Hybrid total hip arthroplasty with a precoated offset stem. Four to nine-year results

The effect of varus stem placement on joint offset during total hip arthroplasty: a virtual study

INTRODUCTION AND AIMS

With total hip replacement (THR), varus alignment of an uncemented stem will increase offset which can have significant detrimental effects on muscular balance, leg length and overall satisfaction. Thus, we used 3D planning software to determine the change in joint offset with increasing varus stem placement.

METHODS

Eight patients undergoing THR had routine computed tomography (CT) scans to allow for 3D hip planning. Each set of CTs was templated with a straight stem and an uncemented acetabular cup. Initial templating was performed to reproduce native leg length and offset. The templated stem was then rotated into varus at 1° intervals, up to 6° varus while offset changes for all varus positions were noted. This was repeated for each of 3 neck angles, 125°, 135° and 135° lateral and for each stem sizes 1, 3, 5 and 7.

RESULTS

Overall, there was a mean 1.5 mm increase in offset for every 1° of varus. The stems with a 125° neck angle had the greatest increase in mean offset at 1.6 mm for every 1° of varus. The stem neck angles of 135° lateral offset and 135° standard offset, had a mean increase in offset of 1.5 mm and 1.4 mm respectively for every 1° of varus. A greater mean increase in offset for every 1° of varus was observed with increasing stem size.

CONCLUSIONS

We have quantified the relationship between alignment and offset with every 1° of varus placement increasing hip offset for straight stems by 1.5 mm. This can be used as a guide for surgeons during THR so that they have a better quantitative understanding of how varus placement of the stem affects the hip offset.

Fixation of the short global tissue-sparing hip stem

AIMS

Short, bone-conserving femoral components are increasingly used in total hip arthroplasty (THA). They are expected to allow tissue-conserving implantation and to render future revision surgery more straightforward but the long-term data on such components is limited. One such component is the global tissue-sparing (GTS) stem. Following the model for stepwise introduction of new orthopaedic implants, we evaluated early implant fixation and clinical outcome of this novel short-stem THA and compared it to that of a component with established good long-term clinical outcome.

METHODS

In total, 50 consecutive patients ≤ 70 years old with end-stage symptomatic osteo-arthritis were randomized to receive THA with the GTS stem or the conventional Taperloc stem using the anterior supine intermuscular approach by two experienced hip surgeons in two hospitals in the Netherlands. Primary outcome was implant migration. Patients were followed using routine clinical examination, patient reported outcome using Harris Hip Score (HHS), Hip Disability And Osteoarthritis Outcome Score (HOOS), EuroQol five-dimension questionnaire (EQ5D), and Roentgen Stereophotogrammetric Analysis (RSA) at three, six, 12, and 24 months. This study evaluated the two-year follow-up results.

RESULTS

In addition to the initial migration pattern of distal migration (subsidence, Y-translation) and retroversion (Y-rotation) also exhibited by the Taperloc stem, the GTS stem showed an initial migration pattern of varization (X-translation combined with Z-rotation) and posterior translation (Z-translation). However, all components stabilized aside from one Taperloc stem which became loose secondary to malposition and was later revised. Clinical outcomes and complications were not statistically significantly different with the numbers available.

CONCLUSION

A substantially different and more extensive initial migration pattern was seen for the GTS stem compared to the Taperloc stem. Although implant stabilization was achieved, excellent long-term survival similar to that of the Taperloc stem should not be inferred. Especially in the absence of clinically proven relevant improvement, widespread usage should be postponed until long-term safety has been established. Cite this article: Bone Joint J 2020;102-B(6):699-708.

Cementless lateralized stems in primary THA: Mid-term survival and risk factors for failure in 172 stems

INTRODUCTION

Increasing the femoral offset when performing total hip arthroplasty (THA) theoretically increases the stresses and risks of the stem not integrating itself into bone. But this concept has not been validated for cementless stems; this led us to conduct a retrospective study to determine: (1) the risk factors for the occurrence of symptomatic femoral radiological abnormalities, (2) the incidence of these abnormal radiological findings, (3) the revision rate for aseptic non-integration of a cementless lateralized stem.

HYPOTHESIS

Young patients with significant femoral canal flare and a small cementless lateralized stem have a higher risk of abnormal osseointegration.

MATERIAL AND METHODS

We analyzed retrospectively 172 consecutive lateralized stems (KHO, Corail™ product line) implanted during primary THA between 2006 and 2012 in 157 patients (mean age 68years±12.6 (20-95), 89% men). Radiographs were used to evaluate osseointegration scores, offset restoration and the Noble index. Kaplan-Meier survival analysis was performed using "symptomatic femoral radiological abnormalities" and "revision for aseptic stem non-integration" as endpoints.

RESULTS

The mean follow-up was 5.9years±2.7 (range, 2-12.4years). Being more than 70years of age (HR=0.7, 95% CI: [0.3-0.9], P=0.004) and having a larger stem (HR=0.6, 95% CI: [0.4-0.9], P=0.03) were protective against symptomatic femoral radiological abnormalities, while increasing the postoperative femoral offset (HR=1.1, 95% CI: [1.01-1.2], P=0.02) was deleterious. The survival free of "symptomatic femoral radiological abnormalities" was 93% (95% CI: 89-97) at 5years and 84% (95% CI: 75-95) at 8years. The survival free of "revision for aseptic stem non-integration" was 98% (95% CI: 96.8-100) at 5years and 97% (95% CI: 95.2-100) at 8years.

DISCUSSION

In this study, the risk factors for symptomatic radiological abnormalities were being less than 70years of age, having a small lateralized stem and restoring a large femoral offset. Lateralized stems used in this study had a 10% rate of symptomatic radiological abnormalities and a 4% rate of revision for aseptic non-integration.

LEVEL OF EVIDENCE

IV, retrospective study.

Primary hybrid THA using a polymethyl methacrylate-precoated stem: A single-center experience with a 10-year minimum follow-up

The high failure rate of cemented femoral components in the 1970s facilitated the improvement of the cementing technique and surface finishes such as polymethylmethacrylate (PMMA)-precoated stems, reporting a survival rate of >95% at 10 years from some studies. However, controversy persists regarding whether precoated femoral stems are associated with a longer revision-free prosthesis survival. The purpose of this study was to evaluate the clinical and radiological outcomes of PMMA-precoated femoral stems, and analyze factors associated with implant survival. We retrospectively reviewed 73 primary hybrid total hip arthroplasties performed using PMMA-precoated femoral stems. The mean age of the patients was 61 years. During the mean follow-up period of 13 years, 18 hips (24.7%) underwent aseptic loosening, and all of the loosened stems were subjected to revision surgery 8.8 years (range 4.6-15.5 years) from the index surgery. Younger age and poor cementing were significantly associated with aseptic loosening (P = 0.013 and P < 0.001, respectively). However, the aseptic loosening rate was also high at 13.1% even with a good cementing technique. In conclusion, the PMMA-precoated stem failed to show expected advantages and needs to be replaced with other surface finish stem designs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1300-1306, 2017.

Compared fixation and survival of 280 lateralised vs 527 standard cementless stems after two years (1-7)

BACKGROUND

Restoring the native hip anatomy increases hip prosthesis survival, whereas increased femoral lateralisation creates high torque stresses that may alter prosthesis fixation. After finding lucent lines around cementless lateralised stems (Corail™, DePuy Synthes, St Priest, France) in several patients, we evaluated the effects of lateralisation in a large case-series. The objective of our study was to compare lateralised vs standard stems of identical design in terms of radiological osteo-integration and survival.

HYPOTHESIS

Lateralised stems, despite being used only when indicated by the anatomical parameters, carry a higher risk of impaired osteo-integration.

MATERIALS AND METHODS

A retrospective study was conducted in 807 primary total hip arthroplasties (THAs) performed between 2006 and 2010 in 798 patients with a mean age of 65 ± 14.2 years. Lateralised stems were used in 280 cases (Corail High Offset KHO, n = 169; and Corail coxa vara KLA, n = 111 cases) and standard stems in 527 cases (Corail KA). Mean follow-up was 2.3 years (range, 1-7 years). The clinical evaluation included determination of the Postel-Merle d'Aubigné (PMA) score. Bone fixation and stability of the implants were assessed by determining the Engh and Massin score and the ARA score on the radiographs at last follow-up. Femoral, acetabular and global offset values were determined before and after THA. Nobles's Canal Flare Index was computed. Survival was estimated using the Kaplan-Meier method with surgical revision for aseptic loosening as the end-point.

RESULTS

The PMA score improved from 12 (10-15) pre-operatively to 17.7 (14-18) (P < 0.05). After THA, in the lateralised stem group, femoral offset was restored in 217 (77%) hips and the mean change vs the pre-operative offset value was -2 mm; in the standard stem group, femoral offset was restored in 440 (83.5%) hips and the mean change was +1 mm. The Engh and Massin score values were similar in the standard stem and lateralised stem groups (24.4 ± 2.2 and 22.6 ± 2.4, respectively, NS). Revision for aseptic loosening was required in 5 patients with lateralised stems (3 KHO and 2 KLA) versus none of the patients with standard stems. There were no cases of excessive femoral offset and the mean change in offset was -2.3mm (-5.3 to -1.1). Noble's index was increased (4.27 ± 0.5 for the loosened lateralised stems, 3.65 ± 0.8 for the well-fixed lateralised stems and 3.82 ± 0.6 for the standard stems), with no significant difference across groups. Overall survival after 3.5 years of follow-up was 94.6% (95% confidence interval, 88.4-100%) with lateralised stems and 100% with standard stems (P < 0.05).

DISCUSSION

The risk of aseptic loosening was significantly higher with the lateralised stem (5/280, 1.8%) than with the standard stem (n = 0). Our findings indicate a need for careful preparation to obtain primary fixation of lateralised stems.

LEVEL OF EVIDENCE

III, retrospective case-control study.

[Femoral offset and hip functioning in total hip prosthesis]

L'offset fémoral est l’élément pronostic le plus important dans l'arthroplastie de la hanche. Sa restauration est devenue de plus en plus une obligation. Toute modification de la valeur native de l'offset retenti sur la qualité du fonctionnement clinique de la hanche. Le but de notre travail était d’évaluer le fonctionnement clinique de la hanche en fonction de la valeur de l'offset fémoral après une arthroplastie. C'est une étude rétrospective effectuée entre 2010 et 2013, comportant 27 patients ayant bénéficiés d'une arthroplastie totale de la hanche. Les patients ayant eu un geste chirurgicale antérieur sur la même hanche ou sur la hanche controlatérale ont été exclus. Les mesures ont été effectuées sur des radiographies standards de la hanche en rotation interne d'environ 15°, avec un agrandissement à 100%. Les résultats cliniques étaient évalués au moyen du score de WOMAC qui était en moyenne de 15,2 points, et le score de Merle d'Aubigné-Postel avec une moyenne de 15 points. Deux autres tests ont été évalués dans notre étude qui sont le step et le hop test. Les meilleurs résultats fonctionnels ont été obtenus chez les patients ayant eu une latéralisation de la tige fémoral avec un offset augmenté.

Fifteen-year results of precoated femoral stem in primary hybrid total hip arthroplasty

Background

There has been controversy whether methylmethacrylate precoating of the cemented femoral stem is a solution for aseptic loosening or rather contributes to increased failure rates in cemented total hip arthroplasties.

Methods

On a retrospective basis, we analyzed 76 primary hybrid total hip arthroplasties from 63 patients with precoated, cemented femoral stems between October 1990 and December 1995. The mean age of the patients was 46.8 years (range, 22 to 77 years) with a minimum follow-up of 14 years (mean, 15.5 years; range, 14 to 19.5 years). Third generation cementing techniques were employed in all cases.

Results

Twenty-four out of 76 cases (31.6%) showed aseptic loosening of the femoral stems, of which 23 stems were revised at an average revision time of 8 years (range, 3 to 14.8 years). The main mode of loosening was cement-stem interface failure in 22 hips (91.7%). Twenty-one out of 24 failed hips (87.5%) demonstrated C2 cementing grades (p < 0.001). Kaplan-Meier survivorship analysis using radiographic aseptic loosening of the femoral stem as the endpoint for failure showed survival rates of 76.5% at 10 years (95% confidence interval [CI], 71.4 to 81.6) and 63.2% at 19 years (95% CI, 57.3 to 69.1).

Conclusions

An early failure of the precoated femoral stem in this study was mainly due to an insufficient cementing technique. Achievement of good cement mantle may improve the survival rates.

Ulnar component surface finish influenced the outcome of primary Coonrad-Morrey total elbow arthroplasty

BACKGROUND

Controversy remains regarding the mechanisms leading to ulnar loosening after elbow replacement. We therefore assessed the loosening rate of the ulnar component as a function of the surface finish of a commonly used implant design.

MATERIALS AND METHODS

This study included 3 groups who received implants with 3 different surface finishes: sintered beads (278 components), polymethylmethacrylate precoating (219 components), and plasma-sprayed beads (205 components).

RESULTS

The 3 groups who received the implants did not differ statistically in age, sex, or underlying diagnosis. The rates of mechanical failure for the sintered, precoated, and plasma-sprayed ulnar components were 6.8%, 12.8%, and 0%, respectively. The 7-year Kaplan-Meier survival rates free of mechanical failure were 93.1% for the sintered-beads group, 83.1% for the precoated group, and 100% for the plasma-sprayed group. Failed precoated ulnar components often failed early and exhibited typical features, including proximal debonding and severe focal or global osteolysis, sometimes leading to periprosthetic insufficiency fractures.

CONCLUSION

Precoating the ulnar component with polymethylmethacrylate can lead to an increased rate of loosening and severe osteolysis. A plasma-sprayed ulnar component is associated with a very low mechanical failure rate with surveillance of less than 10 years.

Minimally invasive surgical approaches and traditional total hip arthroplasty: a meta-analysis of radiological and complications outcomes

Background

Minimally invasive total hip arthroplasty (MITHA) remains considerably controversial. Limited visibility and prosthesis malposition increase the risk of post-surgical complications compared to those of the traditional method.

Methods

A meta-analysis was undertaken of all published databases up to May 2011. The studies were divided into four subgroups according to the surgical approach taken. The radiological outcomes and complications of minimally invasive surgery were compared to traditional total hip arthroplasty (TTHA) using risk ratio, mean difference, and standardized mean difference statistics.

Results

In five studies involving the posterolateral approach, no significant differences were found between the MITHA groups and the TTHA groups in the acetabular cup abduction angle (p = 0.41), acetabular anteversion (p = 0.96), and femoral prosthesis position (p = 0.83). However, the femoral offset was significantly increased (WMD = 3.00; 95% CI, 0.40–5.60; p = 0.02). Additionally, there were no significant differences among the complications in both the groups (dislocations, nerve injury, infection, deep vein thrombosis, proximal femoral fracture) and revision rate (p>0.05). In three studies involving the posterior approach, there were no significant differences in radiological outcomes or all other complications between MITHA or TTHA groups (p>0.05). Three studies involved anterolateral approach, while 2 studies used the lateral approach. However, the information from imaging and complications was not adequate for statistical analysis.

Conclusions

Posterior MITHA seems to be a safe surgical procedure, without the increased risk of post-operative complication rates and component malposition rates. The posterolateral approach THA may lead to increased femoral offset. The current data are not enough to reach a positive conclusion that lateral and anterolateral approaches will result in increased risks of adverse effects and complications at the prosthesis site.

Good diagnostic performance of early migration as a predictor of late aseptic loosening of acetabular cups: results from ten years of follow-up with Roentgen stereophotogrammetric analysis (RSA)

BACKGROUND

Excessive early migration of femoral stems following total hip arthroplasty and tibial components following total knee arthroplasty is associated with their long-term survival and allows reliable early evaluation of implant performance. However, a similar relationship involving acetabular components following hip arthroplasty has not been evaluated. This prospective, long-term study with clinical and Roentgen stereophotogrammetric analysis (RSA) follow-up establishes the existence of this relationship and its associated diagnostic performance.

METHODS

Thirty-nine consecutive patients (forty-one hips) who underwent total hip arthroplasty with a cemented Exeter stem and a cemented Exeter all-polyethylene cup had prospective clinical and RSA follow-up. Patients were evaluated postoperatively at six weeks, at three, six, and twelve months, and annually thereafter. Conventional anteroposterior and lateral radiographs were made at six weeks and at two, five, and ten years postoperatively as well as when indicated. The mean duration of follow-up (and standard deviation) was 9.4 ± 3.2 years. No patients were lost to follow-up; fifteen patients died during the follow-up period.

RESULTS

Eleven acetabular components were observed to be loose on conventional radiographs after a mean of seventy-six months (range, twelve to 140 months). During the first two postoperative years, the failed acetabular components showed markedly greater and more rapid cranial translation and sagittal rotation. Both cranial translation (hazard ratio = 19.9 [95% confidence interval, 4.94 to 80.0], p < 0.001) and sagittal rotation (hazard ratio = 11.1 [95% confidence interval, 2.83 to 43.9], p = 0.001) were strong risk factors for late aseptic loosening. Eight of the eleven failed components showed a distinctive pattern of excessive cranial translation combined with excessive sagittal rotation. The associated diagnostic performance of two-year cranial translation and/or sagittal rotation for predicting late aseptic loosening of the acetabular component was good (area under the receiver operating characteristic curve, 0.88 [95% confidence interval, 0.74 to 1.00; p < 0.001] and 0.84 [95% confidence interval, 0.68 to 1.00; p = 0.001], respectively).

CONCLUSIONS

Early migration, as measured by RSA at two years postoperatively, has good diagnostic capabilities for the detection of acetabular components at risk for future aseptic loosening, and this method appears to be an appropriate means of assessing the performance of new implants or implant-related changes.

Radiographic preoperative templating of extra-offset cemented THA implants: how reliable is it and how does it affect survival?

INTRODUCTION

Securing femoral offset should in theory improve hip stability and abductor muscles moment arms. As problems arise mainly in case of originally increased offset (>40 mm), a range of extra-offset stems is available; the exact impact in terms of fixation, however, is not known.

HYPOTHESIS

Extra-offset stems should more reliably reestablish original femoral offsets exceeding 40 mm than standard femoral components, limiting instability risk without possible adverse effect on fixation.

OBJECTIVE

To compare the ability of five commonly available femoral stem designs to restitute offset exceeding 40 mm, and to assess function and cement fixation at a minimum 6 years' follow-up in a stem conceived to reproduce such offset.

PATIENTS AND METHODS

A continuous series of 74 total hip replacements (THR) in hips with increased (>40 mm) femoral offset was studied. All underwent preoperative X-ray templating on Imagika™ software to assess offset reproduction by five models of stem: four standard, and one Lubinus SP2™ extra-offset stem. A retrospective clinical and X-ray study was conducted with a minimum 6 years' follow-up on the Lubinus SP2™ 117° stems used to try to reproduce offset in the 74 THRs.

RESULTS

Apart from the increased (>40 mm) offset, the cervicodiaphyseal angle was consistently <135°, <130° in 60 femurs (81%) and <125° in 45 (60%). Planning showed the four standard stems to induce (>5mm femoral offset reduction in 50-83% of cases, versus only 25% with the Lubinus SP2™ 117°). All 74 hips received Lubinus SP2™ 117° stems: at a mean 78 months FU (range, 70-94 mo), their mean Postel-Merle d'Aubigné score was 17±1.8 (range, 13-18). Five of the 74 THRs underwent surgical revision: three cases of loosening, in which the stem was replaced, and two of instability, without change of stem. Loosening was not related to offset reproduction quality; two of the three cases were due to initial cementing defect, and the third occurred in a femur with previous history of two osteotomies. There were four cases of dislocation (5.4%: two primary, which were not operated on, and two recurrent, managed by acetabular revision), despite good reproduction of the preoperative offset in three of the four cases. Mean 7-year implant survivorship was 95.1% (±4.8).

DISCUSSION AND CONCLUSION

The anatomic form of the Lubinus™ SP2 117° should in theory provide a uniform cement mantle. Survivorship, however, is less good than for regular offset versions (126° or 135°). On the other hand, it does reproduce anatomy in case of >40mm offset, providing extra offset of more than 51mm. The slightly shorter survivorship requires more long-term surveillance.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Fifteen-year to twenty-year results of cementless Harris-Galante porous femoral and Harris-Galante porous I and II acetabular components

This study examined long-term survivorship of primary total hip arthroplasty (THA) using cementless Harris-Galante porous femoral and Harris-Galante porous I or II acetabular components. Of 113 hips (101 patients) studied, 60 hips (53 patients) were available for follow-up at a mean of 17.2 years after surgery. A total of 10 hips had documented revision, and 2 hips had failed radiographically. The average Harris hip score was 82. Radiographically, 12 hips demonstrated eccentric wear, 8 had osteolysis, and 1 had a broken tine. The overall survival rate was 87.7%; the mean volumetric wear rate was 74.96 mm(3); and the mean polyethylene linear penetration rate was 0.153 mm/y, similar to that of well-cemented THA in other series. This long-term outcome for an early-generation cementless THA is promising and provides a standard by which to judge the newer generation of cementless implants.

Total hip arthroplasty with cement and use of a collared matte-finish femoral component: nineteen to twenty-year follow-up

BACKGROUND

In the mid- to late 1970s, on the basis of laboratory and finite element data, many surgeons in the United States began using collared matte-finish femoral components and metal-backed acetabular components in their total hip arthroplasties. The purpose of this study was to evaluate the long-term results of the use of one such construct in arthroplasties performed by a single surgeon in a consecutive nonselected patient cohort.

METHODS

Between January 1984 and December 1985, 273 patients underwent a total of 304 consecutive nonselected total hip arthroplasties with cement and use of the Iowa femoral component (which is collared, has a proximal cobra shape, and has a matte finish) and a metal-backed TiBac acetabular component performed by a single surgeon. At nineteen to twenty years postoperatively, only two patients (two hips) were lost to follow-up. For clinical evaluation, we attempted to interview all living patients and the families of the patients who had died to verify the status of the hip prosthesis or any revisions. Radiographic evaluation consisted of analysis for loosening and osteolysis as well as wear of the acetabular component.

RESULTS

At the time of the nineteen to twenty-year follow-up, the rate of revision of the arthroplasty for any reason was 10.5% (thirty-two hips) for all patients and 25% (twenty-three hips) for living patients. The rate of revision due to aseptic femoral loosening was 2.6% (eight hips). There was radiographic evidence of loosening of the femoral component in fifteen hips (4.9%), including those that were revised, and femoral osteolysis was seen distal to the trochanters in twenty-two hips (7.2%). The rate of revision due to aseptic loosening of the acetabular component was 7.9% (twenty-four hips), and there was radiographic evidence of acetabular loosening in forty-two hips (13.8%), including those that were revised.

CONCLUSIONS

This study demonstrates the durability of a cemented matte-finish collared femoral component at twenty years postoperatively, with a rate of revision due to aseptic loosening of 2.6%. The metal-backed acetabular component also performed well in many patients, with a 7.9% rate of revision due to aseptic loosening. However, in the living patients, the rate of loosening of the acetabular component, including cases revised because of aseptic loosening, was 30.4%.

Mid-term results of Exeter vs Endurance cemented stems

The mid-term results are reported of 2 uniquely different cemented stems implanted and followed prospectively by a single surgeon. The highly polished, collarless, tapered Exeter stem and the Endurance stem, a collared, roughened, satin finished stem, were inserted through a lateral approach using third-generation cement techniques. A total of 118 hips with the Exeter stem with an average follow-up of 7.25 years and 34 hips with the Endurance stem with an average follow-up of 4.57 years are included in the study. The Exeter patients had no revisions for aseptic loosening (0%) of the femoral stem. In contrast, the Endurance patients had 5 revisions and 2 impending revisions for aseptic loosening (20.5%) of the femoral stem with an average time to failure of 3.72 years. The excellent mid-term results of the Exeter stem support its ongoing use. By contrast, because of the poor early results of this modern cemented Endurance stem design, it is no longer used at our institution.

The design features of cemented femoral hip implants

We undertook a review of the literature relating to the two basic stem designs in use in cemented hip replacement, namely loaded tapers or force-closed femoral stems, and the composite beam or shape-closed designs. The associated stem fixation theory as understood from in vitro studies and finite element modelling were examined with reference to the survivorship results for each of the concepts of fixation.

It is clear that both design principles are capable of producing successful long-term results, providing that their specific requirements of stem metallurgy, shape and surface finish, preparation of the bone and handling of the cement are observed.

Fatigue debonding of the roughened stem-cement interface: effects of surface roughness and stem heating conditions

The aim of this study was to determine the effects of cyclic loading on the debond process of a roughened stem-cement interface used in total hip arthroplasty. The specific goals were to assess the effects of two surgeon-controlled variables (stem heating and degree of stem surface roughness) and to determine if an independent finite element-based fracture mechanics model could be used to predict the debond response. A clamped cantilever beam geometry was used to determine the fatigue debond response of the stem-cement interface and was created using an experimental mold that simulated in vivo cementing conditions. A second experiment was performed using a torsion-loading model representative of the stem-cement-bone composite. For both experiments, two stem heating (room temperature and 50 degrees C) and surface roughness conditions (grit blasted: Ra = 2.3 and 5.1 microm) were used. Finally, a finite element model of the torsion experiment with provision for crack growth was developed and compared with the experimental results. Results from both experiments revealed that neither stem preheating nor use of a stem with a greater surface roughness had a marked effect on the fatigue debond response. There was substantial variability in the debond response for all cases; this may be due to microscopic gaps at the interface for all interface conditions. The debond rate from the finite element simulation (10(-7.31) m/cycle) had a magnitude similar to the experimental torsion model (10(-(6.77 +/- 1.25)) m/cycle). This suggests that within the context of the experimental conditions studied here that the debond response could be assessed using a linear elastic fracture mechanics-type approach.

Primary hip arthroplasty costs are greater in low-volume than in high-volume Canadian hospitals

Despite the widespread success of total hip arthroplasties for treatment of arthritis of the hip, the procedure continues to be targeted for cost control. Our objective was to compare the total in-hospital cost of primary total hip arthroplasties in high-volume and low-volume hospitals. Data concerning the patient-level in-hospital costs of 940 consecutive primary total hip arthroplasties were extracted from the cost accounting system of three Canadian hospitals. Mean in-hospital costs for patients having total hip arthroplasties in a high-volume institution (> or = 300 total hip arthroplasties/year) compared with two low-volume Canadian institutions (< 300 total hip arthroplasties/year) were: overhead costs 1380 US dollars +/- 35 US dollars versus 2432 US dollars +/- 49 US dollars; direct costs 3023 US dollars +/- 93 US dollars versus 4952 US dollars +/- 91 US dollars and total costs 4403 US dollars +/- 117 US dollars versus 7385 US dollars +/- 1 US dollar 38, respectively (all comparisons in US dollars). Lower overhead and direct and total costs were found for primary total hip arthroplasties done in a high-volume Canadian hospital compared with the low-volume centers. Differences in direct costs, made up in large part by the implant cost, accounted for most of the disparity. As total hip arthroplasties continue to be scrutinized for cost containment, doing the procedure in a high-volume center seems to be an effective method of controlling costs.

Precoated femoral component with proximal and distal centralizers: results at 5 to 12 years

One study, confounded by the use of crystalline polyethylene and ceramic heads, reported a high rate of early failure of a precoated femoral component with proximal and distal centralizers. The present study reports the prospective clinical and radiographic results, and 10-year survival data of 166 consecutive hybrid total hip arthroplasties using this femoral component. An A or B cement grade was obtained in 93% of hips. At a mean follow-up time of 7 years (range, 5-12 years), there were only 4 (2.4%) femoral failures. Ten-year survival of this component was 95% (confidence interval, 94%-99%). The rate of radiographic failure and revision of this component implanted with conventional polyethylene and cobalt chrome heads is similar to that reported with other "modern" femoral components.

Pre-coated femoral components in hybrid total hip arthroplasty

We present the medium-term results of hybrid total hip arthroplasties using pre-coated stems with a second-generation cementing technique. The 128 hips in 111 patients (18 men and 93 women) were followed up at a mean of 11 years after surgery. The mean age at the time of surgery was 61 years. Both components of one hip were removed at ten months after surgery for infection. None of the other 127 femoral components showed possible, probable, or definite loosening at the most recent follow-up. Five acetabular components were revised for aseptic loosening, recurrent dislocation, or displacement of the polyethylene liner from the metal shell. The mean Harris hip score at follow-up was 84 points. A pre-coated femoral component with a second-generation cementing technique provides good clinical function and survival in the medium term.

Influence of surface finish in total hip arthroplasty

The influence of femoral component surface finish was investigated by comparing 2 finishes, precoat and satin finish, for 1 cemented total hip arthroplasty (THA) system using 1 acetabular cup design. All surgeries were performed by a single surgeon in 2 consecutive series. Minimum 2-year follow-up outcomes (36 precoat, 25 satin) were compared using Harris Hip Scores, radiographs, and survivorships. The precoat population experienced significantly more radiographic and debonding failures than the satin-finish population, and significantly more pain (P <.05). Comparing failures and nonfailures within the precoat population disclosed neither significant preoperative nor significant cement-grade differences. Because of failure performance of the precoat surface finish, this surgeon no longer implants these components.

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.

THA loading arising from increased femoral anteversion and offset may lead to critical cement stresses

Aseptic loosening of artificial hip joints is believed to be influenced by the design and orientation of the implant. It is hypothesised that variations in implant anteversion and offset lead to changes in the loading of the proximal femur, causing critical conditions to both the bone and cement. The goal of this study was therefore to analyse the role of these parameters on loading, bone strains and cement stresses in total hip arthroplasty (THA). A validated musculo-skeletal model was used for the analysis of muscle and joint contact forces during walking and stair climbing. Two different anteversion angles (4 degrees vs. 24 degrees ) and prostheses offsets (standard vs. long) were analysed. The loads for each case were applied to a cemented THA finite element model. Generally, stair climbing caused higher bone strains and cement stresses (max. +25%) than walking. Variations in anteversion and offset caused changes in the loading environment, bone strain distribution and cement stresses. Compared to the standard THA configuration, cement stresses were raised by increasing anteversion (max. +52%), offset (max. +5%) and their combination (max. +67%). Femoral anteversion, offset and their combination may therefore lead to an increased risk of implant loosening. Analyses of implant survival should consider this as a limiting factor in THA longevity. In clinical practice, implant orientation, especially in regard to pre- and post-operative anteversion, should be considered to be more critical.

Primary hybrid total hip arthroplasty with a roughened femoral stem: integrity of the stem-cement interface

One hundred and two consecutive cemented femoral stems were evaluated in 92 patients at an average 9-year follow-up and a minimum 5-year follow-up (range, 5-14 years). The stem used was cobalt chromium with a collar, normalization steps, and a roughened surface (Ra 40); the stem was inserted using contemporary cementing techniques. This series demonstrated a femoral component aseptic loosening rate of 2.0% and a femoral component survivorship of 97.2 +/- 2.0% at 10 years. One of 2 failed stems was revised at 95 months for failure at the cement-bone interface. The second failed stem showed failure at the cement-bone interface with incomplete debonding radiographically at 65 months. The remaining femoral components did not demonstrate any evidence of debonding at the stem-cement interface. These results compare favorably with other series of cemented femoral stems, as well as with those with a polished surface.

Precoated femoral component in primary hybrid total hip arthroplasty: results at a mean 10-year follow-up

This is a mid-term report at 10 years' mean follow-up of a study of a precoated femoral component used in primary hybrid total hip arthroplasty (THA). Of an original cohort of 98 hips undergoing THA performed by one surgeon, 75 hips in 65 patients (mean age, 67 years) were prospectively followed up for 7 to 12 years (mean, 10 years). All hips had the same porous coated acetabular component and a precoated femoral component (with an oval cross-section) implanted using Simplex bone cement (Howmedica, Rutherford, NJ). There was no femoral component loosening or revision. Two acetabular components in patients with rheumatoid arthritis and protrusio acetabulae had radiographic loosening; however, only 1 was symptomatic and was revised. Acetabular osteolysis was seen in 4 hips (5.3%), and minor femoral osteolysis was seen in 3 hips (4%). Used in this manner in this patient population, precoating is not detrimental to successful fixation at 10 years' mean follow-up of primary hybrid THA.

Early failure of precoated femoral components in primary total hip arthroplasty

BACKGROUND

In an effort to decrease the rate of aseptic loosening, certain cemented femoral components were designed to have a roughened or textured surface with a methylmethacrylate precoating. Reports differ as to whether this step has increased or decreased the rate of failure. This study was designed to evaluate this issue.

METHODS

Five hundred and fourteen hips treated with a cemented Harris Precoat stem (Zimmer, Warsaw, Indiana) were evaluated clinically and radiographically and compared with 254 hips treated with an uncoated Harris Design-2 stem (Howmedica, East Rutherford, New Jersey). Prostheses that had been removed at revision were examined. The cementing and surgical techniques were identical and the population demographics were similar for these two groups.

RESULTS

The mean durations of follow-up were 8.4 and 13.5 years for the Precoat and uncoated Design-2 stems, respectively. At those times, at least forty-nine (9.5%) of the 514 Precoat components and at least ten (3.9%) of the 254 uncoated Design-2 stems had failed (p = 0.006). Five Precoat stems fractured, and no uncoated Design-2 stems fractured. Component failure was associated with use in young, active, heavy men with a diagnosis of avascular necrosis and generally with the use of smaller components. The cementing technique was satisfactory in the majority of the patients, and there were no qualitative differences in cementing technique between the hips that failed and those that did not. The mechanisms of failure of the Precoat prostheses included bone-cement loosening, focal osteolysis, stem fracture, and prosthesis-cement debonding. Fractures of smaller components occurred as a result of fatigue failure and were associated with good distal fixation but proximal stem loosening.

CONCLUSIONS

The rate of failure of roughened, precoated, cemented femoral components was considerably higher and occurred earlier than that of femoral components that were neither textured nor precoated with methylmethacrylate. Younger patients with avascular necrosis had a higher risk of failure; however, this factor alone did not completely explain the differences in outcome between these two components. The causes of aseptic loosening are multifactorial and may be related to component design and size as well as to precoating and surface finish.

Comparison of clinical outcomes in total hip arthroplasty using rough and polished cemented stems with essentially the same geometry

BACKGROUND

Aseptic loosening of the cemented stem is the most common cause of revision of total hip arthroplasties. The loosening is often associated with substantial lysis of the surrounding bone. The surface finish of femoral components is suspected as a contributing factor to this bone lysis. The purpose of this study was to compare the results associated with a rough surface and those associated with a polished surface in a consecutive series of cemented stems with essentially the same geometry.

METHODS

The study included 244 consecutive total hip arthroplasties with a cemented femoral component performed by one surgeon. There was no difference in patient selection criteria or surgical techniques between the group treated with a polished stem and that treated with a grit-blasted stem. All arthroplasties were hybrid, with an uncemented acetabular component. Generally, patients were over the age of sixty years (mean age, 70.6 years). The stems inserted in the initial 122 hips had a grit-blasted surface with a roughness of 2.1 microm. The stem surface in the second 122 hips was polished (roughness, 0.1 microm). The results of clinical and radiographic assessments performed immediately after surgery were compared with those performed at the most recent visit. The average duration of clinical follow-up for the patients treated with the grit-blasted and polished stems was 5.98 years and 5.32 years, respectively.

RESULTS

Four hips treated with the grit-blasted stem had aseptic loosening with substantial surrounding lysis and required revision. An additional two hips in this group had radiographic evidence of substantial lysis and were judged to have an impending need for revision. In contrast, no hip treated with the polished stem required revision, and only one had minimal lysis. This difference regarding failures and impending failures was significant (p = 0.05). The clinical results were comparable, with an Iowa hip rating of 98 points at the time of follow-up in both groups.

CONCLUSIONS

There was a significant difference between grit-blasted and polished stems with respect to the prevalence of revisions and impending revisions, all of which were identified in a relatively short follow-up period. The results in this series favor the use of a polished stem when cement is employed for fixation of the femoral component.