Restoring The Metatarsal Parabola With The Weil Osteotomy
Metatarsalgia may develop from osseous, neurological, vascular or dermal etiologies. The causes are numerous and commonly involve a cavus foot structure, a long second metatarsal, short first metatarsal, hypermobile first ray, iatrogenic pain from forefoot surgery or manifest from a rheumatology-induced systemic disease. When symptoms persist, you may see callus lesions develop under the affected metatarsal. Keep in mind that these lesions can lead to stress fractures and compensation-induced pains in the lower extremity and back.
Conservative treatments range from pressure-reducing pads with foot strapping to oral antiinflammatory medications. When conservative modalities have been exhausted, you may consider over 20 surgical techniques, ranging from condylectomies to oblique osteotomies at the proximal, mid-shaft or distal metatarsal levels. Of these procedures, the Weil osteotomy has gained popularity, based upon the simple technique and stable fixation.1,2
Controversy exists involving floating versus fixated osteotomies. The benefit of employing rigid internal fixation is it allows you to control surgical positioning of the osteotomy. Indeed, rigid internal fixation with the Weil osteotomy should be strongly encouraged when multiple osteotomies to the metatarsals are necessary.
Key Diagnostic Considerations
When the patient has localized pain at the plantar aspect of the second MPJ, a structural etiology may be present. Intensity of the pain may vary from a dull ache or throbbing sensation to a debilitating pain. He or she may experience the symptoms during increased physical activity or (more commonly) with normal daily activities. Keep in mind that chronic second metatarsal pain is a problem seen in a wide spectrum of patients. It may occur in the workplace or it could affect a recreational walker or athlete.
A disrupted metatarsal parabola from a long metatarsal will show a characteristic callus lesion. A Morton’s foot has a short first metatarsal and will cause a pressure overload at the second metatarsal. An elongated or plantarflexed second metatarsal will have similar presenting symptoms. Pain around the plantar aspect of the second MPJ develops from chronic pressure and inflammation, resulting from the weightbearing forces of the long second metatarsal relative to the adjacent metatarsals and the nucleated callus.
As noted above, when conservative therapy fails, proceed to consider surgical options based upon the clinical and structural presentation of the foot. Proper diagnosis of all present osseous deformities is essential. You must evaluate concomitant deformities, such as a hammertoe contracture, hallux valgus and hypermobility. Neglecting these combined deformities in the surgical arena increases the risk of a poor result with reoccurrence, transfer callus lesions, persistent pain and iatrogenically induced deformities that can be more difficult to treat than the initial problem.
Assessing The Radiographic Findings
To evaluate the bone structure, you need to compare the second metatarsal to the adjacent metatarsals, along with evaluating the patient’s foot type. In order to rule out the need for a joint replacement implant arthroplasty procedure, be sure to evaluate osteoarthritic changes to the forefoot. You may discover cortical hypertrophy, stress fractures or a bone lesion, which you should treat with the standard method of care.
To evaluate the metatarsal parabola, take a standard dorsoplantar projection in weightbearing on an orthoposer with a 15-degree projection angle. This view will allow you to do a standard evaluation of the foot bones, which should include measurement of the metatarsal protrusion distance. Remember, the second metatarsal should not exceed 2 mm respective to the first and third metatarsals at the phalangeal joint level. Davies and Saxby describe a simple postoperative measurement of metatarsal shortening that requires drawing a longitudinal bisection of the adjacent metatarsal and following it with two perpendicular lines that are tangent to the distal aspect of the bisected metatarsal and the second metatarsal.3 You can adapt this technique for preoperative evaluation of the metatarsal parabola.
A second view I find to be very informative is a dorsoplantar projection at 0 degrees with a lesion marker of soft wire taped to the area of callus. This will demonstrate the location of the callus at the corresponding MPJ for a stance phase lesion. Stance phase pathology results from an abnormal plantar declination or prominence of the affected metatarsal relative to the adjacent metatarsals. Excessive pressures induce nucleated hyperkeratotic lesions to develop.4 Propulsive phase lesions are often seen with MTPJ capsulitis and soreness at the end of the metatarsal. It is essential to use the 0-degree position with the wire marker since the 15-degree projection will artificially superimpose the wire marker in a more proximal location on the metatarsal. This will also help to determine if a callus is in a non-weightbearing area of the foot that will favor a nucleated porokeratosis or verruca as the pathology.
Evaluation in the sagittal plane using a sesamoid axial projection may be beneficial in borderline situations requiring elevation with shortening. This view has been debated with a questionable value to determine the relative declination of the metatarsal heads.5
Step-By-Step Pointers On The Weil Osteotomy
You may perform the operative procedure while the patient is under general anesthesia or intravenous sedation, using an ankle tourniquet for hemostasis. Make a linear skin incision approximately 3.5 cm long over the distal third of the second metatarsal. Typically, I limit the distal aspect of incision to the base of the proximal phalanx. This will reduce the chance of scar formation that can contribute to dorsal contracture and limits digital swelling. A lazy-S incision is also an acceptable approach and can be beneficial for an adjacent joint capsulotomy or when extending the incision into the second interspace for shortening of the second and third metatarsals.
Once the joint capsule is exposed, identify the base of the proximal phalanx as a reference for the distal aspect of the capsular incision. Once the extensor tendons are retracted laterally, incise the periosteum and capsule while dorsiflexing the toe to protect the articular cartilage. Releasing the collateral ligaments facilitates dorsal displacement and exposure of the metatarsal head.3 You may want to use a McGlamry elevator to further free up the plantar second metatarsal head, especially in the presence of a longstanding submetatarsal phalangeal joint callus.6
Perform the osteotomy with a 10-mm saw blade approximately 0.4 mm thick (Hall Zimmer 5023-138 blade) for a bicortical osteotomy, starting at the dorsal edge of the distal articular cartilage. The plane of the osteotomy is ideal when parallel to the weightbearing surface of the ground.1 This orientation maximizes shortening with minimal dorsal or plantar displacement. If you desire additional elevation, leave the distal cortex intact while passing the sagittal saw blade through for an additional 0.4 mm of elevation, and then transect the proximal plantar cortex. Then you can transpose the metatarsal head proximally with dorsal elevation. You can estimate the amount of shortening by the amount of dorsal cortex overlap at the metatarsal head area, which you will remove with a bone cutting forceps after placing rigid internal fixation. Temporary fixation with a 1.1-mm K-wire is sufficient and should serve as the placement site for the second screw.
After placing the initial screw, a second screw will replace the temporary fixation K-wire. In a small metatarsal, a 1.5-mm screw can be substituted. Both screws are oriented from dorsal proximal to distal plantar. You may prefer using the small diameter cannulated screw where the temporary fixation will serve as the guide wire. You can use a freer elevator to palpate the K-wire prior to measuring to determine proper length.
Using two-pin temporary fixation also helps limit the torque of the screw during fixation to prevent rotary movement of the metatarsal head. You can maintain compression at the osteotomy using a phalangeal clamp to prevent distraction of the osteotomy while placing the fixation. It is essential that screw length is appropriate since a long screw can lead to localized inflammation and plantar pressure irritation requiring early screw removal. Use fluoroscopic imaging intraoperatively to monitor joint position and screw placement.
Perform standard wound closure after placing fixation. Apply compressive dressings with a dorsal betadine splint in order to maintain a plantar grade second digit for two to three weeks. This helps prevent dorsal contracture of the toe. Ambulation is allowed via partial weightbearing in a surgical shoe for three weeks with cane or crutch assistance.
What About Ancillary Procedures?
Combined procedures may include hammertoe correction with a sagittal plane contracture requiring arthroplasty correction. Decreased flexor-extensor tension balancing may require extensor lengthening or flexor tendon transfers. If the patient has a crossover toe deformity, you can combine lateral translation of the metatarsal head with the proximal displacement of the osteotomy in combination with the hammertoe correction. Post-op recovery should then follow the standard of care for the more involved procedure.
The Weil osteotomy is a simple technique you should consider in your arsenal for treating a long metatarsal. You can control the amount of shortening to alleviate the symptoms and adjust it for additional elevation or treatment of a crossover digital deformity. Also be aware that you may have to treat concomitant deformities, such as a hammertoe contracture, hallux valgus and hypermobility, in order to help ensure optimal improvement of the level of function. I find the Weil osteotomy to be a more stable shortening or elevating osteotomy than the ‘V’ osteotomy with results that are more predictable. n
Dr. Cusumano is an Associate of the American College of Foot and Ankle Surgeons.
Dr. Braver (pictured at right) is board certified in foot and ankle surgery by the American Board of Podiatric Surgery. A Fellow of the American College of Foot and Ankle Surgeons, he practices in Englewood, NJ.
References 1. Vandeputte G et al.: The Weil osteotomy of the lesser metatarsals: A clinical and pedoparographic follow-up study. Foot and Ankle International, 21(5); 370-374, 2000. 2. Jiminez AL, Martin DE, and Philips AJ: Lesser metatarsalgia evaluation and treatment. Clin. Podiatric Med. Surg., 7(4); 597-618, 1990. 3. Davies MS and Saxby TS: Metatarsal neck osteotomy with rigid internal fixation for the treatment of lesser toe metatarsalphalangeal joint pathology. Foot & Ankle, 20 (10); pp630-635. 4. Lauf E and Weinraub GM: Asymmetrical osteotomy: A predictable surgical approach for chronic central metatarsalgia. J Foot and Ankle Surgery, 35(6); 550-559, 1996. 5. Schlefman BS: Radiology, ch.1. In Comprehensive Textbook of Foot Surgery, 2nd ed., vol 1, Baltimore, Williams &Wilkins, 1992, pp6-8. 6. McGlamry ED: Lesser Ray Deformities, ch.12. In Comprehensive Textbook of Foot Surgery, 2nd ed., vol 1, Baltimore, Williams &Wilkins, 1992, pp321-387.