BLOG: The latest topics in patellofemoral pain and instability
At the American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America Combined Meeting, Elizabeth A. Arendt, MD, and Seth L. Sherman, MD, led a session about topics on patellofemoral pain and instability.
Lutul D. Farrow, MD, director of sports medicine clinical operations at the Cleveland Clinic, gave a 6-minute whirlwind tour through the examination of the patellofemoral joint. Farrow emphasized that while these may occur in isolation, there often exists overlap between patellofemoral pain and instability. As such, the clinician evaluating the patient for patellofemoral instability should also evaluate for patellofemoral pain and vice versa. Farrow stressed the importance of evaluating patellofemoral pathology in multiple positions, including the standing, sitting, supine and prone positions. Furthermore, dynamic testing, such as squatting from the standing position and seated knee extension, are effective measures to bring out subtle findings that can be overlooked with static testing. A comprehensive physical exam should be utilized to support a thorough history to arrive at an accurate diagnosis and subsequent treatment plan.
Surgical technique spotlight: MPFL reconstruction made simple
Adam B. Yanke, MD, PhD, director of clinical research at Rush University Medical Center, provided pearls on performing a medial patellofemoral ligament reconstruction to treat symptomatic lateral patellar instability. While there are many valid techniques to perform MPFL reconstruction surgery, several key steps can help avoid complications with the procedure and improve the likelihood of success. The anatomometric aspects, as well as native biomechanics, suggest that the strongest components of the medial patellofemoral complex are the anatomic insertions of the MPFL on the patella and femur. Along with this, the length changes of the ligament increase in magnitude the more proximal the insertion is chosen along the extensor mechanism. Yanke stressed that it is crucial to perform anatomic reconstruction of the ligament with favorable anisometry while the knee flexes to avoid over constraint medially.
Jacqueline M. Brady, MD, presented on behalf of Beth E. Shubin Stein, MD, and focused on the role of isolated MPFL reconstruction for patellar instability. In some patients, MPFL reconstruction is a clear choice for treatment in the setting of relatively normal anatomy, but in others, it obviously is not sufficient, and will be put at risk by forces that leave a graft under excessive tension in the setting of malalignment. Unfortunately, there is also a large group of patients in whom we do not know whether MPFL is sufficient: perhaps they have indicators of malalignment such as a small J-sign on exam, patella alta and/or trochlear dysplasia.
Our commonly cited “cutoffs” for adding a tibial tubercle osteotomy to MPFL reconstruction are not based on robust clinical or laboratory evidence. A prospective cohort of patients treated with MPFL reconstruction alone, regardless of anatomical factors (excluding failed previous surgery, the “jumping” J sign, and unloadable chondral injuries causing significant pain), is ongoing and will hopefully help us understand which patients would benefit from bony realignment. An initial publication from this study indicated that recurrence rates were low following MPFL reconstruction, but the study remains underpowered, and we need the full cohort with longer-term follow-up to determine who might benefit from bony realignment in addition to soft tissue reconstruction. We suspect, based on our preliminary data, that the anatomical risk factors will prove inter-related, rather than determining an isolated cutoff for each.
Surgical technique spotlight: Trochleoplasty
David R. Diduch, MD, presented a surgical technique spotlight on deepening trochleoplasty, and highlighted the “thick shell” osteotomy technique popularized by David Dejour, MD, PhD. Diduch emphasized indications for the procedure which are continually being refined. His indications to consider a deepening trochleoplasty include a convex shape (Dejour types B and D) to the proximal trochlear with a spur height greater than 7 mm and evidence that the dysplasia affects patella tracking on exam, typically by the presence of a “jumping” J sign. In general, the combination of patella alta and dysplasia, or a “jumping” J sign on exam, represent a more severe instability problem that requires some bony correction in addition to the MPFL reconstruction. In cases of extreme patella alta, it may be possible to distalize the tubercle and bring the patella into a more normal or at least a flat part of the trochlea (flat on flat can be balanced, whereas convex is a problem) and avoid the need for a trochleoplasty.
MPFL/TTO and return to play
The final talk of the morning patellofemoral session was “Return to play following patellofemoral stabilization surgery.” In his presentation, Andrew J. Cosgarea, MD, reviewed the existing literature on postoperative rehabilitation protocols and likelihood of returning to sports following MPFL reconstruction and tibial tuberosity osteotomy surgery. He concluded that approximately 90% of athletes returned to sports following isolated MPFL reconstruction at about 3 to 6 months after surgery, with 70% returning to the same level, with a low risk of recurrence. Athletes requiring concomitant osteotomies took 1 to 3 months longer and experienced a higher risk of postoperative complications.
Editorial Commentary from John P. Fulkerson, MD
Special thanks to well respected moderators Seth L. Sherman, MD, and Elizabeth A. Arendt, MD, for putting together this Patellofemoral Update for Healio Orthopedics from the recent American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America Combined Meeting. Lutul D. Farrow, MD, emphasized the close link between patellofemoral pain and instability, and attention to detailed evaluation of each patient standing, sitting, supine and prone, always paying close attention to the history. Adam B. Yanke, MD, PhD, emphasized anatomic attachment of all medial patellofemoral reconstruction graft, understood by many as the midpoint of the medial patellofemoral complex (described by one of the AOSSM original research authors, Miho J. Tanaka, MD). Results are good as long as attachment is at the medial complex midpoint below the proximal patella, or as Yanke says “anatomometrically.” Thanks to Yanke for emphasizing the importance of accurate anatomical reconstruction of the medial patellofemoral complex. Jacqueline M. Brady, MD, emphasized that we still have a lot to learn regarding patella stabilization surgery particularly when adding procedures such as tibial tubercle transfer osteotomy (TTO). This has been a key focus point for her and others with their roots at Hospital for Special Surgery. In addition, 3D imaging will add a lot to this understanding in the next few years. Beth E. Shubin Stein, MD, presented her important findings about the efficacy of MPFL reconstruction alone in the face of trochlea dysplasia. I think about her work frequently. One must have a good reason to do more. Trochlea dysplasia alone is insufficient indication for trochleoplasty. TTO should only be done for high tibial tuberosity to trochlear groove measurements and demonstrable lateral tracking. David R. Diduch, MD, a national authority on trochleoplasty, emphasized the importance of the deflecting proximal trochlea spur, particularly in patients with patella alta, and that trochleoplasty may sometimes be avoided by tubercle distalization. Diduch has studied the complexities of trochlea deformity with 3D models and provided logical insights into when and how to implement trochleoplasty. In practice, this ends up being a small number of patella instability patients. Finally, Andrew J. Cosgarea, MD, provided evidence and guidelines about return to play after patella stabilization and confirmed that a high percentage of athletes return to competitive sports after patella stabilization. Return to sport and consistently favorable results of patella instability surgery are predicated on anatomically precise surgery as in ACL and other ligament reconstruction surgeries. Cosgarea is a national authority, along with John Elias, on biomechanical factors in patellofemoral reconstruction.
Original research papers
Miho J. Tanaka, MD, and co-authors from Harvard School of Medicine presented “Medial patellofemoral ligament length change patterns in asymptomatic knees of patients with contralateral patellar instability.” The authors looked at MPFL length using 3D digital knee modeling created from dynamic CT images of 11 asymptomatic knees of patients with contralateral patellar instability. They found MPFL length varied from 0° to 50° of knee flexion and the number of morphologic risk factors present in each knee demonstrated a strong relationship with MPFL length change. The authors encouraged further study to understand the pathoanatomy related to these changes, as well asthe implications for graft placement and assessment of isometry in MPFL reconstruction techniques.
Daniel W. Green, MD, MS, FAAP, FACS, and co-authors from Hospital for Special Surgery presented “Spontaneous correction of external tibiofemoral rotation and tibial tuberosity -Trochlear groove distance occurs after medial patellofemoral ligament reconstruction in fixed or obligator dislocators.” This study found tibiofemoral rotation (TFR) is an important anatomic factor in pediatric patellar instability. In fixed or obligatory patella dislocators, there is increased external rotational deformity of the tibia in relation to the femur (through the knee) compared with controls and traumatic lateral patellar dislocators. In addition, after surgery to restore patella stability, there was a significant decrease in external TFR: 5.5° in the fixed or obligatory dislocator group. This is the first study to show MPFL reconstruction can change intraarticular tibiofemoral rotation in severe cases of pediatric patellar instability.
Noah J. Quinlan, MD, and co-authors from the University of Utah presented “MPFL reconstruction in the pediatric population: Does skeletal maturity affect outcomes and surgical success?” The study evaluated midterm surgical outcomes of MPFL reconstruction in 67 skeletally mature patients and 21 skeletally immature patients. The authors found comparable outcomes in both groups including re-dislocation rate, subjective scores (IKDC) and functional scores. Skeletal immature patients had a higher rate of ipsilateral knee injury, and skeletally mature patients were more likely respond “yes” when asked if they would undergo the same procedure again.
Hayden Baker, MD, and co-authors from the University of Chicago presented “Diagnostic value of MRI and radiographs of the knee to identify osteochondral lesions in acute patella instability.” This study evaluated preoperative images and intraoperative findings from 71 patients undergoing surgery for patella instability. The authors found poor sensitivity and specificity of both X-ray and MRI for identifying loose bodies or osteochondral defects found at the time of arthroscopy and MPFL reconstruction. Further study is warranted to better understand the shortcomings of current imaging strategies and any implications for refinement of our surgical treatment algorithms.
Overall, the Patellofemoral Pain and Instability General Session at the AOSSM-AANA Combined 2021 Annual Meeting was a tremendous success. This session demonstrated the strong interest within our subspecialty societies for educational content relating to the patellofemoral joint. The newly launched Patellofemoral Foundation Experts Course will build on this momentum to provide high-level content to clinicians around the world. Stay tuned for this at www.patellofemoral.org.
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