Distal chevron osteotomy
The distal chevron osteotomy (DCO) is a V-shaped osteotomy in the 1st MT head.
A medial approach gives adequate access and avoids the dorsomedial cutaneous nerve. A medial longitudinal incision is deepened to the capsule of the 1st MTPJ and the metatarsal shaft, obtaining any necessary haemostasis. The plantar part of the capsule is partially exposed to facilitate later double-breasting. The capsule is opened longitudinally and the medial eminence exposed.
The medial eminence is excised with a power saw in line with the medial surface of the metatarsal shaft (not according to the groove in the metatarsal head, which will usually result in excessive excision). The joint is inspected and its alignment relative to the metatarsal shaft (DMAA) assessed.
The attachment of the joint capsule to the posteroinferior part of the metatarsal head is identified. The inferior limb of the osteotomy is made just above this to preserve the capsular attachment to the metatarsal head fragment, as it carries part of the blood supply. The inferior limb of the osteotomy connects this point to the centre of the metatarsal head. By slanting it slightly downwards, the head fragment can be translated downwards. The second limb of the osteotomy is made at about 70deg to the first, aiming to cut across the metatarsal approximately parallel with the joint surface. The head fragment is carefully freed and translated laterally by a combination of pushing the head and pulling the shaft fragments. The head is impacted. There is some disagreement in the literature as to whether fixation is necessary to prevent redisplacement medially; there are no trials, some case series report several redisplacements in non-fixed patients but others report none. We use absorbable pin fixation which has been reported to give stable fixation with few complications (Winemaker 1996, Deorio 2001, Caminear 2005).
If the articular surface is laterally angulated with respect to the shaft (increased DMAA), a medially based wedge can be removed from the superior limb to correct it. If there is significant OA in the MTPJ, the metatarsal can be shortened slightly by removing a slice from the superior limb which can be inserted in the inferior limb to give compensatory plantar displacement (Youngswick osteotomy).
The medial spike is trimmed off and any necessary rounding done. The capsule is repaired to restore soft tissue tension. We use a double-breasting technique. Once the correction is completed, or earlier if more convenient, the degree of residual hallux valgus in the phalanx can be assessed and, if necessary, and Akin osteotomy can be added. Some surgeons use an Akin osteotomy on almost every patient while others are selective; there is no evidence that routine Akin is necessary to obtain good results. Skin closure is as standard for the surgeon.
The capsule is repaired to restore soft tissue tension. We use a double-breasting technique.
Once the correction is completed, or earlier if more convenient, the degree of residual hallux valgus in the phalanx can be assessed and, if necessary, and Akin osteotomy can be added. Some surgeons use an Akin osteotomy on almost every patient while others are selective. The evidence on the benefits of additional Akin osteotomy is inconclusive. Lechler (2012) found that patients who had an additional Akin had greater radiological correction, but no difference in AOFAS scores or satisfaction ratings. In patients who had a scarf osteotomy with or without Akin, Malviya (2007) found no difference in clinical or radiological outcomes. Both studies were retrospective comparisons.
Skin closure is as standard for the surgeon.
The osteotomy is stable to vertical displacement. Overall Shereff (1991) found the chevron more stable than Mitchell, transverse distal, biplanar or basal osteotomies. Patients can walk on it immediately. Some series have used strapping or splintage post-operatively to minimise the risk of recurrent deformity. There are no trials of aftercare methods. Patients may be able to start using soft shoes with plenty of room within 2-3 weeks of surgery.
The osteotomy usually takes 6-8 weeks to unite. Most surgeons take check Xrays early and then around the expected date of union to document initial correction and position of union. However, Murphy (2007) found that only one of 412 post-operative Xrays was noted to be abnormal, and no change in management was made.
Holt (2008) found that braking reaction time had returned to normal 6 weeks after a chevron, scarf or basal first metatarsal osteotomy. Although they did not measure braking response between 2 weeks (when most patients were unable to do the test due to pain) and 6 weeks, it is probably advisable to recommend that patient wait till 6 weeks before driving until further evidence is available.
What is its place?There have been a number of RCTs comparing the DCO to other procedures.
- Klosok (1993) compared the DCO and Wilson procedures. The Wilson group had better correction of hallux valgus angle, while the chevron tended to lose correction between 6month and 3year follow-up. There was less shortening in the chevron group, but more metatarsalgia. Although there are some methodological deficiencies in this trial it can be interpreted as supporting the concept that shortening may be beneficial in correcting hallux valgus without increasing metatarsalgia.
- Resch compared the DCO and proximal closing wedge osteotomy (PCWO). Although the PCWO gave better correction of deformity this was at the cost of more complications, especially metatarsalgia. Overall, the clinical results were similar. The simplicity and good healing potential of the DCO may outweigh the theoretical advantages of a proximal osteotomy.
- Resch (1994) also compared DCO alone with DCO plus adductor tenotomy. Although the tenotomy group had a better correction of hallux valgus angle, the clinical results were similar.
- Saro (2007) compared the chevron osteotomy to the Lindgren-Turan osteotomy (a distal transverse osteotomy stabilised with a screw) in 100 patients. Correction of deformity was better in the Lindgren group but there was no difference in clinical outcomes measured with the EuroQol and AOFAS first ray score.
- Deenik (2007, 2008) compared the chevron osteotomy to the scarf in 136 case. There were no differences in radiological or clinical outcomes, even in initially severe deformities.
Smith (2012) performed a systematic review of studies of the scarf and chevron osteotomies. They found tha thte scarf corrected IMA by 0.88deg more than the chevron. They suggested that the methodological quality of the evidence was such that this apparent difference was not very reliable.
Schneider (2004) reported a large cohort of chevron osteotomies with the longest reported follow-up. 112 osteotomies were followed up for 10-14 years. All had adductor tenotomies and internal fixation was not used. Excellent radiological correction was obtained which did not deteriorate over time. The mean AOFAS score was 89.7 at 10 years. There were two cases of partial avascular necrosis, both asymptomatic.
It is generally advised that distal osteotomies should be displaced laterally by no more than 50% of the metatarsal shaft diameter to prevent instability. Badwey et al (1997) showed that this was achieved by translation 5mm in females and 6mm in males. Some studies (Kinnard 1984, Klosok 1993, Saro 2007) suggest that the chevron achieves less correction of deformity than the Mitchell, Wilson or Lindgren osteotomies (although Kinnard’s series was a small retrospective series). However, Schneider (2004) obtained good clinical results even with pre-operative intermetatarsal angles up to 24deg, while Stienstra et al (2002) displaced the osteotomy by up to 9mm and 10 degrees IMA correction with good clinical results and no redisplacement. Bai (2010) also reported good outcomes from chevron osteotomies (with lateral release) in moderate/severe hallux valgus – mean IMA improved from 17.1 to 7.3 deg and clinical results were comparable with other series. Indeed, Deenik’s RCT found similar correction between scarf and chevron procedures even in severe deformities. While there were some methodological issues with this trial, it suggests the chevron procedure may have wider applicability than previously thought.
Meier and Kenzoara (1985) reported a 20% avascular necrosis (AVN) rate in 60 chevron osteotomies, rising to 40% (4/10) in patients who had a lateral release. Neary (1993) also found that avascular necrosis was commoner after lateral release, but Resch’s RCT and several large cohort studies have failed to confirm this. Kuhn (2005) measured intra-operative blood flow in the metatarsal head with a laser Doppler probe and found a total reduction of 71% in the course of the procedure – interestingly, the medial capsulotomy accounted for three times as much as the lateral release. However, none of their 20 patients developed avascular necrosis. Wilkinson found that 50% of 20 chevron osteotomies had MRI evidence of avascular necrosis, and Resch found altered bone scintigraphy patterns in 4/41 osteotomies. None of these patients developed clinical symptoms. Overall the risk of AVN appears to be about 1-2%, and the clinical result will be affected in few patients. There is little evidence that lateral release increases the risk and this procedure is not contra-indicated.
The chevron osteotomy has become, for many surgeons, the standard osteotomy for mild or moderate hallux valgus. Recent papers have also reported good results in severe deformities with the addition of an adductor tenotomy. Resch's and Deenik’s RCTs showed that DCO can give as good clinical results in a general series as proximal or scarf osteotomy.
Nevertheless, only one series with long-term (>10y) outcome has been reported. Nor has there been any RCT against the Mitchell osteotomy, which is probably the gold standard for mild to moderate deformity. Klosok's RCT against the Wilson, while apparently giving counter-intuitive results, shows that the avoidance of shortening may not be as beneficial as had been thought.
There needs to be further comparative study of the place of the DCO in the management of hallux valgus.