Lisfranc injuries: assessment, diagnosis and management

Universal optimal design in the vertebrate limb pattern and lessons for bioinspired design

This paper broadly summarizes the variation of design features found in vertebrate limbs and analyses the resultant versatility and multifunctionality in order to make recommendations for bioinspired robotics. The vertebrate limb pattern (e.g. shoulder, elbow, wrist and digits) has been proven to be very successful in many different applications in the animal kingdom. However, the actual level of optimality of the limb for each animal application is not clear because for some cases (e.g. whale flippers and bird wings), the basic skeletal layout is assumed to be highly constrained by evolutionary ancestry. This paper addresses this important and fundamental question of optimality by analysing six limbs with contrasting functions: human arm, whale flipper, bird wing, human leg, feline hindlimb and frog hindlimb. A central finding of this study is that the vertebrate limb pattern is highly versatile and optimal not just for arms and legs but also for flippers and wings. One key design feature of the vertebrate limb pattern is that of networks of segmented bones that enable smooth morphing of shapes as well as multifunctioning structures. Another key design feature is that of linkage mechanisms that fine-tune motions and mechanical advantage. A total of 52 biomechanical design features of the vertebrate limb are identified and tabulated for these applications. These tables can be a helpful reference for designers of bioinspired robotic and prosthetic limbs. The vertebrate limb has significant potential for the bioinspired design of robotic and prosthetic limbs, especially because of progress in the development of soft actuators.

Persistent instability in pure ligamentous Lisfranc joint injuries

INTRODUCTION

Lisfranc injuries refer to a specific group of injuries which lead to instability of the tarsalmetatarsal joint. Our hypothesis is that persistent instability is permanent and asymptomatic in subtle unstable injuries of the medial column which have been fixed percutaneously.

OBJECTIVE

To describe the persistent instability of pure ligamentous Lisfranc joint injuries treated with anatomic reduction and percutaneous screws fixation by comparative radiographs of both feet.

MATERIALS AND METHODS

Between 2014 and 2018, 14 patients diagnosed with subtle unstable Lisfranc injury were evaluated. Indications for surgery included widening (diastasis) greater than 2mm between the first and second metatarsal bases, and subluxation greater than 1mm of a metatarsal base from its respective tarsal bone.

RESULTS

Persistent instability was found on the stress radiographs of 11 patients (78.57% 95% CI: 48.60-95.07%) but without clinical connotations. The average AOFAS score evaluated at 18 months post-operatively was of 97.14 (SD±4.68) points. The median follow-up was 24 (RIQ: 18-24) months. In all patients, anatomical reduction on radiographs was evident.

CONCLUSION

We observed a persistent instability of the Lisfranc joint, without clinical connotations. Subtle unstable Lisfranc injuries treated with percutaneous screw fixation have a good clinical and functional outcome.

LEVEL OF EVIDENCE

IV.