A s s e s s m e n t of Intrapelvic C e m e n t and Screws in Revision Total Hip Arthroplasty Thomas
K. F e h r i n g , M D , * W . B o n n e r
G u i l f o r d , MD,-t- a n d J e r r y B a r o n , MD-]-
Abstract: Vascular injury resulting from primary and revision hip arthroplasty has been reported to involve both arterial and venous structures. While such complications are extremely uncommon, removal of intrapelvic cement or screws during revision surgery can be hazardous to intrapelvic structures. Both arterial and venous perforations can occur, depending on the level at which the pelvic wall has been breached, and on the orientation of the intruding matter. Complications can be minimized with careful preoperative assessment of pelvic anatomy. Contrast-enhanced computerized tomography scanning can assist the revision surgeon with preoperative planning in those patients requiring removal of intrapelvic components. This technique appears to be an accurate, simple, and noninvasive method by which these intrapelvic relationships may be examined. Key words: hip, revision, intrapelvic, components, cement, complications.
Vascular injury resulting from primary and revision hip arthroplasty has been reported to involve both arterial and venous structures. ~-4"6-~9 These events have been linked to direct vessel injury during extraction of existing acetabular components. ~3"~5 While such complications are extremely rare, rem o v a l of intrapelvic cement or screws during revision surgery can be hazardous to intrapelvic structures. Both arterial and venous perforations can occur, depending on the level at which the pelvic wall has been breached, and on the orientation of the intruding matter. Similarly, the bladder and ureter may be at risk from extreme intrapelvic penetration by such material. As the n u m b e r of patients presenting for revision hip arthroplasty increases, hip surgeons are being confronted more frequently with revision of acetabular components in which there is significant intrapelvic cement or perforation of the medial acetabular wall with screws. Our goal in the assessment of these
patients was to determine a noninvasive, cost effective way of evaluating patients before surgery with significant intrapelvic cement or screws prior to revision hip arthroplasty. Through the use of contrastenhanced computerized tomography (CT) scanning of the pelvis, we have the ability to define the vascular and visceral structures of the pelvis and their relationships to total hip acetabular components prior to revision surgery.
Materials and Methods Twenty patients with loose, painful acetabular components and significant intrapelvic cement or screws were investigated before surgery. The first three patients in this series were evaluated by traditional radiographic methods, including standard or selective angiography. We were dissatisfied with these techniques; not only were they invasive and costly, but unless both venography and arteriography were performed in multiple projections, complete definition of periacetabular vascular a n a t o m y was not achieved. We therefore abandoned these traditional techniques and developed a contrast-enhanced CT method to evaluate the remainder of the patients in this series. The CT scan protocol consists
From the *Charlotte Orthopaedic Clinic, P.A., Joint Reconstruction Center, Charlotte, North Carolina, and "tCharlotte Memorial Hospital and Medical Center, Charlotte, North Carolina. Reprint requests: Thomas K. Fehfing, MD, 120 Providence Road, Charlotte, NC 28207.
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Fig. 1. Three-dimensional reconstruction generated from axial CT data followed by sample CT slices to illustrate vascular landmarks at different pelvic levels. (A) Normal pelvic anatomy. (B) Level 2: location of artery, vein, and ureters just below SI joints. Artery (A), vein (V), bladder (B), and ureters (arrowheads). (Figure
conthmes)
of an initial 50 cc bolus of contrast (Conray 43, Mallinckrodt, St. Louis, MO) or equivalent given immediately before scanning. This is supplemented by a rapid contrast drip infusion of 200 cc during the examination. The flow of contrast is unrestricted and can be increased by slightly pressurizing the drip bottle. The patient is scanned using contiguous 3 m m thick axial slices throughout the area of interest, beginning above the most proximal screw or cement and continuing through the lower acetabulum. This provides complete definition of the iliac artery and vein, the c o m m o n femoral artery and vein, and their
more prominent branches throughout the component areas. It also gives us information o n the relationship of intrapelvic orthopaedic materials to the ureter, bladder, and bowel, regardless of which portion of the device may intrude o n these structures (Fig. 1). As expected, there is substantial artifact created by the implant materials. However, this can be overcome by comparison of both bone and soft tissue windows to yield diagnostic information as the vessels are followed through the pelvis. All examinations were closely monitored to ensure that all components were thoroughly and completely evaluated.
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Fig. 1. (Conthmed) (C) Level 3: top of quadrilateral plate. (D) Level 4: lower acetabular fovea.
In two cases, the intrapelv!c material was intimately opposed to the femoral vein (Fig. 2). To assure safe removal, a retroperitoneal approach, as reco m m e n d e d by Eftekhar, 5 was used to remove the intrapelvic cement prior to revision. Four of the 20 patients had intrapelvic material within a few millimeters of an important intrapelvic structure. Two of these patients were aseptic cases, and we elected not to disturb the intrapelvic components because of their proximity to major intrapelvic structures (Figs. 3A,B). In these cases we may have elected to remove this material during surgery. How-
ever, because of the knowledge provided by the enhanced CT scan, a concerted effort was made not to disturb the cement (Fig. 3C). In the two other cases, it was mandatory to remove the intrapelvic material because of sepsis or instability (Fig. 4). In each of these cases some prosthetic material was within a few millimeters of an important intrapelvic structure. Because of the proximity, general surgical standby assistance was utilized during the procedure. Fortunately no problems were encountered. All 20 cases involving significant intrapelvic cement or screws were successflxlly reconstructed with-
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Fig. 2. (A) Anteroposterior (AP) view. Note significant intrapelvic cement. (B) CT scan demonstrating intimate apposition of the anterior cement bolus and tile iliac artery and vein.
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9 Fehring et al.
Fig. 3. (A) AP view. Note loose aseptic prosthesis with intrapelvic bolus of cement. (B) lntrapelvic bolus in close proximity to the left ureter. {C) Reconstruction with retained cement.
C
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Fig. 4. (A) AP view. Dislocated prosthesis with malpositioned cup and multiple intrapelvic screws. (B) Lateral view demonstrating posterior dislocation. (Figurecontinues)
out injury to any adjoining intrapelvic structure. CT delineation of intrapelvic anatomy was felt to be satisfactory in all cases in which it was used. Streak artifact was occasionally severe, but the images were still adequate for anatomic assessment.
Normal Anatomy To have a complete understanding of this potential problem, one must be familiar with the course of the major vessels and their changing spatial relationships
Assessment of Intrapelvic Cement and Screws in THA 9 Fehring et al.
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Fig. 4. (Continued) (C) Proximal screw tip 8 mm from iliac artery. (D) Slightly lower slice showing screw tip 4 mm from right ureter.
in the pelvis (Fig. 1). Cadaver dissection and review of contrast enhanced CT scans of the pelvis have shown that at the lower level of the sacroiliac joint, the external iliac artery is anterior and slightly lateral to the iliac vein (Fig. 1B).The ureter is situated immediately posterior or medial to the external lilac vein at this level. As the vessels continue more distally, medial to the quadrilateral plate, the vein becomes more medial to the external iliac artery and less posterior (Fig. 1C). Below the inguinal ligament, they continue as the femoral artery and vein, but the femoral vein is n o w medial to the artery (Fig. ID). The periacetabular vascular anatomy is very well visualized with the enhanced CT scan of the pelvis, and helps explain w h y certain structures are more or less vulnerable at different levels about the acetabulum.
Case Repods
Case 1 A 60-year-old man had an uncomplicated total hip arthroplasty (THA) performed for avascular necrosis in 1975. The hip functioned well until 1987, w h e n he began to experience a progressive increase in pain and a decrease in function. In June 1990, he was referred for consideration of revision arthroplasW. Plain radiographs demonstrated a loose migrated acetabular component with a large bolus of intrapelvic cement (Fig. 2A). The aspiration arthrogram was
positive for loosening and negative for sepsis. A contrast-enhanced CT scan was performed and demonstrated intimate opposition of the intrapelvic cement with the iliac vein and artery (Fig. 2B). A retroperitoneal approach to clear the cement from the iliac vasculature was performed prior to revision. One week later revision arthroplasty with allograft augmentation of the acetabulum was performed without complication.
Case 2 A 71-year-old w o m a n underwent primary THA in January 1988. Following surgery, she had multiple episodes of dislocation that necessitated subsequent revision 2 months later. After that revision, she had multiple dislocations that required manipulative reduction under anesthesia. In May 1988, she had another dislocation that was irreducible with closed means. At this juncture in her care, she was transferred to our service for consideration of revision due to instability. On arrival, she had an aspiration arthrogram that was negative for loosening as well as for infection. Plain radiographs demonstrated a dislocated hip, a malpositioned acetabular component, and multiple screws that had penetrated the pelvic wall in various positions (Figs. 4A,B). Because of the malposition of the acetabular component, it was necessary to remove it and its protruding screws. A contrast-enhanced CT scan of the pelvis was obtained, clarifying the relationship between the four screws and the intrapelvic structures. The most
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inferior screw came within 6 nun of the iliac artery. The most proximal screw came within 8 m m of the iliac artery (Fig. 4C). A third screw was seen to be directed in a horizontal fashion toward the midline, approaching but not violating the right ureter, with a clearance of approximately 4 m m (Fig. 4D). The fourth screw was intrapelvic, but not near any major intrapelvic structure. The existing socket was removed without complication using general surgical standby assistance, and the revised socket was fixed with three 6.5 m m cancellous screws. Two years after surgery, she has no sign of instability, is currently pain-free, and walking unassisted.
Case 3 A 48-year-old man underwent a THA for avascular necrosis in 1972. Before surgery, he had significant drainage from the hip and a nonhemolytic Staphylococcus that was resistant to methicillin was cultured. He was treated with antibiotics and discharged from the hospital without any significant postoperative complications. He was followed at regular intervals and had no particular difficulty until October 1988 w h e n he had a mild traumatic episode to his hip. Subsequent development of intense pain and fever led us to perform an aspiration arthrogram, which was positive for Staphylococcus epidermidis, as well as a blood culture that grew the same organism. His radiographs at this time showed protrusion of the acetabular component with a large bolus of intrapelvic cement (Fig. 5A). Because of his positive aspirate, a thorough debridement, including removal of all cement, was indicated. An enhanced CT scan of the pelvis was obtained, showing that the mass of cement medial to the quadrilateral portion of the acetabulum was well clear of the great vessels (Fig. 5B). Irrigation and debfidement of the hip joint was subsequently performed with removal of all cement. It was n o t e w o r t h y that minimal pus was found in the joint itself. However, w h e n the medial bolus of cement was removed, approximately 10 cc of thick purulent material filIed the acetabulum. Tobramycinimpregnated beads were then placed into the hip joint. Three months later, revision THA using titanium porous-coated implants was performed without complication. The postoperative period was uneventful, and the patient is currently pain-flee and walking without aids.
Discussion The proximity of intrapelvic orthopaedic materials to intrapelvic structures has on occasion resulted in life-threatening hemorrhage during arthroplasty of
the hip. 9 Over the past 25 years, approximately 60 cases of major n o n t h r o m b o e m b o l i c vascular complications of primary and revision hip arthroplasty have been reported in the literature. ~-4"6-~9 These vascular injuries have involved the external iliac artery, the c o m m o n femoral artery, and less frequently, the c o m m o n iliac vein. The mechanisms of injury have included improper placement of spiked retractors, ~-~3 erosion of vessels by prosthetic materials, ~'2"4'6"8"~4"~7thrombosis due to the intense heat of polymerization of cement, 7"~3 and laceration of major vessels during removal of existing acetabular components.~3'~ Although rare in occurrence, complications of vascular injuries in TttA can be life- and limb-threatening. Review of the literature reveals that approximately 35% of reported cases have p e r m a n e n t sequelae, with 10% of these requiring either an above or below knee amputation, and 3% requiring hip disarticulation. In9 Keating recently reported a death from penetration of a branch of an internal lilac artery during revision surgery. 9 Eftekhar stressed the importance of a careful approach w h e n revising intrapelvic components. 5 He reported four cases where acetabular components had migrated beyond the iliopectineal line. In two patients, the external lilac artery was adherent to the cement. In one patient, adhesions formed between the iliac vein and the cement. Motion of the cup produced traction on the iliac vein. These reports stress the potential for serious injury during revision of intrapelvic components. To avoid vascular injuries in revision hip arthroplasty, careful preoperative planning is essential to determine the optimal surgical approach. Knowledge of the spatial relationships between intrapelvic implants and intrapelvic vital structures is particularly important in septic revision where all cement must be removed. In aseptic conditions, it is not necessary to remove all intrapelvic cement, but adherence of intrapelvic cement to the extracted socket is not u n c o m m o n . With the increased use of screws through acetabular components, the potential for vascular injury during revision increases if the pelvic wall has been breached by the screws. 9"2~ The a m o u n t of extruded material is less important than the location of extrusion. This is particularly true in anteriorly extruded cement. This cement m a y not be as apparent on a standard anteroposterior view of the pelvis, but may place the femoral vessels at risk during extraction. In addition to the risk to normal structures, the enhanced CT scan should detect and define any pathologic processes present, including aneurysm, false aneurysm, and abscess.
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Fig. 5. (A) AP view. Gross loosening of the acetabular component with intrapelvic cement. (B) One of the axial enhanced CT slices at point of closest cement impingement. Vessels, ureters, and bladder are clear.
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Traditional radiographic methods to evaluate these structures have included standard and selective angio g r a p h y } '3"~'x4 Disadvantages of these techniques include patient morbidity secondary to the invasiveness of these procedures, relatively high expense, and a lack of complete definition of the periacetabular vascular anatomy, unless both v e n o g r a p h y and arteriography are performed in multiple planes. Also, these procedures do not visualize other important intrapelvic structures at risk. Therefore, to minimize complications and better define the periacetabular a n a t o m y , we believe that contrast-enhanced CT scanning is the most accurate m e t h o d of evaluating intrapelvic cement or screws in revision hip a n h r o p l a s t y . Advantages of contrast-enhanced CT scanning of the pelvis over the m o r e traditional angiographic techniques include lower cost and virtually no morbidity. At o u r institution, the cost of an enhanced CT scan is approximately one fourth that of the combined arteriogram and venogram. Advantages of enhanced CT scanning to the surgeon include the ability to derive m o r e information about the periacetabular vascularity and viscera through a single study. Our current approach to the patient with intrapelvic c e m e n t or screws is guided by enhanced CT scanning of the pelvis. If there is clearly no impingement, acetabular revision can be performed in a standard fashion. If there is intimate contact with a major intrapelvic structure, then a retroperitoneal approach should be employed. We feel this is the safest course of action to avoid catastrophic complications. For those cases where intruding material closely approaches but is not in intimate contact with major intrapelvic structures, we feel that general surgical standby assistance is required. We hesitate to place strict guidelines c o n c e m i n g a safe distance between intruding matter and important intrapelvic structures in this intermediate group. We feel that each case should be individualized as such parameters m a y differ depending on the type of intruding material and the structure at risk. Parameters m a y also change depending o n whether the surgeon is dealing with a septic or aseptic case.
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References 1. Aust JC, Bredenburg CE, Murray DG: Mechanisms of arterial injuries associated with total hip replacement. Arch Surg 116:345, 1981 2. Brentlinger A, ttunter JR: Perforation of the extemal iliac artery and ureter presenting as acute hemorrhagic
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cystitis after total hip replacement. J Bone Joint Surg 69A:620, 1987 Camer SJ: Surgical complications of revision anhroplasty, p. 323. In Tumer R, Scheller A (eds): Revision total hip arthroplasty. Grune and Stratton, New York, 1982 Don:"L, Conaty JP, Kohll R, Harvey JP: False aneurysms of the femoral artery following total hip surgery. J Bone Joint Surg 56A:1059, 1974 Eftekhar NS, Nercessian O: Intrapelvic migration of total hip prostheses. J Bone Joint Surg 71A:1480, 1989 Giacchetto J, Gallagher J: False aneurysm of the common femoral artery secondary to migration of a threaded acetabular component. Clin Orthop 231:91, 1988 Hirsh SA, Robertson H, Gorniowsky M: Arterial occlusion secondary to methylmethacrylate use. Arch Surg 3:204, 1976 Hopkins NFG, Vanhegan JAD, Majieson CW: Iliac aneurysm after total hip anhroplasty. J Bone Joint Surg 65B:359, 1983 Keating EM, Ritter MA, Faris PM: Structures at risk from medially placed acetabular screws. J Bone Joint Surg 72A:509, 1990 Kroese A, Mollerud A: Traumatic aneurysm of tile common femoral artery after hip endoprosthesis. Acta Orthop Seand 46:119, 1976. Lozman tt, Robbins tt: Injury to the superior gluteal artery as a complication of total hip replacement arthroplasty. J Bone Joint Surg 65A:268, 1983 Mallory TH: Rupture of the common iliac vein from reaming the acetabulum during total hip replacement. J Bone Joint Surg 54A:276, 1972 Nachbur B, Meyer RP, Verkkala K, Zurcher R:The mechanisms of severe arterial injury in surgery of.the hip joint. Clin Orthop 141:122, 1979 Neal J, Wachtel TL, Garza OT, Edwards WS: Late arterial embolization complicating total hip replacement. J Bone Joint Surg 61A:429, 1979 Reiley MA, Bond D, Branick RI, Wilson EtI: Vascular complications following total hip arthroplasty. Clin Orthop 89:143, 1972 Salama R, Stravorovsky, MM, lellin A, Weissman SL: Femoral artery injury complicating total hip replacement. Clin Orthop 89:143, 1972 Scullin JP, Nelson CL, Veven EG: False aneurysm of the left external iliac artery following total hip arthroplasty. Clin Orthop 113:145, 1975 Stubbs DH, Domer DB, Johnston RC: Thrombosis of the iliofemoral artery during revision of a total hip replacement. J Bone Joint Surg 68A:454, 1986 Tkaczuk H: False aneurysm of the external iliac artery following hip endoprosthesis. Acta Onhop Scand 47: 317, 1976 Wasielewski RC, Cooperstein LA, Kruger MP, Rubash HE: Acetabular anatomy and the transacetabular fixation of screws in total hip anhroplasty. J Bone Joint Surg 72A:501, 1990
K. F e h r i n g , M D , * W . B o n n e r
G u i l f o r d , MD,-t- a n d J e r r y B a r o n , MD-]-
Abstract: Vascular injury resulting from primary and revision hip arthroplasty has been reported to involve both arterial and venous structures. While such complications are extremely uncommon, removal of intrapelvic cement or screws during revision surgery can be hazardous to intrapelvic structures. Both arterial and venous perforations can occur, depending on the level at which the pelvic wall has been breached, and on the orientation of the intruding matter. Complications can be minimized with careful preoperative assessment of pelvic anatomy. Contrast-enhanced computerized tomography scanning can assist the revision surgeon with preoperative planning in those patients requiring removal of intrapelvic components. This technique appears to be an accurate, simple, and noninvasive method by which these intrapelvic relationships may be examined. Key words: hip, revision, intrapelvic, components, cement, complications.
Vascular injury resulting from primary and revision hip arthroplasty has been reported to involve both arterial and venous structures. ~-4"6-~9 These events have been linked to direct vessel injury during extraction of existing acetabular components. ~3"~5 While such complications are extremely rare, rem o v a l of intrapelvic cement or screws during revision surgery can be hazardous to intrapelvic structures. Both arterial and venous perforations can occur, depending on the level at which the pelvic wall has been breached, and on the orientation of the intruding matter. Similarly, the bladder and ureter may be at risk from extreme intrapelvic penetration by such material. As the n u m b e r of patients presenting for revision hip arthroplasty increases, hip surgeons are being confronted more frequently with revision of acetabular components in which there is significant intrapelvic cement or perforation of the medial acetabular wall with screws. Our goal in the assessment of these
patients was to determine a noninvasive, cost effective way of evaluating patients before surgery with significant intrapelvic cement or screws prior to revision hip arthroplasty. Through the use of contrastenhanced computerized tomography (CT) scanning of the pelvis, we have the ability to define the vascular and visceral structures of the pelvis and their relationships to total hip acetabular components prior to revision surgery.
Materials and Methods Twenty patients with loose, painful acetabular components and significant intrapelvic cement or screws were investigated before surgery. The first three patients in this series were evaluated by traditional radiographic methods, including standard or selective angiography. We were dissatisfied with these techniques; not only were they invasive and costly, but unless both venography and arteriography were performed in multiple projections, complete definition of periacetabular vascular a n a t o m y was not achieved. We therefore abandoned these traditional techniques and developed a contrast-enhanced CT method to evaluate the remainder of the patients in this series. The CT scan protocol consists
From the *Charlotte Orthopaedic Clinic, P.A., Joint Reconstruction Center, Charlotte, North Carolina, and "tCharlotte Memorial Hospital and Medical Center, Charlotte, North Carolina. Reprint requests: Thomas K. Fehfing, MD, 120 Providence Road, Charlotte, NC 28207.
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Fig. 1. Three-dimensional reconstruction generated from axial CT data followed by sample CT slices to illustrate vascular landmarks at different pelvic levels. (A) Normal pelvic anatomy. (B) Level 2: location of artery, vein, and ureters just below SI joints. Artery (A), vein (V), bladder (B), and ureters (arrowheads). (Figure
conthmes)
of an initial 50 cc bolus of contrast (Conray 43, Mallinckrodt, St. Louis, MO) or equivalent given immediately before scanning. This is supplemented by a rapid contrast drip infusion of 200 cc during the examination. The flow of contrast is unrestricted and can be increased by slightly pressurizing the drip bottle. The patient is scanned using contiguous 3 m m thick axial slices throughout the area of interest, beginning above the most proximal screw or cement and continuing through the lower acetabulum. This provides complete definition of the iliac artery and vein, the c o m m o n femoral artery and vein, and their
more prominent branches throughout the component areas. It also gives us information o n the relationship of intrapelvic orthopaedic materials to the ureter, bladder, and bowel, regardless of which portion of the device may intrude o n these structures (Fig. 1). As expected, there is substantial artifact created by the implant materials. However, this can be overcome by comparison of both bone and soft tissue windows to yield diagnostic information as the vessels are followed through the pelvis. All examinations were closely monitored to ensure that all components were thoroughly and completely evaluated.
Assessment of Intrapelvic Cement and Screws in THA
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Fig. 1. (Conthmed) (C) Level 3: top of quadrilateral plate. (D) Level 4: lower acetabular fovea.
In two cases, the intrapelv!c material was intimately opposed to the femoral vein (Fig. 2). To assure safe removal, a retroperitoneal approach, as reco m m e n d e d by Eftekhar, 5 was used to remove the intrapelvic cement prior to revision. Four of the 20 patients had intrapelvic material within a few millimeters of an important intrapelvic structure. Two of these patients were aseptic cases, and we elected not to disturb the intrapelvic components because of their proximity to major intrapelvic structures (Figs. 3A,B). In these cases we may have elected to remove this material during surgery. How-
ever, because of the knowledge provided by the enhanced CT scan, a concerted effort was made not to disturb the cement (Fig. 3C). In the two other cases, it was mandatory to remove the intrapelvic material because of sepsis or instability (Fig. 4). In each of these cases some prosthetic material was within a few millimeters of an important intrapelvic structure. Because of the proximity, general surgical standby assistance was utilized during the procedure. Fortunately no problems were encountered. All 20 cases involving significant intrapelvic cement or screws were successflxlly reconstructed with-
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Fig. 2. (A) Anteroposterior (AP) view. Note significant intrapelvic cement. (B) CT scan demonstrating intimate apposition of the anterior cement bolus and tile iliac artery and vein.
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9 Fehring et al.
Fig. 3. (A) AP view. Note loose aseptic prosthesis with intrapelvic bolus of cement. (B) lntrapelvic bolus in close proximity to the left ureter. {C) Reconstruction with retained cement.
C
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Fig. 4. (A) AP view. Dislocated prosthesis with malpositioned cup and multiple intrapelvic screws. (B) Lateral view demonstrating posterior dislocation. (Figurecontinues)
out injury to any adjoining intrapelvic structure. CT delineation of intrapelvic anatomy was felt to be satisfactory in all cases in which it was used. Streak artifact was occasionally severe, but the images were still adequate for anatomic assessment.
Normal Anatomy To have a complete understanding of this potential problem, one must be familiar with the course of the major vessels and their changing spatial relationships
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Fig. 4. (Continued) (C) Proximal screw tip 8 mm from iliac artery. (D) Slightly lower slice showing screw tip 4 mm from right ureter.
in the pelvis (Fig. 1). Cadaver dissection and review of contrast enhanced CT scans of the pelvis have shown that at the lower level of the sacroiliac joint, the external iliac artery is anterior and slightly lateral to the iliac vein (Fig. 1B).The ureter is situated immediately posterior or medial to the external lilac vein at this level. As the vessels continue more distally, medial to the quadrilateral plate, the vein becomes more medial to the external iliac artery and less posterior (Fig. 1C). Below the inguinal ligament, they continue as the femoral artery and vein, but the femoral vein is n o w medial to the artery (Fig. ID). The periacetabular vascular anatomy is very well visualized with the enhanced CT scan of the pelvis, and helps explain w h y certain structures are more or less vulnerable at different levels about the acetabulum.
Case Repods
Case 1 A 60-year-old man had an uncomplicated total hip arthroplasty (THA) performed for avascular necrosis in 1975. The hip functioned well until 1987, w h e n he began to experience a progressive increase in pain and a decrease in function. In June 1990, he was referred for consideration of revision arthroplasW. Plain radiographs demonstrated a loose migrated acetabular component with a large bolus of intrapelvic cement (Fig. 2A). The aspiration arthrogram was
positive for loosening and negative for sepsis. A contrast-enhanced CT scan was performed and demonstrated intimate opposition of the intrapelvic cement with the iliac vein and artery (Fig. 2B). A retroperitoneal approach to clear the cement from the iliac vasculature was performed prior to revision. One week later revision arthroplasty with allograft augmentation of the acetabulum was performed without complication.
Case 2 A 71-year-old w o m a n underwent primary THA in January 1988. Following surgery, she had multiple episodes of dislocation that necessitated subsequent revision 2 months later. After that revision, she had multiple dislocations that required manipulative reduction under anesthesia. In May 1988, she had another dislocation that was irreducible with closed means. At this juncture in her care, she was transferred to our service for consideration of revision due to instability. On arrival, she had an aspiration arthrogram that was negative for loosening as well as for infection. Plain radiographs demonstrated a dislocated hip, a malpositioned acetabular component, and multiple screws that had penetrated the pelvic wall in various positions (Figs. 4A,B). Because of the malposition of the acetabular component, it was necessary to remove it and its protruding screws. A contrast-enhanced CT scan of the pelvis was obtained, clarifying the relationship between the four screws and the intrapelvic structures. The most
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inferior screw came within 6 nun of the iliac artery. The most proximal screw came within 8 m m of the iliac artery (Fig. 4C). A third screw was seen to be directed in a horizontal fashion toward the midline, approaching but not violating the right ureter, with a clearance of approximately 4 m m (Fig. 4D). The fourth screw was intrapelvic, but not near any major intrapelvic structure. The existing socket was removed without complication using general surgical standby assistance, and the revised socket was fixed with three 6.5 m m cancellous screws. Two years after surgery, she has no sign of instability, is currently pain-free, and walking unassisted.
Case 3 A 48-year-old man underwent a THA for avascular necrosis in 1972. Before surgery, he had significant drainage from the hip and a nonhemolytic Staphylococcus that was resistant to methicillin was cultured. He was treated with antibiotics and discharged from the hospital without any significant postoperative complications. He was followed at regular intervals and had no particular difficulty until October 1988 w h e n he had a mild traumatic episode to his hip. Subsequent development of intense pain and fever led us to perform an aspiration arthrogram, which was positive for Staphylococcus epidermidis, as well as a blood culture that grew the same organism. His radiographs at this time showed protrusion of the acetabular component with a large bolus of intrapelvic cement (Fig. 5A). Because of his positive aspirate, a thorough debridement, including removal of all cement, was indicated. An enhanced CT scan of the pelvis was obtained, showing that the mass of cement medial to the quadrilateral portion of the acetabulum was well clear of the great vessels (Fig. 5B). Irrigation and debfidement of the hip joint was subsequently performed with removal of all cement. It was n o t e w o r t h y that minimal pus was found in the joint itself. However, w h e n the medial bolus of cement was removed, approximately 10 cc of thick purulent material filIed the acetabulum. Tobramycinimpregnated beads were then placed into the hip joint. Three months later, revision THA using titanium porous-coated implants was performed without complication. The postoperative period was uneventful, and the patient is currently pain-flee and walking without aids.
Discussion The proximity of intrapelvic orthopaedic materials to intrapelvic structures has on occasion resulted in life-threatening hemorrhage during arthroplasty of
the hip. 9 Over the past 25 years, approximately 60 cases of major n o n t h r o m b o e m b o l i c vascular complications of primary and revision hip arthroplasty have been reported in the literature. ~-4"6-~9 These vascular injuries have involved the external iliac artery, the c o m m o n femoral artery, and less frequently, the c o m m o n iliac vein. The mechanisms of injury have included improper placement of spiked retractors, ~-~3 erosion of vessels by prosthetic materials, ~'2"4'6"8"~4"~7thrombosis due to the intense heat of polymerization of cement, 7"~3 and laceration of major vessels during removal of existing acetabular components.~3'~ Although rare in occurrence, complications of vascular injuries in TttA can be life- and limb-threatening. Review of the literature reveals that approximately 35% of reported cases have p e r m a n e n t sequelae, with 10% of these requiring either an above or below knee amputation, and 3% requiring hip disarticulation. In9 Keating recently reported a death from penetration of a branch of an internal lilac artery during revision surgery. 9 Eftekhar stressed the importance of a careful approach w h e n revising intrapelvic components. 5 He reported four cases where acetabular components had migrated beyond the iliopectineal line. In two patients, the external lilac artery was adherent to the cement. In one patient, adhesions formed between the iliac vein and the cement. Motion of the cup produced traction on the iliac vein. These reports stress the potential for serious injury during revision of intrapelvic components. To avoid vascular injuries in revision hip arthroplasty, careful preoperative planning is essential to determine the optimal surgical approach. Knowledge of the spatial relationships between intrapelvic implants and intrapelvic vital structures is particularly important in septic revision where all cement must be removed. In aseptic conditions, it is not necessary to remove all intrapelvic cement, but adherence of intrapelvic cement to the extracted socket is not u n c o m m o n . With the increased use of screws through acetabular components, the potential for vascular injury during revision increases if the pelvic wall has been breached by the screws. 9"2~ The a m o u n t of extruded material is less important than the location of extrusion. This is particularly true in anteriorly extruded cement. This cement m a y not be as apparent on a standard anteroposterior view of the pelvis, but may place the femoral vessels at risk during extraction. In addition to the risk to normal structures, the enhanced CT scan should detect and define any pathologic processes present, including aneurysm, false aneurysm, and abscess.
Assessment of Intrapelvic Cement and Screws in THA
9
Fehring et al.
Fig. 5. (A) AP view. Gross loosening of the acetabular component with intrapelvic cement. (B) One of the axial enhanced CT slices at point of closest cement impingement. Vessels, ureters, and bladder are clear.
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Traditional radiographic methods to evaluate these structures have included standard and selective angio g r a p h y } '3"~'x4 Disadvantages of these techniques include patient morbidity secondary to the invasiveness of these procedures, relatively high expense, and a lack of complete definition of the periacetabular vascular anatomy, unless both v e n o g r a p h y and arteriography are performed in multiple planes. Also, these procedures do not visualize other important intrapelvic structures at risk. Therefore, to minimize complications and better define the periacetabular a n a t o m y , we believe that contrast-enhanced CT scanning is the most accurate m e t h o d of evaluating intrapelvic cement or screws in revision hip a n h r o p l a s t y . Advantages of contrast-enhanced CT scanning of the pelvis over the m o r e traditional angiographic techniques include lower cost and virtually no morbidity. At o u r institution, the cost of an enhanced CT scan is approximately one fourth that of the combined arteriogram and venogram. Advantages of enhanced CT scanning to the surgeon include the ability to derive m o r e information about the periacetabular vascularity and viscera through a single study. Our current approach to the patient with intrapelvic c e m e n t or screws is guided by enhanced CT scanning of the pelvis. If there is clearly no impingement, acetabular revision can be performed in a standard fashion. If there is intimate contact with a major intrapelvic structure, then a retroperitoneal approach should be employed. We feel this is the safest course of action to avoid catastrophic complications. For those cases where intruding material closely approaches but is not in intimate contact with major intrapelvic structures, we feel that general surgical standby assistance is required. We hesitate to place strict guidelines c o n c e m i n g a safe distance between intruding matter and important intrapelvic structures in this intermediate group. We feel that each case should be individualized as such parameters m a y differ depending on the type of intruding material and the structure at risk. Parameters m a y also change depending o n whether the surgeon is dealing with a septic or aseptic case.
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References 1. Aust JC, Bredenburg CE, Murray DG: Mechanisms of arterial injuries associated with total hip replacement. Arch Surg 116:345, 1981 2. Brentlinger A, ttunter JR: Perforation of the extemal iliac artery and ureter presenting as acute hemorrhagic
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