Diagnosis of a patella fracture
The diagnosis of a knee-slide fracture is usually made by an x-ray. In this case, the knee joint is x-rayed in two or, if necessary, three planes. Often, the extent of the injury cannot be adequately visualized and a computer tomography (CT) is performed.
Computed tomography can also be used to visualize microfractures that are not visible in the X-ray image. Another useful measure available to the physician is magnetic resonance imaging (MRI) of the knee. The MRI image of the knee allows a better assessment of the cartilage damage behind the kneecap. As the bone breaks, the cartilage behind the patella also breaks at the same time. Since neither X-rays nor CT images can show the cartilage, the knee MRI is a valuable source of information.
Differential diagnoses
A tear of the patellar tendon (patella tendon rupture) with subsequent patella elevation or a tear of the quadriceps tendon with patella depression may be the cause of comparable damage. The anomalies are either two-part (patella bipartita) or three-part (patella tripartita) patella. Usually, the additional bone piece is located in the upper outer quadrant of the patella.
Since this anomaly often exists on both sides, an x-ray of the patella may be helpful. Patella fracture – the patella is broken in the lower third. This fracture is difficult to treat surgically, as it is difficult to place screws, wires, etc. in the smaller lower fragment without further fracturing the fragment. Lateral knee joint x-ray: condition after refixation with wire cerclage
- Thigh bone (femur)
- Kneecap with wire cerclage
- Shinbone (Tibia)
- Fibula (fibula)
X-ray of the knee joint from the front: figure-eight strap and equatorial cerclage
- Wire cerclage
- Fibula (fibula)
- Shinbone (Tibia)
- Kneecap (patella)
- Upper leg bone (femur)
How is the patella fracture treated?
The patella fracture can be treated conservatively and surgically. The longitudinal fracture of the patella and non-displaced fractures can be treated conservatively, all other types of fractures should be treated surgically. In the treatment of patellar fractures, a knee orthosis with limited mobility is prescribed.
The flexion should not exceed 60° within the first three weeks and not exceed 90° until the sixth week. The knee joint should only be loaded with 20 kg within the first three weeks and should be loaded to full load until the sixth week. Until the knee joint is fully loaded, thrombosis prophylaxis, e.g. with low-molecular heparin, must be carried out.
Deviations from this post-treatment scheme must be made in individual cases. Patellar fractures with displaced fractures and a step formation of more than 2 mm and a divergence of the fracture fragments of more than 3 mm should be treated surgically. Cross-fragment fractures and multi-fragment fractures in particular require surgical therapy.The decision on the type of surgical treatment must be adapted to the individual findings.
For surgical treatment, so-called tension belt osteosyntheses, cerclages and screw fixation of the fracture are available. Tension belts are often used for transverse fractures with few fragments and are therefore the most common type of treatment. Two wires are inserted through both fragments in the longitudinal course of the patella.
A wire loop in the form of an 8 is placed around these two wires. By pulling these wire loops, the fragments are rejoined and can heal. In addition, the fracture can be secured by a so-called equatorial cerclage, especially in the case of multi-fragment fractures. In the case of a patella fracture in the form of a transverse fracture with a few fragments, a screw fixation can also be used as an alternative. In hopeless cases, in which no gradual reconstruction is possible, the complete removal of the patella must be considered (patellectomy), otherwise arthrosis will develop in the short term.
