Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery
ISSN: 0284-4311 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/iphs19
Silicone Rubber Implants for Arthrosis of the Scaphotrapezial Joint Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell & Henrik Düppe To cite this article: Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell & Henrik Düppe (1992) Silicone Rubber Implants for Arthrosis of the Scaphotrapezial Joint, Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, 26:2, 173-176, DOI: 10.3109/02844319209016009 To link to this article: http://dx.doi.org/10.3109/02844319209016009
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 3
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iphs19 Download by: [University of California Santa Barbara]
Date: 02 April 2016, At: 03:48
Scand J Plast Reconstr-Hand Surgt2B:J73-176. 1992
SILICONE RUBBER IMPLANTS FOR ARTHROSIS OF THE SCAPHOTRAPEZIAL JOINT
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell' and Henrik Duppe From the Departments of Hand Surgery and 'Diagnostic Radiology, Malmo General Hospital, Lund University, Malmo, Sweden
(Submitted for publication June 7, 1991)
Abstract. Between 1980 and 1983, 10 patients received high performance silicone rubber condylar implants for the treatment of isolated degenerative changes of the scaphotrapezial joint. Early clinical and radiographic results (at a mean of 15 months) were excellent. Late follow up of these 10 together with a further I 1 patients, however, showed migration of the implant and radiological signs of silicone particle synovitis in all but two. We no longer recommend this operation for treatment of isolated arthrosis of the scaphotrapezial joint. Key wordr: arthritis, scaphotrapezial joint, Silastic implant
Although many authors have discussed the treatment of degenerative changes in the basal articulation of the thumb, less attention has been paid to those in the scaphotrapezial articulation. If this joint is affected by isolated arthrosis or pantrapezial arthrosis, the hand is often painful and weak (3). For many years fusion of the joint was the treatment of choice (4). Problems such as delayed healing, reflex sympathetic dystrophy, and-later-increased strain on the adjacent joints were reported (4, 6), so an interpositional hemiarthroplasty using silicone rubber (Silastic) was introduced. Good initial results were obtained (5) but later deterioration of the implants resulted in migration of the fragments (7, 13). These implants were of Kessler design and fabricated from Dow Corning MDX-4-4210 elastomer. Despite these problems interpositional hemiarthroplasty was considered a promising procedure for this condition and a high performance Silastic prosthesis was developed. A report from our clinic in 1983 of 10 patients who had such implants showed excellent results both clinically and radiographically (8). The present study was done to evaluate the long term results of the operation. &and J Plast Reconstr Hand Surg 26
PATIENTS AND METHODS From 1980 to 1986, hemiarthroplasty of the scaphotrapezial joint was done in 21 patients, three men and 18 women, with a Dow Corning high performance Silastic condylar implant (convex Swanson design) as a spacer. Thirteen were reported on the dominant side. The mean age was 65 years (range 55-75). All the patients had isolated degenerative changes in the scaphotrapezial joint. Nineteen patients had idiopathic arthrosis, and in two cases the arthrosis was the result of a distal fracture of the scaphoid. Pain at the base of the thumb at rest and weakness of the hand were invariable findings, and symptoms had lasted for a mean of 3.5 years (range 0.5- 10) before operation. Before operation all the patients had tried conservative treatment such as anti-inflammatory drugs, cortisone injections into the scaphotrapezial joint, thenar strengthening exercises and splinting, but without long-lasting effects. The mean length of follow up was five years (range 2-9 years) postoperatively by the junior author, independently of the operating surgeon. Grip strength was measured by a Martin VigorirneteP (15) and pinch strength with a Mannerfeldt Intrin~icmeter~ ( I). Radiographic assessment was by a senior member of the radiological department. Standard anteroposterior and lateral views of the base of the thumb were taken, together with an additional posteroanterior view of the radiocarpal joint. Five patients were excluded from the study: one died two years after the operation; one had an implant luxation two months after operation leading to removal of the prosthesis; and three developed pantrapezial arthrosis one-four years after the operation. The latter cases underwent removal of the trapezium, including the silicone rubber implant, followed by an extensor carpi radialis longus arthroplasty (12). Surgical technique The surgical technique was virtually the same as that described by Eiken ( 5 ) . The goal is to replace the scaphoid articular surface with a spacer corresponding to the shape of the original surface (Fig. I). To position the prosthesis correctly it is important that the plane of the transection is at right angles to the longitudinal axis of the scaphotrapezial joint. The size of the resected joint face determines the
174
M . K . Kurlsson et ul.
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
Table I. Mean grip strength in operated and contrulateral hand
Grip ( kp*/cm2): Operated hand Contralateral hand Reference value Grip strength in operated hand as percentage of that in contralateral hand *I kp=98.1 kPa
Dominant hand
Non-dominant hand
0.39 0.44 0.74 89
0.4 I
0.59 Not applicable 70
radial abduction are 30-70" and 30-65". respectively ( I 1). The mean extension of the radiocarpal joint was 48", and flexion 63". Reference mean values in this joint accepted by the American Academy of Orthopedic Surgeons are 70" for extension and 75" for flexion. Thirteen of 16 patients moved the thumb to the fifth metacarpophalangeal joint, but the rest had more restricted mobility.
Fig. 1. Postoperative radiograph with prosthesis in right position.
appropriate size of the implant-usually size 10. 1 I , or 12. The smaller diameter of the implant is inserted in the sagittal plane, and the stem is fitted into an intramedullary slot in the scaphoid with a sizing instrument for measuring the slot, so that the prosthesis fits snugly. The thumb and wrist are immobilised in a splint for four weeks after operation.
Strength The mean grip strength was 0.40 kp/cm' (range 0.1 0.8 kp/cm2) ( 1 kp/cm* = 98.1 kPa) (Table I) and pinch strength 210 units (range 60-350 units) (100 units correspond to 23 N) (Table 11). Mean reported values in the dominant hand for women aged 56-60 are 0.74 kp/cm2 for grip strength, and 230 units for pinch grip ( I , 15) (Table I). Ra~iogruphicjndings Ofthe original 21 cases, the 16 in whom the prosthesis remained had further radiographs done. In four
Table 11. Mean pinch strength in operated and contralateraf hand
RESULTS Fourteen of the 21 patients were satisfied with their hand function. We found no correlation of radiographic findings, clinical findings, and the patients' opinions at follow up. Range of movement The mean values were 53" (range 30-75") for volar abduction and 51" (range 20-75") for radial abduction. The reported reference ranges for volar and Scand J Plast Reconstr Hand Surg 26
Pinch strength (units*): Operated hand Contralateralhand Reference value Pinch strength in operated hand as percentage Of that in contralateral hand units = 23
Dominant hand
Non-dominant hand
217 228
200 25 I Not applicable 80
230 95
Silicone implant of the scaphotrapezial joint
175
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
DISCUSSION
Fig. 2. Migrated prosthesis with cysts as in silicone synovitis.
cases the prosthesis was dislocated, in five the implant was fractured and in four there was adjacent bone resorption. Twelve patients had developed carpal bone cysts since the operation, and five had them in more than one carpal bone (Fig. 2). Only two patients had no radiographic abnormalities.
Sick leave Eleven patients had retired before they were operated on, two because of the problems with the base of the thumb. The mean duration of sick leave was 14 weeks for the remaining eight patients, who all returned to work. Complications One patient developed a shoulder-hand-finger syndrome post-operatively, which resolved after physiotherapy. Three patients had hyperaesthesia of the scar, but these had all resolved after one year.
Degenerative changes of the scaphotrapezial joint are usually treated by fusion of the articulation to eliminate pain and to restore a powerful grasp. Bone fusion can be difficult, however, (4,6) and a long period of immobilisation postoperatively is not an attractive prospect. During the last decades, therefore, resection arthroplasties of the scaphotrapezial joint using interposition of biological or alloplastic materials have been attempted (14). Fibrous tissue such as fascia lata, a coiled section of autologous tendon, or lyophilised homologous dura mater may be resorbed ( I , 2, 6, 9, 16), resulting in instability and pain. Kessler et al. (10) reported good results from replacing the trapezia1 articulation surface with a silicone rubber sheet, leaving the corresponding articular surface of the scaphoid intact. Because of the strong compression forces during grasp Eiken (5) concluded (after having used plastic material as spacer in his early scaphotrapezial arthroplasties) that the implant material must be extremely durable and that it must be anchored to prevent dislocation and migration. In 1980, a new implant material, a high performance Silastic, was introduced. Early reports showed that the high performance condylar prosthesis was safe, and that there was no deterioration of the implant or bone reaction (8). Pellegrini and Burton (13) and Eiken et al. (7) discussed bone resorption, instability of implants, and carpal cysts as a result of silicone particle synovitis, after different silicone rubber implants. From the present results it is obvious that the high performance condylar implant ha5 the same disadvantages as its predecessors: it migrates, fractures, and dislocates and there is bone resorption with formation of carpal bone cysts. Despite the advantages of an easy operation, a short postoperative period of immobilisation, as well as 14 of 21 satisfied patients at the follow up, we do not recommend using the high performance condylar implant in the scaphotrapezial joint because of the high incidence of bone resorption and carpal bone cysts as in silicone particle synovitis. REFERENCES I . Brorson H, Werner CO, Thorngren KG. Normal pinch strength. Acta Orthop Scand 1987; 60:66-68. Scand J Plast Reconstr Hand Surg 26
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
176
M. K. Karlsson
et al.
2. Buck-Gramcko D. Operative Behandlung der Sattelgelenk-arthrose des Daumens. Hand Chirurg 1972; 4 105-109. 3. Carstam N, Eiken 0, Andren L. Osteoarthritis of the trapezio-scaphoid joint. Acta Orthop Scand 1968; 39: 354-358. 4. Crosby Brown E, Linscheid RL, Dobyns JH. Scaphotrapezia1 trapezoidal arthrosis. J Hand Surg 1978; 3: 223-234. 5. Eiken 0. Implant arthroplasty of the scapho-trapezia1 joint. Scand J Plast Reconstr Surg 1979; 13: 461468. 6. Eiken 0, Carstam N. Functional assessment of basal joint fusion of the thumb. Scand J Plast Reconstr Surg 1970; 4 122-125. 7. Eiken 0, Ekerot L, Lindstrom C, Jonsson K. Silicon carpal implants: risk or benefit? Scand J Plast Reconstr Surg 1985; 19: 295-304. 8. Eiken 0, Necking L-E. Silicon rubber implants for arthrosis of the scaphotrapezial trapezoidal joint. Scand J Plast Reconstr Surg 1983; 17: 253255.
Srimd J Plasl Rrconstr Hand Surg 26
9. Fromison A. Tendon arthroplasty of the trapeziometacarpal joint. Clin Orthop 1970; 70: 191-199. 10. Kessler I, Baruch A, Hecht 0, Amit S . Osteoarthritis at the base of the thumb. Acta Orthop Scand 1976; 47: 361 -369. 1 I . Lech RE, Bolton PE. Arthritis of the carpometacarpal joint of the thumb. J Bone Joint Surg 1968: 50A: I 171 - 1 1 77. 12. Necking L-E, Eiken 0. ECRL-strip for metacarpal base fixation after excision of the trapezium. Scand J Plast Reconstr Surg 1986; 20: 229-234. 13. Pellegrini VD, Burton RI. Surgical management of basal joint arthritis of the thumb. Long-term results of silicon implant arthroplasty. J Hand Surg 1986; 1 I A: 309-324. 14. Sollerman C, Herrlin K. Abrahamsson SO, Lindholm A. Silastic replacement of the trapezium for arthrosis-a 12-year follow-up study. J Hand Surg 1988; 138: 426429. 15. Thorngren KG, Werner CO. Normal grip strength. Acta Orthop S a n d 1979; 50: 255-266. 16. Wilson JN. Arthroplasty of trapezio-metacarpal joint. Plast Reconstr Surg 1972; 49: 143-148.
ISSN: 0284-4311 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/iphs19
Silicone Rubber Implants for Arthrosis of the Scaphotrapezial Joint Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell & Henrik Düppe To cite this article: Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell & Henrik Düppe (1992) Silicone Rubber Implants for Arthrosis of the Scaphotrapezial Joint, Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, 26:2, 173-176, DOI: 10.3109/02844319209016009 To link to this article: http://dx.doi.org/10.3109/02844319209016009
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 3
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iphs19 Download by: [University of California Santa Barbara]
Date: 02 April 2016, At: 03:48
Scand J Plast Reconstr-Hand Surgt2B:J73-176. 1992
SILICONE RUBBER IMPLANTS FOR ARTHROSIS OF THE SCAPHOTRAPEZIAL JOINT
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
Magnus K. Karlsson, Lars-Eric Necking, Inga Redlund-Johnell' and Henrik Duppe From the Departments of Hand Surgery and 'Diagnostic Radiology, Malmo General Hospital, Lund University, Malmo, Sweden
(Submitted for publication June 7, 1991)
Abstract. Between 1980 and 1983, 10 patients received high performance silicone rubber condylar implants for the treatment of isolated degenerative changes of the scaphotrapezial joint. Early clinical and radiographic results (at a mean of 15 months) were excellent. Late follow up of these 10 together with a further I 1 patients, however, showed migration of the implant and radiological signs of silicone particle synovitis in all but two. We no longer recommend this operation for treatment of isolated arthrosis of the scaphotrapezial joint. Key wordr: arthritis, scaphotrapezial joint, Silastic implant
Although many authors have discussed the treatment of degenerative changes in the basal articulation of the thumb, less attention has been paid to those in the scaphotrapezial articulation. If this joint is affected by isolated arthrosis or pantrapezial arthrosis, the hand is often painful and weak (3). For many years fusion of the joint was the treatment of choice (4). Problems such as delayed healing, reflex sympathetic dystrophy, and-later-increased strain on the adjacent joints were reported (4, 6), so an interpositional hemiarthroplasty using silicone rubber (Silastic) was introduced. Good initial results were obtained (5) but later deterioration of the implants resulted in migration of the fragments (7, 13). These implants were of Kessler design and fabricated from Dow Corning MDX-4-4210 elastomer. Despite these problems interpositional hemiarthroplasty was considered a promising procedure for this condition and a high performance Silastic prosthesis was developed. A report from our clinic in 1983 of 10 patients who had such implants showed excellent results both clinically and radiographically (8). The present study was done to evaluate the long term results of the operation. &and J Plast Reconstr Hand Surg 26
PATIENTS AND METHODS From 1980 to 1986, hemiarthroplasty of the scaphotrapezial joint was done in 21 patients, three men and 18 women, with a Dow Corning high performance Silastic condylar implant (convex Swanson design) as a spacer. Thirteen were reported on the dominant side. The mean age was 65 years (range 55-75). All the patients had isolated degenerative changes in the scaphotrapezial joint. Nineteen patients had idiopathic arthrosis, and in two cases the arthrosis was the result of a distal fracture of the scaphoid. Pain at the base of the thumb at rest and weakness of the hand were invariable findings, and symptoms had lasted for a mean of 3.5 years (range 0.5- 10) before operation. Before operation all the patients had tried conservative treatment such as anti-inflammatory drugs, cortisone injections into the scaphotrapezial joint, thenar strengthening exercises and splinting, but without long-lasting effects. The mean length of follow up was five years (range 2-9 years) postoperatively by the junior author, independently of the operating surgeon. Grip strength was measured by a Martin VigorirneteP (15) and pinch strength with a Mannerfeldt Intrin~icmeter~ ( I). Radiographic assessment was by a senior member of the radiological department. Standard anteroposterior and lateral views of the base of the thumb were taken, together with an additional posteroanterior view of the radiocarpal joint. Five patients were excluded from the study: one died two years after the operation; one had an implant luxation two months after operation leading to removal of the prosthesis; and three developed pantrapezial arthrosis one-four years after the operation. The latter cases underwent removal of the trapezium, including the silicone rubber implant, followed by an extensor carpi radialis longus arthroplasty (12). Surgical technique The surgical technique was virtually the same as that described by Eiken ( 5 ) . The goal is to replace the scaphoid articular surface with a spacer corresponding to the shape of the original surface (Fig. I). To position the prosthesis correctly it is important that the plane of the transection is at right angles to the longitudinal axis of the scaphotrapezial joint. The size of the resected joint face determines the
174
M . K . Kurlsson et ul.
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
Table I. Mean grip strength in operated and contrulateral hand
Grip ( kp*/cm2): Operated hand Contralateral hand Reference value Grip strength in operated hand as percentage of that in contralateral hand *I kp=98.1 kPa
Dominant hand
Non-dominant hand
0.39 0.44 0.74 89
0.4 I
0.59 Not applicable 70
radial abduction are 30-70" and 30-65". respectively ( I 1). The mean extension of the radiocarpal joint was 48", and flexion 63". Reference mean values in this joint accepted by the American Academy of Orthopedic Surgeons are 70" for extension and 75" for flexion. Thirteen of 16 patients moved the thumb to the fifth metacarpophalangeal joint, but the rest had more restricted mobility.
Fig. 1. Postoperative radiograph with prosthesis in right position.
appropriate size of the implant-usually size 10. 1 I , or 12. The smaller diameter of the implant is inserted in the sagittal plane, and the stem is fitted into an intramedullary slot in the scaphoid with a sizing instrument for measuring the slot, so that the prosthesis fits snugly. The thumb and wrist are immobilised in a splint for four weeks after operation.
Strength The mean grip strength was 0.40 kp/cm' (range 0.1 0.8 kp/cm2) ( 1 kp/cm* = 98.1 kPa) (Table I) and pinch strength 210 units (range 60-350 units) (100 units correspond to 23 N) (Table 11). Mean reported values in the dominant hand for women aged 56-60 are 0.74 kp/cm2 for grip strength, and 230 units for pinch grip ( I , 15) (Table I). Ra~iogruphicjndings Ofthe original 21 cases, the 16 in whom the prosthesis remained had further radiographs done. In four
Table 11. Mean pinch strength in operated and contralateraf hand
RESULTS Fourteen of the 21 patients were satisfied with their hand function. We found no correlation of radiographic findings, clinical findings, and the patients' opinions at follow up. Range of movement The mean values were 53" (range 30-75") for volar abduction and 51" (range 20-75") for radial abduction. The reported reference ranges for volar and Scand J Plast Reconstr Hand Surg 26
Pinch strength (units*): Operated hand Contralateralhand Reference value Pinch strength in operated hand as percentage Of that in contralateral hand units = 23
Dominant hand
Non-dominant hand
217 228
200 25 I Not applicable 80
230 95
Silicone implant of the scaphotrapezial joint
175
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
DISCUSSION
Fig. 2. Migrated prosthesis with cysts as in silicone synovitis.
cases the prosthesis was dislocated, in five the implant was fractured and in four there was adjacent bone resorption. Twelve patients had developed carpal bone cysts since the operation, and five had them in more than one carpal bone (Fig. 2). Only two patients had no radiographic abnormalities.
Sick leave Eleven patients had retired before they were operated on, two because of the problems with the base of the thumb. The mean duration of sick leave was 14 weeks for the remaining eight patients, who all returned to work. Complications One patient developed a shoulder-hand-finger syndrome post-operatively, which resolved after physiotherapy. Three patients had hyperaesthesia of the scar, but these had all resolved after one year.
Degenerative changes of the scaphotrapezial joint are usually treated by fusion of the articulation to eliminate pain and to restore a powerful grasp. Bone fusion can be difficult, however, (4,6) and a long period of immobilisation postoperatively is not an attractive prospect. During the last decades, therefore, resection arthroplasties of the scaphotrapezial joint using interposition of biological or alloplastic materials have been attempted (14). Fibrous tissue such as fascia lata, a coiled section of autologous tendon, or lyophilised homologous dura mater may be resorbed ( I , 2, 6, 9, 16), resulting in instability and pain. Kessler et al. (10) reported good results from replacing the trapezia1 articulation surface with a silicone rubber sheet, leaving the corresponding articular surface of the scaphoid intact. Because of the strong compression forces during grasp Eiken (5) concluded (after having used plastic material as spacer in his early scaphotrapezial arthroplasties) that the implant material must be extremely durable and that it must be anchored to prevent dislocation and migration. In 1980, a new implant material, a high performance Silastic, was introduced. Early reports showed that the high performance condylar prosthesis was safe, and that there was no deterioration of the implant or bone reaction (8). Pellegrini and Burton (13) and Eiken et al. (7) discussed bone resorption, instability of implants, and carpal cysts as a result of silicone particle synovitis, after different silicone rubber implants. From the present results it is obvious that the high performance condylar implant ha5 the same disadvantages as its predecessors: it migrates, fractures, and dislocates and there is bone resorption with formation of carpal bone cysts. Despite the advantages of an easy operation, a short postoperative period of immobilisation, as well as 14 of 21 satisfied patients at the follow up, we do not recommend using the high performance condylar implant in the scaphotrapezial joint because of the high incidence of bone resorption and carpal bone cysts as in silicone particle synovitis. REFERENCES I . Brorson H, Werner CO, Thorngren KG. Normal pinch strength. Acta Orthop Scand 1987; 60:66-68. Scand J Plast Reconstr Hand Surg 26
Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery 1992.26:173-176.
176
M. K. Karlsson
et al.
2. Buck-Gramcko D. Operative Behandlung der Sattelgelenk-arthrose des Daumens. Hand Chirurg 1972; 4 105-109. 3. Carstam N, Eiken 0, Andren L. Osteoarthritis of the trapezio-scaphoid joint. Acta Orthop Scand 1968; 39: 354-358. 4. Crosby Brown E, Linscheid RL, Dobyns JH. Scaphotrapezia1 trapezoidal arthrosis. J Hand Surg 1978; 3: 223-234. 5. Eiken 0. Implant arthroplasty of the scapho-trapezia1 joint. Scand J Plast Reconstr Surg 1979; 13: 461468. 6. Eiken 0, Carstam N. Functional assessment of basal joint fusion of the thumb. Scand J Plast Reconstr Surg 1970; 4 122-125. 7. Eiken 0, Ekerot L, Lindstrom C, Jonsson K. Silicon carpal implants: risk or benefit? Scand J Plast Reconstr Surg 1985; 19: 295-304. 8. Eiken 0, Necking L-E. Silicon rubber implants for arthrosis of the scaphotrapezial trapezoidal joint. Scand J Plast Reconstr Surg 1983; 17: 253255.
Srimd J Plasl Rrconstr Hand Surg 26
9. Fromison A. Tendon arthroplasty of the trapeziometacarpal joint. Clin Orthop 1970; 70: 191-199. 10. Kessler I, Baruch A, Hecht 0, Amit S . Osteoarthritis at the base of the thumb. Acta Orthop Scand 1976; 47: 361 -369. 1 I . Lech RE, Bolton PE. Arthritis of the carpometacarpal joint of the thumb. J Bone Joint Surg 1968: 50A: I 171 - 1 1 77. 12. Necking L-E, Eiken 0. ECRL-strip for metacarpal base fixation after excision of the trapezium. Scand J Plast Reconstr Surg 1986; 20: 229-234. 13. Pellegrini VD, Burton RI. Surgical management of basal joint arthritis of the thumb. Long-term results of silicon implant arthroplasty. J Hand Surg 1986; 1 I A: 309-324. 14. Sollerman C, Herrlin K. Abrahamsson SO, Lindholm A. Silastic replacement of the trapezium for arthrosis-a 12-year follow-up study. J Hand Surg 1988; 138: 426429. 15. Thorngren KG, Werner CO. Normal grip strength. Acta Orthop S a n d 1979; 50: 255-266. 16. Wilson JN. Arthroplasty of trapezio-metacarpal joint. Plast Reconstr Surg 1972; 49: 143-148.
