Ueli Studler, Presenter: Nothing to Disclose

Lawrence M. White MD, Abstract Co-Author: Nothing to Disclose

Ali M. Naraghi MBBS, Abstract Co-Author: Nothing to Disclose

Gadi Kahn, Abstract Co-Author: Nothing to Disclose

Paul Marks, Abstract Co-Author: Nothing to Disclose

To determine the frequency of imaging findings and complications related to cross-pins on follow-up MRI examinations in patients who had undergone anterior cruciate ligament (ACL) reconstruction with bioabsorbable cross-pin fixation.

Follow-up MR imaging studies of 222 ACL reconstructions with bioabsorbable cross-pin fixation were retrospectively reviewed by two musculoskeletal radiologists in consensus. Fracture, resorption and migration of the cross-pins as well as posterior cortical breach and prominence at the lateral femoral condyle were recorded. The relationship between the angle (pin angle) formed by the transepicondylar axis and the cross-pins and the presence of cross-pin fractures was investigated on axial images by using the Pearson Chi-Square test. The integrity of the ACL graft and the presence of intraarticular loose fragments were determined.

Forty-nine fractured cross-pins were seen in 37/222 (16.7%) patients. Among these 49 fractured cross-pins, the superior cross-pins (n = 19) were less frequently fractured than the lower cross-pins (n = 30). In 12 patients both pins were fractured. In 40 out of 49 fractured pins, the posterior femoral cortex was the site where the fracture occurred. The posterior femoral cortex was breached by either the superior or lower cross-pins in 63/222 (28.4%) patients with an average length of the protruded portion of 9.5 mm. The fractured cross-pins had migrated in 19 patients over an average distance of 5.4 mm. Partial and total resorption of cross-pins was observed in 7/222 (3%) and 28/222 (12.6%) patients, respectively. Prominent cross-pins were present in 6/222 (2.7%) patients with a mean length of the prominent portion of 3.9 mm. There was a significant relationship (P < .05) between the pin angle and the occurrence of cross-pin fractures. A partial and complete tear of the ACL graft was present in 3/222 (1.4%) and 4/222 (1.8%) patients, respectively. Loose bodies were not observed.

Fractures and posterior cortical breaches of cross-pins are commonly seen in follow-up MRI examinations. There appears to be a relationship between the pin angle and the presence of cross-pin fractures

Familiarity with all aspects of cross-pins at follow-up MRI examinations can help improve image interpretation.

Studler, U, White, L, Naraghi, A, Kahn, G, Marks, P, Anterior Cruciate Ligament Reconstruction Using Bioabsorbable Cross-Pins: MR Imaging Findings at Follow-up Examinations.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8013101.html