BACKGROUND: Hereditary multiple exostosis or hereditary multiple osteochondromas is a very rare clinical condition. Usually, these lesions tend to occur in the pediatric population, remaining silent until adulthood. Moreover, current studies show a small prevalence in the male population. The osteochondromas usually occur at sites with great bone activity and turnover, such as the diaphysis or metaphyseal plates (especially in children) of long bones. Their appearance in short bones (such as vertebrae) is very rare.
METHODS: We present a case of familial HME in a 53-year-old female patient with a very uncommon clinical description of the disease. The patient presented at our hospital with Frankel D-type paraparesis, with multiple osteochondromas (located at the right humerus, bilateral femurs, right tibia, and hip joints, besides the numerous ones over the spinal column) and urinary incontinence. She was suffering from bilateral coxarthrosis and gonarthrosis, which limited severely the range of her movements. An early menopause status was brought into consideration by the patient, being installed circa 15 years before, at 38 years old. She was currently in treatment with bisphosphonates for her concomitant osteoporosis.
CONCLUSIONS: Despite the relatively rare nature of the disease, it may be an important concern for the patient\'s quality of life. Intraspinal processes may trigger paraparesis or other neurological statuses, which may require a surgical treatment. The nature of the lesions is usually benign and do not require further radio- or chemotherapy.

UNASSIGNED: Hereditary multiple exostoses (HME) Masada IIB has traditionally been treated by gradual ulnar lengthening with questionable efficacy in reducing the dislocated head. One-bone forearm (OBF) has been used as a reconstructive procedure in forearm deformities with very scarce literature for HME. The study aims to report short-term results of OBF as a definitive procedure for severe forearm deformities in Masada IIB patients with respect to clinical and radiological parameters.
UNASSIGNED: Four patients with HME Masada IIb were included in this retrospective study. All patients complained of forearm and wrist deformity with an abnormal bony protrusion restricting elbow motion. Indications for OBF were ulnar shortening > 3 cm, dysplastic proximal radius with convex radial head and restricted prono-supination. All patients were examined pre-operatively and post-operatively clinically and radiographically using the Peterson\'s outcome score.
UNASSIGNED: The average age was 13 years (12-14 years). Pre-operative ulnar shortening, carpal slip percentage, and radial articular angle was 3.4 cm, 79.5%, and 47.5°, respectively. All radial heads were dislocated with convex articular surface restricting elbow extension and forearm prono-supination. At the latest follow-up, the mean elbow flexion was 110° with forearm in 10° supination. The mean carpal slip percentage, radial articular angle, and Peterson functional grade was 15%, 22.5°, and 8 points, respectively. The mean follow-up period was 30.25 months with no recurrence.
UNASSIGNED: We recommend one bone forearm as a definitive procedure in HME Masada IIB patients with severe forearm deformities with ulnar shortening > 3 cm and dysplastic proximal radius with a dislocated radial head, for faster return to function.

Osteoid osteoma is a benign bony pathology. It presents either as a solitary lesion or as multiple lesions with a genetic predisposition. Reported more often in teenagers with thrice more common incidence among boys than in girls, it has a predilection for long bones of lower limbs. Less commonly arising from iliac crest or ribs; it is seen to be further rare to have originated from vertebrae or tarsal/carpal bones. Cranial osteomas are detected either incidentally on imaging or present as a bony hard swelling arising from the skull. Spinal intracanal osteomas are extremely rare to encounter in clinical practice. Cervical intracanal lesion in a case of hereditary multiple exostoses (HME) presenting with myelopathy is further rare. Less than thirty such cases have been reported so far. We present here a rare case of HME in a 16-year-old boy with compressive myelopathy secondary to intracanal cervical osteoma at C4 Lamina and spinous process. He had a phenotypical expression of hereditary multiple osteomas with a strong family history of inheritance of trait among first-degree male relatives favoring genetic transmission of disease with variable penetrance. All reported cases, to date, are discussed in a tabulated form.

Ulna distraction by monolateral external fixator (MEFix) is a good option for the treatment of Masada type I and IIb deformities in children with hereditary multiple exostoses (HMEs). However, there is no consensus regarding where to perform ulnar osteotomy. Our hypothesis is that osteotomy at the proximal third of the ulna and progressive distraction with MEFix can simultaneously correct elbow and wrist deformities in patients with HME.
We retrospectively reviewed patients with HME who underwent ulna distraction osteogenesis from June 2014 to March 2019. The carrying angle (CA), radial articular angle (RAA), ulnar variance (UV), radial variance (RV) and range of motion (ROM) of the affected forearm and elbow were clinically assessed before lengthening and at the last follow-up visit. The total ulna lengthening distance (LD) and radiographic outcome were also recorded.
Nineteen patients (20 forearms) with HME aged 9.1 ± 2.4 years at the time of surgery were retrospectively reviewed. The mean follow-up period was 26.1 ± 5.6 months. There were 11 patients (12 forearms) with Masada type I deformities and eight patients (8 forearms) with Masada type IIb deformities. Patients with type IIb deformity had higher RV, lower CA values, less elbow flexion and forearm pronosupination than those with type I deformity (p < 0.05); RV was an independent risk factor for radial head dislocation, with the cut off at RV > 15.5 mm. The mean LDs in patients with type I and type IIb deformities were 33.6 ± 6.6 mm and 41.4 ± 5.4 mm, respectively. The mean CA, UV, RV, forearm pronation and ulna deviation at the wrist improved significantly following surgery in all patients. In particular, five of eight patients (62.5%) with type IIb deformities had concentric reduction of the radiocapitellar joint, while no radial head subluxation was detected in patients with type I deformities at the last follow-up. Three complications were recorded: two pin-track infections and one delayed union.
Distraction osteogenesis at the proximal third of the ulna provides satisfactory clinical and radiological outcomes in patients with Masada type I and IIb deformities. Early treatment of Masada type I deformities is indicated before progression to more complex type IIb deformities.

UNASSIGNED: Hereditary multiple exostoses (HME) disease is hallmarked by cartilaginous osteochondromas secondary to an autosomal dominant mutation within the exostosin gene family. These outgrowths predominantly occur around the long bone physis. An associated disease is dysplasia epiphysealis hemimelica also known as Trevor\'s disease. Trevor\'s disease is hallmarked by intra-articular osteochondromas. While the two diseases are similar, they are not genetically related and often have differing patient presentations.
UNASSIGNED: We report on a case of a 7-year-old female with a familial history significant for HME that presented with an isolated chief complaint of elbow extension block secondary to osteochondromas found both intra-articular and at the olecranon fossa. We present what could be one of the first cases of coexisting HME and Trevor\'s disease of the upper extremity.
UNASSIGNED: Our patient\'s unique presentation of an intra-articular osteochondroma speculated to be a result of Trevor\'s disease, in the presence of an established HME diagnosis. Management for this patient did not deviate heavily from the established approach for HME which entails conservative observation until symptomatic. Due to the substantial loss of range of motion (ROM), surgical intervention took place in the form of exostoses removal and necessary reconstruction of the fossa. The patient\'s ROM subsequently was restored to near normal.

Hereditary multiple exostosis (HME) is an autosomal dominant skeletal disorder characterized by the development of multiple cartilage-covered tumors on the external surfaces of bones (osteochondromas). Most of HME cases result from heterozygous loss-of-function mutations in EXT1 or EXT2 gene.
Clinical examination was performed to diagnose the patients: Whole exome sequencing (WES) was used to identify pathogenic mutations in the proband, which is confirmed by Sanger sequencing and co-segregation analysis: qRT-PCR was performed to identify the mRNA expression level of EXT1 in patient peripheral blood samples: minigene splicing assay was performed to mimic the splicing process of EXT1 variants in vitro.
We evaluated the pathogenicity of EXT1 c.1056 + 1G > T in a Chinese family with HME. The clinical, phenotypic, and genetic characterization of patients in this family were described. The variant was detected by whole-exome sequencing (WES) and confirmed by Sanger sequencing. Sequencing of the RT-PCR products from the patient\'s blood sample identified a large deletion (94 nucleotides), which is the whole exome 2 of the EXT1 cDNA. Splicing assay indicated that the mutated minigene produced alternatively spliced transcripts, which cause a frameshift resulting in an early termination of protein expression.
Our study establishes the pathogenesis of the splicing mutation EXT1 c.1056 + 1G > T to HME and provides scientific foundation for accurate diagnosis and precise medical intervention for HME.

In this study, the effect of heterozygous germline mutations in the heparan sulfate (HS) glycosaminoglycan chain co-polymerases EXT1 and EXT2 on glomerular barrier function and the endothelial glycocalyx in humans is investigated. Heparan sulfate (HS) glycosaminoglycans are deemed essential to the glomerular filtration barrier, including the glomerular endothelial glycocalyx. Animal studies have shown that loss of HS results in a thinner glycocalyx. Also, decreased glomerular HS expression is observed in various proteinuric renal diseases in humans. A case report of a patient with an EXT1 mutation indicated that this could result in a specific renal phenotype. This patient suffered from multiple osteochondromas, an autosomal dominant disease caused by mono-allelic germline mutations in the EXT1 or EXT2 gene. These studies imply that HS is indeed essential to the glomerular filtration barrier. However, loss of HS did not lead to proteinuria in various animal models. We demonstrate that multiple osteochondroma patients do not have more microalbuminuria or altered glycocalyx properties compared to age-matched controls (n = 19). A search for all Dutch patients registered with both osteochondroma and kidney biopsy (n = 39) showed that an EXT1 or EXT2 mutation does not necessarily lead to specific glomerular morphological phenotypic changes. In conclusion, this study shows that a heterozygous mutation in the HS backbone elongating enzymes EXT1 and EXT2 in humans does not result in (micro)albuminuria, a specific renal phenotype or changes to the endothelial glycocalyx, adding to the growing knowledge on the role of EXT1 and EXT2 genes in pathophysiology.

UNASSIGNED: Acquired hip deformities in patients affected by hereditary multiple exostosis (HME) may incur in early hip osteoarthritis and functional limitation requiring primary total hip arthroplasty (THA). Characteristic coxo-femoral joint dysmorphisms in HME may pose a challenge for the orthopaedic surgeon. Here we report our experience in a series of patients with HME treated in our hospital with THA.
UNASSIGNED: With a mean follow-up of 5 years, 10 primary THAs were reviewed; proximal femur deformities, acetabular dysplasia and joint osteoarthritis has been assessed through x-rays and CT-scan evaluation. In all cases hemispheric press-fit cups were used; 4 stem had metaphyseal engagement, 5 had proximal diaphyseal engagement and 1, with anatomical geometry, had metaphyseal fixation. 2 cases required stem cementation, 3 modular neck and 1 lateralised. The clinical data, complications and clinical outcomes, were recorded and analysed.
UNASSIGNED: The mean Harris Hip Score (HHS) increased from 34 preoperative to 86 postoperative; preoperative mean neck shaft angle (NSA) was 150°, head/neck ratio 0.6, offset 31 mm; Wiberg angle 28°, Sharp angle 38°, 1 patient had subluxation grade 4 according to Crowe, 8 hips showed osteoarthritis (Tönnis grade ⩾2 ); 5 femurs were classified as Dorr type C, 2 as type B and 3 as type A. Perioperative complications were not observed.
UNASSIGNED: Primary THA in HME significantly improved clinical and functional outcomes. Press-fit cup fixation together with metaphyseal and proximal diaphyseal stem engagement on reliable bone quality femur, represents a valid option in HME patients with normal acetabular morphology, wide broaden neck and valgus NSA.

OBJECTIVE: Chondrosarcoma is the second most common primary sarcoma of bone: conventional chondrosarcoma accounts for 85% of all cases. Conventional chondrosarcoma may be central or peripheral. Most studies group central and peripheral chondrosarcomas together, although there is growing evidence that their clinical behaviour and prognosis differ. The aims of this study were to analyze any differences in characteristics between central and peripheral chondrosarcomas and to investigate the incidence and role of different syndromes.
METHODS: Data from two international tertiary referral sarcoma centres between January 1995 and December 2018 were retrospectively reviewed. The study population consisted of 714 patients with surgically treated conventional chondrosarcoma of the pelvis and limbs.
RESULTS: In patients with Ollier\'s disease and Mafucci\'s syndrome, 12/20 (60%) and 2/5 (60%) of malignancies, respectively, were in the limbs, most frequently in the proximal humerus, proximal tibia, and in the hands and feet. In patients with hereditary multiple exostosis (HME), 20/29 (69.0%) of chondrosarcomas were in the pelvis and scapula, specifically in the ilium in 13/29 (44.8%) and the scapula in 3/29 (10.3%). In central chondrosarcoma, survival of patients with Ollier\'s disease and non-syndromic patients was the same (p = 0.805). In peripheral chondrosarcoma, survival among HME patients was similar (p = 0.676) in patients with tumours of the pelvis and limbs.
CONCLUSIONS: Both central and peripheral chondrosarcoma have specific characteristics. HME is frequently seen in patients with a peripheral chondrosarcoma, in whom tumours are commonly located in the ilium and scapula. The incidence of Ollier\'s disease is uncommon in patients with a central chondrosarcoma. Disease-specific survival is equal in different subtypes after adjustment for histological grade. The local recurrence-free survival is the same for different locations and subtypes after adjustment for surgical margin. Cite this article: Bone Joint J 2021;103-B(5):984-990.

UNASSIGNED: Hereditary multiple exostosis (HME) is an autosomal dominant disorder affecting the skeletal system, which is characterized by multiple osteochondromas in bones arising from osteochondral ossification and leading to skeletal deformities, short stature, soft tissue, and neurovascular compressive symptoms.
UNASSIGNED: A 10-year-old female a case of HME presented with painless multiple swelling around knees, wrist, and painful varus deformity in the lower third of the right leg. The large exostosis of the right distal tibia was symptomatic and indenting the fibula which required excision along with the segment of the fibula of about 2.5 cm above the syndesmosis adjacent to the exostosis as the mass was adherent to the fibula.
UNASSIGNED: Although distal tibia osteochondromas are rare, they can lead to deformity of the ankle and loss of function if not managed early and properly. Hence, early detection, proper planning, and management of periarticular distal tibia osteochondromas are essential to prevent the development or progression of the deformity. Segmental fibulectomy is required to remove the adherent osteochondromas completely and to prevent the recurrence and secondary surgical procedures. It is very essential to follow up the patient till the skeletal maturity to identify the delayed presentation and late progression of the ankle deformities.