The significance of stem-cement loosening of grit-blasted femoral components

Favorable revision-free survivorship of cemented arthroplasty following failed proximal femoral nail antirotation: a case series with a median follow-up of 10 years

BACKGROUND

Given the ever-increasing rate of failure related to proximal femoral nail antirotation (PFNA), it is expected that an increasing number of PFNA individuals will undergo conversion to total hip arthroplasty (THA). The long-term survivorship of conversion of the initial PFNA to cemented THA is still debated. The aim of this retrospective study was to assess the long-term revision-free survivorship of cemented THAs after initial failures of PFNA in geriatric individuals.

METHODS

Consecutive geriatric individuals who underwent secondary cemented THA after initial PFNA fixation from July 2005 to July 2018, were retrospectively identified from three medical centres. The primary outcome was revision-free survivorship estimated using the Kaplan-Meier method and Cox proportional hazards regression with revision for any reason as the endpoint; secondary outcomes were functional outcomes and key THA-related complications. Follow-ups occurred at 3 months, 6 months, 12 months and then every 12 months after conversion.

RESULTS

In total, 186 consecutive patients (186 hips) were available for study inclusion. The median follow-up was 120.7 months (60-180 months) in the cohort. Kaplan-Meier survivorship with revision for any reason as the end point showed that the 10-year revision-free survival rate was 0.852 (95% confidence interval [CI], 0.771-0.890). Good functional outcomes were seen, and the HHS decreased markedly over the 24th month to the final follow-up interval from 92.2 to 75.1 (each p < 0.05). The overall rate of key THA-related complications was 16.1% (30/186).

CONCLUSION

Cemented THA executed following initial PFNA failure may yield satisfactory revision-free survival and, at least for the initial 10 years after conversion, good functional outcomes and a 16.1% complication rate of key THA-related complications, which supports the trend towards increased use of cemented THA.

Interface abrasion between rough surface femoral stems and PMMA cement results in extreme wear volumes--a retrieval study and failure analysis

During the loosening cascade of cemented rough femoral stems, the destruction of the mantle and the production of cement and metal wear debris occur after the loss of constraint at the interface. Two-dimensional (2D) measurements (light microscopy based morphometry on fragments of mantles and vertical scanning interferometry of femoral stems) permitted mathematical 3D-extrapolations to estimate the wear volumes. Fragments of the cement mantles available lost volumes from 0.85 mm(3) to 494.10 mm(3) (median amount of bone cement wear = 178,426 mg). The harder metal surfaces lost between 1.459 mm(3) and 5.688 mm(3) of material (the median amount of metal wear per surface = 1.504 mg/100 mm(2)). Compared to the loss of material due to the fretting of stems, the abrasion of metal, and cement in defective cement mantles produced wear volumes sufficiently high to induce osteolysis. Though the design of the femoral stem and the handling of bone cement do not represent contemporary design and clinical practice, respectively, an extremely high number of joint replacements still in daily use may be impacted by this study because of possible predicted failures. Once the processes of fragmentation, abrasion, and osteolysis have been realized, the time until revision surgery should not be unduly prolonged.

Short-keeled cemented tibial components show an increased risk for aseptic loosening

BACKGROUND

The choice of implant design plays an important role for primary fixation of a TKA. Short-keeled tibial components allow implantation through a smaller approach with less femorotibial subluxation.

QUESTIONS/PURPOSES

The purpose of this study was to detect early implant failure resulting from aseptic loosening after cemented short-keeled and standard tibial baseplate implantation.

METHODS

Between 2008 and 2010, a group of 160 consecutive patients (with 80 standard and with 80 short-keeled tibial trays) received cemented TKAs. At 1-year followup, patients were examined clinically and radiographs were analyzed regarding aspects of radiolucency. The components were divided into five zones on each radiographic view and the measurements of the 10 zones were added.

RESULTS

The mean sum of radiolucencies was increased significantly with the short-keeled baseplates. In the current study, short-keeled tibial trays revealed a revision rate of 6.3% after 1-year followup. In contrast, none of the standard tibial baseplates were revised.

CONCLUSIONS

The implantation of cemented, short-keeled tibial components is linked to an increased rate of early loosening. Therefore, the indication for cemented, short-keeled component implantation should be reviewed.

LEVEL OF EVIDENCE

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

History and design considerations for arthroplasty around the wrist

The history and evolution of both soft tissue and implant arthroplasty about the wrist are discussed, including carpometacarpal, radiocarpal, and distal radioulnar joints. Technical considerations for arthroplasty are reviewed, including factors affecting implant osseointegration, implant articulation/constraint, and management of complications.

Biotribological properties at the stem-cement interface lubricated with different media

BACKGROUND

Debonding of the stem-cement interface occurs inevitably in-vivo under physiological loading, and pseudo-synovial fluid is subsequently pumped into this interface, serving as the lubricant. However, the influence of protein adsorption onto the femoral stem surface has not been well taken into consideration in previous in vitro studies.

MATERIALS AND METHODS

The biotribological properties at the stem-cement interface were investigated through a series of fretting frictional tests using polished stainless steel 316L stem and smooth bone cement, lubricated by three different media at body temperature, i.e. 100% calf serum, 25% calf serum, and 0.9% saline solution. The surface characterization of the femoral stem was evaluated sequentially using optical microscope, optical interferometer, scanning electron microscope, and Raman spectroscopy.

RESULTS

The friction coefficient generally kept stable during the test, and the minimum value (0.254) was obtained when 100% calf serum was used as the lubricant. Slight scratches were detected within the contact area for the stainless steel 316L stems lubricated by 100% calf serum and 25% calf serum, which was further surrounded by the adsorbed protein film with alveolate feature. Additionally, a wear scar was present within the contact area when 0.9% saline solution was used as the lubricant.

CONCLUSIONS

Protein adsorption onto the stainless steel 316L stem surface affected the biotribological properties at the stem-cement interface under oscillatory fretting mechanism. Generation of wear debris at the stem-cement interface may be postponed by modification of physicochemical properties of the femoral stem to promote protein adsorption.

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

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

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.

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.

Static shear strength between polished stem and seven commercial acrylic bone cements

The stem-cement interface is one of the most significant sites in cemented total hip replacement and has long been implicated in failure of the whole joint system. However, shear strength at this interface has rarely been compared across a range of commercially available bone cements. The present study seeks to address this issue by carrying out a comparative study. The results indicated that the static shear strength was more dependent on cement type than cement viscosity and volume. However, both cement type and viscosity were contributory factors on porosity and micropore size in the cement surface. There was no significant difference between Simplex P and Simplex P with Tobramycin. Although the bone cements were all hand mixed in this study, the static shear strength was significantly larger than the values recorded by other researchers, and the porosity and micropore size showed much lower values. Bone cement transfer films were detected on the stem surface, typically about 4-10 mum thick. They were considered to be an important factor contributing to high friction at the stem-cement interface after initial debonding.

Reproduction of fretting wear at the stem—cement interface in total hip replacement

The stem-cement interface experiences fretting wear in vivo due to low-amplitude oscillatory micromotion under physiological loading, as a consequence it is considered to play an important part in the overall wear of cemented total hip replacement. Despite its potential significance, in-vitro simulation to reproduce fretting wear has seldom been attempted and even then with only limited success. In the present study, fretting wear was successfully reproduced at the stem-cement interface through an in-vitro wear simulation, which was performed in part with reference to ISO 7206-4: 2002. The wear locations compared well with the results of retrieval studies. There was no evidence of bone cement transfer films on the stem surface and no fatigue cracks in the cement mantle. The cement surface was severely damaged in those areas in contact with the fretting zones on the stem surface, with retention of cement debris in the micropores. Furthermore, it was suggested that these micropores contributed to initiation and propagation of fretting wear. This study gave scope for further comparative study of the influence of stem geometry, stem surface finish, and bone cement brand on generation of fretting wear.

Pin-on-disc evaluation of self-reinforced composite poly(methyl methacrylate) for total joint replacements

Femoral components of hip replacements are commonly anchored in the femur with bone cement or poly(methyl methacrylate) (PMMA). Wear or fracture of bone cement can lead to loosening of the femoral component, which drastically affects the success and longevity of hip replacements. Self-reinforced composite PMMA (SRC-PMMA) has been previously developed for potential use, as a precoat material for hip replacements. The composite consists of high strength fibers that have been shown to have greatly improved mechanical properties over bulk PMMA. The goal of this work was to examine SRC-PMMA for improved wear properties, as a function of processing temperature. Pin-on-disc tests were used to characterize and rank the wear rates of SRC-PMMA and PMMA. Composites made with higher processing temperatures had significantly lower wear rates than do PMMA at a significance level of p < or = 0.05. The lowest wear rate was 8.2 microg/m, at a processing temperature of 136 degrees C, compared to a wear rate for PMMA of 13.3 microg/m. At the lowest processing temperature (105 degrees C), a wear rate higher than PMMA was found, and failure was dominated by fiber delamination. In the more completely processed samples (122 degrees C < or = T < or = 150 degrees C), wear rates were equivalent to or better than PMMA, and smoother and more homogenous wear was noted in wear tracks. Fatigue cracks were prominent at higher processing temperatures or when the wear pin was riding orthogonal to fibers. Wear particles were collected and examined. Wear particle diameter and aspect ratio showed no correlation to processing temperature, but were similar to particles retrieved from human tissue samples.

Osteolysis caused by tibial component debonding in total knee arthroplasty

Late failure of total knee arthroplasties usually results from ultrahigh molecular weight polyethylene wear or implant loosening. Early failure from osteolysis is uncommon. However, we treated a patient with a failed total knee arthroplasty from osteolysis that developed 2 years postoperatively. The failure was associated with tibial component debonding from the cement mantle with abundant cement and metal debris. Although there was some third-body debris in the ultrahigh molecular weight polyethylene insert surface, the insert wear was not extensive. Although abundant cement and metal debris were found in the periarticular soft tissues, no ultrahigh molecular weight polyethylene was seen in histologic specimens under polarized light. The osteolysis seems to have been caused primarily by debris generated from debonding and torsional motion at the tibial baseplate-cement interface rather than the bearing surface. Although this failure mechanism has been well recognized in cemented total hip arthroplasties, it has not been reported to be a substantial cause of failure in total knee arthroplasties.

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.

The cemented femoral stem: selecting the ideal patient

A woman who is elderly, lightweight, and low demand has traditionally been considered an ideal candidate for a cemented femoral stem. Patients who are young, heavy, and high demand have been considered higher risk for failure and, therefore, better suited for cementless femoral stems. However, modern cement techniques and implants have improved outcomes in high-risk cohorts, and stress shielding, thigh pain, and osteolysis have emerged as long-term challenges for cementless femoral stems. Recently reported positive bone remodeling around a cemented, triple-tapered, polished, collarless stem behaving according to the taper-slip philosophy of femoral stem fixation may widen the traditional indications for cemented femoral stems. Paradoxically, patients initially thought to be poor candidates for cemented fixation may benefit most from the long-term bone preservation and positive loading characteristics of this new generation of cemented stem technology.

Cemented fixation with PMMA or Bis-GMA resin hydroxyapatite cement: effect of implant surface roughness

Implant surface roughness is an important parameter governing the overall mechanical properties at the implant-cement interface. This study investigated the influence of surface roughness using polymethylmethcrylate (PMMA) and a Bisphenol-a-glycidylmethacyrlate resin-hydroxyapatite cement (CAP). Mechanical fixation at the implant-cement interface was evaluated in vitro using static shear and fatigue loading with cobalt chrome alloy (CoCr) dowels with different surface roughness preparations. Increasing surface roughness improved the mechanical properties at the implant-cement interface for both types of cement. CAP cement fixation was superior to PMMA under static and dynamic loading.

A prospective randomized trial of cemented femoral components with polished versus grit-blasted surface finish and identical stem geometry

This randomized, prospective study compared 2 cemented hip stems that differed only in the surface finish, which was polished or grit blasted. A total of 226 hybrid total hips were evaluated at an average of 4.8 years postoperatively. No stem in either group was loose or revised for aseptic loosening. There was one case of significant distal lysis in the grit-blasted group. There was no statistical difference between polished and grit-blasted stems in incidence of lysis or bone-cement radiolucency. Harris Hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and SF-36 analysis showed no difference between groups. In conclusion, when adequate cement mantles are achieved around the femoral component, little difference in construct durability between polished and grit-blasted surface finish components can be detected at 4.8-year follow-up for this stem design.

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.

Effects of preheating of hip prostheses on the stem-cement interface

BACKGROUND

Debonding of the cement from metal implants has been implicated in the loosening of cemented total hip prostheses. Strengthening of the stem-cement interface has been suggested as a way to prevent loosening of the component. Previously, it was reported that preheating the stem to 44 degrees C reduced the porosity of the cement at the stem-cement interface. The purpose of this study was to determine the effect of stem preheating on the characteristics of the stem-cement interface.

METHODS

The effects of stem preheating, at temperatures of 37 degrees C, 44 degrees C, and 50 degrees C, on the stem-cement interface were studied in a test model and a preparation that closely simulated the clinical situation. Static interface strength was determined initially and after the stems had been kept in isotonic saline solution at 37 degrees C for two weeks. Fatigue lifetimes were measured, and the nature and extent of porosity at the interface were quantified.

RESULTS

Stem preheating had significant effects on the stem-cement interface. Stems preheated to 37 degrees C had greater interface shear strength than stems at room temperature both initially (53% greater strength) and after simulated aging (155% greater strength). Fatigue lifetimes were also improved, and there was a >99% decrease in interface porosity. The setting time of the cement decreased 12%, and the maximum temperature at the cement-bone interface increased 6 degrees C. Similar effects were found after preheating to 44 degrees C and 50 degrees C.

CONCLUSIONS

Stem preheating had significant effects on the stem-cement interface, with significant improvements in the shear strength and cement porosity of the interface. Also, polymerization temperatures at the cement-bone interface increased. The possible biological effects of these increased interface temperatures at the cement-bone interface require further study.