Assessment of whether the rabbit subscapularis tendon model is suitable for studying the human chronic rotator cuff pathology: Discovery of a new ligament connecting the glenoid and subscapularis tendon.

OBJECTIVE: This study aimed to investigate the anatomical relationship between the subscapularis tendon and glenosubscapularal ligament (GSL) that we accidentally identified from our previous study on a rabbit shoulder model and to determine whether this anatomical relationship has an impact on the rabbit shoulder model for studying the human chronic rotator cuff pathology. METHODS: In this study, 15 male New Zealand rabbits aged 12 weeks and weighing 2.5 kg were used. Moreover, 3 rabbits were sacrificed for the anatomical and histological investigation of the relationship between the subscapularis tendon and GSL at baseline. The remaining 12 rabbits underwent the subscapularis tendon tenotomy from the lesser tuberosity using a standardized procedure. The GSL was cut on the left side and preserved on the right side. For histomorphometric analysis, 6 rabbits were first sacrificed at 6 weeks and then the remaining 6 rabbits at 12 weeks. RESULTS: In all the rabbits, GSL was identified, connecting the upper portion of glenoid and subscapularis muscle-tendon junction. The mean thickness of the middle portion of GSL was 1.1±0.2 mm; the mean length of GSL was 8.4±2.3 mm. The mean widths of the proximal and distal attachments were 2.4±0.3 and 4.2±0.5 mm, respectively. The mean size of the native subscapularis muscle fibers was 122.6±4.3 µm2. The mean size of the muscle fibers in shoulders with tenotomy alone was 112.6±6.2 and 102.6±4.8 µm2 at 6 and 12 weeks, respectively. The mean size of the muscle fibers in shoulders with tenotomy plus GSL cut severing was 88.3±9.7 and 56.4±5.2 µm2 at 6 and 12 weeks, respectively. The significant muscle atrophy was observed both at 6 and 12 weeks in the shoulders with tenotomy plus GSL cut compared with those with tenotomy alone as well as those with the native subscapularis. However, the muscle atrophy was not significantly different in the shoulders with tenotomy alone at different time points. CONCLUSION: Because GSL may prevent the subscapularis retraction, the rabbit subscapularis tendon model may not be suitable for studying the human chronic rotator cuff pathology if GSL is neglected or preserved.

Normal Sonographic Anatomy of the Wrist With Emphasis on Assessment of Tendons, Nerves, and Ligaments.

Sonography allows for rapid, cost-effective, noninvasive, and dynamic evaluation of soft tissue structures, thus representing a valuable tool for ruling out musculoskeletal disorders of the wrist. Because of the complexity of the wrist joint, sonographic training and familiarity with normal and variant anatomy are needed to avoid misdiagnosis and improper treatment. The aim of this article is to enlighten readers about the structures representing normal findings or common variants during sonographic evaluations of the wrist. The main text reviews the pertinent gross anatomy and procedures that are recommended to assess the soft tissue structures of the wrist, with particular emphasis given to tendons, nerves, and ligaments. Detailed explanations of the scanning techniques and sonographic appearance of the wrist structures are provided in the figure legends.

The Influence of Component Alignment and Ligament Properties on Tibiofemoral Contact Forces in Total Knee Replacement.

The study objective was to investigate the influence of coronal plane alignment and ligament properties on total knee replacement (TKR) contact loads during walking. We created a subject-specific knee model of an 83-year-old male who had an instrumented TKR. The knee model was incorporated into a lower extremity musculoskeletal model and included deformable contact, ligamentous structures, and six degrees-of-freedom (DOF) tibiofemoral and patellofemoral joints. A novel numerical optimization technique was used to simultaneously predict muscle forces, secondary knee kinematics, ligament forces, and joint contact pressures from standard gait analysis data collected on the subject. The nominal knee model predictions of medial, lateral, and total contact forces during gait agreed well with TKR measures, with root-mean-square (rms) errors of 0.23, 0.22, and 0.33 body weight (BW), respectively. Coronal plane component alignment did not affect total knee contact loads, but did alter the medial-lateral load distribution, with 4 deg varus and 4 deg valgus rotations in component alignment inducing +17% and -23% changes in the first peak medial tibiofemoral contact forces, respectively. A Monte Carlo analysis showed that uncertainties in ligament stiffness and reference strains induce ±0.2 BW uncertainty in tibiofemoral force estimates over the gait cycle. Ligament properties had substantial influence on the TKR load distributions, with the medial collateral ligament and iliotibial band (ITB) properties having the largest effects on medial and lateral compartment loading, respectively. The computational framework provides a viable approach for virtually designing TKR components, considering parametric uncertainty and predicting the effects of joint alignment and soft tissue balancing procedures on TKR function during movement.

Sonographic assessment of transverse carpal ligament after open surgical release of the carpal tunnel.

OBJECTIVE: The aim of this study was to sonographically evaluate the anatomy of the transverse carpal ligament (TCL) after open surgical release in the treatment of carpal tunnel syndrome (CTS) and to establish new ultrasonographic criteria for the completeness of TCL release. METHODS: Thirty-six patients who underwent open surgical release for CTS were recruited prospectively. Patients were evaluated with physical examination and ultrasonography before and after the operation. RESULTS: All patients' symptoms resolved after surgery. TCL was found to be diffusely thickened and to have lost its smooth form after surgery. Postoperative TCL thickness showed a statistically significant increase when compared with preoperative values (p<0.05). CONCLUSION: Sonography is a capable imaging method for assessment of the TCL after open release surgery. In addition, ultrasound may be considered as a complementary tool to exclude diagnosis of incomplete transection of TCL in patients with persistent symptoms.

Assessment of ultrasonographic morphometric measurements of digital flexor tendons and ligaments of the palmar metacarpal region in Icelandic Horses.

OBJECTIVE: To obtain morphometric values for the superficial digital flexor tendon, deep digital flexor tendon, accessory ligament of the deep digital flexor muscle, and suspensory ligament in the palmar metacarpal region of Icelandic Horses. ANIMALS: 50 nonlame Icelandic Horses in training. PROCEDURES: Horses included 2 stallions, 30 geldings, and 18 mares from 4 to 20 years of age with a body mass index from 149.1 to 250.11 kg/m2. Transverse ultrasonographic images were obtained with an 8- to 10-MHz linear transducer and a standoff pad. In both forelimbs, the cross-sectional area, circumference, dorsopalmar width, and lateromedial width were measured 3 times at 5 regions of interest (ROIs). RESULTS: The coefficient of variation for all measurements of each ROI was <5%. Comparisons were performed among and within structures and for each variable at all ROIs. Comparisons among horses revealed homogeneity because no significant influences of age, sex, height at the withers, or body mass index were found. Additionally, a characteristic skin condition interfering with ultrasonographic examination was observed. CONCLUSIONS AND CLINICAL RELEVANCE: The morphometric values of the structures examined were consistent with those reported for other breeds, although some differences were observed.

Material sensitivity study on lumbar motion segment (L2-L3) under sagittal plane loadings using probabilistic method.

OBJECTIVE: In this study, the probabilistic responses of a three-dimensional finite element L2-L3 motion segment, with and without posterior elements, tested under sagittal plane loadings, are presented. Understanding the effect of biologic uncertainties and variations on the biomechanical response provides an insight into spinal behavior under normal and degenerated conditions. METHODS: The biologic variability of 19 spinal components (nucleus, annulus, ligament, cortical/cancellous bone, endplate, and ligaments) in the motion segment was incorporated using statistical distributions into the model. A total of 2000 runs were performed using Monte Carlo probabilistic algorithms to compute the probabilistic response. RESULTS: This study establishes the relative importance of the spinal components in resisting the loading modes. The results show that for an intact motion segment, posterior ligaments are more dominant than intervertebral disc in resisting flexion moment. In extension, the capsular ligaments were found to be the most influential parameter. The intervertebral disc (ie, nucleus and annulus) affects the angular response of the disc body segment more than the hard tissues (ie, cortical and cancellous bone). CONCLUSIONS: The application of the probabilistic analysis provides a new approach whereby the influences of inherent uncertainties and variations in biologic structures can be studied and the biomechanical response assessed.

What happens to the triangular fibrocartilage complex during pronation and supination of the forearm? Analysis of its morphology and diagnostic assessment with MR arthrography.

OBJECTIVE: To evaluate the dynamic morphologic changes of the triangular fibrocartilage complex (TFCC) during pronation and supination of the forearm using high-resolution MR arthrography in cadavers and to evaluate the impact of these changes on the diagnostic assessment of the normal and abnormal TFCC. DESIGN AND SPECIMENS: High-resolution MR arthrography of 10 wrists of cadaveric specimens was obtained in maximum pronation, in the neutral position, and in maximum supination of the forearm. The structures of the TFCC were evaluated by two musculoskeletal radiologists and correlated with anatomic sections. The position of the forearm that allowed the best visualization of normal structures and lesions of the TFCC was determined. RESULTS: The shape and extent of the articular disc as well as the radial portions of the radioulnar ligaments did not change with pronation and supination. The articular disc was horizontal in the neutral position and tilted more distally to align with the proximal carpal row in pronation and supination. The fibers of the ulnar part of the radioulnar ligaments (ulnar attachment of the articular disc) revealed the most significant changes: their orientation was coronal in the neutral position and sagittal in positions of pronation and supination. The ulnomeniscal homologue was largest in the neutral position and was reduced in size during pronation and supination. The extensor carpi ulnaris tendon was centered in its groove in the neutral position and pronation. In supination this tendon revealed subluxation from this groove. The dorsal capsule of the distal radioulnar joint was taut in pronation, and the palmar capsule was taut in supination. The preferred forearm position for analysis of most of the structures of the TFCC was the neutral position, followed by the pronated position. The neutral position was rated best for the detection of ulnar and radial detachments of the TFCC, followed by the pronated position, except for two central perforations of the TFCC which were best seen with supination. CONCLUSION: The articular disc and the surrounding radial portions of the radioulnar ligaments form a rigid, unified complex with the radius without change in their shape in positions of pronation and supination of the forearm, while the ulnar attachment of the TFCC shows important dynamic changes. The neutral forearm position is the best position to analyze both the normal and the abnormal TFCC.

[Re-assessment of the inframammary crease ligament].

OBJECTIVE: An anatomical study was carried out to examine the existence of the inframammary crease ligament. METHODS: 18 breasts of preserved female cadavers were dissected and dyed for the fascia. RESULTS: The so-called inframammary crease ligament described by other authors does not exist. CONCLUSION: The reinforced Cooper's ligament supports the inframammary fold in position.

Quantitative morphology of the lateral ligaments of the spine. Assessment of their importance in maintaining lateral stability.

STUDY DESIGN: This study used human cadaveric material to examine the three-dimensional morphology and biomechanics of the superior and lateral costotransverse ligaments and the intertransverse ligament of the spine. OBJECTIVES: To provide descriptive and quantitative data on the morphology of the lateral ligaments of the spine and to assess their importance in maintaining lateral stability, especially regarding the pathogenesis of idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Ligaments have been reported as being able to stabilize the spine by mechanical constraint and by neurologic feed-back. Midline spinal ligaments have been well studied but do not appear to be effective in maintaining lateral stability because of their sites of attachment. Lateral ligaments of the spine have not been adequately documented in the literature. METHODS: The morphology, sites of attachment, and dimensions of the superior costotransverse ligament, lateral costotransverse ligament, and intertransverse ligament from thoracic level 7 to thoracic level 10 were determined on 32 human cadavers. RESULTS: The intertransverse ligament was found not to be a true ligament. The lateral costotransverse ligament was a true ligament but did not have the characteristics appropriate for involvement in lateral stability. The superior costotransverse ligament also was a true ligament and had all of the characteristics appropriate for involvement in the active lateral balancing of the spine. CONCLUSIONS: In contrast to the midline ligaments of the spine, the superior costotransverse ligament perhaps is the most important ligament for active lateral balancing of the spine and warrants further study, particularly regarding the development of idiopathic scoliosis.