SUMMARY
Fractures involving the base of the fifth metatarsal constitute a substantial proportion of forefoot injuries and present unique challenges related to healing potential. The proximal fifth metatarsal demonstrates regional variations in vascularity, which significantly influence fracture behavior and risk of nonunion. Diagnosis is generally straightforward using standard foot radiographs. Management strategies range from functional treatment with early mobilization to operative fixation, guided by fracture location, displacement, chronicity, and patient activity level.
EPIDEMIOLOGY
Incidence
Fifth metatarsal base fractures are among the most frequently encountered foot fractures
Approximately one-quarter of all metatarsal fractures involve the proximal fifth metatarsal
The majority occur in the tuberosity region (Zone 1)
Patient Profile
Commonly observed in physically active individuals
Increased incidence among athletes, military personnel, and individuals engaged in manual labor
ETIOLOGY
Mechanisms of Injury
Zone 1 fractures typically result from inversion injuries of the hindfoot combined with plantarflexion, producing traction forces at the tuberosity
Zone 2 fractures are associated with adduction forces applied to the forefoot
Zone 3 fractures develop secondary to repetitive loading and chronic stress, often without a clear traumatic event
Predisposing Factors
Concomitant midfoot trauma, including Lisfranc complex injuries
Chronic lateral ankle instability
Structural deformities such as cavus foot and varus hindfoot alignment
ANATOMY
Osseous Anatomy
The fifth metatarsal consists of the tuberosity, base, metadiaphyseal junction, shaft, neck, and head.
The tuberosity serves as the attachment site for the peroneus brevis tendon and the lateral band of the plantar fascia
The metadiaphyseal region lacks direct tendinous insertions and corresponds to a biologically vulnerable zone
The diaphysis demonstrates a gentle dorsal curvature and accommodates insertion of the peroneus tertius tendon
Vascular Considerations
Blood supply to the proximal fifth metatarsal is derived from metaphyseal branches and a diaphyseal nutrient artery. The junction between these territories, corresponding to Zone 2,- represents a relative watershed area, predisposing fractures in this region to delayed healing and nonunion.
Biomechanical Role
Functionally, the fifth metatarsal contributes to lateral column stability and acts as a lever arm during the propulsive phase of gait.
CLASSIFICATION
Anatomic Zonal Classification
Zone 1: Avulsion-type fractures of the tuberosity; typically heal reliably
Zone 2: Fractures at the metaphyseal–diaphyseal junction involving the articulation with the fourth metatarsal; elevated nonunion risk
Zone 3: Proximal diaphyseal stress fractures; frequently chronic and biologically compromised
Radiographic (Torg) Classification
Type I: Sharp fracture line without sclerosis, consistent with acute injury
Type II: Widened fracture line with intramedullary sclerosis, indicating delayed union
Type III: Complete sclerosis and absence of healing response, consistent with nonunion
CLINICAL PRESENTATION
History
Acute fractures often follow a twisting injury
Stress-related fractures may present with insidious lateral foot pain preceding diagnosis
Symptoms
Localized pain along the lateral border of the forefoot
Symptoms are exacerbated by weight bearing and activity
Physical Examination
Point tenderness over the fracture site
Assessment for hindfoot varus and cavus foot deformity
Evaluation of lateral ankle stability
Pain elicited with resisted eversion may suggest associated peroneal tendon involvement
IMAGING
Plain Radiographs
Standard anteroposterior, lateral, and oblique foot views are sufficient in most cases
Signs of chronicity include intramedullary sclerosis and absence of periosteal callus
A plantar fracture gap is associated with inferior healing potential
Advanced Imaging
Bone scintigraphy or MRI may be utilized when stress fracture is suspected but radiographs are normal
CT scanning is valuable for evaluating delayed union, nonunion, and postoperative healing
TREATMENT
Nonoperative Management
Functional immobilization with protected weight bearing is appropriate for nondisplaced Zone 1 fractures
Strict non–weight-bearing immobilization for 6–8 weeks is commonly employed for Zone 2 fractures in non-elite patients and for Zone 3 fractures
Nonoperative treatment of Zone 2 fractures carries a substantial risk of delayed union and refracture
Operative Management
Intramedullary Screw Fixation
Indications
Displaced Zone 1 fractures
Zone 2 fractures in high-demand or competitive athletes
Zone 3 fractures, particularly in the presence of sclerosis or cavovarus alignment
Outcomes
High union rates with earlier return to activity compared to nonoperative care
Plate-and-Screw Fixation
Utilized as a primary option in select cases or as a salvage procedure following failed intramedullary fixation
Provides stable fixation with comparable biomechanical strength
COMPLICATIONS
Delayed union and nonunion, particularly in Zones 2 and 3
Fixation failure due to improper screw size or premature return to activity
Refracture following conservative treatment or hardware removal
Sural nerve irritation related to prominent implants
Persistent pain, most commonly following failed healing of tuberosity fractures
KEY POINTS
Fracture location is the primary determinant of healing potential
Zone 2 fractures represent a biologically high-risk entity
Patient activity level must be integrated into treatment decision-making
Adequate fixation technique and correction of underlying deformity are essential for optimal outcomes