Radiographic definition of pelvic osteolysis following total hip arthroplasty

Use of morphometry to quantify osteolysis after total hip arthroplasty

BACKGROUND

Progressive osteolysis threatens the longevity of hip arthroplasties and radiographic review is recommended. Measurement of osteolytic lesions in a clinical setting has not been achieved easily in the past. Other radiologic investigations provide accurate information but cost and risk to the patient prohibit their use in routine review.

QUESTIONS/PURPOSES

We developed a simple, reliable tool to be used in hip arthroplasty review to quantify osteolytic changes seen on plain film radiographs.

METHODS

A morphometric grid was developed and tested on simulated and actual osteolytic lesions. Four health professionals measured lesions on each of two occasions. Intraclass correlation coefficients (ICC) for interobserver and intraobserver reliabilities were calculated and Bland-Altman plots were constructed for graphic analysis.

RESULTS

The ICCs for interobserver reliability on the simulated and actual osteolytic lesions were in the range 0.90 to 0.96. The values for intraobserver (test-retest) reliability were 0.97 to 0.98. The Bland-Altman plots confirmed agreement and in each case, proximity of the mean to zero indicated no significant bias.

CONCLUSIONS

The data show a morphometric grid is reliable for measuring osteolytic changes after hip arthroplasty.

CLINICAL RELEVANCE

This tool has potential to improve monitoring processes for hip arthroplasty and to be useful in future research studies. Additional work is needed to test for validity and clinical importance of the measurements obtained.

Distribution of periacetabular osteolytic lesions varies according to component design

Using computed tomography, the volume, location, and number of osteolytic lesions were determined adjacent to 38 Harris-Galante 1 (HG-1) acetabular components fixed with screws and 19 porous-coated anatomic (PCA) acetabular components press-fitted without screws. The median implantation times were 16 and 15 years, respectively. The mean total lesion volumes were similar: 11.1 cm(3) (range, 0.7-49 cm(3)) and 9.8 cm(3) (range, 0.4-52 cm(3)), respectively, for hips with HG-1 and PCA components (P = .32). There was a significant difference in the proportion of rim-related, screw or screw hole-related, and combined lesions between the 2 component designs (P < .0001). HG-1 components had more screw and screw hole-related lesions, and PCA components had more rim-related lesions. Although there are concerns regarding screw and screw hole-associated osteolysis, these findings suggest that peripheral fixation may be well maintained in the long term with the use of multiple-hole acetabular components with screw fixation.

Hylamer vs conventional polyethylene in primary total hip arthroplasty: a long-term case-control study of wear rates and osteolysis

The long-term results of Hylamer implants have not been reported previously. Clinical and radiographic results of a consecutive series of 43 patients (45 hips) who had primary total hip arthroplasty using Hylamer liners were compared with those of 37 patients (43 hips) who had conventional liners after 10-year follow-up. The linear wear rates for Hylamer and conventional polyethylene acetabular liners were 0.21 and 0.20 mm/y, respectively. The number of pelvic osteolytic lesions and their size detected on plain radiographs were significantly greater for Hylamer liners. Seven Hylamer hips were revised or are pending revision for osteolysis (16%) compared with 1 control hip. Close radiographic surveillance of patients who have Hylamer liners and evidence of osteolysis found on plain radiographs is warranted.

Pelvic osteolysis relationship to radiographs and polyethylene wear

The relationship of radiographic pelvic osteolysis to computed tomographic (CT) volume and polyethylene wear remains controversial. We evaluated the sensitivity and specificity of radiographs in detecting osteolysis considering CT scan as the true value, in 118 hips with cementless cups. Correlation between osteolysis volume in CT, area of osteolysis in radiograph, and linear wear of polyethylene was assessed. The sensitivity and specificity of anteroposterior radiographs for detection of osteolysis was 57.6% and 92.9%, respectively. Addition of oblique radiographs increased the sensitivity to 64.4% without changing the specificity. The sensitivity increased to 92.8% for lesion more than 1000 mm(3). There was good correlation between 2-dimensional (2D) osteolytic area in radiograph and 3-dimensional (3D) volume (r = 0.74) in CT scan and linear wear of polyethylene showed good correlation with 3D CT volume (r = 0.62) and 2D area in radiograph (r = 0.60). Thus radiographs are useful to screen clinically significant osteolysis.

Magnetic resonance imaging in the diagnosis and management of hip pain after total hip arthroplasty

Evaluation of pain following total hip arthroplasty (THA) can be challenging in the absence of radiographic pathology. This study aimed to examine the diagnostic utility of magnetic resonance imaging (MRI) in the evaluation of enigmatic hip pain following THA. We reviewed a series of patients who were evaluated with MRI after presenting with enigmatic hip pain following THA. MRI was able to demonstrate pathology in the periprosthetic tissues in all hips with minimal artifact. Patients underwent a range of conservative and operative interventions depending on the underlying pathology. If used discriminately in situations where pathology cannot be detected by conventional methods, MRI is a highly effective modality that can aid in the diagnosis of a wide range of disorders thereby allowing the clinician to determine the most appropriate intervention.

Cross-linked compared with historical polyethylene in THA: an 8-year clinical study

Wear particle-induced osteolysis is a major cause of aseptic loosening in THA. Increasing wear resistance of polyethylene (PE) occurs by increasing the cross-link density and early reports document low wear rates with such implants. To confirm longer-term reductions in wear we compared cross-linked polyethylene (irradiation in nitrogen, annealing) with historical polyethylene (irradiation in air) in a prospective, randomized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years (mean, 8 years; range, 7-9 years). The insert material was the only variable. The Harris hip score, radiographic signs of osteolysis, and polyethylene wear were recorded annually. Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed (five patients died, three were lost to followup). At 8 years, the wear rate was lower for cross-linked polyethylene (0.088 +/- 0.03 mm/year) than for the historical polyethylene (0.142 +/- 0.07 mm/year). This reduction (38%) did not diminish with time (33% at 5 years). Acetabular cyst formation was less frequent (39% versus 12%), affected fewer DeLee and Charnley zones (17% versus 4%), and was less severe for the cross-linked polyethylene. The only revision was for an aseptically loose cup in the historical polyethylene group. Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis, showing no signs of aging at mid-term followup.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Computed tomography assessment of pelvic osteolysis and cup-lesion interface involvement with a press-fit porous-coated acetabular cup

We used computed tomography to investigate the 3-dimensional pattern of expansile osteolysis that occurs with a modular cementless acetabular component incorporating a central hole. We measured pelvic osteolysis volume and evaluated how much of the porous-coated surface area was involved with osteolytic defects. Among the 34 total hip arthroplasties we studied, osteolysis almost always originated from the dome hole and typically expanded inferiorly or superiorly without involving the anterior or posterior surfaces of the cup. Larger-volume lesions generally involved greater amounts of the cup surface area, but the cup-lesion interface involvement plateaued at 40% for radiographically stable cups without clinical complications. We hypothesize that the plateauing surface area involvement may explain the absence of cup loosening among these cases despite the presence of large osteolytic lesions.

Can the volume of pelvic osteolysis be calculated without using computed tomography?

The most common method to diagnose and monitor osteolysis is the standard anteroposterior radiograph. Unfortunately, plain radiographs underestimate the incidence and extent of osteolysis. CT scans are more sensitive and accurate but also more expensive and subject patients to more radiation. To determine whether the volume of pelvic osteolysis could be accurately estimated without a CT scan, we evaluated the relationships between CT volume measurements and other variables that may be related to the size of pelvic osteolytic lesions in 78 THAs. Only the area of pelvic osteolysis measured on radiographs, heavy patient activity level, and total volume of wear were associated with the pelvic osteolysis volume measured on CT in the context of the multivariate regression analysis. Despite a strong correlation (r = 0.93, r(2) = 0.87) between these three variables and the volume of pelvic osteolysis measured on CT, estimates of pelvic osteolysis volume deviated from the actual volume measured on CT by more than 10 cm(3) among eight of the 78 THAs in this study. CT images remain our preferred modality when accurate assessments of pelvic osteolysis volume are required.

LEVEL OF EVIDENCE

Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Retroacetabular osteolytic lesions behind well-fixed prosthetic cups: pilot study of bearings-retaining surgery

Background

Osteolytic lesions are common radiological findings behind acetabular prosthetic cups. If the cup is well-fixed, the management is quite controversial. Although implant exchange is the most reliable procedure, in most cases it could be considered overtreatment, with the potential for further morbidity and bone loss. Liner exchange associated with lesion debridement and grafting represents an alternative option that is less invasive. Here we present our experiences from a small pilot study of minimally invasive osteolysis treatment without bearings exchange in patients with no evidence of liner wear.

Materials and methods

Inclusion criteria: retroacetabular osteolytic lesions in ceramic-on-polyethylene or metal-on-polyethylene cementless total hip arthroplasties, affecting more than 50% of the bone–prosthesis interface on anteroposterior radiography. Exclusion criteria: head penetration into the liner, suspected loosening or infection. Six patients were selected, two asymptomatic and four symptomatic. Only the symptomatic patients accepted the proposed treatment (performed between June 2004 and March 2006). All of them received fluoroscopy-assisted lesion debridement through an iliac cortical window, morcellized bone allograft mixed with autologous platelet-rich plasma, joint exploration for culture and lavage through a small capsular window. Patients were followed up clinically and radiologically at six months, 12 months, and then yearly.

Results

Three patients out of four showed clinical and radiological improvement. One showed radiological improvement only, and recently underwent cup exchange for subsequent loosening. The visual analog scale (VAS) values for pain decreased on average, but not significantly. No major complications occurred. No recurrence was noted at 2.25–4 years’ follow-up.

Conclusions

Although the small series does not allow any absolute conclusions to be drawn, the reported results seem to justify further, wider studies. It is still unclear if osteolytic lesions associated with no wear of the poly liner would progress to implant failure if left untreated. Until the problem is better understood, this procedure might represent an interesting way to prevent potential loosening and severe bone loss in intact sockets.

Pre-surgical radiologic identification of peri-prosthetic osteolytic lesions around TKRs: a pre-clinical investigation of diagnostic accuracy

BACKGROUND

Emerging longitudinal data appear to demonstrate an alarming trend towards an increasing prevalence of osteolysis-induced mechanical failure, following total knee replacement (TKR). Even with high-quality multi-plane X-rays, accurate pre-surgical evaluation of osteolytic lesions is often difficult. This is likely to have an impact on surgical management and provides reasonable indication for the development of a model allowing more reliable lesion assessment. The aim of this study, using a simulated cadaver model, was to explore the accuracy of rapid spiral computed tomography (CT) examination in the non-invasive evaluation of peri-prosthetic osteolytic lesions, secondary to TKR, and to compare this to conventional X-ray standards.

METHODS

A series of nine volume-occupying defects, simulating osteolytic lesions, were introduced into three human cadaveric knees, adjacent to the TKR implant components. With implants in situ, each knee was imaged using a two-stage conventional plain X-ray series and rapid-acquisition spiral CT. A beam-hardening artefact removal algorithm was employed to improve CT image quality.After random image sorting, 12 radiologists were independently shown the series of plain X-ray images and asked to note the presence, anatomic location and 'size' of osteolytic lesions observed. The same process was repeated separately for review of the CT images. The corresponding X-ray and CT responses were directly compared to elicit any difference in the ability to demonstrate the presence and size of osteolytic lesions.

RESULTS

Access to CT images significantly improved the accuracy of recognition of peri-prosthetic osteolytic lesions when compared to AP and lateral projections alone (P = 0.008) and with the addition of bi-planar oblique X-rays (P = 0.03). No advantage was obtained in accuracy of identification of such lesions through the introduction of the oblique images when compared with the AP and lateral projections alone (P = 0.13)

CONCLUSION

The findings of this study suggest that peri-prosthetic osteolytic lesions can be reliably described non-invasively using a simple, rapid-acquisition CT-based imaging approach. The low sensitivity of conventional X-ray, even with provision of supplementary bi-planar 45 degrees oblique views, suggests a limited role for use in situ for TKR implant screening where peri-prosthetic osteolytic lesions are clinically suspected. In contrast, the accuracy of CT evaluation, linked to its procedural ease and widespread availability, may provide a more accurate way of evaluating osteolysis around TKRs, at routine orthopaedic follow up. These findings have direct clinical relevance, as accurate early recognition and classification of such lesions influences the timing and aggressiveness of surgical and non-operative management strategies, and also the nature and appropriateness of planned implant revision or joint-salvaging osteotomy procedures.

Computer-assisted technique to delineate osteolytic lesions around the femoral component in total hip arthroplasty

There are currently no ideal quantitative measures assessing osteolysis after total joint arthroplasty. This study reports a new approach for quantification of osteolytic lesions on radiographs of total hip arthroplasty with the hypothesis that computer-assisted lesion quantification improves analysis precision over currently used qualitative visual assessment and thus improves progression monitoring. Duplicate exposure sets of anterior-posterior and frog-leg view radiographs of 15 volunteer total hip arthroplasty patients with radiographically evident periprosthetic lucencies were used. Two independent readers delineated the lesions using on-screen digital marker tools. Based on duplicate readings of the first exposure set only, intraoperator precision had a coefficient of variation (CV) from 1.5% to 3.4%, whereas interoperator precision CV ranged from 3.2% to 4.6%. The reproducibility of the x-ray technique as assessed by single readings of both sets of x-rays was CV 3.2% to 4.8%. The new technique compares favorably to precision of qualitative visual assessment and permits more accurate detection and quantitation of osteolytic lesions.

Periacetabular bone density after total hip arthroplasty a postmortem analysis

To clinically verify the bony response to a press-fit acetabular component, this study assessed 5 postmortem-retrieved pelves with unilateral total hip arthroplasties. Changes in periacetabular bone density between implanted and contralateral bone were assessed with dual energy x-ray absorptiometry and computed tomography. At a mean of 9.1 years postarthroplasty, bone density decreased an average of 1.5% to 7.1% proximal and 12.8% medial to the cup. This supports shorter-term in vivo investigations demonstrating periacetabular stress shielding proximal to press-fit cups as well as computer models predicting bone loss medially, but in much greater magnitudes. Unlike femoral remodeling, the average magnitudes of pelvic bone loss are not extensive; therefore, we question whether periacetabular remodeling should be a primary concern for orthopedic surgeons.

Isolated acetabular liner exchange

During the past two decades, most total hip arthroplasties were performed with metal or ceramic heads on conventional polyethylene, an articulation associated with wear and limited life expectancy. Wear is associated with acetabular osteolysis. Isolated liner exchange has become a common surgical intervention when the acetabular component remains well-fixed. The purpose of isolated liner exchange is to prevent loosening of the components secondary to osteolysis and catastrophic mechanical failure caused by bearing wear-through. Treatment options for polyethylene wear include observation (in the asymptomatic hip), liner exchange, and more extensive revision procedures. Patients frequently present with asymptomatic but substantial polyethylene wear with or without associated osteolysis, the treatment of which is controversial. Other areas of debate include complete acetabular component removal to allow bone grafting and placement of an improved bearing surface, reuse of modular mechanisms, cementation into well-fixed shells, and whether to use periacetabular bone grafting.

Temporal radiographic texture analysis in the detection of periprosthetic osteolysis

Periprosthetic osteolysis is one of the most serious long-term problems in total hip arthroplasty. It has been primarily attributed to the body's inflammatory response to submicron polyethylene particles worn from the hip implant, and it leads to bone loss and structural deterioration in the surrounding bone. It was previously demonstrated that radiographic texture analysis (RTA) has the ability to distinguish between osteolysis and normal cases at the time of clinical detection of the disease; however, that analysis did not take into account the changes in texture over time. The goal of this preliminary analysis, however, is to assess the ability of temporal radiographic texture analysis (tRTA) to distinguish between patients who develop osteolysis and normal cases. Two tRTA methods were used in the study: the RTA feature change from baseline at various follow-up intervals and the slope of the best-fit line to the RTA data series. These tRTA methods included Fourier-based and fractal-based features calculated from digitized images of 202 total hip replacement cases, including 70 that developed osteolysis. Results show that separation between the osteolysis and normal groups increased over time for the feature difference method, as the disease progressed, with area under the curve (AUC) values from receiver operating characteristic analysis of 0.65 to 0.72 at 15 years postsurgery. Separation for the slope method was also evident, with AUC values ranging from 0.65 to 0.76 for the task of distinguishing between osteolysis and normal cases. The results suggest that tRTA methods have the ability to measure changes in trabecular structure, and may be useful in the early detection of periprosthetic osteolysis.

What are the guidelines for the surgical and nonsurgical treatment of periprosthetic osteolysis?

Periprosthetic osteolysis is most often diagnosed by plain radiographs. Because these radiographs routinely underestimate the extent of the lesion, three-dimensional imaging should be used early in the evaluation process to confirm the presenting extent of disease. If the osteolytic process is asymptomatic, scheduled regular follow-up should be instituted until the lesion can be confirmed to be stable or until the decision is made to proceed with surgery. Nonsurgical management with pharmacologic agents has not proved to be effective. If surgery is contemplated, a three-dimensional evaluation with magnetic resonance imaging or helical computed tomography can assist in preoperative planning. Surgical intervention requires complete débridement of the lesional membrane and removal of the wear-generator--with or without component removal and with or without bone grafting, depending on the individual circumstances. A standardized follow-up evaluation mechanism for all patients should be a part of total joint arthroplasty management.

Biochemical markers of bone turnover in aseptic loosening in hip arthroplasty

The aim of this study was to determine the diagnostic value of systemic biochemical markers of bone turnover in aseptic loosening in hip arthroplasty, namely the urine levels of three bone resorption peptides - crosslinked n-telopeptides (NTX), c-telopeptides (CTX I) and deoxypyridinoline (DPD). We compared 52 patients with surgically proven component loosening with 52 patients without clinical or radiological signs of endoprosthetic loosening and 52 healthy individuals. All three markers were measured using commercially available enzyme-linked immunoassays. We found significantly increased levels of DPD in the loosening group (p < 0.05), but there was no significant difference between the loosening group and the two reference groups for the other two markers tested. Our data suggest that DPD can be used as an additional tool in the diagnosis of aseptic loosening in hip arthroplasty but CTX I and NTX have no predictive value in this context.

Incidence and volume of pelvic osteolysis at early follow-up with highly cross-linked and noncross-linked polyethylene

Highly cross-linked polyethylene has shown decreased wear rates as compared to conventional polyethylene. However, the impact of this decrease on the occurrence of osteolysis remains uncertain. Forty hips implanted with noncross-linked Enduron and 36 implanted with 5-Mrad cross-linked Marathon polyethylene had a computed tomography at a minimum of 5 years after arthroplasty. Polyethylene wear, osteolysis incidence, location, and volume were compared. The incidence of osteolysis was statistically greater for patients with noncross-linked Enduron (11/40, 28%) compared to patients with the moderately cross-linked Marathon (3/36, 8%; P = .04). The average lesion volume for hips with Enduron liners (7.5 +/- 6.7 cm(3)) was significantly greater than the average lesion volume for hips implanted with Marathon liners (1.2 +/- 0.1 cm(3), P = .01). Marathon cross-linked polyethylene has shown to have a decreased incidence and volume of pelvic osteolysis. Longer follow-up is necessary to determine if Marathon cross-linked polyethylene will continue to demonstrate the encouraging improved wear and osteolysis characteristics.

The cellular and molecular biology of periprosthetic osteolysis

The generation of prosthetic implant wear after total joint arthroplasty is recognized as the major initiating event in development of periprosthetic osteolysis and aseptic loosening, the leading complication of this otherwise successful surgical procedure. We review current concepts of how wear debris causes osteolysis, and report ideas for prevention and treatment. Wear debris primarily targets macrophages and osteoclast precursor cells, although osteoblasts, fibroblasts, and lymphocytes also may be involved. Molecular responses include activation of MAP kinase pathways, transcription factors (including NFkappaB), and suppressors of cytokine signaling. This results in up-regulation of proinflammatory signaling and inhibition of the protective actions of antiosteoclastogenic cytokines such as interferon gamma. Strategies to reduce osteolysis by choosing bearing surface materials with reduced wear properties should be balanced by awareness that reducing particle size may increase biologic activity. There are no approved treatments for osteolysis despite the promise of therapeutic agents against proinflammatory mediators (such as tumor necrosis factor) and osteoclasts (bisphosphonates and molecules blocking receptor activator of NFkappaB ligand [RANKL] signaling) shown in animal models. Considerable efforts are underway to develop such therapies, to identify novel targets for therapeutic intervention, and to develop effective outcome measures.

The value of anteroposterior pelvic radiographs for evaluating pelvic osteolysis

We investigated the role of conventional radiographs and computed tomography scans for the routine followup of total hip arthroplasty patients. Among 92 total hip arthroplasties with a mean followup of 8.5 years, 94 acetabular lesions were detected among 63 hips using computed tomography and 42 of these hips had osteolysis diagnosed on radiograph. Using computed tomography as a gold standard, the sensitivity of anteroposterior pelvic radiographs for the detection of acetabular osteolysis was 67% and the specificity was 72%. Although smaller lesions were more frequently missed, osteolysis was diagnosed on radiograph in 20 of 22 total hip arthroplasties with lesion volumes of at least 10 mL. Because larger osteolytic lesions were generally detected on radiograph, two-dimensional and three-dimensional lesion sizes correlated. However, the limits of agreement for the volume estimates based on the radiograph area were -14.6 to 18.7 mL. Although radiographs can be useful to screen for clinically important pelvic osteolysis, computed tomography images are necessary to accurately measure lesion volumes.

Nonsurgical management of osteolysis: challenges and opportunities

Osteolysis remains a common mode of total hip arthroplasty failure. In vitro and animal models have been used to determine the pathophysiology of osteolysis by carefully dissecting the biochemical pathways leading to particulate wear debris and periprosthetic bone loss. Numerous cytokines and inflammatory mediators, including TNF-alpha and IL-1, are critical participants in this cascade and may represent prime targets for pharmacologic intervention. Osteoclasts, the end effector cells involved in the osteolytic process, also represent potential targets. Cell surface receptors on osteoclast precursors, such as receptor activator of NF-kappaB (RANK) (on osteoclasts) and RANK-ligand (RANKL) (on stromal cells), provide opportunities to arrest osteoclast maturation. Enhancing the naturally occurring osteoprotegerin is another recent attempt at modulating osteoclast behavior and a possible target for pharmacologic therapies. Other nonoperative strategies include intercepting tumor necrosis factor-alpha activity, interfering with the RANK-RANKL interaction necessary for osteoclast development and maturation, bisphosphonate therapy, and using viral vectors to deliver genes. Although each of these approaches has potential benefits, there are substantial challenges to effective implementation. Until there is convincing evidence of efficacy in human clinical trials, we recommend vigilant screening and appropriate surgery with component loosening or substantial likelihood of loosening, periprosthetic fracture, or major bone loss.

Computed tomographic follow-up evaluation of operative intervention for periacetabular lysis

Computed tomography (CT) accurately evaluates periacetabular lytic lesions. The purpose of this study is to determine the fate of osteolytic lesions after treatment with liner exchange and bone grafting. Fifteen patients who had undergone liner exchange with grafting for progressive lytic lesions, as demonstrated by preoperative CT scans, were identified. Postoperative CT scans were performed at a minimum of 2 years post revision. The largest cross sectional lytic area was compared with the postoperative scan to determine the fate of the lesion. The mean size of the measured lytic lesions preoperatively was 6.38 cm(2). Postoperatively, lesions decreased to 2.94 cm(2) (P = .000). Modular liner exchange with grafting is effective in treating osteolytic lesions in the pelvis, as demonstrated by CT.

High wear rates and extensive osteolysis in 3 types of uncemented total hip arthroplasty: a review of the PCA, the Harris Galante and the Profile/Tri-Lock Plus arthroplasties with a minimum of 12 years median follow-up in 96 hips

BACKGROUND

High wear rates and femoral and acetabular osteolysis have been-and still are-the main problems in uncemented total hip replacement. We reviewed 96 consecutive cementless total hip replacements of 4 different designs.

PATIENTS AND METHODS

21 PCA, 25 Harris Galante Porous/Harris Galante I (stem/cup), 25 Profile pressfit/ Tri-Lock Plus (stem/cup) and 25 Profile HA-coated/Tri-Lock Plus (stem/cup) prostheses were included. The operations were performed in the period 1984-1991. Median follow-up ranged from 12-16 years. Wear and osteolysis were measured.

RESULTS

Mean linear wear rates ranged from 0.17 to 0.21 mm/year in the 4 groups, and there were no statistically significant differences between the groups (p = 0.9, ANOVA). Moderate or extensive osteolysis was found in 46 of the 96 hips included. The association between high and low wear rates (more or less than 0.20 mm/ year) and extent of osteolysis was statistically significant (p < 0.001, t-test). We found poor 12-year survival of the primary prostheses in all 4 groups (50-70%), mainly due to revisions because of wear of the polyethylene liner and/or osteolysis. The infrequently documented Profile/Tri-Lock Plus systems did not perform differently from the PCA and the HG.

INTERPRETATION

The poor long-term results with these uncemented total hip arthroplasties illustrate the necessity of regular radiographic evaluation in order to detect osteolysis and liner failure, which are both generally asymptomatic until catastrophic failure appears.

Revisability of the CHARITE artificial disc replacement: analysis of 688 patients enrolled in the U.S. IDE study of the CHARITE Artificial Disc

STUDY DESIGN

A prospective, randomized, multicenter, FDA-regulated Investigational Device Exemption clinical trial.

OBJECTIVES

To analyze the incidence of, and reasons for, reoperation in all patients (treatment and control) enrolled in the IDE study.

SUMMARY OF BACKGROUND DATA

This is the first report of the incidence and nature of reoperations following lumbar TDR as part of a controlled, prospective, multicenter trial.

METHODS

A total of 688 patients meeting the inclusion and exclusion criteria were enrolled in one of three arms of the study at 14 centers across the United States. This cohort includes 71 nonrandomized cases, 205 randomized cases, and 313 continued access cases, all receiving the CHARITE Artificial Disc, as well as 99 randomized cases in the control group (ALIF with threaded fusion cages and autograft). A detailed analysis was performed of clinical chart notes, operative notes, and adverse event reports for all patients requiring reoperation following their index surgery.

RESULTS

Of the 589 patients with TDR, 52 (8.8%) required reoperation. Of the 99 patients with lumbar fusion, 10 (10.1%) required reoperation, and an additional 2 required surgery for adjacent level disease (P = 0.7401). There were 24 TDR patients who underwent a repeated anterior retroperitoneal approach, with 22 (91.7%) having had a successful removal of the prosthesis. Seven of the 24 TDR prostheses requiring removal were revised to another CHARITE Artificial Disc. The mean time to reoperation in all patients was 9.7 months. A total of 29 patients (4.9%) in the TDR group required posterior instrumentation and fusion as did 10 (10.1%) in the control group (P = 0.0562). At 2 years or more follow-up, 93.9%(553/589 = 93.9%) of patients receiving TDR with the CHARITE Artificial Disc had a successfully functioning prosthesis with a mean of over 7 degrees of flexion-extension mobility.

CONCLUSIONS

Lumbar TDR with the CHARITE Artificial Disc did not preclude any further procedures at the index level during primary insertion, with nearly one third being revisable to a new motion-preserving prosthesis and just over two thirds being successfully converted to ALIF and/ or posterior pedicle screw arthrodesis, the original alternative procedure.

Comparison of CT, MRI, and radiographs in assessing pelvic osteolysis: a cadaveric study

In this study, we compared the accuracy of radiography, computed tomography, and magnetic resonance imaging in assessing periacetabular osteolytic lesions. Using a previously published cadaver model, we created 87 lesions in pelves implanted with total hip replacement components. The sensitivity for detecting lesions was 51.7% for radiography, 74.7% for computed tomography, and 95.4% for magnetic resonance imaging. For all three techniques, sensitivity increased as lesion size increased. Magnetic resonance imaging emerged as the most effective tool for detecting small periacetabular osteolytic lesions (< or = 3 cm). For lesions larger than 3 cm, which are of more concern clinically, computed tomography and magnetic resonance imaging were effective in identifying lesions with detection rates greater than 80%. For radiography and computed tomography, lesion detection was dependent on lesion location, whereas magnetic resonance imaging had consistently good sensitivity in all lesion locations. Although the mean volumetric errors for computed tomography and magnetic resonance imaging (0.3 cm and 0.8 cm) were small compared with mean lesion volume (6.1 cm), computed tomography was more accurate than magnetic resonance imaging at measuring lesion volume, with a lower mean absolute error. This study verifies the problems associated with radiographic detection of osteolysis while showing the effectiveness of computed tomography and magnetic resonance imaging in determining the presence of lesions and assessing their three-dimensional volume.

Magnetic resonance imaging in the evaluation of periprosthetic acetabular osteolysis: a cadaveric study

Periprosthetic osteolysis is a well recognized complication of total hip arthroplasty that leads to implant failure. The ability to accurately assess and visualize the position and volume of periacetabular bone defects is paramount for clinical observation and medical treatment, as well as pre-operative planning of revision surgery. We have developed a modified magnetic resonance imaging (MRI) protocol that is useful in detection and quantification of periacetabular bone loss. The purpose of this study is to compare MRI to plain film analysis in the assessment of periacetabular bone loss using a cadaver model. MRI was 95% sensitive in the detection of lesions. Specificity was 98%, and accuracy was 96%. Lesion detection was not statistically dependent on lesion location (p=0.27). The mean absolute error in determining lesion size was 0.8+/-2.2 cm3. There was a correlation between increasing lesion size and lesion detection (p=0.02, logistic regression). The largest lesion that was missed by MRI analysis measured 2.8 cm3, and all lesions 3.0 cm3 were correctly identified, with a relative error volume measurement of 12.4+/-25.3%. This correlated to an absolute error of 1.4+/-2.4 cm3. Using conventional radiographic analysis, the overall sensitivity of lesion detection was 52%, and the specificity was 96%. Using plain film analysis, identification of true lesions depended on the location with 83% of ilial lesions, 64% of pubic lesions, 55% of ischial lesions, and 0% of posterior wall lesions correctly identified. The modified MRI technique utilized did allow for accurate visualization of simulated osteolytic lesions, and may provide a suitable noninvasive method to provide serial assessment of clinical periacetabular osteolysis without the use of ionizing radiation.

Computed tomography in the assessment of periacetabular osteolysis

BACKGROUND

Computed tomography recently has been proposed as an accurate method for diagnosing periacetabular osteolytic lesions. Several investigators have attempted to validate the accuracy of this technique, but they employed cadaveric and animal models, which cannot replicate the adaptive changes that occur over time in vivo. This study was performed to determine the accuracy of computed tomography in identifying and measuring periacetabular osteolytic lesions in hemipelves retrieved at autopsies of individuals with a previously well-functioning total hip prosthesis.

METHODS

We evaluated nine hemipelves, retrieved at autopsy, that contained a cementless porous-coated acetabular component. The fresh specimens were examined with conventional radiographs and computed tomography and then were embedded and sectioned into 1.5-mm slices for evaluation with slab radiographs. Anteroposterior and iliac oblique plain radiographs as well as axial, coronal, and sagittal computed tomography scans were reviewed to determine the presence and location of any periacetabular osteolytic lesions. These results were then compared with those identified on the slab radiographs. Lesion volume was calculated from computed tomography scans with use of post-processing software.

RESULTS

A total of twenty-three periacetabular osteolytic lesions were identified on the slab radiographs of the nine hemipelves. The plain radiographs identified twelve (52%) of the twenty-three lesions, and the computed tomography scans identified twenty (87%) of the twenty-three lesions. Three medial wall perforations were identified on the computed tomography scans but were not detected on the plain radiographs. Computed tomography was accurate in measuring the volume of the osteolytic lesions (r(2) = 0.997) but tended to overestimate the volumes measured on the slab radiographs. Periacetabular osteolytic lesions appeared on the computed tomography scans and slab radiographs as areas devoid of trabecular bone that were delineated by a sclerotic border and communicated with the joint space.

CONCLUSIONS

In this autopsy model, computed tomography was an accurate method for detecting the location and measuring the volume of periacetabular osteolytic lesions.

Retroacetabular osteolysis: when to operate?

Polyethylene liner exchange for retroacetabular osteolysis should be done before the shell becomes loose. The purpose of this study was to determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell. Between 1992 and 2002, 46 cementless shells were revised at our institution for aseptic osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolysis. Implant stability was confirmed intraoperatively. Of 26 stable and 20 loose shells, the average area of osteolysis on anteroposterior radiographs showed no significant difference, whereas lateral radiographs showed a difference. The percentage of shell circumference with associated osteolysis seen on anteroposterior and lateral radiographs showed a significant difference. Diagnostic criterion of 50% shell circumference associated with osteolysis on lateral films has a sensitivity of 0.84 and a specificity of 0.54, and on anteroposterior views, a sensitivity of 1.0 and a specificity 0.27 for predicting shell loosening. Percent of shell circumference with surrounding osteolysis seems to be more predictive of loosening than the area of osteolysis. When 50% of the shell circumference has osteolysis evident on anteroposterior or lateral radiographs, but preferably anteroposterior radiographs, liner exchange should be considered so that the exchange procedure is still possible, rather than allowing the osteolysis to increase and compromise shell fixation.

Use of a constrained tripolar acetabular liner to treat intraoperative instability and postoperative dislocation after total hip arthroplasty: a review of our experience

Constrained acetabular components have been used to treat certain cases of intraoperative instability and postoperative dislocation after total hip arthroplasty. We report our experience with a tripolar constrained component used in these situations since 1988. The outcomes of the cases where this component was used were analyzed for component failure, component loosening, and osteolysis. At average 10-year followup, for cases treated for intraoperative instability (2 cases) or postoperative dislocation (4 cases), the component failure rate was 6% (6 of 101 hips in 5 patients). For cases where the constrained liner was cemented into a fixed cementless acetabular shell, the failure rate was 7% (2 of 31 hips in 2 patients) at 3.9-year average followup. Use of a constrained liner was not associated with an increased osteolysis or aseptic loosening rate. This tripolar constrained acetabular liner provided total hip arthroplasty construct stability in most cases in which it was used for intraoperative instability or postoperative dislocation.

Fixation and osteolysis with Metasul metal-on-metal articulation

The purpose of this study was to report the prevalence of osteolysis and loss of fixation using Metasul metal-on-metal articulation couples. Ninety-two patients with 96 hips with Metasul articulation couples were followed for 5 to 11 years. By patient self-assessment, 89 (93%) patients scored themselves as good or excellent. The occurrence of osteolysis and the grading of fixation were obtained from plain radiographs. The clinical evaluation for these patients was performed by patient self-assessment. With the use of plain radiographs, there was no osteolysis observed in these 96 hips other than calcar resorption (6 hips [6.3%]). All components were fixed, except for 1 loose cup that was revised, and this level of fixation allowed a fair evaluation for osteolysis around well-functioning implants.

Factors influencing wear and osteolysis in press-fit condylar modular total knee replacements

The purpose of this study was to determine the factors influencing wear and osteolysis in patients who have had total knee arthroplasty with the Press-Fit Condylar modular system. Two-thousand ninety-one primary total knee replacements in 1737 patients were done using the Press-Fit Condylar system at three centers. Radiographic and manufacturing data were obtained for 2016 of the 2091 implants (96.4%). For the 1287 of 2016 knees (64%) with more than 5 years of followup, the prevalence of wear-related failure was 8.3%. The 13-year survivorship for all patients was 82.6%. Cox hazards analysis revealed five variables that were correlated with wear-related failure: patient age, patient gender, polyethylene sheet vendor, polyethylene finishing method, and polyethylene shelf age. We were unable to identify one factor as the defining reason for these wear-related failures. The multiple changes in manufacturing methods during the life of this implant may have precluded such a determination. These results may be specific to inserts sterilized in air with gamma irradiation and should not be generalized to current manufacturing techniques. This study emphasizes the potential deleterious effects that small changes in the manufacturing process may have on the outcome of a prosthesis with an initially favorable survivorship.

Early morbidity of modular exchange for polyethylene wear and osteolysis

This study assessed the early morbidity associated with modular component exchange surgery for the treatment of accelerated polyethylene wear and osteolysis in 55 patients. Review of the surgical records revealed no significant intraoperative complications, little intraoperative blood loss (mean 333 mL), no allogenic blood transfusions, and no recorded postoperative deep vein thromboses. Eighteen percent of patients, however, experienced postoperative dislocation. Five patients dislocated multiple times, 3 of which required rerevision surgery. Two patients required rerevision for femoral implant fractures related to osteolysis and 1 additional patient required rerevision due to catastrophic failure of the acetabular component 5 years postoperatively. With an average follow-up of 30 months, 6 of the 55 patients treated with modular exchange required rerevision. The results of this study suggest that instability is the most prevalent early complication associated with modular component exchange. As such, we believe that more stable constructs should be emphasized, possibly at the expense of polyethylene thickness.

Long-term porous-coated cup survivorship using spikes, screws, and press-fitting for initial fixation

This study examined the long-term outcome of a single institution's experience with 4,289 primary total hip arthroplasties using hemispheric porous-coated cups. Initial fixation was achieved with spikes (255 AML TriSpike cups), by press-fitting with rim screws (427 Arthropor cups) or by press-fitting the component (83 Harris-Galante, 391 ACS Triloc+, 2,537 Duraloc, and 596 Pinnacle cups). Among 203 revised hips, only 18 cups were found to be loose at the time of revision. Using revision for any reason as an end point, 15-year survivorship was 82.9% +/- 5.6% (95% confidence interval) for spiked components, 71.6% +/- 8.5% for press-fit cups with adjunctive rim screws, and 72.0% +/- 12.6% for press-fit components (P<.001, log rank). Using revision for aseptic loosening as an end point, 15-year survivorship was 94.7% +/- 3.4% for spiked cups, 98.4% +/- 1.9% for press-fit cups with screws and 100% +/- 0.1% for press-fit cups. Despite an increasing incidence of polyethylene wear-related revisions, porous-coated acetabular components have demonstrated excellent long-term fixation.

Clinical and radiographic results associated with a modern, cementless modular cup design in total hip arthroplasty

BACKGROUND

First-generation cementless modular cups reproducibly achieved fixation to bone but were associated with unacceptable rates of pelvic osteolysis and mechanical failure. Consequently, second-generation cups were developed with shells that had a limited number of holes (or no holes) as well as improved locking mechanisms, a polished inner surface, and increased conformity with the liner. The purpose of the present study was to evaluate the clinical and radiographic results associated with the use of a second-generation acetabular component for primary total hip arthroplasty.

METHODS

Two hundred and ninety-seven patients underwent 335 consecutive primary total hip arthroplasties that were performed by a single surgeon with a second-generation modular acetabular component. All cups were implanted with a press-fit technique. Ten patients were lost to follow-up, and sixteen died from unrelated causes. The remaining 271 patients (308 hips) were followed clinically (with the Hospital for Special Surgery hip-scoring system) and radiographically for four to seven years.

RESULTS

One cup was revised because of aseptic loosening. There were seven additional revisions: five were performed because of aseptic loosening of the stem with a well-fixed cup, and two were performed because of deep infection. Among the 271 patients who were alive at the time of the last follow-up, 266 (98%) had retention of the cup and 264 (97%) had retention of both components with a good or excellent clinical result. In the group of 229 patients (262 hips) with complete radiographic follow-up, 259 cups were well fixed and the average wear rate (for the 246 hips for which this rate could be calculated) was 0.09 mm/yr. Osteolysis was detected in twelve hips (5%) and was associated with male gender (p = 0.001) and the annual wear rate (p = 0.004). The extent of calcar resorption was also associated with the annual wear rate (p < 0.001).

CONCLUSIONS

This second-generation acetabular cup design predictably achieved bone fixation and was associated with low rates of revision for loosening and osteolysis after intermediate-term follow-up.

Surgical management of polyethylene wear and pelvic osteolysis with modular uncemented acetabular components

Osteolysis, usually associated with polyethylene wear, has become one of the most prevalent complications associated with total hip arthroplasty inserted without cement. Management of osteolysis is challenging because the disorder tends to develop silently and surgical intervention can result in complications. In addition, long-term outcomes are unknown. We discuss the current knowledge and data available on polyethylene wear and pelvic osteolysis with modular uncemented acetabular components. We also outline an algorithm for evaluation and treatment of patients. In general, we see patients with well-fixed components every 2 years, and we base follow-up visits after 6 years on predicted polyethylene wear rates and the presence or absence of pelvic osteolysis.

Computed tomography to assess pelvic lysis after total hip replacement

To assess the accuracy of a computer-assisted computed tomography image analysis program in determining the location and volume of periacetabular osteolysis, we designed an osteolysis model by implanting bilateral total hip replacements in human pelvic cadavers and creating osteolytic lesions of varying sizes. The volumes of 48 defects were measured physically, and axial computed tomography scans were obtained. The computed tomography images were processed with streak artifact reduction and segmentation algorithms. The location and volume of lesions were determined from these images. Eighty-one percent (39 lesions) were identified correctly from the computed tomography scans. Detection was location-dependent. More lesions were detected in the ilium (100%) and at the rim (89%) than in the ischium (78%) or the pubis (50%). Computed tomography overestimated lesion volume by a mean of 0.5 +/- 2.3 cm. The volumetric error was unrelated to lesion location but was dependent on lesion size. As lesion size increased above 10 cm, the mean percentage error decreased to 1.8%. Computed tomography image analysis can be used more accurately than plain radiographs to investigate the effectiveness of treatment and the natural history of pelvic osteolysis.