The dual mobility cup: what problems does it solve?

Dual mobility cups have two points of articulation, one between the shell and the polyethylene (external bearing) and one between the polyethylene and the femoral head (internal bearing). Movement occurs at the inner bearing; the outer bearing only moves at extremes of movement. Dislocation after total hip arthroplasty (THA) is a cause of much morbidity and its treatment has significant cost implications. Dual mobility cups provide an increased range of movement and a may reduce the risk of dislocation. This paper reviews the use of these cups in THA, particularly where stability is an issue. Dual mobility cups may be of benefit in primary THA in patients at a high risk of dislocation, such as those who are older with increased comorbidities and a higher American Association of Anesthesiology grade and those with a neuromuscular disease. They may be used at revision surgery where the risk of dislocation is high, such as in patients with many prior dislocations, or those with abductor deficiency. They may also be used in THA for displaced fractures of the femoral neck, which has a notoriously high rate of dislocation.

Retrieval analysis of squeaking alumina ceramic-on-ceramic bearings.

This multicentre study analysed 12 alumina ceramic-on-ceramic components retrieved from squeaking total hip replacements after a mean of 23 months in situ (11 to 61). The rates and patterns of wear seen in these squeaking hips were compared with those seen in matched controls using retrieval data from 33 'silent' hip replacements with similar ceramic bearings. All 12 bearings showed evidence characteristic of edge-loading wear. The median rate of volumetric wear was 3.4 mm(3)/year for the acetabular component, 2.9 mm(3)/year on the femoral heads and 6.3 mm(3)/year for head and insert combined. This was up to 45 times greater than that of previously reported silent ceramic-on-ceramic retrievals. The rate of wear seen in ceramic components revised for squeaking hips appears to be much greater than in that seen in retrievals from 'silent' hips.

Fixed minidose versus-adjusted low-dose warfarin after total joint arthroplasty: a randomized prospective study.

Widespread use of adjusted low-dose warfarin has been limited by the inconvenience of outpatient laboratory monitoring and the perceived risk of bleeding complications. We sought to determine if the dose of warfarin could be lowered safely even further, eliminating the need for laboratory monitoring and lowering the complication rate. Two hundred forty-five Patients undergoing primary total joint arthroplasty (n = 245) were randomized prospectively to adjusted low-dose warfarin (international normalized ratio [INR], 1.4-1.8) or fixed minidose warfarin (2 mg daily, regardless of INR) before hospital discharge. Prophylaxis continued for 6 weeks, with twice-weekly laboratory monitoring. Patients were followed for bleeding, thromboembolic events, and minor reported complications of warfarin therapy. With the numbers available, the rates of thromboembolic and bleeding events were not significantly different using equivalence analysis. Of patients in the fixed group, 8% had INRs >3.1, necessitating a decrease in dosage to 1 mg. Although such a fixed-dose protocol may simplify outpatient prophylaxis, intermittent monitoring still would be required because a subset of patients achieve a moderate level of anticoagulation and would be at risk for bleeding complications.

Effect of femoral component offset on polyethylene wear in total hip arthroplasty.

Seventeen staged, bilateral total hip arthroplasties performed in 17 patients were reviewed to compare side-to-side polyethylene wear. Implants used on both sides were similar except for implant offset: one hip in each patient was replaced using a femoral component having a standard implant offset, whereas the other side had a lateral offset implant. The mean followup was 5.70 years (range, 2-10.2 years) on the side with a standard femoral implant and 5.67 years (range, 2-9.7 years) on the side with a lateralized femoral component. The only statistically different parameter between the sides was the femoral component offset. All other parameters affecting polyethylene wear, such as period of followup, head size, head type, cup size, cup inclination, medialization of cup, and patient-related factors were similar on both sides. On the side with a standard femoral component, the mean actual prosthetic offset (determined by manufacturer's specifications) was 35.2 mm and the radiologic offset was 31.5 mm. On the side with a lateralized femoral component, the actual prosthetic offset was 42.5 mm and the radiologic offset was 40.1 mm. The difference in offsets between the sides was statistically significant. The mean preoperative offset of the femur was 38.8 mm. Regression analysis revealed that only femoral component offset and cup size correlated significantly with linear wear rate. On the side with a standard femoral component, the linear wear rate was 0.21 mm per year, whereas on the side with a lateralized femoral component, the linear wear rate was 0.10 mm per year. The differences in the linear wear rates were significant. Lateralization of the femoral component in this series more closely restored preoperative hip biomechanics and significantly decreased polyethylene wear.

Cementless femoral fixation in the rheumatoid patient undergoing total hip arthroplasty: minimum 5-year results.

Sixty-two total hip arthroplasties in 49 patients with a diagnosis of rheumatoid arthritis were performed between November 1986 and December 1992. All components were titanium alloy with a circumferential plasma-spray porous coating. Four patients (4 hips) died before 5-year follow-up, and 6 patients (8 hips) were lost to follow-up, leaving 39 patients (50 hips) for review at a minimum 5-year follow-up after surgery (mean, 8 years; range, 5-12 years). There were 12 men and 27 women, with a mean age at time of surgery of 55 years (range, 25-77 years) and a mean weight of 69 kg (range, 42-109 kg). Compared with the preoperative Charnley scores, there was significant improvement in the postoperative scores: pain, from 2.7 to 5.7, and function, from 3.2 to 5.3. Thigh pain was present in 1 patient (1 hip) (2.0%). No femoral fractures occurred intraoperatively with the insertion of the prosthesis. Spot welds consistent with bone ingrowth were identified in all of the femoral components. No femoral components showed evidence of radiographic loosening or required revision for aseptic loosening or incapacitating thigh pain, but 7 acetabular revisions were performed. Uncemented femoral fixation with this component design in rheumatoid patients appears to be a promising treatment.

Primary cementless total hip arthroplasty in octogenarians. Two to eleven-year follow-up.

BACKGROUND: Cementless total hip arthroplasty is an accepted alternative to total hip arthroplasty with cement in younger patients, but it remains controversial for elderly patients. The purpose of this study was to evaluate the clinical and radiographic outcomes of cementless total hip arthroplasty with use of a proximally coated stem in patients who were at least eighty years of age at the time of the operation. METHODS: One hundred and twenty-three cementless total hip replacements were performed for the treatment of osteoarthritis in 114 patients between the ages of eighty and eighty-nine years. Seven patients (eight hips) died within two years after the surgery, seventeen patients (eighteen hips) died more than two years postoperatively but were not followed for at least two years, and five hips were lost to follow-up; this left ninety-two hips in eighty-six patients for review. The mean duration of follow-up was five years (range, two to eleven years). For the clinical evaluation, the Charnley modification of the Merle d'Aubigné and Postel scale was used. In addition, preoperative and postoperative Harris hip scores were available for sixty-nine hips. Seventy-eight hips were followed radiographically for two years or more. The focus of the radiographic evaluation was the status of the fixation of the femoral and acetabular components as well as cup wear. RESULTS: Perioperative medical complications occurred in association with 24% (thirty) of the 123 operations, but there were no deaths. The mean Charnley scores for pain and function for the ninety-two hips that were followed clinically for at least two years improved by 3.0 and 1.4 points, respectively. The sixty-nine hips for which preoperative and postoperative Harris hip scores were available had a mean improvement of 42 points, with a mean score of 82 points at the last follow-up evaluation. Mild thigh pain was present in four patients, but it did not limit their activity. There were no femoral component revisions. All of the femoral components were radiographically stable and had bone ingrowth. No acetabular component failed by loosening, but 41% (thirty) of the seventy-three hips with radiographs available for measurement of wear showed polyethylene wear. Of the seventy-eight cups that were followed radiographically for two years or more, 4% (three) were associated with lysis, but none had been revised. CONCLUSIONS: Cementless fixation in the elderly is safe, effective, and durable at the time of two to eleven-year follow-up.

Total hip arthroplasty using two different cementless tapered stems.

The authors report their 15-year experience with primary total hip arthroplasty using collarless, tapered, porous-coated femoral stems (Trilock and Taperloc) in patients with osteoarthritis, rheumatoid arthritis, and in octogenarians. Excellent clinical results were achieved in all groups at latest followup. For the patients with Trilock stems, Taperloc stems, and patients who were octogenarians and patients with rheumatoid arthritis, Charnley pain scores were 5.6, 5.5, 5.7, and 5.7; Charnley function scores were 5.2, 5.1, 4.2, and 5.3; Harris hip scores were 92, 92, 82, and 93 points, respectively. There was a 2% rate of thigh pain with the Trilock, 4% with Taperloc, 4% in octogenarians, and 2% in patients with rheumatoid arthritis. In 96% of the patients in the Trilock group, in 100% of the patients in the Taperloc group, in 100% of the patients who were octogenarians, and in 100% of the patients with rheumatoid arthritis, femoral components showed radiographic evidence of bone ingrowth. There were six (12%) femoral component revisions in the Trilock group (all secondary to nonmodularity of the component at the time of acetabular revision), one femoral component revision in the Taperloc group and no femoral component revisions in the patients who were octogenarians or who had rheumatoid arthritis. Design features (collarless tapered wedge fit, circumferentially porous-coated) virtually ensure bone ingrowth and are thought to be responsible for the excellent clinical results and longevity.

Late dislocations after cementless total hip arthroplasty resulting from polyethylene wear.

We report 4 cases of polyethylene wear in modular cementless sockets presenting as recurrent dislocation. Before the onset of the dislocations, the patients were functioning without symptoms. This is the first report in the literature of this phenomenon.

Pseudoaneurysm of femoral artery after revision total hip arthroplasty with a constrained cup.

Delayed vascular injury after revision total hip arthroplasty is a rare and unusual complication. We report a case of a mechanical complication in which migration of a constraining ring locking mechanism used during a revision total hip arthroplasty caused a pseudoaneurysm of the common femoral artery.

The bearing surface in total hip arthroplasty: evolution or revolution.

Highly cross-linked polyethylenes represent a new class of polyethylenes that demonstrate dramatic improvements of wear characteristics in laboratory tests. Cross-linked polyethylenes can be manufactured by a number of methods, all of which lead to some changes in the physical properties of the polyethylene. The very limited clinical information about cross-linked polyethylenes available has been favorable. Cross-linked polyethylenes appear to hold promise as an alternative to conventional polyethylene and to hard-on-hard bearing surfaces, but much more clinical information will be required before they can be recommended for routine clinical use.

Routine follow-up office visits after total joint replacement: do asymptomatic patients wish to comply?

A total of 100 patients presenting for routine office follow-up after total hip or knee arthroplasty completed questionnaires evaluating whether they preferred to come to the office for routine follow-up evaluation or whether they would have preferred an evaluation without an office visit. Of 100 patients, 45 would have preferred not to come into the office for a routine evaluation. They were content to mail completed questionnaires and radiographs to their physicians. The other 55 patients preferred office visits. These 2 groups were comparable for age, sex, height, weight, and number of surgeries (P > .11) Preoperative and postoperative scores were similar between the 2 groups (P > .39). None of the patients that would have preferred not to come in to the office believed that quality of care would be compromised. A significant number (45%) of patients would prefer not to come to the office because of the wages saved and time spared. Routine office visits may be eliminated for these patients through the use of health outcome devices, such as the SF-36, along with routine radiographs. The potential to decrease healthcare costs and increase patient satisfaction warrants the identification of these patients. Assessment of the effect on quality of care with elimination of routine follow-up visits requires further study.

Uncemented total hip arthroplasty in Paget's disease of the hip: a report of 5 cases with 5-year follow-up.

Five patients with Paget's disease localized to the acetabulum received cementless acetabular components during total hip replacement. Three were primary surgeries, and 2 were revisions of a failed cemented acetabular component. At an average of 5.8 years (range, 4.8-8.8 years) after the operation, all acetabular components were well fixed radiographically with no migration or loosening. No patients complained of clinical symptoms referable to the acetabular component. No revisions had been performed. The ability of this inherently abnormal bone to proceed through the reparative and remodeling phases of porous ingrowth adds support to the use of uncemented components for acetabular reconstruction in Paget's disease of the hip.

Total hip arthroplasty in patients on long-term renal dialysis.

End-stage renal failure patients on long-term renal dialysis who underwent total hip arthroplasty (THA) were followed. Fifteen hips were implanted in 12 patients. There was a high mortality (58%) and high overall early complication rate (58%) with a deep infection rate of 13%. Of patients, 76% (n = 11) had good clinicoradiologic outcome of the THA before their death or at their latest follow-up. THA in patients on dialysis, however, should be reserved for those among this group who are expected to have a better life expectancy.

Acetabular fracture associated with cementless acetabular component insertion: a report of 13 cases.

Acetabular fracture during insertion of a cementless acetabular component occurred in 13 patients. The preoperative diagnosis was osteoarthritis in 6 patients, rheumatoid arthritis in 2 patients, avascular necrosis in 3 patients, hip fracture nonunion in 1 patient, and developmental dysplasia of the hip in 1 patient. Several different components were used; however, the acetabulum was underreamed by 1 to 3 mm in all cases. The acetabular fracture was identified in 9 of 13 cases intraoperatively. The fracture was identified on postoperative radiographs for the other 4 cases. Fractures were treated by a variety of means, including the addition of augmentation screws in or around the cup, use of autograft bone at the fracture site, modified postoperative weight-bearing status, and immobilization. In 2 cases, the socket needed to be revised after it progressively migrated and failed. One patient had cup migration, and another had a radiolucent line about the cup but was not symptomatic enough to require revision. In 3 of these 4 cases, the fracture was not identified intraoperatively. Underreaming of the acetabulum and use of an oversized acetabular component has been recommended to improve the initial stability of the acetabular component during total hip arthroplasty. Impaction of an oversized component requires bone to undergo plastic deformation if the cup is to be fully seated. Theoretically, this technique provides improved component stability with enhanced osseous ingrowth into the cup. The 13 cases reported in this study demonstrate that acetabular fracture is a complication that may occur in association with uncemented hip arthroplasty, particularly if oversized components are used. The importance of recognizing acetabular fractures intraoperatively and the need to institute appropriate treatment to ensure a stable acetabular component is emphasized. In patients with osteoporotic bone, line-to-line reaming with use of a cementless acetabular component or insertion of a cemented socket may be considered to avoid this significant complication.

Minimum 10-year results of a tapered cementless hip replacement.

Seventy-one total hip arthroplasties with a cementless, wedge fit, cobalt chrome femoral component were reviewed in 60 patients at a minimum 10-year followup (mean, 11.5 years). For the femoral component, the mechanical failure rate was 5% and the revision rate for aseptic loosening was 0%. The mean Charnley scores for pain, function, and motion changed from preoperative mean values of 3.0, 2.7, and 3.2 to followup mean values of 5.7, 5.5, and 5.2, respectively. The followup mean Harris hip Score was 91. The incidence of thigh pain was 1.4% at 10-year followup. Ninety-five percent of femoral components showed radiologic evidence of stable, bone ingrowth fixation, whereas loosening was seen in 5% of stems. Despite the high incidence of acetabular osteolysis, no osteolysis was seen on the femoral side distal to the lesser trochanter. Nonmodularity of the femoral component led to unavoidable revision of stably fixed femoral components in seven (9.8%) hips during the revision of a loose socket. Design features (collarless, tapered, wedge fit, and circumferentially porous coated) were thought to be crucial to the superlative results with the cobalt chrome femoral component.

Factors influencing choice of implants in total hip arthroplasty and total knee arthroplasty: perspectives of surgeons and patients.

To determine the factors influencing surgeons' choice of implants for total hip arthroplasty (THA) and total knee arthroplasty (TKA), 650 surveys were mailed to all active members of the American Association of Hip and Knee Surgeons practicing in the United States; 364 surveys (56%) were completed and returned. Analysis revealed that the average number of total hip and total knee replacements performed by the respondents in 1997 was 81 and 97; there was substantial regional variation. The average number of hip implant and knee implant brands used by these surgeons in 1997 was 2.4 and 1.8. Anticipated improvement in clinical results and cost of components were the most frequently listed reasons for changing brands. Surgeons were also queried about cost reduction programs at their particular institution. The most frequently listed strategies for cost reduction of implants included surgeon cost-awareness programs and volume discounting. More than half of the respondents (53.5%) anticipate manufacturers to decrease the cost of implants in the next 2 years. Most of the respondents (93.7%) currently have the ability to choose a particular implant. About half (46.7%) anticipate losing some or all control of this decision in the next 3 years. These respondents foresee their hospitals requiring the use of a discounted implant in the future. An additional survey was completed by 102 consecutive patients scheduled either for primary THA (64) or primary TKA (38) at our institution. When asked about implant selection, 93.1% responded that their orthopaedic surgeon should choose the prosthesis; 5.9% responded that their physician in consultation with the patient should choose the prosthesis. When asked what should be the primary determinant of implant choice, cost or quality, the overwhelming majority (97.1%) chose quality. A small percentage (2.9%) chose cost and quality. No patient chose cost alone. A large number of patients (84.8%) responded that they would pay additional costs if their insurance companies or health maintenance organizations refused to pay for a better but more expensive implant. Most patients realized how expensive components are, and 51% of the respondents correctly estimated the cost of an implant. Orthopaedic surgeons perceive that they are losing control of implant choice in THA and TKA. Cost of implants is one of the most significant factors influencing which implant is chosen. Patients (the true payors), however, overwhelmingly want their surgeons to choose the implant used at surgery, and they want quality, not cost, to be the primary determinant of this decision.