Patella dislocation: an online systematic video analysis of the mechanism of injury

Background

The mechanism of injury (MoI) for a patellar dislocation has not been fully established. The aim of this study was to use systematic video analysis to determine the MoI of a patella dislocation.

Methods

A systematic search was conducted of three video sharing websites and three popular search engines to identify videos demonstrating a patellar dislocation. Videos were reviewed by three surgeons trained in systematic video analysis, who commented on the position of the lower limb and the situation in which the injury occurred. The results were reviewed to build a consensus of the MoI for each video. Statistical analysis was conducted for interobserver agreement (p < 0.05).

Results

Initial search yielded 603 videos with 13 meeting the inclusion criteria. The injuries were sustained performing a sporting activity (n = 9) or whilst dancing (n = 4). The injury was predominantly sustained during a non-contact situation (n = 10). The most common mechanism was an unbalanced individual with a flexed hip sustaining a valgus force to their flexed knee with the tibia externally rotated.

Conclusions

This study provides some insight into the MoI for a patellar dislocation and the findings may assist in developing injury prevention programmes and rehabilitation protocols as well as guiding future research.

When does the patella dislocate? A systematic review of biomechanical & kinematic studies

Background

Patellar dislocations are a significant injury with the potential for long term problems. Little work has been done on establishing the mechanism by which this injury occurs.

Objectives

To determine the mechanism of injury of a patella dislocation based on the available published literature and compare them to already proposed theories.

Methods

A systematic review of the literature was conducted following searches performed on MEDLINE, EMBASE and ProQuest from the earliest year of indexing using the following search terms in any combination: "patella", "dislocation", "mechanism of injury", "anatomy", "biomechanical" and "risk factor". A broad inclusion criteria was used that included studies that looked at patellar dislocations and instability with respect to the patellofemoral joint (PFJ) kinematics or altered kinematics of the PFJ. Studies that did not address the kinematics or biomechanics of the PFJ were excluded. Studies were appraised based on their methodology using a combination of the Critical Appraisal Skills Programme tool and the Quality Appraisal for Cadaveric Studies.

Results

113 studies were identified from a search of MEDLINE, EMBASE and ProQuest databases. Following application of our inclusion criteria, a total of 23 studies were included in our review. 18 of these studies were cadaveric biomechanical studies. The remaining studies were anatomical, imaging based, and a computer simulation based study.

Conclusions

These biomechanical and kinematic studies provide some evidence that a dislocation is likely to occur during early knee flexion with external rotation of the tibia and contraction of the quadriceps. There is limited evidence to support other elements of proposed mechanisms of dislocation.

Surgical versus conservative management of acute patellar dislocation in children and adolescents: a systematic review

PURPOSE

The goal of this study was to perform a comparative review to determine whether there is a significant difference in the rate of repeat dislocation and clinical outcome between surgical and conservative management of acute patellar dislocation in children and adolescents.

METHODS

A systematic review of the MEDLINE database was performed. English-language clinical outcome studies with a primary outcome/treatment specific to acute patella dislocation in a paediatric population were included. Eleven studies met inclusion criteria; Chi-square analysis, independent t tests and weighted mean pooled cohort statistics were performed where appropriate.

RESULTS

A total of 470 conservatively managed and 157 operatively treated knees were included. Conservatively managed patients were on average 17.0 years and had a mean follow-up of 3.9 years; surgically managed patients were on average 16.1 years and had a mean follow-up of 4.7 years. Conservatively managed knees had a 31% rate of recurrent dislocation rate compared to 22% in surgical knees (p = 0.04). Trochlear dysplasia and skeletal immaturity confer greater risk for recurrent instability. Surgical treatment may provide clinically important quality of life and sporting benefit.

CONCLUSIONS

Surgical treatment of first time patella dislocation in children and adolescents is associated with a lower risk of recurrent dislocation and higher health-related quality of life and sporting function. There is a paucity of evidence on MPFL reconstruction for first time traumatic patella dislocation in this population.

LEVEL OF EVIDENCE

IV.