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Mobility one year after unilateral lower limb amputation: a modern, UK institutional report

Department of Surgery, Darent Valley Hospital, Darenth Road, Dartford, Kent, UK

Received 25 March 2008; received in revised form 23 June 2008; accepted 30 July 2008

Presented at the 55th International Congress of the European Society for Cardiovascular Surgery, St Petersburg, Russian Federation, May 11–14, 2006.

Corresponding author. Tel.: +44 796 8780042, +44 208 3170793.

E-mail address: naren_basu{at}hotmail.com (N.N. Basu).

	Abstract

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 
The aim of this current retrospective study was to assess postoperative mobility one year after above knee (AKA) or below knee amputation (BKA) in a district general hospital. Data on patient demographics, diabetic status, risks for peripheral vascular disease, mortality and mobility at one year were recorded from the vascular database. Seventy-five patients underwent lower limb amputation over a 70-month period (AKA n=31, BKA n=44). Operative mortality was 10% and mortality at one year 13.7%. Fourteen out of the 31 patients (45.1%) who underwent AKA were mobile independently or with a walking stick compared to 54.5% (24/44) in the BKA group (P=0.44). Fifteen patients (48.3%) were diabetic in the AKA group compared to 26 patients (59.1%) in the BKA group (P=0.49). In the under 60 years group and over 60 years group there was no significant difference in type of amputation (P=0.64) or mobility (P=0.69). In this current series, there was no significant rehabilitation benefits in patients undergoing BKA compared to AKA. With an ageing population who inherently have increasing significant medical problems, the perceived benefit in preserving the knee joint may not be as significant as previously reported.

Key Words: Mobility; Amputation; Above knee; Below knee

	1. Introduction

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 
Critical limb ischaemia accounts for more than 80% of all amputations performed in the United Kingdom, out of which 20–30% are secondary to diabetes mellitus [1]. The level of amputation will depend on the potential of healing and rehabilitation. Preservation of the knee joint by performing below knee amputations (BKA) has become more popular since the 1960s when it was realised that above knee amputation (AKA) was associated with significant mortality and morbidity.

Several retrospective studies over the last three decades studied the effects on mortality and mobility when the knee joint was preserved [2–4]. Prior to the 1960s, the ratio of AKA:BKA performed was approximately 6:1. When a ratio of BK:AK amputation >2:1 was achieved, almost 25% of amputations failed, suggesting that the trend to below knee amputation may not be associated with improvement of long-term survival.

Mobility following amputation has a direct impact on quality of life. Preservation of the knee joint is associated with reduced energy expenditure when ambulating with a prosthetic limb. Additionally, ascending level of amputation is associated with increased metabolic demand [5, 6]. However, it remains unclear whether in an aging population with significant co-morbid conditions and poor preoperative mobility, there is any added benefit in performing BKA over AKA.

The aim of this current retrospective study was to assess postoperative mobility one year after above knee (AKA) or below knee amputation (BKA) in a district general hospital.

	2. Method

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 
All adult patients who underwent lower limb amputation over a 70-month period (November 1998–September 2004) at Darent Valley Hospital were identified from theatre records and a vascular surgery database.

Medical records were reviewed for basic patient demographics including age, sex, risk factors for peripheral vascular disease, diabetic status, mortality and functional outcome at one year. Operative mortality was defined as mortality within 30 days of amputation. Data regarding functional outcome was obtained at one year following the operation from follow-up clinic and physiotherapy assessment of the patients. Patients were classified into two groups: independently mobile±with walking stick and wheelchair or bed-bound. Those patients who had successful results from limb prosthesis were included in the former group.

Rehabilitation potential was assessed by a trained physiotherapist with a special interest in amputees during the perioperative period. Patients suitable for prosthesis were sent to a regional centre for appropriate measurements. Intensive physiotherapy with a 2:1 ratio of patient:physiotherapist was conducted on a twice weekly basis (6 h per week) for both in- and out-patients. In-patient physiotherapy was commenced on appropriate patients whose wound had healed satisfactorily.

The level of amputation was classified as BKA (transtibial) and AKA (transfemoral). Patients with variations to these two forms of amputation, those who had bilateral amputations or revision amputations or failed revascularisation procedures were excluded from the study (Table 1).

Univariate analysis was performed using contingency table and Pearson's ² test. Differences were considered statistically significant at a P<0.05.

	3. Results

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 
A total of 125 patients were identified from a computerised vascular registry as having undergone AKA or BKA during this 70 month period. There was inadequate follow-up information on 17 patients. Eleven patients had undergone bilateral amputations or revision amputation of the stump and were excluded.

Operative mortality was 10% (10/97). There was an overall one-year mortality of 13.7% (12/87). All 12 patients were over 60 years of age and the AKA:BKA ratio was 10:2 (Table 2).

The demographic data of the 75 patients are shown in Table 3. The majority of patients in both groups were over the age of 60 years. In both AKA and BKA groups, a combination of vascular occlusive disease and diabetes mellitus accounted for almost 80% of the indications for amputation. In addition, a higher percentage of patients in the AKA group had significant co-morbidities compared to the BKA group.

	4. Discussion

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 
Major lower extremity amputation results in significant morbidity and mortality. Age, albumin level, above knee amputation and lack of previous coronary artery bypass graft are independently related to mortality [7, 8]. However, the choice of amputation still remains a controversial topic.

In the ageing population, pre-operative mobility, co-morbidity and longevity needs to be considered when determining the level of amputation. Both procedures may be performed under general anaesthesia, spinal and local anaesthesia [9]. However, BKA is associated with longer operating time and is technically more challenging [8].

Despite several reports documenting decreasing major amputation rates, possibly due to more aggressive revascularisation and endovascular procedures, other studies have not substantiated this relationship in peripheral vascular disease [10]. Major amputations are generally performed in patients with failed revascularisation procedures who have significant comorbidities. Rehabilitation potential must remain an important factor to any surgeon performing lower limb amputation.

In this study, there was no significant difference in mobility outcome following BKA or AKA at one year. Despite there being more patients mobile independently or with a stick in the BKA group (54.5% vs. 45.1%) the result was not statistically significant, suggesting that the perceived rehabilitation benefits in preserving stump length by performing a BKA may not be as significant as previously reported. Interestingly, there were no differences in mobility in either group when age was considered a single variable. This is contrary to several studies that have shown that mobility is better where the knee joint is preserved [11], with up to 63% of patients able to ambulate independently following an intensive in-patient rehabilitation programme.

Diabetic patients may represent a confounding factor, as the pathophysiology is different given the distal nature of their arterial disease. Additionally, diabetic neuropathy may complicate the rehabilitation process. In our series over 50% of patients had either Type I or II Diabetes Mellitus. It is accepted that diabetes is a major contributor to peripheral vascular disease and hence the inclusion of this disease. There was a higher percentage of co-morbidity factors in the AKA group including cerebrovascular accidents. This would affect rehabilitation potential in this patient group.

It would have been useful to have included the pre-operative mobility status of our patient group as this directly influences postoperative mobility. In addition, the interventional vascular radiology services is limited in our district hospital and comparison with a vascular centre would provide more robust information.

In our current study, rehabilitation was performed on an out-patient basis or patients were transferred to a rehabilitation centre. This may have important qualitative and quantitative implications in terms of rehabilitation received by patients.

Trends in the American Society of Anaesthesiologist grades, seniority of surgeon performing procedure and previous number of revascularisation attempts were not documented, as previous studies have not found significant association of these factors to amputation outcome [8].

Mortality at 30 days and one year was 10% and 17%, respectively. The lower mortality rates in our series (published mortality rates at 30 days (10%) and one year (22–28% [12, 13]) cannot be attributed to diabetic status or age. However, 28 patients were excluded from this study either due to inadequate follow-up data or because revision surgery was performed. It is possible that including these patients may have resulted in a higher mortality rate.

In this contemporary series of lower-limb amputations there was no obvious mobility or mortality benefit in performing a below knee amputation. With an ageing population who inherently have increasing significant medical problems, the perceived benefit in preserving the knee joint may not be as significant as previously reported. Therefore, it is important to take the patient's co-morbidity factors and expected mobility outcome into consideration when deciding to preserve the knee joint.

	References

Top Abstract 1. Introduction 2. Method 3. Results 4. Discussion References

 

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