Coronal malalignment of lower legs depending on the locations of the exostoses in patients with multiple hereditary exostoses

Clinical factors associated with valgus knee deformities in patients with multiple osteochondromas

Multiple osteochondromas (MO) occur in approximately 1 in 50,000 people/yr. One in 3 patients with MO will develop valgus knee deformity (VKD), but the predictive factors for VKD are unclear. The purpose of this study was to examine the factors associated with VKD in patients with MO. From January 2003 to December 2018, 64 patients with MO visited the Nagoya University Hospital for the 1st time. Thirty-three patients with 66 limbs were sequentially included in the study after excluding 12 patients with a history of lower extremity surgery, 15 patients whose knee X-rays were unavailable, and 4 patients whose age at the last examination was <7 years. Limbs with femorotibial angle (FTA) ≥ 175° were defined as the normal group (Group N) and limbs with FTA < 175° as the valgus group (Group V), and clinical factors collected retrospectively from the medical records were compared between the 2 groups. The initial and final X-rays were compared in a subgroup analysis of 8 patients whose initial examination was <10 years old and who were followed for more than 5 years. Twenty-four males and 9 females with a median age of 17 years at the last X-rays were included in the study. The mean follow-up period was 43 ± 53 months, and the median FTA was 174.5°. Group N consisted of 32 limbs and Group V consisted of 34 limbs. Multivariate analysis was performed using the 5 factors with P-values <.15 in the univariate analysis of comparison between the 2 groups, and only medial proximal tibial angle showed significant differences (P < .001). In the subgroup analysis, multivariate analysis showed that the femoral neck-shaft angle showed significant differences between the 2 groups at the initial evaluation (P < .001). Our study suggests that medial proximal tibial angle is associated with VKD in patients with MO. Small neck-shaft angle was significantly associated with VKD, even before it became obvious. In order to study how VKD is formed, imaging of the hip and ankle joints and X-rays of the entire lower extremity should be performed in more cases.

Hereditary multiple exostoses: an educational review

Hereditary multiple exostoses (HME), an autosomal dominant disorder with an incidence of 1:50,000 to 1:100,000, is characterised by the formation of multiple osteochondromas arising from the metaphyses of long and flat bones. These osteochondromas often present as painless palpable lumps, though some cases are symptomatic due to mechanical compression or bursitis. Diagnosis of HME is typically clinical and radiological. WHO diagnostic criteria include ≥ 2 radiological osteochondromas in the juxta-epiphyseal region of the long bones. Genetic testing is reserved for ambiguous cases. HME is associated with mutations in the EXT-1 (exostosin-1) and EXT-2 (exostosin-2) genes. Imaging techniques, including conventional radiography, CT, MRI, ultrasound, and nuclear medicine, play a crucial role in diagnosing and assessing HME, with each modality offering distinct advantages in visualising the lesions and associated complications. Common complications include skeletal deformities, fractures, bursitis, as well as neural and vascular abnormalities. Notably, there is a 10% risk of malignant transformation into secondary chondrosarcoma in HME patients, compared to only a 1% risk in those with solitary osteochondromas. Malignant transformation should be suspected in patients with new-onset pain or specific imaging features in an osteochondroma, such as growth of de cartilaginous cap. In these cases, an MRI should be performed to assess the cartilage cap thickness. Advances in imaging techniques and genetic understanding have improved the management and prognosis of HME. Follow-up is essential to rule out malignant transformation. This review summarises current knowledge on the clinical presentation, pathogenesis, imaging characteristics, complications, and treatment of HME. CRITICAL RELEVANCE STATEMENT: HME is a disorder characterised by the formation of osteochondromas arising from long and flat bones. Multi-modality imaging characteristics, clinical presentation, complications, and treatment are highlighted to familiarise the readers with this entity and offer optimal patient care. KEY POINTS: HME is characterised by multiple osteochondromas on long and flat bones. Imaging for HME includes radiography, CT, MRI, ultrasound, and nuclear medicine studies. Complications include non-malignant complications, such as bone deformities and malignant transformation. Cartilage-cap measurement with MRI or US is key to exclude malignancy. Follow-up is essential to rule out malignant transformation of the osteochondromas.

Lower extremity deformity and its risk factors in patients with solitary osteochondromas

BACKGROUND

This study aimed to demonstrate the occurrence of lower extremity deformities and their risk factors in patients with solitary osteochondromas.

METHODS

We retrospectively reviewed consecutive patients with solitary osteochondromas around the knee. The laterality (left or right), involved bone (femur or tibia), tumor type (pedunculated or sessile), and direction (medial or lateral) were examined. The whole limb length (WLL), mechanical lateral distal femoral angle (mLDFA), and medial proximal tibial angle (MPTA) were measured using teleroentgenogram. Lower limb deformity was defined as a difference of more than 5° in mLDFA or MPTA in both lower extremities or a difference in WLL of more than 1 cm. Patients were divided into two groups, with deformity and without deformity.

RESULTS

Lower extremity deformities were observed in 8 of 83 patients. Significant difference in the type of osteochondroma (p = 0.004) between the groups was observed. Differences in sex, age, laterality, involved bone, direction, and distance from the physis to the osteochondroma between groups were not statistically significant. The sessile type of osteochondroma was a risk factor for lower limb deformity with an odds ratio of 24.0 according to Firth's logistic regression analysis.

CONCLUSION

In our cohort with solitary osteochondroma, lower limb deformities were observed in 8 (9.6%) out of the 83 patients and these were significantly associated with sessile-type tumors. Therefore, patients with sessile-type solitary osteochondroma around the knee require careful surveillance of lower limb alignment with whole leg teleroentgenogram.

Effect of Solitary Osteochondroma on Alignment and Length in the Lower Extremities

BACKGROUND

There is a lack of information about the effects of untreated solitary osteochondroma (SO) on longitudinal growth of the lower extremities in children and adolescents. This study aimed to assess the coronal alignment and length of the lower extremity in patients with SO around the knee and to identify the factors related to the development of deformities.

METHODS

We retrospectively reviewed 111 patients diagnosed with SO around the knee. The patients were classified into 2 groups depending on the location of the SO: 51 in the distal femur and 60 in the proximal tibia. Characteristics of the lesions, such as type, location, size, and distance from the joint line, were determined. Radiographic analysis of the lower limbs included mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, whole-leg length, femoral length, and tibial length.

RESULTS

The mean age at the time of diagnosis was 12.3±3.4 years. No statistically significant differences were found between the affected and contralateral sides for mechanical lateral distal femoral angle and mechanical medial proximal tibial angle in either the distal femur or the proximal tibia groups. In patients with femoral lesions, the femoral and whole-leg lengths were significantly shorter on the affected side than on the unaffected side ( P <0.001 and 0.002, respectively), and the mean differences were 2.1±3.6 and 2.1±4.4 mm, respectively. Univariate logistic regression analysis did not reveal any factors associated with limb length discrepancy (LLD). In patients with tibial lesions, no statistically significant differences were found in LLD.

CONCLUSIONS

SOs around the knee did not cause clinically significant deformity of the lower extremity. However, in contrast to proximal tibia lesions, SO in the distal femur was associated with the shortening of the affected limb. Consideration should be given to the development of LLD in skeletally immature children with SO in the distal femur.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Tibia Valga Correction by Extraperiosteal Fibular Release in Multiple Exostosis Disease

Genu valgum is a frequent deformity encountered in Multiple Hereditary Exostosis (MHE) patients. If left untreated, lower limb deformity leads to poor functional outcomes in adulthood. Our hypothesis was that in some cases, fibular shortening would lead to a lateral epiphysiodesis-like effect on the tibia. We herein report the case of a 6-year-old child with MHE who underwent extraperiosteal resection of the fibula for tibia valga correction. To obtain the lateral release of the calf skeleton, resection included inter-tibio-fibular exostosis along with proximal fibular metaphysis and diaphysis without any osseous procedure on the tibia. Gradual improvement of the valgus deformity occurred during follow-up (HKA from 165° preop to 178° at 27-month follow-up). Lateral release of the fibula led to an increase in the fibula/tibia index (from 93% preop to 96% at follow-up). Studying fibular growth in MHE patients could help understand how valgus deformity occurs in these patients. Even if encouraging, this result is just the report of a unique case. Further research and a larger series of patients are required to assess fibular release as a valuable option to treat valgus deformity in MHE.

Update on imaging of the cervical spine in rheumatoid arthritis

Rheumatoid arthritis is a multisystem, autoimmune, inflammatory disorder with numerous musculoskeletal manifestations. Involvement of the cervical spine is common and may result in severe complications due to synovitis, erosions, pannus formation, spinal instability and ankylosis. The purpose of this article is to review the current role of imaging in the rheumatoid spine, with emphasis on radiographs and MRI.

Lower limb deformities and limb length discrepancies in hereditary multiple exostoses

There is a high rate of lower limb deformity and limb length discrepancy in patients with hereditary multiple exostoses (HME). The aim of this study was to evaluate the type and frequency of lower limbs axial deviation and limb length discrepancy and the type of exostoses being risk factors for theses deformities. We retrospectively reviewed standing full-length radiograph of 32 HME patients (64 limbs) followed in our institution between October 2009 and December 2020. Patient demographics were recorded. Radiographic analysis of the coronal limb alignment was performed, limb length discrepancy was measured and topography of the exostoses was recorded. We propose a classification of lower legs in 2 groups and 4 types according to the presence and the location of exostoses. In group I, there is an intertibio- fibular exostose with fibular origin at the level of the tibiofibular joints. In type IA, at the level of the distal tibiofibular joint with ascension of the distal fibula; in type IB at the level of the proximal tibiofibular joint with a bracketing effect on the proximal tibia and a lateral slope of the proximal tibial growth plate; the type IC is combining features of both IA and IB. In group II, there is no intertibio-fibular exostose coming from the fibula and no growth abnormality is obvious. A clinically notable lower limb discrepancy (LLD) of ≥2 cm was found in 19% of our patients. Approximately 33% of patients had a knee valgus deformity and 44% had an ankle valgus deformity. The knee valgus deformity was due to fibular growth anomalies and not to distal femur anomalies. The majority of lower legs had fibular growth anomalies (72%) which was a significant risk factor for knee valgus deformity and leg length discrepancy. On the contrary, we found no correlation between number, location and volume of distal femoral exostoses and genu valgum nor leg length discrepancy. Presence of intertibio-fibular exostoses is a risk factor for knee valgus deformity and leg length discrepancy. The presence of these exostoses should lead to a close follow-up of the patient.

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.

Risk factors for ankle valgus in children with hereditary multiple exostoses: a retrospective cross-sectional study

PURPOSE

The aim of this study was to identify risk factors for ankle valgus in children with hereditary multiple exostoses (HME).

METHODS

We retrospectively reviewed the medical records of patients with HME who were examined at our hospital between 2010 and 2020. Patients' age and sex were recorded along with radiographic variables including mechanical axis deviation (MAD), mechanical lateral distal tibia angle (LDTA), fibula/tibia length ratio (F/T); distal fibula station according to Malhotra's classification, location of exostoses at the ankle joint and fibular neck/physis width (N/P) ratio, which were measured from radiographs. Binary logistic regression analysis was performed to identify significant independent risk factors for ankle valgus.

RESULTS

There were 61 children (20 girls and 41 boys; 122 ankles) who met the inclusion criteria. The mean age was 10.4 years (sd 3.4) and mean LDTA was 83° (sd 7°). Ankle valgus was found in 64 ankles (52%). In addition to younger age, exostoses involving the lateral aspects of the distal tibial and the medial aspect of the distal fibula (odds ratio (OR) = 4.091; 95% confidence interval (CI) 1.065 to 15.712; p = 0.040), F/T ratio < 0.96 (OR = 4.457; 95% CI 1.498 to 13.261; p = 0.007) and N/P ratio > 1.6 (OR = 2.855; 95% CI 1.031 to 7.907; p = 0.043) were associated with an increased risk of developing ankle valgus, while sex and MAD were unrelated to its occurrence.

CONCLUSION

Young age, exostoses involving both the distal tibia and fibula, the F/T ratio < 0.96 and fibular N/P width ratio > 1.6 seemed to be risk factors of developing ankle valgus.

LEVELS OF EVIDENCE

Prognostic studies, IV.

Outcomes of Temporary Hemiepiphyseal Stapling for Correcting Genu Valgum in Children with Multiple Osteochondromas: A Single Institution Study

Background: Multiple osteochondromas is a rare skeletal disorder characterized by the presence of osteocartilaginous protrusions causing bony deformities, especially around the knee. Guided growth by temporary hemiepiphyseal stapling is the treatment of choice to correct the deformity by modulating the residual physeal growth of the lower limbs. Although this procedure is increasingly practiced, inconclusive evidence exists regarding its effectiveness in children with multiple osteochondromas. The study aims to compare the outcomes of temporary hemiepiphyseal stapling for correcting genu valgum in children with multiple osteochondromas vs. idiopathic cases. Methods: In this retrospective cohort study, we included patients admitted at a single institution from 2008 to 2018. A total of 97 children (77 idiopathic, 20 multiple osteochondromas) were enclosed, accounting for 184 limbs treated by temporary hemiepiphyseal stapling. We investigated if children with multiple osteochondromas had a similar successful rate of correction, rate of complications, and correction velocity compared to children with idiopathic genu valgum. Results: Overall, 151 limbs (82%) achieved complete correction or overcorrection, with idiopathic cases having a significantly higher rate of success compared to pathologic cases (88% vs. 55%; p < 0.001). In addition, multiple osteochondromas children sustained a higher rate of major complications (p = 0.021) and showed significantly lower correction velocity (p = 0.029). Conclusion: Temporary hemiepiphyseal stapling is effective in both idiopathic and multiple osteochondromas children, although the latter often achieved incomplete correction, had a higher risk of complications, and required a longer time of stapling. We suggest to anticipate the timing of intervention; otherwise, children with multiple osteochondromas and severe valgus deformity, approaching skeletal maturity, could undergo combined femoral and tibial stapling.

Longitudinal Observation of Changes in the Ankle Alignment and Tibiofibular Relationships in Hereditary Multiple Exostoses

The longitudinal changes in the tibiofibular relationship as the ankle valgus deformity progresses in patients with hereditary multiple exostoses (HME) are not well-known. We investigated the longitudinal changes and associating factors in the tibiofibular relationship during the growing period. A total of 33 patients (63 legs) with HME underwent two or more standing full-length anteroposterior radiographs. Based on the change in ankle alignments, thirty-five patients with an increase in tibiotalar angle were grouped into group V, and 28 patients with a decreased angle into group N. In terms of the change in radiographic parameters, significant differences were noted in the tibial length, the fibular/tibial ratio, and the proximal and distal epiphyseal gap. However, age, sex, initial ankle alignment, location of osteochondroma, and presence of tibiofibular synostosis did not affect the tibiofibular alignment. The tibial growth was relatively greater than the fibular growth and was accompanied by significant relative fibular shortening in the proximal and distal portions. In pediatric patients with HME, age, sex, initial ankle alignment, location of the osteochondroma, and synostosis did not predict the progression of the ankle valgus deformity. However, when valgus angulation progressed, relative fibular shortening was observed as the tibia grew significantly in comparison to the fibula.