Treatment options for large acetabular defects in hip revision surgery:current options and a custom-made solution

Total hip arthroplasty is referred to as the operation of the century. In this thesis the current treatment options for large acetabular defects are evaluated and a new acetabular implant to treat large acetabular defects is introduced and evaluated. A review of the literature on the current treatment options for large acetabular defects is presented. It showed that Trabecular MetalTM (Zimmer) augment and shells gave the most promising results. Reconstruction with an antiprotrusio cage was the most frequently reported technique, with good results in a physically low demand elderly population. Bone impaction grafting seems not appropriate for pelvic discontinuity and Paprosky type-3B defects. In those cases, a custom-made triflange implant or a cup-cage reconstruction might be the best alternative, but few reports of sufficient quality are available yet. Next a new custom-made acetabular implant for large acetabular defects is introduced including its surgical technique. The accuracy of the placement of the implant is evaluated in a group of 16 patients. This first group is then compared to a second group of 16 patients. The results are promising and a trend towards better surgical accuracy and less complications in the second group is found, despite a higher complexity in cases. Finally, the clinical and radiological follow-up at two years is described using a prospective case series of 50 hips. It shows that this custom-made acetabular implant is a viable option for uncontained acetabular defects and pelvic discontinuity

Personalized Hip and Knee Joint Replacement

This open access book describes and illustrates the surgical techniques, implants, and technologies used for the purpose of personalized implantation of hip and knee components. This new and flourishing treatment philosophy offers important benefits over conventional systematic techniques, including component positioning appropriate to individual anatomy, improved surgical reproducibility and prosthetic performance, and a reduction in complications. The techniques described in the book aim to reproduce patients’ native anatomy and physiological joint laxity, thereby improving the prosthetic hip/knee kinematics and functional outcomes in the quest of the forgotten joint. They include kinematically aligned total knee/total hip arthroplasty, partial knee replacement, and hip resurfacing. The relevance of available and emerging technological tools for these personalized approaches is also explained, with coverage of, for example, robotics, computer-assisted surgery, and augmented reality. Contributions from surgeons who are considered world leaders in diverse fields of this novel surgical philosophy make this open access book will invaluable to a wide readership, from trainees at all levels to consultants practicing lower limb surger

High Variability of Acetabular Offset in Primary Hip Osteoarthritis Influences Acetabular Reaming—A Computed Tomography–Based Anatomic Study

Background: The objectives of the present study were to (1) evaluate the accuracy and reliability of native acetabular offset (AO) measurements performed on conventional supine anterior-posterior (ap) pelvis radiographs with reference to computed tomography (CT) in patients with end-stage hip osteoarthritis (OA); (2) determine the minimum and maximum amount of medialization of the center of rotation (COR) simulating different reaming techniques; and (3) identify patients at increased risk of excessive medialization of the COR.Methods: A consecutive series of corresponding 131 CT scans and radiographs of patients with primary hip OA was evaluated using validated software for three-dimensional acetabular and femoral measurements. We simulated the implantation of a hemispherical press-fit cup comparing anatomic and conventional reaming techniques and assessed corresponding changes in AO.Results: Standardized ap pelvis radiographs allowed for an accurate and reliable assessment of AO compared with CT. Cup placement in the most lateral position (anatomic reaming technique) resulted in a mean implant-related medialization of 5.9 ± 3.4 mm. Anatomic cup placement did not require reaming to the true floor in 64 hips (49%). With the conventional reaming technique, the total medialization of the COR (implant-related and reaming-related) was 6.8 ± 2.9, with 34% of cases having a medialization ≥8 mm.Conclusion: The present study highlights the variability of acetabular anatomy in patients with primary OA. AO can be accurately and reliably determined on conventional radiographs and appears to be independent of femoral shape and geometry. Depending on the preferred reaming technique a substantial number of patients appear at risk for excessive cup medialization

The measurement of wear in hip arthroplasties

Metal-on-metal (MOM) total hip replacement (THR) and resurfacing implants were designed to form a low friction bearing that would improve implant longevity, in response to the ever-aging population. However, the unanticipated release of cobalt chromium wear debris had a detrimental impact on periprosthetic tissue, resulting in many being revised and some designs being recalled. The aim of this thesis was to identify the surgeon, implant and patient factors that contributed to the increased wear of MOM hip arthroplasties and ultimately their failure. A developed software solution was found to provide improved accuracy during the quantification of volumetric wear from the bearing surface of retrieved hip implants, overcoming the limitations of current methods. Through its application, neither diametrical clearance nor manufacture dates were found to influence the wear performance of MOM Pinnacle hips, contrary to previous speculation. A high proportion of Pinnacle and ASR hips had a diametrical clearance below their specifications. Its detrimental impact on ASR bearing wear, further implicated its acetabular design in the increased prevalence of edge loading. The comparably high wear rates and whole blood metal ion levels of the ASR could explain their high revision rates. Nevertheless, the greater toxicity of taper junction debris was identified as the primary contributor to the disproportionately greater revision rates of the ASR XL, compared to its resurfacing form. Bearing wear was successfully located in vivo for the first time and predominantly isolated to the anterosuperior portion of the acetabular component, analogous to cartilage damage mapped in native hips. A potential relationship was also identified between component positioning and the location of this wear. These findings will help inform the management of a million patients worldwide that remain with implanted MOM hips, while influencing future design, quality control and the regulation of all orthopaedic implants

Role of pelvic incidence in hip disorders

The pelvis is a rotating modulator connecting the spine and lower limbs; it helps the body to maintain a vertical position. Pelvic incidence (PI) is fundamental, constant, and unique for each individual measure defined as the angle between the line perpendicular to the sacral plate at its midpoint, and the line connecting this point to the axis of the femoral heads. It regulates spinal curvature and has consequently become an important factor in spinal surgery. It also determines a person’s ability to tilt the pelvis into retroversion, which is needed to help compensate for sagittal spinopelvic malalignment in spinal deformities or ageing. When tilting backward and forward, the pelvis rotates around the femoral heads. Both spinal and hip disorders are common, and they often coexist. Descriptive imaging is essential when specific disorders of the spine and hip are being diagnosed or treated surgically. Previously performed hip replacement is a common condition among patients with a spinal deformity or other spinal disease. Thus a reliable measurement of spino-pelvic alignment is necessary even when a femoral head has been replaced. In addition, disorders of the hip and spine are sometimes related, and, therefore, understanding the complexity and connections of this spinopelvic unit is a widespread clinical challenge. The aims of this thesis were 1) to investigate whether pelvic incidence is associated with the wear of hip implants in the studied sample; 2) to determine if the radiographic measurement of spinopelvic parameters after hip replacement overall (and the implant position of metal-on-metal hip implants in particular) is reliable; and 3) to evaluate the previous evidence on the connection between pelvic incidence and hip disorders in general. The study was based on data collected from 101 patients who underwent large-diameter-head, metal-on-metal hip arthroplasty. A systematic review, along with a quantitative analysis of the literature on the topic, was conducted. In this study, no evidence was found that pelvic incidence is associated with metal wear after metal-on-metal hip replacement. The plain radiograph assessment of the position of the total metal-on-metal acetabular component and the spinopelvic parameters was found to be reliable. Hip replacement did not weaken the interpretation of spinopelvic alignment. In addition, pelvic incidence and hip osteoarthrosis seemed to be unrelated. A possible connection between the low pelvic incidence and femoroacetabular impingement observed in this study should be taken into account when clinical decisions are made in spinal and hip surgery

Geometric Variances in Hip Osteoarthritis and Tribology of the Natural Hip

Osteoarthritis (OA) of the hip joint is a common form of arthritis that often requires surgical intervention using total hip replacement (THR), as treatment using early interventional techniques is still poorly understood. It is hoped that gaining a better understanding of hip geometry, and that using this information in future in-vitro simulations, will contribute to the evidence base regarding the aetiology of OA and the use of early surgical interventions to prevent or delay the onset of hip OA. This thesis aimed to investigate geometric variations in patients with known hip OA and compare them to asymptomatic participants of the same age. The thesis also aimed to develop a novel in-vitro simulation model for the tribological testing of complete natural hip joints. Twenty nine participants were recruited into the study (n=15 control and n=14 hip OA), and the geometry of their hip joints was explored and compared using high resolution (3.0 T) MRI and 3D shape matching software (EndPoint), which in the main, had previously been used for investigating the knee joint. In the study group, obvious shape differences such as superior flattening of the femoral head, differences in the sphericity of the head and acetabulum, and a significantly smaller degree of acetabular anteversion were observed when compared to the asymptomatic group. Experimental work began by validating a new pendulum friction simulator (Mk B) using THR bearings and hemiarthroplasties. One major modification and several minor modifications were required before the simulator could be used to develop the novel complete natural hip joint in-vitro simulation model, which was done successfully using porcine tissue. This model and the novel sample potting methodology developed alongside it can be used in future in-vitro tribological studies of the natural hip joint, and information gained from the MRI study can be used as geometric parameters for future in-vitro simulations

Patient-Specific Implants in Musculoskeletal (Orthopedic) Surgery

Most of the treatments in medicine are patient specific, aren’t they? So why should we bother with individualizing implants if we adapt our therapy to patients anyway? Looking at the neighboring field of oncologic treatment, you would not question the fact that individualization of tumor therapy with personalized antibodies has led to the thriving of this field in terms of success in patient survival and positive responses to alternatives for conventional treatments. Regarding the latest cutting-edge developments in orthopedic surgery and biotechnology, including new imaging techniques and 3D-printing of bone substitutes as well as implants, we do have an armamentarium available to stimulate the race for innovation in medicine. This Special Issue of Journal of Personalized Medicine will gather all relevant new and developed techniques already in clinical practice. Examples include the developments in revision arthroplasty and tumor (pelvic replacement) surgery to recreate individual defects, individualized implants for primary arthroplasty to establish physiological joint kinematics, and personalized implants in fracture treatment, to name but a few

The investigation into modes of failure of total hip replacements

The investigation into modes of failure of total hip replacements was the purpose of this project. This involved the development of a finite element model of a simplified uncemented, simplified cemented and a geometrically real hip in order to study the behaviour of loosening of the prosthesis. Loosening of the femoral and acetabular components in total hip replacements are major long-term complications of hip replacements. Such loosening usually produces substantial loss of supporting bone making revision much more difficult and less successful than primary surgery. Implant loosening can be caused from resorption of the bone around the prosthesis from wear debris, insufficient osseointegration of the bone into the prosthesis and brittle failure of the bone cement

Hip simulator wear testing of the taper-trunnion junction and bearing surfaces of modular hip prostheses

PhD ThesisAdverse reaction to metal debris (ARMD) released from the taper-trunnion junction of modular total hip replacements (THRs) is an issue of contemporary concern, not only in metal-on-metal (MoM) but in ceramic-on-ceramic (CoC) and metal-on-cross linked polyethylene (MoP) THRs. Moreover, there is no consensus in the literature regarding the mechanisms behind material loss at the taper-trunnion junction. The aim of this research work to investigate the material loss, if any, at the taper-trunnion junction of modular CoC and MoP THRs under physiological walking cycles. Following ISO-14242, material loss from the bearing surfaces was also quantified alongside surface topographical and microscopic analysis. After 5 million cycles, the mean material loss from the ceramic bearing surfaces was 0.25mm3, and from the metallic trunnions, it was 0.29mm3 in the CoC hip simulator test. The three-dimensional surface roughness (Sa) of the trunnions on the unworn and worn areas showed a statistically significant decrease from 0.558 ± 0.060 to 0.312 ± 0.028μm respectively (p < 0.001). In the MoP hip simulator test, the mean material loss from the polymeric liners, metallic tapers and trunnions were 14.28, 0.22 and 0.24mm3 respectively. The Sa of the femoral tapers on the unworn and worn areas showed a statistically significant increase from 0.510 ± 0.068 to 0.867 ± 0.233μm respectively (p < 0.001). Until this research, no long-term hip simulator tests had quantified material loss from the taper-trunnion junction of commercially available modular CoC and MoP THRs. Metallic material loss from the taper-trunnion junctions of CoC and MoP THRs may explain the ARMD reported in the literature for these THRs. Material loss at the taper-trunnion junction needs to be measured in preclinical testing using the hip simulator to avoid ARMD and further increase the longevity of modular THRs. Based on the results, the mechanisms responsible for the material loss at the metallic taper still a multivariable process

APPLICATIONS IN VIBROARTHROGRAPHY: ASSESSMENTS OF INSTABILITY IN TOTAL HIP ARTHROPLASTY, CAM-POST ENGAGEMENT IN TOTAL KNEE ARTHROPLASTY, AND VISCOSUPPLEMENTATION IN OSTEOARTHRITIC KNEES

Measurement of joint sounds and vibrations for non-invasive orthopaedic diagnostic purposes has slowly advanced since the 1960s. Most work has been focused in the development of methods for screening of abnormal knees. To date the technique has not gained clinical traction as is it fraught with various obstacles and skepticism. This doctoral thesis is neither an argument in favor of nor against the clinical use of vibroarthrography for musculoskeletal diagnostics in humans, but rather an exploration of its potential in cases of orthopaedic interest. These areas include 1) instability in total hip arthroplasty, 2) cam-post engagement in posterior stabilized total knee arthroplasty, and 3) viscosupplementation in osteoarthritic knees. It was expected that each of these unique cases would be characterized by dynamic phenomena that could be measured in the form of surface vibrations at the skin.Methods previously presented in various vibroarthrography research were adopted, modified, and expounded upon to best suit the needs of each experiment. In a mechanical hip simulator, it was found that vibroarthrography could be effectively used to distinguish the difference between 1 mm and 2 mm of hip separation. In posterior stabilized total knee arthroplasty subjects, it was found that multiple vibroarthrographic features may be used to approximate the occurrence of cam-post engagement, and that vibrations measured at the joint surface may be correlated to cam-post engagement velocity. In osteoarthritic knees, the relationship between clinical evidence, viscosupplementation, and vibroarthrography varied on a case by case basis.To the knowledge of the author, all three of these experiments are the first of their kind. Ultimately, the methods and results presented within provide new foundations for vibroarthrography that may be used to further explore the clinical potential of this noninvasive diagnostic