Introduction: Correct alignment of prosthetic components is considered one of the most important factors for TKR (total knee replacement) survival. It is our aim, in this study, to determine the degree of correlation between measurements made by 2 observers and the assistant navigator during prosthetic knee surgery.

Materials and methods: In a total of 55 non-selected patients, operated with navigator assistance, two resident physicians in our Department, using a computer system measured, during the preoperative period, the ipsilateral and contralateral femorotibial axis, the femoral and tibial axis, and the inclination of the tibial plateau. They also measured, during the postoperative period, the tibiofemoral axis by means of digitalized X-rays. These measurements were compared with those made by the navigator.

Results: The degree of correlation between measurements was variable. The greatest degree of correlation between values was that of the preoperative tibiofemoral axis, with an r of: 0.83 (0.68–0.91 CI 95%) and the lowest degree of correlation was that of the measurements of the posterior tibial inclination.

Conclusions: A large number of axes and useful measurements have been described for the planning of reconstructive knee surgery, but since the introduction of new technologies applicable in this field, it is necessary to determine the degree of reliability and reproducibility of these so they can be correctly used by the orthopedic surgeon in their everyday clinical practice.

Background and goal of study: Although a great percentage of the total postoperative bleeding corresponds to a hidden blood loss in the tissues and joint, visible blood from the drainage is considered the gold standard for monitoring blood loss after a knee arthroplasty. Only one study was not able to find a consistent relationship between the total blood loss and postoperative drained blood. The aim of our study was to assess the usefulness of a postoperative drainage as a monitor of bleeding following a knee arthroplasty.

Material and methods: Fifty patients undergoing unilateral arthroplasty from March to November 2004, were prospectively followed until the fourth postoperative day. Drained red blood cells(RBC) loss was assessed by multiplying the drained blood volume by an haematocrit (Hct) of 30% from a pilot study. Total RBC loss and hidden RBC loss from each patient were calculated. Regression analysis was performed to assess the relationship between the total RBC loss and drained RBC loss.

Results and discussions: The average age of the fifty ASA 2 patients was 72 +− 7 years. Nearly all the procedures were performed under intradural anaesthesia. Cemented technique and tourniquet were used in all cases. The mean total RBC loss was 615 +−197ml. The mean drained RBC loss was 206+− 113ml, and mean hidden RBC loss was 414 +−194ml. Thus the hidden loss was 67% of the total blood loss. Regression analysis shown a poor correlation coefficient between the total RBC loss and drained RBC loss (r= 0.31, p< 0.03).

Introduction: Defects in rotational alignment of the femoral component in total knee replacements (TKR) may cause poor alignment of the extensor apparatus. There are numerous references concerning the correct alignment of the femoral component of a prosthesis: transepicondylar axis, anteroposterior axis, and posterior condylar axis.

Materials and methods: Computer-assisted measurement of the relative differences between the transepicondylar axis, anteroposterior axis and posterior condylar axis in 38 TKR patients, excluding those with varus or valgus deformity greater than 15 degrees.

Results: The difference between the anteroposterior axis and the transepicondylar axis was 3.13 degrees of external rotation in the former.

Between the posterior condylar axis and the transepicondylar axis it was 1.18 degrees of internal rotation in the former.

Between the anteroposterior axis and the posterior condylar axis it was 5.51 degrees of external rotation of the former.

Conclusions: Probably the transepicondylar axis is the best landmark to enable reproducing the biomechanics of the knee in a patient bearing a prosthesis, although it is often difficult to reproduce it precisely. Several studies have noted errors among observers that are too great to make us feel certain that we are doing the best thing.

Although it is accepted that the perpendicular to the anteroposterior axis is reliable and corresponds to 4° of external rotation in relation to the posterior condylar axis, we have observed significant differences from one patient to another.

It would seem preferable to use a combination of the different axes, which we can do with a surgical browser.

Introduction and purpose: To present the clinical, radiological and MRI results of a series of collagen meniscus implants (CMI) with 4–7 years follow-up.

Materials and methods: We implanted 25 CMI from 1997 to 2000 in 20 men and 5 women between the ages of 18 and 48. Five cases were operated on for postmeniscectomy syndrome, 19 for degenerative ruptures and one for acute rupture. We reconstructed the ACL at the same time in 17 cases (68%).

Results: The Lysholm score went from a preoperative mean of 59.9±15.8 to 89.6±6.3 at 2 years (p< 0.003), while the visual analogue pain score went from a preoperative mean of 7.0±1.8 to 2.0±1.6 (p< 0.001).

Conventional radiology showed no deterioration of the joint line. With MRI we saw a certain degree of meniscal regeneration in 68% of the cases. However, the implant tended to become smaller and it was common to see extrusion in frontal sections.

Three cases had persistent pain on the medial side of the knee. In one we removed the CMI and performed an allogeneic meniscus transplantation (AMT). The second case was treated by valgus osteotomy of the tibia and then AMT in the stage. The last case was not treated.

Conclusions: After 4 to 7 years of BMI follow-up, we found no adverse effects for the knee. Clinically the outcome was good in most of the cases (22/25). Regeneration appeared to occur in over one-third of the cases, although the size was smaller than expected.

Introduction: The correct position of the knee arthroplasty components is associated with a better result of the prosthesis.

In the tibial component, both intramedullar and extramedullar instrumentations have been used for its fiability, but in the femoral component intramedullar guides are more precise than extramedullar ones.

The use of the intramedullar guide for the femoral component is not always possible, because a significant deformity of the femoral shaft or when a intramedullar device has been implanted in the femur.

We have studied the alineation of the components of computer assisted total knee arthroplasties in a group of patients with femoral deformities or implants.

Material and methods: We have used the surgical navigator Stryker-Howmedica for the implantation of a knee arthroplasty in a group of 10 patients in which a endomedullar femoral guide can not be used for femoral shaft severe deformities (6 cases): Paget disease (1 case), previous femoral osteomyelitis (2 cases) or previous femoral fractures (3 cases), or a shaft device was in the femoral shaft (4 cases): long hip femoral stem (3 cases) or a femoral nail (1 case) .

We have studied the alineation of femoral and tibial components with a whole-leg X-ray and Computer Tomography.

Results: All the femoral and tibial components have been implanted in a good position (90 +/– 2 degrees in the A-P plane and a femorotibial axe 180 +/– 3 degrees. The alineation in the sagital and axial planes have been inside the desired values in all cases also.

Discussion: It is generally accepted than intramedullary guides for the femoral component is the gold standard in arthroplasty of the knee.

In the last years, the development of computer assisted systems has allowed to obtain femoral and tibial cuts referred to the mechanical axes of the bone, without using mechanical guides for the alineation.

In some studies these navigation systems are better than mechanical instruments in terms of alineation of the components in cases without great deformities.

In this study, with some cases with severe femoral shaft deformities or with some intramedullary devices that does not allow the use of intramedullary femoral guides, we think that the indication to use a surgical navigator should be nearly absolute.