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

[Current design and cement mantle thickness in hip arthroplasty : Theory and analysis of register data]

BACKGROUND

In this article, an overview and comparison of the most commonly used cemented hip stems, grouped into different stem types and cement mantle thickness, is given to see which combination performs well.

METHODOLOGY

Revision rates of cemented stem types were categorized from the Endoprosthesis Register-Germany, and 3‑ and 5‑year revision rates were reported and analyzed. For the research, the focus was on the Exeter, C‑Stem, MS-30, Excia, Bicontact, Charnley, Müller straight stem, Twinsys, Corail, Avenir, Quadra, and the Lubinus SP II stems. An important aspect was which stem is preferred to be implanted and which cementing technique is used with regard to the planned cement mantle thickness. In order to identify a trend in cemented hip arthroplasty, data from the Danish, Swedish, Norwegian, Swiss, New Zealand, English and Australian arthroplasty registers were also compared.

RESULTS AND CONCLUSION

Most countries use cemented prostheses according to the taper slip principle (Exeter, MS30, C‑Stem etc) or the composite beam (Charnley, Excia, Bicontact), which are implanted with a cement mantle thickness of 2-4 mm. However, a trend has emerged in Germany and Switzerland towards the line-to-line technique, with a planned cement mantle thickness of 1 mm (Twinsys, Corail, Avenir, Quadra), following the principle of the Müller straight stem prosthesis and the Kerboul-Charnley prosthesis, even though these are postulated to be "French paradoxes" in themselves. In the EPRD 5‑year results, the newer line-to-line prostheses seem to perform slightly worse. The best results are achieved by the "MS 30" in Germany and the "Exeter" in England. These are polished straight stems with centralizer and subsidence space at the apex with a 2-4 mm cement mantle in good cementing technique.

Collarless Polished Tapered Stems of Identical Shape Provide Differing Outcomes for Stainless Steel and Cobalt Chrome: A Biomechanical Study

Cemented polished tapered femoral stems (PTS) made of cobalt-chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter^® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone-cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone-cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

Femoral Stem Cementation in Hip Arthroplasty: The Know-How of a "Lost" Art

PURPOSE OF REVIEW

To describe the (1) indications, (2) preoperative precautions, and (3) stepwise technical details of modern femoral stem cemented fixation.

RECENT FINDINGS

Femoral stem cementation provides excellent implant longevity with a low periprosthetic fracture rate among patients with compromised bone quality or aberrant anatomy. Unfamiliarity with the details of modern cementation techniques among trainees who may lack frequent exposure to cementing femoral stems may preclude them from offering this viable option to suitable patients in later stages of their careers. As such, maximizing benefit from cemented femoral stem fixation among suitable candidates is contingent upon the meticulous use of modern cementation techniques. In addition to proper patient selection, modern cementation techniques emphasize the use of (1) pulsatile lavage of the femoral canal, (2) utilization of epinephrine-soaked swabs, (3) vacuum cement mixing, (4) retrograde cement introduction, (5) cement pressurization, and (6) the use of stem centralizers. Furthermore, identifying and optimizing the preoperative status of at-risk patients with pre-existing cardiopulmonary compromise, in addition to intraoperative vigilance, are essential for mitigating the risk of developing bone cement implantation syndrome. Further research is required to assess the utility of cemented femoral stem fixation among younger patients.

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant-cement and cement-bone interfaces.Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants' biomechanics.We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis. Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034.

Biomechanical Performance of the Cemented Hip Stem with Different Surface Finish

The integrity of the cemented fixation interface is responsible for the long-term longevity of artificial hip prostheses. Metallic stems with roughened surfaces are considered to provide stronger adhesion with cement. However, clinical studies have reported that roughened stems show a lower survival rate than polished stems. These studies clearly reveal that the causes of artificial stem loosening are very complicated and multifaceted. Therefore, this study was conducted to investigate the mechanical effect of stem surface finish in cemented hip replacement. To accomplish this, a series of cement–metal specimens were tested configurations to assess the mechanical characteristics of the cement–metal interface specimens. A finite elemental model of cemented femoral prostheses was then created, in which the cement–stem interface was assumed to be in different bonding states according to the experimentally measured interface properties. The failure probabilities of the cement mantle and cemented interface under physiological loadings were evaluated. Experimental results indicate that the polished metal produced higher interfacial tensile and lower shearing strengths than the roughened metal. The polished stems were predicted to induce a lower failure probability of cement mantle and higher integrity of the cement–stem interface when compared to the roughened stem. Overall, current results provide significant evidence to support the clinical outcomes of cemented hip prostheses with different stem surface finishes.

Osteolysis as it Pertains to Total Hip Arthroplasty

Osteolysis is a long-term complication of total hip arthroplasty (THA). As the projected number of THAs performed annually increases, osteolysis will likely continue to occur. However, because of advancements in prosthesis design, metallurgy, and enhanced bearing surfaces, fewer revision THAs will be linked to osteolysis and aseptic loosening. Despite these improvements, no preventative therapies are currently available for the management of osteolysis other than removing and replacing the source of bearing wear.

Standard and line-to-line cementation of a polished short hip stem: Long-term in vitro implant stability

The current trend is toward shorter hip stems. While there is a general agreement on the need for a cement mantle thicker than 2 mm, some surgeons prefer line-to-line cementation, where the mantle has only the thickness provided by the cement-bone interdigitation. The aim of this study was to assess if a relatively short, polished hip stem designed for a standard cementation can also be cemented line-to-line without increasing the risk of long-term loosening. Composite femurs with specific open-cell foam to allow cement-bone interdigitation were used. A validated in-vitro biomechanical cyclic test replicating long-term physiological loading was applied to femurs where the same stem was implanted with the Standard-mantle (optimal stem size) and Line-to-line (same rasp, one-size larger stem). Implant-bone motions were measured during the test. Inducible micromotions never exceeded 10 μm for both implant types (differences statistically not-significant). Permanent migrations ranged 50-300 μm for both implant types (differences statistically not-significant). While in the standard-mantle specimens there was a pronounced trend toward stabilization, line-to-line had less tendency to stabilize. The cement cracks were observed after the test by means of dye penetrants: The line-to-line specimens included the same cracks of the standard-mantle (but in the line-to-line specimens they were longer), and some additional cracks. The micromotions and cement damage were consistent with those observed in-vitro and clinically for stable stems, confirming that none of the specimens became dramatically loose. However, it seems that for this relatively short polished stem, standard-mantle cementation is preferable, as it results in less micromotion and less cement cracking. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2736-2744, 2018.

The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental?

Objectives

Favourable results for collarless polished tapered stems have been reported, and cement creep due to taper slip may be a contributing factor. However, the ideal cement thickness around polished stems remains unknown. We investigated the influence of cement thickness on stem subsidence and cement creep.

Methods

We cemented six collarless polished tapered (CPT) stems (two stems each of small, medium and large sizes) into composite femurs that had been reamed with a large CPT rasp to achieve various thicknesses of the cement mantle. Two or three tantalum balls were implanted in the proximal cement in each femur. A cyclic loading test was then performed for each stem. The migration of the balls was measured three-dimensionally, using a micro-computed tomography (CT) scanner, before and after loading. A digital displacement gauge was positioned at the stem shoulder, and stem subsidence was measured continuously by the gauge. Final stem subsidence was measured at the balls at the end of each stem.

Results

A strong positive correlation was observed between mean cement thickness and stem subsidence in the CT slices on the balls. In the small stems, the balls moved downward to almost the same extent as the stem. There was a significant negative correlation between cement thickness and the horizontal:downward ratio of ball movement.

Conclusion

Collarless polished tapered stems with thicker cement mantles resulted in greater subsidence of both stem and cement. This suggests that excessive thickness of the cement mantle may interfere with effective radial cement creep.

Cite this article: E. Takahashi, A. Kaneuji, R. Tsuda, Y. Numata, T. Ichiseki, K. Fukui, N. Kawahara. The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental? Bone Joint Res 2017;6:–357. DOI: 10.1302/2046-3758.65.BJR-2017-0028.R1.

The effect of phosphoric and phosphonic acid primers on bone cement bond strength to total hip stem alloys

Aseptic loosening at alloy-cement interfaces constitutes a main failure mechanism of cemented total hip replacements (THR). As a potential solution we investigated the effect of metal primers containing phosphoric and phosphonic acid on shear bond strength (SBS) of bone cement to THR alloys (CoCrMo, TiAlNb) and pure tin (Sn) substrates (20×8×3 mm). Metal surfaces were modified by polishing or Al₂O₃ blasting and primer application. Substrates without primer treatment served as references. Cylindrical cement pins (Ø 5mm) were polymerised onto substrate surfaces and aging (1, 5, 14 and 150 days) was simulated in aqueous NaCl solution (0.9%) before SBS determination and failure mode evaluation. Regardless of surface roughness and aging time, SBS for THR alloys and Sn was always significantly higher with primer treatment. Compared to untreated reference specimens (≤0.2MPa) SBS values increased even up to 350 fold (TiAlNb, 14 days) or 400 fold (CoCrMo, 5 days). In general, the phosphoric acid containing primer revealed significant higher SBS values on THR alloys compared to the phosphonic acid containing one. Al₂O₃ blasted specimens showed generally higher SBS values than polished ones with the exception of Sn which showed high SBS values in general. With primer treatment on polished Sn a significant reduction of SBS could not be detected even up to 150 days, whereas THR alloys showed only an SBS improvement in the short term (≤14 days). A NaCl-pitting corrosion probably led to an increasing and durable SBS on polished Sn surfaces over time. Compared to modern THR in clinical practice that shows survival rates of 10, 15, 20 or more years, the receivable bond strength enhancements described in this study appeared to be very short. The improved SBS on THR alloys lasted only a few days before it was lost again. In contrast, the phosphoric acid primer treatment of polished Sn appeared to be very promising and may play a key role in further investigations dealing with the prevention of the stem-cement debonding in THR.

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.

Long-term Outcome of Polished Stems in Total Hip Arthroplasty

PURPOSE

The purpose of this study was to evaluate the clinical outcomes and radiologic findings of primary total hip arthroplasty (THA) using cemented polished femoral stems.

MATERIALS AND METHODS

We retrospectively reviewed 91 hips (91 patients) that had undergone primary THA with cemented polished femoral stems who were followed for at least 10 years. The mean age at surgery was 57 years (47-75 years). Mean follow up period was 12.8 years (10.1-14.0 years). Harris Hip Score (HHS) was used for clinical evaluation. Radiologic evaluation was focused on cementing technique including subsidence within the cement mantle, radiolucent lines at the cement-bone or cement-stem interface, cortical hypertrophy, and calcar resorption.

RESULTS

The average HHS was 55.2 points before the surgery that improved to an average of 93.2 points at the final follow-up. According to Barrack classification, there were 50, 32, and 9 cases in A, B, and C grades, respectively. Subsidence of femoral stem was less than 2 mm except in one patient. There were no progressing radiolucent line or loosening of the femoral stem.

CONCLUSION

In this study, THA using cemented polished femoral stems was found to have favorable outcomes in long term follow-up.

High failure rates of the Spectron EF stem at a minimum of 10 year's follow-up

We prospectively followed 112 hips, undergoing THA with a Spectron EF stem. At mean follow-up of 11.2years, 21 patients had died. We obtained radiological follow-up in 99% and clinical follow-up in 100% of the surviving 91 hips. Fifty-four percent demonstrated osteolysis in at least one Gruen zone. Twenty-two hips required revision for all causes, with a further five stems radiologically loose. With endpoint being stem revision for aseptic loosening or radiological failure, survivorship at 11years was 0.783. We believe the addition of a rougher surface finish has contributed to the high levels of osteolysis and stem failure seen with the Spectron EF.

The effect of a collar and surface finish on cemented femoral stems: a prospective randomised trial of four stem designs

PURPOSE

The optimal design for a cemented femoral stem remains a matter of debate. Over time, the shape, surface finish and collar have all been modified in various ways. A clear consensus has not yet emerged regarding the relative merits of even the most basic design features of the stem. We undertook a prospective randomised trial comparing surface finish and the effect of a collar on cemented femoral component subsidence, survivorship and clinical function.

METHODS

One hundred and sixty three primary total hip replacement patients were recruited prospectively and randomised to one of four groups to receive a cemented femoral stem with either a matt or polished finish, and with or without a collar.

RESULTS

At two years, although there was a trend for increased subsidence in the matt collarless group, this was not statistically significant (p = 0.18). At a mean of 10.1 years follow-up, WOMAC scores for the surviving implants were good, (Range of means 89-93) without significant differences. Using revision or radiographic loosening as the endpoint, survivorship of the entire cohort was 93 % at 11 yrs, (CI 87-97 %). There were no significant differences in survivorship between the two groups with polished stems or the two groups with matt stems. A comparison of the two collarless stems demonstrated a statistically significant difference in survivorship between polished (100 %) and matt (88 %) finishes (p = 0.02).

CONCLUSIONS

In the presence of a collar, surface finish did not significantly affect survivorship or function. Between the two collarless groups a polished surface conferred an improved survivorship.

Improved survival of uncemented versus cemented femoral stems in patients aged < 70 years in a community total joint registry

BACKGROUND

Aseptic loosening of the femoral stem remains a significant reason for revision in total hip arthroplasty (THA). Although stem fixation methods have changed over time, there is relatively little evidence supporting cemented or uncemented stems as more durable constructs.

QUESTIONS/PURPOSES

We examined whether there was a difference in survival to revision between cemented and uncemented THA stems (1) for any reason; (2) for aseptic loosening or loosening related to wear/osteolysis; (3) based on patient age groupings (as a proxy for patient activity level); and (4) based on procedural timeframe groupings between cemented and uncemented stems.

METHODS

A total of 6498 primary cemented and uncemented THAs were registered in our community total joint replacement registry between 1991 and 2011. Analysis was performed to compare age, sex, procedural timeframe, and diagnosis for both groups. Our primary outcome was revision of the stem component for aseptic loosening or loosening secondary to wear/osteolysis. Analyses were done using Wilcoxon rank sum tests, Pearson's chi-square tests, Kaplan Meier methods, and Cox regression.

RESULTS

After adjusting for age, sex, primary diagnosis, and procedural timeframe as confounders, cemented femoral stem components were 1.63 times as likely as uncemented stems to be revised for any reason (p = 0.02) and 3.76 times as likely as uncemented stems to be revised for aseptic loosening or loosening related to wear/osteolysis (p < 0.001). When grouped by age, specifically in regard to revisions for aseptic loosening or loosening related to wear/osteolysis, uncemented stems had lower cumulative revision rates in patients aged < 70 years (p < 0.001) compared with cemented stems. There was a trend away from cemented fixation in our registry, which shifted from over 80% cemented stem use in 1996 to 3% in 2011.

CONCLUSIONS

We found that uncemented stems were associated with fewer revisions for aseptic loosening in patients < 70 years old, but when all reasons for revision were considered, neither group demonstrated superior survival. With a mean followup of 6.5 years, longer followup is needed to verify these results over time.

Randomized comparison between the cemented Scientific Hip Prosthesis and Omnifit: 2-year DEXA and minimum 10-year clinical follow-up

Radiostereometry (RSA) of the cemented Scientific Hip Prosthesis (SHP) reported excessive migration and predicted high failure rates. In a prospective randomized clinical trial we compared minimum 10 years results of the SHP (n=38) with the Omnifit-stem (n=37). Two-year bone remodelling, compared with dual energy x-ray absorptiometry and assessed in regions of interest A-D based on the 7 Gruen zones, showed better periprosthetic bone preservation around the SHP in all but one regions (P<.05). At 10 years Harris Hip Score was better for the SHP (P=.0001) but Oxford Hip Score was the same (P=.79). There were no revisions in either group, but radiographic loosening was definite in 1 SHP and 1 Omnifit. Based on earlier RSA studies, the rough surface finish of the SHP was expected to cause cement abrasion, osteolysis and inferior survival. However our clinical and remodelling results could not confirm these expectations, suggesting that the link of early migration and mid-term clinical results is not sufficiently clear for the SHP.

Thermally induced strains and total shrinkage of the polymethyl-methacrylate cement in simplified models of total hip arthroplasty

An evaluation of transient and stabilized strains in the cement mantle during polymerization was carried out in simplified cemented total hip arthroplasty (THA) model. A mathematical approach combined with a simple finite element simulation was used to compare measured and calculated stabilized strain values and to provide the Von Mises stresses at the stem/cement interface due to shrinkage related to temperature decrease after exothermal reaction. A second similar model was carried out to measure stem/cement/mold interfacial shear strength and dimensional changes of the cement mantle to obtain total shrinkage due to temperature decrease plus cement polymerization. The results indicated that positive strain peaks found during the exothermic stage of polymerization have the potential to produce pre-loading cracking. After the initial expansion, it was observed a progressive strain decrease pattern down to stabilized values that takes place near 2h after the cementation. Even though there is a great deal of dispersion in the measured stabilized strain values, in average those values match quite well with the numerical simulations, indicating 4,7 MPa von Mises interfacial stress due to thermal shrinkage. The total cement shrinkage leads to a negative radial stress of 11 MPa and 14 MPa von Mises interfacial stress. Finally, total shrinkage has the potential to enhance gaps in the cement/mold interface.

The twenty-year survivorship of two CDH stems with different design features

Previous studies have shown that anatomical abnormalities of the femur in dislocated hips require the application of special CDH prosthesis for the reconstruction of the proximal femur in total hip arthroplasty (THA). We have retrospectively examined the clinical records and radiographs of 50 patients (67 hips) with low and high dislocations treated with THA in our institution, between January 1987 and December 1994. For the reconstruction of the femur, the stainless steel Charnley CDH stem, with polished surface, monoblock and collarless, was used in 32 hips; the Harris CDH stem, made of CoCr, precoated at the proximal part, modular and with collar was used in 35 hips. At the time of the latest follow-up, 11 Charnley and 6 Harris CDH stems had been revised for aseptic loosening at an average of 14 years (range 6-20) and 13 years (range 2-19), respectively. The survival rate at 20 years, with failure for aseptic loosening as the end point, was 63% for the Charnley and 78% for the Harris CDH stems. These results provide a basis for evaluation of newer techniques and designs.

LEVEL OF EVIDENCE

Therapeutic study, Level IV.

Eleven-year follow-up of second-generation metal-on-metal total hip arthroplasty

PURPOSE

To investigate the cause of failure in matte-surface cemented stems in second-generation metal-on- metal total hip arthroplasty (THA).

METHODS

Records of 26 men and 11 women (39 hips) aged 29 to 72 years who underwent primary cementless THAs by a single surgeon using second-generation metal-on-metal prostheses and were followed up for a mean of 122 (range, 120-141) months were reviewed. Two types of femoral stems were used: a cementless Ti-alloy stem (n=21) and a matte-surface, iron-based alloy, cemented stem (n=18). Clinical outcomes were measured using the Harris hip score. Radiographs were assessed for stem loosening and osteolysis. Patient activity levels were graded. Surfaces of the retrieved femoral stems and periprosthetic tissue samples were examined. Metallic and cement particles were studied. Hypersensitivity to metal was tested.

RESULTS

None of the cementless stems were revised; no osteolysis or stem loosening occurred. In contrast, 7 of 18 matte-surface cemented stems were revised owing to stem loosening or osteolysis. Periprosthetic tissues revealed abundant cement-related particles; 90% were zirconium oxides but a few were iron particles. Histological examination of periprosthetic tissues showed perivascular infiltration of lymphocytes and macrophages containing tiny foreign materials. Metal hypersensitivity was not associated with aseptic loosening.

CONCLUSION

Metal-on-metal THA with cementless components could be recommended for young, active patients to prevent wear and osteolysis. The matte-surface cemented stem is more likely to fail owing to friction during the earlier stage and cement-related biological processes during the later stage.

Randomized comparison between 3 surface treatments of a single anteverted stem design: 84 hips followed for 5 years

Eighty patients (84 hips) randomly received an anteverted cobalt-chromium stem (Lubinus SP2; Waldemar Link, Hamburg, Germany) with matte, polymethyl methacrylate-coated, or polished surface (uncollared). Radiostereometry was used to study migration and wear; and the bone mineral density was studied with dual-energy x-ray absorptiometry at 6 months, 1 year, 2 years, and 5 years. The polished stems had subsided 0.1 to 0.2 mm more at 6 months and 0.3 to 0.4 mm more at 5 years than the matte and precoated versions (P < .0001) and subsided mainly inside the cement mantle. The rotations of the stem and the migration and wear of the cemented cup did not differ between the 3 groups. After 1 and 2 years, the polished stems had lost significantly less bone mineral in Gruen zones 1, 2, 6, and 7 (P = .004 to .03); but this difference had disappeared after 5 years. The period of improved bone remodeling around the polished version coincided with the early period of increased subsidence, suggesting that stem motions inside the mantle resulted in a favorable loading of the proximal femur. Our observations suggest that alternative shapes could be possible on future polished femoral stem designs.

Is the so-called 'French paradox' a reality?: long-term survival and migration of the Charnley-Kerboull stem cemented line-to-line

We have evaluated the in vivo migration patterns of 164 primary consecutive Charnley-Kerboull total hip replacements which were undertaken in 155 patients. The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem before line-to-line cementing. We used the Ein Bild Roentgen Analyse femoral component method to assess the subsidence of the femoral component. At a mean of 17.3 years (15.1 to 18.3) 73 patients were still alive and had not been revised, eight had been revised, 66 had died and eight had been lost to follow-up. The mean subsidence of the entire series was 0.63 mm (0.0 to 1.94). When using a 1.5 mm threshold, only four stems were considered to have subsided. Our study showed that, in most cases, a highly polished double-tapered stem cemented line-to-line does not subside at least up to 18 years after implantation.

Hip resurfacing data from national joint registries: what do they tell us? What do they not tell us?

Current-generation metal-on-metal hip resurfacing implants (SRAs) have been in widespread global use since the 1990s, and in the United States, specific implants have recently been approved for clinical use. Many recent publications describe short-term survivorship achieved by either implant-designing surgeons or high-volume centers. National joint replacement registries (NJRRs) on the other hand report survivorship achieved from the orthopaedic community at large. We therefore reviewed SRA survivorship from national registry data and compared with that reported from individual centers. Additionally, we compared SRA survivorship reported by registries and compared prognosticators for failure with those of conventional total hip arthroplasty (THA). Although resurfacing was associated with an overall increased failure rate in comparison to THA (Australian registry 5-year cumulative revision rate [CRR], 3.7% and 2.7%, respectively), there were exceptions to this. Male patients younger than 65 years with primary osteoarthritis had equivalent results with SRA and THA (Australian registry 5-year CRR, 2.5% and 2.8%, respectively). Head size over 50 mm in diameter was a predictor of surface replacement arthroplasty survivorship and only females with a head diameter of 50 mm or greater (14% of females) had a comparable survivorship to males. Diagnoses other than primary osteoarthritis bear a higher risk of early revision of SRA as compared with THA. Revision of SRA does not lead to reproducible results with rerevision rates of 11% at 5 years. Given these predictors of failure, our review of data from the NJRR suggests stringent patient selection criteria might enhance the survival rates of SRA.

In vitro measurement of interface micromotion and crack in cemented total hip arthroplasty systems with different surface roughness

BACKGROUND

Cemented stems with various surface roughnesses are used in total hip arthroplasty. However, it is not clear how the surface roughness of the stem affects the longevity of the implant. In this study, we investigated the effect of the stem roughness on the micromotion at the bone-cement and cement-implant interface and investigated cracks in the cement layer through in vitro measurement.

METHODS

Stems with the same shape and material but with different surface roughness (polished with Ra=0.05 microm and matte-finished with Ra=0.83 microm) were tested to measure the interface micromotion using custom-made sensors. The stems were implanted in five paired cadaver femurs and cyclic loading was applied to the femoral head to measure the interface micromotion. After loading, we measured the crack length and calculated the crack length density at the cement layer.

FINDINGS

The difference in the interface micromotion between the polished stem and the rough stem was not significant except at the distal region of the cement-bone interface. More cracks were found at the distal region of the polished stem than at the rough stem. The magnitude of the cement crack length density did not correlate with the interface micromotion.

INTERPRETATION

The results showed that the difference in the roughness between the polished and matte finishes did not significantly affect the micromotion and crack of the interface. However, more cement wear particles were expected in the matte-finished stem.

Stem subsidence of polished and rough double-taper stems: in vitro mechanical effects on the cement-bone interface

BACKGROUND AND PURPOSE

Many clinical reports have indicated that polished hip stems show better clinical results than rough stems of the same geometry. It is still unknown, however, what the mechanical effects are of different surface finishes on the cement at the cement-bone interface. We compared mechanical effects in an in vitro cemented hip arthroplasty model.

METHODS

Two sizes of double-taper polished stems and matt-processed polished stems (rough stems) were fixed into composite femurs. A 1-Hz dynamic load was applied to the stems for 1 million cycles. An 8-h no-load period was set after every 16 h of load. Stem subsidence within the cement, and compressive force and horizontal cement creep at the cement-bone interface, were measured.

RESULTS

Compared to rough stems, stem subsidence, compressive force and cement creep for polished stems were a maximum of 4, 12, and 7-fold greater, respectively. There was a strong positive correlation between stem subsidence and compressive force for polished stems. In contrast, a strong negative correlation was found between stem subsidence and compressive force for rough stems. There was also a statistically significant relationship between compressive force on the cement and cement creep for the polished stems, but no significant relationship was found for rough stems.

INTERPRETATION

This is the first evidence that different surface finishes of stems can have different mechanical effects on the cement at the cement-bone interface. Stem subsidence in polished stems resulted in compressive force on the cement and cement creep. The mechanical effects that polished taper stems impart on cement at the cement-bone interface probably contribute to their good long-term fixation and excellent clinical outcome.

Response of human osteoblasts exposed to wear particles generated at the interface of total hip stems and bone cement

Aseptic loosening of total hip replacement is mainly caused by wear particles. Abrasive wear occurs at articulating surfaces or as a consequence of micro-motions at the interface between femoral stem and bone cement. Direct impact of wear particles on osteolysis, the remodeling of the bone stock and a directly affected function of osteoblasts was described. The present study examined the response of human osteoblasts exposed to different wear particles, which were generated in a test device providing oscillating micro-motions at the interface between femoral stem and standard bone cement. Characterization of released particles was performed by quantifying the size distribution and the metal content of the wear debris. Human osteoblasts were incubated with particles obtained from hip stems with different material compositions (Ti-6Al-7Nb and Co-28Cr-6Mo) and rough and smooth surface finishings combined with standard bone cement (Palacos(R) R) containing zirconium oxide particles. Commercially pure titanium particles (cp-Ti) and particulate zirconium oxide (ZrO(2)) were used for comparative analyses. The results revealed significant (p < 0.05) reduction of the cell viability after exposure to higher concentration of metallic particles, particularly from Co-based alloys. In contrast, ZrO(2) alone showed significantly less adverse effects on the cells. When increasing metallic particle concentrations massive inhibition was also observed in the release of cytokines including interleukine-6 (IL-6) and interleukine-8 (IL-8), but the expression of Procollagen I and the cell viability showed the highest reduction after exposure to Co-based alloy particles from rough stems.

In vitro influence of stem surface finish and mantle conformity on pressure generation in cemented hip arthroplasty

BACKGROUND AND PURPOSE

Under physiological loads, debonded cemented femoral stems have been shown to move within their cement mantle and generate a fluid pump that may facilitate peri-prosthetic osteolysis by pressurizing fluid and circulating wear debris. The long-term physiological loading of rough and polished tapered stems in vitro has shown differences in performance, with greater interface pressures generated by the rough stems. In this study we investigated the individual effects of stem surface finish, degree of mantle wear, and mode of loading on the stem pump mechanism.

METHOD

Rough and polished stems were loaded under different regimes in artificially worn cement mantles that permitted either 2 or 5 degrees of rotational stem movement, and the interface pressures were compared.

RESULTS

The pressures generated by the rough and polished stems were similar in either type of mantle. The pattern of pressure generation in the 2-degree mantles was similar to the pressures generated by rough stems after long-term loading, but the high posterior wall pressures fell and the tip pressures increased in the 5-degree mantles. The torsional loads were principal drivers of pressure generation in all areas of the interface other than the implant tip, where axial loading predominated.

INTERPRETATION

Femoral stems with rotational instability under cyclic torsional loads generate elevated interface fluid pressures and flows independently of stem surface finish. The rough surface finish is only important in creating this instability in tapered stems.

In vitro comparison of the effects of rough and polished stem surface finish on pressure generation in cemented hip arthroplasty

BACKGROUND AND PURPOSE

High pressures around implants can cause bone lysis and loosening. We investigated how pressures are generated around cemented femoral stems.

METHOD

We compared the pressures generated by rough and polished tapered stems at their cement interfaces, in an in vitro model, before and after 1 million load cycles.

RESULTS

At the start of the study, the loading of both polished and rough stems generated interface pressures that were not statistically significantly different. After 1 million load cycles, the rough stems generated greater interface pressures than at the start (p = 0.03), with maximum pressure wave amplitudes of 450,000 Pa or 3,375 mm Hg. The pressures generated by polished stems were similar before and after 1 million load cycles, and were lower than the pressures generated by the rough stems (p = 0.01). Stem loading caused micromotion between the stem and cement. Polished stems migrated distally in the cement but retained rotational and axial stability. The rough stems also migrated distally and wore the cement mantle, leading to increased rotational instability.

INTERPRETATION

The change in the rotational micromotion of the rough stem is likely to be the principal cause of the increased stem pump output and to be a key factor in the longevity of cemented femoral implants.

Anatomic and physiologic rationale for various technologies for primary total hip arthroplasty

A number of patients have anatomic or physiologic variations that may adversely affect the performance of a primary total hip arthroplasty. Various technologies have been utilized in an attempt to improve the outcomes for these patients; however, some of these potential solutions are controversial. The authors examined the complete body of literature for scientific evidence regarding the use of these new technologies. The anatomic and physiologic anomalies that were studied include extra-articular deformities, developmental dysplasia, Perthes disease, Type C femoral bone, acetabular bone deficiency, femoral rotational abnormalities, variations that increase the risk of hip dislocation, sickle cell anemia, and extremely small or large bone sizes. This article presents the current scientific evidence and imparts an unbiased view of the use of various technologies to provide individualized solutions for patients who have anatomic or physiologic variations.

The importance of a thick cement mantle depends on stem geometry and stem—cement interfacial bonding

The thickness of the cement mantle around the femoral component of total hip replacements is a contributing factor to aseptic loosening and revision. Nevertheless, various designs of stems and surgical tooling lead to cement mantles of different thicknesses. Opinion is divided on whether a thick mantle enhances implant longevity. This study investigates the effect of cement mantle thickness on accumulated damage in the cement, and how this is influenced by the presence or absence of a proximal collar and on whether the stem—cement interface remains bonded. Three-dimensional finite element simulations incorporating creep and non-linear damage accumulation were performed to investigate cracking in the cement mantles around Stanmore Hips under physiologically informed stair-climbing and gait loads. Cement mantle thickness, stem—cement interfacial bonding, and collar design were varied to assess the interactive effects of these parameters. In all cases, damage levels were three to six times higher when the stem—cement interface remained bonded. Cement mantle thickness had little effect on cement damage accumulation around debonded collared stems but was critical in both bonded and collarless cases, where a thicker mantle reduced cement cracking. Damage around a smooth debonded stem with a collar is thus much less sensitive to cement thickness than around bonded or collarless stems.

Mechanical aspects of degree of cement bonding and implant wedge effect

BACKGROUND

The degree of bonding between the femoral stem and cement in total hip replacement remains controversial. Our objective was to determine the wedge effect by debonding and stem taper angle on the structural behavior of axisymmetric stem-cement-bone cylinder models.

METHODS

Stainless steel tapered plugs with a rough (i.e. bonded) or smooth (i.e. debonded) surface finish were used to emulate the femoral stem. Three different stem taper angles (5 degrees , 7.5 degrees , 10 degrees ) were used for the debonded constructs. Non-tapered and tapered (7.5 degrees ) aluminum cylindrical shells were used to emulate the diaphyseal and metaphyseal segments of the femur. The cement-aluminum cylinder interface was designed to have a shear strength that simulated bone-cement interfaces ( approximately 8MPa). The test involved applying axial compression at a rate of 0.02mm/s until failure. Six specimens were tested for each combination of the variables. Finite element analysis was used to enhance the understanding of the wedge effect.

FINDINGS

The debonded stems sustained about twice as much load as the bonded stem, regardless of taper angle. The metaphyseal model carried 35-50% greater loads than the diaphyseal models and the stem taper produced significant differences. Based on the finite element analysis, failure was most probably by shear at the cement-bone interface.

INTERPRETATION

Our results in this simplified model suggest that smooth (i.e. debonded) stems have greater failure loads and will incur less slippage or shear failure at the cement-bone interface than rough (i.e. bonded) stems.

Effect of antibiotic loading on the shear strength at the stem-cement interface (Shear strength of antibiotic loaded cement)

The purpose of this study was to investigate the effects of addition of antibiotics into cement powder on the shear properties of the cement-metal interface. The approach involved adding 800 mg of teicoplanin to 40 g bone cement powder in the t-800 group, 1,600 mg teicoplanin in the t-1,600 group, and no antibiotic in the control group. Industrially prepared bone cement containing 500 mg of gentamicin was used as group g-500. Each group consisted of ten samples. Cement-metal interfaces were produced using metal discs with porous surfaces (1 microm) and templates at the third minute. Shear stability of specimens was measured in a material testing machine. The ANOVA test was used for comparison between the mean shear results of each group. Results showed that mean shear stress to failure values were 12.28+/-3.35 MPa for the control group, 11.72+/-3.09 MPa for the t-800 group, 13.25+/-2.36 MPa for the t-1,600 group and 13.09+/-2.58 MPa for the g-500 group. No statistically significant differences were found between results of the groups. Results of the study have proven that addition of 1,600 mg of teicoplanin or 500 mg gentamycin in 40 g of bone cement does not decrease the shear strength at the cement-metal interface significantly on the day of application.

Femoral stem wear in cemented total hip replacement

The great success of cemented total hip replacement to treat patients with end-stage osteoarthritis and osteonecrosis has been well documented. However, its long-term survivorship has been compromised by progressive development of aseptic loosening, and few hip prostheses could survive beyond 25 years. Aseptic loosening is mainly attributed to bone resorption which is activated by an in-vivo macrophage response to particulate debris generated by wear of the hip prosthesis. Theoretically, wear can occur not only at the articulating head—cup interface but also at other load-bearing surfaces, such as the stem—cement interface. Recently, great progress has been made in reducing wear at the head—cup interface through the introduction of new materials and improved manufacture; consequently femoral stem wear is considered to be playing an increasingly significant role in the overall wear of cemented total hip replacement. In this review article, the clinical incidences of femoral stem wear are comprehensively introduced, and its significance is highlighted as a source of generation of wear debris and corrosion products. Additionally, the relationship between femoral stem surface finish and femoral stem wear is discussed and the primary attempts to reproduce femoral stem wear through in-vitro wear testing are summarized. Furthermore, the initiation and propagation processes of femoral stem wear are also proposed and a better understanding of the issue is considered to be essential to reduce femoral stem wear and to improve the functionality of cemented total hip replacement.

Survival of polished compared with precoated roughened cemented femoral components. A prospective, randomized study

BACKGROUND

The optimal surface finish for cemented femoral components remains controversial. The purpose of this randomized clinical trial was to compare the survival of two femoral components with similar geometry but substantially different surface finishes.

METHODS

During a five-year period, 201 patients (219 hips) were prospectively randomized to be treated with a total hip arthroplasty with either a polished (Ra, 0.18 to 0.3 microm) or a precoated roughened (Ra, 1.8 to 2.3 microm) cemented femoral component with similar geometry. There were no significant differences between the patient groups in terms of age, sex, weight, preoperative diagnosis, component size, or cement grade. So-called third-generation cementing techniques were used. One hundred and thirteen polished components and 106 precoated roughened components were followed for a mean of 5.3 years. Complete clinical and radiographic data were available for 134 hips at a minimum of five years (mean, 6.1 years; range, five to ten years) postoperatively.

RESULTS

In the entire cohort of 219 hips, there was no significant difference (log rank p = 0.66) in survival, with the end point defined as component removal for any reason or definite radiographic loosening, between the precoated components (96.2%; 95% confidence interval, 90.9% to 100%) and the polished components (97.1%; 95% confidence interval, 93.8% to 100%). There was a periprosthetic fracture in three hips with a polished component. Two precoated roughened components were revised because of loosening, and two polished components were revised: one because of loosening and one because of a nonunion of a periprosthetic fracture. There was no significant difference between the groups with regard to the Harris hip scores or the clinical results. There was also no significant difference with regard to the presence or number of bone-cement radiolucent lines.

CONCLUSIONS

Kaplan-Meier survival analysis showed no significant differences between two types of cemented femoral components with similar geometry but substantially different surface finishes at seven years. In the patient population selected for treatment with a cemented femoral component, the surface finish may not be a crucial factor affecting component survival at a minimum of five years, provided that good cement technique is used.

Medium- and long-term performance of 11,516 uncemented primary femoral stems from the Norwegian arthroplasty register

Primary uncemented femoral stems reported to the Norwegian arthroplasty register between 1987 and 2005 were included in this prospective observational study. There were 11 516 hips (9679 patients) and 14 different designs of stem. Kaplan-Meier survival probabilities and Cox regression were used to analyse the data. With aseptic loosening as the end-point, all currently used designs performed excellently with survival of 96% to 100% at ten years. With the end-point as stem revision for any cause, the long-term results of the different designs varied from poor to excellent, with survival at 15 years ranging between 29% and 97%. Follow-up for longer than seven years was needed to identify some of the poorly-performing designs. There were differences between the stems; the Corail, used in 5456 hips, was the most frequently used stem with a survival of 97% at 15 years. Male gender was associated with an increased risk of revision of x 1.3 (95% confidence interval 1.05 to 1.52), but age and diagnosis had no influence on the results. Overall, modern uncemented femoral stems performed well. Moderate differences in survival between well-performing stems should be interpreted with caution since the differences may be caused by factors other than the stem itself.

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%.

Minimum 10-year survival of Kerboull cemented stems according to surface finish

The optimal surface finish for a cemented THA stem is still debated. We hypothesized surface finish would influence survival of Kerboull cemented hip arthroplasties and a matte finish would have lower survival. We reviewed survival of 433 total hip arthroplasties in 395 patients: 284 consecutive patients (310 hips) were enrolled in a prospective, randomized study of polished (165 hips) or matte finish stems (145 hips) and compared to a historical series of satin stems (123 hips) in 111 patients. The satin and matte finish implants had similar geometry but the polished was quadrangular rather than oval. Finish roughnesses were: polished (radius, 0.04 microm), satin (radius, 0.9 microm), and matte (radius, 1.7 microm). The mean age of the patients at the time of the index arthroplasty was 63.6 years. The survival rate at 13 years, using radiographic loosening as the end point, was 97.3%+/-2.6% for polished stems, 97.1%+/-2.1% for satin stems, and 78.9%+/-5.8% for matte stems. The data suggest survival of Kerboull stems was higher with a polished or satin surface finish than with a matte finish.

LEVEL OF EVIDENCE

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

Stem-cement porosity may explain early loosening of cemented femoral hip components: experimental-computational in vitro study

A combination of laboratory experiment and computational simulation was performed to assess the role of interface porosity on stem migration. The early motion of in vitro prepared cemented femoral components was measured during application of cyclic stair climbing loads. Following testing, transverse sections were obtained and the distribution of pores at the stem-cement interface was determined. Finite element models of cemented stem constructs were developed and a scheme was implemented to randomly assign pores to the stem-cement interface. For a series of 14 in vitro prepared components, pore fractions at the stem-cement interface ranged from 23% to 67%. The majority of pores at the stem-cement interface were less than 1 mm in length with a mean length of 1.27 +/- 2.7 mm and thickness of 0.12 +/- 0.11 mm. For stems with large pore fractions, pores tended to coalesce in longer extended gaps over the stem surface. Finite element and experimental models both revealed strong positive correlations (r(2) = 0.55-0.72; p < 0.0001) between stem-cement pore fraction and stem internal rotation, suggesting that the presence and extent of pores could explain the early motion of the stems. There was an increased volume of cement at risk of fatigue failure with increasing stem migration. Pore fractions greater than 30% resulted in large increases in stem internal rotation, suggesting that attempts to maintain surface porosity at or below this level may be desirable to minimize the risk of clinical loosening.

Total hip arthroplasty with a cemented, polished, collared femoral stem and a cementless acetabular component. A follow-up study at a minimum of ten years

BACKGROUND

Recent studies have suggested that cemented femoral components with a polished surface may provide superior long-term fixation when compared with femoral components with a roughened surface. The purpose of this study was to evaluate the results of total hip arthroplasty with a cemented femoral component with a polished surface finish and compare them with the results of total hip arthroplasty performed with a similar design of cemented femoral component with a rougher surface finish.

METHODS

We retrospectively reviewed a consecutive group of 132 patients (149 hips) in whom primary total hip arthroplasty had been performed by one surgeon using a cemented collared femoral component with a polished (0.1-microm Ra) surface finish and a cementless acetabular component. Ninety-eight patients (115 hips) were followed for a minimum of ten years. We compared the survivorship of this prosthesis with that of a femoral component of similar design but with rougher surfaces (matte or grit-blasted).

RESULTS

No polished stems were revised because of aseptic loosening or demonstrated radiographic evidence of loosening; however, eight hips (5.4%) with a polished stem demonstrated osteolysis distal to the greater or lesser tro-chanter. In contrast, six stems (2.0%) with a matte surface finish of 0.8-microm Ra were revised because of aseptic loosening, and an additional five stems were seen to be loose radiographically. Eleven stems (9.2%) with a grit-blasted surface finish of 2.1-microm Ra were revised because of aseptic loosening, and an additional four stems were seen to be loose radiographically. The difference in the prevalence of revision due to aseptic loosening between the group with the 0.1-microm Ra surface and the group with the 2.1-microm Ra surface was significant (p = 0.001), as was the difference between the prevalence of revision due to aseptic loosening between the group with the 0.8-microm Ra surface and the group with the 2.1-microm Ra surface (p = 0.001). No cups were revised because of aseptic loosening, and one hip had radiographic signs of acetabular loosening.

CONCLUSIONS

This study demonstrated excellent durability of a prosthesis consisting of a cemented, collared, polished femoral component and a cementless acetabular component. While no hips were revised because of aseptic loosening, distal femoral osteolysis was observed in eight hips (5.4%), a higher prevalence than has been reported by others after similar durations of follow-up of tapered, collarless, polished femoral components.

Radiographic failure patterns of polished cemented stems

Changes in cemented femoral component geometry and surface finish have been made to improve predicted results. We studied the failure rates and radiographic failure patterns of four polished femoral stems with different geometries to determine if design changes over time improved our results. We retrospectively reviewed 910 patients with 1031 total hip arthroplasties performed from 1993 to 2003 with a minimum 2-year followup. All arthroplasties used the same cementing technique with polished femoral stems with a surface roughness of 4 microinches but with differing geometries. By 2005, seven stems (0.6%) were revised for aseptic loosening. All loosening started at the cement-bone interface. The time from the onset of loosening to revision averaged 3.3 years. In all but one patient the bone damage was minimal and amenable to simple revision femoral techniques. We found no obvious difference in loosening rates or radiographic failure patterns among the four stem geometries. The patients showed less bone damage and progressed slower than previous reports of failed rough femoral stems.

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.

Long-term survival of a cemented titanium-aluminium-vanadium alloy straight-stem femoral component

We present a retrospective series of 170 cemented titanium straight-stem femoral components combined with two types of femoral head: cobalt-chromium (CoCr) alloy (114 heads) and alumina ceramic (50 heads). Of the study group, 55 patients (55 stems) had died and six (six stems) were lost to follow-up. At a mean of 13.1 years (3 to 15.3) 26 stems had been revised for aseptic loosening. The mean follow-up time for stable stems was 15.1 years (12.1 to 16.6).

Survival of the stem at 15 years was 75.4% (95% confidence interval (CI) 67.3 to 83.5) with aseptic failure (including radiological failure) as the end-point, irrespective of the nature of the head and the quality of the cement mantle. Survival of the stem at 15 years was 79.1% (95% CI 69.8 to 88.4) and 67.1% (95% CI 51.3 to 82.9) with the CoCr alloy and ceramic heads, respectively. The quality of the cement mantle was graded as a function of stem coverage: stems with complete tip coverage (type 1) had an 84.9% (95% CI 77.6 to 92.2) survival at 15 years, compared with those with a poor tip coverage (type 2) which had a survival of only 22.4% (95% CI 2.4 to 42.4). The poor quality of the cement mantle and the implantation of an alumina head substantially lowered the survival of the stem.

In our opinion, further use of the cemented titanium alloy straight-stem femoral components used in our series is undesirable.

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.

Long-term results of the cementless ALLOCLASSIC hip arthroplasty system using a 28-mm ceramic head: with a retrospective comparison to a 32-mm head

One hundred twenty-four total hip arthroplasties in 119 patients, all performed with the cementless ALLOCLASSIC hip arthroplasty system (SL stem and CSF cup; Centerpulse, Winterthur, Switzerland), were analyzed retrospectively. In all hips, a 28-mm head and an ultrahigh-molecular-weight polyethylene inlay were used. Of the 124 hips, 81 could be investigated clinically and radiologically after an average of 150.6 months (range, 133-169 months). Twenty-six patients (26 hips) died in the interim. One of these patients had septic cup loosening. Seventeen hips (16 patients) were not available for follow-up because of health reasons (12 hips in 11 patients), lack of cooperation (3 hips in 3 patients), or loss to follow-up (2 hips in 2 patients). Of the 124 total hip arthroplasties, 4 cups were removed (2 aseptic and 2 septic loosening). No stem had to be removed. If aseptic loosening is defined as the end point, the survival rate is 98.4% (95% confidence interval, 93.8%-99.6%) for the cup and 100% for the stem after 157 months. If revision for any reason is defined as the end point, the survival rate is 95.6% (95% confidence interval, 90.1%-98.3%). Before operation, the average Harris Hip Score was 36.4 points (21-46). At time of follow-up, the average Harris Hip Score was 89.7 points (54-100). Radiolucent lines and osteolyses were found only seldom (mostly in the proximal stem zones).

High failure rate of a modern, proximally roughened, cemented stem for total hip arthroplasty

The role of surface finish on the survivorship of cemented femoral stems continues to be debated. A total of 34 proximally roughened cemented stems were implanted in 33 consecutive patients undergoing total hip arthroplasty by a single surgeon. An alarmingly high failure rate was observed, prompting a retrospective chart review, analysis of radiographs, and evaluation of retrieved stems and pathological specimens. Nineteen patients were available with more than two years follow-up. Of these 19 patients, nine stems had failed (47%) due to severe osteolysis and stem loosening. Failures were significantly more common in the male gender (p<0.005), and young (p=0.05), tall (p<0.002), and heavy patients (p<0.004). All failed revised hips showed severe metallosis, with both gross and microscopic evidence of metallic shedding from the stems. Our findings suggest that this proximally roughened stem is susceptible to early failure. Failure is characterized by stem debonding, subsidence within the cement mantle, shedding of metallic and cement particles due to fretting, and rapidly progressive osteolysis. These findings have been observed with other rough surface finish cemented stems.

The relationship between stem subsidence and improvement in the radiolucency in polished tapered stems

We studied the relationship between stem subsidence and improvement in the initial radiolucency at the bone-cement interface in polished- and rough-surface stems. Stem subsidence was seen in 34 of 42 hips (81.0%), and improvement in the initial radiolucency was seen in 15 hips (35.7%) in collarless polished tapered stems at 1 year after operation. In polished stems, stem subsidence in cases with improvement in the initial radiolucency was significantly greater than in those with no change (average 1.12 mm and 0.48 mm, P<0.005). In rough-surface stems partially coated with polymethylmethacrylate (VerSys Cemented Plus), no stem subsidence and no improvement in the initial radiolucency was seen. In polished stems, stem subsidence leads to cement creep and compressive force on the bone-cement interface and can improve the initial radiolucency.

Ten-year survivorship of rough-surfaced femoral stem with geometry similar to Charnley femoral stem

The aim of this study is to review the 10-year results of 269 cemented total hip arthroplasties performed using the Harvard femoral stem with matte surface finish and Charnley stem-like geometry. This is a retrospective cross-sectional survivorship study. We retrospectively reviewed the results of 269 cemented total hip arthroplasties performed using the Harvard femoral stem in 257 patients (men/women 93:164, mean age 71.2 years) between 1990 and 1994. The median duration of follow-up for the surviving implants was 118 (range 60-129) months. Radiographs were reviewed to evaluate the type of osteoarthritis, cement mantle thickness, alignment of the components, presence of aseptic loosening, and radiolucent lines. Kaplan-Meier survival analysis and Cox proportional hazards analysis were performed to evaluate 10-year survival and the impact of various radiological parameters on the prosthesis survival respectively. Of the 248 eligible patients (260 hips), 6 patients (7 hips) were lost to follow-up, and 67 patients had died at the time of the study; 36 hips (35 patients) underwent revision surgery for aseptic failure (median duration 60 months, range 12-125 months), and 11 hips were revised for septic failure (median duration 24 months, range 10-53 months from the index procedure). The femoral component was revised in all patients, whereas the acetabular component was revised in 27 patients. Ten-year survival for the femoral and acetabular components using aseptic loosening (with and without revision surgery) as an end point was 77.5% (71.5%-83.5%) and 91.1% (87.2%-95%), respectively. Cox regression analysis did not reveal a statistically significant (P > 0.05) effect of various radiological parameters on survival rate. Our results demonstrate that the matte surface finish femoral component (with geometry similar to Charnley femoral component) has less satisfactory long-term survival rate.

The effect of surface finish and of vertical ribs on the stability of a cemented femoral stem: an in vitro stair climbing test

The search for improved femoral fixation in cemented total hip arthroplasty is ongoing. Two design variables, surface finish and stem contour, were evaluated. Sixteen titanium femoral stems of one design were cemented into fiberglass femora. One half of the components had a polished surface and the rest had a roughened finish. Within each group, 4 stems had vertically oriented ribs on the proximal portion and 4 did not. Micromotion was measured in a stair climbing simulator with loading to a joint reaction force of 200 kg for 6 million cycles. Micromotion increased throughout the course of the experiment. Stems with a polished surface had significantly higher micromotion. Although stems with ribs had less micromotion compared with those without ribs, this difference was not statistically significant.

Metallic shedding, surface finish changes, and extensive femoral osteolysis in the loose Spectron EF stem

The addition of a proximal rough surface finish in the satin finish Spectron stem (Spectron EF) reportedly does not alter its clinical performance. However, we have revised 15 Spectron EF stems because of aseptic loosening and extensive femoral osteolysis at early and intermediate-term followup, raising a question as to its safety. We sought to determine which interface has aseptic failure, the presence of massive femoral osteolysis, and the consequences of loosening at the implant-cement interface in the implant's surface finish. Fifteen patients with aseptic loosening of a proximal rough surface-finished Spectron EF stem at intermediate-term followup (Group A) were compared with seven patients having revisions of the same stem for infection or recurrent dislocation but without loosening (Group B). Radiographs for Group A showed debonding at the cement-implant interface and stem subsidence in 13 hips, and severe femoral osteolysis in seven, including two pathologic periprosthetic fractures. During revision surgery, all 13 subsided stems showed a metallic stained pseudomembrane and metallic shedding with polishing of the stem surface. None of the patients in Group B who had revision surgery had these changes. Aseptic failure of the Spectron EF stem was characterized by debonding, subsidence, and metallic shedding with concomitant massive femoral osteolysis and metallosis, which is similar to conditions reported for loose, rough cemented stems, but has not been reported for the satin finish Spectron stem.

LEVEL OF EVIDENCE

Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.