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it acts as a primary restraint against posterior displacement and , in concert with the anterior cruciate ligament ( acl ) , to regulate external rotation of the knee during extension .
the most commonly reported mechanism of injury to the pcl is a posteriorly directed blow to the anterior aspect of the proximal tibia with the knee flexed at 90 .
another mechanism is sudden hyperextension in conjunction with associated varus or valgus force or hyperflexion of the knee .
clinical examination shows a posterior sag and a positive posterior drawer test if the pcl is ruptured or avulsed . in case of avulsion , radiological examination
avulsion of the tibial insertion of the pcl is believed to be an uncommon injury .
a non - displaced bony avulsion can be treated conservatively with a plaster cast , holding the knee flexed and the tibia pulled forward to diminish tension on the pcl .
there is general consensus that a displaced bony pcl avulsion should be surgically reduced and fixed immediately to stabilize the knee joint and prevent non - union .
all publications on the repair of acute bony avulsion of the tibial attachment of the pcl report excellent clinical results [ 1 , 2 , 4 , 6 , 912 , 14 ] .
trickey states that surgical repair of an avulsion the tibial attachment of the pcl after 3  weeks is not successful .
there is one report in the literature of a reduction and screw fixation combined with posterolateral stabilization of a 4.5-year - old bony avulsion of the pcl with good clinical result . to the authors knowledge
, there is no report of pseudo - arthrosis repair of a pcl avulsion fracture .
we report the case of a pseudo - arthrosis repair of a 4-year - old bony avulsion fracture of the pcl using a minimally invasive technique , screw fixation , and bone grafting .
four years prior , she suffered from distorsion trauma of her left knee during a skiing accident . at the time
, the knee was examined both physically and radiologically but the diagnosis of an avulsion fracture of the tibial eminence was not made . in the years following the initial trauma ,
the left knee had a full range of motion without any apparent instability but did show a slight posterior sag .
standard lateral and posterior - anterior radiographs revealed an evident pseudo - arthrosis with a radiolucent and sclerotic line under the posterior tibial eminence .
the avulsed fragment measured 32  mm    24  mm    12  mm ( fig . 
1standard radiographs showing an evident pseudo - arthrosis of the posterior tibial eminence 
  standard radiographs showing an evident pseudo - arthrosis of the posterior tibial eminence 
  magnetic resonance imaging and computed tomography showed pseudo - arthrosis of a large bony avulsion of the tibial attachment of the pcl extending to both the medial and lateral tibial plateau the magnetic resonance imaging also showed an intact pcl and did not reveal any signs of concomitant intra - articular injuries of the knee ( fig .  2 ) .
bone scintigraphy demonstrated increased activity at the proximal left tibia.fig .  2computed tomography revealing a large bony avulsion of the tibial attachment of the pcl .
magnetic resonance imaging shows an intact pcl computed tomography revealing a large bony avulsion of the tibial attachment of the pcl .
magnetic resonance imaging shows an intact pcl it was concluded that the patient s complaints could be caused by the pseudo - arthrosis of a bony avulsion of the tibial attachment of the pcl ; this was deemed an appropriate indication for pseudo - arthrosis repair .
a single 2-g dose of intravenous ceftazidime was administered . under fluoroscopic control , an entrance point for a 10-mm cannulated drill along the medial aspect of the proximal tibia was located .
a stab - incision was made , and the cannulated drill was inserted and directed cranially and posteriorly towards the centre of the pseudo - arthrosis until the tip of the drill was located just subchondral at the lateral tibial plateau .
3).fig .  3positioning of the cannulated drill and its fluoroscopic verification . removed pseudo - arthrosis shows the fibrous tissue and healthy cancellous bone positioning of the cannulated drill and its fluoroscopic verification . removed
pseudo - arthrosis shows the fibrous tissue and healthy cancellous bone the drill and the collected tissue , consisting of normal cancellous bone and fibrous tissue , were removed .
a similar manoeuvre was performed , only now the 10  mm cannulated drill was directed more posteriorly in order to access more of the pseudo - arthrosis .
the fibrous tissue was separated from the healthy cancellous bone for microscopic evaluation ( fig . 
a combination of the removed cancellous bone mixed with homologous bone was used to fill the defect created by the cannulated drill .
a tibial acl guide was used to guide kirschner wires for two 4.5-mm cannulated partially threaded screws .
4removal of the remaining pseudo - arthrosis using a curette and bone grafting of the defect created by the cannulated drill removal of the remaining pseudo - arthrosis using a curette and bone grafting of the defect created by the cannulated drill there was a good fixation and compression of the avulsed fragment .
radiographic evaluation demonstrated good positioning of the screws with all screw threads in the avulsed bony fragment ( fig . 
5standard radiographs showing positioning of the lag screws and complete disappearance of the pseudo - arthrosis of the bony avulsion of the tibial insertion of the pcl standard radiographs showing positioning of the lag screws and complete disappearance of the pseudo - arthrosis of the bony avulsion of the tibial insertion of the pcl postoperatively , the patient was mobilized immediately with a full leg cylinder plaster cast .
there was no weight bearing for the first 6  weeks followed by full weight bearing without the plaster cast .
three months after surgery , the patient was satisfied with the result of the surgical intervention .
radiographs showed a complete disappearance of the pseudo - arthrosis of the bony avulsion of the tibial insertion of the pcl and good incorporation of the bone graft ( fig . 
in this case , there was a good functional result following minimally invasive pseudo - arthrosis repair of a posterior cruciate ligament avulsion fracture . in displaced bony pcl avulsion injuries ,
there is general consensus that surgical reduction and fixation in the acute phase is indicated to stabilize the joint and prevent non - union .
trickey states that surgical repair of an avulsion the tibial attachment of the pcl after 3  weeks is not successful .
kim et al . reported two patients with non - union tibial avulsion fractures who underwent surgical reduction and fixation 19 and 20  months after the causal trauma .
both were described to have grade c ( abnormal ) function postoperatively according to the assessment with the ikdc form .
in contrast , torisu reported good results in three patients with delayed repair of bony pcl avulsion fractures ; he stated that late repair is recommended .
meyers   reported two patients with delayed treatment of displaced pcl avulsion fractures operated three and 6  months after the initial trauma with good functional results .
reported reduction and screw fixation of a 4.5-year - old displaced pcl avulsion fracture . using a posterior approach and single screw fixation , good stability and function of the knee
the case presented here seems to be rather unique due to the fragment size and the approach for pseudo - arthrosis repair . in this case of a 4-year - old pseudo - arthrosis , it was hypothesized that it would be necessary to remove the pseudo - arthrosis tissue to achieve a solid bone union .
the removal of the pseudo - arthrosis tissue and the filling with homologous bone was deemed easier and safer using a medio - anterior rather than a posterior approach .
a minimally invasive technique was used to reduce soft tissue damage and reduce the risk of injury to the popliteal neurovascular branch .
furthermore , a medio - anterior approach was preferred over a posterior one for optimal screw fixation in the centre of the avulsed bony fragment .
partially threaded screws were chosen to achieve a rigid and stable fixation with compression between the bony avulsion fragment and the proximal tibia .
there are no previous reports of similar pseudo - arthrosis repairs , but good results of delayed refixation of pcl avulsion fractures have been described .
therefore , refixation and pseudo - arthrosis repair should be considered as a viable treatment .
a pseudo - arthrosis repair of a 4-year - old bony avulsion fracture of the pcl using a minimally invasive technique , screw fixation , and bone grafting is reported . 
 the case presented seems to be rather unique due to the fragment size and the approach for pseudo - arthrosis repair . 
 there was a good functional result following minimally invasive pseudo - arthrosis repair of a posterior cruciate ligament avulsion fracture . 
 there are no previous reports of similar pseudo - arthrosis repairs , and other authors report good results of delayed refixation of pcl avulsion fractures . 
 therefore , refixation and pseudo - arthrosis repair should be considered as a viable treatment .