Webster, Joseph B. MD; Chou, Teri PhD; Kenly, Michael MD; English, Michael MS4; Roberts, Toni L. DO; Bloebaum, Roy D. PhD
For individuals with lower limb amputations, the attachment and suspension of a prosthesis to the residual limb is the most critical aspect of prosthetic restoration.1,2 It is essential for the suspension method to be secure and the interface between the prosthesis and the residual limb to be comfortable for effective prosthetic use and ambulation. Unfortunately, residual limb pain and skin breakdown remain barriers for successful prosthetic restoration for individuals using current socket suspension methods.2 Although there have been great advances in prosthetic component technology, suspension systems, and interface materials, the need for improved methods of prosthetic suspension remains. This is especially evident in soldiers who have sustained traumatic limb loss during the military conflicts Operation Iraqi Freedom and Operation Enduring Freedom.
These military engagements have seen improved survival rates from catastrophic injuries compared with prior conflicts secondary to improved body armor protection and improved medical field management and evacuation strategies.3 The increased survival rates, however, have resulted in more individuals surviving with limb amputations, which are often complicated by associated soft tissue, orthopedic, vascular, and neurologic injuries.4 These amputations present unique management challenges compared with amputations resulting from disease or other types of trauma. There are significant numbers of these returning service men and women who have shortened residual limb length where socket technology has a limited ability to provide adequate prosthetic suspension.4 There is also a group of returning service men and women with amputations that have significant heterotopic bone formation, which makes using socket technology painful, thus limiting quality of life and daily activity.4–6 In addition, military amputees are typically young, otherwise healthy individuals who maintained a high level of physical activity before their injury.5,6 They have goals of returning to this high level of premorbid function through prosthetic restoration.
The importance of new and innovative methods of prosthetic suspension is also highlighted by the fact that despite medical advances and limb salvage techniques, there is a growing population of individuals with lower limb amputations from vascular disease and diabetic complications.7 This expanding population is becoming more aware of various prosthetic advances, and they have greater expectations to return to higher levels of activity compared with amputees in the past. This population of individuals with amputations is also highly susceptible to skin breakdown complications associated with socket suspension techniques secondary to their vascular disease and diabetes.
Osseointegration is a new technique for prosthetic suspension in individuals with limb loss. With the osseointegration procedure, a titanium implant is surgically inserted directly into the bone of the residual limb. This implant can then serve as an attachment system for connecting and suspending a prosthesis to the residual limb.8–10 This technique is currently being used outside of the United States primarily for individuals with transfemoral level amputations. The procedure has yet to be approved in the United States for use in individuals with lower limb amputations.
The potential advantages of osseointegration over traditional prosthetic fitting with a socket suspension system include reduced pain and reduced risk of skin irritation and breakdown on the residual limb.8–10 Hip range-of-motion and sitting comfort are also improved.11 The osseointegration technique also provides a very secure and stable suspension for the artificial limb prosthetic components. In addition, prosthetic fitting with the osseointegration technique is reported to enhance proprioception, so that the individual with an amputation is better able to determine where the prosthesis is located in relation to the residual limb and the ground. This improved proprioception has the potential benefit of improving gait characteristics, reducing the risk of falling, and improving quality of life.9–14
A limited number of rigorous scientific research studies have examined the risks associated with osseointegrated implant technology.9 From clinical use in European countries, implantation currently requires two operations and a lengthy recovery and rehabilitation period after the operations to assure stabilization of the implant in the bone and at the soft tissue interface. Thus far, the technique has been primarily performed in individuals with transfemoral amputations.9 The primary risks that have been noted include infection at the skin-implant interface, loosening at the bone-implant interface, and bending and breakage of the implant connection between the residual limb and the prosthesis. There is a potential need for additional surgery and residual limb revision because of these complications.9–14 The slowness and length of the rehabilitation program, and the large number of physician and medical center visits have been noted as negative aspects of the osseointegration procedure in the United Kingdom.9
Although osseointegration seems to hold promise as a new technique for prosthetic suspension, it is unclear if individuals with lower limb amputations in the United States will be willing to accept the risks associated with the procedure to gain the potential benefits. Through use of a survey instrument, this study was designed to investigate perceptions and acceptance of osseointegration and to determine variables that correlate with willingness to consider the procedure. This will be of great benefit in determining barriers to osseointegration and in understanding baseline prosthetic and functional limitations for individuals with lower limb amputations. This information will be useful for defining future selection criteria for osseointegration implantation and developing appropriate outcome measurement tools to determine the efficacy of osseointegration implants.
The Institutional Review Board at the University of Utah and the Research Committee at the George E. Wahlen Veterans Affairs Medical Center in Salt Lake City, Utah approved this study before the onset of data collection.
A survey instrument was developed to assess perceptions and acceptance of osseointegration among individuals with lower limb amputations. The survey instrument consisted of four sections with 6 to 15 questions per section. Demographic information collected included age, gender, ethnicity, current medical problems, distance from medical care, and type of community living setting. The second section focused on amputation-related circumstances, including pain, skin breakdown, and technical problems with the participants’ current prosthesis. Section 3 was used to assess the participants’ current activity level. The data from the first three sections allowed the investigators to correlate the participants attributes with their perceptions towards osseointegration. The final section of the survey was organized in a similar fashion to an informed consent document. This section began with a detailed explanation of the procedure including diagrams and pictures followed by a description of potential advantages and disadvantages of the procedure. The questions that followed the information section attempted to identify the participants’ perceptions, concerns, and interest in osseointegration.
The survey was initially administered to 15 individuals in person for validation purposes. These surveys were reviewed and analyzed by hand to clarify and refine the survey. Minor grammatical and format changes were made to the survey based on this validation process. After these modifications, the survey was administered to the remainder of the study population either in person in the clinic setting or by mail using a postage paid return envelope.
Participants included individuals 18 years or older with a lower limb amputation at or above the transtibial level who were willing to complete the survey. Subjects were excluded if they had undergone amputation surgery or had not worn a prosthesis within the past 3 months. Participants were recruited from the Amputee Rehabilitation Programs at both the George E. Wahlen Veterans Affairs Medical Center and the University of Utah.
STATISTICAL METHODS, DATA ANALYSIS, AND INTERPRETATION
Data was coded, entered into a database, and analyzed using STATA 10 statistical software. Responses were described with frequency tables, descriptive statistics, and 95% confidence intervals. Internal consistency of items to a common factor was assessed using Cronbach’s alpha. A multivariable logistic regression was fitted to the survey outcome of willingness to have the osseointegration procedure performed. Correlations between demographic and amputation-related factors with perceptions and acceptance of osseointegration were computed. The study was adequately powered to detect small correlations, and permitting several variables in a regression model without introducing overfitting. p values were calculated using Mann Whitney statistical methods.
Seventy-three subjects completed and returned the survey. Table 1 summarizes the general demographic data for the study population. Seventy-five percent of participants were male and 25% were female. Ninety percent of the participants were aged between 35 and 65 years, 8% were below 35 years, and 2% were greater than 65 years. Whites made up 96% of the study population with blacks, Native Americans, and other ethnic groups each making up less than 1.5% of the population. Forty-five percent of the population reported living in a city location, 19% reported living in a suburban environment, 34% in a rural location, and 1% in some other location type. The majority of individuals surveyed, 51%, stated that they travel greater than 30 miles for their amputation-related medical care. Only 27% of the population reported living within 10 miles of their amputation-related medical care. Medical conditions reported in our population included hypertension in 44%, diabetes in 29%, heart disease in 14%, peripheral vascular disease in 13%, end-stage renal disease in 4%, venous insufficiency in 6%, and chronic obstructive pulmonary disease in 6%. Thirty-six percent of those surveyed reported being employed at the time of the survey. Seventy-five percent of individuals who were employed reported using their prosthesis for work activities.
Table 2 summarizes the amputation-related characteristics of the study population. Seventy-seven percent of the study population had transtibial level amputations, 20% had transfemoral amputations, and 3% had other amputation levels. Only 11% of study participants had their amputation less than 1 year before the time of the survey. Forty-six percent had their amputation between 1 and 5 years before the time of the survey and 33% were more than 5 years out from their amputation. The majority of amputations, 42%, were related to complications from trauma. Complications from diabetes and peripheral vascular disease resulted in 34%, infection 19%, cancer 3%, congenital 1%, and other 1%. Skin sores or breakdown were reported by 24% of the population at the time of the survey. During the past year, 38% of the study participants reported no episodes of skin breakdown. Twenty-eight percent reported one to two episodes of skin breakdown during the past year, 20% reported two to six episodes, and 14% reported more than six episodes of skin breakdown during the past year. Fifty-three percent of the population reported daily residual limb pain and 52% reported daily pain with prosthetic use, whereas 43% reported daily phantom limb pain. Only 3% of the participants reported never having residual limb pain, and 4% reported never having phantom limb pain. The average rating of residual limb pain severity was similar to the average rating of phantom pain severity. Pain interfering with daily activities was reported in 23%, and 26% reported that pain never interferes with their daily activities. Thirty percent of individuals reported their prosthesis becoming loose at least one to two times per week. Thirty-seven percent had loosening of their prosthesis at least one to two times per year, and 25% reported never having loosening of their prosthesis. Episodes of the prosthesis falling off were less common with only 3% of individuals reporting their prosthesis falling off at least one to two times per week. The majority, 63%, reported never having their prosthesis fall off.
Table 3 summarizes the activity-related characteristics of the study population. The population reported being active prosthetic users with 74% of the population wearing their prosthesis for greater than 8 hours daily. Ten percent reported wearing their prosthesis 6 to 8 hours per day. The ability to ambulate long community distances was reported in 49% of the study group. Thirty-nine percent were able to ambulate short community distances, 7% household distances, and 4% were unable to walk with their prosthesis. Fifty-nine percent did not use any assistive device such as cane, crutch, or walker for ambulation. Twenty-three percent used a cane or single crutch, 10% used crutches, and 7% used a walker. Seventy-five percent of individuals reported using their prosthesis for work activities, 11% used their prosthesis for jogging or running, 33% used their prosthesis for biking, 32% used their prosthesis for playing sports, 36% for hiking, and 8% for competitive or team sports. Ability to perform normal daily activities was rated as excellent in 14%, very good in 22%, good in 37%, fair in 18%, and poor in 9%. Among individuals who were employed at the time of the survey, 24% reported problems with the prosthesis interfering with work activities.
PERCEPTIONS AND ACCEPTANCE OF OSSEOINTEGRATION
Of the 73 participants who completed surveys, 33% stated they would consider undergoing the osseointegration procedure, 42% would not consider the procedure, whereas another 25% were uncertain. 44% of individuals had heard of osseointegration before the survey, and of those, 38% had received information from a physician or clinic, 30% received information from media sources, such as television, magazines, and the internet, and 14% received information from their prosthetist. Although these participants had heard of the osseointegration procedure before the survey, this did not seem to influence their decision to consider the osseointegration procedure (p = 0.74).
Examination of correlations between various individual characteristics and willingness to consider osseointegration as a means of prosthetic suspension revealed no significant correlation with general demographic variables, including age, gender or ethnicity, and willingness to accept osseointegration. No significant correlation was found between amputation variables, including level of amputation, time since amputation, or etiology of amputation. It was also interesting that no significant correlation was found with higher rates of skin breakdown or phantom limb pain. There was also no significant correlation found between activity variables, including prosthetic use, ambulation distance, and utilization of assistive devices. Characteristics that did significantly correlate with a participant considering osseointegration are summarized in Table 4. These characteristics included living in a rural community (p = 0.004), pain interfering with daily activity (p = 0.038), and problems with prosthetic fit and prosthesis falling off (p = 0.007). Poor ability to use a prosthesis for home and activities of daily living (ADL) was present in 21% of those willing to consider the osseointegration procedure compared with only 4% in those not willing to consider the procedure, but this finding was not statistically significant.
Improved prosthetic function, improved walking ability, quick and easy attachment of the prosthesis, improved activity level, more secure attachment and suspension, improved comfort and decreased pain with the prosthesis, and prevention of skin breakdown on the residual limb were cited as the top advantages to the procedure among the participants willing to consider the procedure (Table 5). Of the participants who responded that they would not consider having the procedure, risk of skin and bone infections, need for limited activity if the bone or implant breaks, need for multiple surgeries to have implant placed, long recovery and rehabilitation period, risk of a broken bone in the residual limb, and the possible need for additional surgery and shortening of the residual limb were noted as the most important reasons for not considering the procedure (Table 6).
Individuals with transfemoral level amputations are the primary population who are currently receiving osseointegrated implants in European countries. In our investigation, 20% of our population had transfemoral level amputations. Compared with those with transtibial amputations, individuals with transfemoral amputations were more likely to be male (93% compared with 70%) and more likely to be younger (80% less than age 55 compared with 64% of those with transtibial amputations). Individuals with transfemoral amputations had less skin breakdown at the time of the survey (86% with no skin breakdown compared with 75%) and were more likely to have both daily residual limb pain and daily phantom pain. Only 46% of those with transfemoral amputations reported wearing their prosthesis for greater than 8 hours per day compared with 81% of those with transtibial amputations. Thirty-six percent of individuals with transfemoral amputations were able to ambulate long community distances compared with 55% of those with transtibial amputations. Individuals with transfemoral amputations were less likely to ambulate without an assistive device (43% compared with 62%). Those with transfemoral amputations were less likely to be employed (13% compared with 36%) and less likely to use their prosthesis for work activities (26% compared with 60%). A trend was noted in the study that those with transfemoral amputations were more likely to consider osseointegration (47% compared with 31%), but this finding was not statistically significant (p = 0.192).
The term osseointegration has been used to describe a direct structural and functional connection between living bone and the surface of a load carrying implant. Successful osseointegration techniques are currently established in orthopedic joint replacement surgery and in the areas of dentistry and maxillofacial reconstruction.8,14–20 Utilization of osseointegrated implants has the potential to provide individuals with lower limb amputations an improved method of prosthetic suspension that can eliminate many of the complications associated with traditional socket suspension techniques allowing these individuals to lead more active lives. In addition, this technology has the potential to allow prosthetic fitting for selected individuals who are currently not able to wear a prosthesis secondary to residual limb complications.
Although primarily designed to determine perceptions and acceptance of osseointegration among individuals with lower limb amputations, this study revealed some notable findings regarding general demographics, amputation characteristics, and activity characteristics in our population. Our population was a relatively young group of individuals with lower limb amputations, and this group was noted to have a higher percentage of individuals with amputations secondary to trauma compared with the traditional literature.7,21 Individuals who completed the survey were also relatively active with the majority reporting wearing their prosthesis for greater than 8 hours per day. The majority also reported the ability to ambulate community distances without the use of assistive devices. This is important because it is likely that individuals with these types of characteristics will be appropriate candidates for osseointegration as this technology is introduced in the United States.
The incidence of residual limb pain and phantom limb pain reported by our study population is similar to previously published data.22–24 The severity of both residual limb and phantom pain reported by our population was also interesting. Both residual limb pain and phantom limb pain were rated at a relatively high intensity level. Although neither the frequency nor the severity of residual limb or phantom pain correlated to acceptance of osseointegration, it is important to note that pain interfering with activity level did demonstrate a positive correlation with willingness to accept osseointegration.
The literature describing the frequency of skin breakdown in lower limb amputees is limited.2,25 Our population reported a high incidence of skin breakdown with 24% of the population reporting skin breakdown at the time of the survey and 62% reporting skin irritation and skin breakdown during the past year. The lack of a correlation between skin breakdown on the residual limb and acceptance of osseointegration, however, was somewhat surprising to the investigators because it is anticipated that reduction of residual limb skin breakdown will be one of the primary benefits of the osseointegration suspension technique, because it will eliminate the need for the prosthetic socket interface with the residual limb.
Our study found no significant correlation between any general demographic variables, such as age, ethnicity, or gender and acceptance of osseointegration. Our study also failed to reveal any statistically significant correlations between other amputation characteristics such as time since amputation or etiology of amputation. Individuals with transfemoral amputations were more likely to consider osseointegration, but this finding was not statistically significant (0.192).
The positive correlation that we found in our study between living in a rural location and willingness to accept osseointegration is of unclear significance. It is possible that if this correlation holds true in the future that it could represent a challenge for the implementation of this procedure because it is likely that individuals who undergo osseointegration will require close medical follow-up during the perioperative period. However, we did not find a statistically significant correlation between distance from amputation- related medical care and acceptance of osseointegration. It may be that those living in rural locations were not necessarily a greater distance from medical care. This study found that individuals who are unable to use their prosthesis for home and ADL activities were more willing to accept osseointegration as an alternative means of prosthetic suspension compared with individuals who only have difficulty using their prosthesis for higher level activities, but this finding was not statistically significant.
Although not currently approved in the United States, osseointegration has the potential to significantly change the way prosthetic limbs have traditionally been suspended to residual limbs. This study represents the first investigation to examine the perceptions and acceptance of osseointegration in a population of individuals with lower limb amputations. This investigation is felt to represent an important initial step in the development and clinical implementation of osseointegration, because this investigation will help to determine the characteristics of individuals most interested in this technology. This study will aid in defining future selection criteria for osseointegration implantation and focus research and development on the aspects of osseointegration that individuals with lower limb amputations view as the largest barriers to accepting this procedure. Thus, it is expected that this information will facilitate the reduction of osseointegration procedure risks, the enhancement of potential benefits, and the development of innovative rehabilitation strategies.
One of the limitations with this study is the fact that we used a self-report survey tool for data collection. The investigators did not use medical records to verify the data collected. This could have particularly affected the accuracy of some data, such as medical conditions and etiology of amputation. However, this issue did not likely interfere with our primary outcome measurement of whether or not individuals were interested in osseointegration. In addition, the fact that some of the surveys were administered in person and some were administered by mail may have introduced bias into the data collection process if those who completed the survey in person felt pressured to answer questions in a favorable way. Our study results could also be biased if the amputee population that did not complete the survey was significantly different in their characteristics or opinions compared with the group of individuals who completed the survey.
Although our investigation was adequately powered for valid statistical analysis, the population of individuals with amputations surveyed may not represent the general amputee population. This could potentially limit the generalizability of our findings.
Our survey included individuals with both transtibial and transfemoral amputations although osseointegration is currently being performed primarily in individuals with transfemoral level amputations. However, no significant difference between our transtibial and transfemoral amputee populations was identified in the study. We did not include individuals with upper limb amputations in our survey, and this population may be worthy of investigation because individuals with upper limb amputations may also be candidates for osseointegration procedures in the future.
Because there is limited scientific literature examining the type and severity of complications with osseointegration implantation procedures in the amputee population, we were unable to fully describe the frequency and severity of these potential risks in our survey tool. It is also anticipated that by the time this technology is ready to be implemented in the United States, the risk to benefit ratio will be significantly different from what was described in our survey instrument. This should have a favorable impact the willingness of individuals with amputations to accept this technology in the future.
Osseointegration as a new method of prosthetic suspension was met with mixed levels of acceptance by individuals with lower limb amputations in our study population. Addressing the problems of infection prevention, prolonged rehabilitation programs, and possible implant failure will be important to improve the perception and acceptance of osseointegration procedures in the future.
The authors to thank Greg Stoddard, PhD and Dutch Plante, BSN for statistical analysis support and Sam Chipman for administrative support. This material is based upon work supported in part by the Office of Research and Development Rehabilitation R&D Service, Department of Veterans Affairs Health Care System, Salt Lake City, Utah; the Albert & Margaret Hofmann Chair and the Department of Orthopaedics, University of Utah School of Medicine, SLC, Utah.
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KEY INDEXING TERMS: amputation; amputation complications; limb loss; osseointegration; prosthetic suspension; prosthetics; rehabilitation