Introduction

Patellar fractures account for 1% of all skeletal injuries (Muller, Allgower, Schneider, & Willineger, 1979; Weber, Janecki, McLeod, Nelson, & Thompson, 1980). Transverse fracture constitutes 50-80% of patellar fractures. Displaced fractures require accurate reduction and internal fixation to maintain the reduction and to restore the extensor mechanism in the lower limb (Burvant, Thomas, Alexander, & Harris, 1994; Carpenter et al., 1997). Rigid fixation and achieving articular congruity is important to maintain knee function. Fixation can be done with tension band wiring using SS wires only, 2 parallel K-wires with stainless steel wires, fixation can also be achieved with cannulated cancellous screws and SS wires (Max et al., 2013; Nasab, Sarrafan, & Tabatabaei, 2012). However, complications like wire migration, breakage and loss of reduction are common complications reported. In 1950s, the AO group introduced the concept of modified anterior tension band wiring; though this improved the stability of transverse fracture fixation, loss of reduction and implant irritation are not uncommon. Patellar plating are also being done for these fractures.

Though tension band wiring with K-wires and SS wires give good results, there are problems with implant prominence and soft tissue irritation. Cancellous screws with anterior tension band decreases the chances of irritation of soft tissues and the need for implant removal. Cannulated cancellous screws are considered to be a stronger construct compared to k wires due to the inherent strength of the implant design. Recent studies with two cannulated screws instead of two wires for anterior tension band principle have shown to increase the structural stiffness and stability of fracture fixation. Screws with tension band wiring are bio mechanically superior to K-wires and SS wires (Chen, Chen, & Li, 2019; Ramu, Rajender, Anjaneyulu, Keertana, & Raju, 2019).

It is considered that the anterior tension band is necessary for effective compression of the fracture fragments. However, anterior tension band wire requires extensive exposure, and hence biological healing may be compromised. However, there are limited studies that evaluate the mechanical stability of the fractures patella without anterior tension wire. (Chen et al., 2019) in their study on finite element analysis of the role of screw types and anterior band wiring in transverse patella fracture, concluded that use of anterior wire along with full thread screw is preferentially recommended for these fractures (Wang et al., 2014).

Materials and Methods

This a prospective study in 17 patients from 2012-2017, admitted in SRIHER with transverse patella fracture, of which 10 patients were male and 7 female. We included patients with isolated Closed transverse fracture patella and patients between the age group of 20-60 years. We excluded patients with an open fracture. Patients with associated injuries to the distal femur and proximal tibia, Paediatric fractures and poly skeletal ipsilateral lower limb injuries were excluded from the study. Patients were evaluated radiologically with x-rays of the knee AP/LATERAL view. The patients were initially immobilised in an above-knee tube slab. Routine evaluation of the patients for fitness for anaesthesia and surgery were obtained.

The patient were operated in a supine position, under spinal anaesthesia, without a tourniquet. Transverse incision made over the centre of the knee extending upto 10 cm. Fracture fragments are cleaned and all blood clots are removed. Fracture is reduced and held using pointed reduction forceps and provisionally fixed using two 1.2 mm K-wires in a parallel fashion. Care should be emphasised in positioning the K-wires in the centre of the patella. The articular surface is then palpated for any step and then the cannulated drill bit is passed over the 1.2mm K-wires, the length of the screws are measured using a depth gauge and the fracture is fixed using 4mm cannulated cancellous screws of measured length. K-wires are then removed and an 18 gauge stainless steel wire is passed through the screws in a figure of 8 fashion. The medial and lateral patellar retinaculum were closed. The surgical wound was closed in layers with a suction drain into the joint.

Postoperatively patient is immobilised with a long knee brace. Static knee quadriceps exercises were started from postoperative day one. Active knee mobilisation with full weight-bearing with a knee brace and walker support are started on post-op day 3 following removal of the drain.

Postoperative evaluation of the fracture were done with X-rays in the immediate postoperative period and during follow-up. The functional assessment were done at 6 weeks, 3 months and 6 months postoperatively with a knee society score.

Results

There were 17 patients in our study, of which 10 were male and 7 were female patients. Male (58.8%) and female (41.2%) patients were included in the study. The age of the patients varied from 18-60 years. The mean age of the patients was 42 years. The commonest age group in our study was between 31-40 years. In our study, Male patients were more frequently affected than female. The most common mode of injury was following a trivial fall and indirect injury to the lower limb. In our study, 14 patients (82%) had AO 34 C1 simple traverse fracture of the patella and 3 patients had AO 34 C2 (18%) transverse fracture with minimum comminution. Radiological union of the fracture was noted on an average of 11 weeks. The mean flexion range of movement in the knee was 112 degrees. One patient had extensor lag in our study. There were no other complications encountered in our study. There was no case of implant loosening or soft tissue irritation in any of the patients, and the mean knee society score was excellent.

Discussion

Transverse patellar fracture has to be treated with accurate reduction and rigid internal fixation. Though patellar fractures are treated with K-wires and SS wires with good results, soft tissue irritation and hardware migration appears to be a common complication with this technique(5). In our study, we used cannulated cancellous screws with tension band wiring to reduce this complication (Reddy, 2016).

Biomechanical studies done by (Burvant et al., 1994; Carpenter et al., 1997) compared different methods of treating patellar fractures and concluded that cannulated cancellous screws with tension band is superior to K-wires.

(Chen et al., 2019), in a biomechanical study, evaluated the position of cancellous screws and the effectiveness of anterior tension band wiring and concluded that fully threaded cancellous screws which were 5mm deeper to anterior cortex has better function. The additional usage as an anterior tension band increases the effectiveness of the construct. In our study, we used partially threaded cancellous screws, and in all, the patient's anterior tension band wiring was done. We present our experiences with cannulated cancellous screws along with tension band wires anteriorly over the patella used for fixation of transverse fractures of the patella with or without minimal comminution.

In our study, we had 17 patients. (Khan, Dar, Rashid, & Butt, 2016) reported a series of 25 patients in the Indian population with a transverse fracture with or without minimal comminution. In our study, male patients were more frequently injured compared to female. In (Khan et al., 2016) study, there were 18 males (72%) compared to 10 (58.8%) in our study. The average age of the patients in our study was 42 years (range - 18 to 60 years) compared to the mean age of 38 years (range - 24 to 58 years) in (Khan et al., 2016). In our study, the right knee was more commonly involved in 14 patients (82.3%), whereas in their study left knee was more commonly involved (68%).

The most common mode of injury was trivial slip and fall with violent contraction of the quadriceps (indirect injury) in our study compared to fall (72%) in their study. The rest, 28% in I Khan et al. study was RTA; we had no patients with a road traffic accident. In our study, most patients had a simple transverse fracture without comminution (82%) compared to 15 patients (60%) in their study.

All patients achieved fracture union. In our study, the mean time to achieve radiological union was 11 weeks from the time of surgery. I Khan et al., in their study, reported a mean time to a union as 10.7 weeks (range 8-12 weeks) after the surgery.

In our study, the range of movements was flexion from 100° to 115° at 3 months follow-up with a mean flexion range of 112°. I Khan et al. reported a mean ROM of 113.8 °(range 90°-130°) at three months follow up.

(Ahmed, Yousef, Zein, & Ali, 2018), in his study, used two crossed cannulated screws with percutaneous technique without tension band wiring and showed excellent results. In our study, we did not attempt closed reduction as achieving articular reduction and repair of the extensor mechanism is difficult. Tension band wiring, which increases the fixation strength, cannot be achieved by the percutaneous reduction technique. Further mobilisation of the patient can be done early with anterior tension band wiring.

(Khan et al., 2016) in a clinical study of 25 patients with cannulated cancellous screws with anterior tension band wiring, had no patients with implant failure or soft tissue complications. He showed one patient with knee stiffness and one patient with superficial wound infection. In our study, we had one patient with an extensor lag of 15°. This patient had associated Parkinson’s disease. Hence, rehabilitation was difficult in this patient. The lag was not associated with an implant or surgical technique. In our study, no complication like screw prominence or implant failure. We had one patient (5.9%) with extensor lag.

(Nasab et al., 2012) in his study, compared between a bioabsorbable screw and metallic implants and concluded that bioabsorbable implants cause less irritation to soft tissues and no need for implant removal. In our study, we did not use bioabsorbable implants due to the higher cost of these implants. This technique is a good alternate to K-wires and reduces the chance of soft tissue irritation with less chance of implant failure and subsequent second surgery.

Conclusion

Cannulated cancellous screws with anterior tension band is a good option for treating transverse fractures compared to K wires with tension band wiring. This procedure reduces the need for implant removal and avoid complications like implant loosening and back out of hardware commonly seen with K wires with the tension band. Proper positioning of cancellous screws with a figure of eight constructs is important to achieve good results. This method of treatment gives good functional outcome and range of movement in patients with transverse fracture of the patella with or without minimal comminution.

Funding Support

The authors declare that they have no funding support for this study.

Conflict of Interest

The authors declare that they have no conflict of interest for this study.