Keys To Treating Proximal Fifth Metatarsal Fractures

Given the common nature of fractures to the proximal region of the fifth metatarsal in athletes as well as non-athletes, this author discusses emerging insights on diagnostic classifications, screw fixation, chronic fracture treatment and post-op recovery.

Proximal fifth metatarsal fractures are common injuries that can arise in the athletic as well as the non-athletic population. Traditionally, this area is classified based on the work of Torg and colleagues in their classic article describing the zones of injury.¹ Zone 1 refers to a tuberosity fracture. Zone 2 is the traditional Jones fracture located at the junction between the proximal diaphysis and metaphysis of the fifth metatarsal without distal extension beyond the fourth to fifth intermetatarsal articulation. A Zone 3 injury is a proximal diaphyseal fifth metatarsal stress fracture, defined as a stress fracture in the zone of the proximal fifth metatarsal immediately distal to the anatomic area of the Jones fracture.  

Yates and coworkers performed a systematic review looking at the results of conservative versus surgical intervention of the Jones fracture.² The review includes six relevant studies with a total of 237 patients. Of these, 51 percent had non-operative treatment and 49 percent had surgical intervention. Those in the non-operative group had a significantly higher odds ratio of fracture non-union (5.74). The studies included in the systematic review also reported a prolonged healing time and a longer time to return to sports in the non-operative group.

Of the trials using time to union as an outcome measure, three of four trials found favorable results in the operative cohort.² The authors recommended surgical intervention for patients presenting with a Jones fracture as it results in a reduced non-union rate and an improved time to union. Tuberosity fractures (Zone 1) have a good prognosis with conservative treatment. Zone 2 or 3 injuries have a less predictable prognosis when it comes to conservative treatment. The question that I raise is if there is a need to distinguish between Zone 2 and Zone 3 injuries.  

There can be significant confusion on the part of foot and ankle specialists as well as radiologists as to what truly are Zone 2 and Zone 3 injuries. Chuckpaiwong and colleagues have questioned the necessity to differentiate between these two diagnoses.³ They retrospectively reviewed 32 Jones fractures and identified 29 proximal diaphyseal fractures. All fractures healed between 4.8 and 9.8 months with a 78 to 82 percent patient satisfaction rate. Regardless of treatment, the clinical outcomes were not different between the two fracture locations. Surgical patients returned to sport sooner. The surgical patients with fracture site sclerosis or medullary canal obliteration on radiographs had lower satisfaction and higher complication rates than patients without these changes. The authors did not find a reason to distinguish between fractures of the fifth metatarsal in these two locations. They suggested referring to fifth metatarsal base fractures (excluding avulsions) as Jones fractures.

Lee and coworkers actually looked at classifying Jones fractures based on complete fracture and incomplete fracture.⁴ The authors reviewed 86 patients who had surgery and assessed post-op computed tomography (CT) scans to determine bone union. There was a significant difference in the time for bone union. The mean time for bone union in group A (32 patients with complete fracture) was 67.5 days ± 28.8 and it was 103.2 days ± 47.7 for group B (54 patients with incomplete fracture).

The authors also subdivided the cases of incomplete fracture based on the presence or absence of a plantar gap more than 1 mm, and noted a significant difference between these groups as well in the time to achieve bone union.⁴ The mean time for bone union in group B1 (16 patients with incomplete fracture and a plantar gap of less than 1 mm) was 73.9 days ± 26.7 and it was 115.5 days ± 45.4 for group B2 (38 patients with incomplete fracture and a plantar gap of 1 mm or more).

I believe it would be better to treat these fractures using the combination of the diagnostic classifications from the two aforementioned studies. I now identify Zone 2 and Zone 3 injuries as Jones fractures. We can then simply subdivide these Jones fractures into acute or chronic based on the radiographic appearance of the fractures and the duration of symptoms.

Pertinent Insights On Screw Fixation
With any acute injury to the proximal fifth metatarsal, intramedullary screw fixation appears to work well with good predictability. The procedure involves a linear incision along the base of the metatarsal. One should start the incision proximal to the styloid process in order to ensure proper screw placement. Carry dissection down with care to protect the sural nerve and the attachment site of the peroneus brevis tendon. I recommend using what they term the “stop-short” technique. This involves placing a guide wire from the base of the metatarsal but staying just proximal to the fracture site. Keep the wire “high and tight” to allow for proper position. After confirming the alignment of the wire on the AP and lateral views, use a cannulated drill bit to create your guide hole, staying just proximal to the fracture.

This technique has several advantages. The first is the ease of placement of the wire since you are not trying to get exact placement down the intramedullary canal. The second is that the drill bits for most cannulated systems do not have a good self-drilling end. The end of the cannulated drill bit can create more heat especially along the fracture site, which can lead to necrosis of the bone in an area that is already a challenge to heal. After forming the guide hole, use a solid drill bit to create the guide hole. This is typically a 3.2 mm drill bit. One should extend the drill bit along the natural curvature of the fifth metatarsal, trying not to extend distal to the curvature.  

There is much debate about the diameter and length of the screw that the surgeon uses for fixation. There have been no articles that definitively identify what diameter screw one should use. Traditionally, the most common sizes are a 4.5 to 5.5 mm diameter screw and a length of 45 to 55 mm depending on the size of the patient. Surgeons commonly use an AP view to measure the length of this screw.  

Scott and coworkers performed a cadaveric study to determine the average intraosseous diameter of the proximal fifth metatarsal as it relates to screw size selection for Jones fracture stabilization.⁵ Examining 20 fresh-frozen cadaver legs for examination, the authors used a digital caliper to measure the diameter of the medullary canal of the fifth metatarsal. They measured the narrowest portion of the medullary canal just distal to the proximal metaphysis. The mean dorsal to plantar diameter of the fifth metatarsal was 6.475 ± 1.54 (range 4 to 12) mm and the mean medial to lateral diameter was 4.6 ± 0.85 (range 3 to 6) mm. They demonstrated that a 4.5 mm cannulated screw is the narrowest diameter screw that one can use in the average fifth metatarsal and still obtain adequate intraosseous purchase.

In order to assess intramedullary screw fixation of the Jones fracture, Ochenjele and colleagues retrospectively reviewed the computed tomography (CT) scans of 119 patients who met inclusion criteria.⁶ Using interactive three-dimensional models, the authors calculated the following measurements: metatarsal length, “straight segment length” (distance from the base of the metatarsal to the shaft curvature) and canal diameter. The results showed that the diaphysis had a lateroplantar curvature where the medullary canal began to taper. The average straight segment length was 52 mm, which corresponded to 68 percent of the overall length of the metatarsal from its proximal end. The medullary canal cross-section was elliptical rather than circular with the widest width in the sagittal plane and the narrowest width in the coronal plane. The average coronal canal diameter at the isthmus was 5.0 mm. A coronal diameter greater than 4.5 mm at the isthmus was present in 81 percent of males and 74 percent of females. The authors concluded that one could avoid excessive screw length by keeping screw length at less than 68 percent of the length of the fifth metatarsal.⁶ A greater than 4.5 mm diameter screw might be needed to provide adequate fixation for most study patients since the isthmus of the medullary canal for most was greater than 4.5 mm.

DeSandis and colleagues had a recent study with the purpose of defining the morphology of the fifth metatarsal to help guide surgeons in selecting the appropriate screw size preoperatively.⁷ They performed a multiplanar analysis of fifth metatarsal morphology by using CT scans from 241 patients. Researchers analyzed and defined specific parameters — including metatarsal length, distance from the base to the apex of curvature, apex medullary canal width, apex height and fifth metatarsal angle — in AP, lateral and oblique views. The average metatarsal length was 71.4 ± 6.1 mm in the AP view and 70.4 ± 6.0 mm in the lateral view with 95 percent of patients having metatarsal lengths between 59.3 and 83.5 mm and 58.4 and 82.4 mm respectively. The average canal width at the apex of curvature was 4.1 ± 0.9 mm in the AP view and 5.3 ± 1.1 mm in the lateral view with 95 percent of patients having widths between 2.2 and 5.9 mm and 3.2 and 7.5 mm respectively. The average distance from apex to base was 42.6 ± 5.8 mm in the AP view and 40.4 ± 6.4 mm in the lateral view.

The authors concluded that when determining screw length, one should use the lateral radiographs since the distance from the base of the metatarsal to the apex was smaller in the lateral view.⁷ On average, the screw should be 40 mm or less to reduce the risk of distraction. For screw diameter, surgeons should use the AP view because canal shape is elliptical and the study found width to be significantly smaller in the AP view. Most canals can accommodate a 4.0- or 4.5-mm diameter screw, and one should use the largest diameter screw possible.

How To Manage Post-Op Recovery
Postoperative recovery is one week non-weightbearing in a fracture boot. Since this is a small incision, I have the patient remove the dressing on the third post-op day to start to wash the area with soap and water for cleaning. The first post-op visit is approximately seven days after the surgery. At that time, the patient can begin bearing weight in the fracture boot. At six weeks post-op, if the X-ray is stable and patients can walk in the fracture boot with minimal pain, they transition out of the boot and into a shoe. They can start low-impact activities at this time. At 10 weeks post-op, if patients are asymptomatic, they can begin to advance to higher-impact activities as tolerated.

Return to activity can vary with the chronicity of the fracture, sport and the level of competitiveness. The aforementioned studies have shown the chronic fractures, especially those with a plantar gap of greater than 1 mm, take a longer time to heal.

In a systematic review, Roche and Calder assessed the return to sports outcomes for different treatment modalities in patients with proximal fifth metatarsal fractures.⁸ They included 26 studies, of which 22 were level 4 evidence, with only one randomized controlled trial. Functional outcome data were limited to return to sports in most studies with few studies using established scoring systems. Return to sports following intramedullary screw fixation for acute fractures ranged from four to 18 weeks. Acute fractures treated non-operatively had a union rate of 76 percent (pooled) in comparison to 96 percent (pooled) for fractures treated with a screw. In regard to delayed unions, non-operative treatment led to a union rate of 44 percent whereas surgical treatment resulted in a 97 percent union rate. The use of screw fixation healed non-unions in 97 percent of cases. The authors concluded that operative treatment is more likely to lead to successful union of all types of Jones fractures in comparison to non-operative treatments. Early return to play in athletes prior to full radiological union is not advised in case of refracture.

Tailoring Treatment For Chronic Fractures
I believe one should treat the chronic fifth metatarsal fracture differently. There is often an area of sclerosis of the bone that one should remove and replace with graft and more rigid fixation. Beginning at the base of the fifth metatarsal, make a linear incision and extend it more distally to expose the majority of the metatarsal. The fracture site is normally very sclerotic for a few millimeters proximal and distal to the fracture site. Resect the area of sclerosis to healthy, bleeding bone.

There are no studies that recommend autograft versus allograft. I have used both with equally good results. If an autograft is preferable, the surgeon can use a bone harvest set or anterior cruciate ligament reaming set to not only harvest the graft but also prepare the fifth metatarsal. This will allow the surgeon to remove the section of bone and match up the graft size exactly. The graft typically comes through a lateral incision along the body of the calcaneus. The incision to harvest the graft should be at minimum greater than 1 cm posterior and inferior to the lateral malleolus in order to avoid the sural nerve. Using a fluoroscan or C-arm can also help identify the exact location. One needs to fill the graft site within the calcaneus with an allograft. I have found the use of cancellous bone chips to be efficacious and cost-effective. Place the bone graft along the resection site of the fifth metatarsal. I typically use locking plates for fixation.

The postoperative recovery is different in chronic fractures since there needs to be graft incorporation along the fracture as well as the harvest site. One should instruct the patient to leave the dressing alone until the first post-op visit at approximately seven days. I have the patient maintain non-weightbearing in the fracture boot for four weeks. At that point, if the X-rays look stable both at the fracture site and the harvest site, then the patient can begin weightbearing in the fracture boot until six weeks post-op. Then the recovery process is the same as the recovery for the acute fracture. With high-level athletes, obtaining a CT scan may help determine if there is adequate healing for the athlete to start to advance his or her activities.

In Conclusion
We can classify the diagnosis of proximal fifth metatarsal fractures into tuberosity fractures and Jones fractures to eliminate much of the confusion. By then subdividing them into either acute or chronic, this can give the surgeon the best method for treatment and give the patient a realistic timeframe for the return to activity.

Dr. Grambart is the foot and ankle surgeon for the Division of Orthopedics for the Carle Clinic Association in Champaign, Ill. He is a Clinical Instructor at the University of Illinois School of Medicine. Dr. Grambart is the President-Elect of the American College of Foot and Ankle Surgeons.

References

1.     Torg JS, Balduini FC, Zelko RR, Pavlov H, Peff TC, Das M. Fractures of the base of the fifth metatarsal distal to the tuberosity: classification and guidelines for non-surgical and surgical management. J Bone Joint Surg Am. 1984;66(2):209–214.
2.     Yates J, Feeley I, Sasikumar S, Rattan G, Hannigan A, Sheehan E. Jones fracture of the fifth metatarsal: Is operative intervention justified? A systematic review of the literature and meta-analysis of results. Foot (Edinb). 2015 Dec;25(4):251-7
3.     Chuckpaiwong B, Queen RM, Easley ME, Nunley JA. Distinguishing Jones and proximal diaphyseal fractures of the fifth metatarsal. Clin Orthop Relat Res. 2008;466(8):1966-70.
4.     Lee KT, Park YU, Jegal H, Park JW, Choi JP, Kim JS. Prognostic classification of fifth metatarsal stress fracture using plantar gap. Foot Ankle Int. 2013;34(5):691-6.
5.     Scott RT, Hyer CF, DeMill SL. Screw fixation diameter for fifth metatarsal jones fracture: a cadaveric study. J Foot Ankle Surg. 2015;54(2):227-9.
6.     Ochenjele G, Ho B, Switaj PJ, Fuchs D1, Goyal N, Kadakia AR. Radiographic study of the fifth metatarsal for optimal intramedullary screw fixation of Jones fracture. Foot Ankle Int. 2015;36(3):293-301.
7.     DeSandis B, Murphy C, Rosenbaum A, Levitsky M, O’Malley Q, Konin G, Drakos M. Multiplanar CT analysis of fifth metatarsal morphology: implications for operative management of zone II fractures. Foot Ankle Int. 2015; epub Dec 17.
8.     Roche AJ, Calder JD. Treatment and return to sport following a Jones fracture of the fifth metatarsal: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2013;21(6):1307-15.

For further reading, see “A Closer Look At Fixation For Fifth Metatarsal Fractures” in the September 2012 issue of Podiatry Today, “Essential Insights On Treating Fifth Metatarsal Fractures” in the April 2006 issue or “Current Concepts In Treating Fifth Metatarsal Fractures” in the May 2010 issue.

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