An online clinical decision tool to screen for vertebral fragility fractures (Vfrac) in older women presenting with back pain in general practice: protocol for a feasibility study in preparation for a future cluster randomised controlled trial

This feasibility study for a future definitive randomized trial assesses the use and acceptability of a new clinical decision tool to identify risk of a vertebral fracture and those who should be referred for spinal radiography in women aged 65 or over presenting to primary care with back pain.

PURPOSE

Approximately 12% of older adults have vertebral fragility fractures, but currently fewer than one-third are diagnosed, potentially limiting access to bone protection treatment. Vfrac is a vertebral fracture screening tool which classifies individuals into high or low risk of having a vertebral fracture, allowing targeting of spinal radiographs to high-risk individuals. The objective of this study was to investigate the feasibility of conducting a cluster randomized controlled trial to evaluate the use of an online version of Vfrac in primary care.

METHODS

The study will run in six general practices, with three given the Vfrac tool for use on older women (> 65 years) consulting with back pain and three using standard clinical processes for managing such back pain. Anonymised data covering a 12-month period will be collected from all sites on consultations by older women with back pain. Focus groups will be undertaken with healthcare professionals and patients on whom the tool was used to understand the acceptability of Vfrac and identify factors that impact its use. These patients will be sent a paper version of the Vfrac questionnaire to self-complete at home. Outputs of the self-completion Vfrac (high versus low risk) will be compared with the face-to-face Vfrac (high versus low risk), and agreement assessed using Cohen's kappa.

RESULTS

This study will evaluate the use and acceptability of Vfrac within primary care and determine if data on resource use can be collected accurately and comprehensively.

CONCLUSIONS

This article describes the protocol of the Vfrac feasibility study.

TRIAL REGISTRATION

ISRCTN18000119 (registered 01/03/2022) and ISRCTN12150779 (registered 10/01/2022).

"Pregnancy and Lactation Associated Osteoporosis"

Pregnancy-associated osteoporosis (PAO) is a rare condition of skeletal fragility affecting women in pregnancy or the postpartum period. During normal pregnancy and lactation, substantial changes in calcium metabolism and skeletal physiology occur in order to meet the demands of the developing foetus. Whilst these adaptations are reversible and generally of no clinical consequence for the mother, a small number of women will develop osteoporosis and suffer fragility fractures. Vertebral fractures occur most commonly in PAO and are often multiple. Due to the rarity of PAO, systematic study to date has been limited. Aetiology is poorly understood, but traditional osteoporosis risk factors and genetic factors are likely to play a role. A small number of cases may be due to an underlying metabolic bone disorder or monogenic condition. Management of PAO is challenging, due both to a poor evidence base and the fact that spontaneous improvement in BMD is known to occur once pregnancy and lactation are complete. Bisphosphonates, denosumab and teriparatide have all been used in individual patients, but the data supporting their use are currently limited.

P138 Real-world incidence and management of hypocalcaemia after denosumab administration in patients with chronic kidney disease: a UK secondary-care based audit

Background/Aims

Hypocalcaemia is a recognized complication of denosumab therapy in patients with renal impairment. Our local protocol states that patients with creatinine clearance (CrCl) <35ml/min should have blood tests for calcium and renal function weekly for 4 weeks after each denosumab injection. This audit aimed to assess whether such patients underwent appropriate blood monitoring, and to evaluate the incidence, severity and management of hypocalcaemia in this patient population.

Methods

Patients who commenced denosumab between 2011 and March 2020 were eligible for inclusion if they had CrCl <35ml/min. Data collection was undertaken through retrospective review of clinical records and pathology systems.

Results

53 patients fitting the above criteria were identified. One further patient with eGFR 32ml/min was also included, giving 54 patients in total for analysis. The age range of the patients was 76-97, 9/54 (17%) were male. None were on renal replacement therapy. 29/52 patients (56%) missed one or more post-injection blood tests (incomplete data n = 2). The most commonly missed blood tests were the 1st and 4th weekly checks. 18/54 (33%) developed hypocalcaemia at some point after starting denosumab. In 8/18 this was a one-off episode, but 10/18 experienced recurrent hypocalcaemia. Lowest values for adjusted calcium varied from 1.83-2.18mmol/l. Only 3 patients had a value <2.0mmol/l. Patients who did and did not develop hypocalcaemia had a mean (SD) CrCl of 27.3 (5.03) and 27.8 (5.19) respectively. There was no significant difference in CrCl between these two groups (unpaired t-test, p value 0.7338). Comparing those with >1 episode of hypocalcaemia with the rest of the group, again the mean CrCl was not significantly different (26.6 vs. 27.9, p = 0.47). The three patients who developed more severe hypocalcaemia (adjusted calcium <2.00mmol/l) had CrCl values of 33.2, 24.0 and 21.0ml/min. 17/18 patients who developed hypocalcaemia were on combined calcium and vitamin D supplementation. One patient was on vitamin D3 alone due to intolerance of calcium supplements - they developed mild hypocalcaemia only (nadir 2.13mmol/l) and had CrCl 27ml/min. One patient with CrCl 21ml/min became hypercalcaemic on combined supplementation which was later switched to alfacalcidol by the renal team. Hypocalcaemia was most commonly observed 1-week post-injection, but delayed onset of hypocalcaemia 4-6 weeks post-injection was observed in a few cases. Most episodes resolved within 1-2 weeks, almost all within 4 weeks. One patient died 2 weeks after their 2nd denosumab dose from an unrelated cause - adjusted calcium was 2.16 just prior to death. Additional oral calcium was given in two patients; in one of these, hypocalcaemia recurred after a subsequent injection despite additional supplements, and denosumab was discontinued.

Conclusion

In a real-world setting, hypocalcaemia after denosumab in patients with reduced renal function (not on renal replacement therapy) is generally mild and rarely requires treatment.

Disclosure

S.A. Hardcastle: Other; S.H. received conference fee funding from Lilly (UK) in 2018. R. Alshakh: None. J. Webb: None. S. Warren: None. T. Ahmed: None.

P140 Patient experience of osteoporosis telephone consultations

Background/Aims

The COVID-19 pandemic resulted in a rapid change to the use of virtual consultations in both primary and secondary care. Since April 2020, our osteoporosis clinic appointments have predominantly been undertaken by telephone. We wanted to assess our patients’ experience of telephone consultations.

Methods

A patient feedback questionnaire was developed by the osteoporosis team which was validated by the Patient Advice and Liaison Service team (PALS) at the Royal United Hospital Bath. A questionnaire consisting of 15 questions was sent to patients following their telephone consultation. Patient consent to receive the questionnaire was requested by the consulting clinician for each participant. The patients were provided with a stamped addressed envelope to return the completed anonymous questionnaire. Thematic analysis was used to identify themes in the qualitative data.

Results

A total of 39 questionnaires were completed. More than 86% of patients reported that their telephone consultation definitely met their needs. Over 89% answered ‘yes definitely’ to questions regarding understanding of the reason for their appointment, opportunities for questions, clear understandable answers, feeling listened to, and treatment plans. 59% of patients responded ‘yes definitely’ that they were given information prior to the appointment about what would happen in the consultation, 10% reported they hadn’t, with 31% responding they had but to some extent only. 72% of respondents reported that it was clear who they should contact if they had any further questions following the consultation. Regarding preference for future appointments, 47% of patients indicated that they would prefer a mixture of telephone, face to face and video consultations; 24% preferred telephone, 16% preferred hospital face to face, and 3% preferred video. 11% reported that they had no preference. Thematic analysis of individual comments identified positive themes such as flexibility, good communication with clinicians and convenience. Areas for development are around communication with regard to physical barriers such as hearing and telephone signal problems. There are also limitations around both physical examination and the transmission of implicit information (non-verbal communication).

Conclusion

Virtual consultations provide an opportunity to safely assess patients whilst meeting social distancing requirements and minimising patient flow through the hospital. Questionnaire analysis indicates an overall positive experience of telephone consultations. However, most patients would prefer a mixture of face to face, video and telephone consultations in future. There are a number of areas for improvement including: a review of the information provided to patients prior to the consultation, review of contact information for patients following the consultation, and mechanisms for identifying patients with physical/sensory limitations. The information gained through this small review will help us improve the overall telephone consultation experience for our patients.

Disclosure

J.L. Webb: None. S.A. Hardcastle: None. S.M. Warren: None. D.J. Hart: None. J.A. Shipley: None. T. Ahmed: None.

Increased development of radiographic hip osteoarthritis in individuals with high bone mass: a prospective cohort study

BACKGROUND

Individuals with high bone mass (HBM) have a greater odds of prevalent radiographic hip osteoarthritis (OA), reflecting an association with bone-forming OA sub-phenotypes (e.g. osteophytosis, subchondral sclerosis). As the role of bone mineral density (BMD) in hip OA progression is unclear, we aimed to determine if individuals with HBM have increased incidence and/or progression of bone-forming OA sub-phenotypes.

METHODS

We analysed an adult cohort with and without HBM (L1 and/or total hip BMD Z-score > + 3.2) with pelvic radiographs collected at baseline and 8-year follow-up. Sub-phenotypes were graded using the OARSI atlas. Superior/inferior acetabular/femoral osteophyte and medial/superior joint space narrowing (JSN) grades were summed and Δosteophyte and ΔJSN derived. Pain and functional limitations were quantified using the WOMAC questionnaire. Associations between HBM status and change in OA sub-phenotypes were determined using multivariable linear/logistic regression, adjusting for age, sex, height, total body fat mass, follow-up time and baseline sub-phenotype grade. Generalised estimating equations accounted for individual-level clustering.

RESULTS

Of 136 individuals, 62% had HBM at baseline, 72% were female and mean (SD) age was 59 (10) years. HBM was positively associated with both Δosteophytes and ΔJSN (adjusted mean grade differences between individuals with and without HBM β_osteophyte = 0.30 [0.01, 0.58], p = 0.019 and β_JSN = 0.10 [0.01, 0.18], p = 0.019). Incident subchondral sclerosis was rare. HBM individuals had higher WOMAC hip functional limitation scores (β = 8.3 [0.7, 15.98], p = 0.032).

CONCLUSIONS

HBM is associated with the worsening of hip osteophytes and JSN over an average of 8 years, as well as increased hip pain and functional limitation.

Individuals with high bone mass have increased progression of radiographic and clinical features of knee osteoarthritis

OBJECTIVE

High bone mass (HBM) is associated with an increased prevalence of radiographic knee OA (kOA), characterized by osteophytosis. We aimed to determine if progression of radiographic kOA, and its sub-phenotypes, is increased in HBM and whether observed changes are clinically relevant.

DESIGN

A cohort with and without HBM (L1 and/or total hip bone mineral density Z-score≥+3.2) had knee radiographs collected at baseline and 8-year follow-up. Sub-phenotypes were graded using the OARSI atlas. Medial/lateral tibial/femoral osteophyte and medial/lateral joint space narrowing (JSN) grades were summed and Δosteophytes, ΔJSN derived. Pain, function and stiffness were quantified using the WOMAC questionnaire. Associations between HBM status and sub-phenotype progression were determined using multivariable linear/poisson regression, adjusting for age, sex, height, baseline sub-phenotype grade, menopause, education and total body fat mass (TBFM). Generalized estimating equations accounted for individual-level clustering.

RESULTS

169 individuals had repeated radiographs, providing 330 knee images; 63% had HBM, 73% were female, mean (SD) age was 58 (12) years. Whilst HBM was not clearly associated with overall Kellgren-Lawrence measured progression (RR = 1.55 [0.56.4.32]), HBM was positively associated with both Δosteophytes and ΔJSN individually (adjusted mean differences between individuals with and without HBM 0.45 [0.01.0.89] and 0.15 [0.01.0.29], respectively). HBM individuals had higher WOMAC knee pain scores (β = 7.42 [1.17.13.66]), largely explained by adjustment for osteophyte score (58% attenuated) rather than JSN (30% attenuated) or TBFM (16% attenuated). The same pattern was observed for symptomatic stiffness and functional limitation.

CONCLUSIONS

HBM is associated with osteophyte progression, which appears to contribute to increased reported pain, stiffness and functional loss.

Pregnancy-associated osteoporosis: a UK case series and literature review

Mini Abstract: Pregnancy-associated osteoporosis (PAO) is a rare syndrome affecting women during late pregnancy and the early postpartum period. We set out to review the clinical features of ten cases of PAO from a single UK centre. Patients had attended the Royal National Hospital for Rheumatic Diseases, Bath (RNHRD) between January 2000 and June 2016. The principal criterion for inclusion was the occurrence of low trauma fractures either during pregnancy or the immediate post-partum period. Data were obtained from retrospective review of medical notes. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (Hologic ®Discovery system) at the lumbar spine and hip. Data pertaining to the pregnancy, as well as type and duration of treatment received, were reviewed. All ten cases presented with vertebral fractures. In four patients, no risk factors for fracture other than pregnancy or breastfeeding could be identified. Four patients were found to have vitamin D insufficiency at the time of diagnosis, and a further two patients had received treatment with low molecular weight heparin (LMWH). In one case, further investigation led to a diagnosis of osteogenesis imperfecta (OI) confirmed on genetic testing. In terms of treatment, eight out of the ten patients in this series received a bisphosphonate, most commonly risedronate due to its relatively short skeletal retention time. Clinicians should be aware of PAO, a rare but recognised complication of pregnancy. The condition should be especially considered in women presenting with new onset back pain in pregnancy or the postpartum period.

High Bone Mass is associated with bone-forming features of osteoarthritis in non-weight bearing joints independent of body mass index

OBJECTIVES

High Bone Mass (HBM) is associated with (a) radiographic knee osteoarthritis (OA), partly mediated by increased BMI, and (b) pelvic enthesophytes and hip osteophytes, suggestive of a bone-forming phenotype. We aimed to establish whether HBM is associated with radiographic features of OA in non-weight-bearing (hand) joints, and whether such OA demonstrates a bone-forming phenotype.

METHODS

HBM cases (BMD Z-scores≥+3.2) were compared with family controls. A blinded assessor graded all PA hand radiographs for: osteophytes (0-3), joint space narrowing (JSN) (0-3), subchondral sclerosis (0-1), at the index Distal Interphalangeal Joint (DIPJ) and 1st Carpometacarpal Joint (CMCJ), using an established atlas. Analyses used a random effects logistic regression model, adjusting a priori for age and gender. Mediating roles of BMI and bone turnover markers (BTMs) were explored by further adjustment.

RESULTS

314 HBM cases (mean age 61.1years, 74% female) and 183 controls (54.3years, 46% female) were included. Osteophytes (grade≥1) were more common in HBM (DIPJ: 67% vs. 45%, CMCJ: 69% vs. 50%), with adjusted OR [95% CI] 1.82 [1.11, 2.97], p=0.017 and 1.89 [1.19, 3.01], p=0.007 respectively; no differences were seen in JSN. Further adjustment for BMI failed to attenuate ORs for osteophytes in HBM cases vs. controls; DIPJ 1.72 [1.05, 2.83], p=0.032, CMCJ 1.76 [1.00, 3.06], p=0.049. Adjustment for BTMs (concentrations lower amongst HBM cases) did not attenuate ORs.

CONCLUSIONS

HBM is positively associated with OA in non-weight-bearing joints, independent of BMI. HBM-associated OA is characterised by osteophytes, consistent with a bone-forming phenotype, rather than JSN reflecting cartilage loss. Systemic factors (e.g. genetic architecture) which govern HBM may also increase bone-forming OA risk.

Mutations in Known Monogenic High Bone Mass Loci Only Explain a Small Proportion of High Bone Mass Cases

High bone mass (HBM) can be an incidental clinical finding; however, monogenic HBM disorders (eg, LRP5 or SOST mutations) are rare. We aimed to determine to what extent HBM is explained by mutations in known HBM genes. A total of 258 unrelated HBM cases were identified from a review of 335,115 DXA scans from 13 UK centers. Cases were assessed clinically and underwent sequencing of known anabolic HBM loci: LRP5 (exons 2, 3, 4), LRP4 (exons 25, 26), SOST (exons 1, 2, and the van Buchem's disease [VBD] 52-kb intronic deletion 3'). Family members were assessed for HBM segregation with identified variants. Three-dimensional protein models were constructed for identified variants. Two novel missense LRP5 HBM mutations ([c.518C>T; p.Thr173Met], [c.796C>T; p.Arg266Cys]) were identified, plus three previously reported missense LRP5 mutations ([c.593A>G; p.Asn198Ser], [c.724G>A; p.Ala242Thr], [c.266A>G; p.Gln89Arg]), associated with HBM in 11 adults from seven families. Individuals with LRP5 HBM (∼prevalence 5/100,000) displayed a variable phenotype of skeletal dysplasia with increased trabecular BMD and cortical thickness on HRpQCT, and gynoid fat mass accumulation on DXA, compared with both non-LRP5 HBM and controls. One mostly asymptomatic woman carried a novel heterozygous nonsense SOST mutation (c.530C>A; p.Ser177X) predicted to prematurely truncate sclerostin. Protein modeling suggests the severity of the LRP5-HBM phenotype corresponds to the degree of protein disruption and the consequent effect on SOST-LRP5 binding. We predict p.Asn198Ser and p.Ala242Thr directly disrupt SOST binding; both correspond to severe HBM phenotypes (BMD Z-scores +3.1 to +12.2, inability to float). Less disruptive structural alterations predicted from p.Arg266Cys, p.Thr173Met, and p.Gln89Arg were associated with less severe phenotypes (Z-scores +2.4 to +6.2, ability to float). In conclusion, although mutations in known HBM loci may be asymptomatic, they only account for a very small proportion (∼3%) of HBM individuals, suggesting the great majority are explained by either unknown monogenic causes or polygenic inheritance.

LRP5 regulates human body fat distribution by modulating adipose progenitor biology in a dose- and depot-specific fashion

Common variants in WNT pathway genes have been associated with bone mass and fat distribution, the latter predicting diabetes and cardiovascular disease risk. Rare mutations in the WNT co-receptors LRP5 and LRP6 are similarly associated with bone and cardiometabolic disorders. We investigated the role of LRP5 in human adipose tissue. Subjects with gain-of-function LRP5 mutations and high bone mass had enhanced lower-body fat accumulation. Reciprocally, a low bone mineral density-associated common LRP5 allele correlated with increased abdominal adiposity. Ex vivo LRP5 expression was higher in abdominal versus gluteal adipocyte progenitors. Equivalent knockdown of LRP5 in both progenitor types dose-dependently impaired β-catenin signaling and led to distinct biological outcomes: diminished gluteal and enhanced abdominal adipogenesis. These data highlight how depot differences in WNT/β-catenin pathway activity modulate human fat distribution via effects on adipocyte progenitor biology. They also identify LRP5 as a potential pharmacologic target for the treatment of cardiometabolic disorders.

Individuals with high bone mass have an increased prevalence of radiographic knee osteoarthritis

We previously reported an association between high bone mass (HBM) and a bone-forming phenotype of radiographic hip osteoarthritis (OA). As knee and hip OA have distinct risk factors, in this study we aimed to determine (i) whether HBM is also associated with knee OA, and (ii) whether the HBM knee OA phenotype demonstrates a similar pattern of radiographic features to that observed at the hip. HBM cases (defined by DXA BMD Z-scores) from the UK-based HBM study were compared with unaffected family controls and general population controls from the Chingford and Hertfordshire cohort studies. A single blinded observer graded AP weight-bearing knee radiographs for features of OA (Kellgren-Lawrence score, osteophytes, joint space narrowing (JSN), sclerosis) using an atlas. Analyses used logistic regression, adjusting a priori for age and gender, and additionally for BMI as a potential mediator of the HBM-OA association, using Stata v12. 609 HBM knees in 311 cases (mean age 60.8years, 74% female) and 1937 control knees in 991 controls (63.4years, 81% female) were analysed. The prevalence of radiographic knee OA, defined as Kellgren-Lawrence grade≥2, was increased in cases (31.5% vs. 20.9%), with age and gender adjusted OR [95% CI] 2.38 [1.81, 3.14], p<0.001. The association between HBM and osteophytosis was stronger than that for JSN, both before and after adjustment for BMI which attenuated the ORs for knee OA and osteophytes in cases vs. controls by approximately 50%. Our findings support a positive association between HBM and knee OA. This association was strongest for osteophytes, suggesting HBM confers a general predisposition to a subtype of OA characterised by increased bone formation.

Osteophytes, enthesophytes, and high bone mass: a bone-forming triad with potential relevance in osteoarthritis

Objective

Previous studies of skeletal remains have suggested that both enthesophytes and osteophytes are manifestations of an underlying bone-forming tendency. A greater prevalence of osteophytes has been observed among individuals with high bone mass (HBM) compared with controls. This study was undertaken to examine the possible interrelationships between bone mass, enthesophytes, and osteophytes in a population of individuals with extreme HBM.

Methods

Cases of HBM (defined according to bone mineral density [BMD] Z scores on dual x-ray absorptiometry) from the UK-based HBM study were compared with a control group comprising unaffected family members and general population controls from the Chingford and Hertfordshire cohort studies. Pelvic radiographs from cases and controls were pooled and evaluated, in a blinded manner, by a single observer, who performed semiquantitative grading of the radiographs for the presence and severity of osteophytes and enthesophytes (score range 0–3 for each). Logistic regression analysis was used to identify significant associations, with a priori adjustment for age, sex, and body mass index.

Results

In this study, 226 radiographs from HBM cases and 437 radiographs from control subjects were included. Enthesophytes (grade ≥1) and moderate enthesophytes (grade ≥2) were more prevalent in HBM cases compared with controls (adjusted odds ratio [OR] 3.00 [95% confidence interval (95% CI) 1.96–4.58], P < 0.001 for any enthesophyte; adjusted OR 4.33 [95% CI 2.67–7.02], P < 0.001 for moderate enthesophytes). In the combined population of cases and controls, the enthesophyte grade was positively associated with BMD at both the total hip and lumbar spine (adjusted P for trend < 0.001). In addition, a positive association between osteophytes and enthesophytes was observed; for each unit increase in enthesophyte grade, the odds of any osteophyte being present were increased >2-fold (P < 0.001).

Conclusion

Strong interrelationships were observed between osteophytes, enthesophytes, and HBM, which may be helpful in defining a distinct subset of patients with osteoarthritis characterized by excess bone formation.

Jump power and force have distinct associations with cortical bone parameters: findings from a population enriched by individuals with high bone mass

CONTEXT

Little is known of the relationships between muscle function and bone, based on the recently developed technique of jumping mechanography.

OBJECTIVE

Our objective was to determine associations between peak ground reaction force and peak power during a 1-legged hopping test and a single 2-legged jump, respectively, and cortical bone parameters.

DESIGN AND SETTING

This was a cross-sectional observational study in participants from the high bone mass cohort.

PARTICIPANTS

Participants included 70 males (mean age 58 years) and 119 females (mean age 56 years); high bone mass cases and controls were pooled.

MAIN OUTCOME MEASURES

Total hip bone mineral density (BMD) (measured by dual-energy x-ray absorptiometry scanning) and mid-tibial peripheral quantitative computed tomography (Stratec XCT2000L).

RESULTS

Jump power was positively related to hip BMD (standardized β [95% confidence interval]=0.29 [0.07, 0.51], P=.01), but hopping force was not (0.03 [-0.16, 0.22], P=.74) (linear regression analysis adjusted for age, gender, height, and weight). In 113 participants with force and peripheral quantitative computed tomography data, both jump power and hopping force were positively associated with tibial strength strain index (0.26 [0.09, 0.44], P<.01; and 0.24 [0.07, 0.42], P=.01 respectively). Although hopping force was positively associated with bone size (total bone area 0.22 [0.03, 0.42], P=.02), jump power was not (0.10 [-0.10, 0.30], P=.33). In contrast, jump power was inversely associated with endocortical circumference adjusted for periosteal circumference (-0.24 [-0.40, -0.08], P<.01) whereas no association was seen for hopping force (-0.10 [-0.26, 0.07], P=.24).

CONCLUSIONS

Although power and force are both positively associated with cortical bone strength, distinct mechanisms appear to be involved because power was primarily associated with reduced endocortical expansion (reflected by endocortical circumference adjusted for periosteal circumference, and hip BMD), whereas force was associated with increased periosteal expansion (reflected by total bone area).

Friend or foe: high bone mineral density on routine bone density scanning, a review of causes and management

A finding of high BMD on routine DXA scanning is not infrequent and most commonly reflects degenerative disease. However, BMD increases may also arise secondary to a range of underlying disorders affecting the skeleton. Although low BMD increases fracture risk, the converse may not hold for high BMD, since elevated BMD may occur in conditions where fracture risk is increased, unaffected or reduced. Here we outline a classification for the causes of raised BMD, based on identification of focal or generalized BMD changes, and discuss an approach to guide appropriate investigation by clinicians after careful interpretation of DXA scan findings within the context of the clinical history. We will also review the mild skeletal dysplasia associated with the currently unexplained high bone mass phenotype and discuss recent advances in osteoporosis therapies arising from improved understanding of rare inherited high BMD disorders.

High bone mass is associated with an increased prevalence of joint replacement: a case-control study

Objective. Epidemiological studies have shown an association between OA and increased BMD. To explore the nature of this relationship, we examined whether the risk of OA is increased in individuals with high bone mass (HBM), in whom BMD is assumed to be elevated due to a primary genetic cause.

Methods. A total of 335 115 DXA scans were screened to identify HBM index cases (defined by DXA scan as an L1 Z-score of ≥+3.2 and total hip Z-score ≥+1.2, or total hip Z-score ≥+3.2 and L1 Z-score ≥+1.2). In relatives, the definition of HBM was L1 Z-score plus total hip Z-score ≥+3.2. Controls comprised unaffected relatives and spouses. Clinical indicators of OA were determined by structured assessment. Analyses used logistic regression adjusting for age, gender, BMI and social deprivation.

Results. A total of 353 HBM cases (mean age 61.7 years, 77% female) and 197 controls (mean age 54.1 years, 47% female) were included. Adjusted NSAID use was more prevalent in HBM cases versus controls [odds ratio (OR) 2.17 (95% CI 1.10, 4.28); P = 0.03]. The prevalence of joint replacement was higher in HBM cases (13.0%) than controls (4.1%), with an adjusted OR of 2.42 (95% CI 1.06, 5.56); P = 0.04. Adjusted prevalence of joint pain and knee crepitus did not differ between cases and controls.

Conclusion. HBM is associated with increased prevalence of joint replacement surgery and NSAID use compared with unaffected controls.