- Email: [email protected]
Static Ring Fixation for Nonplantigrade Charcot Midfoot Deformity
Static Ring Fixation for Nonplantigrade Charcot Midfoot Deformity Michael S. Pinzur, MD It is now appreciated by the orthopedic foot and ankle community that Charcot foot arthropathy imparts a severe negative impact on health-related quality of life. These effects are not reversed with conventional methods of accommodative treatment. Surgical correction may allow patients a less encumbered ambulation. Traditional methods of internal fixation are not applicable in many of the patients because of morbid obesity, open wounds with osteomyelitis, poor bone quality, and an impaired immune status. The static application of the Illizarov method allows correction of the deformity through a small surgical incision with limited soft-tissue stripping, and maintenance of that correction with a preassembled, 3-level, static circular external fixator. Oper Tech Orthop 18:287-292 © 2008 Elsevier Inc. All rights reserved. KEYWORDS diabetic foot, Charcot foot, neuropathic fracture, neuropathy
T
here has been growing awareness in North America that Charcot foot arthropathy imparts a severe negative impact on patient-reported health-related quality of life.1 The appreciation of the magnitude of this problem has sparked a great deal of renewed interest, leading experts to question the value of the historic accommodative method of treatment. Historically, the acute active phase of Charcot foot arthropathy was treated with a non–weight-bearing total contact cast. When the acute phase resolved, the resulting deformity was treated with custom-fabricated accommodative orthoses with or without bracewear.2 Surgery was advised only for infection, for nonhealing ulcers overlying deformity, or for deformity of sufficient magnitude that was deemed “non-braceable.”3 Many of these patients became wheelchair-bound or eventually underwent lower extremity amputation. A Scandinavian longitudinal observational study suggested that that this disease process simply imparts a temporary nuisance on quality of life and rarely requires surgery.4 This has not been the case in North America, possibly because of the association between morbid obesity and diabetes-related foot morbidity.5 The use of a validated outcomes instrument confirmed that patients often found this treatment to be onerous, with suboptimal results that severely impaired functional independence and health-related quality Loyola University Medical Center, Department of Orthopaedic Surgery & Rehabilitation, Maywood, IL. Address reprint requests to Loyola University Medical Center, Department of Orthopaedic Surgery and Rehabilitation, 2160 South First Ave, Maywood, IL 60153. E-mail: [email protected]
1048-6666/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2009.01.006
of life.1,6 These observations convinced surgeons to apply conventional methods of reconstructive surgery using fracture technology.7-15 The historical method of treatment simply focused on limb salvage and the ability to weight bear, ignoring the encumbrances placed on daily life associated with a Charcot restraint orthotic walker (CROW) or complex lower extremity orthosis. The surgical reconstructive outcomes-based approach defines a favorable result as a patient who is ulcer and infection free and able to ambulate in the community using standard commercially available diabetic therapeutic footwear (depth-inlay shoes with custom accommodative foot orthoses).13 Two recent prospective investigations have demonstrated that treatment with a weight-bearing total contact cast can predictably achieve healing of the destructive process.16,17 However, the early success achieved with accommodative treatment does not appear to be maintained longitudinally. Bevan and Tomlinson have observed that patients with Charcot foot arthropathy who have a radiographic nonlinear relationship between the forefoot and hindfoot, as determined from weight-bearing anteroposterior radiographs, were likely to develop plantar ulcers overlying bony deformity when followed-up longitudinally. Those patients with a linear radiographic relationship were unlikely to develop foot ulcers or infection.18 A concurrent clinical determination was based on a clinical assessment of weight-bearing characteristics. A clinically plantigrade foot was observed to bear weight on the normal plantar weight-bearing surface of the foot. A clinically nonplantigrade foot, likely to de287
M.S. Pinzur
288
Figure 1 (A,B) This 56-year-old morbidly obese diabetic woman presented with an unstable Charcot foot deformity. (C,D) Weight-bearing radiographs. (E,F) Photographs and radiographs. (G,H) One year after surgery. The patient walks with commercially available depth-inlay shoes with accommodative custom foot orthoses.
Static ring fixation for nonplantigrade Charcot midfoot deformity velop an ulcer or infection overlying the deformity, was observed to bear weight through skin that normally was not in a weight-bearing orientation.13 The certified pedorthist is easily able to accommodate a classic rocker-bottom deformity when weight-bearing is being accomplished through normal durable plantar tissues. Current pedorthic technology is unable to effectively dissipate weight-bearing loads when weight-bearing must be accomplished through skin that is not sufficiently strong to bear these loads. When both a clinical demonstration of plantigrade alignment and a radiographic weight-bearing assessment of forefoot-to-hindfoot relationship is colinear, it has been observed that approximately 60% of patients can achieve the arbitrarily defined favorable outcome when treated acutely with a weightbearing total contact cast during the active phase of the disease process, and when managed longitudinally with commercially available therapeutic footwear.13-18 Many patients with nonplantigrade deformity can be treated with correction of the deformity and maintenance of that correction with standard methods of internal fixation. These low-risk hosts are generally not morbidly obese, do not have open wounds with associated osteomyelitis, have good quality bone in the involved foot, and have minimal other diabetes-associated medical comorbidities. High-risk patients are those who are best suited for percutaneous correction of their deformity and maintenance of that correction with a static circular external fixator. The patients best suited for fine-wire fixator treatment have some combination of risk factors that make standard methods of internal fixation a less favorable choice. Members of the target population are often morbidly obese (⬎350 lb), have a large bony deformity, often with a longstanding ulcer overlying infected bone, have regional osteopenia, and are immune compromised. These patients are prone to developing infection as a result of a diabetes-associated impaired immune system, mechanical failure of fixation because of poor-quality bone, or deep infection associated with extensive surgical dissection, swelling, and wound complications with metal implants. The use of circular ring external fixation with tensioned fine wires is a well-accepted albeit complex treatment option available to orthopedic surgeons. It has previously been reported as an option for use in diabetic patients with Charcot arthropathy.8,9,14,19-21
289 pin breakage, severe pain, and the need for constant monitoring of the articulations of the frame construct. The surgical correction is obtained by a well-planned triplane wedge-resection osteotomy at the apex of the deformity. The wedge of bone that is removed should include all infected bone when present. It should be three-dimensionally oriented to allow correction of deformity with apposition of the cut surfaces, and should take into account rotational deformity. A preconstructed, 3-level circular frame is then used simply to maintain the correction without the use of large metal implants. This is a valuable asset in patients in whom the deformity is associated with deep infection and osteomyelitis.
Surgical Technique The first step is a motor unit lengthening of the gastrocnemiussoleus by either a percutaneous triple hemisection of the Achilles tendon or gastrocnemius musculotendinous lengthening (Strayer procedure). This is necessary to negate the deforming force of the calf muscles. The sensory peripheral neuropathy that is well recognized in diabetic patients is accompanied by motor and vasomotor neuropathies. The motor neuropathy affects smaller nerves and muscles (ankle dorsiflexors) earlier in the disease process than the stronger plantarflexors. The motor unit lengthening creates a muscle balance and prevents recreation of the forces that affected the
Rationale for Surgery The desired goal of this surgical technique is to create a noninfected plantigrade foot that can be managed longitudinally with standard, commercially available therapeutic footwear. A favorable result will not have a normal arch, nor will it have normal motion segments. The challenge is maintaining that correction in poor quality bone while avoiding infection. The Illizarov method of correcting deformity takes advantage of limited surgical exposure, limited dissection, and limited soft-tissue stripping at the site of the deformity. The disadvantages associated with the dynamic correction of deformity are prolonged surgical procedures, pin-tract infection and
Figure 2 This three-level static circular ring fixator is constructed before surgery. The top ring has a larger diameter to accommodate the increased diameter of the calf relative to the ankle.
290 original deformity. The vasomotor neuropathy is responsible for much of the associated soft-tissue swelling and the arteriovenous shunting that produces extremely heavy bleeding during the surgery. A limited longitudinal incision is over the apex of the deformity. Correction of the alignment is generally achieved by
M.S. Pinzur removing a triplanar wedge of the bone at the apex of the deformity, perpendicular to the planes of the deformity. Bone cultures are taken to direct antibiotic therapy when indicated. Acceptable clinical alignment is achieved when a “shoeable” foot is created. Optional provisional fixation can be accomplished with a smooth pin. Wounds are loosely
Static ring fixation for nonplantigrade Charcot midfoot deformity reapproximated with simple multiple layer heavy No. 2 nylon sutures (Fig. 1). A preassembled, static, 3–level, circular ring external fixator is then placed over the limb. The rings should be of the smallest available size that do not apply direct pressure to the skin. This ring size-matching avoids wire bending and greatly decreases the potential for pin breakage. Most systems allow the use of a one-size larger ring to accommodate an hourglass calf (Fig. 2). To avoid frame-associated pressure ulcers, the static frame is applied in a stepwise progression. The first step is to position the heel in the center of the foot ring in the orientation of the ring, avoiding pressure from the ring. Two olive wires are drilled through the calcaneus at approximately a 30° angle, parallel with the weight-bearing orientation of the heel. Three wires can be used in extremely large-sized patients. The wires are pretensioned to 120 kg and attached to the foot ring. The forefoot is then aligned to the hindfoot in a clinically plantigrade orientation. Two or three olive wires are then drilled through the metatarsal shafts at approximately a 30° angle. These wires are pretensioned to 120 kg and attached to the foot ring in a compression mode. Compression is achieved by attaching the pin connectors 1 hole posterior to where they lie with the foot in the corrected orientation (Fig. 3). With the ankle positioned at 90°, the leg is positioned with the tibia centered in the proximal ring. Two or three olive wires are drilled through the tibia at approximately a 60° angle. The wires are then pretensioned to 120 kg and attached to the proximal ring. Wires are applied in a similar fashion at the level of the middle ring.
Postoperative Management Patients are allowed to bear approximately 30 lb of weight on the affected limb, using a modified cast shoe lined with plastizote (Fig. 4). The static fixation frame is removed at 8 weeks after surgery, with sedation, in the ambulatory surgical center. A weight-bearing total contact cast is applied for 4 to 6 weeks, depending on clinical stability, radiographic findings, and swelling. Patients are then transitioned into a removable pneumatic fracture boot until the volume of their foot is sufficiently stable to allow fitting with therapeutic footwear.
291
Figure 4 Modified frame shoe. The canvas top of a standard cast shoe has been removed. A layer of plastizote or other pressure-dissipating material is used to cushion weight-bearing. “S” hooks are attached to the shoe and rubber bands are used to attach the shoe to the ring fixator. This allows the patients to bear some weight on the foot in a protected mode. This method is in distinction to frame applications that allow weight-bearing on the frame, adding increased bending forces on the foot wires.
Outcomes This surgical technique is not new. Small case series have been reported by several authors, with similar results.8,9,13,14,19 Comparison with more conventional methods of internal fixation is difficult because of patient selection. This technique is best applied in patients who would predictably fare worst with conventional surgical techniques. Relatively healthy patients of relatively small size, with good bone quality and no open wounds, are most likely to achieve favorable outcomes regardless of the surgical technique. Morbidly obese patients with poor bone quality and open wounds are more prone to wound or mechanical failure with any method of treatment. Pin breakage and pin-tract infection are generally accepted to occur with approximately 3% of fine-wire pins. Most of these complications can be resolved with relief of tented skin, oral antibiotic therapy, or pin removal and replacement.
Figure 3 After correction of the deformity, excision of all infected bone and tendon Achilles lengthening, the following surgical steps are taken for application of the static circular ring: (A) Two olive wires are drilled through the calcaneus at an angle of approximately 30° to one another and parallel to the weight-bearing surface of the heel. With the heel oriented in the center of the foot ring and oriented in the plane of the foot ring, the olive wires are pretensioned to 120 kg and attached to the foot ring. (B) Two olive wires are then passed along the foot ring, through the proximal metatarsal shafts at a 30° angle to one another and parallel to the weight-bearing surface of the forefoot. In this photograph, the forefoot has not yet been corrected and aligned with the hindfoot. (C) The forefoot has now been aligned to the hindfoot. With the forefoot in the corrected position, the olive wires are pretensioned to 120 kg and attached to the front of the foot ring. To obtain compression fixation of the forefoot relative to the hindfoot, the forefoot wires are attached to the foot ring 1 hole proximal to where they naturally sit before attachment, in a “compression” mode. Another option would be to align the forefoot to the hindfoot before frame application and temporarily maintain that correction with a percutaneous smooth K-wire (D, E). Final static ring construct.
M.S. Pinzur
292
Discussion It is now well accepted in North America that Charcot foot arthropathy severely impacts health-related quality of life. This severe negative impact is not reversed with conventional treatment. Correction of deformity to allow patients to walk with commercially available “diabetic shoes” depth-inlay shoes with custom accommodative foot orthosis can be achieved with a combined approach of an osteotomy for alignment and stabilization with external fixation. Although conventional methods of surgical implants are successful in many patients, there is a significant population of patients who are morbidly obese, have large open wounds with draining osteomyelitis, or are poor hosts. Such patients are prone to develop wound failure or deep infection as a result of their impaired immune systems, or mechanical failure because of the poor quality of their bone stock. The advantage of this clinical approach is severalfold. ● ● ●
● ●
Surgery can be performed through small incisions, with little soft-tissue dissection. No implants are left in wounds that are very prone to develop infection. Using the static frame concept, no correction of the deformity is required after application of the circular frame. This lessens the risk for pin-tract infection and pin breakage, and rarely requires the need for tightening nuts and bolts. Casts are avoided, and patients are allowed to take baths a few days after surgery. Some weight-bearing can be tolerated in an immobile patient population that finds great difficulty in maintaining a non–weight-bearing status.
References 1. Dwahan V, Spratt K, Pinzur MD, et al: The AOFAS diabetic foot questionnaire: Stability, internal consistency, and measurable difference. Foot Ank Int 26:717-731, 2005
2. Brodsky JW: The diabetic foot, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle. St. Louis, Mosby, 1999, pp 895-969 3. Pinzur MS, Sage R, Stuck R, et al: A treatment algorithm for neuropathic (Charcot) midfoot deformity. Foot Ankle Int 14:189-197, 1993 4. Fabrin J, Larsen K, Holstein PE: Long-term follow-up in diabetic Charcot feet with spontaneous onset. Diabetes Care 23:796-800, 2000 5. Pinzur MS, Freeland R, Juknelis D: The association between body mass index and diabetic foot disorders. Foot Ank Int 26:375-377, 2005 6. Pinzur MS, Evans A: Health related quality of life in patients with Charcot foot. Am J Orthop 32:492-496, 2003 7. Early JS, Hansen ST: Surgical reconstruction of the diabetic foot. Foot Ankle Int 17:325-330, 1996 8. Farber DC, Juliano PJ, Cavanagh PR, et al: Single stage correction with external fixation of the ulcerated foot in individuals with Charcot Neuroarthropathy. Foot Ank Int 23:130-134, 2002 9. Jolly GP, Zgonis T, Polyzois V: External fixation in the management of Charcot neuroarthropathy. Clin Podiatr Med Surg 20:741-756, 2003 10. Myerson MS, Henderson MR, Saxby T, et al: Management of midfoot diabetic neuroarthropathy. Foot Ankle Int 15:233-241, 1994 11. Papa J, Myerson M, Girard P: Salvage, with arthrodesis, in intractable diabetic neuropathic arthropathy of the foot and ankle. J Bone Joint Surg 75A:1056-1066, 1993 12. Simon SR, Tejwani SG, Wilson DL, et al: Arthrodesis as an early alternative to nonoperative management of Charcot arthropathy of the diabetic foot. J Bone Joint Surg 82A:939-950, 2000 13. Pinzur MS: Surgical vs. accommodative treatment for Charcot arthropathy of the midfoot. Foot Ank Int 25:545-549, 2004 14. Pinzur MS: Neutral ring fixation for high risk non-plantigrade Charcot midfoot deformity. Foot Ank Int 28:961-966, 2007 15. Pinzur MS, Sostak J: Surgical stabilization of nonplantigrade Charcot arthropathy of the midfoot. Am J Orthop 36:361-365, 2007 16. Pinzur MS, Lio T, Posner M: Treatment of Eichenholtz stage I Charcot foot arthropathy with a weight bearing total contact cast. Foot Ank Int 27:324-329, 2006 17. deSouza L: Charcot arthropathy and immobilization in a weight-bearing total contact cast. J Bone Joint Surg 90A:754-759, 2008 18. Bevan WP, Tomlinson MP: Radiographic measure as a predictor of ulcer formation in midfoot Charcot. Paper presented at the Annual Meeting of the American Orthopaedic Foot and Ankle Society. Foot Ank Int 29:568-573, 2008 19. Cooper PS: Application of external fixation for management of Charcot deformities of the foot and ankle. Foot Ank Clin 7:207-254, 2002 20. Pinzur MS: The role of ring external fixation in Charcot Foot arthropathy. Foot Ank Clinics 11:837-848, 2006 21. Pinzur MS: Ring fixation in Charcot Foot and ankle arthropathy. Tech Foot Ankle Surg 5:68-73, 2006
T
here has been growing awareness in North America that Charcot foot arthropathy imparts a severe negative impact on patient-reported health-related quality of life.1 The appreciation of the magnitude of this problem has sparked a great deal of renewed interest, leading experts to question the value of the historic accommodative method of treatment. Historically, the acute active phase of Charcot foot arthropathy was treated with a non–weight-bearing total contact cast. When the acute phase resolved, the resulting deformity was treated with custom-fabricated accommodative orthoses with or without bracewear.2 Surgery was advised only for infection, for nonhealing ulcers overlying deformity, or for deformity of sufficient magnitude that was deemed “non-braceable.”3 Many of these patients became wheelchair-bound or eventually underwent lower extremity amputation. A Scandinavian longitudinal observational study suggested that that this disease process simply imparts a temporary nuisance on quality of life and rarely requires surgery.4 This has not been the case in North America, possibly because of the association between morbid obesity and diabetes-related foot morbidity.5 The use of a validated outcomes instrument confirmed that patients often found this treatment to be onerous, with suboptimal results that severely impaired functional independence and health-related quality Loyola University Medical Center, Department of Orthopaedic Surgery & Rehabilitation, Maywood, IL. Address reprint requests to Loyola University Medical Center, Department of Orthopaedic Surgery and Rehabilitation, 2160 South First Ave, Maywood, IL 60153. E-mail: [email protected]
1048-6666/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2009.01.006
of life.1,6 These observations convinced surgeons to apply conventional methods of reconstructive surgery using fracture technology.7-15 The historical method of treatment simply focused on limb salvage and the ability to weight bear, ignoring the encumbrances placed on daily life associated with a Charcot restraint orthotic walker (CROW) or complex lower extremity orthosis. The surgical reconstructive outcomes-based approach defines a favorable result as a patient who is ulcer and infection free and able to ambulate in the community using standard commercially available diabetic therapeutic footwear (depth-inlay shoes with custom accommodative foot orthoses).13 Two recent prospective investigations have demonstrated that treatment with a weight-bearing total contact cast can predictably achieve healing of the destructive process.16,17 However, the early success achieved with accommodative treatment does not appear to be maintained longitudinally. Bevan and Tomlinson have observed that patients with Charcot foot arthropathy who have a radiographic nonlinear relationship between the forefoot and hindfoot, as determined from weight-bearing anteroposterior radiographs, were likely to develop plantar ulcers overlying bony deformity when followed-up longitudinally. Those patients with a linear radiographic relationship were unlikely to develop foot ulcers or infection.18 A concurrent clinical determination was based on a clinical assessment of weight-bearing characteristics. A clinically plantigrade foot was observed to bear weight on the normal plantar weight-bearing surface of the foot. A clinically nonplantigrade foot, likely to de287
M.S. Pinzur
288
Figure 1 (A,B) This 56-year-old morbidly obese diabetic woman presented with an unstable Charcot foot deformity. (C,D) Weight-bearing radiographs. (E,F) Photographs and radiographs. (G,H) One year after surgery. The patient walks with commercially available depth-inlay shoes with accommodative custom foot orthoses.
Static ring fixation for nonplantigrade Charcot midfoot deformity velop an ulcer or infection overlying the deformity, was observed to bear weight through skin that normally was not in a weight-bearing orientation.13 The certified pedorthist is easily able to accommodate a classic rocker-bottom deformity when weight-bearing is being accomplished through normal durable plantar tissues. Current pedorthic technology is unable to effectively dissipate weight-bearing loads when weight-bearing must be accomplished through skin that is not sufficiently strong to bear these loads. When both a clinical demonstration of plantigrade alignment and a radiographic weight-bearing assessment of forefoot-to-hindfoot relationship is colinear, it has been observed that approximately 60% of patients can achieve the arbitrarily defined favorable outcome when treated acutely with a weightbearing total contact cast during the active phase of the disease process, and when managed longitudinally with commercially available therapeutic footwear.13-18 Many patients with nonplantigrade deformity can be treated with correction of the deformity and maintenance of that correction with standard methods of internal fixation. These low-risk hosts are generally not morbidly obese, do not have open wounds with associated osteomyelitis, have good quality bone in the involved foot, and have minimal other diabetes-associated medical comorbidities. High-risk patients are those who are best suited for percutaneous correction of their deformity and maintenance of that correction with a static circular external fixator. The patients best suited for fine-wire fixator treatment have some combination of risk factors that make standard methods of internal fixation a less favorable choice. Members of the target population are often morbidly obese (⬎350 lb), have a large bony deformity, often with a longstanding ulcer overlying infected bone, have regional osteopenia, and are immune compromised. These patients are prone to developing infection as a result of a diabetes-associated impaired immune system, mechanical failure of fixation because of poor-quality bone, or deep infection associated with extensive surgical dissection, swelling, and wound complications with metal implants. The use of circular ring external fixation with tensioned fine wires is a well-accepted albeit complex treatment option available to orthopedic surgeons. It has previously been reported as an option for use in diabetic patients with Charcot arthropathy.8,9,14,19-21
289 pin breakage, severe pain, and the need for constant monitoring of the articulations of the frame construct. The surgical correction is obtained by a well-planned triplane wedge-resection osteotomy at the apex of the deformity. The wedge of bone that is removed should include all infected bone when present. It should be three-dimensionally oriented to allow correction of deformity with apposition of the cut surfaces, and should take into account rotational deformity. A preconstructed, 3-level circular frame is then used simply to maintain the correction without the use of large metal implants. This is a valuable asset in patients in whom the deformity is associated with deep infection and osteomyelitis.
Surgical Technique The first step is a motor unit lengthening of the gastrocnemiussoleus by either a percutaneous triple hemisection of the Achilles tendon or gastrocnemius musculotendinous lengthening (Strayer procedure). This is necessary to negate the deforming force of the calf muscles. The sensory peripheral neuropathy that is well recognized in diabetic patients is accompanied by motor and vasomotor neuropathies. The motor neuropathy affects smaller nerves and muscles (ankle dorsiflexors) earlier in the disease process than the stronger plantarflexors. The motor unit lengthening creates a muscle balance and prevents recreation of the forces that affected the
Rationale for Surgery The desired goal of this surgical technique is to create a noninfected plantigrade foot that can be managed longitudinally with standard, commercially available therapeutic footwear. A favorable result will not have a normal arch, nor will it have normal motion segments. The challenge is maintaining that correction in poor quality bone while avoiding infection. The Illizarov method of correcting deformity takes advantage of limited surgical exposure, limited dissection, and limited soft-tissue stripping at the site of the deformity. The disadvantages associated with the dynamic correction of deformity are prolonged surgical procedures, pin-tract infection and
Figure 2 This three-level static circular ring fixator is constructed before surgery. The top ring has a larger diameter to accommodate the increased diameter of the calf relative to the ankle.
290 original deformity. The vasomotor neuropathy is responsible for much of the associated soft-tissue swelling and the arteriovenous shunting that produces extremely heavy bleeding during the surgery. A limited longitudinal incision is over the apex of the deformity. Correction of the alignment is generally achieved by
M.S. Pinzur removing a triplanar wedge of the bone at the apex of the deformity, perpendicular to the planes of the deformity. Bone cultures are taken to direct antibiotic therapy when indicated. Acceptable clinical alignment is achieved when a “shoeable” foot is created. Optional provisional fixation can be accomplished with a smooth pin. Wounds are loosely
Static ring fixation for nonplantigrade Charcot midfoot deformity reapproximated with simple multiple layer heavy No. 2 nylon sutures (Fig. 1). A preassembled, static, 3–level, circular ring external fixator is then placed over the limb. The rings should be of the smallest available size that do not apply direct pressure to the skin. This ring size-matching avoids wire bending and greatly decreases the potential for pin breakage. Most systems allow the use of a one-size larger ring to accommodate an hourglass calf (Fig. 2). To avoid frame-associated pressure ulcers, the static frame is applied in a stepwise progression. The first step is to position the heel in the center of the foot ring in the orientation of the ring, avoiding pressure from the ring. Two olive wires are drilled through the calcaneus at approximately a 30° angle, parallel with the weight-bearing orientation of the heel. Three wires can be used in extremely large-sized patients. The wires are pretensioned to 120 kg and attached to the foot ring. The forefoot is then aligned to the hindfoot in a clinically plantigrade orientation. Two or three olive wires are then drilled through the metatarsal shafts at approximately a 30° angle. These wires are pretensioned to 120 kg and attached to the foot ring in a compression mode. Compression is achieved by attaching the pin connectors 1 hole posterior to where they lie with the foot in the corrected orientation (Fig. 3). With the ankle positioned at 90°, the leg is positioned with the tibia centered in the proximal ring. Two or three olive wires are drilled through the tibia at approximately a 60° angle. The wires are then pretensioned to 120 kg and attached to the proximal ring. Wires are applied in a similar fashion at the level of the middle ring.
Postoperative Management Patients are allowed to bear approximately 30 lb of weight on the affected limb, using a modified cast shoe lined with plastizote (Fig. 4). The static fixation frame is removed at 8 weeks after surgery, with sedation, in the ambulatory surgical center. A weight-bearing total contact cast is applied for 4 to 6 weeks, depending on clinical stability, radiographic findings, and swelling. Patients are then transitioned into a removable pneumatic fracture boot until the volume of their foot is sufficiently stable to allow fitting with therapeutic footwear.
291
Figure 4 Modified frame shoe. The canvas top of a standard cast shoe has been removed. A layer of plastizote or other pressure-dissipating material is used to cushion weight-bearing. “S” hooks are attached to the shoe and rubber bands are used to attach the shoe to the ring fixator. This allows the patients to bear some weight on the foot in a protected mode. This method is in distinction to frame applications that allow weight-bearing on the frame, adding increased bending forces on the foot wires.
Outcomes This surgical technique is not new. Small case series have been reported by several authors, with similar results.8,9,13,14,19 Comparison with more conventional methods of internal fixation is difficult because of patient selection. This technique is best applied in patients who would predictably fare worst with conventional surgical techniques. Relatively healthy patients of relatively small size, with good bone quality and no open wounds, are most likely to achieve favorable outcomes regardless of the surgical technique. Morbidly obese patients with poor bone quality and open wounds are more prone to wound or mechanical failure with any method of treatment. Pin breakage and pin-tract infection are generally accepted to occur with approximately 3% of fine-wire pins. Most of these complications can be resolved with relief of tented skin, oral antibiotic therapy, or pin removal and replacement.
Figure 3 After correction of the deformity, excision of all infected bone and tendon Achilles lengthening, the following surgical steps are taken for application of the static circular ring: (A) Two olive wires are drilled through the calcaneus at an angle of approximately 30° to one another and parallel to the weight-bearing surface of the heel. With the heel oriented in the center of the foot ring and oriented in the plane of the foot ring, the olive wires are pretensioned to 120 kg and attached to the foot ring. (B) Two olive wires are then passed along the foot ring, through the proximal metatarsal shafts at a 30° angle to one another and parallel to the weight-bearing surface of the forefoot. In this photograph, the forefoot has not yet been corrected and aligned with the hindfoot. (C) The forefoot has now been aligned to the hindfoot. With the forefoot in the corrected position, the olive wires are pretensioned to 120 kg and attached to the front of the foot ring. To obtain compression fixation of the forefoot relative to the hindfoot, the forefoot wires are attached to the foot ring 1 hole proximal to where they naturally sit before attachment, in a “compression” mode. Another option would be to align the forefoot to the hindfoot before frame application and temporarily maintain that correction with a percutaneous smooth K-wire (D, E). Final static ring construct.
M.S. Pinzur
292
Discussion It is now well accepted in North America that Charcot foot arthropathy severely impacts health-related quality of life. This severe negative impact is not reversed with conventional treatment. Correction of deformity to allow patients to walk with commercially available “diabetic shoes” depth-inlay shoes with custom accommodative foot orthosis can be achieved with a combined approach of an osteotomy for alignment and stabilization with external fixation. Although conventional methods of surgical implants are successful in many patients, there is a significant population of patients who are morbidly obese, have large open wounds with draining osteomyelitis, or are poor hosts. Such patients are prone to develop wound failure or deep infection as a result of their impaired immune systems, or mechanical failure because of the poor quality of their bone stock. The advantage of this clinical approach is severalfold. ● ● ●
● ●
Surgery can be performed through small incisions, with little soft-tissue dissection. No implants are left in wounds that are very prone to develop infection. Using the static frame concept, no correction of the deformity is required after application of the circular frame. This lessens the risk for pin-tract infection and pin breakage, and rarely requires the need for tightening nuts and bolts. Casts are avoided, and patients are allowed to take baths a few days after surgery. Some weight-bearing can be tolerated in an immobile patient population that finds great difficulty in maintaining a non–weight-bearing status.
References 1. Dwahan V, Spratt K, Pinzur MD, et al: The AOFAS diabetic foot questionnaire: Stability, internal consistency, and measurable difference. Foot Ank Int 26:717-731, 2005
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