Persistent morbidity after Medial Patellofemoral Ligament Reconstruction — A registry study with an eight-year follow-up on a nationwide cohort from 1996 to 2014
Introduction
Primary patellar dislocation constitutes approx. three percent of all knee injuries. The incidence has been found to be 42 per 100,000 person years at risk (PYRS) in general and 108 per 100,000 PYRS among young female patients [1]. Generally, patients suffering first-time acute patellar dislocation are treated conservatively, except patients with associated significant osteochondral injury and patients, who do not improve with normal rehabilitation [2], [3]. Recurrent patellar dislocation is associated with patellofemoral osteoarthritis and reduced physical activity and quality of life [4], [5], [6]. Predisposing factors for recurrent instability and dislocation such as trochlear dysplasia, patella alta, femoral antetorsion and an increased tibial tubercle-trochlear groove distance have been identified, and today, it is commonly accepted that each patient should be treated individually in order to address the present predisposing factors [7], [8], [9], [10], [11], [12].
Over the past decades, the surgical treatment options for patella stabilization have increased, and there has been a rise in surgery rates in the United States [13]. During this period, the Medial Patellofemoral Ligament Reconstruction (MPFL-R) has gained popularity. The MPFL is the most important soft-tissue structure, which provides a medial restraining force that protects against lateral patellar dislocation [14], and studies have shown that ligament was torn in up to 100% of the primary patellar dislocations [15]. MPFL-R has shown promising results; yet there is a risk of bias as studies were conducted among homogeneous patient groups and lacked consistency in reporting complications. This makes it difficult to compare the results [16], [17], [18]. Other studies have shown less promising results, pointing out that many patients suffer from persistent morbidity after surgery, especially patients with trochlear dysplasia [19], [20], [21].
This nationwide retrospective registry study aims to investigate the trends in surgery performed on patients with patellar dislocations from 1996 to 2014 and the risk of persistent patellar morbidity (PPM) with an eight-year follow-up after surgery. Hopefully, this will assist the clinician in choosing the right treatment for the right patient.
Section snippets
Methods
The study was conducted as a retrospective registry study with national population data from the Danish National Patient Registry (DNPR) and Statistics Denmark. Since 1976, all patients who seek medical care in a hospital (emergency room/walk-in consultation/hospitalized) in Denmark have been registered with their unique social security number in the national patient registry. Danish legislation imposes hospitals in Denmark to report data to DNPR. Patients are registered from the day they seek
Surgical treatment
From 1996 until 2013, the number of patella-stabilizing surgical procedures was stable, but the types of procedures performed changed with a rise in MPFL-R from 2005 (Figure 1). From 2005 until 2014, 1770 patients received 1956 MPFL-R. In 2014, MPFL-R constituted 75% of all patella-stabilizing surgical procedures and was performed on almost 10% of patients with patellar dislocation. After the introduction of the MPFL-R in 2005, the four-year risk of persistent patellar morbidity remained stable
Discussion
The most important finding in the present study was a 21% risk of PPM within the first eight years after MPFL-R, following an investigating of 1956 procedures. This finding can be interpreted in two ways: On the one hand, it must be perceived as being positive that 79% of patients had no contact with the healthcare system regarding their knees with a diagnosis of recurrent patellar instability or acute patellar dislocation. This is in support of the literature, which presents MPFL-R as an
Conclusion
The 2005 to 2014 period saw a rapid rise in the use of MPFL-R, constituting 75% of all patella-stabilizing surgery in 2014. The overall risk of PPM within eight years after MPFL-R was 21%. MPFL-R was found to have a significantly lower risk of PPM over time as compared with other patella-stabilizing surgery and conservative treatment.
Declaration of interest
None.
References (25)
- et al.
What activities do patients with patellar instability perceive makes their patella unstable?
Knee
(2011) - et al.
Patellar tendon length—the factor in patellar instability?
Knee
(2002) - et al.
Trochleoplasty: historical overview and Dejour technique
Oper Tech Sports Med
(2015) - et al.
High incidence of acute and recurrent patellar dislocations: a retrospective nationwide epidemiological study involving 24.154 primary dislocations
Knee Surg Sports Traumatol Arthrosc
(2017) - et al.
First-time traumatic patellar dislocation: a systematic review
Clin Orthop Relat Res
(2007) - et al.
Surgical versus non-surgical interventions for treating patellar dislocation
Cochrane Database Syst Rev
(2015) - et al.
Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury
Am J Sports Med
(2000) - et al.
Incidence and risk factors of acute traumatic primary patellar dislocation
Med Sci Sports Exerc
(2008) - et al.
Factors of patellar instability: an anatomic radiographic study
Knee Surg Sports Traumatol Arthrosc
(1994) - et al.
Prevalence and patterns of anatomical risk factors in patients after patellar dislocation: a case control study using MRI
Eur Radiol
(2013)