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Background: Radial head subluxation, known as pulled elbow or Nursemaid’s elbow, is a common pediatric condition that occurs when a longitudinal traction force is applied to an elbow that is pronated and extended. Although the stability of the proximal radioulnar joint has been previously examined in cadaveric models, there are no current studies quantifying the biomechanics of nursemaid’s elbow. The purpose of our study was to demonstrate and quantify the axial traction force required to produce a nursemaid’s elbow in a pediatric cadaver specimen. Methods: Two fresh-frozen cadaveric elbows from a single 3 year-old male donor were dissected by a fellowship-trained orthopedic surgeon. An Instron 5944 testing machine with a 2 kN load cell was used to perform uniaxial testing. The radius and humerus were mounted to the Instron machine, and loaded in the axial direction with the elbow in full extension. Loading occurred at a rate of 10 mm/sec for 4 seconds, during which the force and actuator displacement were continuously recorded. The local instantaneous load and extension displacement at the time of subluxation were recorded, and data was synced with high-frame-rate video footage used to confirm the annular ligament subluxation. Results: The load to failure required to produce the nursemaid’s elbow injury in the first elbow was 31N, with a failure displacement of 4.6mm. The second elbow demonstrated a load to failure of 26N, with a failure displacement of 4.6mm. After subluxation, we reduced the annular ligament from the first specimen. The elbow was then re-tested and demonstrated a load to failure of 20N, with a failure displacement of 2.6mm. Conclusion: Axial traction applied to a pediatric cadaver specimen results in subluxation of the annular ligament into the radiocapitellar joint. The mean load to failure is 28.5N, and a lower load to failure was required to produce a recurrent subluxation in a previously injured specimen. Lower load for a recurrent subluxation may be attributed to damage on the annular ligament due to the first subluxation. [Figure: see text]

Background: Transtibial pull-out repair of the medial meniscal posterior root (MMPR) has been largely assessed through biomechanical studies. Biomechanically comparing different suture types would further optimize MMPR fixation and affect clinical care. Purpose/Hypothesis: The purpose of this study was to determine the optimal suture material for MMPR fixation. It was hypothesized that ultra high–molecular weight polyethylene (UHMWPE) suture tape would be biomechanically superior to UHMWPE suture and standard suture. Study Design: Controlled laboratory study. Methods: The MMPR attachment was divided in 24 human cadaveric knees and randomly assigned to 3 repair groups: UHMWPE suture tape, UHMWPE suture, and standard suture. Specimens were dissected down to the medial meniscus, and the posterior root attachments were sectioned off the tibia. Two-tunnel transtibial pull-out repair with 2 sutures, as determined by the testing group, was performed. The repair constructs were cyclically loaded between 10 and 30 N at 0.5 Hz for 1000 cycles to mimic the forces experienced on the medial meniscus during postoperative rehabilitation. Displacement was recorded at 1, 50, 100, 500, and 1000 cycles. Ultimate failure load, displacement at failure, and load at 3 mm of displacement (clinical failure) were also recorded. Results: UHMWPE suture tape had significantly less displacement of the medial meniscus when compared with standard suture at 1 (–0.22 mm [95% CI, –0.41 to –0.02]; P = .025) and 50 (–0.35 mm [95% CI, –0.67 to –0.03]; P = .029) cycles. There were no other significant differences observed in displacement between groups at any number of cycles. UHMWPE suture tape had significantly less displacement at the time of failure than standard suture (–3.71 mm [95% CI, –7.17 to –0.24]; P = .034). UHMWPE suture tape had a significantly higher load to reach the clinical failure displacement of 3 mm than UHMWPE suture (15.64 N [95% CI, 0.02 to 31.26]; P = .05). There were no significant differences in ultimate failure load between groups. Conclusion: The meniscal root repair construct with UHMWPE suture tape may be stronger and less prone to displacement than that with standard suture or UHMWPE suture. Clinical Relevance: UHMWPE suture tape may provide better clinical results compared with UHMWPE suture and standard suture.

Background:The lateral collateral ligament complex of the elbow is important in preventing posterolateral rotary instability of the elbow. Understanding the quantitative anatomy of this ligamentous complex and the overlying extensor musculature can aid in the surgical treatment of problems affecting the lateral side of the elbow.Purpose:To perform qualitative and quantitative anatomic evaluations of the lateral elbow ligamentous complex and common extensor muscle origins with specific attention to pertinent osseous landmarks.Study Design:Descriptive laboratory study.Methods:A total of 10 nonpaired, fresh-frozen human cadaveric elbows (mean age, 42.2 years; all male) were utilized. Quantitative analysis was performed using a 3-dimensional coordinate measuring device to quantify the location of pertinent bony landmarks, tendons, and ligament footprints of the lateral side of the elbow.Results:The extensor carpi radialis brevis was the only humeral footprint found to cross the radiocapitellar joint line, extending a mean 5.9 mm (95% CI, 4.7-7.0) distal to the joint line. With the elbow in full extension, the lateral ulnar collateral ligament (LUCL) humeral footprint was found 7.1 mm (95% CI, 4.7-9.4) anterior and 9.8 mm (95% CI, 8.4-11.2) distal to the lateral epicondyle and 8.6 mm (95% CI, 7.5-9.7) proximal to the radiocapitellar joint line, while the radial collateral ligament humeral footprint was found 6.6 mm (95% CI, 5.5-7.8) anterior and 5.6 mm (95% CI, 4.0-7.2) distal to the lateral epicondyle and 12.7 mm (95% CI, 11.4-14.0) proximal to the radiocapitellar joint line. The center of the ulnar attachment of the LUCL was found 1.4 mm (95% CI, 0.7-2.1) anterior and 2.4 mm (95% CI, 1.2-6.0) proximal to the supinator tubercle and 24.4 mm (95% CI, 22.7-26.1) distal to the radiocapitellar joint line. The center of the ulnar attachment of the annular ligament was found to be 17.3 mm proximal to the supinator tubercle.Conclusion:The current study provides measured distances of LUCL and radial collateral ligament attachments in reference to clinically relevant landmarks, which can potentially aid surgeons in performing more anatomic reconstruction or repair of the lateral ligamentous complex of the elbow.

Objectives: The roles of the medial patellofemoral and patellotibial ligaments in patellofemoral kinematics have been previously reported. However, the effect of isolated and combined surgical reconstruction of these ligaments to restore native patellofemoral kinematics is not well understood. The purpose of this study was to determine the isolated and combined effects of medial patellofemoral and patellotibial ligament deficiency and reconstruction on patellofemoral kinematics. Methods: Sixteen matched-paired female, fresh-frozen, cadaveric knee specimens with a mean age of 53.5 years (range, 26-65) were used. Specimens were tested in five conditions; 1) intact, 2) MPFL or MPTL cut, 3) MPFL and MPTL combined cut, 4) MPFL or MPTL reconstruction, and 5) MPFL and MPTL combined reconstruction. Dynamic testing was performed by taking the knees through range of motion from 0° to 90° of knee flexion at 60 mm/min using a dynamic tensile testing machine by applying a force through the quadricep tendon. Following dynamic testing, knees were tested statically using a lateral load of 45 N applied to the patella at 0°, 30°, 60°, and 90° of flexion. In both dynamic and static loading tests, a motion capture system detected patellar position for each testing state to distinguish changes in patellar kinematics. Linear mixed effects modeling was performed to compare testing states. Results: Isolated MPFL deficiency created the greatest lateral translation of the patella at all knee flexion angles (pConclusions: The MPFL plays the greatest role in medial patellar stability, but the MPTL appears to have a large influence on patella tracking. The MPTL may be most important in preventing patellofemoral osteoarthritis following patella dislocation. Further investigation is needed to evaluate patellofemoral contact pressure following medial patellar ligament reconstruction.

Objectives: Historically, radial meniscal tears were treated with partial or near- total meniscectomy which usually resulted in with poor outcomes. Radial meniscal tears function similar to a total meniscectomy and are challenging to treat. Repair of radial meniscal tears should be performed to prevent joint deterioration and the need for salvage procedures in the future. The purpose of this study was to compare three novel repair techniques for radial tears of the medial meniscus; the two-tunnel, the hybrid, and the hybrid tunnel techniques. We hypothesized that there would be no difference between the three groups in regards to gapping and ultimate failure strength. Methods: Thirty human male cadaver knees (ten matched pairs (n=20) and ten unpaired (n=10)) were used to compare the two-tunnel, hybrid, and hybrid tunnel repairs. A complete radial tear was made at the midbody of the medial meniscus. Repairs were performed according to the described techniques. Specimens were potted and mounted on a universal Instron testing machine where each specimen was cyclically loaded for 1000 cycles before experiencing a pull-to-failure. Gap distances at the tear site, ultimate failure load, and failure location were measured and recorded. Results: After 1000 cycles of cyclic loading, there was no significant difference in displacement between the two-tunnel repair (3.0 mm ± 1.7 mm), hybrid repair (3.0 mm ± 0.9 mm) or hybrid tunnel repair (2.3 mm ± 1.0 mm) (p=0.4042). On pull-to-failure testing there was also no significant difference in ultimate failure strength when comparing the two-tunnel (259 N ± 103 N), hybrid (349 N ± 149 N), or hybrid tunnel (365 N ± 146 N) repairs (p=0.26). However, the addition of vertical mattress sutures to act as a “rip stop” did significantly reduce the likelihood of the sutures pulling through the meniscus during pull-to-failure testing for the hybrid and hybrid tunnel repairs (4/16=25%) when compared to the two-tunnel repair (7/9=78%) (p=0.017). Conclusion: This study biomechanically evaluated two previously described techniques- the two-tunnel and hybrid repair- as well as one novel repair technique- the hybrid tunnel repair. The results showed equivalent biomechanical testing in regard to gap distance and pull to failure strength among each repair. The addition of the vertical mattress sutures to act as a rip stop suture was effective in preventing meniscal cut out through the meniscus. [Table: see text][Table: see text]

Objectives: To quantitatively evaluate the biomechanical effects of a novel peripheral stabilization technique for the treatment of posterior medial meniscus root (PMMR) avulsions and to identify an optimal diagnostic position to assess for the presence of meniscal extrusion. Methods: Meniscal extrusion and tibiofemoral contact mechanics were measured using 3D digitization and pressure sensors, respectively, in ten nonpaired, human cadaver knees. The PMMR of each knee was tested under 6 states: (1) intact; (2) complete root detachment; (3) anatomic transtibial pull-out root repair; (4) anatomic transtibial pull-out repair with peripheral stabilization; (5) nonanatomic transtibial pull-out repair; and (6) nonanatomic transtibial pull-out repair with peripheral stabilization, with randomization of the order of conditions 3 & 4, and 5 & 6. The testing protocol loaded knees with a 1000 N axial compressive force at four flexion angles (0°, 30°, 60°, 90°) in each state. Meniscal extrusion was recorded at 0° and 90° in both loaded and unloaded states at three locations along the peripheral rim of the medial tibial plateau. Degree of meniscal extrusion was defined as the radial displacement of the medial meniscus from three corresponding points on the posteromedial edge of the tibial plateau: (1) posterior border of MCL; (2) posteromedial capsule midway between the MCL and posterior root; and (3) the direct posterior capsule. Peak contact pressure, contact area, and total contact pressure were also recorded for all states at all flexion angles. Results: Statistical analysis investigated the independent effects of flexion, state, and loading using three, distinct two-factor models. In unloaded knees in full extension, the highest degree of meniscal extrusion was observed at the posterior border of the MCL across all repair testing states (p < 0.001). At full extension, loaded knees exhibited significantly higher extrusion in comparison to unloaded across all knee states at the MCL position (mean 1.1 mm, 95% CI [0.8, 1.4], p Conclusion: Anatomic and anatomic with peripheral suture repair techniques best restore contact mechanics of the knee. In current clinical scenarios where knees are unloaded and imaged in full extension, extrusion is best measured in the coronal plane at the posterior border of the MCL. However, this is likely a “best-case” scenario, as this study has shown that the degree of extrusion increases as the knee is loaded and flexed to 90°. When only a non-anatomic repair can be performed the addition of this peripheral stabilization technique may be beneficial for patients in reducing pathologic extrusion of the meniscus. [Table: see text]

Background: Metal screws are traditionally used to fix the coracoid process to the glenoid. Despite stable fixation, metal screws have been associated with hardware complications. Therefore, some studies have advocated for suture button fixation during the Latarjet procedure to reduce the complications associated with screw fixation. Purpose: To biomechanically evaluate the ultimate failure load of a cortical button and self-tensioning suture versus metal screws for coracoid graft fixation during the Latarjet procedure. Study Design: Controlled laboratory study. Methods: Eight matched pairs of fresh-frozen, male cadaveric shoulders (N = 16) underwent the Latarjet procedure. The shoulders of each pair were randomly assigned to 1 of 2 groups: fixation using two 3.75-mm cannulated, fully threaded metal screws or fixation using a double suture button construct. Specimens were secured in a dynamic testing machine and cyclically preconditioned from 2 to 10 N at 0.1 Hz for 10 cycles. After preconditioning, specimens were pulled to failure at a normalized displacement rate of 400% of the measured gauge length per minute. The ultimate failure load and mechanism of failure were recorded for each specimen. Results: The mean ultimate load to failure for screw fixation (226 ± 114 N; 95% CI, 147-305 N) was not significantly different from that for suture button fixation (266 ± 73 N; 95% CI, 216-317 N) ( P = .257). The mean strain at failure for screw fixation (63% ± 21%; 95% CI, 48%-77%) was not significantly different from that for suture button fixation (86% ± 26%; 95% CI, 69%-104%) ( P = .060). The most common mechanism of failure for the screw fixation method was at the bone block drill holes, while an intramuscular rupture at the clamp-muscle interface occurred for the suture button construct. Conclusion: The screw and suture button fixation techniques exhibited comparable biomechanical strength for coracoid bone block fixation of the Latarjet procedure. Clinical Relevance: Metal screws have been reported to be a large contributor to intraoperative and postoperative complications. Therefore, given the results of the current study, a suture button construct may be an alternative to metal screw fixation during the Latarjet procedure. However, further clinical studies are warranted.