Stress Fractures of the Fifth Metatarsal

Home , Fifth metatarsal bone, Metatarsal bones, Tibia

http://dx.doi.org/10.14517/aosm15025 Review Article pISSN 2289-005X·eISSN 2289-0068

Stress fractures of the fifth metatarsal

Jae-Young Lee, Jin-Wha Chung

Department of Orthopedic Surgery, The Catholic University of Korea, Bucheon St. Mary’s Hospital, Bucheon, Korea

A stress fracture can be defined as a spontaneous fracture due to accumulation of stress on a healthy bone. Stress fractures of the 5th metatarsal usually locate to the proximal 1.5 cm of the metatarsal shaft, a characteristic based on anatomical and biomechanical parameters. Many surgeons agree that the postoperative outcome of 5th metatarsal stress fractures tend to be associated with prolonged healing time, with nonunion, and sometimes with refracture. Acute stress fractures have been treated with immobilization using a non-weight-bearing cast, but the incidence of complications (delayed union or nonunion) after non-surgical treatment makes surgical treatment a more favorable treatment option for competitive athletes, even for young adults. Curettage and bone grafting or intramedullary screw fixation, the standard surgical treatment for the 5th metatarsal stress fractures, has been associated with rapid recovery and early return to physical activities. Malalignment or instability of the foot or ankle must be addressed at the time of surgical treatment.

Keywords: Fifth metatarsal; Stress fracture; Metatarsal fracture; Jones fracture

INTRODUCTION 5th metatarsal fractures make it a condition of clinical significance and one that requires an accurate diagnosis In stress fractures, a sustained submaximal external force, and an appropriate treatment [3]. In 1902, Jones sug- which is just inadequate to induce an acute fracture, over- gested that a base fracture of the 5th metatarsal may also lays the bone and causes a characteristic hairline fracture occur as a result of an indirect trauma [4]. A classification that can be seen on radiographs [1]. Stress fractures are system to divide these fractures into groups was devised often found on tibial, metatarsal, and tarsal bones on by Torg et al. [5] in 1984, and many studies have investi- which a lot of weight-bearing occurs and in professionals gated the treatment, classification, and prognosis of base such as athletes, dancers, and military soldiers whose job fractures of the 5th metatarsal. requires overuse of the lower limbs as well as in the normal population [2]. However, stress fractures are distinct ANATOMY AND BIOMECHANICS OF THE 5TH from pathologic fractures that are induced by even trivial METATARSAL BONE force on bones that are pathologically weakened as a result of systemic metabolic or inflammatory diseases or of A metatarsal bone consists of a head, a tibia, a shaft, a severe osteoporosis. base, and a tuberosity. The tuberosity protrudes into the The base of the 5th metatarsal of the foot is the region posterolateral base of the plantar foot and provides the in which the stress concentrates biomechanically; thus, dorsolateral insertion site for the peroneous brevis ten- for anatomical characteristics the prevalence of stress don. The insertion of the lateral fibrous tissue of the fractures is higher in the 5th metatarsal compared to plantar fascia in the direction of the plantar contributes those of other sites. For reasons related to blood flow, the to the stability of the base of the 5th metatarsal bone time taken to bone union is slow, and complications such (Fig. 1). In the 2nd and 3rd metatarsal bones, the base as refractures are common. These factors associated with and the cuneiforms form a lattice-shaped joint that build

Received December 1, 2015; Revised December 23, 2015; Accepted December 23, 2015 Correspondence to: Jin-Wha Chung, Department of Orthopedic Surgery, The Catholic University of Korea, Bucheon St. Mary’s Arthroscopy and Hospital, 372 Sosa-ro, Wonmi-gu, Bucheon 14647, Korea. Tel: +82-32-340-7034, Fax: +82-32-340-2671, E-mail: [email protected] Orthopedic Sports Medicine Copyright © 2016 Korean Arthroscopy Society and Korean Orthopedic Society for Sports Medicine. All rights reserved. CC This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ AOSM by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Arthrosc Orthop Sports Med 2016;3(1):1-5 1 Jae-Young Lee, Jin-Wha Chung. Stress fractures of the fifth metatarsal

Peroneus Peroneus Nutrient brevis tertius artery Metaphyseal arteries

Lateral band of plantar fascia "Avascular zone" Fig. 1. An adduction force on the fifth metatarsal bone is counterbal- anced by a stress force that induces a stress fracture. Between the coun- teracting forces of the 5th metatarsal bone, the rigid fascial and tendi- nous anchors act as a fulcrum. Fig. 2. Blood supply to the fifth metatarsal is provided by a single nutrient artery to the shaft and by the epiphyseal and the metaphyseal arteries to the base and to the tuberosity. a stable anatomical structure. In the 4th and 5th metatarsal bones, the base does not contribute to the stability of the joints in this way. For this anatomical basis, during the tarsal is one of the factors that prevent successful fracture rehabilitation after treatment of the latter two metatarsal healing. Shereff et al. [8] found that whilst vascular supply fractures, adduction and abduction exercises in the axial to the shaft of the 5th metatarsal is provided through one plane are restricted and around 10o of flexion motion is nutrient artery, that to the base of the 5th metarsal is pro- permitted in the sagittal plane [6]. Of the metatarsals, the vided through more than one metadiaphyseal arteries. distal portion of the 5th metatarsal has the most mobility, Because stress fractures of the proximal 5th metatarsal thus movement is permitted relatively freely. Conversely, occur near the medial cortical hole through which the the base of the 5th metatarsal, as the section that receives nutrient vasculature feeds through, upon fracture this the most support from the ligaments and tendons, acts as site is separated from the source of blood vessels leading a lever during metatarsal movement, and therefore is the to formation of an avascular fracture site; this has been region where stress accumulates excessively. The accu- reported to be one of the important anatomical reasons mulation of stress leads to stress fractures at the proximal for the high rate of nonunion or delayed union in 5th 5th metatarsal, especially because of stress that accumu- metatarsal fractures (Fig. 2) [8]. lates with repeated adduction of the foot. By evaluating the fracture site radiographically, we can deduce by way DIAGNOSIS AND CLASSIFICATION OF of the fracture line that the fracture began at the lateral STRESS FRACTURES OF THE FIFTH plantar foot and extended toward the medial dorsal foot. METATARSALS Biomechanical causes of stress on and, therefore, of stress fractures of the base of the 5th metatarsal during Early stress fractures are distinctively associated with a weight-bearing gait include a larger than normal curva- precursory symptom of intermittent pain, rather than ture of the distal shaft of the 5th metatarsal, inversion of acute pain. This mild, intermittent pain is mistakenly the tibia, and cavus foot-induced excessive abduction taken for soft tissue injuries that gradually increase in in- force on the base of the 5th metatarsal [7]. The risk of tensity. Often, this precursory pain suddenly exacerbates stress fractures can also increase if patients already have with a piercing sensation during exercise or during gait. an inversion deformity of the hindfoot. This is because Patients with 5th metatarsal fractures have a history of a an inverted hindfoot leads to a sustained locking of change in habit such as taking up a new sports or an in- the metatarsals during the stance phase of a gait in the crease in the intensity or in the amount of sports activity background of an already low subtalar joint mobility; the and rarely have a history of trauma. metatarsal locking compromises the flexibility of the foot The fractures at the proximal 5th metatarsal can be di- and increases chances of fractures because the foot can- vided into 3 types according to anatomical position. Zone not effectively absorb the shock against ground force. 1 fractures are avulsion fractures that occur at the most The vasculature distinctive to the base of the 5th meta- proximal metatarsal bone, the tuberosity. They occur as

2 www.e-aosm.org Jae-Young Lee, Jin-Wha Chung. Stress fractures of the fifth metatarsal

a result the insertion of the peroneous brevis tendon and prominent. Thus, when stress fractures are suspected plantar facia. Zone 2 fractures occur in the metaphysio- and an early plain radiography is not suggestive of them, diaphyseal junction, and zone 3 fractures occur within imaging should be repeated across a few weeks until they 1.5 cm of the proximal shaft of the 5th metatarsal (Fig. 3). can be seen. Conversely, nuclear medicine test or mag- Fractures of the latter two zones, for reasons related to netic resonance imaging may assist early diagnosis of the anatomical and biomechanical factors, are associated stress fractures. with a high incidence of delayed union, of nonunion, or Torg et al. [5] established a classification system that of refractures. Zone 2 fracture are also known as Jones’ divided the base fractures of the 5th metatarsal into 3 fracture and are usually limited to acute fractures. Be- stages: a type 1, acute injury; a type 2, delayed union; and cause patients’ symptoms and their history of trauma a type 3, nonunion (Fig. 4). Type 1 fractures are acute frac- tend to be ambiguous, it is difficult to differentiate Jones’ tures without expansion of the fracture line or without fractures from stress fractures that arise at the same site intramedullary sclerosis but with trivial hypertrophy of [9]. the cortical bone. Type 2 fractures are those with delayed The stress fractures of the 5th metatarsal, as in other union, mild intramedullary sclerosis, and expansion of metatarsal stress fractures, present with a clear fracture the fracture line or hypertrophy of the cortical bone. Type line at the initial stage on plain radiography. But even 3 fractures are those with an expanded fracture line, hy- when a fracture line cannot be discriminated initially, hypertrophy of the cortical bone, and sclerosis of the intra- pertrophy of the cortical bone that occurs between 2 and medulla that has progressed to a breakage of the bone. 4 weeks of the fracture causes the fracture line to become

Fig. 3. Anatomical classification of the fifth metatarsal fractures: a tuberosity A B C fracture (A), a Jones’ fracture (B), and a diaphyseal stress fracture (C).

Fig. 4. Torg classification of 5th metatarsal fractures: acute fracture (I), delayed union (II), and nonunion (III). www.e-aosm.org 3 Jae-Young Lee, Jin-Wha Chung. Stress fractures of the fifth metatarsal

TREATMENT this approach may lessen the occurrence of complications. As a rule, type 1 fractures classified through the Torg classification system are treated conservatively unless they Tension band wiring are sustained by young athletes. Torg et al. [5] found that Tension band wiring has been introduced as an alterna- for acute stress fractures without displacement cast im- tive to the intramedullary screw fixation for base fractures mobilization alone under non–weight-bearing conditions of the 5th metatarsal. A modified tension band wiring has shown to result in bone union in 93% of patients by that uses 2 screws and wires has also been developed [17]. the 7th week. But Stewart [4] and Dameron [10] found that in those who did not receive surgical treatment, the Inlay bone graft rate of nonunion and delayed union was high. Similarly, Bone graft for union is a conventional alternative to inter- DeLee et al. [11] and Kavanaugh et al. [12] recommended nal fixation. It has the advantage of not requiring an addi- that because conservative treatment of type 1 fractures in tional removal surgery of screws but requires a secondary young athletes necessitate a long time for union and for incision. Specifically, compared to the intramedullary rehabilitation, a surgical treatment is recommended, es- compression screw fixation, bone grafts have the disad- pecially if the patient desires an early return to sports. For vantage that a relatively longer duration, of more than 3 the treatment of type 2 stress fractures, surgical treatment months, is needed for bone union. Surgical difficulties re- is recommended to prevent nonunion. Of the many sur- lated to bone grafting include insufficient removal of the gical treatments, the one described by DeLee et al. [11] sclerotic bone and graft compatibility. which uses compression screws for intramedullary screw fixation is most commonly used. Other treatment meth- Conservative accessory treatments ods include bone grafting, intramedullary screw fixation Conservative treatments such as extracorporeal shock with concomitant bone grafting, and tension band wiring therapy and platelet-rich-plasma injection therapy have [1]. been reported to successfully complement the core treatment for 5th metatarsal fractures. Such supplementary Intramedullary screw fixation treatments are useful when patients are nonresponsive to Intramedullary screw fixation is the conventional method standard treatments, when complications such as non- for the treatment of stress fractures of the 5th metatarsal. union or delayed union exist, or when patients refuse to Several studies have shown favorable outcomes for meta- receive surgical treatment [18]. tarsal stress fractures after using this approach. An study by DeLee et al. [11] has shown good clinical outcomes REHABILITATION AND RETURN-TO-SPORTS of percutaneous screw fixation for metatarsal fractures in 10 patients. Josefsson et al. [13] found that after us- Competitive athletes desiring to return-to-sports at the ing the same method they achieved bone union in all 27 earliest possible date tend to downplay their level of pain patients without complications. In accordance to these at the postoperative follow-up. Because they hurry their previous findings, subsequent studies have shown good return-to-sports before a complete recovery, they tend to clinical outcomes after intramedullary screw fixation, but incur complications such as refractures and nonunion several postoperative complications have been reported. more easily than those who comply to rehabilitation Complications such as a mis-inserted screw during a faithfully [1,19]. It has been shown that most patients subcutaneous insertion, breakage of the opposite cortical who present with complications had disregarded the bone, soft tissue irritation, screw head-induced metatar- postoperative rehabilitation protocol and had returned salgia, peroneous brevis tendon tear, and stimulation of to sports prematurely. Especially in athletes, the point the sural nerve have been shown to be associated with at which the patient returns to sports, which should be intramedullary screw fixation [14,15]. Nowadays, the self- only once a clinical and a radiological union is achieved, tapping screw fixation does not require pre-tapping in should be clearly defined through a collaborative deci- principle, but for type 2 or 3 stress fractures pre-tapping sion made between the coaching staff and the patient. Yet has been recommended to remove intramedullary scle- even a bone union that is achieved through screw inser- rosis and to promote re-establishment of blood flow [16]; tion does not guarantee prevention of refractures at the

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time of screw removal; therefore, removal of the screw in or a nonunion of the fractures are a chief concern, return- currently active professional athletes is recommended to to-activity is expedited by treating the fractures surgically be delayed until their sports career is completed [20]. rather than conservatively. Intramedullary fixation using compression screws, curettage, and bone grafting are CONCLUSION methods of surgical treatment most widely used for stress fractures of the 5th metatarsal. The conventional approach to treat stress fractures of the proximal 5th metatarsal, especially acute fractures, CONFLICT OF INTEREST is that of conservative measures such as non–weight- bearing cast immobilization. But in athletes or in young No potential conflict of interest relevant to this article was patients in whom complications such as delayed union reported.

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