Perthes Lesion: Understanding Shoulder Injuries, Symptoms, Diagnosis, and Treatment

What is a Perthes lesion of the shoulder?

A Perthes lesion of the shoulder is a specific type of anterior-inferior labral injury characterized by an avulsion of the labrum from the glenoid rim, where the periosteum remains intact but is stripped off the glenoid neck, allowing for medial displacement of the labrum.

Understanding the Shoulder Joint and Labrum

To fully grasp a Perthes lesion, it's essential to understand the anatomy of the shoulder. The shoulder, or glenohumeral joint, is a highly mobile ball-and-socket joint formed by the head of the humerus (upper arm bone) and the glenoid fossa (a shallow socket) of the scapula (shoulder blade). This inherent mobility comes at the cost of stability.

The labrum is a crucial ring of fibrocartilage that surrounds the glenoid fossa. Its primary roles include:

• Deepening the socket: It effectively increases the surface area and depth of the glenoid, improving congruence with the humeral head.
• Attachment site: It serves as an attachment point for the glenohumeral ligaments and the long head of the biceps tendon, which are vital for shoulder stability.

Perthes lesions specifically affect the anterior-inferior aspect of this labral ring, an area particularly vulnerable during anterior shoulder dislocations.

What Exactly is a Perthes Lesion?

A Perthes lesion is an injury where the anterior-inferior labrum is torn away, or avulsed, from the glenoid rim. What makes a Perthes lesion distinct from other labral tears, such as a Bankart lesion (another common injury associated with anterior dislocations), is the behavior of the periosteum.

In a Perthes lesion:

• The labrum detaches from the bone.
• The periosteum (the fibrous membrane covering the bone) remains attached to the labrum but is stripped away from the glenoid neck.
• This stripping allows the labrum, still attached to the periosteum, to displace medially (towards the center of the joint).
• Crucially, the intact periosteum can then heal back onto the glenoid, but in a displaced position, effectively trapping the avulsed labrum in a non-anatomic location. This "healed" but displaced labrum can contribute to persistent instability.

This unique characteristic of periosteal integrity distinguishes it from a classic Bankart lesion, where the labrum and periosteum are completely detached from the glenoid, often with a visible defect. The subtle nature of the Perthes lesion can sometimes make it challenging to diagnose on standard imaging.

Causes and Mechanism of Injury

Perthes lesions are overwhelmingly caused by anterior shoulder dislocations. This occurs when the humeral head is forced out of the glenoid socket in a forward direction.

The typical mechanism involves:

• Abduction: Arm lifted away from the body.
• External Rotation: Arm rotated outwards.
• Extension: Arm moved backward.

This position, often seen in contact sports, overhead throwing activities, or falls onto an outstretched arm, puts immense stress on the anterior-inferior capsule and labrum. The forceful leverage of the humeral head against the glenoid rim can tear the labrum from its attachment, leading to a Perthes lesion.

Signs and Symptoms

Individuals with a Perthes lesion typically present with symptoms related to shoulder instability, especially following an initial dislocation. These may include:

• Acute Pain: Severe pain immediately after a dislocation event.
• Recurrent Instability: The most common and defining symptom, characterized by repeated episodes of the shoulder "giving way," subluxing (partially dislocating), or fully dislocating.
• Apprehension: A feeling of fear or unease when the arm is placed in positions of abduction and external rotation, as if the shoulder is about to dislocate.
• Reduced Range of Motion: Especially overhead movements or external rotation.
• Weakness: Particularly in the rotator cuff muscles, as they struggle to stabilize an unstable joint.
• Clicking, Popping, or Grinding Sensations: These sounds or feelings can occur during shoulder movement due to the displaced labrum.

Diagnosis

Diagnosing a Perthes lesion requires a thorough clinical assessment combined with advanced imaging.

• Clinical Examination: A physical therapist or orthopedic surgeon will perform specific tests to assess shoulder stability, range of motion, and pain. The apprehension and relocation tests are particularly useful for identifying anterior instability.
• Imaging Studies:
  • X-rays: Primarily used to rule out associated bone injuries, such as a Hill-Sachs lesion (a compression fracture on the humeral head) or a bony Bankart lesion (a fracture of the glenoid rim). Soft tissue injuries like Perthes lesions are not visible on X-rays.
  • Magnetic Resonance Imaging (MRI): An MRI is the gold standard for visualizing soft tissue structures. An MRI arthrogram, where a contrast dye is injected into the joint before the scan, significantly enhances the visibility of the labrum and can better delineate the extent and type of labral tear, including the subtle features of a Perthes lesion.
  • Computed Tomography (CT) Scan: Less common for labral injuries alone, but can be used to assess bony defects or if MRI is contraindicated.
• Arthroscopy: In some cases, particularly if imaging is inconclusive, or during a planned surgical repair, an arthroscopic examination (a minimally invasive procedure using a small camera) can provide a definitive diagnosis and allow direct visualization of the lesion.

Treatment Approaches

Treatment for a Perthes lesion depends on several factors, including the patient's age, activity level, the degree of instability, and the chronicity of the injury. Due to the inherent instability caused by the displaced labrum, conservative management is often less successful than for other types of labral tears.

Conservative Management

• Initial Immobilization: A brief period of sling immobilization may be used immediately after a dislocation to allow initial healing and reduce pain.
• Pain Management: Rest, ice, and non-steroidal anti-inflammatory drugs (NSAIDs) can help manage pain and inflammation.
• Physical Therapy: A structured rehabilitation program focusing on strengthening the rotator cuff muscles, scapular stabilizers, and improving proprioception (joint awareness) can be attempted. However, for true Perthes lesions with significant labral displacement, conservative therapy often fails to restore adequate stability, particularly in active individuals.

Surgical Intervention

• Arthroscopic Repair: This is the most common and effective treatment for a Perthes lesion. During the procedure, small incisions are made, and specialized instruments are used to:
  • Debride any damaged tissue.
  • Mobilize the medially displaced labrum.
  • Reattach the labrum and its associated periosteum back to the glenoid rim using small surgical anchors (sutures attached to tiny implants).
  • The goal is to restore the normal anatomy and provide mechanical stability to the shoulder joint.

Rehabilitation and Return to Activity

Post-surgical rehabilitation is critical for a successful outcome after Perthes lesion repair. It is a structured, phased process, typically guided by a physical therapist.

• Phase 1: Protection and Early Motion (Weeks 0-6)

  • Immobilization: The shoulder is typically kept in a sling for several weeks to protect the repair.
  • Pain and Swelling Management: Ice and medication.
  • Gentle Passive Range of Motion: Pendulum exercises and very limited passive range of motion, avoiding positions of stress (abduction and external rotation).
  • Scapular and Elbow/Wrist/Hand Exercises: To maintain strength and prevent stiffness in adjacent joints.

• Phase 2: Gradual Range of Motion and Strengthening (Weeks 6-12)

  • Progressive Passive and Active-Assisted Range of Motion: Gradually increasing shoulder movement as tolerated, still avoiding extreme positions.
  • Initiate Isometric Strengthening: Gentle contractions of rotator cuff and deltoid muscles without joint movement.
  • Light Resistance Exercises: Introduction of elastic bands or light weights for rotator cuff and scapular stabilizer muscles.

• Phase 3: Advanced Strengthening and Proprioception (Weeks 12-20)

  • Full Range of Motion: Aiming to achieve full, pain-free range of motion.
  • Progressive Resistance Training: Increasing intensity and complexity of exercises for all shoulder girdle muscles.
  • Proprioceptive Drills: Exercises to improve joint awareness and control (e.g., balance activities on unstable surfaces).
  • Introduction to Sport-Specific Drills: Begin movements relevant to the patient's sport or activity.

• Phase 4: Return to Sport/Activity (Months 4-6+ for overhead athletes)

  • Gradual Return to High-Demand Activities: A progressive return to full activity, typically starting with light, controlled movements and advancing to full participation based on strength, stability, and absence of symptoms.
  • Continued Strength and Conditioning: Maintaining a long-term exercise program to prevent re-injury.

The total rehabilitation time can vary but often ranges from 4-6 months for daily activities, and up to 9-12 months for full return to high-impact or overhead throwing sports.

Prognosis and Long-Term Considerations

The prognosis for a Perthes lesion treated with arthroscopic repair is generally good, with high rates of successful return to activity and resolution of instability. However, several factors influence the outcome:

• Adherence to Rehab: Consistent and proper execution of the rehabilitation program is paramount.
• Quality of Repair: A well-executed surgical repair is essential for restoring stability.
• Patient Factors: Age, activity level, and the presence of other associated injuries (e.g., Hill-Sachs lesion) can influence recovery.

Untreated or inadequately treated Perthes lesions carry a significant risk of recurrent shoulder dislocations due to the persistent instability. Long-term, chronic instability can lead to degenerative changes within the joint, potentially increasing the risk of early onset osteoarthritis of the shoulder. Therefore, appropriate diagnosis and management are crucial to prevent further injury and preserve long-term shoulder health.