Lumbar spinal stenosis and disc alterations affect the upper lumbar spine in adults with achondroplasia

Advances in the mechanism and therapies of achondroplasia

Achondroplasia (ACH), is the prevailing type of genetic dwarfism in humans, caused by mutations in fibroblast growth factor receptor 3 (FGFR3) that are inherited in an autosomal dominant manner. FGFR3 is mainly expressed in condensed mesenchyme, chondrocytes, and mature osteoblasts and osteoclasts, in which it regulates the formation, development, growth, and remodeling of the skeletal system. Mutations in FGFR3 causing ACH result in enhanced FGFR3 signaling through combined mechanisms including enhancing FGF dimerization and tyrosine kinase activity and stabilizing FGF receptors. In ACH, suppression of the proliferation and maturation of chondrocytes in the growth plate leads to a notable reduction in growth plate size, trabecular bone volume, and bone elongation through a profound enhancement of FGFR3 signaling. This review aims to comprehensively outline the cellular and molecular mechanisms contributing to the pathological process of ACH and its potential therapeutic interventions.

TYRA-300, an FGFR3-selective inhibitor, promotes bone growth in two FGFR3-driven models of chondrodysplasia

Achondroplasia (ACH) and hypochondroplasia (HCH), the two most common types of dwarfism, are each caused by FGFR3 gain-of-function mutations that result in increased FGFR3 signaling, which disrupts chondrogenesis and osteogenesis, resulting in disproportionately shortened long bones. In this study, TYRA-300, a potent and selective FGFR3 inhibitor, was evaluated in 3 genetic contexts: wild-type mice, the Fgfr3Y367C/+ mouse model of ACH, and the Fgfr3N534K/+ mouse model of HCH. In each model, TYRA-300 treatment increased nasoanal length and tibia and femur length. In the two FGFR3-altered models, TYRA-300-induced growth partially restored the disproportionality of long bones. Histologic analysis of the growth plate in Fgfr3Y367C/+ mice revealed that TYRA-300 mechanistically increased both proliferation and differentiation of chondrocytes. Importantly, children with ACH can experience medical complications due to foramen magnum stenosis, and TYRA-300 significantly improved the size and shape of the skull and foramen magnum in Fgfr3Y367C/+ mice. Spinal stenosis is also a frequent complication, and TYRA-300 increased the lumbar vertebrae length and improved the shape of the intervertebral discs in both models. Taken together, these studies demonstrate that the selective FGFR3 inhibitor TYRA-300 led to a significant increase in bone growth in two independent FGFR3-driven preclinical models as well as in wild-type mice.

Association between sarcopenia and intervertebral disc degeneration: A bidirectional two-sample Mendelian randomization

BackgroundSarcopenia (SP) and Intervertebral Disc Degeneration (IVDD) are common age-related diseases that significantly affect the physical and mental health of patients. A substantial body of evidence suggests a potential association between SP and IVDD. However, the causal relationship between SP and IVDD remains uncertain.ObjectivesThis study aimed to determine whether the association between SP and IVDD is causal by employing Mendelian randomization (MR) analysis.MethodsGenome-wide association study (GWAS) data related to SP (measured by muscle lean mass, left- and right-hand grip strength, and walking speed) and IVDD were obtained from the UK Biobank and FinnGen. To investigate the causal relationship between SP and IVDD, three MR analysis methods were employed, primarily focusing on the Inverse-Variance Weighted (IVW) approach. The robustness of causal effects was ensured through multiple methods: Instrumental Variables (IVs) were evaluated using F-values; heterogeneity was assessed using Cochran's Q; horizontal pleiotropy was evaluated using MR Egger regression; and outliers was detected using MR-PRESSO and the leave-one-out method.ResultsThe analysis indicates a potential causal relationship between appendicular lean mass (ALM) and the risk of IVDD (OR = 0.89, 95% CI: 0.809-0.98; P < 0.05). Similarly, left-hand grip strength shows a potential causal relationship with IVDD risk (OR = 1.52, 95% CI:1.08-2.14; P < 0.05), as does right-hand grip strength (OR = 1.50, 95% CI:1.09-2.07; P < 0.05). Additionally, a potential causal relationship is observed between IVDD and walking speed (OR = 0.99, 95% CI:0.97-1.00; P < 0.05).ConclusionThe findings suggest that ALM may serve as a protective factor against IVDD, while left- and right-hand grip strength may be risk factors for the development of IVDD. Furthermore, IVDD appears to be a risk factor associated with reduced walking speed. Further research is necessary to elucidate the underlying mechanisms of these associations.

Association Between Radiological Severity of Lumbar Spinal Stenosis and Spinopelvic Parameters in Adult Patients With Achondroplasia

BACKGROUND AND OBJECTIVES

Adults with achondroplasia are more vulnerable to suffer from neurogenic claudication because of a congenital narrow spinal canal, which makes them susceptible to lumbar spinal stenosis (LSS). The study aims to investigate the correlations between sagittal alignment parameters and the degree of LSS in patients with achondroplasia with LSS.

METHODS

The radiological data of adult achondroplasts presented to the neurosurgical clinic of our medical center from 2019 to 2022 were collected. Lumbar stenosis was graded using the Schizas scale, and the dural sac cross-sectional area (DSCA) was measured. The angles defining the spinopelvic parameters comprising lumbar lordosis, thoracolumbar kyphosis, sagittal vertical axis, pelvic tilt, sacral slope, and pelvic incidence were measured. Spearman or Pearson correlation was used to investigate the association between sagittal misalignment and LSS.

RESULTS

A total of 34 achondroplastics were enrolled, with a median age of 44.3 ± 15.5 years, ranging from 18.6 to 78.5 years. Larger thoracolumbar kyphosis was associated with more severe stenosis according to the Schizas scale of the L 12 lumbar level (r = 0.44, P = .020, 95% CI [0.08, 0.70]). Larger sagittal vertical axis correlated with a smaller DSCA at L 23 (r = -0.53, P = .036, 95% CI [-0.81, -0.04]) and L 45 (r = -0.66, P = .004, 95% CI [-0.87, -0.26]). Larger pelvic tilt was demonstrated to be associated with a smaller DSCA of the L 34 lumbar level (r = -0.42, P = .027, 95% CI [-0.68, -0.05]) and the L 45 lumbar level (r = -0.47, P = .011, 95% CI [-0.71, -0.12]).

CONCLUSION

The upper LSS may be attributed to an increased kyphosis of the thoracolumbar spine. On the contrary, the lower LSS seemed to be correlated with a more backward tilt of the pelvis.

Achondroplasia current concept of orthopaedic management

Achondroplasia, the most common form of inherited disproportionate short stature, is caused by mutations in the fibroblast growth factor receptor 3 gene. The typical clinical features of achondroplasia include short stature, rhizomelic disproportion, joint hyperlaxity, spinal deformity and deformity of the upper and lower limbs. The latter are among the challenges of state-of-the-art orthopaedic treatment plans and significantly contribute to the burden of the disease in individuals with achondroplasia. Multidisciplinary preoperative individual decision-making concerning surgical interventions should be considered. New medical treatments for achondroplasia have been developed and (some) have been approved for clinical use in several countries. While the number of research articles on achondroplasia is increasing rapidly, many unknown or controversial orthopaedic topics remain. Furthermore, in view of new medical developments with improvements in growth and potentially other effects, the timing and algorithms of orthopaedic treatments (e.g. guided growth, limb lengthening and deformity correction) need to be re-evaluated. While standing height is the primary research focus in medical therapy, it is crucial to comprehensively assess orthopaedic parameters in this multifactorial disease. The current treatment of patients with achondroplasia requires specialised multidisciplinary centres with transitional care and individual orthopaedic counselling.

European Achondroplasia Forum Practical Considerations for Following Adults with Achondroplasia

Achondroplasia is a lifelong condition requiring lifelong management. There is consensus that infants and children with achondroplasia should be managed by a multidisciplinary team experienced in the condition. However, many people are lost to follow-up after the transition from paediatric to adult care, and there is no standardised approach for management in adults, despite the recent availability of international consensus guidelines. To address this, the European Achondroplasia Forum has developed a patient-held checklist to support adults with achondroplasia in managing their health. The checklist highlights key symptoms of spinal stenosis and obstructive sleep apnoea, both among the most frequent and potentially severe medical complications in adults with achondroplasia. The checklist acts as a framework to support individuals and their primary care provider in completing a routine review. General advice on issues such as blood pressure, pain, hearing, weight, adaptive aids, and psychosocial aspects are also included. The checklist provides key symptoms to be aware of, in addition to action points so that people can approach their primary care provider and be directed to the appropriate specialist, if needed. Additionally, the European Achondroplasia Forum offers some ideas on implementing the checklist during the transition from paediatric to adult care, thus ensuring the existing multidisciplinary team model in place during childhood can support in engaging individuals and empowering them to take responsibility for their own care as they move into adulthood.

Modic changes in the lumbar vertebral column of chondrodystrophic and non-chondrodystrophic dogs with intervertebral disc disease

Introduction

Modic changes (MC) are signs of vertebral pathology visible on magnetic resonance (MR) images that have been associated with low back pain (LBP) and disc degeneration in people. Multiple breeds of dogs also develop MCs and coincident back pain. However, the association between breed, MC, and spinal pathologies has yet to be fully elucidated. This study aimed to identify the prevalence of MC that occur spontaneously in the lumbar vertebral column of dogs diagnosed with intervertebral disc disease (IVDD) and examine their association with demographic criteria and the disc width index (DWI).

Methods

Medical records and lumbar vertebral column MR images were examined from 104 dogs (831 intervertebral disc spaces and adjacent vertebrae), which were divided into three groups: chondrodystrophic dogs (CD; n =54) and non-chondrodystrophic dogs (NCD; n =30) with IVDD as the primary diagnosis, and control dogs (n =20) with other spinal diseases as their primary diagnosis.

Results

Increasing age and a diagnosis of IVDD were significantly associated with MC in dogs (p <  0.001 and p = 0.0062, respectively). In CD dogs with IVDD, Type 2 MC were most prevalent, whereas, in NCD dogs, Type 3 MC were the most prevalent type. Type 2 MC were distributed nearly equally across the lumbar vertebral column, while Type 3 MC were primarily detected at the level of L7-S1.

Discussion

This study demonstrated that MC developed spontaneously in dogs, are common in dogs diagnosed with IVDD, and the type observed varies by breed. Further research is needed to understand the pathogenesis of MC; however, the increased presence of Type 2 MC in CD dogs, similar to what is found in people with disc degeneration, suggests that CD dogs could serve as models for MC in people.

A comparative study on the clinical efficacy of percutaneous endoscopic lumbar discectomy and conventional open surgery in the treatment of lumbar disc herniation

Objective

To analyze the efficacy of single-channel percutaneous endoscopic lumbar discectomy (PELD) and conventional open surgery in the treatment of lumbar disc herniation (LDH).

Methods

This is a retrospective study. A total of 66 patients with LDH admitted to Tianjin Medical University from June 2017 to June 2018 were divided into two groups: the observation group (single-channel PELD) and the control group (posterior lumbar interbody fusion), with 33 cases in each group. The two groups were compared in terms of visual analogue scale(VAS), oswestry disability index (ODI), Japanese Orthopaedic Association Score(JOA), perioperative indicators, clinical efficacy, postoperative complications, changes in inflammatory factors and serum T lymphocyte subsets.

Results

The operation time, incision length, intraoperative blood loss, time in bed, hospital stay in the observation group were all lower than those in the control group. At 7d after treatment, the improvement of ODI, VAS and JOA in the observation group were better than that in the control group. At the last follow-up, there was no significant difference in Cobb angle and lumbar lordosis angle between the two groups. The levels of serum IL-1, IL-6 and TNF-α in the observation group were lower than those in the control group. The degree of reduction of serum CD3+ and CD4+ in the observation group were higher than those in the control group. And the level of elevation of CD8+ in the observation group was lower than that in the control group. Moreover, there was no significant difference in CD4+/CD8+ level between the two groups. The excellent rate of surgical results in the observation group was higher than that in the control group. Complications occurred in both groups, with no significant difference between the two groups.

Conclusions

Single-channel PELD can achieve superior clinical efficacy over conventional open surgery in the treatment of LDH.

Recommendations for neuroradiological examinations in children living with achondroplasia: a European Society of Pediatric Radiology and European Society of Neuroradiology opinion paper

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise.

Hypochondroplasia gain-of-function mutation in FGFR3 causes defective bone mineralization in mice

Hypochondroplasia (HCH) is a mild dwarfism caused by missense mutations in fibroblast growth factor receptor 3 (FGFR3), with the majority of cases resulting from a heterozygous p.Asn540Lys gain-of-function mutation. Here, we report the generation and characterization of the first mouse model (Fgfr3Asn534Lys/+) of HCH to our knowledge. Fgfr3Asn534Lys/+ mice exhibited progressive dwarfism and impairment of the synchondroses of the cranial base, resulting in defective formation of the foramen magnum. The appendicular and axial skeletons were both severely affected and we demonstrated an important role of FGFR3 in regulation of cortical and trabecular bone structure. Trabecular bone mineral density (BMD) of long bones and vertebral bodies was decreased, but cortical BMD increased with age in both tibiae and femurs. These results demonstrate that bones in Fgfr3Asn534Lys/+ mice, due to FGFR3 activation, exhibit some characteristics of osteoporosis. The present findings emphasize the detrimental effect of gain-of-function mutations in the Fgfr3 gene on long bone modeling during both developmental and aging processes, with potential implications for the management of elderly patients with hypochondroplasia and osteoporosis.

Fat infiltration in the thigh muscles is associated with symptomatic spinal stenosis and reduced physical functioning in adults with achondroplasia

BACKGROUND

Symptomatic spinal stenosis is a prevalent complication in adults with achondroplasia. Increased muscle fat infiltration (MFI) and reduced thigh muscle volumes have also been reported, but the pathophysiology is poorly understood. We explored whether the increased MFI and reduced thigh muscle volumes were associated with the presence of symptomatic spinal stenosis and physical functioning.

METHODS

MFI and thigh muscle volumes were assessed by MRI in 40 adults with achondroplasia, and compared to 80 average-statured controls, matched for BMI, gender, and age. In achondroplasia participants, the six-minute walk-test (6MWT), the 30-s sit-to-stand test (30sSTS), and a questionnaire (the IPAQ) assessed physical functioning.

RESULTS

Symptomatic spinal stenosis was present in 25 of the participants (the stenosis group), while 15 did not have stenosis (the non-stenosis group). In the stenosis group, 84% (21/25) had undergone at least one spinal decompression surgery. The stenosis group had significantly higher MFI than the non-stenosis group, with an age-, gender and BMI-adjusted difference in total MFI of 3.3 percentage points (pp) (95% confidence interval [CI] 0.04 to 6.3 pp; p = 0.03). Compared to matched controls, the mean age-adjusted difference was 3.3 pp (95% CI 1.7 to 4.9 pp; p < 0.01). The non-stenosis group had MFI similar to controls (age-adjusted difference - 0.9 pp, 95% CI - 3.4 to 1.8 pp; p = 0.51). MFI was strongly correlated with the 6MWT (r = - 0.81, - 0.83, and - 0.86; all p-values < 0.01), and moderately correlated with the 30sSTS (r = - 0.56, - 0.57, and - 0.59; all p-values < 0.01). There were no significant differences in muscle volumes or physical activity level between the stenosis group and the non-stenosis group.

CONCLUSION

Increased MFI in the thigh muscles was associated with the presence of symptomatic spinal stenosis, reduced functional walking capacity, and reduced lower limb muscle strength. The causality between spinal stenosis, accumulation of thigh MFI, and surgical outcomes need further study. We have demonstrated that MRI might serve as an objective muscle biomarker in future achondroplasia studies, in addition to functional outcome measures. The method could potentially aid in optimizing the timing of spinal decompression surgery and in planning of post-surgery rehabilitation.

Meeting Report from 2nd ICCBH-ERN BOND Spinal Complications in Children and Adults with Achondroplasia Workshop, Dublin, Ireland, 2nd July 2022

A pre-meeting workshop on spinal complications in children and adults with achondroplasia was held in Dublin, Ireland at the 10th International Conference on Children's Bone Health (ICCBH) 2-5 July 2022. The pathophysiology, natural history and medical/surgical management of thoraco-lumbar kyphosis and spinal stenosis remains poorly described in the literature. The structure of the workshop consisted of lectures, a debate and an interactive round table discussion. In total over 100 delegates affiliated to over 70 institutions from 20 countries were in attendance.

Correlation between serum angiotensin-converting enzyme (ACE) levels and intervertebral disc degeneration

Studies have shown that the renin-angiotensin system (RAS) might play an essential role in intervertebral disc degeneration (IDD). The study aimed to investigate the relationship between serum angiotensin-converting enzyme (ACE) concentration and IDD and its predictive value for severe disc degeneration. 245 patients who came to our hospital for low back pain were recruited, and blood samples were collected for routine examination. Descriptive data and demographic parameters were collected. The cumulative grade 1 was calculated by summing up the Pfirrmann grade of all lumbar discs. ACE concentration grouping was determined via tertile split. Correlation analysis and multivariable linear regression analysis were performed to determine the relationship between ACE and IDD. The receiver's degree of disc degeneration (ROC) curve determined the ACE's predictive value. Results indicated that there was no significant difference in demographic parameters among groups. Correlation analysis and multivariate linear analysis showed that ACE was an independent risk factor for IDD. The cumulative grade 1 increased significantly with the increase in ACE concentration, which was consistent with the correlation analysis. Average Pfirrmann grade &lt; 4 indicates mild to moderate degeneration, and grade ≥ 4 indicates severe degeneration in terms of an individual disc. From L1/2 to L5/S1, the mean plasma ACE concentration was significantly higher in the severe degeneration group than in the mild to moderate degeneration group. According to the ROC curve, the cut-off value of ACE levels was 22.5. patients with ACE &gt; 22.5 had severe degeneration. The sensitivity and specificity were 0.762 and 0.521, respectively.

Thoracolumbar stenosis and neurologic symptoms: Quantitative MRI in achondroplasia

Background and Purpose

Whole‐spine magnetic resonance imaging (MRI) studies, to identify structural abnormalities associated with the development of symptomatic spinal stenosis in achondroplasia.

Methods

Forty‐two subjects with achondroplasia were grouped into four age‐related categories. Congenital spinal deformities (vertebral body and disc height, interpedicular distance), acquired spinal degenerative changes, thoracic kyphotic (TK) angle, thoracolumbar kyphotic (TLK) angle, spinal canal widths were evaluated by MRI.

Results

Patients in the first three groups were asymptomatic and younger (group 1: 4.4 ± 0.78 years; group 2: 8.18 ± 0.60 years; group 3: 10.95 ± 0.93 years) than the symptomatic group (group 4: 23 ± 1.30 years). Patients showed height of vertebral bodies, whole canal width, and average lumbar interpedicular distance reduced. Discs degeneration was more pronounced in the lumbar region and in symptomatic adult patients. TK and TLK angles showed a positive correlation with age (p < .05, r = .42; p < .05, r = .41), whereas thoracic and thoracolumbar canal width had a negative correlation (p < .05, r = −.69; p < .05, r = −.58). A negative correlation between lumbar discs degeneration and canal width was found only at L1‐L3 level (p < .05, r = −.35). At L1‐L3, the canal width cutoff value of .59 allowed the differentiation between asymptomatic and symptomatic patients (area under the curve of .966, p < .0001).

Conclusion

In achondroplasia, the spinal canal narrowing, due to accelerated degenerative changes, is a predisposing factor of symptomatic lumbar spinal stenosis. Lumbar canal MRI is a helpful tool to detect the risk of the development of neurological symptoms; in adult patients, a stenosis higher than 60% of upper lumbar canal could be a critical value for the onset of neurological symptoms.

Neurosurgical Evaluation and Management of Adults with Achondroplasia

Much of the current medical discussion for within centers for skeletal dysplasia and specifically patients with achondroplasia focuses on infancy and early childhood. Most neurosurgical concerns arise due to a defect in the endochondral ossification, resulting on early fusion of the synchondrosis. As patients age, the neurosurgical focus shifts from primarily cranial to spinal concerns. Often pediatric neurosurgeons may continue to follow their patients with skeletal dysplasia. However, general adult neurosurgeons and orthopedic surgeons may see these graduated adults in their practice. This article provides a review of the common neurosurgical concerns for patients with achondroplasia.

Total knee arthroplasty in a young patient with achondroplasia

Achondroplasia is a genetic skeletal dysplasia, characterised by dwarfism, with upper and lower limb deformities, that can lead to knee osteoarthritis; the surgical treatment is a challenge due to the particular joint anatomy variances. We present a 40-year-old woman, affected by achondroplasia with severe left knee osteoarthritis; the patient was treated conservatively with poor results. Between the ages of 12 and 17 years, she underwent multiple operative procedures for lower limb lengthening and a partial correction of the valgus deformity, by applying an external fixator. The patient was successfully treated with cemented posterior stabilised, fixed-bearing, total knee arthroplasty. The patient affected by achondroplasia, with severe knee osteoarthritis, should be considered for total joint replacement, which can be carried out with or without additional extra-articular osteotomy for alignment correction. Due to skeletal dysplasia in joint deformities, knee replacement requires careful preoperative planning and special technical considerations.

Current Understanding of the Genetics of Intervertebral Disc Degeneration

Premature degeneration of the intervertebral disc and its association with specific chondrodystrophic dog breeds has been recognized for over a century. Several lines of evidence including disease breed predisposition, studies suggesting heritability of premature intervertebral disc degeneration (IVDD) and association of a dog chromosome 12 (CFA 12) locus with intervertebral disc calcification have strongly supported a genetic component in IVDD in dogs. Recent studies documenting association of IVDD with an overexpressing FGF4 retrogene on CFA 12 have opened up new areas of investigation to further define the pathophysiology of premature IVDD. While preliminary data from studies investigating FGF4 retrogenes in IVDD implicate FGF4 overexpression as a major disease factor, they have also highlighted knowledge gaps in our understanding of intervertebral disc herniation which is a complex and multifactorial disease process.

High prevalence of symptomatic spinal stenosis in Norwegian adults with achondroplasia: a population-based study

Background

Symptomatic spinal stenosis (SSS) is a well-known medical complication in achondroplasia. The reported prevalence of SSS is 10 to 30%, an estimate based on small studies or selected populations. No population-based studies exist currently. Furthermore, the relationship between SSS and physical functioning has not been investigated in detail. The aims of this study were to describe the prevalence of SSS in Norwegian adults with achondroplasia, and to explore the impact of SSS on physical functioning.

Methods

This was a population-based study on Norwegian community-dwelling adults with genetically confirmed achondroplasia. Prevalence of SSS was defined by clinical symptoms, and confirmed by imaging or surgical reports. Physical functioning was assessed by walking capacity (6-min walk test), hand strength (Grippit), and activities of daily living (the Health Assessment Questionnaire, HAQ). Pain was assessed by pain site locations and intensity (Numeric Rating Scale, NRS).

Results

In total, 50 participants were included (27 males, 23 females). Median age was 41 years (range 16 to 87 years), 34 (68%) had SSS. The estimated median age at first symptom onset was 33 years (95% confidence interval (CI) 29 to 43 years), range 10 to 67 years. The majority had multiple spinal levels affected. The walking distance was 110 m shorter in the SSS group (95% CI − 172 to − 40 m) as compared with the non-SSS group (p < 0.01). There was no considerable difference in hand strength between the two groups. Mean HAQ scores (0–3) for walking and hygiene were significantly higher in the SSS group, reflecting more activity limitations. Mean differences were 0.9 (95% CI 0.3 to 1.4, p < 0.01) and 0.6 (95% CI 0.2 to 1.0, p < 0.01). Pain intensity (NRS 0–10) was also significantly higher in the SSS group with a mean difference of 3.2 (95% CI 0.6 to 5.6, p = 0.02).

Conclusions

SSS was highly prevalent in Norwegian adults with achondroplasia, with symptom onset at young age, and multiple spinal levels affected. The presence of SSS was associated with reduced walking distance, activity limitations, and more pain. The findings underline the importance of thorough assessment and monitoring of SSS in achondroplasia, including a formal assessment of physical functioning.