Abstract
Background:
Bone-bridging (arthrodesis of the distal tibia and fibula) at the time of transtibial amputation is a controversial operative technique that is anecdotally reported to improve the weightbearing capacity of the residual limb and to decrease residual limb discomfort.
Methods:
Thirty-two consecutive patients with multiple diagnoses had transtibial amputation with a distal tibial-fibular bone-bridge, all done by a single surgeon (MAP). At an average of 16.3 months after surgery all patients completed the Prosthetics Evaluation Questionnaire (PEQ), a validated outcomes instrument specifically created to evaluate quality of life and functional demands in patients with a lower extremity amputations. Their responses were compared with those of 17 preselected, highly functional transtibial amputees from two academic medical centers who previously had transtibial amputations using a traditional non bone-bridge operative technique; their time since amputation averaged 14.7 years.
Results:
The “nonselected” consecutive patients with a bone-bridged residual limb scored higher (more favorable) in the Ambulation (p = 0.037) and Frustration (p < 0.001) domains of the PEQ and lower (less favorable) in the Appearance (p = 0.025) subscale. Their scores were similar in the other six domains.
Conclusions:
Patients of multiple ages with multiple diagnoses who had bone-bridging of the distal tibia and fibula at the time of transtibial amputation had scores on a validated outcomes instrument that were better than or comparable to those of a selected group of highly functional transtibial amputees. The results of this study suggest that bone-bridging at the time of transtibial amputation may enhance patient-perceived functional outcomes.
INTRODUCTION
Although amputation often is viewed as a failure of treatment, patients with transtibial amputation often lead productive lives. The ongoing Lower Extremity Assessment Project (LEAP, a longitudinal observational study of patients with mutilating lower extremity injuries) has shown that patient-perceived outcomes after limb salvage are similar to those after amputation and prosthetic limb fitting. 1
A long posterior myofasciocutaneous flap is the most commonly used technique in amputation centers in the United States as the method of constructing the soft-tissue envelope. 2,3,14 Fusion of the distal tibia and fibula at the same length was originally advocated by Ertl. 7 Ertl held the opinion that arthrodesis of the distal tibia and fibula allows patients to bear weight through the terminal residual limb bone within the prosthetic socket. This was deemed unlikely because of the elastic modulus of the diaphyseal tibia and the small surface area available for weightbearing; 11 however, more recently the “bone-bridge” (fusion) between the distal tibia and fibula has been reported to create a more stable “platform” for transferring the load of weightbearing between the residual limb and the prosthetic socket (Figure 1). 6,13 This current group proposes that a stable platform allows total contact loading over an enlarged stable surface area (Figure 1).
De Souza Pinto et al. 6 showed that, in standard transtibial amputation, the load of weightbearing can produce widening of the distance between the residual distal tibia and fibula (Figures 2 and 3), which is believed to represent syndesmotic instability that leads to pain with weightbearing. While there is no convincing evidence to support the idea that the use of a bone “bridge” between the distal tibia and fibula increases stability, proponents perceive enhanced stability during the load transfer that occurs during weightbearing, which they believe decreases the pain with weightbearing. 6,13
Weightbearing radiographs taken while wearing a prosthesis after a successful distal tibia-fibular bone bridge at the time of traumatic transtibial amputation.
There appears to be a discrepancy between the results of treatment as perceived by clinicians, and the patient-perceived health-related quality of life. 8,9 Rehabilitation professionals generally have evaluated outcomes after amputation based on ambulatory capacity or the ability to perform tasks of daily living (Functional Independence Measure, FIM). 4,12 While these methods are accurate measures of function and independence, they overlook patient-perceived issues related to self-image and other subjective psychological components related to the daily life of the amputee.
This short fibula abducts relative to the tibia due to the loss of the stabilizing influence of the interosseous membrane. (Reprinted with permission from Pinzur, MS, de Souza Pinto, MAG, Schon, LC, Smith, DG: Controversies in amputation surgery. Instr. Course Lect 52: 448, 2003).
Because there currently is no objective scientific evidence to support or reject the controversial concept of bone-bridging with transtibial amputation, this study attempted to use the Prosthetic Evaluation Questionnaire (PEQ) as a discriminative tool to determine whether bone bridging of the distal tibia and fibula improves patient-perceived outcomes of transtibial amputation.
MATERIALS AND METHODS
Thirty-two consecutive patients who had bone-bridging of the distal tibia and fibula at the time of unilateral transtibial amputation completed the PEQ. The surgery was performed by a single surgeon (MAP). Although the technique was evolving during the period of the study, the procedure consistently included a fibular strut, notching of the lateral tibia, and simple suture as a method of fixation. The surgery was performed in Sao Paulo, Brazil, a country that did not have an internal review board process as part of its healthcare environment at the time of the surgery. The average age of the bone-bridge group was 29.7 (range 15 to 74) years. Amputation was done for trauma in 18, diabetic dysvascular disease or infection in 12, and one each for congenital pseudoarthrosis of the tibia and neoplasm. The average time since bone-bridge surgery was 16.3 months. The prosthetist (a single prosthetist cared for all bone-bridge patients) subjectively rated the “quality” of the residual limbs, based on bony length, bony contour, and soft-tissue envelope. The quality of the residual limbs were rated as very good in 22, good in eight, and fair in two. All were evaluated at least 1 year and less than 2 years after amputation and bone-bridging (Table 1).
A comparison control group was created of 17 selected subjects with unilateral transtibial amputations who were receiving followup prosthetic care at two University Medical Centers. While these subjects had their surgery performed by a variety of surgeons and used a variety of prostheses, all subjectively had excellent residual limb quality and were identified by the amputee clinic director as being highly functional prosthetic users. They were chosen with the goal of representing the best possible result after transtibial amputation using traditional operative techniques. The comparison group were all were highly functional independent community ambulators, were not receiving treatment or taking analgesic medications for pain, and had an optimal residual limb, as rated by both their physician and prosthetist. The comparison group had an average age of 47.4 (range 36 to 68) years and were an average of 14.7 years after transtibial amputation.
The Prosthetic Evaluation Questionnaire (PEQ) was developed as an attempt to bridge the discrepancy between the physicians’ perception of results and the patients’ perception of outcome. 10 The PEQ has nine scales, or domains, associated with function, pain, and the psychosocial issues associated with daily living with a lower extremity amputation. Each scale is graded between 0 and 100, with higher scores reflecting a more favorable patient-perceived attribute. When originally validated, it described an under-appreciated level of concern and frustration in a diverse population of lower limb amputees. 10 Harness et al. 8 confirmed these findings when the instrument was used to develop a benchmark for diabetic dysvascular transtibial lower extremity amputees, the most common independent amputee population in the United States.
Demographics
The questionnaire was translated into Portuguese for the bone-bridge group. Informed consent before surgery was given. Institutional review board approval was obtained in both university systems before completion of the questionnaires by the patients enrolled in the control population. Responses were made using the linear analogue format of the PEQ. Responses were graded from 0 (subjectively poor) to 100 (subjectively excellent). The questionnaires were graded individually and then entered into a database for statistical analysis, based on PEQ validated guidelines. 8,10
Statistical Analysis
Treatment group responses in the nine domain scales of the PEQ (Ambulation, Appearance, Frustration, Perceived Response, Residual Limb Health, Social Burden, Sounds, Utility, and Well Being) were compared using Mann-Whitney U test on SPSS software (v.10, SPSS Inc., Chicago, IL).
RESULTS
The responses in the nine domain scales of the PEQ are summarized in Table 2. Statistical analysis revealed that the scores of the bone-bridge patients were statistically higher (more favorable) in the Ambulation (p = 0.037), and Frustration (p < 0.001) domains of the PEQ, and lower (less favorable) in the Appearance (p = 0.025) domain compared to those in the control group. Differences in the other subscales were not statistically different; however the bone bridge patients tended to score higher (more favorable) on the Social Burden subscale (p = 0.061) (Table 2).
DISCUSSION
Bone-bridging adds operative time, dissection, and potential morbidity to transtibial amputation procedures. There presently is no objective evidence that the potential benefits justify the increased risks and potential morbidity associated with the increased complexity of surgery. In our bone-bridge group of 32 consecutive patients who had amputations for a variety of indications were individuals with diabetes who have been shown to not perform as well as traumatic amputees in the functional domains of the PEQ. 8,10 They likely represent an average bell-shaped curve of what can be expected with the addition of a bone-bridge to a traditional transtibial amputation.
Also indicative of this being a representative group, there was a range in the prosthetist's subjective evaluation of the quality of the residual limbs when a bone-bridge was used. In contrast, the residual limbs in the control population all subjectively had excellent residual limb quality, an attribute that further enhanced prosthetic limb fitting. The control group was preselected to represent the best possible outcome after traditional amputation surgery. Not surprisingly, both groups scored higher in the functional domains of the PEQ than the older and less independent dysvascular benchmark group reported by Harness et al. 8
Descriptive statistics for bone bridge and control treatment groups in Prosthetic Evaluation Questionnaire categories (1–100 grade for each category)
SD = Standard deviation.
Mann-Whitney (Wilcoxon rank-sum) test
In spite of having a substantial proportion of diabetic patients, and patients with poorer residual limbs, the bone-bridge patients had statistically more favorable scores in the important PEQ domains of Ambulation and Frustration. The bone-bridge group had 12 patients who had amputation as a consequence of diabetes, while the comparison group was composed strictly of post-traumatic amputees who historically have scored higher on the PEQ.
The design of this study attempted to make the treatment group representative of the expected spectrum of subjective residual limb quality associated with a group of patients undergoing bone-bridging at the time of transtibial amputation. We purposely attempted to skew the comparison control population to make it representative of the best possible results obtainable with traditional transtibial amputation. A second important flaw is the cultural differences between the two groups. The focus group is from Brazil, as compared with a control population from two large American cities. In spite of providing an unfair advantage to the control group, the bone bridge patients scored more favorably in the important PEQ domains of Ambulation and Frustration.
The normal foot is a unique end-organ with special adaptations to enhance weightbearing. After transtibial amputation, the surface area of the residual limb available for weightbearing is smaller, the bony platform is less capable of accepting the impact involved in weightbearing, and the soft tissues are not as efficient in dissipating both the direct and shearing forces involved in weightbearing load transfer. Bone-bridging at the time of transtibial amputation appears to create a stable platform for weightbearing by eliminating potentially painful motion between the residual tibia and fibula. This enhanced stability may allow the fibula to assume a more active role in load transfer by increasing the weightbearing surface area available to the prosthetic socket. Because there is no reproducible, measurable, or objective evidence that quantifies the actual method of transferring the weightbearing load between the residual limb and the prosthetic socket, we can only speculate on the impact of the bone-bridge. Until such evidence is available, or a randomized trial compares the techniques, the PEQ may be the best method to evaluate the role of bone-bridging. The data from this study suggest that the enhanced weightbearing platform provided by a bone-bridge may improve the functional potential for weightbearing compared to more traditional amputation techniques.