Acromioclavicular joint injuries and, more specifically, separations are commonplace both in general practice and during athletic participation. This article reviews the traditional classification as well as the clinical evaluation of patients with acute and chronic acromioclavicular joint separations. It also highlights many recent advances, principally in the anatomy and biomechanics of the acromioclavicular joint ligamentous complex. The concept of increases in superior translation as well as disturbances in horizontal translation with injuries to this joint and ligaments are discussed. This information, coupled with the unpredictable long-term results with the Weaver-Dunn procedure and its modifications, have prompted many recent biomechanical studies evaluating potential improvements in the surgical management of acute and chronic injuries. The authors present these recent works investigating cyclic loading and ultimate failure of traditional reconstructions, augmentations, use of free graft, and the more recent anatomic reconstruction of the conoid and trapezoid ligaments. The clinical results (largely retrospective), including acromioclavicular joint repair, reconstruction and augmentation with the coracoclavicular ligament, supplemental sutures, and the use of free autogenous grafts, are summarized. Finally, complications and the concept of the failed distal clavicle resection and reconstruction are addressed. The intent is to provide a current, in-depth treatise on all aspects of acromioclavicular joint complex injuries to include anatomy, biomechanics, benchmark studies on instability and reconstruction, clinical and radiographic evaluation, and to present the most recent clinical research on surgical outcomes.

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Evaluation and Treatment of Acromioclavicular Joint Injuries

BackgroundStrengthening exercises for the scapular muscles are used in the treatment of scapulothoracic dysfunction related to shoulder injury. In view of the intermuscular and intramuscular imbalances often established in these patients, exercises promoting lower trapezius (LT), middle trapezius (MT), and serratus anterior (SA) activation with minimal activity in the upper trapezius (UT) are recommended.HypothesisOf 12 commonly used trapezius strengthening exercises, a selection can be performed for muscle balance rehabilitation, based on a low UT/LT, UT/MT, or UT/SA muscle ratio.Study DesignControlled laboratory study.MethodsElectromyographic activity of the 3 trapezius parts and the SA was measured in 45 healthy subjects performing 12 commonly described scapular exercises, using surface electromyography.ResultsFor each intramuscular trapezius ratio (UT/LT, UT/MT), 3 exercises were selected for restoration of muscle balance. The exercises side-lying external rotation, side-lying forward flexion, prone h...

https://journals.sagepub.com/doi/pdf/10.1177/0363546507303560

Rehabilitation of Scapular Muscle Balance Which Exercises to Prescribe

BackgroundDespite numerous surgical techniques described, there have been few studies evaluating the biomechanical performance of acromioclavicular joint reconstructions.PurposeTo compare a newly developed anatomical coracoclavicular ligament reconstruction with a modified Weaver-Dunn procedure and a recently described arthroscopic method using ultrastrong nonabsorbable suture material.Study DesignControlled laboratory study.MethodsForty-two fresh-frozen cadaveric shoulders (72.8 ± 13.4 years) were randomly assigned to 3 groups: arthroscopic reconstruction, anatomical coracoclavicular reconstruction, and a modified Weaver-Dunn procedure. Bone mineral density was obtained on all specimens. Specimens were tested to 70 N in 3 directions, anterior, posterior, and superior, comparing the intact to the reconstructed states. Superior cyclic loading at 70 N for 3000 cycles was then performed at a rate of 1 Hz, followed by a load to failure test (120 mm/min) to simulate physiologic states at the acromioclavicular ...

A Biomechanical Evaluation of an Anatomical Coracoclavicular Ligament Reconstruction

A study of 5 fresh cadaveric shoulders demonstrated that an oblique-sagittal plane which crosses the scapula through the medial border of the coracoid process offers a view of the supraspinatus fossa mostly limited by bone.This view could easily be reproduced by MRI and we called it the Y-shaped view. It allowed a reliable measurement of supraspinatus muscle atrophy by the calculation of the occupation ratio (R) which is the ratio between the surface of the cross-section of the muscle belly and that of the fossa.This ratio was calculated in a prospective study based on 55 shoulders divided into 3 groups with different rotator cuff status: group I, 15 controls; group II, 10 degenerative cuffs, without tears; group III, 30 operated tears. There was no difference between groups I (mean ratio 0.7) and II (mean ratio 0.62), but the ratio was decreased in group III (mean ratio 0.44), in which the extent of the tear in both the sagittal and coronal planes aggravated the muscle atrophy. We propose a three-stage c...

https://www.tandfonline.com/doi/pdf/10.3109/17453679608994685

Atrophy of the supraspinatus belly. Assessment by MRI in 55 patients with rotator cuff pathology.

BackgroundSerratus anterior strengthening is used in prevention and treatment programs for poor scapular control. In certain clinical cases, exercises substantially activating the serratus with minimal upper trapezius activation are preferred.HypothesisThe standard push-up plus would show both the highest serratus anterior activation and lowest upper trapezius/ serratus ratios for both groups and all phases.Study DesignControlled laboratory study.MethodsThirty subjects, grouped as healthy or with mild shoulder dysfunction, were evaluated performing standard push-up plus exercises and modifications on elbows, knees, and against a wall. Surface electromyography of the serratus anterior and upper trapezius was compared between exercises.ResultsBoth groups responded similarly across exercises. The standard push-up plus demonstrated the highest activation of the serratus (to 123%) and lowest trapezius/serratus ratios (< 0.2) during plus phases. The wall push-up plus and phases of other exercises demonstrated h...

Relative Balance of Serratus Anterior and Upper Trapezius Muscle Activity During Push-Up Exercises

Forty-four patients, ranging in age from 17 to 57 years (average, 32), were evaluated an average of 4 years (range, 2 to 9) after surgical reconstruction for Allman- Tossy Grade III acromioclavicular dislocations. Twenty- seven patients underwent repair for acute injuries ( 3 weeks). Coracocla vicular fixation with heavy nonabsorbable sutures was used to correct superior displacement in all cases. In addition, transfer of the coracoacromial ligament to the distal clavicle was performed in 15 of the 27 early re pairs and 17 of the 17 late reconstructions. Overall, 26 of 27 (96%) early repairs and 13 of 17 (77%) late re constructions achieved satisfactory results. There was a trend for better results and return to sports or heavy labor with early repairs; however, this was not statisti cally significant (P = 0.065). When the results of early repairs were compared with those of late reconstruc tions performed more than 3 ...

Surgical Treatment of Complete Acromioclavicular Dislocations

The course of the suprascapular nerve and its distance from fixed scapular landmarks were measured in 90 cadaveric shoulders. In an additional 15 cadavers, three pins were passed at various angles in a general anterior-posterior direction through the middle of the glenoid neck just inferior and lateral to the base of the coracoid process. The distance between the exit site on the posterior glenoid neck and the suprascapular nerve at the base of the scapular spine was recorded for each pin. Inferiorly directed pins were the furthest from the suprascapular nerve and averaged 16 mm. On the basis of these data, a relative safe zone is described in the posterior glenoid neck. Knowledge of the anatomic course of the suprascapular nerve may aid the physician in the diagnosis and treatment of suprascapular neuropathies. Appreciation of the safe zone may help the shoulder surgeon avoid iatrogenic injury to the suprascapular nerve during arthroscopic Bankart procedures and other open surgical procedures requiring dissection of the posterior glenoid neck.

An anatomical study of the suprascapular nerve

The role of shoulder muscles during passive, active, and resistive phases of shoulder rehabilitation exercises was investigated in ten normal subjects with no history of shoulder pathology. Using the scapular plane as a reference, three-dimensional motion of the shoulder was recorded with a computer-aided motion analysis system (VICON) to determine total shoulder elevation. Simultaneously, electromyographic data were acquired on nine shoulder muscles while performing the three phases of shoulder rehabilitation exercises as described by Neer. Fine wire intramuscular electrodes were placed in the following muscles: trapezius, serratus anterior, deltoid (anterior, middle, and posterior separately), supraspinatus, infraspinatus, biceps, and latissimus dorsi. Phase I (passive) exercises performed in the supine position showed the least electromyography (EMG) activity. There was a gradation of EMG activity as one progressed from Phase I (passive) to Phase II (active) to Phase III (resistive) shoulder exercises. Isometric exercises and Phase III resistive exercises showed high levels of activity in the rotator cuff and deltoid muscles. Supine Phase I exercises should be considered in the early postoperative period after shoulder surgery to achieve maximum motion while minimizing shoulder muscle activity. Progression to Phase II and Phase III exercises may proceed as soft tissue and bony healing permit. Phase III exercises performed with an elastic band should provide a satisfactory method to strengthen these muscles.

A kinematic and electromyographic study of shoulder rehabilitation exercises.

Fourteen patients with a posterior-stabilized prosthesis in one knee and a posterior cruciate-retaining prosthesis in the contralateral knee and both scoring good or excellent on the Hospital for Special Surgery (HSS) knee scale were evaluated by isokinetic muscle testing and comprehensive gait analysis at a mean follow-up of 98 months after arthroplasty. The average HSS knee score (93 points) and the average Knee Society score (94 points) were the same for the cruciate-retaining and posterior-stabilized knees. No differences were noted between the cruciate-retaining and the posterior stabilized knees with respect to isokinetic muscle testing parameters (peak torque, endurance, angle of peak torque, and torque acceleration energy) for both quadriceps and hamstrings. No significant differences were found between the cruciate-retaining and the posterior-stabilized knees with regard to gait parameters, knee range of motion, and electromyographic waveforms during level walking and stair climbing. Cruciate-retaining and posterior-stabilized total knee prostheses perform equally well during level gait and stair climbing.

A comparison of isokinetic strength testing and gait analysis in patients with posterior cruciate-retaining and substituting knee arthroplasties

Twenty-three tennis players with a symptomatic full-thickness rotator cuff tear underwent anterior acromioplasty and rotator cuff repair. There were 8 small tears (less than 1 cm), 5 moderate tears (1 to 3 cm), 2 large tears (3 to 5 cm), and 8 massive tears (greater than 5 cm). The dominant shoulder was involved in all patients and all were unable to play tennis before surgery. Eleven patients experienced a traumatic event that caused an injury, 6 while playing tennis, and 12 patients had a gradual onset of symptoms. At average follow-up of 42 months, 19 patients (83%) achieved a good result, were pain-free, and were able to play tennis at their presymptomatic competitive level. Three patients (13%), all with massive tears, had a satisfactory result and were able to play tennis, although at a lower competitive level secondary to weakness. One patient (4%), who also had a massive tear, had an unsatisfactory result and was unable to play tennis.

Peter D. McCann

Papers

Surgical Treatment of Complete Acromioclavicular Dislocations

An anatomical study of the suprascapular nerve

A kinematic and electromyographic study of shoulder rehabilitation exercises.

A comparison of isokinetic strength testing and gait analysis in patients with posterior cruciate-retaining and substituting knee arthroplasties

Repair of rotator cuff tears in tennis players.