Evaluation of the lag sign tests for external rotator function of the shoulder

doi:10.1016/j.jse.2004.01.021

Journal of Shoulder and Elbow Surgery

Volume 13, Issue 3, May–June 2004, Pages 298-304

https://doi.org/10.1016/j.jse.2004.01.021 Get rights and content

Abstract

Rotator cuff lesions pose a serious clinical challenge. The objective of this study was to verify the biomechanical basis for the lag sign clinical tests for rotator cuff dysfunction. The lag sign tests were simulated in vitro by a sensor-guided robotic simulator configured to reproduce in vivo testing conditions. The ability of the test to isolate supraspinatus and/or infraspinatus dysfunction was investigated from 20° to 90° of scapular plane arm elevation. The test was 100% sensitive for lack of all infraspinatus–teres minor force at all elevations tested (6/6 specimens at 20°, 30°, and 60° elevation; 5/5 at 90° elevation). The test was less sensitive to complete loss of supraspinatus force (1/6 specimens testing positive at 20°, 0/6 at 30°, 3/6 at 60°, and 3/5 at 90° elevation). The results of this biomechanical study suggest the lag sign tests to be highly sensitive only for infraspinatus–teres minor muscle dysfunction.

Section snippets

Specimen preparation and mounting

Seven radiographically normal human shoulders (mean patient weight, 84 ± 15 kg; mean age, 60 ± 21 years, with three patients of unknown age) were harvested and frozen before testing. The specimens were thawed at room temperature for 12 hours before dissection of all muscles except for the rotator cuff and deltoid. The muscle bellies of the rotator cuff were bluntly dissected away from the scapula, and particular care was taken to preserve the integrity of the joint capsule and ligaments as well

Results

The results of the lag sign simulations are tabulated according to the number of positive tests versus the number of specimens tested at each elevation angle and combination of SSP and ISP-TM force tested (Table II). One of the seven specimens tested was removed from the series because it exhibited unusual laxity and an extreme external rotation of 104° at 90° elevation, and thus almost no SSP and ISP-TM force was required to hold the test position. The SSP tendon insertion of another specimen

Discussion

The results of this study suggest that it is difficult to distinguish between deficiencies of the SSP and ISP-TM muscles by use of the lag sign tests based on biomechanical considerations alone. Whereas complete loss of ISP-TM force would result in 100% sensitivity at all elevations tested (Table I, 100% SSP force), complete loss of SSP force would be more difficult to detect, especially at lower elevations. Although increasing with elevation, sensitivity for the isolated SSP rupture was still

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2020, Journal of Biomechanics
Healthy shoulder function requires the coordination of the rotator cuff muscles to maintain the humeral head’s position in the glenoid. While glenohumeral stability has been studied in various settings, few studies have characterized the effect of dynamic rotator cuff muscle loading on glenohumeral translation during shoulder motion. We hypothesize that dynamic rotator cuff muscle activation decreases joint translation during continuous passive abduction of the humerus in a cadaveric model of scapular plane glenohumeral abduction. The effect of different rotator cuff muscle activity on glenohumeral translation was assessed using a validated shoulder testing system. The Dynamic Load profile is a novel approach, based on musculoskeletal modeling of human subject motion. Passive humeral elevation in the scapular plane was applied via the testing system arm, while the rotator cuff muscles were activated according to the specified force profiles using stepper motors and a proportional control feedback loop. Glenohumeral translation was defined according to the International Society of Biomechanics. The Dynamic load profile minimized superior translation of the humeral head relative to the conventional loading profiles. The total magnitude of translation was not significantly different (0.805) among the loading profiles suggesting that the compressive forces from the rotator cuff primarily alter the direction of humeral head translation, not the magnitude. Rotator cuff muscle loading is an important element of cadaveric shoulder studies that must be considered to accurately simulate glenohumeral motion. A rotator cuff muscle activity profile based on human subject muscle activity reduces superior glenohumeral translation when compared to previous RC loading profiles.
Reverse shoulder arthroplasty with and without latissimus and teres major transfer for patients with combined loss of elevation and external rotation: a prospective, randomized investigation
2020, Journal of Shoulder and Elbow Surgery
Latissimus dorsi (LD) and teres major (TM) tendon transfers have been performed concurrently with reverse shoulder arthroplasty (RSA) to address combined loss of elevation and external rotation (CLEER) at the shoulder. The purpose of this prospective, randomized study was to compare RSA with and without LD-TM tendon transfer in patients with rotator cuff tear arthropathy and CLEER.
Patients undergoing RSA for rotator cuff tear arthropathy who also had CLEER were randomized into the group undergoing RSA with tendon transfer or the group undergoing RSA without tendon transfer. The primary outcome measure was the Activities of Daily Living and External Rotation (ADLER) score 2 years after surgery. Secondary outcome measures included the Disabilities of the Arm, Shoulder and Hand (DASH) score, American Shoulder and Elbow Surgeons (ASES) score, and Simple Shoulder Test (SST) score.
Both the treatment and control groups showed significant improvements in the ability to perform activities of daily living requiring active external rotation measured by the ADLER score postoperatively. No significant difference in the ADLER, DASH, ASES, or SST score was found between the 2 groups at final follow-up. Resolution of the Hornblower sign occurred postoperatively in 58.3% of patients in the control group and 73.3% of those in the treatment group.
No differences in the ADLER, DASH, ASES, and SST results were found between patients treated with RSA alone and those treated with RSA with LD-TM transfer for rotator cuff tear arthropathy and CLEER. Both groups showed significant improvements in all clinical outcome assessments including functional tasks that require active external rotation.
The effect of the arthroscopic augmentation of the subscapularis tendon on shoulder instability and range of motion: A biomechanical study
2016, Clinical Biomechanics
Anterior shoulder dislocation is common. The treatment of recurrence with glenoid bone defect is still considered controversial. A new arthroscopic subscapularis augmentation has recently been described that functions to decrease the anterior translation of the humeral head. The purpose of the presented study was to examine the biomechanical effect on glenohumeral joint motion and stability.
Eight fresh frozen cadaver shoulders were studied by use of a force guided industrial robot fitted with a six-component force-moment sensor to which the humerus was attached. The testing protocol includes measurement of glenohumeral translation in the anterior, anterior-inferior and inferior directions at 0°, 30° and 60° of glenohumeral abduction, respectively, with a passive humerus load of 30 N in the testing direction. The maximum possible external rotation was measured at each abduction angle applying a moment of 1 Nm. Each specimen was measured in a physiologic state, as well as after Bankart lesion with an anterior bone defect of 15–20% of the glenoid, after arthroscopic subscapularis augmentation and after Bankart repair.
The arthroscopic subscapularis augmentation decreased the anterior and anterior-inferior translation. The Bankart repair did not restore the mechanical stability compared to the physiologic shoulder group. External rotation was decreased after arthroscopic subscapularis augmentation compared to the physiologic state, however, the limitation of external rotation was decreased at 60° abduction.
The arthroscopic subscapularis augmentation investigated herein was observed to restore shoulder stability in an experimental model.
Evaluation and management of adult shoulder pain: A focus on rotator cuff disorders, acromioclavicular joint arthritis, and glenohumeral arthritis
2014, Medical Clinics of North America
Reverse shoulder arthroplasty combined with a latissimus dorsi and teres major transfer for a deficit of both active elevation and external rotation. Results of 15 cases with a minimum of 2-year follow-up
2013, Orthopaedics and Traumatology: Surgery and Research
Citation Excerpt :
However, it does not improve active external rotation in the setting of a teres minor deficit. In cases of an irreparable posterosuperior cuff tear including the teres minor tendon, highlighted by a dropping sign and an external rotation lag sign [1–4], the reverse arthroplasty can enhance the ability to perform activities of daily living at waist level. However, in some instances, clinical results can be adversely affected by the procedure.
Our aim was to assess the clinical and radiological outcomes of reverse shoulder replacements performed in association with a latissimus dorsi and teres major tendon transfer in cases of irreparable posterosuperior cuff tears including the teres minor tendon. Our hypothesis was that the tendon transfers would improve the clinical results of arthroplasty by restoring active external rotation.
Fifteen procedures in 14 patients were performed through a single deltopectoral approach. Both tendons were fixed to the proximal anterolateral aspect of the humeral metaphysis. Mean age at the time of surgery was 67.5 years (range 53 to 82 years). All had severe cuff tear arthropathy (Hamada stage 3 or 4) and severe atrophy or fatty infiltration of the infraspinatus and teres minor on preoperative MRI or CT-scan (Goutallier stage 3 or 4). Preoperative and postoperative functions were assessed by Constant score. Satisfaction was assessed by the Simple Shoulder Test (SST). At follow up, radiographs were examined for radiolucent lines, osteolysis and scapular notching.
The average follow-up after surgery was 33.2 months (range 24 to 60 months). The mean absolute Constant score improved significantly (P = 10^-5) from 23.7 ± 11.5 preoperatively to 61.1 ± 11.9 postoperatively. Forward flexion and external rotation with the arm at the side improved significantly, respectively from 64.7 ± 35.6° preoperatively to 126 ± 34.4° postoperatively (P < 10^-5) and from −8.7 ± 21.3° to 27.3 ± 12.2° (P < 0.0005). Internal rotation was not affected. The mean SST improved from 1.9 ± 1.6 points preoperatively to 7.6 ± 1.8 points postoperatively (P < 0.0005). Twelve patients were very satisfied or satisfied (including one with a bilateral procedure) and 2 were unsatisfied with the final result. At final follow-up, radiographs showed no radiolucent lines around the implants nor scapular notching.
The combined procedure helped restoration of active elevation and external rotation in cases of massive cuff tear including the teres minor tendon.
Therapeutic Level IV.
The influence of superior labrum anterior to posterior (SLAP) repair on restoring baseline glenohumeral translation and increased biceps loading after simulated SLAP tear and the effectiveness of SLAP repair after long head of biceps tenotomy
2012, Journal of Shoulder and Elbow Surgery
Citation Excerpt :
Changes in the applied force in response to changes in length of the tendon with changes in joint orientation were minimized by this spring mechanism. The sensor-guided robotic testing setup, which has been well described,10,11,27 uses a 6-axis industrial robot (KR 15/1, KUKA GmbH, Augsburg, Germany) with force-moment closed-loop feedback control (FMS, IpeA GmbH, Berlin, Germany). The robotic device had a positional repeatability of 0.2 mm for translation and 0.2° for rotation.
Biomechanical studies have shown increased glenohumeral translation and loading of the long head biceps (LHB) tendon after superior labrum anterior to posterior (SLAP) tears. This may explain some of the typical clinical findings, including the prevalence of humeral chondral lesions, after SLAP lesions. The first hypothesis was that SLAP repair could restore the original glenohumeral translation and reduce the increased LHB load after SLAP lesions. The second hypothesis was that SLAP repair after LHB tenotomy could significantly reduce the increased glenohumeral translation.
Biomechanical testing was performed on 21 fresh frozen human cadaveric shoulders with an intact shoulder girdle using a sensor-guided industrial robot to apply 20 N of compression in the joint and 50 N translational force at 0°, 30°, and 60° of abduction. LHB loading was measured by a load-cell with 5 N and 25 N preload. Type IIC SLAP lesions were created arthroscopically, and a standardized SLAP repair was done combined with or without LHB tenotomy.
No significant difference of glenohumeral translation and increased LHB load in SLAP repair compared with the intact shoulder was observed under 5 N and 25 LHB preload, except for anterior translation under 25 N LHB preload. After LHB tenotomy after SLAP lesions, no significant difference of translation was observed with or without SLAP repair.
SLAP repair without associated LHB tenotomy helps normalize glenohumeral translation and LHB loading. The stabilizing effect of the SLAP complex is dependent on the LHB. After biceps tenotomy, SLAP repair does not affect glenohumeral translation.

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^☆: This study was funded by the German Research Foundation (DFG).

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Original articleEvaluation of the lag sign tests for external rotator function of the shoulder☆

Abstract

Section snippets

Specimen preparation and mounting

Results

Discussion

J Shoulder Elbow Surg

J Biomech

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Biomech

J Sci Med Sport

J Biomech

Handbuch der Anatomie und Mechanik der Gelenke unter Berücksichtigung der bewegenden Muskeln

Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan

Clin Orthop

Rotator cuff tear—relationship between clinical and anatomopathological findings

Arch Orthop Trauma Surg

Force analysis of rotator cuff muscles

Clin Orthop

Original article
Evaluation of the lag sign tests for external rotator function of the shoulder☆