Cuneiform fractures are quite rare. While they can occur in isolation, cuneiform fractures are more likely to happen in association with metatarsal injuries. The mechanism of injury for these fractures is usually from an axial load through the foot, though direct crushing forces on the midfoot can causes these fractures also.
The cuneiforms are located on the medial side of the midfoot. All three (medial, middle and lateral) articulate with the navicular proximally. Each articulates with a single metatarsal (MT) distally - medial : 1st MT, middle : 2nd MT; lateral - third MT. The lateral cuneiform also articulates laterally with the cuboid in a variable manner.
The OTA classification of cuneiform fractures uses an alpha-numeric classification scheme. The schematic for cuneiform fractures is 75(modifier) - _ _ . _.
The modifier specifies which cuneiform is involved:
(1) - medial
(2) - middle
(3) - lateral
The first blank - 75(modifier) - _ _ . _ - denotes the degree of articular involvement.
A - extra-articular
B - intra-articular (one of the two articular surfaces).
C - intra-articular (both articular surfaces).
The 75 (mod) A fracture group is further classified (75(modifier) - A _ . _) as:
1 - avulsion
2 - coronal plane
3 - multifragmented
The 75 (mod) B fractures are further classified (75(modifier) - B _ . _ ) as:
1 - saggital plane
2 - coronal plane
The 75 (mod) C fractures are further classified (75(modifier) - C _ . _) as :
1 - undisplaced
2 - displaced
The typical presentation of a cuneiform fracture is of a patient with midfoot pain on weight bearing and possible ecchymosis over the dorsum of the midfoot. The midfoot is tender to palpation and an obvious defect may be appreciated in fracture-dislocations. Fracture dislocations of the cuneiforms are generally with forced plantar flexion and dorsal dislocations.
History and physical exam findings (tenderness with weight bearing and on palpation) plus radiographs make the diagnosis. Radiographs of the foot should include AP, lateral and oblique views - ideally these will be weight bearing films. If the diagnosis remains unclear an CT with coronal reconstructions can be obtained.
Nondisplaced fractures with a stable tarsometarsal joint can be treated closed with a short leg walking cast for 6 weeks. If follow-up x-rays continue to show no displacement, then the cast may be changed to removable boot.
Displaced fractures require an open reduction and internal fixation with screws. When bone loss is present, bone graft may be needed to fill the defect.
The midtarsal joint has limited motion and complications are infrequent.