Category: Midfoot/Forefoot Introduction/Purpose: Proximal fifth metatarsal fractures (PFMF) are among the most common fractures of the foot, and may be subdivided into tuberosity avulsion fracture, Jones fracture, and proximal diaphyseal fracture. However, for Jones fractures and proximal diaphyseal fractures optimal treatment is still debated in literature. The Torg criteria are used in deciding to treat surgically or conservative, whereby Torg type I and II indicates conservative treatment, and type III indicates surgical treatment. Yet failure rates of both management options vary and derive from small study groups. The aim of this study was to compare failure rates after surgical- and conservative treatment of Jones fractures and proximal diaphyseal fractures, to evaluate the incidence of treatment failure, and to assess factors associated with healing difficulties of PFMF. Methods: A total of 1,133 adult patients that were diagnosed and treated for PFMF between 2005 and 2015 in a tertiary care foot and ankle referral center were included. Retrospective chart review recorded patient demographics, suspected risk factors for impaired healing of PFMF (rheumatoid arthritis, diabetes mellitus, osteoporosis, nutritional and hormonal disorders, foot deformities, (neuropathic) arthropathy of the foot and/or ankle and peripheral neuropathy of the lower extremity), and treatment indication. Multivariable logistic regression analysis was used to determine factors associated with healing difficulties. Propensity score matching was used to minimize selection bias between treatments in Jones fractures and proximal diaphyseal fractures. Results: In total, 489(43.2%) patients were diagnosed with a tuberosity avulsion fracture, 391(34.5%) patients with a Jones fracture and 253(22.3%) patients with a proximal diaphyseal fracture. In the tuberosity fracture group, a nonunion was found in 5.3%(25/473) of the patients treated conservatively and in 0%(0/16) treated operatively. For the Jones fractures and proximal diaphyseal fractures the non-union rate for conservative treatment was 10%(35/337) and 5.9%(14/238), and for surgical treatment 11%(6/54) and 0%(0/15), respectively. No independent risk factors for complicating the healing process of PFMF were identified. With propensity score matching, 37 patients treated operatively were matched to 37 patients undergoing conservative treatment. The risk for a nonunion was lower in the operative group compared to the conservative treatment group (relative risk 0.8, P=0.006). Conclusion: In this propensity-matched cohort, surgical treatment for Jones fractures and proximal diaphyseal fractures were associated with better fracture healing compared to conservative treatment. In addition, no factors were found to be associated with healing difficulties of proximal fifth metatarsal fractures.

The insertions of the PB and PF are involved in a significant percentage of proximal fifth metatarsal fractures, which may indicate a relation of the insertions with the fracture mechanism of these fractures.

Category: Midfoot/Forefoot Introduction/Purpose: Jones fractures are among the most common fractures in the foot, mainly occurring in athletes. In order to facilitate return to sport and good functional outcomes, management with intramedullary screw fixation is often recommended [1-3]. While optimal screw dimension and location parameters have varied in the literature, it is clear that maximizing pull-out strength, providing adequate compression across the fracture, and minimizing irritation to surrounding soft tissue structures are of paramount importance. The aim of this study was to improve our guidelines regarding optimal insertion trajectory and screw parameters of Jones fractures by more accurately defining the bony and soft tissue anatomy of the fifth metatarsal bone and its intramedullary canal. Methods: 21 fifth metatarsal bones were harvested from cadaveric feet. Three reference screws were placed on each bone for registration. 3D CT model of each bone with outer cortex, intramedullary canal and the articular cortex was created (Figure A). The insertions of the PB and PF and the reference screws of each bone were carefully digitized and mapped onto corresponding 3D model. The anatomic insertions and the surface areas were determined. Based on the length of the bone, the shape of the intramedullary canal, and the diameter of the canal at its narrowest point, the perceived ideal screw and placement was then modulated for each bone model. Also, the fracture zone where Jones fractures occur was determined (Figure B) based on Lawrence/Botte classification [1]. Screw and thread length were calculated in this position, and the impact of screw placement on the insertion sites of both the PB and PF were recorded. Results: The mean length of the bones was 74.4±3.6 mm, with the narrowest diameter of the intramedullary canal being 4.3±0.7 mm. Ideal screw position was identified as parallel to the cuboid and coaxial with the intramedullary cortex; this placement, however, was found to partially sacrifice the PB and PF insertions in 62% (13/21) and 33% (7/21) of cases, respectively; with an average of 1.6±0.8 mm of the PB and 1.3±0.8 mm of the PF insertion. The mean ideal screw length in this position was found to be 47.8±5.8 mm, with a minimal thread length of 28±6.8 mm and a minimal diameter of 4.5 mm (Figure B). The ratio of screw length to the total bone length was 0.64 (range 0.50-0.72). Conclusion: In order to maximize compression and pull-out strength and minimize sacrifice of the adjacent soft tissue structures during screw placement, Jones fractures should be fixed with hardware parallel to the cuboid and collinear with the intramedullary cortex—which mitigates but does not avoid injury to the peroneal tendon and plantar fascia. Average optimal length of the screw should be 64% of the length of the bone, with a minimum 4.5 mm diameter and 50% thread length (relative to bone length). Given variability in metatarsal anatomy, screw choice should be tailored to the individual.

Category: Midfoot/Forefoot Introduction/Purpose: Proximal fifth metatarsal fractures (PFMF) are among the most common fractures in the foot and can be categorized into three fracture zones [1]. To investigate the fracture mechanism of PFMF in different zones, a better understanding of the anatomy of the bone and its surrounding soft tissues is required. Both the plantar fascia (PF) and the peroneus brevis (PB) tendon insertions are at the base of the fifth metatarsal, and may contribute to the pathophysiology of PFMF. However, the role of the PB and PF insertions in the pathogenesis of PFMF remains unclear. The purpose of this study was to accurately define the footprint of the PB and PF insertions of the base of the 5th metatarsal in relation to the different zones of PFMF. Methods: 21 cadaveric fifth metatarsal bones were harvested from cadaveric feet. All bones were freed of any remaining soft tissue adherence, except for the PB and the PF insertions. Three reference screws with a diameter of 1 mm were placed and secured on each bone with 2 screws distally and 1 screw proximally for registration. All bones were CT scanned to create a 3D bone reconstruction. Next, the insertions of the PB and PF and the reference screws of each bone were digitized and then mapped to its corresponding 3D bone model. In order to describe the three different fracture zones of the 5th metatarsal, an established coordinate system was made for each bone to simulate separate fracture zones (Figure a) based on Lawrence guideline [1]. The shape, location and surface areas of both insertions and their relation to the different fractures zones were determined (Figure b). Results: The insertion of the PB was oval shaped and located on the dorsal side of the base, with a mean surface area of 88.1 ± 46.4 mm2. The PF was oval shaped and situated around the tip of tuberosity, with a mean surface area of 150.7±53.5 mm2. The PB insertion was present in zone 1 fractures in 100% (21/21) of the 5th metatarsal models and 29% (6/21) of the models for zone 2 fractures. The PF insertion was involved in 100% (21/21) of the 5th metatarsal models for zone 1 fractures and 43% (9/21) of the models for zone 2 fractures. Conclusion: Results of this study demonstrate that the insertion of both the PB and PF are involved in all zone 1 PFMF and a significant percentage of zone 2 PFMF. The location of tendon insertions affect the forces exerted on the bone, which may indicate a relation of the insertions of both the PB and the PF with the fracture mechanism of many zone 1 and 2 PFMF. Moreover, in the treatment of these fractures, care should be taken to maintain or restore the anatomy of these insertions to maximize functional outcomes.

Objectives: Patients with Jones fractures (JF) frequently undergo operative management with intramedullary screw fixation. Screw insertion through the base of the fifth metatarsal potentially compromises attachment points of the plantar fascia (PF) and peroneal brevis tendon (PB), and appropriate screw length and diameter remains controversial. The aim of this study was to define the anatomy of the fifth metatarsal bone using CT modeling in order to provide better guidance regarding optimized screw insertion point, screw length, diameter, and thread length and, moreover, to give better insight in the possible compromise of the PB and PF when placing a screw. Methods: Following IRB approval, 21 cadaveric fifth metatarsal bones were harvested. Three reference screws (1mm diameter) were placed and secured on each bone, with 2 screws distally and 1 screw proximally, to act as a geographic register. All bones were CT scanned to create 3D reconstructions using modeling software (Rhinoceros, v5.0). The outer cortex, intramedullary canal and articular cortex of each bone were identified. Using a digitizer (MircoScribe, G2LX), the PB and PF insertions, alongside the reference screws, were mapped onto the corresponding specimen. The total length of the bone, the shape and diameter at the narrowest point of the intramedullary canal were also measured.. Optimal screw diameter and length were calculated in this position, and the impact of screw placement on the insertion sites of both the PB and PF was recorded. Results: The mean length of the bones was 74 ± 3.6mm, with the narrowest diameter of the intramedullary canal being 4.3 ± 0.7 mm. Ideal screw position was identified as parallel to the cuboid and coaxial with the intramedullary cortex, partially sacrificing the PB and PF insertions in 62% (13/21) and 33% (7/21)of specimens respectively, with an average sacrified area of 1.6 ± 0.8 mm of the PB and 1.3 ± 0.8 mm of the PF insertion. The ideal screw length was 48 ± 5.8 mm, with a minimal thread length of 28 ± 6.8 mm and a minimal diameter of 4.5 mm. The screw length:total bone length ratio was 0.64 (range .050-0.72). Conclusion: To maximize compression and pull-out strength, as well as minimize destruction of soft tissue insertions during screw placement for the treatment of JF, screws should be placed parallel to the cuboid and collinear with the intramedullary cortex—mitigating but not avoiding injury to the PB and PF. Average optimal length of the screw should cover 64% of the length of the bone, with a minimum 4.5 mm diameter and 50% thread length. Given variability in anatomy, however, screw choice should be tailored to the individual. Operative treatment of JF, a common foot injury, represent one of the more controversial surgical techniques in foot care today. Improving anatomic understanding of the implications of screw insertion will be paramount to maximizing functional outcomes.