Description
Objective
Currently, there is no accepted protocol to assess the Lisfranc joint with weight-bearing CT. This study introduces a simple, anatomic approach of measuring joint stability in cases of acute, subtle Lisfranc injury.
Background
Injuries to the tarsometatarsal (TMT) region, also known as Lisfranc injuries, are commonly overrepresented in athletes (1). Without accurate diagnosis and treatment, these injuries can lead to midfoot instability and arthritis, potentially having career-ending consequences (2). Diagnosing subtle Lisfranc injuries without gross bone separation can be challenging. In such cases, it is recommended to employ a dynamic imaging modality that enables for weight-bearing assessment. However, traditional weight-bearing radiography has relatively low spatial resolution resulting in variable sensitivity (3). Consequently, the recent introduction of weight-bearing computed tomography (CT) has gained interest due to its three-dimensional visualization of anatomy and its capability to detect subtle fractures and misalignments.
Material & Method
•Inclusion criteria: Acute, unilateral Lisfranc injury with intra-articular fractures and/or avulsion fractures in the TMT 1-3 area without signs of dislocation detected on non-weight-bearing CT.
•Lisfranc joint evaluation: bilateral, single stance, weight-bearing CT scans (RAX, Siemens) within four weeks after the injury occurred.
•35 patients (average age 37, range 21-64) with a total of 110 CT images were analyzed.
•Measurements were done by two independent orthopedic surgeons and tested for agreement using the intraclass correlation coefficient (ICC) with a two-way random effects model.
•Method of measurement: The joint space between the medial cuneiform and the second metatarsal (C1-M2) represents the intraosseous Lisfranc ligament, measured in the coronal plane (images).
•The injury was considered unstable if the C1-M2 distance measured above 2 mm compared to the healthy side.
•Unstable injuries were tested for confirmation with a perioperative stress-test and stabilized with a Homerun screw.
•Stable injuries were treated 6-12 weeks with a walker-boot allowing weightbearing as tolerated and re-tested with weightbearing CT after 12 weeks.
Results
•ICC: excellent inter-rater agreement (0.96, 95% CI 0.89 - 0.98).
•The average C1-M2 distance in healthy feet measured 3,5 mm (± 0.8 mm).
•7 patients were interpreted as unstable with an average of 2.6 mm difference between the injured and health sides.
•Instability was confirmed perioperatively in all seven patients with a fluoroscopic stress-test.
•28 patients, who were deemed stable, exhibited an average of 0.7 mm (± 0.8 mm) difference between the injured and health sides.
•All stable injuries showed no signs of increased C1-M2 diastasis above 0,5 mm at the 12-week follow-up.
Conclusion
In a clinical setting, the use of weight-bearing CT for evaluating Lisfranc joint stability is showing encouraging results. Our method, which involves measuring the C1-M2 distance in the coronal plane, represents an easy, reliable, and reproducible approach.
References:
1: Nunley et al. Classification, investigation, and management of midfoot sprains; Lisfranc injuries in the athlete. Am J Sports Med. 2002.
2: Dubois-Ferriére et al. Clinical outcomes and development of symptomatic osteoarthritis 2 to 24 years after surgical treatment of tarsometatarsal joint complex injuries. J Bone Joint Surg Am. 2016
3: Rankine et al.The diagnostic accuracy of radiographs in Lisfranc injury and the potential value of a craniocaudal projection. Am J Roentgenol. 2012.
