The TPLO procedure was designed to eliminate the need for a cranial cruciate ligament. Mr Slocum realised that when a dog weight-bears on the back legs, the slope on the top of the tibia (tibial plateau) creates a forward force on the tibia. The cranial cruciate ligament becomes taut and this prevents the tibia from slipping forward from the femur. When the cruciate ligament is damaged, the tibia no longer has a restraint so abnomal movement (cranial drawer) can occur.
Mr Slocum therefore realised that if the slope on the tibia could be flattened, then the forward force on the tibia whilst walking would be eliminated. The Slocum TPLO is a technique to rotate the tibial plateu to make it less sloped and therefore a cranial cruciate ligament is no longer required.
A brief guide to the procedure is shown below.
Firstly, x-rays are taken to look for evidence of disease in the stifles and then to assess the slope on the tibial plateau. Lines are marked on the radiograph to be able to measure the angle. A decision is then made as to which size saw blade is most appropriate for the bone and how many degrees must the tibial plateau be rotated. The position for the saw cut is also determined.
The leg is then clipped of hair and cleaned before a needle is inserted into the joint to collect a sample of joint fluid. This is assessed for any gross abnormalities that might delay surgery. An injection of local anaestheticis then injected into the joint to provide some pain relief. Injections of an intravenous antibiotic, a non-steroidal anti-inflammatory drug and morphine are administered to reduce the risk of a surgical infection and to provide pain relief.
The dog is then moved into an operating theatre and positioned for surgery. An incision is made on the cranial medial aspect of the stifle (= front inner side of the leg). The joint is opened to assess the cranial cruciate ligament. Torn/frayed parts of the ligament are removed. The menisci are then examined. The menisci are two "C" shaped cartilages that act as cushions on the top of the tibia. These can be damaged when the femur and tibia slide across each other. Any damaged areas are removed. The joint capsule is then sutured closed.
A metal jig is then applied to the tibia using two metal pins. One is placed at the top of the tibia, the other is placed near the hock (ankle) through a separate small incision. The purpose of the jig is to help align the cut when using the saw and to help stabilise the fragments once the tibia is cut.
A circular saw is then used to make a cut in the top of the tibia. The position of the cut is determined by measurements taken on the pre-operative x-ray film. Marks are made on the edges of the cut before the cut is completed to show how much rotation is required. A metal pin is placed into the fragment and used to lever the tibial plateau into the correct position. The use of another metal pin placed across the fracture and the jig holds the tibial plateau fragment in the right position.
A metal plate is then contoured to place over the tibia. It is screwed into the bone with care to prevent the screws entering the stifle joint. The metal jig and pins are then removed and the wound is sutured closed.
Post-operative x-rays are taken to ensure the plate is correctly placed and that the screws are in the right places. A sterile pad is then adhered to the skin for 12 hours to keep the incision clean. Painkillers are continued as necessary but antibiotics are stopped at the end of surgery.
The dogs normally remain hospitalised overnight. They usually start using the leg within a few days of surgery although exercise should be restricted for several months.
Further x-rays are taken after 6 weeks to assess the bone, plate and screws for any problems. If all is ok on these x-rays then hydrotherapy can be started if required. Further check-ups are not usually required.
Post-operative Complications
As with any surgery, there is a risk of post-operative complications.
The most important one is post-operative infection. It is thought that about 10% of dogs having a TPLO procedure will develop a post-operative infection. This appears to be true where-ever the surgery is performed. Most of the infections are just in the skin and will resolve quickly with a course of antibiotics. On rare occasions, the infections are more severe and may require very long courses of antibiotics and possibly repeat surgeries to flush the bone, apply antibiotic beads or remove the metalwork.
Other complications reported include fractures (the tibial crest at the front of the tibia is weakened by the surgery and can be fractured by the pull of the patella tendon that attaches to it) and screws or plates breaking or loosening.
Equipment
When the TPLO procedure was first introduced by Mr Slocum, a patent applied to the instruments and operation that limited who could perform the surgery. Mr Slocum died a few years ago and this opened up the opportunity for more veterinary surgeons to learn the technique and purchase the equipment.
The photo to the left shows some of the equipment required to perform the TPLO procedure.
The dog is then moved into an operating theatre and positioned for surgery. An incision is made on the cranial medial aspect of the stifle (= front inner side of the leg). The joint is opened to assess the cranial cruciate ligament. Torn/frayed parts of the ligament are removed. The menisci are then examined. The menisci are two "C" shaped cartilages that act as cushions on the top of the tibia. These can be damaged when the femur and tibia slide across each other. Any damaged areas are removed. The joint capsule is then sutured closed.
A circular saw is then used to make a cut in the top of the tibia. The position of the cut is determined by measurements taken on the pre-operative x-ray film. Marks are made on the edges of the cut before the cut is completed to show how much rotation is required. A metal pin is placed into the fragment and used to lever the tibial plateau into the correct position. The use of another metal pin placed across the fracture and the jig holds the tibial plateau fragment in the right position.
When the TPLO procedure was first introduced by Mr Slocum, a patent applied to the instruments and operation that limited who could perform the surgery. Mr Slocum died a few years ago and this opened up the opportunity for more veterinary surgeons to learn the technique and purchase the equipment.