Masashi Neo

Biomechanical Role of Capsular Continuity in Superior Capsule Reconstruction for Irreparable Tears of the Supraspinatus Tendon

Background: Patients with irreparable rotator cuff tears have a defect of the superior capsule, which creates discontinuity of the shoulder capsule in the transverse direction (anterior-posterior direction). This effect is one of the causes underlying shoulder instability after rotator cuff tears. Purpose/Hypothesis: The purpose of this study was to assess the effects of anterior and posterior continuity on shoulder biomechanics after superior capsule reconstruction (SCR). The hypothesis was that capsular continuity in the transverse direction would improve glenohumeral stability after SCR. Study Design: Controlled laboratory study. Methods: Seven fresh-frozen cadaveric shoulders were tested by using a custom shoulder testing system. Subacromial peak contact pressure, glenohumeral superior translation, glenohumeral compression force, and glenohumeral range of motion (ROM) were compared among 5 conditions: (1) intact shoulder, (2) simulated irreparable supraspinatus tendon tear, (3) SCR without side-to-side suturing, (4) SCR with posterior side-to-side suturing, and (5) SCR with both anterior and posterior side-to-side suturing. Results: The creation of an irreparable supraspinatus tear significantly increased glenohumeral superior translation (0° of abduction: 254% of intact [P = .04]; 30° of abduction: 200% of intact [P = .04]) and subacromial peak contact pressure (0° of abduction: 302% of intact [P = .0001]; 30° of abduction: 239% of intact [P = .0006]), decreased glenohumeral compression force (0° of abduction: 85% of intact [P = .004]; 30° of abduction: 87% of intact [P = .0002]; 60° of abduction: 88% of intact [P = .0001]), and increased total ROM (0° of abduction: 16° increase [P = .008]). SCR without side-to-side suturing significantly decreased subacromial peak contact pressure (0° of abduction: 79% of intact [P = .0001]; 30° of abduction: 91% of intact [P = .001]; 60° of abduction: 55% of intact [P = .04]) but did not inhibit glenohumeral superior translation. By adding posterior side-to-side sutures, both glenohumeral superior translation (0° of abduction: 93% of intact [P = .02]; 30° of abduction: 110% of intact [P = .04]) and subacromial peak contact pressure decreased significantly (0° of abduction: 56% of intact [P = .0001]; 30° of abduction: 83% of intact [P = .0003]; 60° of abduction: 46% of intact [P = .04]). Neither SCR with nor SCR without side-to-side suturing ameliorated the tear-associated decrease in glenohumeral compression force and increase in total ROM. Adding anterior side-to-side sutures did not change any measurements compared with SCR with posterior side-to-side suturing. Conclusion: SCR with side-to-side suturing completely restored the superior stability of the shoulder joint by establishing posterior continuity between the graft, residual infraspinatus tendon, and underlying shoulder capsule. Clinical Relevance: Side-to-side suturing between the graft, residual infraspinatus tendon, and underlying shoulder capsule is recommended for SCR in patients with irreparable supraspinatus tendon tears to restore superior stability after surgery.

Biomechanical Effects of Acromioplasty on Superior Capsule Reconstruction for Irreparable Supraspinatus Tendon Tears

Background: Acromioplasty is increasingly being performed for both reparable and irreparable rotator cuff tears. However, acromioplasty may destroy the coracoacromial arch, including the coracoacromial ligament, consequently causing a deterioration in superior stability even after superior capsule reconstruction. Purpose/Hypothesis: The purpose of this study was to investigate the effects of acromioplasty on shoulder biomechanics after superior capsule reconstruction for irreparable supraspinatus tendon tears. The hypothesis was that acromioplasty with superior capsule reconstruction would decrease the area of subacromial impingement without increasing superior translation and subacromial contact pressure. Study Design: Controlled laboratory study. Methods: Seven fresh-frozen cadaveric shoulders were evaluated using a custom shoulder testing system. Glenohumeral superior translation, the location of the humeral head relative to the glenoid, and subacromial contact pressure and area were compared among 4 conditions: (1) intact shoulder, (2) irreparable supraspinatus tendon tear, (3) superior capsule reconstruction without acromioplasty, and (4) superior capsule reconstruction with acromioplasty. Superior capsule reconstruction was performed using the fascia lata. Results: Compared with the intact shoulder, the creation of an irreparable supraspinatus tear significantly shifted the humeral head superiorly in the balanced muscle loading condition (without superior force applied) (0° of abduction: 2.8-mm superior shift [P = .0005]; 30° of abduction: 1.9-mm superior shift [P = .003]) and increased both superior translation (0° of abduction: 239% of intact [P = .04]; 30° of abduction: 199% of intact [P = .02]) and subacromial peak contact pressure (0° of abduction: 308% of intact [P = .0002]; 30° of abduction: 252% of intact [P = .001]) by applying superior force. Superior capsule reconstruction without acromioplasty significantly decreased superior translation (0° of abduction: 86% of intact [P = .02]; 30° of abduction: 75% of intact [P = .002]) and subacromial peak contact pressure (0° of abduction: 47% of intact [P = .0002]; 30° of abduction: 83% of intact [P = .0005]; 60° of abduction: 38% of intact [P = .04]) compared with after the creation of a supraspinatus tear. Adding acromioplasty significantly decreased the subacromial contact area compared with superior capsule reconstruction without acromioplasty (0° of abduction: 26% decrease [P = .01]; 30° of abduction: 21% decrease [P = .009]; 60° of abduction: 61% decrease [P = .003]) and did not alter humeral head position, superior translation, or subacromial peak contact pressure. Conclusion: Superior capsule reconstruction repositioned the superiorly migrated humeral head and restored superior stability in the shoulder joint. Adding acromioplasty decreased the subacromial contact area without increasing the subacromial contact pressure. Clinical Relevance: When superior capsule reconstruction is performed for irreparable rotator cuff tears, acromioplasty may help to decrease the postoperative risk of abrasion and tearing of the graft beneath the acromion.

Biomechanical Characteristics of Osteochondral Defects of the Humeral Capitellum

Background: The repetitive, excessive compression forces in the radiocapitellar joint caused by elbow valgus stresses during throwing motions can result in osteochondritis dissecans (OCD) of the humeral capitellum in adolescent athletes. Purpose: To assess the effect of elbow valgus torque on contact pressure in the radiocapitellar joint and that of central and lateral capitellar osteochondral defects on radiocapitellar joint contact pressure, elbow valgus laxity, and ulnar collateral ligament (UCL) strain. Study Design: Controlled laboratory study. Methods: In 8 matched pairs of fresh-frozen cadaveric upper limbs, lateral osteochondral defects of the humeral capitellum (5-, 10-, 15-, and 20-mm diameters) were evaluated in one side, and central defects were evaluated in the contralateral side. Radiocapitellar joint contact pressure, elbow valgus laxity, and UCL strain were all measured with and without 2 N·m of valgus torque at 30°, 60°, and 90° of elbow flexion in neutral forearm rotation. Results: Applying valgus torque increased contact pressure in radiocapitellar joints with intact or damaged capitula. Contact pressure in joints with 15-mm (90° of elbow flexion) and 20-mm (60° and 90° of elbow flexion) lateral capitellar defects was greater than that in joints with intact capitula. Radiocapitellar contact pressure was greater with a 20-mm lateral capitellar defect than in the same-sized central defect at 60° and 90° of elbow flexion. In both central and lateral defect groups, elbow valgus laxity increased as the size of the capitellar defect increased, and UCL strain remained unchanged regardless of the size of the capitellar defect. Conclusion: Elbow valgus torque increases contact pressure in the radiocapitellar joint. Capitellar osteochondral defects increase elbow valgus laxity and contact pressure without increasing UCL strain. When valgus torque is applied, contact pressure in the radiocapitellar joint is greater with a lateral defect than with a central defect. Clinical Relevance: Adolescent baseball players with capitellar OCD should stop throwing, even if the UCL is intact, to prevent exacerbating the osteochondral defect. Lateral capitellar OCD is more severe than central capitellar OCD.

Accuracy of Pedicle Screw Placement with Robotic Guidance System: A Cadaveric Study.

Study Design. A cadaveric study. Objective. To investigate the accuracy of pedicle screw placement using a robotic guidance system (RGS). Summary of Background Data. RGS is a unique surgery assistance-apparatus. Although several clinical studies have demonstrated that RGS provides accurate pedicle screw placement, very few studies have validated its accuracy. Methods. A total of 216 trajectories performed with the assistance of the RGS in eight cadavers were evaluated. The RGS was used, with different mounting platforms, to drill pilot holes in the thoracic and lumbosacral spine, using 3-mm diameter fiducial wires as trajectory markers. Deviation between the preoperative plan and executed trajectories was measured at the entry points to the vertebrae and at a depth of 30 mm along the wire. Both the deviation from the preoperative plan and the wire position were evaluated in the axial and sagittal planes using computed tomography (CT). Results. The average deviation from the planned wire placement was 0.64 ± 0.59 mm at the entry point and 0.63 ± 0.57 mm at a depth of 30 mm in the axial plane, and 0.77 ± 0.62 mm and 0.80 ± 0.66 mm, respectively, in the sagittal plane. The magnitude of deviation was not affected by the vertebral level or the platform used. The use of an open approach achieved greater screw placement accuracy at a depth of 30 mm in the sagittal plane, compared with the percutaneous approach. The fiducials were placed completely within the pedicle in 93.9% of trajectories in the axial plane (n = 164 pedicles with a width ≥5 mm) and 98.6% in the sagittal plane (n = 216). Conclusion. In this cadaveric study, RGS supported execution of accurate trajectories that were equal or slightly superior to reports of CT-based navigation systems. Level of Evidence: N/A

Biomechanical Analysis of Articular-Sided Partial-Thickness Rotator Cuff Tear and Repair

Background: Articular-sided partial-thickness rotator cuff tears are common injuries in throwing athletes. The superior shoulder capsule beneath the supraspinatus and infraspinatus tendons works as a stabilizer of the glenohumeral joint. Purpose: To assess the effect of articular-sided partial-thickness rotator cuff tear and repair on shoulder biomechanics. The hypothesis was that shoulder laxity might be changed because of superior capsular plication in transtendon repair of articular-sided partial-thickness rotator cuff tears. Study Design: Controlled laboratory study. Methods: Nine fresh-frozen cadaveric shoulders were tested by using a custom shoulder-testing system at the simulated late-cocking phase and acceleration phase of throwing motion. Maximum glenohumeral external rotation angle, anterior translation, position of the humeral head apex with respect to the glenoid, internal impingement area, and glenohumeral and subacromial contact pressures were measured. Each specimen underwent 3 stages of testing: stage 1, with the intact shoulder; stage 2, after creation of articular-sided partial-thickness tears of the supraspinatus and infraspinatus tendons; and stage 3, after transtendon repair of the torn tendons by using 2 suture anchors. Results: Articular-sided partial-thickness tears did not significantly change any of the shoulder biomechanical measurements. In the simulated late-cocking phase, transtendon rotator cuff repair resulted in decreased maximum external rotation angle by 4.2° (P = .03), posterior shift of the humeral head (1.1-mm shift; P = .02), decreased glenohumeral contact pressure by 1.7 MPa (56%; P = .004), and decreased internal impingement area by 26.4 mm2 (65%; P < .001) compared with values in the torn shoulder. In the acceleration phase, the humeral head shifted inferiorly (1.2-mm shift; P = .03 vs torn shoulder), and glenohumeral anterior translation (1.5-mm decrease; P = .03 vs torn shoulder) and subacromial contact pressure (32% decrease; P = .004 vs intact shoulder) decreased significantly after transtendon repair. Conclusion: Transtendon repair of articular-sided partial-thickness supraspinatus and infraspinatus tears decreased glenohumeral and subacromial contact pressures at time zero; these changes might lead to reduced secondary subacromial and internal impingements and consequently progression to full-thickness rotator cuff tear. However, repair of the tendons decreased anterior translation and external rotation and changed the positional relationship between the humeral head and the glenoid. Clinical Relevance: Careful attention should be paid to shoulder laxity and range of motion when transtendon repair is chosen to treat articular-sided partial-thickness rotator cuff tears, specifically in throwing athletes.

Three-Dimensional Analysis of Acromial Morphologic Characteristics in Patients With and Without Rotator Cuff Tears Using a Reconstructed Computed Tomography Model

Background: The relationship between rotator cuff tears and acromial shape has yet to be clarified. As a result, the most suitable location for acromioplasty for the treatment of rotator cuff tears is not known. Purpose: To determine whether any particular change in acromial shape is significantly associated with the presence of rotator cuff tears. Study Design: Cross-sectional study; Level of evidence, 3. Methods: From 2007 to 2010, we examined 25 consecutive patients with unilateral full-thickness rotator cuff tears who underwent arthroscopic repair and 17 consecutive patients with adhesive capsulitis but intact rotator cuffs who underwent arthroscopic capsular release. Before surgery, a reconstructed 3-dimensional computed tomography model was used to evaluate the acromial structure. Changes in the shape of the affected scapula were qualitatively evaluated relative to the unaffected, contralateral scapula by use of proximity mapping. Differences in acromial structure between affected and unaffected shoulders were assessed at the anterior, lateral, and medial edges and the inferior surface. The association between rotator cuff tear size and change in acromial structure was also evaluated. Results: Rates of bony projection at the anterior (>2 mm) and lateral (>3 mm) edges of the acromion in patients with rotator cuff tears were significantly greater compared with rates in patients without rotator cuff tears (P < .01). Tear size was not correlated with changes in acromial structure (P = .37-.73). Conclusion: Bone spurs at the anterior and lateral edges of the acromion are associated with the presence of full-thickness rotator cuff tears in symptomatic patients.Methods: From 2007 to 2010, we examined 25 consecutive patients with unilateral full-thickness rotator cuff tears who underwent arthroscopic repair and 17 consecutive patients with adhesive capsulitis but intact rotator cuffs who underwent arthroscopic capsular release. Before surgery, a reconstructed 3-dimensional computed tomography model was used to evaluate the acromial structure. Changes in the shape of the affected scapula were qualitatively evaluated relative to the unaffected, contralateral scapula by use of proximity mapping. Differences in acromial structure between affected and unaffected shoulders were assessed at the anterior, lateral, and medial edges and the inferior surface. The association between rotator cuff tear size and change in acromial structure was also evaluated.

Effect of Anterior Capsular Laxity on Horizontal Abduction and Forceful Internal Impingement in a Cadaveric Model of the Throwing Shoulder

Background: Excessive anterior capsular laxity (elongation of the anterior capsular ligaments) causes shoulder subluxation during acceleration of the throwing motion, leading to a disabled throwing shoulder. Few biomechanical studies have investigated the relationship between anterior capsular laxity and internal impingement, another cause of the disabled throwing shoulder. Purpose/Hypothesis: The purpose of this study was to assess the effect of anterior capsular laxity on forceful internal impingement during the late cocking phase. The hypothesis was that excessive anterior shoulder laxity caused by elongation of the anterior capsular ligaments will increase the horizontal abduction angle to increase glenohumeral contact pressure. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen cadaveric shoulders were tested with the shoulder abducted to 90° and at maximal external rotation to simulate the late cocking phase of the throwing motion. The angle of external rotation, anterior translation, angle of horizontal abduction, locations of the articular insertion of the rotator cuff tendons (supraspinatus and infraspinatus) on the greater tuberosity relative to the glenoid, and the glenohumeral contact pressure and area during internal impingement were measured. All data were compared between intact and elongated anterior capsule, which was created by repeatedly applying external rotational stretching. Results: Elongation of the anterior capsular ligaments was confirmed by the increase in glenohumeral external rotation and anterior translation after our stretching technique. Location data showed that the posterior half of supraspinatus tendon, the entire infraspinatus tendon, and the posterosuperior labrum were impinged between the greater tuberosity and glenoid. Maximal glenohumeral horizontal abduction (2.2% increase; P = .003) and glenohumeral contact pressure (27.3% increase; P = .04) were significantly increased in the shoulder joint with increased anterior capsular laxity as compared with the intact condition. Conclusion: Increased anterior capsular laxity created by applying repetitive excessive external rotational torque significantly increased horizontal abduction and contact pressure in the glenohumeral joint. Concurrently, the supraspinatus and infraspinatus tendons and posterosuperior labrum were impinged between the greater tuberosity and glenoid. Clinical Relevance: Increased anterior capsular laxity may exacerbate forceful internal impingement during the late cocking phase of the throwing motion.

A biomechanical cadaveric study comparing superior capsule reconstruction using fascia lata allograft with human dermal allograft for irreparable rotator cuff tear

BACKGROUND Biomechanical and clinical success of the superior capsule reconstruction (SCR) using fascia lata (FL) grafts has been reported. In the United States, human dermal (HD) allograft has been used successfully for SCRs; however, the biomechanical characteristics have not been reported. METHODS Eight cadaveric shoulders were tested in 5 conditions: (1) intact; (2) irreparable supraspinatus tear; (3) SCR using FL allograft with anterior and posterior suturing; (4) SCR using HD allograft with anterior and posterior suturing; and (5) SCR using HD allograft with posterior suturing. Rotational range of motion, superior translation, glenohumeral joint force, and subacromial contact were measured at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane. Graft dimensions before and after testing were also recorded. Biomechanical parameters were compared using a repeated-measures analysis of variance with Tukey post hoc test, and graft dimensions were compared using a Student t-test (P < .05). RESULTS Irreparable supraspinatus tear significantly increased superior translation, superior glenohumeral joint force, and subacromial contact pressure, which were completely restored with the SCR FL allografts. Both SCR HD allograft repairs partially restored superior translation and completely restored subacromial contact and superior glenohumeral joint force. The HD allografts significantly elongated by 15% during testing, whereas the FL allograft lengths were unchanged. CONCLUSIONS Single-layered HD SCR allografts partially restored superior glenohumeral stability, whereas FL allograft SCR completely restored the superior glenohumeral stability. This may be due to the greater flexibility of the HD allograft, and the SCR procedure used was developed on the basis of FL grafts.

Return to Sports and Physical Work After Arthroscopic Superior Capsule Reconstruction Among Patients With Irreparable Rotator Cuff Tears

Background: Although sports participation and heavy physical work can contribute to rotator cuff tears, many patients expect to return to these activities after surgery; however, irreparable rotator cuff tears can preclude this outcome. A new surgical treatment—arthroscopic superior capsule reconstruction (SCR)—restores shoulder stability and muscle balance in patients with irreparable rotator cuff tears; consequently, it improves shoulder function and relieves pain. Purpose: To evaluate the rates of return to sports and physical work among patients treated with arthroscopic SCR. Study Design: Cohort study; Level of evidence, 3. Methods: From 2007 to 2014, we performed arthroscopic SCR in 105 patients with irreparable rotator cuff tears, 5 of whom were lost to follow-up. Consequently, 100 patients (mean age, 66.9 years; range, 43-82 years) were enrolled in the study. Before surgery, 26 patients had participated in sports (2 competitive, 24 recreational), and 34 patients had physical work. Rates of return to sports and physical work, the American Shoulder and Elbow Surgeons (ASES) score, active shoulder range of motion, and rate of graft tear were evaluated. The mean time to final follow-up was 48 months (range, 24-88 months). Results: All 26 patients who played sports before their injuries returned fully to them. In addition, 32 patients returned fully to their previous physical work, whereas the 2 remaining patients returned with reduced hours and workloads. As compared with the nonsports group, the sports group had significantly higher postoperative active elevation (160° ± 32° vs 146° ± 39°; P = .04) and higher postoperative ASES scores (97 ± 7 vs 91 ± 12; P = .02). The shoulder range of motion and ASES scores before and after surgery did not differ significantly between the physical and nonphysical work groups (P = .11-.99). The rate of graft tear did not differ between the sports group (4%) and nonsports group (5%) (P = .75) and between the physical work group (6%) and nonphysical work group (5%) (P = .77). Conclusion: Arthroscopic SCR restored shoulder function and resulted in high rates of return to recreational sports and physical work.

Establishment of novel meniscal scaffold structures using polyglycolic and poly-l-lactic acids:

The purpose of this study was to evaluate various types of meniscus scaffolds that mimic the meniscus structure, and to establish a novel cell-free meniscus scaffold with polyglycolic acid or poly-l-lactic acid. Four types of scaffolds were implanted into Japanese white rabbits: poly-l-lactic acid sponge poly-l-lactic acid, PGA-coated PLLA sponge, PGA lamination, and film-coated PGA lamination. Samples were harvested at 8 and 12 weeks after implantation, and a compression stress test was performed. The meniscus size and Ishida scores were evaluated for regenerated tissue. Immunohistochemistry was analyzed by anti-type I, II and X collagen antibodies to investigate the structure of the regenerated tissue, and by anti-iNOS antibody to investigate the inflammatory tissue of the meniscus. The cell nuclei of lymphocytes and foreign body multinucleated giant cells were counted in hematoxylin and eosin staining. Modified Mankin scores for cartilage degeneration were used for assessment after Safranin-O/Fast Green staining. The biomechanical test showed that l- and film-coated PGA lamination exhibited greater strength than s- and PGA-coated PLLA sponge. At 12 weeks, the size of meniscus and the Ishida score in implanted film-coated PGA lamination were improved significantly compared with the defect groups. The type II collagen staining intensity in the PGA lamination lamination is significantly higher than the defect at eight weeks. The staining intensity of iNOS and number of lymphocytes significantly increased in sponge poly-l-lactic acid at eight weeks, and increased in p-PLLA at 12 weeks. Foreign body multinucleated giant cells in implantation groups appeared, especially at eight weeks. The Mankin score for film-coated PGA lamination was significantly lower than for the defect at 12 weeks. Novel meniscal scaffolds especially PGA should possess not only biological but also biomechanical functions. In conclusions, film-coated PGA lamination was the beneficial property for meniscus scaffold from the points of better biomechanical function, good regeneration, and less inflammation with chondroprotective effects.