To study surgical outcome of various surgical procedures of lateral release in valgus knee in total knee arthroplasty

Background: Fixed valgus deformity presents a major challenge in total knee arthroplasty (TKA), especially in moderate or severe cases. In knee arthritis, fixed-varus deformity (50 to 55%) is three times more frequent than fixed-valgus deformity (10 to 15%). Valgus deformity occurs more commonly in rheumatoid arthritis and also in osteoarthritis with hypoplasia of the lateral femoral condyle. Valgus deformity is often associated with flexion or external rotation contracture of the knee. In this study we aim to study the surgical outcome of total knee replacement in valgus deformity via standard medial parapatellar approach using various techniques like Pie –Crusting release of lateral structures or combined technique of pie crusting and standard release of lateral structures. Aim: To evaluate surgical outcome of various surgical techniques via standard medial parapatellar approach in fixed valgus deformity in Total Knee Arthroplasty.Methods: The present study involved both male and female patients with osteoarthritis of knee with valgus deformity. In present series, 26 consecutive patients of osteoarthritis with valgus deformity operated with total knee replacement were included. Previously operated cases of high tibial osteotomy and patients having contraindication for TKA were excluded from the study.Results: Valgus angle in this study was between 13 to 27 degree with average 17.84 degree. These results were comparable to many such similar studies. In our study, post operatively, knee society score was average 87.69 and function knee score was 82.5. Mean range of motion was 105 degree. In our study, mean tibiofemoral alignment improved from 17.84 valgus to 4.7 valgus.Conclusions: Knee society score is excellent with both techniques and there is no difference in both techniques Iliotibial band and posterolateral capsule are most common structures that require release. Initial ligament balancing should be done with pie crusting and then sequential lateral release if require.

Imaging the implant-soft tissue interactions in total knee arthroplasty

BACKGROUND: In Total Knee Arthroplasty (TKA), residual pain may be secondary to soft tissue impingements, which are difficult to visualize around chromium-cobalt implants using medical imaging, so their interactions remain poorly understood. The goal of this work was to establish a protocol for in-vitro imaging of the soft tissues around TKA, usable during throughout the range of motion (ROM). METHODS: The full size range of a commercially available TKA prosthesis was manufactured by 3D-printing in non-magnetic and non-radiopaque polymer and implanted in 12 cadaveric knees. The relations between these implants and the soft tissues (Popliteus tendon, Medial and Lateral Collateral Ligament, Patellar and Quadriceps tendons) were analyzed, using MRI (5 embalmed specimens) and CT scans after injection of the tissues with barium-sulfate (3 embalmed and 4 fresh-frozen specimens). RESULTS: Both MRI and CT scans enabled good identification of the soft tissues before TKA implantation. MRI produced minimal loss in signal and contrast, and neither the low temperature nor the embalming fluids compromised image quality. CT scans were more precise after TKA implantation, particularly the borders of the implant and the differentiation of soft tissues. Full ROM investigation, manual segmentation and three-dimensional reconstructions were possible only with the CT scan. CONCLUSION: The experimental approach described in this study was successful in visualizing the interactions between the soft tissue and the implants before and after TKA and during the full ROM. The coordinate system allows to localize precisely the different anatomic structures and to quantify any change due to prosthetic implantation

Computational Modeling of Nonlinear Behavior in Orthopaedics

Total knee replacement (TKR) is one of the most common orthopaedic procedures performed in the USA and is projected to exceed 4.3 million by 2030. Although TKR surgery has a success rate of 95% at 10 years for most TKR designs, revision surgery still occurs approximately once for every ten primary TKR surgeries. Failure modes in TKR involve the interplay between implant mechanical performance and surrounding biological tissues. The orthopaedic community has turned to computational modeling as an effective tool to analyze these complex interactions and improve patient outcomes. The objective of these studies was to utilize a combined computational and experimental approach to investigate modes of TKR failure where material nonlinearity plays a significant role in the biomechanics under investigation. A finite element (FE) model of a modular TKR taper junction was developed in order to investigate the stress environment in relation to corrosive behavior under in vivo loading conditions. Linear elastic and elastoplastic material models were defined and angular mismatch parametrically varied in order to determine the sensitivity of model predicted stresses to material model selection and taper junction geometry. It was determined that positive angle mismatches cause plastic deformation and overestimated stresses in linear elastic analyses compared to elastoplastic analyses. Calculated stresses were also strongly correlated with angle mismatch when varied ±0.25o. Model stress distributions agreed with corrosion patterns evident on retrieved modular TKR components and magnitudes corresponding with corrosive behavior in vitro. Additionally, a series of passive FE TKR models were developed in order to investigate the intrinsic relationship between TKR component alignment, ligament tensions, and knee kinematics during intraoperative assessments. A kinematically-driven model was developed and validated with an open source dataset, and was able to discriminate clinical outcomes based on calculated ligament tensions when input in vivo kinematics. Patient-specific simulations found greater tension in lateral ligaments for poor outcome patients compared to good outcome patients, and statistically significant differences in tensions for the POL, PFL, DMCL, and ALS ligaments during mid-flexion. A force-driven model was also developed and validated with in vitro cadaver testing, and found that variation in tibial component alignment of ±15o influence intraoperative ligament tensions. However, definitive trends between TKR component alignment and ligament tension were not discerned. Nonetheless, both modeling approaches were found to be sensitive to subclinical abnormalities. These findings suggest mechanical stress is a key contributor to taper junction corrosion and that ligament tensions are the mechanism leading to abnormal function in the passive TKR knee. These studies contributed innovative computational models that provide a foundation to advance the understanding of these complex relationships, and modeling frameworks that exemplify sound verification and validation practices

Preliminary Report of a Hybrid Total Ankle Arthroplasty Combining a Stemmed Intramedullary Tibial Component With Chamfer-Cut Talar Dome.

Total ankle arthroplasty (TAA) is a viable treatment for end-stage ankle arthritis. In our experience, a stemmed intramedullary tibial component combined with a chamfer-cut talar component provides the most stable construct for TAA. We present our technique for placement of this hybrid prosthesis utilizing the INBONE tibial component in combination with the INFINITY talar component. This technique differs from the standard protocol by minimizing use of both patient-specific and standard intraoperative guides. The primary aim of this study is to report our preliminary outcomes with our novel technique. Secondarily, we aim to demonstrate that placement of this hybrid prosthesis is radiographically reproducible and accurate. The first 10 patients undergoing this technique with at least 1 year of follow-up were retrospectively reviewed. Average visual analog pain scale decreased from 7.4 preoperatively to 0.5 at 1 year postoperatively. The average time to weightbearing was 6.4 weeks. Complications were minimal, and no implant-related complications were encountered. First weightbearing ankle radiographs postoperatively were evaluated by 3 reviewers to determine accuracy of the tibial intramedullary stem in relation to the anatomical axis of the tibia. We found that the deviation of the tibial implant from the anatomic axis was on average 0.9°± 0.5° in the coronal plane, and 2.2°± 2.7° in the sagittal plane. Inter-rater reliability was 83%. We conclude that this hybrid technique utilizing a stemmed intramedullary tibial component in combination with a chamfer-cut talar component for TAA is reproducible, accurate, and safe

Advancement of a Forward Solution Mathematical Model of the Human Knee Joint

Sometimes called degenerative joint disease, osteoarthritis most often affects the knee, which is a leading cause of pain and reduced mobility. While early treatment is ideal, it is not always successful in combating osteoarthritis and improving joint function, therefore creating the need for total knee arthroplasty (TKA), which is a late-stage treatment where damaged bone and cartilage are replaced by artificial cartilage. Joint arthroplasty is a common and successful procedure for end-stage osteoarthritis. Unfortunately, TKA patient satisfaction rates lag behind those of total hip arthroplasty [1,2], which remains an impetus to create new designs. Due to ethical issues, time requirements, and prohibitive expenses of testing new designs in vivo, mathematical modeling may be an alternative tool to efficiently assess the kinetics and kinematics of new TKA designs. In general, the knee is one of the most complicated joints in the human body, including multiple articulating surfaces and the complexity of soft tissues encompassing the knee joint. Therefore, mathematically modeling the knee is a challenging and complex process. With increasing computational power and advanced knowledge and techniques, advanced mathematical models of the knee joint can be created utilizing various modeling techniques [3]. Furthermore, mathematical modeling can advance our knowledge related to knee biomechanics, especially those parameters that are otherwise challenging to obtain, such as soft tissue properties and effects pertaining to knee mechanics. Mathematical modeling allows the user to evaluate multiple designs and surgical approaches quickly and cost-efficiently without having to conduct lengthy clinical studies. Mathematical models can also provide insight into topics of clinical significance and can efficiently analyze outcome contributions that cannot be controlled in fluoroscopic studies, such as anatomical, mechanical, and kinematic alignment comparisons for the same subject. Furthermore, mathematical models can evaluate the effect of TKA design concerns such as changing conformity of the polyethylene or using femoral components with single or multi radius designs [3]. The objectives of this dissertation are to advance a forward solution model to create a more sophisticated and physiological representation of the knee joint.This is achieved by developing a muscle wrapping algorithm, integrating a validated inverse dynamics model, adding more muscles, incorporating several different TKA types including revision TKA designs, and expanding the model to include other daily activities. All these modifications are incorporated in a graphical user interface. These advancements increase both functionality and accuracy of the model. Several validation methods have been implemented to investigate the accuracy of the predicted kinetics and kinematics of this mathematical model

Osseointegration for Amputees: Past, Present and Future: Basic Science, Innovations in Surgical Technique, Implant Design and Rehabilitation Strategies

Loss of a leg or arm is a tremendous disability. Immediate and obvious impairments are decreased mobility or diminished functional capacity. Not quite as obvious are the difficulties associated with activities of daily living, quality of life impairments, sometimes loss of independence or employment, and the mental health issues which often accompany limb loss. The interface between native tissue and the prosthetic limb presents the greatest challenge to amputee rehabilitation. Computer-controlled robotic limbs have been widely available since the 1990s. However, the weight of prosthetic limbs, coupled with the difficulty of where to locate the components, requires substantial loads to be transferred through the humanimplant interface. This interface has always been a skin-squeezing mechanism which results in repetitive soft-tissue loading and trauma, in both compression and shear, which inevitably causes multiple problems (pain, skin breakdown and infection, hyperhidrosis, allergic reaction to the material) leading to periodic or prolonged prosthesis disuse. So unfortunately, despite all the effort and expense invested in the prosthetic limb itself, patients often were unable to benefit. Percutaneous EndoProsthetic Osseointegration for Limbs (PEPOL) is a revolutionary technique that involves anchoring a metal implant directly to a patient’s skeleton, then permanently passed through the patient’s skin, and attached to a prosthetic limb. By doing this, the weight of the prosthesis is borne by the patient’s skeleton and is directly powered by muscles, leading to a lighter and more native experience. The skin is no longer compressed and traumatised, eliminating the aforementioned issues. Since learning about this technology in the mid-2000s and performing my first independent procedure in 2009, I have investigated and pioneered the world’s leading surgical techniques and rehabilitative methods for PEPOL. Treating nearly 1000 amputees via the Osseointegration Group of Australia and the MQ Health Limb Reconstruction Centre at Macquarie University has allowed research to be performed on this technology, documented, and discussed in the 2 Body of Work. Patients almost always improve their objective and assessed mobility performance (Overall 38.6% distance improvement on the 6MWT), they wear their prosthetic limb more (Overall 38.1% increase in the Q-TFA Prosthetic Use Score), and they are subjectively more satisfied with their condition as an amputee (Overall 41.1% increase in the Q-TFA Global Score) . While these benefits are consistent, my research has also identified the fortunately limited problems with infection and soft tissue management (29% of all patients required re-operations due to direct or indirect complications). PEPOL clearly provides excellent improvement for the vast majority of patients, and the continued investigation of this technology should lead to even greater improvements in progressing from what is already successful, make it more readily available, and ameliorate its existing challenges

Activity intensity, assistive devices and joint replacement influence predicted remodelling in the proximal femur

Bone morphology and density changes are commonly observed following joint replacement, and may contribute to the risks of implant loosening and periprosthetic fracture, and reduce the available bone stock for revision surgery. This study was presented in the “Bone and Cartilage Mechanobiology across the scales” WCCM symposium to review the development of remodelling prediction methods and to demonstrate simulation of adaptive bone remodelling around hip replacement femoral components, incorporating intrinsic (prosthesis) and extrinsic (activity and loading) factors.An iterative bone remodelling process was applied to finite element models of a femur implanted with a cementless THR (total hip replacement) and a hip resurfacing implant. Previously developed for a cemented THR implant, this modified process enabled the influence of pre- to postoperative changes in patient activity and joint loading to be evaluated. A control algorithm used identical pre- and postoperative conditions, and the predicted extents and temporal trends of remodelling were measured by generating virtual x-rays and DXA scans.The modified process improved qualitative and quantitative remodelling predictions for both the cementless THR and resurfacing implants, but demonstrated the sensitivity to DXA scan region definition and appropriate implant-bone position and sizing. Predicted remodelling in the intact femur in response to changed activity and loading demonstrated that in this simplified model, although the influence of the extrinsic effects were important, the mechanics of implantation were dominant. This study supports the application of predictive bone remodelling as one element in the range of physical and computational studies, which should be conducted in the pre-clinical evaluation of new prostheses

A Study On The Effects Of Cementless Total Knee Arthroscopy Implants’ Surface Morphology With Finite Element Analysis

Total knee arthroscopy is one of the most performed and most successful orthopedic surgeries, with nearly a million procedures performed in 2020 in the United States alone. Due to changing patient demographics, the use of cementless fixation for implant stability is becoming more prevalent amongst recipients. Cementless implants rely on the surface morphology of a porous coating to bond implant to bone; the quality of this bond is dependent on an interference fit and the roughness, or coefficient of friction, between implant and bone. Stress shielding is a comparison of the properties in implanted bone to natural bone; it is a commonly used measurable when using a finite element model to optimize implant design. The purpose of this study is to investigate how different coating types (coefficients of friction) and the location of their application affect the stress shielding response in the tibia. A finite element model was constructed to investigate the impact of these variables. The results concluded that the stress distribution in an implanted tibia is dependent on the coefficient of friction applied at the tip of the stem. Lower friction coefficients applied to the stem tip resulted in higher compressive stresses, and higher friction coefficients resulted in lower compressive stresses. Thus, lower friction coefficients provided more favorable stress shielding responses, however, at the expense of stress concentrations of greater magnitude