Cadaveric Elbows Research Articles

The moving valgus stress test produces more ulnar collateral ligament change in length during extension than during flexion: a biomechanical study

Injuries to the elbow medial ulnar collateral ligament (mUCL) pose a diagnostic challenge, with the moving valgus stress test (MVST) currently accepted as the gold-standard clinical test. This study sought to biomechanically evaluate the change in length of the ulnar collateral ligament (UCL) during flexion-extension using a null hypothesis that the mUCL will not experience a greater change in length with movement than with static loading. Seven fresh-frozen human cadaveric elbows were tested with static and dynamic valgus stress. We measured (1) ligament length with a multi-camera optical system, (2) elbow flexion with an incremental encoder, and (3) valgus deviation with an electronic inclinometer. With a force applied to the wrist to simulate a clinical stress examination, the elbow was flexed and extended in a physiological elbow simulator to mimic the flexion and extension of the MVST. The simulated MVST produced more elongation of the UCL compared with static stress testing (P < .001). Ninety degrees of flexion produced the highest mean change, and the anterior and posterior bands demonstrated different length change characteristics. Comparison of dynamic flexion and extension showed a statistically significant difference in change in length: The mUCL reached the greatest change during extension, with the greatest changes during extension near 90° of flexion. The MVST produces significantly more elongation of the mUCL than either a static test or a moving test in flexion. This study provides biomechanical evidence of the validity of the MVST as a superior examination technique for injuries to the UCL.

Biomechanical comparison of tension band wiring and plate fixation with locking screws in transverse olecranon fractures

Tension band wiring (TBW) is the standard method for treating transverse olecranon fractures, but high rates of complications and reoperations have been reported. Plate fixation (PF) with locking screws has been introduced as an alternative method that may retain the fracture reduction better with a higher load to failure. Twenty paired cadaveric elbows were used. All soft tissues except for the triceps tendon were removed. A standardized transverse fracture was created, and each pair was allocated randomly to TBW or PF with locking screws. The triceps tendon was mounted to the materials testing machine with the elbow in 90° of flexion. Construct stiffness was compared 3 times. Then, the elbows underwent a chair lift-off test by loading the triceps tendon to 300 N for 500 cycles. Finally, a load-to-failure test was performed, and failure mechanism was recorded. The construct stiffness of PF was higher in the first of 3 measurements. No difference was observed in the cyclic test or in load to failure. Hardware failure was the failure mechanism in 8 of 10 TBW constructs, and all failures occurred directly under the twists of the metal wire. Hardware failure was the cause of failure in only 1 elbow in the PF group (P < .01). There was no difference in fracture displacement following fixation with TBW and PF with locking screws in transverse olecranon fractures. However, assessment of the mode of hardware failure identified the metal cerclage twist as the weakest link in the TBW construct.

The column procedure preserves elbow stability on biomechanical testing

PurposeThe effect of open release of a post-traumatic elbow contracture on the stability of the joint has not been so far studied in vivo. Resection of elbow joint capsule, the key element of surgery, was reported to have no effect on the stability of cadaveric elbows. The joint capsule is yet known to participate in maintaining elbow stability as one of secondary stabilizers.MethodsWe assessed elbow joint laxity in 39 patients who underwent an open contracture release via the ‘column procedure’ described by B. Morrey and P. Mansat within the preceeding three to nine months. The measurements were taken with an apparatus designed particularly for this experiment according to the predetermined protocol. A preliminary part of the experiment showed that there was no significant difference between laxity of two elbow joints in healthy volunteers. Laxity of the operated elbows could be then compared with the contralateral joints.ResultsMean absolute difference of laxity between healthy and operated elbows was 1.55° (0.1°–4.1°, SD = 1.1) being significantly lower than 2°, p = 0.0056. The difference of the joint laxity between the operated and healthy elbows did not differ statistically significantly by more than 0.6° from the difference of the laxity of two healthy elbows and, therefore, is not clinically noticeable.ConclusionsOur experiment confirmed that the ‘column procedure’ is a safe procedure which does not compromise the stability of the elbow joint.

Histologic Analysis of 2 Alternative Donor Sites of the Ipsilateral Elbow in the Treatment of Capitellar Osteochondritis Dissecans

To compare the histologic features of the cartilage from the capitellum with 2 proposed alternative donor sites from the ipsilateral elbow in the treatment of capitellar osteochondritis dissecans (OCD): the nonarticulating part of the radial head and the nonarticulating lateral side of the olecranon tip. Ten human cadaveric elbow specimens with macroscopically normal articular surfaces were used to obtain 5-mm osteochondral grafts: 10 from the capitellum (60° anteriorly relative to the humeral shaft), 10 from the radial head (nonarticulating part at 80°), and 4 from the olecranon (lateral side of the olecranon tip). Grafts were fixated in formalin (4% formaldehyde), decalcified, and processed into standard 8-μm-thick hematoxylin and eosin-and Toluidine Blue-stained sections. These were assessed for cartilage thickness, shape of articular surface, and 13 histologic parameters of the International Cartilage Repair Society II. Olecranon scores were excluded from statistical analysis. Mean cartilage thickness was 1.5 ± 0.22mm at the capitellum; 1.3 ± 0.34mm at the radial head; and 1.9 ± 1.0mm at the olecranon. There was no difference in cartilage thickness between the capitellum and radial head (P= .062). All grafts demonstrated a convex articular surface. International Cartilage Repair Society II scores ranged from 82 to 100 for the capitellum, from 81 to 100 for the radial head, and from 67 to 87 for the olecranon tip. There was less chondrocyte clustering at the capitellum (84 ± 14) than in the radial head (94 ± 3.2; P= .019). Mid/deep zone assessment of the capitellum scored higher (97 ± 6.7) than the radial head (91 ± 4.6; P= .038). This study demonstrates appropriate histologic similarities between the cartilage from the capitellum and 2 alternative donor sites of the ipsilateral elbow in the treatment of capitellar OCD: the nonarticulating part of the radial head and the nonarticulating lateral side of the olecranon tip. From an histologic point of view, there seem to be no obstacles to use grafts from these alternative donor sites for reconstruction of the capitellum when performing osteochondral autologous transplantation.

Effect of incremental increase in radial neck height on coronoid and capitellar contact pressures.

Over-lengthening of the radial neck has been shown to affect ulnohumeral kinematics and has been proposed to affect radiocapitellar pressures. We hypothesized that an incremental increase in radial neck height increases the capitellar contact pressure and reduces the coronoid contact pressure. Knowledge of the effects of over-lengthening is clinically important in preventing pain and degenerative changes due to overstuffing. Six human cadaveric elbows were prepared on a custom-designed apparatus simulating muscle loads and passive flexion from 0° to 90° under gravity valgus torque while measuring joint contact pressures in this biomechanical study. Each elbow was tested sequentially starting with the intact specimen followed by insertion of a radial head prosthesis with 0, +2, and +4 mm of radial neck height, respectively. Capitellar mean contact pressures significantly increased after insertion of +2 and +4 mm radial head prostheses (p < 0.03). The capitellar mean contact pressure with a 0 mm radial head prosthesis was 97 KPa. Insertion of +2 mm and +4 mm radial heads increased mean contact pressures to 391 KPa (p = 0.001) and 619 KPa (p = 0.001), respectively, with 90° of elbow flexion. Increasing radial prosthesis height by 2 mm significantly increases capitellar contact pressures and reduces coronoid contact pressures.

Anatomic and Biomechanical Evaluation of Ulnar Tunnel Position in Medial Ulnar Collateral Ligament Reconstruction

Background: Although numerous techniques of reconstruction of the medial ulnar collateral ligament (mUCL) have been described, limited evidence exists on the biomechanical implication of changing the ulnar tunnel position despite the fact that more recent literature has clarified that the ulnar footprint extends more distally than was appreciated in the past. Purpose: To evaluate the size and location of the native ulnar footprint and assess valgus stability of the medial elbow after UCL reconstruction at 3 ulnar tunnel locations. Study Design: Controlled laboratory study. Methods: Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. The anatomic footprint of the ulnar attachment of the mUCL was measured with a digitizing probe. The area of the ulnar footprint and midpoint relative to the joint line were determined. Medial elbow stability was tested with the mUCL in an intact, deficient, and reconstructed state after the docking technique, with ulnar tunnels placed at 5, 10, or 15 mm from the ulnotrochlear joint line. 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, specimens were loaded to failure at 70° of elbow flexion. Results: The mean ± SD length of the mUCL ulnar footprint was 27.4 ± 3.3 mm. The midpoint of the anatomic footprint was located between the 10- and 15-mm tunnels across all specimens at a mean 13.6 mm from the joint line. Sectioning of the mUCL increased elbow valgus rotation throughout all flexion angles and was statistically significant from 30° to 100° of flexion as compared with the intact elbow (P < .05). mUCL reconstruction at all 3 tunnel locations restored stability to near intact levels with no significant differences among the 3 ulnar tunnel locations at any flexion angle. Conclusion: Positioning the ulnar graft fixation site up to 15 mm from the ulnotrochlear joint line does not significantly increase valgus rotation in the elbow. Clinical Relevance: A more distal ulnar tunnel may be a viable option to accommodate individual variation in morphology of the proximal ulna or in a revision setting.

Biomechanical Evaluation of a Modified Internal Brace Construct for the Treatment of Ulnar Collateral Ligament Injuries.

Background:Ulnar collateral ligament (UCL) repair augmented with the “internal brace” construct for the management of acute UCL injuries has recently garnered increasing interest from the sports medicine community. One concern with this technique is excessive bone loss at the sublime tubercle, should revision UCL reconstruction be required. In an effort to preserve the bony architecture of the sublime tubercle, an alternative internal brace construct is proposed and biomechanically compared with the gold standard UCL reconstruction.Hypothesis:The internal brace repair construct will restore valgus laxity and rotation to its native state and demonstrate comparable load-to-failure characteristics with the 3-strand reconstruction technique.Study Design:Controlled laboratory study.Methods:For this study, 8 matched pairs of fresh-frozen cadaveric elbows were randomized to undergo either UCL reconstruction with the 3-ply docking technique or UCL repair with a novel internal brace construct focused on augmenting the posterior band of the anterior bundle of the ligament (modified repair-IB technique). Valgus laxity and rotation measurements were quantified through use of a MicroScribe 3DLX digitizer at various flexion angles of the native ligament, transected ligament, and repaired or reconstructed ligament. Laxity testing was performed from maximum extension to 120° of flexion. Each specimen was then loaded to failure, and the method of failure was recorded.Results:Valgus laxity was restored to the intact state at all degrees of elbow flexion with the modified repair-IB technique, and rotation was restored to the intact state at both full extension and 30°. In the reconstruction group, valgus laxity was not restored to the intact state at either full extension or 30° of flexion (P < .001 and P = .004, respectively). Laxity was restored at 60° of flexion, but the elbow was overconstrained at 90° and 120° of flexion (P = .027 and P = .003, respectively). In load-to-failure testing, the reconstruction group demonstrated significantly greater yield torque (19.1 vs 9.0 N·m; P < .005), yield angle (10.2° vs 5.4°; P = .007), and ultimate torque (23.9 vs 17.6 N·m; P = .039).Conclusion:UCL repair with posterior band internal bracing was able to restore valgus laxity and rotation to the native state. The construct exhibited lower load-to-failure characteristics when compared with the reconstruction technique.Clinical Relevance:In selected patients with acute, avulsion-type UCL injuries, ligament repair with posterior band internal bracing is a viable alternative surgical option that, by preserving bone at the sublime tubercle, may decrease the complexity of future revision procedures.

Articular Exposure between Triceps Reflecting Anconeus Pedicle (TRAP) Approach and Olecranon Osteotomy Approach

OBJECTIVES: To compare percentage of articular exposure of distal humerus between triceps-reflecting anconeus pedicle (TRAP) approach and olecranon osteotomy approach. MATERIAL AND METHODS: 10 fresh cadaveric elbows were randomly allocated into 2 groups. Group 1 (5 elbows) was assigned for olecranon osteotomy approach. Group 2 (5 elbows) was assigned for TRAP approach. After surgical exposures were done, the visible articular surface of distal humerus was painted with oil-based yellow color. Subsequently, all dissected elbows were disarticulated. The remaining invisible articular area was painted with oil-based blue color. A square mesh net was firmly wrapped around the painted articular surface. The number of squares was counted and calculated into percentage of articular exposure. Median was calculated and compared among both groups. RESULT: The olecranon osteotomy exposure group offers median of articular exposure at 57.69%. TRAP exposure group offers 47.45% with statistical significance in the difference between two approaches (Mann-Whitney U test, p = 0.028, 95% CI = 2.1 to 15.9) CONCLUSION: The olecranon osteotomy exposure offers more articular visualization compared with the TRAP approach with statistical significance.

The effect of tendon rotation on distal biceps repair

BackgroundThe distal biceps tendon externally rotates from proximal to distal before inserting onto the radius. Our hypothesis is that an externally rotated (anatomic) repair would re-create native supination moment arm and flexion force, whereas an internally rotated (nonanatomic) repair would result in reduced force transmission.MethodsThe mechanical tests performed in this study measured isometric moment arms and elbow flexion force using a validated elbow simulator as previously published. Mechanical testing was performed on 8 native cadaveric elbows (61 ± 15 years). The distal biceps tendons in all specimens were then incised from their footprint and repaired with anatomic and nonanatomic tendon rotations. After each repair, the specimens were retested. The repair sequence was randomly assigned.ResultsGross observation showed repair site bunching with the nonanatomic repairs. There was no statistical difference in the moment arms between the native, anatomic, and nonanatomic rotations for the 3 forearm angles (P ≥ .352). Analysis showed no statistical difference in flexion force ratio for the elbow at 90° (P ≥ .283).DiscussionThe study showed that biceps tendon rotation does not play a role in supination moment arm or flexion force. Twisting the distal biceps tendon around the tendon axis does not change the direction of its applied force on the tuberosity. Tendon bunching in nonanatomic reattachments increases repair site width, which may lead to tendon-ulnar impingement during forearm rotation.

Ulnar Nerve Strain in Functional Elbow and Shoulder Motions.

Background: Shoulder and elbow motions can affect ulnar nerve strain. However, there is no evidence that links this kind of strain to specific activities. The purpose of this study was to examine ulnar nerve strain at the elbow resulting from normal daily activities. Methods: This study was conducted using thirty fresh frozen cadaveric elbows from subjects who had no deformities or history of previous upper extremity surgery. Strain was calculated based on nerve elongation. Ulnar nerve strain at the elbow from motion related to common daily activities was measured in both normal nerves and nerves in which gliding motion was restricted. The results of these measurement were then compared. Results: Activities related to extreme elbow and shoulder motions, such as cellular phone use, yielded an average strain of 6.3%. In addition, we found that nerve strain increased significantly in conditions in which gliding motion was restricted. Nerve strain due to motion associated with cellular phone use, for example, rose by 69.1%. Conclusions: Elbow flexion and shoulder abduction in daily activities are associated with increases in ulnar nerve strain, but this may not cause permanent damage to the nerve. After nerve gliding motion had been restricted, nerves that normally exhibited less strain often had even increased higher levels of strain than those nerves that normally exhibited high strain.

Lateral Trochlear Ridge: A Non-Articulating Zone for Anterior-to-Posterior Screw Placement in Fractures Involving the Capitellum and Trochlea.

Coronal shear fractures of the distal aspect of the humerus that involve the capitellum and the trochlea are rare; nevertheless, they are difficult to treat because of the complex fracture patterns and osteochondral nature of the fragments, limiting optimal screw placement. The use of anterior-to-posterior screw fixation by a lag technique (without countersinking) could potentially improve the strength of the construct. Our primary research question was to anatomically determine if there is a non-articulating zone for screw placement along the anterior aspect of the lateral trochlear ridge (aLTR) throughout normal elbow range of motion. Eight fresh-frozen cadaveric elbows were used. The region of interest was defined with 3 polymeric pins inserted in the inferior, middle, and superior-most aspects of the aLTR of each elbow, with use of an extensor digitorum communis (EDC) split approach. The elbows were then mounted on a magnetic resonance imaging (MRI)-compatible compression frame and subjected to high-resolution 7-T MRI at 90°, 120°, and 145° of flexion (positions of potential impingement), and at neutral and maximal pronation and maximal supination for each position of flexion. Portions of the aLTR that had free adjacent space were identified using the sagittal and coronal scans. This non-articulating region was identified as the "non-articulating zone" (NAZ). The NAZ was found to encompass the proximal 38.2% (range, 30.2% to 48.9%) of the aLTR, measuring, on average, 5.2 mm in width. It was consistently located either directly adjacent to the apex of the ridge or just medial to it. The distal 61.8% of the aLTR articulated with either the ulna or the radial head in some of the elbows. Our results suggest that there is a portion of the aLTR that, despite being covered with articular cartilage, is non-articulating throughout normal elbow range of motion. In situations in which headless anterior-to-posterior and posterior-to-anterior screw insertion results in inadequate fixation of capitellar-trochlear fractures, anterior-to-posterior lag screw instrumentation along the non-articulating portion of the aLTR may provide a location for additional fixation in some patients. However, because of variation between patients, each case must be individualized.

LUCL internal bracing restores posterolateral rotatory stability of the elbow.

Posterolateral rotatory instability (PLRI) of the elbow occurs from an insufficient lateral collateral ligament complex (LCLC). For subacute LCLC injuries, lateral ulnar collateral ligament (LUCL) internal bracing rather than reconstruction may be a viable option. The purpose of the study was to compare the stabilizing effects of LUCL internal bracing to triceps tendon graft reconstruction in simulated PLRI. Sixteen cadaveric elbows were assigned for either LUCL internal bracing (n = 8) or reconstruction with triceps tendon graft (n = 8). Specimen were mounted and a valgus rotational torque was applied to the ulna to test posterolateral rotatory stability. Posterolateral rotation was measured at 0°, 30°, 60°, 90° and 120° of elbow flexion. Cyclic loading was performed for 1000 cycles at 90° of elbow flexion. Three conditions were compared in each specimen: intact elbow, LUCL and radial collateral ligament (RCL) transected, and then either LUCL internal bracing or reconstruction with triceps tendon graft. Transection of the LUCL and RCL significantly increased posterolateral rotation in all degrees of elbow flexion compared to the intact condition (P < 0.05). Both LUCL internal bracing and reconstruction restored posterolateral rotatory stability to the native state between 0° and 120° of elbow flexion, with no significant difference in improvement between groups. Similarly, LUCL internal bracing and reconstruction groups showed no significant difference in posterolateral rotation compared to the intact condition during cyclic loading. At time zero, both LUCL internal bracing and reconstruction with triceps tendon graft restored posterolateral rotatory stability. As such, this study supports the use of internal bracing as an adjunct to primary ligament repair in subacute PLRI.

Biomechanical comparison of docking ulnar collateral ligament reconstruction with and without an internal brace

Current ulnar collateral ligament (UCL) reconstruction techniques are substantially less stiff and demonstrate lower load to failure compared with the native UCL. UCL repair with the addition of an internal brace has demonstrated superior biomechanical performance compared with docking UCL reconstruction, but internal bracing has not yet been used in UCL reconstruction. To evaluate the time-zero biomechanical performance of aUCL docking technique reconstruction with and without an internal brace compared with native UCL properties. Twelve matched pairs of cadaveric elbows were dissected and fixed at 90° for biomechanical testing. A cyclic valgus torque protocol was used to test the anterior band of the UCL in native specimens. After native specimens were failed, palmaris grafts were used for a docking reconstruction with or without internal brace and were subjected to the same valgus torque test protocol. Torsional stiffness, ultimate failure torque, and ulnohumeral gapping were determined. Stiffness in UCL reconstructions using a standard docking technique (3.0 ± 0.4 N m/deg) were significantly less stiff (P < .001) than native UCL (4.0 ± 0.8 N m/deg), whereas reconstructions using an internal brace (3.6 ± 0.6 N m/deg) were not different (P = .120) compared with native. Ultimate failure torque for standard docking (18.3 ± 4.1 N m) was significantly lower (P < .001) than native UCL (36.9 ± 10.1 N m), whereas the internal brace samples (35.3 ± 9.8 N m) were not different (P = .772) than native. UCL reconstruction with an internal brace augmentation provides superior stiffness and time-zero failure strength when compared with the standard docking technique.

Biomechanical Comparison of Onlay Distal Biceps Tendon Repair: All-Suture Anchors Versus Titanium Suture Anchors

Background: A rupture of the distal biceps tendon is the most common tendon rupture of the elbow and has received increased attention in the past few years. Newly developed all-suture anchors have the potential to minimize surgical trauma and the risk of adverse events because of the use of flexible drills and smaller drill diameters. Purpose/Hypothesis: The purpose was to biomechanically compare all-suture anchors and titanium suture anchors for distal biceps tendon repair in cadaveric specimens. The hypothesis was that all-suture anchors would show no differences in load to failure or displacement under cyclic loading compared with titanium suture anchors. Study Design: Controlled laboratory study. Methods: Sixteen unpaired, fresh-frozen human cadaveric elbows were randomized to 2 groups, which underwent onlay distal biceps tendon repair with 2 anchors. Bone mineral density at the radial tuberosity was evaluated in each specimen. In the first group, distal biceps tendon repair was performed using all-suture anchors. In the second group, titanium suture anchors were applied. After cyclic loading for 3000 cycles, the repair constructs were loaded to failure. The peak load to failure as well as repair construct stiffness and mode of failure were determined. Results: The mean (±SD) peak load was 293.53 ± 122.15 N for all-suture anchors and 280.02 ± 69.34 N for titanium suture anchors (P = .834); mean stiffness was 19.78 ± 2.95 N/mm and 19.30 ± 4.98 N/mm, respectively (P = .834). The mode of failure was anchor pullout for all specimens during load to failure. At the proximal position, all-suture anchors showed a displacement of 1.53 ± 0.80 mm, and titanium suture anchors showed a displacement of 0.81 ± 0.50 mm (P = .021) under cyclic loading. At the distal position, a displacement of 1.86 ± 1.04 mm for all-suture anchors and 1.53 ± 1.15 mm for titanium suture anchors was measured (P = .345). A positive correlation between bone mineral density and load to failure was observed (r = 0.605; P = .013). Conclusion: All-suture anchors were biomechanically equivalent at time zero to titanium suture anchors for onlay distal biceps tendon repair. While the proximally placed all-suture anchors demonstrated greater displacement than titanium suture anchors, the comparable displacement at the distal position as well as the similar load and mechanism of failure make this difference unlikely to be clinically significant. Clinical Relevance: All-suture anchors performed similarly to titanium suture anchors for onlay distal biceps tendon repair at time zero and represent a reasonable alternative.

Arthroscopic visualization of the medial collateral ligament of the elbow

This study aimed to determine the extent to which the medial collateral ligament (MCL) can be visualized during a standard posterior arthroscopic view of the elbow. Eight fresh human cadaveric elbows were placed in a simulated lateral decubitus position. Standard elbow arthroscopy was performed on each specimen using a standard posterior portal for visualization with a 30° arthroscope. The most distal borders of the visible part of the MCL were marked using a spinal needle and tagged using nylon sutures. Subsequently, the elbow was dissected. The overall surface area of the entire MCL and that defined by the suture tags were calculated for each specimen. The mean area of the visible part of the MCL represented 48% of the mean overall area. The arthroscopically tagged part of the posterior band of the MCL represented <50% of the entire MCL. Arthroscopic visualization was not available for most of the posterior bands of the MCL. Less than half of the MCL is visible with a 30° arthroscope from standard posterior portal. Thus, sole reliance on arthroscopic visualization with this manner is not enough to release of the MCL. The variable effort is required to improve the limited visualization during the procedure. Moreover, the individual attention is essential to protect the ulnar nerve because the ulnar nerve is very close to the MCL especially to the anterior band.

Variations in Blood Supply from Proximal to Distal in the Ulnar Collateral Ligament of the Elbow: A Qualitative Descriptive Cadaveric Study

Objectives: The vascular supply of the ulnar collateral ligament (UCL) is unknown. Previous studies have reported varying success in return to play rates after non-operative management of partial UCL tears and suggest a varying healing capacity as possibly related to UCL injury location. The purpose of this study was to analyze the macroscopic vascular anatomy of the ulnar collateral ligament of the elbow. Methods: Eighteen, fresh-frozen, male cadaveric elbows from nine donors were sharply dissected 15 cm proximal to the medial epicondyle. Sixty mL of India Ink was injected through the brachial artery of each elbow. Arms were then frozen at -10°C, radial side down in 15-20° of elbow flexion. A bandsaw was used to section the frozen elbows into 5 mm coronal or sagittal sections. Sections were cleared for visualization using the modified Spalteholz technique. Images of specimens were taken and the qualitative description of the UCL vascularity was undertaken. Results: We consistently found a dense blood supply to the proximal UCL, while the distal UCL was hypovascular. We observed a possible osseous contribution to the proximal UCL from the medial epicondyle in addition to an artery from the flexor/pronator musculature that consistently appeared to provide vascularity to the proximal UCL. The degree of vascular penetration moving from proximal to distal in the UCL ranged from 39-68% of the overall UCL length, with a 49% average length of vascular penetration of the UCL. Conclusion: Our study found a difference in the vascular supply of the ulnar collateral ligament. The proximal UCL was well vascularized, while the distal UCL was hypovascular. This difference in vascular supply may be a factor in the differential healing capacities of the UCL based on the location of injury. An improved understanding of the macroscopic vascular supply of the UCL may aid in the clinical management of partial UCL tears and suggest an indication for treatments with respect to location of UCL injuries.

Unicortical Versus Bicortical Button Fixation For Distal Biceps Brachii Tendon Rupture: A Cadaveric Biomechanical Study

Objectives: Acute distal biceps tendon rupture is an increasingly common and more recognized injury affecting active adults. Operative repair is the preferred treatment, particularly for restoration of elbow function and strength. No prior study has biomechanically compared unicortical versus bicortical distal biceps button fixation under cyclic loading, which is most representative of postoperative physiologic conditions. We hypothesized there would be no difference in loss of force, tendon gap formation, or ultimate failure load following cyclic loading between unicortical and bicortical button techniques for the repair of distal biceps tendon rupture. Methods: Experimental testing with 13 fresh-frozen matched paired cadaver elbows was conducted. One specimen from each pair was randomized to either unicortical or bicortical distal biceps button fixation techniques, with contralateral specimen assigned to the alternate technique. In both arms of the experiment, the distal 2.5 cm of the biceps tendon was whipstitched and the free suture ends threaded in opposite directions through a 2.6 x 12 mm titanium cortical button. A 3.2 mm guide pin was drilled through the central aspect of the radial tuberosity from anterior to posterior, aiming approximately 20° in the ulnar direction. The button was inserted and deployed for either unicortical or bicortical fixation and the free suture limbs tensioned to advance tendon down to bone for final fixation. Loading was performed using an MTS servohydraulic actuator. A 25-N distal biceps preload was applied and each specimen cycled from full extension to 90° of flexion at 0.5 Hz for 3000 cycles using a displacement controlled protocol. All specimens were subsequently loaded to failure at 2 mm/s to simulate an acute postoperative load. Outcome measures were a loss of force from cycle 5 to cycle 3000, tendon gapping during cyclic loading, and ultimate failure load. Results: During cyclic loading, the mean change in force from cycle 5 to cycle 3000 was -0.33 N for the unicortical fixation group and 0.36 N for the bicortical fixation group (p=0.21). The increase in tendon gap for the unicortical fixation group was 1.02 mm and for the bicortical fixation group was 1.83 mm (p=0.37). During failure loading, the unicortical button fixation group had a mean failure load of 170.45 N and the bicortical button fixation group a mean failure load of 181.25 N (p=0.89). Conclusion: No significant differences exist between the two techniques in loss of force and tendon gap formation under cyclic loading conditions. This indicates that both unicortical and bicortical distal biceps button techniques maintained an equivalent stabilization during a simulated 3 month postoperative healing period. Additionally, there was no significant difference in failure load between the two groups indicating an equivalent response in the event of an acute injury. Clinical Relevance: Distal biceps button fixation strength and tendon gap behavior under physiologic cyclic load support the implementation of early postoperative elbow range of motion, imperative in the prevention of elbow stiffness. Unicortical fixation may be sufficient in facilitating optimal bone-tendon apposition and healing, while minimizing risk of iatrogenic injury associated with bicortical fixation.

Correlation of Force to Deformation of the Anterior Bundle of the Medial Collateral Ligament Through Consideration of Band Laxity.

The anterior bundle of the medial collateral ligament (AMCL) resists the loads that arise at the elbow during overhand throwing and has commonly been divided into posterior and anterior bands. While these anterior and posterior bands have been thought to bear the load at different flexion angles, any transition of the load distribution between the two bands is poorly understood and has not considered laxity (slack). This study considers the AMCL as three bands and quantifies the mechanical response to vertical distraction, simulating valgus-load joint opening, through the sequential superposition of the band responses after the elimination of inherent laxity. Eight cadaveric elbow specimens were used for the study. The intact AMCL of each specimen was tested under vertical distraction in a specialized load frame at four elbow flexion angles and then subsequently retested after two longitudinal transections. The greatest laxity at full extension and full flexion belonged to the posterior (1.9 mm) and anterior (2.4 mm) band, respectively. At the lesser and higher flexion angles, the greatest structural stiffness belonged to the anterior and middle band. The overall AMCL was the most structurally stiff at 60°, with approximately 150 N of force required for 2% elongation. This study shows that the different bands of the AMCL may have different load bearing properties at different flexion angles, causing each band to support different proportions of an imposed load. The presence of the laxity may impose a load-bearing delay, causing load-bearing in each band to begin asynchronously. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2027-2034, 2019.

Articulated Joint Distraction in a Cadaveric Model of the Canine Elbow.

The aim of this study was to determine if articulated joint distraction in the canine elbow can effectively maintain a distraction gap between the articular surfaces of the canine elbow under a weight-bearing load. An articulated external skeletal fixator with turnbuckles was applied to seven canine cadaveric elbow specimens. Specimens were potted and mechanically tested at 135° of flexion, while joint contact pressure was recorded at three locations within the elbow. Joint distraction was sequentially increased, and loads of 5 N, 90 N and 180 N were incrementally applied. This process was repeated until no pressure was recorded at each of the three locations within the elbow under 180 N of applied load. To achieve 0 N of joint contact force with 180 N of axial load, the average amount of distraction needed was 2.3 ± 0.71 mm (range, 1.8-3.6 mm) at the distal turnbuckles and 1.67 ± 1.10 mm (range, 1.8-2.7 mm) at the proximal turnbuckles. Results suggest that joint distraction can effectively decrease articular pressure within the canine elbow joint. A maximum of 3.6 mm of distraction between the fixator turnbuckles was necessary to eliminate joint contact for the construct tested. Clinical investigation is necessary to establish if articulated elbow joint distraction is a safe and effective for the treatment of canine elbow osteoarthritis.

Surgical Treatment of Intra-Articular Distal Humeral Fractures by using a Combined Medial and Lateral Approach: An Anatomic Study.

ObjectiveTo determine the visible size of the distal humeral articular surface by using a novel combined medial‐lateral approach as an alternative method of surgical treatment for intra‐articular distal humeral fractures.MethodsIn this anatomical study, 12 adult fresh‐frozen cadaveric elbows were randomly divided into a medial‐lateral group and an olecranon osteotomy group, with 6 in each group. In the medial‐lateral group, a medial approach was first used, and then a lateral approach. The sizes of the distal humeral articular surface exposed by each incision and the joined size were measured and calculated. In the olecranon osteotomy group, a posterior olecranon osteotomy approach was applied, and the maximal visible sizes of the articular surface were marked and calculated. Ratios of the maximal sizes of the distal humeral articular surface of the two approaches were compared.ResultsIn the medial‐lateral group, the medial approach could expose 2/5 of the medial trochlea and 1/3 of the capitellum, while the mean visible size of the distal humeral articular surface was 6.8 cm2, 34.8% of the entire surface; the lateral approach can expose 3/7 of the capitellum and 1/4 of the medial trochlea, while the mean visible size of the distal humeral articular surface was 6.7 cm2, 33.9% of the whole surface; for the combined medial‐lateral approach, the mean scope exposed of the medial and lateral visible articular surface was 38.2% and 43.1%, respectively. Meanwhile, in the olecranon osteotomy group, the posterior olecranon osteotomy was found to expose most of the posterior distal humeral articular surface, except for 1/3 of the anterior trochlea and 1/4 of the anterior capitellum, and the visible range of articular surface was 65.3%. The combined medial‐lateral approach exposed 9.2 cm2 in total, 46.9% of the whole distal humeral articular surface, which averaged 19.6 cm2. However, the visible size of the distal humeral articular surface for the olecranon osteotomy approach was 13.7 cm2, 63.1% of the entire distal humeral articular surface, which averaged 21.3 cm2. There was a significant difference observed between the medial‐lateral group (46.9%) and the olecranon osteotomy group (63.1%) for the maximal visible size of the distal humeral articular surface (t = 7.201, P = 0.001).ConclusionsThe combined medial‐lateral approach can expose 46.9% of the distal humeral articular surface, concentrating on the anterior part, so it can be recommended to treat intra‐articular fractures with a simple pattern in the posterior with the anterior side of the distal humerus less comminuted.