literature analysis showed few articles about this complication , but no publication has described the management of open patella fracture around total knee arthroplasty .
we report a unique case of an open patellar fracture above a total knee arthroplasty , sustained by a 56-year - old female patient .
despite the poor outcome of operative management in patellar periprosthetic fracture , this approach should be considered for acute and post traumatic fractures in young patients with a good remaining bone stock .
the demographic changes with a high rate of aging and active population , as well as the improved life expectancy during the last decades have led to an increase in the number of total knee arthroplasties ( tka ) [ 1 , 2 , 3 , 4 ] , and consequently a raise of post - operative complications . among these complications ,
periprosthetic fracture after tka is the most frequent cause of post - operative pain , and revision surgery .
they may occur in the supracondylar region of the femur , followed by the patella , then the proximal tibia [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] .
this entity can be very challenging to manage , with unpredictable and poor outcome , especially for displaced fracture or in cases with implant loosening [ 1 , 2 , 3 , 4 , 5 , 8 ] . in this article
, we report a unique case of an open periprosthetic patellar fracture that was managed with operative treatment .
it also involves a literature analysis with description of the risk factors and treatment options of this uncommon entity .
a 56-year - old female underwent a cemented postero - stabilized condylar tka with fixed tibial plateau through an antero - medial approach , in our department .
she had severe osteo - arthritis of the left knee with a major stiffness ( irreducible flexum at 25 ) .
initial ( 1 ) and post operative(2 ) knee radiographs before , and after the arthroplasty .
three weeks later , the patient tripped and fell off with all her standing height striking the anterior aspect of the left knee with hyper flexion .
she was taken to the emergency room with left knee pain and a large skin wound .
physical examination showed a large , deep and longitudinal wound measuring 15 cm in length due to a total breakdown of the suture line ( the antero - medial approach performed during the tka ) ( fig . 3 , 4 ) .
fig 3 . a clinical picture showing the open patellar fracture a clinical picture showing the open patellar fracture .
lateral knee radiograph showing the patellar fracture above a total knee arthroplasty , without any signs of implants loosening .
lateral knee radiograph showing the patellar fracture above a total knee arthroplasty , without any signs ofimplants loosening .
the knee radiographs showed a short oblique fracture at the inferior pole of the patella without any loosening of the implants or dislocation of the knee : this fracture is classified as type i according to ortigueraet d.j .
she urgently received intravenous antibiotic ( augmentin , gentamicin ) , as well as tetanus vaccination .
her fracture was temporarily stabilized in a long - leg plaster splint before she was transported to the operating room .
she underwent wound irrigation , debridement of non - viable soft tissue from the wound , open reduction and fixation with a figure - eight cerclage wiring , without any revision of the implants .
the wound was closed without any skin tension , after placing an intra - articular drain .
complementary immobilization with a removable knee pad at full extension , for six weeks was prescribed .
post operative knee radiographs post operative knee radiographs she received intra venous antibiotics : augmentin for 2 weeks associated with gentamicin during the first five days , as well as subcutaneous heparin .
she was discharged from the hospital after she was instructed to remain non - weight bearing with a follow - up in 2 weeks .
at 6 months follow - up , physical examination did not reveal any signs of local or deep infection .
her knee was pain free and she was able to walk without crutches , but she had a mild stiffness : the knee range of motion was 0/60. no antero - posterior or frontal laxities were noted .
clinical pictures at last follow - up showing a clean and dry wound ( 7 ) , and knee range of motion ( 8 , 9 ) clinical pictures at last follow - up showing a clean and dry wound ( 7 ) , and knee range of motion ( 8 , 9 ) .
the patient achieved union of the fracture : knee radiographs showed a healed patellar fracture , with hardware in place .
since the late 1960s , total knee arthroplasty has been the most effective treatment for knee osteoarthritis , providing good functional outcomes and improvement in the patient s quality of life .
constant advances in the joint replacement surgery , and especially the total knee arthroplasties have led to an increase in the number of complications following this type of surgery , such as periprosthetic fractures . [ 1 , 2 , 3 , 4 ] this entity is very challenging to treat even for the most skilled and experienced surgeons [ 7 , 8 , 10 ] .
the femur is the most frequent fracture site , followed by the patella and the tibia [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] .
patella fracture after tka can occur after trauma , or result from a stress fracture due to patella osteonecrosis , which is the most common cause of this type of fracture [ 1 , 2 , 3 , 4 , 5 , 8 , 10 , 11 ] .
chalidis et al ( 2007 ) have reported in a systematic review of a 752 periprosthetic patella fracture that in 88.3% of the cases , the fracture was not associated with a traumatic event , asymptomatic , and discovered during routine follow - up .
many risk factors of these stress fractures have been described in the previous literature [ 1 , 2 , 3 , 4 , 5 , 7 , 8 , 9 , 10 , 11 ] including : 
 poor blood supply for patella after tka especially for antero - medial approach , and in case of lateral release or unwarranted fat pad removal : knee replacement surgery is likely to cause disruption of the vascular peri- patellar network especially the medial and the superior lateral genicular arteries.mal-alignment of the femoral and tibial implantspatella resurfacing arthroplastiesan excessive ( thickness < 15 mm ) or asymmetric bone resection during patella resurfacingosteonecrosis due to bone cement polymerization : the heat of polymerization of the polymethylmethacrylate may exceed the coagulation temperature , causing thermal necrosis of the bonethe use of large central fixation peg designs for patellar implant , instead of small peripheral peg design.revision surgeryosteoporosis and bone losshyperflexion of the kneerhumatod arthritis 
  poor blood supply for patella after tka especially for antero - medial approach , and in case of lateral release or unwarranted fat pad removal : knee replacement surgery is likely to cause disruption of the vascular peri- patellar network especially the medial and the superior lateral genicular arteries . mal - alignment of the femoral and tibial implants patella resurfacing arthroplasties an excessive ( thickness < 15 mm ) or asymmetric bone resection during patella resurfacing osteonecrosis due to bone cement polymerization : the heat of polymerization of the polymethylmethacrylate may exceed the coagulation temperature , causing thermal necrosis of the bone the use of large central fixation peg designs for patellar implant , instead of small peripheral peg design . osteoporosis and bone loss hyperflexion of the knee open patellar fracture above a total knee arthroplasty is a very uncommon injury , and challenging to treat . to our knowledge ,
reported a unique case of patellar fracture associated with open knee dislocation after a total knee arthroplasty .
it was treated with open reduction and internal fixation of the patella with band tension wiring .
greco et al , reported an open tibial shaft fracture below an ipsilateral tka , managed with intramedullary nailing .
some factors should be considered to succeed in the management of this type of fracture such as displacement of the fracture , function of the extensor mechanism , stability of the patellar implant , remaining bone stock [ 1 , 2 , 3 , 4 , 5 , 8 , 9 , 10 , 11 , 13 ] .
it includes immobilization by a brace locked in full extension or a cylinder cast in case of non - operative treatment ; open reduction and internal fixation , implant revision in case of loosening , partial or total patellectomy , repair of the quadriceps tendon or patellar ligament in case of surgical treatment [ 4 , 5 , 7 , 8 ] . the periprosthetic patellar fractures are usually managed by a non - operative treatment especially for type i and ii , because of the high infectious risk of open reduction and internal fixation [ 13 , 14 ] , and consequently a high risk of arthroplasty failure .
literature analysis showed that conservative or non - operative treatment was more successful for the management of non - displaced patella fracture with stable implant and an intact extension mechanism .
ortiguera and berry reported good results in 37 out of 38 peri - prosthetic patellar fractures managed with conservative treatment .
dennis reported a complication rate of 39% of operative treatment ( in a series of thirty one patients who sustained a peri- prosthetic patellar fracture ) .
chalidis s systematic review has shown that open reduction and internal fixation failed in 92% of the cases . in this particular case , we were forced to opt for an internal fixation with a cerclage wiring after intensive wound irrigation , debridement and soft tissue repair .
although no conclusion can be established from a single case report , we think that the successful result in our case can be explained by the relative young age of the patient ( 56 years old ) , the good bone stock , the acute and post - traumatic characteristics of the fracture , the early and adequate management necessary to avoid infectious complication . the surgical management may reduce the ability of patella to heal because of the evacuation of peri - fractural hematoma as well as the supplementary disruption of the vascular network around the patella after a knee replacement surgery .
nevertheless , the high failure rate of the operative treatment in the patellar peri - prosthetic fracture can be explained by : 
 the high proportion of stress , atraumatic fracture ( 88% ) due to osteonecrosis which suggests a poor remaining bone stock.the stress fracture , unlike the acute and post traumatic ones , has a higher risk of non-union.the poor outcome of partial or complete patellectomy , which is a type of operative treatment.in our point of view , the post traumatic fractures in young patients are more likely to heal than stress fractures in the elderly . 
  the high proportion of stress , atraumatic fracture ( 88% ) due to osteonecrosis which suggests a poor remaining bone stock .
the stress fracture , unlike the acute and post traumatic ones , has a higher risk of non - union .
the poor outcome of partial or complete patellectomy , which is a type of operative treatment . in our point of view , the post traumatic fractures in young patients are more likely to heal than stress fractures in the elderly .
peri - prosthetic patella fracture is a very uncommon entity , and challenging to treat , especially the open ones , because of the high risk of infectious complications .
although several previous studies report a high rate of failure and unpredictable results of open reduction for periprosthetic patellar fracture , this approach ( especially the internal fixation with a strong and dynamic construct ) should be considered in young patients with a good remaining bone stock , who sustained an open or a displaced fracture after a high energy trauma .
orthopaedic surgeons should consider open reduction and internal fixation as a good management alternative for periprosthetic patellar fracture , in case of a post traumatic and acute fracture in young patients with a good bone stock .
 introduction : periprosthetic patellar fracture after total knee arthroplasty ( tka ) is a rare complication 
 . their management can be very challenging with unpredictable results . 
 literature analysis showed few articles about this complication , but no publication has described the management of open patella fracture around total knee arthroplasty.case presentation : we report a unique case of an open patellar fracture above a total knee arthroplasty , sustained by a 56-year - old female patient.conclusion:despite the poor outcome of operative management in patellar periprosthetic fracture , this approach should be considered for acute and post traumatic fractures in young patients with a good remaining bone stock . 
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