Fixation, polyethylene wear, and pelvic osteolysis in primary total hip replacement

Tissue engineering in musculoskeletal problems related to haemophilia

This article is a review of how advances in tissue engineering can be applied to the musculoskeletal pathology of patients with haemophilia. This article will also explain the theory that the deterioration of joints in patients with haemophilia is due to biological and mechanical causes. Current concepts of tissue engineering would be to replace the degenerated and damaged tissue by live cells, using them as a biological implant. However, before these new technologies are applied, an appropriate control of their indication and results is required.

Treatment of the young active patient with osteoarthritis of the hip

We compared the five- to seven-year clinical and radiological results of the metal-on-metal Birmingham hip resurfacing with a hybrid total hip arthroplasty in two groups of 54 hips, matched for gender, age, body mass index and activity level.

Function was excellent in both groups, as measured by the Oxford hip score, but the Birmingham hip resurfacings had higher University of California at Los Angeles activity scores and better EuroQol quality of life scores. The total hip arthroplasties had a revision or intention-to-revise rate of 8%, and the Birmingham hip resurfacings of 6%. Both groups demonstrated impending failure on surrogate end-points. Of the total hip arthroplasties, 12% had polyethylene wear and osteolysis under observation, and 8% of Birmingham hip resurfacings showed migration of the femoral component. Polyethylene wear was present in 48% of the hybrid hips without osteolysis. Of the femoral components in the Birmingham hip resurfacing group which had not migrated, 66% had radiological changes of unknown significance.

Ten-year follow-up of an anatomical hydroxyapatite-coated total hip prosthesis

We report our results after ten year follow-up of 107 consecutive ABG-I hip prostheses implanted between June 1990 and December 1992: Only 84 prostheses were still in the study after ten years, but only six patients had undergone surgical revision. We can consider our clinical outcomes as excellent, with a whole-implant survival rate greater than 96%, a mean Merle D'Aubigne and Postel score increasing from 7.97 before operation to 16.17 at ten year follow-up, and a personal subjective assessment as excellent or good in 82.14% of patients. However, radiographic outcomes are more worrying: around 90% of patients show a stress-shielding phenomenon and granulomatous lesions in the proximal femur, and more than 82% suffer polyethylene wear greater than one millimetre (mean 1.68 mm). We think that zirconia stem heads and hooded antiluxation PE inserts are determining factors in the process of PE wear and, secondarily, in cancellous bone resorption and bone osteolysis.

Does pelvic osteolysis occur with a nonmodular uncemented acetabular component?

We present a radiographic follow-up of an uncemented, nonmodular, pure titanium-backed acetabular component at 6 to 12 years postimplantation. Between 1990 and 1992, 130 primary total hip arthroplasties were carried out by 1 surgeon using this implant, in association with both cemented and uncemented femoral components. There were 19 deaths, 5 revisions, and 19 hips lost to follow-up, leaving 87 hips available for review at a mean of 9.6 years. Two revisions were for infection, whereas 3 well-fixed cups were changed at the time of revision of a loose femoral component to allow downsizing to a 28-mm head. No cup has been revised for aseptic loosening. There was no radiographic evidence of periacetabular osteolysis or loosening of any of the cups, even in a subgroup of 31 patients who were 60 years or younger at the time of implantation.

Mechanisms for pumping fluid through cementless acetabular components with holes

The pumping of fluid and polyethylene wear debris from the joint space to the retroacetabular bone is implicated in the pathogenesis of osteolysis. Three possible mechanisms for this pumping: pressure gradients, diaphragm pumping, and piston pumping were studied in vitro in a laboratory model. The simulated activities of rising from a chair and climbing stairs produced high-pressure gradients and high angles of loading that could pump fluid through the apical hole to the retroacetabular bone. A noncongruent liner acted as a diaphragm pump, producing pressures 6 times higher than that seen with a congruent liner. Pistoning motion of the liner produced pressures 8 times higher than when no pistoning occurs. These pumping mechanisms could be mitigated by the use of acetabular components without holes.

Arc-deposited hydroxyapatite-coated cups: results at four to seven years

A second-generation arc-deposited hydroxyapatite-coated acetabular component was developed after detailed analysis of a failed first-generation grit-blasted hydroxyapatite-coated cup. In our prospective multicenter study we aimed to compare clinical results and survivorship of the newly designed cup to the previous cup and to a similarly designed porous-coated cup during the same time period. The effect of bearing surface-alumina-on-alumina to polyethylene-on-metal-was analyzed. Consecutive patients were assigned randomly to one of three groups: arc-deposited hydroxyapatite-coated cup with alumina-on-alumina bearing surface; porous-coated cup with alumina-on-alumina bearing surface; or porous-coated cup with polyethylene-on-metal bearing surface. A fourth comparison group with a grit-blasted hydroxyapatite-coated cup and polyethylene-on-metal bearing surface was culled from a previous study. Acetabular mechanical failure rate is 0.0%, 0.0%, 1.9%, and 11.2% for the arc-deposited hydroxyapatite-coated, porous-coated with alumina bearing surface, porous-coated with polyethylene-on-metal bearing, and grit-blasted hydroxyapatite-coated cup, respectively, at 4- to 7-years' followup. There are no cases of acetabular osteolysis or femoral neck scalloping and no radiolucent lines in any zone with the arc-deposited hydroxyapatite-coated cup. The cups with the alumina-on-alumina bearing surface had less scalloping of the femoral neck than those with a polyethylene-on-metal bearing surface. Early results with this second-generation arc-deposited hydroxyapatite-coated cup are promising.

LEVEL OF EVIDENCE

Therapeutic study, Level I (high-quality randomized trial with statistically significant difference or no statistically significant difference but narrow confidence intervals). See the Guidelines for Authors for a complete description of levels of evidence.

Long-term results with cementless Fitek (or Fitmore) cups

Fitek cementless cups have been adopted in our department in 1989. The first 100 consecutive Fitek implants were analyzed clinically (Harris hip score) and radiographically (anteroposterior and lateral x-rays) with a mean follow-up of 9.7 years. We did not have any case of cup loosening or any other problem requiring cup revision. In this series, we had 86 excellent, 10 good, 2 fair, and 2 poor results. The 2 poor results were because of 2 cases of aseptic loosening of the stem (1 cemented and 1 cementless). The x-rays showed an average angle of cup inclination of 36.5 degrees (range 16 degrees -54 degrees ) after surgery and no variations at the last follow-up. Bidimensional linear wear of the acetabular component showed 6 cases of measurable wear with an average wear rate per year of 0.265 mm. The overall wear rate per year was 0.02 mm. At the time of the last follow-up examination, we had 3 femoral osteolysis and no case of acetabular osteolysis. In our series, we observed "lack of contact" zones above the polar depression in 71 cases immediately after surgery. The average thickness of these lines was 1 (range 0.5-3.5) mm. Of these, at the last follow-up, 61 cases (86%) showed a complete "filling" of the "lack of contact," whereas in 10 (24%), the "filling" was incomplete (4 cases still showing a radiolucent line [<or=0.5 mm] in zone II). In the first group with "complete filling," we found 23 (37%) cases with bone ingrowth and no migration of the cup, whereas 38 (63%) cases showed bone ingrowth with evidence of cup migration. The Mann-Whitney nonparametric U test and the Kruskal-Wallis test showed that the survival rate of the 100 analyzed cups, after a follow-up time of 9.7 years, was 100% (end point: revision for any cause). Fitek cup showed good clinicoradiographic results.

Total hip arthroplasty with the use of nonmodular cementless acetabular component

Sixty-seven hips in 63 patients who underwent total hip arthroplasties with the use of the nonmodular cementless acetabular component and alumina-on-polyethylene bearing surface were available for complete clinical and radiographic review at a mean follow-up period of 7 (range 5-9) years. The mean age was 59 years (range 34-75) years. The mean preoperative Harris hip score of 50 points improved to 93 points at final follow-up. One (1.5%) hip required revision for a recurrent dislocation. No component was loose radiographically at final follow-up. The mean linear wear rate was 0.07 (range 0.01-0.23) mm/y. At a mean follow-up of 7 years, there was no aseptic loosening. Further follow-up, however, is necessary to determine the potential advantage of nonmodular acetabular component for the development of pelvic osteolysis.

The use of cementless expansion acetabular component and an alumina-polyethylene bearing in total hip arthroplasty for osteonecrosis

We performed 114 consecutive primary total hip arthroplasties with a cementless expansion acetabular component in 101 patients for advanced osteonecrosis of the femoral head. The mean age of the patients at surgery was 51 years (36 to 62) and the mean length of follow-up was 110 months (84 to 129).

The mean pre-operative Harris hip score of 47 points improved to 93 points at final follow-up. The polyethylene liner was exchanged in two hips during this period and one broken acetabular component was revised. The mean linear wear rate of polyethylene was 0.07 mm/year and peri-acetabular osteolysis was seen in two hips (1.9%). Kaplan-Meier analysis indicated that the survival of the acetabular component without revision was 97.8% (95% confidence interval 0.956 to 1.000) at ten years.

Our study has shown that the results of THA with a cementless expansion acetabular component and an alumina-polyethylene bearing surface are good.

Polyethylene wear rates with Zirconia and cobalt chrome heads in the ABG hip

We report a radiological analysis of 281 primary cementless ABG total hip arthroplasties performed between 1991 and 1994, with a mean follow-up of 78 months. We compare the polyethylene wear in hips with Zirconia ceramic heads manufactured prior to the introduction of hot isostatic pressing and hips with cobalt chrome heads. The mean linear wear rate was 0.19 mm/yr with 28mm Zirconia heads (n=203), 0.20 mm/yr with 32mm Zirconia heads (n=47) and 0.14mm/yr with 28mm cobalt chrome heads (n=31). We matched each of the 31 patients with 28mm cobalt chrome heads with a patient from the 28mm Zirconia group for gender and age. The mean linear wear rates in these two groups were 0.14mm/yr and 0.19mm/yr respectively (p<0.05). There were 19 revisions for osteo-lysis in 250 hips with Zirconia heads (7.6%) and no revisions in 31 hips with metal heads. We advocate regular review of patients with Zirconia on polyethylene bearing surfaces due to the high linear wear rates and associated osteolysis. (Hip International 2005; 15: 63-70).

Medicolegal aspects of hip and knee arthroplasty

Hip and knee arthroplasties usually are satisfying for the patient and the surgeon; however, these procedures also have considerable risks for generating a medical malpractice lawsuit. Strict adherence to the standard of care and recently implemented patient safety strategies should reduce the surgeon's liability. Expert technical execution of the surgery, timely evidence-based patient treatment, and detailed documentation in the medical record will not only improve the quality of patient care but also will serve as a strong legal defense should the need arise.

Third-body wear testing of a highly cross-linked acetabular liner: the effect of large femoral head size in the presence of particulate poly(methyl-methacrylate) debris

The hip simulator wear performance of an electron beam cross-linked and subsequently melted ultrahigh molecular weight polyethylene against femoral heads of 28-, 38-, and 46-mm diameter in the presence of poly(methyl-methacrylate) particulate debris was contrasted with that of conventional polyethylene against a 46-mm diameter head. Over 5 million cycles of testing, the average wear rate of the conventional polyethylene liners was 29.3 +/- 3.0 mg per million cycles. All highly cross-linked components exhibited marked reduction in wear, with the highest wear measuring 0.74 +/- 0.85 mg per million cycles. This study, using a clinically relevant third-body material, showed the electron beam cross-linked material to be far more resistant to this third-body wear than conventional ultrahigh molecular weight polyethylene, even when very large diameter femoral heads were used.

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.

Uncemented Harris-Galante total hip arthroplasty in patients with osteonecrosis of the femoral head. A 10-16-year follow-up study

BACKGROUND

There have only been a few reports regarding the long-term results of uncemented THAs in patients with osteonecrosis.

PATIENTS AND METHODS

We evaluated the long-term results of 65 consecutive uncemented total hip arthroplasties (Harris-Galante type I prostheses) in 54 men (59 hips) and 5 women (6 hips) with osteonecrosis of the femoral head. The mean age was 53 (33-64) years. The mean duration of follow-up was 12.5 (10-16) years.

RESULTS

9 femoral stems and 3 acetabular metal shells were revised. 2 polyethylene liners were changed due to excessive wear. A girdlestone procedure was done in 2 patients (2 hips) due to delayed deep infection. The mean polyethylene wear was 0.14 mm per year. 3 non-revised hips had pelvic osteolysis and 18 had femoral osteolysis. The 15-year survival rates, using failure defined as the removal of any component for any reason, were 85 (95% CI; 79-91)% for the acetabular and 80 (74-86)% for the femoral component and 70 (63-77)% for any of the components.

INTERPRETATION

The first generation of the HGP design was frequently associated with pain, unstable fixation, and osteolysis. Excessive wear was frequent. The cup showed better durability than the stem.

Cementless porous-coated sockets without holes implanted with pure press-fit technique

We evaluated the use of a pure press-fit technique in 220 porous-coated acetabular components without screw holes at mean follow-up of 6.1 years (4-7.5 years). The socket had a 14 degrees enhanced gradient at the periphery and was underreamed by 1 to 2 mm depending on bone quality. The Harris Hip average score was 44.3 (26-70) preoperatively and 93.1 (66-100) at final follow-up. There were no postoperative gaps in any zone. Nonprogressive radiolucent lines were detected in 4 hips. There was no movement or migration of the acetabular component on the follow-up x-rays. Pelvic osteolysis was not observed. Whereas 5 cups (2.3%) had revisions, none was revised for aseptic loosening. The press-fit technique provides stability in appropriate cases avoiding the theoretical complications related to screws or screw holes.

Reasons for revision hip surgery: a retrospective review

The purpose of this study was to determine the indications for contemporary revision hip surgery in a consecutive series of patients. We retrospectively reviewed the clinical records and radiographs of 439 revision hip surgeries done between 1996 and 2003. Fifty-five percent of the surgeries were for aseptic loosening, 14% were for instability, 13% were for osteolysis around a well-fixed implant, 7% were for infection, 5% were for periprosthetic fracture, 3% were for conversion of a hemiarthroplasty, 1% was for psoas impingement, 1% was for loose recalled implants, and 1% was for implant fracture. As expected, aseptic loosening was the most common reason for revision surgery. Instability was a common reason for early revision whereas revision for osteolysis around a well-fixed implant was a more common reason for late revision.

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.

The uncemented CLS expansion cup as a component of a hybrid system in primary total hip arthroplasty: A prospective study

The purpose of this prospective study is to present the results of 160 primary total hip replacements in 145 patients with a hybrid system composed of the uncemented CLS expansion cup and the cemented MS-30 femoral component. Included in this study were 109 women and 36 men with the mean age of 64.2 years (range 25 to 87) at the time of the surgery. The mean follow-up time was 7.5 years (range 6 to 12). The Harris Hip Score and radiographic analyses were used for the most recent assessment. Five patients died during the follow-up period. Two hips were dislocated and managed by open reduction. The mean Harris Hip Score before surgery was 38.4 (range 15 to 57) and 91.3 (range 64 to 100) at the last follow-up. Although a radiolucent line has been detected around the femoral component in four hips, no revision has been considered yet. No radiological evidence of loosening and detectable migration have been observed in any of the acetabular components. The hybrid replacement, consisting of the uncemented acetabular CLS expansion cup and the cemented MS-30 femoral stem, yielded overall good results after medium-term duration of follow-up. (Hip International 2004; 14: 223-8).

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.

Seven to 10 years followup of an anatomic hip prosthesis: an international study

Hypothetically, hydroxyapatite-coated anatomic-shaped femoral stems and hemispheric acetabular cups should improve biologic fixation of the implant and strength transmission to the bone, improving unsatisfactory results of the first cementless hip prosthesis focused on the stress-shielding phenomenon at the femur and failure of the threaded acetabular cups. A consecutive series of 312 patients who had primary Anatomique Benoist Giraud hip prostheses unilaterally implanted were followed up. We analyzed the clinical and radiographic results and report the outcomes 7-10 years after implantation. Two hundred thirty-two patients were assessed at 7-10 years. The survival rate for the implant was 96.8%; 77.2% of patients had no pain, 72.4% maintained total mobility, and 62.9% were able to walk without restrictions. However, radiologic assessment shows that problems improved but did not disappear. More than 55% of femurs had signs of proximal stress-shielding develop. More important, substantial polyethylene wear was observed in at least 62% of the acetabular inserts at 7-10 years followup.

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.

Degradation of mechanical properties of UHMWPE acetabular liners following long-term implantation

We tested the hypothesis that the mechanical and chemical behavior of gamma radiation-sterilized ultrahigh-molecular-weight polyethylene (UHMWPE) changes after implantation. Relationships between the mechanical behavior and oxidation index were explored in a cohort of 16 consecutive traceable Hexloc acetabular components (Biomet, Warsaw, IN) that were machined from extruded, stearate-containing UHMWPE and gamma sterilized in air. Shelf aging time (average, 0.4 years) and implantation time (average, 11.5 years) were determined for all 16 inserts. The retrieved liners exhibited significant mechanical degradation, which was most severe in the unloaded surface regions. Analysis of the Fourier transform infrared spectroscopy data revealed a significant association between the oxidation index and mechanical degradation of the UHMWPE. The results of this study strongly support the hypothesis that the degradation of mechanical properties for the liners occurred during implantation.

Intermediate-term results after hybrid total hip arthroplasty for the treatment of dysplastic hips

BACKGROUND

In recent studies, good intermediate-term results have been reported after primary hybrid total hip arthroplasty (a cementless acetabular component with a cemented femoral stem) for the treatment of primary osteoarthritis. However, few studies have described the results of this technique in patients with developmental dysplasia of the hip.

METHODS

One hundred primary hybrid total hip replacements were performed in ninety patients to treat degenerative arthritis of the hip secondary to developmental dysplasia. Seventy-one patients (eighty-one hips) were available for clinical and radiographic evaluation. The average duration of follow-up was 10.6 years. There were ten men and sixty-one women. Seventy hips were classified as type 1 (dysplasia); seven, as type 2 (low dislocation); and four, as type 3 (high dislocation), according to the classification system of Hartofilakidis et al.

RESULTS

At the time of the final follow-up, the average Harris hip score was 86 points. Structural autograft was used in fifteen hips to supplement acetabular coverage. Within five years postoperatively, the acetabular component in six of the fifteen hips had an average of 4.5 mm of vertical migration and an average increase in vertical rotation of 3 degrees, but the position appeared to stabilize thereafter. Revisions were performed in two hips because of recurrent dislocation. No acetabular or femoral component was revised because of aseptic loosening. Osteolysis was identified around two acetabular components and two femoral components. The average rate of polyethylene wear was 0.09 mm per year.

CONCLUSIONS

Hybrid total hip arthroplasty for the treatment of symptomatic degenerative arthritis secondary to developmental dysplasia provides favorable results at intermediate-term follow-up. With lower grades of dysplasia, the majority of patients can be treated effectively without a structural bone graft by placement of the cementless acetabular component at a medial or high position.

Radiographic definition of pelvic osteolysis following total hip arthroplasty

BACKGROUND

Radiographs are the standard clinical tool used to monitor patients with pelvic osteolysis after total hip arthroplasty; however, previous reports have questioned the value and accuracy of this method. With use of a cadaveric model, we investigated the accuracy of radiographs in determining the location and size of periacetabular osteolysis.

METHODS

We implanted total hip arthroplasty components in eight cadaveric hips and made four radiographs of each hip from different views. We then removed the components and created two pelvic defects in each hip. We measured the volume of each defect, reimplanted the components, and made another set of radiographs. The defects were then enlarged two more times, with the volume measured and another set of radiographs made each time. In total, 128 radiographs were made of forty-eight lesions. An orthopaedist who was blinded to the location of the lesions assessed the radiographs with regard to the presence and size of osteolytic lesions.

RESULTS

The overall sensitivity for the detection of osteolysis on a single radiograph was 41.5%, and the overall specificity was 93.0%. Sensitivity was dependent on the location and size of the lesions but not on the radiographic view. Sensitivity ranged from 72% for lesions in the ilium to </=15% for lesions in the ischium and acetabular rim. The detection rate for lesions with a volume of >10 cm (3) was significantly higher than that for smaller lesions (p < 0.001). When all four radiographic views of one lesion were analyzed together, sensitivity increased to 73.6%. Despite the low sensitivity, specificity remained high, indicating that once osteolysis is evident radiographically, the likelihood that a lesion truly exists is high. Additionally, we found that the extent of osteolysis was substantially underestimated on radiographs.

CONCLUSIONS

The use of radiographs to assess and monitor osteolysis has both limitations and merits. Using multiple views, an experienced orthopaedist identified only 73.6% of pelvic lesions. However, once a pelvic osteolytic lesion is evident radiographically, the likelihood that it truly exists is high.

Measurement of bone defects adjacent to acetabular components of hip replacement

Computed tomography can assist in the detection of periprosthetic osteolysis, but it has not been used to measure the actual volume of bone defects adjacent to hip replacement components because of the scanning artifact caused by metal. The aim of the current study was to develop a spiral computed tomography technique that provides precise and reliable volumetric measurement of bone defects adjacent to uncemented metal-backed acetabular components. Computed tomography scans were taken of small and large defects of known volume created in the ilium in a bovine hemipelvis and a pelvis from a cadaver. Scans were analyzed by two independent observers. The computed tomography operating conditions were determined that enabled volumetric measurements and that were accurate to within 96% for small and large defects and precise to greater than 98% for small and large defects. This computed tomography technique has the capability to measure accurately and precisely the volume of bone defects in the ilium adjacent to metal-backed acetabular components. This technique has clear advantages over plain radiographs. It will allow investigation of the natural history of osteolytic lesions, enhance preoperative planning, and improve monitoring of the outcomes of treatments of osteolysis.

Management of patients with acetabular socket wear and pelvic osteolysis

Polyethylene wear and pelvic osteolysis are the most common late complications associated with stable cementless total hip implants. This manuscript describes the diagnostic strategies and treatment algorithm used at the senior author's (C.A.E) institution for patients with wear and pelvic osteolysis. This evolving management strategy is based on our experiences and ongoing research. We discuss patient selection, the evaluation of acetabular liner wear, the diagnosis of pelvic osteolysis, the timing of revision, and treatment strategies. According to this algorithm, we revise asymptomatic hips with pending or complete wear-through of the acetabular liner. We also recommend revision for most symptomatic patients with pelvic osteolysis and for patients with large pelvic osteolytic bone defects or a documented increase in osteolytic lesion size in an area of the cementless acetabular component in which a load transfer between the implant and the surrounding bone is likely to occur.

Interobserver and intraobserver variability in radiographic assessment of osteolysis

This study quantified the variability associated with diagnosing periprosthetic osteolysis from the radiographs of total hip arthroplasty patients. Four joint arthroplasty surgeons independently assessed radiographs of 60 patients for evidence of osteolysis in different zones. The surgeons agreed on the presence of lesions in at most 57% of the zones. kappa coefficients, used to quantify the extent of agreement among the surgeons, denoted poor interobserver reproducibility (kappa =.28 to.44). Intraobserver reliability-determined by comparing 2 reviews of the same radiographs done by 1 surgeon 2 weeks apart-was moderate to excellent (kappa =.48 to.84). We also compared the results from the most recent radiograph with those from a time series. Agreement improved when a series was reviewed. Reliable comparisons cannot be made with osteolysis rates reported by different observers. In the research setting, osteolysis rates are more reliable if they are determined by a single reviewer whose intraobserver variability has been reported. In assessing a patient for osteolysis, it is more accurate to analyze a series of radiographs than the most recent radiograph.

A literature review of the association between wear rate and osteolysis in total hip arthroplasty

The establishment of a polyethylene wear rate threshold for the development of osteolysis at the hip would allow surgeons to identify patients at risk for osteolysis and to implement selective, more frequent follow-up. We reviewed publications that met certain criteria for wear and osteolysis measurement. Based on this review, the incidence of osteolysis increases as the rate of wear increases. The literature indicates that osteolysis rarely is observed at a wear rate of <0.1 mm/y. We suggest that a practical wear rate threshold of 0.05 mm/y would eliminate osteolysis. This wear threshold suggests that the new cross-linked polyethylenes would reduce osteolysis, provided that in vivo wear rates mirror those observed in vitro. To facilitate future comparison of published data, we suggest that longitudinal wear studies adopt consistent edge detection-based wear measurement techniques and uniform osteolytic lesion classification and measurement schema.

Two different cementless femoral components in primary total hip arthroplasty

The results of first (51 Harris-Galante stems with an average follow-up of 12.3 years) and second generation (53 MultiLock stems with an average of 6.4 years) cementless femoral stems in total hip replacement were analysed. Ten Harris-Galante stems were revised (9.8% at 8 years and 22.8% at 13 years) and one unstable MultiLock stem (2.6% at 8 years). Thirty-seven Harris-Galante and 45 MultiLock stems were osseo-integrated. Femoral osteolysis was seen in 21 Harris-Galante (26.6% at 8 years and 43.7% at 13 years) and in 3 MultiLock stems (8.0% at 8 years). At intermediate follow-up, second generation stems show less bone remodelling changes than first generation stems at the same interval. Distal osteolysis and pronounced stress-shielding have not been encountered in second generation stems. (Hip International 2002; 12: 289-302).

Midterm outcome of the plasma cup in total hip arthroplasty

One hundred and twenty eight primary total hip arthroplasties (THA) in 104 patients were reviewed to assess mid-term survivorship and clinical outcome of the Plasma cup. Outcome was evaluated clinically, radiographically, and by self-administered questionnaires. Patient mean age at surgery was 51 years, and 52 THAs (41%) were performed for secondary arthritis. Prior to surgery the median Merle DAubigne score was 8. At 59 (standard deviation 18) months this score had improved to 17, and the median Harris hip score was 85. The mean annual polyethylene wear rate was 0.14mm/year. There were no instances of aseptic loosening but 2 cups had small, focal osteolytic lesions at the site of screw holes. Three cups were revised, two for recurrent dislocations, and one for infection. Cup survivorship at 5 years was 97% (Kaplan-Meier).This data suggests that the Plasma cup performs well in the mid-term and may be used safely in a young population with a high incidence of secondary osteoarthritis. (Hip International 2002; 2: 119-25).

The optimal fixation of the cementless acetabular component in primary total hip arthroplasty

The optimal fixation of the acetabular component in primary total hip arthroplasty remains controversial. Long-term follow-up studies show that significant loosening rates occur with cemented acetabular components and that these problems persist despite attempts to improve cementing technique. Cementless acetabular components that rely on biologic fixation can have lower rates of radiographic loosening at 10 years compared with cemented acetabular components. Although revision rates for both modes of fixation are largely equivalent at 10 years, the superior radiographic performance of cementless acetabular components at 10 years suggests that biologic fixation through bone ingrowth may provide more durable long-term implant survival compared with cemented fixation. Osteolysis is the major obstacle to long-term cementless acetabular component survival. Potential future options that may inhibit osteolysis include decreasing bone resorption that results from debris-stimulated foreign body response through the use of medications; decreasing the number of particles generated by using alternative bearing surfaces; and improving bone ingrowth, particularly through the use of growth factors and improved implant materials and designs.

Pattern of osteolysis around two different cementless metal-backed cups: retrospective, radiographic analysis at minimum 10-year follow-up

In this retrospective study, we analyzed the formation of osteolysis with 2 cementless cups to evaluate if surface holes in metal shells influence the radiographic pattern of osteolysis. At a minimum of 10 years' follow-up, serial radiographs of 112 hips with Arthropor cups (having multiple shell holes) and 126 hips with Anatomic Medullary Locking (AML) cups (with no holes) were reviewed. Despite differences in variables other than cup design that can affect polyethylene wear and osteolysis rates, the incidence of osteolysis between the groups was coincidentally similar (47.3%, Arthropor; 47.6%, AML). The time of onset of osteolysis (mean, 7.5 and 7.4 years) also was similar. The radiographic pattern of the osteolytic lesions, which is largely a factor of cup design, differed. The Arthropor group had significantly larger lesions in Charnley zone I and significantly more hips with retroacetabular lesions (Charnley zones I and II); however, these lesions did not compromise cup stability. Patients with AML cups had more and larger lesions in the greater trochanter.

The Harris-Galante total hip arthroplasty: a minimum 8-year follow-up study

A total of 93 Harris-Galante Porous I (HGP- I) prostheses were analyzed with a mean follow-up of 10.2 years. Thigh pain (28 hips) correlated with unstable fixation (P<.005), female gender (P<.045), young age (P<.05), poor distal femoral fill (P<.002), subsidence (P<.0001), and osteolysis (P<.05). Thirteen stems and 6 metallic shell cups were revised. Kaplan-Meier analysis showed 13-year survival rates of 92.5% +/- 5.8% for the metallic shell cup, 79.7% +/- 13% for the HGP-I cup, and 76.3% +/- 14.0% for the stem. Five polyethylene liners were changed because of wear >1 mm. Radiographic loosening occurred in 8 cups. Radiographic bone ingrowth was present in 54 stems, stable fibrous fixation was present in 24 stems, and unstable fixation was present in 15 stems. The mean polyethylene wear was 0.17 mm/y. Eleven hips (11.8%) had acetabular osteolysis, and 24 (25.8%) had femoral osteolysis, the latter being more frequent in unstable stems (P<.007). The HGP-I metallic cup shows better clinical and radiographic results than the stem, which frequently is associated with pain, unstable fixation, and osteolysis. Excessive polyethylene wear is frequent.

Inpatient interdisciplinary rehabilitation after total hip arthroplasty surgery: a comparison of revision and primary total hip arthroplasty

OBJECTIVES

To describe outcomes of revision total hip arthroplasty (THA) patients who underwent interdisciplinary inpatient rehabilitation, and to compare them with primary THA patients.

DESIGN

Descriptive and case-control study.

SETTING

Forty-bed, community-based, freestanding rehabilitation hospital.

PATIENTS

Thirty-nine revision THA subjects, gender- and age-matched with 39 primary THA controls.

INTERVENTION

Inpatient interdisciplinary rehabilitation.

MAIN OUTCOME MEASURES

FIM instrument, length of stay, hospital charges, and disposition location.

RESULTS

The average revision THA patient stayed 10.5 days, improved from an admission FIM score of 89 to a discharge FIM score of 110, and incurred a hospital charge of $10,600. Of the revision THA patients, 98% were discharged home, and orthopedic-related complications were uncommon. No significant differences existed between revision and primary THA patients in any outcome measures. A trend toward higher rehabilitation charges ($12,400 vs $9500, p =.07) was found in revision THA patients who wore a hip orthosis. Otherwise, no differences were found in outcome measures based on the type of revision surgery, the presence of weight-bearing restrictions, or the presence of orthopedic complications.

CONCLUSIONS

THA patients selected for inpatient rehabilitation have favorable short-term functional outcomes. The type of THA (primary vs revision) is not an independent differentiating factor.