External Rotation Position Research Articles

Population-based in silico modeling of anatomical shape variation of the knee and its impact on joint loading in knee osteoarthritis.

Anatomical knee joint features and osteoarthritis (OA) severity are associated, however confirming causals link to altered knee loading is challenging. This study leverages statistical shape models (SSM) to investigate the relationship between joint shape/alignment and knee loading during gait in knee OA(KOA) patients to understand their contribution to elevated medial knee loading in OA. Musculoskeletal (MSK) models were created for the mean as well as the first eightSSM principal modes of variation (-3,-2,-1, +1, +2, +3 standard deviations for each mode) and used as input to a MSK modeling framework. Using an identical KOA gait pattern (i.e., joint kinematics and ground reaction forces), we ran simulations for each MSK model and evaluated medial compartment loading magnitude and contact distribution at the instant of first and second peak of knee joint loading. An increase in external rotation, posterior tibia translation and a decrease in medial joint space and medial femoral condylar size predisposed the medial compartment knee joint to overloading during gait. This was coupled with an anterior and medial shift in contact location with increasing external rotated tibial position and increasing posterior tibial translation with respect to the femur. Next, results also highlighted a posterior shift of the medial compartment loading location with decreasing medial joint space. This study provides important population-based insights on how knee shape and alignment predispose individuals with KOA to elevated medial compartmental knee loading. This information can be crucial in assessing the risk for medial KOA development and progression.

The Effect of Isometric Exercise Position on the Effectiveness of Isolated Work of the Thigh Flexor Muscles Based on the Results of the sEMG Study.

The main function of the hamstring muscles is to bend the knee joint and support the function of the hip extensors. Their frequent injuries are the result of overload related to, among others, dynamic running or jumping, and inadequate preparation for athletics activities. The asymmetry of the work of individual flexor muscle groups is clearly marked in the case of valgus or varus of the knee joint, i.e., in different positions of the lower limb. The aim of the study was to determine the position and form of a rehabilitation exercise in which an isolated group of muscles flexing the knee joint will show the greatest bioelectrical activity. The study involved 25 students of the Jagiellonian University Medical College. The students were aged 20-26. The average age was 22.9 (±1.4). The study participants included 17 women with an average age of 23.0 (±1.1) and 8 men with an average age of 22.6 (±1.9). Women constituted 68% and men 32% of all respondents. All participants agreed to participate in the study. Surface electromyography measurements in both lower limbs provided an initial number of 50 cases. The activity of the knee flexor muscles during isometric contraction with resistance was measured in correlation with three foot and lower leg settings: internal rotation, neutral position, and external rotation. The bioelectrical activity of the semitendinosus muscle is significantly higher (p < 0.01) in the internal rotation position than in the neutral position of the lower leg, while the bioelectrical activity of the biceps femoris muscle is inversely higher (p < 0.01) in the external rotation position than in the neutral position. The results are significant for both average and maximum values of muscle stimulation. During isometric contraction with resistance, the semitendinosus muscle shows the greatest bioelectrical activity in the internal rotation position of the lower leg and foot, and the biceps femoris muscle in the external rotation position of the lower leg and foot. The above information has important implicational applications when improving isolated groups of hamstrings. In the future, this may contribute to more effective rehabilitation of patients with injuries of the muscles described in the article.

Scapular external rotation position during arm elevation related to increased glenohumeral external rotation range of motion in high school baseball players

Scapular external rotation position during arm elevation related to increased glenohumeral external rotation range of motion in high school baseball players

Clinical and radiographic outcomes using standard length of cannulated screws for traditional Latarjet procedure

PurposeThe purpose of this study was to evaluate the clinical and radiographic outcomes of open traditional Latarjet stabilization using 32mm and 30mm long cannulated screws in males and females respectively with a minimum of 2 years’ follow-up. MethodsWe retrospectively reviewed open Latarjet procedures using cannulated screws of standard length with a minimum of 2 years follow-up. Functional evaluation was performed with postoperative Rowe and Walch score, visual analogue scale for pain (VAS) and return to sport. Graft healing was assessed with CT scans at 4 to 6 months postoperatively. Patients were divided into 2 groups according to postoperative radiographic measurements: a bicortical or unicortical screw groups. The α angle between the shaft of the screw and the glenoid subchondral bone was measured for superior and inferior screws. Level of significance was 0.05. The post hoc power analysis was 0.89. ResultsA total of 69 patients met the criteria for inclusion. Of these patients, 60 (87%) were available for final follow-up (n =62 shoulders), with a mean age of 28.4 ±9.5 years (range, 16-55 years) at time of surgery. 56 males (93.3%) and 4 females (6.7%) were included. The mean final follow-up period was a mean of 38 months after the procedure (range, 25-48 months). 8 out 60 patients (13.3%) had persistent apprehension in abduction–external rotation position. One patient (1.7%) had a recurrence of shoulder subluxation. The mean Walch-Duplay score was 90±11.6 points (range, 40-100 points), and the mean Rowe score was 93.4±11 points (range, 50-100 points). The mean VAS score for the evaluation of pain was 0.9±1.3 (range, 0-4). The coracoid healed the glenoid neck in 87.1% (54/62) of the shoulders on the postoperative CT scan. Lower alpha angle for inferior and superior screws had more rate of unicortical fixation (P=0.05 and P=0.04, respectively). 14 out 62 (22.6%) shoulders were found unicortical screws. Six bicortical cases and 2 cases unicortical screws (25%) showed nonunion (p=0.86). There were 2 complications, one patient had hematoma that required drainage, one case had transient axillary nerve palsy which resolved spontaneously. No complications associated with the hardware were found. ConclusionOpen traditional Latarjet procedure using 32 mm and 30mm long cannulated screws in male and females respectively, provided good outcomes with acceptable complication rates. Unicortical screws fixation does not have a higher rate of non-union than bicortical screws.

Trans-axillary sonography in the ABER (ABduction and External Rotation) position: a window to the subscapularis, teres major and latissimus dorsi.

Shoulder ultrasound is a key tool used by musculoskeletal practitioners to diagnose and treat a variety of upper girdle diseases. While magnetic resonance imaging is the cornerstone of shoulder imaging, sonography is readily available, practical and superior in its ability for dynamic assessment of musculoskeletal pathologies. The subscapularis, teres major and latissimus dorsi muscles are commonly involved in a myriad of pathology including myofascial pain and spasticity. There is scarce literature on the assessment of these muscles for diagnostic and therapeutic purposes. Conventional approaches to shoulder ultrasound have not included a dedicated assessment of the subscapularis muscle due to its inherent anatomical location deep to the scapular blade which blocks sound wave penetration. We describe an approach to visualizing the subscapularis muscle as a short addition to the established shoulder sonography format, which also permits assessment of both the latissimus dorsi and teres major muscles, which are important muscles for shoulder spasticity. The patient is imaged in a semi-recumbent position with the arms elevated above and behind the head in the ABduction and External Rotation (ABER) position. The relative ease of positioning and sonographic access to the musculature coupled with the potential for assessment and intervention makes this approach extremely desirable to the musculoskeletal practitioner looking to diagnose or treat muscle belly pathologies of the subscapularis, teres major or latissimus dorsi.

Shoulder Motion Overestimated by Mallet Scores.

Brachial plexus birth injuries (BPBI) occur in up 0.4 to 4.6 per 1000 live births. Weakness about the shoulder and development of glenohumeral joint contractures are common sequalae of BPBI. Shoulder function in children with BPBI is frequently assessed using the modified Mallet classification to evaluate upper extremity motion deficits. The purpose of this study was to assess the accuracy of the abduction, external rotation, and hand-to-mouth Mallet classification scores in children with BPBI using motion capture. A retrospective study of 107 children with BPBI who underwent motion capture assessment and Mallet scores on the same date were reviewed. Motion capture measurements were used to calculate humerothoracic elevation and external rotation joint angles in the abduction/hand-to-mouth and external rotation positions, respectively. The humerothoracic joint angles were converted to the corresponding Mallet scores. Discrepancies between the Mallet scores determined by clinicians and those determined by motion capture were assessed. For abduction, 24.3% of Mallet scores were misclassified during clinical examination. Of the misclassified scores, 22 were overestimated by 1 point and 4 were underestimated by 1 point compared with motion capture. For external rotation, 72.9% of Mallet scores were misclassified during clinical examination. Only 5 patients had an HT elevation that was less than 40 degrees, with 4 of them (80%) having a Mallet hand-to-mouth score of 4. There were no differences in proportion of patients with HT elevation less than 40 degrees who had a Mallet score of 4 or a Mallet score less than 4. There was better agreement in global abduction Mallet scores compared with external rotation and hand-to-mouth Mallet scores. This difference was likely due to the complex compensatory strategies that patients employ while performing external rotation and hand-to-mouth positions. The inaccuracy of the clinically determined Mallet scores is alarming given that they are frequently utilized to assist with surgical indications and are commonly used as outcome measures. Level IV Case series.

Does the Position of the Ankle Matter During the Single Gluteal Bridge in Futsal Players? An Electromyographic Analysis.

The aim of this study was to analyze the muscle activity of the hamstring muscles and the lateral gastrocnemius during different variants of the single-leg bridge (SLB) in futsal players. Cross-sectional study. Twenty-two futsal players (age = 24.8 [3.9]y) volunteered to participate in this study. The participants performed 3 variations of the SLB with the knee flexed at 45°. The first position was performed with the ankle in plantar position with flat support, the second with the ankle in dorsiflexion (DF) with heel support, and the third with the ankle in DF and external rotation (ER) with heel support. The Wilcoxon rank-sum test assessed the difference between variables for samples with the rank-biserial correlation effect size. Spearman correlation coefficients were used to examine the associations of the percentage maximal voluntary isometric contraction for each muscle with peak force and rate of force development with 3 different variances of the SLB. The variation of ankle DF and ER with heel support generated higher muscle activity in BF in concentric (P < .01, effect size [ES] = -0.613); isometric (P < .042, ES = -0.494); and eccentric (P < .005, ES = -0.668) contraction than ankle DF with heel support. In contrast, the variation of ankle DF and ER with heel support generated fewer muscle activity in lateral gastrocnemius in concentric (P < .001, ES = 0.779); isometric (P < .003, ES = 0.708); and eccentric (P < .014, ES = 0.589) contraction than ankle DF with heel support. The position of DF and ER was the best position in SLB to train the BF. It could be convenient to start rehabilitation of the BF with flat foot postition or ankle in DF with heel support and progress with the position of the ankle in DF and ER with heel support.

Effects of repetitive baseball throwing on hip muscle strength and trunk and pelvic motions at the shoulder's maximum external rotation position during the late cocking phase and ball release.

[Purpose] This study aimed to investigate the changes in the trunk and pelvic lateral tilt angles at the shoulder's maximum external rotation during the late cocking phase (MER) and ball release (BR) and hip muscle strength during repetitive throwing. [Participants and Methods] In this study, 12 male baseball players participated. During the throwing, which was filmed using a high-speed video camera, the trunk and pelvic lateral tilt angles toward the nonthrowing side were measured at the MER and BR. Hip muscle strength during abduction, adduction, and external internal rotations were measured on the throwing and nonthrowing sides. Repetitive throwing was performed for nine innings, with 15 pitches per inning. Throwing motion was compared during innings 1, 7, 8, and 9. Hip muscle strength was measured before and after repetitive throwing. [Results] Compared with the trunk lateral tilt angle toward the nonthrowing side at BR in inning 1, the angle in innings 8 and 9 increased. The strength of hip abduction, adduction, and external and internal rotations on the throwing and nonthrowing sides decreased after repetitive throwing. [Conclusion] Hip muscle strength decreases after 135 pitches, and throwing >120 pitches changes the trunk lateral tilt angle at BR.

Kinematic Analysis of Pelvic and Lower Limb Joints during Stand-to-sit Movement in Individuals with Chronic Low Back Pain: A cross-sectional study.

It is crucial to investigate the daily functions commonly utilized by individuals with low back pain (LBP) due to their implications for recurrence and chronicity. Stand-to-sit (StTS) task is one of the more repetitive functions in human daily life. This study aims to evaluate pelvic and lower limb joint kinematics during the StTS task in individuals with Non-Specific Chronic Low Back Pain (NSCLBP) compared to a healthy control group. Pelvic and lower limb joint kinematic data in all three planes were recorded from 20 individuals with LBP and 20 healthy individuals using a Qualisys motion capture system during the StTS task. A Functional Data Analysis statistical approach was employed to compare the kinematic data between the two groups. In the initial phase of the movement, we observed a greater anterior pelvic tilt (P=0.028) and an altered pelvic frontal plane motion pattern (P=0.029) in the LBP compared to the healthy group. The only significant differences between the lower limb joint kinematics of the two groups were a less hip external rotation position (P=0.025) and a more knee adduction pattern (P=0.002) on the right side in the LBP subjects compared to the healthy group. Considering a few differences noted between the two groups across various joints and planes evaluated, it appears that the kinematic pattern of the lower limbs does not significantly differ between the NSCLBP and healthy groups during the StTS task in most comparisons. However, distinct kinematic patterns have been observed in the pelvic region, particularly in the sagittal and frontal planes, between the two groups.

Leg position effects on the femoral neurovascular bundle location during a direct anterior approach total hip arthroplasty: a radiographic study

BackgroundFemoral neurovascular injury is a serious complication in a direct anterior approach (DAA) total hip arthroplasty. However, dynamic neurovascular bundle location changes during the approach were not examined. Thus, this study aimed to analyze the effects of leg position on the femoral neurovascular bundle location using magnetic resonance imaging (MRI).MethodsThis study scanned 30 healthy volunteers (15 males and 15 females) with 3.0T MRI in a supine and 30-degree hip extension position with the left leg in a neutral rotation position and the right leg in a 45-degree external extension position. The minimum distance from the edge of the anterior acetabulum to the femoral nerve (dFN), artery, and vein were measured on axial T1-weighted images at the hip center level, as well as the angle to the horizontal line of the femoral nerve (aFN), artery (aFA), and vein from the anterior acetabulum.ResultsThe dFN in the supine position with external rotation was significantly larger than supine with neutral and extension with external rotation position (20.7, 19.5, and 19.0; p = 0.031 and 0.012, respectively). The aFA in supine with external rotation was significantly larger than in other postures (52.4°, 34.2°, and 36.2°, p < 0.001, respectively). The aFV in supine with external rotation was significantly larger than in supine with a neutral position (52.3° versus 47.7°, p = 0.037). The aFN in supine and external rotation was significantly larger than other postures (54.6, 38.2, and 33.0, p < 0.001, respectively).ConclusionsThis radiographic study revealed that the leg position affected the neurovascular bundle location. These movements can be the risk of direct neurovascular injury or traction.

Effect of different pelvic-drop exercises on hip muscles activity in patients with gluteus medius weakness

BACKGROUND: Pelvic-drop exercise (PD) is unilateral weight-bearing exercise that is frequently performed in rehabilitation sessions because its easy application can trigger moderate-to-high gluteus medius (Gmed) activity. Hip rotation has been applied to effectively facilitate Gmed activity during exercise. OBJECTIVE: To determine the effects of PD with three different hip rotations on Gmed, tensor fasciae latae (TFL), gluteus maximus (Gmax) activity, and Gmed:TFL activity ratio in patients with Gmed weakness. METHODS: Eighteen subjects with Gmed weakness participated. Subjects performed three different forms of PD with neutral hip, hip internal rotation, and hip external rotation position. Surface electromyography was performed to quantify the activity of Gmed, TFL, and Gmax. RESULTS: PD with hip internal rotation showed significantly greater Gmed activity than with neutral hip and hip external rotation (P= 0.005 and P= 0.007, respectively). TFL also showed significantly greater activity during PD with hip interna rotation than neutral hip (P= 0.002). There were no significant differences in Gmax activity (P= 0.095) and Gmed:TFL activity ratio (P= 0.254) among different forms of PD. CONCLUSIONS: PD with hip internal rotation is recommended to stimulate greater Gmed activity while preserving Gmed:TFL muscle activity ratio.

Assessment of proprioception, muscle strength and endurance during dynamic isokinetic test in patients with breast cancer-related lymphedema

BackgroundBreast cancer-related lymphedema is a common complication after breast cancer treatment.This study examined isokinetic proprioception, muscular strength, and endurance by comparing extremity with lymphedema and the extremity without lymphedema in women with breast cancer-related lymphedema. MethodsA total of 15 individuals aged between 35 and 70 years participated in this study. Cybex Humac NORM Isokinetic dynamometer (CSMi, Stoughton, MA) were used to assess upper extremity passive proprioception, active proprioception, kinesthesia, muscle strength, and muscle endurance. The upper extremity lymphedema was measured with the water displacement arm volumetry test using a volumeter. FindingsAll isokinetic measurements demonstrated a statistically significant difference between the extremity with lymphedema and the extremity without lymphedema, suggesting lower scores in the extremity with lymphedema (p < .05). There was a positive correlation between passive internal rotation in the extremity with lymphedema and the time after mastectomy (r= 0.628, p = .012) and a moderate positive relationship was found between the time after lymphedema and passive internal rotation (r = 0.577; p = .024), and active external rotation position sense (r = 0.540; p = .038) in the extremity with lymphedema. Also, a unidirectional positive moderate (r = 0.594; p = .020) relationship was found between the lymphedema stage and passive external rotation in the extremity with lymphedema. InterpretationThe difference in proprioception, muscle strength, and endurance between the extremity with lymphedema and the extremity without lymphedema in women with breast cancer-related lymphedema will provide valuable information in terms of prioritizing these parameters in treatment.

Technical note: Intraoperative ultrasound measurement for evaluating the stability of the inferior tibiofibular joint in patients with ankle fractures

ObjectivesInjury to the tibiofibular syndesmosis is a common complication of ankle fractures. Currently, it is challenging to determine the stability of the tibiofibular joint caused by ankle fractures during surgery. This study aims to establish a standardized method for dynamically evaluating the stability of the inferior tibiofibular joint under intraoperative ultrasound and assess its utility in surgery, thereby assisting in determining the necessity for fixation of the inferior tibiofibular joint after fracture reduction and fixation. MethodsThe stability of the inferior tibiofibular joint was assessed using an intraoperative ultrasonic external rotation stress test, with a torque set at 7.2 N·m. The measured parameters included the width of the inferior tibiofibular space in neutral (N) and external rotation (E) positions, stretch ratio (E/N), and injured/healthy side stretch ratio (I/H). Patients with Weber B or C type ankle fractures were selected as participants. ResultsFor the case with Weber C fracture, the N measurement was 4.22 mm after fracture fixation, while E measured 5.77 mm and E/N ratio was 1.37, which were larger than those on the healthy side (N: 4.17, E: 4.50, E/N:1.08), with an I/H ratio of 1.27. Intraoperative X-ray revealed instability of the inferior tibiofibular joint. After inserting a tibiofibular screw, the N measurement was 4.20 mm, while the E measurement recorded 4.32 mm, resulting in an E/N ratio of 1.03 and an I/H ratio of 0.95, indicating improved joint stability. For the Weber B fracture case, the N measurement was 3.55 mm after fracture fixation, while E measured 3.98 mm and the E/N ratio was 1.12, slightly lower than those on the healthy side (N: 3.94, E: 4.47, E/N: 1.13), with an I/H ratio of 0.99. The intraoperative X-ray revealed stability of the inferior tibiofibular joint. Therefore, no further fixation was performed on it. ConclusionStandardized intraoperative ultrasound stress test allows for real-time, dynamic assessment of the stability of the inferior tibiofibular joint after ankle fracture reduction and fixation, which can help guide the fixation of the inferior tibiofibular joint, thereby reducing the risk of postoperative traumatic arthritis.

Poster 107: Biomechanical Effect of “AIGHL Reconstruction” for Bankart Lesion in Thrower’s Shoulder: A Novel Surgical Treatment to Maintain Maximum Shoulder External Rotation Angle after Surgery

Objectives: For anterior shoulder instability, antero-inferior labral repair (Bankart repair) is a reliable surgery to prevent shoulder dislocation. However, in biomechanical and clinical studies, maximum shoulder external rotation angle is reported to be decreased by about 10 degrees due to shortening of the anterior band of the inferior glenohumeral ligament (AIGHL) length after Bankart repair. For overhead throwing athletes, the 10 degrees reduction in shoulder external rotation makes it difficult to return to the previous performance level, although it does not affect daily activity. To prevent shortening of the AIGHL length, an AIGHL reconstruction was developed using fascia lata graft. Preliminary clinical results in overhead throwing athletes showed that a throwing program could start with complete restoration of maximum shoulder external rotation angle 3 months after AIGHL reconstruction. In this study the effect of AIGHL reconstruction on shoulder external rotation and anterior stability for simulated Bankart lesion in a cadaveric model of a thrower’s shoulder was evaluated (Fig. 1). Methods: Eight cadaveric shoulders were tested at 60° of glenohumeral abduction (90° of shoulder abduction) to simulate throwing motion. Glenohumeral translations at 60° and 90° of external rotation, maximum humeral rotational range of motion, and humeral head shift were measured using goniometer and MicroScribe 3D-digitizer. Each specimen was subjected to five experimental stages: (1) intact condition; (2) simulation of thrower’s shoulder by anterior capsular stretching based on previously reported method; (3) creation of Bankart lesion (AIGHL and the labrum were detached at glenoid side); (4) Bankart repair using three suture anchors; and (5) AIGHL reconstruction using allograft of fascia lata. In the AIGHL reconstruction, allograft was patched between the detached AIGHL and glenoid at maximum shoulder external rotation position to restore the original AIGHL length (Fig. 2). For statistical analysis, linear mixed-effects model and Tukey’s post-hoc analysis were used. Results: After 20% stretching, shoulder external rotation and anterior translation were significantly increased (intact 128.3° and 2.8mm, thrower’s shoulder 141.9° and 7.3mm, p&lt;0.001). Creation of Bankart lesion significantly increased anterior translation (8.3mm) compared with intact condition (p=0.021). Bankart repair completely restored anterior translation (3.0mm) to intact level; however, maximum shoulder external rotation angle after Bankart repair (134.8°) was significantly less than that in thrower’s shoulder (p=0.009). AIGHL reconstruction completely restored anterior translation (6.5mm) to thrower’s shoulder without decreasing maximum shoulder external rotation angle (144.4°) compared with thrower’s shoulder (Fig. 3 &amp; 4). At maximum humeral external rotation, the humeral head was significantly shifted superiorly after creation of Bankart lesion compared with intact condition(p=0.005). After Bankart repair, the humeral head was significantly shifted inferiorly from the Bankart lesion (p=0.003) and was significantly inferior relative to the position after AIGHL reconstruction (p=0.007). Conclusions: While Bankart repair completely restored anterior translation to the intact level (tighter than thrower’s shoulder), AIGHL reconstruction completely restored to the thrower’s level. Furthermore, maximum shoulder external rotation angle was maintained after AIGHL reconstruction although Bankart repair decreased external rotation significantly. Therefore, AIGHL reconstruction can be a useful surgical option for Bankart lesion in overhead throwing athletes to restore anterior stability while maintaining maximum shoulder external rotation angle after surgery.

Improved angle accuracy of tibial plateau osteotomy for total knee arthroplasty using tibial mechanical axis skin-mapping.

The tibial crest is often used as an anatomic landmark for tibial plateau osteotomy (TPO) in total knee arthroplasty (TKA), but it is not very accurate. This study aimed to investigate errors in using the tibial crest as a marker and present a simple approach to improve the angle accuracy of TPO by mapping the tibial mechanical axis (TMA), determined preoperatively, according to the tibial crest on the skin overlying the tibia. We evaluated 50 healthy young volunteers and 100 pre-TKA osteoarthritic knees. The middle tibial crest lines (MTCLs) were marked on the shank tibial skin and covered with Kirschner wires. All participants underwent two sets of anteroposterior (AP) standing radiographs of the lower extremity, with the feet in neutral and external rotation positions. The MTCL-TMA angles were measured and compared. The TMA was mapped onto the tibial skin according to the MTCL-TMA angle prior to TKA and used for TPO. Postoperative outcomes were determined by the angle between the vertical tibial component axis (TCA) and the TMA. The MTCL had no evident relationship with the TMA. A few MTCLs were parallel to the TMA. External rotation of the foot significantly changed the MTCL-TMA relationship. The angle accuracy of the TPO as guided by TMA skin-mapping was 0.83 ± 0.76°. No postoperative errors exceeded 3°. The MTCL was not equivalent to the TMA. The TPO error can be reduced by preoperatively marking the TMA on the tibial skin according to the MTCL.

Patients with recurrent anterior shoulder instability exhibit altered glenohumeral and scapulothoracic joint kinematics during upper limb movement: A prospective comparative study.

Altered shoulder kinematics in patients with recurrent anterior shoulder instability remains poorly understood. This prospective study aimed to quantify in vivo glenohumeral and scapulothoracic joint kinematics and joint-contact positions in patients with shoulder instability and healthy controls. Twenty patients with recurrent anterior shoulder instability (mean 28years) and five patients without shoulder pathology (mean 39years) were scanned using open CT in six static upper limb positions including 90° of abduction, combined abduction and external rotation, 90° of flexion, lift-off position (i.e. reaching behind the back) and the neutral shoulder with external rotation. Image datasets were digitally reconstructed to quantify shoulder joint kinematics and glenohumeral translation. At 90° of abduction, instability patients demonstrated significantly less glenohumeral abduction and a reciprocal increase in upward scapulothoracic rotation compared to controls (mean difference: 13.3°, p=0.038). With the shoulder in combined abduction and external rotation, instability patients showed a significant increase in glenohumeral rotation and a reciprocal decrease in scapulothoracic rotation compared to controls (mean difference: 5.0°, p=0.042). There were no significant differences in humeral head translation in the sagittal plane (anterior-posterior axis) for all motions tested (p>0.05). Scapulothoracic and glenohumeral kinematics are significantly different between patients with recurrent anterior shoulder instability and those with a healthy shoulder. Instability patients compensate for reduced glenohumeral function during abduction by increasing scapular rotation. With the shoulder in combined abduction and external rotation position, greater glenohumeral joint angles without significantly increased humeral head translation suggest altered neuromuscular control in the unstable shoulder.

Effect of thoracic expansion restriction on scapulothoracic and glenohumeral joint motion during shoulder external rotation.

Shoulder external rotation in the throwing motion involves movement of the scapulothoracic and glenohumeral joints, thoracic spine, and the thorax. Restriction of thoracic expansion may decrease scapulothoracic joint motion and compensate by excessive glenohumeral joint motion. However, it is unclear how restricting the expansion of the thorax alters shoulder motion. To elucidate changes in scapulothoracic and glenohumeral joint movements caused by restricted thoracic expansion. Kinematic data were obtained using an electromagnetic tracking device (Liberty; Polhemus), from 18 male participants, during shoulder external rotation in the sitting position with and without restriction of thoracic expansion. The displacements from the start position to the maximum external rotation position were compared, and Pearson's correlation coefficient was calculated. A significant difference was observed in the scapulothoracic posterior tilt angle (P< 0.01) and glenohumeral external rotation angle (P< 0.01). A significant positive correlation existed between scapulothoracic posterior tilt and glenohumeral external rotation (P< 0.05) with and without restriction. Restriction of thoracic expansion decreased scapulothoracic motion and increased glenohumeral motion. Thus, a decrease in thoracic expansion may change scapulothoracic and glenohumeral movements, which may be a risk factor for throwing injuries.

Shoulder Magnetic Resonance Arthrography with the Internal and External Rotation Positions of the Humeral Head in the Evaluation of SLAP Lesions.

We aimed to evaluate the diagnostic performance of shoulder MR arthrography (MRA) acquired in the neutral (N), internal rotation (IR), and external rotation (ER) positions of the shoulder to detect SLAP lesions. Three observers evaluated 130 MRAs to detect SLAP lesions and to calculate labral diastasis in this triple-blinded study. Sensitivity was much higher in the ER (92.5–97.5%) than in the N (60–72.5%) and IR (42.5–52.5%) positions, and the specificity of all the reviewers was 100% in all the positions. The diagnostic accuracy was higher in the ER too (97.7–99.2%). The diastasis length was significantly higher in the ER (median = 2.5–2.8 mm) than in the N (1 mm) and IR (0 mm) positions and was also significantly higher in those patients requiring surgery (p = 0.001). The highest inter-rater agreement values were observed in the ER both in SLAP detection (k = 0.982) and the diastasis length evaluation (ICC = 0.962). The diastasis length threshold in the ER that best separated the patients who did and did not require surgery was 3.1 mm (AUC = 0.833). In 14.6% of the cases, ER enabled the detection of SLAP lesions not identified in the N position. MRA with the ER improves the diagnosis of SLAP lesions and, together with the IR position, provides additional dynamic information about the diastasis of the lesions. It is recommended to perform additional ER and IR scans in the shoulder MRA protocol.

Does critical shoulder angle predict abduction motion and acromion-tuberosity impingement in reverse shoulder arthroplasty?

BackgroundVirtual planning software for reverse shoulder arthroplasty (RSA) has introduced the ability to optimize implant position in an effort to maximize bony impingement–free motion. Abduction impingement typically occurs between the glenoid and polyethylene or between the tuberosities and the acromion or coracoid. Acromion-tuberosity impingement has been considered less desirable, as it may create additional stress on the acromion. Patients with a large acromion overhang may have higher rates of acromion-tuberosity impingement. As the critical shoulder angle (CSA) represents a larger distance from the glenoid face to the acromion, the purpose of this study was to evaluate the impact of implant selection and position on abduction motion and acromion-tuberosity impingement, with a focus on the association to CSA. We hypothesize that a larger CSA will be associated with less abduction motion and an increase in acromion-tuberosity impingement. MethodsThis is a retrospective cohort case series of 85 consecutive patients who underwent RSA from June 2020 to January 2021. Humeral and glenoid components were implanted virtually (SurgiCase) using a standard protocol for a single implant system (DJO AltiVate Short Stem Reverse) with an inset humeral component. Implant variables analyzed included baseplate location (central vs. inferior glenoid), glenosphere lateralization (10 mm vs. 6 mm), and humeral shell (standard vs. semiconstrained). The maximal degree of abduction and location of impingement were recorded at external rotation of 0°, 45°, and 90°. Implant combinations that resulted in no impingement and no motion were recorded. ResultsIncrease in CSA was associated with acromion-tuberosity impingement for nearly every combination at 0° and 45° external rotation; however, there were no significant associations between CSA and maximum abduction motion. Acromion-tuberosity impingement was associated with central glenosphere placement in all degrees of external rotation (P < .001), use of a 10 mm lateralized glenosphere for 0° (P < .001) and 45° (P = .076), and using a standard polyethylene shell for 0° (P = .032) and 45° external rotation (P = .007). Maximal abduction motion was associated with inferior placement (P < .001), and use of a 10 mm lateralized glenosphere (P < .001) in all positions of external rotation but was not influenced by the polyethylene type. ConclusionIncreased CSA is associated with acromion-tuberosity impingement and can be used to screen for patients at risk for bony impingement in abduction. Placement of the glenosphere centrally and use of a 10 mm lateralized glenosphere were associated with higher rates of acromion-tuberosity impingement. Maximal abduction can be achieved using a 10 mm lateralized glenosphere and inferior placement.

Psoas Minor: Major Confusion

Introduction &amp; ObjectiveThe psoas minor muscle is found in the retroperitoneum with close association to the psoas major and iliacus muscles. Major anatomical textbooks fail to offer a clear consensus on psoas minor, providing conflicting information on the insertion site, function, and relationship to the iliopsoas complex. Reported prevalence of the psoas minor muscle ranges from 40‐65% in each individual hip, but available research is limited by sample size or is not representative of U.S. demographics. Accurate descriptions of the structure of the psoas minor muscle would allow for improved hypotheses regarding muscle function and repercussions of muscle dysfunction. This study aims to document the presence and insertion of the psoas minor muscle in a U.S. donor population, suggest an alternative source to lumbar back pain, and discuss ramifications of muscle dysfunction and applicable osteopathic intervention.Materials &amp; MethodsAt this time, eleven donors were evaluated in the Sam Houston State University College of Osteopathic Medicine’s Human Anatomy Lab. The presence or absence of the psoas minor muscle was determined bilaterally. Muscles were manually traced from origin to the tendon and then the point of insertion. If needed, the inguinal ligament and anterior pelvic structures were dissected for better visualization. Findings were recorded in a secure database and photographed.ResultsThe psoas minor muscle was present bilaterally in seven donors, present unilaterally in one donor, and bilaterally absent in three donors. On all donors evaluated, the insertion site was the pectin pubis with distal blending of the tendon with iliac fascia.Significance &amp; ConclusionAnatomical texts have a variety of descriptions for the documented insertion, such as the pectin pubis, iliopubic eminence, arcuate line, pectineal line or iliopubic ramus. In this study, donors with a psoas minor muscle were determined to have a common insertion site: the pectin pubis. Muscle origin (lateral surface of T12‐L1 vertebral bodies and discs) and bilateral presence (n=7/11; 63%) in the study aligned with current literature.Findings of this study support hypotheses of alternative sources of dysfunction that may contribute to lumbar back pain and hip snapping syndrome rather than more commonly reported sources, such as lumbar back musculature or the iliacus and psoas major muscles. Proximal dysfunction of a psoas minor muscle may contribute to lumbar back pain by abnormally rotating the originating vertebrae in the direction of the hypertrophic muscle. Distal dysfunction may contribute to hip snapping syndrome, in which the iliopsoas tendon “snaps” over the iliopectineal eminence when returning the leg from a position of flexion, abduction, or external rotation. From an osteopathic manipulative approach, the psoas minor may be treated with counterstrain techniques or muscle energy to the lumbar spine to restore normal tone and function. We will continue to collect data in an ongoing study in order to provide an evidence‐based recommendation for the reporting of psoas minor insertion and function, as well as the presentation and potential treatment of psoas minor dysfunction.