565177
research-article2014
FAIXXX10.1177/1071100714565177Foot & Ankle InternationalMorris et al
Article
The Effect of Peroneus Brevis Tendon Anatomy on the Stability of Fractures at the Fifth Metatarsal Base
Foot & Ankle International® 1–6 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1071100714565177 fai.sagepub.com
Parisa M. Morris, MD1, Annie G. Francois, MD2, Randall E. Marcus, MD3, and Lutul D. Farrow, MD4
Abstract Background: Nonunion of classic Jones fractures has typically been attributed to the precarious vascular anatomy of the proximal fifth metatarsal. Despite this theory, the operative treatment of these fractures utilizes biomechanical solutions. The purpose of the present study was to evaluate the influence of the peroneus brevis (PB) tendon on the stability of fractures of the proximal fifth metatarsal. Methods: We utilized 5 matched pairs (10 specimens) of fresh-frozen cadaveric specimens. We used 2 loading conditions: (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). Following the creation of the fracture, each lower extremity was statically loaded through the Achilles and PB tendons. Our primary outcome measure was the degree of fracture diastasis with loading of the PB. Anteroposterior images with and without loading were obtained to evaluate fracture separation. We utilized a paired Student t test and the intraclass correlation coefficient (ICC) for all statistical analyses. Results: The average length of the PB footprint was 15.2 mm. The simulated Jones fractures demonstrated greater fracture widening following loading of the PB tendon compared to the simulated avulsion fractures. The simulated avulsion fractures widened 0.4 mm on loading compared to 1.1 mm of widening in the simulated Jones fractures (P = .02). Intraobserver reliability for all radiographic measurements showed substantial agreement (ICC = 0.91). Conclusion: The PB exerted a deforming force on the proximal fragment of simulated Jones fractures. This deforming force was less pronounced in the simulated avulsion fractures. The principal findings of this study were that proximal fifth metatarsal fractures distal to the PB insertion were significantly more unstable than more proximal fractures. Clinical Relevance: 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. Keywords: Jones fracture, nonunion, avulsion fracture, peroneus brevis, metatarsal Fractures of the proximal fifth metatarsal were first described by Sir Robert Jones in 1902 after he personally sustained the injury that now bears his name.6 Since that time, there have been differing definitions of the Jones fracture and wide variability in its recommended treatment as well as outcomes.1,8,22 As explained by Lawrence and Botte9 in 1993, proximal fifth metatarsal fractures can be divided into 3 groups: avulsion fractures of the tuberosity, meta-diaphyseal fractures, and diaphyseal fractures. The classic Jones fracture is a meta-diaphyseal fracture that is generally transverse in orientation and exits medially at the fourth to fifth intermetatarsal region.4 These fractures are not to be confused with fifth metatarsal avulsion fractures, which occur more proximally and typically involve the fifth metatarsal-cuboid articulation. Avulsion fractures occur in the inverted, plantarflexed foot and may be avulsed by the lateral cord of the plantar aponeurosis.17 Avulsion fractures tend to heal
reliably with nonoperative treatment.5,23,24 Conversely, the Jones fracture is associated with a relatively high rate of delayed union and nonunion when treated in a similar fashion, a result often attributed to a poor blood supply.2,7,10,11,18,20,21 The subsequent morbidity from a nonunion 1
Canyon Orthopaedic Surgeons, Avondale, Arizona, USA Department of Orthopaedic Surgery, University of Arizona College of Medicine, Tucson, Arizona, USA 3 Department of Orthopaedic Surgery, University Hospitals Case Medical Center, Cleveland, Ohio, USA 4 Orthopaedic and Rheumatologic Institute, Cleveland Clinic, Garfield Heights, Ohio, USA 2
Corresponding Author: Lutul D. Farrow, MD, Cleveland Clinic Lerner College of Medicine, Cleveland Clinic Sports Health Center, 5555 Transportation Boulevard, Garfield Heights, OH 44125, USA Email: [email protected]
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
2
Foot & Ankle International
can be especially devastating to high-level athletes who desire to return to sport as soon as possible. Consequently, many authors advise surgical fixation of these fractures in active individuals and athletes utilizing intramedullary screw fixation.13,15 When nonoperative treatment is undertaken, however, inadequate immobilization is associated with poorer outcomes.11 This perhaps suggests that biomechanical as well as biological factors contribute to delayed union and nonunion in these fractures.19,20 There have been a few studies that have evaluated various biomechanical aspects of fifth metatarsal base fractures.16,17 Moshirfar et al12 evaluated the biomechanical strength of 2 methods of screw fixation of fifth metatarsal base fractures. However, no study, to our knowledge, has ever investigated the peroneus brevis (PB) as a deforming force on proximal fifth metatarsal fractures in a cadaveric model. The present study aimed to evaluate the mechanical effect of the PB on fifth metatarsal avulsion and metadiaphyseal fractures, investigating the tendon as a source of biomechanical instability. Our primary outcome measure was to evaluate the magnitude (in millimeters) of fracture displacement caused by loading of the PB tendon. We hypothesized that loading of the PB tendon would cause more diastasis of meta-diaphyseal fractures of the fifth metatarsal compared to its avulsion fracture counterpart.
Figure 1. Dissection at the base of the fifth metatarsal. Radiographic marker (arrow) at the base of the fifth metatarsal (MTT). Site of osteotomy (arrowhead) at the distal aspect of the peroneus brevis (PB) insertion.
Materials and Methods We utilized 5 matched pairs of fresh-frozen below-knee cadaveric specimens (10 total specimens). All specimens were obtained from the Life Legacy Foundation (Tucson, Arizona). A human tissue agreement was signed through the Life Legacy Foundation. Each specimen was thawed overnight to room temperature. We then carefully dissected each specimen to expose the fifth metatarsal base, the PB myotendinous unit, and the Achilles tendon (Figure 1). The Achilles tendon was cut approximately 10 cm proximal to its calcaneal insertion, and modified Krakow stitches were placed using No. 5 FiberWire (Arthrex, Naples, Florida), leaving 2 long tails. Next, the PB tendon was transected 8 cm proximal to the tip of the lateral malleolus and whipstitched with No. 5 Ethibond Excel suture (Ethicon, Somerville, New Jersey) with long tails. We then measured the length of the PB tendon footprint at the base of the fifth metatarsal with digital calipers (±0.02-mm instrumental error) (Mitutoyo, Tokyo, Japan). We defined the footprint as the most proximally visualized aspect of the tendon footprint, which was just distal to the insertion of the lateral cord of the plantar aponeurosis, to the most distal aspect of the tendon insertion on the fifth metatarsal. Prior studies describing the Jones fracture in relation to PB tendon anatomy described the meta-diaphyseal Jones fracture as occurring approximately 0.5 cm distal to the splayed insertion of the PB on the metatarsal and almost
Figure 2. Schematic demonstrating the site of the simulated avulsion fracture (proximal line) and the simulated Jones fracture (distal line).
invariably immediately adjacent, or just distal, to the joint between the fourth and fifth metatarsals.8 Using this as a guideline, we utilized a narrow (5 mm wide) osteotome to perform osteotomy either 5 mm proximal to (simulated avulsion fracture) or 5 mm distal to (simulated Jones fracture) the end of the PB footprint (Figure 2). In 5 specimens, we created a simulated meta-diaphyseal Jones fracture outside of the PB tendon insertion, and in their respective matched extremities, we created fractures within the PB footprint, representing a tuberosity avulsion fracture. Two 5.0-mm Steinmann pins were then placed through predrilled holes in the tibia, anterior to the fibula. We then mounted each specimen into a custom testing frame for
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
3
Morris et al
Results
Figure 3. Fluoroscopy and biomechanics setup. The fluoroscopy unit positioned to obtain an oblique image of the foot. The metal frame with peroneus brevis and Achilles tendons loaded.
The primary outcome of interest in our study was the amount of diastasis across our simulated Jones and avulsion fracture sites with loading of the PB tendon. Compared to fractures within the PB footprint, all specimens with a simulated Jones fracture (5/5 specimens) demonstrated greater fracture widening following loading of the PB tendon. Simulated fractures within the PB footprint (simulated avulsion fracture) widened by an average of 0.4 mm following tendon loading. Fractures distal to the PB footprint (simulated Jones fracture) widened by an average of 1.1 mm. This difference in fracture site widening between the simulated avulsion and Jones fractures was statistically significant (P = .02). Interobserver reliability demonstrated near perfect agreement (ICC = 0.91). Three of 5 specimens with a simulated avulsion-type fracture in the footprint had no widening at the fracture site on loading. The PB footprint had an average length of 15.2 mm.
Discussion biomechanical testing (Figure 3). We then statically loaded the Achilles tendon with a 20-lb weight. This kept the ankle plantarflexed against a metal bar placed along the metatarsal heads during testing to simulate weightbearing. A miniature C-arm fluoroscopy unit was then positioned to obtain a true anteroposterior (AP) image of the fifth metatarsal (oblique view of the foot) in the unloaded position (OEC 6800, GE OEC Medical Systems Inc, Salt Lake City, Utah) (Figure 4A and 4C). Of note, a 2-mm radiopaque marker was utilized to serve as calibration for later digital measurements. We then loaded the PB tendon with a 10-lb weight, and the osteotomy site was again imaged (Figure 4B and 4D). Digital measurements of fracture gaps were taken, and differences between the loaded and unloaded fractures were recorded. All official measurements were made by one of us (A.G.F.). Another author (P.M.M.) also performed measurements to determine interobserver reliability using the intraclass correlation coefficient (ICC).
Statistical Analysis The differences between the loaded and unloaded conditions were compared with a paired Student t test to evaluate for statistical significance. A P value of .05 was utilized to determine significance. Interobserver reliability was also determined utilizing the ICC. An ICC value of 0.0 to 0.2 indicated poor agreement, 0.3 to 0.4 indicated fair agreement, 0.5 to 0.6 indicated moderate agreement, 0.7 to 0.8 indicated strong agreement, and greater than 0.8 indicated nearly perfect agreement. All statistical analyses were performed utilizing Microsoft Excel (Microsoft Corp, Redmond, Washington).
The principal finding of this study was that simulated Jones fractures have wider diastasis on loading of the PB tendon compared to their avulsion fracture counterparts. In the present study, all Jones fracture equivalents demonstrated widening of the fracture gap from the unloaded to loaded conditions. Conversely, simulated avulsion fractures within the footprint of the PB showed significantly less diastasis at the fracture sites, with 60% of specimens showing no widening on loading of the PB tendon. Additionally, on AP imaging of the fifth metatarsal, fractures created at the distal border of the PB footprint more closely resembled the “classic” Jones fracture pattern. Fractures created within the PB footprint more closely resembled a typical avulsion-type fracture pattern. The greatest limitation of our study was the simplified model that we utilized for specimen testing. It was not our intention to subject each specimen to physiological loads seen during fracture creation or physiological weightbearing. We simply wanted to explore what effect the pull of the PB would have on the different fracture types. Another potential weakness is the arbitrary loads utilized for peroneus brevis and Achilles tendon loading. Unfortunately there is no similar model described. We wanted to apply enough load to the Achilles tendon to plantar flex the foot. Likewise, we wanted to apply enough load to the peroneus brevis tendon to displace the fracture but not cause failure of the peroneus breves tendon. Proximal fifth metatarsal fractures vary in their mechanisms, recommended treatment options, and respective outcomes according to fracture location.3,4,14 Richli and Rosenthal17 demonstrated that a tuberosity avulsion fracture can occur during hindfoot inversion and results from pulling of the lateral cord of the plantar aponeurosis.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
4
Foot & Ankle International
Figure 4. Fluoroscopic images of the fifth metatarsal base with an unloaded simulated avulsion fracture (A), loaded simulated avulsion fracture (B), unloaded simulated Jones fracture (C), and loaded simulated Jones fracture (D).
Meta-diaphyseal fractures, the so-called Jones fractures, have been demonstrated to occur with ankle plantarflexion with forefoot adduction.9 Although tuberosity avulsion fractures tend to heal with nonoperative management, numerous studies have shown that healing of meta-diaphyseal fractures is somewhat less predictable, especially in active individuals and highly competitive athletes.5,8,10,13,23,24 To evaluate the outcomes of treatment of these injuries in highly competitive athletes, Low et al10 identified 83 meta-diaphyseal fifth metatarsal fractures in football players participating in the National Football League (NFL) Scouting Combine between 1988 and 2002. Of the 46 fractures treated operatively, there were 3 nonunions (6.5%). Of the 40 treated nonoperatively, 8 developed nonunions (20%), although only 3 were symptomatic and required screw fixation.10 The authors concluded that surgical fixation is more favorable than nonoperative treatment in this group.10 This is in agreement with other authors who have recommended operative intervention in the elite athlete.8,16
Mologne et al11 reported the first prospective randomized study comparing cast and operative treatments of metadiaphyseal fifth metatarsal fractures. Of the 18 fractures in the cast group, 5 (28%) developed a nonunion, 1 developed a delayed union, and 2 (11%) had a refracture within 1 year of the original injury.11 The remainder healed uneventfully with a return to running/jumping sports at a median of 15 weeks.11 Of the operative group of 19 fractures, 1 (5.3%) developed a nonunion, requiring repeat surgery.11 The remainder returned to running/jumping sports at a median of 8 weeks, which was significantly sooner than the cast group.11 Current recommendations are for a biomechanical solution to a perceived vascular issue. Our study is one of the first to present the possibility of biomechanical instability at the meta-diaphyseal fracture site as a reason for the relatively high delayed union and nonunion in proximal fifth metatarsal fractures. We found that proximal fifth metatarsal fractures distal to the PB insertion are significantly more unstable than more proximal fractures. The PB exerts
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
5
Morris et al
further investigate the biomechanics of these fracture types. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding Figure 5. Blood supply to the proximal fifth metatarsal.
a deforming force on the proximal fragment of fractures distal to the PB footprint. This deforming force was not exerted on fractures within the footprint. In fact, in our biomechanical model, it appears that the PB tendon may have a stabilizing effect on avulsion-type fractures. 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. The vascular watershed area may not be the only factor predisposing to a nonunion of fifth metatarsal meta-diaphyseal fractures (Figure 5). This would help explain why screw fixation is often recommended to address Jones fractures and why added stability, not biological factors, improves healing. In a prior anatomic study, Richli and Rosenthal17 reported on the anatomy of tendon insertions at the base of the fifth metatarsal, stating that the PB terminates at the broadest part of the tuberosity. We identified the distal extent of the PB tendon footprint at 15.2 mm distal to the insertion of the lateral cord of the plantar aponeurosis on the tip of the tuberosity. The present study provides objective measurements that could be used during the initial evaluation of injury radiographs to help determine whether a fracture likely lies within the PB footprint and might benefit from operative intervention. Ultimately, these objective findings may help better define Jones fractures and avoid confusion when describing these important injuries. In conclusion, the meta-diaphyseal fifth metatarsal Jones fracture has been associated with more delayed union and nonunion than tuberosity avulsion fractures. While this has generally been attributed to a poor blood supply in that region, the operative treatment of nonunions consists of stabilization with an intramedullary screw. The present study suggests that mechanical instability secondary to the deforming force of the PB may play a contributory role in delayed union and nonunion of these fractures. Conversely, by spanning the fracture site of avulsion fractures, the PB insertion may act to stabilize avulsion injuries in a tension band manner. More research is needed to
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by an unrestricted educational grant from the Southwest Orthopaedic Trauma Association.
References 1. Acker JH, Drez D Jr. Nonoperative treatment of stress fractures of the proximal shaft of the fifth metatarsal (Jones’ fracture). Foot Ankle. 1986;7(3):152-155. 2. Clapper MF, O’Brien TJ, Lyons PM. Fractures of the fifth metatarsal: analysis of a fracture registry. Clin Orthop Relat Res. 1995;(315):238-241. 3. Dameron TB Jr. Fractures of the proximal fifth metatarsal: selecting the best treatment option. J Am Acad Orthop Surg. 1995;3(2):110-114. 4. Den Hartog BD. Fracture of the proximal fifth metatarsal. J Am Acad Orthop Surg. 2009;17(7):458-464. 5. Gray AC, Rooney BP, Ingram R. A prospective comparison of two treatment options for tuberosity fractures of the proximal fifth metatarsal. Foot (Edinb). 2008;18(3):156-158. 6. Jones R. I: fracture of the base of the fifth metatarsal bone by indirect violence. Ann Surg. 1902;35(6):697-700.2. 7. Josefsson PO, Karlsson M, Redlund-Johnell I, Wendeberg B. Closed treatment of Jones fracture: good results in 40 cases after 11-26 years. Acta Orthop Scand. 1994;65(5):545-547. 8. Kavanaugh JH, Brower TD, Mann RV. The Jones fracture revisited. J Bone Joint Surg Am. 1978;60(6):776-782. 9. Lawrence SJ, Botte MJ. Jones’ fractures and related fractures of the proximal fifth metatarsal. Foot Ankle. 1993;14(6):358-365. 10. Low K, Noblin JD, Browne JE, Barnthouse CD, Scott AR. Jones fractures in the elite football player. J Surg Orthop Adv. 2004;13(3):156-160. 11. Mologne TS, Lundeen JM, Clapper MF, O’Brien TJ. Early screw fixation versus casting in the treatment of acute Jones fractures. Am J Sports Med. 2005;33(7):970-975. 12. Moshirfar A, Campbell JT, Molloy S, Jasper LE, Belkoff SM. Fifth metatarsal tuberosity fracture fixation: a biomechanical study. Foot Ankle Int. 2003;24(8):630-633. 13. Nunley JA. Fractures of the base of the fifth metatarsal: the Jones fracture. Orthop Clin North Am. 2001;32(1):171-180. 14. Polzer H, Polzer S, Mutschler W, Prall WC. Acute fractures to the proximal fifth metatarsal bone: development of classification and treatment recommendations based on the current evidence. Injury. 2012;43(10):1626-1632. 15. Porter DA, Duncan M, Meyer SJ. Fifth metatarsal Jones fracture fixation with a 4.5-mm cannulated stainless steel screw in the competitive and recreational athlete: a clinical and radiographic evaluation. Am J Sports Med. 2005;33(5):726-733.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
6
Foot & Ankle International
16. Reese K, Litsky A, Kaeding C, Pedroza A, Shah N. Cannulated screw fixation of Jones fractures: a clinical and biomechanical study. Am J Sports Med. 2004;32(7):1736-1742. 17. Richli WR, Rosenthal DI. Avulsion fracture of the fifth metatarsal: experimental study of pathomechanics. AJR Am J Roentgenol. 1984;143(4):889-891. 18. Roche AJ, Calder JD. Treatment and return to sport following a Jones fracture of the fifth metatarsal: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2013;21(6): 1307-1315. 19. Shereff MJ, Yang QM, Kummer FJ, Frey CC, Greenidge N. Vascular anatomy of the fifth metatarsal. Foot Ankle. 1991;11(6):350-353. 20. Smith JW, Arnoczky SP, Hersh A. The intraosseous blood supply of the fifth metatarsal: implications for proximal fracture healing. Foot Ankle. 1992;13(3):143-152.
21. Smith TO, Clark A, Hing CB. Interventions for treating proximal fifth metatarsal fractures in adults: a meta-analysis of the current evidence-base. Foot Ankle Surg. 2011;17(4):300-307. 22. Torg JS, Balduini FC, Zelko RR, Pavlov H, Peff TC, Das M. Fractures of the base of the fifth metatarsal distal to the tuberosity: classification and guidelines for non-surgical and surgical management. J Bone Joint Surg Am. 1984;66(2):209-214. 23. Vorlat P, Achtergael W, Haentjens P. Predictors of outcome of non-displaced fractures of the base of the fifth metatarsal. Int Orthop. 2007;31(1):5-10. 24. Wiener BD, Linder JF, Giattini JF. Treatment of fractures of the fifth metatarsal: a prospective study. Foot Ankle Int. 1997;18(5):267-269.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
research-article2014
FAIXXX10.1177/1071100714565177Foot & Ankle InternationalMorris et al
Article
The Effect of Peroneus Brevis Tendon Anatomy on the Stability of Fractures at the Fifth Metatarsal Base
Foot & Ankle International® 1–6 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1071100714565177 fai.sagepub.com
Parisa M. Morris, MD1, Annie G. Francois, MD2, Randall E. Marcus, MD3, and Lutul D. Farrow, MD4
Abstract Background: Nonunion of classic Jones fractures has typically been attributed to the precarious vascular anatomy of the proximal fifth metatarsal. Despite this theory, the operative treatment of these fractures utilizes biomechanical solutions. The purpose of the present study was to evaluate the influence of the peroneus brevis (PB) tendon on the stability of fractures of the proximal fifth metatarsal. Methods: We utilized 5 matched pairs (10 specimens) of fresh-frozen cadaveric specimens. We used 2 loading conditions: (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). Following the creation of the fracture, each lower extremity was statically loaded through the Achilles and PB tendons. Our primary outcome measure was the degree of fracture diastasis with loading of the PB. Anteroposterior images with and without loading were obtained to evaluate fracture separation. We utilized a paired Student t test and the intraclass correlation coefficient (ICC) for all statistical analyses. Results: The average length of the PB footprint was 15.2 mm. The simulated Jones fractures demonstrated greater fracture widening following loading of the PB tendon compared to the simulated avulsion fractures. The simulated avulsion fractures widened 0.4 mm on loading compared to 1.1 mm of widening in the simulated Jones fractures (P = .02). Intraobserver reliability for all radiographic measurements showed substantial agreement (ICC = 0.91). Conclusion: The PB exerted a deforming force on the proximal fragment of simulated Jones fractures. This deforming force was less pronounced in the simulated avulsion fractures. The principal findings of this study were that proximal fifth metatarsal fractures distal to the PB insertion were significantly more unstable than more proximal fractures. Clinical Relevance: 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. Keywords: Jones fracture, nonunion, avulsion fracture, peroneus brevis, metatarsal Fractures of the proximal fifth metatarsal were first described by Sir Robert Jones in 1902 after he personally sustained the injury that now bears his name.6 Since that time, there have been differing definitions of the Jones fracture and wide variability in its recommended treatment as well as outcomes.1,8,22 As explained by Lawrence and Botte9 in 1993, proximal fifth metatarsal fractures can be divided into 3 groups: avulsion fractures of the tuberosity, meta-diaphyseal fractures, and diaphyseal fractures. The classic Jones fracture is a meta-diaphyseal fracture that is generally transverse in orientation and exits medially at the fourth to fifth intermetatarsal region.4 These fractures are not to be confused with fifth metatarsal avulsion fractures, which occur more proximally and typically involve the fifth metatarsal-cuboid articulation. Avulsion fractures occur in the inverted, plantarflexed foot and may be avulsed by the lateral cord of the plantar aponeurosis.17 Avulsion fractures tend to heal
reliably with nonoperative treatment.5,23,24 Conversely, the Jones fracture is associated with a relatively high rate of delayed union and nonunion when treated in a similar fashion, a result often attributed to a poor blood supply.2,7,10,11,18,20,21 The subsequent morbidity from a nonunion 1
Canyon Orthopaedic Surgeons, Avondale, Arizona, USA Department of Orthopaedic Surgery, University of Arizona College of Medicine, Tucson, Arizona, USA 3 Department of Orthopaedic Surgery, University Hospitals Case Medical Center, Cleveland, Ohio, USA 4 Orthopaedic and Rheumatologic Institute, Cleveland Clinic, Garfield Heights, Ohio, USA 2
Corresponding Author: Lutul D. Farrow, MD, Cleveland Clinic Lerner College of Medicine, Cleveland Clinic Sports Health Center, 5555 Transportation Boulevard, Garfield Heights, OH 44125, USA Email: [email protected]
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
2
Foot & Ankle International
can be especially devastating to high-level athletes who desire to return to sport as soon as possible. Consequently, many authors advise surgical fixation of these fractures in active individuals and athletes utilizing intramedullary screw fixation.13,15 When nonoperative treatment is undertaken, however, inadequate immobilization is associated with poorer outcomes.11 This perhaps suggests that biomechanical as well as biological factors contribute to delayed union and nonunion in these fractures.19,20 There have been a few studies that have evaluated various biomechanical aspects of fifth metatarsal base fractures.16,17 Moshirfar et al12 evaluated the biomechanical strength of 2 methods of screw fixation of fifth metatarsal base fractures. However, no study, to our knowledge, has ever investigated the peroneus brevis (PB) as a deforming force on proximal fifth metatarsal fractures in a cadaveric model. The present study aimed to evaluate the mechanical effect of the PB on fifth metatarsal avulsion and metadiaphyseal fractures, investigating the tendon as a source of biomechanical instability. Our primary outcome measure was to evaluate the magnitude (in millimeters) of fracture displacement caused by loading of the PB tendon. We hypothesized that loading of the PB tendon would cause more diastasis of meta-diaphyseal fractures of the fifth metatarsal compared to its avulsion fracture counterpart.
Figure 1. Dissection at the base of the fifth metatarsal. Radiographic marker (arrow) at the base of the fifth metatarsal (MTT). Site of osteotomy (arrowhead) at the distal aspect of the peroneus brevis (PB) insertion.
Materials and Methods We utilized 5 matched pairs of fresh-frozen below-knee cadaveric specimens (10 total specimens). All specimens were obtained from the Life Legacy Foundation (Tucson, Arizona). A human tissue agreement was signed through the Life Legacy Foundation. Each specimen was thawed overnight to room temperature. We then carefully dissected each specimen to expose the fifth metatarsal base, the PB myotendinous unit, and the Achilles tendon (Figure 1). The Achilles tendon was cut approximately 10 cm proximal to its calcaneal insertion, and modified Krakow stitches were placed using No. 5 FiberWire (Arthrex, Naples, Florida), leaving 2 long tails. Next, the PB tendon was transected 8 cm proximal to the tip of the lateral malleolus and whipstitched with No. 5 Ethibond Excel suture (Ethicon, Somerville, New Jersey) with long tails. We then measured the length of the PB tendon footprint at the base of the fifth metatarsal with digital calipers (±0.02-mm instrumental error) (Mitutoyo, Tokyo, Japan). We defined the footprint as the most proximally visualized aspect of the tendon footprint, which was just distal to the insertion of the lateral cord of the plantar aponeurosis, to the most distal aspect of the tendon insertion on the fifth metatarsal. Prior studies describing the Jones fracture in relation to PB tendon anatomy described the meta-diaphyseal Jones fracture as occurring approximately 0.5 cm distal to the splayed insertion of the PB on the metatarsal and almost
Figure 2. Schematic demonstrating the site of the simulated avulsion fracture (proximal line) and the simulated Jones fracture (distal line).
invariably immediately adjacent, or just distal, to the joint between the fourth and fifth metatarsals.8 Using this as a guideline, we utilized a narrow (5 mm wide) osteotome to perform osteotomy either 5 mm proximal to (simulated avulsion fracture) or 5 mm distal to (simulated Jones fracture) the end of the PB footprint (Figure 2). In 5 specimens, we created a simulated meta-diaphyseal Jones fracture outside of the PB tendon insertion, and in their respective matched extremities, we created fractures within the PB footprint, representing a tuberosity avulsion fracture. Two 5.0-mm Steinmann pins were then placed through predrilled holes in the tibia, anterior to the fibula. We then mounted each specimen into a custom testing frame for
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
3
Morris et al
Results
Figure 3. Fluoroscopy and biomechanics setup. The fluoroscopy unit positioned to obtain an oblique image of the foot. The metal frame with peroneus brevis and Achilles tendons loaded.
The primary outcome of interest in our study was the amount of diastasis across our simulated Jones and avulsion fracture sites with loading of the PB tendon. Compared to fractures within the PB footprint, all specimens with a simulated Jones fracture (5/5 specimens) demonstrated greater fracture widening following loading of the PB tendon. Simulated fractures within the PB footprint (simulated avulsion fracture) widened by an average of 0.4 mm following tendon loading. Fractures distal to the PB footprint (simulated Jones fracture) widened by an average of 1.1 mm. This difference in fracture site widening between the simulated avulsion and Jones fractures was statistically significant (P = .02). Interobserver reliability demonstrated near perfect agreement (ICC = 0.91). Three of 5 specimens with a simulated avulsion-type fracture in the footprint had no widening at the fracture site on loading. The PB footprint had an average length of 15.2 mm.
Discussion biomechanical testing (Figure 3). We then statically loaded the Achilles tendon with a 20-lb weight. This kept the ankle plantarflexed against a metal bar placed along the metatarsal heads during testing to simulate weightbearing. A miniature C-arm fluoroscopy unit was then positioned to obtain a true anteroposterior (AP) image of the fifth metatarsal (oblique view of the foot) in the unloaded position (OEC 6800, GE OEC Medical Systems Inc, Salt Lake City, Utah) (Figure 4A and 4C). Of note, a 2-mm radiopaque marker was utilized to serve as calibration for later digital measurements. We then loaded the PB tendon with a 10-lb weight, and the osteotomy site was again imaged (Figure 4B and 4D). Digital measurements of fracture gaps were taken, and differences between the loaded and unloaded fractures were recorded. All official measurements were made by one of us (A.G.F.). Another author (P.M.M.) also performed measurements to determine interobserver reliability using the intraclass correlation coefficient (ICC).
Statistical Analysis The differences between the loaded and unloaded conditions were compared with a paired Student t test to evaluate for statistical significance. A P value of .05 was utilized to determine significance. Interobserver reliability was also determined utilizing the ICC. An ICC value of 0.0 to 0.2 indicated poor agreement, 0.3 to 0.4 indicated fair agreement, 0.5 to 0.6 indicated moderate agreement, 0.7 to 0.8 indicated strong agreement, and greater than 0.8 indicated nearly perfect agreement. All statistical analyses were performed utilizing Microsoft Excel (Microsoft Corp, Redmond, Washington).
The principal finding of this study was that simulated Jones fractures have wider diastasis on loading of the PB tendon compared to their avulsion fracture counterparts. In the present study, all Jones fracture equivalents demonstrated widening of the fracture gap from the unloaded to loaded conditions. Conversely, simulated avulsion fractures within the footprint of the PB showed significantly less diastasis at the fracture sites, with 60% of specimens showing no widening on loading of the PB tendon. Additionally, on AP imaging of the fifth metatarsal, fractures created at the distal border of the PB footprint more closely resembled the “classic” Jones fracture pattern. Fractures created within the PB footprint more closely resembled a typical avulsion-type fracture pattern. The greatest limitation of our study was the simplified model that we utilized for specimen testing. It was not our intention to subject each specimen to physiological loads seen during fracture creation or physiological weightbearing. We simply wanted to explore what effect the pull of the PB would have on the different fracture types. Another potential weakness is the arbitrary loads utilized for peroneus brevis and Achilles tendon loading. Unfortunately there is no similar model described. We wanted to apply enough load to the Achilles tendon to plantar flex the foot. Likewise, we wanted to apply enough load to the peroneus brevis tendon to displace the fracture but not cause failure of the peroneus breves tendon. Proximal fifth metatarsal fractures vary in their mechanisms, recommended treatment options, and respective outcomes according to fracture location.3,4,14 Richli and Rosenthal17 demonstrated that a tuberosity avulsion fracture can occur during hindfoot inversion and results from pulling of the lateral cord of the plantar aponeurosis.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
4
Foot & Ankle International
Figure 4. Fluoroscopic images of the fifth metatarsal base with an unloaded simulated avulsion fracture (A), loaded simulated avulsion fracture (B), unloaded simulated Jones fracture (C), and loaded simulated Jones fracture (D).
Meta-diaphyseal fractures, the so-called Jones fractures, have been demonstrated to occur with ankle plantarflexion with forefoot adduction.9 Although tuberosity avulsion fractures tend to heal with nonoperative management, numerous studies have shown that healing of meta-diaphyseal fractures is somewhat less predictable, especially in active individuals and highly competitive athletes.5,8,10,13,23,24 To evaluate the outcomes of treatment of these injuries in highly competitive athletes, Low et al10 identified 83 meta-diaphyseal fifth metatarsal fractures in football players participating in the National Football League (NFL) Scouting Combine between 1988 and 2002. Of the 46 fractures treated operatively, there were 3 nonunions (6.5%). Of the 40 treated nonoperatively, 8 developed nonunions (20%), although only 3 were symptomatic and required screw fixation.10 The authors concluded that surgical fixation is more favorable than nonoperative treatment in this group.10 This is in agreement with other authors who have recommended operative intervention in the elite athlete.8,16
Mologne et al11 reported the first prospective randomized study comparing cast and operative treatments of metadiaphyseal fifth metatarsal fractures. Of the 18 fractures in the cast group, 5 (28%) developed a nonunion, 1 developed a delayed union, and 2 (11%) had a refracture within 1 year of the original injury.11 The remainder healed uneventfully with a return to running/jumping sports at a median of 15 weeks.11 Of the operative group of 19 fractures, 1 (5.3%) developed a nonunion, requiring repeat surgery.11 The remainder returned to running/jumping sports at a median of 8 weeks, which was significantly sooner than the cast group.11 Current recommendations are for a biomechanical solution to a perceived vascular issue. Our study is one of the first to present the possibility of biomechanical instability at the meta-diaphyseal fracture site as a reason for the relatively high delayed union and nonunion in proximal fifth metatarsal fractures. We found that proximal fifth metatarsal fractures distal to the PB insertion are significantly more unstable than more proximal fractures. The PB exerts
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
5
Morris et al
further investigate the biomechanics of these fracture types. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding Figure 5. Blood supply to the proximal fifth metatarsal.
a deforming force on the proximal fragment of fractures distal to the PB footprint. This deforming force was not exerted on fractures within the footprint. In fact, in our biomechanical model, it appears that the PB tendon may have a stabilizing effect on avulsion-type fractures. 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. The vascular watershed area may not be the only factor predisposing to a nonunion of fifth metatarsal meta-diaphyseal fractures (Figure 5). This would help explain why screw fixation is often recommended to address Jones fractures and why added stability, not biological factors, improves healing. In a prior anatomic study, Richli and Rosenthal17 reported on the anatomy of tendon insertions at the base of the fifth metatarsal, stating that the PB terminates at the broadest part of the tuberosity. We identified the distal extent of the PB tendon footprint at 15.2 mm distal to the insertion of the lateral cord of the plantar aponeurosis on the tip of the tuberosity. The present study provides objective measurements that could be used during the initial evaluation of injury radiographs to help determine whether a fracture likely lies within the PB footprint and might benefit from operative intervention. Ultimately, these objective findings may help better define Jones fractures and avoid confusion when describing these important injuries. In conclusion, the meta-diaphyseal fifth metatarsal Jones fracture has been associated with more delayed union and nonunion than tuberosity avulsion fractures. While this has generally been attributed to a poor blood supply in that region, the operative treatment of nonunions consists of stabilization with an intramedullary screw. The present study suggests that mechanical instability secondary to the deforming force of the PB may play a contributory role in delayed union and nonunion of these fractures. Conversely, by spanning the fracture site of avulsion fractures, the PB insertion may act to stabilize avulsion injuries in a tension band manner. More research is needed to
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by an unrestricted educational grant from the Southwest Orthopaedic Trauma Association.
References 1. Acker JH, Drez D Jr. Nonoperative treatment of stress fractures of the proximal shaft of the fifth metatarsal (Jones’ fracture). Foot Ankle. 1986;7(3):152-155. 2. Clapper MF, O’Brien TJ, Lyons PM. Fractures of the fifth metatarsal: analysis of a fracture registry. Clin Orthop Relat Res. 1995;(315):238-241. 3. Dameron TB Jr. Fractures of the proximal fifth metatarsal: selecting the best treatment option. J Am Acad Orthop Surg. 1995;3(2):110-114. 4. Den Hartog BD. Fracture of the proximal fifth metatarsal. J Am Acad Orthop Surg. 2009;17(7):458-464. 5. Gray AC, Rooney BP, Ingram R. A prospective comparison of two treatment options for tuberosity fractures of the proximal fifth metatarsal. Foot (Edinb). 2008;18(3):156-158. 6. Jones R. I: fracture of the base of the fifth metatarsal bone by indirect violence. Ann Surg. 1902;35(6):697-700.2. 7. Josefsson PO, Karlsson M, Redlund-Johnell I, Wendeberg B. Closed treatment of Jones fracture: good results in 40 cases after 11-26 years. Acta Orthop Scand. 1994;65(5):545-547. 8. Kavanaugh JH, Brower TD, Mann RV. The Jones fracture revisited. J Bone Joint Surg Am. 1978;60(6):776-782. 9. Lawrence SJ, Botte MJ. Jones’ fractures and related fractures of the proximal fifth metatarsal. Foot Ankle. 1993;14(6):358-365. 10. Low K, Noblin JD, Browne JE, Barnthouse CD, Scott AR. Jones fractures in the elite football player. J Surg Orthop Adv. 2004;13(3):156-160. 11. Mologne TS, Lundeen JM, Clapper MF, O’Brien TJ. Early screw fixation versus casting in the treatment of acute Jones fractures. Am J Sports Med. 2005;33(7):970-975. 12. Moshirfar A, Campbell JT, Molloy S, Jasper LE, Belkoff SM. Fifth metatarsal tuberosity fracture fixation: a biomechanical study. Foot Ankle Int. 2003;24(8):630-633. 13. Nunley JA. Fractures of the base of the fifth metatarsal: the Jones fracture. Orthop Clin North Am. 2001;32(1):171-180. 14. Polzer H, Polzer S, Mutschler W, Prall WC. Acute fractures to the proximal fifth metatarsal bone: development of classification and treatment recommendations based on the current evidence. Injury. 2012;43(10):1626-1632. 15. Porter DA, Duncan M, Meyer SJ. Fifth metatarsal Jones fracture fixation with a 4.5-mm cannulated stainless steel screw in the competitive and recreational athlete: a clinical and radiographic evaluation. Am J Sports Med. 2005;33(5):726-733.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
6
Foot & Ankle International
16. Reese K, Litsky A, Kaeding C, Pedroza A, Shah N. Cannulated screw fixation of Jones fractures: a clinical and biomechanical study. Am J Sports Med. 2004;32(7):1736-1742. 17. Richli WR, Rosenthal DI. Avulsion fracture of the fifth metatarsal: experimental study of pathomechanics. AJR Am J Roentgenol. 1984;143(4):889-891. 18. Roche AJ, Calder JD. Treatment and return to sport following a Jones fracture of the fifth metatarsal: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2013;21(6): 1307-1315. 19. Shereff MJ, Yang QM, Kummer FJ, Frey CC, Greenidge N. Vascular anatomy of the fifth metatarsal. Foot Ankle. 1991;11(6):350-353. 20. Smith JW, Arnoczky SP, Hersh A. The intraosseous blood supply of the fifth metatarsal: implications for proximal fracture healing. Foot Ankle. 1992;13(3):143-152.
21. Smith TO, Clark A, Hing CB. Interventions for treating proximal fifth metatarsal fractures in adults: a meta-analysis of the current evidence-base. Foot Ankle Surg. 2011;17(4):300-307. 22. Torg JS, Balduini FC, Zelko RR, Pavlov H, Peff TC, Das M. Fractures of the base of the fifth metatarsal distal to the tuberosity: classification and guidelines for non-surgical and surgical management. J Bone Joint Surg Am. 1984;66(2):209-214. 23. Vorlat P, Achtergael W, Haentjens P. Predictors of outcome of non-displaced fractures of the base of the fifth metatarsal. Int Orthop. 2007;31(1):5-10. 24. Wiener BD, Linder JF, Giattini JF. Treatment of fractures of the fifth metatarsal: a prospective study. Foot Ankle Int. 1997;18(5):267-269.
Downloaded from fai.sagepub.com at Selcuk Universitesi on February 3, 2015
