Radial Head

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James A Johnson - One of the best experts on this subject based on the ideXlab platform.

  • design of anatomical population based and patient specific Radial Head implants
    Journal of Hand Surgery (European Volume), 2017
    Co-Authors: Emily A Lalone, Graham J W King, Simon R Deluce, Hannah L Shannon, James A Johnson
    Abstract:

    Purpose The objective of this study was to characterize the morphology of the Radial Head and design population-based anatomical and patient-specific Radial Head implants. Methods Computed tomography (CT) images of 50 normal cadaveric upper extremities (34 male, 16 female) were obtained using a 64-slice CT scanner. Surface models were ellipse-fitted and characterized. Using an intersurface distance mapping approach, the surface geometry of the population-based anatomical design (PB-An), 3 distinct patient-specific designs, and an existing axisymmetrical implant (Com-Axi) were compared with the native Radial Head and the overall surface mismatch was measured. Results Morphological analysis indicated that the diameters of the outer and rim ellipses were correlated. The mean mismatch for the existing commercially available axisymmetrical implants was 0.5 ± 0.1 mm.The PB-An implants showed significantly reduced surface mismatch (0.4 ± 0.2 mm). The PS-An implant using 82 parameters in its design (0.1 ± 0.0 mm), had the lowest mean surface mismatch of any of the implants investigated. Conclusions The mean surface mismatch of Radial Head implants may be reduced using reverse engineering techniques to determine the required parameters for both population-based and patient-specific implant designs. Whether there is a significant clinical advantage of a more anatomically shaped Radial Head implant requires additional study. More anatomical implant shapes rely on a surgical technique to accurately position these implants during surgery. It is unclear if this can be achieved clinically using conventional techniques or whether computer-assisted surgery will be required to realize the potential advantages of a more anatomical implant. Clinical relevance This study characterized the morphology of the Radial Head with implications for population-based anatomical implants and patient-specific implants. The overall design of each implant was quantitatively compared with the native Radial Head. This study has implications for the design of patient-specific/anatomical implants and compares their use with commercially available generic implants.

  • implications of Radial Head hemiarthroplasty dish depth on radiocapitellar contact mechanics
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Elizabeth S Irish, Ryan Willing, Graham J W King, Daniel G G Langohr, James A Johnson
    Abstract:

    Purpose To investigate the effect of Radial Head implant dish depth on radiocapitellar joint contact mechanics. Methods Computed tomography images of 13 fresh-frozen cadaveric humeri were reconstructed into 3-dimensional finite element models with accurate cartilage geometry. Native humeri were paired with the corresponding native Radial Heads and axisymmetric Radial Head prosthesis models of the following dish depths: 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. Radiocapitellar contact mechanics were quantified at 4 different flexion angles (0°, 45°, 90°, and 135°) with a 100-N axial load applied to the Radial Head using a modeling protocol previously validated by cadaveric studies. The Radial Head was permitted to translate freely to its optimal position while the humerus was fully constrained. Output variables were contact area and peak contact stress. Results All prostheses had significantly decreased contact area and increased peak contact stress at all flexion angles relative to the native radiocapitellar joint. Contact area increased with prosthesis dish depth until reaching a plateau with a predicted local maximum at a mean depth of 3.2 ± 0.7 mm. Peak contact stress was elevated for both the shallowest and deepest models and reached a predicted local minimum at a mean depth of 1.8 ± 0.3 mm. Conclusions Contact area and peak contact stress were dependent on Radial Head prosthesis dish depth. There was an optimal implant dish depth for radiocapitellar contact mechanics at approximately 2 mm. Clinical relevance Optimizing radiocapitellar contact mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation.

  • effect of Radial Head implant shape on joint contact area and location during static loading
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Hannah L Shannon, Ryan Willing, Graham J W King, Emily A Lalone, Simon R Deluce, James A Johnson
    Abstract:

    Purpose To examine the effect of implant shape on radiocapitellar joint contact area and location in vitro. Methods We used 8 fresh-frozen cadaveric upper extremities. An elbow loading simulator examined joint contact in pronation, neutral rotation, and supination with the elbow at 90° flexion. Muscle tendons were attached to pneumatic actuators to allow for computer-controlled loading to achieve the desired forearm rotation. We performed testing with the native Radial Head, an axisymmetric implant, a reverse-engineered patient-specific implant, and a population-based quasi-anatomic implant. Implants were inserted using computer navigation. Contact area and location were quantified using a casting technique. Results We found no significant difference between contact locations for the native Radial Head and the 3 implants. All of the implants had a contact area lower than the native Radial Head; however, only the axisymmetric implant was significantly different. There was no significant difference in contact area between implant shapes. Conclusions The similar contact areas and locations of the 3 implant designs suggest that the shape of the implant may not be important with respect to radiocapitellar joint contact mechanics when placed optimally using computer navigation. Further work is needed to explore the sensitivity of Radial Head implant malpositioning on articular contact. The lower contact area of the Radial Head implants relative to the native Radial Head is similar to previous benchtop studies and is likely the result of the greater stiffness of the implant. Clinical relevance Radial Head implant shape does not appear to have a pronounced influence on articular contact, and both axisymmetric and anatomic metal designs result in elevated cartilage stress relative to the intact state.

  • the bicipital tuberosity and distal radius are unreliable landmarks for Radial Head implant alignment
    Journal of Shoulder and Elbow Surgery, 2013
    Co-Authors: Ryan N Katchky, James A Johnson, Graham J W King, George S. Athwal
    Abstract:

    Background As more anatomic asymmetric Radial Head implants emerge, it is necessary to determine the optimal landmarks to ensure correct rotational orientation. The bicipital tuberosity and distal radius are possible bony landmarks that can be used for rotational alignment of asymmetric prostheses; however, they have not been validated. The purpose of this study was to evaluate the reliability of the bicipital tuberosity and distal radius as rotational landmarks for orientation of asymmetric Radial Head prostheses. Methods Measurements were made from computer tomography scans of 50 elbows in order to determine the rotational relationships between the Radial Head, bicipital tuberosity, biceps tendon footprint, and distal radius. Results The maximum Radial Head diameter was oriented 65° ± 28° from the bicipital tuberosity, 119° ± 38° from the biceps tendon footprint, 82° ± 29° from the Radial styloid, and 76° ± 28° from the volar surface of the distal radius. All of these landmarks had a significantly greater variance than a proposed acceptable clinical tolerance of 10° ( P Conclusion The results demonstrate that the measured landmarks show no consistent rotational relationship with the maximum diameter of the Radial Head. In order to maximize the utility of more anatomic asymmetric Radial Head implant systems, further studies are necessary to identify more reliable rotational landmarks to ensure optimal implant positioning.

  • the effect of Radial Head excision and arthroplasty on elbow kinematics and stability
    Journal of Bone and Joint Surgery American Volume, 2004
    Co-Authors: Daphne M Beingessner, Cynthia E Dunning, Karen D Gordon, James A Johnson, Graham J W King
    Abstract:

    Background: Radial Head fractures are common injuries. Comminuted Radial Head fractures often are treated with Radial Head excision with or without Radial Head arthroplasty. The purpose of the present study was to determine the effect of Radial Head excision and arthroplasty on the kinematics and stability of elbows with intact and disrupted ligaments. We hypothesized that elbow kinematics and stability would be (1) altered after Radial Head excision in elbows with intact and disrupted ligaments, (2) restored after Radial Head arthroplasty in elbows with intact ligaments, and (3) partially restored after Radial Head arthroplasty in elbows with disrupted ligaments. Methods: Eight cadaveric upper extremities were studied in an in vitro elbow simulator that employed computer-controlled actuators to govern tendon-loading. Testing was performed in stable, medial collateral ligament-deficient, and lateral collateral ligament-deficient elbows with the Radial Head intact, with the Radial Head excised, and after Radial Head arthroplasty. Valgus angulation and rotational kinematics were determined during passive and simulated active motion with the arm dependent. Maximum varus-valgus laxity was measured with the arm in a gravity-loaded position. Results: In specimens with intact ligaments, elbow kinematics were altered and varus-valgus laxity was increased after Radial Head excision and both were corrected after Radial Head arthroplasty. In specimens with disrupted ligaments, elbow kinematics were altered after Radial Head excision and were similar to those observed in specimens with a native Radial Head after Radial Head arthroplasty. Varus-valgus laxity was increased after ligament disruption and was further increased after Radial Head excision. Varus-valgus laxity was corrected after Radial Head arthroplasty and ligament repair; however, it was not corrected after Radial Head arthroplasty without ligament repair. Conclusions: Radial Head excision causes altered elbow kinematics and increased laxity. The kinematics and laxity of stable elbows after Radial Head arthroplasty are similar to those of elbows with a native Radial Head. However, Radial Head arthroplasty alone may be insufficient for the treatment of complex fractures that are associated with damage to the collateral ligaments as arthroplasty alone does not restore stability to elbows with ligament injuries. Clinical Relevance: Kinematics are altered after Radial Head excision, even in elbows with intact ligaments, and additional clinical study is needed in order to determine the long-term effects of this instability. Radial Head arthroplasty alone does not adequately restore stability to elbows that have a ligamentous injury, and concomitant repair of ligaments and muscular origins should be considered at the time of surgical repair.

Graham J W King - One of the best experts on this subject based on the ideXlab platform.

  • design of anatomical population based and patient specific Radial Head implants
    Journal of Hand Surgery (European Volume), 2017
    Co-Authors: Emily A Lalone, Graham J W King, Simon R Deluce, Hannah L Shannon, James A Johnson
    Abstract:

    Purpose The objective of this study was to characterize the morphology of the Radial Head and design population-based anatomical and patient-specific Radial Head implants. Methods Computed tomography (CT) images of 50 normal cadaveric upper extremities (34 male, 16 female) were obtained using a 64-slice CT scanner. Surface models were ellipse-fitted and characterized. Using an intersurface distance mapping approach, the surface geometry of the population-based anatomical design (PB-An), 3 distinct patient-specific designs, and an existing axisymmetrical implant (Com-Axi) were compared with the native Radial Head and the overall surface mismatch was measured. Results Morphological analysis indicated that the diameters of the outer and rim ellipses were correlated. The mean mismatch for the existing commercially available axisymmetrical implants was 0.5 ± 0.1 mm.The PB-An implants showed significantly reduced surface mismatch (0.4 ± 0.2 mm). The PS-An implant using 82 parameters in its design (0.1 ± 0.0 mm), had the lowest mean surface mismatch of any of the implants investigated. Conclusions The mean surface mismatch of Radial Head implants may be reduced using reverse engineering techniques to determine the required parameters for both population-based and patient-specific implant designs. Whether there is a significant clinical advantage of a more anatomically shaped Radial Head implant requires additional study. More anatomical implant shapes rely on a surgical technique to accurately position these implants during surgery. It is unclear if this can be achieved clinically using conventional techniques or whether computer-assisted surgery will be required to realize the potential advantages of a more anatomical implant. Clinical relevance This study characterized the morphology of the Radial Head with implications for population-based anatomical implants and patient-specific implants. The overall design of each implant was quantitatively compared with the native Radial Head. This study has implications for the design of patient-specific/anatomical implants and compares their use with commercially available generic implants.

  • implications of Radial Head hemiarthroplasty dish depth on radiocapitellar contact mechanics
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Elizabeth S Irish, Ryan Willing, Graham J W King, Daniel G G Langohr, James A Johnson
    Abstract:

    Purpose To investigate the effect of Radial Head implant dish depth on radiocapitellar joint contact mechanics. Methods Computed tomography images of 13 fresh-frozen cadaveric humeri were reconstructed into 3-dimensional finite element models with accurate cartilage geometry. Native humeri were paired with the corresponding native Radial Heads and axisymmetric Radial Head prosthesis models of the following dish depths: 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. Radiocapitellar contact mechanics were quantified at 4 different flexion angles (0°, 45°, 90°, and 135°) with a 100-N axial load applied to the Radial Head using a modeling protocol previously validated by cadaveric studies. The Radial Head was permitted to translate freely to its optimal position while the humerus was fully constrained. Output variables were contact area and peak contact stress. Results All prostheses had significantly decreased contact area and increased peak contact stress at all flexion angles relative to the native radiocapitellar joint. Contact area increased with prosthesis dish depth until reaching a plateau with a predicted local maximum at a mean depth of 3.2 ± 0.7 mm. Peak contact stress was elevated for both the shallowest and deepest models and reached a predicted local minimum at a mean depth of 1.8 ± 0.3 mm. Conclusions Contact area and peak contact stress were dependent on Radial Head prosthesis dish depth. There was an optimal implant dish depth for radiocapitellar contact mechanics at approximately 2 mm. Clinical relevance Optimizing radiocapitellar contact mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation.

  • effect of Radial Head implant shape on joint contact area and location during static loading
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Hannah L Shannon, Ryan Willing, Graham J W King, Emily A Lalone, Simon R Deluce, James A Johnson
    Abstract:

    Purpose To examine the effect of implant shape on radiocapitellar joint contact area and location in vitro. Methods We used 8 fresh-frozen cadaveric upper extremities. An elbow loading simulator examined joint contact in pronation, neutral rotation, and supination with the elbow at 90° flexion. Muscle tendons were attached to pneumatic actuators to allow for computer-controlled loading to achieve the desired forearm rotation. We performed testing with the native Radial Head, an axisymmetric implant, a reverse-engineered patient-specific implant, and a population-based quasi-anatomic implant. Implants were inserted using computer navigation. Contact area and location were quantified using a casting technique. Results We found no significant difference between contact locations for the native Radial Head and the 3 implants. All of the implants had a contact area lower than the native Radial Head; however, only the axisymmetric implant was significantly different. There was no significant difference in contact area between implant shapes. Conclusions The similar contact areas and locations of the 3 implant designs suggest that the shape of the implant may not be important with respect to radiocapitellar joint contact mechanics when placed optimally using computer navigation. Further work is needed to explore the sensitivity of Radial Head implant malpositioning on articular contact. The lower contact area of the Radial Head implants relative to the native Radial Head is similar to previous benchtop studies and is likely the result of the greater stiffness of the implant. Clinical relevance Radial Head implant shape does not appear to have a pronounced influence on articular contact, and both axisymmetric and anatomic metal designs result in elevated cartilage stress relative to the intact state.

  • the effect of Radial Head implant length on radiocapitellar articular properties and load transfer within the forearm
    Journal of Orthopaedic Trauma, 2014
    Co-Authors: E A Lanting, Graham J W King, Louis M Ferreira, James A Johnso, George S. Athwal
    Abstract:

    BACKGROUND The effect of Radial Head implant length on forearm biomechanics is not well understood. This study examined the influence of an increase or a decrease in Radial Head implant length on forearm load transfer as measured by interosseous membrane (IOM) tension and changes in radiocapitellar joint contact properties. METHODS An upper extremity simulator was used to examine 6 cadaveric specimens with 5 different Radial Head implant lengths (-4 mm, -2 mm, anatomically correct, +2 mm, and +4 mm). A load-sensing device was woven into the fibers of IOM to quantify its tension. An interpositional pressure measurement sensor was used to determine radiocapitellar joint contact area and pressure. Axial loads of 160 N were applied to the forearm through active pronation and supination with the elbow fixed at 90 degrees of flexion. RESULTS Increasing Radial Head implant length by 4 mm unloaded the IOM in all cases. Decreasing implant length by 4 mm significantly increased the IOM tension (P = 0.005). No significant differences were found in IOM tension between the correct Head implant length and the -2 mm implant (P = 0.29). Contact pressure significantly increased with increasing Radial Head implant length (P = 0.021) and contact area diminished with both an increase and a decrease in Radial Head implant length, but this was not statistically significant (P = 0.051). CONCLUSIONS Increasing Radial Head implant length decreased IOM tension and increased radiocapitellar joint contact pressure. CLINICAL RELEVANCE These findings illustrate the importance of precise restoration of Radial length when performing a Radial Head replacement. If the native Radial Head length is difficult to accurately assess, avoid increasing the length of the Radial Head to prevent detrimental changes in the biomechanics of the forearm and the potential for clinically important radiocapitellar joint pathology.

  • the bicipital tuberosity and distal radius are unreliable landmarks for Radial Head implant alignment
    Journal of Shoulder and Elbow Surgery, 2013
    Co-Authors: Ryan N Katchky, James A Johnson, Graham J W King, George S. Athwal
    Abstract:

    Background As more anatomic asymmetric Radial Head implants emerge, it is necessary to determine the optimal landmarks to ensure correct rotational orientation. The bicipital tuberosity and distal radius are possible bony landmarks that can be used for rotational alignment of asymmetric prostheses; however, they have not been validated. The purpose of this study was to evaluate the reliability of the bicipital tuberosity and distal radius as rotational landmarks for orientation of asymmetric Radial Head prostheses. Methods Measurements were made from computer tomography scans of 50 elbows in order to determine the rotational relationships between the Radial Head, bicipital tuberosity, biceps tendon footprint, and distal radius. Results The maximum Radial Head diameter was oriented 65° ± 28° from the bicipital tuberosity, 119° ± 38° from the biceps tendon footprint, 82° ± 29° from the Radial styloid, and 76° ± 28° from the volar surface of the distal radius. All of these landmarks had a significantly greater variance than a proposed acceptable clinical tolerance of 10° ( P Conclusion The results demonstrate that the measured landmarks show no consistent rotational relationship with the maximum diameter of the Radial Head. In order to maximize the utility of more anatomic asymmetric Radial Head implant systems, further studies are necessary to identify more reliable rotational landmarks to ensure optimal implant positioning.

Shawn W Odriscoll - One of the best experts on this subject based on the ideXlab platform.

  • effect of radiocapitellar achilles disc arthroplasty on coronoid and capitellar contact pressures after Radial Head excision
    Journal of Shoulder and Elbow Surgery, 2018
    Co-Authors: Taghi Ramazanian, James S. Fitzsimmons, Julia A Mullerlebschi, Min Yao Chuang, Anthony M Vaichinger, Shawn W Odriscoll
    Abstract:

    Background Long-term radiographic arthritis has been commonly reported after Radial Head excision. Concern over Radial Head arthroplasty may arise in certain situations including capitellar arthritis, radiocapitellar malalignment, and in young and active patients. We hypothesized that Radial Head excision increases coronoid contact pressures, which may at least be partially reduced by radiocapitellar Achilles tendon disc arthroplasty. Methods Coronoid and capitellar contact pressure was measured on 6 human cadaveric elbows on a custom-designed gravity-valgus simulator under passive flexion from 0° to 90°. Sequential testing, starting with the intact specimen, resection of the Radial Head, and finally, radiocapitellar Achilles tendon disc arthroplasty were performed on each specimen. Results Mean contact pressure of the coronoid significantly increased after Radial Head excision (P  Conclusions Radial Head resection increases contact pressure in the coronoid, especially the lateral coronoid. This study showed that radiocapitellar Achilles disc arthroplasty significantly improves contact pressures on the coronoid after Radial Head resection. Achilles disc arthroplasty could be considered in patients who are not candidates for Radial Head arthroplasty.

  • validation of a simple overlay device to assess Radial Head implant length
    Journal of Hand Surgery (European Volume), 2018
    Co-Authors: Dave R Shukla, James S. Fitzsimmons, Matthias Vanhees, Shawn W Odriscoll
    Abstract:

    Purpose A simple overlay device (SOD) was developed to measure Radial Head implant length. The purpose of this study was to determine the accuracy and reliability of this device for measuring experimental Radial Head implant length. Methods Five fresh frozen cadavers were implanted with sequentially longer implants, adjusted by neck length (0, 2, 4, and 8 mm). Fluoroscopic images were obtained in 4 forearm positions: anteroposterior in supination in full extension, anteroposterior in pronation in full extension, supinated in 45° of flexion, and neutral in 45° of flexion. The SOD measurements (made by 2 observers) were compared with the native original Radial Head (control) to assess implant length. In addition, gapping of the ulnohumeral joint space was measured for comparison purposes. Results The measured Radial Head and neck lengths for the specimens were 33, 39, 31, 34, and 42 mm. The difference between the actual Radial Head and neck lengths and those measured with the SOD template averaged less than 2 mm for all 4 collar sizes, except in 1 measurement in which the bicipital tuberosity could not be visualized. The median intraclass correlation coefficients for observer 1 compared with the SOD were 0.94 to 0.99. The median intraclass correlation coefficients between observers were 0.88 to 0.95. For both observers, elbow position, collar height, and the 2 variables combined did not significantly affect the SOD values. The other method that was evaluated, that of measurement of the ulnohumeral joint space, had higher interobserver variability versus the SOD, and allowed detection of lengthening of over 4 mm. Conclusions The SOD is a reliable method for simply assessing Radial Head length with radiographs and can accurately detect 2 mm or more of proximal Radial lengthening. Clinical relevance The SOD is a simple and accurate method that can help to optimize Radial Head sizing.

  • radiocapitellar contact characteristics during prosthetic Radial Head subluxation
    Journal of Shoulder and Elbow Surgery, 2017
    Co-Authors: Dipit Sahu, James S. Fitzsimmons, Andrew R Thoreson, Shawn W Odriscoll
    Abstract:

    Background Metallic Radial Head prostheses are often used in the management of comminuted Radial Head fractures and elbow instability. We hypothesized that during radiocapitellar subluxation, the contact pressure characteristics of an anatomic Radial Head prosthesis will more closely mimic those of the native Radial Head compared with a monopolar circular or a bipolar circular Radial Head design. Materials and methods With use of 6 fresh frozen cadaver elbows, mean radiocapitellar contact pressures, contact areas, and peak pressures of the native Radial Head were assessed at 0, 2, 4, and 6 mm of posterior subluxation. These assessments were repeated after the native Radial Head was replaced with anatomic, monopolar circular and bipolar circular prostheses. Results The joint contact pressures increased with the native and the prosthetic Radial Head subluxation. The mean contact pressures for the native Radial Head and anatomic prosthesis increased progressively and significantly from 0 to 6 mm of subluxation (native, 0.6 ± 0.0 MPa to 1.9 ± 0.2 MPa; anatomic, 0.7 ± 0.0 MPa to 2.1 ± 0.3 MPa; P P  = .31]; bipolar, 1.7 ± 0.1 MPa to 1.9 ± 0.1 MPa [ P  = .12]). The pattern of increase in contact pressures with the anatomic prosthesis mimicked that of the native Radial Head. Conversely, the circular prostheses started out with higher contact pressures that stayed elevated . Conclusion The articular surface design of a Radial Head prosthesis is an important determinant of joint contact pressures.

  • influence of Radial Head prosthetic design on radiocapitellar joint contact mechanics
    Journal of Shoulder and Elbow Surgery, 2014
    Co-Authors: Dipit Sahu, James S. Fitzsimmons, Lawrence J Berglund, Andrew R Thoreson, David M Holmes, Shawn W Odriscoll
    Abstract:

    Hypothesis Our aim was to test whether anatomically designed metallic Radial Head implants could better reproduce native radiocapitellar contact pressure and areas than nonanatomic implants. Methods The distal humerus and proximal radius from 6 cadaveric upper extremities were serially tested in supination with 100 N of compression force at 4 angles of flexion (0°, 30°, 60°, and 90°). By use of a thin flexible pressure transducer, contact pressures and areas were measured for the native Radial Head, an anatomic implant, a nonanatomic circular monopolar implant, and a bipolar nonanatomic implant. The data (mean contact pressure and mean contact area) were modeled using a 2-factor repeated-measures analysis of variance with P ≤ .05 considered to be significant. Results The mean contact areas for the prosthetic Radial Heads were significantly less than those seen with the intact Radial Heads at every angle tested (P < .01). The mean contact pressures increased significantly with all prosthetic Radial Head types as compared with the native Head. The mean contact pressures increased by 29% with the anatomic prosthesis, 230% with the monopolar prosthesis, and 220% with the bipolar prosthesis. Peak pressures of more than 5 MPa were more commonly observed with both the monopolar and bipolar prostheses than with the anatomic or native Radial Heads. Conclusions The geometry of Radial Head implants strongly influences their contact characteristics. In a direct radius-to-capitellum axial loading experiment, an anatomically designed Radial Head prosthesis had lower and more evenly distributed contact pressures than the nonanatomic implants that were tested.

  • stress shielding around Radial Head prostheses
    Journal of Hand Surgery (European Volume), 2012
    Co-Authors: Cholawish Chanlalit, Dave R Shukla, James S. Fitzsimmons, Kai Nan An, Shawn W Odriscoll
    Abstract:

    Purpose Stress shielding is known to occur around rigidly fixed implants. We hypothesized that stress shielding around Radial Head prostheses is common but nonprogressive. In this study, we present a classification scheme to support our radiographic observations. Methods We reviewed charts and radiographs of 86 cases from 79 patients with Radial Head implants from both primary and revision surgeries between 1999 and 2009. Exclusion criteria included infection, loosening, or follow-up of less than 12 months. We classified stress shielding as: I, cortical thinning; II, partially (IIa) or circumferentially (IIb) exposed stem; and III, impending mechanical failure. Results Of 26 well-fixed stems, 17 (63%) demonstrated stress shielding: I=2, II=15 (IIa = 12, IIb=3), and III=0. We saw stress shielding with all stem types: cemented or noncemented; long or short; and straight, curved, or tapered. The only significant difference was that stems implanted into the Radial shaft had less stress shielding than stems implanted into the neck or tuberosity ( P = .03). The average follow-up was 33 months (range, 13–70 mo). Stress shielding was detectable by an average of 11 months (range, 1–15 mo). The pattern of bone loss was similar in 16 of 17 cases (94%), starting on the outer periosteal cortex. The 3 cases with circumferential exposure of the stem (stage IIb) averaged 2.6 mm (range, 1–4 mm) of exposed stem. Stress shielding never extended to the bicipital tuberosity, and there were no cases of impending mechanical failure. Conclusions Stress shielding around Radial Head prostheses is common, regardless of stem design. However, it is typically minor, nonprogressive, and of questionable clinical consequence. Type of study/level of evidence Therapeutic IV.

James S. Fitzsimmons - One of the best experts on this subject based on the ideXlab platform.

  • effect of radiocapitellar achilles disc arthroplasty on coronoid and capitellar contact pressures after Radial Head excision
    Journal of Shoulder and Elbow Surgery, 2018
    Co-Authors: Taghi Ramazanian, James S. Fitzsimmons, Julia A Mullerlebschi, Min Yao Chuang, Anthony M Vaichinger, Shawn W Odriscoll
    Abstract:

    Background Long-term radiographic arthritis has been commonly reported after Radial Head excision. Concern over Radial Head arthroplasty may arise in certain situations including capitellar arthritis, radiocapitellar malalignment, and in young and active patients. We hypothesized that Radial Head excision increases coronoid contact pressures, which may at least be partially reduced by radiocapitellar Achilles tendon disc arthroplasty. Methods Coronoid and capitellar contact pressure was measured on 6 human cadaveric elbows on a custom-designed gravity-valgus simulator under passive flexion from 0° to 90°. Sequential testing, starting with the intact specimen, resection of the Radial Head, and finally, radiocapitellar Achilles tendon disc arthroplasty were performed on each specimen. Results Mean contact pressure of the coronoid significantly increased after Radial Head excision (P  Conclusions Radial Head resection increases contact pressure in the coronoid, especially the lateral coronoid. This study showed that radiocapitellar Achilles disc arthroplasty significantly improves contact pressures on the coronoid after Radial Head resection. Achilles disc arthroplasty could be considered in patients who are not candidates for Radial Head arthroplasty.

  • validation of a simple overlay device to assess Radial Head implant length
    Journal of Hand Surgery (European Volume), 2018
    Co-Authors: Dave R Shukla, James S. Fitzsimmons, Matthias Vanhees, Shawn W Odriscoll
    Abstract:

    Purpose A simple overlay device (SOD) was developed to measure Radial Head implant length. The purpose of this study was to determine the accuracy and reliability of this device for measuring experimental Radial Head implant length. Methods Five fresh frozen cadavers were implanted with sequentially longer implants, adjusted by neck length (0, 2, 4, and 8 mm). Fluoroscopic images were obtained in 4 forearm positions: anteroposterior in supination in full extension, anteroposterior in pronation in full extension, supinated in 45° of flexion, and neutral in 45° of flexion. The SOD measurements (made by 2 observers) were compared with the native original Radial Head (control) to assess implant length. In addition, gapping of the ulnohumeral joint space was measured for comparison purposes. Results The measured Radial Head and neck lengths for the specimens were 33, 39, 31, 34, and 42 mm. The difference between the actual Radial Head and neck lengths and those measured with the SOD template averaged less than 2 mm for all 4 collar sizes, except in 1 measurement in which the bicipital tuberosity could not be visualized. The median intraclass correlation coefficients for observer 1 compared with the SOD were 0.94 to 0.99. The median intraclass correlation coefficients between observers were 0.88 to 0.95. For both observers, elbow position, collar height, and the 2 variables combined did not significantly affect the SOD values. The other method that was evaluated, that of measurement of the ulnohumeral joint space, had higher interobserver variability versus the SOD, and allowed detection of lengthening of over 4 mm. Conclusions The SOD is a reliable method for simply assessing Radial Head length with radiographs and can accurately detect 2 mm or more of proximal Radial lengthening. Clinical relevance The SOD is a simple and accurate method that can help to optimize Radial Head sizing.

  • radiocapitellar contact characteristics during prosthetic Radial Head subluxation
    Journal of Shoulder and Elbow Surgery, 2017
    Co-Authors: Dipit Sahu, James S. Fitzsimmons, Andrew R Thoreson, Shawn W Odriscoll
    Abstract:

    Background Metallic Radial Head prostheses are often used in the management of comminuted Radial Head fractures and elbow instability. We hypothesized that during radiocapitellar subluxation, the contact pressure characteristics of an anatomic Radial Head prosthesis will more closely mimic those of the native Radial Head compared with a monopolar circular or a bipolar circular Radial Head design. Materials and methods With use of 6 fresh frozen cadaver elbows, mean radiocapitellar contact pressures, contact areas, and peak pressures of the native Radial Head were assessed at 0, 2, 4, and 6 mm of posterior subluxation. These assessments were repeated after the native Radial Head was replaced with anatomic, monopolar circular and bipolar circular prostheses. Results The joint contact pressures increased with the native and the prosthetic Radial Head subluxation. The mean contact pressures for the native Radial Head and anatomic prosthesis increased progressively and significantly from 0 to 6 mm of subluxation (native, 0.6 ± 0.0 MPa to 1.9 ± 0.2 MPa; anatomic, 0.7 ± 0.0 MPa to 2.1 ± 0.3 MPa; P P  = .31]; bipolar, 1.7 ± 0.1 MPa to 1.9 ± 0.1 MPa [ P  = .12]). The pattern of increase in contact pressures with the anatomic prosthesis mimicked that of the native Radial Head. Conversely, the circular prostheses started out with higher contact pressures that stayed elevated . Conclusion The articular surface design of a Radial Head prosthesis is an important determinant of joint contact pressures.

  • influence of Radial Head prosthetic design on radiocapitellar joint contact mechanics
    Journal of Shoulder and Elbow Surgery, 2014
    Co-Authors: Dipit Sahu, James S. Fitzsimmons, Lawrence J Berglund, Andrew R Thoreson, David M Holmes, Shawn W Odriscoll
    Abstract:

    Hypothesis Our aim was to test whether anatomically designed metallic Radial Head implants could better reproduce native radiocapitellar contact pressure and areas than nonanatomic implants. Methods The distal humerus and proximal radius from 6 cadaveric upper extremities were serially tested in supination with 100 N of compression force at 4 angles of flexion (0°, 30°, 60°, and 90°). By use of a thin flexible pressure transducer, contact pressures and areas were measured for the native Radial Head, an anatomic implant, a nonanatomic circular monopolar implant, and a bipolar nonanatomic implant. The data (mean contact pressure and mean contact area) were modeled using a 2-factor repeated-measures analysis of variance with P ≤ .05 considered to be significant. Results The mean contact areas for the prosthetic Radial Heads were significantly less than those seen with the intact Radial Heads at every angle tested (P < .01). The mean contact pressures increased significantly with all prosthetic Radial Head types as compared with the native Head. The mean contact pressures increased by 29% with the anatomic prosthesis, 230% with the monopolar prosthesis, and 220% with the bipolar prosthesis. Peak pressures of more than 5 MPa were more commonly observed with both the monopolar and bipolar prostheses than with the anatomic or native Radial Heads. Conclusions The geometry of Radial Head implants strongly influences their contact characteristics. In a direct radius-to-capitellum axial loading experiment, an anatomically designed Radial Head prosthesis had lower and more evenly distributed contact pressures than the nonanatomic implants that were tested.

  • stress shielding around Radial Head prostheses
    Journal of Hand Surgery (European Volume), 2012
    Co-Authors: Cholawish Chanlalit, Dave R Shukla, James S. Fitzsimmons, Kai Nan An, Shawn W Odriscoll
    Abstract:

    Purpose Stress shielding is known to occur around rigidly fixed implants. We hypothesized that stress shielding around Radial Head prostheses is common but nonprogressive. In this study, we present a classification scheme to support our radiographic observations. Methods We reviewed charts and radiographs of 86 cases from 79 patients with Radial Head implants from both primary and revision surgeries between 1999 and 2009. Exclusion criteria included infection, loosening, or follow-up of less than 12 months. We classified stress shielding as: I, cortical thinning; II, partially (IIa) or circumferentially (IIb) exposed stem; and III, impending mechanical failure. Results Of 26 well-fixed stems, 17 (63%) demonstrated stress shielding: I=2, II=15 (IIa = 12, IIb=3), and III=0. We saw stress shielding with all stem types: cemented or noncemented; long or short; and straight, curved, or tapered. The only significant difference was that stems implanted into the Radial shaft had less stress shielding than stems implanted into the neck or tuberosity ( P = .03). The average follow-up was 33 months (range, 13–70 mo). Stress shielding was detectable by an average of 11 months (range, 1–15 mo). The pattern of bone loss was similar in 16 of 17 cases (94%), starting on the outer periosteal cortex. The 3 cases with circumferential exposure of the stem (stage IIb) averaged 2.6 mm (range, 1–4 mm) of exposed stem. Stress shielding never extended to the bicipital tuberosity, and there were no cases of impending mechanical failure. Conclusions Stress shielding around Radial Head prostheses is common, regardless of stem design. However, it is typically minor, nonprogressive, and of questionable clinical consequence. Type of study/level of evidence Therapeutic IV.

Bernard F Morrey - One of the best experts on this subject based on the ideXlab platform.

  • Radial Head reconstruction in elbow fracture dislocation monopolar or bipolar prosthesis
    Clinical Orthopaedics and Related Research, 2014
    Co-Authors: Robert U Hartzler, Bernard F Morrey, Scott P Steinmann, Manuel Llusaperez, Joaquin Sanchezsotelo
    Abstract:

    Background Monopolar and bipolar Radial Head prosthetic arthroplasties have been used successfully to treat elbow fracture-dislocation with unsalvageable Radial Head fractures. The relative stability of these two designs in different clinical situations is a topic of ongoing investigation.

  • delayed valgus instability and proximal migration of the radius after Radial Head prosthesis failure
    Journal of Shoulder and Elbow Surgery, 2010
    Co-Authors: Roger P Van Riet, Bernard F Morrey
    Abstract:

    Radial Head resection has yielded excellent long-term results in isolated Radial Head fractures. Most comminuted Radial Head fractures are complicated by associated lesions, however, and acute Radial Head replacement is often indicated in these patients. Metal Radial Head prostheses have become the standard treatment of irreparable Radial Head fractures with associated lesions to the elbow or forearm that render the elbow or forearm unstable. The prosthesis has been postulated to act as a temporary spacer while the injured soft tissues heal. Subsequent removal of the prosthesis to decrease pain and increase mobility yielded good to excellent results in previously reported cases. However, we present a patient whose in whom the soft tissues did not heal over a prolonged period, leading to a poor result after removal of a Radial Head implant.

  • importance of a Radial Head component in sorbie unlinked total elbow arthroplasty
    Clinical Orthopaedics and Related Research, 2002
    Co-Authors: Katsunori Inagaki, Shawn W Odriscoll, Patricia G Neale, Eiichi Uchiyama, Bernard F Morrey
    Abstract:

    The effects of a Radial Head component on total elbow arthroplasty kinematics and stability were evaluated using an anatomic design unlinked total elbow prosthesis. An electromagnetic tracking device recorded motion and varus and valgus displacements under various conditions in 10 cadaveric elbows. The motion patterns of the intact elbows and the Sorbie-Questor total elbow prostheses with a Radial Head component were similar, as both tended to have a valgus position in extension, varus at midflexion, and more valgus toward full flexion. Under conditions of simulated muscle loading, the maximum valgus and varus laxity of the elbow prosthesis was, on average, 8.6 degrees +/- 4.0 degrees greater than normal. Without the Radial Head component, however, significant kinematic disturbances and instabilities were seen. The varus and valgus displacements were 13.3 degrees +/- 5.5 degrees greater than the intact elbows. One total elbow arthroplasty without a Radial Head dislocated during testing. Increasing the muscle loading across the elbow significantly enhanced dynamic stability of the total elbow arthroplasties, especially in the extension half of elbow motion where instability is greatest. However, this dynamic enhancement of stability was seen only in those elbows in which the Radial Head component had been implanted. The Radial Head component is an important stabilizer, particularly in extension for this prosthesis, and possibly for other unlinked total elbow prostheses. Although instability of unlinked prostheses depends on the prosthetic design, the use of a Radial Head replacement may be an important factor in preventing such instability. Perhaps even more importantly, a Radial Head component balances the load distribution across the articulation, which could decrease stress on the ulnohumeral articulation and therefore possibly reduce polyethylene wear, osteolysis, and loosening.