A Comprehensive Review on a Prosthetic Finger Fabrication Approach: Clinical Rest Position (CRP) vs Palms and Fingers Extended (PFE)

Creating effective prosthetic fingers involves precise treatment planning and skilled fabrication to restore aesthetic appearance and passive function. Successful outcomes depend significantly on retention and how closely the prosthesis mimics natural finger contours. We analyzed techniques for fabricating finger prostheses with palms and fingers in clinical rest position (CRP) versus palms and fingers extended (PFE) straight out. The aesthetics and function (passive) were also examined when fabricated in these two physiological conditions. We reviewed 20 articles from national and international journals over 20 years. Most literature focuses on extended posture fabrication, with few addressing CRP. This review article compares the CRP and PFE prosthetic finger fabrication approaches and explains how a prosthetic finger fabricated in a CRP offers superior aesthetic and partial functional outcomes and emerges as a promising alternative to the PFE. The potential impact of these findings on prosthodontics is significant, emphasizing the need for further research to validate these results and the ongoing development in the field.


Introduction And Background
Fingers are critical in everyday tasks, from grasping objects to intricate manipulations that define our daily lives.Fingers help us grasp objects, perform our daily functions, and give us an aesthetic appearance [1].The finger is divided into three segments: distal phalanx, middle phalanx, and proximal phalanx.The distal and proximal phalanx are towards each finger's tip and body.
Loss of a finger, whether congenital or acquired, impacts both function and appearance, necessitating prosthetic rehabilitation.Loss of a complete finger or phalanx of a finger could be caused by congenital reasons or acquired [2].Loss of a finger for congenital reasons is due to the absence of a gene responsible for its development.Acquired reasons for the loss of digits or fingers could be because of trauma (accidental loss) or surgical excision.Loss of a finger leads to a complete or partial loss of function and aesthetics.At the same time, the patient has to face mental trauma as there is unwanted attraction by others [2].Achieving a prosthetic finger miming natural contours and function is a significant challenge for prosthodontists.It is also challenging for the operator to make the prosthesis regain a partial day-to-day function (holding glasses, writing, etc.).
Prosthetic finger fabrication represents a multidimensional endeavor encompassing meticulous treatment planning, precise execution of prosthetic design, and the selection of appropriate materials that balance durability and aesthetic fidelity.One crucial aspect often overlooked in this process is the hand's posture clinical rest position (CRP) and palms and fingers extended (PFE) while fabricating these prostheses.Traditionally, prosthetic fingers are designed and fabricated in a PFE straight-out position, mimicking a static posture that does not necessarily reflect the hand's natural resting position.However, recent attention has turned towards exploring an alternative approach: fabricating prosthetic fingers in a CRP.This position acknowledges the natural curvature of the palm and fingers at rest, potentially offering prosthetic solutions that look more natural and intuitively function in everyday activities.This comprehensive review aims to critically examine and compare the outcomes of prosthetic finger fabrication in these two distinct hand postures: PFE and CRP.It compares some literature with different approaches to provide insights that can inform future advancements in prosthetic finger design and enhance the quality of life for individuals requiring prosthetic rehabilitation.

Problem statement for its fabrication
Fabricating prosthetic fingers involves challenges such as cost, durability, retention, and posture considerations.Most literature focuses on materials and retention methods, with limited discussion on the posture of fingers and palms during fabrication.Expensive fabrication, significant wear and tear, loss of material, discoloration, prosthesis retention, and finger posture to be considered in its fabrication have been addressed in the literature [2][3][4][5].Numerous articles are found in the literature elaborating on the material used in its fabrication in terms of cost and durability for their wear and tear and color stability [6][7][8].Many articles are also found in the literature on increasing the retention of the prosthesis with various mechanical tools [1,2,9].However, very few articles in the literature focus on the posture of the finger to be considered, i.e., CRP and PFE [2].This article compares the finger prosthesis when fabricated in CRP versus PFE straight out in terms of its passive functionality and the aesthetic achieved after fabrication.

Methodology
We reviewed 20 case reports detailing techniques for fabricating finger prostheses.The articles were analyzed for aesthetics and functionality in different finger and palm postures: clinical rest and extended straight out.The procedure involved in its fabrication was studied, and the precision and perfection of the prosthesis were considered to evaluate its aesthetics and functionality in two different clinical postures of the prosthetic fingers and palms, i.e., CRP and PFE (straight out).
Published articles, from the year 2008 to 2024, on finger prostheses were collected from online databases of PubMed, Sage journals, DOAJ, Wikipedia, Science Direct, and Google Scholar.Articles published in various national and internationally indexed journals were included in this literature review to ensure up-to-date information and technological advancements.
The articles from non-peer-reviewed journals, opinion pieces, or non-scientific literature and studies that do not specifically address prosthetic finger fabrication were excluded from this literature review.

Review
Prosthetic finger fabrication is pivotal in restoring functional capability and aesthetic appearance for individuals with finger loss or congenital abnormalities.Two primary methods, CRP and PFE, have emerged as key approaches in prosthetic finger design and fabrication.This literature survey aims to comprehensively review and compare these two techniques based on existing research and clinical evidence.It compares two fabrication approaches, CRP and PFE, offering insights into their respective aim, functionality, merits, and demerits in prosthetic finger fabrication, as given in Table 1.The comparison reveals prostheses fabricated in clinical rest position mimic natural finger contours more accurately, enhancing aesthetics and function.Despite its potential benefits, this posture needs to be more represented in literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].It is observed that most of the papers focus on the retention of the prosthesis and the materials used for its fabrication [1,15,19].To enhance the retention of the prosthesis, various retentive aids were used, including osseointegrated implants.Doppen et al. [21] and Goiato et al. [22] described the techniques involved in treating patients with five-finger amputations with osseointegrated implants to retain the finger prosthesis.Materials used in its fabrication included clinical silicone and heat cure acrylic resin as the material of choice with characterized intrinsic and extrinsic colors incorporated, which would match the adjacent skin color [2,[5][6][7][8][10][11][12][13][14][15]17].Caldeira et al. reviewed using silicone material for finger prostheses in amputee patients.They inferred that there were noticeable improvements in aesthetics, passive function, and restoration of self-esteem, which changed their quality of life [4].
The posture of the palms and fingers was studied for its fabrication, from which it was inferred that none of the published articles focussed on the posture of the palms and fingers to be considered for its prosthetic fabrication.However, one article by Kumar et al. in 2023 describes a simple method to fabricate a partially amputated prosthetic finger in a physiological rest position (palms and fingers are slightly curved, and so is the prosthetic finger) with heat cure acrylic resin as a maxillofacial material of choice [2].As documented by Kumar et al. [2], the procedure involved in its fabrication provided an aesthetic and economical way of prosthetically rehabilitating an amputated finger, which regains back the aesthetics and passive functionality to a great extent (Figures 1-2).Meanwhile, prosthetic fingers, if fabricated when all the fingers and palms are extended straight out, are uncomfortable when performing day-to-day functions such as writing or holding objects.

Conclusions
Existing literature offers comprehensive insights into materials, retention techniques, and psychological aspects of prosthetic finger rehabilitation, but the impact of hand posture during fabrication remains unexplored.This thorough review aims to fill this gap by comparing prosthetic rehabilitation of the imputed finger under two different postures: PRE and PFE.This review paper highlights the CRP as a promising approach for advanced prosthetic design and enhanced functional and aesthetic outcomes for individuals requiring finger prostheses.However, the selection of prosthetic finger fabrication methods based on CRP should be carefully tailored to meet each individual's unique needs and functional requirements.More intervention and clinical research are needed to enhance prosthetic fingers' design and fabrication processes.There is no bias in the assessment of individual studies, as stated.
accommodate the extended position of the hand during activities requiring full hand extension.This limitation can affect functionality and usability in tasks such as grasping large objects or reaching for items placed at a distance.is challenging as it may not align perfectly with the residual limb's natural posture during rest.

Finger 8 ][ 19 ]
adaptability to the silicone finger prosthesis, used in patients after finger amputation Good adaptation, aesthetics, patient satisfaction, and good results enhance the quality of life [Kuret et al., terms of aesthetics [16] Pattanaik et al., 2013, Dec Left-hand little finger amputation CRP using Silicone Explains a customized prosthetic finger made with silicone material with a simple hairpin attachment incorporated in the distal interphalangeal joint Attachment helps in the partial restoration of function, thereby improving the functional disability 2024 Kumar et al.Cureus 16(8): e67035.DOI 10.7759/cureus.makesa precise impression of an amputated finger devoid of air-filled spaces This technique minimized the chances of incorporating voids, as equal pressure could be employed during the insertion of the impression cap into the defective finger Jacob et al., finger prosthesis with a modified base of the retention system Regained the psychological, functional, and natural appearance

FIGURE 1 :
FIGURE 1: Prosthetic finger in a physiological rest position (slightly curved) made by heat cure acrylic resin with a retentive finger ring incorporated Source: Ref. [2]

TABLE 1 : Comparative analysis of the fabrication approaches (CRP and PFE)
CRP, Clinical rest position; PFE, Palms and fingers extended

Table 2
compares references regarding retention aids and materials, particularly silicone and acrylic resin, fabrication method, procedure, and merits.

TABLE 2 : Literature review for finger prosthesis
Comparative studies have evaluated the effectiveness of CRP versus PFE fabrication methods in clinical settings.Research suggests that choosing these methods often depends on the individual's needs, occupational requirements, and personal preferences.The CRP fabrication technique provides a significant outcome regarding comfort, functionality, durability, and aesthetic appeal.