Force distribution through the wrist joint in patients with different stages of Kienböck's disease: using computed tomography osteoabsorptiometry

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.

Bone Density Distribution Pattern in the Lateral Wall of the Femoral Intercondylar Notch: Implications for the Direct Insertion of the Femoral ACL Attachment

Background

The ideal position of the femoral bone tunnel in the anterior cruciate ligament (ACL) is controversial. The functional importance of the ACL fiber varies depending on where it is attached to the femur. Functionally important fibers can cause high mechanical stress on the bone, and the Wolff law predicts that bone mineral density will increase at high mechanical stress sites.

Purpose/Hypothesis

The purpose of this study was to use computed tomography imaging to determine the distribution pattern of bone density in the lateral intercondylar wall. It was hypothesized that the high-density area (HDA) of the lateral intercondylar wall would reflect the functional insertion of the ACL as reported in previous anatomic studies.

Study Design

Descriptive epidemiology study.

Methods

Data from 39 knees without ACL injuries were retrospectively collected. The HDA of the lateral intercondylar wall was defined as the region containing the top 10% of the radiodensity values. The shape of the HDA was approximated as an ellipse, and the quadrant method was used to determine the center of the ellipse. The association between the ratio of the minor axis to the major axis of the ellipse and background characteristics was investigated.

Results

According to the quadrant method, the center of the HDA ellipse was 33.6% in the deep-shallow direction and 23.4% in the high-low direction. The center of the ellipse was comparable to the anatomic center of the ACL footprint, as previously reported. The ratio of the minor axis to the major axis of the ellipse was 0.58 (95% CI, 0.54-0.62). There was a significant negative correlation between the ratio of the minor axis to the major axis of the HDA ellipse and the posterior tibial slope (r = -0.38, P = .02).

Conclusion

The center of the HDA ellipse was found to be similar to the anatomic center of the ACL footprint. Considering the mechanical stress responses in bone, the HDA of the lateral intercondylar wall has the potential to represent the ACL insertion, especially functional insertion.

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.

Stress on the posteromedial region of the proximal tibia increased over time after anterior cruciate ligament injury

PURPOSE

Anterior cruciate ligament (ACL) injury induces anterior and rotatory instability of the knee. However, the effect of this instability on the stress distribution in the knee joint in living participants is not clear. The aim of this study was to compare the distribution pattern of subchondral bone density across the proximal tibia in the knees with and without ACL injury, and to investigate the correlation between the distribution patterns of the subchondral bone density and the duration of ACL-deficiency.

METHODS

Radiographic and computed tomography (CT) data pertaining to 20 patients with unilateral ACL injury without combined injury (ACL-deficient group) and 19 nontraumatic subjects (control group) were collected retrospectively. Subchondral bone density of the proximal tibia was assessed using CT-osteoabsorptiometry. Both the medial and lateral compartments of the proximal tibia were divided into three subregions of equal width in the sagittal direction. The percentage of high subchondral bone density areas (HDA%) in each subregion was quantitatively analyzed.

RESULTS

HDA% of the posteromedial region was significantly higher in the ACL-deficient group (mean: 21.6%) than in the control group (14.7%) (p = 0.002). In contrast, HDA% of the anteromedial region was significantly lower in the ACL-deficient group (9.4%) than in the control group (15.3%) (p = 0.048). The logarithm of the time elapsed from ACL injury to CT examination showed a significant correlation with HDA% in the posteromedial region (p = 0.032).

CONCLUSIONS

Subchondral bone density in the posteromedial region significantly increased after ACL injury and correlated with the duration of ACL-deficiency in semi-log manner in meniscus intact knees. The increase in stress on the posteromedial region after ACL injury, which induces a change in the subchondral bone density, justifies early ACL reconstruction after ACL injury.

Matching Kienböck's Treatment Options to Specific Features of Each Case

Kienböck's disease is best understood as a continuous interaction between compromised perfusion and structural deterioration that transitions from an early phase to a late phase. Existing literature has failed to identify any one superior treatment for Kienböck's; many studies even demonstrate no advantage for surgery compared with the natural history. Surgical interventions for early and transitional Kienböck's are designed to preserve or reconstruct the lunate. However, in most studies, the only tool used to assess the lunate itself has been plain radiography that neither reveals critical architectural details (demonstrated by computed tomographic scan) nor the vascular status (demonstrated by magnetic resonance imaging). Most articles, therefore, do not adequately define the preoperative status of the lunate or its alteration through surgical intervention. Critical preoperative features that are best demonstrated by these advanced imaging studies have specific anatomic and physiologic relationships that better correspond with certain surgical interventions, which also pair better with specific patient characteristics. This review explains how to identify, analyze, and strategically match these variables with the treatment interventions available for Kienböck's patients through the early, transitional, and late phases of the disease.

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.

Changes in the Contact Stress Distribution Pattern of the Patellofemoral Joint After Medial Open-Wedge High Tibial Osteotomy: An Evaluation Using Computed Tomography Osteoabsorptiometry

Background:

Medial open-wedge high tibial osteotomy (OWHTO) theoretically causes distalization and lateralization of the tibial tuberosity and the patella.

Purpose/Hypothesis:

The purpose of the study was to identify any changes in the stress distribution of subchondral bone density across the patellofemoral (PF) joint before and after OWHTO through the use of computed tomography (CT) osteoabsorptiometry. We hypothesized that OWHTO would alter the distribution of contact stress in the PF joint.

Study Design:

Case series; Level of evidence, 4.

Methods:

A total of 17 patients (17 knees) who underwent OWHTO were enrolled in this study between September 2013 and September 2015. All patients underwent radiologic examination preoperatively and at 1 year postoperatively, and the distribution patterns of subchondral bone density through the articular surface of the femoral trochlea and patella were assessed preoperatively and >1 year postoperatively using CT osteoabsorptiometry. The quantitative analysis of the obtained mapping data focused on location of the high-density area (HDA) through the articular surface of the PF joint. The percentage of HDA at each divided region of the articular surface of the femoral trochlea and the patella was calculated.

Results:

In the radiologic evaluation, the Blackburne-Peel ratio was significantly reduced (P < .001) after surgery, and the tilting angle of the patella was significantly decreased (P < .001). On CT evaluation, the percentage of HDA in the lateral notch and lateral trochlea of the femur and in the medial portion of the lateral facet of the patella increased significantly after OWHTO surgery (P ≤ .038).

Conclusion:

OWHTO significantly increased the stress distribution pattern of the lateral trochlea of the femur and the medial portion of the lateral facet of the patella. The procedure significantly lowered the patellar height and significantly decreased the patellar tilting angle after surgery.

Stress Distribution Patterns Across the Shoulder Joint in Gymnasts: A Computed Tomography Osteoabsorptiometry Study

Background:

The distribution pattern of subchondral bone density is an indicator of stress distribution over a joint surface under long-term physiologic loading. The biomechanical characteristics of the articular surfaces of the shoulder joint in gymnasts can be determined by measuring this distribution pattern.

Purpose:

To evaluate the distribution of subchondral bone density across the shoulder joint in male collegiate gymnasts and to determine the effects of gymnastic activities on its articular surfaces under long-term loading conditions using computed tomography osteoabsorptiometry (CTOAM).

Study Design:

Descriptive laboratory study.

Methods:

CT image data were obtained from both shoulders of 12 asymptomatic male collegiate gymnasts (gymnast group; mean age, 19.4 years; range, 18-22 years) and 10 male collegiate volunteers (control group; mean age, 20.2 years; range, 18-22 years). The distribution pattern of subchondral bone density across the articular surfaces of each shoulder joint was assessed by CTOAM. Quantitative analysis was performed of the locations and percentages of high-density areas on the articular surface.

Results:

Stress distribution patterns over the articular surfaces differed between the gymnasts and the controls. In the gymnasts, high-density areas were detected on the posterosuperior articular surface of the humeral head and the anterosuperior and/or posterosuperior articular surface of the glenoid. Mean bone density was greater in the gymnasts than in the controls (P < .0001).

Conclusion:

Stress distribution over the articular surfaces of the shoulder joint was affected by gymnastic activities. Stress was concentrated over the superior part of the glenohumeral joint in male collegiate gymnasts.

Clinical Relevance:

The present findings suggest that gymnastic activities increase stress to the articular surfaces of the superior glenohumeral joint. This supports the notion that mechanical conditions play a crucial role in the origin of disorders particular to gymnastic activities.

Vascularized Small-Bone Transfers for Fracture Nonunion and Bony Defects

Vascularized small-bone grafting is an efficient and often necessary surgical approach for nonunion or necrosis of several bones in particular sites of the body, including scaphoid, lunate, distal ulna, and clavicle. The medial femoral condyle is an excellent graft source that can be used in treating scaphoid, ulna, clavicle, or lower-extremity bone defects, including nonunion. Vascularized bone grafting to the small bones, particularly involving reconstruction of damaged cartilage surfaces, should enhance subchondral vascular supply and help prevent cartilage regeneration. Vascularized osteoperiosteal and corticoperiosteal flaps are useful for treating nonunion of long bones.

ARTHROSCOPIC ASSESSMENT OF THE WRIST WITH KIENBÖCK'S DISEASE

Objective

Treatment of Kienböck's disease is challenging and the variability of results, despite the surgical technique, shows that there must be other aspects that can influence outcomes. The objective of this study is determine, through arthroscopic approach, the pattern of impairment of the carpal bones in Lichtman stage III patients.

Method

Wrist arthroscopy was performed in patients with symptoms and evidence of lunate necrosis on x-rays, with signs of 3A and 3B stages. The Outerbridge classification was used to grade the articular status of the carpal bones.

Results

Fifteen patients with stage 3 disease were assessed, five of whom were staged as type 3A and ten as 3B using the Lichtman stages. According to the Outerbridge classification, the lunate sulcus was the most affected with means of 2.8 at 3A and 2.9 at 3B. Other areas were significantly less affected with means of 1.1 and 1.3, respectively.

Conclusion

Arthroscopic assessment of the wrist could aid in surgical decision making, offering more details on cartilage status in stage 3 Kienböck's disease. Level of Evidence III, Study of nonconsecutive patients, without consistently applied reference “gold” standard.

Alteration in stress distribution patterns through the elbow joint in professional and college baseball pitchers: Using computed tomography osteoabsorptiometry

BACKGROUND

Long-term pitching activities change the stress distribution across the elbow joint surface in living subjects, however the influence of the different strength of stress on the stress distribution patterns remain unclear. The aims of this study were to evaluate the distribution of subchondral bone density across the elbow joint in different levels of pitchers, and to reveal the influence of the strength of stress on the elbow joint surface under long-term loading conditions of baseball pitching.

METHODS

The current analysis was performed using computed tomography (CT) image data obtained from the throwing side elbow of 12 nonthrowing athletes (controls), 15 college baseball pitchers (college group) and 13 professional baseball pitchers (professional group). The distribution patterns of subchondral bone density through the articular surface of the elbow joints were assessed using a CT osteoabsorptiometry method. The quantitative analysis was based on location and percentages of high-density area on the articular surface.

RESULTS

High-density area in the college and professional groups were found in the anterior part of the captellum, posterior part of the trochlea and radial head. In the professional group, the percentages of high-density area in the anterior part of the capitellum, posterior part of the trochlea, radial head and olecranon were significantly greater than in the college group.

CONCLUSIONS

Stress distribution on the articular surface of the elbow joint was affected by pitching abilities or competitive levels. Our analysis indicates that high strength of stress in professional baseball players produce potential risk of elbow injuries.

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.

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.

Variable Bone Density of Scaphoid: Importance of Subchondral Screw Placement

Background  Ideal internal fixation of the scaphoid relies on adequate bone stock for screw purchase; so, knowledge of regional bone density of the scaphoid is crucial. Questions/Purpose  The purpose of this study was to evaluate regional variations in scaphoid bone density. Materials and Methods  Three-dimensional CT models of fractured scaphoids were created and sectioned into proximal/distal segments and then into quadrants (volar/dorsal/radial/ulnar). Concentric shells in the proximal and distal pole were constructed in 2-mm increments moving from exterior to interior. Bone density was measured in Hounsfield units (HU). Results  Bone density of the distal scaphoid (453.2 ± 70.8 HU) was less than the proximal scaphoid (619.8 ± 124.2 HU). There was no difference in bone density between the four quadrants in either pole. In both the poles, the first subchondral shell was the densest. In both the proximal and distal poles, bone density decreased significantly in all three deeper shells. Conclusion  The proximal scaphoid had a greater density than the distal scaphoid. Within the poles, there was no difference in bone density between the quadrants. The subchondral 2-mm shell had the greatest density. Bone density dropped off significantly between the first and second shell in both the proximal and distal scaphoids. Clinical Relevance  In scaphoid fracture ORIF, optimal screw placement engages the subchondral 2-mm shell, especially in the distal pole, which has an overall lower bone density, and the second shell has only two-third the density of the first shell.

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.

Long-term stress distribution patterns of the ankle joint in varus knee alignment assessed by computed tomography osteoabsorptiometry

PURPOSE

The stress distribution of an ankle under various physiological conditions is important for long-term survival of total ankle arthroplasty. The aim of this study was to measure subchondral bone density across the distal tibial joint surface in patients with malalignment/instability of the lower limb.

METHODS

We evaluated subchondral bone density across the distal tibial joint in patients with malalignment/instability of the knee by computed tomography (CT) osteoabsorptiometry from ten ankles as controls and from 27 ankles with varus deformity/instability of the knee. The quantitative analysis focused on the location of the high-density area at the articular surface, to determine the resultant long-term stress on the ankle joint.

RESULTS

The area of maximum density of subchondral bone was located in the medial part in all subjects. The pattern of maximum density in the anterolateral area showed stepwise increases with the development of varus deformity/instability of the knee.

CONCLUSIONS

Our results should prove helpful for designing new prostheses and determining clinical indications for total ankle arthroplasty.

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

BACKGROUND

It is important to understand the loading conditions when considering the pathology of shoulder disorders in overhead athletes. However, because throwing is a complicated motion and methods to directly determine stress distribution are complex, direct measurement of the stress distribution across the glenohumeral joint has not been attempted. Subchondral bone density reportedly reflects the cumulative stress acting on a joint surface under actual loading conditions.

QUESTIONS/PURPOSES

To assess alterations in stress distribution across the glenoid cavity caused by pitching, we investigated the distribution of subchondral bone density in nonathletic volunteers and asymptomatic baseball players, including fielders and pitchers.

METHODS

We collected CT imaging data from the dominant-side shoulder of 10 nonathletic volunteers (controls), 10 fielders, and 10 pitchers in a competitive college baseball league (all men aged 19–24 years, mean 20.7 years). We measured the distribution of subchondral bone density of the glenoid cavity using CT osteoabsorptiometry. The obtained stress distribution map was divided into four segments: anterosuperior, anteroinferior, posteroinferior, and posterosuperior regions. We quantitatively analyzed the location and percentages of high-density regions on the articular surface.

RESULTS

The percentages of high-density regions, including the anteroinferior and posterior segments, were greater in pitchers and fielders than in controls. The percentages of high-density regions did not differ between pitchers and fielders.

CONCLUSIONS

The bicentric density patterns indicated that the cumulative force of pitching activity affected the long-term stress distribution across the glenoid cavity.

CLINICAL RELEVANCE

Our data should be useful for analyzing pitching activity and clarifying the pathology of shoulder disorders associated with throwing.

Alterations in stress distribution patterns through the forearm joint surface of the elbow in baseball players assessed using computed tomography osteoabsorptiometry

BACKGROUND

The distribution of subchondral bone density well reflects long-term resultant stress acting on an articular surface in living joints. Consequently, a measurement of the distribution pattern can determine the stress distribution across the elbow joint surface under long-term loading conditions of baseball pitching. Our purpose was to elucidate the characteristic alterations in the distribution pattern of subchondral bone density across the forearm bones of the elbow with pitching activities. The hypothesis is that pitching activities would change the stress distribution in living subjects.

METHODS

The analysis was performed using computed tomography (CT) images obtained from the dominant elbow of ten nonthrowing athletes (control group), ten college baseball fielders (fielder group), and ten college baseball pitchers (pitcher group). The distribution pattern of subchondral bone density through the articular surface of the proximal radius and ulna bones was assessed using CT osteoabsorptiometry.

RESULTS

The maximum density area was located in the posterior part of the trochlea notch in all study participants. This maximum density area was significantly increased in the baseball groups compared with that in the control group. The pitcher group also showed a significant distribution of the maximum density area in the anterior part of the radial head.

CONCLUSION

Our analysis indicates that pitching activities increase actual stress on the articular surface not only in the posterior part of the trochlea notch but also in the anterior part of the radial head. The stress across the elbow may be expanded from the ulnohumeral to the radiohumeral joint by repetitive pitching activities in living subjects.

Distribution of bone mineral density at osteochondral donor sites in the patellofemoral joint among baseball players and controls

BACKGROUND

To theoretically minimize complications of osteochondral graft harvest from the knee, grafts should be obtained from the site of lowest stress distribution across the joint.

HYPOTHESIS

Long-term stress distribution over the patellofemoral (PF) joint surface is not equal in athletes.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Measurement of subchondral bone density can determine long-term resultant stress acting on an articular surface in living joints. Our analysis was performed using computed tomography (CT) image data obtained from bilateral knees of 10 college baseball fielders (fielder group) and 10 college baseball pitchers (pitcher group) and 2 control groups, including 10 college soccer players (soccer group) and 10 nonathletes (nonathlete group). The distribution pattern of subchondral bone density throughout the articular surface of the PF joint was assessed using the CT osteoabsorptiometry method. The quantitative analysis focused on the location of the low-density area at the articular surface to assess potential osteochondral donor sites.

RESULTS

All participants in the pitcher and fielder groups demonstrated a low-density area widely distributed in the proximal part of the lateral trochlea. On the other hand, a high-density area was located in the distal part of the lateral notch, of the medial notch, and of the medial trochlea. No apparent differences in the distribution pattern were found between the baseball groups and the control groups.

CONCLUSION

Our analysis, based on CT osteoabsorptiometry, indicates that the proximal lateral trochlea of the distal femur has the highest percentage area of low bone density at the PF joint level in donor knees of baseball players, soccer players, and nonathlete controls.

CLINICAL RELEVANCE

From a biomechanical viewpoint, the proximal lateral trochlea is the optimal site for harvesting osteochondral grafts in performing mosaicplasty for baseball players. This selection for the donor site may minimize postoperative PF joint symptoms.

OSTEOTOMY OF THE DISTAL RADIUS USING A FIXED-ANGLE VOLAR PLATE

OBJECTIVE

Skewed consolidation of the distal radius, due to sequelae of fractures, may cause functional incapacity, thus leading such patients to present pain, loss of strength and diminished mobility. Based on the excellent results obtained from surgical treatment of unstable fractures of the distal radius through a volar approach and use of rigid fixation with a fixed-angle volar plate, we started to use the same method for osteotomy of the distal radius.

METHODS

A retrospective review was conducted, and 20 patients treated between February 2002 and October 2009 were found. The mean length of follow-up was 43.9 months (range: 12 to 96 months). The surgical indications were persistent pain, deformity and functional limitation subsequent to a dorsally displaced fracture.

RESULTS

The mean preoperative deformity was 27° of dorsal tilt of the distal radius, 87° of ulnar tilt, and 7.3 mm of shortening of the radius. All the osteotomies consolidated and the final mean volar tilt was 6.2°, with ulnar tilt of 69.3° and shortening of 1 mm. The mean mobility of the wrist increased by 19.9° (flexion) and by 24° (extension). Mean forearm supination increased by 23.5° and pronation by 21.7°. Grip strength increased from 13.4 to 34.5 pounds.

CONCLUSION

Use of a fixed-angle volar plate for a volar approach towards osteotomy of the distal radius enables satisfactory correction of the deformities and eliminates the need for removal of the synthesis material caused by tendon complications.

Computed tomography osteoabsorptiometry alterations in stress distribution patterns through the wrist after radial shortening osteotomy for Kienböck disease

PURPOSE

The distribution pattern of subchondral bone density is considered to closely reflect the stress distribution across a joint under physiological loading conditions. Our purpose was to determine alterations in the distribution pattern of subchondral bone density across the distal articular surfaces of the radius and the ulna in patients with Kienböck disease after radial shortening.

METHODS

We collected preoperative and postoperative computed tomography (CT) image data from 7 wrists of 7 patients who had undergone radial shortening for Kienböck disease. We measured the distribution of subchondral bone density through the distal articular surface of the radius and the ulna using a CT osteoabsorptiometry method. The obtained data were quantitatively assessed by calculating the high-density area ratio of the entire radiocarpal joint surface, scaphoid fossa, lunate fossa, and distal ulnar surface.

RESULTS

At the mean postoperative period of 27 months, the mean high-density area ratio in the entire distal articular surface of the radius significantly decreased from 0.413 preoperatively to 0.141 postoperatively. The postoperative value in each fossa demonstrated a significant reduction from 0.253 to 0.096 in the scaphoid fossa and from 0.160 to 0.045 in the lunate fossa. No significant alteration in the value was found in the distal ulna at follow-up.

CONCLUSIONS

Our CT osteoabsorptiometry analysis suggests that the distribution of subchondral bone density in both scaphoid and lunate fossae notably decreases after radial shortening. This indicates that radial shortening unloads the lunate by reducing the actual stress across the distal articular surface of the radius in subjects with Kienböck disease.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Long-term stress distribution patterns across the elbow joint in baseball players assessed by computed tomography osteoabsorptiometry

BACKGROUND

The distribution pattern of subchondral bone density is considered to highly reflect the stress distribution across a joint under long-term physiologic loading conditions. Therefore, the biomechanical characteristics over the elbow joint surface under long-term loading conditions of baseball pitching can be determined by a measurement of the distribution pattern.

HYPOTHESIS

Stress distribution over the elbow joint surface alters with long-term pitching activities.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Computed tomography (CT) imaging data from the dominant elbow of 10 nonthrowing athletes, 10 college baseball fielders, and 10 college baseball pitchers were collected for the current analysis. The distribution of subchondral bone density through the distal articular surface of the humerus was measured using a CT osteoabsorptiometry method. The quantitative analysis of the obtained data focused on location and size of the maximum density area at the articular surface.

RESULTS

The maximum density area of subchondral bone across the articular surface of the distal humerus was located in the posterior part of the trochlea in all subjects. This maximum density area was significantly increased in the pitcher group, compared with that in other groups. Additionally, the pitcher group demonstrated a significant distribution of the maximum density area in the anterior part of the capitellum.

CONCLUSION

The results indicate that actual stress across the elbow is concentrated in the posterior part of the trochlea in humans. Baseball pitching may produce excessive or repetitive stress against not only this part, but also the anterior part of the capitellum. The majority of osteochondritis dissecans lesions affecting the elbow are found in the anterior part of the capitellum in throwing athletes. The results may support an important role of mechanical conditions in the cause of elbow osteochondritis dissecans.

Proximal row carpectomy for advanced Kienböck's disease: average 10-year follow-up

PURPOSE

To evaluate the clinical and radiographic results after a proximal row carpectomy for Lichtman stage III and IV Kienböck's disease at an average 10-year follow-up.

METHODS

Twenty-one patients with either Lichtman stage IIIA, IIIB, or IV Kienböck's disease were treated surgically at an average age of 38 years. At follow-up evaluation, each patient was evaluated subjectively with the Quick Disabilities of the Arm, Shoulder, and Hand and the Patient-Related Wrist Evaluation questionnaires (both are validated, patient-reported questionnaires assessing pain and function) and objectively with an assessment of range of motion and grip strength. Radiographs were obtained to assess the radiocapitate articulation.

RESULTS

Three patients had persistent pain after a proximal row carpectomy requiring a radiocapitate arthrodesis at a mean of 23 months (range, 5-53 months). Two of these 3 patients had preoperative stage IV disease. The remaining 18 patients were evaluated at an average follow-up of 10 years (range, 4-17 years). The average wrist flexion-extension arc was 105 degrees, which averaged 78% of that of the contralateral wrist. Average maximal grip strength was 35 kg, which averaged 87% of that of the contralateral wrist. Average Quick Disabilities of the Arm, Shoulder, and Hand score was 12 points and average Patient-Related Wrist Evaluation score was 17 points, each representing minimal functional limitation. Radiographic analysis at final follow-up demonstrated degeneration of the radiocapitate articulation in 16 patients. Narrowing of the joint space was rated as none in 2 wrists, partial in 10 wrists, and complete in 4 wrists. There was no significant association between the radiographic findings and the subjective and objective outcome.

CONCLUSIONS

At an average follow-up of 10 years, proximal row carpectomy is a reliable and durable procedure for patients with Lichtman stage IIIA or IIIB Kienböck's disease. Caution should be exercised in performing the procedure in patients with stage IV disease because of risk of early symptomatic radiocapitate degeneration.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Kienböck’s disease

Kienböck’s disease is a form of osteonecrosis affecting the lunate. Its aetiology remains unknown. Morphological variations, such as negative ulnar variance, high uncovering of the lunate, abnormal radial inclination and/or a trapezoidal shape of the lunate and the particular pattern of its vascularity may be predisposing factors. A history of trauma is common. The diagnosis is made on plain radiographs, but MRI can be helpful early in the disease. A CT scan is useful to demonstrate fracture or fragmentation of the lunate. Lichtman classified Kienböck disease into five stages. The natural history of the condition is not well known, and the symptoms do not correlate well with the changes in shape of the lunate and the degree of carpal collapse. There is no strong evidence to support any particular form of treatment. Many patients are improved by temporary immobilisation of the wrist, which does not stop the progression of carpal collapse. Radial shortening may be the treatment of choice in young symptomatic patients presenting with stages I to III-A of Kienböck’s disease and negative ulnar variance. Many other forms of surgical treatment have been described.

Long-term subjective and radiological outcome after reconstruction of Kienböck's disease stage 3 treated by a free vascularized iliac bone graft

PURPOSE

Various vascularized bone grafts are used for surgical treatment of Kienböck's disease. Long-term results of free vascularized iliac bone grafts for treatment of Kienböck's disease are not reported in the literature. The purpose of this study is to report the over-10-year results and to compare them with the 5-year results to determine whether the favorable intermediate-term results were maintained.

METHODS

Eighteen patients with Lichtman stage III were treated with free vascularized iliac bone grafting and followed up for a mean period of 13 years. Assessment included active range of wrist motion, grip strength, level of pain measured using the visual analog scale (VAS), and patient disability and functional outcome measured by the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire as well as the Green and O'Brien score. Radiological evaluation included Ståhl index, Youm carpal height index, radioscaphoid angle (RSA), radiolunate angle (RLA) and integration of the free vascularized bone graft. The long-term results were compared with both the preoperative condition and the 5-year results.

RESULTS

Postoperative x-rays showed definite osseointegration of the vascularized bone graft in 89% (16/18). The average flexion-extension arc, the wrist deviation arc, pain, and grip strength improved considerably after surgery, and the results were maintained for a long period. Pronation and supination were not restricted in pre- and postoperative range of motion. The mean DASH score at final follow-up was 8.4 points. The Green and O'Brien score showed 50% excellent, 31% good, and 19% fair results. The average Ståhl index and the average Youm index, improved postoperatively and could be maintained for over 10 years follow-up. Two patients presented with a resorption of the bone graft, with ongoing radiologic progression of Lichtman stage, reduced range of motion, and high pain level.

CONCLUSIONS

Free vascularized iliac bone grafting for Kienböck's disease is a reasonable treatment option, and clinical and radiological improvements last for a long period of time. Long-term restoration of carpal height could be demonstrated. Progression of disease could be prevented in 89% (16 of 18) of patients over a mean time of 13 years.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Bone density spatial patterns in the distal radius reflect habitual hand postures adopted by quadrupedal primates

Primates adopt diverse hand postures during terrestrial and above-branch quadrupedal locomotion--knuckle-walking, digitigrady, and palmigrady--that incorporate varying degrees of wrist dorsiflexion (i.e., extension). Although relationships between hand postures, wrist joint range of motion, and the external properties of wrist bones (e.g., surface morphology) have been examined, the relationship between hand postures and the internal properties of wrist bones (e.g., bone density) remains largely unexplored. Because articular joint surfaces transmit mechanical loads between conjoining limb bones, measures of density (e.g., magnitudes and patterns) in the subchondral cortical plate of bone of the distal radius can be used to evaluate load regimes experienced by the wrist joint in different hand postures. We assessed apparent (i.e. optical) density patterns in several extant catarrhine primate taxa partitioned into different hand posture groups: knuckle-walking apes, digitigrade monkeys, and palmigrade monkeys. Computed tomography osteoabsorptiometry (CT-OAM) was used to construct maximum intensity projection (MIP) maps of apparent densities. High apparent density areas were characterized relative to a dorsal-volar reference plane and compared across hand posture groups. All groups had large percentage areas of high apparent density in the dorsal region of the distal radial articular surface. Only knuckle-walking apes, however, had a large percentage area of high apparent density in the volar region of the distal radial articular surface. These patterns are consistent with radiocarpal articulations in specific hand postures as evidenced by available radiographic data and suggest that the different habitual hand postures adopted by monkeys and African apes during quadrupedal locomotion have different stereotypic loading patterns. This has implications for understanding the functional morphology and evolution of knuckle-walking and digitigrade hand postures in primates.

Increased Radiodensity of the Proximal Pole of the Scaphoid

OBJECTIVES

To determine whether the proximal pole (PP) of the scaphoid is denser than the distal pole (DP) in a diverse population of patients undergoing computed tomography (CT) imaging of the wrist.

METHODS

Sixty-nine patients who had CT of the wrist were retrospective reviewed. We measured CT density of the medullary bone of PP and DP of the scaphoid and calculated PP/DP ratio. To evaluate the variability of PP/DP ratio, we compared the ratios of these 3 groups. These patients were separated into 3 groups based on their diagnoses: group 1, healed scaphoids treated by casting; group 2, scaphoid nonunions; group 3, intact scaphoids.

RESULTS

Proximal pole was denser than DP in most subjects. Proximal pole/distal pole ratio was similar among groups (P < 0.05). Fracture healing, sex, and age did not affect this ratio. However, we did not study scaphoids with avascular necrosis.

CONCLUSIONS

Proximal pole was denser than DP in most of our subjects, including those with intact scaphoids, healing scaphoid fractures, and nonunions.

Habitual use of the primate forelimb is reflected in the material properties of subchondral bone in the distal radius

Bone mineral density is directly proportional to compressive strength, which affords an opportunity to estimate in vivo joint load history from the subchondral cortical plate of articular surfaces in isolated skeletal elements. Subchondral bone experiencing greater compressive loads should be of relatively greater density than subchondral bone experiencing less compressive loading. Distribution of the densest areas, either concentrated or diffuse, also may be influenced by the extent of habitual compressive loading. We evaluated subchondral bone in the distal radius of several primates whose locomotion could be characterized in one of three general ways (quadrupedal, suspensory or bipedal), each exemplifying a different manner of habitual forelimb loading (i.e. compression, tension or non-weight-bearing, respectively). We employed computed tomography osteoabsorptiometry (CT-OAM) to acquire optical densities from which false-colour maps were constructed. The false-colour maps were used to evaluate patterns in subchondral density (i.e. apparent density). Suspensory apes and bipedal humans had both smaller percentage areas and less well-defined concentrations of regions of high apparent density relative to quadrupedal primates. Quadrupedal primates exhibited a positive allometric effect of articular surface size on high-density area, whereas suspensory primates exhibited an isometric effect and bipedal humans exhibited no significant relationship between the two. A significant difference between groups characterized by predominantly compressive forelimb loading regimes vs. tensile or non-weight-bearing regimes indicates that subchondral apparent density in the distal radial articular surface distinguishes modes of habitually supporting of body mass.

Die Kraftübertragung am Handgelenk nach Skaphoid-, Trapezium- und Trapezoideumfusion

Scaphotrapeziotrapezoid (STT) arthrodesis has been proposed to stabilise the radial column and to redirect the load away from the lunate. Midterm effects on force transmission are still unclear. Six patients who were treated with triscaphe arthrodesis were examined after an average of 5 years using CT osteoabsorptiometry of both wrists. STT arthrodesis had been performed in four cases with Kienböck's disease type IIIb and in two cases of scaphotrapeziotrapezoid arthritis. At all contralateral wrists peak mineralisations were found beyond the lunate fossa and in the scaphoid fossa of the distal radius. At the side with STT arthrodesis there was only one peak. In five cases this density maximum was beyond the scaphoid fossa and in one case half beyond the lunate and half beyond the scaphoid fossa. Triscaphe arthrodesis allows load transmission from the lunate to the radial column.

The influence of posterior instrumentation on adjacent and transfixed facet joints in patients with thoracolumbar spinal injuries: a morphological in vivo study using computerized tomography osteoabsorptiometry

STUDY DESIGN

Subchondral mineralization of adjacent and transfixed facet joints was analyzed in patients with thoracolumbar spinal injuries, both before posterior instrumentation and after removal of the spinal implant.

OBJECTIVE

To examine the influence of posterior instrumentation on content and distribution of subchondral mineralization as a correlate of the long-term load acting on the adjacent and transfixed zygapophysial joints.

SUMMARY OF BACKGROUND DATA

Posterior stabilization plays an important role in the treatment of spinal injuries and is a standard technique for the treatment of thoracolumbar spinal fractures. Studies have shown that stress and motion in the adjacent segments are altered in the presence of instrumentation.

METHODS

Twenty-three patients with thoracolumbar spinal injuries had computerized tomography (CT) during the course of routine posttraumatic diagnostics and subsequently received bisegmental posterior fixation with an internal fixator. Second CT were obtained after removal of the fixation device, which was performed on an average of 9.4 months after the trauma. Patients were divided into 2 groups with follow-up CT taken within either less than 3 months (group A: average 7.3 days, 15 patients) or 6 and more months (group B: average 17 months, 8 patients) after the internal fixator had been removed. Quantitative and qualitative CT osteoabsorptiometry were used to assess changes in subchondral mineralization, reflecting the altered load acting on the adjacent and bridged zygapophysial joints.

RESULTS

There was a significant difference between preoperative and postoperative calcium values (P < 0.001) for the whole patient group. Mineralization decrease was significantly more often found than increase (P < 0.001). A separate analysis of the 2 groups of patients revealed significant differences between group A and B (P < 0.001). In group A, a mineralization decrease was found in 61.3% and an increase in 11.0% of the facet joints, while in group B, a mineralization decrease was shown in 21.9% and an increase in 41.0%. No significant differences between adjacent and transfixed facets were found except in group B, in which the suprajacent joints showed a significantly higher mineralization increase than the transfixed joints (P = 0.030).

CONCLUSIONS

Decrease in subchondral mineralization indicates reduced load acting on the examined zygapophysial joints. This finding in patients with early follow-up CT seems to be caused by reduced activity in most of the patients until removal of the spinal implant. In patients with longer intervals between removal of the fixator and second CT, higher loads acting on the adjacent and bridged joints are shown morphologically. Whether or not these changes lead to spondylarthritis has to be studied in a long-term follow-up.

Patterns of subchondral bone mineralization in the distal radioulnar joint

PURPOSE

Studies have shown that it is possible to derive direct knowledge about the actual mechanical conditions of the wrist by analyzing the subchondral mineralization. The aim of the present study was to evaluate the distribution of the subchondral bone mineralization of the distal radioulnar joint (DRUJ) noninvasively in living subjects by using computed tomography (CT) osteoabsorptiometry to gain new information about the long-term loading conditions.

METHODS

Twenty-two wrist joints were investigated in 11 healthy young subjects by means of CT osteoabsorptiometry. The CT scans of the DRUJ were taken in the axial plane in neutral position of the forearm and in both maximum pronation and supination. The CT datasets of 1.5-mm sections were obtained and then transferred to an image-analyzing system. The subchondral bone plate in each section was isolated, reconstructed in 3 dimensions, and converted into a false color series.

RESULTS

The maximum subchondral bone density in the sigmoid notch of the radius was found along the distal border in all wrists. It was located dorsally in 10 wrists, palmarly in 8 wrists, and centrally in 4 wrists. The maximum bone density on the corresponding articular surface of the ulna was found dorsally in 10 cases, centrally in 8 cases, and palmarly in 4 cases. In 13 cases the maximum bone density was found in direct opposition on radius and ulna in neutral position. A statistically significant difference could not be detected in subjects with an ulna minus variance nor in those with a DRUJ angulation greater than 10 degrees .

CONCLUSIONS

Our results show that in the sigmoid notch the load is transmitted through either the dorsal or palmar parts of the joint. In contrast the maximum bone density on the side of the ulna was found dorsally and centrally. We conclude that the ulna receives the maximum load in neutral position and supination, whereas because of the dorsopalmar translation of the ulnar head the radius may lead the ulna with either its palmar or dorsal borders during pronosupination. The ligamentous apparatus, the shape of the joint, and the ulna variance, however, may influence load transmission.

Ulnar variance and subchondral bone mineralization patterns in the distal articular surface of the radius

PURPOSE

Based on biomechanical experiments in specimens it is accepted widely that ulnar length determines loading of distal articular surface of the radius with ulna-minus variance increasing and ulna-plus variance decreasing the loading of the lunate compartment. Nevertheless a direct assessment of the actual loading conditions in the living is currently impossible. The aim of the present study is therefore to evaluate subchondral bone mineralization patterns to provide further information about the role of ulnar length in load transmission through the radiocarpal joint.

METHODS

Twelve wrists of healthy subjects with an average age of 33 years and an average congenital ulna-minus wrist of -2.8 mm (range, -4 to -1 mm) were examined by means of computed tomography-osteoabsorptiometry. A further 5 wrists in healthy subjects with an average age of 52 years and an average congenital ulna-plus variance of +3.0 mm (range, +2 to +4 mm) were examined with the same technique. Seventeen wrist joints of 9 healthy subjects with ulna-zero variance were examined in the control group.

RESULTS

The results show a mainly lunate mineralization pattern in subjects with ulna-minus wrists in 75% of the cases, which is more frequent than in subjects with ulna-zero wrists. The results in ulna-plus variance show a mainly scaphoid mineralization pattern in 100% of cases. The differences in mineralization patterns are statistically significant.

CONCLUSIONS

We conclude from these morphologic results in living subjects that ulnar length determines the peak mineralization patterns of the distal articular surface of the radius with a relatively lesser loading of the lunate fossa in ulna-plus variance and a relatively higher loading history in most cases of ulna-minus variance. The hypothesis, however, that ulna-minus variance is always a sign of a relatively higher loading history of the lunate fossa cannot be supported.

Stress distribution patterns at the coracoacromial arch in rotator cuff tear measured by computed tomography osteoabsorptiometry

When a rotator cuff tear occurs, forces compressing the humeral head toward the glenoid are disturbed, and the kinematics of the glenohumeral joint change. Therefore, stress distributions at the coracoacromial arch in cuff tear shoulders should differ from those in normal shoulders. To investigate this hypothesis, we studied stress distribution patterns at the coracoacromial arch in normal and cuff tear shoulders using a computed tomography (CT) osteoabsorptiometry method, in which bone density correlates directly with long-term physiologic loading. Eight normal subjects and 11 patients with cuff tear were examined. The stress distributions at the undersurface of the acromion and the posterolateral surface of the coracoid process differed markedly between normal and cuff tear shoulders. In cuff tear shoulders, a high-density area was located at the anterior or the anterolateral part of the undersurface of the acromion, while it was located at the posterior part in all but one normal shoulder. Additionally, a high-density area was located at the superior or the lateral part of the coracoid process in most of the cuff tear shoulders; on the other hand, it was located at the base in all but one normal shoulder. We believe that the differences in stress distribution patterns are due to impingement at the coracoacromial arch in cuff tear shoulders. CT osteoabsorptiometry can provide useful information in performing coracoacromial arch decompression for cuff tear shoulders.

Open treatment of stage III Kienböck's disease with lunate revascularization compared with arthroscopic treatment without revascularization

PURPOSE

The goal of this study was to compare the results of open scaphocapitate fusion and revascularization with the results of arthroscopic scaphocapitate fusion and capitate pole excision.

TYPE OF STUDY

Prospective randomized study.

METHODS

Between April 1997 and January 2000, 16 consecutive patients (5 men and 11 women with a mean age of 31 years [range, 18 to 61]) presenting with Kienböck's disease stage IIIA and stage IIIB were randomized to either open scaphocapitate fusion and lunate revascularization (group I) or fully arthroscopic scaphocapitate fusion and capitate pole excision (group II) groups. Cannulated 3.5-mm ASIF screws were used for the purpose of scaphocapitate fixation in both groups. Operation time, hospital stay, time to fusion, range of wrist motion at final follow-up, grip strength, and return to unrestricted activities of daily living were evaluated at 33 months' follow-up.

RESULTS

The mean operating time (153 v 99 minutes), hospital stay (3.6 v 2.3 days), and return to unrestricted daily activities (15 v 5.8 weeks) were shorter in group II. Average time to radiographically evident fusion was shorter in group I (7.25 weeks v 9 weeks). There was a significant increase in grip strength and in range of motion at final follow-up in both groups, and the final grip strength and range of motion was not different between the groups. There were no major complications in either group.

CONCLUSIONS

Although the number of patients was small and the follow-up period was short, arthroscopic scaphocapitate fusion and capitate pole excision in stage IIIA and IIIB Kienböck's disease resulted in shorter operating time, shorter hospital stay, earlier return to unrestricted daily activities, and equal range of motion and grip strength as compared with open scaphocapitate fusion and lunate revascularization. Determination of specific surgical indications for the benefits of arthroscopic treatment of Kienböck's disease must be analyzed in larger studies.

Treatment of Kienbock's disease with capitohamate arthrodesis: pain relief with minimal morbidity

Despite the large number of procedures available for treatment of Kienbock's disease, no single method has emerged as being clearly superior. Ultimately, the goal of treatment must be the relief of pain and maintaining wrist range of motion. The authors' experience with 45 consecutive wrists that had undergone capitohamate fusion for treatment of Lichtman's stage 1, 2, or 3 Kienbock's disease is presented. Average follow-up was 32 months (range, 4 to 107 months). All arthrodeses healed with an average time to fusion of 1.9 months. Postoperatively, 93 percent of patients had either no pain or less pain than they had preoperatively, with preservation of wrist range of motion and improved grip strength (52 percent of normal preoperatively to 72 percent of normal postoperatively). The authors conclude that capitohamate arthrodesis relieves pain in 93 percent of patients with stage 1, 2, or 3 Kienbock's disease and is an effective treatment for this disease.

Subchondral bone mineral density patterns representing the loading history of the wrist joint

Ten cadaver wrists were examined with CT-Absorptiometry in order to assess bone density in the subchondral bone. In normal wrists the distal radius contained two centroids of bone density, one in the lunate fossa and another in the scaphoid fossa. Pathologically altered wrists showed a shift in bone density towards the scaphoid fossa, with the subchondral bone in the lunate fossa and distal ulna becoming less dense. Bone density patterns in the wrist reflect the long-term force transmission. As bone density alters according to loading conditions, this method can be used to determine force transmission patterns before and after wrist surgery.