Quadrangular Space Decompression

Abstract

Background:

The quadrangular (or quadrilateral) space is defined by its anatomical borders and is the passageway for the axillary nerve and posterior circumflex humeral artery (PCHA). Quadrangular space syndrome (QSS) can present due to various compressive pathologies but is commonly seen in overhead athletes. Quadrangular space syndrome can present with neurogenic symptoms including pain and paresthesias, as well as vascular complications from compression of the PCHA including thrombosis, aneurysm formation, and distal emboli.

Indications:

Surgical decompression of the quadrangular space is indicated for severe neurogenic or vascular compromise in the case of QSS refractory to nonoperative treatment.

Technique Description:

After appropriate preoperative physical examination findings and trial of nonoperative treatment, including physical therapy and injections, surgical decompression was indicated. The posterior border of the deltoid was marked, and an incision centered over the posterior border of the deltoid lateral to the axillary fold was made. Posterior border of deltoid was identified and retracted, revealing the interval of the teres minor and major. The nerve to the teres minor was identified, protected, and fibrous bands compressing the nerve were released. The nerve to the teres minor was tracked deep to find the axillary nerve. This was identified and fibrous bands around the nerve were decompressed. The circumflex vessels were protected throughout. Following decompression of the nerves, there was free movement of the nerves indicating adequate surgical decompression.

Results:

Adequate surgical decompression of the axillary nerve and PCHA achieved with resolution of neurogenic symptoms of pain and paresthesias at first postoperative visit.

Discussion/Conclusion:

Quadrangular space syndrome is a rare disorder, can be difficult to diagnose, and is the cause of significant morbidity, particularly in overhead athletes. If symptoms persist after nonoperative treatment, operative decompression of the quadrangular space may be indicated. Adequate surgical decompression results in relief of neurogenic and vascular symptoms.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Hi, my name is Dr. Kier Blevins and I will be presenting on Quadrangular Space Decompression.

The quadrangular (also known as quadrilateral) space is an area of the posterior aspect of the shoulder defined by its anatomic boundaries. The borders are as follows: superiorly you have the teres minor; inferiorly the teres major; the lateral border is the surgical neck of the humerus; and the medial border is the long head of the triceps. This space is important as the axillary nerve and posterior circumflex humeral artery (PCHA) traverse through.

Quadrangular space syndrome (QSS) can be described as neurogenic, vascular, or a combination of both. Neurogenic QSS is defined as paresthesias in the axillary nerve distribution, weakness of the deltoid and/or biceps, and deltoid atrophy. Vascular QSS is defined as claudication, thrombosis, or aneurysm leading to distal emboli. Vascular QSS is typically identified more easily in overhead athletes, as they have increased symptoms with overhead motions. Neurogenic QSS is also typically found in overhead athletes, but they may not have symptoms associated specifically with overhead motions. Often, QSS is seen in the setting of concomitant labral pathology and in patients with residual symptoms after arthroscopic labral repair.

Although there is no gold standard diagnostic test for quadrilateral space syndrome, magnetic resonance imaging (MRI) is often the first imaging study performed. Patients may exhibit atrophy of the teres minor on MRI studies in rare instances. Arteriography may prove useful in demonstrating posterior humeral circumflex artery occlusion with provocative maneuvers often seen in overhead throwers with abduction and external or internal rotation. This is clearly shown in figure B, where there is aberrant flow in the posterior humeral circumflex artery with abduction and external rotation of the patient’s arm.

McAdams and Dillingham published a case series in the American Journal of Sports Medicine describing 4 patients, all overhead athletes, with QSS who underwent quadrangular space decompression. As seen in this table, the patients were all young (17-34), with a negative electromyography (EMG). Imaging was obtained in 3 of 4 patients, which demonstrated teres minor edema in 1 patient who also had a positive computed tomography (CT) angiogram, but was negative in the other 2 patients. Intraoperative findings of fibrous bands were seen in 3 of 4, while venous dilation was seen in the fourth.

The results of McAdams and Dillingham’s case report are seen here. All 4 patients had complete relief of preoperative pain without sensory or motor deficits, and all 4 patients maintained full active and passive range of motion (ROM) postoperatively.

Indications for quadrangular space decompression are severe neurogenic or vascular compromise, failure of conservative treatment (especially in the overhead athlete), positive arteriogram for vascular occlusion, and point tenderness at the area of the quadrangular space. Contraindications are typically limited to cervical spine pathology causing symptoms.

Here is our case presentation of a 17-year-old male pitcher with posterior shoulder pain, worse with pitching, decreased ROM, paresthesias in the axillary nerve distribution, and a negative electromyography (EMG). Here are axillary, zanca, and grashey radiographs of our patient demonstrating no acute osseous abnormality. His magnetic resonance (MR) arthrogram showed some questionable labral pathology without any fatty atrophy of the teres minor muscle belly. Range of motion deficits are as follows: passive flexion at 150° as compared with 180° on the contralateral side, active flexion 160° as compared with 180°, abduction 120° compared to with 180° on the uninjured side, external rotation at the side of 55° compared with 70° and internal rotation behind the back to T10 compared with T8. Axillary cut of the MRI is shown here, followed by a coronal image demonstrating questionable labral pathology.

Prior to operative intervention, the patient underwent conservative measures. He began with physical therapy, followed by an EMG due to his continued neurogenic symptoms. The EMG was negative, and a diagnostic injection of lidocaine into the quadrangular space was positive. Due to the failure of conservative treatment and resolution of symptoms with the lidocaine injection, the decision was made to proceed with surgical intervention.

We recommend no preoperative nerve block be performed to allow for postoperative neuroexamination. The scratch collapse test is a 2-part test, in which the strength of the posterior rotator cuff is tested. Then the cutaneous area of the axillary nerve (in this case, the quadrangular space) is scratched, and the strength of the cuff is retested.

A positive result, indicating an entrapped nerve as demonstrated above, is a collapsing of the arm upon retesting. To position the patient for quadrangular space decompression, the patient is lateral on a bean bag; however, the patient can be positioned in either beach chair or lateral depending on surgeon preference to assess and/or repair labral pathology.

We place the arm in a Spyder arm holder with the arm in slight abduction and forward flexion. The incision is made centered over the posterior border of the deltoid, just lateral to the axillary fold. Superficial dissection is carefully completed to visualize the posterior border of the deltoid, as seen here. The posterior border of the deltoid is then identified and retracted.

Once the posterior border of the deltoid is retracted, careful dissection continues until the interval between the teres major and teres minor is identified, as shown here. Careful dissection in the interval between the teres major and teres minor is conducted until the nerve to teres minor and the PCHA are identified.

Here, vessel loops are placed around the PCHA in order to identify and decompress. In addition, the fibrous bands compressing the nerve to teres minor are released, and the nerve is followed deep to the axillary nerve. This intraoperative video demonstrates the decompressed nerve that is now able to move freely within the quadrangular space.

After quadrangular space decompression, arthroscopic evaluation and labral repair was performed. Here, we have arthroscopic photos of the posterior labral tear and repair.

Common pearls and pitfalls. Often the EMG is negative, and the patient will have associated neurologic symptoms with overhead activity. In addition, ultrasound-guided lidocaine injection may prove useful in making the diagnosis. Regarding surgical technique, landmarks are essential, and decompression should be > 5 cm to ensure all branches of the axillary nerve are decompressed.

Some key pitfalls: QSS may often be missed in posterior shoulder pain and presumed to be an isolated posterior labral tear. The most common presentation is continued posterior pain with overhead activities after previous shoulder arthroscopy in many patients. Surgical pitfalls include inadequate or incomplete decompression if you are unable to correctly identify the teres minor branch which is essential in tracing it back to its origin at the primary axillary nerve.

Our postoperative protocol will be described in the next few slides and is dictated by the associated labral pathology, a posterior labral tear in this case. If there is no associated labral pathology, the postoperative course allows for earlier range of motion, similar to a subacromial decompression. The postoperative protocol involves days 0 to 7 with the patient in a sling at all times, no shoulder ROM and isometric strengthening in the sling. The patient may wean out of the sling by 3 weeks and begin ROM with 90° forward flexion, 20° external rotation, 45° abduction, and internal rotation to the stomach. During this time, no cross-arm adduction is permitted. From weeks 4 to 8, they are to increase active ROM, and strengthening can be done within these limitations while stabilizing the scapula.

From 8 to 12 weeks continue ROM efforts with gentle passive stretching and advance as tolerated with isometric strengthening and progression of weights. Full ROM and sports-related rehabilitation are to begin at 3 months with gradual return to throwing at 4.5 months.

Our patient here is 6 weeks postoperatively and denies paresthesias and pain and states the shoulder feels normal as compared with contralateral nonoperative shoulder. Here, notice the equivalent shoulder strength bilaterally and now a negative “scratch” test result.

In summary, QSS is a rare disorder and is cause for significant morbidity in overhead throwing athletes. Following nonoperative treatment, operative decompression is often indicated and, with complete surgical decompression, there can be significant relief of pain and neurogenic symptoms.

Here are our references.

Thank you.