Osseointegration of Extremity Prostheses: A Primer for the Plastic Surgeon

Utility of Thermal Imaging in Predicting Superficial Infections in Transfemoral Osseointegrated Implants

Background

Superficial infection is a common minor complication of transcutaneous implants that can be challenging to predict or diagnose. Although it remains unclear whether superficial infections progress to deep infections (which may require implant removal), predicting and treating any infection in these patients is important. Given that flap thinning during stage II surgery requires compromising vascularity for stability of the skin penetration aperture, we hypothesized that early skin temperature changes predict long-term superficial infection risk.

Methods

We obtained standardized thermal imaging and recorded surface temperatures of the aperture and overlying flaps 2 weeks postoperatively for the first 34 patients (46 limbs) treated with the Osseointegrated Prosthesis for the Rehabilitation of Amputees transfemoral implant system. We used two-sided t tests to compare temperatures surrounding the aperture and adjacent soft tissues in patients with and without subsequent infection.

Results

During median follow-up of 3 years, 14 limbs (30.4%) developed 23 superficial infections. At patients' initial 2-week visit, mean skin temperature surrounding the aperture was 36.3ºC in limbs that later developed superficial infections and 36.7ºC in uninfected limbs (P = 0.35). In four patients with bilateral implants who later developed superficial infection in one limb, average temperature was 1.5ºC colder in the infected limb (P = 0.12).

Conclusions

Superficial infections remain a frequent complication of transfemoral osseointegration surgery. We did not find differences in early heat signatures between limbs subsequently complicated and those not complicated by superficial infection. Further research should explore more objective measures to predict, diagnose, and prevent infections after osseointegration surgery.

Thighplasty at the Time of Stage-1 Bone-Anchored Osseointegration Surgery

Background

For patients with transfemoral amputations and difficulty tolerating conventional socket-based prostheses, osseointegrated (OI) implants have enabled increased prosthetic use, improved patient satisfaction, and shown promising functional outcomes1,2. Although the use of OI implants effectively eliminates the soft-tissue-related challenges that have plagued socket-based prostheses, the presence of a permanent, percutaneous implant imparts a host of new soft-tissue challenges that have yet to be fully defined. In patients undergoing OI surgery who have redundant soft tissue, we perform a thighplasty to globally reduce excess skin and fat, tighten the soft-tissue envelope, and improve the contour of the residual limb.

Description

First, the orthopaedic surgical team prepares the residual femur for implantation of the OI device. After the implant is inserted, the residual hamstrings and quadriceps musculature are closed over the end of the femur, and the subcutaneous tissue and skin are closed in a layered fashion. Although the anatomic location and amount of excess soft tissue are patient-dependent, we perform a standard pinch test to determine the amount of soft tissue that can be safely removed for the thighplasty. Once the proposed area of resection is marked, we proceed with longitudinal, sharp dissection down to the level of the muscular fascia. At this point, we use another pinch test to confirm the amount of soft-tissue resection that will allow for adequate resection without undue tension3. Excess subcutaneous fat and skin are carefully removed along the previously marked incisions, typically overlying the medial compartment of the thigh in the setting of patients with transfemoral amputations. The thighplasty incision is closed in a layered fashion over 1 or 2 Jackson-Pratt drains, depending on the amount of resection.

Alternatives

Depending on the amount of redundant soft tissue, thighplasty may not be necessary at the time of OI surgery; however, in our experience, excess soft tissue surrounding the transcutaneous aperture can predispose the patient to increased shear forces at the aperture, increased drainage, and increased risk of infection4.

Rationale

Although superficial infectious complications are most common following OI surgery, the need for soft-tissue refashioning and excision is one of the most common reasons for reoperation1,5. Our group has been more aggressive than most in our use of a vertical thighplasty procedure to globally reduce soft-tissue motion in the residual limb to avoid reoperation.

Expected Outcomes

Although much of the OI literature has focused on infectious complications, recent studies have demonstrated reoperation rates of 18% to 36% for redundant soft tissue following OI surgery1,5. We believe that thighplasty at the time of OI not only reduces the likelihood of reoperation but may also decrease infectious complications by reducing relative motion and inflammation at the skin-implant interface4,6.

Important Tips

The thighplasty procedure is ideally performed as part of the first stage of the OPRA (Osseointegrated Prosthesis for the Rehabilitation of Amputees) procedure to limit the likelihood of problematic ischemia-related complications.We utilize a confirmatory pinch test both before and throughout the thighplasty procedure to ensure adequate resection without undue tension.The thighplasty excision pattern utilizes a long vertical limb designed to decrease the circumferential laxity of the residual limb. Maximal tension is borne on the vertical limb and not on the transverse extensions, as these are prone to scar widening and distortion of surrounding tissues.Closed-suction drainage is utilized liberally to decrease the likelihood of a symptomatic seroma.

Acronyms and Abbreviations

OI = osseointegratedOPRA = Osseointegrated Prosthesis for the Rehabilitation of AmputeesPVNS = pigmented villonodular synovitisT-GCT = tenosynovial giant-cell tumor.BMI = body mass indexPMH = past medical history.

Current Concepts in Lower Extremity Amputation: A Primer for Plastic Surgeons

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand the goals of lower extremity reconstruction and identify clinical scenarios favoring amputation. 2. Understand lower extremity amputation physiology and biomechanics. 3. Review soft-tissue considerations to achieve durable coverage. 4. Appreciate the evolving management of transected nerves. 5. Highlight emerging applications of osseointegration and strategies to improve myoelectric prosthetic control.

SUMMARY

Plastic surgeons are well versed in lower extremity reconstruction for traumatic, oncologic, and ischemic causes. Limb amputation is an increasingly sophisticated component of the reconstructive algorithm and is indicated when the residual limb is predicted to be more functional than a salvaged limb. Although plastic surgeons have traditionally focused on limb salvage, they play an increasingly vital role in optimizing outcomes from amputation. This warrants a review of core concepts and an update on emerging reconstructive techniques in amputee care.

Osseointegration for Lower Limb Amputation: Understanding the Risk Factors and Time Courses of Soft Tissue Complications

PURPOSE

Lower-limb osseointegrated prostheses are a novel alternative to traditional socket-suspended prostheses, which are often associated with poor fit, soft tissue damage, and pain. Osseointegration eliminates the socket-skin interface and allows for weight-bearing directly on the skeletal system. However, these prostheses can also be complicated by postoperative issues that can negatively impact mobility and quality of life. Little is known about the incidence of or risk factors for these complications as few centers currently perform the procedure.

METHODS

A retrospective analysis was performed on all patients who underwent single-stage lower limb osseointegration at our institution between 2017 and 2021. Patient demographics, medical history, operative data, and outcomes were collected. Fisher exact test and unpaired t tests were performed to identify risk factors for each adverse outcome, and time-to-event survival curves were generated.

RESULTS

Sixty patients met our study criteria: 42 males and 18 females with 35 transfemoral and 25 transtibial amputations. The cohort had an average age of 48 years (range, 25-70 years) and follow-up period of 22 months (range, 6-47 months). Indications for amputation were trauma (50), prior surgical complication (5), cancer (4), and infection (1). Postoperatively, 25 patients developed soft tissue infections, 5 developed osteomyelitis, 6 had symptomatic neuromas, and 7 required soft tissue revisions. Soft tissue infections were positively correlated with obesity and female sex. Neuroma development was associated with increased age at osseointegration. Neuromas and osteomyelitis were both associated with decreased center experience. Subgroup analysis by amputation etiology and anatomic location did not show significant differences in outcomes. Notably, hypertension (15), tobacco use (27), and prior site infection (23) did not correlate with worse outcomes. Forty-seven percent of soft tissue infections occurred in the 1 month after implantation, and 76% occurred in the first 4 months.

CONCLUSIONS

These data provide preliminary insights into risk factors for postoperative complications arising from lower limb osseointegration. These factors are both modifiable (body mass index, center experience), and unmodifiable (sex, age). As this procedure continues to expand in popularity, such results are necessary to inform best practice guidelines and optimize outcomes. Further prospective studies are needed to confirm the above trends.

Socioecological model-based design and implementation principles of lower limb preservation programs as partners for limb-loss rehabilitation programs- A mini-review

People with lower limb loss, especially of dysvascular etiology, are at substantial risk for both ipsilateral and contralateral reamputation. Additionally, while not as well documented for reamputation, there is recognition that amputation incidence is influenced by not only sociodemographic factors such as sex, race, socioeconomic status, but also by system factors such as service access. A systems strategy to address this disparity within the field of limb-loss rehabilitation is for Limb-loss Rehabilitation Programs (LRP) to partner with medical specialists, mental health professionals, and Limb Preservation Programs (LPP) to provide comprehensive limb care. While LPPs exist around the nation, design principles for such programs and their partnership role with LRPs are not well established. Using a socioecological model to incorporate hierarchical stakeholder perspectives inherent in the multidisciplinary field of limb care, this review synthesizes the latest evidence to focus on LPP design and implementation principles that can help policymakers, healthcare organizations and limb-loss rehabilitation and limb-preservation professionals to develop, implement, and sustain robust LPP programs in partnership with LRPs.

Osseointegration for Lower-Extremity Amputees: Operative Considerations from the Plastic Surgeon's Perspective

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Osseointegration for lower-extremity amputees, while increasing in frequency, remains in its relative infancy compared with traditional socket-based prostheses.

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Ideal candidates for osseointegration have documented failure of a traditional prosthesis and should be skeletally mature, have adequate bone stock, demonstrate an ability to adhere to a longitudinal rehabilitation protocol, and be in an otherwise good state of health.

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Lowering the reoperation rate for soft-tissue complications depends heavily on surgical technique and on the implant device itself; the current gold standard involves a smooth implant surface for dermal contact as well as maximal skin resection to prevent skin breakdown against the prosthesis. This may include the need for thighplasty to optimize skin reduction.

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Interdisciplinary peripheral nerve management, such as targeted muscle reinnervation, performed in tandem with a plastic surgery team can treat existing and prevent future symptomatic neuromas, ultimately improving pain outcomes.

Comparative outcome analysis of osseointegrated reconstruction and replantation for digital amputations

The long-term outcomes of osseointegration for digital amputations are not well established, and it is not known whether osseointegration can achieve similar function and patient satisfaction to conventional surgical options such as replantation and microsurgical toe transfer. We compared the long-term outcomes after digital osseointegration and replantation. Six patients treated by osseointegration and seven patients treated by replantation were included, with median follow-ups of 8 years and 4.6 years, respectively. Outcomes were assessed using the Michigan Hand Outcomes Questionnaire, grip and pinch strength, range of motion, two-point discrimination, Semmes-Weinstein tests, Jebsen-Taylor Hand Function Test and clinical photography. Osseointegration was associated with poorer sensibility and range of motion than replantation; no other differences reached statistical significance. Long-term osseointegration is a safe and effective reconstructive option that can deliver excellent outcomes in appropriately selected patients.Level of evidence: IV.

Extramedullary Osseointegration-A Novel Design of Percutaneous Osseointegration Prosthesis for Amputees

The percutaneous osseointegrated (OI) prostheses have greatly improved the overall quality of life for amputees. However, the long-term maintenance of the OI prostheses is still challenging. A major problem is bone resorption around the bone-implant-skin interface, which might cause implant loosening or osteomyelitis. Another problem is the breakage of connecting components between the intramedullary implant and external prosthesis due to excessive stress. We designed a novel osseointegration implant by changing the bone-implant contact from the inner cortex to the outer surface of cortical bone. In the current study, we compared the extramedullary cap-shaped implants with the intramedullary screw-type implants in rabbits. Osteointegration was confirmed at the interface of bone to implant contact (BIC) in both implant types. The external implant induced intramedullary bone regeneration in the medullary canal and increased the cortical bone density at the end of the stump. This study provides a new perspective on the design of osseointegration implants which might prevent the currently reported complications of the intramedullary OI systems.

The Need to Work Arm in Arm: Calling for Collaboration in Delivering Neuroprosthetic Limb Replacements

Over the last few decades there has been a push to enhance the use of advanced prosthetics within the fields of biomedical engineering, neuroscience, and surgery. Through the development of peripheral neural interfaces and invasive electrodes, an individual's own nervous system can be used to control a prosthesis. With novel improvements in neural recording and signal decoding, this intimate communication has paved the way for bidirectional and intuitive control of prostheses. While various collaborations between engineers and surgeons have led to considerable success with motor control and pain management, it has been significantly more challenging to restore sensation. Many of the existing peripheral neural interfaces have demonstrated success in one of these modalities; however, none are currently able to fully restore limb function. Though this is in part due to the complexity of the human somatosensory system and stability of bioelectronics, the fragmentary and as-yet uncoordinated nature of the neuroprosthetic industry further complicates this advancement. In this review, we provide a comprehensive overview of the current field of neuroprosthetics and explore potential strategies to address its unique challenges. These include exploration of electrodes, surgical techniques, control methods, and prosthetic technology. Additionally, we propose a new approach to optimizing prosthetic limb function and facilitating clinical application by capitalizing on available resources. It is incumbent upon academia and industry to encourage collaboration and utilization of different peripheral neural interfaces in combination with each other to create versatile limbs that not only improve function but quality of life. Despite the rapidly evolving technology, if the field continues to work in divided "silos," we will delay achieving the critical, valuable outcome: creating a prosthetic limb that is right for the patient and positively affects their life.

The bone anchored prostheses for amputees - Historical development, current status, and future aspects

In the past 50 years, bone anchored prostheses have evolved from a concept for experimental treatment to a rapidly developing area in orthopedics and traumatology. Up to date, there are dozens of centers in the world providing osseointegration amputation reconstructions and more than a thousand patients using the bone anchored prostheses. Compared with conventional socket prostheses, the bone anchored prosthesis by osseointegration avoids the debilitating problems related with soft tissues. It also provides physiological weight bearing, improved range of motion, and sensory feedback, all of which contribute to the improvement on quality of life for amputees. The present article briefly reviews the historical development of osseointegration surgery for amputation reconstruction and the current challenges. The implant design characters and surgical techniques of the two types of implants; the screw-type implant (presented by the OPRA system), and the press-fit implants (presented by EEP and OPL systems) are described. The major complications, infections and mechanical failures, are discussed in detail based on the latest evidence. Future aspects and experimental trials aiming to overcome the current challenges are presented.