Recurrent Instability of the Patella (RIP) Score

Why did you develop the RIP Score? Was there a particular clinical experience or patient encounter that inspired you to create this tool for clinicians?

Patellar dislocation is a common presenting complaint, particularly in young patients in our high volume Mayo Clinic sports medicine and orthopedics practice. Historically, first-time dislocation has been managed with conservative, non-operative management in the absence of displaced osteochondral fragments. However, research including epidemiological studies performed at our institution has demonstrated that patients treated conservatively have recurrence rates which are substantial and up to 30-50% at long-term follow-up.

Given that recurrent dislocation has been shown to result in additive osteochondral damage and is a risk factor for future arthritis, and that there is little available in the way of multivariable prediction of recurrence risk, we were inspired to generate the RIP Score in order to better inform patients and surgeons of recurrence risk, and therefore be able to have more meaningful conversations regarding the potential benefits of early intervention and patellar stabilization surgery.

What pearls, pitfalls and/or tips do you have for users of the RIP Score? Do you know of cases when it has been applied, interpreted, or used inappropriately?

We would like to highlight that each patient represents a unique pattern of initial injury and associated risk factors and that these should inform patient-specific treatment, which can be augmented but should not be exclusively driven by RIP Score. Special (and sometimes more infrequent) patient-specific risk factors such as excessive femoral internal rotation, valgus limb alignment, or patholaxity such as that associated with Ehlers-Danlos syndrome are further items that can likely contribute to recurrent dislocation and operative treatment strategy and therefore merit careful evaluation. Furthermore, for patients presenting with dislocation-associated osteochondral fragments, we generally recommend consideration of early open reduction and internal fixation or debridement of the fragments, as technically allowable.

What recommendations do you have for doctors once they have applied the RIP Score? Are there any adjustments or updates you would make to the score based on new data or practice changes?

We recommend physicians apply the RIP Score in appropriately selected patients presenting with first-time patellar dislocationsm and subsequently use it to inform joint discussions on prognostication and the merits as well as risks of both conservative management and surgical intervention. It is critical to treat each patient on a unique, patient-tailored basis and to assess for underlying and potentially occult risk factors such as femoral anteversion. By involving patients in discussions of management strategy through prognostic and graphical aids such as the RIP Score and associated calculator developed together with MDCalc, we believe physicians can strengthen their partnership with the complex but highly rewarding patellofemoral instability patient population.

In terms of updates and adjustments, we put a concentrated effort towards optimizing the size and follow-up of the dataset that led to the generation of the RIP Score by employing a large epidemiological database of over 500,000 people with an initial inclusion period spanning 20 years and mean subsequent follow-up of over 10 years. Given this, while we do continuously evaluate our practice and the accuracy of scores, we have no current adjustments or updates. Of note, we are in the process of coordinating multi-center and potential international validation and potential improvements to the score. We will keep MDCalc up-to-date regarding the outcomes of these!

How do you use the RIP Score in your own clinical practice? Can you give an example of a scenario in which you use it?

We have found the RIP score to be a highly helpful tool in the clinic, for both patient and surgeon, when evaluating and discussing first-time patellar dislocation. In conjunction with clinical history and examination, it has allowed us to provide a more numeric and statistically informed prediction of patients’ likelihood of recurrent dislocation while guiding patients through various additive risk factors using the graphically accessible MDCalc website and/or application.

Subsequently, we have found the RIP Score to be helpful in informing a statistically augmented clinical approach for management of first-time dislocations. In our own clinical practice, we generally recommend consideration of conservative, non-operative management for patients presenting with low RIP Scores (i.e. 0-1) in the absence of intra-articular fragments. Conversely, as RIP score increases along with the likelihood of recurrent dislocation, we recommend consideration of early intervention, patellar stabilization (i.e., MPFL reconstruction) and addressing patients’ individual risk factors for instability such as dysplasia or excessive femoral internal rotation. Together with Dr. Jack Farr, we have compiled an extended commentary for evaluation and statistically-augmented decision making employing the RIP Score in various clinical scenarios which can be accessed on the Patellofemoral Foundation’s Patellofemoral Update series.

Any other research in the pipeline that you’re particularly excited about?

We have a variety of exciting projects in the pipeline, especially in our fields of focus, hip and knee arthroscopy and cartilage/joint preservation. Our RIP and RAPID scores are particular interests and have been hosted for ready graphical in-clinic use through MDCalc. We have ongoing efforts to further prospectively validate, investigate, and improve prognostication for these scores and are additionally looking into complex preservation projects including [hip] periacetabular osteotomy (PAO), and combined knee cartilage and osteotomy work.

Mario Hevesi, MD, is an orthopedic surgery resident at Mayo Clinic in Rochester, Minnesota. He is the recipient of many awards including the John Charnley award from the Hip Society, the Chitranjan S. Ranawat MD award from the Knee Society, and the Patellofemoral Anatomy and Research award from the Arthroscopy Association of North America. Dr. Hevesi’s primary research is focused on hip and cartilage preservation and regeneration.