Low-energy Lisfranc injuries in athletes are frequently subtle and can lead to disastrous long-term outcomes especially when diagnosis is delayed. This case describes a grade 2 injury by Nunley and Vertullo grading in a 39-year-old runner which was initially missed. There were several important lessons to be gained when assessing the tarsometatarsal joint complex such as obtaining comparison weight-bearing views and having a low threshold to proceed to advanced imaging.
Keywords: Lisfranc injury, midfoot sprain, non-operative management, running, grade 2
Low-energy tarsometatarsal joint (TMT) complex injuries are rare and notoriously difficult to diagnose. Delays in correct treatment often lead to poor outcomes with an increased risk of osteoarthritis, chronic pain and functional impairment. This case report describes a typical low-energy grade 2 injury to the TMT joint complex with subsequent initial misdiagnosis and delayed treatment.
A 39-year-old normally fit and well casual runner presented with right foot pain during a 100m sprint event at his child’s school athletic day. The ground was hard and slightly uneven, and he ran as fast as he could. Near the end of the race, as he stepped off his right midfoot, he felt his foot twist slightly and felt a painful pop. He was able to weight-bear for the first two hours before the pain and swelling became too severe. He was assessed at an urgent care centre the following morning.
He was unable to weight-bear. There was a significantly tender 2cm wide and 1cm long fixed firm swelling overlying his medial dorsal midfoot. There was also tenderness over the entire midfoot and 1st and 2nd metatarsal bases, as well as pain with the axial compression of the metatarsals. There was no bruising dorsally nor on the sole of his foot. There was normal passive ankle range of motion, but there was restriction actively. There was normal inversion and eversion. His foot was neurovascularly intact.
Initial non-weight bearing non-comparison x-rays (figure 2, A) showed a borderline displacement of 2mm between the first and second metatarsals, and subtle malalignment along the contour of the second metatarsal and medial side of the medial cuneiform. However, the images were reported by the radiologist to be normal.
The initial treating doctor placed him in a rigid boot and he was instructed to be non-weight bearing, with follow up planned a week later. On follow up he had improved significantly, and a midfoot sprain was thought to be more likely. He was instructed to walk freely out of the boot and was discharged with no further follow up.
10 weeks later, due to ongoing pain he was further reviewed at a sports clinic. His foot remained swollen. His foot posture was slightly cavus. He could not plantarflex while standing. He had laxity of his Lisfranc joint, with increased plantar dorsal grade movement of the first ray. He was tender over the base of the second metatarsal and over the Lisfranc ligament and had pain with midfoot stress.
A repeat x-ray (Figure 1, B and C), this time weightbearing with comparison views clearlyshowed diastasis of the Lisfranc ligament. MRI (Figure 2) confirmed injury with a partial tear involving both the interosseous and plantar aspects of the Lisfranc ligament, a sprain of the dorsal ligament and an undisplaced avulsion fracture at the plantar corner of the second metatarsal base. A small healed proximal intermediate cuneiform cortical fracture was also identified.
Other than Lisfranc injury, before imaging the differential diagnosis in this case included midtarsal joint sprain and stress fracture of the navicular and cuneiform. A tendinopathy seemed less likely due to the sudden onset of pain, but common tendinopathies of the midfoot are extensor and tibialis posterior tendinopathies. See Foot Pain Differential Diagnoses
The injury was assessed as grade 2 by Nunley and Vertullo grading
Due to the injury being missed he initially had no treatment. 10 weeks after injury when the correct diagnosis was made he was treated non-operatively with eight weeks in a rigid walking boot and custom moulded orthotic. On review two weeks after being out of the boot, but still using the orthotic he could walk pain-free but had intermittent paraesthesia over his midfoot, presumably due to injury of the deep peroneal nerves. He was gradually increasing his activities and was counselled about the risk of osteoarthritis.
The tarsometatarsal (TMT) joint complex is comprised of the five metatarsals, the three cuneiforms and the cuboid (figure 3, A). The Lisfranc ligament has an integral role in providing midfoot stability. It attaches from the medial cuneiform to the base of the 2nd metatarsal with its three segments outlined in Figure 3, B4.
When examining the injured midfoot, first note the ability to weight bear, then inspect for any midfoot swelling and plantar bruising. Next palpate the navicular, medial and intermediate cuneiforms, the bases of the five metatarsals and the area over the Lisfranc ligament between the 1st and 2nd metatarsal bases. Stability of the TMT joint complex is assessed through passive pronation and supination of the forefoot, looking for laxity and pain at the area of the Lisfranc ligament. The medial column can be stressed by passively dorsiflexing and abducting the forefoot.
Injuries to the tarsometatarsal joint complex are divided into high and low energy injuries. High-energy injuries are often the result of a motor vehicle crash and result in obvious fractures and dislocations of the TMT joints. Low energy injuries are normally seen in athletes and have been described to occur in two scenarios: plantarflexion injuries and abduction injuries. In the former, there is an axial compression force during plantarflexion, typically when a player steps or falls on the affected player’s heel. In abduction injuries the hindfoot is fixed and sudden abduction of the forefoot occurs. Rarely it can occur from simple running such as in this case.
There is a wide spectrum of injuries described affecting the Lisfranc joint, ranging from partial sprain with no displacement to a ruptured Lisfranc ligament with a wide diastasis. Nunley and Vertullo outlined a useful classification for subtle Lisfranc injuries. The classification uses the appearance on weightbearing x-ray and bone scan. Stage I injuries signifies a sprain with the distance between the 1st and 2nd metatarsals being normal, yet there is pain at the region of the Lisfranc ligament and a positive bone scan. Stage II injuries have a diastasis between the 1st and 2nd metatarsal of between 1 and 5mm on a weightbearing AP x-ray. Stage III injuries have a diastasis of greater than 5mm, and loss of arch height of the midfoot on lateral weight-bearing x-ray. Debate continues as to the best management for TMT injuries with there being no prospective randomised trials.
This case demonstrates several important lessons with regards to Lisfranc injuries. Low-energy Lisfranc injuries are notoriously difficult to diagnose. Delayed or inadequate treatment of such injuries frequently result in osteoarthritis, chronic pain and dysfunction1. X-rays are often normal or have very subtle findings leading to notoriously frequent misdiagnosis. Comparison weight-bearing views are critical, but this is not often possible soon after injury due to pain; this can be done after a few days of rest or by utilising local anaesthesia. X-ray findings are outlined in Table 1. The clinicians index of suspicion should be high and there should be a low threshold for CT, MRI, bone scan or manual stress radiographs under anaesthesia. MRI was performed in this case, and limited data show it has good correlation to operative findings.
|X-ray View||X-ray finding|
|Oblique||Discongruity along the contour of the medial base of the fourth and the medial aspect of the cuboid.|
|Lateral||Dorsal subluxation of the base of the metatarsals|
The initial x-rays showed very subtle signs of Lisfranc injury which were missed. The findings were displacement between the first and second metatarsals of 2mm, and subtle discongruity of the second metatarsal and medial cuneiform line. Follow-up weight bearing x-rays with comparison views were clearly abnormal with a displacement of 2.8mm compared to 1mm of the non-affected foot. His foot posture was slightly cavus, which may be a risk factor for Lisfranc injuries.
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