Treatment of posterior malleolar (PM) ankle fractures remain controversial. Despite increasing recommendation for small PM fragment fixation, high quality evidence demonstrating improved clinical outcomes over the unfixated PM is limited. We describe the medium-to-long term clinical and radiographical outcomes in younger adult patients with PM ankle fractures managed without PM fragment fixation. A retrospective cohort study of patients aged 18–55 years old admitted under our orthopaedic unit between 1st of April 2009 and 31st of October 2013 with PM ankle fractures was performed. Inclusion criteria were that all patients must mobilise independently pre-trauma, have no pre-existing ankle pathologies, and had satisfactory bimalleolar and syndesmotic stabilisation. Open fractures, talar fractures, calcaneal fractures, pilon fractures, subsequent re-injury and major complications were excluded. All PM fragments were unfixated. Clinical outcomes were evaluated using Foot and Ankle Ability Measure (FAAM) with activities of daily living (ADL) and sports subscale, visual analogue scale (VAS) and patient satisfaction ratings. Osteoarthrosis was assessed using modified Kellgren-Lawrence scale on updated weightbearing ankle radiographs. 61 participants were included. Mean follow-up was 10.26 years. Average PM size was 16.19±7.39%. All participants were evaluated for clinical outcomes, demonstrating good functional outcomes (FAAM-ADL 95.48±7.13; FAAM-Sports 86.39±15.52) and patient satisfaction (86.16±14.42%), with minimal pain (VAS 1.13±1.65). Radiographical outcomes were evaluated in 52 participants, showing no-to-minimal osteoarthrosis in 36/52 (69.23%), mild osteoarthrosis in 14/52 (26.92%) and moderate osteoarthrosis in 2/52 (3.85%). Clinical outcomes were not associated with PM fragment size, post-reduction step-off, dislocation, malleoli fractured or syndesmotic injury. PM step-off and dislocation were associated with worse radiographical osteoarthrosis. Other published medium-to-long term studies reported overall good outcomes, with no differences after small fragment fixation. The unfixated smaller posterior malleolus fragment demonstrated overall satisfactory clinical and radiographical outcomes at 10-year follow-up and may be considered a valid treatment strategy

Introduction. The position and orientation of the lower extremities are fundamental for planning and follow-up imaging after arthroplasty and lower extremity osteotomy. But no studies have reported the reproducibility of measurements over time in the same patient, and experience shows variability of the results depending on the protocols for patient positioning. This study explores the reproducibility of measurements in the lower extremity with the patients in “comfortable standing position” by the EOS® imaging system. Materials and Methods. Two whole-body acquisitions were performed in each of 40 patients who were evaluated for a spine pathology. The average interval between acquisitions was 15 months (4–35 months). Patients did not have severe spine pathology and did not undergo any surgery between acquisitions. The “comfortable standing position” is achieved without imposing on the patient any specific position of the lower limbs and pelvis. All the measurements were performed and compared in both 2- and 3-dimensional images. Distances between the centers of the femoral heads and between the centers of the knees and ankles were measured from the front. The profile is shown by the flexion angle between the axis of the femur (center of the femoral head and the top of the line Blumensaat) and the axis of the tibia. Results. The average radiation dose was 0.80 mGy (0.5–1.11). For the first acquisition, the mean distance between the femoral heads was 17.9 cm (15.8–20.2), the mean distance between the middle of the knee joints was 16.7 cm (11.2–23.1) and the mean distance between the medial malleoli was 13.1 cm (0 to 18). For the second acquisition, the mean distance between the femoral heads was 17.9 cm (14.9–21.5), the mean distance between the middle of the knee joints was 16.9 cm (11.4–23.1) and the mean distance between the medial malleoli was 13.6 cm (0–19.4). For all comparisons no significant difference was demonstrated in related samples by Wilcoxon rank test and paired Student t test. Discussion. Two- and 3-dimensional data are not affected by repeated acquisitions several to many months apart in “comfortable standing position.” This work shows the reproducibility of measurements of the lower extremity in the “comfortable standing position” by the EOS® imaging system. Additional research should be considered for combined measures in the face-profile position of each patient

Background Computer navigation is increasingly being recognized as a valuable tool in restoring the mechanical axis post TKR. Its use is as yet not universal due to the costs involved, its availability and the fact that it can be cumbersome and time consuming to use. Additionally it requires the insertion of Schanz pins in the femur as well as the tibia which can be a matter of concern as regards stress fracture and infection. However, it is able to reliably locate the center of the femoral head which is an elusive landmark in the standard method. The center of the ankle involves registration for the medial and lateral malleoli which are subcutaneous and easily palpable. We decided to navigate only the distal femoral cut with a specialized navigation unit called Articular Surface Mounted navigation which does not require the insertion of additional pins through the femur or the tibia. We purposely did not use navigation for the rest of the bony cuts as all the other landmarks i.e. femoral epicondyles, tibial malleoli, and tuberosity etc are all easily palpable. This dramatically reduced the surgical time and increased its user friendliness. We are presenting our results. Aim. To analyse the radiographic results obtained with selective femoral navigation and compare with. standard navigational results from the literature. Non-navigated Knees form personal series. Materials and Methods. We have utilized the ASM navigation for distal femoral cut in 112 knees and obtained long X-rays (scanograms) and routine knee X-rays (AP, Lateral and skyline) to study the mechanical axis and component positioning. We measured the mechanical axis deviation, femoral and tibial angle on AP and lateral films and patellar tilt or subluxation on post-operative X-rays by a digital imaging programme called Image–J. (As suggested by the Knee Society roentgenographic Score). We have compared our results with other navigated series from literature and our own series of non-navigated knees. (113 knees) We also noted the surgical time to perform the operation and the occurrence of any complications. Results. Selective femoral navigation is able to restore the mechanical axis as reliably as other methods of navigation and more reliably than non-navigated knees. On an average, it adds less than 10 minutes to surgical time. Femoral angle, tibial angle patellar tilt and subluxation are similar in both navigated and non-navigated series. Navigation use was not associated with any increased complications and no complication could be ascribed to its use. Selective femoral navigation reduced the outliers in mechanical axis restoration when compared with standard femoral intrameduallry instrumentation. Discussion. Selective distal femoral navigation is a reliable tool in restoring mechanical axis post TKR. It is particularly valuable in knees that have pronounced femoral bowing

Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter- and intra-observer variability. Our observation that there is less than 2 mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA

Traditional screw fixation of the syndesmosis can be prone to malreduction. Suture button fixation however, has recently shown potential in securing the fibula back into the incisura even with intentional malreduction. Yet, if there is sufficient motion to aid reduction, the question arises of whether or not this construct is stable enough to maintain reduction under loaded conditions. To date, there have been no studies assessing the optimal biomechanical tension of these constructs. The purpose of this study was to assess optimal tensioning of suture button fixation and its ability to maintain reduction under loaded conditions using a novel stress CT model. Ten cadaveric lower limbs disarticulated at the knee were used. The limbs were placed in a modified external fixator frame that allows for the application of sustained torsional (5 Nm), axial (500 N) and combined torsional/axial (5Nm/500N) loads. Baseline CT scans of the intact ankle under unloaded and loaded conditions were obtaining. The syndesmosis and the deltoid ligament complex were then sectioned. The limbs were then randomised to receive a suture button construct tightened at 4 kg force (loose), 8 kg (standard), or 12 kg (maximal) of tension and CT scans under loaded and unloaded conditions were again obtained. Eight previously described measurements were taken from axial slices 10 mm above the tibiotalar joint to assess the joint morphology under the intact and repair states, and the three loading conditions: a measure of posterolateral translation (a, b), medial/lateral translation (c, g), a measure of anterior-posterior translation (f), a ratio of anterior-posterior translation (d/e), an angle (Angle 1) created by a line parallel to the incisura and the axis of the fibula, and an angle (Angle 2) created between the medial surfaces of two malleoli. These measurements have all been previously described. Each measurement was taken at baseline and compared with the three loading scenarios. A repeated measures ANOVA with a Bonferroni correction for multiple comparisons was used to test for significance. Significant lateral (g, maximum 5.26 mm), posterior (f, maximum 6.42 mm), and external rotation (angle 2, maximum 11.71°) was noted with the 4 kg repair when compared to the intact, loaded state. Significant posterior translation was also seen with the both the 8 kg and 12 kg repairs, however the incidence and magnitude was less than with the 4 kg repair. Significant overcompression (g, 1.69 mm) was noted with the 12 kg repair. Suture button constructs must be appropriately tensioned to maintain reduction and re-approximate the degree of physiological motion at the distal tibiofibular joint. If inserted too loosely, these constructs allow for supraphysiologic motion which may have negative implications on ligament healing. These constructs also demonstrate overcompression of the syndesmosis when inserted at maximal tension however the clinical effect of this remains to be determined

We present a series of 16 patients who have had a failed ankle arthroplasty converted to an ankle arthrodesis using a surgical technique of bone grafting with internal fixation. We describe our technique using tricortical autograft from the iliac crest to preserve length and an emphasis is placed on maintaining the malleoli and subtalar joint. A successful fusion was achieved in all cases with few complications. Our post operative AOFAS improved to a mean of 70 with good patient satisfaction and compares well to other published series. From this series and an extensive review of the literature we have found fusion rates following failed arthroplasty in patients with degenerative arthritis to be very high. In this group of patients a high fusion rate and good clinical result can be achieved when the principles of this surgical technique are adhered to. It would appear that a distinction should be made between treating patients with poor quality bone and more extensive bone loss, as is often the case with rheumatoid patients; and the patients with a non inflammatory arthropathy and better bone quality. The intramedullary nail would appear to be the preferred option in patients with inflammatory polyarthropathy where preservation of the subtalar joint is probably not of relevance as it is usually extensively involved in the disease process, and a higher rate of complications can be anticipated with internal fixation

Introduction. Evaluation of post-operative soft tissue balancing outcomes after Total Knee Arthroplasty (TKA) and other procedures can be measured by stability tests, with Anterior-Posterior (AP) drawer tests and Varus-Valgus (VV) ligamentous laxity tests being particularly important. AP stability can be quantified using a KT1000 device; however there is no standard way of measuring VV stability. The VV test relies on subjective force application and perception of laxity. Therefore we sought to develop and validate a device and method for quantifying knee balancing by analyzing VV stability. Materials and Methods. Our team developed a Smart Knee Fixture to measure VV angular changes using two dielectric elastomer stretch sensors, placed strategically over the medial and lateral collateral ligaments (see Figure 1). The brace is secured in position with the leg in full extension and the sensors locked with pre-tension. Therefore, contraction and elongation of either sensor is measured and the VV angular deviation of the long axis of the femur relative to that of the tibia is derived and displayed in real time using custom software. EMG muscle activity was previously investigated to confirm there is no resistive activity during the VV test obstructing ligamentous evaluations. The device was validated in two ways:. A bilateral lower body cadaver specimen, secured in a custom test rig, was used to compare the Smart Knee Fixture's readings to those measured from an optical surgical navigation system. Abduction and adduction force was gradually applied as varus and valgus moments with a wireless hand-held dynamometer up to 50N (19.8Nm) at 0 and 15° flexion. Two male volunteers were used to compare the Smart Knee Fixture's readings to those measured from fluoroscopic images. An arthroscopic distal thigh leg immobilizer was used to prevent rotation and lateral movements of the thigh when moments were applied at the malleoli. A C-arm Fluoroscope was then positioned focusing on the center of the joint. The tests were performed at full extension, 10 and 20° of flexion and force was gradually applied to 50N. Results and Discussion. R values were calculated to validate the Smart Knee Fixture's accuracy. Excellent correlation was observed between the Smart Knee Fixture and the gold standard of navigation (see Figure 2). The R values were 0.9909 and 0.9966. Correlation was also observed between Smart Knee Fixture and the measured fluoroscopic angular changes. The R values were 0.9118 and 0.7529. Conclusions. The strong R values allow us to conclude that the Smart Knee Fixture can potentially be used to accurately measure VV angular changes in a clinical setting and hence provide a quantified measure of coronal plane soft tissue balance. Clinical studies are underway to compare TKA patient outcomes to balancing measured by the Smart Knee Fixture. This information should further define balancing goals at the time of surgery. We also envisage broader applications to early detection of ligamentous injury associated with sporting activities, such as multiple ligamentous knee injuries in teenage females

Soft tissue balancing in total knee replacement may well be the determining factor in raising the fair patient satisfaction. The development of intelligent implants allows quantification of reactive loads to applied pressures. This can be tested in dynamic mode such as heel push test at surgery, or in static mode such as when testing for varus/valgus (VV) laxity of the collateral ligaments of the knee. We postulate that a well-balanced knee will have comparable if not equal load distribution across compartments in dynamic loading. When tested for laxity, we anticipate an equal or comparable response to VV applied loads under physiologic load range of 10–50N. This study sought to analyze the relationship between the kinematic (joint motion) and kinetic (force) effects to VV testing in the 0–15 degrees range of flexion. One goal was to demonstrate that testing the knee in locked extension (Screw Home effect) is unreliable and should be abandoned in favor of the more reliable VV testing at 10–15 degrees of flexion. This is a preliminary cadaveric study utilizing data from two hemibodies. The pelvis was fixed in a custom test rig with open or closed chain lower leg testing capability along a sliding rail with foot VV translational. Forces were applied at the malleoli with a wireless hand held dynamometer. Kinematic analysis of the hip-knee-ankle (HKA) tibiofemoral angle was derived from a commercial navigation system with mounted infrared trackers. Kinetic analysis was derived from a commercially available sensor imbedded in a tibial trial liner. Balance was optimized by conventional methods with the use of the sensor feedback until loads were roughly symmetrical and VV testing yielded symmetrical rise in opposite compartments. The VV testing was then performed with the knees locked at the femoral side in axial rotation and translational motion in any plane. Sagittal flexion was pre-set at 0, 10, and 15 degrees and progressive load was applied. Results. From the graphs one can observe significant differences between VV testing at 0 degrees (locked Screw Home), 10 degrees, and 15 degrees of flexion. The shaded area corresponds to the common range of VV stress testing loading pressure, typically less than 35N. The HKA deviates from neutrality no sooner than by the middle of the physiologic test zone. By 35N, the magnitude of the effect is also much less than that observed at 10 and 15 degrees (unlocked from Screw Home). From the kinetic analysis one can also note the significant difference in the High-Low spread throughout the testing range of applied pressure. If the surgeon tests in the low range of applied loads, he/she may not observe the kinematic joint opening effect. The kinetic effect seems more reliable as sensed loads are detectable earlier on. It is clear however that testing at 10–15 degrees offers a much better sensitivity to the VV laxity or stiffness as exemplified in the bottom portions of the figure. Therefore testing in locked Screw Home full extension may lead to underestimation of the true coronal laxity of the joint

We aimed to review the outcome of Agility total ankle replacements carried out in our institution between 2002 and 2006. Follow-up consisted of clinical and radiological review pre-operatively, then at 6 weeks, 6 and 12 months, and annually until 10 years post op. Clinical review included the American Orthopaedic Foot and Ankle Score, satisfaction and pain scores. Case notes were reviewed to determine intra and post-operative complications. 30 arthroplasties were performed in 30 consecutive patients. Pre-operative diagnosis was rheumatoid arthritis(16), primary osteoarthritis(12) and post-traumatic osteoarthritis(2). After a mean follow up of 6.2 years (1.4–10.1), 4 patients had died, and 22 out of the remaining 24 were available for follow-up. Intra operative complications included lateral malleoli fracture(3) and superficial peroneal nerve injury(2). Post operative complications included 1 early death, but this was not related to the surgical procedure. Two patients developed deep infections of the prosthesis. One underwent removal of the implant; the other is on long term oral antibiotic therapy. One patient had delayed union of the syndesmosis and six patients had non-union. On clinical assessment, patients' AOFAS scores improved from mean 40.4 pre-op to 83.5 post-op (p< 0.001). Radiological assessment of the tibial component revealed 25 (93%) patients had lucency in at least one zone in the AP radiograph. We found a relatively high level of re-surgery and complications following Agility total ankle replacement. A 7% revision rate is much higher than would be tolerated in knee or hip arthroplasty, but compares favourably to other studies of TAR. Despite radiological features which suggest loosening, the high rate of re-surgery and complications; patients are generally satisfied with the procedure, reporting lower levels of pain and improved function. Overall we feel that the Agility ankle is an acceptable alternative to ankle arthrodesis, however patients need to be warned of the risk of re-surgery

Worldwide, total ankle replacement is being more frequently offered as an alternative to ankle fusion. Most reports in the literature come from single centres with surgery performed by ‘high volume’ foot and ankle surgeons. We describe the New Zealand experience with the Scandinavian Total Ankle Replacement (STAR). Fifty-two STARs in 49 patients were implanted between September 1998 and May 2005. Eleven surgeons performed between one and thirteen of the operations. Of the 49 patients five were deceased and five refused to participate in the study. The average age at surgery was 64.9 years (range 46-80). There were 26 males and 13 females. The average follow up was 58.2 months. Of the 41 ankles available for review 11 had been revised or fused (27%) at an average of 42 months post surgery. Of the remaining 30 intact ankles recent radiographs were available on all ankles. Of the retained primary ankles, the mean Oxford ankle score was 25.6. This scale has a range from 12, for an asymptomatic ankle, to 60. The mean WOMAC score was 18.9, the SF-12 PH 42 and the SF-12 MH 54. The scores were substantially worse for the group who had been revised or arthrodesed. Perioperative x-ray findings demonstrated intraoperative malleolar fracture occurred in seven patients including one with a complete saw cut transection of the medial malleolus and one who had sustained fractures of both malleoli. The tibial component was undersised in five patients and the talus oversized in at least three patients. Of the 11 revision cases, two were bearing exchanges only. Nine involved either a major revision procedure or tibiotalocalcaneal arthrodesis for subsidence of malaligned components usually in the presence of peri-implant fracture. Of the unrevised cases, the latest x-rays did not demonstrate any significant osteolysis or increased lucent lines. Five cases demonstrated subtle talar or tibial component subsidence when compared with earlier radiographs. Despite overall satisfactory outcomes in the majority of patients the perioperative complication rate and revision rate in infrequent users is concerning. There may be implant and instrumentation elements, which also contribute to these suboptimal outcomes. Level of evidence IV, retrospective review

To develop a useful surgical navigation system, accurate determination of bone coordinates and thorough understanding of the knee kinematics are important. In this study, we have verified our algorithm for determination of bone coordinates in a cadaver study using skeletal markers, and at the same time, we also attempted to obtain a better understanding of the knee kinematics. The research was performed at the Medical Simulation Center of Tzu Chi University. Optical measurement system (Polaris® Vicra®, Northern Digital Inc.) was used, and reflective skeletal markers were placed over the iliac crest, femur shaft, and tibia shaft of the same limb. Two methods were used to determine the hip center; one is by circumduction of the femur, assuming it pivoted at the hip center. The other method was to partially expose the head of femur through anterior hip arthrotomy, and to calculate the centre of head from the surface coordinates obtained with a probe. The coordinate system of femur was established by direct probing the bony landmarks of distal femur through arthrotomy of knee joint, including the medial and lateral epicondyle, and the Whiteside line. The tibial axis was determined by the centre of tibia plateau localised via direct probing, and the centre of ankle joint calculated by the midpoint between bilateral malleoli. Repeated passive flexion and extension of knee joint was performed, and the mechanical axis as well as the rotation axis were calculated during knee motion. A very small amount of motion was detected from the iliac crest, and all the data were adjusted at first. There was a discrepancy of about 16.7mm between the two methods in finding the hip centre, and the position found by the first method was located more proximally. When comparing the epicondylar axis to the rotation axis of the tibia around knee joint, there was a difference of 2.46 degrees. The total range of motion for the knee joint measured in this study was 0∼144 degrees. The mechanical axis was found changing in an exponential pattern from 0 degrees to undetermined at 90 degrees of flexion, and then returned to zero again. Taking the value of 5 degrees as an acceptable range of error, the calculated mechanical axis exceeded this value when knee flexion angle was between 60∼120 degrees. The discrepancy between the hip centres calculated from the two methods suggested that the pivoting point of the femur head during hip motion might not be at the center of femur head, and the former location seemed closer to the surface of head at the weight bearing site. Under such circumstances, the mechanical axis obtained through circumduction of the thigh might be 1∼2 degrees different from that obtained through the actual center of femur head. During knee flexion, the mechanical axis also changed gradually, and this could be due to laxity of knee joint, or due to intrinsic valgus/varus alignment. However, the value became unreliable when the knee was at a flexion angle of 60∼120 degrees, and this should be taken into account during navigation surgery

Introduction. In total knee arthroplasty extramedullary tibial guides could not to be as accurate as requested in obtaining proper alignment perpendicular to the mechanical axis. The aim of this study was to determine the accuracy of an accelerometer-based system (KneeAlign 2; OrthAlign Inc, Aliso Viejo, California) as evaluated by post-op X-rays analysis. Methods. Between March 2012 and May 2012 thirty consecutive patients with primary gonarthrosis were selected for unilateral total knee arthroplasty (TKA) using a handheld surgical navigation system to perform the tibial resection. Navigation procedure: The entire system is provisionally secured to the tibia using a spring placed around the leg and is fixed to the proximal aspect of the tibia using 2-headed pins. Before fixing the system proximally, an aiming arm is used to align the top of the device with the anterior cruciate ligament footprint and the medial one third of the tibial tubercle. Distally, a footplate connected to the tibial jig is used to keep the EM jig a set distance off of the tibial surface. A gyrometer within the navigation unit is then able to calculate the posterior slope of the tibial jig. Subsequent anatomical landmarkings of both the lateral and medial malleoli are identified using the distal aspect of the EM jig to establish the tibia's mechanical axis. Similarly, the gyrometer within the navigation unit is able to calculate the varus or valgus alignment of the tibial jig relative to the tibia's established mechanical axis. Once anatomical registration has been performed, the tibial cutting block is placed at the proximal aspect of the device, and real-time feedback is provided by the navigation unit to the surgeon, who is then able to set the cutting block's varus/valgus and posterior slope alignment before performing the tibial resection. Postoperatively, standing anteroposterior hip-to-ankle radiographs and lateral knee-to-ankle radiographs were performed to determine the varus/valgus alignment and the posterior slope of the tibial components relative to the mechanical axis in both the coronal and sagittal planes. The difference between the intraoperative reading of the tibial varus/valgus alignment and posterior slope provided by the system was compared to the radiographic measurements obtained postoperatively for each respective case. Differences were analysed via standard t test. The critical level of significance was set at P <0.05. Results. Intraoperatively, the average reading provided by the system with regard to varus/valgus alignment before performing the tibial resection was 0.3° ± 0.3° relative to the mechanical axis and 5.4° ± 0.9° in the sagittal plane. The average tibial component alignment postoperatively in the knees with was 0.6° ± 0.3° in the coronal plane (P=0.07) and 4.7° ± 0.9° in the sagittal plane (P=0.07). In no case a difference > 2° from the planned resection was detected in both coronal and sagittal plane. Conclusions. The handheld surgical navigation system combines the accuracy of computer-assisted surgery systems with the ease of use and familiarity of conventional instrument. The system might improve the accuracy of the tibial resection and subsequent tibial component alignment in TKA

Component and limb alignment are important considerations during Total Knee Arthroplasty (TKA). Three-dimensional positioning of TKA implants has an effect on implant loosening, polyethylene stresses, and gait. Furthermore, alignment, in conjunction with other implant and patient variables such as body mass index (BMI) influence osseous loading and failure rates. Fortunately, implant survivorship after TKA has been reported to be greater than 95% at 20 years, despite up to 28% of TKAs having component position greater than 3 degrees from neutral. How good are we at positioning TKA implants? Ritter, et al examined 6,070 primary TKAs and found that from 2–7 degrees of valgus, the failure rate was 0.5% for limb alignment. Importantly 28% of the TKAs were outside the 2–7 degree range in the hands of experienced surgeons. Clearly there is room for improvement in surgical technique, but this improvement must be (1) time efficient and cost effective; (2) have a low complication rate, and (3) be reproducible with a minimal learning curve. A number of technologies have been developed to help surgeons implant and position TKA components including intramedullary guides, patient matched guides based on pre-operative imaging, Computer Assisted Surgery (CAS) based on line-of-sight navigation, and most recently, hand-held navigation. All of these techniques have distinct advantages and disadvantages, but we have found that hand-held navigation in TKA meets the prerequisites. Nam, et al reported the first series with a handheld device in 42 knees, and was able to position 95% of the tibial components within 2 degrees of targeted sagittal slope and 96% within 3 degrees of coronal alignment. Advantages of hand-held navigation include low cost, minimal learning curve, reproducibility surgeon to surgeon, and time efficiency (usually taking less than 3 minutes). The disposable device can be used on all patients with all deformities, including those with retained hardware. Hand held navigation devices create a virtual alignment framework from known osseous landmarks, and this framework is used to position tibial and femoral cutting guides on the bone. Using tibial osseous landmarks, including the ACL footprint proximally and the medial and lateral malleoli distally, the device allows real-time feedback of tibial slope and coronal alignment. On the femur, the device locates and references the centre of rotation of the hip and the centre of the distal femur, which allows for real-time calculation of distal femoral valgus and flexion for the distal femoral cutting block. Receiving three-dimensional, real-time feedback of coronal and sagittal alignment, as well as resection depth, combining limited mechanical instruments aided by hand-held navigation devices is a significant step forward. Thus, this technology represents a significant help to the surgeon and patient

Accurate and reliable registration of the ankle center is a necessary requirement in computer-assisted TKR. There is debate among surgeons over which registration procedure more accurately reflects the true center of the ankle joint. The aim of this study was to compare two different ankle registration landmarks on radiographs and determine how much they differed from the anatomic center of the talus in the frontal plane. Specifically, we asked what the average deviation in tibial mechanical axis registration would be when registering the ankle center using: A) the extreme medial and lateral points; and B) the most distal points, of the respective malleoli. A second question was whether or not BMI had any significant effect on mechanical axis registration error. We reviewed the preoperative hip-to-ankle radiographs of 40 patients who underwent navigated TKR at our institution. The patient cohort was composed of 32 females and 7 males, with a mean age of 69 years (range, 45–84 years) and a mean BMI of 29.9 (range, 14.7–43.3). All radiographs were stored in and reviewed using PACS. No clinically significant divergence from the anatomic center of the ankle was seen when using the Extremes Midpoint technique (mean divergence = 0.2® lateral; SD = 0.5®; 95% CI = −0.3®, −0.1®) or the Distal Midpoint technique (mean divergence = 0.2® lateral; SD = 0.6®; 95% CI = −0.39®, 0®). The mean difference between both techniques was 0.02® (SD = 0.3®; 95% CI = −0.1®, 0.1®; P = 0.68). BMI had no significant effect on the divergence from the true ankle center for either the Extremes Midpoint (R. 2. = 0.002; P = 0.78) or the Distal Midpoint techniques (R. 2. = 0.004; P = 0.90).(Figure 2). The center of the ankle, as determined by using the Extremes Midpoint technique, lied 1.1 mm (SD = 2.6 mm; 95% CI = −1.9 mm to −0.3 mm) from the anatomic axis of the tibia. When determined using the Distal Midpoint technique, the center of the ankle lied 1.7 mm (SD = 2.3 mm; 95% CI = −2.5 mm to −0.98 mm) from the anatomic axis. Although statistically significant (P = 0.028), this difference was not clinically relevant (<3 mm). BMI had no significant effect on these differences (R. 2. = 0.07; P = 0.11; R. 2. = 0.02, P = 0.38).(Figure 3). There is no significant difference between ankle registration using the Extremes Midpoint or the Distal Midpoint techniques and the anatomic center of the ankle. Patients' BMI does not seem to affect the registration of the ankle center with either technique

Navigation of Uni knee arthroplasty (UKA) is not common. Usually the software includes navigation of the tibial as well as the femoral implant. In order to simplify the surgical procedure we thought that navigation of the tibial plateau alone could be a good option. Since 2005 we have been using a mobile bearing UKA of which the ancillary is based on dependent bone cuts. The tibial cut is made first and the femoral cut is automatically performed using cutting blocks inserted between the tibial cut and the distal end of the femur. Although we are satisfied with this procedure, it is not rare we have some difficulties getting the right under correction needed to get a good long-term result. The aim of this paper was to present our computer-assisted UKA technique and our preliminary radiological results in genu varum (17 cases) as well as genu valgum (6 cases) deformities. The series was composed of 23 patients, 10 females and 13 males, aged from 63 to 88 years old (mean age: 75 +/− 8). The mean preoperative HKA (Hip-Knee-Ankle) angle was: 172.35° +/− 2.31° (167° to 176°) for the genu vara and 186.33° +/− 2.87° (182° to 189°) for the genu valga. The goal of the navigation was to get an HKA angle of 177° +/− 2° for genu varum deformity and 183° +/− 2° for genu valgum. We used the SURGETICS® device (PRAXIM, GRENOBLE, FRANCE) in the first six cases and the ORTHOPILOT® device (B-BRAUN-AESCULAP, TUTTLINGEN, GERMANY) in the other cases. The principles are the same for both devices. The 1rst step consists in inserting percutaneously the rigid-bodies on the distal end of the femur and on the proximal end of the tibia. Then, we locate the center of the hip by a movement of circumduction, the center of the ankle by palpating the malleoli and the center of the knee by palpating intra articular anatomic landmarks to get the HKA angle in real time. This step is probably the most important because it allows checking the reducibility of the deformity in order to avoid an over correction when inserting a mobile bearing prosthesis. The 3. rd. step consists in navigation of the tibial cut such as the height of the resection, the tibial slope (3 to 5° posterior tibial slope) and the varus of the implant (2 to 3°). Once the tibial cut was done, we must use the conventional ancillary to perform the femoral bone cuts (distal and chamfer). The last step consists in inserting the trial implants and checking the HKA angle and the laxity of the medial or lateral side. We used postoperative long leg X-Rays to evaluate the accuracy of navigation and plain radiographs to evaluate the right position of the implant. As far as genu varum deformity was concerned, the mean postoperative HKA angle was 177.23° +/− 1.64° (173°–179°). The preoperative goal was reached in 94% of the cases. Moreover, this angle could be superimposed on the peroperative computer-assisted angle, which was 177° +/− 1.43° (p>0.05). For genu valgum, the mean postoperative HKA angle was 181° +/− 1.41° (179°–183°). The preoperative goal was reached in 66% of the cases but the series is too short to give any conclusion. The navigation of tibial plateau alone can be used with accuracy, provided one has the right ancillary to use dependent bone cuts. The procedure is quick and needs only one tibial cutting guide equipped with a rigid-body. Our results, especially in genu varum deformity, are quite remarkable. Regarding genu valgum, the results seem to be less accurate, but the software was designed for medial UKA and the series is short, so, it is too soon to extrapolate any conclusion. The main interest in this navigation is to avoid too much under correction and even better to avoid over correction when the deformity is over reducible. Indeed, when one uses a mobile bearing plateau, the risk is to have a dislocation of the meniscus. So, when tightening the collateral ligaments, checking the lower limb axis may persuade not to use a mobile bearing plateau but rather a fixed plateau

Clinical laxity tests are frequently used for assessing knee ligament injuries and for soft tissue balancing in total knee arthroplasty (TKA). Current routine methods are highly subjective with respect to examination technique, magnitude of clinician-applied load and assessment of joint displacement. Alignment measurements generated by computer-assisted technology have led to the development of quantitative TKA soft tissue balancing algorithms. However to make the algorithms applicable in practice requires the standardisation of several parameters: knee flexion angle should be maintained to minimise the potential positional variation in ligament restraining properties; hand positioning of the examining clinician should correspond to a measured lever arm, defined as the perpendicular distance of the applied force from the rotational knee centre; accurate measurement of force applied is required to calculate the moment applied to the knee joint; resultant displacement of the knee should be quantified. The primary aim of this study was to determine whether different clinicians could reliably assess coronal knee laxity with a standardised protocol that controlled these variables. Furthermore, a secondary question was to examine if the experience of the clinician makes a difference. We hypothesised that standardisation would result in a narrow range of laxity measurements obtained by different clinicians. Six consultant orthopaedic surgeons, six orthopaedic trainees and six physiotherapists were instructed to assess the coronal laxity of the right knee of a healthy volunteer. Points were marked over the femoral epicondyles and the malleoli to indicate hand positioning and give a constant moment arm. The non-invasive adaptation of a commercially available image-free navigation system enabled real-time measurement of coronal and sagittal mechanical femorotibial (MFT) angles. This has been previously validated to an accuracy of ±1°. Collateral knee laxity was defined as the amount of angular displacement during a stress manoeuvre. Participants were instructed to maintain the knee joint in 2° of flexion whilst performing a varus-valgus stress test using what they perceived as an acceptable load. They were blinded to the coronal MFT angle measurements. A hand-held force application device (FAD) was then employed to allow the clinicians to apply a moment of 18Nm. This level was based on previous work to determine a suitable subject tolerance limit. They were instructed to repeat the test using the device in the palm of their right hand and to apply the force until the visual display and an auditory alarm indicated that the target had been reached. The FAD was then removed and participants were asked to repeat the clinical varus-valgus stress test, but to try and apply the same amount of force as they had been doing with the device. Maximum MFT angular deviation was automatically recorded for each stress test and the maximum moment applied was recorded for each of the tests using the FAD. Means and standard deviations (SD) were used to compare different clinicians under the same conditions. Paired t-tests were used to measure the change in practice of groups of clinicians before, during and after use of the FAD for both varus and valgus stress tests. All three groups of clinicians initially produced measurements of valgus laxity with consistent mean values (1.5° for physiotherapists, 1.8° for consultants and 1.6° for trainees) and standard deviations (<1°). For varus, mean values were consistent (5.9° for physiotherapists, 5.0° for consultants and 5.4° for trainees) but standard deviations were larger (0.9° to 1.6°). When using the FAD, the standard deviations remained low for all groups for both varus and valgus laxity. Introducing the FAD overall produced a significantly greater angulation in valgus (2.4° compared to 1.6°, p<0.001) but not varus (p = 0.67) when compared to the initial examination. In attempting to reach the target moment of 18Nm, the mean ‘overshoot’ was 0.9Nm for both varus and valgus tests. Standard deviations for varus laxity were lower for all groups following use of the FAD. The consultants' performance remained consistent and valgus assessment remained consistent for all groups. The only statistically significant change in practice for a group before and after use of the FAD was for the trainees testing valgus, who may have been trained to push harder (p = 0.01). Standardising the applied moment indicated that usually a lower force is applied during valgus stress testing than varus. This was re-enforced by clinicians, one third of whom commented that they felt they had to push harder for valgus than varus, despite the FAD target being the same. We have successfully standardised the manual technique of coronal knee laxity assessment by controlling the subjective variables. The results support the hypothesis of producing a narrow range of laxity measurements but with valgus laxity appearing more consistent than varus. The incorporation of a FAD into assessment of coronal knee laxity did not affect the clinicians' ability to produce reliable and repeatable measurements, despite removing the manual perception of laxity. The FAD also provided additional information about the actual moment applied. This information may have a role in improving the balancing techniques of TKA and the management of collateral ligament injuries with regard initial diagnosis and grading as well as rehabilitation. Finally, the results suggest that following use of the FAD, more experienced clinicians returned to applying their usual manual force, while trainees appeared to use this augmented feedback to adapt their technique. Therefore this technique could be a way to harness the experience of senior clinicians and use it to enhance the perceptive skills of more junior trainees who do not have the benefit of this knowledge