The Reason of a Choice

( 1° chapter of my new book “Small Implants in Knee Recostruction” you can get it here)

Before starting to read this book the reader should know what it is going to explore. Nowadays, in the orthopedic world osteoarthritis, prosthesis, mini-invasive surgery, tissue-saving surgery, small implants, etc. are “hot” topics approached from a multitude of perspectives, which ultimately run the risk of becoming repetitive. Thus, let’s first of all try to create order in these many topics, considering that the philosophy underlying the writing of this book is to repair the degenerative arthritic knee disease of our patients. But which patients? And, what type of arthritis? In our practice, we have come to realize that our patients have progressively changed: they are younger, smarter, more sensitive to pain, more informed, more demanding, and often have an intact or surgically reconstructed anterior cruciate ligament (ACL) [2, 3, 5]. Likewise, even the arthritic knees of our own generation have changed: we see fewer and fewer knees destroyed by an advanced primary arthritis but we increasingly have to manage compartmental diseases.
In many cases, these conditions are the results of sporting injuries, previous meniscectomies, plateau or condylar fractures, osteotomies, or prolonged overuse.



Nevertheless, almost 90% of surgeons worldwide still implant a total prosthesis in these knees, firstly resecting ACL and often, even the posterior cruciate ligament [6-8]. In many cases, in order to maintain the promise of a MIS (mini invasive surgery) to the patients, a small incision is performed, often with higher risks of damages of the noble tissue under skin, a sort of “key-hole” surgery [9-14]. We propose a totally different strategy: tissue sparing surgery (TSS), which does not consider the length of the incision to be more important than the size of the prosthesis [15, 16]. This prosthetic reconstruction, whether uni- or bi-compartmental, saves the two ligaments, which are the true fulcrum of joint biomechanics [17-19]. It involves the minimal removal of bone tissue from the tibia, femoral cartilage removal, sparing of the central pivot, and a small skin incision without damaging the extensor apparatus. It isclear that this surgical solution offers a genuinely minimally invasive surgery of the knee. Nonetheless, there are several considerations that are still matters of debate, including the indications, surgical technique and medium-term results [20-24]. Yet, there is no doubt that with the most recent technological developments, the increasingly precise surgical tools, computer assistance, and more convincing experience with unilateral knee replacement (UKR) [17, 20-22, 25, 26], positive, sometimes exciting, the short term results are possible [18, 27] and have led to very intense interest in this surgical approach to knee arthritis (Fig. 1.2).
In fact, it represents a “historical return,” because the history of knee arthroplasty starts with uni- and bi-uni condylar procedures. However, inaccurate instrumentation, incorrect indications and, consequently, less success guided the choice to a total prosthesis, which was considered easier to implant because it sacrificed everything to achieve a balanced design [5-7].
It is important to know that the three compartments of the knee joint are anatomically different and that each has its own specific biomechanics [31-34]. Thus, reconstructive knee surgery requires a vision of the joint that considers not only the anatomical structures but also the biomechanics as a whole, including muscle forces and ligament constraints. Thus, total knee
replacement (TKR) is not a “biological” replacement but instead creates a new “artificial” joint
with new, albeit abnormal kinematics [31, 35, 36]. Despite new and sophisticated prosthetic designs (gender-specific, one or two radius curvatures, mobile-bearing, etc.), TKR sacrifices the cruciate ligaments, changes the anatomy of the compartments, and in the majority of cases includes medial and lateral condyles of the same size. In addition, it has been widely emphasized that the results of TKR depend on the use of guides, which can lead to significant errors in reconstruction of the mechanical axis of the lower limbs based on the absence of data on proper soft-tissue balancing of the ligaments, thereby affecting both the functionality and the durability of the system [5, 37, 38]. From a surgical point of view, surgical compartmental reconstruction (UKR, UKR + PFA, bi-UKR) is considerably less invasive than total replacement: the ligamentous apparatus remains undamaged, does not require the use of intramedullary tools, and permits a three-dimensional correction of an arthritis deformity [15, 39]. 2Moreover, it preserves bone stock and, in case of failure, can be more easily revised with traditional total arthroplasty [40, 41].In addition to these “surgical” 2advantages, there are also several practical ones, even for thepatient [35, 36, 42, 43]:
• Reduced blood loss, with less need for a blood transfusion, even in the case of simultaneousbilateral implants.