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Pelvic discontinuity in acetabular revision surgery
Abstracts from the AAHKS Seventh Annual Meeting Our study suggested that despite concerns regarding weaker bone quality and the existence of comorbidities such as osteoporosis or other metabolic disorders, uncemented acetabular components functioned well in an elderly population, producing results that were comparable to those seen in a younger comparison group. In fact, there was a lower incidence of both radiolucent lines and polyethylene wear in the elderly group when compared to the younger population, which could have been attributed to decreased mechanic demands on the components. We conclude that advanced age at the time of index surgery does not appear to be a contraindication for the use of uncemented aeetabular components.
PAPER # 10 *ACETABULAR RECONSTRUCTION WITH POROUS COMPONENTS IN DYSPLASTIC HIPS U S I N G A MODIFIED HESS PROTRUSIO SOCKET TECHNIQUE Samer N. Tawakkol, MD, Los Angeles, CA, William Long, MD, Lawrence Dorr, MD Introduction: Total hip replacement in patients with DDH is a challenging and complex operation. The purpose of this study is that cementless acetabular fixation with a modified Hess protrusio technique provides predictable and durable fixation. Materials and Methods: Twenty-nine patients with 36 dysplastic hips were operated with THR by one surgeon. Hemispherical porous coated noncemented acetabular components were used in 32 hips. Patients were followed for an average 6.3 years (five years - 12.5 years). The first eight of these hips were operated with a technique which preserved the medial wall and used a bone graft as necessary to cover superior and lateral defects. In 22 hips protrusio technique was performed to permit creation of a hemispheric acetabular cavity which provided a stable press fit of the acetabular component without the necessity of bone graft. The mean age at the time of the index operation was 45 years (range 22 to 69 years). The Ranawat triangle, femoral head subluxation by the Crowe classification and the medial wall thickness from Kohler's line were measured preoperatively. The acetabular component in relationship to Ranawat's triangle and protrusio beyond Kohler's line, theta angle, and coverage of the bone graft was measured postop. Results: The acetabular revision rate for the study was 6.2 percent at average 6.3 years. Twelve hips were classified as Crowe Grade I, eight as Grade II, eight as Grade III, and eight as Grade IV. With this technique the average mediallzation of the cup beyond Kohler's line was 1 m m for Crowe I and II, 2.6 m m for Crowe HI and 1 m m for Crowe IV. Crowe IV deformities are always reconstructed at the true acetabulum. The bony coverage of the cup laterally was more than 90% in all 24 hips. The femoral head autograft covered less than 30% of the cup in all eight hips. Twenty-two hips were implanted with the protrusio technique and none of these hips have been revised or were loose or had migrated. Discussion: This study demonstrates that acetabular reconstruction in patients with hip dysplasia can be accomplished using cementless fixation. None of the non-cemented cups implanted with the protrusio technique have been revised. The absence of revision is not a superior revision rate when compared to cemented Charnley components at the same time postoperatively. However, cemented Charnley components at the same time do have a higher radiographic loosening rate. Predictable fixation can be obtained with the protmsio technique which does provide the principles of implantation for a hemispherical porous coated acetabular component. This study confirms that bone graft coverage of 30% or less provide a stable construct.
225
PAPER # 11 *CEMENTLESS ACETABULAR REVISION ARTHROPLASTY WITH A POROUS, TITANIUM, MODULAR HEMISPHERICAL COMPONENT Christopher W. Olcott, MD, Rochester, NY, David A. Mattingly, ME), Benjamin E. Bierbanm, ME) Although a fixed, porous-coated, hemispherical acetabular component has become the standard in most revision situations, intermediate and longterm results of such components are limite& The purpose of this study was to assess the efficacy of a cementless acetabular component in revision hip arthroplasty at a range of four-to-ten years. Between December 1987 and March 1992,150 consecutive acetabular revisions were performed by two surgeons. In each case, a hemispherical titanium acetabular shell coated with titanium beads was implanted with or without supplemental dome screw fixation. At a mean follow-up of 6.3 years (range 4 - 10 years), 119 acetabular revisions were available for clinical and radiographic review. Fifty-six of the 119 hips had simultaneous femoral revisions. Each patient was either interviewed or answered a questionnaire for determination of a Harris hip score. Immediate postoperative radiographs were compared to most recent follow-up films for bony fixation, migration, wear and osteolysis. The average postoperative Harris hip score improved to eighty-one from forty-two preoperatively. Twenty-six hips (21.8%) h a v e u n d e r g o n e reoperations: eight (6.7%) for instability, seven (5.9%) for femoral revision, four (3.4%) for reexploration (debridement heterotopic ossification / removal of hardware), two (1.7%) for infection, one (0.8%) for early postoperative migration at three weeks and four (3.4%) for aseptic loosening. Although a variety of femoral components were used in conjunction with this acetabular shell, those with osteolysis and those requiring revision were noted. Seven femoral stems (5.9%) were re'~'ised and another twenty-five demonstrated some degree of osteolysis confined primarily to the proximal zones. Acetabular osteolysis evident in eleven hips was not extensive enough to warrant re-revision. Acetabular liner exchange was performed in the seven hips requiring femoral revision and three hips with instability. Radiographic evidence of acetabular migration was noted in seven hips (6.5%); six of which were associated with a bulk, structural allograft. The results of this cementless, titanium, hemispherical acetabular component outperform those of cemented cups at similar follow-up and compare favorably with other cementless designs. A good clinical and radiographic outcome support its continued use in acetabular revision surgery.
PAPER # 12 PELVIC DISCONTINUITY IN ACETABULAR REVISION SURGERY Daniel J. Berry, MD, Rochester,MN, Arlen D. Hanssen, MD, David G. Lewallen, MD, Miguel E. Cabanela, MD Introduction: Pelvic discontinuity (AAOS Type W bone deficiency, defined as discontinuity between the ihum superiorly and the pubis and ischeum inferiorly) is an uncommon but extremely difficult problem encountered during acetabular revision surgery. No series of more than a few patients has been reported to date. The purpose of this study was to characterize patients at risk for pelvic discontinuity and report the results of treatment of this problem. Materials and Methods: All cases of pelvic discontinuity identified during revision THA at one institution were reviewed. Pelvic discontinuity was classified as Type IVa (3 hips) if it occurred in the absence of severe segmental or combined pelvic bone loss, Type IVb (21 hips) if it occurred in the presence of segmental or combined pelvic bone loss and Type Wc (5 hips) if after previous pelvic irradiation.
* Denotes that something of value was received Presenters are boldface
Treatment for the discontinuity was plating of both columns in 5, plating of one column in 7, stabilization with a Burch-Schneider anti-pmtrusio cage in 13, stabilization with the implant alone in 2 and girdlestone procedure in 2. Nine had bulk structural grafts. All revised patients had particulate allograft and 11 also had autograft at discontinuity site.
226
The Journal of Arthroplasty Vol. 13 No. 2 February 1998
Results: Pelvic discontinuity was identified during 29 of 3,505 consecutive acetabular revisions (incidence = 0.8%). Mean patient age was 61 years (38 to 80). Twenty-seven were female and 2 male. Underlying diagnoses leading to THA were osteoarthritis in 9, rheumatoid arthritis in 7, radiation necrosis in 5, developmental hip dysplasia in 4, and miscellaneous in 4. Female gender, diagnoses of rheumatoid arthritis and radiation necrosis were statistically associated with greater risk of discontinuity than other diagnoses (p<0.05).
Two patients (3 hips) died within 2 years of surgery and two hips were treated for the discontinuity with resection arthroplasty. Thus, 25 hips (24 patients) treated with revision surgery were eligible for follow-up at a minim u m of 2 years. No patients were lost to follow-up. Mean follow-up time was 2.8 years (range 2-7). Ten of the 25 acetabular reconstructions have failed and required revision or resection. Five failed due to aseptic acetabular loosening, 2 due to recurrent dislocation and 3 due to deep infection. Four of the five aseptic failures were Type IVb and one was Type IVc, three of the five failures were cemented sockets (2 double plate, I single plate), one an uncemented socket (single plate) and one a Burch-Schneider cage.
Results: At a minimum of two years follow-up, the mean Harris hip score had improved from thirty-seven to eighty-seven. Mean Chamley scores had improved from preoperative to postoperative values as follows: pain 2.0 to 5.5, function 3.4 to 5.0, and motion 4.5 to 5.2. Re-operations were performed in two hips, one because of a symptomatic trochanteric nonunion and one because of loosening around a cemented femoral component. Groin or buttock pain was completely relieved in thirty-six patients (80%) and partially relieved in an additional four patients (9%). Of the fourteen unipolar cases, ten (71%) had complete relief of their groin or buttock pain. Of the thirty-one bipolar cases, twenty-six (84%) had complete relief of their groin or buttock pain. Nine patients continued to have groin or buttock pain after conversion surgery in spite of satisfactory radiological result. Discussion: Conversion from hemiarthroplasty to total hip arthroplasty can be reliable in the elimination of groin pain (complete relief in 80% of patients and partial or complete relief in 89%). However, there appear to be no consistent factors which can be used to identify those patients who will receive less than a perfect result. Since a significant number of patients will continue to have some groin pain after revision (up to 20%), they need to be warned of this prior to surgery.
Clinically, of the surviving unrevised hips, no or mild pain was present in 87% and moderate pain in 13%. Radiographically, one of the unrevised hips had definite acetabular loosening. For the group of 25 revisions, the outcome with respect to healing of the pelvic discontinuity was definitely healed in 11, possibly but had not definitely healed in 8 and unhealed in 6. The likelihood of a satisfactory outcome (defined as no further acetabular surgery, stable acetabular component, definitely or possibly healed discontinuity and no or mild pain) was 3 / 3 (100%) for Type IVa hips, 8/17 (47%) for Type IVb hips and 3 / 5 (60%) for Type IVc hips for an overall rate of 14/25 (56%). Complications of treatment included partial peroneal nerve palsy in 3, deep infection in 2 and dislocation in 3 hips. Conclusions: This paper provides information on incidence and risk factors for development of pelvic discontinuity. Treatment results correlate with severity of associated pelvic bone loss and previous pelvic irradiation. The complication rate is high and though reconstruction is possible for m a n y patients, continued efforts are needed to improve treatment techniques.
PAPER # 13 *CAN G R O I N PAIN BE ELIMINATED IN A C O N V E R S I O N OF HEMIARTHROPLASTY Christopher Carey, MD, Rajesh Rao, MD, Peter E Sharkey, MD, Kenneth Eng, MS, Richard H. Rothman, MD, William J. Hozack, MD,
Philadelphia, PA Introduction: Long term results of hemiarthroplasty have shown that acetabular erosion and resultant pain may require a conversion to total hip arthroplasty (THA), but there are no data to document the success of such a procedure in eliminating this pain. The purpose of this study is to determine the reliability of a conversion of the hemiarthroplasty to THA in alleviating groin pain. M e t h o d s : F o r t y - f i v e p a t i e n t s w i t h g r o i n or b u t t o c k p a i n a f t e r hemiarthroplasty were evaluated two to seven years after conversion to THA. The demographics of this group include a mean age of sixty-five years (range 32 to 85), mean weight of 145 lbs (range 90 to 260), with eleven men and thirty-four women. The average time from hemiarthroplasty to conversion THA was 3.7 years (range 5 months to 11 years). Fourteen patients had received unipolar endoprotheses (5 cemented and 9 uncemented), and thirty-one received bipolar endoprostheses (11 cemented and 20 cementless). After conversion surgery, eight had received cemented acetabular cups and thirty-seven had received uncemented acetabular cups.
* Denotes that somethingof value was received Presenters are boldface
PAPER # 14 THE PROMISING ROLE FOR FDG-PET I M A G I N G IN THE M A N A G E M E N T OF PAINFUL HIP PROSTHESES David L. Glaser, MD, Philadelphia, PA, Darryl Shnier, MD, Abass Alavi, MD, Francouis Bernard, MD, Jonathan R Garino, MD, Robert H. Fitzgerald, MD Introduction: In determining the etiology of a painful total hip prosthesis, it is crucial to distinguish between an aseptic and septic process. Sites of inflammatory cells have high uptake of [F-18] Fluoro-2-deoxy-2-d-glucose (FDG), making the use of this compound, imaged through positron emission tomography (PET), an appropriate tracer for the detection of sites of inflammation and infection. This report describes the use of FDG-PET in the evaluation of the painful hip arthroplasty. Methods: From July 1996 to February 1997, eight patients with eleven arthroplasties underwent FDGPET scanning for evaluation of a painfulhip prosthesis. A final operative diagnosis was established in seven cases while a clinical diagnosis was determined in the other. Sixty minutes following the intravenous administration of 4.22 MBq/Kg of FDG, tomographic images were obtained of the area of interest on a 3-D volume imaging PET scanner. Studies were read blindly and scored on a 5 point scale with respect to intensity of FDG uptake and the results were compared with outcome. Features predictive of infection versus loosening were evaluated. Results: FDG-PET imaging correctly demonstrated the presence of exte.nsive infection in four prostheses. This diagnosis was confirmed with operating room findings in all four cases. The most important diagnostic features were moderate to marked tracer uptake at the prosthesis bone interface. In five prostheses in four patients, FIX~-PET correctly diagnosed aseptic loosening by demonstrating increased uptake adjacent to the neck of the femoral prosthesis not involving the prosthesis bone interface. The diagnosis of aseptic loosening was confirmed with operative findings in three of these patients, and clinical follow-up in the other patient with bilateral prostheses. Minimal or no FDG uptake was demonstrated in two contralateral prostheses with no clinical evidence for infection or loosening. None of the seven prosthesis considered to be either aseptically loose or normal had uptake of FDG at the prosthesis bone interface. Conclusions: FDG PET scanning is extremely sensitive and very specific for the detection of infection in hip prostheses. The data suggest that FIX; scanning may be able to provide a positive diagnosis of aseptic loosening. FDG-PET scanning is a quick procedure able to provide an answer within 2-3 hours. In our institution, it is cheaper than the conventional indium white cell and bone marrow scan.
PAPER # 10 *ACETABULAR RECONSTRUCTION WITH POROUS COMPONENTS IN DYSPLASTIC HIPS U S I N G A MODIFIED HESS PROTRUSIO SOCKET TECHNIQUE Samer N. Tawakkol, MD, Los Angeles, CA, William Long, MD, Lawrence Dorr, MD Introduction: Total hip replacement in patients with DDH is a challenging and complex operation. The purpose of this study is that cementless acetabular fixation with a modified Hess protrusio technique provides predictable and durable fixation. Materials and Methods: Twenty-nine patients with 36 dysplastic hips were operated with THR by one surgeon. Hemispherical porous coated noncemented acetabular components were used in 32 hips. Patients were followed for an average 6.3 years (five years - 12.5 years). The first eight of these hips were operated with a technique which preserved the medial wall and used a bone graft as necessary to cover superior and lateral defects. In 22 hips protrusio technique was performed to permit creation of a hemispheric acetabular cavity which provided a stable press fit of the acetabular component without the necessity of bone graft. The mean age at the time of the index operation was 45 years (range 22 to 69 years). The Ranawat triangle, femoral head subluxation by the Crowe classification and the medial wall thickness from Kohler's line were measured preoperatively. The acetabular component in relationship to Ranawat's triangle and protrusio beyond Kohler's line, theta angle, and coverage of the bone graft was measured postop. Results: The acetabular revision rate for the study was 6.2 percent at average 6.3 years. Twelve hips were classified as Crowe Grade I, eight as Grade II, eight as Grade III, and eight as Grade IV. With this technique the average mediallzation of the cup beyond Kohler's line was 1 m m for Crowe I and II, 2.6 m m for Crowe HI and 1 m m for Crowe IV. Crowe IV deformities are always reconstructed at the true acetabulum. The bony coverage of the cup laterally was more than 90% in all 24 hips. The femoral head autograft covered less than 30% of the cup in all eight hips. Twenty-two hips were implanted with the protrusio technique and none of these hips have been revised or were loose or had migrated. Discussion: This study demonstrates that acetabular reconstruction in patients with hip dysplasia can be accomplished using cementless fixation. None of the non-cemented cups implanted with the protrusio technique have been revised. The absence of revision is not a superior revision rate when compared to cemented Charnley components at the same time postoperatively. However, cemented Charnley components at the same time do have a higher radiographic loosening rate. Predictable fixation can be obtained with the protmsio technique which does provide the principles of implantation for a hemispherical porous coated acetabular component. This study confirms that bone graft coverage of 30% or less provide a stable construct.
225
PAPER # 11 *CEMENTLESS ACETABULAR REVISION ARTHROPLASTY WITH A POROUS, TITANIUM, MODULAR HEMISPHERICAL COMPONENT Christopher W. Olcott, MD, Rochester, NY, David A. Mattingly, ME), Benjamin E. Bierbanm, ME) Although a fixed, porous-coated, hemispherical acetabular component has become the standard in most revision situations, intermediate and longterm results of such components are limite& The purpose of this study was to assess the efficacy of a cementless acetabular component in revision hip arthroplasty at a range of four-to-ten years. Between December 1987 and March 1992,150 consecutive acetabular revisions were performed by two surgeons. In each case, a hemispherical titanium acetabular shell coated with titanium beads was implanted with or without supplemental dome screw fixation. At a mean follow-up of 6.3 years (range 4 - 10 years), 119 acetabular revisions were available for clinical and radiographic review. Fifty-six of the 119 hips had simultaneous femoral revisions. Each patient was either interviewed or answered a questionnaire for determination of a Harris hip score. Immediate postoperative radiographs were compared to most recent follow-up films for bony fixation, migration, wear and osteolysis. The average postoperative Harris hip score improved to eighty-one from forty-two preoperatively. Twenty-six hips (21.8%) h a v e u n d e r g o n e reoperations: eight (6.7%) for instability, seven (5.9%) for femoral revision, four (3.4%) for reexploration (debridement heterotopic ossification / removal of hardware), two (1.7%) for infection, one (0.8%) for early postoperative migration at three weeks and four (3.4%) for aseptic loosening. Although a variety of femoral components were used in conjunction with this acetabular shell, those with osteolysis and those requiring revision were noted. Seven femoral stems (5.9%) were re'~'ised and another twenty-five demonstrated some degree of osteolysis confined primarily to the proximal zones. Acetabular osteolysis evident in eleven hips was not extensive enough to warrant re-revision. Acetabular liner exchange was performed in the seven hips requiring femoral revision and three hips with instability. Radiographic evidence of acetabular migration was noted in seven hips (6.5%); six of which were associated with a bulk, structural allograft. The results of this cementless, titanium, hemispherical acetabular component outperform those of cemented cups at similar follow-up and compare favorably with other cementless designs. A good clinical and radiographic outcome support its continued use in acetabular revision surgery.
PAPER # 12 PELVIC DISCONTINUITY IN ACETABULAR REVISION SURGERY Daniel J. Berry, MD, Rochester,MN, Arlen D. Hanssen, MD, David G. Lewallen, MD, Miguel E. Cabanela, MD Introduction: Pelvic discontinuity (AAOS Type W bone deficiency, defined as discontinuity between the ihum superiorly and the pubis and ischeum inferiorly) is an uncommon but extremely difficult problem encountered during acetabular revision surgery. No series of more than a few patients has been reported to date. The purpose of this study was to characterize patients at risk for pelvic discontinuity and report the results of treatment of this problem. Materials and Methods: All cases of pelvic discontinuity identified during revision THA at one institution were reviewed. Pelvic discontinuity was classified as Type IVa (3 hips) if it occurred in the absence of severe segmental or combined pelvic bone loss, Type IVb (21 hips) if it occurred in the presence of segmental or combined pelvic bone loss and Type Wc (5 hips) if after previous pelvic irradiation.
* Denotes that something of value was received Presenters are boldface
Treatment for the discontinuity was plating of both columns in 5, plating of one column in 7, stabilization with a Burch-Schneider anti-pmtrusio cage in 13, stabilization with the implant alone in 2 and girdlestone procedure in 2. Nine had bulk structural grafts. All revised patients had particulate allograft and 11 also had autograft at discontinuity site.
226
The Journal of Arthroplasty Vol. 13 No. 2 February 1998
Results: Pelvic discontinuity was identified during 29 of 3,505 consecutive acetabular revisions (incidence = 0.8%). Mean patient age was 61 years (38 to 80). Twenty-seven were female and 2 male. Underlying diagnoses leading to THA were osteoarthritis in 9, rheumatoid arthritis in 7, radiation necrosis in 5, developmental hip dysplasia in 4, and miscellaneous in 4. Female gender, diagnoses of rheumatoid arthritis and radiation necrosis were statistically associated with greater risk of discontinuity than other diagnoses (p<0.05).
Two patients (3 hips) died within 2 years of surgery and two hips were treated for the discontinuity with resection arthroplasty. Thus, 25 hips (24 patients) treated with revision surgery were eligible for follow-up at a minim u m of 2 years. No patients were lost to follow-up. Mean follow-up time was 2.8 years (range 2-7). Ten of the 25 acetabular reconstructions have failed and required revision or resection. Five failed due to aseptic acetabular loosening, 2 due to recurrent dislocation and 3 due to deep infection. Four of the five aseptic failures were Type IVb and one was Type IVc, three of the five failures were cemented sockets (2 double plate, I single plate), one an uncemented socket (single plate) and one a Burch-Schneider cage.
Results: At a minimum of two years follow-up, the mean Harris hip score had improved from thirty-seven to eighty-seven. Mean Chamley scores had improved from preoperative to postoperative values as follows: pain 2.0 to 5.5, function 3.4 to 5.0, and motion 4.5 to 5.2. Re-operations were performed in two hips, one because of a symptomatic trochanteric nonunion and one because of loosening around a cemented femoral component. Groin or buttock pain was completely relieved in thirty-six patients (80%) and partially relieved in an additional four patients (9%). Of the fourteen unipolar cases, ten (71%) had complete relief of their groin or buttock pain. Of the thirty-one bipolar cases, twenty-six (84%) had complete relief of their groin or buttock pain. Nine patients continued to have groin or buttock pain after conversion surgery in spite of satisfactory radiological result. Discussion: Conversion from hemiarthroplasty to total hip arthroplasty can be reliable in the elimination of groin pain (complete relief in 80% of patients and partial or complete relief in 89%). However, there appear to be no consistent factors which can be used to identify those patients who will receive less than a perfect result. Since a significant number of patients will continue to have some groin pain after revision (up to 20%), they need to be warned of this prior to surgery.
Clinically, of the surviving unrevised hips, no or mild pain was present in 87% and moderate pain in 13%. Radiographically, one of the unrevised hips had definite acetabular loosening. For the group of 25 revisions, the outcome with respect to healing of the pelvic discontinuity was definitely healed in 11, possibly but had not definitely healed in 8 and unhealed in 6. The likelihood of a satisfactory outcome (defined as no further acetabular surgery, stable acetabular component, definitely or possibly healed discontinuity and no or mild pain) was 3 / 3 (100%) for Type IVa hips, 8/17 (47%) for Type IVb hips and 3 / 5 (60%) for Type IVc hips for an overall rate of 14/25 (56%). Complications of treatment included partial peroneal nerve palsy in 3, deep infection in 2 and dislocation in 3 hips. Conclusions: This paper provides information on incidence and risk factors for development of pelvic discontinuity. Treatment results correlate with severity of associated pelvic bone loss and previous pelvic irradiation. The complication rate is high and though reconstruction is possible for m a n y patients, continued efforts are needed to improve treatment techniques.
PAPER # 13 *CAN G R O I N PAIN BE ELIMINATED IN A C O N V E R S I O N OF HEMIARTHROPLASTY Christopher Carey, MD, Rajesh Rao, MD, Peter E Sharkey, MD, Kenneth Eng, MS, Richard H. Rothman, MD, William J. Hozack, MD,
Philadelphia, PA Introduction: Long term results of hemiarthroplasty have shown that acetabular erosion and resultant pain may require a conversion to total hip arthroplasty (THA), but there are no data to document the success of such a procedure in eliminating this pain. The purpose of this study is to determine the reliability of a conversion of the hemiarthroplasty to THA in alleviating groin pain. M e t h o d s : F o r t y - f i v e p a t i e n t s w i t h g r o i n or b u t t o c k p a i n a f t e r hemiarthroplasty were evaluated two to seven years after conversion to THA. The demographics of this group include a mean age of sixty-five years (range 32 to 85), mean weight of 145 lbs (range 90 to 260), with eleven men and thirty-four women. The average time from hemiarthroplasty to conversion THA was 3.7 years (range 5 months to 11 years). Fourteen patients had received unipolar endoprotheses (5 cemented and 9 uncemented), and thirty-one received bipolar endoprostheses (11 cemented and 20 cementless). After conversion surgery, eight had received cemented acetabular cups and thirty-seven had received uncemented acetabular cups.
* Denotes that somethingof value was received Presenters are boldface
PAPER # 14 THE PROMISING ROLE FOR FDG-PET I M A G I N G IN THE M A N A G E M E N T OF PAINFUL HIP PROSTHESES David L. Glaser, MD, Philadelphia, PA, Darryl Shnier, MD, Abass Alavi, MD, Francouis Bernard, MD, Jonathan R Garino, MD, Robert H. Fitzgerald, MD Introduction: In determining the etiology of a painful total hip prosthesis, it is crucial to distinguish between an aseptic and septic process. Sites of inflammatory cells have high uptake of [F-18] Fluoro-2-deoxy-2-d-glucose (FDG), making the use of this compound, imaged through positron emission tomography (PET), an appropriate tracer for the detection of sites of inflammation and infection. This report describes the use of FDG-PET in the evaluation of the painful hip arthroplasty. Methods: From July 1996 to February 1997, eight patients with eleven arthroplasties underwent FDGPET scanning for evaluation of a painfulhip prosthesis. A final operative diagnosis was established in seven cases while a clinical diagnosis was determined in the other. Sixty minutes following the intravenous administration of 4.22 MBq/Kg of FDG, tomographic images were obtained of the area of interest on a 3-D volume imaging PET scanner. Studies were read blindly and scored on a 5 point scale with respect to intensity of FDG uptake and the results were compared with outcome. Features predictive of infection versus loosening were evaluated. Results: FDG-PET imaging correctly demonstrated the presence of exte.nsive infection in four prostheses. This diagnosis was confirmed with operating room findings in all four cases. The most important diagnostic features were moderate to marked tracer uptake at the prosthesis bone interface. In five prostheses in four patients, FIX~-PET correctly diagnosed aseptic loosening by demonstrating increased uptake adjacent to the neck of the femoral prosthesis not involving the prosthesis bone interface. The diagnosis of aseptic loosening was confirmed with operative findings in three of these patients, and clinical follow-up in the other patient with bilateral prostheses. Minimal or no FDG uptake was demonstrated in two contralateral prostheses with no clinical evidence for infection or loosening. None of the seven prosthesis considered to be either aseptically loose or normal had uptake of FDG at the prosthesis bone interface. Conclusions: FDG PET scanning is extremely sensitive and very specific for the detection of infection in hip prostheses. The data suggest that FIX; scanning may be able to provide a positive diagnosis of aseptic loosening. FDG-PET scanning is a quick procedure able to provide an answer within 2-3 hours. In our institution, it is cheaper than the conventional indium white cell and bone marrow scan.