Small and similar amounts of micromotion in an anatomical stem and a customized cementless femoral stem in regular-shaped femurs

Background and purpose — High primary stability is important for long-term survival of uncemented femoral stems. Different stem designs are currently in use. The ABG-I is a well-documented anatomical stem with a press-fit design. The Unique stem is designed for a tight customized fit to the cortical bone of the upper femur. This implant was initially developed for patients with abnormal anatomy, but the concept can also be used in patients with normal femoral anatomy. We present 5-year radiostereometric analysis (RSA) results from a randomized study comparing the ABG-I anatomical stem with the Unique femoral stem.

Patients and methods — 100 hips with regular upper femur anatomy were randomized to either the ABG-I stem or the Unique femoral stem. RSA measurements were performed postoperatively and after 3, 6, 12, 24, and 60 months.

Results — RSA measurements from 80 hips were available for analysis at the 5-year follow-up. Small amounts of movement were observed for both stems, with no statistically significant differences between the 2 types.

Interpretation — No improvement in long-term stability was found from using a customized stem design. However, no patients with abnormal geometry of the upper femur were included in this study.     

Periprosthetic bone loss after insertion of an uncemented, customized femoral stem and an uncemented anatomical stem. A randomized DXA study with 5-year follow-up

Background and purpose

Customized femoral stems are designed to have a perfect fit and fill in the femur in order to achieve physiological load transfer and minimize stress shielding. Dual-energy X-ray absorptiometry (DXA) is regarded as an accurate method for detection of small alterations in bone mineral density (BMD) around hip prostheses. We present medium-term DXA results from a randomized study comparing a customized and an anatomical femoral stem.

Methods

100 hips were randomized to receive either the anatomical ABG-I stem or the Unique customized femoral stem, both uncemented. DXA measurements were conducted postoperatively and after 3, 6, 12, 24, 36, and 60 months, and BMD was computed for each of the 7 Gruen zones in the proximal femur.

Results

Results from 87 patients were available for analysis. 78 completed the 5-year follow-up: 35 patients in the ABG group and 43 patients in the Unique group. In both groups, we found the greatest degree of bone loss in the proximal Gruen zones. In zone 1, there was 15% reduction in BMD in the ABG-I group and 14% reduction in the Unique group. In zone 7, the reduction was 28% in the ABG-I group and 27% in the Unique group. The only statistically significant difference between the groups was found in Gruen zone 4, which is distal to the tip of the stem, with 1.6% reduction in BMD in the ABG-I group and 9.7% reduction in the Unique group (p = 0.003).

Interpretation

5-year DXA results showed that because of stress-shielding, proximal bone loss could not be avoided—either for the anatomical ABG-I stem or for the customized Unique stem.Implantation of a prosthesis in the femur alters the load distribution in the host bone, and the femur remodels to adapt to the new mechanical situation (Engh and Bobyn 1988, Bobyn et al. 1992, Engh et al. 1999). A perfect fit and fill in the proximal femur is said to be important to achieve physiological load transfer (Laine et al. 2000). It has therefore been hypothesized that a customized femoral stem could fulfill the criterion for optimal fit and fill, and thus minimize stress shielding in the proximal femur (Bargar 1989). Based on numerical analyses, however, it has been claimed that canal-filling femoral stems may cause stress shielding and subsequently bone atrophy of the proximal femur (Huiskes et al. 1989).In vitro studies on human cadaver femurs have indicated that insertion of a customized stem gives a better pattern and distribution of cortical strains in the proximal femur than anatomical stems (Aamodt et al. 2001, Østbyhaug et al. 2009). In these studies, it was shown that 33–56% of the external cortical strains were retained on the proximal, medial aspect of the femur after insertion of a customized stem whereas the corresponding figure was 10–13% after insertion of a standard, anatomical stem. Long-term bone remodeling is, however, not necessarily reflected in the immediate postoperative mechanical situation in the femur as measured in experimental strain analyses.The present randomized, clinical study was undertaken to compare (by DXA) the medium-term changes in bone mineral density in the proximal femur after insertion of an uncemented, customized femoral stem and an uncemented, standard anatomical femoral stem.     

Good stability of a cementless,anatomically designed femoral stem in aging women: a 9-year RSA study of 32 patients

Background and purpose — We previously reported a transient, bone mineral density (BMD)-dependent early migration of anatomically designed hydroxyapatite-coated femoral stems with ceramic–ceramic bearing surfaces (ABG-II) in aging osteoarthritic women undergoing cementless total hip arthroplasty. To evaluate the clinical significance of the finding, we performed a follow-up study for repeated radiostereometric analysis (RSA) 9 years after surgery.

Patients and methods — Of the 53 female patients examined at 2 years post-surgery in the original study, 32 were able to undergo repeated RSA of femoral stem migration at a median of 9 years (7.8–9.3) after surgery. Standard hip radiographs were obtained, and the subjects completed the Harris Hip Score and Western Ontario and McMaster Universities Osteoarthritis Index outcome questionnaires.

Results — Paired comparisons revealed no statistically significant migration of the femoral stems between 2 and 9 years post-surgery. 1 patient exhibited minor but progressive RSA stem migration. All radiographs exhibited uniform stem osseointegration. No stem was revised for mechanical loosening. The clinical outcome scores were similar between 2 and 9 years post-surgery.

Interpretation — Despite the BMD-related early migration observed during the first 3 postoperative months, the anatomically designed femoral stems in aging women are osseointegrated, as evaluated by RSA and radiographs, and exhibit good clinical function at 9 years.     

5- to 13-year follow-up study on cementless femoral components in revision surgery

The 5- to 13-year follow-up data on 297 cementless revision arthroplasties with extensively coated components (Anatomic Medullary Locking femoral component, DePuy, Warsaw, IN) are reported. A basic classification of the femoral defects was developed. All patients were evaluated clinically and radiographically at a minimum of 60 months. Clinically, the average Postel-d'Aubigné score improved from 4.8 before to a 10.2 after surgery. Definite radiographic instability was noted in seven hips. Five patients were symptomatic and were revised. The mechanical failure rate was 2.4%. The overall complication rate was 5.7%, with a 2.6% dislocation rate. In the presence of bone loss in the proximal metaphyseal region of the femur, fixation of the femoral component is best achieved in the diaphyseal region of the femur using an extensively coated femoral component.     

Integral porous femoral stem: 5- to 8-year follow-up study

The outcome of total hip arthroplasty without cement was prospectively followed in patients who received a titanium taper wedge femoral component with a circumferential titanium plasma spray coating on the proximal surface (Integral femoral stem, Biomet, Warsaw, IN). One hundred ninety femoral components were implanted in 179 patients. Nine patients (9 hips) died prior to their 5-year examination, leaving 170 patients available for follow-up evaluation. Thirty-one of the 170 patients (33 hips) were lost at an intermediate follow-up period of 5 years (mean, 5.8 years, range; 5–8 years), giving a follow-up rate of 82% for patients and hips. The preoperative diagnoses included osteoarthritis (91 hips), avascular necrosis (38), post-traumatic arthritis (10), rheumatoid arthritis (4), congenital dislocation of the hip (3), and fractures (2). The 78 men and 61 women had a mean age of 55 years (range, 18–81 years) and a mean weight of 81 kg (range, 50–136 kg). Preoperative Harris pain and function scores for the hip were 19.9 (range, 0–40) and 55.6 (range, 12–84), respectively. At the most recent follow-up visit, the mean pain score increased to 41.2 (range, 10–44) and the mean function score increased to 93.5 (range, 6–100). Thigh pain was present in 4% of the hips at the most recent follow-up visit. Radiographically, 99% of the femoral components demonstrated spot welds in the porous-coated zone. Two hips had demarcation of the femoral component in the porous-coated zone consistent with fibrous fixation. None of the femoral stems had been revised and there were no signs of aseptic loosening. Additionally, there were no cases of pain that could be directly attributed to the stem and there was no evidence of distal femoral osteolysis. It is concluded that the Integral femoral stem provides excellent clinical and radiographic results at intermediate follow-up periods.     

A randomized clinical trial of cementless femoral stems with and without hydroxyapatite/tricalcium-phosphate coating: an 8- to 12-year follow-up study

To evaluate the effect of hydroxyapatite coating on cementless femoral stem, a prospective randomized clinical trial was conducted. A total of 84 hips from 69 patients were assigned to a hydroxyapatite/tricalcium-phosphate-coated group or a noncoated group. Thirty-two patients (37 hips) who received hydroxyapatite/tricalcium-phosphate-coated stems and 31 patients (38 hips) who received noncoated stems were followed for an average of 127 months. Forty-nine patients (78%) were men, and the average age was 45.5 years. Preoperative diagnosis was osteonecrosis in 62 hips (83%). The mean Harris hip score at the time of final follow-up was 91 points in the coated group and 90 points in the noncoated group. Six acetabular components (3 in each group) were revised. One femoral stem in the noncoated group was loose. There was no statistical difference in the survival distributions of the implants between the 2 groups.     

Efforts to improve cementless femoral stems in THR: 2- to 5-year follow-up of a high-offset femoral stem with distal stem modification (Secur-Fit Plus)

A retrospective review of 81 sequential primary total hip arthroplasties using a cementless, high-offset femoral stem was performed. Follow-up was 24 to 60 months. The average age at the time of surgery was 54 years. The femoral bone types were: 36% Dorr A, 51% Dorr B, and 13% Dorr C. The mean postoperative Harris Hip Score was 95. The mean postoperative Oxford score was 17. Eighty-five percent had no clinical leg-length difference. All stems were radiographically stable. The stem features of hydroxyapatite coating on a rough circumferential titanium arc-deposit proximal surface in conjunction with distal flutes seem to provide immediate stability, making this implant clinically versatile. Potential benefits of increased offset include improved joint stability and avoidance of leg lengthening.     

Total hip arthroplasty using cementless grit-blasted femoral component: a minimum 10-year follow-up study

The grit-blasted cementless Spotorno (CLS) stem, which has excellent survival rates up to 10 years, is widely used in total hip arthroplasty (THA). We investigated the survivorships of CLS stems in THA at a minimum follow-up of 10 years and sought to identify factors that influence outcomes. A total of 227 hips of 191 patients who underwent cementless THA with a CLS stem were retrospectively reviewed at a mean follow-up of 12.3 years. All patients were evaluated clinically and radiographically according to implant type and surgery-related and patient-related factors. Survivorship was 97.2% when femoral revision for any reason was defined as the end point. Femoral revisions were performed in 3 hips because of periprosthetic fractures. Survivorship for all hips, using revision for any reason as the end point, was 92.6%. Two metal-on-metal THAs were revised because of aseptic loosening or osteolysis around the cup. No significant differences were evident for type of stem, type of bearing surface, stem alignment, or patient-related factors. However, a canal fill index of 80% or less was found to affect cortical remodeling, subsidence, and a change in stem position of 5° or more, which indicates that care must be taken not to undersize stems. In addition, in view of the revisions performed, bearing surfaces appear to importantly influence THA survivorship.     

Grit-blasted titanium femoral stem in cementless primary total hip arthroplasty: a 5- to 10-year multicenter study

A total of 133 cementless primary total hip arthroplasties using the Zweymuller-Alloclassic grit-blasted titanium tapered stem were performed in 3 institutions. The patient cohort was divided into 2 subgroups, nonselected and selected, on the basis of excellent bone stock and age (<65 years old at surgery). Acetabular components were all cementless, and bearing surfaces were all alumina-ceramic on polyethylene. After a 7.3-year average follow-up period (range, 5-10 years), 118 primary femoral replacements in 109 patients could be reviewed fully. Mean age at surgery was 55.7 years (range, 27-84 years). According to the Merle d'Aubigne and Charnley rating system, clinical results were graded excellent and good in 89% of hips and fair in 11%. Radiologically, early subsidence >2 mm could be detected in 4 hips (3.4%). Calcar atrophy and spot welds were noted in 77% and 82% of hips. Femoral osteolysis granuloma was noted in 4 hips (3.4%). There has been no stem fracture and no ceramic head breakage. The survivorship at 10 years with definite femoral aseptic loosening (radiographic failure) as the endpoint was 100% (95% Wilson confidence interval, 78.4%-100%; worst scenario, 95.4%). A significant difference between the nonselected and selected patient subgroups was observed only for early reoperation (P =.03) and proximal stress shielding (P =.01). Press-fitting but not filling the femoral canal with a rough titanium, straight, tapered femoral component represents, at intermediate follow-up, a promising cementless option in primary total hip arthroplasty.     

Early migration characteristics of a hydroxyapatite-coated femoral stem: an RSA study

Measurement of early stem subsidence can be used to predict the likelihood of long-term femoral component loosening and clinical failure. Data that examines the early migration pattern of clinically proven stems will provide clinicians with useful baseline data with which to compare new stem designs. This study was performed to evaluate the early migration pattern of a hydroxyapatite-coated press-fit femoral component that has been in use for over ten years. We enrolled 30 patients who underwent THA for osteoarthritis. The median age was 70 years (range, 55–80 years). Patients were clinically assessed using the Harris hip score. Radiostereometric analysis was used to evaluate stem migration at three to four days, six months, one year and two years. We observed a mean subsidence of 0.73 mm at six months, 0.62 mm at one year and 0.58 mm at two years and a mean retroversion of 1.82° at six months, 1.90° at one year and 1.59° at two years. This data suggests that subsidence is confined to the first six months after which there was no further subsidence. The results from this study can be compared with those from novel cementless stem designs to help predict the long-term outcome one may expect from new cementless stem designs.     

Periprosthetic bone loss after insertion of an uncemented,customized femoral stem and an uncemented anatomical stem

Background and purpose Customized femoral stems are designed to have a perfect fit and fill in the femur in order to achieve physiological load transfer and minimize stress shielding. Dual-energy X-ray absorptiometry (DXA) is regarded as an accurate method for detection of small alterations in bone mineral density (BMD) around hip prostheses. We present medium-term DXA results from a randomized study comparing a customized and an anatomical femoral stem.

Methods 100 hips were randomized to receive either the anatomical ABG-I stem or the Unique customized femoral stem, both uncemented. DXA measurements were conducted postoperatively and after 3, 6, 12, 24, 36, and 60 months, and BMD was computed for each of the 7 Gruen zones in the proximal femur.

Results Results from 87 patients were available for analysis. 78 completed the 5-year follow-up: 35 patients in the ABG group and 43 patients in the Unique group. In both groups, we found the greatest degree of bone loss in the proximal Gruen zones. In zone 1, there was 15% reduction in BMD in the ABG-I group and 14% reduction in the Unique group. In zone 7, the reduction was 28% in the ABG-I group and 27% in the Unique group. The only statistically significant difference between the groups was found in Gruen zone 4, which is distal to the tip of the stem, with 1.6% reduction in BMD in the ABG-I group and 9.7% reduction in the Unique group (p = 0.003).

Interpretation 5-year DXA results showed that because of stress-shielding, proximal bone loss could not be avoided—either for the anatomical ABG-I stem or for the customized Unique stem.     

The ESOP-HA modular cementless femoral stem: a study of the results of 165 hip arthroplasties with a minimum of 10-year follow-up

The authors report on more than 10 years’ experience of using a cementless femoral stem, with a two-piece modular design, for indications of primary prosthetic replacement. One hundred and sixty-five prostheses, inserted between 06/11/1991 and 31/12/1994, were reviewed. No patient was lost to follow-up. The probability of 10-year survival of these hip prostheses was assessed using the actuarial Kaplan–Meier method (the endpoint was revision of the arthroplasty regardless of the reason: failure of the femoral or acetabular component, fracture of one piece of the implant etc.). The mean age of the 165 patients (84 women, 81 men) was 64 years. The clinical results were excellent or good in 87.2% of hips. There was no instance of post-operative thigh pain (apart from one case), because of the primary stability of the hydroxyapatite-coated metaphyseal part where stress transmission occurs, while the diaphyseal part, selected in accordance with requirements and smaller in diameter than the femoral canal, remained free in the diaphysis. No significant difference in the results was noted in accordance with the pattern of femoral anatomy encountered; however, the cylindrical femur yielded slightly inferior results (PMA score). Radiological follow-up showed that femoral fixation had been obtained, generally accompanied by obvious signs of bone fixation (endosteal ossification, radiolucencies indicating condensed bone in the smooth zone). A high number of cortical changes was not noted. Two stems were the cause of revision surgery, one because of thigh pain without sealing, the other because the stem fractured. Six acetabular implants were removed without interfering with the femoral stem, because of localised osteolysis around an expandable peg. Two other acetabular implants were replaced: one because poor positioning resulted in recurrent luxation and the other for premature wear of the polyethylene after 7 years. The grounds for revision were failure of the acetabular implant in 8 cases out of 10. Thus, there is sufficient justification for the use of this modular two-piece stem, which has fulfilled its purpose in the majority of patients, enabling us to extend with confidence indications for the cementless stem to all the anatomical types of femur encountered. Our series of patients included almost 78.7% of what are known as “normal” femurs, but in the remaining cases (21.3%) or in more than one in five instances, the modular stem made it possible to extend the indications for a cementless prosthesis to all the patterns of femur encountered, in particular to young adults, who often have femoral dysplasia or a cylindrical femur. The survival curve reflects the life of the implant: implant survival is 96.3%. If acetabular revisions are not included it is 98.8%. Conclusions: A modular system then, consisting of a metaphyseal and diaphyseal part, appears to be a first-rate component which optimises the indication for implantation of a cementless femoral prosthesis in order to obtain the correct performance of a medical service as the survival curve demonstrates.     

A ten- to 15-year follow-up of the cementless spotorno stem

We followed the first 354 consecutive implantations of a cementless, double-tapered straight femoral stem in 326 patients. Follow-up was at a mean of 12 years (10 to 15). The mean age of the patients was 57 years (13 to 81). At follow-up, 56 patients (59 hips) had died, and eight (eight hips) had been lost to follow-up. Twenty-five hips underwent femoral revision, eight for infection, three for periprosthetic fracture and 14 for aseptic loosening. The overall survival was 92% at 12 years (95% CI 88 to 95). Survival with femoral revision for aseptic loosening as an endpoint was 95% (95% CI 92 to 98). The median Harris hip score at follow-up was 84 points (23 to 100). Radiolucent lines (< 2 mm) in Gruen zones 1 and 7 were present in 38 (16%) and 34 hips (14%), respectively. Radiolucencies in zones 2 to 6 were found in five hips (2%). The results for mid- to long-term survival with this femoral component are encouraging and compare with those achieved in primary cemented total hip arthroplasty. The high rate of loosening of the cup and the high rate of pain are, however, a source of concern.     

Prospective 5- to 6-year follow-up study of a cementless acetabular cup

Twenty-seven patients in whom the Ti-Bac acetabular cup (Zimmer, Warsaw, IN) was placed were examined 5 to 6 years after surgery. The cup was inserted line to line, after reaming without further fixation. In all operations, a cemented Müller straight-stem Protazul femur stem (Zimmer) was used. The patients had good pain relief and improved mobility after the operation. Radiographically, only one hip showed radiolucency in the bone—metal interface after 5 to 6 years. One patient was reoperated 3 days after surgery because of dislocation of the acetabular cup. Apart from this, there were no signs of aseptic loosening of any of these uncemented cups.     

A new cemented femoral stem: a prospective study of the Stryker accolade C with 2- to 5-year follow-up

This prospective study evaluates the short-term results of a recently released cemented femoral stem design in primary cemented and hybrid total hip arthroplasty (THA). There were 100 all-cemented and 100 hybrid THAs in the 2-year study group. Good to excellent results were obtained in 96%. There was one reoperation for recurrent dislocation in each cohort (1%) and one single-staged reoperation for sepsis in the cemented cohort. There were 47 THA available for 5-year follow-up. Good to excellent results were maintained in 98%. One additional patient had a revision because of late recurrent dislocation. This study has demonstrated excellent early results and safety with this cemented femoral stem. The features include a dual-wedge geometry with a 0.88-microm Ra surface roughness, proximal macro-normalizations, distal anti-rotation grooves, and an optimized head-and-neck ratio approaching 4:1 using a standard 28-mm head.     

The migration pattern of the Charnley femoral stem: a five-year follow-up RSA study in a well-functioning patient group

Background

Implant stability is considered vital to long-time implant survival in total hip arthroplasty (THA), since loose implants are reported to be a major cause of hip revision. There is an association between early implant micromotion and increased risk of revision. More implant-specific data are needed to establish acceptable levels of early implant movement.

Materials and methods

Thirty-five patients (36 hips) undergoing Charnley THA were followed with repeated clinical, radiographic, and radiostereometric analysis (RSA) over 5 years. Twenty-three patients attended 5 years postoperatively.

Results

The patient group was well functioning based on the radiological and clinical evaluations. The stems constantly moved up to 5 years postoperatively, with subsidence, retroversion, and varus tilt, based on the RSA.

Conclusion

Continuous movement of the Charnley stem was observed up to 5 years postoperatively in a well-functioning patient group. The migration data presented herein could be useful when defining acceptable migration limits for certain types of cemented femoral stems.     

Mid-term results of the cementless CLS stem. A 7- to 11-year follow-up study

Between 1986 and 1990, 335 primary total hip arthroplasty (THA) were performed using the cementless CLS stem. The mean age at surgery was 55.3 years. The retrospective study was performed at an average follow-up time of 8.9 years. A total of 232 patients (69.3%) underwent clinical and radiological examination, 33 patients (9.9%) were interviewed by telephone, and 9 stems (2.7%) had been replaced meanwhile. The mean Harris hip score was 91.7 points, and the mean Merle D'Aubigne score was 16.8 points. One stem had subsided during the first postoperative year. Ectopic ossifications classified as Brooker III were noted in 5.7%, with no Brooker IV being seen. Radiolucent lines were found in 43.5%, and 11% showed enlargement with time. Focal osteolyses were present in 36%, of which 24% progressed with time. At the latest follow-up, we did not find any stem loosening clinically or radiologically.     

Straight tapered titanium stem with alumina bearing in cementless primary total hip arthroplasty: a minimum 5-year follow-up

The aim of this study was to assess the midterm results of primary cementless total hip arthroplasty using a tapered stem and alumina bearing couple in active patients. After a minimum of 5 years of follow-up, 78 arthroplasties in 72 patients were reviewed retrospectively. The mean Harris hip score was 94 points, and 2 hips had thigh pain. All components radiographically demonstrated stable fixation by bone ingrowth and mild stress shielding of the proximal femur were noted in 14% of hips. There was no significant osteolysis or aseptic loosening. There was a ceramic head fracture in 1 hip and audible sounds in 2 hips. The results of total hip arthroplasty with a straight, tapered, proximally porous-coated stem and alumina-on-alumina bearing were encouraging for active patients.     

Treatment of displaced femoral neck fractures: A randomized minimum 5-year follow-up study of screws and bipolar hemiprostheses in 100 patients

In a randomized study of 100 patients having displaced femoral neck fractures (Garden types 3-4), we compared internal fixation using 2 von Bahr screws (n = 53) with a bipolar Variokopf prosthesis (n = 47) . The duration of surgery was shorter and the blood loss was less in the group with screws. Dislocation of the prosthesis occurred in 7/47 patients, all within 4 months. After a minimum follow-up of 5 years, 34 of 53 patients had been reoperated on in the screw group and 3/47 patients in the prosthesis group. No differences in patient mortality were noted between the groups after 2 or 5 years. The bipolar prosthesis seems to be a suitable alternative for primary treatment of displaced femoral neck fractures.