SLR - May 2021 - Henry Turcios

Evaluation of Two Types of Intramedullary Jones Fracture Fixation in a Cyclic and Ultimate Load Model

Reference: Willegger M, Benca E, Hirtler L, Kasparek MF, Bauer G, Zandieh S, Windhager R, Schuh R. Evaluation of Two Types of Intramedullary Jones Fracture Fixation in a Cyclic and Ultimate Load Model. J Orthop Res. 2020 Apr;38(4):911-917.

Level of Evidence: III, Prospective Comparative Case Study

Scientific Literature Review

Reviewed By: Henry Turcios, DPM
Residency Program: Roxborough Memorial Hospital – Philadelphia, PA

Podiatric Relevance: Jones fractures are well studied, routine injuries of the foot with a high incidence of symptomatic delayed union and prolonged immobilization when treated nonoperatively.  Intramedullary fixation has become the gold standard for athletes seeking a quick return to play or the general population seeking relatively early weightbearing. As such, various intramedullary specialty screws have emerged, and the podiatric surgeon is faced with choosing the most appropriate implant. This study compared the biomechanical behavior of an Arthrex Jones fracture specific screw (JFXS) with a conventional DePuy-Synthes cannulated headless compression screw (HCS).

Methods: Ten matched pairs of cadaveric fresh human foot specimen were obtained for this study. Prior to biomechanical testing, bone mineral density (BMD) of each specimen was performed via DEXA scans of the calcaneus and areal BMD measurements. An oscillating saw was used to create a transverse osteotomy at the metaphyseal–diaphyseal junction, then subsequently fixated using either an Arthrex Jones fracture specific solid partially-threaded titanium screw with a small low-profile head or a DePuy-Synthes conventional countersinkable cannulated partially threaded titanium screw. Partial weightbearing was simulated by loading each construct for 1,000 cycles, followed by load to failure testing. The biomechanical behavior of each fixated specimen was evaluated for angulation, stiffness, ultimate load, and modes of failure.

Results: When cyclically loaded, the stiffness property as measured by the slope of the load-displacement curve, there was no significant difference between fifth metatarsals fixed with the Jones fracture specific screw or the cannulated headless compression screw. Mean stiffness at 1,000 load cycles in the JFXS and HCS were 40.6 ± 7.5 and 40.3 ± 13.5?N/mm, respectively (p=0.928). All of the constructs in the JFXS group and nine of ten constructs in the HCS groups survived 1,000 cycles without suffering angulation greater than 10 degrees. Regarding ultimate load until failure, there was again no intergroup statistically significant difference. The most common modes of failure observed in the HCS were proximal screw head cut out and loosening of the screw head. In JFXS constructs metatarsal shaft fracture was the most observed mode of failure, as well as screw head cut out.

Conclusions: Biomechanical testing between the Arthrex Jones fracture specific screw (JFXS) and conventional DePuy-Synthes cannulated headless compression screw (HCS) ultimately showed equivalent ultimate loads and stiffness with cyclical loading. When provided the choice of implants between JFXS and HCS, it seems both are adequately robust options. 

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