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Prediction of Autograft Hamstring Size for Anterior Cruciate Ligament Reconstruction Using MRI

Hollnagel, Katharine MD; Johnson, Brent M. MD; Whitmer, Kelley K. MD; Hanna, Andrew MD; Miller, Thomas K. MD

Clinical Orthopaedics and Related Research: December 2019 - Volume 477 - Issue 12 - p 2677-2684
doi: 10.1097/CORR.0000000000000952
CLINICAL RESEARCH
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Background Hamstring autografts with a diameter of less than 8 mm for ACL reconstruction have an increased risk of failure, but there is no consensus regarding the best method to predict autograft size in ACL reconstruction.

Questions/purposes (1) What is the relationship between hamstring cross-section on preoperative MRI and intraoperative autograft size? (2) What is the minimum hamstring tendon cross-sectional area on MRI needed to produce an autograft of at least 8 mm at its thickest point?

Methods This was a retrospective cohort study of 68 patients. We collectively reviewed patients who underwent ACL reconstruction by three separate fellowship-trained surgeons at the Carilion Clinic between April 2010 and July 2013. We searched the patient records database of each surgeon using the keyword “ACL”. A total of 293 ACL reconstructions were performed during that time period. Of those, 23% (68 patients) had their preoperative MRI (1.5 T or 3 T magnet) performed at the Carilion Clinic with MRI confirmation of acute total ACL rupture. Exclusion criteria included previous ACL reconstructions, multiligamentous injuries, and history of acute hamstring injuries.

After applying the exclusion criteria, there were 29 patients in the 1.5 T magnet group and 39 in the 3 T group. Median age (range) was 29 years (12 to 50) for the 1.5 T group and 19 years (9 to 43) for the 3 T group. The patients were 41% female in the 1.5 T group and 23% female in the 3 T group. Use of 1.5 T or 3 T magnets was based on clinical availability and scheduling. The graft’s preoperative cross-sectional area was compared with the intraoperative graft’s diameter. The MRI measurements were performed by a single musculoskeletal radiologist at the widest point of the medial femoral condyle and at the joint line. Intraoperative measurements were performed by recording the smallest hole the graft could fit through at its widest point. Pearson’s correlation coefficients were calculated to determine the relationship between graft size and tendon cross-sectional area. A simple logistic regression analysis was used to calculate the cutoff cross-sectional areas needed for a graft measuring at least 8 mm at its thickest point. Intrarater reliability was evaluated based on re-measurement of 19 tendons, which produced an overall intraclass correlation coefficient (ICC) of 0.96 95% (CI 0.93 to 0.98). A p value < 0.05 was considered significant.

Results In general, the correlation between MRI-measured hamstring thickness and hamstring graft thickness as measured in the operating room were good but not excellent. The three measurements that demonstrated the strongest correlation with graft size in the 1.5 T group were the semitendinosus at the medial femoral condyle (r = 0.69; p < 0.001), the semitendinosus and gracilis at the medial femoral condyle (r = 0.70; p < 0.001), and the mean semitendinosus and gracilis (r = 0.64; p < 0.001). These three measurements had correlation values of 0.53, 0.56, and 0.56, respectively, in the 3 T MRI group (all p values < 0.001). To create an 8-mm hamstring autograft, the mean semitendinosus plus gracilis cutoff values areas were 18.8 mm2 and 17.5 mm2 for the 1.5 T and 3.0 T MRI groups, respectively.

Conclusions Imaging performed according to routine knee injury protocol can be used to preoperatively predict the size of hamstring autografts for ACL reconstructions. In clinical practice, this can assist orthopaedic surgeons in graft selection and surgical planning.

Level of Evidence Level II, diagnostic study.

K. Hollnagel, Department of Orthopaedic Surgery, University of Toledo, Toledo, OH, USA

B. Johnson, T. K. Miller, Department of Orthopaedic Surgery, Virginia Tech Carilion School of Medicine, Roanoke, VA, USA

K. Whitmer , Department of Radiology, Virginia Tech Carilion School of Medicine, Roanoke, VA, USA

A. Hanna, Virginia Tech Carilion School of Medicine, Roanoke, VA, USA

T. K. Miller, Department of Orthopaedic Surgery, Virginia Tech Carilion School of Medicine, Carilion Clinic Orthopaedics ION, 2331 Franklin Road, Roanoke VA, 24014 USA, Email: tkmilller@carilionclinic.org

Each of the authors certify that neither he or she, nor any member of his or her immediate family, has no commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article.

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.

Clinical Orthopaedics and Related Research® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA approval status, of any drug or device before clinical use.

Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.

This work was performed at Virginia Tech Carilion School of Medicine, Roanoke, VA, USA.

© 2019 by the Association of Bone and Joint Surgeons
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