Injury patterns of medial meniscus posterior root tears

INTRODUCTION: Medial meniscus posterior root tear (MMPRT) can occur in middle-aged patients who have a posteromedial painful popping during light activities. MMPRTs are more common in patients with increased age, female gender, sedentary lifestyle, obesity, and varus knee alignment. However, injury mechanisms of minor traumatic MMPRTs are still unclear. We hypothesized that high flexion activities are the major cause of MMPRTs. The aim of this study was to clarify injury patterns of MMPRTs. MATERIALS AND METHODS: One hundred patients were diagnosed having MMPRTs after posteromedial painful popping episodes. Details of posteromedial painful popping episode, situation of injury, and position of injured leg were obtained from the patients by careful interviews. Injury patterns were divided into 8 groups: descending knee motion, walking, squatting, standing up action, falling down, twisting, light exercise, and minor automobile accident. RESULTS: A descending knee motion was the most common cause of MMPRTs (38%) followed by a walking injury pattern (18%) and a squatting action related to high flexion activities of the knee (13%). The other injury patterns were less than 10%. DISCUSSION: Descending knee motions associated with descending stairs, step, and downhill slope are the most common injury pattern of MMPRTs. High flexion activities of the knee are not the greatest cause of MMPRTs. Our results suggest that the descending action with a low knee flexion angle may trigger minor traumatic MMPRTs

An investigation of the biomechanical factors influencing knee joint function following total knee replacement

Knee replacement surgery is often performed in cases where the pain due to knee osteoarthritis can no longer be effectively controlled by conservative measures. The surgery—which replaces the articular surfaces of the tibia, femur and sometimes the patella with a mix of metal and polyethylene—is one of the most commonly performed lower limb surgeries. Despite patient reports of reduced pain and increased participation in activities of daily living, knee function following total knee arthroplasty (TKA) does not return to normal. Reductions in both passive and active knee range of motion, alterations in magnitude and timing of muscle activity, and changes in knee joint kinetics have all been reported. Comparatively little is known about why knee function is altered following TKA. In an attempt to address this gap in the literature, this thesis was designed to examine the biomechanical factors thought to contribute to reduced knee extensor moments following TKA. In particular, the contribution of alterations in passive knee moments, muscle moment arm lengths, and muscle activation magnitude and timing were examined in detail to determine which factors contributed to reduced knee extensor moment following TKA. To accomplish this goal, two groups--6 healthy controls and 6 individuals who were at least one year post-TKA—were examined in four different studies. The initial study of this thesis, a comprehensive examination of patients and controls during gait and stepping onto a raised surface, had two purposes. This moment data was needed to clearly define the knee moment deficits that existed in the patient – the remainder of the thesis focused on determining why these specific deficits existed. A secondary aim of this first study was to allow for the assessment of muscle activation patterns in this population during weight bearing tasks. Results of study one confirmed the existence of knee extensor moment deficits in the TKA group and also demonstrated that patients exhibited increased gastrocnemius EMG, prolonged stance phase activation of biceps femoris and reduced knee flexion during the loading phase of stance. Analysis of results across the two tasks suggested that reduced knee moments in members of the TKA group may be related to changes in gastrocnemi activation, however, differences in knee joint kinematics between patients and controls made it difficult to draw this conclusion. Study number two was designed to further probe the muscle activation strategies adopted by members of the TKA group. In order to avoid complications involved when comparing muscle activation patterns between groups using different kinematic strategies, seated knee extension was examined. This task was chosen as it challenged the knee musculature while at the same time restricting both groups of participants to use the same knee joint kinematics. The results of this analysis revealed that, while EMG magnitude for quadriceps and hamstrings were similar for both groups, patients exhibited increased amplitude of EMG in both the medial and lateral gastrocnemi. While the first two studies of this thesis focused on the active knee joint moment, in the third study the force required to passively move the knee from a flexed to an extended position was measured and used to estimate the passive moment of the knee joint. This study was based on the rational that if the passive knee moment was altered following TKA it could potentially affect the net knee joint moment. The comparison of patient and control results showed that, while small changes in passive moment were evident in patients, these differences were not large enough to account for changes in the knee extensor moment. The goal of the final thesis study was to examine moment arms of the knee musculature in an attempt to determine if TKA resulted in changes to this variable. However, various methodological issues arose in the course of completing this study. As a result, limited data were produced that sufficiently addressed the question posed. Despite the problems that arose, important issues regarding in vivo moment arm determination were realized and are included for discussion in this thesis. Together, the four studies provided a unique opportunity to observe knee function over a range of activities. The following conclusions were reached. • Changes in passive knee moment did not seem to contribute to reductions in knee extensor moment observed following TKA. • Quadriceps and hamstring muscle function, as evidenced by EMG recording during the seated knee extension task, appeared intact following TKA, suggesting that alteration in the function of these muscles were not directly responsible for reductions in knee extensor moments. • Changes in medial and lateral gastrocnemi activation were observed during knee extension and weight-bearing tasks. These changes may account for reduced knee extensor moment, particularly during the step-up task. • Knee extensor moment reductions during gait appear to be related to the reduced knee flexion exhibited by patients during the stance phase of gait . It was hypothesized that these changes in knee kinematics were directly linked to the increased activation of the gastrocnemi during gait. Although low subject numbers limited the generalizability of the results these conclusions will serve to guide future research in this area and ultimately help improve function and quality of life in this patient population

Spatial Sensors for Quantitative Assessment of Retrieved Arthroplasty Bearings

Evaluation of retrieved joint arthroplasty bearings provides unique evidence related to the physiological environment in which bearing materials are expected to perform. This dissertation describes the development of novel spatial sensors and measurement strategies for standardized, quantitative assessments of arthroplasty bearings, including total knee replacements, unicompartmental knee replacements, and total hip replacements. The approach is to assess bearings that endured a finite duration of function in patients, with particular emphasis on expanding our understanding of the biomechanical conditions specific to bearing function and wear in the physiological environment. Several quantifiable parameters are identified that prove comparable to pre-clinical in vitro tibological evaluations, including knee wear simulation and analytical modeling. These comparisons provide clinical relevance to the existing methodologies, helping to verify that the biomechanical simulations accurately represent the in vivo conditions they are meant to simulate. The broad objective of this dissertation is to improve the longevity and function of arthroplasty bearing materials and designs. Assessments from the retrieved prostheses are discussed within the context of developing comprehensive approaches for the prospective evaluation of new materials and designs in joint replacements

A Biomechanical Analysis of Total and Unicompartmental Knee Arthroplasty Patients during Stair Negotiation Compared to Healthy Controls.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

A Biomechanical Analysis of Trunk Motion During Stair Descent in Total and Unicompartmental Knee Arthroplasty Patients Compared to Healthy Controls.

M.S. Thesis. University of Hawaiʻi at Mānoa 2018

PRIMARY FLEXION AXIS SELECTION IN TOTAL KNEE REPLACEMENTS USING COMPUTATIONAL ANALYSIS

Total knee replacements (TKR) are one of the most frequently implanted medical devices, with over 600,000 procedures performed in the United States in 2012. In order to ensure TKR longevity, wear tests are frequently conducted on these implants prior to patient implantation. Variations in implant geometry, material, and surface treatments are all tested, however, TKR alignment may also play a role in the long-term success of the knee implant. When testing knee designs with complex tibial and femoral geometries it is essential that the implant be aligned as the implant manufacturers intended so as to best represent the function of the implant system. Although critical, a key alignment variable that is largely overlooked is femoral axis selection. Currently, femoral axis alignment is simply selected so as to minimize its effect on implant mechanics during walking simulation; a result that might completely misrepresent the implant designer\u27s intent. The purpose of this study was to create a computational model to determine the effect of femoral axis selection on contact-point bearing migration prior to simulator fixation and examine trends in femoral axis selection based on implant geometry. Using 3D optical scans of seven femurs, 3Matic STL for model remeshing, and COMSOL Multiphysics for simulation this study recreated the single-axis rotation of each femoral component in a wear simulator. The lowest femoral contact point was then tracked between 0º and 120º flexion over four hundred possible femoral axes alignment options. The computational model was verified statistically and calculated the location of the ideal axes of rotation for all seven femurs. Reduction of P/D lowest contact-point translation during simulator flexion was found to be dependent on the range of flexion. Single-axis knee designs were found to exhibit a lower tolerance to varied femoral axes of rotation, but still maintained lower mean P/D displacements. Anterior/posterior translation patterns during simulator flexion were found to vary significantly with femoral axis selection. Interestingly, A/P translation patterns were more consistent between varying flexion axes in implants with multiple axes of curvature compared to single-axis designs. TKR alignment in single-axis simulators clearly affects proximal/distal and anterior/posterior lowest contact-point migration and thus possibly implant mechanics during functional testing. An implant that incorporates a geometry that is minimally affected by malalignment should enhance clinical outcomes and provide more consistent functional measures during simulation and use

Objective clinical performance outcome of total knee prostheses. A study of mobile bearing knees using fluoroscopy, electromyography and roentgenstereophotogrammetry

The aim of the thesis was to to assess with accurate and objective methods the function and fixation of total knee prostheses with special emphasis on mobile bearing total knee designs. The mobile bearing of a rotating platform design showed limited motion or no motion during a step-up task thereby nullifying the theoretical advantages of a mobile bearing prosthesis. Apatite coated implants show excellent mid-term Roentgen Stereophotogrammetric Analysis (RSA) results and offer some clinical advantages above cemented total knee arthroplasty. A prospective RSA study also revealed that the studied mobile bearing design is more predictable and forgiving with respect to micromotion of the tibial component than a posterior stabilised prosthesis. However, mobile bearing prostheses showed to be more demanding for the soft tissue structures surrounding the knee joint. The techniques used in gait analysis and fluoroscopy are sensitive for measurement errors. This restricts the applicability and interpretation of the results acquired when using these methods. In general one needs to be aware of the limitations of measurement tools since one needs accurate and objective methods to assess evidence about the clinical performance of (new) total knee prostheses.Biomet Nederland B.V., DePuy Nederland B.V., Mathys Orthopaedics B.V., Medis medical imaging systems B.V., Medis specials B.V., Smith & Nephew B.V, Stryker Nederland B.V., Wright Medical Nederland B.V., Zimmer Nederland B.V.UBL - phd migration 201