Arthroscopic Approaches to the Shoulder
Arthroscopic Approaches to the Shoulder
General Principles of Arthroscopy
Visualization of anatomic structures in open surgical approaches is straightforward. If a given structure is not visible, it may be exposed by extending the incision, thus expanding the surgical approach. By contrast, visualization of structures in arthroscopic approaches is achieved by using a telescope. The most commonly used arthroscope is angulated 30 degrees at its tip so that the view obtained shows the structures that are 30 degrees from the long axis of the arthroscope and not the structures that are directly in front of the scope. This is the arthroscope described in this book (Fig. 1-73, inset).
Angled scopes are required because the bony structure of the joint allows the arthroscope to be placed only in certain positions. The use of an angled scope allows the surgeon to see “around the corner” and thereby greatly increases the view obtained within any joint.
Visualization of structures using an arthroscope can be achieved in several ways. Moving the scope forward or backward (advancing or withdrawing it) will reveal structures in front of or behind the original view (see Fig. 1-73). Keep the following important points in mind during arthroscopic use:
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Because the scope is angled 30 degrees from its axis, it is not possible to zoom in on an object merely by advancing the scope.
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Angling the scope will change the direction of the view (Fig. 1-75). You will not be able to visualize those structures directly in front of the arthroscope unless you angle it.
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It is possible to change the view by moving the joint while leaving the arthroscope in the same position. This maneuver is vital for full inspection of any joint.
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Figure 1-73 Visualization of structures using an arthroscope is achieved in several ways. Moving the arthroscope forward and backward (advancing or withdrawing) will show you structures in front of or behind your original view. Withdrawing the arthroscope from Position 1 to Position 2 changes the view from B to B′. Because the tip of the scope is angled at 30 degrees from its axis, it is not possible to zoom in on an object merely by advancing the scope.
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Figure 1-74 Rotating the scope will provide a series of views at angles of 30 degrees from the axis of the scope. Rotating the arthroscope 90 degrees counterclockwise from Position 2 to Position 3 changes the view from B′ to C.
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Figure 1-75 Angling the scope changes the direction of the view. It is the only way to be able to visualize those structures directly in front of the scope. Angling the arthroscope from Position 2 to Position 4 changes the view from B′ to A.
Posterior and Anterior Approaches
The shoulder is a large ball and shallow socket joint with a generous capsule that allows a large range of movement in all planes. Therefore, the anatomy of the joint makes it ideal for arthroscopic approaches. However, the shoulder is covered by thick layers of muscles, and this can make arthroscopic approaches somewhat difficult (Figs. 1-76 and 1-77). Neurovascular structures also are potentially at risk in arthroscopic approaches to the shoulder. The presence of the main neurovascular bundle anteroinferior to the joint limits anterior approaches. Other neurovascular structures may also be at risk if the entry portals are inaccurately positioned (see Dangers).
Arthroscopy of the shoulder is indicated for the following:
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Arthroscopic subacromial decompression for chronic rotator cuff tendonitis52
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Treatment of partial thickness tears of the rotator cuff53,54
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Treatment of degenerative disease of the acromioclavicular joint
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Removal of loose bodies
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Treatment of osteochondritis dissecans
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Synovectomy
Numerous arthroscopic portals have been described in shoulder arthroscopy surgery. The posterior portal is the one most commonly used
for diagnostic purposes. It is nearly always used in conjunction with the anterior portal. The combination of these approaches allows the use of the arthroscope along with arthroscopic instrumentation. Usually the arthroscope is inserted via the posterior portal, and instruments are inserted via the anterior portal. However, either portal can be used for either purpose. These two approaches are described in this section.
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Figure 1-76 Anatomy of the shoulder joint. Lateral view of the right shoulder with the lateral aspect of deltoid muscle removed, showing the thick muscular covering of the joint.
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Figure 1-77 Lateral view of glenoid cavity with the humeral head removed.
Position of the Patient
Place the patient supine on the operating table. Elevate the upper half of the table to 60 degrees. Position the patient so that the operative shoulder is off the edge of the table, allowing access to both sides of the shoulder (Fig. 1-78). Prep and drape the arm so that it can be freely manipulated during arthroscopy. This position, known as the beach chair position,10 reduces venous pressure around the shoulder and reduces bleeding. Arm traction is useful in arthroscopic subacromial decompression but is not necessary for diagnostic arthroscopy.
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Figure 1-78 Position of the patient for arthroscopy. Elevate the upper half of the table to 60 degrees. Position the patient so that the operative shoulder is off the edge of the table, allowing access to both sides of the shoulder. This is known as the “beach chair” position.10
Landmarks and Incision
The shoulder is surrounded on all sides by thick muscular coverings (see Figs. 1-51 and 1-76). The joint line cannot be palpated, therefore arthroscopic approaches rely on landmarks distant from the joint.
Landmarks
The acromion and the spine of the scapula form one continuous arch. The bony dorsum and lateral aspect of the acromion are easy to palpate on the outer aspect of the shoulder (see Figs. 1-51, 1-53, and 1-59A).
To identify the coracoid process, drop your fingers distally about 1 in from the anterior edge of the lateral one-third of the clavicle. Press laterally and posteriorly in an oblique line until you feel the coracoid process.
Incisions
Posterior. Make an 8-mm stab incision 2 cm inferior and 1 cm medial to the posterolateral tip of the acromion (Fig. 1-79).
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Figure 1-79 Posterior incision. Make an 8-mm stab incision 2 cm inferior and 1 cm medial to the posterior lateral tip of the acromion.
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Figure 1-80 Anterior incision. Make an 8-mm stab incision halfway between the tip of the coracoid process and the anterior aspect of the acromion.
Anterior. Make an 8-mm stab incision halfway between the tip of the coracoid process and the anterior aspect of the acromion (Fig. 1-80).
Internervous Plane
Posterior
Anterior
Surgical Dissection
Posterior
Place your finger on the coracoid process. Insert the trocar and arthroscopic sheath through the posterior skin incision, aiming the tip of the arthroscope toward your finger (Fig. 1-81). You will enter the glenohumeral joint at a point just above its equator. Although, in theory, the arthroscope may penetrate the rotator cuff between the infraspinatus and teres minor, the scope usually traverses through the substance of the infraspinatus (see Fig. 1-81).
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Figure 1-81 Posterior insertion of the arthroscope. Place your finger on the coracoid process. Insert the trocar and arthroscopic sheath through the posterior skin incision, aiming the tip of the arthroscope toward your finger.
Anterior
Two techniques are possible. The safest technique is to insert the arthroscope through the posterior portal to allow you to visualize the anterior capsule of the shoulder joint. Next, insert a long hypodermic needle through the anterior skin incision and enter the joint under direct vision of the arthroscope. This will ensure that you enter the joint in a correct and safe position (Fig. 1-82).
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Figure 1-82 Anterior insertion of the arthroscope. Insert an arthroscope through the posterior portal to allow you to visualize the anterior capsule of the shoulder joint. Next, insert a long hypodermic needle through the anterior skin incision and enter the joint under direct vision of the scope.