📌 Bennett Lesion and Posterosuperior Internal Impingement: A Common Pitfall

https://youtu.be/ydNTiB5sZVo

https://youtube.com/shorts/BKlONA0UWag

https://youtube.com/shorts/6yHDS7sore4

 

 

📍 Watch Related Shorts

📌 Bennett Lesion: What It Really Represents on Shoulder CT

👉 https://youtube.com/shorts/BKlONA0UWag

📌 Labral Calcification: The MRI Low-Signal Trap

👉 https://youtube.com/shorts/_UNZ5r3dH1M   

📌 Hill-Sachs fracture??— Same CT Look, Different Mechanism

👉 https://youtube.com/shorts/6yHDS7sore4

Let’s look at a case and ask two simple questions.

---

Case Overview

On radiographs and CT:

• Extra-articular ossification / exostosis along the glenoid rim
• Irregular, elongated, crescent-shaped bony density
• Well-corticated margins → chronic process
• Adjacent glenoid rim sclerosis
• Not a loose body

Clinical context:

• Long-term amateur baseball pitcher

→ Diagnosis: Bennett lesion

Bennett lesion is a chronic traction-related exostosis arising from the posteroinferior glenoid rim,
representing traction enthesopathy at the posterior capsulolabral attachment,
related to repetitive stress in abduction and external rotation, especially the late cocking phase.

---

Question 1 — Same Area, Different Diagnosis

Another patient shows:

• Amorphous, high-attenuation intra-articular calcification
• Localized to the posterosuperior labrum
• Bulky, partially fragmented deposit
• MRI: marked edema and labral contour loss

Clinical context:

• 59-year-old woman
• Acute severe shoulder pain for 4 days

→ This is not a Bennett lesion.
→ Basic Calcium Phosphate deposition of the labrum (acute calcific labritis).

---

Question 2 — Hill-Sachs Fracture?

In the Bennett lesion case:

• Subtle posterior humeral head flattening is present

Compare with a true anterior instability case:

• Bony Bankart lesion
• Medially displaced fragment
• Classic Hill-Sachs fracture

Back to the Bennett lesion patient:

• No anterior instability
• No bony Bankart lesion

→ Not a Hill-Sachs fracture

---

So What Is It?

This represents posterosuperior internal impingement.

• In abduction and external rotation,
  the glenohumeral contact point shifts posterosuperiorly
• Leads to repetitive shear stress
• Affects the undersurface of the rotator cuff and posterosuperior labrum

---

Typical MRI Findings

• Posterior/posterosuperior humeral head cysts
• Articular-sided partial-thickness tears
• Undersurface fraying, not bursal-sided
• Posterosuperior labral tear
• Often associated with Bennett lesion or posterior capsular tightness

---

Take-Home Message

If a CT looks like a Hill-Sachs fracture but the anterior instability pattern is absent,
think chronic remodeling from posterosuperior internal impingement, not a fracture.

---

#DrSlothic #SlothicRadiology #BennettLesion #HillSachs #InternalImpingement #ShoulderCT #ShoulderMRI #SportsRadiology #MSKRadiology #RadiologyPitfalls

---

Visualizing MSK Radiology: A Practical Guide to Radiology Mastery
© 2022 MSK MRI Jee Eun Lee All Rights Reserved.
No unauthorized reproduction, redistribution, or use for AI training.