By Osmar V. Lopes Jr., MD, Mario Ferretti, MD, Wei Shen, MD, PhD, Max Ekdahl, MD, Patrick Smolinski, PhD, and Freddie H. Fu, MD

Transcription

1 249 COPYRIGHT Ó 2008 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Topography of the Femoral Attachment of the Posterior Cruciate Ligament By Osmar V. Lopes Jr., MD, Mario Ferretti, MD, Wei Shen, MD, PhD, Max Ekahl, MD, Patrick Smolinski, PhD, an Freie H. Fu, MD Investigation performe at the Department of Orthopaeic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania Backgroun: The success of posterior cruciate ligament reconstruction has varie. The objective of this stuy was to etermine quantitatively an qualitatively the topography an osseous lanmarks of the femoral footprints of the anterolateral an posteromeial bunles of the posterior cruciate ligament in orer to enhance repair. Methos: Twenty unpaire knees from twenty human caavers were evaluate. The surface features of the femoral footprints of the anterolateral an posteromeial bunles of the posterior cruciate ligament were stuie by means of macroscopic observation an three-imensional laser photography. Results: We observe, both visually an with three-imensional laser photography, an osseous prominence locate proximal to the femoral footprint of the posterior cruciate ligament in eighteen of the twenty human knees. This osseous lanmark, enominate the meial interconylar rige, etermine the proximal borer of the posterior cruciate ligament footprint. In eight of the twenty knees, we observe a small osseous prominence between the anterolateral an posteromeial bunles of the posterior cruciate ligament. A clear change in the slope of the femoral footprint of the posterior cruciate ligament was seen between the anterolateral an posteromeial bunles. The average area of the posterior cruciate ligament footprint (an stanareviation) was 209 ± mm 2, the average area of the anterolateral bunle was 118 ± mm 2, an the average area of the posteromeial bunle was 90 ± mm 2. Conclusions: The femoral footprint of the posterior cruciate ligament has a unique surface anatomy, with a meial interconylar rige being frequently present an a meial bifurcate rige being less frequently present. Clinical Relevance: These anatomical finings may assist surgeons in performing posterior cruciate ligament reconstruction in a more anatomical fashion. The posterior cruciate ligament is consiere to be the primary restraint to posterior knee translation an a seconary restraint to varus, valgus, an external rotation of the knee joint 1. It is compose of two functional bunles: the anterolateral bunle an the posteromeial bunle 2,3. It has been emonstrate that these two bunles have istinct patterns of tension uring the range of motion of the knee joint. The anterolateral bunle is taut near 90 of flexion, an the posteromeial bunle is taut at nearly full extension 2,4. The success of posterior cruciate ligament reconstruction has been variable 5,6. Some recent stuies have shown that ouble-bunle posterior cruciate ligament reconstruction can restore knee kinematics better than can single-bunle posterior cruciate ligament reconstruction 7-9. Previous stuies have emonstrate that the placement of the femoral tunnel for the posterior cruciate ligament reconstruction is more important than the placement of the tibial tunnel in terms of restoring graft forces 10,11. Knowlege of the anatomy of the posterior cruciate ligament is crucial to unerstaning the function of its two bunles as well as to improving the outcome of reconstruction surgery. Although many stuies have provie important information about the femoral footprint of the posterior cruciate ligament 2,12-17, we are not aware of any publisheetaile anatomical evaluations of the bone lanmarks an topography of Disclosure: The authors i not receive any outsie funing or grants in support of their research for or preparation of this work. Neither they nor a member of their immeiate families receive payments or other benefits or a commitment or agreement to provie such benefits from a commercial entity. No commercial entity pai or irecte, or agree to pay or irect, any benefits to any research fun, founation, ivision, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immeiate families, are affiliate or associate. J Bone Joint Surg Am. 2008;90: oi: /jbjs.g.00448

2 250 Fig. 1 Anterior view of the left knee in 90 of flexion, showing the two bunles of the posterior cruciate ligament: the anterolateral bunle (white arrow) an the posteromeial bunle (black arrow). All soft tissue, except the posterior an anterior cruciate ligaments, was strippe off. the femoral footprint of the posterior cruciate ligament. In our opinion, a escription of these osseous lanmarks may assist surgeons in selecting the anatomical placement of femoral tunnels uring single or ouble-bunle reconstruction of the posterior cruciate ligament. Thus, the main objective of this stuy was to evaluate qualitatively an quantitatively the bone lanmarks an topography of the femoral footprints of the anterolateral an posteromeial bunles of the posterior cruciate ligament. Materials an Methos Twenty unpaire fresh-frozen human caaveric knees from twenty aults (fifteen men an five women) were use in this stuy. The average age at the time of eath was seventy- Fig. 2 A: Gross appearance of the location of the femoral attachment of the posterior cruciate ligament onto the meial interconylar wall (sagittal view of a left knee). The white arrow inicates the attachment site of the anterolateral bunle, an the black arrow inicates the attachment site of the posteromeial bunle. B: Gross appearance of the meial interconylar rige (black arrows) an the meial bifurcate rige (white arrows).

3 251 Fig. 3 Image mae with three-imensional laser photography, showing the attachment of the anterolateral (AL) an posteromeial (PM) bunles of the posterior cruciate ligament onto the meial femoral conyle in a left knee. Similar to a lateral portal view of the meial conyle, this view shows the meial interconylar wall when the knee is in 90 of flexion. The small picture of the femur in the mile shows the orientation of the specimen. four years (range, fifty-seven to ninety-three years). Caaveric knees that showe severe egenerative changes, signs of fractures, or evience of ligament injury ha been exclue from the stuy. The knees were completely issecte to expose the posterior cruciate ligament an the meial femoral conyle (Fig. 1). The synovial covering of the posterior cruciate ligament was remove, along with the meniscofemoral ligaments. The femoral footprints of the anterolateral an posteromeial bunles of the posterior cruciate ligament coul be ientifie on the basis of the ifferent tension pattern of each bunle uring the range of motion of the knee, with the anterolateral bunle being taut in flexion an the posteromeial bunle being taut in full extension. The bunles were separate carefully with use of blunt issection. The footprints of the anterolateral an posteromeial bunles were carefully efine with ink before all soft tissue was remove to expose the meial wall of the interconylar notch. At first, gross observation of the bone topography, with special attention to the femoral footprints of the anterolateral an posteromeial bunles, was performe in all knees (Fig. 2). Secon, the knees were photographe with a laser threeimensional igitizer camera (VIVID 910 3D Digitizer; Konica Minolta Sensing, Osaka, Japan), an the images were analyze with specific software (Geomagic Stuio 9; Geomagic, Research Triangle Park, North Carolina) (Fig. 3). This noncontact metho allows three-imensional visualization anigital measurements of the observe surface through the analysis of 307,000 triangulation blocks. The precision of the threeimensional images is approximately mm. The accuracy is 0.22 mm for the x axis, 0.16 mm for the y axis, an 0.10 mm for the z axis 18. Thus, it serves as an accurate means of measuring the area of the femoral footprint of the posterior cruciate ligament as well as the istance an length of all observe features. The central point of each area was locate visually on the igital images. The istance between the centers of the anterolateral an posteromeial footprints was measure, an the shortest istance from the center of each bunle s footprint to the ege of the articular cartilage an to the meial interconylar rige was ientifie. The surface anatomy of the meial wall of the interconylar notch was also observe with this metho, with measurements mae of efine osseous lanmarks. We use the terms proximal/istal an anterior/ posterior throughout this article to escribe the location of the structures on the meial interconylar wall when the knee was in the anatomical position. Results The femoral footprints of the posterior cruciate ligaments varie in shape an size. The shape was a semicircle in fifteen of the twenty knees an an oval in five. The femoral attachment of the posterior cruciate ligament was concave in nineteen knees an flat in one. The three-imensional laser igital measurement showe the average area (an stanar eviation) of the femoral posterior cruciate ligament footprint to be 209 ± mm 2, with the average area of the anterolateral bunle measuring 118 ± mm 2 an the average area of the posteromeial bunle measuring 90 ± mm 2. The average istance between the central points of the bunles

4 252 Fig. 4 Image mae with three-imensional laser photography, showing the meial interconylar rige (black arrows) an the meial bifurcate rige (white arrows). This image simulates a lateral portal view of the left knee when the knee is near 90 of flexion. The small picture of the femur in the left corner shows the orientation of the specimen. Fig. 5 Left: Image mae with three-imensional laser photography, showing the meial interconylar wall of the left knee. To emphasize the osseous features on the meial interconylar wall, the femoral shaft is omitte. Note a small rige (the meial bifurcate rige, black arrow) between the anterolateral an posteromeial bunles. Right: A cross section through the entire posterior cruciate ligament footprint with a schematic iagram of the angle forme between the anterolateral (AL) an posteromeial (PM) bunle attachments. The small picture of the femur in the mile shows the orientation of the specimen.

5 253 TABLE I Quantitative Analysis of the Femoral Attachment of the Posterior Cruciate Ligament an Its Lanmarks Mean an Stanar Deviation Footprint area (mm 2 ) Posterior cruciate ligament 209 ± Anterolateral bunle 118 ± Posteromeial bunle 90 ± Length of meial interconylar rige (mm) ± 2.3 Change of slope (eg) 140 ± 12.8 Shortest istance (mm) between articular cartilage ege an center of: Anterolateral bunle 7 ± 1.02 Posteromeial bunle 8 ± 0.99 Distance between centers of anterolateral 11 ± 1.18 an posteromeial bunles (mm) Length of meial bifurcate rige (mm) 5.8 ± 1.38 Distance (mm) from meial interconylar rige to center of: Posterior cruciate ligament 4.36 ± 0.61 Anterolateral bunle 3.63 ± 0.4 Posteromeial bunle 3.13 ± 0.4 was 11 ± 1.18 mm. With the knee at 90 of flexion, the average shortest istances from the centers of the anterolateral an posteromeial bunles to the articular cartilage ege were 7 ± 1.02 mm an 8 ± 0.99 mm, respectively. An osseous prominence locate proximal to the femoral attachment of the posterior cruciate ligament was grossly anigitally ientifie in eighteen of the twenty knees. This osseous prominence was name the meial interconylar rige by the senior author (F.H.F.). With the knee in the anatomical position, the meial interconylar rige runs obliquely through the entire femoral footprint of the posterior cruciate ligament from proximal to istal an from anterior to posterior (Fig. 4). Its average length was ± 2.3 mm. The average istances between the meial interconylar rige an the center point of the posterior cruciate ligament, the anterolateral bunle, an the posteromeial bunle were 4.36 ± 0.61 mm, 3.63 ± 0.4 mm, an 3.13 ± 0.4 mm, respectively. In aition to the meial interconylar rige, we also observe a subtle osseous prominence locate between the femoral footprints of the anterolateral an posteromeial bunles (Fig. 4). It was ientifie in eight of the twenty knees as a iscrete osseous rige on the bone. We propose that it be calle the meial bifurcate rige. The average length of the meial bifurcate rige was 5.8 ± 1.38 mm. In aition, a change of slope was observe between the femoral footprints of the anterolateral an posteromeial bunles (Fig. 5). With use of the meial bifurcate rige as the pivot, the average angle forme by the anterolateral an posteromeial femoral footprints was 140 ± All quantitative ata are given in Table I. Discussion The anatomy of the posterior cruciate ligament has been escribe in several stuies 2,3,12-17,19. The footprint area an the locations of the two bunles have been reporte. However, the etails of the bone anatomy relate to the femoral footprint of the posterior cruciate ligament have not been escribe, to our knowlege. A etaileescription of the femoral footprints of the anterolateral an posteromeial bunles is neee to enable surgeons to accurately place femoral tunnels in posterior cruciate ligament surgery. Girgis et al. 2 reporte the anatomical measurements of the total posterior cruciate ligament footprint, but they i not evaluate the anatomical measurements of each bunle s footprint separately. Harner et al. 15 an Morgan et al. 20 reporte that the femoral attachment of the posterior cruciate ligament spans, on the average, a istance of 32 mm in anterior-toposterior epth. Single-bunle reconstruction may not cover all of the femoral footprint of the posterior cruciate ligament anoes not reprouce the anatomy of the anterolateral an posteromeial bunles or their functional patterns 20. Harner et al. 13 use a igitizing system (accurate to within 0.8 mm) to recor the coorinates of the periphery of the attachment of the posterior cruciate ligament an its bunles. They use thirty equally space points to collect the ata. The average area of the femoral footprint of the posterior cruciate ligament was reporte to be 128 ± 22 mm 2, an they i not fin significant ifferences between the areas of the anterolateral an posteromeial bunles 13. In another anatomic stuy, Takahashi et al. 17 use photographs with a measurement scale (one scale for each photograph of each femur) to evaluate the femoral attachment of the posterior cruciate ligament. They reporte that the area of the anterolateral femoral footprint average 58 ± 25.4 mm 2 an that of the posteromeial femoral footprint average 64.6 ± 24.7 mm 2. These ifferences in the literature may be ue to the ifferent methos use for measurement as well as to ethnic an gener ifferences in the human subjects that were stuie. Our stuy confirme that the anterolateral an posteromeial bunles have istinctive femoral footprints. Our measurements of the average areas of the anterolateral an posteromeial footprints are larger than those previously escribe in the literature. This iscrepancy may be ue to the reasons mentione above an mainly to the fact that the three-imensional analysis use in this stuy may cover the total area of the concave attachment of the posterior cruciate ligament more accurately. Also, it is important to note that we inclue all peripheral fibers of the posterior cruciate ligament attachment in our measurements. We believe that these aitional factors may have contribute to the larger areas that we observe. The location of the femoral footprint of the posterior cruciate ligament has been escribe in many ifferent ways 16,17,19-21.Winetal. 21 reporte that the center of the footprint is locate 1 cm proximal to the articular cartilage.

6 254 Mejia et al. 16 use the o clock metho an suggeste that the posterior cruciate ligament may exten from 12 to 4 o clock in the right knee an from 12 to 8 o clock in the left knee. Takahashi et al. 17 measure the istances between the centers of the anterolateral an posteromeial bunle footprints an the anterior borer of the articular cartilage using a line parallel to the Blumensaat line. The average istances were 9.6 mm an 10.6 mm for the anterolateral an posteromeial bunles, respectively. Morgan et al. 20 efine the centers of the anterolateral an posteromeial bunles by using three ifferent axes in reference to the articular cartilage. Their results showe that the center of the anterolateral bunle originate 13 mm posterior an 13 mm inferior to the borer of the articular cartilage whereas the center of the posteromeial bunle originate 8 mm posterior an 20 mm inferior to the borer of the articular cartilage. In a recent stuy, Ewars et al. 19 use the o clock metho an the center of a circle outlining the posterior aspect of the meial femoral conyle as a reference. The centers of the footprints of the posterior cruciate ligament bunles were foun to be at a variety of o clock positions when measure parallel to the femoral interconylar notch roof or the femoral shaft. On the femoral sie, the center of the anterolateral bunle was, on the average, 7 ± 2 mm from the articular cartilage at 10:20 ± 00:30 o clock, an the center of the posteromeial bunle was 10 ± 3 mm from the articular cartilage at 08:30 ± 00:30 o clock. These previous stuies were conucte with use of ifferent methos, an the results were reporte in ifferent ways. Thus, it may be somewhat confusing for surgeons attempting to choose the appropriate site for placement of the femoral tunnel in a reconstruction of the posterior cruciate ligament. Our finings suggest a ifferent approach for etermining the footprints of the anterolateral an posteromeial bunles. The meial interconylar rige was foun to efine the proximal limit of the posterior cruciate ligament, whereas the meial bifurcate rige was foun to separate the femoral footprints of the anterolateral an posteromeial bunles. We believe that these two riges may be use to assist the surgeon in etermining the placement of the anterolateral an posteromeial tunnels on the femoral sie. During the surgery, both tunnels shoul be place more istally than the meial interconylar rige, an they shoul be separate by the meial bifurcate rige. Previous investigators have reporte that the femoral attachment of the posterior cruciate ligament is relatively planar an approximates a half-moon shape 2,13. In this stuy, we foun that the femoral attachment site of the posterior cruciate ligament was concave in nineteen of twenty knees an was relatively planar in only one specimen. The shape of the femoral attachment site was approximately semicircular in fifteen femora an oval in five. We foun that the two bunles were locate in ifferent planes an there was a change of slope between the femoral footprints of the anterolateral an posteromeial bunles. This fining may also be use to assist in the anatomical placement of femoral tunnels in reconstructions of the posterior cruciate ligament. However, it is important to note that the bone topography reporte here escribes subtle features relate to the femoral footprint of the posterior cruciate ligament. Careful probing an removal of the resiual posterior cruciate ligament soft tissue are necessary to ientify these structures. This stuy ha at least two limitations. First, a relatively small number of knees was examine consiering the great possibility of anatomical variations. Secon, espite the accuracy of the three-imensional laser measurement systems, the measurements relie on human jugment (i.e., etermining the center of a footprint), which may have introuce bias. We emonstrate that the femoral footprint of the posterior cruciate ligament has a unique surface anatomy, with a meial interconylar rige being frequently present an a secon osseous lanmark, the meial bifurcate rige, being ientifie less frequently. These osseous lanmarks may be use as a guie for placement of anatomical femoral tunnels uring reconstructions of the posterior cruciate ligament. n Osmar V. Lopes Jr., MD Mario Ferretti, MD Wei Shen, MD, PhD Max Ekahl, MD Patrick Smolinski, PhD Freie H. Fu, MD Department of Orthopaeic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Suite 1011, Pittsburgh, PA aress for F.H. Fu: ffu@upmc.eu References 1. Groo ES, Stowers SF, Noyes FR. Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament an posterolateral structures. J Bone Joint Surg Am. 1988;70: Girgis FG, Marshall JL, Monajem A. The cruciate ligaments of the knee joint. Anatomical, functional an experimental analysis. Clin Orthop Relat Res. 1975;106: Race A, Amis AA. The mechanical properties of the two bunles of the human posterior cruciate ligament. J Biomech. 1994;27: Fox RJ, Harner CD, Sakane M, Carlin GJ, Woo SL. Determination of the in situ forces in the human posterior cruciate ligament using robotic technology. A caaveric stuy. Am J Sports Me. 1998;26: Garofalo R, Jolles BM, Moretti B, Siegrist O. Double-bunle transtibial posterior cruciate ligament reconstruction with a tenon-patellar bone-semiteninosus tenon autograft: clinical results with a minimum of 2 years follow-up. Arthroscopy. 2006;22: Lipscomb AB Jr, Anerson AF, Norwig ED, Hovis WD, Brown DL. Isolate posterior cruciate ligament reconstruction. Long-term results. Am J Sports Me. 1993;21: Harner CD, Janaushek MA, Kanamori A, Yagi M, Vogrin TM, Woo SL. Biomechanical analysis of a ouble-bunle posterior cruciate ligament reconstruction. Am J Sports Me. 2000;28: Mannor DA, Shearn JT, Groo ES, Noyes FR, Levy MS. Two-bunle posterior cruciate ligament reconstruction. An in vitro analysis of graft placement an tension. Am J Sports Me. 2000;28:

7 Race A, Amis AA. PCL reconstruction. In vitro biomechanical comparison of isometric versus single anouble-bunle anatomic grafts. J Bone Joint Surg Br. 1998;80: Bach BR, Daluga DJ, Mikosz R, Anriacchi TP, Seil R. Force isplacement characteristics of the posterior cruciate ligament. Am J Sports Me. 1992;20: Groo ES, Hefzy MS, Linenfiel TN. Factors affecting the region of most isometric femoral attachments. Part I: the posterior cruciate ligament. Am J Sports Me. 1989;17: Amis AA, Gupte CM, Bull AM, Ewars A. Anatomy of the posterior cruciate ligament an the meniscofemoral ligaments. Knee Surg Sports Traumatol Arthrosc. 2006;14: Harner CD, Baek GH, Vogrin TM, Carlin GJ, Kashiwaguchi S, Woo SL. Quantitative analysis of human cruciate ligament insertions. Arthroscopy. 1999;15: Harner CD, Livesay GA, Kashiwaguchi S, Fujie H, Choi NY, Woo SL. Comparative stuy of the size an shape of human anterior an posterior cruciate ligaments. J Orthop Res. 1995;13: Harner CD, Xerogeanes JW, Livesay GA, Carlin GJ, Smith BA, Kusayama T, Kashiwaguchi S, Woo SL. The human posterior cruciate ligament complex: an interisciplinary stuy. Ligament morphology an biomechanical evaluation. Am J Sports Me. 1995;23: Mejia EA, Noyes FR, Groo ES. Posterior cruciate ligament femoral insertion site characteristics. Importance for reconstructive proceures. Am J Sports Me. 2002;30: Takahashi M, Matsubara T, Doi M, Suzuki D, Nagano A. Anatomical stuy of the femoral an tibial insertions of the anterolateral an posteromeial bunles of human posterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc. 2006;14: Kovacs L, Zimmermann A, Brockmann G, Baurecht H, Schwenzer-Zimmerer K, Papaopulos NA, Papaopoulos MA, Saer R, Biemer E, Zeilhofer HF. Accuracy an precision of the three-imensional assessment of the facial surface using a 3-D laser scanner. IEEE Trans Me Imaging. 2006;25: Ewars A, Bull AM, Amis AA. The attachments of the fiber bunles of the posterior cruciate ligament: an anatomic stuy. Arthroscopy. 2007;23: Morgan CD, Kalman VR, Grawl DM. The anatomic origin of the posterior cruciate ligament: where is it? Reference lanmarks for PCL reconstruction. Arthroscopy. 1997;13: Win WM Jr, Bergfel JA, Parker RD. Evaluation an treatment of posterior cruciate ligament injuries: revisite. Am J Sports Me. 2004;32: