Purpose of the study: Fracture of the medial condyle of the humerus is uncommon in adults. The purpose of this retrospective analysis was to examine the clinical and radiographic outcomes of a single-site series. Material and methods: From January 1990 to December 2004, nine closed fractures of the medial condyle of the humerus were treated surgically in seven men and two women, mean age 31.22 years (range 16–65). No vessel or nerve injury was noted at diagnosis. According to the AO/ASIF classification, all fractures were type B2. Surgery was undertaken on day 2 to 6, via a medial or posterior approach for pin or screw fixation. Postoperatively, the joint was held immobile with a brace for 5.57 weeks (3–8.). Functional and physical outcome were studied using the Mayo Clinic Elbow Performance score. Bone healing and secondary osteoarthritis were assessed on plain x-rays. Results: Six patients were reviewed at mean follow-up of 9.31 years (4.31–16.56), three patients were lost to follow-up. There were no infections. Four patients experienced sensorial disorders in the territory of the ulnar nerve including three with persistent symptoms at last follow-up. Two elbows were slightly painful at last follow-up. Two patients aged 16 and 18 years at trauma exhibited exaggerated valgus. Material was removed for three patients. Mean flexion was 123.83 (90–140), mean extension deficit 3.33 (−10 to 0), mean pronation 82.5 (70–85), mean supination 90, the flexion-extension range 122.16 (90–130). The Mayo Elbow Performance Score was 89.16 (65–100), one patient was dissatisfied, three patients exhibited moderated joint impingement. Hypertrophy of the medial condyle was noted in three patients. All fractures healed. Discussion: These fractures are rare in adults. Few series are reported in the literature, with small populations. The mechanism of the injury can be direct shock on a flexed elbow or indirect shock by fall onto the hand. Valgus deviation and hypertrophy of the medial condyle in adolescents appear to be secondary to secondary growth stimulation. The combination of the initial injury, imperfect reduction, and prolonged postoperative immobilization influences the functional outcome. Conclusion: This work confirms that surgery alone, associating perfect reduction and rigid fixation, can enable early rehabilitation and improved results

Certain technical advances, such as flexible intramedullary fixation and bioreabsorbable implants, have further increased enthusiasm for surgical management of pediatric fractures.» (Flynn et al.). In the Paediatric Surgery Department biodegradable pins of solid polydioxanone (PDS) in management of paediatric fractures have been used since April 1986. PDS pins are too soft for the osteosynthesis in fractures with fragments under high tensile pressures. However, we have successfully carried out a large number of internal fixations in children’s elbows. This is based on accurate distribution of PDS pins and careful positioning of periostal sutures and the adjacent disrupted muscles. Our technique, as presented at the 2nd European Congress of Paediatric Surgery in Madrid in 1997, is to fix temporarily the repositioned fractured fragment with Kirschner’s metal wire. Following osteosynthesis with PDS, the protruding K-wire is left in place for seven days until the limb is safely immobilized. A total of 96 patients were operated. The purpose of the study is to compare osteosynthesis with PDS pins (Group A) with that of metallic K-wire (Group B). Each group consisted of 48 children. General characteristics (age, sex, and fracture types) were statistically the same (P > 0.05). In Group A, with children between 2 and 13 years, or 9.3 on average, 21 children were with the lateral condyle fractures (43.75%), 25 children with medial epicondyle fractures (52.08%), and 2 children with medial condyle fractures (4.16%). In Group B, with children between 2 and 14 years, or 8.7 on average, 26 children were with lateral condyle fractures (54.16%), 19 children with medial epicondyle fractures (39.58%), and 3 with medial condyle fractures (6.25%). The study excludes Milch Type II fractures of medial and lateral condyles. The results have been examined in the follow-up period of one, three, and six months of two different methods according to Flynn’s criteria. After statistical evaluation the differences obtained had no statistical significance (P > 0.05). However, satisfaction score (0 – 10) is significantly higher in Group A than in Group B for both parents and evaluators (P < 0.05). Both treatments exhibit good results with the exception that the use of metal osteosynthetic material requires another operation. If metal wires are used and cut just underneath the skin, protruding with local inflammation may appear. Proper use of PDS pins requires no further operation. This is to the benefit for both the patient and rehabilitation staff

Aims. Electromagnetic induction heating has demonstrated in vitro antibacterial efficacy over biofilms on metallic biomaterials, although no in vivo studies have been published. Assessment of side effects, including thermal necrosis of adjacent tissue, would determine transferability into clinical practice. Our goal was to assess bone necrosis and antibacterial efficacy of induction heating on biofilm-infected implants in an in vivo setting. Methods. Titanium-aluminium-vanadium (Ti6Al4V) screws were implanted in medial condyle of New Zealand giant rabbit knee. Study intervention consisted of induction heating of the screw head up to 70°C for 3.5 minutes after implantation using a portable device. Both knees were implanted, and induction heating was applied unilaterally keeping contralateral knee as paired control. Sterile screws were implanted in six rabbits, while the other six received screws coated with Staphylococcus aureus biofilm. Sacrifice and sample collection were performed 24, 48, or 96 hours postoperatively. Retrieved screws were sonicated, and adhered bacteria were estimated via drop-plate. Width of bone necrosis in retrieved femora was assessed through microscopic examination. Analysis was performed using non-parametric tests with significance fixed at p ≤ 0.05. Results. The width of necrosis margin in induction heating-treated knees ranged from 0 to 650 μm in the sterile-screw group, and 0 to 517 μm in the biofilm-infected group. No significant differences were found between paired knees. In rabbits implanted with sterile screws, no bacteria were detected. In rabbits implanted with infected screws, a significant bacterial load reduction with median 0.75 Log10 colony-forming units/ml was observed (p = 0.016). Conclusion. Induction heating was not associated with any demonstrable thermal bone necrosis in our rabbit knee model, and might reduce bacterial load in S. aureus biofilms on Ti6Al4V implants. Cite this article: Bone Joint Res 2024;13(12):695–702

Cartilage diseases have a significant impact on the patient's quality of life and are a heavy burden for the healthcare system. Better understanding, early detection and proper follow-up could improve quality of life and reduce healthcare related costs. Therefore, the aim of this study was to evaluate if difference between osteoarthritic (OA) and non-osteoarthritic (non-OA) knees can be detected quantitatively on cartilage and subchondral bone levels with advanced but clinical available imaging techniques. Two OA (mean age = 88.3 years) and three non-OA (mean age = 51.0 years) human cadaveric knees were scanned two times. A high-resolution peripheral quantitative computed tomography (HR-pQCT) scan (XtremeCT, Scanco Medical AG, Switzerland) was performed to quantify the bone microstructure. A contrast-enhanced clinical CT scan (GE Revolution Evo, GE Medical Systems AG, Switzerland) was acquired with the contrast agent Visipaque 320 (60 ml) to measure cartilage. Subregions dividing the condyle in four parts were identified semi-automatically and the images were segmented using adaptive thresholding. Microstructural parameters of subchondral bone and cartilage thickness were quantified. The overall cartilage thickness was reduced by 0.27 mm between the OA and non-OA knees and the subchondral bone quality decreased accordingly (reduction of 33.52 % in BV/TV in the layer from 3 to 8 mm below the cartilage) for the femoral medial condyle. The largest differences were observed at the medial part of the femoral medial condyle both for cartilage and for bone parameters, corresponding to clinical observations. Subchondral bone microstructural parameters and cartilage thickness were quantified using in vivo available imaging and apparent differences between the OA and non-OA knees were detected. Those results may improve OA follow-up and diagnosis and could lead to a better understanding of OA. However, further in vivo studies are needed to validate these methods in clinical practice

Chondral defects in the knee have cartilage biomechanical differences due to defect size and orientation. This study examines how the tibiofemoral contact pressure is affected by increasing full-thickness chondral defect size on the medial and lateral condyle at full extension. Isolated full-thickness, square chondral defects increasing from 0.09cm. 2. to 1.0cm. 2. were created sequentially on the medial and lateral femoral condyles of six human cadaveric knees with intact ligaments and menisci. Chondral defects were created 1.0cm from the femoral notch posteriorly. The knees were fixed to a uniaxial load frame and loaded from 0N to 600N at full extension. Contact pressures between the femoral and tibial condyles were measured using pressure mapping sensors. The peak contact pressure was defined as the highest value in the 2.54mm. 2. area around the defect. The location of the peak contact pressure was determined relative to the centre of the defect. Peak contact pressure was significantly different between (4.30MPa) 0.09cm. 2. and (6.91MPa) 1.0cm. 2. defects (p=0.04) on the medial condyle. On the lateral condyle, post-hoc analysis showed differences in contact pressures between (3.63MPa) 0.09cm. 2. and (5.81MPa) 1.0cm. 2. defect sizes (p=0.02). The location of the stress point shifted from being posteromedial (67% of knees) to anterolateral (83%) after reaching a 0.49cm. 2. defect size (p < 0.01) in the medial condyle. Conversely, the location of the peak contact pressure point moved from being anterolateral (50%) to a posterolateral (67%) location in defect sizes greater than 0.49cm. 2. (p < 0.01). Changes in contact area redistribution and cartilage stress from 0.49cm. 2. to 1.0cm. 2. impact adjacent cartilage integrity. The location of the maximum stress point also varied with larger defects. This study suggests that size cutoffs exist earlier in the natural history of chondral defects, as small as 0.49cm. 2. , than previously studied, suggesting a lower threshold for intervention

Introduction. Numerous fluoroscopic studies have been conducted to investigate kinematic variabilities of total knee arthroplasty (TKA). In those studies, subjects having a posterior stabilized (PS) TKA experience greater weightbearing knee flexion and posterior femoral rollback of the lateral condyle. In those same studies, subjects did experience a high incidence of variable medial condyle motion and reverse axial rotation, especially occurring when the cam engaged the post. More recently, a PS TKA was designed to accommodate both gender and ethnicity. Therefore, the objective of this study was to assess in vivo kinematics for subjects having this TKA type to determine if subjects having this PS TKA experienced more optimal knee kinematics. Methods. Twenty-five subjects in this study were asked to perform a deep knee bend to maximum knee flexion and a step-up maneuver while under fluoroscopic surveillance. All subjects were patients of one experienced surgeon and received the same PS TKA. Using a 3D-2D registration technique, the CAD models, supplied by the sponsoring company, were superimposed over x-ray images at specified increments throughout the fluoroscopic footage. The kinematics were then analyzed to evaluate lateral anterior/posterior (LAP) and medial anterior/posterior (MAP) condyle translation as well as axial rotation of the femur with respect to the tibia. Results. During the DKB activity, the average flexion for the PS TKA subjects was 1108°. On average subjects experienced a lateral condyle motion in the posterior direction of 7.3mm, with the maximum amount of posterior rollback being 12.8 mm. These same subjects experienced an average medial condyle motion in the posterior direction of 4.8 mm with the maximum amount of posterior motion being 7.8 mm. Therefore, with the lateral condyle rolling more posterior than the medial condyle, these subjects experienced an average amount of 7.1° of axial rotation, with a maximum of 12.0°. Only one subject in this study experienced a reverse axial rotation from full extension to maximum knee flexion. During the step-up maneuver, subjects consistently experienced a roll forward motion of both their condyles. Discussion. Subjects in this study experienced a high incidence and magnitude of lateral condyle posterior femoral rollback, leading a normal-like axial rotation pattern, although less in magnitude compared to the normal knee. There was variability occurring with the medial condyle as some experience experienced an anterior slide while others rolled in the posterior direction. As seen in previous studies, during mid flexion both condyles experienced a more variable motion pattern. Twenty-five subjects having a posterior cruciate retaining TKA are being added to this study to determine if retention of the PCL in a similarly designed TKA leads to more normal-like kinematic patterns

Background. The anatomy of the human knee is very different than the tibiofemoral surface geometry of most modern total knee replacements (TKRs). Many TKRs are designed with simplified articulating surfaces that are mediolaterally symmetrical, resulting in non-natural patterns of motion of the knee joint [1]. Recent orthopaedic trends portray a shift away from basic tibiofemoral geometry towards designs which better replicate natural knee kinematics by adding constraint to the medial condyle and decreasing constraint on the lateral condyle [2]. A recent design concept has paired this theory with the concept of guided kinematic motion throughout the flexion range [3]. The purpose of this study was to validate the kinematic pattern of motion of the surface-guided knee concept through in vitro, mechanical testing. Methods. Prototypes of the surface-guided knee implant were manufactured using cobalt chromium alloy (femoral component) and ultra-high molecular weight polyethylene (tibial component). The prototypes were installed in a force-controlled knee wear simulator (AMTI, Watertown, MA) to assess kinematic behavior of the tibiofemoral articulation (Figure 1). Axial joint load and knee flexion experienced during lunging and squatting exercises were extracted from literature and used as the primary inputs for the test. Anteroposterior and internal-external rotation of the implant components were left unconstrained so as to be passively driven by the tibiofemoral surface geometry. One hundred cycles of each exercise were performed on the simulator at 0.33 Hz using diluted bovine calf serum as the articular surface lubricant. Component motion and reaction force outputs were collected from the knee simulator and compared against the kinematic targets of the design in order to validate the surface-guided knee concept. Results. Under deep flexion conditions of up to 140° of squatting the surface-guided knee implants were found to undergo a maximum of 22.2° of tibial internal rotation and 20.4 mm of posterior rollback on the lateral condyle. Pivoting of the knee joint was centered about the highly congruent medial condyle which experienced only 1.6 mm of posterior rollback. Experimental results were within 2° (internal-external rotation) and 1 mm (anteroposterior translation) agreement with the design target throughout the applied exercises (Figure 2). Conclusion. The results of this test confirm that by combining a constrained medial condyle with guiding geometry on the lateral condyle, deep knee flexion activities of up to 140° can be performed while maintaining near-natural kinematics of the knee joint. The authors believe that the tested surface-guided implant concept is a significant step toward the development of novel TKR which allows a greater range of motion and could improve the quality of life for active patients undergoing knee replacement. For any figures or tables, please contact the authors directly

Introduction. Surgeons performing a total knee replacement (TKR) have two techniques to assist them achieve proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections, whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the implant migration and kinematics between the two techniques, but the results have been varied. However, these studies have not been done on modern anatomically designed prostheses using radiostereometric analysis (RSA). Anatomical designs attempt to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the major design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one surgical technique may have advantages another. We hypothesize that there would be no difference between GB and MR techniques in implant migration, but that GB might provide better knee kinematics. Methods. Patients were recruited to receive an anatomically designed prosthesis and randomized to groups where the GB or MR technique is used. For all patients in the study, RSA images were acquired at a 2 week baseline, as well as at 6 weeks, 3 months, and 6 months post-operatively. These images were used to collect the maximum total point motion (MTPM) of the tibial and femoral implant components relative to the bone using a model-based RSA software. A series of RSA images were also acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 100°. Model-based RSA software was used to obtain the 3D positions and orientations of the femoral and tibial components, which were used to obtain the anterior-posterior (AP) contact locations for each condyle. Results. Results from 47 patients (27 GB, 20 MR) were analyzed. No significant differences were present between the two surgical techniques for tibial component MTPM at 6 weeks (mean difference=0.02 mm, p=0.61), 3 months (mean difference=0.01 mm, p=0.92), and 6 months (mean difference=0.01 mm, p=0.93) post-operatively. No significant differences were present between the two surgical techniques for femoral component MTPM at 6 weeks (mean difference=0.12 mm, p=0.08), 3 months (mean difference=0.05 mm, p=0.54), and 6 months (mean difference=0.13 mm, p=0.05) post-operatively. On the medial condyle, no significant differences in AP contact location were found at all angles between 0° and 80° of flexion (p-values from 0.28 to 0.95). There was a significant difference medially between the AP contact location of the two surgical techniques at 100° of flexion (p=0.01), indicating more posterior rollback on the medial condyle in the GB technique. On the lateral condyle, no significant differences in AP contact location were found at all angles of flexion (p-values from 0.13 to 0.62). On the medial condyle of the GB group, the AP contact location moved posteriorly 5.83 mm from 0° to 20°, anteriorly 2.60 mm from 20° to 60°, and posteriorly 7.40 mm from 60° to 100°. On the medial condyle of the MR group, the AP contact location moved posteriorly 5.36 mm from 0° to 20°, anteriorly 2.87 mm from 20° to 60°, and posteriorly 3.65 mm from 60° to 100°. On the lateral condyle of the GB group, the AP contact location moved posteriorly 6.87 mm from 0° to 20°, 0.30 mm from 20° to 60°, and 3.61 mm from 60° to 100°. On the lateral condyle of the MR group, the AP contact location moved posteriorly 6.86 mm from 0° to 20°, anteriorly 0.02 mm from 20° to 60°, and posteriorly 3.56 mm from 60° to 100°. Conclusions. The GB and MR techniques are very similar in terms of implant migration and overall kinematics when an anatomical prosthesis design is used for TKR. This study suggests that surgeon preference should be used when deciding which technique to use for implanting this anatomically designed knee replacement. For figures, tables, or references, please contact authors directly

We scanned 25 left knees in healthy human subjects using MRI. Multiplanar reconstruction software was used to take measurements of the inferior and posterior facets of the femoral condyles and the trochlea. A ‘basic circle’ can be defined which, in the sagittal plane, fits the posterior and inferior facets of the lateral condyle, the posterior facet of the medial condyle and the floor of the groove of the trochlea. It also approximately fits both condyles in the coronal plane (inferior facets) and the axial plane (posterior facets). The circle fitting the inferior facet of the medial condyle in the sagittal plane was consistently 35% larger than the other circles and was termed the ‘medial inferior circle’. There were strong correlations between the radii of the circles, the relative positions of the centres of the condyles, the width of the condyles, the total knee width and skeletal measurements including height. There was poor correlation between the radii of the circles and the position of the trochlea relative to the condyles. In summary, the condyles are approximately spherical except for the inferior facet medially, which has a larger radius in the sagittal plane. The size and position of the condyles are consistent and change with the size of the person. However, the position of the trochlea is variable even though its radius is similar to that of the condyles. This information has implications for understanding anterior knee pain and for the design of knee replacements. Cite this article: Bone Joint J 2014;96-B:1623–30

The posterior compartments of the knee are currently accessed arthroscopically through anterior, posteromedial or posterolateral portals. A direct posterior portal to access the posterior compartments has been overlooked due to a perceived high-risk of injury to the popliteal neurovascular structures. Therefore, this study aimed to investigate the safety and accessibility of a direct posterior portal into the knee. This cross-sectional study comprised a sample of 95 formalin-embalmed cadaveric knees and 9 fresh-frozen knees. Cannulas were inserted into the knees, 16mm from the vertical plane between the medial epicondyle of the femur and medial condyle of the tibia and 8 and 14mm (females and males respectively) from the vertical plane connecting the lateral femoral epicondyle and lateral tibial condyle. Landmarks were identified in full extension and cannula insertion was completed with the formalin-embalmed knees in full extension and the fresh-frozen in 90-degree flexion. Posterior aspects of the knees were dissected from superficial to deep, to assess potential damage caused by cannula insertion. Incidence of neurovascular damage was 9.6% (n=10); 0.96% medial cannula and 8.7% lateral cannula. The medial cannula damaged one small saphenous vein (SSV) in a male specimen. The lateral cannula damaged one SSV, 7 common fibular nerves (CFN) and both CFN and lateral cutaneous sural nerve in one specimen. All incidences of damage occurred in formalin-embalmed knees. The posterior horns of the menisci were accessible in all specimens. A medial-lying direct posterior portal into the knee is safe in 99% of occurrences. The lateral-lying direct posterior portal is of high risk to the CFN

Introduction. A common goal of total knee arthroplasty (TKA) is to restore normal knee kinematics. While substantial data is available on TKA kinematics, information regarding non-implanted knee kinematics is less well studied especially in larger patient populations. The objectives of this study were to determine normal femorotibial kinematics in a large number of non-implanted knees and to investigate parameters that yield higher knee flexion with weight-bearing activities. Methods. Femorotibial kinematics of 104 non-implanted healthy subjects performing a deep knee bend (DKB) activity were analyzed using 3D to 2D fluoroscopy. The average age and BMI were 38.1±18.2 years and 25.2±4.6, respectively. Pearson correlation analysis was used to determine statistical correlations. Results. On average, subjects experienced 21.5±7.2 mm, 13.8±8.9 mm, and 27.1°±12.1° of lateral rollback, medial rollback, and external femorotibial axial rotation, respectively (Figure 1). Most rollback occurred in early flexion, with 10.2±6.4 mm and 5.3±6.3 mm of rollback for the lateral and medial condyles, respectively. While the lateral condyle consistently moved posteriorly, the medial condyle experienced 1.8±4.8 mm of anterior sliding between 90° to 120° of flexion. There was a positive correlation between higher weight-bearing flexion and lateral condylar rollback (r=0.5480, p<.0001) (Figure 2), medial condylar rollback (r=0.3188, p=0.001) (Figure 3), and external axial rotation (r=0.5505, p<.0001) (Figure 4). There was an inverse correlation between advancing age and knee flexion (r=-0.7358, p<.0001) as well as higher BMI and flexion (r=-0.3332, p=0.0007), indicating that multiple factors contribute to postoperative range-of-motion. Conclusion. This represents one of the largest studies on normal knee femorotibial kinematics in non-implanted healthy subjects. These results indicate that increased condylar rollback and external axial rotation correlate with increased weight-bearing knee flexion, while increased age and BMI yield decreased flexion. Therefore, in order to achieve higher weight-bearing flexion following TKA, normal-like kinematics such as high rollback and external axial rotation should be incorporated into TKA design. For any figures or tables, please contact the authors directly

Aims. This study aimed to analyze kinematics and kinetics of the tibiofemoral joint in healthy subjects with valgus, neutral, and varus limb alignment throughout multiple gait activities using dynamic videofluoroscopy. Methods. Five subjects with valgus, 12 with neutral, and ten with varus limb alignment were assessed during multiple complete cycles of level walking, downhill walking, and stair descent using a combination of dynamic videofluoroscopy, ground reaction force plates, and optical motion capture. Following 2D/3D registration, tibiofemoral kinematics and kinetics were compared between the three limb alignment groups. Results. No significant differences for the rotational or translational patterns between the different limb alignment groups were found for level walking, downhill walking, or stair descent. Neutral and varus aligned subjects showed a mean centre of rotation located on the medial condyle for the loaded stance phase of all three gait activities. Valgus alignment, however, resulted in a centrally located centre of rotation for level and downhill walking, but a more medial centre of rotation during stair descent. Knee adduction/abduction moments were significantly influenced by limb alignment, with an increasing knee adduction moment from valgus through neutral to varus. Conclusion. Limb alignment was not reflected in the condylar kinematics, but did significantly affect the knee adduction moment. Variations in frontal plane limb alignment seem not to be a main modulator of condylar kinematics. The presented data provide insights into the influence of anatomical parameters on tibiofemoral kinematics and kinetics towards enhancing clinical decision-making and surgical restoration of natural knee joint motion and loading. Cite this article: Bone Joint Res 2024;13(9):485–496

Distal femur fractures (DFF) are common, especially in the elderly and high energy trauma patients. Lateral locked osteosynthesis constructs have been widely used, however non-union and implant failures are not uncommon. Recent literature advocates for the liberal use of supplemental medial plating to augment lateral locked constructs. However, there is a lack of proprietary medial plate options, with some authors supporting the use of repurposing expensive anatomic pre-contoured plates. The aim of this study was to investigate the feasibility of a readily available cost-effective medial implant option. A retrospective analysis from January 2014 to June 2022 was performed on DFF (primary or revision) managed with supplemental medial plating with a Large Fragment Locking Compression Plate (LCP) T-Plate (~$240 AUD) via a medial sub-vastus approach. The T-plate was contoured and placed superior to the medial condyle. A combination of 4.5mm cortical, 5mm locking and/or 6.5mm cancellous screws were used, with oblique screw trajectories towards the distal lateral cortex of the lateral condyle. All extra-articular fractures and revision fixation cases were allowed to weight bear immediately. The primary outcome was union rate. This technique was utilised on sixteen patients; 3 acute, 13 revisions; mean age 52 years (range 16-85), 81% male, 5 open fractures. The union rate was 100%, with a median time to union of 29 weeks (IQR 18-46). The mean follow-up was 15 months. There were two complications: a deep infection requiring two debridements and a prominent screw requiring removal. The mean range of motion was 1–108. o. . Supplemental medial plating of DFF with a Large Fragment LCP T-Plate is a feasible, safe, and economical option for both acute fixation and revisions. Further validation on a larger scale is warranted, along with considerations to developing a specific implant in line with these principles

Background. Previous in vivo fluoroscopic studies have documented that subjects having a PS TKA experience a more posterior condylar contact position at full extension, a high incidence of reverse axial rotation and mid flexion instability. More recently, a PS TKA was designed with a Gradually Reducing Radius (Gradius) curved condylar geometry to offer patients greater mid flexion stability while reducing the incidence of reverse axial rotation and maintaining posterior condylar rollback. Therefore, the objective of this study was to assess the in vivo kinematics for subjects implanted with a Gradius curved condylar geometry to determine if these subjects experience an advantage over previously designed TKA. Methods. In vivo kinematics for 30 clinically successful patients all having a Gradius designed PS fixed bearing TKA with a symmetric tibia were assessed using mobile fluoroscopy. All of the subjects were scored to be clinically successful. In vivo kinematics were determined using a 3D-2D registration during three weight-bearing activities: deep-knee-bend (DKB), gait, and ramp down (RD). Flexion measurements were recorded using a digital goniometer while ground reaction forces were collected using a force plate as well. The subjects then assessed for range of motion, condyle translation and axial rotation and ground reaction forces. Results. During a DKB, subjects implanted a Gradius designed, PS fixed bearing TKA design exhibited an average of 3.35 mm of posterior femoral rollback of the lateral condyle and 2.73 mm of the medial condyle with an average axial rotation of 4.90° in the first 90° of flexion. The average max flexion was 111.4°. From full extension to maximum flexion, the average axial rotation was 4.73°, while the subjects experienced 5.34 and 1.97 mm on the lateral and medial condyle rollback, respectively. During mid flexion from 30 to 60 degrees of flexion, the subjects experienced 1.34° of axial rotation, −1.13 and −0.11 mm of lateral and medial condyle motion. Conclusions. Subjects in this study did experience good weight-bearing flexion and magnitudes of axial rotation and posterior femoral rollback similar to previous PS TKA designs. During mid flexion, subjects in this study did experience less mid flexion paradoxical sliding than other PS TKA, leading to greater mid flexion stability for the patients

Background: It is known that not only the size but also the shape was different between races. We previously compared the distal femur shapes between the American and the Japanese by lateral radiograph and demonstrated the morphological difference in detail. In this study we evaluated the morphologic feature of the lateral and medial condyles separately between the American and the Japanese using MRI in the sagittal plane. Patients and methods: The subjects were 99 American and 41 Japanese adult women. MRI scan of sagittal section through the distal half of the femur was taken with the slice thickness about 4.0 mm. The envelope curve of each condyle was superimposed to be approximated to an ellipse. The length and inclination of two axes of the ellipse were estimated as the parameters of the statistical comparison. Results: The ratio major axis/minor axis of the lateral condyles in American women was significantly larger than that in Japanese, while the ratio of the medial condyles in American was significantly smaller. The inclination of the major axis to the anatomical axis of the distal femur in the American lateral condyles were significantly more than that in Japanese lateral condyles, while both the American and Japanese medial condyles showed similar inclination. Discussion: The morphological feature of both the lateral and medial condyles in American women was significantly different from that in Japanese. The ratio major axis/minor axis and inclination of lateral condyle in American women were different from those in Japanese, while only the ratio was different between the American and Japanese medial condyles. Understanding of these morphological differences between American and Japanese women is beneficial in elucidating discrepancies in normal knee kinematics and in tailoring the design and procedure for successful total knee arthroplasty

Background. The overall goal of total knee arthroplasty (TKA) is to facilitate the restoration of native function following late stage osteoarthritis and for this reason it is important to develop a thorough understanding of the mechanics of a normal healthy knee. While there are several methods for assessing TKA mechanics, these methods have limitations that make them prohibitive to both replicating physiological systems and evaluating non-implanted knees. These limitations can be circumvented through the development of mathematical models that use anatomical and physiological inputs to computationally simulate joint mechanics. This can be done in an inverse or forward manner to solve for either joint forces or motions respectively. The purpose of this study is to evaluate one such forward model and determine the accuracy of the predicted motions using fluoroscopy. Methods. In vivo kinematics were determined during flexion from full extension to 120 degrees for ten normal, healthy, subjects using fluoroscopy and a 3D-to-2D registration method. All ten subjects had previously undergone CT scans allowing for the digital reconstruction of native femur and tibia geometries. These geometries were then input into a ridged body forward model based on Kane's system of dynamics. The resulting kinematics determined through fluoroscopy and the mathematical model were compared for all of the ten subjects. Results. The three kinematic parameters evaluated for this study were the initial positioning and translation of the medial and lateral condylar contact point in addition to the axial position and rotation of the femur with respect to the tibia. The model simulations demonstrated an average of −2.16mm of medial condyle translation, −14.03mm of lateral condyle translation, and 20.09°of axial rotation. Through fluoroscopy, subjects demonstrated an average of −3.63mm of medial condyle translation, −16.02mm of lateral condyle translation, and 15.65°of axial rotation. Comparing these two methods the model predicted on average an additional 1.47mm of medial condyle translation, 1.98mm of lateral condyle translation, and 4.44° less axial rotation compared to the fluoroscopic analysis of the same ten subjects. Conclusion. In comparing the simulation kinematics to the that of the fluoroscopic assessment, the results are comparably similar demonstrating a forward model can be a viable assessment of knee kinematics in the future. By validating mathematical simulation as a feasible means of mechanical assessment, it becomes possible to evaluate mechanics using inputs to reflect extraordinary and theoretical instances such as trauma patients and congenital deformities unable to be assessed by other methods. The nature of the model also allows for a seamless transition to assess TKA mechanics, creating a more efficient means of evaluating both device design and surgical technique

Background. Although early TKA designs were symmetrical, during the past two decades TKA have been designed to include asymmetry, pertaining to either the trochlear groove, femoral condylar shapes or the tibial component. More recently, a new TKA was designed to include symmetry in all areas of the design, in the hopes of reducing design and inventory costs. Objective. The objective of this study was to determine the in vivo kinematics for subjects implanted with this symmetrical TKA during a weight-bearing deep knee bend activity. Methods. In vivo deep knee bend (DKB) kinematics for 21 subjects implanted with symmetrical posterior cruciate sacrificing (PCS) fixed bearing TKA were obtained using fluoroscopy. A 3D-to-2D registration technique was used to determine each subjects anteroposterior translation of lateral (LAP) and medial (MAP) femoral condyles and tibiofemoral axial rotation and their weight-bearing knee flexion. Results. During the DKB, the average maximum weight-bearing flexion was 111.7° ± 13.3°. On average, from full extension to maximum knee flexion, subjects experienced 2.5 mm ± 2.0 mm femoral rollback on lateral condyle −2.5 mm ± 2.2 mm of medial condyle motion in the anterior direction (Figure 1). This medial condyle motion was consistent for the majority of the subjects with the lateral condyle exhibiting rollback from 0° to 60° of flexion and then an average anterior slide of 0.3 mm from 60° to 90° of flexion. On average, the subjects in this study experienced 6.6° ± 3.3° of axial rotation, with most of rotation occurring in early flexion, averaging 4.9° (Figure 2). Discussion. Although subjects in this study were implanted with a symmetrical TKA, they did experience femoral rollback of the lateral condyle and positive axial rotation. Both of these kinematic parameters were normal-like in pattern, compared to the normal knee in early flexion, but in deeper flexion the pattern of motion varied from the normal knee. Also, the magnitude of posterior femoral rollback and axial rotation revealed similarities to previous fluoroscopy studies on subjects implanted with an asymmetrical TKA design. This was only a single surgeon study, so it is unclear if the results are TKA or surgeon influenced. Therefore, it is proposed that more patients be analyzed having this TKA implanted by other surgeons. For any figures or tables, please contact the authors directly

The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivo TKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 35% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years, supine, 16.3 mm3/yr (SD: 27.8) and 11.2 mm3/yr (SD: 18.5) versus standing, 51.3 mm3/yr (SD: 55.9) and 32.7 mm3/yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm3/yr) and 71% of patients at 2 years (Avg: 48.9 mm3/yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Volumetric, weight-bearing wear measurement of TKR using model-based RSA determined an average of 33 mm3/yr at 2 years post-surgery for a modern, non-cross-linked polyethylene bearing. This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, unknown patient activity level, and inability to distinguish wear from plastic creep or deformation under load. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. Further work is needed to validate the accuracy of the measurements in vivo

Aims. The purpose of this study was to explore the correlation between femoral torsion and morphology of the distal femoral condyle in patients with trochlear dysplasia and lateral patellar instability. Methods. A total of 90 patients (64 female, 26 male; mean age 22.1 years (SD 7.2)) with lateral patellar dislocation and trochlear dysplasia who were awaiting surgical treatment between January 2015 and June 2019 were retrospectively analyzed. All patients underwent CT scans of the lower limb to assess the femoral torsion and morphology of the distal femur. The femoral torsion at various levels was assessed using the a) femoral anteversion angle (FAA), b) proximal and distal anteversion angle, c) angle of the proximal femoral axis-anatomical epicondylar axis (PFA-AEA), and d) angle of the AEA–posterior condylar line (AEA-PCL). Representative measurements of distal condylar length were taken and parameters using the ratios of the bianterior condyle, biposterior condyle, bicondyle, anterolateral condyle, and anteromedial condyle were calculated and correlated with reference to the AEA, using the Pearson Correlation coefficient. Results. The femoral torsion had a strong correlation with distal condylar morphology. The FAA was significantly correlated with the ratio of the bianterior condyle (r = 0.355; p = 0.009), the AEA-PCL angle (r = 0.340; p = 0.001) and the ratio of the anterolateral condyle and lateral condyle (ALC-LC) (r = 0.309; p = 0.014). The PFA-AEA angle was also significantly correlated with the ratio of the bianterior condyle (r = 0.319; p = 0.008), the AEA-PCL angle (r = 0.231; p = 0.031), and the ratio of ALC-LC (r = 0.261; p = 0.034). In addition, the bianterior condyle ratio showed a significant correlation with the biposterior condyle ratio (r = -0.324; p = 0.027) and the AEA-PCL angle (r = 0.342; p = 0.021). Conclusion. Increased femoral torsion correlated with a prominent anterolateral condyle and a shorter posterolateral condyle compared with the medial condyle. The deformities of the anterior and posterior condyles are combined deformities rather than being isolated and individual deformities in patients with trochlear dysplasia and patella instability. Cite this article: Bone Joint J 2020;102-B(7):868–873

Purpose. The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Methods. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivoTKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Results. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 0–4% of calculated wear rates being negative compared to 29–39% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years; supine, 16.3 mm. 3. /yr (SD: 27.8) and 11.2 mm. 3. /yr (SD: 18.5) versus standing, 51.3 mm. 3. /yr (SD: 55.9) and 32.7 mm. 3. /yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm. 3. /yr) and 71% of patients at 2 years (Avg: 48.9 mm. 3. /yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Discussion and Conclusion. This study demonstrated TKA wear to occur at a rate of approximately 10 mm. 3. /year and 39 mm. 3. /year in patients imaged supine versus standing, respectively, averaged over 2 years of clinical follow-up. In an effort to eliminate the effect of PE creep and deformation, wear was also calculated between 12 and 24 months as 9.3 mm. 3. (standing examinations), This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, and unknown patient activity level. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. For any figures or tables, please contact authors directly