Amputation, rehabilitation and prosthetic developments

Minor amputations

Minor amputations that are distal to the ankle joint require an abundant blood supply to heal. Unless the foot can be successfully revascularised, wounds following local amputation of single or multiple digits are generally difficult to heal. ^,

Ray amputation

Ray amputation, which involves removal of the toe and partial removal of the metatarsal can be considered in forefoot ischaemia and can ensure a more adequate surgical debridement of the infected or necrotic margins. In 2014 a single centre study, carried out in Singapore, of 150 patients with diabetes with infection or gangrene of the forefoot who underwent ray amputation found that 71% had healed without complication at 1-year follow-up. However, a systematic review carried out in 2012, of 435 partial first ray amputations revealed that a fifth of these patients required more proximal re-amputation within 26 months.

Transmetatarsal amputation

Transmetatarsal amputations (TMA), if technically feasible with or without revascularisation, also produce satisfactory results in forefoot ischaemia.

Intra-operatively, soft tissue should be preserved as much as possible, and consideration is given to leaving the flaps open with delayed closure, as infection and gangrene of the flaps may occur if primary closure is attempted.

A single centre study in Italy from 2016, explored the effects of TMA with revascularisation in 206 patients with diabetes with forefoot infection and gangrene. The authors found that on discharge from hospital, 38% of these patients were ambulating independently, 43% with assistance and 60% were directly discharged home. At 1-year follow-up, the percentage of patients ambulating independently had risen to 77% and 81% of patients were living at home.

A more recent Chinese study from 2019 explored the effects of TMA on 97 patients with diabetes with forefoot gangrene who were unsuitable for revascularisation. The authors found that 64.9% of these patients had their wound completely healed after a median of 8 months.

Midfoot amputations

Amputations of the midfoot include Lisfranc and Chopart amputations. A Lisfranc separates all five metatarsals from the cuboid and their respective cuneiforms, whereas a Chopart amputation removes more of the midfoot and separates the talonavicular and calcaneocuboid joints.

Midfoot amputations have a significant risk of post-operative equinovarus deformity caused by detaching the insertions of peroneal longus, brevis and tibialis anterior as part of the amputation surgery, which in turn leads to unopposed plantarflexion by the gastrocsoleus complex. If midfoot amputations are absolutely necessary, the surgeon should consider inter-operative rebalancing techniques such as Achilles tenotomy, tibialis anterior or extensor digitorum transfer to the talus or even ankle arthrodesis.

Prosthetic options with these amputations are limited and midfoot amputations also have high rates of subsequent proximal revision amputations (i.e., ‘salami-slicing surgery’).

Syme amputation

A Syme amputation involves disarticulation of the ankle joint, removal of both malleoli and securing a long posterior flap containing the heel pad to the anterior tibia to facilitate intermittent weight-bearing. It can be used to successfully treat forefoot gangrene, especially in diabetic patients with dysvascularity. Viability of the posterior flap and heel pad is heavily dependent on the patency of the posterior tibial artery. Thus an ankle-brachial index of less than 0.5 is generally considered to be a contraindication to a Syme amputation.

As the heel pad allows for intermittent weight-bearing, the residual limb in a Syme amputation can be walked on for very short distances without a prosthetic limb (such as when ambulating from the bedroom to the toilet).

Compared to a transtibial amputation (TTA), a Syme amputation offers reduced energy expenditure when ambulating, greater gait stability and thus requires less physiotherapy and gait retraining. However, breakdown and migration of the posterior flap and heal pad may occur if a prosthesis is used regularly. Prosthetic options are also limited with a Syme amputation and there are considerable difficulties in prosthetic fitting as the prosthesis would inevitability be bulky to encompass the bulbous residual limb, which may also impede the contralateral limb when walking.

Transtibial amputation and transfemoral amputation

Approximately half of all referrals to amputee rehabilitation centres in the United Kingdom involve TTAs making it the most common amputation level. The second most common level was transfemoral amputation (TFA) at 34%.

Preservation of the native functioning knee joint has tremendous advantages in terms of mobility with a prosthetic limb.

Compared to independently mobile non-amputees, the energy cost of walking with a prosthetic limb in dysvascular amputees who have undergone a unilateral TTA is increased by 40%, whilst in unilateral transfemoral amputees by 120%. This energy cost can increase to 280% in bilateral transfemoral amputees when mobilising with two prosthetic limbs. The increased energy demands invariably affect an amputee’s ability to use a prosthetic limb with approximately 74% of bilateral amputees not being able to walk with prosthetic limbs 5 years following surgery.

In 2013 a Dutch longitudinal study of 82 patients exploring QoL following lower extremity amputation and found that amputation level was a key factor in determining QoL. Using the RAND-36 questionnaire, the authors noted that transtibial amputees reported better QoL scores compared to transfemoral amputees within the 18 months following an amputation. This was because of a better walking ability leading to greater social participation amongst patients who had a TTA.

A previous British observational study from 2003, of 281 unilateral lower extremity amputees, found that amongst older (>50 years old) amputees, approximately 50% and 60% of transtibial amputees were ambulating independently in the community or at home, respectively 1-year following surgery. Whereas for transfemoral amputees, the respective figures were much lower at 25% and 50%.

Through-knee amputation: knee disarticulation and Gritti–Stokes

Traditionally, through-knee amputation was only considered in those patients who were deemed incapable of walking. The often-quoted Lower Extremity Assessment Project (LEAP) study showed worse outcomes in trauma patients who had knee disarticulation compared to transtibial and TFAs, slower walking speeds and greater difficulty walking on uneven ground or outdoors in bad weather.

However, more recent studies have suggested no significant differences in post-operative complications or functional outcomes in terms of mobility, activities of daily living, QoL or pain between knee disarticulation and transfemoral amputees in both vascular and trauma patients.

With through-knee amputations, the longer lever-arm of the residual limb assists transfers, sitting balance and maintains hip adductor muscle attachment and distal proprioception. ^,

The conventional through-knee amputation (i.e., knee disarticulation) may cause problems related to the leakage of synovial fluid, bulbous femoral condyles and the retained patella, which could potentially cause difficulties with prosthetic socket fitting if the patient becomes ambulatory later on. The Gritti–Stokes amputation theoretically avoids these problems by resecting the bone at the supra-condylar femoral level, enucleating the patella and anchoring it to the distal femur as an end-cap ( Fig. 6.2 ). However excision of femoral condyles could adversely affect the suspension and rotational stability of the applied prosthesis. Enucleating the patella and anchoring it to the distal femur has been associated with femora-patellar non-union and mal-union. In a Gritti-Stokes amputation, the load bearing axis lies posterior to the residual limb. This could to lead to greater mechanical stress on the femur, which in turn could adversely effect ambulation with a prosthetic limb. ^{, ,} Therefore, caution is strongly advised when considering Gritti-Stokes amputation in ambulatory patients.

Due to a longer femoral component and lowered prosthetic knee centre, as well as limited availability of stance and swing phase control mechanisms in the prosthetic knee joint at this level, prosthetic limb fitting can be technically challenging in through-knee amputees.

Hip disarticulation and hemipelvectomy

Hip disarticulation and hemipelvectomy are rare procedures in patients with PAD. They comprise approximately 1% of all lower extremity amputees presenting to UK amputee rehabilitation centres. The majority of these procedures are carried out for neoplasm (usually sarcoma) followed by infection and major trauma, rather than dysvascularity.

The complex neurovascular and visceral anatomy of the pelvic region and relative rarity of these procedures present significant technical, surgical and rehabilitative challenges. With intra-operative blood loss in hemipelvectomy averaging 3 litres and peri-operative mortality as high as 44%, both these operations should be considered as amputations of last resort. Of the survivors, with an integrated multidisciplinary rehabilitative approach, approximately 43% can eventually use a prosthetic limb following either surgery.

Principles in amputation level selection

The selection of the amputation level in major lower extremity amputation can be multifactorial and complicated. Thus, it should be decided on after careful multidisciplinary assessment and discussion between the surgical and rehabilitation teams. However, there are general rehabilitation principles that should be taken into consideration by the vascular surgeon when making this decision, as outlined below. Fig. 6.3 illustrates this decision-making process via an algorithm.

• 1.

  Preserve the native functional knee joint if possible

  • Preserving the native knee joint is the key factor in reducing the energy and metabolic cost when using a prosthetic limb. This should be considered whenever possible, especially if it is anticipated that the patient has the potential to transfer (e.g., from bed to chair) or walk with a prosthetic limb.

• 2.

  In non-ambulatory patients, consider knee disarticulation or Gritti–Stokes amputation

  • In patients who are bed- or chair-bound, a TTA residual limb risks non-healing and may also lead to flexion contractures of the hip and knee joints and thus impeding patient transfers. A knee disarticulation or Gritti–Stokes amputation can avoid these aforementioned complications. These two amputations are also preferable to TFA as they provide longer lever-arms and larger residual limb surface areas, which are more conducive to transferring and promote wheelchair mobility by providing a more stable counterbalance. ^,

• 3.

  TFAs should be considered in fixed knee flexion of ≥30 degrees and/or severe knee arthropathy.

  • A fixed knee flexion deformity of more than 15% can reduce foot clearance during the swing phase, which may impede walking and can lead to quadriceps fatigue and anterior knee pain. Usually, a flexion contracture of 30 degrees is considered the maximum limit for transtibial prosthetic limb fitting. In addition, severe knee arthropathy can also impede walking. Therefore in these two circumstances, a more proximal amputation should be considered.

• 4.

  In ambulatory patients who cannot have a TTA, a TFA is the next best option.

  • In patients where a TTA is not possible but the patient has the potential to walk, a TFA is preferred rather than knee disarticulation or Gritti–Stokes amputation. This is because of problems of prosthetic fitting, which may compromise cosmetic appearance and function. Cosmesis is affected because the prosthetic knee joint extends beyond the length of the femur. Therefore for patients with a through-knee amputation, the femoral component is longer. Functionally, this may mean that sitting in small spaces is more cumbersome or restricted because of this increased length. Conversely, some studies have demonstrated better functional outcomes in patients with a knee disarticulation. This is explained by the longer lever-arm and the fact that the adductor muscles of the hip are preserved in a knee disarticulation. Both of these factors improve the thigh motion for ambulation, decreases energy expenditure and help maintain distal proprioception, which helps facilitate walking with a prosthetic limb. ^,

Transfemoral amputation

The ideal transection of the femur is 12 cm (10–15 cm acceptable) above the native knee joint, which is measured from the medial joint line. This length allows enough clearance for incorporating a prosthetic limb, and avoids using a lowered prosthetic knee centre, which gives an unacceptable cosmetic and functional disability when walking. The exact level of the bone cut will depend on the thickness of the thigh muscles and subcutaneous tissue. In morbidly obese patients with excessive soft tissue coverage, a through-knee amputation should be considered instead.

It is important to ensure adequate myoplastic coverage over the cut femur to reduce pain and discomfort as well as to allow muscle balancing of the hip adductors to abductors and rectus femoris to hamstrings.

If muscle quality is adequate, adductor myodesis should be considered. The procedure, which involves anchoring of muscle to bone (i.e., the femur) via drill holes, reduces the risk of muscle slippage and overhang, creates a dynamic muscle balance, removes tension from the anterior myocutaneous flap, and provides a soft tissue envelope to facilitate limb fitting.

Similarly, a quadriceps myodesis should be considered, which can either be secured to the adductor flap or the posterior femur.

The myoplasty and myodeses should be performed with the hip joint in neutral (in the sagittal plane) and the naturally adducted position of 5-10°. This prevents both hip flexion and abduction contractures and is ideal for prosthetic function.