The midtarsal joint includes the talonavicular and calcaneocuboid joints. It carries the epoym of Chopart, who described an amputation at this level.
Main and Jowett (1975) found that injuries normally occur to both the talonavicular and calcaneocuboid joints together. However, they also identified a "swivel dislocation" (12% of their series) in which the talonavicular joint dislocates, usually medially, and the calcaneum swivels under the talus with the calcaneocuboid joint intact. The axis is the interosseous talocalcaneal ligament.
Midtarsal dislocations may be isolated or be part of more complex injuries involving calcaneal fractures(Ricci et al 2002), subtalar dislocations or fracture-dislocations of the tarsometatatarsal (Lisfranc) joints. Richter et al (2001) noted that the combined Chopart-Lisfranc fracture dislocation had the worst prognosis of any midfoot injury.
Classification
Main and Jowett (1975) classified midtarsal injuries by the direction of displacement (and implied direction of force application) and nature of injury:
- medial displacement (21 cases)
- fracture-sprains
- fracture-subluxations/dislocations
- swivel dislocations
- longitudinal impact injuries (29 cases) - most of these seem to fit the type 2 navicular body fracture described by Sangeorzan (1989)
- lateral displacement
(12 cases)
- fracture-sprains
- fracture-subluxations/dislocations - some of these have "nutcracker" fractures of the cuboid and lateral column collapse; others may have apparently minor bony injuries but represent "occult" midtarsal dislocations (Tountas 1989)
- swivel dislocations - rare in the lateral direction
- plantar displacement (5 cases)
- crush injuries (4 cases)
Richter et al (2004) did not subclassify their series of 110 injuries because they considered there was no consensus about classification and no evidence of correlation between existing classifications and outcome. Richter's series contained more severe injuries than Main and Jowett's, as it comes from the Hanover level 1 trauma centre.
Occult midtarsal subluxation
This refers to injuries in which only apparently minor avulsions (usually from the navicular) and impaction fractures (usually on the cuboid and calcaneum) are visible on the plain radiographs. However, the foot is extremely bruised and swollen and isotope scan (Tountas 1989) or other imaging show injury to the entire midfoot. Splintage in cast for 6-8 weeks produced acceptable results with only minor residual deformities in Tountas' series. However, we suggest consideration should be given to CT in these injuries to assess the extent of damage and possible need for early surgical reconstruction
"Isolated" dislocation of the navicular
Dhillon and Nagi (1999) described 6 cases of dislocation of the navicular without fracture (nearly 20% of midtarsal injuries during the study period). All had additional calcaneocuboid or subtalar joint injuries. Dhillon and Nagi saw navicular dislocation as analogoud to lunate dislocation: the midfoot dislocates with the navicular which is then extruded as the primary injury partly reduces.
Assessment
Both Main and Jowett and Richter et al note that delayed diagnosis may occur. Midtarsal joint injuries should be considered in the assessment of all significant foot injuries and in the polytrauma patient. AP, lateral and oblique plain radiographs are usually enough to make the diagnosis, but CT will often contribute additional information for treatment planning
Management
Closed reduction was required in 16 and open reduction in 7 of Main and Jowett's 69 patients; reductions were held in cast. Richter et al reported 34 closed reductions and 64 open reductions in 110 patients, which may represent more severe injuries and a more aggressive surgical approach in the 1990s. All of Richter's open reductions and 15 of the closed reductions had surgical fixation of the fractures. They noted that ORIF had beter functional results than closed reduction and percutaneous fixation. External fixation was a useful adjunct in 20 patients.
Eleven of Main and Jowett's patients had late reconstructions, mostly triple fusions. However, they deprecated this procedure in favour of more limited fusions because the all patients had residual symptoms with some disability (though this might have reflected the severity of the initial injury). Richter did not comment on late surgery. In general, limited midfoot fusions give adequate results for most pathologies and we would advocate triple fusion only when spcifically indicated by imaging and diagnostic injecions.
References
- Main BJ, Jowett RL. Injuries of the midtarsal joint. JBJS 1975; 57:89-97
- Ricci WM et al. Transcalcaneal talonavicular dislocation. J Bone Joint Surg Am 2002;84-A(4): 557-61
- Richter M et al. Fractures and fracture dislocations of the midfoot: occurrence, causes and long-term results. Foot Ankle Int 2001;22(5): 392-8
- Richter M et al. Chopart fracture-dislocation: initial open reduction provides better outcome than closed reduction. FAI 2004; 25:340-8
- Tountas AA. Occult fracture-subluxation of the midtarsal joint. CORR 1989; 243:195-9