## 4 Discussion  
In a recent study conducted by the authors of the present article [11], it was shown that an additive syndesmotic screw after a.p. fixation of the PM almost restores torsional stability compared to the uninjured initial state. Relaxation of the PITFL alone, using screws placed from posterior, did not restore the initial stability of the upper ankle joint. It is not yet known whether the p.a or the a.p. stabilization leads to different primary stability after PM fixation. The aim of this biomechanical study was to investigate if the direction of screw osteosynthesis has an influence on the primary stability of the osteosynthesis. The results did not show a superiority of one OS regarding biomechanical primary stability.  
Figure 3: Movement of the posterior malleolus—Volkmann triangle—(PM) during load levels of 2 Nm to 12 Nm after osteosynthesis (OS) using posterior-anterior screws or anterior-posterior screws.  
Based on this result, the primary stability of the PM seemed quite comparable for both OS, with a marginal tendency of higher stability using p.a. screws. Thus, the results do not clearly correspond to the statement of [PERSON] et al., who report a biomechanical superiority of posterior osteosynthesis [5]. However, the biomechanical data from cadaver studies are only one of many criteria that should be considered when formulating general recommendations. The cadaver model only hints at the human joint without the muscle tonus.  
A limitation of this biomechanical study is the small number of specimens. To address this, we used effect sizes to describe possible effects. Many other studies work with similarly small sample sizes [1; 12; 13; 14]. The low numbers reflect a low availability of human specimens for test models.  
The literature presents a discussion of the advantages and disadvantages of the dorsal approach and p.a. screw placement. Dorsal reduction and p.a. fixation seems to offer advantages for bone healing, adequate restoration of PITFL integrity, and restoration of tibialar articular surface anatomy [1; 5]. Moreover, there are reports of better clinical postoperative outcome and less osteoarthritis [15; 16]. On the other hand, some authors report higher complication rates such as injury to the fibular artery or flexor pollicis longus tendon for p.a. fixation [17; 18].  
The treatment with the a.p. screw is less invasive and can be performed faster compared to the more complex dorsal approach [19]. Based on our data showing comparable primary stability, stabilization can be achieved by a.p. screw fixation when reduction is easily achieved by ligamentotaxis. The p.a. treatment is the method of choice when reduction obstacles such as intermediate fragments are present.  
We cannot make any statement about the maximum stability of the OS in patients with surgically treated ankle fractures, as we have not examined the OSed specimen until failure. Additional cyclic tests would be useful. In addition, it is difficult to transfer the in vivo load levels into ex vivo fracture models. The test setup attempts to reflect the movement with the highest lever arm on the fracture. The direction of screw insertion, p.a. or a.p., has no significant effect on the primary stability of osteosynthesis of the PM under torsional loading. If it is possible to achieve an adequate reduction result without repositioning obstacles, the a.p. technique could also be used. Due to the complication rates of the approach, the p.a. technique is reserved for fractures with inadequate reduction results due to ligamentotaxis. In the test model, we investigated the effect of screw direction on the primary stability of large fractures of the PM (type 4 according to Bartonicek and Rammelt) under torsional loading. In multifragmentary fractures, especially with intermediate fragments, the direction of the screws, or even the use of an alternative osteosynthesis technique (e.g., plate osteosynthesis), could offer biomechanical advantages. Further studies are necessary in this respect.