3.5 LCP Distal Femoral Osteotomy Plates
Background
Patellar luxation is a common cause of pelvic limb lameness in dogs. Although patella luxation can occur because of trauma, most canine cases of patellar luxation occur because of abnormal femoral and tibial modeling during skeletal development. Traditional surgical correction of canine patellar luxation includes procedures such as sulcoplasty and tibial tuberosity transposition. These techniques are often insufficient in more severe cases resulting in recurrence of patellar luxation. Complex limb deformities involving both the femur and tibia (eg, distal femoral varus, femoral torsion, and a compensatory tibial valgus and/or torsion) typically explain these surgical failures. Distal femoral osteotomy/ostectomy (DFO) was developed to address distal femoral varus (with or without torsion) and has led to markedly improved clinical outcomes. Current implants for canine DFO are not anatomically specific to follow both the femoral procurvatum and condylar morphology, nor do they guide screw trajectory to avoid the femoral intercondylar notch and the femoral trochlea, especially with locking implants. As such, veterinary surgeons may encounter challenges with plate contouring and screw placement.
Plate Design
The recently approved 3.5 LCP DFO plate is indicated for treatment of distal femoral angular deformities and distal femoral fractures. The plate curvature was designed to accommodate procurvatum (anatomical curvature in the sagittal plane) and optimize screw trajectories into the widest portion of the femoral condyle while simultaneously avoiding the regions of the intercondylar notch and femoral trochlea in medium and large breed dogs. The plates are available in 7- or 8-hole lengths to account for variable femoral sizes encountered in medium and large canine patients. Additionally, the plates are specific for left and right limbs (Fig 1). They are compatible with both 3.5 mm locking and cortex screws (Fig 2). The trajectories of the three distal locking screws were designed to avoid the intercondylar notch, maximize screw purchase in the caudal portion of the femoral condyle, while also avoiding cranial screw placement so as to preserve bone for concurrent sulcoplasty (Fig 3). The tapered, curved design minimizes interference of the distal plate with both the patella and periarticular soft tissue. Click here for more detailed information about the 3.5 LCP DFO plate and its features.
Fig 1a–b The left (a) and right (b) 7-hole and 8-hole 3.5 LCP Distal Femoral Osteotomy Plates.
Fig 2 Distribution of LCP and stacked combi holes in the 3.5 LCP Distal Femoral Osteotomy Plate.
Fig 3a-b Screw trajectories on the distal end of the 3.5 LCP Distal Femoral Osteotomy Plate.
Clinical Cases
The following two cases (kindly provided by Michael Kowaleski, North Grafton, Mass, USA, and Erik Asimus, Toulouse, France) illustrate common canine femoral deformities associated with moderate to severe medial patella luxation and demonstrate application of the 3.5 LCP DFO Plate.
Case 1: Distal femoral osteotomy in a 4-year-old, female spayed mixed breed dog with medial patellar luxation
A 4-year- and 6-month-old spayed female mixed breed dog weighing 25.1 kg presented for chronic progressive left pelvic limb lameness. Orthopedic examination and preoperative radiographs revealed a grade 3/4 medial patellar luxation without concurrent cranial cruciate ligament rupture. A preoperative computed tomography (CT) was performed to screen for femoral varus and/or femoral torsion. Femoral varus was documented (anatomical Lateral Distal Femoral Angle [aLDFA] 104°, normal 92-96°). The femoral torsion angle was 26° and was like the unaffected contralateral limb and within the normal range. The planned correction was a 12° lateral closing wedge ostectomy, with concurrent sulcoplasty and tibial tuberosity transposition (Fig 4 ). Click here to read through the detailed surgical procedure.
Fig 4a–c Preoperative CT 3D reconstruction of the left femur. a Mediolateral view illustrates anatomical anteversion of the femoral head and neck and procurvatum of the femur. b Craniocaudal view confirms distal femoral varus (anatomical Lateral Distal Femoral Angle, 104°). c Femoral long axis view shows anteversion angle (26°).
Fig 5a–b Postoperative radiographs demonstrating position of a left, 7-hole, 3.5 LCP DFO plate and associated tibial tuberosity transposition. a Medioateral view. Note that plate contour matches the normal distal femoral procurvatum and screws are positioned caudally away from the trochlea. This allows for an unimpeded sulcoplasty while maximizing screw purchase caudally. The compression applied with the plate has resulted in excellent apposition. The patella is visible within the trochlear groove. b Craniocaudal view. The plate contour matches the anatomical contour of the distal femoral condyle. The anatomical Lateral Distal Femoral Angle is reduced to 92°.
Fig 6a–b Follow up after eight weeks. Clinical signs have resolved, limb use is excellent, and stifle joint range of motion is normal without evidence of pain. a Mediolateral radiograph. The osteotomy has healed. Plate and screw position remain unchanged. The tibial tuberosity transposition is healing, and implants remain unchanged. The patella remains reduced within the trochlear groove. b Craniocaudal view. The osteotomy has healed and is no longer visible. Implants are stable and the patella is tracking normally.
Case 2: Distal femoral osteotomy in a 1-year- and 6-month- old spayed female Appenzell Cattle Dog
A 1.5 year old spayed female Appenzell Cattle Dog weighing 29 kg presented for a second opinion after two previous surgical procedures (Fig 7 and Fig 8) to address a traumatically induced medial patellar luxation. Orthopedic examination and preoperative radiographs revealed a grade 3/4 medial patellar luxation (Fig 8). Femoral varus was documented (aLDFA 104°; normal 92–96°) by CT scan (Fig 9 ). The planned correction was a 10° lateral closing wedge ostectomy, with concurrent sulcoplasty. Click here to read through the detailed surgical procedure.
Fig 7a–b Initial surgery performed at 1 year and 6 months of age. The patellar luxation was treated with a lateral imbrication. No primary orthopedic procedures were performed. Radiographs were obtained six weeks postoperatively, and document persistence of the medial patellar luxation.
Fig 8a–b Revision surgery performed to address persistent patellar luxation. A tibial tuberosity transposition was performed to realign the insertion of the patellar tendon without addressing femoral deformity. Radiographs were obtained two months postoperatively. The patellar luxation persists despite transposition of the tibial tuberosity.
Fig 9a-b Preoperative CT 3D reconstruction of the right femur confirming distal femoral varus (anatomical Lateral Distal Femoral Angle was 104°). Planned correction was to perform a 10° lateral closing wedge ostectomy.
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