Faculty Bibliography

Blood conservation, specifically the avoidance of allogeneic blood transfusion, is becoming an important aspect of preoperative planning and intraoperative decision making in orthopaedic surgery. Knee and hip arthroplasty, as well as certain spine procedures, place patients at risk of significant blood loss. Fibrin sealants are topically applied hemostatic agents that reduce the time required to achieve hemostasis as well as the volume of blood loss. Fibrin sealants may provide additional benefits beyond hemostasis, such as improvements in wound healing and postoperative range of motion as well as lower rates of wound infections.

Nearly 700,000 hip and knee arthroplasties are performed annually in the United States. Although the results in most cases are excellent, implants do fail. Complications like heterotopic ossification, fracture, and dislocation are now relatively rare and easily diagnosed. Differentiating aseptic loosening, the most common cause of prosthetic joint failure, from infection, is important because their treatments are very different. Unfortunately, differentiating between these 2 entities can be challenging. Clinical signs of infection often are absent. Increased peripheral blood leukocytes, erythrocyte sedimentation rate, and C-reactive protein levels are neither sensitive nor specific for infection. Joint aspiration with Gram stain and culture is the definitive diagnostic test. Its specificity is in excess of 90%; its sensitivity is variable, however, ranging from 28% to 92%. Plain radiographs are neither sensitive nor specific and cross-sectional imaging modalities, such as computed tomography and magnetic resonance imaging, can be limited by hardware-induced artifacts. Radionuclide imaging is not affected by orthopedic hardware and is the current imaging modality of choice for suspected joint replacement infection. Bone scintigraphy is sensitive for identifying the failed joint replacement, but cannot be used to determine the cause of failure. Neither periprosthetic uptake patterns nor performing the test as a 3-phase study significantly improve accuracy, which is only about 50-70%. Thus, bone scintigraphy typically is used as a screening test or in conjunction with other radionuclide studies. Combined bone gallium imaging, with an accuracy of 65-80%, offers only modest improvement over bone scintigraphy alone. Presently, combined leukocyte/marrow imaging, with approximately 90% accuracy, is the radionuclide imaging procedure of choice for diagnosing prosthetic joint infection. In vivo leukocyte labeling techniques have shown promise for diagnosing musculoskeletal infection; their role in prosthetic joint infection has not been established. (111)In-labeled polyclonal immunoglobulin lacks specificity. (99m)Tc-ciprofloaxicin does not consistently differentiate infection from aseptic inflammation. (18)F-fluorodeoxyglucose positron emission tomography has been extensively investigated; its value in the diagnosis of prosthetic joint infection is debatable

Constrained acetabular systems are successful in achieving stability in patients with recurrent dislocations, abductor deficiency, or where a source of instability cannot be determined. We report on one patient with 2 dissociations of a tripolar constrained acetabular liner caused by impingement when the patient exceeded the allowed range of motion. The inner liner dissociated from the outer liner, whereas the reinforcing ring remained intact and in place. Despite an extensive literature search, we were unable to find any other published reports concerning this specific mode of failure for this constrained liner. Surgeons should be aware that constrained liners are not infallible and have limitations to range of motion. Maximizing the size of the femoral head may reduce the risk of this mode of failure

PURPOSE: To compare prospectively the accuracy of positron emission tomography (PET) with leukocytes labeled in vitro with (18)F fluorodeoxyglucose (FDG) versus that of conventional scintigraphy with leukocytes labeled in vitro with (111)In oxine in patients suspected of having infection. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; informed consent was obtained from all patients. Patients were 25 men and 26 women aged 32-86 years. In vitro labeling of autologous human leukocytes with FDG and (111)In-oxine was performed according to published methods. Labeling efficiencies and cell viability were determined. Imaging was performed 2.5-5.8 hours after injection of 196-315 MBq of FDG-labeled leukocytes and approximately 24 hours after injection of 17-25 MBq of (111)In-oxine-labeled leukocytes. Forty-three (20 men, 23 women; mean age, 59 years; range, 32-86 years) patients could be successfully imaged with both tracers. Six patients were not injected with FDG-labeled leukocytes because of low labeling efficiency (<35%). Two patients were injected with FDG-labeled leukocytes but were not imaged. One reader interpreted all results as positive or negative for infection. Imaging results were compared with final diagnoses. Labeling efficiencies and cell viabilities were compared by using the paired t test. Differences between PET and scintigraphy were determined by using the McNemar test. RESULTS: For the 43 patients who were imaged with both tracers, labeling efficiency of FDG was lower than that of (111)In oxine (72% +/- 8 [standard deviation] vs 90% +/- 5, P < .001). Viability of FDG-labeled leukocytes was not different from that of (111)In-oxine-labeled leukocytes (98% +/- 1 vs 97% +/- 3). There were no differences between FDG PET and (111)In scintigraphy in terms of sensitivity (87% vs 73%), specificity (82% vs 86%), or accuracy (84% vs 81%). CONCLUSION: PET with FDG-labeled leukocytes was comparable to scintigraphy with (111)In-oxine-labeled leukocytes. Further investigation in a larger population with dedicated PET or PET/computed tomography seems warranted

The objectives of this study were to investigate (18)F-FDG imaging, using a coincidence detection system, for diagnosing prosthetic joint infection and to compare it with combined (111)In-labeled leukocyte/(99m)Tc-sulfur colloid marrow imaging in patients with failed lower extremity joint replacements. METHODS: Fifty-nine patients--with painful, failed, lower extremity joint prostheses, 40 hip and 19 knee--who underwent (18)F-FDG, labeled leukocyte, and bone marrow imaging, and had histopathologic and microbiologic confirmation of the final diagnosis, formed the basis of this investigation. (18)F-FDG images were interpreted as positive for infection using 4 different criteria: criterion 1: any periprosthetic activity, regardless of location or intensity; criterion 2: periprosthetic activity on the (18)F-FDG image, without corresponding activity on the marrow image; criterion 3: only bone-prosthesis interface activity, regardless of intensity; criterion 4: semiquantitative analysis--a lesion-to-background ratio was generated, and the cutoff value yielding the highest accuracy for determining the presence of infection was determined. Labeled leukocyte/marrow images were interpreted as positive for infection when periprosthetic activity was present on the labeled leukocyte image without corresponding activity on the marrow image. RESULTS: Twenty-five (42%) prostheses, 14 hip and 11 knee, were infected. The sensitivity, specificity, and accuracy of (18)F-FDG, by criterion, were as follows: criterion 1: 100%, 9%, 47%; criterion 2: 96%, 35%, 61%; criterion 3: 52%, 44%, 47%; criterion 4: 36%, 97%, 71%. The sensitivity, specificity, and accuracy of labeled leukocyte/marrow imaging were 100%, 91%, and 95%, respectively. WBC/marrow imaging, which was more accurate than any of the (18)F-FDG criteria for all prostheses, as well as for hips and knees separately, was significantly more sensitive than criterion 3 (P < 0.001) and criterion 4 (P < 0.001) and was significantly more specific than criterion 1 (P < 0.001), criterion 2 (P < 0.001), and criterion 3 (P < 0.001). CONCLUSION: Regardless of how the images are interpreted, coincidence detection-based (18)F-FDG imaging is less accurate than, and cannot replace, labeled leukocyte/marrow imaging for diagnosing infection of the failed prosthetic joint

Intraoperative complications of 175 cementless revision total hip arthroplasties done at four institutions using a porous-coated, uncemented, distally slotted, fluted femoral stem were reviewed. Three types of complications were recorded: eccentric reaming, femoral perforation, and femoral fracture. Intraoperative complications occurred in 16 patients (9.1%). There was no statistically significant association between complication rate and type of surgical approach, stem length, stem diameter, or host bone quality. This complication rate is comparable to or lower than that reported with the use of similar uncemented long femoral revision stems

Some complications of joint replacement surgery are easily diagnosed; however, differentiating infection from aseptic loosening is difficult because these entities are remarkably similar at clinical and histopathologic examination. Clinical signs and symptoms, laboratory tests, radiography, and joint aspiration are insensitive, nonspecific, or both. Cross-sectional imaging modalities are hampered by artifacts produced by the prosthetic devices themselves. Radionuclide imaging is not affected by the presence of metallic hardware and is therefore useful for evaluating the painful prosthesis. Bone scintigraphy is useful as a screening test, despite an accuracy of only 50%-70%, because normal results essentially exclude a prosthetic complication. The addition of gallium-67, a nonspecific inflammation-imaging agent, improves the accuracy of bone scintigraphy to 70%-80%. The accuracy of combined leukocyte-marrow imaging, 90%, is the highest among available radionuclide studies. Its success is due to the fact that leukocyte imaging is most sensitive for detection of neutrophil-mediated inflammation (ie, infection). The success of leukocyte-marrow imaging is tempered by the limitations of in vitro labeling. In vivo labeling has been investigated, and a murine monoclonal antigranulocyte antibody appears promising. Some investigations have focused on fluorodeoxyglucose imaging. Although this method is sensitive, specificity is a concern

Purpose: F-18 FDG (FDG) is reportedly useful for detecting infection. Because the procedure is simple, with results being readily available, this prospective study was undertaken to evaluate the utility of FDG imaging for diagnosing infected joint replacements.Methods: 26 pts, 18 females and 4 males between 37 and 87 years old, with 31 joint replacements were studied. 21 pts had single joint replacement (10 hip, 11 knee); 5 pts had bilateral replacements (1 hip, 4 knee). Imaging was performed on a Hybrid PET system, with measured attenuation correction, one hour after administration of 150 MBq FDG. Increased peri-prosthetic uptake compared to adjacent, presumably normal, activity was interpreted as positive for infection.Results: 11 of 31 prostheses were infected. Sensitivity, specificity, and accuracy of FDG were 100%, 55%, and 71% respectively. The PPV was 55% and the NPV was 100%. Excluding the 5 asymptomatic prostheses in pts with bilateral joint replacements, the sensitivity, specificity, and accuracy were 100%, 47%, and 69% respectively. The PPV was 58% and the NPV was 100%. 4 pts with infected prostheses underwent a total of 6 follow-up studies after treatment. In 1 pt with persistent infection, all 3 follow-up studies were true positive. In the other 3 pts in whom infection had been eradicated, follow-up FDG studies were false positive.Conclusion: FDG imaging is sensitive but not specific; consequently, its role in pts with suspected prosthetic infection is limited to that of a screening test. These data also suggest that this technique is not useful for monitoring response to treatment

Foot complications in diabetics often lead to amputation. Ulceration is the most common complication in the diabetic forefoot and underlies more than 90% of cases of pedal osteomyelitis. The diagnosis of osteomyelitis is, nevertheless, difficult, and imaging is an important part of the work-up. Plain radiographs, although useful for anatomical information, are neither sensitive nor specific. Three-phase bone scintigraphy is sensitive but not specific. Labelled leucocyte scintigraphy and MRI are both useful and are complementary to one another. Labelled leucocyte scintigraphy is valuable for diagnosis as well as follow-up of pedal osteomyelitis. MRI offers exquisite anatomical detail, which is invaluable for guiding surgical management. The principal complication in the mid and hind foot is the neuropathic or Charcot joint. Although infection of the neuropathic joint is infrequent, its diagnosis is difficult. The extensive bony changes that accompany this disorder severely diminish the value of radiography and bone scintigraphy. It is not always possible to distinguish the marrow oedema of neuropathy from that of osteomyelitis and the role of MRI in the evaluation of this entity is still uncertain. Uptake of labelled leucocytes in the absence of infection may occur and is owing, at least in part, to haematopoietically active marrow. Combined leucocyte/marrow scintigraphy holds considerable promise for identifying the infected Charcot joint

This study evaluated the role of combined leukocyte/marrow scintigraphy in the assessment of the neuropathic or Charcot joint. METHODS: Seventeen patients with (111)In-labeled leukocyte accumulation in 20 radiographically confirmed Charcot joints underwent 99mTc-sulfur colloid marrow scintigraphy. Studies demonstrating labeled leukocyte accumulation without corresponding activity on marrow images were classified as positive for osteomyelitis. Six of the patients also underwent three-phase bone scintigraphy. Bone scans were interpreted as positive for osteomyelitis when focal hyperperfusion, focal hyperemia and focal bony uptake on delayed images were present. Bone images were also interpreted together with labeled leukocyte images using two different criteria for a positive study. One criterion was the presence of labeled leukocyte activity in a region demonstrating abnormal activity on the bone scan, which was more intense than adjacent marrow activity or marrow activity in the corresponding region of the contralateral foot. The second criterion was either a spatially incongruent distribution of the two tracers or hyperintense activity on the leukocyte study, as compared to the bone scan. RESULTS: Leukocyte/marrow studies were positive for osteomyelitis in 4 of the 20 neuropathic joints. Osteomyelitis was present in three of the four joints, whereas in the fourth, infection was confined to overlying soft tissues. None of the 16 neuropathic joints with negative leukocyte/marrow scans were infected. In one patient who underwent below-the-knee amputation, histological analysis confirmed the presence of hematopoietically active marrow corresponding to areas of congruent activity on the leukocyte and marrow images. Three-phase bone scintigraphy was positive in all six neuropathic joints studied; osteomyelitis was present in two of them. Using the first criterion, leukocyte/bone imaging was also positive in all six. Using the second criterion, leukocyte/bone imaging was positive in the two infected neuropathic joints, as well as in three uninfected ones. Leukocyte/marrow scintigraphy was positive in both infected joints and negative in the four without infection. CONCLUSION: Labeled leukocyte accumulation in the uninfected Charcot joint does occur and is related, at least in part, to hematopoietically active marrow. Leukocyte/marrow scintigraphy is a reliable way to differentiate between marrow and infection as the cause of labeled leukocyte accumulation in the neuropathic joint and, in this series, was superior to both three-phase bone scintigraphy and combined leukocyte/bone scintigraphy