Operative management is the treatment of choice for the majority of displaced patellar fractures. Surgical options include open reduction and internal fixation (ORIF), partial or complete patellectomy, with the choice of treatment dependent on the fracture pattern and the amount of comminution. Although there is no widely accepted classification system for patellar fractures, most are based on an anatomic descriptive classification. Important factors include the location of fracture, direction of fracture lines, and the amount of comminution. In the AO/OTA classification, the patella is delineated as 45 and subdivided into A, B, or C depending on whether the fracture is extra-articular, partial articular without disruption of the extensor mechanism, or complete articular with disruption of the extensor mechanism. For the most part, 45B patella fractures are managed nonoperatively whereas 45A and 45C fractures require surgery.
The patella is an integral component of the extensor mechanism of the knee as well as an articular component of the knee joint. The patella’s position in the body and the nature of its role in lower-limb function cause it to be susceptible to injury. Traction forces that pull the patella cephalad are the result of several different vectors caused by contraction of the quadriceps muscle. The quadriceps muscle, extensor retinaculum, along with the iliotibial band, participates in knee extension. The undersurface of the patella, which articulates with the notch of the femur, has the thickest cartilage found in the body. It is this articulation that acts as a fulcrum for extension. Forces measured at the patellofemoral articulation can be over seven times body weight during routine activities such as stair climbing and squatting. Tensile forces can be well over 3,000 N. The importance of the patella for normal knee function cannot be overestimated. Patellectomy results in the loss of the patellar fulcrum, a decrease in the moment arm, and relative lengthening of the quadriceps. This can lead to instability of the knee, extension lag, atrophy of the quadriceps, and loss of extension strength. Therefore, whenever possible, the patella should be repaired rather than excised.
Total patellectomy is generally indicated when the patella is so severely comminuted that an acceptable reduction and stable fixation cannot be achieved with internal fixation.
Partial patellectomy is indicated for cases that have severe comminution of either the inferior or superior pole that is not amenable to ORIF techniques.
ORIF is indicated for displaced patellar fractures that have fragments large enough to be reduced and stably repaired and is the treatment of choice for the majority of displaced patellar fractures in physiologically young patients. Many comminuted fractures can be salvaged. The goal of surgery is to achieve anatomic reduction of the articular surface with restoration of the continuity of the extensor mechanism. Displacement more than 3 mm and articular incongruity of more than 2 mm are considered strong indications for surgical treatment.
Contraindications and relative contraindications to surgical treatment include nondisplaced or minimally displaced stable fracture patterns. Also, contused or injured skin that precludes safe surgical approaches to the fracture, active infection involving the extremity with the patellar fracture, and medical conditions of the patient that would preclude safe surgical intervention are contraindications for surgery.
An accurate history and careful physical examination should be performed. The mechanism of injury may explain the severity of injury as well as the fracture pattern. It is helpful to know whether the injury occurred as a result of a direct blow (e.g., a fall on the knee) or from resisted flexion of the knee resulting in a traction-type injury.
The physical examination must include a thorough evaluation of the extremity, with the surgeon looking for signs of direct trauma and swelling. The presence of fracture blisters, lacerations, abrasions, and contusions should be documented. It is essential to determine whether the fracture is open. Superficial or small wounds should be checked and if necessary carefully explored to determine whether they are in continuity with the fracture or the knee joint. In displaced patellar fractures, a visible or palpable defect is often noted between the fragments, although this may be masked by significant swelling, which develops rapidly. In some cases, a hemarthrosis is not apparent because of a large retinacular tear that allows blood to dissipate into the surrounding soft tissues. The absence of a hemarthrosis does not rule out a patellar fracture.
The continuity of the quadriceps mechanism is evaluated next. A painful, tense hemarthrosis often complicates this part of the examination. Aspiration of the knee with injection of a local anesthetic usually decreases pain. The patient is asked to contract the quadriceps mechanism and attempt to extend the knee fully. The ability to do this does not rule out a patellar fracture because the medial and lateral retinacula may still be intact, providing partial continuity of the extensor mechanism. However, the inability to lift the leg usually indicates that a patella fracture that tears the medial and lateral retinaculum exists. Gentle stress testing of the knee for stability should be carefully performed. Knee flexion should be avoided because this may further displace the fracture in addition to causing significant discomfort to the patient. The peripheral pulses and the compartments of the leg should be evaluated, and a neurologic examination performed.
The initial radiographs to evaluate a painful knee following injury include anteroposterior (AP), lateral, and axial views of the patella. A supine AP radiograph is obtained, centered over the patella (Fig. 24.1
). The lateral radiograph can be taken as a cross-table lateral, with the knee slightly flexed. For an axial view, a Merchant’s view is most easily and safely obtained in the injured patient (Fig. 24.2
). The patient is placed supine on the x-ray table with the knee flexed 45 degrees over the end of the table. The x-ray beam is angled at 30 degrees from the horizontal, and the cassette is placed perpendicular to this x-ray beam 1 foot below the knee. Comparison views of the uninjured knee can be helpful in selected patients (i.e., those with a bipartite patella). Occasionally in patients with complex fracture patterns, a computed tomography (CT) scan is indicated.
Vertical fractures are often missed on both the AP and lateral views and are best visualized on the axial view. Larger displaced-fracture lines can be readily seen, although smaller nondisplaced-fracture lines are often obscured because of the superimposition of the patella on the femur in the AP view. In most cases, the fracture is more comminuted than is
apparent on the radiographic evaluation. Displacement more than 3 mm and articular incongruity more than 2 mm are indications for surgery.
Figure 24.1. A. AP and lateral radiographs (B) showing a transverse fracture of the patella with comminution of the distal fragment. The lateral view shows significant comminution involving the articular surface in addition to displacement of the proximal and distal pole fragments.
Preoperative drawings should be performed for complex fracture patterns. Surgeons should make a tracing on both the AP and lateral views of the uninjured contralateral side and then superimpose the fracture lines from the injured side onto the normal template. The fixation should be drawn and the procedural steps carefully listed. The operating room should be informed of the equipment required based on the preoperative plan. Equipment needed for surgery usually includes various-sized pointed bone-reduction clamps, small curettes, wire cutters, benders, and wire tighteners, and small Kirschner (K) wires. Power drills and wire drivers will also be necessary. Small and mini fragment screws and instruments should be available.
Figure 24.2. Axial view of the patella showing a vertical fracture of the lateral facet of the patella. There is minimal displacement of the fragments.
Surgery can be undertaken as soon as the patient has been prepared and appropriate preoperative plans completed. If the fracture is open, surgery must be done urgently. Closed fractures should be surgically addressed when the soft-tissue injury and the general condition of the patient permit.
The patient is positioned supine on a standard operating table. Because there is a tendency for the leg to externally rotate, a small bump can be placed under the ipsilateral hip. A tourniquet is placed high on the involved thigh. The procedure can be done under a general or spinal anesthetic. Regional nerve blocks (femoral nerve block) can be very helpful to control postoperative pain. The patient is prepped in a standard fashion, and the leg is draped free by using an extremity drape. The limb is exsanguinated with a sterile Esmarch, and the tourniquet inflated to a pressure appropriate for the size of the leg and the patient’s blood pressure. Before inflating the tourniquet, the quadriceps is pulled distally to ensure that it is not trapped under the tourniquet, which can displace the patella proximally, making reduction more difficult. A sterile bump can be placed behind the knee, which allows the knee to flex 15 to 20 degrees. Appropriate antibiotic prophylaxis should be given before inflating the tourniquet.
The skin incision can be either transverse or longitudinal. A longitudinal incision is preferred when more proximal and distal dissection is necessary for the repair of a comminuted fracture and when later reconstruction procedures are anticipated. For cosmetic reasons, the transverse incision is preferred. It also avoids potential damage to the saphenous branch of the femoral nerve.
The incision is carried down through the subcutaneous tissue and the prepatellar bursa. A hematoma is usually encountered as soon as the bursa is opened, and it usually leads directly into the fracture site (Fig. 24.3
). Care should be taken to minimize direct dissection of the fracture fragments. The soft tissues surrounding the patella often hold nondisplaced fractures in place, and if these are disrupted, the fragments may displace, creating a more complicated and unstable fracture pattern. The major fracture fragments should be exposed. Clot
should be removed with a combination of small curettes and the use of a small suction-tip device. Irrigation should be used liberally to help remove the hematoma and small inconsequential comminuted fragments. The extent of the medial and lateral retinacular injuries should be identified and the edges tagged for later repair. The undersurface of the patella, in addition to the patellofemoral groove, should be inspected for evidence of articular damage. The knee joint should be inspected and irrigated to remove any loose fragments.
Figure 24.3. Surgical exposure through a vertical midline incision showing the transverse fracture of the patella with medial and lateral retinaculum tears. The soft tissues have been left intact over the surfaces of the patella.
Figure 24.4. The hematoma has been evacuated, and the joint and fracture lines have been debrided. The K wires have been advanced retrograde through the patella, and the patella fragments are now ready to be reduced.
After the fracture and the knee joint have been thoroughly irrigated, the fracture edges carefully exposed, and the fracture pattern thoroughly delineated, a preliminary reduction is performed. The small bump behind the knee will need to be removed at this time because flexion of the knee will make the reduction more difficult. In the case of a simple, transverse, middle-third fracture, one can proceed directly to the tension band technique. In other more complex fractures, the goal is to try to reduce the fragments to create a two-part transverse-fracture pattern that can then be further stabilized with a tension band technique. For example, if there is a vertical split through either the proximal or distal fragment, the vertical split is first reduced and held temporarily with large, pointed, reduction forceps. This is then temporarily stabilized with a 1.2-mm K wires. Definitive stabilization of this fragment depends on its size and can be done with either K wires or small-fragment or mini-fragment screws. After this has been performed, the tenaculum clamps and the provisional fixation are removed.
When a transverse fracture pattern has been created, a tension-band wire technique is performed. By using a 2-mm drill, two parallel drill holes are placed in a retrograde fashion through the proximal bony fragment. A 1.6- or 1.8-mm K wire is then advanced through these holes and out through the quadriceps tendon (Fig. 24.4
). They are advanced until the sharp tip of the K wire is fully within the proximal bony fragment. The two fracture fragments are then reduced and held with large, pointed, reduction forceps.
Care should be taken to ensure that the articular surface is anatomically reduced by inspecting both the anterior cortical and posterior articular surfaces. The articular surface can be inspected through the preexisting tears in the retinaculum. If there is no significant tear in the retinaculum, a small, medial or lateral arthrotomy should be made to allow inspection or palpation of the articular surface.
The K wires are then sequentially attached to the drill and advanced into the distal fragment (Fig. 24.5
). They should be advanced distally at least 1 cm beyond the inferior tip of the patella. Once again, the adequacy of the reduction should be checked. A 30-cm segment of 1-mm wire is passed adjacent to the patella and quadriceps mechanism proximally and distally, passing behind the K wires and closely approximated to both the proximal and distal poles of the patella. If this is not achieved, the wire will not obtain adequate fixation and may loosen, eventually resulting in loss of fixation and reduction. To facilitate passage of the wire, pass a 16-gauge angiocatheter through the quadriceps mechanism just above the superior pole of the patella and behind the K wires (Fig. 24.6
). The 1-mm wire is passed through the catheter, which is then removed. The identical technique is performed distally.
To ensure symmetrical tensioning of the wire, a double-loop technique is recommended. A twist is placed in the wire on its continuous side, and on the contralateral side, the two ends of the wires are hand tightened and twisted. Excessive wire is removed. By using either a large needle driver or a large clamp specifically designed for wire tightening, the two ends of the wire are sequentially tightened (Fig. 24.7
). The technique of wire tightening is critical. Before twisting, the wire should be tensioned by lifting up on the clamp. The wire is then gently twisted. This will ensure that both wires twist around each other rather than one wire wrapping around the other wire. The wires are sequentially tightened in this manner until adequate compression has been achieved.
Once again, the quality of the reduction is checked, and the knee is gently flexed to check the stability of the fixation (Fig. 24.8
). The twisted wire is clipped, and the ends are bent over by using a large needle driver and gently flattened by using a bone tamp and a mallet so that they lie close to the superior surface of the bone. The K wires are bent by stabilizing the wire close to the bone with a needle driver and then using the wire bender, trying to bend the wire to 110 degrees. The excess wire is then cut. The remaining wire is then rotated 180 degrees posteriorly and advanced into the quadriceps mechanism. If it is not advanced into the quadriceps mechanism, it will cause excessive irritation, in addition to having an increased chance of backing out. The distal ends of the wires are then cut so they are not excessively prominent within the patellar tendon. The retinacular defects are repaired with absorbable sutures (Figs. 24.9
Figure 24.5. The transverse fracture has been anatomically reduced by using a pointed fracture-reduction clamp, and the K wires have been advanced antegrade through the distal fragment. The K wires are parallel to each other.
Figure 24.6. A 16-gauge angiocath is passed through the quadriceps tendon behind the K wires and just superior to the patella. The cerclage wire is being passed through the angiocatheter, which will then be removed. An identical procedure is then performed through the distal pole.
Figure 24.7. A double-tensioning technique is performed by consecutively tightening each side of the tension band wire. The fracture gap can be seen closed down with this technique.
Figure 24.8. The tension band wires have been tightened, clipped short, and bent. The K wires have not yet been shortened, and the retinaculum has not yet been repaired.
Figure 24.9. The final tension-band construct with the K wires cut and bent and buried within the quadriceps and patellar tendon. The retinaculum has been repaired.
Figure 24.10. Alternative transverse incision with final construct visualized through the wound.
The tourniquet is deflated and hemostasis obtained with electrocoagulation. A suction drain is placed in the knee joint. Closure should be meticulous, including closure of the prepatellar bursa as a separate layer by using 2-0 Vicryl. The subcutaneous tissue is closed by using simple inverted 2-0 Vicryl. Skin closure is dependent on the integrity of the skin. Subcuticular closure gives excellent cosmetic results but should be reserved for those cases without skin injuries and only minimal swelling. If there is concern regarding damage to the skin, nylon sutures should be used. A sterile dressing is applied consisting of fluffs, Webril, and an Ace wrap. The patient is placed into either a knee immobilizer or a hinged knee brace with the knee locked in full extension.
Other variations on the tension-band technique include the use of 4-0 cannulated screws with the tension band wire passed through the cannulated screws and tightened in a standard double-loop technique (Fig. 24.11
). In the case of a distal-pole patella fracture, the tension-band wire technique can be used, although the K wires must be placed closer together so that they both capture the distal fragment. An alternative to this is the use of retrograde cannulated or standard 4.0 screws in addition to a tension band technique. With very small fragments, a single screw can be used. In the case of a stellate fracture, circumferential cerclage wire can be helpful to bundle the fracture fragments together (Fig. 24.12
). In stellate fractures, it is critical not to violate the soft tissues around the fragments because this will cause significant disruption of the fracture fragments.
Postoperative care is dependent on the fracture type and the resultant stability after osteosynthesis. The extremity is usually placed in a well-padded compressive dressing and a knee immobilizer or a hinged knee brace locked in extension. In patients with stable fixation, knee motion is begun immediately. On the first postoperative day, the patient is mobilized out of bed to ambulate weight bearing as tolerated with the knee locked in full extension. The hinges can either be loosened or the knee immobilizer removed for range-of-motion exercises. Active flexion and extension are initiated. Quad sets can be started in the immediate postoperative period. The drain is removed at 48 hours, and the patient is usually discharged home shortly thereafter. Patients are seen in follow-up in approximately 7 to 10 days for a dressing change and suture removal. If the wound is well healed, active extension and straight-leg-raising exercises are begun, and the patient is referred to physical therapy. Patients are seen at 4 to 6 week intervals, and radiographs of the patella are obtained out of the brace. If there is radiographic evidence of healing, progressive resistive exercises are started. The patient is progressively weaned from the brace, depending on the motion and strength. Full rehabilitation usually takes 4 to 6 months. If there are any symptoms or signs of loss of fixation during this postoperative period, range-of-motion exercises are stopped, and the patient is immobilized and followed up closely.
In comminuted fractures where the fixation is less secure, early range of motion is not possible. The repair should be protected in either a knee immobilizer or a knee brace with the hinges locked. The braces are removed only for wound checks and extremity cleansing. Quad sets can be initiated, but the repair is protected until there are signs of healing. Range of motion is delayed for 3 to 6 weeks.
In the immediate postoperative period, the major complications include hemarthrosis and infection. A hemarthrosis can usually be avoided by the use of a postoperative suction drain and a compressive dressing. If the drain was either not used or was removed prematurely, the hemarthrosis can be aspirated. This is necessary only if a tense hemarthrosis causes significant pain or limits rehabilitation.
Infection is a rare but devastating complication. This can usually be avoided by careful timing of surgery and meticulous surgical techniques in addition to the appropriate
perioperative antibiotics. If infection develops, it should be aggressively treated with antibiotics and debridement with drainage. Physical therapy and early range-of-motion activities should be stopped while treating the infection. If the infection involves the knee joint, it must be drained and irrigated surgically. Culture-specific intravenous antibiotics should be used for 3 to 6 weeks. Internal fixation in general should not be removed until the fracture is healed.
Figure 24.11. A. An AP x-ray of a fractured patella. B. A lateral x-ray of a fractured patella. C. AP x-ray of ORIF in which cannulated screws and wire have been used. D. Lateral x-ray of ORIF in which cannulated screws and wire have been used.
Loss of fixation and reduction are other possible complications after surgical repair of patella fractures. This is more common in complex fracture patterns, in noncompliant
patients, and when therapy is overly aggressive. If there are signs of loss of fixation without significant loss of reduction, this can be treated with immobilization. If there are signs of loss of fixation along with loss of reduction, then revision internal fixation is indicated.
Figure 24.12. A. Postoperative AP and (B) lateral radiographs of a comminuted patellar fracture fixed with a combination tension-band and cerclage-wire technique. The articular surface has been restored anatomically.
Delayed union and nonunion are usually the result of either failure of fixation or inadequate initial reduction. The complications can usually be avoided by good reduction and fixation techniques and close postoperative follow-up. Delayed unions can be treated with repeated cerclage-wire techniques. Significant malunions usually require a patellectomy.
Arthrofibrosis and loss of knee motion are relatively common complications after patella fractures. These complications are more common in severely comminuted fractures and those fractures requiring prolonged immobilization. The majority of patients can be treated with aggressive and persistent physical therapy, although an occasional patient will require manipulation under anesthesia. It is my preference to do an arthroscopic evaluation at the time of manipulation. This allows inspection of the patellar surfaces, a direct lysis of the arthrofibrosis involving the suprapatellar pouch and the lateral gutters, in addition to adhesions from the fat pad into the intercondylar notch. Arthroscopic debridement and manipulation should be followed by aggressive physical therapy to maintain motion and increase strength. Retropatellar arthrofibrosis and patella baja are rare but extremely difficult complications to correct and have a negative effect on patellar function and outcomes.
Posttraumatic osteoarthritis results from either inadequate reduction of the articular surface or injuries to the articular surface that occur at the time of injury. In the early stages, arthroscopy and patellar debridement can decrease some symptoms. Ultimately in the young patient, a patellectomy may be the treatment of choice. In the elderly patient who also has involvement of the medial and lateral compartments, a total knee replacement may be the treatment of choice.