Observation of the effect of arthroscopically assisted percutaneous minimally invasive Kirschner wire tension band fixation on the treatment of patellar fractures

Abstract

BACKGROUND:

Patellar fractures are common intra-articular fractures. Arthroscopically assisted reduction and fixation has been shown to advantageous in the treatment of patellar fractures.

OBJECTIVE:

This study aimed to investigate the effect of arthroscopically assisted percutaneous minimally invasive Kirschner wire tension band fixation on the treatment of patellar fractures.

METHODS:

Thirty-four patients with acute closed patellar fractures enrolled in the study and were managed by arthroscopically assisted percutaneous minimally invasive Kirschner wire tension band fixation under epidural anesthesia. Among these patients, 24 were males, and ten were females. The mean age of these patients was 38 $\pm$ 0.8 years (range: 25–62 years). Of these patients, 20 had transverse fractures, five had longitudinal fractures, four had marginal oblique fractures, and five had multifragmentary upper and lower pole. Fracture causes: 25 were caused by falls, and nine were caused by traffic accidents. The time from injury to operation was 6–48 hours, with an average of 23 hours. The average post-operative follow-up was 12.8 months, and at the end of follow-up, the Boestman scoring system was used to evaluate knee joint function.

RESULTS:

All the wounds healed by first intention, and no infections, skin necrosis, joint stiffness, or other complications occurred. Three months after operation, the tension band wire had broken in one patient, but the fracture had united, and this did not affect the prognosis. In eight patients, the average circumference at 10 cm above the patella was 0.6 cm less on the injured side than on the contralateral side. The average Boestman score was 27.5. The final result was excellent in 25 patients, good in eight patients, and acceptable in one patient.

CONCLUSION:

Arthroscopic management of simple patellar fracture with percutaneous minimally invasive Kirschner wire tension band fixation is less invasive than open operation, while still leading to firm fixation, and is conducive to early functional training and functional recovery, and thus is an effective method of management for patellar fractures.

Keywords

Patellar fracture arthroscopy percutaneous tension band internal fixation

1. Introduction

Patellar fractures are common intra-articular fractures, accounting for approximately 1% of all fractures [1]. The choice of treatment depends on the type of fracture, the size of the fragments, the integrity of the knee capsule and extensor apparatus, and the amount of dislocation of the articular fragments [2, 3]; the key to successful treatment is to restore the smoothness of the articular surface and enable early functional training. Even for simple fractures with good alignment, early operation is recommended to allow early postoperative functional training, and to avoid joint stiffness, muscle atrophy, thrombosis, osteoporosis, and other complications caused by long-term fixation [4].

At present, surgical treatment is recommended for fractures with dislocation of more than 2 mm or fracture gaps of more than 3 mm [4, 5, 6]; common fixation methods include the use of traditional Kirschner with wire tension bands, memory alloy patellar claws, hollow screws, patellar needles and the cable pin system [7, 8]. With the popularization of arthroscopic techniques in the management of extra-articular and periarticular fractures, arthroscopically assisted reduction and fixation has been shown to have the advantages of less trauma, faster recovery, and fewer complications.

2. Methods

2.1 General information

A total of 34 patients were included in this study: 24 males and ten females. Their age range was 25–62 years. All cases involved fresh closed fractures caused by direct violence.

Inclusion criteria: fractures were classified according to morphology: 20 cases of transverse fractures, 5 cases of longitudinal fractures, 4 cases of marginal oblique fractures and 5 cases of upper and lower extreme large fractures. All of them were acute closed fractures, with 2 fracture blocks and the maximum displacement of 5 mm.

Exclusion criteria: Open fractures; Fractures older than three weeks; Comminuted fracture with severe displacement; Combined with other intra-articular injuries; Fracture separation greater than 8 mm.

This study was conducted in accordance with the Declaration of Helsinki. The study was approved by the Ethics Committee of the First People’s Hospital of Jingmen. Written informed consent was obtained from all participants.

2.2 Treatment methods

After admission, the patients were assessed in the emergency department to exclude other injuries, and emergency surgery was arranged as soon as possible. In each case, continuous epidural anesthesia or nerve block anesthesia was given during the operation. A tourniquet was placed on the base of the thigh for use if necessary. The patellar contour was drawn on the skin before the operation began. Two 2-mm sterile Kirschner wires were placed on the surface of the patella through the vertical fracture line on both sides of the midline of patella, and a Mobile C-arm X-ray was was used to determine the rough direction of the Kirschner wire placement. Then the area was disinfected and draped, and a knee arthroscope was inserted through the standard approaches, anteromedial and anterolateral to the patellar ligament, to explore the articular cavity. Any blood clots and free bone fragments were removed. If there was no obvious fracture displacement, the fracture fragments were clamped with point-type reduction forceps. In cases of fracture with obvious displacement, the fracture was reduced manually by pressing and massage on the surface of the patella and fixed with towel forceps, in order to restore the articular surfaces under arthroscopic monitoring. In patellar fractures with more than 8 mm separation and displacement, injury to the quadriceps femoris expansion was common; in such cases, if manual reduction was difficult, a 2-cm-long incision was made at the fracture end, the soft tissue and hematoma embedded between the fracture ends were removed, and the fracture ends were fixed temporarily by point-type reduction forceps. For transverse fractures, two 2.0-mm Kirschner wires were inserted from proximal to distal or from distal to proximal. For longitudinal fractures, two Kirschner wires and 0.8 mm steel wire cerclage was used for fixation, and the position was adjusted until the tip of the Kirschner wire could be touched under the skin, the Kirschner wire was placed at the junction of the middle and lower thirds of the thickest, central part of the patella. The smoothness of the articular surface was checked again under arthroscopic monitoring, and X-rays were taken to determine the fracture alignment and Kirschner wire position. A scalpel was used to make 0.5-cm incisions at the entry and exit points of the Kirschner wire. Under the guidance of an epidural anesthesia puncture guide needle (diameter: 1.6 mm), fixation was completed using steel wire cerclage around the patella or a figure-of-eight steel wire tension band on the patellar surface (see Fig. 1A–D for details). Finally, the end of the steel cerclage wire was tightened, and the ends of the Kirschner wire were cut, bent, and buried under the skin. The X-ray images are shown in Fig. 1E and F. The smoothness of the articular surface was assessed under arthroscopy at the end of the operation (Fig. 1G). After the anesthesia had worn off, quadriceps muscle contraction and other functional training were started. The next day, the patients walked, bearing weight on the injured limb. In most cases, postoperative external fixation was not used. Patients were instructed to avoid knee flexion of more than 90 ${}^{\circ}$ for the first four weeks; thereafter, the angle of flexion was gradually increased.

Figure 1.

(A)–(D): Treatment of patellar fracture under the guidance of epidural puncture guide wire: (A) Arthroscopically assisted reduction: posterior point reduction forceps are used to fix the upper and lower fracture fragments. (B) Two Kirschner wires are used to fix the fracture fragments longitudinally; the wire is guided by an epidural puncture needle behind the Kirschner wire. (C) Under the guidance of an epidural anesthesia puncture guide needle, the steel wire is introduced and fixed subcutaneously. (D) The appearance of the skin suture after operation. (E)–(F): The anteroposterior and lateral C-arm X-ray images taken after operation show that the fracture alignment is good and the articular surface is smooth; the internal fixation position is normal. (G): After reduction and fixation, the articular surface is smooth under arthroscopy; the red arrows show the fracture ends.

3. Results

From June 2015 to January 2019, 34 patients with patellar fracture were treated in our department by arthroscopically assisted percutaneous minimally invasive Kirschner wire tension band fixation under epidural anesthesia, with good results. The details are reported below.

In this study, the 34 patients were followed up for 6–15 months, with an average of 12.8 months. Twenty patients had transverse fractures, five had longitudinal fractures, four had marginal oblique fractures, and five had massive upper and lower fractures. The time from injury to operation was 6–48 hours, with an average of 23 hours. At the end of follow-up, all fractures had united, and no infections, skin necrosis, joint stiffness, or other complications had occurred. Three months after operation, in one patient, the tension band wire was found to be broken, but the fracture had united and this did not affect the prognosis. In eight patients, the average circumference at 10 cm above the patella was 0.6 cm less on the affected side than on the contralateral side; the average Bostman score was 27.5 (maximum is 30 points and minimum is 18 points). The final result was excellent in 25 patients, good in eight patients, and acceptable in one patient.

4. Discussion

In this study, 34 patients with simple patellar fractures were treated with arthroscopically assisted percutaneous minimally invasive Kirschner wire tension band fixation under epidural anesthesia. The advantages of this method are that it is a simple operation, associated with relatively little trauma and fast recovery, allowing the patient to mobilize as soon as possible after surgery, and thus is conducive to the recovery of joint function, in line with the concept of Enhanced Recovery After Surgery (ERAS). In this study, all 34 cases of patellar fractures were simple fractures: there were no cases of comminuted or severely displaced fractures. For complex fractures, closed reduction is more difficult than open reduction; although arthroscopically assisted minimally invasive fixation treatment for complex fractures is feasible in theory, it is difficult in practice, so that blindly pursuing minimally invasive surgery will often result in more loss than gain, prolonging the operation and causing more pain for the patients. Therefore, traditional open reduction and internal fixation treatment is still recommended for complex patellar fractures [9, 10, 11, 12].

During the operations, epidural anesthesia puncture needles were used to guide tension band fixation. Because an epidural anesthesia puncture needle is strong and also flexible, it is convenient for the introduction of tension band wire, for either figure-of-eight tension band fixation or cerclage; in addition, it will not damage other structures such as ligaments, blood vessels or nerves, reducing risk to the blood supply of the skin and patella, and to the saphenous nerve-damage to which could cause local numbness after surgery.

There are six main points to note concerning this form of surgery: (1) The percutaneous minimally invasive method is most suitable for simple transverse, longitudinal or massive upper and lower fractures; it is not suitable for the management of complex or comminuted fractures due to the large number of bone fragments involved and the difficulty of intraoperative reduction. (2) After completion of the relevant preoperative examination and exclusion of other complications, operation should be carried out as soon as possible. Operating early reduces the likelihood of blood clot being present between the fracture ends, facilitating fracture reduction. (3) For non-transverse fractures or fractures with small non-displaced bone blocks outside the main fracture block, it is suggested that fixation with steel wire cerclage under the guidance of an anesthesia cannula should be performed; in addition, it was found that in simple steel wire cerclage, placing the Kirschner wire across the patella in front of the K-wire wire helped to prevent the wire from sliding on the patellar surface and losing the effect of cerclage as the wire was tightened for compression. (4) The steel wire should cross the middle and lower thirds of the patellar quadriceps tendon to avoid cutting the ligament; also, cerclage should align close to the edges of the patella to achieve optimal fixation. (5) Closed reduction is not recommended for fractures on the surface of patella, which are difficult to reduce by pressing and massage, or for fractures with more than 8 mm displacement of the fracture ends, in which injuries to the quadriceps expansion are likely [11]. In these cases, it is suggested that a small incision should be made on the surface of the fracture end, hematoma and soft tissue between the fracture ends should be removed under direct vision, allowing more successful reduction. (6) In clinical practice, thoracic fixed steel wire has better flexibility and higher strength than other wires, and is not easy to break, making it convenient for use in fixation under the guidance of an epidural puncture guide needle.

The traditional surgical approach is a transverse curved incision in front of the knee; the incision is parallel to the skin tension line, which leads to an improved cosmetic result and is also conducive to the exposure and repair of the knee extension retinaculum; however, the infrapatellar branch of the saphenous nerve may be damaged during operation, resulting in postoperative local skin numbness. Currently, most surgeons advocate the “front center” anterior longitudinal approach, which is more conducive to protection of the blood supply of the skin in front of the knee; during operation, the incision can be extended up and down, especially in patients who are expected to undergo arthroplasty in the future, to allow sufficient exposure. However, whether an anterolateral arc incision or a median incision of the knee is used, during the operation, both sides of the flap should be freed to expose the fracture ends and the expansion part of the knee extensor apparatus, to ensure the anatomical reduction of the fracture ends and the articular surface [11]; failure to do so may result in postoperative joint adhesions and early arthritis as well. There are other potential disadvantages of open operation: wound pain during functional training affects the success of rehabilitation, postoperative scars affect the appearance, and hypoesthesia may occur around the incision [10]. In recent years, some surgeons have proposed the treatment of patellar fractures by closed reduction and internal fixation. Some surgeons use percutaneous puncture tension band fixation to treat patellar fractures. However, this requires great skill and experience, and taking multiple X-rays increases the body’s exposure to radiation. Some surgeons also adopt percutaneous steel wire cerclage and tension band internal fixation combined with small anterior patellar incision reduction to treat patellar fracture: the incision is smaller than that of traditional operations, reducing the postoperative soft tissue complications; however, with this approach it is remove any blood clots and loose intra-articular bone fragments in the articular cavity, and it is impossible to directly observe the alignment of the joint surface. With the development of arthroscopic technology, arthroscopically assisted closed reduction for the treatment of patellar fractures not only meets the requirements of minimally invasive surgery, but also allows assessment of the injury in the articular cavity by direct observation, and the performance of procedures such as the removal of debris, hematoma, or diseased synovial membrane in the articular cavity, meniscal repair, and the establishment of active bleeding point hemostasis [11].

5. Conclusion

Arthroscopically assisted percutaneous minimally invasive Kirschner wire and tension band fixation under epidural anesthesia in the treatment of simple patellar fracture has the advantages of being a convenient operation that achieves firm fixation, with relatively little trauma and a quick recovery, and it is worthy of clinical popularization.

Funding

None to report.

Availability of data and materials

All data generated or analysed during this study are included in this article. Further enquiries can be directed to the corresponding author.

Footnotes

Acknowledgments

The authors are particularly grateful to all people who helped them with the article.

Conflict of interest

The authors declare that they have no competing interests.

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