In part one of this article on second metatarsal stress fractures, Chris Mallac explored how these injuries occur, and the pathogenesis of second metatarsal stress fracture development. In part two, Chris considers the principles of second metatarsal stress fracture rehabilitation, including return to running, progressive loading and other aspects the clinician needs to consider Stress fractures... MORE
The Buford complex
Chris Mallac looks at a rare and under-recognised variant of normal shoulder anatomy known as the Buford complex. How does it differ from normal anterior shoulder anatomy and what are the implications for clinicians?
The Buford complex is a relatively rare and under-recognised variant of normal shoulder anatomy that affects the antero-superior labrum and the middle glenohumeral ligament (MGHL). Some researchers believe it is a ‘normal’ variant, which is found infrequently in shoulders on MRI and routine shoulder arthroscopies. Others believe that is may be associated with increasing the chance of suffering an intra-articular shoulder pathology.
Anatomy and biomechanics
The glenohumeral ligaments include:
- Superior glenohumeral ligament (SGHL).
- Middle glenohumeral ligament (MGHL)
- Inferior glenohumeral ligament (IGHL) complex, formed by an anterior band, a posterior band and the axillary recess of the joint.
These ligaments are in-foldings of the glenohumeral capsule, extending from the anterior and inferior glenoid margin of the glenoid to the region of the anatomical neck of the humerus (see figure 1)(1-3).
Figure 1: A ‘normal’ shoulder with a structured MGHL and complete labrum
The ‘normal’ MGHL is attached to the anterior surface of the scapula and medial to the articular margin. It then lies obliquely, posterior to the superior margin of the subscapularis muscle and blends with the anterior capsule. Distally it is attached to the anterior aspect of the proximal humerus, below the insertion of the SGHL(4,5). Normal anatomical variants involve the MGHL more often than the other ligaments; the common variations of the anterior middle glenohumeral ligament include a sublabral foramen, a cord-like MGHL and the Buford complex(6)(discussed below).
The rotator cuff interval is the space located between the anterior margin of the supraspinatus muscle and the superior margin of the subscapularis muscle. The joint capsule that covers this space includes the coracohumeral ligament and the SGHL, and lends support to the long head of the biceps tendon. This anatomical space is closely related to the superior labrum and the MGHL.
The anterior superior labrum is the most common site of normal anatomic labral-ligamentous variations. The spectrum of anatomic variations includes an anterior superior labrum that is securely attached to the glenoid rim, sublabral recesses of various sizes, detachment of the labrum, and complete absence of the labmum(6-10).
Stability of the glenohumeral joint
The most important contributor to anterior stability of the glenohumeral joint is the anterior capsular mechanism. This includes:
- The fibrous capsule.
- The glenohumeral ligaments.
- The synovial membrane and its recesses.
- The fibrous glenoid labrum.
- The subscapularis muscle and tendon.
- The scapular periosteum.
The relative contribution of each glenohumeral ligament to joint stability has been the subject of much debate. It has been argued that due to the absence of the MGHL and the SGHL in a large number of subjects around 15 to 21%(4,11), their relative importance to shoulder stability is questionable(12,13). Dissection studies on the glenohumeral ligaments suggest that the IGHL is the most important structure, supporting the shoulder at 90 degrees abduction and external rotation(14). Furthermore, when O’Connell et al measured the tension of the glenohumeral ligaments in cadavers after application of a controlled external torque, it was found that the MGHL does develop the most strain (along with the IGHL) when the arm was at 45 and 90 degrees abduction(15). Therefore, the MGHL is most likely an important stabiliser along with the IGHL.
The Buford complex
The Buford Complex is an anatomical variant of the anterosuperior shoulder anatomy. It was first described by Williams et al who discovered that in some shoulders, an absent anterosuperior labrum with a cord-like structure that resembled the MGHL was found(16). Furthermore, the researchers reviewed the arthroscopic videos of 200 shoulder arthroscopies, and found that 1.5% of subjects had a Buford complex.
This cord-like MGHL originates directly from the superior labrum at the base of the biceps tendon, and crosses the subscapularis tendon to insert on the humerus. The labrum is missing from the antero-superior part of the glenoid, with the remaining labrum in the other three quadrants remaining intact.
In a later research paper, a group of researchers from Texas looked more closely at the superior labrum during routine arthroscopies. They found that the Buford complex was more prevalent than Williams et al has proposed(17). They found that in 108 shoulders studied, they found a Buford complex incidence rate of 6.5%.
It has been argued since by shoulder surgeons and radiologists that this anatomic arrangement may be mistaken for a pathologic lesion on imaging studies and at arthroscopy(6). Recognition of this variation by the radiologist is therefore desirable to avoid the false-positive diagnosis of a glenoid labral tear and unnecessary surgery(6,16). Figure 1 below shows a ‘normal’ shoulder with a structured MGHL and complete labrum. Figure 2 on the other hand shows how the labrum and MGHL look different in a Buford complex.
Is it a problem?
Many radiologists and orthopaedic surgeons believe that the Buford complex is a rare but ‘normal’ variant of shoulder anatomy. However, others argue that it may predispose the shoulder to particular shoulder pathologies. The absence of anterior superior labrum would, in theory, concentrate forces in the superior labrum and the area of insertion of the biceps tendon, which could predispose the patient to a SLAP lesion and other intra-articular lesions. To summarise a few studies that have looked at the pathological nature of the Buford complex:
- Rao et al found that those with a Buford Complex had greater range of motion in both active and passive internal rotation with the arm abducted(18). This may predispose the superior glenohumeral ligament and labrum to greater tensile forces and injury.
- A group of Japanese researchers found in a case study that a patient with a Buford complex suffered from recurrent posterior dislocation of the shoulder. They argue that a lack of a anterosuperior labrum and normal MGHL would predispose a client to excessive translation of the humeral head(19).
- Illahi et al found that those with either a Buford complex or a ‘sublabral foramen’ had a 56% chance of also having a superior labrum anterior-superior (SLAP) lesion compared with shoulders that did not have these variants(17). Normal shoulders on the other hand had only a 12% chance of having a SLAP lesion(17).
- Supporting the above, Bents and Skeete found that in 235 shoulders studied under arthroscopy, 2.5% had a Buford complex, and from these 83% also had a SLAP lesion. This is compared to 17.5% in the shoulders without a Buford complex(20).
- Canillas et al presented a case of a Buford complex associated with anterior glenohumeral instability in which arthroscopic reattachment of the cord-like MGHL was performed with excellent outcome(21).
- Lee et al found that an isolated tear to the cord-like MGHL in the Buford complex presented as a ‘frozen shoulder’, which had failed with steroid injections and physiotherapy(22). Upon arthroscopic investigation, the tear of the MGHL was found and was repaired with a positive outcome experienced by the patient.
Implications for clinicians and athletes
Although the presence of a Buford complex is rare – in just 1.5% to 6.5% of shoulders – if it does occur, it may pose a potential issue for the athlete involved in an overhead sport. The ligaments of the shoulder are crucial for providing passive support to the glenohumeral joint during end of range positions. As mentioned above, the MGHL contributes along with the IGHL to limit external rotation at both 45 and 90 degrees of abduction.
It may be argued for the high-demand athlete in an overhead sport such as a swimmer, cross fit athlete, gymnast, and tennis player, that the presence of a Buford complex may render the shoulder more vulnerable to slight instabilities due to the deficient MGHL and antero-superior labrum. This may then overload other structures in the glenohumeral complex such as the supraspinatus tendon, biceps anchor and subscapularis tendon.
It is a potential, although rare, condition that the clinician needs to consider when dealing with shoulders in athletes who present with rotator cuff lesions and SLAP lesions. The Buford complex can be visualised on magnetic resonance arthogram (MRA), and may be found on routine arthroscopic examinations. Research into the Buford complex and the potential dilemma it poses on athletes has not been studied.
As it is a variant on anatomy, the only possible treatment option if one was needed would be to surgically correct the defect through augmentation of the cord like MGHL. However, the empirical evidence for the success of such a procedure is weak, with only some anecdotal case studies being reported in the literature.
From a non-surgical perspective, it may also be anecdotally argued that selective isolation exercises of the subscapularis may actively augment the stability of the anterior shoulder and may compensate to some degree for a deficient MGHL. To isolate the subscapularis we can use the belly press position activation drill (see figure 3):
To perform the belly press position activation drill:
- Place a Theraband or tube around the wrist (not the hand). If the tubing is around the hand it will encourage wrist flexion to create the movement.
- Hold the elbow out wide and keep the hand on the belly (this position minimises the lat dorsi).
- With the other hand, palpate the pec major (using thumb) and the lat dorsi (using fingers). We do not want these muscles to contract.
- Slowly and using small range, move the hand away from the belly and then back in again. The elbow should not move or change position. This is simply a small rotation movement of the shoulder into internal and external rotation.
- Perform high-repetition sets such as three sets of 20-30 reps as this muscle needs to be trained for endurance.
The Buford complex is a rare but apparently ‘normal’ variant of the shoulder anatomy. However, some authors have suggested that its presence may create overload to the other structures of the shoulder that restrain movements such as the biceps tendon and rotator cuff. Its presence needs to be considered in athletes who present with repetitive shoulder pain that is attributed to rotator cuff lesions and SLAP lesions.
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