الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
Excessive tensile forces across the extensor mechanism represent the main mechanism in most transverse patellar fractures. Surgery is indicated if there is damage to the extensor mechanism, or fractures associated with more than 3-5 mm displacement or 2 mm articular surface step-off. The MTBW technique was considered to be the standard of care, but with many complications. Because of the subcutaneous nature of the patella, fixation devices are irritating to the skin. This gives an advantage to PC fixation with cannulated screws with less postoperative wound complications and earlier rehabilitation. In our study, patients in the crossing screws group were more satisfied with the appearance of the scars, had no wound problems, less skin irritation, and no implant removal in comparison to group B patients who had 10% superficial infection, skin irritation, and 50 % implant removal.
Recent biomechanical studies denied the claimed dynamic principle of MTBW fixation technique and considered it to have a static one. So, the fixation stability may be threatened by the repetitive tension forces which may explain the reported high rates of implant-related complications, such as loosening and K-wire migration. In our study, more skin irritation and implant removal because of skin irritation were encountered in the patients received MTBW with better clinical outcomes for cannulated screws.
The minimally invasive nature of PC crossing screws has biological and mechanical advantages. Our patients managed using crossing screws achieved better knee function, especially in the early follow up period with less pain, early knee motion and less muscular atrophy and intra-articular adhesions. Direct inter-fragmentary compression force provided by the screws could not be offered by the MTBW. Application of the screws in a crossing manner will convert the tension force to pull in opposite directions. With partially threaded screw, this pull may, theoretically, lead to dynamic fracture compression instead of gapping plus improving the direct compression effect of the partially-threaded screws by offering it in 2 planes.
The PC fixation technique was with less pain, early knee motion, less muscular atrophy and intra-articular adhesions due to immobilization, and suspected advantages for joint cartilage perfusion and nutrition because of early motion
Conclusions:
PC or mini-invasive crossing screws is an effective surgical procedure for treatment of displaced transverse patellar fractures. It showed significantly better clinical outcomes than that with the MTBW technique all over the period of follow up as measured with the IOWA score. However, the favorable pain scores and ROM results with crossing screws were more evident at early follow-ups, and comparable between both groups at the final follow-up. The fixation stability and union rates were comparable in both groups with no loosening or migration in the crossing screws group. Further biomechanical and comparative studies on a large scale of patients are recommended.