Management of displaced patella fracture with modified tension band wiring and percutaneous cannulated screws-a dilemma

INTRODUCTION

Patellar fractures are common and it constitutes about 1% of all skeletal injuries.¹ The patella is a sesamoid bone in quadriceps tendon whose main function is to improve the efficiency of quadriceps muscle by increasing the mechanical leverage of the quadriceps tendon. Most patellar fractures are caused by a combination of direct and indirect forces. A very accurate classification of patella fracture has been presented by Hohl and Larson which differentiates between nondisplaced, transverse longitudinal or vertical, lower or upper pole and comminuted (stellate) fracture types.² The treatment of fracture patella has always been a matter of controversy since the earliest of times. A displaced fracture is generally defined by fracture fragment separation of more than 3 mm or an articular incongruency of 2 mm or more. Open fractures, articular step of 2 mm or greater, and loss of knee extension are indications for surgical intervention.³ Haxton (1945) believed that complete and accurate reconstruction of patella is likely to give a joint which will tolerate the stresses and strains better than one in which the normally anatomy is disturbed by total excision.⁴

In this study a series of 30 fracture patellae has been studied and the results obtained after treatment by modified tension band wiring and percutaneous cannulated screws have been assessed and critically analysed.

METHODS

The present study was a prospective comparative study conducted at Dhanwantri Hospital and Research Centre, Jaipur between November 2015 and December 2016. The study was approved in a meeting held by the Ethical Committee of the institute on 13^th August 2015. A total of 30 cases with patella fractures were studied. Sample size was calculated by considering the 80% of average number of patients presented with patella fracture of knee over the period of last three years treated with modified TBW or CC screw.

Inclusion criteria

Participant giving consent to enroll in the study. Patients with patella fracture. Patients of any sex in the age group of 18 to 65 years. Patients who were fit/unfit for surgery. Open patella fracture.

Exclusion criteria

Patella fracture in children. Pathological fractures of the Patella. Patient not giving consent for study. Comminuted patella fracture

Study procedure

All the patients fulfilling inclusion criteria were clinically and radiologically reassessed by a single surgeon. Detailed informed consent was taken and all the pre-operative investigations were done. After pre anesthetic checkup and clearance, patients were taken to OT. All the patients were positioned supine on the radiolucent table with a pad under buttock of affected limb. Skin preparation done with beta scrub & the limb was properly draped.

Group I (modified TBW) patients

A midaxial incision from 5 cm above superior pole of patella to the tibial tubercle made. The skin and subcutaneous tissue in full thickness proximally and distally reflected to expose the entire anterior surface of the patella and the quadriceps and patellar tendons. The patella was then held with a patellar reduction clamp and reduction confirmed by observing articular surface. A 2 mm k-wire passed along the longitudinal diameter of the patella below anterior cortical surface. Another wire passed 5mm apart the first wire. 18-gauge wire was then passed beneath patellar tendon posterior to K-wires. Limbs of wire crossed over anterior patella. Wire passed through quadriceps tendon posterior to wires and tightened by twisting them simultaneously. K-wires then bent 180^o and embedded in quadriceps tendon.

Group II (percutaneous cannulated cancellous screws) patients

Two cannulated screw guide wires passed percutaneously, perpendicular across fracture, which was held in reduction using a patellar clamp, 5 mm below anterior cortical surface drilled with cannulated drill over guide wire. Depth gauge used to measure screw length. And two 4 mm cannulated screws inserted into the patella.

Postoperative care

The limb was placed in extension in a posterior plaster splint or removable knee brace, dressing done after 48hrs. The patient was allowed to ambulate while bearing weight as tolerated on the first postoperative day. The patients were encouraged to perform quadriceps-setting exercises and within a few days should be lifting the leg off the bed. At 10 to 14 days, the sutures were removed. The patients were allowed to ambulate using crutches when active muscular control of the leg was obtained.

Follow up

All the patients were followed up at the six weeks, three months and six months duration. The sixth week assessment included clinical assessment to exclude early complications related to the fracture or surgery, and a routine radiograph to evaluate the fracture position. The three months and six months appointment was scheduled for clinical assessment of fracture healing and a routine radiograph to assess union. Radiological union was assessed by the principal investigator at first, third and sixth month. Clinical data of union including fracture mobility, tenderness and pain was also obtained at each follow-up. The functional outcome was evaluated based on Lysholm knee scoring scale.⁵ The maximum knee score was 100 points and the maximum functional score was 100 points.

Statistical analysis

Data obtained was coded and entered into Microsoft Excel spreadsheet. The categorical data was expressed as rate, ratio and percentage. The continuous data was expressed as mean±SD. A ‘p’ value of less than or equal to 0.05 was considered as statistically significant. Type of study was cohort type prospective study.

RESULTS

The most common people (40%) who sustained patellar fractures were either farmers or non-working class. They were followed by housewives (16.7%), students and drivers. Majority of participants were not having any previous history of illness (about 70%). About 1/3^rd of total participants were having history of previous illness such as diabetes, hypertension, cardiovascular diseases, COPD and previous surgery.

Along with the fracture of the patella, >80% of the participants were not having any associated injuries, while others were having associated forearm fractures, clavicle, metatarsal or head injuries

The comparisons of mean values of knee flexion were greater in TBW group when compared with CC screw group, but this difference was statistically non-significant after using t test (0.08).

In more than 70 % patients Lysholm score was found to be more than 90, while in only about 7% cases it was found to be less than 60. Minimum Lysholm score was found to be 45 and maximum score was 100.

Majority of the participants were having excellent outcome in both CC screw fixation (40%) as well as patella TBW (36.67%). Poor outcome was found in about 10% of the participants which was more in TBW group.

Main post-operative complications that were reported included stiffness of the joint (about 16.7 %) infection of the wound (6.7%) or its delayed union (3.3%). About 2/3^rd of the participants were having excellent post-operative outcome, only 10% participants were having poor post-operative outcome.

The association of the post-operative complications with the operative procedures were that patella TBW was responsible for all the cases of infection 2 (6.67%) and delayed non-union 1 (3.33%). Whereas stiffness was nearly equal in both the techniques. These associations were statistically non-significant after using chi-square analysis.

DISCUSSION

In our study, road traffic accidents were responsible for majority (46.7%) of the patellar fractures. Jabshetty, reported that in 60% of cases, the mechanism of injury was fall on the knee and in other 40% cases it was RTA.⁶ Shobat and Mann reported fall accounted for 82% of cases.¹⁵ In our study, the most common fracture types included transverse, middle third patellar fracture which is consistent with other previous studies.

Carpenter et al in their study presented that open surgical techniques are the standard method for reduction and fixation of displaced patellar fractures, many reports describe the disadvantages and complications associated with traditional surgical treatments of patella fractures.⁷ The common complications of these techniques are infection, loss of fixation, knee stiffness, posttraumatic osteoarthritis, non-union, irritation of the anterior knee caused by internal fixation devices, and cosmetic problems. Because the patella is a subcutaneous bone, fixation devices that have been used for fracture fixation are frequently irritating. Wires and wire knots seem to be particularly irritating to the soft tissues of the anterior knee area. In a report Hung et al which was a large series of patella fractures, the incidence of complications related to wire circlage materials was 47%.⁸ These complications resulted in a delay for patients in returning to their activities of daily living and a need for additional surgery. For this reason, new treatment modalities are being researched to minimize these disadvantages. In our study patella TBW was responsible for all the cases of infection 2 (6.67%) and delayed non-union 1 (3.33%). Whereas knee stiffness was nearly equal in percutaneous technique as well.

A recent study by Leung et al observed fragment displacement of 2 mm in 22%-30% of the patients with early mobilization after tension band wiring.⁹ Secondary postoperative pain due to skin irritation caused by the K-wires or the stainless steel wire can be a common problem which may require an extra surgery for fixation removal. Moreover, the “figure of 8” tension band configuration was proved not the most stable construct for fixation of transverse patella fractures. In the present study, we found that the cannulated screw fixation technique was associated with less pain, and facilitated early knee motion and avoided complications due to immobilization. It has also been demonstrated that early motion has some advantages for joint cartilage perfusion and nutrition. The cannulated screws has the advantages of causing less destruction of the soft tissues and less implant irritation to the soft tissues, reducing the risk of postoperative wound complications and encouraging early rehabilitation.

In our study, the mean range of movements of knee in all the patients was recorded as 106.47+19.48 degrees. By the end of 6 weeks, 26 patients i.e., 86.66 % have gained knee movements and only 4 patients reported stiffness. In study by Dudani et al, 73% of cases had more than 120º of flexion, whereas in Srinivaslu et al series, all (100%) cases had full range of movements.^10,11 In Srinivaslu et al series, normal power was in 93% of patients.¹¹ In the study of Jakobsen et al and Edwards et al reduction in quadriceps strength was seen in 33% and 44% cases respectively.^12,16 The mean Lysholm score observed was 90.70±14.03.

Present study group consists of 30 cases, 15 cases each from both groups. Union was seen in all the cases except one, but the union was faster in cases of cannulated cancellous screw. The average period of union was 12-14 weeks in cases treated with modified tension band wire. In cases of, Cannulated cancellous screw the average time of union was 10-12 weeks.

The results of cases treated with tension band wiring are excellent in 73.3% of cases, fair in 13.3% of cases and poor in 13.3% of cases. In cases of, Cannulated cancellous screw excellent results were found in 80.0% of cases, good in 13.3% and poor in 6.7% of cases. Jabshetty reported that cases treated with tension band wiring are excellent in 50% of cases, good in 40% of cases and poor in 10% of cases.⁶ In cases of, cannulated cancellous screw excellent results were found in 40% of cases, good in 40% and poor in 20% of cases.

In our study, the mean range of movements of knee in patients treated with modified tension band wiring was 107.27±21.20 degrees, whereas it was 105.67±18.32 in the other group. This difference was statistically non-significant (p value=0.05). In patients treated with cannulated cancellous screws on applying t test this difference was found to be statistically significant (p value <0.05). By the end of 6 weeks, 4 patients i.e., 13.33% have gained knee movements of more than 120º. More number was contributed from the CC screw group as compared to the other one.

In modified tension band wiring, 50% of cases showed full range of movement, 40% showed more than 120º of flexion and 10% showed flexion between 90-120º. In Cannulated cancellous screw 40% of cases showed full movement, 40% above 120º flexion and 20% showed flexion between 90-120º. Gaining range of movements was faster in cases treated with tension band wiring because of better fixation and start of knee mobilization after 2 weeks compared to 4 weeks in cases of Cannulated cancellous screw. Quadriceps atrophy may also have occurred because of this longer period of immobilization in Cannulated cancellous screw. Extensor lag was seen in 20% of cases treated with Cannulated cancellous screw and 10% of cases treated with modified tension band wiring.

Patients managed using the CC screw fixation technique achieved better knee function, especially in the early postoperative period. The reported advantages of the percutaneous fixation technique include avoidance of extended incisions, preservation of the blood supply to the patella¹³, and the possibility of a simpler removal of all hardware in the clinical setting.

According to Baydar et al, cannulated screws are more durable against distraction forces than the modified tension band technique to treat transverse patellar fractures.¹⁴ Similar studies have reported that fractures stabilized with a modified tension band displace significantly more than those fixed with screws alone or screws plus a tension band in simulated knee extensions (p<0.05). An advantage of cannulated screws is the potential for percutaneous application.

Two separate studies have demonstrated through biomechanical evaluation that among the 2 methods for patella fixation (modified tension band, cannulated screws with a tension band wired through the screws), the cannulated screws plus the tension band provided the most efficient stabilization, indicating that combining inter-fragmentary screw fixation with the tension band principle seems to provide improved stability over the modified tension band or screws alone for transverse patella fractures.

Tian et al also showed that the cannulated screw tension band was better than the modified K-wire tension band technique.³ Thus this technique should be an effective device for fixation of transverse patella fractures.

CONCLUSION

Patients managed using the CC screw fixation technique achieved better knee function, especially in the early postoperative period. The reported advantages of the percutaneous fixation technique include avoidance of extended incisions, minimal soft tissue dissection, preservation of the blood supply to the patella, and the possibility of easy hardware removal later. These results suggest that the CRCF technique may be a superior alternative to conventional Modified tension band wiring in simple and transverse patellar fracture.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

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