Background

There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty.

Total knee arthroplasty using navigation system is known to be more effective than conventional methods in achieving more accurate bone resection and neutral alignment. Mobile bearing is also known to reduce wear and automatically correct rotational mal-alignment of the tibia but the long-term follow-up results of more than 10 years are extremely rare. The purpose of this study is to investigate the results of clinical and radiologic long-term follow-up and complications of total knee arthroplasty using navigation and multi-directional mobile bearing.

From 2003 to 2006, a total of 111 navigation TKAs using multi-directional mobile bearing design were carried out and reviewed retrospectively. TKAs were performed by two experienced surgeons at one institute. Of the 111 patients, 102 were women and 9 were men. The mean duration of follow-up was 11.4 ± 1.0 years (range, 10.1 to 14.08 years). Clinical outcomes were evaluated in terms of Knee Society Score, Hospital for Special Surgery score, Western Ontario and McMaster University (WOMAC) score, range of motion and complications. Long-term radiological outcomes and survival rates were evaluated at least 10 years.

Average preoperative HSS score was 66.5 ± 9.8 and KSS pain and function score were 25.0 ± 11.8 and 44.5 ± 12.3, respectively. Scores improved to 94.1 ± 8.2, 46.6 ± 11.6 and 88.2 ± 14.6 at the last follow up, respectively. Mean preoperative WOMAC scores of 75.8 ± 16.5 improved to 13.8 ± 16.0 at last follow-up. Five knees required re-operation, two for liner breakage for liner wear, one for distal femoral fracture and one for infection. The estimated 10-year prosthesis survival rates for any reason and for prosthesis-related problems were 95.5% and 97.4%, respectively. TKAs using each techniques resulted in similar good clinical outcomes and post-operative leg alignments. Robotic and navigation TKA appeared to reduce the number of postoperative leg alignment outliers and revision rate compared to conventional TKA.

Background

There are limited previous findings detailed biomechanical properties following implantation with mechanical and kinematic alignment method in robotic total knee arthroplasty (TKA) during walking. The purpose of this study was to compare clinical and radiological outcomes between two groups and gait analysis of kinematic, and kinetic parameters during walking to identify difference between two alignment method in robotic total knee arthroplasty.

Among many factors that influence the outcomes of Total Knee Arthroplasties (TKAs), the mechanical alignment has played major roles for the success of TKA, the survival rates of the implants, and patient functionality. Most, but not all, studies have shown that alignment of the mechanical axis in the coronal plane within a range of 3° varus/valgus is associated with improved long-term function and increased survival rates. Robot-assisted TKA has been developed to improve improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. We hypothesised that robot-assisted TKA would lead to a more accurate leg alignment and component implantation, and thus, improve radiological and clinical outcomes.

Between January 2003 and December 2004, a total of 98 primary TKA procedures were compared: 49 using a robotic-assisted procedure and 49 using conventional manual techniques. The cohorts were followed for 121.2 and 119.5 months on average, respectively. Radiographic assessments of the patients were performed preoperatively and at final follow-up and made according to the Knee Society Roentgenographic Evaluation System (KSRES) which included measurements of the coronal mechanical axis and sagittal and coronal inclinations of femoral and tibial components. The radiographic measurements were made using a PACS (Picture Archiving and Communication System). Clinical assessments were performed preoperatively, and at a final follow-up date that was a minimum of postoperative nine years. The clinical results included ranges of motion (ROM), Hospital for Special Surgery (HSS) scores, Western Ontario and McMaster University (WOMAC) scores (for pain and function).

The radiographic results showed no statistical differences when comparing the means of the two groups. When considering outliers (defined as error ≥ ±3°) for the mechanical axis, femoral coronal and sagittal inclinations, and tibial coronal and sagittal inclinations, the ROBODOC group had zero outliers for all measurements except for one in tibial sagittal inclination. On the other hand, the conventional group had 12 outliers for mechanical axis, 2 for femoral coronal inclination, 3 for femoral sagittal inclination, 3 for tibial coronal inclination, and 4 for tibial sagittal inclination. However, there were no statistically significant differences between groups for ROM, HSS, or WOMAC scores at the final follow-up.

The results of this study support previous work and demonstrate that the ROBODOC-assisted implantation of TKA results in better radiographic outcomes and better ligament balance with equivalent safety when compared to conventional TKA at a minimum follow-up of nine years.

Background

Navigation systems that increase alignment accuracies of the lower limbs have been applied widely in total knee arthroplasty and are currently being adopted for minimally invasive UKA (MIS UKA) with good alignment results. There is little debate that when compared with total knee arthroplasty (TKA), UKA is less invasive, causes less morbidity, better reproduces kinematics, and therefore offers quicker recovery, better range of movement and more physiologic function.

However, despite improved alignment accuracies, advantages of use of navigation system in UKA in clinical outcomes and survivals are still debatable. To the best of our knowledge, no reports are available on the long-term results after UKA performing using a navigation system. The purpose of this prospective study was to compare the radiological, clinical, and survival outcomes of UKA that performed using the navigation system and using the conventional technique at average 8 years follows up.

Background

The most important factors affecting the outcome of a TKA are restoring the normal mechanical axis and achieving optimum soft tissue balance. In the measured resection technique may have accompanying problems in imbalanced patients. Secondly individual variability of the reference points may affect the alignment of the bony cuts and thereby the alignment of the implant. The gap balance technique blends the soft tissue balance with the bony cuts and tries to overcome this problem. However proponents of the measured resection technique argue that no consideration is given to the coronal and rotational alignment of the femoral component in the gap balance technique. The ligament specific navigation assisted gap balance technique, tries to overcome these fallacies. The lateral ligaments and soft tissues act as a reference against which the medial soft tissues are balanced. Thus the reference becomes individualized and any variability is taken care of. Navigation assistance ensures control of the coronal and rotational alignment of the femoral component. The aim of the present study was two fold: - To describe our methodology of ligament specific navigation assisted gap balance technique and analyze the clinico-radiological outcome of our technique over an eight year follow up.

Background

Stability of total knee arthroplasty (TKA) is dependent on correct and precise rotation of the femoral component. Multiple differing surgical techniques are currently utilized to perform total knee arthroplasty. Accurate implant position have been cited as the most important factors of successful TKA. There are two techniques of achieving soft gap balancing in TKA; a measured resection technique and a balanced gap technique. Debate still exists on the choice of surgical technique to achieve the optimal soft tissue balance with opinions divided between the measured resection technique and the gap balance technique. In the measured resection technique, the bone resection depends on size of the prosthesis and is referenced to fixed anatomical landmarks. This technique however may have accompanying problems in imbalanced patients. Prediction of gap balancing technique, tries to overcome these fallacies. Our aim in this study was twofold: 1) To describe our methodology of ROBOTIC TKA using prediction of gap balancing technique. 2) To analyze the clinico-radiological outcome our technique comparison of meseaured resection ROBOTIC TKA after 1year.

This prospective study was undertaken to compare the clinical and radiological results and the in vivo stabilities of anteromedial (AM) and posterolateral (PL) bundle augmentation during anterior cruciate ligament (ACL) reconstruction.

Forty-two ACL partial tears that underwent isolated bundle augmentation (22 AM and 20 PL bundles) were evaluated with a minimum follow-up of 1 year. For in vivo intraoperative stability testing, anteroposterior and external/internal rotation stabilities were measured at 0, 30, 60, and 90° of flexion using a navigation system. Ranges of motion, Lachman and pivot shift test results, Tegner activity scores, and Lysholm knee scores of the AM and PL bundle groups were compared. In addition, Telos arthrometer determined stabilities were compared.

In-vivo intraoperative stability testing showed that mean preoperative anterior translation at 30° of flexion was greater in the AM group (8.7 vs. 6.5, p = 0.04), whereas mean rotational amount was larger in the PL group (by 2.9 at 0° and 3.6 at 30° of flexion). After ACL reconstruction, no significant differences were found between the two groups in terms of anterior and rotational stabilities at any flexion angle. Furthermore, clinical outcomes in the two groups were not significantly different. Lachman and pivot shift test results and instrumented laxity findings were similar for the two groups at final follow up.

In this study, the authors carefully preserved the remnant injured ACL, and achieved excellent anterior stability recoveries and good rotatory stabilities. No significant intergroup difference was found in terms of intraoperative stability or clinical parameters after ACL reconstruction.

The purpose of this study were to evaluate early intra-operative experiences of a custom-fit total knee arthroplasty (TKA) system and to determine the precision of long leg alignment and component placement achieved using this system.

Seventeen patients underwent sagittal MRI of an arthritic knee to determine component placement for TKA from October 2010 and March 2011. Cutting guides were machined to control all intra-operative cuts, and cutting guide placements were recorded by navigation system. Radiographic parameters regarding mechanical axis changes, and inclinations of the femoral and tibial components were measured. Outcome was defined as “excellent” when values of each parameters were within ± 2°, as “acceptable” when within ± 3°, and as “outliers” when >± 3° of optimum.

The cutting guide placement was within ±2° of the target angle for inclinations of femoral and tibial components. The cutting heights were within 2mm for distal femoral and proximal tibia. Mechanical axis changed from a mean of 8.57° varus to 0.49° valgus, and mean coronal inclinations of femoral and tibial components were 89.52° and 90.12°, respectively, at last follow up visits. There were no outliers and all of them were classified as excellent. Mean sagittal inclinations of the femoral and tibial components were 1.06° and 84.56°, respectively. There were no intra-operative or acute post-operative complications.

The custom-fit TKA system system provides an effective, safe means of achieving an accurate mechanical axis and of reducing prosthetic alignment outliers. However, further long term follow-up is needed.

The elevation of the joint line is considered a possible cause of mid-flexion instability in total knee arthroplasty (TKA). The authors evaluated the effects of joint line change on mid-flexion stability in cruciate retaining TKA.

Seventy-nine knees treated by cruciate retaining TKA using a modified balanced gap technique were included in this prospective study. After prosthesis insertion, valgus and varus stabilities were measured under valgus and varus stress using a navigation system at 0, 30, 60 and 90° of knee flexion. Changes of joint lines were measured preoperatively and postoperatively and compared. The knees were allocated to a “No change group (≤4mm, 62 patients)” or to an “Elevation group (>4mm, 17 patients)”. Medio-lateral stabilities (defined as the sums of valgus and varus stabilities measured intra-operatively) were compared in the two groups.

The mean joint line elevation was 4.6mm in the no change group and 1.7mm in the elevation group. Mean medio-lateral stability at 30° of knee flexion was 4.8±2.3 mm in the no change group and 6.3±2.7 mm in the elevation group, and these values were significantly different (p = 0.02). However, no significant differences in medio-lateral stability were observed at other flexion angles (p>0.05).

Knees with a < 5mm joint line elevation provide better mid-flexion stability after TKA. The results of this study suggest that a < 5mm elevation in joint line laxity is acceptable for cruciate retaining TKA.

This study was performed to measure intra-operative varus-valgus laxities from 0° to 90° of flexion during cruciate retaining total knee arthroplasty (TKA) using the modified balanced gap technique. Forty nine patients awaiting unilateral TKA for osteoarthritis were enrolled into this prospective study. Flexion and extension gaps were measured at full extension and at 90° of flexion using a tensioning device before femoral bone cutting. After implantation and closing the medial parapatellar arthrotomy, varus-valgus laxities at 0, 30, 60 and 90° of flexion were also measured using a navigation system.

Mean total varus-valgus laxities were significantly less at 0° of flexion (3.8±1.7°) than at the other selected flexion angles. Mean varus laxity was peaked at 3.1±2.2° at 60° of flexion and reached a nadir of 2.0±1.0° at 0° of flexion, which represented a significant difference. On increasing flexion from 0° to 60°, mean valgus laxity increased from 1.8±1.3° to 2.9±1.6°, which was significant, but no significant difference was found for other angles.

The use of the balanced gap technique for cruciate retaining TKA using a navigation system, which allows accurate soft tissue balancing via real time gap size feedback, could be helpful for achieving good in vivo laxities throughout range of motion without significant mid flexion laxity.

Recently, axial radiography has received attention for the assessment of distal femur rotational alignment, and satisfactory results have been as compared with the CT method. The purpose of this study was to assess rotational alignment of the femoral component in knee flexion by axial radiography and to compare flexion stabilities achieved by navigational and robotic total knee arthroplasty (TKA). In addition, the authors also evaluated the effects of flexion stability on functional outcomes in these two groups.

Sixty-four patients that underwent TKA for knee osteoarthritis with a minimum of follow-up of 1 year constituted the study cohort. Patients in the navigational group (N = 32) underwent TKA using the gap balancing technique and patients in the robotic group (N = 32) underwent TKA using the measured resection technique. To assess flexion stability using axial radiography a novel technique designed by the authors was used. Rotations of femoral components and mediolateral gaps in the neutral position on flexion radiographs was measured and compared. Valgus and varus stabilities under valgus-varus stress loading, and total flexion stabilities (defined as the sum of valgus and varus stability) were also compared, as were clinical outcomes at final follow up visits.

A significant difference was found between the navigation and robotic groups for mean external rotation of the femoral component (2.1° and 0.4°, respectively; p = 0.003). Mean mediolateral gap in neutral at 90° flexion position was 0.17° in the navigation group and 0.07° in the robotic group (p = 0.126), and mean total stability was 7.82° in the robotic group and 8.10° in the navigation group (p = 0.35). Clinically, no significant intergroup difference was found in terms of ranges of motion, HSS scores, KS scores, or WOMAC scores.

Both navigational and robotic techniques provide excellent clinical and flexion stability results. Furthermore, axial radiography was found to provide a useful, straightforward means of detecting rotational alignment, flexion gaps, and flexion stability.

The purpose of this study was to compare posterior tibial slope preoperatively and postoperatively in patients undergoing navigational opening-wedge High tibial osteotomy (HTO) and to compare posterior slope changes for 2 and 3-dimentional (D) navigation versions.

Between May 2009 and September 2010, 35 patients with unicompartmental osteoarthritis and varus deformity were treated by navigation-assisted open-wedge HTO. Patients were randomly divided into two groups according to the version of the Orthopilot (Aesculap) navigation system used; 2D group (18 patients, 2-D version) and 3D group (17 patients, 3-D version). Radiologic evaluations were conducted using pre- and postoperative leg axes. Posterior slope of proximal tibiae were measured using the proximal tibial anatomic axis method.

Postoperatively the mechanical axis was corrected adequately to a mean valgus of 2.81° in 2D group and of 3.15° in 3D group. Mean posterior slopes were well maintained, and measured 7.9° and 10.3° preoperatively and 8.99° and 9.14° postoperatively in 2D and 3D groups, respectively. No significant difference was found between the two navigation versions with respect to posterior tibial slope; mean tibial slope changes were 1.09° and −0.2° in 2D and 3D groups (p = 0.04).

Navigation-assisted opening-wedge HTO greatly improves the accuracy of the desired postoperative mechanical femorotibial axis and posterior tibial slope, and the use of 3D navigation results in significantly less change in posterior tibial slope. The authors recommend the use of the 3D navigation because they provide real time intraoperative information about coronal, sagittal, and transverse axis, which are important for the maintenance of a normal posterior tibial slope.

The preoperative prediction of gap balance after robotic total knee arthroplasty (TKA) is difficult. The purpose of this study was to evaluate the effectiveness of a new method of achieving balanced flexion-extension gaps during robotic TKA.

Fifty one osteoarthritic patients undergoing cruciate retaining TKA using robotic system were included in this prospective study. Preoperative planning was based on the amount of lateral laxity in extension and flexion using varus stress radiograph. After complete milling by the robot and soft tissue balancing, intra-operative extension and flexion gaps were measured using a tensioning device. Knees were subdivided into three groups based on lateral laxities in 0° and 90° of flexion, as follows; the tight extension group (≥ 2mm smaller in extension than flexion laxity), the tight flexion group (≥ 2mm smaller in flexion than extension laxity), and the balanced group (< 2mm difference between laxities). In addition, intra-operative gap balance results were classified as acceptable (0–3mm larger in flexion than in extension), tight (larger in extension than in flexion) or loose (> 3mm larger in flexion than in extension) based on differences between extension and flexion gaps.

During preoperative planning, 34 cases were allocated to the balanced group, 16 to the tight extension group and 1 case was allocated to the tight flexion group. Intra-operative gap balance was acceptable in 46 cases, 4 cases had a tight result, and one case had a loose flexion gap.

We concluded that preoperative planning based on the amount of lateral laxity determined using varus stress radiographs may be useful for predicting intraoperative gap balance and help to achieve precise gap balance during robotic TKA.

We hypothesized that navigation can help provide a well-balanced knee, through real-time feedback of alignment accuracies and gap sizes in flexion and extension. The purpose of this study was to evaluate in vivo stabilities of mediolateral laxity in full extension and anteroposterior laxities in 90° of flexion after navigation-assisted total knee arthroplasty, and to determine the nature of the correlations between these and range of motion (ROM).

Forty-two total knee arthroplasties performed using a navigation system with a minimum two-year follow-up were included. The following were measured at final follow-ups; mediolateral laxities at extension and anteroposterior laxities at 90 degrees of flexion (using stress radiographs and a Telos arthrometer), modified HSS scores (excluding laxity and range of motion), and range of motion (ROM).

At final follow-up the mean modified HSS score was 82% of total points and mean postoperative ROM was 128.1 ± 10.4°. Mean medial laxity was 3.5 ± 1.4°, mean lateral laxity 4.4 ± 2.2°, and mean anteroposterior laxity 7.1 ± 4.1 mm. We found no significant correlation between mediolateral laxity and postoperative ROM. However, a significant correlation was found between postoperative ROM and anteroposterior laxity.

In the present study, the use of a navigation system in total knee arthroplasty was found to improve in vivo stability and produce promising short-term clinical results.

Summary: Using a navigation system in total knee arthroplasty, we obtained good in vivo stability and found the positive correlation between the range of motion and anteroposterior laxity

Only limited data exists concerning outcomes after total knee arthroplasty (TKA) using a surgical robot. We conducted this study to evaluate the clinical and radiographical results in robotic-assisted implantation of TKAs with a minimum follow-up of two years.

A total of 50 primary TKAs using ROBODOC were included in this study. The mean duration of follow-up was 28.3 months. The radiographic measurement with regard to the change of mechanical axis, and the inclination of the femoral and tibial components were assessed. The value within ± 3° of optimum was classified to be “acceptable”, and the value exceeding more than ± 3° to be “outlier” results. Also we evaluated clinical results with the range of motion (ROM), Hospital for Special Surgery (HSS) scores, and Western Ontario and McMaster University (WOMAC) scores.

The mechanical axis was changed from 6.57 varus to 0.81 valgus. Mean coronal inclination of the femoral and tibial component were 88.61 and 89.76 at the last follow up. Also, mean sagittal inclination of the femoral and tibial component were 0.82 and 85.49. On the other hand, all prostheses had no radiolucent lines. On the clinical assessment, the range of motion improved from 124.9 to 128.4, and the improvement of HSS score and Womac score were 70.06 to 95.72 and 65.64 to 28.92 in each. No major adverse events related to the use of the robotic system have been observed. However, one case of the formation of seroma around the pin track and two cases of the partial abrasion of patellar tendon occurred in relation to procedures.

A surgical robot system in TKAs provides good clinical and radiographical results at least 2 years follow-up, however further study for the long term follow-up may be needed. A clear advantage of robot-assisted TKA seems to be ability to execute a highly precise preoperative planning and intraoperaive procedures. But current disadvantages such as increased operating times and inability of adjusting the preoperative planning during the procedure have to be resolved in the future.

Navigation was used to achieve a balanced flexion-extension gap for total knee arthroplasty and it’s 3 years clinical results were reported.

From 112 osteoarthritic knees with varus deformity the flexion and extension gap were measured with distraction of 50 lb/inch using special torque wrench following completion of controlled medial release with guidance of navigation system & tibial bone cut. Distal & AP femoral bony cut were finished according to the data of measurement of flexion-extension gap. After confirmation of the balanced flexion-extension gap by navigation total knee arthroplasty was completed.

The differences between flexion and extension gap varied from case to case, and could be classified into 3 kinds; balanced, tight flexion gap and tight extension gap.

HSS score was 96.7, ROM was 128.5 degree. 39 patients (35%) can have comfortable kneeling 75 patients(67%) can sit with cross leg. Gap technique with navigation could provide excellent clinical results of total knee arthroplasty and 3 classifications of flexion and extension gap should be taken into considerations for balanced total knee arthroplasty

Long term successful results of high tibial osteotomy (HTO) strongly depend on the degree of correction, and inadequate intraoperative measurements of the leg axis can lead to under or over correction, and surgeons have to solve these problems based on personal experience.

This study was undertaken to investigate and compare the clinical and radiological results of navigation assisted open wedge high tibial osteotomy (HTO) versus conventional HTO at 12 months after surgery, for unicompartmental gonarthrosis.

Forty navigated open HTOs with an anterior opening gap of approximately 70% of the posterior gap were included and compared with forty open HTOs performed using the conventional cable technique in terms of intraoperative leg axis assess.

Navigated HTOs corrected mechanical axes to 2.9° valgus (range 0.5–6.2) with few outliers (12.5%), and maintained posterior slopes (7.9±2.3° preoperatively and 8.3±2.8° postoperatively) (P> 0.05). However, in the conventional group, only 63% of cases were within the satisfactory range (valgus 2–5°), and tendencies toward undercorrection and an increase in posterior slope were observed. Clinically both groups showed satisfactory results.

Navigated HTO significantly improved the accuracy of postoperative mechanical axis and decreased correction variabilities with fewer outliers.

Unexpected findings were sometimes observed such as hyper extension, oversize of femoral component, or anterior notching of anterior femoral cortex in total knee arthroplasty (TKA) using computer system. We conducted this study to evaluate these findings by a virtual simulation using ORTHODOC and then confirmed them on real patients with TKA.

Virtual simulations of distal femoral cut in 50 patients using ORTHODOC system were made by way of being perpendicular to mechanical axis (CAOS way) and to intramedullary guide (manual way) in the same knee and measured the difference of sagittal cutting planes. We compared the maximum AP dimensions of femoral condyle parallel to distal cut plane. We also compared sagittal alignment and size of the femoral component in 30 bilateral TKAs, one side using ROBODOC (CAOS way) and the other side using IM guide (manual way).

On virtual simulation, distal femoral cut was more extended (3.1±1.6°) in CAOS than in manual way and anteroposterior size of the femoral condyle in CAOS way was also larger than in manual way (p=0.001). Radiographic sagittal alignment of femoral component performed using CAOS way was slightly more extended than those using manual way, showing a significant difference (p=0.024). The larger femoral components were required in six patients on CAOS and in two patients on manual way, whereas twenty-two patients showed same size on both side.

CAOS can provide more accurate sagittal cut perpendicular to mechanical axis than manual system, which may lead to slightly extended position or larger femoral component.

In total knee arthroplasty, navigation systems that help achieve accurate alignment of the lower limbs have been applied widely, and these techniques are currently being used in minimally invasive unicondylar knee arthroplasty (MIS UKA) with good alignment results. To the best of our knowledge, there are no studies showing whether or not MIS UKA using a navigation system has a significant influence on the clinical results. This prospective study investigated the hypothesis that minimally invasive uni-compartmental knee arthroplasty using navigation system (NA-MIS UKA) will produce better short-term clinical results than MIS UKA without navigation system.

After a minimum two-year follow-up, the short-term functional results included the ranges of motion, Hospital for Special Surgery (HSS) scores, and WOMAC scores and the alignment accuracy of the components of 31 NA-MIS UKAs (NA-MIS group) compared with those of 33 MIS UKAs without a navigation system (MIS group). The surgery time was also recorded and compared.

The HSS and WOMAC scores showed significant improvement at the final follow-up in both groups, showing no significant inter-group difference (p=0.071, p=0.096, respectively). The ranges of motion also showed significant improvements in both groups, but there was no significant difference between two groups (p=.687). However, the surgery time was longer in MIS group than in NA-MIS group. NA-MIS UKA produces significant improvement in the desired mechanical axis with prosthetic alignment outliers compared with that without the navigation system.

However, at the final follow-up, there were no significant differences in any of the functional parameters between the two groups.