16. Trade Allocation y Liquidez no Invertida
16.1. Definición Trade Allocation
A 45-year-old woman was horse riding when she fell off her mount. As she fell her foot was caught in the stirrup. She complained of an isolated injury with pain in her foot only. Examination
This woman’s left foot has swelling in the midfoot region associated with ecchymosis on the plantar aspect. Palpation of the midfoot is tender, particularly between the first and second metatarsal bases. She has no neurovascular deficit but is unable to bear weight on the foot owing to pain. A radiograph is shown in Fig. 42.1.
Figure 42.1
Questions
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What is the diagnosis?•
Describe the radiological findings.118
100 Cases in Orthopaedics and Rheumatology
ANSWER 42
The diagnosis is a Lisfranc injury which is typical with this mechanism of injury. Jacques Lisfranc de Saint-Martin (1790–1847), a field surgeon in Napoleon’s army, described an amputation technique across the five tarsometatarsal (TMT) joints. At the time this was an effective solution to forefoot gangrene secondary to frostbite. This anatomical landmark became known as the Lisfranc joint.
The Lisfranc joint, which represents the articulation between the midfoot and forefoot, is composed of the five TMT joints. The Lisfranc ligament is attached to the lateral margin of the medial cuneiform and medial and plantar surface of the second metatarsal (MT) base. This is the only ligamentous support between first and second rays at midfoot level. A Lisfranc injury encompasses everything from a sprain to a complete disruption of normal anatomy through the TMT joints. Injury to this ligament, even in isolation, will result in functional instability with loss of longitudinal and transverse arches. No intermetatarsal ligaments exist between the first and second MTs. Lisfranc injuries are commonly undiagnosed and carry a high risk of chronic secondary disability.
Initial radiographs should include anteroposterior, lateral and oblique views. Standing radiographs are ideal but often too painful. Good alternatives are stress radiographs with the forefoot in dorsiflexion and abduction.
On the radiographs, dislocation of the TMT joint is indicated by loss of in-line arrange- ment of the lateral margin of the first metatarsal base with the lateral edge of the medial cuneiform; loss of in-line arrangement of the medial margin of the second metatarsal base with the medial edge of the middle cuneiform in the weight-bearing AP view; and the presence of small avulsed fragments (‘fleck sign’), which are additional indications of ligamentous injury and probable joint disruption. A fleck sign seen on the AP radiograph is pathognomonic for a Lisfranc injury (present in 90 per cent of instances). It represents an avulsion fracture from either the second MT base or the medial cuneiform, due to forceful abduction of the forefoot that avulses the Lisfranc ligament between the base of the second MT and the medial cuneiform – as can be seen in this case. On the AP view, the distance between the first and second metatarsals should be less than 2–3 mm. A normal lateral radiographic view of the foot should show the superior border of the first MT base lining up with the superior border of the medial cuneiform. If the dorsal surface of the proximal second MT is higher than the dorsal surface of the middle cuneiform then this is indicative of an injury. On a medial 30-degree oblique view of the foot, the cuboid should align with the medial border of the fourth MT.
MRI is accurate for detecting traumatic injury of the Lisfranc ligament and for predicting Lisfranc joint complex instability. Finally, with an ankle block or intravenous sedation, stress the foot under fluoroscopic examination with pressure on the medial forefoot, pushing laterally while the hindfoot is pushed medially. An AP view of the TMT joints reveals any significant instability.
Non-surgical management should be limited to patients who do not have fractures, or who have fractures that are undisplaced and stable under stress. If the clinical evalua- tion indicates the probability of a mild or moderate sprain and the radiograph shows no diastasis, then immobilization is suggested. Note the anterior tibial tendon can block reduction of a lateral Lisfranc dislocation; similarly, the peroneus brevis tendon can block a medial dislocation reduction. Combined closed reduction and casting has no role in the treatment of unstable injuries. All injuries that are displaced and unstable require surgery. A displacement of more than 2 mm requires open reduction and internal fixation. All
Lisfranc injuries that cannot be reduced and be made to remain stable by closed means should undergo internal fixation.
KEY POINTS