4.10 Acromioclavicular joint

The acromioclavicular joint (ACJ) is the sole skeletal connection between the upper limb and the axial skeleton and provides both strength and stability to the shoulder. The three-dimensional alignment of the joint, particularly in the sagittal plane, is very variable which should be borne in mind, especially when trying to inject the joint. It is rare to find anyone older than 35–40 years of age without some evidence of degenerative change. The ACJ is also one of the most commonly injured joints of the body, accounting for 12% of all dislocations. Controversies regarding indications for surgical treatment of the joint, and the bewildering choice of procedures described, makes this small joint the subject of a disproportionate amount of debate and discussion amongst shoulder specialists.

There are two different groups of patients who present with arthropathy of the ACJ. The first patient is relatively young, in their twenties or thirties, usually male with a background of sporting injury or heavy manual work. Arthropathy in these patients can develop subsequent to a discrete, single episode of trauma to the shoulder or a history of taking part in a contact sport. Heavy manual work with a large amount of overhead lifting may contribute to the development of ACJ arthropathy. The early onset of arthropathy in this group may be related to premature damage to the intra-articular fibrocartilage disc in a similar model to that seen in the knee following meniscal injury.

The second group of patients suffering from the symptoms of ACJ arthropathy are middle-aged and may give a history of manual work or sport. However this is not consistent and presumably there is a constitutional element as with most other joints. The onset of symptoms can often be slow with long periods of minimal discomfort.

The clinical symptoms, signs, and investigations for ACJ pathology are dealt with in Chapter 4.1.

The treatment of patients with mild to moderate arthropathy of the ACJ is non-surgical in the first instance. Advice can be given regarding activity modification, both at work by avoiding overhead tasks and in recreation. For instance, it is not uncommon for patients with a painful ACJ to fail to realise that swimming a mile three times weekly to keep fit is aggravating their arthritic ACJ. Regular analgesia and anti-inflammatory medication can also be discussed, although its effectiveness in the longer term is often not sustained.

Intra-articular injections of steroid are often advocated as an effective treatment of ACJ arthropathy. Whilst this is certainly worth trying in the patient without advanced arthropathy, it is the author’s view that the beneficial effects are often not sustained. Placing the injection accurately can also be difficult and may be improved by the use of ultrasonography or fluoroscopy.

Surgery provides a safe and effective option if conservative treatment has failed, and in patients with severe arthropathy. The principle of surgery involves excising the distal end of the clavicle. Debate regarding whether the procedure is best done open or arthroscopically remains and also the optimal length of clavicle to excise.

Excision of the distal clavicle is usually attributed to Mumford whose name is attached to procedures such as the ‘mini-Mumford’ or ‘arthroscopic Mumford’. According to the literature it is unclear whether Mumford or Gurd performed the first clavicle excision as they both published their techniques in 1941 in relation to the treatment of ACJ dislocation. Ellman was one of the first surgeons to describe arthroscopic excision of the distal clavicle in 1994 since when the arthroscopic technique has become popular.

The ACJ is planar and has no inherent bony stability. Stability of the joint is therefore provided by the coracoclavicular ligaments and the ACJ ligaments with the joint capsule itself playing a minor role.

The conoid ligament inserts more medially on the conoid tubercle of the clavicle than the trapezoid ligament. Selective ligament sectioning work by Fukuda, has demonstrated that the conoid is responsible for constraining anterior and superior displacement of the clavicle, particularly under high load. The trapezoid ligament contributes less to vertical stability of the clavicle but help to stabilize the ACJ under axial compressive load.

The capsule of the ACJ is thickened superiorly and inferiorly to form discrete acromioclavicular (AC) ligaments. The superior ACJ ligament is more substantial and thicker (2–5mm) than the inferior ligament and provides rotational stability of the joint.

The lateral edge of the trapezoid ligament is 16.7mm ± 2.4mm from the articular surface of the clavicle. The medial edge of the trapezoid ligament is 28.2 ± 5.7mm from the end of the clavicle. Looking at the conoid ligament, this inserts on the clavicle between 33.5–49.7mm from the articular surface. There were no significant differences between men and women for the trapezoid ligament insertion although there was for the conoid insertion which was closer to the articular surface in women. The superior AC ligament inserts on the clavicle medially for 5.5mm ± 1.7mm in men and only 3.6mm ± 0.78mm in women. The acromial attachment of this ligament extended for 8.1mm in men and 4.7mm for women.

If we first consider open surgery, it is clear that in order to expose the distal clavicle, the superior AC ligament has to be incised and a limited amount of the delto-trapezial fascia has to be reflected. The minimum amount of bone that should be resected in order to abolish bone contact postoperatively has been shown by Branch to be 5mm. However, this will inevitably lead to loss of stability as the superior AC ligament is also lost and most surgeons recommend an excision of at least 10mm to avoid postoperative pain due to persistent posterior impingement of the clavicle on the acromion. As long as the excised segment is no more than 15mm, the trapezoid ligament should not be damaged.

Arthroscopic excision of the distal clavicle has the perceived advantages of avoiding the pain and potential morbidity of an open surgical exposure and allows resection of the clavicle without disrupting the deltotrapezial fascia. It is also said that arthroscopic excision preserves the superior AC ligament, leading to better preservation of rotational and horizontal stability, although this may not be the case given the evidence presented earlier. If the standard excision of 5mm of clavicle is carried out, this will almost certainly lead to complete detachment of the superior AC ligament in most patients, particularly females. If one wishes to preserve the clavicular attachment of the superior AC ligament it would seem more logical to excise no more than 3–4mm of bone from the clavicle and perhaps a similar amount from the acromion. A secondary advantage of an arthroscopic resection is the ability to perform glenohumeral inspection and treatment of occult pathology.

There are two approaches for arthroscopic ACJ resection: the direct and indirect methods. The common indirect approach involves exposing the ACJ through the subacromial bursa. The advantages of this technique are that the approach is familiar to the surgeon and that secondary impingement can be treated as appropriate. The direct approach involves establishing a viewing portal directly posterior to the ACJ with an anterior working portal; however, establishing a good view initially can be difficult.

Surgical treatment of ACJ arthropathy is both effective and safe. There have been numerous series published giving results in patients having either open resection or arthroscopic resection.

Two studies have attempted to compare open with arthroscopic resection. Freedman et al. randomized 17 military recruits with ACJ pain into two groups; the first group underwent open ACJ resection whereas the second group underwent indirect arthroscopic resection. The only significant finding was that patients in the arthroscopy group had a better improvement in their pain score from baseline to 1 year postoperatively. They highlighted trends suggesting that the arthroscopy group had better results in all the parameters measured, including return to sports, subjective results, and objective shoulder assessment. However, the study groups were small and the authors acknowledge that their results should be interpreted with caution.

Flatow et al. also compared the results of open versus arthroscopic ACJ resection. Their study, however, was retrospective and looked at pain relief only and they did not make any objective assessment. The arthroscopic approach used in this study was the direct technique. They reported good pain relief in both groups, although pain relief occurred much sooner in the arthroscopy group, in fact 3.4 months earlier.

Patients who have an unsatisfactory result following ACJ excision can be split into three groups: those who have persistent pain in the shoulder following good surgery; those patients with pain and/or instability as a result of excessive bone resection; and finally those patients who have pain due to inadequate resection. Clearly in the first group, the failure is with the initial diagnosis rather than a fault of the surgery and the patient must be reassessed and the correct cause of the symptoms established. This is unfortunately rather more difficult after surgery than before. Inadequate bone resection is an uncommon cause of failure of arthroscopic resection. The solution is revision surgery, although the surgeon must be cautious to avoid going too far the other way and resecting too much bone.

The second most common complication after an incorrect diagnosis is the patient with pain due to having had an excessive amount of bone resected from the distal clavicle. This problem is usually seen in patients who have had open surgery. Open surgery will defunction the stabilizing constraints of the AC ligaments. If the resection compromises the coracoclavicular ligaments as well then the patient may develop painful instability of the clavicle, which is quite miserable and difficult to treat. The patient may have the worst of all worlds, with impingement of the acromion against the resected clavicle in elevation, local soft tissue irritation caused by instability of the distal clavicle, and scapular fatigue caused by failure of the link between the clavicle and acromion or scapula—what could be called claviculoscapular dissociation. Stress views of the ACJ will show an increased width in the resection gap with load bearing, which can sometimes be quite dramatic. An x-ray or fluoroscopy of the ACJ with the upper limb fully elevated will sometimes demonstrate acromioclavicular impingement even if the joint space with the arm at rest is 1–2cm. Occasionally some of this group of patients will require revision reconstructive surgery. The author currently uses a semitendinosis free tendon graft that is used to restore stability to the ACJ through a figure-of-eight loop between tunnels in the acromion and distal clavicle. If the clavicle is also vertically unstable, a second loop is passed between the coracoid process and clavicle. Initial stability can be improved between the coracoid and clavicle by using a suture anchor, sling, or TightRope^® (Arthrex) suture.

Dislocations of the ACJ are common injuries, representing around 12% of all dislocations around the shoulder and 8% of all dislocation injuries of the body. By far the commonest mechanism of injury is a fall, landing directly on the tip of the shoulder. The joint can be dislocated as a result of a direct blow to the clavicle, this mode of injury producing some of the more unusual dislocation types as described subsequently.

AC dislocations are universally classified according to the system proposed by Tossy in 1963 and Allman in 1967. These initial classifications were amalgamated to describe the three most common types of dislocation. Three further dislocation patterns (IV, V, and VI) were added by Rockwood in 1984.

A grade I injury involves a partial disruption of the ACJ capsule and ligaments with no deformity or instability. A grade II injury involves complete disruption of the ACJ ligaments although the coracoclavicular ligaments are broadly intact and may be partially damaged. There may be some minor caudal displacement of the acromion although this is often not seen, particularly initially, as the intact coracoclavicular ligaments continue to provide vertical stability. On examination of the ACJ, there is usually some anteroposterior laxity of the joint due to the disruption of the ACJ ligaments. A grade III separation describes an injury in which there is complete disruption of both the ACJ ligaments and coracoclavicular ligaments. This is responsible for the typical ACJ dislocation as seen on radiographs and apparent on clinical examination. However, there is no appreciable posterior displacement of the clavicle and due to the contribution of the intact deltotrapezial fascia, the clavicle is not grossly unstable and there is usually not more than 100% displacement of the acromion relative to the clavicle. Grade IV and V injuries are relatively uncommon but occur in roughly equal proportions and it is important to differentiate them from the more common injuries as results with conservative treatment are often disappointing. A grade IV injury is similar to a grade III with complete tears of the AC and coracoclavicular ligaments, except that there is significant posterior displacement to the extent that the distal clavicle pierces the trapezius muscle and becomes button-holed in an irreducible manner. A grade V dislocation involves extensive separation of the deltotrapezial fascia normally attached to the distal clavicle. This allows significant displacement of the acromion on the clavicle and certainly more than 100% of the thickness of the distal clavicle. A grade VI injury is extremely rare and will never be seen by most shoulder specialists in their lifetime.

The diagnosis of an acute ACJ injury is not particularly difficult. The patient gives a history of acute pain in the shoulder following a fall or direct blow to the shoulder. The pain is sharp and localized to the tip of the shoulder. Examination of the patient reveals tenderness over the injured joint with or without the deformity associated with a dislocation. The distal clavicle should be located by direct palpation and an assessment made of vertical and AP stability. Alignment of the distal clavicle with the acromion should be ensured to avoid missing a grade IV injury. Plain radiographs are usually sufficient to confirm the diagnosis. A standard AP of the shoulder will be taken as part of a trauma series along with an AP view of the ACJ. These views will allow distinction to be made between grade II, III and grade V injuries. It should be borne in mind that due to pain, the patient with a grade V injury may be reluctant to allow the injured arm to hang and in supporting it, may reduce the separation seen on the AP view to resemble a grade III injury. In this situation, clinical examination will allow the correct grade to be diagnosed as these patients have significant vertical instability of the clavicle with no firm end-point. An axial view is essential to allow diagnosis of a grade IV injury in which the distal clavicle will be seen to lie posterior to the acromion. In more subtle injuries a magnetic resonance imaging (MRI) scan will show ACJ capsule disruption, surrounding oedema and possibly signal change in the region of the CC ligaments.

The treatment of grade I and II injuries is non-surgical and consists of symptom relief with analgesia and anti-inflammatory medication. The arm should be supported with an immobilizer and ice packs can be applied to the injured area. Generally speaking, for grade I injuries the symptoms will resolve in a couple of weeks and the patient can return to normal daily and sporting activities relatively quickly. Patients with grade II injuries often experience discomfort for longer, perhaps 4–8 weeks, although treatment is similar. There is no evidence to suggest that prolonged immobilization of grade II injuries facilitates a more prompt recovery or reduces the incidence of later onset pain and arthropathy. Patients should be warned that chronic discomfort is not unusual following a previous grade II injury and may require subsequent surgery.

At the opposite end of the spectrum, most doctors would recommend surgical treatment of grade IV, V, and VI injuries. As their classification suggests, these types of dislocation involve significant displacement with associated soft tissue disruption. Grade IV injuries if neglected or more commonly missed, are very painful, presumably due to the irritation of the trapezius by the distal end of the clavicle and can cause considerable late disability. Grade V injuries, whilst often not as painful initially, are associated with marked deformity due to the prominence of the distal clavicle under the skin. Contrary to popular belief, this deformity is largely caused by the weight of the upper limb pulling the shoulder downwards, with the clavicle remaining relatively undisplaced. Due to this loss or incompetence in the superior suspensory complex of the shoulder, the deltoid and periscapular muscles are required to work much harder than normal to support the upper limb, particularly when the patient is performing repetitive overhead activities. This often results in the patient experiencing fatigue pain located to the scapular region and chronic disability. The patient will complain of an inability to perform overhead activities, describing an aching or dragging sensation in the scapular region.

Whether to treat grade III injuries with surgery or not has been the subject of debate, discussion, and uncertainty for decades and it seems that a clear answer to this dilemma is no nearer than it was 20 years ago. Whilst it is true that most patients with a grade III injury cope perfectly well, both with the deformity and any minor discomfort, there are a minority who continue to be symptomatic and seek further treatment. This is apparent when reviewing the surgical treatment options available for reconstruction of the dislocated ACJ. Of course, if patients with grade III injuries never required surgery, it is unlikely that there would be so many different operations available for reconstruction described in surgical textbooks.

It is generally believed that grade I and II injuries to the ACJ are benign and patients do well once the initial pain of the injury has resolved. However, according to a review published by Shaw, post-traumatic arthritis is relatively common with 40% of patients reporting significant pain at 6 months post-injury and 14% reporting a high level of pain at a minimum of 1 year. Many of these patients ultimately required surgical treatment. Mouhsine et al. studied a group of 33 patients with grade I and II injuries managed conservatively. From this group nine patients required surgery for late ACJ symptoms (chronic pain).

The treatment of grade III injuries provides the most controversy of all ACJ separations and there have been hundreds of articles published on the subject. Dias and other authors have reported up to 50% of patients treated non-operatively will have residual symptoms of pain and weakness. Spencer has reviewed the literature on this subject and points out that there are in fact only nine papers that directly compare conservative treatment with some form of surgical management. Of course, the findings of some of these papers will be heavily influenced by the type of surgical procedure used during the study. Only three of these studies were performed prospectively. Perhaps the best known of all these studies is the work published by Bannister et al. in 1989. In this study 60 patients with grade III injuries were randomized to either standard conservative treatment or surgery with a Bosworth screw that was removed at 6 weeks. Forty-four patients were evaluated at 4 years post-injury. The results in the non-operative group showed 100% patients had good or excellent results; 84% of patients in the operative group had similar results with the remaining 16% fair. Five patients in the operative group had complications of their treatment including loss of reduction and metalwork problems. Despite reporting uniformly good results in the non-operative group, in fact four patients failed treatment and underwent surgery. Operated patients also took longer to return to work and sport. Despite stating that all patients in this study had grade III injuries, in fact 12 had displacement of more than 2cm which is much more likely to represent a grade V injury; these patients in Bannister’s study did better with surgical treatment. Of course it may be argued that there may be potentially better surgical treatments available today than in the 1980s and more objective methods of assessing shoulder function may alter the results seen.

Over the years, there have been numerous different surgical techniques described for the treatment of acute grade III–VI ACJ dislocations. These include direct repair of the coracoclavicular ligaments, usually with some method of temporary stabilization of the joint, using sutures, tape, screws, or plates. Stabilization of the distal clavicle has also been advocated by transfer of the coracoacromial ligament, with or without excision of the distal clavicle, but this technique is more commonly used in the chronic situation. Currently, the preference seems to be towards reduction of the dislocation without formally repairing the disrupted coracoclavicular ligament, with indirect stabilization either with a hook plate, coracoclavicular screw, or using an arthroscopic technique to place sutures between the clavicle and coracoid process. The choice of technique depends on published results, the resources available to the surgeon and their expertise in open or arthroscopic surgery.

Applying a hook-plate to maintain reduction of the reduced ACJ is a relatively simple surgical procedure that has its advocates. The disrupted joint capsule can be repaired simultaneously with or without excision of the intra-articular disc. The plate will require removal at or around 3 months or earlier if there is evidence of osteolysis under the acromion. The hook is designed to be placed posterior to the ACJ and should therefore not interfere with healing or movement in the recovery phase. In a study from Salzburg the results in terms of shoulder function were significantly better in the surgical group, particularly when comparing pain and power. Surgical complications were seen in four of 28 patients with one haematoma, two superficial infections, and one plate eroding the acromion.

The use of a coracoclavicular screw for the treatment of an acute ACJ dislocation is widely attributed to Bosworth. Most surgeons would now use a partially threaded (16mm) 6.5-mm cancellous screw. It is imperative that the screw is placed centrally in the base of the coracoid process to minimize the possibility of pull-out and this can either be done with a conventional open approach or a percutaneous technique using a cannulated system and fluoroscopy. The thread of the screw should cross both cortices of the coracoid and the screw should not be tightened excessively as this will over-reduce the dislocation and lead to ACJ dysfunction. A disadvantage of this type of rigid fixation is that it must be removed before overhead movement of the upper limb can be allowed. Most surgeons would therefore plan to remove the Bosworth screw around 8 weeks after fixation, but there is a possibility of late displacement if the injured coracoclavicular ligaments have not fully healed by this stage.

Coracoclavicular sutures or slings are popular techniques largely because there is no requirement for hardware removal. Perhaps the simplest method within this type is to knot a Dacron^® or PDS 5-mm tape over the clavicle after first passing it around the base of the coracoid. However, this does little to address anteroposterior instability of the clavicle and there is often subsequent loss in reduction as the knot slips or the sling lengthens slightly. Breslow performed a biomechanical study comparing a simple coracoclavicular suture loop passed under the coracoid with a suture fixed into the coracoid using a suture anchor. One proposed advantage of the suture anchor technique is that the suture is instantly fixed and stable on the coracoid when an anchor is used whereas when a suture loop is passed under the coracoid, some movement or slippage can occur, leading to laxity in the construct. Breslow concluded that a similar degree of stability can be achieved after coracoclavicular fixation using a suture anchor or suture loop. However, the use of a suture anchor eliminates the need to pass instruments under the coracoid which can be both difficult and risk neurovascular injury.

A novel technique using a TightRope^® (Arthrex) suture (originally described by Wolf for the reconstruction of chronic acromioclavicular dislocations and subsequently adapted for use in the acute situation and described by Qureshi and Potter) has become popular over the last 3 years. It has all the advantages of the rigid coracoclavicular fixation of a Bosworth screw, with the benefit of flexibility as seen with the suture techniques. One major attraction is that the suture is placed using an arthroscopic technique, both ensuring accurate placement through the coracoid and minimizing disruption to the torn coracoclavicular ligament complex. Finally, as no rigid fixation is employed there is no need for hardware removal prior to a return to normal activities. To insert the TightRope^® suture the base of the coracoid process is identified and debrided arthroscopically. A jig is then used to percutaneously drill a guide wire through the middle of the clavicle approximately 3cm from its distal end and then through the middle of the base of the coracoid. After the guide wire is over-drilled with a cannulated 4mm drill, the TightRope^® suture is pulled through both holes. The suture is tied over a button on the superior surface of the clavicle after reducing the ACJ dislocation manually. At present there are no long-term results of this technique published although interim results have been presented. Clearly this technique requires healing of the coracoclavicular ligament complex to be successful; this is more likely if the dislocation is reduced and stabilized early. It is also not clear at this stage whether the reduced ACJ will become arthritic as a result of the initial dislocation, although secondary treatment of this problem is much easier than the options for reconstructing a symptomatic chronic dislocation of the ACJ. This technique is also very well suited to complex displaced fractures of the distal clavicle, particularly those involving the ACJ, which usually require surgical reduction but are very difficult to treat with conventional methods.

Numerous surgical techniques have been described for the treatment of the chronic, symptomatic ACJ dislocation. It should be said that grade I and II injuries can also be troublesome for the patient and require surgery, although in the absence of significant instability, simple ACJ excision, either open or arthroscopic, is probably sufficient. It is often worthwhile excluding instability in these patients by performing a stress x-ray. Patients with a high-grade separation can complain of several different symptoms justifying surgery, such as local irritation from the prominent distal clavicle, impingement of the unstable joint in elevation, or scapular fatigue pain and weakness. Surgical procedures can be broadly grouped into those relying on a transfer of the coracoacromial ligament based on the Weaver–Dunn procedure; autogenous tendon graft procedures (anatomic coracoclavicular reconstruction); and reconstruction using synthetic ligament and dynamic muscle transfers.

The Weaver–Dunn procedure was originally described in 1972, and has become the ‘gold-standard’ of ACJ reconstruction. The procedure essentially involves detaching the coracoacromial ligament from the acromion and transferring it onto or into the resected distal end of the clavicle to provide stability. The original Weaver–Dunn technique is now usually modified to include augmentation of the repair to provide initial security, preventing subsequent displacement. The coracoacromial ligament is exposed prior to detachment by either splitting anterior deltoid or detaching anterior deltoid from the clavicle and anterior acromion, although the operation can be performed arthroscopically. Detaching the ligament with a small flake of bone from the acromion may promote healing of the transfer and certainly helps to prevent cut-out of the sutures used to secure the transfer. The ligament is placed into the canalized end of the clavicle and secured in place with sutures passed through drill holes in the clavicle. Perhaps not surprisingly, this transfer in itself has little strength in the early phase of healing. There are several ways in which the initial stability of a Weaver–Dunn repair can be improved, using coracoclavicular slings or sutures. Although it is the author’s practice currently to use a PDS tape, the best biomechanical results are seen with a suture anchored into the base of the coracoid and tied through drill holes in the anterior half of the clavicle, which resists translation under a 100N cyclical load. The final construct at 246N is not as strong as the native coracoclavicular ligaments at 590N.

Increasing interest is being expressed in more anatomical reconstructions of the dislocated ACJ using tendon grafts. It has been noted that whilst a coracoacromial ligament transfer prevents superior migration, it is less good at resisting anteroposterior translation. This is not too surprising when one remembers that the coracoacromial ligament takes its origin from the tip of the coracoid and when transferred, inserts into the resected distal end of the clavicle. The native coracoclavicular ligaments of course arise from the base of the coracoid and insert into the undersurface of the clavicle some way from the distal end. With this in mind, surgical techniques have been described using autogenous tendon grafts including palmaris longus, flexor carpi radialis, gracilis, and semitendinosis. It has been the author’s personal experience that there are both early failures associated with anatomical reconstructions using semitendinosis (usually due to the tendon cutting out of the clavicle tunnel) and late failures (mainly seen on the coracoid side and possibly related to failure of revascularization). It is also worth mentioning that harvesting a semitendinosis tendon graft can be associated with donor-site morbidity, which is particularly relevant when the surgical procedure is on the shoulder not the lower limb. It is the author’s current practice to perform a modified Weaver–Dunn procedure for routine primary reconstructions and a semitendinosis tendon graft in revisions and when it is not possible to use the coracoacromial ligament.

Artificial ligament substitutes are not widely used, given the poor results previously seen in anterior cruciate ligament reconstruction in the knee, although following work by Wallace and Neuman, the ‘Surgilig’ technique is gaining interest. The procedure uses a polyester coracoclavicular sling looped under the coracoid and then fixed to the anterior clavicle with a small fragment screw and washer. It is suggested by the Nottingham unit that this procedure can be used for both acute dislocations as well as in revision.

Distal clavicular osteolysis was first described in 1936 and was thought to be secondary to a traumatic injury. In 1982, Cahill published a series of 45 male patients with clavicular osteolysis, suggesting repetitive microtrauma as the aetiology. All but one of his patients were weight-lifters. He noted the presence of microfractures in the subchondral bone in 50% of cases and proposed that repetitive overloading of the joint caused subchondral stress fractures and remodelling. There is certainly evidence of increased osteoclastic activity in many excised specimens. Patients present with pain localized to the ACJ and almost always give a history of regular and intense weight-training or overhead athletic activity. X-rays are often normal in the early part of the natural history and in cases where doubt exists as to the diagnosis, an isotope bone scan or MRI scan will be diagnostic. The condition is self-limiting with appropriate activity modification, although many young male patients are unwilling to cease their training activities. In these circumstances, Auge and Fischer have shown arthroscopic distal clavicle excision, gives good to excellent results in most patients.

In children, the clavicle is surrounded by a thick periosteal sleeve that extends distally to the ACJ. A secondary ossification centre is present at the distal end of the clavicle that fuses with the clavicle at about the age of 19 years. Children and adolescents are much more likely therefore to fracture the distal clavicle than to dislocate the ACJ. The distal ossification centre is usually very difficult to visualize on a plain x-ray and the true diagnosis is often not appreciated. This type of injury is therefore often known as a pseudodislocation. Unless there is significant displacement, conservative management is usually recommended and there is often excellent remodelling. In markedly displaced injuries, open reduction is worthwhile, the clavicle being reduced and replaced back into the periosteal sleeve which is then repaired. Temporary stabilization is provided by a coracoclavicular screw or suture.

The ACJ and subacromial bursa are said to be the primary sources of pain in 60% of patients who have rheumatoid arthritis and a painful shoulder. The symptoms as expected, consist of pain associated with swelling and tenderness over the joint. The radiological changes can be graded using the Larsen system from I to V. Treatment is best instigated by a rheumatologist initially to control the disease systemically. Localized disease in the ACJ can often be mediated by an intra-articular steroid injection and for advanced and resistant cases, ACJ excision as for degenerative arthropathy is effective.