Abstract. BACKGROUND. Hemi-arthroplasty (HA) as a treatment for fractured neck of femur has slightly increased since 2019 and remarkably after the COVID pandemic. The main drawback of the treatment is ongoing cartilage deterioration that may require revision to THR. OBJECTIVE. This study assessed cartilage surface damage in hip HA by reproducing anatomical motion and loading conditions in a hip simulator. METHODS. Experimental design. HA tests were conducted using porcine acetabula and CoCr femoral heads. Five groups (n=4) were included: a control group comprising natural tissue and four HA groups where the acetabula were paired with metal heads to allow radial clearance (RC) classed as small (RC<0.6mm), large (2mm<RC<4mm), extra-large (4mm<RC), and oversized (RC<−0.6mm). Tests were carried out in an anatomical hip simulator that reproduced a simplified twin peak gait cycle, adapted for porcine hip joints, from the ISO 14242 standard for wear of THR prostheses (peak load of 900N). The test length was 6 hours, with photogrammetry taken at 1-hour intervals. Ringers solution was used as a lubricant. RESULTS. No changes were observed in the control group. However, cartilage surface changes were observed in all hemi-arthroplasty groups. Discolouration on the cartilage surface was noticeable at the posterior-superior part of the acetabulum after 1-hour (extra-large and oversized groups). Damage severity and location were characteristic of each clearance group. Of all the groups, the oversized group showed more significant damage. No labrum separation was seen after the simulation. CONCLUSIONS. These results are relevant to understand the effect of femoral head clearance on cartilage damage risk after HA. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Applications of weightbearing computed tomography (WBCT) imaging in the foot and ankle have emerged over the past decade. However, the potential diagnostic benefits are scattered across the literature, and a concise overview is currently lacking. Therefore, we aimed to systematically review all reported diagnostic applications per anatomical region in the foot and ankle. A systematic literature search was performed in the electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science. Search terms consisted of “weightbearing/standing CT and ankle, hind-, mid- or forefoot”. English language studies analyzing the diagnostic applications of WBCT were included. Studies were excluded if they simulated weightbearing CT, described normal subjects, included cadaveric samples or samples were case reports. The modified Methodological Index for Non-Randomized Studies (MINORS) was applied for quality assessment. The added value was defined as the review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and registered in the Prospero database (CRD42019106980). A total of 48 studies (prospective N=8, retrospective N=36, cohort study N=1, diagnostic N=2, prognostic comparative study N=1) were found to be eligible for review. The following diagnostic applications were identified per anatomical area in the foot: ankle (osteoarthritis N=5, ligament injury N=6); hindfoot (deformity N=9); midfoot (Lisfranc injury N=2, flatfoot deformity N=13, osteoarthritis N=1); forefoot (hallux valgus N=12). The identified studies contained diagnostic applications that could not be used on plain radiographs. The mean MINORS equaled 10.1 on a total of 16 (range: 8 to 12). Diagnostic applications of weightbearing CT imaging are most frequently studied in hindfoot deformity, but other area's areas are on the rise. Post-processing of images was identified as the main added value compared to WBRX. However, the findings should be interpreted with caution as the average quality score was moderate. Therefore, future prospective studies are warranted to consolidate the role of WBCT in diagnostic and therapeutic algorithms

Helical plates potentially bypass the medial neurovascular structures of the thigh. Recently, two plate designs (90°- and 180°-helix) proved similar biomechanically behaviour compared to straight plates. Aims of this study were: (1) Feasibility of MIPO-technique with 90°- and 180°-helical plates on the femur, (2) Assessment of distances to adjacent anatomical structures at risk, (3) Comparison of these distances to using medial straight plates instead, (4) Correlation of measurements performed in anatomic dissection with CT-angiography. MIPO was performed in ten cadaveric femoral pairs using either a 90°-helical 14-hole-LCP (Group1) or a 180°-helical 15-hole-LCP-DF (Group2). CT angiography was used to evaluate the distances between the plates and the femoral arteries as well as the distances between the plates and the perforators. Subsequently, the specimens were dissected, and the distances were determined again manually. Finally, all helical plates were removed, and all measurements were repeated after application of straight medial plates (Group3). Closest overall distances between plates and femoral arteries were 15 mm (11 − 19 mm) in Group1, 22 mm (15 − 24 mm) in Group2 and 6 mm (1 − 8 mm) in Group3 with a significant difference between Group1 and Group3 (p < 0.001). Distances to the nearest perforators were 24 mm (15 − 32 mm) in Group1 and 2 mm (1 − 4 mm) in Group2. Measurement techniques (visual after surgery and CT-angiography) demonstrated a strong correlation of r. 2. = 0.972 (p < 0.01). MIPO with 90°- and 180°-helical plates is feasible and safe. Attention must be paid to the medial neurovascular structures with 90°-helical implants and to the proximal perforators with 180°-helical implants. Helical implants can avoid medial neurovascular structures compared to straight plates although care must be taken during their distal insertion. Measurements during anatomical dissection correlate with CT-angiography

Hip joint biomechanics can be altered by abnormal morphology of the acetabulum and/or femur. This may affect load distribution and contact stresses on the articular surfaces, hence, leading to damage and degradation of the tissue. Experimental hip joint simulators have been used to assess tribology of total hip replacements and recently methods further developed to assess the natural hip joint mechanics. The aim of this study was to evaluate articular surfaces of human cadaveric joints following prolonged experimental simulation under a standard gait cycle. Four cadaveric male right hips (mean age = 62 years) were dissected, the joint disarticulated and capsule removed. The acetabulum and femoral head were mounted in an anatomical hip simulator (Simulation Solutions, UK). A simplified twin peak gait cycle (peak load of 3kN) was applied. Hips were submerged in Ringers solution (0.04% sodium azide) and testing conducted at 1 Hertz for 32 hours (115,200 cycles). Soft tissue degradation was recorded using photogrammetry at intervals throughout testing. All four hips were successfully tested. Prior to simulation, two samples exhibited articular surface degradation and one had a minor scalpel cut and a small area of cartilage delamination. The pre-simulation damage got slightly worse as the simulation continued but no new areas of damage were detected upon inspection. The samples without surface degradation, showed no damage during testing and the labral sealing effect was more obvious in these samples. The fact that no new areas of damage were detected after long simulations, indicates that the loading conditions and positioning of the sample were appropriate, so the simulation can be used as a control to compare mechanical degradation of the natural hip when provoked abnormal conditions or labral tissue repairs are simulated

Abstract. Introduction. Bone grafts are utilised in a range of surgical procedures, from joint replacements to treatment of bone loss resulting from cancer. Decellularised allograft bone is a regenerative, biocompatible and immunologically safe potential source of transplant bone. Objectives. To compare the structural and biomechanical parameters of decellularised and unprocessed (cellular) trabecular bone from the human femoral head (FH) and tibial plateau (TP). Methods. Bone pins were harvested from 10 FHs and 11 TPs (27, 34 respectively). Pins were decellularised (0.1% w/v sodium dodecyl sulphate) or retained as cellular controls. QA testing was carried out to assess protocol efficacy (total DNA and histological analysis). Cellular and decellularised FH (n=7) and TP (n=10) were uCT scanned. Material density (MD); apparent density (BV/TV); trabecular connectivity; trabecular number; trabecular thickness (Tb-t) and trabecular spacing were measured. Pins were then compression tested to determine ultimate compressive stress (UCS), Young's modulus and 0.2% proof stress. Results. Total DNA levels of decellularised bone were below 50 ng.mg. −1. dry weight. Cell nuclei and marrow were largely removed. No significant differences in properties were found between decellularised and cellular bone from either anatomical region (p>0.05, Mann-Whitney). No significant differences in biomechanical properties were found between cellular FH and cellular TP (p>0.05) though significant differences in structural properties were found (MD: TP>FH, p=0.001; BV/TV: FH>TP, p=0.001; and Tb-t: FH>TP, p=0.005). Significant differences were found between decellularised FH and decellularised TP (UCS: FH>TP, p=0.001; Young's modulus: FH>TP, p=0.002; proof stress; FH>TP, p=0.001; MD: TP>FH, p<0.001; BV/TV: FH>TP, p<0.001 and Tb-t: FHT>P p<0.001. Conclusion. Decellularisation did not affect the properties of human trabecular bone. Differences were found between the mechanical and structural properties of decellularised FH and TP which could facilitate stratified bone grafts for different applications. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

High ankle sprains (HAS) cause subtle lesions in the syndesmotic ligaments of the distal tibiofibular joint (DTFJ). Current intrinsic anatomical parameters of the DTFJ are determined based on 2D imaging and uncertainty remains whether they differ in a HAS patients. The aim of this study is therefore two-fold: radiographic parameters will be determined in 3D and compared in a healthy vs sprained group. Ten patients with a mean age of 42,56 (SD = 15,38) that sustained a HAS and twenty-five control subjects with a mean age of 47,44 (SD = 6,55) were retrospectively included. The slices obtained from CT analysis were segmented to have a 3D reconstruction. The following DTFJ anatomical parameters were computed using CAD software: incisura width, incisura depth, incisura length, incisura angle, and incisura-tibia ratio. The mean incisura depth in the sprained group was 3,93mm (SD = 0,80) compared to 4,76 mm (SD = 1,09) in the control group, which showed a significant difference (P < 0.05). The mean incisura length in the group of patients with HAS was 30,81 mm (SD = 3,17) compared to 36,10mm (SD = 5,27) in the control group which showed a significant difference (P < 0.05). The other DTFJ anatomical parameters showed no significant difference. This study shows a significant difference in both incisura depth and incisura length between HAS patients and control subjects. These parameters could be used to identify potential anatomical intrinsic risk factors in sustaining a HAS

Several previous pathoanatomical and biomechanical studies focused primarily on the cam morphology as the primary contributor to symptoms of femoroacetabular impingement (FAI) and limited range of motion. However, there is a growing population of individuals with asymptomatic cam morphologies who show no clinical signs; thus, the cam deformity, alone, may not fully delineate an individual's symptomatology or limited motion. These studies expanded beyond the cam morphology, to determine how additional anatomical characteristics could contribute to symptoms and influence functional mobility, using: 1) in vivo analyses, where we asked how specific anatomical parameters (in addition to the cam morphology) can predict individuals at risk of symptoms; 2) In silico simulations, where we examined how pathoanatomical features contributed to adverse loading conditions, resulting in higher risks of hip joint degeneration; 3) In vitro cadaveric experiments, where we examined the contributions of the cam morphology and encapsulating ligaments to joint mechanics and microinstability. This research further highlights that more emphasis should be placed on proper patient selection. There are implications of how structural anatomy can affect musculature, joint loading and stability, which should all be closely examined to improve the effectiveness of hip preservation surgery as well as the understanding of non-surgical management

Purpose. Addressing posterior tibial plateau fractures is increasingly recognized as an important prognostic factor for functional outcome. The treatment of posterior tibial plateau fractures is rather demanding and the implants are still standard, off-the-shelf implants. This emphasizes the need for a more thorough morphological study of the posterior tibial plateau, in order to treat these posterior fractures more adequately. We aimed to demonstrate anatomical variations of the tibia in order to develop better implants. Method. After approval of the ethical committee 22 historically available CT scans of intact left tibia”s were segmented using Mimics (Materialise, Belgium). In order to perform principal component analysis, corresponding meshes are necessary. Mesh correspondence was achieved by deforming one selected source tibia to every other target tibia, through non rigid registration. The non-rigid registration algorithm was based on the algorithm described by Amberg et al (ref). After performing the non-rigid registration, principal component analysis was performed in Matlab (Mathworks, USA). Results. The first 3 components account for 98,1% of the anatomical shape variation of the tibia. The first principal component accounts for 95,4, the second accounts for 1,6% and the third component accounts for the remaining 1,1% of variation. In the first principal component the most marked variation was the length and the shaft width. Shorter tibia”s have a steeper and more angled posterior medial and lateral plateau as where longer tibia”s have a more rounded posterior tibia plateau. On the distal end, the tip of the medial malleolus is more prominent in shorter tibia”s than in longer tibia”s. The orientation of the tibiofibular joint is directed more posteriorly in larger tibias where it is orientated more laterally in smaller tibia”s. The slope of the medial and lateral tibia plateau is not related to the length or width of the plateau. The second principal component shows a relationship between a valgus shaped tibia shaft and its relation to a relatively smaller medial plateau”s compared with straight tibia”s of the same length. Valgus shaped, small tibia shafts have more posteriorly tilted lateral plateau”s compared with straight, broad shafted tibias. The third principal component shows that an angular shaped posterior tibia plateau is related to a more increased anterior bowing. The increase in the posterior tilt is mostly marked in the medial tibia plateau. Conclusion. The majority of tibia shape variations is directly related to the length of the shaft. The clinically known varus and valgus deformations represent only a small percentage of the total variation. Nevertheless, their variation within the second component is large and has a direct relation to the morphology of the tibia plateau. This data coud furthermore be used to improve implant design

Wear of polyethylene is associated with aseptic loosening of orthopaedic implants and has been observed in hip and knee prostheses and anatomical implants for the shoulder. The reversed shoulder prostheses have not been assessed as yet. We investigated the volumetric polyethylene wear of the reversed and anatomical Aequalis shoulder prostheses using a mathematical musculoskeletal model. Movement and joint stability were achieved by EMG-controlled activation of the muscles. A non-constant wear factor was considered. Simulated activities of daily living were estimated from in vivo recorded data. After one year of use, the volumetric wear was 8.4 mm. 3. for the anatomical prosthesis, but 44.6 mm. 3. for the reversed version. For the anatomical prosthesis the predictions for contact pressure and wear were consistent with biomechanical and clinical data. The abrasive wear of the polyethylene in reversed prostheses should not be underestimated, and further analysis, both experimental and clinical, is required

Background:. The term ‘resident's ridge’ originated from trans-tibial ACL reconstruction where a bony ridge on the medial surface of the lateral femoral condyle was mistakenly thought to represent the posterior articular margin of the condyle. This was then mistakenly used to position the ‘over the top’ guide resulting in graft malposition. With anatomical anteromedial ACL reconstruction some surgeons use the same ridge to define the anterior margin of the ACL femoral insertion in order to guide graft placement. However there is debate about whether this ridge is a consistent and reliable anatomical structure. There are no anatomical studies that define the features of the ‘resident's ridge’. Therefore, our aim was to identify whether the ‘resident's ridge’ is a consistent anatomical structure in non-operated human cadaveric femoral specimens. Methods:. Using a digital microscribe, we mapped the medial surface of the lateral femoral condyle in cadaveric human femora denuded of soft tissue. This technique creates an exact 3D model of surfaces and from this we evaluated whether there was an identifiable bony ‘residents ridge’. 23 cadaveric specimens were used. Results:. All 23 specimens had a defined identifiable ridge on the medial surface of the lateral femoral condyle. When viewed anatomically, the proximal extent of the ridge lies at the superior junction of the articular margin and the femoral shaft. From this point, the ridge forms an oblique line travelling proximal-to-distal and anterior-to-posterior to a point approximately 30–40% anterior to the posterior articular margin. The ridge therefore divides the medial surface into anterior 2/3. rd. and posterior 1/3. rd. when viewed anatomically. Conclusion:. This study shows that the “resident's ridge” is a consistent anatomical structure that defines the anterior margin of the ACL insertion. This therefore supports its use as a landmark for femoral tunnel placement in ACL reconstruction surgery

In vitro biomechanical tests allow obtaining important information about stresses and deformations inside the bone, and about the displacements of the prosthetic device under physiological load conditions. This information may be helpful for the development of innovative devices, for the improvement of the existing ones, and for defining optimized procedure for bone reconstruction depending on the typology of bone defects. The definition of a robust and reproducible reference frame is the first step in order to perform a consistent biomechanical test [1]. The aims of the current study was to define an anatomical reference frame for pelvis which can also be applied to a hemi-pelvis. A robust alignment method was sought so as to replicate the anatomical pose during in vitro applications. The intra- and inter- operator repeatability was quantified to corroborate the results. The anatomical reference frame was derived from the anterior pelvic plane [2] and was adapted for in vitro applications. It was based on the following anatomical landmarks: Anterior Superior Iliac Spine (ASIS, defined as the most prominent point on the external iliac surface); Posterior Superior Iliac Spine (PSIS) defined as the upper and most prominent projection on the posterior border of the iliac wing); Pubic Tubercle (PT, defined as the most medial point on the extension of inner line of upper oval foramen). The alignment procedure represented an improved version of a previous procedure [3]. The hemi-pelvis has been positioned on blocks of plasticine close to the landmarks on a 5-screws adjustable plate. Three steps were performed: position of the landmarks at the same height; alignment of the PSIS and PT on a horizontal line parallel to x- direction; position of the setup in front of a 6 degrees of freedom manipulator so that both the manipulator and the 5-screws adjustable plate are in the same reference frame. The manipulator was used to move the specimen in the following steps: clamping and lifting up of the specimen; rotation around x-axis in the posterior direction by 45°; rotation around y-axis in the medial direction by 90°; rotation around x-axis (antero-posterior direction) until PT and ASIS lay in the same vertical plane. Five operators performed the alignment of a male and a female hemi-pelvis, three times each. The repeatability of the current procedure was good, with uncertainties below 1.0° within the same operator, and of less than ±1.5° between operators for the male hemipelvis, and ±2° for the female one. Thanks to the good results the reference frame and the alignment procedure may be adopted for in vitro biomechanical testing on hemi-pelvic specimen, for example to test acetabular bone reconstruction or acetabular prosthetic devices

Hydroxyapatite-coated standard anatomical and customised femoral stems are designed to transmit load to the metaphyseal part of the proximal femur in order to avoid stress shielding and to reduce resorption of bone. In a randomised in vitro study, we compared the changes in the pattern of cortical strain after the insertion of hydroxyapatite-coated standard anatomical and customised stems in 12 pairs of human cadaver femora. A hip simulator reproduced the physiological loads on the proximal femur in single-leg stance and stair-climbing. The cortical strains were measured before and after the insertion of the stems. Significantly higher strain shielding was seen in Gruen zones 7, 6, 5, 3 and 2 after the insertion of the anatomical stem compared with the customised stem. For the anatomical stem, the hoop strains on the femur also indicated that the load was transferred to the cortical bone at the lower metaphyseal or upper diaphyseal part of the proximal femur. The customised stem induced a strain pattern more similar to that of the intact femur than the standard, anatomical stem

Helical plates are preferably used for proximal humeral shaft fracture fixation and potentially avoid radial nerve irritation as compared to straight plates. Aims:(1) to investigate the safety of applying different long plate designs (straight, 45°-, 90°-helical and ALPS) in MIPO-technique to the humerus. (2) to assess and compare their distances to adjacent anatomical structures at risk.

MIPO was performed in 16 human cadaveric humeri using either a straight plate (group1), a 45°-helical (group2), a 90°-helical (group3) or an ALPS (group4). Using CT-angiography, distances between brachial arteries and plates were evaluated. Following, all specimens were dissected, and distances to the axillary, radial and musculocutaneous nerve were evaluated.

None of the specimens demonstrated injuries of the anatomical structures at risk after MIPO with all investigated plate designs. Closest overall distance (mm(range)) between each plate and the radial nerve was 1(1-3) in group1, 7(2-11) in group2, 14(7-25) in group3 and 6(3-8) in group4. It was significantly longer in group3 and significantly shorter in group1 as compared to all other groups, p<0.001. Closest overall distance (mm(range)) between each plate and the musculocutaneous nerve was 16(8-28) in group1, 11(7-18) in group2, 3(2-4) in group3 and 6(3-8) in group4. It was significantly longer in group1 and significantly shorter in group3 as compared to all other groups, p<0.001. Closest overall distance (mm(range)) between each plate and the brachial artery was 21(18-23) in group1, 7(6-7) in group2, 4(3-5) in group3 and 7(6-7) in group4. It was significantly longer in group1 and significantly shorter in group3 as compared to all other groups, p<0.021.

MIPO with 45°- and 90°-helical plates as well as ALPS is safely feasible and showed a significant greater distance to the radial nerve compared to straight plates. However, distances remain low, and attention must be paid to the musculocutaneous nerve and the brachial artery when MIPO is used with ALPS, 45°- and 90°-helical implants. Anterior parts of the deltoid insertion will be detached using 90°-helical and ALPS implants in MIPO-technique.

Aim. The aim of this study is to outline the steps and techniques required to create a patient specific 3D printed guide for the accurate placement of the origin of the femoral tunnel for single bundle ACL reconstruction. Introduction. Placements of the femoral tunnels for ACL reconstruction have changed over the years. Most recently there has been a trend towards placing the tunnels in a more anatomic position. There has been subsequent debate as to where this anatomic position should be. The problem with any attempt at consensus over the placement of an anatomic landmark is that each patient has some variation in their positioning and therefore a fixed point for all has compromise for all as it is an average. Our aim was to attempt to make a cost effective and quick custom guide that could allow placement of the center of the patients’ newly created femoral tunnel in the mid position of their contralateral native ACL femoral footprint. Materials & Methods. We took a standard protocol MRI scan of a patient's knee without ACL injury transferred the DICOM files to a personal computer running OsiriX (Pixmeo, Geneva, Switzerland.) and analysed it for a series of specific anatomical landmarks. OsiriX is an image processing software dedicated to DICOM images. We marked the most posterior edge of the articular cartilage on the lateral wall of the notch (1), the most anterior edge of the articular cartilage of the lateral wall of the notch (2), the most inferior edge of the articular cartilage of the lateral wall of the notch (3) and the center of the femoral footprint of the native ACL. Distances were then calculated to determine the position relative to the three articular cartilage points of the center of the ACL footprint. These measurements and points were then utilised to create a 3D computer aided design (CAD) model of a custom guide. This was done using the 3D CAD program 123Design (Autodesk Ltd., Farnbourgh, Hampshire). This 3D model was then exported as an STL file suitable for 3D printing. The STL file was then uploaded to an online 3D printing service and the physical guide was created in transparent acrylic based photopolymer, PA220 plastic and 316L stainless steel. The models created were then measured using vernier calipers to confirm the accuracy of the final guides. Results. The MRI data showed point 1 (AP), point 2 (distal-ACL), point 3 (Ant-ACL) and point 4 (Post-ACL) at a distance of 59.83, 15, 45.8 and 13.9 respectively. For the 3D CAD model, points 1, 2, 3 and 4 were at a distance of 59.83, 15, 45.8 and 13.9 respectively. For the PA220 plastic model, points 1, 2, 3 and 4 were at a distance of 59.86, 14.48, 45.85 and 13.79 respectively. For the 316L stainless steel model, points 1, 2, 3 and 4 were at a distance of 59.79, 14.67, 45.64 and 13.48 respectively. Lastly, for the photopolymer model, points 1, 2, 3 and 4 were at a distance of 59.86, 14.2, 45.4 and 13.69 respectively. The p-value comparing MRI/CAD vs. PA220 was p=0.3753; for the comparison between MRI/CAD vs. 316L, p=0.0683; lastly for the comparison between MRI/CAD Vs. Photopolymer, p=0.3450. The models produced were accurate with no statistical difference in size and positioning of the center of the ACL footprint from the original computer model and to the position of the ACL from the MRI scans. The costs for the models 3D printed were £3.50 for the PA220 plastic, £15 for the transparent photopolymer and £25 for the 316L stainless steel. The time taken from MRI to delivery for the physical models was 7 days. Discussion. Articles regarding the creation of 3D printed custom ACL guides from the patients contralateral knee do not feature in current literature. There has been much research on custom guides for other orthopaedic procedures such as in total knee arthroplasty for the accurate placement of implants. There has also been research published on the creation of custom cutting jigs from CT for complex corrective osteotomy surgery. This study serves as the first step and a proof of concept for the accurate creation of patient specific 3D printed guides for the anatomical placement of the femoral tunnel for ACL reconstruction. The guides were easy to create and produce taking only a week and with a cost of between £3.50 and £25. The design of the guides was to allow the tip of a standard Chondro Pick (Arthrex inc., Naples, Florida.) (3mm) used to mark the starting point of the femoral tunnel to enter through the guide. The next step for this research is to create guides from cadaveric matched knees and utilise the guides to carry out the creation of the femoral tunnels and to analyse of the placement of the tunnel in relation to the contralateral knee

Transverse patella fractures are commonly encountered in trauma surgery, open reduction and internal fixation are considered the gold standard treatment modality that could permit early knee motion and immediate rehabilitation. Many fixation methods had been defined and compared to each other's in many clinical and biomechanical studies. The aim of this study was to assess the safety and stability of our novel anatomical patella plate and to compare its stability with tension band-wire technique. A total of 12 cadaveric preserved knees (six right and six left patellae) with close patellar size were chosen to form two groups of six samples. Each group received either plate or tension band-wiring fixation for an experimentally created patella fracture. Cyclic load of an average of 350 N was applied for all specimens and after accomplishing 50 cycles the displacements of all fracture edges were recorded. After completing 50 cycles in each group, the average fracture edges displacement measured in the plate group was 1.98 ± 0.299 mm, whereas the average fracture edges displacement measured in the tension band-wire group was 2.85 ± 0.768 mm (p = 0.016). In the operative treatment of displaced transverse patellar fractures, the strength of fixation obtained by titanium curved plates is highly stronger when compared to the fixation with a tension band-wire technique. Fixation with titanium curved plates provides satisfactory stability at the fracture site which allow withstanding the cyclic loads during the postoperative rehabilitation

Malpositioning of the trochanteric entry point during the introduction of an intramedullary nail may cause iatrogenic fracture or malreduction. Although the optimal point of insertion in the coronal plane has been well described, positioning in the sagittal plane is poorly defined. . The paired femora from 374 cadavers were placed both in the anatomical position and in internal rotation to neutralise femoral anteversion. A marker was placed at the apparent apex of the greater trochanter, and the lateral and anterior offsets from the axis of the femoral shaft were measured on anteroposterior and lateral photographs. Greater trochanteric morphology and trochanteric overhang were graded. The mean anterior offset of the apex of the trochanter relative to the axis of the femoral shaft was 5.1 mm (. sd. 4.0) and 4.6 mm (. sd. 4.2) for the anatomical and neutralised positions, respectively. The mean lateral offset of the apex was 7.1 mm (. sd. 4.6) and 6.4 mm (. sd. 4.6), respectively. Placement of the entry position at the apex of the greater trochanter in the anteroposterior view does not reliably centre an intramedullary nail in the sagittal plane. Based on our findings, the site of insertion should be about 5 mm posterior to the apex of the trochanter to allow for its anterior offset. Cite this article: Bone Joint J 2014;96-B:1274–81

A correct ligament loading following TKA surgery is believed to minimize instability and improve patient satisfaction. The evaluation of the ligament stress or strain is however impractical in a surgical setting. Alternatively, tibial trial components containing force sensors have the potential to indirectly assess the ligament loading. These instrumented components quantify the medial and lateral forces in the tibiofemoral joint. Although this method finds clinical application already, the target values for both the force magnitude and medial / lateral force ratio under surgical conditions remain uncertain. A total of eight non-arthritic cadaveric knees have been tested mimicking surgical conditions. Therefore, the specimens are mounted in a custom knee simulator. This simulator allows to test full lower limb specimens, providing kinematic freedom throughout the range of motion. Knee flexion is obtained by lifting the femur (thigh pull). Knee kinematics are simultaneously recorded by means of a navigation system and based on the mechanical axis of the femur and tibia. In addition, the load transferred through the medial and lateral compartment of the knee is monitored. Therefore, a 2.4 mm thick sawing blade is used to machine a slot in the tibia perpendicular to the mechanical axis, at the location of the tibial cut in TKA surgery. A complete disconnection was thereby assured between the tibial plateau and the distal tibia. To fill the created gap, custom 3D printed shims were inserted. Through their specific geometry, these shims create a load deviation between two Tekscan pressure pads on the medial and lateral side. Following the insertion of the shims, the knee was closed before performing the kinematic and kinetic tests. Seven specimens showed a limited varus throughout the range of motion (ranging from 1° to 7° varus). The other knee was in valgus (4° valgus). Amongst varus knees, the results were very consistent, indicating high loads in full extension. Subsequently, the loads decrease as the knee flexes and eventually vanishes on the lateral side. This leads to consistently high compartmental load ratios (medial load / total load) in flexion. In full extension the screw-home mechanism results in increased loads, both medially and laterally. Upon flexion, the lateral loads disappear. This is attributed to slackening of the lateral collateral ligament, in turn linked to the femoral rollback and slope of the lateral compartment. The isometry of the medial collateral ligament contributes on the other hand to the near-constant load in the medial compartment. The above particularly applies for varus knees. The single valgus knee tested indicated a higher load transmission by the lateral compartment, potentially attributed to a contracture of the lateral structures. With respect to TKA surgery, these findings are particularly relevant when considering anatomically designed implants. For those implants, this study concludes that a tighter medial compartment reflects that of healthy varus knees. Be aware however that in full extension, higher and up to equal loads can be acceptable for the medial and lateral compartment

High tibial osteotomy (HTO) is an effective surgical treatment for isolated medial compartment knee osteoarthritis; however, widespread adoption is limited due to difficulty in achieving the planned correction, and patient dissatisfaction due to soft tissue irritation. A new HTO system – Tailored Osteotomy Knee Alignment (TOKA®, 3D Metal Printing Ltd, Bath, UK) could potentially address these barriers having a custom titanium plate and titanium surgical guides featuring a unique mechanism for precise osteotomy opening as well as saw cutting and drilling guides. The aim of this study was to assess the accuracy of this novel HTO system using cadaveric specimens; a preclinical testing stage ahead of first-in-human surgery according to the ‘IDEAL-D’ framework for device innovation.

Local ethics committee approval was obtained. The novel opening wedge HTO procedure was performed on eight cadaver leg specimens. Whole lower limb CT scans pre- and post-operatively provided geometrical assessment quantifying the discrepancy between pre-planned and post-operative measurements for key variables: the gap opening angle and the patient specific surgical instrumentation positioning and rotation - assessed using the implanted plate.

The average discrepancy between the pre-operative plan and the post-operative osteotomy correction angle was: 0.0 ± 0.2°. The R2 value for the regression correlation was 0.95.

The average error in implant positioning was −0.4 ± 4.3 mm, −2.6 ± 3.4 mm and 3.1 ± 1.7° vertically, horizontally, and rotationally respectively.

This novel HTO surgery has greater accuracy and smaller variability in correction angle achieved compared to that reported for conventional or other patient specific methods with published data available. This system could potentially improve the accuracy and reliability of osteotomy correction angles achieved surgically.

Introduction. Glenoid loosening, still a main complication for shoulder arthroplasty, was suggested to be related implant design, surgical aspects, and also bone quality. However, typical studies of fixation do not account for heterogeneity in bone morphology and density which were suggested to affect fixation failure. In this study, a combination of cyclic rocking horse tests on cadaver specimens and microCT-based finite element (microFE) analysis of specimens of a wide range of bone density were used to evaluate the effects of periprosthetic bone quality on the risks of loosening of anatomical keeled or pegged glenoid implants. Methods. Six pairs of cadaveric scapulae, scanned with a quantitative computer tomography (QCT) scanner to calculate bone mineral density (BMD), were implanted with either cemented anatomical pegged or keeled glenoid components and tested under constant glenohumeral load while a humeral head component was moved cyclically in the inferior and superior directions. Edge displacements were measured after 1000, 4000 and 23000 test cycles, and tested for statistical differences with regards to changes or implant design. Relationships were established between edge displacements and QCT-based BMD below the implant. Four other specimens were scanned with high-resolution peripheral QCT (82µm) and implanted with the same 2 implants to generate virtual models. These were loaded with constant glenohumeral force, varying glenohumeral conformity and superior or inferior load shifts while internal stresses at the cement-bone and implant-cement interfaces were calculated and related to apparent bone density in the periprosthetic zone. Results. Mean displacements at the inferior and superior edges showed no statistical difference between keeled and pegged designs (p>0.05). Compression and distraction were however statistically different from the initial reference measurement at even 1000 and 4000 cycles for both implant designs (p<0.05). For both implant designs, superior and inferior distractions were generally highest at each measurement time in specimens where BMD below the lifting edge was lower, showing a trend of increased distraction with decreased BMD. Moreover, the microFE models predicted higher bone and cement stresses for specimens of lower apparent bone density. Finally, highest peak stresses were located at the cement-bone interface, which seemed the weaker part of the fixation. Discussion. With this combined experimental and numerical study, it was shown that implant distraction and stresses in the cement layer are greater in glenoids of lower bone density for both implant designs. This indicates that fixation failure will most likely occur in bone of lower density, and that fixation design itself may play a secondary role. These results have important impact for understanding the mechanisms of glenoid component failure, a common complication of total shoulder arthroplasty

Background. The traditional Kocher approach for lateral elbow exposure is often complicated by injury to the posterior interosseous nerve (PIN) and the lateral ulnar collateral ligamentous (LUCL). Kaplan approach is less commonly used, due to its known proximity to the PIN. Extensor Digitorum Communis (EDC) splitting approach allows possible wide surgical exposure and low risk of LUCL damage. The comparison of PIN injury during surgical dissection among these 3 common lateral approaches was not previously evaluated. We aim to determine the anatomical proximity of the PIN in these 3 common lateral elbow approaches and to define a safe zone of dissection for the surgical exposure. Methods. Cadaveric dissections of 9 pairs of fresh frozen adult upper extremities were performed using EDC splitting, Kaplan and Kocher approach to the radial head sequentially in a randomised order. The radial head and PIN were exposed. A mark was made on the radial head upon the initial exposure during dissection. Measurements from the marked point of the radial head to the PIN were made. Study has been approved by the ethics committee. Results. The EDC splitting approach is associated with a significantly lower chance of encountering the PIN along the entry of dissection to reach the radial head as compared to the Kaplan approach. The Kocher approach has a lower chance of encountering the PIN along the entry of dissection to reach the radial head as compared to both Kaplan and EDC splitting approach. Conclusions. The EDC splitting approach provides adequate exposure without injury to the lateral ligamentous complex nor need to elevate or retract the EDC and ECU muscle mass that could risk injuring the PIN. The Kaplan approach should be done by experienced surgeons who are familiar with the anatomy in this region, with extreme caution due to proximity of the point of entry to the PIN. Level of evidence. IV