Introduction
Quadrilateral Space Syndrome (QSS) is a rare neuro-vascular entrapment disease in which the Axillary Nerve (AXN) or Posterior Humeral Circumflex Artery (PHCA) are entrapped in the quadrilateral space due to injury, fibrous bands, or muscle border hypertrophy.1
The disease typically affects young adults aged 20 to 35, particularly athletes who participate in overhead sports such as volleyball, 2 baseball,3 swimming,4 and other activities that require regular abduction and external rotation, such as yoga or window washing. 5,6 The subscapularis muscle and shoulder capsule border the intermuscular space on the superior side, and the teres major muscle on the inferior side. The long head of the triceps and the surgical neck of the humerus limit it medially and laterally.7 Loose connective tissue, fat, veins, the AXN, and the PHCA are all included.7 Patients are usually advised to start with conservative therapies like physical therapy and activity modification.2 When patients do not respond to conservative therapy for at least six months, surgical decompression is considered.8 The management entails decompression, which entails a variety of techniques that have yet to be validated, particularly among the Indian population. The goal of our research is to grade the various medicinal and surgical treatments for Quadrangular Space Syndrome.
Functional anatomy of axillary nerve
The AXN is located behind the brachial artery and lateral to the radial nerve, in front of the subscapularis. The AXN joins the posterior circumflex humeral artery in the quadrangular space, positioned between the lateral and long heads of the triceps muscle on the inferior side of the subscapularis. The anterior branch of AXN innervates the deltoid muscle, while the posterior branch innervates the teres minor and deltoid. The posterior branch also innervates the skin across the inferior two-thirds of the deltoid muscle’s posterior surface.9
Functional anatomy of posterior humeral circumflex artery
It enters the posterior scapular region after passing via the quadrangular space. It separates into anterior and posterior branches within the quadrangular space, looping antecedently around the humeral surgical neck to give blood to the superior, inferior, and side sections of the humeral head, the glenohumeral joint, and the surrounding shoulder muscles.10,11 The borders of the quadrangular space, as well as the structures that cross through it, are depicted in Figure 1.
Materials and Methods
To reduce the risk of bias in the study, a systematic review protocol was prepared and registered with PROSPERO at the Centre for Reviews and Dissemination, University of York (ID: CRD42022332766). The review protocol can be accessed from https://www.crd.york.ac.uk/prospero/.
Eligibility criteria
The articles which satisfied the inclusion and exclusion criteria were eligible for review. The inclusion criteria were articles written by both Indian and foreign authors until 31st March 2022, articles related to all relevant medical methods and surgical methods of management of QSS, articles experimenting new methods of treatment on animals for human applications were included. Excluded articles included those which were published after 31st March 2022 and the articles focusing on topics other than medical and surgical methods of management of QSS. There was restriction for non-English language of publication. The publications were divided into two groups, which represented articles focusing on medical and surgical management techniques, respectively.
Search strategy
A scoping review was conducted of articles published till March 2022 on PubMed, and Medline using these MeSH terms: Quadrilateral Space Syndrome; Quadrangular Space Syndrome; surgical management; medical management; neurovascular structures; throwing athletes. The citation search was carried out for all the selected articles in study.
Study selection
After applying inclusion and exclusion criteria, two authors (SP and SC) independently assessed all the titles, abstracts, full text articles, and reviews found during the initial search, and relevant publications were shortlisted. All the shortlisted full publications were downloaded and independently examined for relevant data using the data extraction checklist prepared by both authors. The authors and the methods of the investigations were not hidden from the reviewers. Any differences were settled through conversation or the involvement of a third reviewer (SM). The special data needed for the review is mentioned on the checklist (Table 1). We chose and incorporated the articles that contained this information.
Data collection process
The authors created a data extraction form that they used to collect data from any two papers they choose, and it was verified after the pilot trial. Two reviewers (SP and SC) worked separately to gather data from all the studies that were included. Disagreements were addressed through dialogue and the participation of a third independent reviewer (SM). The following features of the study were gathered: i) the research author; ii) the study design; iii) the country and year of publication; iv) the number of participants; v) the participants’ age group; vi) the participants’ gender; and vii) the participants’ ethnicity. The following information was gathered about the methods/techniques used for the medical and surgical management of QSS: i) the previous, existing, and recent methods used for medical and surgical management of QSS; ii) the limitations of the older and existing methods/techniques used for medical and surgical management of QSS iii) the advantages of the various recent and upcoming methods/techniques used for medical and surgical management of QSS.
Risk of bias assessment
Two reviewers (SP and SC) independently conducted the risk of bias assessment that was included in the Data Extraction Form. The risk of bias in systematic reviews (ROBIS) tool was used to assess the risk of bias in our review study.12
Results
Literature search
There were 88 publications found after the initial search in PubMed database. After filtering for the English language, original content, and human involvement, 66 remained. Duplicate articles (n=2) were deleted, and two reviewers (SP and SC) independently assessed these 66 publications. The same two independent reviewers independently examined eight papers found through citation searches for eligibility against the pre-specified inclusion criteria. Disagreements were settled by conversation. After applying the inclusion and exclusion criteria, 16 articles remained. 38 publications were excluded due to irrelevant text and 12 publications due to unavailability of full text. Based on each author’s appraisal and cross-verification, 15 publications were selected for synthesis. One review article namely Dalagiannis D. et al., 202013was eligible for review based on the inclusion and exclusion criteria but was eliminated after reviewers screened them for irrelevant data that was outside the scope of the current review. Figure 2 shows the PRISMA flow chart, which shows the step-by-step literature search and consideration/rejection procedure (Table 1).
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Characteristics of included studies
Table 2 and Table 3 summarize the characteristics of the 15 selected studies. Out of the reviewed 15 publications, three focused on the methods (conservative and advanced) of medical management of QSS (shown in Table 2). These three publications comprised of 2 case reports and 1 case study. Out of the 15 selected publications, 12 articles focused on methods/techniques (previous, recent, and newer) of surgical management of QSS (Table 3). These 12 publications comprised of 3 case series, 2 cadaveric studies, 2 book chapters, 3 review articles, and 2 case reports.
Among the 15 reviewed articles, only four articles focused specifically on describing the various surgical techniques of surgical decompression of QSS along with their advantages and disadvantages. The step-by-step procedure of each proposed surgical approach is mentioned in the results section. Table 4 and Table 5 show the comparison of the anterior and posterior surgical approaches described in these four articles. The parameters used for comparing these two surgical approaches were anatomical ease of identifying involved neuro-vascular structures, technical expertise required to execute the procedure, probabilities of injury to neuro-vascular structures, probabilities of postoperative fibrosis and other complications, and time duration required to complete the procedure.
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Risk of bias assessment
The studies selected for this review study used a variety of methodological techniques. All three phases of the ROBIS tool were utilized to assess the risk of bias in our review study’s methodology. Except for a few points in Domain 2 of Phase 2, all other requirements were met. As a result, the total risk of bias was determined to be minimal.
Commonly used surgical approaches for surgical decompression in QSS are as follows:
Anterior (delto-pectoral) approach
For shoulder arthroplasty, the anterior approach is currently the preferred technique. The patient is positioned in a supine position with the right arm in 90-degree abduction in this method. A 12 cm long incision running from the lateral margin of the coracoid process to the proximal humeral shaft near to the deltoid tuberosity is to be taken on the right side, using bony and surface landmarks (acromion, clavicle, coracoid process, deltoid).27 Within the deltopectoral groove, the clavipectoral membrane is incised. The subscapularis muscle is exposed after retracting the deltoid muscle laterally and the conjoint tendon medially. The AXN can be found on the surface of the subscapularis muscle and close to its lower border. Because it is directly associated with the teres minor belly inferiorly, the lower border of the subscapularis muscle is the most critical region.
The lower border of the teres minor is detected, and quadrangular space is traced by inserting a fingertip horizontally forwards along the plane of the lower border of the teres minor, using rough dissection. The contents of the QS can be dissected using blunt dissection after the QS has been identified. The teres major muscle does not need to be exposed, and the contents of the QS (AXN and PHCA) can be recognized and traced within the QS via blunt dissection. Any fibrous strands or adhesions in the QS and its contents can be removed. This method spares no muscle.27
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Posterior/scapular approach
The patient is put in a lateral decubitus position and a longitudinal incision of approximately 4 cm is made over the posterior shoulder in this surgical approach. The underlying fat within the QS between the teres and the teres major is shown by securing the posterior border of the deltoid and reflecting it supero-laterally. Following that, the AXN and posterior circumflex humeral vessels will be palpated as they exit the QS, and the QS will be located and secured.20
Discussion
In their work, Cahill B.R. and Palmer R.E. (1983) advocated a posterior technique in which a transverse incision was made parallel to the scapula’s spine and curved inferiorly over the rear portion of the humerus. The deltoid was later severed from the scapula’s spine. When teres minor was inserted into the rotator cuff, it became separated and reflected medially. Blunt and sharp dissection were used to decompress quadrangular space. This method produced satisfactory results in 16 of 18 patients.18
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Pitfalls of this technique
Removal of deltoid and teres minor resulted in excess bleeding intra-operatively18
Division of teres minor weakened the rotator cuff and the lateral arm rotation18
The postoperative wide scar may itself compress the neurovascular bundle18
Postoperative chronic pain and formation of poor quality tissue18,20
Francel T.J. et al. (1991) in their study used a vertical or Sshaped incision which was made on the region of highest tenderness, i.e., quadrangular space, and skin flaps were elevated to expose the inferior border of the deltoid, according to their study.20 After incising the deltoid fascia and exposing the teres muscle bellies, the deltoid was retracted superiorly. The quadrilateral space was reached once the fascia between the teres muscle bellies was opened. This procedure did not separate the deltoid and teres minor muscles. The AXN and PHCA were isolated and identified. The motor response of the teres minor and deltoid muscles was validated after nerve stimulation. Finger insertion divides fibrous bands and decompresses space.20
Advantages of this technique
Intact deltoid and teres minor reduced bleeding and quick postoperative shoulder movement is possible20
Fibrous atrophy of the deltoid was prevented20
The postoperative scar was smaller20
In their study, Andermahr J. et al. (2015) emphasized the (anterior) deltopectoral technique, which was commonly employed for practically any shoulder fracture treatment and was frequently recommended, especially in anterior glenoid fractures.27 This method, with a few tweaks, could be used to decompress the QSS surgically.
The (anterior) delto-pectoral technique was also employed by Feigl G. et al. (2018) to view the AXN anteriorly. AXN was found near the inferolateral boundary of the subscapular muscle to enter the QS in 91 out of 92 limbs in their cadaveric investigation. The roof of the area is defined in this manner by the insertion of the subscapular muscle at the lesser tubercle.28
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Limitations
A review of such items was impossible due to a lack of free access to whole text for various publications. Even abstracts were absent in a few papers. This review was limited to only few databases which also is a limitation. This constraint will be addressed in future review papers.