SLR - October 2018 - Eric Krznaric

A Biomechanical Comparison of Fifth Metatarsal Jones Fracture Fixation Methods

Reference: Duplantier, N. L., Mitchell, R. J., Zambrano, S., Stone, A. C., Delgado, D. A., Lambert, B. S., Varner, K. E. (2018). A Biomechanical Comparison of Fifth Metatarsal Jones Fracture Fixation Methods. The American Journal of Sports Medicine, 46(5), 1220–1227.

Reviewed By: Eric Krznaric, DPM
Residency Program: Northwest Medical Center, Margate, FL

Podiatric Relevance:
When evaluating a patient for treatment, it is important to consider the patient's expectations and needs for his or her particular lifestyle. Elite athletes have strong motivations to return to their respective activity as soon as possible. This has led physicians to explore more aggressive treatment options at earlier stages. The Jones fracture has historically been a difficult injury to treat due to complications in healing potential. Athletes who have this injury typically undergo surgery to avoid further complications or delays down the road. This cadaveric study explores mechanical failure rates of two different hardware constructs: intramedullary screw fixation and lateral plantar plating.

Methods: Twelve pairs of male cadaver feet with a mean age of 57 years were separated into either a plate fixation or screw fixation group to conduct comparative testing. An osteotomy with a microsagittal saw was created to simulate a Jones fracture in bilateral fifth metatarsals approximately 2.5 cm distal from the tuberosity. The plate group underwent fixation with a 3.0 mm 4-hole low-profile titanium plate placed plantar-laterally with three locking screws and one nonlocking eccentric compression screw. The screw group had fixation with a 40 or 45 mm, 5.5 mm partially threaded solid titanium intramedullary screw. After fixation, a cyclic cantilever failure testing was conducted to assess mechanical stability. Loading forces were applied using a cyclic cantilever, increasing by 22 N increments per 10 cycles, until each specimen experienced mechanical failure of implant or bone gapping greater than 1 mm (fracture failure). Failure mode, number of cycles to failure, peak failure load, gap width at the last mutual prefailure loading and video data were recorded. Paired 2-tailed t test was used to compare groups.

Results: When comparing the two groups, the plate fixation group experienced significantly higher cycles to failure and peak load failure, respectively, as compared to the screw fixation (63.9 vs. 37.3, P=.01), (159.2 N vs. 96.5 N, P=.01). The plate group also showed a significantly lower gap width in the bone (0.0 mm vs. 3.2, P=.01). The gap width analysis the first round of 10 cycles showed that 40 percent of the screw group failed while none in the plate group failed, and by the third round, all screws had failed while only one plate had failed (according to 1 mm gap increase criteria).

Conclusions: In athletes, early return to activity is associated with increased risk of failure in Jones fractures and thus contributing to healing problems. This study has shown that when compared with intramedullary screw fixation, plantar-lateral plating allowed for significantly greater cycles to failure and peak load before failure, as well as less gap width. This has clinical importance when evaluating primary and revisional Jones fracture treatments. Some limitations included the in vitro testing and lack of variance in stresses applied. A prospective randomized control trial would help explore prevalence in different sports.

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