Proximal Humerus Resection and Endoprosthetic Replacement: An Intraoperative Masterclass

Welcome, fellows, to the operating theater. Today, we're tackling a challenging yet incredibly rewarding procedure: a Proximal Humerus Resection with Endoprosthetic Replacement for a high-grade sarcoma. Our goal is twofold: achieve clear oncologic margins and restore maximal upper extremity function. This demands meticulous planning, precise execution, and a deep understanding of the complex anatomy we'll encounter.

Preoperative Planning: The Blueprint for Success

Before we even make an incision, the battle is won or lost in the planning phase.

Patient Assessment and Imaging

Our patient today has a chondrosarcoma of the proximal humerus. We've thoroughly reviewed the MRI, CT, and PET-CT scans. The MRI gives us exquisite soft tissue detail, delineating the tumor's relationship to the neurovascular bundle and rotator cuff. The CT provides bone detail for osteotomy planning and prosthesis templating. The PET-CT helps rule out systemic metastases.

• Oncologic Templating: We've templated the resection margins based on the MRI, aiming for a wide margin. We've also selected our modular endoprosthesis components, ensuring appropriate stem length, humeral head size, and diaphyseal fit. This involves overlaying templates on the CT scans to predict our bone cuts and the final construct length, aiming for limb length equality and optimal soft tissue tension.
• Neurovascular Mapping: Crucially, we've identified the precise course of the axillary nerve as it wraps around the surgical neck, and the brachial plexus and axillary artery/vein medially. These are non-negotiable structures to protect.

Patient Positioning and Fluoroscopy Setup

For proximal humerus resections, I prefer the beach chair position. This offers excellent exposure to the deltopectoral interval and allows for dynamic assessment of range of motion during reconstruction.

1. Head Positioning: Ensure the head is comfortably supported and slightly flexed, rotated away from the operative shoulder. Protect the eyes and ears.
2. Torso Support: A beanbag or chest roll is placed under the ipsilateral scapula to elevate the shoulder, allowing for posterior access if necessary and preventing the scapula from falling posteriorly.
3. Arm Positioning: The operative arm is draped free, allowing full manipulation. We'll use a sterile arm holder or an assistant for controlled traction and rotation throughout the case. Ensure adequate padding at all pressure points, especially the elbow and ulnar nerve.
4. Fluoroscopy: The C-arm will be positioned to allow for immediate anteroposterior (AP) and lateral views of the proximal humerus and glenoid. This is crucial for confirming osteotomy levels and prosthesis alignment. Ensure the C-arm can swing in and out without contaminating the sterile field.

Surgical Anatomy: Navigating the Deltopectoral Interval

Let's quickly review the critical anatomy. Our primary approach will be the deltopectoral interval.

• Surface Landmarks: Palpate the acromion, coracoid process, and the bulk of the deltoid and pectoralis major muscles.
• Muscular Intervals: The deltopectoral groove lies between the anterior deltoid and the pectoralis major. The cephalic vein runs within this groove – a key landmark.
• Neurovascular Structures:
  • Axillary Nerve: This nerve is paramount. It originates from the posterior cord of the brachial plexus (C5-C6), exits the axilla through the quadrangular space, and wraps around the surgical neck of the humerus, typically 5-7 cm distal to the acromion. It innervates the deltoid and teres minor. Damage here means deltoid paralysis, a devastating functional loss.
  • Brachial Plexus: Medial to the coracoid process, superior to the axillary artery. These are the main nerve roots and cords supplying the entire upper limb.
  • Axillary Artery and Vein: These major vessels run medially to the humerus, deep to the pectoralis minor. They are vital to protect to prevent catastrophic hemorrhage.
• Osteology: We're dealing with the humeral head, greater and lesser tuberosities (attachment sites for the rotator cuff), the bicipital groove, and the surgical neck (a common fracture site and where the axillary nerve is vulnerable).

Intraoperative Masterclass: Step-by-Step Execution

Scalpel, please. Let's begin.

A. Incision and Superficial Dissection

1. Skin Incision: We'll make a longitudinal incision starting just anterior to the acromion, extending distally along the deltopectoral groove for approximately 15-20 cm, depending on the tumor extent. Assistant, ensure gentle traction on the arm to define the landmarks.
2. Subcutaneous Dissection: Using electrocautery, we meticulously dissect through the subcutaneous tissue. Identify and protect the superficial nerves, though typically there are no major ones in this field.
3. Identify Cephalic Vein: Now, look for the cephalic vein running within the deltopectoral groove. Fellows, notice how it acts as our anatomical guide. We'll carefully dissect around it. Depending on its size and the need for exposure, we can either retract it laterally with the deltoid or medially with the pectoralis major. If it's particularly large or in the way, we can ligate and divide it, but always try to preserve it if possible to minimize postoperative edema. In this case, we'll retract it medially.
4. Develop Deltopectoral Interval: Using blunt and sharp dissection, we carefully separate the anterior deltoid from the pectoralis major. Stay superficial to the clavipectoral fascia initially.
5. Divide Clavipectoral Fascia: Once the interval is well-defined, we'll incise the clavipectoral fascia longitudinally. This fascia lies deep to the deltopectoral groove and covers the underlying structures like the coracobrachialis and short head of the biceps.

B. Deep Dissection and Tumor Exposure

Now we're getting deeper. This is where anatomical precision is paramount.

1. Pectoralis Major Release (if necessary): Depending on the tumor's superior extent or the need for wider exposure, we may need to release the pectoralis major tendon from its insertion on the lateral lip of the bicipital groove. In this case, the tumor is relatively contained to the humeral head, so we'll likely preserve its insertion, retracting the muscle medially. If released, we'll tag its tendon for later reattachment.
2. Identify and Protect Axillary Nerve: This is a critical step. With the deltoid retracted laterally, we carefully palpate and visualize the axillary nerve as it emerges from the quadrangular space and wraps around the posterior aspect of the surgical neck. Use a blunt instrument, like a finger or a small Cobb elevator, to gently sweep the deltoid off the humerus distally, identifying the nerve's entry point into the deltoid. We will place a Penrose drain around it for clear identification and protection throughout the case. This nerve is extremely vulnerable during soft tissue dissection around the surgical neck.
3. Identify and Protect Axillary Artery and Vein: Medial to the humerus, deep to the short head of the biceps and coracobrachialis, lie the axillary artery and vein. These must be carefully identified and protected with broad retractors, such as a Darrach or a malleable retractor, keeping them out of harm's way during all bone work.
4. Release Rotator Cuff and Capsule: We now need to address the soft tissue attachments to the proximal humerus.
   • Subscapularis: For an intra-articular resection, we'll release the subscapularis tendon from the lesser tuberosity. Use a sharp scalpel or electrocautery, keeping it close to the bone. Tag the tendon for later repair.
   • Superior and Posterior Capsule: Incise the superior and posterior capsule.
   • Supraspinatus, Infraspinatus, Teres Minor: These tendons attach to the greater tuberosity. We'll release them, again, tagging them for later reattachment to the prosthesis or surrounding soft tissues.
5. Capsulotomy: Perform a comprehensive capsulotomy to fully expose the humeral head and glenoid, allowing for clear visualization of the tumor.
6. Tumor Assessment and Biopsy Confirmation: Visually inspect the tumor's extent, confirming it matches our preoperative imaging. If there's any doubt about the margins, a frozen section biopsy can be taken at this stage from suspected areas.

C. Oncologic Resection

Now for the definitive step: tumor removal.

1. Proximal Humeral Osteotomy: Based on our templating and the tumor's extent, we've predetermined our osteotomy level, ensuring a wide oncologic margin.

   • Mark Osteotomy Site: Use a marking pen or electrocautery to clearly delineate the precise line of our bone cut on the humeral shaft. Fellows, this is where meticulous planning pays off. We aim for at least a 2 cm margin from the macroscopic tumor edge.
   • Protect Soft Tissues: Place broad, malleable retractors circumferentially around the humeral shaft, distal to our osteotomy line. This protects the surrounding soft tissues, especially the axillary nerve and major vessels, from the oscillating saw.
   • Oscillating Saw: Using a sterile oscillating saw, make a clean, perpendicular cut through the humeral shaft at the marked level. Assistant, ensure constant irrigation to prevent thermal necrosis.
   • Specimen Removal: Carefully remove the resected proximal humerus and tumor specimen. Orient it correctly for pathology and send it for final histopathological analysis, confirming our margins.

   
   
   

Here, you can see the precision required for bone cuts, ensuring clear margins while protecting adjacent structures.

D. Reconstruction: Endoprosthetic Implantation

With the tumor safely removed, we now focus on restoring function.

1. Humeral Canal Preparation:
   • Reaming: Begin with a pilot reamer and then sequentially increase the reamer size, preparing the intramedullary canal of the remaining humeral shaft. Ream slowly, under constant fluoroscopic guidance, to ensure central reaming and prevent cortical perforation. We're aiming for a snug fit for the prosthetic stem.
   • Canal Lavage: Thoroughly lavage the canal to remove all bone debris.
2. Trial Reduction:
   • Select the appropriate trial stem, neck, and head components based on our preoperative templating.
   • Insert the trial stem into the humeral canal.
   • Assemble the trial neck and head.
   • Reduce the Shoulder: Carefully reduce the trial prosthesis into the glenoid.
   • Assess Stability and Range of Motion: This is a critical step. Manipulate the arm through a full range of motion – abduction, adduction, internal and external rotation – to assess stability, impingement, and appropriate soft tissue tension. Ensure the limb length is restored. Adjust trial components (e.g., neck length, head size) as needed to optimize these parameters.
   • Soft Tissue Tension: The reconstruction should provide adequate soft tissue tension to prevent dislocation but not be so tight as to restrict motion or cause nerve compression.

3. Prosthesis Implantation:

   • Stem Insertion: We'll be using a cemented stem today for robust fixation in this oncologic setting.
     • Prepare the humeral canal with pulse lavage and dry it thoroughly.
     • Mix the bone cement (PMMA) according to manufacturer instructions.
     • Using a cement gun, retrograde fill the humeral canal, ensuring complete filling without voids.
     • Insert the definitive prosthetic stem, ensuring correct rotational alignment. Hold it firmly in position until the cement polymerizes.
   • Head and Neck Component Attachment: Once the stem is secure, attach the definitive prosthetic neck and head components. Ensure a secure taper lock.
   • Reduction: Carefully reduce the definitive prosthesis into the glenoid.

   
   
   

Here, you can visualize the precision required during the preparation of the bone and the insertion of trial or definitive components, ensuring perfect alignment and fit.

1. Soft Tissue Reattachment: This is crucial for functional recovery and stability.
   • Rotator Cuff: Reattach the remaining rotator cuff tendons (subscapularis, supraspinatus, infraspinatus, teres minor) to the prosthesis. Many prostheses have suture holes or porous coatings for this purpose. Use strong, non-absorbable sutures (e.g., FiberWire) in a mattress or figure-of-eight fashion.
   • Pectoralis Major/Deltoid: If the pectoralis major was released, reattach it to the humerus or prosthesis. Reapproximate the deltoid origin to its insertion if a deltoid split was used, or simply reapproximate the anterior deltoid to the pectoralis major if the deltopectoral interval was used.
   • Capsular Repair: If feasible, perform a capsular repair to further enhance stability.

E. Wound Closure

1. Hemostasis: Ensure meticulous hemostasis using electrocautery.
2. Irrigation: Copiously irrigate the wound with sterile saline.
3. Drain Placement: Place a closed suction drain (e.g., a JP drain) deep to the muscle layer to prevent hematoma formation.
4. Layered Closure:
   • Close the deep fascial layers (e.g., clavipectoral fascia, deltopectoral interval) with absorbable sutures.
   • Close the subcutaneous tissue with inverted absorbable sutures.
   • Close the skin with staples or a subcuticular suture.
   • Apply a sterile dressing.

Pearls and Pitfalls: Navigating Challenges

Even with meticulous planning, complications can arise. Anticipating them is key to salvage.

• Nerve Injury:
  • Axillary Nerve: The most common nerve injured. Prevention: Meticulous dissection, early identification, and protection with a Penrose drain. Salvage: If transected, immediate primary repair or nerve grafting. If stretched, observation is often sufficient, but monitor closely.
  • Brachial Plexus: Less common with this approach, but can be injured by aggressive retraction or direct trauma. Prevention: Careful retraction, avoid excessive traction on the arm.
• Vascular Injury:
  • Axillary Artery/Vein: Catastrophic. Prevention: Always keep broad retractors protecting these vessels, especially during bone cuts and reaming. Salvage: Immediate vascular surgery consultation, direct repair, or grafting. Have vascular clamps and suture readily available.
• Inadequate Oncologic Margins: If intraoperative frozen section suggests positive margins, extend the resection if anatomically feasible. If not, postoperative adjuvant therapy (radiation/chemotherapy) will be necessary.
• Prosthesis Loosening/Infection:
  • Loosening: Can occur due to poor cement technique, mechanical failure, or infection. Prevention: Optimal cement mantle, careful reaming. Salvage: Revision surgery, potentially involving cement removal and new prosthesis.
  • Infection: A devastating complication in endoprosthetic surgery. Prevention: Strict aseptic technique, prophylactic antibiotics, meticulous wound closure. Salvage: Aggressive debridement, IV antibiotics, and potentially a two-stage revision (explant, spacer, reimplant) or even amputation in intractable cases.
• Shoulder Instability/Dislocation:
  • Prevention: Meticulous soft tissue reattachment, appropriate prosthesis sizing, and balanced soft tissue tension.
  • Salvage: Closed reduction if possible. If recurrent, consider open reduction, soft tissue repair, or revision of components.
• Intraoperative Humeral Shaft Fracture: Can occur during reaming or stem insertion, especially in osteoporotic bone. Prevention: Careful reaming, avoid excessive force during stem insertion. Salvage: Cerclage wiring, longer stem, or revision to a different fixation method.
• Cement Mantle Issues: Voids or incomplete cement fill can lead to early loosening. Prevention: Retrograde cementing technique, careful mixing, and pressurization.

Postoperative Management and Rehabilitation

Our job isn't done until the patient is back to their best possible function.

Immediate Postoperative Care

• Pain Management: A multimodal approach is crucial, including nerve blocks, oral analgesics, and potentially patient-controlled analgesia (PCA).
• Immobilization: The arm will be placed in a shoulder immobilizer or sling for 4-6 weeks to protect the soft tissue repairs and allow for initial healing. An abduction brace may be used for specific soft tissue reconstructions.
• DVT Prophylaxis: Standard DVT prophylaxis protocols will be initiated, typically low molecular weight heparin or mechanical compression devices.

Rehabilitation Protocol

Rehabilitation is slow and gradual after such a significant procedure.

• Weeks 0-6 (Protection Phase):
  • Strict Sling Immobilization: Except for hygiene and controlled exercises.
  • Passive Range of Motion (PROM): Initiated gently, often by a therapist, to prevent stiffness. Pendulum exercises, assisted flexion, and external rotation within pain-free limits. Avoid active contraction of reattached muscles.
  • Elbow, Wrist, Hand ROM: Encourage active range of motion for distal joints to prevent stiffness and maintain circulation.
• Weeks 6-12 (Controlled Active Motion Phase):
  • Gradual Discontinuation of Sling: As pain allows and soft tissue healing progresses.
  • Active-Assisted Range of Motion (AAROM): Progress to active-assisted exercises, gradually increasing the patient's own muscle activation.
  • Gentle Active Range of Motion (AROM): Begin active movements within pain-free limits.
  • Isometric Strengthening: Begin gentle isometric exercises for the shoulder musculature.
• Weeks 12+ (Strengthening and Functional Phase):
  • Progressive Strengthening: Introduce light resistance exercises, gradually increasing load as tolerated. Focus on rotator cuff, deltoid, and periscapular muscles.
  • Functional Activities: Incorporate activities of daily living and eventually sport-specific or work-specific tasks.
  • Weight-Bearing/Lifting Restrictions: Patients will have permanent restrictions on heavy lifting or repetitive overhead activities to protect the prosthesis and soft tissue repairs.

Complication Management

• Wound Dehiscence/Infection: Early recognition is key. Aggressive wound care, antibiotics, and surgical debridement if necessary.
• Hardware Failure: Prosthesis loosening, stem fracture, or polyethylene wear can occur long-term. Requires revision surgery.
• Heterotopic Ossification: Can occur, leading to stiffness. Prophylactic radiation or NSAIDs may be considered in high-risk patients.
• Neurovascular Complications: Persistent nerve palsy or vascular compromise requires further investigation and management.

This procedure is a true test of surgical skill and judgment, but with meticulous attention to detail, we can provide our patients with excellent oncologic and functional outcomes. Any questions, fellows?