Patellar tendon rupture

The Patellarsehnenruptur is a tear of the tendon between the lower pole of the kneecap ( patella ) and the shin bumps ( tibial tuberosity ).

Causes

As the tear of the quadriceps tendon is the crack usually implemented by a surge trauma against resistance or a strong tension in flexion of the knee joint. The patellar tendon ( patellar ligament ) is due to the relatively small lever between the fulcrum of the knee joint and the knee cap to the chords with the largest cross-sectional loading of the human body. This can achieve in severely obese people in 1000 kgf / cm ², and more. The Patellarsehnenruptur occurs more frequently at an advanced age in the presence of degenerative changes, metabolic diseases such as diabetes mellitus or arterial disease. Also two-sided ruptures are not uncommon due to the pre-damage.

Diagnostics

The diagnosis can usually already be ensured due to the clinical findings: There is an inability to use the knee actively to stretch against resistance, the typical " Patellahochstand " the good tactile " high wandering" of the patella during flexion of the knee or tension of the thigh extensor muscles as well as the also well palpable " absence " of the patellar tendon. In cases of doubt, if for example the Untersuchbarkeit of the knee is limited by severe swelling and pain, an ultrasound or a magnetic resonance imaging ( MRI or magnetic resonance imaging ) can provide clarity. In some cases, the tendon does not tear itself, but it is a so-called " avulsion fracture " from the tibia or the lower cusp Kniescheibenpol before, which is clearly visible on a conventional radiograph.

Differential Diagnosis

The acute complete loss of stretchability of the knee joint may be caused beside the rare Patellarsehnenruptur also by a much more frequent fracture of the patella. Here is a higher position of the patella or a part thereof palpable. A lateral radiograph of the knee brings a secure distinction in the confirmation or exclusion of a bony involvement. Through this radiograph also secure evidence of a possible differential diagnosis Quadricepssehnenruptur can be found: The Depression of the patella in acute extension deficit. ( see fig. )

Therapy

The treatment is surgical in most cases. Depending on the location of the rupture ( centrally located in the tendon area, proximal to the tip of the patella or distally on the approach to the tibia hump ) a tendon suture is performed, which is fixed in bone close with a suture anchor in the bone. In addition to direct suture of the tendon stumps a cerclage between the patella and the tibia protuberance is applied ( McLaughlin cerclage ), which allows early functional treatment, as they completely relieves the seam of the patellar tendon. In the after-treatment is particularly intense physiotherapy on the application that prevents atrophy of the thigh extensor muscles and maintains the mobility of the knee joint. The surgical removal of the cerclage after three to six months. Very often break the cerclage spontaneously in the context of functional further treatment. In this case, the material should be removed in advance.

Forecast

With consistently performed primary and post-treatment the prognosis is favorable, mostly, the complete restoration of the function of the extensor mechanism can be achieved. Due to early full weight-bearing, which can lead to breakage of the Cerclagedrahtes, but also by post-operative wound infections, the result can be compromised. Depending on the situation, however, come before re- rupture of the tendon especially in degenerative pre-damaged patients.