Furthermost patellar fractures are usually managed operatively. The tension band technique accompanied by longitudinal K-wires has always been the core way for fixation of such injuries [1, 3, 4, 8]. Numerous investigations have shown that the cancellous screws supplemented with tension band wiring yields constant fixation so long as the fracture is properly reduced [7, 15].
Cannulated screw tension band technique was applied for patellar fractures in some studies, in order to provide proper reduction, direct fracture compression and earlier ROM . No loss of fixation had occurred among their patients . Similarly, no hardware loosening, nor loss of fixation had been reported in the current study. The probability of cable-cannulated screw loosening is trivial owing to the dense cancellous bone of the patella and the fact that the distal end of the cannulated screw is threaded. In addition, the cable tightly attaches to the patellar surface to limit the separation of fracture fragments as a tension band technique .
In the present series, patients were put in a postoperative high above knee slab for 3 weeks, with quadriceps contraction exercises commenced soon after operation without weight bearing. After 3 weeks, slab was removed and immediate passive ROM were encouraged to decrease muscular atrophy and intra-articular adhesions. Besides, it may improve articular cartilage nourishment and fracture healing process.
Tian et al. permitted active joint flexion and extension exercises 7 days after the operation. One month later, their patients were permitted to perform partial-weightbearing. Patients were permitted to perform full ambulation after 8 weeks .
Bhati et al. encouraged patients to perform isometric knee extension and straight leg elevation exercises. Partial weight-bearing was permitted up to suture removal. Knee flexion was allowed to less than 45 degrees in the first week and gradually increased to 90 degrees in the 2nd week. The patients were provided with an exercise chart .
Posner et al. patients were put in a 24-hour hinged knee brace which was locked at full extension. Immediate weight-bearing as tolerated with the brace was allowed. At 2-week postoperative visit, formal physical therapy including progressive and controlled active knee flexion movements were commenced. At 8-week postoperative visit, full ROM and active knee flexion was allowed .
Lin et al. didn’t apply any external immobilizers to any of their patients. Patients performed quadriceps contraction exercises soon after the operation. Unrestricted passive ROM was started early postoperatively, depending on the patient’s pain tolerance. Active ROM was encouraged by 3 weeks postoperatively, and full weight-bearing was started by 8 weeks in their study .
Skin irritation is the main complication of the K-wire tension band. In some studies, symptoms attributable to wire irritation necessitated removal in approximately 15% of the cases [18, 19]. In our study two patients (9.5 %) experienced skin irritation generated by wire tails, and one of them required implant removal at 9 months postoperatively. With the cable-cannulated screw tension band technique, the tail of the cannulated screw tightly attaches at the superior or inferior pole of the patella, and the screw threads are not exposed to the patellar surface. Furthermore, the diameter of the cable is only 1.3 mm, and it closely attaches to the patellar surface after being tightened reducing the risk of skin irritation and postoperative activity discomfort .
An article reported that painful hardware was the most common complication which occurred in 30.1 % of patients, and tension band loosening and migration was the second major complication, seen in 11.5 % of patients . Although symptomatic implant irritation is not a serious complication, but it delays rehabilitation and potentially leads to stiffness that may require a second intervention with additional hospitalization and cost .
According to Baydar et al. , cannulated screws are more resistant to distraction forces than the tension band techniques to manage patellar fractures. Additionally, the flexibility of K-wires can neutralize a part of the force that should act on the fractured bone leading to reduced compressive forces on fracture site, unlike cannulated screws tension band fixation [21, 22].
A disadvantage of the screws tension band fixation method includes its technical difficulty . For example, it has been noted that it can be difficult to place K-wires appropriately with a minimally invasive technique, and it may have a substantial learning curve .
Unfortunately, the current study had some limitations. First, the small number of patients. Second, the short duration of follow-up. Third, the lack of comparison to the traditional technique of tension band technique. A fourth limitation is the stainless steel material used in the study. Although it is cheaper, but it is weaker in comparison to titanium screws tension band system and interferes with MRI.