatomy is imperative for patient safety. We have modified our portals to allow more advanced surgery to be performed arthroscopically. These more advanced cases include the arthroscopic management of severely arthritic elbows with large anterior spurs and deformity, severe post-traumatic ankyloses with and without heterotopic
pins. The skin and subcutaneous tissue were removed. The radial nerve was then identified at the interval between the brachialis and the brachioradialis muscles and traced distally. Dissection was stopped on visualization of the radial nerve overlying the supinator muscle. Digital photographs were then taken with a ruler in order to provide a digital scale and measurement. A “line of closest fit” was established digitally and measured between the Steinmann pins and the radial nerve at each portal site. The digital photographs were considered adequate when the entire Steinman pin, radial nerve, and line of closest fit were unobstructed. Figures 2 to 4 visually depict the portal entry, dissection, and measurement process.
Results
Discussion
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Table 2. Average Distances Between Each Portal Site Portal Distal Direct Proximal
Distance to Radial Nerve, mm 4.5 5.42 (0-14) 13.8 5.25 (6-21) 11.1 4.51 (5-18)
NOTE. Values are mean standard deviation (range).
bone, fracture dislocations, and complex elbow instability, which require the use of more anterior portals to access the pathology safely. As our indications have increased, the location, safety, and proximity of these portals needed to be evaluated. The goal is to minimize the risk of severe iatrogenic injury to the neurovascular structures that may arise from improper portal placement and from misdirected operative instruments.21,25,26 This study shows that both portal placement and choice of location plays a major role in the risk associated with iatrogenic nerve injury during elbow arthroscopy. The proximal anterolateral and direct anterolateral portals used in our study were found to be at an increased distance from the radial nerve than the traditional distal portal. Comparison of these portals to the cadaveric work of Field et al.18 displayed a similar distance to the radial nerve. Field et al. placed their proximal anterolateral portal 2 cm proximal and 1 cm anterior to the lateral epicondyle. They found the distance between their proximal portal and the radial nerve to be 14.2 mm without joint distention, compared with 11.1 mm in our study. Field et al. obtained their direct anterolateral portal at 1 cm directly anterior to the lateral epicondyle and found the distance between this portal and the radial nerve to be 9.8 mm without joint distention, compared with 13.8 mm in our study. Like the previous cadaveric works that compared different portal sites,17,18,22 we found a statistically significant increase in distance to the nerve from both the proximal and direct anterolateral portals compared with the traditional distal anterolateral portal. In evaluating our cadavers as well as the data from prior works,17-19,22,24 the original distal anterolateral portal appears to be in closer proximity to the radial nerve than previously thought. Andrews and Carson1 described this portal as 3 cm distal and 1 cm anterior to the lateral epicondyle, and since then it has been investigated in 10 cadaveric studies.13-15,17-23 The mean distance to this portal site was found to range from 3 to 16.13 mm across these studies. Our average distance of 4.5 mm compared similarly to these measurements, and in our analysis the use of the distal anterolateral portal was actually found to be in particularly close proximity to the radial nerve. This conclusion is similar to prior studies that have directly compared the distal site to a more proximal site. Independently, they each found that the distal portal was the least safe in
comparison to more proximal portals.17,18,22 The results of those studies, coupled with the data collected here, show that this distance may not be safe for the patient. Our discovery of 4 Steinmann pins coming in contact with the nerve suggest that this danger may be more alarming than previously discussed. In line with prior works,18,22 use of the traditional distal anterolateral portal may be taking on unnecessary risk for entry in elbow arthroscopy, especially when other portal sites are readily available and proven to be in less proximity to the radial nerve. At our institution, we have used a more anterior portal placement for the past 9 years. Compared with the previously described proximal anterolateral and direct anterolateral portals by Field et al.,15 our portals are placed 1 cm more anterior. The more anterior portal locations were developed as more complicated procedures became more common. A more anterior portal entry location does require the surgeon to aim more posteriorly while inserting the arthroscope toward the joint, thereby entering more laterally. This more anterior placement has the additional benefit of providing the surgeon a safer trajectory in relation to the radial nerve. We investigated 2 modified anterolateral portals more anterior to the previously described sites and found that they are a safe distance from the radial nerve. Direct comparisons to the distal anterolateral portal, which is the most commonly used and cited in the literature,13-15,17-23 revealed a statistically significant increase in safety margin to the radial nerve for both our modified portals. The use of the distal anterolateral portal was associated with increased risk of radial nerve injury in our study as well as in previous works.17,18,22 Future study may focus on comparing the safety profile of our modified portals to the original portals, but it is unlikely that a significant difference will be found with both such small distances and limits on cadaver sample sizes. Performing a cadaveric study of necessary size is likely to not be cost-effective. Limitations A possible limitation in our study was the lack of joint distention. Although it has been established in clinical practice that joint distention improves the distance to the radial nerve at the anterolateral portal site,13,14,18-21 multiple studies have noted the difficulty in maintaining distention in the cadaveric model. It was also shown that continued distention may distort the Table 3. Comparison of Safety Margin to Radial Nerve Portals Distal to direct Distal to proximal Direct to proximal
P Value .0011 .011 .248
P < .5? Yes Yes No
MODIFIED PORTALS: A STUDY ON SAFETY
measurements as a result of saline extravasation into the surrounding tissues as the procedure progresses.13,14,19 Marshall et al.17 noted a reduced elasticity in the cadaveric model that limited the effect of joint distention. Similarly, Stothers et al.22 did not feel that the relationship of the radial nerve to the sheath was significantly changed without the presence of joint distention once the procedure had started. Another limitation is that the insertion of 3 steinmann pins in the same specimen may have distorted the overall soft tissue anatomy in the specimens. Although we acknowledge this may alter measurements, we believe the use of a sharp, rigid pin minimizes any distortion. Gravity may also play a role in the soft tissue anatomy. Our specimens were devoid of the remaining forearm and hands and as such there was minimal pull due to gravity at the elbow joint. The work in this study is also not applicable to elbow arthroscopy performed in the supine position, as the position of the elbow during these procedures was not evaluated.
Conclusions In cadaveric analysis, both the modified proximal and direct lateral portals provide adequate distance from the radial nerve and may be safe for clinical use. In this study, the distal anterolateral portal was in close proximity to the radial nerve and may result in iatrogenic injury in the clinical setting.
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