Union Rate and Rate of Hardware Removal Following Plate Fixation of Metatarsal Shaft and Neck Fractures

Introduction

Metatarsal (MT) fractures are common foot injuries and account for almost half of all foot fractures. ⁶ The 5 metatarsals are the largest bones in the forefoot and are crucial for bearing weight in the final portions of the stance phase. Most MT fractures can be successfully treated without surgery.^4,10 Unstable MT fractures that are displaced and translated more than 50% and/or angulated in the sagittal or coronal plane more than 20 degrees, and fractures involving 2 or more metatarsals are best treated surgically to avoid significant post-traumatic foot pain and/or disability.^1,8 Slight malreduction of the metatarsal length or angulation can result in imbalance of the metatarsal head cascade and post-traumatic metatarsalgia. To date, most research regarding operative treatment of MT fractures has focused on Lisfranc (midfoot) injuries and fifth MT fractures. Despite the large incidence of traumatic first to fourth MT shaft and neck fractures, there are few studies regarding their treatment and outcomes.^2,7

Traditionally, operative treatment of unstable first through fourth MT shaft and neck fractures has been done with open or closed reduction and Kirschner (K) wire fixation. However, K-wire fixation of these MT fractures can lead to poor outcomes if there is residual displacement and angulation. ⁴ Because of concerns of fracture stability, many surgeons use internal plates and screws to repair first through fourth MT fractures. The goal of this study was to be the first of its kind to report the healing rates, fracture angulation, and need for hardware removal of operatively treated first through fourth MT shaft and neck fractures with plate fixation.

Methods

After obtaining institutional review board approval, we reviewed the medical records of all surgically treated closed or open fractures of the first through fourth metatarsal shaft or neck fractures at our institution from October 1, 2008, to December 31, 2014. All proximal metaphyseal fracture, intra-articular tarsometatarsal joint factures, Lisfranc complex injuries, isolated fifth metatarsal fractures, fractures treated at outside facilities, skeletally immature patients, and fractures treated with K-wire fixation or treated nonoperatively were excluded from the study. All surgeries were performed by one of the 4 fellowship-trained foot and ankle surgeons at our institution. All patients included in this study underwent plate and screw fixation of one or more of their metatarsals. Preoperative radiographs were available for 39 of 45 patients (67/75 fractures). Indications for metatarsal plate fixation were fractures that met the following criteria: fractures that were >50% displaced, severely angulated, and fractures that were not able to be closed reduced or felt to be too comminuted for K-wire stabilization. Most of the first metatarsal fractures were unstable comminuted crush injuries with relatively well-maintained alignment (Figure 1). Of the lesser metatarsal fractures, most fractures had a combination of angulation and displacement as an indication for surgery. Evaluated in isolation, angular deformity was present in 58 fractures ranging from 10 to 48 degrees, with an average angulation of 24.8 degrees (Figure 2). There were 4 fractures of the second metatarsal that had dorsal bayonetting of the distal fractures with shortening of the metatarsal. Twenty-two fractures had more than 50% displacement and loss of cortical contact at the fracture site (Figure 3). Nine fractures had severe comminution requiring plate fixation to maintain length of the metatarsals.

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Figure 1.

(A) Preoperative anteroposterior radiographs demonstrating an unstable comminuted crush fracture of the first metatarsal. (B) Postoperative reduction of length and alignment with plate fixation of the first metatarsal fracture.

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Figure 2.

(A) Preoperative anteroposterior (AP) radiographs demonstrating significant displacement and angulation of a third metatarsal shaft fracture. (B) Postoperative AP and lateral radiographs. The postoperative AP radiograph demonstrates coronal plane displacement measured by taking the divergence of the distal and proximal shafts.

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Figure 3.

Anteroposterior radiograph demonstrating sequential fractures of the second, third, and fourth metatarsals with 100% loss of cortical contact in the diaphysis of the second and third metatarsals, and angulation of the fourth metatarsal fractures.

Medical records were reviewed for time to full weight bearing, plate size, fracture location (neck vs shaft), and number of screws on each side of the fracture. Full weight bearing was determined by when the patient demonstrated the ability to fully weight-bear on their foot in the office, and when radiographs demonstrated adequate healing so that the physician allowed the patient to ambulate with their full weight on their foot from that point forward.

Forty-five patients with a total of 75 fractures of their first through fourth metatarsal shaft or necks, who were treated with plate fixation, were included in this study. The second, third, and fourth metatarsals were most commonly involved as compared to the first MT (Table 1) (P < .05). There were 59 shaft fractures and 16 fractures involving the metatarsal necks. Twenty-three patients had an isolated metatarsal fracture, 14 had 2 MT involved, and 8 had 3 MT involved. No patients had more than 3 metatarsal fractures. The average age at time of fracture was 44.5 years (range: 16-94). There were 23 males and 22 females. No patient had bilateral metatarsal fractures requiring operative fixation. Forty of the 45 patients in the study had a documented history of their injury of mechanism. Seventeen (42.5%) feet were injured by a direct blow or trauma to the foot, 17 (42.5%) following a twisting injury, and 6 (15%) following a falling injury.

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Table 1.

Distribution of Metatarsals Involved and Location of Fracture, Demonstrating Final Fracture Alignment.

Metatarsal Fractured	Number	Coronal Displacement, Degrees (Range)	Sagittal Plane Displacement, Degrees (Range)	Neck	Shaft
First	8	1.6 (0-7.1)	1.8 (0-6)	1	7
Second	23	1.6 (0-12.7)	2.2 (0-5.8)	4	19
Third	24	4.75 (0-17.1)	2.3 (0-6)	4	20
Fourth	20	2.5 (0-14.2)	2.5 (0-9.8)	7	13

Sequential radiographs were reviewed for radiographic healing and correlated with the clinical note for absence of pain, tenderness, and warmth at the fracture site (clinical healing). Additionally, final radiographs at time of discharge were reviewed and measured to determine anteroposterior (AP) and lateral malunion angulation (Figure 1). Displacement was measured by taking the divergence of the distal and proximal shafts on lateral radiographs. Because the bones overlap, the plate was used to differentiate the involved metatarsal. The time from surgery to final radiographs was an average 44.5 weeks (range 13-298 weeks).

Measurements were made using a PACS system and software (Sectra, Sweden). Plates used in this study include the Biomet F3 2.5-mm plates, Synthes modular 2.0-, 2.4-, 2.7-mm plates, and Biomet A.L.P.S. 1.5-mm plates. At a minimum of 1-year follow-up, patients were also called to see if the plates bothered them, if they had the plates removed, and if they wanted to have the plate removed. Patients were also asked about the presence of metatarsalgia, and any difficulty with shoe-wear.

Statistical analysis: Multiple linear regression analysis was used to make calculations of statistical significance. A P value <.05 was considered statistically significant.

Results

Plates of various sizes were used depending on surgeons’ choice and the size of the metatarsal fractured. The plate size was documented based on the cortical screw size it was intended to accept. The mean plate size was 2.2 mm (range 1.5-2.7 mm). On variable analysis, there was a shorter time to healing with smaller plate size but this was not statistically significant (P = .07). This may have been influenced by the metatarsal involved and the individual surgeon’s follow-up schedule.

All patients went on to appropriate healing and union of all of their metatarsal fractures. The average time to full weight bearing in an operative shoe was 7.5 ± 1.6 weeks, and time to full clinical and radiographic union was 10.9 ± 2 weeks. Radiographic healing was defined as cortical continuity between the 2 ends of the fracture and the absence of a visible fracture line on the radiographs. There was no significant difference on time to weight bearing and union rate with regard to patient’s age at the time of surgery, body mass index (BMI) or obesity (BMI >30), metatarsal involved, or location of the fracture within the metatarsal. There were no nonunion or delayed unions taking greater than 4 months to heal.

Final radiographs taken at the time of full healing or their final visit were reviewed for any residual deformity. The time from surgery to final radiographs was an average 44.5 weeks (range 13-298 weeks). Two patients had moved out of state but were able to send a copy of their final follow up radiographs at 13 weeks post fixation. These patients were followed locally and went on to heal without a problem. They were contacted for follow-up after 2 years and neither had any complaints or awareness/discomfort associated with their plates or foot. The remainder of the patients in this study were followed up in our office until full healing with a minimum of 3 months’ radiograph follow-up.

The average coronal and sagittal plane angulation was 3.9 and 2.2 degrees, respectively (Table 1). No demographic variable showed statistical significance with regard to sagittal and coronal plane angulation. Fractures located in the neck were found to have higher coronal plane angulation malunion compared to fractures in the shaft (P = .019) (Table 2). No variable was found to be related to final sagittal plane angulation. The degree of angulation was considered not clinically relevant, and no patients had evidence of or complained of any metatarsalgia after recovery.

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Table 2.

Final Bony Alignment Relative to Location of Fracture Within the Metatarsal shaft Versus Metatarsal Neck. ^a

Fracture Location	Number	Coronal Malunion	Sagittal Malunion
Neck	16	6.5 (0-17.1)	2.2 (0.1-9.8)
Shaft	59	3.1 (0.4-14.0)	2 (0-8.2)

a

P = .002.

Twenty-eight of 45 patients (62%) responded to our telephone interview with an average follow-up of 4.4 years with a minimum of 1.1 years. These patients had a total of 51 fractures. None had undergone any additional surgery or treatment for the foot injury since discharge. On direct questioning, 8 patients (28.5% of responders) said their foot bothered them occasionally, which they attributed to the plate. Most of these complaints were of foot cramping or achiness with weather changes, but there were none about palpable hardware or interference with function or shoe-wear. Men were more likely to state that the plate bothers them (7/17 male vs 1/11 females), but there was no statistical difference between the genders (P = .052). No patient had a plate removed and 26 of 27 of patients said they would not want to have their plates removed if offered. No patients had any complaints of metatarsalgia, had any reported difficulty with shoe-wear, or had had custom orthotic inserts made for them since the time of the injury for forefoot pain.

Discussion

Maintaining anatomic alignment following the treatment of unstable MT fractures is the goal in operative management, which is important to maintain a balanced metatarsal cascade necessary for pain-free ambulation. Sanchez et al reviewed 57 central metatarsal fractures treated with K-wire fixation (21) or nonoperatively (36). ⁸ They found no difference in outcomes despite the method of treatment, with 41% having poor and 30% having fair results. Additionally, they found that residual sagittal and coronal angulation most closely correlated with poor functional outcomes. Final average displacement in our study in the coronal and sagittal planes measured less than 5 degrees, which was deemed clinically insignificant. In their study, the most common postoperative complaint was metatarsalgia, seen in 56.8% of patients, although this was not found or reported in any patients in our study.

There are few if any studies that report the actual alignment following fixation of metatarsal fractures. This may be the first study to describe the amount of malunion following open reduction internal fixation using plates. Currently, there are no clear indications on when to use plates versus K-wires for fixation of metatarsal shaft and neck fractures. Moreover, there are very few if any comparison studies with regard to K-wire fixation versus plate fixation on final displacement after 1-4 MT shaft and neck fracture open reduction internal fixation. In a synthetic metacarpal shaft hand study, Curtis et al compared the bending strength of intramedullary 0.062 K-wires to crossed K-wires and 2.5-mm nonlocking plates. ⁵ They reported a load to failure of 1669 N for plate fixation compared with 146 N for crossed K-wires and 110 N for intramedullary K-wire fixation. The plate fixation was also 11 and 15 times stronger in 3-point bending than the crossed and intramedullary K-wires, respectively.

Painful hardware is not uncommon following orthopedic fixation procedures. In our study, approximately 30% of patients reported that they had some degree of hardware irritation or awareness of their fractures. This is in line with other plate fixation procedure such as ankle fractures. Brown et al reviewed 129 unstable ankle fractures treated with plate fixation and found that approximately 31% of the patients reported painful hardware. In the Brown et al study, 22 of the 39 patients who had painful hardware underwent hardware removal with a minimum average of 2 years’ follow-up. In our study, no patient underwent hardware removal, and the majority (26/27) did not desire to have the plate removed. In prior studies using K-wire fixation, all patients required that the K-wires be removed, either in the office or in the operating room.^4,8

More men stated that their foot bothered them. It is not clear why men tended to have more bothersome fixation than women. There was no significant gender difference noted with regard to the size of the plate, minimum amount of screws across the fracture, and time to weight bearing. The patient reports of discomfort were all mild awareness of their foot. Most of these complaints were vague achiness or cramping of the foot, and none had palpable hardware.

In this study, we found that metatarsal neck fractures tended to have higher residual displacement compared with metatarsal shaft fractures. This may be due to the fact that metatarsal neck fractures tend to be more displaced because of intrinsic musculature and flexor tendon displacement.^3,9 Additionally, this could have also been due to the metatarsal neck anatomy and the difficulty in obtaining linear screw fixation distally because of the short segment of distal bone. One limitation of our study involves the measure of displacement following fracture healing. Metatarsal bones curve distally as they change from the neck into the shaft. This may have resulted in an overestimation of the degree of malunion of the fracture. In our practice, K-wires are still used for fixation of most simple metatarsal fractures. However, fractures that have comminution or significant angulation and displacement are treated with plate fixation because of concerns of fracture stability with less rigid fixation. This study did not aim to negate the use of K-wires for metatarsal fracture fixation, only to offer an alternate option that allows immediate fracture stabilization without the potential for delayed loss of fixation or alignment after K-wire removal, and without the potential higher infection rate associated with exposed K-wires. A limitation of this study is that we did not directly compare the outcomes of patients with K-wire fixation with plate fixation of metatarsal fractures.

Conclusion

In this study, we found that plate fixation of first through fourth metatarsal fracture neck and shaft fractures had low rates of malunion. In addition, in our study, the majority of patients did not have hardware irritation and were not bothered by the hardware. Further research will need to be done to determine if plate fixation is superior to K wire fixation.