Abstract
Background:
Bennett lesion is ossification of the posterior inferior glenohumeral ligament complex. Though often asymptomatic, these lesions can become painful and interfere with throwing ability.
Indications:
The Bennett lesion is relatively common among elite throwers, present in 22% to 25% of asymptomatic pitchers. Suggested causes of this lesion include traction on the posterior joint and posterior impingement in the late cocking phase. These lesions can become painful due to displacement and irritation of the joint capsule and axillary nerve. Therefore, efficient arthroscopic treatment of symptomatic lesions is essential.
Technique Description:
The patient is positioned in the lateral decubitus position, and the glenohumeral joint is accessed via posterior and anterior portals. Once the lesion is identified, it may be probed and debrided via the posterior portal. A posterior capsular release is performed, and 4.0 mm burr resection of the lesion is started, viewing from the anterior portal with a 70° arthroscope. Direct visualization through the posterior portal can be used to verify complete lesion resection. If there is a true tear of the posterior labrum, this can be repaired with a knotless suture anchor back to the glenoid, but usually there is delamination that can be left alone after addressing the Bennett lesion.
Results:
We have found good success treating Bennett lesions via the above technique. This is supported by previous literature as well, with return to preinjury levels ranging from 69% to 85% following arthroscopic resection.
Discussion/Conclusion:
Four diagnostic criteria have been described to ensure accurate diagnosis: detection of a bony spur at the posterior glenoid rim on plain x-ray films, best seen on Stryker notch and Bennett view; posterior shoulder pain while throwing; tenderness at the posteroinferior aspect of the glenohumeral joint; and improvement in pain following lidocaine injection. Magnetic resonance imaging is also an excellent diagnostic tool to detect early enthesopathic changes in the posterior glenoid or periosteum, as well as labral pathology. Following arthroscopic resection, 88% of patients were satisfied with their treatment when using these diagnostic criteria. Accurate diagnosis and efficient treatment of Bennett lesions are imperative in the throwing athlete, and when performed correctly, our technique provides significant and lasting improvement for patients.
This is a visual representation of the abstract.
Video Transcript
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Bennett lesion is posterior ossification of the posterior inferior glenohumeral ligament. These lesions were originally described in baseball players and still predominantly affect these athletes, exclusively affecting the dominant shoulder. While this is often asymptomatic, it may become painful and interfere with throwing ability.
Multiple locations for posterior exostoses in throwers have been described, with 70% of these being posteroinferior, 1.33% being directly posterior, and 28% being posterosuperior. These are further divided into stable and unstable lesions, with 55% of stable lesions requiring surgery and 100% of unstable lesions requiring surgery.
The etiology of the Bennett lesion has multiple suggested causes, including traction on the posterior capsule during follow-through, posterior impingement during late cocking, and a wringing action during acceleration.
In terms of epidemiology, this is a relatively common phenomenon among throwers, the vast majority of them being baseball players. One study had 22% to 32% of asymptomatic pitchers having radiographic evidence of the Bennett lesion. However, it is uncommon that these asymptomatic lesions require surgical treatment, as no player in this study who demonstrated a lesion required future intervention. There has also been found to be a temporal relationship, with time playing baseball and the presence of a Bennett lesion.
Bennett lesions often present with deep-seated posterior shoulder pain. This is theorized to be due to irritation of the posterior capsule and axillary nerve and can manifest as pain while throwing as well as decreased velocity. Also, suprascapular nerve entrapment has been described. This has led to isolated infraspinatus atrophy with external rotation weakness on examination. Finally, on imaging, you may notice posterior glenoid cartilage deficiencies as well.
Four diagnostic criteria have been described to ensure accurate diagnosis, which can in fact prove difficult. This includes detection of a bony spur at the posterior glenoid rim on plain x-ray films, best visualized on the Stryker notch or Bennett view, posterior shoulder pain while throwing, tenderness at the posteroinferior aspect of the glenohumeral joint, and improvement in throwing pain following lidocaine injection. That said, the Bennett lesion still often remains a diagnosis of exclusion.
Our case is that of a 21-year-old male collegiate pitcher, who initially presented with deep-seated posterior shoulder pain while pitching, as well as loss of velocity noticed at the beginning of the season. On examination, our patient had 175° of forward elevation, 65° of external rotation, internal rotation to T6, abduction external rotation to 120°, and abduction internal rotation to 40°. He also had a positive O’Brien test; negative speeds, jerk test, and load and shift examination; and 5 out of 5 strength with discomfort of infraspinatus testing.
Our initial treatment consisted of conservative treatment, including physical therapy, as well as a couple of ultrasound-guided corticosteroid injections. This treatment was continued over the course of 1 year with some symptomatic relief; however, our patient could not get back to his baseline performance.
Initial imaging consists of a 3-view series of the shoulder including axillary view, which often is helpful in diagnosing the Bennett lesion by radiograph.
However, on our films, there was no notable posterior ossification of the posterior inferior glenohumeral ligament. However, you can see some posterior drop off of the posterior glenoid. As previously mentioned, a Stryker Notch or Bennett view can also be helpful in diagnosing a lesion.
In comparison, this Bennett view demonstrates the characteristic posterior inferior osteophyte typical of a Bennett lesion. A Bennett view is obtained by angling the tube 5° cephalad with the arm abducted 45° and externally rotated.
Magnetic resonance imaging (MRI) is considered the optimal tool to assess concomitant pathologic lesions in soft tissue. Therefore, MRI is an excellent diagnostic tool to detect early enthesopathic changes in the posterior glenoid or periosteum before mineralization on a plain radiograph or computed tomographic scan is to be determined. Here, you can visualize mineralization of the posterior inferior glenohumeral ligament readily on axial and sagittal MRI series specifically at the 4 to 5 o’clock position on the glenoid.
In our case, our plan was for diagnostic arthroscopy with Bennett lesion resection and possible superior labrum anterior to posterior (SLAP) repair versus biceps tenodesis. Our positioning and equipment included lateral decubitus positioning, with a regional interscalene block, and employment of a 70° arthroscope.
Prior to the procedure, an examination under anesthesia was performed to assess for glenohumeral internal rotation deficiency or signs of laxity. The glenohumeral joint is then accessed via posterior and anterior portals, and a detailed diagnostic arthroscopy is performed. As you can see in our patient, there are fraying and tearing of the long head of the biceps at the superior labral junction, but no peel-back; therefore, a biceps tenodesis was performed. Following this, the lesion should be identified and probed with the switching stick. At this point, you may also establish an accessory posterior portal, if needed. In our case, the posterior portal served as our working portal. To achieve adequate visualization of the extra-articular Bennett lesion, the capsule needs to be released just adjacent to the posterior and posteroinferior labrum. Note the very thickened posterior capsule corresponding to the glenohumeral internal rotation deficit noted on his physical examination. We perform an aggressive posterior capsular release to help improve the internal rotation deficits in these athletes, and the arthrotomy should be extensive enough so that the capsule does not limit one’s visualization or ability to place instruments extra-articularly along the neck of the glenoid to fully assess the lesion. An arthroscopic elevator, curette, and radiofrequency device are very useful in dissecting along the glenoid and exposing the Bennett lesion. It is important to stay on the bone of the glenoid neck while performing this dissection. Here, we are freeing up a portion of the Bennett lesion with an arthroscopic elevator. As this portion of our lesion was loose, we were able to retrieve the loose fragment with an arthroscopic grabber, and the remainder of the lesion was resected using a 4.0-mm burr. Up until this point of the case, we are viewing from the anterior portal using a standard 30° arthroscope.
Here, we switch to a 70° arthroscope viewing through the anterior portal, as this allows for better visualization around the posterior corner of the glenoid. We feel that this is an important consideration for this portion of the procedure. Four-millimeter burr resection is used to fully resect the Bennett lesion. Once full resection was achieved, a shaver was then used to assess the posterior labrum. Direct visualization through the posterior portal can then be used to verify complete lesion resection as well. As you can see here, our lesion is fully resected. If a true tear to the posterior labrum is appreciated, this can subsequently be repaired with a knotless suture anchor back to the glenoid. However, much of the time there is just delamination that can be left alone after addressing the Bennett lesion itself.
A few things to note about this procedure and diagnosis. First, the posterior labrum often remains intact, and no increase in rates of labral tear or internal impingement have been found in patients with Bennett lesions. When the surgeon is performing capsulotomy, emphasis should be placed on cutting just adjacent to the intact labrum to maintain its integrity. One major potential complication of this procedure could be inadvertent injury to the neurovascular structures, most at risk of these being branches of the axillary nerve. This should be avoided with careful dissection and use of a shaver and electrocautery when extra-articular. Also, inadequate resection may lead to persistent symptoms. Finally, do not close the posterior capsular release, as this will aid in the improvement of an internal rotation deficit.
Our postoperative protocol was as follows. We placed the patient in a standard sling for 2 weeks. When performing concomitant SLAP repair or biceps tenodesis, maintain sling for 4 weeks. Start aggressive range of motion, including internal rotation, within the first few days. Abduction internal rotation threshold will vary from athlete to athlete, but a goal of 45° prior to strengthening is a reasonable benchmark. Begin rotator cuff and scapular strengthening at 4 weeks and proceed to an interval throwing program at 12 weeks. Finally, the patient may return to competitive throwing at 6 months.
In terms of patient outcomes, we have found very good success treating Bennett lesions by arthroscopic resection using the discussed technique. All of our patients have returned to throwing, and only a couple not reaching preinjury levels. We have had no complications or reoperations. Arthroscopic resection is well supported in the literature as well, with return to preinjury levels ranging from 69% to 85%.
Thank you very much.
Footnotes
Submitted December 31, 2020; accepted April 19, 2021.
The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.