Pigmented Villonodular Synovitis of the Shoulder: A Case Report and Literature Review

Introduction

Pigmented villonodular synovitis (PVNS) of the shoulder is a proliferative disease of unknown etiology originating from the synovial membrane, tendon sheath, and bursa [1–3]. It is characterized by benign tissue proliferation of the synovium, the tendon sheath, and the bursa [2,3]. The incidence peak is 30–50 years of age and both sexes are equally affected [2,4]. Although the knee joint is most commonly affected, PVNS also commonly affects the hand and hip joints, though cases of shoulder PVNS have been rarely reported in the literature [4–6]. The major symptoms include pain, swelling, stiffness, and mild to severe limited range of motion of the affected joint [2,3]. According to the natural history of the disease, PVNS can lead to pseudo-paralysis and destruction of the shoulder joint, even requiring arthroplasty [2,3]. In the absence of joint destruction, a massive rotator cuff tear may be found during the arthroscopy of the joint, complicating the treatment plan [2]. PVNS can manifest in 2 forms: localized and diffuse. The diffuse form affects the entire synovium of the joint and tends to carry a poorer prognosis [7].

Although the frequency of PVNS is extremely low, especially when referring to shoulder PVNS, and therefore there is limited information in the literature for the optimal treatment and outcome, it is mainly treated arthroscopically by resecting the synovium [2,4]. Magnetic resonance imaging (MRI) is the preferable modality to diagnose PVNS, as diffuse hypodense soft-tissue lesions will be observed in T1 and T2, although the specificity of these findings alone is questionable [3,8].

In this case report, we present the case of a woman with pigmented villonodular synovitis of the left shoulder joint and discuss the various issues involved in arthroscopic surgery for this condition. The anatomical location of shoulder along with the challenging diagnosis even after histologic examination, possibly due to the corticosteroid schemes, suggest a unique case of shoulder PVNS.

Case Report

A 50-year-old woman presented to the clinic with gradual onset left shoulder pain beginning in October 2019. Verbal consent was acquired from the patient for publicly presenting the case. She was treated conservatively by a rheumatologist as a case of synovitis. She underwent multiple intra-articular injections and was prescribed per os corticosteroids, without, however, experiencing any improvement of her symptoms, while rheumatoid arthritis and other rheumatic causes were excluded. Two years later, she presented to our Orthopedics Department with constant, refractory left shoulder pain. On physical examination, tenderness of the shoulder on palpation was observed along with a painful, limited range of motion. Complete blood count pre-operatively was within normal range. Therefore, imaging tests were requested to assist the clinical diagnosis. Radiographs showed no pathological findings, apart from some bone sclerosis of the greater tubercle indicative of rotator cuff tendinopathy (Figure 1).

MRI showed multiple folds of the synovium of villonodular morphology with high magnetic signal in T1 sequence and low magnetic signal in T1 and T2 sequences with fat saturation, in the left shoulder joint. These folds were enhanced after the intravenous infusion of paramagnetic substance. Moreover, degenerative lesions of the greater tubercle coexisted. Some intra-tendon micro-ruptures of the left supraspinatus muscle were also observed (Figure 2). All these findings pointed to pigmented villonodular synovitis.

Arthroscopic debridement and synovectomy were performed using a typical arthroscopic shaver and diathermy in beach chair position under general anesthesia. The posterior, lateral, and anterior arthroscopic portals were utilized. The macroscopic pathologoanatomic findings revealed a yellowish pigmentation of the joint capsule with villonodular morphology. Soft-tissue samples were obtained to be studied thoroughly by an experienced pathologist under a microscope (Figure 3). No macroscopic rotator cuff tears were noted during arthroscopy.

The histopathological findings showed papillary formations consisted of mild hyperplastic synovial cells. The center of the papillae was infiltrated with plasmacytes and other chronic inflammatory cells. No multinucleated giant cells or hemosiderin-Iaden macrophages were observed (Figure 4). The pathologic interpretation was nonspecific chronic synovitis, which in conjunction with the clinical, MRI, and intra-operative findings confirmed the diagnosis of PVNS.

Postoperatively, the patient received pseudo-paralysis zaldiar tb (37.5+325) for 5 days and reported little pain during his immediate postoperative rehabilitation. Shoulder arthroscopy can be associated with great pain postoperatively and our clinic favors a combination of paracetamol and tramadol for adequate pain control. The shoulder was immobilized in a sling for 2 weeks. Passive exercise started at 2 weeks and active exercise with physiotherapy was prescribed at 6 weeks postoperatively. While the patient reported pain at extreme passive and active ROM pre-operatively and an ASES score of 61, at 1-year postoperatively the patient presented pain-free with full active and passive range of motion with an ASES shoulder score of 85 points, indicating a successful surgical outcome.

Discussion

The diagnosis of PVNS is mainly established with the assistance of MRI, physical examination findings, radiographs, and the pathology of the tissue [9]. While radiographs may exhibit periarticular erosions, cystic bone erosions, or early degenerative changes, they generally have low diagnostic value [7,10,11]. Computed tomography (CT) with contrast is useful to outline the bone cyst formations and erosions or to facilitate precise biopsy. However, this imaging method is neither conclusive nor therapeutic and thus is not widely used [11]. On the contrary, MRI is the best imaging method to differentiate PVNS from other synovial diseases that also involve joint effusion, thickening of the synovium, and joint impairment, such as rheumatoid arthritis, tuberculosis, synovial hemangioma, synovial osteochondromatosis, hemophilic arthropathy, synovial arborescent lipoma, and synovial sarcoma [3,12,13]. Synovial sarcoma is actually the primary differential consideration because both entities can present with lobulated synovial soft-tissue masses, normal bone mineralization, and a normal-appearing joint [10]. Low magnetic signal on T1 and T2-weighted sequences are indicative of hemosiderin deposition, as PVNS is a highly vascularized mass that tends to erode bone and bleed [7–8,12,14]. However, hemosiderin deposition is not specific for PVNS as it can also be observed in hemophilia, synovial hemangiomas, neuropathic osteoarthropathy, and chronic renal failure. Eventually, synovial biopsy is the method that officially establishes the diagnosis and can be performed either arthroscopically or via open arthrotomy, depending on the extent of the disease [11]. In our case, despite high clinical suspicion of PVNS based on MRI and intra-operative findings, histopathological analysis did not confirm the diagnosis conclusively. Although not specifically in PVNS, intra-articular corticosteroids have been reported to reduce synovium cell infiltration [15]. This discrepancy might suggest a variation in the disease’s manifestation or a different stage of PVNS. Although the majority of findings support the diagnosis of PVNS, it is crucial to analyze the full spectrum of results, including any atypical features. Continued monitoring and, potentially, further histological analysis are recommended to clarify the atypical aspects of this case. Excluding other possible of differential diagnosis assisted in setting the diagnosis in this case.

Clinically, patients with PVNS commonly present with pain and restricted range of motion in the affected joint. Swelling or synovial mass in the shoulder are not as usual as in the knee, ankle, or elbow. Due to the condition’s slow progression and nonspecific clinical presentation, delayed diagnosis may result in concurrent massive rotator cuff tears leading to pseudo-paralysis or extensive joint damage necessitating joint replacement [4,10,11,14].

The treatment options for PVNS depend mainly on the severity of the disease and the age of the patient. Local steroid injections can offer temporary relief of symptoms. Total replacement of major joints is indicated in elderly patients with destructive joint disease, but not for young, active patients. Arthrodesis has also been reported in the literature as another treatment option for cases of severe and permanent damage to the joint [6]. Radiotherapy can also offer some relief of the symptoms or it can be beneficial as a supplementary treatment after surgical resection for residual disease [8,16]. However, reports in the literature suggest that surgical management is the best for the diffuse form, and early marginal excision is best for the localized form [11,14,17]. Arthroscopic debridement is preferred to open synovectomy due to its ability to allow precise exploration of the joint cavity and because of the lower postoperative morbidity [11,14,18].

A study by Pantazopoulos et al emphasized bone involvement in PVNS to differentiate it from other joint diseases with similar bone lesions [6]. Dorwart et al reported 2 cases with diffuse PVNS of the shoulder, which were both successfully treated with open surgical excision of the proliferative synovium and total shoulder replacement arthroplasty. According to the authors, both patients showed pathologic features of long-standing PVNS, such as papillary synovial hyperplasia with organizing surface fibrin deposits, stromal fibrosis, chronic inflammation, accumulations of macrophages that contain cytoplasmic hemosiderin, and absence of multinucleate giant cells and lipid-laden macrophages [9].

Jong-Hun Ji et al also reported 2 cases of diffuse PVNS with no trauma history, accompanied by rotator cuff tear, cystic changes of the acromion, and subacromial bony erosion. The patients were treated arthroscopically via synovectomy, rotator cuff repair, and acromioplasty, and neither patient had symptomatic recurrence of PVNS at follow-up. The authors highlight the importance of differential diagnosing subacromial erosions with shoulder pain, aiming for an earlier diagnosis and better treatment outcomes [18]. A more recent case series of 6 patients by Li et al demonstrated the outcome of open and arthroscopic synovectomy accompanied by rotator cuff repair, all showcasing favorable post-surgical outcomes [2].

The peak age of incidence has been suggested to be 30–50 years old, but from our case and our literature review, most cases were aged 50–80 years old with the exception of a 30-year-old woman [1,8,9,14,18]. Diagnosis in many patients takes a long time; some of them presented with bone erosions (from the synovial inflammation) or massive rotator cuff tears and most of them experienced complete symptoms resolution after arthroscopic synovectomy [1,8,9,14,18].

Despite shoulder arthroscopic debridement being considered a low-risk procedure, the treating physician should be wary as complications can still arise. Yang et al reported a case of deep brachial pseudoaneurysm following arthroscopic debridement, even requiring embolization, and the disrupted anatomy secondary to PVNS could make differentiation of neurovascular structures more difficult [19].

Conclusions

The treatment of PVNS typically involves surgical intervention, which can be either arthroscopic or open. Arthroscopic surgery is generally considered the most effective approach, particularly for the diffuse form, while joint replacement may be considered for older patients. Diagnosis, however, remains challenging and time-consuming, and consists of MRI and arthroscopy findings, interdisciplinary exclusion of the differential diagnoses, and histopathology examination findings. Long-standing symptoms refractory to conservative treatment with villous and bony involvement can indicate shoulder PVNS. Despite the diagnostic challenges, we successfully performed arthroscopic surgery on a 50-year-old woman diagnosed with pigmented villonodular synovitis of the shoulder, achieving excellent surgical outcomes.