Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks.

Photopolymers with unique curing capabilities were produced by combining living cationic polymerization with network formation and restricted polymer motion. A vinyl ether diol was synthesized as a functional building block and reacted with isophorone diisocyanate to form a highly functionalized vinyl ether polyurethane as a model system with high crosslinking ability. When using a cationic photoinitiator, fast polymerization is observed upon short UV irradiation. Curing proceeds in the absence of light and under ambient conditions without oxygen inhibition. Cationic active sites become trapped dormant species upon network-induced vitrification and surprisingly remain living for several days. The polymerization can be reactivated by additional UV irradiation and/or raised temperature. The curing behavior was studied in detail by using UV and FT-NIR coupled rheology and photo-DSC to simultaneously study spectroscopic and mechanical information, as well as thermal effects.

Combined experimental and theoretical study of the reactivity of γ-Butyro- and related lactones, with the OH radical at room temperature.

The total rates of reaction between four cyclic esters (ß-butyro-, γ-butyro-, γ-valero- and δ-valero-lactones) and the OH radical have been measured relative to the rate of reaction of a reference compound, ethene, at room temperatures. The measurements show that the rates increase with increasing ring size. Theoretical calculations on the four lactones with the inclusion of a fifth, α-methyl-γ-butyrolactone, are broadly in agreement with this picture but provide a more insightful view of the sites at which hydrogen atom abstraction occurs in each molecule.

Arthroscopic electrothermal shrinkage of chronic posterolateral elbow instability: good or moderate outcome in 21 patients followed for an average of 2.5 years.

BACKGROUND: The lateral collateral ligament complex is the key structure involved in recurrent elbow instability. Treatment is surgical, by repair or reconstruction of the lateral collateral ligament complex. We evaluated the effect of arthroscopic electrothermal shrinkage for treatment of chronic posterolateral rotator elbow instability. METHODS: 21 patients, median age 32 (24-50) years, suffering from chronic lateral elbow instability underwent arthroscopic electrothermal ligament shrinkage with a bipolar shrinkage probe. All patients were available for follow-up after median 30 (8-48) months. RESULTS: No complications were seen. The Morrey score increased from 40 to 77 points. The result was moderate (50-80 points) in 10 patients, and in the other patients a good result was achieved (80-95 points). The manual stress radiography showed a mean lateral joint opening of 13 (8-18) mm preoperatively. During follow-up, it decreased to 2 (1-4) mm. INTERPRETATION: Our findings suggest that arthroscopic bipolar ligament shrinkage is sufficient for the treatment of chronic posterolateral rotator elbow instability.

A study for evaluating the effect of the deltoid-flap repair in massive rotator cuff defects.

The repair of massive cuff defects by direct suture often is impossible. In these cases, a repair by musculo-tendineous flaps (latissimus-dorsi, pectoralis or deltoideus) is required. It was the goal of this study to evaluate the result of delta-flap repair in case of massive cuff defects with a diameter of 5 cm or more. Between 1998 and 2000 for all patients who were suffering from a massive rotator cuff tear more than 5 cm a deltoid transfer was performed. A total of 20 patients (14 male, 6 female; age: 60.9+/-8.7 years) were available for a follow-up after 47.2+/-8.0 (range, 36 to 60) month. The operation included an arthroscopic evaluation, acromioplasty with resection of the lateral clavicular end, and biceps tenodesis. The cuff defect was repaired by transfer a muscular flap from the anterior part of the deltoid (about 2 x 6 cm) into the defect. The patients subjectively rated their result-10 excellent, 9 good, and 1 poor. Preoperatively, the Constant amounted 26.3+/-5.1 points. At follow-up, the score significantly increased to 74.5+/-8.5 points. The acromiohumeral distance increased from 4.9+/-1.1 to 9.2+/-1.7 mm. In MRI examination of 11 patients all had an intact flap. Two complications (a wound hematoma and a deep infection) did not influence the result. The repair of massive rotator cuff tears by a deltoid transfer produces acceptable clinical and radiological results.

Operative treatment of deep chondral defects of the patella: results after abrasive arthroplasty and periosteal arthroplasty.

This prospective, non-randomized study was aimed to evaluate the effects of abrasive arthroplasty and periosteal arthroplasty in the treatment of deep chondral defects of the patella. A total of 30 patients in group A (13 male, 17 female, age: 28.7+/-6.9 years) underwent arthroscopic abrasive arthroplasty. The other patients in group B (n=17, 11 male, 8 female, age 26.8+/-7.0 years) underwent periosteal arthroplasty by an autologous periosteal flap. The maximal diameter of the defects was 31.1+/-6.7 (range 20-45 mm). The Lysholm score and the intensity of pain were evaluated preoperatively and at the time of follow-up (3.1+/-1.1, range 2-5 years). The Tegner activity score was evaluated before onset of the symptoms and at the time of follow-up. The Lysholm score increased significantly in both groups (in group a from 36.1+/-7.1 to 42.5+/-6.6 points and in group B from 42.7+/-2.4 to 67.6+/-7.8 points). The result in group B was significantly better than in group A. In group A the intensity of pain was unchanged, whereas patients from group B reported a significant reduction of pain. The level of physical activity (Tegner score) was 5.5+/-2.1 in group A and 5.5+/-2.1 in group B before onset of the complaints. In follow-up, patients from group B (4.9+/-1.2) had a reduced Tegner score in tendency. The patients in group A had a significantly reduced level of physical activity (2.7+/-0.6). A total of 12 patients from group B had a range of motion lesser than 80 degrees in flexion. These patients underwent joint mobilization and control arthroscopy. During control arthroscopy there was always found a stable periosteal flap. Short-term clinical results with periosteal arthroplasty produced a significant reduction in pain and improved Lysholm score in comparison to abrasive arthroplasty.