Proximal Opening Wedge Osteotomy for Hallux Valgus Correction
BACKGROUND
The proximal opening wedge osteotomy is one of the more than 150 procedures described for the treatment of hallux valgus, indicating the complexity of this deformity.
It was first described by Trethowan10 in 1923. Trethowan10 used no fixation, as he thought that by maintaining an intact lateral cortex and using a well-fitting wedge graft, the osteotomy was relatively stable.
The procedure was initially performed mainly for adolescent bunions with questionable results. It was also used in the pediatric population with minimal deformity, prophylactically to prevent progression of the deformity.1,7,9
The proximal opening wedge osteotomy fell out of favor in subsequent years due to concerns regarding stability and nonunion at the osteotomy site. More recently, the possibility of arthritis in the first metatarsophalangeal joint (MPJ) due to “jamming” and recurrence of the deformity as a result of the
metatarsal lengthening created by the opening wedge was questioned.2,3,11
The earlier concerns have largely been addressed by the advent of more refined surgical techniques, superior internal fixation, and improvement in bone grafting. The addition of a distal closing “chevron-type” wedge osteotomy counteracts the lengthened first metatarsal and negates the increased distal metatarsal articular angle (DMAA), which does occur with the proximal opening wedge osteotomy being a rotational osteotomy.
SURGICAL MANAGEMENT
The proximal opening wedge osteotomy is reserved for the correction of moderate to severe (hallux valgus angle >30 degrees and 1-2 intermetatarsal [IM] angle >15 degrees) hallux valgus (HV) deformity.
The procedure is performed in combination with a lateral distal soft tissue release and a closing distal medialbased wedge osteotomy (chevron-type).
Positioning
The patient is placed supine on the table with a bolster under the ipsilateral buttock if the lower limb is too externally rotated.
A thigh tourniquet is used. Although the procedure is done under general anesthetic, a regional block may be
given for postoperative pain relief.
TECHNIQUES
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Exposure
The first part of the procedure is the lateral distal soft tissue release while the first web space is still wide. A 1- to 1.5-cm incision is made on the dorsum of the first web space.
The adductor hallucis tendon is identified and is sharply dissected from its insertion on the proximal phalanx of the hallux.
The dissection is carried proximally and the sesamoid suspensory ligament (between the lateral hallucal
sesamoid and the first metatarsal) is transected. There is no need to release the lateral hallucal sesamoid completely.
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Capsulotomy
A lateral capsulotomy is next performed. At this stage, one should be able to passively push the hallux into ±20 degrees varus.
A medial incision is made, extending from just distal to the first MPJ proximally along the shaft of the first metatarsal to the first tarsometatarsal (TM) joint.
The incision is carried down to the medial capsule (identified by the vertical orientation of its fibers). Care should be taken not to injure the medial cutaneous nerve, which should be in the dorsal flap.
Inferiorly, the dissection is carried down to the abductor hallucis tendon.
A vertical capsular incision is made approximately 2 to 3 mm proximal to the articular surface.
A more proximal incision is made parallel to the first and joined above with an inverted V and inferiorly with a V, thus excising an elliptical piece of capsule.
The width of this capsular piece is determined by the size of the medial eminence and the amount of deformity that is to be corrected (TECH FIG 1).
A horizontal capsular incision is now made from the dorsal extent of the vertical incision, proximally to the first TM joint.
The capsule is then sharply dissected off the medial eminence. The medial eminence is cut with a small oscillating saw.
Care is taken to remain medial to the groove and flush with the medial shaft of the first metatarsal. If there is a significant dorsal bunion, this, too, is resected.
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TECH FIG 1 • Medial capsulotomy. The abductor hallucis tendon is immediately above the lower retractor.
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Osteotomy and Plating
The first TM joint is identified with a needle or under fluoroscopy.
A transverse proximal osteotomy is performed approximately 1 cm from the TM joint.
The osteotomy must not be completed, that is, maintain an intact lateral cortex.
Depending on the set, the osteotomy is carefully prized open with either one or two osteotomes or a small distractor, taking care not to fracture the lateral cortex (TECH FIG 2A).
It is prudent at this stage to use fluoroscopy to determine the amount of opening required to correct the 1-2 IM angle (<8 degrees) and thus deciding on the size wedge plate.
We found two plates that are particularly good in providing stable fixation for early weight bearing and are low profile (Arthrex, Inc., Naples, FL and OrthoLink Medial Wedge Osteotomy Plate, Tornier, Inc., Bloomington, MN) (TECH FIG 2B).
Once the plate is placed, once again the correction is checked under fluoroscopy. The holes closest to the osteotomy are filled first.
Bone obtained from either the excised medial eminence or autologous bone from the medial distal tibial metaphysis is used as bone graft (TECH FIG 2C).
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TECH FIG 2 • A. Opening wedge osteotomy. Maintaining the integrity of the lateral cortex. B. OrthoLink
Medial Wedge Osteotomy Plate for bunion correction (Tornier). C. Placement of the Arthrex plate and bone graft.
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Securing Bone Graft
A 1-cm longitudinal medial incision is made along the distal tibia approximately 2 cm from the tip of the medial malleolus.
The dissection is carried down to bone and a 7-mm trephine needle is used to core out cancellous bone. This can be done several times until enough bone is obtained (TECH FIG 3A).
Once the proximal osteotomy is secured, the distal medialbased closing wedge osteotomy (biplanar chevron) is performed (TECH FIG 3B,C). The resected bone wedge can be used as bone graft as well. If the DMAA is normal, only a “shortening” chevron is required (TECH FIG 3D).
This osteotomy is secured with a cannulated compression screw.
The medial capsulorrhaphy is then completed with 2-0 absorbable suture and the alignment of the hallux is then checked clinically and radiologically (TECH FIG 3E).
Any HV interphalangeus or pronation can be addressed with an Akin osteotomy.
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TECH FIG 3 • A. A trephine needle is used to obtain cancellous autologous bone graft. B,C. Distal medialbased closing wedge osteotomy (biplanar chevron). D. Shortening chevron. E. Intraoperative fluoroscopy to check alignment after the medial capsulorrhaphy.
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Completion
Skin is closed with absorbable 3-0 subcuticular suture.
The foot is bandaged with a compression bandage with or without Reston foam spacer in the first web space (TECH FIG 4).
TECH FIG 4 • Postoperative dressing with Reston foam.
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PEARLS AND PITFALLS
The distal lateral soft tissue release should be done through the first web space, as this gives better visualization of the structures and avoids damage to the articular cartilage if the lateral release is attempted through the medial incision.
A transverse osteotomy is preferable (safer) and is carried out not less than 1 cm distal to the first TM joint.
The osteotomy is carefully prized open with two flat osteotomes or a special distractor (comes with the Tornier set).
Try placing the plate as plantar as possible on the medial surface, as the opening osteotomy tends to plantar flex the first metatarsal.
Intraoperative fluoroscopy is a must! Use it liberally during all stages of the procedure. Once the medial capsulorrhaphy is complete, the first MPJ congruency is checked with fluoroscopy. Varus complications can be reduced by doing so.
Do not overcorrect the first MPJ, expecting it to lose position later. Check the rotation of the hallux.
Do not panic if the lateral cortex is violated. Trust the plate and bone graft.
Do not forget the DMAA and/or HV interphalangeus, which will require a distal biplanar chevron and/or Akin, respectively.
Fifty percent of the success of the procedure is the aftercare. The surgeon must do the follow-up until
discharge (6 weeks).
Use the correct instruments, that is, an appropriate-size oscillating saw/blade. Do not compromise.
P.4200
POSTOPERATIVE CARE
The patient remains on strict bed rest with the operated foot elevated overnight.
The following morning, the patient is mobilized in a wedge-heel postoperative shoe. Weight bearing on the heel as tolerated.
Mobilization of the hallux begins as soon as is comfortable.
Weekly checkup/dressings/strapping for first 2 weeks and then 2 weekly for the following 4 weeks X-rays are obtained at 6 weeks.
The postoperative shoe is discontinued at 6 weeks if x-rays show union. Mobilization, footwear, scar care, and activities are explained to the patient.
A night splint may be used for a further 4 to 6 weeks.
OUTCOMES
The proximal opening wedge osteotomy is a powerful procedure for the correction of moderate to severe HV deformities, which pretty much meets the requirements for an excellent, if not ideal, proximal osteotomy. It is relatively simple with predictable correction, reproducible and stable enough to allow early weight bearing.
The results in the literature are uniformly good.
Wukich et al reviewed 18 of his cases and had an 89% satisfaction rate. The HV angle and 1-2 IM angle improved by 13.5 and 9 degrees, respectively. They found no instances of malunion or nonunion with complete patient satisfaction.5
Cooper et al2 reported on 23 patients also with complete patient satisfaction. They achieved a mean correction of 15 degrees for the HV angle and 7 degrees for the 1-2 IM angle.5
Shurnas8 reported the initial experience on 50 patients. He obtained a mean correction of 20 degrees in the HV angle and 12 degrees in the 1-2 IM angle. Mean time to healing was 5 to 8 weeks with no instances of nonunion, malunion, or delayed union. All patients were satisfied with their outcome. The
mean increase in the first metatarsal length of 1.9 mm was not significant.8
Shurnas8 also reported on a retrospective review of more than 90 patients with a minimum 2-year followup and found better than 90% good and excellent results.
There were five varus overcorrections, one nonunion, one delayed union, and two recurrences.
Saragas6 showed an improvement in the American Orthopaedic Foot and Ankle Society (AOFAS) score from 51.3 to 86.8, with over 90% good or excellent results in 46 patients (64 feet). There were five cases of hallux varus, of which only one was symptomatic. Two developed significant recurrent hallux valgus
deformity but were asymptomatic. A nonunion developed in one case and needed bone grafting.6
Randhawa and Pepper5 reported on 25 proximal opening wedge osteotomies. The hallux valgus angle improved by a mean of 30 degrees and the 1-2 IM angle by 8 degrees. There was an 80% satisfaction rate. They had one hallux varus, one nonunion, and one recurrence.5
Nery et al4 reported on 41 patients (70 feet). They used two types of fixation plates (Darco BOW or Arthrex LPS plate).
A biplanar chevron and/or Akin osteotomy was added as deemed fit depending on the magnitude of the distal angles.
The HV angle improved by a mean of 14 degrees and the 1-2 IM angle by 8 degrees. The AOFAS score improved from a mean 50 to 82. Even though both fixation systems were similar regarding correction capacity and stability, the Arthrex system scored significantly higher than Darco in the AOFAS postoperative evaluation, possibly due to the extremely low profile of the Arthrex, avoiding local
symptoms.4
The earlier studies have found no adverse effects as a result of violating the lateral cortex or the increased length of the first metatarsal.
COMPLICATIONS
The primary author had five varus overcorrections (prior to obtaining intraoperative fluoroscopy), of which one required arthrodesis.
Two developed recurrent HV (asymptomatic). One nonunion requiring bone grafting
Hardware irritation occurred in two cases and led to removal of the internal fixation.
REFERENCES
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Bonney G, Macnab I. Hallux valgus and hallux rigidus: a critical surgery of operative results. J Bone Joint Surg Br 1952;34:366-385.
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Cooper MT, Berlet GC, Shurnas PS, et al. Proximal opening-wedge osteotomy of the first metatarsal for correction of hallux valgus. Surg Technol Int 2007;16:215-219.
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Hardy MA, Grove JR. Opening wedge osteotomy of the first metatarsal using the Arthrex® Low Profile Plate and Screw System(tm). Podiatry Internet J 2007;2(4).
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Nery C, Réssio C, de Azevedo Santa Cruz G, et al. Proximal openingwedge osteotomy of the first metatarsal for moderate and severe hallux valgus using low profile plates. Foot Ankle Surg 2013;19: 276-282.
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Randhawa S, Pepper D. Radiographic evaluation of hallux valgus treated with opening wedge osteotomy. Foot Ankle Int 2009;30: 427-431.
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Saragas NP. Proximal opening-wedge osteotomy of the first metatarsal for hallux valgus using a low profile plate. Foot Ankle Int 2009;30:976-980.
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Scranton PE Jr, Zuckerman JD. Bunion surgery in adolescents: results of surgical treatment. J Pediatr Orthop 1984;4(1):39-43.
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Shurnas PS. Proximal opening wedge osteotomy of the first metatarsal: biomechanical and clinical evaluation. In: Proceedings from the American Academy of Orthopaedic Surgeons Annual Meeting, March 22-26, 2006, Chicago, IL.
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Simmonds FA, Menelaus MB. Hallux valgus in adolescents. J Bone Joint Surg Br 1960;42(4):761-768.
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Trethowan J. Hallux valgus. In: Choyce CC, ed. A System of Surgery. New York: PB Hoeber, 1923:1046-1049.
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Watson TS, Shurnas PS. The proximal opening wedge osteotomy for the correction of hallux valgus deformity. Tech Foot Ankle Surg 2008;7:17-24.