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Swanson double-stem arthroplasty of the hallux: a survivorship analysis
Foot and Ankle Surgery 1999
5: 235–243
Swanson double-stem arthroplasty of the hallux: a survivorship analysis M.J.K. BANKES,∗ R.R. SHAH† AND D.L. GRACE‡ ∗Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex, †St Albans and Hemel Hempstead NHS Trust, Hemel Hempstead, Hertfordshire and ‡Chase Farm Hospital, Enfield, UK
Summary Double-stem Swanson silastic arthroplasty was performed without grommets on the first metatarsophalangeal joints of 45 patients (62 feet). After a mean follow-up of 7 years 3 months (range, 5 years 1 month–9 years 10 months), 91% had been helped greatly with survivorship analysis revealing 94.4% implant survival at 10 years and significant improvements in scores for pain, ambulation, function and shoe wear (P < 0.0001). The mean hallux valgus angle decreased from 37.9° to 24.1° (P < 0.0001). This operation provides high levels of patient satisfaction and has distinct advantages over resection arthroplasty or arthrodesis for lower demand patients with arthritis. There was no correlation between the implant’s radiological appearance and the latest clinical outcome. Keywords: silastic; arthroplasty; hallux; metatarsophalangeal joint; survivorship analysis
Introduction Arthritis of the first metatarsophalangeal joint (MTPJ) is a common and painful condition, with treatment being determined by the disease severity, the extent of any associated deformity, and the patient’s age and activity level. Surgical treatments for severe disease include arthrodesis [1], resection arthroplasty [2], interposition arthroplasty [3] and implant arthro plasty [4]. Whilst arthrodesis is a suitable procedure for active patients demanding stability and durability of the first ray, women often object to the loss of motion and restrictions on footwear imposed by this operation. The Keller procedure can provide excellent pain relief but at the cost of leaving a short weak hallux with potential for dorsiflexion deformity and
Correspondence: Mr M.J.K. Bankes, 18 Howard Walk, London N2 0HB, UK (E-mail: [email protected]). 1999 Blackwell Science Ltd
transfer metatarsalgia, making it suitable for elderly patients only. To overcome these problems, a doublestemmed flexible hinged arthroplasty was developed constructed of High Performance Silicone Elastomer [5]. Whilst good clinical results have been reported in the medium term [6–10], concerns remain about the durability of the implant, silicone synovitis, osteolysis, shortening of the hallux and metatarsalgia [11, 12]. This retrospective study was therefore performed to evaluate the clinical and radiological outcomes of Swanson double-stem silastic first MTPJ arthroplasty.
Patients and methods Between July 1988 and January 1993 45 consecutive patients underwent double-stem silastic arthroplasty of the first MTPJ by or under direct supervision of the senior author (DLG). The main indication was
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Table 1 Scoring system used for subjective evaluation of first MTPJ doublestem silastic arthroplasty
Table 2 Criteria for outcome evaluation of first MTPJ double-stem silastic arthroplasty
Pain 5 None 4 Twinge/occasional mild ache 3 Variable occurrence with or after activity 2 Always with activity/none at rest 1 Severe/at rest Walking 5 Unlimited 4 Mildly restricted (>1 mile) 3 100 yards to 1 mile 2 <100 yards 1 Housebound Function 5 Function without restriction 4 Work on feet with little restriction 3 Most housework, desk work, shopping 2 Limited housework, desk work, shopping 1 None of the above Footwear 5 Wear any shoes 4 Most styles 3 Restricted to some styles only 2 One style 1 Slippers/surgical shoes
Excellent Unhesitatingly would have operation again A lot better from surgery No complications Pain free Satisfactory appearance Any footwear Good Unhesitatingly would have operation again or with reservations A lot or a bit better from surgery Minor complication Pain free or occasional twinge or ache Satisfactory appearance Improvement in choice of footwear Fair Possibly would have operation again Major complication Still painful but better than preoperatively Unhappy with any of appearance, footwear, function, walking or range of motion Poor Anything else
painful arthritis in an unsalvageable first MTP joint with or without hallux valgus. Patients were over 45 years old, except those with rheumatoid arthritis or undergoing the operation as a salvage procedure following previous unsuccessful surgery. Diabetes mellitus, peripheral vascular disease and a history of local infection were contra-indications to the procedure. Surgery was performed under general anaesthesia using a thigh tourniquet, perioperative antibiotic cover and a standard operative technique [5]. Additional surgical procedures performed on the first ray depended on the severity of deformity. These included exostectomy, re-attachment of a distally based medial capsulo-ligamentous flap through drill holes in the first metatarsal, Z-lengthening of the extensor hallucis longus, and release of the lateral capsule and adductor hallucis. Basal osteotomy of the first metatarsal was performed if the preoperative intermetatarsal angle (IMA) was greater than 20° or as part of symmetrical surgery if the other side was greater than 15°. Additional procedures on the lesser rays included hammer toe correction, extensor tenotomy, lesser metatarsal osteotomy, metatarsal head excision and silastic joint replacement of lesser
MTP joints. Skin sutures were removed after 2 weeks and the foot held in a corrective bandage for 4 weeks, following which patients were encouraged to mobilise in a shoe with a soft sole. Complications and the need for further surgery were noted from records. Patients were reviewed in a special clinic a minimum of 5 years after surgery. Subjective evaluation consisted of determining whether the operation was helpful, whether they were happy with the shape of the big toe, whether they would have the same operation again under similar circumstances and any reasons for dissatisfaction. In addition forefoot pain, walking ability, function and footwear were scored using a simplification of that devised by the senior author (Table 1) [13]. Preoperative scores were estimated from patient records and recollection. Clinical evaluation consisted of measurements of passive range of movement at the first MTPJ, with a goniometer measuring the angle between the proximal segment of the hallux and the plantar surface of the foot. Any fixed flexion, extension and rotational deformities were noted. Strength of active flexion and extension at the first MTPJ was graded and sites of calluses, 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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Table 3 Additional procedures performed on the first ray Procedures Medial capsule tightening Exostectomy Z-lengthening EHL Lateral capsular/adductor release Basal osteotomy IPJ fusion
Feet 34 32 29 26 8 2
Table 4 Additional procedures on lesser rays Procedures Bilateral excision metatarsal heads (all rheumatoid) Silastic arthroplasty second MTPJ Correction second hammer toe Correction second and third hammer toes Second metatarsal osteotomy Fifth metatarsal osteotomy Second extensor tenotomy Second and third extensor tenotomies Second to fifth extensor tenotomies
Figure 1 Radiographic zones around the double-stem arthroplasty. Zones 3, 6, 9 and 12 describe lysis of the endosteal surface. Other zones describe lysis adjacent to the implant (after [10]).
tenderness and pain were also noted, with particular attention to the presence of metatarsalgia. Final outcomes were graded as excellent, good, fair or poor (Table 2). 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
Feet 8 7 8 6 1 1 4 1 4
Radiological evaluation was based on weight bearing antero-posterior and lateral radiographs obtained at follow-up and peri-operatively when available. The hallux valgus (HVA) and first-second intermetatarsal (IMA) angles were measured and integrity of the implant graded according to Granberry [11]. Location and severity of periprosthetic sclerosis and lucency, and the extent of new bone formation were categorized as described by Cracchiolo [10] (Figure 1). Statistical analysis was performed using StatView 4.0 software. Confidence intervals for the survivorship analysis were based on the ‘effective number at risk’ [14] using the Rothman equation [15].
Results The study cohort consisted of 45 consecutive patients (62 feet) who received Swanson double-stem silastic first metatarsophalangeal joint arthroplasty in the study period from July 1988 to January 1993. All but three patients (four feet) were women with a mean age of 57 years (range, 25–74 years) at surgery.
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Table 5 Life table for double-stem silastic arthroplasty of first MTPJ with excision of implant as end-point
Years since operation 0 to 1 1–2 2–3 3–4 4–5 5–6 6–7 7–8 8–9 9–10
No. at start
Failure
62 62 61 60 60 60 48 30 19 6
0 1 1 0 0 0 1 0 0 0
Withdrawn
No. at risk
Annual failure rate (%)
Annual success rate (%)
Cumulative survival (%)
95% C.I.
0 0 0 0 0 12 17 11 13 6
62 62 61 60 60 54 39.5 24.5 12.5 3
0 1.6 1.6 0 0 0 2.4 0 0 0
100 98.4 98.4 100 100 100 97.6 100 100 100
100 98.4 96.8 96.8 96.8 96.8 94.4 94.4 94.4 94.4
94.2–100 91.4–99.7 89.0–99.1 88.9–99.1 88.9–99.1 88.8–99.1 85.0–98.0 84.0–98.2 81.9–98.4 73.6–99.0
Figure 2 Survival curve of the first MTPJ arthroplasty with excision as end point. Error bars depict 95% confidence intervals.
Surgery was performed on 15 left feet, 13 right feet, bilaterally in 15, and as staged bilateral procedures in two, separated by 25 and 31 months, respectively. The size of implants used varied: size 5 was used in 20 feet, size 4 in 18 feet, size 3 in 15 feet, size 6 in five feet, size 2 in three feet, and size 1 in one foot, although it is now the senior author’s practice to use smaller implants, usually a size 1 or 2. No titanium grommets were inserted and no stems were covered in Dacron mesh. The most common preoperative diagnosis, affecting 25 feet in 17 patients, was hallux valgus (HVA > 20°) with an unsalvageable joint, usually due to cratering of the metatarsal articular surface. Hallux rigidus affected 18 feet (18 patients),
rheumatoid arthritis nine feet (five patients) and reconstruction following previous surgery was performed in 10 feet (nine patients). Four patients undergoing bilateral surgery had different diagnoses in each foot. Previous surgery consisted of exostectomy (one foot), Keller’s resection arthroplasty (two feet), and Wilson’s osteotomy (one foot). In addition there were two revisions of Helal spacers and one revision of a single stem silastic spacer inserted after trauma. In three feet a sound arthrodesis was revised due to patient dissatisfaction with the loss of movement. Additional procedures performed on the first and lesser rays are shown in Table 3 and 4. Early complications included nine (14%) superficial minor wound infections, which resolved with a 1-week course of oral antibiotic therapy. There were no deep infections. One subject developed a stress fracture of the neck of the second metatarsal 10 months after the operation, which healed with conservative measures. Two patients developed stiffness postoperatively and underwent manipulation under anaesthesia. One patient is awaiting lengthening of EHL for a late hallux extensus deformity. One patient, who underwent bilateral surgery, developed severe reflex sympathetic dystrophy in both feet from which she has made only a partial recovery. Her final outcome remains poor. During the study period only three implants were removed, with survivorship analysis revealing 94.4% implant survival (Table 5; Figure 2). Two were removed for synovitis 28 and 82 months after implantation and one was removed for painful 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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Figure 3 The effect of surgery on foot scores. Error bars give the 95% confidence intervals. All improvements were significant (paired t-test P < 0.002).
fragmentation of the prosthesis after 23 months. Two patients were left with a pseudarthrosis and one had re-implantation 37 months after removal to correct hallux extensus. Despite being ‘poor’ results these three patients were pain-free and satisfied with toe function and appearance when reviewed for this study. The other patient with a poor outcome suffered from rheumatoid arthritis and developed severe metatarsalgia 3 years following bilateral excision of lesser metatarsal heads in addition to the bilateral first MTPJ arthroplasty due to deterioration in the quality of the plantar skin. Forty-one patients were evaluated both clinically and radiologically a mean of 7 years 3 months (range, 5 years 1 month–9 years 10 months) after surgery. One patient had died of unrelated causes 7 years after bilateral surgery; previous follow-up at 4 years had shown a ‘good’ outcome. One patient was unwilling to take part because of work commitments but correspondence with her GP revealed that the implant had not been removed. Two patients (both bilateral) had moved out of the area but were interviewed by telephone. The fate of all 62 implants was therefore known. Subjective data were available on 56 of the 57 surviving implants with objective data on 52. The vast majority (91%) of patients felt they had benefited greatly from the operation, with 3.6% benefiting a little; it made no difference in 1.8%, and 3.6% were made worse. Furthermore, 91% of patients 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
would have the same operation again and 84% were happy with the shape of their big toe. There were statistically significant improvements in the scores for pain, ambulation, function and shoe wear (Figure 3). Transfer metatarsalgia developed in five feet (four patients) although it was only a reason for dissatisfaction in the patient with rheumatoid arthritis mentioned previously. Strength of toe flexion was rated good or excellent in 86% of feet examined and in 79% for extension, with the mean values for passive flexion and extension being 13.2° and 19.2°, respectively. Fixed deformities were common with a pronation deformity present in 31 feet (mean 13°), supination in two feet (mean 5°), flexion in two feet (mean 10°) and extension in seven feet (mean 10°). Clinical outcome was graded excellent in 14 feet, good in 35, fair in five and poor in seven. The mean HVA in those 30 feet with a preoperative HVA > 20° improved from 37.9° to 24.1° (paired t-test, P < 0.0001), with the IMA falling from 12.6° to 10.7° (paired t-test, P=0.046). For the six of eight feet that had undergone basal osteotomy for which both preoperative and follow-up radiographs were available, the mean HVA improved from 51.8° to 22.3° (paired t-test, P=0.0013) and the mean IMA fell from 19.8° to 10.3° (P < 0.0001). Radiographic examination revealed the implant to be durable (Figure 4) with 73% of implants showing no evidence of deformation (grade 0), and 25%
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(a)
(b) FIG. 4
1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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(c)
Figure 4 Radiographs of 56-year-old woman with bilateral implants for degenerative hallux valgus. (a) Preoperative, (b) postoperative and (c) at 9-year review. The clinical result was graded excellent.
showing slight deformation only (grade 1) [11]. One implant was destroyed (grade 2) but the patient was pain-free, had no limitation of activity and had a good final outcome. Sclerosis around the implant occurred most commonly around the phalangeal stem, with 69% of implants showing sclerosis in zone 4 and 65% in zone 2. It appeared less frequently around the metatarsal stem (52% in zone 8 and 48% in zone 10). The distribution of lucencies displayed a similar predilection for the phalangeal stem although they occurred less frequently; lucency occurred in zone 4 in 46%, zone 2 in 38%, zone 8 in 25% and zone 10 in 21%. In five feet the phalangeal stem and in two feet the metatarsal stem was eroding through its respective medial cortex (zones 3 and 9) (Figure 5). The mean number of lucent zones per implant was 1.67 (range, 0–8). When present, the majority (64%) of lucent zones were graded as slight (perpendicular extension from the implant <2 mm), 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
with 24% graded as moderate (2–4 mm) and 12% as severe (>4mm) [10]. There were no lucent zones detected in 13 implants. There was no association between the clinical outcome and the most severe grade of lucency per implant (v2, P=0.75). New bone formation was common with complete osseous bridging present in 23%, >50% encroachment on the hinge space in 23%, <50% encroachment in 31%, and small spurs only in 33%. Despite this there was no correlation between the extent of either new bone formation or osteolysis and the total passive range of motion (unpaired t-tests, P > 0.08). Pre-operative diagnosis also did not influence the extent of new bone formation, P=0.5).
Discussion Swanson claimed Silastic arthroplasty of the first MTPJ offered considerable advantages over
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Figure 5 Severe osteolysis in right hallux of 72-year-old woman, 8 years after bilateral surgery. The lesion in zone 2 in the proximal phalanx on the left had not progressed radiologically for 6 years. Despite these appearances the patient was pain-free, happy with the appearance of her foot and had only minor limitations to her choice of footwear.
arthrodesis and resection arthroplasty [5]. Our study based on a cohort of consecutive patients with a minimum 5-year follow-up shows that this operation provides high levels of patient satisfaction, lasting relief from pain and improved foot function in lower demand patients. Whilst the range of movement imparted by the implant is far less than normal, any mobility of the great toe increases flexion strength during take-off facilitating a more normal gait pattern. These clinical results and implant survival of 94.4% compare favourably with other series of shorter follow-up [6–10] and may exceed those of shoulder [16], ankle [17] and elbow [18] arthroplasty. Despite these reports, scepticism remains due to problems relating to the abrasion and fatigue of the implant and the subsequent host response to wear debris [19]. The integrity of the implants in this study were well preserved, which may reflect careful
patient selection and comprehensive correction of deformities as means to reduce stresses on the implant as much as the design and manufacture of the implant itself. However choice of implant, as in all other areas of arthroplasty, is important and might explain the high rates of mechanical failure found in the series of Granberry whose study population was otherwise very similar to our own [11]. Despite osteolysis and new bone formation being widespread radiologically, this had no influence on the clinical outcome, as previously reported [10, 11]. All eight feet with moderate grade lucencies had good or excellent outcomes and nine of 10 feet with severe osteolysis had good or excellent outcomes. It is now the senior author’s practice to employ titanium grommets with the silastic implant, as there is evidence their use reduces the incidence of radiolucencies [20]. There was a high incidence of 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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postoperative superficial wound erythema in this series, despite the use of perioperative antibiotics. However these all resolved with oral antibiotic therapy alone and did not lead to wound breakdown or deep infection. The published incidence of superficial wound complications varies from 1.1% to 15.1% with the incidence of deep infection ranging from 0 to 3% [6–11]. A total of 728 implants have been reported in these six studies and our own and deep sepsis has developed in only six (0.8%). The stabilizing pseudocapsule that forms in response to the implant [21] seems to improve the outcome of the resulting pseudoarthrosis should the prosthesis need removal. Maintenance of the joint space also allows revision of the implant at a second stage should this be necessary for deformity. Conversion of an unsuccessful implant to an arthrodesis or unconstrained prosthesis is a major undertaking that we believe is rarely indicated, despite opinions to the contrary [22, 23]. In conclusion, Swanson double-stem silastic arthroplasty of the first MTPJ provides high levels of patient satisfaction and has distinct advantages over resection arthroplasty or arthrodesis for lower demand patients with painful arthritis.
References 1 Smith RW, Joanis TL, Maxwell PD. Great toe metatarsophalangeal joint arthrodesis: a user friendly technique. Foot Ankle Int 1992; 13: 367–377. 2 Richardson EG. Keller resection arthroplasty. Orthopedics 1990; 13: 1049–1053. 3 Hamilton WG, O’Malley MJ, Thompson FM et al. Capsular interposition arthroplasty for severe hallux rigidus. Foot Ankle Int 1997; 18: 68–70. 4 Papagelopoulos PJ, Kitaoka HB, Ilstrup DM. Survivorship analysis of implant arthroplasty for the first metatarsophalangeal joint. Clin Orthop 1994; 302: 164–172. 5 Swanson AB, Lumsden RM, Swanson GD. Silicone implant arthroplasty of the great toe: a review of single stem and flexible hinge implants. Clin Orthop 1979; 142: 30–43.
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6 Shankar NS, Asaad SS, Craxford AD. Hinged silastic implants of the great toe. Clin Orthop 1991; 272: 227–234. 7 Laird L. Silastic joint arthroplasty of the great toe: a review of 228 implants using the double-stemmed implant. Clin Orthop 1990; 255: 268–272. 8 McBride DJ, Abdel-Gawad MMK, Anderson EG. Silastic spacer in disorders of the first metatarsophalangeal joint. Egypt Orthop J 1993; 28: 133–144. 9 Moeckel BH, Sculco TP, Alexiades MM et al. The doublestemmed silicone-rubber implant for rheumatoid arthritis of the first metatarsophalangeal joint. J Bone Joint Surg 1992; 74A: 564–570. 10 Cracchiolo A, Weltmer JB, Lian G et al. Arthroplasty of the first metatarsophalangeal joint with a double-stem silicone implant. J Bone Joint Surg 1992; 74A: 552–563. 11 Granberry WM, Noble PC, Bishop JO et al. Use of a hinged silicone prosthesis for replacement arthroplasty of the first metatarsophalangeal joint. J Bone Joint Surg 1991; 73A: 1453–1459. 12 Mondul M, Jacobs PM, Caneva RG et al. Implant arthroplasty of the first metatarsophalangeal joint: a 12 year retrospective study. J Foot Surg 1985; 24: 275–279. 13 Grace DL, Cracchiolo A. A method of evaluating the results of forefoot surgery. Clin Orthop 1985; 198: 208–218. 14 Murray DW, Carr AJ, Bulstrode CJK. Survival analysis of joint replacements. J Bone Joint Surg 1993; 75B: 697–704. 15 Ferdinand RD, Pinder IM. Survival analysis of joint replacements. J Bone Joint Surg 1997; 79B: 878. 16 Brenner BC, Ferlic DC, Clayton ML et al. Survivorship of unconstrained total shoulder arthroplasty. J Bone Joint Surg 1989; 71A: 1289–1296. 17 Kofoed H, Sørensen TS. Ankle arthroplasty for rheumatoid arthritis and osteoarthritis. J Bone Joint Surg 1998; 80B: 328–332. 18 Kraay MJ, Figgie MP, Inglis AE et al. Primary semiconstrained total elbow arthroplasty. J Bone Joint Surg 1994; 76B: 636–640. 19 Shereff MJ, Baumhauer JF. Hallux rigidus and osteoarthrosis of the first metatarsophalangeal joint. J Bone Joint Surg 1998; 80A: 898–908. 20 Sebold EJ, Cracchiolo A. Use of titanium grommets in silicone implant arthroplasty of the hallux metatarsophalangeal joint. Foot Ankle Int 1996; 17: 145–151. 21 DeHeer DH, Owens SC, Swanson AB. The host response to silicone elastomer implants for small joint arthroplasty. J Hand Surg 1995; 20A: S101–S109. 22 Hecht PJ, Gibbons MJ, Wapner KL et al. Arthrodesis of the first metatarsophalangeal joint to salvage failed silicone implant arthroplasty. Foot Ankle Int 1997; 18: 383–390. 23 Koenig RD. Revision arthroplasty utilizing the Biomet Total Toe System for failed silicone elastomer implants. J Foot Ankle Surg 1994; 33: 222–227.
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Swanson double-stem arthroplasty of the hallux: a survivorship analysis M.J.K. BANKES,∗ R.R. SHAH† AND D.L. GRACE‡ ∗Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex, †St Albans and Hemel Hempstead NHS Trust, Hemel Hempstead, Hertfordshire and ‡Chase Farm Hospital, Enfield, UK
Summary Double-stem Swanson silastic arthroplasty was performed without grommets on the first metatarsophalangeal joints of 45 patients (62 feet). After a mean follow-up of 7 years 3 months (range, 5 years 1 month–9 years 10 months), 91% had been helped greatly with survivorship analysis revealing 94.4% implant survival at 10 years and significant improvements in scores for pain, ambulation, function and shoe wear (P < 0.0001). The mean hallux valgus angle decreased from 37.9° to 24.1° (P < 0.0001). This operation provides high levels of patient satisfaction and has distinct advantages over resection arthroplasty or arthrodesis for lower demand patients with arthritis. There was no correlation between the implant’s radiological appearance and the latest clinical outcome. Keywords: silastic; arthroplasty; hallux; metatarsophalangeal joint; survivorship analysis
Introduction Arthritis of the first metatarsophalangeal joint (MTPJ) is a common and painful condition, with treatment being determined by the disease severity, the extent of any associated deformity, and the patient’s age and activity level. Surgical treatments for severe disease include arthrodesis [1], resection arthroplasty [2], interposition arthroplasty [3] and implant arthro plasty [4]. Whilst arthrodesis is a suitable procedure for active patients demanding stability and durability of the first ray, women often object to the loss of motion and restrictions on footwear imposed by this operation. The Keller procedure can provide excellent pain relief but at the cost of leaving a short weak hallux with potential for dorsiflexion deformity and
Correspondence: Mr M.J.K. Bankes, 18 Howard Walk, London N2 0HB, UK (E-mail: [email protected]). 1999 Blackwell Science Ltd
transfer metatarsalgia, making it suitable for elderly patients only. To overcome these problems, a doublestemmed flexible hinged arthroplasty was developed constructed of High Performance Silicone Elastomer [5]. Whilst good clinical results have been reported in the medium term [6–10], concerns remain about the durability of the implant, silicone synovitis, osteolysis, shortening of the hallux and metatarsalgia [11, 12]. This retrospective study was therefore performed to evaluate the clinical and radiological outcomes of Swanson double-stem silastic first MTPJ arthroplasty.
Patients and methods Between July 1988 and January 1993 45 consecutive patients underwent double-stem silastic arthroplasty of the first MTPJ by or under direct supervision of the senior author (DLG). The main indication was
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Table 1 Scoring system used for subjective evaluation of first MTPJ doublestem silastic arthroplasty
Table 2 Criteria for outcome evaluation of first MTPJ double-stem silastic arthroplasty
Pain 5 None 4 Twinge/occasional mild ache 3 Variable occurrence with or after activity 2 Always with activity/none at rest 1 Severe/at rest Walking 5 Unlimited 4 Mildly restricted (>1 mile) 3 100 yards to 1 mile 2 <100 yards 1 Housebound Function 5 Function without restriction 4 Work on feet with little restriction 3 Most housework, desk work, shopping 2 Limited housework, desk work, shopping 1 None of the above Footwear 5 Wear any shoes 4 Most styles 3 Restricted to some styles only 2 One style 1 Slippers/surgical shoes
Excellent Unhesitatingly would have operation again A lot better from surgery No complications Pain free Satisfactory appearance Any footwear Good Unhesitatingly would have operation again or with reservations A lot or a bit better from surgery Minor complication Pain free or occasional twinge or ache Satisfactory appearance Improvement in choice of footwear Fair Possibly would have operation again Major complication Still painful but better than preoperatively Unhappy with any of appearance, footwear, function, walking or range of motion Poor Anything else
painful arthritis in an unsalvageable first MTP joint with or without hallux valgus. Patients were over 45 years old, except those with rheumatoid arthritis or undergoing the operation as a salvage procedure following previous unsuccessful surgery. Diabetes mellitus, peripheral vascular disease and a history of local infection were contra-indications to the procedure. Surgery was performed under general anaesthesia using a thigh tourniquet, perioperative antibiotic cover and a standard operative technique [5]. Additional surgical procedures performed on the first ray depended on the severity of deformity. These included exostectomy, re-attachment of a distally based medial capsulo-ligamentous flap through drill holes in the first metatarsal, Z-lengthening of the extensor hallucis longus, and release of the lateral capsule and adductor hallucis. Basal osteotomy of the first metatarsal was performed if the preoperative intermetatarsal angle (IMA) was greater than 20° or as part of symmetrical surgery if the other side was greater than 15°. Additional procedures on the lesser rays included hammer toe correction, extensor tenotomy, lesser metatarsal osteotomy, metatarsal head excision and silastic joint replacement of lesser
MTP joints. Skin sutures were removed after 2 weeks and the foot held in a corrective bandage for 4 weeks, following which patients were encouraged to mobilise in a shoe with a soft sole. Complications and the need for further surgery were noted from records. Patients were reviewed in a special clinic a minimum of 5 years after surgery. Subjective evaluation consisted of determining whether the operation was helpful, whether they were happy with the shape of the big toe, whether they would have the same operation again under similar circumstances and any reasons for dissatisfaction. In addition forefoot pain, walking ability, function and footwear were scored using a simplification of that devised by the senior author (Table 1) [13]. Preoperative scores were estimated from patient records and recollection. Clinical evaluation consisted of measurements of passive range of movement at the first MTPJ, with a goniometer measuring the angle between the proximal segment of the hallux and the plantar surface of the foot. Any fixed flexion, extension and rotational deformities were noted. Strength of active flexion and extension at the first MTPJ was graded and sites of calluses, 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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Table 3 Additional procedures performed on the first ray Procedures Medial capsule tightening Exostectomy Z-lengthening EHL Lateral capsular/adductor release Basal osteotomy IPJ fusion
Feet 34 32 29 26 8 2
Table 4 Additional procedures on lesser rays Procedures Bilateral excision metatarsal heads (all rheumatoid) Silastic arthroplasty second MTPJ Correction second hammer toe Correction second and third hammer toes Second metatarsal osteotomy Fifth metatarsal osteotomy Second extensor tenotomy Second and third extensor tenotomies Second to fifth extensor tenotomies
Figure 1 Radiographic zones around the double-stem arthroplasty. Zones 3, 6, 9 and 12 describe lysis of the endosteal surface. Other zones describe lysis adjacent to the implant (after [10]).
tenderness and pain were also noted, with particular attention to the presence of metatarsalgia. Final outcomes were graded as excellent, good, fair or poor (Table 2). 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
Feet 8 7 8 6 1 1 4 1 4
Radiological evaluation was based on weight bearing antero-posterior and lateral radiographs obtained at follow-up and peri-operatively when available. The hallux valgus (HVA) and first-second intermetatarsal (IMA) angles were measured and integrity of the implant graded according to Granberry [11]. Location and severity of periprosthetic sclerosis and lucency, and the extent of new bone formation were categorized as described by Cracchiolo [10] (Figure 1). Statistical analysis was performed using StatView 4.0 software. Confidence intervals for the survivorship analysis were based on the ‘effective number at risk’ [14] using the Rothman equation [15].
Results The study cohort consisted of 45 consecutive patients (62 feet) who received Swanson double-stem silastic first metatarsophalangeal joint arthroplasty in the study period from July 1988 to January 1993. All but three patients (four feet) were women with a mean age of 57 years (range, 25–74 years) at surgery.
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Table 5 Life table for double-stem silastic arthroplasty of first MTPJ with excision of implant as end-point
Years since operation 0 to 1 1–2 2–3 3–4 4–5 5–6 6–7 7–8 8–9 9–10
No. at start
Failure
62 62 61 60 60 60 48 30 19 6
0 1 1 0 0 0 1 0 0 0
Withdrawn
No. at risk
Annual failure rate (%)
Annual success rate (%)
Cumulative survival (%)
95% C.I.
0 0 0 0 0 12 17 11 13 6
62 62 61 60 60 54 39.5 24.5 12.5 3
0 1.6 1.6 0 0 0 2.4 0 0 0
100 98.4 98.4 100 100 100 97.6 100 100 100
100 98.4 96.8 96.8 96.8 96.8 94.4 94.4 94.4 94.4
94.2–100 91.4–99.7 89.0–99.1 88.9–99.1 88.9–99.1 88.8–99.1 85.0–98.0 84.0–98.2 81.9–98.4 73.6–99.0
Figure 2 Survival curve of the first MTPJ arthroplasty with excision as end point. Error bars depict 95% confidence intervals.
Surgery was performed on 15 left feet, 13 right feet, bilaterally in 15, and as staged bilateral procedures in two, separated by 25 and 31 months, respectively. The size of implants used varied: size 5 was used in 20 feet, size 4 in 18 feet, size 3 in 15 feet, size 6 in five feet, size 2 in three feet, and size 1 in one foot, although it is now the senior author’s practice to use smaller implants, usually a size 1 or 2. No titanium grommets were inserted and no stems were covered in Dacron mesh. The most common preoperative diagnosis, affecting 25 feet in 17 patients, was hallux valgus (HVA > 20°) with an unsalvageable joint, usually due to cratering of the metatarsal articular surface. Hallux rigidus affected 18 feet (18 patients),
rheumatoid arthritis nine feet (five patients) and reconstruction following previous surgery was performed in 10 feet (nine patients). Four patients undergoing bilateral surgery had different diagnoses in each foot. Previous surgery consisted of exostectomy (one foot), Keller’s resection arthroplasty (two feet), and Wilson’s osteotomy (one foot). In addition there were two revisions of Helal spacers and one revision of a single stem silastic spacer inserted after trauma. In three feet a sound arthrodesis was revised due to patient dissatisfaction with the loss of movement. Additional procedures performed on the first and lesser rays are shown in Table 3 and 4. Early complications included nine (14%) superficial minor wound infections, which resolved with a 1-week course of oral antibiotic therapy. There were no deep infections. One subject developed a stress fracture of the neck of the second metatarsal 10 months after the operation, which healed with conservative measures. Two patients developed stiffness postoperatively and underwent manipulation under anaesthesia. One patient is awaiting lengthening of EHL for a late hallux extensus deformity. One patient, who underwent bilateral surgery, developed severe reflex sympathetic dystrophy in both feet from which she has made only a partial recovery. Her final outcome remains poor. During the study period only three implants were removed, with survivorship analysis revealing 94.4% implant survival (Table 5; Figure 2). Two were removed for synovitis 28 and 82 months after implantation and one was removed for painful 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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Figure 3 The effect of surgery on foot scores. Error bars give the 95% confidence intervals. All improvements were significant (paired t-test P < 0.002).
fragmentation of the prosthesis after 23 months. Two patients were left with a pseudarthrosis and one had re-implantation 37 months after removal to correct hallux extensus. Despite being ‘poor’ results these three patients were pain-free and satisfied with toe function and appearance when reviewed for this study. The other patient with a poor outcome suffered from rheumatoid arthritis and developed severe metatarsalgia 3 years following bilateral excision of lesser metatarsal heads in addition to the bilateral first MTPJ arthroplasty due to deterioration in the quality of the plantar skin. Forty-one patients were evaluated both clinically and radiologically a mean of 7 years 3 months (range, 5 years 1 month–9 years 10 months) after surgery. One patient had died of unrelated causes 7 years after bilateral surgery; previous follow-up at 4 years had shown a ‘good’ outcome. One patient was unwilling to take part because of work commitments but correspondence with her GP revealed that the implant had not been removed. Two patients (both bilateral) had moved out of the area but were interviewed by telephone. The fate of all 62 implants was therefore known. Subjective data were available on 56 of the 57 surviving implants with objective data on 52. The vast majority (91%) of patients felt they had benefited greatly from the operation, with 3.6% benefiting a little; it made no difference in 1.8%, and 3.6% were made worse. Furthermore, 91% of patients 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
would have the same operation again and 84% were happy with the shape of their big toe. There were statistically significant improvements in the scores for pain, ambulation, function and shoe wear (Figure 3). Transfer metatarsalgia developed in five feet (four patients) although it was only a reason for dissatisfaction in the patient with rheumatoid arthritis mentioned previously. Strength of toe flexion was rated good or excellent in 86% of feet examined and in 79% for extension, with the mean values for passive flexion and extension being 13.2° and 19.2°, respectively. Fixed deformities were common with a pronation deformity present in 31 feet (mean 13°), supination in two feet (mean 5°), flexion in two feet (mean 10°) and extension in seven feet (mean 10°). Clinical outcome was graded excellent in 14 feet, good in 35, fair in five and poor in seven. The mean HVA in those 30 feet with a preoperative HVA > 20° improved from 37.9° to 24.1° (paired t-test, P < 0.0001), with the IMA falling from 12.6° to 10.7° (paired t-test, P=0.046). For the six of eight feet that had undergone basal osteotomy for which both preoperative and follow-up radiographs were available, the mean HVA improved from 51.8° to 22.3° (paired t-test, P=0.0013) and the mean IMA fell from 19.8° to 10.3° (P < 0.0001). Radiographic examination revealed the implant to be durable (Figure 4) with 73% of implants showing no evidence of deformation (grade 0), and 25%
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(a)
(b) FIG. 4
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(c)
Figure 4 Radiographs of 56-year-old woman with bilateral implants for degenerative hallux valgus. (a) Preoperative, (b) postoperative and (c) at 9-year review. The clinical result was graded excellent.
showing slight deformation only (grade 1) [11]. One implant was destroyed (grade 2) but the patient was pain-free, had no limitation of activity and had a good final outcome. Sclerosis around the implant occurred most commonly around the phalangeal stem, with 69% of implants showing sclerosis in zone 4 and 65% in zone 2. It appeared less frequently around the metatarsal stem (52% in zone 8 and 48% in zone 10). The distribution of lucencies displayed a similar predilection for the phalangeal stem although they occurred less frequently; lucency occurred in zone 4 in 46%, zone 2 in 38%, zone 8 in 25% and zone 10 in 21%. In five feet the phalangeal stem and in two feet the metatarsal stem was eroding through its respective medial cortex (zones 3 and 9) (Figure 5). The mean number of lucent zones per implant was 1.67 (range, 0–8). When present, the majority (64%) of lucent zones were graded as slight (perpendicular extension from the implant <2 mm), 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
with 24% graded as moderate (2–4 mm) and 12% as severe (>4mm) [10]. There were no lucent zones detected in 13 implants. There was no association between the clinical outcome and the most severe grade of lucency per implant (v2, P=0.75). New bone formation was common with complete osseous bridging present in 23%, >50% encroachment on the hinge space in 23%, <50% encroachment in 31%, and small spurs only in 33%. Despite this there was no correlation between the extent of either new bone formation or osteolysis and the total passive range of motion (unpaired t-tests, P > 0.08). Pre-operative diagnosis also did not influence the extent of new bone formation, P=0.5).
Discussion Swanson claimed Silastic arthroplasty of the first MTPJ offered considerable advantages over
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Figure 5 Severe osteolysis in right hallux of 72-year-old woman, 8 years after bilateral surgery. The lesion in zone 2 in the proximal phalanx on the left had not progressed radiologically for 6 years. Despite these appearances the patient was pain-free, happy with the appearance of her foot and had only minor limitations to her choice of footwear.
arthrodesis and resection arthroplasty [5]. Our study based on a cohort of consecutive patients with a minimum 5-year follow-up shows that this operation provides high levels of patient satisfaction, lasting relief from pain and improved foot function in lower demand patients. Whilst the range of movement imparted by the implant is far less than normal, any mobility of the great toe increases flexion strength during take-off facilitating a more normal gait pattern. These clinical results and implant survival of 94.4% compare favourably with other series of shorter follow-up [6–10] and may exceed those of shoulder [16], ankle [17] and elbow [18] arthroplasty. Despite these reports, scepticism remains due to problems relating to the abrasion and fatigue of the implant and the subsequent host response to wear debris [19]. The integrity of the implants in this study were well preserved, which may reflect careful
patient selection and comprehensive correction of deformities as means to reduce stresses on the implant as much as the design and manufacture of the implant itself. However choice of implant, as in all other areas of arthroplasty, is important and might explain the high rates of mechanical failure found in the series of Granberry whose study population was otherwise very similar to our own [11]. Despite osteolysis and new bone formation being widespread radiologically, this had no influence on the clinical outcome, as previously reported [10, 11]. All eight feet with moderate grade lucencies had good or excellent outcomes and nine of 10 feet with severe osteolysis had good or excellent outcomes. It is now the senior author’s practice to employ titanium grommets with the silastic implant, as there is evidence their use reduces the incidence of radiolucencies [20]. There was a high incidence of 1999 Blackwell Science Ltd, Foot and Ankle Surgery, 5, 235–243
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postoperative superficial wound erythema in this series, despite the use of perioperative antibiotics. However these all resolved with oral antibiotic therapy alone and did not lead to wound breakdown or deep infection. The published incidence of superficial wound complications varies from 1.1% to 15.1% with the incidence of deep infection ranging from 0 to 3% [6–11]. A total of 728 implants have been reported in these six studies and our own and deep sepsis has developed in only six (0.8%). The stabilizing pseudocapsule that forms in response to the implant [21] seems to improve the outcome of the resulting pseudoarthrosis should the prosthesis need removal. Maintenance of the joint space also allows revision of the implant at a second stage should this be necessary for deformity. Conversion of an unsuccessful implant to an arthrodesis or unconstrained prosthesis is a major undertaking that we believe is rarely indicated, despite opinions to the contrary [22, 23]. In conclusion, Swanson double-stem silastic arthroplasty of the first MTPJ provides high levels of patient satisfaction and has distinct advantages over resection arthroplasty or arthrodesis for lower demand patients with painful arthritis.
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