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Tibial Tuberosity Advancement
Product Instructions

Objectives of the Presentation

To understand the tibial tuberosity advancement in the treatment of RCCL in the canine (90 minute presentation).

Key Points of the Presentation

  • TTA was first described by Drs. and Slobodan Tepic at the University of Zurich on 2002.


  • The biomechanics behind the TTA are similar to those of TPLO, and if in fact are true, may provide evidence that TPLO over-corrects the stifle.


  • The procedure it self is simpler than TPLO. Preoperative measurements are made from standard radiographs. A transverse osteotomy is made in the tibial tuberosity, and it is advanced and stabilized utilizing a novel cage and tension band plate. Some specialty equipment is required to complete the procedure.


  • Earlier weight bearing and return to function have been suggested, but studies are not yet available to support these observations.


  • TTA is best suited for large, active dogs. Although little evidence supports its use in smaller dogs and cats, it has provided equally good clinical outcomes in the author's opinion.


  • TTA can be used to repair RCCL in most dogs with few exceptions, where TPLO might be better suited.


Biomechanics

In the diagram marked below, the average canine stifle is loaded with a force F(G). The Achilles tendon reacts with a force F(A) that results in a net force on the tarsal joint F(JT). The patellar tendon reacts with a force F(P) to stabilize the stifle. Consequently, the stifle reacts with a force F(JS) almost parallel to the patellar tendon.

Average Canine Stifle Joint

If we take a close look at the stifle joint, if the tibial plateau is not perpendicular to F(P), then F(JS) does not superimpose the normal compressive force F(N) of the stifle and a tibiofemoral shear force F(S) results. This overloads the CrCL-deficient stifle resulting in cranial tibial thrust or subluxation when the CrCL is torn.

Cranial tibial thrust or subluxation

Cranial tibial thrust or subluxation

Tibial tuberosity advancement positions F(P) perpendicular to the tibial plateau and eliminates F(S) by superimposing F(JS) over F(N).

Lets define the total joint force as being approximately parallel to the patellar ligament. If the patellar ligament and tibial plateau are perpendicular, there is no shear component of the total joint force and no strain on the cruciate ligaments. But the angle between the patellar ligament and tibial plateau changes with flexion and extension, and is 90 degrees at 90 degrees of flexion, the cross-over point. In full extension, the angle between the tibial plateau and patellar ligament is 105 degrees, while in full flexion it is 70 degrees. Thus in full extension the CrCL is loaded, in full flexion the CaCL is loaded relative to the cross-over point.

In the CrCL deficient stifle, we can move the cross-over point to full extension (see next diagram). In the case of the graph, at 45 degrees of flexion, the patellar ligament is at 90 degrees to the tibial plateau, the cruciates are under minimal stress, favoring the CaCL. In other words, moving the tibial tuberosity cranially to a point where the patellar ligament is perpendicular to the tibial plateau, the angle between the patellar tendon and tibial plateau can not exceed 90 degrees. Thus you never reach an angle that would result in loading of the CrCL.

The Procedure

The mediolateral stifle radiograph is used to evaluate the stifle for the correct size TTA implants. It is important to take this radiograph without the tibia in a subluxation, as most dogs with a complete CrCL tear tend to have their stifles in cranial drawer when under sedation. The patellar ligament is represented by a line drawn through the cranial border from the cranial pole of the patella to the tibial tuberosity. The orientation of the tibial plateau is represented by a line drawn through the cranial and caudal margins of the medial tibial plateau. The amount of distance necessary to advance the patellar ligament to make it perpendicular to the tibial plateau is measured, this is the WIDTH of the cage to use (6, 9 or 12 mm). You will determine the length of this cage later. The size of the tension band plate can be selected by using the template. The average 60-80 pound dog requires a 5-hole plate. When the proximal portion of the plate rotates cranially (post-osteotomy) the distal plate will rotate caudally. It is important that the location of the distal plate be centered on the tibial shaft.

Under general anesthesia, the joint is addressed at the surgeon's preference. Medial meniscal release is recommended, and can be performed through a caudomedial approach to the joint at a point caudal to the medial collateral ligament.

The pes anserinus and tibial tendon are scalpel dissected in a line similar to the planned osteotomy. This tendon should be elevated cranially to a point just on the lateral aspect of the cranial border. On the medial aspect, it should be elevated to the medial collateral ligament.

The jig is applied to the proximal most aspect of the cranial tibial border starting at the insertion of the patellar tendon and secured. The number of holes are drilled that correspond to the size of the pre-selected tension band plate.

The transverse osteotomy in the saggital plane of the proximal tibia starts proximally at the the tuber of Gerty and travels distal to a point midway between the cranial border and the tibial shaft.

The tension band plate and fork are inserted into the drilled holes. The osteotomy is then advanced and the width of the osteotomyized tibia measured for cage depth selection. It is important to remember that the widths of the cages are measured mid-distance. In other words, the 9 mm x 25 mm cage will measure 9 mm wide, and 25 mm deep when measured at the point of the fixation ears. These ears must be bent to match the cortex of the bone when inserted.

The cage is placed approximately 4-6 mm below the joint surface and secured caudally. The osteotomy may now be closed over the cage and the distal most hole secured. Now return to the cage and secure the cranial hole at a location just caudal to the first hole of the tension band plate. Secure the last hole of the tension band plate distally. Fill in the osteotomy with a graft.

Place the limb in flexion prior to closure. It is recommended to make a releasing incision in the distal tibial tendon to avoid undue tension on the surgical site, which sometimes causes dogs to chew on the wound.

A postoperative radiograph is taken to assess proper implant placement. A postoperative bandage is recommended for 2 days.

When would I pick TPLO over TTA?

  • Excessive tibial slope, greater than 30 degrees
  • Angular limb deformity
  • Client request or expectation
  • Show dog (TTA MAY show some deformity compared with the normal leg)

Potential complications of the TTA

  • Incisional swelling, 50%
  • Postoperative diarrhea or inappetance, 5-10%.\
  • Incisional dehiscence, 5%
  • Severed long digital extensor tendon
  • Intra-articular penetration by a cage screw
  • Tibial crest failures
  • Patella baja, alta, and patellar luxations
  • Poor plate contouring
  • Implant infection
  • Grade II medial patellar luxation
  • Meniscal pain, tearing postoperative (?)

References

  • Vezzoni, A. Comparison of tibial plateau leveling osteotomy and tibial tuberosity advancement. Proc 2nd World Veterinary Orthopedic Conference; Keystone 2006:47-48.


  • Boudrieau RJ. Tibial tuberosity advancement (TTA): Clinical results. Proc ACVS 2005.


  • Miller JM, Phires PK, Martin RA, Lanz, OI, Grant JW. Effect of tibial tuberosity advancement on the canine cranial cruciate deficient stifle. Abstracts ACVS 2006:E18.


  • Montavon PM, Damur DM, Tepic S. Advancement of the tibial tuberosity for the treatment of cranial cruciate deficient canine stifle. Abstracts 1st World Orthopaedic Veterinary Conference; Munich 2002:152.


  • Montavon PM, Damur DM, Tepic S. Tibial tuberosity advancement (TTA) for the treatment of cranial cruciate disease in dogs: evidences, technique and initial clinical results. Proc ESVOT 2004:254.


  • Tepic S, Damur D, Montavan PM. Biomechanics of the stifle joint. Abstracts of the 1st World Orthopedic Veterinary Conferece, Munich; 2002: 189-190.


  • Nisell R, Nemeth G, Ohlsen H. Joint forces in the extension of the knee: Analysis of a mechanical model. Acta Orthop Scand 1986; 57: 41-46.


  • Imhof J, Voss K, Montavon PM: Tibial tuberosity advancement (TTA) for the treatment of cranial cruciate disease in dogs: evaluation using force plate gait analysis. ECVS 14th Annual Scientific Meeting, Lyons, France 2005.


  • Henderson R, Milton J, The tibial compression mechanism: A diagnostic aid in stifle injuries. J Am Anim Hosp Assoc, 1978;14: 474-479


  • Slocum B, Devine T, Cranial tibial thrust: A primary force in the canine stifle. JAVMA, 1983;183:456-459


  • Tepic S, Montavon P, Is cranial tibial advancement relevant in the cruciate deficient stifle? 12th ESVOT Congress, Munich, 2004: 132-133


  • Shires PK. Dealing with TTA complications. Proc ACVS 2006.


  • Apelt D, Kowaleski M, Boudrieau R. Effect of Tibial Tuberosity Advancement on Cranial Tibial Subluxation in Canine Cranial Cruciate-Deficient Stifle Joints: An In Vitro Experimental Study. Vet Surg, 36:170-177, 2007.


Provided courtesy of Dr. Mayo