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Rehabilitation of an Individual with Transfemoral Amputation Combining Aquatic Ambulation With Prosthetic Socket Incorporating High-Fidelity Skeletal Capture

Cutler, Thomas J. CPO, FAAOP

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Journal of Prosthetics and Orthotics: October 2017 - Volume 29 - Issue 4 - p 206-212
doi: 10.1097/JPO.0000000000000147
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With the complexity of transfemoral prosthetic rehabilitation and the emphasis on quantifying outcomes of medical treatment, it is important for the prosthetic field to make progress in addressing those complexities and to translate that progress into meaningful information by which those advancements may be assessed and tested. In recent years, the concept of skeletal capture has been developed through the High-Fidelity (Hi-Fi) Interface. Current research on the benefit of skeletal capture is limited,1,2 and the outcome measures as reported by patients, although positive when skeletal capture has been executed properly, are somewhat subjective in nature. This case report is an effort to contribute objective quantifiable benefits to the current body of knowledge. With increased rehabilitation potential having been achieved with a socket featuring the Hi-Fi Interface, the resolution of the subject's previous limitations revealed other obstacles to rehabilitation. The subject's attribution of aquatic ambulation as the most beneficial therapeutic element in his rehabilitative success prompts the author to link skeletal capture and aquatic rehabilitation as synergistic elements in this case report. Neither aquatic rehabilitation alone nor skeletal capture alone would likely have produced comparable results.

Skeletal capture is defined3 as the concept of stabilization of an external limb prosthesis with focused compressive forces applied longitudinally along the intact shaft of the femur or other long bone. The compressive forces displace soft tissue as opposed to capturing, containing, and/or stabilizing via the soft tissue. The displacement of the soft tissue is accommodated by relief zones that are either enclosed within the socket/flexible inner liner or open in the form of one or multiple apertures. Skeletal capture is limited in concept to an element of socket design and may be used with various clinical approaches. It may be used in conjunction with elevated vacuum, suction, physical anchoring with pin or lanyard, and other suspension techniques. It is also not an exclusionary socket principle in that skeletal capture can be incorporated into currently utilized ischial containment brim designs and subischial socket designs. Because the subject was provided a subischial socket with the Hi-Fi Interface, that will be the default system discussed for the purposes of this article.



Gottschalk et al.4 explicitly concluded 25 years ago that no transfemoral socket design at that time was capable of controlling the femur in adduction. The importance of preserving femoral adduction is due to the nearly linear relationship between femoral adduction angle and strength. According to Ryser et al.,5 there is a 0.97% average increase in isometric hip abduction strength for every 1° of increased femoral adduction from 30° of hip abduction through 16° of hip adduction. A closer look at the study4 shows that the author determined that there is only one presentation that preserves the femoral adduction angle. This exception occurs in the knee disarticulation amputation level. Notably absent is any mention of the influence of knee disarticulation socket shape,6 which uses skeletal capture as a factor in the preservation of femoral adduction angle. Based on the text, all preservation of femoral adduction angle is attributed to the fact that the adductor magnus muscle is attached to the medial femoral condyle. This inability to harness the abduction forces of the femur in the optimal adduction angle in a transfemoral socket may be the reason for the concerns and the subsequent approach found in later articles7–9 and in Chapter 20 of the Atlas of Amputations and Limb Deficiencies.10 While the Atlas mentions the tensor fasciae latae as a hip abductor, the structure into which the tensor fasciae latae inserts, the iliotibial band, is not mentioned. The primary transfemoral amputation surgical goal is balancing the affected limb against itself. A follow-up telephone call with the editor of the Atlas to get clarification confirmed Gottschalk's adductor myodesis as the preferred technique for transfemoral amputation surgery (Doug Smith, personal communication, April 2015). When asked for clarification with regard to the iliotibial band, it was confirmed that transfer of the iliotibial band from the lateral to the posterior aspect of the femur was an effective way to address hip flexion contractures, and their concern regarding hip abduction contractures was reiterated. Email communication with Dr Gottschalk confirmed that removal of the iliotibial band from the lateral distal attachment point is not considered to be of significance for the individual with transfemoral amputation.

Ropp and Klenow1 demonstrated that ground reaction forces during walking differ between the skeletal capture versus nonskeletal capture socket. This difference is represented visually by a smooth arc in terminal stance on the skeletal capture socket and a dropoff followed by a plateau in terminal stance in the ground reaction force of a nonskeletal capture socket. A telephone conversation with that study subject conveyed a primary perceived benefit of increased stability with the skeletal capture socket. Both sockets used vacuum-assisted suspension. Although the data were presented, no conclusions were made regarding the discrepancy in ground reaction forces. The subject did report more favorably on the Hi-Fi socket compared with the standard socket on Prosthesis Evaluation Questionnaire and Oswestry scores.


A meta-analysis of research with aquatic physical therapy in orthopedic joint replacement revealed little benefit from aquatic-based ambulation.11 On the surface, this conclusion contradicted the experience and opinion of the subject. Further analysis into the methodology of studies in the meta-analysis showed that standard study design was opt-in, that the opt-out rate of eligible subjects reached more than 50%, and that no demographic data are provided regarding the subjects who opted out.12

Dr Bruce Becker, physiatrist and former director of the National Aquatics and Sports Medicine Institute at the University of Washington Department of Rehabilitative medicine, stated that “there are no studies that deal directly with aquatic therapy in LE amputation rehab” but went on to indicate that “there is a considerable amount of evidence that the aquatic environment is a wonderful milieu in which to conduct therapy especially for a bilateral AK [above-knee] amputee. Folks in this category have tremendous difficulty getting cardiovascular exercise, and the water allows that. The combination of water properties reduces pain, increases circulation to healing tissues, reduces edema, [thus] facilitating circulation, and aids in both respiratory and cardiac strengthening. These alone make the aquatic environment very useful in such patients. The absence of fall risk is of course alone worth the trial.”

Research comparing functional rehabilitation outcomes of patients comparable with the subject demonstrates the difference between opting for amputation or continuing with a fused limb. A 2015 article13 shows that subjects sustaining transfemoral amputation as a result of knee replacement complications have a lower functional score than did subjects who refused amputation and walked with a fused knee. What is more troubling is that the mean age of the amputation group was 10 years younger than the nonamputated group.


The subject was a 62-year-old man with a right transfemoral amputation sustained in February 2011 secondary to infection complications from knee replacement surgery. The patient provided informed consent orally for inclusion in this case report. He was weight bearing as tolerated for 18 months before the amputation. After a reported consistent adult body weight of approximately 180 lb, he reached a maximum weight of 350 lb and reported a steady decline in activity caused by suspension complications with his previous prostheses. Despite complications, weight loss continued and was documented at 290 lb at the time of initial physical therapy assessment. The subject stated that he would fall approximately one time per week. The subject reported leg tremors that would complicate sleeping and other activities. The prosthetic componentry at initial evaluation was a Plié microprocessor-controlled knee, dynamic pylon and foot, and seal-in suspension. The subject received two prostheses and four additional sockets in the 3 years following the amputation. Because of the high number of prosthetic sockets that had been provided previously, objective outcome measures were a priority. Physical therapist notes and assessments provided objective data for justification of the prosthesis.

Special considerations of this case: The subject has a transfemoral prosthesis in atypical alignment. It is designed to accommodate the 45° hip flexion contracture (Figure 1). The result is that the subject was unable to wear pants and could only wear shorts when wearing the prosthesis. The anticipated reduction of the hip flexion contracture accommodation would reasonably result in the fabrication of an additional prosthetic socket. The subject complained of loss of suspension with the seal-in liner from Össur. During the initial assessment, a significant invagination appeared in the residual limb at the level of the distal sealing ring during isometric co-contraction of the thigh musculature (Figure 2). This could result in a loss of suction and was determined to be the likely source of loss of suspension in the six previous sockets. Consultation with Össur clinical staff confirmed that although a rare occurrence, contraction-activated invaginations are addressed in educational materials, detected easily during the diagnostic fitting phase, and newer versions of Össur Seal-In liners can accommodate this phenomenon with height-adjustable sealing rings. The subject was changed to a pin-locking suspension to accommodate anticipated volume reductions and to increase confidence on the part of the subject with mechanically anchored suspension. The subject was fit with an appropriately sized Ottobock TF adapt locking liner. The subject reported that the limb tremors were immediately eliminated with the new liner and he proceeded to wean himself from 12 medications over the course of the next 3 months. He was recommended by the author to do this only under the supervision of his physician.

Figure 1
Figure 1:
Subject's original transfemoral socket on the right with alignment line indicating the midline of the socket in the frontal plane. Subject's definitive socket incorporating high-fidelity skeletal capture interface on the left. Note significant accommodation change from end of limb to knee center.
Figure 2
Figure 2:
Patient's limb relaxed in the photo on the left. Patient's limb presenting with physiologic change with isometric contraction on the right. This change is possible cause of complications with seal-in liner.

With the complex prosthetic presentation, the author recognized the need for increased prosthetist involvement with rehabilitation. Major volume loss with increased ambulation and potential weight loss was anticipated. Major correction to alignment was also anticipated with the correction of the hip flexion contracture. The interface uses compression zones to provide additional stability. This compression results in an acceleration of physiological changes that are typical of the preparatory prosthetic process by which atrophy and changes (alignment, unforeseen sensitivities, neuromas, and latent surgical anomalies) are accommodated. In addition, weekly collaboration with therapy staff would benefit the subject by tailoring exercises and providing clinical expertise. The transitional socket (Figure 3) was termed “Interim Dynamic Socket” (IDS) since a preparatory socket had already been provided and to distinguish it from standard diagnostic sockets. The extensive clinical and collaborative efforts were termed the “Interim Dynamic Fitting” (IDF). The IDS and IDF prevent replacing a definitive laminated socket in less than 2 months as well as documenting improvements that can result in reduced health care costs and risks. The IDS consists of a thermoplastic socket with a flexible inner liner. The frame derives durability to last for two or more months from Orfitrans stiff.

Figure 3
Figure 3:
Photo of IDS on the left with patient's original socket on the right. Note the thickness of thermoplastics necessary for the patient's safe ambulation.

Ten-millimeter thickness was used in this case due to the weight of the patient, and additional sockets have been successful with 0.25-in Orfitrans stiff. Deflection of the struts in the compression zones is reduced with 0.25 polyethylene terephthalate strut reinforcements. The inner liner is fabricated from high-density polyethylene chosen for the low coefficient of friction for easy donning. The flexible liner is also useful for adjustments to strut compression and targeted distal support in the socket. The locking mechanism was a Bulldog shuttle lock. The subject was educated in how to adjust socket fit. Atrophy generally ranges from 40% to 60% in resected muscles and 0% to 30% in intact muscles (Jagers 1995).14 The subject was able to use socks and shims to self-manage skeletal capture and socket fit as this atrophy occurred. When atrophy occurs in the distal aspect of the limb, the entire inner liner can be transected in the transverse plane, elevated until the subject reports optimal support, modified, and the inner liner secured in that elevated position.

The subject was evaluated by the physical therapist with the prosthetist present. Endurance, manual muscle test, disability level, and range of motion baselines were established. The subject was initially indicated for aquatic therapy by the prosthetist. After 1 week of physical therapy, it was discovered that aquatic therapy was not, in fact, being provided. The protocol was reviewed at the collaboration visit with the prosthetist and the physical therapist. The subject reported after the therapy session that he was walking on land for a total of 5 minutes during therapy and icing his sound side knee for 3 hours after physical therapy. The physical therapist agreed to include aquatic-based therapy.



The IDS was attached to alignable endoskeletal componentry (Figure 4) via a Ferrier coupler. This allowed the patient to easily change from his existing setup to the aquatic configuration. The aquatic prosthetic configuration was a pylon with a hydraulic articulating ankle/flexible keel foot (Endolite Avalon). The prosthetic knee unit was omitted to increase subject confidence. The articulating ankle could dorsiflex at terminal stance, which would provide additional toe clearance during swing phase and reduce excessive anterior progression of the pylon at the loading response phase of gait. With reduced gravity in the pool, the ankle hydraulic resistance was reduced to the minimum resistance setting. The Ferrier Coupler was later exchanged with the Ottobock 3R80 waterproof prosthetic knee. The knee has a manual lock feature that was used for aquatic ambulation. The patient used water sandals for ambulation in the pool and for protection of the prosthetic foot cover.

Figure 4
Figure 4:
Representative prosthetic component configuration for aquatic ambulation with the IDS.


In the reduced gravity of the aquatic environment, the subject was instructed to ambulate for as long as he felt comfortable. Adjustments to alignment and instructions were provided intermittently. The subject was able to ambulate successfully for 45 minutes. The subject reported pain on the medial aspect of the knee on the sound side at the conclusion of the first aquatic therapy session. Manual simulation of varus reduction forces on the sound knee joint by the author during quiet standing on land reduced subjective pain reports from 8 of 10 to 1 of 10. This was documented in the chart by the therapy staff to justify the prescription of a prefabricated unloading knee orthosis (Townsend Rebel Reliever with Loadshifter). The subject was able to demonstrate single-limb support on the prosthesis in the pool. The subject was able to practice falls and stumble recovery techniques without fear of injury. The subject was provided with weights on his shoulders to increase hip abduction resistance in the pool as his strength grew.

The therapy protocol was straightforward. The subject would have the prosthesis checked upon arrival at the facility for proper fit and volume management. The subject would walk in the pool in his preferred manner for several minutes until visual indicators of elevated stress dissipated (he relaxed). He was then provided with verbal cues to correct gait biomechanics and shifting of center of mass. This was followed with exercises designed to focus on strengthening specific muscles or on teaching tasks related to increasing proficiency in ambulation.


Standard stretching exercise and instruction were provided by therapy staff. Weekly fitting reviews and alignment adjustments occurred before the beginning of therapy exercises. This included changing componentry as needed. Periodic land-based ambulation occurred for assessments, but not for the purpose of developing endurance.


The subject was assessed for endurance, range of motion, and manual muscle testing.


Final documentation was provided by therapy staff at the 120-day assessment for inclusion in the case report. Measures of pertinent data were performed. These measures included the previous assessment measures plus assessment of disability rating. The subject had been provided with his final socket and measurements were taken with the subject's preferred componentry. The subject had also discontinued use of the osteoarthritis knee orthosis with no pain recurrence.


The results of the aquatic rehabilitation incorporated into the IDF protocol are included in Table 1. To prevent conflict of interest, no data or metrics have been included from prosthetist documentation and any metrics that the prosthetist desired were communicated to the physical therapist at the initial assessment.

Table 1
Table 1:
Physical therapy performance metrics

Two anecdotal results worthy of mention are resolution of subject's restless leg syndrome with the liner style and unconfirmed satisfactory calcification of the subject's internal prosthetic knee implant in the sound limb.


A discussion of this case report must look at the critical elements of the intervention and the conditions that predicated the need for and created the complications resolved by the intervention. Discussion of factors contributing to the subject's medical presentation is necessary to improve coordination of care and is critical to gaining any significant macrobenefit from the insights of this case report.

The first critical component is skeletal capture of the femur by the prosthetic socket. The Gottschalk study concluded that the nonskeletal capture socket designs assessed in that study are unable to control the femur at the transfemoral level. The observations of this case report indicate that the Hi-Fi Interface has marked control of the forces exerted by and upon the femur. The evidence indicating this control is the magnitude of correction of the hip flexion contracture pointing to a stronger coupling of the bony anatomy and socket. This improved coupling has been noted in multiple patients fit with Hi-Fi Interfaces by the author. This is evidenced by necessary accommodation of hip flexion contractures where no previous accommodation was necessary in previous sockets. Patients may also demonstrate rotational control of the femur as limitations in hip extension range transition into hip rotation followed by hip abduction (which combine to mimic hip extension). These manifest in a medial whip of the prosthetic knee. The physical therapist noted a 10° reduction of the hip flexion contracture in the first week of aquatic ambulation. With the rapid changes in alignment, the patient required additional clinical adjustments to preserve the rate of rehabilitation. A concern with skeletal capture raised by some has been the deleterious effects of pressure on the femoral shaft. This concern may also be considered in a new light. While this discussion addresses correction with regard to range of motion and strength, an additional query may be warranted to assess whether the forces exerted on the skeletal structures do anything to arrest the 50% demineralization of the femur noted with persons with transfemoral amputations in non-skeletal-capture sockets in Jaegers (1995).14

The second critical component for discussion is importance of aquatic ambulation rehabilitation for persons with amputation. As stated by Dr Becker, there is currently no research specifically addressing aquatic ambulation outcomes for persons with amputation. For that reason, anecdotal observations and patient self-reports hope to provide insights to be considered for future research along this vein. This discussion will cover both the observed objective data as well as some suggestions that will require confirmation for validity of the relationship to be established. Although ischial containment sockets prevent lateral translation of the prosthetic socket with the “bony lock” on the medial aspect of the ischial ramal complex, the supportive nature of the shelf upon which the ischium rests decreases the burden on the hip abductors and must also be considered. This support reduces the biomechanical load on the hip joint and hip abductors. With increased hip abduction burden in subischial sockets, patients benefit from a reduced-gravity environment when transitioning to true femoral support of body weight. Persons with new transfemoral amputations have unique preprosthetic limitations. In addition to commonly prescribed preamputation limitations on weight bearing, any patient with a recent transfemoral amputation does not have a functional method to preserve hip abduction strength during limb healing (persons with transtibial amputation can kneel to preserve strength functionally). Through aquatic ambulation, the subject demonstrated a 900% increase in ambulation time during therapy. This component alone provides medical justification for inquiry into aquatic ambulation protocols. The subject also reported that he “felt better” but stated that it was not just because of the walking. Further inquiry into aquatic rehabilitation shows a significant reduction in blood pressure with warm water activity, from 133/92 to 115/67 (Becker).15 The subject also stated that he was able to relax and stretch more. This confirms studies15 that show increased parasympathetic neuroactivity in warm aquatic environments. It is suspected that the flexor pattern that is a normal symptom of the sympathetic nervous system response is diminished. This means that when persons with amputation feel threatened by a perceived fall risk, their natural response involves muscle tension. Thus, the immersion in water may inhibit this reaction, promoting stretch of the iliofemoral ligaments.

One unforeseen benefit of aquatic ambulation is anecdotal, but with great potential application: internal prosthetic knee implant calcification. After four years of reported pain and unsuccessful calcification of the replaced knee joint, the sound limb engaged in increased activity while in a reduced-gravity environment accompanied by an unloading knee orthosis to address knee pain. After 3 months of knee orthosis use, the patient stated that the orthopedic surgeon reported that he finally achieved satisfactory calcification of the replaced joint. At that point, knee orthosis use was discontinued with no pain recurrence. Shortly after that visit with the subject, the surgeon developed cancer and died, preventing confirmation of this conclusion. With 12,000 instances of serious complications from knee replacement surgery (2%),16 a benefit may be found in aquatic ambulation when rehabilitation is delayed. Ironically, the patients who could likely benefit the most from aquatic ambulation (obese, high fall risk, infection delays, and deconditioned/weak) were very likely the demographic who were also most likely to be excluded from aquatic research. It is a reasonable assumption that subjects who have greater fear of falling or a general aversion to wearing a bathing suit in public due to body image would opt out of the study for personal reasons. Also noted regularly in orthopedic aquatic research methodology is exclusion of subjects based on delays caused by infection. No body mass index or other physiological demographics on excluded subjects were available in the meta-analysis or in other orthopedic aquatic research articles reviewed. A study may be warranted to study aquatic rehabilitation for orthopedic joint replacement subjects who experienced delays.

One unforeseen hurdle in aquatic ambulation with persons with amputation is also anecdotal: additional burden to therapy staff. Although normally not relevant, it becomes important in this particular case as others seeking to validate this report may encounter a similar response. Therapy staff alluded to the inconvenience of changing into a swimsuit and mentioned the impact on documentation duties. Only with adamant insistence on the part of the subject did the therapist agree. Therefore, discussion becomes necessary to understand the reasons behind this reluctance and to apply those rationales to other situations wherein they may arise. Possible reasons include loss of documentation time, time lost to the therapist changing clothes, and the inability to document during treatment without waterproof devices. Just as the infamous Milgram Obedience Experiment indicated how a white lab coat can garner greater respect and compliance, so might also an inquiry into the professional perception of the physical therapist in standard attire compared with swimming attire be worthy of examination. Despite the reasons for initial reticence, the collaboration with therapy staff resulted in tremendous success. Their professionalism that overcame that reluctance should be admired and appreciated as well as being a lesson from which to learn.


While difficult to apply principles from a case report to a wider population, this case report certainly allows the reader to conclude that revisiting principles and practices pertaining to rehabilitation of persons with transfemoral amputations and socket design is warranted. Recognizing that subischial sockets remove the support of body weight at the pelvis has implications for rehabilitation protocols. One may concede the potential viability of skeletal capture as a method to preserve mineral content in the femur in accordance with Wolff's law as opposed to seeing only concern for tissue health. The benefit of increased prosthetist involvement in the rehabilitation process was seen on several occasions where prosthetist intervention was necessary and both disciplines benefited from the cooperative effort. The increased time ambulating in the reduced-gravity environment provides individuals with amputation an opportunity to walk further and for longer durations without fear of injury from a fall. While there was extensive subjective report of benefit crossover from aquatic to land-based ambulation, further research would be necessary to determine the extent of this benefit. Aquatic ambulation for individuals with transfemoral amputation has been exceptionally beneficial for patients dealing with compromised contralateral limbs. Reducing loads allows the patient to regain sufficient strength in the amputated limb and in the intact limb to ambulate safely without causing unnecessary damage to the sound limb.


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high-fidelity; transfemoral; socket; aquatic ambulation; amputation; adductor myodesis; prosthetic; prosthesis

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