What is the step-by-step procedure for treating a fracture of the head of the humerus using PHILOS (Proximal Humerus Interlocking System) plating?

PHILOS Plating for Proximal Humerus Fractures: Surgical Technique

PHILOS (Proximal Humerus Internal Locking System) plating provides stable fixation for displaced proximal humerus fractures through a deltopectoral approach, with the plate positioned 5-8mm below the superior aspect of the greater tuberosity to prevent subacromial impingement, followed by anatomical reduction of fracture fragments and sequential locking screw insertion. 1, 2, 3

Preoperative Planning

Imaging Assessment

• Obtain CT scan with three-dimensional reconstruction to fully characterize the fracture pattern, as plain radiographs underestimate fracture complexity and CT provides superior delineation of fracture lines 4, 5
• Evaluate humeral neck angulation on CT, which directly affects functional outcomes 4
• Assess for associated rotator cuff tears, present in up to 40% of proximal humeral fractures 4

Patient Selection

• PHILOS plating is indicated for displaced 2-part, 3-part, and 4-part proximal humerus fractures 1, 2, 6
• Three-part fractures demonstrate superior outcomes compared to 4-part fractures (mean Constant score 69.1 vs 55) 2
• Consider patient age and bone quality, as younger patients and males achieve better functional results 6

Surgical Technique: Step-by-Step

Patient Positioning and Approach

• Position patient in beach chair position with affected arm free for manipulation 1
• Use deltopectoral approach, which provides excellent exposure of the proximal humerus and clear visualization of the lesser tuberosity, particularly important for 4-part fractures 2
• Identify and protect the cephalic vein laterally 2
• Develop the interval between deltoid (axillary nerve) and pectoralis major (medial and lateral pectoral nerves) 2

Fracture Reduction

• Identify and tag all fracture fragments with stay sutures, particularly the greater tuberosity, lesser tuberosity, and humeral head 2
• Reduce the humeral head to the shaft first, restoring the neck-shaft angle (typically 130-140 degrees) 2
• Restore anatomical neck-shaft angle and stabilize with oblique screws to prevent varus malposition, which is a critical technical point 2
• Reduce and provisionally fix the greater and lesser tuberosities to the humeral head and shaft using heavy non-absorbable sutures through the rotator cuff insertions 2

Plate Positioning (Critical Step)

• Position the PHILOS plate 5-8mm distal to the superior aspect of the greater tuberosity to prevent subacromial impingement, which occurred in 21.4% of cases when plates were positioned too superiorly 3
• Ensure the plate sits flush against the lateral humeral shaft 1
• The plate should be centered on the lateral aspect of the proximal humerus 1

Screw Insertion Sequence

• Insert proximal locking screws first into the humeral head through the fixed-angle holes in the plate 1
• Use multiple proximal locking screws (typically 6-8 screws) to achieve angular stability in the humeral head 1, 3
• Ensure screws achieve subchondral purchase without penetrating the articular surface 1
• Insert oblique screws through the plate to capture and stabilize the tuberosities 2
• Insert distal shaft screws (minimum 3-4 bicortical screws) to secure the plate to the humeral shaft 1

Tuberosity Fixation

• Secure greater and lesser tuberosities with additional sutures passed through the plate holes and rotator cuff tendons 2
• Verify anatomical reduction of tuberosities, as proper tubercle reduction and stabilization is essential for early mobilization and range of motion recovery 2

Verification and Closure

• Perform intraoperative fluoroscopy in multiple planes (AP, lateral, axillary) to confirm:
  • Anatomical reduction of all fragments 2
  • Appropriate screw length without joint penetration 3
  • Restoration of neck-shaft angle 2
  • No hardware impingement 3
• Close deltopectoral interval without repairing, close subcutaneous tissue and skin 2

Postoperative Management

Immediate Postoperative Period

• Immobilize in sling for comfort 6
• Begin pendulum exercises within first week 6
• Radiological union typically achieved within 8 weeks, with mean union time of 13.75 weeks 6, 7

Rehabilitation Protocol

• Initiate early passive range of motion exercises at 2-3 weeks to prevent stiffness, as the locking plate provides sufficient stability for early mobilization 3, 7
• Progress to active-assisted exercises at 6 weeks 6
• Begin strengthening exercises after radiographic union (typically 8-12 weeks) 6, 7

Critical Technical Pitfalls to Avoid

Plate Positioning Errors

• Avoid superior plate placement, which causes subacromial impingement in 21.4% of cases and requires reoperation 3
• Ensure plate is positioned 5-8mm below the greater tuberosity apex 3

Reduction Errors

• Prevent varus malposition by restoring anatomical neck-shaft angle with oblique screws before final fixation 2
• Inadequate tuberosity reduction leads to poor functional outcomes 2

Screw Placement Errors

• Avoid intra-articular screw penetration by using fluoroscopic guidance and appropriate screw length 3
• Ensure adequate subchondral screw purchase to prevent screw loosening (occurred in 3.6% of cases) 3

Expected Outcomes

Functional Results

• Mean Constant-Murley score of 57.9-68.75 achieved at final follow-up 3, 7
• Excellent to good results in 57-60% of patients 6, 3, 7
• Better outcomes in 2-part and 3-part fractures compared to 4-part fractures 2, 6

Complications

• Overall complication rate approximately 39.3% 3
• Avascular necrosis occurs in 7.2% of cases, primarily in 4-part fractures 2, 3
• Subacromial impingement in 21.4% when plate positioned too superiorly 3
• Transient radial nerve symptoms in 7.2% of cases 3
• Reoperation required in up to 28.6% of cases for complications 3