Metatarsal injuries range from simple fractures to severe crush injuries with multiple fractures and soft tissue damage. 2nd and 3rd MT fractures are more commonly seen than 1st and 4th, and all these fractures are less common than 5th metatarsal fractures. The metatarsals also the most common site of stress fractures in the skeleton.
Most of the literature and studies available relate to stress fractures rather than acute injury of the metatarsals with mainly case reports and very small studies on acute fractures.
In children 61% of foot fractures are in the metatarsals.
Petrisor (2006), looked retrospectively at 355 patients with 411 metatarsal fractures. The overall incidence was 6.7 per 10,000 population.
- 1st - 1.5%
- 2nd - 10.2%
- 3rd - 11.2%
- 4th - 9%
- 5th -68%
Nine percent had multiple fractures, 1.2% were open and 1.9% had an associated Lisfranc injury
Other studies show similar figures with 2nd and 3rd more common than 1st and 4th.(Sanchez 1996, Rammelt 2004). Fracture of the 4th MT is uncommon because of the flexibility of the ray and its protected position, and of the 1st because of its relative size and mobility.
Second metatarsal fractures are commonest in the diaphysis and distal metaphysis. 3rd and 4th mainly occur in the distal metaphysis. There is next to no literature on 1st metatarsal fractures; case reports suggest they are commonest at the proximal metaphysis
A retrospective study of 10 open metatarsal fractures (Hoxie 2007), contained 4 grade I, 2 grade II and 4 grade IIIB fractures. All IIIB fractures resulted in an amputation secondary to infection and poor wound healing because of significant soft tissue damage( 1 toe, 1 ray, and 2 Symes).
Whilst not as well defined as the 5th MT fracture, there are several classifications that can be used.
- Aetiological classification
- Acute fracture
- Stress fracture
- Repetitive strain type
- Insufficiency type
- Site of fracture
- Proximal/ base
- Distal/ neck
- Zwipp (2004) described the AO classification of injuries of the foot (as applied to the metatarsals
C Fracture dislocation
As with all fractures they can present with pain, swelling, bruising and deformity
The mechanism of injury can be variable from RTA to crush injury. Crush injuries are mainly transverse or comminuted and are associated with compartment syndrome of the foot. A high index of suspicion is required and urgent fasciotomies performed if clinically suspected.
AP and lateral x-rays should be obtained as standard. Oblique views are particularly useful in proximal injuries to assess the Lisfranc joints.
In the presence of several basal metatarsal fractures/ significant mechanism or severe soft tissue injury a CT to rule out a Lisfranc injury may be required.
1st metatarsal proximal metaphyseal fractures can be difficult to see on plain radiographs and oblique views are recommended.(Lucas 1997)
In delayed presentation/ malunion, an AP and lateral weight bearing can be supplemented with a weight bearing tangential view of the metatarsal heads to assess deformity.(Rammelt 2004).
Undisplaced fractures are treated symptomatically. Methods used include strapping, wooden soled shoes or walking cast for up to 4-6 weeks. The evidence base is poor.
The only prospective study available is by Zenios (2005). This was a RCT of 50 patients with acute lesser metatarsal fractures, treated with walking below knee cast vs elastic support bandage. There was no difference in mobility, analgesic requirements or union at 3 months. However AOFAS scores were higher and pain scores lower in the elastic support bandage group at 3 months and there were plaster related complications such as DVT in the casted group. Most of these fractures, however, were of the 5th metatarsal.
Displacement is more common in the shaft and distal fractures. Basal fractures have the restraints of the capsular attachments, interosseous ligaments as well as the tibialis posterior and peroneus longus insertions. In displaced fractures the goal of treatment is to preserve or restore alignment of the metatarsal heads, to maintain normal weight bearing. Sagittal displacement of the metatarsal head and/or shortening (in oblique fractures) will alter weight bearing and can result in metatarsalgia and plantar keratosis.
Translational displacement can result in mechanical impingment and interdigitial neuroma. In the 1st metatarsal correction of the displacement in the transverse plane aims to prevent a post traumatic hallux valgus or varus. A residual deformity at the dorsal apex of a fracture can result in a corn or exostosis.
Multiple fractures of the metatarsals may increase the likelihood of needing surgery because of the loss of inherent stability from adjacent metatarsals. Shereff (1990) suggests that reduction is required with displacement >3-4mm and angulation >10 degrees in the sagittal plane
Midshaft fractures can be crossed k-wired (2x 1.8 or 2mm wires) after closed or open reduction. Open reduction and plate fixation may be required in comminuted fractures. In intra-articular fractures the 1st TMT or MTP joint should be reconstructed and fixed with mini fragment screws to prevent post traumatic arthritis.
Retrograde intramedullary k-wiring (AO recommendation) can be performed following closed reduction. The wire should be inserted percutaneously through the base of the proximal phalanx. This provides good control of the toe and distal fragment. If placed through the MTP joint dorsal subluxation of the toe and distal fragment can result. Myerson in 2000 also describes the technique via the plantar aspect of the base of the proximal phalanx in order to avoid scarring of the plantar plate and MTP joint stiffness. (Rammelt 2004, Armagan 2001)
Open reduction can be performed through a dorsal incision over the shaft of the metatarsal or webspace for adjacent fractures. If required the K-wire can be inserted antegrade via the fracture site into the distal fragment and proximal phalanx and then backed up into the proximal fragment. Formal plate fixation may be required in comminuted fractures.
There are no outcome studies following operative management of these fractures.
In malunion /delayed presentation if initial management with footwear modification/ orthotics fails, corrective osteotomy may be required.
The metatarsals are the commonest site for stress fractures in the body. They usually present in the normal bone of young adults after repetitive loading without adequate recovery time (Niva 2007) rather than a single traumatic event. Sustained after periods of increased actively in athletes and military recruits (Arndt 2002), they are most common in the 2nd and then 3rd metatarsal neck and diaphysis. The classical “March fractures” of the 2nd and 3rd metatarsals are seen in military recruits. Ballet dancers usually present with base of 2nd metatarsal fractures. The location is dictated by the loading pattern.
Proximal 2nd metatarsal fractures can also be found in non-dancers. In a retrospective case review of 4078 metatarsal fractures(Chuckpaiwong 2007), 84 were 2nd metatarsal stress fractures; of these 12 were at the base of the 2nd metatarsal. All these patients were non-dancers and there was a history of walking or running. There was a 50% non union rate inspite of 6 weeks non weight bearing in a cast/boot. 2/3rds had significant co-morbidites. Decreased bone mineral density was found in 2/3rds.
There are no studies quoting incidence in the general population. Studies of stress fractures in athletes and military recruits state that 7.3-23% occur in the metatarsals (Arndt 2002,Gehmann 2006) with 80-90% in the 2nd and 3rd metatarsals (Chuckpaiwong 2007).
They can present rather with an acute onset. Milgrom (2002) showed in vivo that compression and tension strains in the metatarsals may be sufficiently high to cause rapid fatigue failure of the bone secondary to the number of loading cycles, without an intermediate bone remodelling response which is typically found in stress fractures of the tibia.
Kaye 1998 classifies them as
- Fatigue ( Normal bone with increased load)
- Insufficiency (Abnormal bone with normal load)
They can also be classified by location as with acute fractures.
Reduced bone mineral density - Kaye (1998) reported 8 insufficiency fractures in postmenopausal women and recommended these be investigated and treated as for osteoporotic fractures elsewhere
Inflammatory arthritis - Maenpaa (2002) reported 24 stress fractures in 17 patients with inflammatory arthritis of the foot and ankle (RA/PA/Ank spod/JCA), of which 16/24 were metatarsal. Ankle malalignment was present in 13/16 - varus hindfoot was associated with lateral and valgus associated with medial metatarsal fractures. (Maenpaa 2002)
Metabolic bone disease - the female athletes' triad of amenorrhoea, anorexia and osteoporosis
Repetitive weight bearing activity – Arndt (2002) reported a study of 2nd metatarsal strain, measured in 8 barefoot walking subjects with an osseous pressure measurement staple with and without backpack loading. Increased dorsal strain was found with external loading and plantar muscle fatigue.
Muscle fatigue - Sharkey’s (1995) study of MT strain in 9 cadavers found contraction of plantar flexors of the toes helps counteract the plantar-dorsal bending moments placed on the metatarsal by body weight on heel lift. 50% reduction in the activity of flexors results in a 50% decrease in the number of cycles to failure. Donahue (1999) described a dynamic simulation of the stance phase of gait in 15 loaded cadaveric feet. The influence of simulated muscle fatigue and plantar fasciotomy on strain in the 2nd and 5th metatarsals was measured. Fatigue of FHL and FDL results in a 4 fold decrease in the number of loading cycles before 2nd metatarsal failure.
Footwear - a prospective study (Milgrom 1992) of 390 Israeli army recruits randomised them to train in either standard infantry boots or basketball shoes. 140 stress fractures occurred in 93 recruits of which 7 were in the metatarsals. There was a statistically significant reduced incidence of metatarsal fracture in the basketball shoes group, as well as a reduction in metatarsalgia, heel and arch pain. Viscoelastric materials can improve shoe shock attenuation and reduce stress fractures. Meardon (2009) described a cadaver study in which cadaver feet were "walked" over a force plate wearing semi-custom and fully customised orthoses. Semi-custom orthoses reduced tension strains and shear strain rates, while fully custom orthoses also reduced shear strain and compression rate. No long-term fatigue testing was reported.
Alterations in foot biomechanics have been suggested as an extrinsic factor. However, the theory that 1st ray dorsal mobility predisposes to stress fractures of the 2nd and 3rd metatarsals was tested in a retrospective case control study of 15 female atheletes with previous stress fracture matched with female athelete controls. 1st ray dorsal mobility and systemic hypermobility (Beightons classification) were measured and were not statistically different between groups. Similarly, Davidson (2007) reviewed 50 classical ballet dancers and found no difference between relative 2nd metatarsal length of the 17 feet that had had stress fractures and the 83 feet without.
In ballet dancers the en pointe position is implicated because with the foot fully plantar flexed the middle cuneiform locks in as the keystone of the transverse arch. On weight bearing the leg and hindfoot are one lever arm with a stress concentration at the TMT junction; however the plantar ligaments along with tibialis posterior and peroneus longus result in a stress transfer to the 2nd metatarsal base. Five of the patients in O'Malley's (1996) study were male (no en pointe) supporting the multifactorial aetiology including nutrition, rigorous training and performance schedule, hard floors and uncushioned shoes
Ballerinas may have delayed menarche and episodic amenorrhoea as was the case in this study. Morton's foot with a short 1st metatarsal was not implicated - the average 1st to 2nd ratio was 0.82, with no patient falling below the 0.73 figure quoted by Drez et al to define Mortons foot.
In a retrospective study comparing proximal vs non proximal 2nd metatarsal fractures (Chuckpaiwong 2007), longer duration of symptoms, shorter 1st metatarsal, Achilles contracture, reduced bone mineral density and training < 0.5 hours per week were identified as potential risk factors for proximal fractures. However they only looked at a total of 58 fractures and compared many variables retrospectively between these broad groups.
The patient may complain of pain and swelling in the forefoot with a history of repetitive weightbearing and/or one of the implicated professions. The patient may limp or heel walk. Base of 2nd metatarsal fractures may present in ballerinas with ill-defined midfoot pain increased after a training session - usually in the middle of the performance session (O’Malley).
O’Malley (1996) reviewed 51 professional ballet dancers in New York and looked at 64 fractures of the base of 2nd metatarsal which typically presented with a 2-3 week history insidious onset of midfoot pain. They were tender in the 1st dorsal web space or over the 2nd metatarsal base, with pain on heel raise. 19 (34%) were found on x-ray, 42 patients required a bone scan for diagnosis. All fractures were proximal to the meta/diaphyseal junction. All healed with conservative management. Fourteen parcent had occasional pain whilst dancing. No delayed or non unions were identified.
AP and lateral x-rays +/- oblique views are standard. O'Malley recommended a PA ‘dancers view’ to eliminate overlap of joints at the base of the 2nd metatarsal.
Plain radiographs are initially normal; early callus is diagnostic. Signs on x-ray may be subtle and only present after 14 days
- Longitudinal cortical hypertrophy
- Narrowing of the medullary canal
- Periosteal lucency
- Transverse lines of sclerosis
A technicium 99 bone scan or MRI will detect fractures and bone stress reaction not seen on x-ray. An MRI will also further differentiate a bone stress reaction from a fracture (Niva 2007). CT will confirm a fracture but will not show a stress reaction.
Banal (2009) compared MRI with ultrasound in 37 patients with 41 painful feet, clinical suspicion of stress fracture and normal plain radiographs. MRI identified 13 fractures. The sensitivity of ultrasound was 83%, specificity 76%, positive predictive value 59%, negative predictive value 92%. They felt this was good enough to use ultrasound as the intial investigation in this clincial scenario.
Investigations for osteoporosis are requested where clinically indicated.
The use of orthotics has been proposed as a method of prevention of stress fractures in populations at risk.
Treatment is symtomatic in a short leg cast or hard soled shoe for 6-8 weeks. Harrington (quoted in Gehrmann 2006) found that 7/8 of the dancers in his study returned to dancing painfree after this treatment with 1 describing occasional aching. O'Malley also found that dancers were able to return at an average of 6 weeks, when tenderness resolved.
A series of five case histories of proximal 4th metatarsal fractures in athletic patients at the shaft/base junction showed prolonged healing and recommends that these fractures be likened to the Jones fracture at the same level in the 5th metatarsal and consideration given to initial non weight bearing in a cast for 3-6 weeks.
We have seen two apparent stress fractures in non-dancers which failed to resolve with non-surgical treatment and required bone-grafting and fixation with a minifragment plate.
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