**4.2 Hip fractures**

Generally said a hip-fracture is a break in the upper part of the femur bone. It occurs mostly to the patients over 60 years old. Worldwide the human population growing older is a clear tendency. It is expected such changes can cause higher number of hip fractures increasing from 1.66 million in 1990 to 6.26 million in 2050 [31]. Moreover, it is proved the hip fractures are one of the main reasons for mortality of the old people. For example the mortality to the end of the first year after the trauma reaches 27.3% depending on the kind and the type of hip fracture treatment [32]. These data underline the social importance of the problem and lots of researches concern their efforts for optimization of hip fracture treatment and maximal patient's recovery.

For metal osteosynthesis of proximal femur fracture the implant is placed (inserted) through the lateral cortex and anchors into the hip head. The postoperative complications, which often occur at fracture treatment by osteosynthesis and require an implant change or arthroplasty, are the so called hip head re-fracture and implant penetration into the joint capsule.

The main reason for that is a wrong positioning of the screws into the femoral head–neck fragment. As a criterion for implant position the so called Tip-to-Apex Distance index (TAD – index) is used. The optimal positioning corresponds to TAD – index minimization. For instance, it is the best factor of prognosis to realize the cut out of the hip head and when the TAD – index is less than 24 mm, the cut outs are unfortunately not registered [33]. That means drilling through the lateral cortex along the hip neck axis, which ends when the drill bit tip is as much as possible close to the far cortex of the hip head.

The experimental results for far cortex registration during proximal pig femur drilling along the neck axis are presented in **Figure 16**. The measured proximal femur length is 65 mm. The hip head cortex registration is in a distance 61.7 mm from the contact point [34].

The hip head cortex registration occurs at 1107 AU in **Figure 16** where Ids again takes values less than zero. Then the drilling automatically stops and the robot takes out the drill bit at the initial position.

**147**

*Orthopedic Bone Drilling Robot ODRO: Basic Characteristics and Areas of Applications*

For some types of fractures, like a midshaft clavicle fractures, it is advisable to fix the implants without drilling the second cortex. Comprising uni-cortical far-cortex– abutting locking screw fixation with bi-cortical fixation, it can be seen that both types of fixation have similar mechanical properties concerning axial and torsional loads in the case when the far cortex penetration not occurs [35]. Uni-cortical farcortex-abutting locking screw fixation risks far cortex penetration which requires protection of near anatomical structures [35]. Drilling modes of ODRO as Cortex I (unicortical drilling), Cortex II Find and Cortex II Drill can be used in such cases. One more application of ODRO is related to the proximal humerus fractures. This problem is discussed in [36–38] and here we will present it briefly by citing

*Far cortex registration during proximal pig femur bone drilling along the neck axis. Maximal drilling feed rate = 4 mm/s; drill bit 2.8 mm; Total time 24.84 s, 1235 AU; hole depth 61.7 mm. The values of the integral* 

some sentences from there aiming to show this problem clearer way.

the growing prevalence of osteoporosis [37].

surgeons' experience level; the blunt drill bit [37].

Proximal humerus fractures may occur at the surgical neck, anatomic neck, greater tuberosity, and lesser tuberosity. They are common fractures which can often be seen in elder patients with osteoporotic bone after low level energy impacts. These patients usually have very low bone mineral density and that makes fracture fixation much complicated. Proximal humerus fractures account for 5% of all fractures and represent the third most common osteoporotic fracture [36]. The incidence of these injuries is expected to increase due to the aging population and

Within the surgically treated fractures open reduction and internal fixation using locked plates is the most commonly applied joint-preserving treatment of proximal humerus fractures [38]. Failure rates of locked plating depend on the so-called "overdrilling". Perforation of the joint surface during pilot hole drilling is referred to as "overdrilling" [37]. Possible reasons for the overdrilling include: the restricted tactile feedback especially in osteoporotic bone; the spherical morphology of the humeral head that, together with the angulated locking screw projections, make interpreting of intra-operative X-ray images very complicated; the

Precision drilling to the correct depth could help prevention of overdrilling and significantly increases endurance until screw perforation failure, i.e. reduce failure

The drilling mode "Fixed depth" of ODRO (preliminary set depth of the hole in mm) can be used in such cases when ODRO is applied. When working in this mode,

During bicortical drilling, when the drilling is done manually, the magnitude of the drill bit penetration requires protection of the posterior bone wall. That means

rates of locked plating in an unstable proximal humerus fractures [37].

the set depth of the hole is realized with an accuracy of 0.1 mm.

the obligatory cutting of the tissues immediately after it.

*DOI: http://dx.doi.org/10.5772/intechopen.96768*

*component ds I (red line) are scaled by multiplication of 10−1.*

**Figure 16.**

*Orthopedic Bone Drilling Robot ODRO: Basic Characteristics and Areas of Applications DOI: http://dx.doi.org/10.5772/intechopen.96768*

#### **Figure 16.**

*Latest Developments in Medical Robotics Systems*

the hole are shown in the second row on the display.

*The result of the drilling process; hole-used 35 times drill bit 2.8 mm.*

the hole depth is 26.3 mm for 19.42 s respectively.

**4.2 Hip fractures**

**Figure 15.**

maximal patient's recovery.

to the far cortex of the hip head.

from the contact point [34].

out the drill bit at the initial position.

and implant penetration into the joint capsule.

near cortex (Cortex I), the thickness of the far cortex (Cortex II) and the depth of

At equal drilling conditions – drilling process control algorithm, drill bit diameter, bone specimen, drilling area – the following can be seen in **Figures 12** and **13**: for new drill bit max thrust force is 55 N; for used drill bit max thrust force is 80 N; for new drill bit the hole depth is 23 mm for 13.85 s duration and for used drill bit

At automatic drilling the reasons for the negative final result caused by dulled drill bits should be minimized by feed rate control [30]. Also, it successfully solves the problem of higher drill bit penetration after the end of second cortex. It is real-

Generally said a hip-fracture is a break in the upper part of the femur bone. It occurs mostly to the patients over 60 years old. Worldwide the human population growing older is a clear tendency. It is expected such changes can cause higher number of hip fractures increasing from 1.66 million in 1990 to 6.26 million in 2050 [31]. Moreover, it is proved the hip fractures are one of the main reasons for mortality of the old people. For example the mortality to the end of the first year after the trauma reaches 27.3% depending on the kind and the type of hip fracture treatment [32]. These data underline the social importance of the problem and lots of researches concern their efforts for optimization of hip fracture treatment and

For metal osteosynthesis of proximal femur fracture the implant is placed (inserted) through the lateral cortex and anchors into the hip head. The postoperative complications, which often occur at fracture treatment by osteosynthesis and require an implant change or arthroplasty, are the so called hip head re-fracture

The main reason for that is a wrong positioning of the screws into the femoral head–neck fragment. As a criterion for implant position the so called Tip-to-Apex Distance index (TAD – index) is used. The optimal positioning corresponds to TAD – index minimization. For instance, it is the best factor of prognosis to realize the cut out of the hip head and when the TAD – index is less than 24 mm, the cut outs are unfortunately not registered [33]. That means drilling through the lateral cortex along the hip neck axis, which ends when the drill bit tip is as much as possible close

The experimental results for far cortex registration during proximal pig femur drilling along the neck axis are presented in **Figure 16**. The measured proximal femur length is 65 mm. The hip head cortex registration is in a distance 61.7 mm

The hip head cortex registration occurs at 1107 AU in **Figure 16** where Ids again takes values less than zero. Then the drilling automatically stops and the robot takes

ized by feed rate reduction to 1 mm/s just before the breakthrough.

**146**

*Far cortex registration during proximal pig femur bone drilling along the neck axis. Maximal drilling feed rate = 4 mm/s; drill bit 2.8 mm; Total time 24.84 s, 1235 AU; hole depth 61.7 mm. The values of the integral component ds I (red line) are scaled by multiplication of 10−1.*

For some types of fractures, like a midshaft clavicle fractures, it is advisable to fix the implants without drilling the second cortex. Comprising uni-cortical far-cortex– abutting locking screw fixation with bi-cortical fixation, it can be seen that both types of fixation have similar mechanical properties concerning axial and torsional loads in the case when the far cortex penetration not occurs [35]. Uni-cortical farcortex-abutting locking screw fixation risks far cortex penetration which requires protection of near anatomical structures [35]. Drilling modes of ODRO as Cortex I (unicortical drilling), Cortex II Find and Cortex II Drill can be used in such cases.

One more application of ODRO is related to the proximal humerus fractures. This problem is discussed in [36–38] and here we will present it briefly by citing some sentences from there aiming to show this problem clearer way.

Proximal humerus fractures may occur at the surgical neck, anatomic neck, greater tuberosity, and lesser tuberosity. They are common fractures which can often be seen in elder patients with osteoporotic bone after low level energy impacts. These patients usually have very low bone mineral density and that makes fracture fixation much complicated. Proximal humerus fractures account for 5% of all fractures and represent the third most common osteoporotic fracture [36]. The incidence of these injuries is expected to increase due to the aging population and the growing prevalence of osteoporosis [37].

Within the surgically treated fractures open reduction and internal fixation using locked plates is the most commonly applied joint-preserving treatment of proximal humerus fractures [38]. Failure rates of locked plating depend on the so-called "overdrilling". Perforation of the joint surface during pilot hole drilling is referred to as "overdrilling" [37]. Possible reasons for the overdrilling include: the restricted tactile feedback especially in osteoporotic bone; the spherical morphology of the humeral head that, together with the angulated locking screw projections, make interpreting of intra-operative X-ray images very complicated; the surgeons' experience level; the blunt drill bit [37].

Precision drilling to the correct depth could help prevention of overdrilling and significantly increases endurance until screw perforation failure, i.e. reduce failure rates of locked plating in an unstable proximal humerus fractures [37].

The drilling mode "Fixed depth" of ODRO (preliminary set depth of the hole in mm) can be used in such cases when ODRO is applied. When working in this mode, the set depth of the hole is realized with an accuracy of 0.1 mm.

During bicortical drilling, when the drilling is done manually, the magnitude of the drill bit penetration requires protection of the posterior bone wall. That means the obligatory cutting of the tissues immediately after it.

The drilling through the lateral cortex along the hip neck axis in fractures of the hip joint, as close as possible to the distal hip head cortex, can be performed successfully manually only under continuous X-ray control. This is of the utmost importance for stable fixation of the implant. The use of ODRO in this type of manipulations allows the use of surgical techniques associated with minimally invasive surgery.
