Angell Animal Medical Center
Back in early nineties, Dr. Barclay Slocum introduced the tibial plateau leveling osteotomy (TPLO) for repair of canine cruciate deficient stifles. For nearly two decades this technique has been my procedure of choice in active dogs and larger breed dogs (body weight >25kg) and it seems I am not alone, as a 2014 survey confirmed that TPLO is the most common technique used for cruciate repair in the United States. So when a new method for fixing a torn cruciate comes along, it’s going to have to be something pretty special to make me change my ways.
Figure 1. Simitri implant: femoral component, travel channel insert, tibial component (image courtesy of New Generation Devices and Dr. Neil Embleton)
Simitri Stable in Stride™ (New Generation Devices) offers an interesting “twist” on extracapsular repair by introducing an articulating implant. Although TPLO relies on existing musculature to provide dynamic stabilization of the stifle joint, it does not negate translational or rotational instability (Arthrex now offers a TPLO plate that will incorporate a lateral anti-rotational suture). With an articulating implant, Simitri aims to provide static stabilization and prevent abnormal movement of the tibia on the femur.
The articulating implant consists of three parts, a femoral component, travel channel insert—made of ultra high molecular weight polyethylene—and tibial component (figure 1). Arthroscopy or arthrotomy can be performed as normal to inspect the torn cruciate ligament and/or address meniscal tears (because this is a static fixation, meniscal release is contraindicated) and then the articulating implant can be applied to the medial aspect of the distal femur and proximal tibia. Precise preoperative radiographic planning is imperative in order to choose the appropriate implant size, place the femoral ball at the isometric position on the femoral condyles, and correctly offset the tibial plate. Clearly, this is far more involved than a lateral suture technique, but similarly, it does not require cutting of bone (figures 2 & 3).
According to one study, dogs were weight bearing within 24 hours in 64 of 66 limbs. Though full recovery is four months, similar to TPLO, by three to four weeks postoperatively dogs were going for 20-30 minute leash walks, 3-6 times a day, which is significantly faster than a regular TPLO recovery.
Figure 2. Lateral postoperative plain radiograph following Simitri procedure (image courtesy of New Generation Devices and Dr. Neil Embleton)
Figure 3. Antero-posterior plain radiograph following Simitri procedure (image courtesy of New Generation Devices and Dr. Neil Embleton)
So, what’s the downside? Well, like any other new procedure there is a learning curve. In one study, the incidence of major complications requiring surgical revision was 15.3% (minor complications was 10.2%).
However, the authors report a steep decline in complications with experience. From a cost standpoint, the implant is quite expensive (roughly $500) which makes the procedure similar in price to TPLO. Simitri is contraindicated for dogs with tibial torsion, femoral or tibial varus or valgus, and, at this time, based on current implant options, bodyweight should not exceed 55 kg (120 lbs). As with TPLO, infection can be problematic, necessitating removal of implants. According to unpublished data from New Generation, if sufficient time has passed since surgery (e.g. >6 months), further surgery to stabilize the knee such as TPLO may not be necessary due to the formation of adequate scar tissue around the joint.
In fairness to Simitri, it’s early days, however, gaining acceptance and popularity will be challenging since many veterinary surgeons feel like they already have a sound treatment option for cruciate injury in the dog. Going forward, I see several instances in which Simitri will offer not only an alternative, but potentially a better one:
- The owner who can’t accept the use of an osteotomy to fix ligament problems.
- A cranial cruciate injury in a large three-legged dog where early return to function is highly desirable.
- For those extremely challenging cases of a deranged stifle in which cranial cruciate injury is concurrent with collateral ligament and caudal cruciate ligament trauma.
- Large breed dogs with acute bilateral cruciate injury, where earliest possible return to function is optimal.
Who knows, in another twenty years, we might look back and wonder what new procedure might challenge Simitri.
For more information, please contact Angell’s Surgery Service at 617-541-5048 or email@example.com.
Treatment of canine cranial cruciate ligament disease: A survey of ACVS Diplomates and primary care veterinarians. Duerr FM et al. Vet Comp Orthop Tramatol 2014; 27 (6): 478-83
Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Vet Clin North Am Small Anim Pract 1993 Jul; 23 (4): 777-95
Surgical Technique and Initial Clinical Experience with a Novel Extracapsular Articulating Implant for Treatment of the Canine Cruciate Ligament Deficient Stifle Joint. Barkowski VJ and Embleton NA. Vet Surg 2016; 45 (6) 804-815
Canine stifle biomechanics associated with a novel extracapsular articulating implant predicted using a computer model. Brown NP et al. Vet Surg 2016; 45, 327-335