Patella Fractures and Injuries to the Knee Extensor Mechanism

10.1055/b-0036-129625

Patella Fractures and Injuries to the Knee Extensor Mechanism

Samir Mehta

Extensor mechanism injuries (including injuries to the quadriceps tendon, the patella, and the patellar tendon) occur frequently and result from excessive tension through the extensor mechanism or via a direct blow. Extensor mechanism injuries can lead to stiffness, extension weakness, and patellofemoral arthritis. Nondisplaced fractures or partial tendon injuries with an intact extensor mechanism may be successfully treated nonoperatively. Operative treatment is recommended for injuries that result in an inability to perform a straight leg raise or those that result in fractures demonstrating greater than 2 to 3 mm step-off and 1 to 4 mm of displacement. Early primary repair of a torn tendon or anatomic reduction and fixation of patellar fractures is associated with the best outcomes.

Patella Fractures

The patella is a sesamoid bone connecting the quadriceps tendon and the patellar ligament. As such, the patella is an integral part of the knee extensor mechanism. Anatomically, the fibers of the quadriceps tendon and patellar tendon are in continuity over the dorsal aspect of the patella, whereas medial and lateral expansions of the quadriceps tendon blend with the medial and lateral patellar retinacula.1 Disruption of both the patella and these lateral expansions is needed to completely disrupt the extensor mechanism (Fig. 30.1). Such combined disruption is typical because of the strong tensile loads across the knee; when the patella fails, the soft tissues typically fail as well. The exception occurs when the patella is fractured by a direct blow as the knee is extended; in these injuries the medial and lateral retinacula may be intact, and the extensor mechanism may still function.

Lateral radiograph showing displacement of the inferior pole of the patella.

Mechanically, the patella increases the extension moment arm of the quadriceps between 30 and 50% by displacing its line of action farther away from the center of rotation of the knee.2 During knee movement, the patella experiences high tensile stresses. Because of its superficial position and its high mechanical loads, the patella is prone to injury by both direct and indirect means. The incidence of patella fractures is 1% of all skeletal injuries.3 Direct injuries involve trauma to the anterior knee, such as a fall onto the knee or a motor vehicle accident in which the dashboard impacts the knee. Less often, the patella fails in tension as a result of indirect extension forces applied through the muscle insertions. Regardless of the mechanism of injury, the resulting fracture and associated retinacular tear lead to partial or complete disruption of the extensor mechanism of the knee (Fig. 30.1).

The diagnosis of patella fracture is usually made by the combination of physical examination findings (pain, crepitus, knee effusion, and inability to extend the knee actively) and simple anteroposterior, lateral, and tangential (Merchant) radiographs of the knee. Computed tomography (CT) may be helpful in defining fracture fragments in a comminuted or stellate pattern. Magnetic resonance imaging (MRI) may be useful in cases in which nonoperative treatment is considered to evaluate possible associated retinacular tears or occult osteochondral injury.

Classification

Patella fractures are typically classified very simply by the orientation of the fracture line(s) as seen on plain radiographs. Transverse patella fractures are the most common and result from direct or indirect mechanisms causing the patella to fail in tension (Fig. 30.2). Vertical or stellate fractures usually occur following direct trauma to the anterior knee; in these injuries the primary fracture is oriented about the long axis of the patella (Fig. 30.3). Vertical fractures may not result in disruption of the extensor mechanism and may involve the main body of the patella or just the periphery. The surgeon must also distinguish simple fractures, with just two main fragments, from comminuted fractures with many fracture fragments (Fig. 30.4). This determination may alter the choice of operative tactic. The tangential view best shows the osteochondral fragments. Bipartite patellae are found in 1 to 2% of the population and can be confused with a fracture. However, bipartite patellae have a very classic appearance; they occur in the superolateral corner of the patella, are rounded, and have a smooth, sclerotic border (Fig. 30.5).

A transverse patellar fracture. **(a)** Anteroposterior (AP) and **(b)** lateral radiographs of the knee reveal a transverse fracture of the patella. On the AP view, the femur obscures the patella, but one can discern an apparent transverse fracture of the patella. The proximal fragment (which is more easily seen) is situated more proximally than where it should be; this is a major clue to the diagnosis if one misses the distal fragment that is overlying the femoral condyles. The diagnosis is obvious on the lateral radiograph.

**(a)** Anteroposterior and lateral radiographs of the knee revealing a vertical fracture of the patella *(white arrow)*. On the AP view *(left panel)*, despite the femur, one can see a nondisplaced vertical fracture of the patella. Also seen is a tibial plateau fracture. Unlike a transverse fracture, the plane of a vertical fracture is such that the fracture is not visible on the lateral radiograph *(right panel)*. Nevertheless, the lateral view is still useful because it may demonstrate a joint effusion and can be useful for assessing associated injuries such as exist in this case. **(b)** Postoperative radiographs after open reduction and internal fixation of both the tibial plateau and patellar fractures.

A stellate patella fracture. **(a)** Anteroposterior and lateral radiographs of the knee revealing a supracondylar femur fracture and a poorly defined, minimally displaced, comminuted fracture of the patella. The patient had undergone prior ACL reconstruction with interference screws. **(b)** Computed tomographic images show a stellate fracture pattern, with no fragment being significantly displaced. **(c)** Follow-up radiographs. The patella fracture was treated nonoperatively. The patient was able to perform active knee extension and did not have problems with the patella fracture.

Example of a tripartite patella. Radiograph of the knee reveals two sclerotic, rounded fragments involving the superolateral corner of the patella. This is the classic appearance of a tripartite patella with two secondary ossification centers that remain attached to the main patella fragment by a synchondrosis.

Nonoperative Management

Indications

Nondisplaced patella fractures with an intact extensor mechanism may be treated nonoperatively in a cast or brace.3 Before surgeons decide on nonoperative management, the patient′s ability to maintain the knee in extension against gravity should be determined. This determination can be difficult to make because of the pain of the injury; intra-articular injection of local anesthetic may help alleviate pain and enable patients to demonstrate motor function. One should be aware of transverse fractures that would be likely to have associated retinacular tears. In contrast, minimally displaced vertical patellar fractures may be more safely treated nonoperatively because the retinacula are likely to be intact. Frequently these fractures involve the lateral portion of the patella with little articular involvement and typically without disruption of the extensor mechanism. Because of this, more latitude is permissible when selecting patients for nonoperative management. If the fracture is extra-articular and the extensor mechanism is intact, the fracture may be safely treated nonoperatively with early, unrestricted range-of-motion exercises. For displaced intra-articular fractures or those with an extensor lag, operative management is recommended.

Rehabilitation

Patients are casted with the knee in extension for 4 to 6 weeks, at which time repeat clinical and radiographic examinations are obtained. If the patient is asymptomatic and the radiographs demonstrate evidence of healing, active motion exercises are initiated. The patient begins with knee motion to 30 degrees of flexion and advances by 30 degrees every week until full knee motion is obtained, with a goal of full knee motion by 6 to 8 weeks after injury. Passive motion exercises are to be avoided until it is clear that complete fracture healing is ensured, to prevent potential fracture displacement.

Severely comminuted patella fractures are generally treated operatively, but such fractures in patients with low functional demands may be better treated with nonoperative management (Fig. 30.4).3 Such fractures are usually the result of a high-energy direct blow to the patella where the extensor mechanism remains intact. These fractures are likened to “candy in a sack” and may be treated with brief immobilization for comfort, followed by progressive range-of-motion exercises.4

Patella fractures may also be treated nonoperatively in patients who are nonambulatory and in patients who are not surgical candidates or do not desire surgery. Brief immobilization is undertaken for pain control followed by motion as dictated by clinical symptoms. Following nonoperative management, suboptimal knee function can be anticipated.4 A drop-lock brace can support the knee in extension when needed and may be beneficial in this situation. When the patient is standing, the brace is locked, enabling ambulation. Two sliding locks on the hinges are released with sitting, enabling a normal seated posture.4

Surgical Treatment

Indications

Because the patella has a large chondral surface, indications for treatment of displaced patella fractures are similar to those of other displaced articular fractures. Fractures that are displaced more than 2 mm should be operatively reduced and stabilized; however, a displacement of 2 mm may be difficult to determine radiographically. All patellar fractures causing disruption of the extensor mechanism of the knee also require operative treatment to restore knee extension, regardless of their apparent amount of displacement. Patellar fractures associated with other fractures about the knee, such as tibial plateau fractures and supracondylar femur fractures, should be surgically treated to enable early knee rehabilitation (Fig. 30.3).

The surgeon must choose among three general methods of repair: open reduction and internal fixation, partial patellectomy with tendon reconstruction, and total patellectomy. Total patellectomy is very rarely performed for primary management of patella fractures because at least a portion of the patella can usually be salvaged. Partial patellectomy is usually chosen when the mostly extra-articular distal pole is comminuted; in such cases more secure repair can be obtained by reattaching the patellar tendon to the proximal fragment than by repairing the fracture. This approach spares the need for internal fixation and the patient can be more rapidly rehabilitated without concern of loss of fixation. Occasionally, one might repair a simpler fracture of the upper portion of the patella while excising comminuted fragments of the distal pole, thereby combining both approaches.

Surviving the Night

The mechanism of injury may dictate the need to look for associated injuries (e.g., patella fracture as a result of a dashboard injury should necessitate evaluation of the proximal femur and acetabulum).
Assess the soft tissue envelope (i.e., open fracture) given the superficial nature of the patella fracture, particularly through a direct load.
Maintain knee extension to limit retraction.
Address both the patella and the retinaculum during surgical stabilization.
Use the patellar fracture to access other fractures (e.g., placement of an retrograde intramedullary nail).

Surgical Anatomy

The patella has a somewhat triangular shape, with its apex pointed inferiorly. The proximal three fourths of the articular surface of the patella is covered with articular cartilage, whereas the inferior (distal) pole is extra-articular. The articular surface has a prominent vertical ridge that divides the articular surface into medial and lateral facets. The ridge is located roughly at the junction of the medial and middle thirds of the patella. A second, smaller ridge along the medial patella defines the so-called odd facet. The medial and lateral facets are divided into superior, middle, and inferior portions. Variations in the overall morphology of the patella have been described and classified5; interested readers are referred to this original source because discussion of this topic is beyond the scope of this chapter.

The patella has a complex blood supply. A peripatellar vascular plexus receives contributions from six different arteries that form a circular network around the patella (Fig. 30.6). Thus, the vascular supply to bone fragments is preserved, even in comminuted fractures. Named vessels include the superior geniculate artery from the superficial femoral artery and the four geniculate arteries that branch off the popliteal artery. A final anastomosis to the anterior tibial artery is via the recurrent anterior tibial artery. During surgical exposure and fixation, care must be taken not to devascularize the fragments, which may lead to avascular necrosis, particularly in the comminuted or open fracture patterns.

Schematic depicting the significant collateral blood supply to the patella. This blood supply is at risk in severely comminuted fractures or extensive surgical dissection of the patella, which can lead to avascular necrosis or nonunion.

Surgical Techniques

The patient is positioned supine on a radiolucent table with a small positioning pillow placed beneath the ipsilateral hip so that the patella points straight toward the ceiling. A tourniquet may be used, and if so, it is placed proximally on the thigh. The lower extremity is sterilized and surgical drapes are placed. If using a tourniquet, the limb is exsanguinated, and the knee is flexed to advance the patella before the tourniquet is inflated. A vertical midline incision is performed beginning ~ 6 cm proximal to the patella and extended distally to the tibial tubercle (Fig. 30.7a). In the case of an open fracture, the traumatic wound is utilized to the extent possible, with proximal and distal extensions as needed. Surgical incisions to extend the traumatic wound should be placed carefully to avoid acute angles that create narrow skin flaps. The incision is carried down to the quadriceps tendon proximally and the patellar tendon distally. The medial and lateral retinacula are exposed to the extent that they are disrupted (Fig. 30.7b). At this point, the surgeon must decide on the definitive approach: internal fixation, partial patellectomy, or total patellectomy.

**(a)** Clinical photograph of a patient′s leg prepared for surgery. The patella fracture, quadriceps tendon, and patellar tendon are drawn out. The proposed midline incision is marked as well. **(b)** Photograph after exposure of the extensor mechanism.

Open Reduction and Internal Fixation

Video 30.1 Tension Band Wire and ORIF

Patella fractures are usually repaired by some combination of a tension-band construct, cerclage wire, mini-fragment plates, and interfragmentary screws. The specific construct depends on the pattern of the fracture and the condition of the soft tissues. For successful repair with a tension band, the primary fracture line must be transverse, and the surgeon must be able to reassemble the fracture well enough so that the fracture fragments can withstand compressive forces. In the case of severe comminution where tension band fixation is not possible, the surgeon must excise the comminuted segments or choose cerclage fixation.

First, the fracture fragments are identified and the fracture surfaces are cleaned of hematoma. The fracture fragments may be gently displaced while maintaining their soft tissue attachments to inspect the underlying articular surface. Typically, the largest fragment is rotated to the side ~ 90 degrees to accomplish this (Fig. 30.8). Associated articular impaction injuries of the distal femur may be observed and can be treated through this surgical exposure. The surgeon must carefully look for any osteochondral fragments from the undersurface of the patella. Free osteochondral fragments are frequently found with patella fractures and must be either stabilized or excised.

Drawings of a stable osteochondral fragment. **(a)** The incision is made to expose the knee extensor mechanism. **(b)** The patellar fragments are everted to allow inspection of the articular surface. A separate osteochondral fragment is identified. **(c)** The fragment geometry is such that it keys in place and **(d)** is stabilized by compression between the two main fragments. The Kirchner wires (K-wires) are placed as anterior as possible in the patella.

After the fracture fragments have been identified, isolated, and cleaned, attention is focused on stabilizing the articular surface. Very small bone fragments may be discarded, whereas attempts are usually made to maintain larger osteochondral fragments. If further exposure of the articular surface of the patella is needed to repair osteochondral fragments, a vertical incision extending from the traumatic tear in the lateral retinaculum may enable the patella to be everted 90 degrees.6 Alternatively, Berg7 described the use of tibial tubercle osteotomy to expose comminuted patella fractures. After exposure, the tibial tubercle is predrilled to accept either a 6.5-mm cancellous lag screw or a 4.5-mm bicortical fully threaded screw. An osteotomy of the entire tubercle is made with an oscillating saw; the osteotomized fragment is usually 2 cm wide, 4 cm long, and 1.5 cm thick. The osteotomy can be hinged medially to enable patellar eversion, and repaired securely.7

If the osteochondral fragment is stable within the cancellous bed after reduction, no fixation is required because stabilization will be maintained by compression between the main fracture fragments (Fig. 30.8). If the osteochondral fragment is unstable, then definitive screw fixation is considered. Using the articular surface of the main fracture fragment as a guide, unstable osteochondral fragments are reduced to the major fragment and stabilized provisionally with small-diameter Kirschner wires (K-wires) as necessary (Fig. 30.9). Rigid stabilization of these fragments must be achieved to prevent displacement during postoperative knee motion. To attain such stabilization, I have found that small-diameter screws provide the most reliable fixation. Small-fragment 3.0-mm cannulated screws may be placed over the K-wires used for provisional fixation. Mini-fragment 2.0-mm screws may be used for very small fragments. Screws placed directly within the free osteochondral fragment provide the most stable fixation. Bioabsorbable screws may also be used, but I prefer metallic screws because of the precision with which they can be placed. Lag-screw technique is avoided for fixation of free osteochondral pieces; instead, fully threaded positioning screws should be used (Fig. 30.9). For coronally displaced osteoarticular fragments, the screw is placed perpendicular to the articular surface, taking care to adequately countersink the screw. Sagittally oriented osteochondral fractures are also stabilized with screws, but the screw is placed within the cancellous bone of the fragment roughly parallel to the articular surface. When placing this screw, one must be sure to drill the screw 2 to 3 mm deep to the articular surface to accommodate the screw head, ensuring the screw head does not impinge upon the articular surface.

Drawings of an unstable osteochondral fragment. **(a)** Provisional fixation with a K-wire. **(b)** Fixation with a fully threaded positioning screw. **(c)** Final fixation of the primary transverse fracture with a tension band.

Attention is next focused on the major fracture fragments, with the goal of creating a simple transverse fracture pattern. The smaller fracture fragments are sequentially reduced and stabilized to the larger ones until a two-part equivalent transverse fracture pattern is achieved. Care must be taken to place the screws sufficiently dorsal in the patella to accommodate the more anterior longitudinal K-wires necessary for the tension-band construct. For this type of fixation to be successful, the reconstructed fragments must be fixed well enough that the fracture surfaces can withstand the compression forces generated by the tension band. If such a stable construct cannot be created, it is better to avoid attempting tension-band wiring and instead consider a cerclage wire to hold the comminuted fragments together.

The final step in the reconstruction is to repair the transverse fracture fragments with a tension-band construct. The two fragments of the superior and inferior patella are reduced to one another and held with a Weber or other pointed reduction clamp (Fig. 30.10). Occasionally two reduction clamps are required for adequate control of the fracture reduction. Fracture reduction is verified by palpation or visualization of the articular surface and with fluoroscopy if needed. Using the anterior cortex of the patella as a reduction guide can be misleading. Often, apparently anatomic reduction of the anterior patellar cortex leaves a gap on the articular surface. Digital palpation or use of an instrument to assess the congruity of the articular surface is essential if direct visualization is not possible. If an anatomic reduction is ensured, a 2.0-mm K-wire is introduced into the lateral one third of the patella beginning at the inferior pole and exiting proximally through the superior pole (Fig. 30.11). Ideally, the K-wire should be as close to the dorsal surface (anterior patella) as possible (Fig. 30.12). Depending on the degree of fracture comminution, this may not always be possible. As the K-wire exits the superior pole of the patella, a small longitudinal incision is made in the quadriceps tendon atop the K-wire. The K-wire is then advanced through the quadriceps tenotomy for ~ 5 cm. A second K-wire is introduced in a similar fashion in the medial one third of the patella parallel to the initial K-wire (Fig. 30.12). Although the K-wires are typically drilled freehand, Ong and Sherman8 describe a technique using an anterior cruciate ligament (ACL) drill guide to facilitate drilling the patella and passing sutures.

Intraoperative fluoroscopic view during repair of a transverse patella fracture, showing that the transverse fracture is reduced and clamped while two K-wires are advanced to the fracture.

Drawing of tension-band wiring of the patella, showing how the primary transverse fracture line is reduced and held with pointed reduction clamps while two K-wires are advanced from distal to proximal across the fracture.

Intraoperative fluoroscopic view showing the position of the K-wires after they are advanced across the fracture.

The tension-band wire is then passed (Fig. 30.13). To facilitate inserting the wire through the quadriceps tendon, a 14- or 16-gauge angiocatheter is inserted transversely into the quadriceps tendon deep to the K-wires, just above the superior pole of the patella. Then, beginning at the inferior pole of the patella, 18-gauge surgical wire is passed deep to the distal ends of the K-wires. The cerclage wire is crossed in a figure-of-eight fashion over the anterior patella, and the end on the same side as the tip of the angiocatheter is inserted through the needle to exit through the hub of the needle on the opposite side. After the wire has been passed through the angiocatheter, the angiocatheter is removed. Two loops are created in the cerclage wire and tightened using heavy needle drivers (Fig. 30.14). The use of two separate twists generates greater compression than a single tightening site. During the tightening process, it is important to ensure that both wires wrap around each other, rather than one wire coiling around the remaining straight wire. If the latter occurs, the twists will simply function as a slip knot, and the construct will loosen. Proper twisting of the wires is facilitated by pulling up on the loops equally as they are simultaneously twisted. After tightening, the loops are cut ~ 1 cm long, bent over, and impacted into the soft tissues. Similarly, the superior ends of the K-wires are cut and curled over using pliers (Fig. 30.15). The K-wires are rotated posteriorly until the curled ends are 10 to 15 degrees posterior to the midcoronal plane and are over the tension-band wire, so that the tension band is captured deep to the K-wires when they are impacted into the superior pole of the patella (Fig. 30.15). The knee is flexed to 90 degrees to ensure fracture stability. The distal ends of the K-wires are cut, leaving ~ 1 cm. The tourniquet is deflated, and hemostasis is achieved with electrocautery. Retinacular disruptions are repaired with interrupted nonabsorbable suture. The wound is then irrigated and closed over a suction drain.

Drawing showing placement of an angiocatheter that is inserted transversely into the quadriceps tendon just above, and deep to, the upper end of the K-wires. An 18-gauge surgical wire is then placed around the K-wires in a figure-of-eight fashion.

**(a)** Drawing and **(b)** corresponding intraoperative fluoroscopic view showing the creation of two loops on each vertical segment of the tension-band wire that are twisted, thereby tightening the tension band.

**(a)** Drawing and **(b)** corresponding intraoperative fluoroscopic view demonstrating how the K-wires are cut short and the ends bent, turned, and impacted.

Biomechanical and clinical studies have proven the tension-band technique as described to be an effective method of stabilizing and treating patella fractures (Fig. 30.16). However, it is technically demanding. The most common error is improper placement of the tension-band wire. Failure to approximate the tension-band wire to bone on the superior and inferior poles of the patella, posterior to the quadriceps and patellar tendons, results in soft tissue interposition. If this happens, gapping of the fracture during knee flexion occurs as the tension band is loaded because sliding is possible along the K-wire until the wire meets the bone.9,10 The greatest stress is placed on the construct between 30 and 60 degrees of flexion, which is the range when the joint reactive force is greatest. Therefore, the greatest risk of fracture displacement is in this range.11

Tension-band wiring of a transverse patellar fracture. **(a)** Anteroposterior and lateral radiographs of the knee showing a transverse patellar fracture. Although there is not a large gap, the patient could not perform a leg raise, and there was a step-off of the articular surface. **(b)** Follow-up radiographs after fixation using a traditional figure-of-eight tension-band wire technique.

Alternatively, transverse patella fractures may be stabilized with a modified tension-band technique using 4.0-mm cannulated screws (Synthes, Paoli, PA) (Fig. 30.17). The transverse fracture is reduced as already described. Using a technique similar to introducing the K-wires for the tension-band technique, two 1.25-mm guidewires are inserted into the inferior pole of the patella using fluoroscopic imaging. Just before the guidewires exit the superior pole of the patella, the guidewire length is measured using the external sleeve depth gauge. This should correspond to a screw length that is a few millimeters less than the length of the patella, ensuring that the tip of the screw will remain buried in the bone.

The modified tension-band technique using cannulated screws. **(a)** Anteroposterior and lateral radiographs of the knee revealing a displaced transverse fracture of the patella. **(b)** Post-operative views after open reduction and internal fixation with a modified tension-band technique using two cannulated screws. (Courtesy of Steven Benirschke, MD.)

The guidewires are then advanced through the superior pole of the patella. A 2-cm longitudinal incision is made through the quadriceps tendon over the guidewires that are then advanced through the quadriceps tendon. The guidewires are over-drilled with the appropriate cannulated drill bit. At this point, a standard depth gauge can be used to determine the length of the screw, which should be 4 to 6 mm less than the measurement determined with the depth gauge. A 4.0-mm partially threaded screw is inserted over each guidewire. It is important to ensure that the screws do not extend beyond the superior pole of the patella because the sharp screw threads may cut the cerclage wire or suture leading to fixation failure and fracture displacement.

After the screws are securely positioned, 18-gauge wire is passed through one screw beginning at the inferior pole. Sufficient wire must be pulled through this screw to enable passage through the second screw. The wire is then passed through the second screw again, beginning at the inferior pole and exiting through the superior pole. The wire is then secured using the two-loop technique previously described, although in this case the loops are placed superiorly and inferiorly. Alternatively, large-diameter nonabsorbable suture may be used in place of the cerclage wire.

This technique may be particularly helpful in patients with a bone of good quality in which good screw purchase is ensured. Several biomechanical studies have reported increased strength with the addition of screws, most noticeably in terminal extension.9,11 This may facilitate range of motion in younger patients with good bone quality, whereas the modified tension-band technique is more suitable for elderly patients and fractures with comminution.12,13

When the patella is severely comminuted so that two large, stable fragments cannot be constructed, or when there is additional comminution of the periphery of the patella, a cerclage wire or cerclage plating constructs may be utilized for added stability (Fig. 30.18).

Peripheral plating of a comminuted patella fracture. **(a)** Anteroposterior and lateral radiographs of the knee revealing a comminuted fracture of the patella. Fractures of the femoral shaft and tibial plateau are also apparent. **(b)** Corresponding radiographs taken after internal fixation of all fractures. The comminuted patella was repaired with a construct utilizing two cannulated screws placed perpendicular to the primary fracture line, supplemented by a figure-of-eight tension-band wire and a medial peripheral patellar plate. The plate is a mini-fragment semitubular plate, cut off at the ends, which were bent over and impacted into the patella. Multiple 2.0-mm screws were placed across the patella to buttress the articular surface. **(c)** Merchant view of the reconstructed patella. (Courtesy of Steven Benirschke, MD.)

Displaced vertical fractures do not require a tension band fixation because they are not subjected to the distraction forces seen with the transverse fractures during knee flexion. For the rare, purely vertical patella fracture, lag-screw fixation alone should be sufficient. The patella is exposed through a longitudinal approach over the patella. After exposure of the fracture and removal of fracture hematoma, osteochondral fragments, if present, are stabilized as previously described. The major fracture fragments are then reduced and stabilized with a pointed reduction clamp. Lag screws or positioning screws are utilized to stabilize the fractures.

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