Limb Salvage

Martin M. Malawer

Kristen Kellar-Graney

INTRODUCTION

The shoulder girdle is the third most common site for high-grade extremity sarcomas (1,2). The primary focus of this chapter is to describe limb-sparing resection and reconstruction of high-grade or aggressive shoulder girdle tumors. Resection of a malignant bone tumor of the shoulder girdle and its reconstruction consists of three stages: (a) surgical resection of the tumor following principles of oncologic surgery; (b) reconstruction of the skeletal defect following the principles of orthopedic skeletal reconstruction; and (c) multiple muscle transfers to cover the skeletal reconstruction and to provide support for the extremity and ensure stability of the shoulder girdle. The aim of reconstruction is to provide a stable shoulder girdle that allows a functioning elbow and hand, thus enabling the patient to perform activities of daily living. Each of the techniques described in this chapter for surgical reconstruction of proximal humerus and the shoulder girdle provides for stability, function, durability, range of motion (ROM), and preservation of motor power.

Incidence

Approximately 15% to 20% of all bone sarcomas involve the shoulder girdle. Between 5% and 10% of all soft-tissue
sarcomas involve the periscapular, muscles, deltoid, or axillary space. Metastatic carcinomas and melanomas often spread to the axillary lymph nodes. Bony metastases comprise about 5% to 10% of all surgically treated bony metastatic lesions.

SURGICAL ANATOMY

Tumor Growth and the Anatomy of the Shoulder

Sarcomas grow in a centripetal manner and compress surrounding muscle into a pseudocapsule layer. The pseudocapsule layer contains microscopic fingerlike projections of tumor referred to as satellite nodules. Sarcomas spread locally along the path of least resistance. Surrounding fascial layers resist tumor penetration and provide boundaries to local sarcoma growth. These boundaries form a compartment around the tumor. A sarcoma will grow to fill the compartment in which it arises; only rarely will a sarcoma extend beyond its compartmental boundaries. With reference to bony sarcomas that extend beyond the cortices into the surrounding soft tissues, the term “functional anatomic compartment” refers to the investing muscles that are compressed into a pseudocapsular layer. These muscles provide the fascial borders of the compartment, which has important surgical implications. A wide resection of a bone sarcoma entails removal of the entire tumor and pseudocapsular layer and therefore must encompass the investing muscle layers (compartmental resection).

The functional compartment surrounding the proximal humerus consists of the deltoid, subscapularis and remaining rotator cuff musculature, latissimus dorsi, brachialis, and portions of the triceps.

High-grade sarcomas that extend beyond the bony cortices of the proximal humerus expand the investing muscles that form the compartmental borders and pseudocapsular layer. They grow along the path of least resistance and therefore are directed toward the glenoid and scapular neck by the rotator cuff and glenohumeral joint capsule. Anteriorly, the tumor is covered by the subscapularis, which bulges into and displaces the neurovascular bundle. Only rarely does a proximal humerus sarcoma extend beyond the compartmental borders. In these instances, the tumor usually protrudes through the rotator interval. A wide or compartmental resection for a high-grade sarcoma therefore must include the surrounding muscles that form the pseudocapsular layer, the axillary nerve, humeral circumflex vessels, and the glenoid (extraarticular resection).

Most high-grade scapular sarcomas arise from the region of the scapular neck and body. The compartment consists of all of the muscles that originate on the anterior and posterior surfaces of the scapula. Although not one of the compartmental borders, the deltoid, which attaches to a narrow region of the scapular spine and acromion, may be involved secondarily by a large soft-tissue extension. In most cases, the deltoid is protected by the rotator cuff muscles because the anatomic origin of most tumors is in the neck. Similar to the proximal humerus, the rotator cuff muscles are compressed into a pseudocapsular layer by sarcomas that arise from the scapula. The subscapularis also protects the neurovascular bundle from tumor involvement. The head of the proximal humerus is contained within the compartment surrounding the scapula. Wide resection of a high-grade scapula sarcoma must include the rotator cuff and, in most instances, the humeral head.

PATHOPHYSIOLOGY

Sarcomas, which arise from mesenchymal tissues (mesodermal embryonic layer), grow in a centrifugal manner and form a ball-like mass. Sarcomas typically respect fascial borders and generally grow along paths of least resistance. This growth pattern is in contrast to the invasive growth of carcinomas, which usually penetrate compartmental borders. In sarcomas that arise primarily from bone, cortical breakthrough (extracompartmental growth) causes the surrounding tissues to be compressed, forming a pseudocapsule layer known as the reactive zone. The reactive zone is comprised of fibrovascular structures, inflammatory cells, and tumor nodules. The tumor nodules, known as satellites, are less mature than the cells found in the center of the lesion; however, they are capable of causing local recurrence or metastatic spread. For this reason, the entire reactive zone must be resected. In tumors of the proximal humerus, the deltoid often is involved and must be resected. In those tumors that arise from the scapula, the subscapularis muscle frequently is compressed and protects the brachial plexus and its branches from tumor apposition, thereby allowing for a limb-sparing procedure in lieu of a forequarter amputation. Scapular resections routinely include the subscapularis and infraspinatus muscles as well as the supraspinatus muscle.

Direct tumor extension through joints or articular cartilage is rare and typically occurs as the result of a pathologic fracture. As a result of the small size of the glenohumeral joint, a tumor almost always involves the capsule or the synovium. The long head of the biceps tendon, which is intraarticular, is another pathway by which a tumor may cross the joint.

EVALUATION

Clinical

History and Physical Examination

Patients with bone sarcomas typically present to their primary care physician with complaints of a dull, aching pain of several months’ duration. They often seek medical intervention because the pain has become more severe. This
increased pain can be correlated with tumor penetration of cortical bone, irritation of the periosteum, or pathologic fracture. Severe night pain in the affected extremity is common. Some patients may describe regional tenderness, difficulty in moving the arm, or a palpable swelling or mass. Physical examination of the extremity usually will confirm the presence of a mass or regional swelling and deformity. Children are especially susceptible to referred pain; all regional joints should be examined.

The presenting symptoms for a soft-tissue sarcoma are different and nonspecific. Typically, the mass presents as a slow-growing and painless lesion. Tumors arising in the upper extremity are more palpable and identified earlier than those in the lower extremity.

Imaging Studies

Appropriate imaging studies are key to successful resection of tumors of the shoulder girdle. The most useful preoperative evaluations are computerized axial tomography (CAT), magnetic resonance imaging (MRI), angiography, and three-phase bone scans. A venogram may be warranted if there is evidence of distal swelling or neurologic defects for large tumors of the proximal humerus. Positron emission tomography (PET), a new imaging modality, may be useful in detecting residual or locally recurrent tumor in patients with soft-tissue sarcoma and in evaluating the axillary lymph nodes.

Radiography

Plain radiographs remain an important imaging modality in the evaluation of bone tumors. Because they reveal fine trabecular detail, plain radiographs can make it possible to diagnose bone lesions of the extremities prior to biopsy.

Anteroposterior and lateral views of the shoulder girdle usually can detect sclerotic, blastic, or lytic lesions; increased ossification; or periosteal thickening. Once a bone lesion is found, CAT and MRI are used to evaluate the extent of bone destruction.

Plain radiographs also can help predict the tumor response to induction chemotherapy. A good response is shown by increased ossification and rimming of the lesion by new bone.

Magnetic Resonance Imaging

MRI is a valuable tool for evaluating soft-tissue sarcomas and determining the medullary and soft-tissue involvement of bone tumors, especially those around the glenohumeral joint. MRI is also useful in determining the presence of skip lesions and any tumor extension along the chest wall or posterior scapula. The suprascapular area is often difficult to visualize in patients with large tumors. Additionally, MRI can accurately diagnose a variety of soft-tissue tumors.

MRI enables the surgeon to view a lesion in the axial, sagittal, and coronal planes. This proves beneficial when planning the extent of surgical resection. MRI, however, is known to overpredict the extent of tumor in some cases; this is because it does not distinguish tumor from surrounding edema.

The signal intensity of a tumor is interpreted by comparing it with that of the juxtaposed soft tissue, namely, the skeletal muscle and subcutaneous fat. Both T1- and T2-weighted images are used. MRI is not an effective means of determining the postoperative tumor response to induction chemotherapy.

CAT

CAT is more useful than MRI in determining cortical bone changes and is considered complementary to MRI. It is helpful in depicting mixed sclerotic and lytic lesions. CAT is useful in the restaging of patients prior to surgery to determine the effects of induction chemotherapy, especially the bony response and the amount of tumor necrosis. CAT characteristically demonstrates increased ossification and rimming of the tumor in patients with a good (i.e., greater than 90% tumor necrosis) response. It is also useful in determining the potential planes of tumor resection.

CAT should be performed on a helical scanner, which improves two- and three-dimensional image capacity. The slice thickness should be adjusted so that 10 to 15 cuts are made through the tumor. Intravenous contrast should be administered only to patients with soft-tissue tumor.

Angiography and Venography

Angiography is helpful in evaluating tumors of the shoulder girdle. It is extremely useful in detecting vascular displacement, which is common to tumors with a large extraosseous component, and in determining tumor vascularity. Angiography provides information that helps the surgeon plan the anatomic approach to the tumor and assess the need for ligation of large feeding vessels. The axillary vessels are often displaced but rarely involved by direct tumor invasion. The most important exception are tumors of the axillary space.

Axillary tumors, either sarcomas or carcinomas, may directly invade the axillary sheath. In this situation, the angiogram may still be normal. Axillary venography would show occlusion of the axillary vein. This occurs when tumor infiltrates the axillary sheath and compresses the thin-walled vein. The artery is not occluded because of its high pressure and thick walls. Therefore, axillary venograms are routinely performed for axillary tumors, especially if there are any neurologic defects.

Angiography should be performed with the arm abducted to determine the relationship of the brachial plexus and the axillary vessels to the tumor, the level of the circumflex vessels, and the presence of any anomalies. Angiography is the most reliable study to determine the response to neoadjuvant chemotherapy. Tumor necrosis is indicated by the degree of decrease of tumor vascularity or its total absence If there is a good angiographic response
(i.e., decrease or absence of tumor blush), it is safe to proceed with a limb-sparing resection. Arterial embolization is used routinely prior to any surgery, either intralesional or resection, for hypernephroma. Hypernephromas are extremely vascular, and life-threatening hemorrhage may occur if embolization is not performed.

Angiography should be performed on all tumors of the axillary space. It will demonstrate any vascular displacement (very often inferior or anterior) and vascular anomalies of the axillary vessels. Tumor vascularity is also a variable and is helpful following induction chemotherapy. We have found that venography is an essential and accurate means of determining brachial plexus of axillary sheath involvement or infiltration. The arterial wall is thick and almost never shows signs of occlusion, whereas the axillary vein is a thin-walled structure that is easily compressed and infiltrated by tumor. Occlusion is almost synonymous with vascular sheath and brachial plexus involvement. Therefore, a venogram is performed in addition to evaluating the venous phase of an arteriogram. A positive venogram showing occlusion of the vein in combination with neurologic symptoms of numbness and weakness is almost always indicative of axillary sheath and brachial plexus involvement by tumor.

Bone Scintigraphy

This imaging modality was originally used to determine the amount of medullary or intraosseous extension of bone sarcomas. Currently, the bone scan is used to determine the presence of metastatic and polystotic bone disease and the involvement of a bone by an adjacent soft-tissue tumor.

The appearance of the lesion in the flow and pool phases of a three-phase bone scan helps illustrate the vascular and biologic activity, which may be useful for determining the diagnosis.

Positron Emission Scintigraphy

PET is a technique for measuring the concentrations of positron-emitting radioisotopes within living tissue. Within limits, PET has the ability to assess biochemical changes in the body. Any region of the body that is experiencing abnormal biochemical changes can be seen through PET. It is now possible to obtain improved anatomic localization of activity by overlaying or imprinting the information from PET onto more detailed images of MRI or CAT (3). Malignant tumors characteristically show an increased uptake with PET, whereas benign tumors do not. PET is especially useful in evaluating metastatic involvement of axillary lymph nodes.

BIOPSY

The biopsy site should be carefully selected, and biopsy should be performed under the guidance of the surgeon who will perform the resection. The needle should be inserted away from major vessels and nerves and placed in the line of the planned incision. Contamination resulting from poorly performed biopsy is the primary factor necessitating a forequarter amputation.

Because a majority of sarcomas arising from the shoulder girdle have an extraosseous component, a core or largegauge needle biopsy is usually recommended in lieu of an open biopsy. Multiple tissue cores can be obtained through one puncture site, ensuring adequate tumor sampling for diagnostic purposes.

A biopsy for a tumor of the proximal humerus should be performed through the anterior third of the deltoid muscle because it is often resected during the definitive surgical procedure. Care must be taken to avoid the deltopectoral interval. If a biopsy is performed through the deltopectoral interval, the tumor will contaminate the pectoralis major. The resulting hematoma may spread tumor cells along the axillary vessels to the chest wall (Fig. 15-1).

Biopsies for tumors arising in the body of the scapula are more difficult to perform; however, they are key to determining the type of surgical resection to be performed. A posterior biopsy should be used for tumors arising within the body of the scapula, with the needle inserted along the intended incision site. Tumors arising in the glenoid or lateral scapula should be biopsied along the lateral or axillary aspect of the scapula.

Biopsy for lesions of the clavicle is performed differently than for those lesions of the proximal humerus or scapula. A core needle may injure the underlying vascular structures. Therefore, the biopsy should be performed through an incision made parallel to the long axis of the clavicle.

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