**5. Posterior tibial slope**

and bearing used in a cemented fixation of the joint with modular tibial components" and "… Uncemented/hybrid total knee replacements with posterior stabilised constraint and fixed bearings fare worse than their unconstrained bearing equivalents" [6]. Similar results were carried out by the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) 2017 Annual Report: it describes as "…the use of minimally stabilised prostheses has remained relatively constant over the last 10 years. In 2016, these accounted for 67.4% of the three prosthesis types. The use of posterior stabilised prostheses has declined from 32.9% in 2008 to 25.6% in 2016." It also reports that "…Posterior stabilised and medial pivot prostheses have a higher rate of revision compared to minimally stabilised" stating that "…Posterior stabilised prostheses have a higher cumulative incidence of infection…" and "also have a higher

cumulative incidence of loosening compared to minimally stabilised prostheses" [7].

group…" but "…These differences are clinically not relevant" [8].

femoral component relative to the tibial component.

**4. Kinematic**

26 Primary Total Knee Arthroplasty

More recent meta-analysis obtained the same clinical conclusion [9, 10].

Focusing on the differences in clinical outcomes between TKRs with retention versus sacrifice of the PCL, a Cochrane Review published in 2013 by Verra et al. found 17 randomized controlled trials that lead to following conclusion: "… With respect to range of motion, pain, clinical, and radiological outcomes, no clinically relevant differences were found between total knee arthroplasty with retention or sacrifice of the posterior cruciate ligament. Two statistically significant differences were found; range of motion was 2.4° higher in the posterior cruciate ligament sacrificing group, however results were heterogeneous; and the mean functional Knee Society Score was 2.3 points higher in the posterior cruciate ligament sacrificing

Numerous prostheses have been developed to improve the durability and function of TKR and kinematic principles that have been the focus of current implant designs, have been to replicate the native knee's femoral rollback during flexion and the external rotation of the

In the normal knee, a rolling motion predominates for the first 20° of flexion, which produces a posterior translation of the femoral contact position on the tibia. After 30° flexion, sliding becomes predominant but the net motion remains in the posterior direction [11] and the PCL performs several functions: It guides the rollback of the femoral condyles on the tibial plates during flexion, thus allowing the back portion of the condyles to clear the posterior surface of the tibia at high bending degrees and improving the mechanical efficiency of extensor apparatus; from the point of view of stability, it prevents the posterior subluxation of the tibia on the femur during flexion, with a critical secondary role in stability in varus and valgus with knee flexion [12].

Several studies about CR-TKR evaluated in the past the kinematic of this type of implant: Stiehl et al. in a fluoroscopic analysis showed that CR-TKR "…did not reproduce normal knee Kinematics in any case, but showed a starting point posterior to the tibial midline which translated anteriorly with flexion…" and "…Physiological roll-back has not been demonstrated As widely explained by Sierra and Berry when performing a CR-TKR, modest posterior slope (matching patient's native slope between 3 and 7°) may help reduce tension on the PCL and facilitate knee flexion [15]. Posterior tibial slope (PTS) opens the flexion space, and this helps to obtain flexion without PCL recession. However, excessive slope may lead to compromise the insertion point of the PCL into the tibia, which can lead to flexion instability and to reduced or paradoxical femoral rollback reported more frequently in CR than in PS TKR.

One of the last biomechanical discoveries showed as an "increased PTS was associated with biomechanical effects leading to reductions in quadriceps force, contact stress on PF joint, and force on PCL. However, excessive PTS should be avoided to prevent progressive loosening of the TF joint gap due to the reduction of collateral ligament tension during flexion" [16].

A reduced slope can generally lead to lift-off positive test in flexion whose treatment will be extensively described in the technique paragraph.

In conclusion, evaluating the tibial slope is a crucial phase in CR-TKR, since as recently explained by Dae Kyung Bae et al. the steepness of the PTS is one of the main factors that requires the conversion to PS from a CR-type prosthesis [17].

was elevated 4 and 6 mm, and was partially restored following cruciate excision…" and "… The effect of joint line elevation on normalized quadriceps load and patella-femoral contact

Cruciate-Retaining Total Knee Arthroplasty http://dx.doi.org/10.5772/intechopen.74024 29

A standard midline longitudinal approach is performed with medial parapatellar arthrotomy and lateral patellar dislocation; the knee joint is exposed and the Whiteside line and the transepicondylar axis are marked (they are used as femoral rotational landmarks); the intramedullary femoral guide is drilled into the femur; a 9-mm distal femoral bone resection

For the tibial side, Hohmann retractors are employed to protect lateral and medial soft tissues (critical structures for a correct balancing); the tibial spine is removed using a surgical saw.

Then through the use of an osteotome, a bone island really closer to the distal insertion of PCL is circumscribed (**Figures 4** and **5**). A pin is placed in front of the PCL defining the anterior side of the island (**Figure 6**); we make use of the extramedullary tibial resection guide to align the tibial mechanical axis; an amount of resection equal to the thickness of the tibial arthroplasty component is measured on the less osteoarthritic plateau and tibial resection is performed bewaring not to get across the lateral and medial sides of marked bone island. The employment of the osteotome is an essential step: it allows to incise the posterior cortex avoiding during the tibial plateau excision the risk of avulsion and subsequent detachment

With these precautions, the tibial plateau is removed (**Figures 7**–**9**) and the bone island can be carefully shaped through a nibbler to permit the placement of the posterior side of the tibial

**Figure 3.** Distal femur cut: with the angel wing, you can appreciate the minimal resection in order to maintain the level

pressures was observed only at higher flexion angles…" [22].

is performed with a valgus angle preoperatively planned (**Figure 3**).

**8. Authors' preferred surgical technique**

of the PCL.

of the joint line position.

component (**Figures 10** and **11**).
