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Hyaluronans in the Shoulder

L Funk, 2004

Hyaluronan (HA) is a naturally occurring polymer found in high concentrations in joints. It has a number of functions in the joint of which the main being it action as lubricant and shock absorber (6). HA, which is highly viscous, may provide an important lubrication role in the movement of soft tissues, as well as joints. Such as with the movement of adjacent synovial folds over each other(8), as in the subacromial bursa.

Hyaluronans have been used for treatment of pain relief and inflammation associated with degenerative joint disorders of the knee mainly (1)(2).

Postulated mechanisms of the long-term efficacy of HA include possible action on pain receptors and action on inflammatory cells. It forms a viscous coating over the synovial and cartilage linings, acting as a mechanical barrier over pain receptors and inflammatory cells [Figure 1].

Figure 1: Barrier effect of Hyaluronan

HA also forms a mesh-like network in synovial fluid solution. This network has 'pores' allowing the free passage of small molecules, such as nutrients, but blocking the passage of larger molecules, such as inflammatory cells and proteins [Figure 2].

Figure2: Hyaluronan Mesh in Synovial Fluid

The synthesis of HA by synovial fibroblast cells is influenced by the concentration and molecular weight of the HA in their extra cellular environment. Instilling exogenous HA with a molecular weight >5X10⁵ stimulates HA synthesis in a concentration dependant manner.

HA does not have the know detrimental effects on tendons that corticosteroids have (See Shoulder Injections) and therefore is an attractive alternative to corticosteroids around the sensitive rotator cuff.

Shibata et al [8] prospectively compared HA and steroid injections in patients with rotator cuff tears. There was no difference with respect to the pain relief experienced, range of motion and surgical requirements between the two groups. However, biopsies from the rotator cuff stumps were examined from patients who underwent surgery and showed that the collagen fibres from those injected with HA pre-operatively were significantly denser than those treated with steroid. HA injected patients were more responsive to rotator cuff repair with better outcomes. There was also a link between the number of steroid injections and the outcome of surgery. Repeated steroid injections may cause severe local destruction. They concluded that although local steroid injection is often used for pain, since it has a good analgesic effect, repeated injections are associated with a softer residual cuff, and poor surgical results may be due to the giving way of this soft tissue (7).

HA can be mixed with local anaesthetics and injected into the subacromial bursa or gleno-humeral joint. We have used Ostenil from TRB Chemedica, which is licensed for use in the shoulder in the UK. Our clinical experience after one year is that it is a useful alternative to corticosteroids and provides similar pain relief, without the concern of complications such as rotator cuff damage and fat necrosis. It also seems to be a useful alternative for the Neer injection test (reduction of impingement pain following injection into the subacromial space). So far, we have had no complications related to the Ostenil injections and we are keeping a prospective record of the cases and pain diaries, with results to be available soon.

References:

1) Leardini G., Perbellini A., et al. "Intra-Articular Injections of Hyaluronic Acid in the Treatment of Painful Shoulder," Clinical Therapeutics 1988/ Vol 10.No.5.

2) Raynauld J,P., Choquette D., et al. " Hylan versus Triamcinolone Acetonide Injection for Acute Supraspinatus Tendinitis: Early Report of a Randomised Controlled Trial," Arthritis Rheum (1994) 37 Supp. 9 (S346)

3) Hayes PR, Flatlow EL. "Attrition sign in impingement syndrome." Arthroscopy 2002 Nov-Dec; 18(9): E44

4) www.orthoteers.co.uk

5) Biberthaler., P et al, " Microcirculation Associated with Degenerative Rotator Cuff Lesion," J Bone Joint Surg AM (2003) 85; 475-480

6) Abatangelo G., O'Regan M. "Hyaluronan: Biological role and Function in Articular Joints"
European Journal of Rheumatology and Inflammation 1995; 15: 9-16

7) Shibata et al. Presented at the AAOS, Anaheim, Ca. Feb 1999. Press release from the Academy News Newsletter. 05/02/1999. "Hyaluronate Sodium Eases Pain of Rotator Cuff Tear."

8) Simon LS. Viscosupplementation therapy with intra-articular hyaluronic acid - fact or fantasy? Rheum Dis Clin N Am. 1999. 25(2): 345-357.

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