Key Insights On The Closing Base Wedge Osteotomy For Hallux Valgus

Pages: 26 - 33
Author(s): 
Alaa Mansour, DPM, and Lawrence Fallat, DPM, FACFAS

For patients with moderate to severe hallux valgus and a large intermetatarsal angle, proximal first metatarsal osteotomies may be indicated to achieve an appropriate amount of correction. The closing base wedge osteotomy is a reliable procedure resulting in a strong structural correction and is amenable to multiple fixation techniques. Loison first described and advocated the transverse closing base wedge osteotomy in 1901.1 Juvara modified the procedure in 1919, employing the oblique version of the closing base wedge osteotomy.2  

Controversy has surrounded this procedure due to its relative difficulty and the possibility of associated complications. Some authors have described the closing base wedge osteotomy as technically demanding with little margin for error and have even called for its extinction and replacement with the Lapidus arthrodesis.3-7 Martin and Blitch described the difficulties in the execution of this procedure and presented alternatives to the closing base wedge osteotomy.4 The osteotomy requires precise wedge resection with preservation of the hinge at the medial cortex of the metatarsal. Once the wedge is resected, intraoperative alterations for over- and undercorrection of the intermetatarsal angle can be technically challenging.4

When the procedure first became popular, complications included first metatarsal elevatus, shortening, delayed bone healing and unstable fixation.4,7-11 However, with advances in surgical technique, fixation methods and adequate postoperative weightbearing instruction, outcomes have improved.8,12,13 The closing base wedge osteotomy is a powerful procedure that preserves first ray range of motion while correcting hallux valgus deformities that may not be amenable to distal metatarsal osteotomies.

The primary indication for the closing base wedge osteotomy is a rigid deformity with an intermetatarsal angle of 15 degrees or greater. A rigid deformity is not manually reducible in the transverse plane and indicates the need for an osteotomy that corrects the larger angular deformity. The closing base wedge osteotomy is more effective at correcting moderate to severe deformities in comparison to distal metatarsal osteotomies. This is because the proximal position of the osteotomy is closer to the apex of the deformity, permitting greater angular correction and a more rectus alignment. When it comes to an intermetatarsal angle of 15 degrees or greater, performing a distal metatarsal osteotomy or soft tissue procedure may result in undercorrection and a higher recurrence rate.14,15

Step-By-Step Pearls For The Closing Base Wedge Osteotomy

Make the skin incision along the dorsomedial surface of the first metatarsal and medial to the extensor hallucis longus tendon, extending proximally to the first metatarsocuneiform joint. Take care to identify and retract the branches of the medial dorsal cutaneous nerve that cross at the proximal aspect of the incision. Incise the deep fascia and expose the surface of the first metatarsal. Maintain the periosteum at the base of the metatarsal medially to preserve the vasculature at the osteotomy site.

There are differences among surgeons regarding resection of the medial eminence in hallux valgus surgery. Some surgeons have advocated correction of hallux valgus deformity without any consideration for the medial eminence.16,17 One can resect the eminence after performing the closing base wedge osteotomy but our best outcomes take advantage of the pre-surgical stability of the metatarsal, resecting the medial eminence prior to making the osteotomy.

Following resection of the medial eminence, direct attention to creating the arms of the closing base wedge osteotomy. Orientation of the osteotomy is crucial to the outcome because it dictates the relationship of the first metatarsal to the weightbearing surface of the medial column. Directing the apex of the closing base wedge osteotomy at the medial cortex without breaking through creates a hinge. Position the base of the wedge laterally and keep in mind that the amount of bone you resect should be directly proportional to the amount of correction required. When making the osteotomy, angle the cuts so the osteotomy base is wider plantarly than dorsally to prevent elevatus.

The two variations of the closing base wedge osteotomy include the transverse and oblique methods. The surgeon’s fixation preference determines the orientation of the osteotomy. One generally performs the closing base wedge osteotomy approximately 2 cm distal to the first metatarsocuneiform joint, leaving enough room for fixation. A Kirschner wire (K-wire) can provide an axis guide just lateral to the location of the anticipated hinge. One should insert the K-wire from dorsal to plantar, perpendicular to the weightbearing surface of the foot. The K-wire also serves to protect the hinge from inadvertent cutting of the medial cortex and the surgeon can remove it prior to reciprocal planing of the osteotomy.

The surgeon performs the transverse technique by making the proximal cut perpendicular to the longitudinal axis of the first metatarsal. Prior to making the osteotomy, one can use intraoperative fluoroscopy to determine the osteotomy site by applying a four-hole plate and marking the bone between the second and third holes of the plate. Then mark the proximal arm perpendicular to the long axis of the first metatarsal. Make the distal cut first because of the stability of the first metatarsal. Angle the cut in the transverse plane and make it converge medially with the marked proximal arm. Then make the proximal transverse cut perpendicular to the weightbearing surface along the previously marked area. This determines the final angle of the wedge. The amount of bone to resect depends on the degree of intermetatarsal angle correction necessary to correct the deformity. Templates are available as guides to determine the size of the wedge. After completing both cuts, gently feather the osteotomy at its apex until you can reduce it without breaking the medial hinge.

Ruch introduced the oblique version of the closing base wedge osteotomy because it produces a longer arm and decreases the amount of bone resection.18 The proximal cut is essential to the orientation of the osteotomy because it determines the angle of the osteotomy as well as the placement of fixation. Perform the distal cut first at an angle of 45 degrees to the long axis of the metatarsal. Then perform the proximal arm of the osteotomy, which should intersect the distal arm, creating a medial hinge. The angle of the wedge resected is directly proportional and slightly less than the intermetatarsal angle.

Recognizing The Importance Of The Hinge Concept For Multiple Plane Correction Of Structural Deformities

Christensen and colleagues concluded that the major stabilizing factor of the first metatarsal base osteotomy is the medial cortical hinge.19 They found that osteotomies with an intact hinge exhibited superior stiffness in comparison to osteotomies without a hinge.

The hinge concept is an important tool for correcting structural deformities in multiple planes and necessitates optimal guide orientation to prevent dorsiflexion and shortening of the first metatarsal.8,20 Excessive shortening and elevatus can lead to transfer metatarsalgia and painful calluses under the second metatarsal. The axis of rotation, amount of correction and final position of the metatarsal in weightbearing depend on the integrity of the hinge and size of the wedge. The greatest amount of motion will occur in the plane to which the axis is perpendicular. Essentially, plantarflexion of the first metatarsal will occur with a dorsomedial hinge and elevatus of the first metatarsal will occur with a plantar-medial hinge. Making the osteotomy perpendicular to the first metatarsal will result in dorsiflexion of the first metatarsal. Therefore, we advocate making the osteotomy perpendicular to the weightbearing surface of the foot, ensuring that the first metatarsal will remain parallel with the weightbearing surface.

After removal of the resulting wedge and reduction of the intermetatarsal angle, temporarily fixate the osteotomy with a K-wire. Place the foot into simulated weightbearing and load the foot by using a metallic flat cover from an instrument tray. Using fluoroscopy, take a lateral image during simulated weightbearing to ensure proper alignment of the metatarsal and that no elevatus has occurred.
    
Emerging Concepts With Fixation

Once there is satisfactory alignment and the osteotomy is stable with a K-wire or a bone clamp, one can apply permanent fixation. Fixation techniques for this osteotomy include single screw, double screw, neutralization plate, locking plate and even intramedullary fixation. The two-screw technique employs a compression screw and an anchor screw. Orient the compression screw perpendicular to the osteotomy site. Place the anchor screw perpendicular to the long axis of the first metatarsal to prevent shortening and rotation if the hinge fails.

A variation of the two-screw technique is to insert a screw from the distal medial aspect of the first metatarsal into the intermediate cuneiform and a second screw from the distal lateral aspect of the first metatarsal into the medial cuneiform. This increases stability across the osteotomy site, especially in soft bone, by crossing additional cortices.

For added stability, our preferred method of fixation is an interfragmentary screw with a neutralization plate. Researchers have found that plate fixation is superior to a single screw or K-wire construct.21 This method provides good stability and we especially recommend it if one loses the integrity of the hinge. For this technique, the surgeons can use a 3.0 or 4.0 interfragmentary screw to compress the osteotomy. One usually inserts the interfragmentary screw from distal medial to proximal lateral, crossing perpendicular to the osteotomy. Attach a four-hole, quarter tubular bone plate to the dorsomedial aspect of the metatarsal with 2.7 mm cortical bone screws. Place the screw distal to the osteotomy eccentrically to provide additional compression. If necessary, use an axial loading screw to augment the fixation. One can insert this proximal dorsal to distal plantar and avoid penetrating the plantar cortex in order to prevent violation of the sesamoids.

Postoperative Principles

Following the procedure, place the patient into a below-knee cast for three weeks and give him or her instructions to be non-weightbearing. The patient subsequently transitions into a controlled ankle motion (CAM) boot and stays non-weightbearing until radiographic signs of osseous union are evident. The patient can then begin physical therapy and slowly transition to full weightbearing.

How To Handle Osteotomy Complications

Complications associated with the closing base wedge osteotomy include shortening of the first metatarsal, metatarsal elevatus, transfer metatarsalgia, delayed union and failure of fixation. Most complications occur because of poor technique, failure of fixation and early weightbearing.  

Studies have shown that average shortening of the metatarsal ranges from 1.7 mm to 5 mm.10,11,22-24 Excessive shortening of the first metatarsal can lead to increased pressure on the lesser metatarsal heads, which leads to pain, callus formation and stress fractures.20 Jung and coworkers studied the effects of shortening and elevation of the first metatarsal osteotomy, and concluded that it significantly increased plantar pressures under the lesser metatarsal heads.25 Despite these findings, Banks and colleagues studied shortening of the first metatarsal following the closing base wedge osteotomy and concluded that the reduction in length of the first metatarsal is not excessive, and that elevatus is the major factor that leads to most complications.11

Unlike the Lapidus procedure, which has a high non-union rate of up to 12 percent, the closing base wedge osteotomy has minimal issues with bone healing.3,13,26,27 Multiple studies have found no complications in osteotomy healing with no incidence of delayed union or non-union.22,24,28 Another advantage of this procedure is a low recurrence rate, especially in comparison with distal metatarsal osteotomies.3,29 Dreeben and Mann concluded that if one corrects the intermetatarsal angle to below 10 degrees using a metatarsal base osteotomy, patients with a moderate to severe deformity would not have a recurrence.30  

Ten Keys For Successful Closing Base Wedge Osteotomies

1. Select the appropriate patient who can follow postoperative instructions.
2. Evaluate for hypermobility at the first metatarsocuneiform joint.
3. Determine if first metatarsal elevatus is present.
4. If the patient has a metatarsus adductus foot structure, it may be necessary to create a slightly negative intermetatarsal angle to ensure adequate correction.
5. Select appropriate fixation for the osteotomy.
6. Select the type of osteotomy (transverse or oblique).
7. During dissection, safeguard the periosteum at the medial aspect of the metatarsal.
8. Perform the osteotomy in the correct angle so one can correct the intermetatarsal angle and not create metatarsal elevatus. Do not break the medial cortex.
9. Temporarily stabilize the osteotomy with a K-wire and take a lateral X-ray using the C-arm with the foot loaded. This allows you to visualize the medial column for signs of elevatus.
10. Insert fixation. If you are using a neutralization plate, insert the lag screw first, remove the K-wire and attach the plate.

In Conclusion

The closing base wedge osteotomy is an effective procedure that requires adequate preparation and surgical skill to create successful and reproducible results. The osteotomy allows for greater reduction of moderate to severe intermetatarsal angles in rigid first rays that are not possible with distal metatarsal procedures. Performing the surgery correctly and with utilization of the hinge concept can prevent complications, and facilitate favorable and reproducible outcomes.

Dr. Mansour is a second-year foot and ankle surgical resident at Beaumont Hospital-Wayne in Wayne, Mich.

Dr. Fallat is the Program Director of the foot and ankle surgical residency at Beaumont Hospital-Wayne in Wayne, Mich. He is a Fellow of the American College of Foot and Ankle Surgeons.

References

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Comments

I take some exception to the perpendicular to the floor vs the met. idea for the osteotomy. The HINGE location is the key along with parallel cuts of the wedge. Obviously, making the wedge wider at the bottom will indeed plantarflex the ray but how much? This is difficult to quantify and difficult to perform for consistent results! I have been doing base wedges for 30+ years and feel the location of the hinge has ALWAYS been the problem. When cutting across the met at the base, the medial aspect naturally starts to slope plantarly making the hinge go more plantar-medial as your blade goes more medial, thus creating automatic dorsiflexion no matter whether parallel to the floor or the met! If you angle your saw more medial plantar as you cut, you will naturally leave the hinge DIRECTLY medial or can even create a little more dorsomedial hinge and get plantarflexion to counteract the shortening by doing that. Check this out on some saw bones or cadavers. The paralell to the floor or met makes no difference if the hinge is too plantar medial. Cut a tree down some day and see which way the tree falls with the hinge in different orientations (parallel to the trunk vs parallel to the angled tree next to it) and where you place the hinge! It will fall opposite the hinge! I would be interested in your results on the cadvers or saw bones if you choose to check out my contention!

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