A Guide To Hybrid Screw Fixation In Lesser Metatarsal Surgery

     During the past five years, there has been a large influx of non-traditional bone screws on the orthopedic market for small bone fixation of the foot. Some of these designs have been effective at providing long-term surgical fracture stability with reduced osteotomy fixation morbidity. Additionally, these bone screw designs have found their way into a variety of applications in hindfoot surgery with headless screws, locking plate screws and cannulated self-tapping screws.      When trying to assess the technology available in small fragment fixation, it behooves the foot and ankle surgeon to have an adequate understanding of the proper applications of these screws. Additionally, one must consider the biomechanical forces associated with metatarsal osteotomies that facilitate early postoperative weightbearing and joint mobilization. Unlike traditional AO screw application, hybrid screws typically have unique application protocols to ensure proper purchase and compression of unstable bone fragments.      Improper application of hybrid screws can lead to a higher than normal fixation complication rate. A deviation from application protocols can lead to screws potentially backing out, distraction of osseous fragments and failure to provide appropriate interfragmentary compression. Additionally, hybrid screws can carry a significant increase in cost per unit. This factor alone may sway the foot and ankle surgeon away from using this technology, especially in this day and age of managed care and cost containment in hospitals and surgery centers.

What You Should Know About Forefoot Pain And Metatarsalgia

     Forefoot pain associated with metatarsophalangeal joint (MPJ) dysfunction is a common malady. There are a multitude of etiologies to these disorders with both local and systemic comorbidities that are beyond the scope of this article.1 However, MPJ dysfunction can lead to significant disability and morbidity with pain that is associated with an abnormal increase in plantar pressures and arthrosis.      Once one has made an appropriate diagnosis, surgical goals are focused on relieving plantar metatarsophalangeal joint pressure and restoring normal joint function. Surgeons commonly perform distal metatarsal osteotomies (multiple or single), plantar joint planing procedures and metatarsal head resections along with some level of digital surgery and capsule tendon balancing to relieve forefoot pain.

Understanding The Benefits Of The Weil Osteotomy

     Lowell Scott Weil Sr., DPM, was the first to describe an intraarticular distally placed oblique osteotomy for the treatment of MPJ dysfunction.2 This procedure has enjoyed a high level of scrutiny on the lecture circuit and in peer-reviewed podiatric and orthopedic journals with very favorable results.3      The Weil osteotomy allows the foot and ankle surgeon a great deal of latitude in obtaining the proper position of the metatarsal head fragment. Surgeons may correct the deformity by modifying the metatarsal fragment reduction through translocation and/or angulation.4 The metatarsal head usually decompresses proximally after the osteotomy, resulting in shortening.      Additionally, one can transpose the capital fragment medial or lateral, or angulate it in the frontal plane to reduce varus and valgus deformity. The surgeon can elevate the capital fragment by removing additional bone by wedging or employing double thickness osteotomy saw blades. Surgeons often accompany this procedure with digital fusions to stabilize digital deformities as well as flexor tendon transfers.5

Step-By-Step Surgical Insights

     One would perform the osteotomy at an acute and fairly horizontal angle to the ground and metatarsal shaft, allowing for a generous cortical cancellous shelf amenable to screw fixation. When dealing with concomitant plantar keratoma or a planned metatarsal head length reduction beyond 5 mm, the podiatric surgeon should consider using a thicker saw blade to produce more significant reduction of plantar pressure.6,7      Once one has obtained satisfactory anesthesia, approach the metatarsophalangeal joint through a dorsal curve linear or serpentine incision. Doing so can help prevent scar contracture that can contribute to floating toe syndrome and extension contracture. Place the incision centrally over the joint with a length of approximately 3 cm. The surgeon can easily extend the incision distally to manage complex digital deformities. When addressing adjacent metatarsal deformities, you may elect to employ a two incision or a single interspace approach. Depending on one’s preference, the surgeon would divide the soft tissues to expose the dorsal surface of the metatarsophalangeal joint.      Perform a linear capsulotomy sharply either medial or lateral to the long extensor tendon. Leave the extensor tendon intact at this point and address any remaining soft tissue contracture after the osteotomy fixation through additional extensor tendon or capsule lengthening.      We typically employ a dorsal medial incision to the second and third metatarsals, and employ a lateral dorsal capsulotomy for the fourth and fifth metatarsals. Capsular dissection begins at the dorsal base of the proximal phalanx. After exposing the base, utilizing minimal periosteal dissection facilitates very adequate exposure to the distal metatarsal neck and maintains blood supply at the osteotomy site. Leave the collateral suspensory ligaments intact unless there is significant plantar plate disruption with complex hammertoe deformity.      The most common goal of the Weil osteotomy is to produce offloading of plantar metatarsal head pressure. Variables such as the osteotomy angle, saw blade thickness, capital fragment shortening, angulation or transposition can have a direct impact on osteotomy performance. Preoperative standard radiographs are invaluable at assessing metatarsal parabola length for surgical planning. Intraoperative fluoroscopy allows immediate decision making to obtain the appropriate metatarsal reduction.      Once proper soft tissue retraction is in place, it is common to employ a small sagittal saw with a #138 Hall blade (Zimmer). The osteotomy begins in the dorsal 2 to 3 mm range of the distal articular cartilage. The surgeon typically makes the osteotomy at an angle of 10 to 15 degrees to the metatarsal shaft. Preoperative assessment of the metatarsal declination can alter the orientation of the osteotomy relative to the ground.6,8 The cascading effect is most apparent with the decrease in metatarsal declination from the second to fifth metatarsals.      One would perform the osteotomy in the transverse plane in a complete manner with a well irrigated sagittal saw. After completing the osteotomy, a “proximal release” of the plantar capital fragment occurs. This facilitates decompression of the joint. If preoperative planning calls for greater than 5 mm of length decompression or the metatarsal declination is flat (15 to 17 inches), the surgeon should consider doubling the osteotomy thickness with two parallel blades on the sagittal saw. This technique is effective for more aggressive offloading of the metatarsal head fragment. Remodel the dorsal metatarsal overhang with a rongeur and rotary burr.      Reposition the capital fragment 3 to 5 mm proximally. Additionally, one can transpose the osteotomy or angulate it medially or laterally to correct and balance varus and valgus deformities. Manually compress the osteotomy with plantar digital pressure and temporarily fixate it with one or two 0.045 K-wires. Once you have established temporary fixation, use intraoperative fluoroscopy to confirm the desired position. Spot fluoroscopy can significantly help the surgeon to determine capital fragment placement, especially when one is performing multiple metatarsal osteotomies.

How To Fixate The Osteotomy

     There are a variety of options for fixation of the Weil osteotomy. The osteotomy procedure creates a generous plantar shelf, which allows bicortical fixation. However, the surgeon may choose to fixate the fragment into the cancellous head for effective corticocancellous fixation. Hybrid metatarsal screw fixation allows the foot surgeon to employ a single screw in either of these situations. When it comes to fixation, I prefer to use a 2.0 titanium Charlotte Snap-Off Screw System (Wright Medical) and a more vertical orientation.      Apply the 0.045 K-wire for temporary fixation. This serves as a drill hole for the 2.0 hybrid screw. Place the screw manually with a screwdriver in a clockwise manner into the guide hole and advance it through the periosteum, engaging the two fragments with “two finger tightness.” If one does not employ a second K-wire, the osteotomy may rotate in a clockwise manner with screw application. One may place a periosteal elevator on the right side of the metatarsal head to provide counter pressure and prevent rotation.      Additionally, the surgeon should provide digital pressure on the plantar skin to ensure further stability while applying the screw. One would typically place the screw 5 mm proximal to the osteotomy. Surgeons may add a second screw for additional stability of a more complex osteotomy with varus or valgus translation or medial or lateral transposition.      Once you have established rigid fixation and verified it with fluoroscopy, assess the joint’s range of motion. Additional trimming of the dorsal overhang or the dorsal base of the proximal phalanx helps to prevent dorsal intrusion or jamming of the surgically altered joint. Irrigate the wound and approximate the dorsal capsule. At this time, one can address appropriate additional lengthening of the extensor tendon as well as digital deformities.

Pertinent Insights On Postoperative Care

     Dress the patient’s wounds postoperatively in a Jones type dressing and surgical shoe. We permit immediate weightbearing for the majority of patients. If one performs more than two osteotomies, the patient may wear a weightbearing removable cast walker, according to the surgeon’s comfort level. Patients should change dressings one week later and use a flexible dressing (Coflex, Andover Healthcare) with daily bathing.      Remove the sutures at 14 days and have the patient initiate home physical therapy with range of motion exercises that emphasize sagittal plane motion and toe purchase. At this time, the patient can wear a flexible shoe or sneaker. If postoperative pain and stiffness persist with a stable osteotomy, consult a physical therapist.

Key Considerations With Hybrid Screws

     Lesser metatarsal osteotomies are effective for a variety of indications. Most commonly, forefoot pain is the culprit and can occur from long-term metatarsophalangeal joint instability. One needs to properly assess the unstable MPJ. A digital Lachman test can give the surgeon an indication of the integrity of a plantar plate MPJ injury. Be aware that sagittal plane forefoot deformities with dorsal subluxation of the phalanx and concurrent hammertoe deformity can be further compounded with digital varus or valgus overlap deformity.      Lesser MPJ disorders may also involve hindfoot deformities of equinus, varus or valgus hindfoot, hypermobility and degenerative joint disease. The Weil osteotomy with capsulotendon balancing and digital fusion can provide the surgeon with a variety of modifications to address complex lesser metatarsal issues. When weighing single or multiple lesser metatarsal osteotomies, foot and ankle surgeons may consider hybrid screw fixation techniques that allow early weightbearing, joint mobilization and effective interfragmentary compression with a low screw failure rate.      The screw fixation system should offer the surgeon flexibility in applications, simplicity in design, self tapping, a low profile screw head design and a variety of lengths and widths for metatarsal osteotomy fixation. The aforementioned Snap-Off screw is available in 2.0 mm and 2.7 mm diameters in lengths ranging from 11 mm to 17 mm. Surgeons most commonly employ the 2.0 mm Snap-Off screw in lesser metatarsal surgery. The 2.0 mm screw application is also indicated for tailor bunion repair with either a mini-Z or mini-Chevron osteotomy. The 2.0 mm screws come in lengths of 11 mm, 12 mm and 14 mm. Additionally, the screw design lends creates lag compression with a self tapping design.      The Weil osteotomy creates a generous metaphyseal and diaphyseal surface that is stable in the sagittal plane. Ground reactive forces naturally aid in compression of the two fragments. One may perform hybrid screw fixation in a cortical metaphyseal manner by applying the 2.0 mm Snap-Off screw distal oblique into the metatarsal head. Obtain bicortical fixation by purchasing the plantar cortex with a vertically placed screw.      In either style of fixation, apply temporary stabilization through two cortices vertically with a 0.045 K-wire. If you are performing multiple metatarsal osteotomies, establish the new metatarsal parabola as per your preference with similar 0.045 K-wires for stabilization. One can easily visualize the metatarsal parabola on digital intraoperative fluoroscopy and adjust it accordingly. One can place a second K-wire for secondary stabilization. The 0.045 K-wire serves as a drill hole for application of a 2.0 Snap-Off screw. Apply the pre-drilling technique through both near and far cortical surfaces.      Manually apply the screw through the periosteum with two finger tightness. Pre-drilling with a 0.045 K-wire also reduces clockwise rotation and eliminates distraction of the distal fragment. Typically, I choose a 14 mm 2.0 Snap-Off screw for second and third metatarsal osteotomies. The surgeon typically performs fourth metatarsal osteotomy fixation with 2x blade sagittal saw thickness and fixate it with a 12 mm 2.0 Snap-Off screw.

In Summary

     Hybrid screw fixation for lesser metatarsal osteotomies is an effective tool for managing derangement of the metatarsophalangeal joint complex. The goals of the procedure are to provide relief of plantar forefoot pain with arthrosis and restore MPJ function.      Foot surgeons who are not familiar with these applications can gain comfort with these techniques in cadaver and saw bone workshops provided during CME programs. A proper understanding of the deformity and the relationship to the remainder of the forefoot can help to minimize the associated complications of transfer metatarsalgia, floating toe syndrome, arthrosis and incomplete relief of pain and contracture.      In our experience, the 2.0 mm Snap-Off screw offers a minimal back out rate and provides dependable interfragmentary compression for pressure reduction and decompression of MPJ disorders.      Hybrid screw fixation is another choice for the foot and ankle surgeon in managing forefoot osteotomies. After a short learning curve, one may find that hybrid screws offer stable osteotomy fixation along with minimal hardware-related complications. Dr. Salcedo is a Fellow of the American College of Foot and Ankle Surgeons. He is the the Director of the Podiatric Residency Program at St. Joseph’s Regional Medical Center in South Bend, Ind. Dr. Motyer is a second year resident at St. Joseph’s Regional Medical Center in South Bend, Ind.
 

References:

1. Roukis TS. Central metatarsal head-neck osteotomies: Indications and operative techniques. Clin Podia Med Surg 22: 197-222, 2005.

2. Weil LS. Weil head-neck oblique osteotomy: technique and fixation. Presented at: Techniques of Osteotomies on the Forefoot; October 20-22, 1994 Bordeaux, France.

3. Hofstaetter, SG, et al. The Weil osteotomy, A seven year follow-up. JBJS(Br) 87-B(11): 1507-1511, 2005.

4. Goforth WP, et al. Lesser-metatarsal medial displacement osteotomy for the treatment of digital transverse plane deformities. JAPMA 95(6): 550-555, 2005.

5. Myerson MS, Jung NG. The role of toe flexor-to extensor transfer in correcting metatarsophalangeal joint instability of the second toe. Foot and Ankle Int. 26(9): 675-679, 2005.

6. Grimes J, Coughlin M. Geometric analysis of the Weil osteotomy. Foot and Ankle Int. 27(11):985-992, 2006.

7. Khalafi A, et al. Plantar forefoot pressure changes after second metatarsal neck osteotomy. Foot and Ankle Int. 26(7): 550-555, 2005.

8. Lau JTC, et al. Modifications of the Weil osteotomy have no effect on plantar pressure. Clinic Orth Rel Res 421: 194-198, 2004.