Uncemented Cup Research Articles

Aseptic Loosening of an Uncemented Acetabular Cup

Aseptic Loosening of an Uncemented Acetabular Cup

Preliminary experience with isoelastic total hip arthroplasty using impaction bone grafting

Isoelastic THA using an uncemented acetabular cup fixed with pegs and screws along with a femoral stem containing a core of metal inside polyacetyl resin was used in 51 hips with an average follow up of 4 years 10 months. All cases were immobilized in abduction for 6 weeks post operative with deferred full weight bearing for another 6 weeks. One case failed due to deep infection, and one had extra medullary placement of the distal prosthesis. All others had improvement in the pain and function score; 2 patients were unsatisfied with the result. Excessive femoral reaming was avoided as we preferred to leave behind the “living” cancellous bone to promote ingrowth along the prosthesis. This procedure may be a good alternative in young adults where cemented THA is not the procedure of choice. We attribute the good short term results in this series to the rigid post operative immobilisation (which we have labelled as the “critical period”), filling up of the medullary canal with our technique of bone graft paste prior to prosthesis insertion, and leaving behind the endosteal cancellous bone inside the medullary cavity which possibly hastens bony incorporation of the femoral stem. A unique point in this study was our attempt to study bone formation around the prosthesis by axial CT scans, the results of which are discussed.

The Norwegian Arthroplasty Register: 11 years and 73,000 arthroplasties.

In 1985, the Norwegian Orthopaedic Association decided to establish a national hip register, and the Norwegian Arthroplasty Register was started in 1987. In January 1994, it was extended to include all artificial joints. The main purpose of the register is to detect inferior results of implants as early as possible. All hospitals participate, and the orthopedic surgeons are supposed to report all primary operations and all revisions. Using the patient's unique national social security number, the revision can be linked to the primary operation, and survival analyses of the implants are done. In general, the survival analyses are performed with the Kaplan-Meier method or using Cox multiple regression analysis with adjustment for possible confounding factors such as age, gender, and diagnosis. Survival probabilities can be calculated for each of the prosthetic components. The end-point in the analyses is revision surgery, and we can assess the rate of revision due to specific causes like aseptic loosening, infection, or dislocation. Not only survival, but also pain, function, and satisfaction have been registered for subgroups of patients. We receive reports about more than 95% of the prosthesis operations. The register has detected inferior implants 3 years after their introduction, and several uncemented prostheses were abandoned during the early 1990s due to our documentation of poor performance. Further, our results also contributed to withdrawal of the Boneloc cement. The register has published papers on economy, prophylactic use of antibiotics, patients' satisfaction and function, mortality, and results for different hospital categories. In the analyses presented here, we have compared the results of primary cemented and uncemented hip prostheses in patients less than 60 years of age, with 0-11 years' follow-up. The uncemented circumferentially porous- or hydroxyapatite (HA)-coated femoral stems had better survival rates than the cemented ones. In young patients, we found that cemented cups had better survival than uncemented porous-coated cups, mainly because of higher rates of revision from wear and osteolysis among the latter. The uncemented HA-coated cups with more than 6 years of follow-up had an increased revision rate, compared to cemented cups due to aseptic loosening as well as wear and osteolysis. We now present new findings about the six commonest cemented acetabular and femoral components. Generally, the results were good, with a prosthesis survival of 95% or better at 10 years, and the differences among the prosthesis brands were small. Since the practice of using undocumented implants has not changed, the register will continue to survey these implants. We plan to assess the mid- and long-term results of implants that have so far had good short-term results.

The Danish Hip Arthroplasty Register.

In Denmark (5.3 mill. inhabitants), a national register for total hip replacements was established in January 1995. During the first 4 years, 18,222 primary total hip replacements (THR), 3,343 revisions and 6,071 follow-up examinations have been registered. During the same period, the incidence of primary THR per 100,000 inhabitants has increased from 72 in 1995 to 93 in 1998. The mean age at the primary replacement was 68 years, 59% were women and in 75% primary arthrosis was the diagnosis. An increasing use of uncemented implants has been observed both in primary THR and in revision. 64% of the primary THR were cemented and in revisions of both components, 49% were cemented. The reasons for revision were aseptic loosening in 63% of the cases followed by dislocation in 12% and deep infection in 11%. When assessed by the Harris Hip Score, primary THR and revisions resulted in a considerable improvement in pain and function, with the best results after primary operation. After 3 years, the prosthesis survival of all primary THR was approximately 97%. The lowest survival was observed in younger men with a hybrid prosthesis, usually uncemented cup and cemented stem.

Outcome of total hip arthroplasty in small-proportioned patients

In a prospective, consecutive series, 41 total hip arthroplasties were performed in 27 small-proportioned patients with small femoral dimensions. The 17 female and 10 male patients averaged 23.6 years (range, 14–47 years), and the mean height and weight were 157 cm (range, 132–183 cm) and 53.5 kg (range, 36–84 kg). The most common preoperative diagnosis was juvenile rheumatoid arthritis in 18 patients (28 hips). Most patients were severely disabled in their daily activity, and 68% of the patients were classified as Charnley functional class C. The femoral implants consisted primarily of the proximally porous-coated miniature Anatomic Medullary Locking femoral component (AML/CDH, Depuy, Warsaw, IN) in 33 hips in 22 patients (average stem diameter, 9.5 mm; range, 8–12.0 mm). A porous ingrowth acetabular cup fixed with screws was used in all procedures. At an average follow-up of 51 months, Harris Hip Scores improved significantly from 34 points (range, 0–65 points) preoperatively to 85 points (range, 33–100 points) after arthroplasty. There were no intraoperative complications. There was 1 revision because of femoral implant loosening. Three cementless femoral components showed evidence of nonprogressive subsidence. One patient had significant bilateral acetabular component polyethylene wear and underwent revision. All other femoral and acetabular components were radiographically stable. The relief of pain and improvement of function were dramatic. The miniature AML/CDH femoral component, combined with an uncemented acetabular cup, provides a promising, off-the-shelf alternative in small-proportioned patients

Revision arthroplasty of the acetabulum with restoration of bone stock.

Bone defects on the acetabular side are defined as contained (cavitary) and uncontained (segmental). Contained (cavitary) defects can be treated by morselized allograft bone with an uncemented cup if contact can be made with 50% host bone. If contact cannot be made with 50% host bone, the author prefers to use a ring and a cemented cup. Defining success as a stable implant, no additional surgery, and improvement in hip score of at least 20 points, the success rate was 90% in 51 hips in 51 patients at an average followup of 7 years. Segmental defects involving between 30% and 50% of the acetabulum are treated by minor column allografts (shelf graft), and a cemented or an uncemented cup. In 29 hips in 28 patients with an average followup of 7 years the success rate was 86%. Segmental defects involving more than 50% of the acetabulum are treated by major column allografts. These grafts are fixed by cancellous screws and protected by a reconstruction ring that extends from ilium to ischium. In 33 hips in 32 patients with an average followup of 7 years, the success rate was 76%.

Severe polyethylene wear in uncemented acetabular cup system components: A report of 5 cases

We report 5 cases of severe failure of the polyethylene liner at 4 to 7.4 years after uncemented anatomic medullary locking (AML) total hip arthroplasty, using the acetabular cup system (ACS). The mode of failure was by a combination of wear through to the metal backing and liner fracture. Four of the 5 cases were associated with a 32-mm head. The ACS design is flawed because of a lack of hemispherical geometry resulting in rim loading on a region of the liner that has the thinnest polyethylene. All patients with this type of implant should be monitored for evidence of excessive polyethylene wear.

The acetabular component in total hip arthroplasty

Initial stability is necessary for permanent fixation of acetabular cups. Biologic reactions to submicron particles such as localized bone resorption may lead to implant failure. The aim of the study was to evaluate different fixation principles of acetabular components. Four randomized studies and one case-control study were performed to evaluate different bone cements, different cup designs, use of ceramic coating or not, different type of screws and the need of additional screw fixation or not. Radiostereometry (RSA) makes it possible to analyze small translations and rotations of implants with a high accuracy. This method is suitable for evaluation of early stability and was used in four of the studies. Clinical and radiological follow-up were performed regularly. The cements were tested in the laboratory. 30 patients (mean age 71 years, range: 63-76) received total hip arthroplasties and were randomised to fixation with Boneloc (14) or Palacos cum gentamicin (16) bone cement. The curing temperature was 23 degrees lower for the Boneloc cement but the tensile strength was reduced and the elastic modulus was lower compared to Palacos. The proximal cup migration was greater in the Boneloc group up to 12 months (p 0.04) and these cups migrated medially in contrast to a small lateral migration seen in the Palacos group (p 0.04). Radiolucencies were more pronounced in the Boneloc group at 12 months (p 0.04). 155 patients (171 hips, mean age 50 years, range: 24-64) received uncemented hip arthroplasties. 84 hips were randomised to the PCA and 87 to the Harris-Galante I designs. The 10-year survival rates were 85% for the PCA and 99% for the Harris-Galante I cups (revision as end-point). The wear and clinical results did not differ. 43 patients (mean age 60 years, range 44-68) received uncemented porous cups with a titanium mesh in pure titanium (Harris-Galante II) and were randomised to additional fixation with either biodegradable screws (23, poly-L-lactic acid, PLLA) or screws made of titanium alloy (20). Increased proximal and medial-lateral translations (p 0.02, 0.04) but less rotation around the longitudinal axis (p 0.04) were seen in the PLLA group up to 2 years. There were also more pronounced radiolucencies anteriorly in this group at 2 years. The clinical results did not differ. 23 uncemented porous cups (Harris-Galante II) with hydroxyapatite-tricalciumphosphate coating (HA/TCP) were pair-wise matched to uncoated cups. Up to 2 years, decreased rotations around the horizontal axis were recorded in the HA/TCP-coated cups. Central postoperative gaps were more frequently seen in the HA/TCP group (p < 0.01), but at 2 years radiolucencies were more pronounced in the uncoated group (p < 0.01). The wear and clinical results did not differ. 62 patients (64 hips, mean age 56 years, range: 32-75) were randomized to porous Trilogy cups with (30) and without (34) cluster holes for additional screw fixation. Up to 2 years there were no differences in migration, wear, radiographic findings or clinical results. In conclusion Boneloc cement was associated with poor fixation due to inferior mechanical properties. The PLLA screws did not provide sufficient stability. Unacceptably high failure rates were recorded for the PCA cup. HA/TCP coating improved the fixation and the interface of porous cups. HA/TCP coated porous cups can be fixed without adjunctive screw fixation.

Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases.

To evaluate the long-term clinical and radiographic results of a canine uncemented porous-coated anatomic (PCA) total hip arthroplasty (THA). Prospective study of consecutive clinical patients using survival analysis. Forty-one dogs that underwent PCA THA; nine had bilateral PCA THA (50 prostheses). Gait observation, orthopedic examination, and radiographic assessment were conducted before THA, 6 months after THA, and yearly thereafter. A zonal analysis system was used to document osseous changes in the femur and the acetabulum. Acetabular cup and femoral stem subsidence and migration, femoral canal fill, and implant orientation were measured. Survival analysis of the procedure was conducted. Long-term follow-up was available for 37 dogs (46 prostheses). The median follow-up was 63 months. Limb function was normal for 37 limbs and abnormal for 9 limbs because of dislocation (n = 3), lumbosacral disease (n = 2), degenerative myelopathy (n = 1), autoimmune disease (n = 1), brain tumor (n = 1), or osteosarcoma of the femur (n = 1). All prosthetic stems and cups were fixed by bone ingrowth fixation. Osteolysis was not observed. Bone infarction occurred in five femoral canals (four dogs). The 6-year survival rate for the procedure was 87% (95% confidence interval, 72%-96%). Long-term fixation of the uncemented PCA acetabular cup and stem is successful in dogs, and long-term clinical function is excellent.

Allografting in uncemented acetabular revision.

From 1987 to 1991, a total of 43 acetabular revisions were performed in 39 patients aged 36 to 79 years. In group A (26 revisions in 24 patients), morselized allograft was used to fill in cavitary acetabular defects, and in group B (17 revisions in 15 patients), a solid (bulk) allograft was used to reconstruct defects of the acetabular rim, mainly superiorly. An uncemented acetabular cup was used in all cases. Follow-up ranged from 4 to 7 years. Results demonstrated that while large structural or morselized allografts are useful in reconstructing the anatomy, there is a high rate of loosening due to resorption. The failure rate of bulk graft was higher than that of morselized graft, but because the bone stock in failures is usually restored, a second revision is easier.

Langzeitergebnisse nach zementierten Hüft-Totalendoprothesen bei chronischen Polyarthritiden

As a part of long-term follow up (I) of 544 cemented Müller-curved stem total hip replacements (THR), implanted 1977 to 1983, 207 THR in 163 patients with rheumatoid arthritis (RA) were evaluated 9 to 15 years (11 on an average) postoperatively. The feed back rate was 96.9% so the results are very reliable. 18 cups were loosened (13 already changed), but no stem had to be changed for aseptic loosening. 2 THR (1.0%) had to be revised because of deep infection. Survival rate of Kaplan and Meier for aseptic loosening was 94.6% after 10 years, 83.5% after 15 years. The ARO multi-center-study 1995 (II) includes 3113 THR implanted 1987 and 1988. Within a follow-up period of 7 to 9 years the over all rate of aseptic changing for cemented cups (1.4%) was significantly lower than for uncemented cups (2.9%)--in RA even 1% versus 5.7%. The corresponding rates for stems was 1.0% (cemented) versus 1.8% (uncemented). We contributed 110 THR in 94 patients with RA with feed back of 100%. Because of deep infection one THR had to be changed and two were explanted. But no change of cup or stem because of aseptic loosening was observed. Also in the literature survival rates up to 97% after 10 years or 77% after 25 years even in younger patients with RA can be stated. Cemented THR shows good long-term-results in RA which with uncemented designs have also to be proved. As a consequence of analysing the (few) failures the cemented THR of Wessinghage with optimized bone-cement-implant-compound was introduced. We demand a high feed back rate in long-term follow-ups also with respect to quality management and comparing data.

Acetabular Revision by Using Femoral Head Allograft and Uncemented Cup

Acetabular Revision by Using Femoral Head Allograft and Uncemented Cup

Migration of porous press-fit cups in hip revision arthroplasty: A Radiostereometric 2-Year Follow-up Study of 60 Hips

The migration of 60 press-fit cups fixed with screws was evaluated by radiostereometric analysis for 2 years in 57 patients revised because of aseptic loosening. The mean proximal migration of the cup center increased continuously up to 0.36 mm (range, 0.0–1.6 mm), whereas the migration in the other directions reached a level at 0.3 to 0.4 mm after 6 months. Mean rotations of less than 1° were recorded. Factors influencing motions were cup size, use of bone—grafts, and position of the cup center in the vertical and horizontal directions. Compared with previous stereoradiographic studies of cemented revisions, the migration of the press-fit cup was smaller, however, still higher than previously reported for uncemented cups of the same design used in primary surgery.

Total hip replacement in dysplastic hips using femoral head shelf autografts.

A consecutive series of 30 dysplastic hips were treated with total hip arthroplasty using femoral head autograft shelf reconstruction and were reviewed. Cemented cups were used in 13 hips and uncemented cups were used in 17 hips. The average followup was 8.1 years (range, 5.2-13.3 years). In the cemented group, the average preoperative Harris Hip Score was 44.8 points (range, 22-82 points), and in the uncemented group, it was 45 points (range, 23-61 points). At the final review, the average clinical score was 71.5 points (range, 46-98 points) in the cemented group, and in the uncemented group it was 87.5 points (range, 63-100 points). Of the 30 cases, only 3 had unsuccessful results, giving a success rate of 90%. In terms of the autograft, all united to host bone. Resorption, when seen in either cemented or uncemented cups, was minor and restricted to the lateral nonweightbearing part of the graft. The present study supports using shelf autografts to reconstruct dysplastic hips at the time of total hip arthroplasty. In this series, cemented and uncemented cups performed equally well.

Total hip arthroplasty with shelf grafts using uncemented cups: A long-term follow-up study

A series of 33 hips treated with cementless cups and structural autograft or allograft were reviewed at a minimum follow-up period of 5 years. Seventeen hips received a shelf autograft during primary hip arthroplasty and 16 received an allograft at revision. In the hips receiving autografts, the average preoperative hip score was 45.1 and the score at final review was 87.5, whereas in the revisions reconstructed with allografts, the average preoperative hip score was 44.4 and the score at final review was 82. Overall, only 2 of 33 hips were considered failures, giving a success rate of 94% at an average follow-up period of 6.6 years. Leg-length discrepancy greater than 2 cm was seen in 27 of 33 hips, and at final review only 4 of 33 hips had a leg-length discrepancy greater than 2 cm. All grafts united to host—bone. Resorption, when seen, was minor, with only three grafts showing moderate resorption. Our data support the use of cementless cups with structural allografts and autografts, provided the graft supports less than 50% of the cup.

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.

Failure of the Ring polyethylene uncemented acetabular cup

We report a high rate of failure of the Ring polyethylene cementless cup caused largely by granulomatous osteolysis. We have reviewed 126 prostheses inserted from 1986 to 1992 at from 11 to 90 months after surgery. There was radiological evidence of osteolytic granulomas adjacent to the external surface of the cup in 32%, appearing on average at three years from operation. In a subgroup of 59 prostheses followed for at least four years the incidence of such changes was 54%. A total of 27 cups (22%) have required revision, 21 for granulomatous loosening at an average follow-up of five years. In the retrieved prostheses there was obvious polyethylene abrasion and histological examination confirmed the presence of polyethylene wear debris. We found no significant correlation of osteolysis with cup size, although smaller cups were predominant among those having revision.

Revision for aseptic loosening of uncemented cups in 4,352 primary total hip prostheses. A report from the Norwegian Arthroplasty Register.

From September 1987 until January 1994 the Norwegian Arthroplasty Register recorded 5,021 primary total hip replacements performed with uncemented acetabular components. We compared the survival until revision for aseptic loosening of the cup, in the 11 commonest types (n 4,352). The overall cumulative revision rate for the acetabular components was 3.2% after 5 years and 7.1% after 6 years, with large differences among the designs. With the hydroxyapatite (HA)-coated cups and the hemispheric porous-coated cups, the failure rate was less than 0.1%. Of the unthreaded hemispheric porous-coated cups, Harris-Galante and Gemini (n 626), none had been revised, and of the HA-coated cups, Atoll and Tropic (n 1,943), only 1 had been revised. For the threaded uncoated metal-backed cups, the results varied from no revisions of the PM cups (n 148) to a cumulative 6-year revision rate of 21% for the Ti-Fit (n 300). The all-polyethylene Endler cups (n 334) had a cumulative revision rate of 14%. Women and patients with inflammatory arthritis had poorer results. However, the type and the design of the cups were of far greater importance for the results than patient-related factors.

Ingrowth reduces implant-to-bone relative displacements in canine acetabular prostheses.

We examined bone-to-implant relative displacement of acetabular prostheses acutely and after ingrowth in a canine model. Uncemented hemispherical acetabular cups with titanium mesh pads comprising approximately 26% of the surface of the cup were inserted in eight adult canine hemipelves ex vivo. The acetabular prostheses were fixed with 13 mm titanium screws. Zero, one, and two-screw configurations were tested, with the order of testing randomly assigned. A load simulating 1,000 cycles of canine gait as applied to the acetabular component, and relative displacements were measured at three locations between implant and bone to determine acute fixation. A repeated measures analysis of variance showed that two screws produced only 42% of the average relative displacement of one screw and 14% that of zero screws. Eight adult mixed-breed dogs then underwent unilateral total hip arthroplasty. All acetabula were biologically fixed with two cancellous screws. The results at 4 months showed significantly less relative displacement between the implant and bone than was measured in ex vivo implantations (p = 0.014). Bone ingrowth filled 20 +/- 6% (mean +/- SD) of the available space. The relative displacements of these implants were small in all cases (12 +/- 13 microns) and did not correlate with the amount of bone ingrowth. These data suggest that acetabular fixation with two screws can lead to bone ingrowth and reduced relative motion of the prosthesis under functional loading.

Polyethylene wear in uncemented acetabular components

We measured polyethylene wear in 231 porous-coated uncemented acetabular cups. We divided the hips into two groups according to the fixation of the femoral component, by cementing (n = 97) or press-fit (n = 134). Follow-up was from three to five years. The patients in two sub-groups were matched for weight, diagnosis, sex, age and length of follow-up. The linear wear rate of cups articulated with uncemented femoral components (0.22 mm/year) was significantly higher than the wear rate (0.15 mm/year) of cups articulated within cemented femoral components (p < 0.05). These results can be compared with previously reported wear rates of 0.08 mm/year for cemented all-polyethylene cups and 0.11 mm/year for cemented metal-backed cups. The higher wear rates of uncemented arthroplasties could jeopardize the long-term results of this type of hip replacement.