Secondary Autologous Fat Grafting as a Novel Method to Improve Pain and Appearance of the Residual Fingertip After Amputation

Fingertip amputation is a common problem faced by the hand surgeon. It is estimated that fingertip amputations account for approximately 4.8 million emergency department visits annually in the United States, most commonly because of work-related lacerations and crush injuries.^1,2 Current treatment algorithms focus on minimizing time to recovery and return to work, as well as maximizing postinjury function.^3-5 After fingertip injury, function can be inhibited by over-shortening of the digit, residual stiffness, and pain.^6,7

Chronic pain after fingertip amputation can have a lasting impact on function and patient well-being. Factors leading to pain among these patients include neuroma, scar sensitivity, and loss of adequate soft tissue over the bone.^2,3 Neuroma pain is multifactorial, and a variety of surgical and nonsurgical treatment options have been described in order to prevent neuroma formation or address them secondarily.⁸ Scar contracture leads to hypersensitive fingertips because of the lack of pulp thickness on the fingertip.⁶

Maintenance of adequate soft tissue coverage is a challenging dilemma, as the hand surgeon must balance the desire to maintain length of the digit with the available amount of viable skin and fat. Various techniques have been described in the literature, including further shortening of the digit, using flaps to reconstruct the defect, and allowing the digit to heal by secondary intention.⁶ An ideal technique would allow the surgeon the replace or restore the fat pad of the distal segment to maintain maximum length on the digit without shortening the bone, thereby preserving the distal insertion of the flexor digitorum profundus tendon and hand function.

Fat grafting has shown promise in a variety of cosmetic and reconstructive procedures. It has shown efficacy in applications such as contour resurfacing, wound healing, and restoration of soft tissue in lower extremity residual limbs following amputation.^9-11 The application of fat grafting as a secondary treatment of fingertip amputation pain has not yet been described in the literature. This study presents 7 patients treated with secondary fat grafting to address fingertip pain. It was hypothesized that secondary fat grafting improves patient-reported hyperesthesia, cold sensitivity, fingertip contour, and scarring following distal phalanx amputations.

After institutional review board approval, a single-institution retrospective chart review was performed. Inclusion criteria included patients with history of transdistal phalanx amputation repaired with flaps (ie, local, advancement, and homodigital island) who underwent subsequent fat grafting between the years 2018 and 2020. Patients who underwent fat grafting were identified using Current Procedural Terminology (CPT) codes 15771, 15772, 15773, 15774, and 20926. Exclusion criteria included patients who had fat grafting to locations other than the fingertip, amputations proximal to the distal phalanx, distal phalanx amputations previously reconstructed using methods other than flaps, or records containing incomplete data. Data extracted included patient demographics, mechanism of original injury, time between injury and fat grafting, follow-up time, amount of fat injected, and complications. A Visual Analog Scale (VAS) from 1-10 was used to quantify patient-reported fingertip hyperesthesia, cold sensitivity, contour, and scarring before and after fat grafting, as well as overall satisfaction with fat grafting. Patients were asked questions regarding each of the previous characteristics via a clinical interview. Higher scores on the VAS indicated worse symptoms, with 10 being the worst possible symptoms.

Statistical Analysis

Mean and standard deviation were used to describe continuous variables. Paired sample t test was used to determine significance in difference between means, with P < .05 set as the threshold for significance.

Operative Technique

After the patient was prepped and draped in the standard fashion, a 25-gauge needle was used percutaneously to break up scar bands under each fingertip, which may have caused adhesions to the underlying distal phalanx remnant. About 20-30 mL of fat was harvested from the abdomen using tumescent liposuction. A tumescent solution of 20 mL of 1% lidocaine with 1:100,000 epinephrine and 120 mL of sterile saline was created. About 60 mL of tumescent solution was infiltrated into the abdomen. After waiting 10 minutes for the epinephrine to take stronger effect, fat was manually harvested in the usual, standard fashion using a 3-port liposuction cannula. The fat was purified by transfer to Telfa (Covidien) and washed with normal saline. Between 1 to 3 mL of fat were injected into each fingertip using a blunt 21-gauge needle. The liposuction incision was closed with 4-0 Monocryl (Ethicon) in interrupted fashion, and the finger sites were closed with Dermabond (Ethicon). A tourniquet was not used. A volar resting splint was applied for 14 days. Patients were discharged home on the same day with postoperative instructions to elevation the hand and move the fingers to prevent stiffness. After 2 weeks, there we no activity restrictions.

Patient Demographics

Retrospective chart review identified 13 patients using CPT codes for fat grafting (15771, 15772, 15773, 15774, and 20926) between January 2018 and December 2020, of which 7 met the inclusion criteria (Table 1). A total of 6 patients were excluded (Figure 1). The 7 patients who were included in the study comprised a total of 10 digits. Of the included patients, 4 were male and 3 were female. The average age was 45.1 ± 15.2 years and average body mass index (BMI) was 32.9 ± 6.1 kg/m². One patient was a current smoker, and 2 patients were former smokers. Mechanism of injury was a crush in 6 patients and laceration in 1 patient. Neurectomies were not performed at time of primary reconstruction for any patient. The mean time between initial injury and fat grafting was 25.4 ± 20.6 weeks, and mean follow-up time after fat grafting was 2.9 ± 2.6 months. No intraoperative or postoperative complications were reported for any patients.

Patient-Reported Hyperesthesia and Cold Sensitivity Outcomes

A total of 6 patients had improvement in hyperesthesia after fat grafting, with a mean improvement in VAS of 3.9 (95% CI 1.6-6.1, P = .005) (Table 2, Table 3). In 1 patient, there was no change in hyperesthesia following fat grafting. No patients had worsening of hyperesthesia following fat grafting. Four patients fromhad improvement in cold sensitivity, with mean improvement of 2.8 (95% CI -0.6-6.3 P = .09) on the VAS (Table 2, Table 3). One patient had no change in cold sensitivity following fat grafting. One patient reported worsening of cold sensitivity at last follow-up. Cold sensitivity before fat grafting was not reported in 1 patient because the time between amputation and fat grafting did not include winter months.

Patient-Reported Aesthetic Outcomes

All 7 patients had improvement in fingertip contour, with mean improvement of 3.7 (95% CI 1.8-5.6; P = .003) on VAS (Table 2 and Table 3). One case example is seen in Figure 2. Lastly, 5 patients reported improvement in scarring following fat grafting, with a mean increase of 3.6 (95% CI 0.6-6.5, P = .036) on VAS (Table 2 and Table 3). Two patients did not have any change in scarring after fat grafting.

Patient Satisfaction

Six patients reported overall satisfaction following fat grafting, stating that they would undergo the procedure again if given the choice. At the time of the study, 1 patient was scheduled to undergo a second fat grafting procedure. One patient reported dissatisfaction with the fingertip contour after fat grafting because the residual digit was larger after fat grafting.

Distal phalanx amputation is a common yet challenging problem for surgeons, particularly when there remains a paucity of local soft tissue. A variety of reconstructive options have been described, including further shortening of the digit, local and heterodigital flaps, and in some cases, healing by secondary intention.⁶ Nevertheless, the fine balance between maintenance of finger length and providing adequate soft tissue coverage remains a challenge. Flap closures, such as the V-Y advancement flap, allow for preservation of finger length; however, the fingertip is left with a lack of soft tissue padding homologous to the pulp, resulting in complications such as hypersensitivity to touch, cold sensitivity, and an unaesthetic appearance. This retrospective chart review demonstrates that delayed fat grafting may improve subjective patient-reported outcomes of hyperesthesia, cold sensitivity, perceived contour, and scarring following distal phalanx amputations.

In recent years, there has been a growing body of literature on the clinical effects of fat grafting, particularly the impact of fat grafting as a method of pain and scar reduction in posttraumatic injury patients. Work by Vaienti, Gazzola, Villani, and Parodi,¹² and more recently, de Jongh, Pouwels, and Tan,¹³ demonstrated that autologous fat grafting can be used to treat neuroma pain. Similarly, Fredman, Edkins, and Hultman¹⁴ showed that fat grafting can also decrease neuropathic pain after severe burns. In the amputee population, Malik et al¹⁵ found not only that fat grafting to the residual limb improves pain and scar characteristics but also that fat grafting with stromal vascular filtrate increased volume after fat grafting. Tarallo et al¹⁶ evaluated the effects of injecting adipose tissue-derived stem cells from liposuction aspirate fluid into fingertips 1 week following injury and demonstrated that patients who received injections of liposuction aspirate fluid had decreased healing time, as well as improved cold tolerance, pain, and aesthetic results.

The present study adds yet another clinical application of autologous fat grafting for pain reduction and scar management in the reconstructive patient. The effect of fat grafting to the distal fingertip following amputation on patient-reported outcomes was assessed. In particular, patients who had distal phalanx amputations reconstructed with flaps were included because flap reconstruction preserves finger length at the expense of fingertip volume.⁶ Our findings suggest that autologous fat grafting to the fingertip may decrease hyperesthesia following fingertip amputations. Hyperesthesia is thought to be due to the loss of fingertip pulp following injury, resulting in the skin being closely adherent to the bone remnant and nerve endings. Fat grafting replaces the missing fingertip volume to provide cushioning between the bone and skin, thus emulating the fingertip pulp and decreasing sensitivity. Interestingly, this study suggests there may be a favorable effect of fat grafting on temperature sensitivity that trended towards statistical significance and may have been biased by an outlier in the sample. The mechanism of this improvement in cold sensitivity may be due to the same cushioning effect that improves hyperesthesia. The results also demonstrated an improvement in scarring after fat grafting. Although the mechanism of scar improvement following fat grafting is not well understood, it is hypothesized to be due to the regenerative potential of adipocyte-derived stem cells.¹⁷ As a whole, these findings parallel those found by Tarallo et al¹⁶; however, the present study suggests that improvements in clinical outcomes can also be seen with autologous fat grafting performed weeks to months following the initial injury.

The classic application of autologous fat grafting in plastic surgery is to provide bulk, correct contour deformities, and provide a better aesthetic result. Autologous fat grafting has been used to improve facial, breast, and residual limb contour.⁹ Likewise, this study demonstrates improved patient perception of fingertip contour and patient satisfaction following fat grafting to the fingertip after deforming injuries. Although contour was not quantitatively assessed and, therefore, patient-reported improvements in contour may not correlate with actual improvements, it is nevertheless important to note that ultimately patients themselves reported better contour with fat grafting. Future studies are required to elucidate objective contour improvements and quantify amount of fat take following fat grafting to the distal phalanx. Nonetheless, fat grafting may be a method that surgeons can use to improve fingertip contour following amputations and patient satisfaction.

In addition to improving clinical outcomes following distal phalanx amputation, this study proposes a novel reconstructive technique that allows surgeons to maintain fingertip length during primary distal phalanx amputation repairs because fingertip volume can be restored at a later date. By conserving length of the distal remnant, the distal insertion of the flexor digitorum profundus tendon and nail remnant can be retained. Clinically, this translates to greater flexion of the distal remnant, preservation of hand function, and maintenance of a nail.

The main limitation of this study is the small sample size, and thus the sample may not be representative of the population as a whole. Second, the lack of a control group suggests that definitive conclusions about improvements in patient outcomes cannot be attributed to fat grafting alone. Improvements in sensitivity and scarring from the natural progression of healing following amputations cannot be clearly delineated from improvements from fat grafting. Nevertheless, the average time from primary reconstruction to fat grafting was 25.4 weeks, thus minimizing this confounding factor. Likewise, a cohort of patients who underwent lysis of scar adhesions without fat grafting was not identified, thus the effect of lysis of adhesions cannot be defined from that of fat grafting alone. The retrospective nature of our study poses risk of bias in outcomes reported by patients. Those who elected to undergo fat grafting were at baseline likely more concerned about their primary reconstruction and potentially more invested in the outcomes of fat grafting. Additionally, our study reported outcomes using the VAS, which is inherently subjective as it conveys patient-reported outcomes. Quantitative methods of measurement such as 2-point discrimination to discern improvement in sensation and fingertip measurements to determine improvements in contour deformities were not used. This study also does not quantify the amount of fat take in the distal phalanx via methods such as ultrasound or magnetic resonance imaging; thus, amount of fat graft take and contour improvement attributable to fat grafting are yet to be elucidated. Lastly, the follow-up time after fat grafting may not fully characterize the permanence of the positive effects of fat grafting. Future studies with larger sample sizes, control groups, and long-term follow-up are needed to further elucidate the effects of fat grafting following fingertip amputations, correlate patient-reported outcomes with objective outcomes, and quantify fat take. Furthermore, additional studies are needed to optimize the surgical technique to determine the ideal time between reconstruction and fat grafting, amount of fat to inject, preparation of the recipient site, and effects of multiple rounds of fat grafting.

This study presents an innovative method that utilizes fat grafting following distal phalanx amputations to improve patient-reported outcomes in multiple domains, including hyperesthesia, cold sensitivity, fingertip contour, and scarring. Although future studies are needed to further assess the effects of fat grafting for fingertip amputations, this study suggests that fat grafting is a safe and promising technique that can be utilized to preserve fingertip length while maintaining adequate soft tissue coverage.

Affiliations: ¹Rutgers The State University of New Jersey, West Orange, NJ; 2Rutgers New Jersey Medical School, Newark, NJ; ³Division of Plastic Surgery, Rutgers New Jersey Medical School, Newark NJ

Correspondence: Ashley Ignatiuk, MD; ashignatiuk@gmail.com

Disclosures: The authors disclose no relevant financial or nonfinancial interests.