Porter & Schon: Baxter's The Foot and Ankle in Sport, 2nd ed.

Section 2 - Sport Syndromes

Chapter 4 - Problematic stress fractures of the foot and ankle

James A. Nunley,Anthony S. Rhorer

  

 

Introduction

  

 

Stress fracture of the tarsal navicular

  

 

Stress fracture of the base of second metatarsal

  

 

Stress fracture of the medial malleolus

  

 

Stress fracture of the fifth metatarsal

  

 

Summary

  

 

References

 

   Pearl

  

1   

Subtle, unexplained pain in the foot or ankle in an athlete often is a stress fracture. The best screening examination is a bone scan.

  

2   

Stress fractures of the medial malleolus may be associated with pathologic varus coming from the knee, ankle, or hindfoot. One should search for this because treatment without addressing biomechanics is not always successful.

  

3   

Navicular stress fractures are becoming more recognized; they occur only in the competitive athlete, and surgical intervention often is required in the professional athlete.

  

4   

Second metatarsal base stress fractures in elite dancers must be treated aggressively because they put the dancers' careers at risk.

Introduction

The insidious onset of ill-defined foot and ankle pain in the athlete is a confusing problem for trainers, physicians, and patients. As Americans become more interested in recreational sports and the number of professional and college-level athletes continues to grow, stress fractures of the foot and ankle will continue to become more prominent in the training room, the primary care setting, and the orthopaedic surgeon's office. Understanding the predispositions to such injuries, the various themes common to them, and the mechanisms of diagnosis therefore should be requisite in the armamentarium of physicians treating athletes.

A stress fracture is a complete or incomplete fracture of bone secondary to failure over a prolonged period and marked by repeated stress in a rhythmic, reproducible fashion.

Stress fractures differ from acute fractures in that their course generally is more gradual and their radiographic appearance can be elusive.[1] Stress fractures of the foot and ankle are most common in running athletes, especially those who jump. For example, track athletes, ballet dancers, and basketball players have a high incidence of stress injury. Many studies have implicated biomechanical factors, such as leg-length discrepancies, cavus foot deformities, and limb malalignment. Women have a higher incidence of stress fractures, and amenorrhea often is a concomitant finding in female athletes with these injuries.[2]

Several stress fractures are treated easily with cessation of activity, orthoses, and modification in training. However, there exists in the foot and ankle a subset of stress fractures that are difficult to diagnose and treacherous to treat. These are truly the problematic stress fractures of the foot and ankle.

 

Stress Fracture of the Tarsal Navicular

Unexplained pain of the midfoot in the everyday and high-performance athlete can be a conundrum for both the patient and treating physician. The diagnosis of stress fracture of the tarsal navicular remains an elusive and poorly understood facet of midfoot pain in sports. Treatment of this unusual stress fracture requires an understanding of its presentation, anatomy, imaging, and response to conservative and surgical management. The proper diagnosis of this unusual condition portends an excellent prognosis for the athlete and a rapid return to sport. Therefore it should be part of the repertoire for any physician treating conditions of the foot and ankle in athletes.

Anatomy and presentation

The tarsal navicular serves as a keystone in the medial longitudinal arch and consequently is subjected to tremendous forces through the foot. Moreover, nutrient arteries arising from both the anterior and posterior tibial arteries create a generous supply of blood to the medial and lateral thirds of the navicular. The result is a poorly vascularized zone in the middle third of the bone.[2] Incredible stresses and decreased nutrition make the middle third of the navicular the most common location for stress fracture.

Misdiagnosis of stress fracture of the tarsal navicular generally is the rule rather than the exception. There are several sources of midfoot pain that are more common, including plantar fasciitis, anterior tibial and posterior tibial tendinitis, spring ligament injury, Lisfranc sprain, and degenerative joint disease.[3] Therefore unrelenting symptoms in the seemingly normal midfoot merit further diagnostic workup and probably referral.

Towne et al.[4] first reported stress fracture of the tarsal navicular in 1970. In this series of two patients, each was a distance runner who had experienced midfoot pain with swelling and failure to respond to conservative therapy. Plain radiographs were negative, and only specialized studies were able to reveal the occult fracture. Subsequent reports have corroborated a history of insidious pain in the midfoot that is relieved by rest and exacerbated by forceful striking of the forefoot and with direct palpation of the navicular. [0050] [0060] [0070] A common thread in these reports is the normal appearance of plain radiographs. In most cases the diagnosis must be confirmed by computed tomography (CT), magnetic resonance imaging (MRI), or bone scan.

Imaging

Stress fracture of the tarsal navicular often is overlooked secondary to the low sensitivity of plain radiographs in diagnosing this condition. Some characteristics appreciated on anteroposterior views of the foot have been shown to correlate with navicular stress fractures. These include sclerosis of the proximal border of the navicular; a short first metatarsal; metatarsus adductus and hyperostosis; and stress fracture of the second, third, and fourth metatarsals. Improved imaging techniques have demonstrated that most fractures are linear, lie in the middle third of the navicular, and can be complete or partial.[8]Oblique or supinated radiographs can be useful ( Fig. 4-1 ).

 
 

Figure 4-1  An oblique radiograph of the tarsal navicular demonstrates a stress fracture.

 

 

Radionuclide bone scanning always demonstrates increased isotope uptake and can be a useful adjunct in the diagnosis of ill-defined midfoot pain. Views should include a medial, lateral, and plantar view. Uptake generally will appear in the shape of the navicular on the plantar view.[5] Although radionuclide scanning can assist in localizing the area of concern to the navicular, definitive diagnosis and definition of the fracture pattern require tomography or computer-aided tomography.

The majority of fractures occur in the middle third of the navicular. An anatomic anteroposterior (AP) tomogram views the middle third of the navicular en face and therefore is more likely to identify fractures.[5] However, modern computer-aided tomography has supplanted the use of tomography and is essential in the delineation of fracture pattern. Fine, 1.5-mm cuts are necessary in the axial plain to ensure that small incomplete fractures on the dorsal surface of the bone are not “skipped.” The role of MRI has not been clearly defined but likely will prove useful in the early diagnosis of this condition. Successful identification of the injury and its anatomy is crucial to effective management of the fracture.

Treatment

Complete elucidation of the fracture pattern is important in dictating management of the athlete. Patients with incomplete and nondisplaced complete fractures can respond well to conservative management. When treated in a nonweight-bearing cast for at least 6 weeks, 86% to 100% of patients will go on to union. [0020] [0030] [0040]

Patients with displaced fractures or those who have failed nonoperative management benefit from bone grafting with or without open reduction and internal fixation. Most of these athletes will return to sport within 5 to 7 months. [0020] [0030] [0040] High-performance career athletes and the treating surgeon may elect a more aggressive approach to nondisplaced fractures. Theoretically, surgical management of the injury could expedite the return to sport.

 

Stress Fracture of the Base of Second Metatarsal

Stress fracture of the base of the second metatarsal is an often-misdiagnosed condition that seemingly is exclusive to elite-level ballet dancers. However, fractures of the other metatarsals also are seen in new military recruits and running athletes.[9] These stress metatarsal fractures tend to be more diaphyseal and behave somewhat differently from the base of the second metatarsal. The unique biomechanics of ballet dancing, coupled with the high incidence of hypoestrogenism among female performers, generates an environment conducive to stress fracture of the base of the second metatarsal. High-level ballerinas generally have a narrow window of opportunity and short-lived careers. Therefore rapid diagnosis and treatment of conditions in this population is essential. Outcomes from treatment of second metatarsal fractures are excellent, and this injury usually is not considered to be a career-threatening disability.

Anatomy and Presentation

The most common presentation of stress fracture of the second metatarsal is the insidious onset of midfoot pain. However, ballerinas intermittently will report sudden onset of pain after an increase in training or after a jumping maneuver. Many performers will be able to “dance through” the pain and often do not present until 2 to 6 weeks after the onset of symptoms.[10] Hamilton[11] reported five risk factors for stress fracture in the ballet dancer. They include amenorrhea, anorexia nervosa, cavus foot, anterior ankle impingement, and a Morton's foot (short first metatarsal). Delayed menarche or abnormally long intervals between menses should motivate the clinician to suspect a stress fracture in the presence of pain.

Examination of the foot often is more obfuscating than revealing because patients will exhibit generalized tenderness of the midfoot with palpation and motion. Occasionally tenderness can be localized to the base of the second metatarsal; however, this does not differentiate metatarsal stress fracture from synovitis of the Lisfranc joint.[12]

The nature of this injury is due primarily to the interesting biomechanics of ballet and specifically to the incredible stresses placed on the midfoot when the dancer is in the en pointe position. When en pointe, the ballerina (male dancers dance only on demi-pointe) stands on the tips of her toes with the foot in maximal plantarflexion.[13] Consequently the mechanical axis of the lower extremity is directed straight through the plantarflexed foot. The middle cuneiform serves as a keystone in an arch-type configuration reminiscent of the sturdy arch first introduced in Roman architecture. The base of the second metatarsal is countersunk into this keystone. Furthermore, the plantar ligaments of the second metatarsal base are powerful, owing to the tensile forces experienced from push-off during normal gait. This fortified anchor of the proximal second metatarsal generates a substantial stress riser at the junction of the metaphysis and diaphysis when the dancer is en pointe. Understanding this relationship is important because treatment can be as simple as restricted dance with a moratorium on en pointe maneuvers until union is achieved.

Imaging

The evaluation of the painful foot in a ballerina must include clear weight-bearing views of the foot and ankle. O'Malley et al.[10] recommended a specialized view called the posteroanterior (PA) dancer's view. The dancer's foot is placed with the dorsum on the cassette to eliminate overlap of metatarsals. Approximately 30% of plain films will demonstrate a stress fracture. Bone scintigraphy is positive in 100% of second metatarsal stress fractures; yet Harrington et al.[12] reported positive bone scans in two of their patients diagnosed with synovitis of the second tarsometatarsal joint. In this series, T1-weighted and short tau inversion recovery (STIR) MRI images were used to differentiate stress reaction, fracture, and synovitis. CT with fine cuts also is an effective method to demonstrate a stress fracture of the base of the second metatarsal. The role of MRI has not been clearly defined, but eventually it may supplant scintigraphy as a more effective method for defining pathology at the base of the second metatarsal. Differentiation can help to direct a less disruptive management routine for professional dancers. For example, nonsteroidal treatment and dance modifications for traumatic synovitis may seem more attractive to a professional dancer than 6 weeks of rest.

Treatment

The timing of this injury, in concert with the goals and aspirations of the dancer, should lead the clinician in treatment. Patients usually can expect a full recovery in approximately 6 to 8 weeks. Initial management should include cessation of all dance activity and application of a hard-soled shoe. Pain at the base of the second metatarsal then serves as a barometer for return to activity. The dancer may begin working out but should delay return to jumping and en pointe maneuvers. The rate of recurrence can be as high as 12%. Ballerinas should be reassured that this is rarely if ever a career-ending injury.

Case Study  

An 18-year-old, college-level, female basketball player presented to the sports medicine clinic with a long-standing history of left midfoot pain that had gotten acutely worse. The pain was exacerbated by play and persisted the majority of the season. She had a history of a similar injury that was treated successfully in high school.

Examination demonstrated bilateral pes planovalgus deformities with tenderness over the base of the second metatarsal. Pain was reproduced with motion of the second, third, and fourth tarsometatarsal joints. Plain radiographs and a CT scan (Figs. 4-2, 4-3 and 4-4 [0020] [0030] [0040]) showed a chronic stress fracture at the base of the second metatarsal. She was given a walker boot for daily activity and a rigid shank for her shoe to wear during play. The boot was worn during off times, and the shank was worn during games. She successfully completed the season without limitations. Follow-up images showed a nonunion of the second metatarsal and a healed third metatarsal fracture. At last follow-up, she continued to play at the collegiate level asymptomatically.

 
 

Figure 4-2  An anteroposterior (AP) oblique radiograph shows a chronic stress fracture of the base of the second metatarsal.

 

 

 
 

Figure 4-3  An oblique radiograph shows a chronic stress fracture of the base of the second metatarsal.

 

 

 
 

Figure 4-4  A sagittal computed tomogram (CT) shows a chronic stress fracture of the base of the second metatarsal.

 

 

 

Stress Fracture of the Medial Malleolus

Stress fracture of the medial malleolus is a rare yet consternating condition of the medial ankle often experienced by running and jumping athletes. Although there is a paucity of literature regarding this unusual injury, there are similarities among the patients reported with this condition. In some of the series, patients went on to develop an acute fracture of the medial malleolus.[14] This point underscores the necessity of making the appropriate diagnosis in the avid athlete before a simple injury progresses to a more complex and debilitating injury.

Anatomy and presentation

The majority of patients with stress fracture of the medial malleolus are running and jumping athletes who present with gradual onset of pain over the medial ankle. Pain is exacerbated by activity and is localized to the medial malleolus. [0150] [0160] [0170] [0180] The ratio of male to female occurrence is 3:1, and the mean age of injury is 24 years. Most case reports represent high-performance athletes, of which several are professional.[11] Commensurate with the complete history involving any stress fracture, the treating physician should identify risk factors such as amenorrhea, nutritional deficiency, changes in footwear, and changes in training. Shelbourne et al.[18] identified three criteria for the evaluation of medial malleolar stress fracture. They include tenderness over the medial malleolus with an ankle effusion, pain during activity preceding an acute episode, and a vertical line from the tibial plafond proximally.

Physical examination often demonstrates edema of the medial malleolus with bony tenderness. Patients often will have normal motion in the ankle and subtalar joints and should not have tenderness of the lateral ankle or posterior tibial tendon. Analysis of hindfoot alignment is critical to assess any varus deformity that may exacerbate stresses on the medial malleolus.

A true biomechanical explanation for medial malleolar stress fracture is not described. However, the tensile forces of the medial ankle ligamentous structures ostensibly generate significant stress on the posteromedial concave side of the tibia. The majority of these fractures are vertical. This concept becomes important when one considers proper screw placement for internal fixation.

Imaging

Plain film radiography is requisite in the diagnosis of medial malleolar stress fractures and can be more useful with other problematic stress fractures of the foot. Roentgenograms often show a small area of fissuring at the junction of the tibial plafond and the medial malleolus. Infrequently, this fissure will be accompanied by radiolucent cysts along the fracture line.[12] When one has normal radiographs, bone scintigraphy can be extremely useful. Increased uptake in the area of the medial malleolus is seen uniformly in the presence of a stress fracture. The cases reported in the literature also have used CT and MRI. Although the role of these modalities has not been clearly defined, in isolated cases they have proven useful in defining the anatomy of a fracture or in confirming the diagnosis. Perhaps modern MRI will supplant the use of scintigraphy, given its ability to clearly delineate bony and ligamentous anatomy while defining inflammatory or reactive pathology.

Treatment

Initial management of stress fracture of the medial malleolus should include cessation of sport, with nutritional and endocrine interventions when appropriate. Recreational athletes with small fracture lines can be treated nonoperatively in a short-leg cast or removable boot. Disabling rotation about the ankle and dorsiflexion are key factors in neutralizing the tensile forces that can lead to displacement and delayed union of the injury. Patients treated conservatively should not return to sport until they are asymptomatic, a period of time that averages 6 weeks. Furthermore, patients treated nonoperatively will go on to complete union in about 6.7 months.[11]

Conversely, many authors prefer operative management of this injury, citing the possibility of nonunion and faster return to sport as incentives.

The objective of operative management is to create a construct that counters the tensile forces of the medial malleolus and allows quick rehabilitation. Standard AO technique should be used with either cancellous or cortical lag screws positioned perpendicular to the fracture line. Some surgeons advocate the use of lag screws through a buttress plate. Patients treated with internal fixation return to sport on average at 4.5 weeks and have evidence of union by 4.2 months.[11] The elite or professional athlete may prefer this option because it portends a faster return to activity and theoretically reduces the risk of nonunion or complete fracture. Reider et al.[19] reported a nonunion in a college-level football player who was misdiagnosed and managed conservatively for several months. This athlete went on to heal after operative intervention.

Although such reports are seemingly anecdotal, they highlight the importance of diagnosing and aggressively treating this injury in the high-performance athlete. A malleolar nonunion can lead to significant lost playtime and potentially can be career ending. Isolated medial ankle pain with normal radiographs merits further workup with either bone scintigraphy or MRI, followed by an appropriate scheme of management tailored to the athlete's goals and aspirations.

Case Study  

An elite-level, male, college basketball player began to note pain in the anteromedial distal ankle early in the season. As the season progressed, he had to stop playing because of recalcitrant pain. Physical examination demonstrated tenderness along the anteromedial aspect of the tibia and pain with dorsiflexion. Plain films (Figs. 4-5 and 4-6 [0050] [0060]) showed a small lucency in the anteromedial plafond that may have been consistent with an osteochondral defect. An MRI (Figs. 4-7 and 4-8 [0070] [0080]) did not show a definitive chondral lesion; however, there was high signal in the anterior and medial tibial plafond, suggesting a stress fracture of the medial malleolus. The patient was treated conservatively, and he sat out the remainder of the season. He returned the following year and played successfully without incident.

 
 

Figure 4-5  An anteroposterior (AP) radiograph in an elite college athlete does not show obvious fracture of the medial malleolus.

 

 

 
 

Figure 4-6  A lateral radiograph in an elite college athlete does not show obvious fracture of the medial malleolus.

 

 

 
 

Figure 4-7  T2 coronal images show increased signal in the anterior medial malleolus. Note that this area appears normal on the initial plain radiographs.

 

 

 
 

Figure 4-8  T2 sagittal images show increased signal in the anterior medial malleolus. Note that this area appears normal on the initial plain radiographs.

 

 

Case Study  

An elite-level, male athlete experienced debilitating pain in the ankle. Examination and imaging were consistent with a stress fracture of the medial malleolus. Axial CT images clearly demonstrated involvement of the anteromedial tibial plafond ( Fig. 4-9 ). The player was not able to return to preinjury performance after nonoperative management. Therefore he was treated with internal repair of the vertical fracture fragment ( Fig. 4-10 ).

 
 

Figure 4-9  Axial computed tomography (CT) scan showing stress fracture of the anteromedial tibial plafond.

 

 

 
 

Figure 4-10  Internal repair of vertical stress fracture of the medial malleolus.

 

 

Stress fracture of the hallucal sesamoids

Clandestinely located on the plantar surface of the great toe metatarsophalangeal (MTP) joint, the hallucal sesamoids are an often neglected and inadequately respected pair of tiny bones. They are capable of causing an enormous amount of pain, discomfort, and disability in the running and jumping athlete. Stress fracture of the sesamoid is an unusual and rare diagnosis that requires clinical and radiographic perseverance on the part of the treating clinician.

Anatomy and presentation

Rarely will a patient report focal pain of his sesamoid bones. Rather, he or she often describes a gradual onset of pain about the plantar surface of the great toe. This pain often is exacerbated by dorsiflexion of the hallux. In some instances, pain may be replaced by paresthesia of the great toe. Conversely, the patient may recall a specific incident in which he or she experienced a loud pop or snap on toe-off. Key features of the history should include changes in activity level, adequacy of footwear, and other important risk factors for stress fracture previously described.[20]

Physical examination should include a detailed, segmental analysis of the hindfoot, midfoot, and forefoot. Cavus feet have a penchant for sesamoid injury because of the increased load placed on the first metatarsal head. Direct palpation of the sesamoid will elicit pain. The tibial or medial sesamoid is most commonly involved. Furthermore, one may note decreased dorsiflexion of the first MTP joint and pain with range of motion. The corollary to this finding may be decreased strength of plantarflexion of the first toe.[17]

The hallucal sesamoids increase the mechanical advantage of the flexor hallucis brevis by acting in a mechanism similar to that of the patella; they are intrinsically located at the level of the MTP joint within the substance of the short flexor tendon. This location affords them an articulation with the metatarsal head and subjects them to enormous amounts of force when the phalanx is dorsiflexed and planted. The medial sesamoid is injured more often, owing to its larger size and more demanding role in weight bearing. Approximately 10% of patients have a bipartite sesamoid. This fact becomes important when interpreting plain radiographs of the sesamoid.[17]

Imaging

Plain radiographs of the foot can be more perplexing than useful in the diagnosis of sesamoid stress fracture. The clinician first must understand that a standard lateral view is essentially useless, and an AP of the foot is infrequently revealing. Medial and lateral oblique views of the sesamoids will more clearly visualize the tibial and fibular sesamoids, respectively. Several patients will have normal radiographs or the appearance of a bipartite sesamoid. The role of scintigraphy, CT, and MRI continues to evolve.

Many authors have recommended the use of bone scintigraphy in the evaluation of sesamoid pain. However, the ordering physician must communicate the need to perform oblique scans because a traditional anteroposterior bone scan of the foot can reveal first MTP activity that can obscure the sesamoids. A study of army recruits found no difference in sesamoid bone scan activity between soldiers in basic training for several weeks in comparison with sedentary adults. They cautioned readers about the interpretation of increased uptake in the sesamoid, warning that this may be normal physiologic activity for this bone.[21]

Perhaps axial imaging serves a more important role to the surgeon who potentially will treat the patient with excision of one of the sesamoid fragments. CT is an excellent modality for detection of sesamoid stress fractures. However, obtaining only axial images of the sesamoid can result in a false negative by “skipping” the fracture line. This error can be prevented by supplementing axial CT images with longitudinal cuts through the sesamoid.[22]

Improved availability of high-quality MRI may supplant the use of CT and bone scan because it enables the treating physician to obtain axial and longitudinal images, as well as indicators of stress fracture such as edema. Imaging facilities must use the appropriately sized coil for imaging of the sesamoids to ensure the proper resolution. High-resolution MRI of the sesamoid will show fragmentation and marrow changes in the face of acute stress fracture. Although MRI may not clearly define stress fracture versus avascular necrosis or chronic nonunion, this point is moot because treatment ultimately will be the same.[23]

Treatment

Treatment of this relatively debilitating condition can be rewarding yet frustrating. Most clinicians favor a conservative approach consisting of a nonweight-bearing, short-leg cast for 6 to 8 weeks.[17]Return to jumping and running activity should be graded on the basis of symptomatology. Furthermore, custom orthoses designed to unload the first MTP joint, such as a dancer's pad or a metatarsal bar, can be instituted after completing a course of casting. Because of the obscure diagnosis and the vulnerable physiologic location of the injury, nonunion and delayed union of the hallucal sesamoids is a common occurrence.

Management of the recalcitrant sesamoid fracture is surgeon specific and may include bone grafting or excision of the sesamoid. Authors have reported excellent results for all types of procedures. Potential pitfalls of operative intervention include digital nerve injury and weakness of the great toe flexor. A recent study reported good or excellent outcomes in dancers and in a long jumper treated with a partial excision of the medial sesamoid.[24] Athletes should expect a full recovery but should remain nonweight bearing for 4 to 6 weeks in the postoperative setting, followed by protection of the first MTP joint for another 4 to 6 weeks and a gradual return to activity by 3 to 4 months.

Stress fracture of the hallucal sesamoid should be suspected in the jumping or running athlete with first MTP pain that is refractory to initial conservative management. Notwithstanding that the diagnosis largely is clinical, axial imaging is extremely useful. Longitudinal CT is recommended for definitive revelation of fracture lines and surgical planning. Surgeons and patients will find that diligent treatment of these seemingly diminutive and insignificant bones can lead to a full recovery and return to competitive sport.

Case Study  

A 30-year-old, recreational athlete presented to a foot and ankle surgeon after a several-day history of right forefoot pain. The pain was associated with a long walk and progressed significantly in the week before the office visit. Examination demonstrated edema of the first MTP joint and pain with dorsiflexion. The patient was exquisitely tender over the tibial sesamoid. Plain x-rays showed a fracture of the tibial sesamoid ( Fig. 4-11 ). This was confirmed with CT. She was placed in a compressive boot with no weight bearing on the forefoot for 6 weeks. She was progressively weaned out of the boot and back to full weight bearing. At last follow-up she had full return to activity and radiographic evidence of callous formation.

 
 

Figure 4-11  A plain radiograph demonstrates stress fracture of the hallucal sesamoid.

 

 

 

Stress Fracture of the Fifth Metatarsal

No stress fracture of the foot and ankle has received more discussion and enamored more orthopaedic surgeons than the often-misunderstood stress fracture of the fifth metatarsal. A constant stream of dialogue exists in the literature regarding the history and treatment of fracture disorders of the proximal fifth metatarsal. Accordingly, misuse of the eponym “Jones fracture” is both propagated and defied. True stress fractures in this anatomic location in fact represent an entirely different injury, with its own mechanism and behavior, and should not be confused with the traditional Jones fracture or an avulsion fracture of the tuberosity ( Fig. 4-12 ). This point becomes critical because there are nuances in the treatment of these three distinct injuries.

 
 

Figure 4-12  The three zones of injury at the base of the fifth metatarsal.  Modified from: Lawrence ST, Botte MJ: Foot Ankle Int 4:358, 1993.

 



Anatomy and Presentation

The history and presentation of this injury is useful in discerning the diagnosis of stress fracture over an acute Jones fracture. DeLee et al.[25] defined stress fractures in the metatarsal as spontaneous fractures of normal bone that result from the summation of stresses, any of which by themselves would be harmless. They also reported on a series of patients who met three criteria. These include a prodrome of pain in the lateral foot, ultimately leading to debilitating pain; radiographic evidence of stress fracture; and no history of previous fracture and treatment of the fifth metatarsal. Consequently, patients often report a prolonged period of pain on the lateral border of the foot that may be exacerbated by a jumping or running maneuver. This final event generally is the impetus for a visit to a health care provider.

Understanding the diagnosis of fifth metatarsal stress fracture necessitates a thorough understanding of the anatomy of the lateral border of the foot. The fifth metatarsal itself consists of a head, neck, shaft, base, and tuberosity. The base of the metatarsal has three articulations. They are the cuboid-fourth metatarsal joint, the cuboid-fifth metatarsal joint, and the fourth and fifth intermetatarsal articulation. The peroneus brevis has a broad, fan-like insertion on the dorsal surface of the tuberosity, whereas the peroneus tertius inserts on the diaphysis of the bone slightly more distally. A styloid on the plantar surface of the tuberosity receives the fibers of the lateral band of the plantar aponeurosis.[26]

Variations in the anatomy of the proximal fifth metatarsal are described and can be misleading clues for diagnosing fracture of the tuberosity. These variations include the os peroneus, the os vesalianum, and the secondary ossification center of the tuberosity. The os peroneum is a sesamoid bone located in the tendon of the peroneus longus that may occur in up to 15% of normal feet. The os vesalianum is a similar sesamoid, with a less regular shape, occurring only 0.1% of the time. The secondary ossification center or apophysis of the fifth metatarsal does not appear until after age 8 in females and age 11 in males. The apophysis may be present only in up to 50% of feet. This structure can be differentiated from a fracture because the physeal line runs parallel to the shaft of the bone. Conversely, a fracture in this anatomic location generally is in a plane orthogonal to the diaphysis of the bone.[27] Although the task seems daunting, organization and diagnosis of the myriad fractures of the fifth metatarsal can be simplified by applying a classification scheme.

Fractures of the base of the fifth metatarsal are subdivided into three types. They include type I tuberosity avulsion fractures, type II Jones fractures, and type III stress fractures of the diaphysis.[28] Stress fractures are subdivided further into types A, B, and C, which correspond to early stress fracture, delayed union, and nonunion.[24] This classification scheme is useful because it is anatomically based and describes separate fractures with differing mechanisms. The scope of this topic is large, and therefore we discuss here treatment of stress fracture of the fifth metatarsal.

Imaging

Radiographic diagnosis of fifth metatarsal stress fracture typically is not as elusive as the other bones of the foot and ankle. However, clear interpretation of roentgenograms is critical in defining the type of fracture. Patients who present early in the course of their lateral foot pain may have normal radiographs. The first feature to appear is thickening of the cortex and a small periosteal reaction.[29] The three subtypes of stress fractures can be differentiated radiographically. Type I, or acute or chronic fractures, are characterized by a straight line at the junction of the proximal and middle third of the diaphysis. The bone ends are sclerotic, there is minimal periosteal reaction, and there is no widening. Type II fractures, or delayed unions, will demonstrate widening with hypertrophic periosteum and a wide band of radiolucency across the diaphysis. The medullary canal may be sclerotic. The type III fracture, or nonunion, differs in that the bone ends will appear to be entirely sclerotic, as though the medullary canal were nonexistent.[23]

The clinical and plain radiograph diagnosis of fifth metatarsal stress fractures rarely requires the use of bone scan or MRI. Scintigraphy will demonstrate increased uptake within 72 hours of acute injury but is less specific. As in other stress fractures, MRI will clearly demonstrate a fracture line with surrounding edema and signal change.[26]

Treatment

Management of fifth metatarsal stress fractures is determined on the basis of the needs and goals of the athlete, as well as the radiographic classification of the injury. Surgeons may opt to be more aggressive in professional athletes, who are dependent on a rapid return to play. Conversely, patients may advocate a less invasive approach to initial management. All athletes with this injury should be counseled on the pitfalls that may be encountered, including nonunion and temporary disability. Authors favoring conservative management have reported lackluster results. Specifically, patients are prone to prolonged immobilization and nonunion.[25] Improved results have been demonstrated with surgical intervention, and as such this modality is advocated in most athletes who desire early definitive treatment.

Torg et al.[30] have demonstrated that acute, nondisplaced stress fractures of the fifth metatarsal can be treated successfully with nonweight-bearing immobilization. The importance of compliance with nonweight-bearing status should be emphasized for the first 6 to 8 weeks, as weight bearing has been shown to diminish healing. The management of type II delayed unions is less clear. Nonweight-bearing immobilization is effective but prolonged, and the specter of nonunion is not unreal. Athletes with a strong penchant for an expedited recovery may opt for intramedullary fixation.[31]

Nonunions, or type III stress fractures, have been treated with pulse electromagnetic fields and bone grafting. However, most surgeons now agree that intramedullary fixation promises the most success. Although the type of fixation varies among surgeons, the common theme is a minimally invasive procedure in which the base of the fifth is exposed and a screw is inserted through the canal under fluoroscopic guidance. Drilling of the canal in preparation for the fixation creates an autogenous intramedullary bone graft and stimulates healing at the fracture site. Initial reports of this treatment demonstrated 100% union in less than 8 weeks, with return to sport averaging less than 9 weeks.[22] However, patients should be aware that nonunion is a potential complication and possibly is related to screw diameter.[32]

Stress fracture of the base of the fifth metatarsal is a debilitating injury that requires expertise in diagnosis on behalf of the treating surgeon. Mistaking this injury for a less benign fracture, such as a tuberosity avulsion, can result in painful nonunion and significant loss of playing time. Therefore commensurate management demands a thorough understanding of the anatomy of the fifth metatarsal and the variable fracture patterns existing in this location. Athletes treated correctly can often expect an excellent prognosis.

Case Study  

A 22-year-old, college-level, female soccer goalie noted lateral border of the foot pain after kicking a soccer ball. Physical examination was consistent with fifth and fourth metatarsal tenderness. Plain films demonstrated a fracture at the base of the fifth metatarsal ( Fig. 4-13 ). She underwent percutaneous screw fixation with a 4.5-mm shaft screw (Figs. 4-14 and 4-15 [0140] [0150]) and had full return to sport 6 weeks postoperatively.

 
 

Figure 4-13  Stress fracture of the base of the fifth metatarsal in a female soccer player.

 

 

 
 

Figure 4-14  Anteroposterior (AP) radiograph after percutaneous fixation with a 4.5-mm shaft screw.

 

 

 
 

Figure 4-15  Lateral radiograph after percutaneous fixation with a 4.5-mm shaft screw.

 

 

 

Summary

Poorly defined foot and ankle pain in the athlete can be a consternating and often frustrating condition for athletes, trainers, and physicians. Stress fractures represent a subset of maladies of the foot and ankle that require diligence on behalf of the diagnostician. Careful history and physical examination will illuminate mechanisms of injury specific to each fracture type and risk factor, such as weight loss, amenorrhea, and eating disorders. Moreover, the clandestine fracture often will require advanced imaging modalities, such as CT, bone scintigraphy, and MRI. Therefore a global approach to care of the athlete is advised. This should involve activity modification, improvements in training, nutritional and psychological counseling, as indicated, and definitive orthopaedic intervention. Athletics are an important facet of life, and disability related to sports can be devastating. Accurate diagnosis and successful treatment of problematic stress fractures of the foot and ankle is a rewarding and attainable goal for all trainers and physicians.

 

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