Introduction: A 15 month old tri-coloured Border Collie called Trigger presented with progressive LHS hindlimb lameness. Initially the owners had noted the leg was locking with substantial patient pain. They would massage the knee and feel the patella pop back into place. Recently the acute pain had subsided however the dog was limping regularly.
Examination: The LHS stifle had signicant effusion and pain on manipulation. Drawer and thrust were negative. Lateral patella luxation was present. The patella was grade 3 and could be replaced into the femoral sulcus with digital pressure. The rest of the orthopaedic examination was unremarkable. Hip ROM was normal and pain free.
Diagnostic Imaging: Plain radiographs and CT scan of the pelvis, femurs and stifles were obtained. No substantial angular limb deformity or femoral neck inclination issues were present.
Client Discussion: A range of options were discussed with the clients including standard approaches to MLP management such as sulcoplasty, tibial tuberosity transposition etc.
Lateral patella luxation has a higher failure rate than standard medial cases. Complications include a higher reluxation rate as well as implant issues, late onset ACL disease, infection etc.
Operative Management: Mabel was premedicated with acepromazine and methadone before being induced for anaesthesia with propofol and maintained on isoflurane. Intraoperative patient monitoring included Spo2, ETCO2,BP, ECG, HR and Temp. Preoperative, operative and postoperative IV Fluids were given. Temperature was maintained with a Bair Hugger and warm fluid underblanket.
A medial parapatellar approach to the RHS stifle was made. On inspection there was hypoplasia of the femoral sulcus. There was massive lateral and medial retinacular laxity with a pseudo-sulcus laterally. The entire area was eburnated and diseased. We used a Stryker micro-oscillating saw to remove the sulcus. We used an intraoperative mini C-arm to guide the depth of the cut, which was angled downward from medial to lateral. We templated a No. 6.
PGR and then used four Titanium screws to anchor the base and tap on the PGR. The tibial tuberosity w as still too far laterally located. Using a Stryker micro reciprocating saw, it was transposed medially and secured with four fine K-wires and a 19-gauge Cerclage wire figure-of-eight tension band. Medial imbrication and lateral desmotomy were performed. After copious lavage and suction routine closure was performed. Post-operative radiographs confirmed excellent positioning of the PGR.
Outcome: Trigger was bandaged with a modified Robert Jones bandage for 48hrs. He began gentle leash walks for 10 mins TID after a week of restricted activities. His surgical incision healed well and no reluxation occurred. Follow up xrays a 6 weeks postoperative revealed stable implants, good early osteointegration and no signs of infection.
Discussion: PGR was developed by Kyon and consists of a low friction amorphous diamond like carbon coated artificial groove which slots onto a rapid bone ingrowth base plate with a BioCer surface treatment.
We introduced PGR to NSW in 2015/16 performing the first case and have the longest experience with the technology.
Many routine MLP cases can be dealt with successfully with traditional techniques without the risks associated with a large permanent prosthesis. However in more challenging cases especially with substantial cartilage disease or anatomical malformations PGR is an adaptable technique with very good results. Clients often comment how comfortable the patients are after the procedure.
The procedure is highly modular with many sizes for tiny patients through to giant breeds.
The use of the intraoperative mini C arm is critical in safe osteotomy corridor planning.
In summary PGR is an established technique with very good outcomes in difficult cases.
