Superior Capsular Reconstruction Partially Restores Native Glenohumeral Joint Loads in a Dynamic Biomechanical Shoulder Model.

PURPOSE: To evaluate the effect of an irreparable posterosuperior rotator cuff tear (PSRCT) on glenohumeral joint loads and to quantify improvement after superior capsular reconstruction (SCR) using an acellular dermal allograft. METHODS: Ten fresh-frozen cadaveric shoulders were tested using a validated dynamic shoulder simulator. A pressure mapping sensor was placed between the humeral head and glenoid surface. Each specimen underwent the following conditions: (1) native, (2) irreparable PSRCT, and (3) SCR using a 3-mm-thick acellular dermal allograft. Glenohumeral abduction angle (gAA) and superior humeral head migration (SM) were measured using 3-dimensional motion-tracking software. Cumulative deltoid force (cDF) and glenohumeral contact mechanics, including glenohumeral contact area and glenohumeral contact pressure (gCP), were assessed at rest, 15°, 30°, 45°, and maximum angle of glenohumeral abduction. RESULTS: The PSRCT resulted in a significant decrease of gAA along with an increase in SM, cDF, and gCP (P < .001, respectively). SCR did not restore native gAA (P < .001); however, SM was significantly reduced (P < .001). Further, SCR significantly reduced deltoid forces at 30° (P = .007) and 45° of abduction (P = .007) when compared with the PSRCT. SCR did not restore native cDF at 30° (P = .015), 45° (P < .001), and maximum angle (P < .001) of glenohumeral abduction. Compared with the PSRCT, SCR resulted in a significant decrease of gCP at 15° (P = .008), 30° (P = .002), and 45° (P = .006). However, SCR did not completely restore native gCP at 45° (P = .038) and maximum abduction angle (P = .014). CONCLUSIONS: In this dynamic shoulder model, SCR only partially restored native glenohumeral joint loads. However, SCR significantly decreased glenohumeral contact pressure, cumulative deltoid forces, and superior migration, while increasing abduction motion, when compared with the posterosuperior rotator cuff tear. CLINICAL RELEVANCE: These observations raise concerns regarding the true joint-preserving potential of SCR for an irreparable posterosuperior rotator cuff tear, along with its ability to delay progression of cuff tear arthropathy and eventual conversion to reverse shoulder arthroplasty.

Acromioclavicular and coracoclavicular ligamentous insertion distances depend on the scapular tilt and decrease with anterior direction of the inferior scapula angle.

PURPOSE: A variety of reconstruction techniques exist for the operative treatment of a ruptured acromioclavicular and coracoclavicular ligamentous complex. However, the complication rate remains high; between 5 and 89%. The intraoperative distance between the clavicle, acromion and coracoid is important for the refixation quality. In this study, the influence of scapular deflection on coracoclavicular and acromioclavicular distances was analysed. METHODS: The ligamentous insertions of 24 fresh-frozen human scapulae were exposed. The coracoclavicular and acromioclavicular ligaments were referenced and captured in a rigid body system using a three-dimensional (3D) measurement arm. The inferior angle of the scapula was manually pulled into maximum anterior and posterior deflection, simulating a patient positioning with or without dorsal scapular support, respectively. Based on the rigid body system, the distances between the ligamentous insertions were calculated. Statistical evaluation was performed by setting the distances in anterior deflection to 100% and considering the other distances relative to this position. RESULTS: The scapular deflection had a considerable impact on the distance between the ligamentous insertions. Concerning the conoid ligament, the mean distance was almost doubled when the inferior angle pointed posteriorly compared to anterior deflection (195.3 vs 100.0%; p = 0.028). The insertion of the acromioclavicular capsule also showed a significant association with the direction of deflection (posterior = 116.1% vs. anterior = 100%; p = 0.008). CONCLUSION: Dorsal support shifting the inferior angle of the scapula anteriorly reduces the distance between the ligamentous insertions. Therefore, a patient position on a shoulder table with posterior support of the scapula is recommended to reliability reduce the acromioclavicular joint.

Current concepts in acromioclavicular joint (AC) instability - a proposed treatment algorithm for acute and chronic AC-joint surgery.

BACKGROUND: There exists a vast number of surgical treatment options for acromioclavicular (AC) joint injuries, and the current literature has yet to determine an equivocally superior treatment. AC joint repair has a long history and dates back to the beginning of the twentieth century. MAIN BODY: Since then, over 150 different techniques have been described, covering open and closed techniques. Low grade injuries such as Type I-II according to the modified Rockwood classification should be treated conservatively, while high-grade injuries (types IV-VI) may be indicated for operative treatment. However, controversy exists if operative treatment is superior to nonoperative treatment, especially in grade III injuries, as functional impairment due to scapular dyskinesia or chronic pain remains concerning following non-operative treatment. Patients with a stable AC joint without overriding of the clavicle and without significant scapular dysfunction (Type IIIA) may benefit from non-interventional approaches, in contrast to patients with overriding of the clavicle and therapy-resistant scapular dysfunction (Type IIIB). If these patients are considered non-responders to a conservative approach, an anatomic AC joint reconstruction using a hybrid technique should be considered. In chronic AC joint injuries, surgery is indicated after failed nonoperative treatment of 3 to 6 months. Anatomic AC joint reconstruction techniques along with biologic augmentation (e.g. Hybrid techniques, suture fixation) should be considered for chronic high-grade instabilities, accounting for the lack of intrinsic healing and scar-forming potential of the ligamentous tissue in the chronic setting. However, complication and clinical failure rates remain high, which may be a result of technical failures or persistent horizontal and rotational instability. CONCLUSION: Future research should focus on addressing horizontal and rotational instability, to restore native physiological and biomechanical properties of the AC joint.

Biomechanical Analysis of Coracoid Stability After Coracoplasty: How Low Can You Go?

Background: Arthroscopic coracoplasty is a procedure for patients affected by subcoracoid impingement. To date, there is no consensus on how much of the coracoid can be resected with an arthroscopic burr without compromising its stability. Purpose: To determine the maximum amount of the coracoid that can be resected during arthroscopic coracoplasty without leading to coracoid fracture or avulsion of the conjoint tendon during simulated activities of daily living (ADLs). Study Design: Controlled laboratory study. Methods: A biomechanical cadaveric study was performed with 24 shoulders (15 male, 9 female; mean age, 81 ± 7.9 years). Specimens were randomized into 3 treatment groups: group A (native coracoid), group B (3-mm coracoplasty), and group C (5-mm coracoplasty). Coracoid anatomic measurements were documented before and after coracoplasty. The scapula was potted, and a traction force was applied through the conjoint tendon. The stiffness and load to failure (LTF) were determined for each specimen. Results: The mean coracoid thicknesses in groups A through C were 7.2, 7.7, and 7.8 mm, respectively, and the mean LTFs were 428 ± 127, 284 ± 77, and 159 ± 87 N, respectively. Compared with specimens in group A, a significantly lower LTF was seen in specimens in group B (P = .022) and group C (P < .001). Postoperatively, coracoids with a thickness ≥4 mm were able to withstand ADLs. Conclusion: While even a 3-mm coracoplasty caused significant weakening of the coracoid, the individual failure loads were higher than those of the predicted ADLs. A critical value of 4 mm of coracoid thickness should be preserved to ensure the stability of the coracoid process. Clinical Relevance: In correspondence with the findings of this study, careful preoperative planning should be used to measure the maximum reasonable amount of coracoplasty to be performed. A postoperative coracoid thickness of 4 mm should remain.

Increased Glenohumeral Joint Loads Due to a Supraspinatus Tear Can Be Reversed With Rotator Cuff Repair: A Biomechanical Investigation.

PURPOSE: To evaluate the effect of an isolated full-thickness supraspinatus (SSP) tear on glenohumeral kinematics and contact mechanics, as well as to quantify improvement following rotator cuff repair (RCR). METHODS: Ten fresh-frozen cadaveric shoulders (mean age: 63.1 ± 4.6 years) were tested using a dynamic shoulder simulator. A pressure-mapping sensor was placed between the humeral head and the glenoid. Each specimen underwent the following three conditions: 1) native, 2) isolated full-thickness SSP tear, and 3) RCR. Maximum abduction angle (MAA) and superior humeral head migration (SHM) were measured using 3D motion tracking software. Cumulative deltoid force (CDF) and glenohumeral contact mechanics, including contact area (GCA) and contact pressure (GCP), were assessed at the resting position, as well as at 15°, 30°, 45°, and 60° of glenohumeral abduction. RESULTS: Compared to native, the SSP tear resulted in a significant decrease in MAA (Δ-8.3°; P < .001) along with a SHM of 6.4 ± 3.8 mm, while significantly increasing CDF (Δ20.5 N; P = .008), GCP (Δ63.1 kPa; P < .001), and peak GCP (Δ278.6 kPa; P < .001), as well as decreasing GCA (Δ-45.8 mm2; P < .001) at each degree of abduction. RCR reduced SHM to 1.2 ± 2.5 mm, while restoring native MAA, CDF (Δ1.8 N), GCA (Δ4.5 mm2), GCP (Δ-4.5 kPa) and peak GCP (Δ19.9 kPa) at each degree of abduction (P > .999, respectively). CONCLUSION: In a dynamic biomechanical cadaveric model, increased glenohumeral joint loads due to a full-thickness SSP tear can be reversed with RCR. More specifically, RCR restored native glenohumeral contact area and contact pressure, while preventing superior humeral head migration and decreasing compensatory deltoid forces. CLINICAL RELEVANCE: These time 0 observations indicate that undergoing rotator cuff repair may prevent the development of degenerative changes by significantly reducing glenohumeral joint loads and ensuring sufficiently stable joint kinematics.

Biomechanical Value of a Protective Proximal Humeral Cerclage in Reverse Total Shoulder Arthroplasty.

Reverse shoulder arthroplasty (RSA) is a commonly performed salvage procedure for failed proximal humeral fracture fixation. The rate of intraoperative periprosthetic fractures is higher compared to primary RSA. The goal of this study was to investigate the biomechanical value of a protective cerclage during stem impaction in a revision surgery setting. Twenty-eight fresh-frozen human humeri were used to assess different configurations for steel wire and FiberTape cerclages. A custom-built biomechanical test setup simulated the mallet strikes during the stem impaction process with the Univers Revers prothesis stem. The mallet energy until the occurrence of a first crack was not different between groups. The total energy until progression of the fracture distally to the cerclage was significantly higher in the cerclage groups compared to the native humerus (9.5 J vs. 3.5 J, respectively; p = 0.0125). There was no difference between the steel wire and FiberTape groups (11.4 J vs. 8.6 J, respectively; p = 0.2695). All fractures were located at the concave side of the stem at the metaphyseal calcar region. This study demonstrates that a protective cerclage can successfully delay the occurrence of a fracture during stem impaction in reverse shoulder arthroplasty. A FiberTape cerclage is biomechanically equally efficient compared to a steel wire cerclage.

The forgotten fragment: additional lesser tuberosity fixation of 4-part proximal humeral fractures-a biomechanical investigation.

BACKGROUND: Fractures of the proximal humerus are common. The most frequent surgical treatment option is open reduction and locking plate fixation. Multifragmentary fractures, including 3- and 4-part fractures, are especially challenging to treat because they correlate with an increased risk of fixation failure. In the past, several mechanisms of additional fixation were investigated, but none directly addressed the lesser tuberosity (LT). The goal of this study was to investigate the biomechanical impact of additional anterior fracture fixation in lateral locked plating (LLP) of 4-part proximal humeral fractures (PHFs). METHODS: Twenty-seven fresh frozen human shoulder specimens (mean age, 80 years) with intact rotator cuffs (RCs) were randomized into 4 groups: 3-part PHF with LLP and RC cerclage (n = 6); 4-part PHF with LLP and RC cerclage as standard of care (n = 7); 4-part PHF with LLP, RC cerclage, and 2 anterior 3.5-mm cortical screws (n = 7); and 4-part PHF with LLP, RC cerclage, and additional anterior one-third tubular plate (additional anterior plating [AAP], n = 7). Static load of the RC was simulated with weights. A force-controlled cyclic loading test was performed with a servo-hydraulic testing machine, followed by load-to-failure testing. An optical motion capture system recorded humeral head range of motion. RESULTS: LLP of a 4-part PHF showed more humeral head motion than LLP of a 3-part PHF without fracture of the LT (P < .001). Fixing the LT to the humeral head with two 3.5-mm screws significantly reduced humeral head motion compared with LLP with RC cerclage alone (P < .006). Using AAP significantly increased the construct stiffness compared with the standard of care (P = .03). CONCLUSION: LLP of a 4-part PHF is biomechanically less stable than LLP of a 3-part PHF without fracture of the LT. Additional screw fixation of the LT in 4-part PHFs improves stability compared with LLP alone. In case of metaphyseal comminution, AAP is favorable from a biomechanical perspective.

Glenoid concavity has a higher impact on shoulder stability than the size of a bony defect.

PURPOSE: Surgical treatment of shoulder instability caused by anterior glenoid bone loss is based on a critical threshold of the defect size. Recent studies indicate that the glenoid concavity is essential for glenohumeral stability. However, biomechanical proof of this principle is lacking. The aim of this study was to evaluate whether glenoid concavity allows a more precise assessment of glenohumeral stability than the defect size alone. METHODS: The stability ratio (SR) is a biomechanical estimate of glenohumeral stability. It is defined as the maximum dislocating force the joint can resist related to a medial compression force. This ratio was determined for 17 human cadaveric glenoids in a robotic test setup depending on osteochondral concavity and anterior defect size. Bony defects were created gradually, and a 3D measuring arm was used for morphometric measurements. The influence of defect size and concavity on the SR was examined using linear models. In addition, the morphometrical-based bony shoulder stability ratio (BSSR) was evaluated to prove its suitability for estimation of glenohumeral stability independent of defect size. RESULTS: Glenoid concavity is a significant predictor for the SR, while the defect size provides minor informative value. The linear model featured a high goodness of fit with a determination coefficient of R2 = 0.98, indicating that 98% of the SR is predictable by concavity and defect size. The low mean squared error (MSE) of 4.2% proved a precise estimation of the SR. Defect size as an exclusive predictor in the linear model reduced R2 to 0.9 and increased the MSE to 25.7%. Furthermore, the loss of SR with increasing defect size was shown to be significantly dependent on the initial concavity. The BSSR as a single predictor for glenohumeral stability led to highest precision with MSE = 3.4%. CONCLUSION: Glenoid concavity is a crucial factor for the SR. Independent of the defect size, the computable BSSR is a precise biomechanical estimate of the measured SR. The inclusion of glenoid concavity has the potential to influence clinical decision-making for an improved and personalised treatment of glenohumeral instability with anterior glenoid bone loss.

Metacarpal shaft fixation: a biomechanical comparison of dorsal plating, lag screws, and headless compression screws.

BACKGROUND: Metacarpal shaft fractures are common and can be treated nonoperatively. Shortening, angulation, and rotational deformity are indications for surgical treatment. Various forms of treatment with advantages and disadvantages have been documented. The purpose of the study was to determine the stability of fracture fixation with intramedullary headless compression screws in two types of metacarpal shaft fractures and compare them to other common forms of rigid fixation: dorsal plating and lag screw fixation. It was hypothesized that headless compression screws would demonstrate a biomechanical stronger construct. METHODS: Five matched paired hands (age 60.9 ± 4.6 years), utilizing non-thumb metacarpals, were used for comparative fixation in two fracture types created by an osteotomy. In transverse diaphyseal fractures, fixation by headless compression screws (n = 7) and plating (n = 8) were compared. In long oblique diaphyseal fractures, headless compression screws (n = 8) were compared with plating (n = 8) and lag screws (n = 7). Testing was performed using an MTS frame producing an apex dorsal, three point bending force. Peak load to failure and stiffness were calculated from the load-displacement curve generated. RESULTS: For transverse fractures, headless compression screws had a significantly higher stiffness and peak load to failure, means 249.4 N/mm and 584.8 N, than plates, means 129.02 N/mm and 303.9 N (both p < 0.001). For long oblique fractures, stiffness and peak load to failure for headless compression screws were means 209 N/mm and 758.4 N, for plates 258.7 N/mm and 518.5 N, and for lag screws 172.18 N/mm and 234.11 N. There was significance in peak load to failure for headless compression screws vs plates (p = 0.023), headless compression screws vs lag screws (p < 0.001), and plates vs lag screws (p = 0.009). There was no significant difference in stiffness between groups. CONCLUSION: Intramedullary fixation of diaphyseal metacarpal fractures with a headless compression screw provides excellent biomechanical stability. Coupled with lower risks for adverse effects, headless compression screws may be a preferable option for those requiring rapid return to sport or work. LEVEL OF EVIDENCE: Basic Science Study, Biomechanics.

[Posttraumatic shoulder stiffness]. / Posttraumatische Schultersteife.

Posttraumatic stiffness of the shoulder joint is a frequent and socioeconomically relevant result of injury; however, prior to making the diagnosis as the only cause of a persisting impairment of motion, it is necessary to rule out other sequelae of trauma. Even intensive conservative treatment is mostly accompanied by the stagnation of the impairments of movement. In many cases the treatment of choice is early arthroscopic arthrolysis with a standardized approach and intensive follow-up treatment. In the surgical treatment of proximal humeral fractures with humeral head preservation, arthroscopic arthrolysis with simultaneous implant removal is a form of planned second intervention for improvement of shoulder function in cases of persisting motion deficits after bony consolidation. Despite sometimes substantial limitations of movement, a clinically relevant and lasting improvement of shoulder function can be achieved with arthroscopic arthrolysis in posttraumatic shoulder stiffness.

Comparison of Different Fixation Techniques of the Long Head of the Biceps Tendon in Superior Capsule Reconstruction for Irreparable Posterosuperior Rotator Cuff Tears: A Dynamic Biomechanical Evaluation.

BACKGROUND: In the past decade, superior capsular reconstruction has emerged as a potential surgical approach in young patients with irreparable posterosuperior rotator cuff tears (RCT) and absence of severe degenerative changes. Recently, the use of locally available and biological viable autografts, such as the long head of the biceps tendon (LHBT) for SCR has emerged, with promising early results. PURPOSE/HYPOTHESIS: The purpose of this study was to investigate the effect of using the LHBT for reconstruction of the superior capsule on shoulder kinematics, along with different fixation constructs in a dynamic biomechanical model. The authors hypothesized that each of the 3 proposed fixation techniques would restore native joint kinematics, including glenohumeral superior translation (ghST), maximum abduction angle (MAA), maximum cumulative deltoid force (cDF), and subacromial peak contact pressure (sCP). STUDY DESIGN: Controlled laboratory study. METHODS: Eight fresh-frozen cadaveric shoulders (mean age, 53.4 ± 14.2 years) were tested using a dynamic shoulder simulator. Each specimen underwent the following 5 conditions: (1) intact, (2) irreparable posterosuperior rotator cuff tear (psRCT), (3) V-shaped LHBT reconstruction, (4) box-shaped LHBT reconstruction, and (5) single-stranded LHBT reconstruction. MAA, ghST, cDF and sCP were assessed in each tested condition. RESULTS: Each of the 3 LHBT techniques for reconstruction of the superior capsule significantly increased MAA while significantly decreasing ghST and cDF compared with the psRCT (P < .001 and P < .001, respectively). Additionally, the V-shaped and box-shaped techniques significantly decreased sCP (P = .009 and P = .016, respectively) compared with the psRCT. The V-shaped technique further showed a significantly increased MAA (P < .001, respectively) and decreased cDF (P = .042 and P = .039, respectively) when compared with the box-shaped and single-stranded techniques, as well as a significantly decreased ghST (P = .027) when compared with the box-shaped technique. CONCLUSION: In a dynamic biomechanical cadaveric model, using the LHBT for reconstruction of the superior capsule improved shoulder function by preventing superior humeral migration, decreasing deltoid forces and sCP. As such, the development of rotator cuff tear arthropathy in patients with irreparable psRCTs could potentially be delayed. CLINICAL RELEVANCE: Using a biologically viable and locally available LHBT autograft is a cost-effective, potentially time-saving, and technically feasible alternative for reconstruction of the superior capsule, which may result in favorable outcomes in irreparable psRCTs. Moreover, each of the 3 techniques restored native shoulder biomechanics, which may help improve shoulder function by preventing superior humeral head migration and the development of rotator cuff tear arthropathy in young patients with irreparable rotator cuff tears.

The Glenolabral Articular Disruption Lesion Is a Biomechanical Risk Factor for Recurrent Shoulder Instability.

PURPOSE: To investigate the biomechanical effect of a glenolabral articular disruption (GLAD) lesion on glenohumeral laxity. METHODS: Human cadaveric glenoids (n = 10) were excised of soft tissue, including the labrum to focus on the biomechanical effects of osteochondral surfaces. Glenohumeral dislocations were performed in a robotic test setup, while displacement forces and three-dimensional morphometric properties were measured. The stability ratio (SR), a biomechanical characteristic for glenohumeral stability, was used as an outcome parameter, as well as the path of least resistance, determined by a hybrid robot displacement. The impacts of chondral and bony defects were analyzed related to the intact glenoid. Statistical comparison of the defect states on SR and the path of least resistance was performed using repeated-measures ANOVA and Tukey's post hoc test for multiple comparisons (P < .05). The relationship between concavity depth and SR was approximated in a nonlinear regression. RESULTS: The initial SR of the intact glenoid (28.3 ± 7.8%) decreased significantly by 4.7 ± 3% in case of a chondral defect (P = .002). An additional loss of 3.2 ± 2.3% was provoked by a 20% bony defect (P = .004). The path of least resistance was deflected significantly more inferiorly by a GLAD lesion (2.9 ± 1.8°, P = .002) and even more by a bony defect (2.5 ± 2.9°, P = .002). The nonlinear regression with concavity depth as predictor for the SR resulted in a high correlation coefficient (r = .81). CONCLUSIONS: Chondral integrity is an important contributor to the SR. Chondral defects as present in GLAD lesions may cause increased laxity, influence the humeral track on the glenoid during dislocation, and represent a biomechanical risk factor for a recurrent instability. CLINICAL RELEVANCE: Cartilage deficiency corresponding to GLAD lesions may be a risk factor for impaired surgical outcomes.

Significant Improvement in Shoulder Function and Pain in Patients Following Biologic Augmentation of Revision Arthroscopic Rotator Cuff Repair Using an Autologous Fibrin Scaffold and Bone Marrow Aspirate Derived From the Proximal Humerus.

PURPOSE: To clinically evaluate patients who underwent a biologic augmentation technique in revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated stem cells isolated from bone marrow aspirate (BMA) obtained from the proximal humerus. METHODS: This is a retrospective review of prospectively collected data from patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and BMA obtained from the proximal humerus between 2014 and 2015. Minimum follow-up was 12 months. Outcome measures were collected preoperatively and postoperatively including range of motion as well as American Shoulder and Elbow Surgeons Shoulder Form, Simple Shoulder Test, single assessment numeric evaluation, and visual analog score. In addition, BMA samples of each patient were assessed for the number of nucleated cells and colony-forming units. Regression analysis was performed to investigate whether the number of nucleated cells and colony-forming units had an influence on outcome and failure. RESULTS: Ten patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA obtained from the proximal humerus between 2014 and 2015 were included. The mean follow-up time was 30.7 (range: 12-49) months. Four patients were revised at final follow-up. Postoperative clinical scores improved significantly: American Shoulder and Elbow Surgeons (28.1 ± 5.4 to 60.9 ± 9.0; P < .01), single assessment numeric evaluation (6.6 ± 2.3 to 65.1 ± 10.9; P < .01), visual analog scale (7.2 ± 0.9 to 3.1 ± 0.9; P < .01), and Simple Shoulder Test (1.6 ± 0.5 to 10.3 ± 5.7; P < .01). Postoperative range of motion increased significantly with regard to flexion (97.0 ± 13.6 to 151.0 ± 12.2; P < .01) and abduction (88.0 ± 14.0 to 134.0 ± 15.1; P = .038) but not with external rotation (38.0 ± 5.7 to 50.5 ± 6.5; P = .16). Less pain was correlated to an increased number of nucleated cells (P = .026); however, there was no correlation between failure rate and number of nucleated cells (P = .430). CONCLUSIONS: Patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA demonstrated a significant improvement in shoulder function along with reduction of pain. However, the overall revision rate for this procedure was 40%. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Off-track Hill-Sachs lesions predispose to recurrence after nonoperative management of first-time anterior shoulder dislocations.

PURPOSE: The purpose of this study was to evaluate whether the presence of an off-track Hill-Sachs lesion has an impact on the recurrence rate after nonoperative management of first-time anterior shoulder dislocations. METHODS: A retrospective cohort study was planned with a follow-up via questionnaire after a minimum of 24 months. Fifty four patients were included in the study (mean age: 29.5 years; 16 female, 38 male). All of these patients opted for primary nonoperative management after first-time traumatic anterior shoulder dislocation, in some cases even against the clinician's advice. The glenoid track and the Hill-Sachs interval were evaluated in the MRI scans. The clinical outcome was evaluated via a shoulder-specific questionnaire, ASES-Score and Constant Score. Further, patients were asked to report on recurrent dislocation (yes/no), time to recurrent dislocation, pain, feeling of instability and satisfaction with nonoperative management. RESULTS: In 7 (13%) patients, an off-track Hill-Sachs lesion was present, while in 36 (67%) the lesion was on-track and 11 (20%) did not have a structural Hill-Sachs lesion at all. In total, 31 (57%) patients suffered recurrent dislocations. In the off-track group, all shoulders dislocated again (100%), while 21 (58%) in the on-track group and 3 (27%) in the no structural Hill--Sachs lesion group had a recurrent dislocation, p = 0.008. The mean age in the group with a recurrence was 23.7 ± 10.1 years, while those patients without recurrent dislocation were 37.4 ± 13.1 years old, p < 0.01. The risk for recurrence in patients under 30 years of age was higher than in those older than 30 years (OR = 12.66, p < 0.001). There were no significant differences between patients with on- and off-track lesions regarding patients' sex, height, weight and time to reduction and glenoid diameter. Off-track patients were younger than on-track patients (24.9 ± 7.3 years vs. 29.6 ± 13.6 years). However, this difference was not statistically significant. CONCLUSION: The presence of an off-track Hill-Sachs lesion leads to significantly higher recurrence rates compared to on-track or no structural Hill--Sachs lesions in patients with nonoperative management and should be considered when choosing the right treatment option. Therefore, surgical intervention should be considered in patients with off-track Hill-Sachs lesions. LEVEL OF EVIDENCE: IV.

Dynamic Q-angle is increased in patients with chronic patellofemoral instability and correlates positively with femoral torsion.

PURPOSE: The purpose of the study was to evaluate the frontal gait patterns in patients with chronic patellofemoral instability compared to healthy controls. The hypothesis was that internal-rotation-adduction moment of the knee as altered dynamic Q-angle is evident in patients and correlates positively with increased femoral torsion. METHODS: Thirty-five patients with symptomatic recurrent patellofemoral instability requiring surgical treatment were matched for average age, sex, and body mass index with 15 healthy controls (30 knees). Several clinical and radiographic measurements were taken from each participant: internal and external rotation (hipIR, hipER), Q-angle, tubercle sulcus angle (TS-angle), femoral antetorsion (femAT), tibial tubercle-trochlear groove (TT-TG) distance, and frontal leg axis. Additionally, three frontal gait patterns were defined and recorded: (1) internal-rotation-adduction moment of the knee during normal walking, (2) dynamic valgus of the knee, and (3) Trendelenburg's sign in a single-leg squat. Randomized videography was evaluated by three independent blinded observers. Statistical analysis was performed using regression models and comparisons of gait patterns and clinical and radiological measurements. Furthermore, observer reliability was correlated to gradings of radiological parameters. RESULTS: Patients showed altered dynamic Q-angle gait pattern during normal walking (p < 0.001) compared to healthy controls (interrater kappa = 0.61), whereas highest observer agreement was reported if femAT was greater than 20° (kappa = 0.85). Logistic regression model revealed higher femAT (18.2° ± 12.5 versus 11.9° ± 7.0 (p = 0.004) as a significant variable, as well as lower TT-TG distance (23.6 mm ± 2.8 vs. 16.6 mm ± 4.9, p = 0.004) on evident dynamic Q-angle gait pattern. Dynamic valgus in a single-leg squat was observed significantly more often in patients (p < 0.001) compared to controls (interrater kappa = 0.7). However, besides the static measured Q-angle as the only significant variable on evident dynamic valgus pattern (13.6° ± 4.6 vs. 10.3° ± 5.2, p = 0.003), no radiological parameter was detected to correlate significantly with dynamic valgus and Trendelenburg's sign (n.s.). CONCLUSIONS: Clinical detection of pathologic torsion and bony alignment may be difficult in patients with patellofemoral instability. The present study demonstrated that dynamic Q-angle gait pattern is significantly altered in patients with chronic patellofemoral instability compared to healthy controls. Moreover, dynamic Q-angle correlates positively with higher femoral torsion and negatively with higher TT-TG distance. Therefore, clinical and radiological assessment of maltorsion should be added to the standard diagnostic workup in cases of patellofemoral instability. LEVEL OF EVIDENCE: Level II.

Radiographic alterations in clavicular bone tunnel width following anatomic coracoclavicular ligament reconstruction (ACCR) for chronic acromioclavicular joint injuries.

PURPOSE: To evaluate tunnel widening and its relationship in loss of reduction and clinical outcomes in patients undergoing anatomic coracoclavicular ligament reconstruction (ACCR) using free tendon grafts for chronic acromioclavicular (AC) joint injuries. METHODS: A retrospective chart review was performed on patients undergoing ACCR for type III-VI AC joint injuries between January 2003 and December 2017. For radiographic analysis, pre- and post-operative coracoclavicular distance (CCD) and tunnel width of the medial and lateral clavicular bone tunnel were measured at the earliest (EPO) and latest postoperative follow-up (LPO). To determine the clinical relevance of improvement in clinical outcome score (American Shoulder and Elbow Surgeons score) substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) thresholds were used. RESULTS: Twenty-four patients with a mean clinical follow-up of 37 ± 35 months (mean age 44.7 ± 13.4) were included in the study. Both the medial (5.6 ± 0.2 mmEPO-6.6 ± 0.7 mmLPO; p < 0.001) and lateral (5.6 ± 0.5 mmEPO-6.8 ± 1 mmLPO; p < 0.001) clavicular bone tunnel showed significant widening from EPO to LPO. There was a significant loss of reduction at LPO (CCDLPO 10.1 ± 4 mm) compared to EPO (CCDEPO: 6.2 ± 3.8 mm) (p < 0.001). No significant correlation between loss of reduction and medial (p = 0.45; r = - 0.06) or lateral (p = 0.69; r = - 0.06) tunnel widening was found. Alterations in tunnel width were shown having no influence on clinical outcomes. CONCLUSION: Patients who underwent ACCR using a free tendon graft for the treatment of chronic type III-VI ACJ injuries showed significant clavicular bone tunnel widening during the postoperative course. No correlation between tunnel widening and loss of reduction was shown with radiographic findings having no influence on clinical benefit and satisfaction. STUDY DESIGN: Case Series; Level of evidence, IV.

Graft Tensioning in Superior Capsular Reconstruction Improves Glenohumeral Joint Kinematics in Massive Irreparable Rotator Cuff Tears: A Biomechanical Study of the Influence of Superior Capsular Reconstruction on Dynamic Shoulder Abduction.

BACKGROUND: Superior capsular reconstruction (SCR) for massive, irreparable rotator cuff tears has become more widely used recently; however, ideal tensioning of the graft and the influence on joint kinematics remain unknown. PURPOSE/HYPOTHESIS: The purpose of this study was to assess the effects of graft tensioning on glenohumeral joint kinematics after SCR using a dermal allograft. The hypothesis was that a graft fixed under tension would result in increased glenohumeral abduction motion and decreased cumulative deltoid forces compared with a nontensioned graft. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 10 fresh-frozen cadaveric shoulders were tested using a dynamic shoulder simulator. Each shoulder underwent the following 4 conditions: (1) native, (2) simulated irreparable supraspinatus (SSP) tear, (3) SCR using a nontensioned acellular dermal allograft, and (4) SCR using a graft tensioned with 30 to 35 N. Mean values for maximum glenohumeral abduction and cumulative deltoid forces were recorded. The critical shoulder angle (CSA) was also assessed. RESULTS: Native shoulders required a mean (±SE) deltoid force of 193.2 ± 45.1 N to achieve maximum glenohumeral abduction (79.8° ± 5.8°). Compared with native shoulders, abduction decreased after SSP tears by 32% (54.3° ± 13.7°; P = .04), whereas cumulative deltoid forces increased by 23% (252.1 ± 68.3 N; P = .04). The nontensioned SCR showed no significant difference in shoulder abduction (54.1° ± 16.1°) and required deltoid forces (277.8 ± 39.8 N) when compared with the SSP tear state. In contrast, a tensioned graft led to significantly improved shoulder abduction compared with the SSP tear state (P = .04) although abduction and deltoid forces could not be restored to the native state (P = .01). A positive correlation between CSA and maximum abduction was found for the tensioned-graft SCR state (r = 0.685; P = .02). CONCLUSION: SCR using a graft fixed under tension demonstrated a significant increase in maximum shoulder abduction compared with a nontensioned graft; however, abduction remained significantly less than the intact state. The nontensioned SCR showed no significant improvement in glenohumeral kinematics compared with the SSP tear state. CLINICAL RELEVANCE: Because significant improvement in shoulder function after SCR may be expected only when the graft is adequately tensioned, accurate graft measurement and adequate tension of at least 30 N should be considered during the surgical procedure. SCR with a tensioned graft may help maintain sufficient acromiohumeral distance, improve clinical outcomes, and reduce postoperative complications.

Proximal Humerus and Ilium Are Reliable Sources of Bone Marrow Aspirates for Biologic Augmentation During Arthroscopic Surgery.

PURPOSE: The purpose of this study was to evaluate the number of colony-forming units (CFUs) derived from concentrated bone marrow aspirates (BMAs) that were processed following arthroscopic harvest from either the proximal humerus or the body of the ilium during biologic augmentation of the rotator cuff and acetabular labral repairs. METHODS: Between November 2014 and January 2019, BMA was harvested from the proximal humerus (n = 89) and the body of the ilium (n = 30) during arthroscopic surgery. Following concentration of the aspirate, a 0.5-mL aliquot was further processed and the number of nucleated cells (NC) was counted. Each aliquot was cultured until CFUs were quantifiable. Fluorescence-activated cell sorting analysis and quantitative polymerase chain reaction was performed to confirm presence of mesenchymal stem cells. BMA harvest sites were prospectively assessed and evaluated for differences in age, sex, volume of aspirated BM, and CFUs per milliliter of BMA. RESULTS: The prevalence (38.57 ± 27.92ilium vs. 56.00 ± 25.60humerus CFUs per 106 nucleated cells) and concentration (979.17 ± 740.31ilium vs. 1,516.62 ± 763.63humerus CFUs per 1.0 mL BMA) of CFUs was significantly higher (P < .001, respectively) for BMA harvested from the proximal humerus. Additionally, the estimated total number of cells was significantly higher (P = .013) in BMA from the proximal humerus (97,529.00 ± 91,064.01ilium vs. 130,552.4 ± 85,294.2humerus). There was no significant difference between groups regarding BMA volume (91.67 ± 18.77ilium vs. 85.63 ± 35.61humerus mL; P = .286) and NC count (24.01 ± 5.13ilium vs. 27.07 ± 6.28humerus × 106 per mL BMA; P = .061). The mean age was significantly lower (P < .001) in patients with BMA being harvested from the ilium (30.18 ± 7.63ilium vs. 56.82 ± 7.08humerus years). Patient sex and age had no significant influence on cellular measures within groups (P > .05, respectively). CONCLUSION: Both proximal humerus and the body of the ilium can be considered reliable sources of bone marrow aspirate for the use in biologic augmentation during their respective arthroscopic surgery. Samples of bone marrow aspirate from the proximal humerus yielded a significantly higher amount of CFUs when compared with samples of BMA obtained from the ilium. LEVEL OF EVIDENCE: Level II- prospective laboratorial study.

Cells from a GDF5 origin produce zonal tendon-to-bone attachments following anterior cruciate ligament reconstruction.

Following anterior cruciate ligament (ACL) reconstruction surgery, a staged repair response occurs where cells from outside the tendon graft participate in tunnel integration. The mechanisms that regulate this process, including the specific cellular origin, are poorly understood. Embryonic cells expressing growth and differentiation factor 5 (GDF5) give rise to several mesenchymal tissues in the joint and epiphyses. We hypothesized that cells from a GDF5 origin, even in the adult tissue, would give rise to cells that contribute to the stages of repair. ACLs were reconstructed in Gdf5-Cre;R26R-tdTomato lineage tracing mice to monitor the contribution of Gdf5-Cre;tdTom+ cells to the tunnel integration process. Anterior-posterior drawer tests demonstrated 58% restoration in anterior-posterior stability. Gdf5-Cre;tdTom+ cells within the epiphyseal bone marrow adjacent to tunnels expanded in response to the injury by 135-fold compared with intact controls to initiate tendon-to-bone attachments. They continued to mature the attachments yielding zonal insertion sites at 4 weeks with collagen fibers spanning across unmineralized and mineralized fibrocartilage and anchored to the adjacent bone. The zonal attachments possessed tidemarks with concentrated alkaline phosphatase activity similar to native entheses. This study established that mesenchymal cells from a GDF5 origin can contribute to zonal tendon-to-bone attachments within bone tunnels following ACL reconstruction.

Clinical Application and Outcomes of Upper Extremity Double Plating. / Klinische Anwendung und Ergebnisse der Doppelplattenosteosynthese an der oberen Extremität.

Dual plating in fractures of the upper extremity is well established for the distal humerus. The indication for the use of dual plating has been expanded over the last few years. While dual plating was originally frequently used in revisions of non-unions, it is nowadays also used in primary fixation of diverse complex fractures of the upper extremity. The high biomechanical fixation strength of dual plating is advantageous in regions with high bending and torsional stresses, such as the humeral shaft. An additional anterior plate provides high fixation strength and reduces the risk of loss of reduction in complex proximal humeral fractures and allows for direct fixation of lesser tuberosity fragments. Low-profile plates have been introduced for complex proximal ulna fractures. In dual plating the improved mechanical stability is combined with a reduced risk of implant related soft tissue irritations. The present article provides an overview of current indications for dual plating of upper extremity fractures and outlines technical aspects as well as advantages over conventional fixation techniques.