Minimally invasive medial patellofemoral ligament reconstruction for patellar instability using an artificial ligament: A two year follow-up

Highlights

• Large case series showcasing MPFL reconstruction using artificial ligament.

• High proportion of patients with ligamentous laxity

• Only one re-dislocation secondary to severe fall

• Rehabilitation is quick with no knee brace

• Minimally invasive technique

Abstract

Background

Recurrence of acute patellar dislocation affects approximately 30% of individuals, and up to 75% of those with grade IV instability. The medial patellofemoral ligament (MPFL) is considered to be critical for patellar stabilization. MPFL reconstruction with allografts has been proposed to reduce risk of recurrence, but there is limited evidence about the safety and effectiveness of techniques using synthetic allografts.

Methods

We present a retrospective case series of 29 individuals who underwent a MPFL reconstruction between 2009 and 2012, using an artificial ligament for patellar instability by a single surgeon. Clinical, radiological and functional outcomes were measured at a minimum of 24 months.

Results

31 knees (29 individuals) were followed up for a median of 43 (range: 24–68) months. Using the Crosby and Insall grading system, 21 (68%) were graded as excellent, nine (29%) were good, one (3%) as fair and none as worse at 24 months. The mean improvement in Lysholm knee score for knee instability was 68 points (standard deviation 10). Ligamentous laxity was seen in 17 (55%) of individuals. In this subset, 12 were graded as excellent, four as good and one as fair. The mean improvement in patellar height was 11% at three months follow-up. All knees had a stable graft fixation with one re-dislocation following trauma.

Conclusions

We propose a minimally invasive technique to reconstruct the MPFL using an artificial ligament allowing early mobilization without bracing. This study indicates the procedure is safe, with a low risk of re-dislocation in all grades of instability.

Level of Evidence

Level IV Case Series

Introduction

Acute patellar dislocation frequently leads to recurrence. A systematic review of trials of reconstruction techniques versus conservative rehabilitation reported the rate of re-dislocation after a conservatively managed primary patellar dislocation ranged from 19–54% (5 trials, 339 patients) [1]. This risk is higher in patients with ligamentous laxity, with one retrospective single centre series of 104 individuals treated for patellar dislocation reporting an overall recurrence after an acute dislocation of 30%, and 75% in the subgroup (n = 66) who had ligamentous laxity and abnormal patella position [2].

Various surgical methods have been described in the literature to treat lateral patellar dislocation [3], [4], [5], [6], [7], [8]. Surgical procedures used in Europe have been founded on strict radiographic guidelines, that is, “Le Menu A La Carte”, where all the instability factors are individually corrected [9]. However, the importance of correcting each of these instability factors, alone or in combination is uncertain [9]. There is also uncertainty about the safety and effectiveness of current standard procedures. The above mentioned systematic review comparing surgical repair with conservative rehabilitation in a total of 339 patients with dislocation found no robust evidence of improved clinical (pain, range of motion) or functional (Kujala scores) outcomes in individuals managed with surgical repair [1]. Apart from recurrent dislocation, common post-operative complications reported in the literature are persistent patellofemoral instability, patellofemoral osteoarthritis, loss of flexion, medial subluxation, stiffness and chronic knee pain [1], [3], [7], [8], [10].

The importance of the medial patellofemoral ligament (MPFL) was first described in the late 1950s [11]. A cadaveric study on 25 specimens determined that, biomechanically the MPFL provides 53% of the lateral stabilizing force [12]. It is consequently the most important medial soft-tissue restraint and has been shown to be consistently injured after a patellar dislocation [4]. Brückner was the first to present a technique of transferring the medial part of the patellar ligament to the medial epicondyle to stabilize the patella [13]. But only recently with the evolution of shoulder surgery there has been an increased focus on reconstruction of the MPFL. Several techniques have been described to reduce the high incidence of recurrent dislocation with encouraging clinical results [8].

Numerous sources have been used to reconstruct the MPFL including semitendinosus, semimembranosus, gracilis, quadriceps, vastus medialis retinaculum, or artificial tendons [3], [8], [14], [15], [16]. In 1992, Ellera was the first to describe MPFL reconstruction with an artificial polyester ligament in 30 patients fixed by tunnel fixation on the patella and sub-fascially to the medial femoral condyle [17]. At a minimum of 24 month follow-up, 25 (83%) patients showed improvement with a Crosby and Insall grade of good-excellent [17]. The use of synthetic material is appealing to avoid the morbidity associated with other allograft choices [16]. However, there have been very few other articles describing techniques using synthetic allografts. Nomura et al. in 2000 have recently reported a five year follow-up study of 27 patients treated with MPFL reconstruction with an artificial polyester ligament with staple fixation at the femoral condyle, with 26 (96%) reporting good to excellent outcomes using the Crosby and Insall grading system [5]. But other cohort studies reporting on the use of the artificial ligament question its safety in view of late graft failure, risk of late infection, stiffness, inflammation and cost effectiveness subsequent to use of synthetic allografts [15], [16].

The purpose of our study is:

• To describe a minimally invasive arthroscopically assisted technique to reconstruct the MPFL using a synthetic allograft.

• To describe our post-operative rehabilitation protocol.

• To present data on safety and benefits of the surgical procedure in patellar instability especially in patients with predisposing factors.