## 4 Discussion  
TMT arthrodeis is an effective procedure with potential to correct instability in the midfoot and restore functional anatomy while preserving the range of motion. More than 100 surgical procedures for addressing the pathology of the first TMT joint have been described, with ongoing discussion as to which method is the most effective [16; 17; 18; 19]. This systematic review is the first to synthesize the existing literature regarding the various constructs used to fuse TMT joints and describe their biomechanical and kinetic properties. Our review found that, while crossed screws have traditionally been the chosen method of fixation for TMT arthrodeis, various intramedullary fixation devices and plantar plates are stronger, more stable options. In addition, when performing arthrodeis, kinematic and force distribution analysis revealed that medial/middle columns or individual TMT joints should be prioritized over whole foot or lateral column fusion, as doing so increases pressure on the lateral and posterior aspects of the foot by decreasing range of motion through the critical laterally based joints of the foot. Crossed screw configurations have traditionally been the method of fixation for primary arthrodeis of TMT joints [17; 22; 23]. A total of seven studies compared a variety of constructs against crossed screws across the first three TMT joints [17; 18; 19; 22; 23; 27; 29]. Of those seven studies, five found a significant advantage to alternative constructs compared to crossed screws, with the other two studies finding no significant difference between alternative methods and screw fixation at the first TMT joint [17; 18; 19; 22; 23; 27; 29]. The two constructs that demonstrated no significant difference when compared to crossed screws were a rhomboidal dorsal plate intended to provide transverse and longitudinal stability and an interosseous fiber tape device [18; 23; 29]. Plates placed on the plantar or medial aspect of the foot, locking plates with lag screws, shape-memory staples, and intramedullary fixation devices were the constructs that demonstrated greater biomechanical stability than crossed screws. Specifically, plantar plating was capable of handling greater loads while intramedullary fixation and locking plates with lag screw provided greater resistance to diastasis [19; 22; 27]. These findings are likely explained, at least in part, by the greater cortical bone apposition afforded by these alternative constructs when compared to crossed screws. For example, intramedullary fixation with a three-hole construct or plantar fixation with a four-hole plate allows for six or eight points of bone contact as opposed to only 4 four for crossed screw fixation [22]. In addition, the longitudinal stability along the length axis of the bone provided by the post in the intramedullary fixation device and the plantar plate enables greater force distribution that reduces likelihood of failure at the construct-bone interface [17]. A more in-depth, direct comparison of plantar plating and intramedullary fixation found that plantar plating was able to tolerate significantly higher loads than intramedullary fixation, and that intramedullary fixation was able to provide greater compressive force across the first TMT joint [16]. However, this comparison also found that plantar plating provided more resistance to diastasis than intramedullary fixation. This is likely because intramedullary fixation acts as a load sharing internal splint, resisting both tensile and compressive forces, while plantar plating supports the base of the foot and stabilizes longitudinal arches [27; 31; 32]. By and large, plantar plating is a more stable method of joint fixation than crossed screws, providing greater strength and greater resistance to displacement under load. Similarly, intramedullary fixation is a newer, more stable fixation method that provides a greater area of stabilization across the joint surface, resisting a wide variety of applied forces.