High heterogeneity in in vivo instrumented-assisted patellofemoral joint stress testing: a systematic review

Purpose: Summarize the in vivo instrumented-assisted patellofemoral evaluation methods for quantifying the patellar mobility in response to a known external force. Methods: A systematic review using PubMed, EMBASE, Cochrane Library, and SPORTDiscus electronic databases was conducted to search for studies reporting in vivo instrumented-assisted patellofemoral evaluation of patellar mobility. Searches were conducted in duplicate up to October 2017. Methodologic quality of included articles was assessed using a modified version of the Critical Appraisal Skills Program (CASP) critical appraisal tool. Results: From the original 2614 records, 9 studies comprising 568 individuals (24 ± 4.8 years old, 51.4% females)—355 (62.5%) asymptomatic individuals, 87 (15.3%) patellofemoral pain, and 126 (22.2%) patellofemoral instability patients—were included. The average maximum force applied by the instruments to the patella was 38.9 ± 27.7 N (range 11.25 to 80 N). Patellar displacement ranged from 3.9 to 10.4 mm, medially, and 3.5 to 14.8 mm, laterally, for asymptomatic individuals. For patellofemoral instability patients, these values were higher, ranging from 3.8 to 22.1 mm, medially, and 7.0 to 21.9 mm, laterally, being these mean values similar across the instability subgroups (medial, lateral, or multidirectional). Patellofemoral pain had a mean of 10 mm and 10.9 mm for medial and lateral displacements, respectively. Mean methodological quality score was 9.8 ± 2.6 (range 6–13) out of 18 possible points. Conclusions: There is high heterogeneity within the available instrumented assessment methods and respective measurement outcomes, highlighting the need for better methodological standardization and further developments in this field. This would allow a more accurate and reliable quantification of patellar movement and, subsequently, improve diagnosis, and refine treatment. Level of evidence: Systematic review of level II–IV studies, Level IV.