A biomechanical analysis of articular cartilage of the human elbow and a potential relationship to osteochondritis dissecans

Osteochondritis dissecans in children: location-dependent differences (part II: ankle and elbow)

The classic terminology "osteochondritis dissecans (OCD)" describes a pathologic alteration, centered at the osteochondral junction, involving the subchondral bone and/or its cartilaginous precursor, with risk for lesion instability and disruption of adjacent articular cartilage. Among children and young adults, these sites of osteochondrosis can be a cause of chronic joint pain and are most often found within the knee, the ankle, and the elbow joints. While Part I of this review series focused on shared key definitions, pathophysiologic principles, and imaging considerations, as well as unique differences between lesions at different locations within the knee joint, the current Part II article is devoted to lesions that involve the ankle and elbow joints. Following the outline of the Part I article, an evidence-based literature review on location-specific pathophysiology, imaging considerations, findings of lesion instability, and treatment selection considerations will be discussed for lesions involving the talar dome, capitellum, and humeral trochlea.

Elbow injuries in overhead throwing athletes: clinical evaluation, treatment, and osteopathic considerations

Injury to the elbow is very common in the throwing athlete and can potentially lead to long absences from play and, in the most severe scenarios, medical retirement. The throwing motion is a highly complex series of movements through the entire kinetic chain that results in very high angular velocities and valgus forces at the elbow joint. The repetitive nature of overhead throwing in combination with the high levels of accumulated force at the elbow puts both pediatric and adult athletes at risk of both acute and chronic overuse injuries of the elbow. This review provides an update on common injuries in the throwing athlete and covers clinical presentation, diagnosis, and treatment of these injuries.

Treatment and Early Outcomes of Capitellar Osteochondritis Dissecans

BACKGROUND

Treatment for osteochondritis dissecans (OCD) of the humeral capitellum has been predominantly guided by fragment stability and articular cartilage integrity. Nonoperative management is recommended for stable lesions, whereas surgical intervention is indicated for unstable lesions and those that fail nonoperative care. Several surgical options may be considered, although limited information is available regarding indications for specific surgical techniques and comparative postoperative results.

PURPOSE

To assess surgical outcomes of patients with capitellar OCD treated according to a decision-making approach focused on subchondral bone involvement.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients diagnosed with capitellar OCD at a tertiary academic center were enrolled in a prospective longitudinal cohort study. Patient information was collected at the time of enrollment, and OCD lesions were classified according to the Nelson grade. Clinical and radiologic data were collected both pre- and postoperatively for those undergoing surgical treatment. Surgical procedures were performed based on an evolving treatment framework that included considerations specifically for lesion containment and depth of subchondral bone disease. Timmerman scores were obtained to assess patient functional outcomes.

RESULTS

A total of 154 patients were prospectively enrolled, 19 of whom had bilateral disease. The mean age at presentation was 13.7 years; 39% were gymnasts and 28.5% were primary baseball or softball athletes. Surgery was performed on 145 elbows, including 43 drilling/microfracture procedures, 21 internal fixations, and 63 autologous osteochondral grafting (OG) procedures. Clinically, there were significant improvements in pain, elbow motion, and mechanical symptoms. Timmerman scores significantly improved after each type of surgical procedure. A total of 76% of patients returned to their primary sport. When stratified by the Nelson grade, patients with OG had lower revision surgery rates than those treated with drilling/microfracture and fixation. Furthermore, for Nelson grade 2 lesions, patients treated with OG had significantly better postoperative elbow motion and higher Timmerman scores compared with those treated with other procedures.

CONCLUSION

Using a treatment framework incorporating lesion containment and depth of subchondral bone disease, surgery for capitellar OCD provides clinical, radiologic, and functional improvements. Patients treated with OG may have lower revision rates and better functional outcomes compared with those treated with other surgical techniques, with OG warranting consideration even for lower-grade OCD lesions.

Arthroscopy and Microfracture for Osteochondritis Dissecans of the Capitellum in Adolescent Athletes Shows Favorable Return to Sport: A Systematic Review

PURPOSE

To assess return to sport (RTS) in the high-risk young athlete population with capitellar osteochondritis dissecans (OCD) undergoing arthroscopic microfracture (MFX) with or without debridement as well as associated indications, clinical outcomes, radiographic outcomes, and complications.

METHODS

A literature search of all published literature in the English language from PubMed, EMBASE, Scopus, and Cochrane from database inception to April 4, 2022, was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies presented demographics and outcomes for adolescent (<21 years old) patients diagnosed with capitellar OCD who underwent arthroscopic MFX (or drilling/subchondral drilling) or MFX (or drilling/subchondral drilling) with debridement (or loose body removal/chondroplasty). Studies containing multiple surgical techniques that did not distinguish characteristics and outcomes of individual patients by surgical technique were excluded. Additionally, if there was overlap in patient populations between 2 studies, the study with less outcome data was excluded. Extracted data included study properties, patient demographics, lesion characteristics, surgery details, and patient outcomes, including range of motion, outcome scores, and RTS rates. Bias was assessed via the Methodological Index for Non-Randomized Studies (MINORS).

RESULTS

Nine studies of 136 patients and 138 elbows met criteria. Included articles were published between 2005 and 2020 with MINORS scores of 8 to 14 (50% to 88%). The age ranged from 12.7 to 15.7 years with most patients being involved in baseball or gymnastics and a rate of dominant elbow involvement of 55% to 100%. Patient follow-up ranged from 16 to 138 months. All 9 studies reported RTS, ranging from 65% to 100%. Six of these studies categorized the level to which the patient returned, with patients RTS at the same level of competition ranging from 60% to 100%. Six studies reported complications, with a range rate of 0% to 43%; there were a total of 10 complications, 7 of which required reoperations.

CONCLUSIONS

Arthroscopic MFX with or without arthroscopic debridement is a safe and effective treatment for OCD lesions of the capitellum in young, athletic patients. Included studies reported improved clinical, radiographic, and patient-reported outcomes. Aside from 1 study reporting an RTS of 65%, the rate of RTS ranged from 86% to 100%. The percentage of patients returning to sport at the same level of competition ranged from 60% to 100% with a time to RTS ranging from 4.1 to 5 months. A single study reported a complication rate of 43%, while remaining studies reported complication rates between 0% and 19%, with loose bodies being the most common complication requiring reoperation. Follow-up ranged from 16 to 138 months.

LEVEL OF EVIDENCE

Level IV, systematic review of Level IV studies.

The effect of hemiarthroplasty implant modulus on contact mechanics: an experimental investigation

BACKGROUND

Hemiarthroplasties cause damage to the cartilage that they articulate against, which is a major limitation to their use. This study investigated the use of lower-stiffness materials to determine whether they improve hemiarthroplasty contact mechanics and thus reduce the risk of cartilage damage.

METHODS

Eleven fresh-frozen cadaveric upper extremities were disarticulated and fixed in a custom-built jig that applied a static load of 50 N to the radiocapitellar joint. Flexion angles of 0°, 45°, 90°, and 135° were tested with radial head implants made of cobalt-chrome (CoCr) and ultrahigh-molecular-weight polyethylene (UHMWPE) compared with the native radial head. A Tekscan thin-film sensor was used to measure the contact area and contact pressure between the radius and capitellum.

RESULTS

UHMWPE and CoCr were too stiff in the application of hemiarthroplasty, resulting in lower contact areas and higher contact pressures relative to the native joint. The native contact area was, on average, 42 ± 20 mm² larger than that of UHMWPE (P < .001) and 55 ± 24 mm² larger than that of CoCr (P < .001). UHMWPE had a contact area 13 ± 10 mm² greater than that of CoCr (P = .014).

DISCUSSION AND CONCLUSION

This study shows that even though UHMWPE has a stiffness several times lower than CoCr, the use of this material in hemiarthroplasty led to only a minor improvement in contact mechanics. Neither implant restored contact similar to the native articulation. Investigations into new materials to improve the contact mechanics of hemiarthroplasty should focus on materials with a lower stiffness than UHMWPE.

Osteochondritis Dissecans of Smaller Joints: The Elbow

This review presents the current understanding of the etiology, pathogenesis, and how to diagnose and treat osteochondritis dissecans (OCD) at the elbow joint followed by an analysis of particular characteristics and outcomes of the treatment. OCD is seen in patients with open growth plates (juvenile OCD [JOCD] and in adults [AOCD] with closed growth plates [adult OCD). The etiology at smaller joints remains as unclear as for the knee. Mechanical factors (throwing activities [capitulum] seem to play an important role. Clinical symptoms are unspecific. Thus, imaging techniques are most important for the diagnosis. In low-grade and stable lesions, treatment involves rest and different degrees of immobilization until healing. When surgery is necessary, the procedure depends on the OCD stage and on the state of the cartilage. With intact cartilage, retrograde procedures are favorable while with damaged cartilage, several techniques are used. Techniques such as drilling and microfracturing produce a reparative cartilage while other techniques reconstruct the defect with osteochondral grafts or cell-based procedures such as chondrocyte implantation. There is a tendency toward better results when reconstructive procedures for both the bone and cartilage are used. In addition, comorbidities at the joint have to be treated. Severe grades of osteoarthritis are rare.

The Effects of Initial Rehabilitation Exercise on Range of Motion, Muscular Strength, and Muscle Pain after Surgery for Osteochondritis Dissecans of the Humeral Capitellum in Middle and High School Baseball Players

Background:

This study evaluated the effects of a 4-week initial rehabilitation program in middle and high school baseball players who underwent removal of a loose body from osteochondritis dissecans of the capitellum humerus.

Methods:

Middle and high school baseball players with osteochondritis dissecans of the capitellum humerus were enrolled in this study. Each had more than 3 yr of experience and had undergone arthroscopic removal of loose bodies from the same expert at Kim’s Orthop Special Clinic in Seoul. The initial exercise rehabilitation program was based on a two-stage program. Body composition, range of motion of flexion and extension in the elbow and wrist joints, grip strength, and subjective pain scale were measured before and after rehabilitation. To assess the differences between groups, we used a two-way analysis of variance.

Results:

The range of motion for flexion and extension of the elbow and wrist joints, grip strength, and score on the visual analog scale each were significantly improved following the 4-week program (P<0.001), had an interactive effect in time × group (P<0.001), and had significance between groups (P<0.05).

Conclusion:

The 4-week initial rehabilitation exercise program might improve the overall range of motion of the elbow joint and has a positive therapeutic effect on grip strength and visual analog scores. However, future well-designed studies with more subjects and multicentric research groups are necessary for verification.

Ulnar collateral ligament dysfunction increases stress on the humeral capitellum: a finite element analysis

Background

Repetitive mechanical stress on the elbow joint during throwing is a cause of ulnar collateral ligament dysfunction that may increase the compressive force on the humeral capitellum. This study aimed to examine the effects of ulnar collateral ligament material properties on the humeral capitellum under valgus stress using the finite element method.

Methods

Computed tomography data of the dominant elbow of five healthy adults were used to create finite element models. The elbows were kept at 90° of flexion with the forearm in the neutral position, and the ulnar collateral ligament was reproduced using truss elements. The proximal humeral shaft was restrained, and valgus torque of 40 N·m was applied to the forearm. The ulnar collateral ligament condition was changed to simulate ulnar collateral ligament dysfunction. Ulnar collateral ligament stiffness values were changed to 72.3 N/mm, 63.3 N/mm, 54.2 N/mm, 45.2 N/mm, and 36.1 N/mm to simulate ulnar collateral ligament laxity. The ulnar collateral ligament toe region width was changed in increments of 0.5 mm from 0.0 to 2.5 mm to simulate ulnar collateral ligament loosening. We assessed the maximum equivalent stress and stress distribution on the humeral capitellum under these conditions.

Results

As ulnar collateral ligament stiffness decreased, the maximum equivalent stress on the humeral capitellum gradually increased under elbow valgus stress (P < .001). Regarding the change in the ulnar collateral ligament toe region width, as the toe region elongated, the maximum equivalent stress of the humeral capitellum increased significantly under elbow valgus stress (P < .001). On the capitellum, the equivalent stress on the most lateral part was significantly higher than that on other parts (P < .01 for all).

Conclusion

Under elbow valgus stress with elbow flexion of 90° and the forearm in the neutral position, ulnar collateral ligament dysfunction increased equivalent stress on the humeral capitellum during the finite element analysis. The highest equivalent stress was noted on the lateral part of the capitellum.

Osteochondritis Dissecans of the Capitellum :Review of the Literature

Osteochondritis dissecans (OCD) of the capitellum is a leading cause of elbow disability in adolescent baseball players. Previous studies have not found an association of player position with capitellar OCD. Elbow pain and a longer playing history might be related to progression of capitellar OCD but do not in themselves increase the risk of development of the condition. The cause of capitellar OCD is likely to include a combination of repetitive microtrauma and internal factors, such as ischemia and genetic predisposition. A combination of radiography, computed tomography, magnetic resonance imaging, and ultrasonography have aided our understanding of the pathology of capitellar OCD. Screening using ultrasonography enables early detection and provides an opportunity for successful conservative treatment. Treatment has conventionally included both operative and nonoperative measures based on the stage and size of the lesion, skeletal maturity, subjective symptoms, and structural integrity of the cartilage. Early-stage lesions respond better to nonoperative treatment than those in more advanced stages. Operative indications include persistent symptoms despite nonoperative treatment, symptomatic loose bodies, and displacement or detachment of fragments. J. Med. Invest. 67 : 217-221, August, 2020.

The effect of stem fit on the radiocapitellar contact mechanics of a metallic axisymmetric radial head hemiarthroplasty: is loose fit better than rigidly fixed?

BACKGROUND

Radial head hemiarthroplasty is commonly used to manage comminuted displaced fractures. Regarding implant fixation, current designs vary, with some prostheses aiming to achieve a tight "fixed" fit and others using a smooth stem with an over-reamed "loose" fit. The purpose of this study was to evaluate the effect of radial head hemiarthroplasty stem fit on radiocapitellar contact using a finite element model that simulated both fixed (size-for-size) and loose (1-, 2-, and 3-mm over-reamed) stem fits. It was hypothesized that a loose stem fit would improve radiocapitellar contact mechanics, with an increased contact area and decreased contact stress, by allowing the implant to find its "optimal" position with respect to the capitellum.

METHODS

Finite element models of the elbow were produced to compare the effects of stem fit on radiocapitellar contact of a metallic axisymmetric radial head implant. Radiocapitellar contact mechanics (contact area and maximum contact stress) were computed for 0°, 45°, 90°, and 135° of elbow flexion with the forearm in neutral rotation, pronation, and supination.

RESULTS

The data suggest that the loose smooth stem radial head implant may be functioning like a bipolar implant in optimizing radiocapitellar contact. Over-reaming of 3 mm produced a larger amount of stress concentration on the capitellum, suggesting there may be a limit to how loose a smooth stem implant should be implanted.

CONCLUSIONS

The loose 1 to 2 mm over-reamed stem provided optimal contact mechanics of the metallic axisymmetric radial head implant compared with the fixed stem.

Radial Head Changes in Osteochondritis Dissecans of the Humeral Capitellum

BACKGROUND

Osteochondritis dissecans (OCD) of the elbow has almost exclusively been described in the humeral capitellum, with only a small number of reports describing secondary osteochondral changes in the radial head.

HYPOTHESIS

The authors hypothesized that concomitant radial head lesions (RHLs) would be seen with capitellar OCD and that patients with RHLs would present with more advanced capitellar OCD lesions and would respond better to procedures restoring articular congruity.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 86 elbows from 82 patients (39 female patients; mean ± SD age, 13.8 ± 2.2 years; age range, 9.8-23.6 years) were treated for capitellar OCD and enrolled in a prospective registry. Clinical and radiographic data were compared between those with and without RHLs, with a median follow-up of 10.8 months (interquartile range, 6.2-17.1 months). Magnetic resonance imaging was used to characterize and measure RHLs and OCD lesions. Postoperative clinical results were compared between patients who underwent drilling and those who had osteochondral autograft transplantation surgery (OATS).

RESULTS

RHLs were present in 26 (30%) elbows-17 in the dominant arm. Edema was seen in 22 elbows; 17 had involvement of the anterior third of the radial epiphysis. Cysts were present in 4 elbows: 2 in the anterior third and 2 in the middle third. Blunting of the normal concave contour of the radial epiphysis was present in 10 elbows in the anterior third. Demographic and presenting clinical features were similar between those with and without RHLs. RHLs were more commonly seen in Nelson grade 4 OCD lesions (P = .04) as compared with elbows without RHLs. Elbows with RHLs that underwent OATS (n = 9) trended toward greater improvement in forearm range of motion (P = .058) and fewer persistent mechanical symptoms (P = .06) postoperatively as compared with elbows having RHLs that underwent drilling. There were no postoperative differences in elbows without RHLs that underwent OATS versus drilling.

CONCLUSION

RHLs were seen in one-third of elbows with capitellar OCD. Lesions predominantly occurred in the anterior RH in patients with more advanced capitellar lesions. Short-term clinical follow-up suggested greater improvement in range of motion and resolution of mechanical symptoms for patients with RHLs who were treated with OATS than with drilling.

Ulna-humerus contact mechanics: Finite element analysis and experimental measurements using a tactile pressure sensor

Elbow articular cartilage withstands high compressive and shear forces while protecting the bone from excessive loading. Better understanding of elbow cartilage contact mechanics can provide insight into cartilage degeneration. In this study a tactile pressure sensor was used to measure the contact pressure distribution within the ulno-humeral joint of two cadaver specimens at 20° flexion angle across three different axial loads of 80 N, 110 N, and 140 N. Corresponding 3D finite element (FE) models were constructed from magnetic resonance imaging (MRI) and contact analysis was performed for each specimen with boundary and loading conditions identical to the experiment. Direct comparison between FE results and experimental measurements was conducted for the validation of the FE models and a sensitivity analysis was employed for assessing the effect of cartilage parameters on the model's outputs. The results showed a good agreement between the FE models and the experiments in terms of contact characteristics. The sensitivity analysis demonstrated that outcomes of the model, particularly peak contact pressure is more sensitive to the Poisson's ratio rather than to Young's modulus under static conditions. This result suggests that selection of Poisson's ratio is very critical for accurate prediction of contact mechanics within the ulno-humeral joint.

Bilateral Osteochondritis Dissecans of the Capitellum in Fraternal Twins: A Case Report

CASE

We report the cases of 15-year-old male fraternal twins with bilateral osteochondritis dissecans (OCD) of the capitellum in the absence of syndromic features. At the time of presentation, they had been actively engaged in competitive rhythmic gymnastics for 3 years. Both patients had chronic symptoms in the right elbow, and both underwent arthroscopic evaluation and management.

CONCLUSION

The cases of these 2 patients provide evidence to support the theory that the etiology of OCD may have a genetic background.

Effect of Radial Head Implant Shape on Radiocapitellar Joint Congruency

PURPOSE

Radial head arthroplasty is indicated in displaced fractures in which comminution precludes successful internal fixation. Many types of radial head implants have been developed varying in material, methods of fixation, and degrees of modularity and geometry. The purpose of this study was to investigate the effect of radial head implant shape on radiocapitellar joint congruency.

METHODS

Joint congruency was quantified in 7 cadaveric specimens employing a registration and inter-surface distance algorithm and 3-dimensional models obtained using computed tomography. Forearm rotation was simulated after computer-guided implantation of an axisymmetric radial head, a population-based quasi-anatomic radial head implant, and a reverse-engineered anatomic radial head implant. Inter-surface distances were measured to investigate the relative position of the radial head implant and displayed on 3-dimensional color-contour maps. Surface area was measured for inter-surface distances (1.5 mm) and compared for each radial head geometry.

RESULTS

There were no statistical differences in the contact surface area between radial head implants during active or passive forearm rotation. The joint was more congruent (larger contact surface area) during active forearm rotation compared with passive forearm rotation.

CONCLUSIONS

This study investigated the effect of implant geometry on the radiocapitellar joint contact mechanics by examining a commercially available radial head system (axisymmetric), a quasi-anatomic design, and an anatomic reverse-engineered radial head implant. We found no statistical differences in radiocapitellar joint contact mechanics as measured by 3-dimensional joint congruency in cadaveric specimens undergoing continuous simulated forearm rotation.

CLINICAL RELEVANCE

The importance of choosing an implant that matches the general size of the native radial head is recognized, but the degree to which it is necessary to create an implant that replicates the native anatomy to restore elbow stability and prevent cartilage degenerative changes remains unclear. This study concluded that the geometry of the implant did not have a statistically significant effect on joint contact mechanics; therefore, future work is needed to examine additional factors related to implant design, such as material choice and implant positioning to investigate their influence on joint contact mechanics.

Current Concepts: Osteochondritis Dissecans of the Capitellum and the Role of Osteochondral Autograft Transplantation

Background: Osteochondritis dissecans (OCD) of the capitellum is a painful condition, which often affects young throwing athletes. Our current understanding regarding the etiology, risks factors, diagnosis, and efficacy of the available treatment options has expanded over recent years, however remains suboptimal. Recent data on patient-reported outcomes following osteochondral autograft transplantation (OAT) for the treatment of large osteochondral lesions of the capitellum have been promising but limited. This review seeks to critically analyze and summarize the available literature on the etiology, diagnosis, and reported outcomes associated with OCD of the capitellum and the use of OAT for its treatment. Methods: A comprehensive literature search was conducted. Unique and customized search strategies were formulated in PubMed, Embase, Scopus, Web of Science, and CENTRAL. Combinations of keywords and controlled vocabulary terms were utilized in order to cast a broad net. Relevant clinical, biomechanical, anatomic and imaging studies were reviewed along with recent review articles, and case series. Results: Forty-three articles from our initial literature search were found to be relevant for this review. The majority of these articles were either review articles, clinical studies, anatomic or imaging studies or biomechanical studies. Conclusions: Current evidence suggests that OAT may lead to better and more consistent outcomes than previously described methods for treating large OCD lesions of the capitellum.

The Effect of Radial Head Hemiarthroplasty Geometry on Proximal Radioulnar Joint Contact Mechanics

PURPOSE

To compare the joint contact area and peak contact stress of different radial head (RH) hemiarthroplasty articular profiles for the proximal radioulnar joint (PRUJ) to the native radial head with the hypothesis that the side radius and side angle closest to the native mating ulnar articular profile would provide the best contact mechanics.

METHODS

Finite element models generated from the computed tomography geometry of 14 native elbows (73 ± 17.5 years) were subjected to 12 different RH profiles having varying side radii (flat [r = ∞ mm], 16.25, 8.12, and 4.50 mm) and side angles (0°, 5°, and 10°) under a constant compressive 20-N medial load. Contact areas and peak contact stresses were computed and compared with the native joint.

RESULTS

On average, RH implants significantly reduced PRUJ contact area by 55% ± 16% and increased peak contact stress by 337% ± 241% compared with the native RH. The prosthesis side radius had significant effects on both contact area and stress, but side angle did not. The 16.25-mm radii produced the largest contact areas, and the 4.50-mm radius model generated the smallest contact areas. As the side radius was decreased, peak contact stress was reduced as the contact migrated toward the center of the native ulnar articulation, although the 8.12-mm radius achieved the lowest peak contact stress.

CONCLUSIONS

Whereas RH hemiarthroplasty side radius can affect both contact area and peak contact stress, the magnitude of the effect on contact area is relatively small compared with that of the peak contact stress. Furthermore, although a flat RH side profile with a side angle of 5° more closely matched the side profile of the native ulnas used in the present study, the optimal profile was found to be a smaller radius of 8.12 mm.

CLINICAL RELEVANCE

Optimizing PRUJ contact mechanics after metallic RH hemiarthroplasty may contribute to better clinical outcomes by reducing the potential for native cartilage degeneration.

Osteochondritis dissecans of the elbow

Capitellar osteochondritis dissecans (OCD) can be a significant problem in adolescent overhead athletes. The cause is likely multifactorial secondary to repetitive stresses, biomechanical mismatch, and a tenuous vascular supply of the capitellum. Recent literature reveals that the prevalence is likely higher than previously thought. This, in conjunction with increased levels of athletic competition in children at younger ages, has fed the recent interest in this topic. The literature continues to show that non-operative treatment is still successful for stable lesions. Unstable lesions, therefore, have been the focus of the new literature regarding operative management and outcomes. The aim of this paper is to provide a summary of current literature and an up-to-date approach to the diagnosis, evaluation, and treatment of osteochondritis dissecans of the capitellum.

In vivo three-dimensional elbow biomechanics during forearm rotation

BACKGROUND

It is unclear how elbow kinematics changes during forearm rotation. This study investigated in vivo 3-dimensional elbow kinematics during forearm rotation.

METHODS

We studied 12 normal elbows using in vivo 3-dimensional computed tomography data in maximum forearm supination, neutral, and maximum pronation with the elbows in extension. We measured the motion of the radius and ulna relative to the humerus using a markerless bone registration technique and the contact area of the radiocapitellar joint, proximal radioulnar joint, and ulnohumeral joint using a proximity mapping method.

RESULTS

When the forearm rotated from the supinated position to the pronated position, the radius showed significant varus rotation, internal rotation, and extension relative to the humerus. The center of the radial head significantly translated anteriorly, proximally, and laterally. The ulna significantly rotated in valgus, and the deepest point on the sagittal ridge of the trochlear notch translated medially with forearm pronation. The contact area of the radiocapitellar joint was largest in pronation. The contact area of the proximal radioulnar joint was largest in supination. The contact area of the ulnohumeral joint showed no significant change during forearm rotation.

CONCLUSIONS

In pronation, because of the proximal migration of the radial head, the radiocapitellar joint was most congruent compared with other positions. The proximal radioulnar joint was most congruent in supination. The ulnohumeral joint congruency was not affected by forearm rotation. This study provides useful information for understanding 3-dimensional elbow motion and joint osseous stability related to forearm rotation.

Validation of a Finite Element Humeroradial Joint Model of Contact Pressure Using Fuji Pressure Sensitive Film

A finite element (FE) elbow model was developed to predict the contact stress and contact area of the native humeroradial joint. The model was validated using Fuji pressure sensitive film with cadaveric elbows for which axial loads of 50, 100, and 200 N were applied through the radial head. Maximum contact stresses ranged from 1.7 to 4.32 MPa by FE predictions and from 1.34 to 3.84 MPa by pressure sensitive film measurement while contact areas extended from 39.33 to 77.86 mm2 and 29.73 to 83.34 mm2 by FE prediction and experimental measurement, respectively. Measurements from cadaveric testing and FE predictions showed the same patterns in both the maximum contact stress and contact area, as another demonstration of agreement. While measured contact pressures and contact areas validated the FE predictions, computed maximum stresses and contact area tended to overestimate the maximum contact stress and contact area.

Accuracy assessment of 3D bone reconstructions using CT: an intro comparison

Computed tomography provides high contrast imaging of the joint anatomy and is used routinely to reconstruct 3D models of the osseous and cartilage geometry (CT arthrography) for use in the design of orthopedic implants, for computer assisted surgeries and computational dynamic and structural analysis. The objective of this study was to assess the accuracy of bone and cartilage surface model reconstructions by comparing reconstructed geometries with bone digitizations obtained using an optical tracking system. Bone surface digitizations obtained in this study determined the ground truth measure for the underlying geometry. We evaluated the use of a commercially available reconstruction technique using clinical CT scanning protocols using the elbow joint as an example of a surface with complex geometry. To assess the accuracies of the reconstructed models (8 fresh frozen cadaveric specimens) against the ground truth bony digitization-as defined by this study-proximity mapping was used to calculate residual error. The overall mean error was less than 0.4 mm in the cortical region and 0.3 mm in the subchondral region of the bone. Similarly creating 3D cartilage surface models from CT scans using air contrast had a mean error of less than 0.3 mm. Results from this study indicate that clinical CT scanning protocols and commonly used and commercially available reconstruction algorithms can create models which accurately represent the true geometry.

Contact analysis of the native radiocapitellar joint compared with axisymmetric and nonaxisymmetric radial head hemiarthroplasty

BACKGROUND

Radial head (RH) implants are manufactured from stiff materials, resulting in reduced radiocapitellar contact area that may lead to cartilage degeneration. Although the native RH is nonaxisymmetric, most implants are axisymmetric, potentially contributing to altered contact mechanics. This study compared the joint contact area (Ac) and maximum contact stress (σmax) of axisymmetric and nonaxisymmetric RH implants to the native radiocapitellar joint.

METHODS

The contact mechanics of intact elbows derived from cadaveric computed tomography data (n = 15) were compared with axisymmetric (size: 18, 20, 22 mm) and nonaxisymmetric (size: 16 × 18, 18 × 20, 20 × 22 mm) RH hemiarthroplasty reconstructed elbows using Abaqus finite element software. Under a 100 N load, Ac and σmax were computed for ±90° pronation-supination and 0°, 45°, 90°, and 135° flexion.

RESULTS

Compared with native, both hemiarthroplasty models produced significantly lower Ac and higher σmax (P < .001). In the best orientation, the nonaxisymmetric RH provided significantly larger Ac at 0° and 135° flexion (P = .03, P = .007) and reduced levels of σmax at 45° and 90° flexion (P = .003, P < .001). However, there was also a worst orientation that reduced Ac and increased σmax for all flexion angles (P < .003 for all). The native RH was less sensitive to rotation than the nonaxisymmetric RH in terms of σmax (P < .001). The axisymmetric RH was not sensitive to rotation.

CONCLUSIONS

Whereas a nonaxisymmetric RH can provide improved contact mechanics at certain forearm rotations and flexions, there are also orientations where Ac is reduced and σmax is increased. Axisymmetric designs are more consistent throughout forearm rotation and therefore may be more forgiving than the nonaxisymmetric RH implant design used in this study.

Treatment of osteochondral lesions in the elbow: results after autologous osteochondral transplantation

BACKGROUND

Osteochondral lesions in the elbow still remain a challenging field of surgery. In recent years promising clinical results were described for the osteochondral transplantation technique. The aim of this retrospective study was to evaluate the clinical and radiological outcome in the mid-term follow-up of a large cohort of patients following osteochondral transplantation in the elbow.

METHODS

18 patients with advanced osteochondral lesions of the elbow treated by autologous osteochondral autograft cylinders and a minimum follow-up of 36 months were included in the study. The Broberg-Morrey score (BMS) and the American Shoulder and Elbow score (ASES) were used to assess elbow function and pain, respectively. The joint status was analyzed using plain radiographs and MRI scans taken from all patients at recent follow-up. In addition, the ipsilateral knee joint was examined for donor-site morbidity using the Lysholm knee score.

RESULTS

14 patients were evaluated with a mean follow-up of 7 years (range 3-14 years). The mean BMS was 95.1 (range 72-100) points. The ASES score also showed promising results: pain at worst 1.5 (range 0-5) points, pain at rest 0.4 (range 0-5) points, pain lifting loads 2.8 (range 0-8) points, repetitive movement pain 1.5 (range 0-8) points. The range of motion of the injured elbow was free and equal to the contralateral side. Signs of osteoarthritis could be found on plain radiographs in three patients. The MRIs at follow-up showed graft viability in all patients. However, a slight incongruency of the chondral surface could be detected in two patients. The average Lysholm score was 90.9 (range 0-70) points.

CONCLUSIONS

Osteochondral transplantation in the elbow leads to both clinical and radiographic good-to-excellent mid-term results and therefore represents a reasonable treatment option for advanced osteochondral lesions in the elbow.

LEVEL OF EVIDENCE

Retrospective study; Therapeutic Level IV.

Unique model evokes the supination/pronation deficits found after Mason II fractures

A rapid prototyping model of Mason II fracture was used to investigate baseline recommendations for surgical intervention founded on kinematic forearm rotational blockage. Exact replicas of the radial heads in nine cadaveric specimens were produced and specimens were tested in a physiologic elbow simulator. After testing supination/pronation, the rotations were repeated with native replicas and with replicas modeling 3 mm depressed Mason II fractures with and without a gap of 1 mm between the body and fragment. The fragments were located circumferentially around the radial head at 10, 2 and 6 o'clock positions. There was no statistical difference between the range of motion of the native case and the native replica without fracture. After inclusion of the fracture, seven of the nine specimens showed rotational blockages. A two-way ANOVA found no statistical difference due to type of Mason II fracture (p > 0.87) or fracture location (p > 0.27). A χ-square analysis showed that presence of a kinematic deficit with a fractured radial head was significant (p < 0.03). The results support continued surgical intervention for a 3 mm depressed fracture and also establish the use of the rapid prototype as a model for kinematic investigation of fractures in a cadaveric model when ligamentous attachments are preserved.

In vitro assessment of the contact mechanics of reverse-engineered distal humeral hemiarthroplasty prostheses

BACKGROUND

Distal humeral hemiarthroplasty alters cartilage contact mechanics, which may predispose to osteoarthritis. Current prostheses do not replicate the native anatomy, and therefore contribute to these changes. We hypothesized that prostheses reverse-engineered from the native bone shape would provide similar contact patterns as the native articulation.

METHODS

Reverse-engineered hemiarthroplasty prostheses were manufactured for five cadaveric elbows based on CT images of the distal humerus. Passive flexion trials with constant muscle forces were performed with the native articulation intact while bone motions were recorded using a motion tracking system. Motion trials were then repeated after the distal humerus was replaced with a corresponding reverse-engineered prosthesis. Contact areas and patterns were reconstructed using computer models created from CT scan images combined with the motion tracker data. The total contact areas, as well as the contact area within smaller sub-regions of the ulna and radius, were analyzed for changes resulting from hemiarthroplasty using repeated-measures ANOVAs.

FINDINGS

Contact area at the ulna and radius decreased on average 42% (SD 19%, P=.008) and 41% (SD 42%, P=.096), respectively. Contact area decreases were not uniform throughout the different sub-regions, suggesting that contact patterns were also altered.

INTERPRETATION

Reverse-engineered prostheses did not reproduce the same contact pattern as the native joints, possibly because the thickness of the distal humerus cartilage layer was neglected when generating the prosthesis shapes or as a consequence of the increased stiffness of the metallic implants. Alternative design strategies and materials for hemiarthroplasty should be considered in future work.

Animal models of cartilage repair

Cartilage repair in terms of replacement, or regeneration of damaged or diseased articular cartilage with functional tissue, is the ‘holy grail’ of joint surgery. A wide spectrum of strategies for cartilage repair currently exists and several of these techniques have been reported to be associated with successful clinical outcomes for appropriately selected indications. However, based on respective advantages, disadvantages, and limitations, no single strategy, or even combination of strategies, provides surgeons with viable options for attaining successful long-term outcomes in the majority of patients. As such, development of novel techniques and optimisation of current techniques need to be, and are, the focus of a great deal of research from the basic science level to clinical trials. Translational research that bridges scientific discoveries to clinical application involves the use of animal models in order to assess safety and efficacy for regulatory approval for human use. This review article provides an overview of animal models for cartilage repair.

Cite this article: Bone Joint Res 2014;4:89–94.

Short-term results of arthroscopic treatment of osteochondritis dissecans in skeletally immature patients

BACKGROUND

Osteochondritis dissecans (OCD) of the capitellum occurs in skeletally immature athletes, and most likely results from repetitive trauma during overhead activities. Treatment may consist of activity modifications, internal fixation, abrasion chondroplasty, microfracture, antegrade drilling, retrograde drilling, osteochondral autograft or allograft implantation, chondrocyte implantation, and rib autograft through arthroscopy or arthrotomy. One treatment modality has not been proven to be clearly more effective than the others. This study was undertaken to evaluate our treatment regimen that utilized arthroscopic-assisted treatments of capitellar OCD, including removal of loose bodies, antegrade or retrograde drilling, and chondroplasty in the pediatric population.

METHODS

All patients treated arthroscopically for a diagnosis of capitellar OCD over a 5-year period, were retrospectively reviewed. All were asked to return for follow-up questionnaire and radiographs. Exclusion criteria included those lost to follow-up. Demographics were recorded and range of motion was evaluated preoperatively and at most recent follow-up for flexion, extension, supination, and pronation. Preoperative and the most recent anterior/posterior and lateral radiographs of the elbow were reviewed. A 200-point elbow rating scale was used to assess patient outcomes. The arthroscopic appearance of the lesion was graded. Changes in preoperative to postoperative range of motion and size of lesion were compared using repeated measures analysis of variation.

RESULTS

There were 13 elbows in 12 patients; only 3 of the injuries occurred acutely. Mean age at the time of surgery was 13.1±1.07 (range, 10.8 to 14.6 y). Mean follow-up was 23.4±16.7 months (range, 2 to 60 mo). There were 3 grade I lesions, 2 grade II lesions, 1 grade IV lesion, and 7 grade V lesions. Seven of the lesions underwent transhumeral drilling, 2 transarticular drilling, 3 loose body removals, and 2 had only debridement. There were no postoperative infections or neurovascular injuries. Three of the elbows (20%) required eventual arthrotomy at a mean of 27.9 months after the index procedure. At final follow-up, 67% reported no pain and 33% reported occasional pain. No patients reported any swelling. Eighty-three percent reported no locking or catching and 17% reported occasional locking or catching. No patients reported any activity restrictions. The mean subjective score was 96±6 of 100 and the mean objective score was 100 of 100. Mean extension improved significantly from -17 to -7 degrees (P<0.001).

CONCLUSIONS

Treatment of children with OCD lesions of the capitellum with arthroscopic-assisted debridement and fenestration of the sclerotic rim (trans-humeral if overlaying cartilage is intact), plus fixation of the overlaying cartilage if not securely attached to the subchondral bone permits the return to physical activity, but may not allow return to the injury-inducing sport. Our short-term outcomes obtained using this regimen found this technique to be safe and reliable, but other interventions may be required if continued disability persists.

Osteochondritis dissecans of the elbow: excellent results in teenage athletes treated by arthroscopic debridement and microfracture

Aim

To extend the microfracture procedure, which has been proven successful on osteochondritis dissecans (OCD) lesions in the knee and ankle, to OCD lesions in the elbow.

Methods

Nine young patients were treated by arthroscopic debridement and microfracture by a single surgeon. The average age at operation was 15.0 years (median 15; range 12-19). The average length of the follow-up was 5.3 years (median 5; range 2-9). The follow-up included physical examination and patient interview with elbow function scoring. Success of treatment was determined according to pre-operative and follow-up Mayo Elbow Performance Index scores and the patients’ return to sports.

Results

Eight patients scored excellent results on the follow-up and 1 scored a good result. Four out of 9 patients were able to increase their training intensity, 2 returned to the same level of activity, 2 changed sports (due to reasons unrelated to the health of their elbow), and 1 left professional sports and started training only recreationally. No patients stopped participating in sports altogether.

Conclusions

We advocate arthroscopic microfracturing, followed by a strict rehabilitation regime, as a highly effective treatment for OCD of the humeral capitellum.

Pathomechanical significance of radial head subluxation in the onset of osteochondritis dissecans of the radial head

Osteochondritis dissecans of the elbow mainly involves the capitellum; however, no authors have reported the condition in the radial head with subluxation of the radial head. We report four cases in which osteochondritis dissecans involved the radial head and was accompanied by radial head subluxation. All patients were male and their ages ranged from 11 to 13 years (average, 11.8 years). All lesions were located at the posteromedial aspect of the radial head with anterior subluxation of the radial head. Fragment removal was performed in one case and ulnar osteotomy in two cases; the remaining case was treated conservatively with the prohibition of sports. Three cases had a good outcome, whereas obvious anterior subluxation of the radial head and limitation of elbow flexion remained in the case treated with fragment removal.

Osteochondral transplantation in the elbow leads to good clinical and radiologic long-term results: an 8- to 14-year follow-up examination

BACKGROUND

In the long-term follow-up after debridement, microfracture, or drilling of osteochondral lesions in the elbow, subsequent osteoarthritis is a problem. Osteochondral transplantation for these defects has become a more common procedure. However, long-term results are unknown.

PURPOSE

This study was undertaken to evaluate long-term clinical and radiologic outcomes of advanced osteochondral lesions in the elbow treated with osteochondral transplantation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The study included 8 patients with osteochondral lesions in the elbow who were treated by autologous osteochondral transplantation between 1996 and 2002. Patients (average age, 17 years) were evaluated pre- and postoperatively by Broberg-Morrey score to assess elbow function and by American Shoulder and Elbow Surgeons (ASES) score for pain analysis. In addition, radiographs (at the first postoperative day, and at 5-year and 10-year follow-up) and magnetic resonance images (8 to 12 weeks postoperatively, and at 5-year and 10-year follow-up) were made to evaluate the joint status. At last follow-up (range, 8-14 years postoperatively), 7 of 8 patients were seen for clinical examination and radiologic analysis.

RESULTS

The Broberg-Morrey score increased from an average of 75.9 ± 13.1 to 96.4 ± 2.4 and ASES score significantly improved as follows: worst pain, 7.9 ± 1.1 to 1.6 ± 1.9; rest pain, 3.14 ± 2.7 to 0.6 ± 1.5; weight-lifting pain, 7.6 ± 0.8 to 3.1 ± 1.6; and repetitive movement pain, 5.3 ± 2.4 to 1.6 ± 1.5. Compared with the contralateral side, there was a mean preoperative flexion lag of 12.5° ± 11.6°. At the final follow-up, flexion was free. The mean extension lag was reduced from average 5.4° ± 5.7° to 0°. Radiographs of 2 patients made at final follow-up showed mild signs of osteoarthritis (Kellgren and Lawrence grade I). Postoperative magnetic resonance images showed graft viability in all and a congruent chondral surface in 6 of 7 patients.

CONCLUSION

Clinical long-term results after osteochondral transplantation in the elbow are good to excellent and comparable with midterm results in the literature. Therefore, this technique is a reliable option for satisfactory long-term results regarding treatment of advanced osteochondral lesions in the elbow.

The current state of imaging the articular cartilage of the upper extremity

MR imaging has increasingly been used to image joints since its inception. Historically, there has been more emphasis on the evaluation of internal derangement rather than cartilaginous disease. This article reviews cartilaginous diseases of the upper extremity emphasizing those that can be assessed using current clinical MR imaging protocols and addresses the limitations of current imaging techniques in evaluating the articular cartilage of smaller joints. It also provides a brief overview of novel techniques that may be instituted in the future to improve the diagnostic performance of MR imaging in the evaluation of the articular cartilage of the upper extremity.

The impact of capitellar arthroplasty on elbow contact mechanics: Implications for implant design

BACKGROUND

Radiocapitellar arthroplasty is indicated for capitellar deficiency. Although current implants employ a spherical capitellar surface, the capitellum is elliptical. This has implications for congruency and wear in capitellar arthroplasty. Our objective was to evaluate the contact mechanics of radiocapitellar arthroplasty. We hypothesized that capitellar replacement would decrease joint contact area relative to the native articulation; and an anatomical implant design would replicate more normal contact morphology than a spherical implant.

METHODS

Eight paired humeri and radii were potted in a custom jig. A compressive load of 85N was applied with the articulation flexed at 45° in neutral forearm rotation. Joint casts were made and the articular contact area and shape were quantified. Anatomical and spherical capitellar implants were tested against the native radial head (hemiarthroplasty).

FINDINGS

The contact areas for the anatomical and spherical hemiarthroplasties were 59 and 51% of the native articulation (P<0.005), while the unicompartmental arthroplasties' contact areas were 84 and 89% (anatomical, spherical) of the native articulation (P<0.01). No implant was superior in recreating the native contact shape.

INTERPRETATION

Placement of any capitellar implant resulted in a large decrease in contact area when articulating with a native radial head. This suggests that the radial head cartilage would see a marked increase in contact pressure relative to the native articulation. The unicompartmental arthroplasties demonstrated an even larger reduction in contact area, raising concern about accelerated surface wear. Further investigation needs to correlate these contact mechanics to cartilage wear and implant longevity.

Osteochondral lesions of the capitellum do not affect elbow kinematics and stability with intact collateral ligaments: an in vitro biomechanical study

PURPOSE

Osteochondritis dissecans (OCD) of the capitellum most commonly affects adolescent pitchers and gymnasts, who present with pain and mechanical symptoms. Patients with larger lesions have poorer outcomes, possibly related to increased contact pressures on the surrounding articular surface with or without instability. The purpose of this in vitro study was to determine whether displaced OCD lesions of the capitellum lead to altered kinematics and stability of the elbow.

METHODS

We mounted 9 fresh-frozen cadaveric arms in an upper extremity joint testing system, with cables attaching the tendons of the major muscles to motors and pneumatic actuators. An electromagnetic receiver on the ulna enabled quantification of the kinematics of the radius and ulna with respect to the humerus. We used 3-dimensional computed tomography scans and computer-assisted techniques to navigate sequential osteochondral defects ranging in size from 12.5% to 100% of the capitellum. The arms were subjected to active and passive flexion in both the vertical and valgus positions with the forearm in both pronation and supination.

RESULTS

We found no significant differences in valgus angulation or ulnar rotation between any of the OCD lesions and the intact elbow during flexion, regardless of arm position or forearm rotation.

CONCLUSIONS

Osteochondritis dissecans lesions of the capitellum, both small and large, did not alter the ulnohumeral kinematics and stability with intact collateral ligaments. Therefore, excision of unfixable osteochondral fragments of the capitellum in the setting of intact collateral ligaments can be considered without the risk of creating instability.

Osteochondritis dissecans of the capitellum: current concepts

Osteochondritis dissecans (OCD) of the capitellum is an uncommon disorder seen primarily in the adolescent overhead athlete. Unlike Panner disease, a self-limiting condition of the immature capitellum, OCD is multifactorial and likely results from microtrauma in the setting of cartilage mismatch and vascular susceptibility. The natural history of OCD is poorly understood, and degenerative joint disease may develop over time. Multiple modalities aid in diagnosis, including radiography, MRI, and magnetic resonance arthrography. Lesion size, location, and grade determine management, which should attempt to address subchondral bone loss and articular cartilage damage. Early, stable lesions are managed with rest. Surgery should be considered for unstable lesions. Most investigators advocate arthroscopic débridement with marrow stimulation. Fragment fixation and bone grafting also have provided good short-term results, but concerns persist regarding the healing potential of advanced lesions. Osteochondral autograft transplantation appears to be promising and should be reserved for larger, higher grade lesions. Clinical outcomes and return to sport are variable. Longer-term follow-up studies are necessary to fully assess surgical management, and patients must be counseled appropriately.

Osteochondritis dissecans of the capitellum

Osteochondritis dissecans of the capitellum is a well-recognized cause of elbow pain and disability in the adolescent athlete. This condition typically affects young athletes, such as throwers and gymnasts, involved in high-demand, repetitive overhead, or weightbearing activities. The true cause, natural history, and optimal treatment of osteochondritis dissecans of the capitellum remain unknown. Suspicion of this condition warrants investigation with proper radiographs and magnetic resonance imaging. Prompt recognition of this disorder and institution of nonoperative treatment for early, stable lesions can result in healing with later resumption of sporting activities. Patients with unstable lesions or those failing nonoperative therapy require operative intervention with treatment based on lesion size and extent. Historically, surgical treatment included arthrotomy with loose body removal and curettage of the residual osteochondral defect base. The introduction of elbow arthroscopy in the treatment of osteochondritis dissecans of the capitellum permits a thorough lesion assessment and evaluation of the entire elbow joint with the ability to treat the lesion and coexistent pathology in a minimally invasive fashion. Unfortunately, the prognosis for advanced lesions remains more guarded, but short-term results after newer reconstruction techniques are promising.

MR imaging in congenital and acquired disorders of the pediatric upper extremity

Various congenital and acquired disorders can affect the upper extremity in pediatric and adolescent patients. MR imaging can provide unique anatomic and diagnostic information in the evaluation of many of these disorders, including inflammatory, infectious, neoplastic, and arthritic conditions. This article rounds out the issue on pediatric musculoskeletal MR imaging. It focuses on the evaluation of more common congenital disorders, and mainly sports-related injuries of the shoulder, elbow, and wrist in children. MR imaging can be more challenging in diagnosis of some of these disorders. Features of overuse injuries in skeletally immature athletes are a unifying theme throughout the article.

Elbow pain in pediatrics

The pediatric and adolescent elbow is subject to both acute and chronic overuse injuries. The practitioner should develop a classification system to evaluate all such injuries, with first focusing on whether the injury represents an acute episode or rather it represents a more chronic problem. In addition, localizing the area of pain as being either medial, lateral, or posterior can better help differentiate the diagnosis. Youth baseball pitchers and throwers are particularly at risk for overuse injuries of the elbow, most of which are related to an injury mechanism termed "valgus extension overload". The most common entity related to this is termed "Little Leaguer's Elbow." Treatment is usually conservative, but for some injuries surgery may be required, especially for displaced medial epicondylar avulsion fractures. Other acute injuries also should be easily recognizable by the general clinician including annular ligament displacement (nursemaid's elbow) which represents one of the most common upper extremity injuries presenting to emergency rooms in youngsters under the age of 6. Most studies seem to indicate a hyperpronation reduction technique may be more successful then the flexion/supination technique. It is also important to have an awareness of some of the common elbow fractures seen in the younger patient, in particularly supracondylar fractures owing to their high propensity for complications. When evaluating the elbow for fractures, it is necessary to have an understanding of the appearance of the ossification centers seen on the pediatric elbow.

Compressive properties of cartilage-like tissues repaired in vivo with scaffold-free, tissue engineered constructs

BACKGROUND

It is crucial to develop an effective methodology for restoring adequate compressive properties to osteoarthritic cartilage. We have developed a scaffold-free tissue engineered construct cultured from synovium-derived mesenchymal stem cells. However, the compressive properties of cartilage-like tissues repaired with the construct have not been fully determined.

METHODS

Synovium-derived mesenchymal stem cells were cultured in Dulbecco's modified Eagle's medium to produce the tissue engineered construct. Implantation of the construct into cylindrically-shaped partial defects in femoral cartilage in an experimental porcine model was performed. Six months after implantation, cartilage-like tissues repaired with the construct were subjected to static and cyclic compression tests using a micro-unconfined compression test apparatus developed in our laboratory.

FINDINGS

The developed apparatus was validated in preliminary examinations. The repaired tissues exhibited rate-dependent viscoelastic properties; the compressive modulus was slightly lower than that of normal cartilage at a rate of 4 microm/s, while no difference was observed at a rate of 100 microm/s. In contrast, the repaired tissue without the construct exhibited rate-independent, non-viscoelastic properties. In the cyclic compression test, however, the compressive strain was significantly larger in both repaired tissues as compared with normal cartilage.

INTERPRETATION

Although the quasi-static compressive properties of the repaired tissue with the construct, indicating rate-dependent and viscoelastic behaviors, are comparable to normal cartilage, the cyclic compressive strain increases more rapidly than in normal cartilage. It is suggested that the differences between the tissues and normal cartilage are attributable to the increased permeability of the extracellular matrix.

Intraoperative acoustic evaluation of living human cartilage of the elbow and knee during mosaicplasty for osteochondritis dissecans of the elbow: an in vivo study

BACKGROUND

Autologous osteochondral mosaicplasty for osteochondritis dissecans of the capitellum is being used increasingly in adolescent patients. Little research has been published on the material properties of living human cartilage of the elbow and knee.

HYPOTHESIS

The cartilage of the osteochondritis dissecans lesion is detected as degenerated by ultrasound. The material properties of the cartilage of the intact part of the elbow are not different from those of the intact knee except in thickness.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The authors studied 10 young male athletes with osteochondritis dissecans of the capitellum who underwent mosaicplasty. An acoustic probe was used for measurement, and the wavelet transform method was used. Three parameters were used: signal intensity (index of cartilage stiffness), signal duration (index of roughness), and signal interval (index of thickness).

RESULTS

The cartilage of the osteochondritis dissecans lesion had lower signal intensity than did the intact part of the capitellum. The cartilage of the radial head opposite the capitellum had significantly lower signal intensity and higher signal duration than did other sites. The signal intensity of the radial head was significantly higher in early-stage patients than in late-stage patients, although the macroscopic view was almost all intact. The signal intensity of the plug was decreased significantly after grafting.

CONCLUSION

The osteochondritis dissecans lesion had lower signal intensity than did the intact part of the capitellum. Although the macroscopic view looked intact, the radial head cartilage was degenerated as measured acoustically.

CLINICAL RELEVANCE

Not only the cartilage of the capitellum but the cartilage of the radial head are acoustically degenerated in osteochondritis dissecans patients. Plugs might be damaged in the transplanting procedure, and further follow-up is necessary.