The Effect of Peroneus Brevis Tendon Anatomy on the Stability of Fractures at the Fifth Metatarsal Base

Abstract

Objectives:Fractures of the fifth metatarsal base are not uncommon. Both fracture management and outcomes can differ greatly depending on fracture location. The purpose of the present study is to evaluate the influence of the peroneus brevis (PB) tendon on proximal fifth metatarsal fracture stability. We hypothesize that proximal fifth metatarsal fractures distal to the PB tendon footprint are inherently less stable than more proximal fractures. Methods: We utilized 5 matched pairs of fresh-frozen cadaveric specimens. We carefully exposed the 5th metatarsal and PB tendon. We measured the length of the PB insertion at the base of the fifth metatarsal with calipers. The PB and Achilles tendons were then whip-stitched proximally to facilitate loading. A custom leg holder was fabricated to allow loading and fluoroscopic evaluation. Two conditions were utilized for biomechanical testing; (1) a simulated fracture distal to the PB insertion (Jones equivalent) and (2) a simulated fracture within the footprint of the PB insertion (avulsion equivalent). All fractures were carefully created with a narrow osteotome. Following fracture creation, the plantar flexed foot was statically loaded through the Achilles and PB tendons. Oblique images with and without loading and digital measurements were performed to evaluate for fracture separation. We utilized a paired student T test and intraclass correlation coefficient (ICC) for all statistical analysis. Results: The average length of the PB footprint was 15.2 mm. Compared to fractures within the PB footprint, fractures distal to the PB tendon insertion demonstrated greater fracture widening following loading of the PB tendon. Fractures within the PB footprint widened 0.4 mm on loading ( Figure 1A to 1B) compared to 1.1 mm of widening in the fractures distal to the PB insertion ( Figure 1C to 1D). This difference was significant (p = 0.02). Intraobserver reliability for all radiographic measurements showed substantial agreement. Conclusion: Avulsion fractures at the base of the fifth metatarsal have much better healing potential than the socalled Jones fracture. Poor vascularity has been cited as a cause for poor healing potential following Jones fractures. The principal findings of this study demonstrate that proximal fifth metatarsal fractures distal to the PB insertion are significantly more unstable than more proximal fractures. In our study, the PB exerts a deforming force on the proximal fragment of fractures distal to the PB footprint. This deforming force was less pronounced in fractures within the PB footprint. Our findings help support the notion that a mechanical component may contribute to the poor healing potential of Jones fractures secondary to deformation exerted by the PB tendon. This would help explain why screw fixation is often recommended to address Jones fractures. Further research is needed to evaluate the biomechanics of these fractures.

Anatomic Characteristics of Tissues Attached to the Fifth Metatarsal Bone

“…It is conceivable that the morphologic characteristics of the bone may have been acquired after long-term mechanical stress due to age. Because the cadavers were preserved, biomechanical examination 24 could not be conducted. Another limitation was that the measurement in this study was made by only 1 examiner, however the intrarather reliability showed almost-perfect agreement.…”

“…16 However, risk factors for traction stress have not been fully elucidated, and it has been pointed out that traction stress may have an adverse effect on fracture incidence and healing. 24 If we could understand the characteristics of players with high traction stress and bending stress, it would be easier to identify players at high risk of Jones fractures.…”

Zone II and III fifth metatarsal fractures in athletes

“…Typically, an acute injury to the fifth metatarsal is a result of indirect force secondary to foot plantar-flexion and inversion while the base of the fifth metatarsal is tethered by significant attachments to the calcaneus by the lateral band of the plantar aponeurosis, peroneus tertius tendon to the metaphysis and the peroneus brevis to the tuberosity. Peroneus brevis tendon forces contribute to the development of the Jones fracture and create a deforming force resulting in fracture instability and possible contribution to nonunion [8]. Additionally, bony malalignment of the foot may predispose patients to fifth metatarsal fractures.…”

Peroneus brevis as source of instability in Jones fracture fixation

“…An early mobilization and return to competition is desired, but without compromising the stability of fracture fixation. Impaired healing response can be attributed to a compromised blood supply at the metadiaphyseal region [9,10], but mechanical instability may also play a detrimental role in Jones fracture healing [11][12][13]. It was postulated that early return to unrestricted sports activities might contribute to Level of evidence: Level II, controlled laboratory study Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00264-020-04581-2) contains supplementary material, which is available to authorized users.…”

“…Activation of the peroneus brevis during gait may potentially lead to displacement of the proximal fracture fragment in Zone II and III fractures, which are located distally to the PBT insertion. [1,11,18] Nevertheless, the role of the PBT as source of instability after Jones fracture fixation has been neglected so far. Early post-operative active mobilization may challenge the intramedullary stabilized Jones fracture by means of tensile forces which can lead to prolonged bone healing, or even result in early failure [11].…”