Patella fracture

As the patella fracture of the patella is called in the accident medicine. This fracture usually arises due to dropping or direct impact of the patella with the knee flexed. It usually is transverse or comminuted fractures, often with considerable displacement of the fragments. Except for the very rare longitudinal fracture without displacement patellar fractures must be treated consistently, infrequently a conservative treatment with immobilization. Most surgical treatment is required because a fracture of the patella inadequately dealt with the loss of function of the knee cap and thus a severe dysfunction of the knee joint can have up to walking and standing incapacity for.

• 5.1 Conservative ( non-surgical) therapy
• 5.2 Surgical treatment (principle)
• 5.3 operation 5.3.1 tension band wiring
• 5.3.2 tension band wiring with additional axial drill wires
• 5.3.3 tension band wiring in multi- fragment fractures
• 5.3.4 Lateral Seilzugosteosynthese ( Labitzke )
• 5.3.5 screw fixation
• 5.3.6 Teilpatellektomie
• 5.3.7 Total patellectomy

• 6.1 prophylaxis

Anatomy and function of the knee-cap

The kneecap is in the area roughly triangular-shaped bone that is embedded in the tendon extensor mechanism of the knee joint as a so-called sesamoid. Thus the kneecap transfers a large part of the yield strength of the thigh muscles to the tendon insertion at the head of the tibia. The extensor mechanism is the active extensor of the knee joint. As the only part of the extensor mechanism, the patella articulating contact with the knee joint, it thus acts as a sliding deflection point ( fulcrum ) with increasing flexion. The mating surface of the femoral condyle is called patellares plain bearings. On both sides longitudinally adjacent the patellar ligaments holding the patella runs ( retinaculum ) which transmits a portion of the stretching force and the kneecap centered in the slide bearing

This special arrangement and function of the patella leads to high tensile stress of the bone as well as to an increasing bending stress in flexion. This force resists the kneecap, even at high loads without breaking, so that rather tear the tendon attachments of the quadriceps tendon or patellar tendon spontaneously under overload. Isolated rupture of the bone do not occur.

Injury patterns and consequences of injuries

During a fall on the knee (eg on a stair ) or impact of the diffracted knee with an obstacle (eg a motorcyclist ), there is a direct line of fracture of the patella front surface and in addition to increased through the defense motion tension of Oberschenkelmuskuskulatur. Both individual factors can not lead to a patella fracture. The combined force (direct front wall Impression and tensile stress), however, leads to a complete rupture of the patella. With vigorous action of the muscles results immediately afterwards to a Querzerreißung the reserve stretching apparatus of the kneecap ( patellar retinaculum ): Then the fracture ends soft acutely apart, the leg is no longer enforceable, standing is impossible.

The fracture of the patella in a historical context

The fundamental importance of the kneecap to the upright posture makes the attention paid to their fractures has always been, of course. Because of the near-surface subcutaneous position of the patella, the easy to follow functional sequences, the significant loss of function in the patella fracture and because of the high standards which the patella fracture is to the attending physician, the patella was early in the focus of interest of physicians and patients. In the patella, the patient loses the ability to straighten the leg active, him, it is also impossible to stabilize the knee joint so that it can no longer stand on the injured leg. The clinical picture of patella fracture with the through the skin as Delle palpable fracture, dislocation, and crepitus ( fracture rubbing) was described by Soranus of Ephesus. The casualties are in accordance with the loss of function highly invalid. A special problem in the treatment of patellar fractures resulting from the dislocating muscle pull of the quadriceps muscle, which greatly complicates the Aneinanderheftung the fragments. At the same time it must be considered that there is a joint injury in fractures of this largest sesamoid of the body. A for the purpose of fracture healing Immobilizing ( immobilized ) treatment therefore always involves the risk of stiffening of the knee joint. The results after conservative treatment were therefore made ​​often unsatisfactory. Ambroise Paré had not seen any patients who would not have his life limping. At the beginning of the 20th century resulted in a fracture of the patella often for disability and retirement and in a number of cases, as conservatively as well as after surgical treatment, the death of the patient. The operative treatment of fractures in general has received much impetus from the supply of the patella. On one hand, the functional limitation and the connection with the unhealed fracture was always traceable. On the other hand, the palpable through the skin kneecap offered very early on for seam attempts by surgeons. A first successful suture describes Marc Aurel Severin in 1646. He put the badly healed patella of a clergyman free, freshened on the fracture surfaces, then brought them into close contact as possible and tied them together. Which suture material he used is not known, but the success: In the spring of the clergy could walk again. For later experiments seam silver wires were used as in the critical areas for development of surgery first application of antisepsis by Sir Joseph Lister in a fresh fracture of the patella of a rider in 1877 in London.

Diagnostics

First one is based on symptoms and clinical signs: The typical clinical appearance of complete patellar fracture are stretching inability of the knee joint through the skin palpable gap between the bone pieces ( fragments ) and local pain and swelling. These signs can be a reliable diagnosis even without X-ray diagnostics, which is why the fracture of the patella is a clear defined disease for centuries.

X-ray

With simple radiographs of the knee joint in two planes (from the front and from the side) can be diagnosed reliably each patella fracture. In the drawing, the broken pieces apart and generally with a single transverse or oblique fracture, which corresponds to the typical application of force from the front. This is also the destruction of the articular cartilage surface of the patella to the femoral condyle ( " patellares plain bearing ").

At higher force, such as in traffic accidents or poor bone structure (osteoporosis ) leads to so -called multi- fragment fractures or star fractures that involve a much greater destruction of bone and articular surface, in principle, but primarily have the same effect on knee function.

Radiographically, the appearance of multi- fragment fracture is uncertain, yet here is another diagnostic imaging with CT or MRI rarely useful: During the operation, necessary in any case, you can open identify the fragments and provide accordingly.

Even with the sonography can represent the patella easily. The kneecap is just under the skin and is clearly identified in the total sound reflection at the front surface. It can be seen apart gewichenen fragments and massive effusion. During bone healing, sonography can be used to detect increasing callus.

Classification of patellar fractures

By Bacon and Regazzoni (1994 )

Differential diagnoses

Rarely does the radiographic definition of patellar fracture from a bipartite patella (Latin: bipartite patella ), so a full- dependents during the development of fusion of ossification centers, diagnostic difficulties. While represent fractures with sharp edges, can be found in the bipartite patella rounded edges, the " fragments " are not congruent with each other. Also missing in the bipartite patella is usually the typical clinical findings of patellar fracture.

But even when the physical examination is another possible differential diagnosis can distinguish: In total failure of the knee extensor function and palpable and radiologically demonstrable high level of the patella also a complete tear of the patellar tendon between the kneecap and approach the head of the tibia ( tibial tuberosity ) may be present. Although the even rarer complete tear of the quadriceps tendon leads to stretching as the inability of the patella and the Patellarsehnenruptur. The kneecap is here but not high, as it remains attached to the patellar tendon on the tibia. Both types of tendon ruptures also need to be surgically reattached to the kneecap. To this end, the thread is fixed by drilled holes in the kneecap.

Differential diagnosis tear of the patellar tendon: characters in the X-ray image: high level of the patella.

Therapy

The principle of treatment consists of restoring the entire knee extensor apparatus. In addition, the articular surface of the patella, as with any joint break must be restored to the millimeter. In addition, the Reserve trek apparatus must be sewn next to side of the kneecap. It must be carried out an exercise stable supply to allow early functional treatment. Only all these individual actions lead to the result of bony healing of the fracture with full functionality of the knee joint.

Conservative ( non-surgical) therapy

The classic patellar fracture is a displaced transverse fracture with a wide splaying of the fragments. A conservative therapy ( without surgery ) is only possible with a patellar fracture, if it is a safe non-displaced ( undislozierte ) fracture. These types of fractures can be obtained only with reserve stretching apparatus ( patellar retinaculum ). In addition, fractures of the patella can be caused by special impact to the front surface in the form of longitudinal fractures. This longitudinal fractures soft principle apart very low since no muscle pull attacks across the kneecap. Such fractures are found in large numbers for the conservative therapy. In longitudinal fractures with absence of any dislocation (in this case usually the very strong periosteum is intact ) may even be dispensed with immobilization from the outset and treated early with functional pain -adapted full load.

The treatment consists of temporary immobilization in a plaster or plastic sleeve over the knee joint, thereby splaying of the fragments is prevented. For a limited time the injured leg should not be fully loaded. The cure of the patella is controlled with the aid of X-ray images. While the reduced load on the injured leg is to provide for thrombosis prophylaxis by heparin injections.

Surgical therapy (principle)

Each displaced fracture with splaying of the fragments must be open surgically. In view of the fibers of the extensor mechanism can be removed from the fracture region and the fragments are adapted and composed. Lower buttons with the fingers of the surgeon, the articular surface is restored smooth, yes you in the operation of the front can not see. The position of the individual fragments is controlled during the operation with a mobile X-ray apparatus. To fix the assembled patella, a fixation ( osteosynthesis ) must be performed, which allows a functional post-treatment (exercise therapy). This fixation of the patella must be stable, especially against the muscle strength of the quadriceps while keeping safe the reconstruction of the articular surface.

Open patella fractures, ie fractures with injury to the skin surface must be supplied as an emergency intervention surgically within 6 hours before the potentially invading bacteria may colonize and produce an infection. Due to the joint involvement of the patella, the infection can also spread throughout the knee joint. The osteosynthesis implants are no different than the typical closed ( covered ) fracture of the patella. As prophylaxis of infection in these patients must receive during and after surgery antibiotics. In addition, the Tetanusimpfschutz must be evaluated.

Operation

Operations on the knee done under general anesthesia or spinal anesthesia. It can be applied to reduce blood loss and to improve operational visibility a tourniquet. In smokers and patients with circulatory disorders must be dispensed with tourniquet to avoid possible Wundrandnekrosen.

Tension band wiring

The basic principle of osteosynthesis of the patella is best achieved with the tension band. This method evolved from wire suture method under the engineering aspect of prestressed concrete: Here are steel bars of tensile stability, while the concrete ensures the pressure stability. The decorated bone of the patella is stable under pressure, while a wire loop on the front surface of the knee at the base ( quadriceps tendon ) and the tip ( patellar tendon ) is placed that generates tension stability. The wire loop is advantageously carried out as an O- loop, creating a strangulation of the tendon attachments is avoided. Other surgeons perform the loop in the form of an 8, but with increase in voltage of the wire leads to a narrowing of the tendon attachments. The advantage of the tension band is that stability is maintained in movement of the knee joint, thus changing tension. The compressive stress on the hinged side of the knee cap increases with increasing bending of the joint with an increase of the front tension on the wire. At full extension of the knee joint, but the effect is small pressure on the articular surface of the patella: It is even possible to gape of the fragments. Therefore, the pure tension band is complemented with the aim of axial stability of the osteosynthesis and in extension by two axial Kirschner wires (see below). This arrangement of the osteosynthesis fracture healing in flexion, extension and function is secured.

Particularly attractive is the procedure due to the low cost and material costs and the reliability of results. It is steel wire made ​​of stainless steel is used, which is guided along with a guide through the bone edges of the patella ( see figure to the right ). The ends of the wire loop are then twisted with pliers and abbreviated with a wire cutter. Another advantage of the method is that the patient can move his leg during the entire post-treatment, the functional stress is even a prerequisite for a good result.

Eliminating the need for metal removal after fixation with wire strain on the patient and generates costs, attempts have been made ​​to use absorbable suture loops to tension band. Since these materials but are not inert such as wire, but rather can take up pored cords and therefore fluid from the wound edges, they represent a risk of infection dar. addition, large concentrations of organic acids ( polylactic acid, polymalic acid ) are released in their biodegradation, the surrounding tissue hurt already due to the changed acidic pH. Due to the risks outlined the advantages of unnecessary material removal are neutralized again, so these kinds of procedures are no longer performed.

Tension band osteosynthesis of a simple Patellaquerfraktur

Advanced tension band osteosynthesis of patella fracture with transverse axial drill wires

Tension band wiring with additional axial drill wires

The aim of the tension band is only achieved when the bone of the patella and the type of fracture ensure a compression stability and rotational stability. If there are doubts about the stability of this by the additional introduction of axial powerful drill wires ( K-wires | ) can be achieved. The Kirschner wires are drilled after reduction of the fracture from the top of the kneecap, cross the fracture line and leave the kneecap back at the base of the patellar tendon. The wires should be bored in parallel at a distance of about 2 cm. The wire loop of the tension band is placed in this case not only the tendon exposure in the kneecap, but additionally on the Bohrdrahtenden what the attachment improved. A major side effect of this operation, a variation that a guaranteed position of the joint area is obtained even at reduced in extension of the knee encircling band of tension. This effect is so important that the operation of the Patellazuggurtung is today very often carried out in this variation.

Tension band wiring in multi- fragment fractures

At higher force (eg car accident) and at elevated brittle bones ( osteoporosis) may result in comminuted fractures. The rationale of the supply of such fractures ( all comminuted fractures) consists in the construction of two major fragments from the plurality of fragments. This can be done best and easiest through open adaptation of the individual fragments under vision, with the ultimate reduction must be made in the joint level ( articular cartilage ). Here no error can be accepted. The fragments are connected by short drill wires or screws, which extend parallel to the articular surface of the patella. The direction of the drill wires must each be aligned perpendicular to the respective fracture line. Are all small fragments united to each with a large main fragment above ( Quadricepssehnenansatz ) and bottom ( Patellarsehnenansatz ), these two main fragments can be combined in terms of a classic tension band wiring with two axial drill wires and a cerclage. But sometimes a running around the equator of the patella enclosing cerclage is also necessary to hold the pieces in a form of a patella. In principle, these fractures should be like all the tensioning straps exercise stable. But is the kneecap from many individual fragments, which in part even partial loss of substance have suffered mainly the cancellous bone, is not to achieve this goal and a temporary immobilization of the extremity by plaster displayed. In some cases, an autologous bone graft or bone substitute material must be used in loss of substance.

Lateral Seilzugosteosynthese ( Labitzke )

For this modification a Drahtschlingenosteosynthese the so-called " Seilosteosynthese system Labitzke " is used. It is a primary fragment fixation achieved through drilled longitudinal wires as with a tension band with additional axial drill wires. The bent ends of the wires in the approach of the quadriceps tendon and the patellar tendon is not prior to the patella but laterally guided around a wire loop and clamped to the patella. The wire loop is not monofilament ( single thread ) wire, but a thin polyfilament ( multi-filament ) wire rope. Such a cable can not be swallowed or knotted, but is closed with a final piece. The advantage of the process side should be of the continuous application of pressure to the bone ends. Other authors see the thin wire ropes as problematic " sawed " implants which jeopardize the functional treatment of the substance of the patella. The method is currently regarded as rather reserve method.

Screw fixation

Smooth transverse fractures in young patients with good bone and the rare longitudinal fractures can be stabilized with lag screws after anatomical reduction. Of these, two are usually placed in parallel according to the drill wires from the increased tension band. In the longitudinal fractures transverse to the knee axis. A relevant advantage of screw fixation in relation to the tension band does not exist. However, Biomechanical measurements under laboratory conditions allow higher tensile stresses in screws proceedings against the wire cerclage. It concerns with screws to a static internal fixation, in contrast to the dynamic tension band acting muscle and tendon forces can not use to generate pressure on the fracture ends.

Teilpatellektomie

Received stable bone structure of the fragments is a necessary prerequisite of osteosynthesis. If any part of the patella within the fracture be seriously damaged, so that both bone and articular surface have suffered substantial damage, a partial removal of the patella in exactly the destroyed area may be necessary instead of reconstruction. The different sizes of the obtained approach parts of the tendons ( patella and quadriceps tendon ) can be made into two fragments, each with straight edges fracture after removal of the destroyed substance. These can then unite with tension band wiring or screws into a functional Restpatella.

In the frequent destruction of the lower pole of the patella, the patellar tendon is attached to the Restpatella. For this tendon sutures are used with bone anchors. For temporary protection of the tendon suture a wire loop at the base point of the patellar tendon on the tibia head pulled through ( McLaughling cerclage ).

Total patellectomy

Primary at the initial treatment of a fracture, the complete removal of the kneecap is only displayed when massive, possibly open destruction of the patella. Clinical studies have shown that the clinical results of such primary kneecap removal are bad. In principle, it should be attempted and achieved the reconstruction of the fragments. Patellektomien can be useful and targeted only at very poor healing results with osteoarthritis of the articular surfaces of the patella and femur sliding bearing.

Follow-up treatment

The tension band principle requires a functional treatment of patellar fractures. After short-term postoperative immobilization on resting splint, the patient can be mobilized with the aid of crutches. An unwinding of the operated limb is useful. A Aufbelastung operated with a tension band knee can take place no earlier than about 6 weeks after the operation, because the tensile fracture treatment would overwhelm the stability of the osteosynthesis under load. Due to the relief of the leg must be made subcutaneously in the treatment of thrombosis prophylaxis with heparin syringes. This measure can be terminated only when nearly complete exposure of the extremity.

Results

Crucial for the result, the quality of the restoration of the articular surface and the stable fracture healing. In remaining step formation is the development of osteoarthritis ( degenerative joint disease premature ) are capable of producing pain and disability. Smooth transverse fractures of the patella can lead to excellent results after supply with classic tension band for good. But with more than a quarter of the patients there is restricted movement and pain, has a note on the radiograph can not always be found. These problematic cases with classical tension band are the occasion for the use of other methods of osteosynthesis. But even with the screw fixation and a very rarely performed nailing method Remains a percentage of poorer outcomes.

A risk of impaired wound healing, patients with circulatory disorders, in smokers and diabetics. The skin in the area of injury is significantly damaged by the direct impact and the resulting knee mediated fracture. Through the operation and preparation of the tissue is assumed that an additional perfusion injury. Since kneecap and osteosynthesis is very close under the skin, is at Wundrandnekrosen the risk of contagion of infection in the depth and therefore on fracture and osteosynthesis.

For the result of an operation of central importance, the decision partial or complete resection of the patella ( patellectomy ) early as possible to make in the first operation and then perform the resection immediately. A belated implementation, for example, by absence of healing or symptoms due to cartilage damage does not lead to an improvement in clinical outcome.

Prophylaxis

Is particularly at Fashion sports such as inline skating and skateboarding, but also while skating and cycling the risk of patellar fracture by direct knee impact with increased muscle tension of the knee extensors. It is the recommendation to wear knee pads, because thereby the direct traumatic effect of preventing the bone structure of the knee cap. In vehicle a significant reduction of the once very frequent so-called Dashboardverletzungen could be achieved by modifying the edge of the dash and the seat belts.

Patellar fracture in animals

Patellar fractures in animals include the rare bone fractures. At relatively frequently they are observed in domestic dogs. You have to be almost always treated surgically. In veterinary medicine, mainly found tensioning straps ( cerclage ), possibly together with Kirschner drill wires application in longitudinal fractures and lag screws are used. When breaks the patella tip (apex patellae ) may also be a partial removal, in complicated splinter fractures, a total distance shall be displayed. The osteosynthesis show a rather high complication rate, especially in the form of breakage or loosening of the wire loops. The total distance of the patella in dogs hardly leads to an impairment of the affected leg. All forms of therapy can stop chronic changes of the knee ( gonarthrosis, Gonotrochlose, calcification of the ligamentum patellae ) not entirely.

Literature and sources

• I. Klute, N. Meenen: The fracture of the patella - Modern tension band wiring in a historical context. ( Books about the journal The trauma surgeon 269). Springer -Verlag, Heidelberg 1998, ISBN 3-540-63590-4.
• DW Aitken: Subcutaneous Suture of Fractured Patella. In: British Medical Journal Volume 2, Number 1647, July 1892, pp. 177, ISSN 0007-1447. PMID 20,753,814th PMC 2420779 (Free full text ).
• Albert E.: Textbook of surgery and operative surgery. Urban & Schwarzenberg, Vienna / Leipzig, 1891, pp. 404-410.
• WL Axford: A method of wiring fractures of the patella. In: Annals of Surgery. 8, 1888, pp. 1-5.
• W. Axhausen, G. Schultze: For the treatment of crushing fractures of the patella. In: Zentralbl Chir (14 ) 84, 1959, pp. 534-537.
• R. Babayan, K.-H. Jungbluth, J. Thunich: Patellar fractures. Treatment methods and results. In: Nude traumatology. 5, 1975, pp. 27-30.
• F. Baumgartl: The knee joint: diseases, injuries and their treatment. Springer, Berlin / Gottingen / Heidelberg 1964, pp. 296-318.
• L. Böhler: The technique of bone fracture treatment. 12th and 13th edition. Vol.2 / 2, Wilhelm Maudrich Verlag, Wien 1957, pp. 1586-1617.
• V. Bühren, O. Trentz, Henneberger: Surgical treatment of patellar fracture. In: Surgeon. 60, 1989, p 723-731.
• Curtis MJ: Internal fixation for fractures of the patella. In: J Bone Joint Surg. (Br ) 72 -B, 1990, pp. 280-282.
• R. Labitzke: surgical technique and results of treatment by lateral tension band wiring of the patella and olecranon. In: traumatology. 83, 1980, pp. 450-456.
• F. Magerl: The patello - femoral joint. Causes, forms and combined lesions of the patella. In: Issues Unfallheilkd. 120, 1975, pp. 45-59.
• M. Muller, M. Allgower, R. Schneider, H. Willenegger: Manual of internal fixation - AO technique. 3rd edition. Springer, Berlin / Heidelberg / New York 1988, pp. 1-3, 44-45, 226-228, 565-568.
• F. Pauwels: Surprising success through the application of a tension band in the Patellarfraktur. 83.Tagung In: Langenbeck's Arch Klin Chir 316, 1966, pp. 221-224.
• A. Rueter, C. Burri: Patellar fractures. Discussion and recommendations. In: Issues traumatology. 120, 1975, pp. 91-98.