In vitro comparison of elution characteristics of vancomycin from calcium phosphate cement and polymethylmethacrylate.

BACKGROUND: Calcium phosphate cement [CPC (Biopex)] has been used as the drug delivery system of choice for treatment of infected joint replacement because of its good elution efficiency. The influence of CPC polymerization on the bactericidal activity of vancomycin (VCM) impregnated into CPC has not been investigated. We compared VCM concentration, bactericidal activity, and profile of eluates between CPC and polymethylmethacrylate (PMMA; Cemex RX). METHODS: Test specimens consisted of a powder composite of CPC or PMMA, VCM and solvent (10:0.25:3.3 g). Each test specimen was immersed in sterile phosphate-buffered saline. Eluates obtained on days 1, 3, 7, and 14 and weeks 4, 8, and 12 were evaluated by high performance liquid chromatography (HPLC) and by microbiological assay (MBA). RESULTS: The elution level of VCM from CPC/VCM on day 1 was 8.1 fold greater than that from PMMA/VCM. The detection periods of VCM from CPC/VCM and PMMA/VCM were 8 weeks and 14 days, respectively. The values of eluates from CPC/VCM and PMMA/VCM obtained by HPLC were comparable to those obtained by MBA. HPLC chromatogram showed that the elution profiles of VCM from CPC/VCM and PMMA/VCM on day 1 were very close to those of standard solutions. CONCLUSIONS: CPC could release more VCM over a longer period than PMMA. The polymerization of CPC and PMMA did not alter the inhibitory activity of VCM and did not denature VCM.

The effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bone.

The effects of cryopreservation on tendon allograft have been reported, but remain unclear, particularly the potential effects on mechanical properties and histological changes by ice crystal formation. There are also few studies about effects of heating for sterilization of tendon. We evaluated the effect of cryopreservation or heating on the mechanical properties and histomorphology of rat bone-patellar tendon-bones (BTBs). BTBs were processed by cryopreservation at -80 degrees C for 3 weeks, or heating at 80 degrees C for 10 min. Tensile testing and histomorphological examination were performed. The cryopreservation of tendons showed less influences on their mechanical properties. When cryopreserved BTBs in frozen state were fixed by freeze-substitution method, many spaces were observed in interfibrillar substances. These results suggest that the collagen fibers of cryopreserved tendons were histomorphologically affected by ice crystals. The heating of tendons completely destroyed the collagen fibers of the tendons and is therefore thought to be inappropriate for the sterilization of BTBs.

Cold preservation of rat osteochondral tissues in two types of solid organ preservation solution, culture medium and saline.

We compared Dulbecco's modified Eagle's medium (DMEM), saline, Euro-Collins (EC) solution and University of Wisconsin (UW) solution to determine which was best for cold preservation of rat osteochondral tissues (OCTs). After 7 days' cold preservation, OCTs kept in UW solution had the highest relative viable cell number by the tetrazolium assay and the lowest activity of lactate dehydrogenase released from damaged cells. Histological evaluation revealed chondrocyte deformity, such as shrunken cytoplasm and pyknotic nuclei, particularly in the deeper layer of articular cartilage after preservation in saline and EC solution and predominantly in all layers if preserved in DMEM. In contrast, chondrocyte morphology in all layers of the articular cartilage preserved in UW solution was relatively unchanged and remained similar to fresh OCTs. It is therefore concluded that UW solution is the most suitable for cold preservation of rat OCTs as well as solid organs.

Arthroscopic evaluation after surgical repair of intercondylar eminence fractures.

INTRODUCTION: Patients who undergo surgical repair of intercondylar eminence fracture may have postoperative problems despite good reduction. We used arthroscopy to evaluate the outcomes after surgery to repair intercondylar eminence fractures. MATERIALS AND METHODS: Ten patients (8 men and 2 women; average age at the time of surgery 27.9 +/- 10.0 years, range from 14 to 50 years) with fracture of the tibial intercondylar eminence underwent an arthroscopic reduction and internal fixation with non-absorbable sutures. Preoperative radiological examination showed that there were one Meyer's type-II, eight type-IIIA and one type-IIIB fractures. Clinical symptoms and physical findings for all the patients were evaluated 1 year postoperatively. Radiographic assessment and the Lysholm rating scale were also utilized. Second-look arthroscopy was performed after 1 year when removing the implant. Arthroscopy was used to assess the appearance of the surface of the anterior cruciate ligament (ACL), check for the existence of cyclops and look for interposition of tissue in the lateral and medial joint spaces. RESULTS: One year after the surgery, all ten patients achieved bony union and had negative Lachman and anterior drawer tests. The average Lysholm knee score was 94.5 +/- 7.2 points (range 100-75 points). Arthroscopy showed an irregular surface on the ACL in two of the ten patients, cyclops in two patients, interposition in the lateral joint space in two patients and interposition in the medial joint space in one patient. In the two cases seen with an irregular surface, the ACL was covered with droopy fibrous tissue, but the substance of the ACL was intact. The two patients who had cyclops showed loss of knee extension (5~10 degrees), which was regained by subsequent resection of the cyclops. One patient who had an interposition into the lateral joint space complained of catching, which was released by resection of the interposing tissue. CONCLUSION: Arthroscopic refixation of the intercondylar eminence fracture provided bony union and a good clinical outcome. Cyclops syndrome is one of the causes of loss of knee extension, and soft tissue in the medial or lateral compartment is one of the causes of catching of knee after surgical repair of intercondylar eminence fracture. Cyclops syndrome, which may occur following ACL reconstruction, is one of the causes of loss of knee extension after surgical repair of intercondylar eminence fracture. In patients who have knee complaints, such as catching and loss of knee extension, a second-look arthroscopy is useful for identifying and correcting the problem.