Circumferential Wire Loop Fixation for Patella Fractures: Principles and Surgical Technique

INTRODUCTION TO PATELLAR OSTEOSYNTHESIS

The patella, the largest sesamoid bone in the human body, plays a critical biomechanical role in the extensor mechanism of the knee. It increases the moment arm of the quadriceps tendon, thereby enhancing the mechanical advantage of knee extension. Fractures of the patella disrupt this vital mechanism and often compromise the congruity of the patellofemoral articular surface.

Historically, circumferential wire loop fixation was the most popular and widely utilized technique for the operative management of patella fractures. Operating on a "purse-string" principle, this method involves passing a heavy-gauge wire circumferentially around the patella through the adjacent soft tissues (quadriceps tendon, patellar tendon, and medial/lateral retinacula) to compress the fracture fragments.

While this technique provides concentric compression, it does not achieve the absolute rigid fixation characteristic of modern anterior tension band wiring constructs. Because the wire is threaded through soft tissues rather than directly through osseous tunnels, the construct is inherently slightly elastic. Consequently, a delay of 3 to 4 weeks in initiating active knee motion is mandatory to prevent wire cut-out and loss of reduction. Today, isolated circumferential wiring has been largely replaced by more rigid fixation techniques (such as cannulated screws with tension band wiring) that permit immediate postoperative mobilization. However, circumferential wiring remains an indispensable tool in the orthopedic surgeon's armamentarium, particularly as an adjunctive fixation method for highly comminuted (stellate) fractures where tension band wiring alone is insufficient to capture peripheral fragments.

INDICATIONS AND CONTRAINDICATIONS

Primary Indications

• Severe Comminution (Stellate Fractures): Used as an adjunct to tension band wiring or screw fixation to contain peripheral comminuted fragments that cannot be captured by longitudinal Kirschner wires or screws.
• Inferior Pole Fractures: Can be utilized in conjunction with transosseous sutures or anchor repairs to protect the primary repair of the patellar tendon.
• Osteoporotic Bone: In cases where poor bone stock precludes the secure purchase of screws or K-wires, a circumferential wire can provide a containment "basket" effect.

Contraindications

• Simple Transverse Fractures: Relative contraindication for isolated use, as anterior tension band wiring provides superior biomechanical rigidity and allows for early range of motion.
• Active Infection: Overlying soft tissue infection or intra-articular sepsis.
• Severe Soft Tissue Compromise: Degraded quadriceps or patellar tendons that cannot support the wire without catastrophic cut-out.

BIOMECHANICS AND SURGICAL PRINCIPLES

Understanding the biomechanical limitations of circumferential wire loop fixation is paramount for successful application.

Biomechanical Warning: Unlike anterior tension band wiring, which converts tensile forces at the anterior cortex into compressive forces at the articular surface during knee flexion, circumferential wiring applies static, concentric compression. It does not dynamically neutralize the massive tensile forces generated by the quadriceps during active knee extension.

The Mid-Coronal Plane Principle

The most critical technical aspect of circumferential wiring is the precise anatomical placement of the wire in the coronal plane.
* Ideal Placement: The wire must be centered exactly midway between the anterior cortical surface and the posterior articular surface.
* Anterior Malposition: If the wire is placed too anteriorly, tightening the loop will cause the fracture to gap posteriorly at the articular surface, leading to step-off, incongruity, and rapid post-traumatic osteoarthritis.
* Posterior Malposition: If the wire is placed too posteriorly, tightening will cause the fracture to gap anteriorly, compromising the extensor mechanism and increasing the risk of nonunion.

Surgical Pearl: The wire must be placed intimately close to the osseous borders of the patella, especially at the superior and inferior poles. If the wire is inserted through the tendons too far away from the bone fragments, the fixation will be highly insecure. Under tension, the wire will inevitably cut through the intervening soft tissues, resulting in catastrophic separation of the fracture fragments.

PREOPERATIVE PLANNING AND POSITIONING

Imaging

Standard preoperative imaging includes anteroposterior (AP), lateral, and axial (skyline) radiographs of the knee. Computed Tomography (CT) is highly recommended for comminuted fractures to map the articular surface and plan the trajectory of adjunctive fixation.

Patient Positioning

• The patient is placed in the supine position on a radiolucent operating table.
• A high-thigh pneumatic tourniquet is applied.
• A small bump may be placed under the ipsilateral hip to correct natural external rotation, ensuring the patella faces directly anteriorly.
• The limb is prepped and draped free to allow full, unrestricted flexion and extension of the knee during the procedure.
• Fluoroscopy (C-arm) must be positioned to easily obtain true AP and lateral views of the patellofemoral joint.

SURGICAL APPROACH

1. Incision: A midline longitudinal incision is generally preferred as it provides excellent exposure, is extensile, and avoids the neurovascular complications occasionally seen with transverse incisions. Alternatively, a transverse incision can be used for isolated transverse fractures, offering a cosmetically superior scar, though it limits proximal and distal extension.
2. Dissection: Full-thickness fasciocutaneous flaps are elevated medially and laterally to expose the entire anterior surface of the patella, the extensor retinaculum, the distal quadriceps tendon, and the proximal patellar tendon.
3. Hematoma Evacuation: The fracture site is exposed, and the fracture hematoma is thoroughly irrigated and debrided. Small, devitalized osteochondral fragments that cannot be fixed are excised.
4. Joint Inspection: The articular surface of the trochlea and the interior of the joint are inspected and irrigated to remove any intra-articular debris.

STEP-BY-STEP SURGICAL TECHNIQUE (THE MARTIN TECHNIQUE)

The Martin technique describes the classic, systematic application of the circumferential wire loop.

1. Wire Selection and Preparation

• Select a heavy-gauge, No. 18 stainless steel wire. The stiffness of the No. 18 wire provides the necessary tensile strength to maintain concentric compression.
• Alternative Material Note: While heavy synthetic sutures (e.g., No. 5 FiberWire or Ethibond) have been utilized to avoid hardware prominence, they are generally less satisfactory than stainless steel wire. Synthetic sutures possess inherent elasticity, failing to fix the fragments as securely. Furthermore, they have been associated with the development of chronic prepatellar bursitis, potentially secondary to a localized allergic or foreign-body reaction to the synthetic braided material.

2. Superior Wire Passage

• Begin threading the No. 18 wire at the superolateral border of the patella.
• Pass the wire transversely, immediately adjacent to the superior pole of the patella, directly through the substance of the quadriceps tendon.
• Delivery Method: Because No. 18 wire is highly stiff and difficult to pass blindly through dense tendon, a delivery cannula is required.
  • Option A: Use a large Gallie needle.
  • Option B (Preferred): Thread the wire through a large-bore Intracath (or 14-gauge IV cannula) needle. Insert the needle with the sharp point exiting exactly at the site where the next suture pass is desired. Fit the No. 18 wire into the sharp end of the needle. As the needle is withdrawn, the wire is pulled along its path. This technique is significantly easier and minimizes soft tissue trauma.

3. Medial Wire Passage

• Retrieve the wire at the superomedial pole.
• Pass the medial end of the wire distally along the medial border of the patella.
• Ensure the wire passes through the medial retinaculum exactly midway between the anterior and posterior surfaces of the patella to maintain the mid-coronal plane principle.

4. Inferior Wire Passage

• At the inferomedial pole, pass the wire transversely through the deep substance of the patellar tendon, moving from the medial side to the lateral side.
• The wire must hug the distal border (apex) of the patella intimately.

5. Lateral Wire Passage

• Retrieve the wire at the inferolateral pole.
• Pass the wire proximally along the lateral side of the patella, through the lateral retinaculum, returning to the starting point at the superolateral border.

6. Fracture Reduction and Provisional Fixation

• Before tensioning the wire, the fracture must be anatomically reduced.
• Irrigate the fracture surfaces one final time.
• Approximate the fragments using large pointed reduction forceps (Weber clamps) or a towel clip.
• Palpate the articular surface through the retinacular tears to ensure perfect congruity.

7. Tensioning and Twisting the Wire

• Draw both ends of the No. 18 wire until they are completely taut, removing all slack from the soft tissue loop.
• Twist the ends together using a heavy wire twister or pliers. Pull outward while twisting to ensure the twists advance down to the tissue level without simply spiraling the wire over itself.
• The Double-Twist Modification: A highly effective modification involves using a pretwisted wire (or creating a loop with two separate wires) that allows for tightening at two opposite points (e.g., superolateral and inferomedial).
  > Surgical Pearl: Tightening the wire by twisting at two points opposite each other supplies significantly more even, symmetric pressure across the fracture site, preventing asymmetric tilting of the fragments.

8. Radiographic Confirmation

• Before final closure, confirm the position of the fragments using fluoroscopy.
• Obtain strict AP and lateral views. Pay meticulous attention to the articular surface on the lateral view to ensure no anterior or posterior gapping has occurred as a result of wire tensioning.
• Perform direct visual inspection and palpation of the articular surface if the capsular tears are still open.

9. Hardware Management and Closure

• Once reduction is confirmed, cut off the redundant twisted wire, leaving approximately 1.5 cm of twisted stalk.
• Using a tamp or heavy needle driver, acutely bend and depress the twisted ends deep into the quadriceps tendon. This step is critical to prevent painful subcutaneous hardware prominence.
• Repair the medial and lateral retinacular (capsular) tears meticulously using heavy interrupted sutures (e.g., No. 1 Vicryl or PDS). A robust retinacular repair is essential for restoring the full strength of the extensor mechanism.
• Close the subcutaneous tissues and skin in a standard layered fashion.

POSTOPERATIVE CARE AND REHABILITATION

Because circumferential wire loop fixation through soft tissue is not a rigid construct, the postoperative protocol must be highly conservative compared to modern tension band techniques.

Phase 1: Maximum Protection (Weeks 0 to 3)

• Immobilization: Immediately postoperatively, a posterior splint from groin to ankle is applied to provide absolute immobilization.
• Muscle Activation: The patient is encouraged to perform isometric quadriceps-setting exercises immediately. Within a few days, as pain allows, the patient should be performing straight leg raises (lifting the leg off the bed) to prevent quadriceps atrophy.
• Wound Care: At 10 to 14 days, the surgical incision is inspected, and sutures/staples are removed.
• Transition: Following suture removal, the patient is transitioned to a well-molded cylinder cast or a rigid knee immobilizer locked in full extension.
• Weight-Bearing: The patient is allowed to be ambulatory, weight-bearing as tolerated with the knee locked in extension, using crutches until active, independent muscular control of the leg is reliably obtained.

Phase 2: Controlled Mobilization (Weeks 3 to 6)

• Immobilization Removal: For standard transverse fractures managed with this technique, rigid immobilization can typically be discontinued at 3 weeks.
• Range of Motion: Gentle active and active-assisted range of motion (ROM) exercises are initiated. Passive forceful flexion is strictly prohibited, as it may cause the wire to cut through the tendon and displace the fracture.
• Bracing: A hinged knee brace may be utilized, gradually opening the allowable flexion arc (e.g., 0-30 degrees at week 3, progressing to 0-90 degrees by week 6).

Phase 3: Strengthening and Weaning (Weeks 6 to 8+)

• Crutch Weaning: As muscle power returns and the patient can perform a straight leg raise without an extensor lag, crutches are progressively discarded (usually between 6 to 8 weeks).
• Advanced Rehab: Progressive resistance exercises are introduced once radiographic union is evident.

COMPLICATIONS AND HARDWARE REMOVAL

Hardware Prominence and Breakage

The most common complication specific to circumferential wiring is symptomatic hardware. Because the patella is subcutaneous, the heavy No. 18 wire—especially the twisted knot—frequently causes irritation, bursitis, and pain with kneeling. Furthermore, due to the repetitive cyclic loading of the knee during flexion and extension, the wire will eventually experience fatigue failure and break if left in situ indefinitely.

Hardware Removal Protocol

• Timing: After solid clinical and radiographic fracture union is achieved (typically 6 to 12 months postoperatively), the wire should be removed in almost all instances.
• Technique: Removal is generally a minor outpatient procedure. The twisted ends can usually be palpated through the skin. Under local or light regional anesthesia, a small stab incision is made directly over the knot. The wire is cut near the twisted ends and withdrawn. Because the wire is smooth and sits in soft tissue, it typically extracts with minimal difficulty.

Loss of Reduction

If the wire is placed too far from the bone, or if the patient is non-compliant with the early immobilization protocol, the wire may cut through the quadriceps or patellar tendon. This results in loss of concentric compression, fracture displacement, and potential nonunion. Management of this complication requires revision surgery, often necessitating more rigid fixation techniques or partial patellectomy if the fragments are no longer viable.