Increased loosening of cemented straight stem prostheses made from titanium alloys. An analysis and comparison with prostheses made of cobalt-chromium-nickel alloy

We studied the rate of aseptic loosening of three different types of femoral stems in primary total hip replacement. After a median follow-up of 10.2 years 4/147 CoCrNi (SS77) straight stems (type M.E. Müller) were revised. After a median follow-up of 7.7 years 32/239 Ti-6A1-7Nb (SS77) were revised and after a median follow-up of 5.2 years 52/203 SLS Titanium alloy stems were revised. Whereas the first two stems are of identical design (smooth-blasted, anterior and posterior collar), the SLS stem design is different. Surgical procedure and cementing technique have remained unchanged. There is a significantly higher risk of failure for smaller titanium stem sizes and in males and patients who are physically active. This indicates that the greater elasticity of the Titanium alloy is one of the factors responsible for loosening.     

Long-term outcome of cemented total hip arthroplasty with the Charnley-type femoral stem made of titanium alloy

BackgroundTotal hip arthroplasty is a successful treatment for hip diseases including osteoarthritis, osteonecrosis of the femoral head, and rheumatoid arthritis. Various designs of cemented femoral stems made of stainless steel and titanium alloy have been used. Among them, Charnley-type femoral stems made of stainless steel have often been reported to have good long-term outcome. However, the long-term outcome of the Charnley-type femoral stem made of Ti alloy is yet to be reported. We conducted a retrospective study to assess the long-term outcome of cemented primary total hip arthroplasty with the Charnley-type femoral stem made of Ti alloy.MethodsBetween October 1988 and February 1997, 341 cemented primary total hip arthroplasties with the Charnley-type femoral stem made of Ti alloy were consecutively performed in our hospital. Among these, 164 patients (211 hips) who underwent this procedure were followed up for more than 12 years, and the surgical hips were analysed clinically and radiologically. The mean follow-up period was 20.6 years. Kaplan–Meier survival analyses were performed to assess femoral component survival. Factors affecting stem revision for aseptic loosening were also investigated using log-rank tests.ResultsIn the functional assessment, the preoperative Japanese Orthopaedic Association score significantly improved from 47.2 points preoperatively to 79.0 points at the final follow-up. Eventually, 33 femoral stems were revised, of which 12 were revised for aseptic loosening. In the Kaplan–Meier survival analysis, the 20-year survival rates with stem revision for aseptic loosening and radiological stem loosening at the end points were 95.9% and 97.1%, respectively. Original diagnosis (non-osteoarthritis) was the only significant factor for aseptic loosening of the femoral stem.ConclusionsCemented primary total hip arthroplasty with the Charnley-type femoral stem made of Ti alloy showed excellent outcomes for more than 20 years.     

A retrieval study of capital hip prostheses with titanium alloy femoral stems.

We have examined 26 retrieved, failed titanium-alloy femoral stems. The clinical details, radiological appearances and the histology of the surrounding soft tissues in each patient were also investigated. The stems were predominantly of the flanged design and had a characteristic pattern of wear. A review of the radiographs showed a series of changes, progressive with time. The first was lateral debonding with subsidence of the stem. This was followed by calcar resorption and fragmentation or fracture of the cement. Finally, osteolysis was seen, starting with a radiolucency at the cement-bone interface and progressing to endosteal cavitation. Three histological appearances were noted: granulomatous, necrobiotic and necrotic. We suggest that an unknown factor, possibly related to the design of the stem, caused it to move early. After this, micromovement at the cement-stem interface led to the generation of particulate debris and fracture of the cement. A soft-tissue reaction to the debris resulted in osteolysis and failure of fixation of the prostheses.     

Primary stability of cementless implanted hip stems made of titanium alloy with metaphyseal fixation. A prospective clinical Roentgen-Stereometry-Analysis (RSA) study

AIM: Under early mobilisation and full weightbearing the primary stability of two different cementless hip stems should be examined by using Roentgen Stereometric Analysis (RSA). METHOD: 26 patients (slashed circle 60.8+/-7.5 J., 16 m, 10 w, BMI 27.7+/-3.9 kg/m2) received a total hip arthroplasty with an anatomical designed image-stem (IS) (Smith & Nephew, Schenefeld, Germany), 20 patients (slashed circle 60.0+/-10.9 J., 12 m, 8 w, BMI 27.5+/-3 .7 kg/m2) the Bicontact-stem (BS) (Aesculap, Tuttllingen, Germany). RSA measurements were done before mobilizing, 3 and 6 weeks, 3, 6, 12 and 24 months postoperatively. Furthermore the patients had to estimate their pain on a visually scale (VAS). We registrated the Harris-Hip-Score (HHS) and the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC). RESULTS: Both stems showed the maximum of subsidence in the first 3 months (IS 0.647 mm, BS 0.54 mm). 6 months postoperative the measured migrations were in the range of the accuracy. After 2 years the subsidence was 1.07 mm+/-0.07 mm for the IS-group, 0.97 mm+/-0.18 mm for the BS-group. There were no significant differences in the examined parameters between the both groups. An excellent prostheses function and high activity grade with a high WOMAC score, a high HHS and a low VAS was founded for both groups. CONCLUSION: Both cementless implanted titanium hip stems showed a sufficient primary and midterm stability with excellent clinical results. The measured migrations do not differ from those given in literature for cemented stems.     

A comparison of cemented and cementless titanium femoral components used for primary total hip arthroplasty: a radiographic and survivorship study

Titanium has a low modulus of elasticity that makes it an attractive metal for femoral hip components. We directly compared 2 similar titanium stems, one cemented (n = 102 hips) and the other cementless (n = 78 hips), controlling for the most important surgical variables. The average radiographic follow-up was 6.7 and 7.0 years. Osteolysis below the joint line, zones 2 through 6, was 12.7% (13 of 102) in the cemented group and 0% in the cementless group (P<.001). There were 17 acetabular revisions in each study group. The cementless group had no femoral revisions, whereas 9 acetabular revisions in the cemented group had a simultaneous femoral revision (P=.005). Survivorship, defined as revision of the femur, was 84% for the cemented group and 100% for the cementless group at 10 years. Cementless titanium stems are more resistant to osteolysis and mechanical failure compared with similar cemented titanium stems.     

Increased varus-valgus tilting of screw-fixated knee prostheses: Stereoradiographic study of uncemented versus cemented tibial components

Twenty-six women and three men (34 knees) with osteoarthrosis were operated with the Miller-Galante I (Zimmer, Warsaw, IN) knee prosthesis. The patients were randomized to either cemented or uncemented fixation of the tibial component. All patients received a TiVaAl alloy tibial plate with four pegs and titanium fiber-mesh undersurface. In the uncemented knees four screws were added. The fixation of the tibial component was determined by roentgen stereophotogrammetric analysis during the first 2 postoperative years. Rotations of the entire tibial component were recorded, as well as proximal or distal translation of various parts of the prosthetic edge corresponding to subsidence and lift-off. The uncemented components displayed almost all rotation and translation during the first 6 weeks, whereas the cemented ones displayed a more gradually increasing migration during the 2 years. Tibial component rotation about the sagittal axis was significantly increased in the uncemented knees throughout the investigation period. This corresponded to increased subsidence medially or laterally in the uncemented knees, whereas lift-off was equal in the two groups. Thin (8.5 mm) uncemented tibial components displayed more subsidence than the thicker ones at the medial or lateral edge 3 months after surgery.     

Influence of stem geometry on mechanics of cemented femoral hip components with a proximal bond

Nonlinear, three-dimensional, finite element models of cemented femoral hip components with a proximal stem-Cement bond were developed with use of a Charnley stem geometry and a modified Charnley stem geometry that had a cylindrical cross section over the distal two-thirds of the stem (Distal-Round). Peak tensile stresses in the proximal cement mantle increased 63 and 74% for the Charnley and Distal-Round stems, respectively, when the proximal stem-cement interface was debonded, The shear stresses over the stem-cement interface with a proximal bond were 29%. larger for the Distal-Round stem than for the Charnley stem. After the proximal stem-cement interface was debonded. the peak tensile stresses in the cement mantle were 15% larger for the Distal-Round stem than for the Charnley stem. The results illustrate that stresses within the proximal cement mantle could be substantially reduced for both Charnley and Distal-Round stems through use of a proximal stem-cement bond. However, the risk of debonding may be higher for the Distal-Round stem because of increased shear stresses, and once debonded the risk of further loosening due to failure of the cement mantle would also be higher for the Distal-Round stem.     

5-year clinical and radiostereometric analysis (RSA) follow-up of 39 CUT femoral neck total hip prostheses in young osteoarthritis patients

Background As the number of young patients receiving total hip arthroplasty increases, bone-saving implantations facilitating possible future revision, such as the CUT femoral neck prosthesis, are gaining importance. There have been few medium-term results reported for this prosthesis, however, and its migration pattern has not been analyzed.

Patients and methods 39 consecutive CUT femoral neck prostheses were implanted in 32 patients, mean age 37 (17–58) years, with symptomatic osteoarthritis and either less than 55 years of age or with an anatomic anomaly preventing implantation of a diaphyseal stem (n = 1). Patients were followed prospectively using routine clinical examination and radiostereometric analysis (RSA) at 6, 12, 26, and 52 weeks postoperatively and annually thereafter. This study evaluated the 5-year follow-up results.

Results The mean Harris hip score increased from 26 (3–51) points preoperatively to 84 (66–98), 86 (55–98), and 87 (47–98) points at 3, 12, and 60 months. 3 stems were revised: 1 after luxation following excessive subsidence due to an undersized component and 2 due to persistent strong thigh pain. 5-year survival was 95% (95% CI: 87–100). Initial migration varied widely in magnitude; median total tip migration was 0.42 mm (0.09–9.4) at 6 weeks, 0.92 mm (0.18–5.9) at 1 year, and 1.10 mm (0.13–6.4) at 5 years. Even after high initial migration, stabilization was achieved in 31 of the 35 RSA-evaluable implants. 3 prostheses showed progressive continuous migration throughout the entire follow-up period, and were considered to be loose, suggesting reduced long-term survival.

Interpretation Currently, we cannot recommend the CUT femoral neck prosthesis as a routine treatment option in (young) patients requiring THA. The CUT prosthesis may not reach the 90% survival benchmark at 10 years, and the prosthesis is difficult to implant. If initial stabilization is achieved, however, aseptic loosening is unlikely. A good clinical outcome was seen in the surviving prostheses. We will continue to follow this patient group.     

5-year clinical and radiostereometric analysis (RSA) follow-up of 39 CUT femoral neck total hip prostheses in young osteoarthritis patients

Background As the number of young patients receiving total hip arthroplasty increases, bone-saving implantations facilitating possible future revision, such as the CUT femoral neck prosthesis, are gaining importance. There have been few medium-term results reported for this prosthesis, however, and its migration pattern has not been analyzed. Patients and methods 39 consecutive CUT femoral neck prostheses were implanted in 32 patients, mean age 37 (17-58) years, with symptomatic osteoarthritis and either less than 55 years of age or with an anatomic anomaly preventing implantation of a diaphyseal stem (n = 1). Patients were followed prospectively using routine clinical examination and radiostereometric analysis (RSA) at 6, 12, 26, and 52 weeks postoperatively and annually thereafter. This study evaluated the 5-year follow-up results. Results The mean Harris hip score increased from 26 (3-51) points preoperatively to 84 (66-98), 86 (55-98), and 87 (47-98) points at 3, 12, and 60 months. 3 stems were revised: 1 after luxation following excessive subsidence due to an undersized component and 2 due to persistent strong thigh pain. 5-year survival was 95% (95% CI: 87-100). Initial migration varied widely in magnitude; median total tip migration was 0.42 mm (0.09-9.4) at 6 weeks, 0.92 mm (0.18-5.9) at 1 year, and 1.10 mm (0.13-6.4) at 5 years. Even after high initial migration, stabilization was achieved in 31 of the 35 RSA-evaluable implants. 3 prostheses showed progressive continuous migration throughout the entire follow-up period, and were considered to be loose, suggesting reduced long-term survival. Interpretation Currently, we cannot recommend the CUT femoral neck prosthesis as a routine treatment option in (young) patients requiring THA. The CUT prosthesis may not reach the 90% survival benchmark at 10 years, and the prosthesis is difficult to implant. If initial stabilization is achieved, however, aseptic loosening is unlikely. A good clinical outcome was seen in the surviving prostheses. We will continue to follow this patient group.     

Early failure of revision total hip arthroplasty with cemented precoated femoral components: comparison with uncemented components at 2 to 8 years

This is a retrospective analysis of 2 methods of fixation of the femoral component in 86 consecutive revision arthroplasties, for which all clinical and radiographic data were recorded prospectively. There were 56 cemented revisions using precoated femoral components followed for 2 to 8 years (mean, 4 years) and 30 uncemented, proximally porous-coated femoral revisions followed for 2 to 6 years (mean, 4 years). Of the 56 cemented hips, 31 (55%) had a good or excellent clinical result. Rerevision has been performed in 10 hips, and revision of 3 loose femoral components is pending (23%). Radiographic review of 56 femoral components showed that 16 (29%) had probable or definite loosening. Of 30 cementless hips, 24 (80%) had a good or excellent clinical result. There was radiographic bone ingrowth in 22 of 30 hips (73%). Seven hips (23%) had nonprogressive subsidence, and 3 hips (10%) had progressive subsidence or loosening. Rerevision has been performed in only 2 hips (7%). The high rate of loosening (29%) and rerevision (23%) at a mean follow-up of only 4 years suggests that a precoated femoral component may place increased stress at the already damaged bone-cement interface.     

Revision of cemented hip arthroplasties: 101 hips followed for 5 (4-9) years

101 hips were revised with cemented Lubinus prostheses after failed primary cemented arthroplasty, and followed for 5 (4-9) years. Radiographically, 41 hips (36 femoral stems and 13 acetabular components) had become loose. The use of an intramedullary plug at the revision did not prevent sinking of the prosthesis. No difference was found between conventional or pressure-injection cementation techniques. In cases where the stem was inserted in varus or the acetabular component was in malposition there was increased loosening. Patients below 50 years of age had oftener more than 5 mm sinking of the stem and more prosthesis loosenings.     

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.     

Movement patterns of the C-stem femoral component: an RSA study of 33 primary total hip arthroplasties followed for two years

We used roentgen stereophotogrammetric analysis to follow 33 C-stem femoral components for two years after primary total hip arthroplasty. All components migrated distally and posteriorly within the cement mantle. The mean distal migration was 1.35 mm (sd 0.62) at two years and the mean posterior migration was 1.35 mm (sd 0.69) at two years. All the femoral components rotated into retroversion with a mean rotation at two years of 1.9 degrees (sd 1.1). For all other directions, the prosthesis was stable up to two years. Compared with other tapered prostheses, the distal migration of the C-stem is the same, but posterior rotation and posterior migration are greater.     

Inducible displacements of the cup and the femoral head during active range of motion: Dynamic RSA studies of cemented total hip replacements

We evaluated changes in position of the femoral head relative to the cup and of the cup relative to the pelvis in total hip replacement patients during hip motion 2 years postoperatively. Two patient groups with nine patients in each group were studied. Hip motions, translations of the femoral head center, and cup displacements were recorded with dynamic radiostereometric examination (RSA, 2 exposures/s) during abduction in Group 1 and with use of static RSA exposures at increasing flexion of the hip in Group 2. Conventional radiographic examinations were used to evaluate any radiolucent lines around the cups at 2 years. During active abduction the femoral head center moved medially (median 0.04 mm) and the cup tilted anteriorly (median 0.09 mm). Increments in radiolucent lines at 2 years correlated to medial femoral head penetration, posterior tilt, and retroversion of the cup at 20° of abduction. The extension of radiolucent lines at 2 years showed a positive correlation with proximal inducible displacement of the cup and posterior translation of the femoral head center at maximum hip flexion. Our observations may be of value in understanding the pathogenesis of the loosening process and may be used to facilitate the development of prosthetic designs that optimize hip kinematics. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1686–1693, 2013     

A comparison of collared and collarless femoral components in primary cemented total hip arthroplasty: a randomized clinical trial

Between July 1986 and November 1989, 437 consecutive primary cemented total hip arthroplasties were performed using a straight-stemmed titanium alloy femoral component. Collared and collarless versions of this identical stem were randomly chosen by computer allowing a comparison between 213 collared stems (198 patients) and 224 collarless stems (209 patients). Diagnosis, sex, weight, and average age (72.8 years, collared; 72.0 years, collarless) were similar. Follow-up averaged 76 months (collared) and 72 months (collarless) with 49 patients followed for at least 10 years. Calcar-collar contact was noted in 205 hips (96%) on the initial postoperative radiograph. Early complications, including dislocations (5% each group), were similar. Late complications included 3 deep infections (2 collared, 1 collarless) and 2 postoperative femur fractures (1 each). Hip scores at the most recent follow-up averaged 91.2 and 90.1 in the collared and collarless groups. No or slight pain was noted in 93% of collared and 91.5% of collarless hips. Although no radiographic differences were noted in distal cortical hypertrophy, stem subsidence, and osteolysis, collarless hips lost significantly more medial femoral neck cortical bone (average 0.90 mm vs 0.63 mm). A higher incidence of radiolucent lines in femoral zone VI (20.7% vs 9.4%) was also noted in collarless hips.     

The cone hip stem: a prospective study of 13 patients followed for 5 years with RSA

We operated on 13 patients (14 hips) with dysplastic hips, mean age 42 (28-58) years, with a cementless Cone stem and followed them for 5 years, using the Merle d'Aubigné clinical score, conventional radiography and repeated radiostereometry analyses. The clinical scores improved markedly at 4 months and still more throughout the study. None of the patients complained of thigh pain. No stem showed radiographic subsidence, but 3 stems had radiolucent zones probably indicating fibrous ingrowth. Micromigration was measured at 4 months, 1, 2 and 5 years. The mean subsidence after 5 years was 0.27 mm and the mean posterior micromigration of the head was 0.74 mm. Most of the micromigration took place within the first 4 months. We conclude that the uncemented Cone stem used in dysplastic hips has shown a good clinical outcome so far and was found to be stable on conventional radiographs and using RSA technique.     

Migration of cemented stem and restrictor after total hip arthroplasty: a radiostereometry study of 25 patients with Lubinus SP II stem

The aim of this study was to investigate the migration pattern of the Lubinus SP II prosthesis stem. Migration at the stem-cement and at the bone-cement interface was assessed. Twenty-five patients were studied by radiostereometry during a period of 2 years. The migration of the head, of 2 points on the collar, of the stem tip, and also of the cement restrictor, was measured. The collar and the head were found stable at 2 years' follow-up, whereas an anterior migration occurred at the stem tip (median, 0.3 mm; 25th percentile, 0.04 mm; 75th percentile, 1.27 mm). Virtually no subsidence or axial rotation of the stems was observed. An anterior migration of the restrictor marker was also observed, compatible with a rigid sagittal plane rotation of the stem and of the cement mantle about the collar. Therefore, stem tip migration occurred at the bone-cement interface. Key words: total hip arthroplasty, anatomic stem, radiostereometry, subsidence, bone-cement interface.     

Inferior performance of Boneloc® bone cement in total knee arthroplasty: A prospective randomized study comparing Boneloc® with Palacos® using radiostereometry (RSA) in 19 patients

We compared Boneloc® bone cement with conventional cement (Palacos®) in fixating the tibial component during 2-5 years in 19 patients with gonarthro-sis undergoing total knee arthroplasty in a prospective randomized study. Boneloc displayed significantly larger migration, subsidence and lift-off than Palacos. The difference was identifiable already within 3 months postoperatively, but became significant at 12 months. In the Boneloc group, all components showed subsidence of the posterior part and lift-off of the anterior part of the tibial component, whereas in the Palacos group, the locations of subsidence and lift-off were evenly distributed about the edge of the implant. At 5 years, both Boneloc knees so far investigated were clinical failures with high migration rates. We conclude that, even in total knee arthroplasty, there is a substantial risk that Boneloc leads to inferior clinical results, but later than in hip replacements.