Approach Considerations
There are two primary indications for surgical management of an osteoblastoma within the musculoskeletal system. The first is obtaining a tissue sample that firmly establishes the diagnosis. "When tumor is the rumor, tissue is the issue" is a good rule to remember. It is frequently the case, however, that even with an appropriate, representative tissue sample, it may be very difficult to differentiate the aggressive (stage 3) lesions from osteosarcoma.
The second reason for surgical management is to eliminate the continued structural destruction of bony architecture by this aggressive tumor. It is important to emphasize that repairing the structural bony defect is the secondary consideration, in that it cannot be planned and implemented until diagnosis of the lesion is established.
No specific contraindications for the treatment of osteoblastoma have been documented. General precautions include avoiding harm to a growth plate when operating near one in the skeletally immature patient. When these tumors are removed from the spinal elements, meticulous care to protect the spinal cord during the procedure is mandatory. Similar precautions must be considered for the urinary bladder, the sacral plexus, and other associated pelvic organs when lesions are removed in these locations. Because all patients need some form of surgery in the management of this tumor, they must be able to tolerate anesthesia.
Medical Therapy
The use of radiation or chemotherapeutic measures to treat osteoblastoma has been controversial. Most authorities have maintained that neither treatment has any therapeutic effect on this lesion and that each has more risks than benefits. For instance, postirradiation sarcoma is a well-documented outcome in the management of benign tumors and makes this method of treatment inappropriate for benign, destructive surgically accessible tumors such as osteoblastoma.
Surgical Therapy
The appropriate surgical treatment goal for osteoblastoma is complete excision of the lesion. For stage 2 lesions, the recommended treatment has been extensive intralesional curettage followed by management of the resulting structural defect. After curettage of macroscopic material, a high-speed burr can be used to remove microscopic tumor back to a circumferential margin of normal-appearing bony tissue. Curettage alone is usually inadequate.
In a study of 99 cases of osteoblastoma over 30 years (1974-2006), the local recurrence rate was approximately 24% after curettage alone and bone reconstruction of the resulting defect. The authors concluded that in select cases, recurrence can be minimized by more aggressive surgery. [36]
For stage 3 lesions, wide resection has been recommended to ensure removal of all tumor-bearing and any associated tumor (eg, aneurysmal bone cyst). Wide excision is defined as the excision of the tumor with a circumferential cuff of normal bone and soft tissue around the entity. Such excisions are usually curative for osteoblastoma with an associated aneurysmal bone cyst. [36, 37]
A single-center study by Cao et al (N = 50) assessed the clinical efficacy and safety of intralesional marginal resection (n = 42) as compared with extensive curettage (n = 5) and en-bloc resection (n = 3) for treatment of osteoblastoma in the mobile spine. [38] Surgical complication rates were 38.1% for intralesional marginal resection, 60.0% for curettage, and 0% for en-bloc resection. Recurrence rates for the three treatments were 7.1%, 60.0%, and 0%, respectively; for intralesional marginal resection, recurrence rates were 7.7% for stage 3 lesions and 6.3% for stage 2. Local recurrence occurred in 35.7% of patients who had vertebral artery extension and in 0% of those who did not.
Weber et al compared the clinical success and costs of computed tomography (CT)-guided radiofrequency ablation (RFA) with those of open surgical resection for osteoblastoma as well as spinal osteoid osteoma (OO). [39] They found RFA to be an efficient method for treating osteoblastoma, with results comparable to those of open surgery.
Wang et al found CT-guided percutaneous RFA to be a safe and effective treatment for stage 2 osteoblastoma, especially in cases where there were no neurologic deficits and cortical bone was intact. [40]
Percutaneous image-guided cryotherapy has been used to treat osteoblastoma. [41] It appears to be an effective and safe option, provided that sufficient protective measure are taken to preven damage to nearby critical structures. [42]
A single-center retrospective study by Arrigoni et al found magnetic resonance (MR)-guided focused ultrasound surgery (MRgFUS) to be safe and effective for treating intra-articular osteoblastoma with a good acoustic window. [43] MRgFUS can accomplish tumor ablation without requiring a needle or the use of ionizing radiation, and it can achieve a highly precise and controlled increase in temperature. [44] It delivers small amounts of energy that destroy only the lesion and spare healthy surrounding tissues.
Preparation for surgery
Surgical excision of osteoblastomas must be carefully planned. For instance, embolization 24 hours before definitive surgery may be indicated to help control bleeding of an associated aneurysmal bone cyst; it can also be used to reduce intraoperative bleeding and facilitate complete excision in surgically difficult sites.
A study of a small cohort of patients did not show any evidence of tumor relapse when preoperative embolization was used before surgical resection and reconstruction of cervical spine lesions. [45] A case-control study found that preoperative embolization as an adjunct to surgical management of osteoblastoma may lead to reductions in intraoperative blood loss and blood transfusion volume. [46]
Planning for reconstruction of any critical defect (ie, one in which bony stability is lost) also must be carried out before one may proceed with definitive surgery. For example, those lesions necessitating wide resection for adequate removal of the osteoblastoma may require facet resections that can create an unstable spine. Appropriate preoperative planning for stabilization of such a defect is required for this eventuality.
Operative details
Aggressive lesions must be removed by means of wide resection. If required, internal fixation must be planned for stabilization as noted above (see the images below).
Surgical stabilization with internal fixation was used after wide resection of osteoblastoma of cervical spine (this image depicts same 15-year-old patient shown above).
Surgical stabilization with internal fixation was used after wide resection of osteoblastoma of cervical spine (this image depicts same 15-year-old patient shown above).
Regardless of the method of resection, the surgical margins must be tumor-free if complete excision of the tumor is expected.
Postoperative Care
The application of external bracing, rehabilitation modalities, home healthcare, postoperative pain control, muscle relaxants, pulmonary care, and urinary tract care must be monitored and adequately managed during the postoperative period. Providing the patient and family with written expectations of healing times for the reconstructed site, as well as expected temporary and permanent functional limitations, is also appropriate in this period.
Complications
The most frequent immediate postoperative complications are as follows:
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Wound, urinary tract, and lung infections
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Hemorrhage at the operative site
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Loss of bony stability of the surgical stabilization construct
Tumor recurrence occurs late (ie, months to years) after the procedure, and planning for this eventuality must be done for a scheduled period after the definitive procedure. However, there are no universally accepted time intervals for the period within which such follow-up should occur; accordingly, the range is highly variable. A good rule is to continue these studies until the reported likelihood of regrowth of this tumor is small. It is also important to include chest films; giant cell tumor, osteoblastoma, and chondroblastoma have been reported to metastasize to the lungs.
Long-Term Monitoring
Monitoring for signs and symptoms of infection and bleeding of the operative site, as well as for systemic signs of urinary tract and pulmonary complications, are important during the immediate postoperative period.
Scheduling appropriate studies to reevaluate the patient for local and distant spread after the definitive procedure is necessary at specific postoperative intervals and must be planned and discussed with the patient and family.
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Standard radiograph of osteoblastoma with secondary aneurysmal bone cyst of lumbar spine.
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(Click image to enlarge.) Osteoblastoma with secondary aneurysmal bone cyst. CT findings are nonspecific but help demonstrate extent of lesion arising in vertebral column.
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Oblique and lateral radiographs of ankle reveal lucent lesion within talus.
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Radiograph of cervical spine of 15-year-old girl.
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Radiograph of cervical spine reveals expansile lesion in posterior elements of cervical spine in 15-year-old girl.
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CT of cervical spine reveals expansile lesion in posterior elements.
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Increased radionuclide activity in talus corresponds to site of lesion.
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T1-weighted sagittal MRI of left foot demonstrates lesion in talus with low signal intensity. MRI findings are not specific enough to suggest diagnosis of osteoblastoma but aid in determining extent of lesion.
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T2-weighted sagittal MRI of left foot demonstrates lesion in talus with high signal intensity.
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Surgical stabilization with internal fixation was used after wide resection of osteoblastoma of cervical spine (this image depicts same 15-year-old patient shown above).
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Surgical stabilization with internal fixation was used after wide resection of osteoblastoma of cervical spine (this image depicts same 15-year-old patient shown above).
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Photomicrograph of osteoblastoma (original magnification, X40). Special thanks to Dr Ronald Burns, Palmetto Richland Department of Pathology, for his assistance in obtaining these slides.
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Photomicrograph of osteoblastoma (original magnification, X100). Special thanks to Dr Ronald Burns, Palmetto Richland Department of Pathology, for his assistance in obtaining these slides.
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Photomicrograph of osteoblastoma (original magnification, X400). Special thanks to Dr Ronald Burns, Palmetto Richland Department of Pathology, for his assistance in obtaining these slides.
