Metatarsal fractures remain a common occurrence of acute pathology to the practicing foot and ankle surgeon. Incidence of metatarsal fractures are widely reported between 3.2% and 6.8% of all reported fracture patterns and 35% of all reported pedal fractures.1 Metatarsal fractures make up 61% of reported fractures in pediatric populations.2 Conservative versus surgical approaches toward management generally vary among the first, central, and fifth metatarsals. No well-documented treatment algorithm exists for surgical management; however, decisions are usually made in regards to displacement and angulation. Less than 10° of angulation or 3 to 4 mm of displacement tends to be well-accepted values for consideration of nonoperative intervention. Conservative care traditionally consists of 4 to 6 weeks of non–weight-bearing. Should pathology lie outside these parameters, surgical intervention is usually indicated. Special evaluation should be given for those fractures with sagittal plane involvement, as involvement both dorsally and plantarly can lead to alternation in gait, as well as irritation of adjacent structures. Goals for management of these fractures generally consist of the following: normal fracture healing while maintaining metatarsal length parabola and joint congruity based on metatarsal head displacement.3,4 Special care needs to be given to the first and fifth metatarsals based on significant variations in both blood supplies and soft tissue attachments to these locations. Management of acute fifth metatarsal fractures is a topic widely published on, and these fractures should be managed differently than first or central metatarsal fractures. Nonunion rates of conservatively managed fifth metatarsal range from 6% to 40%.5
Initial workup for these injuries after a thorough clinical history and physical examination generally includes a basic radiographic evaluation consisting of non–weight-bearing plain radiographs. These are used to evaluate the previously mentioned angulation and displacement characteristics of the fracture pattern. Multiple views are required to complete evaluation of the fracture, especially those involving the sagittal plane.
A noncontrast computed tomography (CT) scan may provide benefit for acute highly comminuted fractures and those involving the bases of the metatarsals. For these fracture patterns care with advanced imaging should be taken for evaluation of Lisfranc joint involvement. CT scans also provide value data in cases requiring the need for revision surgery. CT scan remains the imaging modality of choice for evaluation of nonunion metatarsal fractures. Specialized combo scans such as a single photon emission computed tomography can also provide additional information for complex metatarsal fractures and those requiring revision surgery. Generally, these scans are difficult to obtain based on their availability at imaging centers. However, if available to the surgeon, these can be of value when evaluating fractures close to the metatarsal bases or those patterns with concern for nonunion. Magnetic resonance imaging (MRI) without contrast is described in the literature for management of revision metatarsal fractures but usually is limited to those with concern for abnormal stress reactions to the metatarsals, infectious causes of the delayed healing, or those metatarsals with soft tissue attachments that require evaluation congruently.
Once imaging has been completed and a surgical decision is made based on the previously mentioned generally accepted variables, these fractures are corrected traditionally via the Swiss Association for the Study of Internal Fixation (ASIF) principles of fracture management.6 Numerous high-level evidence-based studies have evaluated metatarsal fixation based on anatomy and fixation types.
Evaluating the Need for Revisional Surgery
When evaluating complications of metatarsal fracture healing, it is of utmost importance to identify the most likely causative factor for the failure. For metatarsals that fail to heal properly often causative reasons are multifactorial. An exhaustive exploration into these causes is paramount and should guide additional interventions. Generally speaking, these factors can fall within patient factors or surgeon factors.
Patient factors that often contribute to fracture healing include things such as infection, impaired biology to heal, smoking status, and noncompliance with postoperative instructions or conservative interventions.7 Surgeon factors often include failure to understand the fracture pattern/nonunion pattern, inadequate fixation, and failure to intervene in a timely manner. Prior to any advanced workup or surgical intervention potential for infection must be evaluated.
With postsurgical metatarsal fractures that fail to heal properly, infection and metabolic causes are an important consideration for the foot and ankle surgeon. Stucken et al8 reported that care should be taken to identify patients at risk for infection. These generally include those with impaired healing potential, open fractures, smoking status, delayed wound healing post surgery, or those with previously placed external fixation. Despite patients with obvious clinical signs of infection they also reported via a large multicenter study a significant number of patients with a benign workup, specifically no clinical signs or symptoms and normal laboratory data, who underwent revision surgery and yet still had positive cultures.
Olszewski et al9 reported on the benefits of basic laboratory tests readily available for the practicing foot and ankle surgeon in evaluating the possibility for infection. These included white blood cell count, C-reactive protein, and erythrocyte sedimentation rate. Ordering these tests should be considered in all initial workups for metatarsals exhibiting delayed healing after fractures. In addition to basic diagnostic tests advanced imaging may be utilized to aid in diagnosis.
In addition to infectious causes, impaired biology in the form of metabolic abnormality should be considered when evaluating the need for revision metatarsal surgery. This is especially true when all other apparent causes of impaired healing have been ruled out. Brinker and colleagues described certain metabolic abnormalities leading to biologic delays in bone healing. These most often include abnormalities in parathyroid hormone, calcium, and growth hormone; vitamin D deficiency; and impaired glucose tolerance.10,11 Close collaboration with appropriate physicians to correct any imbalances should be completed prior to additional surgical intervention. Smoking status has been well documented as a causative agent in delayed bone healing and should be addressed prior to any attempted revision surgery.12
Physician Factors Contributing to the Need for Revisional Surgery
If all patient contributing factors to delayed metatarsal healing have been evaluated and deemed noncontributory, attention should turn to surgeon-controlled causative factors. These often include errors in technique, fixation principles, time in the operating room, or failure to intervene in a timely manner. Most often in the setting of revisional metatarsal fractures, physician error is seen in the setting of hypertrophic nonunions. These fractures are widely considered to have the appropriate biology to heal; however, they traditionally need additional stability to heal. Evaluating the type of nonunion present and acting in a timely manner generally leads to better patient outcomes (Figure 22.1). Once the cause of the delayed metatarsal healing has been determined, surgical plans can be initiated.
Implantation of biodegradable and nonbiodegradable antibiotic delivery devices have been discussed and may provide benefits and reduce the need for additional surgical intervention for certain infectious nonunions.13 Implantation of nonbiodegradable antibiotic cement may also provide benefit to the foot and ankle surgeon in cases of loss of metatarsal length by providing a biological membrane conducive to bone grafting later in staged management via the Masquelet technique.14 Care should be taken to ensure local antibiotic delivery is heat stable and of broad spectrum as often culture results will not be available at the time of implantation of these delivery devices. Once cultures return, parenteral antibiotic therapy should be tailored to the results present and de-escalated from board spectrum when possible.
Once the patient has been treated for the infection present, attention can be directed toward stage 2 of the intervention. This often consists of definitive fixation of the fracture with reimplantation of hardware or final adjustment of external fixation as well as any accompanying soft tissue procedures for closure of any residual soft tissue defects. Depending on the amount of bone resected during the initial débridement for the infection, bone grafting may be necessary.
Bone Grafting Considerations for Nonunion and Revisional Metatarsal Fracture Surgery
Owing to the presence of osteogenesis, osteoinduction, and osteoconduction, autologous bone has been the mainstay of management for those situations requiring grafting. All 3 of the above qualities are needed for successful integration of the graft and complete fracture healing.15 Grafting is generally required in atrophic nonunions or those associated with wide resection secondary to primary infection.
Multiple sources for obtaining autologous bone graft have been reported in the literature. Traditionally autologous bone grafting from the ipsilateral anterior iliac crest has been the standard for foot and ankle surgical needs; however, donor sight morbidity has been well documented.16 Younger and Chapman17 reported on these complications and noted a 9% major and 21% minor complication rate associated with this procedure. These major complications included deep infection, hematoma, reoperation, persistent wound drainage, pain lasting >6 months, sensory loss, and painful scars. Despite these complications iliac crest remains historically an ideal choice for grafting secondary to its large amount of both cortical and cancellous grafting material. It provides an excellent source of structural integrity for nonunions requiring structural support during revision surgery.
Based on the previously mentioned comorbidities associated with obtaining iliac crest grafting material, other regional grafting sites have been documented. These additional methods have the benefit of being present in the same surgical field as the metatarsal needing revision surgery. They include the distal tibia and the calcaneus.