Biomechanical comparison of a 3.5 mm anterior locking plate to cannulated screws with anterior tension band wiring in comminuted patellar fractures.

PURPOSE: To date, surgically treated multifragmentary patellar fractures are still associated with high rates of complications, such as i.e. secondary fracture displacement. Osteosynthesis is most frequently performed with screws and cerclages. To increase primary stability, locking plates have been introduced. However, there is still a lack of biomechanical data supporting the superiority of plate fixation compared to screw fixation with cerclages in these cases. The goal of the present study was to conduct biomechanical comparison of these two techniques under dynamic loading conditions. METHODS: A standardized 34-C3 fracture was created in eight pairs of human cadaveric knee joints. Following a randomization protocol, they were fixed with a 3.5 mm anterior locking plate (LP) or cannulated screws with anterior tension band wiring (hybrid osteosynthesis, HO).Subsequently, all constructs were tested for 100 cycles from 90° of knee-flexion to full extension by applying a pulling force to the quadriceps tendon. Outcome parameters were fracture displacement after one cycle, after 100 cycles and implant loosening. Failure was defined as fracture displacement > 2 mm. RESULTS: Biomechanical testing showed significantly less fracture displacement following LP compared to HO both after the first (p = 0.042) and after 100 cycles (p = 0.025). The difference in loosening was significant as well (p = 0.017). Following HO, 5/8 constructs failed during cyclic loading. There was no failure in the LP group. In the HO group, loosening correlated with bone mineral density (R = - 0.857) which was not observed in the LP group (R = - 0.429). CONCLUSION: Anterior locking plate osteosynthesis of comminuted patellar fractures biomechanically provides better primary stability compared to cannulated screws with anterior tension band wiring.

Aortic Replacement After TEVAR-Diameter Correction With Modified Use of the Siena Prosthesis.

BACKGROUND: To report a new technique for diameter correction in patients after thoracic endovascular aortic repair (TEVAR) with large stent-grafts using the Vascutek Siena 4-branch collared prosthesis (Vascutek Terumo, Inchinnan, Scotland, UK) in patients undergoing thoracoabdominal (TA) aortic replacement. METHODS: Within a 24-month period, 39 patients underwent TA replacement at our center. Of these, 6 patients had undergone previous TEVAR with large stent-grafts (42 to 48 mm diameter). Indications for TEVAR were aneurysm formation in 3 patients and residual type B aortic dissection (status post repair of type A dissection) in 3 patients. In these patients, the Vascutek Siena 4-branch prosthesis was used in a reversed fashion, removing the elephant trunk portion and using the sewing collar for diameter correction at the anastomotic site. RESULTS: No 30-day mortality and no stroke or symptomatic spinal cord ischemia was observed. Median diameter of the TEVAR graft at the anastomotic site was 44 mm. Median size of the Siena graft used was 26 mm. Diameter correction was successfully achieved in all patients by tailoring the sewing collar of the Siena 4-branch prosthesis to the individual need according to the diameter of the distal end of the stent-graft. CONCLUSIONS: Using the sewing collar of the Vascutek Siena 4-branch prosthesis for diameter correction in patients undergoing TA replacement after previous TEVAR with large stent-grafts adds a useful adjunct to the armamentarium of options in a growing patient population.