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Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction
THEKNE-02981; No of Pages 6 The Knee xxx (xxxx) xxx
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The Knee
Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction Guido Wierer a,⁎, Thomas Simetinger b, Martin Hudelmaier b, Philipp Moroder a,c, Thomas Hoffelner a,d a
Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Salzburg, Austria Institute of Anatomy and Cell Biology, Paracelsus Medical University Salzburg, Salzburg, Austria c Center for Musculoskeletal Surgery, Campus Virchow, Charitè-Universitätsmedizin Berlin, Berlin, Germany d Department of Orthopedic Surgery, St. Vincent Shoulder & Sports Clinic, Vienna, Austria b
a r t i c l e
i n f o
Article history: Received 8 August 2019 Received in revised form 18 December 2019 Accepted 21 January 2020 Available online xxxx
Background: The goal of this longitudinal study was to investigate the fate of the lateral femoral notch (LFN), which is frequently seen as an impaction fracture of the lateral femoral condyle in patients with anterior cruciate ligament (ACL) tears. Methods: Patients who underwent early ACL reconstruction between 2006 and 2010 were reviewed. If post-injury magnetic resonance images showed an LFN greater than 1.5 mm in depth, patients with untreated LFN were followed. Two blinded observers performed quantitative and qualitative imaging analysis. Results: Sixteen patients (five women, 11 men) were available for follow-up nine years (six to 10 years) post-injury. The median defect area of the LFN significantly decreased from 2.3 cm2 (range: 0.9–3.8 cm2) to 1.6 cm2 (range: 0.4–3.2 cm2) (P b .001). The defect depth did not significantly change from 2.3 mm (range: 2.0–3.6 mm) to 2.5 mm (range: 1.3–3.6 mm) (P N .05). The International Cartilage Repair Society (ICRS) score increased from 1.5 (range: 0–3) postinjury to 2.0 (range: 0–4) at follow-up (P b .01). The Lysholm score was 93 (72–100), the Tegner activity level was 6 (3–9) and the knee injury and osteoarthritis outcome score (KOOS) score was 97 (91–100). Conclusions: The defect area of the LFN decreased overtime, whereas the depth of the impression remained. Focal cartilage lesions were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying. © 2020 Elsevier B.V. All rights reserved.
1. Introduction One of the main mechanisms of anterior cruciate ligament (ACL) tears is a so-called pivot shift injury that results in anterior subluxation of the lateral tibial plateau [1,2]. Traumatic and recurrent subluxation of the lateral tibial plateau making contact with the lateral femoral condyle may cause an impaction fracture of the lateral femoral condyle, also known as the ‘lateral femoral notch sign’ (Figure 1(a)) [3–7]. If the impaction is deeper than 1.5 mm, it is a reliable secondary sign for an ACL injury and should not be mistaken for the physiological condylopatellar sulcus [8–10]. A recent quantitative magnetic resonance imaging (MRI) study showed that the impaction mainly affects the central area of the lateral femoral condyle, which equals more than 30% of ⁎ Corresponding author at: Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria. E-mail address: [email protected]. (G. Wierer).
https://doi.org/10.1016/j.knee.2020.01.009 0968-0160/© 2020 Elsevier B.V. All rights reserved.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
2
G. Wierer et al. / The Knee xxx (xxxx) xxx
A
B
Figure 1. (a) Lateral X-ray displays a lateral femoral notch (LFN) (arrows) and its depth measurement (red line) using the tangent method (black line) according to Warren et al. [30]. (b) Standardized segmentation of the subchondral area (green line) and LFN (asterisk) is demonstrated on sagittal magnetic resonance imaging (Figure 2(a)). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the weight-bearing area and therefore leads to the deformation of the articular surface [11]. However, not only deformation, but also higher cartilage degeneration is assumed due to altered MRI relaxation times one year post-injury [12]. Treatment options with either arthroscopic or open reduction have been described in a limited number of cases [13–15], although, the long-term consequences and evidence-based indications for operative treatment of a lateral femoral notch (LFN) are still unknown. The main goal of this longitudinal study was to evaluate the long-term development of the LFN including depth, volume and area of the defect. We hypothesize that the initial depth of the LFN does not decrease over time if left untreated during early ACL reconstruction. Furthermore, we investigated patient-reported outcome measurements, cartilage degeneration and signs of osteoarthritis, because these parameters may have an impact on treatment algorithms when counseling patients with an LFN. 2. Materials and methods 2.1. Subjects The department's knee database was reviewed between 2006 and 2010 for patients who sustained an acute ACL tear and concomitant LFN greater than 1.5 mm in depth (Figure 1(a)). If ACL reconstruction was performed within three months from injury and the LFN was left untreated during surgery, patients were invited for clinical and radiological follow-up. During the study period a total of 330 primary ACL reconstructions were performed of which 23 patients (seven percent) met the inclusion criteria. Sixteen patients (five women, 11 men) were available for follow-up. At the time of surgery the patients' median age was 24 years (range: 15–53 years) and the median body mass index was 26 (range 20–30). All patients underwent early arthroscopic single-bundle ACL reconstruction using ipsilateral hamstring autografts. Postoperatively patients were mobilized with partial weight bearing and limited flexion up to 90° for two weeks. Thereafter, full weight-bearing and unrestricted range of motion was permitted. Sports activities involving contact or pivot shifting were not recommended for six to nine months postoperatively. The local ethical committee approved this study (415-E/2059/2-2016) and all patients gave their written informed consent to participate in the study. 2.2. Radiological evaluation MRIs were performed using a Philips Ingenia 1.5 Tesla MRI scanner (Philips, Andover, USA) to obtain proton density weighted fast spin echo sequences (TR/TE = 3718/25 ms). Two blinded observers analyzed post-injury and follow-up MRIs using a Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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proprietary software for cartilage segmentation and quality-controlled data analysis (Chondrometrics GmbH, Ainring, Germany) as previously reported by Eckstein et al. [16,17] (Figure 1(b)). Segmentation of the lateral femoral condyle served for 3D reconstruction to measure the depth, area and volume of the LFN according to Hoffelner et al. [11]. In respect to the maximal depth of the LFN it was categorized as Grade 1 (1.5–3.9 mm) or Grade 2 (4.0 mm or more) as previously reported by Herbst et al. [7]. The focal cartilage of the LFN was evaluated according to the ICRS (International Cartilage Repair Society) grading system on post-injury and follow-up MRI [18,19]. Signs of osteoarthritis were classified using the Kellgren–Lawrence classification on bilateral weight-bearing posterior–anterior radiographs made with the knee at 45° of flexion at follow-up. 2.3. Clinical evaluation Patient-reported outcome measurements were evaluated at follow-up using a standardized questionnaire including the Lysholm score, knee injury and osteoarthritis outcome score (KOOS) and Tegner activity score. 2.4. Statistical analysis Descriptive statistics including median, minimum and maximum values of the variables were calculated. The Kolmogorov– Smirnov test was employed to test all variables for normal distribution. Non-normally distributed variables were compared by means of the two independent observers using the Wilcoxon signed-rank test. All P-values were two-tailed and the alpha level was set to 0.05. Statistical analysis was performed using SPSS v.24.0 (IBM Corp., Armonk, NY, USA). A post-hoc power analysis using G*Power 3.1.9.3 (Franz Paul, Kiel, Germany) was used to determine the power of the statistical test. The calculated effect size of 1.33 (mean difference and standard deviation of the defect area between post-injury and follow-up MRI) with an α of 0.05 and a sample size of 16 patients resulted in a power of 0.99. 3. Results 3.1. Radiological outcome The median defect area decreased significantly from 2.3 cm2 (range: 0.9–3.8 cm2) to 1.6 cm2 (range: 0.4–3.2 cm2) after a median follow-up of nine years (range: six to 10 years) (P b .001). The median defect volume decreased significantly from 0.4 cm3 (range: 0.1–0.8 cm3) to 0.3 cm3 (range: 0.1–0.6 cm3) (P b .001). However, the initial median defect depth of 2.3 mm (range: 2.0–3.6 mm) did not significantly change at follow-up (2.5 mm; range: 1.3–3.6 mm) (P N .05). The quantitative MRI measurements are shown in Table 1. Focal cartilage lesions within the LFN were seen in all except two patients post-injury. The median ICRS score increased from 1.5 (range: 0 to three) post-injury to 2.0 (range: 0 to four) at follow-up (P b .01). The median Kellgren–Lawrence score was 1.0 (range: 0 to three) at follow-up. 3.2. Clinical outcome The median Lysholm score was 93 (range: 72–100) and the median Tegner activity level was 6 (range: three to nine). The overall median KOOS was 97 (range: 91–100). Details of the different subgroups are shown in Figure 2. 4. Discussion The main finding of this study was that the defect area of the LFN decreased, whereas the depth remained if left untreated during early ACL reconstruction. Focal cartilage lesions of the LFN were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying in the long-term. Lodewijks et al. [9] recently confirmed that LFN deeper than 1.0 mm is a reliable indirect sign of a torn ACL. They found a positive predictive value of 96% with a high inter- and intra-observer reliability. According to Grimberg et al. [20] not only the depth, but also the location and shape, including a double LFN, seems a reliable indirect sign. Garth et al. [21] earlier revealed that a depression not meeting the reported radiographic depth but located two centimeters or more posterior to the distal extension of Blumensaat's line might be associated with an ACL tear. From intraoperative findings they reported articular cartilage fissures
Table 1 Magnetic resonance imaging of the lateral femoral notch.
Depth (mm) Area (cm2) Volume (cm3) ICRS
Post-injury
Follow-up
Δ
P
2.3 2.3 0.4 1.5
2.5 1.6 0.3 2.0
+0.2 −0.8 −0.1 +1.0
N0.05 b0.001 b0.001 b0.01
± ± ± ±
0.6 (2.0–3.6) 0.8 (0.9–3.8) 0.2 (0.1–0.8) 0.8 (0–3)
± ± ± ±
0.6 (1.3–3.6) 0.7 (0.4–3.2) 0.1 (0.1–0.6) 0.2 (0–4)
Results are shown as median ± standard deviation (range); Δ, median difference; ICRS, International Cartilage Repair Society grading system.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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Figure 2. Graph showing the final results (median, range) of the different KOOS (knee injury and osteoarthritis outcome score) subgroups including symptoms, pain, activities of daily living (ADL), function in sport and recreation, and knee-related quality of life (QoL).
in the plastically deformed portion of the LFN in all of their patients. These findings are in line with several short- to mid-term follow-up studies that reported thinning of the articular cartilage, chondrocyte degeneration and loss of proteoglycan due to bone bruises associated with acute ACL rupture [8,22–24]. Most recently Behzadi et al. [12] reported one-year post-injury prolonged T2 relaxation times of the anterolateral femoral condyle in patients with LFN compared to those without LFN after an ACL tear. However, it is not yet clear whether prolonged T2 relaxation times on MRI can reliably detect cartilage degradation [12]. The present data showed focal cartilage lesions with a median ICRS score of 1.5 in all except two patients post-injury that progressed with a median ICRS score of 1.0 during follow-up. Although the defect area of the subchondral impression was reduced significantly, the defect depth remained. Therefore, early weight bearing mobilization in case of an acute LFN might be contradicting. In fact, the LFN mainly affects the central area of the lateral femoral condyle including more than 30% of the weight bearing area [11]. According to general principles of fracture treatment, surgical reduction is recommended in displaced fractures causing an intra-articular incongruence greater than two millimeters [25]. Herbst et al. [7] described a LFN deeper than two millimeters in more than one-quarter of patients sustaining an acute ACL tear. The authors graded the LFN with a depth of 2.0–3.9 mm as grade I and the LFN deeper than 4.0 mm as grade II. In the present study no grade II notch was included. However, follow-up MRI of an excluded 24-year-old soccer player, who underwent arthroscopically assisted closed reduction and bone grafting of a five-millimeter-deep LFN, demonstrated anatomic reduction 10 years postoperatively (Figure 3(a), (b)) [15]. Consequently, there might be an indication for early surgical reduction in the presence of a deep LFN that leads to deformation of the articular surface [11]. Nevertheless, the present patient cohort with a grade I notch showed satisfying patient-reported outcome scores without any surgical intervention except early ACL reconstruction. Hence, indicating the ‘critical LFN’ for surgical intervention remains challenging and the question whether a grade II notch has to be reduced surgically is still unanswered. Concomitant lesions of the lateral meniscus occurred in half of our patients and are known to significantly correlate with the depth of an LFN [3,7,12]. Although lateral meniscus tears significantly correlated with increased rotatory instability in ACL-injured knees [26], the depth of the LFN itself did not correlate with greater rotatory knee laxity [3]. Therefore, the presence of an LFN itself might not be the right criteria for combined ACL and anterolateral reconstruction [27]. However, further research should
Figure 3. (a) Post-injury magnetic resonance image (MRI) of a 24-year-old soccer player showing a lateral femoral notch (LFN) grade II (arrows). Within 3 days from trauma the patient underwent arthroscopically assisted closed reduction, bone grafting and ACL reconstruction [15]. (b) Follow-up MRI 10 years post-injury demonstrates anatomic reduction of the LFN (arrows) and a minor focal cartilage lesion (International Cartilage Repair Society (ICRS) grade II).
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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Figure 4. (a) Post-injury magnetic resonance image (MRI) of a 26-year-old patient showing a lateral femoral notch (LFN) grade I (white arrows), kissing contusion of the posterolateral tibia (green arrows) and vertical tear of the posterior horn of the lateral meniscus (red arrow). (b) Follow-up MRI demonstrates a residual LFN (white arrows), impaction of the posterolateral tibia and subluxation of the posterior horn of the lateral meniscus (red arrows). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
investigate the correlation between the LFN and its possible concomitant lesions including the anterolateral complex. Especially because patients suffering an ACL tear during high-risk pivoting sports are prone to sustain a concomitant LFN lesion [7,9]. Another frequent concomitant injury of the LFN is a kissing lesion of the posterolateral tibia (Figure 4(a), (b)) [7,28,29]. Herbst et al. [7] previously found bone bruises of the posterolateral tibia in 97% of their cases. In the present study 11 of 16 patients (69%) had a concomitant tibial bone-bruise and three of them sustained a posterolateral impaction fracture. Further research might focus on these concomitant posterolateral tibial lesions and their impact on rotatory instability. A major limitation of this study was that the defect size of the LFN was potentially overestimated in patients with a deep native sulcus intercondylaris. This could be ruled out with MRI examination of the healthy knee. 5. Conclusions In the present study the lateral femoral notch did not show full recovery if left untreated during early ACL reconstruction. The area of the subchondral impression decreased, whereas the depth of the LFN remained. Focal cartilage lesions were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying if the lateral femoral notch was less than four millimeters deep during early ACL reconstruction. Declaration of competing interest Each author declares that he has no commercial associations (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. References [1] Fetto JF, Marshall JL. Injury to the anterior cruciate ligament producing the pivot-shift sign. J Bone Joint Surg Am 1979;61:710–4. [2] Kittl C, El-Daou H, Athwal KK, Gupte CM, Weiler A, Williams A, et al. The role of the anterolateral structures and the ACL in controlling laxity of the intact and ACLdeficient knee. Am J Sports Med 2016;44:15–8. [3] Kanakamedala AC, Burnham JM, Pfeiffer TR, Herbst E, Kowalczuk M, Popchak A, et al. Lateral femoral notch depth is not associated with increased rotatory instability in ACL-injured knees: a quantitative pivot shift analysis. Knee Surg Sports Traumatol Arthrosc 2018;26:1399–405. [4] Olsen O-E, Myklebust G, Engebretsen L, Bahr R. Injury mechanisms for anterior cruciate ligament injuries in team handball. Am J Sports Med 2004;32:1002–12. [5] Koga H, Nakamae A, Shima Y, Iwasa J, Myklebust G, Engebretsen L, et al. Mechanisms for noncontact anterior cruciate ligament injuries. Am J Sports Med 2010;38: 2218–25. [6] Bere T, Flørenes TW, Krosshaug T, Koga H, Nordsletten L, Irving C, et al. Mechanisms of anterior cruciate ligament injury in World Cup alpine skiing. Am J Sports Med 2011;39:1421–9. [7] Herbst E, Hoser C, Tecklenburg K, Filipovic M, Dallapozza C, Herbort M, et al. The lateral femoral notch sign following ACL injury: frequency, morphology and relation to meniscal injury and sports activity. Knee Surg Sports Traumatol Arthrosc 2015;23:2250–8. [8] Cobby MJ, Schweitzer ME, Resnick D. The deep lateral femoral notch: an indirect sign of a torn anterior cruciate ligament. Radiology 1992;184:855–8. [9] Lodewijks PCAM, Delawi D, Bollen TL, Dijkhuis GR, Wolterbeek N, Zijl JAC. The lateral femoral notch sign: a reliable diagnostic measurement in acute anterior cruciate ligament injury. Knee Surg Sports Traumatol Arthrosc 2019;27:659–64. [10] Gentili A, Seeger LL, Yao L, Do HM. Anterior cruciate ligament tear: indirect signs at MR imaging. Radiology 1994;193:835–40. [11] Hoffelner T, Pichler I, Moroder P, Osti M, Hudelmaier M, Wirth W, et al. Segmentation of the lateral femoral notch sign with MRI using a new measurement technique. BMC Musculoskelet Disord 2015;16:217. [12] Behzadi C, Welsch GH, Petersen J-P, Schoennagel BP, Bannas P, Kaul MG, et al. T2 relaxation times of the anterolateral femoral cartilage in patients after ACLreconstruction with and without a deep lateral femoral notch sign. Eur J Radiol 2018;106:85–91.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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[13] Garth WPJ, Wilson T. Open reduction of a lateral femoral notch associated with an acute anterior cruciate ligament tear. Arthroscopy 2001;17:874–7. [14] Sadlo PA, Nebelung W. Arthroscopically assisted reduction of a lateral femoral notch in acute tear of the anterior cruciate ligament. Arthroscopy 2006;22:574. [15] Tauber M, Fox M, Koller H, Klampfer H, Resch H. Arthroscopic treatment of a large lateral femoral notch in acute anterior cruciate ligament tear. Arch Orthop Trauma Surg 2008;128:1313–6. [16] Eckstein F, Benichou O, Wirth W, Nelson DR, Maschek S, Hudelmaier M, et al. Magnetic resonance imaging-based cartilage loss in painful contralateral knees with and without radiographic joint space narrowing: data from the osteoarthritis initiative. Arthritis Rheum 2009;61:1218–25. [17] Wirth W, Hellio Le Graverand M-P, Wyman BT, Maschek S, Hudelmaier M, Hitzl W, et al. Regional analysis of femorotibial cartilage loss in a subsample from the osteoarthritis initiative progression subcohort. Osteoarthr Cartil 2009;17:291–7. [18] Casula V, Hirvasniemi J, Lehenkari P, Ojala R, Haapea M, Saarakkala S, et al. Association between quantitative MRI and ICRS arthroscopic grading of articular cartilage. Knee Surg Sports Traumatol Arthrosc 2016;24:2046–54. [19] Brittberg M, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Joint Surg 2003;85:58–69. [20] Grimberg A, Shirazian H, Torshizy H, Smitaman E, Chang EY, Resnick DL. Deep lateral notch sign and double notch sign in complete tears of the anterior cruciate ligament: MR imaging evaluation. Skeletal Radiol 2014;44:385–91. [21] Garth WP, Greco J, House M a. The lateral notch sign associated with acute anterior cruciate ligament disruption. Am J Sports Med 2000;28:68–73. [22] Faber KJ, Dill JR, Amendola A, Thain L, Spouge A, Fowler PJ. Occult osteochondral lesions after anterior cruciate ligament rupture. Am J Sports Med 1999;27: 489–94. [23] Johnson DL, Urban WP, Caborn DNM, Vanarthos WJ, Carlson CS. Articular cartilage changes seen with magnetic resonance imaging-detected bone bruises associated with acute anterior cruciate ligament rupture. Am J Sports Med 1998;26:409–14. [24] Nakamae A, Engebretsen L, Bahr R, Krosshaug T, Ochi M. Natural history of bone bruises after acute knee injury: clinical outcome and histopathological findings. Knee Surg Sports Traumatol Arthrosc 2006;14:1252–8. [25] Parkkinen M, Madanat R, Mustonen A, Koskinen SK, Paavola M, Lindahl J. Factors predicting the development of early osteoarthritis following lateral tibial plateau fractures: mid-term clinical and radiographic outcomes of 73 operatively treated patients. Scand J Surg 2014;103:256–62. [26] Katakura M, Horie M, Watanabe T, Katagiri H, Otabe K, Ohara T, et al. Effect of meniscus repair on pivot-shift during anterior cruciate ligament reconstruction: objective evaluation using triaxial accelerometer. Knee 2019;26:124–31. [27] Sonnery-Cottet B, Thaunat M, Freychet B, Pupim BHB, Murphy CG, Claes S. Outcome of a combined anterior cruciate ligament and anterolateral ligament reconstruction technique with a minimum 2-year follow-up. Am J Sports Med 2015;43:1598–605. [28] Yoon KH, Yoo JH, Kim K. Il. Bone contusion and associated meniscal and medial collateral ligament injury in patients with anterior cruciate ligament rupture. J Bone Jt Surg Am 2011;93:1510–8. [29] Kaplan PA, Walker CW, Kilcoyne RF, Brown DE, Tusek D, Dussault RG. Occult fracture patterns of the knee associated with anterior cruciate ligament tears: assessment with MR imaging. Radiology 1992;183:835–8. [30] Warren RF, Bach Jr BR. The lateral notch sign of anterior cruciate ligament. Am J Knee Surg 1988;1:119–24.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
Contents lists available at ScienceDirect
The Knee
Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction Guido Wierer a,⁎, Thomas Simetinger b, Martin Hudelmaier b, Philipp Moroder a,c, Thomas Hoffelner a,d a
Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Salzburg, Austria Institute of Anatomy and Cell Biology, Paracelsus Medical University Salzburg, Salzburg, Austria c Center for Musculoskeletal Surgery, Campus Virchow, Charitè-Universitätsmedizin Berlin, Berlin, Germany d Department of Orthopedic Surgery, St. Vincent Shoulder & Sports Clinic, Vienna, Austria b
a r t i c l e
i n f o
Article history: Received 8 August 2019 Received in revised form 18 December 2019 Accepted 21 January 2020 Available online xxxx
Background: The goal of this longitudinal study was to investigate the fate of the lateral femoral notch (LFN), which is frequently seen as an impaction fracture of the lateral femoral condyle in patients with anterior cruciate ligament (ACL) tears. Methods: Patients who underwent early ACL reconstruction between 2006 and 2010 were reviewed. If post-injury magnetic resonance images showed an LFN greater than 1.5 mm in depth, patients with untreated LFN were followed. Two blinded observers performed quantitative and qualitative imaging analysis. Results: Sixteen patients (five women, 11 men) were available for follow-up nine years (six to 10 years) post-injury. The median defect area of the LFN significantly decreased from 2.3 cm2 (range: 0.9–3.8 cm2) to 1.6 cm2 (range: 0.4–3.2 cm2) (P b .001). The defect depth did not significantly change from 2.3 mm (range: 2.0–3.6 mm) to 2.5 mm (range: 1.3–3.6 mm) (P N .05). The International Cartilage Repair Society (ICRS) score increased from 1.5 (range: 0–3) postinjury to 2.0 (range: 0–4) at follow-up (P b .01). The Lysholm score was 93 (72–100), the Tegner activity level was 6 (3–9) and the knee injury and osteoarthritis outcome score (KOOS) score was 97 (91–100). Conclusions: The defect area of the LFN decreased overtime, whereas the depth of the impression remained. Focal cartilage lesions were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying. © 2020 Elsevier B.V. All rights reserved.
1. Introduction One of the main mechanisms of anterior cruciate ligament (ACL) tears is a so-called pivot shift injury that results in anterior subluxation of the lateral tibial plateau [1,2]. Traumatic and recurrent subluxation of the lateral tibial plateau making contact with the lateral femoral condyle may cause an impaction fracture of the lateral femoral condyle, also known as the ‘lateral femoral notch sign’ (Figure 1(a)) [3–7]. If the impaction is deeper than 1.5 mm, it is a reliable secondary sign for an ACL injury and should not be mistaken for the physiological condylopatellar sulcus [8–10]. A recent quantitative magnetic resonance imaging (MRI) study showed that the impaction mainly affects the central area of the lateral femoral condyle, which equals more than 30% of ⁎ Corresponding author at: Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Muellner Hauptstrasse 48, 5020 Salzburg, Austria. E-mail address: [email protected]. (G. Wierer).
https://doi.org/10.1016/j.knee.2020.01.009 0968-0160/© 2020 Elsevier B.V. All rights reserved.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
2
G. Wierer et al. / The Knee xxx (xxxx) xxx
A
B
Figure 1. (a) Lateral X-ray displays a lateral femoral notch (LFN) (arrows) and its depth measurement (red line) using the tangent method (black line) according to Warren et al. [30]. (b) Standardized segmentation of the subchondral area (green line) and LFN (asterisk) is demonstrated on sagittal magnetic resonance imaging (Figure 2(a)). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
the weight-bearing area and therefore leads to the deformation of the articular surface [11]. However, not only deformation, but also higher cartilage degeneration is assumed due to altered MRI relaxation times one year post-injury [12]. Treatment options with either arthroscopic or open reduction have been described in a limited number of cases [13–15], although, the long-term consequences and evidence-based indications for operative treatment of a lateral femoral notch (LFN) are still unknown. The main goal of this longitudinal study was to evaluate the long-term development of the LFN including depth, volume and area of the defect. We hypothesize that the initial depth of the LFN does not decrease over time if left untreated during early ACL reconstruction. Furthermore, we investigated patient-reported outcome measurements, cartilage degeneration and signs of osteoarthritis, because these parameters may have an impact on treatment algorithms when counseling patients with an LFN. 2. Materials and methods 2.1. Subjects The department's knee database was reviewed between 2006 and 2010 for patients who sustained an acute ACL tear and concomitant LFN greater than 1.5 mm in depth (Figure 1(a)). If ACL reconstruction was performed within three months from injury and the LFN was left untreated during surgery, patients were invited for clinical and radiological follow-up. During the study period a total of 330 primary ACL reconstructions were performed of which 23 patients (seven percent) met the inclusion criteria. Sixteen patients (five women, 11 men) were available for follow-up. At the time of surgery the patients' median age was 24 years (range: 15–53 years) and the median body mass index was 26 (range 20–30). All patients underwent early arthroscopic single-bundle ACL reconstruction using ipsilateral hamstring autografts. Postoperatively patients were mobilized with partial weight bearing and limited flexion up to 90° for two weeks. Thereafter, full weight-bearing and unrestricted range of motion was permitted. Sports activities involving contact or pivot shifting were not recommended for six to nine months postoperatively. The local ethical committee approved this study (415-E/2059/2-2016) and all patients gave their written informed consent to participate in the study. 2.2. Radiological evaluation MRIs were performed using a Philips Ingenia 1.5 Tesla MRI scanner (Philips, Andover, USA) to obtain proton density weighted fast spin echo sequences (TR/TE = 3718/25 ms). Two blinded observers analyzed post-injury and follow-up MRIs using a Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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proprietary software for cartilage segmentation and quality-controlled data analysis (Chondrometrics GmbH, Ainring, Germany) as previously reported by Eckstein et al. [16,17] (Figure 1(b)). Segmentation of the lateral femoral condyle served for 3D reconstruction to measure the depth, area and volume of the LFN according to Hoffelner et al. [11]. In respect to the maximal depth of the LFN it was categorized as Grade 1 (1.5–3.9 mm) or Grade 2 (4.0 mm or more) as previously reported by Herbst et al. [7]. The focal cartilage of the LFN was evaluated according to the ICRS (International Cartilage Repair Society) grading system on post-injury and follow-up MRI [18,19]. Signs of osteoarthritis were classified using the Kellgren–Lawrence classification on bilateral weight-bearing posterior–anterior radiographs made with the knee at 45° of flexion at follow-up. 2.3. Clinical evaluation Patient-reported outcome measurements were evaluated at follow-up using a standardized questionnaire including the Lysholm score, knee injury and osteoarthritis outcome score (KOOS) and Tegner activity score. 2.4. Statistical analysis Descriptive statistics including median, minimum and maximum values of the variables were calculated. The Kolmogorov– Smirnov test was employed to test all variables for normal distribution. Non-normally distributed variables were compared by means of the two independent observers using the Wilcoxon signed-rank test. All P-values were two-tailed and the alpha level was set to 0.05. Statistical analysis was performed using SPSS v.24.0 (IBM Corp., Armonk, NY, USA). A post-hoc power analysis using G*Power 3.1.9.3 (Franz Paul, Kiel, Germany) was used to determine the power of the statistical test. The calculated effect size of 1.33 (mean difference and standard deviation of the defect area between post-injury and follow-up MRI) with an α of 0.05 and a sample size of 16 patients resulted in a power of 0.99. 3. Results 3.1. Radiological outcome The median defect area decreased significantly from 2.3 cm2 (range: 0.9–3.8 cm2) to 1.6 cm2 (range: 0.4–3.2 cm2) after a median follow-up of nine years (range: six to 10 years) (P b .001). The median defect volume decreased significantly from 0.4 cm3 (range: 0.1–0.8 cm3) to 0.3 cm3 (range: 0.1–0.6 cm3) (P b .001). However, the initial median defect depth of 2.3 mm (range: 2.0–3.6 mm) did not significantly change at follow-up (2.5 mm; range: 1.3–3.6 mm) (P N .05). The quantitative MRI measurements are shown in Table 1. Focal cartilage lesions within the LFN were seen in all except two patients post-injury. The median ICRS score increased from 1.5 (range: 0 to three) post-injury to 2.0 (range: 0 to four) at follow-up (P b .01). The median Kellgren–Lawrence score was 1.0 (range: 0 to three) at follow-up. 3.2. Clinical outcome The median Lysholm score was 93 (range: 72–100) and the median Tegner activity level was 6 (range: three to nine). The overall median KOOS was 97 (range: 91–100). Details of the different subgroups are shown in Figure 2. 4. Discussion The main finding of this study was that the defect area of the LFN decreased, whereas the depth remained if left untreated during early ACL reconstruction. Focal cartilage lesions of the LFN were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying in the long-term. Lodewijks et al. [9] recently confirmed that LFN deeper than 1.0 mm is a reliable indirect sign of a torn ACL. They found a positive predictive value of 96% with a high inter- and intra-observer reliability. According to Grimberg et al. [20] not only the depth, but also the location and shape, including a double LFN, seems a reliable indirect sign. Garth et al. [21] earlier revealed that a depression not meeting the reported radiographic depth but located two centimeters or more posterior to the distal extension of Blumensaat's line might be associated with an ACL tear. From intraoperative findings they reported articular cartilage fissures
Table 1 Magnetic resonance imaging of the lateral femoral notch.
Depth (mm) Area (cm2) Volume (cm3) ICRS
Post-injury
Follow-up
Δ
P
2.3 2.3 0.4 1.5
2.5 1.6 0.3 2.0
+0.2 −0.8 −0.1 +1.0
N0.05 b0.001 b0.001 b0.01
± ± ± ±
0.6 (2.0–3.6) 0.8 (0.9–3.8) 0.2 (0.1–0.8) 0.8 (0–3)
± ± ± ±
0.6 (1.3–3.6) 0.7 (0.4–3.2) 0.1 (0.1–0.6) 0.2 (0–4)
Results are shown as median ± standard deviation (range); Δ, median difference; ICRS, International Cartilage Repair Society grading system.
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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Figure 2. Graph showing the final results (median, range) of the different KOOS (knee injury and osteoarthritis outcome score) subgroups including symptoms, pain, activities of daily living (ADL), function in sport and recreation, and knee-related quality of life (QoL).
in the plastically deformed portion of the LFN in all of their patients. These findings are in line with several short- to mid-term follow-up studies that reported thinning of the articular cartilage, chondrocyte degeneration and loss of proteoglycan due to bone bruises associated with acute ACL rupture [8,22–24]. Most recently Behzadi et al. [12] reported one-year post-injury prolonged T2 relaxation times of the anterolateral femoral condyle in patients with LFN compared to those without LFN after an ACL tear. However, it is not yet clear whether prolonged T2 relaxation times on MRI can reliably detect cartilage degradation [12]. The present data showed focal cartilage lesions with a median ICRS score of 1.5 in all except two patients post-injury that progressed with a median ICRS score of 1.0 during follow-up. Although the defect area of the subchondral impression was reduced significantly, the defect depth remained. Therefore, early weight bearing mobilization in case of an acute LFN might be contradicting. In fact, the LFN mainly affects the central area of the lateral femoral condyle including more than 30% of the weight bearing area [11]. According to general principles of fracture treatment, surgical reduction is recommended in displaced fractures causing an intra-articular incongruence greater than two millimeters [25]. Herbst et al. [7] described a LFN deeper than two millimeters in more than one-quarter of patients sustaining an acute ACL tear. The authors graded the LFN with a depth of 2.0–3.9 mm as grade I and the LFN deeper than 4.0 mm as grade II. In the present study no grade II notch was included. However, follow-up MRI of an excluded 24-year-old soccer player, who underwent arthroscopically assisted closed reduction and bone grafting of a five-millimeter-deep LFN, demonstrated anatomic reduction 10 years postoperatively (Figure 3(a), (b)) [15]. Consequently, there might be an indication for early surgical reduction in the presence of a deep LFN that leads to deformation of the articular surface [11]. Nevertheless, the present patient cohort with a grade I notch showed satisfying patient-reported outcome scores without any surgical intervention except early ACL reconstruction. Hence, indicating the ‘critical LFN’ for surgical intervention remains challenging and the question whether a grade II notch has to be reduced surgically is still unanswered. Concomitant lesions of the lateral meniscus occurred in half of our patients and are known to significantly correlate with the depth of an LFN [3,7,12]. Although lateral meniscus tears significantly correlated with increased rotatory instability in ACL-injured knees [26], the depth of the LFN itself did not correlate with greater rotatory knee laxity [3]. Therefore, the presence of an LFN itself might not be the right criteria for combined ACL and anterolateral reconstruction [27]. However, further research should
Figure 3. (a) Post-injury magnetic resonance image (MRI) of a 24-year-old soccer player showing a lateral femoral notch (LFN) grade II (arrows). Within 3 days from trauma the patient underwent arthroscopically assisted closed reduction, bone grafting and ACL reconstruction [15]. (b) Follow-up MRI 10 years post-injury demonstrates anatomic reduction of the LFN (arrows) and a minor focal cartilage lesion (International Cartilage Repair Society (ICRS) grade II).
Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009
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Figure 4. (a) Post-injury magnetic resonance image (MRI) of a 26-year-old patient showing a lateral femoral notch (LFN) grade I (white arrows), kissing contusion of the posterolateral tibia (green arrows) and vertical tear of the posterior horn of the lateral meniscus (red arrow). (b) Follow-up MRI demonstrates a residual LFN (white arrows), impaction of the posterolateral tibia and subluxation of the posterior horn of the lateral meniscus (red arrows). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
investigate the correlation between the LFN and its possible concomitant lesions including the anterolateral complex. Especially because patients suffering an ACL tear during high-risk pivoting sports are prone to sustain a concomitant LFN lesion [7,9]. Another frequent concomitant injury of the LFN is a kissing lesion of the posterolateral tibia (Figure 4(a), (b)) [7,28,29]. Herbst et al. [7] previously found bone bruises of the posterolateral tibia in 97% of their cases. In the present study 11 of 16 patients (69%) had a concomitant tibial bone-bruise and three of them sustained a posterolateral impaction fracture. Further research might focus on these concomitant posterolateral tibial lesions and their impact on rotatory instability. A major limitation of this study was that the defect size of the LFN was potentially overestimated in patients with a deep native sulcus intercondylaris. This could be ruled out with MRI examination of the healthy knee. 5. Conclusions In the present study the lateral femoral notch did not show full recovery if left untreated during early ACL reconstruction. The area of the subchondral impression decreased, whereas the depth of the LFN remained. Focal cartilage lesions were found in all except two patients post-injury and progressed during follow-up. However, patient-reported outcome scores were satisfying if the lateral femoral notch was less than four millimeters deep during early ACL reconstruction. Declaration of competing interest Each author declares that he has no commercial associations (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. References [1] Fetto JF, Marshall JL. Injury to the anterior cruciate ligament producing the pivot-shift sign. J Bone Joint Surg Am 1979;61:710–4. [2] Kittl C, El-Daou H, Athwal KK, Gupte CM, Weiler A, Williams A, et al. The role of the anterolateral structures and the ACL in controlling laxity of the intact and ACLdeficient knee. Am J Sports Med 2016;44:15–8. [3] Kanakamedala AC, Burnham JM, Pfeiffer TR, Herbst E, Kowalczuk M, Popchak A, et al. Lateral femoral notch depth is not associated with increased rotatory instability in ACL-injured knees: a quantitative pivot shift analysis. Knee Surg Sports Traumatol Arthrosc 2018;26:1399–405. [4] Olsen O-E, Myklebust G, Engebretsen L, Bahr R. Injury mechanisms for anterior cruciate ligament injuries in team handball. Am J Sports Med 2004;32:1002–12. [5] Koga H, Nakamae A, Shima Y, Iwasa J, Myklebust G, Engebretsen L, et al. Mechanisms for noncontact anterior cruciate ligament injuries. Am J Sports Med 2010;38: 2218–25. [6] Bere T, Flørenes TW, Krosshaug T, Koga H, Nordsletten L, Irving C, et al. Mechanisms of anterior cruciate ligament injury in World Cup alpine skiing. Am J Sports Med 2011;39:1421–9. [7] Herbst E, Hoser C, Tecklenburg K, Filipovic M, Dallapozza C, Herbort M, et al. The lateral femoral notch sign following ACL injury: frequency, morphology and relation to meniscal injury and sports activity. Knee Surg Sports Traumatol Arthrosc 2015;23:2250–8. [8] Cobby MJ, Schweitzer ME, Resnick D. The deep lateral femoral notch: an indirect sign of a torn anterior cruciate ligament. Radiology 1992;184:855–8. [9] Lodewijks PCAM, Delawi D, Bollen TL, Dijkhuis GR, Wolterbeek N, Zijl JAC. The lateral femoral notch sign: a reliable diagnostic measurement in acute anterior cruciate ligament injury. Knee Surg Sports Traumatol Arthrosc 2019;27:659–64. [10] Gentili A, Seeger LL, Yao L, Do HM. Anterior cruciate ligament tear: indirect signs at MR imaging. Radiology 1994;193:835–40. [11] Hoffelner T, Pichler I, Moroder P, Osti M, Hudelmaier M, Wirth W, et al. Segmentation of the lateral femoral notch sign with MRI using a new measurement technique. BMC Musculoskelet Disord 2015;16:217. [12] Behzadi C, Welsch GH, Petersen J-P, Schoennagel BP, Bannas P, Kaul MG, et al. T2 relaxation times of the anterolateral femoral cartilage in patients after ACLreconstruction with and without a deep lateral femoral notch sign. Eur J Radiol 2018;106:85–91.
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Please cite this article as: G. Wierer, T. Simetinger, M. Hudelmaier, et al., Fate of the lateral femoral notch following early anterior cruciate ligament reconstruction, The Knee, https://doi.org/10.1016/j.knee.2020.01.009