Morphological features of the deep component of the posterior inferior tibiofibular ligament.

PURPOSE: The deep component of the posterior inferior tibiofibular ligament (PITFL) was classified by type in this large-scale cadaveric study to provide basic information that will help elucidate the mechanisms underlying ankle joint posterior impingement syndrome. METHODS: This investigation examined 100 legs from 49 Japanese cadavers (mean age at death, 79 ± 11 years; 58 sides from men, 42 from women). In classification, absence of an independent fiber of the deep component of the PITFL were classified as Type I, an independent fiber of the deep component of the PITFL was classified as Type II-a, an independent fiber of the deep component of the PITFL with bundles of fibers connected to the posterior intermalleolar ligament (PIML) was classified as Type II-b, and an independent fiber of the deep component of PITFL with a band shape connected to the PIML was classified as Type III. RESULTS: A deep component of the PITFL was present in all specimens. An independent fiber of the deep component of the PITFL was present in 37 legs (37%), connecting to the deep component of the PITFL and PIML in 26 (70.3%). Several types of deep component of the PITFL were identified: Type I in 63 legs (63%); Type II-a in 11 (11%); Type IIb in 12 (12%); and Type III in 14 (14%). No significant differences were seen between the right and left legs. Type I male were significantly more than Type I female (p < 0.05). Type III female were significantly more than Type III male (p < 0.05). CONCLUSIONS: Strong relationships exist between the PITFL and PIML.