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Hemiarthroplasty augmented with bone graft for the failed hallux metatarsophalangeal Silastic® implant
Foot and Ankle Surgery 17 (2011) e43–e46
Contents lists available at ScienceDirect
Foot and Ankle Surgery journal homepage: www.elsevier.com/locate/fas
Case report
Hemiarthroplasty augmented with bone graft for the failed hallux metatarsophalangeal Silastic1 implant Raymond E. Anakwe FRCS Ed (Tr & Orth)*, Scott D. Middleton MB ChB, Colin E. Thomson BSc (Hons), PhD, John C. McKinley FRCS Ed (Tr & Orth) The Foot and Ankle Service, Department of Trauma & Orthopaedic Surgery, Royal Infirmary of Edinburgh, 51, Little France Crescent, Edinburgh EH16 5SU, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history: Received 10 August 2010 Received in revised form 14 April 2011 Accepted 28 April 2011
Symptomatic failure of Silastic1 implants at the hallux metatarsophalangeal joint can result in the challenging problem of instability which may be painful. There is often marked bone loss making reconstruction difficult. Arthrodesis sacrifices joint movement while excision arthroplasty shortens the ray and is less acceptable to active patients. We describe a case in which reconstruction was achieved by using a porous coated metatarsophalangeal hemiarthroplasty augmented with bone graft with good early results. This previously unreported technique may offer an additional surgical option for reconstruction, maintaining joint movement without compromising future arthrodesis or excision arthroplasty as salvage measures. Long term follow up is required to confirm the success of this technique. ß 2011 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Silastic Hallux rigidus Metatarsophalangeal joint BioPro hemiarthroplasty
1. Introduction Silastic1 joint replacement is associated with particulate wear, local osteolysis and granulomatous change [1,2]. These implants have previously been used in large numbers to replace the hallux metatarsophalangeal joint (MTPJ) and while concerns over early failure mean that they are no longer as commonly used, there are some reports of long term follow up with good results particularly with respect to function and patient satisfaction [3,4]. A characteristic radiographic appearance has been described at the MTPJ, representative of Silastic1 particulate wear and granulomatous degeneration. Radiographs frequently show evidence of osteolysis and cystic change while at surgery, bone loss and synovitis are often noted [1]. The importance of this is debated as it is not always painful and the clinical picture does not always correlate with the radiographic appearances. Symptoms of instability, which may be painful, functional limitation and progressive or unacceptable deformity suggest that the implant has failed and revision or salvage surgery may be contemplated. Long term outcomes have been said to be better where Silastic1 implants are used for hallux rigidus rather than hallux valgus surgery and where they are selected for low demand patients and those over fifty years of age [3,5,6]. Nevertheless, large numbers of patients with Silastic1 implants may be candidates for revision surgery. Salvage of failed Silastic1 hallux MTPJ arthroplasty may be attempted by debridement/synovectomy combined with either
* Corresponding author. E-mail address: [email protected] (R.E. Anakwe).
excision arthroplasty or arthrodesis. The aim is to restore a painless stable joint for weight bearing and push off. Arthrodesis is reported to more reliably achieve excellent levels of patient satisfaction than arthroplasty options but sacrifices joint motion [5,7,8]. It also avoids excessive shortening of the first ray but may be complicated by phalangeal deformity or painful non union. The key benefit of total-toe arthroplasty is that both surfaces of the MTPJ are addressed which allows for both preservation of motion and joint stability. Total joint arthroplasties and in particular, metal on ultra high molecular weight polyethylene (UHMWPE) bearing surfaces are however, susceptible to particulate wear and osteolysis. While not an absolute contraindication to their use for the salvage of failed Silastic1 arthroplasties, this does merit careful consideration, particularly where bone stock is poor. In a previous study, Koenig and Horwitz described the use of the Biomet Total-Toe system for primary and revision surgery [9]. In four of 10 cases where it was used for revision of failed Silastic1 interpositional arthroplasty, further surgery was required due to loosening of the total-toe implant. This was attributed to poor bone stock. We present a case detailing the use of a hallux MTPJ hemiarthroplasty augmented with autologous bone graft and synthetic bone substitute to address a painful failed Silastic1 MTPJ implant in a young patient.
2. Case report A 38-year old woman was referred to the Foot and Ankle service complaining of a painful stiff right hallux MTPJ. She had been treated at the age of 19 for hallux rigidus and had undergone
1268-7731/$ – see front matter ß 2011 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.fas.2011.04.006
[(Fig._1)TD$IG]
e44
[(Fig._2)TD$IG]
R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
Fig. 1. Preoperative radiographs showing osteolysis and evidence of Silastic wear.
Silastic1 interpositional arthroplasty at another centre. She had never been entirely satisfied after this surgery and complained of residual pain. Over several years, her pain had worsened and was now resistant to simple analgesia. She complained of intermittent swelling over the dorsum of the MTPJ and difficulty in obtaining comfortable, fitting shoes. She worked as a nursing assistant and found that prolonged periods of standing exacerbated her symptoms. She had no significant co-morbidities and was a keen recreational hill walker. Clinical examination revealed a warm, sensate, well perfused and normally aligned foot without plantar callosities. There was an area of obvious swelling over the hallux MTPJ which was tender to palpation and the joint was stiff with 208 of dorsiflexion and 158 of plantar flexion only. A dorsomedial curvilinear scar confirmed previous MTPJ surgery. Radiographs confirmed that a Silastic1 implant had previously been inserted and there was evidence of osteolysis with cystic degeneration (Fig. 1). After discussion with the patient, it was clear that arthrodesis was not acceptable to her. We agreed to proceed to joint debridement/synovectomy combined with MTPJ hemiarthroplasty. In view of the degree of degeneration and potential bone loss, we planned to augment the hemiarthroplasty with autologous bone as well as synthetic bone substitute if required. The patient consented to joint arthrodesis should reconstruction prove impossible. At surgery, the previous incision was used and an arthrotomy made medial to the tendon of extensor hallucis longus. There was florid synovitis which was excised with the worn implant. Large cysts in both the proximal phalanx and the metatarsal head were thoroughly curetted and lavaged leaving substantial bony defects but a preserved cortical rim. The proximal phalanx was sized for a medium implant and no further bone resection was required in view of the pre-existing bone loss. We harvested cancellous bone graft from the ipsilateral proximal tibia and packed it into the defects in the proximal phalanx in order to provide solid support
Fig. 2. Postoperative radiographs.
for the prosthesis. The remaining bone graft was used to fill defects in the metatarsal head and this was supplemented with Kasios1TCP artificial bone substitute. Grafted surfaces were contoured to the joint line to reproduce a congruent joint surface in the metatarsal head. We selected a medium porous coated BioPro1 hemiarthroplasty (Port Huron, MI) and implanted this into the proximal phalanx and bed of bone graft. The joint was taken through a range of motion before it was irrigated, the wound closed
[(Fig._3)TD$IG]
R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
e45
Fig. 3. Follow up radiographs at 2 years including stress dorsiflexion view to assess implant alignment and stability.
in layers and soft dressings applied. The patient was allowed to fully weight bear as able in a soft surgical shoe and was discharged home on the day of surgery. We reviewed the patient in the outpatient clinic 3 weeks after surgery. She made a gradual return to normal activities and returned to nursing and recreational walking at 6 weeks with no requirement for regular analgesia. Radiographs show good alignment of the prosthesis and incorporation of the bone graft (Fig. 2a and b). At 12 months, passive dorsiflexion at the MTPJ is 508 with 208 of plantar flexion and she remains asymptomatic. These results and stability of the implant have been maintained at two years (Fig. 3a and b). 3. Discussion The BioPro1 hallux MTPJ hemiarthroplasty (Fig. 3) is a cobalt chrome MTPJ implant available in either a porous coated or non coated form. It has been in use since 1952 and it is a reliable motion preserving option for primary MTPJ arthroplasty [10,11]. It is indicated for use in arthritic degradation of the MTPJ of the great toe resulting in disabling pain, degenerative arthritis (hallux rigidus), rheumatoid arthritis and bunion deformity associated with arthritis of the great MTPJ. It is not specifically licensed for revision surgery and caution is advised where there is bone loss or structural deficiency of supporting subchondral bone [5,12]. Excellent outcomes have been reported in long term studies. These suggest that with good surgery, primary treatment with the BioPro1 hemiarthroplasty allows an improved range of movement at the hallux MTPJ, improved patient reported outcome scores and a reduction in pain localised to the hallux MTPJ [11,13]. Where there is adequate structural support from the bone, this implant is an attractive option for revision surgery as it preserves movement, requires minimal if any further bone resection and it maintains the future options of joint arthrodesis or excision arthroplasty. Proponents of total-toe arthroplasty recommend that the metatarsal head should also be resurfaced however studies using the Biopro hemiarthroplasty for primary surgery show that excellent outcomes are reported even where both sides of the joint are worn and the metatarsal head is not treated [13].
We believe that it is an important part of the revision surgery to undertake a thorough debridement of all Silastic1 material, inflamed synovium and membrane in order to avoid progression of osteolysis. As we expected, the degree of bone loss did not allow the prosthesis to be confidently seated in the proximal phalanx and bone grafting was required. Immediate stability depends on soft tissue tensioning at wound closure and implant loading against the metatarsal head. The combination of a porous coated prosthesis seated in packed autologous bone graft resulted in early relief of symptoms and return to function with sustained good results at two years. Further surveillance is required to judge the longevity and success of this technique but as with any joint arthroplasty, any future management would be guided by patient symptoms. Early results are encouraging. This may offer a wider potential use for the BioPro1 hallux MTPJ hemiarthroplasty. Importantly, the options for excision arthroplasty or arthrodesis have not been compromised. Conflict of interest statement The authors have no conflict of interest. Acknowledgement No external funding or support has been received in the preparation of this manuscript References [1] Verhaar J, Bulstra S, Walenkamp G. Silicone arthroplasty for hallux rigidus. Implant wear and osteolysis. Acta Orthop Scand 1989;60:30–3. [2] Verhaar J, Vermeulen A, Bulstra S, Walenkamp G. Bone reaction to silicone metatarsophalangeal joint-1 hemiprosthesis. Clin Orthop Rel Res 1989;245: 228–32. [3] Harrison WJ, Loughead JM. Silastic metatarsophalangeal arthroplasty: very long-term results of single-stem implants in degenerative joint disease. Foot 2003;13:146–50. [4] Mondul M, Jacobs PM, Caneva RG, Crowhurst JA, Morehead DE. Implant arthroplasty of the first metatarsophalangeal joint: a 12-year retrospective study. J Foot Surg 1985;24:275–9. [5] Esway JE, Conti SF. Joint replacement in the hallux metatarsophalangeal joint. Foot Ankle Clin 2005;10:97–115. [6] Sethu A, D’Netto DC, Ramakrishna B. Swanson’s silastic implants in great toes. J Bone Joint Surg 1980;62-B:83–5.
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R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
[7] Gibson JN, Thomson CE. Arthrodesis or total replacement arthroplasty for hallux rigidus: a randomized controlled trial. Foot Ankle Int 2005;26:680–90. [8] Machacek Jr F, Easley ME, Gruber F, Ritschl P, Trnka HJ. Salvage of a failed Keller resection arthroplasty. J Bone Joint Surg 2004;86-A:1131–8. [9] Koenig RD, Horwitz LR. The Biomet Total Toe System utilizing the Koenig score: a five-year review. J Foot Ankle Surg 1996;35:23–6. [10] Giza E, Sullivan MR. First metatarsophalangeal hemiarthroplasty for grade III and IV hallux rigidus. Tech Foot Ankle Surg 2005;4:10–7.
[11] Townley CO, Taranow WS. A metallic hemiarthroplasty resurfacing prosthesis for the hallux metatarsophalangeal joint. Foot Ankle Int 1994;15:575–80. [12] Biologically Oriented Prostheses (BioPro) Toe M-P Joint. Product Information Sheet. BioPro Inc, Port Huron, MI. BP102303rev1. [13] Kissel CG, Husain ZS, Wooley PH, et al. A prospective investigation of the BioPro hemi-arthroplasty for the first metatarsophalangeal joint. J Foot Ankle Surg 2008;47:505–9.
Contents lists available at ScienceDirect
Foot and Ankle Surgery journal homepage: www.elsevier.com/locate/fas
Case report
Hemiarthroplasty augmented with bone graft for the failed hallux metatarsophalangeal Silastic1 implant Raymond E. Anakwe FRCS Ed (Tr & Orth)*, Scott D. Middleton MB ChB, Colin E. Thomson BSc (Hons), PhD, John C. McKinley FRCS Ed (Tr & Orth) The Foot and Ankle Service, Department of Trauma & Orthopaedic Surgery, Royal Infirmary of Edinburgh, 51, Little France Crescent, Edinburgh EH16 5SU, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history: Received 10 August 2010 Received in revised form 14 April 2011 Accepted 28 April 2011
Symptomatic failure of Silastic1 implants at the hallux metatarsophalangeal joint can result in the challenging problem of instability which may be painful. There is often marked bone loss making reconstruction difficult. Arthrodesis sacrifices joint movement while excision arthroplasty shortens the ray and is less acceptable to active patients. We describe a case in which reconstruction was achieved by using a porous coated metatarsophalangeal hemiarthroplasty augmented with bone graft with good early results. This previously unreported technique may offer an additional surgical option for reconstruction, maintaining joint movement without compromising future arthrodesis or excision arthroplasty as salvage measures. Long term follow up is required to confirm the success of this technique. ß 2011 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Silastic Hallux rigidus Metatarsophalangeal joint BioPro hemiarthroplasty
1. Introduction Silastic1 joint replacement is associated with particulate wear, local osteolysis and granulomatous change [1,2]. These implants have previously been used in large numbers to replace the hallux metatarsophalangeal joint (MTPJ) and while concerns over early failure mean that they are no longer as commonly used, there are some reports of long term follow up with good results particularly with respect to function and patient satisfaction [3,4]. A characteristic radiographic appearance has been described at the MTPJ, representative of Silastic1 particulate wear and granulomatous degeneration. Radiographs frequently show evidence of osteolysis and cystic change while at surgery, bone loss and synovitis are often noted [1]. The importance of this is debated as it is not always painful and the clinical picture does not always correlate with the radiographic appearances. Symptoms of instability, which may be painful, functional limitation and progressive or unacceptable deformity suggest that the implant has failed and revision or salvage surgery may be contemplated. Long term outcomes have been said to be better where Silastic1 implants are used for hallux rigidus rather than hallux valgus surgery and where they are selected for low demand patients and those over fifty years of age [3,5,6]. Nevertheless, large numbers of patients with Silastic1 implants may be candidates for revision surgery. Salvage of failed Silastic1 hallux MTPJ arthroplasty may be attempted by debridement/synovectomy combined with either
* Corresponding author. E-mail address: [email protected] (R.E. Anakwe).
excision arthroplasty or arthrodesis. The aim is to restore a painless stable joint for weight bearing and push off. Arthrodesis is reported to more reliably achieve excellent levels of patient satisfaction than arthroplasty options but sacrifices joint motion [5,7,8]. It also avoids excessive shortening of the first ray but may be complicated by phalangeal deformity or painful non union. The key benefit of total-toe arthroplasty is that both surfaces of the MTPJ are addressed which allows for both preservation of motion and joint stability. Total joint arthroplasties and in particular, metal on ultra high molecular weight polyethylene (UHMWPE) bearing surfaces are however, susceptible to particulate wear and osteolysis. While not an absolute contraindication to their use for the salvage of failed Silastic1 arthroplasties, this does merit careful consideration, particularly where bone stock is poor. In a previous study, Koenig and Horwitz described the use of the Biomet Total-Toe system for primary and revision surgery [9]. In four of 10 cases where it was used for revision of failed Silastic1 interpositional arthroplasty, further surgery was required due to loosening of the total-toe implant. This was attributed to poor bone stock. We present a case detailing the use of a hallux MTPJ hemiarthroplasty augmented with autologous bone graft and synthetic bone substitute to address a painful failed Silastic1 MTPJ implant in a young patient.
2. Case report A 38-year old woman was referred to the Foot and Ankle service complaining of a painful stiff right hallux MTPJ. She had been treated at the age of 19 for hallux rigidus and had undergone
1268-7731/$ – see front matter ß 2011 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.fas.2011.04.006
[(Fig._1)TD$IG]
e44
[(Fig._2)TD$IG]
R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
Fig. 1. Preoperative radiographs showing osteolysis and evidence of Silastic wear.
Silastic1 interpositional arthroplasty at another centre. She had never been entirely satisfied after this surgery and complained of residual pain. Over several years, her pain had worsened and was now resistant to simple analgesia. She complained of intermittent swelling over the dorsum of the MTPJ and difficulty in obtaining comfortable, fitting shoes. She worked as a nursing assistant and found that prolonged periods of standing exacerbated her symptoms. She had no significant co-morbidities and was a keen recreational hill walker. Clinical examination revealed a warm, sensate, well perfused and normally aligned foot without plantar callosities. There was an area of obvious swelling over the hallux MTPJ which was tender to palpation and the joint was stiff with 208 of dorsiflexion and 158 of plantar flexion only. A dorsomedial curvilinear scar confirmed previous MTPJ surgery. Radiographs confirmed that a Silastic1 implant had previously been inserted and there was evidence of osteolysis with cystic degeneration (Fig. 1). After discussion with the patient, it was clear that arthrodesis was not acceptable to her. We agreed to proceed to joint debridement/synovectomy combined with MTPJ hemiarthroplasty. In view of the degree of degeneration and potential bone loss, we planned to augment the hemiarthroplasty with autologous bone as well as synthetic bone substitute if required. The patient consented to joint arthrodesis should reconstruction prove impossible. At surgery, the previous incision was used and an arthrotomy made medial to the tendon of extensor hallucis longus. There was florid synovitis which was excised with the worn implant. Large cysts in both the proximal phalanx and the metatarsal head were thoroughly curetted and lavaged leaving substantial bony defects but a preserved cortical rim. The proximal phalanx was sized for a medium implant and no further bone resection was required in view of the pre-existing bone loss. We harvested cancellous bone graft from the ipsilateral proximal tibia and packed it into the defects in the proximal phalanx in order to provide solid support
Fig. 2. Postoperative radiographs.
for the prosthesis. The remaining bone graft was used to fill defects in the metatarsal head and this was supplemented with Kasios1TCP artificial bone substitute. Grafted surfaces were contoured to the joint line to reproduce a congruent joint surface in the metatarsal head. We selected a medium porous coated BioPro1 hemiarthroplasty (Port Huron, MI) and implanted this into the proximal phalanx and bed of bone graft. The joint was taken through a range of motion before it was irrigated, the wound closed
[(Fig._3)TD$IG]
R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
e45
Fig. 3. Follow up radiographs at 2 years including stress dorsiflexion view to assess implant alignment and stability.
in layers and soft dressings applied. The patient was allowed to fully weight bear as able in a soft surgical shoe and was discharged home on the day of surgery. We reviewed the patient in the outpatient clinic 3 weeks after surgery. She made a gradual return to normal activities and returned to nursing and recreational walking at 6 weeks with no requirement for regular analgesia. Radiographs show good alignment of the prosthesis and incorporation of the bone graft (Fig. 2a and b). At 12 months, passive dorsiflexion at the MTPJ is 508 with 208 of plantar flexion and she remains asymptomatic. These results and stability of the implant have been maintained at two years (Fig. 3a and b). 3. Discussion The BioPro1 hallux MTPJ hemiarthroplasty (Fig. 3) is a cobalt chrome MTPJ implant available in either a porous coated or non coated form. It has been in use since 1952 and it is a reliable motion preserving option for primary MTPJ arthroplasty [10,11]. It is indicated for use in arthritic degradation of the MTPJ of the great toe resulting in disabling pain, degenerative arthritis (hallux rigidus), rheumatoid arthritis and bunion deformity associated with arthritis of the great MTPJ. It is not specifically licensed for revision surgery and caution is advised where there is bone loss or structural deficiency of supporting subchondral bone [5,12]. Excellent outcomes have been reported in long term studies. These suggest that with good surgery, primary treatment with the BioPro1 hemiarthroplasty allows an improved range of movement at the hallux MTPJ, improved patient reported outcome scores and a reduction in pain localised to the hallux MTPJ [11,13]. Where there is adequate structural support from the bone, this implant is an attractive option for revision surgery as it preserves movement, requires minimal if any further bone resection and it maintains the future options of joint arthrodesis or excision arthroplasty. Proponents of total-toe arthroplasty recommend that the metatarsal head should also be resurfaced however studies using the Biopro hemiarthroplasty for primary surgery show that excellent outcomes are reported even where both sides of the joint are worn and the metatarsal head is not treated [13].
We believe that it is an important part of the revision surgery to undertake a thorough debridement of all Silastic1 material, inflamed synovium and membrane in order to avoid progression of osteolysis. As we expected, the degree of bone loss did not allow the prosthesis to be confidently seated in the proximal phalanx and bone grafting was required. Immediate stability depends on soft tissue tensioning at wound closure and implant loading against the metatarsal head. The combination of a porous coated prosthesis seated in packed autologous bone graft resulted in early relief of symptoms and return to function with sustained good results at two years. Further surveillance is required to judge the longevity and success of this technique but as with any joint arthroplasty, any future management would be guided by patient symptoms. Early results are encouraging. This may offer a wider potential use for the BioPro1 hallux MTPJ hemiarthroplasty. Importantly, the options for excision arthroplasty or arthrodesis have not been compromised. Conflict of interest statement The authors have no conflict of interest. Acknowledgement No external funding or support has been received in the preparation of this manuscript References [1] Verhaar J, Bulstra S, Walenkamp G. Silicone arthroplasty for hallux rigidus. Implant wear and osteolysis. Acta Orthop Scand 1989;60:30–3. [2] Verhaar J, Vermeulen A, Bulstra S, Walenkamp G. Bone reaction to silicone metatarsophalangeal joint-1 hemiprosthesis. Clin Orthop Rel Res 1989;245: 228–32. [3] Harrison WJ, Loughead JM. Silastic metatarsophalangeal arthroplasty: very long-term results of single-stem implants in degenerative joint disease. Foot 2003;13:146–50. [4] Mondul M, Jacobs PM, Caneva RG, Crowhurst JA, Morehead DE. Implant arthroplasty of the first metatarsophalangeal joint: a 12-year retrospective study. J Foot Surg 1985;24:275–9. [5] Esway JE, Conti SF. Joint replacement in the hallux metatarsophalangeal joint. Foot Ankle Clin 2005;10:97–115. [6] Sethu A, D’Netto DC, Ramakrishna B. Swanson’s silastic implants in great toes. J Bone Joint Surg 1980;62-B:83–5.
e46
R.E. Anakwe et al. / Foot and Ankle Surgery 17 (2011) e43–e46
[7] Gibson JN, Thomson CE. Arthrodesis or total replacement arthroplasty for hallux rigidus: a randomized controlled trial. Foot Ankle Int 2005;26:680–90. [8] Machacek Jr F, Easley ME, Gruber F, Ritschl P, Trnka HJ. Salvage of a failed Keller resection arthroplasty. J Bone Joint Surg 2004;86-A:1131–8. [9] Koenig RD, Horwitz LR. The Biomet Total Toe System utilizing the Koenig score: a five-year review. J Foot Ankle Surg 1996;35:23–6. [10] Giza E, Sullivan MR. First metatarsophalangeal hemiarthroplasty for grade III and IV hallux rigidus. Tech Foot Ankle Surg 2005;4:10–7.
[11] Townley CO, Taranow WS. A metallic hemiarthroplasty resurfacing prosthesis for the hallux metatarsophalangeal joint. Foot Ankle Int 1994;15:575–80. [12] Biologically Oriented Prostheses (BioPro) Toe M-P Joint. Product Information Sheet. BioPro Inc, Port Huron, MI. BP102303rev1. [13] Kissel CG, Husain ZS, Wooley PH, et al. A prospective investigation of the BioPro hemi-arthroplasty for the first metatarsophalangeal joint. J Foot Ankle Surg 2008;47:505–9.