The medial epicondyle of the distal femur is the optimal location for MRI measurement of semitendinosus and gracilis tendon cross-sectional area

Abstract

PurposeGraft diameter ≥ 8 mm reduces the risk of failure after anterior cruciate ligament reconstruction (ALCR) with hamstring tendon autograft. Pre‐operative measurement of gracilis (GT) and semitendinosus (ST) cross‐sectional area using MRI has been utilized but the optimal location for measurement is unknown. The main purpose of this study was to examine the cross‐sectional areas of GT + ST at different locations and develop a model to predict whether a doubled hamstring graft of GT + ST will be of sufficient cross‐sectional area for ACLR. MethodsA retrospective review was performed of 154 patients who underwent primary ACLR using doubled hamstring autograft. Cross‐sectional area measurements of GT + ST on pre‐operative MRI axial images were made at three locations: medial epicondyle (ME), tibiofemoral joint line (TJL), and tibial physeal scar (TPS) and calculated the correlation of intra‐operative graft size for each location using the Pearson’s correlation coefficient. A receiver operating characteristic (ROC) established a threshold that would predict graft diameter ≥ 8 mm. ResultsMeasurement of GT + ST at the ME had a stronger correlation (r = 0.389) to intra‐operative graft diameter than measurements at the TJL (r = 0.256) or TPS (r = 0.240). The ROC indicated good predictive value for hamstring graft diameter ≥ 8 mm based on MRI measurement at the ME with the optimal threshold with the highest sensitivity and specificity as 18 mm2. ConclusionCross‐sectional area measurement of GT + ST at the ME correlated most closely to intra‐operative diameter of a doubled hamstring autograft compared to measurements at the TJL or the TPS. As graft diameter < 8 mm is correlated with higher failure rates of ACL surgery, the ability to pre‐operatively predict graft diameter is clinically useful. Level of evidenceLevel III, prognostic study.

Can Preoperative MRI Predict Intra-operative Hamstring Graft Size in Double Bundle Anterior Cruciate Ligament Reconstruction?

“…Furthermore, if the size of the hamstring graft can be predicted by routine preoperative MRI, new tests are not essential, which is practical from the perspective of medical costs and patient burden. Hodges et al [12] reported a cut-off value of 18 mm 2 for MRI CSA to create an 8-mm hamstring graft, and Hollnagel et al [14] reported 17.5-18.8 mm 2 . Although these reported cut-off values were based on SB grafts, the results were generally consistent with those obtained in this study with DB grafts.…”

“…The CSA was measured at 4× magni cation with an axial fat-saturated proton density image. The axial slice level was measured at the medial femoral epicondyle [12] and cross-referenced using coronal images. The PACS region of interest tool has been approved by the US Food and Drug Administration for accurately measuring area.…”

“…While consistent MRI protocols yield stronger correlations, [18] studies that have taken measurements with nonstandardised MRI have also yielded consistent results. [12] Finally, correlations with knee function, return to sport, and objective measures such as range of motion and stability were not examined, as they were outside the scope of this study.…”

Can Preoperative MRI Predict Intra-Operative Hamstring Graft Size In Double Bundle Anterior Cruciate Ligament Reconstruction?

“…Furthermore, if the size of the hamstring graft can be predicted by routine preoperative MRI, new tests are not essential, which is practical from the perspective of medical costs and patient burden. Hodges et al [12]. reported a cut-off value of 18 mm 2 for MRI CSA to create an 8-mm hamstring graft, and Hollnagel et al [14].…”

“…The CSA was measured at 4× magni cation with an axial fat-saturated proton density image. The axial slice level was measured at the medial femoral epicondyle [12] and cross-referenced using coronal images. The PACS region of interest tool has been approved by the US Food and Drug Administration for accurately measuring area [15].…”