Aims. Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort. Methods. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A DL workflow was created to measure the FMAA and validated against human measurements. To reflect potential intramedullary guide placement during manual TKA, two different FMAAs were calculated either using a line approximating the entire diaphyseal shaft, and a line connecting the apex of the femoral intercondylar sulcus to the centre of the diaphysis. The proportion of FMAAs outside a range of 5.0° (SD 2.0°) was calculated for both definitions, and FMAA was compared using univariate analyses across sex, BMI, knee alignment, and femur length. Results. The algorithm measured 1,078 radiographs at a rate of 12.6 s/image (2,156 unique measurements in 3.8 hours). There was no significant difference or bias between reader and algorithm measurements for the FMAA (p = 0.130 to 0.563). The FMAA was 6.3° (SD 1.0°; 25% outside range of 5.0° (SD 2.0°)) using definition one and 4.6° (SD 1.3°; 13% outside range of 5.0° (SD 2.0°)) using definition two. Differences between males and females were observed using definition two (males more valgus; p < 0.001). Conclusion. We developed a rapid and accurate DL tool to quantify the FMAA. Considerable variation with different measurement approaches for the FMAA supports that patient-specific anatomy and surgeon-dependent technique must be accounted for when correcting for the FMAA using an intramedullary guide. The angle between the mechanical and anatomical axes of the femur fell outside the range of 5.0° (SD 2.0°) for nearly a quarter of patients. Cite this article: Bone Jt Open 2024;5(2):101–108

Purpose: This cadaveric study examines how changes in femoral entry point for intramedullary instrumentation of total knee replacements affects femoral component positioning.

Methods: Twelve cadaveric lower limb specimens with intact hip, knee and ankle joints were obtained. Total knee navigation instrumentation was secured. Anatomical landmarks required for axes generation were obtained. An initial entry point was made at the center of the distal femur. An intramedullary rod was the introduced into the femur. Five and seven degree cutting blocks were placed onto the rod and positioned against the distal femur with the rotation parallel to the epicondylar axis. The navigation system was then used to generate a varus/valgus angle and flexion/extension angle with respect to the previously generated femoral mechanical axes. This allowed determination of an angle at which the distal femoral cutting block would need to be set to make a neutral distal femoral cut. The guide rod was removed and reinserted five times and measurements recalculated. Data was then collected with entry points 5mm medial, 5mm anterior and 5mm medial and anterior to the initial entry point.

Results: There was no significant difference in varus/ valgus angle with a central compared with 5mm anterior entry point and no difference with a 5mm medial versus 5 mm medial and anterior entry point. The valgus angle required to give a neutral distal femoral cut with a central entry point was 4.98o (SD 0.91o; range 3.5o–6.0o). The valgus angle for a 5mm medial entry point was 6.92o (SD 0.97o, range 5.5o–8.0o). With regards to the sagittal plane a 5mm anterior translation of the entry point changed the flexion/extension angle by 1.58o (SD 0.52o, range 0.5o–2.5o).

Conclusions: Small changes in the entry point can significantly affect component alignment. When moving more medial with the entry point a more valgus angle is required for the cutting block. An entry point at the deepest point of the trochlea may be more reproducible than an anteromedial one but requires a valgus cutting block closer to 5 degrees.

Funding : Commerical funding

Funding Parties : Stryker

Introduction: Appropriate femoral component alignment is important for long-term survival of total knee arthroplasty (TKA). Valgus angle of femoral component is recommended as the angle between mechanical axis and anatomical axis of the femur. Intramedullary guide system is widely used for determining the valgus positioning of femoral component. Entry point of intramedullary guide is one of the key factors for determining valgus angle of femoral component. Some investigators have shown appropriate entry points of intramedullary guide, however, it is still unclear. In this study, appropriate entry point of intramedullary guide system was calculated using three-dimensional digital templating software “Athena” (Soft Cube, Osaka, Japan). Method: Forty-one knees in 34 osteoarthritis patients except valgus deformity (30 females and 4 males, mean age 75.1 years) received TKA and were simulated using “Athena” from January 2009 to March 2009. All cases were grade III or IV in Kellgren-Lawrence index. Radiograph and CT scan image were used for determination of appropriate entry point of femur using “Athena”. The anatomical axis of femur was defined as a line connecting the midpoints of femoral AP and lateral diameter, at 60 mm and 110 mm proximal to the center of intercondylar notch. Two coordinate systems were configured as representation of entry points. One was at the center of intercondylar notch defined as the point of origin in axial view of CT image and the line parallel to the clinical epicondylar axis (cTEA) defined as X-axis. Another coordinate system was the same point of origin but parallel to the line between trochlear groove and the center of intercondylar notch (AP line) defined as Y-axis. Result: In the coordinate system that defined the cTEA as the X-axis, the average of entry point was 0.3± 0.30 mm medial (range, −4.8~ 4.7mm) and 11.6 ± 0.52mm anterior (range, 3.1~ 16.5mm) to the center of intecondylar notch. In the other coordinate system that defined AP line as the Y-axis, the average of entry point was 2.6± 0.29 mm medial (range, −1.5~ 6.3mm) and 11.2±0.52 mm anterior (range, 2.8~ 16.0mm) to the center of intercondylar notch. Discussion: In this study, the appropriate entry point of intramdullary guide was slightly medial and about 11mm anterior to the center of intercondylar notch on average. However, individual entry point varied considerably in distance. These data indicates that it is important to simulate the appropriate entry point of intramedullary guide in preoperative planning

Introduction. Total knee arthroplasty is effective for the management of osteoarthritis of the knee. Conventional techniques utilizing manual instrumentation (MI) make use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. While MI techniques can achieve excellent results in the majority of patients, those with ipsilateral hardware, post-traumatic deformity or abnormal anatomy may be technically more challenging, resulting in poorer outcomes. Computer-assisted navigation (CAN) is an alternative that utilizes fixed trackers and anatomic registration points, foregoing the need for intramedullary guides. This technique has been shown to yield excellent results including superior alignment outcomes compared to MI with fewer outliers. However, studies report a high learning curve, increased expenses and increased operative times. As a result, few surgeons are trained and comfortable utilizing CAN. Patient-specific instrumentation is an alternative innovation for total knee arthroplasty. Custom guide blocks are fabricated based on a patient's unique anatomy, allowing for the benefits of CAN but without the increased operative times or the high learning curve. In this study we sought to evaluate the accuracy of PSI techniques in patients with previous ipsilateral hardware of the femur. Methods. After reviewing our database of 300 PSI total knee arthroplasty patients, 16 were identified (10 male, 6 female) using the Zimmer NexGen Patient Specific Instrumentation System. Fourteen patients included in the study had a preexisting total hip arthroplasty on the ipsilateral side [Figure 1], 1 had a sliding hip screw, and 1 patient had a cephalomedullary nail. Postoperative mechanical axis alignment measurements were performed using plain long-standing radiographs [Figure 2]. The American Knee Society Score was used to evaluate clinical outcomes postoperatively. Results. Sixteen total knee arthroplasties were performed using PSI, all in the setting of previous ipsilateral hardware placement. The average age at the time of surgery was 72, with patients ranging from 56 to 85 years of age [Table 1]. 11 of the included knees had a preoperative varus alignment and 5 had valgus alignment. The average value of a deformity identified via the preoperative planning software was 7.9°(1.5°–15.7°). The average value of a deformity identified via preoperative radiographs was 10.1°(2.2°–14.7°). Average postoperative mechanical axis was 3.1° (1°–5.3°) measured from plain radiographs. Average angle between the FMA and femoral component was 90.0° (85.3°–94.1°). The average angle between the TMA and tibial component was 90.6°(87.6°–92.9°). The average difference between the femoral mechanical and anatomic axes was 5.9°(3.4°–7.0°). The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.4mm(0.0mm–1.1mm). At an average of 4.5 months follow-up, American Knee Society knee scores show an aggregate average score of 82.94. Conclusions. Patient specific instrumentation (PSI) is an innovative technology in TKA that replaces the use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. This study demonstrates that PSI is capable of producing favorable radiographic and clinical outcomes despite preexisting ipsilateral hardware, which may otherwise preclude the use of customary manual instrumentation. We believe PSI is an accurate and effective tool for use in patients with preexisting ipsilateral hardware

Purpose. Use of theguide angle method using intramedullary guide angle for distal femoral cutting in total knee arthroplasty may cause error when rotation of the femur occurs or the insertion point of the intramedullary guide is incorrectly positioned in preoperative radiography. On the other hand, use of the measured cutting method, in which resection of distal femoral condyles is performed according to predicted measured thickness in a preoperative radiograph can allow for correction of these errors intraoperatively. Therefore, we compared these two distal femoral bone cutting methods for restoration of accurate coronal alignment. Methods. Between 2010 and 2012, 47 patients (70 knees) underwent total knee arthroplasty for treatment of osteoarthritis with varus deformity and flexion contracture less than 10 degrees. Bone resection depending on distal femur resection thickness measured before the operation was performed in 38 cases (Group I). Distal femoral cutting using the guide angle was performed in 32 cases (Group II). Radiographic evaluation, including mean value of lower leg mechanical axis angle and the frequency of errors of more than 3 degrees, was performed for comparison between the two groups. Results. In Group I, mechanical axis was corrected from 8.4 ± 4.9 degrees (−7.2 to 16.9) on average before the operation to 0.1 ± 2.4 degrees (−5.87 to 2.98) after the operation, and, in Group II, from 6.7 ± 3.6 degrees (0.4 to 14.7) on average before the operation to 0.5 ± 2.8 degrees (−5.4 to 6.9) after the operation. No statistically significant difference in mechanical axis (p = 0.554) was observed between the two groups after the operation, and no difference in errors of more than 3 degrees was observed between the two groups, with four of 38 cases (11 %) in Group I and six of 32 cases (19%) in Group II (p = 0.495). Conclusions. No significantly different results were observed between the measured resection technique and the existing guide angle technique. Therefore, predictive measurement of distal femoral cutting thickness is another useful method for restoration of accurate coronal alignment

In the last years, 3d printing has progressively grown and it has reached a solid role in clinical practice. The main applications brought by 3d printing in orthopedic surgery are: preoperative planning, custom-made surgical guides, custom-made im- plants, surgical simulation, and bioprinting. The replica of the patient's anatomy, starting from the elaboration of medical volumetric images (CT, MRI, etc.), allows a progressive extremization of treatment personalization that could be tailored for every single patient. In complex cases, the generation of a 3d model of the patient's anatomy allows the surgeons to better understand the case — they can almost “touch the anatomy” —, to perform a more ac- curate preoperative planning and, in some cases, to perform device positioning before going to the surgical room (i.e. joint arthroplasty). 3d printing is also commonly used to produce surgical cutting guides, these guides are positioned intraoperatively on given landmarks to guide the surgeon to perform a specific surgical act (bone osteotomy, bone resection, implant position, etc.). In total knee arthroplasty, custom-made cutting guides have been developed to help the surgeon align the femoral and tibial components to the pre-arthritic condition with- out the use of the intramedullary femoral guide. 3d printed custom-made implants represent an emerging alternative to biological reconstructions especially after oncologic resection surgery or in case of complex arthroplasty revision surgery. Custom-made implants are designed to re- place the original shape and size of the patient's bone and they allow an extreme personalization of the treatment for every single patient. Patient-specific surgical simulation is a new frontier that promises great benefits for surgical training. a solid 3d model of the patient's anatomy can faithfully reproduce the surgical complexity of the patient and it allows to generate surgical simulators with increasing difficulty to adapt the difficulties of the course with the level of the trainees performing structured training paths: from the “simple” case to the “complex” case

It is very difficult to perform total knee arthroplasty (TKA) for severe varus bowing deformity of femur. We performed simultaneous combined femoral supra-condyle valgus osteotomy and TKA for the case had bilateral varus knees with bowing deformity of femurs. Case presentation. A 62-year-old woman consulted our clinic with bilateral knee pain and walking distability. She was diagnosed rickets and had bilateral severe varus bowing deformity of femurs from an infant. Her height was 133 cm and body weight was 51 kg. Bilateral femur demonstrated severe bowing and her knee joint demonstrated varus deformity with medial joint line tenderness, no local heat, and no joint effusion. Bilateral knee ROM was 90 degrees with motion crepitus. Bilateral lower leg demonstrated mild internal rotation deformity. Bilateral JOA knee score was 40 Roentgenogram demonstrated knee osteoarthritis with incomplete development of femoral condyle. Mechanical FTA angles were 206 degree on the right and 201 on the left. She was received right simultaneous femoral supra-condyle valgus osteotomy with TKA was performed at age 63. Key points of surgical techniques were to use the intramedullary guide for valgus osteotomy as temporary reduction and fixation then performed mono-cortical locking plate fixation. Several mono cortical screws were exchanged to bi-cortical screws after implantation of the femoral component with long stem. Cast fixation performed during two weeks and full weight bearing permitted at 7 weeks after surgery. Her JOA score was slightly improved 50 due to other knee problems at 9 months after surgery, her right mechanical FTA was decreased to 173, and she received left simultaneous femoral supra-condyle valgus osteotomy with TKA as the same technique at April of this year. She has been receiving rehabilitation at now. Conclusions. Most causes of varus knee deformity are defect or deformity of medial tibial condyle and TKA for theses cases are not difficult to use tibial augment devices. However the cases like our presentation need supra-femoral condyle osteotomy before TKA. It was easy and useful to use intramedullary guide for valgus osteotomy as temporary reduction and fixation then performed mono-cortical locking plate fixation before TKA

Introduction. Stryker computer navigation system has been used for total knee arthroplasty (TKA) procedures since October 2008 at the Russian Ilizarov Scientific Centre for Restorative Traumatology and Orthopaedics. Material and methods. There have been 126 computer assisted TKA that accounted for 11.5 % of primary TKA within this period (1096 procedures). Arthritis of the knee joints with evident pain syndrome was an indication to TKA surgery. Arthritis of the knee joint of 27 patients (21.4 %) was accompanied by femoral deformity of various etiology with debris found in the medullary canal in several cases. The rest 99 patients (78.6 %) were regular cases of primary TKA. Results. We compared the results of correction of lower limb biomechanical axis with TKA employing navigation and without computer assistance. Regular TKA procedures showed no substantial difference in the correction of biomechanical axis. Complete correction using computer navigation was achieved in 85 % of the cases versus 79 % of the patients without navigation. The deformity up to 3° developed in 14 % of navigated cases and in 17 % of the cases without computer assistance. An error of deformity correction was 3–5° in 4 % of the cases without computer navigation. Those were cases of challenging primary TKA. So the advantages of computer navigation have become evident with greater deformities, and in the cases when intramedullary guide can hardly be used due to severe deformities in the femoral metaphysis and diaphysis, after several operative procedures of osteosynthesis with deformed, obliterating bone marrow canal or presence of debris. Complete correction using computer navigation was achieved in 85.2 % cases versus 42.8 % patients without navigation. Postoperative varus of 2° was observed in 14.8 % cases (valgus or varus deformity of 3° developed in 28.6 % of the cases without computer assistance). Conclusion. What is better: special instrumentation or navigation?. Current instrumentation can provide regular mechanical control of the limb axis and is based on the principles of intramedullary, extramedullary and even double guide placement. Image-free navigation and standard surgical techniques can equally be used for simple cases of primary TKA. Same landmarks are used. These landmarks are determined by a surgeon quite subjectively and can lead to inadequate usage of special instrumentation and computer navigation. However, computer navigation should be used in the cases when intramedullary guide can hardly be used, not desirable or possible. Special instrumentation can fail in setting a valgus angle needed with extraarticular femoral deformity. Navigation allows determining rotation more precisely in the cases when posterior femoral condyles contour (posttraumatic condition, hypoplastic condyles) is distorted. Assessment of ligament balance can be rather subjective when special instrumentation is used. Application of computer navigation is helpful for measurements of flexion and extension gaps sixe and regularity. Computer navigation is contraindicated for contractures and ankyloses of the hip joint. For the rest of the cases the choice of instrumentation is a surgeon's decision

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

Introduction. Total knee arthroplasty (TKA) reliably improves pain and function in patients with knee osteoarthritis (OA), though a substantial percentage of patients remain unsatisfied. Reasons include the presence of complications, persistent pain, and unmet expectations. The aim of this study was to determine whether the sequential addition of accelerometer-based navigation of the distal femoral cut and sensor-assisted soft tissue balancing changed complication rates, radiographic alignment, or patient-reported outcomes (PROs) compared to TKA performed with conventional instrumentation. Methods. This retrospective cohort study included 371 TKAs in 319 patients. All surgeries were performed by a single surgeon in sequential fashion using a measured resection technique with a goal of mechanical alignment. The historical control group, utilizing intramedullary guides for distal femoral resection and surgeon-guided soft tissue balancing, was compared to group 1 (accelerometer-based navigation for distal femoral resection, surgeon-guided balancing) and group 2 (navigated femoral resection, sensor-guided balancing). Primary outcome measures were PROMIS scores including physical function computerized adaptive test (PF CAT), and the Global 10 health assessment (including physical, mental, and pain scores), and Knee Injury Osteoarthritis and Outcome Score (KOOS), measured preoperatively and at 6 weeks and 12 months postoperatively. Radiographic measurements included component position and overall mechanical alignment of the limb and were made at 6 weeks by a single examiner from hip to ankle standing films. Charts were reviewed for pre- and postoperative ROM at 6 weeks, polyethylene insert morphology, and postoperative hematocrit change. Complications were recorded, including manipulation under anesthesia and reoperation. Our study was powered to detect a difference of 1 standard deviation in PF CAT score with 100 patients. Statistical analysis was performed by a statistician including t-tests, multivariate regression, and time series plot analyses. Results. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There was no difference in baseline patient demographics. Patients in group 2 had higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p=0.04). There were no differences in 6-week and one-year postop PF CAT, physical or mental subscores, pain scores, or KOOS scores (all p>0.05). There were 8 total complications in the control group (4.1%), 4 in group 1 (3.8%), and 1 in group 2 (1.4%) (p>0.4). The postoperative mechanical axis of the limb was within 3 degrees of neutral in 71.6% of control patients, 74.8% in group 1, and 85.1% in group 2 (p=0.1). There was no difference in femoral component coronal alignment between groups (p=0.91), though controls had a small but significantly higher degree of flexion in the sagittal plane (6.5 degrees) than groups 1 and 2 (5.4 degrees in both, p=0.003). There was no difference in postoperative ROM or blood loss. Conclusions. The sequential addition of imageless navigation of the distal femoral cut and sensor-guided ligament balancing did not confer any benefit to short term PROs, radiographic outcomes, or complication rates over conventional techniques. While overall mechanical alignment of the limb was improved in groups 1 and 2 compared to controls, this did not reach statistical significance. The additive costs of navigation and soft-tissue balancing technologies may not be justified. For figures, tables, or references, please contact authors directly

Introduction:. Total knee arthroplasty (TKA) is an effective operation for the management of osteoarthritis of the knee. Conventional technique utilizing manual instrumentation (MI) allows for reproducible and accurate execution of the procedure. The most common techniques make use of intramedullary femoral guides and either extrameduallary or intrameduallary tibial guides. While these methods can achieve excellent results in the majority of patients, those with ipsilateral hardware, post-traumatic deformity or abnormal anatomy may preclude the accurate use of these techniques. Patient-specific instrumentation (PSI) is an alternative innovation for total knee arthroplasty. Utilizing magnetic resonance imaging (MRI) or computed tomography (CT), custom guide blocks are fabricated based on a patient's unique anatomy. This allows for the benefits of computer assisted navigation (CAN) but without the increased operative times or the high learning curve associated with it. Furthermore it allows the use of familiar cutting blocks and guides to check the accuracy of the PSI guide blocks. In this study we sought to evaluate the accuracy of PSI techniques in patients with previous ipsilateral hardware, which would make the use of MI technically challenging and possibly subject to inaccuracy. Methods:. After reviewing our database of 300 PSI total knee arthroplasty patients, 16 patients were identified (10 male, 6 female) using the Zimmer NexGen Patient Specific Instrumentation System. Fourteen patients included in the study had a preexisting total hip arthroplasty on the ipsilateral side, 1 had a preexisting sliding hip screw, and 1 patient had a preexisting cephalomedullary nail. Postoperative mechanical axis alignment measurements were performed using plain long-standing radiographs. The American Knee Society Score was used to evaluate clinical outcomes postoperatively. Results:. Sixteen total knee arthroplasties were performed using PSI, all in the setting of previous ipsilateral hardware placement. The average age at the time of surgery was 72, with patients ranging from 56 to 85 years of age. Eleven of the included knees had a preoperative varus alignment and 5 had valgus alignment. The average value of a deformity identified via the preoperative planning software was 7.85°. The average value of a deformity identified via preoperative radiographs was 10.1°. Average postoperative mechanical axis was 3.1° measured from plain radiographs. Average angle between the femoral mechanical axis and femoral component was 90.0°. The average angle between the tibial mechanical axis and tibial component was 90.6°. The average difference between the femoral mechanical and anatomic axes was 5.9°. The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.4 mm. At an average of 4.5 months follow-up, American Knee Society knee scores show an aggregate average score of 82.94. Conclusion:. Patient specific instrumentation is an innovative technology in TKA that replaces the use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. This study demonstrates that PSI is capable of producing favorable radiographic and clinical outcomes despite preexisting ipsilateral hardware, which may preclude the use of customary manual instrumentation. We believe PSI is an accurate and effective tool for use in patients with preexisting ipsilateral hardware

Introduction: The correct position of the knee arthroplasty components is associated with a better result of the prosthesis. In the tibial component, both intramedullar and extramedullar instrumentations have been used for its fiability, but in the femoral component intramedullar guides are more precise than extramedullar ones. The use of the intramedullar guide for the femoral component is not always possible, because a significant deformity of the femoral shaft or when a intramedullar device has been implanted in the femur. We have studied the alineation of the components of computer assisted total knee arthroplasties in a group of patients with femoral deformities or implants. Material and methods: We have used the surgical navigator Stryker-Howmedica for the implantation of a knee arthroplasty in a group of 10 patients in which a endomedullar femoral guide can not be used for femoral shaft severe deformities (6 cases): Paget disease (1 case), previous femoral osteomyelitis (2 cases) or previous femoral fractures (3 cases), or a shaft device was in the femoral shaft (4 cases): long hip femoral stem (3 cases) or a femoral nail (1 case) . We have studied the alineation of femoral and tibial components with a whole-leg X-ray and Computer Tomography. Results: All the femoral and tibial components have been implanted in a good position (90 +/– 2 degrees in the A-P plane and a femorotibial axe 180 +/– 3 degrees. The alineation in the sagital and axial planes have been inside the desired values in all cases also. Discussion: It is generally accepted than intramedullary guides for the femoral component is the gold standard in arthroplasty of the knee. In the last years, the development of computer assisted systems has allowed to obtain femoral and tibial cuts referred to the mechanical axes of the bone, without using mechanical guides for the alineation. In some studies these navigation systems are better than mechanical instruments in terms of alineation of the components in cases without great deformities. In this study, with some cases with severe femoral shaft deformities or with some intramedullary devices that does not allow the use of intramedullary femoral guides, we think that the indication to use a surgical navigator should be nearly absolute

Introduction. Intramedullary femoral alignment guide is mostly used in total knee arthroplasty (TKA). Accurate preoperative plan is critical to get good alignments when we use intramedullary femoral guide, because the center of femoral head cannot be looked directly during operation. Commonly, the planning is carried out using preoperative anteroposterior radiographs of the femur. The angles formed between mechanical axes of the femur and distal femoral anatomic axes (AMA) are measured as reference angles of resection of distal femur, and the entry points of intramedullary femoral guide are also planned. The purpose of this study is to investigate the influence of femoral position on radiographic planning in TKA. Materials and Methods. We examined 20 knees of 20 female patients who received TKA. Fourteen patients suffered from primary osteoarthritis of the knees, and 6 suffered from rheumatoid arthritis. Fifteen patients have varus knee deformities and 5 patients have valgus knee deformities. Long leg computed topography scans were performed in all cases before operations, and all images were stored in DICOM file format. The analyses were performed with computer software (3D template, JMM, Osaka, Japan) using DICOM formatted data. The planes containing the center of femoral head and transepicondylar axes were defined as reference planes, and the reference planes were fixed all through analyses. At first, to assess the influence of femoral rotation, the femur was rotated from 30 degrees external rotation to 30 degrees internal rotation in 5 degrees increments in full extension. After that, to examine the influence of knee flexion, the knee was bended from full extension to 30 degrees flexion in 5 degrees increments in neutral rotation. Reconstructed coronal planes parallel to the reference planes were made, the angles between mechanical axes of the femur and distal femoral anatomic axes (AMA) and the distance from entry points to the center of femoral intercondylar notch were measured in each position. The distal anatomic axes were made by connecting the center of femoral canal at 8 centimeters proximal to joint line and that at 16 centimeters proximal to joint line. The entry points of intramedullary femoral guide were defined the points where distal anatomic axes meets intercondylar notch. Results. The mean AMA was 6.8 degrees in neutral position, 7.1 degrees in 10 degrees external rotation, 7.3 in 20 degrees external rotation, 7.2 in 30 degrees external rotation, 6.2 in 10 degrees internal rotation, 5.5 in 20 degrees internal rotation, 4.6 in 30 degrees internal rotation, 6.9 in 10 degrees flexion, 7.2 in 20 degrees flexion, 7.8 in 30 degrees flexion, respectively. The entry points moved 3.9 millimeters laterally in 20 degrees external rotation and 3.6 millimeters medially in 20 degrees internal rotation relative to neutral position. Discussion and Conclusion. Femoral position affected on preoperative planning using anteroposterior radiographs. It is important to get a correct anteroposerior view of total femur, because the femur was easy to rotate in knee disorders

Purpose. Most of revision TKA needs bone reconstruction. The success of revision TKA depends on how well the bone reconstruction can be done. The method of reconstruction includes bone cementing, metal augmentation, allogenic bone graft, APC and tumor prosthesis, etc. In moderate to severe bone defect, allograft is needed. However, allogenic bone graft is surgically demanding and needs long operation time, which is very risky to the elderly patients. The authors revised an alternative method of bone defect reconstruction using cementing method with multiple screws augmentation. Methods. There were 12 cases of patients with large defect which could not be reconstructed with metal augment from April 2012 to April 2014. The authors performed 3 to 5 screws fixation on the defect site. Sclerotic bone is prepared with burring for better cementing. 3 ∼ 5 screws according to the size of defect. The length of screw fixation was determined as deep to the bone until stable fixation just beneath the implant. When drilling for the screw insertion, intramedullary guide is put into the medullary canal so as not to interfere with implant insertion. The defect is filled with cement during prosthesis fixation. Weight bearing was permitted on postoperative 3rd day, as usual manner of primary TKA. Results. According to the AORI classification, there were 10 cases of 2A and 2 cases of 2B. Mean follow up period was average 15 months. The number of screw insertion was 4.3 ea (2∼8). Average operation time was 1 hour and 57 minutes. Mean ROM was 107.9. HSS score, KSS score ad WOMAC score were 86.3, 92.8 and 11, respectively. There were no case of infection and loosening at the last follow-up. Conclusion. Cementing with multiple screws augmentation technique is a good alternative of bone reconstruction

The stemmed tibial implant has enabled the salvage of challenging situations of bone loss in primary knee arthroplasty. This ease of use has unfortunately led to the adoption of stemmed implants in situations where this may not be warranted. In general uncontained defects of less than 5 mm may be dealt with using cement fill techniques. Defect of less than 10mm require bone grafting techniques and those above 10 mm require stems and wedges. In the third category however long term results suggest that good results are only attainable in 65% of cases whether grafts or wedges are used. The use of intramedullary guides in this setting is re-addressed to allow the accurate placement of cuts enabling the use of pegged (or non-stemmed) implants. In addition with the advent of navigation this may be a special situation where non-stemmed implants may be selected over stemmed implants

Preoperative templating essential. Make the right skin incision: most lateral, leave appropriate skin bridge from older incisions, be prepared for plastic surgical consultation for skin expanders or flaps. Release scarring in the medial and lateral gutters. Elevate a proper medial capsular sleeve. Release scarring between patellar ligament and front of tibial plateau. Pin the patellar tendon. Perform a quadriceps release OR a tibial tubercle osteotomy in the very stiff knee. Extract the prior components in an axial direction. Use intramedullary guides to align the cuts. Localise the joint line position by the level of the patellar tendon

The use of extramedullary and intramedullary guides to prepare the tibial cut was studied comparatively in 100 consecutive primary total knee arthroplasties Low Contact Stress rotating platform. Each type of guide was used in 50 consecutive cases for a total of 100 cases. An ideal tibial alignment (90°± 2°) was obtained in 42 cases (84%) using the intramedullary system (IM group) and in 36 cases (74%) using an extramedullary alignment system (EM group) (p = 0.14). A posterior slope of 10° (± 2°) was achieved in 45 cases (90%) in IM group and in 40 cases (80%) in EM group 2 (p =0.16). The difference was not statistically significant but a greater accuracy was demonstrated when using an IM tibial alignment system

Introduction. Two aspects are very important for knee joint replacement – restoration of biomechanical limb axis and achieving ligaments balance. Computer navigation allows us to do all this. Material and methods. We analysed 94 knee joint replacement surgeries using computer navigation by “STRYKER”. Results. There is no substantial difference between results of correction of biomechanical axis with computer navigation and without it in case of uncomplicated joint replacement. So, completer correction of axis (varus/valgus zero degrees) with computer navigation was achieved in 84% of cases versus 79% without navigation. There was varus or valgus deformity up to two degrees in 12% after surgery (without navigation −17% of cases). Error in deformity correction without application of navigation was three-five degrees in 4% of cases (all were challenging joint replacement). Advantages of navigation are obvious in case of large deformities, and also when insertion of intramedullary guide is undesirable or impossible. Use of navigation requires good skills of joint replacement, because landmarks should be chosen precisely and possibility of error during determining the center of rotation for the femoral head should be taken into consideration. Duration of surgery without navigation is 82.6±16.4 minutes and is much longer in the beginning of the learning curve (one hour longer or more). After acquiring skills the surgery takes 118±15.6 minutes. Conclusion. We evaluate use of navigation system as a modern and in-demand trend. Use of navigation should be started after getting good skills of joint replacement. Violation of the technology of determining landmarks leads to wrong virtual modeling and serious errors in positioning components. Advantages of navigation are obvious in evident bone deformity, when it is impossible or undesirable to open a medullary canal

Introduction. The conventional bone resection technique in TKA is recognized as less accurate than computer-assisted surgery (CAS) and patient-matched instrumentation (PMI). However, these systems are not available to all surgeons performing TKAs. Furthermore, it was recently reported that PMI accuracy is not always better than that of the conventional bone resection technique. As such, most surgeons use the conventional technique for distal femur and proximal tibia resection, and efforts to improve bone resection accuracy with conventional technique are necessary. Here, we examined intraoperative X-rays after bone resection of the distal femur and proximal tibia with conventional bone resection technique. If the cutting angle was not good and the difference from preoperative planning was over 3º, we considered re-cutting the bone to correct the angle. Methods. We investigated 117 knees in this study. The cutting angle of the distal femur was preoperatively determined by whole-length femoral X-ray. The conventional technique with an intramedullary guide system was used for distal femoral perpendicular resection to the mechanical axis. Proximal tibial cutting was performed perpendicular to the tibial shaft with an extramedullary guide system. The cutting angles of the distal femur and proximal tibia were estimated by intraoperative X-ray with the lower limb in extension position. When the cutting angle was over 3º different from the preoperatively planned angle, re-cutting of distal femur or proximal tibia was considered. Results. On the intraoperative X-ray, the average femoral cutting angle difference from preoperative planning was 0.1º (SD: 2.6º) and the average tibial cutting angle was 1.1º varus (SD: 1.8º). Over 3º and 5º outlier cases were observed in 15 knees and 5 knees on the femoral side and in 15 knees and 3 knees on the tibial side respectively. Cutting angle correction was performed in 18 knees on the distal femur and 17 knees on the proximal tibia. On the postoperative X-ray, over 3º and 5º outliers were observed in 16 knees and only 1 knee on the femoral side and in 11 knees and no cases on the tibial side respectively. Cases with outliers over 3º were not different between intra- and postoperative estimation; however, the number of over 5º outliers was decreased from 8 knees (6.8%) to 1 knee (0.9%) including both the femoral and tibial sides (p < 0.05, Chi-square test). Discussion. Precise bone cutting technique is important for TKA; however, the bone resection accuracy of the conventional technique is far from satisfactory. CAS, PMI, and portable navigation have been developed for precise bone resection in TKA. However, these new technologies involve additional cost and have not been clearly shown to improve accuracy. Most surgeons currently use the conventional technique, and we think it is possible to improve bone resection accuracy with the conventional technique in TKA. Our method is simple and requires just one intraoperative X-ray. This is cost-effective and can be performed by most surgeons. Our results indicate that a single intraoperative X-ray can reduce the number of excessive bone resection angle outliers in TKA

Introduction. Functional outcomes of mechanically aligned (MA) total knee arthroplasty have plateaued. The aim of this study is to find an alternative technique for implant positioning that improves functional outcomes of TKA. Methods. We prospectively randomized 100 consecutive patients undergoing TKA into two groups: in the group A an intramedullary femoral guide and an extramedullary tibial guide were used with aim to obtain a neutral traditional mechanical alignment; in the group B an extramedullary femoral guide set on distal femoral condyles and an extramedullary tibial guide neutrally aligned were used to obtain an adaptation of the conventional MA technique. Patients were followed-up clinically with the Short Form Health Survey (SF-12), Oxford Knee Score (OKS) and Visual Analogue Score (VAS) questionnaires pre-operatively and then at 1 year post-operatively. Mechanical alignment was calculated on standing weight bearing Xray pre- and post-operatively. T-test was used to compare the results between groups. Results. Both groups showed an improvement of clinical scores. At 1 year of follow-up OKS and SF-12 were significantly higher in group B: 47,6 ±0.75 and 46.5 ±0.76 respectively; VAS was similar in both groups. Values of mechanical alignment changed from 6.45 ±8.45 to 0.25 ±0.91 for group A and from 6.8 ±7.94 to 2.5 ±4.7 for group B. Conclusion. This study shows that adjusted mechanical alignment (AMA) with a small under-correction of frontal deformity lead to improved functional scores following total knee replacement compared to conventional technique of neutral alignment. These results are satisfactory at short follow-up but long-term studies are needed to evaluate the difference in the rate of wear of the prosthetic components