Femoral Internal Torsion Greater than Twenty-Five Degrees and/or External Tibial Torsion Greater than Thirty Degrees as Measured by Computed Tomography are Threshold Values for Axial Alignment Correction in Patellofemoral Instability.

OBJECTIVES: Patellofemoral instability (PFI) has multiple predisposing anatomic factors including ligamentous hyperlaxity, coronal and axial malalignment, patella alta, trochlea dysplasia, excessive lateral patellar tilt, and excessive lateral Q vector. Yet, few studies have analyzed surgical thresholds for performing axial alignment corrective osteotomies in the treatment of PFI and patella maltracking. The objective of this systematic literature review was to determine if there is a threshold for axial plane alignment that triggers surgical correction for treatment of patellar instability in the published literature.

METHODS: Using a predetermined search strategy, a systematic literature search of 10 major databases and grey literature resources was completed. Only studies reporting on patellar instability with outcomes were included. Radiologic indications, additional procedures, outcomes, and complications were reported. Titles and abstracts were screened, and full text manuscripts were then selected and extracted. Variables related to radiographic and clinical parameters, patient demographics, surgery performed, surgical correction, complications, and reoperations were recorded pre-operative and post-operative.

RESULTS: A total of 1132 abstracts and titles were screened by two reviewers yielding 15 eligible studies. The reported threshold identified in our study for axial plane alignment that triggers surgical correction in most of the published literature when discussing PFI was either tibial torsion greater than 30 degrees and/or femoral anteversion greater than 25 degrees. Following rotational osteotomy of one or both long bones, one study (7%) reported improvements in tubercle-sulcus angle, two studies (13%) reported improvements in femoral-tibial angle, four studies (27%) reported decreases in tibial torsion. For patient reported outcomes, seven studies (47%) reported improvement in Kujala score, five studies (33%) reported postoperative improvement in Lysholm, and four studies (27%) reported improved International Knee Documentation Committee (IKDC) score. Nine studies (60%) reported pre-operative femoral anteversion; however, only two studies compared pre- and post-operative values (one study reported a decrease in anteversion where another study reported an increase in anteversion).

CONCLUSION: When treating PFI, the reported threshold for axial plane alignment that triggers surgical correction in most of the published literature was tibial torsion greater than 30 degrees and/or femoral anteversion greater than 25 degrees as measured by CT. However, there is no consensus on axial alignment measurement technique.

LEVEL OF EVIDENCE: III.