Classification and Treatment of Fifth Metatarsal Fractures: A Comprehensive Review, Study notes of Medicine

Download Classification and Treatment of Fifth Metatarsal Fractures: A Comprehensive Review and more Study notes Medicine in PDF only on Docsity! TRAUMA 0891-8422/95 $0.00 + .20 FIFTH METATARSAL FRACTURES Biomechanics, Classification, and Treatment Harold W. Vogler, DPM, Nils Westlin, MD, PhD, Alan J. Mlodzienski, DPM, and Finn Bojsen Moller, MD, PhD Fracture of the fifth metatarsal is a commonly encountered podiatric ortho- pedic clinical event.': 4, 8, 15, 17, 19, 22, 25, 29 The statistical frequency for all types of fifth metatarsal fractures collectively compared against other foot fractures is unknown, Two recent studies from one of the author's Institutions (NW) have identified the proximal junctional diaphyseal-metaphyseal Jones fracture fre- quency rate as 0.7%-1.9% in a combined total of 10,988 foot fractures.lv P Classification of the different forms of fifth metatarsal fracture primarily are based on anatomic location and fracture personality, The tuberosity and proxi- mal junctional diaphyseal fractures have received the most attention in the literature owing to the confusion regarding the most effective form of treat- ment.>3, 4, 5, 11, 15, 16, 17, 20, 29 The distal capitak.cervical, and shaft fractures are less controversial with regard to treatment concepts, but review of the literature also demonstrates considerable variation in treatment methods for these fractures. Surgeon preference, training, and patient-related parameters playa role in the decision for various forms of treatment as welL This article defines a classification system for fifth metatarsal fractures based on anatomic site, time of encounter, and fracture morphology, and uses this model to direct the surgeon toward an appropriate method of treatment. Addi- tionally, the biomechanics of the fifth metatarsal segment and its interactions are explored to help the clinician understand how fracture occurs within this bone. The biomechanical behavior of this segment and its attachments can be From the Foot and Ankle Medical Center, Tampa, Florida (HWV), and the Panum Institute of the University of Copenhagen, Copenhagen, Denmark (HWV, FBM);Malmo Gen- eral Hospital, Malmo, Sweden (HWV) (NW); and the Presbyterian Medical Cente.r, and the Pennsylvania College of Podiatric Medicine, Philadelphia, Permsylvarua (AM,HWV) CLINICS IN PODIATRIC MEDICINE AND SURGERY VOLUME 12 • NUMBER 4 • OCTOBER 1995 725 726 VOGLERet al used to help the surgeon understand treatment concepts within the classifica- tion scheme, ANATOMY AND BIOMECHANICS The fifth metatarsal functions with an independent axis of motion." The direction and range of motion are determined by orientation of its, axis an~ by ,its ligamentous and tethering soft tissue attachments, These factors dictate primarily dorsiflexion and plantarflexion with inversion-eversion a,s the potential move- ments of this segment." Strong plantar ligaments extendmg from the os calc,ls span the cuboid to insert at the plantar fifth metatarsal base:23 A small cub?td fifth metatarsal ligament is present at the undersurface to remforce the tension surface of this joint, as is a small slip of plantar fascia." An interosseous ligament locks the base against the fourth metatarsal.l"" A dorsal cuboid fifth metatarsal ligament spans the top of the proximal joint to promote dorsal stability.w " The peroneus brevis attachment at the tuberosity base provides a powerful dynamic tensile loading capacity with some posterior axial compression as a result of its longitudinal course from the fibular malleolus to the metatarsal base, The contribution to joint stability from peroneus tertius is minimal, as its course emanates proximally and is dosiflexory. It fires during swing phase and brieflv at heel contact phase of gait. Fracture of the fifth metatarsal does not occur during swing or early stance phase; however, a small medial compressive load against the fourth metatarsal is possible with this orientation. The fifth metatarsal is cradled with muscle investitures from the flexor digiti quinti brevis arising from the plantar base region, which sometimes extend more distally to insert laterally on the shaft as well as on the lateral fifth proximal phalanx: 111\' abductor digiti minimi may have a small insertion on the base of the fifth metatarsal and, occasionally, on the mid-shaft as it progresses toward its fin.,1 insertion on the base of the proximal phalanx.' As such, it could help cradle this segment laterally and perhaps biomechanically. Intermetatarsal stability is aided by the fourth dorsal interosseous muscle, which originates from both the medial fifth metatarsal shaft and base and from the adjacent area of the lateral fourth metatarsal. The plantar interosseous muscle has no substrate on the fourth metatarsal or the proximal links and thus plays no role in stabilizing the base, The morphology of the bone demonstrates a longitudinal dorsal convexity, lik, the other metatarsals, to help neutralize bending moments (flexural neutralize- tion) in the loaded closed kinetic chain state. It is the terminal link of the outer part of lateral column of the foot, completing a curved segmented beam link.1"" for~ed by the ~ompani~:m compo~ents of the os calcis and cuboid. Its design \. defmed by a, distal ar~cular capital segment, a narrowed cervical region th.\! becomes continuous WIth a dense cortical midregion or shaft with an isthmus The isthmus ~as surgical significance for osteosynthesis medullary axial fixation pro~edures ~Imilar to the, t~bial isthm,us; this is discussed subsequently. Proc- ressmg proxImally: a transition occurs mto a metaphyseal expansion, terminatinc at t~e most pr~x1.~nal ~nd, lateral ends with a narrow tuberosity. The~ .1r~' coru:;rder~ble :,ar~a~Ions m SIze and shape.' These anatomic design changes have engmeermg significance for load acceptance. Loading of the fifth metatarsal segment under ordinary gait mechanics i- generat~d t~rough a, combined mechanism of induced compression f~om' it- compamon lmks proximally and from distal gravitational forces at the m t t . I h d L d t d d ' , e a .1rs., ea. oa accep ance epen s on intact mtegrity of the interface segme t I ft ti tt h t 29 32 M bid I ' n s In,so Issue a ac men S.· or 1 oadmg occurs during competitive athletics FfFTH METATARSAL FRACTURES 729 Figure 2. Comminuted capitum fifth metatarsal fracture with companion fourth metatarsal cervical fracture, in satisfactory alignment for closed treatment. Figure 3. "Dancer's fracture" of the fifth metatarsal cervical neck region. This is usually a spiral fracture that heals well with closed treatment, unless the patient is a competitive athlete or performer. 730 VOGLERet al Figure 4. Healed"dancer'sfracture"withfreshtransversetractionfractureat the tuberosity. suggests an underlying torque force mediated by bending and twisting, most commonly an inversion and plantarflexed foot load.s" 11,31 It often requires open reduction and internal fixation in the competitive dancer or athlete, but other- wise heals well with castings- (Fig, 5). Shaft Shaft fracture is often comminuted, occasionally with open wounds, and results from direct violence or impact. Missile wounds can be difficult to manage and produce open fracture with segmental defect that requires special care, including external fixation and subsequent reconstruction" (Fig. 6A,B,C,D,£). Closed comminutions can often be managed with casting until consolidation occurs." If consolidation failure occurs, segmental reconstruction with bone graft and possible plating is a good solution. Junctional Fracture at the anatomic transition from the cortical shaft with its isthmus to the proximal metaphysis presents the most difficult treatment challenge and questions. This is the classic Jones fracture, described as 1.5 to 3.0 em distal to the tuberosity': 4. 11, 18, 29 (Fig. 7). This site represents an anatomic and engineering change in configuration, predisposing it to failure under certain loading situa- tions." Transition occurs from the shaft cortical structure to a compliant meta- physeal expansion. Thus, there is a geometric contribution with the change in morphology as well as a materials strength conslderation.w v The combination of biomechanical forces and engineering phenomena unique to this area create the stage for a flexural overload causing either acute fracture or stress fracture. Diagnosis is often made by a combination of clinical examination and radio- graphic and, occasionally, more complex modern imaging techniques. Treatment depends on the activity level of the patient and whether the fracture is acute, FlFTHMFrATARSAL FRACJl.JRfS 731 Fi~u~e5.,"Dancer's fracture" internally fixed with double 2,0 mm compression lag screws, This ISfaIrly easy owing to the long spiral surfaces. ~atigue,,or chronic nonunion with medullary sclerosis.v'v 17.23.31.33This fracture ISnotOrIOUS for prolonged healing and nonunion. I, 2. S. 100-14, 16, 17,20, 23. 31), 33 As a result, surgery has become the accepted norm and common for the athlete and ~thers who desire more rapid rehebtlitation.'>' •. 16, 20, 30. 33 Medullary screw fixa- tion has emerged as the technique of choice for acute or fatigue-related failurev 14,1~,18, 20(Fig. BA,B). Cannulated screws have taken this concept a step further owmg to their greater ease of insertion (Fig. 9). TUberosity The styloid process at the fifth metatarsal base as well as its more distal metaphyseal expansion form the proximal tuberosity flare." Its rigid attachments of ligaments, tendons, and capsule make it a very stable substrate that is locked firmly against its counterparts-the cuboid and fourth metatarsal base. There is a,lmost total agreement regarding the pathomechanics of fracture through this slte.<Il·17,19.22-24,29Avulsions represent tensile mediated overloads via traction from the various ligaments and dynamics of the peroneus brevis tendon during inversion and plantar flexion movements.22.24.31The avulsions are often irregular but are small and virtually always include portions of the insertion of the peroneus brevis and the plantar ligament or fascia insertions (Fig. 10). These fractures must be assessed carefully in adolescents who have a secondary growth plate4•29 (Fig. 11). The significant features of concern with this fracture relate to whether it enters the cuboid joint and the amount of distraction present- 17,D, 29 (Fig. 12). It can also be almost transverse, where it enters the intermetatarsal joint (Fig. 13). The forces operational for this pattern are a frictional. pivot, ~ilh the heel elevated in conjunction with external leg and talar rotation creating adduction at the midfoot and hindfoot, with the forefoot fixed during perfor- mance. The tensile overload is directed through the peroneus brevis, the lateral 734 VOGLER et al Figure 7. Classic "junctional" fresh Jones fracture with comminuted butterfly fragment. Figure 8. A, Stress Jones fracture in a young soccer athlete. B, Repaired with 4.5 mm AO axial medullary malleolar screw. FIFTHMETATARSAL FRACTURES 735 Figure 9. ACE (ACE Medical Company, EI Segundo, California) 4.5 titanium lag screw, cannulated delivery on skeletal model. Figure 10. Small tuberosity avulsion fractures resulting from dynamic traction from the ~eroneus brevis and long plantar ligament slip. This heals well with minimal immobiliza- tion treatment. Figure 11. Intra-articular tuberosity fracture, nondisplaced, with a small secondary growth center at its classic location. 736 VOCLERet al Figure 12. Displaced intra-articular tuberosity fracture. This needs open reduction and internal fixation. Tension banding is best. TREATMENT The most important question for many fifth metatarsal fractures is whether to use surgical versus nonsurgical treatment. Working from the anatomic classi- fication, this discussion progresses from distal to proximal. Fractures of the capitum can be infraction compression injuries, which are usually stable and well positioned (see Fig. 1). If they are intra-articular with significant fragmentation, closed reduction can be attempted, or minimal open reduction may be considered, if possible. This is often not possible, and excision Figure 13. Transverse traction tuberosity fracture in the intermetatarsal joint. This requires simple immobilization. FIFTHMETATARSAL FRACTURES 739 Figure 15 (Continued). C, Internal fixation demonstrating sliding splintage in the cervical fjfth metatarsal fracture and splintage with interfragmentary screws in the fourth metatarsal. D, The final healed anatomic situation. 41% stress fractures." There are no known statistics for the rate of permanent nonunion.". 13 The Swedish studies indicate that about 59%of the Jones fractures can be anticipated to be stress fractures. This fracture most often affects younger patients.te 13. 14, 30 Cannulated screws offer the additional advantage of ease of insertion and indirect reduction for fixation of this fracture. Newer cannulated ACE titanium 4,5-mrn lag Screws with a lower profile head represent a simple method of delivery with the necessary' screw design and the superior metallurgic strength of titanium (Fig. 19). The 4.0-mm A-O lag screw appears inviting, but it has a small "root diameter" at the run out, predisposing the screw to fracture as it passes the isthmus of the metatarsal shaft, exposing it to considerable bending moments." This is avoided with the newer 4.5-mm cannulated titatium lag SCrews,The anatomic shaft isthmus creates an interference fit with the screw, Screws longer than 46 mm should be avoided as they may penetrate the medial distal cortex. Consolidation is rapid and dependable with medullary screw delivery; clinical union can take place as soon as 7 weeks, compared to 15 weeks for casting,12.14, IS. 20 The screw should be left in place for competitive athletes until the end of their careers because of to the high rate of refracture following retrieval.'>Occasionally, screw head prominence can be troublesome and may require early removal following union. It is not clear whether sclerotic nO,n- unions require decortication with bone grafting rather than medullary axial compression screw repair, Torg et al'v 30. 33 believe that inlaid bone grafting was 740 VOGLERet al Figure 16. Classic medullary splintage for shaft fracture. Figure 11. Acute Jones fracture in classic location. FIFTH METATARSAL FRACTIJRES 741 L1H -A"2 Figure 18. Healed Jones fracture with 4.5 mm AD axial medullary compression screw. required, whereas Delee et al" believe axial compression screw alone is effective. Clearly, axial compression screw fixation is easier and may represent a better method of treatment, even for chronic nonunions. Thus, current recommendation for treatment of the acute or stress-related Jones fracture is insertion of medullary lag screws (4.5-mmcannuLatedtitanium screws) for the active patient. If the medullary canal and isthmus are small, a 4.0-mrn lag screw with washer can be used. If the site is very sclerotic, consider- ation should be given to an inlaid Torg bone graft; alternatively, a local bone graft with an axial compression 4.5-mrn cannulated titanium screw can be used. Non-weight-bearing casting can be considered for high-risk patients and those with no particular urgency for recovery." 14, 30 In the event of delayed union Figure 19. Anatomic model demonstrating ACE (ACE Medical Company, EI Segundo, California) 4.5 mm titanium cannulated lag screw axial delivery. 744 VOGLERet al Figure 22. A, Oblique avulsion fragment, partially displaced, nonarticular. B, Tension banding of prior avulsion fragment, with splintage pins. flFfH METATARSALFRACfURES 745 Figure 23. A, Lag screw fixation of small avulsion fragment with a secondary anti rotation splintage pin. B, Accidental "telescoping" of 3.5 mm screw with inaccurate delivery. Illustration continued on following page 746 VOGLER el al Figure 23 (Continued). C, Small displaced avulsion fragment, intra-articular. 0, Repaired with proper Jag screw delivery. References 1. Arangio GA: Proximal diaphyseal fractures of the fifth metatarsal (jones' fracture): Two cases treated by cross-pinning with review of 106cases. Foot Ankle 3:293-296, 1983 2. Carp L: Fracture of the fifth metatarsal bone with special reference to delayed union. Ann Surg 86,308-320, 1927 3. Chapman M: Fractures and dislocations of the foot. In Mann R (ed). DuVries' Surgery of the Foot, ed. 5. St. Louis, CV Mosby, 1986,pp 737-742 4. Dameron TB: Fractures of the fifth metatarsal.] Bone Joint Surg 7A:788-792, 1975 5. DeJee JC, Evans ]P, julian ]: Stress fracture of the fifth metatarsal. Am J Sports Moo 1L349-353, 1983 6. Dorfman, G: Determination of treatment in fractures of the fifth metatarsal shaft. J Foot Surg 17:16-21, 1978 7. Durant JH: Partial ostectomy of the fifth metatarsal base. J Foot Surg 17:118-120, 1978