Orthopedics

Feature Article 

In-Hospital Morbidity and Mortality of Traumatic Lower-Extremity Amputations

Samuel F. Thompson, MD; Kristopher B. McCall, MD; Dil V. Patel, MD; Wade A. Schwerdtfeger, MD; Julie Stoner, PhD; Kimberly Hollabaugh, MS; David C. Teague, MD

Abstract

Traumatic lower-extremity amputations often result in complications and surgical revisions. The authors report the in-hospital morbidity and mortality of traumatic lower-extremity amputations at a metropolitan level I trauma center for a large rural region and compare below-knee (BK) vs higher-level amputation complications. They retrospectively reviewed 168 adult patients during a 10-year period (2005 to 2015) who had a traumatic injury to the lower extremity that required an amputation. Main outcome measurements included amputation level, complication rates, intensive care unit (ICU) admission rates, length of stay, total trips to the operating room (OR), and Injury Severity Score (ISS). A total of 95 patients had through-knee/above-knee (TK/AK) amputations, and 73 patients had BK amputations. The majority of injuries occurred in the non-urban setting. The TK/AK group had higher ICU admission rates (76% vs 35%, P<.0001), longer overall hospital length of stay (22.0 vs 15.5 days, P=.01), more total OR trips (6.5 vs 5.0, P=.04), and higher ISS (17.0 vs 11.5, P<.0001). A complication was experienced by 64% of all patients during the initial hospitalization. The TK/AK group had higher complication rates than the BK group, including wound infection, pulmonary embolus, rhabdomyolysis, compartment syndrome, and death. Patients with TK/AK traumatic amputations have a greater burden of injury with higher complication rates, increased ICU admissions, increased length of stay, and increased ISS and require more return trips to the OR compared with patients with BK amputations. [Orthopedics. 2020;43(6):e561–e566.]

Abstract

Traumatic lower-extremity amputations often result in complications and surgical revisions. The authors report the in-hospital morbidity and mortality of traumatic lower-extremity amputations at a metropolitan level I trauma center for a large rural region and compare below-knee (BK) vs higher-level amputation complications. They retrospectively reviewed 168 adult patients during a 10-year period (2005 to 2015) who had a traumatic injury to the lower extremity that required an amputation. Main outcome measurements included amputation level, complication rates, intensive care unit (ICU) admission rates, length of stay, total trips to the operating room (OR), and Injury Severity Score (ISS). A total of 95 patients had through-knee/above-knee (TK/AK) amputations, and 73 patients had BK amputations. The majority of injuries occurred in the non-urban setting. The TK/AK group had higher ICU admission rates (76% vs 35%, P<.0001), longer overall hospital length of stay (22.0 vs 15.5 days, P=.01), more total OR trips (6.5 vs 5.0, P=.04), and higher ISS (17.0 vs 11.5, P<.0001). A complication was experienced by 64% of all patients during the initial hospitalization. The TK/AK group had higher complication rates than the BK group, including wound infection, pulmonary embolus, rhabdomyolysis, compartment syndrome, and death. Patients with TK/AK traumatic amputations have a greater burden of injury with higher complication rates, increased ICU admissions, increased length of stay, and increased ISS and require more return trips to the OR compared with patients with BK amputations. [Orthopedics. 2020;43(6):e561–e566.]

Amputation of a mangled extremity is often regarded as the oldest surgical procedure.1 Major innovations in the history of amputation surgery include the use of a tourniquet and vessel ligation by French surgeon Ambroise Pare in the 16th century, the posterior flap amputation described by James Yonge in the 17th century, the “Guillotine” amputation described by Guillot in the 18th century, and the advent of antisepsis and anesthesia in the mid-19th century.2 More modern surgical advancements led to a dramatic decrease in mortality associated with amputations, and modern rehabilitation and prosthetic advancements greatly improve functional outcomes following amputation of a lower limb.

Lower-extremity amputation level affects functional outcomes following surgery. Energy cost of ambulation is greater for more proximal-level amputations.3 Patients with below-knee (BK) and unilateral amputations enjoy greater quality of life and improved functional outcome scores compared with those with through-knee (TK), above-knee (AK), and bilateral amputations.4 However, controversy exists when comparing functional outcomes between TK and AK amputations.4,5

Trauma is a significant cause of lower-extremity amputations in the United States, accounting for 17% of major lower-extremity limb loss in 2005.6 More than two-thirds of trauma-related amputations occur among adolescents and young working-age adults.7,8 These injuries disproportionately affect men.5,9,10 Traumatic lower-extremity amputations often result in complications and surgical revisions.9–11 Current understanding of the in-hospital morbidity and mortality associated with traumatic lower-extremity amputations of varying anatomic levels is limited.

The principal aim of this study was to characterize the in-hospital morbidity and mortality of traumatic lower-extremity amputation patients treated at a metropolitan level I trauma center for a large rural region. The authors hypothesized that patients having TK and AK amputations experience an increased burden of injury with longer hospital stays, more surgical procedures, and more complications compared with those sustaining amputations below the level of the knee.

Materials and Methods

After institutional review board approval was obtained, the authors retrospectively reviewed all patients who had a traumatic lower-extremity injury requiring amputation at their institution between January 1, 2005, and December 31, 2015. Patients were treated at a level I trauma center that serves a metropolitan population of 1.25 million people and has a catchment area of 68,595 square miles, 98% of which consists of rural regions. Eligible patients sustained traumatic injuries to the lower extremity that required BK or more proximal-level amputations. These injuries included traumatic amputations, major soft tissue injuries (degloving and severe crush injuries), dysvascular extremities, Gustilo type IIIB and IIIC fractures, and severe foot injuries. Patients were excluded if they had been transferred from another facility more than 24 hours after injury, had an amputation performed at the referring hospital prior to transfer, or were younger than 15 years. Amputations were completed by both orthopedic trauma surgeons and on-call orthopedic surgeons trained in other subspecialties.

Demographic data were recorded, including age, sex, body mass index (BMI), location of injury, smoking status, and history of diabetes mellitus. Injury characteristics included mechanism of injury, level of amputation, intensive care unit (ICU) admission rates, total length of hospital stay, total length of intensive care unit stay, number of total trips to the operating room (OR), 30-day all-cause readmission rates, and Injury Severity Score (ISS). In addition, the type and number of complications were recorded, including wound infection requiring debridement in the OR, wound dehiscence requiring a return trip to the OR for closure, deep venous thrombosis (DVT), pulmonary embolus, rhabdomyolysis, compartment syndrome, and death.

Amputations were categorized as BK or TK/AK. Hip disarticulations were included in the TK/AK category. Patients with amputations of both lower extremities were classified according to the higher-level amputation between the extremities. The death date was used as the date of discharge to calculate length of stay in patients who died. Injury location ZIP codes were used to categorize urban vs non-urban injuries. US Census data from 2010 were used to define an urban area as a population of 50,000 or more.

Proportions were compared between amputation levels using Fisher’s exact test for small frequency counts or chi-square test for nominal categorical measures. Tests for trend were conducted using Cochran-Armitage exact trend test for ordinal categorical measures. Continuous measures were compared between amputation levels using the Wilcoxon rank-sum test. Logistic regression models were used to compare associations between amputation levels and other demographic and clinical outcomes.

Results

A total of 869 patients required an amputation at the authors’ institution during the study period. A total of 168 patients (126 male, 42 female) had a traumatic lower-extremity amputation and met inclusion criteria (Table 1). Seven patients had an amputation of both lower extremities, totaling 175 lower-extremity amputations. Eighty-one (46.3%) amputations were AK, 20 (11.4%) were TK, and 74 (42.3%) were BK. Seventy-three patients were in the BK group, and 95 patients were in the TK/AK group. In the BK group, 55 patients were male and 18 patients were female. In the TK/AK group, 71 patients were male and 24 were female. The median age for all patients was 37.0 years (range, 15.0–89.0 years). The median age of the BK group and the TK/AK group was 35.0 and 41.0 years, respectively (P=.17). The median BMI for all patients was 28.0 kg/m2. The median BMI of the BK group and the TK/AK group was 26.7 and 28.4 kg/m2, respectively (P=.08).

Patient Characteristics

Table 1:

Patient Characteristics

The most common mechanisms of injury were motorcycle (26%) and motor vehicle (21%) collisions (Table 2). Additional injury mechanisms included motor vehicle vs pedestrian (11%), auger or other farm implement (10%), gunshot wound (9%), work-related crush injuries (6%), oil field crush injuries (3%), forklift accidents (3%), falls from a height (3%), and all-terrain vehicle accidents (3%). Less common mechanisms of injury included pedestrian vs train, dog attack, boating accident, plane crash, assault, and blast injury.

Mechanism of Injury

Table 2:

Mechanism of Injury

The entire cohort experienced a high complication occurrence (Table 3). Overall, 109 (65%) patients experienced a complication. In the TK/AK group, 70 (74%) patients experienced at least 1 complication, compared with 39 (53%) patients in the BK group (P=.01). Wound infection was the most common complication, occurring in 70 (42%) total patients. Wound infection occurred in 42 (44%) patients in the TK/AK group and 28 (38%) patients in the BK group (P=.53). Wound dehiscence occurred in 10 (14%) patients in the BK group and 4 (4%) patients in the TK/AK group (P=.05). Deep venous thrombosis occurred in 21 (22%) patients in the TK/AK group and 5 (7%) patients in the BK group (P=.01). Pulmonary embolus occurred in 4 (4%) patients in the TK/AK group and in no patients in the BK group (P=.13). Rhabdomyolysis occurred in 14 (15%) patients in the TK/AK group and in 2 (3%) patients in the BK group (P=.01). Intensive care unit admission rates and hospital length of stay were higher among patients with rhabdomyolysis compared with those without rhabdomyolysis (81% vs 56% [P=.06] and 31.5 days vs 19 days [P=.26], respectively). Compartment syndrome occurred in 5 (5%) patients in the TK/AK group and 2 (3%) patients in the BK group (P=.7). Seven (7%) patients in the TK/AK group died, whereas 1 (1%) patient in the BK group died (P=.14). Five patients died of cardiac arrest, 2 patients died of septic shock, and 1 patient died of a traumatic brain injury. The median number of days from injury until death was 7 in the TK/AK group and 28 in the BK group (P=.19).

Complications

Table 3:

Complications

The ICU admission rates were higher in the TK/AK group (Table 4). Sixty-nine (73%) patients in the TK/AK group were admitted to the ICU, whereas 25 (34%) patients in the BK group required ICU admission (P<.0001). The odds of having a TK/AK amputation were higher in patients admitted to the ICU (odds ratio, 5.8; 95% confidence interval, 2.6–12.7; P<.0001). The median ICU length of stay was similar in the TK/AK group compared with the BK group: 9.5 days (range, 2–60 days) and 9.0 days (range, 2–32 days), respectively (P=.36). The overall median length of hospital stay for all patients was 20 days (range, 1–100 days). Patients in the TK/AK group had a longer median length of stay than those in the BK group: 22 days (range, 3–100 days) and 15.5 days (range, 1–84 days), respectively (P=.01). The median number of required trips to the OR for management of the amputated extremity in the TK/AK group was 6.5 compared with 5.0 in the BK group (P=.04). The median number of total required trips to the OR during the hospital stay (including nonorthopedic procedures) was also greater in the TK/AK group (6.5) than in the BK group (5.0) (P=.04). The median number of trips to the OR prior to amputation formalization was 5.0 in the TK/AK group and 4.0 in the BK group (P=.23). There was no difference in the number of trips to the OR to manage a complication between the 2 groups: 2.0 trips in the TK/AK group and 2.0 trips in the BK group (P=.38). Thirty-day readmission rates were higher in the BK group (18%) than in the TK/AK group (6%) (P=.03).

Injury and Outcome Characteristics

Table 4:

Injury and Outcome Characteristics

Injury Severity Score data were available for 94% of patients. The median ISS was higher in the TK/AK group (17.0) than the BK group (11.5) (P<.0001). The Abbreviated Injury Scale (AIS) abdomen score was 3+ in 20% of patients in the TK/AK group and 9% of patients in the BK group (P=.05).

The majority of patients in both groups had amputations in the non-urban setting: 65.8% of BK amputations and 58% of TK/AK amputations occurred in the non-urban setting (P=.28). Sixty-eight percent of patients injured in non-urban locations experienced at least 1 complication, compared with 63% of patients injured in urban settings; however, this difference did not reach statistical significance (P=.6). Mortality rates were greater among patients injured in urban settings compared with non-urban settings: 9% and 1%, respectively (P=.03). However, no other complications were significantly different between the urban and non-urban groups.

Discussion

Trauma-related lower-extremity amputations are associated with significant early morbidity and mortality as well as poor long-term functional outcomes.5,11–13 Consistent with previous reports, the current authors found a steep in-hospital burden of injury across all patients. The overall complication rate was 65%, with nearly 3 in 4 patients in the TK/AK group experiencing a complication. The most common complication was wound infection, occurring in 42% of patients studied. Nearly 5% of patients died during their initial hospital stay. These injuries were associated with multiple OR trips, high ISS, and extended ICU and hospital length of stay.

Limited data have been published on early complications and outcomes following traumatic lower-extremity amputations. Using the National Trauma Data Bank, Low et al10 reviewed 2879 patients who underwent major lower-extremity amputations secondary to trauma. They found that 27.5% of patients experienced a major postsurgical complication. In their cohort, hospital length of stay averaged 22.7 days, and overall in-hospital mortality was 6.2%. Increased delay of time to initial procedure and African American race were associated with higher odds of postsurgical complications and longer hospital length of stay. In a retrospective review of 74 traumatic lower-extremity amputations managed at a large metropolitan trauma center, Kobayashi et al9 reported an overall complication rate of 32.4%. In their cohort, the overall mortality rate was 4.1%, median ISS was 16, median length of hospital stay was 16 days, and median ICU length of stay was 7 days.

To the current authors’ knowledge, no study has previously compared in-hospital morbidity and mortality by level of traumatic lower extremity amputation. The authors found that patients who had TK/AK amputations experienced a greater burden of disease than those in the BK group, with higher rates of DVT, rhabdomyolysis, wound infection, pulmonary embolus, compartment syndrome, and death. Several factors may have contributed to these findings. Injury Severity Scores were higher in the TK/AK group (17.0 vs 11.5, P<.0001). Abbreviated Injury Scale head, AIS chest, and AIS abdomen scores were also higher in the TK/AK group. One would expect increased overall injury severity associated with an amputation to lead to worse early outcomes and higher complication rates. In addition, higher-level amputations are perhaps more likely to result from higher-energy mechanisms with potentially greater wound contamination. The ICU readmission rates, median hospital length of stay, and number of OR trips were also significantly greater for patients in the TK/AK group, which is a reflection of the increased morbidity seen in this group of patients. Rates of wound dehiscence and readmission were significantly higher in the BK group, perhaps owing to the less forgiving soft tissue envelope of the leg compared with the thigh and the likelihood of transtibial amputation level necessarily occurring through or proximate to the zone of injury.

The majority of patients included in this study had injuries in a non-urban setting. Accessibility to trauma center care in the United States varies across geographic regions, and rurality is a known barrier to timely care.14,15 In 2010, nearly 30 million Americans had no access to a level I or level II trauma center within 60 minutes, with rural populations being disproportionally affected.15 Individuals of rural populations are at a significantly increased risk of having serious injuries requiring hospitalization compared with those living in urban settings.16,17 Mortality rates following traumatic injury are also higher among rural residents than non-rural residents, and greater urban-rural disparity in mortality has been observed in the Midwest and South.18 Among the current cohort, the authors found higher mortality rates among patients injured in urban locations than those injured in non-urban settings: 9% vs 1%, respectively. However, sample sizes in these groups were small. Apart from mortality, the authors found no other statistically significant difference in complication rates between patients injured in urban and non-urban settings.

Debate continues regarding limb salvage vs amputation of severe, traumatic lower-extremity injuries. The Military Extremity Trauma Amputation/Limb Salvage study compared outcomes of amputation and limb salvage in a retrospective cohort of 324 service members deployed to Afghanistan or Iraq who had major lower-limb injuries. They found that patients with a unilateral or bilateral amputation had significantly better Short Musculoskeletal Functional Assessment outcomes than patients treated with limb salvage.19 In contrast, the Lower Extremity Assessment Project found similar functional outcomes for limb salvage and amputation in a civilian population. In their prospective, multicenter study of 569 patients with severe leg injuries, no significant differences in Sickness Impact Profile scores were found between the groups at 2 and 7 years after injury.12,20 Regardless of the decision to amputate or attempt limb salvage, long-term functional outcomes for these injuries remain poor, and patients have significant psychological distress with low overall rates of return to work.19–22

Notable limitations of the current study exist. The total number of patients included was relatively small. In addition, data from the trauma registry were missing for 11 patients. The study design was retrospective. Study outcomes were limited to in-hospital morbidity and mortality, and the authors were unable to collect long-term functional outcome data.

Conclusion

Major traumatic lower-extremity amputations result in significant in-hospital morbidity and mortality. Patients having traumatic TK/AK amputations have a greater burden of injury with higher complication rates, increased ICU admissions, longer hospital stays, and increased ISS and require more return trips to the OR compared with patients with BK amputations.

References

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Patient Characteristics

CharacteristicTK/AKBK
Patients, No.a9573
Amputations, No.10174
Male/female, No.71/2455/18
Age, median, y41.035.0
BMI, median, kg/m228.426.7
Current smoker, No.38 (40%)28 (38.4%)
Injured in rural location, No.b55 (57.9%)48 (65.8%)

Mechanism of Injury

MechanismNo.

TotalTK/AK (n=95)BK (n=73)
MCC452322
MVC361620
Pedestrian vs automobile19181
Auger/farm implement17125
GSW1679
Other crush injury1174
Oil field crush injury633
Forklift accident624
Fall550
ATV523
Othera963

Complications

ComplicationNo. (%)P

TK/AK (n=95)BK (n=73)
Wound infection42 (44.2)28 (38.4).53
Wound dehiscence4 (4.2)10 (13.7).05
DVT21 (22.1)5 (6.8).01
Pulmonary embolus4 (4.2)0 (0.0).13
Rhabdomyolysis14 (14.7)2 (2.7).01
Compartment syndrome5 (5.3)2 (2.7).70
Death7 (7.4)1 (1.4).14

Injury and Outcome Characteristics

CharacteristicTK/AK (n=95)BK (n=73)P
LOS, median, d22.015.5.01
ICU admission, No.69 (73%)25 (34%)<.0001
ICU LOS, median, d9.59.0.36
OR trips, median, No.6.55.0.04
Injury Severity Score, median17.011.5<.0001
AIS abdomen score 3+, No.18 (20%)6 (9%).05
Authors

The authors are from the Department of Orthopedic Surgery and Rehabilitation (SFT, WAS, DCT) and the Department of Biostatistics and Epidemiology (JS, KH), University of Oklahoma College of Medicine, and University of Oklahoma School of Medicine (DVP), Oklahoma City, Oklahoma; and the Dedicated Orthopedic Center of East Texas (KBM), Lufkin, Texas.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Samuel F. Thompson, MD, Department of Orthopedic Surgery and Rehabilitation, University of Oklahoma College of Medicine, 800 Stanton L Young Blvd, AAT-3400, Oklahoma City, OK 73104 ( samuel-thompson@ouhsc.edu).

Received: February 14, 2019
Accepted: July 29, 2019
Posted Online: August 06, 2020

10.3928/01477447-20200721-15

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