Minimally‐invasive excision of a scapular osteochondroma on the ventral surface: A case report and literature review

Key Clinical Message Osteochondroma on the ventral scapula is clinically rare and can incur pseudo‐winged scapula and snapping syndrome if not treated. In this regard, surgical excision is suggested, if possible, with a minimally invasive approach to accelerate physical recovery. Abstract Osteochondroma is a common benign bone tumor, characterized by a cartilage‐capped osseous protuberance with cortical and medullary continuity with the underlying native bone. Osteochondroma is commonly found in the long bones, such as the proximal humerus, distal femur, and proximal tibia, but rarely seen in flat bones. We report a case of pedunculated osteochondroma on the ventral surface of left scapula in a young adult woman. She presented with a slight pseudo‐winged scapula, occasional pain, and snapping sound with motion of the left shoulder. The tumor was surgically resected using a minimally invasive approach, and an excellent outcome was obtained.


| INTRODUCTION
Osteochondroma is a common benign bone tumor, characterized by a cartilage-capped osseous protuberance with cortical and medullary continuity with the underlying native bone. 1 Osteochondromas may be pedunculated or sessile; and 90% of the cases present as solitary form, while 10% as multiple form in the context of hereditary multiple exostoses (HME). 2 They are commonly found in the long bones, such as the proximal humerus, distal femur, and proximal tibia, but scapular involvement is relatively rare.It has been reported that scapular osteochondromas account for only 3%-4.5% of all reported osteochondromas. 3capular osteochondromas are usually asymptomatic before growing larger to induce mechanical effects, and lesions on ventral surface might lead to snapping scapula syndrome, which is characterized by an audible or palpable grinding sensation experienced with scapular abduction. 4Scapular pseudo-winging can also be caused by ventral osteochondromas, a cosmetic defect necessitating surgical treatment. 4e report a case of pedunculated osteochondroma on the ventral surface near the medial border of left scapula in a young female.She presented with a slight pseudowinged scapula, occasional pain, and snapping sound with motion of the left shoulder.The tumor was surgically resected using a minimally invasive approach and an excellent outcome was obtained.

| CASE HISTORY/ EXAMINATION
A 28-year-old female patient presented with occasional pain and snapping sound at the left scapula for more than 2 years.She reported that the symptoms became more frequent recently, even affecting the motion of the left shoulder.The past history is unremarkable except that she had a surgery for otitis media at a local hospital 2 years prior.Physical examination revealed a mild winged-scapula which was snapping with the left scapular motion, and slight tenderness at the medial border of the left scapular spine.The motor and sensory function of the left extremity was normal.

| METHODS
Radiographs and computed tomography (CT) threedimensional (3-D) reconstruction of the left scapula revealed a pedunculated exostosis arising from the ventral surface (Figure 1A,B).The patient was diagnosed with an osteochondroma of the left scapula and admitted into the orthopedic ward.Soon after the surgery was performed under general anesthesia, with the patient put in a prone position, the tumor localized and marked according to 3-D printing model out of the scapular CT.A 3.5 cm incision was made along the medial edge of the left scapula (Figure 2A,B).By pulling up the lower margin of the trapezius muscle and splitting bluntly along the muscle fiber of the rhomboid muscle, the tumor was exposed and entirely excised using an osteotome from its base, which measured 1.8 × 1.0 × 1.0 cm in size (Figure 2C).Bone wax was packed on the cut bony surface to stop bleeding and the incision was closed in layers.The histopathology confirmed the diagnosis of osteochondroma, with a cartilaginous cap thick around 1 mm (Figure 3).

| CONCLUSION AND RESULTS
The postoperative radiograph revealed complete removal of the tumor from its base on the ventral surface of the left scapula (Figure 4).The symptoms of the patient relieved immediately after the surgery, and the patient was encouraged to start progressive functional exercise of the left shoulder girdle.At the follow-up of one and a half months postoperatively, the symptoms were completely disappeared, and the range of motion of the left should recovered almost normal in all directions without any discomfort.At the latest one-year follow-up, the patient reported no abnormalities, and the radiographs revealed no signs of recurrence (Figure 5).tumors arise from the ventral surface of scapula may produce pseudo-winging of scapula, 10-14 and snapping scapula syndrome. 7,15Scapular pseudo-winging needs to be differentiated from typical winged scapula which is usually a consequence of scapular muscles palsy such as serratus anterior, or structural abnormalities, for instance, rotator cuff tear, fracture malunion, and glenohumeral instability. 27Neurovascular compression can sometimes be caused by the osteochondroma on specific locations. 28iagnosis of scapular osteochondroma is generally not a problem given its clinical features and findings of imaging including radiographs, CT or MRI.Radiographs and CT can clearly show the location and size of the lesion.MRI can illustrate the thickness of cartilaginous cap, of which greater than 3 cm in children or 2 cm in adults indicates malignant degeneration. 29However, MRI examination was not appointed for this patient, considering the cost and the time, plus the benign nature of the tumor initially estimated by the clinical and radiographic features.Small lesions without symptoms are suggested to be monitored and followed up as the tumor growth ceases with the closure of the epiphyseal plate. 19Symptomatic large tumors usually warrant surgical excision.Pseudo-winging and snapping affecting the appearance and function of the scapula are also indications for surgical resection. 30owever, most scapular osteochondromas need surgical treatment for symptomatic or cosmetic reasons, or for averting potential malignant transformation.The risk of malignant transformation is estimated at 1% in solitary tumors or 3%-5% in multiple tumors, with increased risk in the sessile compared to the pedunculated. 28,30The recurrence after operation is usually due to unclear resection margins.The operation can be performed by open or arthroscopy approach. 24In the present case, the exostosis that gradually enlarged and produced symptoms for more than 2 years, was surgically resected for mechanical symptoms and pseudo-winged scapula appearance.The surgery was performed using a minimally invasive approach based on 3D printing model, with a minor incision and muscle-sparing technique, 5,8,24 and an excellent outcome was yielded with the symptoms disappeared and the left shoulder function fully recovered without recurrence at the latest one-year follow-up after the surgery.

F
I G U R E 1 (A) Radiograph showing a pedunculated bony mass extruding from the left scapula ventral surface.(B) Computed tomography (CT) scanner 3D reconstruction showing a bony exostosis near the medial border on the ventral of the left scapula.F I G U R E 2 (A) The surgery was performed with the patient in prone position and the tumor was marked on the body surface according to the scapular 3-D printing model.(B) The tumor was exposed during the operation.(C) The tumor was removed en bloc from its base.

F I G U R E 3
Histopathology demonstrated the tumor with normal bony trabeculae, and overlied regular cartilage cap, confirming the diagnosis of osteochondroma.F I G U R E 4 (A) & (B) Radiographs immediately after surgery showed that the osteochondroma was completely resected.F I G U R E 5 (A) & (B) Radiographs one-year after surgery showed that the osteochondroma was completely resected.T A B L E 1 Similar cases of scapular osteochondroma on ventral wall reported in the literature.Author(s) (year) recurrence of mass at 2 years follow-up Sivananda P, et al.(2014)11