Arthroscopic surgery is the gold standard for the treatment of many orthopedic conditions [1, 2]. It is used in the diagnosis and treatment of intra-articular disorders of major joints, such as impingement, instability, and osteochondral lesions. Evidence-based benefits include lower morbidity, shorter admissions, and early recovery. It is usually a safe procedure; however, it does not come without risks. Arthroscopies are performed in restricted spaces adjacent to neurovascular bundles, with an obvious risk of injury to these structures ^[3]. In this article, we discuss a 76-year-old lady who developed a circumflex humeral artery pseudoaneurysm a decade after her shoulder arthroscopy. Post-operative pseudoaneurysm formation is recognized in the lower limb; however, only a few cases have been recorded following shoulder arthroscopy [1, 4, 5, 6]. Our review of the literature confirms that pseudoaneurysms of the circumflex humeral artery have not been reported yet.

A 76-year-old female patient presented to her general practitioner with pulsatile posterior right shoulder swelling for 2 months. She had a history of osteoarthritis but was otherwise fit and well and not taking any medication. An ultrasound scan (US) in the community demonstrated a 23 mm hypoechoic lesion in the right deltoid region with flow on color imaging. The patient was referred to the local Vascular Surgical Team, who advised an angiographic computed tomography (CT) scan, which demonstrated a 23 × 15 mm pseudoaneurysm arising from the circumflex humeral artery (Fig. 1). Clinical history revealed that the patient suffered from right-sided subacromial impingement and a partial supraspinatus tendon tear 15 years ago. The patient underwent arthroscopic subacromial decompression and rotator cuff repair 12 years ago. She had an arthroscopic procedure combined with a mini-open approach, with the incision placed on the anterolateral aspect of the shoulder, 4 cm below the lateral edge of the acromion. The rotator cuff repair was carried out using one anchor in a single-row. Given that the patient had symptoms for a long time and the findings were of a partial tear involving more than 50% of the thickness of the tendon with a good quality margin, the decision was made to repair the tear. She was then followed up immediately and for 3 months after the procedure. She had experienced intermittent shoulder pain between these consultations but continued to have a good range of movements, specifically abduction at 160°. She was discharged from the clinic, given the satisfactory clinical outcome. The patient denied a history of trauma or any procedure, including injections to her right shoulder, in the decade preceding her presentation with swelling. The case was discussed at the multidisciplinary team meeting and referred to the interventional radiology team for catheter angiography and embolization. The right radial artery was accessed with a 5-French introducer sheath (Radiofocus® Transradial Kit, Terumo Corporation). Digital subtraction angiography of the axillary artery confirmed the presence of a pseudoaneurysm arising from the posterior circumflex humeral artery with no demonstrable outflow vessel (Fig. 2). The inflow vessel was cannulated with a microcatheter (0.021” J-tip DirexionTM, Boston Scientific) and embolized with a selection of 3 mm and 4 mm coils (Nester®, Cook Medical) with satisfactory occlusion on the post-procedural angiogram and no immediate post-procedural complications. A duplex ultrasound performed 12 months after the embolization confirmed thrombosis of the pseudoaneurysm (Fig. 3) and patent right axillary, brachial, and radial with satisfactory flow.

The arterial wall is made of three concentric layers: the tunica adventitia, media, and intima, from outer to inner, respectively. A true aneurysm is dilation, which involves all three layers. Conversely, a pseudoaneurysm is a defect that is bounded only by the adventitia or adjacent perivascular tissue, forming an extravascular hematoma [4, 6]. Pseudoaneurysms have the potential to expand and rupture, which can result in life-threatening bleeding ^[7]. Pseudoaneurysm formation is a known complication of knee and ankle arthroscopy. However, pseudoaneurysms of the circumflex artery following shoulder arthroscopy have not been previously reported. There is a 5.8% to 9.5% incidence of complications in arthroscopic shoulder surgery, as reported by Weber et al. This is supported by Brislin et al,. who identified similar rates of 4.8–10.6% ^[1]. Based on existing literature, shoulder arthroscopy poses a comparatively higher risk of injury to the cephalic vein and thoracoacromial artery ^[1]. The literature on arterial pseudoaneurysms following shoulder arthroscopy is reviewed below (Table 1). Our case study is unique as the patient presented more than a decade after surgery, whereas those described above presented within weeks to months. Most cases of pseudoaneurysm formation are related to branches of the thoracoacromial artery with injury at the anterior portal site [1, 4], but none have been reported from the posterior circumflex artery or posterior portals. Lo et al. from their study on five fresh frozen cadaveric specimens concluded that there was a higher risk to the cephalic vein when placing the 5 o’clock or anterior port as compared to a posterior port ^[8]. Meyer et al. reported similar findings: by placing the 5 o’clock portal, the axillary artery and nerve had a higher risk of injury ^[9]. In contrast, Yang et al. reported the case of a 49-year-old patient who underwent arthroscopic lysis of adhesions and extensive debridement of the glenohumeral joint 9 months prior to developing a left deep brachial artery pseudoaneurysm. They noticed that the injury sustained was not because of the anterior portal, given the anatomy of the deep brachial artery. Hence, a high suspicion of iatrogenic injury should be kept in mind. In general, an US can confirm a pseudoaneurysm as it shows the arterial blood flow. The advantages are that the US is quick, cheap, and does not utilize ionizing radiation, although there is a degree of operator dependence. Cross-sectional or catheter angiography is used to identify a pseudoaneurysm ^[10] with greater objectivity than ultrasound, although it requires the use of intravenous contrast and involves ionizing radiation. Both ultrasound and CT angiography are common modes of investigation. There are several treatment options for pseudoaneurysms, for example, a covered stent, percutaneous thrombin injection, ultrasound-guided compression, transcatheter embolization, and surgical ligation [4, 10]. Cameron et al. reported a venous pseudoaneurysm at the anterior portal site, which was managed by surgical excision [1, 4, 10]. As upper limb pseudoaneurysms are rare, there is no consensus on the preferred management. The treatment option should be tailored to the individual based on their co-morbidities and risk of procedural complications. Choo et al. treated their patient with a less invasive procedure, notably thrombin injection with transcatheter embolization, as the patient suffered from cardiac disease and coagulopathy. This technique has a success rate of 93–100% ^[1]. To our knowledge, our case is the first to use a transradial approach to embolize an upper limb aneurysm. A transradial approach is commonly utilized in coronary angiography, with multiple studies reporting reduced procedure-related complications and shorter hospital stays ^[11]. If there is a delay in the diagnosis and management of a pseudoaneurysm, there is a risk of pain, limb ischemia, and amputation. Our case is quite unique compared to previously reported cases given the considerable length of time from surgery to diagnosis and treatment of the pseudoaneurysm. Additionally, this is the first reported case of a pseudoaneurysm in the posterior humeral circumflex artery.

Vascular injury is an uncommon complication following shoulder arthroscopy. However, a pseudoaneurysm should be considered in patients who present with swelling at the surgical site, regardless of the post-operative period. Prompt recognition and early intervention with a multidisciplinary approach can prevent rupture and associated morbidity.

1. As pseudoaneurysms are quite uncommon, there is often an incorrect or delayed diagnosis
2. When suspected, prompt diagnosis and treatment are warranted, with a referral to a vascular surgeon or interventional radiologist
3. Treatment plans need to be discussed as part of a multidisciplinary team to optimize the outcome.