End-range Positions Research Articles

Outcomes of active cervical therapeutic exercise on dynamic intervertebral foramen changes in neck pain patients with disc herniation

BackgroundTo better understand biomechanical factors that affect intervertebral alignment throughout active therapeutic exercise, it is necessary to determine spinal kinematics when subjects perform spinal exercises. This study aims to investigate the outcomes of active cervical therapeutic exercise on intervertebral foramen changes in neck pain patients with disc herniation.MethodsThirty diagnosed C4/5 and/or C5/6 disc-herniated patients receiving an 8-week cervical therapeutic exercise program were followed up with videofluoroscopic images. The dynamic changes in the foramen were computed at different timepoints, including the neutral position, end-range positions in cervical flexion-extension, protrusion-retraction, and lateral flexion movements.ResultsThe results showed that the active cervical flexion, retraction, and lateral flexion away from the affected side movements increased the area of the patients’ intervertebral foramen; while the active extension, protrusion, and lateral flexion toward the affected side reduced the areas of intervertebral foramen before treatment. After the treatment, the active cervical flexion significantly increased the C2/3, C3/4, and C6/7 foramen area by 5.02–8.67% (p = 0.001 ~ 0.029), and the extension exercise significantly reduced the C2/3 and C4/5 area by 5.12–9.18% (p = 0.001 ~ 0.006) compared to the baseline. Active retraction movement significantly increased the foramen area from C2/3 to C6/7 by 3.82–8.66% (p = 0.002 ~ 0.036 with exception of C5/6). Active lateral flexion away from the affected side significantly increased the foramen by 3.71–6.78% (p = 0.007 ~ 0.046 with exception of C6/7).ConclusionsThe 8-week therapeutic exercises including repeated cervical retraction, extension, and lateral flexion movements to the lesion led to significant changes and improvements in intervertebral foramen areas of the patients with disc herniation.Trial registrationISRCTN61539024

Transfer learning from an artificial radiograph-landmark dataset for registration of the anatomic skull model to dual fluoroscopic X-ray images

Registration of 3D anatomic structures to their 2D dual fluoroscopic X-ray images is a widely used motion tracking technique. However, deep learning implementation is often impeded by a paucity of medical images and ground truths. In this study, we proposed a transfer learning strategy for 3D-to-2D registration using deep neural networks trained from an artificial dataset. Digitally reconstructed radiographs (DRRs) and radiographic skull landmarks were automatically created from craniocervical CT data of a female subject. They were used to train a residual network (ResNet) for landmark detection and a cycle generative adversarial network (GAN) to eliminate the style difference between DRRs and actual X-rays. Landmarks on the X-rays experiencing GAN style translation were detected by the ResNet, and were used in triangulation optimization for 3D-to-2D registration of the skull in actual dual-fluoroscope images (with a non-orthogonal setup, point X-ray sources, image distortions, and partially captured skull regions). The registration accuracy was evaluated in multiple scenarios of craniocervical motions. In walking, learning-based registration for the skull had angular/position errors of 3.9 ± 2.1°/4.6 ± 2.2 mm. However, the accuracy was lower during functional neck activity, due to overly small skull regions imaged on the dual fluoroscopic images at end-range positions. The methodology to strategically augment artificial training data can tackle the complicated skull registration scenario, and has potentials to extend to widespread registration scenarios.

Ligament deformation patterns of the craniocervical junction during head axial rotation tracked by biplane fluoroscopes

BackgroundFrequently, treatment decisions for craniocervical injuries and instability are based on imaging findings, but in vivo ligament kinematics were poorly understood. This study was to determine in vivo deformation patterns of primary ligaments in the craniocervical junction (i.e., C0–2), including the cruciform ligament, alar ligaments, and accessory ligaments, during dynamic head axial rotation. MethodsThe skulls and cervical spines of eight asymptomatic female subjects were dynamically imaged using a biplane fluoroscopic imaging system, when they performed left and right head axial rotations. Using a 3D-to-2D registration technique, the in vivo positions and orientations of cervical segments were determined. An optimization algorithm was implemented to determine ligament wrapping paths, and the resulting ligament deformations were represented by percent elongations. Using paired t-tests, ligament deformations in the end-range position were compared to those in the neutral position. FindingsNo significant differences were observed in segmental motions during left and right head rotations (p > 0.05). In general, slight deformations occurred in each component of the cruciform ligament. For the alar ligaments, the ipsilateral ligament was lengthened from −0.7 ± 13.8% to 16.6 ± 15.7% (p < 0.001*). For the accessory ligaments, the contralateral ligament was lengthened from −2.9 ± 7.5% to 10.1 ± 6.2% (p < 0.001*). InterpretationThis study reveals that there are distinct deformation patterns in craniocervical junction ligaments during dynamic axial head rotation. These ligament deformation data can enhance our understanding of the synergic function of craniocervical junction ligaments, and guide the treatment of craniocervical instability.

Motion of the multi-segmented spine in elite dancers during passé and arabesque.

The spinal biomechanics of dance tasks have received little study and no studies have used a multi-segmented spinal model. Knowledge of how the segments of the spine move may be useful to the dance clinician and dance educator. What is the direction and amount of motion of the primary segments of the spine in elite dancers during an arabesque and a passé? This observational study examined 59 elite dancers performing an arabesque and a passé using a three-dimensional motion analysis system with the trunk divided into a series of five segments: pelvis, lower lumbar, upper lumbar, lower thoracic and upper thoracic spine. For the arabesque, all spinal segments moved in the same direction within each plane and the majority of total spinal motion occurred in the thoracic spine. Thoracic segments were at or near end range position at completion of the arabesque. For the passé, the spinal segments moved in different directions within each plane and the majority of total spinal motion occurred in the lumbar spine. Dance clinicians and dance educators may benefit from the knowledge that thoracic hypomobility in any plane may limit arabesque performance and that attempts to instruct dancers to achieve a position of passé without flexion of the lumbar spine may be a valid aesthetic ideal but also an unrealistic functional expectation.

Lumbar spine angles and intervertebral disc characteristics with end-range positions in three planes of motion in healthy people using upright MRI

Understanding changes in lumbar spine (LS) angles and intervertebral disc (IVD) behavior in end-range positions in healthy subjects can provide a basis for developing more specific LS models and comparing people with spine pathology. The purposes of this study are to quantify 3D LS angles and changes in IVD characteristics with end-range positions in 3 planes of motion using upright MRI in healthy people, and to determine which intervertebral segments contribute most in each plane of movement. Thirteen people (average age = 24.4 years, range 18–51 years; 9 females; BMI = 22.4 ± 1.8 kg/m2) with no history of low back pain were scanned in an upright MRI in standing, sitting flexion, sitting axial rotation (left, right), prone on elbows, prone extension, and standing lateral bending (left, right). Global and local intervertebral LS angles were measured. Anterior-posterior length of the IVD and location of the nucleus pulposus was measured. For the sagittal plane, lower LS segments contribute most to change in position, and the location of the nucleus pulposus migrated from a more posterior position in sitting flexion to a more anterior position in end-range extension. For lateral bending, the upper LS contributes most to end-range positions. Small degrees of intervertebral rotation (1–2°) across all levels were observed for axial plane positions. There were no systematic changes in IVD characteristics for axial or coronal plane positions.

THE EFFECTS OF POSTERIOR TIBIAL MOBILIZATION ON MENISCAL MOVEMENT: AN IN-SITU INVESTIGATION

Anterior knee pain during knee extension may be related to a meniscal movement restriction and increased meniscal load during function. One method of treatment involves the use of manual posterior mobilization of the tibia to specifically target the meniscotibial interface of the knee joint. The purpose of this study was to measure motion at a cadaveric medial meniscus anterior horn during a posterior tibial mobilization. Prospective, multifactorial, repeated-measures laboratory study. Eight unembalmed cadaveric knee specimens were mounted in a custom apparatus and markers were placed in the medial meniscus, tibia and femur. The tibia was posteriorly mobilized in two randomized knee positions (0 degrees and 25 degrees) using three randomly assigned loads (44.48N, 88.96N, and 177.93N). Markers were photographed and digitally measured and analyzed. All load x position conditions produced anterior displacement of the meniscus on the tibia, where the displacement was significant [t (7) = -3.299; p = 0.013] at 0 degrees loaded with 177.93N (mean 0.41 ± 0.35 mm). The results of 2(position) x 3(load) repeated measures ANOVA for meniscotibial displacement produced no significant main effects for load [F (2,14) = 2.542; p = 0.114) or position [F (1,7) = 0.324, p = 0.587]. All load x position conditions produced significant posterior tibial and meniscal displacement on the femur. The 2(position) x 3(load) repeated measures ANOVA revealed a significant main effect for load for both femoral marker displacement relative to the tibial axis [F (2,14) = 77.994; p < 0.001] and meniscal marker displacement relative to the femoral marker [F (2,14) = 83.620; p < 0.001]. Use of a mobilization technique to target the meniscotibial interface appears to move the meniscus anteriorly on the tibia. It appears that this technique may be most effective at the end range position. 2 (laboratory study).

Description and Intrarater Test-Retest Reliability of a Reverse-Action Method to Assess Ankle Evertor Muscle Performance: The I-to-V Test.

Purpose: Reverse action (RA) of the ankle evertor muscle is when the proximal attachment moves toward the distal attachment, moving the lower leg in the frontal plane when the foot and ankle are fixed on the ground and inducing ankle eversion. The purpose of this study was to describe an RA method for measuring ankle evertor muscle performance. Method: Eighteen healthy individuals were recruited for this study. To assess the RA of their ankle evertors, the participants sat with their knees together and their feet firmly planted on the floor, then spread their knees as far apart as possible. A tester used a measuring tape to measured the distance (in cm) between the medial tibial tuberosity of the tested side and that of the non-tested side. In the end range position of the RA, ankle evertor electromyographic activity was recorded simultaneously. The intra-class correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to establish the intrarater test-retest reliability. The correlation between each performance value and muscle activity was assessed using a linear correlation model. Results: The proposed method of assessing RA performance was highly reliable (ICC=0.95) and had a low SEM (1.63 cm); in addition, the performance value showed a strong positive correlation with ankle evertor muscle activity (ρ=0.90; 95% CI: 0.79, 0.95; p=0.01). Conclusions: The proposed RA method of assessing the ankle evertor muscles can be used as a simple, reliable, economical performance test. It can also be used as an alternate method of testing the peroneal muscles rather than selectively measuring ankle evertor performance because hip external rotation occurs when performing RA.

Static Progressive Orthoses

Purpose: The purpose of this research is to increase understanding of the current levels of evidence supporting the use of static progressive orthoses, and to provide clarity on appropriate diagnoses, outcome measures, and duration of use for this intervention. Rationale: Static progressive orthoses are an intervention commonly provided for clients with stiffness and/or limited range of motion (ROM) of upper extremity joints, due to trauma or injury. This type of orthosis incorporates nonelastic components to apply force to the stiff joint or tissue, holding it at end-range position to improve passive motion. There are only a limited number of studies on the use of static progressive orthoses for the upper extremity with a small number of clients enrolled. Design: A literature search of the current evidence supporting static progressive orthoses for treatment of stiff upper extremity joints was performed to identify information regarding common diagnoses of clients treated with this type of orthotic intervention, outcomes achieved, wearing schedules, and duration of orthotic use. Participants: This research examined the current levels of evidence supporting the use of static progressive orthoses for clients with limitations in ROM of the upper extremity following surgery or trauma (orthopedic pathologies). Analytic Methods: The current evidence supporting the use of static progressive orthoses is found in 11 studies on the elbow, 2 studies on the forearm, 3 studies on the wrist, 2 studies on stiff fingers, and 2 systematic reviews. The data provided in these 20 studies on client diagnoses, type of orthotic design, outcome measures, and duration of use are analyzed and described. Conclusions: Clients benefit from the use of static progressive orthoses by demonstrating increased ROM, increased function and grip strength, and decreased pain. The current evidence includes 20 studies that present information on appropriate client diagnoses, outcome measures, protocols of use, and average duration of wear.

Effects of Joint Position on the Distraction Distance in Patients with Adhesive Capsulitis of Glenohumeral Joint

The purpose of this study was to investigate the effects of joint position on the distraction distance in patients with adhesive capsulitis of glenohumeral joint. The study was conducted upon 20 adults in their 40's with the findings of adhesive capsulitis of glenohumeral joint. These subjects were subdivided into 3 groups, which were a group with neutral position(n=7), second group with resting position(n=7) and third group with end-range position(n=6). After having the subject wearing sleeveless shirts exposing armpit and lying straight on the plinth, a physical therapist with OMT qualification pulled glenohumeral joint at the Grade III of Kaltenborn-Evjenth traction; and the distance between glenoid fossa and humeral head was measured with ultrasound. Following the application of traction, the group with resting position() exhibited the longest distance between humeral head and glenoid fossa, and it was followed by neutral position() and end-range position() in this order. From the comparison of these groups, there was no significant difference in distraction distance between resting position and neutral position; and there was again no significant difference in distraction distance between end-range position and neutral position. However, there was a significant difference in distraction distance between end-range position and resting position(p

Atlanto-axial facet displacement during rotational high-velocity low-amplitude thrust: An in vitro 3D kinematic analysis

BackgroundVery little is known about the kinematics of the upper cervical spine in particular during Manual Therapy techniques. In fact no data about displacement of the atlanto-axial joint during High-Velocity Low-Amplitude (HVLA) thrust are available. Knowing the precise kinematics of these vertebrae might allow a better comprehension of such important technique and possible vital structures involvement. MethodsA Zebris CMS20 ultrasound-based motion tracking system was adopted. Twenty fresh human cervical specimens were used in this study. Facet joint displacements of C1 relative to C2 were analysed during three consecutive HVLA thrusts into rotation. Displacement during the thrust and the maximum displacement reached with the manoeuvre were analysed. ResultsDescriptive statistics showed a mean Norm displacement during the thrust of 0.5 mm (SD ± 0.5). The maximum displacement, representing the overall facet movement from neutral to end-range position, indicated a Norm value of 6.0 mm (SD ± 3.4). Heterogeneous displacement directions were found during the thrust. Intra and inter-rater reliability reached an insufficient reproducibility level. Considering the amount of displacement induced, no statistical significant differences between the registrations were shown. ConclusionDisplacement during the execution of HVLA thrust is unintentional, unpredictable and not reproducible. On the other hand and in accordance with other studies, the displacement induced with the present technique seems not to be able to endanger vital structure on the Spinal Cord and the Vertebral Artery. This study also adds to a better comprehension of the kinematic of the atlanto-axial segment during the performance of HVLA manipulation.

Effects of joint position on the distraction distance during grade III glenohumeral joint distraction in healthy individuals.

[Purpose] The study investigated the effects of joint position on the distraction distance during Grade III glenohumeral joint distraction in healthy individuals. [Subjects and Methods] Twenty adults in their forties without shoulder disease were randomly divided into neutral position group (NPG; n = 7), resting position group (RPG; n = 7), and end range position group (ERPG; n = 6). After Kaltenborn Grade III distraction for 40s, the distance between glenoid fossa and humeral head was measured by ultrasound. [Results] The average distances between the humeral head and glenoid fossa before distraction were 2.86 ± 0.81, 3.21 ± 0.47, and 3.55 ± 0.59 mm for the NP, RP, and ERP groups. The distances after applying distraction were 3.12 ± 0.51, 3.86 ± 0.55, and 4.35 ± 0.32 mm. Between-group comparison after applying distraction revealed no significant differences between the NP and RP groups, while there was a statistically significant difference between the NP and RP groups, as well as between the NP and ERP groups. [Conclusion] Joint space was largest in ERP individuals when performing manual distraction.

Positional effects of transforaminal interbody spacer placement at the L5–S1 intervertebral disc space: a biomechanical study

Background contextTransforaminal lumbar interbody fusion (TLIF) is an increasingly used alternative fusion method over anterior and posterior lumbar interbody fusions. There are conflicting results on the optimal positioning of interbody devices. No study has addressed the lumbosacral segment, L5–S1, where the lordotic configuration presents unique challenges. PurposeTo determine if there are biomechanical and/or anatomical advantages related to the positioning of an interbody device at L5–S1, either anterior or posterior to the neutral axis. Study designAn in vitro biomechanical study using human cadaveric lumbar specimens. MethodsLumbar specimens were biomechanically tested using pure moments with and without compressive axial loading. Testing was performed in intact and after TLIF with the implant posterior (TLIF-post) and anterior (TLIF-ant) to neutral axis. Segmental range of motion (ROM) and stiffness were analyzed at the L5–S1 surgical level and the adjacent L4–L5 level. Neuroforaminal height measurements of L5–S1 were analyzed in neutral and end range positions. ResultsCompared with the intact condition, ROM decreased more than 75% at L5–S1 and stiffness increased up to 270% with TLIF. There was no significant difference between anterior or posterior placement for ROM and stiffness. There was a change in L5–S1 neuroforaminal height based on the placement, with posterior placement showing a significant increase compared with anterior placement. There were no relative changes in neuroforaminal height under loading after TLIF. Compressive load did not affect the magnitudes or resulting significance of outcome measures at L5–S1 after either TLIFs. ConclusionsAn interbody spacer with the addition of posterior instrumentation significantly enhances the mechanical stability of L5–S1 regardless of interbody position. There were noticeable increases in terms of construct stability and stiffness after both TLIF-ant and TLIF-post in comparison with the intact condition. A posteriorly placed interbody implant did result in the distraction of the neuroforamin. Positioning an interbody implant at L5–S1 for TLIF with posterior instrumentation should be at the discretion of the surgeon without consequence to biomechanical stability.

Toward Understanding Normal Craniocervical Rotation Occurring During the Rotation Stress Test for the Alar Ligaments

The rotation stress test is recommended for assessing alar ligament integrity. Although some authors, in the literature regarding the rotation stress test, accept that rotation will occur during testing, estimates of range occurring with a normal test response vary between 20 and 40 degrees. None of these estimates are based on formal examination of the test. The purposes of this study were: (1) to examine the range of craniocervical rotation occurring during rotation stress testing for the alar ligaments in individuals who are healthy and (2) to investigate a measurement protocol for quantifying rotation. A within-subject experimental study was conducted. Sixteen participants underwent magnetic resonance imaging in neutral and end-range rotation stress test positions. Measurements followed a standardized protocol relative to the position of the axis. A line connecting the transverse foramena of the axis created a reference plane. The position of the occiput in the head-neutral position was calculated as the angle formed between a line joining the foramena lacerum and the reference plane. Measurements were repeated at the end-range test position. Total rotation of the occiput was calculated as the difference in angles measured in neutral and test positions. Measurement was performed on 4 occasions, and reliability of measurements was assessed using the standard error of measurement (SEM) and the intraclass correlation coefficient (ICC). Measurement of rotation of the occiput relative to a stabilized axis ranged between 1.7 and 21.5 degrees (X=10.6, SD=5.1, SEM=1.14, ICC=.96, 95% confidence interval=.90-.98). Sustaining the test position for imaging increased the potential for loss of end-range position and image quality. Testing could be performed only in the neutral position, not in 3 planes as commonly described. The range of craniocervical rotation during rotation stress testing of intact alar ligaments should typically be 21 degrees or less. Rotation may be quantified using the method protocol outlined.

Reliability of a Measure of Total Lumbar Spine Range of Motion in Individuals with Low Back Pain

Measuring lumbar spine range of motion (ROM) using multiple movements is impractical for clinical research, because finding statistically significant effects requires a large proportion of subjects to present with the same impairment. The purpose of this study was to develop a single measure representing the total available lumbar ROM. Twenty participants with low back pain performed three series of eight lumbar spine movements, in each of two sessions. For each series, an ellipse and a cubic spline were fit to the end-range positions, measured based on the position of the twelfth thoracic vertebra in the transverse plane of the sacrum. The area of each shape provides a measure of the total available ROM, whereas their center reflects the movements' symmetry. Using generalizability theory, the index of dependability for the area and anterior-posterior center position was found to be 0.90, but was slightly lower for the mediolateral center position. Slightly better values were achieved using the spline-fitting approach. Further analysis also indicated that excellent reliability, and acceptable minimal detectable change values, would be achieved with a single testing session. These data indicate that the proposed measure provides a reliable and easily interpretable measure of total lumbar spine ROM.

Anchor Placement on the Glenoid Faceplate Does Not Improve Stability With Bankart Repair (SS-02)

Introduction Some surgeons recommend that suture anchors used during Bankart repair should be placed a few millimeters on the glenoid faceplate to enhance stability. However, there is risk with placing the anchors in this location due to the potential problem of anchor back-out and early arthritis. Also, it has been suggested that a Bankart lesion should be repaired with a bumper of the capsulolabral tissue created to obtain a more stable shoulder. However, it has not been biomechanically determined that these techniques really improve stability. The purpose of this study was to determine 1) whether the shoulder would become stable by creating a bumper, and 2) whether placing the suture anchors on the glenoid faceplate would make the shoulder more stable. Methods Nine fresh-frozen cadaveric shoulders (mean age, 75 years) were investigated. A custom testing machine with a six-degree-of-freedom load-cell was utilized. With a 50-N axial force applied to the humerus, the humeral head was translated in the anterior direction and the peak translational force was measured at both the end-range (60° of abduction relative to the scapula and maximum external rotation) and mid-range (60° of abduction and neutral rotation) positions with the intact capsule, with a Bankart lesion, and after Bankart repair with and without a bumper. Bankart repair was performed at five different positions (glenoid rim, glenoid surface-2 mm (2 mm inside from the glenoid rim), glenoid surface-5 mm, scapular neck-2 mm (2 mm medial on the scapular neck from the glenoid rim), and scapular neck-5 mm). Bumper was created gathering up the capsule to form a thickened mass of tissue. Results The peak translational force which significantly decreased after creating a Bankart lesion returned to almost the intact condition level after Bankart repair at both arm positions. However, there were no significant differences between the forces after Bankart repair with and without the bumper. The force significantly decreased after scapular neck fixation-2 mm and −5 mm compared to the one after glenoid rim fixation. However, there were no significant differences between the forces after glenoid rim fixation and glenoid surface fixation-2 mm at both arm positions. On the other hand, the force significantly increased at the end-range position and decreased at the mid-range position after glenoid surface fixation-5 mm. Conclusion Although some surgeons recommend that the suture anchors should be placed on the glenoid faceplate surface, our data showed that glenoid faceplate fixation did not make the shoulder more stable. The shoulder did not become more stable even after creating the bumper.

Biomechanical analysis of axial distraction mobilization of the glenohumeral joint – A cadaver study

The axial distraction mobilization techniques are frequently employed for treating patients with joint hypomobility. However, there is a lack of basic biomechanical studies and description of this procedure. The purpose of this study was to analyze humeral head displacement while performing an axial distraction mobilization of the glenohumeral joint. Twelve experienced orthopedic physical therapists participated. Distraction mobilization techniques were performed in three different positions of glenohumeral abduction on a fresh cadaveric specimen. Outcome measures were displacements of the humeral head center during distraction mobilization. Result indicated that displacement of the humeral head was largest in the resting position (27.38 mm) followed by the neutral (22.01 mm) and the end range position (9.34 mm). There were significant differences for both the displacement of the humeral head ( p < 0.002) and the distraction forces used ( p < 0.015) among the three joint positions. Greater gain in mobility was obtained in distraction at the end range position. In conclusion, during distraction mobilization, the force applied by the therapist and displacement of the humeral head depends on the joint position tested. Our results also provide rationales for choosing end range distraction mobilization for improving joint mobility.

Comparison of High-Grade and Low-Grade Mobilization Techniques in the Management of Adhesive Capsulitis of the Shoulder: Randomized Controlled Trial

In many physical therapy programs for subjects with adhesive capsulitis of the shoulder, mobilization techniques are an important part of the intervention. The purpose of this study was to compare the effectiveness of high-grade mobilization techniques (HGMT) with that of low-grade mobilization techniques (LGMT) in subjects with adhesive capsulitis of the shoulder. One hundred subjects with unilateral adhesive capsulitis lasting 3 months or more and a > or =50% decrease in passive joint mobility relative to the nonaffected side were enrolled in this study. Subjects randomly assigned to the HGMT group were treated with intensive passive mobilization techniques in end-range positions of the glenohumeral joint, and subjects in the LGMT group were treated with passive mobilization techniques within the pain-free zone. The duration of treatment was a maximum of 12 weeks (24 sessions) in both groups. Subjects were assessed at baseline and at 3, 6, and 12 months by a masked assessor. Primary outcome measures included active and passive range of motion and shoulder disability (Shoulder Rating Questionnaire [SRQ] and Shoulder Disability Questionnaire [SDQ]). An analysis of covariance with adjustments for baseline values and a general linear mixed-effect model for repeated measurements were used to compare the change scores for the 2 treatment groups at the various time points and over the total period of 1 year, respectively. Overall, subjects in both groups improved over 12 months. Statistically significant greater change scores were found in the HGMT group for passive abduction (at the time points 3 and 12 months), and for active and passive external rotation (at 12 months). A statistically significant difference in trend between both groups over the total follow-up period of 12 months was found for passive external rotation, SRQ, and SDQ with greater change scores in the HGMT group. In subjects with adhesive capsulitis of the shoulder, HGMTs appear to be more effective in improving glenohumeral joint mobility and reducing disability than LGMTs, with the overall differences between the 2 interventions being small.

Comment on the Classics

We examined the architectural properties of the rotator cuff muscles in 10 cadaveric specimens to understand their functional design. Based on our data and previously published joint angle-muscle excursion data, sarcomere length operating ranges were modeled through all permutations in 75 masculine medial and lateral rotation and 75 masculine abduction at the glenohumeral joint. Based on physiologic cross-sectional area, the subscapularis would have the greatest force-producing capacity, followed by the infraspinatus, supraspinatus, and teres minor. Based on fiber length, the supraspinatus would operate over the widest range of sarcomere lengths. The supraspinatus and infraspinatus had relatively long sarcomere lengths in the anatomic position, and were under relatively high passive tensions at rest, indicating they are responsible for glenohumeral resting stability. However, the subscapularis contributed passive tension at maximum abduction and lateral rotation, indicating it plays a critical role in glenohumeral stability in the position of apprehension. These data illustrate the exquisite coupling of muscle architecture and joint mechanics, which allows the rotator cuff to produce near maximal active tensions in the midrange and produce passive tensions in the various end-range positions. During surgery relatively small changes to rotator cuff muscle length may result in relatively large changes in shoulder function.

Active stability of the glenohumeral joint decreases in the apprehension position

Background. Muscle forces that compress the glenohumeral joint during mid-ranges of motion may lead to increased translational forces in end-range positions, such as the apprehension position, where symptoms of anterior instability occur. Objective. The objective of this study was to quantify active stability provided by eight shoulder muscles in mid-range and end-range positions through muscle force vector analysis. Methods. Lines of action were derived from a geometric model and muscle force magnitudes were estimated with electromyography-based techniques. Resultant muscle force vectors were calculated by summing individual muscle force vectors. Results. Compared to mid-range positions, lines of action of resultant force vectors were more anteriorly directed in end-range positions compared to 15° of abduction, up to 26°. Consequently, anterior stability was lowest in the apprehension position. The magnitudes of the resultant force vectors were comparable to other studies. Based on a sensitivity analysis, lines of action of resultant force vectors vary up to 6° within the population. Conclusions. Data obtained from this model will improve conservative management, post-surgical rehabilitation, and strength training protocols. Relevance. In the apprehension position, muscle forces may promote anterior humeral head translation, predisposing the glenohumeral joint to anterior instability when other stabilizing mechanisms such as the glenohumeral capsule are not functioning normally.

Changes in Abduction and Rotation Range of Motion in Response to Simulated Dorsal and Ventral Translational Mobilization of the Glenohumeral Joint

Translational mobilization techniques are frequently used by physical therapists as an intervention for patients with limited ranges of motion (ROMs). However, concrete experimental support for such practice is lacking. The purpose of the study was to evaluate the effect of simulated dorsal and ventral translational mobilization (DTM and VTM) of the glenohumeral joint on abduction and rotational ROMs. Fourteen fresh frozen shoulder specimens from 5 men and 3 women (mean age=77.3 years, SD=10.1, range=62-91) were used for this study. Each specimen underwent 5 repetitions of DTM and VTM in the plane of scapula simulated by a material testing system (MTS) in the resting position (40 of abduction in neutral rotation) and at the end range of abduction with 100 N of force. Abduction and rotation were assessed as the main outcome measures before and after each mobilization procedure performed and monitored by the MTS (abduction, 4 N m) and by a servomotor attached to the piston of the actuator of the MTS (medial and lateral rotation, 2 N m). There were increases in abduction ROM for both DTM (mean=2.10 , SD=1.76 ) and VTM (mean=2.06 , SD=1.96 ) at the end-range position. No changes were found in the resting position following the same procedure. Small increases were also found in lateral rotation ROM after VTM in the resting position (mean=0.90 , SD=0.92 , t=3.65, P=.003) and in medial rotation ROM after DTM (mean=0.97 , SD=1.45 , t=2.51, P=.026) at the end range of abduction. The results indicate that both DTM and VTM procedures applied at the end range of abduction improved glenohumeral abduction range of motion. Whether these changes would result in improved function could not be determined because of the use of a cadaver model.