This study concerned the development and validation of a hardware and software biomeasurement system, which was designed to be used by physiotherapists, general practitioners and other healthcare professionals. The purpose of the system is to detect and assess gait deviation in the form of reduced post-operative range of movement (ROM) of the replacement hip joint in total hip arthroplasty (THA) patients. In so doing, the following original work is presented: Production of a wearable, microcontroller-equipped system which was able to wirelessly relay accelerometer sensor data of the subject’s key hip-position parameters to a host computer, which logs the data for later analysis. Development of an artificial neural network is also reported, which was produced to process the sensor data and output assessment of the subject’s hip ROM in the flexion/extension and abduction/adduction rotations (forward and backward swing and outward and inward movement of the hip respectively). The review of literature in the area of biomeasurement devices is also presented. A major data collection was carried out using twenty-one THA patients, where the device output was compared to the output of a Vicon motion analysis system which is considered the ‘gold standard’ in clinical gait analysis. The Vicon system was used to show that the device developed did not itself affect the patient’s hip, knee or ankle gait cycle parameters when in use, and produced measurement of hip flexion/extension and abduction/adduction closely approximating those of the Vicon system. In patients who had gait deviations manifesting in reduced ROM of these hip parameters, it was demonstrated that the device was able to detect and assess the severity of these excursions accurately. The results of the study substantiate that the system developed could be used as an aid for healthcare professionals in the following ways: · To objectively assess gait deviation in the form of reduced flexion/extension and abduction/adduction in the human hip, after replacement, · Monitoring of patient hip ROM post-operatively · Assist in the planning of gait rehabilitation strategies related to these hip parameters.

The number of patients electing to undergo total hip arthroplasty (THA) in the United States has been projected to double by the year 2030, with a growing number of these patients below the age of 65 years. This cohort of patients not only desires to return to pain free daily activity, but wishes to participate in recreation and sporting activities. However, many of these patients report pain, impairments, and functional limitations following THA. The number one deficit observed for patients who fail conventional post-operative rehabilitation is persistent weakness of the hip abductor muscles. In order to safely progress these patients back to their desired activity level, appropriate postoperative rehabilitation programs need to be developed. The primary objective of this dissertation was to examine the effectiveness of a hip abductor strengthening program on subjective and objective outcomes following THA. The secondary aims of this study were to document hip muscle activation and lower extremity movement patterns during functional exercises; and to compare shortterm subjective and objective clinical outcomes for subjects following THA compared to controls. Several observations were made from our results. First, the lunge, single leg squat, and step-up and over exercises may be appropriate to include in post-operative rehabilitation programs to transition THA subjects from static strengthening exercises to dynamic activities. Second, subjects at 6- and 12-weeks following THA continue to exhibit strength and functional deficits, which contributes to decreases in activity level. Third, the addition of an exercise program targeting the hip abductor muscles following THA may help to improve subjective and objective outcomes compared to conventional post-operative rehabilitation. Finally, findings from our results are summarized and we propose a model to develop patient-specific rehabilitation programs.

Class of 2017 Abstract / Objectives: The first aim is to assess efficacy of aspirin versus enoxaparin in preventing a venous thromboembolism (VTE) after a total knee arthroplasty (TKA) or total hip arthroplasty (THA) within 30 days after discharge. The second aim is to assess the safety of aspirin versus enoxaparin in preventing major bleeding events after a TKA or THA within 30 days after discharge. Methods: This study was a retrospective cohort study with data obtained from an online Veterans Affairs (VA) hospital database. For analysis, the primary outcome was assessed with a Chi-Square test, and the secondary outcome was reported with descriptive statistics.Results: Results: Demographics for 374 patients (TKA, n = 275; THA, n = 99): 90% male, average age of 65, average body mass index (BMI) of 32, 26% smokers, 72% had a history of hypertension, and 60% had a history of dyslipidemia. VTE events 30 days post-operatively: enoxaparin (n = 2), enoxaparin/aspirin (n = 1), and aspirin (n = 2) (P-value = 0.78). Safety events (major bleeding events): enoxaparin (n = 42), enoxaparin/aspirin (n = 7), and aspirin (n = 4). Conclusions: There was no significant difference between the treatment groups for VTE rate 30 days post- operation. The enoxaparin treatment group had the greatest number of safety events compared to the other groups.

Contexto: O objetivo do estudo foi avaliar a reprodutibilidade intra e interobservador da versão acetabular e femoral da prótese total de quadril. Materiais e métodos: estudo prospectivo incluindo 101 indivíduos submetidos a prótese total de quadril, sendo 114 quadris desde 2008, com imagens de tomografia computadorizada incluindo os componentes acetabular e femoral da prótese e os côndilos femorais. Resultados: Para avaliação intraobservador o coeficiente de correlação interclasse foi para o observador A de 0.99 para versão acetabular e femoral com intervalo de confian- ça (IC) de 0.98-1.00, para o observador B de 0.98 para versão acetabular (IC de 0.97- 0.99) e de 0.88 para versão femoral (IC de 0.83-0.92), para o observador C de 0.98 para versão acetabular (IC de 0.97-0,99) e de 0.83 para versão femoral (IC de 0.76-0.88). Para avaliação interobservador o coeficiente de correlação interclasse foi calculado com as medidas da primeira leitura de cada observador e em seguida da segunda leitura, sendo a primeira leitura da versão acetabular de 0.99 (IC de 0.98-1.00), a segunda leitura da versão acetabular de 0.99 (IC de 0.98-1.00), a primeira leitura da versão femoral de 0.99 (IC de 0.98-1.00), a segunda leitura da versão femoral de 0.96 (IC de 0.94-0.97). Conclusão: Com os resultados obtidos, podemos concluir que as medidas tomográficas de versão acetabular possuem excelente reprodutibilidade tanto inter quanto intraobservador, as medidas de femoral possuem excelente reprodutibilidade interobservador e de boa a excelente reprodutibilidade intraobservador. / Context: The objective of the study was to evaluate the reproducibility intra e interobserver of acetabular and femoral version after total hip arthroplasty. Materials and methods: prospective studying including 101 individuals after total hip arthroplasty, 114 hips since 2008, with computed tomography images including the components of acetabular and femoral prothesis and the femoral condyle. Results: intra-observer coefficient of interclass correlation was 0.99 for observer A for acetabular and femoral version (IC of 0.98-1.00), for B 0.98 for acetabular version (IC of 0.97-0.99) and 0.88 for femoral version (IC of 0.83-0.92), for C 0.98 for acetabular version (IC of 0.97-0.99) and 0.83 for femoral version (IC of 0.76-0.88). For inter-observer evaluation, the interclass correlation coefficient was calculated with the measurements of the first reading of each observer and the second reading, the first reading of the acetabular version was 0.99 (IC of 0.98-1.00), the second reading of the acetabular version was 0.99 (CI 0.98-1.00), the first reading of the femoral version was 0.99 (CI of 0.98-1.00), the second reading of the femoral version was 0.96 (CI of 0.94- 0.97). Conclusion: With the results obtained, we can conclude that the tomographic measurements of acetabular version have excellent inter- and intraobserver reproducibility, femoral measurements have excellent interobserver reproducibility and good to excellent intraobserver reproducibility.

Computational modeling in the field of biomechanics is becoming increasingly popular and successful in practice for its ability to predict function and provide information that would otherwise be unobtainable. Through the application of these new and constantly improving methods, kinematics and joint contact characteristics in pathological conditions of femoroacetabular impingement (FAI) and total hip arthroplasty (THA) were studied using a lower extremity computational model. Patients presenting with FAI exhibit abnormal contact between the femoral neck and acetabular rim leading to surrounding tissue damage in daily use. THA is the replacement of both the proximal femur and acetabular region of the pelvis and is the most common surgical intervention for degenerative hip disorders. A combination of rigid osteoarticular anatomy and force vectors representing soft tissue structures were used in developing this model. Kinematics produced by healthy models were formally validated with experimental data from Burnfield et al. This healthy model was then modified to emulate the desired morphology of FAI and a THA procedure with a range of combined version (CV) angles. All soft tissue structures were maintained constant for each subsequent model. Data gathered from these models did not provide any significant differences between the kinematics of healthy and FAI but did show a large amount of variation in all THA kinematics including incidents of dislocation with cases of lower CV angles. With the results of these computational studies performed with this model, an increased understanding of hip morphology with regards to STS has been achieved.

Aseptic loosening due to wear-induced osteolysis remains a leading cause of failure in total hip arthroplasty (THA), particularly in revision cases beyond the second decade of use. Historically, there have been large amounts of variability of wear within individual THA patient cohorts. Evidence indicates that femoral head damage can be a cause of this variability. While femoral head damage as a result of third body particles and subluxation and dislocation events has been well documented, direct quantifiable linkage between femoral head damage and wear acceleration remains to be established. Due to large ranges of observed retrieval damage, wear testing protocols for simulating third body and other damage effects have been subject to a wide range of variability, making it difficult to know where the clinical reality lies. To study the effect of retrieval femoral head damage on total hip implant wear, a damage-feature-based finite element (FE) formulation which allowed for wear prediction due to individual damage features developed. A multi-scale imaging procedure was also developed to globally map and quantify micron-level damage features appearing on retrieval femoral heads. This allowed for wear simulations of damage patterns observed on specific retrieval femoral heads. Retrieval damage was shown to be highly variable among patients, and capable of producing up to order-of-magnitude wear increases when compared to undamaged head wear rates. Damage following dislocation and subsequent closed reduction maneuvers was particularly detrimental, with average wear rate increases equal to half an order of magnitude. These data were used to develop wear testing protocols for simulating clinically-occurring third body and other damage effects.

Polyethylene wear and micromotion of the implant play an important role in multifactorial etiology of osteolysis leading to aseptic loosening of the acetabular components. Despite excellent results in primary total hip arthoplasty in a 10-15 year perspective there are still unsolved problems. The weakest link is the longevity of the actabular component. Young and active patients have a clearly worse outcome than older patients. Consequences of polyehtylene wear and ways to reduce wear have therefore been in focus during recent years. Radiostereometry (RSA) is the golden standard in measuring in vivo micromotions. In 4 clinical studies including 332 patients we used therefore RSA to record the efficacy of fixation of cemented and uncemented cups. The amount of wear of old and newly designed polyethylenes (PE) was related to cup stability and radiological and clinical measures of outcome. This study showed that cementless cups inserted with pressfit technique do not need additional augmentation. Screws and pegs increase the risk for radiolucencies and osteolystic lesions but are helpful tools in cases where primary stability is jeopardized. In the second decade clinically silent osteolysis is common for the porous coated Harris Galante cup with unsealed screw holes. The locking mechanism of the PE liner in this cup is unsatisfactory and an increase of liner dissociations is expected. EtO sterilized PE displayed high in vivo wear and we do not recommend its continued use but close monitoring of patients with earlier inserted EtO sterilized implants. The substantially reduced wear in cemented highly cross-linked PE cups without any negative in vivo tradeoffs might have a substantial impact on choice of material and operating technique in the near future. However, we still recommend its restrained use in controlled series until longer follow-up data is available. Nevertheless, the short term in vivo results of modern highly cross-linked PE look promising and ight improve the outcome of cemented and uncemented hip arthroplasties by reducing complication and revisions.

New surgical approaches for total hip arthroplasty (THA) are being developed to reduce muscle damage sustained during surgery, in the hope to allow better muscle functioning afterwards. The goal of this study was to compare the muscle sparing anterior (ANT) approach to a traditional lateral (LAT) approach with three-dimensional motion analysis. Kinematics and kinetics were obtained with an infrared camera system and force plates. It was hypothesized that (1) the ANT group would have closer to normal range of motion, moments and powers, compared to the LAT group, and that (2) the ANT group would have higher peak hip abduction moment than the LAT group. Forty patients undergoing unilateral THA for osteoarthritis between the ages of 50 and 75 (20 ANT, 20 LAT) were asked to perform three trials of walking, stair ascent and stair descent. Patients were assessed between six to twelve months postoperatively. Twenty age- and weight-matched control participants (CON) provided normative data. Results indicated that both THA groups had gait anomalies compared to the CON group. Both THA groups had reduced hip abduction moment during walking (CON vs. ANT: p<0.001; CON vs. LAT: p=0.011), and the ANT group had a significantly lower hip abduction moment compared to the LAT group (p=0.008). Similar results were observed during stair descent, where the ANT group had reduced peak hip abduction moment compared to the CON group (p<0.001) and the LAT group (p=0.014). This indicates that the anterior approach did not allow better gait and stair climbing ability after THA. It is therefore thought that other variables, such as preoperative gait adaptations, trauma from the surgery, or postoperative protection mechanisms to avoid loading the prosthetic hip, are factors that might be more important than surgical approach in determining the mechanics of THA patients after surgery.

New surgical approaches for total hip arthroplasty (THA) are being developed to reduce muscle damage sustained during surgery, in the hope to allow better muscle functioning afterwards. The goal of this study was to compare the muscle sparing anterior (ANT) approach to a traditional lateral (LAT) approach with three-dimensional motion analysis. Kinematics and kinetics were obtained with an infrared camera system and force plates. It was hypothesized that (1) the ANT group would have closer to normal range of motion, moments and powers, compared to the LAT group, and that (2) the ANT group would have higher peak hip abduction moment than the LAT group. Forty patients undergoing unilateral THA for osteoarthritis between the ages of 50 and 75 (20 ANT, 20 LAT) were asked to perform three trials of walking, stair ascent and stair descent. Patients were assessed between six to twelve months postoperatively. Twenty age- and weight-matched control participants (CON) provided normative data. Results indicated that both THA groups had gait anomalies compared to the CON group. Both THA groups had reduced hip abduction moment during walking (CON vs. ANT: p<0.001; CON vs. LAT: p=0.011), and the ANT group had a significantly lower hip abduction moment compared to the LAT group (p=0.008). Similar results were observed during stair descent, where the ANT group had reduced peak hip abduction moment compared to the CON group (p<0.001) and the LAT group (p=0.014). This indicates that the anterior approach did not allow better gait and stair climbing ability after THA. It is therefore thought that other variables, such as preoperative gait adaptations, trauma from the surgery, or postoperative protection mechanisms to avoid loading the prosthetic hip, are factors that might be more important than surgical approach in determining the mechanics of THA patients after surgery.

The design of an uncemented hip arthroplasty implant affects its long-term survival. Characteristics such as the form and the finish of the implant are crucial in order to achieve the best possible conditions for long-term implant survival. In this thesis we hypothesized that different shapes of stems and cups used in primary and revision total hip arthroplasty (THA), and their finish with hydroxyapatite (HA) coating affect implant stability and thus long-term survival. In 2 prospective cohort studies the clinical outcome, the stability measured with radiostereometric analysis (RSA), and the periprosthetic changes in bone mineral density (BMD) measured with dual-energy x-ray absorptiometry (DXA) were investigated in 2 uncemented THA implants – the CFP stem and the TOP cup. In 3 register studies the effect of HA coating on uncemented THA implants used in primary and revision arthroplasty was investigated. Both implants investigated in the prospective cohort studies showed an excellent short-term clinical outcome with good primary stability, but neither their novel form nor the finish with HA protected the implants from the proximal periprosthetic demineralization that usually occurs around other uncemented THA implants. The register studies revealed that HA coating on cups used in primary and revision THA is a risk factor for subsequent revision of the implant. The use of HA coating on the stem in primary THA did not affect long-term survival. Additionally, the shape of an implant plays a crucial role for implant stability and survival. In conclusion, this thesis highlights that the finish of implants with HA coating does not prevent periprosthetic proximal femoral bone loss and can even enhance the risk of revision of both primary and secondary cups. Importantly, the shape of uncemented THA implants affect their stability, showing that the implant form is a crucial factor for the long-term survival.