OSSEOINTEGRATION OF THE TIBIA AFTER A PRIMARY AMPUTATION

Background: Transtibial amputation (TTA) reconstruction via press-fit osseointegration permits direct skeletal connection between a patient's residual limb and the prosthetic leg. Osseointegration reconstruction has predominantly been utilized in transfemoral amputation (TFA), resulting in overwhelmingly positive functional and quality-of-life improvements compared with traditional socket prostheses(1-3). The adoption of this technology has been slower in TTA, likely because patients undergoing TTA have superior mobility compared with those undergoing TFA, leading some clinicians to believe that their mobility cannot be further improved. However, patients undergoing TTA are still plagued by a degree of socket-related issues and decreased quality of life that is similar to those undergoing TFA(4). With the safety of osseointegration demonstrated in the literature(5-7) and the high prevalence of TTAs in the general population(8), it is important that osseointegration be utilized in the rehabilitation and reconstruction offered to patients undergoing TTA. Description: Planning starts with anteroposterior and lateral radiographs as well as computed tomography to optimally size the implant. The surgical procedure begins with exposure of the residual tibia, revising the bone cut if needed, and taking routine deep cultures. Reaming is performed over a centrally placed intramedullary guidewire, followed by sequential broaching up to the implant size under fluoroscopic guidance. The implant is then impacted into place. The muscles are closed in a purse-string fashion, followed by skin closure and the creation of a stoma. The external components are then attached to the implant. Alternatives: Traditional prostheses are attached to the residual limb via suction sockets. Patients who have undergone an amputation and are dissatisfied with the resulting quality of life or mobility can undergo attempted modification of their socket or liner components by a prosthetist. Alternatively, these patients can modify or limit their activities and forgo prosthetic limb support entirely. Other surgical options that may improve socket fit include revision amputation, residual bone lengthening, or soft-tissue contouring. Additional osseointegration implant designs also exist(9). Rationale: Suction sockets are known to cause multiple issues for patients who have undergone an amputation, including skin ulceration, sweating, poor fit, residual limb pain, physical disability, and impaired quality of life(10,11). TTA patients can be affected as substantially as TFA patients(4,12). The poor functionality of the socket is exacerbated in patients whose residual soft-tissue envelope is either in excess or fails to provide proper cushioning against the circumferential squeezing of a socket. Osseointegration bypasses these issues by linking patient and prosthesis via direct skeletal connection. Of the different design options available, press-fit osseointegration is the most commonly utilized and simplifies the implantation process into a single stage, in contrast with alternative 2-stage designs(9). Press-fit osseointegration has been successfully performed in patients having had an amputation for a variety of etiologies(13-15). Expected Outcomes: Outcome studies consistently showed improvements in patient physical function, prosthesis wear time, overall satisfaction, and quality of life following conversion to osseointegration from traditional socket prostheses(5,16). We recently reported on 31 consecutive osseointegration patients (13 TTA and 18 TFA) with a follow-up of 18 months(15). Overall and functional outcome domains of the Patient-Reported Outcomes Measurement Information System (PROMIS) and Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) improved significantly, as did performance on physical function tests. The most common complications following prosthetic osseointegration-which have been better documented in studies of femoral osseointegration-are superficial soft-tissue infections responsive to oral antibiotics(15,17) and, much less commonly, periprosthetic fractures that are treatable with implant retention and standard internal-fixation techniques(18). Important Tips: Template an implant that matches the inner diameter of the diaphyseal bone. Do not cement press-fit osseointegration implants for any reason(19). In cases of a short residuum with a greater proportion of proximal tibial metaphyseal bone, favor broaching after under-reaming to impact cancellous bone. Distal stress fractures with implantation do not typically affect implant stability. Perform tight, circumferential muscle closure around the bone-implant interface with absorbable sutures, creating a biologic purse string. Excise excess subscarpal fat and skin from the anterior and/or posterior flaps prior to closure(20). Graduated, partial weightbearing typically begins around week 4 and progresses to full weightbearing by week 10 to 12.