Standard evaluation and diagnosis of pincer-type femoroacetabular impingment (FAI) relies on anteroposterior (AP) radiographs, clinical evaluation, and/or magnetic resonance imaging (MRI). However, the current evaluation techniques do not offer a method for accurately defining the amount of acetabular rim overcoverage in pincer-type FAI. Several studies have remarked on the particular problems with radiographic evaluation, including beam divergence, difficulty with defining the acetabular rim, and pelvic tilt. Some studies have proposed methods to mitigate these issues; however, radiographic analysis still relies on projected and distorted images, making it difficult to acquire an accurate quantitative estimate of the amount of crossover. We propose a technique that utilises computed tomography (CT) data to accurately quantify the amount of acetabular crossover while accounting for known diagnostic problems, specifically pelvic tilt.

This work describes a novel method that utilises CT data of a patient's afflicted hip joint region to assess the amount of acetabular overcoverage due to pincer deformity. The amount of overcoverage was assessed using a spline curve defined through the segmentation of the acetabular rim from CT data. To mitigate pelvic tilt, the user selected points to define both the pubic symphysis and the promontory in a lateral digitally reconstructed radiograph. The algorithm corrected the pelvic tilt by adjusting to a defined neutral position (in our case, a 60°), and the user adjusted for slight rotation differences ensuring there was a vertical line connecting the symphysis and the sacrococcygeal joint.

After successfully repositioning the pelvis, the algorithm computed the amount of acetabular overcoverage. The algorithm identified the superolateral point of the acetabulum and the most inferior points of the anterior and posterior rim. A line, the mid-acetabular axis, was constructed between the superolateral point and the midpoint of the most inferior points on the anterior and posterior rims; the mid-acetabular axis was extended anterior and posterior to create a plane. Crossover occurred when the anterior rim of the acetabulum intersected this plane. If an intersection occurred, the algorithm measured the length of the mid-acetabular axis, and the length and width of the section representing overcoverage. These points were then projected onto anteroposterior DRRs and again measured to generate a basis of comparison.

We tested our method on four cadaveric specimens to analyze the relationship between radiographic assessment and our technique. We simulated varying degrees of impingement in the cadavers by increasing the amount of pelvic tilt and defining that as the neutral position for a given trial. Moreover, we assessed interobserver variability in repositioning the pelvis as to the effect this would have on the final measurement of crossover length and width.

The software achieved consistent, quantitative measurements of the amount of acetabular overcoverage due to pincer deformity. When compared with conventional radiographic measurements for crossover, there was a significant different between the two modalities. Specifically, both the ratios of crossover length to acetabular length and crossover width to crossover length were less using the CT-based approach (p < 0.001). Moreover, there were no significant differences between observers using our approach.

The proposed technique can form the basis for a new way to diagnosis and measure acetabular overcoverage resulting in pincer impingement. This computational method can help clinicians to accurately correct for tilt and rotation, and subsequently provide consistent, quantitative measurement of acetabular overcoverage.

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.

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: 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.

Aim: The purpose of this retrospective study was to evaluate the migration and survival of the femoral component following cementless total hip replacement in patients with osteonecrosis of the femoral head in comparison to patients with osteoarthritis of the hip. Methods: The study included 31 patients who underwent 35 cementless total hip replacements for advanced osteo-necrosis of the femoral head and 49 patients with 58 total hip arthroplasties for osteoarthritis. The migration analysis of the femoral component was performed with the Einzel-Roentgen-Bild-Analyse (EBRA). Results: The follow-up for the patients with osteonecrosis and osteoarthritis of the hip was 6.1 and 5.9 years. Five stems (15.2%) from the osteonecrosis and two stems (3.6%) from the osteoarthritis group were revised for aseptic loosening. The median stem subsidence in the patients with osteonecrosis and osteoarthritis was 1.7mm (95% CI, 1 to 3.5) and 0.65mm (95% CI, 0.5 to 0.8), respectively (p< 0.01). Survivorship analysis with stem revision as endpoint for failure showed in the osteonecrosis and osteoarthritis group of 74.5% (95% CI, 56.1% to 92.8%) and 96.4% (95% CI, 91.5% to 100%), respectively (p< 0.05). Conclusions: The signiþcant difference in the subsidence and survival of the femoral component in the patients with osteonecrosis and osteoarthritis of the hip indicates that the bone around the prostheses is obviously inßuenced by the osteonecrosis. Young patients diagnosed with osteonecrosis of the femoral head should be treated with the most conservative treatment to preserve the hip joint.

We performed a retrospective analysis of the clinical and radiological outcomes of total hip replacement using an uncemented femoral component proximally coated with hydroxyapatite. Of 136 patients, 118 who had undergone 124 primary total hip replacements were available for study. Their mean age was 66.5 years (19 to 90) and the mean follow-up was 5.6 years (4.25 to 7.25). At the final follow-up the mean Harris hip score was 92 (47.7 to 100). Periprosthetic femoral fractures, which occurred in seven patients (5.6%), were treated by osteosynthesis in six and conservatively in one. We had to revise five femoral components, one because of aseptic loosening, one because of septic loosening and three because of periprosthetic fracture. At the final follow-up there were definite signs of aseptic loosening in two patients.

Radiologically, proximal femoral bone loss in Gruen zones I and VI was evident in 96.8% of hips, while bone hypertrophy in zones III and V was seen in 64.7%. In 24 hips (20.2%) the mean subsidence of the stem was 3.7 mm which occurred within the first 12 postoperative weeks. This indicated poor initial stability, which might have been aggravated by early weight-bearing. The high rate of failure in our study suggests that proximal femoral bone loss affects the long-term survival of the replacement.