**2. DCS versus CBP in complex supracondylar femoral fractures: a biomechanical study**

Distal femoral fractures represent a challenge for orthopedic surgeons, and despite numerous biomechanical studies, the optimal implant is still controversial [1–4]. However, while plates with angular stability and retrograde interlocking nails are nowadays the best choice for treatment, CBP and DCS were the most used implants until the development of these innovative implants [5].

In a biomechanical study from 2009, the authors compared the mechanical rigidity of the bone/implant (DCS or CBP) construct in complex supracondylar femoral fractures [5, 6].

Twelve synthetic composite femoral bones were fixed in the distal part with six DCS and six CBP, and then, the authors performed by osteotomy a bone defect of 1.5 cm to simulate a complex supracondylar fracture type A3/AO (**Figure 1**).

The femurs were sectioned in the midshaft, and the proximal part of the distal fragments was fixed in a metallic adapter sleeve. The bone-implant constructs were tested for seven types of loading: (1) internal compression; (2) external compression; (3) anterior compression; (4) posterior compression; (5) axial compression; (6) external torsion; and (7) internal torsion.

The compression tests were realized up to 350 N, and the applied torsion attended 25 Nm. The tests were repeated six times in order to establish the statistic dispersion. All the measurements for DCS were realized with or without compaction screw.

The compression force and loading force were measured by a M221B04 (PCB Piezotronics force transducer), while linear deformation values for the compression were measured using two inductive transducers applied in frontal axis (TD1) and sagittal axis (TD2) (**Figure 2**).

Data acquisition was realized by a six-channel admittance bridge, an interface board, and a digital data acquisition system DAQ1200 connected to a laptop.

According to study measurements, by reporting the loading/unloading force to the transducer (TD1 and TD2) displacement, we represented hysteresis cycles as diagrams for the femur/DCS (with and without compaction screw) and for femur/ CBP (**Figure 2**).

By analyzing these measurements and diagrams, the authors obtained preliminary results regarding DCS versus CBP, which were statistically processed by

#### **Figure 1.**

*(A–B) Radiographic aspect of a synthetic composite femur with osteotomy and fixed with DCS and (C–D) radiographic aspect of a synthetic composite femur with osteotomy and fixed with CBP.*

**111**

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

calculating the mean stiffness (square mean error) and the "*p*" value. The stiffness

*(A) Deformation measuring methods. Transducers: TD1—frontal axis; TD2—sagittal axis; (B) internal compression (DCS/CBP). Six loading tests. TD1 deformations, 12–16% higher for CBP than DCS; TD2 deformations, comparable for CBP versus DCS. Negative values (osteotomy closure). Mechanical hysteresis* 

After the interpretation of the statistical study (DCS with compaction screw/ CBP), the authors noticed that the femur-DCS construct is more stable in all compression types except the posterior and axial one, where CBP seems to be more

While, in 2002, Jaakkola et al. [5] found that there is no biomechanical advantage of CBP over DCS on plastic bones, this biomechanical study on synthetic composite femurs suggests that DCS is better than CBP in most loading tests, and the compaction screw for DCS confers an increased stability to the construct.

**3. Biomechanical analysis of four different types of implants in humeral** 

The surgical treatment for humeral shaft fractures is still debatable as long as, according to comparable rate of union, the "nailers" sustain a close intramedullary technique (despite an increased risk of shoulder pain), while the "platers" emphasize the advantages of the open reduction internal fixation (ORIF; with no shoulder morbidity, despite the risk of radial nerve injury) [7, 8]. Some studies in the literature advocate the mechanical advantages of intramedullary nails [9], while other authors enhance the advantages of weight bearing on crutches with plate fixation

The aim of a biomechanical study from 2010 was to evaluate the mechanical behavior of four different types of implants used for internal fixation of commi-

In 12 synthetic composite bones, the authors simulated a comminution in the middle third of diaphysis by removing a 38-mm thick fragment. The bones were separated in four groups, and the fractures were instrumented with four types of implants: (1) a locked compression plate (LCP; Synthes®) with six holes; (2) an intramedullary static locked (Medimetal®) nail inserted in a retrograde manner; (3) a long monoaxial locked plate type AxSOS (Stryker®) fixed with four screws (with a longer "working length"); and (4) a classic 13 holes long dynamic compression

The mechanical tests were performed on a loading machine LLOYD LRX 5kN (UK), which allows traction-compression tests with forces up to 5000 N, on

of the two implants differs significantly if *p* < 0.05 (95% reliability).

for patients with associated lower limb fractures [10].

plate (DCP) with six cortical screws (**Figure 3**).

nuted humeral shaft fractures [11].

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

resistant for TD2 transducer.

**Figure 2.**

*(both implants).*

**shaft fractures**

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

#### **Figure 2.**

*Recent Advances in Biomechanics*

**a biomechanical study**

femoral fractures [5, 6].

(6) external torsion; and (7) internal torsion.

sagittal axis (TD2) (**Figure 2**).

CBP (**Figure 2**).

**2. DCS versus CBP in complex supracondylar femoral fractures:** 

implants until the development of these innovative implants [5].

Distal femoral fractures represent a challenge for orthopedic surgeons, and despite numerous biomechanical studies, the optimal implant is still controversial [1–4]. However, while plates with angular stability and retrograde interlocking nails are nowadays the best choice for treatment, CBP and DCS were the most used

In a biomechanical study from 2009, the authors compared the mechanical rigidity of the bone/implant (DCS or CBP) construct in complex supracondylar

Twelve synthetic composite femoral bones were fixed in the distal part with six DCS and six CBP, and then, the authors performed by osteotomy a bone defect of 1.5 cm to simulate a complex supracondylar fracture type A3/AO (**Figure 1**).

The femurs were sectioned in the midshaft, and the proximal part of the distal fragments was fixed in a metallic adapter sleeve. The bone-implant constructs were tested for seven types of loading: (1) internal compression; (2) external compression; (3) anterior compression; (4) posterior compression; (5) axial compression;

The compression tests were realized up to 350 N, and the applied torsion attended 25 Nm. The tests were repeated six times in order to establish the statistic dispersion. All the measurements for DCS were realized with or without compaction screw. The compression force and loading force were measured by a M221B04 (PCB Piezotronics force transducer), while linear deformation values for the compression were measured using two inductive transducers applied in frontal axis (TD1) and

Data acquisition was realized by a six-channel admittance bridge, an interface

According to study measurements, by reporting the loading/unloading force to the transducer (TD1 and TD2) displacement, we represented hysteresis cycles as diagrams for the femur/DCS (with and without compaction screw) and for femur/

By analyzing these measurements and diagrams, the authors obtained preliminary results regarding DCS versus CBP, which were statistically processed by

*(A–B) Radiographic aspect of a synthetic composite femur with osteotomy and fixed with DCS and (C–D)* 

*radiographic aspect of a synthetic composite femur with osteotomy and fixed with CBP.*

board, and a digital data acquisition system DAQ1200 connected to a laptop.

**110**

**Figure 1.**

*(A) Deformation measuring methods. Transducers: TD1—frontal axis; TD2—sagittal axis; (B) internal compression (DCS/CBP). Six loading tests. TD1 deformations, 12–16% higher for CBP than DCS; TD2 deformations, comparable for CBP versus DCS. Negative values (osteotomy closure). Mechanical hysteresis (both implants).*

calculating the mean stiffness (square mean error) and the "*p*" value. The stiffness of the two implants differs significantly if *p* < 0.05 (95% reliability).

After the interpretation of the statistical study (DCS with compaction screw/ CBP), the authors noticed that the femur-DCS construct is more stable in all compression types except the posterior and axial one, where CBP seems to be more resistant for TD2 transducer.

While, in 2002, Jaakkola et al. [5] found that there is no biomechanical advantage of CBP over DCS on plastic bones, this biomechanical study on synthetic composite femurs suggests that DCS is better than CBP in most loading tests, and the compaction screw for DCS confers an increased stability to the construct.

## **3. Biomechanical analysis of four different types of implants in humeral shaft fractures**

The surgical treatment for humeral shaft fractures is still debatable as long as, according to comparable rate of union, the "nailers" sustain a close intramedullary technique (despite an increased risk of shoulder pain), while the "platers" emphasize the advantages of the open reduction internal fixation (ORIF; with no shoulder morbidity, despite the risk of radial nerve injury) [7, 8]. Some studies in the literature advocate the mechanical advantages of intramedullary nails [9], while other authors enhance the advantages of weight bearing on crutches with plate fixation for patients with associated lower limb fractures [10].

The aim of a biomechanical study from 2010 was to evaluate the mechanical behavior of four different types of implants used for internal fixation of comminuted humeral shaft fractures [11].

In 12 synthetic composite bones, the authors simulated a comminution in the middle third of diaphysis by removing a 38-mm thick fragment. The bones were separated in four groups, and the fractures were instrumented with four types of implants: (1) a locked compression plate (LCP; Synthes®) with six holes; (2) an intramedullary static locked (Medimetal®) nail inserted in a retrograde manner; (3) a long monoaxial locked plate type AxSOS (Stryker®) fixed with four screws (with a longer "working length"); and (4) a classic 13 holes long dynamic compression plate (DCP) with six cortical screws (**Figure 3**).

The mechanical tests were performed on a loading machine LLOYD LRX 5kN (UK), which allows traction-compression tests with forces up to 5000 N, on

**Figure 3.** *(A) Locked plate; (B and C) locked nail; and (D) DCP-buttress plate.*

variable speeds (0.01–800 mm/min) and an accuracy of minimum 0.2%. The compression forces were measured using the force cell of the machine (0.01% precision), and the deformations were measured with a resolution of 0.1 microns. For the testing trials, we used the Nexygen and Ondio producer provided software. All of the constructs were submitted to torsion essays in external and internal rotation as to obtain the same amount of torque [11].

According to the measured values, the authors obtained load-deformation diagrams corresponding to the four types of implants and two types of torsion loading (**Figure 4**).

The load-deformation diagrams were compared and statistically analyzed for each type of implant.

The shorter LCP proved to be the most rigid implant for each type of loading essay, the mean values of the loading being the highest in the entire group. This construct with a short angular stable plate and a small working length is unfortunately a stiff device that concentrates stress at the bone-screw interface.

The intramedullary locked nail showed to be the most elastic implant of all types of loading but, at the same time, the less rigid implant in torsion.

The classic DCP demonstrated, surprisingly, in all types of torsional loading, a mechanical behavior close to the AxSOS angular stable plate; this result is related to the fact that by using longer plates with few screws placed far from fracture site

#### **Figure 4.**

*Load-deformation diagrams corresponding to the four types of metallic implants loaded in external rotation: (a) locked nail; (B) DCP; (C) AxSOS plate; and (D) LCP.*

**113**

**Figure 5.**

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

(bigger working length), the torsional stress is distributed more evenly on the entire length of the plate, the mechanical stress between bone and screws is reduced, and

**4. Clinical and experimental studies for optimal stabilization** 

The high incidence of osteoporosis in the elderly population and the high mechanical load on the proximal femur make the trochanteric region a common

Due to the different types of fracture patterns, each with its own characteristics, a universally applicable implant is very difficult to set. The fixation strength for a pertrochanteric fracture is determined by different variables such as bone quality, bone fragment geometry, fracture reduction, implant design, and implant placement [12]. Numerous studies show that the implant used, as well as its placement, is very

Depending on the implant position, the types of implants used can be extramed-

The dynamic hip screw (DHS) and the blade plate are commonly used implants in pertrochanteric fractures. Due to the longer length of the lever arm, they are subjected to a higher bending stress, making the risk of fatigue fractures or cutout higher than intramedullary implants (**Figure 5**). Moreover, the placement of such an implant requires large incisions with soft tissue damage and deperiostation. In these conditions, the local vascularization is greatly impaired, and the risk of local

Furthermore, immediate restoration of weight bearing is not entirely possible,

and considering the mean age of the patients, this is of vital importance. Intramedullary implants existed since the development of the Y-profile Küntscher nail and due to the implant position in the medullary canal, they all share a less bending force compared to extramedullary implants. Also, the surgical technique required for their implantation minimizes the soft tissue damage [16]. The most common intramedullary implants are the gamma nail and the proximal femoral nail (PFN). Since 1994, extensive clinical and experimental investigations conducted in Germany have led to the development of an intramedullary gliding nail (GN). This system has the biomechanical advantages of an intramedullary locked implant, and because of the double-T angle blade profile, the gliding

screw system creates an increased resistance [17] (**Figure 6**).

*(A) Extramedullary DHS system and (B) intramedullary GN system.*

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

the entire construct became an elastic one.

important for a successful outcome [13–15].

fracture site.

ullary or intramedullary.

complications is higher.

**of trochanteric fractures: the gliding nail**

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

(bigger working length), the torsional stress is distributed more evenly on the entire length of the plate, the mechanical stress between bone and screws is reduced, and the entire construct became an elastic one.
