Anatomy & Indications

Corrective osteotomy involves the surgical transection of bone (osteotomy) to correct a skeletal deformity . It is an elective procedure, requiring optimal patient health, meticulous preoperative planning, and appropriate instrumentation. The primary indication for corrective osteotomy is when a malunion or developmental abnormality results in significant functional impairment, rather than solely cosmetic concerns.

Key Indications for Corrective Osteotomy:

• Angular Limb Deformities (ALD): Correction of limb angulation, rotation, or shortening due to abnormal bone growth, often resulting from premature physeal closure. Examples include radius curvus, valgus, and varus deformities.

• Hip Dysplasia:

◦ Triple Pelvic Osteotomy (TPO): Performed to rotate the acetabulum, providing greater dorsal coverage for the femoral head, particularly in skeletally immature dogs.

◦ Intertrochanteric Varus Osteotomy: Corrects an excessive angle of inclination of the femoral neck (valgus deformity) by removing a medial wedge of bone, restoring hip joint stability.

• Patellar Luxation: Femoral osteotomies (derotational, angular, opening/closing wedge) are employed in large and giant breeds with severe distal femoral torsion or angulation to realign the extensor mechanism and stabilize the patella.

• Malunion/Nonunion of Fractures: Correction of fractures that have healed in an unacceptable position or failed to unite, leading to altered biomechanics and lameness.

• Elbow Incongruity: Dynamic proximal ulnar osteotomy may be indicated for humeral ulnar subluxation or in the management of fragmented coronoid processes.

• Arthrodesis: Osteotomy and preparation of articular surfaces (e.g., talar and tibial) are performed to achieve a desired functional angle for joint fusion, such as 135-145 degrees for canine talocrural arthrodesis or 115-125 degrees in cats.

Step-by-Step Surgical Technique (General Principles for Long Bones)

1. Preoperative Planning:

◦ Radiographic Evaluation: Comprehensive radiographs are critical. Use magnified acetate templates (4% or 15% magnification) or digital planning software (e.g., OrthoViewVET, Orthoplan Elite) to "reduce" the deformity, determine osteotomy location, angle, and size of implants (diameter and length).

◦ CORA Methodology: Identify the Center of Rotation of Angulation (CORA) for precise planning of uni- or biapical corrections.

2. Patient Positioning and Draping: Position the animal for optimal axial alignment. Drape to allow maximum visualization of the entire limb for visual confirmation of alignment during the procedure.

3. Surgical Approach: Execute an open approach to adequately expose the bone segment requiring osteotomy.

4. Periosteal Elevation: Make a longitudinal incision through the periosteum and elevate it as a layer using an osteotome or periosteal elevator.

5. Osteotomy Creation:

◦ Powered Bone Saw/Gigli Wire: Efficient for bone transection, requires constant irrigation to prevent thermal necrosis.

◦ Drill Holes and Osteotome: A row of closely spaced holes (K-wire or 1.5-2.0mm drill bit) is drilled along the planned osteotomy line, and a narrow osteotome is used to connect the holes. This creates an irregular surface that enhances stability during reduction.

◦ Wedge Osteotomies: Specifically for angular corrections (closing or opening wedges).

◦ Stairstep Osteotomy: A technically challenging option for bone lengthening, providing some inherent stability but prone to thin fragments.

6. Realignment: Carefully realign the bone segments based on the preoperative plan and intraoperative visual assessment. Ensure axial alignment of both proximal and distal joints relative to the bone shaft.

7. Fixation: Apply chosen implants to rigidly stabilize the osteotomy site in its corrected position.

Variations

• Osteotomy Types:

◦ Closing Wedge Osteotomy: Removal of a geometric wedge of bone (e.g., from the medial side of the femoral neck for intertrochanteric varus osteotomy) to correct valgus or other angular deformities.

◦ Opening Wedge Osteotomy: Creation of a wedge-shaped gap in the bone that is then opened to correct varus or other angular deformities, often necessitating bone grafting of the defect (e.g., for pes varus).

◦ Transverse Osteotomy: A straight cut across the bone, used for conditions requiring bone lengthening (e.g., dynamic proximal ulnar osteotomy).

• Fixation Methods:

◦ Bone Plates: Dynamic Compression Plates (DCPs), Limited Contact DCPs (LC-DCPs), Locking Compression Plates (LCPs), and Veterinary Cuttable Plates (VCPs) are commonly used for rigid internal fixation. VCPs can be stacked to increase stiffness in small patients. Hook plates are specific for certain osteotomies (e.g., intertrochanteric femoral osteotomy).

◦ Bone Screws: Used alone as lag screws for interfragmentary compression (e.g., articular fractures) or in conjunction with plates. Cortical, cancellous, and locking screw types are available.

◦ Pins and Wires: Intramedullary (IM) pins, Kirschner wires, Steinmann pins, cerclage wire, and tension band wires offer various fixation options, often used in combination (e.g., plate-rod constructs for increased stability).

◦ External Skeletal Fixators (ESF): Types I, II, III, circular, and hybrid fixators provide rigid or semi-rigid external support. Indicated for unstable fractures, open fractures, or for gradual deformity correction via distraction osteogenesis (e.g., in radial/ulnar deformities).

◦ Polymethylmethacrylate (PMMA) Bone Cement: Frequently used in neurosurgery for vertebral stabilization, particularly in areas of thin cortical bone or where cancellous bone predominates, by connecting pins or screws.

Instrumentation

• General Orthopedic Instruments: Osteotomes, periosteal elevators, bone-holding forceps, rongeurs.

• Bone Saws: Power saws, Gigli wire.

• Drilling Equipment: Surgical drills (high-speed air drills often preferred for laminectomies), drill bits of various sizes (e.g., 1.5mm, 2.0mm, 2.5mm, 3.2mm, 4.5mm), drill guides, and drill stops for precise depth control and safety, especially in vertebral or small bone surgery.

• Measuring Devices: Depth gauges for screw length determination.

• Specific Implants: Full inventory of plates (DCP, LC-DCP, LCP, VCP, hook plates, reconstruction plates), screws (cortical, cancellous, locking, self-tapping, non-self-tapping), pins (Steinmann, Kirschner, positive-profile threaded), and wires (cerclage, tension band) as appropriate for case load.

• Advanced Imaging: Intraoperative fluoroscopy is highly recommended for complex procedures (e.g., minimally invasive osteosynthesis, articular fracture repair, spinal fixation) to ensure accurate implant placement and reduction.

Post-Operative Management

• Immobilization:

◦ Generally, external coaptation (splints, casts) should be avoided for long-bone fractures repaired with internal fixation due to the risk of creating a fulcrum at the fracture site.

◦ However, external support (splints/casts) is often necessary for specific sites (e.g., carpus, metacarpus, phalanges) or to protect less rigid internal fixations (e.g., lag screws in phalanges, intramedullary pins in metacarpals).

◦ For joint surgery, immobilization may be performed, but excessive or prolonged immobilization should be minimized to promote motion and cartilage health.

• Activity Restriction: Crucial for successful healing. Strict cage confinement, limited leash walks, and gradual increase in activity over weeks to months are mandated, depending on the bone and type of repair.

• Pain Management: A multi-modal approach to analgesia is vital. NSAIDs, gabapentin, amantadine, and sometimes corticosteroids (with careful consideration of side effects) may be used. Opioids are typically administered in the immediate postoperative period.

• Physical Rehabilitation: Early, controlled mobilization and physical therapy are highly recommended to prevent muscle atrophy, improve range of motion, and facilitate functional recovery, especially after neurosurgery and long-bone repairs.

• Monitoring: Regular radiographic evaluation is necessary to assess bone healing progression and monitor implant integrity.

• Implant Removal:

◦ Skeletally immature animals: All plates on long bones should be removed at the time of clinical union to prevent growth deformities.

◦ Adult animals: Ideally, all plates on long bones should be removed, though this is often limited by economic factors. Owners should be informed of potential reasons for removal (e.g., implant-associated complications like stress shielding or rare osteosarcoma).

◦ Pins: May migrate and typically require removal once stability is achieved.

Complications & Outcomes

• Malunion/Nonunion: Inadequate reduction, insufficient or unstable fixation, and premature weight-bearing are primary causes. Can lead to persistent lameness, decreased range of motion, abnormal wear, and progressive degenerative joint disease.

• Infection: While aseptic technique minimizes risk, infection can occur, particularly with implants or if bone grafting is performed in contaminated sites.

• Implant Failure: Loosening, bending, breakage, or migration of plates, screws, or pins can occur, especially with less rigid constructs or poor bone quality. Locking plates generally offer superior fixation in compromised bone.

• Neurovascular Trauma: Risk during surgical approaches, particularly in regions with critical nerves and vessels (e.g., supracondylar humerus, cervical spine, sacral body).

• Growth Disturbances: Corrective osteotomies in young, growing animals must carefully consider growth plate activity. Iatrogenic physeal damage can lead to further limb deformities .

• Femoral Neck Resorption: A potential complication after capital physeal fracture repair, especially with larger implants. Minimally invasive techniques and early implant removal may help mitigate this.

• Postoperative Pain & Swelling: Can be significant, requiring robust analgesic protocols and potentially cold compresses to manage.

• Soft Tissue Complications: Seroma formation, wound dehiscence, or local irritation from implants.

• Overall Prognosis: With meticulous preoperative planning, advanced surgical techniques, and diligent postoperative care, the prognosis for restoring limb function and reducing pain after corrective osteotomy is generally favorable. Functional outcomes for pet animals following arthrodesis at appropriate angles are satisfactory, though limb circumduction may occur at faster gaits.

For Veterinary Professionals: Corrective Osteotomy Guide