A Closer Look At The Modified Offset V Osteotomy For Hallux Valgus

There has been much discussion about the surgical treatment algorithm for hallux abductovalgus with the protocol often relying on the preoperative severity of the deformity. We mainly determine this severity by mathematical measurements.

In theory, hallux abductovalgus begins with weakening of the medial metatarsophalangeal (MPJ) capsule and erosion of the intersesamoid ridge. Downstream effects include frontal plane rotational changes of the hallux and metatarsal, further medial MPJ soft tissue attenuation and lateral soft tissue contracture leading to hallux abduction toward the second metatarsal.¹ Progression of hallux abductovalgus accelerates due to intrinsic destabilization such as concomitant pes planus and first ray hypermobility.²

With the medial longitudinal arch collapse occurring in pes planus, a triplane deforming force occurs in the first ray. The first metatarsal dorsiflexes, everts and adducts, and the first intermetatarsal angle consequently increases during stance phase.³ Due to the altered pedal biomechanical properties, hallux abductovalgus is often a progressive deformity that may lead to other subsequent lower limb pathologies if one does not adequately address the deformity.²

As we mentioned earlier, the treatment protocol often depends on the severity of hallux abductovalgus, which clinicians often calculate using the hallux abductus angle and the intermetatarsal angle. Surgeons often utilize distal metatarsal procedures for mild to moderate deformity and reserve more proximal procedures for more severe deformities.² Diaphyseal osteotomies are generally indicated for moderate hallux abductovalgus deformities but some surgeons have employed them for severe hallux valgus.^2,4,5 The lead author typically denotes any deformity less than 15 degrees of intermetatarsal angle as mild to moderate, between 15 and 18 degrees as moderate to severe and greater than 18 degrees as a severe hallux abductovalgus deformity.

Key Considerations With Bunion Procedure Selection
Despite our growing knowledge of hallux abductovalgus pathogenesis, procedure selection is often inconsistent among foot and ankle surgeons. Dayton and colleagues demonstrated that the center of rotation angulation (CORA) for hallux valgus lies at the first tarsometatarsal joint.⁶ Accordingly, by performing any osteotomy distal to the CORA, surgeons are essentially creating an entirely new CORA and, in effect, creating a new pathology in a previously non-pathologic bone. The authors also note that many procedures neglect to address the hallux abductovalgus deformity in the frontal plane. However, to the best of our knowledge, there are no studies to date that demonstrate long-term dysfunction or recurrence of the bunion deformity when comparing proximal to distal procedures.

The literature has shown that the modified Lapidus arthrodesis is a technically demanding procedure that warrants much experience in order to achieve successful results.⁷ In instances when the surgeon is not comfortable with the procedure or in the cases of a shortened first metatarsal or a patient with comorbidities who is not medically fit for excessive periods of non-weightbearing, other procedures may be indicated.⁸

The shaft osteotomies are popular because of their ability to correct higher intermetatarsal angles and allow quick recovery.⁵ Patients with osteosynthesis may bear weight immediately with full recovery in eight to 12 weeks. As a result, when it comes to patients who want symptomatic relief without an extensive non-weightbearing protocol, it is our belief that the indications for diaphyseal osteotomies for the correction of hallux abductovalgus should expand. Complications with diaphyseal osteotomies, although possible, are rare and relatively easy to address.  

While the Lapidus procedure may be able to adequately address the CORA in a patient with increased intermetatarsal angles, the procedure is not without a higher potential of complications, such as non-union, shortening and elevation of the first ray, and pseudarthrosis. Specifically, Saffo and colleagues found a 12 percent rate of non-union and pseudarthrosis following first tarsometatarsal joint fusion in 44 patients.⁹ These complications can be devastating and difficult to rectify in an elective arena. Length of recovery is also an issue, especially in a revisional situation. Authors have advocated many modifications for osteosynthesis but the general recommendation is still six weeks of non-weightbearing with possible early weightbearing in a select group of patients. The extended non-weightbearing period may put the patient at an increased risk of venous thromboembolism.¹⁰

The offset V osteotomy gained popularity in two separate techniques published by Kalish and Bernbach in 1987 and Vogler in 1989 as a modified chevron osteotomy with a long dorsal wing and short plantar wing.^11,12 The Kalish osteotomy arms are angled at 55 degrees and the apex of the osteotomy lies slightly distal to that of the Vogler osteotomy, which is angled at 40 degrees.^11,12 Although Vogler recommended a single Kirschner wire (K-wire) oriented perpendicular to the long dorsal arm of the osteotomy, modifications have emerged for both osteotomies to allow for two sites of fixation. Regardless of the specific type of offset V osteotomy, there is more transverse plane correction with this procedure than in numerous other procedures due to the long dorsal arm.⁴

Pertinent Insights On The Offset V Osteotomy From A Recent Retrospective Review
In a retrospective review, we sought to demonstrate our surgical results with the offset V osteotomy for hallux abductovalgus correction.

Eight female patients (nine feet) at a mean age of 57.4 were included in this retrospective analysis. Inclusion criteria were a prominent bunion deformity with a high intermetatarsal angle and all patients selected were from the year 2014 and had no previous history of a bunion surgery. Exclusion criteria were those who had any other procedure performed for a hallux valgus deformity other than an offset V osteotomy. We evaluated the first and second intermetatarsal angle and hallux abductus angle with a goniometer to determine the radiographic correction achieved.

We calculated the intermetatarsal angle with standard AP radiographs, using the longitudinal bisection of the first and second metatarsals and the midline of the articular cartilage of the base and head as the reference points for the bisection. When concomitant metatarsus adductus was present, we calculated the true intermetatarsal angle by subtracting 15 degrees from the metatarsus adductus angle and adding that number to the intermetatarsal angle. We calculated the metatarsus adductus angle between the longitudinal bisection line of the second metatarsal and a line perpendicular to the transverse axis of the tarsus. We calculated the hallux abductus angle as the angle between the longitudinal bisection of the first metatarsal and the proximal phalanx of the hallux.

We used an ankle tourniquet for all procedures and scrubbed each foot in the usual aseptic manner. The incision was dorsal medial and parallel to the extensor hallucis longus tendon. Deepening the incision, we performed sharp and blunt dissection with meticulous technique, taking care to avoid all neurovascular and tendinous structures. We proceeded to dissect capsular and periosteal tissues, exposing the first MPJ, metatarsal shaft and proximal phalangeal shaft if needed. Performing a subsequent through and through offset V osteotomy in the metaphyseal-diaphyseal junction of the first metatarsal, the angle on average was around 45 to 55 degrees and the dorsal arm extended proximally to around 25 to 40 mm in length. Employing standard AO technique, we utilized two solid, fully threaded cortical screws for fixation of the osteotomy. We also performed an oblique Akin osteotomy in seven out of the nine feet and fixated each with one cannulated, partially threaded screw.

The mean preoperative intermetatarsal angle was 18.0 degrees and the mean postoperative intermetatarsal angle was 9.4 degrees. One patient had concomitant metatarsus adductus and we calculated the true intermetatarsal angle in this case using the aforementioned formula. The average preoperative hallux abductus angle was approximately 35 degrees and the average postoperative hallux abductus angle was approximately 14 degrees.

Assessing The Studies On First Metatarsal Diaphyseal Osteotomies
Multiple studies have compared first metatarsal diaphyseal osteotomies. Using bone models, Unal and coworkers compared the following osteotomies: the offset V, scarf, Mau, Myerson’s modification of the Ludloff osteotomy, and a modified Mau using a proximal plantar arm with a longer dorsal arm.¹³ All osteotomies had fixation with two screws and three point bending evaluation for maximum load to failure, displacement at maximum load and stiffness. The authors reported that the stiffness of the Ludloff osteotomy was significantly lower than that of all other procedures and the stiffness of the Mau osteotomy was significantly greater than all other procedures except for the offset V osteotomy.

Shaw and colleagues performed a similar study by comparing maximum load to failure, energy accepted prior to failure and stiffness.¹⁴ They compared these through the use of a computer-controlled hydraulic tensile testing environment and a clamp at an angle of 15 degrees to best simulate the normal physiologic metatarsal declination angle. The authors demonstrated that the offset V osteotomy had significantly greater maximum load to failure and energy accepted prior to failure in comparison to inverted scarf, Mau and Ludloff osteotomies.

Gonda and colleagues compared Kalish and Vogler osteotomies in bone models with regard to maximum load to failure, displacement at maximum load and stiffness.¹⁵ They found that the Kalish osteotomy demonstrated significantly increased maximum load to failure and stiffness over the Vogler osteotomy. This was theoretically due to the shorter lever arm in the Kalish osteotomy between the apex of the osteotomy and the area of weightbearing as well as the increased cross-sectional area of the apex site in the Kalish osteotomy.

It is our belief that surgeons may employ the offset V osteotomy for moderate hallux abductovalgus correction in the transverse plane. Additionally, patients who are not comfortable being non-weightbearing for extensive periods of time may be more inclined toward this procedure due to its early weightbearing protocol (six weeks post-op in a stiff-soled shoe) without needing cast immobilization. Sanhudo has used this procedure in the context of moderate and severe hallux abductovalgus deformity, and has found a mean improvement in American Orthopedic Foot and Ankle Society (AOFAS) scores of 39.68 in a study of 34 patients.⁵ Similar to our results, there were significant improvements in intermetatarsal and hallux abductus angle parameters in the Sanhudo study.

In Conclusion
By retrieving records from the past year on a select group of patients undergoing the offset V osteotomy, we sought to demonstrate that the offset V osteotomy is a useful procedure for patients who cannot take an extended period of time off from work or their daily activities. In the senior author’s private practice patient population, the offset V osteotomy is the preferred procedure for patients with an intermetatarsal angle of at least 15 degrees. In both our study and in our practice’s regular protocol, the postoperative course on average involves initial limited weightbearing in a postoperative shoe followed by a return to full weightbearing in regular shoes in two weeks. Physical therapy on average lasted four weeks and started after two weeks from the date of surgery.  

The offset V osteotomy continues to be a useful and economical procedure in certain types of patients due to the intermetatarsal angle correction one can achieve, verified stability, and a favorable postoperative protocol in rehabilitation.

Dr. Visser is the Director of the Foot and Ankle Surgery Residency Program within SSM Health DePaul Hospital in St. Louis.

Dr. Malik is a third-year foot and ankle surgical resident at SSM Health DePaul Hospital in St. Louis.

Mr. Malek is a third-year student at the College of Podiatric Medicine and Surgery at Des Moines University.

References

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9. Saffo G, Wooster MF, Stevens M, Desnoyers R, Catanzariti AR. First metatarsocuneiform joint arthrodesis: a five-year retrospective analysis. J Foot Surg. 1989;28(5):459-465.
10. Gilheany MF, Amir OT. Metatarsocuneiform joint resection arthroplasty for atraumatic osteoarthrosis: an alternative to arthrodesis. J Foot Ankle Surg. 2013;52(1):122-124.
11. Kalish SR, Bernbach MR. Modification of the Austin bunionectomy. Reconstructive Surgery of the Foot and Leg: Update 1987, Podiatry Institute Publishing, Tucker, GA, pp. 86-89.
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15. Gonda E, Bauer GR, Hillstrom HJ, Song J, Cho HH, Lundberg LA. Stability of the offset V-osteotomy: test jig development and saw bone model assessment. J Am Podiatr Med Assoc. 2001;92(2)82-89.

For further reading, see “Mastering The Technical Approach To The Scarf Bunionectomy” in the January 2013 issue of Podiatry Today, “Why The Lapidus Bunionectomy Is The Best Procedure For Severe Bunions” in the December 2011 issue or “Is The Miami Phalangeal Osteotomy A Viable Alternative To The Akin Osteotomy?” in the September 2011 issue.

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