Loosening of threaded acetabular components. Radiographic manifestations

Intra- and interrater reliabilities and a method comparison of 2D and 3D techniques in cadavers to determine sacroiliac screw loosening

Sacroiliac (SI) screw loosening may indicate persistent instability, non-union and contribute to pain. Yet, there is no reliable objective measurement technique to detect and monitor SI screw loosening. In 9 cadaveric pelvises one of two SI screw was turned back approximately 20 mm and subsequently assessed by optical measurement, fluoroscopy and a 3D scan using an image intensifier. CTs were segmented and a contour-based registration of the 3D models and the fluoroscopies was performed to measure SI backing out (X-ray module). Three independent observers performed measurements with three repetitions. Deviation of the measurement techniques to the 3D scan, intra- and interrater reliabilities and method equivalence to the 3D scan were assessed. The X-ray module and two fluoroscopic measurement techniques yielded a difference less than 5 mm compared to the 3D scan and equivalence to the 3D scan. Intrarater reliability was for two observers and almost all techniques very good. Three fluoroscopic measurement techniques and optical measurements displayed a very good interrater reliability. The 3D scan and X-ray module yielded the most precise values for SI screw loosening but only the fluoroscopic measurement of the inlet lateral loosening displayed a good reliability and equivalence to the 3D scan.

Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years

BACKGROUND AND PURPOSE

In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland.

PATIENTS AND METHODS

3,668 implants fulfilled our inclusion criteria. The previous data included years 1980-2001, whereas the current study includes years 1987-2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987-1996 and those operated 1997-2006.

RESULTS

The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987-1996 (62%; 95% CI: 57-67) and cementless group 2 (58%; CI: 52-66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62-80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987-1996 (0.49; CI: 0.32-0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001).

INTERPRETATION

Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.

Cemented versus cementless total hip replacements in patients fifty-five years of age or older with rheumatoid arthritis

BACKGROUND

results obtained from single-center studies indicate that a cemented total hip replacement is the treatment of choice for the management of patients over fifty-five years of age with rheumatoid arthritis. The aim of this study was to analyze population-based survival rates for cemented and cementless total hip replacements in patients aged fifty-five years or over with rheumatoid arthritis in Finland.

METHODS

between 1980 and 2006, a total of 6000 primary total hip replacements performed for the management of rheumatoid arthritis in patients who were fifty-five years of age or older were entered in the Finnish Arthroplasty Registry. 4019 of them fulfilled our inclusion criteria and were subjected to analysis. The implants were classified into one of three possible groups: (1) a cementless group (a noncemented proximally porous-coated stem and a noncemented porous-coated press-fit cup), (2) a cemented group 1 (a cemented, loaded-taper stem combined with a cemented, all-polyethylene cup), or (3) a cemented group 2 (a cemented, composite-beam stem with a cemented, all-polyethylene cup).

RESULTS

cementless stems and cups, analyzed separately, had a significantly lower risk of revision for aseptic loosening than cemented implants in patients who were fifty-five years of age or older with rheumatoid arthritis. The fifteen-year survival rate of cementless total hip replacements (80%) was comparable with the rates of the cemented groups (86% in cemented group 1 and 79% in cemented group 2) when revisions for any reason were used as the end point.

CONCLUSIONS

cementless and cemented total hip replacements produced comparable long-term results in patients who were fifty-five years of age or older with rheumatoid arthritis.

LEVEL OF EVIDENCE

therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Cementless total hip arthroplasty in patients with severely dysplastic hips and a previous Schanz osteotomy of the femur: techniques, pitfalls, and long-term outcome

BACKGROUND AND PURPOSE

Historically, a Schanz osteotomy of the femur has been used to reduce limp in patients with severely dysplastic hips. In such hips, total hip arthroplasty is a technically demanding operation. We report the long-term results of cementless total hip arthroplasty in a group of patients who had all undergone a Schanz osteotomy earlier.

PATIENTS AND METHODS

From 1988 through 1995, 68 total hip replacements were performed in 59 consecutive patients previously treated with a Schanz osteotomy. With the cup placed at the level of the true acetabulum, a shortening osteotomy of the proximal part of the femur and distal advancement of the greater trochanter were performed in 56 hips. At a mean of 13 (9-18) years postoperatively, we evaluated these patients clinically and radiographically.

RESULTS

The mean Harris hip score had increased from 51 points preoperatively to 93 points. Trendelenburg sign was negative and there was good or slightly reduced abduction strength in 23 of 25 hips that had not been revised. There were 12 perioperative complications. Only 1 cementless press-fit porous-coated cup was revised for aseptic loosening. However, the 12-year survival rate of these cups was only 64%, as 18 cups underwent revision for excessive wear of the polyethylene liner and/or osteolysis. 6 CDH femoral components had to be revised due to technical errors.

INTERPRETATION

Our results suggest that cementless total hip arthroplasty combined with a shortening osteotomy of the femur and distal advancement of the greater trochanter can be recommended for most patients with a previous Schanz osteotomy of the femur. Because of the high incidence of liner wear and osteolysis of modular cementless cups in this series, nowadays we use hard-on-hard articulations in these patients.

Total hip arthroplasty for primary osteoarthritis in patients fifty-five years of age or older. An analysis of the Finnish arthroplasty registry

BACKGROUND

According to the long-term results obtained from the Scandinavian arthroplasty registries, cemented total hip replacement has been the treatment of choice for osteoarthritis of the hip in elderly patients. The aim of the present study was to analyze population-based survival rates of the cemented and cementless total hip replacements performed for primary osteoarthritis in patients fifty-five years of age or older in Finland.

METHODS

From 1980 to 2004, a total of 50,968 primary total hip replacements that met our criteria were entered in the Finnish Arthroplasty Registry. The success rate of different implant groups was analyzed. The implants included were classified in one of the following four groups: implants with a cementless, straight, proximally circumferentially porous-coated stem and a modular, porous-coated press-fit cup (cementless group 1); implants with a cementless, anatomic, proximally circumferentially porous-coated and/or hydroxyapatite-coated stem with a modular, porous-coated and/or hydroxyapatite-coated press-fit cup (cementless group 2); a hybrid total hip replacement consisting of a cemented stem combined with a modular, press-fit cup (the hybrid group); and a cemented loaded-taper or composite-beam stem combined with an all-polyethylene cup (the cemented group).

RESULTS

Cementless total hip replacements, as well as cementless stems and cups analyzed separately, had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements (p < 0.001). When revision for any reason was the end point in survival analyses, however, there were no significant differences among the groups. In patients between the ages of fifty-five and sixty-four years, the fifteen-year survival rates of the two cementless groups (78% and 80%) were higher than that of the cemented group (71%) with revision for aseptic loosening as the end point. In patients who were sixty-five to seventy-four years old, the fifteen-year survival rate of the implants in cementless group 1 was 94%, while cemented total hip replacements had an 85% survival rate. In patients who were seventy-five years old or more, no significant differences were detected among the total hip replacement groups; all of them had survivorship of >90% at ten years.

CONCLUSIONS

In patients who were fifty-five years of age or older, the long-term survival of cementless total hip replacements was comparable with that of cemented replacements. In patients who were fifty-five to seventy-four years old, straight porous-coated cementless stems had better long-term survival than the cemented stems. In patients who were seventy-five years of age and older, there were no significant differences in the results. Multiple wear-related revisions of the cementless cups in the present study indicate that excessive polyethylene wear was a major clinical problem with modular cementless cups in all age groups.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

High long-term loosening rate of conical screw cups

BACKGROUND

Acetabular screw cups seem to give high primary stability. We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up.

PATIENTS AND METHODS

We examined 92 uncemented titanium alloy conical screw cups prospectively. Implant migration was assessed with a digital high-precision method (EBRA) with an accuracy of 1.0 mm.

RESULTS

After mean 11 (0.5-18) years, 87 patients were available for examination and 5 patients had died. 32 implants had been revised and 7 cases showed radiographic evidence of loosening. The 10-year survival rate was 71%. Migration of more than 1 mm occurred in 53 hips. Implant survival was strongly associated with an annual migration of greater than 0.2 mm.

INTERPRETATION

The long-term behavior of this cup is not satisfactory. In spite of extraordinarily high primary implant stability, secondary osseointegration of this cup often fails. The annual migration rate represents a valid parameter for prediction of implant survival.

Total hip arthroplasty for rheumatoid arthritis in younger patients: 2,557 replacements in the Finnish Arthroplasty Register followed for 0-24 years

BACKGROUND

The results of total hip arthroplasty (THA) in young patients with rheumatoid arthritis (RA) have been reported in only a few studies. On a nationwide level, the outcome of THA in these patients is unknown. We evaluated the population-based survival of THA in patients under 55 years of age with RA and factors affecting the survival.

PATIENTS

Between 1980 and 2003, 2,557 primary THAs performed for RA in patients less than 55 years of age were reported to the Finnish Arthroplasty Register.

RESULTS

Proximally circumferentially porous-coated uncemented stems had a 15-year survival rate of 89% (95% CI 83-94) with aseptic loosening as endpoint. The risk of stem revision due to aseptic loosening was higher with cemented stems than with proximally porouscoated uncemented stems implanted during the same period (RR 2.4; p < 0.001). In contrast, Cox regression analysis showed that the risk of cup revision was significantly higher for all uncemented cup concepts than for all-polyethylene cemented cups with any cup revision as endpoint. There were no significant differences in survival between the THR concepts.

INTERPRETATIONS

Uncemented proximally circumferentially porous-coated stems and cemented all-poly-ethylene cups are currently the implants of choice for young patients with RA.

Modes of failure of a threaded acetabular cup : a radiographic study with EBRA of 42 revised cups

A radiographic study of a singular type of threaded cup, revised due to aseptic loosening, was performed with Einzel-Bild-Roentgen-Analyse (EBRA) to detect eventual risk factors and patterns of loosening. Fifty-three cups of 50 patients were revised. Forty-two cups could be measured with EBRA. No cup had obvious osteolysis, 33 cups demonstrated early migration, and all cups had migrated at the time of revision. Twenty-eight of the cups had a change of inclination and 21 of anteversion, respectively. The mean migration was 1.9 mm in the medial and 7.9 mm in the cranial direction; the mean wear rate was 0.2 mm/year. Cups with early migration had a higher migration rate. All male patients had early migration; medially placed cups had less migration than the other cups. Wear was not significantly affected by the migration of the implant. No cup had a complete radiolucent line, and the only radiographic sign for loosening was the change of position of the cup. Medial placement showed less migration in case of loosening. Regular radiographic follow-up is recommended for the examined implant, and the cup should not be used in the future.

Uncemented total hip arthroplasty for primary osteoarthritis in young patients: a mid-to long-term follow-up study from the Finnish Arthroplasty Register

INTRODUCTION

The survival of total hip arthroplasties (THAs) has been considered to be poor in young patients. We evaluated the population-based survival of uncemented THA for primary osteoarthritis (OA) in patients under 55 years of age and the factors affecting survival.

METHODS

The Finnish Arthroplasty Register was established in 1980. Between that year and 2003, 92,083 primary THAs were entered in the register, 5,607 of which were performed for primary OA in patients under 55 years of age. Using records from these 5,607 THAs, we selected uncemented femoral and acetabular components that had been used in more than 100 operations during the study period. Survival of both components (cup/stem) and their combinations were analyzed separately with the Kaplan-Meier analysis and the Cox regression model.

RESULTS

All uncemented stems studied showed a survival rate of over 90% at 10 years. The Biomet Bi-Metric stem had a 95% (95% CI 93- 97) survival rate even at 15 years. Overall survival of the extendedly porous-coated Lord Madréporique stem (p = 0.003) and the proximally porous-coated Anatomic Mesh stem (p = 0.0008) were poorer than that of the Biomet Bi-Metric stem. When endpoint was defined as stem revision for any reason, results were generally similar; there was no difference, however, between the survival rates of the Lord Madréporique stem and the Bi-Metric stem. Of the acetabular components, the Biomet Universal, the ABG Il and the Harris-Galante II cups showed < 90% survival rates at 10 years with aseptic loosening as endpoint; at 13 years the corresponding survival rates were 94% (95% CI 91-97) for the Biomet Universal and 95% (95% CI 91-98) for the Harris-Galante II cups with aseptic loosening as endpoint. The PCA Pegged porous-coated uncemented cup showed a poor 13-year survival rate of 68% (95% CI 59-78) with aseptic loosening as endpoint. However, when endpoint was defined as any revision (including exchange of liner), the 10-year survival rates of all brands of cup except Harris-Galante II declined to under 80%.

INTERPRETATION

Modern second-generation uncemented stems, with proximal circumferential porous- or HA-coating, seem to be a good choice for young patients with primary OA. Similarly, modern press-fit porous- and HA-coated cups appear to have good endurance against aseptic loosening in these young patients. However, liner revisions were common; thus, survival rates of uncemented cups were unsatisfactorily low. Polyethylene wear and unfavorable locking mechanisms between the metal shell and the polyethylene liner and their sequelae remain matters of concern in this young and active group of patients.

Radiographic comparison of pegged and keeled glenoid components

Glenoid loosening is one reason for failure of total shoulder arthroplasty. Several factors, including radiographic lucency, have been shown to be associated with glenoid loosening. The purpose of this study was to assess the correlation between glenoid design and immediate radiographic lucency in a prospective randomized clinical trial. Total shoulder arthroplasty was performed in 43 patients over a 2-year period. Twenty-three patients were randomized into the keel group and twenty patients into the pegged group. Postoperative radiographs obtained within 6 weeks of surgery were evaluated by 3 raters to determine glenoid lucency. On a scale from 0 (no lucency) to 5 (gross lucency and component loosening), the rate of lucency was 39% (9/23) in the keeled components, which was significantly higher than the rate of 5% (1/20) observed in the pegged components (P = .026). Patient age, gender, and glenoid size did not significantly affect glenoid component lucency (P > .05). The consistency reliability among raters (Cronbach alpha) was 0.87, and the intertester reliability was 0.87. Pegged glenoid components have less radiographic lucency when compared with keeled glenoid components in the immediate postoperative period.

Total hip arthroplasty for primary osteoarthrosis in younger patients in the Finnish arthroplasty register. 4,661 primary replacements followed for 0-22 years

BACKGROUND

Many studies have found a higher risk of revision after hip arthroplasty in younger patients. We evaluated the population-based survival of total hip arthroplasty (THA) in patients under 55 years of age and the factors affecting survival.

METHODS

The Finnish Arthroplasty Register was established in 1980, and 74,492 primary THAs were entered into the register between 1980 and 2001. 4,661 of these were evaluated, all of which had been performed for primary osteoarthrosis on patients under 55 years of age.

RESULTS

Proximally circumferentially porous-coated uncemented stems implanted between 1991 and 2001 had a 10-year survival rate of 99 (95% CI 98.5-99.6)% with aseptic loosening as endpoint. The risk of stem revision due to aseptic loosening was higher in cemented stems than in proximally porous-coated (RR 5.5, p < 0.001) or HA-coated (RR 6.6, p = 0.01) uncemented stems implanted during the same period. According to Cox regression analysis of cups implanted 1991-2001, the risk of revision for all-polyethylene cemented cups was 3.0 times as high as that for press-fit porous-coated uncemented cups with aseptic loosening as endpoint (p = 0.01). However, when the endpoint was defined as any revision (including exchange of liner), there was no longer any difference between these two concepts, the 10-year survival rates being 94 (92.1-95.5)% for press-fit porous-coated uncemented cups and 93 (88.5-97.6)% for all-polyethylene cemented cups (p = 0.9).

INTERPRETATION

Modern uncemented stems seem to have better resistance to aseptic loosening than cemented stems in younger patients. Thus, for younger patients, uncemented proximally circumferentially porous- and HA-coated stems are the implants of choice. Press-fit porous- and HA-coated uncemented cups may have better endurance against aseptic loosening than cemented cups in younger patients. However, when all revisions (including exchange of liner) are taken into account, the survival of modern uncemented cups is no better than that of all-poly cemented cups.

Radiographic comparison of two glenoid preparation techniques in total shoulder arthroplasty

We compared the prevalence of periglenoid radiolucencies between two glenoid component preparation techniques used in total shoulder arthroplasties. Seventy-two consecutive patients with primary osteoarthritis had total shoulder arthroplasties using one prosthetic system with flat-back keeled polyethylene glenoid components. Thirty-seven shoulders had glenoid implants that were cemented after standard curettage preparation of the keel slot. Thirty-five shoulders had glenoid implants that were cemented after using bone compaction to prepare the keel slot. The immediate postoperative and 2-year postoperative radiographs were examined to evaluate the presence and progression of periglenoid radiolucencies. The curettage group had a higher rate (38%) of keel radiolucencies than the compaction group (11%) seen on the immediate postoperative radiographs. Both groups had progression of periglenoid radiolucencies with time. Progression of the radiolucent lines was worse in the curettage group 2 years after arthroplasty. Preparation of the glenoid component keel slot with the bone compaction technique seems to achieve better fixation of flat-back keeled polyethylene glenoid components in total shoulder arthroplasties.

A 10-year minimum follow-up of hydroxyapatite-coated threaded cups: clinical, radiographic and survivorship analyses with comparison to the literature

We evaluated the clinical, radiographic, and survivorship outcomes in a series of 418 threaded hydroxyapatite-coated acetabular cups (Arc2f; Osteonics, Allendale, NJ) implanted in a consecutive series of 384 patients undergoing primary total hip arthroplasty. In all cases, the cup was screwed into the prepared acetabulum. Bone screws were used to provide secondary fixation. At a minimum 10-year follow-up, 304 cups were available for analysis. The cumulative survivorship (mechanical failure as endpoint) at that time was 99.43% +/- 0.0104. Two hundred seventy-six hips were available for full clinical and radiographic review at or after the tenth anniversary. No unstable implants were noted; all implant fixation interfaces were classified as "stable bone ingrown," and the cup migration rate was zero. Based on the survivorship achieved with this implant, our results compare favorably with survivorship reported for the best cemented and cementless acetabular implant designs.

Total hip arthroplasty with use of the cementless Zweymüller Alloclassic system. A ten to thirteen-year follow-up study

BACKGROUND

The Zweymüller Alloclassic total hip arthroplasty system is widely used, although few intermediate-term studies have been published. The purpose of the present study was to evaluate the clinical and radiographic results of this system after ten years.

METHODS

One hundred and twenty-four consecutive primary total hip arthroplasties were performed with the Zweymüller Alloclassic cementless system at our institution between February 1988 and March 1991, and 104 hips (ninety-four patients) were retrospectively reviewed after a minimum duration of follow-up of ten years. The mean age of the patients at the time of the arthroplasty was 62.3 years (range, twenty-five to seventy-seven years). The mean duration of follow-up was 11.3 years. Standard radiographs were made for all patients immediately after the operation, at six and twelve months, and annually thereafter for at least ten years. Cox multivariate regression analysis was performed to assess the influence of various factors on survival of the implant.

RESULTS

The cumulative probability of not having a revision of any prosthetic component for any reason was 94.1% (95% confidence interval, 91.9% to 96.3%) at twelve years in the best-case scenario and 85.3% (95% confidence interval, 82.1% to 88.5%) at twelve years in the worst-case scenario for the entire series of 124 hips. Among the 104 hips in the follow-up study, three acetabular components and no stems were revised. Two hips had level-4 pain according to the system of Merle D'Aubigné and Postel. Seven acetabular components (7%) were loose at twelve years, and all stems had radiographic evidence of stable fixation. Acetabular cup loosening was related to a vertical cup angle (p = 0.0008, Student t test), acetabular wear of > or =1 mm (p = 0.001, Fisher exact test), and a 32-mm femoral head (p = 0.001, Fisher exact test). Although femoral osteolysis was seen in eighteen hips (17%) at twelve years, all osteolytic cavities were proximal and focal.

CONCLUSIONS

The Zweymüller Alloclassic prosthesis, particularly its femoral stem, demonstrated good results and durable fixation at a minimum of ten years of follow-up.

Survivorship of rough-surfaced threaded acetabular cups. 382 consecutive primary Zweymüller cups followed for 0.2-12 years

We studied prospectively 382 cementless (Zweymüller stem) and hybrid (cemented stem) primary total hip replacements and used a cementless grit-blasted titanium alloy threaded cup. After a median 5 (0.2-12) year follow-up, 1 cup was exchanged, 2 cups were removed for deep sepsis, and 3 cups showed definite loosening; of these, 2 subsequently required revision. Actuarial calculation methods indicated a 10-year survivorship of 99% with cup retrieval for any cause (clinical failure), definite cup-loosening (radiographic failure), and revision for aseptic cup-loosening as endpoints. These intermediate results exceed those from smooth-surfaced screw rings and compare favorably with those from cemented cups and cementless, press-fit, metal-backed cups.

Acetabular screw rings and surface treatment

The Zweymüller truncated self tapered threaded ring is forged in pure titanium with a 3- to 5-mu grit blasted surface roughness. Among 167 consecutive primary total hip arthroplasties prospectively studied, two threaded components failed to achieve initial stability, with one requiring almost immediate revision. One hundred twenty-six hips have been fully documented with a 5-year minimum followup. The mean modified Harris hip score improved from 44.4 points preoperatively to 91 points at 7 years average followup (range, 60-121 months). Bone to implant gap rate decreased from 54.7% after surgery to 2.4% at last review, with only one detectable early migration that had secondary stable osseointegration. Annual linear wear of more than 0.2 mm per year could be detected in only one ceramic on polyethylene bearing surface with one corresponding femoral osteolysis granuloma. At the 9- to 10-year interval, the survivorship with definite loosening as a failure was 98.7%. Delayed loosening by failure of an initially stable reconstruction, progressive lucencies, liner disassociation, or worrisome osteolysis have not been observed. These midterm results are much better than those of former screw rings with smooth surface finishes. The main reason for the general failure and justified abandonment of threaded polished components may not be the screw in mechanism of their primary fixation, but the lack of an appropriate surface for bone ingrowth and osseointegration.

Mittelmeier ceramic-ceramic prosthesis after 10 years

The clinical status of 83 Mittelmeier ceramic-ceramic (Mark II) cementless total hip prostheses (Autophor, Osteo AG, Selzach, Switzerland) implanted between 1978 and 1984 was analyzed. Retrieved tissue from the revised hips was studied histologically. The mean patient age was 47.5 years (range, 19-71 years). One or both components of 12 hips were revised (16% at 16 years in the survival study). Eleven acetabular components and seven stems were revised, with three of the sockets fractured. The mean follow-up period for the patients with unrevised hips was 12.3 years. Osseointegration was uncommon in both the cup and stem. Radiographic cup loosening was observed in 53% of hips at 16 years in the survival study, with most having a complete radiolucent line of 2 mm around the cup. Radiographic stem loosening appeared in 15% of hips at 16 years. Fibrous stable fixation was present in 64% of stems. Significant radiographic acetabular wear was not observed in any hip. The Mittelmeier Mark II prosthesis had worse long-term results than reported with cemented or other uncemented prostheses. Although there was no significant acetabular wear, intracellular ceramic wear debris was seen in the retrieved tissues.

Primary total hip arthroplasty with the Karl Zweymüller first-generation cementless prosthesis. A 5- to 9-year retrospective study

A consecutive series of 72 primary total hip arthroplasties were performed in 70 patients using the first-generation Zweymüller cementless titanium press-fit femoral and threaded acetabular components (AlloPro, Baar, Switzerland). Twelve hips were excluded from the study because of insufficient follow-up evaluation, including one patient who underwent a socket revision within the first 2 weeks. Sixty total hip arthroplasties with an average follow-up period of 80 months (range, 60-108 months) were retrospectively reviewed. Clinical results were graded excellent or good in 54 cases (90%), fair in 3 (5%), and poor in 3 (5%) with 2 early implant failures (1 acetabular cup and 1 femoral stem in 2 hips). Cumulative survival rates at the 6- to 7-year interval, with failure defined as revision and/or loosening are 98.47% (SD, 2.0%) for the femoral component (1 single septic and loose stem, revised at 5 years), 97.08% (SD, 2.72%) for the screw ring (2 unstable but only 1 revised), and 95.56% (SD, 3.36%) for both components. This encouraging experience with the first-generation prosthesis supports the rationale for continued use of the new Zweymüller Alloclassic stem and open-back screw ring available since 1988.