computer - assisted surgery has been popularized in orthopedic surgery in the last 10 years . whilst a number of recent randomized control trials have shown some benefit in terms of implant position over conventional jig - based referencing,1
many navigation systems require the use of reference arrays , which are fixed to the tibia and femur with pins .
a 58-year - old man with a diagnosis of varus osteoarthritis ( oa ) of the right knee underwent navigated total knee arthroplasty ( tka ) using standard technique .
we use a passive reflector - based system ( brainlab , feldkirchen , germany ) with fixation of the femoral reference array using two 3-mm - diameter threaded pins .
these are inserted anteriorly through stab incisions , with the knee in flexion , as proximally as the tourniquet will allow .
tibial pins are inserted in the mid diaphysis into the subcutaneous surface of the tibia [ figure 1 ] .
all pins are bicortical in order to maintain secure fixation for the duration of surgery .
peroperative photographs ( a ) insertion of tibial and femoral reference arrays ( b ) the styloid used to map out the tibia and femur computer registration is performed with digitalization of the hip and ankle centers and specific landmarks of the knee . a size 6 generation ii cemented femoral implant and a size 6 generationii cemented tibial component were implanted with an 11-mm polyethylene insert .
the patient had some pain and thigh swelling postoperatively , but this was considered to be in keeping with recent surgery .
he was discharged on the third postoperative day , having satisfied physiotherapy and occupational therapy goals .
he reported 3 days later with increased right thigh pain , swelling , and a limited range of movement .
an ultrasound guided diagnosis of a quadriceps hematoma at the site of the femoral pins was made .
this was confirmed by computerized topography ( ct ) with intravenous contrast [ figure 2 ] , which showed a large quadriceps hematoma and active bleeding into the femoral canal from a branch of the superficial femoral artery as it entered linea aspera at the site of pin insertion .
two ct scan images showing active bleeding into the femoral canal on day 10 , the hematoma was evacuated and two 14-mm unicortical screws were inserted into the femur at the site of the bleed to tamponade the bleed .
unicortical screws were used to reduce the risk of further arterial injury with bicortical screws and the ct scan also showed unicortical injury . at 2 weeks post presentation
he then had a flexion of 090 , but also had some persistent swelling and was prescribed a short course of diazepam .
he showed continued improvement since the second operation and had no further complications at the final followup 6 months later [ figure 3 ] .
computer navigated tka has the potential advantage of improved implant position , which is known to reduce the rate of aseptic loosening .
there have been a number of studies reporting complications of computer navigated tka among these .
bhling et al.,9 chin et al.,10 and bthis et al.11 demonstrated longer tourniquet time with computer navigation .
kalairajah et al.12 reported a longer tourniquet time as well as a statistically significant decrease in blood drainage .
chauhan et al.13 and jenny et al.4 found that computerized navigation was associated with a longer operating time .
stckl et al.14 reported one case of poor tibial tracker stability , related to osteoporotic bone , resulting in abandonment of computer navigation , from 64 patients .
hernadez - vaquero15 reported four cases of failed pin fixation ( three iliac crest and one femur ) requiring abandonment of computer navigation from a total of 112 patients .
our report is the only case of arterial injury in the literature related to navigation pin usage .
if the patient develops an unexpected postoperative swelling with increasing pain this diagnosis needs to be taken into consideration .
 the use of computer navigation has the potential to improve implant position in total knee arthroplasty ( tka ) , but pin fixation of reference arrays introduces an additional potential source of complications . 
 we report a case of vascular injury related to the insertion of a femoral pin during navigated tka . 
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