Alterations in magnetic resonance imaging characteristics of bioabsorbable magnesium screws over time in humans: a retrospective single center study.

OBJECTIVES: This study aimed to examine the alterations in magnetic resonance imaging (MRI) characteristics of bioabsorbable magnesium (Mg) screws over time in a single center study in humans. METHODS: Seventeen patients who underwent medial malleolar (MM) fracture or osteotomy fixation using bioabsorbable Mg screws and had at least one postoperative MRI were included in this retrospective study. Six of them had more than one MRI in the postoperative period and were subject of the artifact reduction measurements. 1.5T or 3T MRI scans were acquired in different periods in each patient. The size and extent of the artifact were assessed independently by two experienced radiologists both quantitatively (distance measurement) and qualitatively (Likert scale). RESULTS: In the quantitative measurements of the six follow-up patients the screw's signal loss artifact extent significantly decreased over the time, regardless of the MRI field strength (p<0.001). The mean artifact reduction was 0.06 mm (95% confidence interval [CI]: 0.05-0.07) for proton density weighted [PDw] and 0.04 mm (95% CI: 0.03-0.05) for T1 weighted (T1w) sequences per week. The qualitative assessments similarly showed significant artifact reduction in all MRI sequences. Different imaging findings, like bone marrow edema (BME), liquid collections, and gas formation were reported. The overall inter-reader agreement was high (κ=0.88, p<0.001). CONCLUSIONS: The time-dependent artifact reduction of Mg screws in postoperative controls might indicate the expected self-degradation of the Mg implants. In addition, different MRI findings were reported, which are characteristic of Mg implants. Further MRI studies are required to get a better understanding of Mg imaging properties.

Comparison of SCAphoid fracture osteosynthesis by MAGnesium-based headless Herbert screws with titanium Herbert screws: protocol for the randomized controlled SCAMAG clinical trial.

BACKGROUND: Scaphoid fractures are the most common carpal fractures. They often need to be treated by surgery, where the use of a compression screw is the globally accepted gold standard. Surgeons may choose between different implant materials including titanium alloys, which remain in the body or are removed after healing. An alternative are biodegradable magnesium-based implants. Properties of magnesium alloys include high stability, osteoconductivity, potential reduction of infections and few artifacts in magnetic resonance imaging (MRI). The aim of this trial is to demonstrate non-inferiority of magnesium-based compression screws compared with titanium Herbert screws for scaphoid fractures. METHODS: The trial is designed as a multicenter, blinded observer, randomized controlled parallel two-group post market trial. Approximately 190 patients will be randomized (1:1) with stratification by center either to titanium or magnesium-based compression screws. Follow-up is 1 year per patient. Surgical procedures and aftercare will be performed according to the German treatment guideline for scaphoid fractures. The first primary endpoint is the patient-rated wrist evaluation (PRWE) score after 6 months. The second primary endpoint is a composite safety endpoint including bone union until 6 months, no adverse device effect (ADE) during surgery or wound healing and no serious ADE or reoperation within 1 year. The third primary endpoint is the difference in change MRI artifacts over time. Non-inferiority will be investigated for primary endpoints 1 (t-test confidence interval) and 2 (Wilson's score interval) using both the full analysis set (FAS) and the per protocol population at the one-sided 2.5% test-level. Superiority of magnesium over titanium screws will be established using the FAS at the two-sided 5% test-level (Welch test) only if non-inferiority has been established for both primary endpoints. Secondary endpoints include quality of life. DISCUSSION: This study will inform care providers whether biodegradable magnesium-based implants are non-inferior to standard titanium Herbert screws for the treatment of scaphoid fractures in terms of wrist function and safety. Furthermore, superiority of magnesium-based implants may be demonstrated using MRI, which is used as surrogate endpoint for screw degradation. TRIAL REGISTRATION: DRKS, DRKS00013368 . Registered Dec 04, 2017.

Polyvinyl alcohol gel prevents adhesion re-formation after adhesiolysis in a rabbit model.

BACKGROUND: Chronic pain, infertility, and bowel obstructions are possible consequences of abdominal adhesions, which can highly affect the patient's quality of life. Patients in whom adhesiolysis has been performed are at high risk for recurrence of adhesions. For that reason, the present study focused on the re-formation of adhesions after adhesiolysis and on the possibility of avoiding it by using the adhesion barrier polyvinyl alcohol (PVA)-gel. MATERIALS AND METHODS: A randomized controlled study was conducted to prove the effectiveness of PVA-gel in reducing postoperative adhesion re-formation after relaparotomy. Moreover, ultrasound was evaluated as a noninvasive technique to determine abdominal adhesion in a rabbit model. All animals underwent an initial laparotomy to cause adhesions and subsequent adhesiolysis in the relaparotomy. PVA-gel was placed onto a side wall defect in 12 animals. Another 12 rabbits served as a control group without PVA-gel being used. Ultrasound before final laparotomy was performed to predict the prevalence of adhesions. Macroscopic evaluation of adhesion formation and planimetry were used to determine the amount of adhesion. RESULTS: PVA-gel was found to reduce significantly the amount of adhesion formation after relaparotomy (P = 0.0001) in comparison with the control group. Here severe adhesion formation was found to develop. The positive-predictive value (100%) for adhesion evaluation using ultrasound is highly satisfying in the rabbit model. CONCLUSIONS: Adhesion re-formation after relaparotomy was found to decrease significantly through the use of PVA-gel. Ultrasound as a noninvasive technique of adhesion detection is a sufficient and reliable method for detecting adhesion formations.

Status of immune mediators in complex regional pain syndrome type I.

Complex regional pain syndrome type I (CRPS-I) can affect an extremity after minor trauma or operation. The pathogenesis of this syndrome is unclear. It has clinical signs of severe local inflammation as a result of an exaggerated inflammatory response, but neurogenic dysregulation is also a contributor. Several studies investigated the role of inflammatory mediators and cytokines thus far; however, the results are heterogeneous and vary between different settings. This review summarizes recent study results that show a clear underlying inflammatory response at the local site, where systemic responses seem to be inconsistent. An induction of CRPS-like symptoms by application of neuroinflammatory mediators was shown recently. Local inflammation is involved in the pathophysiology of CRPS-I. We must expand our knowledge of pathophysiologic mechanisms, and we are still far away from using inflammatory markers in diagnosis and follow-up of CRPS-I.

Outcome of allogeneic vascularized knee transplants.

Transplantation of vascularized knee joints is a novel approach in Composite Tissue Allotransplantation (CTA). In 1996 our group started a clinical knee transplantation project and six transplantations have been performed since. Key problems identified early were the monitoring of acute rejection and choice of an immunosuppressive regime. One graft was lost due to postoperative infection and one due to of noncompliance where the patient discontinued the immunosuppressant regime. In three cases late rejection lead to necrosis and graft dysfunction after 15, 16 and 24 months, respectively. Exit-strategies were arthrodesis in one patient and Above Knee Amputation in two cases. With retrospective analysis after initial five cases the treatment protocol was improved. The immunosuppressive drug regime was altered, femoral diaphysis and knee joint grafting was combined and a vascularized block of donor skin and subcutaneous tissue was harvested with the graft (sentinel skin graft). The sentinel skin graft enabled us to monitor acute rejection by clinical and histological examination and avoid late rejection by rapid treatment with high dose steroids. In summary, over a four-year period, one of six allogeneic vascularized knee transplants has survived, one was lost from a surgical site infection, one by noncompliance and three by late rejection. Analysis of our data leads us to suggest that knee transplantation should be limited to a combined injury consisting of extensive loss of cartilage and bone, deficient extensor mechanism and soft tissue and skin defects without any signs of infection. Transplantation should only be taken into consideration as last option before Above Knee Amputation in an otherwise healthy patient under 35 years of age.