Failure Analysis in Patients With Patellar Redislocation After Primary Isolated Medial Patellofemoral Ligament Reconstruction

Abstract

Background: Reconstruction of the medial patellofemoral ligament (MPFL) has become a popular surgical procedure to address patellofemoral instability. As a consequence of the growing number of MPFL reconstructions performed, a higher rate of failures and revision procedures has been seen. Purpose: To perform a failure analysis in patients with patellar redislocation after primary isolated MPFL reconstruction. Study Design: Case series; Level of evidence, 4. Methods: Patients undergoing revision surgery for reinstability after primary isolated MPFL reconstruction were included. Clinical notes were reviewed to collect demographic data, information on the primary surgery, and the mechanism of patellar redislocation (traumatic vs nontraumatic). Preoperative imaging was analyzed regarding femoral tunnel position and the prevalence of anatomic risk factors (ARFs) associated with patellofemoral instability: trochlear dysplasia (types B through D), patella alta (Caton-Deschamps index >1.2, patellotrochlear index <0.28), lateralization of the tibial tuberosity (tibial tuberosity–trochlear groove distance >20 mm, tibial tuberosity–posterior cruciate ligament [TT-PCL] distance >24 mm), valgus malalignment (mechanical valgus axis >5°), and torsional deformity (internal femoral torsion >25°, external tibial torsion >35°). The prevalence of ARF was compared between patients with traumatic and nontraumatic redislocations and between patients with anatomic and nonanatomic femoral tunnel position. Results: A total of 26 patients (69% female) with a mean age of 25 ± 7 years were included. The cause of redislocation was traumatic in 31% and nontraumatic in 69%. Position of the femoral tunnel was considered nonanatomic in 50% of patients. Trochlear dysplasia was the most common ARF with a prevalence of 50%, followed by elevated TT-PCL distance (36%) and valgus malalignment (35%). The median number of ARFs per patient was 3 (range, 0-6), and 65% of patients had 2 or more ARFs. Patients with nontraumatic redislocations showed significantly more ARFs per patient, and the presence of 2 or more ARFs was significantly more common in this group. No significant difference was observed between patients with anatomic versus nonanatomic femoral tunnel position. Conclusion: Multiple anatomic risk factors and femoral tunnel malposition are commonly observed in patients with reinstability after primary MPFL reconstruction. Before revision surgery, a focused clinical examination and adequate imaging including radiographs, magnetic resonance imaging (MRI), standing full-leg radiographs, and torsional measurement with computed tomography or MRI are recommended to assess all relevant anatomic parameters to understand an individual patient’s risk profile. During revision surgery, care must be taken to ensure anatomic placement of the femoral tunnel through use of anatomic and/or radiographic landmarks.

Ability of Medial Patellofemoral Ligament Reconstruction to Overcome Lateral Patellar Motion in the Presence of Trochlear Flattening: A Cadaveric Biomechanical Study

“…24 Trochlear dysplasia is present in up to 96% of patients with patellar instability and is a well-described risk factor for recurrent lateral patellar dislocation. 3,9,10,15,18,25,38,40 In the setting of trochlear dysplasia, it has been proposed that the addition of trochleoplasty is an available surgical option to correct the abnormal trochlear shape and restore patellar alignment within the trochlear groove. 1,4,12,35,39 Trochleoplasty, however, is a technically demanding procedure, and there is concern that it is associated with an increased risk of arthritis and persistent pain.…”

Patellar instability MRI measurements are associated with knee joint degeneration after reconstruction of the medial patellofemoral ligament

“…Isolated MPFL reconstruction was performed by specialized orthopedic sports surgeons as previously described [19][20][21]. In brief, an anatomical double-bundle technique with an autologous gracilis tendon was applied.…”

Complex patellofemoral reconstruction leads to improved physical and sexual activity in female patients suffering from chronic patellofemoral instability

“…Given the complex interaction between dynamic muscle action, passive soft tissue restrains, surface geometry of the patellofemoral joint, and limb alignment, PFI is based on a multifactorial pathogenesis [ 10 , 27 , 46 ]. Anatomic risk factors, including trochlear dysplasia, valgus malalignment, torsional deformity, patella alta, and a lateralized position of the tibial tuberosity as well as insufficiency of the medial patellofemoral ligament (MPFL) must be taken into consideration for surgical treatment [ 3 , 10 , 27 , 28 , 47 ]. Whereas isolated MPFL reconstruction (MPFL-R) may be appropriate in most patients, complex reconstruction procedures are indicated in patients with additional risk factors [ 10 ].…”

“…Anatomic risk factors, including trochlear dysplasia, valgus malalignment, torsional deformity, patella alta, and a lateralized position of the tibial tuberosity as well as insufficiency of the medial patellofemoral ligament (MPFL) must be taken into consideration for surgical treatment [ 3 , 10 , 27 , 28 , 47 ]. Whereas isolated MPFL reconstruction (MPFL-R) may be appropriate in most patients, complex reconstruction procedures are indicated in patients with additional risk factors [ 10 ]. Combined MPFL-R and bony corrections such as realignment osteotomies and trochleoplasty are invasive and technically demanding, but have proven to be effective for the treatment of chronic PFI [ 13 , 24 , 26 , 38 ].…”

“…Over the last years, research on PFI has mainly focused on functional outcomes [ 1 , 4 , 13 , 14 , 24 , 26 , 35 , 44 ], re-dislocation rates [ 10 , 12 , 15 , 18 , 43 ], and return to sports [ 30 , 36 , 45 ]. Recently, research concerning Quality of Life (QoL) after MPFL-R has gained more attention [ 4 , 5 , 17 , 19 , 21 , 22 ].…”