Background

Computer-assisted navigation systems for total knee arthroplasty (TKA) were introduced to improve implantation accuracy and to optimize ligament balancing. Several comparative studies in the literature confirmed an effect on the component position and other studies could not confirm these results. For ligament balancing most studies found no significant influence on the clinical outcome using a navigation system for TKA. In the literature there were no reports of mid-term results after navigated TKA. With our study we wanted to show if the use of a navigation system for TKA will have an influence on the component's position and on the clinical results at 5-year follow up.

Introduction: Based on the benefits of less postoperative pain and accelerated rehabilitation associated with minimally invasive implanted unicompartmental knee joint replacement new surgical approaches have been developed for total knee replacement. New side-cutting implantation instruments were proposed for the minimally invasive surgical technique. Different randomized studies have shown improved component position in association with the use of navigation systems for TKA as compared with standard implantation instruments. There is a lack of randomized studies showing whether the same level of accuracy provided by computer-assistance is possible when using a minimally invasive approach and the side-cutting jigs. We hypothesized an imageless navigation system leads to improved component positioning in the coronal and sagittal plane when compared with a non-navigated study group. Both cohorts were operated on with a mini-subvastus surgical approach using side-cutting instruments. We questioned whether clinical outcomes were affected by the application of the navigation system at 3 months followup.

Methods: 100 patients were randomized to undergo computer-assisted TKA or non-navigated TKA using a mini-subvastus surgical approach and side-cutting implant instrumentation. The radiographic parameters, clinical outcomes and knee scores were evaluated 3 months postoperative.

Results: The mechanical axis of the limb was within 3° varus/valgus in 76 % of the patients who had navigated procedures versus 66 % of patients who had conventional surgery. The tibial slope showed a rate of inaccuracy of 3° or less for 78 % of the patients in the navigated total knee arthroplasty group versus 66 % of the patients in the conventional group. Clinical outcomes and knee scores were similar in both groups.

Conclusion: The navigated study group showed a trend to a higher implantation accuracy but the differences were not significant. We think the reasons were the cutting direction from medial to lateral – longer cutting distance – and the insufficient cutting-jig fixation. We cannot recommend the use of the MIS Quad-Sparing™ instrumentation without a navigation system. With computer-assistance the implantation accuracy could duplicate the findings in the literature for non-navigated cohorts using a standard surgical approach. Using a navigation system for minimal invasive subvastus TKA did not influence the 3-month clinical outcome.

Background: In the literature are different data about the allogenic blood transfusion rate after total knee replacement. The common intention in orthopedic surgery is to reduce the requirement for allogenic blood transfusions by optimizing the blood management. The aim of this study is to determine the efficacy of the mechanical autotransfusion system OrthoPAT (Haemonetics Corp., MA, USA) to reduce the postoperative allogenic blood transfusion rate.

Method: According to the preliminary performed power analysis we did a prospective controlled study including 104 patients which were randomized in a group A (OrthoPAT for intra- and postoperative blood salvage and retransfusion, n = 52 patients) and a control group B (no retransfusion system was used, n = 52 patients) All patients had a primary osteoarthritis of the knee and were operated on without use of a tourniquet. We implanted in all patients a cemented posterior stabilized total knee prosthesis design (LPS-Flex Mobile, Zimmer, IN, USA). In group A the autotransfusion system was used for 6 hours (intra- and postoperatively) and the collected blood was retransfused. The retransfused blood is anticoagulanted, filtered and centrifuged to separate waste products. Red cells are washed with saline and reconcentrated to a high haematocrit. The preoperative data for cardiopathy, angiopathy, preoperative anemia or anticoagulant treatment showed no significant differences for group A and B. Because of missing data we finally were able to use the results of 98 patients: 48 group A and 50 in group B. The indications for a blood transfusion were influenced by the clinical symptoms of anemia, the hemoglobin value (hemoglobin < 8.0 g/dl) and the anamnesis of cardiovascular diseases. Evaluation was done with the medical history and the pre-/postoperative hemoglobin values, postoperative blood loss and postoperative need of allogenic blood transfusion.

Results: The two groups showed no significant differences relating to the demographic data or the medical history. 16 patients (33 %) of the retransfusion group who in mean received 281 ml of salvaged blood needed allogenic blood transfusion compared with 22 patients (44 %) of the control group B (p = 0,306). The hemoglobin values of group A versus the control group showed after the donation of the salvaged blood a significant difference (p = 0,027) but no longer at the 3rd and 5th day postoperative.

Conclusions: The use of the autotransfusion system seems to reduce the postoperative allogenic blood transfusion rate but not statistical significant. At the 3rd and 5th day postoperatively no significant differences of the hemoglobin values could be stated comparing group A with group B. For us this was a clue showing that the quality of the erythrocytes after the reclamation was reduced.

Introduction: With non-fusion stabilization surgery technique, the demands on the pedicle screw system have increased. The screw implants require a high press fit for optimum bone integration and a high pullout strength to guarantee primary stability. We compared the cylindrical screw design from a pedicle screw system with the conical design in regard to the insertional torque and pullout strength.

Methods: Three human cadaver specimens L1 – L5 (15 vertebrae, 30 pedicles) were fitted with pedicle screws on both sides. The pedicles were randomized to one of two screw types: 1) cylindrical pedicle screw, 2) conical. A computer tomographic bone density measurement was performed beforehand. The insertional torque was measured while inserting the pedicle screws. The correct position of the screw was verified using computer tomography. In order to test the pullout strength, the preparations were divided up into individual vertebrae and fixed.

Results: The mean peak insertional torque for the conical screws was significantly higher than that for the cylindrical screws. The pullout strength showed no significant difference between the two types of pedicle screws. With both the conical and the cylindrical pedicle screws, the pullout strength and insertional torque significantly decreased with decreasing bone density in the preparations.

Conclusions: Statements in the literature about the effect on insertional torque and pullout strength of using a conical or cylindrical pedicle screw design vary. The two screw designs in our study only differed in regard to their internal diameter. The significantly higher insertional torque values found for the conical screws could describe the improved screw press-fit behavior. The pullout strength was not significantly affected by the conical design. No correlation was found between the insertional torque and pullout strength. In order to optimize the adjustment of insertional torque and pullout strength, we recommend the conical pedicle screw design for non-fusion surgical techniques for the surgical treatment of degenerative diseases of the lumbar spine.

Aims: Because of the limitation of exposure inherent in minimally invasive surgical techniques for total knee replacement surgery, there is a significant risk of malalignment, malrotation, femoral notching and failure of soft tissue balance.

Methods: In this randomized study 50 patients with osteoarthritis of the knee, underwent TKR through a minimally invasive exposure using a navigation system; while a control group of 50 patients underwent the same surgery without navigation.

A subvastus approach was used with a less than 10 cm incision. Femoral component alignment is established with an intramedullary, and the tibial component, with an extramedullary alignment guide. The navigation system was used for fine adjustment and verification of cutting block position. The navigation system used for the study was the VectorVision® CT-Free Knee 1.5.1.

Results: The accuracy of prosthetic components positioning was significantly higher in the navigation group. The navigation system offered an objective analysis of medial and lateral ligament tension in full extension and 90 ° of flexion. In 8 cases navigation avoided femoral notching. No navigation related complications were registered. The additional surgery time for computer-assisted TKR was a mean 21 minutes. The nonnavigated implantation technique reached perfect component positioning in 62 % of the TKR.

Conclusion: Computer-assisted TKR results in predictable and accurate alignment, avoidance of femoral notching, avoidance of malrotation and appropriate balance of the soft tissue. Performing minimally invasive TKR without navigation has a higher risk of increased rate of unsatisfactory outcomes with shorter prosthetic survivorship when compared to the use of navigation.

Introduction: Optimal component position in all planes and well balanced soft tissues lead to a good clinical outcome and long-term survival after total knee arthroplasty. We investigated the implantation accuracy of navigated total knee arthroplasty at 3 months followup and the influence on the clinical outcome at 2 years followup.

Patients and Methods: Forty-four patients (44 procedures) were enrolled in our prospective study. One half of the surgeries were performed using a computed tomography based navigation system, and one half of the surgeries were performed without computed tomography navigation. Outcomes were based on the Insall knee score parameters, anterior knee pain, patient satisfaction, feeling of instability, and step test. The radiographic parameters were the mechanical axis, tibial slope, lateral distal femoral angle, and medial proximal tibial angle.

Results: The radiographic measurements showed no differences between both groups (patients within ± 3° inaccuracy range in computed tomography based/computed tomography free groups; mechanical axis 86%/81%, tibial slope 95%/91%, lateral distal femoral angle 95%/91%, medial proximal tibial angle 91%/95%). The cumulative error of alignment showed no difference between the study groups. Seventeen of 21 (81%) patients fulfilled four criteria in the CT based group, and 15 of 21 (71.4%) patients fulfilled four criteria in the comparison group. Nineteen of 21 (90.5%) patients in both groups achieved three criteria in an optimal manner. An increased (p < 0.001) Insall knee score was found for changes over time in both study groups; however, there were no differences between the CT based or CT free patient groups. The postoperative ROM in both groups showed no difference at the 3-month and 2-year followup examinations. Both groups had an increase (p ≤ 0.002) in ROM between the 3-month and 2-year followup examinations. The examination of ligament balancing in full extension showed a higher rate of a stable soft tissue situation in the CT free navigation group but the difference was not significant. In 30° of flexion we detected a better (p = 0.004) ligament situation medially and laterally in the CT free group. The anterior drawer test showed a better (p = 0.035) stability in the CT free navigation group.

Discussion: The computed tomography free system provided equal radiographic results, but we found improved ligament balancing in the computed tomography free group. The computed tomography based module has an optimal preoperative planning procedure, but is more expensive and time consuming.

Introduction: The benefits of postoperative wound drainage in patients with total knee arthroplasty (TKA) with regards to mobilisation and wound healing were studied. We wanted to determine the efficacy of an autologous blood retransfusion system.

Materials and Methods: 150 patients with TKA were divided into three groups of 50 patients:

A) Three wound drainages with an autotransfusion system and suction;

Haemoglobin values, blood transfusion requirements, blood loss, postoperative range of motion, knee society score and rate of complications were observed and recorded. All patients were operated without tourniques for lower blood loss during total knee replacement.

Results: In the group of patients with wound drainage and a retransfusion system the requirement of postoperative additional blood transfusion was not significantly less than in the group without wound drainage. Group A had the most blood loss of all. The group without wound drainage had more haematoma and wound healing complications. Best results were observed within the group with one intraarticular drainage without suction. The rate of complications was not increased and the blood transfusion requirements were the lowest.

Conclusion: This study shows that total knee replacement involving one intraarticular wound drainage without suction attains the best results. During the last four years we used this wound drainage technique in 787 TKAs and can confirm all findings of this study.

Introduction: Existing data in the literature is supporting either patellar retention or patellar resurfacing during primary TKA. There is no clear answer for the question in which cases the patella should be retained or resurfaced during primary TKA.

Materials and Methods: In this prospective study 2 groups of patients with a mean follow up of 34 months after TKA were compared. 83 patients (98 TKA) were implanted with a TKA with patellar retention (group 1) while 93 TKA (86 patients) were done including a patellar resurfacing (group 2). The patients were randomized according to the year of birth. The NexGen® MBK and the LPS were implanted. A dome shaped patellar prosthesis with 3 pegs was used for patellar resurfacing. Clinical Outcomes were based on the knee society score parameters, anterior knee pain, patient satisfaction, feeling of instability, step test while component position and limb alignment were measured by standard radiographs.

Results: No statistical differences between both groups with regard to post-operative anterior knee pain and knee society score were found. We found no pre-operative predictor factors for the development of post-operative anterior knee pain for each group and both together. Patellar maltracking was worse in group 1 than in the resurfaced group (3 cases with patellar subluxation in group 1 versus 2 cases in group 2).

Conclusion: According to the not significant differences for the clinical outcomes between group 1 and 2 we routinely retain the patella. Patellar resurfacing is done only in selective cases.