No abstract

Upper extremity musculoskeletal modeling is becoming increasingly sophisticated, creating a growing need for subject-specific muscle size parameters. One method for determining subject-specific muscle volume is magnetic resonance imaging (MRI). The purpose of this study was to determine the validity of MRI-derived muscle volumes in the human forearm across a variety of muscle sizes and shapes. Seventeen cadaveric forearms were scanned using a fast-spoiled gradient echo pulse sequence with high isotropic spatial resolution (1mm(3) voxels) on a 3T MR system. Pronator teres (PT), extensor carpi radialis brevis (ECRB), extensor pollicis longus (EPL), flexor carpi ulnaris (FCU), and brachioradialis (BR) muscles were manually segmented allowing volume to be calculated. Forearms were then dissected, muscles isolated, and muscle masses obtained, which allowed computation of muscle volume. Intraclass correlation coefficients (ICC(2,1)) and absolute volume differences were used to compare measurement methods. There was excellent agreement between the anatomical and MRI-derived muscle volumes (ICC = 0.97, relative error = 12.8%) when all 43 muscles were considered together. When individual muscles were considered, there was excellent agreement between measurement methods for PT (ICC = 0.97, relative error = 8.4%), ECRB (ICC = 0.93, relative error = 7.7%), and FCU (ICC = 0.91, relative error = 9.8%), and fair agreement for EPL (ICC = 0.68, relative error = 21.6%) and BR (ICC = 0.93, relative error = 17.2%). Thus, while MRI-based measurements of muscle volume produce relatively small errors in some muscles, muscles with high surface area-to-volume ratios may predispose them to segmentation error, and, therefore, the accuracy of these measurements may be unacceptable.

The Bankart lesion is considered the critical lesion in anterior shoulder instability, in which the anteroinferior glenoid labrum separates from the glenoid rim. Technical advances in arthroscopy have ushered in a shift from open to arthroscopic Bankart repair. When one is performing an arthroscopic Bankart repair, proper portal placement is critical for success in labral preparation and anchor placement. Frequently, standard anterior portals are insufficient for inferior glenoid anchor placement and suture shuttling. The posterolateral portal-located 4 cm lateral to the posterolateral corner of the acromion-simplifies and improves anchor placement, trajectory, and anatomic capsulolabral repair of the inferior glenoid. We present our preferred technique for capsulolabral repair of the inferior glenoid.

Purpose:The purpose of this study was to measure and compare the subjective, objective, and radiographic healing outcomes of single-row (SR), double-row (DR), and transosseous equivalent (TOE) suture techniques for arthroscopic rotator cuff repair.Materials and Methods:A retrospective comparative analysis of arthroscopic rotator cuff repairs by one surgeon from 2004 to 2010 at minimum 2-year followup was performed. Cohorts were matched for age, sex, and tear size. Subjective outcome variables included ASES, Constant, SST, UCLA, and SF-12 scores. Objective outcome variables included strength, active range of motion (ROM). Radiographic healing was assessed by magnetic resonance imaging (MRI). Statistical analysis was performed using analysis of variance (ANOVA), Mann — Whitney and Kruskal — Wallis tests with significance, and the Fisher exact probability test <0.05.Results:Sixty-three patients completed the study requirements (20 SR, 21 DR, 22 TOE). There was a clinically and statistically significant improvement in outcomes with all repair techniques (ASES mean improvement P = <0.0001). The mean final ASES scores were: SR 83; (SD 21.4); DR 87 (SD 18.2); TOE 87 (SD 13.2); (P = 0.73). There was a statistically significant improvement in strength for each repair technique (P < 0.001). There was no significant difference between techniques across all secondary outcome assessments: ASES improvement, Constant, SST, UCLA, SF-12, ROM, Strength, and MRI re-tear rates. There was a decrease in re-tear rates from single row (22%) to double-row (18%) to transosseous equivalent (11%); however, this difference was not statistically significant (P = 0.6).Conclusions:Compared to preoperatively, arthroscopic rotator cuff repair, using SR, DR, or TOE techniques, yielded a clinically and statistically significant improvement in subjective and objective outcomes at a minimum 2-year follow-up.Level of Evidence:Therapeutic level 3.

Objectives: Current knowledge of the appropriate site of osteochondral allograft harvest to match glenoid morphology for the purposes of glenoid resurfacing is lacking. This has led to difficulty with adequately restoring the geometry of the glenoid using current available techniques. The purpose of this study was to quantify the articular surface topography of the glenoid and medial tibial plateau via 3-dimensional (3D) modeling to determine if the medial tibial articular surface provides an anatomic topographic match to the articular surface of the glenoid. We hypothesized that the medial tibial plateau will provide a suitable osteochondral harvest site due to its concavity and anatomic similarity to the glenoid. Methods: Computed tomography (CT) was performed on four cadaveric proximal tibias and four scapulae, allowing for 16 glenoid-tibial comparative combinations. 3D CT models were created and exported into point cloud models. A local coordinate map of the glenoid and medial tibial plateau articular surfaces was created. Two zones of the medial tibial articular surface (anterior and posterior) were quantified. The glenoid articular surface was defined as a best-fit circle of the glenoid articular surface maintaining a 2mm bony rim (Figure 1). This surface was virtually placed on a point on the tibial articular surface in 3D space. The tibial surface was segmented and its 3D surface orientation was determined by an eigenvector in the direction of its surface. 3D orientation of the glenoid surface was reoriented so that an eigenvector in the direction of the glenoid surface matched that of the tibial surface (Figure 2). The least distances between the point-clouds on the glenoid and tibial surfaces were calculated. The glenoid surface was rotated 360 degrees around the eigenvector with one degree increments and the mean least distance was determined at each rotating angle. A non-parametric wilcoxon signed rank statistical analysis was performed to compare the findings between the anterior and posterior aspects of the medial tibial articular surface with respect to the glenoid. Results: When the centroid of the glenoid surface was placed on the medial tibial articular surface, it covered approximately two-thirds of the anterior or posterior tibial surfaces. Overall, the mean least distance difference in articular congruity of all 16 glenoid-medial tibial surface combinations was 0.74mm (Std. Deviation +/-0.13). The mean least distance difference of the anterior and posterior two-thirds of the medial tibial articular surface was 0.72mm (+/-0.13) and 0.76mm (+/-0.16), respectively. There was no significant difference between and the anterior and posterior two-thirds of the tibia with regard to topographic match of the glenoid (p=0.187). Conclusion:We describe a novel methodology to quantify the topography of the tibial and glenoid articular surfaces. The findings suggest that the medial tibial articular surface provides an appropriate anatomic match to the glenoid articular surface. To the authors knowledge, th...