Chapter 5: Normal arthroscopic examination

The normal arthroscopic examination consists of both a glenohumeral arthroscopy and endo­scopy of the subacromial space. It is important to devise a consistent routine for shoulder arthroscopy so that the examination is always thorough. This routine examination starts with the tendon of the long head of biceps, moves above it to the cuff, below it and forwards to the anterior capsular structures, down along the anterior labrum into the infraglenoid recess. Finally, the examination goes up along the posterior labrum looking at the back of the humeral head, the bare area, the synovial reflection, the insertion of infraspinatus and the posterior gutter (Figure 5.1).

Figure 5.1 A structured method of examining the joint starts with the long head of biceps (1), passes up to look at the cuff (2), then down to the anterior structures (3), down to the inferior recess (4), back up the posterior glenoid (5) and finally looking at the back of the humeral head, the bare area and infraspinatus insertion (6).

Long head of biceps

The primary landmark of shoulder arthroscopy is the tendon of the long head of biceps (LHB). This originates from the supraglenoid tubercle of the scapula but, from the arthroscopist's view, it appears to coalesce with the glenoid labrum, and in particular to flow out from the posterior labrum (Figures 5.2, 5.3 and 5.4). The tendon then arcs its way across the top of the joint, at the same time passing anteriorly over the top of the humeral head (Figures 5.5, 5.6, 5.7 and 5.8). The tendon is round in cross-section as it leaves the labrum, flattens out as it crosses the head, and then becomes rounder as it passes out of the joint below the transverse humeral ligament and into the bicipital canal (Figures 5.9, 5.10, 5.11 and 5.12).

Figure 5.2 The long head of biceps tendon arises from the labrum.

Figures 5.3 to 5.12 Long head of biceps.

Only one structure can be confused with the long head of biceps - the other intra-articular tendon, the upper border of the tendon of subscapularis. Such different structures could be confused if the arthroscope is inserted too far into the joint. It then comes to rest against the anterior capsular structures and the sub­scapularis tendon. The arthroscopist's first view will then be a close-up, magnified view of a glistening white tendon, which will be assumed to be the primary landmark, the long head of biceps. As the arthroscope is rotated or piston-ed, it soon becomes obvious that the tendon is the subscapularis and the arthroscope should be withdrawn until the biceps flicks into view.

Two variations of the tendon should not be confused for pathological abnormalities. Firstly, the tendon may have a translucent synovial mesentery coming down from the direction of the rotator cuff, which may be vestigial, looking like an adhesion (Figure 5.13), or complete, looking like a transparent sheet (Figure 5.14). Secondly, the tendon may have a cleavage line running down it, as though it were made of two bundles.

Figure 5.13 Occasionally there is a synovial adhesion to the long head of biceps tendon

Figure 5.14 Rarely the synovium may infold the biceps tendon like a mesentery.

Rotator cuff

Keeping to the routine, the next part of the joint to inspect is the rotator cuff. The arthroscope is passed over the top of the long head of biceps and carefully withdrawn with rotation to get a good view of the rotator cuff (Figure 5.15). It is important not to withdraw so far that the arthroscope comes out of the joint, which is easily done at this point. Care should be taken to visualize correctly the rotator cuff that is now seen, and not the undersurface of the acro­mion. This may be mistakenly visualized through a massive rotator cuff tear, where the edges of the tear have retracted out of view (Figure 5.16). The arthroscope is now passed along the fibres of the rotator cuff and the humerus internally rotated to examine the inser­tion of the cuff (Figure 5.17). This is the area where cuff tears start, and small cuff tears could be missed. Often the tendon appears to thin out in a crescentic line at the musculotendi­nous junction, and this should not be mistaken for a tear.

Figure 5.15 Normal rotator cuff above the biceps.

Having visualized the intra-articular portion of supraspinatus, the arthroscope is passed below the long head of biceps and into the intra-articular triangle.1 This is the triangle bounded above by the long head of biceps, medially by the glenoid and anterosuperior labrum, and is the guide to the anterior capsu­lar structures.

Figure 5.16 Massive rotator cuff tear. The undersurface of the acromion is seen directly, there is no cuff, nor can the retracted cuff edges be seen.

Figure 5.17 The insertion of the rotator cuff.

Subscapularis tendon

The most obvious structure is the subscapularis tendon (Figure 5.18), the secondary landmark of shoulder arthroscopy. The superior border is quite clearly intra-articular, lying in a synovial recess between the superior glenohumeral and middle glenohumeral ligaments. This synovial recess is a constant anatomical feature2 - the opening to what used to be termed the subsca­pularis bursa. This is a misnomer for a bursa is, by definition, a synovial sac containing synovial fluid which does not connect with a joint. The subscapularis recess is actually a constant synovial outpouching, as is the supra­patellar  pouch   in the knee, and the term 'subscapulars bursa' should be dropped in favour of 'subscapulars recess' or pouch. The entrance to the subscapulars recess is called the foramen of Weitbrecht. In the lateral decubi­tus position used for shoulder arthroscopy, the subscapularis recess is the lowermost part of the joint, and is favoured by gravity as a hiding place for loose bodies.

Figure 5.18 Subscapularis (s) appearing from behind the middle glenohumeral ligament (m).#

Glenohumeral ligaments

The glenohumeral ligaments are always a source of great interest, as such a high propor­tion of shoulder disability is related to anterior dislocation or subluxation. The anterior shoul­der capsule was described by Galen, but the three glenohumeral ligaments were only descri­bed and named in the last century. The import­ance of these ligaments has really only come to the fore with the advent of shoulder arthro­scopy, as they are far more obvious from inside the joint than from outside. A great amount has been written about the glenohumeral ligaments and their importance in recurrent dislocation, but for those interested in shoulder arthroscopy the paper of Turkel et al[3] is essential reading (Figure 5.19).

Figure 5.19 Anatomy of the glenohumeral ligaments according to Turkel et al. (From Turkel SJ, Panio MW, Marshall JL et al, Stabilizing mechanisms preventing anterior dislocation of the glenohumeral joint, J Bone Joint Su/g(1981)63A 1208-17.)

The superior glenohumeral ligament lies above the subscapularis recess and makes up the superior margin of the foramen of Wiet-brecht. This ligament is often partially hidden by the long head of biceps when arthroscoping from the posterior portal (Figure 5.20).

Figure 5.20 The superior glenohumeral ligament is often hidden by the long head of the biceps tendon, b = biceps, h = humerus, I = labrum, g = glenoid.

The middle glenohumeral ligament varies from a thin membranous structure (Figure 5.21) to a thick ligament, although its position is constant. The middle glenohumeral ligament can always be found crossing obliquely down across the subscapularis bursa and hiding all but the upper leading edge of the tendon from view (Figure 5.22).

Figure 5.21 The middle glenohumeral ligament may be thin and wispy.

Figure 5.22 Alternatively, the middle glenohumeral ligament may be thick.

The inferior glenohumeral ligament is the strongest and most important of the glenohu­meral ligaments. The superior band is constant and can be seen passing downwards and outwards beneath the middle glenohumeral ligament (Figures 5.23 and 5.24). Often the inferior glenohumeral ligament can distinctly be seen as a prolongation of the anterior labrum (Figure 5.25). O'Brien and Warren[4] have looked in detail at the gross and microscopical nature of this ligament. They liken the ligament to a hammock, strung between the glenoid and the humeral head (Figure 5.26). The two ropes holding the hammock are the anterior superior band and, at the back, the posterior superior band. They have shown that the ligament thickens at these two points and that the configuration of the collagen bundles varies within the ligament, passing coronally between the glenoid and the humerus in the thickened superior bands, and sagittally in the substance of the ligament between these bands. So it is the latter that makes up the infraglenoid recess which, with the arm at the side, is a capacious space (Figures 5.27, 5.28 and 5.29).

Figures 5.23, 5.24 and 5.25 The superior band of the inferior glenohumeral ligament originates from the labrum.

Figure 5.26 The inferior glenohumeral ligament can be likened to a hammock, the superior bands at the front and the back being the ropes which hold up the hammock.

Figures 5.27, 5.28 and 5.29 The infraglenoid recess is a capacious space below the humeral neck.

Figures 5.30, 5.31 and 5.32 The inferior and posterior glenoid labrum.

Figures 5.33 and 5.34 The bare area of the humerus.

Figure 5.35 A needle used as a probe.

Figure 5.36 Verres needle used as a probe

The arthroscope is now rotated within the infraglenoid recess to see the synovial reflec­tion on the humeral neck. The arthroscope is now withdrawn gradually with rotation, for it is easy to withdraw too far at this point and exit the joint through the puncture point in the posterior capsule. As the arthroscope is rotated, so the posterior glenoid labrum can be seen (Figures 5.30, 5.31 and 5.32) and behind it the posterior gutter or synovial recess. As the arthroscope is rotated in the other direction, so the posterior surface of the humeral head is observed. At this point, it is important to look carefully at the synovial reflection, or so-called bare area of the humeral head (Figures 5.33 and 5.34) as it is easy for the inexpert arthro-scopist to mistake this for a Hill-Sachs lesion. The difference is that the bare area coalesces with the synovial reflection on the neck of the humerus, whereas a Hill-Sachs lesion has a ridge of bone or cartilage between it and the bare area. The bare area often has small pits or holes in it which can clearly be seen, and the junction between it and the articular surface of the head is more normal than the rounded-off fracture of a Hill-Sachs lesion. Further with­drawal and rotation brings the arthroscope back into the triangle between the long head of biceps, the humeral head and the glenoid.

Hook probe

As with arthroscopy of the knee, further tactile information can now be gleaned by the use of a hook probe. This is more difficult to insert than in the knee, and when learning it is often easier to start probing with a 14- or 12-gauge needle (Figure 5.35), or a Verres needle (Figure 5.36). The needle will cause less damage on inser­tion, and will also establish a flow through the joint. This clears any blood that may at this stage have started to obscure vision. If a hook probe is used it often helps to make a track with a sharp obturator and cannula from the anterior portal and then pass the hook down this track. Probing the glenoid labrum may show a Bankart lesion, or confirm one, if suspected. The ligaments can be probed in turn and then the long head of biceps and the superior cuff can be palpated.

On completion of the examination, the joint is thoroughly flushed through, the fluid removed from the shoulder, and the probe and arthro­scope withdrawn.

Bursoscopy

Examination of the bursa, or bursoscopy, is more difficult than glenohumeral arthroscopy, but should be a routine part of the examination, particularly if clinically the patient has a painful arc of motion. The arthroscope is reinserted through the posterior portal with a blunt obtu­rator inserted. The cannula and trochar are directed just under the acromion.

The most common fault of the inexperienced arthroscopist is failure to enter the bursa. In order to do this, the arm should be alongside the body, for this will increase the potential space available. Distraction of the arm is then applied in the direction of the feet, and the key is to push the cannula until the coracoacromial ligament can be felt on the tip of the blunt trochar. The trochar is moved from side to side and the coracoacromial ligament can be felt to flick from side to side (in fact it is the trochar flicking over the lateral edge of the ligament). If this manoeuvre is not performed, then the bursa may not be entered. If the arthroscope is not in the bursa when the fluid is switched on, it will create an extrabursal mass, which makes entry of the bursa almost impossible. The arthroscopist will then see an appearance as though the space was full of 'cobwebs' (Figure 5.37).   If  the  bursa  has  been  successfully entered, the arthroscopist will see a large synovially lined space (Figure 5.38). Orientation within this space is far more difficult than within the shoulder joint, and the insertion of two needles to mark the anterior edge of the acromion (Figure 5.39) - one at the lateral margin and another at the acromioclavicular joint - will help at this stage. The arthroscope is rotated upwards to examine the inferior surface of the acromion, which at this point is covered by the insertion of the coracoacromial ligament (Figure 5.40). Turning the arthroscope laterally, the edge of the acromion can be seen and the origin of the lateral multipennate section of the deltoid. The arthroscope is then rotated down to examine the superior surface of the rotator cuff (Figures 5.41, 5.42 and 5.43). When the examination is complete, the bursa is flushed out and the arthroscope and needles withdrawn. The skin puncture can be closed either with a single suture or with adhesive skin closure strips.

Figure 5.37 If the arthroscope is in the subacromial areolar tissue, posterior to the bursa, the space will seem to be full of 'cobwebs'.

Figure 5.38 The bursa, when successfully entered, is a large space.

Figure 5.39 Orientation within the bursa is aided by placing needles to each side of the coracoacromial ligament, at the anterior edge of the acromion.

Figure 5.40 The undersurface of the acromion is covered by the insertion of the coracoacromial ligament.

Figures 5.41, 5.42 and 5.43 The upper surface of the rotator cuff as seen during bursal endoscopy.

It is very important to make a drawing of the findings in the notes, as this is a far better reminder of what the joint and bursa actually looked like than a written documentary. A simple pattern upon which findings can be drawn is shown in Figure 5.44.

Figure 5.44 A simple pattern upon which the findings of shoulder arthroscopy can be drawn.