Introduction. Appropriate osteotomy alignment and soft tissue balance are essential for the success of total knee arthroplasty (TKA). The management of soft tissue balance still remains difficult and it is left much to the surgeon's subjective feel and experience. We developed an offset type tensor system for TKA. This device enables objective soft tissue balance measurement with more physiological joint conditions with femoral trial component in place and patello-femoral (PF) joint reduced. We have reported femoral component placement decreased extension gap. The purpose of the present study was to analyze the influence of femoral component size selection on the decrease of extension gap in posterior-stabilized (PS) TKA. Material & Method. 120 varus type osteoarthritic knees implanted with PS TKAs (NexGen LPS flex: Zimmer) were subjected to this study. All TKAs were performed using measured resection technique with anterior reference. The femoral component size was evaluated intra-operatively using conventional femoral sizing jig. The selected femoral component size was expressed by the antero-posterior (AP) size increase (mm) comparing to that of original femoral condyles. Gap measurements were performed using a newly developed offset type tensor device applying 40lbs (178N) of joint distraction force. Firstly, conventional osteotomy gaps (mm) were measured at extension and flexion. Secondary, component gaps (mm) after femoral trial placement with PF joint reduced were evaluated at 0° and 90° of knee flexion. To compare conventional osteotomy gaps and component gaps, estimated extension and flexion gaps were calculated by subtracting the femoral component thickness at extension (9mm) and flexion (11mm) from conventional osteotomy gaps respectively. The decrease of gap at extension and flexion were calculated with estimated gaps subtracted by component gaps. The simple linear regression analysis was used to evaluate the influence of selected femoral component size on the decrease of gap after femoral component placement. Results. The mean extension and flexion conventional osteotomy gaps were 25.7 and 28.2 mm, and estimated gaps were 16.7, 17.2 mm respectively. The component gaps were 11.1, 16.9 mm at 0° and 90° of knee flexion respectively. Extension joint gap was significantly decreased as much as 5.6mm after femoral component placement, but flexion gap showed no significant differences. Selected femoral component size showed a positive correlation to the decrease of gap after femoral component placement (Fig 1). Discussion & Conclusion. This result indicates that AP femoral component size variation affects not only flexion gap but also extension gap in PS TKA. With the larger femoral component size selected, the more protrusion of posterior condyles would increase the more tension on the posterior structures and resulted in the more decrease of joint gap after femoral component placement at full extension. This mechanism might play a physiological role on the prevention of knee hyper-extension, and would be affected by flexion contracture. Accordingly, we conclude that the surgeon should aware of the effect of femoral component placement on the gap control, and femoral component size selection affects not only flexion gap but also extension gap after femoral component placement in PS TKA

Introduction. While TKA procedures have demonstrated clinical success, medial/lateral overhang of the femoral component in total knee arthroplasty (TKA) of ≥3mm may be associated with an increased risk of knee pain, and distal femoral size may vary across ethnic populations. The aim of this study was to determine and compare the prevalence of femoral component overhang among an inclusive (non-segmented) and Asian-identified (Asian-segmented) population, using a flexible intramedullary-rod, posterior referencing method. Methods. CT Scans from bilateral lower limbs of skeletally mature subjects (981 inclusive, 267 Asian-identified), without bone pathology were prospectively acquired. Bones were segmented and landmarks were modeled using a flexible intramedullary-rod, posterior referencing method. Femoral components were virtually positioned by aligning the lateral implant edge with the lateral bone edge, where the anterior flange meets the anterior chamfer. Medial and lateral component overhang was measured at three zones: (1) intersection of the anterior flange and anterior chamfer (medial only), (2) anterior chamfer mid-line, and (3) distal face mid-line. The central tendency of the samples was determined using the observed mean and median and the 95% confidence interval. Results. In this study, the percentages of the inclusive population that had predicted fit with overhang <3mm were 98.9% at Zone 1 (medial), 99.7% and >99.9% at Zone 2, and 99.2% and 98.4% at Zone 3, for medial and lateral measurements, respectively. The percentages of the Asian-identified population with predicted overhang <3mm were 98.4% at Zone 1 (medial), 99.6% and >99.9% at Zone 2, and 99.1% and 98.3% at Zone 3, for medial and lateral measurements, respectively. Discussion and conclusion. This virtual study demonstrates the femoral components of this knee system are predicted to fit over 98.3% of the inclusive and Asian-identified population with overhang less than 3mm, using a flexible intramedullary-rod, posterior referencing method. When evaluating the fit of an implant, it is important to match the implant placement per the design intent of the system

Background. Under- or oversizing of either component of a total knee implant can lead to early component loosening, instability, soft tissue irritation or overstuffing of joint gaps. All of these complications may cause postoperative persistent pain or stiffness. While survival of primary TKA's is excellent, recent studies show that patient satisfaction is worse. Up to 20% of the patients are not satisfied with the outcome as and residual pain is still a frequent occurrence. The goal of this study was therefore to evaluate if the sizing of the femoral component, as measured on a 3D-reconstructed projection, is related to patient reported outcome measures. From our prospectively collected TKA outcome database, all patients with a preoperative CT and a postoperative X-ray of their operated knee were included in this study. Of these 43 patients, 26 (60,5%) were women and 17 (39,5%) were men. The mean age (+/−SD) was 74,6 +/− 9 years. Methods. CT scans were acquired. All patients underwent TKA surgery in a single institution by one surgical team using the same bi- cruciate substituting total knee (Journey II BCS, Smith&Nephew, Memphis, USA). Using a recently released X-ray module in Mimics (Materialise NV, Leuven, Belgium), this module allows to align the post-operative bi-planar x-rays with the 3D- reconstructed pre-operative distal femur and to determine the 3D position of the bone and implant models using the CAD- file of the implant. This new technique was validated at our department and was found to have a sub-degree, sub-millimeter accuracy. Eleven zones of interest were defined. On the medial and the lateral condyle, the extension, mid-flexion and deep flexion facet were determined. Corresponding trochlear zones were defined and two zones were defined to evaluate the mediolateral width. In order to compare different sizes, elastic deforming mesh matching algorithms were implemented to transfer the selected surfaces from one implant to another. The orthogonal distances from the implant to the nearest bone were calculated. Positive values represent a protruding (oversized) femoral component, negative values an undersized femoral component. The figure shows the marked zones on the femoral implant. The KOOS subscores and KSS Satisfaction subscore were evaluated. Results. Two-step cluster analysis based on the clinically relevant zones on both medial (zone 12, 14 and 17) and lateral (zone 2, 5 and 9) femoral condyle of the implant, led to the formation of two clusters. Cluster 1 contained 23 patients with, in general, an undersized femoral component (negative values) whilst cluster 2 contained 20 patients with in general an oversized femoral component (positive values). (see graph) No significant differences were found between both clusters regarding demographics. Regarding PROM data, a significant difference was found for KOOS Symptoms (p=0.037) and a KOOS Pain (p=0.05). Other PROMs are not significantly different between both clusters. Conclusion. Our data shows that undersizing the femoral component results in less postoperative pain and symptoms. The clinical consequence of this study is that in case of in between femoral component sizes, the smallest size should be chosen to diminish the occurrence of postoperative pain and symptoms

Introduction. In total knee arthroplasty, patients sometimes have pain in the posterolateral part of the knee. One possible cause is the impingement of the popliteus tendon against femoral components. In the literature, the incidence has been reported to be 1–4%. The purpose of this study is to quantify the amount of posterolateral overhang of the femoral component using 3-D templating software. Methods. We investigated 40 knees with varus osteoarthritic knees (Male 6 knees and Female 34 knees), all cases were grade 2 or lower in Kellgren Lawrence classification. Three-dimensional preoperative planning software was used to simulate the replacement of femoral component. The distal femur was simulated to cut 9 mm thickness on the lowest point of the medial condyles with 6 degrees valgus. The femoral mediolateral axis was simulated to be parallel to the surgical epicondylar axis. The size of femoral components was decided by anteroposteriol dimension of distal femur. Mediolateral location of the femoral component was that the lateral edge of the femoral components is just on the lateral cortex of the femur. In coronal plane, amount of M-L overhang of the femoral component was measured in 3 Zones (distal, proximal, center) on the surface of the posterior condyle cut (Figure 1). Results. The mean amounts of M-L overhang averaged of 3 zone were 1.0±13 mm in medial condyle and 3.7±1.5 mm in lateral (P<0.01). The number of cases in which M-L overhang was larger than 3 mm were 5 knees (12.5%) in medial condyle and 25 knees (62.5%) in lateral (P<0.01). In lateral condyles, over 3 mm overhanging cases were 25 knees in proximal zone, 21 knees in center zone and 8 knees in distal zone. There were significant differences in each zones (P<0.01). Discussion and Conclusion. Over 3 mm overhang in the poterolateral part of the fumer was present in 25 knees in 40 knees (62.5%). Furthermore, all cases had over 3 mm overhang in proximal zone. There is the popliteal sulcus in proximal zone of the posterolateral part of the fumer (Figure 2). To our knowledge, this is the first report on the objective data of posterolateral overhang of the femoral component. In view of the case with popliteus tendon impingement, rounded and reduced shape of the posterolateral corner in the femoral component would be beneficial (Figure 3)

Introduction. Current clinical practice in total knee arthroplasty (TKA) is largely based on metal on polyethylene bearing couples. A potential adverse effect of the stiff metal femoral component is stress shielding, leading to loss of bone stock, periprosthetic bone fractures and eventually aseptic loosening of the component. The use of a polymer femoral component may address this problem. However, a more flexible material may also have consequences for the fixation of the femoral component. Concerns are raised about its expected potential to introduce local stress peaks on the interface. The objective of this study was to analyze the effect of using a polyether-etherketone (PEEK-Optima®) femoral component on the cement-implant interface. We analyzed the interface stress distribution occurring during normal gait, and compared this to results of a standard CoCr component. Materials and methods. An FEA model was created, consisting of a femoral component cemented onto a femur, and a polyethylene tibial component. A standard loading regime was applied mimicking an adapted gait cycle, according to ISO14243-1. The implant-cement interface was modelled as a zero-thickness layer connecting the implant to the cement layer. Femoral flexion/extension was prescribed for the femur in a displacement controlled manner, while the joint loads were applied to pivoting nodes attached to the tibial construct, consistent with the ISO standard. Implant-cement interface properties were adopted from a previous study on CoCr interface debonding. [1]. . Results. The highest stresses were found during the heel strike phase of the walking cycle (Figure 1). Both for the PEEK-Optima® (A) and CoCr implant (B), the highest stresses were found near the chamfers of the posterior condyles, which is the location where tibiofemoral contact occurred. Also around the pegs, small stress intensities were found. Surprisingly, the CoCr implant produced higher peak Von Mises stresses than the PEEK-Optima® implant. Figure 1. Von Mises stress distribution at the implant-cement interface in case of a PEEK-Optima® (A) and a CoCr (B) femoral component. Discussion. In contrast with our initial assumption, the current results show that the cement-implant interface stresses with a PEEK-Optima® component were lower and more focal than with a CoCr component. However, the significance of this difference is yet unknown, as additional data on the strength of the implant-cement interface strength of PEEK-Optima® components is needed for the prediction of implant loosening. We furthermore intend to expand the current simulations with more demanding tasks, such as stair climbing and rising from a chair, as such high flexion tasks may be more detrimental to the implant-cement interface. In conclusion, this study warrants further investigation of the use of PEEK-Optima® as a replacement for CoCr in femoral TKA components

Introduction. Patellofemoral (PF) complications are among the most frequently observed adverse events after total knee arthroplasty (TKA). It has been reported that PF complications after TKA include decreasing knee range of motion, anterior knee pain, quadriceps and patellar-tendon rupture, patellar subluxation, and partial abrasion and loosening of the patellar component. Although recent improvements in surgical technique and prosthetic design have decreased these complications, the percentage of patients who have a revision TKA for PF complications still ranged up to 6.6% to 12%. For the present study, we hypothesized that the alignment of the femoral component is correlated with PF contact stress. The purpose of this study was to investigate the relationship between femoral component alignment and PF contact stress in vivo, using a pressure sensor in patients who had favorable extension-flexion gap balance during TKA. Methods. Thirty knees with medial compartment osteoarthritis that underwent posterior stabilized mobile-bearing TKA using identical prostheses (PFC Sigma RPF; Depuy, Warsaw, IN, USA) by a single surgeon (TM) with modified gap technique under a computed tomography (CT)-based navigation system (Vector Vision 1.61; Brain Lab, Heimstetten, Germany) were evaluated. PF contact stress was measured intraoperatively and compared with the alignment of the femoral component including intraoperative navigation data concerning medial shift of the patella and lateral tilt of the patella, postoperative coronal femoral component angle (alpha angle), postoperative sagittal femoral component angle (gamma angle), postoperative condylar twist angle (CTA), postoperative lateral condylar lift-off angle, and postoperative mechanical femoral component angle (mFCA). In addition, postoperative Insall-Salvati ratio (I-S ratio) was measured by dividing the length of patellar tendon by the greatest diagonal length of the patella. Results. Maximum PF stress was 2.4 ± 1.9 MPa, medial shift of the patella was 2.6 ± 1.5 mm, and lateral tilt of the patella was 8.5 ± 4.2 degrees. The PF contact stress was not correlated sagittal and coronal alignment of the femoral component and patella tracking, whereas rotational alignment of the femoral component was negatively correlated with the PF contact stress (r = −0.718, p < 0.01). Discussion and conclusion. Multiple regression analysis shows that PF contact stress correlates with CTA, I-S ratio positively correlates with PF contact stress in Spearman correlation analysis. The results of the present study showed a negative correlation between maximum stress in the PF joint and CTA. It has been reported that excessive external rotation increases the medial flexion gap, leading to symptomatic flexion instability of the femoral component. In addition, external rotation of the femoral component can cause relative medialization of the trochlear groove during flexion, resulting in anterior knee pain. Therefore, we should carefully decide the proper rotational alignment of the femoral component. It has been reported that PF contact stress in a normal knee was from 2.1 to 2.9 MPa in a cadaveric study. In the present study, patients with rotational alignment of the femoral component after TKA between 1.2° and 2.2° internally rotated from CEA had PF contact stress in this normal range

Introduction. Polyetheretherketone (PEEK) has been proposed as an implant material for femoral total knee arthroplasty (TKA) components. Potential clinical advantages of PEEK over standard cobalt chrome alloys include modulus of elasticity and subsequently reduced stress shielding potentially eliminating osteolysis, thermal conduction properties allowing for a more natural soft tissue environment, and reduced weight enabling quicker quadriceps recovery. Manufacturing advantages include reduced manufacturing and sterilization time, lower cost, and improved quality control. Currently, no PEEK TKA implants exist on the market. Therefore, evaluation of mechanical properties in a pre-clinical phase is required to minimize patient risk. The objectives of this study include evaluation of implant fixation and determination of the potential for reduced stress shielding using the PEEK femoral TKA component. Methods and Materials. Experimental and computational analysis was performed to evaluate the biomechanical response of the femoral component (Freedom Knee, Maxx Orthopedics Inc., Plymouth Meeting, PA; Figure 1). Fixation strength of CoCr and PEEK components was evaluated in pull-off tests of cemented femoral components on cellular polyurethane foam blocks (Sawbones, Vashon Island, WA). Subsequent testing investigated the cemented fixation using cadaveric distal femurs. The reconstructions were subjected to 500,000 cycles of the peak load occurring during a standardized gait cycle (ISO 14243-1). The change from CoCr to PEEK on implant fixation was studied through computational analysis of stress distributions in the cement, implant, and the cement-implant interface. Reconstructions were analyzed when subjected to standardized gait and demanding squat loads. To investigate potentially reduced stress shielding when using a PEEK component, paired cadaveric femurs were used to measure local bone strains using digital image correlation (DIC). First, standardized gait load was applied, then the left and right femurs were implanted with CoCr and PEEK components, respectively, and subjected to the same load. To verify the validity of the computational methodology, the intact and reconstructed femurs were replicated in FEA models, based on CT scans. Results. The cyclic load phase of the pull-off experiments revealed minimal migration for both CoCr and PEEK components, although after construct sectioning, debonding at the implant-cement interface was observed for the PEEK implants. During pull-off from Sawbones the ultimate failure load of the PEEK and CoCr components averaged 2552N and 3814N respectively. FEA simulations indicated that under more physiological loading, such as walking or squatting, the PEEK component had no increased risk of loss of fixation when compared to the CoCr component. Finally, the DIC experiments and FEA simulations confirmed closer resemblance of pre-operative strain distribution using the PEEK component. Discussion. The biomechanical consequences of changing implant material from CoCr to PEEK on implant fixation was studied using experimental and computational testing of cemented reconstructions. The results indicate that, although changes occur in implant fixation, the PEEK component had a fixation strength comparable to CoCr. The advantage of long term bone preservation, as the more compliant PEEK implant is able to better replicate the physiological loads occurring in the intact femur, may reduce stress shielding around the distal femur, a common clinical cause of TKA failure. For any figures or tables, please contact the authors directly

Radiographic assessment of component rotation has been impossible without using computed tomography or magnetic resonance imaging. The purpose of the present study was to assess the rotational alignment of the femoral component using plane radiography. Eighty-three patients from 89 knees who underwent primary total knee arthroplasty (TKA) were evaluated radiographically before and after surgery using kneeling view, a postero-anterior projection vertical to the tibia at 70 to 80° flexion of the knee. In this view, the transepicondylar axis and posterior condylar line can be seen. The condylar twist angle was 5.7±1.6° preoperatively and 2.6±0.9° postoperatively. The external rotation of the femoral component was 3.2±1.1°. Plane kneeling view radiographs taken before and after TKA can be used to assess the rotational alignment of the femoral component. Axial images of patellofemoral articulation were then superimposed to the kneeling view images along the outline of the femoral component. Combination of kneeling view and axial view can demonstrate the relationship between the rotational alignment of the femoral component and the patellofemoral joint after TKA

In total knee arthroplasty (TKA), rotational alignment of the femoral component is determined by the measured resection technique, in which anatomical landmarks serve as determinants, or by the gap balancing technique, in which the femoral component is positioned relative to the resected aspect of the tibia. The latter technique is considered logically more favorable for obtaining rectangular extension and flexion gaps. However, in patients with severe changes attributed to osteoarthritis and/or a severely limited range of motion, it is difficult to perform adequate posterior clearance (e.g. bone spur excision) before resecting the posterior femoral condyle, often causing unbalanced extension and flexion gaps after resection. Thus, the gap balancing technique is more technically demanding and requires higher skill. We employed a computed tomography (CT)-based navigation system to develop a simple and standardized surgical technique by performing two assessments: Assessment 1, we investigated the relationship between the position of the femoral component determined by the gap balancing technique and anatomical landmarks; and Assessment 2, we placed the femoral component at the position determined by the measured resection technique and within the acceptable gap-balanced range determined in Assessment 1. In Assessment 1, 18 knees with osteoarthritis were treated by posterior stabilized TKA for varus deformity. The extension-flexion balance after resection of the distal femoral condyle and the proximal tibia was within 3° in all cases. Posterior bone resection was performed parallel to the resected aspect of the tibia and at 90° of flexion under constant compression applied using a tensor. In other words, the rotational alignment of the femoral component was determined by the gap balancing technique, and its position relative to the posterior condylar axis (PCA) and clinical transepicondylar axis (CEA), which are landmarks in the measured resection technique, and the condylar twist angle (CTA; the angle between the CEA and PCA) were measured, and their relationships were quantitatively determined. The CTA, which was determined based on the preoperative CT data, was 4.7– 9.6° (mean, 7.05 ± 1.35°), while the aspect of the femoral resection was 3.0–8.3° externally rotated (mean, 5.6 ± 1.6°) to the PCA; a strong positive correlation was found between the rotational alignment of the femoral component and the CTA (p < 0.0001, R. 2. = 0.871). The aspect of the femoral resection was 0.3–2.6° internally rotated (mean, 1.4 ± 0.6°) to the CEA, and no correlation with the CTA was apparent. In Assessment 2, 39 knees with an extension-flexion balance ≤3° were examined to determine the internal-external rotation balance. Based on the results of Assessment 1, we employed the measured resection technique and placed the femoral component by rotationally aligning the target, which was 1.4° internally rotated to the CEA. The final rotational alignment of the femoral component was 2.0 ± 0.6° internally rotated to the CEA; the internal-external rotation balance at 90° of flexion was good and more toward external rotation by 0.72 ± 1.61°. The results demonstrated that the measured resection technique enables placement of the femoral component within an acceptable range of rotational alignment

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

Purpose. The complication of patellofemoral compartment was quite often in total knee arthroplasty. One of the impotant factors in these complications would be the femoral component rotation in TKA. To determine the rotation of the femoral component, the reference of the surgical epicondylar axis (SEA), posterior condylar axis (PCA), AP axis with three dimensional model achieved from computed tomography data were considered. There are some limitations with pre-oprerative CT-based planning such as radio exposure, cost, time and detection of the depth of cartilage. We evaluate the determination of the femoral component rotation with image-free registration method to compare with three-dimensional template system. Material and Methods. Thirty six knees were evaluated to determine the femoral component rotation. The reference points were marked to measure the PCA (posterior condylar axis), SEA (surgical transepicondylar axis), and APA (anteroposterior axis, Whiteside line) intra-operatively and calculated the angle from PCA to SEA and PCA to APA with Image free navigation system (BrainLAB). Those knees were preoperatively evaluated the angle deviation from SEA to PCA with three dimensional template system. These angle deviations, which suggested the femoral component rotation obtained from preoperative template system, were statistically compared with the femoral rotation angle in clinical situation. Results. The mean angle from PCA to SEA was external rotated 2.7 degrees (SD=1.8 degrees) with the template system. During image- free system in TKA, the mean angle from PCA to SEA was external rotated 2.2 degrees (SD=4.5 degrees), and the mean angle from APA to SEA was 0.5 degrees (SD=4.4 degrees). Discussion. The preoperative 3 dimensional template system showed the small ranges and standard deviations in PCA and SEA even when the residual cartilage of the surface at the femur was not considered to evaluate. Meanwhile, the three reference axes obtained from image free navigation system showed the large amount of deviations and thus the variability in these references was difficult to decide the rotation of the femoral component. Now navigation system provided the appropriate gap balance during knee motion. This gap-navigation technique would be one of the keys to obtain the proper rotation of the component

Purpose. External rotation of the femoral component is one factor that favors a satisfactory clinical result. New technologies have been developed to precisely implant the components of a total knee arthroplasty, including computer-assisted surgery (CAS) and patient-specific instruments (PSIs). The aim of this study was to compare the precision of CAS and PSIs when determining the orientation of the femoral component. Methods. A total of 65 patients operated on in 2008 with CAS had pre- and post-operative computed tomography (CT) in which the posterior condylar angle (PCA) was measured. The same pre- and post-operative measurements were performed for 27 patients operated on in 2010 with the assistance of PSI. For both populations, the antero-posterior femoral cuts were directed to implant the femoral component 3° of external rotation from the pre-operative posterior condylar line (PCL). Results. The pre-operative parameters for both groups were identical. The post-operative PCA was not significantly different between the CAS and PSI groups, but the pre- to post-operative difference in PCA for the PSI group indicated a diminution of 2 ± 2° compared to no change in the CAS group. A total of 28% of the patients operated on with CAS had their femoral component more internally rotated after the surgery compared to the pre-operative measurements. Conclusion. Both PSI and CAS achieve the same objective of externally rotate the femoral component in the transversal plan, even if CAS, some femoral components still remains less rotated than the plan

Background. Fractures of the femoral component are well reported complications that present a challenging task in revision total hip arthroplasty. Albeit being uncommon, with an incidence of 0.23–11%, the consequences can be devastating. Its extraction being a demanding undertaking that is potentially detrimental to the remaining host bone. Several techniques have been described to address this complex issue prior to revision: drilling of the exposed part of the femoral stem and attaching a threaded extraction device, surface undercutting with an extraction device wedged in, femoral trephine techniques, creation of a femoral cortical window, an extended femoral osteotomy procedure, as well as extraction by means of retrograde nail impaction. Here we present the modified technique we employed in the revision of a failed cementless extensively porous coated femoral component that had fractured at the neck-stem interface. Technique. The proximal femoral component was visualized and an orthopedic burr and a femoral osteotome employed surrounding the component. Utilizing a Midas Rex® MR7 drill with its metal cutting attachment, a circular recess was created in the shoulder of the femoral component. This facilitated the application of the distal end of a universal slap hammer. The component was retrieved successfully with no associated bone loss negating the need for a femoral osteotomy. Discussion. Revision hip arthroplasty is a perplexing field where unpredictable prosthetic failures require innovation to tackle the unique problems encountered. Our method allows a safe and efficient alternative in retrieving femoral components with no associated complications

Background. Proper femoral component placement plays a key role in the success of a total knee replacement (TKR). Controversy exists on which technique should be used to ensure proper femoral component placement. This two-part study compares gap balancing (GB) and measured resection (MR) techniques used in TKR, investigating femoral component position and early clinical outcomes. Methods. Femoral component position was analyzed in 95 consecutive knees that underwent primary TKR. Both GB and MR cutting blocks from the same knee system were sequentially placed on the operative knee, marking the pin sits. A standardized photograph (Figure) was taken prior to making final femoral cuts. Relative rotation was determined based on measurements made from a commercially available software. Clinical comparison was made using 50 consecutive GB patients and 50 consecutive MR patients. Clinical outcome measures were Knee Society Scores (KSS), knee range of motion (ROM), functional ROM (FROM), tourniquet time, and patients having manipulations under anesthesia (MUA). Results. The GB technique resulted in relative external and internal rotation of the femoral component in 41% and 17% knees respectively. Forty 42% of knees had no relative rotation. Mean pre and 1 year post-operative knee ROM for the MR cohort was 116.4±14.3. °. and 115±12.9. °. respectively, with FROM of 103.0±17.2. °. The GB cohort had mean pre and 1 year post-operative knee ROM values of 113.9±10.8. °. and 116.8±13.6. °. respectively, with FROM of 96.0±22.5. °. Mean 1 year pain and function KSS in the MR cohort were 92.5±10.7 and 85.4±18.9. In the GB cohort, the mean 1 year KSS values were 95.7±6.7 and 84.9±19.58 for pain and function respectively. Clinical outcome measures were not statistically different. Conclusion. We found that the GB technique resulted in external rotation relative to the MR technique. Despite these intraoperative findings we found no significant clinical differences

Purpose. To validate accuracy of transepicondylar axis as a reference for femoral component rotation in primary total knee arthroplasty. Methods. A prospective study done from dec 2010 to dec 2011 at tertiary centre. 80 knees were included (43 females and 21 males). All surgeries were carried out by one senior arthroplasty surgeon. All patients undergoing primary total knee replacement were included and all revision cases were excluded. Intraoperative assessment of TEA was done by palpating most prominent point on lateral epicondyle and sulcus on medial epicondyle and passing a k wire through it. Confirmation is done under image intensifier C arm with epicondylar view. Postoperative TEA was assessed by taking CT scan, measuring condylar twist angle and posterior condylar angle. Also correlation of femoral component rotation with postoperative anterior knee pain was assessed. Results. The mean PCA was around 4° with TEA as reference and only 10% patients required an additional lateral release of which 2% patient had preop patellar maltracking. No postoperative patellar maltracking was seen. Anterior knee pain was present in 8% patients. No postop infection is noted. Alignment ranging from 3° to 9° external rotation. Conclusion. TEA is most accurate reference for femoral component rotation even in severely deformed arthritic knees. Key words – Transepicondylar axis, total knee arthroplasty, femoral component rotation,

Introduction. Primary mechanical fixation and secondary biologic fixation determine the fixation of an uncemented femoral component. An optimized adequacy between the implant design and the proximal femur morphology allows to secure primary fixation. The femoral antetorsion has to be considered in order to reproduce the center of rotation. A so-called «corrected coronal plane » including the center of the femoral head has therefore been defined. The goal of this study was to evaluate the proximal metaphysal volume and to design a straight femoral component adapted to this corrected coronal plane. Materials and Methods. 205 CT-scans (performed in 151 males and 54 females free of hip arthritis) have been analyzed with a three-dimensional reconstruction. The mean age was 68.5 years (35–93). A corrected coronal plane has been defined including the center of the femoral head and the axis of the intramedullary canal. Five levels of sections (at a defined distance from the center of the femoral head) have been selected: 12.5mm, 50mm, 70mm, 90mm and 120mm. Three intramedullary criteria have been studied: volume between the 50mm and the 90mm sections (C1), the medial-lateral distance of the intramedullary canal (C2) at the 50mm, 70mm, and 90mm levels, and the A-P distance (C3) at the 50mm, 70mm, and 90mm levels (respectively C3–50, C3–70, and C3–90). The femoral head diameter, the femoral offset and the canal flare index (CT flare) have also been measured. Results. The mean head diameter was 47.7mm (38–56). The mean femoral offset was 44mm. The mean canal flare index was 4.68 (2.71 to 7.86). Based on the different measurements a femoral component with a range of 10 different sizes has been designed. Discussion. The morphological parameters of the studied population were comparable with published data. Radiological and CT-scan data have already been used in order to design femoral implants. However, these data did not consider the femoral antetorsion. The use of the corrected coronal plane allowed for optimized measurements when compared with previous methods in order to design a femoral component. Conclusion. The original method used in this study was to consider the corrected coronal plane in the design of a femoral component that respects the femoral antetorsion

Introduction. There is many reports about complications with a resurfacing total hip arthroplasty (RHA). One of the most common complications is the femoral neck fracture. A notch and malalignment were risk factors for this. For an accurate implanting the femoral component in RHA, we performed 3D template and made a patient specific template (PST) using 3D printer and applied this technique for a clinical usage. We report a preliminary early result using this novel technique. material and method. We performed 10 RHAs in nine patients (7 male, 2 female) from June 2009 to March 2010 due to osteonecrosis in 7 hips and secondary osteoarthritis in 3hips with a mean age of 48 years (40-60). We obtained a volumetric data from pre-operative CT and planned using 3D CAD software. Firstly, size of femoral components were decided from the size planning of cups. We aimed a femoral component angle as ten degrees valgus to the neck axis in AP and parallel in lateral view avoiding a notch. We measured femoral shaft axis and femoral neck axis in AP and lateral view using 3D processing software. PSTs were made using Laser Sintering by 3D printer which had the heat tolerance for sterilization in order to insert the femoral guide wire correctly. We operated in postero-lateral approach for all the patients PST has the base (contact part) fit to poterior inter trochanteric area. It has the arm reached from the base and sleeve hole to insert the guide pin into the femoral head. We measured the femoral component angle in three dimensions using the 3D processing software postoperatively. We compared the difference of this angle and the pre-operative planed angles. We also investigated the operation time, the volume of bleeding during operation and complications. Results. The mean femoral neck angle is 131.9±7.2°. The mean femoral component angle in AP view is 142.5±5.4°. The mean femoral component angle in lateral view is 0.1±1.2°. The mean calculated difference in AP view is 3.5±2.8°. And the mean calculated difference in lateral view is 0.9±0.7°. The mean operation time was 120±25 minutes. The mean volume of bleeding was 401±325ml. No major complication was noted. Discussion. By planning three-dimensional, it was possible to make an accurate preoperative planning. Though it is a very preliminary report with a small number of cases, we are encouraged to continue this procedure from this data. An application of PST for implanting femoral component in resurfacing THA brought us an accurate implanting as planned. This technique do not prolong an operation time, cost less and can be done with less invasions compared with a navigation system

Introduction. Proper femoral component rotation is a crucial factor in successful total knee arthroplasty (TKA). Femoral component rotation using anatomic landmarks has traditionally been established by referencing the transepicondylar axis (TEA), Whiteside's Line (WSL), or the posterior condylar axis (PCA). TEA is thought to best approximate the flexion-axis of the knee, however WSL or PCA are commonly used as surrogates of the TEA in the operating room due to their accessibility. The relationship of these anatomic landmarks has been previously investigated in anatomic and computed tomography based studies. The relatively few knees evaluated have limited the power of these studies. Patient Specific Instrumentation (PSI) utilizing magnetic resonance imaging (MRI) is an emerging technology in total knee replacement. The purpose of this study was to use magnetic resonance imaging based planning software to assess the relationship of WSL and PCA to the TEA and to determine if the relationships were influenced by the magnitude of the pre-operative coronal deformity. Methods. Five hundred sixty total knee replacements were performed in 510 patients utilizing PSI. The Materialize preoperative planning software was utilized to determine the rotational relationships of TEA, WSL, and PCA (Fig 1). The coronal plane deformity of each patient was also evaluated utilizing the MRI-based imaging and planning software. Results. The WSL is externally rotated by 90.36 degrees (SD ±2.3 degrees) compared to the TEA and the PCA is 2.38 degrees (SD ±1.6 degrees) internally rotated compared to the TEA in the overall population (p<0.001). The relationship of WSL to TEA has more variability than the relationship of PCA to TEA. In the overall population only 77% of WSL and 74% of PCA based resection will be within 2 degrees of the TEA. The PCA is more internally rotated in females and in valgus knees (P<0.001) however is not affected by the degree of valgus deformity (p = 0.211). Discussion. Femoral component rotation is determined based on one of three axis options. Classic studies have shown that the TEA is perpendicular to the WSL and the PCA is 3 degrees internally rotated to the TEA. However, there is wide variation in the relationships. Our MRI based evaluation shows that both WSL and PCA approximate the TEA in valgus knees regardless of the degree of deformity. Our study also shows that on average the PCA is 2.38 degrees internally rotated compared to the TEA, not the previously assumed 3 degrees. Our study indicates that the PCA is more internally rotated compared to the TEA in female patients and patients with valgus deformity. Males with varus knees may only require a 2 degree internal rotation correction rather than the historically established 3 degrees. WSL also shows more variability in its relationship to the TEA compared to the PCA. Advanced imaging can assist surgeons in assessing their options for femoral component rotation in TKA. Our data indicates that the relationships of axis options and historical assumptions may need to be reassessed as imaging technology advances

Summary. There is tremendous variability amongst surgeons' ability to reference anatomic landmarks. This may suggest the necessity of other objective methods in determining femoral alignment and rotation. Introduction. Despite the durability of total knee arthroplasty, there is much room for improvement with regards to functional outcome and patient satisfaction. One important factor contributing to poor outcomes after TKA is malrotation of the femoral component. It has been postulated that this is due to failure of surgeons to correctly reference bony landmarks, principally the femoral epicondyles, however, this is unproven. The purpose of this study was to evaluate the accuracy of joint surgeons and trainees in identifying anatomic landmarks for positioning the femoral component and to determine the effect of prior training and experience. Methods. 23 surgeons (17 attending surgeons, 6 trainees) participated in this study. Using custom-made computer software, each surgeon interactively defined the epicondylar axis (EA), the anterior-posterior axis (AP) of the distal cut (Whiteside's Line) on 3D computer models of 10 normal femora reconstructed from CT scans. Each surgeon then aligned a standard distal cutting guide on the resected distal surface of each femoral model. A standardized procedure was employed to determine the true location of the epicondyles, the direction of Whiteside's Line and the orientation of the cutting guide. Each participant was surveyed to ascertain their extent of formal training in joint arthroplasty, their annual volume of TKA cases, and whether they routinely aligned their TKAs using Whiteside's and the transepicondylar axis. The difference between the ideal and surgeon-selected parameters were calculated and correlated with data describing each surgeon's training and experience. Results. Landmark selection and guide placement was highly variable between surgeons. Overall, surgeons placed Whiteside's line in 1.83°± 7.01° of internal rotation vs. the calculated axes. Additionally, surgeons placed the transepicondylar axis in 1.40°± 3.72° of internal rotation vs. the calculated axes. On average, the guide was placed in 1.44°± 2.59° of additional internal rotation in comparison to the selected transepicondylar axis. Surgeons who routinely utilized the transepicondylar axis intraoperatively placed the guide significantly closer to the selected transepicondylar axis than those who did not (0.74°± 1.28° vs. 1.85°± 3.05°, p=.0024). Surprisingly, fellowship training, years of training, and volume of cases per year had no statistical effect the outcome of placement. Conclusion. This study suggests that there is tremendous variability amongst surgeons' ability to accurately reference the femoral epicondyles, Whiteside's line, and the transepicondylar axis. Our results also indicate that surgeons are not able to identify Whiteside's line with sufficient reliability for it to be a dependable indicator of correct component alignment in TKA. Our data also support the use of other methods to reliably determine correct rotational alignment of the femoral component in total knee arthroplasty

Introduction. In the case of bipolar hemiarthroplasty, surgeons are often faced with only migration of outer head and severe osteolysis in acetabulum without loosening of femoral component. There has been much debate regarding the merits of removing or retaining stable femoral components in such cases. The purpose of this study was to determine whether revision of an isolated acetabular component without the removal of a well-fixed femoral component [Fig. 1] could be successfully performed. Materials and methods. Thirty-four hips of 33 patients who were followed up for a minimum of 1 year were examined. There were 29 women and 4 men. The average time from primary operation to revision surgery was 12.5 years (range, 0.0 to 17.9 years), and the average follow-up time after revision was 5 years (range, 1.1 to 15.2 years). The average age of the patients at the time of the index revision was sixty-four years (range, thirty-two to seventy-eight years). The reason for acetabular revision was migration of outer head in twenty-eight hips, disassembly of bipolar cup in four hips and recurrent dislocation in two hips. Of the thirty-four femoral components, twenty-seven were cementless and seven were cemented. In nine hips, we performed bone grafting to osteolysis of the proximal femur around the stem. Acetabular components were revised to an acetabular reinforcement ring with a cemented cup in 26 hips, to cementless acetabular components in 8 hips, and to cemented cup in 1 hip. Results. The average Japan Orthopaedic Association hip score improved from 50.7 to 86.1 points after revision surgery. One femoral component (3%) was revised because of periprosthetic fracture, three years after the index acetabular revision and eighteen years after the initial bipolar hemiarthroplasty. Radiographic evaluation of the thirty-three femoral components that were not revised demonstrated no evidence of loosening or subsidence. There were no dislocation or deep infection. Thirty-three (97%) of the acetabular components were judged to be stable at the final follow-up. A nonprogressive radiolucent line of less than 2 mm was observed in one case. Conclusion. We recommend that isolated acetabular revision be considered in cases of failed bipolar hemiarthroplasty with a well-fixed femoral component