Bone tumors are tumors invading the bone primarily or secondary due to metastasis. Primary bone tumors can be malignant or benign. Among malignant primary bone tumors, chondrosarcomas, composed of chondrocytes, present with variable degrees of malignancy. According to various studies, it comes third after osteosarcoma and multiple myeloma as the most common primary malignant bone tumors in all age groups. However, being a tumor of adulthood, chondrosarcoma is the second most common primary malignant bone tumor after multiple myeloma [1, 2]. As presentation, they most commonly affect the axial skeleton (pelvis, sternum, scapula) then the proximal femur and proximal humerus. In the case of chondrosarcoma, the degree of malignancy is not always correlated with histology since sometimes chondrosarcomas with similar histological descriptions could be benign in the hand but malignant if affecting the long bones. Hence, tumor location is an important factor in tumor aggressiveness. Chondrosarcomas are typically found in older patients (40–75 years) with slight male predominance. They are divided based on histopathology into two types: Conventional or primary type (80–90%) and non-conventional or secondary forms arising from benign cartilage lesions as osteochondromas or enchondromas. These benign tumors can be solitary or may present with multiple lesions, which are more common, as in cases of Maffucci syndrome or Ollier’s disease [3,4]. Furthermore, chondrosarcomas can be subdivided based on a particular histological grading system which determines the prognosis and guides the treatment. Most of them are low grade (1 or 2) and characterized by a similar histological appearance to enchondromas. Grade 3 is dedifferentiated chondrosarcomas developing initially from low-grade chondroid lesions to high-grade neoplasm (spindle cells, high nuclear atypia, and rare cartilaginous matrix on histology) [5,6]. In addition to dedifferentiated chondrosarcomas, two more subtypes of primary chondrosarcomas are clear cell chondrosarcoma and mesenchymal chondrosarcoma. Clinical presentation varies according to tumor grade and location. Pain, redness, and edema are the main signs and symptoms when predominantly involving long bones but it can also present with gastrointestinal (bowel obstruction) or genitourinary (bladder obstruction) symptoms if affecting the pelvic bones or with a pathologic fracture in high-grade tumors. Radiographs are the first step in establishing the diagnosis. It helps identifying whether it is a lytic or blastic lesion, low-grade or high-grade chondrosarcomas. For more illustration, low-grade chondrosarcomas appear as lucent medullary lesions with intralesional calcifications (popcorn pattern), cortical thickening, and endosteal erosions. On the other hand, destroyed cortex and soft-tissue mass expansion are seen in high-grade lesions. Magnetic resonance imaging (MRI) is useful for comprehensive evaluation of primary tumor and possible marrow and soft-tissue involvement. Detection of cortical involvement, matrix calcification, and deep endosteal scalloping in low-grade neoplasms is best accomplished by computed tomography. In general, early diagnosis of chondrosarcoma is associated with a favorable prognosis and histopathology remains the cornerstone that guides us to the most appropriate treatment modality. The management of chondrosarcomas is mainly operative either by intralesional curettage or wide surgical excision. Curettage with adjuvant treatment is reserved for central low-grade tumors located in the extremities (minimal rate of metastasis) [7,8]. Indications for wide surgical excision include intermediate and high-grade chondrosarcomas, low-grade lesions in the axial skeleton, and cases of soft tissue or joint involvement [9,10]. Chemotherapy and radiation therapy are known to be less effective for most chondrosarcomas. Chemotherapy use in dedifferentiated chondrosarcomas is controversial. However, it is useful as neoadjuvant for mesenchymal chondrosarcomas ^[11]. Radiotherapy can be beneficial in cases of unresectable lesions or after intralesional curettage as adjuvant therapy ^[12]. Histological grade correlates with survival. About 90% of Grade 1, 60–70% of Grade 2, 30–50% of Grade 3, and <10% of de-differentiated chondrosarcomas have a 5-year survival rate.

A 62-year-old female patient presented to our orthopedic clinic at Bahman University Hospital in Beirut, Lebanon, for pain and minimal limitation in the range of motion in her left shoulder for several months. No history of trauma was reported. She is known to have a type 2 diabetes mellitus. Her family history revealed that her father had a “non-bony” cancer. Pain is at rest exacerbated by passive flexion and abduction. Her pain was well controlled by non-steroidal anti-inflammatory drugs but then became more severe and resistant. On inspection, there was no redness, but mild swelling was inspected. Palpation showed mild tenderness over the proximal humerus. No decrease in the passive range of motion but limitations in the active range of motion were noted. The range of motion was 0–90° of abduction, 0–100° of flexion and external rotation at side 0–30°, internal rotation to T9-T10 vertebral height. Neurovascular examination is intact. There were no major abnormal laboratory findings.

As the next step, X-rays of the left shoulder were done and revealed a lytic lesion with endosteal scalloping and cortical changes (Fig. 1). To assess soft-tissue involvement, MRI of the left shoulder was performed which showed a heterogenous expensile mass mainly hypointense on T1 (Fig. 2) and hyperintense on T2 (Fig. 3a) and STIR (Fig. 3b) with chondroid matrix involving head, surgical neck, and proximal diaphysis of the left humerus measuring 82 × 43 mm. The mass showed periosteal thickening and extraosseous extension. There was no extension into glenohumeral or acromioclavicular joint but there was mild sub-acromial effusion. Moreover, rotator cuff tendons were intact with no extension.

For metastatic assessment, positron emission tomography scan was performed. No abnormal findings were seen beside the lytic hypermetabolic lesion involving the humeral head, metaphysis, and proximal diaphysis of the left humerus. For definitive diagnosis, an incisional biopsy was done which showed cartilaginous tumor growing into lobules of varying sizes. Chondrocytes were double nucleated, moderately enlarged, hyperchromatic, rarely mitotic, and located within lacunae. Furthermore, the matrix was solid and pale blue. Hence, a diagnosis of left proximal humerus chondrosarcoma was confirmed with findings correlated with a Grade 1 lesion. Unfortunately, the patient had difficult circumstances that forced her to procrastinate during the management plan. Thus, the MRI was repeated 5 months later for pre-operative planning and comprehensive evaluation of tumor progression. It revealed a mild increase in tumor size to 85 × 48 mm with no other significant changes. The patient was planned for a limb salvage procedure with wide surgical excision and reconstruction.

Intraoperatively, the patient was put in a beach chair position with a support arm holder and under general anesthesia. An extended deltopectoral approach was adopted. A careful dissection of the subcutaneous tissue with retraction of the cephalic vein was performed. Opening of the deltopectoral interval and incision with dissection of the clavipectoral fascia just lateral to the conjoint tendon was followed meticulously to avoid musculocutaneous nerve injury until reaching the bone. Osteotomy of the proximal humerus 12-cm distal from the apex was performed (Fig. 4). Then, reconstruction of the proximal humerus was done with a cemented shoulder hemiarthroplasty using Modular Universal Tumor and Revision System (MUTARS^®), a single design implant system coated with titanium. After the final implant assembly, the prosthesis was covered by a polyethylene tube which was attached to the joint capsule, then tightened and fixed over and under the pads of the prosthesis. The rotator cuff tendons were fixed with sutures to the meshes of the tube proximally at the level of the implant metaphysis which acts as the greater and lesser humeral tuberosities, whereas the mesh around the diaphysis was the site of reattachment of the deltoid and pectoralis major muscles. Lavage and hemostasis were performed. Three layers of closure and a closed suction drainage were attached. Finally, the shoulder was put in a sling immobilizer to assist in shoulder stability and recovery. Post-operative X-rays were taken at the same day (Fig. 5).

The patient had a smooth post-operative course with hospital discharge at day 5 after surgery. During her hospital stay, physical therapy with passive shoulder immobilization was initiated. Moreover, 20 sessions of physiotherapy were done after discharge. There is no chemo or radiotherapy received. Histopathology showed a cartilaginous proliferation with focal myxoid changes, moderate cellularity, mild-to-moderate nuclear atypia, and rare mitosis. There was no necrosis seen. It also showed that the tumor infiltrates the periosteal soft tissue at the level of the head of the humerus. However, the surgical margin was free with a distal surgical margin at 4 cm from the tumor. Immunohistochemical study reveals diffuse positivity of the tumor cells for S100 with low expression of Ki67. Hence, the diagnosis after resection showed a moderately differentiated Grade 2 chondrosarcoma measuring 9.5 cm. After 3 months of follow-up, the functional results were acceptable showing no pain and active abduction limitation to 90° with no passive limitation in range of motion. After 1 year, the patient is doing very well with active abduction reaching 110–115°, forward flexion 120°, 10–15° external rotation, and internal rotation reaching T7-T8 vertebral height.

Chondrosarcomas, whether low-grade or high-grade tumors, are a heterogenous type of bone neoplasms classified based on histology ^[11]. Being heterogenous, they have various morphological characteristics depending on if they are conventional or non-conventional ^[13]. Moreover, the clinical behavior of this pathology varies according to the location of the disease and histology. Thus, a chondrosarcoma in a hand can be of indolent form while a long bone tumor will be more aggressive. Chondrosarcomas are most commonly found in the axial skeleton. Proximal humerus chondrosarcomas localization is relatively a rare entity of this heterogenous group ^[14]. The primary approach to this kind of bone neoplasm can be made by imaging alone although biopsy is the diagnostic modality of choice if uncertainty occurs. A coordinated multidisciplinary approach is necessary to manage patients with chondrosarcomas since most are resistant to chemotherapy and radiation therapy ^[11]. Hence, surgery is the treatment modality of choice [15-17]. In the past, surgeons had limited choices for treating proximal humerus tumors and they lastly resorted to a scapulohumeral disarticulation for such tumors. However, the advancements in surgical and biomedical engineering fields provided orthopedists with better surgical options regarding bone tumor resection and subsequent limb reconstruction. Furthermore, the evolution of various diagnostic techniques helped in the diagnosis of the tumor in an earlier stage that can be more adequately managed along with saving the limb. Therefore, a disarticulation procedure is rare nowadays and reserved for cases with brachial plexus or axillary involvement [18-20]. New reconstruction techniques have been developed to decrease as much as possible the probability of future recurrences and preserve the shape and function of the limb allowing the patient to stay involved in his/her daily activities [21,22]. It usually involves wide surgical resection with negative margins but with the least possible to preserve functionality. There is no specific best reconstruction technique for all patients. Each patient is a unique case that needs a specific technique according to his/her age, comorbidities, life expectancy, lifestyle, and the need to preserve functionality [23,24]. Recent advances in orthopedic oncology allowed proximal humerus reconstruction through various techniques: autografts, allografts, implanted prostheses, or prosthetic-biological composites [22,24-28]. Younger patients with long life expectancy are most suited for an allograft as its functionality improves with time and successful allograft reconstruction has a low probability for a revision surgery even after decades [14,29,30], whereas patients who receive chemotherapy or radiotherapy and/or have healing defects (diabetes, advanced age, neurovascular, or metabolic disorders) may have high complication rates (chondrolysis, graft failure, subchondral collapse, and implant fracture) if they undergo allograft reconstruction [22,24-28,30-34]. On the other hand, autograft is best indicated for pediatric patients and young patients with long life expectancy and good bone quality at the donor site as it has the best osteointegrative potential. Growing plates can be used in children to assist the development of the shoulder. However, this technique often requires long surgical duration, an increasing amount of graft harvest, and thus donor site morbidity [35-41]. Moreover, anatomical implanted prostheses are indicated in advanced-age or middle-aged patients with damage to the deltoid muscle or axillary nerve. This modality has less surgical time and demand than the previous modalities and it is associated with earlier functional recovery; however, it has a limited durability and restricted functional outcome [42-49]. Furthermore, reverse shoulder prostheses are preserved for middle-aged patients having maintained deltoid insertion and axillary nerve and request high functional abilities. This type of prostheses has also a limited durability but it has a better mobility than the anatomical endoprostheses [42,50-55]. Prosthetic biological composites are indicated for both young mid-age patients with high functional demands and medium or long life expectancy. This modality is a long complex procedure with relatively high mechanical complications but with subsequent fair durability and satisfactory functional outcomes [56-61]. Nevertheless, biological treatment compared to endoprostheses and allograft-prosthesis composite had more complications thus necessitating more subsequent re-interventions ^[26]. Despite there is no best reconstruction method, reverse shoulder arthroplasty yields the most satisfactory functional outcomes [45,53,62]. The primary objective for all the aforementioned techniques is to restore shoulder stability and mobility. Chondrosarcomas necessitate challenging multidisciplinary management. An approach balancing between an extensive tumor resection respecting the oncological principles and a limb-sparing procedure preserving the complex shoulder anatomy and its functionality creates a huge burden on the surgeon. In our case, we took into consideration its particularities and the principles of each technique to decide on the best treatment modality that can provide the patient with acceptable shoulder stability and functionality. The tumor was not extending into the glenohumeral or acromioclavicular joints, the patient is <70 years of age, and she was able to achieve forward flexion more than 90°; thus, we decided to go for hemiarthroplasty. The tumor, according to the last MRI 2 months preoperatively, was 85 mm in length into the humeral diaphysis, and thus, an extensive resection of the proximal humerus and humeral shaft was required. Thereby, we needed a long-stem tumoral prosthesis able to restore length, stability, and motion. Hence, the decision was made on a cement MUTARS® titanium-coated endoprosthesis which was developed to treat major osseous defects in the extremities. After careful dissection and a thorough assessment of the extent of tumor invasion, no surrounding soft tissue or joint space involvement was seen. Thus, a Malawer type 1 intra-articular proximal humerus resection at 12 cm from the apex of the humeral head with a maximal preservation of the surrounding soft tissue was performed. To prepare the medullary canal, progressive rasping was performed to a size of 12 mm. We applied the cement within the medullary cavity, then we mounted and impacted a 10 mm in diameter and 160 mm in length original titanium coated MUTARS® stem. After cement hardening, proximal components were assembled with the appropriate rotation. A trial cap was used to control muscle tension and then removed after sufficient tension was achieved. Around 20° of implant retroversion was applied and the final MUTARS® components were assembled. Finally, an attachment polyethylene terephthalate tube was packed around the implant. Its role is to facilitate reattachment of the joint capsule and the remaining tendinous insertion (rotator cuff, deltoid, pectoralis major) to the prosthesis. The tube was then tightened and fixed under the pads of the MUTARS® components. Finally, muscles and tendons were fixed with non-resorbable sutures to the meshes of the tube. The histopathological examination postoperatively showed an evolved grading of the disease from Grade 1 at the time of biopsy to Grade 2 moderately differentiated chondrosarcoma measuring 9.5 cm with negative resection margins. In addition to the localization and since the progression of the tumor grade and size was relatively slow, the oncological outcome is favorable, and humeral reconstruction is expected to last as predicted. The post-operative course was uneventful with no major complications. No chemotherapy or radiotherapy was needed. Moreover, she received progressive functional rehabilitation with remarkable improvement in shoulder function (passive abduction and forward flexion to 90°) and pain score. Recent follow-up revealed satisfactory functional status and no disease recurrence. Continuous follow-up is being done. Despite the 7-month delay between the diagnosis and surgical treatment which resulted in an increase in tumor grade and size, we were able to obtain an acceptable functional and pain-free outcome in the first 3 months after surgery. The MUTARS® system proved in our case that it can help patients requiring extensive proximal humeral resection to regain their shoulder joint functionality in a short period of time. Note that this case is the first reported one in Lebanon and the Middle East. Furthermore, the literature showed limited studies on the outcome of the MUTARS® system reconstruction for proximal humerus chondrosarcomas. Therefore, our case management and outcomes could encourage the use of this system in similar cases in the future for better outcomes clinically and functionally and to increase life expectancy.

Proximal humerus localization for chondrosarcoma is rare and its management is challenging. Surgery is the best resort for definitive treatment since frequent resistance to chemotherapy and radiotherapy is found with most subtypes. Nowadays, reconstruction techniques have been proved to give promising outcomes. Hence, the MUTARS® system, developed to replace major osseous defects, showed in our case favorable outcomes. However, further comparative studies should be conducted to prove the efficacy of this system relative to other treatment options to support the use of the MUTARS system in similar cases in the ultimate interest of patient benefit and satisfaction.

Localized symptomatic large proximal humerus chondrosarcomas could be definitely cured surgically by excising the large defects and implanting a MUTARS shoulder hemiarthroplasty system that showed in our case promising functional and clinical outcomes.