Chronic Nonunion in a Patient With Bilateral Supracondylar Distal Femur Fractures Treated Successfully With Twice Daily Low‐Intensity Pulsed Ultrasound

A 77-year-old woman was involved in a motor vehicle accident and sustained an open comminuted left distal femur fracture and a closed right distal femur fracture. She initially underwent irrigation and debridement of the open left distal femur wound, open reduction, internal fixation (ORIF) of the left distal femur fracture with an LCP (locking condylar plate), and ORIF of the right distal femur fracture with the LISS (less invasive stabilization system) plate. Early failure and instability of the right LISS plate from proximal screws disengaging from the femoral shaft was found 11 days later. This required revision surgery with removal of the LISS plate and fixation with an LCP. Eight months later, as a result of right distal femur nonunion, she underwent removal of hardware including the LCP, takedown of pseudoarthrosis, and repeat ORIF of the right distal femur with a new LCP and right iliac crest autologous bone graft. The left femur was not healing, but overall bone position was maintained with no overt hardware failure, thus delaying nonunion determination. Ultimately, 14 months from the time of her accident, as a result of fracture of the proximal femoral screws and infection of hardware, she underwent irrigation and debridement, left distal femur removal of hardware, takedown of nonunion, and refixation with a new, longer LCP and new, nonlocking and locking screws. Nineteen months from the time of her initial accident, she presented to a university-based multidisciplinary musculoskeletal rehabilitation clinic for her initial assessment by the authors (Z.W., J.F.) with bilateral nonunions involving her supracondylar femurs. She was treated with low-intensity pulsed ultrasound (LIPUS) applied directly to the nonunion sites at the distal femurs. The LIPUS was applied for 20 minutes, twice daily, with each fracture site receiving 2 treatments per day for a total of 4 uses daily, for a period of 8 weeks. No adverse effects of daily application of the device were noted by the patient. A program of gentle passive and active range of motion exercises was also initiated. After 2 months of ultrasound therapy, radiographs showed solid osseous union across the fracture sites bilaterally. At 8-month follow-up, approximately 3 years from her initial surgery, her fractures continue to show union. She does not require analgesics and is able to ambulate independently with the use of a walker. Ultrasound technology exists in a variety of different formats, ranging from high-intensity, focused ultrasound for tissue ablation and surgical excision to low-intensity, short-burst ultrasound for diagnostic imaging and therapeutic purposes. Commercially available LIPUS devices were approved by the US Food and Drug Administration for conservative management of acute fresh fractures in 1994 and the treatment of nonunions in 2000. These devices generate pressure waves that are delivered by means of a transducer applied directly externally to the skin with water-based gel. The signal consists of a 1.5-MHz ultrasound wave pulsed at 1 kHz with a 20% duty cycle at an intensity of 30 mW/cm2 spatial average and temporal average. Treatment is generally self-administered to the fracture site on a daily basis for 20 minutes until fracture healing, and can be used in a home-based setting. The precise mechanism of action of LIPUS is unknown. It has been postulated that ultrasound wave-mediated mechanical stimulation of transmembrane molecules can influence downstream events within the cell microenvironment, inducing expression of genes that exert positive effects on fracture healing [1, 2]. It has also been hypothesized that ultrasound may increase blood flow to fracture sites [3] and potentially increase intracellular calcium concentration [4], which induces proteoglycan synthesis contributing to calcification and maturation of cartilage. Evidence for the clinical application of LIPUS can be found in the conservative management of acute fractures of the tibia, distal radius, and scaphoid [5-7]. Despite the lack of randomized trials and significant population heterogeneity, several case series studies have shown promise in the treatment of established nonunions (Table 1) [8-13]. Jingushi et al [12] examined long bone fractures treated postoperatively with ultrasound and found close to 90% healed when ultrasound was applied within 6 months. They suggested LIPUS be considered first-line treatment for postoperative nonunions. Romano et al [14] summarized that LIPUS is an efficacious, conservative, and safe device with reported union rates of 70% to 93%, relatively few side effects, and potential avoidance of revision surgery and thus healthcare saving costs of approximately $13, 000-$15, 000 per case. Chan et al [15] demonstrated a dose-dependent response to LIPUS in animal models in which enhanced bone formation was seen with protracted courses of therapy. The present patient sustained bilateral supracondylar femur fractures (Figure 1), and despite revision surgeries continued to demonstrate persistent bilateral nonunions (Figure 2). After the twice daily application of LIPUS, both sites healed within 2 months (Figure 3). Compared with the literature, the patient's healing time was accelerated, but the age of the fracture and time elapsed since the last surgery were similar to previously published data as seen in Table 1. Her rapid recovery could potentially be attributed to a dose-dependent effect given the twice daily application of LIPUS. Tramatic bilateral supracondylar femur fractures. Bilateral distal femur nonunion prior to low-intensity pulsed ultrasound. Osseous union 2 months after low-intensity pulsed ultrasound therapy. To our knowledge, this is the first case reported in the literature demonstrating the twice daily application of LIPUS to assist with healing of supracondylar distal femur nonunions.

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