**6. The XS nail for the treatment of fractures under tension: patella and olecranon**

In patella fractures, the surgical treatment with the AO tension belt osteosynthesis system is the golden standard today, but the results are not always good on the long term. Dislocation and functional deficit (limited mobility) can be as high as 20–50% of all cases [34].

One explanation is that the tendon insertions and the retinaculum create a gap between the tension-band wires and the bone, thus a very tight fixation cannot be achieved; because of this, loosening occurs after loading [35].

Moreover, due to the fact that the AO tension band is placed on the anterior surface of the patella, there is a distraction in the fracture site on the articular surface, which causes fracture gaps, dislocations, nonunion, and finally implant failure (**Figure 14**).

#### **Figure 14.**

*(A and B) AO 34-C1 fracture of the patella; (C and D) internal fixation with tension band and cerclage wire; (E and F) failure of the construct tension band and cerclage wire; and (G and H) revision surgery with XS nail osteosynthesis.*

#### *Recent Advances in Biomechanics*

As a result, an implant that allows compression of the entire fracture surface was needed. To achieve this, the XS nail entitled Tension Band Compression Nail (TCN) was developed and placed centrally in the patella; this implant allows equally distributed compression on the whole surface by muscular distraction [35] (**Figure 15**).

In a biomechanical study, the authors divided 30 sawbone patellas into four types of fractures. Proximal third, middle, distal third, and Y-pattern fractures were obtained by osteotomy. Osteosynthesis was carried out using one XS nail, two XS nails, and standard AO tension band. The three-part Y-pattern fractures were fixed with an additional circular wire system (cerclage) in the AO tension band group (**Figure 16**).

Plastic and total deformations were recorded, while the sawbone patellas were submitted to a force of 250 and 500 N at 30°. The batch with XS nail sets the lowest value in the entire lot. The highest deformation occurred in the AO tension band group, and a significant gap appeared between the fragments. No gap was registered in the XS-nail group.

Smaller differences were recorded in the Y-pattern group based on the strength of the circular wire put in close contact with the bone that was added to the tension band group. We must mention that in real clinical cases this is not possible because of the soft tissue interposition.

The experimental data show that the XS nail system is a viable alternative to the AO tension band due to its good fixation of the fragments and less deformation under physiological loading. This implant's characteristics will allow patients to recover faster and with better long-term results.

Tension band wiring of olecranon fractures has been the standard choice since 1963. However, migrations of the Kirschner wires and cerclage failure were reported in up to 80% of the cases [36]. Even a numerical model of the tension band wiring technique proved that high von Mises stresses were seen at the bridge between two fragments connected by the Kirschner wire [37].

The plate osteosynthesis alternative may aggravate a soft tissue lesion, usually caused by direct trauma.

The intramedullary XS nail is a new form of osteosynthesis that allows uniform compression of the fracture surfaces by central positioning the implant. Moreover, increased fixation in the cortical bone can be obtained by locking the 4.5 mm nail with threaded 2.4 mm wires. The surgical technique is easy and protective for the soft tissues due to the intramedullary position.

In a clinical study from 2006, 80 olecranon fractures were treated with XS nail osteosynthesis, and after a follow-up period of 16 months, the results were good in 93.2% of the cases [38] (**Figure 17**).

The XS nail represents, in our opinion, a future possibility in the treatment of olecranon fractures, especially in the elderly population, where bone quality is deficient.

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**Figure 17.**

**Figure 16.**

*Clinical and Experimental Biomechanical Studies Regarding Innovative Implants in Traumatology*

**7. Clinical and biomechanical studies regarding plates with polyaxial stability for fractures of distal radius and proximal humerus**

*(A) Displaced fracture of the olecranon and (B) osteosynthesis with XS nail.*

*Patella test without osteotomy in the hydraulic machine: (A) frontal view and (B) lateral view.*

Among the elderly, distal radius is the second most common fracture location after hip fractures. Mauck et al. [39] presented a wide variety of fracture patterns. Dorsal and metaphyseal radius fractures are usually treated with closed reduction

*DOI: http://dx.doi.org/10.5772/intechopen.91728*

**Figure 15.**

*(A) TCN with locking aiming device; (B) Kirschner wire aiming device; and (C) compression screw placement.*

*Clinical and Experimental Biomechanical Studies Regarding Innovative Implants in Traumatology DOI: http://dx.doi.org/10.5772/intechopen.91728*

**Figure 16.** *Patella test without osteotomy in the hydraulic machine: (A) frontal view and (B) lateral view.*

**Figure 17.** *(A) Displaced fracture of the olecranon and (B) osteosynthesis with XS nail.*
