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Biomedical subjects

Mark W Rodosky

Publications and source records attributed to Mark W Rodosky.

11 recordsLinked to original sources
PubMed2006

Symptomatic os acromiale.

Os acromiale, the joining of the acromion to the scapular spine by fibrocartilaginous tissue rather than bone, is an anatomic variant that has been reported in approximately 8% of the population worldwide. It is more common in blacks and males than in whites and females. Although it is often an incidental finding, os acromiale has been identified as a contributor to shoulder impingement symptoms and rotator cuff tears. When nonsurgical management of a symptomatic os acromiale fails to relieve symptoms, surgical intervention is considered. Options include os acromiale excision, open reduction and internal fixation, and arthroscopic decompression. Excision usually is reserved for small to midsized fragments (preacromion) or after failed open reduction and internal fixation. Persistent deltoid dysfunction may result from excision of a large os acromiale. Open reduction and internal fixation preserves large fragments while maintaining deltoid function. Cannulated screw fixation has been shown to result in good union rates. Arthroscopic techniques have shown mixed results when used for treating impingement secondary to an unstable os acromiale. Associated rotator cuff tears may be addressed arthroscopically or through an open transacromial approach, followed by open reduction and internal fixation of the os acromiale.

Acromion↗
PubMed2004

Biomechanical function of surgical procedures for acromioclavicular joint dislocations.

PURPOSE: Surgical procedures for treatment of acromioclavicular (AC) joint dislocation replace the coracoclavicular (CC) ligaments to minimize motion, allow scarring, and increase the subsequent stability of the joint. The purpose of this study was to evaluate the biomechanical function of the surgically repaired or reconstructed (CC Sling, Rockwood Screw [DePuy Orthopaedics, Warsaw, IN], and Coracoacromial [CA] Ligament Transfer Construct) AC joint after AC joint dislocation. TYPE OF STUDY: A cadaver study using a convenience sample. METHODS: Twelve cadaveric shoulders were tested using a robotic/UFS testing system. Three external loading conditions (anterior, posterior, or superior load of 70 N) were applied to intact and surgically repaired or reconstructed AC joint. The resulting kinematics of the AC joint and in situ forces in the CC ligaments or surgical constructs was determined. RESULTS: For the CC Sling, anterior and posterior translation significantly increased by 110% and 330% in response to an anterior and posterior load, respectively. However, the posterior translation for the Rockwood Screw significantly decreased by 60%. Anterior, posterior, and superior translation for the CA Ligament Transfer Construct significantly increased by 110%, 360%, and 100%, respectively. The coupled translations also significantly increased for the CC Sling and CA Ligament Transfer Construct in response to all loading conditions. In contrast, the coupled translations for the Rockwood Screw tended to decrease. Furthermore, the in situ forces increased significantly for all 3 surgical constructs compared with the intact CC Ligaments in response to an anterior and posterior load. CONCLUSIONS: At time zero, increases in the primary and coupled motion for the CC Sling and CA Ligament Transfer Construct could comprise the initial healing period prescribed for AC joint dislocation. Our findings also suggest that the Rockwood Screw provides a highly rigid fixation and may explain the complications frequently seen in clinical practice. CLINICAL RELEVANCE: Current surgical procedures do not have the appropriate stiffness to restore the stability of the intact joint before healing. Therefore, our results may lead to the design and development of new repairs, reconstructions, and rehabilitation protocols for AC joint dislocation.

Acromioclavicular Joint↗
PubMed2004

Internal impingement: findings on magnetic resonance imaging and arthroscopic evaluation.

PURPOSE: The purpose of this study was to examine preoperative shoulder magnetic resonance imaging (MRI) and intraoperative arthroscopic findings in throwing athletes with a clinical diagnosis of internal impingement. TYPE OF STUDY: Retrospective review. METHODS: A retrospective review of the surgical indications for 769 shoulder arthroscopic procedures performed from 1997 to 2000 revealed 9 throwing athletes with a diagnosis of severe internal impingement. Each had failed treatment that included a minimum of 3 months of rehabilitation. Preoperative MRIs in all 9 were read by a fellowship-trained musculoskeletal radiologist blinded to the operative findings. Findings at arthroscopy were culled from the operative reports. RESULTS: On both MRI and at arthroscopy, all 9 athletes had posterosuperior labral lesions, 1 had a humeral head articular cartilage lesion, and 1 had a SLAP lesion. Additional findings on MRI included humeral head edema, subchondral cystic changes, posterosuperior glenoid sclerosis, and rotator cuff tendonopathy predominantly in the infraspinatus. At arthroscopy, there were additional findings of articular-sided partial rotator cuff tears not shown on MRI. CONCLUSIONS: Both MRI and arthroscopic findings described labral and humeral head articular cartilage lesions. These findings may be indicative of internal impingement in throwing athletes. LEVEL OF EVIDENCE: Level III, diagnostic.

Adult↗
PubMed2004

Reflexive muscle activation alterations in shoulders with anterior glenohumeral instability.

BACKGROUND: Patients with glenohumeral instability have proprioceptive deficits that are suggested to contribute to muscle activation alterations. HYPOTHESIS: Muscle activation alterations will be present in shoulders with anterior glenohumeral instability. STUDY DESIGN: Posttest-only control group design. METHODS: Eleven patients diagnosed with anterior glenohumeral instability were matched with 11 control subjects. Each subject received an external humeral rotation apprehension perturbation while reflexive muscle activation characteristics were measured with indwelling electromyography and surface electromyography. RESULTS: Patients with instability demonstrated suppressed pectoralis major and biceps brachii mean activation; increased peak activation of the subscapularis, supraspinatus, and infraspinatus; and a significantly slower biceps brachii reflex latency. Supraspinatus-subscapularis coactivation was significantly suppressed in the patients with instability as well. CONCLUSIONS AND CLINICAL RELEVANCE: In addition to the capsuloligamentous deficiency and proprioceptive deficits present in anterior glenohumeral instability, muscle activation alterations are also present. The suppressed rotator cuff coactivation, slower biceps brachii activation, and decreased pectoralis major and biceps brachii mean activation may contribute to the recurrent instability episodes seen in this patient group. Clinicians can implement therapeutic exercises that address the suppressed muscles in patients opting for conservative management or rehabilitation before and after capsulorraphy procedures.

Adult↗
PubMed2004

Biomechanical rationale for development of anatomical reconstructions of coracoclavicular ligaments after complete acromioclavicular joint dislocations.

BACKGROUND: Surgical treatments of complete acromioclavicular joint dislocations replace or reconstruct the coracoclavicular ligaments with a single structure and do not account for the anatomical variance of each ligament in the design. PURPOSE: To evaluate the cyclic behavior and structural properties of an anatomic tendon reconstruction of the coracoclavicular ligament complex after a simulated acromioclavicular joint dislocation. STUDY DESIGN: Controlled laboratory study. METHODS: Cyclic loading followed by a load-to-failure protocol (simulated dislocation) of the normal coracoclavicular ligament complex was performed and repeated after an anatomic reconstruction on the same specimen (n = 9). The anatomical reconstruction consisted of a semitendinosus tendon that replicated the direction and orientation of both the trapezoid and conoid ligaments. RESULTS: The coracoclavicular ligament and anatomical reconstruction complexes had clinically insignificant (<3 mm) permanent elongation after cyclic loading. The stiffness and ultimate load of the coracoclavicular ligament complex (60.8 +/- 12.2 N/mm and 560 +/- 206 N) were significantly greater than for the anatomical reconstruction complex (23.4 +/- 5.2 N/mm and 406 +/- 60 N), respectively (P < .05). Further analysis of the complexes revealed a 40% decrease in the bending stiffness of the clavicle after the simulated dislocation and failure of the normal coracoclavicular ligament complex (P < .05), which contributed to the diminished properties of the anatomic reconstruction. CONCLUSIONS: The low level of permanent elongation after cyclic loading suggests that the anatomic reconstruction complex could withstand early rehabilitation; however, the decrease in the structural properties and stiffness of the clavicle should be considered in optimizing the anatomic reconstruction technique. CLINICAL RELEVANCE: Despite the differences compared to the normal coracoclavicular ligament complex, the anatomical reconstruction complex more closely approximates the stiffness of the coracoclavicular ligament complex than current surgical constructs, and the incorporation of biological tissue could improve the overall structural properties with healing.

Acromioclavicular Joint↗
PubMed2003

Arthroscopic biceps tenodesis using the percutaneous intra-articular transtendon technique.

Traditional management of end-stage pain and degeneration of the proximal biceps tendon has included open tenodesis of the biceps tendon. Several methods have been described. More recently, however, arthroscopic techniques have been developed. This article introduces a novel method of arthroscopic biceps tenodesis that does not require any specialized hardware.

Arm↗
PubMed2003

Joint compression alters the kinematics and loading patterns of the intact and capsule-transected AC joint.

High compressive loads are transmitted through the shoulder across the acromioclavicular (AC) joint to the axial skeleton during activities of daily living and can lead to early joint degeneration or instability. The objective of this study was to quantify the effect of joint compression on the biomechanics of the intact and capsule-transected AC joint during application of three loading conditions. A robotic/universal force-moment sensor testing system was utilized to apply an anterior, posterior or superior load of 70 N in combination with 10 or 70 N of joint compression to fresh-frozen cadaveric shoulders (n=12). The application of joint compression to the intact AC joint decreased the posterior translation in response to a posterior load (-6.6+/-2.5 vs -3.7+/-1.0 mm, p<0.05). Joint compression also decreased the in situ force in the superior AC capsule by 10 N while increasing the joint contact force by 20 N for all loading conditions (p<0.05). The application of joint compression to the capsule-transected AC joint significantly decreased the amount of posterior and superior translation during posterior (-12.7+/-6.1 vs -5.5+/-3.2 mm, p<0.05) and superior (5.3+/-2.9 vs 4.2+/-2.3 mm, p<0.05) loading, respectively, while significantly increasing the coupled translations (anterior-posterior, superior-inferior or proximal-distal) in all loading conditions (p<0.05). The joint contact force also significantly increased by 20 N for all loading conditions (p<0.05). This quantitative data suggests: (1) common surgical techniques such as distal clavicle resection, which initially reduce painful joint contact, may cause unusually high loads to be supported by the soft tissue structures at the AC joint; and (2) compressive loads transmitted across a capsule-transected AC joint could be concentrated over a smaller area due to the increased coupled motion and joint contact force.

Acromioclavicular Joint↗
PubMed2003

Viscoelastic behavior and structural properties of the coracoclavicular ligaments.

During contact sports such as football, hockey or rugby, the coracoclavicular ligaments are commonly ruptured. Currently, the limited biomechanical data on the properties and function of these ligaments have led to debate on the "gold standard" treatment for these injuries. Therefore, the objective of this study was to characterize the geometry, viscoelastic behavior and structural properties of the coracoclavicular ligaments (n=11). The trapezoid and conoid were found to have similar length (9.6+/-4.4 vs. 11.2+/-4.1 mm) and cross-sectional area (103+/-43 vs. 69+/-51 mm2), respectively (P>0.05). Static and cyclic stress relaxation tests were then performed, followed by uniaxial tensile testing with the insertions of each ligament aligned to ensure a uniform distribution of load across the fibers. No significant differences were observed for the trapezoid and conoid during the static (36+/-8% vs. 31+/-7%) and cyclic (23+/-12% vs. 16+/-6%) stress relaxation tests, respectively (P>0.05). Similarly, no statistically significant differences were found between the trapezoid and conoid for linear stiffness (83+/-40 vs. 70+/-23 N mm(-1)), ultimate load (312+/-133 vs. 266+/- 108 N), energy absorbed at failure (820+/-576 vs. 752+/- 410 N mm), percent elongation (74+/-47% vs. 62+/-22%) and elongation at failure (5.8+/-2.2 vs. 6.1+/-1.6 mm), respectively (P>0.05). A comparison of our data to previous studies suggests that the complex fiber orientation of these ligaments has a significant role in determining the maximum load that can be transferred between the clavicle and scapula by each bone-ligament-bone complex. Our findings also further confirm the functional role of the coracoclavicular ligaments in supporting the upper extremity, and provide data for reconstruction and rehabilitation protocols as well as computational models.

Acromioclavicular Joint↗
PubMed2003

Effect of arthroscopic procedures on the acromioclavicular joint.

The objective of the current study was to determine the effect of arthroscopic acromioplasty, and combined acromioplasty and distal clavicle resection on joint kinematics and in situ forces in response to an anterior, posterior, and superior load of 70 N. The loading conditions were applied to 10 fresh-frozen cadaveric shoulders using a robotic and universal force and moment sensor testing system. Translations in response to a posterior load increased by approximately 30% after combined acromioplasty and distal clavicle resection when compared with the intact and acromioplasty conditions. The in situ force in the trapezoid and conoid ligaments increased significantly from 13 +/- 15 N to 40 +/- 25 N and 13 +/- 13 N to 38 +/- 28 N, respectively, between the intact and combined acromioplasty and distal clavicle resection conditions during anterior loading. The results suggest that an arthroscopic acromioplasty alone does not significantly affect the mechanics of the acromioclavicular joint with these loading conditions. However, an acromioplasty combined with a distal clavicular resection does result in significant increases in joint motion and ligament forces. In some circumstances, such as after a previous joint separation, the increased forces in the coracoclavicular ligaments could result in additional damage to weak ligaments.

Acromioclavicular Joint↗
PubMed2002

Shoulder injuries in the athlete.

Shoulder injuries are common in the athletic population. Injuries can be a result of repetitive overhead use or from direct trauma. Common injury sites include the rotator cuff, glenohumeral joint, acromioclavicular joint, biceps tendon, scapulothoracic articulation, and sternoclavicular joint. The identification, physical exam, and treatment options of these conditions will be discussed.

Biomechanical Phenomena↗