Musculoskeletal Biopsies and Ablations

Peter L. Munk

Musculoskeletal Biopsy

Introduction

Responsibility for musculoskeletal biopsy varies considerably from one department to the next. In many institutions, this has fallen into the hands of the interventional radiologist because biopsy of bone is quite different than traditional soft tissue biopsy of the type typically practiced in abdominal or pelvic imaging (1,2). The instruments and technique utilized are different, and analgesia with or without sedation is almost always required. The way in which a biopsy is performed also has profound implications on the surgery performed by the orthopedic oncologist if a sarcoma is diagnosed. Because of this, the importance of proper planning of the biopsy (the route that the biopsy is performed through, and the area of the tumor sampled) cannot be overemphasized. This latter point will be repeatedly made. Biopsy of soft tissue masses of the musculoskeletal system is very similar to that of soft tissue biopsy elsewhere with the proviso, once again, that biopsy requires careful planning so that the definitive surgery is not compromised (1).

Contraindications

Absolute

1. Incomplete imaging and staging of the lesion prior to biopsy (1)

2. International normalized ratio (INR) greater than 1.5

3. Uncooperative or unwilling patient or inability to obtain informed consent from the patient or responsible caregiver

4. Uncertainty about planned definitive surgical excision route. The biopsy path must follow the same path that the surgeon plans to use to definitively excise the tumor as sarcomas have a high propensity to seeding the biopsy tract. Because of this, the biopsy tract must be removed at the time of definitive surgery, and an ill-conceived or incorrectly planned route can significantly compromise surgery performed—it may convert a limb-sparing procedure into an amputation, or a curative procedure into one for which cure cannot be achieved. If any uncertainty whatsoever exists about the biopsy path, consultation with the surgeon who will perform the definitive surgery is mandatory (1,2).

Relative

1. Platelet count below 50,000 per µL or recent use of platelet inhibitors. The risk of hematoma is increased in these situations, and tracking of a hematoma can spread sarcoma.

Preprocedure Preparation

1. Definitive locoregional imaging must have been completed. In most instances, this consists of cross-sectional imaging, preferably magnetic resonance imaging (MRI).

2. The type of image guidance for the procedure should be decided, and the equipment booked.

3. Surgical consultation, including full clinical assessment and tentative planning of definitive surgery in order to permit assessment of the required biopsy route

4. Informed consent must be obtained for the biopsy either from the patient or a responsible caregiver.

5. Arrangement of day care bed and availability of nursing staff to monitor the patient and to provide analgesia + / – sedation (which is often required for bone biopsies).

6. The patient should be on nil per os (NPO) except for medications from midnight the day before the procedure.

7. Arrangements should be made for the patient to be escorted home after the procedure if medications have been administered. Under rare circumstances, where this is not possible, it may be necessary for a longer day care admission or possibly even an overnight stay.

Procedure

1. Patient preparation

a. Intravenous access is required. Patients are closely monitored by a nurse who can administer sedation (midazolam) and/or analgesia (fentanyl) during the procedure. Electrocardiogram (ECG) and oxygen saturation monitoring are recommended.

b. The patient must be placed in a comfortable position that can be maintained throughout the course of the procedure.

c. Bone tumors with mineralization present are usually done in the author’s institution with computed tomography (CT) guidance in order to accurately document the position of the needle. In this way, the portion of the tumor being sampled is known. Very large destructive tumors can on occasion be biopsied under fluoroscopic guidance, although this is exceptional. Soft tissue masses are usually biopsied with sonographic guidance. Bone tumors with soft tissue components associated with the osseous lesion can often be successfully biopsied using sonographic guidance as well (1).

d. Patient positioning must allow optimal access to the biopsy site via the route decided upon at the time of surgical planning and consultation with the orthopedic oncologist.

e. The area to be accessed is then sterilized and draped.

2. Physician preparation

a. Thorough hand washing and gloving are mandatory, and the use of facial shield or goggles is recommended.

b. Use of needle receptacle and devices that avoid the necessity of recapping needles is strongly recommended.

3. Biopsy procedural details

a. Typically, the patient receives a small amount of midazolam (Versed) prior to initiating the procedure.

b. The skin is anesthetized with 2% lidocaine and a 25-gauge needle.

c. A skin incision is made longitudinally (never transversely) approximately 1 cm in length. This not only allows easier access for instruments but also allows the surgeon to clearly see the puncture site utilized for the biopsy and ensure that it should be excised at the time of surgery. (If preferred, a suture can be placed afterward to aid in identification of the biopsy site.)

d. Infiltration of biopsy tract with local anesthesia (2% lidocaine using a 20- or 22-gauge spinal needle): The tract is first carefully planned (which with CT may require placement of a localization grid), and calculation of the distance from the puncture site to the target area within the tumor is made so an appropriate-length needle can be selected. The target area in the tumor is chosen based on the route to be used by the surgeon and the location of viable (non-necrotic or mucinous) tissue. The route to be selected should not violate an uncontaminated compartment and must avoid neurovascular structures
(which would have to be resected at the time of surgery if contaminated with sarcoma). These issues will have been discussed ahead of time with the referring surgeon (1,2).

e. The needle is then introduced along the preplanned route.

(1) All biopsies of both bone and soft tissue should be core biopsies; fine needle aspiration is of no value in this situation.

(2) A large variety of different devices suitable for core biopsy exist on the market. Most will provide cores between 20 gauge and 12 gauge in diameter; in the author’s institution, a 14-gauge device is used. Devices for bone biopsy are typically variants of the Jamshedi-type needle. This needle has small teeth at the end and is capable of cutting through bone.

(3) It is recommended that biopsies be done coaxially, the Jamshedi needle going through an outer sheath allowing for multiple core biopsies to be obtained through the same access site. The tip of the needle where the sample is being obtained from should be recorded in order to document the tissue site being sampled.

(4) Soft tissue samples can be obtained using spring-loaded cutting needles as with biopsies performed in the abdomen and pelvis (1).

f. A minimum of three cores should be obtained whenever possible. Different departments will have different protocols for evaluation of musculoskeletal tumors, so consultation ahead of time with the reading pathologist will be helpful in ensuring that the number and type of samples required are obtained (i.e., fresh vs. formalin, etc.). The type of samples and pathologic examination required should be decided ahead of time and the appropriate tubes, receptacles, and requisitions prepared in advance.

g. At the conclusion of the procedure, the needle is removed, and pressure is placed over the puncture site in order to ensure that homeostasis is achieved. This is particularly important in patients who may have borderline laboratory values or be on platelet inhibitors.

Postprocedure Management

1. The patient is monitored from 2 to 4 hours, depending on the amount of analgesia and sedation administered. In most cases, at the conclusion of this time, the patient is ready to go home.

2. The puncture site is checked every 15 minutes for the first hour and hourly thereafter.

Results

1. Core needle musculoskeletal biopsy is a highly successful technique producing diagnostic results in 90% to 93% of patients. Diagnostic yields tend to be slightly higher with patients with malignant disease and slightly lower in patients with benign disease.

2. Typically, in patients with extensive myxoid or necrotic material, there is a higher risk of obtaining nondiagnostic biopsy material; therefore, every effort must be made to sample solid, viable portions of tumor.

3. Patients having definitive surgical procedures after poorly planned biopsies require a different or more complex procedure in up to 19% of cases, with conversion to amputation from limb-sparing procedure in approximately 5% of this subset.

Complications

1. Tumor seeding along the tract of the biopsy. This may occur in 5% to 10% of cases; however, because the tract is usually excised at the time of definitive surgery, this does not pose a problem in most patients (1).

2. Bleeding and hematoma

3. Contamination of the neurovascular bundle or an uncontaminated compartment. This is usually the result of a poorly planned biopsy route.

4. Infection—very rare

5. Inadequate tissue: This is due to either obtaining an inadequate number of samples or sampling a necrotic or myxoid tumor. It is always preferable to obtain additional core biopsies if any doubt exists as to whether sufficient tissue is available.

Management of Complications

1. If a poorly planned biopsy/attempted excision has been performed (a “whoops” procedure), consultation with the surgeon with complete disclosure of procedural details is essential. This may allow construction of a suitable alternate surgical plan that may still permit a satisfactory clinical outcome. This is often highly challenging or may not be possible. Use of radiotherapy and/or chemotherapy prior to or following the surgical excision may be of benefit (1).

2. Hematomas can be minimized by careful compression and monitoring of the biopsy site, particularly in patients with coagulopathy or platelet dysfunction.

3. Infection may require treatment with antibiotics.

Radiofrequency and Cryoablation of Musculoskeletal Lesions

Introduction

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