二氧化碳激光器的临床应用

氧化碳激光器的临床应用以下程序演示了多功能CO2激光器在马外科手术中的广泛应用。这些程序中均应用到了二氧化碳波长的独特性质，并经受了时间的考验。这项技术可以广泛的应用于马属动物外科手术，作为外科医生要熟悉使用激光切割，体积烧蚀和凝血仪。一般来说，二氧化碳激光的益处在于邻近组织极小创伤的精确解剖，良好的止血效果。利用激光束的热性能，以杀死细菌或剥离肿瘤细胞相邻面。当考虑使用该仪器进行外科手术时，外科医生应该考虑到靶组织的热特性，并了解一个特定波长对该组织的影响。相邻组织（如骨和韧带）的差热吸收特性为解剖面的精细选择和附近热敏感组织能量谨慎应用的需求提供了机会。外科手术中，在使用激光之前，外科医生应该首先确定手术的目标。如果精确的组织破坏或切口是必要的，则说明要使用大功率超脉冲模式和聚焦光斑尺寸。如果要使组织凝血且温和加热，则需求低功耗连续模式的散焦斑尺寸。直到医生习惯于预测激光能量在组织中的影响，选择功率设置基于能源的可观察性，通常建议在正式开始手术切口之前选取不相关组织的一处“测试点”进行试验。在一般情况下，外科医生应该选择使用自己可控的安全和精度的范围内可获得的最高功率。初学者则应该从较低的功率开始逐渐增加功率设置，以获得使用激光器的经验在没有深入了解二氧化碳波长对组织的影响，也没有使用激光器的外科医生实习经验的情况下尝试这些操作将不会得到满意的结果。皮肤肿瘤对于马来说，黑色素瘤，乳头状瘤，肉状瘤，纤维瘤，鳞状细胞癌是常见的皮肤肿瘤。这些肿块可用二氧化碳激光烧灼或汽化。在病变处用盐酸甲哌卡因进行局部浸润麻醉，脱敏手术部位，避免邻近正常组织受到激光热效应的影响（图6）。

当需要进行组织学诊断时，通常在大规模切除或汽化肿瘤之前进行肿瘤的切除活检，一般使用50W的超脉冲模式与0.2毫米聚焦光斑（比功率约150000W/cm2）。这种模式和电源功率设置保证了将细胞结构损伤降低到最小且提供了高效的组织切除技术。大疣状肿块最好以高功率连续的模式将其从它们生长的组织处分离并最大限度的止血。肿瘤的基部可采用50W的功率、1毫米散焦斑（比功率约为7000W/平cm2）进行汽化，以脉冲向心模式从正常皮肤边缘开始向病变中心作用。使用这种技术可以完全除去耳廓结节而不损坏下面的软骨。站立的马的眼睑肿瘤在适当保定的情况下可以被很好的剔除，但对于眼角膜、球结膜鳞状细胞癌来说，最好的治疗方案是马进行全身麻醉以提供足够的稳定性来保证此类病变组织的精确剔除（图7）。空心塑料波导可通过二氧化碳激光铰接臂的存在来蒸发马病变的皮肤。因为在1米的纤维路径中能量衰减的变化从10%到50%，激光试验脉冲在最初得到应用，并调节功率达到理想的临床效果。一般外科手术中推荐将50W功率应用于灵活可控的波导中的应用。二氧化碳激光对汽化的精确控制是治疗皮肤肿瘤的一个优点。只要有足够的皮肤，我们可以通过常规缝合皮下组织和皮肤来弥补肿瘤的切除或造成烧灼的缺陷。如果没有，可以采用第二种办法来促进手术部位切口的愈合。可以外用抗菌药膏直至伤口收缩并形成完整的上皮组织。除去大的播散性皮肤损伤后，可以进行一次皮肤移植用健康的肉芽组织填充缺陷皮肤部位。这些病变成功治疗的预后主要是靠特定肿瘤生物学行为的功能。经过上述皮肤肿瘤激光治疗后可能会通过控制其复发做到长期缓解效果。这组肿瘤中，鳞状细胞癌的复发率最高。为此，病变的可视区域要尽可能的与大面积的正常皮肤一起被清除。此外，在手术结束时，要用功率30W的连续模式、1mm散焦光斑（比功率约3800W/cm2）照射组织，对瘤床进行清洁消毒。这样做的目的是要小心加热烧灼肿瘤边缘来杀死残余肿瘤或转移性病变的边界细胞。对皮肤肿瘤激光治疗的主要优点是在很多案例或其他治愈的病例中，激光的动态效应和热杀伤效应对肿瘤边缘细胞的影响能够提供长久有效的缓解治疗效果。激光清创、消毒清创、受污染的伤口均能对马造成伤害。常规的外科手术治疗包括清创，抗生素冲洗，并使用排水管清理伤口中累积的血清和血液。二氧化碳激光器提供了清创和消毒伤口的有效手段。局部浸润麻醉之后，使用高功率连续模式（50到80W），1mm散焦斑（功率密度约7000至10000W/cm2）来汽化失活和坏死组织。将功率降低至30W的连续模式并使用5mm光斑（功率密度约150W/cm2），此时激光束可以顺利通过一个网状图案的手术视野落在消毒伤口的表面。使用快速激光辅助治疗可以让外科医生在低功率设置的情况下顺利、有效的消毒大面积组织。创面应保持湿润，防止组织局部脱水。视觉端点用于确定给定区域的适当治疗，用一缕蒸汽引起组织非常轻微的收缩。组织出现明显的收缩和热烫表明应用过热致使组织蛋白变性凝固。在伤口处来回反复加热比一次性操作使组织过热的治疗方法更好。二氧化碳激光器的精确效果使得它非常适合于这种类型的程序。用激光清创消毒后，组织平面近似于完成一次多层次的常规原发性闭合。除非组织缺损非常严重，否则术后不需要使用排水管。在适当的时候给予全身抗生素和预防破伤风。对污染伤口进行激光治疗的优势在于有效清除失活组织，减少活菌在其中存活的能力。这些相同的优点可以通过使用二氧化碳激光剥离软组织或马的骨髓炎病灶来体现。激光血管吻合术激光将一定量的热能应用于组织的独特能力已被用于开拓一个被称为“组织融合”或“组织焊接”的软组织外科学新领域。虽然许多波长可以用来完成这项任务，但二氧化碳激光是一种用于烧灼血管壁来切断血管的有效工具。激光修复血管的生物力学与缝合修补术相似。笔者采用了以下协议成功修复了两匹指掌侧固有动脉切断，有严重腕掌侧伤口的两匹马。在全麻的状态下对马采用激光聚变技术断开指状血管并且每单位绷带放置在与球关节水平位置。切断的边缘动脉应用小牛头犬血管夹固定住并用锋利的解剖刀清创。四在5-0铬制肠线缝合线被放置在90度的间隔血管壁周围以用于在使用激光能量时稳定动脉的切割表面。这个激光仪必须能够精确、稳定的输出非常低的功率，从而使胶原血管壁内无坏死或汽化。根据激光的光斑尺寸调整输出功率，使组织表面能量密度达到100〜175W/cm2。例如，2.5mm的光斑大小，7W的连续功率时的比能量密度为150W/cm2。加热组织时，在确认光点的精确尺寸要通过由激光烧灼湿润的木制压舌板来精确测量激光束的直径。医生应该意识到虽然氦-氖瞄准照射和二氧化碳的能量束在一个适当的调谐激光器中是同心的，但两光束的直径的精确可能不完全相同。机头离靶组织的精确距离要求在使用激光能量的整个过程中用聚焦传导，使得光斑直径为2.5mm,确保组织表面使用正确的功率密度。在使用激光能量时组织要保持干燥，液化组织和变色区域的视觉终端用于确定组织充分加热。组织表面上不存在含炭物质。焦炭的形成表明，能量密度过高，发生碳化。组织焊接过程中重复旋转血管，沿着表面的四个吻合边缘温施加激光能量直到整个确保边缘密封。松开夹子和eschmark绷带来评价血管修复的安全性。如果当时渗血，就要收紧止血带，然后用生理盐水冲洗渗血区域。重复这个过程，直到得到血被止住。四处缝线留在原处，为修复提供旋转稳定性。组织焊缝张力较强，但在扭转应变能力很弱。使用激光辅助血管修复的优点是减少血管壁中出现外来物质。这有助于伤口愈合，减少局部肉芽肿或瘢痕组织的形成，降低后续的管腔闭塞的倾向。激光去势马采取背侧卧保定，在阴囊基底沿着睾丸大弯处用50W超脉冲和0.2mm的聚焦光斑做一个椭圆形的皮肤切口（平均功率密度约75000W/平cm2）。切口是先通过皮肤，皮下组织，阴囊筋膜，用激光棒将这些组织放置在张力下，可支持激光束（见图2）睾丸本身可以支撑激光束，但睾丸表面的血管会在不必要的复杂解剖时意外出血。通过用50W连续功率、1mm散焦光斑模式来分开正中中线，去除整块阴囊正中中线来增强止血（功率密度约7000W/cm2）。结扎腹中线上直径大于1mm的血管，采用钝性分离将疏松的网状筋膜从睾丸上剥离，激光采用后者的功率和模式设置。结扎精索，用#1聚对二氧环己酮（PDS）采用单一连续垂直褥式缝合方式缝合切口，缝合顺序为阴囊筋膜，皮下组织和剩余的正中中缝。使用激光器的优点是切开血管丰富或淋巴淤滞的组织时出血较少。

清除肉芽组织肉芽伤口在马的四肢极为普遍的，对于简单愈合来说是一个困难的挑战。旺盛的肉芽组织（“伤口愈合后的疤”）必须被清除，来延迟或使伤口二次愈合。因为肉芽组织由丰富的毛细血管组成，使用二氧化碳激光器有助于清创。类似于清除皮肤肿瘤的治疗方案，这种类型的操作程序说明了二氧化碳激光器可以作为一种“体积烧灼”仪器使用。清除大部分肉芽组织首先使用50-80W的连续功率，1mm散焦光斑的激光照射周围的靶组织（功率密度约7000至10000W/cm2）来达到良好的止血作用。清除时先用无创伤钳轻轻夹起病变一角，然后通过激光束来回照射扩大病灶直径（图8）。遇到直径大于1或2mm的血管时要进行结扎。一旦清除了肉芽组织，该区域将用80W连续功率，2mm光斑的激光束画出交叉阴影线（功率密度约2500W/cm2）。大的光斑尺寸和“喷枪消融技术”确保了比较均匀的清创技术及良好的止血效果。快速激光辅助技术可以在规定的区域传递能量一个光滑的表面。一旦皮表之下的肉芽组织顺利清除，伤口可以用整形外科技术缝合使其恢复健康或后期皮肤移植。使用激光进行清除的主要优点是能使清创组织表面出血显著减少。手掌/脚掌的指关节神经切断术手掌/足底指关节神经切除术通常作为手指和足趾后三分之一慢性跛行和对翼尾第三关节骨折的最后治疗手段。切断神经后正常的愈合反应的结果是在神经切断面形成一个小的组织良好的神经瘤。从以往病例分析，这个过程的主要并发症之一是神经瘤的形成。这个过程的特征在于神经末梢切割端杂乱的再吻合并伴随着两神经组织和鞘（雪旺氏细胞）的增生。尽管在一些情况下努力减少创伤和出血，避免神经瘤的形成，密封神经外膜，以防止切割端神经轴浆的泄露，但马神经瘤的形成发展的主要因素仍保持猜测的态度。在对十匹超过23个月的马的研究调查中，用18426W/cm2CO2激光理疗仪来使被手术刀片切断的神经断端有足够的热密封性，防止神经再支配或形成神经瘤。经过多年使用CO2激光理疗仪对马进行手掌/足底指关节神经切断来看，笔者认为当激光器使用的参数与描述的治疗Morton神经瘤相似，那么神经瘤是极其罕见的。将马圈养在畜栏中十四天，每天更换绷带，之后再牵溜两周直至马恢复正常的日常活动。应在术后前十天用非类固醇抗炎药物治疗来减少手术部位的炎症反应。使用CO2激光理疗仪进行手掌指关节神经切断术的优点在于神经瘤的形成率低。应避免使用高于推荐值的功率密度，否则术后马将出现跛行且数周内触诊切口部位敏感性增强。虽然此类神经炎症是暂时的，也可以用药物治疗，但是这种可以轻松避免的并发症也不是我们希望看到的。SELECTEDCLINICALAPPLICATIONSFORTHECARBONDIOXIDELASERThefollowingproceduresdemonstratetheversatilitythecarbondioxidelaserinequinegeneralsurgery.Eachoftheseproceduresmakesuseofuniquepropertiesofthecarbondioxidewavelengthandhaswithstoodthetestoftime.Thetechniquesdescribedcanbeappliedtoawiderangeofproceduresinequinesurgeryasthesurgeonbecomesfamiliarwithuseofthelaserasacutting,volume-ablating,andcoagulatinginstrument.Ingeneral,thebenefitsofthecarbondioxidelaserrelatetoprecisedissectionwithminimaltraumatoadjacenttissues,goodhemostasis,anduseofthethermalpropertiesofthelaserbeamtokillbacteriaortumorcollsadjacenttotheplaneofdissection.Whencontemplatinguseofthisinstrumentforsurgery,thesurgeonshouldconsiderthethermalpropertiesofthetargettissuesandunderstandtheeffectofaparticularwavelengthonthattissue.Differentialthermalabsorptionpropertiesofadjacenttissues(suchasboneandligament)provideopportunitiesforselectiveandpreciseplanesofdissectionaswellasaneedforcarefulapplicationoftheenergynearthermallysensitivetissues.Beforeusingalaserinsurgery,thesurgeonshouldfirstidentifythesurgicalgoal.Ifprecisetissuedestructionorincisionisrequired,useofhigh-powersuperpulsemodeandnfocusedspotsizeareindicated.Ifalargeareaoftissueablationorvaporizationisdesired,highpowerandacontinuousmodewithdefocusedspotsizearebest.Ifcoagulationandgentleheatingoftissueisthegoal,lowpower,acontinuousmode,andadefocusedspotsizeaivrequired.Untilthesurgeonbecomesaccustomedtothepredictableeffectsoflaserenergyontissue,selectingpowersettingsbasedonanobservableeffectoftheenergyasitiscarefullyappliednoncritidatostspot''oftissueisrecommendedbeforeactuallybeginningthesurgicalincision.Ingeneral,thesurgeonshouldusethehighestpoweravailablethatthesurgeoncancontrolsafelyandwithprecision.Havingsaidthat,novicesshouldstartwithlowerpowersandincreasepowersettingsasexperiencewiththelaserisachieved.Attemptingtheseprocedureswithoutathoroughunder-standingofthetissueeffectsofthecarbondioxidewavelengthandpracticaltrainingfromsurgeonsexperiencedwithuseoflasersmayresultinlessthansatisfactoryresults.CutaneousNeoplasiaMelanomas,papillomas,sarcoids,fibromas,andsquamouscellcarcinomasarecommoncutaneoustumorsinthehorse.Thesemassescanbeexcisedorvaporizedusingthecarbondioxidelaser.Anesthesiaisachievedwithlocalinfiltrationofmepivacainehydrochloridebeneaththelesion,desensitizingtheoperativesiteandprotectingadjacentnor-maltissuefromthethermaleffectsofthelaser(Fig.6).Whenahistologicdiagnosisisdesired,anexcisionalbiopsyofthetumorismadeusing50Wofpowerinthesuperpulsemodewithafocusedspotsizeof0.2mm(powerdensity,approximately150,000W/cm2)beforeablationorvaporizationofthemass.Thismodeandpowersettingprovideefficientexcisionoftissuewithminimaldisruptionofcellulararchitecture.Largeverrucousmassesarebestseparatedfromtheirbaseusinghighpowerandcontinuousmodetomaximizehemostasis.Thebaseofthetumormaythenbevaporizedusing50Wofpower,adefocusedspotsizeof1mm(powerdensityapproximately7000W/cm2),andapulsedmodeinacentripetalpattern,beginningwithamarginofnormalskinandworkingtowardthecenterofthelesion.Auricularsarcoidcanbecompletelyremovedusingthistechniquewithoutdamagingtheunder-lyingcartilage.Althougheyelidtumorsmayberemovedinthestandinghorseprovidedadequatecontrolofthepatientcanbeassured,squamouscellcarcinomaofthecorneaandbulbarconjunctivaarebesttreatedwiththehorseundergeneralanesthesiatoprovidethestabilityrequiredtoremovesuchlesionsprecisely(Fig.7).Thewoundshouldbekeptmoistduringthistreatmenttopreventlocaldehydrationoftissues.Thevisualendpointusedtodetermineadequatetreatmentofagivenareaistheproductionofawispofsteamandveryslightshrinkageoftissue.Markedcontractionandblanchingoftissuesindicatetheapplicationofexcessiveheat,whichcausescoagulationanddenaturationoftissueprotein.Makingmultiplepassesoverthewoundisbetterthanoverheatingthetissueswithasingletreatment.Thepreciseeffectofthecarbondioxidelasermakesitideallysuitedforthistypeofprocedure.Subsequenttolaserdebridementandsanitization,thetissueplanesareapproximatedwithmultiplelayerstoaccomplisharoutineprimaryclosure.Exceptinthemostextremecasesoftissueloss,theuseofdrainspostoperativelyisnotnecessary.Systemicantibioticsandtetanusprophylaxisareadministeredwhenappropriate.Theadvantageoflasertreatmentofcontaminatedwoundsistheefficientdebridementofdevitalizedtissueandtheabilitytodiminishthepopulationofviablebacteriapresenttherein.Thesesameadvantagescanbeappreciatedbyusingthecarbondioxidelaserforthesofttissuedissectionofdrainagetractsassociatedwithosteomyelitislesionsinhorses.Laser—AssistedVascularAnastomosisTheuniqueabilityoflaserstoapplyacontrolledamountofthermalenergytotissuehasbeenusedtopioneeranewareaofsofttissuesurgerydescribedas"tissuefusion"or"tissuewelding."Althoughmanywavelengthscanbeusedtoaccomplishthistask,thecarbondioxidelaserisaneffectivetoolforfusingthewallsofseveredbloodvessels.Thebiomechanicsofthelaserrepairofvesselsaresimilartothoseofsuturerepair.14Theauthorhasusedthefollowingprotocoltosuccessfullyrepairseveredpalmardigitalarteriesintwohorseswhosustainedseverelacerationsofthepalmaraspectofthepastern.LaserfusionofsevereddigitalvesselsisperformedwiththehorseundergeneralanesthesiaandanEschmarkbandageplacedatthelevelofthefetlockjoint.Theseveredmarginsofthearteryshouldbestabilizedwithsmallbulldogvascularclampsanddebridedusingsharpdissectionwithascalpel.Fourstaysuturesof5-0chromicgutareplacedat90-degreeintervalsaroundthevesselwalltostabilizethecutsurfacesofthearteryduringapplicationofthelaserenergy.Thelasermustbecapableofpreciseandstablepoweroutputatverylowpowerinordertocoagulatethecollagenwithinthevesselwallwithoutnecrosisorvaporization.Thepoweroutputisadjustedforthespotsizeofthelaserinordertoachieveanenergydensityofbetween100to175W/cm2atthetissuesurface.Ataspotsizeof2.5mm,forexample,7Wofcontinuouspowerproducesanenergydensityof150W/cm2.Thelaserenergyisappliedbetweenthestaysutures,whichareplacedundertensionbyanassistanttorigidlyapposethecutmarginsofthevessel.Anaccuratespotsizeisconfirmedbeforeheatingthetissuebyfiringthelaserontoamoistenedwoodentonguebladeandmeasuringtheprecisediameterofthepointofimpactofthelaserbeam.Thesurgeonshouldbeawarethatalthoughtheheliumneonaimingbeamandthecarbondioxideenergybeamareconcentricinaproperlytunedlaser,theprecisediameterofthetwobeamsmaynotbeexactlythesame.Theprecisedistanceofthehandpiecetothetargettissuerequiredtoachievethe2.5mmspotsizemustbemaintainedbyuseofafocusingguidethroughouttheapplicationoflaserenergytoensurecorrectpowerdensityatthetissuesurface.Thetissueiskeptdryduringtheapplicationoflaserenergyandthevisualendpointoftissueliqueficationanddiscolorationisusedtodetermineadequateheatingofthetissue.Nocharformationshouldexistatthetissuesurface.Thedevelopmentofcharindicatesthattheenergydensityistoohighandthecarbonizationisoccurring.Thetissueweldingprocessisrepeatedbyrotatingthevesselandapplyinglaserenergyalongallfoursurfacesoftheanastomosisuntiltheentiremarginissealed.TheclampsareremovedandtheEschmarkbandageisloosenedtoevaluatethesecurityofthevascularrepair.Ifleakageispresent,thetourniquetistightenedandtheareaofleakageiscleanedofbloodbyrinsingwithsaline.Theprocessisrepeateduntilanadequatesealisobtained.Thefourstaysuturesareleftinplacetoproviderotationalstabilitytotherepair.Tissueweldshavereasonablygoodstrengthintension,butareweakwhensubjectedtotorsionalstrain.Theadvantageofusingthelasertoassistinvascularrepairistoreducetheamountofforeignmaterialpresentinthevascularwall.Thisaidshealingandminimizesthetendencyforlocalizedgranulomaorscartissueformationandsubsequentluminalocclusion.ScrotalAblationCastrationThecarbondioxidelaserisveryusefulforgeneraldissectionofvasculartissuesaroundthehead,neck,andperinealregion.Descriptionoftheuseofthecarbondioxidelaserforcastrationofhorsesservesasanexampleofgeneralsofttissuedissectionthatusespthelaserasacuttinginstrumentandillustratestechniquesthatcanbeusedinmanyotherprocedures.Thehorseispositionedindorsalrecumbencyandanellipticalskinincisionismadeoverthebaseofthescrotumalongthegreatercurvatureofthetesticlesusing50Wofsuperpulsepowerinfocuswithaspotsizeof0.2mm(averagepowerdensity,approximately75,000W/cm2).Theincisionisadvancedthroughtheskin,subcutaneoustissue,anddartosfasciabyplacingthosetissuesundertensionwithalaserrod,whichalsoservestobackstopthelaserbeam(seeFig.2).Thetesticleitselfcanservetobackstopthelaserbeam,buthemorrhageofvesselsonthesurfaceofthetesticleinadvertentlyoccursandneedlesslycomplicatesthedissection.Themedianraphaeandthescrotumarethenremoveden-blocbydividingthebaseofthemedianraphaewith50Wofcontinuouspowerinthedefocusedmode,usinga1-mmspotsizetoenhancehemostasis(powerdensity,approximately7000W/cm2).Vesselsinthemedianraphaewithadiameterlargerthan1-mmareligated.Thelooseareolarfasciaisthenstrippedfromthetesticlesusingbluntdissectionandthelaserusingthelatterpowerandmodesettings.Thespermaticcordsareligatedandtheincisionisclosedwith#1polydioxanonesuture(PDS)inasinglecontinuousverticalmattresssuturepatternthatincorporatesthednrtosfascia,thesubcuticulartissues,andtheremnantofthemedianraphae.Jheadvantagesofusingthelaserforthistypeofprocedurearerelativelybloodlessdissectionofvascular-richtissuesandlymphostasis.RemovalofGranulationTissueGranulatingwoundsareextremelycommonintheextremitiesofhorsesandareadifficultchallengeforuncomplicatedhealing.Exuberantgranulationtissue("proudflesh")mustbeeliminatedtopermitdelayedorsecondarywoundclosure.Becausethistissueisextremelyvascular,useofthecarbondioxidelaserishelpfulfordebridement.Similartotheprotocolusedforremovalofcutaneoustumors,thistypeofprocedureillustratestheuseofthecarbondioxidelaserasa"volumeablation"instrument.Thebulkofthegranulatingmassisremovedbyfirstpassingthelaserbeamaroundtheperipheryofthetargettissueusing50to80Wofcontinuouspowerwithadefocused1-mmspotsize(powerdensity,approximately7000to10,000W/cm2)toachievegoodhemostasis.Thedissectionisadvancedbygentlyelevatingonecomerofthelesionwithatraumaticforcepsandpassingthelaserbeambackandforthacrosstheexpandingdiameterofthelesion(Fig.8).Vesselsgreaterthan1or2mmindiameterareligatedastheyareencountered.Oncethemassofgranulationtissuehasbeenremoved,thebasemaythenbesculptedbypassingthelaserbeamacrossthetissuebedinacrosshatchpatternusing80Wofcontinuouspoweranda2-mmspotsize(powerdensity,approximately2500W/cnr).Thelargespotsizeandan''airbrushablationtechniqueCensurearelativelyevendebridementandgoodhemostasis.TheSwiftlaseattachmentcanalsoaidinaccomplishingasmoothsurfacebyspreadingtheenergyoverauniformarea.Oncethegranulationtissuehasbeendebridedsmoothlybelowtheskinsurface,thewoundcanbeclosedusingplasticsurgicaltechniques,lefttohealbysecondintention,orgraftedatalatertime.Theprincipaladvantageofusingthelaserforthisdissectionisadramaticreductioninhemorrhagefromthesurfaceofthedebridedtissue.Palmar/PlantarDigitalNeurectomyPalmar/plantardigitalneurectomyisusuallyperformedasalastresorttreatmentforchroniclamenessofthecaudalonethirdofthedigitandwingfracturesofthethirdphalanx.Thenormalhealingresponsetoseveringanerveendingistheformationofasmallwell-organizedneuromaattheendofthecutsurfaceofthenerve.Historically,oneoftheprincipalcomplicationsofthisprocedurehasbeenpainfulneuromaformation.Thisprocessischaracterizedbyadisorganizedreanastomosisofthecutendsoftheseverednerveendingsthatisaccompaniedbyhyperplasiaofbothneuraltissueandsheath(Schwann)cells.Factorsresponsibleforthedevelopmentofpainfulneuromasinhorsesremainamatterofspeculation,althougheffortstoavoidpainfulneuromaformationhavegenerallyincludedeffortstominimizetraumaandhemorrhageandinsomecasestosealtheepineuriumtopreventleakageofaxoplasmfromthecutendsofthenerve.Inonestudy,applicationof18,426W/cm2ofC02laserenergytothedistalstumpofnervesthatwereseveredwithascalpelbladeresultedinadequatethermalsealingofthenervestumptopreventreinnervationorpainfulneuromaformationin10horsesovera23-monthperiod6Aftermanyyearsofusingthecarbondioxidelasertoperformpalmar/plantardigitalneurectomyonhorses,theauthor'simpressionisthatpainfulneuromasareextremelyrarewhenthefollowingprotocol,whichuseslaserparameterssimilartothosedescribedfortreatmentofMorton'sneuromasinhumans,isused.3Thesurgeryisperformedwiththehorseundergeneralanesthesia.Eschmarkbandagesareplacedatthelevelofthefetlockjointtoelimi-natehemorrhage.A2-cmskinincisionismadewithascalpelimmedi-atelydorsaltotheligamentoftheergot.Theincisionisadvancedwithacombinationofbluntandsharpdissectiontoexposetheneurovascularbundlethatcontainsthepalmardigitalarteryandnerve.Careistakennottodisruptthelargelymphaticvesselsthatcommonlycrosstheincisionatthissite.ThesevesselsareeasilyidentifiedonlywithcorrectapplicationoftheEschmarkbandage.Theconnectivetissuethatsur-roundstheneurovascularbundleisopenedandthepalmardigitalnerveisisolatedwithcaretakentopreservethenervesheathorepineurium.A3-or4-cmsectionofthenerveisremovedbyfirstdividingthenervedistallyusing10Wofcontinuouspowerwithaspotsizeof0.2mm(powerdensity,approximately30,000W/cm2)(Fig.9).Theepineuriumisretractedandtheproximaldivisionismadeusingthesamelaserparameters.Theepineuriumisthenpulledbackovertheproximalcutsurfaceofthenerveandisligatedwith3-0silk.Theincisionisclosedwithasinglesubcutaneoushorizontalmattresssutureof3-0PDSandskinsuturesof2-0nyloninacruciatepattern.Figure9.Anopticalbackstopisusedtoisolatetheposteriordigitalnervefromtheadjacenttissuesbeforeactivationofthelaser.Thehorseisconfinedtoastallfor14dayswithdailybandagechangesandiswalkedinhandforanother2weeksbeforereturningtonormaldailyactivity.Nonsteroidalanti-inflammatorymedicationshouldbeadministeredforthefirst10postoperativedaystominimizeinflammationatthesurgerysite.Theadvantageofusingthecarbondioxidelaserforpalmardigitalneurectomyislowincidenceofneuromaformation.Useofpowerdensitiesabovethoserecommendedshouldboavoidedbecauseuseofhighpowerscancauseapostoperativeneuritis,withhorsesshowingl