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. 2015 Aug 21:16:217.
doi: 10.1186/s12891-015-0677-0.

Segmentation of the lateral femoral notch sign with MRI using a new measurement technique

Thomas Hoffelner  1 , Isabel Pichler  2 , Philipp Moroder  3 , Michael Osti  4 , Martin Hudelmaier  5 , Wolfgang Wirth  6 , Herbert Resch  7 , Alexander Auffarth  8
Affiliations

Segmentation of the lateral femoral notch sign with MRI using a new measurement technique

Thomas Hoffelner et al. BMC Musculoskelet Disord. .

Abstract

Background: The goal of this present study was to precisely determine the dimension and location of the impaction fracture on the lateral femoral condyle in patients with an ACL rupture.

Methods: All patients with post-injury bi-plane radiographs and MRI images after sustaining a tear to the anterior cruciate ligament were included. Lateral radiographs of the affected knee were inspected for a lateral femoral notch sign. MRIs of patients with a lateral condylopatellar sulcus ≥1.5 mm were used to segment and measure the lateral condylopatellar sulcus. The MRI examination was interpreted by an expert in musculoskeletal radiology. The study was approved by the ethics committee of the state of Salzburg.

Results: A "lateral femoral notch sign"was seen in 50 patients. The average total surface area of the lateral femoral condyle was 3271.7 mm(2) (SD 739.5 mm(2)). The defect had a mean surface area of 266.1 mm(2) (SD 125.5 mm(2)), a mean volume of 456.5 mm(3) (SD 278.5 mm(3)), a mean depth of 3.0 mm (SD 0.8 mm). On average 169 mm(2) (SD 99.6 mm(2)) of the surface of the condyle were affected by the impaction fracture which corresponds to 5.2% (SD 2.8%) of the surface of the lateral femoral condyle. In 51 % the impaction fracture was located in the central-external area of the femoral condyle.

Conclusions: In cases of a clinically suspected ACL rupture lateral radiographs of the knee should be checked for a lateral femoral notch sign further MRI for confirmation should be performed. Knowing of the precise defect on the lateral femoral condyle is an additionally valuable information, as concomitant injuries to a rupture of the anterior cruciate ligament increase the risk for early-onset osteoarthritis in the future.

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Figures

Fig. 1
Fig. 1
Measurement technique to determine the depth of the femoral notch on lateral x-rays
Fig. 2
Fig. 2
Segmentation of the MRI. (a) sagittal MRI with lateral femoral notch. Alignment of the axis: (b) line parallel to the axis of the femoral shaft running through the deepest point of the intercondylar notch (pink line), (c) most posterior aspect of the lateral femoral condyle (dark blue line), “weight bearing area” (light blue line), both parallel to the axis of the femoral shaft. (d)Segmentation of the defect: the subchondral bone area (green line), (e) marking of the defect (curved pink line), (f) area of the defect (light blue area)
Fig. 3
Fig. 3
Schematic figure of the segmentation of the lateral femoral condyle in six segments (2D, transversal): anterior-internal (AI), anterior-external (AE), central-internal (CI), central-external (CE), posterior-internal (PI), posterior-external (PE). Internal correlates to the medial aspect, external to the lateral aspect of the condyle. The red circle illustrates the average distribution of the affected areas of the lateral femoral condyle
See this image and copyright information in PMC

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