Metatarsal (MTT) fracture is a common cause of lower limb pain and functional disability. Despite the incidence1 of these fractures, they receive little attention in the literature.2 In fact, there are 75 new cases of MTT fracture per 10,000 people per year. The prevalence of MTT fractures varies between 3% and 7% of all fractures and, more specifically, occur in 35% of all foot fractures.3–5 These fractures may occur as an isolated injury, concurrent with additional MTT fractures, or in combination with fractures/dislocations of the Lisfranc joint.1
Rigid ligamentous anchors between the heads of central MTTs provide protection against displacement of simple fractures; however, depending on the intensity and direction of the traumatic forces, these bones can divert to a multiaxial plane.6,7 Treatment aims to restore alignment of the MTTs, preserving the longitudinal and transverse arch of the forefoot and a normal weight distribution under the MTT heads. If these goals are not achieved, disabling metatarsalgia is a common consequence.8
Retrograde fixation with Kirschner (K) wires and exteriorization of the wires at the plantar skin is the gold standard of surgical treatment.8–11 Because of the common complications such as hypertrophic scars, painful calluses, and plantar plate tears,12–14 we suggest surgical treatment by anterograde fixation. In this article, we focus on diagnosis, management, and clinical evaluation of lesser MTT fractures treated with this less invasive technique.
MECHANISM OF INJURY
MTT fractures can result either from direct or indirect violence. These fractures are associated with a wide variety of injuries ranging from isolated simple fractures of one MTT to multiple injuries with serial fractures and severe soft tissue impairment. Most MTT fractures are a result of low-energy trauma, but high-energy crush injuries do occur with some frequency due to motorcycle accidents.15,16
MTT fractures can occur at any location on the bone. They are generally categorized according to the anatomic location: proximal metaphyseal, diaphyseal, cervical (neck), and cephalic (head).17 Diaphyseal fractures are more commonly oblique, but they can occur in different patterns. These fractures tend to shorten because of the pull of intrinsic muscles.12 Distal fractures (neck and head) are often transverse or short oblique. If deviation is present, they predominate in plantar and lateral directions.13 Central MTT fractures (second, third, and fourth) occur more frequently than do first MTT fractures. In addition, multiple fractures are more common than isolated ones.12
In general, lesser MTT fractures without deviation are treated conservatively. Fractures with small displacement, without shortening or angulation, can also be treated without surgery.8,9
Fractures with sagittal plane displacement can alter load distribution under the MTT heads, resulting in mechanical pain, painful calluses under the MTT heads, and traumatic neuroma formation.8 Shereff18 recommends surgical treatment of any fracture with radiographic displacement of >3 to 4 mm and angulation of >10 degrees with no distinction between central rays (second and third) and lateral rays (fourth and fifth) (Table 1).
Patients with lesser MTT fractures who require surgery but present extensive soft tissue disruption with skin blisters or abrasions should have their treatment delayed. It typically takes 10 to 15 days for soft tissue to heal before surgical intervention.13
Patients with significant comorbidities or vascular impairment were excluded the study.
Lesser MTT fractures (II to V) with surgical indication confirmed by radiographs of the foot in anterior/posterior, internal oblique (45 degrees), and side views.
Absence of comorbid conditions that prevented surgery.
Absence of associated fractures.
The goal of treatment is to maintain a functional forefoot. Details that should be considered to optimize healing include the MTT parabola, the sagittal plane position of the MTT heads, and bone-to-bone contact.16 Herein, we chose distal traction and closed reduction with anterograde percutaneous pinning as our treatment of choice.
The patient is placed supine on a fluoroscopy table. Using fluoroscopy guidance, a small 5 mm surgical incision is made in the dorsal aspect of the foot 10 mm distal from the base of the affected MTT. With a sharp pointed instrument, a small tunnel is created in the dorsal cortex of the MTT until the intramedullary space is reached. When performing this maneuver, it is very important to preserve the plantar cortex of the MTT. A 1.5- or 2.0-mm K-wire with 15 degrees of angulation at its distal end is then inserted until it reaches the proximal edge of the fracture (Figs. 1A–F). Closed reduction is performed with longitudinal traction of the toe and manipulation of the forefoot. When closed reduction is impossible, a sharp reduction percutaneous clamp is recommended to align the fracture (Fig. 2). Fluoroscopy is used to guide insertion of the rest of the K-wire to the distal end of the MTT. It is vital that perforation of the MTT head is avoided (Figs. 3A–F). Finally, the proximal end of the K-wire is cut and bent above the skin level to allow for easy removal of the wire.
This study and the corresponding informed consent documents were submitted and approved by the Research Ethics Committee at our hospital. Enrollment of patients was initiated in 2003. Between 2003 and 2008, 14 patients with lesser MTT fractures were evaluated. All patients met surgical indications according to Shereff’s18 recommendations (Table 1). Eight female and 6 male patients were included in our study. The average age was 39 years, ranging from 14 to 70 years.
Patients underwent standard clinical and radiologic evaluation. Each patient answered a questionnaire containing information about the mechanism of injury, comorbidities, and lifestyle. A total of 20 fractures (77%) were located in the neck of the MTT and 6 were in the diaphysis (23%). In addition, 6 fractures involved only one MTT (57%) and 8 involved multiple MTTs (43%). The second MTT was singly affected in 14% of the patients. In combination with other fractures, this bone type was fractured in 57% of the patients. The most common mechanisms of trauma were simple torsions (43%), direct trauma (36%), and motorcycle accidents (21%). In our sample, 6 patients reported comorbidities: 4 with hypertension and 2 with diabetes, and 21% of the patients in the study were smokers.
We used the American Orthopaedic Foot and Ankle Society’s (AOFAS) forefoot functional score for postoperative clinical evaluation 6 months after surgery. Fracture healing was confirmed by x-ray 8 weeks after surgery. Table 2 presents the percentages of fractures according to the location. Table 3 presents the general incidence of MTT fractures. AOFAS functional scores, assessed 6 months postoperatively, were, on average, 98 points (range, 85 to 100).
Complications after surgical treatment of central MTT fractures are uncommon. However, if the goals of the treatment are not achieved, disabling metatarsalgia is a common consequence. Malunion and delayed union are occasionally encountered, but nonunion is rarely a concern.17 Using the standard retrograde technique, the most common complications include hypertrophic scars, painful calluses, and plantar plate tears.12–14 Open reduction and internal fixation of these fractures with plate and screws may disrupt the soft tissue envelope and result in high incidences of skin problems.1,16
Using the anterograde technique, we did not encounter any of the complications described in the literature. We do, however, recommend that careful attention be paid during insertion of the K-wire. Perforation of the plantar cortex of the MTT may complicate introduction of the wire into the intramedullary space. If this occurs, the technique may not be completed.
Following surgery, a posterior plaster splint for pain control is applied and maintained for 2 weeks. Afterwards, a non–weight-bearing boot is worn for another 4 weeks. The K-wire is removed 6 weeks postoperatively. Weight-bearing on the foot is initiated as soon as the wire is removed. Rehabilitation with physical therapy should begin after 6 weeks.
MTT fractures are among the most common forefoot injuries.3,4,15 The frequency of these fractures is 10 times greater than the Lisfranc joint fractures.19 Therefore, it is important to identify specific populations at risk for MTT fractures. MTT fractures are the most common forefoot fractures obtained in motorcycle accidents,6 but they occur most often through low-energy trauma, as a result of direct trauma or simple torsion.6,17
In our study, 69% of the patients were victims of low-energy trauma and 31% were victims of high-energy trauma, which is in accordance with the literature data.3,6,16 We observed that the most affected anatomic location was the neck of the second and third MTTs (43%). In agreement with other reports in the literature, multiple MTT involvement was more common (57%) than isolated fractures.1,6,7
Variables such as obesity, female sex, diabetes mellitus, and degree of deviation may worsen clinical postoperative results.16 Coincidentally, the 2 patients in our study with AOFAS clinical scores below 100 points were females and diabetic; however, these results were not statistically significant (P>0.005). Smoking did not appear to alter postoperative results in our sample (P>0.005).
Most MTT fractures are treated conservatively, with or without immobilization.12 Surgical treatment is reserved for those fractures with > 3 to 4 mm of deviation or >10 degrees of angulation, to prevent complications.14 If properly diagnosed and managed, these fractures have a favorable prognosis and low complication rates. Without proper treatment, these fractures can lead to serious changes in gait balance and foot load distribution.1,7,20 In this study, we show that patients treated with an anterograde percutaneous technique have high functional AOFAS clinical scores in the postoperative period that averaged above 95 points. No complications related to this type of treatment were identified.
CONCERNS/FUTURE OF TECHNIQUE
The standard treatment for lesser MTT fractures is retrograde fixation with K-wires, violation of the fracture site, and exteriorization of the wires in plantar skin.12–14 Complications described for this type of treatment include painful calluses, potential injury to the flexor tendons, and plantar plate tears.9,13–15 The advantage of percutaneous pinning is the ability to maintain vascularity to the fractured bone. No extensive dissection is used and, subsequently, the soft tissue envelope is not disrupted. The main disadvantage is the inability to directly visualize or manipulate the fracture.
Despite the small number of patients in our sample, our chosen treatment was sufficient to properly treat lesser MTT fractures, while avoiding the common postoperative complications of other treatments. This treatment provides stability in only one plane but is feasible because of the intrinsic stability of these fractures, because of lack of motion, soft tissue attachments, and stable proximal articulations.7,16 Prospective studies with higher numbers of patients are required to determine, more specifically, the limitations of this treatment.
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Keywords:© 2014 by Lippincott Williams & Wilkins
metatarsal fractures; percutaneous treatment; foot fractures; minimally invasive treatment