A 52 year old male presents to the ED with a right knee injury. He slipped while running, landing awkwardly on his right knee, with his foot caught behind him. He felt a “pop” and immediately had severe sharp right knee pain. He was unable to weight bear and states that his knee was swollen immediately afterwards. He denies any other injuries. He is otherwise healthy and is on no medications.
On exam, his vitals are within normal limits. There is obvious swelling of the right knee and has a palpable defect 2 cm above the patella which is extremely tender to palpation. He is unable to perform a straight leg raise. The remainder of the knee exam is non-contributory and he is neurovascularly intact.
He is clinically diagnosed with a quadriceps tendon rupture.
Quadriceps are the knee extensors, therefore rupture is most likely when the knee is flexed with simultaneous quadriceps contraction.1
-Age <40: Less common. Often occurs in athletes, particularly those who do not stretch activity, as a result of jumping and landing with the knee flexed. Patellar tendon rupture is more common in this age group
-Age >40: More common. Weaker tendons rupture more easily, so a fall onto a knee, or trying to prevent a fall onto the knees is typical.
Risk factors,2, 3
-Age (more common in patients >40 years of age)
-Male gender
-Type 2 Diabetes
-Renal disease
-Medications associated with tendon rupture (fluoroquinolones)
-Typically a clinical diagnosis, and is one of the “cannot miss diagnosis” in acute knee injuries.
-There is often a palpable defect ~2 cm above the patella where the tendon has been torn.
-Patients with a complete tear will be unable to perform a straight leg raise.
-Patients with a partial tear are unable to extend their knee against resistance – the ability to forcibly extend the knee against resistance is a critical part of the knee exam.
Investigations
XRays:
-May show a patella that is below expected anatomic position (patella baja). Of note, patella alta (or high-riding patella) can be a sign of patellar tendon rupture.
Ultrasound
-Can be a useful modality if diagnosis is uncertain. Often primary investigation available in the ED to supplement clinical exam findings.
MRI
-Best diagnostic modality, but cannot be obtained in the ED – this is typically a modality ordered by surgeons for surgical planning
ABOVE: Normal Knee XRay (left) and low-riding patella (right). The Insall Salvatti Index is the ratio of the patellar tendon length (red line) to the patellar length (yellow line). Normal is 0.8-1.2. Source: https://radiopaedia.org/articles/insall-salvati-ratio
Management
-Early surgical repair is important to maximize recovery, especially in complete tears. The distal tendon is avascular, so it will not heal well non-operatively.1
-Non-operative treatment (RICE, splinting, non-weightbearing) may be an option in partial tears or in patients with poor baseline mobility.
-Either way, orthopedic surgery should be consulted within a timely matter, usually within a week, to guide management. As time goes on difficulty of repair increases, as does probability of failed repair. The ED physician should provide adequate analgesia as needed, immobilize the knee, and advise non-weightbearing while the patient is in the ED.
Back to our patient
Orthopedic surgery is contacted, and a plan is made to see the patient in clinic the following day to plan surgical repair. The patient’s knee is immobilized in extension, and an outpatient MRI is ordered. The patient undergoes surgical repair later that week.
All case histories are illustrative and not based on any individual
Case Report
A 32 year old male presents to a rural Emergency Department with a complaint of traumatic left foot pain. He was playing recreational football this evening. While crouching, the patient was tackled by another player who landed on his hyper-plantar flexed left foot from behind. The patient had immediate onset of pain in the middle of his foot and was unable to weight-bear.
On physical examination, you notice significant bruising and swelling of the mid-foot. There is tenderness to the medial mid-foot specifically at the 1st-2nd tarsal-metatarsal articulations. X-rays of the foot appear normal. You are concerned about the possibility of a ligamentous Lisfranc injury.
Lisfranc injuries are those that involve the tarsal-metatarsal joints. A spectrum of injury exists from ligamentous to fracture-dislocation. Up to 20% – 40% of injuries to the Lisfranc complex are missed in the Emergency Department. Unrecognized and untreated injuries can lead to long-term instability through the midfoot. As this region of the foot is responsible for a significant load during weight bearing, instability can accelerate degenerative changes in the foot resulting in chronic pain and disability
The injury is named after Jacques Lisfranc de St. Martin, a French surgeon and gynecologist performed forefoot amputations at the tarsometatarsal joint on cavalrymen, during the 1815 Napoleonic wars. Although he didn’t specifically describe the injury, it has since been recognised in equestrians and occurring as a result of a trapped plantar flexed foot in the stirrup during a fall.
Other mechanisms have been described including high velocity injuries (sports injuries, foot on brake pedal MVA) and low velocity injuries (Stepping off a curb awkwardly). Low velocity injuries are more likely to be missed than high velocity injuries.
The Lisfranc ligament complex is comprised of 3 ligaments. The dorsal (red), interosseous (blue) and the plantar (green) Lisfranc ligaments. The Interosseous ligament is the largest and the dorsal ligament is the smallest.
The first and second rays have unique ligamentous anatomy wherein no intermetatarsal ligaments exist, but extreme strength is imparted by dorsal, interosseous, and plantar bundles of ligament binding the lateral aspect of the medial cuneiform bone with the medial head of the second metatarsal bone—the Lisfranc ligamentous complex. Only the dorsal and plantar Lisfranc ligaments are accessible to ultrasound.
PoCUS of the Lisfranc joint and dorsal lisfranc ligament (DLL)
Lisfranc injuries are one of the most commonly missed orthopaedic injuries in the Emergency Department. Normal X-rays are often falsely reassuring to providers and patients are discharged with a diagnosis of “soft-tissue injury”. These injuries result in midfoot instability and often require definitive surgical management.
PoCUS has been studied as a method of early detection of these injuries. Specifically, assessment of the dorsal lisfranc ligament (DLL) between the second metatarsal (M2) and the medial cuneiform(C1). PoCUS also has the advantages of being significantly cheaper and more accessible than CT and MRI. Further investigation is needed to validate this method of diagnosis, however ultrasound findings of a disrupted DLL and a widened C1-M2 interval compared to the contralateral side may increase your suspicion when pre-test probability is high.
Technique
Linear probe-MSK setting starting at a depth of 2cm
Place probe in transverse orientation over the proximal aspect of the 1st-2nd metatarsals with the probe indicator to the patient’s right
Slide the transducer proximally until you locate the medial cuneiform and identify the junction between the medial cuneiform (C1) and the 2nd metatarsal (M2)
The medial cuneiform will have an angulated contour appearance in contrast to the round appearance of the metatarsals
Sweep to identify the dorsal lisfranc ligament (DLL)
Assess the DLL for a fibrillar pattern, normal echogenicity and contour
Measure the DLL width and the C1-M2 distance compare to the contralateral side
Measure the C1-M2 distance with weightbearing (if patient tolerates) to compare
Apply colour doppler to assess for hyperemia
PoCUS Findings
Medial Cuneiform (C1), 2nd Metatarsal (M2)
Note the angulated contour of C1 and the smooth contour of M2 – this sectional plane is important when locating the dorsal Lisfranc ligament. The ligament appears hypoechoic with a fibrillar pattern, typical for other ligaments more commonly visualized with PoCUS e.g MCL, ATFL.
1. Normal image – Arrows = dorsal Lisfranc ligament
2. Normal Clip and annotated image. Note how the dorsalis pedis a. frequently overlies the dorsal Lisfranc ligament (yellow lines)
3. Normal clip. Note how there is no separation of C1/M2 while counterstressing the 1st and 2nd rays
4. Thickened, convex contour
5. DLL disrupted, wide joint space
6. Widening C1-M2 with weightbearing
Video Case
Limitations
Anisotropy – Irregular dorsal contour of foot can result in difficult perpendicular imaging of doral Lisfranc ligament. Stand-off gel pad may help.
History of prior trauma – chronic Lisfranc injury may result in joint widening
Bilateral injuries – inability to compare sides to judge joint space widening
Application
Standard foot radiographs should be performed in all cases of suspicion for Lisfranc Injury. Weight bearing radiographs should also be performed if tolerated (the ability to fully weight bear is often limited in the acute setting)
HIgh velocity injuries result in significant soft tissue swelling, and although non-weight bearing radiographs may not be diagnostic, the index of suspicion for Lisfranc injury will be high. Immobilization +/- early CT and follow up with foot and ankle specialist is recommended. For these, high pretest probability injuries, PoCUS findings are unlikely to change management significantly. A clear Lisfranc ligament rupture on PoCUS may trigger a request for CT/MRI earlier than otherwise considered. In most cases advanced imaging and a clear diagnosis is not usually possible until the swelling has subsided.
In low velocity injuries, soft tissue swelling is less pronounced. in the acute presentation the ability to perform weight bearing radiographs is limited by pain. Index of suspicion for Lisfranc injury may be low-moderate and the decision to immobilize and refer for specialist follow up can be difficult. While there is limited published evidence for PoCUS test characteristics in Lisfranc injury, a positive scan (injury + disrupted ligament / widening of C1/M2) is likely to be highly specific. Patients with positive PoCUS findings should therefore be immobilized and referred for specialist follow up. In those with negative or inconclusive findings, management and disposition will depend on degree of clinical suspicion and correlated with radiographic findings.
In summary, PoCUS provides a useful additional piece of information that can be plugged into a bayesian diagnostic pathway. What is the pretest probability of a particular diagnosis? After reviewing radiographs and performing PoCUS is the diagnosis more or less likely?
More evidence is required to fully understand the test characteristics of PoCUS for Lisfranc injury. Would the addition of plantar views improve sensitivity?
Although the performing the scan takes only a few minutes, it is quite technically challenging for the novice. As with all MSK PoCUS, repeated practice in numerous patient presentations will increase operator speed and accuracy.
Finally, although we still need the cavalry, PoCUS can help us decide which regiment and how quickly we need them!
References
Mayich DJ, Mayich MS, Daniels TR. Effective detection and management of low-velocity Lisfranc injuries in the emergency setting: principles for a subtle and commonly missed entity. Can Fam Physician. 2012;58(11):1199-e625. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498011
Woodward, S., Jacobson, J.A., Femino, J.E., Morag, Y., Fessell, D.P. and Dong, Q. (2009), Sonographic Evaluation of Lisfranc Ligament Injuries. Journal of Ultrasound in Medicine, 28: 351-357.
Döring, S., Provyn, S., Marcelis, S., Shahabpour, M., Boulet, C., de Mey, J., De Smet, A., De Maeseneer, M. (2018). Ankle and midfoot ligaments: Ultrasound with anatomical correlation: A review. Eur J Radiol.107:216-226.
Kaicker, J., Zajac, M., Shergill, R., & Choudur, H. N. (2016). Ultrasound appearance of the normal Lisfranc ligament. Emergency Radiology, 23(6), 609-614.
DeLuca, M.K., Walrod, B. and Boucher, L.C. (2020). Ultrasound as a Diagnostic Tool in the Assessment of Lisfranc Joint Injuries. J Ultrasound Med, 39: 579-587.
Marshall, J., Graves, N.C., Rettedal, D.D., Frush, K., Vardaxis. V. (2013). Ultrasound Assessment of Bilateral Symmetry in Dorsal Lisfranc Ligament. The Journal of Foot and Ankle Surgery, 52(3): 319-323.
Rettedal, D.D., Graves, N.C., Marshall, J.J. et al. Reliability of ultrasound imaging in the assessment of the dorsal Lisfranc ligament. J Foot Ankle Res 6, 7 (2013).
