Take aways from the 41th AOT Course in Halle - Copy

Take aways from the case discussion in the 41th trauma course in Halle

Requires direct bone contact or small gaps and does only tolerate small interfragmentary movement → absolute stability
This can be achieved surgically only by open anatomical reduction and absolutely stable internal fixation with interfragmentary compression or a small stable gap.
Strain theory of Perren and Cordey: direct bone formation can only occur if the interfragmentary strain is smaller than the failure strain of the newly formed bone tissue [1]. Accordingly, only strains less than 2% can allow direct fracture healing [2].

A majority of fractures heal via the indirect or secondary route.
Secondary fracture healing occurs with relative stability in the fracture area.
Relative stability is achieved surgically by indirect reduction and bridging internal (angular stable plate osteosynthesis, intramedullary nailing) or external fixation (external fixator) [3, 4].
Even with relative stability, the right amount of interfragmentary strain must be present to achieve successful fracture healing. If the fixation is too rigid or too flexible, delayed healing or non-union will result [5].

Minimizing shear and torsional movements at the gap promotes fracture healing.
Even a slightly bigger nail diameter results in disproportionately increased stiffness.
Greater system stiffness, in turn, results in less movement at the fracture gap.
The play of the nail inside the medullary cavity should be kept as small as possible.
Thus, choosing the largest possible nail diameter makes biomechanical sense, due to its superior stiffness.

Both nail and and plating systems have become reliable treatment modalities for distal femur fractures. [1]
While proponents of each treatment modality will debate on pros and cons of both IMN and LP, there is still no clear consensus on a gold standard.
Stabilization of distal femur fractures with locking plates can cause inconsistent and asymmetric formation of periosteal callus, which may be attributed to the high stiffness of the fixation construct. [2]
Fractures treated with intramedullary nailing were found to have a 93.9% union rate, an average time to union of 19.2 weeks, an average arc of motion of 105.1 degrees, with an average of 14.4 degrees of malalignment. [1]
Fractures treated with locking plates were found to have a 90.2% union rate, an average time to union of 20.5 weeks, an average arc of motion of 104 degrees, with an average of 12.6 degrees of malalignment. [1]

The quality of the fracture healing outcome and the rate of healing decreases with increasing fracture gap size.
Large fracture gaps can create critical size defects that supress healing and lead to non-unons.
A critical size defect might be defined as exceeding 1.5-3 times the diameter of the bone [2].
Larger osteotomy gaps lead to significantly more fibrocartilage and a lower amount of newly formed blood vessels in the gap healing area compared to osteotomy gaps of medium size.
From a clinical point of view, the use of operating techniques that avoid damage to the vascular system and allow reduction of the bone fragments, to achieve small fracture gaps, are important if we are to ensure proper fracture healing.