Structured Abstract
Background
Hip disarticulations are proximal lower extremity amputations with high postoperative complication and mortality rates. The purpose of the study was to evaluate hip disarticulation outcomes at our institution. Targeted Muscle Reinnervation (TMR) is an effective surgical technique shown to reduce pain in amputees. A secondary goal of the study was to evaluate the impact of implementing TMR on this patient population.
Methods
A retrospective review was performed for patients who underwent hip disarticulation with and without TMR between 2009 and 2020. Information on one-year mortality, thirty-day complication rates, operation times, surgical charges, and pain scores was collected.
Results
Fifty-one patients underwent hip disarticulation, eight of which had TMR performed at the time of their hip disarticulation. The one-year mortality rate was 37% with 30-day infection, readmission, reoperation, and rates of 37%, 39%, and 27% respectively. The thirty-day major complication rate was 47% overall but not statistically significantly different between groups. There were no differences between groups with regard to 30-day readmission, reoperation, and infection rates.
Conclusions
Our results represent one of the largest series of hip disarticulation outcomes. Performing TMR at the time of hip disarticulation did not negatively affect outcomes and may be a beneficial adjunct to improve pain. Further research is warranted.
Keywords: Hip disarticulation, Amputation, Targeted muscle reinnervation, Nerves
Abbreviations: Targeted Muscle Reinnervation (TMR), transcutaneous electrical nerve stimulation (TENS)
1. Introduction
Hip disarticulations are proximal lower extremity amputations indicated for a variety of etiologies. Making up only 0.5% of lower limb amputations, hip disarticulations are considered to be radical procedures most commonly performed for cancer, infection, and ischemia (i.e. chondrosarcoma, infected proximal hip hardware, and acute arterial ischemia). Complication rates for this surgery, including events such as infection, wound healing, and hematoma formation, have been reported to be as high as 60%.1,2 The five-year mortality rates for hind-limb amputations are reported in the literature as high as 55%.3 The high morbidity and mortality rate after hip disarticulation makes it is imperative to find solutions to optimize patient outcomes.
Patients with lower extremity amputations often suffer from chronic pain.4,5 A recent study by Mioton et al. demonstrates that patients undergoing proximal lower limb amputation, including hemipelvectomy, are at increased odds of experiencing Phantom Limb Pain (PLP) than their below-knee counterparts.6 No clear management strategy has been proven effective across the board to treat post-amputation pain through a myriad of modalities including pharmacotherapy, physical and occupational therapy, transcutaneous electrical nerve stimulation (TENS) units, and hypnotherapy have shown mixed results. TMR has emerged as an effective surgical technique for the amputee population. This technique transfers severed peripheral nerves into recipient motor nerves in the residual limb. It can either be performed preemptively at the time of major limb amputation or subsequent to amputation after the development of pain. In either setting, research has demonstrated that TMR decreases both phantom limb pain and residual limb pain.7,8 Currently no data exists specifically evaluating the use of TMR in the hip hip disarticulation population.
Patients undergoing hip disarticulation are often suffering from complicated disease processes with poor prognoses. Understanding the benefits of TMR at more distal amputation levels, our team applied a multidisciplinary approach to hip disarticulation theorized to decrease post-operative pain. The hip disarticulation is performed by orthopedic surgery, followed by TMR and soft tissue reconstruction by plastic surgery. The primary goals of this study are: 1) to compare the impact of implementing a multi-disciplinary TMR approach to hip disarticulation on postoperative complications, and 2) to evaluate the overall outcomes of hip disarticulation at our institution. Secondary goals are to evaluate operative time, associated cost increase, and patient-reported pain outcomes of the non-TMR and TMR cohorts.
2. Materials and methods
After appropriate IRB approval, a retrospective chart review was performed to collect data from patients who underwent hip disarticulation at The Ohio State Wexner Medical Center between 2009 and 2020. The demographic information collected included age, sex, race, ethnicity, BMI, pre-operative smoking history, and oncologic history. Preoperative information included date of surgery, surgeon, type of surgery, indication, and plastic surgery involvement. Primary outcomes collected included 30-day infection, 30-day readmission, 30-day reoperation, major complications, minor complications, phantom limb pain, and one-year mortality. Secondary outcomes collected included significant post-operative events (ED visits, recurrence of cancer), pain scores, surgical time from incision to closure, and total charge of surgery. The TMR group was identified based on information in the surgery encounter.
2.1. Inclusion criteria
Inclusion in the study included those undergoing hip disarticulations at a single academic institution, >18 years of age, with complete data on primary outcomes.
2.2. Statistical analysis
The SPSS Statistics program was used to analyze the results of the study. Continuous variables, including OR time and surgical charges, were compared using independent t-tests. We compared 30-day complications rates using chi-square tests. The Fisher test was used when the expected count was insufficient for traditional Chi-square analysis. A statistically significant p-value is considered to be less than 0.05.
3. Results
A retrospective review identified 51 patients who underwent hip disarticulation and were eligible for inclusion in the study. Eight of the 51 had TMR treatment. Of the 51 patients, 67% had hip disarticulation for oncologic indications and 33% due to infectious causes. Plastic surgery was involved in the reconstruction of 27% of the patients. The mean age of the non-TMR group was 58 years ± 16. The mean age of the TMR group at the time of surgery was 61 years ± 13. Additional patient characteristics and surgical indications are summarized in Table 1A and divided by treatment in Table 1B.
Table 1A.
Patient characteristics.
| n (%) (n = 51) | ||
|---|---|---|
| Sex | ||
| Male | 23 (45) | |
| Female | 28 (55) | |
| Race | ||
| White | 45 (88) | |
| Black | 3 (6) | |
| Other | 1 (2) | |
| Unknown | 2 (4) | |
| Mean age, y (SD) | 59.00, 15.39 | |
| Radiation History Preop | 16 (31) | |
| Chemotherapy Preop | 21 (41) | |
| Indication for Amputation | ||
| Cancer | 34 (67) | |
| Infection | 17 (33) | |
Table 1B.
Patient characteristics, by treatment.
| TMR, n (%) (n = 8) | Non-TMR, n (%) (n = 43) | ||
|---|---|---|---|
| Sex | |||
| Male | 4 (50) | 19 (44) | |
| Female | 4 (50) | 24 (56) | |
| Race | |||
| White | 6 (75) | 39 (91) | |
| Black | 0 (0) | 3 (7) | |
| Other | 1 (12) | 0 (0) | |
| Unknown | 1 (12) | 1 (2) | |
| Mean age, y (SD) | 61.00, 13.26 | 58.00, 15.88 | |
| Radiation History Preop | 3 (38) | 13 (30) | |
| Chemotherapy Preop | 5 (63) | 16 (37) | |
| Indication for Amputation | |||
| Cancer | 7 (88) | 27 (63) | |
| Infection | 1 (12) | 16 (37) | |
Among the 51 patients, the one-year mortality rate was 37% overall. For all 51 patients, 37% had an infection within 30 days. 39% were readmitted and 27% had another operation within 30 days (Table 2A). 47% had a major complication within 30 days of their amputation with the most common major complication being infection (Table 3A).
Table 2A.
Post-surgical outcomes.
| n (%) (n = 51) | |
|---|---|
| 30-day Infection | 19 (37) |
| 30-day Readmission | 20 (39) |
| 30-day Reoperation | 14 (27) |
| One-Year Mortality | 19 (37) |
Table 3A.
Postsurgical complications.
| n (%) (n = 51) | ||
|---|---|---|
| Major Complication | 24 (47) | |
| Abscess | 6 | |
| Infection | 7 | |
| Hematoma | 1 | |
| Dehiscence | 5 | |
| Sepsis | 3 | |
| Cardiac Event | 3 | |
| Minor Complication | 2 (4) | |
| Superficial Dehiscence | 1 | |
| Hematoma | 0 | |
| Cellulitis | 1 | |
| Abscess | 0 |
The one-year mortality was not statistically significant for non-TMR vs. TMR treatment. There were also no differences between groups with regards to 30-day infection readmission, reoperation rates (Table 2B). The 30-day major complications and one-year mortality rates were not significantly different between groups (Table 3B).
Table 2B.
Comparison of post-surgical outcomes, by treatment.
| TMR, n (%) (n = 8) | Non-TMR, n (%) (n = 43) | Χ2, p-value | |
|---|---|---|---|
| 30-day Infection | 3 (38) | 16 (37) | 0.988 |
| 30-day Readmission | 5 (63) | 15 (35) | 0.142 |
| 30-day Reoperation | 2 (25) | 12 (28) | 0.866 |
| One-Year Mortality | 3 (38) | 16 (37) | 0.914 |
Table 3B.
Postsurgical complications, by treatment.
| TMR, n (%) (n = 8) | Non-TMR, n (%) (n = 43) | Χ,2 p-value | ||
|---|---|---|---|---|
| Major Complication | 2 (25) | 22 (51) | 0.173 | |
| Abscess | 1 | 5 | ||
| Infection | 1 | 6 | ||
| Hematoma | 0 | 1 | ||
| Dehiscence | 1 | 4 | ||
| Sepsis | 0 | 3 | ||
| Cardiac Event | 0 | 3 | ||
| Minor Complication | 2 (25) | 0 (0) | 0.022* | |
| Superficial Dehiscence | 1 | 0 | ||
| Hematoma | 0 | 0 | ||
| Cellulitis | 1 | 0 | ||
| Abscess | 0 | 0 |
For the TMR cohort of eight patients, 75% of the patients received TMR on three nerves. One patient had TMR on two, and one patient received one nerve transfer. The nerves utilized to accomplish nerve grafting were harvested from the distal amputated limb when possible. All eight patients had the sciatic nerve coapted, six had the femoral, and one had the obturator. Additionally, three patients had a nerve autograft and three had a nerve protector used around their nerve coaptations. Patient-reported outcomes were obtained in five patients at follow-up (range 1–6 months) in the TMR cohort. Pain scores were reported as an average of 2.2/10.
The average OR time for the 32 patients with reported OR times available was 4.8 h with a range of 1.5–10.5. Mean OR time was significantly shorter for the non-TMR group in comparison to the TMR group. The non-TMR cohort (n = 24) averaged a total OR time of 4.2 h with a 1.5–8.5 range. This is compared to the TMR cohort (n = 8) with an average of 6.3 h with a 3.5–10.5 range (p = 0.037*). An increase in operative time was not associated with an increase in post-operative complications. The time from incision to closure for the first TMR patient with hip disarticulation was 10.5 h. The time for the most recent patient in 2020 was 3.7 h.
On average, the charge for the surgery for the non-TMR group was $44,670.16 compared to the average charge for the TMR group at $104,949.19. This demonstrates a 57% increase in charges with the TMR treatment (p = 0.028*).
4. Discussion
Hip disarticulation is a procedure wrought with high complication and mortality rates, regardless of the indication. The surgery represents 0.39% of amputations performed annually, and as a result, there is limited scientific literature on patient outcomes and best practices.10 The published five-year mortality rates are as high as 55%.2,3,9 At our institution we care for a large number of patients undergoing hip disarticulation for a variety of indications.11, 12
We evaluated a total of 51 patients who had multidisciplinary surgical care over a 10-year period. Our data aligns with previous publications on hip disarticulations as it also demonstrates high morbidity and mortality rates. Moura et al. reported a complication rate of approximately 44% as well as a one-year survival rate of only 56% in their 16 patient hip disarticulation series.2 Furthermore, little is known about the quality of life and development of chronic pain in this patient population. In a larger group of proximal amputees, including hemipelvectomy patients, it was reported that they are 1.53 times more likely to experience PLP than patients undergoing below-knee amputations.6 However, patient-reported outcomes are underutilized in the hip disarticulation population specifically. In our study, we report pain scores for 63% of the TMR patients. While this only assesses a small number of our overall cohort, it indicates that TMR may be beneficial in improving post-amputation pain. Assessing these measures provides clarity regarding patient quality of life and may allow us to optimize this procedure.
First described in 2004 by Kuiken and Dumanian, TMR has emerged as an effective treatment of amputee pain.13 In more distal extremity amputations, TMR has demonstrated improvements in phantom limb pain, residual limb pain, and quality of life measures.8,14,15 In a 2018 study, researchers found that TMR treatment is 3–4 times more likely to decrease phantom and residual limb pain compared to an untreated amputee control group.1 With the desire to improve outcomes and quality of life in the vulnerable hip disarticulation patient population, TMR has recently been implemented at our institution at the time of hip disarticulation. An early look into these patients revealed that the eight patients who had TMR performed at the time of their hip disarticulation had no change in 30-day readmission, reoperation rate, and incidence of wound healing complications despite an increase in overall operative time.
In our effort to comprehensively evaluate the addition of both a surgical team and procedure to hip disarticulation alone, we focused our attention on cost and the importance of balancing outcomes with cost. It should be noted that charges do not necessarily reflect actual costs in terms of reimbursement to the healthcare system. This data is important to consider when determining whether the positive outcomes of the intervention outweigh the overall cost associated with it. In order to evaluate the cost of surgery for the two cohorts, we determined the mean hospital charges. The overall charge difference between groups was 54%. Considerations for this price increase for TMR included the added cost attributed to the use of nerve allografts and nerve wraps. Another consideration is the increased operative time involved in performing TMR. The average increase in OR time for the TMR group was over 1.9 h compared to the non-TMR group. Performing TMR does increase operative time, thereby increasing cost; however, we examined our operative times since our first patient undergoing TMR at the time of hip disarticulation in 2018. The time from incision to closure was 10.5 h. The surgery for our most recent hip disarticulation patient was 3.7 h, or a 65% decrease in time. As surgeons continue to implement this intervention, OR times will decrease, potentially increasing the cost-benefit for TMR.
At the hip disarticulation level, more data needs to be collected to determine if TMR is a beneficial intervention. Our results corroborate previously published work indicating that this patient population is at high risk for postoperative complications and mortality. Careful consideration should be given before TMR is performed due to the increased operative time and costs associated with the care of the patient. It should be approached in a cost-efficient manner that may limit the use of manufactured nerve products and allografts which can drastically increase the cost of TMR. Instead, it is recommended to employ direct nerve coaptation, or the utilization of spare parts surgery and/or the use of autografts if direct nerve coaptation is not possible. Future studies need to focus on patient outcomes after TMR for this particular patient population. If performing TMR improves post-operative outcomes and quality of life in this patient population then it should be strongly considered for use in hip disarticulations.
The study has several limitations. This study was limited by a small sample size; however, this study reflects one of the largest single-institution hip disarticulation series available. We recognize the TMR cohort within this group was especially small at eight patients; however, it represents a shift in care at our institution. The nature of the retrospective review was a limitation because it affected the available data. The absence of patient-reported pain outcomes was a limitation as they were not collected nor available for non-TMR controls. Therefore, a direct comparison of pain and quality of life between the two groups could not be made. Information on the Oral Morphine Equivalent (OME) was not available in the patient charts. Future studies could use this as a surrogate for quantifying pain. Furthermore, hip disarticulation is a radical surgery with a high one-year mortality rate. In our cohort, this was 37% among the 51 patients. This affects the available data for follow-up information, including long-term complications. Finally, a complete cost-effectiveness study would help determine the threshold of when we would consider TMR on hip disarticulation.
5. Conclusions
Hip disarticulations are wrought with complications, and our study continues to demonstrate the significant morbidity associated with this procedure. In our cohort, the addition of TMR did not worsen patient outcomes despite the increase in operative time. To fully evaluate the role of hip disarticulation, more prospective data and new attention to patient-reported outcomes are needed to assess quality of life and pain control in this vulnerable patient population.
Author contributions
Design: AH, JW, AO, AM.
Data synthesis: AH, JW, AO, SS.
Drafting article: AH, JW, AO.
Revising article: AH, JW, AO, EG.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Declaration of competing interest
The authors have no conflicts of interest.
Acknowledgements
None.
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