Cadaveric Elbows Research Articles

The loads developed by epicondylar and epitrochlear muscles across the elbow joint. A dynamic simulated model

The radio-humeral joint has traditionally been believed to support most of the loads transmitted through the elbow. Load transfer through the elbow has been a controversial issue since the publication of the first biomechanical studies on the subject, most of which were based on extrinsic forces acting on the extended joint. The present study analyzes load distribution across the six different compartments in the elbow while the joint is flexed, as well as the intrinsic forces generated in the epicondylar and epitrochlear muscles.Ten cadaveric elbows were positioned at 90° of flexion, forearm in a neutral position and wrist at 0°. Tekscan sensors were used for measuring intraarticular pressures.Forces generated by epitrochlear muscles results in a series of loads that affect mainly the anteromedial facet (40%), followed by the posterolateral facet (34%) of the ulnohumeral joint, with the flexor carpi ulnaris generating the heaviest loads (43% on the anteromedial and 38% on the posterolateral facets). Conversely, the forces generated by the epicondylar muscles, similar in behavior but with an opposite direction, convey heavier loads to the elbow’s anterolateral facet (45%), followed by the radiohumeral joint (26%) with the extensor carpi ulnaris generating the heaviest loads (54% on the anterolateral facet and 17% on the radiohumeral joint).Our results indicate that the elbow joint exhibits a characteristic load distribution pattern that depends on the muscles, as intrinsic forces are generated by the epicondylar and epitrochlear muscles. The anterior portion of the ulnohumeral joint is the area bearing the heaviest loads.

Effect of Radiocapitellar Joint Over/Under Stuffing on Elbow Joint Contact Pressure

Comminuted radial head fractures are commonly treated by surgical resection or replacement with a prosthesis. A potential problem with radial head replacement is overlengthening of the radial neck ("overstuffing" of the radial head), which has been shown to affect both ulnohumeral kinematics and radiocapitellar pressures. We hypothesized that an overstuffed radial head prosthesis increases capitellar pressure and reduces coronoid pressure. Seven human cadaveric elbows were prepared on a custom-designed apparatus simulating stabilizing muscle loads, and passively flexed from 0° to 90° under gravity valgus torque while joint contact pressures were measured. Each elbow was tested sequentially with different neck lengths, starting with the intact specimen followed by insertion of understuffed (-2 mm), standard-height (0 mm), and overstuffed (+2 mm) radial head prostheses in neutral forearm rotation, 40° pronation, and 40° supination positions, respectively. Capitellar mean contact pressures significantly increased after insertion of an overstuffed radial head prosthesis. In valgus position with neutral forearm rotation, capitellar mean contact pressure on the joint with an intact radial head averaged 227 ± 70 kPa. Insertion of understuffed, standard-height, and overstuffed radial head prostheses changed the mean contact pressures to 152 ± 76 kPa, 212 ± 68 kPa, and 491 ± 168 kPa, respectively. The overstuffed radial head group had significantly lower whole coronoid mean contact pressures (153 ± 56 kPa) compared with the intact (390 ± 138 kPa) and standard-height (376 ± 191 kPa) radial head groups. An increase in radial prosthesis height significantly increases capitellar contact pressures and reduces coronoid contact pressures. Restoration of the anatomic radial head height is critical when performing radial head arthroplasty to maintain normal joint biomechanics. Elevated capitellar contact pressures can potentially lead to pain and early degenerative changes.

Biomechanical comparison of novel ulnar collateral ligament reconstruction with internal brace augmentation vs. modified docking technique.

Ulnar collateral ligament (UCL) reconstruction (UCLR) is a common surgery among baseball pitchers. UCL repair combined with augmentation using high-strength tape, referred to as an internal brace, was developed as an alternative to UCLR in select patients with the benefit of allowing these athletes to return to sport (RTS) faster. A combined UCLR with an internal brace may allow players indicated for a UCLR to RTS more expeditiously. Twenty-four cadaveric elbows were divided into 3 groups: 12 specimens into the modified docking (MD) group, 6 into the double-docking (DD) group, and 6 into the double docking with internal brace augmentation (DDA) group. This allowed a 1:1 comparison of the MD to the DD and the MD to the DDA. Valgus cyclic testing of native and reconstructed specimens was executed at 90° elbow flexion. After preconditioning, all specimens were cycled between 2 and 10 Nm for 250 cycles. Reconstructed specimens continued to a torque test to catastrophic failure step. Outcome data included intracyclic stiffness, maximum cyclic rotational displacement, gap formation, and failure torque. Cyclic stiffness of the constructs remained constant throughout the entirety of the torque-controlled cycling phase. The DDA group resulted in a 38% increase in cyclic stiffness from native testing (not statistically significant) and a statistically significant 54% increase from the MD (P=.002). The DDA mean cyclic stiffness was significantly greater than the Native (P<.001), DD (P=.025), and MD (P<.001) groups. Between reconstruction groups, mean gap formation was greatest among the MD group (2.51°±1.59°) and least for the DDA group (1.01°±0.57°) but did not reach statistical significance. Tape augmentation to the modified UCLR (DDA group) improved cyclic stiffness and reduced gap formation compared with the MD group.

Anatomic study of an anterior portal for percutaneous internal fixation of capitellum fractures.

Fractures of the capitellum are uncommon and difficult to treat surgically. Capitellar open reduction-internal fixation uses a lateral open approach with posterior-to-anterior or anterior-to-posterior screw fixation. We investigated the use of an anterior portal for placement of anterior-to-posterior screw fixation through cadaveric measurement of the anatomic relationships from an anteriorly to posteriorly placed Kirschner wire (K-wire) to anterior elbow structures and calculated the percentage of articular surface accessed from the anterior portal. Eight fresh-frozen cadaveric elbows without radiographic or cutaneous evidence of prior trauma or surgery were used for this study. An arthroscopic proximal anteromedial portal was cannulized, and the radiocapitellar joint was evaluated. A single 1-cm portal was placed 1 cm distal to the elbow flexion crease and based lateral to the biceps tendon. The location of the portal was confirmed with a spinal needle, and blunt dissection with a hemostat was performed down to capsular tissue and for arthrotomy. A spinal needle sheath was threaded over a blunt switching stick and served as a cannula for placement of a 0.062 K-wire. Articular mapping was performed with cartilage scraping by the K-wire; the K-wire was then placed at the perceived center along the proximal-to-distal and radial-to-ulnar axis of the capitellum. Fluoroscopic confirmation of the wire's location was performed. Under loupe magnification, anatomic dissection was performed and the shortest distance measurements were recorded with digital calipers from the K-wire to the dissected structures. Capitellar articular measurements were recorded, in addition to the articular area defined by the K-wire. Data analysis was performed, and the average distance and standard deviation (in millimeters) were calculated. For structures that were pierced by or touching the K-wire, the distance was recorded as 0.1 mm. The average distance from the K-wire to the radial, lateral antebrachial cutaneous, and median nerves was 1.8 mm, 11.5 mm, and 28.0 mm, respectively. The average distance from the median cubital vein and biceps tendon was 3.7 mm and 13.4 mm, respectively. The pin track pierced the brachioradialis and supinator muscles in all but 1 specimen. The average capitellar articular surface marked was 39.1% of the calculated articular footprint of the capitellum. The anterior portal to the capitellum is directly adjacent to the radial nerve and lateral antebrachial cutaneous nerve, where each is susceptible to injury. We recommend blunt dissection and insertion of a cannula to allow drilling and placement of internal fixation in a relatively safe manner with respect to neurovascular structures.

Biomechanical comparison of continuous compression implants versus tension band fixation for transverse olecranon fractures

PurposeTension band wiring (TBW) is considered the ‘gold standard’ for fixation of transverse olecranon fractures (OTA/AO 2U1B1d). However, this approach requires a large exposure, can be technically demanding and operator-dependent, and is associated with hardware prominence. Continuous compression implants (CCI) may address these limitations. To the authors' knowledge, a comparison between TBW and CCI has not been performed. Therefore, this study was designed to compare biomechanical properties of CCI to TBW for 2U1B1d olecranon fractures using human cadaver elbows. MethodsA transverse olecranon fracture was simulated in eight matched pairs of cadaveric elbows. Matched pairs were used for comparison of TBW and CCI. Cyclic loading was performed at both 10 N and 500 N, with gap formation and load to failure recorded. Results: No significant difference in gap formation at 10 N (p > 0.3) or 500 N (p = 0.6), or load-to-failure (p=.00.41), was observed between the two groups. DiscussionCCI fixation requires a smaller incision, is easy to perform, and involves low-profile implant that may reduce morbidity. Based on biomechanical properties that match the gold standard, continuous compression nitinol implants are an appropriate option for fixation of transverse olecranon fractures with potential advantages over tension band wiring.

Immunofluorescence analysis of sensory nerve endings in the periarticular tissue of the human elbow joint.

To investigate the dynamic aspects of elbow stability, we aimed to analyze sensory nerve endings in the ligaments and the capsule of elbow joints. The capsule with its anterior (AJC) and posterior (PJC) parts, the radial collateral ligament (RCL), the annular ligament (AL), and the ulnar collateral ligament with its posterior (PUCL), transverse (TUCL) and anterior parts (AUCL) were dissected from eleven human cadaver elbow joints. Sensory nerve endings were analyzed in two levels per specimen as total cell amount/ cm2 after immunofluorescence staining with low-affinity neurotrophin receptor p75, protein gene product 9.5, S-100 protein and 4',6-Diamidin-2-phenylindol, Carbonic anhydrase II and choline acetyltransferase on an Apotome microscope according to Freeman and Wyke's classification. Free nerve endings were the predominant mechanoreceptor in all seven structures followed by Ruffini, unclassifiable, Golgi-like, and Pacini corpuscles (p ≤ 0.00001, respectively). Free nerve endings were observed significant more often in the AJC than in the RCL (p < 0.00002). A higher density of Ruffini endings than Golgi-like endings was observed in the PJC (p = 0.004). The RCL contained significant more Ruffini endings than Pacini corpuscles (p = 0.004). Carbonic anhydrase II was significantly more frequently positively immunoreactive than choline acetyltransferase in all sensory nerve endings (p < 0.05). Sensory nerve endings were significant more often epifascicular distributed in all structures (p < 0.006, respectively) except for the AJC, which had a pronounced equal distribution (p < 0.00005). The high density of free nerve endings in the joint capsule indicates that it has pronounced nociceptive functions. Joint position sense is mainly detected by the RCL, AUCL, PUCL, and the PJC. Proprioceptive control of the elbow joint is mainly monitored by the joint capsule and the UCL, respectively. However, the extreme range of motion is primarily controlled by the RCL mediated by Golgi-like endings.

The lateral collateral ligament complex of the elbow in a Thai population: an anatomical study of 56 cadaveric specimens.

The purpose of this study was to investigate the anatomical features of the lateral collateral complex (LCC) of the elbow in a Thai population. We dissected 56 cadaveric elbows and described the LCC three-dimensionally in sagittal and coronal planes. We found that the characteristics differed from previous reports in other ethnic populations. In the sagittal plane, the centre of the origin of the LCC was located 3 mm anteriorly and 4 mm inferiorly to the apex of the lateral humerus epicondyle, and in the coronal plane it was 4 mm deep. The vertical distance between the origin of the lateral ulnar collateral ligament (LUCL) and the lateral epicondyle and the distance from the LUCL insertion to the border of the ulnar bone differed significantly between sexes. These data may be useful for surgeons during reconstruction of injures to the LCC of the elbow.Level of evidence: V.

Poster 185: Flexor Pronator Mass Contribution to Elbow Valgus Stability: A Biomechanical Project

Objectives:Identify the main muscle in the flexor pronator mass (the pronator teres (PT), flexor carpi radialis (FCR), flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU)) that contributes most to valgus stability at a greater range of elbow motion (60-150 degrees) than in previous studies.Methods:8 cadaveric elbows in an in vitro biomechanical study were investigated. The specimens were mounted on a custom apparatus from the distal humerus to the fingers. Each muscle group of the flexor pronator mass was relatively loaded based on physiologic cross-sectional area. There were 6 loaded conditions: all loaded, unloaded PT, unloaded FCR, unloaded FDS, unloaded FCU, and all unloaded. A 2 N-m valgus torque was applied at a rate of 1 mm/sec. Valgus angle was measured for each loaded condition, especially between all loaded and one unloaded muscle. This allowed an increase in valgus angle for one unloaded muscle. The higher increase in valgus angle indicated the higher the contribution of that released muscle to valgus stability. This was performed at 60, 90, 120, and 150 degrees of elbow flexion to cover the range at which the UCL tears during the late cocking and early acceleration phases of throwing. The measurements were made in two conditions: first with the UCL intact and second with the UCL resected at the anterior bundle.Results: There was a statistical significance in the mean change in valgus angle at all flexion angles and load conditions when the UCL was intact vs when it was resected (3.76 ± 2.78 SD vs 4.82 ± 2.99 SD degrees).The valgus angle was statistically mostly increased in the “all unloaded” condition when compared to all the other loaded conditions at all flexion angles involving both when the UCL was intact and resected.Unloading one individual flexor pronator muscle did not significantly affect the valgus stability of the elbow.There was a trend towards FDS as being the primary flexor pronator stabilizer when the elbow was taken from an all-loaded condition to one muscle that was unloaded (P value = 0.169).At 150 degrees, the elbow was statistically significantly most stable compared to all the other flexion angles.At 90 degrees, the elbow was most unstable with an increase in valgus angle of 1.2 degrees between intact and resected UCL conditions.At 60 degrees with the UCL resected, there was not a statistical significant difference in valgus angle between all unloaded and unloaded FDS conditions signifying that the FDS contributed most to valgus stability. Conclusions: Physical examination of the UCL is best performed with the elbow at 90 degrees with the forearm in neutral (most unstable out of the flexion angles we tested).At 150 degrees, the elbow is most stable to valgus stress.When the UCL is injured, the FDS appeared to contribute most to valgus stability at 60 degrees out of the four flexor pronator muscles.There was a trend towards FDS as being the primary flexor pronator stabilizer.Rehabilitation of the flexor-pronator mass should focus on the FDS. Figure 1.Figure 2.Table 1.Two-group comparisons of mean valgu angle under different loading conditionsTable 2.Two-group comparisons between all unloaded condition and other loaded conditions at 60˚ elbow flexion with resected UCL.

A new all-suture tension band tape fixation technique for simple olecranon fractures versus conventional tension band wire fixation: a comparative biomechanics study.

Simple transverse or short oblique olecranon fractures without articular comminution are classified as Mayo type IIA fractures and are typically treated with a tension band wire construct. Because of the high reoperation rates, frequently because of prominent hardware, all-suture tension band constructs have been introduced. It was the purpose to compare the biomechanical performance of conventional tension band wire fixation with a new all-suture tension band tape fixation for simple olecranon fractures. Mayo type IIA olecranon fractures were created in 20 cadaveric elbows from 10 donors. One elbow of each donor was randomly assigned to the tension band wire technique (group TBW) or tension band tape (Arthrex, 1.3-mm SutureTape) technique (group TBT). Both groups were cyclically loaded with 500 N over 500 cycles, after which a uniaxial displacement was performed to evaluate load to failure. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, where failure was defined as fracture gap formation greater than 4.0 mm. There was no significant difference in gap formation after 500 cycles between the TBW (1.8 mm±1.3 mm) and the TBT (1.9 mm±1.1 mm) groups (P=.854). The TBT showed a tendency toward greater construct stiffness compared with the TBW construct (mean difference: 142 N/mm; P=.053). Ultimate load to failure was not significantly different comparing both groups (TBW: 1138 N±286 N vs. TBT: 1126 N±272 N; P=.928). In both groups, all repairs failed because of >4.0-mm gap formation at the fracture site and none because of tension band construct breakage. Our study shows that the TBT technique produces equivalent or superior biomechanical performance to the TBW for simple olecranon fractures. The TBT approach reduces the risk of hardware prominence and as a result mitigates against the need for hardware removal. The TBT technique offers a clinically viable alternative to TBW.

Biomechanical Comparison of Ulnar Collateral Ligament Reconstruction With and Without Suture Augmentation

Background: A common concern associated with elbow ulnar collateral ligament (UCL) reconstruction is the amount of time required for recovery and rehabilitation. For example, for Major League Baseball pitchers, the average time to return to competition ranges from 13.8 to 20.5 months. Suture tape augmentation has shown the ability to provide additional soft tissue stability across other joints in the body. By providing an additional checkrein to the UCL reconstruction while the graft is healing, it may be possible to accelerate the rehabilitation process in overhead athletes and thus effect a quicker return to sports. Purpose: To compare elbow valgus stability and load to failure between UCL reconstruction with and without suture tape augmentation. Study Design: Controlled laboratory study. Methods: Fresh-frozen cadaveric elbows (N = 24) were dissected to expose the UCL. Medial elbow stability was tested with the UCL intact, deficient, and reconstructed utilizing the 3-strand docking technique with or without suture augmentation. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion-tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, reconstructed specimens were loaded to failure at 70° of elbow flexion. Results: UCL-deficient elbows demonstrated significantly greater valgus rotation when compared with intact and internally braced reconstructed elbows at every angle of flexion tested and when compared with unbraced UCL-reconstructed elbows at 50° to 120° of flexion (P < .05). There were no significant differences between intact and UCL-reconstructed elbows with and without suture augmentation at any flexion angle tested. When loaded to failure, unbraced reconstructed elbows failed at a significantly lower torque as compared with elbows with UCL reconstruction with suture tape augmentation (P < .01). Conclusion: In this cadaveric model, 3-strand UCL reconstruction with suture augmentation did not overconstrain the elbow throughout all flexion angles when compared with the native state and UCL reconstruction alone, while providing greater load to failure. Clinical Relevance: Suture tape augmentation may provide the additional strength necessary to accelerate rehabilitation after UCL reconstruction.

Needle arthroscopy for exploration of the elbow joint: a case series of six dogs with preliminary cadaveric study

Case history: Dogs (n = 6) suffering from elbow-associated lameness for a median of 3.5 (min 2, max 12) months duration requiring arthroscopic exploration according to imaging results were prospectively included in this study. Clinical findings: Dogs that met the inclusion criteria were of various breeds with a median body weight of 18 (min 13.2, max 34.5) kg and median age at presentation of 11 (min 6, max 96) months. Results of imaging modalities (radiographs and/or CT) were consistent with developmental elbow disease in all of the dogs. Arthroscopic findings: Feasibility of the needle arthroscopy procedure was first assessed in a preliminary cadaveric study. Disease-free cadaveric forelimbs (n = 12) were collected from adult dogs (n = 6) euthanised for reasons unrelated to the present study. Elbow exploration was performed, beginning with needle arthroscopy (1 mm, 0° angle scope) followed by standard arthroscopy (2.4 mm, 30° angle scope) through a medial approach. The ease of introduction, range of motion and the quality of visualisation were assessed subjectively and presence of iatrogenic introduction lesions and extent of field of vision (assessed by the number of anatomical structures visualised) were scored and statistically compared. Needle arthroscopy allowed inspection of all structures at risk for medial/caudal compartment disease in all joints considering the occasional need for multiple portals. In the clinical setting, elbow exploration was found to be similar to that in cadaver joints in 4/6 dogs. The lower quality of vision provided by needle arthroscopy was a limitation of the technique, and 2/6 clinical cases required conversion to standard arthroscopy for full visualisation of the joint. No introduction lesions were noted with needle arthroscopy in either the cadaveric or clinical studies. Conclusions and clinical relevance: Needle arthroscopy allowed safe visualisation of all the structures of the medial and caudal compartment in disease-free cadaveric elbows, suggesting that needle arthroscopy is an appropriate technique for diagnosis and assessment of lesions of developmental elbow disease. However, the low quality of vision provided by the 1 mm scope, and the small diameter of the sleeve, which limited fluid inflow, combined with fragility of the device were major drawbacks that prevented consistent full exploration of the joint and detailed lesion assessment in clinical situations. Improvement of the device is thus necessary before use of the technique in clinical practice can be recommended.

Anatomic Study of the Medial Collateral Ligament in Thai Population: A Cadaveric Study of 56 Elbows.

This study aims to elucidate basic anatomic and geometric features of MCL, providing more accurate and detailed information, as guidance for surgeons, to improve patient's outcome of the treatment. The anterior bundle (AB), posterior bundle (PB) and transverse bundle (TB) ligament of 56 fresh frozen Thai cadaveric elbows, were measured and recorded, comprise key ligament's geometric features, footprints and dimensions, and its relation to bony landmarks. Sagittal and coronal planes were used in respect of the anatomical position. The mean distance between the center of AB origin and the apex of medial epicondyle is as follows: 2.97 ± 2.21mm anteriorly, 4.73 ± 1.60mm inferiorly in the sagittal plane, and 4.23 ± 1.13mm deep from the epicondyle in the coronal plane. Its dimension is 6.23 ± 1.02mm in width and 45.97 ± 6.75mm in length. The ligament's insertion triangular shape has its base located 28.44 ± 3.51mm anterior from the posterior olecranon border, and 22.52 ± 2.49mm superior from the inferior ulnar border. The tip located 50.79 ± 4.86mm anterior from the posterior olecranon border and 17.64 ± 2.80mm superior from the inferior ulnar border. Apprehension of the precise geometries and distances of the ligament's footprint relative to key anatomical point is crucial. This stereographically comprehended data are useful for surgeon as reference points to obtain stability, motion, kinetic, and kinematic properties of the elbow. Level V evidence. The online version contains supplementary material available at 10.1007/s43465-022-00648-x.

Multiple Perforations of the ECRB Tendon Using an Innovative Standardized, Reproducible Technique; A Cadaveric Study on Accuracy and Prospective Clinical Safety Assessment Pilot Study. No Adverse Effects in the First 122 Patients with Lateral Epicondylitis.

In LE (Lateral Epicondylitis) otherwise known as Tennis Elbow, the Extensor Carpi Radialis Brevis (ECRB) tendon is most commonly involved. In the majority of studies, injections are performed with a lack of standardization. The Instant Tennis Elbow Cure (ITEC) device has been developed to perform reproducible and standardized perforations by multiple needles. The goal of this pilot study was to estimate the accuracy of this ITEC device by means of a cadaveric study and to assess the clinical safety of this procedure. Ten cadaveric arms were injected using the ITEC device. The location and depth of the ECRB tendon was measured by ultrasound imaging. The accuracy of the infiltration was assessed by locating the injected dye through dissection and arthrotomy of the cadaveric elbow. A prospective clinical pilot study was conducted to assess the safety of the ITEC device in treating patients with chronic LE. An optional infiltration with an injection fluid was carried out?? Primary outcome measures were side effects and complications of the ITEC device occurring within a follow up period of 8 weeks after treatment. In all cadaveric elbows the injection fluid ( in this case an injection fluid) was located at the ECRB tendon. In one cadaver, a minimal amount of dye was found intra-articular and in 3 cadavers a small quantity was located in the surrounding tissue of the ECRB tendon. 122 patients with LE were treated with the ITEC device. No adverse effects or complications were reported at 8-week follow up. Treatment of LE using the ITEC device appears accurate and safe. It may improve future research since it is reproducible and it can be performed in a standardized way.

Paper 12: Biomechanical Comparison of Anatomic Restoration of the Ulnar Footprint Versus Traditional Ulnar Tunnels in Ulnar Collateral Ligament Reconstruction

Objectives:Current techniques for ulnar collateral ligament (UCL) do not reproduce the anatomic ulnar footprint of the UCL. The purpose of this study was to describe a novel UCL reconstruction technique that utilizes proximal-to-distal ulnar bone tunnels to better recreate the anatomy of the UCL and compare the biomechanical profile at time zero between this technique, the native UCL, and the traditional docking technique. Our hypothesis was that the biomechanical profile of the anatomic technique is similar to the native UCL and traditional docking technique.Methods:Ten matched cadaveric elbows were potted with the forearm in neutral rotation. The palmaris longus tendon graft was harvested, and bones were sectioned 14 cm proximal and distal to the elbow joint. Specimen testing included: (1) native UCL testing performed at 90° flexion with 0.5 Nm valgus moment preload, (2) cyclic loading from 0.5-to-5 Nm valgus moment for 1000 cycles at 1 Hz, and (3) load to failure at 0.2 mm/s. Elbows then underwent UCL reconstruction with one elbow of each pair receiving the classic docking technique using either anatomic (proximal-to-distal) or traditional (anterior-to-posterior) tunnel locations. Specimen testing was then repeated, as described above.Results:There was no difference between maximum load at failure or valgus angle between the anatomic or traditional tunnel location techniques (34.90 ± 10.65 Nm vs. 37.28 ± 14.26 Nm, P = 0.644) or the native UCL (45.83 ± 17.03 Nm, P = 0.099). Additionally, there was no difference in valgus angle after 1000 cycles across the anatomic (4.58 ± 1.47°), traditional (4.08 ± 1.28°), or native UCL (4.07 ± 1.99°). Anatomic group and the native UCL had similar valgus angles at failure (24.13 ± 5.86° vs. 20.13 ± 5.70°, P = 0.083), while the traditional group had a higher valgus angle at failure compared to the native UCL (24.88 ± 6.18° vs. 19.44 ± 5.86°, P = 0.015).Conclusions:UCL reconstruction with the docking technique utilizing proximal-to-distal ulnar tunnels to restore the anatomic ulnar footprint better recreates the anatomy of the UCL while providing valgus stability comparable to reconstruction with docking technique using traditional anterior-to-posterior ulnar tunnel locations. These results suggest that utilization of the anatomic tunnel location in UCL reconstruction has similar biomechanical properties compared to the traditional method at the time of initial fixation (i.e., not accounting for healing following reconstruction in vivo) while keeping the ulnar tunnels further from the ulnar nerve. Further studies are warranted to determine if an anatomically based UCL reconstruction results in differing outcomes compared to traditional reconstruction techniques.

Valgus fatigue and nonlinear damage accretion of the anterior bundle of the elbow medial collateral ligament (AMCL)

Failure by fatigue is one mechanism by which ligaments can rupture, with the accumulation of damage gradually degrading the ligament strength. Baseball pitchers who perform repeated high-level throwing continuously subject the medial ligament complex of the elbow to extreme levels of loading, which can lead to fatigue and eventual rupture. This study sought to investigate this behavior and quantify the fatigue properties of the anterior bundle of the medial collateral ligament (AMCL) with respect to valgus elbow torque. Eleven pairs of cadaveric elbow specimens were used for this study. One side of each pair was tested in vertical elongation at four flexion angles and then tested to failure at 90° of flexion. The contralateral specimens were tested in valgus fatigue at 90° of flexion using a specialized apparatus with application of known moments based on the elongation failure load. The average tensile failure load for the AMCL was 595.3 ± 201.9 N. During cycling, the average increase in the maximum valgus rotation angle was 4.77° ± 2.82°. The average maximum stretch of the AMCL middle band increased from 1.066 ± 0.017 to 1.076 ± 0.018 near the time of fatigue failure. The average cycles to failure for specimens tested at 90% and 80% of the estimated failure torque were 3211 ± 4721.33 and 25063 ± 30487.58, respectively. The nonlinear non-dimensional fatigue life and damage accretion results work in conjunction to predict the fatigue properties for a valgus elbow motion of arbitrary torque magnitude at 90° of elbow flexion.

Lag screw osteosynthesis of simple olecranon fractures: A biomechanical comparative study.

Olecranon fractures are most frequently stabilized by tension band wiring (TBW), which unfortunately leads to relevant implant removal rates due to K-wire migration and soft tissue irritation. As lag screw osteosynthesis (LSO) might be a gentle and effective alternative in simple fracture patterns, the goal of the present study was to biomechanically compare LSO with TBW in simple olecranon fractures at a cadaver model. A simple olecranon fracture (Mayo type IIA) was created in eight pairs of human cadaver elbows, which were pairwise fixed by either TBW or two transcortical 4.0 mm lag screws. Biomechanical testing was conducted as a pulling force, applied to the triceps tendon in a 90° position. First, cyclic loading between 10 and 300 N was performed for 50,000 cycles. Afterward, maximum load was raised by 0.02 N/cycle until construct failure, what was defined as displacement >2 mm. Besides fracture displacement, failure cycle and failure load, the modes of failure were analyzed. Within the first five cycles, there was no significant difference in displacement (median TBW: 0.2 mm; LSO: 0.5 mm; p = 0.091). Both after 2000 (median TBW: 0.2 mm; LSO: 0.6 mm; p = 0.042) and after 20,000 cycles (median TBW: 0.4 mm; LSO: 0.9 mm; p = 0.027), the difference was significant. Failure cycle (median TBW: 72,639 cycles; LSO: 43,429 cycles; p = 0.017) and failure load (median TBW: 702 N; LSO: 303 N; p = 0.025) differed significantly as well. TBW mostly (6/8) failed at the lock of the cerclage wire, whereas most LSO constructs (5/8) failed as a pullout of the proximal fragment. In conclusion, to our biomechanical findings at human cadaver specimens, simple olecranon fractures treated by LSO show higher dislocation rates and lower failure loads compared to conventional TBW and mostly fail by pullout of the proximal fragment.

Radiocapitellar Contact Characteristics After Osteochondral Defect Repair Using a Novel Hybrid Reconstructive Procedure

Background:Many procedures to reconstruct osteochondral defects of the elbow radiocapitellar (RC) joint lack versatility or durability or do not directly address the subchondral bone structure and function.Purpose/Hypothesis:To biomechanically characterize the RC joint contact area, force, pressure, and peak pressure before and after reconstruction of osteochondral defects using a novel hybrid reconstructive procedure. It was hypothesized that the procedure would restore the contact characteristics to the intact condition.Study Design:Controlled laboratory study.Methods:A total of 10 cadaveric elbows (mean age 67 ± 2.7 years) were dissected to isolate the humerus and radial head. RC contact area, contact force, mean contact pressure, and peak contact pressure were measured with the elbow at 45° of flexion and neutral forearm rotation at compressive loads of 25, 50, and 75 N. Osteochondral defects 8 and 11 mm in diameter were created at the center of the capitellum; the defects were then reconstructed with a titanium fenestrated threaded implant, countersunk in the subchondral bone, with an acellular dermal matrix allograft sutured in place on top of the implant. Five conditions (intact, 8-mm defect, 8-mm repair, 11-mm defect, and 11-mm repair) were tested and results were compared using repeated-measures analysis of variance.Results:Both 8- and 11-mm defects significantly increased RC mean contact pressure at all compressive loads (P ≤ .008) and significantly increased peak contact pressure at compressive loads of 50 and 75 N (P < .002) compared with the intact condition. Repair of the 8-mm defect significantly decreased RC mean contact pressure at 25- and 50-N loads (P ≤ .009) and significantly decreased peak contact pressure at 50- and 75-N loads (P ≤ .035) compared with the defect condition. Repair of the 11-mm defect decreased mean contact pressure significantly at all compressive loads (P ≤ .001) and peak contact pressure at 50- and 75-N loads (P < .044) compared with the defect condition.Conclusion:RC joint contact pressure was restored to intact conditions while avoiding increased peak contact pressure or edge loading after repairing osteochondral defects related to osteochondrosis with a novel hybrid reconstruction technique.Clinical Relevance:This hybrid procedure that addresses the entire osteochondral unit may provide a new treatment option for osteochondral defects.

Overhead arm positioning in the rehabilitation of elbow dislocations: An in vitro biomechanical study

Study DesignIn vitro biomechanical study. IntroductionElbow stiffness is a common complication following elbow dislocation. Overhead exercises have been proposed to initiate early motion to reduce stiffness through employing gravity to stabilize the elbow. The implications of this position with regard to elbow kinematics after dislocation have not been reported. Purpose of the StudyTo determine the influence of the overhead position on elbow stability following combined medial and lateral collateral ligament (MCL and LCL) injuries. MethodsPassive and simulated active extension were performed on 11 cadaveric elbows with the arm in the overhead, dependent, and horizontal positions and with the forearm in pronation, neutral, and supination. Internal-external rotation (IER) and varus-valgus angulation (VVA) of the ulnohumeral joint were assessed for the intact elbow and after simulated MCL-LCL injury. Repeated-measures analyses of variance were conducted to analyze the effects of elbow state, arm position, forearm rotation, and extension angle. ResultsDuring passive extension with the arm overhead, the pronated position resulted in more internal rotation than supination (-2.6 ± 0.7°, P = .03). There was no effect of forearm rotation on VVA. The overhead position increased internal rotation relative to the dependent position when the forearm was neutral (-8.5 ± 2.5°, P = .04) and relative to the horizontal position when the forearm was supinated (-12.7 ± 2.2°, P= .02). During active extension, pronation increased valgus angle compared to the neutral (+1.2 ± 0.3°, P= .04) and supinated (+1.5 ± 0.4°, P= .03) positions, but did not affect IER. There was no difference between active and passive motion with the arm overhead (P > .05). DiscussionMovement of the injured elbow in the overhead position most closely replicated kinematics of the intact elbow compared to the other arm positions. ConclusionsOverhead elbow extension results in similar kinematics between an intact elbow and an elbow with MCL and LCL tears. As such, therapists might consider early motion in this position to reduce the risk of elbow stiffness after dislocation.

Locking suture repair versus ligament augmentation—a biomechanical study regarding the treatment of acute lateral collateral ligament injuries of the elbow

BackgroundLateral collateral ligament (LCL) tears are frequently observed in fractures and dislocations of the elbow. Recent biomechanical evidence suggests that additional ligament augmentation may improve repair stability. The aim of this biomechanical in-vitro study was to compare the resistance of a locking suture repair of the LCL with a ligament augmentation technique.Material and methodsEight fresh frozen cadaveric elbows were evaluated for stability against varus/posterolateral rotatory forces (3 Nm). A strain gauge (µm/m; negative values) was placed at the origin and insertion of the lateral ulnar collateral ligament (LUCL) and cyclic loading was performed for 1000 cycles. We analyzed three distinct scenarios: (A) native LCL, (B) locking transosseou suture repair of the LCL, (C) simple LCL repair with additional ligament augmentation of the LUCL.ResultsThe mean measured strain was − 416.1 µm/m (A), − 618 µm/m (B) and − 288.5 µm/m (C) with the elbow flexion at 90°; the strain was significantly higher in scenario B compared to C (p = .01). During the cyclic load (1000) the mean measured strain was − 523.1 µm/m (B) and − 226.3 µm/m (C) with the elbow flexion at 60°; the strain was significantly higher in scenario B compared to C (p = .01). No significant difference between the first and the last cycles was observed (p = .09; p = .07). One failure of the LCL repair was observed after 1000 cycles; none of the ligament augmentations failed.ConclusionLigament augmentation (C) provides higher resistance compared to the native LCL (A) and to the locking suture repair technique (B). Both techniques, however, hold up during 1000 cycles. While ligament augmentation might enhance the primary stability of the repair, future clinical studies have to show whether this increase in resistance leads to negative effects like higher rates of posttraumatic elbow stiffness.Level of evidenceBasic science study, biomechanics.

Percutaneous ultrasound-guided ulnar nerve release technique compared to open technique: A cadaveric study.

Objectives: To evaluate the outcomes of a novel percutaneous ultrasound-guided technique for release of ulnar nerve entrapment at the elbow when compared to standard open release Methods: One single surgeon performed an ultrasound-guided percutaneous release of the cubital tunnel on a group of five cadaveric elbows and open release on five others. All procedures were timed, and incision lengths were recorded. Meticulous anatomic dissection was then performed to assess the complete release of the carpal tunnel and iatrogenic injuries. Results: No significant difference was found between the two groups in terms of complete release and iatrogenic injury, whereas Operative time was significantly shorter for the US-guided technique. Incomplete releases of the nerve were found only during the first two trials in each group, while the third, fourth, and fifth trials showed a complete ulnar nerve release in both series, highlighting a fast learning curve for both techniques. All of this through a significantly smaller incision in the US-guided technique. Conclusions: This study highlights the similar effects of these two techniques in terms of complete release of the ulnar nerve, with no clear superiority of one over the other in terms of morbidity rate. Both have a fast learning curve for an ultrasound-trained surgeon, with the US-guided technique being a less traumatic and quicker alternative procedure.