Accurate cup placement in total hip arthroplasty (THA) for the patients with developmental dysplasia of the hip (DDH) is one of the challenges due to distinctive bone deformity. Robotic-arm assisted system have been developed to improve the accuracy of implant placement. This study aimed to compare the accuracy of robotic-arm assisted (Robo-THA), CT-based navigated (Navi-THA), and manual (M-THA) cup position and orientation in THA for DDH. A total of 285 patients (335 hips) including 202 M-THAs, 45 Navi-THAs, and 88 Robo-THA were analyzed. The choice of procedure followed the patient's preferences. Horizontal and vertical center of rotation (HCOR and VCOR) were measured for cup position, and radiographic inclination (RI) and anteversion (RA) were measured for cup orientation. The propensity score-matching was performed among three groups to compare the absolute error from the preoperative target position and angle. Navi-THA showed significantly smaller absolute errors than M-THA in RI (3.6° and 5.4°) and RA (3.8° and 6.0°), however, there were no significant differences between them in HCOR (2.5 mm and 3.0 mm) or VCOR (2.2 mm and 2.6 mm). In contrast, Robo-THA showed significantly smaller absolute errors of cup position than both M-THA and Navi-THA (HCOR: 1.7 mm and 2.9 mm, vs. M-THA, 1.6 mm and 2.5 mm vs. Navi-THA, VCOR:1.7 mm and 2.4 mm, vs. M-THA, 1.4 mm and 2.2 mm vs. Navi-THA). Robo-THA also showed significantly smaller absolute errors of cup orientation than both M-THA and Navi-THA (RI: 1.4° and 5.7°, vs. M-THA, 1.5° and 3.6°, vs. Navi-THA, RA: 1.9° and 5.8° vs. M-THA, 2.1° and 3.8° vs. Navi-THA). Robotic-arm assisted system showed more accurate cup position and orientation compared to manual and CT-based navigation in THA for DDH. CT-based navigation increased the accuracy of cup orientation compared to manual procedures, but not cup position.
Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation. Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated.Aims
Methods
Three-dimensional (3D) weight-bearing alignment of the lower extremity is crucial for understanding biomechanics of the normal and pathological functions at the hip, knee, and ankle joints. In addition, implant position with reference to bone is a critical factor affecting the long-term survival of artificial joints. The purpose of this study was to develop a biplanar system using a slot-scan radiography (SSR) for assessing weight-bearing alignment of the lower extremity and for assessing implant positioning with respect to bone. A SSR system (Sonial Vision Safire 17, Shimadzu, Kyoto, Japan) with a custom-made rotation table was used to capture x-ray images at 0 deg and 60 deg relative to the optical axis of an x-ray source [Fig.1]. The SSR system uses collimated fan beam x-rays synchronized with the movement of a flat-panel detector. This system allows to obtain a full length x-ray image of the body with reduced dose and small image distortion compared with conventional x-ray systems. Camera calibration was performed beforehand using an acrylic reference frame with 72 radiopaque markers to determine the 3D positions of the x-ray source and the image plane in the coordinate system embedded in the reference frame. Sawbone femur and tibia and femoral components of the Advance total knee system (Wright Medical Technology, Arlington, TN, USA) were used. Computed tomography of the sawbone femur and tibia was performed to allow the reconstruction of the 3D surface models. For the component, the computer aided design (CAD) model provided by the manufacturer was used. Local coordinate system of each surface model was defined based on central coordinates of 3 reference markers attached to each model. The sawbone femur and tibia were immobilized at extension, axial rotation, and varus deformity and were imaged using the biplanar SSR system. The 3D positions of the femur and tibia were recovered using an interactive 2D to 3D image registration method [Fig.2]. Then, the femoral component was installed to the sawbone femur. The 3D positions of the femur and femoral component were recovered using the above-mentioned image registration method. Overall, the largest estimation errors were 1.1 mm in translation and 0.9 deg in rotation for assessing the alignment, and within 1 mm in translation and 1 deg in rotation for assessing the implant position, demonstrating that this method has an adequate accuracy for the clinical usage.
Computed tomography (CT) based preoperative planning provides useful information for severe TKA and revision TKA cases, such as the amount of augmentation, length of stem extension and component alignment, to achieve correct alignment and joint line. In this study, we evaluated TKA alignment performed with CT preoperative planning. 7 primary TKAs for severe deformity and 3 revision TKAs were included. CT preoperative planning was performed with JIGEN (LEXI, Japan). Constrained condylar prosthesis (LCCK, Zimmer) were used in all case. For femoral component, axial alignment was decided by controlled IM rod insertion to femoral canal. Rotational alignment was decided according to anterior cortex that usually was not compromised. For tibial component, axial alignment was set to perpendicular to tibial mechanical axis. Coverage and joint line level were carefully decided. The amount of bone resection of bilateral distal and posterior femoral condyle and proximal tibia was measured, respectively. Stem extension length and offset were selected according to components position and canal filling. Amount of augmentation was also estimated bilateral distal and posterior femoral condyle, respectively. Postoperative component alignment was evaluated three-dimensionally with Knee-CAS (LEXI, Japan).Introduction
Materials and Methods
In measured resection (MR) technique it is sometimes not easy to equalize extension gap (EG) and flexion gap (FG) because the size of femoral component is generally determined only depending on the anteroposterior and mediolateral size of femoral condyle in MR technique. In order to equalize the EG and FG, femoral implant size should be determined so that the FG is similar to the EG. We developed the novel sizing technique of femoral component to equalize the EG and FG in MR technique. The purpose of this study was to examine the usefulness of this technique. Before surgery, the condylar twist angle: CTA (angle between the transepicondylar axis and the posterior condylar axis) was determined for individual knees by transepicondylar view (X ray) or CT. During surgery, after osteophyte was removed EG was made and measured. Knee was flexed in 90° and the specially made tensor which upper paddle has the medial inclination angle (same as the CTA) was inserted to FG before posterior femoral osteotomy. Then, the appropriate traction force was applied to FG. Under this condition, the correct rotational alignment of femur relative to tibia was obtained, and then, the size of femoral component could be determined so that the FG was similar to the EG by measuring the distance between tibial cut surface and posterior cut level of the respective size of femoral conponent. 23 knees that undergone TKA for end stage medial osteoarthritis were examined and the final EG and FG were measured. EG and FG were measured at the mediolateral center of the gap without any trial component.Background
Methods
Recently, the short stem, taken on preservation of the femoral bone, is available on total hip arthroplasty and on femoral head prosthetic replacement. The handling of the short stem is easier than that of standard stem on implantation of femur. However, it would be difficult to make the direction of stem axis straight in femoral marrow cavity. Actually we experienced that the lateral cortical bone of the proximal femur was ground unevenly on rasping for implantation of the short stem. The aim of this study was to identify the efficacy of dulled rasp on implanting the short stem. We examined 42 hips of 39 patients who underwent the primary total hip arthroplasties with short stems in our institution from August 2011 to April 2014. Primary diseases were 28 osteoarthritides, 6 idiopathic osteonecrosises of the femoral heads and 5 others. We categorized N group as using standard rasp with sharpened blades and M group as using modified rasp with dulled blades named ‘Mild Rasp’, and analyzed with the statistical methods.Objective
Subjects and Methods
Friction between bearing surfaces in Total Hip Arthroplasty has been a main target of applied tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid lubrication in wet environment. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. We have examined 19 cases which were followed for more than two years. Sixteen cases for primary THA and three for revision THA, and 3 were male and 16 were female. Sixteen cases were osteoarthritis, one osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.1 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner. Surface touch is similar to hard surface with oil or lotions. No PE wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris.
When we perform total knee arthroplasty (TKA), the accurate osteotomy and implant setting is important as follows to improve long-term results. As means to perform osteotomy exactly, patient specific surgical instruments (PSI) patient specific surgical instruments planning based on pre-operative MRI (Signature, Materialise) and Image-free navigation system (Navi: Knee unlimited; BrainLAB) exist. However, there is not the report to compare which is exact for the same patient at the same time using two methods. We report to compare the osteotomy plans by two methods. Nine cases of TKA (Vanguard Complete Knee System, PS, BIOMET) operated on by one operator in our hospital from October 2012 to September 2013. 78.0 years average age (71–81 years old), sex was 6 cases women, 3 men.Purpose
Materials
Reducion of friction between bearing surfaces in Total Hip Arthroplasty is a main target of biological tribology. MPC (2-Methacryloyloxyethyl phosphorylcholine) has a similar properties to those of cell membranes, and can reduce friction with fluid luburication. We have used crosslink polyethylene with MPC polymer coating for primary and revision THA since 2011. Eighty one cementless THA were performed with closslink polyethlene liner with MPC polymer in our hospital. We have examined 21 cases which were followed for more than one year. Eighteen cases for primary THA and three for revision THA, and 3 were male and 18 were female. Seventeen cases were osteoarthritis, two osteonecrosis of femoral head and two rheumatoid arthritis. Average age of patients at THA was 60.4 years old. In the OR, we have experienced a very wet and slippery feeling on the bearing surface of polyethylene liner every time. Surface touch is similar to skin with lotions. No wear were measured on the X-ray display and no infections and no fractures were occurred during follow up. MPC polymer coating in THA can be useful for reduction of friction and generation of wear debris.
Modular femoral stems of Total Hip Arthroplasty (THA) have been designed to fit the metaphysis and diaphysis separately. Clinical results with modular femoral stems are reported to be satisfactory, but there exists several concerns with modular implant connections, including fretting corrosion, fracture of implant, and dissociation the stem from the proximal sleeve. Recently, we have become aware of another potential consequence of the modular design: sleeve deformation secondary to forces encountered during insertion. In our patients, we noted that the stems would not fully seat in the machined taper of the sleeve, indicating that some type deformation to the sleeve had occurred. We began an in vivo study to characterize this phenomenon. The objectives of this study were (1) Does deformation occur by impacting the sleeve into the metaphysis? (2) If so, quantify the sleeve deformation in hip arthroplasty patients. One man and 7 women undergoing primary THA were enrolled. This project was approved by IRB. This modular system (4-U CLS; Nakashima Medical Co., Japan) consists of a metaphyseal sleeve that connects with the diaphyseal stem via a Morse taper. The sleeve was impacted into the metaphysis first, followed by the stem. A custom taper gauge for each size of sleeve (Figure 1A) was inserted into the sleeve before and after impacting the sleeve into the metaphysis, and the distance between the top of the sleeve and the top of the gauge was measured using a caliper (* in Figure 1B). Deformation was defined as the difference in distance between the before and the after impacted dimensions. Preoperative femoral morphology, assessed using Dorr classification system, was type A in 2 hips, type B in 5 hips, and type C in 1 hip.INTRODUCTION:
MATERIALS AND METHODS:
It is said that the mechanical stress is a main factor to advance degenerative osteoarthritis. Therefore, to keep the joint stability is very important to minimize mechanical stress. Methods to evaluate bone-related factor are almost established, especially in hip dysplasia. On the other hand, it is unclear how much each soft tissue contribute to the joint stability. In this study we evaluated the soft tissue contribution for hip joint stability by distraction testing using MTS machine. We used seven fresh frozen hips from four donors, whose race was all western and reason of death was not related to hip disease in all cases. Average age of them at death was 83 years old. Mean average weight and height were each 52 kg and 162 cm. We retrieved hemi pelvis and proximal femur which kept hip joint intact. We removed all other soft tissue except iliofemoral ligament, pubofemoral ligament, ischiofemoral ligament and capsule. The hemi-pelvis mounted on angular-changeable fixator and the femur fixed to MTS machine (Figure 1). XY sliding table was used to minimize the horizontal direction stress during distraction. MTS machine was set to pull the femur parallel to its shaft by 0.4 mm/sec velocity against pelvis after 10N compression and to keep 5 mm distance for 5 seconds. We measured the force at 1 mm, 3 mm, 5 mm distraction. In case the joint was dislocated, the maximum force just before dislocation was recorded. The specimen was changed its posture as neutral (flexion0° abduction0° external rotation0°), flexion (flexion60° abduction0° external rotation0°), abduction (flexion0° abduction30° external rotation0°) and extension (extension20° abduction0° external rotation0°). Each position was measured in six sequential conditions, which are normal, Incised iliofemoral ligament, Circumferentially incised capsule, resected capsule, labral radial tear and resected labrum. After measurement joint surface was observed to evaluate the joint condition.[Introduction]
[Materials & Methods]
To explain the knee kinematics, the vector of the quadriceps muscle, the primary extensor, is important and the relationship of the quadriceps vector (QV) to other kinematic and anatomic axes will help in understanding the knee. Knee kinematics is important for understanding knee diseases and is critical for positioning total knee arthroplasty components. The relationship of the quadriceps to knee has not been fully elucidated. Three-dimensional imaging now makes it possible to construct a computer based solid model of the quadriceps and to calculate the vector of the muscle as individual parts and as a whole. Two studies are presented, one American and one Japanese subjects. Using CT data from subjects who had CT for reasons other than lower extremity pathology (American) or specifically for the study (Japanese), 3-D models of each quadriceps component (vastus medialis, intermedius, lateralis and rectus femoris) were generated. Using principal component analysis for direction and volume for length, a vector for each muscle was constructed and addition of the vectors gave the QV. Three anatomic axes were defined: Anatomic Axis (AA) – long axis of the shaft of the femur; Mechanical Axis (MA) center of the femoral head to the center of the trochlear and the Spherical Axis (SA) – a line from the geometric center of the head of the femur to the geometric center of the medial condyle of the femur at the knee. Fourteen American cases (mean age 39.1, 9 male 5 female) and 40 Japanese subjects (mean age 29.1, 21 male, 19 female) were evaluated. In all subjects the quadriceps vector at the level of the center of the femoral head was anterolateral to the center of the femoral head. The position of the QV was more lateral in Japanese compared to Americans; and, in Japanese, the vector was more lateral and posterior for women than for men. In both study populations, the QV was most closely aligned with the SA as compared to the AA or the MA. The vector representing the quadriceps pull, originating at the top of the patella, progresses proximally toward the We conclude that the QV as calculated progresses from the top of the patella to the mid-femoral neck and the SA is most closely parallel to this vector.
Revision Total Hip Arthroplasty can be challenging in case of thin or fragile femur. Primary Bipolar Hip Prosthesis (BHP) is also difficult in severe osteoporosis case. We have used titanium alloy cementless stem with interlocking screws for revision THA since 2003, and primary BHP in senile case since 2007. Thirty four cementless THA were performed with interlocking stem (27 S-LOCK and 7 Delta-LOCK) since 2007, and 26 cases were followed for more than one year. Two for primary THA and 24 for revision THA, 3 were male and 23 were female. Seven primary Bipolar Hip Prosthesis with interlocking screw stem for femoral neck fracture were also followed more than one year. All seven BHP cases were female. Stress shielding in X-ray film were observed in 3 revision THA cases during follow up, but no pain were complained. No breakage of screws and stems were observed, and no infections and no fractures were occurred. In case of loosened stem, long interlocking stem can bypass the weak point of femur after removal of cement or metal stem tip. Patients can walk immediately after revision THA or primary BHP. Cementless interlocking stem in THA and BHP is useful for management of thin or fragile femoral cortex.
Infection and skin ulcer are major problems in Total Knee Arthroplasty (TKA) and Bipolar Hip Prosthesis (BHP). Sugar (sucrose) has been used for wound care in many countries because it absorbs fluid, stimulates granulation, and suppress growth of bacteria. Trafermin ∗∗∗∗∗ recombinant human basic fibroblast growth factor ∗∗∗∗∗ FGF ∗∗∗∗∗ accelerates granulation process and improves quality of wound healing. We have used sucrose and trafermin for treatment of infection after TKA and BHP. Six infected TKA with skin ulcer and one infected BHP with fistula were treated with Trafermin and sugar. TKA were performed in four osteoarthritis and two rheumatoid arthritis, and BHP was for femoral neck fracture. Implants were removed in three cases because of deep infection. One was male and six were female, average age were 60.8 years old ranged 43 to 77. Follow-up period were one to 5 years. Four cases were related to MRSA. Sugar treatment were performed for two to 23 weeks, and Trafermin was sprayed once a day for two to 16weeks. In BHP case, sugar therapy was performed intermittently. In two deep infected TKA cases, infection ceased in one to 4 month and revision TKA were performed. In other four TKA cases, infection were ceased in two to 16 weeks. In BHP case, fistula closed in three years. Combination of Trafermin and sugar is useful for management of infection and skin ulcer after TKA and BHP
Progression of osteoarthritis (OA) of the knee is related to alignment of the lower extremity. Postoperative lower extremity alignment is commonly regarded as an important factor in determining favourable kinematics to achieve success in total knee arthroplasty (TKA) and high tibial osteotomy (HTO). An automated image-matching technique is presented to assess three-dimensional (3D) alignment of the entire lower extremity for natural and implanted knees and the positioning of implants with respect to bone. Sawbone femur and tibia and femoral and tibial components of a TKA system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the 3D bone models and the component computer-aided design models were projected onto extracted contours of the femur, tibia, and implants in frontal and oblique X-ray images. Threedimensional position of each model was recovered by minimizing the difference between the projected outline and the contour. The relative positions were recovered within −0.3 ± 0.5 mm and −0.5 ± 1.1° for the femur with respect to the tibia, −0.9 ± 0.4 mm and 0.4 ± 0.4° for the femoral component with respect to the tibial component, −0.8 ± 0.2 mm and 0.8 ±0.3° for the femoral component with respect to the femur, and −0.3 ± 0.2 mm and −0.5 ± 0.4° for the tibial component with respect to the tibia. Clinical applications were performed on 12 knees in 10 OA patients (mean age, 72.5 years; range, 62–87 years) to check change in the 3D mechanical axis alignment before and after TKA and to measure position of the implant with regard to bone. The femorotibial angle significantly decreased from 187.8° (SD 10.5) to 175.6° (SD 3.0) (p=0.01). The 3D weight-bearing axis was drawn from the centre of the femoral head to the centre of the ankle joint. It intersected significantly medial (p=0.01) and posterior (p=0.023) point at the proximal tibia before TKA. The femoral component rotation was 3.8° (SD 3.3) internally and the tibial component rotation was 14.1° (SD 9.9) internally. Compared with a CT-based navigation system using pre-and post-operative CT for planning and assessment, the benefit to patients of our method is that the post-operative CT scan can be eliminated.
Infection is one of major problems in Total Knee Arthroplasty (TKA) or Bipolar Head Prosthesis (BHP). We have used Calcium Phosphate Paste (CPP) for treatment of infected TKA and BHP, and followed up for minimum one year. CPP is a mixture of alpha Tri-Calcium Phosphate, Tetra-Calcium Phosphate, Calcium Hydrogen Phosphate and Hydroxyapatite. CPP harden in 10 minutes and its stiffness increases to maximum in 3 days. Infected TKA were diagnosed in four osteoarthritis and four rheumatoid arthritis knees, and BHP infection were observed in two femoral neck fracture cases from 2001 to 2007. Two were male and eight were female, average age were 67.3 years old ranged 39 to 80. Follow-up period were one to 7 years. Six cases were MRSA infection, three MSSA, one was unidentified but diagnosed with clinical data. In TKA cases, CPP (10–12g) with vancomycin hydrochloride or tobramycin were filled on the back side of PMMA articulated surface spacers, and in BHP cases, CPP with antibiotics were filled in acetabulum. In all TKA cases, infection ceased in 2 to 4 month and revision TKA ware performed. One recurrence of infection was observed during follow up in BHP infection, and nine patients can walk with/without a cane. No venous thromboembolism were observed.
Change in the joint line in TKA has been recognized as an important parameter in association with post-operative soft tissue tension, range of motion, and knee kinematics. In general, the joint line has been assessed only in tibial side based on the bony reference point of tibia. However, the joint line should also be assessed in the femoral side. This is because a replaced femoral condyle often does not accurately restore the geometry of the original condyle, depending on the alignment, the size, or the design of the component. This discrepancy, especially in the geometry of the distal and posterior condyle will greatly affect the knee kinetics in association with the soft tissue tension. Objective of this study was to investigate how joint line was changed in femoral and tibial condyle by TKA. We have developed a method to assess the femoral-joint line and the tibial joint line three-dimensionally and quantitatively by the 3D model image matching to biplanar computed radiography. Twenty-knees underwent TKA and 3D joint line examination. Most of the knees demonstrated the significant proximal movement of the medial joint line in tibia, while the lateral joint line was restored. The significant distal movement of the distal femoral joint line was demonstrated in most of the knees, and it was demonstrated more frequently in medial condyle. Most of the knees demonstrated the significant anterior movement of posterior femoral joint line while no knee demonstrated the significant posterior movement. From the results of this report, it was proved that the joint line can be changed by TKA procedure not only in tibial condyle but also in distal and posterior femoral condyles with considerable variations. In addition, it was also proved that there can be a difference in the change in the joint line between medial and lateral condyle.
Award for the best student biomaterials paper (US$ 2,000); a proper certificate
One of major problems in Total Hip Arthroplasty is thigh pain. We have examined the effect of femoral canal injection of Calcium Phosphate Paste (CPP) for cementless THA. CPP is a mixture of alpha Tri-Calcium Phosphate, Tetra-Calcium Phosphate, Calcium Hydrogen Phosphate and Hydroxyapatite. This paste harden in 10 minutes and its stiffness increases to 80Mpa in 3days. Cementless THA were performed in 45 osteoarthritic hips from 1999 to 2002. Eight of 40 patients were male and 32 were female, average age were 62.4 years old ranged 43 to 81. In 11 hips, CPP (10–12g) were filled as a femoral canal filler around the distal end of stem. In 34 hips, as a control, no CPP were filled in the canal. Proximal part of the stem was HA coated on rough metal surface. No thigh pain were observed in CPP group patients. In control group, five hips (14.7%) showed thigh pain (p<
0.05), but walking disability and pain were mild in the first year and improved by the next year. CPP filled in the canal were absorbed slowly on X-ray film, but prevention of thigh pain lasts for long time maximum 3 years. No infections and pulmonary embolism were observed in both series. Filling CPP into the gap between stem tip and femoral canal is useful technique to prevent thigh pain after cementless THA.
Single plane 2D-3D image matching procedure using fluoroscopic images with CAD data of components has been a gold standard of the in-vivo knee kinematics analysis after total knee arthroplasty (TKA). Numerous literatures have highlighted the “Condylar lift-off” (CLO) phenomenon that is thought to be the cause of eccentric polyethylene wear. However, these reports have not taken account of the 3D geometry of tibial polyethylene insert (TPI). We have developed a system for analyzing static 3D relationship between femoral and tibial component after TKA accurately utilizing the biplanar computed radiography. By applying this system to fluoroscopic knee motion analysis, it has been possible to analyze the 3Dbehavior of femoral component on the TPI by reducing the error in determining the out of plane translation and rotation. Four knees underwent TKA and postoperative knee motion analysis. Knee kinematics was analyzed by translation of medial and lateral estimated contact points of femoral component on TPI. CLO was defined as the separation of femoral component from TPI by more than 1 mm. All 4 knees showed the “tilting” of femoral condyle relativeto tibial base plate in coronal plane (this phenomenon has been generally recognized as CLO) resulted from that one femoral condyle contacted with the lower potion in convex geometry of the TPI while the other contacted with the higher potion. This was occurred by a rotation of femoral condyle. However, no CLO was demonstrated in this series. This might be because that recorded knee motions were relatively slow and supported by examiners. From the results of this report, it was proved that a tilting of femoral component relative to tibial base plate in coronal plane not always indicates CLO. For detailed analysis of knee kinematics after TKA, it was thought to be necessary to take account of the geometry of TPI.
