Percutaneous Screw Fixation of Proximal Fifth Metatarsal Fractures.

Abstract

Metatarsal fractures are one of the most common injuries of the foot, accounting for approximately 5% to 6% of all fractures confronted in the outpatient setting¹. Approximately 45% to 70% of these fractures involve the fifth metatarsal, which have been described using a 3 zonal approach in 1993 by Lawrence and Botte². Zone 2 fractures are difficult to manage given their retrograde vascular supply, leading to higher rates of nonunion^1,3. Jones fractures (zone 2) are primarily treated surgically, with the 2 main methods being intramedullary screw fixation and plate fixation³. Surgical management leads to higher rates of union when compared with nonoperative modalities. Presented here is a technique for zone 2 intra-articular Jones fractures with minimal to moderate displacement via open reduction and internal fixation. This technique is not recommended for comminuted fractures or those with proximal split fractures. Starting with the foot lateral, this technique requires meticulous marking of the anatomical landmarks of the distal fibula as well as the fifth metatarsal to establish the precise starting point for the guidewire. Using a mini c-arm, a high and inside positioning should be confirmed prior to advancing the guidewire from proximal to distal while remaining positioned in the center of the medullary canal. Capitalizing on the variable pitch of a 5.0-mm headless compression screw, the Jones fracture is compressed to ensure primary bone healing. The incision is then closed, and a soft wrap is utilized followed by 2 weeks of non-weight-bearing and progressive protective weight-bearing until a complete recovery is achieved.

Background: Open reduction and internal fixation (ORIF) for the operative treatment of zone-2 intra-articular Jones fractures with minimal to moderate displacement is recommended because of the high rate of nonunion associated with nonoperative treatment. The blood supply to this region is minimal because of its retrograde flow, leading to high rates of nonunion with nonoperative treatment. The presently described technique offers reduction and fixation of a zone-2 fracture, as well as improved functional outcomes and nonunion rates. This approach is minimally invasive, as it is performed percutaneously, leading to a decrease in soft-tissue damage, infection rates, and operative time.

Description: The zone-2 fifth metatarsal ORIF technique begins with the use of a marking pen to outline the distal fibula and the head of the fifth metatarsal for proper orientation. Fluoroscopy is utilized to identify the landmarks so that a guidewire can be placed into the proximal dorsal aspect of the fifth metatarsal. Placement is confirmed on multiple radiographic images. The guidewire is then slowly inserted down the medullary canal of the fifth metatarsal, with placement verified on multiple fluoroscopic images. Once placement is confirmed, screw size is estimated with use of radiographic measurements. An incision is made bluntly and dissected down, going high and medial in order to protect the sural nerve and the peroneus brevis tendon insertion. The path is then drilled with use of a cannulated screw system. Biomechanically, a full-core screw is preferable, ranging from 4.5 to 5.5 mm depending on the canal diameter. For the example procedure shown in the video, a full-core 5-mm screw was inserted until appreciable reduction of the fracture was observed on fluoroscopic visualization, with additional confirmation on multiple radiographic views. Once satisfied with the placement, the guidewire is removed and the site is irrigated and closed with use of 3-0 nylon suture. A weight-based combination of short and long-acting local anesthetics (ropivacaine and lidocaine) is then injected around the incision site as part of a postoperative multimodal pain regimen. The area is then cleaned and dried. Xeroform, 4 × 4s, Army battle dressings, and a soft wrap are then applied, followed by a postoperative boot.

Alternatives: Poor surgical candidates include those with neuropathic feet, local infection, presence of severe vascular insufficiency, and comorbidities that would make surgery dangerous. Such patients can undergo nonoperative treatment, which includes 4 to 6 weeks of non-weight-bearing in a cast until union is confirmed radiographically. Once union is confirmed, patients undergo 4 to 6 more weeks of weight-bearing in a boot. One meta-analysis found that nonoperative treatment led to nonunion rates between 15% and 30%, notably higher than with operative treatment (0% to 11%)⁶. Most cases of zone-2 fifth metatarsal fracture are treated operatively, with intramedullary screw or plate fixation being the primary techniques. Intramedullary screw fixation is the technique featured in the present video, and offers the advantage of decreased soft-tissue injury, infection, and operative time because of its percutaneous approach. Percutaneous screw fixation is not recommended for comminuted fractures or those with proximal-split fracture patterns^7,8. Fractures with these patterns should be critically evaluated with additional radiographic work-up. ORIF utilizing hook plates or fracture-specific plate implants may be warranted in these cases. In cases of chronic nonunion or fractures with sclerotic margins, an additional percutaneous incision over the fracture site is recommended to fenestrate the fracture edges and allow bone grafting prior to screw insertion^7,8.

Rationale: ORIF of zone-2 intra-articular Jones fractures with minimal to moderate displacement with use of an intramedullary screw is a low-risk and highly successful surgical approach to these common fractures. Because of the watershed region at zone 2 of the fifth metatarsal, nonunion rates with nonoperative treatment are relatively high (between 15% and 30%)^4,6. Another study of 22 patients showed a 100% union rate following operative treatment of acute Jones fracture⁵. These studies, along with others, provide strong evidence to suggest the benefit of early operative treatment with use of screw fixation, as compared with nonoperative treatment.

Expected outcomes: Postoperatively, these patients are managed with a standard protocol established by our institution. The first 2 weeks include being in a soft wrap and postoperative boot while being non-weight-bearing. The patient should keep the incision clean and dry, elevate the foot/ankle often, and follow activity guidelines. Sutures are removed at 2 to 6 weeks postoperatively, and the boot should be used for all weight-bearing ambulation, with crutches being utilized for the transition. Additionally, ankle range-of-motion exercises and strengthening should begin. Weight-bearing should transition as follows: 25% at week 3, 50% at week 4, 75% at week 5, and 100% at week 6. At weeks 6 to 8, walking and physical therapy should be increased and previous exercises should be continued. At weeks 8 to 12, pool or treadmill activity should begin, and it should be increased thereafter. Patients should expect evidence of radiographic union between weeks 6 and 10, with a meta-analysis showing union rates with screw fixation between 89% and 100%⁶.

Important tips: Guidewire insertion should be proximal and dorsal, allowing the guidewire to enter at the high and inside position. To do so, palpate the proximal aspect of the fifth metatarsal and outline the contour on the skin, then mark the incision 1 to 3 cm proximal to this to avoid unnecessary soft-tissue tension and potential wound issues. This incision is parallel and generally inferior to the sural nerve, but arborization and branching are highly variable. Utilizing a high and inside starting point avoids the more lateral and plantar insertion of the peroneus brevis. The high and inside starting point is verified under anteroposterior, lateral, and oblique radiographic views. This position biomechanically avoids plantar gapping and reduces the risk to soft-tissue structures.Utilizing a mini c-arm or fluoroscopy unit allows multiple views for ideal screw alignment to be obtained quickly, with decreased radiation exposure.Utilizing an all-cannulated system allows for a seamless transition from drilling to screw placement.Avoid making the incision too close to the proximal aspect of the fifth metatarsal, as this would cause unnecessary soft-tissue tension and potential wound issues. The incision should be made 1 to 3 cm proximal to the proximal aspect of the fifth metatarsal.Use adequate soft-tissue retraction, as protecting the sural nerve is paramount during screw insertion.Do not allow the patient to be weight-bearing immediately. We strongly recommend that the patient be non-weight-bearing for 2 weeks and then perform progressive protected weight-bearing in a postoperative boot for 4 weeks.

Acronyms and abbreviations: AP = anteroposteriorABD = abdominal gauze dressingDVT = deep vein thrombosis.