Abstract

Background

Since 2011, the knee service at the Nuffield Orthopaedic Centre has been offering a neutralising medial opening wedge high tibial osteotomy (HTO) to a group of patients presenting with early medial osteoarthritis of the knee, varus alignment and symptoms for more than 2 years. During development of this practice an association was observed between this phenotype of osteoarthritis and the presence of CAM deformity at the hip.

Purpose of the Study and Background

With a strong political agenda for change towards patient-centred healthcare, the notion of shared decision-making is reported to substantially improve patient experience, adherence to treatment and health outcomes. In clinical practice however, observational studies have shown shared decision-making is rarely implemented and patient preferences are seldom met.

The aim of this study was to measure the extent of shared decision-making in clinical encounters involving physiotherapists and patients with low back pain.

Introduction

Anteromedial osteoarthritis of the knee (anteromedial gonarthrosis-AMG) is a common form of knee arthritis. In a clinical setting, knee arthritis has always been assessed by plain radiography in conjunction with pain and function assessments. Whilst this is useful for surgical decision making in bone on bone arthritis, plain radiography gives no insight to the earlier stages of disease. In a recent study 82% of patients with painful arthritis had only partial thickness joint space loss on plain radiography. These patients are managed with various surgical treatments; injection, arthroscopy, osteotomy and arthroplasty with varying results. We believe these varying results are in part due to these patients being at different stages of disease, which will respond differently to different treatments. However radiography cannot delineate these stages. We describe the Magnetic Resonance Imaging (MRI) findings of this partial thickness AMG as a way of understanding these earlier stages of the disease.

Bone marrow is an environment rich in its diversity of cell types and niches. Both hematopoietic and osteogenic stromal cells are present and have been studied extensively. Less is known about the function of one of the most abundant cell types in the bone marrow: adipocytes. There are several hypotheses that have been proposed including: passive role as a space filler; active role in the body's general lipid metabolism; role in providing a localized energy reservoir for emergency situations affecting the bone or hematopoiesis; support of differentiation or function of other cell types (such as bone, endothelial, and other stromal cells).

There are several human pathologies associated with increases in adipocyte hypertrophy or proliferation including changes associated with aging, osteoporosis, and osteonecrosis. The reasons for these changes are poorly understood. One etiology associated with both osteoporosis and osteonecrosis, corticosteroid therapy, has been shown to increase the lipid content of osteoblasts and adipocytes.

With osteonecrosis, several pathogenetic mechanisms involving adipocytes have been proposed:

Mechanical - increased size and number cause increased intraosseous pressure and decreased venous outflow

The possibility that adipocytes may actually play an active role in propagating specific pathologic features has only recently been discussed. This is in part due to our increasing understanding that adipocytes have an endocrine role in metabolism.

Only recently have scientists tried to identify specific cellular mechanisms that may be involved in the pathogenesis of osteonecrosis. Results from these studies will not only contribute to our understanding of the disease of osteonecrosis (and other diseases such as osteoporosis) but will also help us to appreciate the multiple functionalities of the heretofore unappreciated adipocyte.

The Johns Hopkins University Department of Orthopaedics at the Good Samaritan Hospital, Baltimore, Maryland USA

Introduction: Historically, bone scintigraphy has been advocated as a useful diagnostic tool for patients with suspected osteonecrosis or in screening for multifocal disease. The principle aim of this study was to evaluate the sensitivity of bone scanning relative to magnetic resonance imaging in the diagnosis of osteonecrosis.

Methods: Forty-eight patients presented with suspected osteonecrosis of the shoulder, hip, knee, or ankle. All patients underwent simultaneous (less than three months apart) bone scans and magnetic resonance imaging studies as part of a diagnostic work-up. Histological confirmation of osteonecrosis was obtained for all suspected lesions in the study. The diagnostic yield for each imaging modality was then assessed and compared.

Results: All one hundred sixty-three (100%) histologically confirmed lesions were identified by magnetic resonance imaging, while only ninety-one lesions (56%) were identified by bone scan. There was complete uniformity of bone scans with magnetic resonance images in only 38% of patients (eighteen of forty-eight). Bone scanning identified 72% of lesions (forty-seven of sixty-five) in oligofocal patients (less than two involved joints) compared with 45% of the lesions (forty-four of ninety-eight) in multifocal patients (more than two joints involved). Sensitivity of the lesions was highest for the knee and hip and lower for the shoulder and ankle. Larger and later stage lesions had higher bone scan sensitivity.

Conclusions: The results of this study have demonstrated the low sensitivity of bone scintigraphy for diagnosing symptomatic osteonecrosis. Bone scanning did not detect 44% of the lesions (seventy-two of one hundred sixty-three). This study does not support the use of bone scans as a diagnostic or screening tool for this disease.

Introduction: Cementless total hip arthroplasty has been advocated for osteonecrosis of the femoral head (ONFH) as these patients are generally younger and more active than patients with osteoarthritis (OA). Since introduced in the early 1980’s, there have been several generations of cementless total hip prostheses. This study examined the outcome of the femoral stem of four generations of uncemented total hip prostheses.

Materials and Methods: One hundred and fifty-eight hips in 135 osteonecrosis patients (71 men, 64 women) who had a mean age of 46 years (range, 17 to 83) were included. The total number of prostheses included: PCA™ (77), E Series™ (47), Meridian™ (18), and Citation™ (16) (all Stryker, Mahwah, New Jersey). The mean follow-up was 105.5 +/− 60.8 months (range, 20 to 257 months). As part of an ongoing IRB-approved study, data collected includes Harris Hip (HHS) and QOL scores, re-operations (including revisions), and complications.

Results: The femoral components of 142 cases were not revised. These patients had a mean HHS of 86.3 +/− 13.2 points. Of the 15 revisions (9.6%), the primary reasons were loosening and/or significant osteolysis, but there was one infection and one chronic dislocation. The revisions included 10 PCA™ (13.0%) with a mean time to revision of 85 months (range, 25 to 132); 2 E Series™ (4.3%) with a mean time to revision of 85 months (2 cases in one patient; 68 and 101 months); 2 Meridian™ (11.1%) with a mean time to revision of 193 months (2 cases; 98 and 107 months); and 1 Citation™ (6.3%) with a time to revision of 30 months. The pooled revision rate of the 2^nd, 3rd, and 4^th generation was 5 of 80 (6.3%).

Discussion: There were no significant difference in revision rates between the different generations of uncemented femoral components (Chi Square, p=.433). However, the revision rates for the later generations were lower than the earlier generations.

Introduction: In the evaluation of various treatments that may have an effect on bone, there are certain inherent difficulties in selecting an appropriate outcome measure to determine whether a specific treatment is efficacious. This is particularly true for clinical studies.

Methods: Using Pubmed, a service of the U.S. National Library of Medicine that searches MEDLINE and other life science journals for citations of biomedical articles, a review of the current instruments used for outcome measures relating to osteonecrosis and bone blood flow was conducted. Abstracts from previous ARCO meetings were also reviewed.

Results: For the treatment of osteonecrosis, most outcome measures have focused on pain relief, surgery or need for surgery, disease progression (advancing stage), and change in lesion size. The first three options may be influenced by investigator bias and knowledge/experience. The last option may also be influenced by the technique used.

Imaging techniques continue to gain in sophistication. Gd-enhanced MRI can be used to assess perfusion of the diseased tissue. Doppler ultrasonography has also been used to estimate blood flow noninvasively. Near Infrared Spectroscopy (NIRS) can be used to measure tissue oxygenation.

While there has been recent interest in using biomarkers or genetic markers in the diagnosis and analysis of disease progression, more research is needed to determine the sensitivity and specificity of these techniques with respect to osteonecrosis.

Conclusion: Although there are a number of tests that can be used to evaluate the effect of a specific treatment on osteonecrosis, the definitive assessment will likely remain whether the disease progresses to the point that major surgery (resurfacing, vascularized fibular grafting, total joint replacement, e.g.) is required to relieve pain and restore function.

Developments in motion analysis technology over the last two decades have enhanced our understanding of human locomotion. However, such advances in knowledge are futile if no practical use is made of them. Scientists and engineers need to make the most of these developments by forging stronger links with orthopaedic surgeons and applying further advances in their knowledge to clinical problems for the long-term benefit of patients. This need has been identified by many in the field of biomechanics and a “serious attempt [has been made] to take gait analysis out of the research laboratory and into the clinic” (Whittle, 1996 pp.58). For this reason, the aim of this research is to develop an objective and quantitative classification tool that uses motion analysis to aid orthopaedic surgeons and therapists in making clinical decisions. Practical applications of this tool would include joint degeneration monitoring; diagnostics; outcome prediction for surgical intervention; post-operative monitoring and functional analysis of joint prosthesis design. The classification tool (Jones, 2004), based around the Dempster-Shafer theory, is logical and visual; as the progression from obtaining clinically relevant measurements to making a decision can be clearly followed. The current study applies the tool to identify knee osteoarthritis (OA) and post-operative recovery following total knee replacement (TKR) surgery. Knee function data from 42 patients (22 OA and 20 normal (NL)) were collected during a clinical knee trial (Holt et al., 2000). Nine of the OA patients were followed at 3 stages following TKR surgery. Using the tool, a subject’s knee function data are transformed into a set of belief values: a level of belief that the subject has OA knee function, a level of belief that the subject has NL knee function and an associated level of uncertainty. These three belief values are then characterized in a way that enables the final classification of the subject, and the variables contributing to it, to be represented visually. Initial studies using this technique have provided encouraging results for accuracy, validity and clinical relevance (Jones, 2004). The tool was able to differentiate between the characteristics of NL and OA knee function with 98% accuracy. The belief values and simple visual output showed the variation in the extent to which patients had:

developed OA and;

Furthermore, the visual output enabled straightforward comparison between subjects and indicated the variables that were most influential in the decision making process for comparison with clinical observations and quality of life scores. The tool is generic, and, as such, would be applicable to a wide range of pathological classification and predictive problems.

Results Holt, C.A. et al. (2000). Computer Methods in Biomechanics and Biomedical Engineering 3. Lisbon. Gordon and Breach Science Publishers SA. pp.289–294. Jones L. (2004). The development of a novel method for the classification of osteoarthritic and normal knee function. PhD Thesis. Cardiff University Whittle, M.W. (1996). Gait analysis: an introduction. 2nd Edition. Oxford; Boston: Butterworth-Heinemann.

Introduction: Multiple classification systems for avascular necrosis of the hip have been developed to assist physicians in the diagnosis and treatment of this potentially debilitating disorder. However, this lack of consistency makes clinical decision making difficult when comparing publications. The purpose of this study was to quantify the classification systems reported since 1985 (post-MRI) and identify consistent factors which would allow cross-publication comparisons to be made.

Materials and Methods: The authors performed a PubMed search for reports of outcome studies concerning treatment methods of hip avascular necrosis that were the initial basis for analysis. All studies reported since 1985 were included in the analysis if outcomes of greater than 10 patients treated for this disease were reported. Classification systems utilizing at least one factor were also identified. Tabulation of how frequently these classification systems were used in terms of the number of studies reporting results was performed.

Results: Fifteen major classification systems utilizing more than one radiographic factor were identified with 9 having one to three modifications reported throughout the literature. Additionally, 14 systems utilized either MRI or anatomic factors. Cross-publication analysis revealed five major classification systems which were utilized in greater than 80% of the reported studies.

Discussion: This analysis of the reported classification systems for avascular necrosis of the femoral head revealed several similarities between systems. A cross system analysis can be made if data is collected according to patient symptoms, magnetic resonance imaging findings, and x-ray findings which would allow for the use of any staging system.

Introduction: Evidence-based medicine is a form of practice in which the physician accesses relevant, state-of-the-art research findings to guide the care of the individual patient (Gordon and Cameron, 2000). Therefore, evidence-based medicine should influence the decision making process when developing a treatment algorithm for early stage osteonecrosis. It was the purpose of this project to explore the literature concerning surgical options that are used currently to treat early stage osteonecrosis.

Materials and Methods: Literature searches were conducted using PubMed (National Library of Medicine, USA) to identify journal articles pertaining to the treatment of pre-arthrosis osteonecrosis during the past decade. The articles were screened to include only those with greater than 5 patients and greater than two year follow-up.

Results: Published reports in medical journals included: core decompression with and without nonvascular grafting (18); core decompression augmented with BMP or bone marrow cells (2); bone cement (1); vascularized graft – fibular or iliac (10); osteotomy (26); osteotomy and vascularized grafts (3); trap-door procedure (2); and hemiarthroplasty/resurfacing arthroplasty (9). There was one review of nonoperative treatment, but no clinical studies. There were only a few case reports concerning osteochondral graft/osteochondroplasty; which did not meet the inclusion criteria. Several classification systems were used: Ficat and Arlet (55%); University of Pennsylvania / Steinberg (21%); Japanese Investigational Committee (13%); Marcus (2%); Myers (3%); ARCO (5%), and other (1%). A majority of reports included follow-up of 5 years or greater (91%). Most studies (91%) were not randomized, control-matched, or prospective.

Discussion: Several surgical options are available for the treatment of pre-arthrosis osteonecrosis. However, it is not possible to apply evidence-based medicine practices to the research relating to the treatment of osteonecrosis as most of the research is not controlled and not comparative. This represents a substantial void in our knowledge base concerning osteonecrosis which remains to be filled.

Introduction: The response of osteoblasts to dexamethasone is dose-dependent. While low doses are used to stimulate osteoblasts to maintain their phenotype, high doses are cytotoxic. The purpose of this study was to test the hypothesis that mechanical stimulation alters the response of osteoblast-like cells to dexamethasone.

Materials & Methods: MG-63 cells were propagated on 6-well Flexcell plates (flexible silicone membranes) under standard culture conditions. One half of the plates were subjected to biaxial strain at a frequency of 0.5 Hz through an imposed vacuum pressure of -7kPa (~1% stretch; 0.01 strain) for 42 hours using the Flexercell Apparatus. Replicate samples were maintained under static conditions. Simultaneously, the cells were exposed to either 0, .001, .01, or .1 nM of dexamethasone. The wells were then spiked with tritiated thymidine for 6 hours. The results were normalized to the control values. Triplicate wells were included for each experimental condition; and the experiment was repeated four times. Data were analyzed by JMP statistical package (SAS).

Results: Increasing doses of dexamethasone resulted in decreasing cellular proliferation. For the unflexed cells, we noted the following reduction in proliferative capacity: 0.86% ± 0.09 (.001nM), 0.50% ± 0.07 (.01nM), and 0.39% ± 0.07 (.1nM). Similar results were observed for the cells exposed to cyclic loading: 0.89% ± 0.12 (.001nM), 0.52% ± 0.08 (.01nM), and 0.47% ± 0.07 (.1nM).

Discussion: Our results confirmed the work of others that there is a decrease in the proliferation of osteoblasts (incubated under static conditions) when exposed to high levels of dexamethasone. Although cyclic loading had no effect on the proliferative response of osteoblasts to dexamethasone, it may still have had an effect on cellular metabolism or function, which remains to be evaluated.

Introduction: In a previous study (ARCO, 2002), we reported that the clinical results of revision total hip arthroplasty for osteonecrosis patients were less satisfactory than those found for a matched group of osteoarthritis patients. The aim of this study was to evaluate the potential factors that may have contributed to these findings.

Materials and Methods: This study included 34 hips in 30 osteonecrosis patients who had undergone revision of a femoral total hip arthroplasty component. There were 19 men (22 hips) and 11 women (12 hips) who had a mean age of 46.1 years (range, 28 to 69 years). The surgeries were performed between March 1984 and January 2001. Most femoral stems (91%) were implanted without cement. Prostheses were of different stem lengths, but most (97%) were proximally porous-coated. The mean follow-up was 8.2 years [range, 0.1 (a re-revision) to 19.8 years]. A physical examination as well as patient and physician outcome forms were collected at each visit. Preoperative x-rays were categorized according to the technique of Della Valle and Paprosky. A Kaplan-Meier survival analysis was performed (PEPI statistical software package).

Results: Risk factors for osteonecrosis included 15 corticosteroid, 8 alcohol, 7 trauma, and 4 unknown. This was the first revision in 27 cases, second revision in 5 cases, and third revision in 2 cases. Preoperatively, the defects included 4 Type I, 9 Type II, 15 Type IIIA, 2 Type IIIB, 1 Type IV, and 3 unknown types. Of the 34 hips, the femoral component was re-revised in 12 cases. One of the failures was the only fully porous coated stem that was implanted. One of the 3 cemented implants failed, as compared to 11 of the 31 implanted without cement. Survival rates were 90.9% (74.4%–97.1%) at 5 years, 54.8% (24.9%–81.6%) at 10 years, 54.8% (19.9%–85.6%) at 15 years, and 27.4% (1.7%–88.9%) at 20 years. There was no relationship between frequency of re-revision and defect category, risk factors, or age.

Discussion: Although there was a high failure rate (12/34; 34%) in this patient cohort, over 50% survived at least 10–15 years. The lack of a relationship between the patient age or the extent of defect and re-revision suggest that other factors concerning this disease need to be examined.

Interbody fusion is increasingly widely used as a treatment for intervertebral disc disorders, but the biomechanics of the procedure are not well understood. The compressive loads through the spine are largely carried by the implant or bone graft, which typically rests on a relatively small area of the vertebral body. As the compressive strength of the bone is very low, subsidence of the implants into the vertebral bodies is a common clinical complication.

Previous biomechanical studies of spinal fusion have concentrated on the stiffness of the constructs, which is important in promoting fusion. Preliminary studies have shown that there are large differences in compressive strength between different implant systems, and gave an insight into the biomechanical factors that are important in determining the strength of spinal fusion constructs. This paper reports part of a larger on going study comparing anterior and posterior fusion systems, with various methods of fixation.

A major problem in interpreting the results of these tests is to distinguish between initial settling of the implants and the onset of failure to construct. We have developed a novel technique using acoustic emission monitoring to detect microcracking in the bones, which allows the onset of failure to be distinguished from initial bedding in of the implants.

Two implant systems were tested, the Syncage and the Contact fusion cage. The cages were implanted into porcine lumbar spines at L4-L5, and the implanted motion segment was then dissected out. Steel plates were mounted on each end using bone cement to ensure an even distribution of load through the vertebral body. The complete constructs were then loaded in compression, using acoustic emission sensors to detect microcracking in the bones. The load was cyclically increased in o.5kN steps until failure occurred.

The acoustic emission technique gave a sensitive indication of the onset of damage in the bones and allowed the initial settling of the implant under load to be identified. Using cyclic unloading and reloading, it was possible to accurately identify whether this damage had weakened the construct or increased its strength by redistributing stress concentrations. Initial results indicate that the Contact fusion cage fails at a much lower load than the Syncage in this model; this is ascribed to the very small contact areas between the cage and the vertebral body, which results in high compressive stresses in the bone. Under large compressive loads it appears that the constructs become unstable, and fail by buckling and plastic collapse of the vertebral bodies. Various failure models are therefore possible depending on which part of the vertebral body starts to collapse first.