You are in: eMedicine Specialties > Orthopedic Surgery > HAND AND UPPER EXTREMITY Bennett FractureArticle Last Updated: Jan 11, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Steven V Priano, MD, Assistant Professor of Orthopedic Surgery, Department of Orthopedics and Sports Medicine, Ohio State University College of Medicine and Public Health Steven V Priano is a member of the following medical societies: American Academy of Orthopaedic Surgeons Coauthor(s): Mark E Baratz, MD, Professor, Department of Orthopaedics, Drexel University College of Medicine; Residency Director, Department of Orthopaedics, Allegheny General Hospital; Consulting Staff, Allegheny Orthopaedic Associates Editors: Michael S Clarke, MD, Clinical Associate Professor, Department of Orthopedic Surgery, University of Missouri-Columbia School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas R Hunt III, MD, John D Sherrill Professor of Surgery, Director, Division of Orthopedic Surgery, Surgeon in Chief, UAB Upper Extremity Fellowship, UAB Highlands Hospital, University of Alabama at Birmingham School of Medicine; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Harris Gellman, MD, Consulting Surgeon, Broward Hand Center, Voluntary Clinical Professor of Orthopedic Surgery and Plastic Surgery, Departments of Orthopedic Surgery and Surgery, University of Miami School of Medicine Author and Editor Disclosure Synonyms and related keywords: thumb CMC fractures, thumb carpal-metacarpal fracture, thumb carpometacarpal fracture, Bennett's fracture, Bennett's fractures, thumb injury, thumb fracture INTRODUCTIONSection 2 of 11
  In 1882, Edward Hallaran Bennett, MD, described the fracture of the base of the first metacarpal that bears his name. Bennett described the anatomic details of the fracture and suggested that early diagnosis and treatment are imperative to prevent loss of function of this highly mobile joint.1, 2, 3, 4, 5 ProblemUnless properly recognized and treated, this intra-articular fracture subluxation may result in an unstable arthritic joint with secondary loss of motion and pain. Because the thumb carpometacarpal (CMC) joint is critical for pinch and opposition, this injury may severely affect function. FrequencyThe thumb is a highly mobile border digit. For that reason, injury to this ray is common. EtiologyAxial loading of a partially flexed thumb metacarpal causes this injury. PathophysiologyThumb CMC joint stability is maintained by 5 ligaments and the articular contours. The most critical of these stabilizers is the volar oblique ligament. This ligament courses from the volar lip of the trapezium to the volar ulnar corner of the thumb metacarpal base. The injury occurs when an axial force is transmitted through a partially flexed thumb metacarpal. The portion of the metacarpal onto which the volar oblique ligament inserts remains in anatomic position, and the remainder of the articular base subluxates in a dorsal, radial, and proximal direction because of the pull of the abductor pollicis longus (APL). ClinicalPatients present with swelling and pain at the thumb base. On examination, motion is limited and CMC instability is frequently noted with gentle stress of the thumb metacarpal. INDICATIONSSection 3 of 11
Closed reduction and thumb spica cast immobilization can be effective in the treatment of some Bennett fractures. Generally, cases characterized by small avulsion fractures and minimal articular incongruity and instability can be managed in this fashion. These patients must be carefully monitored with serial radiography. The strong pull of the abductor pollicis longus (APL) frequently leads to displacement. As a result, open or closed reduction combined with internal fixation is frequently required. More than 1 mm of articular incongruity after closed reduction is an indication for operative intervention. This degree of articular incongruity is associated with an increased rate of articular degeneration in the thumb CMC joint over time.2, 3, 5, 6 RELEVANT ANATOMYSection 4 of 11
The thumb affords prehensile abilities that were essential in human evolution. The bony anatomy of the thumb consists of 2 phalanges and a metacarpal, which articulates with the trapezium bone in the distal carpal row. The metacarpal is actually a primordial phalanx. The CMC joint consists of an articulation between the trapezium and the metacarpal base composed of 2 reciprocally interlocking saddles with perpendicular longitudinal axes. Ligamentous stability at the trapeziometacarpal joint is maintained by the anterior (volar) and posterior oblique ligaments, the anterior and posterior intermetacarpal ligaments, and the dorsal radial ligament. The anterior (volar) oblique ligament originates on the trapezium and inserts into the volar ulnar beak of the thumb metacarpal. This is the most important ligament in maintaining CMC stability. The dorsal ligament is not as strong as the volar ligament but is reinforced by the APL. CONTRAINDICATIONSSection 5 of 11
Contraindications to closed treatment include an open fracture, an unstable fracture, unsuccessful closed reduction with residual articular incongruity greater than 1 mm, or instability and joint subluxation. WORKUPSection 6 of 11
Imaging Studies
Related eMedicine topics: TREATMENTSection 7 of 11
Medical therapyClosed reduction and thumb spica cast immobilization are effective in the treatment of Bennett fractures if the reduction can be maintained. The closed reduction technique consists of thumb traction combined with metacarpal extension, pronation, and abduction. Direct downward pressure is applied to the dorsal radial metacarpal base. The strong pull of the APL frequently leads to displacement, necessitating open reduction and internal fixation or closed reduction with percutaneous pinning. More than 1 mm of articular incongruity or persistent CMC joint subluxation after closed reduction indicates the need for surgical treatment.2, 3, 5, 7, 8 Surgical therapyGenerally, closed reduction utilizing the technique described above followed by percutaneous K-wire fixation is successful. Two 0.045-inch K-wires are drilled through the dorsal radial thumb metacarpal base into the reduced volar ulnar fragment. If the fragment is very small, reduction may be maintained by placing the K-wire from the thumb metacarpal into the trapezium or the index metacarpal. Maintaining thumb abduction is essential to preserving the first web space. If adequate reduction cannot be achieved utilizing this percutaneous technique, open reduction and internal fixation is performed. An L-shaped incision is made over the subcutaneous border of the thumb metacarpal. The incision is carried down radially to allow for subperiosteal reflection of the thenar musculature and direct visualization of the joint. Towel-clip forceps are extremely valuable in obtaining and temporarily maintaining reduction. Fixation is achieved using either K-wires or mini screws (2.0 mm).2, 3, 5, 7, 8 Follow-upA well-molded thumb spica cast is utilized for 2-6 weeks depending on the stability obtained at surgery. Once the cast is discontinued, a thermoplastic splint is fabricated and a protected mobilization program is initiated until fracture healing is complete. COMPLICATIONSSection 8 of 11
Displaced intra-articular fractures predispose the patient to arthritis and loss of motion within the affected joints. Unfortunately, even after restoration of articular congruity, some patients develop posttraumatic arthritis secondary to the osteocartilaginous injury sustained as a result of the initial trauma . Loss of motion also occurs following prolonged immobilization. Rigid fixation enables patients to initiate movement sooner postoperatively, minimizing this problem. Other potential postoperative complications include loss of reduction with recurrent joint subluxation and instability, infection, and sensory nerve injury. OUTCOME AND PROGNOSISSection 9 of 11
The prognosis for Bennett fractures is most closely related to the amount of energy associated with the original injury. High-energy injuries produce comminution, articular surface damage, and extensive soft-tissue injury, leading to a poor outcome. With anatomic restoration of the joint surface and reestablishment of stability, the outcome is routinely good, especially in low-energy injuries with simple fracture patterns and limited soft-tissue involvement. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Article Last Updated: Jan 11, 2008 | ||||||||||||||||||||||||||
