Background The interpretation of metal ion concentrations and their role in clinical management of patients with metal-on-metal implants is still controversial. Questions/Purposes We questioned whether patients undergoing hip resurfacing with no clinical problems could be differentiated from those with clinical (pain, loss of function) and/or radiographic (component malpositioning, migration, bone loss), problems based on metal ion levels, and if there was a threshold metal level that predicted the need for clinical intervention. Furthermore, we asked if patient and implant factors differed between these functional groups. Methods We retrospectively identified 453 unilateral and 139 bilateral patients with ion measurements at minimum followup of 12 months (mean, 4.3 years; range, 1-12.9 years). Patients were designated as well functioning or poorly functioning based on strict criteria. The acceptable upper levels within the well-functioning group were determined from the 75th percentile plus 1.59 interquartile range. The sensitivity and specificity of these levels to predict clinical problems were calculated. Results Well-functioning group ions were lower than the poorly functioning group ion levels. The acceptable upper levels were: chromium (Cr) 4.6 lg/L, cobalt (Co) 4.0 lg/L unilateral and Cr 7.4 lg/L, Co 5.0 lg/L bilateral. The specificity of these levels in predicting poor function was high (95%) and sensitivity was low (25%). There were more males in the well-functioning group and more females and smaller femoral components in the poorly functioning group. Conclusions Metal levels higher than these proposed safe upper limits can predict problems with metal-on-metal resurfacings and are important parameters in the management of at-risk patients.
A retrospective study was conducted to investigate the changes in metal ion levels in a consecutive series of Birmingham Hip Resurfacings (BHRs) at a minimum ten-year follow-up. We reviewed 250 BHRs implanted in 232 patients between 1998 and 2001. Implant survival, clinical outcome (Harris hip score), radiographs and serum chromium (Cr) and cobalt (Co) ion levels were assessed. Of 232 patients, 18 were dead (five bilateral BHRs), 15 lost to follow-up and ten had been revised. The remaining 202 BHRs in 190 patients (136 men and 54 women; mean age at surgery 50.5 years (17 to 76)) were evaluated at a minimum follow-up of ten years (mean 10.8 years (10 to 13.6)). The overall implant survival at 13.2 years was 92.4% (95% confidence interval 90.8 to 94.0). The mean Harris hip score was 97.7 (median 100; 65 to 100). Median and mean ion levels were low for unilateral resurfacings (Cr: median 1.3 µg/l, mean 1.95 µg/l (< 0.5 to 16.2); Co: median 1.0 µg/l, mean 1.62 µg/l (< 0.5 to 17.3)) and bilateral resurfacings (Cr: median 3.2 µg/l, mean 3.46 µg/l (< 0.5 to 10.0); Co: median 2.3 µg/l, mean 2.66 µg/l (< 0.5 to 9.5)). In 80 unilateral BHRs with sequential ion measurements, Cr and Co levels were found to decrease significantly (p < 0.001) from the initial assessment at a median of six years (4 to 8) to the last assessment at a median of 11 years (9 to 13), with a mean reduction of 1.24 µg/l for Cr and 0.88 µg/l for Co. Three female patients had a > 2.5 µg/l increase of Co ions, associated with head sizes ≤ 50 mm, clinical symptoms and osteolysis. Overall, there was no significant difference in change of ion levels between genders (Cr, p = 0.845; Co, p = 0.310) or component sizes (Cr, p = 0.505; Co, p = 0.370). Higher acetabular component inclination angles correlated with greater change in ion levels (Cr, p = 0.013; Co, p = 0.002). Patients with increased ion levels had lower Harris hip scores (p = 0.038). In conclusion, in well-functioning BHRs the metal ion levels decreased significantly at ten years. An increase > 2.5 µg/l was associated with poor function.
IntroductionBack pain (BP) is one of the most frequent symptoms to appear during the last period of pregnancy and a high incidence has been described in several studies [2,6,7,9,14,17]. Since 1984 modern studies of BP also need to include patient-oriented assessment [23]. Self-administered questionnaires are the most common instruments to assess patient perspective in evaluating the clinical picture, and the usefulness of these instruments [20, 21] is widely accepted. BP during pregnancy has been quantitatively evaluated in some recent papers, but only a few studies analyzed the symptoms from a qualitative-quantitative point of view, using a validated patient-oriented tool [16,25].During 2001, we performed a study to assess the incidence and severity of BP during the last period of pregnancy, through a modern and comprehensive assessment of the patient's perspective [18]. That study demonstrated that the incidence of BP in pregnancy is high (about twothirds of our sample have BP symptoms), but most often BP causes only low-grade disability.Until now no multicenter and prospective clinical studies on the natural course of BP after pregnancy have been available (multicenter studies are commonly accepted as providing a more representative sample). We performed the follow-up of the previous studied sample; consequently, we acquired data from a multicenter sample. We used a validated patient-oriented measurement, the Roland questionnaire, to obtain more comprehensive and consistent Abstract Back Pain (BP) is one of the most frequent symptoms during the last period of pregnancy, and high incidence has been described in several studies. Until now no wide, multicenter and prospective clinical studies on the natural course of BP after pregnancy have been available. We performed a multicenter follow-up study in a sample of pregnant women using the Italian validated version of the Roland questionnaire to assess the evolution of BP after pregnancy and identify prognostic factors. Each center had to re-evaluate at least 75% of the initially enrolled women, with latency of 1 year after delivery. At the follow-up, we acquired substantial clinical data concerning the post-delivery period. The evaluation of symptom evolution was based on the Roland questionnaire. At followup, 53% of re-evaluated women had no BP symptoms. Moreover, there was a significant improvement of patient-oriented assessment in women who suffered BP after delivery. With regard to the predictive factors, the presence of BP before pregnancy implied a 3.1-fold higher probability of improvement after delivery. In conclusion, women without history of BP before pregnancy and who complain of these symptoms during pregnancy require greater attention, because they have a lower possibility for improvement. Conversely, in women with a history of BP, pregnancy represents a transient period of worsening symptoms, probably due to the temporary para-physiological mechanical condition.
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