The mean ten-year results of metal-on-metal hybrid hip resurfacing arthroplasty.

AIMS: This study presents the long-term survivorship, risk factors for prosthesis survival, and an assessment of the long-term effects of changes in surgical technique in a large series of patients treated by metal-on-metal (MoM) hip resurfacing arthroplasty (HRA). PATIENTS AND METHODS: Between November 1996 and January 2012, 1074 patients (1321 hips) underwent HRA using the Conserve Plus Hip Resurfacing System. There were 787 men (73%) and 287 women (27%) with a mean age of 51 years (14 to 83). The underlying pathology was osteoarthritis (OA) in 1003 (75.9%), developmental dysplasia of the hip (DDH) in 136 (10.3%), avascular necrosis in 98 (7.4%), and other conditions, including inflammatory arthritis, in 84 (6.4%). RESULTS: The mean follow-up time was 10.5 years (1 to 20). Using revision for any reason as the endpoint, the overall survivorship at 15 years was 89.4% (95% confidence interval (CI) 86.8 to 91.4). There was a substantial increase between the first and second generation of surgical technique (86.6% vs 90.1%; p = 0.05). Men with idiopathic OA had a 15-year survivorship of 94.5% and women, 82.2% (p = 0.001); gender was not a risk factor after stratification by component size and aetiology. Using revision for excessive wear (ion levels > 7 µg/l associated with symptoms or adverse local tissue reactions) as the endpoint, the 15-year survivorship was 98.5%. Risk factors for revision for all modes of failure were an underlying pathology of hip dysplasia, a contact patch to rim (CPR) distance of 7 mm or less, an age at surgery of 55 years or less, and a femoral component size of 46 mm or less. Specific risk factors for aseptic failure of the femoral component were early surgical technique, a cementless metaphyseal stem, and a body mass index of 24 kg/m2 or less. CONCLUSION: HRA is a viable concept; metal-on-metal bearings are well suited for this procedure when a well-designed device is properly implanted. The best results were obtained in men with OA, but survivorship was better for other underlying pathologies and for women after changes were made to the technique of implantation. Lifetime durability is a possible outcome for many patients despite a high level of activity. Cite this article: Bone Joint J 2018;100-B:1424-33.

Risk factors for wear-related failures after hip resurfacing in patients with a low contact patch to rim distance.

AIMS: A contact patch to rim (CPR) distance of < 10 mm has been associated with edge-loading and excessive wear. However, not all arthroplasties with a low CPR distance show problems with wear. Therefore, CPR distance may not be the only variable affecting the post-operative metal ion concentrations. PATIENTS AND METHODS: We used multiple logistic regression to determine what variables differed between the patients who had high and low cobalt (CoS) and chromium (CrS) serum ion concentrations within a cohort of patients with low (< 10 mm) CPR distances. A total of 56 patients treated with unilateral hip resurfacing arthroplasty (HRA) had CoS and CrS ion studies performed more than one year after surgery. The mean age of the patients at the time of surgery was 51.7 years (29 to 70), with 38 women (68%) and 18 men (32%). RESULTS: It was seen that 47 patients had low ion levels (< 7µg/L) and nine had high ion levels (≥ 7µg/L). We found increased risks of high wear with decreasing CPR distance. CONCLUSION: The use of CPR distance measurements to predict hips at risk for elevated wear is needed for all patients with HRA. We recommend that patients with low CPR distances have at least one serum ion study performed while patients with CPR distance > 10 mm do not need routine ion studies. We believe that patients with low CPR distance and low ions do not need repeat ion studies unless the patient becomes symptomatic or has substantial radiographic changes. Cite this article: Bone Joint J 2017;99-B:865-71.

Hip resurfacing for osteonecrosis: two- to 18-year results of the Conserve Plus design and technique.

AIMS: Hip resurfacing arthroplasty (HRA) is an alternative to conventional total hip arthroplasty for patients with osteonecrosis (ON) of the femoral head. Our aim was to report the long-term outcome of HRA, which is not currently known. PATIENTS AND METHODS: Long-term survivorship, clinical scores and radiographic results for 82 patients (99 hips) treated with HRA for ON over a period of 18 years were reviewed retrospectively. The mean age of the 67 men and 15 women at the time of surgery was 40.8 years (14 to 64). Patients were resurfaced regardless of the size of the osteonecrotic lesion. RESULTS: The mean clinical follow-up was 10.8 years (2 to 18). The mean University of California, Los Angeles hip scores at the last follow-up were 9.3, 9.4, 9.2 and 6.8 for pain, walking, function and activity, respectively. A total of six hips underwent revision surgery, four for loosening of the femoral component and two for loosening of the acetabular component. Using any revision as an end point, the 15-year Kaplan-Meier survivorship was 90.3%. There were no wear-related failures. There were no femoral failures among the hips reconstructed with a cemented metaphyseal stem. A total of five hips showed narrowing of the femoral neck; all stabilised and remain asymptomatic, 21 showed signs of femoral neck impingement. CONCLUSION: To our knowledge, this is the first report of a series of HRA performed for ON with 15-year survivorship. Our data confirm that patients with advanced stages of ON of the femoral head are excellent candidates for HRA. Cite this article: Bone Joint J 2016;98-B:901-9.

Are there differences in Hip Biomechanics after hybrid and cementless resurfacing arthroplasty?

There is a paucity of information regarding the clinical performance of the fully cementless metal-on-metal hip resurfacing designs. We compared the biomechanical reconstruction between the two hips of a group of patients treated with a hybrid resurfacing design on one side and a new, fully cementless version of the same resurfacing design on the other side.We retrospectively identified 20 patients with a hybrid hip resurfacing on one side and a fully cementless device on the contralateral side. The cemented femoral components were implanted with a target angle stem to shaft angle of 140° while the cementless femoral components were implanted with the aim to replicate the natural neck to shaft angle.No significant differences were observed post-operatively in femoral offset or leg length despite implantation with a larger metaphyseal stem to femoral shaft angle in the hybrid group. Both hybrid and cementless designs provide similar biomechanical reconstructions.

[Metal-on-metal hybrid hip resurfacing. Development and current state]. / Der Metall-Metall-Hybridoberflächenersatz des Hüftgelenks. Entwicklung und aktueller Stand.

Worldwide the employment of surface replacements using metal-on-metal components as an option, particularly for the young and active patient, has gained broad acceptance. Part of the attraction for hip resurfacing is its conservative nature as a prosthetic solution for hip arthritis. It is anatomical, replicating the normal hip and limb length, preserving proximal femoral bone, and is a truly minimally bone invasive approach with excellent outcome of joint function. The purpose of this article is to show the data of 1,000 Conserve(c) Plus hybrid metal-on-metal prostheses in a consecutive study of 1,140 patients with a follow-up of 5.6 years. The current Kaplan and Meier survival estimates of the prosthesis, using any conversion to total hip replacement as the end point, were 98.1% at 3 years [95% confidence interval (CI): 96.8-98.9%], 96.7% at 4 years (95% CI: 94.8-97.8%), and 95.2% at 5 years (95% CI: 93.0-96.8%). The mean postoperative Harris hip score was 93.3. The current state of metal-on-metal surface replacement is positive. The new generation of hip resurfacing has a lot of improvements. The purpose of this review of the procedure is to point out the definite improvements from earlier designs using polyethylene as well as to highlight the overall results and durability achieved by one surgeon's extensive experience and to assess the results from other series and centers. We also want to point out the areas where further investigation is needed.

Background of metal-on-metal resurfacing.

Hip resurfacing is not a new concept and attempts to treat hip arthritis without resecting the femoral head and neck have been made since the 1950s. The resurgence of new and better-engineered metal-on-metal bearings has provided the means to develop a viable prosthetic solution from a concept that was once abandoned. The lessons drawn from the early resurfacing era led to modern designs all using a cementless fixation of the acetabular component and a short metaphyseal stem designed for component alignment on the femoral side. Currently, only metallic devices can be manufactured with sufficient strength as a thin one-piece shell, combining excellent wear properties for large femoral heads and a bone-conserving device on the acetabular side. The early results of these new designs are extremely encouraging but the rapid development of the procedure needs to be controlled by appropriate training programmes to ensure its future success.

EBRA-FCA for measurement of migration of the femoral component in surface arthroplasty of the hip.

Studies on the migration of an implant may be the only way of monitoring the early performance of metal-on-metal prostheses. The Ein Bild Roentgen Analyse--femoral component analysis (EBRA-FCA) method was adapted to measure migration of the femoral component in a metal-on-metal surface arthroplasty of the hip using standard antero-posterior radiographs. In order to determine the accuracy and precision of this method a prosthesis was implanted into cadaver bones. Eleven series of radiographs were used to perform a zero-migration study. After adjustment of the femoral component to simulate migration of 3 mm the radiographs were repeated. All were measured independently by three different observers. The accuracy of the method was found to be +/- 1.6 mm for the x-direction and +/- 2 mm for the y-direction (95% percentile). The method was validated using 28 hips with a minimum follow-up of 3.5 years after arthroplasty. Seventeen were sound, but 11 had failed because of loosening of the femoral component. The normal (control) group had a different pattern of migration compared with that of the loose group. At 29.2 months, the control group showed a mean migration of 1.62 mm and 1.05 mm compared with 4.39 mm and 4.05 mm in the failed group, for the centre of the head and the tip of the stem, respectively (p = 0.001). In the failed group, the mean time to migration greater than 2 mm was earlier than the onset of clinical symptoms or radiological evidence of failure, 19.1 versus 32.2 months (p = 0.001) and 24.8 months (p = 0.012), respectively. EBRA-FCA is a reliable and valid tool for measuring migration of the femoral component after surface arthroplasty and can be used to predict early failure of the implant. It may be of value in determining the long-term performance of surface arthroplasty.

[Tripolar arthroplasty for recurrent total hip prosthesis dislocation]. / Reprise de prothèses totales de hanche instables par prothèses tripolaires.

PURPOSE OF THE STUDY: The purpose of this study was to assess the results of revision surgery for recurrent total hip prosthesis dislocation using a tripolar prosthesis composed of a conventional stem with a mobile head of an intermediary prosthesis measuring more than 40 mm and a modified cup. This technique was used in two centers in Rouen France and Los Angeles USA. MATERIAL AND METHODS: Twenty-one hips in 21 patients were operated on. The mobile heads measured 40 to 47 mm. Mean patient age was 70 years (range 29-92). The indication for the tripolar prosthesis was reserved for extremely unstable hips in patients with major risk factors for recurrent dislocation. These 21 patients had experienced 95 dislocations. The acetabular cup was custom-made for the large-diameter heads. A cemented polyethylene cup was used in 14 cases and a press-fit metal-backed around a polyethylene insert in 7. The polyethylene thickness varied from 6.5 to 16 mm for the cemented cups and 4 to 5 mm for the press-fit cups. Fourteen femoral stems were left in place as were two press-fit cups where only the inserts were changed. Mean follow-up was 5.4 years (range 3-11.8). RESULTS: There has been no recurrent dislocation for 20 hips. One patient experienced a dislocation one week after surgery which required a second revision procedure to reposition the acetabular implant. Final outcome was good at 7.6 years for this hip. One patient who had not had any recurrent dislocation died 4 years after the revision surgery due to a cause unrelated to the prosthesis. Two patients were lost to follow-up at 3.7 and 6 years, both were pain free and had no radiological anomalies. Infection occurred in one patient undergoing chemotherapy for a myeloma; the head and neck had to be resected. For the 20 other patients, functional outcome, assessed with the UCLA score, showed improvement in pain (5.8 preoperatively, 9.2 at last follow-up), walking (4.8 and 8 respectively), function (4 and 6 respectively), and daily activities (3.3 and 5.2 respectively). A revision procedure was necessary for one patient during the 4(th) year because of a fracture of the polyethylene insert on a metal-back cup; the insert alone was changed. Excepting the patient with infection, there were no cases of certain or probable loosening during the follow-up. DISCUSSION: The tripolar prosthesis with a mobile cup and a large-diameter head appears to be a reliable solution for these severely unstable hips. The procedure can often be limited to the acetabular component, reducing morbidity. The thickness of the polyethylene cup is a limitation which may affect long-term survival. Search for a highly wear-resistant couple continues.

Polyethylene wear characteristics in vivo and in a knee stimulator.

Validation of a wear simulator requires that the device produce a similar type and amount of wear and particles of a comparable morphology as occurs clinically. Using techniques previously established to compare polyethylene particles from hip simulators to those from retrieved tissues, particles isolated from six revised posterior stabilized knee replacements were characterized and compared to particles generated from the same knee design worn in a knee simulator. The particles produced in the knee simulator were of comparable size but had less variability in their form factor compared to the particles produced in vivo. Comparable wear features were seen on the articulating surfaces in both groups. These results indicate that this knee joint simulator is able to reproduce a baseline type of wear that is similar to that in vivo and should encourage further use of this device to better understand knee component wear and function.

Duration of symptoms and outcome of hemiresurfacing for hip osteonecrosis.

Thirty-seven hips with Ficat Stage II, III, or early IV osteonecrosis were treated with hemiresurfacing. The purpose of this study is to analyze specifically the clinical and radiographic results of patients who had hemiresurfacing to refine the indications for the procedure and identify factors substantially affecting clinical outcome and survivorship. At an average followup of 6.5 years, the average University of California Los Angeles hip scores for pain, walking, function, and activity improved significantly from 4.3, 6.0, 5.3, and 4.2 to 8.0, 8.8, 7.9, and 5.8. The overall survivorship was 79%, 59%, and 45% at 5, 10, and 15 years. Eleven hips have been converted: 10 hips for acetabular cartilage wear and one hip for femoral loosening. The average time to conversion was 7.5 years. A longer duration of symptoms before surgery (16.6 months versus 12.1 months) was associated with a worse acetabular cartilage grading and suggested a relationship with a shorter time to conversion, although the difference was not statistically significant at the 5% level. Survivorship is better when preoperative symptoms are present for 1 year or less, possibly because the articular cartilage is healthier. When necessary, conversion to total hip replacement can be done without adverse results.

The John Charnley Award. Wear is a function of use, not time.

Polyethylene wear (linear penetration) in 37 hip replacements was assessed from digital images using a validated two-dimensional, edge detection-based computer algorithm. Patient activity was assessed with a pedometer, a step activity monitor and a simple visual analog scale. Joint use was related to wear at the 90% confidence level. Without three recognized outliers, wear was highly correlated to use. The visual analog scale activity rating was significantly related to wear for the 24 hip replacements with standard polyethylene. Univariate regression analysis indicated that male gender, height, weight (which were both highly correlated to male gender) and hip center of rotation were significantly correlated to wear. Multivariate regression analysis indicated that male gender, femoral off-set, and Hylamer were significantly correlated to wear. Based on the wear and activity data from the 24 hip replacements with standard polyethylene, the average volumetric wear rate per million cycles with a 70 kg patient weight was 30 mm3. This unique in vivo result can be considered a target wear rate for standard polyethylene in hip simulator studies.

Use of a magnet to retrieve a broken scalpel blade.

The retrieval of metallic foreign bodies, such as screws, drill bits, needles, and scalpel blades, from the surgical wound during orthopaedic surgery is often a time-consuming procedure. The extra time and dissection may result in increased morbidity. We report a case during a hip arthroplasty in which a broken surgical blade could not be located with surgical dissection even with the aid of an image intensifier. The broken blade finally was retrieved with the introduction of a magnet.

Innovations in design and technology. The story of hip arthroplasty.

The current study reviews the early history of surgeon-initiated trial and error development in hip joint arthroplasty and the subsequent methodological evolution to proper criteria for hypothesis testing using bioengineers and other research scientists. The interplay and relationships to industry, universities, scientific organizations, and the Food and Drug Administration with respect to device development in hip arthroplasty are reviewed. The ethics of and responsibilities to involved parties are outlined, citing the history of many contemporary developments. Examples are provided from the evolution and introduction of unsuccessful innovations, and the problems inherent in the current methodology of the approval process from the Food and Drug Administration using the 5-10K, Investigative Device Exemption, and the Pre-Market Approval protocols. The pros and cons of randomized trials for devices are outlined with the conclusion that they are not appropriate for device introduction. The proper, rational methodology for introduction of new devices is a phased-in clinical trial process after pertinent bench testing. Finally, the ethical dilemmas created by managed care are addressed. Industry involvements of the surgeon-spokesmen are cited.

Relationship between body mass index and activity in hip or knee arthroplasty patients.

The weight of patients has not been demonstrated to have a consistent effect on the rate of polyethylene wear in clinical studies of total joint replacement. For this reason, we analyzed the relationship between quantitative activity, measured with a pedometer, and body mass index, a measure of obesity. Data were acquired for 209 individuals, 22-82 years of age; all were independent community walkers. One hundred and fifty-one had a well functioning total hip or knee replacement. Analysis of variance was used to evaluate the relationship between activity and body mass index, with adjustments for confounding variables. The 58 individuals with no total joint prosthesis averaged 7,781 steps per day, which was higher (p < 0.01) than those with a total hip (5,869 steps per day) or knee (4,597 steps per day) replacement. The subjects with no total joint prosthesis were, however, younger than the patients with a prosthesis (p < 0.01), and the body mass index of the patients with a total knee replacement was higher than that of the patients with a hip replacement and that of the subjects with no prosthesis (p < 0.01). After adjustment for differences in age, gender, and Charnley class, a higher body mass index (greater obesity) was associated with lower activity (p = 0.05). With regard to the rate of polyethylene wear, decreased ambulatory activity may counterbalance increased weight, which could, at least in part, explain why weight has not had a consistent effect on polyethylene wear in clinical studies. Wear is a function of use, not time. The effect of obesity on activity should be considered in radiographic studies of wear and other outcome assessments of total joint replacements.