SUMMARY 5th Metatarsal Base Fractures are among the most common fractures of the foot and are predisposed to poor healing due to the limited blood supply to the specific areas of the 5th metatarsal base. Diagnosis is made with plain radiographs of the foot. Treatment can include protected weight bearing, immobilization or surgery depending on location of fracture, degree of displacement, and athletic level of patient. Epidemiology Incidence frequent injury encountered in primary care setting base of 5th metatarsal fractures account for 25% of all metatarsal fractures 90% are zone 1 fractures Demographics athletes, military recruits, and manual laborers Etiology Pathophysiology mechanism of injury plantarflexion and hindfoot inversion leads to zone 1 fractures forefoot adduction leads to zone 2 fractures repetitive microtrauma leads to zone 3 fractures Associated conditions concomitant midfoot injuries (i.e. Lisfranc injury) lateral ankle ligamentous laxity cavus foot and varus hindfoot deformities ANATOMY Osteology divided into tuberosity, base, metadiaphysis, diaphysis, neck, and head base and tuberosity login to view 4 more bullets metadiaphyseal region login to view 1 more bullet diaphysis login to view 2 more bullets neck login to view 2 more bullets head login to view 1 more bullet Blood supply blood supply provided by metaphyseal vessels and diaphyseal nutrient artery zone 2 (Jones fracture) represents a vascular watershed area, making these fractures prone to nonunion Biomechanics fifth metatarsal forms lateral border of forefoot functions as a lever in gait during push-off CLASSIFICATION Lawrence and Botte Anatomic Classification Class Description Zone 1 PseudoJones fx Proximal tubercle avulsion Due to long plantar ligament, lateral band of the plantar fascia, or contraction of the peroneus brevis May extend into cubometatarsal joint Nonunion uncommon Zone 2 Jones fx Metaphyseal-diaphyseal junction Involves the 4th-5th metatarsal articulation Vascular watershed area Acute injury Increased risk of nonunion (15-30%) Zone 3 Proximal diaphyseal fracture Distal to the 4th-5th metatarsal articulation Stress fracture in athletes Associated with cavovarus foot deformities or sensory neuropathies Increased risk of nonunion Torg Radiographic Classification Class Characteristics Fracture Age Type I Narrow fracture line without intramedullary sclerosis Acute Type II Widened fracture line with intramedullary sclerosis Delayed Union Type III Widened intramedullary canal with no callus Nonunion PRESENTATION History antecedent pain in setting of stress fracture, rapid increase in workload or change in training regimen Symptoms location pain over lateral border of forefoot, especially with weight bearing aggravating/alieving factors worse on weightbearing Physical Exam inspection rare skin tenting from zone 1 fractures tenderness to palpation along bone at fracture site varus hindfoot alignment during weightbearing cavus foot deformity excessive lateral wear pattern on shoe treads fifth metatarsal head callosity motion evaluate for lateral ligamentous instability and whether varus hindfoot is correctable provocative tests pain with resisted foot eversion (indicates peroneal tendon weakness) IMAGING Radiographs recommended views AP, lateral and oblique foot images findings details fracture pattern and location intramedullary sclerosis and lack of periosteal callus reaction indicative of chronicity login to view 1 more bullet plantar fracture gap lends poor prognosis for union with nonoperative treatment plantarflexed first metatarsal and high Meary's angle indicating cavovarus deformity Bone scan indications suspicion for stress fracture with equivocal radiographs findings uptake within diaphysis CT indications to evaluate degree of fracture healing in setting of delayed/nonunion or following surgical fixation MRI indications suspicion for stress fracture with equivocal radiographs or bone scan findings high signal stress reaction and edema TREATMENT Nonoperative protected weight bearing in stiff soled shoe, boot or cast indications login to view 1 more bullet outcomes login to view 2 more bullets non-weight bearing short leg cast for 6-8 weeks indications login to view 2 more bullets outcomes login to view 1 more bullet Operative intramedullary screw fixation indications login to view 4 more bullets outcomes login to view 1 more bullet open reduction internal fixation with plate and screws indications login to view 2 more bullets outcomes login to view 1 more bullet TECHNIQUES Protected weight bearing in stiff soled shoe, boot, or cast technique advance weight bearing as tolerated by pain union achieved by 8 weeks, fibrous unions are infrequently symptomatic early return to work but symptoms may persist for up to 6 months Non-weight bearing short leg cast for 6-8 weeks technique advance weight bearing with signs of radiographic callus (around 4-6 weeks) zone 3 fractures often require 6-7 weeks of non-weight bearing immobilization reports of extracorpeal shock wave with similar union rates as internal fixation for zone 3 stress fractures Intramedullary screw fixation approach patient supine with bump under hip and fluoroscopy immediately available percutaneous/ limited open approach short longitudinal incision proximal to tuberosity, parallel with plantar surface soft tissue blunt dissection past sural nerve branches to tuberosity, between peroneus longus and brevis tendons using fluoroscopy, K-wire starting position superior and medial on tuberosity ("high and inside" position) login to view 1 more bullet reduction k-wire placed intramedullary, fluoroscopy to confirm location soft tissue protector placed and wire may be removed or cannulated drill used to open canal and drill pilot hole sequentially tap to be able to place screw larger than 4mm diameter instrumentation tap can be used to measure appropriate length screw 4.5mm, 5.5mm, or 6.5mm diameter partially-threaded screw placed login to view 1 more bullet fluoroscopy must be used to confirm all threads cross fracture site and no distal cortical perforation if fracture gap persists or in cases of nonunion/revision, bone graft material may be added at fracture site rehabilitation short period of non-weight bearing (1-3 weeks) followed by protected weightbearing and beginning therapy focusing on range of motion and non-impact aerobic exercises running and impact activities commenced at 6 weeks if surgical site pain-free and signs of radiographic callus Open reduction with plate and screw internal fixation approach longitudinal incision centered over proximal 5th metatarsal bone work typical plantar fracture gap and/or rotational displacement able to be reduced instrumentation 3mm plate bent to contour to plantar-lateral surface of bone to compress fracture COMPLICATIONS Nonunion incidence nonunion rates for Zone 2 injuries are as high as 15-30% risk factors zone 2 and zone 3 fractures due to vascular supply smaller diameter screws (<4.5mm) associated with delayed or nonunion nutritional (vitamin-D) or hormonal (thyroid) deficiencies treatment revision intramedullary screw fixation with use of bone grafting Failure of fixation risk factors elite athletes return to sports prior to radiographic union fracture distraction or malreduction due to screw length login to view 2 more bullets treatment revision internal fixation Refracture incidence 33% of zone 2 fractures following nonoperative treatment risk factors cavovarus foot deformity, stress fractures, vitamin-D insufficiency, removal of intramedullary screw treatment internal fixation with surgical correction of cavovarus deformity if present leave screw in place until end of patient's athletic career Painful hardware incidence rare complication following intramedullary screw fixation risk factors screw head left prominent can irritate sural nerve branches treatment modified shoewear Sural nerve injury risk factors direct trauma during screw insertion prominent screw head impinging on nerve branches login to view 1 more bullet treatment prevented by using tissue protector during procedure and sinking screw head Chronic pain uncommon, result of zone 1 fracture nonunion after initial conservative treatment treatment fragment excision and reattachment of peroneus brevis tendon