The patella is the largest sesamoid bone in the human body and a component of the knee joint. After patellectomy, the quadriceps muscle strength decreases during knee extension. Therefore, the patella plays a role in protecting the knee joint, enhancing quadriceps muscle strength, and facilitating the smooth movement of the knee joint trochlea. During treatment, efforts should be made to ensure the articular surface on the posterior side of the patella remains intact, with its medial and lateral aspects forming smooth articular surfaces with the anterior parts of the femoral condyles, thereby reducing the incidence of patellofemoral arthritis.

bubble_chart Etiology

Fractures are caused by direct violence and indirect violence. Direct violence often results from external force directly striking the patella, such as impacts or kicks, and the fractures are mostly comminuted. The patellar tendon membrane, the tendon membranes on both sides of the patella, and the joint capsule usually remain intact, but transverse fractures may also occur. Indirect violence is typically due to a sudden contraction of the quadriceps muscle, leading to a traction injury. For example, when suddenly slipping, the knee joint is in a semi-flexed position, and the quadriceps contracts abruptly, pulling the patella upward while the patellar ligament fixes the lower part of the patella, resulting in a patella fracture. Indirect violence causes transverse fractures with significant displacement, and the patellar tendon membrane and the lateral expansions are severely torn.

bubble_chart Clinical Manifestations

After a fracture, there is a large amount of intra-articular hemarthrosis, with static blood and swelling in the prepatellar subcutaneous tissue. In severe cases, blisters may form on the skin. In displaced fractures, the gap between the fracture lines can be palpated. Anteroposterior and lateral X-rays of the patella can confirm the diagnosis. For suspected longitudinal or marginal fractures of the patella, axial views must be taken for verification.

Obvious history of trauma, pain in the affected limb, limited movement. X-ray can determine the location and displacement of the fracture.

bubble_chart Treatment Measures

For the treatment of fresh patella fracture, the smoothness of the articular surface should be maximally restored, firm internal fixation should be applied, and early knee joint movement should be initiated to prevent the occurrence of traumatic arthritis.

(1) Gypsum splint or cast fixation

This method is suitable for non-displaced patella fractures, requiring no manual reduction. After aspirating the intra-articular hematoma and applying a bandage, a long-leg Gypsum splint or cast is used to immobilize the affected limb in an extended position for 3–4 weeks. During the Gypsum immobilization period, quadriceps contraction exercises should be performed. After removing the Gypsum splint, knee joint flexion and extension exercises should be initiated.

(2) Open reduction and fixation

There are various methods of internal fixation for patella fractures, which can be divided into two categories: one requires a certain period of external fixation after internal fixation, while the other involves more robust internal fixation that does not require external fixation.

1. Modified tension band wire internal fixation

(1) Indications a. Transverse patella fracture; b. Reducible comminuted patella fracture.

(2) Surgical procedure A transverse arcuate incision is made anterior to the patella to expose the fracture line. Starting from the fracture surface of the distal fragment, two 1.5mm diameter Kirschner wires are inserted retrograde to fix the fracture ends. A hand is inserted into the joint cavity to confirm the smoothness of the patellar articular surface, and a wire is looped around the Kirschner wires for fixation. The other wire is fixed in the same manner.

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2. Resection of the superior or inferior pole of the patella with reattachment of the quadriceps tendon

(1) Smaller bone fragments or comminuted fracture parts are resected. The patellar ligament is reattached to the upper segment of the patella, or the quadriceps tendon is reattached to the lower segment of the patellar fracture.

(2) Postoperative management The area is bandaged with ample dressing, and a long-leg Gypsum cast is applied in an extended position for 3 weeks. After removing the Gypsum, non-weight-bearing joint exercises are initiated. At 6 weeks, crutch-assisted gradual weight-bearing walking is started, along with intensified joint range-of-motion and quadriceps strength training. This method preserves the function of the patella, promotes rapid healing, restores quadriceps function, and avoids issues of fracture nonunion or articular surface irregularity.

3. Total patellectomy

This is indicated for severely comminuted fractures that cannot be reduced or partially resected. When resecting comminuted fracture fragments, care should be taken to preserve the periosteum and quadriceps tendon membrane as much as possible. After resection, the torn expansion and joint capsule are sutured to restore normal tension. The quadriceps tendon is then pulled down and sutured to the patellar tendon. If direct suturing is not possible, a quadriceps tendon turnover repair can be performed. A "V"-shaped incision is made in the quadriceps tendon, and the resected tendon flap is turned downward to repair the defect formed after patellectomy. Alternatively, the lateral muscle of the thigh and the lateral portion of the quadriceps tendon can be turned downward to repair the defect at the patellectomy site. Postoperatively, a Gypsum splint is applied for 4 weeks, followed by knee flexion and extension exercises.