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ORIF Patella Fracture With a Tension Band Construct

Blum, Laura MD; Hake, Mark MD

Journal of Orthopaedic Trauma: August 2017 - Volume 31 - Issue - p S8–S9
doi: 10.1097/BOT.0000000000000891
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Summary: Patellar fractures can occur as a result of direct or indirect injuries. Indirect injury is more common and occurs when the patella fails in tension when the force exerted by the extensor mechanism exceeds that of the bone. Common mechanism of indirect injury is rapid knee flexion with fully contracted quadriceps muscle. Treatment with a tension band construct is indicated for transverse patella fractures without significant comminution. This can be performed with 18-gauge wire and either 2 parallel, longitudinally oriented cannulated screws or 2 Kirschner wires. Biomechanical studies have shown higher load to failure when performed with cannulated screws. We presented our technique for management of a transverse patella fracture with disrupted extensor mechanism using tension banding technique with cannulated screws.

Department of Orthopaedic Surgery, Michigan Medicine, Ann Arbor, MI.

Reprints: Mark Hake, MD, University of Michigan Health Systems, 1500 E Medical Center Drive, Ann Arbor, MI 48109 (e-mail: mhake@med.umich.edu).

The authors report no conflict of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jorthotrauma.com).

Video available at:http://links.lww.com/JOT/A17.

Accepted May 09, 2017

Open reduction with tension banding is indicated for management of transverse patella fractures with disrupted extensor mechanism1 and minimal comminution. Relative indications include articular step-off greater than 2 mm1 extra-articular displacement more than 3 mm, or associated fractures about the knee to allow for earlier rehabilitation.

Tension banding functions by converting tensile forces exerted by the knee extensor mechanism into compressive forces at the articular surface. The classic tension banding technique involves 2 parallel, longitudinal Kirschner wires with tension wire wrapped around their exposed ends and over the anterior surface of the patella in a figure of 8 pattern. However, when compared with more recent tension banding techniques using cannulated screws, Kirschner wires have a higher rate of hardware prominence2 and implant migration3 and have been shown to have lower load to failure rates.2

Options for managing more complex patellar fractures include interfragmentary screws, mini fragmentary plates, anterior locked plating, cerclage wiring, and mesh plating. Multifragmented fractures can be converted into 2-part fractures by fixing the proximal pieces into a single large fragment and the inferior pieces into a second large fragment. When using this method, any horizontal screws should be placed anteriorly to leave room posteriorly closer to the articular surface for cannulated screw. This will act to compress the fracture and avoid gapping at the articular surface. An arthrotomy is indicated for complex fractures to help to better visualize the articular surface and ensure adequate reduction. Partial patellectomies should be reserved for complex fractures of the inferior pole of the patella in which fixation cannot be achieved, although recent data suggest that there is little difference in outcomes between open reduction internal fixation and partial patellectomy.4

We present a case of a 23-year-old man who sustained a ground level fall directly onto his left knee. He was found to have a transverse extra-articular fracture of the inferior pole of the patella with minimal comminution and a disrupted extensor mechanism. He elected to proceed with open reduction and internal fixation with a tension band construct.

The patient was positioned supine on a radiolucent table with a bump under his ipsilateral hip. A nonsterile tourniquet can be used, although it is not mandatory. A standard, midline longitudinal approach was used centered over the patella, extending 2 fingerbreadths above and below the patella. The infrapatellar branch of the saphenous nerve travels in a medial to lateral direction along the inferior aspect of the patella and as a result, patients often experience numbness along the inferior lateral aspect of the knee after surgery.

Dissection is carried down through subcutaneous tissues to the level of the quadriceps tendon proximally and patellar tendon distally, exposing the disrupted retinaculum (see Video, Supplemental Digital Content 1, http://links.lww.com/JOT/A17). The fracture site is exposed, and soft tissue and hematoma are debrided from the area. A bump can be placed under the knee to aid in visualization of the fracture site. The bump should be moved to a position under the ankle during the reduction. The edges of the fracture are cleared of the periosteum to avoid interposition in the fracture site and resultant malreduction. The fracture is reduced with 2-pointed reduction forceps and confirmed using fluoroscopy.

Guidewires are then inserted as close to the articular surface as possible without breaching the articular cortex. These can be started proximally or distally, although we prefer to start the screws in the smaller of the 2 pieces, which typically is the distal fragment. Before measuring, fluoroscopy should be used to ensure that tips of the guidewires are flush with the far cortex of the patella, and soft tissue should be cleared from the entry site of the guidewire. The surgeon should choose screws that are slightly shorter than the measured length to ensure that they do not breach the superior cortex, which could create shearing and lead to breakage of the tension band wire.

Both guidewires are then overdrilled, and either 3.5- or 4.0-mm cannulated screws are inserted over the guidewire. Again, after screw placement, fluoroscopy should be used to confirm that screws do not breach the superior cortex of the patella. Guidewires are then removed, and two 18-gauge wires are inserted through the cannulated screws. The wires are then tensioned in a figure of 8 wire with the knots at the superior aspect of the construct so that they can be buried in the quadriceps tendon to avoid implant prominence after final tensioning. Care should be taken to ensure that the wire is placed adjacent to the bone without soft tissue interposition. Final tensioning should be performed simultaneously to ensure equal compression along the fracture site. After final tensioning is completed and knots are buried in quadriceps tendon, fluoroscopy is used to confirm adequate reduction and stability of the construct throughout knee range of motion. Before closure, the knee is carefully flexed under fluoroscopic guidance to confirm stability of the construct.

Layered closure is completed, including repair of the disrupted retinaculum. The patient is able to bear weight as tolerated with a knee brace locked in extension and can flex the knee to 30 degrees when at rest. Progressive range of motion exercises are initiated 6 weeks postoperatively.

Open reduction with a tension band construct is widely accepted treatment for transverse fractures of the patella with minimal comminution. Postoperatively, many patients complain of persistent quadriceps deficit compared with the contralateral side. Lebrun et al report an extensor lag greater than 5 degrees in 20% of patients.3 Patients experience symptomatic hardware as frequently as 38%.3 However, there are trends in improved patient-reported outcome scores in tension band constructs with cannulated screws compared with those with Kirschner wires.3,5 Knee stiffness and nonunion are uncommon. According to Melvin et al, patellofemoral arthritis is more likely to occur after partial patellectomy because of increased contact pressures.1

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REFERENCES

1. Melvin JS, Mehta S. Patellar fractures in adults. J Am Acad Orthop Surg. 2011;19:198–207. Review.
2. LeBrun CT, Langford JR, Sagi HC. Functional outcomes after operatively treated patella fractures. J Orthop Trauma. 2012;26:422–426.
3. Carpenter JE, Kasman RA, Patel N, et al. Biomechanical evaluation of current patella fracture fixation techniques. J Orthop Trauma. 1997;11:351–356.
4. Bonnaig NS, Casstevens C, Archdeacon MT, et al. Fix it or discard it? A retrospective analysis of functional outcomes after surgically treated patella fractures comparing ORIF with partial patellectomy. J Orthop Trauma. 2015;29:80–84.
5. Tian Y, Zhou F, Ji H, et al. Cannulated screw and cable are superior to modified tension band in the treatment of transverse patella fractures. Clin Orthop Relat Res. 2011;469:3429–3435.
Keywords:

patella fracture; surgical technique; tension band

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