Medial Opening Wedge Osteotomy with Distal Soft Tissue Realignment Procedure for the Treatment of Moderate to Severe Hallux Valgus

Matthew Di Silvestro, MSc, M.D., FRCSC
Queensway Carleton Hospital
Ottawa, ON


The exact definition of what constitutes moderate or severe hallux valgus (HV) is not clear. However, an intermetatarsal angle between the first and second metatarsal (1-2 IMA) greater than 15 degrees and a HV angle above 40 degrees is often considered to be too great to be managed with a distal osteotomy1-5. There have been numerous proximal procedures done in conjunction with distal soft tissue balancing to address more severe deformities6-14. The proximal first metatarsal medial opening wedge osteotomy (PMOW) with distal soft tissue realignment and possible distal biplanar chevron osteotomy provides technical, biomechanical and patient advantages.


Technical Advantages

The procedure can be performed under general or regional anesthetic. An ankle block with sedation and the tourniquet placed around the ankle is often sufficient anesthesia. This operation can be done in a minor procedure room without an anesthetist. Performing the procedure in this setting helps to mitigate its impact on limited hospital resources. A mini C-arm is also beneficial. Surgical time is approximately 40 minutes with experience.

The osteotomy is relatively easy to learn and perform under image intensification8,10. Care must be taken to ensure that the lateral cortex is preserved. A slightly oblique osteotomy can be used in order to add stability to the lateral cortical hinge by placing it within the first tarsometatarsal joint capsule. This also makes a lag screw across the osteotomy site a possibility. The plantar proximal screw is best suited as a lag screw as it tends to be less prominent when inserted obliquely.

Elevation of the first ray is a concern with proximal procedures, thus the wedge may be placed slightly dorsally to facilitate plantar flexion of the first metatarsal. Often the contralateral wedge fixation plate fits better in this situation.

Often poor tracking of the first MTP joint becomes evident after this powerful correction if the Distal Metatarsal Articular Angle (DMAA) is increased. A distal biplanar chevron may be done to correct this deformity. If residual HV interphalangeus or pronation persists an Akin osteotomy may be added (see Figure 1a and 1b).


Figure 1a: 24-year-old male with moderately severe hallux valgus.


Figure 1b: Six weeks post PMOW, Distal Chevron Biplanar, Aikin Osteotomy.

Stabilization of the osteotomy site is simplified with a low profile wedge plate designed for the procedure. The wedge comes in 0.5mm increments ranging from 1 to 7mm. The correction can be checked with simulated weight-bearing under image intensification. Approximately three degrees of correction of the intermetatarsal angle can be expected per 1mm of opening at the osteotomy site. The medial eminence is packed into the osteotomy site as bone graft.

Biomechanical Advantages

Lapidus suggested an association of HV with hypermobility of the first TMTJ4. Hypermobility of the first ray is the most frequently listed indication for a Lapidus4. Proximal osteotomy of the first metatarsal has been shown to reduce sagittal plane motion of the first ray by 50%1,2. Coughlin hypothesized that increased sagittal mobility of the 1st ray occurs as a result of HV and isn't a primary cause of the deformity. Realignment of the 1st ray with a joint sparing proximal osteotomy restores the normal relationship of the intrinsic and extrinsic muscles, as well as the plantar aponeurosis which leads to a reduction in 1st ray motion.

A transfer lesion is a diffuse, clinically symptomatic callus that develops beneath the 2nd metatarsal head because of inadequate weight-bearing on the 1st metatarsal and great toe. Procedures that cause shortening or elevation of the 1st ray such as the Lapidus procedure may exacerbate this problem. In contrast, the PMOW has been shown to increase 1st metatarsal length by 2.3mm8. Positioning the wedge more dorsally can facilitate plantar flexion of the 1st ray and further offload the 2nd metatarsal. Mann et al. reported persistence of a transfer lesion in only five of 58 feet following a proximal crescentic osteotomy7. The creation of a transfer lesion postoperatively is relatively rare.8

Patient Advantages

Immediate heel weight-bearing in a postoperative sandal is permissible because of the stability of fixation. The average time to radiographic healing is six weeks10 (see Figure 2a and 2b). Nonunion is relatively rare: approximately 1%10. Other proximal procedures, such as the Lapidus procedure, require up to six weeks of non-weight-bearing and have a nonunion rate of up to 12% in some reports15. A relatively early return to work at six weeks has been reported in 80% of patients undergoing a PMOW10. This may be related to immediate weight-bearing and the short time to union. Patient satisfaction with the PMOW at 2.4 years has been reported to be good to excellent in 90% of patients10.


Figure 2a: Preoperative weight-bearing.




Figure 2b: Osteotomy healed at six weeks postoperative.


PMOW Disadvantages and Complications

Some disadvantages and complications are associated with the PMOW as with all other hallux valgus surgery. Symptomatic hardware despite the low profile titanium plate and screws is the most common complication (10%) with PMOW10. Placing the plate more dorsally and using the contra-lateral plate when necessary seems to make the hardware less problematic. Nonunion and hallux varus at 1% and 2% respectively are relatively uncommon10. Proper patient selection may improve the nonunion rate. A limited distal lateral release by avoiding an incision in the 1st web space may decrease the incidence of hallux varus. Finally, the added cost of the procedure-specific wedge plate and screws may be a disadvantage. However, performing the surgery under an ankle block in a minor procedure room may offset this cost.


Proximal first metatarsal procedures are often necessary to correct moderate to severe hallux valgus deformities. Many of these procedures are technically difficult to perform and have many associated complications that occur at an unacceptable rate. The proximal first metatarsal opening wedge osteotomy with a distal soft tissue realignment procedure and often a distal biplanar osteotomy is a reproducible and powerful correction for moderate to severe hallux valgus that allows early weight-bearing and is relatively simple to learn and perform. However, the surgeon must be cognizant of the risk of the hallux varus because of the power of this osteotomy.


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