Total ankle replacement: Implant Manufacturer's guidelines for post-operative rehabilitation: A review of literature

Abstract

Introduction

Total ankle replacements (TARs) is emerging as a successful alternate treatment option to arthrodesis for surgical treatment of end stage ankle arthritis. This has led to manufacturers producing a selection of implants. There is wide variations in post-operative rehab protocols being adopted for treatment following TAR surgery. This depends on choice of implants and manufacturer recommendations too. Following the author's investigation, a lack of standardisation between manufacturer post-operative protocols was identified. The aim of this project was to analyse similarities and differences in guidelines for: choice of immobilisation, weight-bearing (WB) status, of range of movement (ROM) exercises and Physiotherapy.

Method

Current commonly used TAR implants in the UK were identified using National Joint Registry's 2020 Annual Report. Additional implants were included after accessing data regarding the TAR market. Individual company websites were researched for information available on public domain for post op management guidelines and the results were summarised.

Results

Only 7 implants were reviewed as 6 companies either did not provide post-operative protocols or recommended a surgeon guided rehabilitation process. Different manufacturers allow partial WB by week 2, week 3 and week 7. One protocol suggested full WB from week 4 whereas two others suggested it from week 6. Choices of immobilisation varied as one company suggested casting alone for 6 weeks, two suggest casting followed by a period in a boot, one suggests splinting and a boot and one uses all 3 types of immobilisations. ROM exercises were mentioned by three manufacturers and were encouraged from week 2 and 3. Physiotherapy was mentioned in four protocols, two of which suggest intervention from week 6, one from week 7 and the other mentions the importance of therapy rather than specific timelines.

Conclusion

There are differences between post op TAR guidelines from the implant manufacturers regarding the categories analysed. The variation in the data collected makes it challenging to suggest a singular protocol to be followed after TAR surgery.

Contribution of paper

• -There is currently little consensus surrounding post TAR protocols between manufacturers.
• -Further research into intervening variables may identify the feasibility of creating a standardised set of post-operative protocols for this patient group.

1. Introduction

TAR surgical procedures and implants have been developing since the 1970's and have become increasing popular since the 1990's.¹ There are currently over 13 different prosthetics on the market that are structurally diverse to suit a range of patients and between 2018 and 2022, the National Joint Registry (NJR) have on record 4234 total ankle procedures being performed in the UK alone.² There is emerging evidence in literature suggesting there are promising medium and long-term benefits to TAR. For example, TARs have high survival rates of the implants used averaging 90.6 % after 5 years, low complication rates (ranging from 1.6 % to 14.7 %) and positively impact ROM.^1,3 The post-operative interventions that a patient is given following surgery are predominantly guided by the manufacturer of the implant and the consultant who performed the surgery.⁴ Compared to other joint arthroplasties, TARs have little to no standardisation between manufacturers and consultants for post-operative management, as demonstrated in Mazzotti et al. (2021) systematic review comparing the TAR post-operative protocol of 84 studies.⁵

The following literature review aims to compare and contrast the current guidelines suggested by the prosthesis suppliers following TAR surgery regarding the categories: post-operative weight bearing status, choice of immobilisation, permittance of ROM exercises and the input of physiotherapy.

The ankle joint, also known as the talocrural joint, is a synovial hinge joint that is created by the articulation of the distal ends of the tibia and fibula with the talus.⁶ The tibia and fibula form a mortise shape which allows only uniaxial movement within the sagittal plane to occur,⁷ hence, an individual can achieve up to 25° dorsiflexion and 50° of plantarflexion.⁸ The mortise structure of the ankle also limits the range of movements available by creating a physical blockage around the talus. To ensure the talus remains anchored in place, many ligaments, tendons, and muscles surround the joint medially, laterally, anteriorly and posteriorly. The sturdy anatomy of the ankle allows it to function effectively so the joint can withstand repetitive high loading, act as a shock absorber and contribute to balance correction.⁹

Through trauma or disease, the ankle structure can become compromised which can cause loss of function, pain, reduced range of movement and muscle atrophy. There are several conservative methods to manage ankle pain which include analgesia, physiotherapy intervention, orthotics, and specialist footwear as well as steroid injections. However, conservative management is not always effective at relieving ankle pain so surgical options are available to patients. These options include ankle arthroscopy whereby debris in the joint space is cleared using a minimally invasive tool and distraction arthroplasty which involves setting the ankle bones using a metal frame. Stem cells are inserted into drilled holes in the cartilage of the joint to stimulate the natural repair process.¹⁰ Arthrodesis is another intervention option that involves fusing the joint to a set position using pins, rods, plates and screws.¹¹ A total ankle replacement is where damaged bone and cartilage are removed from the joint and the articulating surfaces of the talus and tibia are replaced by a prosthetic implant.^10,11 The specific type of surgery will be decided by the consultant and patient together as factors such as patient age and interests, stage of disease, bone quality, degree of deformity, range of movement (ROM) and the surrounding soft tissue damage need to be considered when choosing the most appropriate treatment.^12,13

2. Methodology

2.1. Search strategy

Initial research regarding the common TAR implants used in the United Kingdom was carried out by searching the most recent ‘Annual Report’ entry on National Joint Registry (NJR).¹⁴ 10 prostheses were identified and included for further investigation. The Mobility Total Ankle System, Apex 3D TAR System, Hintermann Series H3 TAR System and Kinos Axiom Total Ankle System were added after comparing the data with the ‘Total Ankle Replacement Market – Growth, trends, COVID-19 impact and forecasts (2022–2027)’¹⁵ and ‘Current Trends in Total Ankle Replacement’.¹⁶ The. Common search engines such as Google were used to look up the company names provided by the NJR. These were then combined with the implant name itself followed by ‘-postoperative protocol’. The data provided on the manufacturer website was deemed true and was included in the literature review.

The process of the literature search is depicted in Fig. 1.

Fig. 1.

Flow diagram of the literature search strategies.

3. Results

There were large discrepancies between what manufacturers suggest is the best way to rehabilitate a patient who has recently undergone surgery using their implant (as summarised in Fig. 2). There were some similarities between companies that also mirror the data collected by other research surrounding general post-operative protocols for TARs, however there is an apparent lack of consistency regarding the advice offered. Some manufacturers do not provide any specific guidelines and suggest the consultant should be deciding the protocol to be followed after surgery. The following implants will not be included in the discussion as there is insufficient data to accurately compare them to other products: INFINITY Ankle, INBONE II Ankle, Integra Cadence Total Ankle System, BOX Total Ankle Replacement, Apex 3D TAR System and Kinos Axiom Total Ankle System.

Fig. 2.

A summary of manufacturer guidelines following TAR surgery.^{20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39}

3.1. Weight bearing status

In prior research, weight bearing (WB) has been allowed at different points: some surgeons allow WB immediately, yet some encourage non-WB for up to 8 weeks.^5,17 When comparing the guidelines set by the manufacturers, a similar result emerges. The Hintermann Series H3 TAR allows WB as tolerated immediately after surgery however suggests most patients will be able to do this from the end of week 1.1/3 of the implants used are allowed to have partial weight put through them by the end of week 2, these include STAR Ankle, Zenith and Trabecular Metal Total Ankle (TM Total Ankle). By week 4, STAR Ankle suggest some of their patients can start to be full WB as tolerated and by week 6 all STAR Ankle replacements are allowed to fully weight bear. Zenith and TM Total Ankle mirror a similar pattern as all patients can weight bear in their cast/splint with no WB precautions by week 6.

Vantage Total Ankle System aim for some of their patients to be partially WB by week 3 and all of them by week 6 which is slightly later than the previously mentioned devices. The manufacturers do not explicitly define when full WB can be restarted but they do predict that more strenuous activities, such as golf, can be resumed by 3–4 months and a full recovery is likely to take up to 6 months. Similarly, patients with a Mobility Total Ankle System do not have specific guidelines relating to WB status. In the post-operative protocol, there are general mobility guidelines that state by 3 weeks walking can be performed when wearing a boot.

Salto Talaris Total Ankle Prosthetics (ST Total Ankle prosthesis) have the most delayed WB guidelines as the manufacturers encourage non-WB for the first 6 weeks. WB as tolerated can then begin by week 7 when a boot or ankle brace has been supplied to the patient.

3.2. Choice of immobilisation

The choice of immobilisation used to follow a TAR tends to be casting, splinting, and using a supportive boot or a combination of the above.⁵ Most guidelines suggest a period of casting followed by a period of time in a boot before returning to regular function. STAR Ankle, Zenith, Hintermann Series H3 TAR and Mobility Total Ankle System all state casting should be used immediately following surgery for a minimum of 2 weeks. Zenith replacements were advised into wearing a removable cast/boot by week 2 for 4 weeks when support is removed completely. Mobility Total Ankle System patients are advised to remain in a cast for an extra week (until week 3) before being transferred to a boot for the final 3 weeks of immobilisation. The companies producing STAR Ankle prosthesis and Hintermann Series H3 TAR recommend remaining in plaster cast for the whole initial 6 week period with no further immobilisation after the 6 weeks.

ST Total Ankle prosthesis and TM Total Ankle both recommend splinting after surgery followed by a boot to limit movement for the duration of recovery. Manufacturer guidelines suggest TM Total Ankle patients should be held in a neutral position using a splint for the first 2 weeks post-operatively, then be progressed on to partially WB in a boot until week 10 where the patient should slowly start to be weaned off of the aid. ST Total Ankle Prosthesis follows a different pattern as the guidance mentions splinting, casting and using a boot throughout recovery. Immediately, ST Total Ankle Prosthesis patients should be splinted in a neutral position for 3 weeks. The patient can then either be put into a cast or continued to be held in the splint for the next 3 weeks (all non-WB). From week 7 onwards the patient is able to wear a boot or ankle brace to re-accustom themselves to normal WB.

Vantage Total Ankle System did not mention what form of immobilisation is recommended following surgery.

3.3. Range of movement (ROM) exercises

Following surgery and immobilisation, ROM exercises are key for regaining good function of the joint by breaking down scar tissue and preventing the joint from stiffening up.¹⁸ Only ST Total Ankle Prosthesis, Hintermann Series H3 TAR and TM Total Ankle suggest the introduction of ROM exercises in their post-operative guidelines which differ between each other. ST Total Ankle Prosthesis manufacturers suggest implementing ROM exercises from week 3 until week 6. These exercises are described as ‘self-directed’ and do not specify which particular exercises should be included. TM Total Ankle patients are encouraged to participate in ROM exercises earlier (from week 2) which follow a specific protocol provided by the consultant.

The Hintermann Series H3 TAR encourages patients to start stretching and strengthening their operated ankle once their cast is removed at 6 weeks. They specifically mention focusing on triceps surae when performing exercises however have not provided a specific programme to be followed by patients.

Mobility Total Ankle System instructions mention the importance of ROM mobility exercises but do not overtly state they should be included in a patient's programme until they have had physiotherapy input.

3.4. Physiotherapy intervention

All joint arthroplasties require a course of physiotherapy treatment following the surgery to ensure ROM is improved, functional strength and proprioception are regained, pain and inflammation are managed and independent mobility is achieved.¹⁹ The STAR Total Ankle protocol does not mention the need for physiotherapy intervention following surgery, unlike the other prosthetics in review. The Vantage Total Ankle System encourages the surgeon to decide whether physiotherapy input is appropriate or not. The Zenith and Mobility Total Ankle System all encourage patients to be seen by a physiotherapist 6 weeks post TAR once all immobilisation devices have been removed. ST Total Ankle Prosthesis manufacturers suggest doing a stretching, strengthening and ROM exercise programme prescribed by a physiotherapist from week 7 as a patient is weaning off of their boot/brace. The TM Total Ankle and Hintermann Series H3 TAR patients are advised to mirror the ST Total Ankle Prosthesis patients by performing a regular exercise programme but attending physiotherapy is not explicitly mentioned.

4. Discussion

A TAR is primarily used to treat end stage OA and patients require a rehabilitation programme following surgery. This literature review aimed to explore the recommended post-operative guidelines provided by different implant manufacturers. Upon examination, it is clear that each implant provider suggests different protocols to be used regarding the different categories investigated after surgery with little standardisation throughout. Across all guidelines analysed in this review, there was no mention of other intervening variables on recovery and therefore on the post-operative protocol used. These variables include the underlying pathology causing the need for surgery, other co-morbidities had by the patient such as diabetes, hypertension, and osteoporosis as well as the impact of additional procedures (e.g tendon transfer) on healing timelines. Moreover, the lifestyle choices of the patient and techniques used for wound management and infection control need to be taken into account when creating a post-operative protocol for a patient. Finally, the surgeon carrying out the procedure will influence the rehabilitation steps taken by their patient, therefore the level of experience had by the surgeon could alter the protocol used after surgery. Further research needs to be carried out regarding the effects of different intervening variables on the rehabilitation guidance after TAR surgery before being able to create a more standardised guideline to be followed, if at all possible.

5. Conclusion

The findings of this literature review have highlighted there is currently little consensus surrounding post TAR protocols between manufacturer companies. The results demonstrate there are some similarities between suggested guidelines, such as all patients will be allowed to perform some form of WB by week 6, however there are notable differences across all categories looked at. The lack of advice offered by 6 of the prosthesis companies reduces the size of the sample analysed and therefore has negatively affected the generalisability of the review to patients with those specific implants. Due to the diversity of the data collected, it would be inappropriate and challenging to provide a homogenous set of TAR post-operative guidelines for surgeons and patients to follow. However, this review paper could be a catalyst for further research to be collected in an attempt to create a more succinct set of post-operative guidelines/protocols. A discussion looking at the impact of intervening variables on TAR recovery may help decide whether a general set of guidelines is feasible for this group of patients. If so, further data to demonstrate the discrepancies between what surgeons actually recommend and do following surgery compared to the implant company's advice may aid with emphasising the main similarities and differences to consider when creating a standard protocol.

Funding

This research did not receive any specific funding from an agency.

Conflict of interest

None of the authors have a conflict of interest that could influence the results obtained.

Author statement

Kathleen Bryden. Conceptulization, investiagtion, writing – original draft, Jayasree Ramaskandhan: Resources, writing – review and editing, Malik Siddique: Writing – review and editing.

Declaration of competing interest

This research did not receive specific funding from anagency. None of the authors have a conflict of interest thst could infleucne the results obtained.