Effect of PARP-1 Inhibition on Rotator Cuff Healing: A Feasibility Study Using Veliparib in a Rat Model of Acute Rotator Cuff Repair.

BACKGROUND: PARP-1 (poly[ADP-ribose]) was shown to influence the inflammatory response after rotator cuff tear, leading to fibrosis, muscular atrophy, and fatty infiltration in mouse rotator cuff degeneration. So far, it is not known how PARP-1 influences enthesis healing after rotator cuff tear repair. HYPOTHESIS/PURPOSE: This study aimed to examine the feasibility of oral PARP-1 inhibition and investigate its influence on rat supraspinatus enthesis and muscle healing after rotator cuff repair. The hypothesis was that oral PARP-1 inhibition would improve enthesis healing after acute rotator cuff repair in a rat model. STUDY DESIGN: Controlled laboratory study. METHODS: In 24 Sprague-Dawley rats, the supraspinatus tendon was sharply detached and immediately repaired with a single transosseous suture. The rats were randomly allocated into 2 groups, with the rats in the inhibitor group receiving veliparib with a target dose of 12.5 mg/kg/d via drinking water during the postoperative recovery period. The animals were sacrificed 8 weeks after surgery. For the analysis, macroscopic, biomechanical, and histologic methods were used. RESULTS: Oral veliparib was safe for the rats, with no adverse effects observed. In total, the inhibitor group had a significantly better histologic grading of the enthesis with less scar tissue formation. The macroscopic cross-sectional area of the supraspinatus muscles was 10.5% higher (P = .034) in the inhibitor group, which was in agreement with an 8.7% higher microscopic muscle fiber diameter on histologic sections (P < .0001). There were no statistically significant differences in the biomechanical properties between the groups. CONCLUSION: This study is the first to investigate the influence of PARP-1 inhibition on healing enthesis. On the basis of these findings, we conclude that oral veliparib, which was previously shown to inhibit PARP-1 effectively, is safe to apply and has beneficial effects on morphologic enthesis healing and muscle fiber size. CLINICAL RELEVANCE: Modulating the inflammatory response through PARP-1 inhibition during the postoperative healing period is a promising approach to improve enthesis healing and reduce rotator cuff retearing. With substances already approved by the Food and Drug Administration, PARP-1 inhibition bears high potential for future translation into clinical application.

Incidence of injuries among lacrosse athletes: a systematic review and meta-analysis.

OBJECTIVES: The purpose of this systematic review was to determine the incidence of injuries among lacrosse athletes and the differences in rates of injury by location and gender. METHODS: The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were implemented to conduct this systematic review.[1] The following variables were extracted from each of the included articles: location of injury, gender of patient, and incidence of injury among study population. The methodological quality of the included studies was assessed using mixed-methods appraisal tool (MMAT) version 2018.[2] Estimated rates were reported as pooled proportion with 95% CI. Rates of injury were calculated as a rate per 1000 athletic exposures (AEs), defined as an athlete participating in 1 practice or competition in which he or she was exposed to the possibility of athletic injury. RESULTS: This study found that the highest injury rate among lacrosse athletes was to the lower leg/ankle/foot with a rate of 0.66 injuries per 1000 AEs (95% CI, 0.51, 0.82). This injury pattern was also found to be the highest among both male and female lacrosse athletes. No statistical significance was detected when comparing rates of injury across gender, regardless of location. The injury pattern with the lowest rates of injury for female athletes being to the shoulder/clavicle and the neck for male athletes. CONCLUSION: The highest rate of injury among lacrosse athletes was to the lower leg/ankle/foot. As participation in lacrosse continues to rise, there is a greater need for understanding the rate of injury and injury characteristics for physicians and trainers to provide effective care to lacrosse athletes.

Spatial Anatomy of the Radial Nerve in the Extended Deltopectoral Approach.

The goal of this study was to define safe zones to prevent radial nerve injury in an extended deltopectoral approach. Relative distances of the upper margin (UMRN) and lower margin (LMRN) of the radial nerve to the proximal and distal borders of the pectoralis major and deltoid insertions were measured in 20 cadaveric arms. Four proximal humeral zones were identified (zone I, proximal border of the pectoralis major tendon to the proximal border of the deltoid tendon; zone II, proximal border of the deltoid tendon to the distal border of the pectoralis major tendon; zone III, distal border of the pectoralis major tendon to the distal border of the deltoid tendon; and zone IV, distal to the distal border of the deltoid tendon). On fluoroscopic measurement, mean distances between the UMRN and the proximal border of the pectoralis major tendon and the proximal border of the deltoid tendon were 71.6±2.1 mm and 26.2±2.5 mm, respectively. The incidence of the radial nerve in the spiral groove within each defined zone was as follows: zone I, 0%; zone II, 50%; zones III and IV, 100%. There was a significant association between anatomic zone and radial nerve entry into the spiral groove, χ2(3, N=88)=64.53, P<.001. The proximal border of the pectoralis major tendon to the proximal border of the deltoid tendon (zone I) is a safe location to avoid injury to the radial nerve. We recommend placing cerclage wires proximal to zone I from lateral to medial to avoid entrapment of the radial nerve. [Orthopedics. 2023;46(1):e31-e37.].

Evaluation of Sports Medicine Fellowships in the United States Based on Academic Productivity.

BACKGROUND: Institutional academic productivity remains an influential factor in an applicant's selection of fellowship training. This study aimed to determine the quality and quantity of research in the United States orthopaedic sports medicine fellowship programs and identify those with highest productivity. METHODS: The Arthroscopy Association of North America Fellowship Directory was used to evaluate 88 fellowships in the United States. Publication data and Hirschberg indices (h-index) were collected from the Scopus database. Subanalysis was performed based on the number of publications and mean h-index. RESULTS: Total number of publications per faculty member ranged from 0 to 866, with a median of 20. The median h-index per faculty member was 9. The number of fellows was correlated with a higher mean average h-index of faculty members (P = 0.05). The five programs with the highest number of publications included Hospital for Special Surgery, Rush University, University of Pittsburgh Medical Center, Mayo Clinic in Rochester, and Boston Children's Hospital. CONCLUSIONS: Most academic productivity in sports medicine is produced by a relatively small number of fellowship programs in the United States. Of interest, the number of fellows or faculty does not affect significantly the quality or quantity of research productivity at top institutions.

Regional gene therapy for bone healing using a 3D printed scaffold in a rat femoral defect model.

At the present time there are no consistently satisfactory treatment options for some challenging bone loss scenarios. We have previously reported on the properties of a novel 3D-printed hydroxyapatite-composite material in a pilot study, which demonstrated osteoconductive properties but was not tested in a rigorous, clinically relevant model. We therefore utilized a rat critical-sized femoral defect model with a scaffold designed to match the dimensions of the bone defect. The scaffolds were implanted in the bone defect after being loaded with cultured rat bone marrow cells (rBMC) transduced with a lentiviral vector carrying the cDNA for BMP-2. This experimental group was compared against 3 negative and positive control groups. The experimental group and positive control group loaded with rhBMP-2 demonstrated statistically equivalent radiographic and histologic healing of the defect site (p > 0.9), and significantly superior to all three negative control groups (p < 0.01). However, the healed defects remained biomechanically inferior to the unoperated, contralateral femurs (p < 0.01). When combined with osteoinductive signals, the scaffolds facilitate new bone formation in the defect. However, the scaffold alone was not sufficient to promote adequate healing, suggesting that it is not substantially osteoinductive as currently structured. The combination of gene therapy with 3D-printed scaffolds is quite promising, but additional work is required to optimize scaffold geometry, cell dosage and delivery.

Regional Gene Therapy with Transduced Human Cells: The Influence of "Cell Dose" on Bone Repair.

Regional gene therapy using a lentiviral vector containing the BMP-2 complementary DNA (cDNA) has been shown to heal critical-sized bone defects in rodent models. An appropriate "cellular dose" needs to be defined for eventual translation into human trials. The purpose of this study was to evaluate bone defect healing potential and quality using three different doses of transduced human bone marrow cells (HBMCs). HBMCs were transduced with a lentiviral vector containing either BMP-2 or green fluorescent protein (GFP). All cells were loaded onto compression-resistant matrices and implanted in the bone defect of athymic rats. Treatment groups included femoral defects that were treated with a low-dose (1 × 106 cells), standard-dose (5 × 106 cells), and high-dose (1.5 × 107 cells) HBMCs transduced with lentiviral vector containing BMP-2 cDNA. The three control groups were bone defects treated with HBMCs that were either nontransduced or transduced with vector containing GFP. All animals were sacrificed at 12 weeks. The bone formed in each defect was evaluated with plain radiographs, microcomputed tomography (microCT), histomorphometric analysis, and biomechanical testing. Bone defects treated with higher doses of BMP-2-producing cells were more likely to have healed (6/14 of the low-dose group; 12/14 of the standard-dose group; 14/14 of the high-dose group; χ2(2) = 15.501, p < 0.001). None of the bone defects in the control groups had healed. Bone defects treated with high dose and standard dose of BMP-2-producing cells consistently outperformed those treated with a low dose in terms of bone formation, as assessed by microCT and histomorphometry, and biomechanical parameters. However, statistical significance was only seen between defects treated with high dose and low dose. Larger doses of BMP-2-producing cells were associated with a higher likelihood of forming heterotopic ossification. Femurs treated with a standard- and high-dose BMP-2-producing cells demonstrated similar healing and biomechanical properties. Increased doses of BMP-2 delivered through higher cell doses have the potential to heal large bone defects. Adapting regional gene therapy for use in humans will require a balance between promoting bone repair and limiting heterotopic ossification. Impact statement Critical bone loss may result from complex traumatic bone injury (i.e., open fracture or blast injury), revision total joint arthroplasty, and spine pseudoarthrosis. This is a challenging clinical problem to treat and regional gene therapy is an innovative means of addressing it. This study provides information regarding the quantity of cells or "cell dose" of transduced cells needed to treat a critical-sized bone defect in a rat model. This information may be extrapolated for use in humans in future trials.

Cutting, Impingement, Contact, Endurance, Flexibility, and Asymmetric/Overhead Sports: Is There a Difference in Return-to-Sport Rate After Arthroscopic Femoroacetabular Impingement Surgery? A Systematic Review and Meta-analysis.

BACKGROUND: Previous studies have established a classification of sports based on hip mechanics: cutting, impingement, contact, endurance, flexibility, and asymmetric/overhead. No previous review has compared the outcomes of hip arthroscopy for femoroacetabular impingement syndrome (FAIS) using this classification. PURPOSE: To determine whether the rate of return to sport differs among cutting, impingement, contact, endurance, flexibility, and asymmetric/overhead athletes who undergo hip arthroscopy for FAIS. We also aimed to identify differences in patient characteristics, intraoperative procedures performed, and time to return to play among the 6 sport categories. STUDY DESIGN: Systematic review and meta-analysis. METHODS: Three electronic databases were searched for eligible articles. Two reviewers independently screened the titles, abstract, and full-text articles using prespecified criteria. Eligible articles were those that reported the rate of return to sport (defined by the number of hips) after hip arthroscopy for FAIS in athletes of all levels. Data collected were patient age, sex, body mass index, type of sport, rate and time to return to sport, and intraoperative procedures performed. A mixed effects model was used for meta-analysis. RESULTS: A total of 29 articles and 1426 hip arthroscopy cases were analyzed with 185 cutting, 258 impingement, 304 contact, 207 endurance, 116 flexibility, and 356 asymmetric/overhead athletes. The mean age was similar among the 6 subgroups (P = .532), but the proportion of female athletes was significantly higher in flexibility, endurance, and asymmetric/overhead sports as compared with impingement and contact athletes. Flexibility athletes had the highest rate of return to sport after hip arthroscopy for FAIS (94.8%), whereas contact athletes had the lowest rate (88%). The longest mean ± SD time (8.5 ± 1.9 months) to return to sport was reported in cutting sports, while endurance athletes returned faster than the rest (5.4 ± 2.6 months). The difference in rate and time to return to sport, as well as the intraoperative procedure performed, did not reach statistical significance among the 6 subgroups. There was evidence of publication bias and study heterogeneity, and the mean Methodological Index for Non-randomized Studies score was 13 ± 2.6. CONCLUSION: Flexibility athletes had the highest rate of return to sport after hip arthroscopy for FAIS, while endurance athletes returned the fastest. The difference in rate and time to return to sport and intraoperative procedures performed did not reach statistical significance among the 6 subgroups. These results are limited by the evidence of publication bias and should be interpreted with caution. Laboratory-based studies are necessary to validate the classification of sports based on hip mechanics.

Superior Capsule Reconstruction Using Fascia Lata Allograft Compared With Double- and Single-Layer Dermal Allograft: A Biomechanical Study.

PURPOSE: To biomechanically characterize superior capsule reconstruction (SCR) using fascia lata allograft, double-layer dermal allograft, and single-layer dermal allograft for a clinically relevant massive irreparable rotator cuff tear involving the entire supraspinatus and 50% of the infraspinatus tendons. METHODS: Eight cadaveric specimens were tested in 0°, 30°, and 60° abduction for (1) intact, (2) massive rotator cuff tear, (3) SCR using fascia lata, (4) SCR using double-layer dermis, and (5) SCR using single-layer dermis. Superior translation and subacromial contact pressure were measured. Statistical analysis was conducted using repeated measures ANOVA or paired t test with P < .05. RESULTS: Massive rotator cuff tear significantly increased superior translation of the humeral head at all abduction angles (P < .05). At 0° abduction, all SCR conditions significantly decreased superior translation compared with the massive tear but did not restore translation (P < .05) to intact. Fascia lata and double-layer dermis SCR restored superior translation to intact at 30° and 60° of abduction, but single-layer dermis did not. Subacromial contact pressure at 0° of abduction significantly decreased with SCR with fascia lata and double-layer dermis compared with tear. At 30°, all SCR conditions significantly decreased subacromial contact pressure. Single-layer dermis graft thickness significantly decreased more than fascia lata during testing (P = .02). CONCLUSION: For SCR tensioned at 20° glenohumeral abduction, all 3 graft types may restore superior translation and subacromial contact pressure depending on the glenohumeral abduction angle; fascia lata and double-layer dermis may be more effective than single-layer dermis. CLINICAL RELEVANCE: If a dermal graft is to be used for SCR, consideration should be given to doubling the graft for increased thickness and better restorative biomechanical properties, which may improve clinical outcomes following SCR.

Can We Identify Why Athletes Fail to Return to Sport After Hip Arthroscopy for Femoroacetabular Impingement Syndrome? A Systematic Review and Meta-analysis.

BACKGROUND: No previous systematic review has focused on the athletes who fail to return to sport after hip arthroscopy for femoroacetabular impingement syndrome (FAIS). PURPOSE: To review the literature on the athletes who fail to return to sport after hip arthroscopy for FAIS to determine the rate of nonreturning athletes and explore the reasons for their inability to return to sport after arthroscopic FAI surgery. STUDY DESIGN: Systematic review and meta-analysis. METHODS: Three electronic databases were searched for eligible articles. Two reviewers independently screened the titles, abstracts, and full-text articles using prespecified criteria. Eligible articles were those that clearly stated the rate of athletes who did not return to sport after hip arthroscopy for FAIS. Data collected were the rate of patients who did not return to sport, the level of competition (high level, recreational, or mixed), the type of sport, comments on patients who did not return to sport, the rate of subsequent hip surgeries (total hip replacement or revision hip arthroscopy) in nonreturning athletes, and the reported reason for not returning to sport. A random-effects model was used for meta-analysis. RESULTS: Twenty studies were eligible for inclusion, and 1093 athletes were analyzed. The weighted rate of athletes who did not return to sport after hip arthroscopy for FAIS was 12.1% (95% CI, 7.7-17.4). Only 2 studies (2/20;10%) reported the age of the athletes who did not return, while sex was reported in 3 studies (3/20;15%). The estimated proportion of athletes who did not return to sport because of hip-related issues was significantly greater than the percentage of athletes who did not return for reasons unrelated to their hip (74.3% vs 22.3%; P < .0001). Persistent hip pain was the most commonly reported factor (52/110 patients; 47.2%) associated with failure to return to sport. Whether the nonreturning athletes underwent any subsequent hip procedure after hip arthroscopy for FAIS was reported in only 4 out of 20 studies (20%). There was evidence of publication bias and study heterogeneity. CONCLUSION: The estimated rate of athletes who did not return to sport after hip arthroscopy for FAIS was 12%, with the majority of athletes being unable to return because of persistent hip pain. There is a severe lack of evidence on the athlete characteristics and clinical course of the nonreturning athletes, and the rate of subsequent hip procedures is unknown. The outcomes and reasons for athletes not returning to sport should be reported in detail to improve patient care.

Surgical anatomy of the axillary artery: clinical implications for open shoulder surgery.

BACKGROUND: Axillary artery injury is a devastating complication related to anterior shoulder surgery and can result in significant morbidity and/or mortality. The purpose of our study was to evaluate the course of the axillary artery in relation to bony landmarks of the shoulder and identify variations in artery position with humeral external rotation. MATERIALS AND METHODS: Dissection of 18 shoulders (9 fresh whole-body cadavers) with simulated vessel perfusion using radiopaque dye was performed. The axillary artery position was measured from multiple points including 2 points on the coracoid base (C1 and C2), 3 points on the coracoid tip (C3-C5), 4 points on the glenoid: superior, middle, and inferior glenoid (D1-D4), and 2 points on the lesser tuberosity (L1 and L2). Fluoroscopic measurements were taken and compared at 0° and 90° of external rotation (F1 vs. F1' and F2 vs. F2'). Manual and fluoroscopic measurements were compared with one another using Kendall's τb correlation. RESULTS: There were 6 male and 3 female cadavers with an average age of 67.2 ± 9.3 years (range: 49-77 years). The mean distance from the axillary artery to the coracoid base (C1 and C2) measured 21.1 ± 7.3 and 22.3 ± 7.4 mm, respectively, whereas the mean distance to the coracoid tip (C3, C4, and C5) measured 30.7 ± 9.3, 52.1 ± 20.2, and 46.5 ± 14.3 mm, respectively. Measurements relative to the glenoid face (D1, D2, and D3) showed a progressive decrease in mean distance from superior to inferior, measuring 31.6 ± 10.3, 16.5 ± 7.5, and 10.3 ± 7.3 mm, respectively, whereas D4 (inferior glenoid to axillary artery) measured 17.8 ± 10.7 mm. The minimum distance from the axillary artery to any point on the glenoid was as close as 4.1 mm (D3). There was a statistically significant difference in F1 (0° external rotation) vs. F1' (90° external rotation) (18.5 vs. 13.4 mm, P = .03). Kendall's τb correlation showed a strong, positive correlation between manual and fluoroscopic measurements (D4: 16.0 ± 12.5 mm vs. F1: 18.5 ± 10.7 mm) (τb = 0.556, P = .037). CONCLUSION: The axillary artery travels an average of 1-1.8 cm from the inferior glenoid margin, which puts the artery at significant risk. In addition, the artery is significantly closer to the inferior glenoid with humeral external rotation. Surgeons performing anterior shoulder surgery should have a thorough understanding of the axillary artery course and understand changes in the position of the artery with external rotation of the humerus.

Posterior Inferior Comminution Significantly Influences Torque to Failure in Vertically Oriented Femoral Neck Fractures: A Biomechanical Study.

OBJECTIVES: To evaluate axial fracture obliquity and posterior inferior comminution in vertically oriented femoral neck fractures (FNFs) in the physiologically young patient. A biomechanical investigation was designed to evaluate the impact of these fracture elements on torque to failure using cannulated screw (CS) and sliding hip screw fixation. METHODS: Four Pauwels III FNF models were established in synthetic femurs: (1) vertically oriented in the coronal plane (COR), (2) coronal plane with axial obliquity (AX), (3) coronal plane with posterior inferior comminution (CCOM), and (4) coronal plane with axial obliquity and posterior inferior comminution (ACOM). In each group (n = 10), specimens were fixed using either 3 CSs or a sliding hip screw with supplemental antirotation screw (SHS). Quasistatic cyclic ramp-loading to failure was performed using a custom testing jig combining axial preloading and torsional ramp-loading. The primary outcome was torque to failure, defined as angular displacement ≥5 degrees. RESULTS: In the CS group, torque to failure was 40.2 ± 2.6 Nm, 35.0 ± 1.4 Nm, 29.8 ± 1.5 Nm, and 31.8 ± 2.2 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In the SHS group, torque to failure was 28.6 ± 1.3 Nm, 24.2 ± 1.4 Nm, 21.4 ± 1.2 Nm, and 21.0 ± 0.9 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In both constructs, groups with posterior inferior comminution demonstrated significantly lower torque to failure compared to the COR group (P < 0.05). The CS construct demonstrated higher torque to failure in all groups when compared to the SHS construct (P < 0.01). CONCLUSIONS: Posterior inferior comminution significantly affects torque to failure in vertically oriented FNFs. Three peripherally placed CSs may resist combined axial and torsional loading better than a sliding hip screw construct.

Early Results From the American Joint Replacement Registry: A Comparison With Other National Registries.

BACKGROUND: The American Joint Replacement Registry (AJRR) was created to capture knee and hip arthroplasty data in the United States. The purpose of this study was to compare early reports from the AJRR to other national registries to identify topics for future analysis. METHODS: Hip and knee arthroplasty data were extracted from the AJRR, Australia, New Zealand, United Kingdom, Norway, and Sweden from 2014 to 2016. Hip arthroplasty data including femoral and acetabular fixation, bearing surface, head size, dual-mobility bearings, resurfacing, and revision burden were compared. Knee arthroplasty data including polyethylene type, unicondylar arthroplasty, mobile bearings, cruciate-retaining implants, patella resurfacing, and revision burden were compared. Registry characteristics and patient demographics were reported using descriptive statistics. RESULTS: In 2016, the AJRR captured 28% of arthroplasty procedures performed in the United States compared with 95%-98.3% among other registries. Cementless femoral fixation was 96.7% in the AJRR compared with 21.8%-63.4%. Ceramic and 36-mm heads were most common in AJRR; all other registries reported that metal and 32-mm heads were most popular. Dual-mobility articulations were used in 8% of primary and 28% of revision total hip arthroplasty procedures in the AJRR. The AJRR reported a unicondylar knee arthroplasty rate of 3.2% compared with 5.1%-13.3% in other registries, but the highest rates of posterior-stabilized total knee arthroplasties (48.5% compared to 8.2%-28.7%) and patella resurfacing (93.9% compared to 2.4%-51.6%). CONCLUSION: Several differences in hip and knee arthroplasty practices exist between the United States and other countries. Future studies should focus on understanding why differences in practice trends exist and assess outcomes associated with these practices. LEVEL OF EVIDENCE: Level III, retrospective.

Additional Dorsal Fibrocartilage Repair in a Combined Radial Collateral Ligament and Dorsal Fibrocartilage Injury of the Thumb Metacarpophalangeal Joint.

The purpose of this study was to evaluate the necessity of an additional dorsal fibrocartilage (DFC) repair in combined radial collateral ligament (RCL) and DFC injuries of the thumb metacarpophalangeal joint (MPJ). Eight cadaveric thumbs were used. Ulnar/radial deviation, prosupination, and volar/dorsal laxity were measured. Serial sectioning was performed of the RCL and the DFC. The RCL followed by the DFC were then reattached sequentially. Measurements were performed for intact, RCL cut, RCL+DFC cut, RCL repair alone, and RCL+DFC repair. The neutral position shifted ulnarly, pronated, and subluxed volarly after RCL+DFC cut. Volar subluxation was reduced with RCL+DFC repair compared with RCL repair alone. With external loading, ulnar deviation, pronation, and volar laxity increased significantly after RCL+DFC cut. Ulnar deviation reduced significantly with RCL+DFC repair (12.4°, 10.8°, and 10.9°) compared with RCL repair alone (14.4°, 14.3°, and 18.9°) at 0°, 30°, and 60°, respectively. Pronation reduced significantly with RCL+DFC repair (7.1° and 9.4°) compared with RCL repair alone (10.2° and 12.6°) at 0° and 30°, respectively. Volar subluxation reduced significantly with RCL+DFC repair (0.9 mm and 1.2 mm) compared with RCL repair alone (2.1 mm and 1.8 mm) at 30°and 60°, respectively. Radial collateral ligament repair alone does not restore anatomic dorsoradial stability of the thumb MPJ in a combined RCL and DFC injury. Combined repair of the RCL and the DFC is recommended to reduce the MPJ to its native position and minimize postoperative laxity. [Orthopedics. 2019; 42(2):e268-e272.].

The significant effect of the medial hamstrings on dynamic knee stability.

PURPOSE: While hamstring autograft is a popular option for the general population, BTB autograft is still significantly more popular among professional athletes due to concerns of altering knee kinematics with hamstring harvest. This study seeks to quantify the contribution of the medial hamstrings to knee stability. METHODS: Valgus knee laxity, anterior tibial translation, and rotational motion were measured in eight fresh-frozen cadaveric knees after forces were applied on the tibia in each plane (coronal, sagittal, and axial). Four muscle loading conditions were tested: (1) physiologic fully loaded pes anserinus, (2) semitendinosus only loaded, (3) gracilis only loaded, and (4) unloaded pes anserinus. The protocol was then repeated with the ACL transected. RESULTS: In the ACL intact knee, the neutral position of the tibia with an unloaded pes anserinus was significantly more externally rotated (p < 0.01) and anteriorly translated (p < 0.05) at all knee flexion angles than a tibia with a physiologic loaded pes anserinus. Applying an external rotation torque significantly increased external rotation for the fully unloaded (p < 0.001), gracilis only loaded (p < 0.001), and semitendinosus only loaded (p < 0.01) conditions at all flexion angles. Applying a valgus torque resulted in a significant increase in laxity for the fully unloaded condition only at 30° of flexion (p < 0.05). Applying an anterior tibial force resulted in significant increase in anterior translation for the fully unloaded condition at all flexion angles (p < 0.01), and for the gracilis only loaded condition in 30° and 60° of flexion (p < 0.05). Similar results were seen in the ACL deficient model. CONCLUSION: The medial hamstrings are involved in rotational, translational, and varus/valgus control of the knee. Applying anterior, external rotation, and valgus forces on the hamstring deficient knee significantly increases motion in those planes. Harvesting the gracilis and semitendinosus tendons alters native knee kinematics and stability. This is clinically relevant and should be a consideration when choosing graft source for ACL reconstruction, especially in the elite athlete population.

The biomechanical evaluation of a novel 3-strand docking technique for ulnar collateral ligament reconstruction in the elbow.

BACKGROUND AND HYPOTHESIS: The original 2-strand docking technique for elbow ulnar collateral ligament reconstruction has recently been modified to use a 3-strand graft. To date, no biomechanical study has compared the 2 techniques. We hypothesized that the 3-strand docking technique would restore valgus laxity to its native state, with comparable load-to-failure characteristics to the 2-strand docking technique. MATERIALS AND METHODS: Sixteen fresh cadaveric elbows were matched to the corresponding contralateral side from the same individual to create 8 matched pairs and were then randomized to undergo ulnar collateral ligament reconstruction using either the 2- or 3-strand technique. Valgus laxity and rotation measurements were quantified using a MicroScribe 3DLX digitizer at various flexion angles for the native state, transected state, and 1 of the 2 tested reconstructed ligaments. Each reconstruction was then tested to failure. RESULTS: Valgus laxity for the intact state at elbow flexion angles of 30°, 60°, 90°, and 120° was 7° ± 2°, 7° ± 2°, 6° ± 1°, and 5° ± 2°, respectively. These values were similar to those of both reconstruction techniques. On load-to-failure testing, there was no significant difference in any parameter recorded. Yield torques for the 3- and 2-strand reconstructions were 13.4 ± 4.80 N/m and 11.8 ± 4.76 N/m, respectively (P = .486). The ultimate torques were 15.7 ± 6.10 N/m and 14.4 ± 5.58 N/m for the 3- and 2-strand techniques, respectively (P = .582). CONCLUSION: The 3-strand docking technique was able to restore valgus laxity to the native state, with similar load-to-failure characteristics to the 2-strand docking technique.

Dorsoradial Instability of the Thumb Metacarpophalangeal Joint: A Biomechanical Investigation.

PURPOSE: To define the role of the dorsal capsule and associated dorsal fibrocartilage (DFC) and their interactions with the radial collateral ligament (RCL) as a thumb metacarpophalangeal (MCP) joint stabilizer. METHODS: Eight cadaveric thumbs were mounted onto a custom jig with 20 N of muscle load applied. The thumb position in space was digitized to measure ulnar-radial, pronation-supination, and volar-dorsal laxity at 0°, 30°, and 60° MCP joint flexion. Serial sectioning was performed and measurements were repeated for the intact state, proper RCL insufficiency, proper and accessory (complete) RCL insufficiency, complete RCL with 50% DFC (radial) insufficiency, and complete RCL with complete DFC insufficiency. RESULTS: Ulnar-radial deviation, pronation-supination, and volar-dorsal translation significantly changed at 30° and 60° MCP joint flexion when comparing complete RCL insufficiency with complete RCL with 50% DFC insufficiency. At 30° flexion, significant increases were found in ulnar deviation, pronation, and volar translation, and there was a decrease in supination. At 60° flexion, ulnar deviation, pronation, and volar translation increased and radial deviation decreased significantly. At 30° flexion, the resting position significantly pronated and translated volarly. At 60° flexion, the resting position significantly shifted ulnarly, pronated, and translated volarly. CONCLUSIONS: The DFC acts as a secondary stabilizer of the thumb MCP joint, working in tandem with the RCL. It acts by stabilizing the MCP joint dorsoradially when external forces are applied across the joint. This cadaveric study shows that RCL insufficiency with a concomitant DFC injury is less likely to be stable than RCL injuries alone, and that this effect is more pronounced with MCP joint flexion. CLINICAL RELEVANCE: Increasing incompetence of the secondary stabilizers of the RCL, such as the DFC, will likely result in increased clinical instability upon physical examination. The results of this study also suggest the need to consider repair of the DFC at the time of RCL repair.

Evaluating the Femoral-Side Critical Corner in Posterior Cruciate Ligament Reconstruction: The Effect of Outside-In Versus Inside-Out Creation of Femoral Tunnels on Graft Contact Pressure in a Synthetic Knee Model.

PURPOSE: To characterize and compare the graft contact characteristics of outside-in (OI) and inside-out (IO) femoral tunnels during single-bundle reconstruction of the anterolateral bundle of the posterior cruciate ligament in a synthetic knee model. METHODS: Femoral tunnels were separately made in 16 synthetic femora (8 OI and 8 IO). Achilles tendon allografts were fixed using suspensory fixation with a pressure sensor between the allograft and femoral tunnel. Grafts were cyclically loaded; force, contact area, contact pressure, and peak pressure at the aperture were measured. This process was repeated using the same allograft to assess the other tunnel angle in a separate specimen. RESULTS: IO specimens showed higher mean contact pressure at all loading cycles, with significance shown at 50 N (P = .02). Peak pressure was also greater in IO specimens at all loading cycles and reached statistical significance at 100 N (P = .04). IO specimens had a lower contact area at 150 N (P = .04). No statistically significant differences in force were observed between the 2 groups. CONCLUSIONS: OI creation of the femoral tunnel for anterolateral bundle reconstruction of the posterior cruciate ligament resulted in decreased mean and peak contact pressures at the femoral aperture compared with IO tunnel creation at the specific trajectories and loading parameters tested in this synthetic femoral model. These biomechanical data suggest that OI creation of the femoral tunnel may help reduce in vivo graft contact pressure at the femoral aperture. CLINICAL RELEVANCE: These data suggest that a tunnel drilled from OI may result in less graft pressure at the femoral aperture, which may prevent graft elongation and optimize graft survival.

Biomechanical Analysis of an S1 Pedicle Screw Salvage Technique via a Superior Articulating Process Entry Point.

STUDY DESIGN: Biomechanical, cadaveric study. OBJECTIVE: To compare the fixation strength of a novel S1 pedicle screw insertion technique in a revision setting to a standard S1 pedicle screw and an L5 pedicle screw. SUMMARY OF BACKGROUND DATA: Fusions to the sacrum remain a difficult clinical challenge. Very few salvage techniques exist when a nonunion occurs. METHODS: The biomechanical integrity of three screw fixations, L5 pedicle screws, a standard S1 pedicle screw, and an S1 pedicle screw placed via a superior articulating process entry point (SAP S1), was characterized by performing pullout tests using cadaveric specimens including L5 and sacrum. RESULTS: SAP S1 constructs (735.5 ±â€Š110.1 N/mm) were significantly stiffer than standard S1 (P = 0.005) and L5 (P = 0.02) constructs. There was no statistically significant difference between the L5 constructs and the standard S1 constructs for linear stiffness. There was no statistical difference between the three fixations for yield load, displacement at yield load, and energy absorbed to yield load.The ultimate pullout force for the SAP S1 was statistically higher than the standard S1 (1213.7 ±â€Š579.6 vs. 478.6 ±â€Š452.9 N; P = 0.004). Displacement at ultimate load was significantly greater for L5 screw fixation (3.3 ±â€Š1.1 mm) compared to the other two constructs. Both the L5 (2277.4 ±â€Š1873.3 N-mm) and SAP S1 (2628.2 ±â€Š2054.4 N-mm) constructs had significantly greater energy absorbed to ultimate load than the standard S1 construct (811.7 ±â€Š937.6 N-mm), but there was no statistical difference between the L5 and SAP S1 constructs. CONCLUSION: S1 pedicle screw fixation via an SAP entry point provides biomechanical advantages compared to screws placed via the standard S1 or L5 entry point and may be a viable option for revision of a failed L5-S1 fusion with a compromised standard S1 entry point. LEVEL OF EVIDENCE: N/A.

Pelvic discontinuity: modern techniques and outcomes for treating pelvic disassociation.

Pelvic discontinuity is an uncommon condition that usually presents in the revision total hip arthroplasty population. However, its incidence will most likely increase due to the increasing number of primary and revision total hip arthroplasties (THA) done in recent years. Pelvic discontinuity (acetabular disassociation) is perhaps one of the more challenging cases for the hip arthroplasty surgeon to manage. Historically, the management of pelvic discontinuity has been wrought with many challenges. What follows is a review of the current techniques and outcomes for acetabular reconstruction in patients with acetabular disassociation including: porous metal components, internal fixation with acetabular reconstruction, acetabular distraction with jumbo cups, cup and cage construct, and the use of custom triflange.The complexity of pelvic discontinuity and with the myriad of options available to the hip arthroplasty surgeon to address this particular issue, preoperative planning becomes all the more essential.

A common polymorphism in the LDL receptor gene has multiple effects on LDL receptor function.

A common synonymous single nucleotide polymorphism in exon 12 of the low-density lipoprotein receptor (LDLR) gene, rs688, has been associated with increased plasma total and LDL cholesterol in several populations. Using immortalized lymphoblastoid cell lines from a healthy study population, we confirmed an earlier report that the minor allele of rs688 is associated with increased exon 12 alternative splicing (P < 0.05) and showed that this triggered nonsense-mediated decay (NMD) of the alternatively spliced LDLR mRNA. However, since synonymous single nucleotide polymorphisms may influence structure and function of the encoded proteins by co-translational effects, we sought to test whether rs688 was also functional in the full-length mRNA. In HepG2 cells expressing LDLR cDNA constructs engineered to contain the major or minor allele of rs688, the latter was associated with a smaller amount of LDLR protein at the cell surface (-21.8 ± 0.6%, P = 0.012), a higher amount in the lysosome fraction (+25.7 ± 0.3%, P = 0.037) and reduced uptake of fluorescently labeled LDL (-24.3 ± 0.7%, P < 0.01). Moreover, in the presence of exogenous proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein that reduces cellular LDL uptake by promoting lysosomal degradation of LDLR, the minor allele resulted in reduced capacity of a PCSK9 monoclonal antibody to increase LDL uptake. These findings are consistent with the hypothesis that rs688, which is located in the ß-propeller region of LDLR, has effects on LDLR activity beyond its role in alternative splicing due to impairment of LDLR endosomal recycling and/or PCSK9 binding, processes in which the ß-propeller is critically involved.