[Choice of internal fixation methods for posterior malleolus fracture in both biomechanics and clinical application].

ABSTRACT

OBJECTIVE: To study the biomechanical effects and the clinical outcome of different internal fixation methods in treating posterior malleolus fractures. METHODS: (1) Biomechaniccal study of 18 pairs of posterior malleolus fracture models was conducted, in which all the cases were divided into 3 groups as I, II and III (n=12), according to different fracture degrees that included specimens with 1/4, 1/3 and 1/2 of articular facets fractured respectively; Each group was further divided into 2 subgroups as group A and group B. Group A was fixed with 2 steel half-thread tensile screws whose diameter was 4.0 mm; and group B was fixed with "T-shaped" steel distal-radius plates and 4 screws. The uploading experiment was carried out by settling the specimen on an experiment machine at its neutral position, and the data were collected and managed. (2) Clinical Applications 31 cases with closed trimalleolar fractures were treated from 2009.1-2010.12 in our hospital, in which 14 with posterior malleolus fractures ≤ 2 5% of the capital diameter of the tibial plafond were fixed with screws, and 17 with posterior malleolus fractures >25% of the capital diameter of the tibial plafond were fixed with steel plates. Prospective cohort study of these cases were carried out. The outcome was assessed using a Leeds Scoring System. RESULTS: The mechanical fixation strengths of the plates for 1/4, 1/3 and 1/2 facets of posterior malleolus fractures were all higher than those of the screw groups [(4.10 ± 0.13) kN vs. (4.6 0 ± 0.27)kN, (3.20 ± 0.12)kN vs. (4.12 ± 0.14)kN and (1.98 ± 0.18)kN vs. (3.72 ± 0.18)kN, respectively, P<0.05]. For the clinical study ,the mean follow-up period was 12 months (6-18 months), all the cases acquired bone union, and the mean time for healing was 10 weeks ( 8-12 weeks). In the evaluation of therapeutic effects, we found that 28 cases were excellent and 3 good, which was 100% satisfying. CONCLUSION: If only 1/4 of the posterior articular facet is involved, 2 screws are enough to supply the stability; but for the fractures involve more than 1/4 facet, the plate fixation supplies more stable fixation and is superior to simply screws.