Abstract
Aim of study
To report outcomes of tendo-Achilles lengthening (TAL) followed by weight-bearing total contact cast (TCC) in the out-patient setting for patients presented with midfoot Charcot neuroarthropathy (CN) and, develop a new classification system for midfoot CN based on this experience.
Patient and methods
Published evidence suggests that tight Achilles-gastrocnemius-soleus complex is the deforming force in the initiation and progression of midfoot CN and TAL has shown to improve the range of ankle dorsiflexion and reduction of midfoot plantar pressures. We utilised this technique in the out-patient setting followed by weight-bearing TCC for all new patients who presented with a diagnosis of midfoot CN from February 2018.
We report their outcomes after a 12 months follow-up and propose a new classification system based on the clinical and radiographic parameters.
Results
TAL followed by weight-bearing TCC was performed in 33 feet. In 30 feet, the disease progression either stopped or receded to a lower stage on the new classification system. The procedure was well tolerated by patients in an out-patient setting and there were no reported complications such as wound healing, complete transaction of tendon or deep vein thrombosis. At 12 months follow-up, 30 of 33 pts returned to their pre-procedure level of mobilisation with their usual walking aids or customised shoes. The inter-observer agreement was k = 0.86 for read 1 and k = 0.96 for read 2; and intra-observer agreement ranged from 0.93 to 1.00 for the double read indicating excellent inter-observer and intra-observer agreement.
Conclusion
TAL followed by weight-bearing TCC is a safe and well tolerated procedure when performed in an out-patient setting. The Charcot disease of the midfoot slowed in the early stages of midfoot CN and in some cases, receded. The new classification system is easy to use, reliable, reproducible and sensitive enough to detect changes in the disease progression.
Keywords: Midfoot Charcot, Neuropathic ulcer, Osteomyelitis, Tendo-achilles lengthening, Total contact casting
1. Introduction
Charcot neuroarthropathy (CN) of the foot is a progressive, non-infectious osteoarthropathy in patients with peripheral neuropathy, which result in gradual destruction of the foot architecture.1 The deformity typically begins in the medial column and progresses to the lateral column.2 The collapse of the midfoot and of the arch creates a rocker-bottom deformity and gradually the insensate skin can break down, resulting in ulceration and increased risk of osteomyelitis.3
The presence of foot ulceration is noted to be the critical negative prognostic risk factor when treating patients with CN.4, 5, 6 It is estimated that up to one-third of people with diabetes will develop a diabetic foot ulcer over the course of their lifetime7,8 representing 40 times greater risk of lower extremity amputation.9 Therefore, early recognition and identification of potentially modifiable risk factors for ulceration is the key to amputation prevention as the 5-year mortality for patients with diabetes after amputation ranges from 52% to 80%.10
Progressive ankle equinus is considered as one the major deforming force in the initiation and progression of midfoot break.1,11, 12, 13 The prevalence of ankle equinus is reported to be around 37% in patients with diabetes.11 The combination of motor neuropathy resulting in contracted gastrocnemius-soleus muscle complex and stiff and short Achilles tendon7,14 places a plantar-flexion force on the arch of the foot during normal gait resulting in midfoot break.6,15 As the hindfoot equinus worsens, failure of osseo-ligamentous structures result in a classic ‘rocker bottom deformity’ and the pull of tibialis posterior or anterior muscle results in coronal plane deformities.
Hamilton et al.16 were the first to report the use of gastrocnemius recession for the management of diabetic foot ulcers. Tendo-Achilles lengthening (TAL) is reported to be equally effective in improving the ankle range of dorsiflexion, reduction of peak plantar pressures in the forefoot and midfoot, and improve overall walking ability.6,17,18 As summarised by Rogers et al.19 several investigators reported TAL with total contact casting (TCC) decreases the deforming forces at the midfoot and has the potential to avert the development of Charcot foot or ankle.
Following a review of literature,6,18 we changed our treatment pathway to include TAL and weight-bearing TCC for management of forefoot ulcers and noted marked improvement in their clinical outcomes (unpublished data). During this process, we noted improvement in the calcaneal pitch (Fig. 1a and b), a sign of hindfoot equinus, hence extended its indications to patients with midfoot CN. We report our experience of TAL and weight bearing TCC for all patients with midfoot CN and chart their disease progression on the new classification system.
Fig. 1.
a: Calcaneal pitch before TAL
b: Calcaneal pitch after TAL
2. Patients and methods
Before 2018, the TAL was performed in an operating theatre setting. After a successful pilot, and relevant institutional approval, all the TAL procedures were performed in the out-patient setting since February 2018. Patients were provided with written advice and formal written consent was obtained before the start of procedure. We excluded patients with evidence of osteomyelitis on plain radiographs and who had combined midfoot and hindfoot CN. Hospital governance approval was sought for the retrospective analysis of notes and radiographs.
2.1. Percutaneous Tendo-Achilles lengthening (TAL)
The procedure is performed with the patient supine and the involved leg held in a gentle figure of 4-position. After antiseptic skin preparation, 1% lignocaine is injected over the area of intended incisions. With an assistant holding the ankle in gentle dorsiflexion, two hemi-sections of distal tendo-Achilles are made, first directed medially around 1 cm from its insertion, and second directed laterally around 2 cms proximal to the first incision. No attempt of forceful ankle dorsiflexion is made to avoid potential complete tendon transection. A third cut directed medially 2 cms proximal to the second cut can be performed at the operator’s discretion if they felt that a neutral ankle position could not be achieved with gentle passive stretch when the knee in flexion. The skin incisions are covered with steristrips and simple dressing; and with the knee flexed, the ankle is immobilised in a neutral below knee cast for 6 weeks. The patient is encouraged to weight-bear following application of the cast. The majority in our case-series walked without additional supports, using their pre-procedure aids. All patients were prescribed oral thromboprophylaxis for the duration of casting.
A weight-bearing cast in neutral ankle position allows controlled lengthening of the tendon without the risk of over-lengthening. Patients are counselled for weakness of the leg for up to 7 months post-procedure.18 The weight-bearing protocol after TAL is illustrated in Fig. 2.
Fig. 2.
Weight-bearing protocol after TAL.
2.2. Radiological parameters used for analysis
Schon et al.9 described three radiological parameters that are reproducible on the weight-bearing antero-posterior (AP) and lateral radiographs; the dorsal and lateral talar-first metatarsal angles (Meary’s angles), calcaneal pitch and cuboid height. The lateral talar-first metatarsal line (Meary’s angle, Line A in Fig. 3a) signifies the medial column integrity.
Fig. 3.
a: Weight-bearing lateral radiograph showing sagittal parameters.
Fig. 3b: Weight-bearing AP radiograph showing dorsal Meary’s line.
Lateral column involvement and collapse is inherently associated with ulceration which can be assessed by a decrease in cuboid height (Line C in Fig. 3a).20 It is measured as the distance from the plantar surface of the cuboid to a line drawn from the calcaneal tuberosity to the fifth metatarsal head (Line B in Fig. 3a). This is positive if the plantar surface of cuboid is above Line B and negative, if below this line; this is similar to the system proposed and validated by Schon et al.21
The transverse plane deformity as measured on the dorsal talar-first metatarsal angle (Line D in Fig. 3b) was not associated with plantar foot ulceration.2,22 However, restoration of this line is significant post-surgery to avoid medial bony prominences.
2.3. New classification system
A new classification system was designed combining the clinical features and radiographic parameters on standard weight-bearing radiographs. The aim was to accurately describe the anatomic location of the disease, guide treatment options based on stage of the disease, and as a useful monitoring tool which is sensitive to change as the disease progresses.
To determine the effectiveness of this new classification system, we staged a consecutive group of patients presented to Basildon University Hospital Diabetic Foot Clinic from March 2013 till December 2019 with a diagnosis of midfoot CN and had follow-up with radiographs for minimum of 12 months. We monitored their disease progression on the new classification system and compared the outcomes when TAL was performed in the initial stage of presentation from February 2018.
The new classification system has 4 stages (stage 1–4), with each next stage representing the severity of the disease (Table 1).
Table 1.
New staging system, clinical presentation, radiological findings and treatment.
| Stage | Clinical Presentation | Radiological findings | Treatment |
|---|---|---|---|
| Stage 1- Initial stage | Similar to Eichenholtz stage 0- Hyperthermic, painful and oedematous foot with a temperature difference of >2 °C Patients are noted to have equinus deformity with tight tendo-Achillis-gastroc-soleus complex |
Fig. 4a–b Weight bearing Lateral view-
|
Percutaneous TAL followed by weight bearing TCC for 6weeks as per protocol in Fig. 2. Patients are followed at 3 m, 6 m and at one-year with weight bearing radiographs. |
| Stage 2a- Pre- ulceration | As in stage 1. May have bony prominence on the dorso-medial surface of foot. No plantar bony prominences seen Hindfoot equinus with tight tendo-Achilles-gastroc-soleus complex |
Fig. 5a–b Weight bearing Lateral view-
|
Percutaneous TAL followed by weight bearing TCC for 6weeks as per protocol in Fig. 2. Patients are monitored for progression of the deformity with weight bearing radiographs and skin temperature measurement repeated every 3 months. Patients may benefit from exostectomy if the bony lump cannot be accommodated in their usual footwear |
| Stage 2b: Pre-ulceration | Rocker bottom deformity of foot but without skin ulceration. The plantar bony prominences can vary from the medial to lateral depending on the columns of the foot involved. Without intervention, the progression to ulcer is likely |
Fig. 6a and b Weight bearing Lateral view-
|
Percutaneous TAL in clinic followed by weight bearing TCC for 6weeks as per protocol in Fig. 2. Bespoke footwear to accommodate deformity or exostectomy Sagittal radiographic parameters of lateral Meary’s angle and cuboid height are monitored for progression. Single-stage reconstruction is recommended before skin ulceration. |
| Stage 3A (Stage 2b + superficial ulcer) | Superficial ulcer over the bony prominence with no MRI proven changes of osteomyelitis |
Radiological features similar to Stage 2b Weight bearing Lateral view-
|
Trail of Percutaneous TAL + well padded accommodative weight bearing TCC for 6weeks as per protocol in Fig. 2. If ulceration persists or MRI shows unequivocal changes then the treatment suggested would be as described for stage 3b |
| Stage 3B (Stage 2b + Deep ulcer) | Deep ulcer over the bony prominence with radiographic changes of osteomyelitis |
Fig. 7 Weight bearing Lateral view-
|
2-stage surgical reconstruction recommended |
|
Stage 4 Midfoot CN plus ankle or subtalar joint involvement |
Disease involving the midfoot and hindfoot joints The combined hindfoot and midfoot deformity could be driven by the midfoot deformity happening first, typically at the talo-navicular joint, but could also be driven by the hindfoot deformity from the tightness of tibialis posterior tendon happening first causing varus/valgus hindfoot deformity which in turn will increase the forces going through the midfoot leading to midfoot break. Clinically, the ankle is floppy and unstable with lateral bony prominence from lateral malleolus. Plantar ulcer with additional lateral ulcers could be seen. |
Fig. 8 Navicular extruded dorsally and cuboid plantarly. Secondary osteomyelitis of mid-tarsal and/or lateral malleolus is noted in the presence of ulcer/s |
Strict non-weight bearing in neutrally aligned TCC with weekly changes. Non-operative treatment has limited benefit as the ankle is often floppy and unstable. When an ulcer is present, a 2-stage procedure is recommended. With the combined deformity, hindoot is stabilised first to correct the calcaneo-tibial alignment with either an intramedullary or extramedullary device and thereafter, the midfoot stabilised using the principles of Superconstruct or external fixation. |
Stage 1 (Fig. 4a and b): This is similar to Eichenholtz stage 0 with patients presenting with hot, swollen foot.
Fig. 4.
a and b: Weight-bearing lateral and AP radiographs showing stage 1 disease.
Radiographs: Negative or minimal radiographic changes. No break in lateral and dorsal Meary’s line and positive cuboid height.
Suggested treatment: TAL and weight-bearing TCC
Stage 2a (Fig. 5a and b): Minimal clinical deformities mostly in the transverse plane, but may present with hot swollen foot. No plantar bony prominences seen.
Fig. 5.
a and b: Weight-bearing lateral and AP radiographs showing stage 2a disease.
Radiographs: Break in lateral and dorsal Meary’s line but positive cuboid height.
Suggested treatment: TAL and weight bearing TCC, followed by accommodative footwear and orthoses or exostectomy, if the bony prominence is not able to be adequately protected or offloaded within the custom made shoes.
Stage 2b (Fig. 6a and b): Patient has classic plantar rocker bottom deformity but, no ulcer.
Fig. 6.
a and 6b: Weight-bearing lateral and AP radiographs showing stage 2b disease.
Radiographs: Break in lateral and dorsal Meary’s line, and negative cuboid height.
Suggested treatment:
-
•
TAL and weight bearing TCC
-
•
If the disease process stabilised (no progression of cuboid height)- accommodative footwear ± localised exostectomy
-
•
If the radiographs show progression of lateral Meary’s angles or cuboid height-single-stage reconstruction is recommended.
Stage 3, Stage of ulceration (Stage 2b + ulceration) (Fig. 7): The ulcers are typically seen under the plantar bony prominences, this could be superficial (3A) or deep with underlying osteomyelitis (3B), similar to Wagner23 and Brodsky24 classification.
Fig. 7.
Weight-bearing lateral radiographs showing stage 3 disease.
Radiographs: Break in lateral Meary’s line (critical angle of >27°22), negative cuboid height ± signs of osteomyelitis.
Suggested treatment:
Stage 3A-
-
•
TAL and weight bearing TCC
-
•
If ulceration persists: Exostectomy and weight-bearing TCC
-
•
If ulcer persists or the radiographs show progression of sagittal parameters: a two-stage reconstruction is recommended.
Stage 3B: Two-stage surgical reconstruction.
The stages of 3A and 3B are soft subdivisions as it is difficult to reliably differentiate these two stages with the available investigations,4,25 hence it is safe to assume that the presence of any degree of skin breakdown can result in local colonisation and potential osteomyelitis. It is thus recommended to have a guarded approach for stage 3A with a trial of TAL and proceed to a 2-stage reconstruction if the ulcer fails to resolve.
Stage 4, Midfoot + Hinfoot Charcot (Fig. 8): Patients have midfoot Charcot (any stage as described above) + Charcot involvement of the ankle and/or subtalar joint.
Fig. 8.
Weight-bearing lateral radiograph showing stage 4 disease.
Secondary varus deformity of hindfoot is seen due to tightness of the tibialis posterior muscle, this results in prominence of the lateral malleolus and potentially additional lateral ulceration.
Suggested treatment:
-
•
Two-stage reconstruction in the presence of ulceration or a single stage procedure if no ulcer is seen.
-
•
Hindfoot is stabilised first followed by the midfoot
2.4. Statistics
Standard descriptive statistics were calculated and reported. Inter-observer and intra-observer reliability was tested using kappa coefficient. For this, a total of 12 observers (4 Foot & Ankle surgeons, 3 vascular surgeons, 2 Radiologists, one Endocrinologist, one specialist podiatrist and one specialist nurse) were given a set of 10 radiographs of midfoot CN to stage the pathology using the new classification system, and the process was repeated a week later. The results were tabulated to calculate the kappa coefficient. Free marginal multi-rater kappa was used to compare the inter-observer agreement between 12 raters for read 1 and read 2 and Cohen’s kappa was used to assess the intra-observer agreement (Medcalc statistics, Belgium).
3. Results
A total of 148 patients (169 feet) with the diagnosis of midfoot CN satisfying our inclusion and exclusion criteria were included for the analysis, age range 36–91years (mean 67years), 95males:53females; and 83right:86left.
Stage 1 disease was seen in 12 feet, stage 2a in 63 feet, stage 2b in 57 feet, stage 3 in 24 feet and stage 4 in 13 feet. Excluding the patients with stage 4 disease, of the remaining 156 feet, the naviculo-cuneiform joint was the most commonly involved joint in 54 feet (34.6%) followed by the talo-navicular joint and tarso-metatarsal joints (TMTJ) in 51 feet each (33% each), Table 2.
Table 2.
Distribution of patients based on the location and stage of disease process (Number of feet).
| Total- 169 feet | Stage 1 | Stage 2a | Stage 2b | Stage 3 | Stage 4 |
|---|---|---|---|---|---|
| Talo-Navicular joint (n = 51) | 3 | 17 | 23 | 8 | |
| Naviculo-Cuneiform joint (n = 54) | 1 | 22 | 24 | 7 | |
| Cuneiform-TMTJ (n = 32) | 3 | 18 | 6 | 5 | |
| Naviculo-Cuneiform-TMTJ (n = 11) | 2 | 3 | 3 | 3 | |
| TMTJ (n = 8) | 3 | 3 | 1 | 1 | |
| Midfoot & Hindfoot (n = 13) | 13 | ||||
| Total | 12 | 63 | 57 | 24 | 13 |
Of the 156 feet, the plantar ulcer was seen in 24 feet (15%), slightly more when TMTJs were involved (9 feet), followed by the talo-navicular joint (8 feet) and naviculo-cuneiform joint (7 feet).
3.1. Significance of middle column
Of the 53 feet that involved the TMTJ, when the disease process involved isolated medial or the lateral columns (11 feet), the disease did not progress beyond stage 2a and none developed ulceration. However, when the middle column was involved (42 feet), the ulceration was seen in 9 feet (17%); and a classic rocker bottom deformity without ulceration in 11 feet (21%) hence, a combined risk of 38% (20 feet) for ulceration or potential to ulcer due to significant bony prominence, Table 3.
Table 3.
Staging depend on the columns of foot when the TMTJ was involved.
| N = 53 | Stage 1 | Stage 2a | Stage 2b | Stage 3 | Stage 4 |
|---|---|---|---|---|---|
| Medial column (n= 6) | 1 | 5 | |||
| Middle column (n=15) | 1 | 7 | 5 | 2 | |
| Lateral column (n=4) | 2 | 2 | |||
| Medial + Middle column (n=20) | 2 | 10 | 5 | 3 | |
| Middle + Lateral column (n=1) | 1 | ||||
| Medial + Lateral column (n=1) | 1 | ||||
| All 3 columns (n=6) | 1 | 1 | 4 |
3.2. Results after TAL and weight-bearing TCC
This procedure was performed in a total of 33 feet since February 2018. Stage 1 disease was seen in 9 feet, stage 2a in 14 feet, stage 2b in 6 feet and stage 3A in 4 feet.
-
•
Stage 1 (similar to Eichenholtz stage 0): of 9 feet, in none of the patients, the disease progressed to stage 2a.
-
•
Stage 2a: of 14 feet, the disease progressed to stage 2b in 2 feet; this was due to secondary tightness of tibialis posterior tendon.
-
•
Stage 2b: of 6 feet, in none of the patients, the disease progressed to stage 3 (ulceration), two were treated with custom shoes, exostectomy in 3 feet and in one-patient, the disease progressed on sagittal radiographs hence underwent single-stage reconstruction.
-
•
Stage 3A: of 4 feet, the ulcer gradually resolved in 3 feet. One patient underwent 2-stage reconstruction for a non-healing ulcer when MRI was equivocal for osteomyelitis.
3.3. Calcaneal pitch following TAL
Calcaneal pitch which is a measure of hindfoot equinus, improved by an average of 6° (4–11°). In patients with stage 2b disease, besides improved calcaneal pitch, cuboid height improved to stage 2a in 3 feet.
3.4. Validity and reproducibility of the classification
Inter-observer agreement was k = 0.86 (95% CI 0.78–0.94) for read 1 and k = 0.96 (95% CI 0.90–1.00) for read 2, indicating excellent inter-observer agreement. Intra-observer agreement ranged from 0.93 to 1.00 for the double read of the 12 observers, indicating excellent intra-observer agreement.
4. Discussion
The bony deformities associated with midfoot CN are secondary to a combination of sensory, motor and autonomic neuropathy which initiates the midfoot break in the medial column and culminate with plantar bony prominences. The insensate skin under these bony prominences breaks resulting in ulceration and consequent osteomyelitis, which is a precursor to amputation.3,19 Presence of skin ulceration therefore is a negative prognostic factor hence, the primary goal of diabetic foot management is to prevent ulcer formation.4, 5, 6
Equinus deformity from progressive tightness of gastroc-soleus muscle complex from motor neuropathy, and functionally short tendon fibres secondary to electron microscopic changes within the collagen fibres and non-enzymatic glycosylation,14 result in increased peak plantar pressures in the forefoot and midfoot. The resultant opposing moments in the midfoot initiates the midfoot break, typically in the joints of medial column. Once the process is initiated, with continued inflammation, gradual failure of osseo-ligamentous structure of midfoot results in plantar bony prominences and a typical rocker bottom foot. 6, 15 Once the failure of osseo-ligamentous structure is initiated the final position of midfoot in transverse plane is determined by tightness of tibialis posterior and tibialis anterior muscles. However, these transverse plane deformities are not associated with plantar ulceration.21
As summarised by Rogers et al.19 TAL with total contact casting (TCC) has the potential to decrease the deforming forces at the midfoot, reduces the plantar peak pressures and improves the ankle range of movements and consequently, the patients’ ability to walk. Armstrong et al.6 reported marked improvement in the peak plantar pressures after TAL and Mueller et al.18 in their randomised controlled trail demonstrated TAL followed by TCC was associated with reduced risk of forefoot ulceration.
4.1. New classification
Eichenholtz26 described a radiological classification which, despite advances in imaging, is still in use today. This is a radiological evolution of the condition through time and does not include clinical manifestations and lacks the validation. It is subjective when defining the end of one stage and the beginning of the next stage. Brodsky27 and Sammarco28 classification systems define the anatomical location of the disease and are useful when communicating the location of the disease. Classification system by Schon et al.20 defines the clinical and radiological location of the disease, however it does not guide the treatment options based on the findings.
The proposed new classification system combines the clinical features and radiographic parameters on standard weight-bearing radiographs with an aim to accurately describe the anatomic location of the disease and guide the treatment options based on the stages of disease. We used this classification to chart the progression of the disease in patients who attended our Diabetic Foot clinic from 2013 and noted the disease process to progress in some patients from stage 1 to stage 3, when managed in non-weight bearing TCC. Following the introduction of TAL and weight bearing TCC, we noted the disease process stabilised in 30 of 33 feet at 12 months follow-up, and in 3 feet, the disease improved from stage 2b to stage 2a.
The new classification system has proven to be valuable in monitoring the disease progression using the parameters such as lateral Meary’s angles and cuboid height in patients with stage 2b disease. In one patient, when such progression was noted, the midfoot was surgically stabilised.
This new classification system was noted to be easy to use as assessed independently by 12 experienced medical staff of different specialities, and noted to have excellent inter- and intra-observer validity.
4.2. Assessment of stability of midfoot CN
The primary desirable outcome in the management of CN is a stable plantigrade foot. Radiological fusion across the midfoot joints often is difficult to assess more so in the presence of internal fixation devices.29 In this series, we concluded the midfoot to be stable when there is no change in any of the sagittal parameters on the weight-bearing radiographs. The radiographs are repeated at 2 week intervals from the time of change in the weight-bearing status.
4.3. Weakness of study
The aim was to report the progression of midfoot CN following TAL and weight-bearing TCC and to chart their progression using the new classification system. As this series included patients from one centre, the number of patients available for analysis was small but, still showed significant changes in the disease progression with early intervention. We plan a multicentre prospective observational study to assess this in larger patient group.
5. Conclusion
In this case series, early TAL followed by weight-bearing TCC either halted or slowed the progression of midfoot CN.
A new classification system was designed with an aim to identify the midfoot CN in the early stages and direct treatment based on the stage of the disease and can be used as an effective monitoring tool. This classification is easy to use and is reproducible amongst clinical staff in all settings.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
CRediT authorship contribution statement
Madhu Tiruveedhula: Conceptualization, Methodology, Investigation, Writing – original draft. Anna Graham: Methodology, Validation, Writing – review & editing. Ankur Thapar: Formal analysis, Writing – review & editing. Shiva Dindyal: Validation, Writing – review & editing. Michael Mulcahy: Methodology, Investigation, Writing – review & editing.
Declaration of competing interest
None.
Contributor Information
Madhu Tiruveedhula, Email: madhutiruveedhula@gmail.com.
Anna Graham, Email: Anna.graham6@nhs.net.
Ankur Thapar, Email: a.thapar@nhs.net.
Shiva Dindyal, Email: doctordindyal@hotmail.com.
Michael Mulcahy, Email: Michaelmulcahy1900@gmail.com.
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