Osteonecrosis is a potentially devastating condition with poorly defined pathogenesis that can affect several anatomical areas with or without a previous traumatic insult. Post traumatic osteonecrosis (PON) in the foot and ankle has been commonly described in the talus and navicular but rarely in the distal tibia. PON of the distal tibia is a rarely reported and infrequent complication of fracture dislocations of the ankle. Its scarcity can lead to misdiagnosis and inappropriate management due to a lack of clinical knowledge or suspicion with resultant severe functional compromise. We aim to highlight the clinical and radiological features of PON of the distal tibia and report the findings in a series of four patients following a fracture dislocation of the ankle. Three patients sustained a SER4 fracture dislocation and one patient sustained a PER4 fracture dislocation in keeping with standard patterns of injury seen in most trauma units. In each case, PON of the distal tibia presented with progressive anterolateral tibial plafond collapse and valgus deformity of the ankle. The radiological features previously reported in the literature are based on plain film x-ray, CT and MRI but no description of SPECT-CT findings. One of the patients in the series underwent SPECT-CT following clinical suspicion of PON and thus we describe the findings not previously reported. Our objective is to highlight this rare condition as a potential cause for ongoing pain following fracture dislocation of the ankle as well as advocating the use of SPECT/CT as a useful imaging modality to aid in the diagnosis

The incisura fibularis (IF) provides intrinsic stability to the ankle joint complex by interlocking the distal tibia and fibula. Despite a high frequency of ligamentous ankle injuries, scant attention has been given to the morphology of the IF morphology incisura fibularis in the onset and development of these lesions. Therefore, we systematically reviewed the relation between ligamentous ankle disorders and the morphometrics of the IF. A systematic literature search was conducted on following databases: PubMed, Embase and Web of Science. Search terms consisted of ‘ankle trauma’, ‘ankle injury’, ‘ankle sprain’, ‘ankle fracture’, ‘tibiofibular’, ‘fibular notch’, ‘fibular incisura’, ‘incisura fibularis’, ‘morphometric analysis’, ‘ankle syndesmosis’, ‘syndesmotic stability’. The evaluation instrument developed by Hawker et al. was used to assess the quality of the selected studies. This protocol was performed according to the PRISMA guidelines and is registered on PROSPERO (CRD42021282862). Nineteen studies were included and consisted of prospective cohort (n=1), retrospective comparative (n=10), and observational (n=8) study design. Comparative studies have found certain morphological characteristics in patients with ankle instability. Several studies (n=5) have correlated a shallow IF depth with a higher incidence of ankle injury. A significant difference has also been found concerning the incisura height and angle (n=3): a shorter incisura and more obtuse angle have been noted in patients with ankle sprains. The mean Hawker score was 28 out of 36 (range=24-31). A shallower IF is associated with ligamentous ankle lesions and might be due to a lower osseous resistance against tibiofibular displacement. However, these results should be interpreted in light of moderate methodological quality and should always be correlated with clinical findings. Further prospective studies are needed to further assess the relation between the incisura morphometrics and ligamentous disorders of the ankle joint. Keywords: ankle instability, ankle injury, incisura fibularis, fibular notch, tibiofibular morphometrics, ankle syndesmosis

Abstract. Objectives. The syndesmosis joint, located between the tibia and fibula, is critical to maintaining the stability and function of the ankle joint. Damage to the ligaments that support this joint can lead to ankle instability, chronic pain, and a range of other debilitating conditions. Understanding the kinematics of a healthy joint is critical to better quantify the effects of instability and pathology. However, measuring this movement is challenging due to the anatomical structure of the syndesmosis joint. Biplane Video Xray (BVX) combined with Magnetic Resonance Imaging (MRI) allows direct measurement of the bones but the accuracy of this technique is unknown. The primary objective is to quantify this accuracy for measuring tibia and fibula bone poses by comparing with a gold standard implanted bead method. Methods. Written informed consent was given by one participant who had five tantalum beads implanted into their distal tibia and three into their distal fibula from a previous study. Three-dimensional (3D) models of the tibia and fibula were segmented (Simpleware Scan IP, Synopsis) from an MRI scan (Magnetom 3T Prisma, Siemens). The beads were segmented from a previous CT and co-registered with the MRI bone models to calculate their positions. BVX (125 FPS, 1.25ms pulse width) was recorded whilst the participant performed level gait across a raised platform. The beads were tracked, and the bone position of the tibia and fibula were calculated at each frame (DSX Suite, C-Motion Inc.). The beads were digitally removed from the X-rays (MATLAB, MathWorks) allowing for blinded image-registration of the MRI models to the radiographs. The mean difference and standard deviation (STD) between bead-generated and image-registered bone poses were calculated for all degrees of freedom (DOF) for both bones. Results. The absolute mean tibia and fibula bone position differences (Table 1) between the bead and BVX poses were found to be less than 0.5 mm for both bones. The bone rotation differences were found to be less than 1° for all axes except for the fibula Z axis rotation which was found to be 1.46°. One study. 1. has reported the kinematics of the syndesmosis joint and reported maximum ranges of motion of 9.3°and translations of 3.3mm for the fibula. The results show that the accuracy of the methodology is sufficient to quantify these small movements. Conclusions. BVX combined with MRI can be used to accurately measure the syndesmosis joint. Future work will look at quantifying the accuracy of the talus to provide further understanding of normal ankle kinematics and to quantify the kinematics across a healthy population to act as a comparator for future patient studies. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Epiphysiodesis is a commonly used treatment for lower limb angular deformities. However, in recent years, distal tibial growth modulation using ‘eight plates’ or screws has emerged as an alternative treatment for paediatric foot and ankle disorders, such as CTEV. Our objective was to assess the efficacy of distal tibial modulation in correcting various paediatric foot and ankle disorders. Methods. This retrospective study analysed 205 cases of paediatric foot and ankle disorders treated between 2003 and 2022, including only cases where the eight plate or screw was fixed on the anterior surface of the distal tibia. Our aim was to measure post-operative changes in dorsiflexion, the distal tibial angle, and the tibiocalcaneal angle by examining clinical records and radiology reports. Results. We identified nine cases (nine feet) meeting the full inclusion criteria, comprising seven cases of CTEV, one case of arthrogryposis, and one case of cavovarus foot. The cohort consisted of five male and four female patients, with a mean age of 10 years and 9 months at the time of surgery. Seven cases involved the left tibia, and two cases involved the right tibia. The mean time between pre-operative X-ray to surgery was 168 days, and the mean turnaround time between surgery and post-operative X-ray was 588 days. A mean change in the distal tibial angle of 4.33 degrees was noted. However, changes in dorsiflexion were documented in only one case, which showed a change of 13 degrees. Notably, our average distal tibial angle was significantly lower than reported in the literature, at 4.33 degrees. Additionally, some studies in the literature used the Oxford Ankle Foot Questionnaire for Children to assess pre- and post-operative outcomes, but it is important to note that it is validated only for children aged 5 to 16. Furthermore, most cases reported an improved tibiocalcaneal angle except for an anomaly of 105 degrees. We assessed satisfactory patient outcomes using patient notes. Out of the 6 procured notes, one has been discharged. The rest are still under yearly or 6-monthly review and are at various stages, such as physiotherapy, removing the eight plate, or requiring further surgery. The most common presentations at review are plantaris deformity and pain. Conclusions. Our study suggests that distal tibial growth modulation can be an effective treatment option for selected paediatric foot and ankle disorders. However, due to the limited number of cases in our study, the lack of documentation of changes in dorsiflexion, and a lack of pre- and post-operative outcomes using a standardised method, further research is needed to investigate this procedure's long-term outcomes and potential complications. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction and Objective. Forced external rotation is hypothesized as the key mechanism of syndesmotic ankle injuries. This complex trauma pattern ruptures the syndesmotic ligaments and induces a three-dimensional deviation from the normal distal tibiofibular joint configuration. However, current diagnostic imaging modalities are impeded by a two-dimensional assessment, without taking into account ligamentous stabilizers. Therefore, our aim is two-fold: (1) to construct an articulated statistical shape model of the normal ankle with inclusion of ligamentous morphometry and (2) to apply this model in the assessment of a clinical cohort of patients with syndesmotic ankle injuries. Materials and Methods. Three-dimensional models of the distal tibiofibular joint were analyzed in asymptomatic controls (N= 76; Mean age 63 +/− 19 years), patients with syndesmotic ankle injury (N = 13; Mean age 35 +/− 15 years), and their healthy contralateral equivalent (N = 13). Subsequently, the statistical shape model was generated after aligning all ankles based on the distal tibia. The position of the syndesmotic ligaments was predicted based on previously validated iterative shortest path calculation methodology. Evaluation of the model was described by means of accuracy, compactness and generalization. Canonical Correlation Analysis was performed to assess the influence of syndesmotic lesions on the distal tibiofibular joint congruency. Results. Our presented model contained an accuracy of 0.23 +/− 0.028 mm. Mean prediction accuracy of ligament insertions was 0.53 +/− 12 mm. A statistically significant difference in anterior syndesmotic distance was found between ankles with syndesmotic lesions and healthy controls (95% CI [0.32, 3.29], p = 0.017). There was a significant correlation between presence of syndesmotic injury and the morphological distal tibiofibular configuration (r = 0.873, p <0,001). Conclusions. In this study, we constructed a bony and ligamentous statistical model representing the distal tibiofibular joint Furthermore, the presented model was able to detect an elongation injury of the anterior inferior tibiofibular ligament after traumatic syndesmotic lesions in a clinical patient cohort

Introduction and Objective. Intramedullary nails are frequently used for treatment of unstable distal tibia fractures. However, insufficient fixation of the distal fragment could result in delayed healing, malunion or nonunion. The quality of fixation may be adversely affected by the design of both the nail and locking screws, as well as by the fracture pattern and bone density. Recently, a novel concept for angular stable nailing has been developed that maintains the principle of relative stability and introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction. It incorporates polyether ether ketone (PEEK) inlays integrated in the distal and proximal canal portions of the nail for angular stable screw locking. The nail can be used with new standard locking screws and low-profile retaining locking screws, both designed to enhance cortical fixation. The low-profile screws are with threaded head, anchoring in the bone and increasing the surface contact area due to the head's increased diameter. The objective of this study was to investigate the biomechanical competence of the novel angular stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared with four other nail designs in an artificial bone model under dynamic loading. Materials and Methods. The distal 70 mm of thirty artificial tibiae (Synbone) were assigned to 5 groups for distal locking using either four different commercially available nails – group 1: Expert Tibia Nail (DePuy Synthes); group 2: TRIGEN META-NAIL with Internal Hex Captured Screws (Smith & Nephew); group 3: T2 Alpha with Locking Screws (Stryker); group 4: Natural Nail System featuring StabiliZe Technology (Zimmer) – or the novel angular stable TN-Advanced nail with low-profile screws (group 5, DePuy Synthes). The distal locking in all groups was performed using 2 mediolateral screws. All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure, with monitoring by means of motion tracking. Results. Initial nail toggling of the distal tibia fragment in group 5 was significantly lower as compared with group 3 in varus (p=0.04) or with groups 2 and 4 in flexion (p≤0.02). In addition, the toggling in varus was significantly lower in group 1 versus group 4 (p<0.01). Moreover, during dynamic loading, within the course of the first 10,000 cycles the movements of the distal fragment in terms of varus, flexion, internal rotation, as well as axial and shear displacements at the fracture site, were all significantly lower in group 5 compared with group 4 (p<0.01). Additionally, group 5 demonstrated significantly lower values for flexion versus groups 2 and 3 (p≤0.04), for internal rotation versus group 1 (p=0.03), and for axial displacement versus group 3 (p=0.03). A trend to significantly lower values was detected in group 5 versus group 1 for varus, flexion and shear displacement – with p ranging between 0.05 and 0.07 – and versus group 3 for shear displacement (p=0.07). Cycles to failure were highest in group 5 with a significant difference to group 4 (p<0.01). Conclusions. From a biomechanical perspective, the novel angular stable intramedullary nail concept with integrated PEEK inlays and low-profile screws provides ameliorated resistance against nail toggling and loss of reduction under static and dynamic loading compared with other commercially available intramedullary nails used for fixation of unstable distal tibia fractures

Unstable distal tibia fractures are challenging injuries requiring surgical treatment. Intramedullary nails are frequently used; however, distal fragment fixation problems may arise, leading to delayed healing, malunion or nonunion. Recently, a novel angle-stable locking nail design has been developed that maintains the principle of relative construct stability, but introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction, without the requirement for additional intraoperative procedures. The aim of this study was to investigate the biomechanical competence of a novel angle-stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared to a conventional nail in a human cadaveric model under dynamic loading. Ten pairs of fresh-frozen human cadaveric tibiae with a simulated AO/OTA 42-A3.1 fracture were assigned to 2 groups for reamed intramedullary nailing using either a conventional (non-angle-stable) Expert Tibia Nail with 3 distal screws (Group 1) or the novel Tibia Nail Advanced system with 2 distal angle-stable locking low-profile screws (Group 2). The specimens were biomechanically tested under conditions including quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure of the bone-implant construct, with monitoring by means of motion tracking. Initial axial construct stiffness, although being higher in Group 2, did not significantly differ between the 2 nail systems, p=0.29. In contrast, initial torsional construct stiffness was significantly higher in Group 2 compared to Group 1, p=0.04. Initial nail toggling of the distal tibia fragment in varus and flexion was lower in Group 2 compared to Group 1, being significant in flexion, p=0.91 and p=0.03, respectively. After 5000 cycles, interfragmentary movements in terms of varus, flexion, internal rotation, axial displacement and shear displacement at the fracture site were all lower in Group 2 compared to Group 1, with flexion and shear displacement being significant, p=0.14, p=0.04, p=0.25, p=0.11 and p=0.04, respectively. Cycles to failure until both interfragmentary 5° varus and 5° flexion were significantly higher in Group 2 compared to Group 1, p=0.04. From a biomechanical perspective, the novel angle-stable intramedullary nail concept has the potential of achieving a higher initial axial and torsional relative stability and maintaining it with a better resistance towards loss of reduction under dynamic loading, while reducing the number of distal locking screws, compared to conventional locking in intramedullary nailed unstable distal tibia fractures

Cutting rodent's bone ends and irrigation of the medullary canal is the common method used for cells collection in allogenic transplantation, however it does not yield sufficient cells for autologous transplantation. The aim of this experiment was to establish and validate a method for bone marrow collection for autologous MSCs transplantation. Two collection methods were examined: 1) Transection of the bone ends and irrigation of the medullary canal, 2) Trephining of the bone with a hypodermic needle without aspiration. Then cell harvesting was compared in the idealised laboratory situation and under simulated surgery. First, two lower limbs were harvested from the same rat cadaver for comparison, bone marrow in one limb was collected by cutting the femoral head and the distal tibia and irrigation of the canal through drilled holes at the distal end of the femur and proximal end of the tibia. Other limb, hypodermic needle was used as a trephining tool into the medullary canal multiple times without applying negative pressure and rinsed from inside and outside. Second, bone marrow was harvested from another rat's cadaver in the surgery room to simulate the conditions needed for autologous transplantation. The number of cells from irrigation method was 1.28*106 cells, whereas that from trephining method reached 17*106. The number cells from the bone marrow harvested in the surgery room was found 29.6*106. We report a novel technique for harvesting cells for autologous cell therapy from only one limb. A significantly larger number of cells from bone marrow could be collected using the needle trephining method. There is no negative effect on the viability of cells after bone marrow harvesting in the surgery room

Trochlear dysplasia is a specific morphotype of the knee, characterized by but not limited to a specific anatomy of the trochlea. The notch, posterior femur and tibial plateau also seem to be involved. In our study we conducted a semi-automated landmark-based 3D analysis on the distal femur, tibial plateau and patella. The knee morphology of a study population (n=20), diagnosed with trochlear dysplasia and a history of recurrent patellar dislocation was compared to a gender- and age-matched control group (n=20). The arthro-CT scan-based 3D-models were isotropically scaled and landmark-based reference planes were created for quantification of the morphometry. Statistical analysis was performed to detect shape differences between the femur, tibia and patella as individual bone models (Mann-Whitney U test) and to detect differences in size agreement between femur and tibia (Pearson's correlation test). The size of the femur did not differ significantly between the two groups, but the maximum size difference (scaling factor) over all cases was 35%. Significant differences were observed in the trochlear dysplasia (TD) versus control group for all conventional parameters. Morphometrical measurements showed also significant differences in the three directions (anteroposterior (AP), mediolateral (ML), proximodistal (PD)) for the distal femur, tibia and patella. Correlation tests between the width of the distal femur and the tibial plateau revealed that TD knees show less agreement between femur and tibia than the control knees; this was observed for the overall width (TD: r=0.172; p=0.494 - control group: r=0.636; p=0.003) and the medial compartment (TD: r=0.164; p=0.516 - control group: r=0.679; p=0.001), but not for the lateral compartment (TD: r=0.512; p=0.029 - control: r=0.683; p=0.001). In both groups the intercondylar eminence width was strongly correlated with the notch width (TD: r=0.791; p=0.001 - control: r=0.643; p=0.002). The morphology of the trochleodysplastic knee differs significantly from the normal knee by means of an increased ratio of AP/ML width for both femur and tibia, a smaller femoral notch and a lack of correspondence in mediolateral width between the femur and tibia. More specifically, the medial femoral condyle shows no correlation with the medial tibial plateau

Anatomical atlases document safe corridors for placement of wires when using fine-wire circular external fixation. The furthest posterolateral corridor described in the distal tibia is through the fibula. This limits the crossing angle and stability of the frame. In this paper we describe a new, safe Retro-Fibular Wire corridor, which provides greater crossing angles and increased stability. In a cadaver study, 20 formalin-treated legs were divided into two groups. Wires were inserted into the distal quarter of the tibia using two possible corridors and standard techniques of dissection identified the distance of the wires from neurovascular structures. In both groups the posterior tibial neurovascular bundle was avoided. In group A the peroneal artery was at risk. In group B this injury was avoided. Comparison of the groups showed a significant difference (p < 0.001). We recommend the Retro-Fibular wire technique whereby wires are inserted into the tibia mid-way between the posteromedial border of the fibula and the tendo Achillis, at 30° to 45° to the sagittal plane, and introduced from a posterolateral to an anteromedial position. Subsequently, when using this technique in 30 patients, we have had no neurovascular complications or problems relating to tethering of the peroneal tendons

Background. Finite element (FE) models are frequently used in biomechanics to predict the behaviour of new implant designs. To increase the stability after severe bone loss tibial components with long stems are used in revision total knee replacements (TKR). A clinically reported complication after revision surgery is the occurrence of pain in the stem-end region. The aim of this analysis was the development of a validated FE-model of a fully cemented implant and to evaluate the effect of different tibial stem orientations. Methods. A scanned 4th generation synthetic left tibia (Sawbones) was used to develop the FE-model with a virtually implanted fully cemented tibial component. The 500 N load was applied with medial:lateral compartment distributions of 60:40 and 80:20. Different stem positons were simulated by modifying the resection surface angle posterior to the tibias shaft axis. The results were compared with an experimental study which used strain gauges on Sawbones tibias with an implanted tibial TKR component. The locations of the experimental strain gauges were modelled in the FE study. Results. Similar patterns and magnitudes of the predicted and experimentally measured strains were observed which validated the FE-model. An increase of strain at the most distal gauge locations were measured with the stem-end in contact to the posterior cortical bone. More uniform strain distributions were observed with the stem aligned to the intramedullary canal axis. The load distribution of 80:20 shifts the strains to tensile laterally and a large increase of compressive strain in the medial distal tibia. Conclusions. A contributory factor of the clinically reported stem-end pain is possibly the direct effect of contact of the tibial stem-end to the posterior region of the cortical bone. The increased load to the medial tibial compartment is more critical for the development of pain

Conventional non-steroidal anti-inflammatory drugs (NSAIDs) and newer specific cyclo-oxygenase-2 (cox-2) inhibitors are commonly used in musculoskeletal trauma and orthopaedic surgery to reduce the inflammatory response and pain. These drugs have been reported to impair bone metabolism. In reconstruction of the anterior cruciate ligament the hamstring tendons are mainly used as the graft of choice, and a prerequisite for good results is healing of the tendons in the bone tunnel. Many of these patients are routinely given NSAIDs or cox-2 inhibitors, although no studies have elucidated the effects of these drugs on tendon healing in the bone tunnel. In our study 60 female Wistar rats were randomly allocated into three groups of 20. One received parecoxib, one indometacin and one acted as a control. In all the rats the tendo-Achillis was released proximally from the calf muscles. It was then pulled through a drill hole in the distal tibia and sutured anteriorly. The rats were given parecoxib, indometacin or saline intraperitoneally twice daily for seven days. After 14 days the tendon/bone-tunnel interface was subjected to mechanical testing. Significantly lower maximum pull-out strength (p < 0.001), energy absorption (p < 0.001) and stiffness (p = 0.035) were found in rats given parecoxib and indometacin compared with the control group, most pronounced with parecoxib

Background. Patients presenting to fracture clinic who have had initial management of a fracture performed by Accident and Emergency (A+E) often require further intervention to correct unacceptable position. This usually takes the form of booking a patient for a general anaesthetic to have manipulation under anaesthesia (MUA) or open surgery. Methods. Prospective data collection over a 6-month period. Included subjects were those that had initial management of a fracture performed by A+E, who went on to require re-manipulation in fracture-clinic. Manipulations were performed by trained plaster technicians using entonox analgesia followed by application of moulded cast. Radiographs were reviewed immediately post-manipulation by treating surgeon and patient managed accordingly. A retrospective review of radiograph images was performed by two doctors independently to grade the outcomes following manipulation. Results. 38 patients with 39 fractures included in study. Sites of fracture included 32 distal radius, 2 ankle, 1 spiral distal tibia and fibula, 3 metacarpal and 1 proximal phalanx of finger. 22 patients had anatomical/near-to anatomical reduction at post fracture-clinic manipulation of fracture and was the as well as definitive management (satisfactory outcome). 13 patients had a outcome 2 (minimally displaced but and satisfactory reduction of the fracture) at post fracture-clinic reduction. 12 of these were deemed acceptable went onto outcome 1 for definitive management with 1 going to outcome 2 (requiringed further manipulation). 4 patients had unsatisfactory reduction of fracture outcome 3 at post fracture-clinic reduction and all of these patients went onto outcome 3 (required surgery). Conclusions. This study supports the practice of possible primary reduction and if required, re-manipulation and cast moulding using only entonox analgesia, of selected patient cases fractures by trained plaster technicians. Without this intervention, almost all of these cases will have required an MUA or additionally Kirscher wire or open fixation. There is potential to utilise a plaster technician in A+E, reducing the need for further fracture clinic appointments, being more acceptable to patients and having a resultant cost-saving implication. Level of Evidence. Level 3

Background. Bio-Active Glass (BAG) is a promising bone graft substitute for large bone defect reconstruction because of its favourable osteoconductive, antibacterial and angiogenic properties. Potentially, it could also mechanically reinforce the defect, thus making it suitable for load-bearing defects. However, the mechanical properties of the reconstructive layer consisting of BAG/bone allograft mixtures are unknown. The goals of this study therefore were, first, to measure the mechanical properties of different BAG/bone graft mixtures and, second, to investigate to what extent such mixtures could reinforce distal tibial defects using micro-FE analysis and high-resolution CT scans. Materials and Methods. Four different BAG/bone graft mixtures were impacted in a cylindrical holder, mechanically tested in confined compression and scanned with micro-CT. From these images, bone graft material and glass were segmented using two different threshold values. The interface between bone and BAG was modelled separately by dilating the glass phase. Micro-Finite-Element (FE) models of the composites were made using a Young's modulus of 2.5 GPa for bone and 35 GPa for BAG. The Young's modulus for the interface region was determined by fitting experimental and micro-FE results for the same specimens. (82 μm resolution) CT scans of a 9 mm region of the distal tibia of 3 subjects were used. Micro-FE models of this region were made to determine its stiffness in the original state, with a simulated cortical defect and after a mixture of BAG/bone was modelled in the defect. Results. The confined compression tests showed a strong dependence of the modulus of the BAG/bone composite on the amount of BAG, ranging from 116.7 ± 18.2 to 654.2 ± 35.2 MPa. The micro-FE results could well reproduce these measured moduli, when using a stiffness of 25 MPa for the interface layer. The micro-FE analyses of the cortical defect demonstrated that the stiffness of the tibial segment would be reduced by 13 ± 3 % with the defect. Treatment with the BAG/bone composite could restore the stiffness to 101 ± 6 % of its original value. Discussion. The experiments demonstrate that BAG/bone mixtures have a composition-dependent stiffness, in the range of that of trabecular bone, which can be well estimated from micro-FE analyses. Furthermore, the tibial micro-FE analyses demonstrate that these mixtures potentially can restore the stiffness of large bone defects at this site. Future development of the model may predict mechanical behaviour of BAG/bone mixtures patient specifically

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

Objectives

The purpose of this study was to compare the results and complications of tibial lengthening over an intramedullary nail with treatment using the traditional Ilizarov method.

The feasibility of bone transport with bone substitute and the factors which are essential for a successful bone transport are unknown. We studied six groups of 12 Japanese white rabbits. Groups A to D received cylindrical autologous bone segments and groups E and F hydroxyapatite prostheses. The periosteum was preserved in group A so that its segments had a blood supply, cells, proteins and scaffold. Group B had no blood supply. Group C had proteins and scaffold and group D had only scaffold. Group E received hydroxyapatite loaded with recombinant human bone morphogenetic protein-2 and group F had hydroxyapatite alone.

Distraction osteogenesis occurred in groups A to C and E which had osteo-conductive transport segments loaded with osteo-inductive proteins. We conclude that scaffold and proteins are essential for successful bone transport, and that bone substitute can be used to regenerate bone.

A cavovarus foot deformity was simulated in cadaver specimens by inserting metallic wedges of 15° and 30° dorsally into the first tarsometatarsal joint. Sensors in the ankle joint recorded static tibiotalar pressure distribution at physiological load.

The peak pressure increased significantly from neutral alignment to the 30° cavus deformity, and the centre of force migrated medially. The anterior migration of the centre of force was significant for both the 15° (repeated measures analysis of variance (ANOVA), p = 0.021) and the 30° (repeated measures ANOVA, p = 0.007) cavus deformity. Differences in ligament laxity did not influence the peak pressure.

These findings support the hypothesis that the cavovarus foot deformity causes an increase in anteromedial ankle joint pressure leading to anteromedial arthrosis in the long term, even in the absence of lateral hindfoot instability.

Achieving deep flexion after total knee replacement remains a challenge. In this study we compared the soft-tissue tension and tibiofemoral force in a mobile-bearing posterior cruciate ligament-sacrificing total knee replacement, using equal flexion and extension gaps, and with the gaps increased by 2 mm each. The tests were conducted during passive movement in five cadaver knees, and measurements of strain were made simultaneously in the collateral ligaments. The tibiofemoral force was measured using a customised mini-force plate in the tibial tray. Measurements of collateral ligament strain were not very sensitive to changes in the gap ratio, but tibiofemoral force measurements were. Tibiofemoral force was decreased by a mean of 40% (sd 10.7) after 90° of knee flexion when the flexion gap was increased by 2 mm. Increasing the extension gap by 2 mm affected the force only in full extension. Because increasing the range of flexion after total knee replacement beyond 110° is a widely-held goal, small increases in the flexion gap warrant further investigation.