1. General Overview & Epidemiology
Injuries to the first ray (thumb) are common in athletes and manual laborers.
Fractures: Metacarpal base fractures are the most frequent, with Bennett's fractures being the most common type.
Ligaments: The Ulnar Collateral Ligament (UCL) injury, often called "Skier's Thumb" (acute) or "Gamekeeper's Thumb" (chronic), is the most common ligamentous injury of the hand.
Demographics: Typically seen in young adults involved in sports (skiing, football, basketball) or falls where the thumb is forced into abduction.
2. Relevant Anatomy
The thumb consists of the first metacarpal and two phalanges (proximal and distal).
First CMC Joint: A unique saddle joint allowing wide Range of Motion (ROM) but susceptible to instability. Volar beak ligament and dorsoradial ligament are so important.
MCP Joint Ligaments: The UCL and RCL (Radial Collateral Ligament) provide lateral stability.
Muscular Pull: Three muscles provide deforming forces at the base of the thumb 1)abductor pollicis longus (PIN) 2) extensor pollicis longus (PIN) 3)adductor pollicis (Ulnar n.)
Abductor Pollicis Longus (APL) pulls the metacarpal shaft radially and proximally, while the Adductor Pollicis rotates the fragment, leading to the classic displacement seen in Bennett's fractures.
Biomechanics
very limited axial rotation
average flexion-extension of 53 degrees
average abduction-adduction of 42 degrees
3. Clinical Presentation & Physical Examination
Clinical Complaints:
Pain and swelling at the base of the thumb or the "web space."
Weakness in pinching or grasping objects.
Visible deformity or shortening.
Physical Examination Findings:
Tenderness: Localized over the 1st CMC joint (fractures) or MCP joint (ligaments).
UCL Stress Test: The MCP joint is stressed in valgus at 0° and 30° of flexion. Greater than 30° of laxity or 15° more than the uninjured side indicates a complete tear.
Palpable Mass: A "bunching" over the MCP joint may indicate a Stener Lesion (where the adductor aponeurosis is trapped between the torn ligament ends).
4. Radiological Findings
· Roberts View: A true AP view of the thumb, essential for visualizing the CMC joint.
· True Lateral of Thumb: Hand pronated 30 degrees and beam angled 15 degrees distally
· Stress X-rays: Occasionally used to evaluate UCL stability, though now often replaced by MRI or Ultrasound.
· MRI/Ultrasound: The gold standard for identifying a Stener Lesion, which prevents the UCL from healing without surgery.
5. Classifications
Metacarpal Base Fractures
Bennett Fracture: A two-part intra-articular fracture at the base of the 1st metacarpal.
Rolando Fracture: A comminuted (usually Y or T-shaped) intra-articular fracture of the base.
Extra-articular Base Fracture: Does not involve the joint surface; generally more stable.
UCL Injuries (Skier's Thumb)
Grade I: Sprain (stretch).
Grade II: Partial tear.
Grade III: Complete tear (instability on stress test).
Fracture Type | Articular Involvement? | Description |
Extra-articular Oblique | No | Diagonal line, joint surface intact. |
Extra-articular Transverse | No | Straight horizontal line, joint surface intact. |
Bennett | Yes | Two-part fracture with a palmar ulnar fragment. |
Rolando | Yes | Three-part "Y" or "T" shaped fracture. |
Comminuted | Yes | Multiple fragments involving the joint surface. |
6. Treatment Strategies
Non-Surgical Treatment
Indications: Extra-articular fractures with <30° angulation, Grade I/II UCL sprains, or nondisplaced base fractures.
Management: Thumb Spica Cast or splint for 4–6 weeks.
Surgical Treatment
Bennett/Rolando: Requires Percutaneous K-wire fixation or ORIF with mini-screws to restore joint congruity and counteract the pull of the APL muscle.
UCL (Stener Lesion): Surgical repair is mandatory because the displaced ligament cannot heal across the aponeurosis. Repair involves a bone anchor or suture pull-out.
Criteria Dictating Treatment
extra-articular fracture (<30 degrees angulation)
Bennett's fracture (<1mm articular step-off)
Rolando (comminution dictates operative strategy)
7. Prognosis and Complications
Prognosis: Good with anatomical reduction, though the thumb MCP joint often remains slightly stiffer than before.
Malreductions may lead to early short-term stiffness or instability and long-term radiographic arthritis
Prognostic variables
Favorable
acute intervention
extra-articular fracture
negative
Bennett fracture
Rolando fracture
severely comminute fracture
delayed intervention
Complications:
Post-traumatic Arthritis: High risk in Rolando fractures if the joint surface is not perfectly restored.
Chronic Instability: Leads to weak pinch grip if UCL tears are missed.
Cold Intolerance: Common after hand surgery.
Malunion
8. Key Points (Summary)
Pinch Power: The primary functional goal is restoring strong thumb-to-finger pinch.
Rule out Stener: Always suspect a Stener lesion in complete UCL tears; it won't heal in a cast.
Anatomy of Bennett: The "small fragment" stays in place (held by the volar oblique ligament), while the "large shaft" moves. You must reduce the shaft to the fragment.
Early Motion: CMC joints are prone to stiffness; start ROM as soon as the surgeon deems the fixation stable.
Expert Tip: If you're treating a "Boxer's Fracture" (5th MC) and a "Bennett's" (1st MC) in the same hand, prioritize the Bennett's. The thumb is your "hand's CEO"—it needs to be stable for everything else to work.
Literature & References
AO Principles of Fracture Management: Core guidelines for internal fixation of Bennett and Rolando fractures.
Green’s Operative Hand Surgery: The definitive text for UCL repair techniques and Stener lesion diagnosis.
Journal of Bone and Joint Surgery (JBJS): Studies consistently show better outcomes for operative management of displaced intra-articular thumb base fractures.
Boyer MI, et al.: Classic literature on the management of 1st metacarpal base fractures.