The posterior tibial slope angle (PTS) in posterior cruciate retaining total knee arthroplasty influences the knee kinematics, knee stability, flexion gap, knee range of motion (ROM) and the tension of the posterior cruciate ligament (PCL). The current technique of using an arbitrary (often 3–5 degrees) PTS in all cases seldom will restore native slope in cruciate retaining TKA. Questions/Purposes: The primary objective was to determine if we could surgically reproduce the native PTS in cruciate-retaining total knee arthroplasty. The second objective was to determine if reproduction of native slope was significant – ie influenced clinical outcome.

We evaluated the radiographic and clinical outcomes of a series of consecutive total knee arthroplasties using the PFC sigma cruciate-retaining total knee system in 215 knees. The tibial bone cut was planned to be parallel to the patient's native anatomical slope in the sagittal plane. An “Angel Wing” instrument was placed on the lateral tibial plateau and the slope of the cutting guide adjusted to make the cutting block parallel to the patient's native tibial slope. All true lateral radiographs of the knee were measured for PTS using a picture achieving and communication system (PACS). PTSs were measured with reference to the proximal tibial medullary canal (PTS-M) and the proximal tibial anterior cortex (PTS-C). The knee ROM, Knee Society Score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and SF-12 at the last follow-up were evaluated as clinical outcomes.

The mean preoperative PTS-M was 6.9±3.3 degrees and the mean postoperative PTS-M was 7±2.4 degrees. The mean preoperative PTS-C was 12.2±4.2 degrees and the mean postoperative PTS-M was 12.6±3.4 degrees. There was no significant difference form the preoperative and postoperative PTS measurement in both techniques (p>0.05). We used an arbitrary 3 degrees as an acceptable range for PTS-M reproduction. The PTS-M was reproduced within 3 degrees in 144 knees (67%); designated as Group A. The 71 knees with a difference more than 3 degrees in (33%) were designated as Group B. Group A showed significantly larger gain in ROM compared with group B (p=0.04). Group A also had significantly better improvement in Knee society score and WOMAC score and SF-12 physical score when compare with group B (p<0.01).

Our modification of standard surgical technique reliably reproduced the native tibial slope in cruciate-retaining total knee arthroplasty. More importantly, reproduction of the patient's native PTS within 3 degrees resulted in better clinical outcomes manifested by gain in ROM and knee functional outcome scores.

Introduction. The first VRAS TKA was performed in New Zealand in November 2020 using a Patient Specific Balanced Technique whereby VRAS enables very accurate collection of the bony anatomy and soft tissue envelope of the knee to plan and execute the optimal positioning for a balanced TKA. Method. The first 45 VRAS patients with idiopathic osteoarthritis of the knee was compared with 45 sequential patients who underwent the same TKA surgical technique using Brainlab 3 which the author has used exclusively in over 1500 patients. One and two year outcome data will be presented. Results. One year outcome dataVely Brainlab Significance Oxford 43.4 40.5 P=0.01 WOMAC 8.4 14.1P=0.02 Forgotten Joint Score 72.2 58.3 P=0.01 KOOS ADL91.3 85.8 P=0.04 Normal 83.3 74.2P =0.048 Activity Pain 8.6 18.4 P=0.009 ROM 127 124 P=0.01 Patient Satisfaction 98% 95% P=0.62 Operation again 100% 91% P=0.055 The two year data will be available for the ASM Conclusion: The one year outcome data shows a significantly better Oxford, WOMAC, Forgotten Joint score, KOOS ADL, Normal score and ROM scores and the activity pain is less compared to the authors extensive experience with Brainlab 3

Introduction. Robotics have been applied to total knee arthroplasty (TKA) to improve surgical precision in components’ placement, providing a physiologic ligament tensioning throughout knee range of motion. The purpose of the present study is to evaluate femoral and tibial components’ positioning in robotic-assisted TKA after fine-tuning according to soft tissue tensioning, aiming symmetric and balanced medial and lateral gaps in flexion/extension. Materials and Methods. Forty-three consecutive patients undergoing robotic-assisted TKA between November 2017 and November 2018 were included. Pre-operative radiographs were performed and measured according to Paley's. The tibial and femoral cuts were performed based on the individual intra-operative fine-tuning, checking for components’ size and placement, aiming symmetric medial and lateral gaps in flexion/extension. Cuts were adapted to radiographic epiphyseal anatomy and respecting ±2° boundaries from neutral coronal alignment. Robotic data were recorded, collecting information relative to medial and lateral gaps in flexion and extension. Results. Patients were divided based on the pre-operative coronal mechanical femoro-tibial angle (mFTA). Only knees with varus deformity (mFTA<178°), 29 cases, were taken into account. On average, the tibial component was placed at 1.2°±0.5 varus. Femoral component fine-tuning based on soft-tissues tensioning in extension and flexion determined the following alignments: 0.2°±1.2 varus on the coronal plane and 1.2°±2.2° external rotation with respect to the trans-epicondylar axis (TEA) as measured on the CT scan in the horizontal plane. The average gaps after femoral and tibial resections, resulted as follows: 19.5±0.8 mm on the medial side in extension, 20.0±0.9 mm on the lateral side in extension, 19.1±0.7 mm on the medial side in flexion and 19.5±0.7 mm on the lateral side in flexion. On average, the post-implant coronal alignment as reported by the robotic system resulted 2.0°±1.5 varus. Discussion. The proposed robotic-arm assisted TKA technique, aiming to preserve the integrity of the ligaments, provides balanced and symmetric gaps in flexion and extension and an anatomic femoral and tibial component's placement with post-implant coronal alignment within ±2° from neutral alignment

Background. Total knee arthroplasty (TKA) is an effective surgical procedure to alleviate excruciating pain and correct dysfunction due to severe knee deformity. The satisfaction rate with current TKA is 80%, While 20% of the patients report uncomfortable feeling during stair descending and deeply knee bending. Preserving the ligaments might allow a restoration close to the natural function, although sacrifice of the ACL is common with the conventional TKA technique. The current bicruciate-retaining (BCR) TKA would be a way to go concerning this issue. This study aimed at evaluating the intraoperative kinematics and joint laxity on BCR TKA if the native function would be replicated and thus assessing the range of motion (ROM) at final followup. Methods. BCR TKAs were performed in 22 knees (12 women, 10 men, average aged 67.2-year-old) with image-free navigation system (Kolibli. TM. ) under general anesthesia. The intraoperative kinematics was evaluated about flexion extension gap (FEG), anterior-posterior translation (APT, bi-condylar rollback) and axial rotation (AR, medial pivot) with passive motion. These kinematic patterns were assessed with the post-operative ROM. Results. There was no paradoxical anterior translation in any cases. The implant kinematics was regulated to the medial pivot motion at early flexion phase and the bi-condylar rollback motion to full flexion angle. The mean flexion was changed from 132 degrees at preoperation to 126 degrees at followup, and the mean flexion contracture improved from 4 degrees to 1 degree. Conclusion. BCR TKA were preserved the nature kinematics including the medial pivot motion and rollback mechanism. Postoperative ROM was quite similar when the preoperative knee flexion was not restricted

Aim: To compare between the number of steps and instruments required for total knee arthroplasty (TKA) using 3 different techniques. The proposed techniques were conventional technique, conventional technique with patient-specific pin locators and CAOS technique using patient-specific templates (PST). Patients and methods: Zimmer/Nexgen was used as the standard implant and templating system for TKA. A Comparison was done on the number of steps and instruments required for TKA when performed with conventional technique, conventional technique with patient-specific pin locators and CAOS technique with patient-specific templates (PST) used as cutting guides. Results: The essential steps and instruments required for conventional TKA without surgical approach or bone exposure were average 70 steps with 183 different instruments; for conventional technique with patient-specific pin locators, they were average 20 steps with 40 instruments and two templates; for CAOS technique using PST, they were average 10 steps with two templates and 15 accessory instruments. CAOS PST technique required an average of 4 days for preoperative preparation and templates fabrication. Conclusion: CAOS technique using PST could make TKA less complicated in light of essential steps and instrumentation required. Although this technique required accurate preoperative preparation, it could offer less technical errors and shorter operative time compared to conventional TKA techniques. The errors’ rate for each technique was still depending on the surgeon's skills and training; however, CAOS technique with PST required shorter learning curve

Introduction. Design evolution of total knee arthroplasty (TKA) has improved implant durability and clinical outcomes. However, it has been reported that some patients have limited satisfaction with their operated knees [1]. In view of better patient satisfaction, there have been growing interests in anatomically aligned TKA. The anatomically aligned TKA technique aims to replicate natural joint line of the patients [2][3]. However, restoration of natural joint line may be difficult for the knees with severe deformity, as their joint alignment with respect to bony landmarks at a time of surgery may be critically different from their pre-diseased state. The purpose of this study is to investigate alignment of the tibial growth plate with respect to tibial anatomical landmarks for possible application in estimation of pre-diseased joint alignment. Methods. Three-dimensional tibial models were created from CT scans of 22 healthy Japanese knees (M7:F15, Age 31.0±12.6 years) using Mimics (Materialise NV, Leuven, Belgium). The mid-sagittal plane of the tibia was defined by medial margin of the tibial tuberosity, origin of the PCL and center of the foot joint. The tibial plateau (or joint line plane) was determined by following three points; a dwell point of aligned femur on lateral tibial articular surface, and two points at anterior and posterior rim of medial tibial articular surface defined within sagittal plane that coincide with dwell point of femur on medial tibia. All measurements were made with respect to the mid-sagittal plane. The shape of the tibial growth plate (GP) was extracted using Livewire function and mask editing tools of Mimics. To determine 3D orientation of the GP, moment of inertia axes were calculated for the 3D model. The inertia axes were also determined for medial and lateral half of the GP (Figure 1). Results. Tibial plateau (TP) had 2.38±1.78 degrees of varus and 11.37±3.76 degrees of posterior inclination. In coronal view, the GP axis was in varus alignment to the normal axis of the TP by 3.29±1.45 degrees. The shape of the GP is found to be different for medial and lateral half. The posterior inclination of the medial half tends to follow the TP, while the lateral half is twisted anteriorly (Figure 2). The GP medial half was in 5.03±2.89 degrees valgus and 1.62±2.37 degrees anteriorly inclined relative to the TP. The GP lateral half was in 10.38±2.62 degrees varus and 18.11±3.79 degrees anteriorly inclined relative to the TP. Discussion. The results from 22 healthy knees suggested that the tibial growth plate is aligned to tibial plateau in varus orientations with relatively small deviations. Distinctive shape difference for medial and lateral half of the growth plate was also observed. Limitation of this study is a number of subjects available for the analysis. Future study should consider inclusion of arthritic knees with various levels of deformities. For figures/tables, please contact authors directly.

Why are total knees being revised? Aseptic loosening, poly wear, and instability account for up to 59% of revision TKA procedures. Younger and more active patients are placing greater demands on total knee arthroplasty (TKA) implants and international registries have documented a much higher rate of TKA failure in this population. Implant designs utilised in the active patient population should focus on optimisation of long term wear properties and minimising interface stress. Instability after TKA, often related to technical concerns at the time of the index procedure, accounts for by far the greatest subset of failures, excluding infection, in the early revision TKA patients (<5 years). The inability to achieve a rectangular flexion gap with certain TKA techniques for certain deformities has been documented. The adverse clinical consequence of flexion gap asymmetry has also been published in peer reviewed manuscripts. Techniques should be considered that optimise flexion space balance and enhance mid-flexion stability in active, physically demanding patients. This surgical demonstration will highlight gap balancing techniques and a new rotating platform TKA system as an option for the active patient population

Previous studies examined failure mechanisms for revision TKA performed between 1986 and 2000. These studies demonstrated that a majority of failures occurred in the first few years, with a disproportionate amount for infection and implant-associated failure mechanisms. Since these studies were published, efforts have been made to improve implant performance and instruct surgeons towards best practice total knee arthroplasty techniques. Recently our center participated in a multi-center evaluation of revision TKA cases during 2010 and 2011. The purpose was to report a detailed analysis of the failure mechanism and the time to failure to determine whether the failure mechanism of primary TKA has changed over the past 10–15 years. Further, we evaluated the effect of failure mechanism on extent of revision and whether revision surgery was performed at the same location as the index procedure. We identified 844 revisions of failed primary TKA. Aseptic loosening was the predominant mechanism of failure (31.2%), followed by instability (18.7%), infection (16.2%), polyethylene wear (10.0%), arthrofibrosis (6.9%), and malalignment (6.6%). Mean time to failure was 5.9 years (range 10 days to 31 years). 35.3% of all revisions occurred less than 2 years after the index arthroplasty, with 60.2% in the first 5 years. In contrast to previous reports, polyethylene wear is not a leading failure mechanism and rarely presents before 15 years. Implant performance is not a predominant factor of knee failure. Early failure mechanisms are primarily surgeon-dependent

Introduction. This community Arthroplasty Register is an individual initiative to document arthroplasty procedures performed from 2007 to date in a sample area in Cairo, Egypt. Currently, there is no published study or official documentation of the indications for arthroplasty, types of implants or the rate of total hip and knee arthroplasty (THA & TKA). Although the population of Egypt reached 80,394,000, the unofficial estimate of the rate of joint replacement is less than 10,000 per year. This rate is less than 10% of what is currently done in UK, a country with similar or even less population than Egypt. This indicates the unmet need for TKA in Egypt, where the knee OA is prevailing and there is a call for documentation and a registry. Methods. The registry sheet is 3 pages; pre-, intra- and post-operative. It is available in printed format and online as demonstrated below . www.knee-hip.com. During the registry period, there were 282 cases collected prospectively and 206 collected retrospectively. This initial analysis included only prospectively collected data of 157 TKA and 125 THA. Results. For THA, the mean age was 48 years ranging from (19–86). Female to male ratio was 1.15:1. The rate of uncemented THA was 84.8%, Cemented was 10.2% and hybrid THA was 5%. We have observed significant growth in the uncemented type of fixation. The rate of primary was 54.4 % (complex primary 26.4%), Conventional THA techniques were done for 56.15%, while computer assisted surgery was used in 43.85% of cases. For TKA, there was 71.33% primary and 19.7% complex primary, 8.97% revision arthroplasty. A female to male ratio was 2.92:1. The main indication for TKA was OA in 87.26%. Preoperative radiographic evaluation showed that 47% had severe varus and 15% had significant bone defect. Conventional TKA techniques were done for 73.2%, while computer assisted surgery was sued in 26.8 % of cases

Introduction: I always aim for neutral mechanical axis alignment. My principles of a successful TKA are proper alignment in all 3 planes, soft tissue balance in extension first, flexion gap balancing by parallel to tibial cut technique, maintenance of joint line, correct sizing of femoral component, and proper cement fixation. Long-term Survivorship: There is long-term data that supports the efficacy and durability of the neutral position of the proximal tibial cut. Over a 20-year follow-up there was a 92.6% success rate in my study. Other authors have found similarly successful survivorship for mechanical failure. Balance Technique in TKR: My technique to balance the knee is a balance extension gap first, which requires medial soft tissue balancing. Next, I balance the flexion gap parallel to the tibial cut. Our Results: In one study, I examined the clinical and radiographic data of 68 varus knees. Average post-operative mechanical alignment was 0 ± 3 degrees. There were no outliers which displays the reproducibility of the technique. This is the method of choice in the hands of most surgeons

Introduction: I always aim for neutral mechanical axis alignment. My principles of a successful TKA are proper alignment in all 3 planes, soft tissue balance in extension first, flexion gap balancing by parallel to tibial cut technique, maintenance of joint line, correct sizing of femoral component, and proper cement fixation. Long-term Survivorship: There is long-term data that supports the efficacy and durability of the neutral position of proximal tibial cut. Over a 20-year follow-up there was a 92.6% success rate in my study. Other authors have found similarly successful survivorship for mechanical failure. Balance Technique in TKR: My technique to balance the knee is a balance extension gap first, which requires medial soft tissue balancing. Next, I balance the flexion gap parallel to the tibial cut. Our Results: In one study, I examined the clinical and radiographic data of 68 varus knees. Average post-operative mechanical alignment was 0 ± 3 degrees. There were no outliers which displays the reproducibility of the technique. This is the method of choice in the hands of most surgeons

Computer-assisted techniques in total knee replacement (TKR) have been introduced to improve bone cuts execution and relevant prosthesis components positioning. Although these have resulted in good surgical outcomes when compared to the conventional TKR technique, the surgical time increase and the use of additional invasive devices remain still critical. In order to cope with these issues, a new technology in TKR has been introduced also for positioning prosthetic components according to the natural lower-limb alignment. This technique is based on custom-fit cutting block derived from patient-specific lower-limb scan acquisition. The purpose of this study is to assess the accuracy of the custom-fit technology by means of a knee surgical navigation system, here used only as measurement system, and post-operative radiographic evaluations. Particularly, the performances of two different custom-fit cutting blocks realized from as many scan acquisitions have been here reported. Thirty patients affected by primary knee osteoarthritis were enrolled in this study. Fifteen patients were implanted with GMK® (Medacta-International, Castel San Pietro, CH) and as many patients with Journey® (Smith&Nephew, London, UK). Both TKR designs were implanted by using custom-fit blocks for bone cut executions provided by the same TKR manufacturers according to a pre-operative web planning approved by the surgeon. Particularly, the cutting block for the former design was built from CT scan acquisition of the hip, knee and ankle, whereas that for the latter design from MRI scans acquisition of the knee and X-ray lower-limb overview. A knee surgical navigation system (Stryker®-Leibinger, Freiburg, Germany) was used for recording intra-operative alignment of bone cuts as performed by means of the custom-fit cutting blocks and relevant component positioning. Prosthetic components alignments were also assessed post-operatively on X-ray images according to a shape-matching technique. The accuracy of the custom-fit blocks was evaluated through the comparison between pre-operative planning, and intra/post-operative data. Discrepancies above 3° and millimeters were considered as outliers. Within the patient cohort, nine cases were fully analyzed at the moment and here reported. Over them and except for one case, the discrepancy between pre-operative planned femoral/tibial resection level on the frontal plane and the corresponding measured intra-operatively was within 3 mm, being 5 mm in the worse case. Two outliers were observed for the corresponding femoral/tibial cut rotational alignment. Particularly, in one patient, the discrepancy in femoral cut alignment was of 8° in flexion and 6° in external rotation; in another patient this was of 4° in extension and 4° in external rotation in the femoral and tibial cut alignment, respectively. Post-operative radiographs evaluations for the final prosthetic components revealed that femoral/tibial alignment were within 3° in all cases, except for those patients that were already outliers. These preliminary results reveal the efficacy of the custom-fit cutting block for TKR. These were generally fitted properly and final prosthetic components were accurately placed, although some discrepancies were observed. This new technology seems to be a valid alternative to conventional and computer-assisted techniques. More consistent conclusions can be deduced after final evaluation of all patients

Introduction. Multiple techniques exist for performance of Total Knee Arthroplasty (TKA). In April 2010, MyKnee® Patient-Specific Instrumentation (Medacta International, SA, Castel San Pietro, Switzerland) was approved for use in TKA in the United States. The present retrospective study seeks to evaluate early results of this technique. 29 consecutive patients (30 consecutive TKA operations) underwent TKA using the MyKnee cutting-blocks. These results were compared to 30 consecutive patients utilizing Standard TKA method. The findings represent the author's first MyKnee patients, and thus early learning curve for this technique. IRB approval for retrospective research was obtained prior to the evaluation of the data. Methods. 30 consecutive patients (14 males, 16 females) underwent TKA using the MyKnee technique. Pre-operative long-standing radiographs were taken and compared to 6-week post-operative radiographs. Intraoperative data includes the femoral and tibial resections thickness: Distal Medial femoral, Distal Lateral femoral, Posterior Medial Femoral, Posterior Lateral femoral, Medial Tibia, and Lateral Tibia. These were compared to the Planned vs. Actual resections. Tourniquet time was recorded as a measure of speed of surgery. These were compared to 30 consecutive patients using Conventional TKA technique. Intraoperative complications were also recorded. Results. For the MyKnee group, 21 patients had pre-operative varus deformities with a mechanical alignment of 7.8° (range 1.2°-15.2°). 7 patients had Pre-operative valgus deformities averaging 6.9° (range 1.3°-14.5°). 2 patients were neutral. Post-operative alignment for all patients (n=23) was varus 1.92° (range 0°-5.8°). 78% of patients were within 3° and 97% of patients were within 3.6°. Only 1 patient was outside 3.6°, measuring 5.4° valgus (Figure 3). In comparison, the Standard TKA group had 21 patients with pre-operative varus deformities averaging 7.3° (range 0°-16.5°) while 7 knees were valgus 6.3° (range 1.2°-10.6°) and one was neutral. Post-operative alignment for these patients measured varus 1.85°. 79% of patients were within 3°; however the outliers were much more dramatic ranging 3.5°-9.2°. 30 Femora and 21 Tibial resections were available for review using the MyKnee technique. The Actual vs. Planned resections for the Distal Medial Femoral resection was 9.5 vs. 9.1mm respectively. Further Actual vs. Planned Femoral resections include Distal Lateral Femoral 8.4 vs. 6.3mm; Posterior Medial Femoral 9.3 vs. 9.5mm; and Posterior Lateral Femoral 8.6 vs. 7.0mm. The Actual vs. Planned Tibial resections recorded include Medial 6.07 vs. 6.29mm and Lateral 9.36 vs. 8.19mm. Statistically, there is no significant difference in post-op degree (1.85° vs. 1.92°). Tourniquet time (TT) averaged 32.97 minutes in the Standard TKA group vs. 37.03 minutes in the MyKnee group, which isn't significantly different. However, the final 15 MyKnee patients had an average time of 33.46 minutes. EBL was minimal each cohort. No intraoperative complications were recorded in either group. Discussion. Many techniques exist for performance of TKA. The present study shows definitively that Intraoperative resections and Post-operative alignments can be accurately achieved with pre-operative CT planning and using Patient-Specific Instrumentation. In conclusion, using Patient-Specific Instrumentation is safe, quick, and accurate in performance of TKA

Background. Total knee arthroplasty (TKA) is a cost-effective surgical procedure for degenerative knee disease and has good long-term results. However, these results are not always related to patient satisfaction and functional outcome. With an increasing demand of surgeons and patients on functioning of total knee implants, the need for adequate objective outcome measures is high. Imaging of the knee is commonly used in clinical practice and research to objectively measure many different outcome parameters concerning the implant, such as alignment and complications.1 However, techniques on comparison of the sagittal contour of the knee before and after implant placement are scarce. Goal. To develop and describe a standardized method for measuring the sagittal contour of the implant in a 3D model of the knee before and after implant placement. Methods. Images of the static knee of a subject are obtained in-vivo using fluoroscopy over a 180° sweep at 15 frames per second (MultiDiagnost Eleva, Philips, The Netherlands). A 3D model of the knee is constructed in accompanying software (3D-RX, Philips, The Netherlands) and is subsequently imported in OsiriX imaging software (Pixmeo, Switzerland). In Osirix, a reproducible coordinate system is obtained using the bone stub axis and the anatomical epicondylar axis as references [Fig. 1]. We quantified the sagittal contour of the distal femur in two parameters: the flexion angle of femoral component and the sagittal profile of the implant. To measure the flexion angle, the image is located in the midtrochlear plane. The angle is measured between the bone stub axis and the neutral line of the femoral component [Fig. 2]. To measure the sagittal profile of the distal femur, the lengths of three lines connecting the anatomical epicondylar axis of the distal femur and the outer border of the femur/prosthesis are summed. This is done both anterior and posterior [Fig. 3]. These profiles are measured in planes of the lateral and medial condyle and of the midtrochlear plane. Due to the reproducible coordinate system, the profiles can be compared for the knee before and after implant placement. Conclusion. Using fluoroscopy and readily available 3D imaging software we have developed a technique for measuring valuable parameters concerning implant placement in TKA. This technique can be used for scientific purposes concerning comparison of the knee before and after implant placement and to study its effect on functional and biomechanical outcome after TKA

When dealing with the patella in total knee arthroplasty (TKA) there are three philosophies. Some advocate resurfacing in all cases, others do not resurface, and a third group selectively resurfaces the patella. The literature does not offer one clear and consistent message on the topic. Treatment of the patella and the ultimate result is multifactorial. Factors include the patient, surgical technique, and implant design. With respect to the patient, inflammatory versus non-inflammatory arthritis, pre-operative presence or absence of anterior knee pain, age, sex, height, weight, and BMI affect results of TKA. Surgical technique steps to enhance the patellofemoral articulation include: 1) Restore the mechanical axis to facilitate patellofemoral tracking. 2) Select the appropriate femoral component size with respect to the AP dimension of the femur. 3) When performing anterior chamfer resection, measure the amount of bone removed in the center of the resection and compare to the prosthesis. Do not overstuff the patellofemoral articulation by taking an inadequate amount of bone. 4) Rotationally align the femur appropriately using a combination of the AP axis, the transepicondylar axis, the posterior condylar axis, and the tibial shaft axis. 5) If faced with whether to medialise or lateralise the femoral component, always lateralise. This will enhance patellofemoral tracking. 6) When resurfacing the patella, only evert the patella after all other bony resections have been performed. Remove peripheral osteophytes and measure the thickness of the patella prior to resection. Make every effort to leave at least 15 mm of bone and never leave less than 13 mm. 7) Resect the patella. The presenter prefers a freehand technique using the insertions of the patellar tendon and quadriceps tendon as a guide, sawing from inferior to superior, then from medial to lateral to ensure a smooth, flat, symmetrical resection. Medialise the patellar component and measure the thickness of reconstruction. 8) When not resurfacing the patella, surgeons generally remove all the peripheral osteophytes, and some perform denervation using electrocautery around the perimeter. 9) Determine appropriate patellofemoral tracking only after the tourniquet is released. 10) Close the knee in flexion so as not to tether the soft tissues about the patella and the extensor. With or without patellar resurfacing, implant design plays in important role in minimizing patellofemoral complications. Newer designs feature a so-called “swept back” femur in which the chamfer resection is deepened, and patellofemoral overstuffing is minimised. Lateralizing the trochlear groove on the anterior flange, orienting it in valgus alignment, and gradually transitioning to midline have improved patellofemoral tracking. Extending the trochlear groove as far as possible into the tibiofemoral articulation has decreased patellofemoral crepitation and patellar clunk in posterior stabilised designs. With respect to the tibial component, providing patellar relief anteriorly in the tibial polyethylene has facilitated range of motion and reduced patellar impingement in deep flexion. On the patella side, the all-polyethylene patella remains the gold standard. While data exist to support all three viewpoints in the treatment of the patella in TKA, it is the presenter's opinion that the overwhelming data support patella resurfacing at the time of primary TKA. It is clear from the literature that the status of the patellofemoral articulation following TKA is multifactorial. Surgical technique and implant design are key to a well-functioning patellofemoral articulation. Pain is the primary reason patients seek to undergo TKA. Since our primary goal is to relieve pain, and there has been a higher incidence of anterior knee pain reported without patellar resurfacing, why not resurface the patella?

In May 2010, MyKnee® patient-specific instrumentation was approved for use in this procedure in the USA. This technique uses a pre-operative CT scan of the lower extremity to plan the surgery. Images of the hip, knee, and ankle are reconstructed digitally to assess pre-operative deformity as well as size of the knee. Surgery is then planned with the goals of restoring a neutral mechanical axis of limb and providing correct sizing and placement of implants after the surgery. From this plan, patient-specific jigs are created to perform the surgery achieving the planned result without sacrificing speed of surgery or increasing complexity of the procedure. The present study seeks to evaluate both intraoperative and radiographic results of this procedure. IRB approval for retrospective research was obtained prior to evaluation of the data. Thirty consecutive patients (14 males, 16 females) underwent TKA using the MyKnee technique by the senior author. Pre-operative long-standing radiographs were taken and compared to 6-week post-operative radiographs. Intraoperative data includes the femoral and tibial resection thickness: distal medial femoral, distal lateral femoral, posterior medial femoral, posterior lateral femoral, medial tibia, and lateral tibia. These were compared to the planned vs. actual resections. Tourniquet time was recorded as a measure of speed of surgery. These were compared to 30 consecutive patients using standard TKA technique by the same author. Intraoperative complications were also recorded. For patients with varus pre-operative deformities (n = 21), the mechanical alignment was 7.8° (range 1.2° to 15.2°). Seven patients had pre-operative valgus deformities averaging 6.93° (range 1.3° to 14.5°). Two patients were neutral. Post-operative alignment for all patients (n = 30) was varus 1.92° (range 0° to 5.8°). Seventy-eight percent of patients were within 3° and 97% of patients were within 3.6°. In comparison, post-operative alignment for standard TKA patients measured varus 1.85°, which was not statistically significant. Seventy-nine percent of patients were within 3°; however the outliers were more dramatic ranging 3.5° to 9.2°. Thirty femoral and 21 tibial resections were available for review using the MyKnee technique. The actual vs. planned resections for the distal medial femoral resection was 9.5 vs. 9.1mm respectively. Further actual vs. planned femoral resections include distal lateral femoral 8.4 vs. 6.3mm; posterior medial femoral 9.3 vs. 9.5mm; and posterior lateral femoral 8.6 vs. 7.0mm. The actual vs. planned tibial resections recorded include medial 6.07 vs. 6.29mm and lateral 9.36 vs. 8.19mm. Tourniquet time averaged 32.97 minutes (range 25 to 54) in the standard TKA group vs. 37.03 minutes (range 1 to 71) in the MyKnee group. This difference was not significant. However, the final 15 MyKnee patients had an average time of 33.46 minutes. No intraoperative complications occurred. Many techniques exist for performance of TKA. Patient-specific cutting blocks allow the surgeon to pre-operatively determine resection depths, rotations, alignment, and sizing prior to the operative procedure itself. The present study shows that intraoperative resections and post-operative alignments can be accurately achieved with pre-operative CT planning and using patient-specific instrumentation. For the typical varus knee deformity, cartilage will exist on the lateral side of the knee. This can cause measurement error when measuring the lateral compartments as the CT scan is based on bone only. This can be seen in 2.1mm and 1.6mm differences in the distal lateral femoral and posterior lateral femoral resections respectively. Thus, this difference can be explained by the false measurement of intact cartilage. More accurate results could be obtained if the cartilage was removed and bone measured. Valgus knees, being diseased in the lateral compartment, did not show such variance as expected in planned vs. actual resections. Intraoperative speed of surgery is important to all participants in TKA: surgeon, hospital, and patient. Obviously accuracy should not be sacrificed for speed so it is important for any new technology introduced to the market to accelerate surgery not compromise results. In the current study, the average times of MyKnee vs. standard TKA surgery were comparative and not significantly different using a two-sample T-test. The standard TKA average tourniquet time may appear faster than other reported literature; however the surgeon is on the end of learning curve with the system. The MyKnee average tourniquet time represents the initial procedures in the learning curve and can be considered slower than what they will eventually be as the author gains more experience with the technique. Efficiency was demonstrated with the decrease in tourniquet time for the last 15 patients. Furthermore, the goals of surgery were maintained radiographically. Regardless of the deformity, the patient's post-operative mechanical axes averaged 1.85° for standard technique and 1.92° for the MyKnee group, not statistically significantly different. These results were obtained via long-standing x-rays, which are well known to be prone to error in alignment secondary to potential flexion and rotation of the extremity. The standardised protocol for acquisition of the X-ray, attempts to prevent these errors and X-rays are routinely re-done if the technician feels error has occurred. The technique also appears safe as no intra-operative complications occurred and were recognised within the first six weeks post-operative. In conclusion, using patient-specific instrumentation (MyKnee) is safe, quick, and accurate in performance of TKA

Introduction. Cementless total knee arthroplasty (TKA) has several advantages compared to the cemented approach, including elimination of bone cement, a quicker and easier surgical technique, and potentially a stronger long-term fixation. However, to ensure the successful long-term biological fixation between the porous implant and the bone, initial press-fit stability is of great importance. Undesired motion at the bone-implant interface may inhibit osseointegration and cause failure of biological fixation. Initial stability of a cementless femoral implant is affected by implant geometry, bone press-fit dimension, and characteristics of the porous coating. The purpose of this study was to compare the initial fixation stability of two types of porous femoral implants by quantifying the pull-out force using a paired cadaveric study design. Methods. The two types of cementless TKA femoral implants evaluated in this study had identical implant geometry but different porous coatings (Figure 1). The first type had a conventional spherical-bead coating (Type A), while the second type had an innovative irregularly-shaped-powder coating (Type B). The porous coating thickness was equivalent for both types of implants, thus the dimensional press-fit with bone was also equivalent. Three pairs of cadaveric femurs were prepared using standard TKA surgical technique, with each pair of the femurs receiving one of each porous implant type. An Instron 3366 load frame (Norwood, MA, USA) was used to pull the femoral implant out from the distal femur bone (Figure 2). The testing fixture was designed to allow free rotation between the implant and the actuator. The pullout was performed under a displacement control scheme (5 mm/min). Peak pull-out force was recorded and compared between the two implant groups. Results. Mean pull-out force for the Type B porous femoral implants (512 ± 246 N) was greater than that of the Type A porous femoral implants (310 ± 185 N), although the difference was not statistically significant (p>0.05) (Figure 3). Discussion. This paired cadaveric study showed that the innovative Type B porous coating provides equivalent and potentially greater pull-out force than the conventional Type A porous coating. Lack of statistical significance could be attributed to the limited sample size. Although pull-out testing is not a physiological loading scenario for TKA implant, it provides a relevant assessment of the implant-bone press-fit stability. With all other factors the same, the greater pull-out force observed in the Type B implants is likely related to the higher roughness and friction of the new porous coating. Previous experiments have shown that the Type B porous coating has significantly greater friction against Sawbones surface (coefficient of friction 0.89) compared to Type A porous coating (coefficient of friction 0.50), which was consistent with the findings in this study. Greater initial fixation stability is more favorable in cementless TKA as it reduces the risk of interface motion and better facilitates long-term biological fixation

INTRODUCTION. Balancing accurate rotational alignment, minimal overhang, and good coverage during total knee arthroplasty (TKA) often leads to compromises in tibial component fit, especially in smaller-sized Asian knees. This study compared the fit and surgical compromise between contemporary anatomic and non-anatomic tibial designs in Japanese patients. METHODS. Size and shape of six contemporary tibial component designs (A:anatomic, B:asymmetric, C-F:symmetric) were compared against morphological characteristics measured from 120 Japanese tibiae resected following TKA surgical technique. The designs were then digitally placed on the resected tibiae. Each placement selected the largest possible component size, while ensuring <1mm overhang and proper alignment (within 5° of neutral rotational axis). When a compromise on either alignment or overhang was required (due to smaller-sized component unavailable), the design was flagged as “no suitable component fit” for that bone. Tibial coverage was compared across designs. Next, 32 femora were randomly selected from the dataset onto which each design was evaluated in two placements, the first maximizing coverage without attention to rotation and the second enforcing rotational accuracy. Downsizing was identified if in the second placement, enforcing rotational accuracy, required a smaller component size compared the first placement. The degree of mal-alignment while maximizing coverage, the incidence of downsizing, and difference in coverage between the two placements were compared across designs. Statistical significance was defined at p<0.05. RESULTS. Design A closely matched the tibial morphology and had better size and shape conformity than Designs B-F (select metrics shown in Fig. 1). Design A exhibited higher average coverage (92%) than other designs in all ethnicities (85–87%, Fig. 2A) (p<0.01). Designs D-F had no suitable component fit in 1.6–2.4% of the bones (Fig. 2B). Coverage generally decreased with reduced component size (Fig.2C), with Design A having higher coverage than Designs B-F across all sizes. In the randomly selected 32 tibiae, enforcing rotational accuracy significantly compromises coverage in Designs B-F (Fig.3A) (p<0.01), with up to 15% in individual bones. In contrast, coverage of Design A was not influenced by enforcing rotational accuracy (p=0.52). Designs B-F were found to require downsizing on 41–66% of bones due to >5° rotation, with components internally rotated beyond 10° on 31–59% of the bones (Fig.3B). In contrast, Design A required downsizing on only 6% of the bones, caused by small mal-rotations (<10°). Designs B-D and F required downsizing of ≥2 sizes on 3–16% of bones; while a single downsize was sufficient for Design A (Fig.3C). DISCUSSION. The anatomic design not only has the closest match to the natural tibia, but also consistently has the highest coverage across bone sizes. It also exhibits fewer incidences of downsizing and reduced propensity for mal-alignment than the non-anatomic designs investigated. In contrast, in the non-anatomic tibial component designs, ensuring rotation accuracy considerably compromised tibial coverage. This result, suggests that many non-anatomic designs do not fully accommodate variations in bone anatomy in the Japanese patients, thus forcing a compromise

The process by which pathologic scar tissue forms after TKA and restricts functional range of motion is relatively poorly understood. Arthrofibrosis may develop in patients who have normal intra-operative range of motion (ROM). However, passive flexion, extension, or both can become restricted and painful, sometimes several weeks after surgery following an early post-operative period of normal motion. The response to both nonsurgical and surgical treatment is often unsatisfactory. Arthrofibrotic scar contains dense fibrous tissue with abundant fibroblasts. Heterotopic bone is frequently found in patients with arthrofibrosis. Stiffness may result from inadequate postsurgical pain management or rehabilitation or from a biologic process that causes rapid proliferation of scar tissue. Genetic factors also may play a role, although it is difficult to predict which patients are at increased risk for arthrofibrosis after TKA. Surgical technique also can contribute; oversizing the femoral component, overstuffing the patella, or rotational malalignment can play a role. Manipulation can be helpful, particularly during the first three months after surgery. However, maintaining motion long term also requires an effective pain management and physical therapy program after manipulation. Arthroscopy may also have a role to remove scar tissue in the suprapatellar pouch and medial and lateral gutters usually between six months and one year after TKA. After one year following TKA, open surgical release or revision surgery is the most effective method to increase motion. However, only modest gains are likely to be achieved and pain may not be improved

Hypothesis. Custom cutting blocks can produce similar alignment compared to computer navigated and conventional total knee arthroplasty (TKA) techniques. Method. We conducted a retrospective review of 37 patients who underwent TKA by a single surgeon in a teaching hospital setting. Groups were conventional method (10), computer assisted navigation (10), and custom blocks (18). The custom group was further subdivided to CT and MRI based blocks. Post-operative alignment was measured (blinded) using full length weight bearing radiographs at 18 weeks on average. Hospital records were reviewed to determine operative time, transfusion requirements, length of hospital stay, complications and cost. Results. Post-operative mechanical axis was within 3 degrees of neutral in 100% of the navigation group, 70% of the conventional group and 50% of the custom block group. Average alignment was within 1.8, 3.1 and 3.6 degrees of neutral for each group respectively. The operative time was greater for the computer navigation group (86.7 min) compared to the conventional (72.1) and MRI custom block groups which involved unfamiliar instrumentation (73.8). CT based block procedures involved otherwise familiar instruments and averaged 61.2 minutes. Length of hospital stay and complications were similar for all three groups. Total cost was the least for the conventional group. Increased costs were associated with computer equipment, pre-operative advanced imaging and custom blocks. Conclusions. Custom cutting blocks in this small series obtain worse radiographic positioning of total knee arthroplasty components compared to conventional and computer navigation techniques. Further studies with greater number of patients, CT alignment analysis and long-term follow-up are required