Magnetic resonance imaging analysis of the bioabsorbable Milagro interference screw for graft fixation in anterior cruciate ligament reconstruction

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months.

The Nottingham health profile-experiences after hip revision arthroplasty

INTRODUCTION

Considering patients after hip revision arthroplasty postoperative quality controls allows an evaluation of the individual implant situation as well as the achieved postoperative quality of life. With regard to a possible loss of data reliable statements about the used implant system with special consideration to the implant survival rate could not be received. In this connection standardized self-assessment questionnaires like the Nottingham Health Profile (NHP) are in the centre of interest. The main focus of this study was to demonstrate a correlation between the Nottingham Health Profile and the Merle d'Aubigne (MDA) Score.

PATIENTS AND METHODS

Fifty-one patients after femoral stem revision were re-examined. All patients received a written appointment for an ambulatory re-examination together with the NHP 4 weeks before. The clinical evaluation was carried out by using the MDA Score. Correlations between the NHP and the MDA were calculated.

RESULTS

Overall the data of 39 patients could be evaluated completely. Three patients (5.9%) did not appear to the ambulatory re-examination, four patients (7.8%) deceased in the meantime. With further five patients (9.8%) the NHP questionnaire could not be rated due to an incorrect treatment. The mean follow-up after revision was 5.8 years. Correlations between the category 'Pain' NHP/MDA as well as to the combination of the NHP-categories 'Pain' + 'Physical Mobility' and the total MDA-Score could be demonstrated.

CONCLUSION

Out of our personal experiences the use of the NHP makes an individual follow-up evaluation after revision hip arthroplasty possible. Patient-referred changes can lead to direct re-examinations. Correlation coherences between the NHP and the MDA could be demonstrated equivalent to already published results. In what way a survival rate analysis of an implant by using the NHP is possible could not be answered clearly. It has to be included that wrong answered questionnaires lead to an additional drop-out rate beneath the lost to follow-up rate.

[Evaluation of regional wall motion abnormalities of the heart--comparison with doppler tissue echocardiography, MR-tagging and levocardiography]

PURPOSE

To compare the visual analysis of magnetic resonance imaging (MRI) with the tagging technique and Doppler tissue echocardiography with invasive ventriculography in detecting and quantifying regional left ventricular wall motion abnormalities.

MATERIALS AND METHODS

Sixteen patients with coronary artery disease and a history of prior myocardial infarction underwent invasive ventriculography, Doppler tissue echocardiography and MR-tagging within one week. Regional wall motion abnormalities (WMA) were detected in all patients. WMA were graded as normal = 1; hypokinetic = 2; akinetic = 3; or dyskinetic = 4. For agreement between MRI, echocardiography, and ventriculography the kappa coefficient (kappa) according to Cohen was calculated.

RESULTS

The kappa coefficient (kappa) was 0.962 for agreement between MRI and echocardiography and 0.602 for agreement between MRI and ventriculography as well as between echocardiography and ventriculography.

CONCLUSION

Reliable analysis of regional left ventricular wall motion abnormalities is feasible using visual analysis of MR-tagging. MRI and Doppler tissue echocardiography detect more WMA than invasive ventriculography and grade them as more severe.

Fiber-laser-pumped continuous-wave singly resonant optical parametric oscillator

We report on what is to our knowledge the first continuous-wave (cw) optical parametric oscillator (OPO) that is pumped by a tunable fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled LiNbO(3) crystal in a four-mirror ring cavity. At a pump power of 8.3 W provided by the wavelength-tunable Yb-doped fiber laser, the singly resonant OPO generates 1.9 W of 3200-nm cw idler radiation. The singly resonant OPO was tuned from 1515 to 1633 nm (signal) and from 3057 to 3574 nm (idler) by means of the crystal temperature and poling period. We obtained a wide idler tuning range, from 2980 to 3700 mn, by tuning the wavelength of the fiber laser from 1032 to 1095 nm.

Acute influence of beta-adrenergic antagonists on left ventricular diastolic function: contrasting results after administration of celiprolol and metoprolol

Various beta-adrenergic receptor antagonists have different effects on myocardial function. A clinical study was performed in 30 patients with symptomatic coronary artery disease and systemic hypertension to compare the effects of single intravenous doses of 0.15 mg/kg celiprolol (n = 16) (third generation beta-blocking agent) and metoprolol (n = 14) (second generation) on left ventricular diastolic function. Parameters derived from pressure, volume, flow, time intervals and their combination were used to characterise diastolic function. After celiprolol administration, parameters of diastolic myocardial function improve (dp/dtip-; relaxation time constant T1, peak filling rate PFR; first-third filling rate FF1/3 or diastolic wall stress-time integral Sigdiasc) or remain unchanged. In contrast, after metoprolol administration parameters of diastolic function seem to be deteriorated (dp/dtip-, T1; Sigdiasc). This indicates an improvement in myocardial relaxation and filling under the influence of celiprolol but not under metoprolol. The left shift of the pressure-volume loops after celiprolol (n = 13), in contrast to metoprolol, supports this interpretation. Celiprolol did not show any deterioration of diastolic function in patients with coronary heart disease and arterial hypertension under these acute conditions.

Diastolic heart function--pathophysiology, characterization, and therapeutic approaches

In recent years diastolic cardiac function has attracted increasing attention since parameters of diastolic function were found to be altered earlier or more specifically than parameters of systolic function. Diastolic cardiac function is determined by both active (muscular relaxation, redistribution of calcium, synchronization, etc.) and passive (myocardial structure, fibrosis, etc.) factors. As a consequence, a comprehensive assessment of diastolic cardiac function cannot be based on one single parameter. For a complete analysis of diastolic function it is necessary to perform invasive diagnostic procedures involving the measurement of atrial and ventricular pressures, as well as the registration of volume changes with a high time resolution. In addition, it is necessary to measure wall thickness and ventricular configuration, so that apart from filling parameters the stress-strain relationship can be obtained. Noninvasive techniques (Doppler echocardiography, radionuclear ventriculography, apexcardiography) may suggest alterations in diastolic function as well. They ought to be complemented by additional diagnostic procedures (pulmonary pressure, stress testing, etc.). Therapy must consider potentially harmful effects on diastolic function parameters, particularly if changes in myocardial oxygen consumption may result (heart rate, parietal wall stress). Calcium antagonists (verapamil, diltiazem, nifedipine), phosphodiesterase inhibitors (milrinone), beta-adrenergic agonists and antagonists with vasodilating effects (e.g., celiprolol) all have beneficial effects on diastolic myocardial function. A range of diastolic function parameters is being reviewed in the following paper. Their role in the estimation of cardiac function and their responsiveness to therapy in hypertrophy, cardiomyopathy, and coronary heart disease is being discussed.