Alternative opportunities for fracture fixation are constantly discussed with the aim to support or even enhance fracture healing.Citation1 Choosing one over the other may be demanding, especially when considering the impact of additional, biological constraints such as comorbidities or complex, multiple traumata. So far, the AO-principles of absolute and relative stability formed the basis for a conceptual approach to proper fracture fixation. However, so far mechano-biological consequences of these fixations have been rarely considered.Citation2 Nevertheless, the mechano-biological interplay during tissue regeneration is essential for fast and effective healing, especially if the biology is compromised and regenerative capacity limited.Citation3 In such cases, protecting the remaining biological capacity without overstressing the mechanical capabilities is the key.Citation4 A modern, comprehensive fracture fixation should not only rely on initial stabilization and immediate functional results but should focus on a fixation that respects and supports the biological healing potential, i.e. by preservation of blood supply without overstraining the mechano-biological capabilities of the tissue and the mechanical capacity of the fracture fixation.
Locking plates and screws have risen in popularity and their advantageous application for patients with compromised bone quality appears indisputable. Conventional plates and screws retain superior strength in the presence of sufficient bone quality. New concepts such as double-plating, staggered plating, locked nailing or plate independent lag screws combined with locking plate fixation have so far not been proven to be superior in large clinical cohorts. However, all these options illustrate the ongoing discussion on how to enhance fracture healing by choosing a customized fracture fixation strategy that intends to find patient-specific mechano-biologically optimized solutions.
More general approaches that enable quantification of tissue stimulation directly or indirectly via implant stiffness may help to optimize healing results.Citation5 Fixation with more flexible configurations that enable regenerative tissue deformation as a healing stimulus and callus formation as a quantifiable healing indicator shows advantages. Undeniably, a well-reduced simple fracture with adequate fixation will most certainly heal faster than a fracture with a sizeable remaining gap.Citation6 However, such an optimal situation will also fail in healing, if biological capacity is impaired for instance through insufficient capacities of the patient's mesenchymal stromal cells, immune competence,Citation7 insufficient vascularityCitation8 or excessive shear at the fracture gap.Citation5
Modern fracture care is driven by a delicate interplay between robustness and speed of healing that needs to be adapted for each individual patient. The differences between nail and plate fixation are generally not different in terms of union and implant failure.Citation9 However, it is exemplary that the complications reported in this present studyCitation10 are one non-union and 19 mal-alignments for the faster healing intramedullary nail fixation versus one implant failure (after non-union) and just 3 mal-unions for the dual-plate fixation. Presumably, both faster healing and higher incidence of mal-unions might be caused by the higher interfragmentary motion with the un-locked nailing versus the quite rigid dual-plating with short plate working length. Surgeons need to adapt the fixation not only through proper implant choice, but based on individual patient conditions and a corresponding and suitable implant configuration. The conventional AO-principles need to be extended to consider the patient specific, local tissue stimulation.
Thus, current studies such as the present oneCitation10 are welcome and needed to trace out the advantages and disadvantages of an ever-growing pool of possibilities for fracture fixation. However, this pool should also be assessed and channeled based upon more universal principles such as local regenerative tissue healing potential and stimulation. The diamond concept for biological enhancement targets the four layers of osteogenic cells, osteoconductive scaffolds, growth factors and proper mechanical environments. However, only mechano-biology fully incorporates local effects. It is about time that this general framework is translated into a comprehensive mechano-therapy for skeletal regeneration.
CONFLICT OF INTEREST
The author has no conflict of interest to declare.
REFERENCES
- Perren SM “Evolution of the internal fixation of long bone fractures.” J Bone Joint Surg Br. 2002;84.8:1093–1110. doi:10.1302/0301-620X.84B8.13752.
- Augat P, Simon U, Liedert A, Claes L. “Mechanics and mechano-biology of fracture healing in normal and osteoporotic bone.” Osteoporos Int. 2005;16.2:S36–S43. doi:10.1007/s00198-004-1728-9.
- Giannoudis PV, Gudipati S, Harwood P, Kanakaris NK. “Long bone non-unions treated with the diamond Concept: a case series of 64 patients.” Injury. 2015;46:S48–S54. doi:10.1016/S0020-1383(15)30055-3. PMID: 26747919
- Schmidt-Bleek K, Petersen A, Dienelt A, Schwarz C, Duda GN. “Initiation and early control of tissue regeneration–bone healing as a model system for tissue regeneration.” Expert Opin Biol Ther. 2014;14.2:247–259. doi:10.1517/14712598.2014.857653.
- Epari DR, Kassi JP, Schell H, Duda GN. “Timely fracture-healing requires optimization of axial fixation stability.” JBJS. 2007;89.7:1575–1585.
- Augat P, Margevicius K, Simon J, Wolf S, Suger G, Claes L. “Local tissue properties in bone healing: influence of size and stability of the osteotomy gap.” J Orthop Res.. 1998;16.4:475–481. doi:10.1002/jor.1100160413.
- Reinke S, Geissler S, Taylor WR, Schmidt-Bleek K, Juelke K, Schwachmeyer V, Dahne M, Hartwig T, Akyüz L, Meisel C, et al. “Terminally differentiated CD8+ T cells negatively affect bone regeneration in humans.” Sci Transl Med. 2013;5.177:177ra36–177ra36.
- Lienau J, Schmidt-Bleek K, Peters A, Haschke F, Duda GN, Perka C, Bail HJ, Schütze N, Jakob F, Schell H. “Differential regulation of blood vessel formation between standard and delayed bone healing.” J Orthop Res. 2009;27.9:1133–1140. doi:10.1002/jor.20870.
- Wang A, et al. “Meta-analysis of postoperative complications in distal femoral fractures: retrograde intramedullary nailing versus plating.” International Journal of Clinical and Experimental Medicine. 2016;9.10:18900–18911.
- UIVS-2017-0247 – Interlocking intramedullary nailing versus locked dual plating fixation for femoral shaft fractures in patients with multiple injuries. Journal of Investigative Surgery. In press.