Brett Fritsch

Variability in static alignment and kinematics for kinematically aligned TKA

BACKGROUNDnTotal knee arthroplasty (TKA) significantly improves pain and restores a considerable degree of function. However, improvements are needed to increase patient satisfaction and restore kinematics to allow more physically demanding activities that active patients consider important. The aim of our study was to compare the alignment and motion of kinematically and mechanically aligned TKAs.nnnMETHODSnA patient specific musculoskeletal computer simulation was used to compare the tibio-femoral and patello-femoral kinematics between mechanically aligned and kinematically aligned TKA in 20 patients.nnnRESULTSnWhen kinematically aligned, femoral components on average resulted in more valgus alignment to the mechanical axis and internally rotated to surgical transepicondylar axis whereas tibia component on average resulted in more varus alignment to the mechanical axis and internally rotated to tibial AP rotational axis. With kinematic alignment, tibio-femoral motion displayed greater tibial external rotation and lateral femoral flexion facet centre (FFC) translation with knee flexion than mechanical aligned TKA. At the patellofemoral joint, patella lateral shift of kinematically aligned TKA plateaued after 20 to 30° flexion while in mechanically aligned TKA it decreased continuously through the whole range of motion.nnnCONCLUSIONSnKinematic alignment resulted in greater variation than mechanical alignment for all tibio-femoral and patello-femoral motion. Kinematic alignment places TKA components patient specific alignment which depends on the preoperative state of the knee resulting in greater variation in kinematics. The use of computational models has the potential to predict which alignment based on native alignment, kinematic or mechanical, could improve knee function for patients undergoing TKA.

Multifactorial analysis of dissatisfaction after primary total knee replacement

BACKGROUNDnThe aims of this study were to identify the prevalence and causes of dissatisfaction in a cohort of private practice patients, and to compare the psychological characteristics of dissatisfied patients to matched, satisfied controls.nnnMETHODSnUnilateral TKR patients were evaluated to identify those dissatisfied with their TKR. Dissatisfied and satisfied patients were matched in terms of age, gender, follow-up duration and body mass index (BMI). Psychological evaluation was performed using the Pain Catastrophizing Scale (PCS), Depression, Anxiety and Stress Scale (DASS) and the Multidimensional Health Locus of Control (MHLC) scale. The preoperative grade of osteoarthritis, prevalence of comorbidities, and postoperative functional outcomes, were also compared.nnnRESULTSnA cohort comprised 301 patients (response rate 71%), with 24 patients (eight percent) dissatisfied at a mean follow-up of 37months (range eight to 74months). Persistent pain was the most common reason for dissatisfaction (n=10). Dissatisfied patients reported a significantly higher mean PCS score (P=0.03), higher depression component of the DASS (P=0.02) and lower internal locus of control (P=0.02). The dissatisfied group exhibited reduced improvement (P<0.05) in the Oxford Knee Score (OKS) and range of motion (ROM), as well as a lower preoperative grade of osteoarthritis compared to satisfied patients.nnnCONCLUSIONSnDissatisfied patients exhibit an altered psychological profile to matched satisfied controls. In addition, they have lesser improvements in the OKS and ROM. Thus, both physical as well as psychological factors contribute to dissatisfaction. Identification of these factors may help in planning focused interventions to address dissatisfaction.

Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review

PURPOSEnThis study aimed to systematically review the literature and identify factors which would contribute to the intraoperative correction of FFD to frame a potential surgical algorithm or predictive model to guide intraoperative decision-making.nnnMETHODSnElectronic searches of six databases were undertaken in April 2016 according to the PRISMA guidelines, and the reference lists of studies searched. Quality of studies was assessed using the STROBE checklist, and the Downs and Black Scores.nnnRESULTSnTwenty-five studies investigating 10, 679 knees were found to satisfy the inclusion and exclusion criteria. These studies described a variety of pre-operative and intra-operative factors which contribute to the development or correction of post-operative FFD. The only patient predictor of post-operative FFD was pre-operative FFD. The intra-operative steps described to correct FFD were: distal femoral resection, soft-tissue balancing (in the posterior and medial compartments), sagittal component flexion and posterior condylar offset. However, no studies investigated these in an integrated model.nnnCONCLUSIONnThis review has identified various pre-, intra- and post-operative factors predictive of post-operative FFD. In practice, these factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity.

Symptomatic relief in medial opening wedge high tibial osteotomies for the treatment of knee osteoarthritis is influenced by concurrent procedures and preoperative pain level

Objectives Medial compartment osteoarthritis (OA) in the younger patient is technically challenging to treat. Medial opening wedge high tibial osteotomy (MOWHTO) is an option for surgical treatment; however, there remains a lack of evidence to establish the procedure as the preferred treatment option. The literature remains inconsistent with regard to patient characteristics and surgical factors that determine patient outcomes, particularly with respect to procedure survival and pain relief. The purpose of this study is to (i) describe the patient demographics and surgical outcomes of a consecutive series of MOWHTOs for treatment of medial knee OA; (ii) determine the procedure survivorship up to 10 years postsurgery and (iii) identify patient and surgery-related factors associated with pain relief following MOWHTO. Methods A cohort of 210 patients was identified that underwent MOWHTO between 2002 and 2013. Patient demographics and complications were extracted from the clinical research database. Procedure survival analysis was conducted using a Kaplan-Meier analysis. All patients completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire preoperatively and postoperatively with pain relief identified as the difference between pre- and postoperative KOOS-pain subscale. A partial least square regression model was fitted to identify predictors of pain relief. Results Males comprised 84% of the cohort, which had a median age of 51 years (95%u2009CI 42 to 57 years). Patients were overweight on average, with a median BMI of 28.9u2009kg/m2 (95%u2009CI 23 to 36u2009kg/m2) and 36% of patients underwent concomitant procedures. A complication rate of 3.8% was observed. Survivorship was 97.7% at 5u2009years and 80% at 10 years, with median time to conversion in those requiring total knee replacement of 7 years (95%u2009CI 5 to 8). Patients undergoing cartilage treatment and bilateral procedures experienced increased pain relief compared with average, while there was reduced pain relief in patients with lower preoperative pain. Conclusion MOWHTO is an effective procedure for relief of pain associated with medial knee OA, even in older and heavier patients. Patients and clinicians can expect an average procedure survival of 12.5 years and a maximum of 21 years, with effective pain relief influence by cartilage treatment and preoperative pain score. Level of evidence IV. Case series.

New and evolving technologies for knee arthroplasty—computer navigation and robotics: state of the art

Computer-assisted navigation was introduced as an adjunct to total knee arthroplasty (TKA) with the potential of improving positioning and alignment of TKA implants. Computer-assisted surgery (CAS) can be divided into: passive (navigated TKA) or semiactive and active (robotic TKA). Passive CAS has shown improved results regarding alignment in TKA compared with conventional instrumentation but it has several possible complications such as registration errors, pin site complications, increased surgical time and a potentially longer learning curve. Robotic TKA has been developed to eliminate the possible error in the preparation of bone surfaces by the surgeon. There is still little evidence on these systems but the early results are encouraging. Despite better results in accuracy with both CAS systems, clinical benefits are still subject of debate. Additional research is required to fully define the costs and benefits of robotics in regular medical practice.

Patient Variation Limits Use of Fixed References for Femoral Rotation Component Alignment in Total Knee Arthroplasty

BACKGROUNDnOptimal rotational alignment of the femoral component is a common goal during total knee arthroplasty. The posterior condylar axis (PCA) is thought to be the most reproducible reference in surgery, while the transepicondylar axis (TEA) seems to better approximate the native kinematic flexion axis. This study sought to determine if rules based on patient gender or coronal alignment could allow reliable reproduction of the TEA from the PCA.nnnMETHODSnThree-dimensional models based on preoperative computed tomography were made representing a patients arthritic knee joint. The landmarks were defined and angular relationships determined.nnnRESULTSnThe population group of 726 patients contained large anatomic variation. When applying the standard reference rule of 3° external rotation from the PCA, 36.9% of patients would have a rotational target greater than ±2° from their TEA. When applying the mean external rotation of the TEA from the PCA (1.85°) from this population, this proportion dropped to 26.0% of patients. The use of statistically significant gender and coronal alignment relationships to define the femoral rotation did not reduce the proportion of patients in ±2° error.nnnCONCLUSIONnThis study shows that gender and coronal alignment relationships to the TEA to PCA angle are not clinically significant as a quarter of patients would still have a target for rotation greater than ±2° from the TEA using these relationships. Superior tools for orienting rotational cuts directly to the TEA in surgery or preoperative identification of relevant patient-specific angles might capture the proportion of patients for whom standard reference angles are not appropriate.

Patient-Specific Simulated Dynamics After Total Knee Arthroplasty Correlate With Patient-Reported Outcomes

BACKGROUNDnComponent alignment variation following total knee arthroplasty (TKA) does not fully explain the instance of long-term postoperative pain. Joint dynamics following TKA vary with component alignment and patient-specific musculoskeletal anatomy. Computational simulations allow joint dynamics outcomes to be studied across populations. This study aims to determine if simulated postoperative TKA joint dynamics correlate with patient-reported outcomes.nnnMETHODSnLandmarking and 3D registration of implants was performed on 96 segmented postoperative computed tomography scans of TKAs. A cadaver rig-validated platform for generating patient-specific simulation of deep knee bend kinematics was run for each patient. Resultant dynamic outcomes were correlated with a 12-month postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS). Axa0Classification and Regression Tree (CART) was used for determining nonlinear relationships.nnnRESULTSnNonlinear relationships between the KOOS pain score and rollback and dynamic coronal alignment were found to be significant. Combining a dynamic coronal angular change from extension to full flexion between 0° and 4° varus (long leg axis) and measured rollback of no more than 6 mm without rollforward formed a kinematic safe zone of outcomes in which the postoperative KOOS score is 10.5 points higher (Pxa0= .013).nnnCONCLUSIONnThe study showed statistically significant correlations between kinematic factors in a simulation of postoperative TKA and postoperative KOOS scores. The presence of a dynamic safe zone in the data suggests a potential optimal target for any given individual patients joint dynamics and the opportunity to preoperatively determine a patient-specific alignment target to achieve those joint dynamics.

Quantitative MRI Evaluation of Tunnel placement in ACL Reconstruction

Introduction: Positioning of the graft ACL in the native footprint center is important to replicate the anatomy and function of the ACL for each individual patient. It is known that incorrect bone tunnel placement for the reconstructed ligament is a contributor to poor clinical outcomes postoperatively. Currently the success of tunnel placement is determined by training and experience of the treating surgeon and there is no universally accepted quantifiable and objective method to evaluate the execution of these decisions. The goal of this project was to develop a quantitative routine assessment to assist pre-surgical planning and also evaluate the execution of femoral and tibial bone tunnel placement in ACL reconstructed knees. Methods: The study recruited failed primary ACL reconstructed patients (N=25) who consented to undergo revision ACL reconstruction to establish the placement of the graft ACL tunnel apertures in the femur and tibia. Prior to surgery each participant underwent high resolution 3 T MRI of their injured knee and 3D models were generated through segmentation of soft and hard tissue knee structures. During surgery previous graft tunnels and prominent reference landmarks visible on MRI and arthroscopically were registered using intraoperative navigation to act as the reference standard. The placement of the tunnel apertures in the femur and tibia were measured in all three planes using a novel measurement method. Results: Preliminary result show that the measurement method can assess the placement of tunnel apertures in the femur and tibia within 0.1 – 1.0 mm of the intraoperative data, using reference landmarks identifiable in MRI and arthroscopically. Additionally, the area of the tunnel aperture, bone tunnel volume can be evaluated. Reliability and validation of the novel method is ongoing using medical imaging and intraoperative navigation to register the placement of bone tunnels in revision ACL reconstruction patients. Conclusions: Correct placement of graft ACL bone tunnels inside the native ACL footprint is critical to the outcome of ACL reconstruction. Development of an accurate reproducible method for assessment of tunnel placement relative to the anatomical footprint should provide a simple method for objectively assessing ACL reconstructions. Preliminary results of this routine assessment suggests that graft tunnel placement can be objectively assessed to assist clinicians to evaluate and improve ACL reconstruction technique and evaluation of ACL reconstruction outcomes.