Knee Surgery Department | Total Knee Replacement (TKR)

	Total Knee Replacement (TKR)
	After the first successful series of hip prosthesis in the 1950’s and 60’s, it seemed only natural that surgeons would then try and design a prosthesis for the knee. The first attempts were based on simple biomechanical models, similar to the ones already successfully used with regard to the hips ; a stem cemented in the femur which was articulated by a hinge with a tibial diaphysis. But if the biomechanics of the hip were quickly « domesticated» by the surgeons, the knee did not reveal its secrets as quickly and the first trials were a little discouraging. The prosthetic knee surgery did not finally take off until the 1980’s. But in the 1990’s trained hands made it as reliable as hip surgery. We now propose a twenty-six image technical demonstration showing the placement of a rotary knee prosthesis. This is, in our opinion, the only one capable of restoring satisfactory mobility in the case of an asymmetrical arthrosis of a genu varum. Our philosophy of placing a total knee prosthesis rests upon

	an absence of « ligamentary release ». We do not touch, or as little as possible, the ligaments that stabilise the knee and assures the proprioception. conservation of the posterior cruciate ligament rotating mobile plateau		bent knee + ligaments

	In the case presented, there is a marked wear and tear of the cartilage upon an important genu varum with loss of the anterior cruciate ligament.		side view of arthrosis
	front view of arthrosis		side view of arthrosis

	Setting up : anaesthesia in the majority of cases, is done by « rachianalgesia » which can be supplemented by a light sedation. The patients are stretched out on their back. We do not place an inflatable tourniquet. The inferior member rests on motorised splint that enables flexion and extension to be obtain easily (this can be done without the aid of an assistant		setting up the prosthesis

	On the first table are found the classic surgery instruments and several sterile pneumatic motors that allow for the sawing or perforation of the bone structure. A second table is allocated to the ancillary permitting the placing of the prosthesis. The term « ancillary » designates a specific instrumentation created specially for this type of prosthesis and will aid the surgeon in placing a total knee prosthesis. In our case, this ancillary is reduced to the strict minimum. One is also able to make out a tray that contains trial prostheses of different sizes, one of which will be the best adapted to the morphology of knee concerned.
	surgical instruments		ancillary material

	The operation starts with an vertical cut of 15 centimetres, centred on the patella. Next, one then moves towards the interior of the knee, opens the articulation by sectioning the quadriceps tendon in the direction of its fibers for 5 to 6 centimetres top to bottom by opening the patellar wing.
	para-patellar access		incision cut

	One can then dislocate the patella towards the exterior, giving access to the femoral condyles. One can then make a final decision concerning the arthrosic lesions and verify the quality of the anterior cruciate ligament of the knee. In this particular case the cartilage of the internal tibial femoral compartment has almost completely disappeared and there are very serious lesions on the outside. The anterior cruciate ligament no longer exists. It is exceptional that the posterior cruciate ligament (PCL) be injured.		arthrosis - the knee opened

	The placing of prosthetics implants imposes a search for reliable osseous landmarks. Therefore it is imperative, at the beginning of the intervention, to practice an ablation of the osteophytes which might impair identification. One can also practice an ablation of the meniscuses who no longer have a reason to be there.		ablation of the meniscuses

	The placing of the prosthetic femoral component depends upon a re-polishing of the femoral condyle. The surgeon must shape the inferior extremity of the femur in order to adapt it to the prosthesis. In order to do this, he has at his disposition a set of templates which adapt in a very precise manner and allows for a minimum of bone removal. In principle, one starts by a resection of the anterior part of the femur.		template 1

	The second incision is very important. It is at this point that the surgeon decides which orientation, between the horizontal axis of the articulation and the femur axis, is to be taken. This axis varies from one patient to another and it is a careful study of the X-rays before the operation that will dictate which path is the best one to follow.		template 2

	In order to do this, one places a stem in the interior of the femur and using a protractor, prepares the inferior cut. A special template is then fixed on the femur with two pins. It is on this template, using an oscillating saw, that the one removes a sizeable quantity of bone. The cuts should be very precise for the prosthesis at the end of the operations, will be fitted together upon the inferior extremity of the femur by force. As one progresses with the femoral cuts, the template becomes more and more precise.

	axes template		horizontal cut

	bevel 1 template		bevel 2 template

	When the inferior extremity of the femur is ready, the surgeon has, at his disposition, prosthetic trial pieces which allows him to verify the precision of his work. These trial pieces are exact reproductions of the final pieces. These trial pieces will also allow him to continue the operation. If one wishes that the tibial piece has a harmonious leeway with the femoral piece, it is indispensable that it be correctly positioned. In the case of a classic prosthesis, non- rotating, the positional identification of the different components is made independently for both the tibia and the femur. In many cases, numerous surgeons start by preparing the tibia before the femur. To us, it seems more logical not to proceed in such a manner. We will search, once the femoral trial piece is in place, for what we call the « center of the knee ». This knee center is classically situated a little inside of the tibal tubercle on which the patellar tendon is inserted. Unfortunately, in reality, this is not always the case. If there happens to be an asymmetrical arthrosis like in the large deformations of the tibia, this « knee center » could be situated well into the interior on the tibial plateau. In this case, if the classical reference is kept one risks to compromise the final result ending with a painful knee with limited amplitudes of flexibility.

	Thus, we prefer to be guided by the local anatomy searching in a systematic manner the « knee center » in the following way : the trial prosthesis is left in place, the knee is extended, and a ruler is placed on the axis of the trochlea. Its projection on the tibia automatically gives the right reference. The latter will be marked with an electric scalpel and a squared point.		knee center 1

	knee center 2		knee center 3

	During the operation, in order to limit the risk of infection, the surgeon regularly washes the operating site with a sterile physiological serum. For this purpose, he has at his disposition, a motorised washing system that sends out pressurised water.		lavage

	The following step consists of preparing the tibial section. We prefer to utilise an external viewer applied to anterior face of the tibia. This viewer makes an 90 degree angle with the diaphysis axis. And thanks to an oscillating saw, one is able to obtain a section plane upon which the tibial support can be applied.		protection of the posterior cruciate ligament (PCL)

	placing the tibial viewer		the tibial viewer

	One can then place the tibial trial piece and the femoral piece and verify that they are satisfactorily adapted. It is then possible to test the kinematics of the new articulation. One can also verify that the axis of the inferior limb is normalised and that the ligamentary tension, with regard to extension and flexion, is correct.		tibial trial plateau

	If such is the case, then all that remains is to place the definitive pieces. These are impacted by force and kept in place due to the precision of the bony sectioning. We clearly prefer this method over the two piece cementing system. A ten year observation period has proven to us that the bony holding was excellent and maintained through out time without any problem. However, in the case of a bone with osteoporosis, cementing the pieces could be justified. First the support is posed upon the tibia. This receives the polythene tibial plateau. Then the femoral condyle is impacted.		placing the plateau

	support and plateau		final prosthesis

	Only in rare occasions do we place a prosthesis on the patella, as the rotating concept of the tibial plateau diminshes the constraints. In general, the simple ablation of the osteophytes is sufficient. In certain cases, a complementary gesture upon the external wing is necessary. Again, but even more rarely, one must displace the tibal tubercle upon which the patellar tendon is inserted. At the end of the operation the incision is sewn up on three planes. A vacuuming drainage of the articular cavity (Redon-Jost drains) is put in place and left for several days. Re-education begins on the following day after surgery. Hospitalisation is from 10 to 12 days. Physiotherapy lasts about 2 months.