Percutaneous, image-guided musculoskeletal biopsies provide an accurate, rapid, and cost-effective method for helping clinicians diagnose benign and malignant musculoskeletal lesions.  In patients who present with nonspecific physical findings, imaging studies, and laboratory values, percutaneous biopsy can lead to a rapid and accurate diagnosis and allow implementation of the most appropriate therapy. Most biopsies can be performed using local anesthesia, with the addition of conscious sedation if necessary.
Various imaging modalities can be used to target the lesion, including computed tomography (CT) scanning, fluoroscopy, ultrasound (US) scanning, and magnetic resonance imaging (MRI). The procedure is safe, with major complications uncommonly reported. When proper techniques are used, nondiagnostic or insufficient specimens are obtained in only approximately 8-10% of biopsies. Accuracy is expected to be 70-100% and is improved with expert cytopathologic interpretation. [2, 3, 4, 5, 6, 7] A 2009 review of 309 biopsies noted that image-guided core needle biopsy was particularly effective in diagnosing homogenous soft tissue tumors.  Rimondi et al also noted the reliability of percutaneous CT-guided biopsy after analyzing 2027 cases over a period of 18 years. 
Morbidity and Mortality
The prevalence of complications associated with musculoskeletal biopsy is low and depends on the type of needle selected and on anatomic location. Reported incidence of complications ranges from 0-10%. Risk of significant complication should be less than 1% and is considered to be much less than the risk of an open surgical biopsy under general anesthesia. Complications may include the following:
Bleeding requiring transfusion is rare. In one series, 2 of 94 patients had psoas hematomas and 1 of 94 patients had aortic puncture (the patient was asymptomatic); in 2 of 94 patients, the procedures were aborted secondary to patient discomfort.  In another series, 1 of 176 patients had subcutaneous hematoma. In yet another series, no transfusion was needed (0 of 43 patients) with significant hematoma.
Infection is a possible complication of musculoskeletal biopsy.
Neurologic injury can occur because anesthetizing major motor nerves is possible and may create paresis or paralysis. The depth and extent of anesthesia can progress throughout the procedure; recovery should occur within 3-4 hours. In one series, 7.7-10.5% of patients experienced radicular pain after transpedicular biopsy. Additional neurologic injuries that may occur include spinal cord compression secondary to postbiopsy hematoma, as well as direct needle puncture of the cord, dural tube, or exiting nerve roots during the procedure. While rare, significant cord compression may occur, particularly with biopsy of hypervascular vertebral lesions, such as metastatic renal cell carcinoma; neurosurgical consultation is recommended, and surgical decompression may be required.
There is a small but definite increase in fracture risk following bone biopsy, particularly in weight-bearing bones, such as the femur. Risk of postbiopsy fracture can be decreased through the use of smaller bone needles; however, no needle is completely without risk. The patient should be informed of this potential risk before the procedure, during the informed consent process. Significant worsening of local pain with ambulation after the procedure should prompt further clinical evaluation and possibly additional imaging.
Limitations and Contraindications
Limitations and/or contraindications for musculoskeletal biopsy are as follows:
Bleeding diatheses: Coagulation disorders should be corrected prior to biopsy; fresh-frozen plasma can be administered immediately prior to biopsy to temporarily correct prothrombin time, activated partial thromboplastin time, and the international normalized ratio.
Inaccessible sites include the following: 
- Sclerotic lesions next to major arteries
- Bone surrounded by infected soft tissues
- C1 and the odontoid process of C2 lesions
Biopsy of hemorrhagic lesions frequently is less accurate, even with core needle biopsy. Prebiopsy imaging can help guide needles to areas with less vascularization. A fine needle should be used if a path is in close proximity to vessels or if a hemorrhagic lesion is suspected.
Imaging modalities for guidance
The choice of imaging guidance depends to some degree on operator preference; options include ultrasonography (US), CT scanning, fluoroscopy, and MRI.  In general, biplane fluoroscopy can be used for superficial bony lesions, while CT scanning is preferred for deeper lesions and lesions in anatomically complex areas. US scanning obviates the need for ionizing radiation and can be used if an accompanying soft-tissue mass or cortical destruction is present.
On rare occasions, MRI may be used to visualize lesions occult to CT scanning and to visualize the procedure in real time. However, MRI is of limited use in sclerotic lesions, in a relatively small number of interventional MRI systems, and with less cumulative operator experience. In a 2007 study of 45 biopsies, MRI was better for diagnosing bone lesions than soft tissue lesions. 
Choice of needle systems is important. Sclerotic lesions require a trephine-type needle, such as the Ackerman or Craig needle (George Tiemann and Company, Long Island City, NY). These needles consist of an outer trocar, which remains fixed in the lesion and allows the removal of more material without the need for repositioning. The Ostycut needle (Angiomed/Bard Products, Karlsruhe, Germany) is a trephine-type needle with screw threads that allows easy advancement with a turning motion. A fine cutting needle, such as an 18-gauge spinal needle, an 18- to 22-gauge Chiba needle (Cook, Bloomington, IN), or a 20- to 22-gauge E-Z-EM needle (E-Z-EM Inc, Westbury, NY), can be passed in a coaxial fashion through the outer needle or trocar to obtain material for histopathology. See the images below.
For lytic or destructive lesions, biopsy can be performed using any of a number of small-bore (18- to 22–gauge) needles, including the Chiba, E-Z-EM, and spinal needles. Additional options include small-bore fine needles that obtain core samples, such as the Franseen (Cook, Bloomington, IN), Rotex (Havel's Inc, Cincinnati, OH), and Westcott (Becton, Dickinson, and Company; Franklin Lakes, NJ) needles. In addition, automated core biopsy devices, such as the Tru-Cut needle (Baxter Healthcare Corp, Deerfield, IL) can be used to obtain slices of tissue for analysis, inserted either coaxially or directly into the lesion if frank cortical destruction or an associated soft-tissue mass is present.
An important consideration when choosing appropriate needle systems is the amount of tissue expected to be required for accurate pathologic diagnosis. The bore size of a biopsy needle is inversely related to gauge; thus, a smaller-gauge needle will yield a larger specimen for analysis. For example, an 11-gauge Craig needle will yield significantly more specimen per pass than will a 22-gauge Chiba needle. Therefore, the choice of needle should balance the need for a sufficient specimen with the increase in local complications that may result from the use of a larger-bore (smaller-gauge) needle.
Some authors propose a complementary role for fine-needle aspiration biopsy and core biopsy, suggesting that both be performed during each biopsy procedure.  The rationale behind this proposal is that there are instances when the specific diagnosis will be made by one technique and not the other, so that the overall accuracy of the procedure will be improved when both techniques are used.
Hodge found aspiration-type needles to perform well in the diagnosis of malignant disease and infection, with the added benefit of smaller bore and no necessary skin incision.  Hodge also found a complementary role for cytopathologic and histopathologic specimens, to increase diagnostic accuracy. Additionally, an algorithm has been proposed that could direct the choice of fine-needle aspiration or core biopsy based on imaging findings and preprocedural differential diagnosis. The final decision regarding the choice of fine-needle aspiration biopsy, core needle biopsy, or both should depend on the cytopathologic resources available and the expected lesion pathology. 
The choice of biopsy route is crucial to success.
The transpedicular approach prevents the leaking of cerebrospinal fluid or the spread of infection or tumor, as long as the medial pedicular wall remains intact.
Paraspinal approaches may be technically difficult secondary to a lack of purchase obtained with an angled approach to the vertebral body.
Some lesions may not be good candidates for percutaneous biopsy. Specifically, hypervascular metastases, such as renal cell carcinoma with posterior vertebral body and/or spinal canal extension, are at increased risk of cord compression if biopsy is performed. Biopsy of a compression fracture should be performed under CT-scan guidance; if the compression is too great, a percutaneous biopsy may not be appropriate.
Many biopsies can be performed using only 1% lidocaine local anesthesia. For rib lesions, intercostal block can be performed using 0.25% bupivacaine. For deeper or painful lesions, conscious sedation with intravenous Versed (midazolam) or Valium (diazepam) and pain control with Demerol (meperidine) or Sublimaze (fentanyl) is used. The needle tract can be anesthetized using 1% lidocaine for added pain control during placement of the needle.
The decision to proceed with percutaneous biopsy should be made after reviewing pertinent imaging studies and consulting with appropriate clinical staff, as well as on a case-by-case basis. For example, radionuclide bone scanning may be useful to delineate additional lesions that may be more easily accessible and pose less risk of biopsy-related complication. A fluorodeoxyglucose–positron emission tomography (FDG-PET) scan also may be appropriate, when there is clinical necessity to further depict (with CT or MR co-registration information) metabolically active portions of a lesion to guide needle placement.
Care should be taken when selecting a lesion for biopsy to avoid biopsy at the site of a fracture. Specimen from a routine, nonmalignant fracture can appear similar microscopically to a sarcoma and present a significant diagnostic challenge to the pathologist. An exception is the vertebral body, where biopsy of a suspected pathologic fracture may be both appropriate and diagnostic.
Additional considerations exist when planning pediatric musculoskeletal biopsy. As with adults, adequate sedation and pain control are required for patient comfort and safety. Frequently, intravenous sedation with pentobarbital (2-6 mg/kg) for children younger than 7 years and use of midazolam (0.05 mg/kg) for older children will achieve the desired effect. Fentanyl citrate (1-3 µg/kg IV) also may be used for pain control.
Biopsy-site skin preparation with eutectic mixture of local anesthetic (EMLA) cream (a combination of lidocaine and prilocaine) and addition of sodium bicarbonate to the 1% lidocaine local anesthetic solution (to decrease pH and reduce stinging during administration) also are useful. General anesthesia will be required for procedures that are expected to be lengthy, complicated, or painful; for biopsy of anatomically elegant areas with little margin for patient motion; and for severely anxious and frightened patients. When possible, US scanning should be used for biopsy guidance to avoid ionizing radiation.
Lesions should be superficial and visible by fluoroscopy. Biplane fluoroscopy is helpful in determining the placement of a needle directly into a lesion. For fluoroscopically visible superficial lesions, degree of confidence is high for obtaining an adequate position for the biopsy. Lesions that are not seen well in 2 planes should be approached using other appropriate imaging modalities. False-positive findings are uncommon and usually result from primary chondroid lesions. False-negative findings result from sampling error, small round-cell tumors, or chondroid lesions, such as chondrosarcoma diagnosed as enchondroma. Close follow-up studies must be performed in these patients.
Using CT scanning, lytic or blastic bone lesions with or without associated soft-tissue mass can be visualized. CT scanning provides a high degree of confidence. Biopsy can be performed on densely sclerotic lesions but may require a larger trephine-type needle. False-positive findings are unlikely in CT. False-negative findings are rare. In one study of 176 core biopsies and 45 fine-needle aspirations, accuracy for core biopsy was 93%, and for fine-needle aspiration, 80%. Only 8% of biopsies were nondiagnostic or insufficient. [20, 21] Low-dose CT guidance appears to be as aeffective as higher-dose approaches.  CT fluoroscopy guidance provides biopsy results similar to those of conventional CT guidance. See the image below.
MRI guidance can be used if the lesion is not seen well on fluoroscopy or CT scan. MRI-compatible needles are available (E-Z-EM Inc; Somatex, Berlin, Germany; MDTech, Gainesville, FL). The needles may have higher nickel content in a low–magnetic-susceptibility alloy. Placing the frequency-encoding direction parallel to the needle path and the phase-encoding direction perpendicular to the path can reduce artifacts. Carbon-fiber needles have been developed that lack susceptibility artifacts but are almost invisible on MRI. 
Many newer MRI systems (eg, Magnetom Open, Siemens, Erlangen, Germany) have incorporated improved access for interactive interventional procedures. The units may include radiofrequency-shielded liquid crystal display screens for visualizing images, as well as foot-pedal control of image acquisition for the operator. Studies have shown time of procedure and incidence of complications to be the same or lower than those with CT- or US-guided procedures. MRI is exquisitely sensitive to marrow abnormalities even when CT scanning does not demonstrate a distinct abnormality. Therefore, MRI-guided biopsy provides the operator with a high degree of accuracy with which to target abnormal marrow. 
US guidance can be used to acquire specimens efficiently from a variety of soft-tissue tumors and processes. Advantages include real-time visualization of the needle's position and a lack of ionizing radiation. If biopsy of a soft-tissue malignancy is performed, consultation with the surgeon is necessary to ensure that the biopsy tract is removed during the surgical procedure. Both fine-needle and core needle biopsy specimens can be obtained using standard devices. US scanning can also be used to localize affected muscle groups and to guide biopsy of childhood neuromuscular diseases. US-guided biopsy of bone lesions can be performed when cortical destruction is present, acting as a window to allow passage of the needle into the medullary cavity. Biopsy of associated soft-tissue mass also is performed easily. 
If histology yields only peripheral blood elements in an obviously destructive mass, the biopsy should be repeated. The repeat biopsy should be directed at a slightly different area of the lesion, and more material should be aspirated if possible. No more than 3 percutaneous biopsies of the same lesion should be performed, because the likelihood of subsequent positive findings is small.
Seeding of tumor along the biopsy tract
Tract seeding is rare, having been reported in less than 0.01% of patients undergoing abdominal biopsy. The occurrence rate can be expected to be similar for most bony lesions. An exception is primary bone sarcoma, in which the needle entry site should be marked on the skin in indelible ink so that the tract can be excised when the patient undergoes definitive surgery.
Type of anticipated tumor
Small round-cell tumors, such as spinal lymphoma and myeloma, are difficult to diagnose definitively, particularly in normal red-marrow-producing sites, such as the spine and pelvis. In one study, the use of larger-bore needles was suggested to increase the amount of recovered material, along with the use of frozen-section analysis or touch-preparation cytopathologic analysis to ensure that adequate material is obtained.  The diagnostic yield for biopsy of sclerotic bone lesions is lower than that of lytic lesions; preprocedural knowledge of the possible need for additional samples is necessary when biopsy of a sclerotic lesion is undertaken. 
Review of all available pertinent imaging studies is again required, as these may disclose a concomitant lytic lesion for which fewer samples may be needed or disclose an additional lesion in which the biopsy route will pose less risk. When such a choice is available, biopsy of the lytic lesion is favorable to that of a similarly positioned sclerotic lesion.
Soft-tissue tumors with large myxoid or necrotic components
Imaging can direct the biopsy path away from these areas. Radionuclide bone scanning, FDG-PET scanning, CT scanning, and MRI all may be valuable to depict areas of low tracer uptake fluid attenuation/signal intensity and those lacking contrast enhancement, as seen with necrosis or mucinous/myxoid material. The modalities may also aid in appropriate biopsy path planning. Frozen-section and/or touch-preparation cytoanalysis should be performed. If biopsy results are not concordant with expectations, the needle should be redirected to sample additional areas of the lesion. These techniques can increase the accuracy rate 88-94% in this subset of patients.
Biopsy of the correct lesion is imperative for accurate and timely patient care. In one study, previously mentioned, biopsy was performed at an incorrect vertebral level in 1 of 94 patients.  The patient did not have a reported complication; however, this case underscores the need for thorough review of preprocedural imaging studies. The authors in that case also recommended obtaining a visual CT scan or MRI of the lesion that is consistent with the suggested lesion prior to biopsy.