Proximal Fifth Metatarsal Fractures

In 1902, Sir Robert Jones [21] was the first to describe a fracture of the proximal fifth metatarsal. Since this first report, extensive clinical research and basic science reports have characterized fractures in this region and demonstrated that some fractures of the proximal fifth metatarsal are troublesome to treat [4,22-31]. Thus, all fractures at the proximal end of the fifth metatarsal cannot be considered together when discussing mechanism of injury, treatment options, and outcomes.

Anatomy

Anatomy of the proximal fifth metatarsal has been previously described and reviewed [3,32-34]. The fifth metatarsal bone consists of the base, tuberosity (ie, the styloid process), diaphysis, neck, and head. The metaphyseal base articulates proximally with the cuboid bone and medially with the fourth metatarsal bone. Dorsal and plantar cuboideometatarsal ligaments, an inter-

metatarsal ligament, and the joint capsule provide stability at the proximal tarsometatarsal joint. On the dorsolateral aspect of the tuberosity, the tendon of the peroneus brevis inserts. Distal to the tuberosity, the peroneus tertius inserts on the dorsal surface of the metatarsal diaphysis. A lateral band of the plantar aponeurosis inserts on the tip of the tuberosity, linking the tuberosity to the lateral margin of the medial calcaneal tubercle. The flexor digiti minimi brevis muscle of the small toe originates from the plantar surface of the base of the fifth metatarsal bone. Dorsal and plantar interosseous muscles also arise from the diaphysis of this bone.

Blood supply to the proximal fifth metatarsal is important with regard to fracture healing. In 1927, Carp [23] reported on 21 fractures of the proximal fifth metatarsal and cited vascular insufficiency as a potential etiology contributing to the high incidence of observed delayed unions in his series. Subsequently, Smith and colleagues [24] described the intraosseous blood supply of the fifth metatarsal from a cadaver model. Blood supply originates from three potential sources: the nutrient artery, the metaphyseal perforators, and the periosteal arteries (Fig. 1). The nutrient artery enters the bone medially from the middle one third of the diaphysis and terminates in linear branches proxi-mally and distally. Metaphyseal arteries arise from the surrounding soft tissue and penetrate the metaphysis, branching in a random distribution. A watershed area between these two distributions corresponds to the region of poor fracture healing noted clinically.

The proximal fifth metatarsal has been classified into three separate fracture zones (Fig. 2) [4,22,34]. Zone 1 is most proximal and includes the metatarso-cuboid articulation, the insertion of the peroneus brevis tendon, and the lateral plantar aponeurosis. Fractures in this zone are typically avulsion-type fractures and can extend intra-articularly. These fractures usually result from an indirect mechanism of injury, such as an acute inversion of the foot [3,22,33,34].

Zone 2 corresponds to the metaphyseal-diaphyseal junction (fractures here are "true" Jones fractures). Stewart [35] defined a true Jones fracture as a transverse fracture at the junction of the diaphysis and the metaphysis without extension distal to the fourth-fifth intermetatarsal articulation. Fractures gener-

Watershed Area Metatarsal
Fig. 1. Intraosseous blood supply to the proximal fifth metatarsal demonstrating a potential watershed area between the randomly distributed metaphyseal perforators and the linear terminal branches of the nutrient artery.
5th Metatarsal Tuberosity Fracture
Fig. 2. Anatomatic fracture zones of the proximal fifth metatarsal. (Copyright 1993 by the American Orthopaedic Foot and Ankle Society (AOFAS), originally published in Foot and Ankle International, July/August 1993, Vol. 14(6) page 360 and reproduced here with permission.)

ally begin laterally in the more distal portion of the tuberosity and extend transversely or obliquely into the area of the medial cortex where the fifth metatarsal articulates with the fourth metatarsal [3,33,34]. Mechanism of injury is believed to occur when a large adduction force is applied to the forefoot with the ankle plantar flexed (eg, pivoting or cutting maneuver with most of the body weight on the metatarsal heads) [33,34]. When high load on the plantar aspect of the fifth metatarsal head creates a large bending motion, the bone fractures at the junction of the proximal diaphysis and the metaphysis.

Zone 3 includes the proximal 1.5 cm of the diaphysis. Injuries in this region usually represent a stress or fatigue mechanism: repeated normal loads applied beneath the fifth metatarsal head over a relatively short period of time. The prevalence of proximal diaphyseal stress fractures from the literature is difficult to assess because many clinical series do not distinguish between zone 2 and zone 3 fractures. Kavanaugh and colleagues [36] reported that 41% of their patients who had proximal fifth metatarsal fractures had prodromal symptoms. Zelko and coworkers [31] identified a fracture line with periosteal reaction at initial presentation in 67% of patients.

Torg and colleagues [27] suggested a classification system to distinguish the healing potential of proximal diaphyseal fifth metatarsal fractures: (1) acute, (2) delayed union, and (3) nonunion (Table 1). Acute (type I) fractures are described as clinically acute (although prodromal pain may have been present) and defined radiographically by sharp fracture margins, minimal or no periosteal reaction, and minimal cortical hypertrophy. Delayed-union (type II) fractures are characterized by history of previous injury or fracture and characterized radiographically by some periosteal reaction, widened fracture margins, and some intramedullary sclerosis. Nonunion (type III) fractures are characterized by a clinical history of repetitive trauma or recurrent symptoms and characterized radiographically by sclerosis obliterating the medullary canal and blunted fracture edges.

Table 1

Classification of proximal diaphyseal fifth metatarsal fractures

Table 1

Classification of proximal diaphyseal fifth metatarsal fractures

Classification

Clinical Radiographic

Acute (type I) Delayed union (type II) Nonunion (type III)

Acute injury Sharp fracture margins without widening New onset pain Minimal cortical hypertrophy

Minimal periosteal reaction History of previous injury Slight fracture widening Persistent pain New periosteal bone formation

Some intramedullary canal sclerosis Repetitive injury Definite fracture widening with blunted edges Recurrent symptoms Abundant periosteal bone formation

Complete obliteration of intramedullary canal

Data from Torg JS, Balduini FC, Zelko RR, et al. Fractures of the base of the fifth metatarsal distal to the tuberosity. J Bone Joint Surg Am 1984;66(2):209-14.

Data from Torg JS, Balduini FC, Zelko RR, et al. Fractures of the base of the fifth metatarsal distal to the tuberosity. J Bone Joint Surg Am 1984;66(2):209-14.

Treatment

Treatment of avulsion fractures (zone 1) is generally straightforward. The recommended treatment of these injuries is symptomatic care [1-3,22,36]. There has been little difficulty reported in obtaining successful healing of these injuries regardless of fragment size or degree of displacement, or for nondisplaced intraarticular fractures [30,34,37]. Weight bearing as tolerated in a hard-sole postoperative shoe with ice, elevation, and a compressive elastic wrap for swelling control is usually adequate. A functional brace (walker boot) or short-leg walking cast may be useful for increased comfort but is generally not necessary. Most fractures heal by bony union or by an asymptomatic fibrous union within 6 to 8 weeks [33,34,37]. Quill [3] reported clinical union at an average of 6.1 weeks in 14 patients who had nonoperative treatment of avulsion fracture. Occasionally, operative management is required in the event of significant articular step-off (greater than 2-3 mm), fragments involving greater than 30% of the articular surface, or a symptomatic nonunion [1,2,30,33,34]. In these situations, excision of the small fragment, open reduction and internal fixation with an interfragmentary screw, closed reduction and Kirschner wire fixation, or tension band wiring can be performed [3,30,33,34].

The suggested treatment of acute nondisplaced Jones fracture and Torg type 1 (acute) diaphyseal stress fractures is non-weight-bearing ambulation in a short-leg cast for 6 to 8 weeks [3,22,33,34]. Exceptions to this include the highperformance athlete or the informed patient who refuses nonoperative management [3,22,33,34]. Two published series have documented the nonoperative treatment outcomes of acute true Jones fractures [27,38]. Torg and colleagues [27] reported on 15 acute Jones fractures treated nonoperatively with protected weight bearing and cast immobilization. Ninety-three percent healed at an average of 6.5 weeks. One patient had a symptomatic nonunion that required operative management before union was obtained. Clapper and coworkers [38] reported on 235 true acute Jones fractures. In their series, union occurred in only

72% of patients, whereas 28% had clinical and radiographic evidence of nonunion at 25 weeks after injury. These 7 patients were treated with intramedullary screw fixation, and 100% union was achieved in all patients at an average of 12.1 weeks. High incidence of delayed union and nonunion has led many surgeons to consider more aggressive treatment for these fractures.

Operative management has been suggested for patients who have acute displaced fractures, who have failed or refuse nonoperative management, and who have Torg type II and III diaphyseal stress fractures. Early surgical intervention may also be a reasonable option in high-performance athletes and even some recreational athletes who have acute Jones fractures [3,27,33,34].

Fig. 3. A 30-year-old professional athlete who had an acute proximal fifth metatarsal fracture. Operative management with intramedullary screw fixation resulted in clinical and radiographic union. (A,B) Preoperative radiographs demonstrating acute fracture. (C,D) Postoperative radiographs demonstrating a healed fracture with a cannulated intramedullary screw.

Fig. 3. A 30-year-old professional athlete who had an acute proximal fifth metatarsal fracture. Operative management with intramedullary screw fixation resulted in clinical and radiographic union. (A,B) Preoperative radiographs demonstrating acute fracture. (C,D) Postoperative radiographs demonstrating a healed fracture with a cannulated intramedullary screw.

Acute Metatarsal Fracture

The goal of early operative management is to minimize risk of nonunion, delayed union, and possible refracture and to decrease the return time to athletic activity. Options for surgical intervention include closed reduction with intra-medullary screw, intercalated corticocancellous bone graft, open reduction and internal fixation with minifragment plate and screws, tension band construct, or closed reduction and Kirschner wire fixation [1,2,10,25,26,28,29,33,34,36]. Bone grafting can also be added for biologic supplementation.

Internal fixation with intramedullary screw fixation has become a popular method of surgical management of these fractures, with reports of increased union rates and rapid recovery (Fig. 3) [10,25,26,28,36]. Intramedullary screws offer the benefits of compression across the fracture site without the need to open the fracture site or strip the periosteum. Kavanaugh and colleagues [36] reported on 13 proximal fifth metatarsal fractures treated with a 4.5-mm malleolar screw and demonstrated a 100% union rate with no refractures. DeLee and coworkers [10] reported a 100% union rate with no complications after intramedullary screw fixation with a 4.5-mm malleolar screw in 11 athletes. Mean times to clinical and radiographic union were 4.5 weeks and 7.5 weeks, respectively.

The use of cannulated screws has also been reported [25,26,28]. Reese and coworkers [28] reported on 15 patients treated with cannulated screws ranging in diameter from 4.0 to 6.5 mm. Mean times to healing clinically and radiographi-cally were 7.9 weeks and 7.3 weeks, respectively. There were no refractures or nonunions. These investigators concluded that cannulated screw fixation was a reliable method of internal fixation and allowed quick return to activity. Their biomechanical analysis comparing cannulated and solid stainless steel and titanium screws demonstrated that all screws with a diameter less than 4.0 mm did poorly with fatigue testing; it was recommended that the largest screw possible be used for surgical fixation. Porter and colleagues [26] followed 23 patients treated with a 4.5-mm cannulated intramedullary screw for proximal fifth metatarsal fractures (Jones fractures). They reported no refractures and a 100% clinical healing rate. All patients returned to sports at a mean time of 7.5 weeks; however, 2 patients suffered re-injury but did not need operative treatment.

Although intramedullary screw fixation has demonstrated excellent outcomes and early return to full activity, there are reports in the literature of complications after intramedullary screw fixation [25,29]. Wright and colleagues [29] reported on six refractures after cannulated screw fixation of Jones fractures in athletes (screw size ranged from 4.0 to 5.0 mm). Despite clinical and radiographic union, 3 patients sustained a refracture the day after return to full activity, and 3 other patients experienced refracture 2.5 to 4.5 months after return to activity. These investigators recommended use of a larger-diameter screw in athletes who have a larger body mass index and use ofan orthosis upon return to activity. Larson and coworkers [25] followed 15 patients who underwent cannulated screw fixation of a Jones fracture. They reported six treatment failures: four refractures and two symptomatic nonunions. Only 1 of the 6 patients who failed initial operative management had complete radiographic union upon return to full activity. These researchers concluded that return to full activity before complete radiographic union, especially among elite athletes, was predictive of failure.

Plain radiographs may be difficult to interpret for complete radiographic healing. In the patient who desires early return to high-level activities, further testing may be necessary. Currently, the authors obtain a CT scan of the foot and, in consultation with radiologists, use artifact subtraction software to remove the signal of the fixation devices to allow circumferential assessment of bony healing.

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Responses

  • harvey
    Do u have to get surgery jones fracture blood supply?
    3 years ago

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