Previous fluoroscopic analyses of Total Hip Arthroplasty (THA) determined that the femoral head slides within the acetabular cup, leading to separation of certain aspects of the articular geometries. Although separation has been well documented, it has not been correlated to clinical complications or a more indepth understanding of the cause and effect. Surgical technique is one of the important clinical factors when considering THA procedures, and it is hypothesized, that it could affect the magnitude and occurrence of femoral head separation (sliding) in THAs. Hence, the objective of this study was to determine and compare in-vivo THA kinematics for subjects implanted with a THA using two different surgical approaches. Thirty seven subjects, each implanted with one of two types of THA were analysed under in vivo, weight-bearing conditions using video fluoroscopy while performing a sit-to-stand activity. Ten subjects were implanted by Surgeon 1 using a long incision postero-lateral approach (G1); while a further 10 subjects were implanted by the same surgeon using a short incision posterolateral approach (G2). The remaining 17 subjects were implanted using the anterolateral approach; 10 by Surgeon 2 (G3) and seven by Surgeon 3 (G4). All patients with excellent clinical results, without pain or functional deficits were invited to participate in the study (HHS >
90). 3D kinematics of the hip joint was determined, with the help of a previously published 2D-to-3D registration technique. From a completely seated position to the standing position, four frames of the fluoroscopy video were analysed. Subjects in all groups experienced some degree of femoral head separation at all increments of the sit-to-stand activity that were analysed. The magnitude and frequency of separation greater than 1.0mm varied between each surgeon group, between incision types, between incision lengths and between the two types of THA that were analysed. The average maximum separation was 1.3, 1.1, 1.3 and 1.4mm for G1, G2, G3 and G4 respectively. Though there was no difference in the average maximum separation values for the 4 groups, the maimum separation varied significantly. While the maximum separation in G2 was 1.8mm, the maximum separation in G4 was 3.0mm. G1 and G3 had maximum separation values of 2.3mm and 2.4mm respectively. This study suggests that there may be a correlation between incision lengths and surgical approach with femoral head separation in THAs. The maximum separation that was seen among all groups was a subject with a traditional long incision, while the short incision group had less incidence of separation. Results from this study may give researchers and implant developers a better understanding of kinematics around the hip joint and how they vary with respect to different surgical techniques. Further analysis is being conducted on the subjects before definitive conclusions can be made.
Previosuly, Komistek et al. have shown that the kinematics of the patellofemoral joint is altered after a TKA surgery. Specifically the implanted patella experiences significantly less rotation than the natural patella. Also, in early flexion, the patellofemoral contact positions differed significantly between implanted and non-implanted patellae. It was also found that some of TKA subjects experience patellofemoral separation. These kinematical differences may lead to adverse mechanical conditions and increase fatigue or cause loosening of the implant components. This study’s objective was to determine the three-dimensional patellofemoral kinematics and correlate it with the in vivo sound (vibrations) detected using accelerometers for subjects having a TKA and a non-implanted knee under in vivo, weight bearing conditions. The correlation of the knee mechanical conditions with the vibration data may indicate new parameters that may be used to diagnose the condition of the articular cartilage or implant components. Fifteen subjects (average age 71.8 ±7.4years) having one implanted knee (mobile bearing Hi-Flex PS) and the healthy contralateral knee, performed
deep knee bend to maximum flexion, chair rise and stair climb activities under fluoroscopic surveillance. Three miniature, piezoelectric, three-axial accelerometers were attached to the patella and femoral epicondyle. The study was approved by the Institutional Review Board and informed consent was obtained from all subjects. The sensors detected the vibration magnitudes and frequencies of the articulating patellofemoral joint surfaces. The signals were amplified and low-pass filtered at 5 kHz by a signal conditioner. The 3D tibiofemoral and patellofemoral kinematics were derived for both knees using a previously published 3D-to-2D registration technique. The 3D bone models were recovered from CT scans, while implant models were obtained from the manufacturer. The patellofemoral rotations were described using the Grood and Suntay convention. The kinematics and sound data were synchronized and recorded under fluoroscopic surveillance, for 10 patients. Then a subset of seven subjects having a TKA was re-analyzed for their contralateral (non-implanted) knee. The vibration signal was then converted to audible sound and correlated with the 3D kinematics. On average, the subjects achieved more flexion with their TKA (103.4°±15.9°) than with their contralateral knee (96.3°±18.3°). The patellofemoral kinematics varied between the TKA and nonimplanted patella groups; the resurfaced patella experienced less flexion, less medial rotation and less tilt than the contralateral patella. The patellar flexion results were consistent with previously reported literature for both TKA and non-implanted patellae. Also, the resurfaced patellae contacted the femur more proximally than healthy patellae. Audible signals were found for both groups of subjects. The frequency analysis demonstrated that specific frequencies were in similar range for both groups, but the magnitudes and variations were different for the TKA and contralateral knees. This study correlated 3D patellofemoral kinematics with sound under in vivo conditions for three different activities. Variable audible signals were detected for TKA and non-implanted knees. Vibration magnitude and frequency identification, under in vivo conditions, for TKA may lead to a better understanding of wear and failure modes with respect to the patellofemoral mechanics, more specifically, the patellar insert. Currently this initial study is being expanded to degenerated knee joints and failed TKAs for possible applications of the vibration analysis to the early diagnosis of knee arthritis, detection of implant loosening or wear and monitoring of implant osteointegration progress.
Many nonoperative techniques exist to alleviate pain in unicompartmental osteoarthritic knees including physical therapy, heel wedges and off-loading knee braces [ We have analyzed five patients with moderate to severe osteoarthritis in both step up and step down activities with two different knee braces and also without a knee brace. Fluoroscopy of the five patients performing these activities was obtained as well as a CT scan of the knee joint for each patient. 3-D models of the femur and tibia were obtained from manual segmentation and overlaid to the fluoroscopy images using a novel 3-D to 2-D registration method [ All five patients experienced substantially less pain when performing the step up and step down activities with a knee brace versus without a knee brace. It should be noted that none of the five patients were obese, which can limit brace effectiveness. Preliminary results show that medial condyle separation was increased by 1.4–1.6 mm when using a knee brace versus not using a knee brace during the heel-strike and 33% phases of step up and step down activities. Also, the condylar separation angle was reduced by an average of 1.5–2.5°. Finally, consistently less condylar separation was seen during step down versus step up activities (0.5–1 mm), which can be attributed to a greater initial impact force on the knee joint during step down versus step up activities.
This research is to relate functional outcomes to kinematics in high flexion CR and PS total knees by using the Total Knee Function Questionnaire in patients who had previously undergone kinematic analyses. Patients were identified who had primary total knee arthroplasty and had undergone kinematic analyses using fluoroscopy. The Total Knee Function Questionnaire was sent to these patients, and data was obtained for 14 CR knees (NexGen CR-Flex, Zimmer) and for 13 PS knees (Legacy LPS-Flex, Zimmer). The questionnaire evaluates baseline activities of daily living, advanced activities, and recreational activities and exercises. CR patients reported higher satisfaction and that their knees felt more “normal” than PS patients. Some baseline activity scores were significantly higher for CR than for PS knees. Limitations in baseline activities were related to kinematic constraints, including flexion, lateral and medial anterior-posterior (A-P) translations, and tibiofemoral axial rotation. Kinematic data were related to difficulty data for advanced and recreational activities of kneeling, squatting, gardening, and stretching. Comparisons between kinematic data and patient feedback on knee function provided unique information about differences between CR and PS high flexion implants. CR patients had better function than PS patients in walking on even ground or uphill or sitting. CR patients had higher activity scores for recreational than for advanced activities, while activity scores for the PS patients were similar between these activities. Kinematic variables that affected function for some activities included extremes of flexion, A-P translations of lateral and medial condyles, and axial rotation intervals.
Previous in vivo studies have not documented if ethnicity or gender influence knee kinematics for the healthy knee joint. Other measurements, such as hip-knee-ankle alignment have been previously shown to be significantly different between females and males, as well as Japanese and Caucasian populations in the young healthy knee [ The 3D, in vivo, weight bearing normal knee kinematics was determined for 79 healthy subjects, including 48 Caucasians, 24 Japanese, 42 males, and 37 females. Each participant performed deep knee bend activity from a standing (full extension) to squatting to a lunge motion, until maximum knee flexion was reached. The study was approved by the Institutional Review Board and informed consent form was obtained from all subjects. The 3D bone models, created by segmentation from MR images, were used to recreate the 3D knee kinematics using the previously described fluoroscopic and 3D-to-2D registration techniques (Fig. 1) [ Most subjects achieved very high flexion, however substantial variability occurred in all groups. Range of motion (ROM) varied from 117° to 177°, while average external rotation was 31°± 9.9° for all subjects. Japanese and female subjects achieved greater ROM than Caucasian (p=0.048) and male (p=0.014) subjects. From full extension to 140° of flexion (which 87% of subjects achieved), few significant differences between any of the populations were observed. At deeper flexion, the external rotation was higher for female than for male subjects, however not statistically significant (p=0.0564 at 155°). Also at deep flexion, the adduction was significantly higher for female subjects. The translations of the lateral condyle were very similar between respective groups, but at deep flexion, the medial condyle remained significantly more anterior for females, leading to greater axial rotation and ROM. As ACL laxity increased, flexion/extension ROM significantly increased (r2=0.184, p<
0.001). In addition, ACL laxity was also higher for females (6.8 mm) compared to males (5.6 mm, p=0.011), as well as Japanese (7.5 mm) compared to Caucasian (5.6 mm, p=0.0002) subjects. High variability and ROM in knee kinematics were similar to those seen in previous studies of healthy subjects during a deep knee bending activity [
Considerable differences in kinematics between different designs of knee prostheses and compared to the natural knee have been seen in vivo. Most noticeably, lift off of the femoral condyles from the tibial insert has been observed in many patients. The aim of this study was to simulate lateral femoral condylar lift off in vitro and to compare the wear of fixed bearing knee prostheses with and without lift off. Twelve PFC Sigma cruciate retaining fixed bearing knees (DePuy, Leeds, UK) were tested using six station simulators (Prosim, Manchester, UK). The kinematic input conditions were femoral axis loading (maximum 2.6 kN), flexion-extension (0–58°), internal/external rotation (±5°) and anterior/posterior displacement (0–5 mm). Six knees were tested under these standard conditions for 4 million cycles. Six knees were tested under these conditions with the addition of lateral femoral condylar lift off, for 5 million cycles. The lubricant used was 25% newborn calf serum. Wear of the inserts was determined gravimetrically. Under the standard kinematic conditions the mean wear rate with 95% confidence limits was 8.8 ± 4.8 mm 3/million cycles. When femoral condylar lift off was simulated the mean wear rate increased to 16.4 ± 2.9mm 3/million cycles, which was statistically significantly higher (p <
0.01, Students t-test). The wear patterns on the femoral articulating surface of all the inserts showed more burnishing wear on the medial condyle than the lateral. However, in the simulation of lift off the medial condyle was more aggressively worn with evidence of adhesion and surface defects. The presence of lateral femoral condylar lift off accelerated the wear of PFC Sigma cruciate retaining fixed bearing knees. The lateral lift off produced uneven loading of the bearing, resulting in elevated contact stresses and hence more wear damage to the medial side of the insert. The implications of condylar lift off include increased wear of the polyethylene and possible osteolysis.
The objective of the present study was to analyse kinematics of subjects having a UKA during stance phase of gait, where the ACL was intact at the time of the operative procedure. Femorotibial contact positions for nineteen subjects (15 medial UKA (MUA); 14 lateral UKA (LUA); HSS >
90, post-op >
3 yrs) were analysed using video fluoroscopy. During stance-phase of gait, on average, subjects having a medial UKA experienced 0.8 mm of anterior motion (7.7 to – 2.3 mm), while subjects having a lateral UKA experienced −0.4 mm (0.9 to – 2.1 mm) of posterior femoral rollback (PFR). Eight of 15 subjects having a medial UKA and two out of four lateral UKA experienced PFR. Eight of 15 subjects having a medial UKA experienced normal axial rotation (average = 0.9 degrees) and one out of four subjects having a lateral UKA experienced normal axial rotation (average = −6.0 degrees). High variability in the kinematic data for subjects experiencing an anterior slide and opposite axial rotation suggests that these subjects had an ACL that was not functioning properly and was unable to provide an anterior constraint force with the necessary magnitude to thrust the femur in the anterior direction at full extension. Progressive laxity of the ACL may occur over time, and at least in part, lead to premature polyethylene wear occasionally seen in UKA. Our results support the findings of other studies that the ACL plays a significant role in maintaining satisfactory knee kinematics, which may also, in part, contribute to UKA longevity.
The objective of this present study was to determine the in vivo kinematic patterns for subjects implanted with a patellofemoral arthroplasty (PFA). Twenty subjects, all having a PFA, were studied (<
2 years post-op) under fluoroscopic surveillance to determine patellofemoral contact positions, sagittal plane, and medial/lateral translation using a skyline view. The patellofemoral contact patterns for each subject having a PFA was highly variable, 11.9 mm of translation. The average amount of patella rotation during the full flexion cycle was 26.3 degrees, while one subject experienced 48.6 degrees. The average amount of medial/lateral translation was 3.8 mm (5 >
5 mm). Five subjects experienced grater than 5 mm of motion. This was the first study to ever determine the in vivo kinematics for subjects having a PFA and the in vivo medial/lateral translation patterns of the patellofemoral joint. Subjects in this study experienced high variability and some abnormal rotational patterns. Most of the subjects who underwent PFA in this study had a previous history of subluxed or dislocated patella which affects the normal patella tracking, especially regarding tilting and translation. This tracking may also be directly affected by patellofemoral conformity, a consequence of femoral implant design. Finally, after PFA the patello-tibial tilt angle is influenced by the anteroposterior positioning of the femoral component. The results of this very first in vivo kinematic study may play an important role, not only for design consideration of patellofemoral replacement but also for surgical technique in order to obtain optimal implant positioning.
The objective of this present study is to conduct a comparative analysis of the kinematic data derived for all subjects having a TKA who were analysed over the past eight years at our laboratory. Femorotibial contact positions for 705 subjects having either a fixed bearing PCR or PS TKA or mobile bearing TKA were analysed in three-dimensions using video fluoroscopy. During a deep knee bend, all PS TKA types subjects experienced a medial pivot motion, averaging −3.8 of lateral condyle posterior femoral rollback (PFR), respectively. Subjects having a fixed bearing PCR TKA experienced only −0.7 mm of lateral condyle PFR and an anterior slide of 1.6 mm for the medial condyle. Twenty-nine percent of the PCR TKA analysed had a lateral pivot and 71% experienced a medial pivot. Subjects having a mobile bearing TKA experienced −2.8 mm of lateral condyle PFR and 0.4 mm of medial condyle anterior slide. Fifty-one percent of the moble bearing implants experienced a medial pivot and 43% experienced a lateral pivot. During gait, PS and PCR fixed bearing TKA types experienced similar kinematic patterns. Subjects having a mobile bearing TKA experienced minimal motion, probably due to the mobile bearing TKA having greater sagittal conformity and had the lowest standard deviation. There was great variability in the data comparing various TKA designs. Subjects in this multicentre analysis predominantly experienced a medial pivot motion, although certain TKA designs did demonstrate a lateral pivot motion.