CORR Insights®: Are Gait Parameters for Through-knee Amputees Different From Matched Transfemoral Amputees?

Where Are We Now?

Designed as an observational investigation from eight Level I trauma centers to establish reasonable expectations for patients with mutilating limb injuries, the Lower Extremity Assessment Project (LEAP) study by Bosse and colleagues [1] gave us tremendous insight into both the functional and the subjective patient-reported outcomes associated with traumatic lower-extremity amputation.

The functional outcomes of the patients who underwent knee disarticulation in the LEAP study differed greatly from my favorable clinical experience [2, 4-9]. Bosse and colleagues [1] found that knee disarticulation amputees reported more pain and difficulty with functional prosthesis use than similar patients who underwent traditional transfemoral amputation. While most of our patients were older and did not undergo amputation because of trauma, we observed far better clinical outcomes than the LEAP investigators. This discrepancy in observed clinical outcomes led Schuett and colleagues [10] to objectively address the functional gait differences between patients undergoing these two very different amputation levels.

It wasn’t until I discussed this dilemma with several of the participating surgeons involved in the LEAP study that I understood the disparity. The surgeons who participated in the LEAP study were comfortable performing traditional transosseous transtibial and transfemoral amputations, followed by total surface bearing prosthetic limb fitting. They understood that the transosseous amputees would not be able to end bear in a prosthesis, so they created traditional total surface bearing amputation stumps, attempting, when possible, to create a cushioned myofasociocutaneous soft-tissue envelope. Similarly, the prosthetists in the LEAP study who fit their patients with prostheses were familiar enough with the socket accommodations to use a total surface bearing prosthetic socket.

This was not the case for the patients with knee disarticulation. In fact, the LEAP study was performed before the now well-accepted concept of damage-control orthopaedics, which minimizes the additional trauma of surgery at the initial surgical débridement to allow the zone of injury to recover before performing the definitive reconstructive surgery. Most of the knee disarticulation patients in the LEAP study underwent surgery within the zone of injury, with a resultant soft tissue envelope that rarely had sufficient retained gastrocnemius muscle to create an end pad for cushioning the load of weight bearing. Those of us familiar with following knee or ankle disarticulation amputees longitudinally have appreciated that favorable prosthetic fitting could only be achieved when a cushioned end pad is created at the time of surgery [4, 5].

Where Do We Need To Go?

After reading the current study [10], we are still left with gaps in our knowledge regarding the terminal end organs of weight bearing in both groups. It is well accepted that the functional outcome of the transfemoral amputee is closely related to the length of the residual femur and the quality of the soft-tissue envelope [3]. But we do not know the length of the residual femurs or the quality of the soft-tissue envelope in the transfemoral group, nor is there a description of the end-bearing capacity of the knee disarticulation subjects. It is difficult to compare functional task performance in these two groups if we do not have a better appreciation of the quality of the patients’ amputation stumps.

We need to compare apples to apples. We have seen a change in amputee clinics when amputee clinics were previously staffed primarily by orthopaedic surgeons to the current model where these clinics are generally staffed by specialists in physical medicine and rehabilitation. Few orthopaedic residents currently have the opportunity to attend amputee clinics where they can observe the end result of the surgery. The modern patient-care model is just as challenging for our physical medicine and prosthetist colleagues who are not familiar with technical aspects of a myofasciocutaneous flap to create a soft-tissue envelope. Would our sports medicine colleagues transfer supervision of an ACL reconstruction to a rehabilitation specialist? Would our joint arthroplasty colleagues assign longitudinal management of their joint replacement patients to a specialist in rehabilitation?

If we accept this modern patient-care model of transferring the rehabilitation of our amputation patients to other providers, we should then attempt to understand the attributes of our surgery that are essential to improve prosthetic limb fitting. Damage-control orthopaedics allows the zone of injury to recover, so that we can create a durable cushioned terminal end organ of weight bearing with soft tissues that are capable of transferring weight-bearing loads.

While there has been a tremendous fervor in favor of the bone bridge in transtibial amputation to enable end bearing, we have not yet seen objective evidence that transtibial amputees with a distal tibia-fibular bone bridge are actually capable of end bearing, or whether their functional outcomes are actually improved compared to a well-performed traditional transtibial amputation.

The theoretical advantage of disarticulation is the creation of a large surface area capable of distributing the load of weight bearing. That said, neither knee disarticulation nor Syme’s ankle disarticulation amputees have fared well when they do not possess an adequate soft-tissue envelope [5]. Until we create amputation stumps as carefully as our arthroplasty surgeons prepare joints for a joint replacement, this dilemma will persist.

How Do We Get There?

In the words of my mentor Ernest Burgess, “The first step is to appreciate amputation as constructive surgery.” Dr. Burgess stressed that amputation should be the first step in the rehabilitation process. We need to refocus residency education to consider amputation surgery as constructive surgery, not failure-mode surgery. These observations are theoretical at best. We need to study gait performance based on the length of the amputation residual limb for specific amputation levels, and the load dampening characteristics of the soft tissue envelope end pad in disarticulation levels. Obtaining this objective data from the gait lab will allow us to emulate our sports medicine and joint arthroplasty colleagues, so that we can compare amputation levels and level-specific surgical techniques.