Search

Background and purpose Modular cementless revision prostheses are being used with increasing frequency. In this paper, we review risk factors for the outcome of the Link MP stem and report implant survival compared to conventional cemented long-stem hip revision arthroplasties. Patients and methods We used data recorded in the Swedish Hip Arthroplasty Register. 812 consecutive revisions with the MP stem (mean follow-up time 3.4 years) and a control group with 1,073 cemented long stems (mean follow-up time 4.2 years) were included. Kaplan-Meier analysis was used to determine implant survival. The Cox regression model was used to study risk factors for reoperation and revision. Results The mean age at revision surgery for the MP stem was 72 (SD 11) years. Decreasing age (HR == 1.1, 95% CI: 1--1.1), multiple previous revisions (HR == 2.6, 95% CI: 1.1--6.2), short stem length (HR == 2.4, 95% CI: 1.1--5.2), standard neck offset (HR == 5, 95% CI: 1.5--17) and short head-neck length (HR == 5.3, 95% CI 1.4--21) were risk factors for reoperation. There was an overall increased risk of reoperation (HR == 1.7, 95% CI: 1.3--2.4) and revision (HR == 1.9, 95% CI: 1.2--3.1) for the MP prostheses compared to the controls. Interpretation The cumulative survival with both reoperation and revision as the endpoint was better for the cemented stems with up to 3 years of follow-up. Thereafter, the survival curves converged, mainly because of increasing incidence of revision due to loosening in the cemented group. We recommend the use of cemented long stems in patients with limited bone loss and in older patients. [ABSTRACT FROM AUTHOR]

Background and purpose The validity of various data sources for the assessment of the outcome quality of medical devices was investigated by comparative analysis of the published data sources available for a sample of implants. It was the aim of the study to determine the performance of this implant and to identify potential bias factors inherent to the various datasets. Methods A comprehensive literature search was carried out from English-language, peer-reviewed journals and worldwide reports from national arthroplasty registers. Publications from Medline-listed journals were included. The main parameter was revision rate, calculated as ''revisions per 100 observed component years'' to allow adjusted direct comparison of different datasets. Results Of 16 clinical studies that met the inclusion criteria, 9 originated from the implant developer's hospital. In the clinical studies category, publications from the developer's hospital suggested considerably lower revision rates than the other datasets. In fact, the values quoted were 5.5 times below the average of all other studies, and 9.51 times lower than in the Australian arthroplasty register. These differences are statistically significant. Interpretation The cementless Taperloc stem is an implant that shows good performance regarding revision rates in registry data and in clinical studies. However, the excellent results published by the developer's clinic are generally not reproducible by other surgeons. In terms of reference data, registry data are able to make an important contribution to the assessment of clinical sample-based studies, particularly regarding evaluation of the extent to which published results are reproducible in daily routine. [ABSTRACT FROM AUTHOR]

Background and purpose Hip resurfacing (HRS) procedures have gained increasing popularity for younger, higher-demand patients with degenerative hip pathologies. However, with concerns regarding revision rates and possible adverse metal hypersensitivity reactions with metal-on-metal articulations, some authors have questioned the hypothesized superiority of hip resurfacing over total hip arthroplasty (THA). In this meta-analysis, we compared the clinical and radiological outcomes and complication rates of these 2 procedures. Methods A systematic review was undertaken of all published (Medline, CINAHL, AMED, EMBASE) and unpublished or gray literature research databases up to January 2010. Clinical and radiological outcomes as well as complications of HRS were compared to those of THA using risk ratio, mean difference, and standardized mean difference statistics. Studies were critically appraised using the CASP appraisal tool. Results 46 studies were identified from 1,124 citations. These included 3,799 HRSs and 3,282 THAs. On meta-analysis, functional outcomes for subjects following HRS were better than or the same as for subjects with a THA, but there were statistically significantly greater incidences of heterotopic ossification, aseptic loosening, and revision surgery with HRS compared to THA. The evidence base showed a number of methodological inadequacies such as the limited use of power calculations and poor or absent blinding of both patients and assessors, possibly giving rise to assessor bias. Interpretation On the basis of the current evidence base, HRS may have better functional outcomes than THA, but the increased risks of heterotopic ossification, aseptic loosening, and revision surgery following HRS indicate that THA is superior in terms of implant survival. [ABSTRACT FROM AUTHOR]

Background and purpose — A shortened tibial stem could influence the early prosthetic fixation. We therefore compared the short stem to the standard-length stem using radiostereometric analysis (RSA) as primary outcome measure. Patients and methods — 60 patients were randomized to receive a cemented Triathlon total knee arthroplasty (TKA) with a tibial tray of either standard or short stem length. The patients were blinded regarding treatment allocation. The micromotion of the tibial component was measured by RSA postoperatively, at 3 months, and after 1 and 2 years; clinical outcome was measured with the American Knee Society score (AKSS) and the knee osteoarthritis and injury outcome score (KOOS). Results — The maximum total point motion (MTPM) for the standard stem was 0.36 (SD 0.16) mm at 3 months, 0.51 (SD 0.27) mm at 1 year, and 0.54 (SD 0.28) mm at 2 years. For the short stem, it was 0.42 (0.24) mm, 0.59 (0.43) mm, and 0.61 (0.39) mm. 4 short-stemmed components and 2 standard-stemmed components had more than 0.2 mm of migration between the first- and second-year follow-up, and were classified as continuously migrating. Interpretation — The short-stemmed cemented tibial prosthesis showed an early prosthetic migratory pattern similar to that of the standard-stemmed cemented Triathlon knee prosthesis. The number of continuously migrating tibial plates in each group is predictive of a lower revision rate than 5% at 10 years. [ABSTRACT FROM AUTHOR]

Background and purpose - Muscle atrophy is seen in patients with metal-on-metal (MOM) hip implants, probably because of inflammatory destruction of the musculo-tendon junction. However, like pseudotumors, it is unclear when atrophy occurs and whether it progresses with time. Our objective was to determine whether muscle atrophy associated with MOM hip implants progresses with time. Patients and methods - We retrospectively reviewed 74 hips in 56 patients (32 of them women) using serial MRI. Median age was 59 (23-83) years. The median time post-implantation was 83 (35-142) months, and the median interval between scans was 11 months. Hip muscles were scored using the Pfirrmann system. The mean scores for muscle atrophy were compared between the first and second MRI scans. Blood cobalt and chromium concentrations were determined. Results - The median blood cobalt was 6.84 (0.24-90) ppb and median chromium level was 4.42 (0.20-45) ppb. The median Oxford hip score was 34 (5-48). The change in the gluteus minimus mean atrophy score between first and second MRI was 0.12 (p = 0.002). Mean change in the gluteus medius posterior portion (unaffected by surgical approach) was 0.08 (p = 0.01) and mean change in the inferior portion was 0.10 (p = 0.05). Mean pseudotumor grade increased by 0.18 (p = 0.02). Interpretation - Worsening muscle atrophy and worsening pseudotumor grade occur over a 1-year period in a substantial proportion of patients with MOM hip implants. Serial MRI helps to identify those patients who are at risk of developing worsening soft-tissue pathology. These patients should be considered for revision surgery before irreversible muscle destruction occurs. [ABSTRACT FROM AUTHOR]

Background and purpose - Perioperative hyperglycemia has been associated with adverse outcomes in several fields of surgery. In this observational study, we identified factors associated with an increased risk of hyperglycemia following hip and knee replacement. Patients and methods - We prospectively monitored changes in glucose following primary hip and knee replacements in 191 patients with osteoarthritis. Possible associations of patient characteristics and operation-related factors with hyperglycemia (defined as glucose > 7.8 mmol/L in 2 consecutive measurements) and severe hyperglycemia (glucose > 10 mmol/L) were analyzed using binary logistic regression with adjustment for age, sex, operated joint, and anesthesiological risk score. Results - 76 patients (40%) developed hyperglycemia, and 48 of them (25% of the whole cohort) had severe hyperglycemia. Glycemic responses were similar following hip replacement and knee replacement. Previously diagnosed diabetes was associated with an increased risk of hyperglycemia and severe hyperglycemia, compared to patients with normal glucose metabolism, whereas newly diagnosed diabetes and milder glucose metabolism disorders had no effect. In patients without previously diagnosed diabetes, increased values of preoperative glycosylated hemoglobin (HbA1c) and fasting glucose on the day of operation were associated with hyperglycemia. Higher anesthesiological risk score-but none of the operation-related factors analyzed-was associated with an increased risk of hyperglycemia. Interpretation - Perioperative hyperglycemia is common in primary hip and knee replacements. Previously diagnosed diabetes is the strongest risk factor for hyperglycemia. In patients with no history of diabetes, preoperative HbA1c and fasting glucose on the day of operation can be used to stratify the risk of hyperglycemia. [ABSTRACT FROM AUTHOR]

Background and purpose - NSAIDs are commonly used in the clinic, and there is a general perception that this does not influence healing in common types of human fractures. Still, NSAIDs impair fracture healing dramatically in animal models. These models mainly pertain to fractures of cortical bone in shafts, whereas patients more often have corticocancellous fractures in metaphyses. We therefore tested the hypothesis that the effect of an NSAID is different in shaft healing and metaphyseal healing. Methods - 26 mice were given an osteotomy of their left femur with an intramedullary nail. 13 received injections of indomethacin, 1 mg/kg twice daily. After 17 days of healing, the femurs were analyzed with 3-point bending and microCT. 24 other mice had holes drilled in both proximal tibias, to mimic a stable metaphyseal injury. A screw was inserted in the right tibial hole only. After 7 days of indomethacin injections or control injections, screw fixation was measured with mechanical pull-out testing and the side without a screw was analyzed with microCT. Results - In the shaft model, indomethacin led to a 35% decrease in force at failure (95% CI: 14-54). Callus size was reduced to a similar degree, as seen by microCT. Metaphyseal healing was less affected by indomethacin, as no effect on pull-out force could be seen (95% CI: -27 to 17) and there was only a small drop in new bone volume inside the drill hole. The difference in the relative effect of indomethacin between the 2 models was statistically significant (p = 0.006). Interpretation - Indomethacin had a minimal effect on stable metaphyseal fractures, but greatly impaired healing of unstable shaft fractures. This could explain some of the differences found between animal models and clinical experience. [ABSTRACT FROM AUTHOR]

Background and purpose - The optimal hip replacement for young patients remains unknown. We compared patient-reported outcome measures (PROMs), revision risk, and implant costs over a range of hip replacements. Methods - We included hip replacements for osteoarthritis in patients under 60 years of age performed between 2003 and 2010 using the commonest brand of cemented, cementless, hybrid, or resurfacing prosthesis (11,622 women and 13,087 men). The reference implant comprised a cemented stem with a conventional polyethylene cemented cup and a standard-sized head (28- or 32-mm). Differences in implant survival were assessed using competing-risks models, adjusted for known prognostic influences. Analysis of covariance was used to assess improvement in PROMs (Oxford hip score (OHS) and EQ5D index) in 2014 linked procedures. Results - In males, PROMs and implant survival were similar across all types of implants. In females, revision was statistically significantly higher in hard-bearing and/or small-stem cementless implants (hazard ratio (HR) = 4) and resurfacings (small head sizes (< 48 mm): HR = 6; large head sizes (≥ 48 mm): HR = 5) when compared to the reference cemented implant. In component combinations with equivalent survival, women reported significantly greater improvements in OHS with hybrid implants (22, p = 0.006) and cementless implants (21, p = 0.03) (reference, 18), but similar EQ5D index. For men and women, National Health Service (NHS) costs were lowest with the reference implant and highest with a hard-bearing cementless replacement. Interpretation - In young women, hybrids offer a balance of good early functional improvement and low revision risk. Fully cementless and resurfacing components are more costly and do not provide any additional benefit for younger patients. [ABSTRACT FROM AUTHOR]

Background and purpose - There has been a recent trend towards the use of greater femoral head sizes in an attempt to improve function and enhance stability after primary hip replacement. This has been associated with the use of alternative bearings, theoretically to reduce wear and improve implant longevity. Methods - We examined the influence of these variables on patient-reported outcome measures (PROMs) for a consecutive series of primary hip replacements using National Joint Registry (NJR) and PROMs-linked data. To minimize the confounding influence of implant design factors, the single most commonly used brand in England and Wales (DePuy Corail Pinnacle) was examined. Improvement in patient hip-specific outcomes (Oxford hip score, OHS), general health outcomes (Euroqol, EQ-5D), and rates of self-reported complications (bleeding, wound problems, re-admission, and reoperation) were compared for different head sizes (28-mm, 32-mm, and 36-mm) and bearings (metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), and ceramic-on-ceramic (CoC)), adjusting for differences in case mix. Results - At a mean follow-up of 7 months, improvements in OHS and EQ5D index were similar for 28-mm and 36-mm heads. A 32-mm head was associated with poorer function (OHS: 20, 99% CI: 19-21, p = 0.002; EQ5D index: 0.39, 99% CI: 0.36-0.42, p = 0.004), although these small differences may not be of clinical importance. There were no statistically significant benefits of either CoP or CoC bearings compared to a MoP bearing. Complication rates were similar within comparisons of head sizes or bearings. Interpretation - In this short-term study, we did not find any functional benefits of larger head sizes or alternative bearings, after adjusting for other influences. We question their use in routine primary hip replacement given the lack of evidence of improved long-term survival in the literature. [ABSTRACT FROM AUTHOR]

Background and purpose - The osteogenic potency of erythropoietin (EPO) has been documented. However, its efficacy in a large-animal model has not yet been investigated; nor has a clinically safe dosage. The purpose of this study was to overcome such limitations of previous studies and thereby pave the way for possible clinical application. Our hypothesis was that EPO increases calvarial bone healing compared to a saline control in the same subject. Methods - We used a porcine calvarial defect model. In each of 18 pigs, 6 cylindrical defects (diameter: 1 cm; height: 1 cm) were drilled, allowing 3 pairwise comparisons. Treatment consisted of either 900 IU/mL EPO or an equal volume of saline in combination with either autograft, a collagen carrier, or a polycaprolactone (PCL) scaffold. After an observation time of 5 weeks, the primary outcome (bone volume fraction (BV/TV)) was assessed with high-resolution quantitative computed tomography. Secondary outcome measures were histomorphometry and blood samples. Results - The median BV/TV ratio of the EPO-treated collagen group was 1.06 (CI: 1.02-1.11) relative to the saline-treated collagen group. Histomorphometry showed a similar median effect size, but it did not reach statistical significance. Autograft treatment had excellent healing potential and was able to completely regenerate the bone defect independently of EPO treatment. Bony ingrowth into the PCL scaffold was sparse, both with and without EPO. Neither a substantial systemic effect nor adverse events were observed. The number of blood vessels was similar in EPO-treated defects and saline-treated defects. Interpretation - Topical administration of EPO on a collagen carrier moderately increased bone healing. The dosing regime was safe, and could have possible application in the clinical setting. However, in order to increase the clinical relevance, a more potent but still clinically safe dose should be investigated. [ABSTRACT FROM AUTHOR]

Background and purpose It is difficult to evaluate glenoid component periprosthetic radiolucencies in total shoulder arthroplasties (TSAs) using plain radiographs. This study was performed to evaluate whether computed tomography (CT) using a specific patient position in the CT scanner provides a better method for assessing radiolucencies in TSA. Methods Following TSA, 11 patients were CT scanned in a lateral decubitus position with maximum forward flexion, which aligns the glenoid orientation with the axis of the CT scanner. Follow-up CT scanning is part of our routine patient care. Glenoid component periprosthetic lucency was assessed according to the Molé score and it was compared to routine plain radiographs by 5 observers. Results The protocol almost completely eliminated metal artifacts in the CT images and allowed accurate assessment of periprosthetic lucency of the glenoid fixation. Positioning of the patient within the CT scanner as described was possible for all 11 patients. A radiolucent line was identified in 54 of the 55 observed CT scans and osteolysis was identified in 25 observations. The average radiolucent line Molé score was 3.4 (SD 2.7) points with plain radiographs and 9.5 (SD 0.8) points with CT scans (p = 0.001). The mean intra-observer variance was lower in the CT scan group than in the plain radiograph group (p = 0.001). Interpretation The CT scan protocol we used is of clinical value in routine assessment of glenoid periprosthetic lucency after TSA. The technique improves the ability to detect and monitor radiolucent lines and, therefore, possibly implant loosening also. [ABSTRACT FROM AUTHOR]

Background and purpose Limb lengthening is performed for a diverse range of orthopedic problems. A high rate of complications has been reported in these patients, which include motor and sensory loss as a result of nerve damage. We investigated the effect of limb lengthening on peripheral nerve function. Patients and methods 36 patients underwent electrophysiological testing at 3 points: (1) preoperatively, (2) after application of external fixator/corticotomy but before lengthening, and (3) after lengthening. The limb-length discrepancy was due to a congenital etiology (n = 19), a growth disturbance (n = 9), or a traumatic etiology (n = 8). Results 2 of the traumatic etiology patients had significant changes evident on electrophysiological testing preoperatively. They both deteriorated further with lengthening. 7 of the 21 patients studied showed deterioration in nerve function after lengthening, but not postoperatively, indicating that this was due to the lengthening process and not to the surgical procedure. All of these patients had a congenital etiology for their leg-length discrepancy. Interpretation As detailed electrophysiological tests were carried out before surgery, after surgery but before lengthening, and finally after completion of lengthening, it was possible to distinguish between the effects of the operation and the effects of lengthening on nerve function. The results indicate that the etiology, site (femur or tibia), and nerve (common peroneal or tibial) had a bearing on the risk of nerve injury and that these factors had a far greater effect than the total amount of lengthening. [ABSTRACT FROM AUTHOR]

Background and purpose Hydroxyapatite (HA) coating is believed to improve bone-implant ingrowth and long-term survival of prostheses. Recent studies, however, have challenged this view. Furthermore, HA particles may produce third-body wear and initiate aseptic loosening of implants. We report the performance of HA- and porous-coated acetabular cups in a prospective randomized trial. Methods This was an 8-year follow-up study of our previously published prospective randomized study to compare clinical outcomes, survival, periprosthetic bone mineral density, migration, and wear rates of HA- and porous-coated acetabular cups. Dual X-ray absorptiometry (DXA) and Ein Bild Roentgen Analyse (EBRA) measurements were used. 100 patients who underwent unilateral cementless total hip arthroplasty were randomized to either porous-coated cups or HA-coated cups. Patients were examined preoperatively and at 3, 6, and 9 months, and also 1, 3, and 8 years after surgery. 81 patients were available for 8-year follow-up, 40 with porous-coated cups and 41 with HA-coated cups. Results Age, sex, bone mineral density, and clinical results (Harris hip score) were similar in the 2 groups. The survival, wear, and migration patterns of the cups were also similar in both groups. The results of periprosthetic bone mineral density scans in region of interest 2 was in favor of the porous-coated cups, but there were no differences between the 2 groups in all the remaining regions of interest. Interpretation HA coating had no statistically significant effect on clinical results, survival, wear, or migration at the 8-year follow-up. [ABSTRACT FROM AUTHOR]

Background It is unclear whether it is safe to convert above-elbow cast (AEC) to below-elbow cast (BEC) in a child who has sustained a displaced diaphyseal both-bone forearm fracture that is stable after reduction. In this multicenter study, we wanted to answer the question: does early conversion to BEC cause similar forearm rotation to that after treatment with AEC alone? Children and methods Children were randomly allocated to 6 weeks of AEC, or 3 weeks of AEC followed by 3 weeks of BEC. The primary outcome was limitation of pronation/supination after 6 months. The secondary outcomes were re-displacement of the fracture, limitation of flexion/extension of the wrist and elbow, complication rate, cast comfort, complaints in daily life, and cosmetics of the fractured arm. Results 62 children were treated with 6 weeks of AEC, and 65 children were treated with 3 weeks of AEC plus 3 weeks of BEC. The follow-up rate was 60/62 and 64/65, respectively with a mean time of 6.9 (4.7-13) months. The limitation of pronation/supination was similar in both groups (18 degrees for the AEC group and 11 degrees for the AEC/BEC group). The secondary outcomes were similar in both groups, with the exception of cast comfort, which was in favor of the AEC/BEC group. Interpretation Early conversion to BEC cast is safe and results in greater cast comfort. [ABSTRACT FROM AUTHOR]

Background and purpose The micro-architecture of bone has been increasingly recognized as an important determinant of bone strength. Successful operative stabilization of fractures depends on bone strength. We evaluated the osseous micro-architecture and strength of the osteoporotic human femoral head. Material and methods 6 femoral heads, obtained during arthroplasty surgery for femoral neck fracture, underwent micro-computed tomography (microCT) scanning at 30 μm, and bone volume ratio (BV/TV), trabecular thickness, structural model index, connection density, and degree of anisotropy for volumes of interest throughout the head were derived. A further 15 femoral heads underwent mechanical testing of compressive failure stress of cubes of trabecular bone from different regions of the head. Results The greatest density and trabecular thickness was found in the central core that extended from the medial calcar to the physeal scar. This region also correlated with the greatest degree of anisotropy and proportion of plate-like trabeculae. In the epiphyseal region, the trabeculae were organized radially from the physeal scar. The weakest area was found at the apex and peripheral areas of the head. The strongest region was at the center of the head. Interpretation The center of the femoral head contained the strongest trabecular bone, with the thickest, most dense trabeculae. The apical region was weaker. From an anatomical and mechanical point of view, implants that achieve fixation in or below this central core may achieve the most stable fixation during fracture healing. [ABSTRACT FROM AUTHOR]

Background and purpose Large-size hip articulations may improve range of motion (ROM) and function compared to a 28-mm THA, and the low risk of dislocation allows the patients more activity postoperatively. On the other hand, the greater extent of surgery for resurfacing hip arthroplasty (RHA) could impair rehabilitation. We investigated the effect of head size and surgical procedure on postoperative rehabilitation in a randomized clinical trial (RCT). Methods We followed randomized groups of RHAs, large-head THAs and standard THAs at 2 months, 6 months, 1 and 2 years postoperatively, recording clinical rehabilitation parameters. Results Large articulations increased the mean total range of motion by 13° during the first 6 postoperative months. The increase was not statistically significant and was transient. The 2-year total ROM (SD) for RHA, standard THA, and large-head THA was 221° (35), 232° (36), and 225° (30) respectively, but the differences were not statistically significant. The 3 groups were similar regarding Harris hip score, UCLA activity score, step rate, and sick leave. Interpretation Head size had no influence on range of motion. The lack of restriction allowed for large articulations did not improve the clinical and patient-perceived outcomes. The more extensive surgical procedure of RHA did not impair the rehabilitation. This project is registered at ClinicalTrials.gov under # NCT01113762. [ABSTRACT FROM AUTHOR]

Background and purpose Different results after shoulder arthroplasty have been found for different diagnostic groups. We evaluated function, pain, and quality of life after shoulder arthroplasty in 4 diagnostic groups. Patients and methods Patients with shoulder arthroplasties registered in the Norwegian Arthroplasty Register from 1994 through 2008 were posted a questionnaire in 2010. 1,107 patients with rheumatoid arthritis (RA), osteoarthritis (OA), acute fracture (AF), or fracture sequela (FS) returned completed forms (65% response rate). The primary outcome measure was the Oxford shoulder score (OSS), which assesses symptoms and function experienced by the patient on a scale from 0 to 48. A secondary outcome measure was the EQ-5D, which assesses life quality. The patients completed a questionnaire concerning symptoms 1 month before surgery, and another concerning the month before they received the questionnaire. Results Patients with RA and OA had the best results with a mean improvement in OSS of 16 units, as opposed to 11 for FS patients. Both shoulder pain and function had improved substantially. The change in OSS for patients with AF was negative (-11), but similar end results were obtained for AF patients as for RA and OA patients. Quality of life had improved in patients with RA, OA, and FS. Interpretation Good results in terms of pain relief and improved level of function were obtained after shoulder arthroplasty for patients with RA, OA, and-to a lesser degree-FS. A shoulder arthropathy had a major effect on quality of life, and treatment with shoulder replacement substantially improved it. [ABSTRACT FROM AUTHOR]

Background and purpose Feasibility is an important parameter when choosing which patient-reported outcomes (PRO) to use in a study. We assessed the feasibility of PROs in a hip registry setting. Methods Primary total hip arthroplasty (THA) patients (n = 5,747) who had been operated on 1-2, 5-6, or 10-11 years previously were randomly selected from the Danish Hip Arthroplasty Register and sent 2 PRO questionnaires: 1 generic (EuroQoL-5D or SF-12 health survey) and 1 disease-specific (hip dysfunction and osteoarthritis outcome score (HOOS) or Oxford 12-item hip score). We compared response rates, floor and ceiling effects, missing items, and the need for manual validation of forms. Results 4,784 patients (mean age 71 years, 57% females) were included (83%). The response rates ranged from 82-84%. Statistically significantly different floor and ceiling effects ranged from 0% to 0.5% and from 6.1% to 46%, respectively. Missing items ranged from 1.2% to 3.4%, and 0.8-4.3% required manual validation (p < 0.009). A hypothetical repeat study found that group sizes from 51 to 1,566 are needed for subgroup analysis, depending on descriptive factor and choice of PRO. Interpretation All 4 PROs fulfilled a priori set criteria, with the exception of ceiling effects. The high ceiling effects were attributed to postoperative administration and good outcome for THA. We conclude that all 4 PROs are appropriate for administration in a hip registry. [ABSTRACT FROM AUTHOR]

Background and purpose We have previously shown that early fracture callus of rat rib has viscoelastic and contractile properties resembling those of smooth muscle. The cells responsible for this contractility have been hypothesized to be myofibroblast-like in nature. In soft-tissue healing, force generated by contraction of myofibroblasts promotes healing. Accordingly, we tried to identify myofibroblast-like cells in early fibrous callus. Animals and methods Calluses from rat rib fractures were removed 7, 14, and 21 days after fracture and unfractured ribs acted as controls. All tissues were analyzed using qPCR and immunohistochemistry. We analyzed expression of smooth muscle- and myofibroblast-associated genes and proteins including alpha smooth muscle actin (αSMA), non-muscle myosin, fibronectin extra domain A variant (EDA-fibronectin), OB-cadherin, connexin-43, basic calponin (h1CaP), and h-caldesmon. Results In calluses at 7 days post-fracture, there were statistically significant increases in expression of αSMA mRNA (2.5 fold), h1CaP mRNA (2.1 fold), EDA-fibronectin mRNA (14 fold), and connexin-43 mRNA (1.8 fold) compared to unfractured ribs, and by 21 days post-fracture mRNA expression in calluses had decreased to levels approaching those in unfractured rib. Immunohistochemistry of 7 day fibrous callus localized calponin, EDA-fibronectin and co-immunolabeling of OB-cadherin and αSMA (thus confirming a myofibroblastic phenotype) within various cell populations. Interpretation This study provides further evidence that early rat rib callus is not only smooth muscle-like in nature but also contains a notable population of cells that have a distinct myofibroblastic phenotype. The presence of these cells indicates that in vivo contraction of early callus is a mechanism that may occur in fractures so as to facilitate healing, as it does in soft tissue wound repair. [ABSTRACT FROM AUTHOR]

Background and purpose The trabecular metal tibial monoblock component (TM) is a relatively new option available for total knee arthroplasty. We have previously reported a large degree of early migration of the trabecular metal component in a subset of patients. These implants all appeared to stabilize at 2 years. We now present 5-year RSA results of the TM and compare them with those of the NexGen Option Stemmed cemented tibial component (Zimmer, Warsaw IN). Patients and methods 70 patients with osteoarthritis were randomized to receive either the TM implant or the cemented component. RSA examination was done postoperatively and at 6 months, 1 year, 2 years, and 5 years. RSA outcomes were translations, rotations, and maximum total point motion (MTPM) of the components. MTPM values were used to classify implants as 'at risk' or 'stable'. Results At the 5-year follow-up, 45 patients were available for analysis. There were 27 in the TM group and 18 in the cemented group. MTPM values were similar in the 2 groups (p == 0.9). The TM components had significantly greater subsidence than the cemented components (p == 0.001). The proportion of 'at risk' components at 5 years was 2 of 18 in the cemented group and 0 of 27 in the TM group (p == 0.2). Interpretation In the previous 2-year report, we expressed our uncertainty concerning the long-term stability of the TM implant due to the high initial migration seen in some cases. Here, we report stability of this implant up to 5 years in all cases. The implant appears to achieve solid fixation despite high levels of migration initially. [ABSTRACT FROM AUTHOR]

Background and purpose Controversies still exist regarding the best surgical procedure in the treatment of periprosthetic infection after total hip arthroplasty (THA). Based on data in the Norwegian Arthroplasty Register (NAR), we have compared the risk of re-revision after 4 different surgical procedures: 2-stage with exchange of the whole prosthesis, 1-stage with exchange of the whole prosthesis, major partial 1-stage with exchange of stem or cup, and minor partial 1-stage with exchange of femoral head and/or acetabular liner. Methods Between 1987 and 2009, 124,759 primary THAs were reported to the NAR, of which 906 (0.7%) were revised due to infection. Included in this study were the 784 revisions that had been performed by 1 of the 4 different surgical procedures. Cox-estimated survival and relative revision risks are presented with adjustment for differences among groups regarding gender, type of fixation, type of prosthesis, and age at revision. Results 2-stage procedures were used in 283 revisions (36%), 1-stage in 192 revisions (25%), major partial in 129 revisions (17%), and minor partial in 180 revisions (23%). 2-year Kaplan-Meier survival for all revisions was 83%; it was 92% for those re-revised by 2-stage exchange procedure, 88% for those re-revised by 1-stage exchange procedure, 66% for those re-revised by major partial exchange procedure, and it was 76% for those re-revised by minor partial exchange. Compared to the 2-stage procedure and with any reason for revision as endpoint (180 re-revisions), the risk of re-revision increased 1.4 times for 1-stage (p == 0.2), 4.1 times for major partial exchange (p < 0.001), and 1.5 times for minor partial exchange (p == 0.1). With infection as the endpoint (108 re-revisions), the risk of re-revision increased 2.0 times for 1-stage exchange (p == 0.04), 6.0 times for major partial exchange (p < 0.001), and 2.3 times for minor partial exchange (p == 0.02). Similar results were found when the analyses were restricted to the period 2002-2009. Interpretation In the Norwegian Arthroplasty Register, the survival after revision of infected primary THA with 2-stage implant exchange was slightly superior to that for 1-stage exchange of the whole prosthesis. This result is noteworthy, since 2-stage procedures are often used with the most severe infections. However, debridement with exchange of head and/or liner but with retention of the fixed implant (minor revision) meant that there was a 76% chance of not being re-revised within 2 years. [ABSTRACT FROM AUTHOR]

Background and purpose The choice of either all-polyethylene (AP) tibial components or metal-backed (MB) tibial components in total knee arthroplasty (TKA) remains controversial. We therefore performed a meta-analysis and systematic review of randomized controlled trials that have evaluated MB and AP tibial components in primary TKA. Methods The search strategy included a computerized literature search (Medline, EMBASE, Scopus, and the Cochrane Central Register of Controlled Trials) and a manual search of major orthopedic journals. A meta-analysis and systematic review of randomized or quasi-randomized trials that compared the performance of tibial components in primary TKA was performed using a fixed or random effects model. We assessed the methodological quality of studies using Detsky quality scale. Results 9 randomized controlled trials (RCTs) published between 2000 and 2009 met the inclusion quality standards for the systematic review. The mean standardized Detsky score was 14 (SD 3). We found that the frequency of radiolucent lines in the MB group was significantly higher than that in the AP group. There were no statistically significant differences between the MB and AP tibial components regarding component positioning, knee score, knee range of motion, quality of life, and postoperative complications. Interpretation Based on evidence obtained from this study, the AP tibial component was comparable with or better than the MB tibial component in TKA. However, high-quality RCTs are required to validate the results. [ABSTRACT FROM AUTHOR]

Background and purpose There is disagreement in the literature about the importance of patellofemoral joint degeneration and knee pain for the outcome of unicompartmental knee arthroplasty (UKA). We therefore investigated the importance of selected predictors including patellofemoral joint degeneration and the location of preoperative knee pain for the early outcome of UKA. Patients and methods The study group comprised 260 consecutive patients from 5 hospitals who underwent Oxford UKA for anteromedial osteoarthritis. Data were collected at baseline and included pain location, radiologically observed degeneration of the patellofemoral joint including subluxation of the patella, intraoperative cartilage status of the patellofemoral joint, disease-specific knee status, and Oxford knee score (OKS). Outcomes were evaluated after 1 year using the OKS, global patient satisfaction, and global patient result. Results The average OKS score at baseline was 24 (SD 7), and it was 40 (SD 8) at the 1-year follow-up. 94% of the patients claimed improvement after the operation and 90% were satisfied with the UKA. Lateral subluxation of the patella was a predictor of poor outcome, and the preoperative OKS score was also a predictor of outcome. Full-thickness cartilage loss at any location gave a similar outcome to that with a normal or near-normal joint surface, and likewise, preoperative anterior knee pain was not a predictor of outcome. Interpretation We conclude that the good early outcome after UKA in this study is in line with the best reported results. Patellofemoral degeneration should not be considered a contraindication to Oxford UKA. Patients with lateral subluxation of the patella have an increased risk of a poor result after UKA and should preferably be offered a total knee replacement. [ABSTRACT FROM AUTHOR]

Background and purpose Deep vein thrombosis is common after total joint replacement. It is frequently asymptomatic, and it is unclear whether this leads to longer-term problems such as post-thrombotic syndrome and leg ulceration. We investigated whether the postoperative prevalence of ulceration in patients who had undergone primary total hip replacement (THR) or total knee replacement (TKR) was higher than that found in a control group who had not undergone total joint replacement. Methods The study group consisted of patients who had undergone THR or TKR at one orthopedic center 12-16 years previously without routine chemothromboprophylaxis, and who had not undergone revision surgery. The control group was recruited via primary care. All participants were recruited by post and asked to complete a questionnaire. Age- and sex-adjusted prevalence of self-reported leg ulceration was calculated, and logistic regression was used to determine whether there were any associations between THR or TKR and leg ulceration. Results Completed questionnaires were received from 441 THR patients (54% response rate), 196 TKR patients (48%) and 967 control participants (36%). No statistically significant differences in age- and sex-adjusted prevalence of ulceration were found between the groups, for either lifetime prevalence or prevalence over the previous 15 years. Interpretation Patients who undergo THR and TKR without chemothromboprophylaxis are unlikely to be at a higher risk of long-term venous ulceration than the normal population. [ABSTRACT FROM AUTHOR]

Background and purpose Slipped capital femoral epiphysis (SCFE) is often treated by surgical fixation; however, no agreement exists regarding technique. We analyzed the outcome of in situ fixation with Steinmann pins. Patients and methods All 67 subjects operated for slipped capital femoral epiphysis at Haukeland University Hospital during the period 1990--2007 were included. All were treated by in situ fixation with 2 or 3 parallel Steinmann pins (8 mm threads at the medial end). The follow-up evaluation consisted of clinical examination and hip radiographs. Radiographic outcome was based on measurements of slip progression, growth of the femoral neck, leg length discrepancy, and signs of avascular necrosis and chondrolysis. Results 67 subjects (41 males) were operated due to unilateral slips (n == 47) or bilateral slips (n == 20). Mean age at time of diagnosis was 13 (7.2--16) years. Mean age at follow-up was 19 (14--30) years, with a mean postoperative interval of 6.0 (2--16) years. The operated femoral neck was 9% longer at skeletal maturity than at surgery, indicating continued growth of the femoral neck. At skeletal maturity, 12 subjects had radiographic features suggestive of a previous asymptomatic slip of the contralateral hip. The total number of bilateral cases of SCFE was 32, i.e half of the children had bilateral SCFE. 3 subjects required additional surgery and mild avascular necrosis of the femoral head was seen in 1 patient. None had slip progression or chondrolysis. Interpretation In situ pinning of SCFE with partly threaded Steinmann pins appears to be a feasible and safe method, with few complications. The technique allows further growth of the femoral neck. [ABSTRACT FROM AUTHOR]

Background and purpose The Essex-Lopresti lesion is thought to be rare, with a varying degree of disruption to forearm stability probable. We describe the range of radial shortening that occurs following a fracture of the proximal radius, as well as the short-term outcome in these patients. Patients and methods Over an 18-month period, we prospectively assessed all patients with a radiographically confirmed proximal radial fracture. Patients noted to have ipsilateral wrist pain at initial presentation underwent bilateral radiography to determine whether there was disruption of the distal radio-ulnar joint suggestive of an Essex-Lopresti lesion. Outcome was assessed after a mean of 6 (1.5--12) months using clinical and radiographic results, including the Mayo elbow score (MES) and the short musculoskeletal function assessment (SMFA) questionnaire. One patient with a Mason type-I fracture was lost to follow-up after initial presentation. Results 60 patients had ipsilateral wrist pain at the initial assessment of 237 proximal radial fractures. Radial shortening of ≥≥ 2mm (range: 2--4mm) was seen in 22 patients (mean age 48 (19--79) years, 16 females). The most frequent mechanism of injury was a fall from standing height (10/22). 21 fractures were classified as being Mason type-I or type-II, all of which were managed nonoperatively. One Mason type-III fracture underwent acute radial head replacement. Functional outcome was assessed in 21 patients. We found an excellent or good MES in 18 of the 20 patients with a Mason type-I or type-II injury. Interpretation The incidence of the Essex-Lopresti lesion type is possibly under-reported as there is a spectrum of injuries, and subtle disruptions often go unidentified. A full assessment of all patients with a proximal radial fracture is required in order to identify these injuries, and the index of suspicion is raised as the complexity of the fracture increases. [ABSTRACT FROM AUTHOR]

Introduction Microdialysis can detect ischemia in soft tissue. In a previous study, we have shown the development of ischemia in the femoral head removed from patients undergoing total hip replacement. That study also raised some methodological questions that this study tries to answer: what is happening in the dead space around the catheter in the drill canal, and is there an equilibrium period after the insertion of the catheter? Material and methods In an ex-vivo study using 5 syringes with 5 mL human blood, a microdialysis catheter was inserted and microdialysis was performed over 3 h. In an in-vivo study, a drill hole was made in the proximal part of the femur in 6 mature Gööttingen minipigs and microdialysis was performed over 3 h. The pigs were kept normoventilated during the experiment. Results The ex-vivo microdialysis results showed that lactate kept a steady level and glucose and glycerol both fell; pyruvate fell but leveled out. The mean lactate/pyruvate ratio increased from 13 (SD 4) to 32 (SD 6) (p < 0.001). In vivo, relative recovery was 57% (SD 11). Lactate increased, pyruvate stayed constant, and glucose and glycerol levels fell. The lactate/pyruvate ratio increased from 30 (8) initially to 37 (8) after 1 h (p == 0.007) but no statistically significant change from 1 to 2 h was observed. Interpretation The ex-vivo study showed a clear washout pattern, and was different from what we see in bone. The in-vivo study indicated that an equilibrium period is necessary or that a reference measurement in healthy bone must be used when performing short measurements in bone. [ABSTRACT FROM AUTHOR]

Background and purpose Few authors have considered the outcome after acute traumatic rotator cuff tears in previously asymptomatic patients. We investigated whether delay of surgery, age at repair, and the number of cuff tendons involved affect the structural and clinical outcome. Patients and methods 42 patients with pseudoparalysis after trauma and no previous history of shoulder symptoms were included. A full-thickness tear in at least 1 of the rotator cuff tendons was diagnosed in all patients. Mean time to surgery was 38 (6--91) days. Follow-up at a mean of 39 (12--108) months after surgery included ultrasound, plain radiographs, Constant-Murley score, DASH score, and western Ontario rotator cuff (WORC) score. Results At follow-up, 4 patients had a full-thickness tear and 9 had a partial-thickness tear in the repaired shoulder. No correlation between the structural or clinical outcome and the time to repair within 3 months was found. The patients with a tendon defect at follow-up had a statistically significantly lower Constant-Murley score and WORC index in the injured shoulder and were significantly older than those with intact tendons. The outcomes were similar irrespective of the number of tendons repaired. Interpretation A delay of 3 months to repair had no effect on outcome. The patients with cuff defects at follow-up were older and they had a worse clinical outcome. Multi-tendon injury did not generate worse outcomes than single-tendon tears at follow-up. [ABSTRACT FROM AUTHOR]

Background We evaluated the accuracy and repeatability of a 3D method for polyethylene acetabular cup wear measurements using computed tomography (CT). We propose that the method be used for clinical in vivo assessment of wear in acetabular cups. Material and methods Ultra-high molecular weight polyethylene cups with a titanium mesh molded on the outside were subjected to wear using a hip simulator. Before and after wear, they were (1) imaged with a CT scanner using a phantom model device, (2) measured using a coordinate measurement machine (CMM), and (3) weighed. CMM was used as the reference method for measurement of femoral head penetration into the cup and for comparison with CT, and gravimetric measurements were used as a reference for both CT and CMM. Femoral head penetration and wear vector angle were studied. The head diameters were also measured with both CMM and CT. The repeatability of the method proposed was evaluated with two repeated measurements using different positions of the phantom in the CT scanner. Results The accuracy of the 3D CT method for evaluation of linear wear was 0.51 mm and the repeatability was 0.39 mm. Repeatability for wear vector angle was 17°°. Interpretation This study of metal-meshed hip-simulated acetabular cups shows that CT has the capacity for reliable measurement of linear wear of acetabular cups at a clinically relevant level of accuracy. [ABSTRACT FROM AUTHOR]

Background and purpose Thrombophilia represents a risk factor both for idiopathic and secondary osteonecrosis (ON). We evaluated whether clotting changes in idiopathic ON were different from corticosteroid-associated ON. As platelet-rich plasma has been proposed as an adjuvant in surgery, we also assessed whether platelet and serum growth factors were similar to those in healthy subjects. Methods 18 patients with idiopathic ON and 18 with corticosteroid-associated ON were compared with 44 controls for acquired and inherited thrombophilia. Platelet factor 4 (PF4), transforming growth factor- ββ1, platelet-derived growth factor-BB (PDGF-BB), and vascular endothelial growth factor were assayed in the supernatants of thrombin-activated platelets, in platelet lysates, and in serum from 14 ON patients and 10 controls. Results Idiopathic ON patients had higher plasminogen levels (median 118%) than controls (101%) (p == 0.02). Those with corticosteroid-associated ON had significantly higher D-dimer (333 ng/mL) and lower protein C levels (129%) than controls (164 ng/mL, p == 0.004; 160%, p == 0.02). The frequency of inherited thrombophilia was not different from the controls. No statistically significant differences were found between idiopathic and corticosteroid-associated ON. 20 of the 36 ON patients were smokers. (The controls were selected from smokers because nicotine favors hypercoagulability). ON patients had significantly higher serum PF4 levels (7,383 IU/mL) and PDGF-BB levels (3.1 ng/mL) than controls (4,697 IU/mL, p == 0.005; 2.2 ng/mL, p == 0.02). Interpretation Acquired hypercoagulability was common in both ON types, but the specific changes varied. The release of GF from platelets was not affected, providing a biological basis for platelet-rich plasma being used as an adjuvant in surgical treatment. [ABSTRACT FROM AUTHOR]

Background and purpose The Harris hip score (HHS), a disease-specific health status scale that is frequently used to measure the outcome of total hip arthroplasty, has never been validated properly. A questionnaire is suitable only when all 5 psychometric properties are of sufficient quality. We questioned the usefulness of the HHS by investigating its content validity. Methods We performed a systematic review based on a literature search in PubMed, Embase, and the Cochrane Library for descriptive studies published in 2007. 54 studies (59 patient groups) met our criteria and were included in the data analysis. To determine the content validity, we calculated the ceiling effect (percentage) for each separate study and we pooled data to measure the weighted mean. A subanalysis of indications for THA was performed to differentiate the populations for which the HHS would be suitable and for which it would not. A ceiling effect of 15% or less was considered to be acceptable. Results Over half the studies (31/59) revealed unacceptable ceiling effects. Pooled data across the studies included (n = 6,667 patients) suggested ceiling effects of 20% (95%CI: 18-22). Ceiling effects were greater (32%, 95%CI:12-52) in those patients undergoing hip resurfacing arthroplasty. Interpretation Although the Harris hip score is widely used in arthroplasty research on outcomes, ceiling effects are common and these severely limit its validity in this field of research. [ABSTRACT FROM AUTHOR]

Background and purpose The current treatment for femoral fractures in children is mostly operative, which contrasts with treatment of other long bone fractures in children. We analyzed treatment injuries in such patients in Finland in order to identify avoidable injuries. Our other aims were to calculate the incidence of these fractures and to describe the treatment method used. Methods The Patient Insurance Centre (PIC) provides financial compensation of patients who have sustained an injury in connection with medical care. We retrospectively analyzed incidence, treatment methods, and all compensation claims concerning treatment of femoral fractures in children who were 0-16 years of age during the 8-year period 1997-2004. Results The incidence of childhood femoral fractures in Finland was 0.27 per 1,000 children aged < 17 years, and two-thirds of the patients were treated operatively during the study period. 30 compensation claims were submitted to PIC during the 8-year study period. The compensation claims mainly concerned pain, insufficient diagnosis or treatment, extra expenses, permanent disability, or inappropriate behavior of medical personnel. Of the claims, 16 of 30 were granted compensation. Compensation was granted for delay in treatment, unnecessary surgery, and for inappropriate surgical technique. The mean amount of compensation was 2,300 euros. Of the injuries that led to compensation, 11 of 16 were regarded as being avoidable in retrospect. Interpretation The calculated risk of a treatment injury in childhood femoral fracture treatment in Finland is approximately 2%, and most of these injuries can be avoided with proper treatment. [ABSTRACT FROM AUTHOR]

Background and purpose In the city of Trondheim, Norway, diabetic lower-limb amputations accounted for one-third of all lower-limb amputations (LLAs). In an attempt to reduce this rate, a diabetic foot team was established in 1996. We present the incidence of LLA in Trondheim as measured 10 years later. Patients and methods In 2004-07, we registered all LLAs performed in Trondheim and then compared the data with previously published data from 1994-1997. From 1996 through 2006, we registered the activity of the diabetic foot team and we also registered the number of vascular procedures performed on citizens of Trondheim from 1998 through 2006. Results Comparing the two 3-year periods 1994-97 and 2004-07, we observed a decrease in all non-traumatic LLAs. The incidence of diabetic major LLAs per 103 diabetics per year decreased from 4.0 to 2.4, and in patients with peripheral vascular disease we observed a decrease in LLAs from 18 to 12 per 105 inhabitants per year. 5,915 consultations on diabetic subjects were conducted by the diabetic foot team during the period 1996-2006. From 1998 to 2006, the rate of vascular procedures decreased in the non-diabetic population, and was unchanged in diabetic subjects. Interpretation In the population of Trondheim city there appears to have been a reduction in the rate of vascular obstructive lower-limb disease between the two 3-year periods 1994-97 and 2004-07. In our judgment, the decline in diabetic LLA also reflects better care of the diabetic foot. [ABSTRACT FROM AUTHOR]

Background Current techniques for measuring in vivo polyethylene wear suffer from a range of problems, resulting in an unacceptable lack of repeatability and/or insufficient accuracy when they are used to measure the low wear rates associated with new, highly crosslinked polyethylene. We describe an improved CT method for measurement of 3D femoral head penetration in PE acetabular cups that has sufficient accuracy and repeatability to allow assessment of the wear potential of modern implants. Method The accuracy and repeatability of the CT-scan method was determined by blindly repeating measurements on a precisely calibrated 28-mm prosthetic head and by comparing them with direct metrological measurements on 10 acetabular specimens with in vitro wear from machining, and on 8 explanted acetabular specimens with in vivo wear. Results The intra- and interobserver errors in femoral head diameter were 0.036 mm (SD 0.044) and 0.050 mm (SD 0.022), respectively. CT estimated femoral head penetration in both all-poly and metal-backed acetabular components with accuracy ranging from 0.009 to 0.245 mm (mean 0.080; SD 0.067). Interpretation We found that the CT method is rapid, is accurate, and has repeatability and ease of availability. Using a slice thickness of 0.0625 mm, this method can detect wear-and also the threshold for the wear rate that causes osteolysis-much earlier than previous methods. [ABSTRACT FROM AUTHOR]

Background and purpose Autonomic neuropeptide Y (NPY) is involved in local bone remodeling via the central nervous system. However, the role of peripheral neuronal NPY in fracture healing is not known. We investigated the relationship between bone healing and side-specific occurrence of NPY in angular and straight fractures. Methods Tibial fractures in Sprague-Dawley rats were fixed with intramedullary pins in straight alignment and anterior angulation. The samples were analyzed by radiography, histology, and immunohistochemistry (IHC) between 3 and 56 days postfracture. Results In the angular fractures, radiography and histology showed a 3.5-fold increase in callus thickness on the concave side compared to the convex side at day 21, whereas a 0.2-fold reduction in callus thickness was seen on the convex side between days 21 and 56. IHC showed regenerating NPY fibers in the callus and woven bone in both fractures at day 7. In angular fractures, a 5-fold increase in NPY fibers was observed on the concave side compared to the convex side at 7 days, whereas a 6-fold increase in NPY fibers was seen on the convex side between 21 and 56 days; only a 0.1-fold increase in NPY fibers was seen on the concave side during the same time period. In straight fractures, similar bony and neuronal changes were observed on both sides. Interpretation The increase in NPY innervation on the convex side appears to correlate with the loss of callus thickness on the same side in angular fractures. Our results highlight the probable function of the peripheral NPY system in local bone remodeling. [ABSTRACT FROM AUTHOR]

Background and purpose The natural history of, and predictive factors for outcome of cartilage restoration in chondral defects are poorly understood. We investigated the natural history of cartilage filling subchondral bone changes, comparing defects at two locations in the rabbit knee. Animals and methods In New Zealand rabbits aged 22 weeks, a 4-mm pure chondral defect (ICRS grade 3b) was created in the patella of one knee and in the medial femoral condyle of the other. A stereo microscope was used to optimize the preparation of the defects. The animals were killed 12, 24, and 36 weeks after surgery. Defect filling and the density of subchondral mineralized tissue was estimated using Analysis Pro software on micrographed histological sections. Results The mean filling of the patellar defects was more than twice that of the medial femoral condylar defects at 24 and 36 weeks of follow-up. There was a statistically significant increase in filling from 24 to 36 weeks after surgery at both locations. The density of subchondral mineralized tissue beneath the defects subsided with time in the patellas, in contrast to the density in the medial femoral condyles, which remained unchanged. Interpretation The intraarticular location is a predictive factor for spontaneous filling and subchondral bone changes of chondral defects corresponding to ICRS grade 3b. Disregarding location, the spontaneous filling increased with long-term follow-up. This should be considered when evaluating aspects of cartilage restoration. [ABSTRACT FROM AUTHOR]

Background and purpose The Kaplan-Meier (KM) method is often used in the analysis of arthroplasty registry data to estimate the probability of revision after a primary procedure. In the presence of a competing risk such as death, KM is known to overestimate the probability of revision. We investigated the degree to which the risk of revision is overestimated in registry data. Patients and methods We compared KM estimates of risk of revision with the cumulative incidence function (CIF), which takes account of death as a competing risk. We considered revision by (1) prosthesis type in subjects aged 75-84 years with fractured neck of femur (FNOF), (2) cement use in monoblock prostheses for FNOF, and (3) age group in patients undergoing total hip arthroplasty (THA) for osteoarthritis (OA). Results In 5,802 subjects aged 75-84 years with a monoblock prosthesis for FNOF, the estimated risk of revision at 5 years was 6.3% by KM and 4.3% by CIF, a relative difference (RD) of 46%. In 9,821 subjects of all ages receiving an Austin Moore (non-cemented) prosthesis for FNOF, the RD at 5 years was 52% and for 3,116 subjects with a Thompson (cemented) prosthesis, the RD was 79%. In 44,365 subjects with a THA for OA who were less than 70 years old, the RD was just 1.4%; for 47,430 subjects > 70 years of age, the RD was 4.6% at 5 years. Interpretation The Kaplan-Meier method substantially overestimated the risk of revision compared to estimates using competing risk methods when the risk of death was high. The bias increased with time as the incidence of the competing risk of death increased. Registries should adopt methods of analysis appropriate to the nature of their data. [ABSTRACT FROM AUTHOR]

Background Unstable implants in bone become surrounded by an osteolytic zone. This is seen around loose screws, for example, but may also contribute to prosthetic loosening. Previous animal studies have shown that such zones can be induced by fluctuations in fluid pressure or flow, caused by implant instability. Method To understand the roles of pressure and flow, we describe the 3-dimensional distribution of osteolytic lesions in response to fluid pressure and flow in a previously reported rat model of aseptic loosening. 50 rats had a piston inserted in the proximal tibia, designed to produce 20 local spikes in fluid pressure of a clinically relevant magnitude (700 mmHg) twice a day. The spikes lasted for about 0.3 seconds. After 2 weeks, the pressure was measured in vivo, and the osteolytic lesions induced were studied using micro-CT scans. Results Most bone resorption occurred at pre-existing cavities within the bone in the periphery around the pressurized region, and not under the piston. This region is likely to have a higher fluid flow and less pressure than the area just beneath the piston. The velocity of fluid flow was estimated to be very high (roughly 20 mm/s). Interpretation The localization of the resorptive lesions suggests that high-velocity fluid flow is important for bone resorption induced by instability. [ABSTRACT FROM AUTHOR]

Background and purpose There have been few reports of large series of ankle replacements. The aim of this study was to document and evaluate the early results of a nationwide series of total ankle replacements (TARs) performed using second- and third-generation implants. Methods Records of total ankle replacements performed between February 2000 and November 2005 were retrieved from the New Zealand National Joint Registry and retrospectively reviewed at a mean of 28 months after the primary procedure. At 6 months post surgery, patient scores were generated from questionnaires. Comparisons between patient scores and categorical variables were made using ANOVA. Regression analyses using Cox proportional-hazards modeling were performed to determine predictors of failure. A Kaplan-Meier survivorship curve was used to describe the rate of prosthetic survival. Results 202 total ankle replacements were performed in 183 patients. 14 prostheses (7%) failed. The overall cumulative 5-year failure-free rate was 86%. An unfavorable patient score at 6 months after the initial procedure turned out to be a good predictor of subsequent failure. The cumulative 5-year failure-free rate was 65% at 5 years for patients with an unfavorable score, and 95% for those who had a favorable patient score. Each 1-point increase in the patient score (i.e. poorer outcome) corresponded to a 5% relative increase in the risk of failure (p < 0.05). In addition, longer operative time for the primary procedure was found in the group of TARs that subsequently failed (p < 0.05). Interpretation The National Joint Registry appears to be a useful tool for monitoring the trends in TAR surgery. [ABSTRACT FROM AUTHOR]