^DEFINITION

^{The patella, the largest sesamoid bone, is an essential component for knee extension (in conjunction with the patellar and quadriceps tendons) and provides leverage to the quadriceps mechanism. Fractures of the patella have the potential to disrupt the extensor mechanism.}

^{Fractures of the patella can impact knee function, as these are often articular injuries.}

^{Management of patellar fractures must restore any disruption to the extensor mechanism while ensuring minimal disruption of the articular surface.}

^{Descriptive terms (stellate or comminuted, transverse, vertical, apical or inferior pole, and sleeve) are used to classify patellar fractures.}

 

 

^ANATOMY

 

^{The articular surface is composed of medial and lateral facets, with the medial facet having the most variability in size and shape. Horizontal ridges further subdivide the medial and lateral facets. An odd facet lies at the most medial aspect of the articular surface. The undulating nature of the articular surface can make interpretation of the lateral radiograph difficult. The distal pole of the undersurface is extra-articular, which is an important consideration when addressing injuries in this region (FIG 1).}

 

^{The superior pole of the patella serves as an attachment for the quadriceps tendon. The most superficial portion of the quadriceps tendon courses over the anterior patellar surface and is contiguous with the patellar tendon. The patellar tendon courses from the apex of the patella to the tibial tubercle.}

 

 

 

^{FIG 1 • Patellar anatomy. The major facets include the medial, lateral, and odd facets. The medial and lateral facets are further subdivided by subtle horizontal ridges.}

 

 

^{The patellar retinaculum is composed of thickenings of the fascia lata of the thigh in addition to the}

^{aponeurosis of the vastus medialis and lateralis.15 In addition to stabilizing the patella, the retinaculum acts as a secondary extensor. An intact retinaculum in the setting of a displaced patellar fracture may allow for extension of the knee. The retinaculum is often torn in conjunction with an extensor mechanism injury.}

 

^{Multiple arteries about the knee supply a peripatellar plexus, although the main intraosseous blood supply is from a distal to proximal direction.16}

 

^{The patella acts to increase the moment arm of the extensor mechanism by displacing the quadriceps tendon anteriorly. This increased moment arm is most critical during terminal extension, when the quadriceps is}

^{otherwise at a mechanical disadvantage.9}

 

^{Due to the small contact area of the articular surface and the high level of compressive forces generated by the extensor mechanism, the contact stress on the patellofemoral joint has been estimated to be higher than}

^{any other major weight-bearing joint.5}

 

^PATHOGENESIS

 

^{Fractures of the patella may result from direct force to the anterior knee, indirect forces transmitted through the extensor mechanism, or a combination of both.}

 

^{The patella is particularly susceptible to injury from direct blows given its superficial location and minimal soft tissue envelope.}

 

^{The portion of the patella articulating with the femur moves from distal to proximal with increasing degrees of}

^flexion.

 

⁴⁹³

^{The fracture pattern for direct blows to the patella has been shown to correspond to the articulating portion of the patella at the time of injury, thus corresponding to the amount of knee flexion at time of injury.1}

 

^{Indirect forces causing fracture can be caused by unanticipated and rapid flexion of the knee while the quadriceps is also firing. Fractures from an indirect mechanism tend to be less comminuted than those from}

^{direct trauma.5}

 

^{NATURAL HISTORY}

 

^{Depending on the type of fracture and involvement of the retinaculum, various amounts of long-term extensor lag and weakness can be expected. The long-term effect on range of motion likewise depends on fracture pattern and displacement.}

 

^{There is an increased incidence of osteoarthritis of the knee after patellar fracture. The increased rate of arthritis may be both from initial cartilage injury and posttraumatic arthritis due to articular cartilage incongruity. Despite advances in techniques and technology, outcomes after operative fixation still show functional impairment.}

 

^{PATIENT HISTORY AND PHYSICAL FINDINGS}

 

^{Physical examination findings are as follows:}

 

 

^{Often, a defect can be palpated in the patella.}

 

^{New onset of joint effusion after injury localizes within the capsule of the knee. A knee effusion may not be present if there is disruption of the retinaculum, allowing hematoma to escape from the joint capsule. A significant effusion can increase tension on the limited soft tissue envelope resulting in necrosis of the skin.}

 

^{The position of the patella (baja vs. alta) and palpation of defects with the patella, quadriceps tendon, or patellar tendon can help differentiate between patellar fracture and ligamentous extensor disruption.}

 

^{Pain can limit the ability to test for active extension of the knee or for extensor lag. Introduction of local anesthesia after aspiration of hematoma can aid in assessment of extensor function. The surgeon should note any extravasation of local anesthetic to evaluate intra-articular extension of skin defects.}

 

^{Aspiration: The surgeon notes the amount of fluid aspirated. The presence of fat lobules in the syringe signifies a fracture extending into the knee capsule.}

 

 

 

^{FIG 2 • A. In the Merchant view, the knee is allowed to bend to 45 degrees, and the x-ray beam is angled at 30 degrees to the horizon. The x-ray cassette is placed perpendicular to the leg on the proximal tibial diaphysis. (continued)}

 

 

^{Patients with patellar fractures are able to actively extend the knee in marginal or longitudinal fracture types or with intact secondary extensors (ie, retinaculum). Knee extension is usually not possible with displaced transverse fractures.}

 

^{History is critical in determining a direct versus indirect cause of fracture. Patellar fractures caused by a highenergy direct cause (ie, head-on motor vehicle accident with dashboard injury) are often associated with other injuries to the knee.}

 

^{Peripheral pulses and neurologic function must be examined.}

 

^{Knee stability should be evaluated. Patellar fractures may be accompanied by cruciate ligament injury or associated knee dislocation.}

 

^{Open fractures will require urgent operative management and are associated with an increased rate of}

^{nonunion and infection.19 Open fractures also connote higher energy and an increased likelihood of associated injury.}

 

^{Physical examination must include a thorough secondary survey for other associated injuries. Distal femur fractures and acetabular injuries are commonly associated in highenergy motor vehicle accidents owing to transfer of force through the flexed knee (eg, dashboard injury).}

 

^{IMAGING AND OTHER DIAGNOSTIC STUDIES}

 

^{Anteroposterior (AP) and lateral views of the knee and an axial view of the patella provide sufficient information for nearly all fracture types.}

 

^{In the trauma setting, the Merchant view13 is best tolerated ( FIG 2A).}

 

^{A bipartite patella, arising from failed fusion of patellar ossification centers, can be mistaken for a fracture.}

^{Bipartite patellae are most commonly located superolaterally and occur more frequently in males. In 40% of individuals with a bipartite patella, the contralateral patella will also be bipartite7 ( FIG 2B,C).}

 

^{The normal Insall-Salvati ratio (height of the patella over the distance from the inferior pole to the tibial tubercle) is about8 1.0.}

 

^{Values less than 0.8 represent patella alta and possible patellar tendon rupture. Patella alta may also be seen in patellar sleeve fractures in the pediatric population.}

 

^{Values greater than 1.2 represent patella baja and possible quadriceps tendon rupture.}

 

 

⁴⁹⁴

 

 

 

^{FIG 2 • (continued) B,C. Bipartite patella. Note the classic superolateral position of this multipartite patella and the sclerotic margins.}

 

^{DIFFERENTIAL DIAGNOSIS}

^{Quadriceps rupture Patellar tendon rupture Bipartite patella}

^{Ligamentous or meniscal injury Distal femur or tibial plateau fracture}

^{Inflammatory arthritis or septic arthritis}

^{Osteochondral injury}

 

^{Patellar dislocation or retinacular injury Severe hemarthrosis}

 

 

^{NONOPERATIVE MANAGEMENT}

 

^{Fractures must meet two criteria to be managed nonoperatively:}

 

 

^{No associated extensor mechanism disruption (ability to perform an active straight-leg raise without significant lag)}

 

^{Less than 2 mm of displacement of the articular surface or less than 3 mm separation of the fracture fragments.3, 6 (Less displacement is tolerated by some authors in the presence of transverse fractures.4)}

 

^{The described period of immobilization varies. Historically, patients were kept in a long-leg or cylinder cast for 4 to 6 weeks. Current nonoperative management involves early functional treatment.}

 

^{Our preference for nonoperative treatment includes full weight bearing with crutches and a hinged knee brace.}

 

 

^{The leg is maintained in extension for 3 weeks, 0 to 30 degrees of flexion for 3 weeks, followed by full motion with physiotherapy as needed.}

 

^{High-impact activity including contact sports is allowed at 12 weeks.}

 

^{Nonoperative management of appropriate fractures results in good overall results, with loss of flexion the most common complication.4, 5}

^{SURGICAL MANAGEMENT}

 

^{Operative treatment is the preferred treatment for the majority of fractures not meeting the nonoperative criteria outlined earlier. Treatment is aimed at anatomic reconstruction of the articular surface and restoration of the extensor mechanism.}

 

^{Open reduction and internal fixation is the treatment of choice.}

 

^{Cases with severe comminution of the inferior or superior pole may be considered for partial patellectomy with reapproximation of the patellar tendon.}

 

^{Functional deficits without a patella are significant, therefore a total patellectomy should only be reserved for the most severe cases where reconstruction is not possible.}

 

^{Methods involving arthroscopy or external fixation have not gained widespread use.}

 

^{Soft tissue management is essential due to the limited soft tissue envelope covering the patella. This care for soft tissue begins in the emergency department. Splints or knee immobilizers must be accompanied by copious padding to minimize complications from pressure. Similarly, early aspiration of the hemarthrosis can prevent pressure necrosis.}

 

^{Preoperative Planning}

 

 

^{Operative timing is dictated by patient condition, presence of open fractures, and condition of the soft tissues. Fracture imaging is reviewed.}

 

^{Necessary equipment for surgical stabilization should be available.}

 

^{Examination under anesthesia is critical, as evaluation of coexisting ligamentous injuries is often limited by}

^{patient pain prior to surgery. Lachman, pivot shift, posterior drawer, and varus-valgus testing should be undertaken before preparing the surgical site.}

 

^{Concomitant injuries may be addressed in the same surgery.}

 

^Positioning

 

^{Patients are placed in the supine position on a radiolucent table.}

 

^{A small bump (eg, rolled blanket or 1 L intravenous fluid bag wrapped in a towel) under the ipsilateral hip will internally rotate the limb placing the patella in a more advantageous surgical position.}

 

^{If a tourniquet is used, it must be placed as proximally as possible on the thigh. The quadriceps must not be trapped under}

 

⁴⁹⁵

^{the tourniquet, as this may retract the patella superiorly, hindering fracture reduction. The knee is flexed to 90 degrees before elevating the tourniquet. If the retinaculum is disrupted and the superior patella is high-riding,}

^{the quadriceps should be pulled distally before inflating the tourniquet.20}

 

^Exposure

 

^{Longitudinal incisions should be used. Although a transverse incision can be made, this does not allow for an extensile exposure if needed.}

 

^{We use a longitudinal incision to facilitate exposure and allow extension to the tibial tubercle for wire augmentation when needed. A longitudinal exposure is better tolerated for future reconstructive surgeries and may therefore be beneficial in elderly patients or patients with preexisting osteoarthritis.}

 

^{A transverse approach follows the skin lines and may be preferable cosmetically. A transverse approach minimizes risk of injury to the infrapatellar branch of the saphenous nerve.}

 

^{Dissection is carried through the patellar bursa to expose the fracture site. Hematoma is often encountered upon opening bursa. Hematoma is cleared from the fracture site with copious irrigation and small curettes. The fracture line is followed to the retinacular tissue; the surgeon identifies the superior and inferior leaves of retinaculum and tags them for later repair.}

 

^{The fracture edges should be defined clearly. Reapproximation of the dorsal, cortical fracture edges will allow for an indirect reduction of the articular surface, particularly in transverse fracture patterns.}

 

^{Reduction of the pieces can be obtained by hyperextending the knee (via a small bump placed under the ankle) and pointed reduction clamps on the inferior and superior pole of the patella. Use of a K-wire as a joystick or a dental pick can facilitate reduction.}

 

^TECHNIQUES

• ^{Tension Band Wiring}

^{Tension band wiring can be used to stabilize transverse fracture patterns. More complex fracture patterns can use a tension band construct if the fracture can be converted to a transverse pattern by fixation of smaller comminuted pieces with screws or Kirschner wires. Tension band constructs may also be used for more distal pole fractures, with Kirschner wires placed more closely together to capture the fragment.}

^{Two 1.6- to 2.0-mm Kirschner wires will span the fracture in parallel (TECH FIG 1A). They can be introduced through the fracture site into the proximal fragment in a retrograde fashion or into the distal fragment in an antegrade fashion.}

 

 

 

 

^{TECH FIG 1 • Tension band fixation. A. Fracture reduction is maintained with a Weber clamp while Kirschner wires are passed. B. A large angiocatheter is used for ease of wire placement deep to Kirschner wires and beneath the quadriceps tendon. (continued)}

 

 

^{The Kirschner wire is delivered until flush with the fracture line, and the fracture reduction is obtained and held with patellar reduction clamps or Weber clamps.}

 

^{Fracture reduction is checked by palpating the articular surface with a Freer elevator (or by finger palpation if the rent in the retinaculum allows). When encountered, small articular fragments without attached subchondral bone may be discarded. Depressed articular fragments are gently reduced by a Freer elevator.}

 

⁴⁹⁶

 

 

 

^{TECH FIG 1 • (continued) C. Heavy needle drivers are used simultaneously to tension the cerclage wire.}

^{D. Lateral view of the final construct after capturing the cerclage wire in the bent end of the Kirchner wires.}

 

 

^{Once the fracture is sufficiently reduced, the Kirschner wire is delivered through the opposite fracture fragment.}

 

^{A lateral fluoroscopic view may help to ensure appropriate fracture reduction and Kirschner wire placement.}

 

^{Ideally, the Kirschner wires will be about 5 mm below the anterior surface of the patella.14 The Kirschner wire should be clipped to leave roughly 1 cm of prominence below the inferior pole of the patella.}

 

^{A 1.0-mm thick (18 g) cerclage wire is passed just deep to the Kirschner wires, abutting the superior pole of the patella. Care must be taken to leave little to no intervening soft tissue between the superior patella and the tension band. If the wire does not abut the bone, the patient will ultimately have an extensor lag.}

 

^{A 16-gauge angiocatheter may be passed through the quadriceps mechanism and the wire advanced through the catheter to aid in placement of the wire (TECH FIG 1B).20}

 

^{The cerclage wire is passed distally in a similar fashion, ensuring the wire abuts the distal pole of the}

^patella.

 

 

^{The wire is looped around the anterior aspect of the patella. Alternatively, the wire may be crisscrossed in a figure-8 pattern.}

 

^{Prior to tensioning, the surgeon verifies that the Kirschner wires capture the cerclage wire.}

 

^{To ensure even tensioning, a two-loop tensioning technique is used. A twist is made in the cerclage wire on the opposite side of the two free ends of the wire. The free ends are gently twisted. These two loops are sequentially tightened with a large needle driver (TECH FIG 1C). The loop is lifted to tension the wire}

^{and then twisted.20}

 

^{Wires are sequentially tensioned until appropriate compression is visualized and palpated at the fracture site.}

 

^{The ends of the twists are clipped, bent over, and tamped into bone to minimize prominence.}

 

^{The superior portion of the Kirschner wire is bent and then cut, leaving a hook to capture the cerclage wire. The Kirschner wire is rotated and tamped into the superior pole of the patella. The inferior tip of the wire is cut to avoid excessive length within the patella tendon while leaving enough wire to maintain position of the cerclage wire (TECH FIG 1D).}

 

^{Retinacular defects are repaired with absorbable braided suture, a critical step in restoring the extensor mechanism.}

 

^{The tourniquet is deflated (if used), and hemostasis is obtained. The wound is thoroughly irrigated. A suction drain is placed as needed, and the wound is closed with buried absorbable sutures followed by simple nylon sutures.}

 

^{A well-padded sterile dressing is applied with padding over the leg from the malleoli to the proximal thigh. A knee immobilizer is placed.}

 

⁴⁹⁷

• ^{Modified Tension Band with Cannulated Crews}

   

  ^{As advocated by Carpenter et al,5 cannulated screws may be used in place of Kirschner wires in a}

  ^{tension band construct for transverse fracture patterns ( TECH FIG 2A-C). This construct has shown to be superior biomechanically to the Kirschner wire tension band construct, resisting larger forces and}

  ^{resulting in less fracture gaping with loads.5}

   

  ^{Reduction is obtained as described earlier, with the guidewires for the 4.0- or 4.5-mm partially threaded cannulated screws used in place of Kirschner wires.}

   

   

   

  ^{TECH FIG 2 • A-D. Radiographs of cannulated screw and tension band construct. A. Lateral radiograph demonstrating a transverse patellar fracture. B. AP view of final screw and cerclage construct. C. Lateral view showing that the screw threads are slightly prominent and not entirely within bone. D. Final construct of cannulated screw with cerclage wire. The threads remain entirely within bone.}

   

   

  ^{Screws are placed over the guidewires using a lag technique and are left short of the distal cortex. If the screws are long (past the cortex), the wires will not abut the bone and are at risk for being cut by the ends of the screw. A lateral fluoroscopic view is helpful in verifying screw placement.}

   

  ^{A 0.8-mm (18-gauge) wire is passed through a single cannulated screw, looped back over the anterior surface of the patella, and advanced through the second screw. Alternatively, 1.6-mm cable can be placed through 4.5-mm cannulated screws.}

   

  ^{After bringing the two ends of the wire together, a two-loop tightening technique is used as described earlier, and the twists are buried (TECH FIG 2D).}

   

  ⁴⁹⁸

• ^{Interfragmentary Screws without Tension Banding}

   

  ^{Although occasionally used with tension band constructs to convert complex fracture patterns into}

  ^{transverse patterns, screw fixation can also be used alone (TECH FIG 3). This construct is particularly}

  ^{suited for simple fracture patterns with articular displacement and an intact retinaculum.}

   

   

   

  ^{TECH FIG 3 • Radiographs of lag screw construct. A,B. AP and lateral injury films. C. Postoperative radiograph. Note bicortical screw purchase.}

   

   

  ^{Lag screw fixation is often the method of choice for longitudinal fractures requiring operative management. Lag screw fixation for transverse fractures is also a suitable option, especially in patients with good bone stock. Multiple biomechanical studies have shown two cortical lag screws to be nearly as}

  ^{strong as2 or stronger than5 tension band alone in good quality bone.}

   

  ^{After obtaining reduction with pointed forceps, 3.5- or 4.5-mm cortical screws are used in lagging fashion across fracture sites.}

   

  ^{Closure and retinacular repair are undertaken as described earlier.}

• ^{Plate Fixation}

   

  ^{Severely comminuted fractures or those with bone loss may be treated with open reduction and internal fixation with minifragment plates and screws. This will allow for restoration for the extensor mechanism and prevent the need for a patellectomy.}

   

  ^{Provisional reduction of the fracture is obtained with K-wires, reduction clamps, and minifragment screws as necessary.}

   

  ^{Minifragment plates are then undercontoured to fit the dorsal cortex of the patella. Usually, two to three plates are applied.}

   

   

   

  ^{TECH FIG 4 • Plate fixation. A,B. AP and lateral postoperative radiographs showing plate fixation using minifragment plates for fixation of a severely comminuted fracture of the patella. The plates used in this case should have been contoured to fit the superior pole better. In addition, two of the plates used in this case were 2.7-mm plates, which we no longer use in our plate constructs (opting for 2.0- or 2.4-mm plates).}

   

   

  ^{The plate is then applied to the patella, with screw fixation through the proximal hole of the plate from the superior pole of the patella to the inferior pole. The plate is then compressed to bone distally, and a second screw is placed through the most distal hole from the inferior pole to the superior pole (TECH FIG 4).}

   

  ^{It is essential to have a well-contoured plate to limit soft tissue irritation. Locking plates can be used in poor quality bone, but the screws will not compress the plate to bone therefore the plates must be anatomically contoured.}

   

   

  ^{Typically, we use 2.0- or 2.4-mm plates as these provide adequate stabilization and limited soft tissue irritation.}

   

• ^{Partial Patellectomy}

⁴⁹⁹

 

^{Partial patellectomy is often advocated for comminuted fractures of the patella when a portion of the patella is significantly comminuted. Often, this comminution occurs at the patellar pole, with inferior pole fractures being more common.}

 

^{After a standard approach as discussed previously, the comminuted fracture fragments are identified. If restoration of the comminuted site is not possible, the comminuted fragments are removed. Preservation of as large a portion of the articular surface as possible is critical.}

 

^{Multiple (usually three) longitudinal drill holes are made through the remaining portion of the patella such that the entrance point of the tendinous attachment will be as near to the articularsurface as possible.}

^{The amount of holes is equal to the number of sutures plus one.}

 

 

 

^{TECH FIG 5 • Partial patellectomy. A. Comminuted distal pole of patella fracture, an ideal fracture pattern for the construct. B. Suture placement prior to tensioning and tying. Two sutures and three drill holes are used.}

 

 

^{Nonabsorbable suture with a tendon-grasping stitch (eg, Krackow) is used to attach the adjacent tendon (usually patellar tendon) through the drill holes. Suture is tied with the knee in neutral or hyperextension (TECH FIG 5). The suture, similar to the cerclage wires previously, must be tied directly on the bone (usually superior pole of the patella).}

 

^{Repair may be augmented by a tension band construct through the patella and tibial tubercle or by Mersilene tape, although we do not commonly perform such augmentation.}

 

 

^{Retinaculum is repaired with absorbable suture. Closure is as described earlier.}

 

 

^{PEARLS AND PITFALLS}

 

 

	The surgeon should ensure that ▪ This common error can cause fracture site distraction. When tension band wires have little to the fracture is loaded, the fragments can displace on the no intervening tissue between Kirschner wire until the tension band becomes taut.5 This will the wire and the patella when leave the patient with a lag. passing under the Kirschner wires at the proximal and distal poles.     Cannulated screws must be left ▪ Protrusion of the screw past the distal cortex creates a short of the far cortex if used with stress riser in the tension band.5 Additionally, the tension a tension band construct. In band does contact the screw tip rather than the bone, contrast, when using screw in a lessening compression forces on the bone through the lagging fashion, bicortical tension construct. The tension band wire can also break purchase affords a better along the edge of the screw if the screw is protruding too far. construct.     There is a delicate balance ▪ Passive range-of-motion exercises ought to begin as soon between early range of motion to as surgeon comfort allows. Intraoperative knee range of promote better long-term range motion resulting in gaping at the fracture site and poor of motion and protection of intraoperative bone stock may lead to the decision for fixation to avoid loss of reduction. delayed passive range of motion.     When possible, complex fracture ▪ Fixation of longitudinal comminuted fragments with patterns are converted into interfragmentary screws often allows the fracture pattern to simpler or transverse patterns. be treated as a simpler transverse pattern.

 

 

 

^{POSTOPERATIVE CARE}

⁵⁰⁰

 

^{Passive knee range of motion and gentle active range of motion begins once soft tissue healing is ensured. We use an abundance of padding postoperatively underneath any bracing until postoperative soft tissue swelling resolves.}

 

^{Patients are allowed to bear full weight with crutches and the knee fully extended in a knee immobilizer or hinged knee brace immediately postoperatively.}

 

 

^{We prefer 3 weeks with the knee in extension, 3 weeks of knee flexion from 0 to 30 degrees through a hinged knee brace, and then full knee flexion out of a hinged knee brace.}

 

^{Full weight bearing out of a brace is allowed once signs of fracture healing are evident on postoperative imaging, usually around 6 weeks.}

 

^{Although straight-leg raising and quadriceps sets with the knee extended may begin immediately postoperatively, quadriceps strengthening with resistance is held until signs of fracture healing appear.}

 

^{For fracture fixation deemed unstable during intraoperative range of motion, initiation of knee motion may be held until fracture healing is evident.}

 

^{Rehabilitation must keep in mind the compressive forces on the patella during knee flexion. Compressive}

 

^{forces are greater than seven times body weight on each leg during stair climbing and reach nearly eight times body weight while squatting.12}

 

 

^OUTCOMES

^{Outcomes depend on maintenance of fracture reduction.}

^{In a review of 320 patients with patellar fractures (212 treated nonoperatively) with a mean follow-up of}

^{8.9 years, Boström3 reported that 24% of patients did not consider themselves fully recovered; moderate or severe pain persisted in 31% of patients. The range of mobility was normal in 90% of patients, with the majority of restriction of motion in elderly patients. Ninety-one percent of patients had fracture union.}

^{In a series of 30 patients with isolated, unilateral patellar fractures, anterior knee pain during activities of daily living was experienced by 24 (80%) of the patients. Clinical improvement occurred over the first 6 months. However, functional impairment persisted at 12 months, with objective testing demonstrating}

^{deficits in strength, power, and endurance in the knee extensor mechanism on the injured side.10 Long-term (6.5 year) functional follow-up of 40 isolated, ipsilateral patellar fractures was obtained by}

^{LeBrun et al.11 The mean normalized SF-36 physical composite score and the mean normalized Knee Injury and Osteoarthritis Outcome Scores were statistically different from reference population norms. Removal of symptomatic fixation was required in 52% of the patients, whereas 38% of those with retained fixation self-reported implant-related pain at least some of the time. Biodex dynamometric testing revealed a mean isometric extension deficit of 26% between the uninvolved and involved sides for peak torque.}

^{Extension power deficits over 30% were noted when compared with the contralateral side.11}

^{Functional outcomes after long-term follow-up of tension band wiring have been reported to be the same as agematched standards.17}

 

 

^{COMPLICATIONS}

^{The historical complication rate of operative intervention for patellar fractures varies in the literature. Although a recent study on perioperative complications reported a rate of 25%,18 historical rates are much lower.3}

^{Infection rates are low and can be minimized by the use of perioperative antibiotics and careful soft tissue handling. Few postoperative infections are deep infections involving the joint.3, 18}

^{Patients often note palpable hardware, given the thin overlying tissue. Although we do not routinely remove hardware, patients in whom the hardware becomes symptomatic may have hardware removal after fracture consolidation. Hardware removal rates have varied in the literature from 10% to 60% with}

^{tension band constructs.17, 18}

^{Smith et al18 reported fracture displacement of more than 2 mm in 22% of patients treated with tension band wiring. All patients with significant displacement requiring reoperation were weight bearing without bracing between 3 and 5 weeks. In the remainder of cases with loss of fixation, the most common cause was technical error.}

^{Nonunion with tension band techniques done technically correct is a rare complication, occurring in less than 1% of fractures fixed in this manner.5}

^{Decreased knee range of motion is another possible complication. Flexion is more commonly lost than extension. At times, this loss of motion can be due to intra-articular adhesions and can benefit from arthroscopic release.}

^{As with many intra-articular fractures, posttraumatic osteoarthritis develops in the injured extremity at a rate greater than that of the uninjured extremity. Reported rates of osteoarthritis vary greatly.}

 

 

^REFERENCES

1. ^{Atkison PJ, Haut RC. Injuries produced by blunt trauma to the human patellofemoral joint vary with flexion angle of the knee. J Orthop Res 2001;19:827-833.}

    

    

2. ^{Benjamin J, Bried J, Dohm M, et al. Biomechanical evaluation of various forms of fixation of transverse patellar fractures. J Orthop Trauma 1987;1:219-222.}

    

    

   ⁵⁰¹

    

3. ^{Boström A. Fracture of the patella: a study of 422 patellar fractures. Acta Orthop Scand Suppl 1972;143:1-80.}

    

    

4. ^{Braun W, Wiedemann M, Rüter A, et al. Indications and results of nonoperative treatment of patellar fractures. Clin Orthop Relat Res 1993;(289):197-201.}

    

    

5. ^{Carpenter JE, Kasman R, Matthews LS. Fractures of the patella. J Bone Joint Surg Am 1993;75A:1550-1561.}

    

    

6. ^{Edwards B, Johnell O, Redlund-Johnell L. Patellar fractures: a 30-year follow-u Acta Orthop Scand 1989;60:712-714.}

    

    

7. ^{Green WT. Painful bipartite patellae: a report of three cases. Clin Orthop Relat Res 1975;(110):197-200.}

    

    

8. ^{Insall J, Goldberg V, Salvati E. Recurrent dislocation of the high-riding patella. Clin Orthop Relat Res 1972;88:67-69.}

    

    

9. ^{Kaufer H. Mechanical function of the patella. J Bone Joint Surg Am 1971;53(8):1551-1560.}

    

    

10. ^{Lazaro LE, Wellman DS, Sauro G, et al. Outcomes after operative fixation of complete articular patellar fractures: assessment of functional impairment. J Bone Joint Surg 2013;95(14):e96 1-8.}

     

     

11. ^{LeBrun CT, Langford JR, Sagi HC. Functional outcomes after operatively treated patella fractures. J Orthop Trauma 2012;26:422-426.}

     

     

12. ^{Matthews LS, Sonstegard DA, Henke JA. Load-bearing characteristics of the patello-femoral joint. Acta Orthop Scand 1977;48:511-516.}

     

     

13. ^{Merchant AC, Mercer RL, Jacobsen RH, et al. Roentgenographic analysis of patellofemoral congruence.}

    ^{J Bone Joint Surg Am 1974; 56(7):1391-1396.}

     

     

14. ^{Nerlich M, Weigel B. Patella. In: Ruedi TP, Murphy WM, eds. AO Principles of Fracture Management. New York: Thieme, 2000: 487-501.}

     

     

15. ^{Reider B, Marshall JL, Koslin B, et al. The anterior aspect of the knee joint. J Bone Joint Surg Am 1981;63(3):351-356.}

     

     

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