Open Reduction and Internal Fixation of the Patella

Andrew L. Rosen

Patient Presentation

1. History of direct trauma to knee¹
   
2. History of indirect severe quadriceps contraction
   
3. Localized knee pain

Indications

1. Displacement of fracture greater than 3 mm
   
2. Articular step-off greater than 2 mm
   
3. Open fractures²

Contraindications

1. Minimally displaced fracture with intact extensor mechanism
   
2. Severe comminution
   
3. Distal pole fractures
   
4. Severe or chronic medical illnesses³

Physical Examination

1. Swelling, ecchymosis, contusions
   
2. Inability to perform straight leg raise against gravity or resistance

Diagnostic Tests

1. Standard anteroposterior (AP) and lateral x-rays
   
2. Computed tomography (CT) scans rarely needed

Special Considerations

1. Fracture pattern should be determined preoperatively. Most fractures are transverse in the central or distal third of the patella. Vertical or comminuted fractures are uncommon and more difficult to treat.
   
2. Distal or proximal (rare) pole fractures may need to be repaired with partial patellectomy and tendon to bone repair.⁴

Preoperative Planning and Timing of Surgery

1. Most fractures can be treated electively.
   
2. Fractures associated with superficial skin abrasions can be treated early.
   
3. Open fractures must be treated emergently.

Special Instruments

1. Large bone reduction tenaculum
   
2. 18-gauge wire
   
3. 16-gauge angiocatheter
   
4. Kirschner wires (K-wires): 0.062 or 2.0 mm

Anesthesia

Options are spinal anesthesia with intravenous sedation as needed, or general anesthesia.

Patient and Equipment Positions

1. Supine on regular operative table
   
2. “Bump” padding under ipsilateral hip
   
3. Tourniquet placed on upper thigh, inflated following exsanguination of the leg

Surgical Procedure⁵

1. Anterior, midline skin incision, beginning about 3 to 4 cm proximal to superior pole of patella, extending over inferior pole of patella
   
2. Full-thickness skin flaps created medially and laterally; avoid multiple layers
   
3. Fracture site identified, explored, irrigated with removal of small fragments

Tension Band for Transverse Fractures⁶

1. Reduction performed with bone reduction tenaculum placed midline and anterior.
   
2. Reduction examined, adjusted. Finger placed through medial retinacular tear, which may need to be extended or created to allow palpation of articular surface reduction.
   
3. Two parallel K-wires drilled from longitudinally (can start distal or proximal) through midpatella, across fracture site
   
4. Angiocath inserted across quadriceps tendon from medial touching posterior aspect of wires
   
5. Angiocath inserted across patellar tendon from medial to lateral, touching posterior aspect of both distal K-wire ends; needle removed and wire crossed over anterior surface of patellar and inserted through catheter and quadriceps tendon
   
6. Wire placed in figure-of-eight (crossed over anterior surface of patella) or square pattern, knot created, and tensioned at the medial superior aspect of patella
   
7. Knot cut, buried near K-wire in quadriceps tendon
   
8. K-wires drilled more proximally, leaving approximately 2 to 3 mm of wire distal to tension band wire. Bending distal wires adds security to prevent wire migration but makes removal more difficult.7
   
9. Proximal K-wire ends cut, 1 cm longitudinal incision made in quadriceps tendon over each K-wire. K-wires bent to a hook shape, turned posteriorly, and hammered into proximal patellar surface with bone tap.

Screw Fixation for Vertical Patterns

1. Reduction with bone tenaculum oriented horizontally.
   
2. Retinacular incision made medially to allow palpation of articular surface.
   
3. Partially threaded screws (solid or cannulated) oriented transversely.

Tips and Pearls

1. Use of a figure-of-eight-shaped wire construct is ideal for transverse fractures with some comminution.
   
2. Use of a square-shaped wire construct can minimize anterior prominence of the tension band in thin patients.
   
3. Place knot in close approximation to bent proximal end of medial wire for easier retrieval if hardware removal necessary.

Dressings, Braces, Splints, and Casts

1. Nonadherent gauze, covered with dry gauze and cotton cast padding
   
2. Rigid immobilization in full extension with side-strut plaster splints, cylinder fiberglass or plaster cast, or a locked hinged-knee brace

Postoperative Care

1. Immediate weight bearing allowed as tolerated in rigid extension device
   
2. Period of extension immobilization controversial, influenced by fracture pattern and patient systemic conditions
   
3. Active flexion with passive extension started early
   
4. Active extension allowed later with resistive exercises delayed until fracture union apparent on radiographs

References

1. Koval KJ, Kim YH. Patella fractures. Evaluation and treatment. Am J Knee Surg 1997;10:101–108

2. Torchia ME, Lewallen DG. Open fractures of the patella. J Orthop Trauma 1996;10:403–409

3. Pritchett JW. Nonoperative treatment of widely displaced patella fractures. Am J Knee Surg 1997;10:145–148

4. Hung LK, Lee SY, Leung KS, Chan KM, Nicholl LA. Partial patellectomy for patellar fracture: tension band wiring and early mobilization. J Orthop Trauma 1993;7:252–260

5. Wiss DA. Fractures. Philadelphia: Lippincott-Raven, 1998

6. Browner BD. Skeletal Trauma: Basic Science, Management, and Reconstruction. Philadelphia: Saunders, 2003

7. Wu CC, Tai CL, Chen WJ. Patellar tension band wiring: a revised technique. Arch Orthop Trauma Surg 2001;121:12–16

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