Figure 26.1 (a) A 51-year old overweight insulin-dependant diabetic male had a persistent plantar ulcer that continued to return after several episodes of treatment. (b) A dorsal skin flap was used to obtain successful healing at hallux amputation level
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(a)
(b)
Figure 26.2 (a,b) The 53-year old diabetic patient developed this ischaemic ulcer. (c) A plantar-based flap was successful in providing a stable amputation through the proximal phalanx of the hallux
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(c)
Figure 26.2 (Continued)
the best results are achieved following resection of a lateral (first or fifth) metatarsal.
Central metatarsal resection requires sufficient bony resection to allow secondary wound closure.
When more than one metatarsal needs to be removed, the residual forefoot becomes very narrow and tends to develop an equinus (plantar flexion) deformity, which is difficult to accommodate with therapeutic footwear.
To ensure the most favourable outcome, these individuals are best treated with midfoot amputation.20
Midfoot Amputation Amputation at the middle level of the foot can be performed at the transmetatarsal or tarsal, metatarsal (Lisfranc) levels.
Both provide an excellent weight-bearing platform for walking.
Late equinus deformity can be avoided by performing a percutaneous Achilles tendon length- ening at the time of surgery, and managing the patient in a below-knee total contact walking cast for 4 weeks following the surgery.14 Amputation through the distal metatarsal shafts minimises the loss in walking propulsion at the cost of an appreciable rate of re-ulceration under one or all of the residual metatarsal ends.
This can be avoided by performing the surgery through the proximal metaphyses, at the cost of a decreased lever arm to assist propulsion.21,22
Hindfoot Amputation Except for special circumstances, hindfoot amputation should be avoided due to the high risk for the late development of non-correctable ankle equinus due to the overpowering effect of the ankle plantar flexors (Figure 26.5). There is recent interest in performing this amputation level
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(a)
(b)
Figure 26.3 (a) Preservation of the proximal metaphysis of the second toe prevented the hallux from migrating laterally. (b) This foot had a complete amputation of the second toe. The foot is at high risk for the development of a severe hallux valgus deformity with a bony prominence prone to ulcerate
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(a)
(b)
Figure 26.4 (a) A partial first ray resection allowed the second toe to be prominent. (b) Pressure in the early post-operative period produced a transfer pressure lesion in the second toe. (c,d) Multiple toe resections created a smooth border. The absence of prominent toes allowed successful therapeutic shoe fitting
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(c)
(d)
Figure 26.4 (Continued)
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(a)
(b)
Figure 26.5 (a,b,c,d) This insulin-dependent diabetic male underwent open hindfoot amputation as treatment for infection. In spite of immobilisation in a below-the-knee cast, the patient has developed a severe equinovarus deformity that precluded weight bearing. Note the significant bony prominence underlying the anterior aspect of the calcaneus. This deformity cannot be accommodated with therapeutic footwear. The patient will require an ankle disarticulation (Syme’s)
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(c)
(d)
Figure 26.5 (Continued)
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(a)
(b)
Figure 26.6 (a) Residual limb following one-stage Syme’s ankle disarticulation. (b) This patient was able to quickly become a successful walker with a ‘Canadian’ Syme’s prosthesis
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in conjunction with ankle fusion only in individuals who do not, or will not be able to, obtain a prosthesis (Syme’s ankle disarticulation) due to entitlement or financial reasons. Combining ankle fusion with hindfoot amputation allows apropulsive ambulation with a modified high- topped shoe.
Syme’s Ankle Disarticulation Syme’s ankle disarticulation allows end bearing within a prosthetic socket, using the normal weight-bearing tissue of the heel. When the surgery is successful, these individuals resume normal walking with a prosthesis and rarely have late complications (Figure 26.6).2 The two critical factors necessary to achieve a successful Syme’s ankle disarticulation are preservation of the posterior tibial artery and securing the heel pad to the tibia with non-absorbable sutures.2,23