The overall accuracy of PB of bone lesions reported in the literature varies from 66% to 96% (1,10,11,14-16). However, the method of evaluation of skeletal PB accuracy varies greatly in the different series reported. Because PB is also useful in excluding a diagnosis, evaluation of accuracy must take into account both true-positive and true-negative results. However, true-negative and false-negative results are difficult to confirm (10). They require a second test or adequate follow-up (10). Nevertheless, the accuracy of PB of skeletal lesions is reliably evaluated in some series. Debnam and Staple reported that an accurate diagnosis was made or disease was excluded in 81% of patients or 74% of biopsy sites (17). Murphy et al. found a 94% overall accuracy in 160-closed biopsies (10).
The accuracy of trephine biopsy depends on many different factors: the nature of the lesion, its location and radiologic appearance, the accuracy of the preoperative radiologic assessment, careful selection of the biopsy site and choice of adequate instruments, approach and method of radiologic guidance, biopsy technique with emphasis on specimen adequacy, especially sampling of multiple cores in different locations, and expertise of the pathologist and the bacteriologist and close cooperation between them and the radiologist.
PB has a high diagnostic accuracy in bone metastases ranging from 79% (16) to 96% (1), and PB should be preferred to surgical open biopsy when a bone metastasis is suspected (Fig. 27). In some cases, such as bone metastases from hepatocarcinoma or thyroid carcinoma, the histopatho-logic examination may indicate the precise nature of the primary neoplasm. Most authors accept that some primary neoplasms of bone such as myeloma, plasmacytoma, lymphoma, and Ewing's tumors can be accurately diagnosed by PB. However, the value of PB in the diagnosis of other primary bone neoplasms such as bone sarcomas is still under debate. Most authors found that needle biopsy provides lower diagnostic accuracy than open biopsy in primary musculoskeletal tumors (13,18,19). Mankin et al. obtained a 60% rate of accuracy with needle biopsy as compared with 76% of incisional biopsies in primary musculoskeletal tumors (13). The diagnostic accuracy rate of PB in primary bone tumors was 79% in a referral cancer center (18). In another study, the diagnostic accuracy of PB was only 78% in primary soft-tissue tumors (19). However, PB also causes less complications than open surgery in primary musculoskeletal tumors (13). In each individual case, however, the decision must be taken in consultation with the orthopedic surgeon.
Diagnostic accuracy of PB in skeletal tuberculosis is very high. In a series of 21 cases of vertebral tuberculosis, an accurate diagnosis was obtained in 20 cases (95.2%) (1). This high rate of accuracy may be due to several factors: both histologic and bacteriologic examination may lead to a correct diagnosis; bone tuberculosis produces a large amount of pus (Fig. 28); and diagnosis is not impaired by antibiotic treatment prescribed without specific diagnosis. However, pathologic examination is sometimes nonspecific, and may, in some cases, mimic those of a nontuberculous pyogenic bone infection (14). Morre et al. obtained an 80% accuracy rate in 117-pyogenic bone infections (16). In another study, the causative microorganism was isolated in only 15 (55.5%) of 27 pyogenic disc infections (1). Histological features suggestive of pyogenic infection were found in half the cases with negative bacteriologic examination (1). This relatively
low accuracy rate of PB in pyogenic disc infection as compared to spinal tuberculosis has several explanations: definitive diagnosis is only possible when the bacteriologic examination is positive, patients often received antibiotics prior to biopsy, and spontaneous resolution with elimination of the microbial agent is possible.
Finally, percutaneous image-guided biopsy is a cost-effective procedure for most musculoskeletal lesions (11,20). In a study by Fraser-Hill et al., the estimated cost of CT-guided biopsy was $442 compared with $1658 for open surgical biopsy (20). In a series including 83% of
FIGURE 28 Disc biopsy in spinal tuberculosis at L4-L5 level with opacification of a prevertebral abscess.
primary musculoskeletal tumors, Skrzynski et al., evaluated the hospital charges for the closed biopsy to be $1106, compared with $7234 for the open biopsy (19). According to Springfield and Rosenberg, it is likely that these data provide a basis for the recommendation of outpatient needle biopsies for properly selected primary musculoskeletal tumors (21).
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