The Effect of Surgeon Caseload on the Relative Revision Rate of Cemented and Cementless Unicompartmental Knee Replacements: An Analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man.

BACKGROUND: Unicompartmental knee replacement (UKR) offers substantial benefits compared with total knee replacement (TKR) but is associated with higher revision rates. Data from registries suggest that revision rates for cementless UKR implants are lower than those for cemented implants. It is not known how much of this difference is due to the implant or to other factors, such as a greater proportion of high-volume surgeons using cementless implants. We aimed to determine the effect of surgeon caseload on the revision rate of matched cemented and cementless UKRs. METHODS: From a group of 40,522 Oxford (Zimmer Biomet) UKR implants (30,814 cemented, 9,708 cementless) recorded in the National Joint Registry, 14,814 (7,407 cemented, 7,407 cementless) were propensity-score matched. Surgeons were categorized into 3 groups: low volume (<10 cases/year), medium volume (10 to <30 cases/year), and high volume (≥30 cases/year). The effect of caseload on the relative risk of revision was assessed with use of Cox regression. RESULTS: The 10-year survival rates for unmatched cementless and cemented UKR implants were 93.3% (95% confidence interval [CI] = 89.8% to 95.7%) and 89.1% (95% CI = 88.6% to 89.6%), respectively, with the difference being significant (hazard ratio [HR] = 0.59; p < 0.001). Cementless UKR implants had a greater proportion of high-volume surgeon users than cemented implants (30.4% compared with 15.1%). Following matching, the 10-year survival rates were 93.2% (95% CI = 89.7% to 95.6%) and 90.2% (95% CI = 87.5% to 92.3%), which were still significantly different (HR = 0.76; p = 0.002). The 10-year survival rates for matched cementless and cemented UKR implants were 86.8% (95% CI = 73.6% to 93.7%) and 81.8% (95% CI = 73.0% to 88.0%) for low-volume surgeons, 94.3% (95% CI = 92.2% to 95.9%) and 92.5% (95% CI = 89.9% to 94.5%) for medium-volume surgeons, and 97.5% (95% CI = 96.5% to 98.2%) and 94.2% (95% CI = 90.8% to 96.4%) for high-volume surgeons. The revision rate for cementless implants was lower for surgeons in all 3 caseload groups (HR = 0.74, 0.79, 0.80, respectively). CONCLUSIONS: Cementless fixation decreased the revision rate by about a quarter, whatever the surgeon caseload. Caseload had a profound effect on implant survival. Low-volume surgeons had a high revision rate with cemented or cementless fixation and therefore should consider either stopping or doing more UKR procedures. High-volume surgeons performing cementless UKR demonstrated a 10-year survival rate of 97.5%, which was similar to that reported in registries for the best-performing TKRs. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Bone cement usage modalities at a multi-site university hospital centre.

BACKGROUND: Although cements are widely used during arthroplasty procedures, few recommendations exist regarding their optimal usage modalities, which, nevertheless, govern the long-term surgical outcomes. No detailed information is available on how cements are used in French hospitals. The objectives of this questionnaire survey among surgeons working at a multi-site university hospital in France were to describe practices, determine whether these varied with surgeon experience, and look for differences compared to recommendations. HYPOTHESIS: Cementing techniques vary widely among surgeons at a university hospital. MATERIAL AND METHODS: A questionnaire was sent to the five orthopaedic departments of our university hospital to collect data on the surgeons (age, sex, years of experience), their practice (type of implants used, annual number of arthroplasties with each arthroplasty type and each indication, and proportion of cemented arthroplasties), the type of cement used, and the cementing technique. RESULTS: Of the 34 surgeons, 21 completed the questionnaire, 20 males and 1 female with a mean age of 41 years (range, 31-59 years) and a mean of 11 years (range, 1-29 years) of experience. High-viscosity antibiotic-loaded cement was preferred by 20 (95%) surgeons, notably for knee arthroplasties, of which the median annual numbers were 55 (range, 0-218) and 8 (range, 1-40) for primary and revision cemented procedures, respectively. Various cementing techniques in ambient air were used: 12/21 (57%) surgeons used pulsed lavage to prepare the bone before cementation and 18/21 (86%) applied the cement to both the bone cuts and the implant. Of the 18 surgeons who performed knee arthroplasties, 12 used pulsed lavage, including 9 of the 11 surgeons with more than 5 years of experience and only 3 of the 7 less experienced surgeons. Similarly, of the 12 surgeons who used pulsed lavage for cemented arthroplasties, 11 were among the 12 surgeons who performed more than 15 cemented arthroplasties annually and 1 was among the 6 who performed fewer cemented arthroplasties. DISCUSSION: Cementing techniques varied widely, reflecting the dearth of recommendations and controversial results of published studies. In our centre, the use of pulsed lavage to improve bone preparation and cement application to both the bone and the implant should be promoted, as both techniques are universally advocated. Our study demonstrates the need to provide surgeons with opportunities to exchange their experiences about the other aspects of cementing in order to harmonise practices and to optimise the use of cement. LEVEL OF EVIDENCE: IV, questionnaire survey.

More complications with uncemented than cemented femoral stems in total hip replacement for displaced femoral neck fractures in the elderly.

Background and purpose - Total hip replacement (THR) is the preferred method for the active and lucid elderly patient with a displaced femoral neck fracture (FNF). Controversy still exists regarding the use of cemented or uncemented stems in these patients. We compared the effectiveness and safety between a modern cemented, and a modern uncemented hydroxyapatite-coated femoral stem in patients 65-79 years of age who were treated with THR for displaced FNF. Patients and methods - In a single-center, single-blinded randomized controlled trial, we included 69 patients, mean age 75 (65-79) and with a displaced FNF (Garden III-IV). 35 patients were randomized to a cemented THR and 34 to a reverse-hybrid THR with an uncemented stem. Primary endpoints were: prevalence of all hip-related complications and health-related quality of life, evaluated with EuroQol-5D (EQ-5D) index up to 2 years after surgery. Secondary outcomes included: overall mortality, general medical complications, and hip function. The patients were followed up at 3, 12, and 24 months. Results - According to the calculation of sample size, 140 patients would be required for the primary endpoints, but the study was stopped when only half of the sample size was included (n = 69). An interim analysis at that time showed that the total number of early hip-related complications was substantially higher in the uncemented group, 9 (among them, 3 dislocations and 4 periprosthetic fractures) as compared to 1 in the cemented group. The mortality and functional outcome scores were similar in the 2 groups. Interpretation - We do not recommend uncemented femoral stems for the treatment of elderly patients with displaced FNFs.

Regional bone loss following femoral neck fracture: A comparison between cemented and cementless hemiarthroplasty.

The aim of this prospective, randomised study was to measure and evaluate regional bone mineral changes and clinical results following the use of cemented and cementless hemiarthroplasty (HA) for treatment of femoral neck fracture in elderly patients. The study comprised 60 patients, 30 with cemented HA (group A) and 30 with cementless HA (group B). All patients underwent osteodensitometry of the contralateral hip, lumbar spine and bilateral distal femur. Dual-energy x-ray absorptiometry (DEXA) was scheduled at 1 month, 6 months and 1 year after surgery. Harris Hip Score (HHS) was used for functional assessment. Overall mortality rate was 20.3% within 1 year after surgery. There were no significant differences in morbidity, mortality and hospital stay between the two groups of patients. The implantation of cemented prosthesis took statistically significantly longer than that of cementless prosthesis (79.03±3.59 vs 68.02±5.97min; p=0.00). Functional score in patients treated with cemented HA was significantly higher compared with those with cementless HA. There was a trend of less intensive reduction of bone mineral density (BMD) in regions of interest of the lumbar spine and ipsilateral distal femur in patients with cemented HA (group A), whereas bone loss was less pronounced for the contralateral hip and distal femur in patients treated with cementless HA (group B). Management of displaced femoral neck fractures in elderly patients with cemented and cementless HA provides a comparable outcome with regard to morbidity and mortality; however, functional outcome of patients treated with cementless HA tends to be lower. There is less intensive BMD reduction in lumbar spine and ipsilateral distal femur in patients treated with cemented HA, whereas BMD reduction in patients treated with cementless HA is more likely to be less intensive in contralateral hip and distal femur.

What should be the preferred choice of hemiarthroplasty technique in American Society of Anesthesiologists (ASA) class III patients with femoral neck fractures? Cemented or cementless.

The hypothetical basis of this trial specifies that hemiarthroplasty applications without cement will prove to be superior to applications with cement in terms of survival, complications, clinical and radiological improvements in the early stages of femoral neck fracture cases, which belongs to the Society of Anesthesiologists (ASA) class III group. Society of Anesthesiologists (ASA) class III elderly patients (minimum 70 years of age), who had undergone surgical interventions for femoral neck fractures were classified into two groups as those undergoing the intervention without cement (Group A) and those undergoing the procedure with cement (Group B), and these were retrospectively evaluated. The patients were followed up for a mean duration of 47.4 and 44.8 months, respectively. Survival in the early stage, duration of stay in the intensive care, intraoperative cardiac indexes, complications, clinical and radiological parameters were the main factors used in the evaluation and comparisons. The mean duration of operation in Group B cases was determined to be statistically significantly longer than that of Group A (p<0.001). The postoperative stay at the intensive care unit in both groups and the rate of mortality for 6 months in Group B were determined to be statistically significantly high (p<0.05). In group B, significant depressive findings were determined in the comparison of the intra-operative pre-and post-cement cardiac indexes. In the clinical assessment, no statistically significant results were obtained, although higher final Harris scores were determined in Group A cases (p=0.581). In the treatment of femoral neck fractures, bipolar hemiarthroplasty applications without cement provide favourable early and short-term results, which are at least as effective as the applications with cement.

Minimum 5-year follow-up for primary THA using a tapered, proximally coated cementless stem.

The purpose of this study was to assess the survivorship of a proximally coated, cementless femoral stem used for total hip arthroplasty at a minimum 5-year follow-up by assessing clinical outcomes and implant survival. A total of 936 primary total hip arthroplasties were performed in 854 patients by 3 high-volume surgeons between 2001 and 2007. Patients included 385 men and 469 women with a mean age of 56 years (range, 20-88 years) and a mean follow-up of 7 years (range, 5-11 years). The aseptic revision rate related to the femoral component was 0.3%. Three patients underwent revision of the femoral component. Mean postoperative Harris Hip Score improved to 91 points (range, 70-100 points). When stratified by primary cause of total hip arthroplasty, no differences were found in implant survivorship or postoperative Harris Hip Scores. With the exception of the 3 patients who underwent revision surgery, postoperative radiographic evaluation of the stems demonstrated no progressive radiolucencies, component malalignment, change in component position, or implant subsidence at most recent follow-up.These results are encouraging and indicate a 0.3% revision rate for the femoral component. The cause of primary total hip arthroplasty did not affect the clinical outcomes. These types of prostheses will provide patients with a stable implant that is expected to have excellent durability and longevity.

The up to 25-year survival and clinical performance of 2,340 high gold-based metal-ceramic single crowns.

PURPOSE: This study aimed to present the up to 25-year clinical performance and survival of 2,340 high gold-based metal-ceramic single crowns placed in a specialist prosthodontic practice. MATERIALS AND METHODS: All crowns provided to 670 patients between 1984 and 2008 were sequentially recruited. Each crown/tooth combination was given a prognostic evaluation at cementation. Patients were recalled in 2008 and 2009 for examination, and patient records were scrutinized for any retreatment. Estimated cumulative survival, standard error, and differences in survival between groups were calculated using the Kaplan-Meier method, Greenwood formula, and log-rank test, respectively. Crown status (six-field classification) was reported within 5-year groupings and for 7, 10, and 12 years. RESULTS: The up to 10-year and 25-year estimated survival rates of the 2,211 favorably rated crowns were 97.08% ± 0.45% and 85.40% ± 2.19%, respectively. The up to 12-year survival for crowns in the postimplant era was 94.4% ± 2.78%. No significant differences related to sex, tooth type, or tooth position were demonstrated. Nonvital teeth had lower overall survival rates than vital teeth, but not in crowns placed in the postimplant era. Actual 10-year outcomes closely matched the estimated 10-year survival. Biologic factors accounted for 101 of the 133 failures, while mechanical factors accounted for 8 failures and patient concerns accounted for 24 failures. Porcelain fracture requiring replacement occurred in 4 crowns. CONCLUSIONS: The clinical performance of the crowns was excellent. Biologic factors accounted for the majority of failures. Material stability was excellent. Patient complaints of unacceptable esthetics resulted in 22 crowns being replaced after a mean clinical service time of 14 years.

A survey on the use of techniques, materials in dental implantology practice.

PURPOSE: To present results of a survey on the status of an implantology amongst implant-practicing dentist across the world in 2009. MATERIALS AND METHODS: A questionnaire was sent to the members of EAO (European Association of Osseointegration), ICOI (International Congress of Osseointegrated Implants), ISOI (Indian Society of Oral Implantologists), Asian Academy of Osseointegration (AAO), Deutsche Gasellschaft Fur Orale Implantologie (DGOI), Philippines Implant Organization, Korean Society of Oral Implantologist, Japanese Association of OralIimplantologists, Chinese Dental Association, Pakistan Dental Association, asking for the personal (anonymous) background data and their implantology concepts. Specific questions dealt with level of recognition of implants, use of implants, superstructures, techniques followed, and materials used. RESULTS: A total of 1500 (63.6%) of the 2358 questionnaires were answered. Dental implants were the most preferred treatment modality for restoring the missing teeth. Threaded implants were the most preferred. Cement retained implant prosthesis was the most preferred restoration procedure. Dentists believe that the general dentist should practice dental implant treatment modality, preferably teamwork. Immediate loading was the much-accepted concept among the dentists of the developed nations. CONCLUSION: Dental implants were much accepted treatment modality for the replacement of missing teeth. Most the dentists follow the well documented technique and proven materials, which have been documented in the literature, an evidenced based practice, thus, delivering the best to their patients. Dentists from the developing nations agreed to have standardization in implants.

Survival rates for porcelain laminate veneers with special reference to the effect of preparation in dentin: a literature review.

UNLABELLED: The porcelain laminate veneer is an elective restoration, often placed in the absence of disease for purely esthetic reasons. As such, it would appear desirable that the success rate of the technique was 100%. It is therefore the purpose of this paper to review the literature on porcelain laminate veneer survival by searching dental databases containing clinical trials of porcelain veneer restorations. References of selected trials were also screened to identify relevant studies. Each paper that was included was examined to ascertain if preparation into dentin affected survival. A total of 24 papers were included in the review. It was concluded that survival rates of porcelain laminate veneers are rarely 100%, and there is reasonable evidence indicating that a veneer preparation into dentin adversely affects survival. CLINICAL RELEVANCE: A review of the literature has indicated that porcelain laminate veneer survival is rarely 100%. Accordingly, patients should be made aware of this before embarking on this elective restorative technique. Clinicians should also be aware that the ideal preparation for porcelain veneers remains within enamel.

Cost savings of using a cemented total hip replacement: an analysis of the National Joint Registry data.

The debate whether to use cemented or uncemented components in primary total hip replacement (THR) has not yet been considered with reference to the cost implications to the National Health Service. We obtained the number of cemented and uncemented components implanted in 2009 from the National Joint Registry for England and Wales. The cost of each component was established. The initial financial saving if all were cemented was then calculated. Subsequently the five-year rates of revision for each type of component were reviewed and the predicted number of revisions at five years for the actual components used was compared with the predicted number of revisions for a cemented THR. This was then multiplied by the mean cost of revision surgery to provide an indication of the savings over the first five years if all primary THRs were cemented. The saving at primary THR was calculated to be £10 million with an additional saving during the first five years of between £5 million and £8.5 million. The use of cemented components in routine primary THR in the NHS as a whole can be justified on a financial level but we recognise individual patient factors must be considered when deciding which components to use.

[PMMA augmentation of pedicle screws: results of a survey in Germany]. / PMMA-Augmentation von Pedikelschrauben: Ergebnisse einer Umfrage in Deutschland.

BACKGROUND: The anchorage of pedicle screws can be challenging in the osteoporotic spine. A promising technique are cement augumented pedicle screws. The goal of this study was to gain more information regarding application of pedicle screw augmentation in Germany. MATERIALS AND METHODS: Participants of the National German Spine Congress 2009 were invited to participate in an internet-based anonymous survey regarding application of pedicle screw augmentation. The questionnaire was related to different aspects of materials and procedures for pedicle screw augmentation. The frequency of answers was divided according to the specialty state of the surgeons: orthopaedic and trauma surgeons vs. neurosurgeons. The Mantel-Haenszel test was applied to evaluate the differences between the groups. RESULTS AND CONCLUSION: 69 (64 %) orthopaedic and trauma surgeons and 39 (36 %) neurosurgeons participated (n = 108). Nearly 80 % of the participants use cement-augmented pedicle screws in their daily practice. Almost 2/3 of the specialists apply cannulated screws or other special screws. The Expedium (Company) screws are particularly preferred. The insertion of screws is combined with kyphoplasty or vertebroplasty in 20 % of the cases. The balloon kyphoplasty was applied most commonly. There was no statistical difference between the surgeon groups regarding the different techniques. The main indications for pedicle screw augmentation were osteoporosis, intraoperative findings as well as loosening of screws, and revision. The most frequently observed complication is cement extravasation into the spinal canal (28 %). The cost issue is considered as being important but unknown to most of the participants. It can be assumed that the use of pedicle screws in Germany is well established in spine surgery, without as yet a standard technique being established.

[Cemented total hip arthroplasty in Germany - update 2010]. / Stand der zementierten Hüftendoprothetik in Deutschland 2010.

BACKGROUND: The results of a national survey from 1998 showed that only around 10 % of orthopaedic surgeons in Germany had strictly implemented modern third-generation cementing techniques in total hip arthroplasty (THA). A 2005 update showed an improvement up to 29.4 %. The study was repeated in 2010 in order to evaluate the current situation and to determine whether modern cementing techniques have become more popular. MATERIAL AND METHODS: A detailed, slightly modified questionnaire regarding cement and bone preparation, cementing techniques on acetabulum and femur, and implant types was sent to 492 German orthopaedic and trauma hospitals, as well as to visiting surgeons with an interest in THA. The survey was conducted over 6 months. The response rate was 51.8 %, 255 questionnaires were available for evaluation and statistical analysis. RESULTS: Palacos R+G bone cement remained the most widely used cement (52.2 %). The mixing times given varied significantly. Vacuum mixing systems have again become more popular (85.2 %). In the femur 78.6 % of the surgeons attempted to preserve cancellous bone and 77.8 % used pulsatile (jet) lavage. Retrograde cement application via a cement gun was done in 85.8 %. Cement restrictors were used in more than 98 %. Only 72.7 % of the surgeons implemented sustained cement pressurisation and preferred a cement mantle thickness over 2 mm (55.2 %). Only 18.1 % drilled multiple small acetabular keyholes and 66.5 % used jet lavage. In 67.9 % no cement gun was used and in 70.7 % the cement was applied at high viscosity. Cement pressurisation was done manually in 89.1 %. The Müller straight stem device remained the most popular implant. Only 7.4 % of the centres implanted less than 20 and 40.3 % more than 100 cemented stems per year, whereby higher THA volumes correlated with better cementing technique. CONCLUSION: The results of this survey demonstrate that, in comparison to 2005, the current state of cemented THA, in particular cementing technique has generally significantly improved. Future emphasis should focus on continued surgeon education and training, as the cementing techniques are of utmost importance for long-term durability.

[Treatment results after cemented hemiprosthesis for care of unstable pertrochanteric femoral fractures in the elderly]. / Behandlungsergebnisse nach zementierter Hemiprothese zur Versorgung instabiler pertrochantärer Femurfrakturen alter Patienten.

BACKGROUND: The optimal treatment strategy for unstable trochanteric fractures in the elderly is still controversial because of the frequent failure of osteosynthesis. METHODS: A cohort of patients with unstable trochanteric fractures who were treated with cemented hemiarthroplasty and presented in our department during the period 2003-2009 was analyzed. Complications, reoperations, walking ability and full weight bearing were documented. RESULTS: A total of 91 patients were included (mean age 87.7±6.8 years) and predominantly 31A2 fractures (89%) were treated. There were 3.3% reoperations in the cohort and the 30 day mortality was 5.5%. At least 1 general complication occurred in over 50% of the patients. However, 30% of the patients had lower urinary tract infections, disturbances of electrolyte balance or transitory psychotic symptoms. On average full weight bearing could be performed at 3.5 (±3) days after the operation. CONCLUSION: Cemented hemiarthroplasty is a safe treatment strategy for unstable trochanteric fractures in the elderly, which allows early full weight bearing. Because of frequent general complications, more interdisciplinary units and centres of excellence are needed to handle this challenging cohort.

No superiority of cemented metal-on-metal over metal-on-polyethylene THA in a randomized controlled trial at 10-year follow-up.

In a randomized controlled trial, 102 cemented Stanmore 28-mm metal-on-metal total hip arthroplasties (THAs) were compared to 98 metal-on-polyethylene THAs in 195 patients. At a mean follow-up of 10 years, 11 patients (11 hips) were lost to follow-up, 53 patients (55 hips) died, and 6 patients (6 hips) underwent revision. Average age of the surviving patients was 79 years. Harris Hip Scores and Oxford Hip Scores had increased significantly in both groups (P=.000). Ten years postoperatively, mean Harris Hip Score was 86 in the metal-on-metal patients and 87 in the metal-on-polyethylene patients (P=.441); Oxford Hip Scores were 27 and 24, respectively (P=.494). Wear was present in 30 of 52 polyethylene cups. Periprosthetic radiolucencies were seen in 57% of the metal-on-metal patients and in 52% of the metal-on-polyethylene patients (P=.680); they were mainly seen in DeLee & Charnley's zones 1 and 2. Serum cobalt and chromium concentration were higher in the metal-on-metal group (cobalt 1.1, chromium 1.0 vs 0.5 and 0.5 mug/L, respectively; P<.001). Patients with high ion levels (maximum 9.5 and 11 mug/L, respectively) all showed high Harris Hip Scores and few or no periprosthetic radiolucencies, and none were revised. Ten-year survival was 95.5% in the metal-on-metal group (4 revisions) and 96.8% in the metal-on-polyethylene group (2 revisions; P=.402). All revisions were indicated for aseptic loosening. One case of aseptic lymphocytic vasculitis-associated lesions and no pseudotumors were observed. The absence of clinical superiority of the cemented metal-on-metal bearing and the concerns over their biological effects have led us to favor the cemented metal-on-polyethylene THA.

Clinical and radiological follow-up of the Aequalis third-generation cemented total shoulder replacement: a minimum ten-year study.

There are no long-term published results on the survival of a third-generation cemented total shoulder replacement. We describe a clinical and radiological study of the Aequalis total shoulder replacement for a minimum of ten years. Between September 1996 and May 1998, 39 consecutive patients underwent a primary cemented total shoulder replacement using this prosthesis. Data were collected prospectively on all patients each year, for a minimum of ten years, or until death or failure of the prosthesis. At a follow-up of at least ten years, 12 patients had died with the prosthesis intact and two had emigrated, leaving 25 available for clinical review. Of these, 13 had rheumatoid arthritis and 12 osteoarthritis. One refused radiological review leaving 24 with fresh radiographs. Survivorship at ten years was 100% for the humeral component and 92% for the glenoid component. The incidence of lucent lines was low. No humeral component was thought to be at risk and only two glenoid components. The osteoarthritic group gained a mean 65 degrees in forward flexion and their Constant score improved by a mean 41.4 points (13 to 55). The rheumatoid group gained a mean of 24 degrees in flexion and their Constant score improved by 29.4 points. This difference may have been due to failure of the rotator cuff in 75% of the patients with rheumatoid arthritis. Thus a third-generation total shoulder replacement gives an excellent result in patients with osteoarthritis and an intact rotator cuff. Patients with rheumatoid arthritis have a 75% risk of failure of the rotator cuff at ten years.

Survival and clinical function of cemented and uncemented prostheses in total knee replacement: a meta-analysis.

Using meta-analysis we compared the survival and clinical outcomes of cemented and uncemented techniques in primary total knee replacement. We reviewed randomised controlled trials and observational studies comparing cemented and uncemented fixation. Our primary outcome was survival of the implant free of aseptic loosening. Our secondary outcome was joint function as measured by the Knee Society score. We identified 15 studies that met our final eligibility criteria. The combined odds ratio for failure of the implant due to aseptic loosening for the uncemented group was 4.2 (95% confidence interval (CI) 2.7 to 6.5) (p < 0.0001). Subgroup analysis of data only from randomised controlled trials showed no differences between the groups for odds of aseptic loosening (odds ratio 1.9, 95% CI 0.55 to 6.40, p = 0.314). The weighted mean difference for the Knee Society score was 0.005 (95% CI -0.26 to 0.26) (p = 0.972). There was improved survival of the cemented compared to uncemented implants, with no statistically significant difference in the mean Knee Society score between groups for all pooled data.

Re-intervention on crowns: what comes next?

AIM: It is the aim of this paper to consider the treatment instituted when re-intervention is deemed necessary on a tooth which has previously been crowned. METHODS: A detailed sample of treatment records of patients has been established at the NHS Business Services Authority (Dental Services Division), consisting of records containing indirectly placed restorations for patients of age 18 years or older from January 1991. For each tooth treated with a crown, the subsequent history of intervention on that tooth was recorded. RESULTS: There were data on 47,474 crowns available for analysis, with metal-ceramic (bonded) crowns dominating the data (overall, 80% of crowns being these). There were 10,426 crowned teeth with re-interventions in the study period, with 36% of the re-interventions involving recementing, 17% being replacement crowns, 13% direct restorations, 12% root treatment, and 19% of crowned teeth being extracted and/or replaced by a denture. The longer the interval since crown placement, the higher the proportion of extractions or direct restoration and the lower the proportion of recementing. CONCLUSIONS: Recementation is the most frequently recorded re-intervention, with the incidence of this decreasing with increasing age of the crown. In 17% of re-interventions, the next intervention was a replacement crown.

Robust design for acetabular cup stability accounting for patient and surgical variability.

The stability of cementless acetabular cups depends on a close fit between the components and reamed acetabular cavities to promote bone ingrowth. Cup performance and stability are affected by both design and environmental (patient-dependent and surgical) factors. This study used a statistically based metamodel to determine the relative influences of design and environmental factors on acetabular cup stability by incorporating a comprehensive set of patient-dependent and surgical variables. Cup designs with 2 mm or 3 mm intended equatorial bone-implant interferences appeared to perform the best, improving implant stability with smaller mean and variability in cup relative motions and greater mean and smaller variability in ingrowth areas. Cup eccentricity was found to have no effect on implant performance. Design variables did not contribute as much to the variation in performance measures compared to the environmental variables, except for potential ingrowth areas.

Effect of etidronate in preventing periprosthetic bone loss following cemented hip arthroplasty: a randomized, double blind, controlled trial.

INTRODUCTION: Periprosthetic bone loss occurs after insertion of a total hip prosthesis and is often a result of stress shielding or altered loading of the proximal femur. Preventing the bone loss, which may threaten the prosthesis survival, with an antiresorptive drug would be highly advantageous. MATERIALS AND METHODS: Our study investigated the effect of cyclic etidronate therapy on periprosthetic, contralateral hip, and spine bone mineral density (BMD) in a one-year, prospective, randomized, double-blind study in 31 patients after cemented hip arthroplasty. Etidronate was taken orally in a regimen repeated every 14 weeks, and periprosthetic BMD was measured with dual energy X-ray absorptiometry (DXA) in the total periprosthetic area and in the seven Gruen zones at 1 week (baseline), 6 weeks, 3 months, 6 months, and 12 months postoperatively. RESULTS: In the etidronate group there were significant temporal BMD decreases measured in Gruen zones 2, 3, 6, and 7 and in the entire proximal femur; the greatest decrease was 12.9% and was measured in zone 7 at six months. Also in the etidronate group, there was a significant 2.8% temporal BMD increase in the spine at 12 months. In the placebo group there were significant temporal BMD decreases measured in Gruen zones 1, 2, 3, 5, 6, and 7 and in the entire proximal femur; the greatest decrease was 25.5% and was measured in zone 7 at 12 months. There were no significant differences between the mean BMD measurements of the etidronate and placebo groups. CONCLUSION: These findings suggest that cyclic etidronate therapy has no significant effect in suppressing periprosthetic bone loss after cemented hip arthroplasty.