Proximal Humerus Resection and Endoprosthetic Reconstruction: An Intraoperative Masterclass

Introduction and Epidemiology

The proximal humerus constitutes a highly prevalent anatomic site for primary malignant bone tumors, representing the third most common location for osteosarcoma, superseded only by the distal femur and proximal tibia. It is also a site of predilection for primary chondrosarcomas in adult cohorts and Ewing sarcomas in pediatric and adolescent populations. Furthermore, the proximal humerus represents the second most common site of metastatic disease involving the appendicular skeleton. It frequently harbors secondary osteolytic or osteoblastic lesions from renal cell carcinoma, breast carcinoma, prostate adenocarcinoma, lung carcinoma, and thyroid cancer. In advanced presentations, metastatic tumors may involve the entire shoulder girdle, necessitating management strategies that parallel the rigorous en bloc resection and reconstruction principles applied to primary osseous sarcomas.

Historically, the standard of care for high-grade malignancies of the shoulder girdle was the morbid forequarter amputation (Berger operation) to achieve definitive oncologic margins. However, the advent of neoadjuvant chemotherapy protocols, high-resolution cross-sectional imaging, and sophisticated modular endoprosthetic designs have fundamentally revolutionized surgical oncology of the upper extremity. In the contemporary era, limb-sparing resection of the proximal humerus can be successfully executed in approximately 95 percent of patients presenting with high-grade or low-grade sarcomas. Forequarter amputations are now rarely indicated, typically reserved as a salvage procedure for massive tumors demonstrating irreversible neurovascular encasement, fungating soft tissue extension, or profound ischemic compromise of the distal limb.

Endoprosthetic reconstruction remains the most ubiquitous and reliable technique for restoring massive proximal humeral defects following oncologic extirpation. This reconstructive modality is versatile, employed successfully following both intra-articular and extra-articular resections. The primary objective of endoprosthetic reconstruction extends far beyond merely bridging the skeletal defect; it mandates the meticulous integration of local muscle transfers to establish dynamic shoulder stability, provide a robust, well-vascularized soft tissue envelope over the metallic prosthesis, and preserve a highly functional distal extremity (elbow, wrist, and hand).

Tumors arising in this anatomic region frequently exhibit a significant extraosseous soft tissue component. This necessitates wide en bloc resection margins that must unequivocally incorporate biopsy tracts, involved muscle compartments, and adjacent fascial planes to prevent local recurrence. Secondary soft tissue sarcomas that secondarily invade the proximal humerus require identical oncologic resection principles, demanding a comprehensive understanding of compartmental anatomy.

Surgical Anatomy and Biomechanics

A profound, three-dimensional understanding of the complex anatomy of the shoulder girdle is an absolute prerequisite for executing safe, oncologically sound resections while preserving maximal distal limb function. The shoulder girdle comprises the clavicle, scapula, and proximal humerus, which function synergistically through a highly coordinated series of articulations: the glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic joints.

The muscular anatomy of the shoulder is broadly categorized into intrinsic and extrinsic groups. The intrinsic musculature, notably the rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis) and the deltoid, are frequently compromised or entirely resected depending on the tumor's extraosseous extension and compartmental involvement. The extrinsic muscles, including the pectoralis major, latissimus dorsi, and teres major, serve as critical anatomic landmarks during the initial dissection and are vital assets for subsequent soft tissue reconstruction and prosthetic coverage.

Neurovascular proximity is the primary determinant of limb salvage feasibility. The brachial plexus and axillary vessels traverse the axilla in intimate relation to the coracoid process and the subscapularis muscle belly. The axillary nerve, traversing the quadrangular space alongside the posterior circumflex humeral artery, is particularly vulnerable during proximal humerus resections. It courses approximately 5 to 7 centimeters distal to the lateral acromial edge, providing critical innervation to the deltoid and teres minor. Preservation of the axillary nerve is paramount for postoperative shoulder abduction and dynamic stability; however, its oncologic sacrifice is mandatory if the tumor extends into the quadrangular space or directly invades the epineurium.

The radial nerve dictates the distal extent of safe dissection and osteotomy. Exiting the axilla through the triangular interval, it spirals around the posterior humerus within the spiral groove, accompanied by the profunda brachii artery. Distal osteotomies must be meticulously planned with direct visualization and protection of the radial nerve to prevent devastating postoperative wrist drop and loss of extrinsic finger extension.

Biomechanically, the native glenohumeral joint is inherently unstable, relying heavily on dynamic muscular stabilizers (the rotator cuff force couples) rather than static ligamentous or osseous constraints. Following proximal humeral resection, the total loss of the rotator cuff and the articular capsule fundamentally alters these biomechanics. The primary biomechanical challenge in endoprosthetic reconstruction is preventing inferior subluxation of the prosthesis under the gravitational weight of the dependent limb. This mandates meticulous static suspension techniques, universally utilizing synthetic mesh (e.g., Trevira) attached to the acromion, remaining glenoid, or clavicle, supplemented by dynamic stabilization through regional muscle transfers.

Indications and Contraindications

Patient selection for limb-sparing surgery of the proximal humerus hinges on the absolute prerequisite of achieving negative oncologic margins without compromising the viability and neurologic function of the distal extremity. Rigorous preoperative staging is required to ensure the tumor does not encase the major neurovascular bundle or extensively invade the thoracic wall, which would preclude a functional salvage.

The surgical classification system for shoulder girdle resections (derived from the Malawer and Enneking classifications) dictates the specific operative approach. Types I through III represent intra-articular resections, whereas Types IV through VI are extra-articular, involving en bloc resection of the glenohumeral joint and variable portions of the scapula. Type I resections (intra-articular proximal humerus) are generally contraindicated for high-grade tumors with intra-articular extension due to an unacceptably high risk of local recurrence stemming from microscopic joint contamination. The Tikhoff-Linberg resection (Type VI) represents an aggressive limb-sparing option for extensive tumors, involving en bloc resection of portions of the scapula, clavicle, and proximal humerus in conjunction with all muscles inserting onto and originating from the involved osseous structures.

Pre Operative Planning and Patient Positioning

Comprehensive preoperative imaging is the cornerstone of successful limb-sparing surgery. Magnetic Resonance Imaging (MRI) of the entire humerus is mandatory to delineate the intraosseous extent of the tumor, identify intramedullary skip metastases, and meticulously evaluate extraosseous soft tissue extension. The precise anatomic relationship of the tumor mass to the axillary vessels, brachial plexus cords, and specific muscle compartments dictates the planned resection margins.

Computed Tomography (CT) of the chest is required for systemic staging to rule out pulmonary metastases. In cases of complex anatomy or large tumors displacing the neurovascular bundle, CT angiography provides critical roadmapping of the axillary and brachial vessels. Three-dimensional (3D) modeling and patient-specific cutting guides (PSI) are increasingly utilized to ensure precise osteotomy levels, particularly when attempting to preserve the deltoid insertion or when navigating complex extra-articular glenoid resections.

Biopsy principles must be strictly adhered to; a poorly planned biopsy can convert a limb-salvage candidate into an amputee. The biopsy tract must be placed longitudinally and positioned such that it can be excised en bloc with the definitive tumor specimen without compromising the creation of viable fasciocutaneous flaps. Transverse incisions or biopsies that violate multiple compartments or contaminate major neurovascular structures are strictly contraindicated.

For patient positioning, the beach chair or modified lateral decubitus position is utilized, depending on surgeon preference and posterior extension of the tumor. The beach chair position offers excellent access to the anterior and lateral shoulder girdle and facilitates intraoperative fluoroscopy. The entire forequarter, from the sternal notch to the fingertips, must be prepped and draped free to allow full, unhindered manipulation of the limb during dislocation, resection, and endoprosthetic trialing. A sterile tourniquet may be placed on the distal arm if the planned resection level permits, though it is rarely utilized for proximal third resections.

Detailed Surgical Approach and Technique

Incision and Exposure

An extended deltopectoral approach is the standard workhorse for proximal humerus resections. The incision begins at the lateral third of the clavicle, courses over the coracoid process, and extends distally along the deltopectoral groove toward the lateral border of the biceps brachii. If a previous biopsy tract is present, the incision must incorporate the tract with a minimum 1 to 2-centimeter elliptical margin of healthy skin.

Thick fasciocutaneous flaps are elevated medially and laterally to preserve the subdermal plexus. The cephalic vein is identified within the deltopectoral interval. Depending on venous drainage dominance and tumor proximity, the vein may be preserved and retracted laterally with the deltoid or ligated and excised to facilitate exposure.

The deltoid muscle is meticulously inspected for tumor involvement. If the tumor extends into the anterior deltoid, the involved portion is resected en bloc with the specimen. If the deltoid is free of tumor, it is retracted laterally. In massive tumors, the deltoid insertion on the deltoid tuberosity may need to be partially or completely released to facilitate adequate exposure of the proximal and middle humeral diaphysis.

Neurovascular Isolation and Muscle Releases

The conjoined tendon (short head of the biceps and coracobrachialis) is identified at its origin on the coracoid process. Retracting the conjoined tendon medially exposes the underlying neurovascular bundle. The axillary artery and vein, along with the cords and terminal branches of the brachial plexus, are meticulously dissected, mobilized, and protected with vessel loops.

The anterior humeral circumflex vessels are identified crossing the operative field transversely and are sequentially ligated. The pectoralis major insertion on the lateral lip of the bicipital groove is isolated. For wide margins, the pectoralis major tendon is transected near its insertion, tagged with heavy non-absorbable sutures, and reflected medially. This provides excellent access to the inferior capsule and the latissimus dorsi and teres major insertions.

The axillary nerve and posterior humeral circumflex vessels must be identified traversing the quadrangular space. If the tumor anatomy permits an intra-articular resection (Type I or II) with adequate margins, the axillary nerve is preserved. If the tumor breaches the posterior cortex, exhibits significant extraosseous extension, or involves the teres minor, the axillary nerve must be sacrificed to achieve clear oncologic margins.

The latissimus dorsi and teres major tendons are identified at the medial lip of the bicipital groove and transected. Distally, the radial nerve is identified in the interval between the brachialis and the lateral head of the triceps. It is traced proximally into the spiral groove to ensure it is completely free from the planned osteotomy site and the distal extent of the tumor mass.

Osteotomy and En Bloc Resection

The level of the humeral osteotomy is determined based on preoperative MRI measurements, typically aiming for a 3-centimeter marrow margin distal to the most distal extent of the tumor or skip lesion. The periosteum is incised circumferentially, and Hohmann retractors are placed to protect the radial nerve and profunda brachii vessels posteriorly.

A transverse osteotomy is performed using an oscillating saw under continuous saline irrigation. A sample of the distal medullary marrow is immediately sent for frozen section analysis to definitively confirm a negative intramedullary margin prior to proceeding with reconstruction.

With the humerus mobilized distally, attention is turned to the glenohumeral joint. For an intra-articular resection, the anterior capsule is incised, and the rotator cuff tendons (subscapularis, supraspinatus, infraspinatus, teres minor) are transected near their insertions on the tuberosities. The long head of the biceps tendon is tenotomized. The proximal humerus is then delivered from the wound en bloc.

For an extra-articular resection (Type V), the dissection proceeds entirely outside the joint capsule to prevent tumor spillage. The coracoacromial ligament is divided, and osteotomies of the acromion, base of the coracoid, and glenoid neck are performed to remove the entire glenohumeral joint en bloc without breaching the articular capsule.

Endoprosthetic and Soft Tissue Reconstruction

Following copious pulsed lavage irrigation and confirmation of absolute hemostasis, the distal humerus is prepared for the endoprosthetic stem. The medullary canal is sequentially reamed to the appropriate diameter. Endoprosthetic reconstruction can utilize cemented or cementless stems. Cemented fixation with polymethylmethacrylate (PMMA) provides immediate mechanical stability and is preferred in patients with poor bone quality, metastatic disease, or those requiring immediate postoperative radiation. Cementless, porous-coated stems (hydroxyapatite-coated) are utilized in younger patients with excellent bone stock to facilitate long-term biologic osteointegration.

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