Because less than 2% of all amputations are at the hip disarticulation level,¹ the typical physiatrist, therapist, or prosthetist may not be familiar with the associated general fitting considerations and biomechanical requirements necessary for optimal gait. In the absence of direct volitional control over the major joint segments of the lower extremity, the choice and alignment of prosthetic componentry constitute critical considerations. In the absence of a residual extremity, active control of such prostheses is limited to movements of the pelvis and lumbar spine. This poses challenges to prosthetic gait training and mastery. Even with thoughtful prosthetic design and fabrication, the wear time of prostheses in this cohort is often reduced.

Prostheses at these amputation levels often have higher rejection rates because of their increased energy requirements, weight, and greater coverage of the body. Available evidence is limited, but suggests that successful long-term acceptance of prostheses at these proximal amputation levels ranges between 35% and 76%.^2,3

The ability of the user to control the prosthesis through muscular activity is greatly reduced at this amputation level, with control movements limited to motions of the pelvis and lumbar spine. As a result, middle-aged individuals with hip disarticulation walk approximately 40% slower and expend approximately 80% more energy than able-bodied individuals.⁴ Energy requirements at this amputation level are considerably higher for elderly amputees.⁵ However, in their report on seven elderly individuals with hip disarticulation amputation, Chin et al⁶ reported on five subjects with adequate physical fitness to attain and maintain community ambulation with their prostheses. Subsequent case studies have continued to report on successful prosthetic outcomes observed among elderly users of hip disarticulation prostheses.^7,8

Although technologic advances such as lighter componentry, more dynamic designs, and softer interface materials have resulted in improved prostheses, acceptance and optimal prosthesis use remain challenging. For many individuals who regularly use a prosthesis, the reduced energy requirements and increased speed of alternative forms of mobility preclude complete daily reliance on prosthetic ambulation. For example, elderly amputees can move twice as fast with a wheelchair and expend only 25% as much energy compared with their use of a hip disarticulation prosthesis.⁵ Similarly, among a small cohort of established users of hemipelvectomy prostheses, the mean time to walk 400 m was 43% longer
with the prosthesis compared with walking with crutches and no prosthesis.⁹ It is understandable that even successful prosthesis users may limit their wear time to an average of 6 hours per day.¹⁰ However, the recent development of new technologies specifically designed for hip disarticulation devices is transforming challenges into opportunities for improved outcomes.

The successful fitting of a hip disarticulation prosthesis relies on the appropriate evaluation of the patient’s motivation, balance, core strength, and load-bearing tolerance, along with the prosthetist’s ability to capture and translate movements of the pelvis into prosthetic motion during swing while providing a secure, stable platform during stance. Greater motivation is generally required for successful ambulation with a prosthesis at this amputation level compared with that needed by most patients with a transfemoral or transtibial amputation. The possibility of successful prosthesis use can only be properly assessed when the patient has been given an accurate portrayal of the benefits, challenges, and limitations specific to a hip disarticulation prosthesis. Unrealistic expectations regarding the ease and energy costs of ambulation may result in early rejection of the prosthesis. After the patient has been given a reasonable understanding of the challenges inherent in the use of a hip disarticulation prosthesis, they can have a realistic discussion with the rehabilitation team to determine if there is sufficient motivation to proceed with a prosthetic fitting.

Superior balance on one leg is a strong positive indicator for prosthesis use because such balance is needed to successfully don and ambulate with a hip disarticulation prosthesis using minimal assistive aids.¹¹ As such, the demonstration of adequate single-leg balance is a prerequisite for any consideration of prosthetic management.

The strength of the core abdominal muscles should be assessed. Strength is demonstrated by creating a posterior pelvic tilt and should be evaluated because it is the main biomechanical motion used to initiate hip and knee flexion during gait and is needed for efficient ambulation. The patient should be able to demonstrate active pelvic tilt motions using the muscles of the lower back and abdomen. As a related consideration, the most successful prosthesis users are also able to maintain a lower body weight so that the full range of pelvic tilt may be captured within the prosthesis. The presence of any redundant or fleshy tissue should be noted because it must be contained and shaped to create reaction surfaces for proper prosthetic function. Further, excessive redundant tissues distal to the ischium necessitate a more distal placement of the hip joint, compromising its efficiency.

The distal aspect of the ischial tuberosity should be evaluated with respect to its load-bearing tolerance. Available gluteal tissue should be assessed for its ability to supplement axial loading. The bony prominences of the pubis and iliac crests and, in some instances, the residual femoral head should also be noted because they will require relief within the interface. If ischial weight bearing will be poorly tolerated, an alternative socket design must be considered to distribute weight-bearing loads more broadly through total surface bearing principles.

The prosthetic socket is a crucial connection between the patient and their prosthesis and must facilitate comfortable axial support, efficient ambulation, and consistent suspension. Appropriate socket designs create abdominal compression to contain soft tissue and adequately capture the control movements of the underlying pelvic anatomy. Similarly, anatomic contouring in the lumbar region is used to create a volumetrically tight and accurate anterior-posterior fit between the sacrum and lower abdomen. Compressive mediolateral dimensions are also necessary to preserve coronal stability during gait. Specifically, mediolateral measurements should be recorded over the iliac crests and between the trochanter and the iliac crests, and they should be reflected in the prosthetic socket.

The hip disarticulation interface must serve four purposes: adequate coronal support, sagittal capture of pelvic movements, secure suspension, and appropriate weight-bearing surfaces and contours. New thermoplastic materials have been developed that greatly increase patient tolerance of the hip disarticulation sockets. Rigid laminated frames can be coupled with flexible thermoplastic inner sockets to provide both proximal flexibility and comfort at the edges of the socket as well as adequate rigidity at the attachment site of the hip joint and over the iliac crests (Figure 1). Although thermoforming offers a variety of flexible materials and ease of fabrication, it constitutes a thicker construction and represents a heavier alternative to rigid sockets.

Traditional hip disarticulation socket designs encompass the affected pelvis, contain the gluteal tissue and ischial tuberosity, and provide mediolateral stability by compressing the contralateral pelvis toward the affected side through the design of the interface. Suspension is accomplished by compression over one or both iliac crests, and an anterior closure is normally used.

Novel socket design configurations include the creative use of suction or vacuum designs with reduced contralateral trim lines (Figure 2), interface designs that use separate iliac crest attachments, flexible liners and frames, and other unique shapes that attempt to maintain appropriate stability and suspension but provide greater comfort and range of motion around the pelvis (Figure 3). However, little research has been done on hip disarticulation socket design and the variety of configurations currently used.

Impression techniques vary based on patient presentation and the preferences of the treating prosthetist. Weight-bearing impression techniques are often preferred at the hip disarticulation level because they allow the patient to have some distal end bearing while creating the impression. These approaches capture a socket shape
conducive to skeletal loading. Houdek et al¹² advocated the use of deformable materials beneath the patient to assist in defining the primary weight-bearing skeletal structure during the impression capture. Wedges or forms are often used to compress the anterior-posterior dimension to better capture pelvic motion when using the prosthesis (Figure 4). Care must be taken to prevent excessive mediolateral tissue displacement during this procedure.

An alternative technique that is gaining popularity can be characterized as static compression. In this approach, the patient is not actively bearing weight while the impression is taken. Rather, the tissues of the residual limb are precompressed using plastic film or stout tape. The patient then remains standing on the sound side limb while the impression is obtained with casting or digital scanning techniques.

When designing the socket for an individual using a hemipelvectomy prosthesis, in the absence of pelvic anatomy for weight bearing, care must be taken to create additional soft-tissue compression and containment. Prosthesis design for this level of amputation can be very challenging for many reasons, including the limited weight-bearing area and restrictive trim lines leading to a loss of range of motion and comfort. Providing abdominal pressure and compressing the soft tissue on the amputated side in a diagonal fashion will aid in weight bearing (Figure 5). Additional support may be gained from the costal margins and sound side ischium if needed (Figure 5).