Abstract
Recurrent patellar dislocation, often caused by medial patellofemoral ligament (MPFL) injury, is commonly treated with MPFL reconstruction. Traditional open techniques are invasive, whereas arthroscopic single-bundle methods may not fully restore native ligament anatomy. This Technical Note presents an improved arthroscopic double-bundle MPFL reconstruction technique featuring (1) dual-anchor patellar fixation for anatomical restoration; (2) fluoroscopy-free femoral tunnel placement (12 mm distal and 6 mm posterior to adductor tubercle); and (3) real-time graft isometry testing to ensure optimal tension. The technique provides biomechanical stability while minimizing invasiveness. Although promising, long-term outcomes require further study, and the procedure demands surgical expertise.
Technique Video
Recurrent patellar dislocation is a common patellofemoral joint disorder that has a greater incidence in young athletes.1,2 The medial patellofemoral ligament (MPFL) is a key structure in maintaining patellar stability, and its damage is one of the main causes of patellar instability and recurrent dislocation.3 MPFL reconstruction has become the standard method for treating recurrent patellar dislocation, aiming to restore patellar stability and reduce the recurrence of dislocation.4 However, traditional open MPFL reconstruction is more invasive, with more scarring.5
With the development of arthroscopic techniques, arthroscopic MPFL reconstruction has gradually become a less-invasive and effective surgical approach. Currently, some arthroscopic MPFL reconstructions use a single-bundle technique.2 Although Kang et al.6 demonstrated comparable clinical outcomes between single- and double-bundle reconstructions, Wu et al.7 reported better clinical outcomes with double-bundle reconstruction. This divergence may stem from the double-bundle technique's superior ability to replicate the native ligament's band-shaped anatomy,8 coupled with its biomechanically proven advantages in ultimate load (213 N vs 171 N) and stiffness (17.1 N/mm vs 13.1 N/mm).9,10 Furthermore, the arthroscopic reconstruction techniques reported in the literature lack real-time monitoring of graft length and tension, which may lead to improper graft tension and affect the surgical outcomes.
This Technical Note will provide a detailed introduction to the improved arthroscopic double-bundle MPFL reconstruction technique and describe how real-time graft length and tension monitoring is conducted during surgery to ensure that the graft meets physiological requirements.
Surgical Technique
The patient is placed in a supine position on a standard operating table. The operative limb is prepared with antiseptic solution and draped, ensuring exposure of the mid-thigh region.
Graft Preparation
A 2-cm longitudinal incision is made approximately 2 cm medial to the tibial tuberosity on the operative side. The semitendinosus tendon is harvested using a closed tendon stripper. The tendon is then cleaned, trimmed, and reinforced with high-strength nonabsorbable sutures at both ends. The midpoint is marked for reference.
Arthroscopic Portal Establishment and Examination
A standard anterolateral portal is created to perform a diagnostic arthroscopy, in which patellofemoral joint alignment, loose bodies, ligamentous injuries, and meniscal pathology are evaluated. If necessary, an anteromedial portal is established for further interventions such as loose body removal or cartilage repair.
A 1.5-cm longitudinal incision is made at the proximal third of the medial patella (Fig 1A, portal P1), followed by palpation of the medial femoral epicondyle. Through the deep fascia and extra-articular space, a dissection is carried out toward the medial femoral epicondyle, the distal medial portal is established (Fig 1B, portal P2), and the proximal medial portal is created under direct visualization (Fig 1A, portal P3).
Fig 1.
Arthroscopic portal placement for medial patellofemoral ligament reconstruction. (A) The medial patellar portal 1 (P1) is positioned at the medial mid-upper third of the patella (1.5 cm incision). Through P1, a clamp dissects to locate the distal medial portal (P2), and under direct visualization via P1, the proximal medial portal (P3) is established. (B) The distal medial portal (P2) is localized using a clamp via the medial patellar incision. (Note: A and B depict different patients.)
Femoral Tunnel Placement
The arthroscope is introduced through portal P1 to access the medial subcutaneous space. Using portal P3 as the working portal, subcutaneous fat is debrided. The arthroscopic view is then switched to portal P3, whereas portal P2 serves as the working portal to identify and dissect the adductor tendon. (Fig 2A) The femoral tunnel is positioned 12 mm distal and 6 mm posteriorly to the adductor tubercle,11 with the location marked using radiofrequency ablation (Fig 2B). A 2.0-mm Kirschner wire (K-wire) is inserted at the designated point and drilled obliquely anterior-superiorly through the femoral condyle (Fig 2C), ensuring it penetrates the far cortex without exiting the skin.
Fig 2.
Determination of the femoral tunnel position in medial patellofemoral ligament reconstruction. Left knee in 30° flexion and hip FABER orientation (supine). (A) Viewing through the proximal medial portal (P3), the adductor tendon is identified and dissected arthroscopically. (B) Viewing through the proximal medial portal (P3), a radiofrequency ablation is inserted via the distal medial portal (P2) to mark a point 12 mm distal and 6 mm posterior to the adductor tubercle (AT) as the femoral fixation site for ligament reconstruction. (C) A 2.0-mm Kirschner wire (red arrowhead) is inserted anterosuperiorly through the designated point. (D) Arthroscopic view confirmed proper Kirschner wire placement (red arrowhead) at the target position. (FABER, flexion-abduction-external rotation.)
Patellar-Side Anchor Fixation
At the proximal third of the medial patella, a 1-cm cortical decortication is performed. Two 3.0-mm suture anchors are placed at the medial mid-upper third of the patella, securing the central 1 cm portion of the graft. (Fig 3).
Fig 3.
Left knee in a supine position. Two suture anchors are used to fix the graft at the medial mid-upper third of the patella.
Graft Isometry Testing
A traction suture is first passed through portal P1 and looped around the positioning K-wire before being retrieved back through P1. The graft is subsequently advanced along the suture and passed around the K-wire under tension (Fig 4). The knee is then taken through a full range of motion while arthroscopically monitoring graft displacement. Graft movement of less than 2 mm confirms optimal isometry and validates the femoral tunnel site, whereas displacement exceeding 2 mm necessitates tunnel repositioning and retesting until satisfactory isometry is achieved (Video 1).
Fig 4.
Left knee in 30° flexion and hip FABER orientation (supine). Viewing through the proximal medial portal (P3), the double-bundle graft is passed around the Kirschner wire (red arrowheads). (FABER, flexion-abduction-external rotation.)
Femoral Tunnel Drilling
Once the optimal femoral tunnel site is confirmed, the K-wire is advanced through the skin. A 6-mm drill (based on graft diameter) is used to create the femoral tunnel over the K-wire, ensuring full femoral penetration (Fig 5A). A pulling suture is introduced to assist in graft passage.
Fig 5.
Graft fixation on the femoral side. Left knee is in 30° flexion and hip FABER orientation (supine). Viewing is through the proximal medial portal (P3). (A) A 6-mm diameter drill is used to prepare the femoral tunnel. (B) The double-bundle graft (red arrowheads) is pulled into the femoral tunnel under tension. (C) An interference screw is used to fix the double-bundle graft (red arrowheads). (D) Arthroscopic visualization through the standard anterolateral portal confirms extra-articular positioning of the double-bundle graft (red arrowheads). (FABER, flexion-abduction-external rotation.)
Graft Fixation
Under arthroscopic visualization, the graft sutures are pulled to advance the graft into the femoral tunnel. The graft is first tensioned maximally, followed by several full-range flexion-extension cycles to optimize tension. (Fig 5B) The patellofemoral joint alignment and patellar tracking are reassessed to confirm smooth trochlear engagement, ensuring no impingement, obstruction, or medial overcorrection.
With the knee flexed to 30°, a 6 × 25-mm bioabsorbable interference screw is inserted to secure the graft in the femoral tunnel (Fig 5C). A final assessment confirms that the graft remains extracapsular (Fig 5D).
Finally, the surgical site is irrigated, and the incisions are closed and dressed.
Discussion
MPFL reconstruction has become an essential treatment for preventing recurrent dislocations in patients with recurrent patellar dislocation.2,12,13 On the patellar side, there are single-bundle and double-bundle reconstructions. Anatomical studies have shown that the MPFL attachment on the patellar side is band-like, measuring approximately 22 to 34 mm in length.8 Therefore, its patellar attachment is a band-shaped structure, and single-bundle reconstruction has difficulty restoring the width of this attachment. The authors of biomechanical studies also have found that double-bundle reconstruction is superior to single-bundle reconstruction, with the former providing greater ultimate load and lower patellar side failure rates compared with the latter.9 Although Hu et al.2 reported an arthroscopic MPFL reconstruction technique claiming to be double-bundle, it only used a single tunnel on the patellar side. We believe this technique is essentially a single-bundle reconstruction. Therefore, we have chosen a double-anchor fixation technique on the patellar side to bring the graft closer to the original band-like structure and better simulate the natural anatomical structure of the MPFL, providing stronger mechanical support and stability.
Our study presents 2 significant improvements in arthroscopic MPFL reconstruction. First, compared with tactile anatomical landmarks2,8,14 and the Schöttle point,2,15,16 this technique refined the femoral tunnel positioning by using direct arthroscopic visualization of the adductor tubercle as the anatomical reference (12 mm distal and 6 mm posterior11), eliminating the need for fluoroscopy and its associated radiation risks.17 More importantly, we introduced a standardized intraoperative isometry testing protocol that represents a major advancement in surgical precision. During passive knee flexion-extension cycles, we quantitatively assess graft movement around the K-wire, accepting <2 mm displacement as optimal isometry. This objective measurement significantly improves upon previous subjective tension assessments, enabling immediate intraoperative adjustments. The combination of anatomical accuracy and dynamic isometry verification addresses the well-documented limitations of conventional techniques (52%-72% accuracy for landmark-based methods16) while ensuring proper graft function throughout the full range of motion. This dual approach significantly enhances the reliability and postoperative stability of MPFL reconstruction.
Despite its theoretical advantages, this technique’s long-term outcomes require validation through large-scale studies and follow-up (Table 1). In addition, the operational complexity and learning curve of the arthroscopic graft length testing are also issues that need attention. Surgeons must undergo systematic training and repeated practice to master this technique, ensuring high surgical success rates and optimal postoperative recovery for patients (Table 2). In conclusion, arthroscopic double-bundle MPFL reconstruction with intraoperative graft isometry testing offers a more precise and reliable treatment for recurrent patellar dislocation.
Table 1.
Advantages and Disadvantages
| Advantages | Disadvantages |
|---|---|
| Fluoroscopy-free anatomical precision: direct arthroscopic visualization of the adductor tubercle. | Steep learning curve: requires more cases to master portal placement and isometry testing. |
| Dynamic isometry validation: real-time detection of graft isometry. | Extended operative time: much more time for isometry testing vs conventional techniques. |
| Minimally invasive approach: combines arthroscopic femoral tunnel placement with limited open patellar fixation. | Uncertain long-term efficacy: long-term outcomes require validation through large-scale studies. |
Table 2.
Pearls and Pitfalls
| Pearls | Pitfalls |
|---|---|
| Accurate graft isometry: Ensure real-time isometry testing during surgery to prevent overtensioning or undertensioning. | Inaccurate tunnel placement: Failure to accurately position the femoral and patellar tunnels can compromise stability. |
| Double-bundle reconstruction: This better simulates the natural MPFL anatomy and provides improved mechanical support. | Inadequate visualization: Poor visualization of key anatomical structures can lead to misalignment or ineffective reconstruction. |
| Fluoroscopy-free and anatomical femoral tunnel localization: Properly assess anatomical landmarks like the adductor tubercle for accurate tunnel placement, while eliminating radiation exposure. | Technical complexity for beginners: Surgeons without sufficient experience may struggle with this complex procedure, increasing the risk of complications. |
MPFL, medial patellofemoral ligament.
Disclosures
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 82102610, 52273119); Chongqing Natural Science Foundation Key Project (No. CSTB2023NSCQ-LZX0018); Research project of Fujian Medical University Union Hospital (No. 2024XH032, 2024XH034); Chongqing medical scientific research project-Joint project of Chongqing Health Commission and Science and Technology Bureau (No. 2024GDRC006); Youth Talent Support Program of the First Affiliated Hospital of Chongqing Medical University (No. BJRC2021-02); and The Science and Technology Research Project of Chongqing Education Commission (No. KJQN202200404).
Footnotes
Shixin Nie, M.D., Ph.D., and Chengjie Lian, M.D., Ph.D., contributed equally to this work and are co-first authors.
Supplementary Data
This video presents our arthroscopically assisted double-bundle MPFL reconstruction technique, highlighting the critical role of dynamic intraoperative isometry testing. After the induction of general anesthesia, the patient is positioned supine with the operative left limb in 30° knee flexion and hip FABER orientation to optimize surgical access. The procedure begins with harvest of the semitendinosus tendon through a 2-cm medial tibial incision, which is then prepared by reinforcing both ends with high-strength sutures and marking the midpoint for later double-bundle fixation. After establishing standard anterolateral and medial viewing portals for diagnostic arthroscopy, the medial patellar portal (P1) is created at the patella's mid-upper third. Through careful extra-articular dissection, the distal (P2) and proximal (P3) medial portals are established under direct visualization. Viewing through P3, the critical femoral tunnel preparation commences with identification of the adductor tendon and the adductor tubercle through P2, followed by precise placement of a 2.0-mm K-wire 12 mm distal and 6 mm posterior to the adductor tubercle through P2, eliminating fluoroscopy need. Attention then turns to patellar fixation, where two 3.0-mm suture anchors recreate the native MPFL's broad insertion at the medial patellar mid-upper third. After that, the dynamic isometry testing is performed by passing a traction suture through P1 around the K-wire, while the surgical team collaborates to assess graft kinematics during passive knee motion. Finally, after enlarging the tunnel to 6.0 mm, the graft is secured with a bioabsorbable interference screw at 30° flexion following arthroscopic confirmation of extra-articular positioning. Postoperative computed tomography is used to verify optimal tunnel placement, completing this anatomy-focused reconstruction that combines fluoroscopy-free precision with real-time biomechanical validation through dynamic isometry testing. (FABER, flexion-abduction-external rotation.)
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
This video presents our arthroscopically assisted double-bundle MPFL reconstruction technique, highlighting the critical role of dynamic intraoperative isometry testing. After the induction of general anesthesia, the patient is positioned supine with the operative left limb in 30° knee flexion and hip FABER orientation to optimize surgical access. The procedure begins with harvest of the semitendinosus tendon through a 2-cm medial tibial incision, which is then prepared by reinforcing both ends with high-strength sutures and marking the midpoint for later double-bundle fixation. After establishing standard anterolateral and medial viewing portals for diagnostic arthroscopy, the medial patellar portal (P1) is created at the patella's mid-upper third. Through careful extra-articular dissection, the distal (P2) and proximal (P3) medial portals are established under direct visualization. Viewing through P3, the critical femoral tunnel preparation commences with identification of the adductor tendon and the adductor tubercle through P2, followed by precise placement of a 2.0-mm K-wire 12 mm distal and 6 mm posterior to the adductor tubercle through P2, eliminating fluoroscopy need. Attention then turns to patellar fixation, where two 3.0-mm suture anchors recreate the native MPFL's broad insertion at the medial patellar mid-upper third. After that, the dynamic isometry testing is performed by passing a traction suture through P1 around the K-wire, while the surgical team collaborates to assess graft kinematics during passive knee motion. Finally, after enlarging the tunnel to 6.0 mm, the graft is secured with a bioabsorbable interference screw at 30° flexion following arthroscopic confirmation of extra-articular positioning. Postoperative computed tomography is used to verify optimal tunnel placement, completing this anatomy-focused reconstruction that combines fluoroscopy-free precision with real-time biomechanical validation through dynamic isometry testing. (FABER, flexion-abduction-external rotation.)