Transarticular spread of Ewing's sarcoma across the sacroiliac joint: CT and MRI correlation

Decancellation sacral osteotomy in iliosacral tumor resection: a technique for precise sacral margins

En bloc resection of iliosacral sarcomas is a surgical challenge. There are substantial risks of inadequate margins, local recurrence, and nerve root loss when pelvic sarcomas involve sacral root canals and foramina. The decancellation technique uses principles similar to transpedicle decancellation in spinal deformity correction to perform the sacral osteotomy in iliosacral tumor resection. The technique aims at improving sacral margins and minimizing loss of neural function. We performed a decancellation osteotomy in five patients with sarcomas requiring difficult oblique or sagittal sacral osteotomies and selective root sacrifice. Through laminectomy and without anterior exposure, a precise full-thickness osteotomy of the sacrum was performed without major technique-related morbidities or complications. This was followed by formal pelvic resection and reconstruction. Surgical margins were adequate in all patients and all tumor-free nerve roots were preserved.

Transarticular spread of Ewing sarcoma mimicking septic arthritis

Transarticular spread of tumor is rare; it has only been reported in the sacroiliac joint, intervertebral disk spaces, and facet joints. The anatomic and kinetic characteristics of the sacroiliac joint, as well as the changes the joint undergoes during a lifetime, make it particularly vulnerable to transarticular tumor invasion. Although extremely rare, Ewing sarcoma can extend through the sacroiliac joint and be virtually indistinguishable radiologically from septic arthritis. Furthermore, the clinical presentation of a child with Ewing sarcoma can be similar to that of a child with osteomyelitis. Laboratory values are quite nonspecific and are not always helpful in differentiating between the entities. Therefore, the possibility of sacroiliac joint transarticular Ewing sarcoma should be considered in a child presenting with hip pain, despite clinical, radiological and laboratory findings suggesting an infectious process.

A Case Report of an Uncommon Cause of Cauda Equina Symptoms

OBJECTIVE

This case report discusses a patient who presented with right-sided buttock pain of apparently uncomplicated mechanical origin that was eventually diagnosed as a primary Ewing sarcoma/primitive neuroectodermal tumor of the sacrum.

CLINICAL FEATURES

A 32-year-old male full-time student presented for care with right-sided buttock pain.

INTERVENTION AND OUTCOME

After examination, the patient was referred to his general practitioner for urgent magnetic resonance imaging, the report revealed no explanation for the presenting symptoms. After further imaging and biopsy, an eventual diagnosis of Ewing sarcoma/primitive neuroectodermal tumor was reached. The patient died 12 months later.

CONCLUSION

This case highlights a nondiscal cause for cauda equina symptoms. It emphasizes potential diagnostic complexities that may present due to preconceptions based upon the probability of symptoms being related to a specific disease process.

Osteoblastoma crossing the sacro-iliac joint

Osteoblastoma is a rare primary bone tumour which is well-described in the spine and sacrum. We report a case of histologically confirmed osteoblastoma in a 20-year-old male which crossed the sacroiliac joint. This has not previously been described to our knowledge. The imaging features of osteoblastoma and sacroiliac joint involvement by bone tumours are reviewed.

Transarticular invasion of bone tumours across the sacroiliac joint

PURPOSE

The purpose of this study was to evaluate the pattern of tumour spread across the SI articulation, correlating with cadaveric anatomic observations, in order to better understand the local spread of tumour and to assist in the assessment of local staging.

MATERIAL AND METHODS

Twenty-four consecutive patients (14 male, 10 female; age range 22-89 years, mean 52 years) with primary bone tumours of the iliac bone or sacrum abutting the SI joint, in whom surgical resection of the SI joint was performed, were studied following institutional ethics approval. In all patients, preoperative magnetic resonance (MR) imaging studies of the pelvis and SI joint were reviewed for imaging evidence of transarticular extension across the SI joint. Gross pathologic and histologic assessment of possible transarticular SI joint tumour extension was performed in all patients. Nine cadaveric pelvic specimens without pelvic neoplastic disease (4 male, 5 female; age range 20-84 years, mean 59 years, median 58 years) were anatomically dissected and the articular anatomy of the SI joint examined macroscopically.

RESULTS

Twelve of the twenty-four patients demonstrated imaging and histological evidence of transarticular SI joint invasion. Eight tumours infiltrated only the interosseous ligamentous aspect of the SI joint. In the remaining four cases, extensive tumour infiltrated both the cartilaginous and ligamentous aspects of the joint. No case showed tumour involvement isolated to the cartilaginous aspect of the joint. Among the cadaveric specimens studied, degenerative changes were found involving the majority of cases (6/9), with cartilage thinning and fibrillation and antero-superior marginal osteophytes seen involving the cartilaginous portion of the SI joint articulation. Four of the nine specimens demonstrated central ossification bridging the iliac and sacral aspects of the ligamentous (interosseous) SI joint.

CONCLUSION

Tumour invasion across the SI articulation favours its interosseous ligamentous portion. Factors influencing transarticular tumour extension and its preferential course across the interosseous component of the articulation have been discussed. It is particularly important to assess the interosseous ligamentous portion of the SI articulation when locally staging primary pelvic bone tumours subjacent to the SI articulation, as this will have a significant impact on planning surgical management.

Sacral infiltration in pelvic sarcomas: joint infiltration analysis II

The incidence and characteristics of sacral infiltration in pelvic sarcomas were analyzed. Fifty-one patients with a pelvic sarcoma (chondrosarcoma, 15 patients; Ewing's sarcoma, 23 patients; and osteosarcoma, 13 patients) abutting the sacroiliac joint had surgical treatment. Tumor infiltration into the sacrum was suspected based on preoperative images in 18 patients; 15 of 18 patients had histologic tumor invasion. There was a significant difference of median volume of sarcomas with and without infiltration. One of 23 Ewing's sarcomas, seven of 15 chondrosarcomas, and seven of 13 osteosarcomas penetrated the sacroiliac joint into the sacrum. Logistic regression test showed that diagnosis was the most important factor influencing sacral infiltration. Twelve tumors infiltrated through the posterior part of the joint, two tumors infiltrated through the anterior part, and one large tumor infiltrated through an unknown route. To obtain wide surgical margins, patients at risk (elderly, large tumor, or diagnosis of osteosarcoma or chondrosarcoma) for sacral involvement may require extended internal hemipelvectomy with the medial margin extending into the sacrum. High quality imaging studies should be used to assess the need for transarticular resection.

Incidence and mechanisms of infiltration of sarcomas in the shoulder

The intraarticular infiltration of sarcomas around the shoulder was analyzed. Of 58 sarcomas located around the shoulder, which were treated between 1993 and 1998, 15 osteosarcomas, 12 chondrosarcomas, and one Ewing's sarcoma that abutted the shoulder were selected. Radiologic images of 28 tumors were analyzed and compared with pathologic examinations. In 17 of 28 sarcomas (15 in the proximal humerus and two in the scapula), joint infiltration was suspected radiologically because of the existence of a tumor mass probably inside the joint or disruption of the joint surface and protrusion of the tumor. Seven of 17 tumors with radiologically positive and zero of 11 tumors with radiologically negative findings showed histologically positive findings for tumor inside the joint. Four of 11 osteosarcomas and three of four chondrosarcomas of the proximal humerus showed histologic findings of joint infiltration. Pericapsular extension was seen in two patients, direct articular spread with a pathologic fracture was seen in two patients, direct articular spread was seen in one patient, direct articular spread with pericapsular extension was seen in one patient, and pericapsular extension with a pathologic fracture was seen in one patient. The current study showed that pericapsular or direct articular infiltration into the glenohumeral joint is a phenomenon in sarcoma around the shoulder. Exact assessment of tumor existence inside the joint can be difficult in osteosarcoma and chondrosarcoma, so abnormal radiologic findings should be regarded as proof of existence of tumor, and extraarticular wide resection should be planned.