In a patient with a Jones-type fracture of the base of the fifth metatarsal that shows a persistent radiolucent fracture line and slight increased displacement at four weeks while in a walking boot, what is the recommended next step in management?

Management of Fifth Metatarsal Base Fracture with Persistent Lucency and Increased Displacement at 4 Weeks

Obtain MRI without IV contrast immediately to assess the true extent of injury, bone marrow edema, and risk of progression to complete nonunion, then proceed to orthopedic surgical consultation for consideration of intramedullary screw fixation. 1

Why Advanced Imaging is Critical Now

• The persistent radiolucent fracture line at 4 weeks with increased displacement indicates this fracture is not healing appropriately with conservative management alone. 1
• The American College of Radiology identifies the fifth metatarsal base as a high-risk location for stress fractures prone to delayed union or nonunion. 1
• MRI without IV contrast is the single most appropriate advanced imaging modality for this clinical scenario, providing superior sensitivity and specificity compared to repeat radiographs or bone scintigraphy. 1
• MRI will reveal occult fracture extension, the true extent of osseous injury, and high-risk features such as cortical signal abnormality or intramedullary sclerosis that are invisible on plain films. 1
• Each 1-unit increase in MRI grading correlates with approximately 48 days longer return-to-activity time, providing crucial prognostic information. 1

Classification Determines Treatment Path

• This fracture pattern (persistent lucency with displacement at 4 weeks) likely represents a Type II injury (delayed union) based on the Torg classification system. 2
• Type I fractures show a narrow fracture line without intramedullary sclerosis (acute). 2
• Type II fractures demonstrate widening of the fracture line with evidence of intramedullary sclerosis (delayed union). 2
• Type III fractures show complete obliteration of the medullary canal by sclerotic bone (established nonunion). 2

Why Conservative Management Has Failed

• Only 40% of acute fifth metatarsal base fractures treated with weight-bearing methods progress to union, compared to 93% with non-weight-bearing cast immobilization. 2
• The walking boot you have been using likely allowed excessive motion and weight-bearing, preventing adequate healing. 2
• Follow-up radiographs before 6-8 weeks rarely alter management in uncomplicated cases, but your increased displacement and persistent lucency at 4 weeks represents a complication requiring escalation. 3
• Conservative treatment should not extend beyond 6-8 weeks without advanced imaging when the fracture line remains lucent on radiographs. 1

Surgical Intervention is Likely Indicated

• Type II fractures (delayed union) in active patients should be treated operatively, particularly when conservative management has already failed. 4
• Intramedullary screw fixation is the preferred surgical technique for Jones-type fractures at the metadiaphyseal junction. 4
• Of 10 Type II fractures initially treated with immobilization and weight-bearing, only 7 healed (mean 15.1 months) and 3 eventually required bone grafting for nonunion. 2
• In contrast, surgical treatment with medullary curettage and bone grafting achieved healing in 8 of 9 established nonunions within a mean of 3 months. 2

Surgical Planning Considerations

• Screw length should be kept less than 68% of the total fifth metatarsal length to avoid excessive length and potential complications. 5
• A screw diameter greater than 4.5 mm is needed in 81% of males and 74% of females to provide adequate fixation at the isthmus. 5
• The medullary canal has a lateroplantar curvature beginning at approximately 52 mm from the base, which corresponds to the "straight segment" suitable for screw placement. 5

Alternative if MRI is Contraindicated

• If MRI is unavailable or contraindicated, obtain CT without IV contrast as the alternative imaging modality. 1
• CT accurately evaluates the true osseous extent of injury and cortical fragmentation, though it is less sensitive than MRI for early stress-related bone changes. 1

Critical Pitfalls to Avoid

• Do not continue conservative management beyond 6-8 weeks with a persistent lucent fracture line, as this significantly increases the risk of progression to established nonunion requiring more extensive surgery. 1
• Do not rely on repeat plain radiographs alone to guide management at this stage—they lack the sensitivity to detect intramedullary sclerosis and early nonunion changes. 1
• Avoid prolonged immobilization without surgical intervention in Type II fractures, as this leads to muscle atrophy and stiffness without improving union rates. 6, 2