Short term efficacy of subtalar arthroscopy combined with medial calcaneal-talar joint distraction in minimally invasive treatment of diabetic patients with calcaneal fractures: a retrospective study

Abstract

Background

The surgical treatment and management of postoperative soft tissue complications in diabetic patients with displaced calcaneal fractures are still controversial. We aimed to evaluate the short-term efficacy of percutaneous minimally invasive screw fixation in treatment of diabetic patients with Sanders II and III calcaneal fractures under subtalar arthroscopy assisted by preoperative musculoskeletal ultrasonic locating lateral calcaneal branch (LCB) of the sural nerve and calcaneal-talar joint distraction device.

Methods

The clinical data of 52 diabetic patients diagnosed with Sanders II or III calcaneal fractures from March 2016 to August 2020 were followed up and analyzed. There were 23 patients of type II and 29 patients of type III, 34 males and 18 females, with a mean age of 61.7 ± 14.5 years (range: 45–72 years). Preoperative musculoskeletal ultrasonography was routinely examined to locate LCB of the sural nerve. During surgery, we performed arthroscopic percutaneous prying reduction screw fixation assisted by medial calcaneal-talar joint distraction. Incision healing, local skin paraesthesia and other conditions were observed regularly at 3 days, 6, 12 months, and the last follow-up after surgery. Also, we measured the length, width, height, Böhler angle, and Gissane angle of the calcaneus on lateral and axial x-rays. Visual analogue pain scale (VAS), American Orthopedic Foot and Ankle Society (AOFAS) score and Maryland score were used to evaluate the efficacy.

Results

52 patients were followed up for 23.7 ± 3.2 months (range: 20–28 months) without incision-related complications. Calcaneal radiographic parameters (length, width, height, Böhler/Gissane angle) were improved after surgery, and the differences were all statistically significant (P<0.05). There was no difference between calcaneal radiographic parameters at 6,12 months and the last follow-up compared with 3 days after surgery without significant loss in overall morphology (P>0.05). Postoperative VAS, AOFAS scores, and Maryland scores were significantly improved compared with those before surgery (P<0.05).

Conclusions

Preoperative ultrasonic locating LCB of the sural nerve and arthroscopic percutaneous minimally invasive screw fixation of Sanders II and III calcaneal fractures with the assistance of calcaneal-talar joint distraction have good short-term efficacy and clinical feasibility in diabetic patients.

Background

The incidence of calcaneal fractures accounts for about 2.0% of all fractures and axial compressive forces caused by falls from heights or traffic accidents are the main causes [1]. Due to the special anatomical structure of the calcaneus, there are different joint axes in the three-dimensional direction. It has been confirmed that about 75.0% of calcaneal fractures are intra-articular fractures [2]. The main goal of surgery is to achieve anatomical reduction and consistency of the posterior talocalcaneal joint surface as much as possible. As an important factor affecting the prognosis of calcaneal fractures, Sanders classification divides calcaneal fractures into types I-IV based on coronal CT imaging results of the posterior talocalcaneal joint. Thereinto, different types often indicate potential differences in outcome [3].

The traditional L-shaped lateral incision provides good visibility for internal fixation of the calcaneus and facilit ates direct reduction, but there is a soft tissue complication rate of approximately 7.0% including wound hematoma, infection, and necrosis [4]. Also, the sinus tarsi approach has a relatively small incision and less soft tissue irritation, which can directly expose the posterior articular surface of the calcaneus and part of the lateral wall. However, there exists lateral calcaneal branch (LCB) of the sural nerve around the incision and about 9.6% of patients still experience sural nerve injury postoperatively [5, 6]. All of these related complications can lead to an unfavorable prognosis and even require secondary surgery, seriously affecting the quality of life of patients. As one of the independent risk factors for wound healing after calcaneal fracture surgery, diabetes may cause microangiopathy and further interferes with local blood supply to the calcaneus [7]. At the same time, peripheral neuropathy accompanied by diabetes is possibly aggravate ischemia of the affected extremities [8]. For such patients with combined calcaneal fractures, surgical treatment should pay particular attention to the scope of surgical incision and reasonable dissection. With the continuous advancement of minimally invasive techniques, percutaneous screw fixation under arthroscopy for treatment of calcaneal fractures has gradually shown good short-term outcome. It is mainly applied to Sanders II and III calcaneal fractures and capable of effectively reducing soft tissue complications exactly as incision infection [9–11]. Moreover, the use of different styles of distraction devices provides an indirect auxiliary role in arthroscopic assisted reduction of Sanders II and III fractures [10, 12].

It should be noted that operating under arthroscopy is likely to damage peroneus tendons and LCB of the sural nerve, resulting in local pain, numbness, and other sensory abnormalities through the incision [3, 13, 14]. Using distraction device can potentially affect the positioning of the operated foot, percutaneous screw placement, intraoperative fluoroscopy, etc. Currently, there is still a lack of relatively standardized instruments and operating procedures. Therefore, how to fully utilize the advantages of distraction device in arthroscopic treatment and accurately avoid injury to LCB of the sural nerve to minimize adverse factors associated with wound healing and unnecessary pain is an important issue.

In this study, we firstly performed preoperative musculoskeletal ultrasound to locate LCB of the sural nerve in diabetic patients with Sanders II and III calcaneal fractures. The medial distraction device was used to assist in reduction with minimally invasive percutaneous cannulated screw fixation under subtalar arthroscopy. With relatively good glycemic control, we aimed to identify the practicality of this surgical treatment, clarify the necessity of locating LCB of the sural nerve, and explore the specific indications of distraction. Importantly, a comprehensive assessment on short-term efficacy will largely contribute to a feasible guidance for the precise management of these patients.

Methods

Study design and data collection

From May 2016 to August 2020, patients with Sanders II or III calcaneal fractures confirmed by X-ray and CT were consecutively recruited from our orthopedic department. Inclusion criteria was: (1) unilateral fresh, closed calcaneal fractures; (2) combined with type 2 diabetes and received systematic treatment with a course of more than 3 months; (3) an age of more than 18 years old; (4) the time from injury to surgery of less than 10 days; (5) undergoing arthroscopic assisted percutaneous screw fixation. Exclusion criteria was: (1) other types of diabetes or diabetic comorbidities such as prediabetes, etc. (2) foot deformity or combined with fractures in other parts of the foot; (3) severe osteoporosis; (4) intraoperative change to open incision; (5) the follow-up time of less than 30 months. A total of 52 patients met the inclusion criteria and were enrolled in this study (Fig. 1). Clinical characteristics such as age, gender, BMI, the cause of injury, and diabetes duration, etc. were collected and recorded by the same doctor. This study was approved by the ethical committee of the Third Affiliated hospital of Soochow University and each patient needed to sign an informed consent form relevant with diabetic patient’s vulnerability to surgical complications including incision infection, skin edge necrosis, delayed healing or non-healing fracture, etc.

Fig. 1.

A flow chart of the studied patients in relation to the inclusion/exclusion criteria

Surgical treatment and postoperative rehabilitation

All patients underwent high-frequency musculoskeletal ultrasound (Aplio i800, Canon, Japan) to assess and locate LCB of the sural nerve (Fig. 2). The surgeries were completed by the same group of surgeons within a tourniquet time (≤ 90 min) after stable blood glucose control preoperatively (fasting blood glucose<8.0 mmol/L). With general anesthesia, the patient was placed in a lateral decubitus position. A 3.5 mm Steinmann wire was inserted at the calcaneal tuberosity, and a self-made calcaneal reduction device (Chinese patent No.: CN201810081218.2, Fig. 2) fixed in the calcaneal body was used for performing closed reduction with compression to preliminarily correct the varus/valgus displacement, length, and width of the calcaneus. After externally rotating the affected foot away from the malleolar canal, two K-wires were inserted into the body of the calcaneus and the talus with a depth of approximately 2.5–3.0 cm, respectively. We installed a joint distraction device on the medial side of subtalar joint (Wuyang, China, Fig. 2) to continue correcting the deformity of the calcaneus and simultaneously expand the joint space. Following establishing subtalar arthroscopic observation and operative approaches at the anterolateral and posterolateral areas of the distal fibula, we thoroughly cleaned the hematoma, free bone fragments, and detached articular cartilage under the principle of preserving the interosseous talocalcaneal ligament as much as possible. Subsequently, we performed a percutaneous leverage reduction and inserted a 2.0 mm K-wire in a direction perpendicular to the articular surface for temporary support and fixation. In addition, 2 to 3 more 2.0 mm K-wires were placed along the axis of the calcaneus for auxiliary fixation. By confirming the overall reduction in the lateral and axis X-rays, we used the K-wires as guides to insert one 4.0 mm fully threaded hollow compression screw (Waston, China) to support the articular surface and two 6.5 mm screws (Waston, China) to maintain the length, height, and axial alignment of the calcaneus. Ensure that screws were of appropriate length and position. At last, we reevaluated the reduction and fixation of the calcaneus through X-rays and direct visualization with arthroscopy (Fig. 2).

Fig. 2.

Preoperative ultrasonic localization of LCB of the sural nerve; Cross-section and long axis of LCB of the sural nerve in the hindfoot; The location of the sural nerve in the hindfoot; Distraction device; Self-made calcaneal reducer; Percutaneous prying reduction under subtalar arthroscopy assisted by distraction device; Correct the width of the calcaneus using a self-made reducer; Axial screw fixation; Vertical joint surface support screw fixation; Immediate incision after surgery

In the first 24 h postoperatively, patients were instructed to start flexion and extension exercises of the ankle and toe joints. Within 8 weeks, joint function and muscle strength training without weight bearing on the affected limb were the main focus. After 8–10 weeks, partial weight-bearing training was started and full weight-bearing training was carried out according to the fracture healing condition after 10–12 weeks. In the postoperative and follow-up time, patients were required to regularly measure blood glucose, receive standardized hypoglycemic treatment, and collaborated with endocrinologists for glycemic control as necessary to better maintain stable blood glucose levels and reduce soft tissue complications.

Observation and follow-up indicators

The main records include the time of discharge after surgery, incision complications (infection, necrosis, skin pain/numbness around the incision), and the time of weight bearing. At postoperative 1, 2, 3, 6, 12 months and the last follow-up, regular outpatient visits were conducted for radiographic measurement of the length, width, height, Böhler angle/Gissane angle of the calcaneus and evaluation of fracture healing. At the same time, visual analogue pain scale (VAS), American Orthopedic Foot and Ankle Society (AOFAS) score [15] and Maryland score [16] were used to assess the overall prognosis of patients.

Statistical analysis

SPSS 26.0 (IBM, USA) statistical software was used for analysis. Categorical variables including the cause of injury, gender, and Sanders types were described in the form of numbers (no.) and percentages (%). Kolmogorov Smirnov test was applied to assess whether continuous variables were normally distributed. In this study, the relevant numerical variables involved in baseline characteristics, calcaneal morphology, and postoperative functional scores such as age, BMI, the duration of diabetes, operation time, calcaneal length/width/height, Böhler/Gissane angle, and AOFAS score, etc. were followed normal distribution and demonstrated homogeneity of variance. Continuous variables were presented in the form of mean ± standard deviation and the comparisons at different follow-up time points were performed using one-way analysis of variance. For all the tests, P < 0.05 was considered statistically significant.

Results

General characteristics

52 patients had an average age of 61.7 ± 14.5 years (range: 45–72 years) and there were 34 males and 18 females. Among them, there included 23/29 patients of Sanders types II/III, 31/21 patients on the left/right sides, and 37/15 patients with high fall/traffic accident injuries, respectively. As a whole, it was consistent with the social trend of male dominated high-risk occupations and the major injury mechanism of calcaneal fractures induced by axial violence. The average duration of diabetes was 2.7 ± 2.1 years (range: 1–6 years). The time from injury to surgery for all patients was 6.2 ± 2.9 days (range: 5–10 days). Preoperative levels of both blood glucose and glycated hemoglobin A_1c were 6.8 ± 1.3 mmol/L and 7.4 ± 2.2%.

All patients successfully completed the surgery, 13 patients underwent intraoperative bone grafting with an average operation time of 65.6 ± 10.4 min (range: 62–85 min). After surgery, the average time of hospitalization, full weight-bearing, and fracture healing was 3.1 ± 3.5 days (range: 3–7 days), 11.2 ± 1.4 weeks (range: 10–13 weeks), and 10.9 ± 1.6 weeks (range: 10–14 weeks), respectively (Table 1).

Table 1.

Baseline characteristics of patients

Cause of injury (no.)	52
High fall injury (no./%)	37/71.2%
Traffic accident injury (no./%)	15/28.8%
Gender (male/female, no.)	34/18
Age (x ± s, y)	51.7 ± 14.5
BMI (x ± s, kg/m2)	26.3 ± 5.8
Duration of diabetes (x ± s, y)	2.7 ± 2.1
Sanders classification (no.)	52
Type II (no./%)	23/44.2%
Type III (no./%)	29/55.8%
Preoperative fasting blood glucose (x ± s, mmol/L)	6.8 ± 1.3
Preoperative glycated hemoglobin A1c (x ± s, %)	7.4 ± 2.2
Preoperative waiting time (x ± s, d)	6.2 ± 2.9
Operating time (x ± s, min)	65.6 ± 10.4
Postoperative hospitalization time (x ± s, d)	3.1 ± 3.5
Full weight bearing tine (x ± s, w)	11.2 ± 1.4
Fracture healing time (x ± s, w)	10.9 ± 1.6

no., number; y, year; d, day; w, week

Comparisons of radiographic parameters and functional results

At 3 days, 6 and 12 months, and the last follow-up after surgery, there were statistically significant differences in the length, width, height, Böhler angle, and Gissane angle of the calcaneus compared with those before surgery(F = 27.888, P<0.001;F = 62.780, P<0.001;F = 133.553, P<0.001;F = 187.867, P<0.001;F = 423.008, P<0.001); By comparing the above calcaneal radiographic parameters at 3 days, 6 and 12 months, and the last follow-up postoperatively, no statistically differences could be observed (P > 0.05), indicating that there was no significant loss of reduction after fracture fixation (Table 2; Fig. 3).

Table 2.

Comparisons of radiographic parameters before and after surgery

Parameters	Calcaneal length (x ± s, mm)	Calcaneal width (x ± s, mm)	Calcaneal height (x ± s, mm)	Böhler angle (x ± s, °)	Gissane angle (x ± s, °)
Before surgery	63.2 ± 5.1	38.4 ± 3.3	31.5 ± 3.6	14.5 ± 3.5	92.3 ± 7.2
Post-surgery 3 days	71.1 ± 4.8	32.7 ± 2.4	42.9 ± 3.2	29.8 ± 4.5	126.3 ± 5.6
Post-surgery 6 months	70.7 ± 4.6	32.5 ± 2.1	42.6 ± 2.9	29.3 ± 3.9	125.8 ± 4.3
Post-surgery 12 months	70.6 ± 4.2	32.1 ± 2.2	42.6 ± 3.0	29.1 ± 2.7	125.6 ± 4.2
Last follow-up	70.4 ± 4.2	31.9 ± 2.3	42.5 ± 2.8	29.0 ± 2.4	125.4 ± 4.3
F value	27.888a/0.227b	62.780a/1.366b	133.553a/0.176b	187.867a/0.543b	423.008a/0.361b
P value	<0.001a/0.878b	<0.001a/0.254b	<0.001a/0.913b	<0.001a/0.653b	<0.001a/0.781b

^aComparisons of the data before surgery and in post-surgery 3 days, 6 months, 12 months and the last follow-up

^bComparisons of the data in post-surgery 3 days, 6 months, 12 months and the last follow-up

Fig. 3.

A line graphs of the changes in key parameters

At 6, 12 months and the last follow-up after surgery, VAS, AOFAS score, and Maryland score were significantly improved compared with those before surgery, and the differences were statistically significant(F = 301.157, P<0.001;F = 293.186, P<0.001;F = 338.684, P<0.001). At the last follow-up, according to the AOFAS score, there were 21 excellent cases, 25 good cases, 6 fair cases, respectively, and the excellent /good rate was 88.5%; according to the Maryland score, there were 20 excellent cases, 25 good cases, 7 fair cases, and the excellent/good rate was 86.5% (Table 3; Fig. 3).

Table 3.

Comparisons of preoperative and postoperative scores

Scoring items	VAS (x ± s)	AOFAS scores (x ± s)	Maryland scores (x ± s)
Before surgery	6.7 ± 1.9	38.2 ± 12.3	61.2 ± 11.5
Post-surgery 6 months	1.7 ± 0.6	92.8 ± 5.1	93.7 ± 3.8
Post-surgery 12 months	1.5 ± 0.7	93.9 ± 4.4	94.0 ± 3.3
Last follow-up	1.4 ± 0.4	94.6 ± 5.3	94.2 ± 2.7
F value	301.157	293.186	338.684
P value	<0.001	<0.001	<0.001

VAS, Visual analogue pain scale; AOFAS, American Orthopedic Foot and Ankle Society

Complications

The average follow-up time was 23.7 ± 3.2 months (range: 20–28 months). On the premise of relatively good blood sugar control, the incisions all healed in one stage without wound infection, skin necrosis, or local sensory abnormalities caused by sural nerve injury and other related complications. At postoperative 6 months, X-ray examination showed that all patients had no fracture line of the calcaneus, significant longitudinal percussion pain, obvious abnormal skin sensation on the lateral side of the hindfoot, screw breakage or loosening, obvious bulging of the lateral wall of the calcaneus, and evident varus deformity of the hindfoot. 3 patients experienced irritation of the peroneal tendon within 2 weeks after surgery, and the distal end of the lateral malleolus often had tenderness during the follow-up period. The symptoms were effectively improved after oral administration of non-steroidal anti-inflammatory drugs and local treatment with shock wave. 2 patients had symptoms of subtalar arthritis at postoperative 6 months, including pain and swelling which could be worsened after increased activity. The symptoms were moderately alleviated after the screw was removed from the posterior articular surface of subtalar joint and local debridement with soft tissue releasing. All patients did not undergo secondary repair surgery such as fracture revision and joint fusion. Typical cases are shown in Figs. 4 and 5.

Fig. 4.

Sanders II type calcaneal fractures with posterior articular surface collapse and displacement; Lateral axial X-rays of the calcaneus on post-surgery day 2; Arthroscopic reduction of the subtalar joint surface under direct vision; Postoperative sagittal CT of subtalar articular surface of the calcaneus on post-surgery day 2; Lateral axial X-rays of the calcaneus 6 months after surgery

Fig. 5.

Sanders III type calcaneal fractures with posterior articular surface collapse and displacement; Lateral axial X-rays of the calcaneus on post-surgery day 2; Arthroscopic reduction of the subtalar joint surface under direct vision; Postoperative sagittal CT of subtalar articular surface of the calcaneus on post-surgery day 2; Lateral axial X-rays of the calcaneus 6 months after surgery

Discussion

In this study, musculoskeletal ultrasound was applied to locate LCB of the sural nerve in Sanders II and III calcaneal fracture patients with diabetes for the first time. Still, we used self-made reduction and distraction devices to assist in prying reduction of the collapsed joint surface and the correction of calcaneal morphology under direct visualization with subtalar arthroscopy. After an average follow-up of 23.7 months, the overall shape, pain symptoms and hind foot function of the calcaneus were significantly improved. Common complications such as wound infection and local skin sensation abnormalities are rare. This surgical method has good clinical feasibility and should be considered as an important means of minimally invasive treatment for such patients.

Feasibility assessment of surgical methods

For displaced Sanders II and III calcaneal fractures, poor reduction or loss of position of the posterior articular surface can lead to biomechanical changes in the subtalar and ankle joints, thereby accelerating the development of traumatic arthritis [3, 17]. In 2002, Rammelt et al. [18] first used percutaneous minimally invasive screw fixation assisted by subtalar arthroscopy to treat Sanders II calcaneal fractures and achieved positive results. Subsequently, Pastides et al. [19] and Law et al. [20] pointed out that this surgical approach has the characteristics of small incisions, light injury, preservation of local blood supply, visualization of fracture reduction, rapid recovery, and short hospitalization time, which can be used as an advantageous technique for treating Sanders II and III calcaneal fractures. The clinical prognosis in the near and medium term after surgery is similar to that of open surgery with less soft tissue irritations [9, 10, 21, 22]. It is worth noting that hollow screw fixation may have risks such as insufficient strength and loss of reduction in the early postoperative period compared to fixation with conventional locking plate screw fixation performed in an open incision [23].To our best knowledge, both the method of reduction and the position of screws play a decisive role. In addition, multiple factors such as poor patient compliance, premature weight-bearing, and bone graft or not can also lead to potential displacement after fracture fixation [21].

Associated biomechanical analysis has confirmed that sufficient biomechanical stability at the intra-articular fracture line of the posterior joint surface is feasible by fixation with one transverse screw alone when adequate support beneath the posterior joint surface is provided by the other screws [24]. Luo et al. [25] have demonstrated that subtalar arthroscopy-assisted fixation with hollow screws for the core areas of the calcaneus such as calcaneal tuberosity, posterior joint surface, and calcaneal anterior part can enhance and sustain the overall fixation strength and quality of reduction. Also, Feng et al. [9] reported that using row screw technology to support percutaneous screw placement could effectively prevent the re-collapse and displacement of the subtalar joint surface. By contrast with Sanders IV fractures, the overall injury severity of type II and III fractures is relatively mild. Considering that the stress-bearing trabecular bone in calcaneal structure is mainly distributed in calcaneal tuberosity and the posterior joint surface [25, 26], the fixation with one supporting screw perpendicular to the posterior joint surface and another screw directed from the calcaneal tuberosity to the posterior joint surface typically usually has sufficient stress resistance to prevent re-displacement of the fracture [24, 27, 28].

In this study, the screw placement followed the “three-point fixation” principle [24, 29] and three threaded hollow screws were placed along the direction of the stress-bearing trabecular bone and the fracture line to support and fix subtalar joint, calcaneal tuberosity, and calcaneocuboid joint [25]. Postoperative follow-up confirmed that this fixation method could buttress the posterior joint surface in multiple planes and effectively maintain the bony stability and calcaneal morphology after reduction. Although the row screw technology similar to the “raft” fixation may have greater bearing capacity on the joint surface, the placement of several screws in different channels horizontally close to the subtalar joint surface may easily cause irritation to peroneus longus and brevis tendons, which in turn causes persistent pain on the lateral side of the calcaneus postoperatively [24, 30, 31]. Still, Song et al. thought the crossed screws might be possible to provide considerable biomechanical stability as rafting screws [32] and this kind of technology needs to be optimized based on the balance between stability and unnecessary injury. Therefore, given the significant differences in patient positioning, fracture type, subtalar arthroscopic approach setting, screw placement, and time to full weight-bearing after walking in existing studies, the specific indications and medium-long-term efficacy of arthroscopic assisted percutaneous screw fixation for Sanders II and III calcaneal fractures still remain to be further verified by high-level clinical evidence [12, 21].

Management of soft tissue complications and the necessity of sural nerve localization

The incidence of local wound nonunion, secondary infection, ulcer, etc. tends to increase due to the decrease of terminal blood supply and peripheral neuropathy in patients with diabetes [8, 33]. It was mentioned that the patients in this study had a relatively short duration of diabetes with an average of 2.7 years, which indicated a less possibility to have macrovascular, microvascular or neuropathic complications [34, 35]. However, the above lesions were commonly insidious and in an irreversible stage once clinically diagnosed [36]. Also, the cumulative effect of the adverse metabolic characteristics associated with diabetes in different stages can potentially lead to the continuous pathological changes of blood vessels, nerves and other soft tissues [34]. As a result, the selection of surgical methods for such patients with Sanders II and III calcaneal fractures should fully consider the accuracy of reduction and the minimization of soft tissue complications. At the same time, effective postoperative glycemic control plays an essential role in improving overall efficacy and we must pay special attention to the changes in glycemic levels and make timely treatment or adjustment. To our best knowledge, the treatment regimen before admission (oral hypoglycemic drugs, basic insulin, or premixed insulin) can be continued after discharge.

Although subtalar arthroscopy-assisted percutaneous screw fixation of fractures can effectively reduce the incidence of infection, the sural nerve cannot be directly visualized during the operation. It may cause iatrogenic injury to LCB or anastomotic branches of the sural nerve [5, 11, 37], with an injury rate of approximately 6.0-9.6% [6, 38]. However, the existing data on cadaveric studies is relatively limited and it is still impossible to determine the safe area without nerve and blood vessel distribution on the lateral side of the calcaneus [39]. In recent years, high-frequency ultrasound has been widely used in structural evaluation of neuromuscular system diseases, which can visually display the trunk, epineurium, internal nerve bundle, nerve bundle membrane, and a few interneural vessels of superficial nerve bundles [40]. In this study, no patient experienced symptoms related to sural nerve injury after surgery, potentially illustrating the necessity of preoperative positioning of sural nerve.

The use of distraction device

Actually, it is difficult to insert an arthroscope into the subtalar joint without iatrogenic cartilage damage during the actual surgical operation due to the narrow space, which may result in a possibility of insufficient fracture reduction and subtalar joint reconstruction [37, 41]. Indirect reduction and fixation of Sanders II and III calcaneal fractures with distraction device are mostly performed under L-shaped and tarsal sinus incisions, and the evidence for using subtalar arthroscopy combined with minimally invasive percutaneous screw fixation is relatively limited [10, 11, 42–45]. Previously, Wang et al. [10] used a vertebral distraction device to retract both the medial and lateral sides of calcaneal body during closed reduction of fractures and correction of varus deformities in lateral decubitus position. However, it was not conducive to arthroscopic observation, screw placement and intraoperative X-rays in a certain extent. Also, the self-made three-plane distraction device used by Luo et al. [42] was cumbersome, which might impede the reduction and cause significant damage to soft tissues.

In this study, we used a medial calcaneal-talar joint distraction device to distract the subtalar joint space under lateral decubitus position. It could effectively contribute to adjust the shape of the calcaneus without affecting arthroscopic portals, lateral screw placement, fluoroscopy, and reduction. The technique was integrally similar to the one used by Gao et al. [11], which involved simultaneous medial and lateral distraction of the subtalar joint. By contrast, we recognized that medial distraction alone was particularly suitable for patients with calcaneal varus displacement and easier to perform in lateral decubitus position. It should be noted that medial subtalar joint distraction is only one of the auxiliary treatment methods, and continuous distraction for a certain period may also lead to unnecessary bone damage, postoperative pain, and swelling aggravation due to excessive fluid extravasation [37]. Continuously simplifying the design of distraction device and improving its accuracy in assisting repositioning remains an urgent problem to be solved in the process of minimally invasive treatment of calcaneal fractures.

Limitations and prospects

Several limitations existed in this study: (1) There may be some errors in radiographic measurements of relevant morphological parameters, which may easily lead to potential statistical bias; (2) Relatively small sample size, restrictive type of diabetes, short follow-up time, and insufficient evidence level of retrospective design were all likely to affect transparency and credibility of the findings. Repeatable conclusions still remain to be confirmed by large-sample and long-range data; (3) Lack of comparative outcomes in the surgical treatment using routine open incisions; (4) Although the use of medial distraction device conduced to fracture visualization and reduction, the individualized use indications needs to be clarified; (5) Ultrasonic localization of the sural nerve needs to be performed after the swelling has subsided significantly, which may lead to a prolonged hospitalization. Medication or physical therapy was needed to accelerate the resolution of local swelling if necessary.

In view of the underlying impact of diabetes on bone mass, we will strive to thoroughly evaluate the optimal position and number of percutaneous screws by integrating biomechanical testing and finite element analysis to ensure that patients can obtain good long-term outcomes.

Conclusions

At present, the overall treatment technique of minimally invasive percutaneous screw fixation for Sanders II and III calcaneal fractures under arthroscopic visualization has become increasingly regularized and standardized. On the basis of well glycolytic control, preoperative musculoskeletal ultrasonic locating LCB of the sural nerve combined with medial distraction of subtalar joint can provide more comprehensive evidence for arthroscopic assisted reduction, screw placement and lessen postoperative soft tissue complications in such patients with diabetes.

Abbreviations

VAS

Visual analogue pain scale

AOFAS

American Orthopedic Foot and Ankle Society

LCB

Lateral calcaneal branch

no.

Number

y

Year

d

Day

Author contributions

Xiaoyu Dai, Kejie Wang, and Wenge Ding designed the study and wrote the article. Chenyang Xu, Kai Ding, and Yige Zhang collected and recorded the data. Xiaoyu Dai and Wenge Ding provided the funding. Xiaoyu Dai, Chenyang Xu, and Wenge Ding did the operations. Kai Ding and Yige Zhang did the data analysis. Xiaoyu Dai and Wenge Ding revised the manuscript. All authors read and approved the final manuscript.

Funding

General program of National Natural Science Foundation of China(81272017); Basic Research Project of Changzhou science and Technology Bureau (CJ20200112); Major Projects of Changzhou Municipal Health Commission (ZD202330).

Data availability

The datasets generated and analyzed during the current study are not publicly available due to limitations of ethical approval involving the patient data and anonymity but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the Declaration of Helsinki and its later amendments or comparable ethical standards. The study protocol was approved by the local institutional review board (Ethics committee of The Third Affiliated Hospital of Soochow University). In this retrospective study, written informed consent was obtained from all patients included in this study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.