**3.1. Surgical approaches**

A straight anterior skin incision allows exposure for medial and lateral structures and it's the standard skin incision for TKA. Arthrotomy may be done from the medial or lateral side. Anteromedial arthrotomy is the most used approach on TKA and provides excellent exposure of the knee joint (**Figure 7**). After eversion or patella lateral subluxation, the knee is flexed. One must be aware of avulsing off the patellar tendon from the tibial tubercle, if there is too much tension.

Because the most important component of blood supply runs medially, anteromedial approach could affect patellar circulation, and some authors have advocated subvastus and midvastus approaches (**Figure 8**). They are less invasive and can be used specially in moderate knee deformity.

For fixed valgus deformities, the lateral parapatellar approach may be considered. A mild lateral skin incision is made and extended over the lateral border of the tibial tubercle. In the original description, a thin segment of the tubercle is osteotomized with the attached patellar tendon. A medial periosteal hinge is maintained along with the infrapatellar fat pad, which is used for later closer of the lateral retinacula. Some surgeons suggest not to osteotomize the tibial tubercle, turning it into a less invasive approach.

**3.2. Surgical theories**

at the level of the superior pole of the patella.

*3.2.1. Anatomical, mechanical alignment, and gap balance technique*

is suitable for most TKA and allows great exposure of the knee joint.

favored for those who defended cruciate retention implants.

Since the beginning of the implants and instruments, two concepts that guide surgical techniques were established: gap balance and measured resection technique. Universally spread, gap balance surged for cruciate substituting prostheses. Measured resection technique was

**Figure 8.** Subvastus approach does not sacrifice the extensor mechanism (blue line) and it is useful specially for minimal invasive approaches. In midvastus approach (red line), the oblique medial vastus is split sharply in line with its fibers,

**Figure 7.** Anteromedial approach to the knee. After a medial skin incision, a medial parapatellar arthrotomy is made. It

Planning Primary Total Knee Arthroplasties http://dx.doi.org/10.5772/intechopen.72775 11

For gap balance technique, either the femur or tibia may be osteotomized first. The main goal is to equalize flexion and extension gaps, most of the time transforming a trapezoidal gap into a rectangular gap (**Figure 9**). For those who favor to start cutting proximal tibial (at about 8–10 mm below the less worn tibial plateau surface), it should be perpendicular to the MAT, and when posterior cruciate ligament (PCL) is sacrificed, the flexion gap opens up a few millimeters more. That situation can implicate in a slightly upper distal femur cut, which can elevate the joint line and bring the patella in a lower position. Distal femoral cut is often parallel to the tibial cut, following the transepicondylar axis. Rotational alignment of the femur is tuned by ligament release or femoral rotation. In a varus knee, when the surgeon opts for

Extended approaches have been described and are very useful in stiff knees and great deformities. Coonse and Adams described a quadriceps turndown. The quadriceps are split down the middle, in an inverted "V" fashion, at about 1 cm above the patella, so the patella could be turned down, allowing the exposure of the joint. Quadriceps snip was described by Insall by an oblique incision at the proximal apex of the quadriceps tendon, at about a 45° angle, directly in line with the fibers of the vastus lateralis. It relaxes the extensor mechanism and protects the tibial tubercle. Tibial tubercle osteotomy enhances exposure and it could be very useful in stiff knees. Tibial crest should be osteotomized 8–10 cm below the tibial tubercle, using the oscillating saw and osteotomes. The shape of osteotomy is trapezoidal, 5-m long, 2-cm wide, and 1.5-cm wide distally. The entire extensor mechanism is then elevated proximally.

Limited approaches are described and could be useful, especially when planning unicompartmental arthroplasties. Limited approaches are part of a traditional extensile approach, and the surgeon tends to use it as he becomes familiar with the surgical technique.

**Figure 7.** Anteromedial approach to the knee. After a medial skin incision, a medial parapatellar arthrotomy is made. It is suitable for most TKA and allows great exposure of the knee joint.

**Figure 8.** Subvastus approach does not sacrifice the extensor mechanism (blue line) and it is useful specially for minimal invasive approaches. In midvastus approach (red line), the oblique medial vastus is split sharply in line with its fibers, at the level of the superior pole of the patella.

#### **3.2. Surgical theories**

moveable bone cutting line, perpendicular to MAF and MAT. At the end of the methodology process, it automatically shows the type of deformity, the MAFÂ, and soft tissue releasing sequence (**Figure 6**). Then, scientific references used to build the application are presented.

The application ATJ® has proved to be useful in the context of planning TKA. It has revealed accuracy when measuring the MAFÂ when compared to the manual form of planning. It was

A straight anterior skin incision allows exposure for medial and lateral structures and it's the standard skin incision for TKA. Arthrotomy may be done from the medial or lateral side. Anteromedial arthrotomy is the most used approach on TKA and provides excellent exposure of the knee joint (**Figure 7**). After eversion or patella lateral subluxation, the knee is flexed. One must be aware of avulsing off the patellar tendon from the tibial tubercle, if there

Because the most important component of blood supply runs medially, anteromedial approach could affect patellar circulation, and some authors have advocated subvastus and midvastus approaches (**Figure 8**). They are less invasive and can be used specially in moder-

For fixed valgus deformities, the lateral parapatellar approach may be considered. A mild lateral skin incision is made and extended over the lateral border of the tibial tubercle. In the original description, a thin segment of the tubercle is osteotomized with the attached patellar tendon. A medial periosteal hinge is maintained along with the infrapatellar fat pad, which is used for later closer of the lateral retinacula. Some surgeons suggest not to osteotomize the

Extended approaches have been described and are very useful in stiff knees and great deformities. Coonse and Adams described a quadriceps turndown. The quadriceps are split down the middle, in an inverted "V" fashion, at about 1 cm above the patella, so the patella could be turned down, allowing the exposure of the joint. Quadriceps snip was described by Insall by an oblique incision at the proximal apex of the quadriceps tendon, at about a 45° angle, directly in line with the fibers of the vastus lateralis. It relaxes the extensor mechanism and protects the tibial tubercle. Tibial tubercle osteotomy enhances exposure and it could be very useful in stiff knees. Tibial crest should be osteotomized 8–10 cm below the tibial tubercle, using the oscillating saw and osteotomes. The shape of osteotomy is trapezoidal, 5-m long, 2-cm wide,

and 1.5-cm wide distally. The entire extensor mechanism is then elevated proximally.

Limited approaches are described and could be useful, especially when planning unicompartmental arthroplasties. Limited approaches are part of a traditional extensile approach, and the surgeon tends to use it as he becomes familiar with the surgical technique.

also capable of reducing the planning time by more than a half [11, 12].

**3. Surgery**

**3.1. Surgical approaches**

10 Primary Total Knee Arthroplasty

is too much tension.

ate knee deformity.

tibial tubercle, turning it into a less invasive approach.

#### *3.2.1. Anatomical, mechanical alignment, and gap balance technique*

Since the beginning of the implants and instruments, two concepts that guide surgical techniques were established: gap balance and measured resection technique. Universally spread, gap balance surged for cruciate substituting prostheses. Measured resection technique was favored for those who defended cruciate retention implants.

For gap balance technique, either the femur or tibia may be osteotomized first. The main goal is to equalize flexion and extension gaps, most of the time transforming a trapezoidal gap into a rectangular gap (**Figure 9**). For those who favor to start cutting proximal tibial (at about 8–10 mm below the less worn tibial plateau surface), it should be perpendicular to the MAT, and when posterior cruciate ligament (PCL) is sacrificed, the flexion gap opens up a few millimeters more. That situation can implicate in a slightly upper distal femur cut, which can elevate the joint line and bring the patella in a lower position. Distal femoral cut is often parallel to the tibial cut, following the transepicondylar axis. Rotational alignment of the femur is tuned by ligament release or femoral rotation. In a varus knee, when the surgeon opts for

during flexion. When the ligament is left too tight it could increase posterior stress, causing a movement described by Insall as "open like a book" and "lift-off" of the tibial tray. When the PCL is insufficient, it could cause a paradoxal movement of rolling forward in flexion, limiting flexion by posterior impingement. The tibial cut is made preserving its mild varus and femur cut is made preserving its natural valgus. Equalization of the gaps is not strictly

Planning Primary Total Knee Arthroplasties http://dx.doi.org/10.5772/intechopen.72775 13

During the evolution of the implants some concepts were mixed and the surgeon conquered freedom to make bone cuts a little bit off the outliers. Even for situations when the PCL is preserved, conformed tibial surfaces could be used. Sometimes, the surgeon can choose not to cut the bone perpendicular to the mechanical axis, sparing extensive ligament releases.

The refinement of surgical techniques, implant designs and an individualized tendency of surgical treatment have contributed to resurrection of the discussion about restoration of the

Some authors have noticed that neutral mechanical alignment does not restore biomechanics

Kinematic Alignment (KA) aims to restore constitutional alignment, ligament tension, and the joint's line level and orientation [16, 17]. Hungerford, Kenna, and Krakow defended a slight varus alignment for the tibia in relation to the MAT. They are considered precursors

According to Howell et al., there are three kinematic knee axis: the primary femoral axis, wich is a transverse axis of femur around which the tibia flexes and extends; the secondary femoral axis, wiich is a traverse axis in the femur around which the patella flexes and extends; and the longitudinal tibial axis, around which the tibia internally or externally rotates on the femur [19] (**Figure 11**). Each axis is parallel or perpendicular to the natural joint line between the femur

The preoperative plan of a kinematic TKA can be done by using MRI exams in order to estimate chondral and bone erosion [20–22]. These parameters are used to compensate implant's position that should be parallel to the primary and secondary kinematic femoral axis. A

The KA principle is a promising alternative for the execution of TKA. In the centers where it was adopted, the results in the short and medium term were favorable [22], with the premise of restoration of the biomechanics of the knee, which may point to a new paradigm. Nevertheless, studies on durability and long-term function are needed before universal adop-

Its applicability in patients with a higher degree of bone erosion should also be evaluated cautiously because of the increased risk of malalignment, which may be caused by the difficulty

in identifying the references that guide the positioning of the bone cutting guides.

native's knee anatomy and preservation of the articular line.

patient-specific implant or a conventional implant can be used.

in a significant part of the population [13–15].

and tibia throughout the motion arc.

tion of this new methodology.

necessary.

on KA [18].

*3.2.2. Kinematic alignment*

**Figure 9.** Before ligament releasing, there is usually a trapezoidal gap.

not releasing medial ligaments he usually needs to add external rotation to the femoral cuts. Some references help to establish the appropriate rotation: transepicondylar axis, posterior femoral condyles, Whitside's line (trochlear groove axis), tibial shaft axis, and ligament tension. In some situations, even a small degree of internal rotation could be applied. Before implant is settled, the gap must be rectangular and symmetrical (**Figure 10**).

The measured resection technique aims not to move the joint line position. That situation, in theory, preserves knee's anatomy, sparing the PCL, when possible. Some advocate that preserving the PCL has advantages as it is an important varus/valgus stabilizer of the knee; it can absorb stress; and it can control the movement of rolling back of the femur onto the tibia

**Figure 10.** Rectangular gap. Before the implant is set, there must be a rectangular gap.

during flexion. When the ligament is left too tight it could increase posterior stress, causing a movement described by Insall as "open like a book" and "lift-off" of the tibial tray. When the PCL is insufficient, it could cause a paradoxal movement of rolling forward in flexion, limiting flexion by posterior impingement. The tibial cut is made preserving its mild varus and femur cut is made preserving its natural valgus. Equalization of the gaps is not strictly necessary.

During the evolution of the implants some concepts were mixed and the surgeon conquered freedom to make bone cuts a little bit off the outliers. Even for situations when the PCL is preserved, conformed tibial surfaces could be used. Sometimes, the surgeon can choose not to cut the bone perpendicular to the mechanical axis, sparing extensive ligament releases.
