infection is probably the most dangerous and feared complication after total hip arthroplasty ( tha ) . since timely treatment is mandatory to increase the chance of success , careful patient monitoring and prompt irrigation and debridement of possibly infected wounds are essential .
absorbable sutures are widely used for wound closure after tha , and vicryl plus ( ethicon , johnson & johnson ) combines the features of a well known absorbable suture ( vicryl ) with a broad - spectrum antibacterial agent ( triclosan ) .
a few cases of adverse reactions to vicryl / vicryl plus have reported to date   in contrast with the worldwide circulation of these products in most fields of surgery ; however , interestingly , three cases were described as mimicking infection after tha . the present paper aims to present another two cases , whose clinical history , histopathological and laboratory findings are so distinctive ( and consistent with previous reports ) as to define a novel , exceptional tha complication , the  suture - related pseudoinfection ( srpi ) .
a 63-year - old woman with displaced femoral neck fracture of the left hip underwent cementless ceramic - on - ceramic tha through straight lateral approach .
the patient had no relevant risk factors for infection ( immunocompetent , non - diabetic with normal body mass index and no history of recent infections ) except light smoking ( less than 10 cigarettes per day ) , and surgery was completed within 80  min .
antibiotic prophylaxis was obtained with a short intravenous course of cefazolin ( 2  g before operation , followed by 1  g 61422  h later ) .
the trochanteric digastrics tendon split and the fascial incision were sutured with vycril plus # 2 , while subcutaneous tissue was sutured with vycril plus # 2 and # 0 in the deep layer and vycril plus # 2/0 in the superficial layer .
two deep suction drains were maintained for 48  h and removed at first dressing change .
the post - operative course was uneventful : body temperature normalized ( below 37  c ) 2  days after surgery , the wound was dry with no signs of inflammation or hematoma , c - reactive protein ( crp ) levels halved every 2  days , and the hip was mobile and pain - free .
the patient was therefore discharged home 8  days after surgery . on the 14th postoperative day
skin staples were removed and on the fifth week the patient was seen in the outpatient clinic ; x - rays and clinical examination were extremely satisfactory , and she was allowed to abandon her crutches and to resume ordinary life activities . in the ninth week from index surgery the patient , previously pain - free , started to complain of tenderness , warmth and redness of the skin around the scar .
she was examined immediately after symptom onset and a minimal seropurulent discharge was noticed from a small sinus , which was carefully dilated with a sterile swab , allowing the exudate to drain and microbiological samples to be collected ( with negative results ) .
blood tests detected mildly elevated crp ( 1.4  mg / dl ) and erythrocyte sedimentation rate ( esr ) ( 60  mm / h ) , but no elevation of white blood cell ( wbc ) count .
ultrasonographic ( us ) examination of the hip demonstrated an abscess in the deep layer of the hypodermis , with several sinus tracts towards the surface .
the presence of local signs ( warmth , redness , swelling , tenderness and fluid discharge ) , us signs ( abscess ) and laboratory signs ( elevated crp ) of surgical site infection convinced us to schedule immediate irrigation and debridement ( i d ) within 1  week from complication onset .
the debridement was performed through the pre - existing scar , with excision of multiple sinus tracts .
a massive abscess , with purulent grey - yellowish content , was retrieved in the deep subcutaneous tissue , extending along the whole incision .
after culture and histological sampling , the cavity was debrided and irrigated with diluted iodopovidone and saline solution .
the fascia , apparently intact , was then incised and the pertrochanteric space was inspected . since no signs of infection were retrieved below the fascia , surgical gowns , gloves and instruments were replaced before splitting the digastrics tendon and opening the periprosthetic capsule ; within the joint just a few milliliters of clear fluid were found .
thorough irrigation was performed after microbiological sampling . since the infection seemed not to have spread below the fascia , and given the risk of ceramic rupture associated with head and liner exchange , no attempt was made to remove them .
the wound was closed in a standard fashion , but employing as few sutures as possible so as not to leave an excessive amount of foreign material in a potentially infected surgical site , and two suction drains ( whose tips were sent to the microbiology laboratory for further cultures ) were placed . during the procedure , immediately after culture sampling , an empirical course of antibiotics was started ( teicoplanin 800  mg and levofloxacin 1  g i.v . ) and was confirmed postoperatively ( teicoplanin 600  mg q.d . and levofloxacin 500  mg b.i.d . ) . on the first postoperative day the patient was already pain - free , her body temperature normalized and the wound healed regularly .
crp stayed within the range throughout the hospitalization , after normalizing with sinus drainage 3  days before surgery .
no cultures were positive , but given the strong suspicion of infection and the absence of adverse reactions to antibiotics , the patient was discharged home 7  days after i d with an oral 4-week therapy ( cotrimoxazole 800  mg/160  mg b.i.d . and levofloxacin 500  mg q.d . ) .
the histological examination of the collected material demonstrated a giant - cell foreign - body reaction , where some amorphous birefringent material was clearly visible ( fig . 
gc giant cell , fb foreign body ( haematoxylin and eosin , original magnification 200 ) foreign - body reaction in the superficial hypodermis .
gc giant cell , fb foreign body ( haematoxylin and eosin , original magnification 200 ) even though the patient was asymptomatic , she was followed up monthly with physical examinations and blood tests ( fig . 
2 ) , and 8  weeks after i d another mild crp elevation ( 1.6  mg / dl ) was noticed without reasonable causes , except minimal scar inflammation and extrusion of suture material .
the wound was treated with iodopovidone solution and daily dressing change and healed in a week after complete extrusion of the foreign material .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) c - reactive protein kinetics of patient # 1 .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) a 64-year - old woman affected by bilateral hip osteoarthritis underwent cementless ceramic - on - ceramic right hip tha through straight lateral approach .
she had no relevant risk factors for infection , surgery was uncomplicated and lasted about 70  min .
the same antibiotic prophylaxis , surgical technique and suture materials were employed as in case # 1 . the post - operative course was similarly uneventful : body temperature never exceeded 37  c , the wound was dry with no signs of inflammation or hematoma , crp fell within the normal range in 12  days , and the hip was mobile and pain - free .
the patient was therefore discharged to the rehabilitation facility as soon as an inpatient rehab bed was available , 8  days after surgery .
on the 15th postoperative day skin staples were removed , she returned home and on the fifth week the patient was seen in the outpatient clinic with excellent functional recovery and x - rays .
she was allowed to abandon her crutches and to resume ordinary life activities . in the eighth week after tha , almost as in case # 1 , the patient , previously pain - free , started complaining of tenderness , warmth and redness of the scar , with mild elevation of body temperature ( 37.5  c ) .
she was seen 3  days after symptom onset and no drainage was noticed from the scar , but it was extremely painful on palpation .
blood tests detected mildly elevated crp ( 1.5  mg / dl ) and esr ( 50  mm / h ) , but no wbc count elevation .
ultrasonographic examination of the hip demonstrated a bulky pertrochanteric abscess , with several sinus tracts perforating the fascia towards the surface .
the presence of local signs ( warmth , redness , swelling and tenderness ) , us signs ( abscess ) and laboratory signs ( elevated crp ) of surgical site infection persuaded us to schedule prompt reoperation for i d .
the debridement was performed through the pre - existing scar and a massive abscess , with purulent grey - yellowish material , was retrieved in the deep hypodermis .
several fistulae perforated the fascia and allowed the exudates to spread in the pertrochanteric space .
after culture and histological sampling , the cavity was debrided and irrigated with diluted iodopovidone and saline solution .
the fascia was then incised , trans - fascial fistulae excised and the pertrochanteric space debrided and irrigated similarly .
since the abductor mechanism seemed to be intact and the preoperative us examination did not show joint space effusion , surgical gowns , gloves and instruments were replaced before splitting the digastrics tendon and opening the joint capsule ; the same healthy periprosthetic environment was found as in case # 1 .
the procedure was completed as previously described , with microbiological sampling , careful joint irrigation but without head / liner exchange , and administering the same intravenous empirical antibiotic therapy . on the first postoperative day
no cultures ( either intraoperative or postoperative on drainage tube tips ) were positive , but given the strong suspicion of infection and the absence of adverse reactions to antibiotics , the patient was discharged home 13  days after i d with an oral 4-week therapy ( amoxicillin 1  g t.i.d . and levofloxacin 500  mg q.d . ) .
histological examination of the material collected showed the same pattern of foreign - body reaction : a mixed inflammatory cell infiltrate , with multinucleated giant cells and amorphous birefringent material ( fig . 
3).fig .  3foreign - body reaction in the superficial ( a ) and deep ( b ) hypodermis .
gc giant cell , fb foreign body , vs vascular space ( haematoxylin and eosin , original magnification 400 ) foreign - body reaction in the superficial ( a ) and deep ( b ) hypodermis .
gc giant cell , fb foreign body , vs vascular space ( haematoxylin and eosin , original magnification 400 ) during the postoperative clinical and laboratory follow - up ( fig . 
4 ) , the patient demonstrated an elevated crp ( 1.3  mg / dl ) 5  weeks after reoperation , associated with suture material extrusion .
frequent wound care allowed complete recovery and renormalization of crp within 2  weeks , without any further recurrence.fig . 
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) c - reactive protein kinetics of patient # 2 .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) fourteen months after right hip tha , the patient , satisfied with the previous joint replacement despite the complication , requested left hip tha as originally planned . in order to minimize the risk of foreign - body reaction , a different suture material with no colouring or antibacterial agents was selected ( undyed polysorb ) , and the closure was performed using as few and as thin sutures as possible . from the sixth to the ninth postoperative week
the patient complained about suture material extrusion through the scar and mild local tenderness , but no blood test abnormalities , ultrasonographically detectable abscess or significant functional impairment occurred .
two years after the first joint replacement and 10  months after the second one , the patient is extremely satisfied with her bilateral tha .
a 63-year - old woman with displaced femoral neck fracture of the left hip underwent cementless ceramic - on - ceramic tha through straight lateral approach .
the patient had no relevant risk factors for infection ( immunocompetent , non - diabetic with normal body mass index and no history of recent infections ) except light smoking ( less than 10 cigarettes per day ) , and surgery was completed within 80  min .
antibiotic prophylaxis was obtained with a short intravenous course of cefazolin ( 2  g before operation , followed by 1  g 61422  h later ) .
the trochanteric digastrics tendon split and the fascial incision were sutured with vycril plus # 2 , while subcutaneous tissue was sutured with vycril plus # 2 and # 0 in the deep layer and vycril plus # 2/0 in the superficial layer .
two deep suction drains were maintained for 48  h and removed at first dressing change .
the post - operative course was uneventful : body temperature normalized ( below 37  c ) 2  days after surgery , the wound was dry with no signs of inflammation or hematoma , c - reactive protein ( crp ) levels halved every 2  days , and the hip was mobile and pain - free .
the patient was therefore discharged home 8  days after surgery . on the 14th postoperative day
skin staples were removed and on the fifth week the patient was seen in the outpatient clinic ; x - rays and clinical examination were extremely satisfactory , and she was allowed to abandon her crutches and to resume ordinary life activities . in the ninth week from index surgery the patient , previously pain - free , started to complain of tenderness , warmth and redness of the skin around the scar .
she was examined immediately after symptom onset and a minimal seropurulent discharge was noticed from a small sinus , which was carefully dilated with a sterile swab , allowing the exudate to drain and microbiological samples to be collected ( with negative results ) .
blood tests detected mildly elevated crp ( 1.4  mg / dl ) and erythrocyte sedimentation rate ( esr ) ( 60  mm / h ) , but no elevation of white blood cell ( wbc ) count .
ultrasonographic ( us ) examination of the hip demonstrated an abscess in the deep layer of the hypodermis , with several sinus tracts towards the surface .
the presence of local signs ( warmth , redness , swelling , tenderness and fluid discharge ) , us signs ( abscess ) and laboratory signs ( elevated crp ) of surgical site infection convinced us to schedule immediate irrigation and debridement ( i d ) within 1  week from complication onset .
the debridement was performed through the pre - existing scar , with excision of multiple sinus tracts .
a massive abscess , with purulent grey - yellowish content , was retrieved in the deep subcutaneous tissue , extending along the whole incision .
after culture and histological sampling , the cavity was debrided and irrigated with diluted iodopovidone and saline solution .
the fascia , apparently intact , was then incised and the pertrochanteric space was inspected . since no signs of infection were retrieved below the fascia , surgical gowns , gloves and instruments were replaced before splitting the digastrics tendon and opening the periprosthetic capsule ; within the joint just a few milliliters of clear fluid were found .
thorough irrigation was performed after microbiological sampling . since the infection seemed not to have spread below the fascia , and given the risk of ceramic rupture associated with head and liner exchange , no attempt was made to remove them .
the wound was closed in a standard fashion , but employing as few sutures as possible so as not to leave an excessive amount of foreign material in a potentially infected surgical site , and two suction drains ( whose tips were sent to the microbiology laboratory for further cultures ) were placed . during the procedure , immediately after culture sampling , an empirical course of antibiotics was started ( teicoplanin 800  mg and levofloxacin 1  g i.v . ) and was confirmed postoperatively ( teicoplanin 600  mg q.d . and levofloxacin 500  mg b.i.d . ) . on the first postoperative day the patient was already pain - free , her body temperature normalized and the wound healed regularly .
crp stayed within the range throughout the hospitalization , after normalizing with sinus drainage 3  days before surgery .
no cultures were positive , but given the strong suspicion of infection and the absence of adverse reactions to antibiotics , the patient was discharged home 7  days after i d with an oral 4-week therapy ( cotrimoxazole 800  mg/160  mg b.i.d . and levofloxacin 500  mg q.d . ) .
the histological examination of the collected material demonstrated a giant - cell foreign - body reaction , where some amorphous birefringent material was clearly visible ( fig . 
gc giant cell , fb foreign body ( haematoxylin and eosin , original magnification 200 ) foreign - body reaction in the superficial hypodermis .
gc giant cell , fb foreign body ( haematoxylin and eosin , original magnification 200 ) even though the patient was asymptomatic , she was followed up monthly with physical examinations and blood tests ( fig . 
2 ) , and 8  weeks after i d another mild crp elevation ( 1.6  mg / dl ) was noticed without reasonable causes , except minimal scar inflammation and extrusion of suture material .
the wound was treated with iodopovidone solution and daily dressing change and healed in a week after complete extrusion of the foreign material .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) c - reactive protein kinetics of patient # 1 .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl )
a 64-year - old woman affected by bilateral hip osteoarthritis underwent cementless ceramic - on - ceramic right hip tha through straight lateral approach .
she had no relevant risk factors for infection , surgery was uncomplicated and lasted about 70  min .
the same antibiotic prophylaxis , surgical technique and suture materials were employed as in case # 1 .
the post - operative course was similarly uneventful : body temperature never exceeded 37  c , the wound was dry with no signs of inflammation or hematoma , crp fell within the normal range in 12  days , and the hip was mobile and pain - free .
the patient was therefore discharged to the rehabilitation facility as soon as an inpatient rehab bed was available , 8  days after surgery . on the 15th postoperative day
skin staples were removed , she returned home and on the fifth week the patient was seen in the outpatient clinic with excellent functional recovery and x - rays .
she was allowed to abandon her crutches and to resume ordinary life activities . in the eighth week after tha , almost as in case # 1 , the patient , previously pain - free , started complaining of tenderness , warmth and redness of the scar , with mild elevation of body temperature ( 37.5  c ) .
she was seen 3  days after symptom onset and no drainage was noticed from the scar , but it was extremely painful on palpation .
blood tests detected mildly elevated crp ( 1.5  mg / dl ) and esr ( 50  mm / h ) , but no wbc count elevation .
ultrasonographic examination of the hip demonstrated a bulky pertrochanteric abscess , with several sinus tracts perforating the fascia towards the surface .
the presence of local signs ( warmth , redness , swelling and tenderness ) , us signs ( abscess ) and laboratory signs ( elevated crp ) of surgical site infection persuaded us to schedule prompt reoperation for i d .
the debridement was performed through the pre - existing scar and a massive abscess , with purulent grey - yellowish material , was retrieved in the deep hypodermis .
several fistulae perforated the fascia and allowed the exudates to spread in the pertrochanteric space .
after culture and histological sampling , the cavity was debrided and irrigated with diluted iodopovidone and saline solution .
the fascia was then incised , trans - fascial fistulae excised and the pertrochanteric space debrided and irrigated similarly . since the abductor mechanism seemed to be intact and the preoperative us examination did not show joint space effusion , surgical gowns , gloves and instruments were replaced before splitting the digastrics tendon and opening the joint capsule ; the same healthy periprosthetic environment was found as in case # 1 .
the procedure was completed as previously described , with microbiological sampling , careful joint irrigation but without head / liner exchange , and administering the same intravenous empirical antibiotic therapy . on the first postoperative day
no cultures ( either intraoperative or postoperative on drainage tube tips ) were positive , but given the strong suspicion of infection and the absence of adverse reactions to antibiotics , the patient was discharged home 13  days after i d with an oral 4-week therapy ( amoxicillin 1  g t.i.d . and levofloxacin 500  mg q.d . ) .
histological examination of the material collected showed the same pattern of foreign - body reaction : a mixed inflammatory cell infiltrate , with multinucleated giant cells and amorphous birefringent material ( fig . 
3).fig .  3foreign - body reaction in the superficial ( a ) and deep ( b ) hypodermis .
gc giant cell , fb foreign body , vs vascular space ( haematoxylin and eosin , original magnification 400 ) foreign - body reaction in the superficial ( a ) and deep ( b ) hypodermis .
gc giant cell , fb foreign body , vs vascular space ( haematoxylin and eosin , original magnification 400 ) during the postoperative clinical and laboratory follow - up ( fig .  4 ) ,
the patient demonstrated an elevated crp ( 1.3  mg / dl ) 5  weeks after reoperation , associated with suture material extrusion .
frequent wound care allowed complete recovery and renormalization of crp within 2  weeks , without any further recurrence.fig . 
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) c - reactive protein kinetics of patient # 2 .
the two grey vertical lines represent the procedures ( tha and i d ) , while the grey horizontal line represents the highest value of the normal crp range ( 1  mg / dl ) fourteen months after right hip tha , the patient , satisfied with the previous joint replacement despite the complication , requested left hip tha as originally planned . in order to minimize the risk of foreign - body reaction , a different suture material with no colouring or antibacterial agents was selected ( undyed polysorb ) , and the closure was performed using as few and as thin sutures as possible . from the sixth to the ninth postoperative week the patient complained about suture material extrusion through the scar and mild local tenderness , but no blood test abnormalities , ultrasonographically detectable abscess or significant functional impairment occurred .
two years after the first joint replacement and 10  months after the second one , the patient is extremely satisfied with her bilateral tha .
the two cases presented demonstrate that an adverse reaction to an absorbable suture after total hip replacement might determine a clinical condition that can not be reliably differentiated from a surgical site infection .
both cases were standard , uncomplicated procedures performed on low - risk patients , had an uneventful early postoperative course with no complaints up to the 8th9th postoperative week .
they then developed local , systemic , us and laboratory signs of surgical site infection .
although no positive cultures were available , i d could not have been questioned or delayed , given the high probability of infection and the negative prognostic impact of the elapsed time [ 1 , 4 , 5 ] .
because of this latter concern , joint aspiration was not attempted and both hips were quickly reoperated .
the patients had a mild recurrence 8 and 5  weeks , respectively , after i d , likely because the same suture material was used as in the primary surgery , but in a smaller amount .
however , knowledge of the histological diagnosis , awareness of having reused the suture material that elicited the first foreign - body reaction , and the similar presentation and timing suggested that we provide simple wound care , without any surgical or antibiotic treatment , and the relapses self - healed without any consequences . to the best of our knowledge
, only three other cases of adverse reaction to suture material mimicking a periprosthetic joint infection have been reported to date , by sayegh and coworkers   ( table  1 ) .
those three patients received the same resorbable suture as in our series , but without antibacterial agent ( vicryl instead of vicryl plus ) .
interestingly , the timing is almost identical : 8 and 7  weeks after index sugery in our series ( with recurrences 8 and 5  weeks after i d , respectively ) ; 6 , 8 and 9  weeks after index surgery in sayegh et al.s series ( with no mention of possible relapses ) . on the other hand , the eosinophilia described by sayegh et al .
was not confirmed in our two patients , who showed a normal total wbc count , with minor elevation of neutrophil percentage but normal neutrophil count .
eosinophils were within the normal range for percentage and for count . while the three previously described patients had an extensive involvement of all the layers from the hypodermis to the intracapsular space , our two patients had a relatively superficial involvement , with no penetration of the glutei muscle cuff .
we believe that this might depend on capsular repair , which we never performed after a straight lateral approach , but might have been performed by sayegh and coworkers , especially if a posterolateral approach was used . however , this explanation is conjectural , since surgical approach and capsular repair are not mentioned by the above authors.table  1synoptic table summarizing the main clinical information from the three cases reported by sayegh et al .  
( i , ii and iii ) and the two cases presented here ( iv and v)iiiiiiiv ( # 1)v ( # 2)suture materialvicryl 
 vicryl 
 vicryl 
 vicryl plus 
 vicryl plus 
 presentation time ( weeks after surgery)89687local inflammation+++++draining sinus+++body temperature ( c)37.93739<3737.5crpelevatedelevatedelevatedelevatedelevatedwbcnormal with eosinophilianormal with eosinophilianormal with eosinophilianormalnormalabscess locationextensive ( from subcutaneous to intracapsular)extensive ( from subcutaneous to intracapsular)extensive ( from subcutaneous to intracapsular)superficial ( prefascial)superficial and intermediate ( pre- and subfascial , with no extension through the glutei muscles)recurrencenot mentionednot mentionednot mentionedyes ( 8  weeks later)yes ( 5  weeks later ) synoptic table summarizing the main clinical information from the three cases reported by sayegh et al .  
( i , ii and iii ) and the two cases presented here ( iv and v ) the two cases presented are the first suture - related pseudoinfections whose recurrence after absorbable suture material re - implantation is documented
. similar timing but different extents between first episode and recurrence confirm the hypothetical aetiopathogenesis , since the same material was used but in different amounts .
all the reported five patients had the wound closed with coated vicryl , a synthetic suture material made of polyglactin 910 , which is a copolymer obtained from 90  % glycolide and 10  % l - lactide .
its resorption is completed by hydrolysis within 5670  days from implantation ( which corresponds perfectly to the latency of the psuedoinfection ) .
it is used worldwide in most surgical fields , and recently became available associated with an antibacterial agent , triclosan ( vicryl plus ) .
few adverse reactions have been reported to date : holzheimer described inflammation and occasional sinus discharge in 12 patients after subcutaneous suture with vicryl or vicryl plus and skin closure with dermabond glue in patients operated for hernia , varicose veins and soft tissue tumors .
the complication occurred 38  weeks after the index procedure , and only in two patients was an infection demonstrated .
local inflammation after wound healing is likely under - reported , since suture extrusion is a common and benign complication of surgical wounds , often overlooked by patients and general practitioners .
drake and coworkers   clearly demonstrated that this phenomenon depends both on the material ( vicryl is more prone to extrusion than polysorb ) and on the volume ( the more knots , the higher the risk ) . on the other hand , some cases of foreign - body reactions to suture material might have been classified as surgical site infection with false - negative cultures , since histological samples are not routinely collected by all surgeons .
it is well known that preoperative culture sensitivity is only fair ( 0.70 from joint aspiration in infected tha according to qu et al . , and possibly lower from sinus discharge swabs ) , and even intraoperative culture sensitivity is suboptimal ( 0.94 according to spangehl et al . ) .
dealing with a supposed periprosthetic joint infection with no positive cultures is thus not an exceptional experience for orthopaedic surgeons .
however , in the presented  cases several elements make occult infection extremely unlikely : multiple cultures ( preoperative swabs , three intraoperative samples and postoperative cultures on drain tips ) were negative without any preoperative antibiotic administration , the histological examination found a mixed inflammatory infiltrate with lymphomonocytes prevailing over neutrophils , and the relapses self - healed after complete suture absorption or extrusion . remarkably , in our patient # 2 , who received a subsequent contralateral tha sutured with undyed polysorb , made of lactomer ( another glycolide / lactide copolymer ) coated with a mixture of a caprolactone / glycolide copolymer and calcium stearoyl lactylate , the absorption phase was not uneventful , although the reaction was milder than after the first surgery .
the role of the suture material therefore seems to be important , but likely less important than the patient s aptitude to foreign - body reaction . in conclusion ,
the five cases described to date allow us to define a somewhat novel complication of total hip replacement , the suture - related pseudoinfection ( srpi ) .
srpi is characterized by local and systemic signs of inflammation occurring 69  weeks after tha , when sutures are absorbed .
a sterile abscess is usually located in the subcutaneous tissue , with possible superficial seropurulent drainage and deep extension through the fascia .
the phenomenon can not be reliably differentiated from a postoperative infection at the time of its presentation , and only the negative result of all the microbiological samples , the benign course and the histological examination allow the differential diagnosis , which is always ex post .
thus , even though this complication might possibly self - heal after complete absorption of the foreign material , we strongly advice against nonsurgical management , which would surely worsen the prognosis of a true , more common postoperative infection . the awareness of this exceptional phenomenon leads to some clinical considerations .
first , the principle that only early periprosthetic joint infections are eligible for simple irrigation and debridement should not be overemphasized .
if strict exclusion criteria were applied [ 4 , 912 ] , some of the reported five patients might have been candidates for two - stage revision arthroplasty , since more than 6  weeks had elapsed from implantation and no microbiological diagnosis was available . the acute onset and the short interval from onset to treatment , rather than from implantation to onset , should be considered a relevant positive factor in favour of a prosthesis - sparing surgery .
second , histological specimens should always be collected when potential periprosthetic joint infections are debrided .
third , the smallest possible volume of suture material should be left in every wound , especially in the subcutaneous tissue , where little tensile strength is required and foreign - body reactions seem to be more devastating due to extensive fat necrosis . in our routine surgical practice , deep subcutaneous suture after tha is now obtained with # 0 suture only ( instead of using two or three # 2 stitches ) , and the number of knots has been reduced from four to three .
fourth , if a srpi is suspected , closing the wound after i d with a suture material with low propensity to induce foreign - body reaction might lower the chance and the severity of possible recurrences .
 absorbable sutures are widely used for wound closure after total hip replacement . here 
 we present two cases of suture - related foreign - body reaction that perfectly mimicked a periprosthetic joint infection , with sterile abscess formation and physical and laboratory signs of inflammation acutely presenting 78  weeks after surgery , at the time of suture absorption . 
 both recurred with analogous timing after irrigation and debridement , likely due to re - using the same suture material . 
 multiple negative microbiological samples and positive histological samples showing a foreign - body reaction are the fundamental steps towards the diagnosis of a suture - related pseudoinfection ( srpi ) . 
 only three other cases have been reported to date , but the recurrence , together with the self - healing course after relapse , represents a completely novel feature and possibly the strongest demonstration of the supposed aetiopathogenesis . 
 the knowledge of this possible complication leads to some clinical implications : all potential periprosthetic joint infections should routinely undergo not only microbiological but also histological sampling ; caution should be used when recommending prosthesis exchange for potential infections occurring in the time range of suture absorption ; lastly , if srpi is suspected , a suture with low propensity to induce foreign - body reactions should be chosen after irrigation and debridement and the volume of absorbable material left in the wound should be as small as possible . 
Introduction
Case report
Case #1
Case #2
Discussion