Characteristics of nonunion after arthroscopic ankle arthrodesis: A multi-center retrospective cohort study

doi:10.21203/rs.3.rs-2460834/v1

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Characteristics of nonunion after arthroscopic ankle arthrodesis: A multi-center retrospective cohort study

https://doi.org/10.21203/rs.3.rs-2460834/v1

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Background

Nonunion is a major complication of arthroscopic ankle arthrodesis. However, the characteristics and risk factors of nonunion are not well understood. This retrospective multi-center observational study aimed to clarify the characteristics of nonunion after arthroscopic ankle arthrodesis.

Methods

We included 154 patients who underwent arthroscopic ankle arthrodesis at one of five institutions. Patients were divided into two groups: union and nonunion, and the groups were compared. Age, sex, body mass index, diabetes, smoking, corticosteroid use, diagnosis, treatment information, treatment protocol, radiographic evaluation, and patient-reported outcomes were recorded and analyzed.

Results

On radiographs, bony union was observed in 142 ankles (91.0%) but not in 12 ankles (9.0%). Postoperative radiographic tibial bony gap (mm) was significantly larger in the nonunion group (medial = 1.98, center = 1.65, anterior = 2.21, middle = 1.72, posterior = 3.01) (mm) compared to the union group (medial = 1.35, center = 1.13, anterior = 1.28, middle = 1.03, posterior = 2.03) (mm). Furthermore, the visual analog score (VAS) of pain and pain-related self-administered foot evaluation questionnaire (SAFE-Q) subscale score significantly worsened in the nonunion group (VAS = 3.83, SAFE-Q subscale score = 69.8) than in the union group (VAS = 1.35, SAFE-Q subscale score = 76.6).

Conclusion

A larger radiographic tibiotalar bony gap was observed in the nonunion group. Other measurement outcomes were not associated with nonunion. Additionally, patient-reported outcomes markedly worsened in the nonunion group.

Arthroscopic ankle arthrodesis

Multi-center retrospective study

Radiologic evaluation

Arthroscopic ankle arthrodesis (AAA) is an effective and reliable surgical method for treating patients with end-stage tibiotalar osteoarthritis [1]. Many studies have described the advantages of AAA, such as small invasion, fewer complications, rapid union, and shorter hospitalization compared with open ankle arthrodesis [2–8].

Despite these advantages, nonunion remains a major complication of ankle arthrodesis. According to a previous case series, the nonunion rate was 2.6–9.1% [4, 7–11]. Nonunion has been associated with poor patient outcomes and a high revision rate. Therefore, a method to improve the union rate is required. Obesity and the number of screws utilized for the procedure are the only statistically proven risk factors reported for nonunion after AAA [2, 7]. Furthermore, smoking and preoperative tibiotalar alignment are factors associated with delayed union after AAA [4, 9]. However, these risk factors were only reported in most case series of AAA with less than 100 cases. A large sample size study may clarify the risk factors for nonunion after arthroscopic ankle arthrodesis.

The purpose of the present study was to clarify the characteristics of nonunion after arthroscopic ankle arthrodesis based on a multi-center study. We hypothesized that there would be some differences in radiographic evaluation between the union and nonunion groups.

Study design

This observational retrospective multi-center clinical trial involved data from five institutions that performed arthroscopic ankle arthrodesis in more than 10 cases from 2000 to 2020. This study was approved by the appropriate institutional review board. Following personal information protection laws, patients were allowed to opt out of this study through public announcements published by each institution. All procedures in this retrospective study were performed according to the ethical standards of each institution's committee on human experimentation and complied with the Helsinki Declaration of 1964 and its later versions.

Inclusion criteria involved patients older than 18 years who underwent primary AAA between January 2000 and December 2020. A minimum follow-up period of 1 year was ensured. Patients who underwent talocalcaneal arthrodesis before or during the procedure or could not be followed up for more than 1 year were excluded. We used a standardized data sheet to collect patient measurement outcomes. The data sheet consisted of questions on demographics, diagnosis, treatment information, treatment protocol, radiographic evaluation, and patient-reported outcomes. Even if some missing data were found, they were included in the study. Each surgeon filled out a data sheet about patients treated at each institution. The filled data sheet was sent to and summarized by the first author.

Treatment methods

All ankles were treated with AAA at one of the five institutions. All patients were diagnosed with ankle disease (primary osteoarthritis, posttraumatic osteoarthritis, rheumatoid arthritis, hemophilic arthritis, idiopathic necrosis of the talus, or unclear). Diagnosis and surgical treatment were performed by each institution's foot and ankle board surgeons.

Surgical technique

All intra-articular procedures were performed under arthroscopy in a standardized manner for every case, as described by Ferkel and Hewitt [5]. The remaining cartilage was removed from the joint surface of the tibia and talus. Next, an abrader and bone chisel were used to remove the subchondral bone of the tibia and talus until the bleeding surface was exposed. After the intra-articular procedure, tibiotalar screw fixation was performed under image intensifier control. Only cannulated or headless cancellous screws were used to fix and fuse the tibiotalar joint. The type of product used was inconsequential. The type of screw (headless or not), the number of screws, the maximum diameter of the screw, and the direction of the screw (from medial or lateral) were determined by each surgeon and recorded as measurement outcomes in all cases.

Postoperative treatment

Each surgeon performed postoperative treatment. During the postoperative non-weight-bearing period, all ankles were stabilized with external fixation (cast, splint, or brace). The duration of the nonweightbearing period and the type of external fixation were determined by each surgeon and recorded in all cases as measurement outcomes.

Measurement outcome

Patient demographics (age, sex, body mass index (BMI), risk factors, such as presence of diabetes, smoking history, and corticosteroid use), diagnosis (primary osteoarthritis, rheumatoid arthritis, posttraumatic osteoarthritis, hemophilic arthritis, necrosis of the talus, paralytic drop foot, or unclear diagnosis), treatment information, treatment protocol, radiographic evaluation, and patient-reported outcomes were recorded and analyzed.

Treatment information and treatment protocol included operative time, low-intensity pulsed ultrasound (LIPUS) use, teriparatide use, duration of nonweightbearing period, the largest diameter of screws, number of screws, type of screws (cannulated cancellous screw or headless cancellous screw), and direction of screws (from medial or lateral) (Fig. 1A).

Radiographs were assessed for preoperative osteoarthritis (OA) grade, pre-and postoperative coronal tibiotalar angles, correction angle, postoperative tibiotalar bony gap, and evidence of radiographic union. Preoperative OA grade was assessed using conventional weightbearing ankle radiography and the Takakura-Tanaka classification [12]. In cases of valgus alignment, the ankle valgus was graded. The tibiotalar angle was defined as the angle perpendicular to the tibial axis and the talar joint line on the preoperative and postoperative coronal plane radiographs (Fig. 1B, 1C). The correction angle was defined as the absolute value of the difference between the preoperative and postoperative tibiotalar angles. The postoperative tibiotalar bony gap was defined as the distance between the tibia and the talar joint surface in the coronal and sagittal plane radiographs taken immediately after surgery (Fig. 2). A union was defined as the observation of a bridging callus at the anterior tibiotalar joint on the sagittal plane radiograph. Non-union was defined as a union taking longer than 12 months or secondary surgery for the treatment of nonunion before 12 months postoperation.

Patient-reported outcomes utilized the visual analog scale (VAS) of pain, the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale, and the self-administered foot evaluation questionnaire (SAFE-Q). Patient-reported outcomes were evaluated during the final follow-up period for each patient. The final follow-up period was not recorded in this study; however, the patients were followed for at least 1 year.

Statistical analysis

All required data were analyzed using EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan), a graphical user interface for R (The R Foundation for Statistical Computing, version 4.0.3). Data analysis was used to compare the patients who achieved ankle union. Fisher's exact test was used to determine if there were significant differences between categorical variables, and the Mann-Whitney U test was used to determine significant differences between continuous variables. The level of significance was set at p < 0.05.

Patient characteristics

This study included 156 patients who underwent primary arthroscopic ankle arthrodesis. There were 48 (30.8%) men and 108 (69.2%) women (median age, 66 years; range, 25–87). On radiographs, 142 ankles (91.0%) achieved bony union (group U), while 14 ankles (9.0%) did not achieve bony union after the primary surgery (group N). In group N, four ankles underwent revision surgery, while 10 ankles did not. There were no statistically significant differences in the demographics and diagnoses of the two groups (Table 1). Similarly, there were no statistically significant differences in the treatment information and protocol of the two groups (Table 2).

Table 1

Patient charactaristics.
	Union group	Nonunion group	p-value
Age (years)	64.8 ± 11.7	71.1 ± 9.62	0.065
Sex (male/female)	48/94	4/10	0.775
BMI (kg/m²)	25.0 ± 3.97	27.0 ± 5.54	0.210
Diabetes (p/n)	20/122	5/9	0.051
Smoking (p/n)	11/95	1/11	0.999
Corticosteroid use (p/n)	4/138	1/13	0.379
Diagnosis			0.536
Osteoarthritis	66	8
Reumatoid artiritis	5	1
Posttraumatic arthritis	61	4
Hemophilia	3	0
Necrosis of talus	1	0
Paralytic drop foot	1	0
Unclear	5	1
BMI; body mass index.
(p/n); positive/negative
*; significantly different between 2 groups (p < 0.05)

Table 2

Treatment information and protocol.
	Union group	Nonunion group	p-value
Operative time (minutes)	159 ± 45	159 ± 49	0.920
LIPUS use (p/n)	8/132	2/12	0.226
Teriparatide use (p/n)	2/138	1/13	0.250
nonweightbearling period (weeks)	3.5 ± 1.9	2.8 ± 1.6	0.147
Most large diameter of screws			0.383
6.5mm	125	11
7.0mm	16	3
Number of screws			0.697
2	1	0
3	125	12
4	16	2
Type of screw			0.438
CHS	125	11
HCS	16	3
Direction of screws			0.720
Medial 2 screws	1	0
Medial 3 screws	83	10
Medial 4 screws	16	2
Medial 2 screws and lateral 1 screws	39	2
Medial 1 screws and lateral 2 screws	3	0
LIPUS; low-intensity pulsed ultrasound.
CCS; cannulated cancellous screw
HCS; headless cancellous screw
Direction of screws; the direction of insertion of the screws from the medial or lateral side in the coronal plain radiograph. (Fig. 1a)
(p/n); positive/negative
*; significantly different compared with intact (p < .05)

Radiologic evaluations

There was no statistically significant difference in the preoperative OA grades, pre-and postoperative coronal tibiotalar angles, and correction angles of the two groups. In contrast, the postoperative tibiotalar bony gap was significantly larger in Group N than in Group U, except for the lateral gap in the coronal view (Table 3).

Table 3

Radiologic evaluation.
	Union group	Nonunion group	p-value
Takakura-Tanaka classification			0.818
Stage2	3	0
Stage3a	5	0
Stage3b	29	4
Stage4	68	6
valgus	3	0
preoperative tibiotalar angle (°)	7.29 ± 7.80	8.31 ± 7.46	0.385
postoperative tibiotalar angle (°)	2.32 ± 2.89	2.44 ± 2.64	0.517
correction angle (°)	5.4 ± 6.3	6.8 ± 6.3	0.237
Tibiotalar bony gap (mm)
medial	1.35 ± 1.42	1.98 ± 0.98	0.030^*
center	1.13 ± 1.13	1.65 ± 1.00	0.035^*
lateral	1.57 ± 1.71	2.36 ± 1.77	0.081
anterior	1.28 ± 1.29	2.21 ± 1.16	0.007^*
middle	1.03 ± 1.91	1.72 ± 1.06	0.017^*
posterior	2.03 ± 1.26	3.01 ± 1.27	0.029^*
Preoperative tibiotalar angle; the angle between perpendicular to the tibial axis and talar joint line in the pre-operative coronal plain radiograph. (Fig. 1b)
Postoperative tibiotalar angle; the angle between perpendicular to the tibial axis and talar joint line in the post-operative coronal plain radiograph. (Fig. 1c)
Tibiotalar bony gap; measured as the minimum distance between tibial plafond and talar dome. (Fig. 2)
*, significantly different compared with intact (p < .05)n.

Patient-reported outcomes

The VAS pain score was significantly higher in group N than in group U. Additionally, the JSSF ankle/hindfoot scale and SAFE-Q pain scores were significantly lower in group N than in group U (Table 4).

Table 4

Patient-reported outcome.
	Union group	Nonunion group	p-value
VAS for pain (mm)	1.35 ± 1.88	3.83 ± 2.91	< 0.001^*
JSSF scale (100 points)	86.8 ± 15.0	73.6 ± 8.91	< 0.001^*
SAFE-Q
Pain and pain-related (100 points)	76.6 ± 28.6	69.8 ± 8.74	0.025^*
Physical functioning and daily living	67.5 ± 29.1	62.2 ± 17.9	0.159
(100 points)
Social functioning (100 points)	74.7 ± 33.9	70.8 ± 21.9	0.132
Shoe-related (100 points)	71.0 ± 30.5	70.8 ± 20.4	0.557
General health and well-being	73.7 ± 32.9	69.4 ± 17.4	0.091
(100 points)
VAS; visual analog scale
JSSF scale; the japanese society for surgery of the foot scale
SAFE-Q; self-administered foot evaluation questionnaire
*, significantly different compared with intact (p < .05)

The most novel result of this study was that the postoperative bony gap on plain radiographs was significantly larger in the nonunion group after arthroscopic ankle arthrodesis. Furthermore, postoperative pain assessment using the VAS of pain, JSSF scale, and SAFE-Q were significantly worse in nonunion patients than in fusion cases.

In this study, the union and nonunion rates after arthroscopic ankle arthrodesis were 91.0% and 9.0%, respectively. The nonunion rate in a previous case series, including over 50 ankles, was reported to be between 2.6% and 9.1% [4, 7–11]. These studies included 50–118 ankles, with only one study involving more than 100 ankles. The present study included 156 ankles, the largest case series and one of the strengths of this study. The union rate in this study did not differ from that in previous studies, and we considered it comparable.

The method for evaluating bone union after arthrodesis is controversial. Jain et al. described bridging trabeculae or callus without failure of internal fixation or change in position as the criteria for union with radiographic evidence [9]. Quayle et al. described union crossing the joint line on plain radiographs or computed tomography scans [13]. Both descriptions were vague and unclear. In addition, it is challenging to evaluate bridging calluses on coronal plane radiographs. Bony union was defined as the bridging callus at the anterior tibiotalar joint on the sagittal plane radiograph, which we considered the easiest to evaluate on plain radiographs. CT scans are more effective in evaluating bony unions; however, multiple CT scans are problematic in terms of cost and radiation exposure.

BMI, diabetes, smoking history, and steroid use, which were said to be associated with nonunion in previous reports, were not associated in this study. The small number of patients with obesity may have influenced our results. For example, the mean BMI of patients in the report by Quayle et al. was approximately 28 [13]. Similarly, few patients were eligible for diabetes, smoking, or steroid use. In particular, diabetes was not significantly different but had a small P-value, which may have been affected by a lack of detection.

It is interesting to note that a larger bony gap in the radiographs was revealed with nonunion. To date, no similar reports have been published. We consider that the bony gap reflects the small tibiotalar bony contact area due to the incompatibility of the tibiotalar joint surface, residual tibiotalar subchondral bone, or poor tibiotalar alignment. In arthroscopic ankle arthrodesis, it is thought that a larger tibiotalar bony contact area influences the tibiotalar bony union. If a larger tibiotalar bony gap remains on the postoperative plain radiograph, careful follow-up and postoperative treatment protocols may be warranted.

Patient-reported outcomes significantly worsened in the nonunion group; however, the difference was relatively minor in the present study. In addition, the proportion of patients who underwent reoperation in group N was also small (4/14, 28.6%). This result may be attributed to the fact that analgesia is obtained through medication or the ankle is stable even if bony fusion has not been achieved (fibrous union, etc.). However, although the differences in patient-reported outcomes were minor, a need still exists to increase the union rate in primary AAA.

This study had several limitations. First, this study had a retrospective design and inadequate numbers for matched-group analysis. Second, ankle union was assessed using only plain radiographs. Third, this multi-center study included multiple surgeons and evaluators of measurement outcomes. Finally, the sample size may have been too small for some measurement outcomes. Nonetheless, the present study had a larger sample size than previous reports.

The union rate after AAA was 91.0% in this multi-center, retrospective cohort study involving five institutions. A larger radiographic tibiotalar bony gap was observed in the nonunion group. Furthermore, the VAS and SAFE-Q pain scores were significantly worse in the nonunion group.

VAS

the visual analog scale

SAFE-Q

self-administered foot evaluation questionnaire

AAA

arthroscopic ankle arthrodesis

BMI

body mass index

LIPUS

low-intensity pulsed ultrasound

osteoarthritis

JSSF

Japanese Society for Surgery of the Foot

Ethics approval and consent to participate:

This study was approved by the appropriate institutional review board of Sapporo Medical University. All procedures in this retrospective study were complied with the Helsinki Declaration of 1964 and its later versions. We obtained written informed consent to participate in this study from all patients.

Consent for publication: Not applicable.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests: The authors declare that they have no competing interests.

Funding: Not applicable.

Authors' contributions:

KT analyzed all data and and wrote this manuscript. AT provided strong support for data analysis and manuscript writing. AT, SY, KA, KS, KN and KW provided patient data for each of them. All authors read and approved the final manuscript."

Acknowledgements:

The authors would like to thank the Japanese Society for Foot and Ankle Surgery for their support in preparing the manuscript.

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No competing interests reported.

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Characteristics of nonunion after arthroscopic ankle arthrodesis: A multi-center retrospective cohort study

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Abstract

Background

Methods

Results

Conclusion

Figures

Introduction

Materials And Methods

Study design

Treatment methods

Surgical technique

Postoperative treatment

Measurement outcome

Statistical analysis

Results

Patient characteristics

Radiologic evaluations

Patient-reported outcomes

Discussion

Conclusion

Abbreviations

Declarations

References

Additional Declarations

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