Evaluation of acetabular cup initial fixation by using resonance frequency principle.

The clinical practice shows that the loosening of acetabular cups is more frequent than stem loosening. With standard cups, the incidence of dislocation failure is highest in the first year after arthroplasty implantation. The aim of the study was to quantitatively evaluate the implant-bone stability of a cementless acetabular cup prosthesis by using a device based on resonance frequency analysis. The evaluation of this device was done by finite element analysis and in vitro experiments. It was shown that not all the resonance frequencies can be measured by our device. The resonance frequencies vary within the range of 500-3000 Hz. The proposed power spectrum measurement gives the information about the absolute stiffness of the press-fit implant.

Results of treatment of periprosthetic femoral fractures after total hip arthroplasty.

Periprosthetic fractures are the third most common reason for revision total hip arthroplasty. Surgical treatment of periprosthetic fractures belongs to the most difficult procedures due to the extensive surgery, elderly polymorbid patients and the high frequency of other complications. The aim of this study was to evaluate the results of operatively treated periprosthetic femoral fractures after total hip arthroplasty. We evaluated 47 periprosthetic fractures in 40 patients (18 men and 22 women) operated on between January 2004 and December 2010. The mean follow-up period was 27 months (within a range of 12-45 months). For the clinical evaluation, we used modified Merle d'Aubigné scoring system. In group of Vancouver A fractures, 3 patients were treated with a mean score of 15.7 points (good result). We recorded a mean score of 14.2 points (fair result) in 6 patients with Vancouver B1 fractures, 12.4 points (fair result) in 24 patients with Vancouver B2 fractures and 12.7 points (fair result) in 7 patients with Vancouver B3 fractures. In group of Vancouver C fractures, we found a mean score of 16.2 points (good result) in 7 patients. Therapeutic algorithm based on the Vancouver classification system is, in our opinion, satisfactory. Accurate differentiation of B1 and B2 type of fractures is essential. Preoperative radiographic images may not be reliable. If in doubt, checking the stability of the prosthesis fixation during surgery should be performed.

Methotrexate released in vitro from bone cement inhibits human stem cell proliferation in S/G2 phase.

Methotrexate (MTX) released from bone cement showed a useful local effect in animal models of bone tumours. However, local toxic reactions such as impaired wound healing were observed in areas surrounding the MTX-loaded implant. Therefore, we hypothesised that MTX released from bone cement would have harmful effects on human mesenchymal stem cells (MSC)-one of the basic components of bone marrow and tissue reparatory processes. Moreover, elution of MTX was calculated from implants prepared either with liquid or powdered MTX. During the 28-day incubation, the cement compounded with liquid MTX showed the highest elution rate of the drug. MTX released from pellets produced a significant decrease in proliferation of MSC as a consequence of a blockade of their cell cycle in the S/G2 phase. These findings indicate impairment of stem cell function in marginal areas surrounding the MTX-loaded cement and may help to explain problems with regeneration of tissues in these locations.

Use of two parallel oxygenators in a very large patient (2.76 m2) for an acute "A" dissecting aortic aneurysm repair.

The very large patient (weight 142 kg, height 197 cm, body surface 2.76 m2) was referred to acute operation with dissecting type A ascending aortic aneurysm. The calculated blood flow was 6.63 l/min. To anticipate potential difficulties with perfusion and oxygenation two oxygenators connected in parallel were incorporated into the circuit. Bentall procedure with ACB to the RCA was performed. The perfusion was uneventful. Bypass time was 259 minutes, cross clamp time 141 minutes, circulatory arrest 7 minutes. The highest oxygenators gas flow was 2.6 l/min with maximum FiO2 0.42. The use of two in parallel connected oxygenators is a very effective, easy and safe method in such extreme perfusions, offering to the perfusionist a great reserve of oxygenator output.

Perioperative hyperfractionated high-dose rate brachytherapy combined with external beam radiotherapy in the treatment of soft tissue sarcomas.

AIMS AND BACKGROUND: Low-dose rate brachytherapy alone or in combination with external beam radiotherapy represents a well-established adjuvant treatment in soft tissue sarcomas following surgical resection. The experience with high-dose radiotherapy in this indication is limited. The purpose of our study was an evaluation of the viability of perioperative hyperfractionated high-dose rate brachytherapy in combination with external beam radiotherapy for primary and recurrent soft tissue sarcomas. PATIENTS AND METHODS: From February 1998 through June 2002, 10 adult patients with soft tissue sarcomas were treated by interstitial perioperative high-dose rate brachytherapy and external beam radiotherapy. TNM classification was pT2bpN0pM0 in 9 patients and pT1bpN0pM0 in 1 patient. Grade of differentiation was G1 (2 patients), G2 (n = 1), G3 (n = 5), G4 (n = 2). Surgical margins were negative in 7 cases, close in 2 cases and positive in 1 case. The tumor was localized in an extremity in all cases. Hyperfractionation 3 Gy twice daily at 10 mm from the plane of sources was used for brachytherapy, with total doses 18-30 Gy. The patients received external beam radiotherapy with doses 40-50 Gy after brachytherapy. Follow-up periods were between 24-71 months (median, 46). RESULTS: Local control of the disease was achieved in all 10 patients. Distant metastases occurred in 2 cases. One patient was disease free after salvage surgery and chemotherapy, and one patient died of lung disease progression 14 months after brachytherapy. In one case, subcutaneous fistula occurred after radiotherapy and was cured by an excision. Six patients experienced grade 1 or 2 fibrosis and 1 case a mild peripheral neuropathy was recorded. CONCLUSIONS: Our study on a small number of patients suggests that perioperative hyperfractionated high-dose rate brachytherapy with doses 8 x 3 Gy in combination with external beam radiotherapy 40-50 Gy is a promising method to achieve high biological doses in the postoperative radiotherapy of soft tissue sarcomas without severe late morbidity and warrants further research.