Bone grafting developments used in veterinary orthopaedics part two

Transcription

1 Vet Times The website for the veterinary profession Bone grafting developments used in veterinary orthopaedics part two Author : John Innes, Peter Myint Categories : Vets Date : September 7, 2009 JOHN INNES and PETER MYINT illustrate how advanced technology allows veterinary surgeons to incorporate bone grafting in their treatment of fractures and arthrodeses In the first part (VT 39.31) of this two-part article, the authors outlined the various allografts available for bone grafting in dogs, including demineralised bone matrix (DBM), cancellous chips, cancellous blocks and dowels, and cortical sections and struts. In this second part, case studies describe where these products have been useful in promoting bone healing. Cruciate ligament rupture A three-year old Labrador presented with unilateral cranial cruciate ligament rupture. The surgeon elected to perform tibial tuberosity advancement (TTA). Pre-operative planning An extended 135 mediolateral radiograph of the stifle was taken for implant sizing. The TTA template (Kyon, Switzerland) was then used to calculate the advancement distance to produce a patella tendon/tibial plateau angle of 90 at full extension ( Figure 1). A line was drawn tangentially to the tibial plateau and the template was adjusted until a line perpendicular to the tangent intersected with the cranial border of the patella tendon origin. The distance of advancement was read from the template this equated to the required cage size. 1 / 19

2 The template was also used to calculate the maximum size of the plate that could be attached to the tibial tuberosity. Sequential plate transparencies were offered up to the radiograph until the maximum plate size was determined. Patient preparation A standard surgical clip was performed from the hip to just above the tarsus. The foot was covered with an impermeable barrier, and the dog positioned in dorsolateral recumbency with the affected limb on the lower side. The foot was suspended from a stand that was positioned on the animal s dorsal side. Fourquarter draping with an additional impermeable layer was used and an adhesive, transparent incise drape was placed over the exposed skin. Surgical approach A medial approach to the stifle and proximal tibia was performed, followed by medial arthrotomy to assess meniscal damage. Using the eight-hole drill guide, the required number of holes were predrilled into the tuberosity using a 2.0mm drill bit. A partial curvilinear tibial tuberosity osteotomy was performed using an oscillating saw although the proximal aspect of the tuberosity was not completely cut until the plate was secured in place. Implant placement A fork of appropriate size was inserted into the plate, which was then hammered on to the tuberosity using a fork inserter. Once the osteotomy was complete the fragment was advanced using a spreader. The appropriate size cage was attached to the main body of the tibia using a 2.4mm self-tapping screw (Figure 2). With the stifle in full flexion, the tuberosity was compressed distally against the tibia, using the cage as a fulcrum, and secured with boneholding forceps. The plate was then secured to the tibia with two self-tapping screws (2.7 mm diameter for plates with two to five holes, and 3.5mm for plates with six holes or more). The cranial part of the cage was attached to the tuberosity, above the level of the plate, using a 2.4mm screw. Bone grafting Grafting the osteotomy gap with allograft was performed as recommended for this technique. A 3cc vial of freeze-dried canine cancellous chips (2-4mm;Veterinary Tissue Bank, Wrexham) was opened and rehydrated with sterile Hartmann s solution in a Galli pot. The graft was packed into the void created by the advancement osteotomy to provide an osteoconductive scaffold for bone 2 / 19

3 healing with concomitant mechanical support during the healing process. Closure of the surgical site was routine. Follow-up At a routine eightweek postoperative check, healing of the osteotomy was noted on radiography of the stifle joint. Lameness was improved and cranial tibial thrust in the stifle joint was eliminated. Bilateral palmar ligament rupture This five-year old bearded collie presented with bilateral palmar ligament rupture, having fallen over a 3m high wall. The dog exhibited a bilaterally palmigrade stance and radiographs confirmed rupture of the palmar supporting ligaments of the carpus at all three joint levels, necessitating bilateral pancarpal arthrodesis. Patient preparation Both limbs were clipped from just below the elbow joint to the level of the main carpal pad. An impervious barrier was taped in position over the toes. The patient was positioned in dorsal recumbency with the operative limbs retracted caudally. The limbs were freedraped and a sterile impervious drape wrapped over the foot (Figure 3). Sterilised cohes ive dressing was then tightly wrapped around the foot and progressed proximally to act as an Esmarch bandage;at the level of the proximal antebrachium, the dressing was twisted and used as a tourniquet. Because allograft was to be used, there was no need to clip and prepare the proximal limbs, saving considerable time. Surgical approach The surgical technique was similar for both limbs. A skin incision was made through the cohesive dressing on the dorsal aspect of the carpus from the distal third of the antebrachium to the distal third of the third metacarpal bone. Care was taken to avoid the cephalic vein. The subcuticular tissues were then stapled to the cohesive dressing on each side of the incision to isolate the wound. Subcutaneous tissues were incised and the extensor carpi radialis (ECR) tendon of insertion identified on the medial aspect of the carpus. Lateral to this, the common tendon of the digital extensor (CDE) muscle was identified and protected. Fascia between the ECR tendon and the CDE tendon was incised and the CDE tendon retracted 3 / 19

4 laterally. The joint capsule at all three joint levels was incised and the carpus flexed to open the joint space. Articular cartilage was removed using a combination of sharp dissection and curettage with manual and powered instruments. The subchondral plate of the radius was penetrated with two to three small drill holes to encourage mesenchymal cell migration. Bone graft preparation A 3cc vial of demineralized bone matrix (DBM;Veterinary Tissue Bank, Wrexham;Hoffer, Griffon et al, 2008) for osteoinduction, was mixed with a 3cc vial of freeze-dried canine cancellous chips (0.1-1mm;Veterinary Tissue Bank, Wrexham) and rehydrated with sterile Hartmann s solution in a Galli pot. This provided enough graft for both carpi. Implant placement A 3.5mm/2.7mm pancarpal arthrodesis plate (Veterinary Instrumentation, Sheffield) was positioned such that a central screw hole was over the radial carpal bone. The screw was placed and then the most proximal and distal screw holes were filled with appropriate screws. The screws and plate were carefully removed and the allograft, mixed with DBM, was packed in all the joint spaces. The plate was replaced and the screws re-inserted before inserting all remaining screws. Closure was routine and postoperative radiography revealed satisfactory placement of all implants (Figure 4). Each distal limb was then placed in Robert Jones dressings for 48 hours prior to external coaptation for six weeks. Radiographic union of the arthrodesis was noted at routine radiography eight weeks postoperatively (Figure 5). Comminuted tibial fracture The five-year-old German shepherd crossbreed dog was involved in a road traffic accident and sustained a closed, comminuted fracture of the right tibial diaphysis with severe bruising of the soft tissues (Figure 6). There were no other significant injuries. The fracture was considered reconstructable and neutralisation plate and screw fixation was planned. 4 / 19

5 As is policy for all diaphyseal fractures in skeletally mature dogs, bone grafting of the fracture site was planned. Patient preparation Following the trauma, the dog was stabilised overnight and was then prepared for surgery to take place the next day. Following induction of anaesthesia, an epidural anaesthetic was administered using a combination of morphine and bupivicaine. The right pelvic limb was clipped and prepared from the level of the proximal femur to the main pad of the pes. The dog was placed in right lateral recumbency for surgery via a medial approach to the right tibia. Surgical approach A craniomedial incision over the tibia was made and the underlying fascia incised. The saphenous vein was preserved. A combination of lag screws and cerclage wire were used to reconstruct the distal fragment. A 14-hole broad 3.5 DCP was contoured to the craniomedial aspect of the tibia and applied to the bone to fixate the proximal and distal fragments. Bone grafting A 3cc vial of Veterinary Tissue Bank DBM was opened and rehydrated. The graft was packed around the fracture site (Figure 7) prior to routine closure. Postoperative care Radiography revealed good fracture reduction and reconstruction with satisfactory placement of all implants (Figure 8). The dog was hospitalised for a further 24 hours for analgesia and nursing care prior to discharge with analgesics for the next eight weeks. Initially, this involved a combination of carprofen (Rimadyl, Pfizer) and paracetamol/codeine (Pardale V) for five days, with continued analgesia on carprofen only. Follow-up Fracture healing progressed and at eight weeks, this severe comminuted fracture exhibited 5 / 19

6 radiographic union. Summary Advances in bone grafting technology now make allografts available to the wider community, and allow veterinary surgeons to incorporate bone grafting in their everyday treatment of fractures and arthrodeses, while maximising efficiency and maintaining standards in the operating room. Further reading Hoffer M J, Griffon D J and Schaeffer D J et al (2008). Clinical applications of demineralized bone matrix: A retrospective and case-matched study of seventy-five dogs, Veterinary Surgery 37(7): / 19

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8 Figure 1 (left). Templating the cage size for the tuberosity advancement. 8 / 19

9 Figure 2 (above). Securing the TTA cage to the tibia. The plate can be seen attached to the tuberosity, but has yet to be secured to the tibial diaphysis. 9 / 19

10 Figure 3. Dog prepared for bilateral carpal arthrodesis incorporating allografting;there is no need to prepare for autogenous graft retrieval, saving preparation and anaesthetic time as well as patient morbidity. 10 / 19

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12 Figure 4 (far left). Immediate postoperative radiographs indicating suitable implant placement and anatomical alignment. 12 / 19

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14 Figure 5 (left). Eight-week postoperative radiograph confirming union of the arthrodesis. 14 / 19

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16 Figure 6. Radiograph of the severely comminuted diaphyseal tibial fracture in a five-year-old crossbred dog. 16 / 19

17 Figure 7 (above). The rehydrated demineralised bone matrix (DBM) was packed around the fracture site. 17 / 19

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19 Figure 8 (right). Postoperative radiograph of the reconstructed tibial fracture showing good fracture reduction and satisfactory placement of all implants. Fracture healing progressed well. 19 / 19 Powered by TCPDF (