Ertl Below-Knee Amputation Using a Vascularized Fibular Strut in a Nontrauma Elderly Population: A Case Series

Dynamic topology optimization of 3D-Printed transtibial orthopedic implant using tunable isotropic porous metamaterials

In this paper, we introduce the design and manufacturing process of a transtibial orthopedic implant. We used medical-grade polyurethane polymer resin to fabricate a 3D porous architected implant with tunable isotropy, employing a high-speed printing method known as Continuous Liquid Interface Production (CLIP). Our objective is to enhance the weight-bearing capabilities of the bone structures in the residual limb, thereby circumventing the traditional reliance on a natural bridge. To achieve a custom-made design, we acquire the topology and morphology of the residual limb as well as the bone structure of the tibia and fibula, utilizing computed tomography (CT) and high-resolution 3D scanning. We employed a dynamic topological optimization method, informed by gait cycle data, to effectively reduce the mass of the implant. This approach, which differs from conventional static methods, enables the quantification of variations in applied forces over time. Using the Euler-Lagrange energy approach, we propose the equations of motion for a homologous multibody model with three degrees of freedom. The versatility of the Solid Isotropic Material with Penalization (SIMP) method facilitates the integration of homogenization methods for microscale porous architectures into the optimized domain. The design of these porous architectures is based on a bias-driven tuning symmetry isotropy of a Triply Periodic Minimal Surface (Schwarz Primitive surface). The internal porosity of the structure significantly reduces weight without compromising the isotropic behavior of the implant.

Effect of Function-Based Approach to Nontraumatic Major Lower Extremity Amputation on 5-Year Mortality

BACKGROUND

Five-year mortality rates after lower extremity amputation in the chronic wound population have long been regarded as high and inevitable. We theorize that function-based surgical technique and multidisciplinary care improve mortality and assess our institution's mortality rates after major lower extremity amputation (MLEA).

STUDY DESIGN

We performed a retrospective review of patients who underwent primary nontraumatic MLEA at our institution from 2010 to 2013. Major amputations included below knee amputation, through knee amputation, and above knee amputation. Our function-based surgical approach to MLEA is guided by 4 tenets: (1) optimization of limb biomechanics, (2) maximal soft tissue preservation, (3) multidisciplinary team approach, and (4) addressing nerves during primary amputation to prevent postamputation pain. Kaplan-Meier analysis and Cox regression were performed to estimate cumulative 5-year mortality and to identify predictors of 5-year mortality, respectively.

RESULTS

A total of 188 patients underwent MLEA. Median Charlson Comorbidity Index was 4. Estimated 5-year mortality was 40% overall and 43% for diabetic patients. When stratified by amputation level, 5-year mortalities were 36.3% for below knee amputation, 60.9% for through knee amputation, and 44.0% for above knee amputation. Charlson Comorbidity Index (hazard ratio 1.24, p < 0.001) and end-stage renal disease (hazard ratio 3.38, p < 0.001) were the strongest predictors of 5-year mortality.

CONCLUSIONS

We demonstrate the lowest mortality rate reported for MLEA. Improved functional and mortality outcomes can be achieved with a function-based surgical approach to MLEA and close follow-up by a multidisciplinary team. Future studies, using standardized reporting of mortality data and incorporating patient-reported outcomes, are warranted to correlate return to function and mortality.

Targeted Muscle Reinnervation Improves Pain and Ambulation Outcomes in Highly Comorbid Amputees

BACKGROUND

Approximately 200,000 people undergo a lower extremity amputation each year. Following amputation, patients suffer from chronic pain, inability to ambulate, and high mortality rates. Targeted muscle reinnervation is a nerve transfer procedure that redirects transected sensory and mixed nerves into motor nerves to treat neuroma and phantom limb pain. This study evaluates outcomes with prophylactic targeted muscle reinnervation at the time of below-knee amputation.

METHODS

This is a cohort study comparing 100 patients undergoing below-knee amputation with primary targeted muscle reinnervation and 100 patients undergoing below-knee amputation with standard traction neurectomy and muscle implantation. Outcome metrics included the presence of residual and phantom limb pain, pain severity, opioid use, ambulation ability, and mortality rates.

RESULTS

The targeted muscle reinnervation group was on average 60 years old with a body mass index of 29 kg/m2. Eighty-four percent had diabetes, 55 percent had peripheral vascular disease, and 43 percent had end-stage renal disease. Average follow-up was 9.6 months for the targeted muscle reinnervation group and 18.5 months for the nontargeted muscle reinnervation group. Seventy-one percent of targeted muscle reinnervation patients were pain free, compared with 36 percent (p < 0.01). Fourteen percent of targeted muscle reinnervation patients had residual limb pain, compared with 57 percent (p < 0.01). Nineteen percent of targeted muscle reinnervation patients had phantom limb pain, compared with 47 percent (p < 0.01). Six percent of targeted muscle reinnervation patients were on opioids, compared with 26 percent (p < 0.01); and 90.9 percent of targeted muscle reinnervation patients were ambulatory, compared with 70.5 percent (p < 0.01).

CONCLUSION

Targeted muscle reinnervation reduces pain and improves ambulation in patients undergoing below-knee amputation, which may be critical in improving morbidity and mortality rates in this comorbid patient population.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Translating Technique into Outcomes in Amputation Surgeries

The department of surgery at Washington University is putting increased emphasis on outcomes for amputees. This multidisciplinary effort begins with choosing the correct surgery and incorporating the latest technical advances in amputation surgery.

Management of advanced plexiform neurofibromatosis of the foot presenting with skeletal deformation and intractable pain: an indication for proximal amputation

Plexiform neurofibromas of the foot are rare and often present with significant pain, deformity, and functional impairment secondary to their locally invasive behavior. While treatment has traditionally focused on attempts at radical resection, a lack of consensus among surgeons has hindered the establishment of a well-defined algorithm to guide the management of these highly co-morbid peripheral nerve sheath tumors. We present the case of an advanced plexiform neurofibroma of the right foot in a 24-year-old male with neurofibromatosis type 1. The patient presented following accelerated tumor growth with extensive osseous erosion, intractable pain, and progressive ankle instability that limited his capacity to ambulate and wear shoes. A modified transtibial amputation with a vascularized fibular bone graft (Ertl procedure) was performed without complication. Following graduated rehabilitation, postoperatively, the patient regained functional independence and was able to ambulate without pain in a customized prosthesis after 3 months. Plexiform neurofibromas of the foot present a complex challenge for foot and ankle surgeons. On the basis of our experience and previously reported cases, we advocate for amputation over aggressive attempts at advanced limb salvage for patients with extensive skeletal destruction, joint instability, and/or intractable pain caused by tumor mass effect.