P. 586

An Urban Experience
including luxation or aseptic loosening. Custom metallic rim augmentation prostheses coated in hydroxyapatite or trabecular metal for bone on-growth have been employed with success. Cemented acetabular components are placed within these augmentation shells.
Sti e Joint:
Total knee replacement (TKR) has to date been limited to canine patients for the treatment of severe osteoarthritis or juxta-articular bone loss using a commercially available unconstrained femoral metal component on a cemented polyethylene tibial component with or without a metallic base-plate. Thus far a commercial system is yet to be marketed for the feline patient. Current salvage options for multi-ligamentous disruption of the canine or feline sti e include multiple ligament reconstruction with or without ancillary trans-articular support which is fraught by challenges in attaining concomitant isometricity of
all support structures. Extra-articular support without ligamentous reconstruction has been reported with a paucity of objective data and is contingent upon periarticular  brosis.
Semi-constrained TKR devices have been commercially offered as custom made units for selected patients. Both uniaxial hinged and rotating hinged TKR akin to
the human semi-constrained total knee replacement prostheses have been custom made by the author and used in salvage arthroplasty procedures for both cats and dogs. Additionally, these implants can be extended proximally or distally with appropriate  xation to provide articulating prostheses for replacement of tumours of the distal femur and proximal tibia. Generally dual element  xation using a cemented stem for immediate stability and an abutment collar plus a plate for bone on-growth is employed.
Custom medial compartment replacement which consists of a metallic femoral and tibial bearing surface with an interposed mobile-bearing polyethylene liner is now also available for dogs with unicompartmental sti e disease associated with end stage cartilage erosion meniscal pathology.
Tibio-tarsal Joint:
Both partial and total hock replacement is a promising technology being investigated by the author and others but limited case numbers and short duration of follow-up preclude conclusions on ef cacy at this time. This allows potentially effective treatment of pain and disability arising from developmental or traumatic conditions of the tibio- tarsal joint as an alternative to pantarsal arthrodesis.
Shoulder Joint:
Orthopaedic conditions of the shoulder joint are an important cause of thoracic limb lameness in the dog. Articular and comminuted fractures of the proximal
aspect of the humerus or distal aspect of the scapula have a guarded prognosis after surgical repair, with
a high rate of articular scapular fractures resulting in long-term lameness. Arthrodesis is the most commonly described technique for management of dogs with severe traumatic, degenerative or congenital shoulder pathology unresponsive to medical management and where long-term joint stability could not be otherwise achieved. Very satisfactory clinical function can be achieved. By contrast, in people, total shoulder replacement has become the standard of care for many clinical conditions affecting the shoulder joint although anatomic, biomechanical and functional differences between species preclude direct comparison.
The author has recently used a custom made semi- constrained total shoulder prosthesis to treat end-stage gleno-humeral arthrosis and bone loss, using both cemented and uncemented prostheses. The technique has allowed the operated dogs to return to satisfactory levels of activity. The semi-constrained prosthesis provides a stable scapulo-humeral joint and can facilitate recovery of severely atrophic shoulder musculature. The procedure has potential as an alternative to shoulder arthrodesis in selected cases.
Elbow Joint:
For end stage medial compartment disease of the canine elbow, a custom focal partial joint replacement is now commercially available consisting of a metallic humeral insert and a polyethylene ulnar insert in the region of
the medial coronoid process. Joint access had been developed via a medial epicondylar osteotomy, but more recently a caudo-medial approach is advocated. Custom medial compartment replacement is also now possible for resurfacing larger areas and for speci c indications
in dogs which are deemed too large or too small for the commercially available devices.
Replacement of the elbow joint (TER) has been possible for several years and three implant systems have been introduced commercially, The Iowa, The TATE and The Sirius. Whilst complication rates have reduced over time, TER remains challenging and the complication rate both immediately postoperatively and in the longer term remains high. Earnest efforts are continually being expended by various groups to improve outcomes. Custom total elbow replacement is also now possible with 3D printed customised implants for speci c indications such as end stage traumatic disruption and congenital deformity.

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