Purpose. Malrotation of the femur has been documented in as few as 0% and as many as 28% of fractures treated with an intramedullary(IM) nail. Patients with more than 15 degrees of malrotation sometimes require derotation osteotomy. Recognizing malrotation intraoperatively is the most efficient way to avoid corrective surgery. The purpose of this paper is to inform orthopaedic surgeons of the best estimate of incidence of femoral malrotation after IM nailing. This may lead to increased attention toward intraoperative control of malrotation. Method. A literature search was performed by a library sciences professional. Two authors excluded papers not relevant to the study in two stages with clearly outlined criteria and adjudication. Inter-observer agreement was measured with the kappa statistic. Data extraction was performed by the same two authors with measure of agreement and adjudication from a third author. Data extraction included: incidence of malrotation, method used for measurement of malrotation and use of intraoperative techniques to minimize malrotation. Results. Six-hundred-and-seventy-one papers were identified in 3 databases. First stage exclusion based on title and abstract yielded 149 papers. Second stage exclusion based on full text review yielded 51 papers. Inter-observer agreement for exclusion of papers was “very good” (93%, kappa=0.843). The overall incidence of post-traumatic malrotation of the femur after IM nailing was 6%, 95% CI (5%, 8%). The incidence of malrotation identified by clinical examination alone was 3%, 95% CI (2%, 4%), while malrotation diagnosed by radiographic examination (CT, ultrasound and biplanar radiography) was 15%, 95% CI (10%, 20%). If intraoperative techniques to minimize malrotation were applied, incidence decreased to 9%, 95% CI (2%,16%) while without intraoperative attention to rotation, incidence was 19%, 95% CI (13%, 26%). Conclusion. We have found femoral malrotation after IM nailing to be reported in 19% of cases when measured objectively. The present study offers the best available report of incidence for post-traumatic malrotation of the femur by combining all available studies, from Kunchner's initial publication on intramedullary nailing of the femur to date. Jaarsma and Tornetta have reported that clinical examination is poor for detection of malrotation when compared with CT. Our study supports this finding. The quoted incidence for malrotation is consistently lower when measured by clinical examination compared to radiographic measures. This suggests that surgeons under-recognize malrotation intra-operatively, and therefore often fail to correct it. This study has found that any intraoperative effort to minimize rotation decreases its incidence to 9%. It is therefore crucial to have radiographic methods, such as those described by Krettek (lesser trochanter, cortical width and cortical diameter) available for use intra-operatively to diagnose malrotation

INTRODUCTION. It has been reported that the rate of complications around the patella after Total Knee Arthroplasty(TKA) is 1–12%, and the patella dislocation is the most common one. PURPOSE. We will report a case that had the patella dislocation after TKA caused by malrotation of the components. CASE. 67 years old, Female. The chief complaint was an instability of the right patella. She had undergone TKA due to osteoarthritis at another hospital. After 2 months, she felt a subluxation of the patella. And after 4 months, she had a reoperation of medial reefing and revision of the patella at the same hospital, and the doctor allowed her to flex her right knee within 70 degrees. However, after 3 months, she started experiencing pain with a feeling of dislocation and got it corrected and immobilized with a knee brace. 2 weeks later, she visited our hospital for the first time. STATUS. 148cm, 65kg. She could gait with an extension knee brace. Tenderness was seen around the right patella. She could bend her right knee from 0 degrees to 60 degrees. Extension lag and instability of varus and valgus were not existent. An X-ray showed the FTA was 172 degrees on the right side. The right knee had a TKA(Stryker Scorpion Energy®/fixed surface), and the measurements of component after TKA were almost good. However, the patella had lateral subluxation. A CT image showed the femoral component inserted in internal rotation of 8 degrees from CEA and tibia component inserted in internal rotation of 23 degrees from the left Akagi line. We diagnosed right knee dislocation because of rotation failure of the components. COURSE OF TREATMENT. We replaced implants which were produced by the same company. We replaced the tibial component externally referring to the Akagi's line. On the femur side, we augumented the femur component at the posterolateral and replaced it referring to the CEA. We made a lateral release and used a CCK surface. We did not replace the patella because the surviving patella bone was thin and patella tracking was satisfactory.2 weeks after the operation, she could bend her knee from 0 degrees to 120 degrees and walk with a cane. An X-ray showed the patella was reduced and a CT scan showed the appropriate rotation angle. DISCUSSION. Regarding the treatment of patella dislocation after TKA, when there is malrotation of components, revision is recommended. The definition and the degree of malrotation are still controversial. It was reported that when total internal rotation angle was more than 7 degrees, Revision is recommended. This patient obtained the stability of patella due to the proper rotation angle of components

Introduction. Malrotation of the femoral component is a cause of patellofemoral maltracking after TKA. Its precise effect on the patellofemoral (PF) mechanics has not been well quantified. The aim of this study was to investigate the effect of malrotation of the femoral component on PF initial contact area, initial contact pressure and wear after 4 million full gait cycles in TKA using a knee simulator. Moreover, the influence of the counterface material (CoCr or OxZr) on PF wear was also investigated. Materials & Methods. Femoral components (FCs) were cemented onto specially designed fixtures, allowing positioning of the FC in different angles of axial rotation. Patellar buttons and FCs were then mounted in a Prosim knee simulator. Patellofemoral contact mechanics. Seven axial rotation configurations were tested: neutral (FC parallel to the epicondylar axis), 2.5° endo- and exorotation, 5° endo- and exorotation and 7.5° endo- and exorotation. Patellar contact location, contact area and contact pressure were measured dynamically during 20 gait cycles with a Tekscan sensor covering the patella collecting data at a rate of 100 frames per second. Patellofemoral wear. For three alignments (neutral, 5° endo- and exorotation), a PF wear test of 4 million cycles in bovine serum (diluted to 40%) was done with three CoCr and three OxZr components on conventional ultra-high molecular weight polyethylene (UHMWPE, density: 0.93mg/mm. 3. ). Every 0.5 million cycles the test lubricant was replaced, the patellar samples were cleaned and dried and polyethylene wear was measured gravimetrically. A linear regression model was used to calculate the wear rate of each patellar sample. Aggregate wear rates were determined for each test condition by pooling the measurements of all three patellar samples. Results. For all six endorotation and exorotation configurations, the contact area was significantly lower and the contact pressure significantly higher than the neutral position (p < 0.001, Figs 1 and 2). In the patellofemoral wear test, the highest average wear rate was found in the group of endorotated CoCr femoral components (0.54 mm. 3. /Mcycle), but this is still only 11% of a typical tibiofemoral wear rate with the same CoCr component (5 mm. 3. /Mcycle). The following trends in the average wear rates could be observed: the average wear rate for CoCr (0.34 mm. 3. /Mcycle) was higher than for OxZr (0.19 mm. 3. /Mcycle) and the average wear rate for 5° endorotation (0.35 mm. 3. /Mcycle) was higher than for 5° exorotation (0.21 mm. 3. /Mcycle) and neutral alignment (0.23 mm. 3. /Mcycle) (Figs 3 and 4). None of these differences reached statistical significance (p=0.05), though. Discussion. Our results indicate that both internally and externally malrotated femoral components significantly decrease contact areas and significantly increase contact pressures in the patellofemoral joint. These significant changes in contact pressure didn't translate in significant changes in wear, however. Overall, patellofemoral wear is very small compared to tibiofemoral wear, in all the configurations that we investigated. Based on our results, we can conclude that clinical problems with patellar maltracking after femoral component malrotation seem not to be related to increased wear, but rather to pain and patellar instability

Purpose. Unicompartmental knee replacement (UKR) is an established, bone preserving surgical treatment option for medial compartment osteoarthritis (OA). Early revision rates appear consistently higher than those of total knee replacement (TKR) in many case series and consistently in national registry data. Failure with progression of OA in the lateral compartment has been attributed, in part, to surgical technical errors. In this study we used navigation assisted surgery to investigate the effects of improper sizing of the mobile bearing and malrotation of the tibial component on alignment and lateral compartment loading. Method. A total of eight fresh frozen cadaveric lower limbs were used in the study. After thawing overnight, a Brainlab navigation system with an Oxford (Biomet, Inc) medial UKR module was used to capture the native knee anatomy and alignment using a digitizing probe. Following registration, the case was performed with navigation verified neutral cuts and an ideal insert size was selected to serve as a baseline. The bearing thickness was subsequently increased by 2 mm increments to simulate progressive medial joint overstuffing. Excessive tibial internal rotation of 12 was also simulated at each of the intervals. Knee alignment in varus or valgus was recorded in real time for each surgical scenario with the knee in full extension and at 20 of flexion. Lateral compartment peak pressure was measured using a Tekscan pressure map. Results. Incremental overstuffing of the medial compartment with inserts of increasing thickness resulted in a progressive shift to more valgus knee alignment. Internally rotated sagittal cuts at 12 resulted in a further valgus shift for a given insert size. The valgus shift was detectable at full extension however it was more pronounced at 20 of flexion. Conclusion. The intentional technical errors of overstuffing and malrotation in UKR produced coronal valgus knee alignment and a greater load shift to the lateral compartment. These errors can be construed to contribute to the higher early failure rates associated with UKR when compared to TKR. Special care should be taken to ensure a neutral sagittal tibia cut and appropriate bearing selection. The Intra operative verification of knee alignment should be conducted at 20 of flexion where such errors will be easier for the surgeon to detect and rectify

Introduction. Malpositioning of the tibial component is a common error in TKR. In theory, placement of the tibial tray could be improved by optimization of its design to more closely match anatomic features of the proximal tibia with the motion axis of the knee joint. However, the inherent variability of tibial anatomy and the size increments required for a non-custom implant system may lead to minimal benefit, despite the increased cost and size of inventory. This study was undertaken to test the hypotheses: . 1. That correct placement of the tibial component is influenced by the design of the implant. 2. The operative experience of the surgeon influences the likelihood of correct placement of contemporary designs of tibial trays. Materials and Methods. CAD models were generated of all sizes of 7 widely used designs of tibial trays, including symmetric (4) and asymmetric (3) designs. Solid models of 10 tibias were selected from a large anatomic collection and verified to ensure that they encompassed the anatomic range of shapes and sizes of Caucasian tibias. Each computer model was resected perpendicular to the canal axis with a posterior slope of 5 degrees at a depth of 5 mm distal to the medial plateau. Fifteen joint surgeons and fourteen experienced trainees individually determined the ideal size and placement of each tray on each resected tibia, corresponding to a total of 2030 implantations. For each implantation we calculated: (i) the rotational alignment of the tray; (ii) its coverage of the resected bony surface, and (iii) the extent of any overhang of the tray beyond the cortical boundary. Differences in the parameters defining the implantations of the surgeons and trainees were evaluated statistically. Results. On average, the tibial tray was placed in 5.5 ± 3.1° of external rotation. The overall incidence of internal rotation was only 4.8%: 10.5% of trainee cases vs. 0.7% of surgeon cases (p < 0.0001). The incidence of internal rotation varied significantly with implant design, ranging from 1.7% to 6.2%. Bony coverage averaged 76.0 ± 4.5%, and was less than 70% in 8.6% of cases. Tibial coverage also varied significantly between designs (73.2 ± 4.3% to 79.2 ± 3.8%; p < .0001). Clinically significant cortical overhang (>1 mm), primarily in the posterior-lateral region, was present in 12.1% of cases, and varied by design, as expressed by the area of the tray overhanging the cortical boundary (min: 2.3 ± 6.7 mm. 2. ; max: 4.7 ± 7.9 mm. 2. ; p < .0001). The surgeons and the trainees also differed in terms of the incidence of sub-optimal tibial coverage (10.0% vs. 14.4%, p < 0.001), and cortical overhang (7.4% vs. 9.7%, p < 0.001). Discussion. 1. Malrotation, bony coverage and cortical overhang are all strongly influenced by the design of the tibial tray selected and the experience of the surgeon. 2. Compared to trainees, experienced surgeons tend to position tibial trays in more external rotation, and with less concern for reduced bony coverage and cortical overhang than trainees. 3. This study supports the hypothesis that improvements in the outcome and reliability of TKR may be achieved through attention to implant design

Introduction

Stiffness postTotal Knee Replacement (TKR) is a common, complex and multifactorial problem. Many reports claim that component mal-rotation plays an important role in this problem. Internal mal-rotation of the tibial component is underestimated among surgeons when compared to femoral internal mal-rotation. We believe the internal mal- rotation of thetibial component can negatively affect the full extension of Knee. We performed an in-vivo study of the impact of tibial internal mal-rotation on knee extension in 31 cases.

In TKA, prosthetic femoral and tibial implants must be symmetrically placed and matched in the mechanical axis and the ligament gaps must be correctly balanced. The collateral ligaments are the key guide, as they arise from the epicondyles of the distal femur, are perpendicular to the AP axis of Whiteside, and are coincident with the transtibial axis of the proximal tibial surface. A perpendicular bisection of the transtibial axis creates the AP axis of the tibia which is coincident in space with the AP axis of Whiteside (Berger). Measured distal femoral resection targets including TEA, AP axis of Whiteside, and 3 degrees external to the posterior condylar axis works because the stout posterior cruciate ligament limits laxity in flexion, allowing for the anatomical variation of these landmarks to be accommodated. The Insall, Ranawat gap balancing methods work to balance the knee in flexion, often matching the results of a measured resection, but guaranteeing a symmetrically balanced flexion gap. Distal femoral internal rotation can result if the medial collateral is over-released, but experience has shown this not to be a problem if the gaps are well balanced. Tibial tray position must be placed coincident with the AP axis of the tibia, which also is coincident with Akagi's line (line from medial margin of patellar tendon to center of the posterior cruciate ligament). The surgeon can make a line from the AP axis of Whiteside to the anterior tibial which matches the AP tibial axis.

Introduction

Stiffness post Total Knee Replacement (TKR) is a common, complex and multifactorial problem. Many reports claim that component mal-rotation plays an important role in this problem. Internal mal-rotation of the tibial component is underestimated among surgeons when compared to femoral internal mal-rotation. We believe the internal mal-rotation of the tibial component can negatively affect the full extension of Knee. We performed an in-vivo study of the impact of tibial internal mal-rotation on knee extension in 31 cases.

Introduction. Post-operative clinical outcomes of TKA are dependent on a multitude of surgical and patient-specific factors. Malrotation of the femoral and/or tibial component is associated with pain, accelerated wear of the tibial insert, joint instability, and unfavorable patellar tracking and dislocation. Using the transepicondylar axis to guide implantation of the femoral component is considered to be an accurate anatomical reference and is widely used. However, no gold standard currently exists with respect to ensuring optimal rotation of the tibial tray. Literature has suggested that implantation methods, which reference the tibial tubercle, reduce positioning outliers with more consistency than other anatomical landmarks. Therefore, the purpose of this evaluation is to use data collected from intraoperative sensors to assess the true rotational accuracy of using the mid-medial third of the tibial tubercle in 98 TKAs. Methods. The data for this evaluation was retrieved from 98 consecutive patients who underwent primary TKA from the same highly experienced surgeon. Femoral component rotation was verified in every case via the use of the Whiteside line, referencing the transepicondylar axis, and confirming appropriate patellar tracking. Tibial tray rotation was initially established by location of the mid-medial third of the tibial tubercle. Rotational adjustments of the tibial tray were evaluated in real-time, as the surgeon corrected any tibiofemoral incongruency and tray malpositioning. The initial and final angles of tibial tray rotation were captured with intraoperative video feed, and recorded. A z-test of differences between pre- and post-rotational correction was performed to assess the statistical significance of malrotation present in this cohort. Results. All patients in this study received a primary TKA, using the mid-medial third of the tibial tubercle to dictate tibial tray rotation. After the sensor-equipped tibial insert was implanted, it was shown that 63.1% of patients exhibited unfavorable rotation. Of those patients, 70% were shown to have internal rotation; 30% were shown to have external rotation. The average malrotation of the tibial tray deviated from a neutral position by 6.3° ± 4.3°, ranging from 0.5° to 19.2°. The z-test of differences yielded a p-value <0.0001, indicating that the proportion of malrotation was statistically significant. The 95% confidence interval of this cohort was calculated to be between 44.8% and 71.8% of malrotation. Discussion. Malrotation in TKA isassociated with poor clinical outcomes. While no gold standard anatomic landmark currently exists for positioning the tibial tray, the mid-medial third of the tibial tubercle is widely used as a reference. However, the data from this evaluation demonstrates that, not only is this landmark insufficient for establishing optimal rotation (p < 0.0001), but that it had guided the surgeon to an average of 6.3° outside of the optimized implant congruency zone. The large confidence interval indicates that the rotational alignment of the tibial tray—based on the location of the mid-medial third of the tibial tubercle—is not only inaccurate, but also highly variable. Based on this intraoperative sensor data, we suggest that care should be taken when utilizing the tibial tubercle as the sole rotational landmark for the tibial tray

Introduction. Tibial component malrotation is one of the commonest causes of pain and stiffness following total knee arthroplasties, however, the assessment of tibial component malrotation on imaging is not a clear-cut. Aim. The objective of this study was to assess tibial component rotation in cases with pain following total knee replacement using MRI with metal artifact reduction technique. Methods. In 35 consecutive patients presented to our clinic between January 2016 and April 2017 with persistent unexplained moderate to severe pain for at least 6 months following total knee arthroplasties after exclusion of infection, MRI evaluation of tibial component rotation using O-MAR technique-(Metal Artifact Reduction for Orthopedic implants) to improve visualization of soft tissue and bone by reducing artifacts caused by metal implants- was done according to the technique of Berger et al. Results. 25 cases showed internal rotation of tibial component, 5 cases showed neutral rotation, 5 cases showed external rotation with presence of abnormal intraarticular fibrous bands. Conclusion. Two main conclusions are obtained from this study:. Firstly: Internal rotation of tibial component must be excluded in all cases of persistent pain following total knee replacement. Secondly: Magnetic resonance imaging with the newly developed metal artifact reduction techniques is a very useful tool in evaluating cases of unexplained pain following total knee replacement

Purpose. Incidence of malrotation of femoral fractures after intramedullary nailing is as high as 28%. Prevention of malrotation is superior to late derotation osteotomy. The lesser trochanter (LT) profile has been in use for some time as a radiographic landmark of femoral rotation. One of the authors has previously described a linear regression model that describes the relationship of the LT to rotation. This paper aims to validate the use of this equation in predicting femoral rotation. Method. A survey was created and circulated online. Twenty images of cadaveric femurs of known rotation were chosen randomly from a large series. Thirty individuals with varying degrees of orthopaedic experience were invited to participate. Participants were asked to take measurements of the LT in a standardized fashion. Inter-observer variation for predicted rotation and the precision of predicted rotation was calculated. Results were grouped into those with the LT readily visible and those with the LT hidden by the femoral shaft. Results. A pilot study found the standard deviation for films with the LT hidden was 10.8 degrees, and only 6.0 degrees for films with the LT visible. The mean difference between the predicted and actual rotation was equally high in both groups (18.3 and 17.3 degrees respectively). Conclusion. Preliminary results found that the LT must be clearly visible to predict femoral rotation. This suggests that the surgeon should place the femur in a neutral or externally rotated position. In a favourable position most predictions were within a 6.0 degree spread, which would be sufficient to prevent a fifteen degree malrotation. Predicted rotation was however not precise enough to prevent a fifteen degree malrotation, regardless of LT visibility. The precision of predicted rotation may be improved by using a non-linear model. Such a model has recently been designed by a group of engineers at the University of Manitoba. The r squared value of the non-linear model was 0.88, in comparison to 0.78 for the linear equation. Precision may be further improved by using the contra-lateral LT for comparison

Even though primary total knee arthroplasty involves resurfacing the joint with metal and plastic it is much more of a soft tissue operation than it is a bony procedure. The idea that altering the planned bony resection by a few degrees on either the tibial or femoral side of the joint might somehow eliminate the multifactorial pain complaints and reduced patient satisfaction seen in some 20% or more of cases in reported clinical series is clearly overly optimistic. Axial alignment is important, but no more so than the level of distal femoral resection, tibial and femoral rotation, tibial resection level and downslope and femoral sagittal plane alignment. The real problem is that errors in component positioning are common, rarely made one at a time, and are made more common by greater procedural complexity. No matter the resection method (let alone the resection target!) errors are commonly linked and iterative. For example: femoral malrotation on an under-resected distal femur (in a knee with minimal arthritic wear to begin with) can contribute to corresponding tibial malrotation helped by a “floated” tibial trial on an all too often overly resected and downsloped tibial surface that has been recut to allow full extension with the under-resected femur (and now also results in AP laxity in flexion). Small changes in the alignment target will not fix this!. On the other hand: Kinematic alignment individualised to the patient's anatomy as a means of reducing soft tissue imbalance and minimizing ligamentous releases is actually a reasonable objective and a laudable goal on the surface. The problem with operationalizing this widely relates to what is currently required to try and reliably achieve this goal using currently available implants and technology. In the early 1980's the proponents of “anatomic” alignment with a residual 2- to 3-degree varus tibial resection and corresponding joint obliquity were Hungerford and Krackow. This concept was widely adopted but proved to be fraught with difficulty in the hands of community based surgeons in that era due to common excessive varus tibial resection errors and resulting premature implant failures. Recent reports on kinematic alignment involve a plethora of technology combinations including pre-operative CT (or MRI) for 3D reconstruction and planning, custom jig fabrication, and navigated bony preparation or individualised bony cuts off of patient specific jigs. The goal is to allow customised resections that “estimate” original cartilage thickness and bone erosion and seek to replicate the original however native anatomy and provide better precision for bone resection. Even when successful this is often followed by placement of a standard implant not too different from those in the 80's and 90's which may well have one femoral articular “J curve” for all patents, a single patellofemoral groove design and anatomic shape for all, and that makes use of a central keel on a nonanatomic tibial design with limited sizing increments, all implanted into a patient without an ACL and not infrequently PCL deficient as well. And all of this is done with the hope of restoring the normal original knee kinematics!. The frequent combination of several of the above factors clinically in a single knee may help explain some of the variability in results of kinematic alignment reported by some authors even after excluding certain pre-operative deformities (excess valgus or varus). For now mechanical alignment methods and instrumentation should remain the standard of care for routine TKA practice for most, and in complex primary cases for all

Stiffness after total knee arthroplasty (TKA) is a common problem occurring between 5% and 30% of patients. Stiffness is defined as limited range of motion (ROM) that affects activities of daily living. A recent International Consensus on definition of stiffness of the knee graded stiffness as mild, moderate or severe (90–100, 70–89, <70, respectively) or an extension deficit (5–10, 11–20, >20). Stiffness can be secondary to an osseous, soft tissue, or prosthetic block to motion. Heterotopic bone or retained posterior osteophytes, abundant fibrotic tissue, oversized components with tight flexion or extension gaps or component malrotation can all limit knee motion. Infection should always be considered in the knee that gradually loses motion. Alternative causes include complex regional pain syndrome and Kinesiophobia that can limit motion without an underlying mechanical cause. The evaluation of knee stiffness radiographs of the knee and cross-section imaging should be performed if component malrotation is considered. A metal suppression MRI assists in quantifying the extent of fibrosis and its location in the anterior or posterior compartment of the knee. Inflammatory markers and joint aspiration as indicated to rule out infection. Arthrofibrosis, or post-surgical fibrosis, is related to abnormal scar formation after surgery that leads to loss of motion. The cause of arthrofibrosis is multifactorial and likely related to genetic host factors. Current research is focusing on molecular signatures that may better identify patients at risk. In addition, therapeutic interventions are being studied that best prevent fibrosis and its recurrence and include the use of anti-inflammatories, corticosteroids, Colchicine, biologic medications (IL-1 inhibitors) and low-dose radiation. Early treatment of the stiff TKA includes physical therapy and manipulation under anesthesia (MUA). MUA performed within 3 months may have the greatest increase in ROM but notable improvement can occur up to 6 months after TKA. After six months, arthroscopic or open surgery is recommended for persistent stiffness. Arthroscopic lysis of adhesions can improve ROM greater than 1 year after index TKA. Average improvement of ROM for both MUA and arthroscopic lysis of adhesions (usually in conjunction with MUA) is approximately 30 degrees. The outcome after open lysis of adhesions are reportedly poor but current adjuvant therapies may improve these clinical outcomes as this addresses the biologic, in addition to the mechanical, basis of fibrosis. Component revision performed for component malposition and stiffness has variable outcomes but a recent study reports a mean increase in ROM of 20 degrees and a modest improvement in overall knee function. The cause of post-operative stiffness after TKA is a complex interplay of the patient, surgeon, and post-operative factors. Correct diagnosis of the underlying cause of the stiff total knee is essential to optimizing treatment outcomes. More research in needed in how to best prevent and treat the biologic risk factors and pathways that contribute to post-surgical fibrosis

Total knee arthroplasty belongs today to one of the standard operation in orthopaedic surgery. During the last years the number of the total knee arthroplasty has dramatically increased. The prognosis for the future have shown also an increasing tendence. The Swedish Regiter Study and others showed that the results after total knee replacement not almost dependant on the design of the prothesis. More important are patient selection, operation technique and the postoperative therapy. The goals of modern knee replacement surgery are restoring mechanical alignment, preserving of the joint line, balancing ligament with a well balanced extension and flexion gap to reach maximum stability and movement. Bone resection is the simple part of a total knee operation. Ligament balancing with equal extention and flextion gap represents a major chalange for the surgeon which may consequantly affect the stability both in extention and flextion. Stability of total knee arthroplasty is dependant on correct and percise rotation of the femoral component. Femoral component malrotation has been associated with numerous adverse sequelae, including patellofemoral and tibiofemoral instability, knee pain, arthrofibrosis, and abnormal knee kinematics. A great number of early revision today are due to malrotation of the femoral component. Multiple differing surgical techniques are currently utilized to perform TKA. femur first (measured resection). tibia first (gap balancing). In the classic femur first technique the excision of the bone done indepentaly after one another followed by ligament balancing in flextion and extension. There are 4 bony landmarks deciding the rotational position of the femur. The epicondylar line, whiteside line, the dorsal condyles and anetroir-posterior axis. All these landmarks are associated with problems and failure to define exactly these bony landmarks intraoperatively. This may lead not seldom to malrotation of the femural component, consequently instability, limitation of function and increased wear. In the tibia first technique excision of the femur especially for flexion done dependant on the excision of the tibia. This carried out using a tensor. With using this technique the rotation of the femur will be oriented mainly at the ligament balancing espcialy in flexion. Flexion instability and patellae maltacking will be avoided. We present our preferrd tibia first technique using a new tensor system. With this system it is possible to reach a well balanced extension and flextion gap. A 3° release is only needed in special cases. The rotation position of the femur depend primerly on the released soft tissue in extension. Also an exact reconstruction of the dorsal offset as well as an exact anterior or posterior referencing can be guaranteed with the instruments by infinitely variable ap movement. The use of bony landmarks also possible. we think our new tensor present a step forwards in understanding the biomechanics of the knee and offer a new development of the instruments used in knee replacement. This could be useful especialy in cases of revision

Introduction:. Malrotation of the tibial component is a common error in TKR, and has been frequently cited as the cause of clinical symptoms. Correct rotational orientation of the tibial tray is difficult to achieve because the resected surface of the tibia is internally rotated and is not symmetrical in shape. This suggests that anatomically contoured components may lead to improved rotational positioning. This study was undertaken to test the hypotheses: . 1. Use of an anatomically shaped tibial tray can reduce the prevalence of malrotation and cortical over-hang in TKA while increasing coverage of the resected tibial surface, and. 2. Component shape has more influence on the results of surgical trainees compared to experienced surgeons. Materials and Methods:. A standard symmetric design of tibial tray was developed from the profiles of 3 widely used contemporary trays. Corresponding asymmetric profiles were generated to match the average shape of the resected surface of the tibia based on a detailed morphometric analysis of anatomic data. Both designs were proportionally scaled to generate a set of 7 different sizes. Computer models of eight tibias were selected from a large anatomic collection. The proximal tibia was resected perpendicular to the canal axis with a posterior slope of 5 degrees at a depth of 5 mm (medial). Eleven experienced joint surgeons and twelve trainees individually determined the ideal size and placement of each tray on each of the 8 resected tibias. The rotational alignment, coverage of the resected bony surface, and extent of overhang of the tray beyond the cortical boundary were measured for each implantation. Differences in the parameters defining the implantations of the surgeons and trainees were evaluated statistically. Results:. Bony coverage was significantly greater with the asymmetric vs. the symmetric design (87.0 ± 4.1% vs. 75.6 ± 4.0%; p < 0.0001). Coverage was less than 75% in 37% of symmetric trays, whereas the worst coverage obtained with the asymmetric design was 77.0%. Clinically significant cortical overhang (>1 mm) was present in 35% of symmetric vs. 11% of asymmetric cases (p < 0.0001). On average, the asymmetric tray was placed in 4.1 ± 3.7° of external rotation vs. 1.6 ± 4.6° for the symmetric tray (p < 0.0001). The tray was implanted in some degree of internal rotation in 24% of cases, 15% for the asymmetric design vs. 33% for the symmetric (p < 0.0001). There was minimal difference between the results of implantations performed by trainees vs. experienced surgeons, in terms of tibial coverage (p = 0.245), cortical overhang (p = 0.735), or the prevalence of internal rotation (p = 0.147). Trainees placed 6.3% of all cases in severe internal rotation (>5°) compared with 12.5% of surgeon cases (p = 0.154). Discussion. 1. The incidence of malrotation was substantially less with anatomical vs symmetrical tibial trays. 2. The asymmetric design was also associated with a large reduction in cortical overhang and increased coverage of the resected tibial surface. 3. There was no overall difference between the performance of trainees and experienced joint surgeons, regardless of the design of the implant. This suggests that current training and surgical guides are inadequate in achieving correct positioning of the tibial component in TKR

Purpose. Femoral component malrotation is a common cause for persisting symptoms and revision following total knee arthroplasty (TKA). There is ongoing debate about the most appropriate use of femoral landmarks to determine rotation. The Sulcus Line (SL, See Figure 1) is a three-dimensional curve produced from multiple points along the trochlear groove. Whiteside's Line, also known as the anteroposterior axis (APA), is derived from single anterior and posterior points. The purposes of the three studies presented are to i) assess the SL in a large clinical series, ii) demonstrate the effect of parallax error on rotational landmarks, and iii) assess the accuracy of a device which transfers a geometrically corrected SL onto the distal cut surface of the femur. Methods. The first study assessed the SL using a large, single surgeon series of consecutive patients (n=200) undergoing primary TKA. The postoperative CT scans of patients were examined to determine the final rotational alignment of the femoral component. In the second study measurements were taken in a series of 3DCT reconstructions of osteoarthritic knees (n=44) comparing the rotational landmarks measured along either the mechanical axis or the coronal axis of the trochlear groove. The third study assessed the accuracy of a novel trochlear alignment guide (TAG) using cadavers (n=10). Results. The mean position of the femoral component in the clinical series was 0.6° externally rotated to the surgical epicondylar axis, with a standard deviation of 2.9° (range −7.2° to 6.7°). On the 3DCT reconstructions the APA (88.2°±4.2°) had significantly higher variance when compared with the SL (90.3°±2.7°) (F=5.82, p=0.017). An axis derived by averaging the SL and the PCA+3° produced a significant decrease in both the number of outliers (p=0.03 vs PCA, p=0.007 vs SL) and the variance (F=6.15, p=0.015 vs SL). The coronal alignment of the SL varied widely relative to the mechanical axis (0.4°±3.8°) and the distal condylar surface (2.6°±4.3°). The results of the cadaver study found that using the TAG and the SL produced less variability than the APA (SD 2.0° compared to 3.7°). In addition, this level of accuracy was maintained when using the TAG to transfer the SL onto both the distal femoral condyles and the distal cut surface of the femur. Conclusions. The multiple points used to determine the SL confer anatomical and geometrical advantages and therefore it should be considered a separate rotational landmark to the APA. These findings suggest that much of the variability in the measurement of the APA, documented in the literature, is caused by parallax error. A new device, the TAG, is able to accurately transfer a geometrically correct SL on to the distal cut surface of the femur. This allows accurate comparison between the SL and other landmarks, including the PCA, which is likely to decrease the risk of femoral component malrotation

Introduction. Rotational or axial alignment is an important concept in total knee surgery. Malrotation of the femoral component can lead to patellofemoral maltracking, pain and stiffness. In reconstruction surgery of the knee, achievement of correct rotation is even more difficult because of the lack of anatomical landmarks. The linea aspera is often the only remaining landmark, but its reliability is questionable. Goal of research. Can custom-made 3D-guides help with rotational alignment of the knee after a wide resection of the distal femur?. Material and methods. Custom-made 3D-guides were designed from CT-scans, with the help of the commercially available Mimics software (Materialise NV, Leuven, Belgium) and SolidWorks (SolidWorks Corp., MA, USA). Anterior was defined as 90° relative to the PCL, with the center of the best-fitting inner cylinder, inside the femoral diaphysis, as rotation point. Firstly, the accuracy of the 3D-guides was tested. Twelve 3D-guides, on different heights, were made for 3 cadaveric femora. Anterior was marked with a pin and the position was evaluated with CT-scan. Secondly, to mimic surgery, seven reconstruction prostheses were placed in 4 cadavers, using the 3D-guide to indicate anterior and cutting surface. Resection height was aimed at 13cm. The position of the prostheses was also evaluated using CT-scan. Results. First test: The pins deviated on average 0.65° (SE: 0.75°) from anterior. Eighty-three percent deviated less then 1° from anterior, and only 2 pins deviated more than 1° (1.5° and 2.6°). The resection height indicated by the 3D-guide was on average 2.4mm (SE: 0.7mm) to high. Second test: The 7 reconstruction prostheses deviated on average 3.1° (SE: 2,18°) from anterior, with 4 prostheses deviating more than 1°. The 2 prostheses in endorotation were placed more lateral then was planned, while the 2 in exorotation were placed more medial. Deviation in the coronal and sagittal plane was respectively 1.56° (SE: 1.64°) and 1.84° (SE: 1.04). The mean height was 12.9cm. Discussion. The 3D-guides were accurate in indicating a previously established ‘anterior’ point on the femur and the resection height, but when used to position the femoral component during surgery they inadequately controlled rotation. The 3D-guides did not take into account that centering of the prosthesis could be a problem. When the prosthesis was place more medial or more lateral than anticipated the rotation point of the component was changed and when then aligned with the previously indicated anterior mark, it was placed respectively in exorotation and endorotation. Future research. Will aim to develop custom-made 3D-guides that also guide centering of the femoral component. Repercussion on function and kinematics of improved axial alignment will be evaluated with knee simulator testing and a control group

In years past, the most common reason for revision following knee replacement was polyethylene wear. A more recent study indicates that polyethylene wear is relatively uncommon as a cause for total knee revision counting for only 10% or fewer of revisions. The most common reason for revision currently is aseptic loosening followed closely by instability and infection. The time to revision was surprisingly short. In a recent series only 30% of knees were greater than 5 years from surgery at the time of revision. The most common time interval was less than 2 years. This is likely because of the higher incidence of infection and instability that occurs most commonly at a relatively early time frame. Evaluation of a painful total knee should take into account these findings. All total knees that are painful within 5 years of surgery should be assumed to be infected until proven otherwise. Therefore, virtually all should be aspirated for cell count, differential, and culture. Alpha-defensin is also available in cases in which a patient may have been on antibiotics within a month or less, as well as cases in which diagnosis is a challenge for some reason. Instability can be diagnosed with physical exam focusing on mid-flexion instability which can be usually determined with the patient seated and the knee in mid-flexion, with the foot flat on the floor at which point sagittal plane laxity can be discerned. This is also frequently associated with symptoms of giving way and recurring effusions and difficulty descending stairs. A new phenomenon of tibial de-bonding has been described, which can be a challenge to diagnose. Radiographs can appear normal when loosening occurs between the implant and the cement mantle. This seems to be more common with the use of higher viscosity cement. Obviously this is technique dependent since good results have been reported with the use of high viscosity cement. Component malposition can cause stiffness and pain and relatively good results have been reported by component revision when malrotation has been confirmed with CT scan. When infection, instability and loosening are not present, extra-articular causes should be ruled out including lumbar spine, vascular compromise, complex regional pain syndromes and fibromyalgia, and peri-articular causes such as bursitis, tendonitis, tendon impingement among others. One of the most common causes of pain following total knee is unrealistic patient expectations. Performing total knee replacement in early stages of arthritis with only mild to moderate symptoms and radiographic changes has been associated with persistent pain and dissatisfaction. It may be prudent to obtain the immediate preoperative x-rays to determine if early intervention was undertaken and patients have otherwise normal appearing total knee x-rays and a negative work up. A recent study indicated that this was likely a cause or a major contributing factor to persistent pain following otherwise a well performed knee replacement. A national multicenter study of the appropriateness of indications for TKA also indicated that early intervention was a major cause of persistent pain, dissatisfaction, and failure to improve following total knee replacement

Stiffness remains one of the most common, and challenging postoperative complications after TKA. Preoperative motion and diagnosis can influence postoperative motion, and careful patient counseling about expectations is important. Postoperative stiffness should be evaluated by ruling out infections, metal allergy, or too aggressive physical therapy. A careful physical and radiographic examination is required. Manipulation under anesthesia (MUA) in selected cases can be helpful. The best timing to perform MUA is between the 6th and 10th week postoperatively. Careful technique is required to minimise the risk of fracture or soft tissue injury. This requires complete paralysis! For more chronic stiffness, revision may be indicated if an etiology can be identified. An excessively thick patellar resurfacing, an overstuffed tibia insert, an oversized femoral component, or gross malrotation should be corrected. During revision, thorough synovectomy, release of contractures, ligamentous balancing and restoration of the joint line is required. Careful attention to component rotation, and sizing is critical. Downsizing components is helpful to place less volume into the joint space. Patients should be counseled that the results of revision for stiffness are mixed and somewhat unpredictable. More frequent postoperative nurturing is helpful to guide rehabilitation progress. Manipulation after revision at 6 weeks is almost expected

Stiffness after TKR is a frustrating complication that has many possible causes. Though the definition of stiffness has changed over the years, most would agree that flexion > 75 degrees and a 15-degree lack of extension constitutes stiffness. This presentation will focus upon the potential causes of a stiff TKR, intra-operative tips, the post-operative evaluation and management, and the results of revision for a stiff TKR. The management of this potentially unsatisfying situation begins pre-operatively with guidance of the patient's expectations; it is well-known that pre-operative stiffness is strongly correlated with post-operative lack of motion. At the time of surgery, osteophytes must be removed and the components properly sised and aligned and rotated. Soft-tissue balancing must be attained in both the flexion/extension and varus/valgus planes. One must avoid overstuffing the tibio-femoral and/or patello-femoral compartments with an inadequate bone resection. Despite these surgical measures and adequate pain control and rehabilitation, certain patients will continue to frustrate our best efforts. These patients likely have a biological predisposition for formation of scar tissue. Other potential causes for the stiff TKR include complex regional pain syndrome or joint infection. Close followup of a patient's progress is crucial for the success in return of ROM. Should motion plateau early in the recovery phase, the patient should be evaluated for manipulation under anesthesia. At our institution, most manipulations are performed within 3 months post-operative under an epidural anesthetic; patients will stay overnight for continuous epidural pain relief and immediate aggressive PT. The results of re-operations for a stiff TKR are variable due to the multiple etiologies. A clear cause of stiffness such as component malposition, malrotation or overstuffing of the joint has a greater chance of regaining motion than arthrofibrosis without a clear cause. Although surgical treatment with open arthrolysis, isolated component or complete revision can be used to improve TKR motion, results have been variable and additional procedures are often necessary