Rockwood Adults CH64

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SECTION FOUR • Lower Extremity

Technique

a buttress plate over the apex of the medial malleolar fracture has typically been used (see Fig. 64-10). Biomechanical studies, however, have suggested that the use of screws alone may be suf- ficient. Toolan et al. 383 in a large cadaveric study found that lag screws placed perpendicular to the osteotomy (and parallel to the plafond) were significantly stronger than an antiglide plate. Dumigan et al. 96 in their comparison using synthetic bones found that two 3.5-mm parallel fully threaded cortical screws placed 1 cm proximal and parallel to the tibial plafond resulted in the stiffest construct when a transverse load was applied, simulating loading in external rotation, although plate fixation with two screws both proximal and distal to the fracture site was found to be the stiffest construct under offset axial load- ing conditions. There are no clinical studies in the published literature comparing these constructs but McConnell and Tor- netta have reported their outcomes with this injury mechanism. They report that 42% of their patients seen over a 5-year period with vertical shear medial malleolar fractures were found to have associated plafond impaction. The nine patients that they describe underwent fixation with screws (two cases) or anti- glide plates (six cases) followed by immobilization nonweight- bearing for 8 to 10 weeks. After a mean of 2.4 years of follow-up good clinical and radiographic outcomes were achieved. 240 K-wire fixation alone of medial malleolar fractures has pre- viously resulted in disappointing results potentially due to their inadequate biomechanical properties. 287 An alternative is the use of threaded K-wires. Biomechanical testing has resulted in equiv- ocal results with no difference in strength to cancellous screws with offset axial loading but with lower pull-out strength. 323 Clinical results have been more encouraging; Koslowsky et al. reported the results of 76 patients with medial malleolar frac- tures treated in this manner. There were no episodes of non- union or construct failure and good functional outcomes. A large number of this cohort developed posttraumatic osteoarthritis but this may have been related to their other injuries. 194 An alternative technique that has been proposed for small fractures is the use of a contoured T-plate, able to provide rigid fixation to the small comminuted fracture fragments. A small case series of three patients found good radiologic outcomes 12 and encouraging biomechanical results have been achieved by the same group. 11 Loveday et al. 222 report the use of a suture anchor in similar situations.

✔ ✔ Medial Malleolar Fixation: KEY SURGICAL STEPS

❑ Longitudinal incision placed directly over the malleolus ❑ Blunt dissection is performed down to bone in order not to injure the great saphenous vein and nerve ❑ Removal of bone debris and periosteal flap ❑ Reduce and hold with small reduction clamp, with proximal tine through drill hole ❑ Place two 35-mm partially threaded cancellous screws with washers The patient is set up as described for fibular fixation. The medial malleolus is most commonly approached through a longitudinal incision placed directly over the malleo- lus. Where there is individual preference for a hockey-stick incision, this is generally convex anteriorly, beginning just anterior to the malleolus. The skin is incised and then blunt dissection is performed down to bone in order not to injure the great saphenous vein and nerve. The fracture is usually transverse in orientation, and should be distracted with an instrument to allow removal of bone debris, and inspection of the talus. A flap of periosteum from the proximal tibial frag- ment is commonly found to have been pulled into the frac- ture and this requires to be extracted. A temporary fixation of the fracture is performed using a small reduction clamp, and a small drill hole is placed just proximal to the fracture to allow seating of one of the points of the clamp. The other point is placed at the tip of the malleolar fragment. The frac- ture is reduced by a combination of progressive compres- sion with the reduction clamp with one hand, and manual correction of translation with the other. Placing the index finger over the anterior corner of the fragment and pushing posteriorly and laterally, so that the anterior surface is flush, is usually sufficient to obtain anatomical reduction, which is then confirmed fluoroscopically. Definitive fixation is with two parallel 2.5-mm cancellous screws, with washers in osteopo- rotic bone. The screws cross the fracture orthogonally and are typically 35-mm long—longer screws do not have a longer thread and there is no advantage in placing the thread further from the relatively dense subchondral bone. Where the frag- ment is too small, comminuted, or fragile to accept two lag screws, one screw and a threaded wire may be sufficient, but the author ’ s preference in this situation is to use a TBW. The setup, approach, and fracture reduction for a TBW are as above. Two parallel 1.6-mm K-wires are driven orthogo- nally across the fracture and into the distal tibia to a depth of approximately 30 mm (see Fig. 64-22). A 30-mm small fragment cortical screw with a washer is placed approximately 20 mm proximal to the fracture. The screw is orientated orthogonal to the surface of the tibia in the coronal plane, and so lies obliquely in the metaphysis. A 1.2-mm flexible wire is placed around the K-wires and screw in a figure-of-eight. To maximize compression and minimize progressive loosening during recovery it is important to place this wire against the bone of the distal fragment (rather than placing it superficial

Preoperative Planning

✔ ✔ Medial Malleolar Fixation:

PREOPERATIVE PLANNING CHECKLIST

❑ Radiolucent

OR table

❑ Supine. ❑ Radiolucent block under injured ankle

Position/positioning aids

❑ C -arm from contralateral side

Fluoroscopy location

❑ S mall fragment screws and washers

Equipment

❑ 250 mm Hg

Tourniquet