Esthetic, functional, and prosthetic outcomes with implant-retained finger prostheses

A biomechanical study of osseointegrated patient-matched additively manufactured implant for treatment of thumb amputees

Thumb amputations leads to 50 % loss in hand functionality. To date, silicone vacuum prosthesis and autologous transplantation are the most adopted treatment solutions: nevertheless, vacuum prostheses lack in stability and cause skin issue and surgical treatment is not always accepted by patients. Osseointegrated implants were demonstrated to enhance stability, restore osseoperception and increase the time of prosthesis use. Thumb amputations present varying stump sizes: a standard size implant cannot address specificity of each patient, while a patient matched solution can meet surgeon requirements, by geometrical features of implant. The fixture presented in the current paper is the first additively manufactured patient matched osseointegrated implant for the treatment of thumb amputees. The current work aims to verify and validate a predictive finite element model (FEM) for mechanical strength of the presented fixture. FEM was demonstrated to correctly evaluate the mechanical strength of patient matched device. Minimum strength requirements were calculated in different core diameters: FEM were experimentally validated. Safety factor of 1.5 was guaranteed. Finally, considerations on performance of the prototype were carried out by means of insertion tests in Sawbones and axial pull-out force assessment. Cadaver tests to evaluate the entire procedure and production process are ongoing.

Treatment of Nonreplantable Total Thumb Amputation at the CMC Level Using Index Finger Pollicization

BACKGROUND

Pollicization of the index finger is a rarely performed reconstructive option for patients with total thumb amputations with nonsalvageable carpometacarpal (CMC) joint and thenar muscles. Successful pollicization can provide basic grasp and pinch to help patients carry out activities of daily living. We present a retrospective review of 4 patients who underwent index finger pollicization for traumatic total thumb amputations.

METHODS

A retrospective review of 4 cases of pollicization using an injured index finger for traumatic thumb amputation was performed. Patients available for follow-up were contacted for functional assessment. Outcomes including range of motion (ROM), grip strength, key pinch, 2-point discrimination, and Disabilities of the Arm, Shoulder, and Hand score were obtained. Functional thenar muscle and the CMC joint were absent in all cases. Injury mechanism was firework in 2 patients and crush in 2 patients.

RESULTS

The time from injury to pollicization ranged from 8 days to 17 months. Follow-up time ranged from 10 weeks to 3 years. Three patients regularly used the pollicized thumb in activities of daily living such as writing. Tip pinch and lateral pinch along with grip strength were weak in all cases; the best recorded pinch strength was 24% and grip strength was 25% compared with the contralateral hand. The ROM of the pollicized thumb was limited.

CONCLUSIONS

Index finger pollicization following total thumb amputation can be a viable last-resort option for patients. The pollicized digit acts as a sensate post and avoids further morbidity from the traumatized extremity.

Osseointegrated Metallic Implants for Finger Amputees: A Review of the Literature

Digital trauma amputations and digital agenesis strongly affect the functionality and aesthetic appearance of the hand. Autologous reconstruction is the gold standard of treatment. Unfortunately, microsurgical options and transplantation procedures are not possible for patients who present contraindications or refuse to undergo transplantation from the toe (e.g. toe‐to‐thumb transplantation). To address these issues, osseointegrated finger prostheses are a promising alternative. The functional assessments registered during follow‐up confirmed the promising outcomes of osseointegrated prostheses in the treatment of hand finger amputees. This review outlines (a) a detailed analysis of osseointegrated finger metallic components of the implants, (b) the surgical procedures suggested in the literature, and (c) the functional assessments and promising outcomes that demonstrate the potential of these medical osseointegrated devices in the treatment of finger amputees.

Agamy E, Fekry Mohamed G. Clinical Evaluation of the Effect of Implant-Supported and Implant Retained Distal Extension Removable Partial Dentures on the Supporting Structures

Objective: To evaluate and compare the effect of implant supported versus implant retained removable partial denture restoring Kennedy's class I cases on the supporting structures by measuring modified gingival index and probing depth for abutment teeth and implants. Subjects and Methods: Twelve patients; who had Kennedy class I mandibular partially edentulous ridge extending distal to the first or second premolar,   were selected from the outpatient clinic, Prosthodontics Department, Faculty of Dentistry, Minia University. The patients were classified into two equal groups; according to the implant superstructures either dome shaped abutment or ball and socket attachment.  Each Patient of both groups had two implants in second molar position (one in each side) and received removable partial denture of the same design. Patients were followed up for one year clinically. Group I: Six patients received RPD supported by dome shaped short abutments.  Group II six patients received RPD retained by ball and socket attachments. Results: Results revealed that, there was no statistically significant difference between the two groups regarding modified gingival index and probing depth around the abutment teeth and implant abutment. Conclusion:  The use of dome shaped abutment or ball and O-ring attachment have the same effect on gingival index and probing depth around natural abutments and implants in Kennedy class I mandibular situations.

Novel approaches to fitting and implanting finger and nail prosthetics

PURPOSE

This work presents unique designs for prosthetic restoration of the distal finger. We first discuss fitting a prosthetic nail in order to restore the cosmetic deficit caused by partial or complete nail injury. This concept is inspired from snap fit and lanced sheet metal technology. We also discuss new approaches to designing and fitting a full fingertip prosthetic with a special suspension and a socket for more complete cosmetic fingertip restoration.

METHODS

The designs utilize the compliance and higher strain level of hinges to fit the prosthesis with either the residual nail or to the distal-most aspect of the amputated fingertip. These techniques require preparation of the residual nail to match the fabricated nails well as design of a snap fit nail prosthetic. The socket and suspension design of the full fingertip prosthetic is formed with a spring shape and has an open end to allow proper molding, fit, and suspension.

RESULTS

The introduced approaches simplify the assembly steps and propose unique, cosmetically appropriate, and potentially less irritating prosthetic options compared to what has been previously used. The socket of the finger has an ability to expand and can be worn on any stump size.

CONCLUSION

Low cost, fewer parts, ease of assembly and user friendly are the main attributes of the introduced designs. Future work to finalize these designs and trial them in humans is needed.

Past, Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by synthetic polymers bringing about significant improvements in fabrication and greater realism and utility. These traditional methods have now been disrupted by the advanced manufacturing revolution, radically changing the materials, methods, and nature of prosthetics. In this report, traditional synthetic polymers and advanced prosthetic materials and manufacturing techniques are discussed, including a focus on prosthetic material degradation. New manufacturing approaches and future technological developments are also discussed in the context of specific tissues requiring aesthetic restoration, such as ear, nose, face, eye, breast, and hand. As advanced manufacturing moves from research into clinical practice, prosthetics can begin new age to significantly improve the quality of life for those suffering tissue loss or disfigurement.

Reverse digital artery cross-finger flap for reconstruction of failed finger replantation

PURPOSE

This study aimed to describe the reverse digital artery cross-finger flap (RDAC flap) in the treatment of failed finger replantation.

METHODS

This study retrospectively reviewed the records of patients who underwent modified RDAC flap reconstructions for failed finger replantation and assessed their outcomes. Of the patients who underwent soft tissue reconstructions for finger injuries between March 2011 and February 2015, we enrolled 11 patients in whom RDAC flap reconstruction procedures were performed to treat the failed replantations.

RESULTS

The flaps survived in all cases, with a mean static, two-point discrimination value of 5.3 mm (range, 4-7 mm) in the healed flaps. The sizes of the flaps ranged from 2 × 1 cm² to 2.3 × 1.5 cm².

CONCLUSION

The RDAC flap was introduced by Lai et al., and it is a mixed form with the advantages of both cross-finger flap and heterodigital island flap. Our results suggest that it could provide reliable coverage of the sensate soft tissue of fingers with failed replantation.

Advancements in Soft-Tissue Prosthetics Part A: The Art of Imitating Life

Physical disfigurement due to congenital defects, trauma, or cancer causes considerable distress and physical impairment for millions of people worldwide; impacting their economic, psychological and social wellbeing. Since 3000 B.C., prosthetic devices have been used to address these issues by restoring both aesthetics and utility to those with disfigurement. Internationally, academic and industry researchers are constantly developing new materials and manufacturing techniques to provide higher quality and lower cost prostheses to those people who need them. New advanced technologies including 3D imaging, modeling, and printing are revolutionizing the way prostheses are now made. These new approaches are disrupting the traditional and manual art form of prosthetic production which are laborious and costly and are being replaced by more precise and quantitative processes which enable the rapid, low cost production of patient-specific prostheses. In this two part review, we provide a comprehensive report of past, present and emerging soft-tissue prosthetic materials and manufacturing techniques. In this review, part A, we examine, historically, the ideal properts of a polymeric material when applied in soft-tissue prosthetics. We also detail new research approaches to target specific tissues which commonly require aesthetic restoration (e.g. ear, nose and eyes) and discuss both traditional and advanced fabrication methods, from hand-crafted impression based approaches to advanced manufactured prosthetics. We discuss the chemistry and related details of most significant synthetic polymers used in soft-tissue prosthetics in Part B. As advanced manufacturing transitions from research into practice, the five millennia history of prosthetics enters a new age of economic, personalized, advanced soft tissue prosthetics and with this comes significantly improved quality of life for the people affected by tissue loss.

Osseo integrated finger prosthesis with a custom abutment

One of the most regularly encountered forms of partial hand loss causing physical, psychosocial and financial burden to an individual is the finger amputation followed by trauma. The prosthetic rehabilitation of amputated finger is a good treatment option, when compared to all other means of complex and unaffordable options. Osseointegrated implant retained silicone finger prosthesis with innovative prosthetic designs can provide the patient a life changing experience.

Impact of silicone prosthesis on hand function, grip power and grip-force tracking ability after finger amputation

BACKGROUND

Literature mostly describes the cosmetic role of prostheses for finger amputation. The impact on hand function has not been systematically explored.

OBJECTIVES

Our aim was to describe the impact of silicone finger prostheses on hand function and gripping ability.

STUDY DESIGN

Prospective descriptive cross-sectional study.

METHODS

We included 42 adult patients with partial or complete single- or multiple-digit amputation of one hand. We evaluated hand function of the injured hand without and with the prosthesis with the Southampton Hand Assessment Procedure, and grip power and tracking ability with a grip-force tracking system.

RESULTS

Southampton Hand Assessment Procedure grip index scores were slightly higher when using the prosthesis as compared to not using it (though not reaching the minimum real difference reported in the literature), except for lateral grip. Grip power was not significantly affected by prosthesis use for power grip and lateral grip and slightly diminished for tip grip. Tracking errors only differed with respect to the signal type but not with respect to using the prosthesis.

CONCLUSION

A minimum improvement of hand function can be expected at best with silicone prostheses for finger amputation, accompanied by a slight decrease in tip grip power.

CLINICAL RELEVANCE

Based on our results, an evidence-based explanation can be given to patients after finger amputation regarding the functional benefits that can be expected from a silicone prosthesis.

Looking Ahead to Engineering Epimorphic Regeneration of a Human Digit or Limb

Approximately 2 million people have had limb amputations in the United States due to disease or injury, with more than 185,000 new amputations every year. The ability to promote epimorphic regeneration, or the regrowth of a biologically based digit or limb, would radically change the prognosis for amputees. This ambitious goal includes the regrowth of a large number of tissues that need to be properly assembled and patterned to create a fully functional structure. We have yet to even identify, let alone address, all the obstacles along the extended progression that limit epimorphic regeneration in humans. This review aims to present introductory fundamentals in epimorphic regeneration to facilitate design and conduct of research from a tissue engineering and regenerative medicine perspective. We describe the clinical scenario of human digit healing, featuring published reports of regenerative potential. We then broadly delineate the processes of epimorphic regeneration in nonmammalian systems and describe a few mammalian regeneration models. We give particular focus to the murine digit tip, which allows for comparative studies of regeneration-competent and regeneration-incompetent outcomes in the same animal. Finally, we describe a few forward-thinking opportunities for promoting epimorphic regeneration in humans.

Reconstruction of the traumatized thumb

BACKGROUND

The goals of thumb reconstruction include the restoration of thumb length, strength, position, stability, mobility, sensibility, and aesthetics. It is a rare event when all of these objectives can be achieved, and prioritization should be based on the goals and functional demands of the patient.

METHODS

In this article, the authors review the most common reconstructive strategies for all types of traumatic thumb defects.

RESULTS

Replantation is approached first as the primary option for most amputations. Nonreplantable injuries are organized using a simple classification adapted from Lister, dividing thumb amputations into four functional categories: soft-tissue deficit with acceptable length, subtotal amputation with borderline length, total amputation with preservation of the carpometacarpal joint, and total amputation with destruction of the carpometacarpal joint. Within each category, relevant microsurgical and nonmicrosurgical reconstructive techniques are discussed, with a focus on appropriate technique selection for a given patient. Evidence and outcomes data are reviewed where available, and case examples from our own experience are provided.

CONCLUSIONS

Given that available options now range from simple gauze dressings to complex microsurgical reconstruction, preservation of reconstructive flexibility is essential and should be facilitated by judicious preservation of intact structures. The divergence of available reconstructive pathways underscores the importance of knowing one's patients, understanding their motivation, and assessing their goals. Only in properly matching the right reconstruction with the right patient will a mutually satisfactory result be achieved.

Stress distribution in implant retained finger prosthesis: a finite element study

BACKGROUND

Finger amputation may result from congenital cause, trauma, infection and tumours. The finger amputation may be rehabilitated with dental implant-retained finger prosthesis. The success of implant-retained finger prosthesis is determined by the implant loading. The type of the force is a determining factor in implant loading.

OBJECTIVE

To evaluate stress distributions in finger bone when the loading force is applied along the long axis of the implant using finite element analysis.

METHOD

The finite element models were created. The finger bone model containing cortical bone and cancellous bone was constructed by using radiograph. Astra Tech Osseo Speed bone level implant of 4.5 mm diameter and 14 mm length was selected. The force was applied to the top of the abutment along the long axis of the implant.

RESULTS

Finite element analysis indicated that the maximum stress was located at the head of abutment screw. The minimum stress was located in the apical third of the implant fixture. The weakest point was calculated by safety factor which is located in the spongy bone at apical third of the fixtures. Finally, 4.9 times yield stress of spongy bone was needed for the deformation of the spongy bone.

CONCLUSION

Finite element study showed that when the force was applied along the long axis of the implant, the maximum stress was located around the neck of the implant and the cortex bone received more stress than cancellous bone. So, to achieve long term success, the designers of implant systems must confront biomaterial and biomechanical problems including in vivo forces on implants, load transmission to the interface and interfacial tissue response.