A Bennett fracture is an intra-articular fracture-dislocation of the base of the first metacarpal at the trapeziometacarpal (thumb CMC) joint. It is characterized by a two-part fracture with a small triangular "beak" fragment that remains attached to the trapezium via the ulnar collateral ligament, while the metacarpal shaft displaces radially, dorsally, and proximally due to the pull of the abductor pollicis longus. [1-3] This is an inherently unstable injury that, if inadequately treated, leads to post-traumatic osteoarthritis, weakness, and loss of thumb function. [4-5]
1. History
- Mechanism: Axial load on a partially flexed thumb — classically a punch, fall onto an outstretched hand, or contact sports injury (e.g., "fight bite" position, ball impact) [3][6]
- Ask about hand dominance, occupation (manual labor vs. desk work), and sport participation
- Timing of injury, prior thumb/hand injuries, and any prior treatment attempts
- Severity of pain, ability to grip or pinch, and any prior thumb instability
- Important negatives: open wound (open fracture), numbness/tingling (neurovascular compromise), other associated hand injuries
2. Alarm Features
- Open fracture (skin breach over the thumb base)
- Neurovascular compromise — diminished capillary refill, absent radial pulse at the thumb, or sensory deficit in the radial nerve distribution
- Significant comminution suggesting a Rolando fracture (T- or Y-shaped) or severely comminuted pattern, which carries a worse prognosis [6-7]
- Associated carpometacarpal dislocation of adjacent digits (rare "diagonal" CMC injury pattern) [8]
- Neglected or delayed presentation (>2 weeks) — more difficult reduction and higher complication rates [9]
3. Medications
- Acute pain management: NSAIDs (ibuprofen 400–600 mg q6–8h, ketorolac 15–30 mg IV/IM in the ED), acetaminophen; opioids for severe pain as a bridge
- Local/regional anesthesia: Hematoma block at the fracture site or radial nerve block at the anatomical snuffbox for reduction attempts and pain control
- Contraindications: Avoid NSAIDs if significant bleeding risk or renal impairment; avoid excessive opioid prescribing at discharge
- Postoperative: short course of oral analgesics; antibiotic prophylaxis if open fracture or percutaneous pin placement per institutional protocol
4. Diet
- No specific acute dietary modifications
- Adequate calcium and vitamin D intake for bone healing (general fracture guidance)
- Smoking cessation counseling — smoking impairs fracture healing and increases nonunion risk
5. Review of Systems
- MSK: Pain with grip, pinch, or thumb opposition; swelling at thumb base; difficulty with fine motor tasks
- Neuro: Numbness or tingling in the thumb or radial aspect of the hand (superficial branch of radial nerve)
- Vascular: Skin color changes, temperature differences in the thumb
- General: Other injuries if trauma was high-energy (wrist, forearm, other digits)
6. Collateral History and Family History
- Witnesses to mechanism (especially in sports or altercation)
- Occupational demands — manual laborers and athletes require more aggressive restoration of anatomy [9]
- Family history is generally not contributory, though underlying connective tissue disorders or metabolic bone disease may affect healing
- Social context: hand dominance, smoking status, compliance with immobilization
7. Risk Factors
- Contact sports: boxing, football, rugby, skiing (pole-related)
- Falls onto outstretched hand
- Altercations (punching injuries)
- Young males (mean age at injury ~30–33 years; predominantly male) [10-11]
- Manual laborers at higher risk of functional impairment if inadequately treated [9]
8. Differential Diagnosis
- Rolando fracture: Comminuted or T/Y-shaped intra-articular fracture of the thumb metacarpal base — more fragments, worse prognosis [1][7]
- Extra-articular fracture of the first metacarpal base: Does not involve the joint surface; more forgiving of residual angulation due to CMC joint compensatory motion [6][12]
- Thumb CMC dislocation (without fracture): Pure ligamentous injury at the trapeziometacarpal joint [3]
- Ulnar collateral ligament injury (Gamekeeper's/Skier's thumb): MCP joint instability, not CMC joint [1][13]
- Trapezium fracture: Vertical intra-articular fracture of the trapezium can mimic or coexist with Bennett fracture [14]
- Scaphoid fracture: Snuffbox tenderness; different location but similar mechanism
- "Reverse Bennett" (baby Bennett): Intra-articular fracture-dislocation of the base of the 5th metacarpal [5]
9. Past Medical History
- Prior thumb or hand fractures, CMC arthritis, or ligamentous injuries
- Metabolic bone disease (osteoporosis, vitamin D deficiency)
- Rheumatoid or inflammatory arthritis affecting the hands
- Previous hand surgery
- Chronic conditions affecting healing: diabetes, peripheral vascular disease, immunosuppression
10. Physical Exam
- Inspection: Swelling and ecchymosis at the thenar eminence/thumb base; possible visible deformity with thumb shortening and adduction
- Palpation: Point tenderness over the base of the first metacarpal and the CMC joint; crepitus with axial loading
- Axial grind test: Axial compression with rotation of the thumb metacarpal reproduces pain and may demonstrate instability/crepitus at the CMC joint
- ROM: Painful and limited thumb opposition, abduction, and pinch
- Neurovascular exam: Assess radial and ulnar digital nerve sensation, capillary refill, and radial artery pulse
- Assess for associated injuries: UCL stress testing at the MCP joint, examine other digits and wrist
11. Lab Studies
- Routine labs are generally not indicated for isolated Bennett fractures
- Preoperative labs if surgical fixation planned: CBC, BMP, coagulation studies per institutional protocol
- Consider inflammatory markers if infection is a concern (open fracture)
12. Imaging
- First-line: PA, lateral, and oblique radiographs of the thumb (Robert view — true AP of the thumb with the hand hyperpronated — is the best view for the thumb CMC joint) [13][15]
- Classic finding: triangular beak fragment at the ulnar base of the first metacarpal remaining in anatomic position, with the metacarpal shaft displaced radially and proximally
- Assess articular step-off and fragment displacement
- CT scan: Indicated for surgical planning, comminuted fractures, or when plain films are equivocal; superior for assessing articular congruity and fragment size [16]
- Fluoroscopy: Used intraoperatively but has been shown to underestimate articular step-off and displacement — surgeons should be aware of this limitation [16-17]
- MRI is generally unnecessary unless ligamentous injury is suspected
13. Special Tests
- Gedda classification of Bennett fractures:
- Type 1: Large ulnar fragment with subluxation
- Type 2: Impaction fracture without subluxation
- Type 3: Small avulsion fragment with dislocation [18]
- Eaton-Littler classification: Used for grading post-traumatic CMC arthritis on follow-up radiographs [11][19]
- Point-of-care ultrasound may identify fracture and joint effusion but is not standard
14. ECG
- Not applicable for isolated Bennett fracture
- Obtain if procedural sedation is planned for reduction
15. Assessment
Bennett fracture is an unstable, intra-articular fracture-dislocation of the thumb CMC joint. The deforming forces (abductor pollicis longus pulling the shaft proximally and radially, adductor pollicis pulling it into adduction) make this fracture inherently difficult to maintain in a reduced position with casting alone. [3][6] Inadequate treatment leads to first web space narrowing, adduction contracture, loss of pinch/grip strength, and accelerated CMC osteoarthritis. [5][20] Even with adequate surgical treatment, radiographic arthritis is common at long-term follow-up (up to 100% at 6 years), though most patients remain functionally asymptomatic. [4][11]
16. Treatment Plan
- Non-displaced or minimally displaced (<1 mm step-off): Thumb spica cast immobilization for 4–6 weeks with close radiographic follow-up at 1 week to ensure no displacement — this is rarely sufficient as most Bennett fractures are unstable [6]
- Displaced fractures (>1 mm articular step-off): Surgical fixation is the standard of care [6][16]
- Closed reduction and percutaneous pinning (CRPF): Preferred initial approach; K-wires placed across the fracture and/or across the CMC joint. Systematic review data suggest CRPF is preferable to ORIF, with lower rates of fixation failure (2.9% vs. 8.2%) and comparable functional outcomes [19]
- Open reduction and internal fixation (ORIF): Reserved for irreducible fractures, large fragments amenable to screw fixation, or failed closed reduction [4][20]
- Arthroscopically assisted percutaneous fixation: Shorter immobilization, fewer complications, and better return-to-work rates compared to open surgery [21]
- Reduction goal: articular step-off ≤1–2 mm to minimize risk of post-traumatic arthritis [6][22]
- Post-fixation: thumb spica splint/cast for 4–6 weeks; K-wire removal at 4–6 weeks
- Radiographic fracture union typically achieved at 5 weeks [20]
17. Disposition
- ED disposition: Thumb spica splint, sling for comfort, and urgent hand surgery referral within 5–7 days for all displaced Bennett fractures
- Admission criteria: Open fractures, polytrauma, neurovascular compromise, or need for emergent operative fixation
- Observation: Generally not needed for isolated closed Bennett fractures
- Specialist consultation: Hand or orthopedic surgery consultation for all Bennett fractures, as nearly all require operative fixation [3][6]
18. Follow-Up / Return Precautions
- Follow-up: Hand surgery within 5–7 days of ED visit; repeat radiographs at 1 week to assess for displacement in splinted patients
- Return precautions: Worsening pain, numbness/tingling in the thumb, skin color changes, increasing swelling not relieved by elevation, or splint becoming too tight
- Expected recovery: Radiographic union ~5 weeks; pinch and grip strength recovery to ~90–98% of contralateral side by 4–6 months; long-term DASH scores are excellent (mean 3.0–8.8) with high patient satisfaction (87–94%) [4][10-11][18]
- Return to sport/work: Typically 6–12 weeks depending on occupation and sport; manual laborers may require longer rehabilitation [9]
- Long-term: Radiographic CMC arthritis is common but usually asymptomatic; adduction deformity is significantly correlated with development of symptomatic arthritis [20]
References
1. Thumb Trauma: Bennett Fractures, Rolando Fractures, and Ulnar Collateral Ligament Injuries. — Carlsen BT, Moran SL. The Journal of Hand Surgery. 2009.
2. Bennett Fractures: A Biomechanical Model and Relevant Ligamentous Anatomy. — Kang JR, Behn AW, Messana J, Ladd AL. The Journal of Hand Surgery. 2019.
3. Fractures and Dislocation of the Base of the Thumb Metacarpal. — Liverneaux PA, Ichihara S, Hendriks S, Facca S, Bodin F. The Journal of Hand Surgery, European Volume. 2015.
4. 7-Year Follow-Up After Open Reduction and Internal Screw Fixation in Bennett Fractures. — Leclère FM, Jenzer A, Hüsler R, et al. Archives of Orthopaedic and Trauma Surgery. 2012.
5. The 'Mirrored' Bennett Fracture of the Base of the Fifth Metacarpal. — Goedkoop AY, van Onselen EB, Karim RB, Hage JJ. Archives of Orthopaedic and Trauma Surgery. 2000.
6. Fractures of the Base of the First Metacarpal: Current Treatment Options. — Soyer AD. The Journal of the American Academy of Orthopaedic Surgeons. 2001.
7. Fractures of the Basal Joint of the Thumb. — Howard FM. Clinical Orthopaedics and Related Research. 1987.
8. Bennett Fracture Combined With Hamate Fracture: Carpometacarpal Joint 'Diagonal' Fracture and Dislocation: A Case Report. — Wu WB, Du YF, Wang HX, Liang F. BMC Musculoskeletal Disorders. 2023.
9. Management of Neglected Bennett Fracture in Manual Laborers by Tension Fixation. — Mahmoud M, El Shafie S, Menorca RM, Elfar JC. The Journal of Hand Surgery. 2014.
10. Long-Term Patient-Reported Outcomes Following Bennett's Fractures. — Middleton SD, McNiven N, Griffin EJ, Anakwe RE, Oliver CW. The Bone & Joint Journal. 2015.
11. Functional and Radiological Outcomes of Bennett's Fractures Treated by Iselin's Technique: About 29 Cases With 6-Year (2-14) Follow-Up. — Duché T, Lambrey PJ, Chantelot C, Saab M. Orthopaedics & Traumatology, Surgery & Research : OTSR. 2024.
12. Thumb Fractures and Associated Injuries: An Evidence Based Review to Guide Treatment. — Yang BW, Kamal RN, Shapiro LM. The Journal of Hand Surgery. 2026.
13. Acute Finger Injuries: Part II. Fractures, Dislocations, and Thumb Injuries. — Leggit JC, Meko CJ. American Family Physician. 2006.
14. Treatment of Bennett, Rolando, and Vertical Intraarticular Trapezial Fractures. — Foster RJ, Hastings H. Clinical Orthopaedics and Related Research. 1987.
15. ACR Appropriateness Criteria Acute Hand and Wrist Trauma. — Expert Panel on Musculoskeletal Imaging:, Torabi M, Lenchik L, et al.' Journal of the American College of Radiology : JACR. 2019.
16. Accuracy of Fluoroscopic Examination in the Treatment of Bennett's Fracture. — Yin Y, Wang Y, Wang Z, et al. BMC Musculoskeletal Disorders. 2021.
17. Accuracy of Fluoroscopy in Closed Reduction and Percutaneous Fixation of Simulated Bennett's Fracture. — Capo JT, Kinchelow T, Orillaza NS, Rossy W. The Journal of Hand Surgery. 2009.
18. Outcomes of Percutaneous Pinning for Interfragmentary Fixation in Treating Bennett Fractures With Tiny Avulsion Fragments. — Huang HK, Huang YC, Hung WC, et al. Orthopedics. 2022.
19. Open Reduction and Internal Fixation Versus Closed Reduction and Percutaneous Fixation in the Treatment of Bennett Fractures: A Systematic Review. — Greeven APA, Van Groningen J, Schep NWL, Van Lieshout EMM, Verhofstad MHJ. Injury. 2019.
20. Closed Reduction External Fixator Fixation Versus Open Reduction Internal Fixation in the Patients With Bennett Fracture Dislocation. — Li Z, Guo Y, Tian W, Tian G. Chinese Medical Journal. 2014.
21. Bennett Fracture: Arthroscopically Assisted Percutaneous Screw Fixation Versus Open Surgery: Functional and Radiological Outcomes. — Pomares G, Strugarek-Lecoanet C, Dap F, Dautel G. Orthopaedics & Traumatology, Surgery & Research : OTSR. 2016.
22. Simulated Bennett Fracture Treated With Closed Reduction and Percutaneous Pinning. A Biomechanical Analysis of Residual Incongruity of the Joint. — Cullen JP, Parentis MA, Chinchilli VM, Pellegrini VD. The Journal of Bone and Joint Surgery. American Volume. 1997.