Glenoid stress distribution in baseball players using computed tomography osteoabsorptiometry: a pilot study

Paradoxical Change in Subchondral Bone Density in the Medial Compartment of the Proximal Tibial Articular Surface After High Tibial Osteotomy: A Detailed Subchondral Bone Density Analysis

BACKGROUND

High tibial osteotomy (HTO) aims to realign the varus knee to alleviate stress in the medial compartment. However, detailed information on the impact of HTO on stress distribution across the tibiofemoral joint surface still needs to be completely elucidated.

PURPOSE/HYPOTHESIS

The present study aimed to analyze the subchondral bone density distribution to validate the alignment threshold causing paradoxical changes. We hypothesized that there would be a paradoxical stress change in the medial compartment beyond a specific threshold for lower limb realignment after HTO.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective clinical study of 32 knees from 30 patients who underwent medial opening-wedge HTO between 2015 and 2019 was conducted at Hokkaido University Hospital. The subchondral bone density across the tibiofemoral joint was analyzed using computed tomography-osteoabsorptiometry before and after HTO. The high-density area (HDA) within the medial and lateral compartments and their subregions, which were quartered in the coronal plane, was specifically examined.

RESULTS

The hip-knee-ankle angle, medial proximal tibial angle (MPTA), joint line obliquity (JLO), and joint line convergence angle significantly changed after HTO (P < .01). The HDA of the medial compartment to the total HDA ratio decreased from 83% to 77%. Paradoxically, the HDA in the most central subregion of the medial compartment increased from 24% to 30%. There were significant differences between MPTA and JLO in patients with and without paradoxical changes in the HDA. MPTA and JLO cutoff values causing paradoxical changes in the HDA were 94° and 4°, respectively.

CONCLUSION

There was a paradoxical stress increase in the M4 region at the medial compartment associated with the MPTA and JLO beyond specific thresholds. Therefore, surgical planning should be cautiously performed to prevent overcorrection, which can lead to adverse stress distribution changes.

Computed tomography Osteoabsorptiometry: Review of bone density, mechanical strength of material and clinical application

Computed Tomography (CT) imaging is an effective non-invasive examination. It is widely used in the diagnosis of fractures, arthritis, tumor, and some anatomical characteristics of patients. The density value (Hounsfield unit, HU) of a material in computed tomography can be the same for materials with varying elemental compositions. This value depends on the mass density of the material and the degree of X-ray attenuation. Computed Tomography Osteoabsorptiometry (CTOAM) imaging technology is developed on the basis of CT imaging technology. By applying pseudo-color image processing to the articular surface, it is used to analyze the distribution of bone mineralization under the articular cartilage, evaluate the position of prosthesis implantation, track the progression of osteoarthritis, and determine the joint injury prognosis. Furthermore, this technique was combined with indentation testing to discuss the relationship between the high bone density area of the articular surface, the mechanical strength of the bone, and the anchorage stability of the implant, in addition to the study of the relationship between mechanical strength and bone density. This narrative study discusses the pre- and postoperative evaluation of medical device implantation position, orthopedic surgery, and the clinical treatment of bone injury and degeneration. It also discusses the research status of CTOAM technology in image post-processing engineering and the relationship between bone material and mechanical strength.

Effect of periacetabular osteotomy on the distribution pattern of subchondral bone mineral density in patients with hip dysplasia

Despite the availability of long-term follow-up data, the effect of pelvic osteotomy on the natural history of osteoarthritis is not yet fully understood, partly because there is untapped potential for radiographs to better describe osteoarthritis. Therefore, this study aimed to assess the distribution of subchondral bone mineral density (BMD) across the acetabulum in patients with hip dysplasia immediately (2 weeks) and 1 year after undergoing periacetabular osteotomy (PAO). To that end, we reviewed 40 hips from 33 patients with developmental dysplasia of the hip who underwent PAO between January 2016 and July 2019 at our institution. We measured subchondral BMD through the articular surface of the acetabulum using computed tomography osteoabsorptiometry, dividing the distribution map into nine segments. We then compared the subchondral BMD between 2 weeks and 1 year after PAO in each area. At 2 weeks after PAO, the high-density area tended to be localized particularly in the lateral part of the acetabulum, whereas 1 year after PAO, the high-density area moved to the central and lateral parts. The percentage ratios of the subchondral BMD for the central-posterior, lateral-central, and lateral-posterior areas relative to the central-central area were significantly decreased at 1 year after PAO, as compared to those at 2 weeks after PAO. These findings suggest that loading was altered by PAO to be more similar to physiological loading. A long follow-up observational study is warranted to confirm the association between early changes in subchondral BMD by PAO and joint degeneration.

Influence of differences in bone morphology on the distribution patterns of subchondral bone density across the trapeziometacarpal joint

We aimed to clarify the effects of morphological patterns of the trapezium and first metacarpal on the distribution of subchondral bone density across the articular surface of the trapeziometacarpal (TMC) joint using computed tomography osteoabsorptiometry. Thirty-three patients with normal TMC joints were evaluated. The percentages of the high-density areas in the radial-dorsal and ulnar-volar regions of the trapezium were significantly higher than that in the ulnar-dorsal region, and that of the ulnar-dorsal region of the first metacarpal was significantly lower than in the other three regions. The percentage of the high-density area of the radial-dorsal region of the trapezium and trapezial inclination (TI) showed a significant positive correlation, and the percentages of the high-density areas in the ulnar-dorsal and ulnar-volar regions had significant negative correlations with TI at the articular surface of the first metacarpal. These results indicate that bony morphologic differences in the trapezium affect the distribution pattern of subchondral bone density through the TMC joint.

Four-dimensional computed tomography evaluation of shoulder joint motion in collegiate baseball pitchers

The purpose of this study is to evaluate the glenohumeral contact area, center of glenohumeral contact area, and center of humeral head during simulated pitching motion in collegiate baseball pitchers using four-dimensional computed tomography (4D CT). We obtained 4D CT data from the dominant and non-dominant shoulders of eight collegiate baseball pitchers during the cocking motion. CT image data of each joint were reconstructed using a 3D reconstruction software package. The glenohumeral contact area, center of glenohumeral contact area, center of humeral head, and oblateness of humeral head were calculated from 3D bone models using customized software. The center of glenohumeral contact area translated from anterior to posterior during maximum external rotation to maximum internal rotation (0.58 ± 0.63 mm on the dominant side and 0.99 ± 0.82 mm on the non-dominant side). The center of humeral head translated from posterior to anterior during maximum external rotation to maximum internal rotation (0.76 ± 0.75 mm on the dominant side and 1.21 ± 0.78 mm on the non-dominant side). The increase in anterior translation of the center of glenohumeral contact area was associated with the increase in posterior translation of the center of humeral head. Also, the increase in translation of the center of humeral head and glenohumeral contact area were associated with the increase in oblateness of the humeral head. 4D CT analyses demonstrated that the center of humeral head translated in the opposite direction to that of the center of glenohumeral contact area during external rotation to internal rotation in abduction in the dominant and non-dominant shoulders. The oblateness of the humeral head may cause this diametric translation. 4D CT scanning and the software for bone surface modeling of the glenohumeral joint enabled quantitative assessment of glenohumeral micromotion and be used for kinematic evaluation of throwing athletes.

Stress distribution pattern in the distal radioulnar joint before and after ulnar shortening osteotomy in patients with ulnar impaction syndrome

Ulnar shortening osteotomy (USO) for ulnar impaction syndrome potentially leads to degenerative changes of the distal radioulnar joint (DRUJ). This study was performed to evaluate the effect of the sigmoid notch morphology on the stress distribution pattern of the DRUJ using computed tomography (CT) osteoabsorptiometry (CT-OAM). We reviewed the pre- and postoperative transverse CT images of 15 wrists that had undergone USO. The examined wrists were classified into two groups based on the sigmoid notch morphology: the linear-type notch (type L) and the curved-type notch (type C). We calculated and statistically compared the percentage of the high-density area (%HDA) in each divided region of the sigmoid notch. In type L, %HDA was significantly larger in the distal-dorsal region of the sigmoid notch before USO. Postoperatively, in type L, no specific regions showed a significantly different %HDA. In type C, %HDA was significantly larger in the distal-volar region of the sigmoid notch before USO. Postoperatively, %HDA of type C was significantly larger in the proximal-volar region. Our results suggest that in patients with ulnar impaction syndrome, morphological evaluation of the sigmoid notch can serve as a predictor of osteoarthritis in the DRUJ with or without USO.

Stress-Distribution Pattern Across the Glenohumeral Joint in Collegiate and Professional Baseball Players: A Computed Tomography Osteoabsorptiometry Study

Background:

The influence of long-term loading conditions on the articular surfaces of the glenohumeral joint can be determined by measuring stress-distribution patterns. Long-term pitching activity changes the stress distribution across the glenohumeral joint surface; however, the influence of competitive level on stress-distribution patterns remains unclear.

Purpose:

To use computed tomography (CT) osteoabsorptiometry (CTOAM) to evaluate the distribution of subchondral bone density across the glenohumeral joint in collegiate and professional baseball players as well as to determine the effects of pitching activity on the articular surfaces.

Study Design:

Descriptive laboratory study.

Methods:

We evaluated 73 shoulders in 50 baseball players. CT imaging data were obtained from the dominant-side shoulder of 12 professional pitchers (PP group) and 15 professional fielders (PF group). CT imaging data were also obtained from both shoulders of 12 asymptomatic collegiate pitchers (CP group) and 11 collegiate fielders (CF group). The pattern of distribution of subchondral bone density across the articular surfaces of each glenohumeral joint was assessed by CTOAM. As a measure of bone density, the mean Hounsfield units (HU) were obtained for each joint surface, and the absolute values of the dominant shoulder were compared for each group.

Results:

Stress-distribution patterns over the articular surfaces differed between the dominant and nondominant sides in the CP group as well as between both collegiate groups versus the PP group. In the CP group, the mean HU of the humeral head surface were greater on the nondominant versus dominant side (P = .035). On the dominant side, the mean HU of the humeral head surface and glenoid were greater in the CP versus the PP group (P = .001 and .027, respectively).

Conclusion:

Stress distribution on the articular surface of the glenohumeral joint was affected by pitching ability and competitive level. Our analysis indicates that the traction force on the glenohumeral joint surface might be greater than compression force during pitching.

Clinical Relevance:

The present findings suggest that pitching activity results in low stress to the articular surfaces of the glenohumeral joint. This supports the notion that mechanical conditions play a crucial role in the etiology of disorders specific to pitching activity.

Effect of High Tibial Osteotomy on the Distribution of Subchondral Bone Density Across the Proximal Tibial Articular Surface of the Knee With Medial Compartment Osteoarthritis

BACKGROUND

The effect of high tibial osteotomy (HTO) on the stress distribution across the knee joint is not completely understood. Subchondral bone density is considered to reflect the pattern of stress distribution across a joint surface.

PURPOSE

To assess the distribution of subchondral bone density across the proximal tibia in nonarthritic knees and in the knees of patients with osteoarthritis (OA) before and after HTO.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We retrospectively collected radiological and computed tomography data from 16 patients without OA (control group) and 17 patients with OA. Data from the OA group were collected before and 1.5 years after HTO. Subchondral bone density of the proximal tibia was assessed with computed tomography-osteoabsorptiometry. The locations and percentages represented by high-density areas (HDAs) on the articular surface were quantitatively analyzed.

RESULTS

The ratio of the HDA of the medial compartment to the total HDA (medial ratio) was significantly higher in the preoperative OA group (mean, 80.1%) than in the control group (61.3%) (P < .001). After HTO, the medial ratio decreased significantly to 75.1% (P = .035 in comparison with preoperative values) and was significantly correlated with the hip-knee-ankle angle in both groups: control (r = -0.551; P = .033) and OA (r = -0.528; P = .043). The change in medial ratio after HTO was significantly correlated with the change in hip-knee-ankle angle (r = 0.587; P = .035). In the medial compartment, the HDA in the most lateral region of 4 subregions increased after HTO, but that in 3 medial subregions decreased.

CONCLUSION

In this exploratory study, HTO shifted the HDA of the medial compartment of the proximal tibial articular surface toward the lateral compartment. In contrast, the HDA of the most lateral region of the medial compartment increased after HTO. This change in subchondral bone density may result from the change in stress distribution.

Characterization of glenoid bone remodeling in professional baseball pitchers

OBJECTIVE

To characterize the appearance, location, severity, and prevalence of focal glenoid retroversion on shoulder MRI in professional baseball pitchers versus age-matched controls.

MATERIALS AND METHODS

In this retrospective review, two musculoskeletal radiologists evaluated shoulder MRI examinations from 40 professional baseball pitchers and 40 age-matched controls. Images were scored for the presence of a focal posterior glenoid convexity and the clock face positions involved. A consensus interpretation was also performed. A third reader identified the presence of additional shoulder abnormalities.

RESULTS

After consensus, 60% (24/40) of pitchers were found to have focal glenoid retroversion versus 20% (8/40) of controls (p = 0.001). The most apparent location was posterior or posterior-superior, from 7.75 o'clock to 10.5 o'clock (median, 9.75 o'clock; interquartile range, 9.25-10 o'clock). The median clock angle of involvement was greater in pitchers than in controls (30° vs. 0°; p < 0.001). Interreader agreement regarding the presence or absence of focal glenoid retroversion was moderate (Cohen's kappa, 0.49). Focal glenoid retroversion was more prevalent among subjects with additional shoulder abnormalities (p = 0.014).

CONCLUSIONS

Glenoid remodeling occurs in the throwing shoulder of professional baseball pitchers and manifests as focally convex morphology of the posterior or posterior-superior glenoid. This type of remodeling does not appear to be associated with a lower prevalence of injuries related to posterior-superior impingement.

The adaption of the bony microstructure of the human glenoid cavity as a result of long-term biomechanical loading

Structural arrangements of the bony microstructure of a joint through adaptational processes are thought to be determined by the biomechanical demands and its changes. Pursuing this theory of "form follows the biomechanical function", the load distribution of the glenoid cavity, as it is mirrored in its mineralization pattern, should link not only to its thickness distribution, but also will have an impact onto the trabecular network below. To prove and confirm this hypothesis, we analysed the mineral distribution in correlation to the subchondral bone plates thickness and the distribution of architectural parameters of the trabecular network below. Our findings clearly state an inhomogeneous but regular and reproducible mineral distribution pattern in respect to the biomechanical demands and a thickness of the subchondral bone plate which shows a significant correlation (78-93%). As for the trabecular network below, the distribution of the analysed parameters also revealed an inhomogeneous distribution with a regular pattern in correlation to the biomechanical impact. We found distinctive maxima of material distribution and stability (bone volume 79%, plate-like architecture 77%) situated below areas of high long-term load intake. With increasing depth, the trabecular network administers the expression of each structural parameter following the fact that the strain energy gets more and more evenly distributed and changes from a high degree of differentiation just beneath the SBP to a more equal distribution within the deeper areas. After all, the biomechanical situation of a joint directly influences the bony formation of the subchondral bone plate and the trabecular network below.

High incidence of posterior glenoid dysplasia of the shoulder in young baseball players

BACKGROUND

Rounding of the posterior glenoid rim is observed in young throwing athletes with internal shoulder impingement and is considered developmental dysplasia of the glenoid. The aim of our study was to determine the incidence rate of dysplastic changes of the glenoid within a group of 92 young baseball players.

METHODS

The study group included 92 male baseball players, with a mean age of 14.63 years. Of these patients, 30 were diagnosed with Little Leaguer's shoulder and 62 with a painful baseball-throwing shoulder with no abnormal findings on x-ray. The posterior glenoid rim of the affected shoulder was compared with the contralateral nonpainful shoulder, with the 2 following outcomes measured on radiographs obtained using the modified Bernageau imaging method: the distance between the anterior and posterior glenoid rims and the presence or absence of dysplasia of the posterior glenoid rim.

RESULTS

The mean distance between the anterior and posterior glenoid rims was significantly shorter in the painful shoulders (mean, 26 mm) than in the nonpainful shoulders (mean, 29 mm; P < .0001). Dysplasia of the posterior glenoid rim was identified in 89 painful shoulders (96.7%), with 9 cases (9.7%) identified on the unaffected contralateral side (P < .001). The presence of dysplasia was not correlated with the age at which baseball playing began.

CONCLUSION

The incidence of dysplasia of the posterior glenoid rim is high (96.7%) among young baseball players with a painful shoulder. The identified dysplasia may be related to impaired development of the inferior peripheral secondary glenoid ossification center due to repetitive throwing.

Is There an Association Between Borderline-to-mild Dysplasia and Hip Osteoarthritis? Analysis of CT Osteoabsorptiometry

BACKGROUND

The definitive treatment of borderline-to-mild dysplasia remains controversial. A more comprehensive understanding of the etiology of osteoarthritis (OA) and clarification of any possible association between borderline-to-mild dysplasia and the pathogenesis of OA are essential.

QUESTIONS/PURPOSES

(1) Does the distribution of acetabular subchondral bone density increase according to dysplasia severity? (2) Is there an association between borderline-to-mild dysplasia and OA pathogenesis?

METHODS

We evaluated bilateral hips of patients with developmental dysplasia of the hip who underwent eccentric rotational acetabular osteotomy (ERAO) for inclusion in the dysplasia group and contralateral hips of patients with unilateral idiopathic osteonecrosis of the femoral head (ONFH) who underwent curved intertrochanteric varus osteotomy (CVO) for the control group. ERAO was performed in 46 patients and CVO was performed in 32 patients between January 2013 and August 2016 at our institution. All patients underwent bilateral hip CT. The study included 55 hips categorized according to dysplasia severity: (1) borderline-mild, 19 hips (15° ≤ lateral center-edge angle [LCEA] < 25°); (2) moderate, 20 hips (5° ≤ LCEA < 15°); (3) severe, 16 hips (LCEA < 5°); and (4) control, 15 hips. Thirty-seven dysplastic hips (age < 15 or > 50 years old, prior hip surgery, subluxation, aspherical femoral head, cam deformity, and radiographic OA) and 17 control hips (age < 15 or > 50 years old, bilateral ONFH, LCEA < 25° or ≥ 35°, cam deformity, and radiographic OA) were excluded. CT-osteoabsorptiometry (OAM) predicts physiologic biomechanical conditions in joints by evaluating subchondral bone density. We evaluated the distribution of subchondral bone densities in the acetabulum with CT-OAM, dividing the stress distribution map into six segments: anteromedial, anterolateral, centromedial, centrolateral, posteromedial, and posterolateral. We calculated the percentage of high-density area, which was defined as the upper 30% of Hounsfield units values in each region and compared least square means difference estimated by the random intercept model among the four groups.

RESULTS

In all regions, the percentage of high-density area did not differ between the borderline-mild group and the control (eg, anterolateral, 16.2 ± 5.6 [95% CI, 13.4 to 18.9] versus 15.5 ± 5.7 [95% CI, 12.4 to 18.5, p = 0.984]; centrolateral, 39.1 ± 5.7 [95% CI, 36.4 to 41.8] versus 39.5 ± 4.7 [95% CI, 36.6 to 42.5, p = 0.995]; posterolateral, 10.9 ± 5.2 [95% CI, 8.0 to 13.8] versus 15.1 ± 6.8 [95% CI, 11.7 to 18.5, p = 0.389]). In the anterolateral region, a smaller percentage of high-density area was observed in the borderline-mild group than in both the moderate group (16.2 ± 5.6 [95% CI, 13.4-18.9] versus 28.2 ± 5.1 [95% CI, 25.5-30.9], p < 0.001) and the severe group (16.2 ± 5.6 [95% CI, 13.4-18.9] versus 22.2 ± 6.8 [95% CI, 19.2-25.2, p = 0.026).

CONCLUSIONS

Our results suggest that the cumulative hip stress distribution in borderline-to-mild dysplasia was not concentrated on the lateral side of the acetabulum, unlike severe dysplasia.

CLINICAL RELEVANCE

Based on the stress distribution pattern, our results may suggest that there is no association between borderline-to-mild dysplasia and the pathogenesis of OA. Further studies are needed to evaluate the association between borderline-to-mild dysplasia and instability of the hip.

Bone mineralization changes of the glenoid in shoulders with symptomatic rotator cuff tear

PURPOSE

Computed tomography osteoabsorptiometry (CTO) is a method to analyze the stress distribution in joints by measuring the subchondral bone density. The purpose of this study was to evaluate the bone mineralization changes of the glenoid in shoulders with rotator cuff tears by CTO and to evaluate whether rotator cuff tears are associated with stress changes in the glenoid.

METHODS

In total, 32 patients, who were diagnosed with unilateral rotator cuff tears and underwent arthroscopic rotator cuff repair, were enrolled in this study. They underwent CT scanning of both shoulders pre-operatively and the glenoid was evaluated using CTO. Hounsfield units (HU) in seven areas of the glenoid were compared between the affected and unaffected sides.

RESULTS

The central area of the glenoid on the affected side had significantly lower HU than on the unaffected side among all patients. Focusing on the rotator cuff tear size and the subscapularis tendon, only patients with larger cuff tears or with subscapularis tendon tears showed significantly lower HU in the central area of the affected side.

CONCLUSIONS

This study showed a decrease in bone mineralization density in the central glenoid in shoulders with rotator cuff tear. This change was observed in the case of larger cuff tears and subscapularis tendon tears. Our results help clarify the changes in stress distribution in the shoulder joint caused by symptomatic rotator cuff tears.

Variation in stress distribution patterns across the radial head fovea in osteochondritis dissecans: predictive factors in radiographic findings

BACKGROUND

Predictive factors for the development of osteoarthritis in adolescent osteochondritis dissecans (OCD) of the humeral capitellum remain unclear. The objectives of this study were to assess subchondral bone density in the radial head fovea of patients with OCD and to evaluate stress distribution in the radiocapitellar joint. The relationship between radiologic classification and stress distribution, according to multivariate ordinal regression analysis, was also investigated.

METHODS

Computed tomography (CT) imaging data from 54 male patients with OCD (mean age, 13.1 years) were collected. Stress in the radial head fovea was measured using CT osteoabsorptiometry. A stress map was constructed and divided into 4 sections, and percentages of high-density regions in each section were quantitatively analyzed. Multivariate ordinal regression analyses were performed of bone density, incorporating the stage, location, and size of the OCD lesion and the presence of medial elbow disturbance in the radiographic images.

RESULTS

The percentage of high-density area in the anteromedial, posteromedial, and the anterolateral sections of the radial head fovea were significantly increased compared with the posterolateral section. Multivariate ordinal regression analysis revealed that the location and size of the lesion and a history of excessive valgus stress were associated with imbalances in the radial head fovea.

CONCLUSIONS

When the OCD lesion is large and located laterally and a medial epicondyle disturbance is apparent on radiographs, the risk for developing advanced radiocapitellar osteoarthritis should be considered. These findings can be useful in the decision-making process for treating OCD.

Shoulder Injuries in the Overhead-Throwing Athlete: Epidemiology, Mechanisms of Injury, and Imaging Findings

The unparalleled velocity achieved by overhead throwers subjects the shoulder to extreme forces, resulting in both adaptive changes and pathologic findings that can be detected at imaging. A key biomechanical principle of throwing is achieving maximum external rotation, which initially leads to adaptive changes that may result in a pathologic cascade of injuries. In addition to the well-established concepts of glenohumeral internal rotation deficit and internal impingement, osseous and soft-tissue injuries of the shoulder unique to overhead athletes are illustrated. The epidemiology and biomechanics of throwing injuries are reviewed, and examples from the authors' institutional experience with competitive, collegiate, and professional baseball players are provided to demonstrate the constellation of unique imaging findings seen in overhead throwing athletes. Given the widespread popularity of baseball, and other sports relying on overhead throwing motions at all playing levels from recreational to professional, it is important for radiologists in various practice settings to be familiar with the special mechanisms, locations, and types of shoulder injuries seen in the overhead throwing population. ^© RSNA, 2018.

Pathomechanics and Magnetic Resonance Imaging of the Thrower's Shoulder

Repetitive, high-velocity overhead throwing can lead to several adaptive changes in the throwing shoulder, which over time lead to structural microtrauma and eventually overt injury. MR imaging is a useful imaging modality to evaluate these changes and to characterize their acuity and severity. Understanding the throwing motion and the effects of this motion on the structures of the shoulder can help radiologists to recognize these findings and provide useful information to referring physicians, which may affect the treatment of these athletes. This article reviews shoulder pathomechanics and MR imaging findings in overhead throwing athletes.

Alteration of Stress Distribution Patterns in Symptomatic Valgus Instability of the Elbow in Baseball Players: A Computed Tomography Osteoabsorptiometry Study

BACKGROUND

Repetitive valgus stress applied during a throwing motion can lead to various elbow disturbances, including ulnar collateral ligament (UCL) injury. Subchondral bone density reportedly reflects the cumulative force on a joint surface under actual loading conditions.

PURPOSE

(1) To evaluate the distribution of subchondral bone density across the elbow joint in asymptomatic baseball pitchers and symptomatic valgus instability pitchers and (2) to clarify the alterations in stress distribution pattern associated with symptomatic UCL insufficiency pitching activities.

STUDY DESIGN

Controlled laboratory study.

METHODS

Computed tomography (CT) imaging data were collected from the dominant-side elbow of 7 nonathletic volunteers (controls), 12 asymptomatic pitchers (asymptomatic group), and 12 symptomatic valgus instability pitchers with UCL insufficiency (symptomatic group). Bone mineral density across the elbow joint was measured with CT osteoabsorptiometry. A 2-dimensional mapping model was divided into 4 areas of the distal end of the humerus and 5 areas of the ulna with the radial head. The locations and percentages of high-density areas on the articular surface were quantitatively analyzed.

RESULTS

High-density areas in the asymptomatic and symptomatic groups were found in the anterolateral and posteromedial parts of the humerus and in the radial head, posteromedial to the ulna. The high-density areas in the anterior and posteromedial of the humerus, the radial head, and the posteromedial part of the ulna in the controls were smaller than those in the baseball group. In the symptomatic group, the percentages of high-density areas in the anterolateral part of the humerus (mean, 36.3%; 95% CI, 31.9%-40.7%) and the anterolateral part of the ulna (mean, 31.7%; 95% CI, 24.3%-39.1) were significantly greater than those in the asymptomatic group (P = .047 and P < .0001, respectively).

CONCLUSION

Symptomatic UCL insufficiency was associated with characteristic high-stress distribution patterns on the anterolateral part of the capitellum and the anterolateral part of the ulna. The current results indicate that symptomatic UCL insufficiency produces excessive and cumulative stress in the elbow joint.

CLINICAL RELEVANCE

The information obtained from the CT images can useful for early detection of overstress conditions of the elbow joint.