Arthroscopic Transosseous Suture Bridge for Repairing Avulsion Fractures of the Tibial Insertion of the Anterior Cruciate Ligament：A Mini Tunnel Technique

doi:10.21203/rs.3.rs-4683244/v1

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Arthroscopic Transosseous Suture Bridge for Repairing Avulsion Fractures of the Tibial Insertion of the Anterior Cruciate Ligament：A Mini Tunnel Technique

https://doi.org/10.21203/rs.3.rs-4683244/v1

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The study presents a novel arthroscopic transosseous suture bridge technique for repairing avulsion fractures of the tibial insertion of the anterior cruciate ligament (ACL), specifically tailored for adolescent patients. This minimally invasive surgical approach combines elements of both the transosseous tunneling and suture bridge techniques, aiming to reduce impact on the bone bed while ensuring stable fixation. Over a seven-year period, 39 patients with Meyers-Mckeever types II, III, and IV tibial avulsion fractures underwent this procedure. The surgery had an average duration of 52.7 minutes and resulted in decreased swelling and pain within two months postoperatively. All patients achieved full knee extension and over 120° of flexion. X-rays confirmed complete fracture healing within six to 12 months, and negative anterior drawer and Lachman tests indicated stable fixation. Significant improvements were seen in Lysholm and IKDC scores, reflecting enhanced knee function. This technique offers several advantages: it is effective, stable, minimally invasive to growth and development, and particularly suitable for adolescents due to the reduced impact on the bone bed and successful avoidance of epiphyseal plate injury.

Transosseous

Suture bridge

Anterior cruciate ligament

Tibial avulsion fracture

Arthroscopy

The avulsion fracture at the tibial insertion of the anterior cruciate ligament (ACL) is a rare type of knee joint injury, commonly seen in adolescents, accounting for 2.5% of all pediatric knee injuries [1]. Because the fracture occurs at the tibial attachment site of the ACL, the fracture fragment can be easily displaced due to the pull of the ligament, and manual reduction often yields poor results. In clinical practice, numerous instances of comminuted ACL avulsion fractures have been encountered, where simple screw fixation has proven to be inadequate for restoring the ligament's tension [2]. Consequently, displaced avulsion fractures at the tibial attachment require surgical treatment, either through open repair or arthroscopically assisted techniques, with the latter being considered the superior approach.

In children, the tibial insertion of the ACL is not fully ossified, and the tendon-bone interface consists of only a thin layer of fibro-cartilage, making it difficult for screws to achieve effective fixation. Some scholars had adapted the suture bridge technique, originally used for rotator cuff repair, for repairing avulsion fractures at the tibial insertion site of the ACL [3, 4]. This technique uses cables to generate high contact pressure, providing robust fixation and achieving excellent therapeutic outcomes, without the need for a second surgery to remove the device. However, due to the requirement of inserting three or four anchors, and considering that the bone bed at the tibial insertion site in children is relatively small, the insertion of too many anchors might have a significant impact on the bone bed in children [5, 6].

The study introduced a modified surgical approach that combines the arthroscopic transosseous technique with the suture bridge technique for the treatment of avulsion fractures at the tibial insertion of the ACL. The researchers pulled out the tail thread through two mini bone tunnels and secured the sutures below the tunnel, reducing the impact on the bone bed and successfully avoiding injury to the epiphyseal plate. The refined surgical skills and enhanced clinical efficacy of this technique are reported in the subsequent findings.

1.1 General Data

A retrospective analysis was conducted on 39 cases of various types of tibial avulsion fractures of the ACL admitted to our department from July 2016 to July 2023. There were 22 males and 17 females, aged between 13 and 45 years (average 25.2 years). All patients in this group had a clear history of trauma, including 17 cases of traffic accident injuries, seven cases of falls from a height, and 15 cases of sports injuries. They exhibited varying degrees of pain, swelling, and limited mobility, with positive anterior drawer tests and Lachman tests. Preoperatively, patients underwent thorough knee joint CT-3D and MRI examinations to ascertain the type of fracture and to check for any concomitant meniscal injuries. According to the Meyers-Mckeever classification[7], there were 15 cases of type II, 20 cases of type III, and 4 cases of type IV.

This is an observational study. The Research Ethics Committee of the Affiliated Hospital of North Sichuan Medical College has confirmed that no ethical approval is required. Adhering to the ethical principles of the 1964 Declaration of Helsinki, we obtained informed consent forms signed by all patients' guardians prior to the operation.

1.2 Technical Methods
1.2.1 Modified Minimal Bone Tunnel Creation Method

Initially, the anesthetic epidural needle was modified by straightening its tip to create a hollow steel needle for bone tunneling. The outer diameter of this needle was 1.8 mm, and the inner diameter was 1.2 mm, which was suitable for positioning with a 1.0 mm Kirschner wire (K-wire). Using an ACL reconstruction aiming device, 1mm K-wires were placed on the medial and lateral sides at the anterior edge of the bone bed, with a minimum distance of 10 mm between the two wires. Subsequently, the epidural needle was fitted over the K-wire, and the tunnel was manually and slowly drilled open. This method results in a smaller diameter bone tunnel, positioned at the junction of the footprint area bone bed and the articular cartilage surface, thus having minimal impact on the bone bed.

1.2.2 Intraoperative Suture Bridge Technique

All patients were operated by the same surgical team under arthroscopy. Anesthesia was performed using lumbar anesthesia, with the patient in a supine position and a tourniquet applied to the thigh. Surgical approaches included the anteromedial and anterolateral portals of the knee joint. Arthroscopy was conducted first to inspect the joint, and a probe was used to identify the location, size, and type of the bone fragment. The edges of the bone fragment and the interior of the bone bed were freshened with a shaver.

Initially, a suture anchor with attached sutures was placed on the medial edge of the bone bed, and a suture hook was used to pass the sutures through the ligament. After the tail sutures were crossed, they were passed through the tissue between the ligament and the fracture fragment. Then, using an ACL aiming device, two minimal bone tunnels were created on the medial and lateral sides of the anterior edge of the bone bed, and PDS (polydioxanone) sutures were used to pull the anchor suture tails out of the tunnels. The bone fragment was reduced under arthroscopy, and the tail sutures were gradually tightened and secured with a locking anchor (Fig. 1).

Before the end of the surgery, the knee joint was flexed and extended to carefully check whether the bone fragment was firmly fixed and whether the ACL had regained its tension, ensuring that the bone fragment had close contact and no displacement during extension. After thorough hemostasis, the wound was irrigated with a large amount of physiological saline and then sutured. Large cotton pads and elastic bandages were wrapped from the foot to above the knee joint.

1.3 Postoperative Management and Rehabilitation

Postoperatively, the affected limb was bandaged with an elastic bandage, and a knee brace was used to keep the knee in an extended position for four weeks. Isometric contraction exercises for the quadriceps muscles began on the first postoperative day. The knee flexion should not exceed 30° within the first two weeks post-surgery, reach 90° by four weeks, and achieve full range of motion by eight weeks. Partial weight-bearing with crutches was allowed after four weeks, and full weight-bearing was achieved by eight weeks post-surgery. Deep squatting exercises are permitted after six months, and return to competitive sports was allowed after one year.

1.4 Follow-up and Efficacy Observation

During follow-up, the duration of the surgery and the amount of bleeding were recorded. Symptoms such as swelling, pain, joint effusion, postoperative fracture reduction, and joint mobility were observed. X-rays were taken at one, three, six, and 12 months post-surgery to monitor changes in the fracture position and the healing process. At the end of the follow-up, the stability of the knee joint was assessed using the anterior drawer test and the Lachman test. The efficacy was evaluated based on the Lysholm scores[8] and International Knee Documentation Committee (IKDC) functional scores [9].

1.5 Statistical Analysis

Analysis was performed using the SPSS 22.0 statistical software. Data that conform to a normal distribution were represented as the mean ± standard deviation. The preoperative and postoperative Lysholm scores were compared using a paired t-test, with a P-value less than 0.05 indicating a statistically significant difference.

Patients were followed for 12 to 18 months, averaging 15.6 months. The surgical duration averaged 52.7 minutes, ranging from 45 to 62 minutes. Approximately 10 to 30 milliliters of bleeding occurred during surgery. No neurovascular injuries were found. Three cases of postoperative joint swelling occurred and were alleviated with needle aspiration. By two months after surgery, swelling had decreased, pain had become less intense, and there were no restrictions on knee extension. Additionally, all patients achieved knee flexion beyond 120°. Fractures healed within six to 12 months postoperatively, with no instances of loosening, refracture, or displacement, and both the anterior drawer test and the Lachman test were negative. By the end of the follow-up period, the Lysholm and IKDC knee joint functional scores had significantly improved from preoperative levels. (Table 1).

Table 1. Knee joint Lysholm and IKDC scores (paired t test)

	Preoperation	Final follow-up
Lysholm	55.21±9.84	92.02±7.16 *
IKDC	48.26±10.86	93.56±7.71 *

*: P < 0.05 (Paired t test)

IKDC: International Knee Documentation Committee;

Tibial avulsion fractures of the ACL are a rare type of injury, predominantly occurring in adolescents or young individuals during sports-related accidents [1]. Current treatment methods have evolved from traditional open reduction and internal fixation surgery to arthroscopic minimally invasive fixation techniques using sutures, screws, wires, anchors, and even buttons [1-6]. Early fixation methods such as screws, wires, or loop plates were unsuitable for comminuted fractures and the thin bone fragments in adolescents, leading to issues like bone fragment displacement, fragmentation, and rotational instability. The main reasons for these adverse outcomes were improper restoration of ACL tension and inadequate fixation of the bone fragments [10].

Many scholars began to apply the suture bridge technique, originally used for rotator cuff repair, to ACL tibial avulsion fractures, proving it to be a promising technique[11]. Hapa et al. [12] conducted a biomechanical study of three fixation methods using a sheep model, confirming that under cyclic loading conditions, the strength of high-strength suture weaving fixation was significantly higher than that of screw fixation and simple suture anchor fixation. Eggers et al. [13] showed in biomechanical tests that the suture bridge technique using multiple anchors and high-strength sutures had a higher ultimate failure load than screw and suture fixation, but the use of multiple anchors could greatly increase the surgical cost. Therefore, the arthroscopic suture bridge technique combined with transosseous tunnels and tail suture locking anchor fixation might be a very suitable technique.

Boutsiadis et al. [14] described an enhanced arthroscopic suture fixation for ACL avulsions. This four-point technique involved creating four angled 2.9 mm tibial tunnels at specific bone bed locations, securing the ligament and bone fragments with sutures, and fixing them with pegs after pulling the tail sutures through the tunnels. It offered stable fixation, reduced risks of bone bridge and tunnel issues, and accommodated various fragment sizes. However, it might impact the bone bed and carried growth disruption risks due to epiphyseal area traversal.

This study combined the arthroscopic transosseous tunneling technique with the suture bridge technique, achieving a three-point fixation pattern through anchors along the inner edge of the bone bed and double mini tunnels on the anterior edge of the tibia. This technique could anatomically reduce and immediately stabilize fixation regardless of the size of the avulsed bone fragments. Especially in adolescents, the avulsed bone fragments at the ACL tibial insertion site were very thin and prone to fragmentation, but the high-strength sutures from the anchors provided a strong tensile force, allowing the ACL to regain tension. Therefore, rapid rehabilitation training and early recovery of joint function were possible. The results of this study showed that all fractures healed within six to 12 months post-operation, with no loosening, re-fracture, or displacement, and the knee joint function recovered well. At the final the follow-up, the Lysholm and IKDC functional scores of the knee were significantly improved compared to preoperative levels. These results were similar to the other studies [15,16].

In summary, the suture bridge technique conforms to the principle of tension-side fixation, and the internal anchors can close the inner edge of bone block. The minimal impact of the bone tunnel on the bone bed is beneficial for the fractures healing. The tail sutures are fixed on the distal side of the bone tunnel, successfully avoiding the epiphyseal plate, thus having a minimal impact on growth and development. Therefore, the arthroscopic transosseous suture bridge technique for repairing ACL tibial avulsion fractures has a definite therapeutic effect, stable fixation, minimal impact on the bone bed, and is particularly suitable for the treatment of ACL tibial avulsion fractures in adolescents.

This retrospective study has a small sample size, potentially biasing the reliability of the findings. It also lacks long-term follow-up data, being based on short-term outcomes. Future large-scale and long-term studies are needed to bolster the research's credibility.

Conflicts of Interest:

The authors have no relevant financial or non-financial interests to disclose.

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No competing interests reported.

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Arthroscopic Transosseous Suture Bridge for Repairing Avulsion Fractures of the Tibial Insertion of the Anterior Cruciate Ligament：A Mini Tunnel Technique

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