The Use of Fluoroscopy Leads to Improved Identiﬁcation of the Femoral Lateral Collateral Ligament Origin Site When Compared With Traditional Tactile Techniques Thomas R. Pfeiffer, M.D., Elmar Herbst, M.D., Ajay C. Kanakamedala, B.S., Jan-Hendrik Naendrup, B.S., Richard E. Debski, Ph.D., and Volker Musahl, M.D.
Purpose: To determine whether a ﬂuoroscopic technique can be used to improve the accuracy of the determination of the femoral origin of the lateral collateral ligament (LCL). Methods: A 1-cm incision was made over the lateral epicondyle in 13 fresh-frozen cadaveric knee specimens, and the LCL origin was determined ﬁrst by palpation and then with a previously described ﬂuoroscopic method. Both points for the LCL origin were marked with 2-mm Kirschner wires. The distances between the center of the anatomic LCL origin and the LCL origin points determined by palpation and ﬂuoroscopic imaging were calculated. An independent t-test was used to compare the distances between the anatomic LCL origin center and the determined LCL origin points. Results: The LCL origin points determined by ﬂuoroscopic imaging were signiﬁcantly (P ¼ .005) closer to the anatomic center of the LCL origin point than the ones determined by palpation (3.2 mm 1.6 mm vs 5.0 mm 1.6 mm, respectively). A total of 92.7% ﬂuoroscopically determined LCL origin points were within a 5 mm radius surrounding the anatomic LCL origin point. In contrast, only 53.8% LCL origin points determined by palpation were within a 5 mm radius surrounding the anatomic LCL origin point. Conclusions: The use of palpation to identify the LCL origin may not be an accurate method for performing an isometric and anatomic LCL reconstruction. The use of ﬂuoroscopic imaging appears to be a feasible method for identifying the LCL origin in clinical practice and may increase the accuracy of LCL origin identiﬁcation. Fluoroscopic guidance improves accuracy in determining the anatomic LCL origin, which may help avoiding tunnel malplacement during LCL reconstruction. Clinical Relevance: The use of a previously described radiographic method for identifying the LCL origin may be used to achieve a more anatomic LCL reconstruction.
he identiﬁcation of the lateral collateral ligament (LCL) origin is paramount to performing a successful LCL reconstruction,1 and various surgical
From the Department of Orthopaedic Surgery, Trauma Surgery and Sports Medicine Cologne Merheim Medical Center, Witten/Herdecke University (T.R.P., J-H.N.), Cologne, Germany; Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh (T.R.P., E.H., A.C.K., J-H.N., R.E.D., V.M.), Pittsburgh, Pennsylvania, U.S.A.; and the Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technical University Munich (E.H.), Munich, Germany. The authors report that they have no conﬂicts of interest in the authorship and publication of this article. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received November 9, 2017; accepted March 26, 2018. Address correspondence to Volker Musahl, M.D., Department of Orthopaedic Surgery, Center for Sports Medicine, University of Pittsburgh, 3200 S Water Street, Pittsburgh, PA 15203, U.S.A. E-mail: [email protected]
Ó 2018 by the Arthroscopy Association of North America 0749-8063/171371/$36.00 https://doi.org/10.1016/j.arthro.2018.03.035
techniques have been described.2-4 Typically, during LCL reconstruction, the LCL origin point is identiﬁed by a lateral incision and manual palpation using the lateral femoral epicondyle as an anatomic landmark.2,3,5-7 However, recent studies have suggested that the LCL may not originate on the center of the lateral epicondyle.8-12 Rather, it may originate at a point 3.1 to 4.6 mm posterior to the apex of the lateral epicondyle, which suggests that the aforementioned method of palpation may not be an accurate way to identify the anatomic origin of the LCL.9,10 Moreover, tissue attrition and soft tissue swelling may make identiﬁcation of anatomical landmarks challenging in the intraoperative setting,13,14 thus also reducing the use of palpation. The current trend toward minimally invasive procedures for complex reconstructions and revision operations has also made it more difﬁcult to identify the origin of the LCL by palpation. One cadaveric study found that placing the LCL origin farther than 5 mm
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from the center of the LCL origin leads to decreased isometry and increased residual instability,1 highlighting the clinical importance of anatomic LCL reconstruction. Given the importance of identiﬁcation of the anatomic LCL origin point for successful outcomes after LCL reconstruction as well as the aforementioned trend toward reducing the invasiveness of these surgeries, there is a need for a minimally invasive technique for identifying the LCL origin point. An ideal technique would be easy to learn, repeatable, and more accurate than other comparable methods. The use of radiographic imaging may offer such a method. Reproducible intraoperative radiographic landmarks are already commonly used in various other orthopaedic procedures such as medial patellofemoral ligament reconstruction.15 LCL reconstruction is similarly amenable to the use of intraoperative ﬂuoroscopy. It was recently shown that a ﬂuoroscopic technique could be used to identify the LCL origin point. This technique ﬁnds the average position of the LCL origin to be at a point 58% of the anterior to posterior femur length across the Blumensaat line and 2.3 mm inferior on a lateral radiograph.13 Further data on the reliability and accuracy would be valuable in conﬁrming the accuracy, reliability, and reproducibility of this technique. The purpose of this cadaveric study was to determine whether a ﬂuoroscopic technique can be used to improve the accuracy of the determination of the femoral origin of the LCL. It was hypothesized that, when compared with palpation of the lateral femoral epicondyle, the use of ﬂuoroscopic imaging to determine the LCL origin point would lead to more accurate identiﬁcation of the origin site of the LCL, that is, decreased distance between the identiﬁed point and the anatomic center of the anatomic origin of the LCL.
Methods Thirteen fresh-frozen cadaveric knee specimens intact from the distal femur to proximal tibia were obtained and thawed for 24 hours. Each specimen was placed in 90 of ﬂexion. A 1-cm horizontal incision over the lateral epicondyle identiﬁed by palpation was made on the lateral side of the knee. A Kelly clamp was used to dissect away subcutaneous tissue and fascia to reach the capsule. The lateral epicondyle of the femur, the popliteal tendon, and the proximal ﬁbers of the LCL, inserting into the posterior edge of the epicondyle, were then palpated and used as guiding landmarks. When the examiner identiﬁed the area, in which the origin of the LCL was assumed, the position was marked manually with the tip of the index ﬁnger. Guided by the ﬁngertip, a 2-mm Kirschner wire (K-wire) was drilled into the palpated origin of the LCL; in most of the
Fig 1. Depiction of the ﬂuoroscopically determined “Kamath ideal” point, on a straight lateral radiograph of a left knee using the method of Kamath et al.13 The average position of the lateral collateral ligament (LCL) insertion was found to be at a point 58% of the anterior-posterior femur length across the Blumensaat line and 2.3 mm inferior to the Blumensaat line. K-wires are visible, marking the LCL insertion point determined by palpation (K-wire mark 1) and ﬂuoroscopy (K-wire mark 3) and the anatomic center of the LCL insertion point (K-wire mark 2).
specimens, this point was slightly posterior to the tip of the lateral epicondyle. A radiographic technique for determining the origin of the LCL was then performed as previously described.12 Brieﬂy, a straight lateral radiograph was obtained of each knee specimen using a live ﬂuoroscopic imaging device (Fluoroscan InSight Mini C-Arm System; Hologic, Marlborough, MA). For each radiograph, a line corresponding to the Blumensaat line was drawn across the lateral femoral condyle. A point was then marked on the lateral femoral condyle at a point 58% from the anterior to the posterior ends of the Blumensaat line and 2.3 mm inferior to the Blumensaat line on a perpendicular line (Fig 1). To simulate the setting of the operating room and to determine the effectiveness and practicality of this method in the clinical setting, these radiographic measurements were ﬁrst performed by gross inspection without the use of any measurement tools or supportive devices, and a K-wire was drilled into the identiﬁed point, that is, the ﬂuoroscopic LCL origin point. This was done by ﬁrst identifying the anterior to posterior midpoint of the lateral femoral condyle and then placing the K-wire slightly posterior, that is, about a tenth of the total anterior to posterior length of the lateral femoral condyle, to that point. All subcutaneous tissue, fascia, and capsular structures were then dissected away until only the femur, tibia, and ligamentous structures were remaining. The anatomic LCL origin area was dissected, and the center was marked with a radiographic radiolucent marker. The 2
IDENTIFICATION OF THE FEMORAL LCL ORIGIN
previously inserted K-wires were cut to a length of 2 mm. A second straight lateral radiograph, which also included the 13.0-mm reference marker for measurement purposes, was obtained. Radiographic measurements were then performed as previously described by Kamath et al. using Image J Software (NIH, Bethesda, MD) to determine the LCL origin point, termed the “Kamath ideal” point. Using the reference marker, the marked radiographs were scaled and analyzed with Image J Software. Based on the 13.0-mm reference marker and Image J software, the precision of these measurements was 0.1 mm. The coordinates of the center of the radiolucent marker identifying the dissected center of the anatomic LCL origin site were then used as the ideal anatomic point. This point was then compared with the 3 other identiﬁed points, that is, the palpated origin point, the ﬂuoroscopic origin point, and the “Kamath ideal” point, and the distances between the anatomic LCL origin site and these 3 other points were calculated. The identiﬁcation of the palpated origin point, the ﬂuoroscopic origin point, and the anatomic LCL origin site was performed independently by 2 resident orthopaedic surgeons (T.R.P. and E.H.) trained in the use of ﬂuoroscopy. One resident performed the entire protocol on 6 specimens, and 1 performed it on 7 specimens. To determine the intraobserver reliability for the measurement protocol, the primary observer (T.R.P.) completed all measurements a second time at a separate sitting 1 week later. To determine interobserver reliability, a second blinded and independent observer (J-H.N.) performed all measurements. An intraclass correlation coefﬁcient (ICC) was calculated for the measurements of the 2 observers. To qualify the ICC, the following commonly used guidelines were set: (ICC 0.2) slight agreement; (0.21 ICC 0.40) fair agreement; (0.41 ICC 0.60) moderate agreement; and (0.61 ICC 0.80; 0.81 ICC 1) almost perfect agreement.16 Descriptive statistics, including means and standard deviations, were calculated for continuous data. An independent t-test was used to compare the distances between the anatomic LCL origin point and the determined LCL origin points. McNemar’s test was used for nominal dichotomous results. All statistical analyses were performed using SPSS software (v24; IBM). Using G*Power 22.214.171.124 (Franz Paul, Kiel, Germany), a post hoc power analysis was performed to determine the power of the present study. Using the results of the t-test comparing the differences between determination by ﬂuoroscopy and palpation with respect to the distance to the anatomic center of the LCL origin point, an effect size of 0.94 was calculated. Using this effect size, as well as a ¼ 0.05 and sample size of n ¼ 13, a power of 0.93 was determined.
Table 1. Descriptive Statistics for the Specimens Used in This Study No. of specimens Mean age (yr) No. of specimens per examiner Examiner 1 Examiner 2 Gender Male Female Side Left Right
13 62.5 5.8 6 7 9 4 8 5
Thirteen specimens were included in the ﬁnal analysis. Descriptive statistics are listed in Table 1. The distances from the anatomic LCL origin point to the LCL origin points determined by palpation and ﬂuoroscopic imaging were 5.0 mm 1.6 mm and 3.2 mm 1.6 mm, respectively. There was a signiﬁcant difference between these 2 methods (P ¼ .005). The distribution of the LCL origin points determined by palpation and ﬂuoroscopic imaging is shown in Figure 2. There was greater variance when determining the LCL origin point by palpation and less LCL origin points positioned within a 5 mm radius (Appendix Table 1). The distribution of LCL origin points within 5 mm and 3 mm radii around the anatomic LCL origin point is shown in Table 2. One of 13 (7.7%) of the LCL origin points determined by ﬂuoroscopic imaging was out of the critical radius of 5 mm around the anatomic LCL origin. In contrast, 5 of 13 (38.5%) of the palpated LCL origin points were out of the critical radius of 5 mm around the anatomic LCL origin. There was a statistically signiﬁcant difference in the number of points within the critical radius of 5 mm determined by ﬂuoroscopy and palpation (P ¼ .045). The average distances from the palpated and ﬂuoroscopically determined LCL origin points to the center of the anatomic LCL origin point as well as the standard deviation for each examiner are illustrated in Figure 3. In general, the palpated LCL origin points, which were out of the 5 mm radius around the anatomic LCL origin, were located anterior to the center of the anatomic origin site. There was no signiﬁcant difference in the mean distance from the anatomic LCL origin point to the palpated (P ¼ .549) or ﬂuoroscopic LCL (P ¼ .732) origin points between examiner 1 and examiner 2 in the corresponding knees for each examiner. Table 3 displays the comparison of the “Kamath ideal” point, the ﬂuoroscopic LCL origin point determined by gross inspection, the anatomic LCL origin point, and palpated LCL origin point. There was a signiﬁcant
T. R. PFEIFFER ET AL.
Fig 2. Distribution of the lateral collateral ligament (LCL) insertion points determined by palpation and ﬂuoroscopic imaging in a coordinate system, placed on the lateral aspect of the knee. The point of origin is positioned in the anatomic LCL insertion point and the x-axis is parallel to the Blumensaat line. A circle with a radius of 5 mm indicates the previously described area of isometry.1
difference between the distance from the palpated LCL origin point to the “Kamath ideal” point (P < .001) and the distance from the ﬂuoroscopic LCL origin point to the “Kamath ideal” point (P ¼ .002). There was no signiﬁcant difference between the location of the “Kamath ideal” point and the ﬂuoroscopic LCL origin point (P ¼ .526). The ICC for intraobserver and interobserver reliability were 0.788 and 0.898, respectively, thus indicating moderate intraobserver and almost perfect intraobserver reliability.
The primary ﬁnding of this study was that, compared with the use of palpation, a radiographic technique for identifying the origin of the LCL leads to increased accuracy in the identiﬁcation of the LCL origin point. More accurate determination of the LCL origin points has the potential to reduce the risk of eccentric tunnel positioning during LCL reconstruction and thus minimize the associated complications of eccentric tunnel positioning, including decreased isometry and risk of excess varus laxity. Furthermore, the data from the present study show that this previously described radiographic technique13 is highly reproducible, accurate, and able to be performed with acceptable results by previously inexperienced users. The present study found the anatomic LCL origin point at 58% 3.5% from the anterior to posterior
ends of the Blumensaat line and 4.1 mm 3.5 mm inferior to it on a perpendicular line, which aligns well with a previous study that found it at 58% 4.7% and 2.3 mm 2.3 mm. Therefore, this study provides additional evidence that this radiographic method is an accurate method for identifying the anatomic LCL origin point in the laboratory setting. Moreover, when this ﬂuoroscopic measurement was performed in a simulated surgical setting without the use of any measurement tools or devices, the identiﬁed LCL origin point was 62% 3.9% from the anterior to posterior ends of the Blumensaat line and 3.5 mm 2.5 mm inferior to it on a perpendicular line. Given that this point was within 2 mm as well as 1 standard deviation of the ideal LCL origin point, this suggests that this technique is both a reliable and accurate method that is feasible in everyday clinical practice. This contrasts with
Table 2. Proportion of LCL Insertion Points Placed Within a Radius of 5 mm and a Radius of 3 mm Around the Anatomic LCL Insertion Point Fluoroscopy Palpation
5 mm Radius 12/13 7/13
P Value .0455
3 mm Radius 11/13 3/13
P Value .0046
NOTE. Using McNemar’s test, LCL insertion points determined by ﬂuoroscopic imaging were found to be signiﬁcantly more often placed within the 5 mm/3 mm radius than insertion points determined by palpation (P < .05). LCL, lateral collateral ligament.
IDENTIFICATION OF THE FEMORAL LCL ORIGIN
Fig 3. Bar chart of the average distance from the determined lateral collateral ligament (LCL) insertion point using palpation and ﬂuoroscopy to the center of the anatomic LCL insertion point for examiner 1 and examiner 2. For both examiners, LCL insertion points determined by ﬂuoroscopy were signiﬁcantly closer to the anatomic center of the LCL insertion point compared with the ones determined by palpation. *P < .05.
the method of palpation, with which the identiﬁed LCL origin points had a standard deviation in the anteriorposterior plane almost 3 times higher than that of the ﬂuoroscopically determined LCL origin points. Therefore, completely relying on the method of palpation may lead to anisometric LCL origin points and residual instability. Based on a graft length variation of less than 2 mm throughout knee ﬂexion, which is assumed to be a clinically acceptable range for posterolateral corner reconstruction,17,18 previous studies have found that placing the LCL origin points within a 5 mm radius around the center of the anatomic LCL origin leads to isometry.1 Using a ﬂuoroscopic technique, 92.7% (12/13) of identiﬁed LCL origin points were within 5 mm of the anatomic LCL origin point, in contrast to 54% (7/13) of LCL origin points determined by palpation. When identifying the LCL origin by palpation, surgeons might be falsely guided by the tip of the lateral epicondyle and thus place the tunnel anterior of the true origin site, which was observed in this study. Tunnel malplacement could lead to decreased isometry
with increased distance between the ﬁxation points in higher ﬂexion angle. Given the important role of the LCL in contributing to stability at the knee,19,20 this anisometry could, in turn, lead to knee instability and put patients at risk for the development of osteoarthritis, ﬂexion deﬁcits, or graft migration.21 This study has several implications for clinical practice. Given that the lateral femoral epicondyle may not serve as an accurate landmark for identifying the LCL origin point,8-12 the improved accuracy of ﬂuoroscopic imaging could lead to a smaller number of nonanatomic LCL reconstructions and to improved clinical and functional outcomes after surgery. In addition, the trend toward more differentiated diagnosis of the directions of knee instability displayed in the modiﬁed Fanelli classiﬁcation requires the surgeon to address the insufﬁcient structures individually.22,23 This is also reﬂected in the development of new anatomic reconstruction techniques of the posterolateral corner.24-26 Fluoroscopic identiﬁcation of the LCL origin would also enable surgeons to use a smaller incision during LCL reconstruction surgery.
Table 3. Comparison of “Kamath Ideal” Point (Precise Determination of the LCL Insertion Point Using the Technique by Kamath et al.13), Fluoroscopic LCL Insertion Point (Using the Technique by Kamath et al. in a Simulated Surgical Setting Without the Use of Any Measurement Tools), Anatomic LCL Insertion Point (the Center of Anatomic LCL Insertion Point), and Palpated LCL Insertion Point (Determined by Palpation) Percentage length from anterior to posterior Distance to the Blumensaat line (inferior) Distance to ideal Kamath point
Kamath Ideal 58% (per deﬁnition) 2.3 mm (per deﬁnition) e
Fluoroscopic Imaging 62% 3.9% 3.5 mm 2.5 mm 3.4 mm 1.8 mm
Center Insertion 58% 3.5% 4.1 mm 3.5 mm 3.1 mm 2.4 mm
Palpation 54% 9.6% 4.8 mm 3.2 mm 5.6 mm 2.3 mm
NOTE. The LCL insertion points were compared with respect to the percentage position of the femur length across the Blumensaat line, the distance inferior to the Blumensaat line, and the distance to the “Kamath ideal” point. LCL, lateral collateral ligament.
T. R. PFEIFFER ET AL.
Limitations This study has limitations. Only cadaveric knees were used in this study, which may limit the extrapolation of these ﬁndings to the use of these measurements in live human patients. The study design did not evaluate the inﬂuence of the examiner’s level of education on the results of the use of palpation or ﬂuoroscopy to determine the LCL origin point. Furthermore, a larger skin incision could potentially result in better ability to accurately palpate the LCL origin. As the positions of the LCL origin point were marked consecutively, being inﬂuenced by the prior placed K-wire on the ﬂuoroscopic determination in the surgery-like setting cannot be ruled out. In addition, no LCL reconstruction was performed in this study. Therefore, only theoretical conclusions about isometry and overconstraint could be made.
Conclusions The use of palpation to identify the LCL origin may not be an accurate method for performing an isometric and anatomic LCL reconstruction. The use of ﬂuoroscopic imaging appears to be a feasible method for identifying the LCL origin in clinical practice and may increase the accuracy of LCL origin identiﬁcation. Fluoroscopic guidance improves accuracy in determining the anatomic LCL origin, which may help avoiding tunnel malplacement during LCL reconstruction.
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Appendix Table 1. The Raw Data for the Anatomic, Palpated, and Fluoroscopic Insertion Site With X and Y Values and Calculated Distances
Specimen 1 2 3 4 5 6 7 8 9 10 11 12 13 Mean Minimum Maximum Standard
Anatomic LCL Insertion Point
Palpated LCL Insertion Point
Fluoroscopic LCL Insertion Point
X 119.4 122.4 107.8 118.0 102.3 93.7 99.2 112.2 85.8 105.1 100.3 143.5 102.3 e e e e
X 120.6 117.0 114.2 117.7 101.6 92.3 107.4 107.8 84.0 103.0 106.3 141.7 99.9 e e e e
X 121.3 122.9 109.4 114.4 104.5 91.6 97.3 109.7 87.9 107.6 108.1 141.7 100.6 e e e e
Y 80.6 66.0 80.7 77.8 78.1 72.7 80.4 74.7 61.0 63.4 76.4 67.0 75.5 e e e e
LCL, lateral collateral ligament.
Y 74.6 63.0 80.5 82.7 74.4 68.7 78.8 76.5 56.4 60.6 75.5 68.2 77.8 e e e e
Y 80.3 63.3 83.3 80.7 80.6 72.8 77.7 75.6 62.5 65.4 77.3 68.3 75.5 e e e e
Distance Anatomic Insertion to Palpated Insertion 6.1 6.1 6.4 4.9 3.8 4.3 8.4 4.8 4.9 3.6 6.0 2.1 3.3 5.0 2.1 8.4 1.6
Distance Anatomic Insertion to Fluoroscopic Insertion 1.9 2.8 3.1 4.6 3.4 2.1 3.3 2.7 2.4 3.2 7.8 2.1 1.7 3.2 1.7 7.8 1.6