Rockwood Adults CH64

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CHAPTER 64 • Ankle Fractures

technique to be unsatisfactory in unstable fractures. Moreover the load-to-failure has been shown to be only 60% that of con- ventional plating. 99 Biodegradable implants may reduce late hardware-related problems. However, these devices are more challenging to use, producing less mechanical compression 90 and a less stable con- struct compared with conventional screws. 5 Although prom- ising early outcomes have been reported with biodegradable intramedullary fixation, 321 concerning rates of osteolysis, sterile wound sinuses, and malunion in 26% of cases, suggest that the early degradation of these implants remains problematic partic- ularly with the use of polyglycolide implants. 42,119

(in a number of forms), tension band wiring, and plate fixa- tion. The most commonly used technique is with unicortical lag screws (see Fig. 64-11), augmented with washers where the fragment is comminuted or soft. 266,367 Typically, two parallel 4-mm partially threaded cancellous screws are used, inserted perpendicular to the fracture line. Where the fragment is too small to accept two screws, one screw and a K-wire will afford some rotational stability. It remains unclear what the opti- mal screw length is but an overly long screw with threads in metaphyseal bone may have little grip. 318 Avoidance of screw penetration of the joint is ensured on the AP fluoroscopy image which is collinear with the medial joint space (because of the frustral shape of the talus): An internally rotated mortise view will not demonstrate this clearly. 128,131,322 Awareness of screw orientation in the sagittal projection is also important: Femino et al. 109 examined 10 cadaveric limbs and found that insertion of a screw in the posterior colliculus resulted in tendon abut- ment in all specimens and tendon damage in half. Unicortical screws have occasionally been observed to undergo pull-out failure in poor bone. Bicortical screws provide a significantly greater resistance to pull-out 305 and maximum torque before screw stripping. 318 These may either cross the lat- eral tibial cortex 118,305 or the medial tibial cortex proximal to the fracture. 203 Clinical results have been encouraging. A retrospec- tive cohort study, using screw lengths of 60 to 105 mm, found a significantly lower rate of screw loosening in the patients with bicortical fixation and no episodes of metalwork removal or nonunion. 318 Another retrospective cohort in patients over 55 years did, however, report a complication rate of 17% includ- ing nonunion, malunion, and symptomatic metalwork. 187 Bioabsorbable polylactide screws have been used for fixation of medial malleolar fractures with comparable results to stain- less steel screws. Bucholz et al. undertook an RCT comparing the two and found similar levels of complications and similar patient-reported outcomes. The rate of metalwork removal was higher in patients with stainless steel screws (18% vs. 4%) but there was one inflammatory reaction in the bioabsorbable screw group. 50 The concept of tension band wire (TBW) fixation of frac- tures was first described by Lord Lister in 1883. Tension band wiring of the medial malleolus can achieve good compression and security, particularly in the face of small fragments or fragile bone (see Fig. 64-22). 64,126 Biomechanical studies have shown TBW constructs to be stronger under tension than unicorti- cal cancellous screws, 118,171,287 and good long-term functional and radiographic outcomes have been achieved with the tech- nique. 177,287 Ostrum and Litsky 287 reported on a cohort of 32 patients after a 1-year follow-up. There were no cases of non- union and one case of malunion. The main limitation of this technique is symptomatic metalwork, with a reported rate of 7%. 287 In an attempt to reduce this incidence a fiber wire suture has been reported as an alternative to the stainless steel wire commonly used, but does not appear to have the same biome- chanical strength. 118 The medial malleolar component of SAD fractures typi- cally comprises a vertical fracture line with a degree of plafond impaction. Fixation of this medial malleolar fragment requires control of the vertical shear forces acting on the fracture and

Potential Pitfalls and Preventive Measures

Management of Lateral Malleolar Fractures: POTENTIAL PITFALLS AND PREVENTSIONS Pitfall Prevention

• Clinically there is a fracture but no

• Examine the deltoid ligament

distal to the medial malleolus and the proximal fibula to exclude a Maisonneuve fracture

abnormality is seen on radiographs

• Stability of joint uncertain

• Assess congruence of the

mortise on initial and follow-up radiographs. If congruent, use walking test and reassess

• Bone very osteoporotic or comminuted, skin in poor condition or diabetic patient

• Consider IM fibular nail

• Postoperative

• Fibula malreduced; check length and/or rotation; revise surgery

joint incongruent, abnormally wide medial clear space present

• Failure to reduce the syndesmosis

• Syndesmotic reduction is

notoriously hard to assess without comparing postoperative axial images of both ankles. Closed reduction is more likely to be successful if the fibular fracture is reduced and the foot held in neutral, but an open reduction is more accurate; obtain CT and revise surgery

• Distal screws penetrate talus

• Use unicortical cancellous screws distally

• Painful hardware

• Remove plate after fracture healing

or peroneal tendon irritation

Medial Malleolar Fixation A number of surgical techniques for fixation of the medial mal- leolus have been described. Selection depends upon the size and integrity of the fragment. Options include screw fixation