This is some exciting news, and I have to thank my friends in Sydney, for allowing me to share this. Dr Andrew Levien from VSOS, Dr Daniel James from SVES, and Dr Tristram Bennet from SASH have been pioneering a project with famous human surgeon A/Prof Munjed Al Muderis, to create a new technique/implant for dogs with distal limb loss. Distal limb loss is most commonly the result of bone neoplasia or severe trauma. What is limb sparing? Limb sparing is the term used to describe any procedure where the alternative option is amputation - so basically it aims to do just this, 'spare' the limb. Limb sparing might be of particular importance when one of the other limbs is injured or osteoarthritic, as pets generally require a minimum of 3 limbs to ambulate. The important thing with limb sparing, is that in the process of sparing the limb, the animal is happy and pain-free. Limb sparing Options:
Here is the current list of limb sparing options for dogs with bone cancers (typically osteosarcoma). Fortunately, they have been investigated/published in the literature, but unfortunately they all have significant down-sides and high rates (nearing 100%) of complications. - Radiation therapy (risk of post-radiation fractures is high). - Cortical allograft - this is taking a graft/segment of cortical bone from another dog (allograft = same species) and plating it into the defect created by ostectomy. It is never expected to heal or incorporate with the patient's bone but acts as a buttress for the dog's lifespan - Cortical radial autograft with intra-operative irradiation or pasteurisation - this is removing the bone, irradiating or pasteurising it, and replacing it back into the defect and stabilising with a bone plate - Ceramic and metal endoprosthesis (these can be 3D printed to match the defect) - This is utilising a prosthesis to insert into the defect, and it is generally plated into the bone. It is also never expected to heal - Distraction osteogenesis - removing the affected segment of bone, then using the principles of distraction osteogenesis (distracting the proximal and distal bone segments apart forming bone) to fill the defect with new bone - Microvascular ulnar autograft - for distal radial osteosarcomas (a common site), the defect is replaced with ulnar from the same dog (autograft=same individual). Microvascular anastomosis is also performed, which is where the source artery to the ulnar is anastomosed to a neighbouring artery and vein after transposition (requires specialised training and equipment) - Ulnar roll over. The distal ulnar is rolled into the radial defect and plated - Bone transport - This is where a bone segment is moved into the adjacent defect forming new bone via distraction osteogenesis - Segmental ostectomy with acute limb shortening - Partial limb amputation with custom orthotic (generally some form of strap-on device. These tend to be poorly tolerated by patients and limb use can be suboptimal) - Cementoplasty - the neoplastic medulla is reamed and replaced with cement +- local chemotherapy
The aim of a transcutaneous osseointegration is to provide the patient with a new distal limb, that is incorporated into the patient's own bone. This is not an entirely new concept, however the team of vets in Sydney Dr Andrew Levien (VSOS) Dr Daniel James, Dr Tristram Bennett are benefitting from the experience and resources of human surgeon A/Prof Munjed Al Muderis who, along with his engineering team are responsible for implant design as well as surgical implantation in the most successful program of human osseointegrated limb prostheses worldwide. The vets have been collaborating with Osseointegration International engineers to meet the design challenges of size and anatomy for domestic pet patients. Let's talk about some of these amazing cases.
Sunday Firstly here’s Sunday. Sunday sadly lost her pes to maternal trauma in her first weeks of life but was lucky enough to be adopted by Matt, who was conveniently an expert in canine rehabilitation. Sunday was initially trialled with an array of different custom socket prostheses over her early life which afforded some (cumbersome) function. Due to the discomfort of the prosthetics, she refused to allow them to be attached at all by the time she was 1 year of age. Most of Sunday’s exercise was swimming performed at a rehabilitation centre, and she would only walk briefly on soft surfaces. Her owner Matt was determined to keep her fit and look after her spine and joints while he waited for the technology to be available to have her using the affected limb meaningfully again. She still used her limb when walking and it would touch the ground when playing on the grass, so Matt felt that she really wanted to walk on the limb again and full amputation was not considered the best option for her. Matt was aware of the work of Osseointegration International (OI) from television (Munjed’s life-changing surgeries and fascinating life story are popular fodder for TV series). At this stage, though, while the OI system had a very successful track record in over a thousand people, data on long-term outcome in dogs was severely lacking. Some serious conversations followed about just how unknown the unknowns were. A CT was performed for templating and revealed the remarkable difference in tibial growth pattern between the weight bearing and non-weight bearing sides. The tibia grew significantly longer and thinner versus the contralateral limb. The small medulla provided challenges for implant design, however a prototype was developed. After some manufacturing delays and planning, a date was set for surgery. Coincidentally for Sunday, surgery was performed on a….Sunday! (this apparently led to much confusion). This was to allow two orthopods and an engineer to assist, as well as a big contingent from SASH. Just to raise the stakes for the first case, a full Bondi Vet crew were also in tow. In many ways the surgery is familiar to surgeons performing regular hip replacement, but alignment is much simpler (no joint to luxate) and the implant is placed much tighter. Frighteningly tight, to grip the cortical endosteum. Fashioning the stoma from the soft tissue closure is very important also. Sunday walked very well on a small rubber stopper placed on the protruding interface day 2 after surgery and her limb use went from strength to strength. The fate of the soft tissues of the stoma was varied with moderate skin necrosis in areas. The skin margin retracted back from the smooth surface of the planned trans-cutaneous component over time which is disappointing but not a major concern. Matt follows Sunday’s stoma health closely and has identified one important infection that resolved with culture based antimicrobial therapy. He has also experimented with a lot of different limb designs with the most important feature seemingly to have significant padding- she doesn’t like the jarring going straight into her bone, unsurprisingly. She walks regularly and has great quality of life, but the presence of a stoma means this will never be a set-and-forget procedure. Holly
Meet the second case we are going to discuss – Holly the cat, who lost both her distal pelvic limbs. Holly was on her very first adventure outside after immigrating from England when she was chased under a car by the neighbourhood bully cat. She required intensive care and serial debridements of both pelvic limbs as part of her initial treatment. It soon became apparent to her attending surgeon, Dr Vaughan Moore, that she was going to loose a lot of tissue and that this was going to happen bilaterally. Holly was a patient that would traditionally need to be humanely euthanised, however Holly was much loved and her owners were keen to find a solution for her. By the time she had healthy residual limb stumps, Holly had lost the distal portion of her tibia bilaterally and the design process began whilst her owners struggled to manage a cat who kept trying to get herself around, traumatising her healing stumps. Cats ask a lot of an implant with their ‘untamed’ behaviour and three dimensional lifestyle, and their tibial canal size is small. For these reasons, Holly’s implants were manufactured in Chrome cobalt, a stronger material than titanium. Titanium was then sprayed on the outer surface to facilitate Osseointegration. Holly’s surgery to give her two new pelvic limbs (back legs) went very well. The prosthesis again, had a scarily tight fit. Her limb use has been remarkable from the beginning and has become increasingly normal looking as the external prosthetic length has been increased. The success of Holly's case so far has brought great joy to many people involved with her. She’s a really likeable cat who we traditionally would have had no way of saving.
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