Radiological factors influencing femoral and acetabular failure in cemented Charnley total hip arthroplasties

Risk factors for a radiolucent line around the acetabular component with an interface bioactive bone cement technique after primary cemented total hip arthroplasty

Aims

The main aims were to identify risk factors predictive of a radiolucent line (RLL) around the acetabular component with an interface bioactive bone cement (IBBC) technique in the first year after THA, and evaluate whether these risk factors influence the development of RLLs at five and ten years after THA.

Methods

A retrospective review was undertaken of 980 primary cemented THAs in 876 patients using cemented acetabular components with the IBBC technique. The outcome variable was any RLLs that could be observed around the acetabular component at the first year after THA. Univariate analyses with univariate logistic regression and multivariate analyses with exact logistic regression were performed to identify risk factors for any RLLs based on radiological classification of hip osteoarthritis.

Results

RLLs were detected in 27.2% of patients one year postoperatively. In multivariate regression analysis controlling for confounders, atrophic osteoarthritis (odds ratio (OR) 2.17 (95% confidence interval (CI), 1.04 to 4.49); p = 0.038) and 26 mm (OR 3.23 (95% CI 1.85 to 5.66); p < 0.001) or 28 mm head diameter (OR 3.64 (95% CI 2.07 to 6.41); p < 0.001) had a significantly greater risk for any RLLs one year after surgery. Structural bone graft (OR 0.19 (95% CI 0.13 to 0.29) p < 0.001) and location of the hip centre within the true acetabular region (OR 0.15 (95% CI 0.09 to 0.24); p < 0.001) were significantly less prognostic. Improvement of the cement-bone interface including complete disappearance and poorly defined RLLs was identified in 15.1% of patients. Kaplan-Meier survival analysis for the acetabular component at ten years with revision of the acetabular component for aseptic loosening as the end point was 100.0% with a RLL and 99.1% without a RLL (95% CI 97.9 to 100). With revision of the acetabular component for any reason as the end point, the survival rate was 99.2% with a RLL (95% CI 97.6 to 100) and 96.5% without a RLL (95% CI 93.4 to 99.7).

Conclusion

This study demonstrates that acetabular bone quality, head diameter, structural bone graft, and hip centre position may influence the presence of the any RLL.

Cite this article: Bone Joint Open 2021;2(5):278–292.

Does vacuum mixing affect diameter shrinkage of a PMMA cement mantle during in vitro cemented acetabulum implantation?

Radiolucent lines on immediate postoperative cemented acetabular component radiographs between the PMMA bone cement mantle and bone are an indicator of an increased risk of early loosening. The cause of these lines has yet to be identified. Thermal and chemical necrosis, fluid interposition and cement shrinkage have all been suggested in the literature. The aim of the study reported here was to take an engineering approach - eliminating confounding variables present during surgery - to quantify the size of the interstice created by cement shrinkage when a 50 mm diameter flanged acetabular cup is implanted in a model acetabulum with a 52 mm hemispherical bore under controlled conditions using vacuum and non-vacuum mixed cement. Irrespective of the mixing method used, a significant interstice was created between the bone cement and the mock acetabulum. When the cement was mixed under vacuum the interstice created between the mock acetabulum and the cement mantle was 0.60 mm ± 0.09 mm; when the cement was mixed under non-vacuum conditions the interstice created was 0.39 mm ± 0.15 mm. Possible explanations for radiolucent lines are discussed.

Acetabular Subchondral Bone Decortication and Its Role in the Outcome of Cemented Total Hip Replacement in Young Patients

Purpose

Long-term fixation of cemented acetabular components can be problematic in younger active patients. Our technique is put forward to improve outcomes and maximize implant survivorship in this particular patient population.

Materials and Methods

We report on a cohort of young adult patients (less than 55 years old) with cemented total hip replacement (THR) using a novel technique in preparing and cementing the acetabulum with a minimum follow-up of 10 years (mean follow-up, 14 years). Retrospectively collected data on clinical and radiological outcomes were reviewed.

Results

Sixty-five THRs were performed with the minimum study follow-up period. Average age for patients was 44 years old (range, 19–55 years). The mean Hip Disability and Osteoarthritis Outcome Score for patients at final appointment was 92.7. Radiographs taken at an average of 14 years after operation showed 63 of 65 hips showed no evidence of any radiological loosening. Cup survivorship was 100% at the end of the study period.

Conclusion

Our technique of preparing the acetabulum in combination with cement fixation is reproducible with excellent results in a cohort of patients prone to early aseptic loosening of the acetabular component.

Total hip arthroplasty: a still evolving technique

It has been advocated that total hip arthroplasty (THA) is probably the most successful surgical intervention performed in Medicine. In the 1960s, Sir John Charnley not only introduced, but also modified and improved the technique of cemented arthroplasties. The concepts on biological fixation established by Pillar and Galante served as the foundation for the development of uncemented implants that are now used worldwide. Currently, THA is a worldwide widespread surgery performed on millions of people. However, keeping abreast of the large number of information available on these procedures, especially on implant fixation, designs, different tribological pairings, and the long-term results can be challenging at times. This article is a brief update on the main aspects of THA.

The Interaction of Caseload and Usage in Determining Outcomes of Unicompartmental Knee Arthroplasty: A Meta-Analysis

BACKGROUND

Outcomes after unicompartmental knee arthroplasty (UKA) are variable and influenced by caseload (UKA/y) and usage (percentage of knee arthroplasty that are UKA), which relates to indications. This meta-analysis assesses the relative importance of these factors.

METHODS

MEDLINE (Ovid), Embase (Ovid), and Web of Science (ISI) were searched for consecutive series of cemented Phase 3 Oxford medial UKA. The primary outcome was revision rate/100 observed component years (% pa) with subgroup analysis based on caseload and usage.

RESULTS

Forty-six studies (12,520 knees) with an annual revision-rate ranging from 0% to 4.35% pa, mean 1.21% pa (95% confidence interval [CI], 0.97-1.47), were identified. In series with mean follow-up of 10-years, the revision-rate was 0.63% pa (95% CI, 0.46-0.83), equating to a 94% (95% CI, 92%-95%) 10-year survival. Aseptic loosening, lateral arthritis, bearing dislocation, and unexplained pain were the predominant failure mechanisms with revision for patellofemoral problems and polyethylene wear exceedingly rare. The lowest revision-rates were achieved with caseload >24 UKA/y (0.88% pa; 95% CI, 0.63-1.61) and usage >30% (0.69% pa; 95% CI, 0.50-0.90). Usage was more important than caseload; with high usage (≥20%), the revision-rate was low, whether the caseload was high (>12 UKA/y) or low (≤12 UKA/y; (0.94% pa; 95% CI, 0.69-1.23 and 0.85% pa; 95% CI, 0.65-1.08), respectively); with low usage (<20%), the revision-rate was high, whether the caseload was high or low (1.58% pa; 95% CI, 0.57-3.05 and 1.76% pa; 95% CI, 1.21-2.41, respectively).

CONCLUSION

To achieve optimum results, surgeons, whether high or low caseload, should adhere to the recommended indications such that ≥20%, or ideally >30% of their knee arthroplasties are UKA. If they do this, then they can expect to achieve results similar to those of the long-term series, which all had high usage (>20%) and an average 10-year survival of 94%.

The Relative Merits of Cemented and Uncemented Prostheses in Total Hip Arthroplasty

The results of modern cemented and uncemented total hip arthroplasties are outstanding and both systems have their advantages and disadvantages. This paper aims to examine the designs of different types of prostheses, some history behind their development and the reported results. Particular emphasis is placed on cemented stem design and the details of cementing technique.

[Predictive factors of aseptic loosening of cemented total hip prostheses]

Introduction

Le descellement aseptique constitue la principale complication à long terme et signe la faillite de la prothèse totale de hanche. Les causes de descellement aseptique sont multiples et souvent intriquées. Le mal positionnement des implants reste le facteur le plus incriminé. D’autres facteurs liés au patient et à la prothèse prédisposent également au descellement mais à des degrés divers.

Méthodes

A travers une étude rétrospective portant sur 64 descellements aseptiques de prothèse totale de hanche, nous avons tenté d’individualiser les facteurs de descellement lié au patient, au type d’implant et à la technique chirurgicale et d’en dégager les recommandations visant à minimiser ce risque. Il s’agissait d’une étude rétrospective analytique portant sur 64 descellements aseptiques. La classification utilisée est celle de la Société Française de Chirurgie Orthopédique et Traumatologique.

Résultats

La moyenne d’âge au moment de la première arthroplastie était de 40 ans. Elle était de 62 au moment du descellement. La tige type Charnley a été implantée dans 55 cas, celle de type Muller dans 9 cas. La pièce cotyloïdienne a été bien positionnée dans 69% des cas avec une inclinaison moyenne de 47,8°. Les tiges étaient remplissantes dans 86% des cas avec un cimentage Grade A dans 60% des cas. Le délai moyen de la survenue du descellement était de 12 ans. 72% des prothèses avaient une survie supérieure à 10 ans. L’analyse statistique des résultats a individualisé les facteurs de risque du descellement que sont: L’âge, l’indexe de masse corporelle, le niveau d’activité, l’inclinaison de la cupule, le déport fémoral et la qualité du cimentage.

Conclusion

Une réduction significative des descellements aseptiques des prothèses totales de hanche ne pourra être obtenue que par une plus grande rigueur dans la sélection des patients, une plus grande sûreté dans l’acte technique et un meilleur choix de l’implant à poser.

Impaction grafting of the acetabulum with ceramic bone graft substitute: high survivorship in 43 patients with a mean follow-up period of 4 years

BACKGROUND AND PURPOSE

Loss of bone stock remains a challenge in revision hip surgery. Grafting with allograft is well established, but there are problems with availability, cost, infection, antigenicity, reproducibility, and stability of the created construct. BoneSave is a biphasic porous ceramic consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite. In vitro and in vivo studies, including its use mixed with allograft, have shown good results in impaction grafting. This is the first reported series of its use alone in impaction grafting of the acetabulum.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single centre. All patients received uncemented acetabular components. They were followed up radiographically, together with self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Mean follow-up was 4 years. 5 patients died during follow-up, with their constructs in situ. The survivorship of the acetabular component was 98% (95% CI: 85-100) at 7 years. 1 acetabular component was revised for infection and there was 1 radiographic acetabular failure. The median OHS was 36 (6-48), the median SF12 PCS was 36 (14-57), the median SAPS was 75 (0-100), and the median SF12 MCS was 50 (23-64). The graft material had incorporated in all 3 zones of the acetabulum in 33 out of 37 cases with complete radiographic follow-up.

INTERPRETATION

Medium-term results show that BoneSave alone is a reliable material for impaction grafting of contained defects in the acetabulum at revision surgery.

Impaction grafting of the acetabulum with ceramic bone graft substitute mixed with femoral head allograft: high survivorship in 43 patients with a median follow-up of 7 years: a follow-up report

BACKGROUND AND PURPOSE

Restoration of bone stock at revision hip surgery remains a challenge. Alternative graft materials with suitable mechanical properties for impaction grafting have been sought due to issues with infection, antigenicity, cost, and availability of allograft. We have previously presented good short-term results of the use of BoneSave, a biphasic porous ceramic bone graft substitute, consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite, in a 50:50 mix with femoral head allograft. We now present the medium-term results.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single center. 34 patients received uncemented acetabular components and 9 received cemented components. Patients were followed up radiographically and with the self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and the Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Median follow-up of the surviving patients was 80 (69-106) months. 15 patients died during the follow-up period, 14 with their construct in situ. The survivorship of the grafted acetabulum and acetabular component was 94% (95% CI: 99-78) at 7 years. 1 patient had been revised for aseptic loosening of the acetabulum and 1 for deep infection. The mean OHS was 31 (SD 12), the mean SF12 physical-component score (PCS) was 38 (SD 13), the median SAPS was 83 (0-100), and the median SF12 mental-component score (MCS) was 55 (23-65). The graft material became incorporated in all 3 zones of the acetabulum in 23 out of 24 cases that had complete radiographic follow-up.

INTERPRETATION

These medium-term results show that BoneSave is a reliable material for impaction grafting of the acetabulum when used in conjunction with femoral head allograft.

Radiographic grading of femoral stem cementation in hip arthroplasty

OBJECTIVE:

To determine intra and interobserver agreement of the grading system for femoral cementation in hip arthroplasty proposed by Barrack.

METHODS:

Immediate anteroposterior and lateral postoperative radiographs of 55 primary total hip arthroplasties were assessed by two observers familiar with the use of this grading system. The assessments were performed on two separate occasions by each observer and independently. The statistical analysis measured the Kappa coefficient, which determines the degree of agreement between tests with categorical variables.

RESULTS:

Intraobserver Kappa coefficient varied from 0.43 to 0.68, demonstrating moderate to substantial strength of agreement; interobserver Kappa coefficient varied from 0.19 to 0.44, demonstrating slight to moderate strength of agreement.

CONCLUSION:

Intra and particularly interobserver agreement are limited in this grading system, even when used by trained individuals. Level of Evidence III, Study of nonconsecutive patients; without consistently applied reference "gold" standard.

Involvement of extracellular Hsp72 in wear particle-mediated osteolysis

Wear particle-mediated osteolysis is one of the major problems affecting long-term survival of orthopaedic prostheses, frequently progressing to failure of fixation and revision surgery. Upon challenging with wear particles, macrophages and various other types of cells release soluble factors that stimulate the resorptive activity of osteoclasts and impair the function and activity of osteoblasts. Extracellular Hsp72 has been reported to activate macrophages and up-regulate pro-inflammatory cytokine production, although its role in osteolysis has not been established yet. The purpose of our study was to evaluate the involvement of this protein in the inflammatory response to wear particles that leads to periprosthetic osteolysis. To this end, we used interfacial tissues and blood samples from patients undergoing revision surgery due to aseptic loosening of cementless acetabular cups. Confocal microscopy indicated that Hsp72 co-localises with CD14(+) cells of interfacial tissues. Levels of Hsp72 in the culture media from periprosthetic membranes cultured ex vivo decreased along culture time and Hsp72 levels in sera from patients were lower and under the assay detection limit compared with those from age-matched control subjects. This suggests that interfacial tissues are not actively producing the protein but likely recruit it from peripheral circulation. Incubation of human macrophages with titanium (Ti) particles decreased the release of Hsp72 into culture media. Treatment with recombinant human Hsp72 enhanced considerably IL-6 levels in culture media which were not modified after macrophage co-stimulation with Ti particles, while pre-incubation with Hsp72 increased the Ti particle-induced TNF-α and IL-1β production. Altogether, these data indicate that extracellular Hsp72 amplifies the inflammatory response to wear debris by interacting with resident macrophages in periprosthetic tissues.

Comparison of flanged and unflanged acetabular cup design. An experimental study using ceramic and cadaveric acetabuli

BACKGROUND AND PURPOSE

Adequate depth of cement penetration and cement mantle thickness is important for the durability of cemented cups. A flanged cup, as opposed to unflanged, has been suggested to give a more uniform cement mantle and superior cement pressurization, thus improving the depth of cement penetration. This hypothesis was tested experimentally.

MATERIALS AND METHODS

The same cup design with and without flange (both without cement spacers) was investigated regarding intraacetabular pressure, cement mantle thickness, and depth of cement penetration. With machine control, the cups were inserted into open-pore ceramic acetabular models (10 flanged, 10 unflanged) and into paired cadaver acetabuli (10 flanged, 10 unflanged) with prior pressurization of the cement.

RESULTS

No differences in intraacetabular pressures during cup insertion were found, but unflanged cups tended to migrate more towards the acetabular pole. Flanged cups resulted in thicker cement mantles because of less bottoming out, whereas no differences in cement penetration into the bone were observed.

INTERPRETATION

Flanged cups do not generate higher cementation pressure or better cement penetration than unflanged cups. A possible advantage of the flange, however, may be to protect the cup from bottoming out, and there is possibly better closure of the periphery around the cup, sealing off the cement-bone interface.

Cemented total hip stem design influence on adaptative cortical thickness and femoral morphology

INTRODUCTION

Five-year following total hip implantation femur adaptive morphology was compared between two groups differing only in their femoral stem design.

MATERIAL AND METHODS

Group 1, recruited prospectively, included 51 Dédicace stems(Stryker-Howmedica) and group 2, retrospectively matched to group 1, comprised 51 Kerboull MK3 stems (Stryker-Howmedica). While MK3 prosthetic system increases in size homogeneously (widening along the whole length as the implant dimension increases), the Dédicace prosthetic system provides various metaphyseal widths for a given diaphyseal size. We opted for primary fixation (press fit according to the "French paradox") prior to cementing in both cases, despite the risk of discontinuity in the cement mantle. The homogeneous dimensioning of the MK3 stem enables distal primary fixation, whereas the Dédicace range allows differentiated adaptation to diaphyseal length and metaphyseal caliber. The following parameters were measured and calculated: Noble index, femoral cortical thickness score of Barnett and Nordindiaphyseal filling and stress-shielding at three levels around the stem.

RESULTS

Bone-remodeling, assessed on X-ray, was without clinical impact, whether it took the form of spongialization or stress-shielding. The sole factor tending to induce stress-shielding was a high degree of canal filling by the distal third of the stem, more frequently encountered with the MK3 model. Metaphyseal filling was equivalent with all stems. In the matched series on the contralateral healthy side, femoral spongialization was comparable.

LEVEL OF PROOF

Level III; case/control study.

The condition of the cement mantle in femoral hip prosthesis implantations--a post mortem retrieval study

Despite numerous studies demonstrating the characteristics of the optimal cement mantle in joint replacement, the clinical state of the cement mantle is rarely assessed. A random sample of 214 cemented implanted femoral hip components was retrieved post mortem from Hamburg, Germany, and sectioned to investigate the quality of the cement mantle. The most common observation made in at least one measured region per retrieval was debonding (82% of stems), followed by a thin cement mantle (74%), stem-bone contact (48%), soft tissue at the stem interface (44%), no cement-bone interdigitation (30%), a gap at the stem interface (28%), voids in the cement (22%) and cracks and blood in the cement mantle (<10%). 21% of stems demonstrated complete debonding of the interface. However, distributions of all other defects were local, with less than 10% of stems demonstrating any imperfection in more than 21% of the regions assessed. No progressive damage was observed with implantation duration. The results suggest that current implantation technique may be adequate for proper implant function over the service life in the older patient population. However, for younger and more active patients, perfection of the cementation technique is crucial, particularly in modern implant systems such as resurfacing. The frequency of almost all defects could be further reduced by careful implantation technique, providing the increased service life necessary for the ever younger, more physically demanding, patient population.

Monitoring surgical performance: an application to total hip replacement

RATIONALE, AIMS AND OBJECTIVES

Inadequate surgical implantation of a hip replacement may result in decreased patient satisfaction and reduced implant survival. The objective was to monitor surgical performance in hip replacement.

METHOD

The study took place at a teaching centre. All primary total hip replacements were prospectively included in the series. For each hip replacement, intraoperative technical errors, cup and stem fixation and position, and postoperative complications were recorded. If all items rated were correct, the procedure was considered as correct. The Cumulative Sums (CUSUM) test was used to monitor the performance of the centre. A 90% proportion of successful procedures was considered as adequate performance and a 75% proportion of successful procedures was deemed as inadequate performance. Meetings were conducted to discuss the results of monitoring.

RESULTS

Eighty-three total hip replacements were monitored. Overall, 28 procedures (34%) were considered inadequate. The most potent reasons for inadequate performance were cup positioning and stem fixation. The CUSUM test signalled after the second procedure that performance was inadequate. After the first meeting, despite an improvement was seen, the CUSUM test raised an alarm indicating inadequate performance. The study was stopped after the second meeting because of funding reasons before it could be demonstrated that performance had reached the desired level.

CONCLUSION

This study has demonstrated that implementing a dedicated system to monitor surgical performance in a teaching hospital improves the quality of implantation of total hip replacements. Nonetheless, the target of ninety percent of adequate primary total hip replacement could not be reached and efforts should be continued.

The influence of a suction device on fixation of a cemented cup using RSA

The quality of technique used at the time of socket cementation is crucial in ensuring a durable long-term result of the implant. We asked whether a new instrument, an aspirator retractor introduced into the wing of the ilium before socket preparation and cementation, would enhance cement fixation as defined by RSA and radiographic examination. We randomized 38 patients into two groups. The surgical technique was identical between the groups with the exception of the use of the aspirator retractor. Patients were followed clinically and with radiostereometry at a minimum of 2 years. We compared gross radiographic appearances, including the depth of penetration of cement and the incidence of postoperative and 2-year radiolucent lines. There was no difference in proximal migration between the two groups. No improvement of fixation was proven from the measured translations and rotations of the socket in the suction group. We found no difference in the number or extent of radiolucent lines or the depth of cement penetration when the iliac suction device was used in conjunction with contemporary cementing techniques. Although the data suggest no short-term advantage in this small study, we will continue to follow these patients presuming there will be improved outcomes in the longer term and since the device provides an easier method of obtaining adequate fixation, especially if technical difficulties are encountered during the pressurization procedure.

Once-weekly oral medication with alendronate does not prevent migration of knee prostheses: A double-blind randomized RSA study

BACKGROUND AND PURPOSE

Early migration of joint replacements is an effect of poor fixation and can predict late loosening. By reducing the bone resorption after implantation of a joint replacement, it should be possible to enhance the initial fixation of the implant. We studied the effect of once-weekly treatment with alendronate after knee replacement.

PATIENTS AND METHODS

We recruited 60 patients (60 knees) with gonarthrosis who were scheduled for a total knee replacement. They were operated on with identical implants and uncemented fixation. 30 patients were treated with a bisphosphonate (alendronate) and 30 patients underwent placebo treatment. The treatment started postoperatively and continued on a weekly basis for 6 months. The fixation of the implants was measured with repeated radiostereometry for 2 years.

RESULTS

There was no difference in migration of implants between the two groups.

CONCLUSION

With uncemented fixation of knee implants, no benefit of once-weekly treatment with alendronate, starting postoperatively, could be seen during a 2-year follow-up period.

Pulsed lavage reduces the incidence of radiolucent lines under the tibial tray of Oxford unicompartmental knee arthroplasty: pulsed lavage versus syringe lavage

The aim of the study was to determine whether the incidence of radiolucencies can be reduced using pulsed lavage before cementing the tibia in unicompartmental knee arthroplasty (UKA). We prospectively studied a consecutive series of 112 cemented Oxford UKA in 100 patients in two centres. In group A (n = 56) pulsed lavage and in group B (n = 56) conventional syringe lavage was used to clean the cancellous bone. The same standardised cementing technique was applied in all cases. At a minimum follow-up of one year patients were evaluated clinically and screened radiographs were obtained. The cement bone interface under the tibial plateau was divided into four zones and evaluated for the presence of radiolucent lines. All radiographs were evaluated (n = 112), and radiolucencies in all four zones were found in two cases in group A (4%) and in 12 cases in group B (22%) (p = 0.0149). Cement penetration showed a median of 2.6 mm (group A) and 1.5 mm (group B) (p < 0.0001). We recommend the routine use of pulsed lavage in Oxford UKA to reduce the incidence of radiolucency and to improve long-term fixation.

Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip arthroplasty: a prospective study using computed tomography-assisted osteodensitometry

Stress-shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high-demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)-assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n = 21) versus noncemented (n = 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press-fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (-45 to -53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (-11 to -20%). Cancellous BD decrased only ventral (-21 to -31%) and in two scans cranial (-11 and -12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press-fit component. Long-term results are required to prove whether third-generation cementing technique protects periprosthetic BD and thereby improve implant survival.

Does use of a "rim cutter" improve quality of cementation of the acetabular component of cemented exeter total hip arthroplasty?

A randomized controlled trial was performed to assess the effect of a rim cutter device on cement mantles in modern elective total hip arthroplasty using a flanged acetabular component. Forty patients were randomized to a rim cutter (21) or control (19) group. A statistically significant improvement in cement penetration was demonstrated in zone 1 (10.1 vs 8.6 mm, P = .023), and in cement mantle thickness in zones 2 and 3 (7.8 and 6.7 mm vs 5.7 and 5.4 mm [P < .001 and P = .017]), with a reduced incidence of bottoming out of the socket (1/21 vs 8/19 [P = .007]). Cement mantle thicknesses greater than 8 mm were achieved more consistently in the rim cutter group (30% vs 2%). This technique improves cement penetration and mantle thickness in a reliable manner.

Acetabular cortical and cancellous bone density and radiolucent lines after cemented total hip arthroplasty: a prospective study using computed tomography and plain radiography

INTRODUCTION

The aim of this prospective study was to evaluate load-transfer mechanisms and stress patterns of periacetabular cortical and cancellous bone after cemented total hip arthroplasty (THA) in vivo using computed tomography (CT) assisted osteodensitometry. In addition we analyzed the efficacy of CT in detecting radiolucent lines around the acetabular component compared to plain radiography.

MATERIALS AND METHODS

Twenty-two cemented acetabular cups were investigated using conventional sequential axial CT scans (Ø 8 days and 26 months post-OP) and plain radiography (Ø 5 days and 40 months post-OP). CT assisted osteodensitometry was used to determine cancellous and cortical bone bone density (BD). Radiolucent lines were evaluated using both CT and plain radiography.

RESULTS

Significant BD loss at the time of follow-up was only detectable ventral to the cup (cortical bone: -16%, P = 0.001; cancellous bone: -31%, P = 0.001). The BD changes dorsal and cranial to the cup were not significant. Postoperatively no radiolucent lines were observed in the cement-bone interface by CT, while on plain radiography acetabular lucent lines were seen in 12 out of 22 cases.

CONCLUSION

CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.

Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement--a finite element study

Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study, is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in vitro testing, we used commercially available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley.

In vitro pressurization of the acetabular cement mantle: the effect of a flange

A model was developed to assess the effect of an acetabular flange on pressure within different zones of the cement mantle during insertion. Two prosthetic designs were assessed in 3 different sizes. Flanged components produced significantly higher mean pressures than unflanged ones (P < .01). The effect of a flange was more pronounced at the rim than at the pole. Delayed insertion resulted in a further significant rise in mean pressure (P < .01), but this did not compensate for the lack of a flange. This experimental model supports the use of a flange to increase pressure within the cement mantle on component insertion. The beneficial effect is more marked in the area that is most likely to show deficiency in the cement-bone interface on postoperative radiographs.

The influence of initial pressurization and cup introduction time on the depth of cement penetration in an acetabular model

BACKGROUND

Acetabular cementation during total hip arthroplasty is considered difficult mainly due to the appearance and anatomy of the acetabulum. Improved cementation technique has been shown to improve the longevity of acetabular components.

METHOD

We designed a ceramic model to investigate the effect of varying the initial cement pressurization and cup introduction times on the depth of cement penetration. 4 groups were prepared, 2 of which involved varying initial cement pressurization and cup introduction times. Group 3 involved initial cement pressurization with no cup introduction, while group 4 involved cup introduction with no prior cement pressurization.

RESULTS AND INTERPRETATION

Most cement penetration occurred in the early pressurization phase, and we conclude that a relatively early and longer cement pressurization time and late cup introduction are positive factors for increased cement penetration in the acetabulum model.

Tight fit technique in primary hybrid total hip arthroplasty for patients with hip dysplasia

This article presents the midterm results of hybrid total hip arthroplasty for patients with hip dysplasia by use of a tight fit technique for the femoral component. We followed up 113 hips in 99 patients for a mean of 11 years. All final femoral rasps used in this study overrasped by 0.5 to 1.0 mm for stem insertion, resulting in relatively thin cement mantles. Both components of one hip were removed because of infection. The other 5 acetabular components were revised for osteolysis, recurrent dislocation, or dislodgement of the polyethylene liner. No femoral component was revised for aseptic loosening. We conclude that the tight fit technique using a canal-filling stem may produce good long-term results for patients with hip dysplasia.

Postoperative clodronate decreases prosthetic migration: 4-year follow-up of a randomized radiostereometric study of 50 total knee patients

BACKGROUND

We have previously reported that 6 months of oral treatment with clodronate reduced the migration of the NexGen total knee prosthesis during the first postoperative year, as measured by radiostereometry (RSA). We now report the 4-year results.

METHODS

This was a double-blind randomized study, using RSA with maximal total point motion (MTPM).

RESULTS

With analysis according to the "intention to treat" principle, the only remaining difference between the groups at 4 years was reduced rotation around the transverse axis (a secondary variable) in the clodronate group. However, 3 patients (all clodronate) did not take any tablet after surgery. If they are excluded, there was an almost statistically significant difference between the groups at 4 years regarding MTPM from baseline, with the clodronate group showing 25% less migration. From 1 to 4 years, there was no difference in migration rate by MTPM, but there was a continuous increase in rotation around the transverse axis in the controls, which differed from the clodronate group. There were no cases of aseptic loosening. 2 patients had migration of more than 1.3 mm from baseline to 4 years; neither of them had taken clodronate. The others had migration of less than 0.9 mm.

INTERPRETATION

Because migration was clearly reduced by clodronate during the first postoperative year, and there was still a difference at 4 years when analyzed per protocol, it appears likely that this treatment can diminish the risk of loosening. The difference in the number of outliers also points in this direction, and may be more relevant than mean migration values.

Is removal of subchondral bone plate advantageous in cemented cup fixation? A randomized RSA study

There is uncertainty regarding whether and how the subchondral bone plate should be treated during acetabular preparation for cemented cup fixation in a total hip arthroplasty. We hypothesized that removing the bone plate would improve the cement-bone interface without jeopardizing the initial cup stability, and therefore, be advantageous to long-term cup survival. We randomized 50 patients with primary osteoarthritis into two groups, one for removal and one for retention of the subchondral bone plate. The patients were evaluated during 2 years followup using repeated radiostereometric examinations, analyses of radiolucent lines, and clinical followups. Patient scoring was done using the Western Ontario and McMaster Universities Osteoarthritis Index, the Short Form-12, and the Harris hip score. Removal of the subchondral bone plate resulted in a superior cement-bone interface with less development of radiolucent lines. The radiostereometry results showed small migrations in both groups. We found no differences in cup stability between groups, although a difference was observed in rotational behavior with the removal group stabilizing in a slightly vertical position whereas the retention group showed slight but progressive rotation into a more horizontal position. No differences were found during clinical followups. Removing the subchondral bone plate, where possible, improves the cement-bone interface without jeopardizing the stability, implying better long-term cup survival. However, it is a more demanding surgical technique.

LEVEL OF EVIDENCE

Therapeutic study, Level I (high quality randomized controlled 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.

The correlation between immediate radiolucent lines and early implant migration in cemented acetabular components

Periacetabular radiolucent lines (RLLs) on postoperative radiographs have been associated with early loosening of the acetabular component. It has also been shown that excessive migration of an implant corresponds to an increased incidence of later clinical failure. This study relates RLLs on anterior-posterior hip radiographs taken 10 days and 6 months postoperatively to implant migration detected by roentgen stereophotogrammetric analysis. We have shown that RLLs in DeLee and Charnley zone III in the first week postoperatively as well as at 6 months are positively and significantly (P < .05) associated with migration detected by roentgen stereophotogrammetric analysis. No significant association was found for zone I or II at either 10 days or at 6 months. Considering the limitations in observing RLLs, their presence in zone III appears to reflect on the mechanical stability of the acetabular cup from the beginning. This indicates that zone III, which represents the inferomedial aspect of the acetabulum, might have to receive special attention when preparing the acetabulum and implanting the acetabular cup.

The cemented all-polyethylene acetabular cup: factors affecting survival with emphasis on the integrated polyethylene spacer: an analysis of the effect of cement spacers, cement mantle thickness, and acetabular angle on the survival of total hip arthroplasty

Four hundred seven primary total hip arthroplasties were performed using a cemented, direct compression molded all-polyethylene acetabular component. Based on a double-blinded randomization schedule, one group received acetabular cups with cement spacers made from polyethylene integrated into the cup, whereas the other group received the same acetabular cups with the polyethylene spacers removed. Patients were followed up for an average of 6.5 years. During this follow-up period, there were 3 revisions for acetabular cup loosening and 40 acetabular cups that had a global radiolucent line at least 1 mm wide. Acetabular cups with polyethylene spacers were found to have a significantly higher initial rate of failure (P < .0380) when compared with cups without cement spacers. Yet, polyethylene spacers resulted in a significantly thicker and more uniform cement mantle in zones 1, 2, and 3 (P < .0001). Cups initially placed at an angle of 45.0 degrees to 50.5 degrees had the highest survival rate compared with all possible angle ranges (P < .0158).

Prediction of Charnley femoral stem aseptic loosening by early post-operative radiological features

We describe the association between immediate post-operative radiological appearances and early aseptic failure of total hip replacement. Sixty-three hips were entered into the aseptic failure group and 138 into the control group. Alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was associated with failure in Gruen zones 6 (p=0.040) and 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). Grade of cementation was associated with failure for Barrack grades C (p=0.001) and D (p=0.001). This study has demonstrated that easily applied radiological criteria can be used to identify 'hip arthroplasties at risk' from the immediate post-operative radiograph.

Peri-acetabular radiolucent lines: inter- and intra-observer agreement on post-operative radiographs

Peri-acetabular radiolucent lines (RLLs) seen on "early" post-operative radiographs have been identified as a potential predictor of long-term implant performance. This study examines the inter- and intra-observer variation encountered when assessing such radiographs. Four consultant orthopaedic surgeons assessed the presence, extent and width of RLLs in 220 radiographs performed on 50 patients taken one to two weeks, six weeks, six months and one year following surgery. Inter-observer agreement was fair at 7-14 days but improved to moderate to good in films at six and 12 months. Intra-observer agreement was moderate to good at 7-10 days but again improved to good at 6 and 12 months. When only the presence or absence of RLLs was considered, both inter-observer and intra-observer agreement improved for both the six-month and one-year radiographs. This experiment shows that caution must be used for the interpretation of RLLs on hip radiographs taken during the very early post-operative period. We recommend that films taken at least six weeks to six months following surgery should be used for assessment to reduce observer variation. For optimum results, a single experienced observer should do the assessment with a simple classification.

Migration of the acetabular component: effect of cement pressurization and significance of early radiolucency: a randomized 5-year study using radiostereometry

BACKGROUND

Cementing technique is a crucial factor in prosthesis fixation. No randomized studies have been published, however, comparing the outcome of conventional fingerpacking with the outcome of pressurization of the cement prior to cup insertion.

PATIENTS AND METHODS

We randomized 50 THAs to either fingerpacking or sequential pressurization (including individual pressurization of each anchorage hole) and followed the patients with RSA for 5 years. The penetration of cement into the anchorage holes was measured on digital radiographs. Postoperative radiolucent lines around the cup were correlated to later RSA results. For clinical evaluation, we used SF-36 and HHS.

RESULTS

The pressurized group of THAs was more stable regarding changes in inclination. We found no other difference in the migratory behavior. The cement penetration into the anchorage holes was deeper with the pressurization technique than with fingerpacking. For the whole group taken together, there was a strong relation between the presence of radiolucent lines as measured on the postoperative radiograph and later migration observed by RSA at 2 and 5 years.

INTERPRETATION

Pressurization of the cement produced better cement penetration and increased the cup stability in terms of changes in inclination. Early findings of radiolucent lines can predict later unfavorable cup migration.

Improved acetabular pressurization gives better cement penetration: in vivo measurements during total hip arthroplasty

During total hip arthroplasty, the intraoperative cementation pressure was measured inside one of the acetabular anchorage holes. Patients were randomized to pressurization of cement with either a conventional pressurizer or a sequential method including individual pressurization of each anchorage hole. The pressure was correlated to the cement penetration measured on digital radiographs. The early peak pressures were higher for the sequential method, resulting in a significantly better penetration of 2.8 mm compared with 0.7 mm with the conventional pressurizer. We found a strong correlation between early peak cementation pressures and cement penetration into the cancellous bone of the anchoring holes, indicating a cause-effect relationship at this early stage. The highest peak pressures were achieved during the later cup insertion, but these pressures did not correlate with the cement penetration. We conclude that conventional methods for cement pressurization in the acetabulum may not be optimal.

The role of cemented sockets in 2004: is there one?

Cement fixation of the acetabular cup in total hip arthroplasty (THA) has evolved through multiple generations of cement technology. Whereas cement technology has produced improvements in cemented femoral fixation, the cemented socket still produces inconsistent results. Even with our current knowledge that cemented cups require exposure of cancellous bone, a clean and dry socket, and adequate bony coverage of the cup, surgeons such as myself are unable to control radiolucency at the bone-cement interface. The technical difficulty of cementing the acetabular cup has led to the increasing prevalence of cementless acetabular cups. Although cementless fixation has resulted in increased incidence of osteolysis, the surgical procedure is less technically demanding, and the long-term mechanical fixation results have been more consistent. Given the experiential learning curve that most orthopedic surgeons face with cemented fixation of the acetabular cup component, the role of the cemented socket in THA today is limited.

A new bleeding model of the human acetabulum and a pilot comparison of 2 different cement pressurizers

In this cadaver study, we compared 2 different acetabular cement pressurizers (Exeter and Bernoski type) in paired human acetabula with simulated intraosseous bleeding. Pressure transducers were used to record intra-acetabular pressures during pressurization. Anteroposterior radiographs of the entire specimens were taken. Subsequently, standardized 3-mm-thick sections were cut through the acetabula, which were then microradiographed to evaluate cement penetration. Adequate pressurization was obtained with either pressurizer. The peak and sustained pressures obtained with the Exeter pressurizer (peak, 80 kPa; sustained, 38 kPa) tended to be higher than the pressures obtained with the Bernoski pressurizer (73 kPa; 24 kPa; P > 0.05). Accordingly, a tendency toward improved cement penetration into cancellous bone was found using the Exeter pressurizer (P >.05).

Radiographic evaluation of Charnley cups used in first-time revision: repeated observations for 7-15 years

The radiographs of 46 consecutive polyethylene cups used in cemented first-time revision of the acetabulum were studied up to a mean of 10.7 years (range, 0.5-16.3 years). Six cups developed loosening, of which 2 were revised. New radiolucent lines appeared mainly up to the 3 years follow-up. Progression of radiolucencies to new regions was noted in 28 (61%) cups. This progression occurred as an increase in extension from the periphery to the central region of the interface, whereas the width only showed minor changes. Our findings indicate that even radiolucent lines with a width <1.0 mm should be given attention because these lines can surround the cup before significant migration (>5 mm) is established. True lateral radiographs exposed to visualize the interface add information concerning presence of loosening. According to our opinion, complete radiolucent lines on either the anterior-posterior or lateral view, with a width of 0.3 to 0.5 mm or more, should be regarded as radiographic failure.

Acetabular options

Cemented acetabular options have failed anywhere between 10% and 23% over the years and have not improved with increasing cement technology. Cementless technology, however, has basically stopped the problems of prosthesis loosening; however, wear has become a major concern. With present day cement techniques, no radiolucent lines, and a compression-molded polyethylene acetabular component, there is less than a 1% failure rate. The question is, however, whether cementing is technically feasible. Even for experienced surgeons, there is at least a 10% chance of a radiolucent line. Therefore, clinicians should work to develop better bearing surfaces so that cementless technology can be used extensively.

A method for improving acetabular preparation during cemented all-polyethylene acetabular component insertion during total hip arthroplasty

Long-term outcome from cemented acetabular components has been correlated with the presence of radiolucency on early postoperative radiographs. We describe a means for enhancing acetabular bed preparation to decrease blood at the bone-cement interface and to obtain better pressurization of the cement into the cancellous bone of the acetabulum during cemented acetabular component insertion.

Comparison of preoperative radiographs and intraoperative findings of fixation of hemispheric porous-coated sockets

BACKGROUND

The radiographic criteria for identification of loose cementless acetabular components have not been well established. The purpose of this study was to compare the radiographic appearance of a hemispheric porous-coated cementless cup fixed with screws with the intraoperative findings with regard to the fixation status.

METHODS

The quality of the cup fixation was evaluated at fifty-two hip revisions that were performed, for reasons other than infection, at an average of 89.9 months (range, 33.8 to 150.1 months) after the primary operations. The fixation status at the revision surgery was compared with the findings on sequential anteroposterior and lateral radiographs of these sockets. Sequential radiographs of an additional 100 total hip replacements that had not required a reoperation and that had been followed for an average of 121 months were also measured.

RESULTS

Loosening of the socket was radiographically identified by (1) radiolucent lines that initially appeared after two years, (2) progression of radiolucent lines after two years, (3) radiolucent lines in all three zones, (4) radiolucent lines 2 mm or wider in any zone, or (5) migration. The sensitivity of these criteria was 94%, and the specificity was 100%. The criteria had a positive predictive value of 100% and a negative predictive value of 97%.

CONCLUSIONS

The most predictive radiographic findings for early diagnosis of loosening of a hemispheric porous-coated cup were progression of radiolucent lines more than two years after the operation and any new radiolucent line of 1 mm or wider that appeared more than two years postoperatively. Sequential anteroposterior and lateral radiographs are necessary to assess the time of onset and progression of radiolucent lines in order to identify loose hemispheric porous-coated cups accurately.

Clodronate prevents prosthetic migration: a randomized radiostereometric study of 50 total knee patients

In a double-blind study, we randomized 50 patients to receive peroral clodronate medication or placebo from 3 weeks before until 6 months after a total knee replacement with a cemented NexGen implant. Migration of the tibial components was measured by radiostereometry at 1 year. Clodronate reduced prosthetic migration, as measured by maximum total point motion, from 0.40 mm to 0.29 mm (p = 0.01). This confirms that the early postoperative migration is related to bone resorption and thus the biology of the bone bed. Since early migration is related to late loosening, 6 months of clodronate medication might reduce the risk of loosening.

Poor bone quality or hip structure as risk factors affecting survival of total-hip arthroplasty

BACKGROUND

The principal long-term complication after total hip arthroplasty (THA) has been aseptic fixation failure. Many hip prostheses and operative techniques have been developed to improve outcomes, but few measures have been taken to cope with poor bone quality or hip structure. We assessed risk factors for aseptic fixation failure after THA.

METHODS

We assessed, by multivariate analysis, survival of 405 primary Charnley THAs to identify risk factors for aseptic fixation failures. We also investigated risk factors for development of rapid polyethylene wear (penetration depth of the femoral head into the socket polyethylene > or = 2 mm/year)

FINDINGS

In the entire series of 405 THAs, with use of radiographic fixation failure or revision for a loose socket as the endpoint, development of rapid polyethylene wear and the preoperative diagnosis of atrophic osteoarthrosis (defined by scarce osteophyte formation) were identified as risk factors for socket loosening (p < or = 0.02). A medullary canal with an unfavourable geometry (a stovepipe canal, Noble's canal-flare index < 3.0) was the only risk factor for femoral fixation failure (p < or = 6.7x10(3)). The only variable related to development of rapid polyethylene wear was the type of steel used in the femoral prosthesis--Ortron 90 prostheses significantly lowered the rate of development of rapid wear from 12.7% to 0.4%. In the 248 THAs in which these femoral prostheses were used, socket survival was affected only by the preoperative diagnosis of atrophic osteoarthrosis (for radiographic fixation failure and revision, p=4.0x10(-5) and p=0.042, respectively).

INTERPRETATION

In THA, the critical risk factors are poor bone quality, which manifests as atrophic osteoarthrosis, for socket survival and poor bone structure for femoral-prosthesis survival. To ensure longer durability of THAs, these factors should be assessed further and efforts, especially biological initiatives, should be made to resolve them.