Introduction
Transfemoral amputations have devastating consequences—patients are left with significant functional, psychological and social issues that decrease their quality of life.1–5 Currently a socket prosthesis is the most common means of improving function in the residual limb.4,6–8 However, high forces are applied from a prosthetic socket to the soft tissue of the residual limb.6 This may result in chronic skin irritation and sores, chronic residual limb pain, prosthesis intolerance, unreliable suspension, decreased mobility and reduced quality of life in the affected individuals.2–5,7
Osseointegration provides an alternative for patients who are suffering from the adverse effects of traditional socket prosthesis.1–10 The aim of osseointegration is to create a direct transcutaneous skeletal attachment for a prosthesis, thus negating the need for a socket.1,6,8–10 Patients who successfully undergo osseointegration may have improvements in quality of life, prosthetic use, range of motion in the residual limb, mobility, prosthetic fixation and sensory perception compared with traditional socket prosthess.6,8
Osseointegration is still a relatively novel technique in the field of limb amputation.2,11,12 Reported complications include mechanical failure of the implant and infection.1,4,6 The primary aim of this study was to review abutment failures in patients who underwent transfemoral osseointegration and to identify risk factors that may contribute to these failures. The secondary aim was to review rates of other complications associated with osseointegration in transfemoral amputees.
Methods
The study was undertaken through the osseointegration and targeted muscle reinnervation surgical and rehabilitation program at The Alfred, Victoria, Australia. This program was redesigned in 2016, with the establishment of a multidisciplinary team, formal selection and rehabilitation protocols and prospective data collection of outcomes. Ethics approval was obtained through The Alfred’s ethics committee [414/16]. A retrospective chart analysis was conducted of all patients who underwent transfemoral osseointegration between January 2000 and June 2019 in a consecutive series. For selection into the osseointegration program, patients must have reported failure with using a traditional socket-based prosthesis. Patients were excluded if they were aged less than 18 years or if the clinical notes were incomplete.
Each selected patient undergoes a two-stage osseointegration procedure using the Osseointegration Prostheses for the Rehabilitation of Amputees (OPRA) implant system. This implant was modified in late 2017, using a more durable material for the fixture and abutment. The first stage involves intramedullary placement of a fixture into the femur of the residual limb. The fixture is left unloaded in the residual bone to allow integration over a period of at least six months. The second stage involves extensive refashioning of the soft tissues and percutaneously placing an abutment into the fixture (Figure 1). Finally, patients undergo a strict rehabilitation protocol that gradually increases the load on the implant, followed by mobilisation and activity training (Table 1).
Data sources reviewed included scanned operation reports, clinical notes, pre-and postoperative radiography and rehabilitation notes. Data collected were age, gender, weight, body mass index, smoking status, comorbidities, reason for limb loss, postoperative complications, use of mobility aids and patient activity. Abutment failure was classified as either a fractured, bent or loose abutment within the fixture. Osseointegration failure was defined as the primary fixture not achieving integration into the medullary canal of the bone it was implanted into—that is, a loose fixture.
All data collected were de-identified and analysed using Microsoft® Excel software version 15.31 (Microsoft Corporation, Redmond, Washington, USA). Continuous data are expressed as median ± interquartile range (IQR) and categorical data are expressed as counts and percentages. Statistical significance was set at a two-sided p value of 0.05 and calculated using a Mann-Whitney U test for continuous data and a Fisher exact test for categorical data.
Results
During the 19-year period of the study a total of 19 lower limbs were osseointegrated in 18 patients (12 males and six females), and no patients were excluded from the study. Of these, 17 patients had a single transfemoral osseointegration and one patient was osseointegrated in all four limbs. Two patients underwent transfemoral osseointegration through the updated program protocol and were implanted with the newer system. One patient died during the study period due to metastatic renal cell carcinoma unrelated to the osseointegration program. The median age of this group was 49 years old.
Of the 18 patients, two (one male and one female) failed to achieve osseointegration and had their implants removed. There were two statistically significant differences between these two patients and the remainder of the group: non-compliance (p < 0.05, Fisher exact test) and active smoking. Non-compliance was defined as not following the graded six-month rehabilitation protocol post second stage surgery. One patient was an avid sportsperson and we believe their heavy use of the osseointegrated limb during rehabilitation led to the fixture loosening. The other patient declined follow-up during the rehabilitation period and self-managed against medical advice. Both their fixtures were later removed at another institution. Both patients were active smokers as well, compared with only two active smokers in the 16 patients who achieved osseointegration.
No patients suffered from a fatal complication such as death, myocardial infarction, pulmonary embolism or stroke from the surgery. A total of 37 complications were reported in 15 patients. After the first stage, two patients suffered from severe pain in the osseointegrated limb and one patient developed a postoperative haematoma which required a return to theatre. After the second stage, the most common complication was abutment failure, occurring 46 times in 11 patients. The second most common complication was severe pain in the osseointegrated limb, occurring in eight patients, and these patients were successfully managed through the pain service with neuropathic agents. Soft-tissue infections occurred in five patients. Three patients had superficial cellulitis which was managed with antibiotics alone. Two patients had a collection requiring a washout and debridement in theatre. One patient suffered from a haematoma and one patient suffered from a seroma, and both had a return to theatre for a washout (Table 2).
Observing specifically the two patients who underwent the updated osseointegration program, neither suffered any complications after the first stage. Post second stage, one patient reported minor skin irritation at the stoma site of their abutment. There have been no reported abutment failures with the newer osseointegration system.
Eleven transfemoral amputees (61%) had at least one abutment failure (total 46, median 1 ± 0–6.5 IQR). Of these patients, eight were male and three were female (Table 3). The median age of patients with abutment failures was 16 years younger than those who did not suffer an abutment failure (p < 0.05). All seven patients who were walking more than three kilometres per day and reported high use of the osseointegrated prosthesis had at least one abutment failure (p < 0.05). There was no statistical significance in median body mass index, gender, reason for limb loss and active smoking status between patients that had an abutment failure compared with patients that did not.
With regards to postoperative activity in the 16 patients who achieved osseointegration, 10 were using their osseointegrated prosthesis for more than 10 hours a day. Seven patients reported walking greater than three kilometres a day, and the remaining nine patients, while less active, were still able to mobilise with their prosthesis (Table 3).
Discussion
Osseointegration is defined as when an implant has no relative progressive movement with the bone that it is in direct contact with.2,13 The success of osseointegration fundamentally relies on three aspects—precise surgical technique, sufficient recovery period to allow bony ingrowth and controlled loading of the implant to allow for bone remodeling.2,11,13 The technique of osseointegration in the treatment of amputees is still relatively novel and was first carried out in 1990 in Sweden on a transfemoral amputee.13,14 OPRA, a standardised surgical and rehabilitative protocol, was later developed in 1999.13–16 In 2016, a more stringent preoperative assessment by a multidisciplinary team of surgeons, prosthetists, rehabilitation physicians and psychologists was established. The surgical technique was improved to deal with the soft-tissue sequelae as well as instituting a new modified osseointegration system to address abutment failures.
Conventional socket-based prostheses are an important tool in the rehabilitation of transfemoral and transhumeral amputees.15 However, approximately one-third of amputees complain of ongoing skin problems with socket prosthesis such as ulceration, skin irritation, fluctuating stump volume and pain.8,14 Furthermore, 72 per cent of amputees report excess perspiration causing fitting issues with socket prosthesis.14 Proven benefits of the osseointegrated prosthesis in comparison with a socket prosthesis are quicker donning and doffing, increased range of motion in the affected limb, increased prosthetic use, improved gait and reduced energy expenditure with walking.1,14–16 Patients also have better tactile perception transmitted through a bone-anchored prosthesis and hence improved interaction with their environment—this is known as osseoperception.1,2 Lastly, when looking at standardised measures, the current literature reports that 69–95 per cent of patients report an improvement in quality of life with an osseointegrated prosthesis comparted with their previous socket-based prothesis.1,14
The Alfred program offers osseointegration only to patients who have failed conventional socket-based prosthesis. While osseointegration has many potential benefits for patients, the program is not without complications. The cumulative survival of rate of implants in this cohort was 89 per cent, which is comparable to previous reported survival rates of 80–92 per cent.1,9,17 In this study, the common factor among both patients whose prosthesis failed to osseointegrate was non-compliance with the rehabilitation protocol and active smoking. Controlled graded increases in weight offloading and activity are important to allow bone mineralisation, strengthening and remodelling around the implant.14 If there is an early and rapid increase in implant loading, it is at risk of loosening. As such, updated eligibility criteria for the osseointegration program now include the patient having a thorough understanding of the rehabilitation protocol and displaying an ability to comply.1,14,15 Other reported reasons for failure to achieve osseointegration are infection, immunosuppression such as chemotherapy or systemic steroids, heavy smoking, diabetes mellitus and a body mass greater than 100 kg.2,4,15
A prospective observational study by Brånemark and colleagues in 20141 reported that 96 per cent of patients who underwent transfemoral osseointegration suffered from one or more complications. In the current study, 83 per cent of all patients suffered at least one complication. The most commonly reported complication in the literature is superficial skin infections, with rates reported between 28 and 58 per cent.1,9,16,17 In contrast, only three patients in this study (17%) suffered from superficial skin infections. This difference may be explained by the fact that our program has a large plastic and reconstructive surgery involvement.
Mechanical abutment failures were the most common complication in this study. Of the 18 transfemoral amputees, 11 (61%) suffered from at least one abutment failure. This rate is higher than the 8 per cent reported by Brånemark and colleagues2 but more comparable to the 45 per cent reported by Sullivan and colleagues.15 Younger age and high self-reported levels of postoperative activity were the two statistically significant patient factors identified in mechanical abutment failures in this study. It could be inferred that younger patients were more active and hence placed greater mechanical strain on the abutment. In the study by Sullivan and colleagues,15 all abutment failures were secondary to high impact falls. Of note, with the updated rehabilitation program and use of the newer modified implant, no abutment failures have occurred.
In evaluating the kinetics of transfemoral amputees with osseointegrated fixations, multiple sectional forces occur across all three axes of the abutment during periods of walking.4,7 Furthermore, during a fall, the load applied to the residual limb is non-linear and dynamic, causing high magnitude stress on the abutment.18 Due to these factors, it is postulated that abutment failures are secondary to repetitive high-impact forces such as those encountered in heavy manual labour, running and jumping and in patients with a high body mass index.15 It should be noted that in the setting of high mechanical stress, the ability for the abutment to fail is an inherent safety design of the system.4,18 By the abutment failing, large forces are prevented from being transmitted to and overloading the fixture and residual bone.4,19–21 This prevents damage to the fixture or a peri-prosthetic fracture from occuring.4,19–21 Fixture damage and peri-prosthetic fractures are more serious and difficult complications to manage.
Certain limitations are inherent in this study. The retrospective study design and low patient numbers make statistical analysis problematic. Reporting errors could have occurred as patients were treated across multiple hospitals and rehabilitation services with differing medical documentation and incomplete data on falls. Furthermore, patients undergoing osseointegration were generally seeking increased activity and wishing for better function and thus may have been more likely to stress the abutment leading to failure. Finally, during the nineteen-year period of the osseointegration program, patient selection and counselling became stricter to improve understanding of the rehabilitation protocol and compliance. Therefore, patient selection was not uniform during the study period.
Conclusion
Osseointegration is an option for select amputees for whom traditional socket prostheses are unsuitable. Bone-anchored prostheses have the advantage of no socket-related skin problems as well as increased range of motion, mobility and quality of life. However, the osseointegration program is not without complications and mechanical failure. The rehabilitative protocol is also strict and can be prolonged. Patient selection and appropriate counselling are vital, especially with regards to activities of daily living and functional expectations.
Acknowledgements
The data in this paper have also been presented at RMSANZ 2017, the second annual scientific meeting of the Rehabilitation Medicine Society of Australia and New Zealand, 17–20 September 2017, Canberra, Australia.
Patient consent
Patients/guardians have given informed consent to the publication of images and/or data.
Conflict of interest
Steven Gray is the company director of the Australian sponsor of the OPRA system manufactured by Integrum AB, Sweden.
Funding declaration
The authors received no financial support for the research, authorship, and/or publication of this article.
Revised: June 21, 2020 AEST