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. 2021 Feb 26;9(2):2325967120985530.
doi: 10.1177/2325967120985530. eCollection 2021 Feb.

Noniatrogenic Medial Patellar Dislocations: Case Series and International Patellofemoral Study Group Experience

Alexander E Loeb  1 , Jack Farr  2 , Shital N Parikh  3 , Andrew J Cosgarea  1
Affiliations

Noniatrogenic Medial Patellar Dislocations: Case Series and International Patellofemoral Study Group Experience

Alexander E Loeb et al. Orthop J Sports Med. .

Abstract

Background: Most patellar dislocations occur in a lateral direction because of a summed lateral force vector and predisposing anatomic risk factors. Medial patellar instability is rare and is a well-recognized iatrogenic complication of an overly aggressive lateral retinacular release. Noniatrogenic medial patellar dislocations are rare. The management of these injuries is not well described.

Purpose: To describe the experience of the International Patellofemoral Study Group with patients with noniatrogenic medial patellar dislocation.

Study design: Case series; Level of evidence, 4.

Methods: Members of the International Patellofemoral Study Group (N = 64) were surveyed between October 2018 and April 2019. This group was chosen because of its wide referral base and interest in patellar instability. Specialists who had encountered a patient with medial patellar instability were sent a questionnaire inquiring about details of the case, including patient demographics, medical history, level of athletic competition, injury characteristics, and treatment. Cases were confirmed by physical examination records and, in some cases, with findings on advanced radiographic imaging.

Results: The survey response rate was 73% (47/64). Three of the 47 specialists (6.4%) reported they had seen a case of noniatrogenic medial patellar dislocation, for a total of 6 cases. Four cases were described as recurrent medial dislocations in the setting of hypermobile Ehlers-Danlos syndrome; 2 were treated nonoperatively, 1 underwent lateral patellofemoral ligament reconstruction, and 1 underwent derotational osteotomies. Two medial-sided patellar dislocations in collegiate athletes were sports-related injuries that required surgical debridement but no ligamentous reconstruction. None of the patients had persistent or recurrent instability at the time of their most recent follow-up.

Conclusion: Noniatrogenic medial patellar dislocations are extremely rare. This case review suggests that the treatment of first-time medial patellar instability in patients without known risk factors should follow the same principles as the treatment of lateral instability with no known risk factors, which is nonoperative management. For patients with documented risk factors and recurrence, surgery to address the risk factors may be appropriate.

Keywords: collegiate athlete; lateral patellar dislocation; medial patellar dislocation; noniatrogenic.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: A.E.L. has received hospitality payments from Zimmer Biomet. J.F. has received research support from Active Implants, Arthrex, Episurf, Fidia Pharma, JRF Ortho, Moximed, Novartis, Organogenesis, Samumed, Vericel, and Zimmer Biomet; consulting fees from Aastrom Biosciences, Aesculap/B.Braun, Arthrex, Cartiheal, Ceterix, Cook Biotech, DePuy Synthes, Exactech, ISTO Technologies, MedShape, Moximed, Organogenesis, Osiris, Regentis, RTI Surgical, Samumed, Vericel, Zimmer Biomet, and ZKR Orthopedics; speaking fees from Aastrom Biosciences, Arthrex, Moximed, Organogenesis, Vericel, and Zimmer Biomet; and royalties from Arthrex, Biopoly, DePuy Synthes, Organogenesis, Springer, and Thieme Medical Publishers and has stock/stock options in MedShape and Ortho Regenerative Tech. S.N.P. has received education payments from CDC Medical and speaking fees from Synthes. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
(A) Lateral, (B) axial, and (C) anteroposterior radiographs of the left knee of a 19-year-old man showing patella alta and a shallow trochlear groove.
Figure 2.
Figure 2.
Fat-saturated T2-weighted axial (A, B) and sagittal (C, D) magnetic resonance imaging scans of the left knee of a 19-year-old man showing lateral retinacular disruption at the (A) patellar insertion (arrow) and (B, C) edema within the anterior medial femoral condyle (chevrons) and (D) lateral patella (arrowhead).
Figure 3.
Figure 3.
T2-Weighted axial magnetic resonance imaging scan of the right knee of a 21-year-old woman showing medial femoral condyle edema, high-grade chondral lesion, and joint effusion.
Figure 4.
Figure 4.
Axial computed tomography image showing medial dislocation of the patella in a 26-year-old woman. Reprinted with permission from Springer Nature: Miller et al.
See this image and copyright information in PMC

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