Intra-articular Stabilisation refers to any surgery where the stabilising method is done inside the stifle (knee) joint. These surgeries aim to replace the original cranial cruciate ligament with a ‘new one’.
This is the most common surgical technique for the treatment of a torn cranial cruciate ligament in people.
What is intra-articular stabilisation surgery?
Tearing of the cranial cruciate ligament leads to the abnormal movement (instability) between the femur and the tibia (the two bones of the stifle or knee as it is called in people). The term ‘stabilisation’ refers to surgical treatment to prevent this abnormal movement.
Intra-articular means ‘inside the joint’. So ‘intra-articular stabilising surgery’ refers to any surgery where the stabilising method is done inside the stifle (knee) joint. These surgeries aim to replace the original cranial cruciate ligament with a ‘new one’ and this is the most common surgical technique for the treatment of a torn cranial cruciate ligament in people.
The earliest described surgery for the treatment of cranial cruciate ligament rupture in a dog was an intra-articular technique (Paatsama 1952). A strip of muscle sheath (fascial lata graft) was taken from one of the thigh muscles and passed through drill holes in the femur and tibia bones so that it crossed the joint in a similar fashion to the torn ligament. Historically, this was a very important piece of work that led to the development of many other similar intra-articular techniques over the next 40 years or so.
Since 1952, many different materials have been used to try and replace the torn cranial cruciate ligament, including tissues taken from other parts of the body (for example muscle sheath, tendon and even skin), donor ligaments from deceased dogs, and synthetic materials like nylon, carbon fibre, polyester, polyethylene and many other variants. There has been little development of intra-articular stabilisation since the mid 1990s, but more recently, clinical research has been revived with the use of donor ligament grafts, newer synthetic materials and better ways of attaching the replacement ligament to the bone.
How does intra-articular stabilisation surgery work?
Very simply, the normal cranial cruciate ligament acts like a rope that tethers the femur and tibia together, preventing the tibia from sliding forwards, twisting inwards and overextending.
Intra-articular techniques attempt to replicate the function of the cruciate ligament by replacing it with an artificial one.
Copying the exact function of the cranial cruciate ligament is challenging. The ligament has very specific attachment points on the femur and the tibia inside the stifle (knee), and in people, the success of surgery relies on accurately matching these with the replacement ligament. Dogs’ stifles (knees) come in all shapes and sizes and consistently identifying these attachment points and placing the new ligament correctly is not easy. In fact, most techniques based on the fascia lata/tendon/skin graft make no attempt to do so and accept that the joint will still have some abnormal movement (instability) after surgery.
The normal cranial cruciate ligament should be tight all the time, whether the stifle (knee) is flexed, extended or anywhere in between. In order to achieve this, there are two strands to the ligament that twist slightly around each other and that make slightly different contributions to stability depending on the joint angle. The cranial cruciate ligament is very strong but does have a small amount of stretch in it. None of the replacement ligaments currently used, whether based on tissue or synthetic materials can match all of the properties of the normal ligament. Tissue grafts taken from the patient are not as strong as healthy cranial cruciate ligament. For example, the commonly used fascia lata graft has not much more than a quarter of the strength of the normal cranial cruciate ligament immediately after surgery (Butler 1983). Even at maximum strength, the grafted ligament cannot withstand the same loads as a healthy cranial cruciate ligament.
There is a risk that the grafted ligament will stretch soon after surgery and the stifle (knee) will not be stable. Despite this, the reported results after intra-articular stabilisation with biological grafts have been good (see prognosis below). Synthetic grafts on the other hand can be made to withstand huge loads, but they have no stretch, and this makes it very important that they are placed exactly at the original ligament footprints. If this is not achieved, then joint movement will be limited, the drill tunnels will widen through rubbing of the synthetic fibres against the bone, and eventually the replacement material will break.
What does intra-articular stabilising surgery involve?
The procedure may vary slightly depending on your surgeon and they will be able to provide you more specific information.
Under general anaesthesia, the affected stifle (knee) is surgically explored. This allows the cranial cruciate ligament injury to be confirmed and the meniscal cartilages to be inspected. Between a third to a half of dogs with a cranial cruciate ligament tear will have an injury to the meniscal cartilage. Any torn meniscal cartilage is removed. Some surgeons prefer to inspect the joint and remove the cartilage with keyhole surgery (arthroscopy).
The way that the graft or synthetic ligament is passed into the stifle and then anchored depends on the chosen technique and surgeon’s preference. A commonly reported technique, using biological graft surgery is called the ‘over-the-top’ technique (figure below). In this surgery, a fascia lata graft (muscle sheath), including part of the patellar tendon is passed into the front of the joint through the soft tissues, then between the femur and tibia (along the path of the original cranial cruciate ligament) and finally around the back (over the top) of the femur. The graft is pulled tight and anchored outside the joint.
Biological grafts can be stitched to the surrounding tissues or anchored to the bone using screws/spiked washers/staples.
Some techniques involve drilling tunnels that enter the joint at the attachments of the cranial cruciate ligament on the femur and tibia. The replacement ligament (biological graft or synthetic) is then passed through these tunnels, tightened and then firmly anchored at each end. Modern synthetic grafts are often anchored with interference screws.
Current areas of development in intra-articular stabilisation surgery include:
- 1. The use of keyhole (arthroscopic) surgery to perform intra-articular stabilisation.
- 2. Newer synthetic ligaments placed with more accuracy and better fixation to the bone.
- 3. Donor ligaments from deceased dogs.
What does post-operative care involve?
Some surgeons will place a bandage on the operated leg to immobilise the stifle for sometime after surgery
Anti-inflammatory painkillers are usually given for around two weeks after surgery (tablets or a liquid that is put on food).
Additional painkillers may be provided at the discretion of the surgeon.
Some surgeons may dispense antibiotic tablets to be given at home after surgery.
Restricted activity is required after surgery to allow the surgical wounds to heal. This usually entails confinement to a pen or a room downstairs, avoiding running, jumping on/off furniture, boisterous play and stairs.
The requirement for further rest depends on the ligament replacement technique. Biological grafts need to be protected while they become incorporated into the joint and strengthen – commonly this entails 6-8 weeks of confinement to one room with lead walks in the garden and then 6-8 weeks of gradually increasing lead walks. Synthetic grafts, anchored with interference screws should be able to withstand high loads immediately after surgery, so a much shorter rest period is usually required.
Follow up visits
An appointment at your vets will be required for the surgical wound to be examined and any skin stitches/staples to be removed 10 – 14 days after surgery.
A re-examination, usually by the surgeon, is carried out 6 – 8 weeks after surgery to make sure that recovery after surgery is progressing as expected. As the grafts are not visible on x-rays follow-up x-rays are not required.
Unfortunately, regardless of treatment (or lack of treatment) all dogs are likely to be predisposed to development of osteoarthritis in the affected joint following cranial cruciate ligament disease, because of this it is recommended that they maintain a slim body condition. Your vet will be able to give you more information regarding weight control plans if this is required.
Hydrotherapy and physiotherapy may be recommended by the surgeon performing the intra-articular stabilisation. The technique chosen and surgeon preference dictate when these can be started. This is something that should be discussed before the surgery is carried out so that appropriate plans can be made ahead of time.
What is the prognosis following intra-articular stabilisation?
The reason for the failure of the cranial cruciate ligament in dogs is due to a progressive weakening (degeneration) and this can be associated with a high level of inflammation and a less ‘friendly’ joint environment. It is within this context that any biological graft needs to survive. This is not the same in humans, where the joint and the ligament were normal before the ligament was ruptured (it is usually a sporting injury in people, not a degenerative process).
Good results have been reported using many different intra-articular techniques. However, many of the scientific publications that report outcomes after intra-articular stabilisation are now quite old, and pre-date the use of validated owner-assessed outcomes and the more stringent metrics that might now be expected for a peer-reviewed publication.
Shires et al, in 1982, reported that 93% of 29 dogs treated with a fascia lata, over-the-top intra-articular technique showed no lameness after recovering from surgery. Closer inspection of their results however reveals that five dogs with mild lameness and another two with obvious lameness were excluded from their analysis, so the true figure of success is lower. The surgery did not stabilise the stifle in any of the dogs that were re-examined.
A study by Denny and Barr (1987) from the University of Bristol reported a success rate of 91% in 100 dogs. Success was defined as either no lameness or only mild lameness (77% had no lameness, 14% had a slight lameness).
Force plate analysis has become an accepted objective method for measuring lameness in dogs. There are two commonly quoted publications using force plate measurements to monitor the recovery of dogs after intra-articular stabilisation surgery using biological grafts. Conzemius et al (2005) reported that outcomes after the ‘over-the-top’ intra-articular stabilising technique were not as good as those following lateral suture stabilisation and tibial plateau levelling osteotomy. Jevens et al (1996) reported better outcomes with an extracapsular technique than with a fascia lata intra-articular technique. Differences in study design make it difficult to make reliable comparisons between different intra-articular techniques or comparison with other surgical treatments for cranial cruciate rupture.
Arthritis of the affected stifle is not prevented by intra-articular stabilisation (Vasseur 1992).
What are the risks of intra-articular stabilisation?
Unfortunately, complications can occur with any surgical procedure. The complication rate for intra-articular stabilisation surgery are considered to be low.
The greatest risks after intra-articular stabilisation are:
- 1. Stretching or failure of the graft
- 2. Injury to the meniscal cartilage after surgery
- 3. Surgical infection. The risk of infection is higher with synthetic grafts than with biological grafts
- 4. Other risks include bleeding, wound healing problems and loosening of the implants (e.g. screw/staple) used for securing the ligament replacement
Which dogs will benefit from intra-articular stabilisation?
Intra-articular stabilisation is likely to be of benefit to all dogs with a torn cranial cruciate ligament when compared to non-surgical management.
Some dogs present with failure of the cranial cruciate ligaments in both stifles at the same time. In these dogs, there will inevitably be a high load on the operated leg very soon after surgery which increases the risk of stretching a biological graft while it is still weak.
Large breeds and overweight dogs will also place large forces on the graft, increasing the risk that a biological graft will stretch or fail.
Biological graft techniques like the fascia lata technique do not require expensive implants which can make these surgeries more affordable.
Author: Richard Whitelock BVetMed DipECVS DVR DSAS(Orth) FRCVS
Richard Whitelock is an RCVS Specialist Small Animal Orthopaedics and a clinically active surgeon, with over 20 years’ of experience dealing with all aspects of small animal orthopaedic disease, a high proportion of which have had cranial cruciate ligament disease. He qualified in 1989 from the Royal Veterinary College (RVC) and then spent four years in general practice before returning to the RVC to study radiology (Diploma in radiology 1994). Richard completed a small animal surgical residency at the Department of Veterinary medicine, University of Cambridge 1994-1998 (ECVS diploma in small animal surgery 1997, RCVS diploma in small animal surgery (orthopaedics) 1998). He was a Founding member and Director of Davies Veterinary Specialists in 1998 and Head of Orthopaedics until July 2016 then the Director of Small Animal Surgery, Department of Veterinary Medicine, University of Cambridge until July 2019. Richard was the previous President of the European College of Veterinary Surgeons (2011) and Fellow of the RCVS and now works as a Specialist Veterinary Surgeon at The Grove Referrals, in Fakenham.
Editor: RCVS Knowledge Communications Team
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