Arthroscopic reconstruction of the medial patellofemoral ligament in skeletally immature patients using the modified sling procedure: a novel technique for MPFL reconstruction

Abstract

Background: Patellar dislocation is common in young people. Although isolated anatomic double-bundle reconstruction of the MPFL is a common and effective surgical treatment for patellofemoral instability, concerns about the risk of injury to the epiphysis remain.

Methods: A total of 21 children and adolescents (9 males, 12 females; mean age: 10.7 years; range: 8 to 13 years) with recurrent patella dislocation or symptomatic instability following a primary dislocation were enrolled in the study. In all patients, double-bundle medial patellofemoral ligament (MPFL) reconstruction and femoral sling procedure were performed under arthroscopy, using an anterior half peroneus longus tendon (AHPLT) autograft. Functional outcomes were evaluated preoperatively and during follow-ups based on Kujala and Lysholm scores. Radiological examinations including radiographs, 3D-CT, and MRI were performed pre- and post-operatively.

Results: Among two-year postoperative follow-up (range: 24-42 months) showed significant improvement in functional scores (p < 0.01). The Lysholm score increased from 68 (44.5) to 100 (0) and the Kujala score increased from 26 (34.5) to 100 (2) The patellar tilt angel improved significantly (p < 0.01) from 24.3° ± 10.4 preoperatively to 11.9° ± 7.0 postoperatively. MRIs performed 6- and 12-months post operation did not show any signs of dysfunction of the reconstructed MPFL or cartilage degeneration.

Study design: Case Series; Level of evidence, 4.

Conclusion: Arthroscopic reconstruction of the MPFL using the modified sling procedure is an effective procedure for the treatment of patellar instability in skeletally immature patients.

Keywords: Adductor magnus; Arthroscopy; Medial patellofemoral ligament; Patellofemoral instability; Peroneus longus tendon; Reconstruction.

Scheme 1.

Postoperative schematic diagram of knee joint. White arrow: anterior half peroneus longus tendon autografts; black arrow: adductor magnus tendon

Fig. 1

Preoperative and postoperative computerized tomography (CT) scans of the patellar tilt angle (the angle between the femoral posterior condylar line and the line defining the maximal patellar width)

Fig. 2

a Five approaches distributed around the knee; b the incision made for harvesting of the anterior half peroneus longus tendon (AHPLT); c the peroneus longus tendon; d the braided AHPLT

Fig. 3

Arthroscopic the medial patellofemoral ligament (MPFL) reconstruction procedure. a Tear of the MPFL and the capsule was viewed at the patellar attachment (11 o’clock position); b A superomedial capsular window above the synovia plication in the medial gutter was created from inside; c The adductor magnus tendon proximal to the MPFL was exposed through the capsular window; d The proximal insertion of the adductor magnus was separated by a right-angle clamp and a shuttle suture was threaded; e The implanted autograft was introduced under the suture guidance and fixed with a sling around the adductor magnus tendon; f The double-bundle autograft was located at the outer layer of the capsule and fastened to the medial facet of the patella. White arrow: adductor magnus; black arrow: capsure; * autograft; # MPFL

Fig. 4

After surgery, patients were followed up every 6 months. The inflammatory response was present postoperatively at 6 months (a, b), but was disappeared postoperatively at 12 months (c, d). The reconstructed ligament healed well and no signs of dysfunction were observed in both time points. Relaxation, creep deformation or discontinuity of the reconstructed MPFL was considered to be dysfunction. White arrow: reconstructed MPFL; *: inflammatory response