The foot can be divided in to the hindfoot, midfoot, and forefoot. For the purpose of this review, we will be looking at common etiologies of foot pain stemming from midfoot pathology. The midfoot consists of the tarsal navicular, cuboid, and three cuneiform bones. Traumatic fractures to the tarsal bones account for only 2% of extremity fractures, but due to their weight bearing status, injury can lead to significant morbidity (Alexander James Kiener, 2017).
The tarsal navicular is found on the medial portion of the foot and is flanked superiorly by the talus and distally by the cuneiform (Jackson, 2014). The tarsal navicular serves as the attachment site for the posterior tibial tendon and the spring ligament (J. Benjamin Jackson). Navicular fractures can be classified as traumatic or secondary to stress fracture (Wedmore, 2015). Navicular stress fractures are the third most common stress fracture (Alissa J Burge, 2014). Patients with stress fractures of the navicular typically complain of a gradual development of pain over weeks to months (Wedmore, 2015). The typical mechanism for a traumatic navicular fracture is a crushing and twisting force around the midfoot (Wedmore, 2015). Avulsion fractures can also be seen in injuries to the posterior tibial tendon and spring ligament (Alexander James Kiener, 2017).
The cuboid sits on the lateral side of the midfoot and articulates with the calcaneus (Alexander James Kiener, 2017). Fractures of the cuboid occur due to crush injuries or falls from raised elevations. These fractures rarely occur in isolation (Wedmore, 2015 (Alexander James Kiener, 2017).
The Lisfranc joint complex is also known as the tarsometatarsal joint. (Alissa J Burge, 2014). It consists of the articulation between the cuneiforms and the proximal portion of the base of the first, second, and third metatarsal (Wedmore, 2015). It also includes the base of the fourth and fifth metatarsal, which will articulate with the cuboid (Wedmore, 2015). The base of the second metatarsal acts as one of the main stabilizers of the midfoot due to its articulations with C1, C2, and C3 (Alexander James Kiener, 2017). There is also a complex dorsal, plantar, and interosseous ligament network that acts to stabilize the joint (Mulcahy, 2018). The Lisfranc ligament connects the base of the second metatarsal to the lateral surface of the medial cuneiform (Wedmore, 2015). Injury to this ligament alone can lead to joint instability (Mulcahy, 2018).
High energy trauma related to falls and motor vehicle accidents can lead to fracture-dislocation injuries to the tarsometatarsal joint. Low energy indirect injuries occur when the midfoot is forced into plantarflexion or forefoot abduction (Mulcahy, 2018). In football players, this is typically seen in a lineman’s blocking stance since it puts the foot in a plantarflexed position (Alissa J Burge, 2014). High energy trauma injuries can be classified by the amount of tarso-metatarsal joint congruency and displacement of the metatarsal bases. The low energy injuries can be classified based on the Nunley classification, which is graded based on degree if diastasis of the medial cuneiform and second metatarsal base (Mulcahy, 2018). A missed Lisfranc ligament tear can lead to loss of the longitudinal arch and the development of midfoot arthritis (Alissa J Burge, 2014). However, a midfoot sprain typically returns to athletic activity on average by 13.8 days (Scott Meyer, 1994).
The posterior tibialis muscle and spring ligament also support the medial longitudinal arch (Amy Y I Ting, 2008). Damage to the posterior tibialis muscle can lead to development of a pes planus deformity (Amy Y I Ting, 2008). Injury to the posterior tibialis muscle can be acute or chronic. Tendon degeneration starts slowly with tenosynovitis and tendinosis but can progress to partial tearing, which can lead to insufficiency of the tendon (Amy Y I Ting, 2008). The spring ligament spans from the calcaneus to the navicular (Amy Y I Ting, 2008). Injury of the spring ligament typically occurs with tendinosis or tearing of the posterior tibialis tendon (Amy Y I Ting, 2008).
Diagnosing these various pathologies can be challenging. To help diagnose Lisfranc injury, a provider can perform the piano key test. This involves pressing down on the metatarsal head and developing pain at the metatarsal base (Mulcahy, 2018). Also pathognomonic of Lisfranc injury is plantar arch ecchymosis (Mulcahy, 2018). Other key parts of the physical exam include evaluating the midfoot for development of pes planus or hindfoot valgus.
Fractures of the midfoot are amongst the most commonly missed fractures (Alexander James Kiener, 2017). Weight bearing radiographs should be done in patients in which midfoot pathology is suspected. Weight bearing views and contralateral views of the foot can help assess for changes in foot alignment (Alissa J Burge, 2014). When evaluating radiographs for a Lisfranc injury, you may see widening of the Lisfranc interval and a fleck sign may also be seen (Alissa J Burge, 2014; Alexander James Kiener, 2017). Radiographs are also used as a first step in evaluating for stress fracture of the midfoot (Alissa J Burge, 2014). However, radiographs typically do not show a stress fracture (John R Fowler, 2011).
MRIs with a 1.5T or 3T magnet can evaluate the midfoot for soft tissue pathology and stress injury. When evaluating for low velocity Lisfranc injury, an MRI can look for alterations in the Lisfranc ligament (Alissa J Burge, 2014). An MRI will also show marrow edema in stress reactions and stress fractures will appear as linear abnormalities within bone with surrounding marrow edema (Alissa J Burge, 2014).