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Letters to the Editor to:

Scientific Articles:
Ellen J. MacKenzie, Michael J. Bosse, Renan C. Castillo, Douglas G. Smith, Lawrence X. Webb, James F. Kellam, Andrew R. Burgess, Marc F. Swiontkowski, Roy W. Sanders, Alan L. Jones, Mark P. McAndrew, Brendan M. Patterson, Thomas G. Travison, and Melissa L. McCarthy
Functional Outcomes Following Trauma-Related Lower-Extremity Amputation
J Bone Joint Surg Am 2004; 86: 1636-1645 [Abstract] [Full text] [PDF]
*Letters to the Editor: Submit a response to this article

Electronic letters published:

[Read Letter to the Editor] Unsupported Conclusions Regarding Outcomes of BK vs AK Amputations
Jacquelin Perry, M.D., Sc.D. (Hon)   (27 January 2005)
[Read Letter to the Editor] Dr. Mackenzie responds to Dr. Perry
Ellen J MacKenzie, Michael J. Bosse, The LEAP Study Team   (27 January 2005)
[Read Letter to the Editor] Dr. Mackenzie responds to Mr. Moretto
Ellen J MacKenzie, Michael Bosse and the LEAP Study Group   (21 December 2004)
[Read Letter to the Editor] Evaluating Functional Outcomes Following Lower Extremity Amputation
David F. Moretto   (21 December 2004)

Unsupported Conclusions Regarding Outcomes of BK vs AK Amputations 27 January 2005
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Jacquelin Perry, M.D., Sc.D. (Hon),
Chief Emeritus, Pathokinesiology Service
Rancho Los Amigos National Rehabilitation Center, Downey, CA 90242

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Re: Unsupported Conclusions Regarding Outcomes of BK vs AK Amputations

PKLAB{at}LAREI.org Jacquelin Perry, M.D., Sc.D. (Hon)

To the Editor:

Recently my attention was directed to the article in the Journal, “Functional Outcomes Following Trauma-Related Lower Extremity Amputation” (1). This multi- center study is a monumental mass of data and imparts valuable information about the psychological impact of traumatic amputations, but the authors also made two major, unsupported conclusions.

First, the outcome of AK amputations was presented as superior to BK results, but this conclusion is contradicted by other data. The SIP scores identified AK outcome equaled or exceeded that of BK amputations (2) This interpretation, however, is refuted by a statement in the text-- “none of the differences were significant at the p< 0,05 level”(3). Another contradiction states “walking speed of BK’s was significantly better”(4). The percent of patients with a walking speed equal or faster than 4 ft/sec was 62% for BK’s versus 43.5% for AK’s.(5) The inability to walk independently over uneven ground was greater for AK’s, 23.1% than BK,11.3%.(6). Lastly is the challenge to statistical significance by the threefold difference in numbers of subjects in the AK and BK groups (AK 34, BK 109,)(7). Failure to identify the age pattern of each group, introduces the high probability of comparing non-matched groups, particularly in reference to AK amputees.

A second area of concern is the statement that the “level of technical sophistication of the prostheses did not appear to have an impact on outcome” (8) yet no supporting data were presented in the body of the paper, though the readers who used the Journal's website found some data in the electronic appendix of the article. The assumption of no difference is consistent with energy cost studies of amputees walking by Rancho and other labs. (9, 10) They, too, found no significant differences between the SACH, Seattle light, Flex foot and other models. The Flex-foot (high tech), however, provides significantly greater dorsiflexion in terminal stance (9, 10,11), which increases step length and gives a higher push-off power peak in pre- swing (12). I’ve been told that only the more vigorous amputees (i.e. runners) can activate the flexible shafts of the high tech prostheses. The difference in prosthetic mechanics between amputee walking and running has not been reported.

A final concern is the implications of relying on statically non- significant data for much of the information discussed in the text. Among the 59 data items listed in the three tables, only 10 have statistical significance at p<0.05 and another 19 reached p <0.2. Yet the 59 data items were discussed with equal emphasis, even though the authors acknowledged p,.05 as the customary index of significance and used p< 0.2 for their modeling.

These inconsistencies are strong evidence, that the over whelming mass of data became “mind boggling” and resulted in a product, which was not adequately analyzed. The authors implied a 7 yr follow-up was in progress. Hopefully, this will be used to correct or explain the inconsistencies.

I brought this to your attention because the prestige of the JBJS imposes a status of validity that is not warranted by this paper.

Sincerely yours

Jacquelin Perry, M.D. Professor Emeritus, Department of Orthopaedics Surgery, University of Southern California, Los Angeles CA

References (most locate the text citations)

1. MacKenzie EJ, Bosse MJ, Castillo RC, Smith DG, Webb LX, et al. Functional outcomes following trauma-related lower-extremity amputation. 2004: 86A; 8, 1636-1645.

2. Ibid 1641;Table III, 1.

3. Ibid 1640; 2; 6. (Page/ paragraph/ line)

4. Ibid 1642; 1, 15

5. Ibid 1640;Table II

6. Ibid 1640,Table II

7. Ibid 1639, Table I

8. Ibid 1643; 3, 2

9. Torburn L, Powers CM, Guiterrez R, Perry J. Energy expenditure duringimmobilization in dysvascular and traumatic below-knee amputees. A comparison of five prosthetic feet. J Rehabil Res Dev 1995;32;111-119

10. Barth DG, Shumacher I, Sienko-Thomas. Gait analysis and energy cost of below- knee amputees wearing six different prosthetic feet. J Proset Orthot 1992;4;63-75.

11. Goh JC, Solomonidis SE, Spence WD, Paul JP Biomechanical evaluation of SACH and uniaxial prosthetic feet. Prosthet Orthot Int. 1984:8:147-154

12. GitterA, Czerniecki JM, DeGroot DM: Biomechanical analysis of the influence of prosthetic feet on below-knee amputee walking. Am J Phys Med Rehabil: 1991; 70: 142-148.
Dr. Mackenzie responds to Dr. Perry 27 January 2005
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Ellen J MacKenzie,
Professor
Johns Hopkins Bloomberg School of Public Health,
Michael J. Bosse, The LEAP Study Team

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Re: Dr. Mackenzie responds to Dr. Perry

emackenz{at}jhsph.edu Ellen J MacKenzie, et al.

To the Editor:

We thank Dr. Perry for her comments on our study, "Functional Outcomes Following Trauma–Related Lower Extremity Amputation (1). She raises two concerns about the conclusions we reach. The first concern is focused on our interpretation of the finding of no significant differences in SIP outcomes for persons undergoing below the knee and above the knee amputations. As Dr. Perry correctly points out, the comparison of outcomes can be confounded by differences in patient populations. To adjust for these potential confounders (such as age) we performed multivariate regressions. All of our conclusions are based on the results of these regressions. As we stated in the paper, the result of no difference in SIP outcomes surprised us as well. The finding of no difference could be related to our choice of outcome. Although the SIP has been shown in previous studies to have good measurement properties, its responsiveness to small changes in daily function is less well documented (2)(3).

It is important to emphasize that we did find significant differences in other outcomes – specifically patients undergoing BK amputations had faster walking speeds and had fewer problems walking on uneven ground. These seemingly contradictory results suggest to us that while a below the knee amputation may indeed be associated with better lower-limb function per se (as measured by walking speed), this difference may not always translate into improved function in daily activities (as perceived and reported by the patients in context of the SIP). This may be due to the fact that individuals undergoing either a BKA or an AKA experience similar frustrations and challenges following amputation that can easily overwhelm the actual degree of lower limb impairment. Indeed, some of the most powerful predictors of SIP outcome were education, race, and degree of self-efficacy. More research is needed to better understand how these patient characteristics influence the translation of impairment into disability so that appropriate post-acute care interventions can be developed and targeted to those most in need. Our results suggest that if we can do a better job at addressing these needs, a BKA compared to an AKA would indeed result in better functional outcomes and quality of life. We do acknowledge both here and in the paper that our conclusions are based on a relatively small number of AKA patients. We believe our results, however, underscore the potential for poor outcomes – not based as much on level of amputation but on the personal resources brought by the patient to the recovery process. We should emphasize that we are certainly not suggesting that an AKA versus a BKA in any way results in better outcomes as Dr. Perry suggests in her letter.

Dr. Perry also raised some concern about our finding of no difference in outcome by the technical sophistication of the device. Although she references studies that appear to corroborate our finding, Dr. Perry is correct in emphasizing that our study was not designed to address this complicated research question. We agree and very carefully point out in the article that this finding “must be interpreted with considerable caution.” Most importantly, our study was limited in its ability to measure the quality of prosthetic fit and the extent to which the type of prosthesis actually matched the needs of the individual. However, we thought it important to make note of our results to underscore the urgent need for controlled trials to better delineate the relationship between device characteristics and outcomes. Dr. Perry raises some interesting hypotheses about the correlation of performance and the amputee’s baseline needs and expectations. We look forward to studies that can address these hypotheses.

We appreciate the opportunity to engage in further dialogue about the results of our paper. We hope the criticisms raised will serve to fuel further investigations in this important area of research.

Ellen J. MacKenzie PhD, Michael J. Bosse MD, and the LEAP Study Team

1. MacKenzie E, Bosse MJ, Castillo R et al. Functional outcomes following trauma –related lower–extremity amputation. J Bone Joint Surg Am. 2004; 86(8): 1636-1645.

2. McDowell I and Newell C. Measuring Health. New York: Oxford University Press, 1996: 431-438.

3. De Bruin AF, De Witte LP, Stevens F et al. Sickness Impact Profile: The state of the art of a generic functional status measure. Soc Sci Med. 1992; 35:1003-1014.
Dr. Mackenzie responds to Mr. Moretto 21 December 2004
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Ellen J MacKenzie,
Professor
Johns Hopkins School of Public Health,
Michael Bosse and the LEAP Study Group

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Re: Dr. Mackenzie responds to Mr. Moretto

emackenz{at}jhsph.edu Ellen J MacKenzie, et al.

To the Editor:

We would like to thank Mr. Moretto and the American Academy of Orthotists and Prosthetists for their comments on our recent article (1). The points they raise regarding our conclusions are noteworthy and deserve further discussion.

First, they question the appropriateness of using the Sickness Impact Profile (SIP) as a measure of outcome following amputation. They suggest that our results finding no difference in outcomes for individuals undergoing below the knee versus above the knee amputation may be due to a lack of sensitivity of the SIP. We do not believe this to be the case. The SIP has been well validated for a variety of illnesses and injury, including orthopedic trauma (2, 3). It has also been shown to correlate well with the more recently developed Musculoskeletal Functional Assessment (4). Most importantly, however, the SIP has been shown to be sensitive to changes over time and to differences in treatment . We too, however, were surprised to see no significant difference in SIP scores for individuals undergoing above the knee versus below the knee amputation. This lack of difference was consistent across the domains of the SIP (as reported in Appendix table). Furthermore, although not specifically reported in the paper, we found no difference in the percentage returning to work (among those working before the injury). Kaplan- Meier estimates of the proportion returning to work by 24 months were 0.42 and 0.56 for below the knee versus above the knee amputations. These differences are not statistically significant after controlling for potential confounders. It is important to emphasize, however, that even though we found no differences in SIP and return to work outcomes, the mean walking speed of patients with below the knee amputations (as measured by a physical therapist) was significantly faster than for patients with an above the knee amputation. These results suggest that while a below the knee amputation may indeed be associated with better lower-limb function per se (as measured by actual walking speed), this difference does not always translate into improved function in daily activities (as perceived and reported by the patients). This may be due to the fact that all patients experience similar frustrations and challenges following amputation that can easily overwhelm the actual degree of lower limb impairment. More research is needed to better understand the relationship between impairment, activity limitations and restrictions in participation so that appropriate post-acute care interventions can be developed and targeted to those most in need.

We would like to emphasize here that we believe the more important finding of our study is that regardless of the level of amputation, outcomes were on average quite poor. 43% of all patients had an overall SIP score of >=10 points, indicative of severe disability and only 54% had returned to work.

Mr. Moretto also questioned our conclusion that “the results call into question the advisability of fitting patients with the more sophisticated (and expensive) prostheses, given that the low tech devices appeared to yield equivalent outcomes.” As we carefully point out in the article, our finding of no difference in outcome by the technical sophistication of the device “must be interpreted with considerable caution.” The study was limited in its ability to measure the quality of prosthetic fit and the extent to which the type of prostheses actually matched the needs of the individual. For this reason we concluded that “no definitive recommendations can be made.” However, we thought it important to make note of our results (albeit limited in their interpretation) to underscore the urgent need for controlled trials to better delineate the relationship between device characteristics and outcomes in terms that our meaningful to the individuals wearing the devices. In answer to the specific question raised by Mr. Moretto, the level of technical sophistication was indeed similar for both above the knee and below the knee prostheses (see Appendix table).

Finally, we concur with Mr. Moretto’s belief that multi-disciplinary research is critical to a study of outcomes following amputation. Although we did include two prosthetists in our rating of the device sophistication, these individuals were not consulted regarding the choice of outcome measures. In retrospect, we would have benefited from inclusion of a prosthetist on the study team. We certainly look forward to future collaborations with members of the Academy in addressing the important issues raised by our study.

1. MacKenzie E, Bosse MJ, Castillo R et al. Functional outcomes following trauma –related lower–extremity amputation. J Bone Joint Surg Am. 2004; 86(8): 1636-1645.

2. McDowell I and Newell C. Measuring Health. New York: Oxford University Press, 1996: 431-438..

3. Jurkovich G, Mock C, MacKenzie E, Burgess A, Cushing B, deLateur B, et al. The Sickness Impact Profile as a tool to evaluate functional outcome in trauma patients. J Trauma 1995; 39:625-31.

4. Martin DP, Engelberg R, Agel J, Swiontkowski MF. Comparison of the Musculoskeletal Function Assessment questionnaire with the Short Form- 36, the Western Ontario and McMaster Universities Osteoarthritis Index, and the Sickness Impact Profile health-status measures. J Bone Joint Surg Am. 1997; 79(9):1323-35.
Evaluating Functional Outcomes Following Lower Extremity Amputation 21 December 2004
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David F. Moretto,
President
American Academy of Orthotists and Prosthetists

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Re: Evaluating Functional Outcomes Following Lower Extremity Amputation

tgorski{at}oandp.org David F. Moretto

TO THE EDITOR:

On behalf of the members of the American Academy of Orthotists and Prosthetists, I would like to express my admiration for the authors’ efforts to explain functional recovery following amputation in the recently published article, Functional Outcomes Following Trauma-Related Lower Extremity Amputation. JBJS, 2004 Aug; 86-a (8):1636-45.

We noted that the principal aim of this study was to examine functional outcomes following trauma related amputations. As such, we would ask the authors to comment on the selection and appropriateness of the Sickness Impact Profile (SIP), recognizing that this is a quality of life instrument that typically provides a descriptive profile of changes in a person’s behavior due to sickness.

We believe that the failure of the authors to report any differences in functional outcomes (as measured with the SIP) between patients who had undergone an above knee amputation as compared with below knee amputation may relate more to the sensitivity and selection of the instrument, than to the functional ability based on level of amputation as previously documented. ,

Additionally, would the authors please clarify and place into context their claim that “the results call into question the advisability of fitting patients with the more sophisticated (and expensive) prosthesis, given that the low tech devices appeared to yield equivalent outcomes”, given that the authors chose to select the above mentioned questionnaire with its noted limitations. Unfortunately, no information was provided regarding a possible correlation between the level of sophistication of the prostheses and the amputation levels within the population, which may effect this conclusion.

Finally, we believe that the use of a multi-disciplinary research team, including suitably qualified prosthetists and therapists, can address these issues by looking at outcomes from different clinical and patient perspectives. By doing so we assure that the quality measures and instruments chosen are the most appropriate.

Professionally Yours,

David Moretto CP, FAAOP President, American Academy of Orthotists and Prosthetists.