Predicting ACL Tears from X-Rays
Abstract & Commentary
Synopsis: The presence and size of a bony prominence on the anterior tibia was statistically associated with an increased incidence of ACL tears.
Source: Pecina M, et al. Tuberculum intercondylare tibiae tertium as a predictive factor for anterior cruciate ligament injury. Am J Sports Med. 2001;29(6):709-711.
Tuberculum intercondylare tibiae tertium is a small bony prominence located anterior to the medial tibial prominence on the tibia. Portions of the anterior horn of the medial meniscus and the anterior medial fibers of the ACL attach there. Its presence is variable. Pecina and colleagues noted a correlation of its presence with the patients they treated with ACL tears and looked for a statistical correlation.
Over a 3-year period this group from Croatia treated 171 patients surgically for an ACL tear. A controlled group of 120 patients treated for anterior knee pain were matched by age and sex. Lateral radiographs were examined for the presence of this bony prominence, which sits just in front of the tibial spines. They measured the height and width of the prominence relative to the tibial plateau and expressed its size as a ratio to take into account radiographic magnification differences. They found that the tuberculum intercondylare tibiae tertium was present in 32.2% of patients with ACL tears and present in only 13.3% of controlled patients without ACL tears. The difference was statistically significant. Furthermore, they found that larger tubercles were correlated statistically with the presence of ACL tears. They conclude that the presence of this bony prominence puts the patient at higher risk for ACL tear and could be used as a radiographic risk factor when evaluating a patient for an acute knee injury.
Comment by David R. Diduch, MS, MD
Tuberculum intercondylare tibiae tertium was first described by Parson in 1906 and termed Parson’s knob. It later became known also by the term Parson’s tubercle. The bony prominence is present to a variable degree and includes attachment of a portion of the anteromedial fibers of the ACL. It sits just in front of the medial tibial imminence and can be seen on a lateral x-ray of the knee when present. Pecina et al performed a relatively simple study based on an astute observation. They compared radiographs of patients with ACL tears and a matched group of patients without ACL tears and found a statistical difference. The presence and size of the Parson’s tubercle correlates strongly with an ACL tear. How this functions mechanistically is unclear. As the tubercle is present anteriorly it may impinge the ACL for a hyperextension mechanism or produce stress on the fibers with a pivoting movement. These issues are yet to be addressed. However, this is the first study to make the correlation between ACL tear and the presence of the tubercle. It would have been helpful if they had broken down their ACL tears into acute vs. chronic. We all know that chronic ACL tears are associated with increased prominence of the tibial spines. It is conceivable that the tuberculum intercondylare would increase in size as well with a chronic ACL tear.
Dr. Diduch, Associate Professor, Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, VA, is Editor of Sports Medicine Reports.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content