Osteophyte growth in early thumb carpometacarpal osteoarthritis

The passive biomechanics of the thumb carpometacarpal joint: An in vitro study

The thumb carpometacarpal (CMC) joint facilitates multidirectional motion of the thumb and affords prehensile power and precision. Traditional methods of quantifying thumb CMC kinematics have been largely limited to range-of-motion (ROM) measurements in 4 orthogonal primary directions (flexion, extension, abduction, adduction) due to difficulties in capturing multidirectional thumb motion. However, important functional motions (e.g., opposition) consist of combinations of these primary directions, as well as coupled rotations (internal and external rotation) and translations. Our goal was to present a method of quantifying the multidirectional in vitro biomechanics of the thumb CMC joint in 6 degrees-of-freedom. A robotic musculoskeletal simulation system was used to manipulate CMC joints of 10 healthy specimens according to specimen-specific joint coordinate systems calculated from computed tomography bone models. To determine ROM and stiffness (K), the first metacarpal (MC1) was rotated with respect to the trapezium (TPM) to a terminal torque of 1 Nm in the four primary directions and in 20 combinations of these primary directions. ROM and K were also determined in internal and external rotation. We found multidirectional ROM was greatest and K least in directions oblique to the primary directions. We also found external rotation coupling with adduction-flexion and abduction-extension and internal rotation coupling with abduction-flexion and adduction-extension. Additionally, the translation of the proximal MC1 was predominantly radial during adduction and predominantly ulnar during abduction. The findings of this study aid in understanding thumb CMC joint mechanics and contextualize pathological changes for future treatment improvement.

Oxygen-ozone therapy for pain relief in patients with trapeziometacarpal osteoarthritis: a proof-of-concept study

PURPOSE

Trapeziometacarpal osteoarthritis (TMC-OA) is a prevalent hand disorder affecting a growing number of people worldwide. While a multidisciplinary approach might provide additional advantages, the analgesic and anti-inflammatory role of intra-articular oxygen-ozone (O2O3) injections combined with physical therapy is still unknown. To assess the impact of a multimodal therapeutic approach combining O2O3 injections with physical therapy in patients with TMC-OA.

MATERIALS AND METHODS

A prospective open-label study conducted in the Physical and Rehabilitation Medicine Unit of the "Renato Dulbecco" University Hospital of Catanzaro. We assessed patients with TMC-OA who had not responded to standard medical therapy. Participants received O2O3 therapy and targeted physical therapy for 4 weeks. Pain relief, muscle strength, and physical functioning were assessed at baseline and after 4, 12 and 24 weeks (respectively T0, T1, T2, and T3).

RESULTS

Seventeen patients with a mean age of 67.1 ± 6.1 years were included in the study. Short-term improvements in pain intensity were observed (T0: 6.221 ± 1.514; T1: 3.172 ± 1.1451; p < .001) and were maintained over a 24-week follow-up period (T0: 6.221 ± 1.514; T3: 4.393 ± 1.438; p: 0.006). Significant changes were reported also in terms of muscle strength and physical functioning. O2O3 therapy was well-tolerated with no adverse effects.

CONCLUSIONS

A combination of O2O3 injections and physical therapy might be considered in patients with TMC-OA. Further investigation is warranted to assess the effectiveness of O2O3 therapy in managing TMC-OA.

Systematic review of computed tomography parameters used for the assessment of subchondral bone in osteoarthritis

OBJECTIVE

To systematically review the published parameters for the assessment of subchondral bone in human osteoarthritis (OA) using computed tomography (CT) and gain an overview of current practices and standards.

DESIGN

A literature search of Medline, Embase and Cochrane Library databases was performed with search strategies tailored to each database (search from 2010 to January 2023). The search results were screened independently by two reviewers against pre-determined inclusion and exclusion criteria. Studies were deemed eligible if conducted in vivo/ex vivo in human adults (>18 years) using any type of CT to assess subchondral bone in OA. Extracted data from eligible studies were compiled in a qualitative summary and formal narrative synthesis.

RESULTS

This analysis included 202 studies. Four groups of CT modalities were identified to have been used for subchondral bone assessment in OA across nine anatomical locations. Subchondral bone parameters measuring similar features of OA were combined in six categories: (i) microstructure, (ii) bone adaptation, (iii) gross morphology (iv) mineralisation, (v) joint space, and (vi) mechanical properties.

CONCLUSIONS

Clinically meaningful parameter categories were identified as well as categories with the potential to become relevant in the clinical field. Furthermore, we stress the importance of quantification of parameters to improve their sensitivity and reliability for the evaluation of OA disease progression and the need for standardised measurement methods to improve their clinical value.

Characterization of Trapezial Pommel in Relation to Radiographic and Wear Patterns in Carpometacarpal Osteoarthritis

BACKGROUND

Trapezial pommel, or ulnar osteophyte positioned at the vertex of the saddle-shaped facet, is a consistent structural appearance in osteoarthritis (OA) of the first carpometacarpal. This study investigates its relation to radiographic measures (modified Eaton staging and thumb OA [ThOA] index) and wear patterns (trapezial surface morphology and cartilaginous eburnation).

METHODS

In all, 137 whole trapezia were explanted from 116 patients and evaluated for Eaton staging, morphology (saddle, cirque, or dish), and eburnation (degree of cartilaginous effacement) of the articular surface of the trapezium. In total, 131 Robert's views and 126 stress views were reviewed by 2 blinded senior surgeons for ThOA index and pommel size. Statistical analyses included Spearman correlation and linear regression.

RESULTS

Standardized pommel size achieved good intrarater reliability (correlation coefficient: 0.80-0.98) and moderate interrater reliability (correlation coefficient: 0.60-0.67). The ThOA index and pommel size were significantly correlated across Robert's (rs = 0.51) and stress views (rs = 0.64). The ThOA index better distinguished between stages compared with pommel size. All the radiographic measures inversely correlated with preserved cartilage and varied across morphologies. Pommel size differed significantly between dish and saddle, and the ThOA index was significantly different between all morphologies when using stress views.

CONCLUSIONS

We reliably quantified the pommel feature and demonstrated significant correlations with other radiographic and topologic measures of arthritic disease. If future studies can demonstrate that the pommel is a pathogenic process in ThOA and its correction can curb disease progression, the identification of the pommel feature may help guide targeted intervention.

Early Degenerative Changes in a Spontaneous Osteoarthritis Model Assessed by Nanoindentation

Understanding early mechanical changes in articular cartilage (AC) and subchondral bone (SB) is crucial for improved treatment of osteoarthritis (OA). The aim of this study was to develop a method for nanoindentation of fresh, unfixed osteochondral tissue to assess the early changes in the mechanical properties of AC and SB. Nanoindentation was performed throughout the depth of AC and SB in the proximal tibia of Dunkin Hartley guinea pigs at 2 months, 3 months, and 2 years of age. The contralateral tibias were either histologically graded for OA or analyzed using immunohistochemistry. The results showed an increase in the reduced modulus (Er) in the deep zone of AC during early-stage OA (6.0 ± 1.75 MPa) compared to values at 2 months (4.04 ± 1.25 MPa) (*** p < 0.001). In severe OA (2-year) specimens, there was a significant reduction in Er throughout the superficial and middle AC zones, which correlated to increased ADAMTS 4 and 5 staining, and proteoglycan loss in these regions. In the subchondral bone, a 35.0% reduction in stiffness was observed between 2-month and 3-month specimens (*** p < 0.001). The severe OA age group had significantly increased SB stiffness of 36.2% and 109.6% compared to 2-month and 3-month-old specimens respectively (*** p < 0.001). In conclusion, this study provides useful information about the changes in the mechanical properties of both AC and SB during both early- and late-stage OA and indicates that an initial reduction in stiffness of the SB and an increase in stiffness in the deep zone of AC may precede early-stage cartilage degeneration.

Development of a method to investigate strain distribution across the cartilage-bone interface in guinea pig model of spontaneous osteoarthritis using lab-based contrast enhanced X-ray-computed tomography and digital volume correlation

OBJECTIVE

Strain changes at the cartilage-bone interface play a crucial role in osteoarthritis (OA) development. Contrast-Enhanced X-ray Computed Tomography (CECT) and Digital Volume Correlation (DVC) can measure 3D strain changes at the osteochondral interface. Using lab-based CT systems it is often difficult to visualise soft tissues such as articular cartilage without staining to enhance contrast. Contrast-Enhancing Staining Agents (CESAs), such as Phosphotungstic Acid (PTA) in 70% ethanol, can cause tissue shrinkage and alter tissue mechanics. The aims of this study were, firstly, to assess changes to the mechanical properties of osteochondral tissue after staining with a PTA/PBS solution, and secondly, to visualise articular cartilage during loading and with CECT imaging in order to compare strain across the interface in both healthy and OA joints using DVC.

DESIGN

Nanoindentation was used to assess changes to mechanical properties in articular cartilage and subchondral bone before and after staining. Hindlimbs from Dunkin-Hartley guinea pigs were stained with 1% PTA/PBS at room temperature for 6 days. Two consecutive CECT datasets were acquired for DVC error analysis. In-situ compression with a load corresponding to 2x body weight was applied, the specimen was re-imaged, and DVC was performed between the pre- and post-load tomograms.

RESULTS

Nanoindentation before and after PTA/PBS staining showed similar cartilage stiffness (p < 0.05), however, staining significantly decreased the stiffness of subchondral bone (∼9-fold; p = 0.0012). In severe OA specimens, third principal/compressive (εp3) strain was 141.7% higher and shear strain (γ) was 98.2% higher in tibial articular cartilage compared to non-OA (2 - month) specimens. A 23.1% increase in third principal stain strain and a 54.5% significant increase in the shear (γ) strain (p = 0.0027) was transferred into the mineralised regions of calcified cartilage and subchondral bone in severe OA specimens.

CONCLUSIONS

These results indicate the suitability of PTA in PBS as a contrast agent for the visualisation of cartilage during CECT imaging and allowed DVC computation of strain across the cartilage-bone interface. However, further research is needed to address the reduction in stiffness of subchondral bone after incubation in PBS.

Dorsal Subluxation of the First Metacarpal During Thumb Flexion is an Indicator of Carpometacarpal Osteoarthritis Progression

BACKGROUND

Measurable changes in patients with progression of thumb carpometacarpal (CMC) osteoarthritis (OA) include joint space narrowing, osteophyte formation, subluxation, and adjacent-tissue changes. Subluxation, an indication of mechanical instability, is postulated as an early biomechanical indicator of progressing CMC OA. Various radiographic views and hand postures have been proposed to best assess CMC subluxation, but 3D measurements derived from CT images serve as the optimal metric. However, we do not know which thumb pose yields subluxation that most indicates OA progression.

QUESTIONS/PURPOSES

Using osteophyte volume as a quantitative measure of OA progression, we asked: (1) Does dorsal subluxation vary by thumb pose, time, and disease severity in patients with thumb CMC OA? (2) In which thumb pose(s) does dorsal subluxation most differentiate patients with stable CMC OA from those with progressing CMC OA? (3) In those poses, what values of dorsal subluxation indicate a high likelihood of CMC OA progression?

METHODS

Between 2011 and 2014, 743 patients were seen at our institutions for trapeziometacarpal pain. We considered individuals who were between the ages of 45 and 75 years, had tenderness to palpation or a positive grind test result, and had modified Eaton Stage 0 or 1 radiographic thumb CMC OA as potentially eligible for enrollment. Based on these criteria, 109 patients were eligible. Of the eligible patients, 19 were excluded because of a lack of interest in study participation, and another four were lost before the minimum study follow-up or had incomplete datasets, leaving 86 (43 female patients with a mean age of 53 ± 6 years and 43 male patients with a mean age of 60 ± 7 years) patients for analysis. Twenty-five asymptomatic participants (controls) aged 45 to 75 years were also prospectively recruited to participate in this study. Inclusion criteria for controls included an absence of thumb pain and no evidence of CMC OA during clinical examination. Of the 25 recruited controls, three were lost to follow-up, leaving 22 for analysis (13 female patients with a mean age of 55 ± 7 years and nine male patients with a mean age of 58 ± 9 years). Over the 6-year study period, CT images were acquired of patients and controls in 11 thumb poses: neutral, adduction, abduction, flexion, extension, grasp, jar, pinch, grasp loaded, jar loaded, and pinch loaded. CT images were acquired at enrollment (Year 0) and Years 1.5, 3, 4.5, and 6 for patients and at Years 0 and 6 for controls. From the CT images, bone models of the first metacarpal (MC1) and trapezium were segmented, and coordinate systems were calculated from their CMC articular surfaces. The volar-dorsal location of the MC1 relative to the trapezium was computed and normalized for bone size. Patients were categorized into stable OA and progressing OA subgroups based on trapezial osteophyte volume. MC1 volar-dorsal location was analyzed by thumb pose, time, and disease severity using linear mixed-effects models. Data are reported as the mean and 95% confidence interval. Differences in volar-dorsal location at enrollment and rate of migration during the study were analyzed for each thumb pose by group (control, stable OA, and progressing OA). A receiver operating characteristic curve analysis of MC1 location was used to identify thumb poses that differentiated patients whose OA was stable from those whose OA was progressing. The Youden J statistic was used to determine optimized cutoff values of subluxation from those poses to be tested as indicators of OA progression. Sensitivity, specificity, negative predictive values, and positive predictive values were calculated to assess the performance of pose-specific cutoff values of MC1 locations as indicators of progressing OA.

RESULTS

In flexion, the MC1 locations were volar to the joint center in patients with stable OA (mean -6.2% [95% CI -8.8% to -3.6%]) and controls (mean -6.1% [95% CI -8.9% to -3.2%]), while patients with progressing OA exhibited dorsal subluxation (mean 5.0% [95% CI 1.3% to 8.6%]; p < 0.001). The pose associated with the most rapid MC1 dorsal subluxation in the progressing OA group was thumb flexion (mean 3.2% [95% CI 2.5% to 3.9%] increase per year). In contrast, the MC1 migrated dorsally much slower in the stable OA group (p < 0.001), at only a mean of 0.1% (95% CI -0.4% to 0.6%) per year. A cutoff value of 1.5% for the volar MC1 position during flexion at enrollment (C-statistic: 0.70) was a moderate indicator of OA progression, with a high positive predictive value (0.80) but low negative predictive value (0.54). Positive and negative predictive values of subluxation rate in flexion (2.1% per year) were high (0.81 and 0.81, respectively). The metric that most indicated a high likelihood of OA progression (sensitivity 0.96, negative predictive value 0.89) was a dual cutoff that combined the subluxation rate in flexion (2.1% per year) with that of loaded pinch (1.2% per year).

CONCLUSION

In the thumb flexion pose, only the progressing OA group exhibited MC1 dorsal subluxation. The MC1 location cutoff value for progression in flexion was 1.5% volar to the trapezium , which suggests that dorsal subluxation of any amount in this pose indicates a high likelihood of thumb CMC OA progression. However, volar MC1 location in flexion alone was not sufficient to rule out progression. The availability of longitudinal data improved our ability to identify patients whose disease will likely remain stable. In patients whose MC1 location during flexion changed < 2.1% per year and whose MC1 location during pinch loading changed < 1.2% per year, the confidence that their disease would remain stable throughout the 6-year study period was very high. These cutoff rates were a lower limit, and any patients whose dorsal subluxation advanced faster than 2% to 1% per year in their respective hand poses, were highly likely to experience progressive disease.

CLINICAL RELEVANCE

Our findings suggest that in patients with early signs of CMC OA, nonoperative interventions aimed to reduce further dorsal subluxation or operative treatments that spare the trapezium and limit subluxation may be effective. It remains to be determined whether our subluxation metrics can be rigorously computed from more widely available technologies, such as plain radiography or ultrasound.

Bone morphological changes of the trapezium and first metacarpal with early thumb osteoarthritis progression

BACKGROUND

Thumb carpometacarpal osteoarthritis is characterized by osteophyte growth and changes in the curvature of the articular surfaces of the trapezium and first metacarpal. The aim of this longitudinal study was to quantify in-vivo bone morphology changes with osteoarthritis progression.

METHODS

The study analyzed an observational dataset of 86 subjects with early thumb osteoarthritis and 22 age-matched asymptomatic controls. CT scans of subjects' affected hands were acquired at enrollment (year 0), and at 1.5, 3, 4.5, and 6-year follow-up visits. Osteoarthritic subjects were classified into stable and progressive groups, as defined by osteophyte volume and the rate of osteophyte growth. Trapezium height, width, and volar facet recession, along with first metacarpal volar beak recession and recession angle, were quantified.

FINDINGS

Mean trapezium width increased 12% over six years in the progressive osteoarthritis group. Trapezium volar recession of the progressive osteoarthritis group was significantly greater than stable at enrollment (P < 0.0001) and year 6 (P < 0.0001). The first metacarpal volar beak of the progressive osteoarthritis group recessed significantly faster than stable (P = 0.0004) and control (P = 0.0003). In year 6, volar beak surfaces in subjects with progressive osteoarthritis were flatter with reduced curvature, measuring -8.7 ± 4.0 degrees, compared to the stable osteoarthritis (P < 0.0001) and control groups (P = 0.0003), which maintained nominal curvatures, measuring 0.7 ± 2.5 and 0.2 ± 3.2 degrees, respectively.

INTERPRETATION

Our results demonstrate significant recession and reduction in the angle of the first metacarpal volar beak in progressive osteoarthritis. Flattening of the first metacarpal volar beak may have important associations with carpometacarpal joint contact and loading migrations, further propagating osteophyte formation and bony remodeling. This work highlights the volar beak of the first metacarpal as a region of morphology change with disease.

Characterizing response to a dynamic stability modeled approach for thumb carpometacarpal joint pain: A retrospective study

STUDY DESIGN

Retrospective case series.

INTRODUCTION

Literature trends indicate that thumb dynamic stabilization may benefit clients with thumb carpometacarpal (CMC) joint pain and arthritis. There is minimal research investigating whether client characteristics predict responsiveness to hand therapy for thumb dynamic stabilization.

PURPOSE OF THE STUDY

1) To investigate how adults with thumb CMC joint pain responded to a hand therapy dynamic stabilization modeled intervention. 2) To determine if various client factors influenced responsiveness and to what extent.

METHODS

An electronic medical record search identified adults treated from August 2009 through December 2015 for thumb CMC joint pain. Radiographs were retrospectively staged. Outcome measures were 1) Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) total disability score and 2) Numerical Pain Rating Scale (NPRS). Paired t-tests were performed to compare pre and post treatment measures. Multivariate analyses were used to investigate predictive factors.

RESULTS

A total of 249 charts were analyzed. Large overall significant effects were noted for disability score (QuickDASH P <.001, X = 12.1, Cohen's d = 0.9). The average improvement of 2.1 (SD = 2.6) points exceeded the minimal clinically important difference (MCID) of 1.7 points on the NPRS pain scale. Significant predictors of QuickDASH Scores were radiographic staging, bilateral hand involvement and initial pain ratings. Significant predictors for change in pain scores (meeting or exceeding the minimal clinically important difference for the NPRS) were bilateral thumb involvement and initial "pain at worst" rating.

CONCLUSION

After completing hand therapy with a dynamic stabilization approach, clients had less pain and disability. Those who had unilateral thumb pain, or those who started with higher pain levels were most likely to have clinically meaningful improvements in pain. Clients in early CMC osteoarthritis (OA) stages responded better than those in later stages, indicating that early referral to therapy is important.

Evaluation of the PROMIS Upper Extremity Against Validated Patient-Reported Outcomes in Patients With Early Carpometacarpal Osteoarthritis

PURPOSE

Internal consistency, construct, and criterion validity of the Patient-Reported Outcomes Measurement Information System (PROMIS) upper extremity (UE) v1.2 were evaluated in patients with early-stage carpometacarpal (CMC) osteoarthritis (OA). We hypothesized that in patients with early CMC OA, PROMIS UE scores would: (1) be lower than those in asymptomatic controls; (2) correlate with established patient-reported outcomes; (3) correlate with pinch and grip strengths; and (4) not correlate with radiographic disease progression.

METHODS

Patients with early CMC OA (modified Eaton stage 0 or 1) and matched asymptomatic control patients completed the PROMIS UE, Australian and Canadian Osteoarthritis Hand Index, and Patient-Rated Wrist-Hand Evaluation at 2 time points. The PROMIS UE's internal consistency was evaluated by Cronbach's alpha, construct validity by Spearman correlation coefficients among the patient-reported outcome measures, and criterion validity using measures of strength. A floor or ceiling effect was indicated if more than 15% of patients achieved the lowest or highest possible score.

RESULTS

The PROMIS UE had high internal consistency. Patients with early CMC OA had a lower score than healthy controls (average, 42 vs 54, respectively). We observed moderate to high correlations between the PROMIS UEv1.2, Australian and Canadian Osteoarthritis Hand Index, and Patient-Rated Wrist-Hand Evaluation and good criterion validity when compared to key pinch and grip strengths. The PROMIS UE did not correlate to radiographic disease severity.

CONCLUSIONS

The PROMIS UE had a high correlation with Australian and Canadian Osteoarthritis Hand Index and a moderate correlation with Patient-Rated Wrist-Hand Evaluation. The PROMIS UE had high internal consistency and good criterion validity.

CLINICAL RELEVANCE

The PROMIS UE is a valid assessment for disability in patients with early CMC OA and can serve as a clinical adjunct to an outcome assessment.

An Anatomical Evaluation of the Trapezium and Its Relationship to Basilar Joint Osteophytic Change

BACKGROUND

To perform a comprehensive osteologic investigation into trapezium anatomy and investigate the relationship between anatomical factors and osteophyte formation, focusing on sex-specific differences.

METHODS

This was a cadaveric study involving 1233 trapezia and first metacarpals. Two subgroups ("Control" and "Main Study") were established. The "Control" cohort was used to identify features of the trapezium in specimens devoid of osteophytic change. The prevalence and severity of osteophytic change were investigated in the "Main Study" cohort. Sex differences were specifically assessed. Regression analyses were used to identify factors associated with osteophyte formation.

RESULTS

Three discrete surface morphologies exist at the trapezium trapeziometacarpal (TM) facet: heart, quadrilateral, and bean. Controlling for height, men have a larger trapezium TM facet surface area. However, the trapezium assumes the same off-center saddle shape in both sexes. The presence of osteophytes at the basilar joint is a common finding; no differences in osteologic prevalence exist between sexes. The progression of osteophytic change complements the radiographic Eaton-Littler classification system. The trapezium TM facet increases the surface area with incremental osteophyte involvement, with the degree of surface area expansion correlated with increases in the severity of osteophytic change. Increased age, increased surface area, bean morphology, and decreased volar joint depth are associated with more severe osteophyte formation.

CONCLUSIONS

Anatomical features of the trapezium may contribute to osteophyte development. Although the prevalence of osteophytic disease appears equal between sexes, sex differences exist in some anatomical parameters. These differences may help explain the increased prevalence of symptomatic basilar joint disease in women.

Effects of type II collagen hydrolysates on osteoarthritis through the NF-κB, Wnt/β-catenin and MAPK pathways

Osteoarthritis (OA), a degenerative disease, has attracted extensive attention all over the world. In this study, a rat model involving medial meniscus resection (MMx) and anterior to medial collateral ligament (ACL) operation was successfully established to study the effects of bovine cartilage hydrolysates rich in type II collagen peptides (BIIP) on cartilage protection. The results of histological analysis indicated that oral administration of BIIP at doses of 200 and 500 mg kg^-1 d^-1 ameliorated cartilage degeneration. Moreover, the potential targets of BIIP affecting OA in vivo were studied by proteomics, and the effects of BIIP on OA through signaling pathways, such as NF-κB, Wnt/β-catenin and MAPK, were further explored at mRNA and protein levels. BIIP downregulated the expression of IL-6, RUNX2, NF-κB p65, HIF-2α, β-catenin and p-JNK, which may be the main factor leading to the prevention of OA. These results suggest that BIIP can be used as a novel potential substance of functional foods to exert chondroprotective action.

Osteophyte volume calculation using dissimilarity-excluding Procrustes registration of archived bone models from healthy volunteers

Osteophytes are associated with later stage osteoarthritis and are most commonly described using semiquantitative radiographic grading systems. A detailed understanding of osteophyte formation is, in part, limited by the ability to quantify bone pathology. Osteophytes can be quantified relative to pre-osteoarthritic bone, or to the contralateral bone if it is healthy; however, in many cases, neither are available as references. We present a method for computing three-dimensional (3D) osteophyte models using a library of healthy control bones. An existing data set containing the computed tomography scans of 90 patients with first carpometacarpal osteoarthritis (OA) and 46 healthy subjects were utilized. A healthy bone that best fit each OA subject's bone was determined using a dissimilarity-excluding Procrustes registration technique (DEP) that minimized the influence of dissimilar features (ie, osteophytes). The osteophyte model was then computed through Boolean subtraction of the reference bone model from the OA bone model. DEP reference bones conformed significantly better to the OA bones (P < .0001) than by finite difference iterative closest point registration (root mean squared distances, 0.33 ± 0.05 and 0.41 ± 0.16 mm, respectively). The effect of library size on dissimilarity measure was investigated by leave-k-out cross-validation randomly reducing k from 46 to 1. A library of n ≥ 31 resulted in less than 10% difference from the theoretical minimum value. The proposed method enables quantification of osteophytes when the disease-free bone or the healthy contralateral bone is not available for any 3D data set. Quantifying osteophyte formation and growth may aid in understating the associated mechanisms in OA.