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The Segond Fracture: A Bony Injury of the AnterolateralLigament of the Knee

Steven Claes, M.D., Ph.D., Thomas Luyckx, M.D., Evie Vereecke, Ph.D.,and Johan Bellemans, M.D., Ph.D.

Purpose: The purpose of this study was to investigate the relation of the Segond fracture with the anterolateral ligament(ALL) of the knee. Methods: To identify the soft-tissue structure causative for the Segond fracture, a study was set up tocompare anatomic details of the tibial insertion of the recently characterized ALL in cadaveric knees (n ¼ 30) withradiologic data obtained from patients (n ¼ 29) with a possible Segond fracture based on an imaging protocol search. Thespatial relation of the ALL footprint with well-identifiable anatomic landmarks at the lateral aspect of the knee wasdetermined, and this was repeated for the Segond fracture bed. Results: In all of the included cadaveric knees, a well-defined ALL was found as a distinct ligamentous structure connecting the lateral femoral epicondyle with the antero-lateral proximal tibia. The mean distance of the center of the tibial ALL footprint to the center of the Gerdy tubercle(GT-ALL distance) measured 22.0 � 4.0 mm. The imaging database search identified 26 patients diagnosed with a Segondfracture. The mean GT-Segond distance measured 22.4 � 2.6 mm. The observed difference of 0.4 mm (95% confidenceinterval, e1.5 to 2.2 mm) between the GT-ALL distance and GT-Segond distance was neither statistically significant (P ¼.70) nor clinically relevant. Conclusions: The results of this study confirmed the hypothesis that the ALL inserts in theregion on the proximal tibia from where Segond fractures consistently avulse, thus suggesting that the Segond fracture isactually a bony avulsion of the ALL. Clinical Relevance: Although the Segond fracture remains a useful radiographicclue for indirect detection of anterior cruciate ligament injuries, the Segond fracture should be considered a frankligamentous avulsion itself.

lready in 1879, years before the discovery of ra-

Adiographs, the French surgeon Paul Segonddescribed a remarkably constant avulsion fracturepattern at the proximolateral tibia as a result of forcedinternal rotation applied to cadaveric human knees.1

The eponymous Segond fracture was reported tooccur in the tibial region “definitely posterior and above

From the Department of Orthopedic Surgery, AZ Hospital (S.C.), Herentals;epartment of Orthopedic Surgery and Traumatology, University Hospitalseuven (T.L.), Leuven; Department of Development and Regeneration atulak, Faculty of Medicine, Catholic University Leuven (E.V.), Kortrijk; andepartment of Orthopedic Surgery, Ziekenhuis Oost-Limburg (J.B.), Genk,elgium.First prize winner of the biennial ISAKOS John J. Joyce Award, 2013, ate ninth biennial International Society of Arthroscopy, Knee Surgery &rthopaedic Sports Medicine Congress, Toronto, Ontario, Canada, May 2013.The authors report that they have no conflicts of interest in the authorship

nd publication of this article.Received August 19, 2013; accepted May 29, 2014.Address correspondence to Steven Claes, M.D., Ph.D., Department ofrthopedic Surgery, AZ Hospital, Nederrij 133, B-2200 Herentals, Belgium.-mail: steven.claes@azherentals.be� 2014 by the Arthroscopy Association of North America0749-8063/13587/$36.00http://dx.doi.org/10.1016/j.arthro.2014.05.039

Arthroscopy: The Journal of Arthroscopic and Related

the tibial tubercle.”1 At this anatomic location, Segond1

furthermore designated the existence of “a pearly,resistant, fibrous band which invariably showedextreme amounts of tension during forced internalrotation [of the knee]” (Fig 1).Later on, in 1936, Milch2 was the first author to

report the radiologic aspect of this enigmatic lesionshowing “striking uniformity” in 3 of his patients.Rather by accident, Milch had stumbled on the exper-imental work of Segond1 and explained his radiologicfindings as an “avulsion of the iliotibial band at itsinsertion behind Gerdy’s tubercle.” The Segond fracturethen became largely neglected in the orthopaedicliterature until Woods et al.3 correlated the Segondfracture with the presence of significant knee instabilityin 1979, exactly 100 years after the first description ofthe fracture by Segond. In 4 acute cases with a positive“lateral capsular sign” (i.e., Segond fracture) on radi-ography, a concomitant rupture of the anterior cruciateligament (ACL) was shown. This report, together withthe work of Goldman et al.4 and Hess et al.,5 hasfounded the current pathognomonic association ofSegond fractures with ACL tears at least in the adultpopulation.6

Surgery, Vol -, No - (Month), 2014: pp 1-8 1

Fig 1. Segond’s drawing showing hiseponymous avulsion fracture in a rightknee1 compared with a plain radio-graph of a right knee showing aSegond fracture (arrow).

2 S. CLAES ET AL.

Strikingly, although the fracture described by Segond1

has gained worldwide recognition in standard ortho-paedic textbooks as a diagnostic clue for ACL injury,7

the clinical relevance of the Segond fracture itself hasnever been fully recognized to date. As a consequence,the anatomic structure responsible for the avulsion ofthis bony flake from the lateral tibial plateau has beenpoorly studied. Although Segond briefly mentioned a“pearly, resistant, fibrous band,” later literature remainsunclear on the precise anatomic substrate potentiallycausing this enigmatic avulsion fracture (Fig 1).Recently, the precise anatomic details of the newly

described anterolateral ligament (ALL) of the humanknee have been provided.8 In brief, the ALL wasidentified as a distinct ligamentous structure origi-nating on the lateral femoral epicondyle and insertingon the anterolateral tibia, showing firm attachmentsto the body of the lateral meniscus along its obliquecourse at the lateral aspect of the knee. The purposeof this study was to investigate the relation of theSegond fracture with the ALL of the knee. We hy-pothesized that the tibial ALL insertion in cadavericknees would match the constant location from whereSegond fractures seemingly avulse on knee magneticresonance imaging (MRI) of clinical Segond fracturecases.

MethodsTo identify the soft-tissue structure causative for the

Segond fracture, a study was set up to compareanatomic details of the tibial insertion of the recentlycharacterized ALL in cadaveric knees (n ¼ 30) withradiologic data obtained from patients (n ¼ 29) with apossible Segond fracture based on an imaging protocolsearch. The spatial relation of the ALL footprint withwell-identifiable anatomic landmarks at the lateralaspect of the knee was determined, and this wasrepeated for the Segond fracture bed.

AnatomyThe characteristics of the tibial insertion of the ALL

were investigated in 30 unpaired, formalin-fixed, hu-man cadavers obtained by the Body Donation Programof the University of Leuven, Leuven, Belgium (17 menand 13 women; mean age at death, 81 years). Speci-mens with a gross deformity at the knee, signs ofosteoarthritis of the lateral tibiofemoral compartment,or a damaged ACL during dissection were excludedfrom the study.The precise dissection technique has been described

previously.8 In brief, dissection was started by creating alarge rectangular cutaneous flap, centered on the lateralaspect of the flexed knee. The iliotibial band (ITB), theextensor apparatus, and the short head of the bicepsfemoris, as well as the tendon, were cleared from sub-cutaneous fat tissue. Then, the ITB was cut transverselyat approximately 6 cm proximal to the lateral femoralepicondyle. The ITB was carefully released to its tibialattachment on the Gerdy tubercle, thus sharply cuttingthe so-called Kaplan fibers9 attaching to the lateralintermuscular septum, as well as the lateral retinac-ulum. Indeed, according to Seebacher et al.,10 the ITBforms the most superficial distinct tissue layer (layer I)on the lateral aspect of the knee, only attached to thedeeper layer (layer II) anteriorly at the lateral patellarretinaculum. With the ITB reflected, the “superficiallamina of the capsule”10 was visualized. The lateralcollateral ligament (LCL) was palpated with the knee inslight varus, and the lamina encompassing the LCL wasthen carefully incised posteriorly and parallel to theLCL. With the knee flexed to 60�, an internal torquewas subsequently applied on the foot, thereby revealingtaut, distinct fibers running from the region of thelateral femoral epicondyle to the proximal tibia poste-rior to the Gerdy tubercle. These fibers could be clearlydelineated from the slack and thin joint capsule (layerIII) lying anteriorly (Fig 2). Subsequently, careful

SEGOND FRACTURE: BONY ALL AVULSION 3

isolation of all visible fibers of this ligamentous struc-ture was performed at its insertional zone at the prox-imal tibia, posterior and proximal from the Gerdytubercle, along its course upward to the lateral femur.Care was taken not to damage intersecting fibers withthe proximal LCL. Furthermore, the lateral meniscus,the lateral inferior geniculate artery, the LCL, and thepopliteus tendon were isolated.The insertion sites of the LCL and ALL were delineated

using small metal pins. Afterward, a digital caliper withan accuracy of 0.01 mm (Mit500196-20; Mitutoyo,Kawasaki, Japan) was used to measure the dimensionsof the isolated ALL and its relation to nearby anatomicstructures: The depth of the lateral “tibial synovialrecessus”8 (i.e., the distance between the cartilage sur-face and the insertional fold of the ALL at the proximaltibia), and the distance of the center of the ALL insertionto both the fibular LCL insertion and the Gerdy tubercle(i.e., GT-ALL distance) were recorded, with the latterforming the primary outcomemeasure of this part of thestudy. The ligament was then detached from its tibialinsertion, and the width of the tibial ALL footprint wasmeasured after marking its edges with the digital caliper.A calibrated flexible ruler was fixed at the femoralmetaphysis, and standardized digital photographs wereobtained from a lateral and anterior point of view.

RadiologyA computerized search was performed of all imaging

protocols produced by our institution’s department ofradiology from January 1, 2006, until February 1, 2012.From all radiographs, computed tomography (CT)scans, MRI scans, and ultrasound examinations per-formed in this period, only protocols containing the

Fig 2. Lateral view of a typical right knee during dissection.With the ITB reflected, the ALL fibers are clearly distin-guishable from the thin anterolateral joint capsule anteriorto it. (BFT, biceps femoris tendon; FH, fibular head; JC, jointcapsule; LFE, lateral femoral epicondyle.)(Reprinted withpermission from Claes et al.8)

term “Segond” were reviewed. All the correspondingradiographic images were manually checked for theexistence of an avulsion fracture in the region of thelateral proximal tibia, and images were excluded if notypical Segond fracture was apparent. Images notcontaining a clear calibration scale were excluded aswell. Patient charts were reviewed to identify the timebetween injury and radiologic diagnosis of the Segondfracture; both hospital charts and medical imaging scansof these patients were studied to determine the status ofthe ACL. The plain radiographs were evaluated for thesize, shape, orientation, and degree of displacement ofthe Segond fracture fragment and for radiographicevidence of associated osseous and soft-tissue injuries.When available, the magnetic resonance (MR) and/orCT images of these knees were subsequently analyzedwith particular interest in the characteristics of both theavulsed bony fragment and the corresponding fracturebed on the proximal tibia. Furthermore, measurementof the absolute distance between the center of the ITBinsertion on the tibia (middle of the Gerdy tubercle)and the center of the bony bed of the proximolateraltibia from where the Segond fragment had avulsed (i.e.,GT-Segond distance) was obtained. To measure thisdistance, the “position curser” tool of the AGFA PACSsoftware package (Agfa Healthcare, Mortsel, Belgium)was used to transpose the correct location of the Gerdytubercle and the fracture socket from the coronalimages to the calibrated axial slides (Fig 3). Subse-quently, the absolute distance in millimeters betweenthe 2 points on the axial view was recorded, and thisGT-Segond distance was then studied as the primaryoutcome measure of this part of the study. Further-more, the depth of the “lateral tibial synovial recess”was measured using the same criteria as in the anatomypart of the study (i.e., the distance between the lateraledge of the tibial cartilage surface and the insertionalfold of the ALL at the proximal tibia). Finally, themaximum width of the fractured “Segond bony frag-ment” was measured. The individual measurementswere performed and repeated twice by 2 observers.

StatisticsA 2-sided 95% confidence interval for the difference in

distances between the anatomy and radiology parts of thestudy was constructed based on a t distribution, allowingunequal variances (Satterthwaite approximation). An Ftest was used to compare the variability between bothgroups. All analyses were performed using SAS software,version 9.2, of the SAS System for Windows (SAS Insti-tute, Cary, NY). Given the observed normal distributionof the difference between the GT-ALL and GT-Segonddistances with an SD of 2.51 mm, the post hoc poweranalysis showed that if the true difference in the GT-ALLand GT-Segond mean values is 2.3 mm (i.e., 20% of thetotal mean tibial footprint width of the ALL), this study

Fig 3. Typicalmeasurement sequencefor distance between center of Gerdytubercle and center of Segond fracturebed (i.e., GT-Segond distance) onMRIimages of a left knee. (A) At first, thecenterof theGerdy tubercle is foundbyalternated scrolling through both the(A.1) frontal and (A.2) axial slices; acrosshair is then placed at this position(arrows). (B) Subsequently, the centerof the Segond fracture bed on theproximal tibia is delineated in a similarfashion, by scrolling through both thelinked (B.1) frontal and (B.2) axialimages and placing a crosshair at thisdesignated location (arrows). Finally,a calibrated measurement of the dis-tance between the 2 crosshairs (GT-Segond distance) is performed usingdedicated software.

4 S. CLAES ET AL.

will be able to reject the null hypothesis that the popu-lation means of the GT-ALL and GT-Segond measure-ments are equal with a power of 0.843. The type I errorprobability associatedwith this test of this null hypothesiswas set at a ¼ .05.

Results

AnatomyIn all 29 cadaveric knees, a well-defined ALL was

found as a distinct ligamentous structure connecting thelateral femoral epicondyle with the anterolateral prox-imal tibia. The mean depth of the lateral recess

measured 6.5 � 1.5 mm. The mean width of the tibialfootprint of the ALL equaled 11.3 � 2.8 mm. The meandistance of the center of the tibial ALL footprint to thecenter of the Gerdy tubercle (GT-ALL distance)measured 22.0 � 4.0 mm, whereas the distance be-tween the center of the ALL footprint and the insertionof the LCL on the fibular head averaged 21.3 � 4.1 mm.

RadiologyThe database search identified 26 patients (20 male

and 6 female patients; mean age, 35 years) diagnosedwith a Segond fracture on plain radiographs. Review ofthe respective hospital charts of the patients showed

SEGOND FRACTURE: BONY ALL AVULSION 5

that the diagnosis of a Segond fracture was made at amean of 7.6 days after the sustained knee injury, with17 patients (65%) being diagnosed with a Segondfracture on the same day on which the knee injuryoccurred. In 5 patients the status of the ACL could notbe determined because only CT images were availablefor analysis. An accompanying ACL injury was diag-nosed in 95% of the remaining patients, of whom 2(10%) showed an intercondylar eminence fracture.Furthermore, most patients underwent MRI (n ¼ 19) ofthe injured knee at our institution, some of whomalso underwent CT scanning (n ¼ 7). Thus a total of 19Segond fractures were available for calibrated MRImeasurements of the previously mentioned distances.The mean depth of the lateral recess on imaging

measured 6.0 � 1.1 mm. The mean width of the frac-tured tibial bone fragment equaled 14.5 � 2.5 mm. Themean distance of the center of the Segond fracturebed on the tibia to the center of the Gerdy tubercle(GT-Segond distance) measured 22.4 � 2.6 mm.

Statistical AnalysisThe mean GT-ALL distance obtained during dissec-

tions equaled 22.0 mm (SD, 4.0 mm), whereas themean GT-Segond distance measured on MRI was22.4 mm (SD, 2.6 mm). This difference of 0.4 mm(95% confidence interval, �1.5 to 2.2 mm) betweenthe 2 distances was neither statistically significant (P ¼.70) nor clinically relevant. The depth of the lateraltibial recess obtained during dissection and on MRI alsocorresponded well. Table 1 summarizes the mostimportant results.

DiscussionThe results of this study confirmed the hypothesis that

anatomic data on the tibial ALL insertion site wouldmatch the constant anatomic location on the proximaltibia from where Segond fractures do avulse.In 1879, years before the discovery of radiographs,

the French surgeon Paul Segond tried to resolve thecause of bloody knee effusions that were often seenafter a twisting knee injury.1 While subjecting cadavericknees to forced rotational loads, he noticed the occur-rence of a curiously consistent avulsion fracture at thelateral tibial rim, in communication with the knee jointand thus plausibly causing the observed hemarthrosis.

Table 1. Summary of Measured Distances Both in Cadavers and

Depth of LateralTibial Recess (mm)

Width of ALL FootprFracture Fragmen

ALL (n ¼ 29)* 6.5 � 1.5 11.3 � 2.8Segond (n ¼ 19)y 6.0 � 1.1 14.5 � 2.5

NOTE. Data are given as mean � SD.NA, not applicable.*Distances for ALL measurements in cadaveric knees (Anatomy part ofyMeasurements derived from MRI images of patients with Segond fractu

In 1936 the Segond fracture was recognized onradiographs in the first clinical cases presented byMilch.2 Only in the late 1970s was the clinical impor-tance of this remarkably constant knee fractureemphasized. Indebted to the work of Dr. Jack Hugh-ston, the first correlation of the Segond fracture withthe presence of significant knee instability was shownby Woods et al.3 in 1979. In all of the 4 acute cases witha positive “lateral capsular sign” on radiographs, aconcomitant rupture of the ACL was shown. This study,together with the work of Goldman et al.4 and Hesset al.5 (9 and 14 cases, respectively), has established thewidely recognized pathognomonic association betweenSegond fractures and ACL ruptures.11,12 Although thecurrent literature is clearly lacking series with a largecohort analysis, some studies do suggest that aSegond fracture might occur in 9% to 12% of all ACLinjuries.5,13

The Segond fracture is generally described as anavulsion-type fracture, indicating the detachment of abone fragment by the pull of a ligament or tendon fromits insertion point. However, although Segond1 himselfbriefly reported on the existence of a “pearly, resistant,fibrous band” attached to his eponymous fracture, laterliterature has remained unclear on what structureactually causes the avulsion. The “iliotibial band,”2,14,15

the “(meniscotibial portion of the) middle one-third ofthe lateral capsular ligament,”3,16 the “anterior (obli-que) band of the lateral collateral ligament,”15,17 andthe “anterior arm of the short head of the biceps fem-oris”18 have all been named as the potential anatomicculprit. Yet, vague descriptions and the obvious lack ofdetailed illustrations or photographs of these anatomicstructures have led to much confusion about the pre-sumed anatomy and function of Segond’s enigmatic“pearly, fibrous band.” Likewise, the Segond fracture isnowadays merely considered a pathognomonic radio-graphic feature for a ruptured ACL, and the clinicalrelevance of the Segond fracture itself has only beenpoorly investigated. Johnson16 noted, for instance, thatthe occurrence of a bony Segond fracture attached to anintact “lateral capsular ligament” suggested a “strengthbeyond that previously attributed to this ligament.”Furthermore, he suggested a link between a lesion tothis “lateral capsular ligament” and the occurrence of acertain knee instability pattern, what he called the

on MRI Images

int/Segondt (mm)

Distance to Fibular Head(LCL Insertion) (mm)

Distance to GerdyTubercle (mm)

21.3 � 4.1 22.0 � 4.0NA 22.4 � 2.6

study).res (Radiology part of study).

6 S. CLAES ET AL.

“lateral pivot shift.” More recently, Campos et al.15

suggested that fibers of the ITB and the so-calledanterior oblique band are important factors in thepathogenesis of the Segond fracture.Recently, the precise anatomic details of the ALL of

the human knee have been provided.8,19,20 In brief, theALL was identified as a distinct ligamentous structureoriginating on the lateral femoral epicondyle andinserting on the anterolateral tibia, showing firmattachments to the body of the lateral meniscus alongits oblique course at the lateral aspect of the knee.Given the course of the ALL and its presumed role incontrolling internal rotation of the tibia relative to thefemur, it was hypothesized that the ALL could be theanatomic culprit in Segond fractures, and the results ofthis study have confirmed this hypothesis.The main finding of our seriesdthe largest series of

Segond fractures (n ¼ 26) in the current literaturedisthe confirmation of the hypothesis that the ALL in-serts precisely in the region on the proximal tibia fromwhere Segond fractures consistently avulse. Further-more, our series showed that the occurrence of aSegond fracture is strongly associated with a concomi-tant ACL injury because 95% of the patients in thisstudy showed ACL abnormalities on medical imaging.These results are in line with the vast majority of thecurrent literature on Segond fractures, classicallymentioning correlations ranging between 75%21 and100%4,5 in the adult population.6 The results of thisstudy therefore underscore that the Segond fracture canbe regarded as a strong indication of the presence of anintra-articular ligament injury12 but, above all, that aSegond fracture represents a frank ligamentous avul-sion itself. In this view the Segond fracture should notbe uniquely regarded as a useful radiographic clue forACL injury but should be regarded as a bony injury ofthe ALL as well.

Given its anatomic location at the anterolateral edge ofthe knee, the ALL has been suggested to function as astabilizer for internal rotation.8 Indeed, our qualitativefindings in the anatomic part of this study are in linewiththe remarks of Segond,1 who described “invariably.extreme amounts of tension during forced internalrotation” occurring in the “pearly, fibrous band.”Although the ALLwas previously found to become tensewith forced internal rotation between 30� and 90� ofknee flexion,8,22 further kinematic analysis is needed toformally establish a potential role for the ALL in com-mon knee instability patterns involving excessive inter-nal rotation such as the pivot shift.23,24 In addition, moreresearch is needed to delineate the clinical effect of aSegond fracture on knee stability in the ACL-deficientknee and to establish an eventual role for concomitantSegond fracture treatment in these patients.

LimitationsThis study did have its limitations. To prove the

hypothesis that the Segond fracture is caused by anavulsion of the ALL, a comparison between 2 differentsets of data of different origin (cadaveric knees vimaging) was performed. However, with all theincluded MR images being calibrated, excellent accu-racy of 2-dimensional MRI measurements (i.e., dis-tances) on “clinical” MR images has extensively beenreported in the orthopaedic literature.25-27 Given thedifferent nature of the data sets, this study by definitiondelivers only indirect proof of the presumed causal linkbetween Segond fractures and the ALL. Ideally, per-forming a study involving the production of a Segondfracture in cadaveric knees by a forced provocativemovement with subsequent dissection of the fracturefragment and its attached soft tissues would be the onlyway to provide direct proof of the hypothesis. In fact,such a study would imply the exact replication of

Fig 4. (A) Typical Segond fracture asobserved on a frontal MRI sequence ofa left knee (radiology part of study). (B)Frontal view of ALL in a dissected leftknee (anatomy part of study). Theparallel between the location of theSegond fracture bed and the tibial ALLinsertion can be easily appreciated. Theyellow arrows depict the ALL on boththe MR image and cadaveric dissection.(LFC, lateral femoral epicondyle; LM,lateral meniscus.)

Fig 5. (A) Three-dimensional recon-structed CT image of Segond fracturecase in a left knee (radiology part ofstudy). (B) Lateral view of ALL in adissected left knee (anatomy part ofstudy). The parallel between the loca-tion of the Segond fracture bed and thetibial ALL insertion can be easilyappreciated (blue arrows). The yellowasterisk indicates the intercondylareminence fracture. (FH, fibular head;LFE, lateral femoral epicondyle.)

SEGOND FRACTURE: BONY ALL AVULSION 7

experiments performed by Segond himself. However,because the exact provocative mechanism of a bonyALL injury is still unclear, these complex experimentswere regarded as beyond the scope of this study. On theother hand, direct comparison of typical MR or CTimages of a Segond fracture case with the preciseanatomic findings on the ALL’s tibial insertion bearssuch a high degree of self-evidence (Figs 4 and 5) thatthe repetition of Segond’s experiments was consideredredundant.

ConclusionsThe results of this study confirmed the hypothesis

that the ALL inserts in the region on the proximal tibiafrom where Segond fractures consistently avulse, thussuggesting that the Segond fracture is actually a bonyavulsion of the ALL.

AcknowledgmentThe authors thank Cedric Depuydt for his appreciated

contribution to the study.

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