INTRODUCTION. Tibiofemoral contact at the base of the articular surface spine in posterior-stabilized total knee arthroplasty (TKA) implants can lead to spine fracture [1]. Revision TKA implants also have an articular surface spine to provide sufficient constraint when soft tissues are compromised. While some revision TKA designs have metal reinforcement in the articular surface spine, others rely solely on a polyethylene spine. This study used finite element analysis (FEA) to study the effect of metal reinforcement on stresses in the spine when subjected to posteriorly directed loading. METHODS. Two clinically successful Zimmer Biomet revision TKA designs were selected; NexGen LCCK with metal reinforcement and all-poly Vanguard SSK. The largest sizes were selected. FEA models consisted of the polyethylene articular surface and a CoCr femoral component; LCCK also included a CoCr metal reinforcement in the spine. A 7° and 0° tibial slope, as well as 3° and 0.7° femoral hyperextension, were used for the LCCK and SSK, respectively. A posteriorly directed load was applied to the spine through the femoral component (Figure 1). The base of the articular surface was constrained. The articular surfaces for both designs are made from different polyethylene materials. However, for the purpose of this study, to isolate the effect of material differences on stresses, both were modeled using conventional GUR1050 nonlinear polyethylene material properties. Femoral component and metal reinforcement were modeled using linear elastic CoCr properties. Additionally, the LCCK was reanalyzed by replacing the metal reinforcement component with polyethylene material, in order to isolate the effect of metal reinforcement for an otherwise equivalent design. Frictional sliding contact was modeled between the spine and femoral/metal reinforcement components. Nonlinear static analyses were performed using Ansys version 17 software and peak von mises stresses in the spine were compared. RESULTS. Peak von mises stresses were predicted towards the base of the anterior aspect of the spine in both designs (Figure 2). In LCCK, the high stresses were also predicted on the medial and lateral edges of the anterior spine, matching the tibiofemoral contact (Figure 3). The LCCK with metal reinforcement design predicted 14% and 31% lower stress than LCCK and SSK all-poly designs. DISCUSSION. Clinical reports of spine fracture in TKA highlight the need for further understanding of the biomechanics of spine loading. Here, through comparison of two clinically successful devices, the effect of multiple design factors was quantified. Inclusion of metal reinforcement in the spine, as well as differences in the conforming geometry between the femoral component and the articular surface, resulted in a 31% decrease in polyethylene stress for the LCCK as compared to the all-poly SSK; of which only 16% was attributed to the metal reinforcement. Further improvements to articular surface design, as well as polyethylene material advances, have the potential to result in all-poly designs with strength characteristics equivalent to or exceeding those of designs with metal reinforcement

Introduction. The hip-knee-ankle (HKA) angle between the mechanical axis of the femur (FM) and the mechanical axis of the tibia (TM) is the standard parameter to assess the coronal alignment of the lower extremity. TM is the line between the center of the tibial spines notch (Point T) and the center of the tibial plafond. However, this theory is based on the premise that TM coincides the anatomical axis of the tibia (TA). Fig.1a shows typical varus knee with medial shift of the tibial articular surface. In this case, TM does not coincide TA. Fig. 2 demonstrates the error of HKA angle when Point T locates medial to TA. Fig.2a shows normal alignment. Fig.2b shows varus alignment. Fig. 2c shows the tibia with medial shift of the tibial articular surface. The tibia has 7 degrees varus articular inclination in Fig.2b and 2c. However, HKA angle is 0 degree in Fig.2c. HKA angle underestimates varus deformity in knees with medial shift of the tibial articular surface. However, the degree of medial shift of the tibial articular surface is obscure. In this study, detailed anatomical configuration of the proximal tibia was evaluated. The effect of the value of HKA angle on the coronal alignment in TKA was then discussed. Methods. This study consists of 117 knees. On the AP view radiograph of the tibia, three distance and two angle parameters were measured. Those were tibial articular surface width, distance between medial edge of the tibial articular surface and Point T, distance from TA to Point T. Angle between TM and TA, and the varus inclination angle of the tibial articular surface relative to the perpendicular line to TA. Results. The mean width of the tibial articular surface was 87.8mm. The mean distance between Point T and medial edge of the articular surface was 43.6mm. Point T located at the center of the tibial articular surface. The mean distance from TA to Point T was 5.6mm. The mean angle between TM and TA was 1.0 degrees. The inclination angle of the tibial articular surface was 8.2 degrees. Discussion. The results clearly showed that varus knees had medial shift of the tibial articular surface. In such knees, the ankle shifts laterally relative to the Point T and HKA angle underestimates the varus deformity. The value of HKA angle also influences the evaluation of the coronal alignment of the lower extremity in TKA (Fig. 3). When the tibial tray is set based on the tibial articular surface width in order to cover the cut surface of the tibia, HKA angle shows the alignment as valgus when the tibial tray is set perpendicular to TA (Fig. 3a). In order to obtain zero degree of HKA angle, the tibial tray should be set perpendicular to TM. This alignment is varus (Fig. 3b). Reduction osteotomy is one procedure to match the value of HKA angle and the true alignment (Fig. 3c). In this technique, HKA angle is zero degree, and TM and TA coincide. For figures, please contact authors directly.

In vivo oxidative degradation in ultra-high molecular weight polyethylene (UHMWPE) has gained significant attention in recent years, especially with the discovery of unanticipated oxidation in retrieved highly cross-linked bearings. While significant attention has been paid to mechanical property changes caused by oxidation, there has been little focus on understanding how wear rates are affected by these in vivo changes. Recent work has demonstrated the possibility of machining wear pins from retrieved UHMWPE bearings, but leveling of the pins removed the in vivo articular surface.[1] The goal of this study is to determine whether wear pins can be produced utilizing the native articular surface. Three materials were used for this study: a short-duration retrieved mobile-bearing conforming tibial insert with minimal oxidation (non-oxidized); a shelf-aged, oxidized, non-conforming fixed bearing tibial insert (oxidized); and standard NIST 1050 bar stock (NIST). Utilizing both conforming and non-conforming devices tests the technique over a range of articular curvatures, while testing a highly oxidized material tests the feasibility of maintaining the native surface when machining wear pins with compromised mechanical properties. FTIR analysis was performed at the articular surface of the devices near where the pins were taken, using ketone peak height as an indicator of oxidation. Wear rates were determined using a six station AMTI OrthoPod with an applied load of 100 N in multidirectional motion for a total of 2 million cycles. The oxidized material had a surface ketone level of 0.26, the non-oxidized device had a ketone level of 0.05, and the NIST sample had a ketone level less than 0.01. Two pins of each material were machined to ¼″ diameter with a length of the through thickness of the tibial inserts; soak controls were also produced. Figure 1 shows mass loss data for all six pins tested. Wear rates between the two pins of each group were fairly repeatable, and the wear rates of the different groups could be easily differentiated. The pins machined from NIST bar stock showed the best match-up, but pins machined from retrieved devices also showed good repeatability, with the non-conforming device showing better results than the conforming device. The ability to produce repeatable wear results with pins machined from in vivo devices is an important step in understanding how the wear rate changes over time in vivo. By maintaining the native articular surface, this test will give a more true representation of the in-vivo wear rate. This method will enable future investigations into how wear rates are affected by oxidation, absorbed chemical species, or other changes that occur in vivo

Restoration of joint line in total knee arthroplasty (TKA) is important for kinematics of knee and ligamentous balance. Especially in revision TKA, it may be difficult to identify the joint line. The aim of this study is to define the relationship between epicondyles and articular surface using CT based three-dimensional digital templating sofware $“Athena” (Soft Cube, Osaka, Japan). 137 knees with osteoarthritis, all caces were grade 2 or lower in Kellgren-Lawrence index, were investigated. Perpendicular lines were dropped from the prominences of the medial and lateral femoral epicondyles to the most distal points of articular surfaces and distances of the lines were measured on the axial and coronal planes. The femoral width was measured as the distance between medial and lateral epicondyles. Each of the distance described above was converted to a ratio by dividing by the femoral width. On the axial plane, the average distance from epicondyles to the posterior articular surfaces were 29.4±2.2mm on the medial side and 21.2±2.3mm on the lateral side. The average of the femoral width was 75.2±4.1mm. On coronal plane, the average distance from epicondyles to the distal articular surfaces were 25.2±2.8mm on the medial side and 21.4±2.5mm on the lateral side. The ratio for the distance from epicondyles to the distal and posterior joint line compared to femoral width was 0.39±0.02, 0.28±0.03, 0.33±0.03 and 0.28±0.03. The distance from epicondyles to the distal and posterior joint line correlates with the femoral width of the distal femur. This information can be useful in determining appropriate joint line

INTRODUCTION. Contemporary PCL sacrificing Total Knee Arthroplasty (TKA) implants (CS) consist of symmetric medial and lateral tibial articular surfaces with high anterior lips designed to substitute for the stability of the native PCL. However, designs vary significantly across implant systems in the level of anteroposterior constraint provided. Therefore, the goal of this study was to investigate kinematics of two CS designs with substantially different constraint levels. The hypothesis was that dynamic knee simulations could show the effect of implant constraint on kinematics of CS implants. METHODS. LifeModeler KneeSIM software was used to analyze contemporary CS TKA (X) with a symmetric and highly dished tibia and contemporary CS TKA (Y) with a symmetric tibia having flat sections bounded by high anterior and posterior lips, during simulated deep knee bend and chair sit. The flat sections of CS-Y implant are designed to allow freedom prior to motion restriction by the implant lips. Components were mounted on an average knee model created from Magnetic Resonance Imaging (MRI) data of 40 normal knees. Relevant ligament/tendon insertions were obtained from the MRI based 3D models and tissue properties were based on literature values. The condyle center motions relative to the tibia were used to compare the different implant designs. In vivo knee kinematics of healthy subjects from published literature was used for reference. RESULTS. Prior publications on in vivo kinematics of healthy knees showed that normal knee motion is characterized by an overall medial pivot. This includes greater, consistent posterior rollback of the lateral condyle than medial (Fig 3). In contrast, CS implant X showed symmetric motion including paradoxical anterior sliding until 120° flexion. This caused a more anterior location for both femoral condyles in flexion as opposed to the posterior location seen in healthy knees. CS implant Y with flat sections showed even greater anterior sliding than CS-X. These trends were seen for chair sit activity as well. Thus, while CS-X showed less paradoxical sliding, both implants suffered from kinematic deficits due to absence of the PCL (Fig. 1 and Fig. 2). CONCLUSION. The two CS implants showed different kinematic performance confirming the hypothesis that implant design affects kinematics of CS TKA. Absence of the PCL in contemporary CS implants resulted in kinematic deficits. In particular, a symmetric implant with flat sections connecting the anteroposterior implant lips showed excessive paradoxical anterior sliding. These data showed both the need and opportunity for novel designs to address the limitations of contemporary CS implants

Introduction. Highly crosslinked ultrahigh-molecular-weight polyethylene (XLPE) reduces wear and osteolysis in total hip arthroplasty, but it is unclear if XLPE will provide the same clinical benefit in total knee arthroplasty (TKA). Adhesive and abrasive wear generally dominate in polyethylene acetabular components, whereas fatigue wear is an important wear mechanism in polyethylene TKA tibial inserts. The wear resistance of XLPE depends on the crosslink density of the material, which may decrease during in vivo mechanical loading, leading to more wear and increased oxidation. To examine this possibility, we measured crosslink density and oxidation levels in loaded and unloaded locations of retrieved tibial inserts to evaluate the short-term performance of XLPE material in TKA. Materials and Methods. Forty retrieved XLPE tibial inserts (23 remelted, 17 annealed) retrieved after a mean time of 18 ± 14 months were visibly inspected to identify loaded (burnished) and unloaded (unburnished) locations on the plateaus of each insert using a previously published damage mapping method. For each insert, four cubes (3 mm3) were cut from loaded and unloaded surface and subsurface locations (Fig. 1). Swell ratio testing was done according to ASTM F2214 to calculate crosslink density of the cubes. With a microtome, 200 μm sections were taken adjacent to the cubes and oxidation was assessed with Fourier transform infrared spectroscopy following ASTM F2102 (Fig. 2). Surface oxidation was measured in the sections adjacent the surface cubes and subsurface oxidation was measured in sections adjacent to the subsurface cubes. The effects of location (surface vs. subsurface in the loaded and unloaded regions) and thermal treatment (annealed vs. remelted) on crosslink density and oxidation were assessed with repeated measures generalized estimating equations (GEEs), with the implant treated as the repeated factor. Results are presented as means and 95% confidence intervals and the level of significance was α=0.05. Results. Crosslink density was associated with location within the polyethylene tibial inserts (p<0.001), while oxidation was associated with both location (p<0.001) and heat treatment (p=0.003). The loaded surface (location 1 in Fig. 1) had 13% lower crosslink density than all other locations (p<0.001 for each), and greater oxidation than all other locations (Fig. 3). Specifically, oxidation of the loaded surface was 0.29[0.17,0.40] greater (two times greater) than that of the unloaded surface (p < 0.001), whereas subsurface areas of loaded and unloaded regions differed by only 0.03[0.00,0.07] (p<0.022). Additionally, surface oxidation was over 7-fold greater than subsurface oxidation in the loaded region (difference: 0.56[0.44,0.68], p<0.001). Annealed XLPE had 2-fold greater oxidation than remelted XLPE (difference 0.159, 95% CI = 0.045, 0.126), and this was independent of location within the inserts. Conclusions. In vivo loading of XLPE decreased the crosslink density and increased the oxidation in areas that underwent wear and deformation at the articular surface of TKA inserts. Nonetheless, in these short term retrievals, no clinical complications were attributed to the change in material properties. However, if crosslink density continues to decrease with load over time, XLPE may not provide a clinical advantage over conventional polyethylene in TKA

Introduction

Knee joint should be aligned for reconstruction of the function in Total Knee Replacement(TKR). Although a surgeon try to correct the alignment of a knee joint, sometimes varus/valgus alignment has been tried in order to reconstruct function of knee joint. As a result, the varus or valgus alignment affects to ligaments and soft tissue, and the contact condition is changed between femoral component and tibial insert. One of important factor, wear characteristics of an implant can be changed due to the contact condition. In this study, we performed static contact tests from extension to flexion in varus and valgus to define the effect to contact condition when the alignment is varus or valgus.

Introduction. A search of the literature indicates several constrained total knee arthroplasty (TKA) systems are at risk for articular surface lockdown bolts backing out. The backing out of a lockdown bolt may lead to an unstable and/or painful knee and may necessitate revision. Upon backing out, the bolt may damage implant components and surrounding tissues. To date, studies in the literature have not simulated or replicated loosening of bolts in TKA. Therefore, the objectives of this study were to 1) develop a set of physiological loading parameters that challenge bolted articular surfaces; 2) evaluate whether significant bolt torque is lost during application of this loading to a CCK device with a bolt as a secondary locking mechanism. Materials and Methods. Physical test parameters to loosen lockdown bolts were developed based on loading experienced during activities of daily living. Sinusoidal waveforms and timing were used to simulate worst case walking gait conditions. Compared to data from everyday activities in instrumented TKR patients, anterior posterior loads and internal/external torques exceeding the absolute maximums observed were selected. To transfer more shear and torsion to the joint interface, compressive load lower than typically reported for walking gait was used. Frequency was representative of walking gait motion. The offset in torsional waveform enables a ratcheting motion to drive a loose bolt out of the joint: during external femoral rotation of a left knee, reduced compressive load and posterior directed femoral loading on a CCK spine creates a potential articular surface lift-off. The lift-off may grab the underside of the front bolt shoulder while external (CCW) rotation loosens the bolt. These loading conditions exist during toe-off of walking gait. Two CCK devices were evaluated to capture potential difference in performance: a medium articular surface combination and a smaller articular surface combination. Testing was performed on a load frame capable of rotation and vertical / horizontal translation. Results. No bolts completely loosened when fully tightened. However, average loss in bolt torque of 39.3% on the medium and 21.5% on the smaller articular surface was observed. Loading led to reorientation of the articular surfaces verified by markings on the components. Additional constructs that were under-tightened intentionally to one-quarter of target torque value lost all bolt torque and completely backed out. Discussion and Significance. The backing out of lockdown bolts in TKA has been reported in the literature but not replicated in-vitro. A challenging, physiologically relevant set of loading parameters was developed and applied to a CCK device with an articular surface lockdown bolt. Upon loading, the bolts experienced statistically significant loss of bolt torque which may be attributed to articular surface reorientation. Selected loading parameters led to complete bolt back-out in under-tightened constructs

The avascular nature of articular cartilage relies on diffusion pathways to obtain essential nutrients and molecules for cellular activity. Understanding these transport pathways is essential to maintaining and improving the health of articular cartilage and ultimately synovial joints. Several studies have shown that joint articulation is associated with fluid and solute uptake although it remains unclear what role sliding motion independently plays. This study investigates the role of sliding with a non-stationary contact area on the uptake of small molecular weight tracers into articular cartilage. Ten-millimeter diameter cartilage-bone plugs were obtained from porcine knee joints and sealed into purpose made diffusion chambers. The chambers were designed to eliminate diffusion from the radial edge and only allow diffusion through the articular surface. The bone side of the chamber was filled with PBS to maintain tissue hydration while the cartilage side was filled with 0.01mg/ml fluorescein sodium salt (FNa) prepared using PBS. Sliding loads with a non-stationary contact area were applied across the articular surface by a custom apparatus using a 4.5 mm diameter spherical indenter. A moving contact area was chosen to represent physiological joint motions. Reciprocal sliding was maintained at a rate of 5 mm/s for 2 and 4 hours. Control samples were subject to passive diffusion for 0, 4, and 88 hours. After diffusion tests, samples were snap frozen and 20 µm cross-sectional cuts were taken perpendicular to the sliding direction. Samples were imaged using a Zeiss AxioImager M2 epifluorescent microscope under 5× magnification with a filter for FNa. Intensity profiles were mapped from the articular surface to the subchondral bone. Unloaded control samples demonstrated minimal solute uptake at 4 hours penetrating less than 5% of the total cartilage depth. By 88 hours solute penetration had reached the subchondral bone although there was minimal accumulation within the cartilage matrix indicated by the relatively low intensity profile values. Samples that had been subjected to reciprocal sliding demonstrated accelerated penetration and solute accumulation compared to unloaded samples. After 1 hour of reciprocal sliding, the solute had reached 40% of the cartilage depth, this increased to approximately 80% at 4 hours, with much higher intensities compared to unloaded controls. Sliding motion plays an important role in the uptake of solutes into the cartilage matrix. Maintaining joint motion both post injury and in the arthritic process is a critical component of cartilage nutrition. Samples that had been subject to reciprocal sliding demonstrated accelerated solute penetration and accumulation in the cartilage matrix, exceeding steady state concentrations achieved by passive diffusion

Introduction. Contemporary total knee systems accommodate for differential sizing between femoral and tibial components to allow surgeons to control soft tissue balancing and optimize rotation. One method some manufacturers use to allow differential sizing involves maintaining coronal articular congruency with a single radius of curvature throughout sizes while clipping the medial-lateral width, called a single coronal geometry system. Registry data show a 20% higher revision rate when the tibial component is smaller than the femur (downsizing) in the DePuy PFC system, a single coronal system, possibly from increased stresses from edge loading or varying articular congruency. We examined a different single coronal geometry knee system, Smith & Nephew Genesis II, to determine if edge loading is present in downsized tibial components by measuring area and location of deviation of the polyethylene articular surface damage. Methods. 45 Genesis II posterior-stabilized polyethylene inserts (12 matched and 33 downsized tibial components) were CT scanned. 3D reconstructions were registered to corresponding pristine component reconstructions, and 3D deviation maps of the retrieved articular surfaces relative to the pristine surfaces were created. Each map was exported as a point cloud to a custom MATLAB code to calculate the area and weighted center of deviation of the articular surfaces. An iterative k-means clustering algorithm was used to isolate regions of deviation, and a shrink-wrap algorithm was applied to calculate their areas. The area of deviation was calculated as the sum of all regions of deviation and was normalized to the area of the articular surface. The location of deviation was described using the weighted center of deviation and the location of maximum deviation on the articular surfaces relative to the center of the post (Fig. 1). Pearson product moment correlations were conducted to examine the correlation between length of implantation (LOI) and the medial and lateral areas of deviation for all specimens, matched components, and downsized components. Results. The mean LOIs for downsized and matched tibial components were not different (36±28 months vs 46±26 months, p=0.24). Areas of deviation for the medial and lateral sides for both downsized and matched components increased with LOI (p<0.001). Medial and lateral sides of matched retrievals were not different in location of maximum deviation, maximum deviation, and weighted center of deviation (p>0.4). The matched and downsized retrievals did not have different centers of deviation in the medial-lateral direction, maximum deviations, or locations of maximum deviations (p>0.1). Discussion. Our results suggest that downsizing the tibial component in the Genesis II system, a single coronal geometry system, did not affect the area or location of deviation on the articular surface. Overall, the weighted center of deviation remained close to the dwell point and did not change as a function of tibial downsizing. However, we saw deviation patterns biased peripherally for inserts with low LOI in both matched and downsized cohorts. With increasing LOI, the deviation expanded to cover the majority of the available articular surface. Our results suggest the need to further examine this and other systems determine the effects of differential sizing. For figures/tables, please contact authors directly.

Abnormal patella height has been found to be one of the main reasons for abnormal contact between patella and trochlear groove leading to patellar instability in children. Many methods have been described to diagnose patellar instability but most of them are justified only in adults. The reason being incomplete ossification in the paediatric population. These methods have been divided into direct and indirect methods. We analysed the MRI scan of knee of 57 children between 12–14 years of age with no previous diagnosis of patellar instability. Patients with a diagnosis of patellar instability, previous surgery on the knee or trauma and poor MRI scan were excluded from the study. We used Insall -Salvati Index (ISI), Caton-Deschamp Index (CDI) and Patella-Trochlear Index (PTI) and compared the results. We found that 40% of measurements by CDI and 41% by ISI showed patella alta in patients with normal patella height. 10% of patients in PTI readings had value suggestive of abnormal patella height. We concluded that PTI is a more reliable index to be used in children as it uses the length of articular surface and does not rely on bony landmarks. Studies done show PTI is a more reliable and accurate method of measuring patella height

This study investigated concurrent talar dome injuries associated with tibial pilon fractures, mapping their distribution across the proximal talar dome articular surface. It compared the two main mechanisms of injury (MOI), falling from a height and motor vehicle accident (MVA), and whether the fractures were open or closed. From a previously compiled database of acute distal tibial pilon fractures (AO/OTA 43B/C) in adults of 105 cases, 53 cases were identified with a concurrent injury to the talar dome with a known mechanism of injury and in 44 it was known if the fracture was open or closed. Case specific 2D injury maps were created using a 1x1mm grid, which were overlayed in an Excel document to allow for comparative analyses. A two-way ANOVA was conducted that examined the effect of both MOI and if the fracture was open or closed on what percentage of the talar dome surface was injured. There was a statistically-significant difference between the average percentage of injured squares on the talar dome by both whether the fracture was open or closed (f(1)=5.27, p= .027) and the mechanism of injury (f(1)=8.08, p= .007), though the interaction between these was not significant (p= .156). Open injuries and injuries that occurred during an MVA were more likely to increase the surface area of the talar dome injuries. We have identified both MOI and if the fracture was either open or closed impacts the size of the injury present on the talar dome. Future research will investigate the aetiology of the differences noted, highlighting the clinical implications. Surgeons treating tibial pilon fractures caused by either a MVA or an open fracture, should be aware of an increased risk of large injuries to the surface of the talar dome

Tibial pilon fractures are typically the result of high-energy axial loads, with complex intra- articular fractures that are often difficult to reconstruct anatomically. Only nine simultaneous pilon and talus fractures have been published previously, but we hypothesised the chondral surface of the dome is affected more frequently. Data was acquired prospectively from 154 acute distal tibial pilon fractures (AO/OTA 43B/C) in adults. Radiographs, photographs, and intra-operative drawings of each case were utilised to document the presence of any macroscopic injuries of the talus. Detailed 1x1mm maps were created of the injuries in each case and transposed onto a statistical shape model of a talus; this enables the cumulative data to be analysed in Excel. Data was analysed using a Chi-squared test. From 154 cases, 104 were considered at risk and their talar domes were inspected; of these, macroscopic injuries were identified in 55 (52.4%). The prevalence of talar dome injury was greater with B-type fractures (53.5%) than C-type fractures (31.5%) (ρ = .01). Injuries were more common in men than women and presented with different distribution of injuries (ρ = .032). A significant difference in the distribution of injuries was also identified when comparing falls and motor vehicle accidents (ρ = .007). Concomitant injuries to the articular surface of the dome of the talus are relatively common, and this perhaps explains the discordance between the post-operative appearance following internal fixation and the clinical outcomes observed. These injuries were focused on the lateral third of the dome in men and MVAs, whereas women and fall mechanism were more evenly distributed. Surgeons who operatively manage high-energy pilon fractures should consider routine inspection of the talar dome to assess the possibility of associated macroscopic osteochondral injuries

Introduction. It has been reported that the tibial articular surface of coronal aligment is parallel to the floor in the whole-leg standing radiographs of the normal knee. The purposes of this study are to investigate the relationship between the tibial articular surface and the ground on the whole-leg standing radiographs after total knee arthroplasty(TKA). Sturdy Design and Methods. 20 knees after TKA were studied retrospectively. The 20 participants were mean age at 76.7 years; and 3 male and 17 female. Using whole-leg standing radiographs, we mesuared the pre- and postoperative hip-knee- ankle angle(HKA), the tibial joint line angle(TJLA), and the tibial component Coronal tibial angle(CTA). The difference in each parameter was compared and examined. Results. HKA improved from 11.3 ° (varus) to 2.2 ° (varus). TJLA was preoperative − 0.63 ° (varus) to postoperative − 0.17 (varus), and the tibial component was almost parallel to the ground. The CTA was 90.0 ° and it was a good installation position. Conclusions. In the past kinetic analysis, it is reported that the tibial articular surface tilts outward during walking. By tilting outwardly, load stress may concentrate on the medial compartment. Therefore, the horizontal plane of the joint surface may be advantageous for load distribution at the knee joint. In the result of this study the components were installed horizontally in whole-leg standing position

Restoration a joint's articular surface following degenerative or traumatic pathology to the osteochondral unit pose a significant challenge. Recent advances have shown the utility of collagen-based scaffolds in the regeneration of osteochondral tissue. To provide these collagen scaffolds with the appropriate superstructure novel techniques in 3D printing have been investigated. This study investigates the use of polyɛ-caprolactone (PCL) collagen scaffolds in a porcine cadaveric model to establish the stability of the biomaterial once implanted. This study was performed in a porcine cadaveric knee model. 8mm defects were created in the medial femoral trochlea and repaired with a PCL collagen scaffold. Scaffolds were secured by one of three designs; Press Fit (PF), Press Fit with Rings (PFR), Press Fit with Fibrin Glue (PFFG). Mobilisation was simulated by mounting the pig legs on a continuous passive motion (CPM) machine for either 50 or 500 cycles. Biomechanical tensile testing was performed to examine the force required to displace the scaffold. 18 legs were used (6 PF, 6 PFR, 6 PFFG). Fixation remained intact in 17 of the cohort (94%). None of the PF or PFFG scaffolds displaced after CPM cycling. Mean peak forces required to displace the scaffold were highest in the PFFG group (3.173 Newtons, Standard deviation = 1.392N). The lowest peak forces were observed in the PFR group (0.871N, SD = 0.412N), while mean peak force observed in the PF group was 2.436N (SD = 0.768). There was a significant difference between PFFG and PFR (p = 0.005). There was no statistical significance in the relationship between the other groups. PCL reinforcement of collagen scaffolds provide an innovative solution for improving stiffness of the construct, allowing easier handling for the surgeon. Increasing the stiffness of the scaffold also allows press fit solutions for reliable fixation. Press fit PCL collagen scaffolds with and without fibrin glue provide dependable stability. Tensile testing provides an objective analysis of scaffold fixation. Further investigation of PCL collagen scaffolds in a live animal model to establish quality of osteochondral tissue regeneration are required

INTRODUCTION. The specific factors affecting wear of the ultrahigh molecular weight polyethylene (UHMWPE) tibial component of total knee replacements (TKR) are poorly understood. One recent study demonstrated that lower conforming inserts produced less wear in knee simulators. The purpose of this study is to investigate the effect of insert conformity and design on articular surface wear of postmortem retrieved UHMWPE tibial inserts. METHODS. Nineteen NexGen cruciate-retaining (NexGen CR) and twenty-five NexGen posterior-stabilized (NexGen PS) (Zimmer) UHWMPE tibial inserts were retrieved at postmortem from fifteen and eighteen patients respectively. Articular surfaces were scanned at 100×100μm using a coordinate measuring machine (SmartScope, OGP Inc.). Autonomous mathematical reconstruction of the original surface was used to calculate volume loss and linear penetration maps of the medial and lateral plateaus. Wear rates for the medial, lateral and total articular surface were calculated as the slope of the linear regression line of volume loss against implantation time. Volume loss due to creep was estimated as the regression intercept. Student t-tests were used to check for significant. RESULTS. The NexGen CR and NexGen PS patient groups were approximately the same age at time of implantation (mean±SD: 72.1±9.9 and 68.7±8.8 years respectively, p=0.260) and implantation times were not significantly different (8.7±3.1 and 9.1±3.7 years, p=0.670). Both groups showed high variability in wear scars. No significant difference in wear rates on the total surface (mean±SE: 11.89±5.01 mm. 3. /year vs. 11.09±4.18 mm. 3. /year, p=0.905). However, NexGen CR components showed significantly higher volume loss due to creep than NexGen PS components (70.22±47.07 mm. 3. vs. 31.30±41.15 mm. 3. , p=0.007). These results were reflected on the medial and lateral sides, with no significant differences in wear rates on the medial side (p=0.856) or lateral side (p=0.633) and higher volume losses due to creep associated with the NexGen CR components. While NexGen CR and NexGen PS showed a near equal mean percentage of volume loss on the medial side (CR: 52.4±11.7%, PS: 52.5±11.6%), a paired t-test showed that NexGen PS components showed a higher volume loss on the medial side (p=0.056), NexGen CR components did not (p=0.404). DISCUSSION. The combination of higher conformity and more kinematic constraint in NexGen CR components may create larger contact areas with higher stresses, leading to higher volume loss due to creep observed in this study. However, these factors did not produce increased wear rates in the population. Constrained components may maintain more loading on medial side and limit sliding distance on lateral side, causing more wear medially. Total wear rates were very similar and resembled the previously reported rate of 12.9 ± 5.97 mm. 3. /year for retrieved Miller-Galante II (Zimmer) components, which features a near flat articulating surface. These findings indicate that materials factors may be most important in producing wear and that higher conformity alone does not decrease wear. For any figures or tables, please contact authors directly

Pathologies such as Scapho-Lunate Advanced Collapse (SLAC), Scaphoid Non-union Advanced Collapse (SNAC) and Kienbock's disease can lead to arthritis in the wrist. Depending on the articular surfaces that are involved, motion preserving surgical procedures can be performed. Proximal Row Carpectomy (PRC) and Four Corner Fusion (4CF) are tried and tested surgical options. However, prospective studies comparing the two methods looking at sufficient sample sizes are limited in the literature. The purpose of this study was to prospectively compare the early results of PRC vs 4CF performed in a single centre. Patients with wrist arthritis were prospectively enrolled (2015 to 2021) in a single centre in Vancouver, Canada. Thirty-six patients and a total of 39 wrists underwent either a PRC (n=18) or 4CF (n=21) according to pre-operative clinical, radiographical, and intra-operative assessment. Patient-Rated Wrist Evaluation (PRWE) scores were obtained preoperatively, as well as at six months and one year post operatively. Secondary outcomes were range of motion (ROM) of the wrist, grip strength, reoperation and complication rates. Statistical significance was set at p=0.05. Respectively for PRC and 4CF, the average PRWE scores at baseline were 61.64 (SD=19.62) and 63.67 (SD=20.85). There was significant improvement at the six-month mark to 38.81 (SD=22.95) (p=0.031) and 41.33 (SD=26.61) (p=0.007), then further improvement at the 12month mark to 33.11 (SD=23.42) (p=0.007) and 36.29 (SD=27.25) (p=0.002). There was no statistical difference between the two groups at any time point. Regarding ROM, statistical difference was seen in pronation for the PRC group at the 6month mark from an average of 72.18 deg to 61.56 deg and in flexion at the 12 month mark from 47.89 deg to 33.50 deg. All other parameters did not show statistically significant difference post operatively. For ROM of the 4CF group, only flexion at the 12month mark showed statistically significant change from an average of 48.81 deg to 38.03 deg. There was no statistical difference in pre-operative ROM between the two groups. One patient in the 4CF group required a revision for delayed union, and three patients ended up with ulnar sided wrist pain. Patients undergoing PRC and 4CF showed significant improvement in post operative PRWE scores, this reflects existing literature. For 4CF care must be taken to minimise ulnar sided wrist pain by relatively shortening the unar sided carpal column mass. ROM analysis showed that patients lost some wrist flexion ROM post-operatively at the 12month mark with both PRC and 4CF. However, other ROM parameters were unchanged

Knowledge of the premorbid glenoid shape and the morphological changes the bone undergoes in patients with glenohumeral arthritis can improve surgical outcomes in total and reverse shoulder arthroplasty. Several studies have previously used scapular statistical shape models (SSMs) to predict premorbid glenoid shape and evaluate glenoid erosion properties. However, current literature suggests no studies have used scapular SSMs to examine the changes in glenoid surface area in patients with glenohumeral arthritis. Therefore, the purpose of this study was to compare the glenoid articular surface area between pathologic glenoid cavities from patients with glenohumeral arthritis and their predicted premorbid shape using a scapular SSM. Furthermore, this study compared pathologic glenoid surface area with that from virtually eroded glenoid models created without influence from internal bone remodelling activity and osteophyte formation. It was hypothesized that the pathologic glenoid cavities would exhibit the greatest glenoid surface area despite the eroded nature of the glenoid and the medialization, which in a vault shape, should logically result in less surface area. Computer tomography (CT) scans from 20 patients exhibiting type A2 glenoid erosion according to the Walch classification [Walch et al., 1999] were obtained. A scapular SSM was used to predict the premorbid glenoid shape for each scapula. The scapula and humerus from each patient were automatically segmented and exported as 3D object files along with the scapular SSM from a pre-operative planning software. Each scapula and a copy of its corresponding SSM were aligned using the coracoid, lateral edge of the acromion, inferior glenoid tubercule, scapular notch, and the trigonum spinae. Points were then digitized on both the pathologic humeral and glenoid surfaces and were used in an iterative closest point (ICP) algorithm in MATLAB (MathWorks, Natick, MA, USA) to align the humerus with the glenoid surface. A Boolean subtraction was then performed between the scapular SSM and the humerus to create a virtual erosion in the scapular SSM that matched the erosion orientation of the pathologic glenoid. This led to the development of three distinct glenoid models for each patient: premorbid, pathologic, and virtually eroded (Fig. 1). The glenoid surface area from each model was then determined using 3-Matic (Materialise, Leuven, Belgium). Figure 1. (A) Premorbid glenoid model, (B) pathologic glenoid model, and (C) virtually eroded glenoid model. The average glenoid surface area for the pathologic scapular models was 70% greater compared to the premorbid glenoid models (P < 0 .001). Furthermore, the surface area of the virtual glenoid erosions was 6.4% lower on average compared to the premorbid glenoid surface area (P=0.361). The larger surface area values observed in the pathologic glenoid cavities suggests that sufficient bone remodelling exists at the periphery of the glenoid bone in patients exhibiting A2 type glenohumeral arthritis. This is further supported by the large difference in glenoid surface area between the pathologic and virtually eroded glenoid cavities as the virtually eroded models only considered humeral anatomy when creating the erosion. For any figures or tables, please contact the authors directly

Isolated talonavicular arthrodesis is a common procedure particularly for posttraumatic arthritis and rheumatoid arthritis. Two surgical approaches are commonly used: the medial and the dorsal approach. It is recognized that access to the lateral aspect of the talonavicular joint can be limited when using the medial approach and it is our experience that using the dorsal approach addresses this issue. We performed an anatomical study using cadaver specimens, to compare the amount of articular surface that can be accessed, and therefore prepared for arthodesis, by each surgical approach. Medial and dorsal approaches to the talonavicular joint were performed on each of 11 cadaveric specimens (10 fresh frozen, 1 embalmed). Distraction of the joint was performed as used intraoperatively for preparation of articular surfaces during talonavicular arthrodesis. The accessible area of articular surface was marked for each of the two approaches using a previous reported technique. Disarticulation was performed and the marked surface area was quantified using an immersion digital microscribe, allowing a three dimensional virtual model of the articular surfaces to be assessed. The median percentage of accessible total talonavicular articular surface for the medial and dorsal approaches was 71% and 92% respectively. This difference was significant (Wilcoxon Signed Ranks Test, p< 0.001). This study provides quantifiable measurements of the articular surface accessible by the medial and dorsal approaches to the talonavicular joint. These data support for the use of the dorsal approach for talonavicular arthrodesis

Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings. Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens. Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or convex shape, the perfect AP angle aligned with a tangent to the subchondral surface extending from center to posterior plateau on CT. Phase Three: Based on the CT protocol created in Phase Two, mean medial slope (5.2°+/-2.3° posterior) was significantly less than lateral slope (7.5°+/-3.0° posterior) in 54 knees (p<0.001). In individual specimens, the difference between medial and lateral slopes was variable, ranging from 6.8° more laterally to 3.1° more medially. In a paired comparison of right and left knees from the same cadaver, no differences were noted between sides (medial p=0.43; lateral p=0.62). On average there is slightly more tibial slope in the lateral plateau than medial plateau (2° greater). However, individual patients may have substantially more lateral slope (up to 6.8°) or even more medial slope (up to 3.1°). Since tibial slope was similar between contralateral limbs, evaluating slope on the uninjured side provides a template for sagittal plane reduction of tibial plateau fractures