Abstract
The recent study published in AJSM titled “The Predicted Position of the Knee Near the Time of ACL Rupture Is Similar Between 2 Commonly Observed Patterns of Bone Bruising on MRI” by Kim-Wang et al, 2 which appears to contain data similar to those provided in “Determination of the Position of the Knee at the Time of an Anterior Cruciate Ligament Rupture for Male Versus Female Patients by an Analysis of Bone Bruises” by Owusu-Akyaw et al, 3 was a concerning read. First, the patient numbers presented in these papers just don’t add up! Second, how can the time of an anterior cruciate ligament (ACL) injury be determined by magnetic resonance imaging (MRI)? It’s not possible. A third concern is the overlap with prior published studies, which can be considered “salami science.” Fourth, the interpretation of their findings is incorrect.
The stated purpose of the 2018 study by Owusu-Akyaw et al was “to compare knee positions at the time of a noncontact ACL injury between sexes.” The authors tested 15 patients’ MRI scans selected from a cohort of 136 MRI scans. Kim-Wang et al studied 50 of 136 ACL-injured patients in an attempt to clarify “whether the position of the knee near the time of injury differs between patients evaluated with different patterns of bone bruising, particularly with regard to valgus angles.”
The study by Kim-Wang et al has at least one major methodological flaw, in that there was clear selection bias to include MRI scans only from patients who had 3 or 4 bone bruises in the medial and lateral compartments of the knee. The authors studied only 50 patients, 20 of whom they placed in the 3 bone bruise group and 30 of whom they placed in the 4 bone bruise group. The authors claimed that these 50 patients and two bone bruise patterns constituted 59% of bone bruise patterns observed, but 59% of 136 is equal to 80, not 50. Where are the 30 missing patients? Despite the authors’ best efforts to support their long-standing concept of a quadriceps-induced knee extension ACL injury mechanism, they found appreciable valgus (distal tibial abduction of 8° is significant valgus) as part of the injury mechanism. Despite their significantly flawed method (eg, the inaccurate patient numbers and selection bias), the data from both Kim-Wang et al and Owusu-Akyaw et al clearly demonstrate the role of valgus in the mechanism of ACL injury. Other AJSM studies examined similar variables that were shown to contribute to the mechanism of ACL injury (eg, Hewett et al 1 ).
We respectfully request that the authors report the findings from all 136 patients, which would decrease the selection bias in their study. The authors should not select those MRI scans that suit their knee extension no valgus long-standing narrative, and should repeat their study using accepted and proper methods. These authors must also properly interpret the valgus mechanism observed and reported in multiple prior AJSM studies.
Footnotes
One or more of the authors has declared the following potential conflict of interest or source of funding: T.E.H. has received support from Sparta Science. C.D.L. has received consulting fees from Arthrex. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
