Imaging of the Acromioclavicular Joint: Anatomy, Function, Pathologic Features, and Treatment.

The acromioclavicular joint is an important component of the shoulder girdle; it links the axial skeleton with the upper limb. This joint, a planar diarthrodial articulation between the clavicle and the acromion, contains a meniscus-like fibrous disk that is prone to degeneration. The acromioclavicular capsule and ligaments stabilize the joint in the horizontal direction, while the coracoclavicular ligament complex provides vertical stability. Dynamic stability is afforded by the deltoid and trapezius muscles during clavicular and scapular motion. The acromioclavicular joint is susceptible to a broad spectrum of pathologic entities, traumatic and degenerative disorders being the most common. Acromioclavicular joint injury typically affects young adult males and can be categorized by using the Rockwood classification system as one of six types on the basis of the direction and degree of osseous displacement seen on conventional radiographs. MRI enables the radiologist to more accurately assess the regional soft-tissue structures in the setting of high-grade acromioclavicular separation, helping to guide the surgeon's selection of the appropriate management. Involvement of the acromioclavicular joint and its stabilizing ligaments is also important for understanding and classifying distal clavicle fractures. Other pathologic processes encountered at this joint include degenerative disorders; overuse syndromes; and, less commonly, inflammatory arthritides, infection, metabolic disorders, and developmental malformations. Treatment options for acromioclavicular dysfunction include conservative measures, resection arthroplasty for recalcitrant symptoms, and surgical reconstruction techniques for stabilization after major trauma.

The relationship of the acromion to the distal clavicle in normal and symptomatic degenerated acromioclavicular joints.

INTRODUCTION: Although degenerative osteoarthritis of the acromioclavicular joint is a common finding on technical investigations, not every patient experiences pain or function loss. The difference between symptomatic and asymptomatic patients is currently not elucidated. Therefore, we want to investigate the acromioclavicular relationship in normal, asymptomatic, and symptomatic degenerated ACJ. MATERIALS AND METHODS: 84 normal ACJ, 39 asymptomatic degenerated ACJ, and 30 symptomatic degenerated ACJ were 3D reconstructed. The morphological dimensions and the relationship of the acromion and distal clavicle were measured using computational software. The reproducibility of this technique was evaluated using inter- and intra-observer reliability. RESULTS: The mean anteroposterior and superoinferior distance of both the clavicle and acromion was significantly larger in asymptomatic and symptomatic degenerative ACJ compared to the normal ACJ (p < 0.001). In symptomatic osteoarthritic ACJ, both the anterior and posterior borders of the acromion were significantly more anterior to the borders of the clavicle than in the normal group and asymptomatic group (p < 0.001). Subsequent ROC curve analysis resulted in a sensitivity of 86.7% and a specificity of 88.6% for anterior subluxation of the ACJ. This technique showed an excellent inter- and intra-observer reliability. CONCLUSIONS: In patients with degenerative ACJ, both the distal clavicle and acromion are enlarged. In asymptomatic patients, the AC relationship is the same as in normal patients, in contrast, in patients with symptomatic degenerative ACJ, the acromion is subluxated anteriorly compared to the clavicle.

Repair of the entire superior acromioclavicular ligament complex best restores posterior translation and rotational stability.

PURPOSE: The acromioclavicular ligament complex (ACLC) is the primary stabilizer against horizontal translation with the superior ACLC providing the main contribution. The purpose of this study was to evaluate the specific regional contributions in the superior half of ACLC, where the surgeon can easily access and repair or reconstruct, for posterior translational and rotational stability. METHODS: The superior half of ACLC was divided into three regions; Region A (0°-60°): an anterior 1/3 region of the superior half of ACLC, Region B (60°-120°): a superior 1/3 region of the superior half of ACLC, and Region C (120°-180°): a posterior 1/3 region of the superior half of ACLC. Fifteen fresh-frozen cadaveric shoulders were used. Biomechanical testing was performed to evaluate the resistance force against passive posterior translation (10 mm) and the resistance torque against passive posterior rotation (20°) during the following the four conditions. (1) Stability was tested on all specimens in their intact condition (n = 15). (2) The ACLC was dissected and stability was tested (n = 15). (3) Specimens were randomly divided into three groups by regions of suturing. Stability was tested after suturing Region A, Region B, or Region C (n = 5 per group). (4) Stability was tested after suturing additional regions: Region A + B (0°-120°), Region B + C (60°-180°), or Region A + C (0°-60°, 120°-180°, n = 5 per group). RESULTS: The translational force increased after suturing Region A when compared with dissected ACLC (P = 0.025). The force after suturing Region A + B was significantly higher compared to the dissected ACLC (P < 0.001). The rotational torque increased after suturing Region A or Region B compared with dissected ACLC (P = 0.020, P = 0.045, respectively). The torque after suturing the Region A + C was significantly higher compared to the dissected ACLC (P < 0.001). CONCLUSION: The combined Region A + B contributed more to posterior translational stability than Region B + C or Region A + C. In contrast, combined Region A + C contributed more to posterior rotational stability than Region A + B or Region B + C. Based on these findings, surgical techniques restoring the entire superior ACLC are recommended to address both posterior translational and rotational stability of the AC joint.

Biomechanical comparison of two biplanar and one monoplanar reconstruction techniques of the acromioclavicular joint.

INTRODUCTION: The purpose of this proof-of-concept study was to investigate the biomechanical performance of two surgical techniques, namely (1) the double Tight-Rope fixation with an additional acromioclavicular FiberTape fixation (DTRC) and (2) the fixation of the clavicle to the acromion and coracoid in a bipodal manner (Bipod) using a Poly-Tape and FiberTape. Both techniques intend to address vertical and horizontal instability after acromioclavicular dislocation. They were compared with the commonly used (3) double Tight-Rope (DTR) technique, which only stabilizes the clavicle to the coracoid. MATERIALS AND METHODS: The acromioclavicular joint (ACJ) of 18 composite Sawbone shoulder specimens (6 per reconstruction group) were tested for posterosuperior elongation (70N cyclical load, 1500 cycles), load-to-failure and stiffness. RESULTS: After 1500 cycles, the DTRC, Bipod and DTR group showed an elongation of 0.45 mm (SD 0.14 mm), 1.19 mm (SD 0.54 mm), and 0.46 mm (SD 0.15 mm), respectively. Although the elongation of the Bipod group was increased when compared to the other two groups (Bipod versus DTRC p = 0.008; Bipod versus DTR p = 0.006), the difference was less than 0.7 mm. The DTRC showed a higher load-to-failure of 656.1N (SD 58.1 N) compared to the Bipod [531.1 N (SD 108.2N) (p = 0.039)] and DTR group [522.8 N (SD 32.8 N) (p = 0.033)]. CONCLUSION: The DTRC and the DTR group resulted in similar low elongation, while the elongation in the Bipod technique was slightly higher. Even though this difference of 0.7 mm shows statistical significance, it most likely has no clinical relevance. When testing in posterosuperior direction, which is the clinically relevant load vector, an additional fixation of the clavicle to the acromion did not reduce elongation in this study. It is, furthermore, questionable if the benefit of an increased load-to-failure in combination with no improvement in elongation and stiffness as seen in the DTRC group outweighs the possible risks and increased costs coming with the DTRC refixation.

Effects of 3 Different Elastic Therapeutic Taping Methods on the Subacromial Joint Space.

OBJECTIVE: The purpose of this study was to examine the effects of 3 different elastic therapeutic taping methods on the subacromial joint space in healthy adults. METHODS: Pre-/post-test laboratory study method was used in this study. Forty-eight healthy adults with no prior history of shoulder injury or surgery and no history of dominant shoulder pain in the past 6 months were enrolled in the study. Participants were placed into 3 groups (8 males and 8 females per group) on the basis of a consecutively assigned allocation design. A baseline measurement of the acromiohumeral distance (AHD) was taken by using diagnostic ultrasonography for every participant. On the basis of group assignment, participants were then taped according to the Kinesio Tape (Kinesio Tex Classic Tape) guidelines in one of 3 conditions: (1) taping of the supraspinatus from insertion to origin; (2) taping of the anterior and posterior deltoids from insertion to origin; and (3) a combination of both techniques. After a 5-minute wait period, the AHD was remeasured with the tape intervention in place, with each participant serving as his or her own control. RESULTS: Data analysis showed a statistically significant increase in AHD when using the taping technique over the anterior and posterior deltoids (Condition 2). The subacromial space increased in both males and females when the supraspinatus was taped from insertion to origin (Condition 1), but not at a statistically significant level. Condition 3, in which both taping techniques were used simultaneously, did not show an increase at a statistically significant level. CONCLUSIONS: The application of the Kinesio Tape from insertion to muscle origin of the supraspinatus or the anterior and posterior deltoid increased the subacromial joint space.

Ultrasound of the coracoacromial ligament in asymptomatic volunteers and patients with shoulder impingement.

BACKGROUND: The coracoacromial ligament is part of the coracoacromial arch, which is considered to be involved in shoulder impingement. PURPOSE: To compare the coracoacromial ligament on ultrasound in asymptomatic volunteers and in patients with subacromial shoulder impingement. MATERIAL AND METHODS: Twenty-nine asymptomatic volunteers (mean age, 35.5 years) and 29 patients (mean age, 49.9 years) with shoulder impingement, diagnosed by experienced shoulder surgeons, were prospectively included. Two radiologists obtained and analyzed ultrasound images of the coracoacromial ligament in the longitudinal axis. RESULTS: The ligament thickness was 1.4 ± 0.2 mm at its midportion, 1.8 ± 0.4 mm at the coracoid, and 2.1 ± 0.6 mm at the acromion in asymptomatic volunteers compared with 1.3 ± 0.2 mm, 1.9 ± 0.5 mm, and 1.9 ± 0.5 mm in impingement patients for observer 1. The ligament length was 30.6 ± 2.4 mm in asymptomatic volunteers compared with 30.4 ± 3.6 mm in impingement patients for observer 1. An anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers for both observers (observer 1: 10% (3/29) versus 45% (13/29), P value <0.01; observer 2: 10% (3/29) versus 38% (11/29), P value <0.03). The comparison of the remaining parameters of the coracoacromial ligament, such as the thickness, length, echogenicity, and fibrillation did not reveal significant differences between volunteers and patients. CONCLUSION: While thickness or length of the coracoacromial ligament were similar in volunteers and patients with shoulder impingement, an anteriorly convex shape of the superficial contour of the coracoacromial ligament was significantly more frequent in impingement patients compared with asymptomatic volunteers.

The biomechanical influence of the deltotrapezoid fascia on horizontal and vertical acromioclavicular joint stability.

INTRODUCTION: Many studies have investigated the biomechanical influence of the acromioclavicular (AC) and coracoclavicular (CC) ligaments on the stability of the acromioclavicular joint (ACJ). It has been shown that augmentation of the CC ligaments alone can result in residual horizontal instability. Our hypothesis was that the DTF would have a significant stabilizing effect on horizontal ACJ stability. MATERIALS AND METHODS: In a biomechanical in vitro study a sequential injury of the ACJ was created on eight shoulders from full body, which were placed in an upright sitting position. The translation and rotation of the clavicle were measured in relation to the acromion using an optical navigation system in various states during thoracic-humeral elevation, abduction, and horizontal adduction. The three states were: an intact shoulder, complete sectioning of the AC ligaments, and a circular lesion of the DTF. RESULTS: Compared to the intact state we found a significant increase in anterior rotation of the clavicle of 1.11° (p = 0.012) and a tendency in lateral translation of 2.71 mm (p = 0.017) in relation to the acromion, with a combined lesion of AC ligaments and DTF. No significant differences were found between the intact state and the isolated dissected AC ligaments as well in adduction as elevation. CONCLUSION: A combined lesion of the AC ligaments and the DTF resulted in a quantitatively small but significant increase in anterior rotation and a tendency in lateral translation of the clavicle in relation to the acromion. These differences were quantitatively small, so that the clinical relevance of the stabilization effect of combined AC ligaments and DTF injuries is questionable.

Transarticular fixation by hook plate versus coracoclavicular stabilization by single multistrand titanium cable for acute Rockwood grade-V acromioclavicular joint dislocation: a case-control study.

BACKGROUND: Hook plate (HP) is popularly used for acute and severely displaced acromioclavicular (AC) dislocations. However, subacromial impingement and acromion osteolysis induced by transarticular fixation are notorious. The current case-control study was to compare transarticular fixation by HP to coracoclavicular (CC) stabilization by single multistrand titanium cable (MSTC). METHODS: Between January 2006 and August 2009, 24 patients with acute AC dislocations were surgically treated by open reduction and transarticular fixation with HP. These patients were matched to a series of 24 patients, who were managed by CC stabilization with MSTC in the same period. All AC dislocations were graded as Rockwood type V. Implant was removed 8-12 months after the primary operation in all patients, and 12 months at least were needed to assess the maintenance of AC joint. Functional results were evaluated before implant removal as well as in the last follow-up based on Constant-Murley criteria. RESULTS: There were no differences of demographic data including age, dominant gender and side, injury-to-surgery interval, operation time and follow-up period. In terms of functionality, Constant score was 95.8 ± 4.1 in MSTC group, while 76.7 ± 8.0 in HP group before implant removal (P < 0.001). In detail, MSTC was superior to HP in pain, ROM and activities. Constant score was significantly improved to 86.1 ± 5.7 after hardware removal for patients in HP (P < 0.001). Degenerative change of acromioclavicular joint presented in 16 patients (66.7%) in patients treated by HP, while it was found in only 3 patients (12.5%) treated by MSTC (P < 0.001). CONCLUSIONS: MSTC is superior to HP for the treatment of Rockwood type-V acromioclavicular dislocation both before and after removal of the implant. Hardware removal is of great benefits for functional improvement in patients treated by HP.

Acromioclavicular joint ligamentous system contributing to clavicular strut function: a cadaveric study.

HYPOTHESIS: We hypothesized that the clavicle overrides the acromion during certain shoulder motions for individuals with acromioclavicular (AC) joint separation producing clinical symptoms. We measured 3-dimensional clavicular and scapular motions in AC joint separation models during humerothoracic motions, which should be impacted by the loss of AC joint continuity. MATERIALS AND METHODS: Ten shoulders from 6 whole cadavers were used. The scapular and clavicular motions were measured in intact and AC joint separation models using an electromagnetic tracking device. The measurement was performed during shoulder abduction with humerothoracic neutral rotation. It was also measured during shoulder abduction with humerothoracic internal rotation, which could cause clavicular overriding. The kinematic changes caused by ligament sectioning were evaluated in these 2 arm motions. RESULTS: The clavicle completely overrode the acromion in all AC separation models during abduction with internal rotation, but not in any shoulders during abduction with neutral rotation. Upward clavicular rotation increased, posterior clavicular rotation decreased, and external scapular rotation decreased with ligament sectioning. These kinematic changes were common for both of the measured arm motions. Scapular upward rotation and posterior tilt did not change because of ligament sectioning during abduction with neutral rotation. However, these scapular rotations significantly decreased with ligament sectioning during shoulder abduction with internal rotation. CONCLUSION: Scapular and clavicular kinematics were affected in AC separation models. Abduction with humeral internal rotation resulted in a decrease in scapular posterior tilt and upward rotation in AC separation models, and thereby could lead to AC joint articulation dysfunction.

Arthroscopically assisted stabilization of acute high-grade acromioclavicular joint separations in a coracoclavicular Double-TightRope technique: V-shaped versus parallel drill hole orientation.

BACKGROUND: The arthroscopically assisted Double-TightRope technique has recently been reported to yield good to excellent clinical results in the treatment of acute, high-grade acromioclavicular dislocation. However, the orientation of the transclavicular-transcoracoidal drill holes remains a matter of debate. HYPOTHESIS: A V-shaped drill hole orientation leads to better clinical and radiologic results and provides a higher vertical and horizontal stability compared to parallel drill hole placement. STUDY DESIGN: This was a cohort study; level of evidence, 2b. METHODS: Two groups of patients with acute high-grade acromioclavicular joint instability (Rockwood type V) were included in this prospective, non-randomized cohort study. 15 patients (1 female/14 male) with a mean age of 37.7 (18-66) years were treated with a Double-TightRope technique using a V-shaped orientation of the drill holes (group 1). 13 patients (1 female/12 male) with a mean age of 40.9 (21-59) years were treated with a Double-TightRope technique with a parallel drill hole placement (group 2). After 2 years, the final evaluation consisted of a complete physical examination of both shoulders, evaluation of the Subjective Shoulder Value (SSV), Constant Score (CS), Taft Score (TF) and Acromioclavicular Joint Instability Score (ACJI) as well as a radiologic examination including bilateral anteroposterior stress views and bilateral Alexander views. RESULTS: After a mean follow-up of 2 years, all patients were free of shoulder pain at rest and during daily activities. Range of motion did not differ significantly between both groups (p > 0.05). Patients in group 1 reached on average 92.4 points in the CS, 96.2 % in the SSV, 10.5 points in the TF and 75.9 points in the ACJI. Patients in group 2 scored 90.5 points in the CS, 93.9 % in the SSV, 10.5 points in the TF and 84.5 points in the ACJI (p > 0.05). Radiographically, the coracoclavicular distance was found to be 13.9 mm (group 1) and 13.4 mm (group 2) on the affected side and 9.3 mm (group 1) and 9.4 mm (group 2) on the contralateral side. The distance of neither the affected side nor the contralateral side differed significantly between both groups (p > 0.05). In group 1, eight patients (53 %) and in group 2 four patients (31 %) revealed signs of dynamic posterior instability (p > 0.05). Clavicular drill hole enlargement was found to be equally distributed in group 1, whereas group 2 displayed a cone-shaped form. CONCLUSION: The Double-TightRope technique yields good to excellent clinical results in both V-shaped and parallel drill hole placement. Partial recurrent vertical and horizontal instability represents a problem in both techniques. So far, no significant differences regarding clinical or radiologic results have been found. Long-term results are needed to reveal possible advantages in terms of clinical and radiologic acromioclavicular stability.

The new 4-dimensional computed tomographic scanner allows dynamic visualization and measurement of normal acromioclavicular joint motion in an unloaded and loaded condition.

OBJECTIVE: Using 4-dimensional computed tomographic scanner to determine the motion pattern of the acromioclavicular (AC) joint during adduction of the arm, with and without resisted superior elevation. METHODS: Sixteen healthy volunteers (5 women and 11 men; mean ± SD age, 42 ± 11 years). Four different motions were measured: AC joint width, anteroposterior translation, superoinferior translation, and opening of the superior aspect of the joint. Measurements between arm positions of neutral, adduction, and loaded were compared. RESULTS: Predominant movement is posterior translation (1.1 ± 0.9 mm, P = 0.001); in the coronal plane, superior translation of the clavicle (0.6 ± 0.5 mm, P = 0.001) and some opening of the superior joint space. Changes in the AC joint width and anteroposterior translation were significantly related to age (P = 0.016 and P = 0.006). CONCLUSIONS: Four-dimensional computed tomographic scans record the motion pattern of an asymptomatic AC joint and demonstrated that in adduction plus resisted elevation of the arm, the main movement of the AC joint is posterior and superior translation of the clavicle.

Acromioclavicular motion after surgical reconstruction.

PURPOSE: A retrospective long-term study was carried out to determine whether there was any correlation between the clinical motion of the acromioclavicular joint evaluated by a test we set up using 90° of abduction and 0° of external rotation against resistance [90°/0°RTest] and the cross arm test (compared to the healthy side) and full return to everyday activities after surgical repair. METHODS: A clinical and radiographic evaluation was carried out on 51/80 subjects at a 5.4-year mean follow-up, treated for acromioclavicular joint dislocation with an extra-articular artificial loop, between 2000 and 2006. RESULTS: The 25 subjects with ossifications obtained a normal acromioclavicular joint motion, on both the horizontal and vertical planes. There was a correlation between the normal motion of the reconstructed acromioclavicular joint (compared to the healthy side) in these 25 patients and full clinical recovery, whilst there was no correlation between the Constant score, the simple shoulder test, the radiographic evaluation on one hand and the clinical motion of the joint on the other. Two patients had recurrent dislocation. Three had mobilization of the screws without reduction loss, or negative clinical outcome. CONCLUSIONS: A postoperative radiographic evaluation should be correlated with a clinical evaluation of the acromioclavicular joint motion (normal, hypermobile, unstable). Normal acromioclavicular joint motion was observed in subjects who developed significant ossifications. The study shows that the clinical evaluation of acromioclavicular joint motion is a simple and trustworthy method to assess the clinical result of a surgical repair. LEVEL OF EVIDENCE: Diagnostic study investigating a diagnostic test, Level III.

Measure of horizontal and vertical displacement of the acromioclavicular joint after cutting ligament using X-ray and opto-electronic system.

INTRODUCTION: Surgical versus orthopedic treatments of acromioclavicular disjunction are still debated. The aim of this study was to measure horizontal and vertical acromion's displacement after cutting the ligament using standard X-ray and an opto-electronic system on cadaver. MATERIALS AND METHODS: Ten cadaveric shoulders were studied. A sequential ligament's section was operated by arthroscopy. The sequence of cutting was chosen to fit with Rockwood's grade. The displacement of the acromion was measured on standard X-ray and with an opto-electronic system allowing measuring of the horizontal displacement. Statistical comparisons were performed using a paired Student's t test with significance set at p < 0.05. RESULTS: Cutting the coracoclavicular ligament and delto-trapezius muscles cause a statistical downer displacement of the acromion, but not after sectioning the acromioclavicular ligament. The contact surface between the acromion and the clavicle decreases statistically after sectioning the acromioclavicular ligament and the coracoclavicular ligament with no effect of sectioning the delto-trapezius muscles. Those results are superposing with those dealing with the anterior translation. DISCUSSION: The measure concerning the acromioclavicular distance and the coracoclavicular distance are superposing with those of Rockwood. However, there is a significant horizontal translation after cutting the acromioclavicular ligament. Taking into account this displacement, it may be interesting to choose either surgical or orthopedic treatment. CONCLUSION: There is a correlation between anatomical damage and importance of instability. Horizontal instability is misevaluated in clinical practice.

The Coupled Kinematics of Scapulothoracic Upward Rotation.

BACKGROUND: Scapulothoracic upward rotation (UR) is an important shoulder complex motion allowing for a larger functional work space and improved glenohumeral muscle function. However, the kinematic mechanisms producing scapulothoracic UR remain unclear, limiting the understanding of normal and abnormal shoulder movements. OBJECTIVE: The objective of this study was to identify the coupling relationships through which sternoclavicular and acromioclavicular joint motions contribute to scapulothoracic UR. DESIGN: This was a cross-sectional observational study. METHODS: Sixty participants were enrolled in this study; 30 had current shoulder pain, and 30 had no history of shoulder symptoms. Shoulder complex kinematics were quantified using single-plane fluoroscopy and 2D/3D shape matching and were described as finite helical displacements for 30-degree phases of humerothoracic elevation (30 degrees-60 degrees, 60 degrees-90 degrees, and 90 degrees-120 degrees). A coupling function was derived to estimate scapulothoracic UR from its component motions of acromioclavicular UR, sternoclavicular posterior rotation, and sternoclavicular elevation as a function of acromioclavicular internal rotation. The proportional contributions of each of the component motions were also calculated and compared between phases of humerothoracic elevation and groups. RESULTS: Scapulothoracic UR displacement could be effectively predicted using the derived coupling function. During the 30- to 60-degree humerothoracic elevation phase, acromioclavicular UR accounted for 84.2% of scapulothoracic UR, whereas sternoclavicular posterior rotation and elevation each accounted for < 10%. During later phases, acromioclavicular UR and sternoclavicular posterior rotation each accounted for 32% to 42%, whereas sternoclavicular elevation accounted for < 11%. LIMITATIONS: Error due to the tracking of sternoclavicular posterior rotation may have resulted in an underprediction of its proportional contribution and an overprediction of the proportional contribution of acromioclavicular UR. CONCLUSIONS: Acromioclavicular UR and sternoclavicular posterior rotation are the predominant component motions of scapulothoracic UR. More research is needed to investigate how these coupling relationships are affected by muscle function and influenced by scapular dyskinesis.

Release of growth factors after arthroscopic acromioplasty.

It has recently been postulated that a variety of growth factors may be released from cancellous bone after an acromioplasty. The aim of this study was to demonstrate the presence of growth factors in the subacromial space after acromioplasty. Between October 2006 and March 2007, 23 patients underwent arthroscopic acromioplasty. A sample of at least 3 ml of fluid from the shoulder was obtained 15 min after the end of the procedure. At the same time another sample of 3 ml of the patient's venous blood was obtained as a control. The concentrations of growth factors in the fluids collected were determined using enzyme-linked immunosorbent assay (ELISA). The growth factors assayed were platelet-derived growth factor-AB (PDGF-AB), basic fibroblast growth factor basic (bFGF) and transforming growth factor beta 1 (TGF-beta1). The concentrations of TGF-beta1 (p = 0.0001), PDGF-AB (p = 0.02), and bFGF (p < 0.0001) were significantly higher in the fluid from the subacromial space than in the blood sample. There are high concentrations of several growth factors in the subacromial space after acromioplasty.

Relative contribution of acromioclavicular joint capsule and coracoclavicular ligaments to acromioclavicular stability.

HYPOTHESIS: We hypothesized that both the AC joint capsule and CC ligaments are biomechanically robust structures in the anterior-posterior (AP) and superior-inferior (SI) planes with low loads, and that these ligaments provide essential function in AC joint stability. MATERIALS AND METHODS: Anterior-posterior (AP) and superior-inferior (SI) AC joint translations were quantified in 6 cadaver matched pairs with AC joint compressions of 10N, 20N and 30N, and with translational loads of 10N and 15N. Either the AC joint capsule or CC ligaments were transected, and measurements were then repeated. Biomechanical characteristics of the remaining AC joint capsule or CC ligaments were compared. RESULTS: There were significant increases in AP translation with the cut AC joint capsule, and significant increases in SI translation with the cut CC ligaments (P < 0.0001). Compression significantly decreased translation (P < 0.0001). DISCUSSION: Our study is supported by, and further develops, recent studies and anatomical knowledge. It offers two interpreted pieces of information for the sports medicine physician to consider for reconstruction of the AC joint. First, resection of the distal clavicle may have a detrimental effect. Second, repair of the AC joint capsule, in addition to the customarily repaired CC ligaments, appears to have a beneficial effect. CONCLUSION: The AC joint capsule is a robust anatomical structure that contributes significantly to the AC joint stability, especially in the AP plane. Compression increases stability. LEVEL OF EVIDENCE: Basic science study.

Structural changes in the acromioclavicular joint measured by ultrasonography during provocative tests.

The acromioclavicular joint (ACJ) is a common source of pain and disability. Several provocative tests are used to diagnose ACJ lesions. The aim of this study was to evaluate anatomic changes of the ACJ using dynamic ultrasonography during provocative tests. Eighty ACJs of 40 healthy volunteers were subjected to dynamic ultrasonographic examinations. Examinations were performed in a resting position and during passive external rotation, cross body adduction, and active compression testing. Deep joint space distance and capsule displacement were measured ultrasonographically. Mean deep joint space distances during cross body adduction (6.4 +/- 1.6 mm) and active compression (6.6 +/- 1.8 mm) testing were significantly smaller than during passive external rotation testing (7.7 +/- 1.7 mm, P < 0.01) or rest (8.1 +/- 1.8 mm, P < 0.01). Mean capsule displacements during active compression (3.5 +/- 0.8 mm) and cross body adduction (3.4 +/- 0.7 mm) testing were significantly greater than those during passive external rotation testing (2.9 +/- 0.7 mm, P < 0.01) or rest (2.5 +/- 0.7 mm, P < 0.01). Dynamic ultrasonography revealed that the cross body adduction and active compression tests applied more stress to the ACJ than the passive external rotation test, which suggests that these two tests are likely to be more useful provocative tests for the diagnosis of ACJ lesions. Furthermore, the dynamic properties of ultrasonography could be used to estimate the suitability and validity of provocative tests in other musculoskeletal diseases.

Geometric Morphology of the Coracoacromial Ligament: A Cadaveric Study.

The coracoacromial ligament (CAL), which restrains superior displacement of humeral head, connects the acromion and coracoid process. Due to the ligament's variations and its role in shoulder pain, CAL was investigated in this study. Sixty shoulders of 34 cadavers, from persons aged 61-98 (80.95 ± 8.81) years at death time, were dissected. The lengths of lateral (LBL) and medial borders (MBL), widths of acromial (AIW) and coracoid insertions (CIW), and thicknesses of lateral (LSTAI) and medial (MSTAI) sides of acromial insertions were measured by digital caliper. The data were subjected to statistical analysis. 24 (40%) V-shaped, 12 (20%) broad-banded, 9 (15%) quadrangular, 9 (15%) Y-shaped, and 6 (10%) multiple-banded types were identified. The mean total LBL, MBL, AIW, CIW, LSTAI, and MSTAI were 34.94 ± 4.59 mm, 33.58 ± 5.31 mm, 29.82 ± 9.48 mm, 12.62 ± 3.95 mm, 1.29 ± 0.17 mm, and 0.90 ± 0.22 mm, respectively. The mean LBL (39.12 ± 4.29 mm), MBL (36.48 ± 3.9 mm), and CIW (37.01 ± 3.39 mm) were significantly greatest in quadrangular type (p<0.001). The mean AIW was slightly greatest in quadrangular type (p=0.069). The mean LSTAI was significantly greatest in multiple-banded type (1.45 ± 0.10 mm, p<0.001) whereas the mean MSTAI was significantly greatest in quadrangular type (1.23 ± 0.23 mm, p<0.001). CAL is quite variable regarding morphology, dimensions, and insertion features. Despite common knowledge, MSTAI and MBL of CAL can be greater than lateral counterparts in some types. To obtain complete release of CAL at acromion, the clearance of ligament fibers in an area with the dimensions of around 16 mm in mediolateral and 15 mm in anteroposterior direction, beginning from the lateral edge of acromial insertion, is recommended.

Complete 3D kinematics of upper extremity functional tasks.

Upper extremity (UX) movement analysis by means of 3D kinematics has the potential to become an important clinical evaluation method. However, no standardized protocol for clinical application has yet been developed, that includes the whole upper limb. Standardization problems include the lack of a single representative function, the wide range of motion of joints and the complexity of the anatomical structures. A useful protocol would focus on the functional status of the arm and particularly the orientation of the hand. The aim of this work was to develop a standardized measurement method for unconstrained movement analysis of the UX that includes hand orientation, for a set of functional tasks for the UX and obtain normative values. Ten healthy subjects performed four representative activities of daily living (ADL). In addition, six standard active range of motion (ROM) tasks were executed. Joint angles of the wrist, elbow, shoulder and scapula were analyzed throughout each ADL task and minimum/maximum angles were determined from the ROM tasks. Characteristic trajectories were found for the ADL tasks, standard deviations were generally small and ROM results were consistent with the literature. The results of this study could form the normative basis for the development of a 'UX analysis report' equivalent to the 'gait analysis report' and would allow for future comparisons with pediatric and/or pathologic movement patterns.

Injuries to the acromioclavicular joint.

Injuries to the acromioclavicular joint are common but underdiagnosed. Sprains and minor subluxations are best managed conservatively, but there is debate concerning the treatment of complete dislocations and the more complex combined injuries in which other elements of the shoulder girdle are damaged. Confusion has been caused by existing systems for classification of these injuries, the plethora of available operative techniques and the lack of well-designed clinical trials comparing alternative methods of management. Recent advances in arthroscopic surgery have produced an even greater variety of surgical options for which, as yet, there are no objective data on outcome of high quality. We review the current concepts of the treatment of these injuries.