Tuesday, June 9, 2009

Glenohumeral joint now thought to cause subacromial impingement syndrome

Anomalies in the morphology of the acromion may not be the cause of subacromial impingement syndrome as has been theorized by some shoulder surgeons. Japanese researchers said they now believe the glenohumeral joint pathologies may be more to blame, including glenoid spurs and greater tuberosity irregularities.

“There is no relationship between impingement syndrome and factors of acromial morphology, such as the shape or slope of the acromion,” said Hiroshi Hashiguchi, MD, of Nippon Medical School in Tokyo.

Hashiguchi and colleagues based their conclusions on results of a radiographic analysis they performed comparing acromion morphology in patients with and without a positive impingement sign.

He reported these findings at the American Academy of Orthopaedic Surgeons 76th Annual Meeting, here.

Glenohumeral instability

“The major factor in the development of impingement syndrome is instability of the glenohumeral joint due to dysfunction of the rotator cuff. Narrowing of the supraspinatus outlet is not the cause of impingement syndrome. Narrowing of the outlet is an effect of the impingement phenomenon,” Hashiguchi said.

glenoid spurs
Hashiguchi said that glenoid spurs, represented here, may be the cause of subacromial impingement.

Images: Hashiguchi H

The researchers now theorize that anterosuperior glenohumeral instability arising from a weak or imbalanced rotator cuff rotator may be mostly to blame, according to their abstract.

For their study, Hashiguchi and colleagues obtained AP shoulder and lateral scapular radiographs for 192 patients with the impingement sign and 184 patients without it. Both groups’ mean age was about 53 years. Patients were excluded from both groups if they had shoulder pain or stiffness, rotator cuff tears or calcium deposits or if they played overhead sports.

Factors analyzed

Using the two groups’ radiographs, investigators identified and statistically analyzed such factors as shape of the greater tuberosity, bone spur formation on the inferior glenoid and in the subacromial area and the overall acromion morphology.

Investigators used the Bigliani classification for the acromion arch shape, where type 1 is flat, type 2 is curved and type 3 is hooked. They also measured the slope of the acromion arch and calculated the size of any subacromial bone spurs.

Both groups’ radiographs showed a similar frequency of sclerotic change in the greater tuberosity, but the group with the positive impingement sign demonstrated more tuberosity irregularities than the controls.

subacromial spurs

Results of the study indicated a
higher incidence of subacromial
spurs in the group with a positive
impingement sign.

Greater tuberosity irrgularities

Greater tuberosity irrgularities were also related to impingement syndrome.

“Regarding shape of the acromion, there was no significant difference between the two groups. There was also no significant difference in mean values of the slope of the acromion between the two groups,” he explained.

Spur size, location

The main difference the investigators noted between the two groups’ shoulder radiographs was a statistically higher incidence of inferior glenoid spurs in the group with a positive impingement sign. However, the overall frequency of subacromial spurs was not different between the two group, Hashiguchi noted.

“The size of subacromial spur in the impingement group was significantly higher in the control group,” he said.

Hashiguchi added, “This study revealed that radiographic factors related to impingement syndrome are the inferior glenoid spur, the irregularities of the greater tuberosity and the size of the subacromial spur.”

He said during the discussion period acromioplasty for subacromial decompression is a solution for patients with impingement syndrome, but at the outset it is more typically caused by degeneration of the rotator cuff from overloading.

For more information:
  • Hiroshi Hashiguchi, MD, can be reached at Nippon Medical School Hospital, Department of Orthopaedic Surgery, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan; +81-3-3822-2131; e-mail: hashi.h@d6.dion.ne.jp. He has no direct financial interest in any products or companies mentioned in this article.
  • Hashiguchi H, Ito H, Egawa Y, Murashige R. Analysis of radiographic findings on patients with subacromial impingement syndrome. Paper #556. Presented at the American Academy of Orthopaedic Surgeons 76th Annual Meeting. Feb. 25-28, 2009. Las Vegas.
  • ORTHOPAEDICS TODAY EUROPE 2009; 12:10 Susan M. Rapp

My thoughts:

I believe that there are factors in the subacromial space that affect the rotator cuff. Spurs from the acromioclavicular joint contribute to crowding of the rotator cuff. When we do a shoulder scope we often see fraying of the surface of the rotator cuff tendons as they rub against the spur. I do agree, however, that it is an imbalance of the shoudler joint related to specific areas of stiffness and weakness that lead to shoulder pain, impingement and eventually a tear of the tendon.

I often tell patients that the painful shoulder is often "out of balance" with selected areas of capsular stiffness and rotator cuff weakness. Therapy is often helpful to stretch and strengthen the shoulder thereby rebalancing the joint and relieveing the pain.

I am not sure of the true significance of the spur on the glenoid. Time and further studies will be needed.