Limb Amputation and Limb Deficiency

Timothy R. Dillingham, MD, Liliana E. Pezzin, PhD, Ellen J. Mackenzie, PhD

Disclosures

South Med J. 2002;95(8) 

In This Article

Materials and Methods

Data from the Healthcare Cost and Utilization Project, Nationwide Inpatient Sample (HCUP-NIS) from 1988 through 1996 were used to develop estimates of limb-loss and limb-deficiency incidence rates in the United States. The HCUP-NIS, a component of the Agency for Healthcare Research and Quality (AHRQ) Healthcare Cost and Utilization Project (HCUP3), is a stratified probability sample designed to approximate a 20% nationwide sample of community, nonfederal, short-term hospitals. Excluded from the database are admissions to federal hospitals, psychiatric hospitals, and substance-abuse treatment facilities. The HCUP-NIS contains discharge abstracts for all stays in the sampled hospitals, which total approximately 6.5 million records annually. Data for the 1988-1992 HCUP-NIS were drawn from a sampling frame that included hospitals in 11 states; by 1996, the sampling frame had expanded to encompass hospitals in 19 states. For all years, hospital-specific weights were developed to obtain national estimates of hospital and discharge parameters.

Data abstracted for each hospital discharge include patient demographics, a principal diagnosis and up to 14 secondary diagnoses coded using the Clinical Modification of the 9th Revision of the International Classification of Diseases (ICD9-CM), a primary procedure and up to 14 secondary procedures, length of hospital stay, discharge status and destination, and expected primary source of payment for the hospital charges.

As a first step, an algorithm was developed to select all patients discharged from acute-care hospitals nationwide between 1988 and 1996 who had either an amputation-related procedure or a limb-deficiency-related diagnosis (referred to as limb-loss-related discharges). Specifically, the initial study population consisted of discharges with (1) a procedure code for upper-limb or lower-limb amputation (ICD-9CM 84.00-84.09, 84.10-84.19, or 84.91); (2) a diagnosis code of traumatic amputation (ICD-9CM 885.0-887.7 or 895.0-897.7); or (3) a diagnosis code identifying congenital deformities of the limbs (ICD-9CM 755.2-755.4).

All limb-loss-related discharges were then classified hierarchically into mutually exclusive categories according to etiology as (1) trauma-related (ICD 810-839, 880-884, 885-887.7, 895-897.7, 925-929, 942-949, or 958-959); (2) congenital deficiency (newborn discharge designation in combination with a congential reduction anomaly ICD 755.2-755.29, 755.3-755.39, or 755.4); (3) cancer-related (ICD 170.4-170.8, 171.2-171.3, or 172.6-172.7); (4) dysvascular (ICD 040.0, 250.0-250.9, 440.0-440.9, 442.0-442.9, 443.0-443.9, 444.0-444.9, 682.0-682.9, 686.0 -686.9, 707.0-707.9, 728.86, 730.0-730.9, or 785.0-785.9); or (5) other etiology. Records grouped in the "other etiology" category were then examined in depth. Whenever appropriate, records were reclassified into 1 of the 4 main groups, and our classification algorithm was refined to better reflect the etiology of limb loss. For example, discharges with a cause of injury (E-code) related to trauma, such as "late effects of accident" or "injury to blood vessel," were moved into the trauma-related category. The refinement of our classification algorithm continued until records could no longer be categorized into one of the more specific groups. The final category of "other etiology," which contained less than 2% of the sample, primarily included discharges for amputations due to complications of procedures, internal derangement of joints, and other joint disorders. These unclassified discharges were excluded from analyses.

An important part of our effort was the identification of discharges that were presumed to be new or incident cases of limb deficiency and amputation. For instance, discharges that were for rehabilitation (V57.0-V57.9) or reattachment of extremity (ICD 84.21-84.29) were excluded from our analysis of incidence. Discharge records of non-newborn patients that had a code indicative of limb deficiency but no other limb-loss-related diagnosis and no limb-loss-related procedure codes, were also excluded, since it was most likely that these discharges did not identify new cases of limb deficiency, but rather individuals for whom the congenital limb deficiency was included as a comorbid diagnosis. New cases of congenital deficiency, therefore, were identified based on a diagnosis of limb deficiency combined with a newborn code noted in the record for that admission.

Etiology-specific limb-loss-related discharges were further classified into mutually exclusive categories according to the level of the amputation. Lower-limb levels for dysvascular, trauma-related, and cancer-related amputations were classified as toe(s), foot, ankle, transtibial (below-knee), through-knee, transfemoral (above-knee), hip disarticulation, and pelvic. Upper- limb amputations were classified as thumb, finger(s), hand, wrist, transradial, through-elbow, transhumeral, shoulder, and forequarter amputation levels. With the exception of trauma-related discharges for which specific codes for bilateral upper or bilateral lower limb amputations were available, whenever 2 amputation procedures were done during the same hospitalization, the most proximal level of amputation was chosen for classification. Discharges involving upper-limb congenital deficiencies were classified according to type and level into transverse, longitudinal hand, longitudinal radial, and longitudinal humeral. Lower-limb congenital deficiencies were classified as transverse, longitudinal toe, longitudinal foot, longitudinal fibular, longitudinal tibial, and longitudinal femoral. As with amputation levels, limb-deficiency types were classified into mutually exclusive categories, with lower-limb anomalies hierarchically superceding upper-limb anomalies whenever multiple deficiencies were identified during a single discharge with the newborn designation. Multiple-limb anomalies were identified when they occurred, however.

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