Advancing body contouring: A comprehensive review of intramuscular fat grafting techniques, outcomes, and safety considerations

Abstract

Intramuscular fat grafting has emerged as a transformative technique in aesthetic surgery, particularly within modern body contouring procedures where high-definition contouring and selective volume enhancement are desired. While subcutaneous fat grafting remains a foundational approach, intramuscular injection has been suggested to provide superior definition, projection, and dynamic contouring in selected anatomical regions. Nevertheless, its clinical adoption remains controversial due to ongoing concerns regarding safety, variable fat retention, and inconsistent reporting of complications. A structured literature search was conducted in PubMed, ScienceDirect, and the Cochrane Library using database-specific combinations of intramuscular- and fat grafting-related terms, yielding 495 reports. Ultimately, 45 studies met the inclusion criteria and were retrieved. Analysis focused on safety, fat retention, and clinical outcomes. The included studies suggested favorable aesthetic outcomes and generally positive reported satisfaction across selected facial, truncal, and extremity applications, although outcome reporting was heterogeneous and often non-standardized. While animal models present conflicting retention data, clinical series have described acceptable volume persistence in selected settings. Safety appeared to be strongly region-dependent. While intramuscular gluteal injection remains associated with a prohibitive embolic risk, non-gluteal ultrasound-guided applications reported low rates of major complications in the reviewed literature, although the available evidence remains limited. In conclusion, this review summarizes reported intramuscular fat grafting techniques and synthesizes the available evidence on outcomes and region-specific safety considerations. Future studies must focus on comparing this approach to subcutaneous grafting in larger cohorts.

Introduction

Fat grafting was first reported in 1893 by a German surgeon, Dr. Gustav Neuber, who used adipose tissue from the arm to correct depressed facial scars.^1,2 This was soon followed by another report from Dr. Victor Czerny, who excised a lipoma and grafted it into the breast to correct a defect which resulted from the excision of nodules. Soon after, Brunning published the first innovative technique for fat grafting, which consisted of using a syringe to inject fat into the subcutaneous tissues.¹ Until then though, fat grafting was reported to cause a high-rate of complications and resorption making it an unappealing procedure for surgeons. In 1995, Dr. Coleman described the first technique that involved processing the fat before grafting it, thus revolutionizing fat grafting by improving both safety and outcomes.²

Ever since, there has been significant advancements in the field and fat grafting has become an essential procedure performed by plastic and reconstructive surgeons. However, thus far, most techniques have been focused on subcutaneous fat grafting, with little attention and research exploring the efficacy, safety, and patient outcomes of intramuscular fat grafting.² For the purpose of this review, intramuscular fat grafting refers to the placement of autologous fat within the substance of a target muscle, rather than within the subcutaneous, subfascial, or supramuscular planes, with the aim of enhancing contour, projection, or dynamic soft-tissue definition.

Direct injection of processed autologous fat into muscle tissue has been proposed as a means of enhancing volume and muscular definition in selected anatomical regions. However, whether this approach offers superior outcomes to subcutaneous grafting remains incompletely established.² With growing interest in high-definition body contouring, intramuscular fat grafting has emerged as a potential adjunct for achieving more pronounced muscular definition in appropriately selected patients. Indeed, several authors have reported techniques that employ intramuscular fat grafting to improve the aesthetic results of the male chest, abdominal wall, face and even lower limbs.3, 4, 5, 6, 7

The increasing popularity of intramuscular fat grafting raises several questions regarding optimal technique, patient outcomes, fat graft survival, and safety. We therefore conducted this comprehensive review to summarize the currently reported techniques, applications, outcomes, and safety considerations associated with intramuscular fat grafting across anatomical regions.

Methods

Search strategy

A structured literature search was conducted in November 2025 in PubMed, ScienceDirect, and the Cochrane Library to identify studies evaluating intramuscular fat grafting. Searches were limited to English-language reports. Search terms were adapted to the syntax of each database and combined intramuscular- and fat grafting-related keywords. To maximize sensitivity, broad terminology and synonymous fat grafting terms were used. The full database-specific search strategies are provided in Supplementary Material 1. No publication date restrictions were applied.

Eligibility criteria

Studies were eligible if they were original investigations in human or animal models that evaluated intramuscular fat grafting and reported outcomes related to safety, fat graft retention, technical feasibility, or clinical efficacy. Included study designs comprised clinical studies, experimental studies, cadaveric studies, and case series relevant to the aims of this review.

Studies were excluded if they were review articles, conference abstracts without full-text availability, duplicate publications, or studies that did not provide relevant information on intramuscular fat grafting outcomes. Studies focused exclusively on non-intramuscular planes without relevant intramuscular content were also excluded.

Study selection

All retrieved reports were imported into Rayyan and underwent deduplication before screening. After removal of duplicate and clearly ineligible reports, two independent reviewers screened titles and abstracts. Full-text reports of potentially eligible studies were then assessed for inclusion. Disagreements were resolved through discussion and, when necessary, adjudication by a third reviewer. Rayyan-assisted automation was used only as a preliminary aid to flag clearly irrelevant reports during early screening; however, the exact rule set used in this step was not retained in reproducible form and is therefore acknowledged as a limitation.

Reasons for exclusion at the full-text stage included non-intramuscular technique, absence of relevant safety or clinical outcome information, duplicate reporting of the same cohort, insufficient methodological detail, or failure to meet the predefined eligibility criteria.

Data synthesis

The included studies were reviewed with emphasis on study design, anatomical application, technical approach, use of imaging guidance, reported complications, fat graft retention-related findings, and clinical outcomes. Because the included evidence was highly heterogeneous and consisted predominantly of technical reports, retrospective case series, cadaveric studies, and experimental investigations, a quantitative meta-analysis was not performed. Instead, a qualitative narrative synthesis was undertaken, with findings organized by anatomical region and thematic domain, including technique, retention, clinical outcomes, and safety considerations.

A formal risk-of-bias assessment was not performed because the included literature comprised markedly heterogeneous study designs, many of which were descriptive or non-comparative, limiting the utility of a single standardized appraisal tool for this review’s aims.

Results

Study selection

The literature search identified 495 reports across PubMed (n = 106), ScienceDirect (n = 367), and the Cochrane Library (n = 22). After removal of 110 duplicate reports, 50 reports excluded at the preliminary screening stage using Rayyan-assisted ineligibility filtering, and 46 reports removed for other reasons, 289 reports underwent title and abstract screening. Of these, 202 were excluded, leaving 87 reports sought for retrieval. Thirteen reports could not be retrieved, and 74 full-text reports were assessed for eligibility. Twenty-nine reports were excluded at the full-text stage. Ultimately, 45 studies were included in the review (Figure 1).

Figure 1.

PRISMA flow diagram.

Fat graft survival and retention

Early preclinical research suggested that the recipient plane may influence fat graft survival. In 1996, Guerrero-Santos et al. reported in a rat model that subcutaneous fat grafts were eventually absorbed, whereas intramuscular grafts demonstrated substantially greater persistence, with a reported half-life of up to five years.⁸ Tsimponis et al. further examined recipient-site effects and found that adipocyte survival was greatest in the pectoralis major muscle, followed by the latissimus dorsi muscle and then the subcutaneous plane. The authors also observed that graft survival was directly proportional to graft volume and was significantly reduced in irradiated tissues, although the pectoralis major retained superior survival relative to the other recipient sites.⁹

In a clinical setting, reports on facial augmentation using the fat autograft muscle injection (F.A.M.I.) technique drew on the principles described by Coleman and the anatomically targeted approach detailed by Amar and Fox. Favorable aesthetic impressions were reported after treatment, although standardized patient-reported outcome measures and objective volumetric assessments were not consistently provided.2, 3, 4

By contrast, Jin et al. compared intramuscular and subcutaneous fat grafting in a murine model and found lower graft weight retention in the intramuscular group at 8 weeks. Nevertheless, histologic analyses showed similar vascularity and graft quality between groups.¹ Taken together, these findings suggest that while intramuscular placement may offer a favorable biologic recipient environment in some settings, volume persistence remains variable and may depend on local vascular, metabolic, and mechanical factors.^1,8,9

Reported clinical applications and techniques

Fat autograft muscle injection (F.A.M.I.) technique

The F.A.M.I. technique involves intramuscular autologous fat grafting within the muscles of facial expression to restore facial volume. This approach targets superficial, intermediate, and deep muscular planes, including the frontalis, orbicularis oculi, zygomaticus major, platysma, mentalis, and buccinator muscles. Fat is injected retrogradely from muscle origin toward insertion, parallel to the muscle fibers.² Clinical reports described favorable aesthetic impressions and patient satisfaction at short-term follow-up; however, standardized outcome measures and objective volumetric assessments were generally lacking.2, 3, 4

Pectoralis muscle definition

In the context of postmastectomy reconstruction, Serra-Renom et al. described a multistage protocol involving tissue expansion, definitive implant placement, and serial subcutaneous and intramuscular fat grafting around the pectoralis major. In that series, capsular contracture did not exceed Baker grade I.¹⁰ For male pectoral augmentation, Hoyos and Perez reported 154 procedures involving superficial, intermediate, and deep lipoplasty followed by intra- and submuscular fat grafting. Serious complications, including hematoma and abscess, were reported in 2% of cases and were treated without reported long-term sequelae.⁶ In gynecomastia correction, Pilanci et al. reported improved satisfaction when intramuscular fat grafting was used as an adjunct to liposuction and glandular excision or excision alone.¹¹

Oblique-serratus complex

The Multi-SHOT technique (Multiple Serratus- and High-Oblique LipoTransfer), developed by Hoyos et al., uses real-time ultrasound mapping to guide intramuscular fat grafting to the serratus anterior and the superior third of the internal and external oblique muscles.¹² In the reported series, no major complications were observed; minor adverse events included one case of transient hyperpigmentation and one mild febrile episode.¹² Flores et al. also described an ultrasound-guided approach in which 20–50 mL of fat were deposited retrogradely along oblique and serratus muscle fibers. In a series of 11 patients, ultrasound demonstrated a statistically significant increase in muscle thickness, with no embolic events or hematomas reported in that series.¹³

Abdominal wall applications

Several techniques have been described for intramuscular abdominal wall enhancement. The Rectus Abdominis Fat Transfer (RAFT) technique involves intramuscular fat grafting to the rectus abdominis during abdominoplasty.^5,14 In a one-year follow-up study of 62 patients, the average rectus abdominis cross-sectional thickness increased from 1.4 cm to 2.3 cm, and 94% of patients demonstrated identifiable intramuscular fat persistence.⁵ Two patients developed small superficial oil cysts that were treated with aspiration.^5,14

Viaro et al. described ultrasound-guided rectus abdominis fat grafting (UGRAFT) in 10 patients, with no major complications reported.¹⁵ Danilla et al. reported the SPARTAN technique (Semilunaris Parallel to Rectus Fat Transfer) in 51 patients, likewise without major complications reported.¹⁶ The U-FEMME technique, described by Proto et al., was performed in 105 patients, with no major complications reported; minor complications such as seroma and anemia occurred in 13 patients.¹⁷

Gluteal augmentation

The gluteal region differed substantially from other anatomical applications. A meta-analysis by Condé-Green et al., including 4105 patients, found that intramuscular injection was used in approximately half of gluteal fat grafting cases and reported a major complication rate of 0.32%, including fatal fat embolism.¹⁸ Earlier clinical reports had described gluteal augmentation with fat grafting, including intramuscular approaches.^19,20 Data from the Multi-Society Task Force and subsequent literature suggested that after recommendations to restrict grafting to the subcutaneous plane, mortality decreased from 1 in 3448 in 2017 to 1 in 14,952 in 2019.^21,22 Cadaveric and anatomical studies further demonstrated that deep injection may allow fat migration between planes and increase the risk of vascular injury.^23,24 Unlike other anatomical applications reviewed in this study, the gluteal region has a distinct and unfavorable safety profile, and contemporary evidence strongly discourages deep or intramuscular injection.^18,21, 22, 23, 24

Lower limb augmentation

Shi et al. examined the retention rate of intramuscularly transplanted fat in denervated limbs compared with controls. The authors reported significantly greater retention in the denervated limb between weeks 4 and 12. Immunohistochemical analyses showed increased vascular density at 12 weeks and a higher density of adipose-derived stem cells at 2 weeks in the denervated muscle.⁷ These findings suggest that local mechanical and physiologic conditions may affect intramuscular graft persistence, although these data derive primarily from experimental models and should be extrapolated to clinical practice with caution.⁷

Gastrocnemius augmentation

Escandón et al. analyzed calf augmentation outcomes in 2455 patients and found that subfascial implant placement was used in most cases, whereas fat injection alone was used less frequently. Overall patient satisfaction was high, although satisfaction in fat-grafting cases was lower than that reported for implant-based approaches. More than half of patients undergoing fat grafting required a second procedure, primarily because of asymmetry or volume loss.²⁵ However, much of this literature involved mixed augmentation techniques and not exclusively intramuscular graft placement, which limits direct inference regarding true intramuscular outcomes.²⁵

Arm definition

Hoyos et al. described a technique combining ultrasound-assisted lipolysis with intramuscular fat grafting to the deltoid, biceps brachii, and triceps brachii muscles.²⁶ In a retrospective cohort of 289 patients, reported grafting volumes ranged from 50 to 150 mL for the deltoid, 30 to 100 mL for the biceps, and 50 to 120 mL for the triceps. Minor complications included transient bruising and temporary dysesthesia. No hematoma, necrosis, infection, or fat embolism was reported. Reported patient satisfaction reached 97% at follow-up extending to 24 months, although outcome assessment was not standardized across the broader literature.²⁶

Complications and safety considerations by anatomical region

The safety profile of intramuscular fat grafting appeared to vary substantially by anatomical region.

In facial applications, no blindness, stroke, or clinical fat embolism events were reported in the reviewed intramuscular-specific studies.2, 3, 4 However, complication reporting in these studies was limited, and the absence of catastrophic events in relatively small series should not be interpreted as proof of zero risk.

Across non-gluteal truncal and extremity applications, major complications were infrequently reported. Reported adverse events were generally minor and included bruising, transient dysesthesia, superficial oil cysts, febrile episodes, seroma, anemia, hematoma, and abscess in isolated cases.^5,6,12, 13, 14, 15, 16, 17^,26 Several recent ultrasound-guided series reported no major complications, although most available studies were non-comparative case series and complication reporting was inconsistent.^12,13,15, 16, 17^,26

The gluteal region represents a distinct safety category. Unlike other intramuscular applications, intramuscular gluteal fat grafting has been associated with fatal macroscopic fat embolism.^18,21, 22, 23, 24 Cadaveric and anatomical studies suggest that deep injection may disrupt fascial planes, facilitate fat migration, and increase the risk of venous injury and embolic complications.^23,24 Accordingly, the current evidence supports avoidance of deep and intramuscular injection in gluteal augmentation.^18,21, 22, 23, 24

Discussion

Physiology and the three-zone theory

Fat graft survival is governed by a complex sequence of biologic events in which grafted adipose tissue may undergo either successful integration or progressive resorption and fibrosis. This dual trajectory explains why some cells successfully mature into adipocytes to accumulate fat, while others undergo apoptosis and resorption. Eto et al. formalized this concept in the “three-zone survival theory,” which stratifies the avascular fat graft according to nutrient proximity: (1) the surviving zone, where adipocytes and adipose-derived stem cells (ASCs) remain viable through diffusion; (2) the regenerating zone, where adipocytes perish but ASCs may contribute to tissue regeneration; and (3) the necrotizing zone, where sustained hypoxia leads to irreversible necrosis and fibrosis.²⁷

Determinants of graft survival

Graft retention likely depends on the balance between adipocyte survival, tissue regeneration, resorption, and necrosis. Key determinants of this balance include recipient site vascularity, graft composition, and injection volume. Highly vascularized recipient sites may provide a more favorable environment for graft survival by facilitating oxygen delivery, nutrient exchange, and waste removal.^3,27 A well-vascularized recipient bed may also help limit ischemic injury and support more favorable graft incorporation. Smaller graft aliquots may also favor retention because they reduce the volume of poorly perfused central tissue and may limit necrosis and inflammatory change.²⁷ Accordingly, strategies that improve graft distribution, preserve cellular integrity, and potentially enhance regenerative support may contribute to better outcomes.

The intramuscular vs. subcutaneous debate

The available literature does not provide a uniform conclusion regarding whether intramuscular grafting is superior to subcutaneous grafting. While several studies have favored intramuscular placement on the basis of the rich vascularity of muscle tissue,2, 3, 4^,8 Jin et al. reported lower weight retention in intramuscular grafts than in subcutaneous grafts in a murine model.¹ This apparent discrepancy may be partly explained by distinguishing between “viability” and “weight retention.” Jin et al. noted that despite weight loss, the histological quality of intramuscular grafts remained sound. One possible explanation is that muscle provides a vascular environment that supports cellular viability while also exposing the graft to greater metabolic demand than subcutaneous tissue, potentially contributing to reduced volume persistence despite acceptable histologic quality.¹ Thus, intramuscular grafting may offer a biologically favorable recipient environment in some settings, while still being subject to variable volume loss depending on local metabolic and mechanical factors. Future prospective studies using standardized imaging and outcome measures will be important to better characterize this trade-off.¹

Anatomical applications: face, trunk, and extremities

The implications of these principles vary considerably according to anatomical region, recipient muscle characteristics, and procedure-specific safety considerations. In the face, the F.A.M.I. technique is intended to address deeper structural volume loss, including changes related to muscular atrophy and skeletal support, rather than only superficial soft-tissue depletion. By placing grafts within the muscles of facial expression, this approach may improve graft support and contour in selected patients; however, long-term survival rates and optimal patient selection remain insufficiently defined.2, 3, 4 Importantly, although no blindness, stroke, or clinical fat embolism events were reported in the reviewed intramuscular facial studies, this should not be interpreted as proof of zero vascular risk, particularly given the broader facial fat grafting literature describing rare but serious vascular complications.^28,29

In the thoracic region, combining expansion with fat grafting in reconstructive pectoralis cases may help improve soft-tissue quality and mitigate complications related to irradiated tissue and implant-based reconstruction.¹⁰ In body contouring, ultrasound-guided grafting of the oblique-serratus complex has been used to enhance upper trunk definition and create a more athletic torso contour in selected patients,^12,13 while abdominal wall techniques such as RAFT seek to improve rectus definition in patients who may not achieve the desired result with liposuction alone.^5,14 Similarly, techniques such as U-FEMME have been described to enhance feminine athletic contouring through ultrasound-guided intramuscular augmentation of selected muscle groups.¹⁷

Safety considerations differ substantially in the gluteal region. Unlike other anatomical applications, intramuscular gluteal fat grafting has been associated with fatal macroscopic fat embolism, and current safety recommendations strongly favor restriction of graft placement to the subcutaneous plane.^18,21,23,24 Cadaveric and mechanistic evidence further supports avoidance of deep-plane injection by demonstrating high-risk vascular pathways and injection-related mechanisms associated with embolic complications.^28,29

In the lower limbs, experimental data suggest that local mechanical stress may influence neovascularization and graft retention, raising the possibility that reduced muscle activity could favor persistence in selected settings.⁷ For gastrocnemius augmentation, fat grafting may offer a less invasive alternative to implant-based augmentation, although repeat procedures are often required because of asymmetry or limited volume persistence.²⁵ Finally, arm definition procedures increasingly rely on intraoperative ultrasound to improve plane control and to support gender-specific contouring goals while minimizing the risk of inadvertent intravascular injection.²⁶

Donor site variability and selection

Donor site selection remains a debated aspect of fat grafting because of reported heterogeneity in adipocyte characteristics and graft behavior across harvest sites.^3,30,31 Earlier theories favored donor sites such as the buttocks and outer thighs on the basis of presumed differences in lipogenic activity and tolerance to hypoxia, whereas later work questioned whether any donor site is consistently superior.^3,32 Markey and Glogau discussed donor-site considerations and technical comparisons in autologous fat grafting, while Rohrich et al. and Ullmann et al. found no significant differences in viability or graft outcomes across commonly used donor sites such as the abdomen, flank, and thigh.30, 31, 32 Overall, contemporary practice appears to prioritize tissue availability, surgeon preference, and procedural goals over any universally accepted superior donor site, although certain region-specific preferences have been described.³

Intraoperative imaging and processing

Real-time ultrasound appears to be an important adjunct for improving procedural safety and plane control during intramuscular fat grafting. By providing direct visualization of the target plane, ultrasound may reduce the risks associated with blind injection and help avoid unintended vascular or excessively deep placement.^{12,13,15,17,26} Ultrasound may also facilitate more uniform graft distribution, which could improve contact between the graft and the recipient bed.^5,15

Once harvested, lipoaspirate processing requires balancing purification of the graft with preservation of cellular integrity.³ Although removal of contaminants is necessary, excessive centrifugation may compromise graft viability by damaging cellular components. Some authors have suggested that centrifugation parameters may affect outcomes differently depending on graft volume and recipient site, with excessive processing potentially being more problematic in large-volume applications. Accordingly, processing protocols should be tailored to the clinical context, with moderate handling favored over excessively aggressive processing that could impair graft quality.^3,27

Biological enhancement strategies

Recent work has explored biologic enrichment strategies as a means of improving graft persistence and regenerative potential. Enrichment with adipose-derived stem cells (ASCs) has shown promise in improving volume retention in preclinical and review-based literature, although much of this evidence is not specific to intramuscular grafting.33, 34, 35 Insulin has been reported to promote adipose-derived stem cell differentiation after fat grafting and may support graft survival.³⁶ Similarly, stromal vascular fraction (SVF) and nanofat have been investigated as adjuncts to improve graft quality and tissue regeneration. SVF-enriched grafts have shown encouraging volumetric persistence in some studies, while nanofat has been associated with improved histologic architecture and capillary density in regenerative applications.37, 38, 39, 40, 41, 42, 43, 44 Future research should determine whether these strategies translate meaningfully to intramuscular fat grafting specifically.

Limitations

Our review has several limitations. First, the available literature on intramuscular fat grafting is composed predominantly of low-level and heterogeneous evidence, including retrospective case series, technical reports, cadaveric studies, and experimental investigations. Second, outcome reporting varied substantially across studies, ranging from subjective aesthetic impressions and non-standardized patient satisfaction to imaging-based and histologic endpoints, which limited direct comparison across reports. Third, because of the breadth of included study designs and the lack of sufficiently comparable datasets, we did not perform a meta-analysis or formal risk-of-bias assessment. Fourth, this review was not prospectively registered, and no publicly accessible protocol was used. Finally, although the screening workflow and aggregate record counts were preserved, some granular methodological details, including database-specific yields, exact Rayyan automation-filter criteria, and a fully itemized numerical breakdown of full-text exclusion reasons, were not retained in reproducible form. In addition, the apparent absence of catastrophic complications in some non-gluteal series may reflect limited sample size and inconsistent reporting rather than true absence of risk. These limitations should be considered when interpreting the findings (Table 1).

Table 1.

Summary of reported complications and safety considerations by anatomical region.

Muscle group / region	Major complications	Minor complications / safety notes
Facial expression muscles	No blindness, stroke, or clinical fat embolism was reported in the reviewed intramuscular-specific studies; however, available data are limited, and rare but serious vascular complications are reported in the broader facial fat grafting literature.	Transient edema or bruising, small nodules, contour irregularities, and occasional need for touch-up procedures were reported.
Pectoralis major	No deaths, pulmonary embolism, or fat embolism were reported. In reconstructive series, capsular contracture was not reported to increase relative to standard reconstruction.	Isolated hematoma and infection were reported in a small proportion of cases; low-grade capsular contracture and improved satisfaction were described when intramuscular grafting was used as an adjunct in selected settings.
Oblique-serratus complex	No major complications were reported in the reviewed series, including no reported fat embolism or reoperation.	Rare transient hyperpigmentation and mild febrile episodes were reported; no significant hematomas or nerve injury were described in the reviewed studies.
Abdominal wall (rectus / internal oblique)	No deaths, fat embolism, or abdominal compartment syndrome related to intramuscular grafting were reported in the reviewed studies.	Reported complications were predominantly minor and included seroma, small oil cysts, anemia, and contour irregularities. In the U-FEMME series, the overall complication rate was approximately 12%, all minor.
Gluteal region	Historical intramuscular gluteal fat grafting has been associated with fatal fat embolism, with prior mortality estimates in the literature approximating 1:3000 in earlier reports. Risk appears lower with subcutaneous-only injection, but deep and intramuscular injection remains strongly discouraged.	In more recent subcutaneous-only ultrasound-assisted series, reported complications were generally minor, such as seroma and asymmetry. Current safety recommendations support restricting graft placement to the subcutaneous plane.
Calf (gastrocnemius)	In the broader calf augmentation literature, reported major complication rates were low and were driven primarily by implant-related events; no clear excess major risk attributable to intramuscular fat grafting itself was identified from the limited available data.	Fat-graft techniques reported few severe adverse events but often required secondary procedures because of asymmetry or limited volume persistence. Overall complication rates in mixed-technique calf augmentation literature remained modest.
Arms (deltoid, biceps, triceps)	No major complications were reported, including no hematoma requiring surgery, necrosis, deep infection, pulmonary embolism, or fat embolism.	Minor complications included bruising and temporary dysesthesia, all of which resolved without invasive treatment or long-term functional deficit.

Conclusion

Intramuscular fat grafting has evolved from a theoretical concept to an increasingly utilized adjunct in selected body contouring procedures, with potential value for enhancing contour and muscular definition in appropriately selected patients. The available literature suggests promising outcomes in selected anatomical regions, including the pectoralis and rectus abdominis, where a vascular recipient bed may support graft incorporation. However, any potential benefit must be balanced against region-specific safety considerations. While intramuscular grafting may have a role in selected upper body and extremity applications when careful plane control and ultrasound guidance are used, intramuscular gluteal injection remains associated with an unacceptable embolic risk and should be avoided. Future studies should emphasize standardized definitions, prospective comparative designs, consistent reporting of complications and patient-centered outcomes, and clearer plane-specific technical reporting.

Declaration of competing interest

The authors declare that they have no conflicts of interest related to this article.