The prevalence of erosive osteoarthritis in carpometacarpal joints and its clinical burden in symptomatic community-dwelling adults.

OBJECTIVE: To estimate the prevalence of erosive disease in first carpometacarpal joints (CMCJs) and investigate its clinical impact compared with radiographic thumb base (TB) osteoarthritis (OA). PATIENT AND METHODS: Standardized assessments with hand radiographs were performed in participants of two population-based cohort studies in North Staffordshire with hand symptoms lasting ≥1 day in the past month. Erosive disease was defined as the presence of eroded or remodeled phase in ≥1 interphalangeal joint (IPJ) or first CMCJ following the Verbruggen-Veys classification. Hand pain and function were assessed with Australian/Canadian Hand Osteoarthritis Index (AUSCAN). Prevalence was estimated by dividing the number of persons with erosive lesions by population size. Linear and logistic regression analyses were used to contrast clinical determinants between persons with erosions and with radiographic TB OA. Results were presented as mean differences and odds ratios (ORs) with 95% confidence intervals (95% CI), adjusted for age, sex and radiographic severity.
RESULTS: 1,076 participants were studied (60% women, mean age 64.7 years (SD 8.3); 24 persons had erosive disease in the TB. The prevalence of erosive disease in first CMCJs was 2.2% (95% CI 1.4, 3.3). Only 0.5% (95% CI 0.2, 1.2) had erosive disease affecting IPJs and first CMCJs combined. More persons with erosive disease of first CMCJs reported pain in their TB than persons with radiographic TB OA, AUSCAN pain and function scores were similar.
CONCLUSION: Erosive disease of first CMCJs was present in 2.2% of subjects with hand pain and was often not accompanied by erosions in IPJs. Erosive disease was associated with TB pain, but not with the level of pain, when compared with radiographic TB OA.

Introduction

Osteoarthritis (OA) of the thumb base (TB) is defined as OA in the first carpometacarpal joint (first CMCJ) with or without scaphotrapezoid joint (STJ) OA. It often occurs together with OA at other sites in the hand2, 3, however isolated OA of first CMCJ is also described. The prevalence of radiographic first CMCJ or STJ OA is described as up to 35.8% in the general population aged >55 years, whereas prevalences of symptomatic first CMCJ OA in adults from the general population aged over 60 or 70 years are estimated at 1.9% and 4.1%, respectively. TB OA can be recognized radiographically by osteophytes, joint space narrowing, sclerosis and cysts. These features are assessed as part of the Kellgren–Lawrence (KL) grading system that is commonly used for grading the presence and severity of radiographic OA in the hand.

The clinical burden of first CMCJ OA is considerable. Radiographic TB OA has the highest association with hand pain compared with other hand OA joint groups. Radiographic TB OA is also associated with a risk of reduced grip strength. Studies on self-reported pain and disability showed that the burden is highest in patients with combined finger and TB OA3, 10. The presence of first CMCJ OA contributed more to pain and disability than interphalangeal joints (IPJs) OA in a population with symptomatic hand OA.

More recently, erosive hand OA has become a focus of interest. The pathophysiology of erosive OA is unclear and whether erosive OA should be considered as a separate disease entity or a more severe stage of hand OA is also unclear. Most previous studies on erosive OA have focused on the IPJs1, 11, 12. Information on the presence of erosions in first CMCJs remains scarce13, 14, despite the availability of a standardized (OARSI) scoring method. In 1968, Peter et al. already described that erosive OA can involve the first CMCJ ‘occasionally’. In 1990, Cobby et al. reported that erosions in first CMCJ can be present in OA patients up to 51% in combination with erosions of metacarpophalangeal joints and STJs. No specific frequency for erosive disease in first CMCJs only was given in that study. No knowledge is available whether erosive OA in the IPJs is a different phenotype than erosive disease in the TB.

Erosive OA is a radiographic subset of hand OA with a higher clinical burden (pain, functional limitations) than non-erosive hand OA16, 17, 18. It is unclear what the clinical impact is of erosive disease in the TB.

In an earlier study we performed in the Rotterdam Study we detected erosive lesions in first CMCJ. However, due to the study design (where the selection of hand radiographs was focused on IPJs in this sample), these erosive lesions could not be investigated in more detail in that particular study.

The aims of the present study are to describe the frequency of erosive disease in first CMCJs with its co-occurrence of erosive disease in IPJs and the presence of concordant pain and radiographic OA in the same TB. Also clinical outcomes such as pain and function are compared between radiographic TB OA with erosive disease in the TB.

Methods

Population and study design

Data were collected from the Clinical Assessment Study of the Hand (CAS-HA) and Knee (CAS-K), both prospective, population-based, observational cohort studies in North Staffordshire. Study protocols of these studies are described elsewhere in detail19, 20. In short, all adults aged ≥50 years registered with two general practices were invited to participate in a two-stage postal survey. When they indicated that they had experienced hand symptoms within ≤12 months on the first postal questionnaire, they were invited to the research clinic. Those who attended the research clinic were included in the CAS-HA study (n = 623). CAS-K participants (n = 819) were recruited from a further three different general practices using recruitment methods identical to CAS-HA, except that participants were invited for a clinical assessment in the CAS-K study when they reported knee pain (rather than hand symptoms) within last year. Ethical approval was obtained from the North Staffordshire Local Research Ethics Committee and all participants gave written consent. Only CAS-HA or CAS-K participants who indicated that they experienced hand symptoms (pain, aching, stiffness) ≥1 day during last month are included in this paper.

Radiographic assessment and scoring

Plain radiographs were completed of each hand in posteroanterior view. Distal, proximal and thumb interphalangeal joint (DIPJ, PIPJ and first IPJ) and first CMCJ were scored by two trained assessors (MM scored n = 521, JH scored n = 555), blinded for clinical data. Joints were scored for presence and severity of OA with the Kellgren–Lawrence (KL) grade. The KL-score, graded from 0 to 4, is based on the presence and size of osteophytes, joint space narrowing, sclerosis, cysts and altered shape of bony ends: 0 = no OA, 1 = doubtful OA, 2 = definite OA (requiring the minimal presence of an osteophyte to classify an individual as having OA22, 23), 3 = moderate OA, 4 = severe OA21. Both observers re-scored fifty pairs to calculate inter- and intra-observer reliability. Inter-observer reliability (kappa) for the presence of hand OA was 0.50 (percentage agreement (PA) 90%). The intra-observer reliability for presence of hand OA was excellent (kappa = 0.92 and 0.85, PA 98% and 98% for reader 1 and 2, respectively).

Erosive disease were scored by the Verbruggen–Veys scoring system and defined as the presence of eroded (E-phase) or remodeled, irregular, sclerotic subchondral plates (R-phase) in DIPJs, PIPJs, first IPJs and first CMCJs. The Verbruggen–Veys scoring does not include first IPJs and first CMCJs; however the same rules for DIPJs/PIPJs were applied to these joints. Fig. 1, Fig. 2 show examples of erosive disease in first CMCJs. Additionally the OARSI (OsteoArthritis Research Society International) atlas was used as a guide to score first CMCJs for erosions. Erosions were scored by a single reader (WK), blinded for clinical data. The intra-observer reliability for erosive disease as a dichotomous variable in the Verbruggen–Veys scoring method was excellent (kappa = 0.94).

Fig. 1

Example of first CMCJ erosion, E-phase.

Fig. 2

Example of first CMCJ erosion, R-phase.

Sample selection for scoring erosive disease in hand radiographs

The majority of hand radiographs were scored for erosions; exceptions were those radiographs that had no or very few osteoarthritic features. The assumption was that erosions are not present in subjects with near normal radiographs. To determine the selection for scoring erosions, KL-scores in the DIPJs, PIPJs, first IPJs and first CMCJs were summed to form an overall score (KLsum) for every participant. The population was divided in subgroups by the summation scores (range 0–72). All radiographs in subgroups with KLsum ≥3 were scored. Random samples of at least 10% of subgroups with KLsum <3 were screened and no erosive OA was seen.

OA definitions

The presence of pain in the thumb was determined from hand drawings; participants shaded areas where they had experienced pain lasting ≥1 day during past month. Radiographic TB OA was defined as KL-grade ≥2 in at least one first CMCJ or STJ. Symptomatic radiographic TB OA was defined as having radiographic TB OA combined with concordant pain of the TB. Erosive disease in the TB was defined as having ≥1 E- or R-phase in the first CMCJs. Erosive disease in the IPJs is defined as having at least 1 E- or R-phase in the DIPJ, PIPJ or first IPJ.

Exclusions

Individuals were excluded from the analyses if medical records from general practitioners and the local Rheumatology hospital were reviewed to identify patients with systemic inflammatory rheumatic diseases (e.g., rheumatoid arthritis, psoriatic arthritis) or if there was evidence of inflammatory changes on the radiographs, identified by a musculoskeletal radiologist. Those with no or missing radiographic data or no hand symptoms (pain, aching, stiffness) ≥1 day during last month were also excluded.

Clinical outcomes

General characteristics of age and sex were recorded in postal surveys and height and weight were measured at the research clinics held at a local Rheumatology outpatients clinic. Participants also reported their occupation the postal survey. People with lower supervisory and technical work, semi-routine or routine work, were classified as manual occupational class.

Hand pain and stiffness

The pain and stiffness subscale of the Australian/Canadian Hand Osteoarthritis Index (AUSCAN) was completed by all participants (range 0–20 and 0–4, respectively). Self-reported pain was also assessed with the pain subscale of the Arthritis Impact Measurement Scales health status questionnaire (AIMS-2, range 0–10). Higher scores indicate more pain or stiffness.

Hand function and performance

Self-reported hand function was assessed with the function subscales of the AUSCAN (range 0–36) and AIMS-2 (range 0–10). Higher scores represent more limitation in hand function. The maximum gross and pinch grip strength was assessed with the JAMAR dynomometer (Sammons Preston, Chicago, IL) and B&L pinch gage (B&L Engineering, Tustin, CA), respectively. In addition, the Grip Ability Test (GAT) was performed in the CAS-HA participants. The GAT consisted of three tasks (putting a flexigrip stocking over the non-dominant hand, putting a paperclip on an envelope, pouring water from a jug into a cup), which participants had to perform within 2–3 min27, 28. Scores are based on the time to complete the three tasks; higher scores correspond to poorer hand function. GAT scores of <20 are considered normal.

General health perceptions

General health perceptions were measured by the Short-Form 12 (SF-12), a widely used generic health status questionnaire yielding summary component scores for physical health (PCS, 0–100) and mental health (MCS, 0–100), where lower scores represent poorer perceived health and the population average is 50.

Esthetic and impact of hand problems

Appearance of the hand was measured with the aesthetics subscale of the Michigan Hand Outcomes Questionnaire (MHQ, range 0–100). The impact of hand symptoms on health status was measured with the impact subscale of the AIMS-2 (range 0–10). Higher scores represent more satisfaction with aesthetics of the hand and a higher negative impact.

Statistical analysis

Prevalence of erosive disease of the thumb in the population with radiographic TB OA and concordant radiographic TB OA with pain is the proportion of individuals with erosive disease of the thumb. Associated 95% confidence intervals (95% CI) were calculated based on a binomial distribution.

Linear regression analyses were used to investigate differences in clinical characteristics between participants with and without erosive TB disease. The beta-estimate is presented as the mean difference (with 95% CI), adjusted for age and sex and in addition for the sum of KL-score of both first CMCJs (in order to adjust for the severity radiographic TB OA). Logistic regression analyses were used to investigate differences in any or concordant TB pain between participants with and without erosive TB disease and were presented as odds ratios (ORs), also adjusted for age, sex and in addition for the sum of KL-score of both first CMCJs.

Data were analyzed with SPSS, version 20 (SPSS Inc, Chicago, Illinois).

Results

Clinical characteristics and demographics

The cohorts yielded a combined sample of 1,442 potentially eligible participants. Participants with incomplete radiographs (n = 56), without hand symptoms ≥1 day during last month (n = 266) and those with inflammatory disease (n = 44) were excluded [Fig. 3], leaving a total of 1,076 eligible participants (60% women, mean age 64.7 years (SD 8.3)).

Fig. 3

Flowchart of selection of CAS-K & CAS-HA participants for erosive OA analyses.

In 56% (n = 605) pain was present in any left or right TB, of which 364 persons had bilateral thumb pain. Radiographic TB OA was present in 54% (n = 585) of participants, of which 396 persons (67%) had bilateral radiographic TB OA. All STJs with a KL-grade ≥2, also had at least one first CMCJ with a KL-grade ≥2. Of all persons with radiographic thumb OA, 954 first CMC joints had a KL-score of at least 2 (517 left first CMCJs, 437 right first CMCJs). Of these 954 joints, 493 joints were painful (262 left first CMCJs, 231 right first CMCJs). In all persons with hand symptoms, 540 persons (50%) were of manual occupational class. In persons with radiographic thumb OA, 274 out of 585 persons (47%) were of manual occupational class (Table I).

Table I

Baseline characteristics of 1,076 persons in the population with hand symptoms lasting ≥1 day during last month

Female, no. (%)	650 (60)
Age (years), mean (SD)	64.7 (8.3)
BMI (kg/m2), mean (SD)	29.1 (5.1)
Pain in any left or right TB, no. (%)	605 (56)
Radiographic TB OA, no. (%)∗	585 (54)
Concordant TB pain and radiographic TB OA†, no (%)	330 (31)
Persons with erosive disease‡ in any first CMCJs, no. (%)	24 (2.2)
Persons with erosive disease exclusively first CMC, no. (%)	18 (1.7)
Persons with erosive disease in first CMCJ combined with interphalangeal joints, no. (%)	6 (0.5)
Persons with erosive disease only in interphalangeal joints (DIPJ/PIPJ), no. (%)	74 (6.9)
Manual occupational class§ in persons with hand symptoms, no. (%)	540 (50)
Manual occupational class in persons with radiographic TB OA, no. (%)	274 (47)
Manual occupational class in persons with concordant TB pain and radiographic TB OA, no. (%)	162 (49)
Manual occupational class in persons with erosive disease in any first CMCJ, no. (%)	15 (63)

SD = standard deviation, BMI = Body Mass Index, DIPJ = distal interphalangeal joint, PIPJ = proximal interphalangeal joint.

Presence of Kellgren and Lawrence grade ≥2 in at least one joint with KL ≥2 in carpometacarpal joint (first CMCJ) or STJ in any hand.

Radiographic TB OA combined with thumb pain.

At least having one eroded (E-phase) or remodeled joint (R-phase), according to the Verbruggen–Veys scoring method.

Manual occupational class was classified as lower supervisory and technical work, semi-routine or routine work.

In 31% (n = 330) of the participants, concordant TB pain and radiographic TB OA was seen, of which 162 were of manual occupational class (Table I).

Occurrence and prevalence of erosive disease in the TB

Of the 1,076 individuals, 24 had at least one E- or R-phase in any first CMCJ. The prevalence of erosive disease in first CMCJ was 2.2% (95% CI 1.4, 3.3) (Table I). Of these 24 persons (10 males, 14 females), 15 persons (62.5%) were of manual occupational class. Of these 15 persons, six were males (6/10 = 60%) and nine were females (9/15 = 64.3%).

Twenty-four patients had at least one erosive lesion in the first CMCJs with four persons having both first CMCJs involved. Of the 28 joints affected, 23 were an E-phase and five were an R-phase.

Of the 28 first CMCJs with an erosive lesion, 22 joints were concordantly painful. These painful joints were present in 19 patients.

In 1.7% (n = 18) of participants erosive disease was exclusively present in first CMCJs and only 0.5% (n = 6) had erosive disease in both the IPJs and first CMCJs. Of the 1,076 patients, 98 had EOA in 1 IPJ, first CMC or both (Table I).

In the population with radiographic TB OA, the prevalence of erosive disease was 4.1% (95% CI 2.6, 6.1), whereas in the population with concordant pain in the TB and radiographic TB OA a prevalence of 5.8% (95% CI 3.5, 8.8) was seen, as shown in Table IIi. The prevalence of erosive disease in the TB was higher for men than women in all groups. The Supplementary Table S1 showed the prevalences stratified for the age categories 50–59 years, 60–69 years, 70–79 years and 80 years or older. The highest prevalence of erosive disease in the TB was seen in men in the age category of 70–79 years.

Table II

Prevalence of erosive disease in carpometacarpal joints (first CMCJ) in populations aged >50 years with radiographic TB OA and concordant TB pain with radiographic TB OA, stratified for sex

Prevalence erosive disease in TB	All	Males	Females
Population with radiographic TB OA	24/5854.1 (2.6, 6.1)	10/2074.8 (2.3, 8.7)	14/3783.7 (2.0, 6.1)
Population with concordant TB pain and radiographic TB OA	19/3305.8 (3.5, 8.8)	7/1026.9 (2.8, 13.6)	12/2285.3 (3.1, 9.5)

Numbers are absolute numbers with percentages and 95% CI.

Population with radiographic TB OA = at least one joint first carpometacarpal joint (first CMCJ) or STJ with Kellgren–Lawrence (KL) grade ≥2.

Population with concordant TB pain and radiographic TB OA = pain in left of right TB combined with having first CMCJ or STJ with KL grade ≥2 in the painful joint.

Clinical burden of erosive disease in first CMCJs in relation to radiographic TB OA

All those with erosive disease of the thumb had radiographic TB OA, patients with erosive disease of the first CMCJs reported more often thumb pain than those with radiographic TB OA after adjustment for age and sex (OR 3.5 (95% CI 1.2, 10.5)) (Table III). However, after additional adjustment for radiographic severity the OR is 2.7 (95% CI 0.9, 8.3) (Table III). Patients with erosive disease of the thumb were slightly older than those with radiographic TB OA (Table III). KL-scores of the first CMCJs were also higher in those with erosive disease of the thumb than those with radiographic TB OA (adjusted difference 2.6 (95% CI 1.7, 3.4)), as shown in Table III. Persons with erosive disease in the thumb reported higher values for pain on the AUSCAN and function on both AUSCAN and AIMS-2, and lower absolute scores for power and pulp grip, GAT, perceived physical health and appearance of their hands (Table III). However, when these outcomes were adjusted for age, sex and additionally for the sum of KL-scores in first CMCJs (reflecting the radiographic severity), no statistical significant difference was seen.

Table III

Demographic characteristics and clinical outcomes in persons with erosive disease in carpometacarpal joints (first CMCJ) compared with the radiographic TB OA subpopulation (n = 585), with mean differences in outcomes

Outcome	Persons with radiographic TB OA (n = 561), mean (SD)	Persons with first CMCJ erosive disease (n = 24), mean (SD)	Adjusted∗ mean difference (95% CI)	Adjusted† mean difference (95% CI)
Female, no. (%)	364 (65%)	14 (58%)	−6.6% (−26.7, 13.6)	–
Age (years)	67.0 (8.1)	70.8 (7.2)	3.8 (0.4, 7.1)	–
BMI (kg/m2)	29.1 (5.2)	29.3 (5.9)	0.4 (−1.8, 2.5)	–
Sum of KL of first CMCJ	4.1 (2.2)	6.9 (1.4)	2.6 (1.7, 3.4)	–
Sum of KL of IPJs and first CMCJs	15.6 (12.6)	22.4 (13.0)	5.2 (0.5, 9.9)	–
AUSCAN pain	6.9 (4.3)	7.5 (3.9)	0.7 (−1.1, 2.4)	0.4 (−1.5, 2.2)
AUSCAN stiffness	1.2 (1.0)	1.0 (1.0)	−0.2 (−0.6, 0.2)	−0.2 (−0.6, 0.2)
AUSCAN function	11.1 (8.3)	12.7 (8.5)	1.6 (−1.8, 5.0)	1.1 (−2.4, 4.6)
AIMS-2 Pain subscale	3.9 (2.4)	3.8 (2.3)	−0.04 (−1.0, 1.0)	−0.02 (−1.1, 1.0)
AIMS-2 Hand/finger function	2.3 (2.2)	2.6 (1.9)	0.3 (−0.6, 1.1)	−0.004 (−0.9, 0.9)
AIMS-2 Impact subscale	2.2 (2.2)	2.2 (1.7)	0.1 (−0.8, 1.0)	0.2 (−0.7, 1.2)
Power grip (lbs)	48.0 (25.1)	45.1 (23.9)	−2.9 (−10.0, 4.1)	−2.8 (−10.0, 4.4)
Pulp pinch (lbs)	9.9 (4.0)	9.6 (3.7)	−0.2 (−1.5, 1.0)	−0.02 (−1.3, 1.2)
GAT: Grip ability test	32.4 (12.2)	31.5 (11.3)	−2.6 (−9.3, 4.2)	−2.4 (−9.3, 4.6)
SF-12 PCS	37.5 (11.8)	34.5 (11.8)	−1.6 (−6.3, 3.1)	−2.1 (−7.0, 2.8)
SF-12 MCS	50.8 (10.6)	50.5 (12.0)	−0.8 (−5.2, 3.6)	−0.8 (−5.3, 3.8)
MHQ Appearance subscale	70.6 (21.6)	65.9 (22.8)	−4.7 (−13.7, 4.3)	−3.5 (−12.7, 5.8)

Values are means (SD) unless stated otherwise, first CMCJ = first carpometacarpal joint, BMI= Body Mass Index, KL= Kellgren and Lawrence score, IPJs = distal interphalangeal joints, proximal interphalangeal joints and thumb interphalangeal joints, AUSCAN = Australian/Canadian Hand Osteoarthritis Index, AIMS-2 = Arthritis Impact Measurement Scales health status.

PCS = Physical component summary score, MCS = Mental component summary score.

Adjusted for age and sex (exception: crude mean differences for age and sex).

Adjusted for age, sex and sumKL of first CMCJ, 1 lb = 0.453 kg.

Clinical burden of erosive disease in thumb in relation to radiographic TB OA in the same thumb

Nineteen out of 24 patients with erosive disease of the thumb had concordant pain in the TB, whereas 310 persons with radiographic TB OA reported concordant pain (adjusted OR for age and sex: 3.3 (95% CI 1.2, 8.9), adjusted OR for age, sex and radiographic severity: 1.7 (95% CI 0.6, 4,9)). However, when the level of pain was compared between the persons with radiographic TB OA and concordant pain no difference was found in pain, stiffness, functional limitations as assessed by AUSCAN, power grip, pulp pinch strength and performance of the GAT. Also no relevant differences were seen in the AIMS-2 Impact subscale, PCS and MCS between patients with erosive disease in the thumb and those with concordant pain and radiographic OA in TB (data not shown).

Clinical burden of erosive disease in first CMCJs in relation to erosive OA of interphalangeal joints

Erosive disease in first CMCJs was more often present in men than in women, which is especially remarkable since erosive OA of IPJs was most prevalent in women. No large differences were found in pain, stiffness, functional limitations, performance tests, appearance and impact between persons with erosive disease in the thumb and those with erosive disease in the IPJs (data not shown).

Discussion

We studied the prevalence of erosive disease in first CMCJs in 1,076 individuals from a population based cohort, and found a prevalence of 2.2% in persons from the general population with hand symptoms. Only a few people had both erosive OA in the IPJs and erosive disease in the first CMCJs, while the rest have erosive lesions in first CMCJs or in IPJs exclusively. Persons with erosive disease in the first CMCJs reported more often pain in the affected joint and had higher sum scores of the KL-grade in first CMCJs compared with persons with radiographic TB OA; males tended to be more often affected by erosive disease in the first CMCJs. No differences in the level of hand pain, stiffness or functional limitations were seen between persons with erosive lesions in first CMCJs and persons with concordant pain and radiographic OA of the TB.

As expected, the prevalence of erosive lesions in first CMCJs is low in the general population with hand symptoms. We found that 4.1% of adults aged ≥50 years with radiographic TB OA have erosive lesions in first CMCJs. An intriguing finding was that erosive lesions in first CMCJ were more prevalent in males, in contrast to interphalangeal erosive OA that affected women more often17, 31. Strenuous manual activities in males have previously been linked to TB OA and those occupational exposures prevalent in the local population (e.g., occupations in the pottery industry) could also explain the gender difference. Fontana et al. reported in a case–control study that occupational risk factors (such as manual occupations or professions with repetitive thumb use) were not associated with a higher prevalence of OA in first CMCJs. The latency period from occupational exposure to the development of OA and even erosive OA is not known. It is possible that continued overuse and mechanical loading once OA has developed could possibly lead to the development of erosive OA, however longitudinal data are needed to investigate this further.

This study also showed that the co-occurrence of erosive lesions in first CMCJs with IPJs is rarely present; most erosive lesions in the first CMCJs occurred isolated without erosions in the IPJs. This was an interesting finding, since it can give us insight in the pattern of occurrence of erosions in hand joints and whether erosive disease in first CMCJs behaves differently from erosive lesions in IPJs only. At the moment, it is unclear whether erosive OA in general is a separate entity from hand OA (e.g., a disease with a systemic pathogenesis) or whether it is a severe subset of OA. Recently, Haugen et al. reported that erosions of the hand was associated with a higher odds of knee subchondral bone attrition (compared with persons with no OA in the DIPJ/PIPJ), which is considered as a result of bone remodeling due to biomechanical stress and appears radiographically like central erosions of IPJs. They also reported that erosive hand OA is not associated with bone mineral density (BMD), which was used as a proxy for systemic bone changes. These results suggested that erosive OA may be a result of mechanical load through the joints leading to a more severe disease. However, Zoli et al. reported that erosive OA is associated with lower BMD suggesting that persons with erosive OA are more likely to develop osteoporosis. This result might be biased, since the population of Zoli et al. consisted of post-menopausal women only. Increased age, parity and years since menopause are possible confounders of the association between reduced BMD and osteophytosis. Another large Finnish population-based study showed that the presence of OA in first CMCJ (n = 282 with KL grade 2, n = 120 with KL grade 3–4) was associated with lower combined cortical thickness and lower metacarpal index, used as indicators of cortical bone mineral mass, compared to persons without OA in their first CMCJs (n = 3,166). Unfortunately in this study, no erosive OA of the interphalangeal joints or first CMCJs was differentiated or comparison was made between erosive OA vs non-erosive OA in the first CMCJs. Other studies showed that factors such as higher C-reactive protein, an increased power Doppler signal and synovitis on ultrasound is associated with erosive OA39, 40, and familial predisposition suggesting an underlying systemic cause for erosive OA.

Previous studies showed that patients with erosive OA showed more often pain and disability, suggesting that it is a severe form of radiographic hand OA17, 42. In the present study, persons with erosive disease in the first CMCJs showed lower absolute values in the pulp pinch and power grip. When adjusting for age, sex and KL-score, no statistical significant difference was seen. No other research has examined grip and pinch strength for this specific subset of erosive disease but a relationship has been seen between increasing radiographic hand OA severity and reduced grip and pinch strength. As there is evidence that erosive OA may be a more severe form of hand OA rather than a separate entity, it is possible that lower scores could be due to OA in the first CMCJs itself, and not to its erosive nature. Another explanation that we could not detect a significant difference is the relatively low number of persons with erosive disease in first CMCJs. Further studies are needed to confirm these results.

The additional value of the present study was that detailed assessments of the hand were collected (e.g., clinical examination, AUSCAN, AIMS-2 and SF-12). This made it possible to quantify pain, functional limitation and health status in erosive disease in a general population with hand symptoms in more detail than previous studies have allowed. Although we found a difference in the prevalence of concordant pain between persons with erosive disease and radiographic OA in the thumb, there was no difference found in the level of hand pain, stiffness or functional limitations on both AUSCAN and AIMS-2 subscales nor in grip strength, pinch grip strength, PCS, and MCS. An explanation could be that other patient effects that contribute to pain, such as genetic or psychosocial factors (e.g., expectation and experience of patients)44, 45 are also influencing the scores on these questionnaires and therefore could not discriminate these groups.

Persons with erosive disease of the thumb did not report poorer overall perceived physical health than persons with concordant pain and radiographic OA of the TB, as reflected by the PCS. No older studies on erosive lesions of first CMCJs and health status are available. Bijsterbosch et al. reported no difference in health-related quality of life in persons with erosive OA of the IPJs compared with persons with non-erosive OA, but no subgroup analysis with erosive disease in first CMCJs was available.

Several limitations in the present study deserve mentioning. Although both cohorts gathered comparable data, they were assembled in subtly different ways – one on the basis of knee symptoms, the other on the basis of hand symptoms in the past 12 months. Biased estimates from the knee cohort would be a concern although the difference in prevalence estimates between the two cohorts was not large which justifies their combination. Another limitation could be the methods used to determine the presence of erosive disease in first CMCJs. Until present there is no consensus about how erosive disease in the thumb should be defined and whether it should be considered as the same phenotype as interphalangeal erosive OA. An under- or overestimation of the prevalences is possible, since the hand drawings for indicating pain in the thumb were not restricted to the TB. Finally, the absolute number of persons with erosive lesions in first CMCJs was not large and may be too small to detect differences in the clinical outcome measures when compared with persons with concordant pain and radiographic OA of the TB. Studies with larger numbers of erosive disease in first CMCJs are needed to confirm these findings.

In conclusion, we have identified erosive lesions in first CMCJs, mostly isolated without involvement with interphalangeal erosive OA. Although no statistic differences in hand pain or function was found in persons with erosive disease in TB compared with those with radiographic TB OA, a difference in the prevalence of pain was seen. We hope our systematic description of erosive OA in first CMCJs will facilitate further investigations in this topic.

Author contributions

All authors have made substantial contributions to the following: (1) the conception and design of the study, or acquisition of data, or analysis and interpretation of data, (2) drafting or revising the article critically for important intellectual content, (3) final approval of the version to be submitted.

Conflict of interest

None of the authors have any conflicts of interest to disclose regarding this manuscript.