A Population-Based Assessment of Potential Patients for Targeted Muscle Reinnervation
Charles T Tuggle, MD, MHS; Cheryl K Zogg, MSPH, MHS; Fatima Mirza, MPH; James E Clune, MD; Yale University, New Haven, CT
Targeted muscle reinnervation (TMR) is a surgical procedure used to greatly improve motor control in upper limb prostheses. Currently, a small number of institutions in the US perform TMR. There is limited information on the number of patients who could potentially benefit from TMR and use of a pattern-recognition myoelectric prosthesis. The objective of this study was to quantify and characterize patients eligible for TMR in the US on a national scale.
Patients undergoing transhumeral or shoulder disarticulation amputations secondary to trauma or oncologic resection were identified in the 2001-2014 NIS. Discharge weights were used to generate national estimates. Differences in patient-level demographic/clinical parameters, and hospital-level factors were compared based on differences in amputation level and index indication using standard descriptive statistics. Annual hospital volume and the average number of patients per year were calculated. Distances relative to known TMR centers in Maryland/Texas were compared to presently unmet need in New York using geospatial mapping of state-level discharge registry data.
A weighted total of 4,477 patients met inclusion criteria (overall mean 320 patients/year), of whom 3,561 (78.5%) underwent transhumeral amputation and 978 (21.6%) underwent shoulder disarticulation. The majority of patients undergoing both operations were White (59.5%, 55.7%), males (68.5%, 63.5%), aged 18-64y (69.9%, 63.6%). More than one-half of patients requiring transhumeral amputation did not present with any CCI-recorded comorbidities. Patients, depending on age, tended to be insured by either private insurance (37.0%, 32.9%) or Medicare (26.7%, 35.2%). The majority of hospitals performing these procedures were large (76.3%, 70.3%), urban teaching hospitals (81.4%, 87.6%).
Pediatric (63.5% of 17 amputations/year) and adult (78.6% of 222 amputations/year) amputations were most often trauma-related, while amputations in the elderly (67.0% of 87 amputations/year) were most often performed for cancer management. Median hospital volume was 6 amputations per year. Annual rates of amputations did not change over time but were concentrated in ~100 hospitals, many of which serve geographic areas outside of currently available TMR range.
These findings represent the first nationwide study to identify and examine upper extremity amputation patients eligible for TMR, demonstrating that there are many more patients who could benefit from TMR than our system's current operative and prosthetic capacity. Eligible patients tend to be young, healthy, and privately-insured. Designating regional centers that offer TMR may streamline the operative management and fitting of advanced prostheses for upper extremity amputees, greatly improving the lives of affected patients after amputation.
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