Stefan G. Hofstaetter and Hans-Joerg Trnka
DEFINITION
Subluxation or dislocation of the metatarsophalangeal (MTP) joints results in a disruption of the fibers of the plantar plate, which is the central structure of the MTP joint dislocation. The plate provides a cushion to the joint and weightbearing forces.
The key point in deciding how to treat this pathology is to determine whether the pathology leads to abnormal pressure distribution in the forefoot.
ANATOMY
The proximal phalanx and the fibrocartilaginous plantar plate form an anatomic and functional unit at the MTP joint.
The plate is the major factor of dorsoplantar stability.
The plantar plate attaches to the proximal phalanx and the plantar fascia, but except for the two collateral ligaments, it is without substantial fibrous attachment to the metatarsal head.14
The extensor digitorum longus tendon extends to the proximal phalanx and the proximal interphalangeal joint.
Antagonists of the extensor mechanism are the flexor tendons and the plantar plate.
The function of the interossei and lumbrical muscles is to hold the proximal phalanx in a neutral position.
PATHOGENESIS
High functional stresses of weight bearing and repetitive hyperextension of the MTP joint can lead to attenuation or rupture of the plantar plate, followed by subluxation or dislocation of the toe.
A hallux valgus deformity is often associated with a subluxated second MTP joint.5,10
The hallux pushes the second toe lateral, which may lead to instability and maybe to subluxation.
It may also result from an excessive length of the second or third metatarsal relative to the first metatarsal.
The second MTP joint is then biomechanically more subject to the pressure of tight stockings or shoes.
Once the plantar plate is elongated and ruptured, the dorsal capsule and the extensor tendon become contracted, leading to a chronically dislocated MTP joint.14
NATURAL HISTORY
Weil presented in 1992 in Europe a joint-preserving, intraarticular shortening osteotomy, and Barouk first published it in 1996.1
Researchers from Europe have shown in anatomic, clinical, and radiologic studies the advantages of the Weil osteotomy compared to alternative procedures.9,14,15
A dorsal soft tissue release with pin fixation,3 silicone implants,4 metatarsal neck osteotomies without fixation (Helal osteotomy),8,12 and MTP joint excisional arthroplasties6 have been reported in the literature as surgical alternatives. However, a high rate of complications such as nonunions, malalignments, and transfer lesions are associated with these alternative surgical procedures.
PATIENT HISTORY AND PHYSICAL FINDINGS
Physical examination methods include the following:
Determining circulatory status is necessary to assess not only the feasibility of an individual procedure but also whether multiple procedures can be performed, if necessary.
Clinical examination of cutaneous sensory response may indicate a systemic disease such as diabetes.
The drawer test is used to evaluate the stability of all the MTP joints and the reducibility of lesser toe deformities in plantarflexion. How stable overall is the first ray?
Passive range of motion: Normal range of motion is 60 to 80 degrees full extension to 40 degrees full flexion; loss of flexion may be a result of the contracted extensor tendons or because the proximal phalanx lies dorsal to the second metatarsal head.
Each patient must be analyzed individually, with attention to a detailed history and a careful clinical examination. Ruling out differential diagnosis is mandatory.
History of painful forefeet over a long period of months or years
The pain usually occurs dorsally over the toe and on the plantar side of the metatarsal head.
Plantar keratosis: This callus is a circumscribed keratotic area under the metatarsal head that usually corresponds with the patient's complaints (FIG 1).
Hammer toe: A hammer toe deformity may lead to MTP joint subluxation, dislocation, or both. However, MTP joint subluxation and dislocation can also lead to a hammer toe deformity.
FIG 1 • Plantar aspect of the foot with a hyperkeratotic area under the second metatarsal head.
A simultaneous hallux valgus deformity may lead to dorsiflexion forces in the second MTP joint. The great toe may cross under the second toe (“crossover toe deformity”).
A prominent dorsal base of the proximal phalanx is easily palpated.
Tightness of extensor tendons: The toe cannot be plantarflexed due to pain and to shortening of the extensor muscle and interossei dorsalis muscle.
Rarely a third or fourth toe is subluxated.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Dorsoplantar and lateral weight-bearing radiographs should be obtained to rule out fractures or associated injuries and degenerative arthritic changes.
All radiographs are examined for the length of the second and third toe relative to the first and the alignment (Maestro line).
Radiographs must be obtained for subluxation or dislocation to assess joint congruency of the lesser MTP joints (FIG 2).
A “gun barrel” sign may be seen on the AP radiograph. The diaphysis of the proximal phalanx projects as a round hole in the area of the distal condyle of the proximal phalanx.
The articular cartilage of the adjoining surfaces leaves a “clear space” of 2 to 3 mm. This clear space diminishes with progression of the hyperextension of the MTP joint.
Avascular necrosis of a lesser metatarsal head with infraction (Freiberg infraction) may be seen.
The hallux valgus angle and the intermetatarsal angle are measured.
Pedobarography is highly sensitive to peak pressures in the foot. It allows static and dynamic qualitative measurement of pedal pressures and load distribution for specific areas of the foot. Load imbalance may also be detected, as well as insufficiency of the first ray.
DIFFERENTIAL DIAGNOSIS
Morton neuroma
Freiberg infraction (avascular necrosis of the metatarsal head)
Rheumatoid arthritis
Nonspecific synovitis
Metatarsal head fracture
FIG 2 • Severe subluxated second and third metatarsophalangeal joint with an associated hallux valgus deformity.
NONOPERATIVE MANAGEMENT
Initial treatment options for metatarsalgia include shoe wear modifications, metatarsal pads, and custom-made orthoses.
Trimming of the callus mechanically
Orthotics for the foot
Reduce forefoot pressure
Lower heel to reduce metatarsal head pressure (avoid highheeled shoes)
Carefully placed metatarsal pad proximal to painful metatarsal head
If metatarsalgia is due to a ruptured volar plate (such as in rheumatoid arthritis), often a stiff, full-length insole that limits MTP hyperextension of the foot is useful.
However, conservative treatment in an already existing dislocation is of no benefit, and surgical intervention is indicated.11
SURGICAL MANAGEMENT
The Weil osteotomy is a joint-preserving, intra-articular shortening osteotomy and has been recommended for the treatment of metatarsalgia resulting from a dislocated or subluxated MTP joint.
The goal of the Weil osteotomy is first to alter load transmission through the forefoot by shifting the plantar fragment proximal to the area of the lesion, where thicker and more compliant soft tissue is still present, and second to resolve the hammer toe deformity or MTP subluxations that are increasing or resulting in metatarsalgia.
Preoperative Planning
All radiographic images are reviewed for subluxation or dislocation, alignment of the metatarsal heads, hallux valgus deformity, degenerative changes of the joints, and claw toes.
If there is a hallux valgus deformity or a hypermobile first tarsometarsal joint, this pathology should be corrected to achieve a satisfying result.
The length of shortening is measured on the plain radiographs. The second metatarsal should be even with or shorter than the first, and the third should be shorter than the second metatarsal.
During the preoperative physical examination the surgeon must look for plantar keratotic disorders.
The tightness of the extensor tendon is palpated.
A drawer test of the dislocated MTP joint should be included in the examination under anesthesia (FIG 3).
Positioning
The patient is positioned supine on the operating table.
The surgery is performed either under general anesthesia or using a regional ankle block supplemented with intravenous or oral sedation.
An Esmarch tourniquet may be used to obtain a bloodless field.
Approach
A 3-cm longitudinal incision is made dorsal over the metatarsal for a single osteotomy, over the web space for a double osteotomy, and over two metatarsals for a triple osteotomy.
A small amount of soft tissue dissection is done to identify the extensor tendons, which are lengthened in a Z fashion.
A transverse or longitudinal capsulotomy of the MTP joint is used to identify the junction of the head and neck.
FIG 3 • A, B. The surgeon grasps the base of the proximal phalanx and attempts to sublux or dislocate the joint with a dorsally directed force.
TECHNIQUES
EXPOSURE OF METATARSAL
Make a 3-cm longitudinal incision dorsal over the metatarsal for a single osteotomy (TECH FIG 1A,B) or over the web space for a double osteotomy.
Perform a small amount of soft tissue dissection to identify the extensor tendons, and lengthen them in a Z fashion (TECH FIG 1C–E).
Incise the joint capsule in a transverse fashion and release the collateral ligaments if necessary.
TECH FIG 1 • A, B. Dorsal skin incision. C–E. Z lengthening of the extensor digitorum longus tendon; the extensor digitorum brevis tendon is usually cut. F, G. Exposure of the metatarsal with two Hohmann retractors; the head is exposed using an elevator.
Expose the metatarsal head with two small Hohmann retractors. Maximally plantarflex the toe and expose the metatarsal head with the help of an elevator (TECH FIG 1F,G).
Take care not to strip the plantar soft tissue attachments to aid in stabilizing the osteotomy and maintain vascularity to the head.
OSTEOTOMY AND BONY SLICE EXTRACTION
Use a 2-mm bony slice extractor to lift the plantar fragment because the axis of motion of the MTP joint has changed with plantarflexion of the metatarsal head.
Expose the metatarsal head and mark the osteotomies (TECH FIG 2A).
Use an oscillating saw to perform the osteotomy at the dorsal portion of the metatarsal head without finishing the second cortex totally to avoid a free-gliding plantar fragment (TECH FIG 2B).
The second osteotomy through both cortices is 2 mm under the dorsal cut (TECH FIG 2C,D).
The bony slice can now be easily removed (TECH FIG 2E,F).
TECH FIG 2 • A. Exposure of the metatarsal head and marking of the two osteotomy levels. B. Osteotomy at the dorsal aspect of the metatarsal head. C, D. Plantar osteotomy of the metatarsal head. E, F. Removal of the bony slice after the osteotomies.
FIXATION OF THE MOBILE FRAGMENT
Grasp the plantar mobile fragment with a pointed reduction clamp and shift it proximally to achieve the requisite amount of shortening that was measured preoperatively on the dorsoplantar radiographs (TECH FIG 3A).
The second metatarsal should be even with or shorter than the first, and the third should be shorter than the second metatarsal.
The plane of the osteotomy should be as parallel to the ground surface as possible. Secure the osteotomy with a special 2-mm titanium “snap off screw” (Wright Medical Technology) (TECH FIG 3B). Use a 12-mm length for the second metatarsal and 11 mm for the other metatarsals.
Remove the resulting dorsal protuberance over the metatarsal head remnant with a rongeur or the edge of the saw blade (TECH FIG 3C,D).
Repair the overlying Z-lengthened extensor tendon and suture the skin.
TECH FIG 3 • A. Positioning of the plantar fragment. B. Fixation of the Weil osteotomy with a snap off screw (Wright Medical Technology). C, D. Modeling of the dorsal protuberance with a rongeur or the edge of the saw blade.
POSTOPERATIVE CARE
Dressings and a tight bandage are used to protect the suture and to prevent swelling.
The patient's toes are taped in slight plantarflexion.
Weight bearing with a postoperative shoe is allowed after the first postoperative day (FIG 4A).
Patients should wear the postoperative shoe for 6 weeks.
Postoperative imaging includes dorsoplantar and lateral radiographs (FIG 4B–D).
Passive motion (starting on the 5th postoperative day) of the MTP joint is indicated and necessary to prevent postoperative extension contracture.
If swelling occurs, foot elevation, cryotherapy, and elastic stockings may keep the swelling down.
OUTCOMES
Clinical results of the Weil osteotomy have been promising. Outcomes include a significant reduction of pain, a significant reduction in plantar callus formation, a low dislocation rate, and increased ambulatory capacity.
No malunion or pseudarthrosis was documented in the literature.
Bony and soft tissue modifications such as lengthening of the extensor tendon, 2-mm bony slice extraction, and insertion of a Kirschner wire from the tip of the toe across the MTP joint and the osteotomy into the metatarsal, in a position of 5 degrees plantarflexion (in severely subluxated contracted cases), may prevent postoperative dorsiflexion contracture.
FIG 4 • A. Postoperative shoe. B. Preoperative radiographs with hallux valgus deformity and subluxation of second and third metatarsophalangeal joint. C. Chevron osteotomy with pin fixation along with a Weil osteotomy on the second, third, and fourth rays. D. Seven-year radiograph showing maintenance of corrected lesser metatarsophalangeal joints.
Boyer and DeOrio2 described good results of a single-pin fixation for a combined metatarsal neck osteotomy with proximal interphalangeal joint resection arthroplasty and flexor digitorum longus transfer in severely dislocated MTP joints and severe hammer toe deformities.
COMPLICATIONS
Reported complications in the literature are floating or stiff toes, a high rate of postoperative dorsiflexed contracture and transfer metatarsalgia in cases of excessive shortening with variable rates, and a limitation of the range of motion in the MTP joint.7,9
REFERENCES
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2. Boyer ML, DeOrio JK. Metatarsal neck osteotomy with proximal interphalangeal joint resection fixed with a single temporary pin. Foot Ankle Int 2004;25:144–148.
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13. Trnka HJ, Mühlbauer M, Zettl R, et al. Comparison of the results of the Weil and Helal osteotomies for the treatment of metatarsalgia secondary to dislocation of the lesser metatarsophalangeal joints. Foot Ankle Int 1999;20:72–79.
14. Trnka HJ, Nyska M, Parks BG, et al. Dorsiflexion contracture after the Weil osteotomy: results of cadaver study and three-dimensional analysis. Foot Ankle Int 2001;22:47–50.
15. Vandeputte G, Dereymaeker G, Steenwerckx A, et al. The Weil osteotomy of the lesser metatarsals: a clinical and pedobarographic follow-up study. Foot Ankle Int 2000;21:370–374.
16. Winson IG, Rawlinson J, Broughton NS. Treatment of metatarsalgia by sliding distal metatarsal osteotomy. Foot Ankle 1988;9:2–6.