A Reverse Suture Anchor Technique for Arthroscopic Posterior Cruciate Ligament Avulsion Fractures Repair

Abstract

Posterior cruciate ligament avulsion fractures of the tibia account for approximately 20% of knee ligament injuries. Currently, arthroscopic suture anchor bridge repair has been widely adopted because of its excellent biomechanical properties and long-term prognosis. However, traditional techniques require the anchor to be placed at a nearly vertical angle into the posterior tibial bone bed, presenting technical challenges such as limited vision and narrow operating space, which can lead to issues like anchor displacement or insufficient depth. To address these problems, this study introduces a reverse anchor repair technique, which not only simplifies the surgical steps and shortens the learning curve but also effectively avoids iatrogenic damage to adjacent vascular and neural structures.

Recent studies have found that when the knee joint is subjected to hyperextension trauma or a posterior-directed force on the proximal tibia (common in traffic accidents or sports injuries), the tibial insertion of the posterior cruciate ligament (PCL) is prone to avulsion fractures.1, 2, 3 The incidence of such injuries in acute knee trauma is 3% to 4.5%.⁴ In the early stage of injury, the bone fragment pulled by the ligament often forms a fracture gap as the result of synovial entrapment or joint fluid obstruction, making traditional conservative treatment prone to delayed healing or nonunion and subsequently leading to serious complications such as knee instability and degenerative changes.^1,5,6 Therefore, early active surgical intervention has become a clinical consensus.

When traditional open reduction and internal fixation is used for the treatment of PCL avulsion fractures of the tibia, a long incision and extensive soft-tissue dissection are necessary, which can readily damage the neurovascular structures in the popliteal fossa and pose risks of complications such as fat liquefaction, and scar adhesion.7, 8, 9 Consequently, arthroscopic minimally invasive techniques have gradually emerged as the mainstream option for treating such injuries. Studies in the literature have indicated that the arthroscopic suture anchor bridge technique can offer favorable biomechanical stability and satisfactory clinical outcomes; however, its technical difficulties should not be overlooked.^10,11 On the one hand, because of the deep anatomical location of the PCL insertion, precise placement of the anchor presents operational challenges. On the other hand, postoperative complications such as anchor loosening, suture cutting, or redisplacement of the bone fragment may occur. In response to these technical bottlenecks, this study proposes a reverse anchor repair technique. This surgical approach, through the design of a reverse anchor fixation path, achieves anatomical reduction of the fracture fragment while significantly enhancing the mechanical stability, thereby further optimizing the overall treatment effect.

Surgical Technique

Patient Position, Surgical Approach, and Arthroscopy

Figure 1 presents the preoperative imaging data of the patient scheduled for surgery. The patient is placed in the supine position with the knee flexed at 90°. The medial meniscus, lateral meniscus, articular cartilage, anterior cruciate ligament, PCL, and other structures are explored through the standard anteromedial and anterolateral arthroscopic approaches (Video 1). Under the direct vision of arthroscopy, a puncture needle is used to puncture and locate the posterior medial part of the knee joint. Then, an incision of approximately 0.5 cm is made to establish the posteromedial approach (Fig 2). The radiofrequency ablation device (Smith & Nephew, Andover, MA) is used to remove the synovial hyperplasia on the surface of the PCL and shape the bony edge (Fig 3, Table 1). Finally, freshening is performed approximately 2 mm in front of the bone fragment.

Fig 1.

The figure shows the preoperative 3-dimensional computed tomography images of the patient's left knee joint, with the arrow pointing to the avulsion fracture fragment.

Fig 2.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The medial portal is the observation portal. The arthroscope is introduced between the posterior cruciate ligament insertion and the medial femoral condyle and is used to access the posteromedial aspect of the knee joint. Puncture localization is performed using a needle from the posteromedial side of the knee joint.

Fig 3.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The medial portal is the observation portal. A radiofrequency is employed to clean the edges of the bone fragment. The posteromedial portal serves as an instrument-based access pathway.

Table 1.

Technical Pearls and Pitfalls

Pearls	Pitfalls
1.Use a shaver to remove synovial tissue around the bone fragment, thereby preventing it from being embedded in the fracture space. 2.The length of narrow bone canal is about 1∼1.5 cm, measured by equal length Kirschner wire.	1.The position where the sutures passed through the ligament should be as close as possible to the bone fragment.
3.With the assistance of the suture passer, the 3 differently colored tail lines of the anchor are crossed through the central base of the PCL.	2.For larger bone fragments, the posterior edge of the bone tunnel is prone to being obscured, and meticulous operation is required.
4.The PDS suture was introduced into the articular cavity with an epidural needle. 5.The anchor is reversely inserted into the bone tunnel by traction on the PDS suture. At the same time, the anchor sutures are led out through the anteromedial approach and tightened to fix anchor at the junction of the wide and narrow bone tunnels
6.After the bone fragment is restored, anchor sutures is fixed with two outer row anchors.

PCL, posterior cruciate ligament; PDS, polydioxanone.

Anchor Placement

An incision length of approximately 2 cm is established at a position approximately 1 cm medial to the tibial tuberosity. A tibial targeting device (Smith & Nephew) is positioned at approximately 2 mm at the leading edge of the bone fragment and a 2.0-mm Kirschner wire (Wego, Shandong, China) is inserted to create a narrow bone tunnel (Fig 4 A and B). After the tip of the wire slightly penetrates the articular cartilage, use an equivalent-length Kirschner wire to measure the depth of the tunnel (Fig 5). Guided by the Kirschner wire, a broad bone tunnel is meticulously created using a 4.5-mm drill bit (Smith & Nephew), with the drilling terminating approximately 1.0 to 1.5 cm proximal to the articular cartilage surface (Table 1). An epidural needle with a polydioxanone (PDS) suture (Ethicon, Somerville, NJ) is introduced into the bone tunnel. Subsequently, the needle is removed, leaving only the PDS suture within the bone tunnel (Fig 6, Table 1). A knot is then tied at the distal end of the PDS suture to the suture of the 3.0-mm anchor (Johnson & Johnson, Shanghai, China, Fig 7). The anchor is reversely inserted into the bone tunnel by traction on the PDS suture. At the same time, the anchor sutures are led out through the anteromedial approach and tightened to fix anchor at the junction of the wide and narrow bone tunnels (Table 1).

Fig 4.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. Tibial targeting device (Smith & Nephew) is positioned at approximately 2 mm at the leading edge of the bone fragment (A) and a 2.0-mm Kirschner wire (Wego) is inserted to create a narrow bone tunnel (B). A spinal needle, equipped with a polydioxanone suture, is accurately inserted into the joint space via the bone tunnel.

Fig 5.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. After the tip of the wire slightly penetrates the articular cartilage, use an equivalent-length Kirschner wire to measure the depth of the tunnel.

Fig 6.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. A spinal needle, equipped with a polydioxanone suture, is accurately inserted into the joint space via the bone tunnel.

Fig 7.

The patient is placed in supine position with the left knee remaining 20° flexion and abduction. The posteromedial portal is the observation portal. A knot is tied at the distal end of the polydioxanone suture to the suture of the 3.0-mm anchor.

Bone Fragment Fixation

With the assistance of the suture grasper (Smith & Nephew), the 2 differently colored tail lines of the anchor are crossed through the central base of the PCL (Fig 8 A and B, Table 1). The tibial targeting device is positioned at the posterior-medial and posterior-lateral edge of the bone fragment to establish 4.5-mm bone tunnels, respectively (Fig 9). Anchor sutures are crossed into the posterior edge bone tunnel of the bone fragment, and then pull them out from the front of the tibia (Fig 10). After repositioning the bone fragment to the attachment sites, the anchor sutures are tightened to ensure intimate contact between the bone fragment and the bone bed. Subsequently, the sutures are securely fixed to the surface of the tibia using 2 outer row anchors (Double Medical, Xiamen, China, Fig 11, Table 1). The bone fragment is then confirmed to be firmly fixed (Fig 12 A-C). Figure 13 presents the postoperative imaging data of the patient for surgery.

Fig 8.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. With the assistance of the suture grasper, the 2 differently colored tail lines of the anchor are crossed through the central base of the posterior cruciate ligament (A, B).

Fig 9.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. The tibial targeting device is positioned at the posterior-medial and posterior-lateral edge of the bone fragment to establish 4.5-mm bone tunnels, respectively.

Fig 10.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. Anchor sutures are introduced into the posterior edge bone tunnel of the bone fragment.

Fig 11.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. After repositioning the bone fragment to the attachment sites, the sutures are securely fixed to the surface of the tibia using 2 outer row anchors.

Fig 12.

The patient is placed in a supine position with the knee flexed at 90° for arthroscopic surgery on the left knee. The posteromedial portal is the observation portal. (A) Intraoperative arthroscopic. (B) Coronal. (C) Sagittal. The sutures of the 3.0-mm anchors cross the central base of the PCL and are pulled out through the tibial tunnels; coronal (B) and sagittal (C) The sutures are compressed and fixed using 2 outer row anchors.

Fig 13.

The figure presents the postoperative 3-dimensional computed tomography image of the patient's left knee joint. The arrows respectively indicate the avulsed fracture fragment and the 4.5-mm bone tunnels.

Postoperative Reconstruction

During the first 2 weeks, patients perform ankle pumps, straight leg raises, and isometric contractions. Starting at week 4, flexion/extension exercises from 0° to 90° are introduced. By week 6, weight-bearing with brace protection begins, increasing flexion/extension range to 0° to 120°. At week 8, the brace is removed, allowing full weight-bearing walking and gradual return to daily activities.

Discussion

The PCL constitutes a crucial structure for maintaining the stability of the knee joint, and its integrity is of paramount importance in restricting posterior tibial translation and controlling rotational stress.¹² Tibial avulsion fractures of the PCL can give rise to flexion-rotation instability of the knee, abnormal lateral stress, and hyperextension disorders, accelerating the process of joint degeneration.^13,14 Research indicates that anatomical reduction in combination with biomechanical stability can markedly enhance the knee joint function scores and reduce the incidence of traumatic arthritis.^15,16 Although significant progress has been made with an arthroscopic technique, there is still controversy over the selection of internal fixation methods. Traditional screw fixation can provide immediate stability, but it carries the risk of bone fragment fragmentation, especially for comminuted fractures or patients with open epiphyses.^17,18 High-strength suture fixation avoids bone loss but may cause bone fragment tilting due to uneven compression, affecting stability and healing.¹⁹ Although the suture bridge technique has good biomechanical properties, it faces problems such as nerve injury from excessive anchor implantation angles and insufficient holding power of cancellous bone anchors.^10,20 To address these deficiencies, this technique significantly reduces the difficulty of anchor implantation by the reverse direction and embedding the anchor at the junction of the wide and narrow parts of the bone tunnel. The anchor is implanted at a depth of 1 to 1.5 cm from the tibial plateau surface, taking advantage of the cortical bone thickness to effectively prevent anchor pullout. The cross-suture design significantly increased the contact pressure between the bone fragment and the bone bed.

In knee joint surgery, adequate exposure of the surgical field is a prerequisite for comprehensive assessment of the lesion and precise treatment. During the operation, the following points should be noted (Table 1): (1) The position where the suture passes through the ligament should be as close as possible to the bone fragment to avoid cutting damage to the posterior cruciate ligament by the suture. (2) For larger bone fragments, the posterior edge of the bone tunnel is prone to being obscured, and meticulous operation is required. (3) To maintain the stability of the bone fragment's reduction, the suture should be closely adhered to the bone surface and uniform pressure should be applied to prevent the bone fragment from tilting due to uneven force. Currently, although the designed length of the fine bone tunnel (1-1.5 cm) can meet the basic fixation strength, because of the special nature of cancellous bone, the fixation anchor may experience micromovement as the result of osteoporosis (Table 2). The ideal length of the narrow bone tunnel requires further research.

Table 2.

Advantages and Disadvantages

Advantages	Disadvantages
1.Optimizes the surgical process.	1.Need to establish more bone tunnels, the possibility of multiple bone canals conflict.
2.The bone fragment is capable of undergoing precise anatomical reduction.	2.Fixation anchor may experience micromovement due to osteoporosis.
3.Restores its biomechanics as much as possible.

This study has the following limitations. First, the reverse anchoring technique requires the establishment of multiple bone tunnels, which is more likely to cause interference risks between tunnels compared with traditional methods (Table 2). During the operation, the angle of the positioning device needs to be precisely adjusted to optimize the spatial distribution of the tunnels. Second, although this technique has innovative advantages, its biomechanical properties still need to be systematically verified. Biomechanical experiments are required to validate its stability and clinical efficacy.

Disclosures

All authors (C.M., J.W., M.L., C.Q., W.Z., Y.Y., C.H.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

The patient is positioned supine with the knee flexed at 90°. Arthroscopic surgery is performed using a 30° scope and a standard approach through the medial and lateral portals of the knee joint. The synovium between the anterior and posterior cruciate ligaments is cleared with a planer knife to expose the posterior compartment. Under the direct vision of arthroscopy, a puncture needle is used to puncture and locate the posterior medial part of the knee joint. Then, an incision of approximately 0.5 cm is made to establish the posteromedial approach. The synovium at the lower stop of the posterior cruciate ligament is cleared by a posteromedial approach and the location of the fracture can be found. Clean the front of the fracture site using radiofrequency and a planer knife. The posterior cruciate ligament is separated from the surrounding synovium tissue with a radiofrequency, and freshened at about 2㎜ of the posterior edge of the bone fragment. The incision length of approximately 2 cm is established at a position approximately 1 cm medial to the tibial tuberosity. The tibial targeting device is positioned at approximately 2 mm at the leading edge of the bone fragment and a 2.0-mm Kirschner wire is inserted to create a narrow bone tunnel. When the Kirschner wire penetrates the joint cavity, the length of the narrow bone tunnel is measured using an equivalent length wire. Subsequently, a 4.5-mm bone tunnel is drilled, with a length that was 1 to 1.5 cm shorter than the length of the narrow bone tunnel. The spinal needle is inserted through the bone tunnel into the joint cavity. The thread PDS suture is passed through the spinal needle. The spinal needle is removed and PDS suture is retained. A knot is then tied at the distal end of the PDS suture to the suture of the 3.0-mm anchor. The anchor is reversely inserted into the bone tunnel by traction on the PDS suture. At the same time, the anchor sutures are led out through the anteromedial approach and tightened to fix anchor at the junction of the wide and narrow bone tunnels. With the assistance of the suture grasper, the 2 differently colored tail lines of the anchor are crossed through the central base of the PCL. Then, the bone tunnels of 4.5㎜were established by locating the posterior inner and posterior outer edges of the bone fragment with tibial targeting device. The anchor sutures are introduced into the bone tunnels at the posterior edge of the bone fragment and led out of the joint cavity. After repositioning the bone fragment to the attachment sites, the anchor sutures are tightened to ensure intimate contact between the bone fragment and the bone bed. Subsequently, the sutures are securely fixed to the surface of the tibia using 2 outer row anchors. The bone fragment is then confirmed to be firmly fixed.