Abstract

Objective. We performed total knee arthroplasty (TKA) without patella resurfacing in patients with osteoarthritis (OA) of the knee. The purpose of the present study was to evaluate the clinical results and the appropriateness TKA without patella resurfacing. Methods. A total of 61 patients (61 affected knees) who had undergone a Low Contact Stress mobile − bearing knee arthroplasty (LCS− TKA) (Depuy, Warsaw, IN. USA) 10 years or more before the present study were enrolled. The LCS− TKAs did not include patella resurfacing. The patients' mean age was 77.7 ± 6.1 years (range: 59−94 years). The mean follow-up period was 121 ± 2.4 months (range: 120−129 months). The clinical evaluation used the scoring system for OA of the knees issued by the Japanese Orthopaedic Association (JOA score). We defined patellofemoral (PF) pain, crepitation, patellar clunk syndrome, spin-out, and reoperation as complications. We also used X-Ray imaging to measure the component angle, patella height, lateral shift ratio, tilting angle, femorotibial angle, posterior condylar offset and joint line, and evaluated the localization of sclerotic changes in the patella. All of the LCS− TKAs were performed by one surgeon using the midvastus approach. During the operation, the osteophyte around the patella was resected, and the osteophyte on the articular surface was shaped using a bone saw. For statistical analysis we performed Mann-Whitney's U test and adopted a significance level of P<5%. Results. The average JOA score improved significantly from 46.2 ± 10.4 before the LCS− TKA to 82.6 ± 6.1 after the LCS− TKAs (P = 0.0002). No cases of patellar clunk syndrome or spin-out. occurred. Revision surgery was performed for two cases, one involved an infection, and the other involved a patella fracture. Postoperative PF pain was found in 6 patients (6 affected knees) at the final evaluation. However, in these patients, the pain was less severe than it had been preoperatively, and revision surgery for PF pain was needed or performed. The postoperative radiological evaluation was favorable on the whole. The localization of sclerotic changes in the patella on X-ray were in 32 cases around tip of the patella, on the other no remarkable change were in 29 cases. Conclusion. The clinical and radiological evaluations of the patella non−resurfacing mobile bearing total knee arthroplasty was favorable overall. Treatment of the patella in total knee arthroplasty remains controversial. We suggest that the patella in LCS−TKAs does not always need to be resurfaced

Peri-prosthetic wound infections can complicate total knee arthroplasty (TKA) in 1–1.5% of cases and may require the input of a combined orthopaedic and plastic surgery team. Failure of optimal management can result in periprosthetic joint infection, arthrodesis or in severe cases limb amputation. A retrospective 11-year review of TKA patients was undertaken in a single unit. Data was collected on a proforma and patient demographics were identified by case note analysis. Incidence of periprosthetic wound infections was recorded. A protocol to standardise treatment was subsequently developed following multidisciplinary input. 56 patients over 11 years developed periprosthetic wound infection. 33 patients were available for analysis. The male:female ratio 1:0.7 with a mean age of 70 years (range: 32–88 years). 5 (15%) developed superficial infections, 4 (12%) patients developed cellulitis requiring antibiotics, 14 (42%) with superficial wound dehiscence and 2 (6%) required washout of the prosthesis with long-term antibiotic therapy. 4 (12%) were managed without plastics involvement, one leading to arthrodesis and 4 (12%) had plastic surgical input, with one leading to arthrodesis. The mean time before plastic surgical review after initial suspicion of infection was 13 weeks. The management of periprosthetic wound infections following TKA are variable and can require a multidiscplinary ortho-plastic approach. Early plastic surgical involvement in specific cases may improve outcome. Our proposed management protocol would facilitate in standardising the management of these complex patients

Introduction. For nearly 58% of total knee arthroplasty (TKA) revisions, the reason for revision is exacerbated by component malalignment. Proper TKA component alignment is critical to functional outcomes/device longevity. Several methods exist for orthopedic surgeons to validate their cuts, however, each has its limitations. This study developed/validated an accurate, low-cost, easy to implement first-principles method for calculating 2D (sagittal/frontal plane) tibial tray orientation using a triaxial gyroscope rigidly affixed to the tibial plateau of a simulated leg jig and validated 2D tibial tray orientation in a human cadaveric model. Methods. An initial simulation assessed error in the sagittal/frontal planes associated with all geometric assumptions over a range of positions (±10°, ±10°, and −3°/0°/+3° in the sagittal, frontal, and transverse planes, respectively). Benchtop experiments (total positions - TP, clinically relevant repeated measures - RM, novice user - NU) were completed using a triaxial gyroscope rigidly affixed to and aligned with the tibial tray of the fully adjustable leg-simulation jig. Finally, two human cadaveric experiments were completed. A similar triaxial gyroscope was mounted to the tibial tray of a fresh frozen human cadaver to validate sagittal and frontal plane tibial tray orientation. In cadaveric experiment one, three unique frontal plane shims were utilized to measure changes in frontal plane angle. In cadaveric experiment two, measurements using the proprosed gyroscopic method were compared with computer navigation at a series of positions. For all experiments, one rotation of the leg was completed and gyroscopic data was processed through a custom analysis algorithm. Results. Mathematical simulations showed that over the range of tested orientations, error from our geometric assumptions would be less than 1° and 0.2° in the sagittal and frontal planes, respectively. Results of all bench-top experiments are shown in Figure 1. The average angular error during the TP experiment (black bars) was 1.09°±0.80° and 0.60°±0.46° in the sagittal/frontal planes. The average angular error during the RM experiment (white bars) in the sagittal/frontal planes was 0.27°±0.25° and 0.30°±0.23°. The average angular error from the NU experiment (grey bars) in the sagittal/frontal planes was 1.50°±1.57° and 0.82°±0.77°. During cadaveric experiment one (Figure 2), computed frontal plane angles were 2.83°±0.98°, −1.67°±1.99°, and −4.33°±0.53° after placing distinct 2° lateral, 2° medial, and 4° medial shims. Finally, the average angular error from cadaveric experiment two (Figure 3) over all positions was 1.73°±1.12° and 1.56°±1.45° in the sagittal and frontal planes, respectively. Discussion. Despite the high frequency of TKA procedures, a significant number fail and need to be revised for improper component alignment. This study showed through a first-principles approach that surgeons can assess 2D orientation of the tibial component intraoperatively with 1° of accuracy with a single triaxial gyroscope rigidly affixed to the tibial plateau. Moreover, this study showed through the use of a cadaveric model that surgeons could assess 2D alignment of the tibial component with a gyroscope rigidly affixed to the tibial plateau. To our knowledge, this is first method to offer true 2D tibial tray orientation assessment using only a single triaxial gyroscope

Aim: To compare the function in two groups of high demand patients with a total knee arthroplasty (TKA) – one group using a posterior cruciate sacrificing (PCS) prosthesis and the other a posterior cruciate retaining (PCR) prosthesis of similar design. Method: Patients were eligible for the study if they were greater than two years from surgery, less than 65 years of age and without other co-existing morbidity to significantly decrease their physical activities. Group A underwent surgery by one surgeon who routinely retained the posterior cruciate ligament whereas Group B underwent surgery by one surgeon who routinely sacrificed the PCL. A mobile bearing TKA of similar design was used in each group. All patients were selected and assessed by an independent assessor using a questionnaire developed specifically to assess higher levels of activity not usually assessed by other knee scores. Results: Group A (28 TKA in 20 patients) were matched with Group B (25 TKA in 19 patients) for age, length of follow-up and range of motion. The gross activity score was 3.36 in Group A compared with 3.12 in Group B. The combined walking, running and stair climbing score was significantly better in Group A (7.68 compared to 6.64 in Group B). Group B perceived their TKA was closer to a normal knee (2.00 compared to 2.32) with decreased anterior knee pain. Conclusions: Retaining the PCL in TKA results in better function without significant complications

PURPOSE. Total knee arthroplasty (TKA) is a successful technique for treating painful osteoarthritic knees. However, the patients' satisfaction is not still comparable with total hip arthroplasty. Basically, the conditions with operated joints were anterior cruciate ligament (ACL) deficient knees, thus, the abnormal kinematics is one of the main reason for the patients' incomplete satisfaction. Bi-cruciate stabilized (BCS) TKA was established to reproduce both ACL and posterior cruciate ligament (PCL) function and expected to improve the abnormal kinematics. However, there were few reports to evaluate intraoperative kinematics in BCS TKA using navigation system. Hence, the aim in this study is to reveal the intraoperative kinematics in BCS TKA and compare the kinematics with conventional posterior stabilized (PS) TKA. Materials and Methods. Twenty five consecutive subjects (24 women, 1 men; average age, 77 years; age range, 58–85 years) with varus osteoarthritis undergoing navigated BCS TKA (Journey II, Smith&Nephew) were enrolled in this study. An image-free navigation system (Stryker 4.0 image-free computer navigation system; Stryker) was used for the operation. Registration was performed after minimum medial soft tissue release, ACL and PCL resection, and osteophyte removal. Then, kinematics including tibiofemoral rotational angles from maximum extension to maximum flexion were recorded. The measurements were performed again after implantation. We compared the kinematics with the kinematics of paired matched fifty subjects who underwent conventional posterior stabilized (PS) TKA (25 subjects with Triathlon, Stryker; 25 subjects with PERSONA, ZimmerBiomet) using navigation statistically. Results. Preoperative tibiofemoral rotational kinematics were almost the same between the three implants groups. Kinematics at post-implantation found that tibia was significantly internally rotated compared to the kinematics at registration in all three implants at maximum extension position (p<0.05), however the tibial rotational position with BCS TKA was significantly externally rotated at maximum extension position, compared to the other two implant position (p<0.05). The tibial rotational position with Triathlon PS TKA was externally rotated at 60 degrees of flexion compared to the other two implant position, however the results were not statistically significant. Discussion and Conclusion. Previous study found that PCL resection changed tibial rotational position and the amount of tibial internal rotation, affecting postoperative maximum flexion angles. This study found that BCS TKA can reduce the amount of rotational changes, compared to conventional PS TKA. Further studies are needed to investigate the kinematic changes in BCS TKA affect the postoperative clinical outcomes

Purpose Of Study. The in vivo evaluation of patellofemoral contact pressures in a posterior stabilized compared to posterior cruciate sacrificing total knee arthroplasty (TKA). Methods. A prospective descriptive non randomized study was performed on 8 patients. A standard approach to a TKA was performed using a balanced gap technique, while the patella was prepared for a resurfacing. The trial components for the posterior stabilized (PS) TKA where inserted including the gas sterilized pressure transducer (a patella button). Soft tissue was approximated and the knee was taken through full range of movement. Patellofemoral pressure was measured and captured continuously through the full range of movement. The posterior cruciate sacrificing (CS) components were inserted into the same patient and the procedure repeated. In addition, anterior translation of the tibia relative to the femur was measured at 90 degrees. The transducer was removed and final components, including a patella resurfacing were inserted. Results. Significantly lower patella femoral pressures were found for PS TKA compared to CS TKA in full flexion [129.0 ± 21.7 N vs. 109.9 ± 32.1 (p = 0.038173)]. The change in patellofemoral pressure between flexion and extension was significantly lower in PS TKA compared to CS TKA [109.0 ± 21.6 N vs. 90.5 ± 32.0 (p = 0.0037690)]. In addition mean anterior translation at 90° flexion in the CS TKA (6.4 ± 3.2 mm) was significantly less than in PS TKA (17.0 ± 2.6) (p = 0.000072). Conclusion. Significantly lower patellofemoral pressures were found in full flexion with PS TKA compared to CS TKA. The change in patellofemoral pressure in a PS TKA compared to CS TKA was also significantly lower. This study provides possible clinical data when considering patella resurfacing. NO DISCLOSURES

In selected patients, knee arthrodesis is a well-recognised salvage procedure after infected total knee arthroplasty (TKA). Several procedures of arthrodesis have been introduced and should be adapted to the individual situation of the patient. In our center we regularly treat elderly patients after multiple revision operations; in 36% defects of the bone, soft tissue or the extensor mechanisms are present. In these cases we prefer arthrodesis to reimplantation. Because of the high rate of non-unions when using an external fixator, we perform arthrodesis by use of an intramedullary rod system. The objective of this study was to compare the results of different rod systems for knee arthrodesis after TKA infection. We reviewed the results of 3 rod systems in 34 patients: cementless system (Brehm; n=9), cement rod usually used in tumor patients (Mutars; n=7) and a regular cement rod system (Link; n=18). In the group of cementless rods we had to explantate 3 rods because of a relapse of the infection. This is most propably due to the technical design of the system: in poor soft tissue situation the tissue is compressed by the voluminary docking part which causes continuous necrosis. This problem can be avoided by an early tissue flap. Of the Mutars rod system we had to explantate 2 systems; one because of an infection, the other one due to telescoping, which can be avoided by use of a longer stem with the option to interlock. In the group of the Links system no revision was necessary. In our opinion, arthrodesis of the knee using a rod system is a satisfactory salvage procedure following an infected TKA, especially in elderly patients, and can provide reliable, painless extremity and satisfactory quality of life

Cementless fixation for total knee arthroplasty (TKA) has been proposed as an alternative to cemented for several reasons, of which the most important is the possibility of increased survival. The purpose of this study was to compare the ten-year survival of TKA in a unique prospective randomised trial of cemented versus cementless fixation. A consecutive series of patients was randomised to undergo either cemented or cementless Press-Fit Condylar (PFC®) TKA. There were 219 patients (277 TKA) in the cemented group and 177 (224 TKA) in the cementless group. There were no significant differences in age, gender or diagnosis between the two groups. A single surgeon (PJG) performed or directly supervised all operations. The prosthesis used in all cases was the posterior-cruciate-retaining PFC® knee replacement system. Independent clinical review was performed at six months, annually until five years, and finally at ten years after surgery. Using revision surgery as the end-point, logrank analysis was used to compare the ten-year survival of the two groups. The mean interval of follow-up was 6.3 years (range, 2.0–11.7). At the last review, 104 patients (138 TKA) had died, without need for revision. All patients were traced and there was no loss to follow-up. In the cemented group, seven arthroplasties were revised; five for infection and two for exchange of polyethylene inserts. Ten-year survival was 96.5% (95% CI, 90.9–98.7%). In the cementless group, six arthroplasties were revised; three for aseptic loosening, one for infection, one for instability and one resizing for anterior knee pain. The ten-year survival was 96.6% (95% CI, 89.6–98.9%). There was no significant difference in the survival of the two groups. The long-term survival of cementless PFC® TKA is not significantly different from their cemented counterparts. The use of less expensive cemented implants, therefore, can make a significant impact on health resource planning

In a clinical setting, there is a need for simple gait kinematic measurements to facilitate objective unobtrusive patient monitoring. The objective of this study is to determine if a learned classification model's output can be used to monitor a person's recovery status post-TKA.

The gait kinematics of 20 asymptomatic and 17 people with TKA were measured using a full-body Xsens model¹. The experimental group was measured at 6 weeks, 3, 6, and 12 months post-surgery. Joint angles of the ankle, knee, hip, and spine per stride (10 strides) were extracted from the Xsens software (MVN Awinda studio 4.4)¹.

Statistical features for each subject at each evaluation moment were derived from the kinematic time-series data. We normalised the features using standard scaling². We trained a logistic regression (LR) model using L1-regularisation on the 6 weeks post-surgery data2–4.

After training, we applied the trained LR- model to the normalised features computed for the subsequent timepoints. The model returns a score between 0 (100% confident the person is an asymptomatic control) and 1 (100% confident this person is a patient). The decision boundary is set at 0.5.

The classification accuracy of our LR-model was 94.58%. Our population's probability of belonging to the patient class decreases over time. At 12 months post-TKA, 38% of our patients were classified as asymptomatic.

To describe the longitudinal trends in patients with obesity and Metabolic Syndrome (MetS) undergoing TKA and the associated impact on complications and lengths of hospital stay.

We identified patients who underwent primary TKA between 2006 – 2017 within the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database. We recorded patient demographics, length of stay (LOS), and 30-day major and minor complications. We labelled those with an obese Body Mass Index (BMI ≥ 30), hypertension, and diabetes as having MetS. We evaluated mean BMI, LOS, and 30-day complication rates in all patients, obese patients, and those with MetS from 2006-2017. We used multivariable regression to evaluate the trends in BMI, complications, and LOS over time in all patients and those with MetS, and the effect of BMI and MetS on complication rates and LOS, stratified by year.

270,846 patients underwent primary TKA at hospitals participating in the NSQIP database. 63.71% of patients were obese (n = 172,333), 15.21% were morbidly obese (n = 41,130), and 12.37% met criteria for MetS (n = 33,470). Mean BMI in TKA patients increased at a rate of 0.03 per year (0.02-0.05; p < 0 .0001). Despite this, the rate of adverse events in obese patients decreased: major complications by an odds ratio (OR) of 0.94 (0.93-0.96; p < 0 .0001) and minor complications by 0.94 (0.93-0.95; p < 0 .001). LOS also decreased over time at an average rate of −0.058 days per year (-0.059 to −0.057; p < 0 .0001). The proportion of patients with MetS did not increase, however similar improvements in major complications (OR 0.94 [0.91-0.97] p < 0 .0001), minor complications (OR 0.97 [0.94-1.00]; p < 0 .0330), and LOS (mean −0.055 [-0.056 to −0.054] p < 0 .0001) were found. In morbidly obese patients (BMI ≥ 40), there was a decreased proportion per year (OR 0.989 [0.98-0.994] p < 0 .0001). Factors specifically associated with major complications in obese patients included COPD (OR 1.75 [1.55-2.00] p < 0.0001) and diabetes (OR 1.10 [1.02-1.1] p = 0.017). Hypertension (OR 1.12 [1.03-1.21] p = 0.0079) was associated with minor complications. Similarly, in patients with MetS, major complications were associated with COPD (OR 1.72 [1.35-2.18] p < 0.0001). Neuraxial anesthesia was associated with a lower risk for major complications in the obese cohort (OR 0.87 [0.81-0.92] p < 0.0001). BMI ≥ 40 was associated with a greater risk for minor complications (OR 1.37 [1.26-1.50] p < 0.0001), major complications (1.11 [1.02-1.21] p = 0.015), and increased LOS (+0.08 days [0.07-0.09] p < 0.0001).

Mean BMI in patients undergoing primary TKA increased from 2006 - 2017. MetS comorbidities such as diabetes and hypertension elevated the risk for complications in obese patients. COPD contributed to higher rates of major complications. The obesity-specific risk reduction with spinal anesthesia suggests an improved post-anesthetic clinical course in obese patients with pre-existing pulmonary pathology. Encouragingly, the overall rates of complications and LOS in patients with obesity and MetS exhibited a longitudinal decline. This finding may be related to the decreased proportion of patients with BMI ≥ 40 treated over the same period, possibly the result of quality improvement initiatives aimed at delaying high-risk surgery in morbidly obese patients until healthy weight loss is achieved. These findings may also reflect increased awareness and improved management of these patients and their elevated risk profiles.

Aims: Kinematic and pointing procedures, are used for non-image based navigated implantation of TKA. Pointing procedures require exact knowledge about the landmarks. In this anatomical study, landmarks are defined and repeatedly referenced. The precision and the reproducibility are evaluated, by means of inter- and intra- observer study. Using the landmarks, the axes of the femur and tibia are calculated. Methods: The specific landmarks of 30 femur and 27 tibia specimens, were palpated by 3 surgeons and digitised by means of a photogrammetric system, as used intra-operatively. The recorded data are evaluated. Results: The specific landmarks can be referenced with great precision. The vectors that influence the implant position, show femoral a mean inter-observer deviation of 0,9mm and 1,0mm tibial. The repeating accuracy of every single observer was 1,5mm femoral and 1,0mm tibial. The calculated long axes at the femur and tibia, thus reach a precision of 0.1° (min-max:0°–0,9°) at the femur and 0,2° (min-max:0°–1,1°) at the tibia. The short axes at the distal femur and at the proximal tibia, exhibit an average deviation of 0,7° to 1,9° (min-max: 0°–11,3°). Conclusion: Long axes (mechanical axes) can be determined exactly, the precision of the short axes (rotational axes) is unsatisfactory, although palpation of landmarks were accurate. Therefore, palpation of more than one rotational axis at the femur and the tibia, is mandatory and should be visualized on the monitor during the operation.

Which parameters are related with a forgotten knee after TKA?

The operated knee was said forgotten when it was similar to the normal controlateral knee in all situations.

When a restriction existed, the knee was considered as not forgotten.

470 patients operated with a stabilised mobile bearing knee were examined with a minimal follow up of 5 years and answered to this question.

4 groups of parameters: patient, prosthesis, surgery and post operative care were compared to the binary answer to the forgotten knee question.

48% of the patients had a forgotten knee one year after the TKA;

The following factors had a significant negative correlation with the forgotten knee:

low SF12 psychological profile; Patellofemoral dysplasic arthritis (p = 0,01);

We found no correlation between the following factors and the forgotten knees:

gender, BMI, approach, cemented or not, patellar resurfacing; preoperative Oxford and Knee Society knee scores;

The forgotten knee is a simple objective clinical item because the answer to the question is binary and does not accept any unprecision. It is highly correlated with surgical scores and patients expectation scores (p = 0,0001).

The forgotten knee is a painless and asymptomatic knee identical to a normal knee.

Surgical factors have the highest infiuence on this parameter compared to patient or prosthetic related factors.

Introduction. Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femolo-tibial joint as well as posterior-stabilized polyethylene insert, even if posterior cruciate ligament (PCL) is sacrificed after total knee arthroplasty (TKA). The purpose of this study is an investigation of in vivo kinematics of three different tibial insert designs using computer assisted navigation system intra-operatively in TKA. Materials and Methods. Sixty-four consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker, New Jersey, USA) were performed using computer assisted navigation system. During surgery, three different designs of polyethylene tibial trial inserts (PS, CS, and cruciate-retaining (CR) polyethylene insert) were inserted respectively after implantation of femoral and tibial components. The kinematic parameters of the soft-tissue balance were obtained by interpreting kinematics curve, which display bicompartmental gaps throughout the range of motion (ROM) after implantation of each trial insert (Figure. 1). During record of kinematics, the surgeon gently lifted the experimental thigh three times, flexing the hip and knee. Deviation of these three values in each ROM was calculated in each tibial insert in each patient for descriptive analysis. Results. Regarding to values of compartmental gaps, there are no significance between three inserts in both medial and lateral compartments (Figure 2a, b). On medial compartmental gaps, the values of deviations were significantly higher in CR insert than both of PS and CS insert in ROM of over 45 degrees in extension (Fig 3a). In addition, concerning lateral compartmental gaps, the values of deviations were significantly higher in CS insert than both PS and CS insert in all ROM (Fig 3b). Furthermore, there was no significance between PS and CS insert in overall range of motion in both medial and lateral compartmental gaps (Fig 3a, b). Discussion. These results demonstrated that CS polyethylene insert has a stability of femoro-tibial joint nearly as well as PS polyethylene insert. While PS insert may leads to surface damage on open box and has necessity of cutting more bone of femur, some problems involving management of PCL are enumerated in CR inserts. The main design feature of Triathlon CS insert is single radius and rotary arc, in addition, the posterior lip is same as that of Triathlon CR, which can be the factor to avoid paradoxical anterior movement and to permit internal and external rotation between femoral and tibial component. Due to the design features and benefits, there is a high possibility that CS insert can lead same ROM as PS insert, although PS design can produce more ROM than the other type of insert type. Based on these backgrounds, it is suggested that CS insert may have an additional choice in TKA with some advantages especially in concerning of high activity patients like middle aged patients

Today TKA belongs to a standard care in orthopaedics and traumatology. The number of the annual implantations has clearly increased during the last years and also in the future an increasing rate to be expected.

Also the number of Revision TKA and the treatment of complicated pathologies in the primary care will increase in the same way.

Therefore the requirements of the surgeon rised as well as a suitable and accurate systems will be needed. Beside revision cases, traumatic-, post-traumatic- and RA-patients demonstrate partly distinctive bone and ligamentous pathologies.

Beside the primary implant components and instrumentation-systems, modern knee systems must include also modular revision systems compatible with the primary systems to be able to carry out complicated primary as well as light to moderately severe recision cases. Besides, also the possibility should be able to change within the system (with constant bone-cuttings) on higher degrees of the constrain.

With the TC-Primary and TC-Revision system fulfils the above mentioned criteria so that nearly every situation can be handled.

We present our experience using this system in cases of revisions, traumatic, post-traumatic and RA-cases The handling of bone and ligamentous defects will be demonstrated. In particular the possibility the use of the TC-Revision also in primary TKA as P a so named “extension primary system” will be emphasized.

By the Modulary and compatibility of the TC-Primary and TC-Revision systems, the use of Wedges and Stems as well as the possibility of the different degrees of the constrain a knee family permits us to treat complicated primary as well as mild to moderate revision cases.

Introduction

Schatzker V & VI tibial plateau fractures are serious life-changing injuries often resulting in significant complications including post-traumatic arthritis. Reported incidence of secondary TKA following ORIF of all tibial plateau fractures is 7.3% and 13% for Schatzker V & VI tibial. This study reports a 15-year single centre experience of CEF of Schatzker V & VI fractures including PROMs and incidence of secondary TKA. This study was approved by the local Institutional board.

The accurate positioning of the total knee arthroplasty affects the survival of the implants(1). Alignment of the femoral component in relation to the native knee is best determined using pre- and post-operative 3D-CT reconstruction(2). Currently, the scans are visualised on separate displays. There is a high inter- and intra-observer variability in measurements of implant rotation and translation(3). Correct alignment is required to allow a direct comparison of the pre- and post-operative surfaces. This is prevented by the presence of the prostheses, the bone shape alteration around the implant, associated metal artefacts, and possibly a segmentation noise.

The aim is to create a novel method to automatically register pre- and post-operative femora for the direct comparison of the implant and the native bone.

The concept is to use post-operative femoral shaft segments free of metal noise and of surgical alteration for alignment with the pre-operative scan. It involves three steps. Firstly, using principal component analysis, the femoral shafts are re-oriented to match the X axis. Secondly, variants of the post-operative scan are created by subtracting 1mm increments from the distal femoral end. Thirdly, an iterative closest point algorithm is applied to align the variants with the pre-operative scan.

For exploratory validation, this algorithm was applied to a mesh representing the distal half of a 3D scanned femur. The mesh of a prosthesis was blended with the femur to create a post-operative model. To simulate a realistic environment, segmentation and metal artefact noise were added. For segmentation noise, each femoral vertex was translated randomly within +−1mm,+−2mm,+−3mm along its normal vector. To create metal artefact random noise was added within 50 mm of the implant points in the planes orthogonal to the shaft. The alignment error was considered as the average distance between corresponding points which are identical in pre- and post-operative femora.

These preliminary results obtained within a simulated environment show that by using only the native parts of the femur, the algorithm was able to automatically register the pre- and post-operative scans even in presence of the implant. Its application will allow visualisation of the scans on the same display for the direct comparison of the perioperative scans.

This method requires further validation with more realistic noise models and with patient data. Future studies will have to determine if correct alignment has any effect on inter- and intra-observer variability.

Summary:

Smaller increments in the antero-posterior dimensions of femoral components allows significant improvements in balancing of the knee after TKA with restoration of more normal soft-tissue stability.

Introduction: The success of total knee arthroplasty (TKA) is dependent on many factors. Postoperative extremity and component alignment are important determinants of outcome and longevity and malalignment results in higher failure rates. Computer-assisted (CAS) navigation devices were developed to improve implant positioning but their use increases the complexity of the surgery. The aim of this study is to assess the radiological outcome of conventional techniques versus CAS for TKA performed by an expert and other group performed by a beginner in CAS. Methods: 90 patients patients with knee arthritis were prospective randomized into 3 groups: CAS performed by an expert, CAS performed during the learning curve and conventional technique (manual instrumentation) performed by an expert. Preoperative and postoperative clinical examinations were performed at four weeks, six months, and one year by an independent physician who was blinded to the surgical technique. Preoperative and postoperative radiographic measurements of the anterior-posterior mechanical axis and the sagittal tibial and femoral axes were evaluated by an observer who was blinded to the surgical technique. The Knee Society Scoring System was used to asses clinical and functional outcomes. All variables were analysed for differences between the groups either by Student’s t-test or the Mann-Whitney U test. Results: There was no differences in implant positioning between the CAS groups. The mechanical axis of the leg was significantly better in the two CAS groups (96%, within +/−3° varus/valgus) compared with the conventional Group (78%, within +/− 3° varus/valgus). The frontal and sagittal alignment of the femoral component and the frontal tibial alignment were also more precise in the CAS groups. Improvement occurred in the Knee Society scores up to one year post-operatively and was similar for the three groups. No significant difference between the groups could be found at any time point in the study, with the mean difference being 3.5 points (95% CI;18.6 to 13.6). Conclusions: We have not shown differences in the precise positioning of implants during the learning curve in computer-assisted total knee arthroplasty. Computer-assisted total knee arthroplasty gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation

Background

The accurate positioning of the total knee arthroplasty affects the survival of the implants(1). Alignment of the femoral component in relation to the native knee is best determined using pre- and post-operative 3D-CT reconstruction(2). Currently, the scans are visualised on separate displays. There is a high inter- and intra-observer variability in measurements of implant rotation and translation(3). Correct alignment is required to allow a direct comparison of the pre- and post-operative surfaces. This is prevented by the presence of the prostheses, the bone shape alteration around the implant, associated metal artefacts, and possibly a segmentation noise.