Patellofemoral Update focuses on the causes, prevention and treatment of patellofemoral disorders. The blog is sponsored by The Patellofemoral Foundation whose mission is to improve the care of individuals with anterior knee pain through targeted education and research. The Patellofemoral Foundation offers additional online education resources on its website.

Take a common sense approach to surgery on the lateral retinaculum of the patella

It is well-established that isolated lateral releases do not lead to successful long-term outcomes when performed for patella instability or anterior knee pain. Recently in a landmark paper, Al Merchant, MD pointed out that overzealous lateral releases lead to severe iatrogenic medial patella instability with catastrophic consequences for the patellofemoral joint and patient.

One of the conceptual problems with “lateral release” has occupied my mind for a while. I would like to elaborate on the lateral retinaculum with the goal of better portraying its actual anatomical purpose. I will also provide an easy surgical option to address lateral retinacular tightness without having to sacrifice the stability the lateral retinaculum provides to the patellofemoral (PF) joint.

Anatomy

Christian Lattermann


The lateral retinaculum can be divided into the superficial oblique and the deep transverse retinaculum. While the superficial oblique layer consists of fibers that are longitudinally oriented and proceed into the anterior part of the patellar tendon, the deep transverse layer originates from the deep fascia lata and inserts directly into the patella.

This layer is only about 2 cm to 3 cm wide and does not extend distally into the patella tendon. Both layers are dynamized through the vastus lateralis and tensor fascia latae.

Biomechanical concept

Figure 1. The MPFL and LR build a rein for the patella. If the LR is cut, this rein is lost and allows the patella to tilt upwards but at the same time loses the control during initial flexion.

Credit: Latterman C


The lateral retinaculum provides a mechanical restraint to medial translation of the patella during the initiation of knee flexion. However, it also provides stability against sagittal rotation of the patella during the initial knee flexion.

The interplay of the medial PF ligament and the lateral retinaculum allows for the patella to be guided into the trochlear groove during initial knee flexion. Much like a jockey leads a horse, both reins are needed for this to happen in a controlled fashion. If one of the two reins is missing, then guidance is lost (Figure 1).

Clinically, we assess this sagittal rotation by assessing patellar tilt. If the entire lateral retinaculum is divided (as done in an arthroscopic lateral release), then the patella shows significant lateral tilt, sometimes as much as 90°. In a normally configured PF joint with a good PF engagement index (Dejour), no patella alta (Caton or IS ratio) and a normal trochlear morphology, this potentially can be tolerated. In those cases, patients who may get better are the ones who have isolated tight lateral retinaculum. This is also a group of patients for whom isolated lateral release is considered therapeutic. The problem is the patients are often difficult to identify. Even with a diligent radiographic and MRI examination to assess the PF bony morphology, it is nearly impossible to identify these patients correctly.

Figure 2. Pictured are the two layers of the retinaculum (superficial and deep) (a). The deep layer is cut as posterior as possible (b). The deep layer can be sutured to the superficial layer and allow for a functional lengthening (c). This can be done through a 2-cm to 3-cm incision.

Credit: Lattermann C

Unfortunately, the more likely scenario is that the bony PF anatomy is less well defined, a borderline patella alta is present and the patient has a Dejour type A or B trochlea. In that case, the same lateral release may lead to a destabilization of the lateral restraint with a sagittal patella rotation (“tilt”) that forces the medial patella facet to become the primary weightbearing facet during initial flexion. Not only is the medial facet often very short, but its articular cartilage is also not used to the encountered load and can cause wear and subsequent pain and swelling. In the worst cases, the patients end up with a paradoxical medial instability as published by Sanchis-Alfonso and colleagues.

One way to avoid this difficult issue is to abstain from performing a lateral retinacular release and instead do a lateral retinacular lengthening as described by Biedert in his book, Patellofemoral Disorders.

Technique

A small (2-cm to 3-cm) incision is made directly along the lateral edge of the patella (Figure 2). The subcutaneous fat is carefully moved to the side such that the retinaculum is fully exposed. Sometimes an extension of the PF bursa has to be removed. Then a 15-blade is used to score the lateral retinaculum lengthwise over 2 cm to 3 cm proximally from about the superior patella pole to just short of the inferior pole or the common lateral arthroscopic portal.

Once the retinaculum is scored it can be grabbed with an Edson forceps and using the tenotomy scissors the two layers can be carefully divided. In parts, this division can be achieved bluntly, in other parts the two layers have to be carefully separated in a “nick and spread” technique. Once this preparation is done the two layers can be easily separated and the deep layer can be cut as far posteriorly as possible.

The cut through the deep layer is extended all the way distal into the arthroscopic portal to allow for mobility between the layers. Then the knee is positioned in full extension and the patella is carefully tilted to neutral or just past neutral. More often than not, the deep layer will now glide past the superficial layer by anywhere between 5 mm to 15 mm and naturally position the two layers at the correct length. The lengthened retinaculum can then be secured at this length using a 2-0 vicryl suture in a running stitch technique.

Even though no studies have been published to my knowledge comparing lateral retinacular lengthening against release, I strongly believe lengthening is safer, conceptually sound and may avoid the iatrogenic patella instabilities. In light of the fact, this is just as easily doable as a traditional lateral release. I believe there are no downsides and many upsides to doing a lengthening rather than a release. During the past few decades, we have learned very rarely is there a structure that can just be cut away with impunity and the lateral retinaculum is not one of them.

References:

Biedert RM, et al. Patellofemoral Disorders: Diagnosis and Treatment. 2004.

Lattermann C, et al. Sports Med Arthroscopy. 2007;doi:10.1097/JSA.0b013e318042af30.

Lattermann C, et al. Lateral retinacular release for anterior knee pain: A systematic review of the literature. J Knee Surg. 2006;19:278-284.

Sanchis-Alfonso V, et al. Arthroscopy. 2015;doi 10.1016/j.arthro.2015.01.028.

Christian Latterman, MD, is an associate professor, vice chairman for orthopedic research, director of the Center for Cartilage Repair and Restoration for the Department of Orthopedic Surgery at the University of Kentucky. He can be reached at the University of Kentucky, 740 South Limestone, Lexington KY 40536; email: Christian.Lattermann@uky.edu.

Disclosure: Lattermann reports he is a paid consultant for Cartiheal, Ceterix, Varicel and receives research support from Smith & Nephew.

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