Tension Band Fixation of Patellar Fractures

Overview

Patellar fractures account for about 1% of all skeletal injuries; about half are undisplaced with an intact extensor mechanism (AO). The patella acts as a fulcrum between the quadriceps and patellar tendons. Patellofemoral loads can reach up to 7 times body weight, so fixation must withstand large forces; the patella's lever arm adds about 60% to extension force in the last 15° of extension, which is why patellectomy weakens extension (AO).

The tension band principle (AO) uses correctly placed wires to convert the distracting forces across a transverse fracture into compression at the articular surface during knee flexion, allowing earlier union and immediate motion. Early active flexion is essential for the principle to work (Campbell). The anterior tension band introduced in the 1950s, as modified by the AO/ASIF, remains the landmark advance in patellar fixation, although recent literature increasingly supports plates and screws for comminuted patterns (Rockwood).

Campbell's Concepts: Patellar Fractures

• Preserve patellar bone stock whenever possible; reserve partial or total patellectomy for severe comminution that cannot be fixed.

• Minifragment fixation combined with axial cannulated screws helps preserve bone stock.

• Typical construct: Antegrade or retrograde 4 mm cannulated screws, with nonabsorbable suture or suture tape passed through the screws in a figure-of-eight and tensioned.

• Augmentation: A second figure-of-eight suture tape, from the quadriceps insertion to the inferior pole or through a transosseous tunnel in the tibial tubercle, depending on the injury pattern. Use direct vision and fluoroscopy to make sure tensioning does not create patella baja.

• Gravity flexion test before closure helps decide how much motion to allow postoperatively.

• Campbell prefers heavy synthetic suture to wire; data suggest similar performance with possibly less soft tissue irritation.

Evaluation

• Active extension does not exclude a patellar fracture if the retinaculum (auxiliary extensor mechanism) is intact (AO). In displaced fractures, the gap may be palpable; always assess quadriceps and patellar tendon integrity and the knee ligaments (AO).

• Imaging: AP, lateral (at about 30° flexion) and tangential (skyline, about 45°) views; the Insall–Salvati ratio detects patella alta or baja from tendon rupture (AO). CT helps define comminution and plan fixation (Rockwood); Rockwood's authors obtain CT when comminution is suspected or fragments are obscured.

• Bipartite patella (2–3% of the population, bilateral in 50%) has rounded, sclerotic margins, usually superolateral, and must not be confused with a fracture (AO).

• In open injuries or suspected traumatic arthrotomy, perform a saline load test (Rockwood).

Classification

Indications

Nonoperative (Rockwood; AO)

• Intact extensor mechanism and articular incongruity of less than 3 mm (Rockwood); almost any pattern (transverse, stellate, vertical) can then be treated closed. In Böstrom's 422 fractures, 98% of minimally displaced fractures treated nonoperatively had good or excellent results (Rockwood).

• Severe comorbidity precluding anesthesia, or nonambulatory patients (Rockwood).

• Treatment: hinged brace locked in extension (or a well-molded cylinder cast) for 4–6 weeks, early weight bearing in extension, isometric quadriceps and straight-leg raises; start motion after radiographic consolidation (Rockwood; AO).

Operative

• Fragment displacement (gap) of more than 2 mm or articular step-off of more than 2 mm (AO); Rockwood uses more than 3 mm of articular incongruity.

• Osteochondral fragments causing loose bodies (AO; Rockwood).

• Proximal or distal pole fractures with loss of active extension (AO); disrupted extensor mechanism (Rockwood).

• Open fractures (Rockwood).

Choosing the Construct

• Modified anterior tension band (K-wires or cannulated screws) is the most commonly used fixation for transverse fractures (AO).

• Isolated screws are suitable only for longitudinal (type B) fractures; 3.5 or 4.5 mm screws alone may suffice for simple transverse or longitudinal fractures in good bone (AO; Rockwood).

• Cannulated screws (4 mm) with a tension band through them are biomechanically stronger than K-wire constructs (AO; Rockwood), and clinically had a 50% lower rate of symptomatic implants (Rockwood).

• Plates (low-profile 2.4–2.7 mm minifragment, mesh or patella-specific plates) for complex multiplanar or inferior pole fractures (AO; Rockwood).

• Partial or total patellectomy is strongly discouraged unless reduction and fixation are impossible (AO).

• Rockwood authors' algorithm: Intact extensor mechanism with <3 mm step → nonoperative; disrupted extensor mechanism → transverse fracture: cannulated screw tension band (wire or suture); transverse with additional fragments: interfragmentary screws plus tension band, dorsal plate, cerclage, or partial patellectomy; purely longitudinal (B1/B2): interfragmentary screws alone.

Preoperative Planning

• Examine knee stability under anesthesia to exclude associated ligament (e.g., cruciate) injuries (AO).

• Implants (AO): 1.25 mm cerclage wire and 1.6, 1.8 or 2.0 mm K-wires; 3.5 mm cortical screws; bioabsorbable pins (1.6–2.0 mm) for osteochondral fragments; heavy (No. 5) nonabsorbable suture; 4 mm cannulated screws.

• Rockwood minimum set: 3.5 and 2.7 mm cortical screws (small and minifragment sets), 1.6 and 2 mm K-wires, 18-gauge wire or No. 5 nonabsorbable suture, 14- or 16-gauge angiocatheters for wire passage, 4.0 mm cannulated screws, pointed reduction forceps, wire benders and a Hewson suture passer.

• Plan to "simplify" the fracture: reduce and fix small fragments with lag screws, K-wires or bioabsorbable pins to create a pattern suitable for a tension band; anticipate these implants and their paths (Rockwood).

• Timing: Open fractures need antibiotics, tetanus prophylaxis and urgent debridement; standard rigid fixation is appropriate without gross contamination. For closed fractures, wait 1–2 weeks if there is major swelling or abrasions (Rockwood).

• A fascia iliaca block was as effective as a femoral nerve block and simpler and safer in Level I evidence (Rockwood).

Positioning

1. Supine on a radiolucent table with a small bump under the hip to control external rotation (AO; Rockwood).

2. A movable bump under the knee (slight flexion) or ankle (extension) helps during the case (AO; Rockwood).

3. A tourniquet improves visualization (AO); Rockwood's authors place a nonsterile high-thigh tourniquet but rarely inflate it.

4. C-arm opposite the surgeon (AO).

Surgical Approach (Technique 59.16)

1. Incision: A longitudinal midline incision is preferred (Campbell; AO; Rockwood). It can be extended in either direction, protects the infrapatellar branch of the saphenous nerve, and does not compromise later surgery such as arthroplasty (AO; Rockwood). Alternative: a transverse curved incision with its apex on the distal fragment. Avoid severely contused skin, or excise a small area of it (Campbell).

2. Dissect in the plane between the subcutaneous fascia and the extensor apparatus; dissecting between skin and subcutaneous tissue risks wound-edge necrosis (AO). Raise full-thickness flaps with minimal superficial dissection (Rockwood).

3. Reflect skin and subcutaneous tissue proximally and distally to expose the whole anterior patella and both tendons (Campbell).

4. If the fragments are widely separated, assume the extensor retinaculum is torn; explore it medially and laterally (Campbell).

5. Remove small free bone fragments and clot. Inspect the joint, particularly the patellofemoral groove, for osteochondral fractures, and irrigate thoroughly (Campbell; AO; Rockwood).

6. Seeing the articular surface: Work through the fracture or retinacular tears, extending them if needed to admit a finger (Rockwood). If the retinaculum is intact, a limited lateral parapatellar arthrotomy with patellar eversion (Gardner) allows direct visualization (Rockwood; AO). Arthroscopic assessment is possible but technically harder with no proven advantage (AO).

Reduction

1. Reduce large fragments directly with pointed reduction forceps (AO; Campbell).

2. Knee position: Types A and C reduce better with the knee extended; longitudinal type B fractures reduce better in flexion (AO). Rockwood reduces with the knee slightly flexed.

3. Judge reduction by palpating the articular surface for step-off and gaps (AO; Campbell). Do not rely on fluoroscopy or the dorsal cortex alone; multiplanar fluoroscopy including internal and external rotation views shows malreduction better than the lateral view alone (Rockwood).

Tension Band Wiring (Technique 59.17)

Principle and Configurations

• Classic AO configuration: One wire passes transversely through the quadriceps tendon insertion at the superior pole, over the anterior patella, and through the patellar tendon insertion; it is tightened until the fracture is slightly overcorrected (opening at the articular surface). A second wire passes through transverse drill holes in the superior and inferior poles of the anterior patella (Campbell).

• Schauwecker variant: The wire crosses the anterior surface in a figure-of-eight (Campbell).

• Biomechanics (Rockwood): The modified anterior tension band with retinacular repair outperforms cerclage or interfragmentary wiring; cerclage alone allowed gaps up to 20 mm. A horizontal four-limb figure-of-eight improved interfragmentary compression. Modified tension band with cannulated lag screws had the highest failure load in a cadaver model.

• Campbell's preference: Cannulated screws with a figure-of-eight suture tape tension band, for fractures that can be reduced anatomically.

K-Wire Modified Anterior Tension Band — Steps

1. Approach the fracture as above; clean clot and small fragments; assess retinacular tears and the trochlea; lavage the joint (Campbell; Rockwood).

2. Reduce the main fragments accurately, paying particular attention to a smooth articular surface (Campbell).

3. K-wires: With the fracture reduced and clamped, drill two parallel K-wires (2 mm in Campbell; 1.6 mm in Rockwood; 1.6–2.0 mm in AO) perpendicular to the fracture, about 5 mm deep to the anterior surface, dividing the patella into thirds (Campbell; AO; Rockwood). The wires usually end up closer to the articular surface than to the anterior surface (AO).

   • Outside-in: Pass the wires after reduction (AO).

   • Inside-out (retrograde): Flip the proximal fragment 90° to expose the fracture surface, drill the wires from the fracture proximally, then reduce, clamp and advance them distally (Campbell; AO; Rockwood).

4. Leave the wire ends long, protruding beyond both poles (Campbell).

5. Tension band: Pass an 18-gauge wire (Campbell; Rockwood) or a 1.25 mm wire about 30 cm long (AO) transversely through the quadriceps tendon insertion, as close to bone as possible and deep to the protruding K-wires, over the anterior patella, then through the patellar tendon insertion deep to the K-wires.

   • A large-bore angiocatheter, injection needle or the sharp end of a drain can be used as a passer; this also protects the tendon (AO; Rockwood).

   • Keep the wire as close to bone as possible, with minimal intervening tendon (AO; Rockwood).

6. Cross the wire over the front in a figure-of-eight (Campbell; AO; Rockwood).

7. Check the reduction by palpating the articular surface with the knee extended, before tensioning (Campbell; AO).

8. Tighten: Twist both arms simultaneously and symmetrically; tensioning at two sites (e.g., at the corners of the figure-of-eight) gives more symmetric compression and better stability under cyclic loading (Rockwood). Twist at least three times but do not overtighten, which can cause articular gapping, comminution or wire failure (Rockwood). Placing the twist superiorly, where soft tissue cover is thicker, reduces prominence (Rockwood). AO advises tensioning with the knee in 90° flexion when a patellotibial wire is used, to avoid patella baja.

9. Bend the superior ends of the K-wires sharply (Campbell: anteriorly; Rockwood: posteriorly), cut them short, rotate them 180° and impact them into the superior patella behind the wire loop to prevent migration and irritation (Campbell; AO; Rockwood).

10. Cut the inferior ends short just beyond the cerclage, or bend them posteriorly; AO leaves the distal ends unbent for easier later removal.

11. Repair retinacular tears and the arthrotomy with multiple interrupted (figure-of-eight) nonabsorbable or absorbable sutures, watertight (Campbell; AO; Rockwood).

Cannulated Screw Tension Band

1. Same exposure and reduction (Rockwood).

2. Place two guide wires for cannulated screws perpendicular to the fracture, 5 mm deep to the anterior cortex (Rockwood). Rockwood's authors insert them retrograde from just deep to the patellar "nose" to the proximal pole.

3. Drill over the guide wires, measure, and insert 4.0 mm partially threaded (blunt-tip) cannulated screws, giving lag compression (Rockwood; Campbell; AO).

4. Screw tips must not protrude from bone: a wire tensioned over a sharp screw tip breaks quickly; the wire should be tensioned over the patellar margin instead (Rockwood).

5. Pass a single wire (at least 18-gauge) or heavy suture through each screw, cross the limbs in a figure-of-eight over the anterior patella, and tighten both simultaneously; bend the twists posteriorly into deep soft tissue (Rockwood).

Variations

• Comminuted fractures: Horizontal minifragment lag screws convert the fracture to a transverse pattern before a modified tension band (Campbell; Rockwood). For star-shaped (34C3) fractures, a circumferential 1.25 mm (or 1.6 mm) cerclage around the patellar equator, then vertical K-wires and a figure-of-eight band (AO).

• Stellate fractures unsuitable for a tension band: Lotke–Ecker longitudinal anterior banding plus cerclage — two parallel 2 mm tunnels 1 cm from the medial and lateral borders, a looped 18-gauge wire through them, tightened over the cerclage (Rockwood).

• Poor bone or distal pole comminution: Augment with nonabsorbable suture in the tendons or an additional minifragment locking plate (Rockwood).

• Coronal split of the anterior cortex: Often captured by the anterior tension band; otherwise excise it (Campbell).

• Pole fractures: Best stabilized with lag screws, with an anterior tension band (or a wire through a cannulated screw) to neutralize bending forces; protect transosseous repairs of the patellar tendon with a patellotibial cerclage (AO).

• Suture instead of wire: Braided polyester suture was 75% stronger than wire, and double-strand FiberWire had significantly higher failure loads than stainless steel; braided suture reduced reoperation rates (Rockwood).

• Plate fixation: Temporary K-wire fixation, then locking or nonlocking 2.4–2.7 mm plates; contour mesh plates around the margins for multiplanar fixation and use empty holes for suture fixation of retinaculum or tendon (Rockwood).

• Perform an intraoperative gravity flexion test to assess stability, so that motion can start early (Campbell).

Partial Patellectomy (AO)

• Prefer partial over total patellectomy whenever possible; results were poor when more than 40% of the patella was removed.

• Reattach the tendon to the anterior part of the remaining fragment to prevent patellar tilt and reduce patellofemoral contact forces; protect transosseous sutures with a patellotibial cerclage in poor bone.

• Total patellectomy is rarely indicated (unfixable comminution, failed fixation, infection, tumor, patellofemoral arthritis).

Postoperative Care

• Place the limb in extension in a removable knee brace (Campbell).

• Day 1: Walking with weight bearing as tolerated; start isometric and straight-leg exercises (Campbell). Early motion and full weight bearing are recommended (AO).

• Sutures: Remove at 14–21 days (Campbell).

• Motion: The amount of early active motion is decided intraoperatively according to the stability of the repair; active ROM can usually start once the wound has healed (2–3 weeks) (Campbell). Rockwood describes weight bearing as tolerated in a hinged brace with flexion limited to 30° for 4 weeks, then progressive ROM; CPM may help.

• Weak fixation or unreliable patient: Full weight bearing in a cylinder cast in extension for 6 weeks before a hinged brace (Rockwood). Delay active motion until healing if fixation is less stable or retinacular tears are extensive (Campbell).

• 6–8 weeks: If radiographs show healing, progressive resistance exercises and discontinue the brace; return to unrestricted activity once quadriceps strength has returned (Campbell).

• With a patellotibial cerclage, allow weight bearing in a hinged brace limited to 90° (AO).

Complications

• Symptomatic implants: The most common complication (AO); removal for soft tissue irritation is reported in up to 40% (Rockwood). K-wires and implant prominence over 5 mm predicted removal (Rockwood). Wait at least 12 months before removal (AO).

• Reoperation: 33.6% overall in a meta-analysis, so patients should be counseled (Rockwood).

• Loss of motion: Probably the most common functional problem (AO). Most patients reach 90° flexion; if not achieved by 8 weeks, consider manipulation under anesthesia, taking care to avoid rerupture or refracture (Rockwood).

• Wound problems and infection: Avoid raising subcutaneous flaps (Rockwood). Postoperative infection after open patellar fractures has been reported up to 10.7%; debride and retain stable fixation, with culture-directed antibiotics for 6 weeks (Rockwood).

• Loss of reduction: Usually from inadequate fixation or noncompliance; revise if the extensor mechanism fails or displacement is unacceptable (AO).

• Nonunion: Rare (up to 15%), associated with transverse and open fractures and nonoperative treatment; revise with rigid fixation and autograft in active patients (Rockwood).

• Patella baja: Avoid by tensioning patellotibial wires with the knee at 90° and comparing patellar height with the contralateral knee (AO).

• Posttraumatic arthritis: At removal of tension band hardware, 73% had grade II–III cartilage irregularity despite good Lysholm scores (Rockwood).

Note: Circumferential Wire Loop

This was once the most popular technique. Because it does not give rigid fixation, knee motion has to be delayed by 3–4 weeks, and it has largely been replaced by rigid techniques. It can still be used as an adjunct in comminuted fractures; Campbell uses a variation with nonabsorbable suture tape to augment repairs.

References

1. Rudloff MI. Fractures of the lower extremity. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 59, Techniques 59.16–59.17.

2. Odat MM. Patella. In: Buckley RE, Moran CG, Apivatthakakul T, eds. AO Principles of Fracture Management. 3rd ed. Stuttgart: Thieme; 2017. Chapter 6.7.1. (Turkish edition: AO Kırık Tedavisinin Prensipleri.)

3. Lim PK, Chalmers CE, Scolaro JA. Patellar fractures and dislocations and extensor mechanism injuries. In: Tornetta P III, Ricci WM, Ostrum RF, McKee MD, Ollivere BJ, de Ridder VA, eds. Rockwood and Green's Fractures in Adults. 10th ed. Philadelphia: Wolters Kluwer; 2024. Chapter 60. (Turkish edition: Erişkin Kırıkları.)