A low morbidity surgical approach to the sheep femoral trochlea.

1.2 MB·English

by  Orth, Patrick

OrthandMadryBMCMusculoskeletalDisorders2013,14:5
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TECHNICAL ADVANCE Open Access
A low morbidity surgical approach to the sheep
femoral trochlea
Patrick Orth1,2 and Henning Madry1,2*
Abstract
Background: The ovine stifle joint is an important location for investigations onthe repair ofarticular cartilage
defects in preclinical large animals. The classical medial parapatellar approach to the femoral trochlea is hazardous
because of thehighrisk of postoperative patellar luxation. Here, wedescribe a low morbidity surgical exposureof
theovine trochlea without the necessity for intraoperative patellar luxation.
Methods: Bilateral surgical exposure ofthe femoral trochlea of thesheep stifle joint was performed using the
classical medial parapatellar approach with intraoperative lateral patellar luxationand transection of the medial
patellar retinaculum in28 ovine stifle joints. A low morbidity approach was performed bilaterally in116 joints
through a mini-arthrotomy without the need to transect themedial patellar retinaculum or theoblique medial
vastus muscle nor surgical patellarluxation. Postoperatively, all72 animals were monitored to exclude patellar
luxations and deep wound infections.
Results: Thenovelapproachcouldbeperformedeasilyinalljointsandsafelyexposedthedistaltwo-thirdsofthe
medialandlateraltrochlearfacet.Nopostoperativepatellarluxationswereobservedcomparedtoapostoperative
patellarluxationrateof25%experiencedwiththeclassicalmedialparapatellarapproachandare-luxationrateof80%
followingrevisionsurgery.Nosignsoflameness,woundinfections,orempyemawereobservedforbothapproaches.
Conclusions:Themini-arthrotomypresentedhereyieldsgoodexposureofthedistalovinefemoraltrochleawitha
lowerpostoperativemorbiditythantheclassicalmedialparapatellarapproach.Itisthereforesuitabletocreatearticular
cartilagedefectsonthefemoraltrochleawithouttheriskofpostoperativepatellarluxation.
Keywords:Cartilage,Sheep,Trochlea,Patella,Luxation,Invivo
Background From a human articular cartilage repair standpoint,
Preclinical models of articular cartilage repair are of para- the trochlea is an important location to create cartilage
mount importance to translate experimental approaches defects [11], since the clinical outcome of defects at this
into the clinical situation [1]. The sheep or goat stifle joint anatomical site is unfavorable compared with lesions in
is one preferred model for those studies [2-4] as it the femoral condyles [12]. Moreover, the sheep trochlea
combines unique advantages over other species, such as is plane with a large surface, making it an ideal site to
similarities in the repair capacity of articular cartilage study articular cartilagerepair ina standardized manner.
defectsandsimilarbiomechanicalpropertiesincludinglong The surgical exposure of the trochlea by the classical
bone dimensions and body weight to humans [5,6]. The medial parapatellar approach involves the intraoperative
mechanical loading environment occurring in sheep and luxation of the patella. While easy to perform in patients
goatsiswellunderstood[7-9]andtheyareeasiertohandle [13], a significant rate of postoperative patellar luxations
thanpigsorhorses,includinganesthesia[10]. may occur in sheep or goats when applying the classical
approach. Such patellar luxations are based on the
differentanatomyoftheovineandcaprinestiflejointwhen
*Correspondence:[email protected] compared to the human knee: in extension, the patella is
1CenterofExperimentalOrthopaedicsandOsteoarthritisResearch,Saarland located proximal to the trochlea and glides within the
University,Homburg/Saar,Germany
2DepartmentofOrthopaedicSurgery,SaarlandUniversityMedicalCenter, trochlear groove only in flexion of the stifle joint. This
Homburg/Saar,Germany
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special feature of the more posteriorly angled trochlea, in Classicalmedialparapatellarapproach
combinationwitharelativelysmalllateralfemoralcondyle, Prior to development of the novel less-invasive surgical
makes complications very likely if a medial parapatellar approach, exposure of the ovine femoral trochlea has
incisionandlateralpatellarluxationischosen.Inaddition, been performed by the use of the classical medial para-
the ovine medial retinaculum is mostly stronger and more patellarapproach in28stiflejointsin14sheep.
difficult to repair after transection. Besides, even if no According to the report of Allen et al. [17], a medial
patellar luxation occurs, osteoarthritis may frequently parapatellar skin incision was made from 5 cm proximal
result from using the classical approach, possibly jeop- to the patella to apoint 5cm distal to the tibial tubercle.
ardizingsurgicalresultsconsiderably[14]. With the proximal incision, the oblique medial vastus
Here,we describe alow morbidity surgical exposureof muscle often had to be incised to allow for luxation of
the ovine femoral trochlea with reduced risk for patellar the patella. The joint capsule was opened medial and
luxation. parallel to the patellar tendon with transection of the
medial patellar retinaculum. The patella was luxated
laterally and retracted by the use of a Hohmann re-
Methods
tractor. For closure of the capsule, absorbable sutures
Studydesign
were applied (Vicryl; size 2; Ethicon, Norderstedt,
Surgical exposure of the femoral trochlea of the sheep
Germany). The subcutaneous tissue and the skin inci-
stifle joint was performed by the same surgeon (HM)
sionwereclosedusingVicrylsize2/0and2,respectively.
using either a standard medial parapatellar approach
Simple interrupted suture patterns were applied for all
with luxation of the patella (n=14 sheep) or a novel
anatomicallayers.Aluminiumbandagespraywasapplied
mini-arthrotomy without intraoperative patellar luxation
tothewounds.
(n=58).Allsheep(n=72)wereallowedfullweight-bearing
and full range of motion immediately postoperatively.
Novelless-invasiveapproach
Animals operated for previous [15,16] or unpublished
The novel approach to the ovine femoral trochlea was
studies of experimental articular cartilage repair served
applied in116arthrotomiesin58sheep.
assubjectstodescribethesurgicalapproaches.
Animalpositioninganddraping
The sheep were placed in a supine position with both
Animals
hindlimbs untied (Figure 1A). The skin over both stifle
Healthy, skeletally mature, Merino ewes aged between 2
joints was shaved consecutively using a gross and a fine
and 4 years (mean body weight [BW], 70±20 kg)
received water ad libitum and were fed a standard diet. electric shaver. No tourniquet was applied, limbs were
aseptically(Braunol,Braun,Melsungen,Germany)prepared
Osteoarthritis was excluded on preoperative X-rays of
forsurgery.Linensheetswereplacedontotheabdomenof
the stifle joints. All animal experiments were conducted
the sheep to extend the sterile area (Figure 1B). The
in accordance with the national legislation on protection
hindlimbs were then put through fenestrated linen sheets,
of animals and the National Institutes of Health (NIH)
allowing covering of the proximal, lateral and medial
Guidelines for the Care and Use of Laboratory Animals
(NIH Publication 85–23, Rev 1985) and were approved borders and leaving open a triangular operative site
(Figure 1C). The fenestrated sheets were secured with
bythelocalgovernmental animal care committee.
towel clips. Impermeable plastic drapes (70 × 70 cm)
were used to wrap lower limb and claw. Full extension
Anesthesia of hip and stifle joints during wrapping of the lower leg
Following a 12-hour fast, animals were sedated with 2% is crucial to avoid later shifting of the drapes during
Rompun (Bayer, Leverkusen, Germany) at 0.05 mg/kg intraoperative joint mobilization (Figure 1B). Adhesive
BW and endotracheally intubated after intravenous tapes were used to fixate the plastic drape around the
administration of 20 ml of 2% propofol (AstraZeneca, claws. Stockinettes are a more expensive alternative for
Wedel, Germany) and carprofen (1.4 mg/kg BW; Pfizer, thewrappingofthelowerlimb.
Berlin, Germany).Anesthesiawasmaintained by inhalation
of 1.5% isoflurane (Baxter, Unterschleißheim, Germany) Surgicalapproach
and intravenous administration of propofol (6–12 mg/kg Important landmarks include the patella, the patellar
BW/h). At the day of the operation and the first or second ligament, and the tibial tubercle (Figure 2) [17]. Under
postoperative day, respectively, animals routinely received constant pull on the hindlimb to ensure full extension of
analgesia (carprofen; 1.4 mg/kg BW; Pfizer, Berlin, thehipandstiflejoint,a straight skinincision of4–5cm
Germany) and antibiotics (amoxicillin clavulanate; length was made, extending from a point 1cm medial of
30mg/kgBW;Pfizer). the inferior pole of the patella towards the tibial
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Figure1Keyproceduresofthenovelless-invasivesurgicalapproach.Thesheepwereplacedinasupineposition(A).withlinensheets
ontotheabdomentoextendthesterilearea(B).Fullextensionofhipandstiflejointsbyaxiallypullingbothhindlimbsduringwrappingiscrucial
tolateravoidapossibleshiftingofthedrapesduringintraoperativejointmobilization(B).Fenestratedlinensheetsareusedtocoverthe
proximal,lateralandmedialborders,leavingopenatriangularoperativesite(C).Followingtheslightlyobliqueskinincision(length4–5cm)and
arthrotomy,exposureofthedistaltwothirdsofthelateralandmedialfacetofthefemoraltrochleaisachieved(D).Thispreservestheoblique
medialvastusmuscleandthemedialpatellarretinaculumandretainsthepatellainaproximalpositionwithouttheneedforitsintraoperative
surgicalluxation(Figure2).Eachfemoralcondyle(E)aswellastheanteriorthirdofeachmeniscus(E;arrow)canalsobesafelyexposedwhen
applyingdifferentdegreesofstiflejointflexion.Forclosureofthecapsule,non-absorbablesutureswereused(F).Thesurgicalwounds(F)were
closedinlayersbysimpleinterruptedsuturepatterns.Finally,aluminiumbandagespraywasapplied(G).
tubercle. This oblique incision takes in account that the axial pull on the hindlimb and full extension of stifle and
trochlear groove does not run in parallel to the femoral hip joints now allowed exposure of the distal two thirds
shaft but is orientated at an angle of 20 ± 5 from proxi- of the lateral and medial facet of the femoral trochlea
molateral to distomedial [17]. Utmost care was taken to (Figure 1D). Most importantly, by the use of this
prevent the oblique medial vastus muscle from any approach, the patella was neither everted nor luxated out
damage inthe proximalpart ofthewound.Thesubcuta- ofthepatellofemoraljoint.Instead,itistiltedlaterallyand
neous tissue was divided in the line of the skin incision displaced proximally by the use of a Hohmann retractor
by the use of an electrocautery, ensuring hemostasis. and maximal extension of the hip and stifle joint. In
The medial border of the patellar tendon was exposed addition, the medial patellar retinaculum is not trans-
and the joint was entered by cutting through the joint ected, minimizing the risk for postoperative patellar
capsule. Importantly, this distal location of the arthrot- luxations. Furthermore, the medial and lateral femoral
omypreservesthemedialpatellarretinaculum(Figure2). condyle (Figure 1E, Figure 2) as well as the anterior
Since the synovium and the joint capsule are intimately third of both menisci (Figure 1E) can also be exposed
related [17], the capsular incision also opened the easily using this approach when applying different
synovium. Small Weidtlaner wound retractors served to degreesofstiflejointflexion.
facilitate exposure. Care was taken not to damage the
cartilaginous joint surface of the trochlea during Woundclosure
arthrotomy. For better exposure of the femoral troch- The surgical wounds (length 4–5 cm; Figure 1F) were
lea, the parapatellar fat pad was either retracted with closed in layers. First, the medial extensor mechanism
a Langenbeck retractor or partially resected. A small (capsule and patellar tendon) was meticulously recon-
Hohmann retractor was then placed between the patellar structed. This suture is of paramount importance with
ligament close to the inferior patellar pole and the proxi- regardtothepreventionofpostoperativepatellarluxations.
molateral femoral condyle (Figure 2). This retractor was Therefore, we chose the non-absorbable Ethibond suture
usedtoliftthepatellaandretainitinaproximalposition (size 6; Ethicon, Norderstedt, Germany) to ascertain a
without intraoperative surgical luxation. The additional biomechanically stable reconstruction of the extensor
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interrupted suture patterns were applied for all anatomical
layers. Finally, an aluminium bandage spray was applied to
thewounds(Figure1G).
Postoperativemonitoring
All 58 animals were continuously monitored over
6 months to exclude postoperative patellar luxations,
deepwoundinfection, orempyema.
Patellarluxation
The animals were examined daily over the first 5 weeks
and weekly for the remaining observation period by
adspection for clinical signs of patellar luxation such as
abnormalities in hindleg carriage, stance, or lameness.
Additionally, with the sheep in a sitting position,
thorough palpation of the joints was conducted and they
were put through a range of motion. Digital pressure
was applied to the medial border of the patella to test
for its stability and exclude luxation. The different
grades of patellar luxation in sheep are given in Table 1.
X-ray was performed only in the case of uncertainty
uponclinicalexamination.
Deepwoundinfectionsandempyema
All stifle joints were examined clinically for redness,
hyperthermia, swelling, and secretion and body
temperature was measured daily over the first 3 weeks
andweeklyfor theremaining observation period.
Results
Classicalmedialparapatellarapproach
Priortodevelopmentoftheless-invasivesurgicalapproach,
exposureoftheovinefemoraltrochleahadbeenperformed
Figure2Schematicdrawingofthesurgicalanatomyofthenovel bilaterally using the standard medial parapatellar approach
lowmorbidityapproach.Thedescribedless-invasivesurgicalapproach withintraoperativelateralluxationofthepatellain28stifle
allowsforaminimallyinvasiveexposureofthedistaltwothirdsofthe
joints (n =14 animals). Inadvertent postoperative luxation
medialandlateraltrochlearfacetinsheep.
of the patella was frequently observed in 7 stifle joints
Itpreservestheobliquemedialvastusmuscleaswellasthemedial
patellarretinaculumthatwouldhavetobetransectedusingtheclassical (25%) (n=5 animals); two animals (14%) suffered from
medialparapatellarapproach.Especiallyasnointraoperativepatellar bilateral patellar luxations. Anteroposterior X-rays were
luxationisneeded,theriskforpostoperativepatellarluxationsis performed in two animals to verify the clinical diagnosis
decreasedcomparedtotheclassicalapproach.Moreover,flexionofthe
(Figure 3). The postoperative interval until luxation was of
stiflejointallowsforagoodexposureofthemedialandlateralcondyle
14–21 days. Luxations were grade II (n=2) and grade III
aswellastheanteriorthirdofbothmenisci.Theskinincisionisdepicted
indarkred.F:femur;QT:quadricepstendon;OMV:obliquemedialvastus (n=5), indicating that manual reposition was always
muscle;MPR:medialpatellarretinaculum;P:patella;LT:lateraltrochlear feasible(Table1).Therefore,animalswerefirsttreatedwith
facet;MT:medialtrochlearfacet;LC;lateralfemoralcondyle;MC:medial anti-inflammatorymedication(carprofen)foroneweek.As
femoralcondyle;PL:patellarligament;FI:fibula;T:tibia.Foreaseof
lameness worsened in all animals, surgical stabilization of
visualization,theremainingpartsofthequadricepsmuscleaswellas
the patella was performed by revision with capsular and
othercapsularstructuresandpartsoftheovineanatomyarenotshown.
retinacular imbrication. Of note, the previously applied
absorbablesutureswerenotdetectableanymorewithinthe
mechanism.AdditionalEthibondsutures(size3)servedfor subcutaneous tissue or at the level of the capsule at the
tight closure of the capsule (Figure 1F). The intermediate time of revision surgery (3–4 weeks postoperatively),
softtissuelayer,thesubcutaneoustissue,andtheskinwere indicating their significantly faster absorption compared to
readapted using absorbable sutures (Vicryl; size 2, size 2/0, humans. One animal with bilateral luxations did not
size2,respectively;Ethicon,Norderstedt,Germany).Simple survive the revision surgery due to complications during
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Table1Gradesofpatellarluxationinsheep
Grade Patellaatexamination Luxation Reposition Reluxation Lameness Bonedeformities
I reduced manualbydigitalpressure spontaneous rare mild seldom
II reducedinextension manualbydigitalpressure manualbydigitalpressure upon resolvable sometimes
andluxatedinflexion orspontaneousinflexion orspontaneousinextension manipulation skippinglameness
III luxated spontaneous manualbydigitalpressure frequent severe often
IV luxated permanent notpossible permanent crouchingstance veryoften
Patellarluxationsinsheepareevaluatedaccordingtothegradingscalesdevelopedforsmallanimalssuchascatsanddogs[50,62].Diagnosiscanbemadeupon
clinicalexamination;radiographicanalysisisnotnecessary.Clinicalsignsatadspectionincludeabnormalitiesingaitorhindlegcarriagewiththestiflejointflexed,
lameness,lockingoftheaffectedlimbinextension,and-especiallyinbilateralluxations-crouching,bowleggedorknock-kneedstance.
anesthesia. Out of the five revised stifle joints, four successful. Anesthesia was uneventful. There were no
exhibited re-luxation of the patella with necessity for intraoperative complications. Surgical time was between
sacrifice of 2 sheep. Other severe complications such as 15 and 20 min per joint. The sheep recovered quickly, as
deepwoundinfectionsorempyemawerenotobserved. indicated by their rise already at 1–2 hours and the full
weightbearing on both operated hindlimbs 24 hours
Novelless-invasiveapproach postoperatively. Upon clinical examination, no signs of
The surgical procedure was performed bilaterally in 116 lameness (assessable in bilaterally operated animals only
joints(n=58sheep).Exposureofthetrochleawasalways upon full weightbearing), deep wound infections, or
empyemawereobservedatanytimepoint.Skinincisions
healed 2 weeks after surgery. No patellar luxations were
observed in any of the sheep operated with the novel
surgicalapproach.
Discussion
Theauthors describe a less-invasive surgical approach to
theovinestiflejoint,allowingforalowmorbidityexposure
of the femoral trochlea without the need for intraoperative
patellar luxation. This approach was applied in 116 stifle
jointsandistechnicallyeasy,safe,andyieldsgoodexposure
of the distal two thirds of the trochlea. Surgical benefits
include the preservation of important structures, such as
the medial patellar retinaculum, the oblique medial vastus
muscle, and of patellar blood supply. Importantly, post-
operative patellar luxation never occurred. This approach
therefore may be valuable to create articular cartilage
defectsontheovinefemoraltrochlea.
The sheep or goat stifle joint is a key animal model
reflecting many features of the human knee, including
the relative sizes of articulating bones, the straight leg
axis, or the existence of cruciate ligaments, menisci,
asymmetrical collateral ligaments, and a bicondylar dis-
tal femur [2-4,6]. Compared to other large animals such
as horses, sheep and goats have the advantages of easy
handling and cost effectiveness [10]. However, goats can
prove more difficult to house than sheep [18]. Besides,
although the articular cartilage is thicker in goats (up to
1.9mm)than insheep (0.3-0.7 mm)[19],goatsaremore
susceptible to spontaneous osteoarthritis [18]. Therefore,
wehereapplied sheep ratherthan thegoat model.
Figure3Anteroposteriorradiographicviewofarightovine Regarding articular cartilage defects, the sheep has
stiflejointwithagradeIIIpatellarluxation.Theluxatedpatella been used as animal model for partial- [20] and full-
(arrowheads)canbeidentifiedproximolateraltothelateralfemoral
thickness [21-23] chondral and osteochondral defects
epicondylus(star),dislocatedoutsideofthepatellargroove.
[11,24,25]. Several studies also used the ovine stifle joint
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to test implants [26] and as a model for osteoarthritis predispositionforpatellarluxationinsheep[50].Altogether,
[27,28],cruciate ligament reconstruction[29,30], ormenis- these factors may favour a unilateral experimental set-up,
cus repair [31]. However, the classical medial parapatellar allowing foratleastonepain-freehindlegtofacilitatepost-
arthrotomyincludessurgicalpatellarluxation,unnecessarily operativerisingandstanding.
increasing the risk for postoperative complications such as Clinical signs of patellar luxation include persistent,
patellarluxation.Withaviewofanimalwelfareandprotec- abnormal hindleg carriage with the stifle joint flexed,
tion,aless-invasivesurgicalapproachwithreducedriskfor lameness, and -especially in bilateral luxations- crouching,
patellarluxationisrequired. bowlegged or knock-kneed stance (Table 1), and may
To date, most studies on articular cartilage repair in usually be perceived upon postoperative weightbearing
sheep used the medial femoral condyle [21-25,32-41], (circa 24 hours after surgery). The suspected diagnosis can
perhaps because of its uncomplicated surgical exposure. be affirmed by clinical examination: When luxated, the
Despite an improved histological grading of chondral patella is palpable laterally, with a grinding sensation when
defects at the ovine trochlea compared with the condyle being mobilized and a snapping sound upon reduction.
after 8, 10, and 12 weeks [42], the trochlea is underre- Although not necessary routinely, additional radiological
presented in these investigations [11,34]. This may in examination by X-ray (anteroposterior (Figure 3) or flexed
partbeduetothedecreasedthicknessofnormalcartilage dorsoproximal-dorsodistal radiographic views [50]) may
at the trochlea compared with the femoral condyles [19] confirmthediagnosis.Inthisreport,theinitialtreatmentof
or the tibial plateau [43], although proteoglycan levels of these grade II-III luxations was non-operatively, but as
trochlear and condylar cartilage are similar [44,45]. Yet, lameness and non-weightbearing worsened, soft tissue
due to its plane and large cartilaginous surface, the ovine revision surgery (capsular and retinacular imbrication) was
trochlea is suitable for cartilage repair studies. The here performed. In order to preserve the femoral trochlea,
described surgical approach not only allows for a safe osseous reconstruction procedures initially developed for
exposure of this important anatomical site, but also the canine model [50] such as trochleoplasty [51] or tibial
gives access to the medial and lateral femoral condyle tuberosity transposition [52] were avoided here. Intri-
andbothmenisci. guingly, the postoperative rate of re-luxations was of 80%.
The preclinical sheep model is prone to rather high Ingoodagreement,failureratesof80%and50%havebeen
postoperative complication rates which might not always reported for the surgical treatment of patellar luxations in
bereported.Theseincludewounddehiscenceorinfections llamas [52] and dogs [53], respectively. Thus, although the
duetonon-anatomicalwoundclosuresignoringthelayered mild temperament and relatively small body size of sheep
structure of the soft tissue, the reduced antiseptic environ- generally renders them amenable for the operative
mentcausedbythenatureoftheanimalmodelitself,miss- treatment of orthopedic problems [51,52,54], we do not
ing routing in draping, insufficient surgical experience and recommend revision surgery in the case of postoperative
knowledge of the anatomical structures, or extended oper- patellarluxationsinthisanimalmodel.
ation times [46]. Besides, complication rates in the sheep Interestingly,absorbablesuturematerialsweredegraded
model are additionally increased by the fact that reduced much faster in sheep than in humans. For the closure
loading of the operated hindlimb can only be achieved by of the joint capsule, the relatively high concentrations
extendedmeasuressuchasapplyingsplints,harnesses[47], of inflammatory cytokines [32] and activated matrix
plastercasts[48],orhangingtheanimalsinslings[49]. metalloproteinase-2 [55] of the ovine synovial fluid
In the present report, patellar luxations only occurred might explain this finding, while the elevated mean
followingthe classicalmedialapproachwithintraoperative body temperature of sheep (38-40°C) compared to
patellarluxationandtransectionofthemedialpatellarreti- humans [56,57] may contribute to a generally faster
naculum. Thus, although considered a standard approach degradation of absorbable foreign materials. Therefore,
forclinicalandpreclinicalpurposes[17],westronglyadvise althoughappliedinroutineprotocolsforkneearthrotomies
against this erroneous surgical technique in future trans- in patients and in various sheep studies [36,42,48,58-60],
lational animal experiments and in veterinary surgery. Vicryl and other absorbable sutures are inadvisable for the
This serious complication may additionally be provoked reconstruction of the biomechanically important extensor
by the specific anatomy of the ovine patellofemoral joint mechanism. In veterinary medicine, monofilament and
(small lateral femoral condyle, patella located outside thicker absorbable sutures are used successfully for this
andproximaltothetrochleargrooveinextension,prox- purpose [61]. Here, we applied non-absorbable suture
imolateral to distomedial angle of the trochlear groove materials, but the potential risk of postoperative fistula
[17]), together with the high loading forces resulting formation has to be acknowledged and further evaluated
from an unprotected rise from the lying down position in future investigations. Regarding the suture pattern,
[49]. Besides,thehighluxationratefollowingthe classical interruptedsuturesarepreferablecomparedtocontinuous
approach may possibly be ascribed in part to a genetic sutures[61].
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Conclusions 11. KandelRA,GrynpasM,PilliarR,LeeJ,WangJ,WaldmanS,ZalzalP,HurtigM:
Patellar luxation is a frequent complication when the Repairofosteochondraldefectswithbiphasiccartilage-calcium
polyphosphateconstructsinasheepmodel.Biomaterials2006,27:4120–4131.
classical medial parapatellar arthrotomy is performed in
12. KreuzPC,SteinwachsMR,ErggeletC,KrauseSJ,KonradG,UhlM,SudkampN:
sheep. Its diagnosis can be made be simple physical Resultsaftermicrofractureoffull-thicknesschondraldefectsindifferent
examination -X-ray is not necessary for its confirmation. compartmentsintheknee.OsteoarthritisCartilage2006,14:1119–1125.
13. HarwinSF:Themedialparapatellarapproachtotheknee.JKneeSurg
The presented approach to the femoral trochlea avoids
2003,16:43–47.
the need for intraoperative surgical patellar luxation. It 14. BeveridgeJE,ShriveNG,FrankCB:Meniscectomycausessignificantinvivo
is technically easy, safe, and yields excellent exposure of kinematicchangesandmechanicallyinducedfocalchondrallesionsina
sheepmodel.JOrthopRes2011,29:1397–1405.
the distal part of the trochlea. Having used this technique
15. HeiligensteinS,CucchiariniM,LaschkeMW,BohleRM,KohnD,MengerM,
in 116 arthrotomies, patellar luxation never occurred. MadryH:Invitroandinvivocharacterizationofnon-biomedicaland
However, the surgeon still must be mindful of this severe biomedicalgradealginatesforarticularchondrocytetransplantation.
TissueEngPartCMethods2011,17:829–842.
complication,especiallywhentheproximalincisioniscar-
16. HeiligensteinS,CucchiariniM,LaschkeMW,BohleRM,KohnD,MengerMD,
ried our too far, extending into the oblique medial vastus MadryH:Evaluationofnonbiomedicalandbiomedicalgradealginatesforthe
muscleortransectingthemedialpatellarretinaculum. transplantationofgeneticallymodifiedarticularchondrocytestocartilage
defectsinalargeanimalmodelinvivo.JGeneMed2011,13:230–242.
Competinginterests 17. AllenMJ,HoultonJE,AdamsSB,RushtonN:Thesurgicalanatomyofthe
Theauthorsdeclarethattheyhavenocompetinginterests. stiflejointinsheep.VetSurg1998,27:596–605.
18. LittleCB,SmithMM,CakeMA,ReadRA,MurphyMJ,BarryFP:TheOARSI
Authors’contributions histopathologyinitiative-recommendationsforhistologicalassessments
POandHMwereequallyinvolvedinconceptionanddesignofthestudy, ofosteoarthritisinsheepandgoats.OsteoarthritisCartilage2010,
surgicaltreatmentandanimalcare,acquisition,analysisandinterpretationof 18(Suppl3):S80–S92.
thedata,anddraftingofthemanuscriptandrevisingitcriticallyfor 19. FrisbieDD,CrossMW,McIlwraithCW:Acomparativestudyofarticular
importantintellectualcontent.Bothauthorsreadandapprovedthefinal cartilagethicknessinthestifleofanimalspeciesusedinhumanpre-
manuscript. clinicalstudiescomparedtoarticularcartilagethicknessinthehuman
knee.VetCompOrthopTraumatol2006,19:142–146.
Authors’information 20. LuY,HayashiK,HechtP,FantonGS,ThabitG3rd,CooleyAJ,EdwardsRB,
POisworkingasaresidentattheDepartmentofOrthopaedicSurgery, MarkelMD:Theeffectofmonopolarradiofrequencyenergyonpartial-
SaarlandUniversityMedicalCenter,andasapostdoctoralfellowatthe thicknessdefectsofarticularcartilage.Arthroscopy2000,16:527–536.
CenterofExperimentalOrthopaedics,SaarlandUniversity.HMisworkingasa 21. OrthP,GoebelL,WolframU,OngMF,GraberS,KohnD,CucchiariniM,
registrarattheDepartmentofOrthopaedicSurgery,SaarlandUniversity IgnatiusA,PapeD,MadryH:Effectofsubchondraldrillingonthe
MedicalCenter,andisthedirectoroftheCenterofExperimental microarchitectureofsubchondralbone:analysisinalargeanimalmodel
Orthopaedics,SaarlandUniversity. at6months.AmJSportsMed2012,40:828–836.
22. DorotkaR,WindbergerU,MacfeldaK,BindreiterU,TomaC,NehrerS:
Acknowledgements Repairofarticularcartilagedefectstreatedbymicrofractureanda
SupportedbyagrantfromtheDeutscheForschungsgemeinschaft three-dimensionalcollagenmatrix.Biomaterials2005,26:3617–3629.
(DFGMA2363/1–3). 23. DorotkaR,BindreiterU,MacfeldaK,WindbergerU,NehrerS:Marrow
stimulationandchondrocytetransplantationusingacollagenmatrixfor
Received:26May2012Accepted:31December2012 cartilagerepair.OsteoarthritisCartilage2005,13:655–664.
Published:3January2013 24. BurksRT,GreisPE,ArnoczkySP,ScherC:Theuseofasingleosteochondral
autograftpluginthetreatmentofalargeosteochondrallesioninthe
References femoralcondyle:anexperimentalstudyinsheep.AmJSportsMed2006,
1. ReinholzGG,LuL,SarisDB,YaszemskiMJ,O'DriscollSW:Animalmodelsfor 34:247–255.
cartilagereconstruction.Biomaterials2004,25:1511–1521. 25. MunirahS,SamsudinOC,ChenHC,SalmahSH,AminuddinBS,Ruszymah
2. MartiniL,FiniM,GiavaresiG,GiardinoR:Sheepmodelinorthopedic BH:Articularcartilagerestorationinload-bearingosteochondraldefects
research:aliteraturereview.CompMed2001,51:292–299. byimplantationofautologouschondrocyte-fibrinconstructs:an
3. RorvikAM,TeigeJ:Unstablestifleswithoutclinicalorradiographic experimentalstudyinsheep.JBoneJointSurgBr2007,89:1099–1109.
osteoarthritisinyounggoats:anexperimentalstudy.ActaVetScand 26. BellemansJ:Osseointegrationinporouscoatedkneearthroplasty.The
1996,37:265–272. influenceofcomponentcoatingtypeinsheep.ActaOrthopScandSuppl
4. MurphyJM,FinkDJ,HunzikerEB,BarryFP:Stemcelltherapyinacaprine 1999,288:1–35.
modelofosteoarthritis.ArthritisRheum2003,48:3464–3474. 27. YoungAA,McLennanS,SmithMM,SmithSM,CakeMA,ReadRA,MelroseJ,
5. NewmanE,TurnerAS,WarkJD:Thepotentialofsheepforthestudyof SonnabendDH,FlanneryCR,LittleCB:Proteoglycan4downregulationin
osteopenia:currentstatusandcomparisonwithotheranimalmodels. asheepmeniscectomymodelofearlyosteoarthritis.ArthritisResTher
Bone1995,16:277S–284S. 2006,8:R41.
6. OsterhoffG,LofflerS,SteinkeH,FejaC,JostenC,HeppP:Comparative 28. HeppP,OsterhoffG,NiederhagenM,MarquassB,AignerT,BaderA,Josten
anatomicalmeasurementsofosseousstructuresintheovineand C,SchulzR:Perilesionalchangesoffocalosteochondraldefectsinan
humanknee.Knee2011,18:98–103. ovinemodelandtheirrelevancetohumanosteochondralinjuries.
7. TaylorWR,EhrigRM,DudaGN,SchellH,SeebeckP,HellerMO:Onthe JBoneJointSurgBr2009,91:1110–1119.
influenceofsofttissuecoverageinthedeterminationofbone 29. LuY,MarkelMD,NemkeB,WynnS,GrafB:Comparisonofsingle-versus
kinematicsusingskinmarkers.JOrthopRes2005,23:726–734. double-tunneltendon-to-bonehealinginanovinemodel:abiomechanical
8. TaylorWR,EhrigRM,HellerMO,SchellH,SeebeckP,DudaGN:Tibio- andhistologicalanalysis.AmJSportsMed2009,37:512–517.
femoraljointcontactforcesinsheep.JBiomech2006,39:791–798. 30. FabbricianiC,MulasPD,ZiranuF,DeriuL,ZarelliD,MilanoG:Mechanical
9. Bylski-AustrowDI,MalumedJ,MeadeT,GroodES:Kneejointcontact analysisoffixationmethodsforanteriorcruciateligament
pressuredecreasesafterchronicmeniscectomyrelativetotheacutely reconstructionwithhamstringtendongraft.Anexperimentalstudyin
meniscectomizedjoint:amechanicalstudyinthegoat.JOrthopRes sheepknees.Knee2005,12:135–138.
1993,11:796–804. 31. KohnD,WirthCJ,ReissG,PlitzW,MaschekH,ErhardtW,WulkerN:Medial
10. KitchenH:Sheepasanimalmodelsinbiomedicalresearch.JAmVetMed meniscusreplacementbyatendonautograft.Experimentsinsheep.J
Assoc1977,170:615–619. BoneJointSurgBr1992,74:910–917.
OrthandMadryBMCMusculoskeletalDisorders2013,14:5 Page8of8
http://www.biomedcentral.com/1471-2474/14/5
32. BenazzoF,CadossiM,CavaniF,FiniM,GiavaresiG,SettiS,CadossiR, 54. KanepsAJ:Orthopedicconditionsofsmallruminants.Llama,sheep,goat,
GiardinoR:Cartilagerepairwithosteochondralautograftsinsheep: anddeer.VetClinNorthAmFoodAnimPract1996,12:211–231.
effectofbiophysicalstimulationwithpulsedelectromagneticfields. 55. MiyamotoK,IshimaruJ,KuritaK,GossAN:Synovialmatrix
JOrthopRes2008,26:631–642. metalloproteinase-2indifferentstagesofsheeptemporomandibular
33. GuoX,WangC,ZhangY,XiaR,HuM,DuanC,ZhaoQ,DongL,LuJ,Qing jointosteoarthrosis.JOralMaxillofacSurg2002,60:66–72.
SongY:Repairoflargearticularcartilagedefectswithimplantsof 56. RecabarrenSE,VergaraM,LlanosAJ,Seron-FerreM:Circadianvariationof
autologousmesenchymalstemcellsseededintobeta-tricalcium rectaltemperatureinnewbornsheep.JDevPhysiol1987,9:399–408.
phosphateinasheepmodel.TissueEng2004,10:1818–1829. 57. IgonoMO,MolokwuEC,AliuYO:Seasonalvariationsinrectaltemperature
34. HoemannCD,HurtigM,RossomachaE,SunJ,ChevrierA,ShiveMS, ofYankasasheep.VetResCommun1983,6:223–226.
BuschmannMD:Chitosan-glycerolphosphate/bloodimplantsimprove 58. vonRechenbergB,AkensMK,NadlerD,BittmannP,ZlinszkyK,NegesK,
hyalinecartilagerepairinovinemicrofracturedefects.JBoneJointSurg AuerJA:Theuseofphotooxidized,mushroom-structuredosteochondral
Am2005,87:2671–2686. graftsforcartilageresurfacing–acomparisontophotooxidized
35. HurtigMB,NovakK,McPhersonR,McFaddenS,McGannLE,MulDrewK, cylindricalgraftsinanexperimentalstudyinsheep.Osteoarthritis
SchacharNS:Osteochondraldoweltransplantationforrepairoffocal Cartilage2004,12:201–216.
defectsintheknee:anoutcomestudyusinganovinemodel.VetSurg 59. MrosekE,ErggeletC,McDonaldJA,KurzH:Hyaluronansynthasesinnormal
1998,27:5–16. andregeneratingjointcartilage.CellsTissuesOrgans2003,173:93–104.
36. vonRechenbergB,AkensMK,NadlerD,BittmannP,ZlinszkyK,KutterA, 60. NussKM,AuerJA,BoosA,vonRechenbergB:Ananimalmodelinsheep
PooleAR,AuerJA:Changesinsubchondralboneincartilageresurfacing– forbiocompatibilitytestingofbiomaterialsincancellousbones.BMC
anexperimentalstudyinsheepusingdifferenttypesofosteochondral MusculoskeletDisord2006,7:67.
grafts.OsteoarthritisCartilage2003,11:265–277. 61. BootheHW:SutureMaterials,TissueAdhesives,Staplers,andLigating
37. FroschKH,DrengkA,KrauseP,ViereckV,MiosgeN,WernerC,SchildD, Clips.InTextbookofsmallanimalsurgery.3rdedition.EditedbySlatterD.
SturmerEK,SturmerKM:Stemcell-coatedtitaniumimplantsforthe Philadelphia:WBSaundersCo;2003:235–244.
partialjointresurfacingoftheknee.Biomaterials2006,27:2542–2549. 62. VasseurP:Stiflejoint.InTextbookofsmallanimalsurgery.3rdedition.Edited
38. Tytherleigh-StrongG,HurtigM,MiniaciA:Intra-articularhyaluronan bySlatterD.Philadelphia:WBSaundersCo;2003:1854–1861.
followingautogenousosteochondralgraftingoftheknee.Arthroscopy
2005,21:999–1005. doi:10.1186/1471-2474-14-5
39. PearceSG,HurtigMB,ClarnetteR,KalraM,CowanB,MiniaciA:An Citethisarticleas:OrthandMadry:Alowmorbiditysurgicalapproach
investigationof2techniquesforoptimizingjointsurfacecongruency tothesheepfemoraltrochlea.BMCMusculoskeletalDisorders201314:5.
usingmultiplecylindricalosteochondralautografts.Arthroscopy2001,
17:50–55.
40. UhlM,LahmA,BleyTA,HaberstrohJ,MrosekE,GhanemN,ErggeletC:
Experimentalautologousosteochondralplugtransferinthetreatment
offocalchondraldefects:magneticresonanceimagingsignsof
technicalsuccessinsheep.ActaRadiol2005,46:875–880.
41. TibeskuCO,SzuwartT,KleffnerTO,SchlegelPM,JahnUR,VanAkenH,
FuchsS:Hyalinecartilagedegeneratesafterautologousosteochondral
transplantation.JOrthopRes2004,22:1210–1214.
42. JonesCW,WillersC,KeoghA,SmolinskiD,FickD,YatesPJ,KirkTB,Zheng
MH:Matrix-inducedautologouschondrocyteimplantationinsheep:
objectiveassessmentsincludingconfocalarthroscopy.JOrthopRes2008,
26:292–303.
43. ArmstrongSJ,ReadRA,PriceR:Topographicalvariationwithinthe
articularcartilageandsubchondralboneofthenormalovinekneejoint:
ahistologicalapproach.OsteoarthritisCartilage1995,3:25–33.
44. LittleCB,GhoshP:Variationinproteoglycanmetabolismbyarticular
chondrocytesindifferentjointregionsisdeterminedbypost-natal
mechanicalloading.OsteoarthritisCartilage1997,5:49–62.
45. LittleCB,GhoshP,BellengerCR:Topographicvariationinbiglycanand
decorinsynthesisbyarticularcartilageintheearlystagesofosteoarthritis:
anexperimentalstudyinsheep.JOrthopRes1996,14:433–444.
46. HarropJS,StyliarasJC,OoiYC,RadcliffKE,VaccaroAR,WuC:Contributing
factorstosurgicalsiteinfections.JAmAcadOrthopSurg2012,20:94–101.
47. AndersonDR,GershuniDH,NakhostineM,DanzigLA:Theeffectsofnon-
weight-bearingandlimitedmotiononthetensilepropertiesofthe
meniscus.Arthroscopy1993,9:440–445.
48. RussliesM,BehrensP,EhlersEM,BrohlC,VindigniC,SpectorM,KurzB:
Periosteumstimulatessubchondralbonedensificationinautologous
chondrocytetransplantationinasheepmodel.CellTissueRes2005, Submit your next manuscript to BioMed Central
319:133–142. and take full advantage of:
49. HahnJA,WitteTS,ArensD,PearceA,PearceS:Double-platingofovine
criticalsizeddefectsofthetibia:alowmorbiditymodelenabling
continuousinvivomonitoringofbonehealing.BMCMusculoskeletDisord • Convenient online submission
2011,12:214. • Thorough peer review
50. ShettkoDL,TrostleSS:Diagnosisandsurgicalrepairofpatellarluxations
• No space constraints or color figure charges
inaflockofsheep.JAmVetMedAssoc2000,216:564–566.
51. BaronRJ:Laterallyluxatingpatellainagoat.JAmVetMedAssoc1987, • Immediate publication on acceptance
191:1471–1472. • Inclusion in PubMed, CAS, Scopus and Google Scholar
52. VanHoogmoedL,SnyderJR,VasseurP:Surgicalrepairofpatellarluxation
• Research which is freely available for redistribution
inllamas:7cases(1980–1996).JAmVetMedAssoc1998,212:860–865.
53. WillauerCC,VasseurPB:Clinicalresultsofsurgicalcorrectionofmedial
luxationofthepatellaindogs.VetSurg1987,16:31–36. Submit your manuscript at
www.biomedcentral.com/submit