A study in Volume 52 Number 4, 2015, of the Journal of Rehabilitation Research & Development presents 15 years of experience with Orthodynamics’ Integral Leg Prosthesis (ILP), an attachment system used in osseointegration. It reports the changes in clinical outcomes during the evolution of device designs and concurrent refinement of operative techniques: three systematic and empirically driven iterations. These changes, determined by clinical outcomes, were necessary to limit infection at the stoma and deep bone and implant interface.
(a) Design iteration A and (b) design iteration B. In design A, a portion of the distal post (2) and endomodule (3) were coated with (c) Spongiosa-Metal 2 to provide structured surface for skin and bone attachment and ingrowth. Both design iterations had bone-stabilizing bracket attachments (1). Images courtesy of the study authors and the Journal of Rehabilitation Research & Development.
Between January 1999 and December 2013, 69 patients with transfemoral amputations, four of whom had bilateral transfemoral amputations, were fitted with ILPs by a single German surgeon in a two-stage surgical procedure. Because of specific risks inherent to the ILP attachment method, particularly the risk of infection, patients were mainly those with traumatic amputations; excluded were patients with conditions that would be expected to limit not only an early, robust, and persistent wound healing response and osseointegration but also prevent continued protection of the stoma and the bone-implant interface over the patient’s remaining life span, jeopardizing implant longevity. Patients were assessed for the emotional stability and intelligence required to undergo rehabilitation and to understand the need for conscientious lifelong stomal wound care and hygiene.
(a) Assembled final ILP implant iteration (design C). (b) Modular components of iteration: (1) femoral stem, (2) temporary cover screw, (3) dual cone adapter, (4) safety screw, (5) sleeve, (6) rotating disc and temporary screw (until prosthetist has made final adjustments), (7) final propeller screw, and (8) provisional screw.
Device design iterations and surgical techniques evolved during these years. Because the first two design iterations and surgical procedures were similar and clinical outcomes were closely parallel, patients receiving the first two designs and procedure iterations were placed in group 1 (n=30), and the patients fitted with the final design were placed in group 2 (n=39). Infection rate and planned and unplanned surgical interventions were statistically compared. Data demonstrated that the high rate of stoma-associated infections seen in group 1 was dramatically reduced in group 2. Of the 39 patients with 42 implants in group 2, none had operative interventions secondary to infection. All group 2 patients remained infection-free without the use of antibiotics by following a simple, defined wound-hygiene protocol. The researchers concluded that the final iteration of the osseointegrated intramedullary device allowed a biologically stable skin stoma that remained infection-free without chronic use of antibiotics. The reduction in the infection rate was attributed to the clinically based, empirically driven changes in design and surgical techniques.
The researchers stated that since changes and improvements of designs and procedures have brought forth a dramatic amelioration of the initial problem of infection at the skin and implant interface, they feel the osseointegrated ILP can now be considered as an alternative method for the rehabilitation of people with amputations.
