SURGICAL MANAGEMENT

Roger A. Mann Jeffrey A. Mann

The distal soft tissue procedure and proximal metatarsal osteotomy has been widely used for bunion corrections for more than 30 years. It is a reliable, reproducible procedure that can be used to treat a wide range of bunion deformities.

The procedure is indicated for a hallux valgus deformity with an incongruent metatarsophalangeal joint, an intermetatarsal angle of more than 10 to 12 degrees, and a distal metatarsal articular angle of less than 10 degrees.

It is carried out in three main steps:

Release of the contracted lateral capsular structures: the adductor hallucis tendon, the transverse metatarsal ligament, and the lateral joint capsule

By freeing up these three structures, the sesamoid sling can be replaced beneath the first metatarsal head.

Preparation of the medial joint structures

Exposure and plication of the medial joint capsule Excision of the medial eminence

Exposure of the base of the first metatarsal and proximal crescentic metatarsal osteotomy

TECHNIQUES

• Release of the Lateral Joint Structures

Exposure

Make a 2.5-cm incision on the dorsal aspect of the first web space between the first and second metatarsal heads.

Deepen this incision through the subcutaneous tissue.

Place a Weitlaner retractor to expose the web space.

On the floor of the web space lies the adductor hallucis, which passes obliquely to insert into the lateral sesamoid and the base of the proximal phalanx (TECH FIG 1A,B).

Identify the capsule between the subluxated fibular sesamoid and the lateral base of the first metatarsal head.

TECH FIG 1 • A. Dissection of the first web space, showing the adductor hallucis tendon. B. Diagram of TECH FIG 1A illustrating the insertion of the adductor hallucis tendon into the base of the proximal phalanx and lateral sesamoid. Note the position of the transverse metatarsal ligament. (continued)

Use a scalpel to release the capsule. By extending the incision distally in this interval, detach the adductor hallucis tendon from its insertion into the base of the proximal phalanx.

Detach the adductor tendon from the lateral aspect of the fibular sesamoid, dissecting proximally until the flexor hallucis brevis muscle tissue is noted (TECH FIG 1C).

Place a Weitlaner retractor between the first and second metatarsal heads, placing the transverse metatarsal ligament under tension (TECH FIG 1B,D).

Transect the transverse metatarsal ligament.

While carrying out this step, it is important that only ligamentous tissue is cut because directly beneath the ligament lies the common nerve to the first web space and the accompanying vessels.

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TECH FIG 1 • (continued) C. The adductor tendon has been detached from the lateral aspect of the fibular sesamoid and is being held in the forceps. D. The transverse metatarsal ligament is placed under tension using a Weitlaner retractor. E. The scalpel has been placed through the dorsal aspect of the lateral joint capsule of the first metatarsophalangeal joint. F. Diagram of TECH FIG 1E, illustrating the lateral joint capsule of the first metatarsophalangeal joint. G. The origin of the lateral joint capsule has been stripped off the metatarsal head, creating the flap of tissue held in the forceps.

Release the Lateral Joint Capsule

Make an incision through the dorsal aspect of the joint capsule at the level of the joint line, and pass the knife blade to the plantar aspect of the metatarsal (TECH FIG 1E,F).

With the blade well seated against the bone, pass the scalpel proximally, stripping the origin of the capsule off the metatarsal head over a distance of about 1.5 cm.

This creates a flap of the lateral joint capsule to be used later in the repair (TECH FIG 1G).

Bring the hallux into about 25 degrees of varus, which ensures that no lateral contracture remains.

• Preparation of the Medial Joint Capsule

Approach the medial joint capsule through a longitudinal incision in the midline starting at the middle of the proximal phalanx and proceeding proximally just past the medial eminence.

Identify the plane between the subcutaneous tissue and the joint capsule; take care to work along this plane.

Dissecting dorsally at first, pull the skin flap away from the capsule to expose the dorsal medial cutaneous nerve, which is then carefully retracted.

Next, dissect the skin flap off the plantar half of the capsule until the abductor hallucis muscle and tendon are identified.

Take care in this area because the plantar medial cutaneous nerve lies just plantar to the abductor tendon.

The capsulotomy that we prefer starts with a vertical cut in the medial joint capsule, made 2 to 3 mm proximal to the base of the proximal phalanx.

Make a second, parallel cut 3 to 8 mm proximal to the first cut, depending on the severity of the hallux valgus deformity. A more severe deformity requires more resection of tissue from the medial joint capsule (TECH FIG 2A).

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Bring together these two parallel capsular cuts dorsally through an inverted V-shaped incision.

On the plantar side, make an upright V-shaped incision through the abductor hallucis tendon that ends at the tibial sesamoid (TECH FIG 2B).

Remove this capsular tissue (TECH FIG 2C).

While making the cut through the abductor hallucis tendon, keep the tip of the knife blade inside the joint to avoid damaging the plantar medial cutaneous nerve.

Make an incision through the joint capsule on the dorsal aspect of the medial eminence.

TECH FIG 2 • A. Exposure of the medial joint capsule, showing the parallel cuts that represent the vertical limbs of the capsulotomy. B. Diagram of TECH FIG 2C, demonstrating the shape of the medial joint capsulotomy. C. Removing the medial joint capsular tissue. D. A dorsal incision is made, and the capsular flap is peeled proximally and plantarward. E. The medial eminence has been completely exposed. The sagittal sulcus is demonstrated by the Freer elevator. (continued)

Peel the capsular flap proximally and plantarward until the medial eminence is completely exposed (TECH FIG 2D-F).

Perform an osteotomy to remove the medial eminence.

Start the osteotomy 1 to 2 mm medial to the sagittal sulcus; the osteotomy is in line with the medial aspect of the metatarsal shaft (TECH FIG 2G).

The medial eminence can be removed with a 16-mm osteotome or with a saw blade. This is strictly the choice of the operating surgeon.

After performing the osteotomy, inspect the metatarsal to be sure there are no rough edges of bone. Rongeur off any bony prominence.

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TECH FIG 2 • (continued) F. Diagram of the medial eminence after the capsular flap has been retracted. Note the sagittal sulcus. G. The osteotomy—to remove the medial eminence—is started 1 to 2 mm medial to the sagittal sulcus and is performed in line with the medial aspect of the metatarsal shaft.

• Approach to the Proximal Crescentic Osteotomy

   

  Make an incision directly over the extensor hallucis longus tendon, from just proximal to the metatarsal cuneiform joint distally about 2.5 to 3 cm.

   

  Usually, a large vessel crosses this plane; cut or cauterize it when the approach is made.

   

   

  Mobilize the extensor tendon and retract it either medially or laterally to expose the metatarsal shaft. As the metatarsal shaft is exposed, it is not necessary to be subperiosteal.

   

  Working just above the periosteal plane allows the tissues to move easily.

   

  Identify the metatarsal cuneiform joint.

   

  Make a mark on the metatarsal 1 cm distal to the joint; this is where the crescentic osteotomy will be created.

   

  Make a second mark on the metatarsal 1 cm distal to the osteotomy site; this is where the screw will be placed that stabilizes the osteotomy (TECH FIG 3A,B).

   

  To confirm that the osteotomy site is correct, note the flare on the lateral aspect of the metatarsal that marks the junction of the diaphyseal and metaphyseal bone.

   

  This is located about 1 cm distal to the metatarsal cuneiform joint.

   

  Advance a guide pin for the 4.0-mm cannulated screw, a short distance into the metatarsal, beginning at the marked site.

   

  The pin should be angled at about 50 degrees to the long axis of the metatarsal in the sagittal plane (TECH FIG 3B). At this angle, the pin and subsequent screw will pass into the plantar aspect of the proximal metatarsal fragment and will not violate the joint.

   

  Carry out the osteotomy using a crescent-shaped saw blade.

   

  This blade comes in two lengths. It is easier to start with a shorter blade and then use the longer blade if necessary to complete the osteotomy (TECH FIG 3B,C).

   

  Positioning of the foot in preparation for the osteotomy is a critical part of this procedure.

   

  Sit at the side of the table holding the foot in one hand.

   

   

  Hold the foot in a neutral position in regard to dorsiflexion-plantarflexion and inversion-eversion. Place the saw with the concavity facing proximally toward the heel.

   

  The angle of the saw blade should be neither perpendicular to the bottom of the foot nor perpendicular to the metatarsal but about halfway between those positions (see TECH FIG 3B).

   

  Start the osteotomy cut by applying firm pressure to the blade.

   

  After making the initial cut into the bone, carefully evaluate the position of the saw blade to be sure that it will cut through the lateral cortex of the metatarsal shaft.

   

  Sometimes in a wide metatarsal, the blade will not penetrate both cortices.

   

  If the medial cortex is not completely cut, it is safe and simple to complete the osteotomy in this area.

   

  However, it is difficult and potentially dangerous to complete an osteotomy laterally, as there is a major artery in the space between the first and second metatarsals that could be harmed.

   

  Make the cut by moving the saw in a medial-lateral direction along the arc of the saw blade.

   

  While cutting, apply a little bit of pressure to the blade toward the heel, as this helps to stabilize the blade in the plane of its cut.

   

  Once the cut is established, moving the saw blade back and forth without a lot of pressure plantarward will produce a nice smooth cut.

   

  It is important that the cut passes all the way through the metatarsal so that the distal portion of the bone is totally free and has no bony attachments to the proximal fragment.

   

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  TECH FIG 3 • A. The first metatarsal shaft is exposed. The Freer elevator points to the metatarsocuneiform joint. One centimeter distal to the joint marks the site of the osteotomy, and 1 cm more distally marks the screw insertion site. B. Diagram of the first metatarsal shaft demonstrating the metatarsocuneiform joint. Note the osteotomy site and angle of the saw blade. Also note the screw

  insertion site. C. The osteotomy is performed with a crescent-shaped saw blade.

   

   

  If a medial piece of bone is still present, use a 4- to 6-mm osteotome to cut through the bone.

   

  Pass a knife blade along the medial side of the cut to be sure that the cut is completely free of any bony or periosteal attachment.

   

  Return your attention to the first web space.

   

  Place a figure-8 suture of 2-0 chromic into the cut end of the adductor hallucis tendon. It is easier to place this stitch before the osteotomy site has been reduced.

• Correction of the Osteotomy

   

  Correcting the osteotomy is the most technically demanding part of the bunion procedure.

   

  The objective is to stabilize the base of the metatarsal while rotating the distal portion of the metatarsal around the osteotomy site.

  Aligning the Metatarsal

   

  The first step is to push the proximal portion of the cut metatarsal in a medial direction so that it is at the medial excursion of the metatarsal cuneiform joint. This can be accomplished with a Freer elevator (TECH FIG 4A).

   

  Grasp the metatarsal head firmly with your other hand and rotate the distal aspect of the metatarsal in a lateral direction around the osteotomy site.

   

  Examining the osteotomy site demonstrates that the distal fragment rotates no more than 2 to 3 mm around the “crescent” (TECH FIG 4B).

   

  Hold the osteotomy site in this alignment and drill the previously placed guide pin across the osteotomy site until the plantar cortex is engaged.

   

  Once this occurs, the osteotomy site is reasonably stable.

   

  Measure the guide pin to determine the screw length, which is usually 28 to 30 mm.

   

  When learning to perform this procedure, or if there is a question as to the alignment of the osteotomy, at this point, obtaining a radiograph is warranted.

   

  If the guide pin is not providing adequate stability, a second pin or Kirschner wire can be used for supplemental fixation while evaluating the radiograph.

   

  If the radiograph shows that the intermetatarsal angle is not sufficiently closed down, remove the guide pin and remanipulate the osteotomy site until the intermetatarsal angle is adequately corrected.

  Screw Placement

   

  While holding the osteotomy site corrected, overdrill the guide pin with the appropriate-sized drill for the cannulated screw set (TECH FIG 5A).

   

  Usually, it is adequate to advance the drill to a position just past the osteotomy site, so that the guide pin does not back out when the drill is removed.

   

  Use a countersink, mainly on the distal side of the screw hole, to make the screw head less prominent. However,

   

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  excessive countersinking can cause the screw head to be pulled through the screw hole site and produce instability of the osteotomy site.

   

   

   

  TECH FIG 4 • A. The osteotomy is corrected by pushing the proximal portion of the cut metatarsal in a medial direction (note the Freer elevator) while rotating the distal aspect of the metatarsal in a lateral direction around the osteotomy site. B. Diagram of the osteotomy site. The surgeon's hand is pushing the metatarsal shaft in a lateral direction. The Freer elevator is pushing the metatarsal base in a medial direction. Note the 2- to 3-mm overhang on the lateral aspect of the osteotomy site.

   

   

  Place a partially threaded 4.0-mm cannulated screw across the osteotomy site and carefully tighten it (TECH FIG 5B).

   

  Be cautious as the screw is tightened because the island of bone is only about 5 or 6 mm and can be cracked if the screw is tightened too firmly.

   

   

   

  TECH FIG 5 • A. The osteotomy site is being held while the cannulated drill is advanced over the guide pin.

  B. The cannulated screw has been placed to stabilize the osteotomy site.

   

  Verifying Stability

   

  Check the stability of the osteotomy site by moving the distal fragment in the sagittal plane, looking for any motion at the osteotomy site.

   

  Mild instability of the osteotomy can be addressed by carefully tightening the screw or by adding a small-diameter Kirschner wire for supplemental fixation.

   

  Occasionally, a small plate may need to be added to the first metatarsal to secure the osteotomy if there is gross instability.

• Reconstruction of the Medial Joint Capsule

   

   

  The first step in reconstructing the medial joint capsule is to hold the great toe in correct alignment: Neutral dorsiflexion-plantarflexion

   

  Zero to 5 degrees of varus

   

  Rotate the toe to correct pronation, which brings the sesamoids back underneath the metatarsal head.

   

  Reduction of the sesamoids has been achieved if they are visible along the plantar aspect of the medial eminence.

   

  Pull the proximal joint capsule distally to see whether the proximal and distal flaps of the capsule juxtapose one another (TECH FIG 6A).

   

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  TECH FIG 6 • A. With the toe held in neutral position, the medial capsular flaps are checked for proper alignment. B. The first suture for repairing the medial joint capsule is placed as plantar as possible; it incorporates the abductor hallucis tendon. C. A total of four to six sutures are used to repair the medial joint capsule.

   

   

  If they do, then the capsular flaps are approximated.

   

  If insufficient capsule has been removed, then more capsular tissue needs to be removed before it is plicated.

   

  The capsular flaps should not be overlapped in a pants-over-vest fashion, as this creates too much bulk over the medial eminence.

   

  To repair the medial capsule, place four to six sutures of 2-0 chromic into the joint capsule with the toe held in correct alignment.

   

  The first suture is placed as plantar as possible and incorporates the abductor hallucis tendon (TECH FIG 6B).

   

  The suture line progresses dorsally (TECH FIG 6C).

   

  Once the sutures are placed and tied, check the alignment of the toe.

   

  The toe should be in neutral position as far as varus and valgus is concerned, or possibly, in a little bit of varus.

   

  In general, if the final alignment of the toe is in more than 5 degrees of valgus, extracapsular tissue should be removed.

   

  Return your attention to the first web space.

   

  Sew the adductor hallucis tendon (already tagged with a suture) to the flap of capsule that was stripped off the metatarsal head.

   

  If the toe had been positioned in a little too much varus when plicating the medial capsule, tension can be placed on this web space repair to prevent a hallux varus from occurring.

   

  Thoroughly irrigate the wounds with antibiotic solution and then close them with interrupted silk.

  Apply a sterile compression dressing and then release the tourniquet.

   

   

  PEARLS AND PITFALLS

   

  Indications ▪ Incongruent metatarsophalangeal joint

  • Intermetatarsal angle of more than 10-12 degrees

  • Distal metatarsal articular angle of less than 10 degrees

First web space dissection

• Release the entire adductor hallucis tendon off its insertion in the sesamoid and proximal phalanx.

• Check adequate release of lateral structures by pulling the toe into maximum varus.

• Do not dissect plantar to the transverse metatarsal ligament.

Medial capsulotomy

• Start with a 3-mm medial capsulotomy for a milder bunion deformity and a larger medial capsulotomy for a more advanced bunion deformity.

• Avoid the dorsal and plantar medial cutaneous nerves.

• When plicating the medial capsule, do not overlap the capsular flaps in a “pants-over-vest” fashion, as this creates too much bulk over the medial eminence.

   

  Medial eminence osteotomy

  • The median eminence osteotomy is started 1 to 2 mm medial to the sagittal sulcus and is performed in line with the medial aspect of the metatarsal shaft.

     

    Crescentic metatarsal osteotomy

  • The crescentic osteotomy is performed 1 cm distal to the metatarsocuneiform joint, at the flare of the base of the proximal phalanx.

  • The angle of the saw blade for the osteotomy cut should be neither perpendicular to the bottom of the foot nor perpendicular to the metatarsal but about halfway between those positions.

     

    Fixation of metatarsal osteotomy

  • The guide pin for the cannulated screw should be angled at about 50 degrees to the long axis of the metatarsal.

  • Leave adequate bone bridge (1 cm) between the cannulated screw and the metatarsal osteotomy.

  • Avoid penetrating the metatarsal cuneiform joint with the screw fixating the osteotomy site.

     

    Correcting metatarsal osteotomy

  • Avoid overcorrection or undercorrection of the metatarsal osteotomy. Check the alignment with a Fluoroscan if there is any doubt as to the degree of correction.

POSTOPERATIVE CARE

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The initial postoperative dressing is changed 1 to 2 days after surgery.

A dressing incorporating firm gauze and adhesive tape is used to hold the toe in correct alignment. The patient is permitted to ambulate in a postoperative shoe.

The patient is seen about 8 to 10 days after surgery, at which point the sutures are removed and a radiograph is obtained.

Based on the alignment of the toe in this radiograph, it is determined how the toe is dressed—namely, into a little more varus or valgus or held in a neutral position.

The dressings are changed on a weekly basis to ensure that the alignment of the toe remains correct. At 3 to 5 weeks after surgery, another radiograph is obtained to confirm the alignment of the toe.

If the alignment is not correct, it can still be corrected by pulling the toe into more varus or valgus, depending on what the radiograph dictates.

After 8 weeks, the dressings are removed and the patient is started on range-of-motion exercises.

OUTCOMES

Proximal metatarsal osteotomy and distal soft tissue release decreases the bunion deformity to an average of 10 degrees and decreases the intermetatarsal angle to an average of 5 degrees.

A 90% to 95% rate of patient satisfaction has been reported as well as improvements in pain level and improvements in overall function.

COMPLICATIONS

Recurrence of hallux valgus deformity Hallux varus

Dorsiflexion of metatarsal osteotomy Nonunion of osteotomy site Delayed union of osteotomy site

SUGGESTED READINGS

1. Coughlin MJ, Anderson RB. Hallux valgus. In: Coughlin MJ, Saltzman CL, Anderson RB, eds. Mann's Surgery of the Foot and Ankle, ed 9. Philadelphia: Elsevier, 2014:155-321.

    

    

2. Dreeban S, Mann RA. Advanced hallux valgus deformity: long-term results utilizing the distal soft tissue procedure and proximal metatarsal osteotomy. Foot Ankle Int 1996;17:142-144.

    

    

3. Thordarson DB, Rudicel SA, Ebramzadeh E, et al. Outcome study of hallux valgus surgery—an AOFAS multi-center study. Foot Ankle Int 2001;22:956-959.