Total knee replacement (TKR) smart tibial trials have load-bearing sensors which will show quantitative compartment pressure values and femoral-tibial tracking patterns. Without smart trials, surgeons rely on feel and visual estimation of imbalance to determine if the knee is optimally balanced. Corrective soft-tissue releases are performed with minimal feedback as to what and how much should be released. The smart tibial trials demonstrate graphically where and how much imbalance is present, so that incremental releases can be performed. The smart tibial trials now also incorporate accelerometers which demonstrate the axial alignment. This now allows the surgeon the option to perform a slight recut of the tibia or femur to provide soft-tissue balance without performing soft-tissue releases. Using a smart tibial trial to assist with soft-tissue releases or bone re-cuts, improved patient outcomes have been demonstrated at one year in a multicentre study of 135 patients (135 knees).

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):78–83.

INTRODUCTION:. Despite clear clinical advantages Unicompartimetal Knee Replacement still remain an high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how malalignment increases the rate of aseptic failure even more than in TKR. Computer-assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide despite no still proven clinical advantages. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested, even in partial knee reconstruction, as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of the study is to present a prospective study comparing 2 groups of UKR s using either a computer assisted technique or a CT-based Patient Specific Instrumentation. MATERIALS AND METHODS:. Since January 2010, 54 patients undergoing UKR because medial compartment arthritis were enrolled in the study prospectively. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or patient specific instrumentation group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA). In group B (27 knees) the implant (GMK Uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The surgical time and complications were documented in all cases. Six months post-operatively the patients underwent to the same radiological investigation to determine the frontal femoral component angle (FFC), the frontal tibial component angle (FTC), the hip-knee-ankle angle (HKA) and the sagittal orientation (slope) of tibial/femoral components. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients in each group with all 5 parameters within the desired range was calculated. Furthermore the 2 groups were clinically assessed using KSS and Functional score. RESULTS:. There were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axes, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. Discussion:. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical differences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

INTRODUCTION. Despite clear clinical advantages Unicompartimetal Knee Replacement (UKR) still remain a high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how in coronal tibial malalignment beyond 3° as well as tibial slope beyond 7° increase the rate of aseptic failure. Likewise, overcorrection in the coronal plain is a well recognised cause of failure because of an overweighting on the controlateral compartment. Furthermore it has been shown how in UKR surgery even using short narrow intramedullary guide this can cause errors in both coronal planes. Computer assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of this prospective study is to present comparing 2 groups of UKRs using either a computer assisted technique or a CT based PSI. MATERIALS AND METHODS. Since January 2010 54 patients undergoing UKR because of medial compartment arthritis were prospectively enrolled in the study. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or PSI group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA USA). In group B (27knees) the implant (GMK uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-Based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The duration of surgery and all the complications according to Kim classification were documented in all cases. Six months after surgery each patient had long-leg standing anterior-posterior radiographs and lateral radiographs of the knee. The radiographs were assessed to determine the Frontal Femoral Component angle (FFC), the Frontal Tibial Component angle (FTC), the Hip-Knee-Ankle angle (HKA) and the sagittal orientation (slope) of both tibial and femoral component. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients from each group with all 5 parameters within the desired range was calculated. Furthermore at the latest follow-up the 2 groups were clinically assessed using KSS and Functional score. RESULTS. At the last assessments there were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axis, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. DISCUSSION. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical diffences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

Introduction. The importance of frontal and rotational alignment in total knee arthroplasty has been published. Together with conventional instrumentation, computer navigation has been used for many years now. The pro's and con's of navigation are well known since. Materials & Methods. We present the results of our first 200 total knee arthroplasties with a Patient Specific Instrument System, called Signature (Biomet). With this system an MRI of the hip, knee and ankle is performed. Based on these images, mechanical axis and rotational landmarks are decided. Preoperative planning and templating is done with a computer program. Alignment, rotation, slope, size, positioning and gaps are planned with the software. Based on this templating a femoral guide and a tibial guide are custom made (Materialise) for each patient that will allow only one unique fit and position. Both of these guides are no cutting guides but pinning guides. From that stage on Vanguard Total Knee (Biomet) is implanted with this system applying conventional surgical techniques and rules. Preoperative alignment was measured on standing full leg X-rays. Rotational alignment was set according to the epicondylar axis. Slope was by default fixed at 3° posterior slope. Femoral flexion was set at 3° by default. Sizing was done with the system. Tourniquet time, blood loss, mean Hb drop and lateral release rate as hospital stay were analyzed. Postoperative full leg X-rays and CT scan were analyzed. Results. Preoperative alignment range between 18° varus and 19° valgus. Sizing was accurate in 82% of cases. Postoperative alignment was accurate in 90% of cases with a range between 0° and 2°. The 2° of varus was often seen on a standing full leg but not on the lying CT scan. Our normal range of alignment is +/− 3°. Rotational alignment was better in valgus knees in the PSI group. Tourniquet time was 10 minutes shorter. The blood loss was dramatically reduced since intramedullary canals were not violated. Mean Hb drop was 1,2 g/dl. No lateral releases were performed. Hospital stay was 5 days (return to home). Extra cost was MRI and guides for a total of 500 euros. Conclusions. Patient specific templating gives excellent results both clinically and radiographically. OR time is reduced resulting in cost reduction. Avoiding IM rods will reduce blood loss and possible bone marrow embolisation. Especially in minimally invasive valgus knees this system is advantageous, helping in femoral rotational and tibial alignment. Signature allows to apply conventional surgical techniques with navigation-like control on the cuts

Introduction: No comparison between minimally invasive TKR using traditional alignment guides and computer navigation systems has been documented in the literature. The aim of this prospective randomised trial is compare the radiological results of 2 different groups of TKRs performed with a less invasive surgical approach (mini-parapatellar) using either a traditional hand guided technique (MIS) or the assistance of a computer assisted alignment system (MICA). Materials and Methods: Since 2004 seventy-four patients undergoing TKR with the same implant have been enrolled in the study. Inclusion criteria included a body-mass index less than 30, no major ligamentous laxity, no flexion deformity and no previous open knee surgery. Patients were randomly assigned to either the traditional or computer-assisted alignment group opening a closed envelope just prior to the skin incision. In the MIS group (37 knees) a minimally invasive approach was performed using an intramedullary femoral guide and an extramedullary tibial guide. In the MICA group (37 knees) the implant was positioned using a CT-free computer assisted alignment system (Vector Vision, version 1.52, BrianLAB, Munich, Germany) using the same minimally invasive surgical approach (mini-parapatellar). The duration of surgery was documented in all cases. Eight months after surgery each patient had long-leg standing anterior-posterior radiographs and lateral radiographs of the knee. All the radiographs were always taken with a standardized protocol with the same magnification. The radiographs were assessed by an independent radiologist blinded to the original procedure to determine the frontal femoral component angle (FFC), the frontal tibial component angle (FTC), the hip-knee-ankle angle (HKA) and the sagittal orientation (slope) of both femoral and tibial components. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients from each group with all 5 parameters within the desired range was calculated. Results: The mean surgical time was 89.4 minutes (range: 75–112) in the MICA group and 75.84 minutes (range: 48–106) in the MIS group. This difference was statistically significant (p< 0.001). The alignment of the femoral component as determined by the slope was significantly better in the MICA group (p< 0.001). Comparison of the FTC angle showed a statistically better alignment in the MICA group (p< 0.029). There were no statistical significant differences in HKA, FFC angles and in the slope of the tibial component between the 2 groups. All the implants in the MICA group achieved HKA and FTC angles aligned within this range while only 31 implants (83.8%) in the MIS group achieved similar accuracy. These differences in HKA and FTC angles were statistically significant (p=0.025). Thirty-six (97.3%) implants in the MICA group achieved a femoral slope aligned within 3 degrees of the desired position compared with 31 (83.8%) implants in the MIS group. In the MICA group 36 implants (97.3%) achieved a tibial slope aligned within this range while in the MIS group 33 implant (86.5%) achieved a similar result. A FFC angle aligned within 3 degrees of the desired position was achieved in 35 (94.6%) and 32 (86.5%) of the implants in the MICA and MIS groups respectively. These differences in femoral and tibial slope and FFC angle were not statistically significant. A statistically significant difference (p< 0.001) in the total number of outliners was seen with 158 and 181 in the MICA and MIS groups respectively. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the MICA group (p=0.001). Thirty-three implants (89.2%) in the MICA group and 20 (54.1%) in the MIS group were correctly aligned in all measured parameters. Discussion: Minimally invasive joint replacement has become increasingly popular driven both by the orthopaedic community and patient expectations. However, malalignment has been identified as a potential problem when performing joint replacement surgery through small incisions. Minimally invasive techniques can make implant positioning more difficult by limiting visualisation of anatomical landmarks. As the matter of fact many theory has been proposed for knew more conservative surgical approaches to the soft tissue such as the mid-vastus or sub-vastus even without any consideration about what already centuries ago biologist had established. At the beginning of the last century Bizozzero already compared muscle to nerve as perpetual tissues which can recover after an injury only with scared. However recently, after initial enthusiasm, authors have recommended caution when using mini-invasive techniques for total joint replacement. Computer-assisted surgery has the potential to address the difficulties of correct component positioning and alignment in minimally invasive knee replacement. Recently a prospective randomised study comparing computer navigation assisted minimally invasive TKR to conventional TKR reported a lower incidence of radiological outliners and better pain score in the computer navigation group. In this prospective randomized the comparison of the radiological results showed statistically significant differences between the 2 groups for component positioning both in the coronal plane and sagittal plane. The desired femoral slope and FTC angle were achieved in significantly more patients in the MICA group than the MIS group. Furthermore the results supported previous studies showing a statistically significant reduction in the number of outliners in the computer-assisted technique. In addition, the number of implants with all parameters aligned within desired values was statistically higher in the MICA group. No complications were seen in either group however the surgical time was statistically longer in the MICA group. Longer follow-up will be needed to demonstrate any correlation between the lower numbers of outliners and superior clinical outcome and implant survivorship in the computer navigation group

Two computer assisted techniques (CT and a fluoro-guide based system) were used to insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. The accuracy and variability of component positioning were compared. Clinical data was collected pre-operatively and is being collected post-operatively. Standing AP and lateral knee X-rays as well as skyline X-rays were collected pre-operatively and post-operative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Results are showing accurate insertions of the Oxford knee femoral component using both systems.

To review two computer-assisted techniques for inserting Oxford Unicompartmental Knee arthroplasties. CT based and fluro based techniques were compared with regards to accuracy and variability of component positioning.

Currently we are able to use either a CT based system or a fluro based system to accurately insert the femoral component of the Oxford Unicompartmental Knee arthroplasty.

Computer assist techniques are allowing us to perform minimally invasive arthroplasty procedures with great accuracy.

Patients were all seen in a pre-admission clinic where pre-operative clinical survey data were collected. All patients had standing AP and lateral knee X-rays as well as skyline X-rays pre-operatively. Post-perative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Patients are being followed post-operatively with SF-36, WOMAC, Knee Society Scores, and X-rays. Patients being operated on with the CT based system had pre operative CT scans. Intra-operatively a DRB was fixed to the patient’s femur and the chosen computer assisted technique was used to direct the rotation of the tibial cut as well as the alignment of the femoral cutting jig. To date we have completed seventeen computer assisted Oxford Unicompartmental Knee Arthroplasties. The average error in the AP plane using CT based system was 3.2 degrees and 2.1 degrees for the lateral plane. The average error in the AP plane using the fluro-based system was 2.2 degrees and 1.3 degree for the lateral plane.

Funding: NSERC, IRIS, ORDCF

Two computer assisted techniques (CT and a fluoro-guide based system) were used to insert the femoral component of the Oxford Unicompartmental Knee arthroplasty. The accuracy and variability of component positioning were compared. Clinical data was collected pre-operatively and is being collected post-operatively. Standing AP and lateral knee X-rays as well as skyline X-rays were collected pre-operatively and post-operative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Results are showing accurate insertions of the Oxford knee femoral component using both systems.

To review two computer-assisted techniques for inserting Oxford Unicompartmental Knee arthroplasties. CT based and fluro based techniques were compared with regards to accuracy and variability of component positioning.

Currently we are able to use either a CT based system or a fluro based system to accurately insert the femoral component of the Oxford Unicompartmental Knee arthroplasty.

Computer assist techniques are allowing us to perform minimally invasive arthroplasty procedures with great accuracy.

Patients were all seen in a pre-admission clinic where pre-operative clinical survey data were collected. All patients had standing AP and lateral knee X-rays as well as skyline X-rays pre-operatively. Post-perative full length AP and lateral femur X-rays were completed in order to measure alignment of the femoral component. Patients are being followed post-operatively with SF-36, WOMAC, Knee Society Scores, and X-rays. Patients being operated on with the CT based system had pre operative CT scans. Intra-operatively a DRB was fixed to the patient’s femur and the chosen computer assisted technique was used to direct the rotation of the tibial cut as well as the alignment of the femoral cutting jig. To date we have completed seventeen computer assisted Oxford Unicompartmental Knee Arthroplasties. The average error in the AP plane using CT based system was 3.2 degrees and 2.1 degrees for the lateral plane. The average error in the AP plane using the fluro-based system was 2.2 degrees and 1.3 degree for the lateral plane.

Funding: NSERC, IRIS, ORDCF

Introduction: There has been significant development in computer technology in recent years and this has led to applications in orthopaedic surgery. Of particular interest is computer assisted joint arthroplasty to enable accurate insertion of the components based on CT generated images of the patient’s bones. Methods: Twenty-five patients have undergone computer assisted total knee arthroplasty using a computer guidance system (Vector Vision, Brain Lab, Munich) implanting a PFC cruciate retaining total knee replacement (TKR) (Depuy, Leeds). Pre-operative CT scans were obtained from each patient and alignment and sizing were calculated before surgery. Intra-operatively, an infrared camera tracked the instruments and the patient’s limb was accurately mapped in space by surface matching the bone and comparing it with the CT scan. For the purpose of the study the computer generated alignments and sizing were evaluated along with the use of traditional instruments and stored in a database. Results: These have been evaluated comparing computer assisted and instrumented knee arthroplasty. Variables measured include the AP femoral cuts, rotational femoral alignment, and tibial axis alignment in AP and lateral planes. Conclusions: Computer assisted orthopaedic surgery has undergone a rapid development in the last 18 months to enable real-time intra-operative images to be viewed in a moving limb with a degree of accuracy previously not possible. The use of this technology may lead to more accurate alignment of hip and knee prostheses and therefor help to reduce wear in the long-term