Francesco Traina

Early diagnosis of ceramic liner fracture. guidelines based on a twelve-year clinical experience

Osteolytic lesions due to wear debris are the major long-term problem associated with total hip replacement1. To avoid wear debris, hard-bearing-surface total hip prostheses with improved tribological properties have been introduced into surgical practice. Ceramic surfaces have had some promising long-term results2, and modern metal-backed alumina cups have been associated with very good clinical results3-5. Alumina has excellent tribological properties and a very high Youngs modulus that leads to very good compression strength, but it has poor bending strength: it has no way to deform6. This means that ceramic can break without warning. Under normal physiologic conditions, modern ceramics never reach their fatigue limit, so ceramic head fractures are rare (a rate of 0.004%7 in one study). In contrast, ceramic liner fractures are not well recognized, and their frequency could be underestimated (Fig. 1). In addition, it is difficult to identify patients who are at risk because liner fractures can be due to multiple causes: dislocation, impingement, malpositioning, and microseparation8,9. Fig. 1 A ceramic liner fracture. The diagnosis is often difficult to make on the basis of standard radiographs. A fragment of ceramic is visible near the calcar (arrow). The liner was found to be fractured (arrow) at revision surgery. While many efforts have been made to improve the ceramic manufacturing process and the surgical technique for inserting ceramic components10, little has been reported regarding the early diagnosis of ceramic fracture. When a ceramic fracture involves the liner and is the consequence of repeated microtrauma, the diagnosis is rarely made early, except when ceramic fragments are visible on radiographs. Moreover, decision-making regarding revision surgery after a ceramic-on-ceramic prosthesis has failed is difficult: the ceramic fragments that have spread into the periarticular space are abrasive and …

MicroCT examination of human bone specimens: effects of polymethylmethacrylate embedding on structural parameters

X‐ray microtomography permits the nondestructive investigation of trabecular and cortical bone specimens without special preparation of the sample. To do a quantitative characterization, the cross‐section images have to be binarized, separating bone from nonbone. For this purpose, a widely used method is uniform thresholding. However, for commonly available microtomography scanners which use a polychromatic X‐ray source, it is unclear what effect the surrounding medium (e.g. air, saline solution, polymethylmethacrylate) has on the threshold value used for the binarization. In the literature an easy procedure to find the optimal uniform threshold value for a given acquisition condition is reported. By applying this procedure, the present work investigated whether a microtomography scan of trabecular bone samples in air or embedded in polymethylmethacrylate gave the same results in terms of structural parameters. The gold standard, that is, histological sections, was used as a reference. Two fixed threshold values were found, one for the microtomography scans performed in air and one for the scans with the same samples embedded in polymethylmethacrylate. These were applied on the correspondent microtomography images for the estimation of structural parameters, such as bone volume fraction, direct trabecular thickness, direct trabecular separation and structure model index. Paired comparisons were made in bone volume fraction between histological sections and microtomography cross‐sections for the same bone samples scanned first in air and then embedded in polymethylmethacrylate, by which no significant differences were found. Paired comparisons were also made in bone volume fraction, direct trabecular thickness, direct trabecular separation and structure model index for the same samples over volumes of interest of 4 × 4 × 4 mm3 between microtomography scans in air and scans with the samples embedded in polymethylmethacrylate. Neither these comparisons showed significant differences. This leads to the conclusion that structural parameters estimated by microtomography for human trabecular bone samples scanned either in air or embedded in polymethylmethacrylate are not affected by the surrounding medium (i.e. presence or absence of polymethylmethacrylate), provided that the corresponding optimal threshold value is applied for each acquisition condition.

Sex differences in hip morphology: Is stem modularity effective for total hip replacement?

Total joint arthroplasty, one of the most successful orthopaedic procedures, predictably relieves pain and improves function for patients with a painful arthritic hip joint1. This high success rate has increased patient expectations, particularly those regarding hip function, after the surgery. To achieve better function and to reduce the implant dislocation rate, more attention has been given to the role of the restoration of femoral offset and soft-tissue balancing2,3. Surgeons today are committed to restoring the anatomy in each case independent of the patients age or sex or the pathological condition of the hip. Anatomic studies of hip anatomy, specifically on the femoral side, have shown sex-based anatomic differences4-8. Women tend to have a shorter femoral neck, a thinner femoral shaft, a lower cervicodiaphyseal (CCD) angle, a lower femoral offset, and greater anteversion of the femoral neck (Fig. 1). These differences should be addressed during revision hip surgery in order to restore hip anatomy. In particular, to achieve proper soft-tissue balancing, the femoral offset should be accurately restored. The femoral offset is represented by the perpendicular distance from the center of the femoral head to the long axis of the femur (Fig. 2). McGrory et al.9 found a correlation between a lack of restoration of femoral offset and abductor muscle weakness and limping. These results depend on hip mechanics, with a fulcrum between body weight and the hip abductors (Fig. 3). The length of the lever arm of the hip abductors is smaller than that of body weight. Therefore, the abductors must generate a force that is larger than body weight to maintain a level pelvis. In contrast, an increase in femoral offset increases the lever arm of the abductors, reducing the force required to balance body weight and thereby …

Fracture of Ceramic Bearing Surfaces following Total Hip Replacement: A Systematic Review

Ceramic bearing surfaces are increasingly used for total hip replacement, notwithstanding that concern is still related to ceramic brittleness and its possible mechanical failure. The aim of this systematic review is to answer three questions: (1) Are there risk factors for ceramic component fracture following total hip replacement? (2) Is it possible to perform an early diagnosis of ceramic component failure before catastrophic fracture occurs? (3) Is it possible to draw guidelines for revision surgery after ceramic components failure? A PubMed and Google Scholar search was performed and reference citations from publications identified in the literature search were reviewed. The use of 28 mm short-neck femoral head carries an increased risk of fracture. Acetabular component malposition might increase the risk of ceramic liner fractures. Synovial fluid microanalysis and CT scan are promising in early diagnosis of ceramic head and liner failure. Early revision is suggested in case of component failure; no consensus exists about the better coupling for revision surgery. Ceramic brittleness remains a major concern. Due to the increased number of ceramic on ceramic implants, more revision surgeries and reports on ceramic components failure are expected in the future. An algorithm of diagnosis and treatment for ceramic hip failure is proposed.

The predictive Power of Surface Profile Parameters on the Amount of Wear Measured In Vitro on Metal-On-Polyethylene Artificial Hip Joints

Abstract Various studies report a weak correlation between the average surface roughness Ra of metallic ballheads and the observed wear rate of the polyethylene cups coupled to them. The aim of this study is to verify, with controlled in vitro experiments, whether other parameters such as the total roughness Rt, and the skewness Rsk are better predictors of the polyethylene wear when the metallic heads present a surface conditioning that varies substantially from specimen to specimen, as is usually the case with retrieved specimens. Twelve CoCrMo (cobalt-chromium-molybdenum) ballheads were intentionally damaged in order to reproduce a wide spectrum of surface conditioning and were then subjected to the standard wear test against polyethylene cups, using a hip joint wear simulator. After 2 × 106 cycles the weight lost by the cups was assessed with a gravimetric procedure, and the surface roughness of the metallic ballheads was qualified in terms of Ra, Rt, and Rsk. The various parameters were correlated to the weight loss using a linear regression analysis. The skewness Rsk showed a coefficient linear regression R2 = 0.80, while the average roughness Ra, used in most previous studies, presented an R2 = 0.56. It was concluded that when specimens with substantially different surface conditioning are compared, as in retrievals analysis, it is also important to report the skewness Rsk so that qualify the surface roughness of the specimens can be qualified.

Current concepts in the biopsy of musculoskeletal tumors: AAOS exhibit selection.

BACKGROUND A musculoskeletal tumor biopsy can involve fine needle aspiration, core needle biopsy, or incisional biopsy. Controversy regarding the diagnostic yield of these biopsy techniques continues. The purpose of this article is to summarize the current concepts in the biopsy of musculoskeletal tumors. METHODS We performed a literature review of clinical articles reporting on the biopsy of bone and soft-tissue primary tumors. Clinical articles were excluded on the basis on abstract content if they represented case reports, review or opinion articles, or technique descriptions. Eighteen of the thirty-nine articles that remained were excluded because the results did not indicate the diagnostic accuracy of the various biopsy techniques. Thus, twenty-one articles with diagnostic data on the biopsy of bone and soft-tissue tumors were included in this review. RESULTS Core needle biopsy appeared to be more accurate than fine needle aspiration, and incisional biopsy appeared to be more accurate than both of these techniques, but the differences did not reach significance. Incisional biopsy was more expensive than the percutaneous biopsy methods. In deep musculoskeletal tumors, incorporation of ultrasonography or computed tomography for guidance is easy and safe and can be useful for increasing the accuracy of the biopsy. Advantages of a percutaneous technique compared with an incisional one are the low risk of contamination and the minimally invasive nature. Certain anatomic locations and histologic types were associated with diagnostic difficulty. Vertebral tumors had the lowest diagnostic accuracy regardless of the biopsy technique. Myxoid, infection, and round cell histologies were associated with the lowest diagnostic accuracy. CONCLUSIONS The current literature has not clarified the optimal biopsy technique for the diagnosis of bone and soft-tissue tumors. However, core needle biopsy is usually preferable to incisional biopsy because of the low risk of contamination and the low cost. In addition, the use of imaging guidance increases the diagnostic accuracy of musculoskeletal biopsies and reduces the risk of complications. If the result of a percutaneous biopsy is nondiagnostic, a small incisional biopsy should be performed. LEVEL OF EVIDENCE Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Revision of ceramic hip replacements for fracture of a ceramic component: AAOS exhibit selection

Revision of a total hip arthroplasty due to fracture of a ceramic component is rare. The fracture rate of ceramic components has been reported to be between 0.004%1 and 0.05%2 for femoral heads and between 0.013%2 and 1.1%3 for acetabular liners. Nevertheless, this problem is occurring more frequently because of the increasing use of ceramic total hip replacements. Revision arthroplasty performed because of a fractured ceramic component carries a high risk of failure: the fragments of the failed component are sharp and harder than metal; if left in the articular space, these fragments would act as an abrasive paste, and the use of a metal head against a polyethylene liner in the revision arthroplasty would quickly lead to catastrophic wear and failure of these new total hip implants4-6 (Fig. 1). Thus, revision arthroplasty performed because of a fractured ceramic component is difficult and the failure rate has been reported to be as high as 31%6. Fig. 1 Early failure of a revision arthroplasty performed because of fracture of a ceramic femoral head. The aims of the present study were to evaluate the outcome of revision total hip arthroplasty performed specifically to treat fracture of a ceramic component, to identify technical factors affecting the outcome, to propose some tips and tricks to make the process of revising a total hip arthroplasty for this reason easier, and to suggest guidelines for the treatment of a ceramic component fracture. From 1990 to 2009, 8022 primary ceramic hip prostheses were implanted at our institute; 3275 (40.8%) were in men and 4747 (59.2%) were in women. Additional patient demographic information is given in Table I. Kaplan-Meier curves with revision for ceramic fracture as the end point were computed to evaluate the rate of ceramic fracture. The analysis …

Risk factors for ceramic liner fracture after total hip arthroplasty.

The aim of this study was to detect risk factors for ceramic liner fractures. 26 cementless ceramic on ceramic (COC) total hip arthroplasties (THA) revised because of ceramic liner fracture in 24 patients were compared with 49 well-functioning COC THA performed in 49 patients. Demographic parameters, type of ceramic of the liner, size and neck length of the femoral head, cup abduction angle, cup anteversion, femoral off-set, height of the centre of rotation and the incidence of noisy hips during follow-up examination were compared. A greater number of cups placed outside the optimal range of cup anteversion was found in the fracture group (p = 0.03). An audible noise was detected in 21 cases (80.7%) in the fracture group and in 3 cases (6.1%) in the non-fracture group (p = 0.001). A cup anteversion angle out of the optimal range of 15°+/-10° was found to be a risk factor for ceramic liner fracture and the presence of a noisy hip frequently anticipated the failure. In our opinion neck-to-cup impingement with head subluxation and edge loading on the liner rim could have an important role in the onset of noise and subsequent liner failure, and cup malposition contributes to this mechanism of failure.

Effect of the initial implant fitting on the predicted secondary stability of a cementless stem

A numerical model able to investigate the influence of biomechanical factors on the long-term secondary stability of implants would be extremely useful for the design of new cementless prosthetic devices. A purely biomechanical model of osseo-integration has been developed, formulated as a rule-based adaptation scheme. Due to its complexity, the problem was divided into three steps: preliminary implementation of the model (proof of concept); implementation of the complete model and investigation of the model solution; and model validation. The paper describes the first of these three steps. The model was implemented as a discretestates machine, and the few parameters required were derived from the literature. It was then applied to a real clinical case. The study was conducted using the frictional contact finite element model of a human femur implanted with a cementless anatomical stem. A stable solution was achieved after between three and 15 iterations for all initial positions considered. Similar initial conditions yielded similar final configurations. The model predicted all initial configurations, with the exception of a partial osseo-integration, ranging between 62% (distal fit) and 78% (proximal fit) of the viable interface. This is in good agreement with the values reported in the literature that never exceed 75%, even in the best conditions, and report better clinical results for proximal fit. For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening.

Ceramic-On-Metal for Total Hip Replacement: Mixing and Matching Can Lead to High Wear

Ceramic-on-ceramic and metal-on-metal bearing surfaces are often employed for total hip replacement because of their resistance to wear. However, they have some limits: brittleness is a major concern for ceramic, and ion release is a drawback for metal. To reduce the effect of these limitations, a hybrid coupling of ceramic-on-metal has been proposed. The theoretical advantage of this new coupling might lead orthopedic surgeons to use it indiscriminately. We asked whether the wear rate of this innovative solution was comparable with that of ceramic-on-ceramic, which is considered to be the gold standard for wear resistance. In a hip simulator study, we tested the wear pattern of a hybrid ceramic-on-metal coupling supplied by the same distributor; in particular, three different configurations were tested for 5 million cycles: 36-mm ceramic-on-ceramic, 32-mm and 36-mm ceramic-on-metal. These combinations were gravimetrically and geometrically evaluated. After 5 million cycles, the volumetric loss for the metal acetabular cups (Phi 36-mm) was 20-fold greater than that of the ceramic cups of the same size (Phi 36-mm); a volumetric loss of 4.35 mm(3) and 0.26 mm(3) was observed, respectively, for ceramic-on-metal and ceramic-on-ceramic combinations. Significant statistical differences were observed between all 36-mm different combinations (P < 0.0001). The increased diameter of the 36-mm ceramic-on-metal configuration resulted in a lower volumetric loss compared with that of the 32-mm ceramic-on-metal configuration. Our findings showed an increase in wear for the proposed hybrid specimens with respect to that of the ceramic-on-ceramic ones. This confirms that even in the case of ceramic-on-metal bearings, mixing and matching could not prove effective wear behavior, not even comparable with that of the ceramic-on-ceramic gold standard.