![]() Amputation of each specimen was performed at the level of tibial tuberosity. Six pairs of fresh-frozen ( – 20 ☌) human cadaveric lower legs without any prior fractures were used in this study.Ī range of motion (ROM) of at least 15° dorsiflexion and 25° plantar-flexion of the ankle was defined as necessary and tested in all ankles.Īll specimens were thawed for 24 h at room temperature before preparation and testing. The treatment strategy for Group II represents the standard of care in most hospitals.Įthical approval for the study was given by the institutional review board. Following fixation of the medial and lateral malleolus and stabilizing the ankle with a syndesmotic screw, the PMF was treated with a direct screw osteosynthesis in Group I, while in Group II the PMF was not addressed. The main difference between the two study groups was related to the treatment of the PMF. It analyzed ankles with a trimalleolar fracture in three different positions of the foot – neutral position (NP), dorsiflexion (DF) and plantar-flexion (PF) – under axial loading to measure six predefined distances within the ankle that could point to signs of instability. This study was conducted to mimic loading of the ankle under full weight bearing during different phases of the gait cycle. ![]() However, this type of loading loading is not the normal one an ankle has to bear during walking. reported that the stability achieved with a direct screw osteosynthesis of a PMF is superior to syndesmotic screw stabilization under torsional loading. ![]() Additionally, a meta-analysis and a clinical long-term study showed favorable results for the former. were able to show that a direct screw osteosynthesis is beneficial versus an indirect screw osteosynthesis of PMFs. Not just the size of the fragment is important but also its shape in relation to the syndesmotic complex. The ideal treatment of a posterior malleolar fracture fragment (PMF) is an ongoing debate in the current literature. Direct screw osteosynthesis of a small PMF stabilizes the ankle more effectively than a positioning screw. Clinically, this becomes relevant in certain phases of the gait cycle. ConclusionsĪdditional reduction and fixation of a small PMF seems to neutralize rotational forces in the ankle more effectively than a sole syndesmotic screw. No significant differences were detected between the groups for each one of the measured distances in any of the three foot positions. Group II demonstrated a significantly increased inward rotation of the fibula compared with Group I. ![]() In plantar-flexion, significant differences were detected between the groups with regard to rotational instability. CT scans of each specimen were performed in intact and fixated states in neutral position, dorsiflexion and plantar-flexion of the ankle. Six predefined distances within the ankle were measured under axial loading. In Group I the PMF was addressed by direct screw osteosynthesis, whereas in Group II the fragment was not fixed. Materials and methodsĪ trimalleolar fracture with a PMF of less than 25% articular surface area was created in 6 pairs of fresh-frozen human cadaveric lower legs. The specimens were randomized into 2 groups stabilized by internal fixation including a positioning screw for syndesmotic reconstruction. This study investigated the effects of a small posterior malleolar fragment (PMF), containing less than 25% articular surface area, on ankle joint stability via computed tomography (CT) scanning under full weight bearing in a human cadaveric ankle fracture model.
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