Mastering The Scarf Bunionectomy

Author(s): 
By Lowell Scott Weil Jr., DPM

While the great majority of hallux valgus deformities can be accommodated with a wide toe-box shoe, secondary deformities, such as painful hammer digit syndrome and metatarsalgia, coupled with patient demands, often drive the need for operative intervention. In addition, some individuals are averse to wearing any type of special shoes and wish to have the deformity corrected rather than accommodated. When an operation is indicated in your opinion and in concert with the patient’s wishes, the goals for the ideal hallux valgus operation are as follows: • joint congruity with full, pain-free range of motion postoperatively; • improved cosmesis and the ability to wear varied shoe styles; • minimum postoperative disability and interference with the activities of daily living; and • minimal and salvageable complications. At the Weil Foot and Ankle Institute, performing hallux valgus surgery over the years has taken us through the McBride, Keller, Chevron, crescentic, closing base wedge and Lapidus procedures. Although each of these procedures was successful for the perfect indication, the versatility and predictability for success was not optimal. We have used the Scarf bunionectomy as our primary hallux valgus procedure since 1990. The procedure is versatile, structurally sound, has a wide range of indications and applications, and allows for an early, functional recovery. The surgical technique is not purely an osteotomy but rather a combination of techniques involving a fibular sesamoidal release, Scarf osteotomy, a unique form of rigid internal fixation, capsule-tendon balancing and a rigorous postoperative rehabilitation. Each and every component of this bunionectomy contributes to the success. Key Benefits Of The Scarf Osteotomy The Scarf osteotomy has great versatility as it allows several important benefits, including lateralization of the head-shaft fragment to reduce the IM angle. Unlike the crescentic or proximal Chevron, this lateral displacement does not increase the PASA, thereby maintaining joint congruity and avoiding the long-term complication of arthrosis. Other advantages of the procedure include: • medialization of the capital fragment (in cases of hallux varus); • plantar displacement to increase the first ray load; • dorsal displacement to decrease the ray or tibial sesamoid load; • elongation in cases of a short first metatarsal; • shortening in cases of a long first metatarsal or severe deformity; • transverse plane rotation up to 15 degrees to correct an increased PASA; and • axial rotation (supination) in cases of first metatarsal pronation. The indications for the Scarf osteotomy are: hallux valgus deformity with an intermetatarsal (IM) angle of 12 to 24 degrees, increased PASA and range of motion of the first metatarsophalangeal joint of greater than 40 degrees without severe joint arthrosis. Pertinent Surgical Pearls For The Scarf Osteotomy The Scarf osteotomy is only one of the three components of the Scarf bunionectomy. The first step is releasing the metatarsophalangeal, lateral sesamoidal complex, followed by a Scarf osteotomy of the first metatarsal with supportive and rigid fixation. The final step is medial capsulorrhaphy and capsuloplasty. The addition of a phalangeal osteotomy (Akin or shortening) is commonly performed with the Scarf bunionectomy. You would perform the procedure under a combination of intravenous sedation and local anesthesia. Administer a Mayo block, utilizing 15 to 20 cc of 0.5% bupivicaine, just prior to inflating an ankle tourniquet to 250 mm/hg. Use a medial incision approach where the skin of the plantar surface meets the skin of the dorsum. The length of the incision varies depending on the intended horizontal length of the osteotomy. Identify and preserve the neurovascular structures, and retract the wound edges using four flexible skin hooks. Encircle the foot with the hooks and clamp them laterally. Make a lenticular capsular incision, removing a small ellipse of capsule adjacent to the dorso-plantar midline of the metatarsal head. Then reflect the capsule and periosteum dorsally along the medial side of the metatarsal head and shaft, and distally to the base of the proximal phalange, preserving the dorsal capsule. Your subsequent plantar reflection should expose the joint while preserving the vascular network just proximal to the sesamoids. Then deepen the reflection more proximally via blunt dissection. Neither the dissection nor the Scarf cut jeopardizes this blood supply. You would subsequently place a self-retaining retractor between the plantar capsule and metatarsal head to allow for exposure and release of the suspensory ligament of the fibular sesamoid. Remove the fibular sesamoid only in cases of severe arthrosis to the undersurface of the first metatarsal head. Why The Osteotomy Guide Is Essential Always perform the Scarf osteotomy with an osteotomy guide. First, insert a .045 K-wire 3 to 4 mm below the dorsal medial surface of the metatarsal head and direct it at a lateral and plantar declination of about 25 degrees, aiming just plantar to the fourth metatarsal head. The proper direction of this guide pin is essential since it will formulate the displacement of the metatarsal head-shaft fragment. If you direct the pin laterally and plantarly, there will be lateral and plantar displacement of the metatarsal. If you direct it slightly proximal, it will cause a small shortening of the metatarsal as well. In the great majority of cases, plantar displacement of 2 to 3 mm is desirable to offset any elevatus of the first metatarsal and decrease the load under the second metatarsal. Then you would pace the osteotomy guide over the pin and direct it toward the long axis of the metatarsal shaft and the inferior and proximal portion of the metatarsal, extending to about 2 cm distal to the metatarsal cuneiform articulation. The osteotomy should end about 3 to 4 mm above the plantar cortex. Making this cut at the plantar portion of the metatarsal is essential to avoid stress risers leading to stress fractures. Use a 20 mm wide sagittal saw to make the long cut. In cases of large IM angles, you would increase the length of this osteotomy in order to transpose a greater volume of bone and prevent recurrence due to reverse buckling of the IM angle. The typical length of the osteotomy is about 40 mm but can be as long as the entire length of the metatarsal shaft to the cancellous bone in the base of the metatarsal. Wrapping Up The Scarf Osteotomy As you make the cut through the shaft in a lateral direction, pay careful attention to avoid burying the saw blade into the inter-metatarsal space. This will enable you to preserve the vital structures in this area. Rotate the osteotomy guide toward the dorsal distal metatarsal and use a 12-mm wide sagittal saw blade to create the dorsal cut. Make this cut about 5 mm proximal to the margin of the dorsal cartilage and at a 70- to 90-degree angle to the long axis cut. It is essential to keep this distal cut in the cancellous bone of the metatarsal head in order to avoid troughing and channeling during the lateral displacement. Proceed to remove the osteotomy guide distally. Connect the vertical and horizontal cuts by using the side of the saw blade as a cutting tool. You can make alterations of the distal cut to correct the PASA up to 15 degrees. Finally, complete the plantar cut, connecting the long cut of the shaft at a 45-degree angle to form a locking mechanism once the bones are displaced and compressed. The head-shaft is now mobile. While an assistant places a small clamp on the intact shaft and pulls medially, displace the free floating head shaft laterally until you encounter resistance. Hold the hallux firmly with pressure in a proximal direction while applying the specially designed Scarf bone clamp. Then you should fixate the osteotomy with the two-threaded head screws. Place the distal screw obliquely into the metatarsal head to add additional longitudinal compressive support to the plantar fragment. This also helps prevent any possible irritation of the sesamoid apparatus by a penetrating screw. Typically, we use threaded head screws that will be flush with the dorsal cortex and avoid the minor complication of a prominent screw head. Place the second screw dorsal to plantar transcortically. Following fixation, align the great toe congruently to the first metatarsal head. At this point, you can determine whether to perform a phalangeal osteotomy (Akin) to correct a hallux abductus interphalangeus deformity. Inside Insights On Performing The Akin Osteotomy The Akin osteotomy is primarily performed to centralize the course of the extensor and flexor hallucis longus tendons on the first MPJ. The osteotomy also renders a more pleasing cosmetic result for patients. You would perform the procedure from a medial approach about 8 to 10 mm distal to the insertion of the flexor hallucis brevis tendon and articular surface of the proximal phalanx. After identifying and protecting the flexor hallucis longus tendon, perform a closing wedge osteotomy perpendicular to the long axis of the proximal phalanx. Using a small bone oscillating saw, remove a 2 to 4 mm triangular section of bone. Preserve the lateral cortex and manipulate the hallux medially to close the osteotomy. Fixate the osteotomy with a threaded head screw angled obliquely. Then remove the redundant bone on the medial side of the head and shaft of the metatarsal, preserving the plantar articulation of the tibial sesamoid. Use a rotary burr to smooth the dorsi-medial aspect of the metatarsal head that is the most likely site of postoperative prominence. You can accomplish capsuloplasty with a 2-0 absorbable suture, placing the suture immediately medial to the tibial sesamoid and connecting it to the dorsal portion of the capsule. The tensioning of the repair is important to correct the deformity but should not cause a postoperative hallux varus. Close the wound with a subcuticular suture of 5-0 absorbable and augmented with 1/2-inch steri-strips. Bandage the great toe but do not make any additional attempts at correction through the use of the bandage. Apply a 6-inch elastic bandage with mild tension from the toes to the mid-calf. What About Postoperative Care? Use a typical postoperative surgical shoe and permit the patient to bear weight without crutches or a cane. The patient may use NSAIDs for 10 days. Keep in mind that you may augment the NSAIDs with moderate analgesic drugs if necessary. Most patients experience little to almost no postoperative pain, probably due to the long duration of local anesthesia. Instruct your patients to limit weightbearing to the essentials: going to the bathroom and getting something to eat. The elastic bandage should be removed and reapplied daily. During this time, the patient should rotate the subtalar joint and ankle for several minutes to prevent splinting of the musculature. One week after surgery, remove all bandages. Radiographs should confirm maintenance of fixation. At this time, the patient should be evaluated by a physical therapist, who can provide a comprehensive program in home physical therapy. Use a 3-foot long, 2-inch wide piece of an Esmarck bandage to exercise the great toe. With the foot held at a right angle to the leg, place the strip around the patient’s great toe. The patient holds the strip similar to holding the reins on a horse. The patient will then plantarflex the great toe against resistance of the Esmarck. Initially, patients will provide little resistance as they flex the toe plantarly. However, with time and confidence, they can increase the tension for a dynamic exercise of the great toe flexors. Patients should perform the flexion at three sets of 25 each for a total of 75 times, twice a day. There are no sutures to remove so the patient may resume bathing immediately after the bandages are removed. Tell the patient he or she can leave the steri-strips in place until they come off with wear. Instruct patients to return to a roomy athletic shoe. We have found the surgical shoes are non-supportive, do not control swelling and are just not comfortable to wear. The power of this procedure allows us to have confidence that the correction will be maintained. Keep in mind that patients will supinate for several weeks postoperatively until the strength and comfort of the great toe is sufficient to offload the medial side of the foot. Caution the patient again to avoid extended periods of weightbearing or any type of physical exercise in a weightbearing mode for an additional five to six weeks. They may drive a car when they have the confidence and comfort to step on the brake in an emergent situation. Most patients are able to accomplish this in one to two weeks following surgery. Seven weeks after surgery, take a radiograph. Usually, you’ll find that bone healing is complete enough to allow full activity to their tolerance. Range of motion and strengthening exercises should be continued for a total of eight weeks. After performing more than 4,000 Scarf bunionectomies, we have found that it takes three to five months for complete reduction of swelling, full range of motion, and maximum improvement. Some patients say it can be as long as one year. In Summary The Scarf bunionectomy has been proven to be a versatile and powerful procedure for correcting various degrees of hallux valgus deformity. Through modifications of bone cut lengths and in combination with a phalangeal osteotomy, you can address most hallux valgus deformities. In cases of extreme ligamentous laxity of the first ray or arthrosis of the first metatarso-cuneiform joint, the Lapidus operation may be more appropriate. The results of the Scarf bunionectomy compare favorably with the results reported for other popular bunion surgeries. But in the whole realm of choice, you must consider which operation allows the patient to ambulate postoperatively without a cast or the use of crutches as well as return to bathing and a closed athletic shoe in one to two weeks. Which procedure allows the performance of bilateral surgery, maintains cost effectiveness and returns the patient to the desired lifestyle more quickly? The Scarf bunionectomy clearly excels in these areas. It has been said that surgery is both a science and an art. We believe bunion surgery is as much art as science, which explains the success of so many procedures in one surgeon’s hands and the failure in another’s hands. The Scarf bunionectomy is a technically demanding procedure that has a large learning curve. However, once you master it, the procedure can provide a highly predictable and satisfying outcome for patients. Dr. Weil is the Fellowship Director of the Weil Foot and Ankle Institute in Des Plaines, Ill. He holds an MBA and is a Fellow of the American College of Foot and Ankle Surgeons.

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