- Email: [email protected]
Reconstructive arthroplasty of the metacarpophalangeal joint using the extensor loop operation
R E C O N S T R U C T I V E A R T H R O P L A S T Y OF T H E M E T A C A R P O P H A L A N G E A L JOINT U S I N G T H E E X T E N S O R L O O P O P E R A T I O N By STEWARTH. HARRISON,F.R.C.S., L.D.S.R.C.S. Department of Plastic Surgery, IVexham Park Hospital, Slough, and the Medical Research Council Rheumatism Unit, Taplow, Bucks THERE are three methods of dealing with a joint disabled by rheumatoid arthritis, arthrodesis, excision arthroplasty or prosthetic arthroplasty. Arthrodesis is a last resort and the purpose of this paper is to present methods used to restore muscle balance in excision arthoplasty of the metacarpo-phalangeal joint with or without the use of a prosthesis. Grant (1958) has described this joint as a condyloid joint which can perform the four components of circumduction, flexion, extension, abduction and adduction. In order to re-establish function in the joint by arthroplasty, it is necessary to restore muscle balance whether a prosthesis is used or not. The M e c h a n i s m o f the D e f o r m i t y . - - T h e three main deformities which appear successively are ulnar drift, subluxation and limitation of extension. There are many theories on the causation of ulnar drift but certain facts are known. A definite cause of ulnar drift is a tear of the radial side of the dorsal hood. This is seen in traumatic cases and causes ulnar displacement of the fingers but not subluxation. Furthermore, a tear of the radial collateral ligament produces ulnar drift and subluxation while rupture of both collateral ligaments produces subluxation, dislocation and loss of extension. In rheumatoid arthritis synovial proliferation can distend the radial side of the capsule of the metacarpo-phalangeal joint and thus initiate the deformity of ulnar drift. Rupture of the radial collateral ligament will follow concurrently with progressive joim destruction. Ultimately both collateral ligaments will rupture and the joint will go into a position of subhixation and extension of the fingers will become limited. There is, however, one interesting anatomical feature of the extensor mechanism which is perhaps not so well known. Figure I shows an area of dense fibrous tissue arising from the dorsum of the base of the proximal phalanx. It is lined by synovial membrane and attached to the capsule. This tongue of fibrous tissue is involved early in rheumatoid arthritis, leaving pitted erosions at its attachments on the dorsum of the proximal phalanx. This is particularly seen in the first metacarpo-phalangeal joint when it is associated with a slight degree of subluxation, and is the preliminary stage preceding Z deformity of the thumb. The area of thickened capsule may prevent subluxation in a similar manner to the volar plate. It actively participates in the extension of the metacarpo-phalangeal joint, as the extensor tendon has no direct insertion into the base of the proximal phalanx. The importance of the capsular attachments in maintaining stability and alignment of the joint can be clearly seen in those cases in which gross radiological erosion on the radial side of the metacarpal with partial detachment of the collateral ligament would be expected to show a subluxation, but often remain in alignment as can be seen in Figure 2. If one unwisely does a synovectomy in the latter cases, the digit may then pass into a position of ulnar displacement and subluxation even though the radial collateral ligament has not suffered any further damage as a result of the surgery. Thus, as a result of the destructive pathological process, and the disruptive effect of surgery, the mechanism of extension, balance and stability may be lost. 3~* 307
308
BRITISH JOURNAL OF PLASTIC SURGERY
R e c o n s t r u c t i o n o f the Joint.--First Stage.--Any radial deviation of the wrist is corrected by ulnar styloidectomy and splinting for six weeks. It is often not possible to maintain alignment of the fingers after excision arthroplasty in the presence of a radial deviation of the wrist as can be seen in Figure 3. This shows a recurrence of ulnar drift after excision arthroplasty.
FIG. I FIG. 2 FIG. 3 Fig. i . - - T h e dorsal plate or thickened capsule through which the mechanism of extension is transmitted to the base of the proximal phalanx, is seen held in the forceps. Fig. 2 . - - G o o d alignment can be seen to be maintained in the second metacarpo-phalangeal joint despite gross bone destruction at the attachment of the radial collateral ligament. Fig. 3.--Shows a recurrence of ulnar drift after excision arthroplasty in which radial deviation of the wrist had not been corrected prior to operation.
Second Stage.--After excision of 2 cm. of the metacarpal head and neck, an extensor loop operation (Fig. 4) is performed. This consists simply of a detachment of half the extensor tendon dissected distally to the level of the base of the proximal phalanx. The slip is passed through a drill-hole which is made in the base of phalanx and made to emerge through the dorsum FIG. 4 of the bone close to the proximal margin where it is Shows the method of insertion of half sutured to the main tendon of the extensor on the the extensor tendon into the base of dorsum. the proximal phalanx. This procedure has three objectives : to maintain the correct alignment of the extensor tendon ; to provide an insertion into the base of the phalanx ; to prevent subluxation. The flexor tendon is now decompressed by a longitudinal incision made in the volar plate. If gross flexor synovial involvement is present, then a separate approach should be made to the flexor tendon through the palm. The reason for this decompression is that a post-operative flare-up of rheumatoid arthritis affecting the flexor synovial sheath will inhibit recovery of movement and, if this should continue, then permanent limitation of movement may result. In long-standing cases of subluxafion the theca should be incised at the base of the proximal phalanx in order to increase the angle of incidence of the flexor tendon and thus diminish the risk of subluxation. Weakness of grip follows shortening of muscles as a result of excision of 2 cm. of bone. This occurs because the contraction of a muscle fibre is maximal at its greatest effective length. A silasfic prosthesis may therefore be inserted in order to occupy part
RECONSTRUCTIVE ARTHROPLASTY USING EXTENSOR LOOP OPERATION
309
of the space created by excision of the head. Finally, the transplantation of the extensor indicis proprius to reinforce the first interosseous has now been abandoned because in the majority of cases it is possible to develop the first interosseous muscle strongly enough to function as an abductor and stabilise the index finger against the thumb in apposition. Furthermore, the extensor indicis proprius is required as a tendon transplant in the event of a rupture of the extensor tendons. It is also important to maintain the integrity of the radial and ulnar intrinsic muscles as they are concerned in the stability of the arthroplasty. The extensor tendon is split to gain access to the joint and this is repaired at the end of the operation. Post-operatively a moulded splint is applied with dynamic slings and should be maintained for a period of six weeks. During this period intensive exercises in and out of the splint are required. Figure 5 shows a suitable splint made of acrylic by injection moulding at the Plastic Surgery Centre, Mount Vernon Hospital, by the dental mechanics.
FIG. 5 Moulded acrylic splint with extension bar and elastic slings extending over the metacarpo-phalangeal arthroplasty. CONCLUSIONS
The object of correcting a joint deformity is to restore alignment and function. In order to do this, the mechanism of the deformity should be understood. Excision arthroplasty of the metacarpo-phalangeal joint should be performed on patients who have gross ulnar drift, subluxafion and limited extension. Grip is important to the rheumatoid patients in order to support themselves and aid propulsion. The restoration of extension is also important, particularly for the housewife who requires a fiat hand for many of her household duties. Total incapacity of the hand, however, occurs only when pinch is lost and one of the important aspects of arthroplasty is re-alignment of the fingers to the thumb. The introduction of inert substances such as silastic may be a valuable contribution to small joint surgery, but should be regarded only as an adjuvant to the main objective in arthroplasty, which is the restoration of muscle balance. All rheumatoid patients are seen at a joint clinic held with Dr Barbara Ansell, Consultant Rheumatologist, of the Medical Research Council Rheumatism Unit, Taplow, Bucks., and I acknowledge with thanks her constant help and advice in dealing with these patients. GRANT, J. C. B. (I958).
"
REFERENCE Method of Anatomy ", 6th ed. Baltimore : Williams & Wilkins.
308
BRITISH JOURNAL OF PLASTIC SURGERY
R e c o n s t r u c t i o n o f the Joint.--First Stage.--Any radial deviation of the wrist is corrected by ulnar styloidectomy and splinting for six weeks. It is often not possible to maintain alignment of the fingers after excision arthroplasty in the presence of a radial deviation of the wrist as can be seen in Figure 3. This shows a recurrence of ulnar drift after excision arthroplasty.
FIG. I FIG. 2 FIG. 3 Fig. i . - - T h e dorsal plate or thickened capsule through which the mechanism of extension is transmitted to the base of the proximal phalanx, is seen held in the forceps. Fig. 2 . - - G o o d alignment can be seen to be maintained in the second metacarpo-phalangeal joint despite gross bone destruction at the attachment of the radial collateral ligament. Fig. 3.--Shows a recurrence of ulnar drift after excision arthroplasty in which radial deviation of the wrist had not been corrected prior to operation.
Second Stage.--After excision of 2 cm. of the metacarpal head and neck, an extensor loop operation (Fig. 4) is performed. This consists simply of a detachment of half the extensor tendon dissected distally to the level of the base of the proximal phalanx. The slip is passed through a drill-hole which is made in the base of phalanx and made to emerge through the dorsum FIG. 4 of the bone close to the proximal margin where it is Shows the method of insertion of half sutured to the main tendon of the extensor on the the extensor tendon into the base of dorsum. the proximal phalanx. This procedure has three objectives : to maintain the correct alignment of the extensor tendon ; to provide an insertion into the base of the phalanx ; to prevent subluxation. The flexor tendon is now decompressed by a longitudinal incision made in the volar plate. If gross flexor synovial involvement is present, then a separate approach should be made to the flexor tendon through the palm. The reason for this decompression is that a post-operative flare-up of rheumatoid arthritis affecting the flexor synovial sheath will inhibit recovery of movement and, if this should continue, then permanent limitation of movement may result. In long-standing cases of subluxafion the theca should be incised at the base of the proximal phalanx in order to increase the angle of incidence of the flexor tendon and thus diminish the risk of subluxation. Weakness of grip follows shortening of muscles as a result of excision of 2 cm. of bone. This occurs because the contraction of a muscle fibre is maximal at its greatest effective length. A silasfic prosthesis may therefore be inserted in order to occupy part
RECONSTRUCTIVE ARTHROPLASTY USING EXTENSOR LOOP OPERATION
309
of the space created by excision of the head. Finally, the transplantation of the extensor indicis proprius to reinforce the first interosseous has now been abandoned because in the majority of cases it is possible to develop the first interosseous muscle strongly enough to function as an abductor and stabilise the index finger against the thumb in apposition. Furthermore, the extensor indicis proprius is required as a tendon transplant in the event of a rupture of the extensor tendons. It is also important to maintain the integrity of the radial and ulnar intrinsic muscles as they are concerned in the stability of the arthroplasty. The extensor tendon is split to gain access to the joint and this is repaired at the end of the operation. Post-operatively a moulded splint is applied with dynamic slings and should be maintained for a period of six weeks. During this period intensive exercises in and out of the splint are required. Figure 5 shows a suitable splint made of acrylic by injection moulding at the Plastic Surgery Centre, Mount Vernon Hospital, by the dental mechanics.
FIG. 5 Moulded acrylic splint with extension bar and elastic slings extending over the metacarpo-phalangeal arthroplasty. CONCLUSIONS
The object of correcting a joint deformity is to restore alignment and function. In order to do this, the mechanism of the deformity should be understood. Excision arthroplasty of the metacarpo-phalangeal joint should be performed on patients who have gross ulnar drift, subluxafion and limited extension. Grip is important to the rheumatoid patients in order to support themselves and aid propulsion. The restoration of extension is also important, particularly for the housewife who requires a fiat hand for many of her household duties. Total incapacity of the hand, however, occurs only when pinch is lost and one of the important aspects of arthroplasty is re-alignment of the fingers to the thumb. The introduction of inert substances such as silastic may be a valuable contribution to small joint surgery, but should be regarded only as an adjuvant to the main objective in arthroplasty, which is the restoration of muscle balance. All rheumatoid patients are seen at a joint clinic held with Dr Barbara Ansell, Consultant Rheumatologist, of the Medical Research Council Rheumatism Unit, Taplow, Bucks., and I acknowledge with thanks her constant help and advice in dealing with these patients. GRANT, J. C. B. (I958).
"
REFERENCE Method of Anatomy ", 6th ed. Baltimore : Williams & Wilkins.