Keywords

1 Introduction

Paralabral ganglion cysts (GC) are uncommon with a prevalence of 2.3% [1]. The cyst’s wall is formed by dense fibrous connective tissue, and its content is a very viscous fluid rich in hyaluronic acid and mucopolysaccharides [2]. It is formed either by myxoid degeneration of periarticular connective tissues or by a synovial fluid leak in the periarticular tissues through capsular tears at the labral-glenoid junction via a one-way valve mechanism [3, 4].

Magnetic resonance imaging (MRI) studies have shown that the most common location of the cysts is posterosuperior in 71–90% of cases, mainly at the spinoglenoid notch, and may extend anterosuperiorly or posteroinferiorly [1, 3]. The GC size may vary from 0.5 to 6 cm and 59% are large and multilocular [1].

GC expansion may compress the suprascapular nerve above the spinoglenoid notch resulting in supra and infraspinatus muscle denervation, or more often at the spinoglenoid notch leading to isolated infraspinatus atrophy. Not all ganglion cysts, however, result in nerve compression, which occurs in 13–62% of cases particularly when the GC’s average size is 3 cm [1, 3, 5, 6]. GC are associated with posterior labral tears in 48–59% of cases [3, 4, 7], or superior labral anterior-posterior (SLAP) tears in 43–50% of cases [5, 6, 8]. More importantly, 93% of cysts are located in the same quadrant as the labral tear [4].

Symptomatic cysts present with deep and diffuse posterior shoulder pain and weakness of external rotation. The reported average time from onset of symptoms to surgery is 8 months [5, 9]. Nerve compression by a ganglion cyst, however, requires early diagnosis and surgical decompression to avoid irreversible muscle atrophy and long-term disability [10].

Arthroscopic techniques have evolved over the last decade, and can now address both the GC and any associated labral lesion with successful outcomes and low morbidity. There are two techniques of cyst decompression, either intraarticular or subacromial. In the intraarticular procedure, the GC is decompressed from within the joint without direct visualisation of the cyst, either through a posterosuperior capsulotomy just above the labrum [8, 11,12,13,14] or through a labrum tear [5, 15,16,17,18].

Disadvantages of the intraarticular approach include the risk of suprascapular nerve injury, as the nerve lies within 1.8 cm from the posterior glenoid rim [19, 20], incomplete decompression due to a restricted field, and the presence of large and multilocular cysts. In order to mitigate these risks several authors prefer decompression of the cyst in the subacromial space under direct vision with careful dissection and nerve protection [6, 21,22,23,24,25].

2 Indications

Symptomatic ganglion cyst in the spinoglenoid area with MRI evidence of muscle denervation or atrophy and diagnosis of suprascapular neuropathy with electromyography and nerve conduction studies.

3 Contraindications

  • Asymptomatic cysts

  • Other causes of denervation

4 Author Preferred Technique

Arthroscopic spinoglenoid cyst decompression through the subacromial space.

4.1 Pre-operative Planning

Prior to anaesthesia clinical notes and imaging studies are reviewed and the correct side is marked. It is important to ensure that all instruments required for the procedure are available and in working order. These may include the water management inflow/outflow pump, camera and light source, radiofrequency system, joint shaver system, suture anchors, surgical set of arthroscopic instruments (suture manipulators, cutters, graspers, and bird-beak tissue penetrators), and twist-in 6 and 8.25 mm cannulas.

4.2 Patient Positioning

The procedure is performed under interscalene cervical plexus block and balanced general anaesthesia in the beach chair position. A limb positioner or traction system is used. Preventative measures mitigating the risk of skin and neurovascular compression are taken, using heel pads, a cushion beneath the knees and protection of the ulnar nerve of the contralateral elbow. The head and neck should remain in neutral alignment.

4.3 Portal Design

The shoulder is marked to allow for percutaneous localisation of the appropriate portal position. A two-portal surgical technique is used for the intraarticular stage: standard posterior for visualisation (P) and anterosuperior (AS) through the rotator cuff interval used as a working portal for anchor insertion and suture management if required (Fig. 39.1).

Fig. 39.1
A photograph of a shoulder marked for the intraarticular stage of the procedure. The markings are P M, P, L, and A S.

Portal position. PM posteromedial, P posterior, L lateral, AS anterosuperior

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Three portals are required for the subacromial stage of the procedure. A viewing posterior portal (P), a lateral working portal (L) and a posteromedial portal (LP) for infraspinatus retraction (Fig. 39.2).

Fig. 39.2
A photograph of a shoulder marked for the subacromial stage of the procedure. The markings are P M, P, and L.

Portal position. PM posteromedial, P posterior, L lateral

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Twist-in 6 and 8.25 mm anterosuperior cannulas are used to facilitate unimpeded suture and anchor instrumentation. Accurate portal placement is crucial for optimal visualisation and achieving the correct working angle for the arthroscopic instruments. This is assisted with an outside-in technique using an 18-gauge spinal needle.

4.4 Step-by-Step Description of the Technique

Arthroscopic spinoglenoid cyst decompression through the subacromial space.

4.4.1 Intraarticular Stage: Management of Labral Lesions

We establish a standard posterior portal through the soft spot and the scope is inserted in the glenohumeral joint. An anterosuperior portal is created through the rotator interval using an outside-in technique with the help of an 18-gauge spinal needle. Diagnostic arthroscopy identifies any associated intra-articular pathology. Any posterior labral tear or SLAP tear if present is debrided or repaired depending on the lesion type.

4.4.2 Subacromial Stage: Spinoglenoid Ganglion Cyst Decompression

  1. 1.

    Subacromial bursectomy: The scope is moved to the subacromial space through a posterior portal and a standard subacromial bursectomy is performed through a lateral working portal.

  2. 2.

    Exposure of the spinoglenoid notch: Gentle dissection advancing from anterior to posterior with a motorised shaver identifies the scapular spine between the supraspinatus anteriorly and the infraspinatus muscles posteriorly (Fig. 39.3). Dissection with a motorised shaver should not extend beyond the safe zone 1 cm medial to the glenoid rim. At this stage the infraspinatus muscle is retracted using a probe inserted through an accessory posteromedial portal, to improve visualisation (Fig. 39.4). The cyst is usually found between the scapular spine and the posterior rim of the glenoid. A probe can be used to palpate the posterior rim of the glenoid and progress medially identifying the cyst (Fig. 39.5), which is then incised and the viscous content can be aspirated with a shaver (Fig. 39.6).

Fig. 39.3
An arthroscopic image of the subacromial space. The labeled parts are S S, I S T, and S S T.

Anatomy landmarks in the subacromial space. SS spine of scapula, IST infraspinatus muscle, SST supraspinatus muscle

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Fig. 39.4
An arthroscopic image of subacromial space. The labeled parts are the retractor, S S T, I, R I M, and I S T.

Anatomy landmarks in the subacromial space. IST infraspinatus muscle, SST supraspinatus muscle, RIM glenoid rim

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Fig. 39.5
An arthroscopic image of the cyst location in subacromial space. The labeled parts are S S, G C, I S T, and S S T.

Cyst location in the subacromial space. GC ganglion cyst, SS spine of scapula, IST infraspinatus muscle, SST supraspinatus muscle

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Fig. 39.6
An arthroscopic image of the incised and viscous content of the ganglion cyst in the subacromial space.

Discharged viscous content of the cyst in the subacromial space

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4.5 Complications

Momaya et al. (2017) in a systematic review of 269 shoulders reported only 2 (0.74%) complications. A case of superficial soft tissue infection and one case of adhesive capsulitis [10]. Other authors reported no complications or recurrences at 24 [6] and 51 months, of follow-up [5].

4.6 Post-operative Care

For isolated cyst decompression, a sling is used for the first week. Passive range of motion exercises is allowed from the first day. In the second week, active exercises start as tolerated, and in the third week, a strengthening exercises program commences. Full return to activities is expected at 6 weeks.

4.7 Outcome

Recent studies have confirmed that combined treatment of cyst and labrum lesions achieves excellent functional outcome scores [6, 8, 10, 18, 21, 23,24,25].

Following cyst decompression, external rotation strength recovery has been reported in 85–100%, of cases [5,6,7, 16]. Overall, 95.2% of athletes were able to return to sport, and 88% were at the preinjury level [10].

5 Conclusion

Paralabral ganglion cysts are located mainly posterosuperiorly at the spinoglenoid notch and in more than half the cases are associated with labral tears and suprascapular nerve compression. Nerve compression by a ganglion cyst requires early diagnosis and surgical decompression to avoid irreversible muscle atrophy and long-term disability.

The authors’ preferred technique is a decompression of the cyst in the subacromial space under direct vision with careful dissection and suprascapular nerve protection, associated with an intraarticular repair of any labral lesions if present. Cyst decompression achieves excellent functional outcome scores and high rates of external rotation strength recovery.