Two-millimetre diameter operative arthroscopy of the ankle is safe and effective

Abstract Purpose Technical innovation now offers the possibility of 2-mm diameter operative arthroscopy: an alternative to conventional arthroscopy that no longer uses inner rod-lenses. The purpose of this study was to assess whether all significant structures in the ankle could be visualized and surgically reached during 2-mm diameter operative arthroscopy, without inflicting iatrogenic damage. Methods A novel, 2-mm diameter arthroscopic system was used to perform a protocolled arthroscopic procedure in 10 fresh-frozen, human donor ankles. Standard anteromedial and anterolateral portals were utilized. Visualization and reach with tailored arthroscopic instruments of a protocolled list of articular structures were recorded and documented. A line was etched on the most posterior border of the talar and tibial cartilage that was safely reachable. The specimens were dissected and distances between portal tracts and neurovascular structures were measured. The articular surfaces of talus and tibia were photographed and inspected for iatrogenic damage. The reachable area on the articular surface was calculated and analysed. Results All significant structures were successfully visualized and reached in all specimens. The anteromedial portal was not in contact with neurovascular structures in any specimen. The anterolateral portal collided with a branch of the superficial peroneal nerve in one case but did not cause macroscopically apparent harm. On average, 96% and 85% of the talar and tibial surfaces was reachable respectively, without causing iatrogenic damage. Conclusion 2-mm diameter operative arthroscopy provides safe and effective visualization and surgical reach of the anterior ankle joint. It may hold the potential to make ankle arthroscopy less invasive and more accessible.

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2-Mm Diameter Operative Tendoscopy of the Tibialis Posterior, Peroneal, and Achilles Tendons: A Cadaveric Study

Foot & Ankle International ◽

10.1177/1071100719895504 ◽

2019 ◽

Vol 41 (4) ◽

pp. 473-478 ◽

Cited By ~ 3

Author(s):

Tobias Stornebrink ◽

Sjoerd A. S. Stufkens ◽

Daniel Appelt ◽

Coen A. Wijdicks ◽

Gino M. M. J. Kerkhoffs

Keyword(s):

New Technology ◽

Proximal Part ◽

Tendon Sheath ◽

Tibialis Posterior ◽

Cuboid Bone ◽

Iatrogenic Damage ◽

Fresh Frozen ◽

Effective Visualization ◽

Neurovascular Structures ◽

Portal Tracts

Background: Technical innovation now offers the possibility of 2-mm-diameter operative tendoscopy with disposable arthroscopes and tablet-like control units. The promises of new technology should be critically scrutinized. Therefore, this study assessed whether 2-mm-diameter operative tendoscopy of the tibialis posterior, peroneal, and Achilles tendons was safe and effective in a cadaveric model. Methods: A 2-mm-diameter arthroscopic system was used to perform a tendoscopic procedure in 10 nonpaired, fresh-frozen, human ankles. Standard tendoscopic portals were utilized. Visual examination and operative reach with tailored tendoscopic instruments within the tendon sheaths were recorded and documented. Adhesiolysis and vincula resections were performed. After dissection, distances between portal tracts and neurovascular structures were measured and the tendons were inspected for signs of iatrogenic damage. Results: The entire tendon sheath and tendon of the tibialis posterior, peroneus brevis, and Achilles tendons were visualized and reached with tailored operative instruments. The proximal part of the peroneus longus tendon was visible and reachable from proximally up to the cuboid bone distally. Adhesiolysis and vincula resections were successfully performed in all specimens. The mean distances between portal tracts and local neurovascular structures ranged between 9.4 and 19.2 mm and there were no cases of contact. None of the tendons showed signs of iatrogenic damage. Conclusion: Two-millimeter-diameter operative tendoscopy provided safe and effective visualization and operative reach of the tibialis posterior, peroneal, and Achilles tendons. Clinical Relevance: Compared with current practice, 2-mm-diameter operative tendoscopy has the potential to make tendoscopy around the ankle less invasive and more accessible. Diagnostic, interventional, and second-look procedures might be performed at substantially reduced risk, time, and costs.

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Effectiveness of the Saline Load Test in Diagnosis of Traumatic Ankle Arthrotomies in Varying Arthrotomy Locations

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00326 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0032

Author(s):

Erin Ohliger ◽

Sara Lyn Miniaci-Coxhead

Keyword(s):

Methylene Blue ◽

Cadaveric Study ◽

Load Test ◽

Blue Staining ◽

Direct Visualization ◽

Anteromedial Portal ◽

Significant Difference ◽

Anterolateral Portal ◽

Fresh Frozen ◽

Ankle Trauma

Category: Ankle, Trauma Introduction/Purpose: The purpose of this study was to investigate the amount of fluid required and the sensitivity of the saline load test to identify an intra-articular arthrotomy of the ankle. Limited prior studies have been conducted in arthroscopic models with proposed volumes ranging from 30 ml to 60 ml. Due to this range it was inferred that volume needed to detect arthrotomy would vary based on site of arthrotomy. Using cadavers without prior ankle trauma or surgeries we aim to assess volume needed to detect ankle arthrotomies at varying arthrotomy locations. Methods: A cadaveric study was conducted using 20 thawed, fresh-frozen below knee amputations. Cadavers were randomly divided into four groups of five and an ankle arthrotomy was made using a 4 mm trochar at standard ankle portal sites; anteromedial, anterolateral, posteromedial, and posterolateral. To confirm intra-articular location, a scope was inserted for direct visualization. A 18-gauge needle was then inserted into the anteromedial portal, except for the anteromedial arthrotomy where the needle was inserted into the anterolateral portal, and saline mixed with methylene blue was loaded into joint. During the injection, the known arthrotomy site was viewed for extravasation. Amount of saline required to diagnose arthrotomy was recorded. All injections were confirmed as intra-articular by demonstrating methylene blue staining of the anterior joint by open exploration. Results: The saline volume required to achieve extravasation ranged from 3 mL to 11 mL. The median saline volume required to achieve extravasation was 5.3 mL. A total of 8 mL was required to achieve 90% sensitivity, 10 mL for 95% sensitivity and 11 mL for 99% sensitivity. For the anterolateral, anteromedial, posteromedial, and posterolateral arthrotomy sites the median saline volume needed to detect a traumatic arthrotomy was 5.2 ml, 6.2 ml, 5 ml, and 4.8 ml respectively. There was no statistically significant difference in volume needed to detect arthrotomies across all four locations. Conclusion: A minimum injection of 10 mL is recommended to identify 95% of traumatic arthrotomies approximately 4 mm in size. Prior studies performed in arthroscopic models with prior ankle pathology may overestimate volume needed to detect arthrotomies. No difference in volume needed to detect extravasation was found across all four arthrotomy locations.

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Morphometric evaluation of features of remodeling of chondrocites of joint surfaces of temporomandibular joint of experimental animals in hyperglycemia

Journal of Education, Health and Sport ◽

10.12775/jehs.2021.11.06.014 ◽

2021 ◽

Vol 11 (6) ◽

pp. 137-142

Author(s):

Mykhailo Hnatiuk ◽

Lesia Rubas

Keyword(s):

Temporomandibular Joint ◽

Structural Changes ◽

Articular Surface ◽

White Male ◽

Relative Volume ◽

Male Rats ◽

Intercellular Substance ◽

Temporal Fossa ◽

Articular Surfaces ◽

Joint Surfaces

Aim: to study morphometrically the peculiarities of remodeling of chondrocytes of the articular surfaces of the temporomandibular joint in hyperglycemia.Materials and methods: Quantitative morphological methods were used to study diameters of chondrocytes and their nuclei, nuclear-cytoplasmic relationship in these cells, relative volume of damaged chondrocytes, intercellular-chondrocytic relationship in mature chondrocytes of the articular surfaces of the temporomandibular joint of 45 laboratory mature white male rats with simulated diabetes.Results: A comprehensive analysis of the morphometric parameters presented in the article showed that they did not differ in the articular surfaces of the temporal fossa and mandibular head of the intact temporomandibular joint. The expressed structural changes of chondrocytes were revealed at a monthly and a two-month diabetic arthropathy of this joint.Conclusions: Proceeded studies and obtained results suggest that prolonged hyperglycemia leads to diabetic arthropathy of the TMJ, which is characterized by atrophy of chondrocytes, violation of nuclear-cytoplasmic relationships, an increase in the relative volume of damaged chondrocytes and volume of intercellular substance. The detected changes in quantitative morphological parameters depended on the duration of hyperglycemia and dominated in the cartilaginous tissue of the articular surface of the mandibular head.

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The temporomandibular joints, muscles of mastication, and the infratemporal and pterygopalatine fossae

Anatomy for Dental Students ◽

10.1093/oso/9780199234462.003.0033 ◽

2013 ◽

Author(s):

Martin E. Atkinson

Keyword(s):

Temporal Bone ◽

Articular Surface ◽

Mandibular Condyle ◽

Jaw Movements ◽

Synovial Joints ◽

Articular Surfaces ◽

Temporomandibular Joints ◽

Mandibular Fossa ◽

Muscle Groups ◽

Muscles Of Mastication

It is essential that dental students and practitioners understand the structure and function of the temporomandibular joints and the muscles of mastication and other muscle groups that move them. The infratemporal fossa and pterygopalatine fossa are deep to the mandible and its related muscles; many of the nerves and blood vessels supplying the structures of the mouth run through or close to these areas, therefore, knowledge of the anatomy of these regions and their contents is essential for understanding the dental region. The temporomandibular joints (TMJ) are the only freely movable articulations in the skull together with the joints between the ossicles of the middle ear; they are all synovial joints. The muscles of mastication move the TMJ and the suprahyoid and infrahyoid muscles also play a significant role in jaw movements. The articular surfaces of the squamous temporal bone and of the condylar head (condyle) of the mandible form each temporomandibular joint. These surfaces have been briefly described in Chapter 22 on the skull and Figure 24.1A indicates their shape. The concave mandibular fossa is the posterior articulating surface of each squamous temporal bone and houses the mandibular condyle at rest. The condyle is translated forwards on to the convex articular eminence anterior to the mandibular fossa during jaw movements. The articular surfaces of temporomandibular joints are atypical; they covered by fibrocartilage (mostly collagen with some chondrocytes) instead of hyaline cartilage found in most other synovial joints. Figures 24.1B and 24.1C show the capsule and ligaments associated with the TMJ. The tough, fibrous capsule is attached above to the anterior lip of the squamotympanic fissure and to the squamous bone around the margin of the upper articular surface and below to the neck of the mandible a short distance below the limit of the lower articular surface. The capsule is slack between the articular disc and the squamous bone, but much tighter between the disc and the neck of the mandible. Part of the lateral pterygoid muscle is inserted into the anterior surface of the capsule. As in other synovial joints, the non-load-bearing internal surfaces of the joint are covered with synovial membrane.

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The Captain’s View: A Novel Radiographic View to Assess Axial Alignment of the Calcaneus

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00426 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0042

Author(s):

Brian Velasco ◽

Bruno Moura ◽

John Kwon

Keyword(s):

Soft Tissues ◽

Articular Surface ◽

Lateral Wall ◽

Varus Deformity ◽

High Rate ◽

Clear Correlation ◽

Lateral Side ◽

Axial Alignment ◽

Wide Range ◽

Fresh Frozen

Category: Hindfoot, Trauma Introduction/Purpose: The axial alignment of the calcaneus has paramount importance in the management of these fractures. The Harris view has long stood as the recommended radiograph to assess axial alignment. However, given the obliquity at which the radiograph is obtained, it doesn´t represent a true axial view and is subject to inaccuracies secondary to rotational malpositioning of the foot and mismeasurement of angulation. Multiple reports have described the axial alignment as a surgical outcome, but usually this assessment of the residual deformity have no described method. The objectives of this study are to evaluate the capacity of Harris view to assess axial alignment in a cadaveric model and to describe the use of a true AP view of the calcaneus that we have named Captain´s view. Methods: Five below knee amputated fresh-frozen cadaveric specimens were used in the study. For each specimen, the soft tissues over the lateral side were removed to access to the lateral wall. A small wedge of the cuboid was removed to visualize the center of the calcaneocuboid articular surface. LCA-guide and a cannulated drill were used to create a tunnel in the axis of the calcaneus. An oblique osteotomy was performed in order to simulate a non-comminuted fracture. Varus deformity was created by inserting solid radiolucent wedges into the osteotomy to create models of 10, 20, and 30 degrees of varus angulation. Harris and Captain views were obtained for each specimen with 0 (control), 10, 20, and 30 degrees of varus malalignment. Measurements of the deformity were made digitally on each fluoroscopic image. Results: The average degrees of varus in Harris views were 10,9 (5,5-16); 11,5 (8,2-13,6); and 18,3 (13,3-23,6) for 10,20 and 30 degrees of deformity respectively. The average degrees of varus in Captain´s view were 13,0 (7,3-20,9); 18,4 (11,7-23,5); and 28,2 (24,4-31,1) for 10,20 and 30 degrees of deformity respectively. The average degrees of error for varus deformity in Harris views were 4,1 (41%); 8,4 (42%) and 11,6 (39%) for 10,20 and 30 degrees of deformity respectively. The average degrees of error for varus deformity in Captain´s views were 4,8 (48%); 3,6 (18%) and 2,8 (8%) for 10,20 and 30 degrees of deformity respectively. Conclusion: The results of this study show a high rate of mismeasurement for both radiographic views. Despite the average angles have a clear correlation with the severity of varus, the wide range of error observed between specimens make this assessment unreliable and inaccurate. We observed an improvement of accuracy of captain´s view for more severe deformities, but not with Harris views which maintain a 40% mismeasurement in all the settings. Therefore, intraoperative Harris views should not be used in isolation to evaluate axial alignment and Captain´s view provides an additional perspective that can be useful to rule out severe deformities.

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

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120962103 ◽

2020 ◽

Vol 8 (11) ◽

pp. 232596712096210

Author(s):

Daisuke Momma ◽

Wataru Iwamoto ◽

Kaori Endo ◽

Kazuki Sato ◽

Norimasa Iwasaki

Keyword(s):

Bone Density ◽

Stress Distribution ◽

Distribution Pattern ◽

Subchondral Bone ◽

Shoulder Joint ◽

Glenohumeral Joint ◽

Articular Surface ◽

Articular Surfaces ◽

Subchondral Bone Density ◽

Collegiate Gymnasts

Background: The distribution pattern of subchondral bone density is an indicator of stress distribution over a joint surface under long-term physiologic loading. The biomechanical characteristics of the articular surfaces of the shoulder joint in gymnasts can be determined by measuring this distribution pattern. Purpose: To evaluate the distribution of subchondral bone density across the shoulder joint in male collegiate gymnasts and to determine the effects of gymnastic activities on its articular surfaces under long-term loading conditions using computed tomography osteoabsorptiometry (CTOAM). Study Design: Descriptive laboratory study. Methods: CT image data were obtained from both shoulders of 12 asymptomatic male collegiate gymnasts (gymnast group; mean age, 19.4 years; range, 18-22 years) and 10 male collegiate volunteers (control group; mean age, 20.2 years; range, 18-22 years). The distribution pattern of subchondral bone density across the articular surfaces of each shoulder joint was assessed by CTOAM. Quantitative analysis was performed of the locations and percentages of high-density areas on the articular surface. Results: Stress distribution patterns over the articular surfaces differed between the gymnasts and the controls. In the gymnasts, high-density areas were detected on the posterosuperior articular surface of the humeral head and the anterosuperior and/or posterosuperior articular surface of the glenoid. Mean bone density was greater in the gymnasts than in the controls ( P < .0001). Conclusion: Stress distribution over the articular surfaces of the shoulder joint was affected by gymnastic activities. Stress was concentrated over the superior part of the glenohumeral joint in male collegiate gymnasts. Clinical Relevance: The present findings suggest that gymnastic activities increase stress to the articular surfaces of the superior glenohumeral joint. This supports the notion that mechanical conditions play a crucial role in the origin of disorders particular to gymnastic activities.

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Safe Zone for Percutaneous Screw Fixation - Talonavicular Fusion

Foot & Ankle Orthopaedics ◽

10.1177/2473011418s00430 ◽

2018 ◽

Vol 3 (3) ◽

pp. 2473011418S0043

Author(s):

Ashish Shah ◽

Sung Lee ◽

Sameer Naranje ◽

Zachariah Pinter ◽

Robert Stibolt ◽

...

Keyword(s):

Medial Branch ◽

Screw Insertion ◽

Anterior Branch ◽

Bony Landmarks ◽

Medial Plane ◽

Extensor Hallucis Longus ◽

Hindfoot Deformities ◽

Fresh Frozen ◽

Optimal Fusion ◽

Neurovascular Structures

Category: Hindfoot Introduction/Purpose: Talonavicular fusion has been established as a reliable intervention for degenerative, inflammatory, and traumatic joint lesions as well as hindfoot deformities. In order to achieve optimal fusion, various versions of the procedure have been introduced in literature and have remained a topic of contention, with the most common variation involving the insertion of 1 to 3 screws dorsomedially and dorsolaterally. Dorsolateral screw placements commonly cause neurovasculature injury. The purpose of our cadaveric study was first to establish the safety of the dorsolateral percutaneous screw insertion in relation to these dorsal neurovascular structures, and then subsequently to standardize the ideal placement of the dorsolateral screw by comparing two insertion sites based on consistent bony landmarks. Methods: Ten fresh-frozen cadaver legs amputated at the knee were used for this study. Percutaneous cannulated screws were inserted to perform isolated talonavicular arthrodesis. The screws were inserted at 3 consistent sites: “medial screw” at dorsomedial navicular where it intersected at the medial plane of the first cuneiform, “central screw” at the edge of dorsal navicular between medial and intermediate cuneiforms, and “lateral screw” at the edge of dorsal navicular between intermediate and lateral cuneiforms. Superficial and deep dissections were carried out to identify any injured nerves, arteries, and tendons. Results: The mean age at death in our sample of cadavers was 80.1 ± 7.5 years (range 68 to 92) and had the BMI of 21.8 ± 2.4 (range 18.1 to 25.1). There were 5 males (50.0%) and 5 females (50.0%). The medial screw injured the anterior tibialis tendon in 2 cases (20.0%), the central screw injured the extensor hallucis longus tendon in 3 cases (30.0%), and the lateral screw injured the anterior branch of SPN, lateral branch of SPN, and medial branch of DPN once each in a total of 3 cases (30.0%). Conclusion: TN fusion with central screw placement at the interspace between the medial and intermediate cuneiforms protects the neurovasculatures of the foot to a superior extent than lateral screws between the intermediate and lateral cuneiforms.

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Ulnar articular surface 3-D landmarks and ecomorphology of small mammals: a case study of two early Miocene typotheres (Notoungulata) from Patagonia

Earth and Environmental Science Transactions of the Royal Society of Edinburgh ◽

10.1017/s1755691016000141 ◽

2015 ◽

Vol 106 (4) ◽

pp. 315-323 ◽

Cited By ~ 8

Author(s):

Nahuel A. Muñoz ◽

Guillermo H. Cassini ◽

Adriana M. Candela ◽

Sergio F. Vizcaíno

Keyword(s):

Small Mammals ◽

Articular Surface ◽

Principal Component ◽

Proximal Part ◽

Early Miocene ◽

Articular Surfaces ◽

Functional Value ◽

Forelimb Movements ◽

Morphological Patterns

ABSTRACTArticular surfaces reflect the relative movements between adjacent bones, and the ones involved in the elbow joint provide information about forelimb movements and may be useful for making inferences about the substrate use. The proximal articular surface of the ulna was examined through 3-D geometric morphometrics, in order to assess its usefulness as a proxy for paleoecological interpretations; particularly for two small mammals from the early Miocene of Patagonia. The sample was composed of 22 extant small mammals (rodents, carnivorans and primates) and two extinct typotheres: Hegetotherium mirabile (Hegetotheriidae) and Interatherium robustum (Interatheriidae). Forty-five landmarks were taken and principal component analysis (PCA) was used to explore the morphospace structure. The results of PCA for the whole surface were inconclusive; therefore, successive analyses were made, subdividing the surface into sub-units. The PCA for the proximal part of the trochlear notch was the most informative, allowing the recognition of morphospaces with functional value: one for digging rodents and another for most climbers. Neither typothere would have had a specialisation for climbing or digging in the features analysed. This study allows morphological patterns on different parts of a joint to be detected; interpreted, at least partially, as differential responses to different kinds of mechanical stress.

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Anatomical data on the craniocervical junction and their correlation with degenerative changes in 30 cadaveric specimens

Journal of Neurosurgery Spine ◽

10.3171/spi.2005.3.5.0379 ◽

2005 ◽

Vol 3 (5) ◽

pp. 379-385 ◽

Cited By ~ 13

Author(s):

Stefan A. König ◽

Axel Goldammer ◽

Hans-Ekkehart Vitzthum

Keyword(s):

Articular Cartilage ◽

Articular Surface ◽

Craniocervical Junction ◽

Degenerative Changes ◽

Content Type ◽

Articular Surfaces ◽

Anatomical Data ◽

Grade Ii ◽

Grade Iii ◽

Fine Print

>Object. The goal of this project was to measure vertebral dimensions at the craniocervical junction and to investigate degenerative changes in this region and their correlations with the anatomical data. These studies will assist in an understanding of biomechanical conditions in this region, which are clinically relevant in cases of cervicogenic headaches and vertigo. Methods. The authors examined 30 cadaveric specimens obtained from patients ranging in age from 24 to 88 years at death. Measurements of angles of the vertebrae were conducted using an imprint method. Microsections of osseous endplates and articular cartilage were graded according to their degrees of degeneration by using the Petersson classification (0, no sign of degeneration; I, superficial degeneration with several fragmentations; II, deeper degeneration with cartilaginous disintegration and penetrating ulceration; or III, complete cartilaginous degeneration with the appearance of subchondral bone in > 50% of the articular surface). The authors found Grade I changes in 100% of the occiput specimens. In the superior articular cartilage of C-1 no changes (Grade 0) were found in two specimens, whereas 6% of the specimens exhibited Grade II changes and 89% exhibited Grade I changes. In the inferior articular cartilage of C-1, 57% of the specimens displayed Grade I changes, 14% Grade II, and 20% Grade III changes. In the superior articular cartilage of C-2, 62.5% of the specimens displayed Grade I changes and 25% Grade II changes. At the occiput—C1 level the authors found a higher frequency of degeneration at the upper left articular surface of the atlas (Quadrants 1 and 3), and at the C1–2 level they found a higher frequency of degeneration at the upper left and upper right articular surfaces of the axis (Quadrants 2 and 3, respectively). Using the McNemar test, the authors investigated the frequency of affection of single quadrants in a left—right side comparison (lateral reversal). Significant differences were identified for Quadrant 2 of the upper left articular surface of C-2 and Quadrant 3 of the upper right articular surface of C-2. These results correlate with the analysis of single articular surfaces of the axis, but contradict the results for the atlas, in which no significant difference in the left—right side comparison was found. Conclusions. Severe degeneration in the atlantooccipital joints appears to be a rare condition, with no Grade II or III degeneration found in the occipital condyles and 6% Grade I, 89% Grade II, but no Grade III changes in the superior articular cartilage of the atlas. Degeneration of the inferior articular cartilage of C-1 and the superior articular cartilage of C-2 indicates that the atlantoaxial joint faces more intense mechanical exposure, which is increased at the upper joint surfaces.

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THE EFFECT OF ARTICULAR SURFACE SHAPE AND TENDON FORCES OF TOTAL WRIST ARTHROPLASTY SYSTEMS: A FINITE ELEMENT STUDY

Journal of Musculoskeletal Research ◽

10.1142/s0218957712500212 ◽

2012 ◽

Vol 15 (04) ◽

pp. 1250021 ◽

Cited By ~ 1

Author(s):

Matthew B. A. McCullough ◽

Brian D. Adams ◽

Nicole M. Grosland

Keyword(s):

Finite Element ◽

Articular Surface ◽

Surface Shape ◽

Element Analysis ◽

Future Directions ◽

Ulnar Deviation ◽

Articular Surfaces ◽

Total Wrist Arthroplasty ◽

Flexion Extension ◽

Wrist Arthroplasty

In order to better understand the behavior of the total wrist implant systems, finite element analysis (FEA) was used to model the articular surfaces of two unconstrained total wrist arthroplasty (TWA) devices. After creating models based on manufacturer specifications, simulations of flexion, extension, radial deviation, ulnar deviation and circumduction were run with simulated moments from surrounding tendons under displacement control. In addition, simulations were run under positioning that represented a pronated and supinated forearm as well as unstable conditions. Understanding implant behavior and capabilities as related to the shape of the articular surfaces is important for proper prescription of implants as well as determining future directions for the design of arthroplasty devices.

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