Syringomyelia and vertebral osteochondromas in patients with multiple hereditary exostosis

An update on the imaging of diaphyseal aclasis

Solitary osteochondromas are common, benign hyaline cartilage-capped exostoses that primarily arise from the metaphyses of long and flat bones. Diaphyseal aclasis is an autosomal dominant condition resulting from EXT1 or EXT2 gene mutations and is characterized by multifocal osteochondromas. These can result in a wide spectrum of complications, such as skeletal deformity, neurological and vascular complications, adventitial bursa formation, fracture, and rarely malignant transformation to peripheral chondrosarcoma. In this review, we outline in detail the multimodality imaging features of DA and its associated complications.

The Incidence of Vertebral Exostoses in Multiple Hereditary Exostoses and Recommendations for Spinal Screening

BACKGROUND

Multiple hereditary exostoses (MHE) lead to the development of pedunculated or sessile osteocartilaginous lesions. Vertebral involvement occurs in MHE and encroaching intracanal exostoses can result in devastating consequences. Magnetic resonance imaging (MRI) of the entire spine has been used to screen for vertebral exostoses to detect high-risk patients. The primary purpose of this investigation is to determine the incidence of vertebral and encroaching intracanal exostoses in patients with MHE. A secondary purpose is to determine if pelvis and rib exostoses serve as "harbinger" lesions of vertebral involvement in MHE.

METHODS

A retrospective chart review was performed on 39 patients (21 male and 18 female individuals) with MHE who underwent routine spinal screening with noncontrast entire spine MRI. The average age at screening was 12.3 years (range, 3 to 17 y). Screening was ordered consecutively on patients seen during the study period who were between ages 8 and 18 years or had complaints that could be related to encroaching intracanal exostoses.

RESULTS

The incidence of vertebral exostoses in this cohort of 39 patients with MHE was 28% (11 total). An encroaching intracanal exostosis was seen in 3 patients (2 cervical, 1 thoracic). Nonencroaching vertebral exostoses were discovered in 8 patients. Sufficient pelvis and rib imaging to determine the presence of pelvis and rib exostoses was available in 8 of those with vertebral exostoses and 19 of those with no vertebral exostoses on screening MRI. In this cohort, the sensitivity and specificity of the presence of both pelvis and rib exostoses for determining the presence of spinal involvement in MHE are 88% and 5%, respectively.

CONCLUSIONS

Based on the results of this cohort, vertebral exostoses are common in MHE, and screening MRI of the entire spine can be used to determine which patients need close observation. If a more selective screening protocol is utilized, an entire spine MRI could be obtained for patients who desire increased physical activity levels or for patients with both pelvis and rib exostoses. At a minimum, treating physicians should monitor patients with MHE closely for neurological symptoms and have a low threshold to obtain advanced spinal imaging.

LEVEL OF EVIDENCE

Level III-diagnostic.

Total Hip Arthroplasty for Secondary Coxarthrosis in Patients with Hereditary Multiple Exostoses: Minimum 5-Year Follow-up Results and Surgical Considerations

Background

Hereditary multiple exostoses (HME) is an autosomal dominant disorder. The lesion in the proximal femoral metaphysis can bring about hip dysplasia and subsequent degenerative arthritis. Due to its rare prevalence, there have been a few case reports of total hip arthroplasty (THA) for osteoarthritis secondary to HME. The aim of this study was to report mid- to long-term outcomes of THA in HME patients and discuss special considerations that should be taken into account during surgery.

Methods

We retrospectively evaluated the clinical and radiological results of THA for osteoarthritis secondary to HME in 11 hips of 9 patients after a minimum follow-up of 5 years (mean, 9.9 years). There were 3 men (3 hips) and 6 women (8 hips), with a mean age of 53.6 years (range, 46.8–58 years) at the index surgery in this study. Harris hip score (HHS) was used for clinical outcome assessment, and radiologically, implant stability, radiolucent lines, liner wear, and any sign of osteolysis or implant loosening were evaluated. Postoperative complications including infection, deep vein thrombosis, and dislocations were also investigated.

Results

Cemented stems and cementless cups with the conventional polyethylene liner were used in bilateral hips of a single patient. In the other cases, cementless implants were used with ceramic-on-ceramic bearings. The mean HHS improved from 34.8 preoperatively to 92.5 postoperatively. Polyethylene liner wear and osteolysis were observed in 1 patient with cemented stems. Radiolucent lines were observed in 2 different cases. However, the femoral stems remained stable. There were no surgery-related complications except heterotopic ossification during follow-up.

Conclusions

Despite the several surgical considerations, the mid- to long-term clinical and radiological outcomes of THA in HME patients were satisfactory. The abnormal, wide mediolateral diameter of the proximal metaphysis should be considered in selecting and inserting the stem with adequate anteversion. Leg length discrepancy was also common, so teleradiographs should be obtained before surgery. Intraoperative leg length evaluation might be difficult due to the morphologic changes in the proximal femur after mass excision and individual bone length differences.

Prospective spine at risk program for prevalence of intracanal spine lesions in pediatric hereditary multiple osteochondromas

STUDY DESIGN

Retrospective cohort study OBJECTIVES: To determine prevalence of hereditary multiple osteochondromas (HMO) and utility of MRI surveillance in a prospective Spine at Risk (SAR) program. Unidentified intraspinal exostoses in HMO can lead to neurologic injury in children during sedated procedures but no MRI guidelines exist. We sought to determine the prevalence and age of intraspinal exostoses from MRIs, and indications for MRI surveillance.

METHODS

Retrospective review was performed of pediatric HMO patients who underwent total spine MRIs at a single institution after a prospective SAR program was instituted. Charts were reviewed for MRI indication and findings, symptoms, surgery, and location of other exostoses. Fisher's exact test was used to compare categorical variables and T test to compare continuous variables. Predictive value of pelvic/rib exostoses was calculated for intraspinal lesions.

RESULTS

Forty-three patients with HMO underwent total spine MRIs with average age of 11.5 years. Fifteen (35%) patients had exostoses on vertebral column, eight (19%) had intra-canal spinal exostoses. Higher prevalence of spine lesions occurred in symptomatic patients than asymptomatic (any spinal lesion: 73% prevalence in symptomatic vs 22% in asymptomatic, p < 0.005; intra-canal spinal lesion: 46% vs 9%, p < 0.05). Only two of the 11 'symptomatic presentations' could be attributable to intracanal spinal exostoses. Only one intra-canal exostosis found on asymptomatic surveillance was treated surgically. Presence of pelvic or rib exostoses were not strongly predictive of intra-canal lesions (23% PPV, 85% NPV, 63% sensitivity, 51% specificity).

CONCLUSIONS

Even with the presence of intra-canal exostoses, true symptomatic lesions are rare. Rib and pelvic lesions were not predictive of intra-canal lesions in our population. We recommend obtaining MRIs at time of preoperative evaluation in asymptomatic children old enough to not need sedation, or in patients with true neurologic symptoms to prevent unnecessary sedation of younger children for surveillance MRI.

LEVEL OF EVIDENCE

III.

Late presentation of spinal cord compression in hereditary multiple exostosis: case reports and review of the literature

INTRODUCTION

Osteochondromas are usually found in the long bones of patients with hereditary multiple exostoses (HME). The spine is reported to be involved in over 50% of cases, but few of these patients are symptomatic as the result of an existing spinal exostosis.

METHODS

We reviewed the current literature in order to find the right approach to patients with HME-complicated spinal exostosis and describe three paediatric patients that were diagnosed late with spinal cord compression due to cervical exostosis.

RESULTS

Our three cases were all late presentations with neurology and unfortunately had minimal improvement of neurology after the lesion was surgically removed. There is general agreement that late presentation of spinal cord injury due to osteochondromas involving the cervical spine may cause severe and irreversible neurological sequelae. Our literature review revealed that there are no clear-cut guidelines to develop more comprehensive screening measures for these patients.

CONCLUSIONS

A high index of suspicion is the most important factor for correct diagnosis and appropriate management. Physicians who treat HME should bear in mind that thorough history taking and a neurological examination at follow up are essential for these patients. Clearer guidelines for the development of more comprehensive screening programmes are essential.

LEVEL OF EVIDENCE

IV.

Is Routine Spine MRI Necessary in Skeletally Immature Patients With MHE? Identifying Patients at Risk for Spinal Osteochondromas

BACKGROUND

Multiple hereditary exostoses (MHE) is an autosomal dominant condition leading to development of osteochondromas throughout the body. Although long bones are most often affected, spine involvement may occur and usually requires advanced imaging for diagnosis. However, the high cost of detection, infrequent occurrence, and very low likelihood of spinal cord compression and neurological injury, create a management conundrum. The purpose of our investigation is to identify patients at greatest risk for spinal lesions and refine indications for advanced imaging.

METHODS

All MHE patients in a 24-year period were retrospectively reviewed. Skeletally immature patients with advanced imaging of the spine were further evaluated. The demographic characteristics, family history, clinical presentation, past surgical history, tumor burden, and distribution of patients with spinal lesions were compared with those without.

RESULTS

In total, 227 MHE patients were identified and 21 underwent advanced spinal imaging. Spinal lesions were found in 8 of the 21 screened patients (38.1%, 3.5% overall), of which 4 were intracanal and 1 was symptomatic (4.8%, 0.4% overall). Only the symptomatic patient underwent excision of the spinal lesion. Patients with spinal lesions had higher tumor burden than those without (median, 28.5 vs. 19 locations; P=0.010). There was a significant association with rib (P=0.018) and pelvic (P=0.007) lesions, which may serve as "harbinger" lesions. The presence of both a rib and a pelvic lesion used as a screening tool for spinal lesions produces a sensitivity of 100% and specificity of 69%.

CONCLUSIONS

Symptomatic spinal involvement in children with MHE is rare and tends to occur in patients with higher tumor burden. We recommend limiting advanced spine imaging to children with neurological symptoms or with rib and pelvic "harbinger" lesions. Patients without these findings are unlikely to have spine involvement needing intervention. This approach offers an opportunity to avoid unnecessary testing and substantially reduce costs of diagnostic imaging.

LEVEL OF EVIDENCE

Level III.

Total knee arthroplasty in patients with multiple hereditary exostoses

We present a case report of a patient with severe valgus deformity of the right knee due to multiple hereditary exostoses (MHEs) treated with total knee arthroplasty (TKA). The surgical management of MHE affecting the knee encompasses exostoses resection, joint deformity rectification, and limb-length discrepancy alignment. On rare occasions, distraction osteogenesis and TKA have been used to correct valgus deformities of the knee. TKA in MHE patients with knee involvement has only been described in 6 cases. Several considerations, such as extensive knowledge of frequently occurring skeletal aberrations, are required to successfully correct the deformities associated with MHE via TKA. This report describes a case of severe valgus knee deformity with a rotational component in MHE managed with TKA, the surgical technique, and future recommendations.

Syringomyelia in hereditary multiple exostosis

We describe five children with Hereditary Multiple Exostosis (HME) who also had syringomyelia. Of these, four had a tethered cord/fibrolipoma. No spinal osteochondromas were found in these patients. All had antecedent neurological signs or symptoms that prompted spinal imaging with MRI. Of all patients with HME seen in the Midwest Regional Bone Dysplasia Clinic from 1982 to present, 44% (17/39) of patients had signs or symptoms concerning for possible cord-related neurological findings. However, only 10 of 39 had spinal imaging. Assuming that all individuals with syringomyelia were identified, then 5/39 (13%) were in that way affected. This, of course, is a minimal estimate given that many were not imaged. The incidence of syringomyelia appears to be increased in this population, and seems to be unrelated to spinal osteochondromas. A low threshold for obtaining spinal MRI in patients with Hereditary Multiple Exostosis seems rational. © 2016 Wiley Periodicals, Inc.

Cervical cord compression in pediatrics with hereditary multiple exostoses: a report of two cases and review of the literature

Hereditary multiple exostoses (HME) generally involves the long tube bone or flat bone. Spinal involvement is rare, particularly in young children. We report two cases of children with HME who have myelopathy because of cervical spine involvement and then review the literature to clarify the clinical characteristics of spinal cord HME involvement in young children. In our cases and previously reported cases, neurological deficits remained in cases with acute onset, but other cases with slow onset showed almost complete recovery after surgery. This suggests that the assessment of spinal lesions before trauma is very important.