Silicone suspension of external prostheses. A new era in artificial limb usage

SILICONE SUSPENSION OF EXTERNAL PROSTHESES A NEW ERA IN ARTIFICIAL LIMB USAGE MICHAEL HEIM,

MICHAEL WERSHAVSKI,

HANNA NADVORNA,

SHIFRA T. ZWAS,

ITZHAK SIEV-NER,

MORRIS AZARIA

From the Chaim Sheba Medical Centre, Tel Hashomer, Israel

The use of silicone inner sockets, with or without the incorporation of shuttle locks, has greatly improved the function of artificial limbs. They cushion and protect the stump and provide a means for prosthetic suspension, allowing more comfortable use, especially in patients with ischaemic stumps. They also allow greater movement at the proximal joint. J Bone Joint Surg [Br] 1997;79-B:638-40. Received 18 October 1996; Accepted after revision 12 February 1997

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The use of silicone in prosthetics is not new. It has two main functions, namely, protection of the amputation stump and suspension of the prosthesis. Protection is afforded by either custom-made or ‘off-the-shelf’ socks or by the addition of Silipads or strips which insulate bony prominences in the stump from pressure from the prosthesis. Suspension can be achieved either by the use of a silicone stump alone or by incorporation into the silicone sleeve of a rigid metal pin which locks into an appropriate receptacle in the prosthesis itself. This shuttle-lock principle was introduced in 1989 by Fillauer, Pritham and Filla2 uer for transtibial amputees (Fig. 1). We have used a similar principle with transfemoral and below-elbow prostheses.

eventually had a right transfemoral amputation and was left with an ischaemic stump. He was fitted with a number of vacuum and pelvic-band suspended sockets, but continued to complain of discomfort and the cumbersome prosthesis. He was then fitted with a moulded silicone inner socket containing a shuttle-lock system (Fig. 2). No other suspension system was necessary and he is very pleased with the result. He reports no pain and the snugness of the fit gives him the feeling that the prosthesis is actually ‘part of himself’. Case 2. A 26-year-old man had an above-knee amputation after a motor-vehicle accident. There was extensive softtissue damage and the stump, which is 16.5 cm long, has painful scars and an uneven surface area. A custom-made silicone liner with a shuttle-lock system was constructed and has given him complete satisfaction. Case 3. A 45-year-old man lost his right arm below the elbow in 1988. He subsequently had a number of bodypowered functional prostheses, but was always disturbed by the construction of the socket which limited movement at the elbow. A shuttle lock with a silicone liner was made to replace the regular M¨unster socket which incorporates the olecranon, with an outer socket designed to avoid impingement on elbow movement. This system has allowed additional freedom for the elbow and retained all other functions.

CASE REPORTS Case 1. A 51-year-old man with peripheral vascular disease had 12 vascular reconstructive operations in 18 months. He

M. Heim, MB ChB, Professor and Orthopaedic Consultant M. Wershavski, MD, Resident I. Siev-Ner, MD, Orthopaedic and Physiatric Consultant H. Nadvorna, MD, Physiatric Consultant M. Azaria, MD, Director Department of Orthopaedic Rehabilitation S.T. Zwas, MD, Professor and Director Department of Nuclear Medicine Chaim Sheba Medical Centre, Tel Hashomer Hospital, Tel Hashomer 52621, Israel. Correspondence should be sent to Professor M. Heim. ©1997 British Editorial Society of Bone and Joint Surgery 0301-620X/97/47350 $2.00 638

DISCUSSION The method of attachment of an external prosthesis to the limb stump is a major consideration. In the leg, gravity and the body-weight act downwards, and help to force the stump into the socket. Suspension of the prosthesis is only necessary during the swing phase of walking. In the arm continuous suspension of the prosthesis is needed to overcome the tendency of gravity to disconnect it from the stump. The various suspension mechanisms available include anchoring belts, corsets, and straps and sockets shaped to utilise bony prominences for anchorage. They usually extend proximal to the joint above, and therefore limit the range of movement. Prosthetic vacuum sockets are used in transfemoral amputations: this method of suspenTHE JOURNAL OF BONE AND JOINT SURGERY

SILICONE SUSPENSION OF EXTERNAL PROSTHESES

Fig. 1 Diagram showing the principles of the silicone liner with the shuttle-lock fixation device.

Fig. 2a

sion does not limit hip movement. To ensure a constant vacuum, the stump-prosthesis interface has to be perfect to prevent it being lost. In patients with vascular problems the stumps become very painful under excess vacuum. To distribute pressure and protect the amputation stump, inner sockets made of soft materials are often provided. Silicone liners protect the stump and also act as suspension mechanisms. The liner can be put on and removed easily by rolling it on and off the stump and it offers a snug total contact interface with both the cutaneous surface and 3 the socket. The amount of suspension is adequate for elderly, relatively sedentary, below-knee amputees. More active patients, however, require a stronger suspension 4 mechanism. Silicone sleeves with shuttle-lock systems have proved successful. The silicone liner, which applies universal, total contact pressure, also assists in defining the final shape and size of the stump. This design has now been used for other amputation stumps. Short transfemoral stumps are well contained in the sleeve and the fixation of the shuttle lock into the prosthetic socket gives adequate suspension without causing pain. The total contact and minimum vacuum force allow its use with marginally ischaemic stumps. This also allows amputees to wear their prostheses for longer periods. In below-elbow amputees incorporation of the olecranon (M¨unster design) was the usual method of suspension, but this limits elbow movement. Silicone sleeves with shuttle-

Fig. 2b

Photographs showing the right thigh stump covered by the silicone inner socket and the shuttle-lock pin (a) and the interior of the transfemoral socket with the receptacle portion for the shuttle-lock pin (b).

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M. HEIM,

M. WERSHAVSKI,

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lock suspension give superior comfort with increased freedom of movement. One result is the more frequent use of the prostheses by the amputees. Silicone liner replacement is required more often than for normal stump socks, but the minor increase in cost is far outweighed by the benefits. We wish to thank Mr Chanoch Bar-Goren, Chief Prosthetist of Gapim Industries Ltd, for his illustrations and assistance in the preparation of this manuscript. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

S. T. ZWAS,

ET AL

REFERENCES 1. Boot DA, Young NJ. A new directly moulded patellar-tendon-bearing socket. Prosthet Orthot Int 1985;9:112-4. 2. Fillauer CE, Pritham CH, Fillauer KD. Evaluation and development of the silicone suction socket (3S) for below-knee prostheses. J Prosthet Orthot Int 1989;1:92-103. 3. Kristinsson O. The ICEROSS concept: a discussion of a philosophy. Prosthet Orthot Int 1993;17:49-55. 4. Braddom LR. Lower limb prosthetics. In: Physical medicine and rehabilitation. Philadelphia, etc: WB Saunders Co, 1996; 298-300. 5. Madigan RR, Fillauer KD. 3-S prosthesis: a preliminary report. J Pediatr Orthop 1991;11:112-7.

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