1 Introduction

The posterior cruciate ligament (PCL) lesions represent a disabling problem, impairing walking, daily living activities and sports practice. The incidence of isolated PCL tears ranges from 3 % to 16 %,¹ increasing to 40%–96.5 % in multi-ligamentous knee injuries.² High energy direct trauma typically sustained in motor vehicle accidents or hyperflexion/hyperextension of the knee occurring during contact sports represents the most frequent injury mechanism of PCL.²

The PCL comprises two separate bundles, the anterolateral and posteromedial, with different anatomical and biomechanical properties. The first bundle is taut in knee flexion, and the second in extension.³ Therefore, isolated lesions of PCL bundles, despite being uncommon, could result in knee instability near extension or flexion.³ Moreover, excessive loadings and shear stresses on the patellofemoral joint, resulting in chronic anterior knee pain and early osteoarthritis, were shown in patients with PCL lesions.^4–6

Although its synovial coverage and high potential for spontaneous healing,⁷ surgical reconstruction should be considered in Grade II and III PCL tears, especially in young, high-demand sports patients,⁸ and several arthroscopic surgical techniques were described in the last decades. Single bundle (SB) PCL reconstruction with autograft or allograft was the most widely performed, providing good outcomes and complications.^9–11 More recently, the double-bundle (DB) technique was proposed to restore the normal anatomy of the PCL.^12–14 However, no differences between DB and SB grafts were found using a transtibial or an inlay technique.¹⁵

More recently, the all-inside PCL (ai-PCL) reconstruction technique was described.^16–18 This technique has significant advantages, such as less bone removal, reduced risks of vascular injuries, better positioning of the femoral tunnel using an out-in drilling technique, and more exact socket shape and placement. Nevertheless, as with any new surgical procedure, it requires expert surgeons in the field of arthroscopic surgery of the knee to be adequately performed.

The present investigation describes the surgical technique of all-inside SB-PCL (aiPCL) reconstruction and reports the rate of complications and the clinical outcomes in a cohort of female patients with isolated PCL tears.

2 Methods

2.2

2.2 Surgical technique

The senior author (P.V.) performed the surgical procedure. The patient is positioned in a supine position under spinal anaesthesia, with the inferior limb in a leg holder, allowing a full range of motion of the knee. A standard diagnostic arthroscopy is performed through anterolateral and anteromedial portals to confirm the preoperative diagnosis and to test with a probe the biomechanical properties of the remnant fibres of PCL in both complete knee extension and at 90^o of knee flexion.

2.2.1

2.2.1 Graft harvesting

The quadrupled semitendinosus tendon (ST) was our choice for the PCL graft in all patients. The ST was harvested using a 3 cm longitudinal incision at the level of pes anserinum, approximately 1–2 cm medial to the tibial tuberosity. After detaching the tibial insertion of the ST, a no. 2 Vicryl wire was used to perform a pulling suture with a “baseball stitch” configuration without traversing the tendon tissue. Then, pulling through such a suture, the ST is isolated from its reflexed branches and directed to the gastrocnemius, and it is harvested using an open-ended tendon stripper. The ST tendon is quadrupled to obtain a graft with a minimum diameter of 7–8 and armed to the fixation system chosen at the two extremities (Tight-Rope and Tight-Rope RT; Arthrex, Naples, FL).

2.2.2

2.2.2 Bone tunnels

The posteromedial portal is created, and a cannula is inserted into it (Fig. 1). The trapezoid area is identified. The tibial footprint is debrided with a burr through the posteromedial cannula and the tibial guide is inserted through the anteromedial portal, with the arthroscope in the posteromedial portal. Then, a tibial half-tunnel is created using a retrodrilling (Flipcutter drill; Arthrex, Naples, FL) with a diameter equal to that of an ST quadrupled graft and 30–35 mm long.

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Fig. 1 The cannula inserted into the posteromedial portal.

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This particular step of the surgical procedure is made with caution to obtain a good position of the tibial tunnel, avoiding lesions of the posterior capsule. Indeed, we used to insert a metallic instrument into the posteromedial cannula, protecting the posterior capsule from the leak of the drill (Fig. 2). Then, a loop suture wire is inserted in the tunnel through the AM portal for further graft passing.

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Fig. 2 The metallic instrument into the posteromedial cannula.

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In the same manner, but with an out-in technique, the femoral half-tunnel is performed by inserting the femoral guide through the anteromedial portal after a careful debridement of the intercondylar notch and of the medial aspect of the medial femoral condyle (Fig. 3). Another loop suture wire with a different colour of the tibial one is inserted into the femoral half-tunnel through the AM portal.

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Fig. 3 Femoral guide in the femoral half-tunnel through the anteromedial portal.

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2.2.3

2.2.3 Graft passing and fixation

At this point, two suture wires acting as shuttles in both the femur and tibia are available for graft passing in the AM portal (Fig. 4). The introduction of the double fixation system in the joint can start only after the measurement of the length between the femoral cortex and the joint space. This distance must be reported in the proximal part of the suture. After that, we passed the graft with the proximal side anchored at a TightRope (Arthrex, Naples, USA) fixation system.

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Fig. 4 The two suture wires acting as shuttles in both the femur and tibia.

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With the arthroscope in the AL portal, we use a chamfered obturator introduced through the cannula of the PM portal as a pulley to facilitate the passage of the graft in the tibia until the metal plate is out of the tibial cortex. Then, the graft is gradually introduced partly into the tibia and the femur. With the arthroscope in the AM portal, the sutures were retrieved from the AL portal to determine the tension of the femoral portion of the system. The recovery of the graft in the half-femoral tunnel was completed up to the landmark of the graft. Then, with the knee flexed at 70° and in anterior drawer stress, we complete the graft tensioning by pulling the emerging sutures from the tibial cortex tightened on the metal plate (Fig. 5).

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Fig. 5 Graft tensioning.

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3 Results

4 Discussion

After aiPCL reconstruction, a statistically significant improvement in the Lysholm score was found in female patients with isolated grade II or grade III PCL lesions at a mean follow-up of 3 years. The mean Lysholm score improved from 64.08 ± 13.06 points to 88.12 ± 13.33 points after surgery, and 80 % of the patients described the function of their knee as good or excellent.

From a functional viewpoint, according to the IKDC objective score, posterior drawer test grades A and B were detected in 69.5 % and 21.7 % of the patients, respectively, demonstrating that aiPCL reconstruction was able to restore anteroposterior stability of the knee in 91.2 % of the patients. Furthermore, all patients had negative dial tests at 30⁰ and 90⁰ of knee flexion. On the other hand, no statistically significant improvement in Tegner score was detected after surgery. However, in our series, we had only three professional athletes, and 2 (66.6 %) of them returned to sports participation at the same pre-injury level. Furthermore, all patients returned to participate in recreational sports.

Our clinical results are similar to those reported in the literature about standard SB or DB-PCL reconstruction techniques. Li et al.²¹ compared the outcomes of two groups of patients who underwent SB and DB-PCL reconstruction with a transtibial technique, reporting a postoperative Lysholm score of 88.0 ± 0.42 and 89 ± 3.8 in the SB and DB group, respectively. Furthermore, they reported a Tegner score of 6.2 ± 0.9 points in the SB group and 6.8 ± 1.2 points in the DB group. However, when considering the posterior drawer test, Li et al.²¹ reported that 81.9 % of the patients in the SB group had a grade A or B, while this percentage increased to 91.7 % in the DB group. Then, with 69.5 % of patients with grade A and 21.5 % with grade B posterior drawer test, our functional results are closer to the DB group than the SB group.

Song et al.²² reviewed at a mean follow-up of 140 months 66 patients who underwent PCL reconstruction: 36 with trans-tibial technique (group A) and 30 with an inlay technique (group B). The mean preoperative Lysholm score was 59.9 ± 16.4 points in group A and 54.5 ± 13.8 points in group B, and it increased to 89.9 ± 9.7 and 92.1 ± 10.4 points in group A and B patients, respectively. Moreover, the preoperative Tegner score was 2.5 points in the transtibial group and 2.3 points in the inlays group, and it increased after surgery to 5.9 and 6.0 in group A and B patients, respectively.²² Also, these results are similar to those obtained in our patients, showing that all-inside reconstruction, based on the functional outcomes, is a valid alternative to trans-tibial and inlay techniques. Moreover, since we had no intraoperative/postoperative complications, the aiPCL reconstruction technique is a safe surgical option to manage isolated PCL tears. However, we know that high arthroscopic skills are needed to perform correctly.

Osti et al.²³ reported a complication rate of 5.4 % of the inlay all-inside PCL reconstruction technique, and the most important was a lesion of the popliteal artery. Although it should be confirmed with further studies with a greater sample size, we believe that using the retrodrilling technique instead of the anterograde drill can avoid or reduce the onset of vascular lesions. Kim et al. evaluated ten studies about PCL reconstruction, showing that 7 of these reported a complication related to surgery, including problems related to the chosen fixation system (screws to interference screws) over that loss of tension in the graft resulting from the weakening of the cancellous bone of the tibia around the screw. Retrodrilling allowed us to perform the bone tunnels, sparing the cancellous bone of the tibial metaphysis. Furthermore, the cortical suspension guarantees a stable fixation of the graft without causing a failure of the cancellous bone underlying the graft.

Another debated aspect of the PCL reconstruction procedures remains the graft choice. Given its high capacity for integration and biomechanical proprieties, the bone-patellar tendon-bone (BPTB) is the most commonly used. Achilles tendon allograft is preferred for the absence of donor-site morbidity and multilegamentous injuries, while hamstrings are usually chosen for primary strength and low donor-site morbidity.³ Chen et al.²⁴ demonstrated in a porcine model that the semitendinosus quadrupled graft has the highest breaking load properties compared to BPTB and Achilles grafts. In addition, the semitendinosus quadrupled graft has a large section and, consequently, a great bone-tendon interface for integration.²⁴ For these reasons, and the relative ST harvesting facility with low donor site morbidity, we considered the quadruplicated ST as a good alternative to both BPTB and duplicate ST grafts, also taking into account that the harvesting of a single tendon affects minimally the kinematics of the knee.

However, as with any other surgical technique, several disadvantages of the aiPCL reconstruction technique should be underlined. Firstly, the surgical technique requires dedicated instrumentation, which differs from those commonly used for reconstructing PCL. Another aspect that should be considered is the inadequate graft length; indeed, if the ST tendon is too short (<26 cm), it cannot be wholly quadrupled, and it is necessary to use an ST and gracile tendon quadrupled graft. Moreover, the graft passing through the bone tunnels is critical. The tangling of the TightRope sutures may make the system completely unusable.

The most important limitation of our study is undoubtedly the small sample size. Still, it is principally correlated to the rarity of isolated PCL tears and the recent development of all-inside devices for arthroscopic PCL reconstruction. It would be helpful for future studies to increase the sample size to obtain more representative data comparing the various arthroscopic reconstruction techniques. Furthermore, it would be beneficial to integrate our data with radiographic evaluations assessing the incidence of osteoarthritis at a long-term follow-up to define a possible correlation between the time from injury to surgery and the onset of knee osteoarthritis.

Conclusions

The arthroscopic aiPCL reconstruction seems safe and effective.

CRediT authorship contribution statement

Stefano Petrillo: Conceptualization, and writing – original. Filippo Migliorini: data interpretation and writing – revision. Fabrizio Bertelle: Data curation, and writing – original. Piero Volpi: Supervision.

Consent to participate

All patients were able to understand the nature of their treatment and provided written consent to use their clinical and imaging data for research purposes.

Consent to publish

All patients were able to understand the nature of their treatment and provided written consent to use their clinical and imaging data for research purposes.

Ethical approval

The present study was approved by the Ethics Committee board of San Raffaele University of Milan, Italy (ALLCCP, Em. 225–2024). The present study was conducted according to the principles expressed in the Declaration of Helsinki.

Availability of data and materials

the datasets generated during and/or analysed during the current study are available throughout the manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.