Press-Fit Bone-Anchored Prosthesis for Individuals with Transtibial Amputation.

Abstract

Background: This video article describes the use of bone-anchored prostheses for patients with transtibial amputations, most often resulting from trauma, infection, or dysvascular disease. Large studies have shown that about half of all patients with a socket-suspended artificial limb experience limited mobility and limited prosthesis use because of socket-related problems. These problems occur at the socket-residual limb interface as a result of a painful and unstable connection, leading to an asymmetrical gait and subsequent pelvic and back pain. In almost all of these cases, a bone-anchored prosthesis may result in substantial improvements in mobility and quality of life.

Description: This technique is preferably performed in a single-stage procedure. Preoperative implant planning is imperative when designing the custom-made implant (BADAL X, OTN Implants). These images should be visible on screen in the operating room throughout the procedure to guide the surgeon. The patient is positioned with the knee on a silicone cushion. The planned soft-tissue resection is marked, after which the resection of all layers is performed, including large nerves and neuromas, with high cuts performed under traction. Exposure of the residual bone following revision osteotomy is carried out according to the design. The medullary canal is prepared and perpendicular cutting of the tibial and fibular remnant are performed, with the latter cut at a level 1 to 2 cm higher than the former. The intramedullary component is inserted under fluoroscopic guidance, after which the distal end of the tibia is prepared utilizing the typical drop shape. Two transverse locking screws are inserted with the standard "freehand" technique. The soft tissues are contoured and closed over the implant, after which the stoma is created and the dual cone is mounted. Finally, pressure bandages are applied, and postoperative imaging is performed. After the surgical procedure, most patients stay 1 or 2 nights in the hospital, depending on the magnitude of the surgery (e.g., bilateral implantation of a bone-anchored implant) and the patient's comorbidities.

Alternatives: Simultaneous major leg amputation and bone-anchored prosthesis implantation is not advocated as treatment. First, a rehabilitation program with a socket-suspended prosthesis should be completed before patients can apply for a bone-anchored prosthesis. After rehabilitation, satisfaction with a prosthetic socket may be adequate, thereby not indicating the need for a bone-anchored prosthesis. Contraindications for bone-anchored implant surgery include severe diabetes (with complications), severe bone deformity, immature bones, bone diseases (i.e., chronic infection or metastasis), current chemotherapy, severe vascular diseases, pain without a clear cause, obesity (body mass index >30 kg/m²), and smoking.

Rationale: Approximately half of patients who undergo a major lower-limb amputation are able to utilize an artificial leg acceptably well with a socket-suspended prosthesis. However, the other half of patients experience limitations resulting in reduced prosthesis use, mobility, and quality of life. Limb-to-prosthesis energy transfer is poor because of the so-called "pseudojoint" (i.e., the soft-tissue interface), and gross mechanical malalignment is common. Furthermore, transtibial amputees may experience irritation from pistoning and suction at the residual limb-socket interface. These issues result in skin problems and difficulties with socket fit because of fluctuation in the size of the residual limb size, resulting in a decrease in overall satisfaction and confidence in mobility. An osseointegration implant creates a direct skeletal connection between the residual limb and artificial leg, in which energy transfer is optimal and mechanical alignment is radically improved.

Expected outcomes: In an unpublished prospective study performed at our center with a 5-year follow-up, a total of 21 patients with a transtibial amputation received a titanium tibial osseointegration implant (BADAL X, OTN Implants) with additional proximal transverse locking screw fixation for primary stability. Most patients were male (71%), had a traumatic amputation (67%), and underwent a 2-stage surgical procedure (64%). Prosthesis wearing time was measured with use of the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) Prosthetic Use Score (PUS), and health-related quality of life was measured using the Q-TFA Global Score (GS). Both measurements improved significantly comparing preoperative baseline values using a socket-suspended prosthesis to all follow-up moments after bone-anchored prosthesis treatment: Q-TFA PUS baseline 53, 6-month 90, 1-year 88, 2-years 91, 5-years 89; Q-TFA GS baseline 38, 6-month 71, 1-year 80, 2-year 77, 5-year 78. The third question of the Global Score was separately assessed. This question asks, "How would you summarize your overall situation as an amputee?" A clear tendency for improvement was observed as 43% stated their situation to be "extremely poor" or "poor" at baseline, while only 19% stated their situation to be "good" or "extremely good", which changed at 5-year follow-up to 6% stating the situation to be "poor" and 94% stating the situation to be "good" or "extremely good". An implant survival of 95.5% was achieved at 5-year follow-up. One individual experienced progressive septic implant loosening resulting in a through-knee amputation. The individual had undergone primary transtibial amputation due to dysvascular problems, and preoperative duplex ultrasonography had shown no signs of aortoiliac occlusive disease. However, repeat examination displayed dysvascular disease progression, with the patient admitting having refrained from nicotine cessation. No bone infection, periprosthetic fracture, intramedullary stem breakage, or aseptic loosening occurred. Nine individuals experienced 12 events of low-grade soft-tissue infections all successfully treated with oral antibiotics. Nine individuals also experienced 12 events of high-grade soft-tissue infections, successfully treated with oral antibiotics 8 times, and requiring parenteral antibiotics or surgical treatment in 1 and 3 cases, respectively. This resulted in an infection/implant-year used ratio of 0.24. Hypergranulation tissue and stoma tissue redundancy occurred 2 and 4 times, respectively. We concluded that the mid-term results of this type of treatment were acceptable, especially in patients with nonvascular amputations. Since 2020, we have performed the surgery using a single-stage procedure as the standard choice, based on cost and convenience factors, and the results seem to be no different from our previous 2-stage strategy (unpublished data).

Important tips: Preoperative implant planning: the procedure should be guided by comprehensive surgical instructions and use a custom-made implant design, with the aim of performing the procedure in a single stage.Patient positioning and setup: a knee cushion support may be beneficial.Soft-tissue marking: plan the resection area liberally, and plan the stoma anterior to the surgical approach (if not possible, directly in the wound).Soft-tissue correction and exposure of residual bone: liberally resect soft-tissue redundancy.Revision osteotomy with guided shortening: utilize water-cooled power sawing.Medullary canal preparation and the perpendicular osteotomy plane: use fluoroscopy to guide drilling.Insertion of the intramedullary component: in case of little resistance, use bone morphogenetic protein-2 (InductOs; Medtronic) and bone impaction grafting for augmentation.Use transverse locking screws for primary stabilization of the implantSoft-tissue contouring and closure: do not close the muscle fascia over the implant.Aperture creation and dual-cone insertion: perform a 2-stage procedure only in cases with bone reconstruction, with the second stage performed after a 10 to 12-week interval.Bandage: leave the bandage applied for 48 hours.Postoperative imaging and follow-up: our institutional follow-up schedule is 6 months, then 1, 2, 5, and 10 years postoperatively.Introduction rehabilitation protocol: The standard program is 4 weeks and starts 3 weeks after a single-stage surgery. Patients may fully load the prosthesis at the start of the rehabilitation, provided the pain score does not exceed a 5 on a scale from 0 to 10.Rehabilitation: make videos to compare patient mobility at postoperative time points and to assess progression.Results and conclusions: implant loosening is rare, and soft-tissue infections typically occur often in the first 2 years and require nonoperative treatment.

Acronyms and abbreviations: BAP = bone-anchored prosthesisBMI = body mass indexCT = computed tomographyOTI = osseointegration tibia implantK-wire = Kirschner wireDCA = dual-cone adapterBIG = bone impaction grafting.