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A Quantitative Analysis of Subchondral Bone Density Around Osteochondritis Dissecans Lesions of the Capitellum

Published:August 25, 2021DOI:https://doi.org/10.1016/j.jhsa.2021.06.020

      Purpose

      In capitellar osteochondritis dissecans (OCD), unstable lesions generally demonstrate signs of subchondral sclerosis. We postulate that OCD lesions have abnormal subchondral bone density. We aimed to quantify the subchondral bone thickness around OCD lesions using conventional computed tomography (CT) imaging.

      Methods

      This retrospective study included 15 patients with capitellar OCD (OCD group) and 12 patients with an unaffected radio-capitellar joint (control group). We constructed 3-dimensional humerus models using CT data and quantified the bone density with colored contour mapping to determine the subchondral bone thickness. We measured the thickness relative to the condylar height at the centroid and lateral, medial, superior, and inferior edge points of the OCD lesion, and compared the findings between the groups. We then correlated the CT measurements with the magnetic resonance imaging measurements.

      Results

      Subchondral bone thickness at the centroid and lateral, medial, superior, and inferior edges in the OCD group was significantly higher than that in the control group. Correlation analyses revealed that the magnetic resonance imaging measurements highly correlated with the CT subchondral bone measurements.

      Conclusions

      We found that there is a zone of increased subchondral bone thickness around OCD lesions that should be considered during drilling, microfracture, or other reconstruction methods. We observed a high correlation with low errors between the measurements taken from conventional CT images and the measurements from magnetic resonance imaging, suggesting that both modalities are useful in clinical decision making.

      Type of study/level of evidence

      Diagnostic IV.

      Key words

      Osteochondritis dissecans (OCD) of the capitellum is an elbow disorder involving the articular cartilage surface and underlying subchondral bone, which is commonly seen in adolescent overhead-throwing or weight-bearing athletes.
      • Iwasaki N.
      • Kato H.
      • Ishikawa J.
      • Saitoh S.
      • Minami A.
      Autologous osteochondral mosaicplasty for capitellar osteochondritis dissecans in teenaged patients.
      • Nissen C.W.
      Osteochondritis dissecans of the elbow.
      • Ruch D.S.
      • Cory J.W.
      • Poehling G.G.
      The arthroscopic management of osteochondritis dissecans of the adolescent elbow.
      • Schenck Jr., R.C.
      • Goodnight J.M.
      Osteochondritis dissecans.
      • Yadao M.A.
      • Field L.D.
      • Savoie III, F.H.
      Osteochondritis dissecans of the elbow.
      Although nonsurgical treatment is often sufficient to promote healing, unhealed lesions may require surgery.
      • Iwasaki N.
      • Kato H.
      • Ishikawa J.
      • Saitoh S.
      • Minami A.
      Autologous osteochondral mosaicplasty for capitellar osteochondritis dissecans in teenaged patients.
      ,
      • Peterson R.K.
      • Savoie III, F.H.
      • Field L.D.
      Osteochondritis dissecans of the elbow.
      ,
      • Ruchelsman D.E.
      • Hall M.P.
      • Youm T.
      Osteochondritis dissecans of the capitellum: current concepts.
      There are multiple surgical options used to address capitellar OCD, including arthroscopic debridement, drilling, microfracture, and osteochondral autologous transplantation (OAT).
      • Iwasaki N.
      • Kato H.
      • Ishikawa J.
      • Saitoh S.
      • Minami A.
      Autologous osteochondral mosaicplasty for capitellar osteochondritis dissecans in teenaged patients.
      ,
      • Ruch D.S.
      • Cory J.W.
      • Poehling G.G.
      The arthroscopic management of osteochondritis dissecans of the adolescent elbow.
      ,
      • Baumgarten T.E.
      • Andrews J.R.
      • Satterwhite Y.E.
      The arthroscopic classification and treatment of osteochondritis dissecans of the capitellum.
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      Arthroscopic treatment of osteochondritis dissecans of the capitellum.
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      • Jones K.S.
      Arthroscopic surgery for isolated capitellar osteochondritis dissecans in adolescent baseball players: minimum three-year follow-up.
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      Osteochondritis in the female gymnast’s elbow.
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      Results of arthroscopic debridement for osteochondritis dissecans of the elbow.
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      • Dandy D.J.
      Results of drilling osteochondritis dissecans before skeletal maturity.
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      • Micheli L.J.
      • Waters P.M.
      • Bae D.S.
      Early results of drilling and/or microfracture for grade IV osteochondritis dissecans of the capitellum.
      • Takahara M.
      • Mura N.
      • Sasaki J.
      • Harada M.
      • Ogino T.
      Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum.
      • Takahara M.
      • Ogino T.
      • Sasaki I.
      • Kato H.
      • Minami A.
      • Kaneda K.
      Long term outcome of osteochondritis dissecans of the humeral capitellum.
      • Bexkens R.
      • van Bergen C.J.A.
      • van den Bekerom M.P.J.
      • Kerkhoffs G.M.M.J.
      • Eygendaal D.
      Decreased defect size and partial restoration of subchondral bone on computed tomography after arthroscopic debridement and microfracture for osteochondritis dissecans of the capitellum.
      • Bexkens R.
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      • Ogink P.T.
      • van Bergen C.J.A.
      • van den Bekerom M.P.J.
      • Eygendaal D.
      Clinical outcome after arthroscopic debridement and microfracture for osteochondritis dissecans of the capitellum.
      • Camp C.L.
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      • Degen R.M.
      • Sinatro A.L.
      • Altchek D.W.
      Arthroscopic microfracture for osteochondritis dissecans lesions of the capitellum.
      • Oka Y.
      • Ikeda M.
      Treatment of severe osteochondritis dissecans of the elbow using osteochondral grafts from a rib.
      • Sato K.
      • Mio F.
      • Hosoya T.
      • Ito Y.
      Two cases with osteochondritis dissecans of the capitulum humeri treated with costal osteochondral graft transplantation.
      • Shimada K.
      • Tanaka H.
      • Matsumoto T.
      • et al.
      Cylindrical costal osteochondral autograft for reconstruction of large defects of the capitellum due to osteochondritis dissecans.
      • Shimada K.
      • Yoshida T.
      • Nakata K.
      • Hamada M.
      • Akita S.
      Reconstruction with an osteochondral autograft for advanced osteochondritis dissecans of the elbow.
      • Yamamoto Y.
      • Ishibashi Y.
      • Tsuda E.
      • Sato H.
      • Toh S.
      Osteochondral autograft transplantation for osteochondritis dissecans of the elbow in juvenile baseball players: minimum 2-year follow-up.
      In some cases, these procedures aim to promote fibrocartilage formation by debriding the necrotic subchondral bone and stimulating the deficient subchondral bone. An OAT procedure is performed for larger unstable defects using an osteochondral graft transplanted from a remote site such as the knee or rib to reconstruct the defect and engraft to the subchondral and deeper bone.
      Unstable OCD lesions generally demonstrate signs of subchondral sclerosis, which may reflect reduced healing potential or disease progression.
      • Takahara M.
      • Mura N.
      • Sasaki J.
      • Harada M.
      • Ogino T.
      Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum.
      ,
      • Mihara K.
      • Tsutsui H.
      • Nishinaka N.
      • Yamaguchi K.
      Nonoperative treatment for osteochondritis dissecans of the capitellum.
      An understanding of this area of subchondral sclerosis may be beneficial for surgical planning. This knowledge may be helpful for surgeons to determine the depth of drilling or the amount of sclerotic bone that may impede healing and should be removed for grafting. However, knowledge regarding the subchondral bone at the OCD lesion is limited when using conventional radiography, computed tomography (CT), or magnetic resonance imaging (MRI).
      • Takahara M.
      • Mura N.
      • Sasaki J.
      • Harada M.
      • Ogino T.
      Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum.
      ,
      • Satake H.
      • Takahara M.
      • Harada M.
      • Maruyama M.
      Preoperative imaging criteria for unstable osteochondritis dissecans of the capitellum.
      • Itsubo T.
      • Murakami N.
      • Uemura K.
      • et al.
      Magnetic resonance imaging staging to evaluate the stability of capitellar osteochondritis dissecans lesions.
      • Iwasaki N.
      • Kamishima T.
      • Kato H.
      • Funakoshi T.
      • Minami A.
      A retrospective evaluation of magnetic resonance imaging effectiveness on capitellar osteochondritis dissecans among overhead athletes.
      The primary aim of this study was to quantify the subchondral region of an OCD lesion with colored contour mapping using advanced CT modeling and to compare the subchondral bone thickness with the unaffected capitellum. A secondary aim was to assess the correlations between CT and MRI measurements.

      Methods

      This retrospective study was conducted following approval from the institutional review board; the requirement for written informed consent by the patients was waived. Using International Classification of Diseases-9 and -10 codes, we identified patients who were diagnosed with OCD at 1 of 5 urban hospitals in the Northeastern United States between January 2004 and July 2018. We included patients aged 12–20 years who had OCD of the capitellum with an accessible CT scan. The exclusion criteria included patients with an open capitellar physis on conventional radiographs, any history of an elbow fracture, previous elbow surgery, and CT scans of insufficient quality.
      We identified 15 OCD patients with an average age of 14.4 ± 2.3 years who had a CT scan (OCD group). As a control, we identified 12 patients with evidence of an intact capitellum who underwent CT scan for treatment of other upper extremity conditions, including elbow sprain, ligament injuries, joint loose bodies, and tumors in the forearm bones with a grossly normal capitellum (control group). The average age of the controls was 18.6 ± 2.6 years. We excluded patients with an open capitellar physis on conventional radiographs, any fracture, lesion, or bone abnormality at the capitellum. Capitellar lesions and abnormalities, including osteophyte formation, sclerotic changes, and irregularities on the articular surface, were inspected on standard radiographs and CT used in clinical practice.
      Demographic information including age, sex, height, weight, body mass index, race, sporting activities, dominant limb, duration of symptoms, and traumatic onset was collected by manual chart review. The primary sport was baseball for 5 patients, gymnastics for 3 patients, and the rest of the patients participated in football, lacrosse, cheerleading, soccer, or basketball; patients who played throwing sports (baseball, football, lacrosse, or basketball) or weight-bearing sports (gymnastics or cheerleading) accounted for 87% (13/15). The dominant limb was involved in 10 patients (67%), and the 5 other patients who had the OCD of the non-dominant limb were gymnasts or soccer players who equally use both limbs. Clinical examination and plain radiographic findings were also collected, including the presence of capitellar tenderness, elbow range of motion (flexion-extension), and physis status of the medial epicondyle, which is the last distal humerus ossification center to fuse.
      • Case S.L.
      • Hennrikus W.L.
      Surgical treatment of displaced medial epicondyle fractures in adolescent athletes.
      • Gottschalk H.P.
      • Eisner E.
      • Hosalkar H.S.
      Medial epicondyle fractures in the pediatric population.
      • Pathy R.
      • Dodwell E.R.
      Medial epicondyle fractures in children.
      Nine patients (60%) had capitellar tenderness and 6 (40%) had an open physis of the medial epicondyle (Table 1).
      Table 1Osteochondritis Dissecans Patient Characteristics
      Continuous variables are presented as average ± standard deviation.
      VariableData (n = 15)
      Demographics
       Age (years)14.4 ± 2.3
       Sex (n; %)
      Male11; 73%
      Female4; 27%
       Height (m)1.70 ± 0.12
       Weight (kg)67.2 ± 21.2
       Body mass index (kg/m2)22.8 ± 4.2
       Race (n; %)
      Caucasian15; 100%
       Sporting activities (n)
      Baseball5
      Gymnastics3
      Football2
      Lacrosse1
      Cheerleading1
      Soccer1
      Basketball1
      None1
       OCD on dominant limb (n; %)10; 67%
       Duration of symptom (weeks)18.3 ± 23.2
       Traumatic onset (n; %)4; 27%
      Physical findings
       Capitellar tenderness (n; %)9; 60%
       Range of motion (degrees)
      Flexion133.6 ± 12.3
      Extension–5.6 ± 20.1
      Imaging findings
       Physis status of the medial epicondyle (n; %)
      Open7; 47%
      Closed8; 53%
       Lateral wall involvement (n; %)5; 33%
      Continuous variables are presented as average ± standard deviation.

      Three-dimensional CT model reconstruction

      We used CT Digital Imaging and Communications in Medicine data set with a slice thickness of 1.25 mm or thinner (pixel size of 0.2–0.4 mm), which was undertaken on clinical CT scanners. The original image files were obtained through the institutional picture archiving and communication system database. Digital data were then imported into an image processing MvIndev/Bone Simulator software (Orthree), and 3-dimensional models of the humerus bones were constructed using a semi-automatic segmenting technique.

      Osteochondritis dissecans lesion characteristics

      Using the Bone Simulator software, the OCD surface was marked on the 3-dimensional model and the surface area was measured—this technique has previously shown almost perfect intra- and interobserver agreement.
      • Bexkens R.
      • Oosterhoff J.H.
      • Tsai T.Y.
      • et al.
      Osteochondritis dissecans of the capitellum: lesion size and pattern analysis using quantitative 3-dimensional computed tomography and mapping technique.
      The centroid of the OCD lesion was then determined. A cylinder was computationally approximated to the capitellum and trochlea to define its diameter as a condylar height. The center axis of the cylinder was aligned in line with the flexion-extension axis of the elbow joint.
      • Miyamura S.
      • Oka K.
      • Abe S.
      • et al.
      Altered bone density and stress distribution patterns in long-standing cubitus varus deformity and their effect during early osteoarthritis of the elbow.
      Subsequently, the tangential plane through the axis and the sagittal plane perpendicular to the axis were determined at the centroid. Using these planes, the lateral, medial, superior, and inferior edges of the lesion were determined (Fig. 1A, B).
      Figure thumbnail gr1
      Figure 1Schematic illustrations of the regions of interest. Measurement of the subchondral bone thickness is performed on the A tangential plane and B sagittal plane; the solid contours that are representing the bone density as a 10-step gradation are obtained from shade contours. On the 3-dimensional models, the OCD lesions (red) are identified and the following points are determined: C, centroid; L, lateral edge; M, medial edge; S, superior edge; and I, inferior edge of the lesion. C The OCD lesion characteristics are measured on the tangential and sagittal cross-sections. The dotted line represents the coronal plane. CL, lesion centroid location; CW, capitellar width; LW, lesion width; LI, lateral inset.
      Based on previous studies, the mediolateral width of the lesion, the distance from the lateral border of the capitellum to the centroid, and lateral inset, defined as the distance from the lateral border of the capitellum to the lateral edge of the lesion, were measured.
      • Johnson C.C.
      • Roberts S.
      • Mintz D.
      • Fabricant P.D.
      • Hotchkiss R.N.
      • Daluiski A.
      Location of osteochondritis dissecans lesions of the capitellum.
      ,
      • Vezeridis A.M.
      • Bae D.S.
      Evaluation of knee donor and elbow recipient sites for osteochondral autologous transplantation surgery in capitellar osteochondritis dissecans.
      To account for potential differences in skeletal size, the measurements were normalized by using relative percentages, calculated as the length relative to the capitellar width. We also measured in the sagittal plane.
      • Johnson C.C.
      • Roberts S.
      • Mintz D.
      • Fabricant P.D.
      • Hotchkiss R.N.
      • Daluiski A.
      Location of osteochondritis dissecans lesions of the capitellum.
      The plane, including the axis, was determined as parallel to the humeral shaft as a coronal plane, and its proximal direction was defined as 0°. As a reference to this plane, the angle of the centroid and the angle between the superior and inferior edges (sagittal lesion width) were measured (Fig. 1C).

      Subchondral bone thickness measurement

      The bone density was analyzed using the Mechanical Finder software (version 10.0; Research Center for Computational Mechanics). To determine the threshold of the subchondral bone density, we defined the subchondral bone to be of high density if the bone density was 20% higher than the average density of an entire articular region. First, an axial plane, perpendicular to the coronal plane, was determined to contact the proximal surface of the created cylinder. The humerus model was then divided by the axial plane, and the distal part was defined as the entire articular region. After the 3-dimensional bone models were meshed with 1.0-mm linear tetrahedral elements, the voxel density of each element was computed and the values of all elements in this region were averaged.
      Subsequently, the contours representing the bone density were obtained in the tangential and sagittal planes. According to the threshold of the subchondral bone density, the lesion thickness was measured at the centroid and lateral, medial, superior, and inferior edge points. The measurements were normalized by using relative values calculated as a percentage relative to the condylar height (Fig. 2).
      Figure thumbnail gr2
      Figure 2Contours of bone density distributions along with CT images in a corresponding plane. Magnified images of the solid contour with 10-step gradation are obtained from shade contour images. Orange–yellow junction indicates 20%-higher bone density than the average density of the region of interest (subchondral bone density threshold). A Tangential cross-sections of the OCD humerus. B Sagittal cross-sections of the OCD humerus. C Tangential cross-sections of the control humerus. D Sagittal cross-sections of the control humerus. On both tangential and sagittal cross-sections, subchondral bone is thicker at the OCD lesion in the OCD humerus when compared with the control humerus. Note that A and B show the same patient as shown in A–F. The dotted double arrow represents condylar height. The dotted circle represents the outline of the cylinder that is approximated to the capitellum and trochlea. Its diameter indicates the condylar height. L, lateral edge; C, centroid; M, medial edge; S, superior edge; and I, inferior edge of the lesion.
      The volumetric bone density of the OCD lesion was calculated as the voxel density in Hounsfield Units. A sphere centering at the OCD lesion centroid with a radius of the mediolateral lesion width was created, and the intersectional region with the humerus model was determined as a region of interest of the OCD lesion. The bone density was calculated by averaging Hounsfield Unit values of each voxel within the region of interest.

      Magnetic resonance imaging measurement

      Twelve of the 15 OCD patients underwent an MRI examination at the time of the CT (Fig. 3). Magnetic resonance imaging was acquired in multiple planes including sagittal, axial, and coronal planes. The maximum thickness of the lesion was measured in each plane, and normalization was performed to calculate the relative percentage by dividing it by the capitellar width.
      • Johnson C.C.
      • Roberts S.
      • Mintz D.
      • Fabricant P.D.
      • Hotchkiss R.N.
      • Daluiski A.
      Location of osteochondritis dissecans lesions of the capitellum.
      ,
      • Vezeridis A.M.
      • Bae D.S.
      Evaluation of knee donor and elbow recipient sites for osteochondral autologous transplantation surgery in capitellar osteochondritis dissecans.
      Additionally, the error of the measurements was calculated between CT subchondral thickness and MRI measurements.
      Figure thumbnail gr3
      Figure 3Conventional CT and T1-weighted MRI images of the capitellar OCD of the same patient as shown in A and B. A CT sagittal plane. B CT axial plane. C CT coronal plane. D MRI sagittal plane. E MRI axial plane. F and MRI coronal plane. The double arrow represents the maximum thickness of the OCD lesion.

      Statistical analysis

      The values of the CT subchondral bone thickness were compared between OCD and control groups using the Mann-Whitney U test.
      To evaluate the correlation between the size of the lesion and the degree of increased bone density, we correlated the volumetric bone density of the OCD lesion with the mediolateral lesion width using Spearman correlation coefficients (R). Furthermore, we determined the correlation between the CT subchondral bone thickness and the MRI measurements. For the correlation analyses, we used the maximum of the CT subchondral bone tangential and sagittal thickness. The strength of correlation was classified as slight (R < 0.2), low (0.2 ≤ R < 0.4), moderate (0.4 ≤ R < 0.7), or high (R ≥ 0.7).
      • Guilford J.P.
      Because there is no similar data that we are aware of, we conducted an a priori sample size estimate to identify the meaningful difference in subchondral bone thickness of 5 mm at the center of the capitellum (α = 0.05, 1-β = 0.9, two-tailed). The lesions beyond a depth of 5 mm are targeted in debriding and stimulating the subchondral bone. Consequently, the minimum sample size was 12 specimens for the OCD group and 10 specimens for the control group.

      Results

      Osteochondritis dissecans lesion characteristics

      The OCD lesion characteristics are presented in Table 2. The average lesion surface area was 144 ± 33.2 mm2.
      Table 2Osteochondritis Dissecans Lesion Characteristics
      VariableData (n = 15)
      Surface area (mm2)144.8 ± 33.2
      Tangential assessment
       Capitellar width (mm)21.2 ± 2.5
       Mediolateral lesion width
      Percentage (%)54.4 ± 6.6
      Absolute value (mm)11.5 ± 1.8
       Lesion centroid location
      Percentage (%)38.9 ± 10.1
      Absolute value (mm)8.2 ± 2.2
       Lateral inset
      Percentage (%)12.5 ± 8.9
      Absolute value (mm)2.6 ± 1.9
      Sagittal assessment
       Lesion centroid location (degrees)126.1 ± 12.4
       Sagittal lesion width (degrees)70.7 ± 17.9
      In tangential assessment, the average capitellar width was 21.2 ± 2.5 mm. Relative to this, the average mediolateral width of the OCD lesion was 54.4 ± 6.6% (11.5 ± 1 .8 mm), the average location of the OCD lesion centroid was 38.9 ± 10.1% (8.2 ± 2.2 mm), and the average lateral inset was 12.5 ± 8.9% (2.6 ± 1.9 mm). In sagittal assessment, the centroid of the lesion was located an average of 126.1 ± 12.5° and the average sagittal lesion width was 70.7 ± 17.9°.
      In the OCD group, the volumetric bone density of the OCD lesion was moderately correlated with the lesion size (R = 0.605; P < .05).

      Subchondral bone thickness analysis

      The tangential thickness of subchondral bone in the OCD group was significantly higher than that in the control group at the lateral edge (41.4 ± 14.8% vs 6.2 ± 5.2%; P < .05), centroid (33.7 ± 12.4% vs 12.8 ± 6.9%; P < .05), and medial edge (30.7 ± 13.9% vs 14.1 ± 6.1%; P < .05). Similarly, the sagittal thickness in the OCD group was significantly higher than that in the control group at the superior edge (22.8 ± 9.1% vs 13.9 ± 8.3%; P < .05), centroid (31.6 ± 11.1% vs 12.7 ± 6.8%; P < .05), and inferior edge (26.4 ± 12.1% vs 4.1 ± 4.8%; P < .05) (Fig. 4).
      Figure thumbnail gr4
      Figure 4Comparison in subchondral thickness between OCD and control groups. A Tangential thickness. B Sagittal thickness. ∗P < .05; ∗∗P < .01: Significant difference with higher subchondral bone thickness for the OCD group than for the control group. The error bar represents the standard deviation.
      In the OCD group, the absolute values of the tangential thickness were 9.2 ± 3.1 mm at the lateral edge, 7.6 ± 2.9 mm at the centroid, and 6.8 ± 3.0 mm at the medial edge. Those of the sagittal thickness were 5.1 ± 2.0 mm at the superior edge, 7.1 ± 2.5 mm at the centroid, and 5.9 ± 2.7 mm at the inferior edge. In the control group, those of the tangential thickness were 1.4 ± 1.2 mm at the lateral edge, 2.9 ± 1.6 mm at the centroid, and 3.2 ± 1.3 mm at the medial edge. Those of the sagittal thickness were 3.2 ± 2.0 mm at the superior edge, 2.9 ± 1.6 mm at the centroid, and 1.0 ± 1.1 mm at the inferior edge.

      Magnetic resonance imaging analysis

      The correlations between MRI measurements and CT subchondral bone thickness are presented as distribution plots in Figure 5. Analyses revealed that MRI measurements were highly correlated with CT subchondral bone thickness measurements (R = 0.75–0.84). In addition, the mean error of the measurements between MRI and CT measurements were 4.9% between MRI sagittal and CT sagittal thickness, 6.2% between MRI axial and CT tangential thickness, and 9.1% between MRI coronal and CT tangential thickness.
      Figure thumbnail gr5
      Figure 5Correlations between CT and MRI measurements. A Between MRI sagittal thickness and CT sagittal thickness. B Between MRI axial thickness and CT tangential thickness. C Between MRI coronal thickness and CT tangential thickness. Delta indicates the mean error of the measurements between CT and MRI measurements. R, Spearman correlation coefficients.

      Discussion

      In this study, we quantified subchondral bone thickness using conventional CT scans and compared 15 patients with capitellar OCD with 12 control patients. Our results showed that patients with capitellar OCD had greater subchondral bone thickness when compared with patients who had elbows without OCD lesions.
      Although stable OCD lesions have the potential to heal, healing in unstable lesions is less predictable.
      • Iwasaki N.
      • Kato H.
      • Ishikawa J.
      • Saitoh S.
      • Minami A.
      Autologous osteochondral mosaicplasty for capitellar osteochondritis dissecans in teenaged patients.
      ,
      • Peterson R.K.
      • Savoie III, F.H.
      • Field L.D.
      Osteochondritis dissecans of the elbow.
      ,
      • Mihara K.
      • Tsutsui H.
      • Nishinaka N.
      • Yamaguchi K.
      Nonoperative treatment for osteochondritis dissecans of the capitellum.
      ,
      • Roberts S.
      • McCall I.W.
      • Darby A.J.
      • et al.
      Autologous chondrocyte implantation for cartilage repair: monitoring its success by magnetic resonance imaging and histology.
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      Osteochondritis dissecans of the elbow. A long-term follow-up study.
      Subchondral sclerosis surrounding the lesion is commonly interpreted as a sign of an unstable lesion.
      • Takahara M.
      • Mura N.
      • Sasaki J.
      • Harada M.
      • Ogino T.
      Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum.
      ,
      • Mihara K.
      • Tsutsui H.
      • Nishinaka N.
      • Yamaguchi K.
      Nonoperative treatment for osteochondritis dissecans of the capitellum.
      In juvenile knee OCD, it is theorized that sclerosis is a reaction to prevent the expansion of the lesion, but it may also be a barrier to healing.
      • Schenck Jr., R.C.
      • Goodnight J.M.
      Osteochondritis dissecans.
      ,
      • Aglietti P.
      • Buzzi R.
      • Bassi P.B.
      • Fioriti M.
      Arthroscopic drilling in juvenile osteochondritis dissecans of the medial femoral condyle.
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      • Ramirez A.
      • Abril J.C.
      • Chaparro M.
      Juvenile osteochondritis dissecans of the knee: perifocal sclerotic rim as a prognostic factor of healing.
      Similarly, in capitellar OCD, sclerosis might suggest progression toward an unstable lesion with reduced healing potential; however, this has not been well-studied quantitatively.
      • Takahara M.
      • Mura N.
      • Sasaki J.
      • Harada M.
      • Ogino T.
      Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum.
      ,
      • Mihara K.
      • Tsutsui H.
      • Nishinaka N.
      • Yamaguchi K.
      Nonoperative treatment for osteochondritis dissecans of the capitellum.
      Our bone density measurements showed increased subchondral bone thickness around the OCD lesion. Additionally, correlation analysis showed that larger OCDs tend to have higher bone density. With standard imaging, it is difficult to assess the morphology and characteristics of this sclerotic area. Our method enabled us to visualize the subchondral bone thickness at the OCD lesion as a colored contour map derived from conventional CT images. This knowledge may be helpful to surgeons in determining the amount of sclerotic bone tissue that may serve as an impediment to healing when performing arthroscopic debridement, drilling, microfracture, or OAT procedures.
      The quantification of the thickness of bone at the base of an OCD lesion is relevant to decision-making in surgical procedures. In debridement, microfracture, and drilling, the goal is to debride or puncture the subchondral bone sufficiently to allow marrow elements to egress into the lesion bed.
      • Lewine E.B.
      • Miller P.E.
      • Micheli L.J.
      • Waters P.M.
      • Bae D.S.
      Early results of drilling and/or microfracture for grade IV osteochondritis dissecans of the capitellum.
      ,
      • Camp C.L.
      • Dines J.S.
      • Degen R.M.
      • Sinatro A.L.
      • Altchek D.W.
      Arthroscopic microfracture for osteochondritis dissecans lesions of the capitellum.
      ,
      • Logli A.L.
      • Bernard C.D.
      • O’Driscoll S.W.
      • et al.
      Osteochondritis dissecans lesions of the capitellum in overhead athletes: a review of current evidence and proposed treatment algorithm.
      Our data suggest that the depth of puncture should be about 7.5 mm to penetrate beyond this sclerotic area. This data also has applications for OAT procedures that involve harvesting plugs of subchondral bone with a hyaline cartilage cap to be transferred into a defect. Adequate osseous integration of the transplanted plug in the subchondral bone is important for the stability of the plugs and for the survival of the hyaline cartilage to maintain a smooth articular surface.
      • Bexkens R.
      • Hilgersom N.F.J.
      • Britstra R.
      • et al.
      Histologic analysis of 2 alternative donor sites of the ipsilateral elbow in the treatment of capitellar osteochondritis dissecans.
      • Kock N.B.
      • Hannink G.
      • van Kampen A.
      • Verdonschot N.
      • van Susante J.L.
      • Buma P.
      Evaluation of subsidence, chondrocyte survival and graft incorporation following autologous osteochondral transplantation.
      • Schub D.L.
      • Frisch N.C.
      • Bachmann K.R.
      • Winalski C.
      • Saluan P.M.
      Mapping of cartilage depth in the knee and elbow for use in osteochondral autograft procedures.
      Osteochondral autologous transplantation plugs heal to the subchondral and deeper bone and OAT plugs greater than 1 cm in thickness should generally be able to bypass this area of subchondral sclerosis to allow for optimal bony ingrowth.
      In our study, the primary sport of 13 of the 15 patients with OCD was throwing or weight-bearing sports. Furthermore, all the throwing athletes developed OCD in the dominant limb and the 5 patients who had the OCD of the non-dominant limb were gymnasts or soccer players. This supports the theory that compressive forces at the relatively poorly vascularized capitellum are associated with OCD development; however, it is unclear if subchondral sclerosis is a reaction to repetitive stress and consequently if the sclerosis leads to the development of chondral lesion, subchondral sclerosis is a secondary consequence following a chondral injury, or the chondral injury and subchondral sclerosis develop together depending on the degree of stress encountered. Our data cannot give insight into causality—it was too small to identify a pattern in sporting activities.
      To date, several researchers compared CT scans and MRIs with intraoperative findings for the purpose of investigating diagnostic accuracy.
      • Satake H.
      • Takahara M.
      • Harada M.
      • Maruyama M.
      Preoperative imaging criteria for unstable osteochondritis dissecans of the capitellum.
      ,
      • van den Ende K.I.M.
      • Keijsers R.
      • van den Bekerom M.P.J.
      • Eygendaal D.
      Imaging and classification of osteochondritis dissecans of the capitellum: X-ray, magnetic resonance imaging or computed tomography?.
      However, to our knowledge, there is no study that directly compares these modalities in terms of a quantitative evaluation of bone density around an OCD lesion. In our study, CT and MRI measurements showed a high correlation with low measurement errors when determining subchondral bone thickness. This demonstrated that the bone density alterations of the subchondral bone detected by CT scans have a reasonable correlation to the signal changes in MRI. As our study showed a reasonable correlation between MRI and CT scans for thickness measurements, it may be worthwhile in future studies to use both MRI and CT data in retrospective analyses to increase study cohort sizes for similar studies.
      There are several limitations to this study. First, there may be referral bias, as the patients in this study sought care at a tertiary center. In addition, not all patients with OCD underwent CT scanning, and this subset of patients may have thicker subchondral bone relative to others. That represents a spectrum bias because only patients with a certain level of disease activity might have undergone these investigations and were included in our study. Second, the controls were not normal healthy elbows; CT imaging was performed as part of the work-up for a different underlying pathology. Nonetheless, the controls had a normal-appearing radio-capitellar joint on CT scanning. Third, the mean age of the control group was older than those with OCD lesions. However, the capitellum was skeletally mature in both groups (ie, the physis of the capitellum was closed on radiographic imaging although some still had an open physis of the medial epicondyle). We also identified a low correlation of subchondral bone thickness with age in the control group (see Appendix E1, available online on the Journal’s website at www.jhandsurg.org). Thus, we do not believe that the overall skeletal maturity of the distal humerus altered the results substantially. Fourth, the cohort was a sample of convenience with a limited number of subjects, which could lead to sampling errors. Furthermore, not all the patients underwent the same imaging modality, which could introduce errors however, our analysis demonstrated a high correlation between conventional CT and MRI.
      We report a method of measurement for subchondral OCD lesions using contour mapping. This technique enabled us to quantify increases of the subchondral bone thickness in the region of an OCD lesion. Furthermore, we found that the subchondral bone measurements on conventional CT images are highly correlated with MRI measurements, suggesting that although surgeons may prefer different imaging modalities for OCD lesions, both may be useful when evaluating sclerosis at the capitellar defect site.

      Acknowledgments

      We thank Ko Temporin, MD, PhD, for helpful discussions and excellent contributions to this study. This work was supported by Japan Society for the Promotion of Science, Japan (JSPS) KAKENHI Grant Number JP 21K16684.

      Appendix E1

      Correlation analysis between age and subchondral bone thickness in the control group

      Using the CT measurements for the control group, we determined Spearman correlation coefficients (R) between age and maximum thickness of the subchondral bone in tangential and sagittal thickness. The strength of correlation was classified as slight (R < 0.2), low (0.2 ≤ R < 0.4), moderate (0.4 ≤ R < 0.7), or high (R ≥ 0.7).
      • Guilford J.P.
      Correlation analyses revealed that age showed positive low correlation with both tangential (R = 0.24; P = .448) and sagittal (R = 0.33; P = .292) subchondral bone thickness in the control group.

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