1. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 1POROUS TTADeveloped by:
[email protected] 2. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 21. IntroductionOne of the most common visits to a veterinary hospital is related to limb in the dog´s paws.Controversy exists for explaining this although it is thought that first cause is stifle´s affection, evenover coxofemoral joint. Since the beginning of the 20thcentury Anterior Cruciate Ligament (ACL)rupture in dogs has been widely studied including details related to its origin, how to diagnose it andwhat treatment is the most efficient. Scientific discussion has not brought conclusive results. Whydo patients´ cruciate ligaments rupture? How should affection be diagnosed? And finally, if patientsuffers cruciate ligament affection ¿how should it be treated; conservative or surgical treatment?And related to surgical treatment ¿what technique: intracapsular, extracapsular or osteotomy?Consensus is established about what is the origin of cruciate ligament affection: most of evaluatedand treated patients with this affection did not shown a traumatic origin. Stifle is affected byinflammatory/degenerative processes that accompanied by subsequent microtraumas generateaffection of ACL collagen ultrastructure and losing of functionality.Diagnose of this pathology includes clinical examination following by radiographic examinations andother current methods (Magnetic Resonance, CT scan, ultrasound scan, ….) allowing the surgeon toview rupture of cruciate ligament and/or joint´s changes due to ACL affection.Maybe question most repeated in last 40 years in Veterinary Science is what should be done afterdiagnosing ACL pathology. Multiple techniques have emerged during these last years supported bybest achieved results. They argued better immediate results, retarding joint degenerative pathology.These innovative techniques were fostered by several factors: emerging diagnosing methods,development of new biomaterials and implants, news skills of surgeons, etc. But maybe main reasonis that none of these techniques provides successful results in all cases.Tibial tuberosity advancement was first described by Dr. Maquet. This belgium surgeon arguedthat advancing the tibial tuberosity would reduce femorotibial contact forces in extensionposition as well as retropatellar pressures in patients with stifle arthrosis.Montavón, Tepic et al. (2002) argued that this behavior is similar in the dog so tibial tuberosityadvancement (TTA) counteracts cranial shear femorotibial forces in stifles with defective anteriorcruciate ligament. TTA tries to achieve a patella tendon angle of 90 degrees to the tibial plateauwith the stifle in 135 degrees of extension. This was studied using a 3D finite elements model for3D reconstruction corresponding to a human cadaver knee specimen. This study demonstratedthat TTA technique reduced non only femoropatellar contact forces but also femorotibial contactforces in extension position.Decreasing of retropatellar pressure in dog after TTA has been experimentally demonstratedrecently (Hoffmann et al 2009). This reduction should protect patellar and femoral articular cartilageavoiding ulterior injures. 3. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 32. Adventages1. Simplify the surgical technique: partial osteotomy of crista tibiae enhances fixation stability insuch a way that fixation plate has a smaller size and lesser amount of screws is needed.2. Shorten the convalescence: bone defect created after crista tibiae advancement is refilled by aporous titanium cage providing an excellent fixation removing the need to place graft/bonesubstitutes or similar.3. POROUS TTA cage´s porosity fosters osteconduction accelerating bone ingrowth andstabilization.4. It is a minimally invasive surgical technique due to smaller size of the implant. This osteotomyallows a shorter skin incision providing higher posterior comfort for patient (Artiles 2012).5. Resources optimization: surgical procedure requires common used instruments in a veterinaryhospital avoiding spending money in specific instruments. It is an excellent solution and its priceis very interesting.6. Technique is rapid, simple and reproductible. No bending of any implant.3. ImplantsThe POROUS TTA procedure was developed by Instituto Tecnologico de Canarias through iterationsduring clinical testing to best meet the exacting demands of the procedure.• POROUS TTA CagesPorous cages are made of Ti6Al4V ELI (ISO 5832-3). Several tibial tuberosity advancements areprovided (5 sizes: 12, 9, 6.5, 4.5 and 3 mm) and several widths for each advancement: 3 differentwidths for advancements of 12, 9 and 6.5 mm; and 2 different widths for lesser advancements of 4.5and 3 mm.Multiple sizes of cages are disposable so surgeon has enough options during surgical procedure. Inorder to decide which cage must be used it is important to understand nomenclature of cage´scodification. Code includes three geometric measures of the cage: thickness (A), coinciding withvalue of required tibial tuberosity advancement; width (B) and length (H).Cage´s Code: A x B x H• A: Advancement• B: Width• H: Length 4. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 412X23X30 12X20X30 12X17X309X20X26 9X17X26 9X14X266.5X17X20 6.5X14X20 6.5X11X204.5X11X13 4.5X8X133X7X8 3X5x8• PlatesPlates are made of Titanium (Ti CP Grade 4, ISO 5832-2) so they are able to bent. It allows bestadjustment to dog anatomy although in most cases bending is not needed.There are 6 sizes of plates distinguishing two groups according to their width: 7 mm or 4 mm. Widerplates will be used in biggest dogs so they provide greater holes for using screws with greaterdiameter.Plates are non-straight excluding smaller one (4R). This fact provides polyvalence and bestadjustment to crista tibiae. 5. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 5Plates dispose of two holes for cortex screws in crista tibiae (color code shown in the followingimage: holes with diameter of 2.9 mm, red; holes with diameter of 2.2 mm, green) excluding smallerone with has only one hole.They have only one greater hole for tibial screw (color code shown in the following image: holeswith diameter of 3.7 mm, blue; holes with diameter of 2.9 mm, red; and holes with diameter of 2.2mm, green)Related to plate code, width (not confuse with thickness which is 1 mm in all plates) is linked withthe number on its name. The following letter is linked to its size: large (L), medium (M) and small (S).The letter R is an exception for the only one straight plate.• Self-tapping Cortex screwsScrews are made of Titanium alloy (Ti6Al4V, ISO 5832-3). Screws are self-tapping and Hex Head. Sethas four different measures of diameter (3.5, 2.7, 2 and 1.5 mm). Each diameter offers severallengths showed in the following table:Ø 1.5 mm Ø 2 mm Ø 2.7 mm Ø 3.5 mmØ 1.5 x 6 mm Ø 2 x 6 mm Ø 2,7 x 14 mm Ø 3,5 x 16 mmØ 1.5 x 8 mm Ø 2 x 8 mm Ø 2,7 x 16 mm Ø 3,5 x 18 mmØ 1.5 x 10 mm Ø 2 x 10 mm Ø 2,7 x 18 mm Ø 3,5 x 20 mmØ 1.5 x 12 mm Ø 2 x 12 mm Ø 2,7 x 20 mm Ø 3,5 x 22 mmØ 1.5 x 14 mm Ø 2 x 14 mm Ø 2,7 x 22 mm Ø 3,5 x 24 mmØ 2 x 16 mm Ø 2,7 x 24 mm Ø 3,5 x 26 mmØ 2,7 x 26 mm Ø 3,5 x 28 mmØ 3,5 x 30 mmWidth: 7 mm Width: 4 mm 6. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 64. Surgical procedureSurgical procedure is explained step by step:Patient´s placement: patient is placed in dorsalrecumbency over side of the limb to besurgically treated. The other limb is tied to astand in the opposite side. Surgical approach islocated on medial aspect of tibia positionedsuch that lateral side is in contact with thetabletop. If patient presents bilateral rupturesof both ACL, it is possible to accomplishsurgical procedure of both stifles bypositioning dog in supine recumbent position.Modified Maquet Procedure is going to becarried out so crista tibiae osteotomy is partialin distal direction. A skin incision is made onthe medial aspect separated 1 cm to cranialedge and starting from 1 cm proximal toinsertion of ACL to 1 cm distal to end of cristatibiae. If patellar dislocation must be treatedtoo, then approach will be enlarged.Incision is developed at the crural fascia,proper retracting of the tibia. Vascular damagemust be minimized. Musculature of the lateralaspect must not be unaltered. Incision mustbe deeper in the caudal zone to patellarligament because spreader will be inserted inthis zone.Location of the hole at the distal end of theosteotomy for controlling crack propagation(Maquet hole). This point must be in the distalzone of the crista tibiae, nearly to 4 m ofcranial border on average (in a large dog thecortex is approximately 5mm thick and in asmall dog approximately 3mm). Location isshown in the image (hole accomplished).1234 7. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 7After location, Maquet hole will be drilled byusing a drill with diameter of 2, 2.5 or 2.9 mmdepending on patient. Avoiding bone andsurrounding tissues damage by using enoughirrigation.Spreaders must be used in order to achieve awide surgical vision. A specific one spreader(provided by POROUS TTA technique) has toprotect the patellar tendon allowing saw guidewill be inserted through it at the same time.Most dorsal zone of the patellar tendon mustbe located in order to protect the tendon.Spreader will be used with this purpose.The saw guide is provided for ensuringosteotomy standardization. The saw is slottedin order to insert saw blade presenting a holethat must coincide with Maquet Point in itsproper location. For location, guide must beplaced inside the spreader. Afterwards, drillused previously for drilling Maquet hole mustbe placed new again in the distal hole of thesaw guide such guide maintains optimalpositioning during bone sawing. Guide mustbe placed guaranteeing proper osteotomy´sangle by turning around Maquet hole. In thecase of medium- big patients, saw guide mustbe positioned just caudal to patellar ligament.After guide´s positioning, osteotomy must beexecuted by using an oscillating saw. A sawblade with a thickness of approximately0.7mm should be used. Osteotomy must bedistally extended ending in the Maquet hole,protected by the drill. Abundant irrigationmust be used during bone sawing.Saw guide is removed and surgeon must checkif small bony bridge persists. In this case,osteotomy must be gently completedremoving the small bony bridge using thesame oscillating saw. Spreader must belocated in the same position in order topreserve patellar ligament. Copious irrigationshould be used.56789 8. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 8On completion of the osteotomy, crista tibiaeadvancement will start. Spreader has beensimply used for patellar ligament protectionbut now it will be used for spreading andholding open the osteotomy. In thepreoperative planning, the advancement wascalculated (using whatever of several existingmethods). It is suggested to open theadvancement (value of selected cage)increased in one additional millimeter.This process must be carried out carefully andslowly, allowing the bone time to adjust,taking advantage of it elasticity. The spreadershould be used with great caution in order toavoid crista tibiae´s fracture. Providedspreader could be blocked so opening couldbe controlled. If surgeon is not in possessionof this adjustable spreader, it is possible to usespreaders with well-known commonmeasures.Cage selection. Multiple sizes of cages aredisposable so surgeon has enough optionsduring surgical procedure: five tibial tuberosityadvancements (12, 9, 6.5, 4.5 and 3 mm) andseveral widths for each advancement (moredetails in this document, in 3. Implants). Thedepth of the osteotomy should be measuredwith a drill depth gauge for selecting propercage size.After proper osteotomy opening, cage shouldbe inserted into space generated by thespreader. Whole cage must be inserted intothe bone.Medial side of the cage must be fully orpartially in contact with medial bone cortex.The proximal end of the cage will lie below theproximal extremity of the tibial tuberosity.Ensure that there is no tendency for soft tissueto be “dragged” in between the cage and thebone.Other important detail is location of proximaltip of the cage. This RX picture shows a correctimplantation. It is possible to modify the tibialtuberosity advancement by controlling thislocation. Spreader should be removed oncecage is inserted.101112 9. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 9Selection of the plate. There are 6 sizes ofplates distinguishing two groups according totheir width: 7 mm or 4 mm. There are 3models of each width with several lengths:large (L), medium (M) and small (S). Plates arenon-straight excluding smaller one (4R). Thisfact provides polyvalence and best adjustmentto crista tibiae. Plate should be selectedaccording to dog size.Plates dispose of two holes for cortex screwsin crista tibiae and one greater hole for tibialscrew. It is possible to use cortex screws withdiameters of 3.5, 2.7, 2 and 1.5 mm.Plates with 7 mm of width have one tibial holeof diameter 3.7 mm and two holes of 2.9 mmin crista tibiae. For plates with 4 mm of width,crista holes are 2.2 mm whereas tibial hole is2.9 mm in non-straight plates and 2.2 mm inthe straight one (4R).Plate fixation for osteotomy stabilization. Platelocation influences on load transmission. Itmust be first fixed tibial screw. Its locationmust stay always at least 1 cm (in the directionof axial axis) below distal tip of the osteotomy(Maquet hole). Screw must not be fullytightened (only until be in contact with theplate).Second screw to be inserted will be cristatibiae proximal screw. A gentle compressionbetween cage and crista tibiae fragmentshould be performed before proximal screwimplantation in order to enhance porouscage´s stability.Its location depends on crista tibiae´sanatomy. Plate should be oriented such anglebetween tibial axis and crista tibiae fragmentwould be 40 degrees. Hole for screw must bepreviously drilled by using the proper drillaccording to screw´s diameter to beimplanted. Cortex self-tapping screws areprovided with diameters of 3.5, 2.7, 2 and 1.5mm, with several lengths. So it isrecommended measuring for selection theproper screw´s length.141513 10. P O R O U S T T A S u r g i c a l T e c h n i q u e Page 10A different drill to previously used for tibialhole should be used because plates havegreater holes for crista tibiae screws(excepting 4R where holes have samediameter). Proximal screw must be fullytightened and later on tibial screw toopreviously implanted. Only in very energeticdogs should be necessary to implant cristatibiae distal screw. Anyway it could beimplanted if surgeon desires to preventloosening of proximal screw.Finally surgical skin must be closed. It isminimally invasive procedure so scar is veryshort.5. Postoperative caresIt is required a period of controlled activity so it is essential that running, jumping, and general“rough and tumble” with other pets is avoided for the first 6 weeks. It is advisable your pet beencouraged to take frequent short leash walks.For proper following of surgical procedure carried out, it is required radiograph exams almost takinglateral views four and eight weeks after implantation.6. SupportDo not hesitate to contact with this mail if you have any question related to this surgical procedure:
[email protected] (phone: 928189613)16