Introduction. The low-contact stress (LCS) knee prosthesis is a mobile-bearing design with modifications to the tibial component that allow for meniscal-bearing (MB) or rotating-platform (RP). The MB design had nonconstrained anteroposterior and rotational movement, and the RP design has only nonconstrained rotational movement. The anterior soft tissues, including patellar tendon (PT), prevent anterior dislocation of the MB. The PT may consistently be exposed to overstressing. Therefore, we hypothesized that the PT thickness and width in MB prosthesis revealed more morphological changes than those of RP prosthesis due to degeneration of the PT induced by much mechanical stress of the MB movement. To confirm this hypothesis, we analyze the PT thickness and width induced by mobile-bearing inserts. Objectives. Sixty LCS prostheses in 30 patients were analyzed. The average follow-up time was 61 months. MB prosthesis was used on one side of the knee and RP prosthesis was used on the contralateral side of the knee. All patients were chosen from group with no clinical complication, and all had achieved passive full extension and at least 90°of flexion. The average Hospital for Special Surgery Score was 94.6 ± 2.7. Methods. We measured the thickness and width of PT at joint line level, which were confirmed by sagittal section using ultrasound in knee extension between MB and RP design prosthesis. Results. The mean thickness of PT was 4.7 mm (1.2) with MB and 4.7 mm (1.0) with RP design prosthesis. The mean width of PT was 30.6 mm (3.2) with MB and 31.3 mm (3.5) with RP design prosthesis. No significant differences were found between both groups. Conclusion. The current results showed that the PT thickness and width in MB prosthesis did not reveal more morphological changes than those of RP prosthesis due to degeneration of the PT induced by much mechanical stress of the MB movement. The possible reasons are the following: (1) We did not remove infra-patellar fat pad, which might play shock absorber of mechanical stress from MB, and prevent from significant degeneration of PT, (2) MB inserts did not stimulate the middle of the PT directly, unlike LCS A/P-Glide inserts, and might come into contact with the both ends of the PT and (3) MB inserts did not move so as to cause degeneration in the PT

The Step Holter is a software and mobile application that can be used to easily study gait analysis. The application can be downloaded for free on the App Store and Google Play Store for iOS and Android devices. The software can detect with an easy calibration the three planes to detect the movement of the gait. Before proceeding with the calibration, the smartphone can be placed and fixed with a band or stowed into a long sock with its top edge at the height of the joint line, in the medial side of the tibia. The calibration consists in bending the knee about 20 to 30 degrees and then making a rotation movement, leaving the heel fixed to the ground as a rotation fulcrum. After calibration, the program records data related to lateral flexion, rotation, and bending of the leg. This data can be viewed directly from the smartphone screen or transmitted via a web link to the Step Holter web page . www.stepholter.com. by scanning a personal QR code. The web page allows the users to monitor the test during its execution or view data for tests done previously. By pressing the play button, it is possible to see a simulation of the patient's leg and its movement. With the analyze button, the program is capable of calculating the swing and stance phase of every single step, providing a plot with time and percentages. Finally, with the Get Excel button, test data can be conveniently exported for more in-depth research. The advantage of this application is not only to reduce the costs of a machine for the study of gait analysis but also being able to perform tests quickly, without expensive hardware or software and be used in specific spaces, without specialized personnel. Furthermore, the application can collect important data concerning rotation that cannot be highlighted with the classic gait analysis. The versatility of a smartphone allows tests to be carried out not only during walking but also by climbing or descending stairs or sitting down or getting up from a chair. This software offers the possibility to easily study any kind of patients; Older patients, reluctant to leave their homes for a gait analysis can be tested at home or during an office control visit. Step Holter could be one small step for patients, one giant leap for gait study simplicity. For any figures or tables, please contact authors directly

Introduction. Achieving high flexion after total knee arthroplasty (TKA) is one of the most important clinical results, especially in eastern countries where the high flexion activities, such as kneeling and squatting, are part of the important lifestyle. Numerous studies have examined the kinematics after TKA. However, there are few numbers of studies which examined the kinematics during deep knee flexion activities. Therefore, in the present study, we report analysis of mobile-bearing TKA kinematics from extension to deep flexion kneeling using 2D-3D image matching technique. Materials and Methods. The subjects were 16 knees of 8 consecutive patients (all women, average age 75.9), who underwent primary mobile-bearing PS TKA (P.F.C. sigma RP-F: Depuy Orthopedics Inc., Warsaw, IN, USA) between February 2007 and May 2008. All cases were osteoarthritis with varus deformity. Postoperative radiographs were taken at the position of extension, half-squatting and deep flexion kneeling 3 month after the surgery, and the degrees of internal rotation of the tibial component was measured by 2D-3D image matching technique. Pre- and post-operative ROM was recorded. Then, we compared the absolute value and relative movement of tibial internal rotation between extension, half-squatting and deep flexion kneeling, and evaluated the correlation of the ROM and the internal rotation. Results. The mean preoperative ROM was from -12 to 118 degrees. After the surgery, ROM was from -2 to 123 degrees. Clinical scores of all cases were significantly improved after surgery. Internal rotation of tibial component was -6.8 to 9.7 (mean, 1.7) degrees at half-squatting position, and -7.2 to 13.6 (mean; 1.9) degrees at kneeling position. There was no correlation between maximum flexion angle and tibial rotation during flexion. There was significant negative correlation between tibial internal rotation angle in extension and tibial rotational movement from half-squatting to deep flexion kneeling (R; -0.824, P<0.05). Discussion. The internal rotation of the tibia during high flexion is well known as medial pivot movement in intact knee. And several reports have suggested that the medial pivot movement is related to maximum flexion angle after TKA. In the present study, we showed that there was significant negative correlation between the tibial internal rotation angle in extension and tibial rotational movement from half-squatting to deep flexion kneeling. This result suggested that the internal rotation of the tibial component in extension prevent the medial pivot movement of the knee during deep flexion. Therefore, the rotational alignment of tibial component may have the effect to the flexion angle after TKA

Conventional wisdom holds that aseptic failure of proximal ingrowth femoral stems should be addressed by revision to a longer femoral stem dependent upon more distal fixation. This is a reliable and time-honoured strategy with a high likelihood of success provided secure initial fixation of the revision stem is obtained. Yet, stems reliant upon more distal diaphyseal fixation are accompanied by a greater risk of physiologic thigh pain attributable to the differential in flexural stiffness of the femoral shaft compared with the prosthetic stem. Contemporary proximal ingrowth femoral stems have become the most popular device used in total hip arthroplasty and are traditionally reserved for primary procedures. Nevertheless, the flat tapered design offers a tight fit between the medial and lateral endosteal cortices of the femur, unimpeded by an increasing anteroposterior dimension of the stem, and provides a secure geometrical block to rotational movement of the stem. In instances when the primary stem is not fit to the endosteal cortex on the anteroposterior radiograph, such as with the Corail or SROM devices, the opportunity may exist for revision with a flat tapered proximal ingrowth stem that is upsized to abut the endosteal femoral cortex. Such a strategy preserves the diaphyseal femur for subsequent revision in these typically young patients and avoids the issue of thigh pain in this active population. Likewise, revision of a well-fixed long stem that is associated with unrelenting thigh pain may be similarly accomplished by revision to a flat proximal ingrowth stem provided the integrity of the upper femur can be maintained during the revision. A prophylactic cerclage wire around the proximal femur is a helpful adjunct when using flat tapered proximal ingrowth stems in the revision setting

Background. A navigation system is useful tool to evaluate the intraoperative knee kinematics. Rheumatoid arthritis (RA) patients often need to have TKA operation, however, there are few TKA kinematics studies comparing RA and Osteoarthritis (OA) patients. Objective. The purpose of this study was to evaluate intraoperative TKA kinematics, and to describe the difference of kinematics between RA and OA patients. Materials and methods. Seventy-four patients, 86 knees were included in this study. Unilateral posterior stabilized TKAs were performed (male 14, female 72, age 70 ± 1.1 years) using navigation system. Sixty-one knees had OA and 25 had RA. Evaluation items are coronal gaps, AP translation and rotation. Coronal gaps were defined as the distance between the femoral and tibial cut surface. Medial and lateral gaps are also measured. AP translation was defined as the sagittal movement between the center of femoral and tibial condyle. Rotation was defined as axial difference of axis between femur and tibia. All items were evaluated by navigation system at every 10 degrees of knee flexion from 0 degrees of extension to 140 degrees of deep flexion. Results. In extension range, mean medial joint gaps (RA / OA) were 22.5 / 21.6 mm at 0 degree and decreased to 17.3 /15.0mm at 40 degrees, respectively. They were significantly different at 40 degrees. Lateral joint gaps were 16.4, 15.5mm at zero degree and slightly decreased to 21.0 / 20.0 mm at 40 degrees. In flexion range, mean medial joint gaps were 17.3 / 17.2 mm, 20.9 / 21.6 mm and 34.9 / 37.3 mm at 50 / 90 mm and 140 degrees. Mean lateral joint gaps were 16.4 / 15.5 mm, 21.8 / 21.6 mm and 29.0 / 31.4 mm. Both gaps were increased as knee was bent deeply(see Figure 1). Regarding to AP translation, femoral component was once moved 6.5 / 6.1 mm forward up to 50 degrees, then moved 25.8 / 23.5 mm backward with flexion. There was no significant difference (see Figure 2). Rotation kinematics showed significant difference in early flexion range. Consecutive external rotation of femur was recognized in RA group, but internal rotation was occurred in OA group from 0 to 60 degrees. External rotation was recognized in both groups from 60 degrees to deep flexion (see Figure 3). Conclusion. In this study, although joint gaps and AP translation were almost similar between RA and OA, it became clear that most significant difference was rotation movement in early range of knee flexion. It recognized opposite rotation between two groups. The limitation of this study was the situation of under anesthesia and no muscle strain were loaded during the measurement of knee kinematics. However, navigation system is available not only for the accurate implantation but also the measurement of intra operative knee kinematics

At present, wear investigations of total hip replacement (THR) are performed in accordance with the ISO standard 14242, which is based on empirically determined relative motion data and exclusively describes the gait cycle. However, besides continuous walking, a number of additional activities characterize the movement sequences in everyday life and influence the wear rates as well as the size and shape of wear debris. Disagreements of in vitro and in vivo wear mechanisms seemed to be a result of differences between in vitro and in vivo kinematics and dynamics. This requires an optimization of the current test procedures and parameters. Hence, the aim of the present study was to evaluate most frequent activities of daily living, based on available in vivo data, in order to generate parameter sets according to loading and rotational movements close to the physiological situation. For the generation of angular patterns, time-dependent three-dimensional trajectories of reference points were used from the HIP98 database of Bergmann. The data set was evaluated and interpolated using analytical techniques to simulate consecutive smooth motion cycles in hip wear simulators or further test devices. The calculated relative joint movement was expressed by an ordered set of three elementary rotations and was complemented with three force components of the joint contact force to generate kinematically and dynamically consistent parameter sets. The obtained sets included the activities walking, knee bending, stair climbing and a combined load case of sitting down and standing up for an averaged patient. Generated slide tracks, created by the use of the angular patterns, demonstrated differences according to the kinematics between selected daily life activities and those established for the ISO standard 14242. In particular, for the relative flexion-extension rotational movement, routine activities showed significant higher ranges of motion. Additionally, the depicted force pattern underlined that the prevailing force component varied considerably between different activities. These deviations in range of motion and joint forces could be attributed to disagreements between in vitro and in vivo results of THR wear testing. The Integration of frequent activities of daily living in the in vivo test protocol could be realized by means of the sequential arrangement of the four investigated activities

Introduction. Shoulder motion results from a complex interaction between the interconnected segments of the shoulder girdle. Coordination is necessary for normal shoulder function and is achieved by synchronous and coordinated muscle activity. During rotational movements, the humeral head translates on the glenoid fossa in the anterior-posterior plane. Tension developed by the rotator cuff muscles compresses the humeral head into the glenoid fossa. This acts to limit the degree of humeral head translation and establishes a stable GH fulcrum about which the arm can be moved. Previous studies have been limited by the use of contrived movement protocols and muscular coordination has not been previously considered with regard to shoulder rotation movements. This study reports the activation profile and coordination of 13 muscles and 4 muscle groups during a dynamic rotational movement task based on activities of daily living. Methods. Eleven healthy male volunteers were included in the study. Electromyography (EMG) was recorded from 13 muscles (10 surface and 3 fine-wire intramuscular electrodes) using a wireless EMG system. EMG was recorded during a movement task in which the shoulder was consecutively rotated internally (phase 1) and externally (phase 2) with a weight in the hand. Muscle group data was calculated by ensemble averaging the activity of the individual component muscles. Mean signal amplitude and Pearson correlation coefficient (PCC) analysed muscle activation and coordination, respectively. Results. The mean length of phase 1 (internal rotation) and phase 2 (external rotation) was 1.1s (SD+0.15) and 1.09s (SD+0.18), respectively with no significant difference between them. Mean signal amplitude was significantly higher during external rotation for the anterior, middle and posterior deltoid, teres major and the rotator cuff muscles (Table 1). Significant positive correlations were identified between the activation patterns of the deltoid and rotator cuff groups (PCC=0.95, p=<0.001), the deltoid and latissimus dorsi-teres major groups (PCC=0.74, p=<0.001) and the latissimus dorsi-teres major and rotator cuff groups (PCC=0.87, p=<0.001) (Figure1). Discussion. The subscapularis is extensively described as an internal rotator of the glenohumeral joint; however, during this study it was primarily active during external rotation. During activities of daily living the subscapularis balances the force generated by the supraspinatus and infraspinatus by contracting eccentrically as external rotation progresses. This balance between the anterior and posterior rotator cuff maintains anterior-posterior stability of the humeral head on the glenoid fossa. There is a highly coordinated and synchronous relationship between all the major muscle groups of the shoulder during rotational activities, which ensures glenohumeral joint stability. The function of the shoulder muscles is task specific. This has important implications when considering the impact of muscle pathology on shoulder dysfunction and the treatment strategies employed

Total knee arthroplasty (TKA) is an exceptionally successful and robust treatment for disabling knee disease, but many efforts continue to improve patient postoperative satisfaction and performance. One approach to improving performance is to restore TKA motions closer to those in healthy knees. Based upon an idealized model of knee motions, it is possible to design tibiofemoral articulating surfaces to promote natural kinematics and force transfer (Fiedler et al., Acta Bioeng Biomech, 2011). Such an asymmetric design is expected to promote rollback in stance phase that continues through deeply flexed activities. The purpose of this study is twofold: (1) To determine if a TKA designed on a theoretical basis achieves the proposed motions in vivo, and (2) To track postoperative kinematic patterns with examinations at 6–12 weeks, 6 months and one year postoperatively. This paper reports results of the initial cohort that has completed 6–12 week and 6-month examinations. Eight patients, including 3 females, with unilateral TKA for varus osteoarthritis provided written informed consent prior to beginning the study. Patients averaged 66±9 years, 168±14cm, and 28±3 BMI. Patients performed three weightbearing activities observed using pulsed x-ray flat-panel imaging at 30Hz: stepping up from flexion to extension on a 20cm step, lunging to maximum flexion with the foot placed on a 20 cm step, and kneeling to maximum flexion with the shin placed on a padded support. Three-dimensional knee kinematics were quantified using model-image registration to determine flexion, tibial internal rotation, anteroposterior movement of the femoral condyles (relative to the tibial AP center) and average center of rotation (CoR) in the transverse plane. During the maximum-flexion lunge and kneeling activities subjects exhibited average knee flexion of 104°–110° and tibial internal rotation of 2°–6° (Table 1). At 6–12 weeks, the medial/lateral condyles were at −3mm/−8mm and −1mm/−6mm during maximum flexion lunge and kneeling, respectively. During the stair activity from 0° to 70° flexion, there were small tibial internal rotations (1°/5°) and anterior medial (2mm/5mm) and lateral (3mm/3mm) condylar translations at both time points (Figure 1). The average CoRs for the stair activity were medial +18% and +5% for the 6–12 week and 6-month exams, respectively. It has long been assumed knee kinematics change during a patient's first one or two postoperative years. In our early post-op cohort, changes in weight-bearing kinematics over the first 6 postoperative months are small. In maximal flexion activities, patients exhibited flexion similar to similar cohorts studied at least one year post-op (Clin Orthop, 410:131–138, 2003). Similarly, kinematics during the weight-bearing step activity were similar in pattern and magnitude to those previously reported for posterior cruciate-retaining (CR) TKA at least one year post-op (Clin Orthop, 426:187–193, 2004). The average CoRs were medial for the stair activity, which is normal for healthy knees but uncommon for CR TKA. Early post-op results with an asymmetric CR TKA implant intended to promote physiologic motion show flexion and stair kinematics similar to many successful CR designs at longer follow-up. The medial CoR indicates closer-to-physiologic motion than commonly is observed in CR TKA

Introduction. Recently, tibial insert design of cruciate-substituting (CS) polyethylene insert is employed. However, in vivo kinematics of using CS polyethylene insert is still unclear. In this study, it is hypothesized that CS polyethylene insert leads to stability of femolo-tibial joint as well as posterior-stabilized (PS) polyethylene insert, even if PCL is sacrificed after TKA. The purpose of this study is an investigation of in vivo kinematics of femolo-tibial joint with use of CS polyethylene insert before and after PCL resction using computer assisted navigation system intra-operatively in TKA. Materials and Methods. Twenty-four consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker) were performed using computer assisted navigation system. In all patients, difference between extension and flexion gap was under 3mm after bony cut of femur and tibia. During surgery, CS polyethylene tibial trial insert were inserted after trial implantation of femoral and tibial components, before and after resection of PCL, respectively. The kinematic parameters of the soft-tissue balance, and amount of coronal (valgus/varus), sagittal (anterior/posterior) and rotational relative movement between femur and tibia were obtained by interpreting kinematics, which display tables throughout the range of motion (ROM) (Figure1). During record of kinematics, the surgeon gently lifted the experimental thigh three times, flexing the hip and knee. In each ROM (30, 45, 60, 90, max degrees), the data were analyzed with paired t-test, and an ANOVA test, and mean values were compared by the multiple comparison test (Turkey HSD test) (p < 0.05). Results. In coronal (valgus/varus) movement, there are no difference between before and after resection of PCL in all ROM. Regarding to amount of sagittal movement of tibia, tibia was slightly shifted approximately 0.75mm posteriorly in 60 degrees of flexion (p=0.013). There are no significance between before and after PCL resection in the other ROM. In addition, concerning ROM, maximum extension angle is significantly lower, and maximum flexion angle is significantly higher after than before PCL resection. Discussion. These results demonstrated that CS polyethylene insert might have a stability of femoro-tibial joint nearly after PCL resection as well as before PCL resection. The main design feature of Triathlon CS insert is single radius and rotary arc, in addition, the posterior lip is same as that of Triathlon CR, which can be the factor to avoid paradoxical anterior movement and to permit internal and external rotation between femoral and tibial component. This study was localized at point of certain situation that difference between extension and flexion gap is under 3mm after bony cut of femur and tibia during surgery. Due to the design features and benefits, there is a high possibility that use of CS insert without PCL can lead same stability as PCL remained, and improvement of ROM. Based on these backgrounds, it is suggested that CS insert may have an additional choice of PCL resection in case of tight gap of flexion in TKA

Aims

Computer hexapod assisted orthopaedic surgery (CHAOS), is a method to achieve the intra-operative correction of long bone deformities using a hexapod external fixator before definitive internal fixation with minimally invasive stabilisation techniques.

The aims of this study were to determine the reliability of this method in a consecutive case series of patients undergoing femoral deformity correction, with a minimum six-month follow-up, to assess the complications and to define the ideal group of patients for whom this treatment is appropriate.