Familial patellar dislocation associated with t(15;20) (q24;q13.1)

Identification of eight genes associated with recurrent patellar dislocation

The inheritance of recurrent patellar dislocation (RPD) is known, but the susceptible gene remains unidentified. Here, we performed the first whole exome sequencing (WES) cohort study to identify the susceptible genes. The results showed eight genes were associated with this disease. Notably, the carboxypeptidase D (CPD) gene showed the highest relevance based on its gene function and tissue expression. Single-cell sequencing results indicate that the CPD gene is involved in the pathophysiological process of RPD through granulocytes. Implicated pathways include nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and Wnt/β-catenin signaling, potentially influencing CPD's role in RPD pathogenesis. This study identified the susceptible gene and investigates the potential pathogenesis of RPD, which provided a new prospect for the understanding of RPD. Besides, it would offer the theoretical basis for disease prevention and genetic counseling.

Trochlea dysplasia, increased TT-TG distance and patella alta are risk factors for developing first-time and recurrent patella dislocation: a systematic review

PURPOSE

The aim of the study was to perform a systematic review and best knowledge synthesis of the present literature concerning biomechanical risk factors for developing first-time and recurrent patella dislocation.

METHODS

The study was performed as a systematic review following PRISMA guidelines. PubMed and EMBASE were systematically searched. Studies investigating participants with risk factors for first-time as well as recurrent patella dislocation were included. The records were screened, and data extracted independently by two researchers supervised by a third independent assessor. The study was registered in PROSPERO.

RESULTS

A total of 6233 records were screened, and 50 studies met the inclusion criteria. The biomechanical risk factors: trochlear dysplasia, increased tibial tuberosity-trochlear groove distance (TT-TG), and patella alta were found to be statistically significantly associated with patella dislocation in several publications and were thus recognized as risk factors for patella dislocation. The soft-tissue stabilizers: longer and thinner MPFL ligament, increased number of type 2C and decreased number of type 1 muscle fibers, and joint laxity were found to be statistically significantly associated with patella dislocation in a few publications, but due to limited evidence, no conclusion was made on this matter.

CONCLUSION

There is strong evidence in the literature that abnormalities of bony stabilizers, trochlear dysplasia, increased TT-TG distance, and patella alta are risk factors for patella dislocation. There is less evidence that soft-tissue stabilizers are risk factors. The study emphasizes the importance of a thorough investigation of bony stabilizers in clinical decision-making.

LEVEL OF EVIDENCE

Level IV.

Familial association and epidemilogical factors as risk factors for developing first time and recurrent patella dislocation: a systematic review and best knowledge synthesis of present literature

PURPOSE

The aim of our study was to perform a systematic review and best knowledge synthesis of the present literature concerning the familial association and epidemiological factors as risk factors for developing first-time and recurrent patella dislocation.

METHODS

The study was conducted according to the PRISMA guidelines and registered in PROSPERO. EMBASE and PubMed were systematically searched on the 5th of May 2022. Studies investigating participants with genetic and epidemiological risk factors for the first time as well as recurrent patella dislocation were included. The records were screened, and data were extracted independently by two researchers supervised by a third independent assessor.

RESULTS

A total of 6,649 records were screened, and 67 studies were included. Familial association was described as a risk factor for patella dislocation in 17 studies. One study found that participants with a family history of patella dislocation had a 3.7 higher risk for patella dislocation in the contralateral asymptomatic knee, and another study found a family history of PD in 9% of 74 participants. Eleven studies found an accumulation of patella dislocation across generations in specific families. Additionally, a range of genetic syndromes was associated with patella dislocation. Young age is a well-investigated risk factor for patella dislocation, but the results are inconsistent. Only five and eight studies investigated skeletal immaturity and gender as risk factors for patella dislocation, respectively.

CONCLUSION

There may be a familial association with patella dislocation, but further investigation is necessary to determine the strength and etiology of the association. There is weak evidence that epidemiological risk factors, such as age, skeletal immaturity, gender, and BMI are risk factors for patella dislocation.

LEVEL OF EVIDENCE

IV.

Anatomical characteristics and potential gene mutation sites of a familial recurrent patellar dislocation

Background

Recurrent patellar dislocation is the result of anatomical alignment and imbalance of restraint of bone and soft tissue. We investigate the anatomical characteristics of the knee joint in a family of patients with recurrent patella dislocation, and to screen the possible pathogenic genes in this family by whole exome sequencing in 4 patients and 4 healthy subjects, so as to provide theoretical basis for the pathogenesis of this disease.

Methods

The data related to patella dislocation were measured by imaging data. The peripheral blood DNA of related family members was extracted for the whole exome sequencing, and then the sequencing results were compared with the human database. By filtering out synonymous variants and high-frequency variants in population databases, and then integrating single nucleotide non-synonymous variants of family members, disease-causing genes were found.

Results

All patients in this family have different degrees of abnormal knee anatomy, which is closely related to patella dislocation. The sequencing results of patients and normal persons in this patella dislocation family were compared and analyzed, and the data were filtered through multiple biological databases. Find HOXB9 (NM_024017.4:c.404A>G:p.Glu135Gly),COL1A1(NM_000088.3:c.3766G>A:p.Ala1256Thr),GNPAT(NM_014236.3:c1556A>G:p.Asp519Gly),NANS(NM_018946.3:c.204G>C:p.Glu68Asp),SLC26A2(NM_000112.3:c.2065A>T:p.Thr689Ser) are nonsynonymous variants (MISSENSE). Through Sanger sequencing, the identified mutations in HOXB9 and SLC26A2 genes were only present in samples from patients with recurrent patellar dislocation.

Conclusions

The patients with recurrent patellar dislocation had markedly abnormal knee anatomy in this family. HOXB9 gene and SLC26A2 gene were found to be the possible pathogenic genes or related genes for patella dislocation.

The effect of increased femoral anteversion on the morphological and trabecular microarchitectural changes in the trochlea in an immature rabbit

Increased femoral anteversion (FA) has been recently demonstrated as one risk factor for recurrent patellar dislocation (RPD). However, it has been still unclear whether the increase of FA can result in patellar dislocation, and subsequent morphological and trabecular microarchitectural changes in the trochlea has not been investigated. Forty knees from 20 rabbits at 3 months of age were included. The right knees underwent surgery with internal rotation of distal femur to increase FA, with the left knees acting as internal controls. The surgical knees were called operated group, and non-operated knees were control group. Micro-CT scans for distal femur were acquired after 4 months of surgery. In the operated group, a boss located proximal to the entrance of the groove was formed. The central trochlear height was significantly greater, sulcus angle was significantly greater, both lateral and medial trochlear slope were significantly lower, and boss height was significantly greater in comparison to the control group. Regarding the microarchitectural changes, the trabecular thickness were increased by 67.5% at the groove, 33.0% and 29.5%, at the medial and lateral femoral condyle, and trabecular number were decreased by 37.8% and 26.5% at the groove and medial femoral condyle. This study provided a novel animal model of trochlea dysplasia by femoral rotational osteotomy and increased FA. These changes were associated with the load redistribution in the patellofemoral joint after the increase of FA.

Management of the first-time lateral patellar dislocation

BACKGROUND

Little guidance exists on the management of the first-time patellar dislocation. The aim of this article was to review current guidance for management of this condition.

METHODS

Recent meta-analyses, systematic reviews and current consensus documents relating to first-time patellar dislocation were sourced. An instructional lecture was then created and delivered at the acute knee injuries session at the British Orthopaedic Association 2019 annual conference, which was presented on behalf of the British Association for Surgery of the Knee. This article has been written based on this lecture.

RESULTS

There is a paucity of literature relating to management of the first-time patellar dislocation. Many studies are of poor design, with inadequate follow-up, making it difficult to draw conclusions from them. However, based upon available information and consensus from working groups it is recommended that patients presenting with first-time dislocation should be assessed to ensure they have not sustained an alternative or associated injury that may require surgical intervention, be assessed and counselled for the risk of recurrent dislocation, and be referred for initial conservative treatment. Surgical stabilisation should be reserved for patients with recurrent instability.

CONCLUSIONS

Most patients with a first-time patellar dislocation can be managed conservatively, having excluded associated injuries. Due to the poor quality of the literature, care must be taken interpreting the results of studies. It is clear that further research is required in this field.