Lateral Patellar Instability

Abstract

ä Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology.Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient.ä Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity.ä Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment.ä Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability.ä Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation.ä Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta.ä The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding.ä Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30°to improve patient outcomes and reduce recurrence rates.Patellar dislocations account for 3.3% of all knee injuries, with a reported rate of 42 per 100,000 persons per year 1,2 . These injuries most commonly occur in young girls and women, with >70% of first-time patellar dislocations taking place while participating in sport-related activity 1,3 . The majority of patellar dislocations occur in non-contact injuries when the knee is subject to valgus stress while extended during a planting or pivoting motion 3 . Common risk factors for recurrent lateral patellar instability include patella alta, increased tibial tubercleto-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity 4,5 . The overall recurrence rate after a first-time patellar dislocation is approximately 30%, but can increase to >70% when multiple risk factors are present 4 . Predisposing clinical and anatomical variables should Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://l...

Clinical outcomes of derotational femoral osteotomy combined with medial patellofemoral ligament reconstruction in patients with patellar dislocation and increased femoral anteversion unaffected by the pattern of distribution of femoral torsion

“…Meanwhile, Noonan et al studied the time when femoral torsion became the leading pathological factor for patellar dislocation [28]. Patellofemoral joint disease is a complex multifactorial problem, and "à la carte" is considered a strategy for treating patellar dislocation [10,26,35]. We should focus on the main factors for patellar dislocation in each patient.…”

Clinical and Radiological Outcomes After Combined ACL and MPFL Reconstruction Versus Isolated ACL Reconstruction for ACL Injury With Patellar Instability

“…In summary, the current study showed that in patients after an ACL injury with PI, cAMR could produce better clinical and radiological results than iACLR. Because previous studies have shown that MPFLR can significantly correct patellar maltracking, relieve anterior knee pain, and subsequently enable a high-level and safe return to sports, 5,15 cAMR tended to yield better clinical outcomes. It is also possible that these preferable improvements were closely associated with a restabilized restable patellofemoral joint.…”

Correlation between flat foot and patellar instability in adolescents and analysis of related risk factors

“…The stability of the patella is also affected by the height of the patella and the alignment of the lower limbs. High patella leads to the inability of the patella to smoothly enter the femoral trochlear, resulting in poor matching of the motion trajectory during flexion and extension of the knee joint, which is prone to dislocation; Uneven alignment of the lower limbs, such as increased femoral anteversion angle, knee valgus, and tibial rotation, all increase the risk of patellar dislocation [7] . The results of this study suggest that excessive weight and excessive ligamental laxity may be risk factors for patellar instability, increasing the risk of patellar dislocation during exercise.…”

“…6 Patellar dislocation accounts for 3.3% of all knee joint injuries, with an overall recurrence rate of approximately 30% after the first patellar dislocation. 7 Patellar instability is mainly caused by structural abnormalities of the knee joint, such as dysplasia of the femoral trochlear groove, high patella, looseness of the medial patellar retinaculum, enlargement of the knee joint Q angle, and tibial rotation. 6,8 Patellar instability is also recognized as one of the important pathogenic factors leading to patellofemoral arthritis and chondromalacia of the patella in the later stage.…”