Glenohumeral arthroscopy portals established using an outside-in technique: neurovascular anatomy at risk

The anatomy and function of the low posterolateral portal in addressing posterior labral pathology

PURPOSE

A standard posterior portal allows excellent visualization of the glenohumeral joint but is inadequate for anchor placement because of its parallelism to the glenoid surface. The purpose of this study was to describe the low posterolateral portal for glenohumeral arthroscopy, describe the anatomy of the portal and surrounding structures, and discuss the portal's usefulness in addressing posterior and inferior shoulder pathology.

METHODS

Five cadaveric shoulders were dissected after placement of a spear through the low posterolateral portal. The location was identified via a spinal needle, 2 to 4 cm lateral and 4 to 5 cm inferior to the posterolateral corner of the acromion. Measurements from the spear to the anatomic structures were recorded with a caliper. Seventeen patients with posterior labral pathology were included in this study. The low posterolateral portal was established while visualizing through the anterosuperolateral or posterior portal. The spear and anchor were inserted through the low posterolateral portal.

RESULTS

Five shoulders were dissected, and the neurovascular structures relative to the low posterolateral portal were identified. The portal was 13.8 +/- 1.6 mm from the axillary nerve and 13.4 +/- 1.2 mm from the posterior humeral circumflex artery. In the retrospective review the low posterolateral portal was created without difficulty or complication in all 17 patients. The portal was extremely helpful for anchor insertion in the posteroinferior glenoid. It was useful in suture passage through the posterior and inferior labrum and in suture management.

CONCLUSIONS

The low posterolateral portal provides the optimal angle for insertion of instruments and anchors, resulting in a more anatomic repair.

CLINICAL RELEVANCE

The standard 3 portals are not optimal for approaching posterior and inferior labral tears, and use of the low posterolateral portal improves access and treatment.

Anatomic risks of shoulder arthroscopy portals: anatomic cadaveric study of 12 portals

PURPOSE

The purpose of this anatomic cadaveric study was to determine with trocars in situ the relationships of 12 shoulder arthroscopic portals frequently used with the adjacent musculotendinous and neurovascular structures.

METHODS

Twelve shoulders of embalmed cadavers installed in a beach-chair position were dissected. Twelve different portals were established by using their authors' description: posterior "soft point," central posterior, anterior central, anterior inferior, anterior superior, 5 o'clock portal, Neviaser, superolateral, transrotator cuff approach, Port of Wilmington, anterolateral, and posterolateral. Six of these portals were placed on each shoulder so that each portal was studied 6 times. Dissections were conduced with trocars in situ to take into account their volume. The distance to the adjacent relevant neurovascular structures at risk (axillar and suprascapular nerves, axillar and suprascapular arteries, and cephalic vein) were measured, arm at side, by using a calliper. Musculotendinous structures crossed by portals were noticed.

RESULTS

The cephalic vein was injured twice by anterior portals. The 5 o'clock portal is at most risk of neurovascular injury. It is located at mean distances to the axillar artery and nerve of 13 and 15 mm, respectively. Other anterior, posterior, superior, and lateral portals are safe with mean distances higher than 20 mm. No musculotendinous rupture nor large injury occurred.

CONCLUSIONS

The present study shows that the trocars placement of the studied portals did not create, except for the cephalic vein, any lesion of the neurovascular adjacent structures.

CLINICAL RELEVANCE

This study suggests, except for the 5 o'clock portal, the safety of the shoulder arthroscopic portals tested regarding to the neurovascular adjacent structures.

A comparison of risk between the lateral decubitus and the beach-chair position when establishing an anteroinferior shoulder portal: a cadaveric study

PURPOSE

The purpose of this study was to assess, using a technique that minimally distorts the normal anatomy, the risk of injury when establishing a 5 o'clock shoulder portal in the lateral decubitus versus beach-chair position.

METHODS

The anteroinferior portal was simulated with Kirschner wires (K-w) drilled orthogonally at the 5 o'clock position in 13 fresh frozen human cadaveric shoulders. The neighboring neurovascular structures were identified through an anteroinferior window made in the inferior glenohumeral ligament. Their relations to the K-w and surrounding structures were recorded in both positions.

RESULTS

The median distance from the musculocutaneous nerve to the K-w was shorter in the lateral decubitus position than in the beach chair position (13.16 mm v 20.49 mm, P = .011). The cephalic vein was closer to the portal in the beach-chair position than in the lateral decubitus position (median 8.48 mm v 9.93 mm, P = .039). The axillary nerve was closer to the K-w in the lateral decubitus position than in the beach-chair position (median 21.15 mm v 25.54 mm, P = .03). No differences in the distances from the K-w to the subscapular and anterior circumflex arteries were found when comparing both positions. The mean percentage of subscapular muscle height from its superior border to the K-w was 53.03%.

CONCLUSIONS

This study showed the risk of injury establishing a transubscapular portal in either position. The musculocutaneous nerve and the cephalic vein are the most prone to injury. In general, the beach-chair position proved to be safer.

CLINICAL RELEVANCE

Inserting anchor devices orthogonally would permit stronger fixation but presents the risk of damaging neurovascular structures. This study focused on showing the neurovascular risk of performing full orthogonal insertion. Considering the good results reported with the usual superior-anterior portals, we do not recommend performing a transubscapular portal in routine shoulder arthroscopy.

The superior-medial shoulder arthroscopy portal is safe

PURPOSE

The superior-medial (SM) shoulder arthroscopic portal (Neviaser portal) is the portal anatomically closest to the suprascapular nerve, and any potential benefits of this portal would be mitigated if risk of suprascapular nerve injury were significant. The purpose of this study is to determine the safety of the SM arthroscopic shoulder portal. We hypothesize that the SM shoulder arthroscopic portal is safe.

METHODS

Twelve fresh cadaveric shoulders were securely positioned to simulate shoulder arthroscopy in the beach-chair position with the arm at the patient's side in neutral rotation. An SM portal was established 1 cm medial to the acromion and 1 cm posterior to the clavicle, and a 5.5-mm burr sheath was oriented toward the acromioclavicular joint. The skin and trapezius were resected, the supraspinatus was retracted, and the suprascapular nerve was identified. The distance between the sheath and the nerve was measured by 2 independent observers with calipers. A safe distance was defined as 10 mm.

RESULTS

The measured distances between the nerve and burr ranged from 18.5 to 35.7 mm, with a mean of 24.2 +/- 5 mm. The distance is significantly greater than the safe distance of 10 mm (P < .0001).

CONCLUSIONS

This study shows that the SM portal is safe. The distance between an instrument oriented toward the acromioclavicular joint via the SM portal and the suprascapular nerve was 18.5 mm or greater in all specimens.

CLINICAL RELEVANCE

Our study has clinical relevance because the SM portal is useful for arthroscopic rotator cuff repair, arthroscopic superior labrum repair, and arthroscopic distal clavicle excision.

The accessory posteromedial portal revisited: utility for arthroscopic rotator cuff repair

Arthroscopic rotator cuff repair is a technically challenging procedure. Accessory arthroscopic portals have been described that allow for optimal suture anchor placement, suture management, and knot tying. We describe here the usefulness of an accessory posteromedial portal that facilitates direct suture retrieval through the posterior aspect of a rotator cuff tear. This portal is created approximately 4 to 5 cm medial to the posterolateral corner of the acromion and 2 cm inferior to the scapular spine. The accessory posteromedial portal is especially useful when a retracted tear of the infraspinatus or teres minor is encountered. Because these tendons retract in a posterior and medial direction, the accessory posteromedial portal places the tendon-penetrating device in an ideal position for suture passage through the posterior portion of the rotator cuff tear. This portal also allows placement of margin convergence sutures for large U-shaped or L-shaped tears by permitting a direct "hand-off" of the suture to or from a second penetrating device that is placed through a standard anterior portal. If multiple suture anchors are required (as in the case of large or massive cuff tears, or when double-row fixation is employed), sutures can be pulled out through the accessory posteromedial portal to facilitate suture management.