Hans-Joerg Trnka and Stefan G. Hofstaetter
DEFINITION
The first reports of a distal metatarsal osteotomy date back to Reverdin, who described in 1881 a subcapital closing-wedge osteotomy for the correction of hallux valgus deformity.
The chevron osteotomy has become widely accepted for correction of mild and moderate hallux valgus deformities. In the initial reports by Austin and Leventen1 and Miller and Croce,13 no fixation was mentioned. They suggested that the shape of the osteotomy and impaction of the cancellous capital fragment upon the shaft of the first metatarsal provided sufficient stability to forego fixation.
To increase the indication for this technically simple osteotomy, internal fixation and a lateral soft tissue release have been added.
ANATOMY
The special situation distinguishing the first metatarsophalangeal (MTP) joint from the lesser MTP joints is the sesamoid mechanism.
On the plantar surface of the metatarsal head are two longitudinal cartilage-covered grooves separated by a rounded ridge. The sesamoids run in these grooves.
The sesamoid bone is contained in each tendon of the flexor hallucis brevis; they are distally attached by the fibrous plantar plate to the base of the proximal phalanx.
The head of the first metatarsal is rounded and cartilagecovered and articulates with the smaller concave elliptic base of the proximal phalanx.
Fan-shaped ligamentous bands originate from the medial and lateral condyles of the metatarsal head and run to the base of the proximal phalanx and the margins of the sesamoids and the plantar plate.
Tendons and muscles that move the great toe are arranged in four groups:
Long and short extensor tendons
Long and short flexor tendons
Abductor hallucis
Adductor hallucis
Blood supply to the metatarsal head
First dorsal metatarsal artery
Branches from the first plantar metatarsal artery
PATHOGENESIS
Extrinsic causes
Hallux valgus occurs predominantly in shoe-wearing populations and only occasionally in the unshod individual.
Although shoes are an essential factor in the cause of hallux valgus, not all individuals wearing fashionable shoes develop this deformity.
Intrinsic causes
Hardy and Clapham found in a series of 91 patients a positive family history in 63%.
Coughlin2 reported that a bunion was identified in 94% of 31 mothers whose children inherited a hallux valgus deformity.
Association of pes planus with the development of a hallux valgus deformity has been controversial.
Hohmann was the most definitive that hallux valgus is always combined with pes planus.
Coughlin2 and Kilmartin7 noted no incidence of pes planus in the juvenile patient.
Pronation of the foot imposes a longitudinal rotation of the first ray, which places the axis of the MTP joint in an oblique plane relative to the floor. In this position the foot appears to be less able to withstand the deformity pressures exerted on it by either shoes or weight bearing.
The simultaneous occurrence of hallux valgus and metatarsus primus varus has been frequently described. The question of cause and effect continues to be debated.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patient history often includes:
Pain in narrow shoes
Symptomatic intractable keratoses beneath the second metatarsal head (in 40% of patients)
Lateral deviation of the great toe
Pronation of the great toe
Keratosis medial plantar underneath the interphalangeal joint
Bursitis over the medial aspect of the medial condyle of the first metatarsal head
Hypermobility of the first metatarso-cuneiform joint
Physical examination for hallux valgus deformity includes the following:
Hallux valgus angle: Normal is 15 degrees or less.
Intermetatarsal angle: Normal is 9 degrees or less.
Measurement of the position of the medial sesamoid relative to a longitudinal line bisecting the first metatarsal shaft
Grade 0: no displacement of sesamoid relative to the reference line
Grade I: overlap of less than 50% of sesamoid relative to the reference line
Grade II: overlap of greater than 50% of sesamoid relative to the reference line
Grade III: sesamoid completely displaced beyond the reference line
Joint congruency: measuring the lateral displacement of the articular surface of the proximal phalanx with respect to the corresponding articular surface of the metatarsal head, as seen on a dorsoplantar roentgenogram
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs of the foot should always be obtained with the patient in the weight-bearing position with AP, lateral, and oblique views. The following criteria are examined:
Hallux valgus angle
Intermetatarsal angle
Sesamoid position
Joint congruency
Distal metatarsal articular angle: the relationship between the articular surface of the first metatarsal head and a line bisecting the first metatarsal shaft (normal is 10 degrees or less)
Arthrosis of the first MTP joint
DIFFERENTIAL DIAGNOSIS
Ganglion
Hallux rigidus
NONOPERATIVE MANAGEMENT
Comfortable wider shoes
Orthotics?
Spiral dynamics physiotherapy in adolescents
SURGICAL MANAGEMENT
Indications
Symptomatic hallux valgus deformity with a first intermetatarsal angle of up to 16 degrees
Stable first metatarso-cuneiform joint
Contraindications
Narrow metatarsal head so that adequate translation is not possible
Intermetatarsal angle of more than 16 degrees
Impaired vascular status
Skeletally immature patient
Severe osteoarthritic changes
Preoperative Planning
Standard weight-bearing AP and lateral radiographs are mandatory.
The hallux valgus and intermetatarsal angles and tibial sesamoid position are measured.
A preoperative drawing is helpful.
Clinical examination includes measurement of active and passive range of motion of the first MTP joint as well as inspection of the foot for plantar callus formation indicative of transfer metatarsalgia and stability of the first tarsometatarsal joint.
Positioning
The foot is prepared in the standard manner.
The patient is positioned supine.
An ankle tourniquet is optional.
Approach
The lateral soft tissue release is performed through a dorsal approach.
The chevron osteotomy is performed through a straight midline incision.
TECHNIQUES
LATERAL SOFT TISSUE RELEASE
The procedure is typically performed under a peripheral nerve block.
Make a dorsal 3-cm longitudinal incision over the first web space (TECH FIG 1A).
Continue deep dissection bluntly.
Insert a lamina spreader and a Langenbeck retractor to expose the first web space.
Divide the lateral joint capsule (metatarso-sesamoid ligament) immediately superior to the lateral sesamoid. Fenestrate the lateral capsule at the first MTP joint (TECH FIG 1B,C). Apply a varus stress to the hallux to complete the lateral release (TECH FIG 1D).
TECH FIG 1 • A. Skin incision over the first web space. B, C. Release of the metatarso-sesamoidal ligament. D. The great toe is brought into 20 degrees varus to demonstrate the release of the lateral structures.
Place one or two sutures between the lateral capsule of the first MTP joint and the periosteum of the second metatarsal.
CHEVRON OSTEOTOMY
Externally rotate the leg. Make a second skin incision at the medial aspect of the first MTP joint (TECH FIG 2A).
Perform careful dissection to avoid any damage to the dorsomedial nerve. Open the medial MTP joint capsule with an inverted L-type incision (TECH FIG 2B,C). Inspect the joint for degenerative changes.
Expose the metatarsal head and place Hohmann retractors dorsal and plantar just extra-articular of the first MTP joint. The plantar Hohmann retractor protects the plantar artery to the metatarsal head, and the dorsal retractor protects the dorsal intra-articular blood supply originating from the capsule.
Minimally shave the medial eminence to achieve a plane surface but also to preserve as much metatarsal head width as possible (TECH FIG 2D). This is one of the most important principles if a chevron osteotomy is carried out in a moderate to severe deformity.
TECH FIG 2 • A. Medial skin incision for the osteotomy. B, C. Inverted L-type capsular incision. D. The medial eminence is minimally resected.
TECH FIG 3 • A–C. A guidewire marks the apex of the osteotomy. It should be 10 degrees inclined from medial to lateral, and pointing at the head of the fourth metatarsal. D. The osteotomy is performed using an osteotomy guide.
Drill a 1.0-mm Kirschner wire slightly dorsal to the center of the exposed medial eminence. This wire is generally inclined 20 degrees from medial to lateral, aiming at the head of the fourth metatarsal (TECH FIG 3A–C). In the situation of an elevated position of the first metatarsal, the inclination may be increased. If shortening or lengthening of the first metatarsal is needed, the wire may be aimed to the fifth or third metatarsal head.
Using a saw guide (TECH FIG 3D), make two cuts with an oscillating power saw so that they form an angle of 60 degrees proximal to the drill hole.
Once the capital fragment is freely mobile, pull the metatarsal shaft medially by using a towel clip while pushing the metatarsal head laterally with the help of the thumb of the other hand (TECH FIG 4A,B).
If the distal metatarsal articular angle is increased, a wedge from the distal dorsal cut may be excised to place the metatarsal head in a more varus position. If there is only a minor increase of the distal metatarsal articular angle, this may also be achieved by impacting the metatarsal head onto the shaft.
Insert a guidewire for a cannulated Charlotte multiuse compression screw (Wright Medical Technology) from the distal dorsal metatarsal shaft obliquely to lateral plantar of the metatarsal head (TECH FIG 4C,D).
TECH FIG 4 • A, B. The metatarsal head is pushed laterally while the metatarsal shaft is pulled medially. C, D. A guidewire for the 3.0 Charlotte multiuse compression screw (Wright Medical Technology) is placed.
Check the position of the osteotomy and the guidewire with a C-arm or a FluoroScan.
Measure the length of the screw with the cannulated depth gauge (TECH FIG 5A). The multiuse compression screws are designed to be totally self-tapping and selfdrilling. However, to avoid dislocation of the head, use the cannulated drill (TECH FIG 5B) and cannulated head drill (TECH FIG 5C).
Insert the screw (TECH FIG 5D).
Excise the medial eminence in line with the metatarsal shaft, taking care not to excise too much bone off the metatarsal head (TECH FIG 5E).
While an assistant holds the great toe in a slightly overcorrected position, repair the medial joint capsule with U-type sutures, and tighten the first web space sutures (TECH FIG 5F).
TECH FIG 5 • A. Length determination using the depth gauge. B. Predrilling with the Charlotte cannulated drill. C. Preparing a countersunk area with the Charlotte cannulated head drill. D. The screw is inserted until the head is completely countersunk within the bone. E. The medial eminence is resected. F. Closing of the medial capsule with U-type sutures.
FIG 1 • Rathgeber postoperative shoe (OFA Rathgeber, Germany).
POSTOPERATIVE CARE
Starting immediately postoperatively, ice application to the foot is helpful to reduce swelling.
Provided that the bone quality was intraoperatively sufficient, patients are allowed to walk with a postsurgical type shoe (OFA Rathgeber) (FIG 1) on the same day (limited for 4 weeks).
Weekly changes of the tape dressing are necessary.
An alternative to weekly dressing changes is the postoperative hallux valgus sock, which also reduces postoperative edema (FIG 2).
Radiographs are taken intraoperatively and at 4 weeks of follow-up.
After radiographic union is achieved, normal dress shoes with a more rigid sole are allowed.
After 4 weeks physiotherapy to achieve normal forefoot function is recommended (FIG 3).
OUTCOMES
In the early years of this technique it was limited to patients 50 years and younger. This was represented by the study of Johnson et al,5 which established a contraindication for using a chevron osteotomy in patients older than 50 years. However, Trnka21–23 and Schneider19 have proven that age is not a limiting factor for the chevron osteotomy.
FIG 2 • Postoperative hallux valgus compression stocking for use after suture removal.
Another important issue that was stretched out over the years was the combination of a lateral soft tissue release and a distal chevron osteotomy. Earlier reports have expressed concern about an increased risk of avascular necrosis if a lateral release is performed in addition to a chevron osteotomy. Jahss,6 Mann,9–11 and Meier and Kenzora12 have all suggested that avascular necrosis frequently accompanies distal Chevron with lateral soft tissue release, citing an incidence of up to 40%. Pochatko16 and Trnka21–23 could not support this in their publications and found no increased risk of avascular necrosis.
Chevron osteotomy was for many years limited to mild hallux valgus deformities.18,20 Designed primarily without fixation, the concern was stability and loss of fixation. As it became more obvious that a lateral soft tissue release is important for correction of more severe deformities, this concern gained weight. According to papers by Harper4 and Sarrafian,18 lateral displacement is limited up to 50% of metatarsal width.
Over a period of 14 years we have modified and developed the chevron osteotomy. By reviewing each step of the development with clinical studies, we now perform a chevron osteotomy with lateral soft tissue release and single screw fixation.
FIG 3 • A 72-year-old woman before surgery (A) and after surgery (B).
Trnka et al22 reported in 2000 a series of 43 patients (57 feet) with 2-year and 5-year follow-up. Radiographic evaluation revealed a preoperative average hallux valgus angle of 29 degrees and a preoperative average intermetatarsal angle of 13 degrees. At the 2-year follow-up, those angles averaged 15 and 8 degrees, respectively, and at the 5-year follow-up, they averaged 16 and 9 degrees. The results at these two follow-up periods proved that the chevron osteotomy is a reliable procedure for mild and moderate hallux valgus deformity and that there are no differences in outcome based on age.
Schneider et al19 reported in 2004 a series of 112 feet (73 patients) with a minimum follow-up of 10 years. For 47 feet (30 patients), the results were compared with those from an interim follow-up of 5.6 years. The AOFAS score improved from a preoperative mean of 46.5 points to a mean of 88.8 points after a mean of 12.7 years. The first MTP angle showed a mean preoperative value of 27.6 degrees and was improved to 14.0 degrees. The first intermetatarsal angle improved from a preoperative mean of 13.8 degrees to 8.7 degrees. The mean preoperative grade of sesamoid subluxation was 1.7 on a scale of 0 to 3 and improved to 1.2. Measured on a scale of 0 to 3, arthritis of the first MTP joint progressed from a mean of 0.8 to 1.7. The progression of arthritis of the first MTP joint between 5.6 and 12.7 years postoperatively was statistically significant. Excellent clinical results after chevron osteotomy not only proved to be consistent but also showed further improvement over a longer follow-up period. The mean radiographic angles were constant, without recurrence of the deformity. So far, the statistically significant progression of first MTP joint arthritis has not affected the clinical result, but this needs further observation.
Sanhudo17 retrospectively reviewed 50 feet with moderate to severe hallux valgus deformity in 34 patients with a mean follow-up of 30 months. There was a mean AOFAS score improvement of 39.6 (44.5 to 84.1) points. The hallux valgus angle and intermetatarsal angle improved a mean of 22.7 degrees and 10.4 degrees, respectively. He concluded that the chevron osteotomy is also indicated for moderate to severe hallux valgus deformity.
COMPLICATIONS
Avascular necrosis of the metatarsal head
A lateral release does not increase the incidence.16
Hallux varus
Malpositioning
Loss of fixation
REFERENCES
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· Coughlin MJ. Roger A. Mann Award. Juvenile hallux valgus: etiology and treatment. Foot Ankle Int 1995;16:682–697.
· Hardy RH, Clapham JC. Observations on hallux valgus based on a controlled series. J Bone Joint Surg-Br 1951;33:376–391.
· Harper MC. Correction of metatarsus primus varus with the chevron metatarsal osteotomy. An analysis of corrective factors. Clin Orthop Relat Res 1989;253:180–198.
· Johnson JE, Clanton TO, Baxter D, et al. Comparison of chevron osteotomy and modified bunionectomy for correction of mild to moderate hallux valgus deformity. Foot & Ankle 1991;12:61–68.
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