March 15, 2022
3 minute read
Biography: John P. Fulkerson, MD, is a professor of orthopedic surgery at Yale University and president of the Patellofemoral Foundation.
Disclosures: Fulkerson does not report any relevant financial information.
Since the description of the anteromedialization tibial tuberosity osteotomy for realignment and unloading of the patella in 1983, the indications have changed.
Publications have consistently demonstrated the efficacy of the procedure, including Stephen A. Klinge’s 2019 study showing good long-lasting results and avoidance of arthroplasty at a minimum follow-up of 15 years after tubercle osteotomy anteromedial tibialis (AMTTO). To a certain extent, this seems logical – optimize the tracking of the ball joint and lift it a little to unload it. We showed this in biomechanical studies in 1990.
But now, with 3D prints of dysplastic knees, we can see that there is another reason why anteromedialization is important. Dysplastic trochleas curve laterally to meet a side-tracking patella – essentially opening the trochlear portal laterally (see Figure 1) where the patella sits and waits in extension. Then the patella can engage the trochlea and the result is a curvilinear path for the patella as the trochlea holds the patella and brings it medially, deeper into the trochlea in flexion, and a little laterally even further in flexion.
This puts a different twist on our understanding and sometimes behooves us to help the patella enter medially into the dysplastic curved trochlea so that it can remain permanently stable and arrest recurrent patella dislocations and optimize focal loads, with l additional help from medial patellofemoral reconstruction. Anteriorization tilts it and unloads the vulnerable distal pole.
We now understand, in 3D studies at Yale University with Kristin E. Yu, Daniel R. Cooperman, MD, William McLaughlin, MD, Brian G. Beitler, and Christopher Schneble, MD, that the patella and trochlea appear to be congruent in patellofemoral dysplasia. joints, the patella often overlapping the lateral condyle with a shortened, but nevertheless congruent, medial facet. Antero-medial displacement of the patella (less than 50% of my patients have recurrent patellar instability) in patients with a lateral tracking vector should allow the patella to more securely engage the dysplastic trochlea, lift the distal pole to further facilitate engagement and also to offload the distal articular surface of the patella to minimize and hopefully prevent progressive joint rupture.
As we understand this more fully using 3D imaging, we realize that trochleoplasty can be best used to remove the proximal aspect of the medial ridge (as described in Osteological Details by Yu), when a tubercle tibialis is moved distally and/or medially. My main indication for trochleoplasty is currently associated with distalizing and medializing tibial tubercle transfer, with the aim of flattening the proximal medial ridge (to allow smooth entry of the patella into the trochlea).
These guidelines are similar to those of David R. Diduch, MD, but the only deepening is medial ridge recession, while trochlear joint congruence is maintained because no deepening is performed laterally. This can usually be done arthroscopically.
Our observations were also that the most lateralized patella on a flat proximal trochlea (Dejour B) quickly follows the proximal trochlea, congruently, to engage the deeper trochlea more medially. Transferring the medial or anteromedial tibial tubercle allows the patella to be brought to the deeper trochlea sooner and therefore reduces or eliminates the risk of lateral dislocation in these patients without requiring trochleoplasty.
Trochleoplasty is usually not required at the time of AMTTO in patellar instability surgery. Adding anteriorization and a small distalization to the TTO facilitates bridging of the less prominent or flat proximal ridge – a more common situation. This explains why Fotios Paul Tjoumakaris, MD, and James P. Bradley, MD, achieved such good results in their study of anteromedial TTO, with slight distalization, in athletes.
This 3D information helps us understand why Joseph N. Liu, MD, and Beth E. Shubin Stein, MD, have had consistently good results with MPFL reconstruction alone for the treatment of trochlear dysplasia in patients with with patellar instability who had no lateral tracking or need for TTO. Our current observations, using 3D prints, suggest proximal medial spur recession trochleoplasty combined with AMTTO in cases where the proximal medial ridge spur is prominent and not necessary for deepening. in the presence of a flat proximal trochlea when the patella can be maintained in a stable congruent relationship with the flattened trochlea by MPFC reconstruction (MPFL or MQTFL) and transfer of tibial tuberosity if necessary to optimize alignment.
Fulkerson JP, et al. Am J Sports Med. 1990 ; doi: 10.1177/036354659001800508.
Klinge SA, et al. Arthroscopy. 2019; doi:10.1016/j.arthro.2019.02.030.
LiuJN, et al. Am J Sports Med. 2018; doi: 10.1177/0363546517745625.
Tjoumakaris FP, et al. Am J Sports Med. 2010;doi:10.1177/0363546509357682.