The distance between the sural nerve and ideal portal placements in lateral subtalar arthroscopy: a cadaveric study

BACKGROUND: There have been limited studies assessing the relative safety of lateral portals for subtalar arthroscopy in terms of their distance from the sural nerve and its branches. The aim of this cadaveric study was to assess and compare the distance of lateral subtalar arthroscopy portal sites to the sural nerve and its branches. MATERIALS AND METHODS: Twenty embalmed cadaveric lower limbs were dissected exposing the nerves and tendons and subtalar arthroscopy portals were replicated using pins. The anatomically important distances were measured with a digital caliper. Statistical analysis of the data was performed using SPSS for Windows 11.5 (SPSS Inc, Chicago, IL) using Friedman Tests and Wilcoxon Signed Ranks tests. RESULTS: The median distance of the anterior and middle subtalar portals to the nearest nerve was 21.3 mm and 20.9 mm, respectively, and 11.4 mm for the posterior portal. There was no statistically significant difference between anterior and middle portals (p=0.87) but there was statistically significant difference between anterior versus posterior and middle versus posterior portals (p=0.001 in each comparison). CONCLUSION: The anterior and middle subtalar portals were both less likely to damage important structures than the posterior subtalar portal. CLINICAL RELEVANCE: The results of this study can be of value to the surgeon when planning arthroscopic procedures to the subtalar joint from the lateral approach.     

经胫后肌腱鞘建立踝关节镜后方共轴入路的解剖学研究

目的进行经胫后肌腱鞘建立踝关节镜后方共轴入路的解剖学研究。方法在20具踝关节标本上以克氏针建立共轴入路,测量克氏针与后方重要神经、肌腱、血管的距离。在5具新鲜踝关节标本上,以2.7mm30°关节镜建立共轴入路,镜下观察并测量以上距离。结果内侧关节镜入路的体表标志为内踝尖上方5～12mm(平均8mm),外侧入路的体表标志为外踝尖上方8～24mm(平均15mm)。经过胫后肌腱鞘、腓骨后缘建立共轴入路,不但把关节镜、镜下器械与后方重要神经血管结构与后关节囊隔开,同时增加了它们之间的距离。经过此入路可以观察到距骨关节面的后1/2～2/3、外侧踝关节间隙、内侧踝关节间隙、后关节囊、胫距关节间隙,能清楚地看到踝穴与距骨的动态关系。可以通过后外侧入路进入手术器械进行镜下手术。结论经胫后肌腱鞘的踝关节镜后方共轴入路,具有操作简便、安全性好、镜下视野清楚、操作空间大的优点。     

Coaxial portals for posterior ankle arthroscopy

Purpose: The authors performed a cadaveric study on 10 ankles and retrospectively reviewed 29 arthroscopic synovectomies to determine the trajectory, minimal safe distances, and complications using a new approach for posterior ankle arthroscopy. Type of Study: Anatomic study and case series. Materials and Methods: A posterolateral portal was established immediately posterior to the peroneal tendon sheath. While staying within the posterior ankle capsule, an inside-out technique was then used to establish the posteromedial portal directly behind the medial malleolus adjacent to the posterior tibial tendon. The cadaveric ankles were frozen, sectioned, and photographed to measure the proximity of neurovascular structures to these coaxial portals. From 1988 to 1994, arthroscopic synovectomy was performed on 23 patients (29 ankles) with hemophilia using these modified portals. Results: Results of the anatomic study showed that the posterior tibial nerve and posterior tibial artery were located a mean distance of 5.7 mm (SEM, 0.6 mm) and 6.4 mm (SEM, 0.7 mm) from the edge of the cannula, respectively. Neither penetration nor contact of nerve or vessel was observed at either posterior portal. In the 29 clinical cases, posterior capsular synovectomy was achieved arthroscopically with no detectable complications at an average 45-month follow-up. Conclusions: Our anatomic data show that the coaxial portals described here are essentially equidistant to the neurovascular structures compared with conventional portals. Our clinical results suggest that his technique for posteromedial and posterolateral portals is safe, effective, and reproducible.     

Coaxial portals for posterior ankle arthroscopy: An anatomic study with clinical correlation on 29 patients

Purpose: The authors performed a cadaveric study on 10 ankles and retrospectively reviewed 29 arthroscopic synovectomies to determine the trajectory, minimal safe distances, and complications using a new approach for posterior ankle arthroscopy. Type of Study: Anatomic study and case series. Materials and Methods: A posterolateral portal was established immediately posterior to the peroneal tendon sheath. While staying within the posterior ankle capsule, an inside-out technique was then used to establish the posteromedial portal directly behind the medial malleolus adjacent to the posterior tibial tendon. The cadaveric ankles were frozen, sectioned, and photographed to measure the proximity of neurovascular structures to these coaxial portals. From 1988 to 1994, arthroscopic synovectomy was performed on 23 patients (29 ankles) with hemophilia using these modified portals. Results: Results of the anatomic study showed that the posterior tibial nerve and posterior tibial artery were located a mean distance of 5.7 mm (SEM, 0.6 mm) and 6.4 mm (SEM, 0.7 mm) from the edge of the cannula, respectively. Neither penetration nor contact of nerve or vessel was observed at either posterior portal. In the 29 clinical cases, posterior capsular synovectomy was achieved arthroscopically with no detectable complications at an average 45-month follow-up. Conclusions: Our anatomic data show that the coaxial portals described here are essentially equidistant to the neurovascular structures compared with conventional portals. Our clinical results suggest that his technique for posteromedial and posterolateral portals is safe, effective, and reproducible.Arthroscopy: The Journal of Arthroscopic and Related surgery, Vol 16, No 8 (November-December), 2000: pp 836–842     

Arthroscopic release for lateral epicondylitis: a cadaveric model.

At least 10 different surgical approaches to refractory lateral epicondylitis have been described, including an arthroscopic release of the extensor carpi radialis brevis tendon. The advantages of an arthroscopic approach include an opportunity to examine the joint for associated pathology, no disruption of the extensor mechanism, and a rapid return to premorbid activities with possibly fewer complications. A cadaveric study was performed to determine the safety of this procedure. Ten fresh-frozen cadaveric upper extremities underwent arthroscopic visualization of the extensor tendon and release of the extensor carpi radialis brevis tendon. The specimens were randomized with regard to the use of either a 2.7-mm or a 4.0-mm 30 degree arthroscope through modified medial and lateral portals. Following this, the arthroscope remained in the joint, and the portal, cannula track, and surgical release site were dissected to determine the distance between the cannula and the radial, median, ulnar, lateral antebrachial, and posterior antebrachial nerves, and the brachial artery and the ulnar collateral ligament. No direct lacerations of neurovascular structures were identified; however, the varying course of the lateral and posterior antebrachial nerves place these superficial sensory nerves at risk during portal placement. As in previous reports, the radial nerve was consistently in close proximity to the proximal lateral portal (3 to 10 mm: mean, 5.4 mm). The ulnar collateral ligament was not destabilized. Arthroscopic release of the extensor carpi radialis brevis tendon appears to be a safe, reliable, and reproducible procedure for refractory lateral epicondylitis. Cadaveric dissection confirms these findings.     

Ankle arthroscopy: neurovascular and arthroscopic anatomy of standard and trans-achilles tendon portal placement

Ankle arthroscopy is an accepted method of evaluating ankle disorders. Accurate arthroscopic portal placement is essential because of the proximity of superficial and deep neurovascular and tendinous structures of the ankle. In order to define this anatomy as it pertains to safe portal placement, five fresh frozen cadaver ankles were dissected after standard arthroscopic portals were placed anteriorly and posteriorly. All structures were identified. The distances to these structures from the most lateral portals were recorded. Five other ankles were arthroscoped using standard portals and evaluated. In addition, a trans-achilles tendon (TAT) approach was evaluated for portal use. Ankle arthroscopy can be performed in a safe, reproducible manner when the following recommendations are followed: (a) outline tendinous structures, and remain parallel to them with the knife blade to avoid laceration of underlying structures; (b) penetrate only the skin with the knife to avoid laceration of superficial nerves in the subcutaneous tissue; (c) perform pre- and postneurovascular examination; and (d) understand that anterocentral and posteromedial portals are potentially hazardous to their respective neurovascular bundles. The TAT approach, based only on cadaver studies, appears anatomically safe and offers the potential advantage of an additional posterior portal.     

Arthroscopy of the elbow: Anatomy,portal sites,and a description of the proximal lateral portal

Cadaveric studies were carried out to evaluate the safety and value of the standard portals used in elbow arthroscopy. The dissections were performed in 12 fresh cadaveric specimens. Each portal was assessed in terms of its safety with respect to nearby important structures. A proximal lateral portal was evaluated and has subsequently been used in 62 patients. A straight posterior (transhumeral) portal was also studied. We have found that in arthroscopy of the elbow joint, the proximal approaches (proximal medial and proximal lateral), are safer than the anteromedial and anterolateral approaches. All areas of the anterior compartment can be visualized using these two portals, and we recommend that they be the standard anterior portals used in elbow arthroscopy. All of the posterior approaches are safe.     

The safety of the posterior ankle arthroscopy in management of posterior ankle impingement: A cadaveric study

BackgroundArthroscopic management of the posterior ankle impingement with the patient in supine position has the advantage of dealing with anterior ankle pathology at the same time without the need to change position of the patient. This study aims at evaluation of the safety of portal establishment and instrumentation of this technique.MethodsSixteen fresh-frozen cadaver specimens were used. The relationships of the posteromedial and posterolateral portals to the adjacent tendons and nerves and the relationship of the coaxial portal tract with the posterior ankle capsule and the flexor hallucis longus tendon were studied.ResultAngle θ₁ between the intermalleolar line and the posterior ankle coaxial portal tract averaged 1° (−10° to 22°). Angle θ₂ between the intermalleolar line and the metal rod where the neurovascular bundle started to move averaged 19° (10° to 30°). Angle θ₃ between the intermalleolar line and the metal rod where it reached the lateral border of the Achilles tendon was larger than angle θ₂ in all specimens. The angle of safety (θ_s) averaged 18° (−1° to 26°).ConclusionsInjury to the tendon, nerves or vessels is possible during establishment of the portals and resection of the os trigonum.     

Arthroscopic triple fusion joint preparation using two lateral portals: A cadaveric study to evaluate efficacy and safety

BackgroundArthroscopic triple fusion has several advantages over open techniques, but its use has yet to become widespread. Preliminary published techniques use five portals with neurovascular risk. Our aim was to assess the safety and efficacy of an alternative lateral two portal technique.MethodsFour cadaveric hindfeet were arthroscopically prepared for a triple fusion using two lateral portals. The distance to relevant subcutaneous nerves was measured as well as the prepared joint surface percentage.ResultsMean distance from mid-lateral portal to the nearest sural nerve branch was 22.3 mm (range 20–24 mm) and from the dorsolateral portal to the intermediate branch of the superficial peroneal nerve was 7.8 mm (range 4–11 mm). Mean percentages of joint preparation were 63% (talar head), 62% (navicular), 75% (calcaneum) and 74% (cuboid).ConclusionsTwo lateral arthroscopic portals allow adequate joint preparation for triple fusion procedures. The proximity of subcutaneous nerves is important to appreciate when using these portals.     

Posterior ankle arthroscopy: an anatomic study

BACKGROUND: Ankle arthroscopy has generally been performed with use of anterior portals with the patient in the supine position. Little has been published on ankle arthroscopy performed with use of posterior portals, particularly with the patient in the prone position. The purpose of the present study was to evaluate the relative safety and efficacy of ankle arthroscopy with use of posterior portals with the limb in the prone position. METHODS: Thirteen fresh-frozen cadaver specimens were used. Posterolateral and posteromedial portals were established. Arthroscopy was performed, and the extent of the talar dome that could be visualized was marked. Four-millimeter plastic cannulae were filled with oil and were placed in the portals for use as reference landmarks on magnetic resonance imaging studies. The proximity of the portal cannulae to the adjacent structures was measured on standard magnetic resonance images and then during careful dissection. The distances measured by dissection were compared with the measurements made on magnetic resonance images. RESULTS: An average of 54% (range, 42% to 73%) of the talar dome could be visualized. The average distance between a cannula and adjacent anatomic structures after dissection was 3.2 mm (range, 0 to 8.9 mm) to the sural nerve, 4.8 mm (range, 0 to 11.0 mm) to the small saphenous vein, 6.4 mm (range, 0 to 16.2 mm) to the tibial nerve, 9.6 mm (range, 2.4 to 20.1 mm) to the posterior tibial artery, 17 mm (range, 19 to 31 mm) to the medial calcaneal nerve, and 2.7 mm (range, 0 to 11.2 mm) to the flexor hallucis longus tendon. The magnetic resonance images demonstrated very similar distances except in the case of the distance between the posteromedial cannula and the tibial nerve, which often was difficult to specifically identify on magnetic resonance imaging studies. CONCLUSIONS: The findings of the present cadaveric study suggest that, with the patient in the prone position, arthroscopic equipment may be introduced into the posterior aspect of the ankle without gross injury to the posterior neurovascular structures. Limited clinical trials should be carried out to confirm this finding.     

不同体位下肘关节镜常用入路与周围神经的解剖关系

目的 比较不同体位下各种肘关节镜入路与毗邻神经血管的解剖关系,评价肘关节镜操作中各种标准入路的安全性及应用价值.方法 选用新鲜尸体肘关节10个进行解剖,测量9种标准肘关节镜入路与毗邻神经血管的最近距离,并根据各入路下关节镜检的镜下视野及操作灵活性评价其应用价值. 结果肘关节镜人路与毗邻神经距离受注水膨胀关节、肘关节伸直或屈曲及前臂旋前或旋后体位变化影响.肘关节屈曲90°前臂旋后、中立、旋前位,前外侧入路关节镜套管与桡神经距离分别为(2.9±1.1)mm、(4.5±1.5)mm、(5.8 ±1.7)mm,穿刺造成神经损伤风险大;肘关节伸直前臂旋后位2例肘关节中套管与桡神经直接接触.近端前内侧或近端前外侧人路观察肘关节前间室、后正中人路观察后间室视野良好且穿刺风险小.后方入路均安全. 结论近端前内侧或近端前外侧入路优于前内侧或前外侧人路,与后正中入路结合应用可基本满足多数肘关节镜手术的要求,是一组安全、有效的人路点.     

The new subclavian portal and modified neviaser portal for arthroscopic rotator cuff repair

Shoulder arthroscopy and the introduction of suture anchors has provided the surgeon with the ability to repair rotator cuff tears through minimal incisions. Rotator cuff repair involves the use of several portals, such as the posterior portal, the anterior portal, the anterior superior portal, the anterior inferior portal, and the Neviaser portal. The authors have developed 2 additional portals, the new Subclavian portal and the modified Neviaser portal, to improve the safety and efficacy of rotator cuff repair and solve a number of problems associated with traditional repair techniques. The subclavian portal is located directly below the clavicle, 1 to 2 cm from the acromioclavicular joint, and instruments are aimed medial to lateral. The modified Neviaser portal changes the angle of insertion of the Neviaser portal. Instruments are aimed 20° from the horizontal plane and 45° anterior, directly at the suture anchor. Repair techniques using each portal were reviewed. Twenty cadaveric shoulders were dissected for each portal and the anatomy from each portal was documented. The cadaveric dissections showed that this portal passes greater than 6 cm from the brachial plexus, musculocutaneous nerve, and subclavian artery and vein, and 4.7 cm from the cephalic vein. The modified Neviaser portal was shown to be safer than the Neviaser portal because it passes on top of the supraspinatous muscle, thereby protecting the suprascapular nerve. These portals provide an optimal angle of approach to the rotator cuff tendon and suture anchor as well as improved safety and efficacy in the repair of rotator cuff tears.     

Ankle anatomy for the arthroscopist. Part I: The portals

Proper portal placement is critical to performing good diagnostic and therapeutic arthroscopy. When the portals are positioned improperly, visualization can be impaired, making diagnosis and treatment more difficult. Three main anterior portals are available in arthroscopy of the ankle: anteromedial, anterolateral, and anterocentral. Posterior portals are also routinely used in ankle arthroscopy and can be established at a posterolateral or posteromedial position or directly through the Achilles tendon. Because of the potential for serious complications, the anterocentral and transAchilles portals are no longer used. Other portals have been described to obtain more complete access, particularly to the posterior compartment of the ankle joint. This work reviews the relationships that exist between the most important anatomic structures and arthroscopic portals of the ankle.     

Anatomical structures at risk in the arthroscopic Broström-Gould procedure: A cadaver study

BackgroundThe Broström Gould procedure is the gold standard for repair of lateral ankle ligament injury and ankle instability. This procedure has demonstrated excellent short- and long-term outcomes in the orthopedic literature. Arthroscopic Broström Gould techniques have become increasingly popular among some foot and ankle orthopedic surgeons. Typically, this technique requires standard anteromedial and anterolateral portals along with an accessory lateral working portal. The exact location of this portal is variable within the available described surgical techniques. The objective of this cadaveric study is to establish a standard entry point for and to assess the safety of the accessory lateral portal with respect to nearby anatomical structures.MethodsTen fresh-frozen below-knee cadaver specimens were used. The location of the accessory lateral portal was created 1.5 cm anterior to the distal tip of the fibula. A small vertical incision was made at this point, followed by insertion of a Kirschner wire into the joint. The wire was then gently impacted into the fibula. Superficial dissection was subsequently carried out around the entry point to identify the peroneal tendons, superficial peroneal nerve branches, and sural nerve branches. Structures were marked with colored push pins, and distance was measured between the nearest edge of the Kirschner wire and each of the three anatomic structures listed. Any instances of structural contact or damage were documented.ResultsThe average distance from the Kirschner wire to the peroneal tendon was 16.1 (±4.41) mm. The average distance from the wire to the superficial peroneal nerve and sural nerve was 13.11 (±6.79) mm and 12.33 (±4.08) mm, respectively. There were no instances of injury to any of the studied structures. However, there was a notable amount of variability in the proximity of structures in question for each cadaver. A branch of the superficial peroneal nerve was measured as close as 2 mm and as far as 24 mm in separate cadaver specimens.ConclusionArthroscopic Broström Gould procedures are a safe and effective method for lateral ankle ligamentous repair but are not without risk. Accessory lateral portal placement is relatively safe but should be meticulously executed to avoid damage to nearby anatomical structures.     

Posterior tibial nerve lesions in ankle arthroscopy

Ankle arthroscopy provides a minimally invasive approach to the diagnosis and treatment of certain ankle disorders. Neurological complications resulting from ankle arthroscopy have been well documented in orthopaedic and podiatric literature. Owing to the superficial location of the ankle joint and the abundance of overlying periarticular neurovascular structures, complications reported in ankle arthroscopy are greater than those reported for other joints. In particular, all reported neurovascular injuries following ankle arthroscopy have been the direct result of distractor pin or portal placement. The standard posteromedial portal has recognized risks because of the proximity of the posterior neurovascular structures. There can be considerable variability in the course of these portals and their proximity to the neurovascular structures. We found one report of intra-articular damage to the posterior tibial nerve as a result of ankle arthroscopy in the English-language literature and we report this paper as a second case described in the literature.     

Anatomic Study of Anterior and Posterior Ankle Portal Sites for Ankle Arthroscopy in Plantarflexion and Dorsiflexion: A Cadaveric Study in the Japanese Population

Arthroscopy is an important and minimally invasive diagnostic and therapeutic tool. However, the risk of injury to the neurovascular structures around the portals exists during arthroscopy of the ankle. In the present study, we measured the distance between each portal and the adjacent neurovascular structures with the foot in plantarflexion and dorsiflexion in the Japanese population. Standard anterolateral (AL), anteromedial, posterolateral (PL), and posteromedial portal positions were identified in 6 fresh adult cadaveric feet. The skin was dissected from the underlying tissue to visualize the adjacent neurovascular structures as noninvasively as possible. The superficial peroneal nerve was the structure closest to an anterior (i.e., AL) portal (3.2?±?4.2 and 8.3?±?3.9?mm in plantarflexion and 5.2?±?4.3 and 10.8?±?4.1?mm in dorsiflexion), followed by the saphenous nerve and great saphenous vein (SpV). The distance from the superficial peroneal nerve to the AL portal and from the saphenous nerve and great SpV to the anteromedial portal increased significantly with dorsiflexion and decreased significantly with plantarflexion. The sural nerve was the structure closest to the posterior (i.e., PL) portal (10.4?±?4.8?mm in plantarflexion and 8.5?±?3.9?mm in dorsiflexion), followed by the lesser SpV. The distance from the sural nerve, saphenous nerve, and lesser SpV to the PL portal and from flexor hallucis longus, posterior tibial artery, and tibial nerve to the posteromedial portal increased significantly in plantarflexion and decreased significantly in dorsiflexion. These findings could help to prevent damage to the neurovascular structures during ankle arthroscopy.     

Anatomical study of the ankle with view to the anterior arthroscopic portals

This article evaluates the risk of interference with the neurovascular structures in the four anterior ankle arthroscopic portals, described on each side of the extensor tendons: anteromedial, medial midline, anterocentral and anterolateral. Complications after ankle arthroscopies have been described in up to 17%, most being neurovascular. To quantify the neurovascular risks we dissected 68 cadaveric feet and evaluated the correlations between tendons, vessels and nerves. The mean distance between tibialis anterior and extensor hallucis longus and between extensor hallucis longus and extensor digitorum longus is 4 mm, but in 10-20% these tendons are in apposition or are overlapped. The tibialis anterior vascular bundle was absent in 11.8%, was located between the tibialis anterior and the extensor hallucis longus in 3% and between the extensor hallucis longus and the extensor digitorum longus in 64.7%. A peroneal vascular bundle or branches of the tibialis anterior vascular bundle were located lateral to the extensor digitorum longus/peroneus tertius tendon in 88.2%. Transverse vascular branches were identified in 41.2% over the medial side of the joint line and in 52.9% over the lateral side. The deep peroneal nerve was located between the extensor hallucis longus and the extensor digitorum longus tendons in 58.8%. The superficial peroneal nerve had branches located between the tibialis anterior and the extensor hallucis longus tendons in 2.9%, between the extensor hallucis longus and the extensor digitorum longus tendons in 23.5% and lateral to the extensor digitorum longus/peroneus tertius tendon in 32.4%. These results show that the anteromedial and medial midline portals are the safest. The anterolateral portal should be noted not only for the risks to the superficial peroneal nerve, but also to the peroneal vessels.     

The radial portal for scaphotrapeziotrapezoid arthroscopy

The scaphotrapeziotrapezoidal (STT) joint is a complex joint in which the arthroscope and instruments can be used through the radial midcarpal and STT-ulnar portals. This report describes a new arthroscopic portal at the STT joint to complete and improve the evaluation and treatment of this joint by arthroscopy: The STT-radial (STT-R) portal is situated immediately radial to the abductor pollicis longus at the STT level. Five cadaveric wrist specimens were dissected immediately after the portal was established, and photographed to determine the proximity of neurovascular structures. Magnetic resonance imaging evaluation of 15 hands was performed to measure the proximity of the radial artery. A cadaveric distal scaphoid excision was also created arthroscopically to show the real usefulness of this portal. Results of the anatomic study showed that no lesions of nerves or vessels were seen at this portal. Magnetic resonance imaging showed that the radial artery was located at a safe distance from the portal. The distal scaphoid excision was performed 15 minutes after the STT portals were established. Our results suggest that this new portal is safe and effective.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 5 (May-June), 2003: pp 547–553     

Posterior arthroscopic approach to the ankle

Purpose: The purpose of this study is to verify the safety of a new technique for a posterior arthroscopic approach to the ankle. This technique was recently described in literature. The technique uses a modified posteromedial portal, a different way of introducing the instruments into the portal, and the tendon of the flexor hallucis longus (FHL) as a landmark to work in the posterior compartment. Type of Study: Anatomic study. Methods: The technique was performed on 10 (4 fresh and 6 fresh-frozen) below-knee amputation specimens, which were then dissected. The instruments were left in place, and anatomic dissections were performed to determine the relationship to the surrounding neurovascular structures. Then the instruments were removed, and the distance of the neurovascular structures from the posteromedial portal was recorded. Another medial portal, 1 cm more proximal, was also created to measure the distance of this latter portal from the nervous structures. Results: None of the anatomic dissections showed injuries to the neurovascular bundle either during penetration of the instruments or during procedures in the posterior compartment laterally to the tendon of the FHL. This latter is the landmark to prevent damage to the more medially located nerves and vessels. The new posteromedial portal is located, on average, 13.3 mm (range, 11 to 17 mm) from the posterior tibial nerve, 14.7 mm (range, 8 to 20) from the calcaneal branch (which may be single or multiple, and may vary as needed the height of bifurcation from the posterior tibial nerve), and 17.3 mm (range, 15 to 21 mm) from the posterior tibial artery. A posteromedial portal located 1 cm more proximally is on average 2.9 mm closer to the nervous structures. Conclusions: Based on these anatomic data, there appears to be relatively little risk to the surrounding neurovascular structures with this new technique. Therefore, this technique appears to be relatively safe in the treatment of intra-articular and extra-articular pathology.