Distal chevron metatarsal osteotomy for hallux valgus

Modified chevron distal metatarsal osteotomy

The modified chevron osteotomy is simply a more proximal placement of the apex of the osteotomy in the metatarsal head. Potential problems of this modification of the chevron osteotomy are instability of the osteotomy and insufficient metaphyseal bony contact. Proper placement of the osteotomy cuts is mandatory. The metatarsal osteotomy must be internally fixed. With some modifications, however, the chevron osteotomy can be used for more severe deformities (up to 35 degrees of hallux valgus and up to 15 degrees of first to second intermetatarsal diversion). As an alternative, the valgus appearance of the hallux can be corrected by an additional few degrees with an additional osteotomy of the proximal phalanx. This phalangeal osteotomy augments cosmetic correction only if the metatarsophalangeal joint has been rendered congruent in the corrected position. Also, a basal osteotomy of the proximal phalanx adjacent to the distal metatarsal osteotomy may cause more limitation of motion of the first metatarsophalangeal joint than a single osteotomy. The patient should be informed of this possibility.

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  Make a medial midline incision, protecting the dorsal veins and dorsal and plantar sensory nerves to the medial side of the hallux ( Fig. 44.1 ; left arrow depicts sensory branch of superficial peroneal nerve, and right arrow shows accessory extensor hallucis longus.).

  

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  When the capsule is exposed, make a longitudinal incision along the dorsomedial aspect of the first metatarsal.

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  Begin the second limb of the capsulotomy 1 to 2 mm proximal to the base of the proximal phalanx and in a coronal plane at right angles to the first limb of the capsulotomy ( Fig. 44.2 ).

  

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  Extend the coronal incision plantarward 1 to 2 mm proximal to the junction with the tibial sesamoid ( Fig. 44.3 ).

  

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  Raise the capsule, beginning medially and plantarward, by sharply dissecting it from the inside out and off the most prominent part of the medial eminence until its dorsal aspect is reached ( Fig. 44.4 ).

  

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  Maintain the incision close to bone, curving over the medial eminence as the contour demands, and take a full-thickness piece of capsule from the medial eminence and proximally along the metatarsal shaft for 3 to 4 cm. This should leave the fascial attachment of the abductor hallucis in continuity with the periosteum and fascial covering of the first metatarsal shaft.

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  Ensure that the plantar aspect of the metatarsal head where it meets with the shaft is adequately exposed so that the plantar osteotomy cut can be made under direct vision. Remove the medial eminence.

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  Using a 0.062-inch Kirschner wire and starting 1.0 to 1.3 cm proximal to the subchondral bone and in the center of the first metatarsal head, drill a hole from medial to lateral, marking the apex (arrow) of the intended osteotomy ( Fig. 44.5 ).

  

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  Mark the limbs of the osteotomy with a sharp osteotome or a marking pen, and begin the osteotomy with the dorsal cut. Avoid pushing the saw blade in and out of the bone; slowly glide the blade across the head-neck fragment with gentle back-and-forth rather than in-and-out movements.

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  When there is no further resistance to the blade laterally, extract it and return to the centering hole. Ensure that the dorsal and lateral aspects of the cortical bone have been incised.

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  Begin the plantar limb of the osteotomy at a point approximately 30 degrees from the midline or 60 degrees from the original dorsal osteotomy. Make this cut slowly and deliberately at right angles to the bone, exiting plantarward 2 to 3 mm proximal to where the articular surface of the metatarsal head meets the shaft. A small, right-angle retractor pulling the capsule plantarward increases exposure ( Fig. 44.6 ; arrows show distal chevron ostetomy).

  

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  If the osteotomy cuts have been made appropriately, the capital fragment usually displaces laterally with minimal lateral pressure. If this is not the case, either the osteotomy cuts are not parallel or the plantar cortex, dorsal cortex, or both have not been penetrated laterally.

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  If gentle pressure on the head fragment does not displace it laterally while the shaft fragment is held stable, reposition the saw blade, being careful not to start the saw until the blade is in the depths of the osteotomy cut.

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  When the capital fragment has been freed from the proximal fragment, shift it laterally 4 to 5 mm ( Fig. 44.7 ).

  

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  Impact the head fragment on the shaft by applying gentle pressure to the hallux.

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  While holding the capital fragment straight on the metatarsal shaft, internally fix the osteotomy. Insert one or two 0.062-inch Kirschner wires obliquely across the osteotomy site (top arrow) ( Fig. 44.8 ). Bottom arow shows overhang of proximal metatarsal resected.

  

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  Begin inserting the first wire dorsomedially and far enough proximally in the shaft to leave cortical bone between the pin and the cancellous portion of the distal-medial shaft when the overhanging ridge of bone is made flush with the capital fragment. Direct the wire so that it reaches the lateral aspect of the capital fragment.

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  Insert the second wire into the metatarsal head at a point 3 to 4 mm plantar and parallel to the first.

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  Test the osteotomy for stability and gently open the metatarsophalangeal joint by pushing the toe laterally.

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  Examine the entire surface of the metatarsal head with a small Freer elevator to locate any Kirschner wire points. If the joint has been entered, retract the wire slightly so that it rests in subchondral bone. Because the entrance of the wire into subchondral bone and its exit through the cartilage of the head usually can be felt while drilling, withdrawing the wire about 2 mm usually places it in the proper position.

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  Circumduct the hallux on the first metatarsal head; if any catching occurs, reinspect the joint for wire points. If there is any doubt, obtain radiographs.

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  Incise the overhanging segment on the medial side of the proximal fragment and with a rasp, smooth it flush with the capital fragment ( Fig. 44.9 ).

  

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  Place the hallux on the metatarsal head in a congruous position, which can be determined by flexing, extending, abducting, adducting, and rotating the hallux on the first metatarsal head and observing the foot from the top ( Fig. 44.10 ).

  

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  While an assistant holds the toe reduced, close the capsular incision by first closing its proximal part with two or three interrupted 2-0 or 3-0 absorbable sutures.

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  Dorsally, pass the needle through the periosteum and deep fascia, over the metatarsal shaft, and through the accessory extensor hallucis longus tendon.

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  Plantarward, the strong tissue is the deep, investing fascia over the abductor hallucis and the tendinous edge of this muscle; anchoring the capsular repair proximally before beginning the distal repair is important. Close the plantar-medial corner of the capsule with one or two interrupted sutures.

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  The most important sutures, which hold the hallux congruously on the metatarsal head, form a pants-over-vest closure as follows. Enter the transverse limb of the capsular incision 2 to 3 mm plantar to the apex of the incision from the outside in; turn the needle 180 degrees and reenter the corner of the capsule from the outside in. Reverse the needle 180 degrees and reenter it from the inside out, still on the proximal part of the capsule. Place the final pass of the stitch through the distal capsule on the dorsal side of the apex of the incision. Pull the capsule into the corner in a pants-over-vest manner and suture it. During capsular closure, observe the dorsal aspect of the foot while an assistant externally rotates the foot slightly to judge the proper alignment of the hallux.

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  To obtain more correction of the valgus deformity, carefully imbricate the transverse or coronal limb of the capsulotomy. Do not attempt to correct hallux valgus interphalangeus by pulling the hallux into a more varus position at the metatarsophalangeal joint with imbricating sutures during capsular repair, because hallux varus can develop if the imbrication is too tight. In most instances, close the transverse limb by approximating the edges, unless the capsule is so redundant that it requires partial excision. Finish closing the capsule at any weak points.

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  The hallux should be in neutral to 5 degrees of valgus at completion of the capsulorrhaphy. Correct any varus by removing capsular sutures one at a time and observing the position of the hallux. Begin by removing one or more transverse limb sutures. If necessary, remove all of the distal capsular repair and start over.

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  Secure hemostasis and close the wound in layers. Apply a forefoot dressing with the hallux taped in the proper position.