Bennett's fracture

Definition/Description

A Bennett's fracture, also known as a Bennett's fracture-dislocation is an intra-articular fracture of the base of the first metacarpal which leads to dislocation of the first carpometacarpal joint. The fracture involves the joint between the first metacarpal and the proximal carpal bone, the trapezium. The fracture is unstable and has an inadequate reduction/fixation which leads to long term consequences such as osteoarthritis, weakness, or loss of function of the first carpometacarpal joint.¹ This joint is called the carpometacarpal (CMC) joint, and is normally stabilized by a ligament called the deep ulnar ligament. Due to the position of the fracture fragment there is some detachment of this ligament from the bone, causing a dislocation of the joint.²

Clinically Relevant Anatomy

The first carpometacarpal joint is unique, it has only an articulation between the trapezium and the base of the first metacarpal. The articulation is saddle-shaped which allows greater motion. ¹ The ligaments in this joint are the anterior (volar) and posterior oblique ligaments, the anterior and posterior intermetacarpal ligaments, and the dorsal radial ligament. The anterior oblique ligament is the most important for stability in the carpo-metacarpal joint.³

Differential Diagnosis

Very common injuries on the first metacarpal are gamekeepers thumbs, Rolando fractures and Bennett's fracture.

The first differentiation clue can be found during the inspection/palpation of the location of the injury. Bennett's fractures are associated with pain and weakness of the pinch grasp and swelling and ecchymosis over the carpal metacarpal joint of the thumb. The patient will be unable to perform functional tasks such as tying a shoe or using a key. Possible complications can be infection, malunion or nonunion, arthritis and stiffness with contracture.⁴

Examination

If Bennett's Fracture is suspected, the subjective history of the patient should include trauma to the hand or thumb followed by immediate pain and swelling or ischemia.⁵ 

On physical examination a Bennett's fracture of the first carpo metacarpal joint may present with:

• visible deformity if the fracture is displaced
• pain and swelling +/- ecchymosis over carpo metacarpal joint of the thumb
• tenderness to touch
• warmth over area in acute phase
• decreased pinch grasp and decreased grip strength¹³  A CT scan should be ordered to evaluate the extent of the damage. On these CT scans a Bennett's fracture will present can as an intra-articular fracture and dislocation of base of the first metacarpal. Even though there is a dislocation there should still be a small fragment of the first metacarpal that continues to articulate with trapezium.
  

Medical Management

Bennett fractures have several options of management. Each treatment has it’s advantages and disadvantages.¹

Type I
The first type of management is closed reduction and plaster casting. This is a non-invasive procedure and remains the first option if possible.The major issue in closed reduction is to obtain and maintain adequate fracture reduction to allow healing in an anatomical position. Consequences of an inaccurate reposition are pain and grip weakness in short term and osteoarthritis of the first metacarpal joint in long term. Hence it is recommended to let these fractures be treated by specialist hand surgeons.
All the variant methods of closed reduction involve traction on the thumb to pull metacarpal distally with concurrent pressure pushing the metacarpal base medially to return it to anatomical position. Closed reduction is performed under adequate analgesia/sedation follow by plaster cast immobilization for ±6 weeks.¹ A cast with the thumb in a moderate adduction and opposition is most effective by reducing the fracture fragments.⁶

Type II
A second method of reduction involves reduction of the fracture followed by percutaneous insertion of a Kirschner wire through the base of the metacarpal across the joint and into the trapezium to hold the reduction in place. The wire remains in place for about 4 weeks after which a rehabilitation program is started.¹

Type III
This last treatment is necessary when there is a significant displacement (>3mm).⁷ Type III involves an open reduction, which involves opening up the fracture and reduction under direct vision followed by insertion of either Kirschner wires (Fig1) or lag screws in order to hold the reduction in place. Like the second type of management, after the reduction there is an immobilization period of 4 weeks.
This type is preferable where there is a large proximal fragment and that ORIF should be used where the fracture is irreducible or a Kirschner wire is unable to be passed across the fracture.⁸

Physical Therapy Management

Generally, hand fractures are treated by immobilization with a cast or splint. The use of static and dynamic splinting in the treatment of hand injuries is essential in many cases to maximize functional outcome. Protocols for rehabilitation must be based upon stability of the fracture and fracture management (operative, nonoperative). 
Treatment consists of active, passive, and resistive exercises.⁹ For exercises do we need some revalidation materials. The muscles need to be stronger because the fracture has weaked them. In the rehab the PowerWeb is a very handy material. It gives resistance to all the movements in the hand- or wristjoint. In the web the patient can do a flexion, extension, opposition, abduction or adduction against resistance. The patient must pay attention that he doesn’t overload the joints. Another helpful tool is the exercise putty. It has the same intention as the PowerWeb. With these exercises the muscles of the thumb will be much stronger than before and this is necessary for the revalidation of the Bennett’s Fracture.

The goal of rehabilitation is to decrease pain and restore function. Modalities such as cold packs may be beneficial for controlling pain. Special attention should be paid to preserve full function of the uninvolved fingers, especially if the dominant hand is involved. This will be done by strengthening exercises e.g. finger flexion exercises. Exercise intensity and difficulty should be progressed until full function is achieved.¹⁰
Soft tissue mobilization and joint mobilization is also a possibility to apply.¹¹ The earlier the patient starts with rehabilitation, the earlier there are results in recovery of mobility and strength. This can result to an earlier return to work.¹²

Resources

Articles:
- C. BROWNLIE; “Bennett Fracture Dislocation: Review and Management”; Australian Family Physician vol 40, No. 6, June 2011 (Level: 1B)
- KJAER-PETERSEN K. et al.; “Bennett’s fracture”, Journal of Hand Surgery, 1990 Feb; 15(1):58-61 (Level:1B)
- HOWARD FM.; “Fractures of the basal joint of the thumb”, Clinical Orthopaedics and Related Research, 1987 Jul;(220):46-51(Level:2C)
- CULLEN J.P. Et al; Simulated Bennett Fracture Treated With Closed Reduction and Percutaneous Pinning; The journal of Bone and Joint Surgery, 1997 (Level: 4)
- Zhang X. Et al.; Treatment of a Bennett Fracture Using Tension Band Wiring, Journal of Hand Surgery, 2012, Volume 37, issue 3, p427-433. (Level: 2B)
- Sandra Richards Saunders, “Physical Therapy Management of Hand Fractures”, Journal of the American physical therapy association, 1989 (level : 5)
- Joe Godges, “Physical Therapy Protocols for Conditions of Wrist and Hand Region”, KP So Cal Ortho PT Residency , 2004 (Level : 5)
- Feehan, L. M., and K. Bassett. "Is There Evidence for Early Mobilization Following an Extraarticular Hand Fracture." Journal of Hand Therapy 24 Nov. 2008 (Level : 1A)

Sites:
- Physioroom.com Bennett’s Fracture. http://www.physioroom.com/injuries/
hand_and_wrist/bennetts_fracture_full.php (Accessed 5/05/2013)
- Mark E Baratz, MD; Chief editor: Harris Gellman, Bennett Fracture, Medscape
reference http://emedicine.medscape.com/article/1238036-overview#a05
(Accessed 5/05/2013)
- Dr MAULIK S. Et al.; “Bennett fracture dislocation”, Radiopaedia, 2012.
http://radiopaedia.org/articles/bennett-fracture-dislocation (Accessed 5/05/2013)
- MDGuidelines.com, Return to work is the best measure of healthcare outcomes.
www.mdguidelines.com/fracture-fingers-and-thumb (Accessed 5/05/2013)

Book:
- Dell, P. C., and R. B. Dell. "Management of Carpal Fractures and
Dislocations." Hunter - Mackin - Callahan Rehabilitation of the Hand and
Upper Extremity. Eds. E. J. Mackin, et al. 5th ed. Philadelphia: Mosby, Inc.,
2002. 1171-1184.

References
- C. BROWNLIE; “Bennett Fracture Dislocation: Review and Management”; Australian Family Physician vol 40, No. 6, June 2011 [^{1.0, 1.1, 1.2,1.3, 1.4}]
- Physioroom.com Bennett’s Fracture. http://www.physioroom.com/injuries/hand_and_wrist/bennetts_fracture_full.php (Accessed 5/05/2013) [^2.0]
- Mark E Baratz, MD; Chief editor: Harris Gellman, Bennett Fracture, Medscap reference http://emedicine.medscape.com/article/1238036-overview#a05 (Accessed 5/05/2013) [^3.0]
- KJAER-PETERSEN K. et al.; “Bennett’s fracture”, Journal of Hand Surgery, 1990 Feb; 15(1):58-61 [^4.0]
- HOWARD FM.; “Fractures of the basal joint of the thumb”, Clinical Orthopaedics and Related Research, 1987 Jul;(220):46-51 [^5.0]
- CULLEN J.P. Et al; Simulated Bennett Fracture Treated With Closed Reduction and Percutaneous Pinning; The journal of Bone and Joint Surgery, 1997 [^6.0]
- Dr MAULIK S. Et al.; “Bennett fracture dislocation”, Radiopaedia, 2012. http://radiopaedia.org/articles/bennett-fracture-dislocation (Accessed 5/05/2013) [7.0]
- Zhang X. Et al.; Treatment of a Bennett Fracture Using Tension Band Wiring, Journal of Hand Surgery, 2012, Volume 37, issue 3, p427-433. [^8.0]
- Sandra Richards Saunders, “Physical Therapy Management of Hand Fractures”, Journal of the American physical therapy association, 1989 [^9.0]
- MDGuidelines.com, Return to work is the best measure of healthcare outcomes. www.mdguidelines.com/fracture-fingers-and-thumb (Accessed 5/05/2013) [^10.0]
- Joe Godges, “Physical Therapy Protocols for Conditions of Wrist and Hand Region”, KP So Cal Ortho PT Residency , 2004 [^11.0]
- Feehan, L. M., and K. Bassett. "Is There Evidence for Early Mobilization Following an Extraarticular Hand Fracture." Journal of Hand Therapy 24 Nov. 2008 [^12.0]
- Dell, P. C., and R. B. Dell. "Management of Carpal Fractures and Dislocations." Hunter - Mackin - Callahan Rehabilitation of the Hand and
Upper Extremity. Eds. E. J. Mackin, et al. 5th ed. Philadelphia: Mosby, Inc., 2002. 1171-1184. [^13.0]

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