Patella Fractures Treatment & Management

Updated: Oct 10, 2018
  • Author: Alexandra K Schwartz, MD; Chief Editor: Thomas M DeBerardino, MD  more...
  • Print
Treatment

Approach Considerations

Indications for operative treatment of a patella fracture include the following:

  • Disruption of the extensor mechanism
  • Articular incongruity with more than 2 mm of stepoff
  • More than 3 mm of separation between primary fracture fragments

Relative contraindications to closed treatment of patella fractures include the following [18, 19, 20] :

  • Open fractures
  • Intra-articular displacement with disruption of the extensor mechanism

Contraindications to operative repair of patella fractures include the following:

  • Preexisting lack of active extensor function
  • Fixed flexion contractures of the knee

Future treatment options may include osteochondral allograft reconstructions of the patella for posttraumatic arthritis. Bioabsorbable fixation methods may reduce the frequency of hardware-related symptoms.

Next:

Nonoperative Therapy

If the fracture is not displaced and the extensor mechanism is intact, the fracture may be treated by means of immobilization. This usually involves placing the affected extremity in a cylinder cast for 4-6 weeks. The patient is allowed to bear weight in the cast.

Once radiographic evidence indicates union and clinical signs of healing (nontender to palpation) are present, the patient is changed to a removable brace. A hinged knee brace is used during ambulation. A program emphasizing range of motion and strengthening is then implemented. Once the patient is able to perform a straight leg raise without extensor lag and has greater than 90º of knee flexion, brace use may be discontinued. With proper patient selection, good results can be expected in approximately 90% of patients with nondisplaced fractures.

Previous
Next:

Surgical Therapy

For displaced patellar fractures, surgical treatment is warranted to maximize the potential for successful outcomes. Operative treatment aims to restore extensor function, align articular incongruities, and allow early motion. Operative treatment is carried out on an emergency basis if the fracture is open or if an associated traumatic arthrotomy is present.

Preparation for surgery

Evaluation of the extent of comminution is critical in preoperative planning. The various possible implants should be available, and the choice may be dictated by the fracture pattern. In addition, the patient should be informed of the possible need for fragment excision (see the image below) and patellar ligament advancement to the remaining patella if he or she has irreparable comminution.

Chondral fragments from comminuted patella fractur Chondral fragments from comminuted patella fracture.

Operative details

Fixation can be accomplished in a variety of ways. The most common method is a tension band technique (see the images below). The biomechanical principle of tension band fixation is to convert a tensile force into a compressive force while the knee is flexed. If a fractured patella were to be brought through a range of motion, tension and distraction would be present at the fracture site. By placing a tension band at the anterior surface, this tensile force is converted into a compressive force, thereby aiding in fracture healing. [21, 22, 11, 23, 24]

Postoperative anteroposterior radiograph of patell Postoperative anteroposterior radiograph of patella fracture.
Postoperative lateral radiograph of patella fractu Postoperative lateral radiograph of patella fracture.
Postoperative sunrise view of patella fracture. Ve Postoperative sunrise view of patella fracture. Vertical fracture is stabilized with lag screw.

The tension band technique often begins with placing two parallel Kirschner wires (K-wires). Placement of K-wires is not mandatory but is often performed to aid with rotational control. These wires can be placed outside-in after the fracture is reduced and provisionally stabilized with a reduction clamp.

Another technique by which to place K-wires is the inside-out technique. This involves drilling the wires through the fracture site prior to reduction. Once the wires are passed through the fracture, the wire end nearest the fracture surface is made flush with the fracture. The fracture is then reduced, and the wires are advanced across the fracture. The ideal level of the pins is in the center of the patella, approximately 5 mm below its anterior surface. Intraoperative fluoroscopy may be used to guide placement of hardware.

Once the K-wires are placed, a 1-mm or 1.25-mm tension band wire is placed as close to the border of the patella as possible. Keeping the tension band at the anterior half of the patella is very important. The tension band is made into a figure-eight or figure-zero shape. It should lie as close to bone as possible throughout its entire course. A 14- or 16-gauge intravenous catheter facilitates the passage of the wire through the soft tissue.

The figure-zero configuration has more stability against torsional force. However, it can cut into the retinacula, and if this should occur, the tension band would be lost. This is especially true if the wire is at the posterior half of the patella. For this reason, most surgeons prefer the figure-eight configuration.

As the tension band is tightened with the knee extended, the articular surface must be evaluated. This can be performed by using fluoroscopy or by palpating the undersurface of the patella through the medial and lateral retinacular defects.

After fracture fixation, the arc of motion is assessed. This should be done while the undersurface of the patella is palpated through the medial and/or lateral retinacular defects.

The twisted ends are cut in such a way as to leave approximately 1 cm of wire. These ends are then bent over with a large needle driver, then rotated so that they lie within soft tissue. They should not be left proud, because they can cause irritation of the overlying skin.

The K-wires are also cut. The proximal ends are bent over, again by using a large needle driver. The ends are rotated so as to lie within the quadriceps tendon and are advanced until the ends contact the proximal pole of the patella. The distal ends are then cut to avoid prominence within the patellar ligament.

Circumferential cerclage wires [25]  are helpful for stellate fractures. A 1-mm cerclage wire may be placed around the periphery of the patella. If this measure is combined with tension band fixation, the circumferential cerclage should be placed first.

Modifications of the tension band technique include the use of cannulated screws instead of K-wires. [26]  This may allow compression across stable fractures. After placement of cannulated screws from distal to proximal, the 1-mm or 1.25-mm wire is passed through the center of the cannulated screws, and the wire ends are twisted as described above.

Tension band wiring is possible only after the fracture has been converted to a two-part fracture. Additional fracture fragments can be secured by using supplementary small fragments or mini-fragment screws. This, in essence, allows conversion of a comminuted fracture to a two-part fracture.

Wurm et al prospectively evaluated clinical outcomes in 35 patients with patella fractures who were treated with an angular stable patella plate rather than tension band wiring. [27] Only one implant-related complication occurred, and none of the patients had any deficits in extension capabilities. Patients classified their knee function in daily life as an average of 77% of their pretrauma function; only kneeling or squatting was a problem for some. The authors suggested  that the patella plate may yield reduced complications and improved functional outcome versus tension band wiring, especially for patients with a multipart or comminuted fracture or with osteoporotic bone.

If the fracture is at the most proximal or distal pole, adequate fixation may not be achievable with hardware. In such cases, nonabsorbable heavy suture material can be used for the repair. This involves placing several sets of suture in the patellar or quadriceps tendon, using a locking and running stitch (eg, a Krackow stitch). The suture ends are then brought through the patella via drill holes and tied securely at the opposite end of the fracture. A five-pointed star lattice suture fixation technique for transverse patella fractures has been described by Tang et al. [28]

In rare instances (eg, cases of severe and irreparable comminution), a partial or a total patellectomy must be performed. Because the long-term outcomes with these techniques are poor, they should be used only as a last resort. With a partial patellectomy involving at least one third of the patella, a loss of motion of approximately 18° can be expected. With a total patellectomy, loss of motion, loss of strength, and knee instability with stair-climbing occur. Therefore, it is essential to try to salvage as much patella as possible in all fractures.

After fixation of a patella fracture, closing the arthrotomy and repairing the retinacula are vital. These measures add to the healing of the extensor mechanism and help prevent patellar subluxation. A drain may be placed into the knee joint before closure. The patient is then placed in a well-padded sterile dressing, and a knee immobilizer or hinged knee brace is locked in extension.

Previous
Next:

Postoperative Care

First-generation cephalosporins are given before the surgical incision and for approximately 24 hours postoperatively. The standard protocols for any open fracture should be followed, with aminoglycosides added for contaminated open wounds. Tetanus shots should be updated as indicated for open fractures. Contaminated open wounds may require several repeat irrigations. If the capsule was penetrated, the knee joint should be closed over a drain.

Routine surgical incisions may be followed in an outpatient setting. Sutures or staples generally are removed at 14-21 days. Open fracture wounds should be inspected approximately 48 hours after surgery. Persistent drainage or erythema should warn the surgeon of possible underlying infection. Infection should be aggressively treated (eg, with intravenous antibiotics, surgical irrigation and debridement, or both).

Postoperative rehabilitation is dependent on the fracture pattern, the stability of fixation, and the status of the soft tissue. Early range of motion may be initiated if the fracture pattern allowed stable fixation and no wound problems exist. However, comminuted fractures with less than optimal fixation should be monitored closely for stability and progressive signs of radiographic healing.

Direct communication between the surgeon and the therapist is essential to ensure proper rehabilitation. All patients should be counseled regarding the importance of attaining and maintaining full knee extension. Patients should avoid using pillows under the knee; rather, they should place a heel roll or towel to allow gravity to act on the knee.

Previous
Next:

Complications

Infection

Infection rates as high as 2-10% have been reported. Wound healing also may be problematic, especially with associated soft-tissue lesions. This high rate is attributable to the subcutaneous location of the patella, with lack of overlying soft tissue. To allow healing, the knee often must be immobilized so that further stress on the soft tissue is avoided. Deep infections necessitate surgical debridement and prolonged antibiotic therapy. Untreated infections can lead to septic arthritis and a poor prognosis.

Stiffness

Stiffness often occurs after prolonged immobilization. If the patient is amenable to early motion, physical therapy may be initiated once the soft tissues have stabilized. Patellar mobilizing exercises are mandatory to allow better tracking of the patella. If arthrofibrosis ensues, additional procedures (eg, manipulation under anesthesia or arthroscopy) may be required.

Hardware prominence

Hardware prominence can largely be prevented by means of careful intraoperative technique. Wire ends should lie within soft tissue and not immediately subcutaneously. As many as 15% of patients with symptoms require hardware removal once the fracture is healed.

Prominent wires at the anterior surface of the patella near the prepatellar bursa can lead to prepatellar bursitis. Therefore, it is important to ensure that K-wires and cerclage wires are shortened as much as possible.

Loss of fixation or reduction

Loss of fixation or reduction can occur in as many as 20% of fractures treated with internal fixation. It often is due to inadequate fixation, unrecognized comminution, or aggressive postoperative therapy. If only minimal displacement occurs, the fracture may be treated with immobilization until healing occurs. With loss of extensor mechanism or unacceptable incongruity, the fracture must be revised with hardware or by a partial patellectomy.

Previous