Surgical outcomes of hip and knee arthroplasties for primary osteoarthritis in patients with Alzheimer's disease: a nationwide registry-based case-controlled study.

We compared the length of hospitalisation, rate of infection, dislocation of the hip and revision, and mortality following primary hip and knee arthroplasty for osteoarthritis in patients with Alzheimer's disease (n = 1064) and a matched control group (n = 3192). The data were collected from nationwide Finnish health registers. Patients with Alzheimer's disease had a longer peri-operative hospitalisation (median 13 days vs eight days, p < 0.001) and an increased risk for hip revision with a hazard ratio (HR) of 1.76 (95% confidence interval (CI) 1.03 to 3.00). Dislocation was the leading indication for revision. There was no difference in the rates of infection, dislocation of the hip, knee revision and short-term mortality. In long-term follow-up, patients with Alzheimer's disease had a higher mortality (HR 1.43; 95% CI 1.22 to 1.70), and only one third survived ten years post-operatively. Increased age and comorbidity were associated with longer peri-operative hospitalisation in patients with Alzheimer's disease.

Adverse reaction to metal debris is more common in patients following MoM total hip replacement with a 36 mm femoral head than previously thought: results from a modern MoM follow-up programme.

We conducted a retrospective study to assess the prevalence of adverse reactions to metal debris (ARMD) in patients operated on at our institution with metal-on-metal (MoM) total hip replacements with 36 mm heads using a Pinnacle acetabular shell. A total of 326 patients (150 males, 175 hips; 176 females, 203 hips) with a mean age of 62.7 years (28 to 85) and mean follow-up of 7.5 years (0.1 to 10.8) participating in our in-depth modern MoM follow-up programme were included in the study, which involved recording whole blood cobalt and chromium ion measurements, Oxford hip scores (OHS) and plain radiographs of the hip and targeted cross-sectional imaging. Elevated blood metal ion levels (> 5 parts per billion) were seen in 32 (16.1%) of the 199 patients who underwent unilateral replacement. At 23 months after the start of our modern MoM follow-up programme, 29 new cases of ARMD had been revealed. Hence, the nine-year survival of this cohort declined from 96% (95% CI 95 to 98) with the old surveillance routine to 86% (95% CI 82 to 90) following the new protocol. Although ARMD may not be as common in 36 mm MoM THRs as in those with larger heads, these results support the Medicines and Healthcare Products Regulatory Agency guidelines on regular reviews and further investigations, and emphasise the need for specific a follow-up programme for patients with MoM THRs.

Individually assessed boldness predicts Perca fluviatilis behaviour in shoals, but is not associated with the capture order or angling method.

Selectivity of recreational angling on fish behaviour was studied by examining whether capture order or lure type (natural v. artificial bait) in ice-fishing could explain behavioural variation among perch Perca fluviatilis individuals. It was also tested if individually assessed personality predicts fish behaviour in groups, in the presence of natural predators. Perca fluviatilis showed individually repeatable behaviour both in individual and in group tests. Capture order, capture method, condition factor or past growth rate did not explain variation in individual behaviour. Individually determined boldness as well as fish size, however, were positively associated with first entrance to the predator zone (i.e. initial risk taking) in group behaviour tests. Individually determined boldness also explained long-term activity and total time spent in the vicinity of predators in the group. These findings suggest that individual and laboratory-based boldness tests predict boldness of P. fluviatilis in also ecologically relevant conditions, i.e. in shoals and in the presence of natural predators. The present results, however, also indicate that the above-mentioned two angling methods may not be selective for certain behavioural types in comparison to each other.

Surveillance of Patients with Metal-on-Metal Hip Resurfacing and Total Hip Prostheses: A Prospective Cohort Study to Investigate the Relationship Between Blood Metal Ion Levels and Implant Failure.

BACKGROUND: We designed a prospective, single-center study to assess whether blood metal ion levels could predict implant failure in patients managed with unilateral metal-on-metal hip resurfacing or total hip arthroplasty. METHODS: Five hundred and ninety-seven patients who had received unilateral Articular Surface Replacement prostheses at least twelve months earlier were recruited. Blood metal ion levels were compared between the group of patients with failed implants and the group with non-failed implants. Implant failure was defined as prostheses associated with revision, an intention to revise, or poor patient-reported hip function (Oxford Hip Score, <31 of 48). Specificity, sensitivity, area under the curve, positive and negative predictive values, and odds ratios were calculated. Logistic regression analysis was used to identify other risk factors for implant failure. RESULTS: Patients with failed arthroplasty had significantly higher blood cobalt and chromium ion levels than did patients with non-failed arthroplasty (p < 0.01). Blood cobalt ion levels were disproportionately raised in patients with failed total hip arthroplasty (8.2 µg/L) compared with patients with failed hip resurfacing (2.5 µg/L) (p = 0.018). Blood chromium ion levels were not significantly different in patients with failed total hip arthroplasty and failed hip resurfacing (p = 0.058). The maximum value of either metal ion had good discriminant ability to predict implant failure (area under the curve, 0.76). A 7-µg/L cutoff had a positive predictive value of 0.75 (95% confidence interval, 0.66 to 0.82) and a negative predictive value of 0.82 (95% confidence interval, 0.78 to 0.86). In patients managed with total hip arthroplasty, for each increase of 1 µg/L there was a 23% (p < 0.001) increase in the odds of them being in the failed group. For patients managed with hip resurfacing, the increase in odds was 5% (p < 0.001). CONCLUSIONS: Raised levels of blood metal ions were associated with failed metal-on-metal hip resurfacings and total hip arthroplasties. A threshold level of 7 µg/L had inadequate sensitivity to be used in isolation as a screening test for implant failure, but it provided nearly optimal misclassification rates. No level had a perfect positive predictive value, and so we discourage surgeons from performing revision surgery based on blood metal ion levels alone. Levels of cobalt ions were raised out of proportion to levels of chromium ions in failed total hip arthroplasty and may reflect a different mechanism for metal ion generation. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Surgical outcomes of primary hip and knee replacements in patients with Parkinson's disease: a nationwide registry-based case-controlled study.

We evaluated the duration of hospitalisation, occurrence of infections, hip dislocations, revisions, and mortality following primary hip and knee replacement in 857 patients with Parkinson's disease and compared them with 2571 matched control patients. The data were collected from comprehensive nationwide Finnish health registers. The mean follow-up was six years (1 to 13). The patients with Parkinson's disease had a longer mean length of stay (21 days [1 to 365] vs 13 [1 to 365] days) and an increased risk for hip dislocation during the first post-operative year (hazard ratio (HR) 2.33, 95% confidence intervals (CI) 1.02 to 5.32). There was no difference in infection and revision rates, and one-year mortality. In longer follow-up, patients with Parkinson's disease had higher mortality (HR 1.94, 95% CI 1.68 to 2.25) and only 274 (34.7%) were surviving ten years after surgery. In patients with Parkinson's disease, cardiovascular and psychiatric comorbidity were associated with prolonged hospitalisation and cardiovascular diseases also with increased mortality.

Spacer prostheses in two-stage revision of infected knee arthroplasty.

At present, no consensus exists on the best spacer alternative for the management of two-stage exchange arthroplasty of infected knee arthroplasties. In this retrospective study, patient records of 24 patients, who had undergone two-stage revisions in which resterilised prosthetic components were used as spacers, were reviewed. The outcome was compared to that of operations performed during the same period (1993-2003) using cement spacers (n=10). With an average follow-up of 32 months, control of infection was achieved in 26 cases (76%), with good or excellent clinical outcome in 19 cases (56%). Treatment failed and resulted in amputation at the level of the thigh before reimplantation in one case. Three patients did not undergo reimplantation. In four cases (12%) infection relapsed. The reinfection rate did not differ between the two spacer groups. Patients treated with resterilised components had a superior range of motion during the period between the two stages. Operative time was shorter and there was less blood loss in the reimplantation arthroplasty when a prosthetic spacer was used. We consider resterilised prosthetic components a safe and effective alternative to cement spacers in the management of infected knee arthroplasties.

Increased volumetric wear of polyethylene liners with more than 3 years of shelf-life time.

We analyzed 20 retrieved gamma-sterilized polyethylene liners (Biomet Hexloc). The long-term durability varied significantly depending on shelf-life time before implantation. Liners with a shelf-life time of 3 years or more evinced significantly ( P 0.002) higher volumetric wear than those with a shelf life time less than 3 years. Infrared spectroscopy and scanning calorimetry showed that all explanted implants underwent substantial in vivo oxidation and crystallization. The oxidative ageing of polyethylene renders the polyethylene liner susceptible to severe wear. Scanning electron microscopy of the bearing surface of the liner revealed abrasive wear as a dominant mechanism. Moreover, poor acetabular design produces excessively thin liners, substandard locking mechanism, and backside wear of the liner. The primary reason for severe wear in the Hexloc liner was poor modular design and oxidative degradation of the polyethylene.

Bipolar hemiartroplasty in the treatment of hip fracture: are special centres necessary for the optimal outcome?

BACKGROUND AND AIMS: This study compares retrospectively clinical follow-up of 72 bipolar arthroplasties made either by specialist surgeons or residents. MATERIAL AND METHODS: 72 patients with a life-expectancy of more than three years were selected to have bipolar arthroplasty for the treatment of femoral collum fracture at Tampere University Hospital district during 1993-1995. The average age of the patients was 70 (47-92) years. All patients were followed at least 4 years for mortality as well as primary and late complications. A group of 49 (68%) patients could be followed more carefully by clinical examination, by questionaire or by phone. RESULTS: 20 (28%) patients died during the first three years after surgery and four (6%) patients were re-operated. The bare preoperative clinical estimation made by the senior consultant surgeon did not predict good enough the life expectancy of the patients. Four patients had been revised, all operated by a senior surgeon. There were no revisions among the patients operated by junior doctors. No statistical differences were found between the patients operated by junior or senior surgeons or between cemented and cementless prostheses in pain, walking distances, limping, getting in to a car, need of support or sitting in high or normal chair. CONCLUSIONS: The bipolar arthroplasty was found to give reproducible results also when residents take the responsibility of hip fracture treatment.

Protection of femoral neck taper in revision of acetabular component.

In hip revision restricted to the acetabular component, the taper of a modular stem is in constant danger of scratching. We used a plastic syringe to protect the taper of the femoral component. A plastic syringe of appropriate size remains well in place and offers a novel and inexpensive protective device for the taper of the femoral component available in every operation room.

The Finnish Arthroplasty Register: report of the hip register.

The Finnish Arthroplasty Register was established in 1980. Between 1980 and 1999, 62,841 primary and 12,224 revision total hip arthroplasties (THA) were recorded. The annual number of both primary and revision THA has increased: in 1999, the incidence of primary THAs was 93/100,000. 174 implant designs have been used, but the 6 commonest implants comprised 82% in 1999. Since the late 1980s, more than 40% of the hips were inserted without cement. Over 47% of the cementless primary hip prostheses were used in patients younger than 60 years and over 93% of the cemented primary hips were used in patients 60 years or older. The 10-year survival rate was 72 (95% CI 67-76)% in patients younger than 55 years and 90 (89-91)% in patients older than 70 years. The commonest reasons for revision were aseptic loosening (65%), dislocation (9%) and infection (7%). In revisions, the 5-year survival of the cementless hip prosthesis improved over time: it was 85 (82-87)% in 1985-1989, 89 (88-91)% in 1990-1994 and 92 (88-95)% in 1995-1999. There are striking differences between the Arthroplasty Registers of Scandinavia as regards the end-point definition of survival. The Finnish Arthroplasty Register considers all reasons for revisions as the end-point of survival, but the Swedish register takes into account only aseptic loosening, so direct comparisons between registers are not possible. Recent data from the Finnish Arthroplasty Register indicate that the results of total hip replacements are improving in Finland. With the civic registration number, one can link and match data files. For example, with use of the Finnish Cancer Register, we found no increase in the risk of cancer after a THA.

Thompson hemiarthroplasty is superior to Ullevaal screws in treating displaced femoral neck fractures in patients over 75 years. A prospective randomized study with two-year follow-up.

BACKGROUND AND AIMS: The Finnish orthopaedic tradition has preferred hemiarthroplasty to internal fixation in femoral neck fracture treatment, while in Sweden internal fixation has been the method of choice. We decided to study whether internal fixation would prove superior to hemiarthroplasty even in displaced femoral neck fractures in patients over 75 years old. MATERIAL AND METHODS: We randomized 32 displaced femoral neck fractures in patients over 75 years old to receive internal fixation or hemiarthroplasty. RESULTS: Fifteen (47%) patients died within two years. Seven of 16 (44%) patients in the internal fixation group were reoperated, none in the hemiarthroplasty group (p = 0.007). Seven of the complications in the internal fixation group developed during the first year and it would have been unethical to continue the study. CONCLUSIONS: We conclude that displaced femoral neck fractures in patients over 75 years should be treated by arthroplasty.

Alarming wear of the first-generation polyethylene liner of the cementless porous-coated Biomet Universal cup: 107 hips followed for mean 6 years.

Wear of the socket liner and resulting osteolysis are the major causes of failure in cementless hip arthroplasties. We report alarming wear of the first-generation polyethylene liner of the cementless porous-coated Biomet Universal cup. Radiographs of 107 primary hip arthroplasties were analyzed retrospectively. The mean follow-up time was 74 (47-91) months. The linear wear of the polyethylene liners was assessed using a modification of the Livermore method. The median linear wear was 1.0 (0-6.2) and the median linear wear rate was 0.17 mm/year. There was a statistically significant difference between the 28 mm and 32 mm femoral head groups both in the volumetric wear and in the volumetric wear rate. The median linear wear was 0.28 mm/year and 0.14 mm/year for the 32 mm and 28 mm heads, respectively. So far, 14 revisions have been performed or have been scheduled because of excessive wear of the polyethylene liner. In regression analysis, the factors related to the wear rate were the 32 mm size of the femoral head and screw fixation of acetabular shell. We found that the cases with calcar rounding were associated with significantly greater wear. Possible reasons for increased wear of the Hexloc liner may be the cylindrical design, thin polyethylene, and poor quality of the polyethylene. Regular clinical and radiographic follow-ups are recommended especially for hips with 32 mm femoral heads or with screw fixation. If progressive wear of the liner is observed, revision must be considered.

The effects of cementless femoral stem shape and proximal surface texture on 'fit-and-fill' characteristics and on bone remodeling.

We measured the post-operative radiological "fit and fill" of two different femoral stem designs, one with a straight proximally porous-coated (Bi-Metric, n=50) and the other with a proximally anatomic, hydroxyapatite-coated and distally over-reamed stem (ABG, n=26). A comparison was then made between the clinical and radiological 5-year follow-up data of these two series and also of the bone remodeling changes around the stems. The observed differences in "fit and fill" parameters in the metaphyseal region were minute. However, in the diaphyseal bone the straight stem had substantially more cortical contact. The clinical results were excellent for both groups. Subsidence (>2 mm) was more frequent with the anatomical ABG stems, although the ABG stems had better bone ingrowth in the lower metaphyseal area. The present results indicate that the anatomical design may improve the fit and fill of a femoral stem in the metaphysis. On the other hand, a looser fill of the diaphyseal bone made the stems of this type more susceptible to subsidence. The straight stem with tight diaphyseal fit showed excellent stability, but the good bone ingrowth and remodeling around the distal part of the stem indicates stress transfer through this region and increased stress shielding of the proximal metaphyseal femur.

Poor survival of cementless Biomet total hip: a report on 1,047 hips from the Finnish Arthroplasty Register.

In Finland, almost 50% of all hip replacements done after 1989 have been inserted without cement. Biomet components have been the most commonly used implants in cementless arthroplasties. Between 1985 and 1997, 4,300 prostheses were implanted because of primary osteoarthrosis. 4 different acetabular component designs have been identified as Biomet implants (Mallory-Head, Romanus, T-TAP, Universal) and were used in 1,047 hips. The 9-year survival of all arthroplasties using Biomet cups was only 65 (95% CI 61-69)% while that of arthroplasties using T-TAP-cups was only 58 (52-65)%. In contrast, the 7.5-year survival of arthroplasties using Romanus cups was 85 (79-91)%. The 98 (96-99)% 5-year survival of arthroplasties with Mallory-Head cups should be interpreted cautiously, since similar results of arthroplasties using the Universal cup with the same type of liner decline sharply to 93 (88-98)% only 1 year later. The poor survival of Biomet cementless prostheses in our series seems to be related to the poor survival of the cup. This finding was common to all metal shell designs using Hexloc liners. We recommend that Biomet cups with Hexloc liners should not be used and patients who have had them inserted should undergo regular clinical and radiographic follow-ups.

Bone inductive potential and dose-dependent response of bovine bone morphogenetic protein combined with type IV collagen carrier.

Using type IV collagen as carrier, the expression of bovine bone morphogenetic protein (bBMP) activity and the relation of ectopic bone formation to BMP dosage in the reconstitution were investigated in BALB mice. Visible heterotopic bone was induced by GuHCl-extracted bovine BMP at a minimal dose of 0.5 mg within 21 days after the BMP was covalently bound to type IV collagen of weight 5.6 mg. The dose-dependent osteogenetic response of BMP was retained in the BMP/type IV collagen composite. As the BMP dose increased in the reconstitution, the integrated intensity and area of bone and cartilage formation, as quantified by a computerized scanner, were enhanced. Degradation of the collagenous carrier was improved by BMP, and neovascularization of the implant site initiated by type IV collagen was also observed. The covalent binding of BMP to type IV collagen postponed the time-sequence of ectopic bone development induced by BMP alone. The conclusion was that the exaggerated and extended effects of type IV collagen on BMP are mainly due to chemotaxis to progenitor cells, immunogenetically inert, vascular initiation and biodegradability in type IV collagen.