Minimally Invasive Treatment of Inversion Shortening Calcaneal Fractures in the “Out‐In” Position

Abstract

Objective

Heel fractures need extensive surgical incisions and are challenging to successfully reposition using traditional prying. The goal of this study is to evaluate the clinical effectiveness of using a Kirschner pin‐guided distractor to treat inversion shortening calcaneal fractures in the “out‐in” position.

Methods

A total of 40 data from 37 patients with inversion shortened calcaneal fractures from January 2018 to March 2020 were reviewed. Preoperative lateral and axial X‐rays and 3D CT were taken to assess the fracture type, and minimally invasive internal fixation was performed in the “out‐in” position with distractor repositioning, and intraoperative and postoperative images were taken to assess fracture repositioning and fixation. During the follow‐up period, the postoperative functional recovery status was assessed using the VAS score, AOFAS score, and FAOS score. Paired‐samples t‐test was used for all data comparisons.

Results

All cases received a mean follow‐up of 28.49 ± 3.25 months, and the mean fracture healing time was 7.84 ± 0.71 weeks. The postoperative images showed well‐fixed fracture repositioning, and calcaneal height, length, width, and inversion angles were significantly improved. At the final follow‐up, the calcaneal height, length, and width recovered from 39.35 ± 4.44mm, 79.35 ± 2.7mm, and 45.75 ± 2.87mm preoperatively to 50.93 ± 3.18mm, 82.23 ± 1.90mm, and 39.67 ± 1.58mm postoperatively (p < 0.001; p < 0.001; p < 0.001). The calcaneus inversion angle restored from 7.73° ± 2.26° to 3.80° ± 1.80° (p < 0.001). Böhler's angle and Gissane's angle improved from 13.13° ± 3.02° and 105.15° ± 8.94° to 27.95° ± 3.41° and 122.85° ± 5.54° (p < 0.001; p < 0.001). No non‐healing fractures, osteomyelitis, or traumatic arthritis were observed.

Conclusion

Minimally invasive internal fixation with distractor repositioning in the “out‐in” position is effective in the treatment of inversion shortening calcaneal fractures while restoring the anatomy and protecting the soft tissue.

Sanders type II calcaneal fracture with minimally invasive surgical treatment in the “Out‐In” Position.

Introduction

Calcaneal fractures are mostly due to high‐energy injuries and are often associated with severe soft tissue injuries. The fracture line often involves the subtalar articular surface and results in the loss of calcaneal height, length, width, and force line angle. ¹ Calcaneal fractures often result in inversion shortening displacement under shear stress, ² and if not effectively corrected, the abnormal force line relationship of the foot and ankle will seriously affect the patient's prognosis. ³ , ⁴

The open reduction and fixation of calcaneal fractures are usually performed in the side decubitus position through an extended L‐shaped approach from the lateral, ⁵ a technique that has the advantages of complete exposure and direct visualization for repositioning. ⁶ , ⁷ However, indirect repositioning such as prying is usually performed for medial wall repositioning, which may not restore the normal length, resulting in an inversion shortening deformity. Although there are clinical reports of good results using temporary external fixation bracing and repositioning in the medial position, ⁸ there may be shortcomings such as occlusion of fluoroscopy and obstruction of internal fixation placement. In addition, skin necrosis rates of this technique have been reported to be as high as 13.8%–29%. ⁹ Therefore, how to effectively reposition the medial wall and protect the soft tissues is an important factor affecting the outcome of inversion‐shortening calcaneal fractures.

In this case series study, we attempt to validate the following hypotheses. This combined surgery: (i) can effectively reestablish the ankle's natural force line and restore inversion shortening displacement in the out‐in position; (ii) can obtain smaller surgical incisions and protect soft tissue; and (iii) is more likely to experience positive clinical results in patients with inversion shortening calcaneal fracture.

Materials and Methods

Patient Information

We retrospectively analyzed 37 patients (20 men and 17 women), 40 feet (16 left, 24 right) with inversion shortening calcaneal fractures who had been admitted to the hospital from January 2018 to March 2020. The average age of the patients was 41.16 ± 12.92 (18–65) years old. Causes of injury included falling from a height (24 patients) and traffic accidents (13 patients). The average time from injury to operation was 7.57 ± 2.01 days. The classification of the fracture adopted Sanders Classification, ¹⁰ II (18 patients), III (16 patients), and IV (6 patient), (Table 1). All patients underwent relevant assessment during admission to evaluate fracture types and exclude surgical contraindications.

TABLE 1.

Basic information of the included 37 patients.

Item	Demographic data
Age, years (range)	41.2 (18–65)
Sex (male:female)	21:19
Sanders classification (II:III:IV)	9:8:3
Cause of injury (fall injury:traffic accidents)	2:3
Time before operation, days (range)	7.6 (4–10)
Operation time, min (range)	67.2 (51–135)
Intraoperative blood loss, mL (range)	13.4 (5–30)

Note: Data are presented as median (range) or n.

Inclusion and Exclusion Criteria

We included all patients: (i) over 18 years old; (ii) with sanders II‐IV calcaneal fractures; (iii) who used a Kirschner pin‐guided distractor during minimally invasive surgery and operated in the “out‐in” posture.

Patients excluded were those: (i) with open fractures; (ii) with soft tissue infection at the nail placement site; (iii) with ipsilateral lower extremity injury; (iv) with diabetic peripheral neuropathy; (v) with vasculitis of the affected lower limb; (vi) with a previous history of ankle injury or traumatic arthritis; (vii) with loss of follow‐up.

This study has been approved by the Medical Ethics Committee (code number 2023ZSZY‐LLK‐026), and informed consent was obtained from all included patients.

Method of Operation

Anesthesia and Position

The procedure was performed under successful anesthesia. A tourniquet was applied to the root of the affected thigh. The affected limb was placed in abduction on the table.

Installation of Retractors

In the “out” position (Fig. 1E), the heel bone was positioned medially upward, the location of the Kirschner's wire puncture points was positioned and marked at the talar neck and 2 cm anterior to the calcaneal tubercle of the affected foot (Fig. 1F). A 2.5‐cm diameter pin was inserted vertically at each of the puncture points; if the wire is placed in the distal tibia, the ankle cushioning influences the bracing and cannot be effectively stretched to correct the shortened angular deformity and the expanders were sheathed along the needle hole and then opened (Fig. 1G,H). A detail to be noted during the procedure is that the needle is centered close to the anterior edge of the tip of the medial ankle to avoid injury to the saphenous nerve, saphenous vein, and anterior tibial tendon. The lateral and axial positions were examined again to determine the recovery of the shortening and inversion.

Fig. 1.

A 59‐year‐old male with Sanders type II calcaneal fracture with fall injury of right foot. X‐rays and CT images of presurgery (A–D). “Out” position (E): to expose the medial wall. Point marks (F); Insert two Kirschner wires (G); Significant correction of calcaneal varus after spreading (H); Perspective after the guide is propped open, and temporarily fixation with Kirschner wires (I). “In” position (J): the bed can be tilted more to expose more lateral walls depending on whether a tarsal sinus incision is needed. Postoperative images (K, L).

Temporary Fixation

Recovery of the Calcaneal Varus Angle was assessed intraoperatively according to the axial radiographic angle of the foot, described by Zhang et al., ¹¹ that is, the foot is perpendicular to the photographic platform and the X‐ray tube points to the midpoint of the medial and lateral malleolus, then temporarily used Kirschner wire to maintain the fracture position after reduction (Figure 1I).

Repositioned Internal Fixation

The affected limb was retracted to the operating table so that the lateral calcaneus was facing upward (Figure 1J), and a minimally invasive incision or pry resetting could be made in this position. For most Sanders II fractures (Figure 1A–D), prying can restore the flatness of the articular surface. A Kirschner pin can be placed beside the calcaneal tubercle to pry for the posterior lingual bone block. ¹² Under the traction of the guided distractor, the articular surface step was confirmed by the axial graph. The larger fracture could be pried with a pin through a small incision, and temporarily fixed after satisfactory reduction. After satisfactory repositioning of the surface at all angles by intraoperative fluoroscopy, guide needles were inserted and screws were placed for internal fixation (Figure 1K,L). For Sanders III‐IV fractures, a lateral tarsal sinus incision was made, the articular surface is repositioned under direct vision, and a parallel fixation is made below the articular surface to the medial sustentaculum tali with the pin. The bony cavity below the articular surface was filled with allograft bone graft. The length, height, width, Gissane's angle, and Böhler's angle were confirmed by X‐ray. Finally, suitable plates and screws were selected to fix according to the fracture characteristics.

Postoperative Management

The lower extremities of patients were actively exercised after awakening from anesthesia. X‐ray films and CT were reviewed in the first week after surgery. Patients underwent imaging at 1, 3, and 6 months postoperatively. Partial weight‐bearing activities with the aid of a walker were instructed 4 weeks after surgery. After 6–8 weeks, patients were able to start ambulating with crutches and partly weightbearing. Eight weeks after surgery, depending on the healing condition of the fracture, patients were gradually able to walk with weight.

Evaluation Indicators

Assessment of Böhler's angle, Gissane's angle, Achilles height, width and length recovery, calcaneal varus and valgus angle, recovery of the joint surface, and the occurrence of arthritis. The functional recovery of the affected ankle joint was evaluated using the AOFAS score ¹³ and FAOS score. ¹⁴ VAS pain score and SF‐36 scores ¹⁵ are used to assess the quality of life. Postoperative complications were monitored, and intraoperative data such as operation time and intraoperative blood loss were collected.

Statistical Methods

Data entry and statistical analysis were performed using SPSS25.0 (IBM，Chicago) statistical software. The Kolmogorov–Smirnov test was used to verify whether the distribution conforms to normal distribution. Paired t‐tests were used to assess the comparison of the pre‐and post‐treatment effects. Data were expressed as $\stackrel{\mathrm{-}}{X}$ ± s. The α value of the inspection level was set to 0.05.

Results

Clinical Results

All patients underwent successful surgical treatment, and there was no attrition to surgical follow‐up. A total of 21 cases were treated by the sinus tarsi approach (STA) and 19 cases were treated by the percutaneous approach (PA). The average operation time was 62.18 ± 25.24 min, and the average intraoperative blood loss was 12.38 ± 8.77 mL. All patients received an average follow‐up of 28.49 ± 3.25 months, with a mean fracture healing time of 7.84 ± 0.71 weeks, and 28 (28 feet) of them underwent internal fixation removal after 1 year. The height, length, and width of the calcaneal were more accurately rectified (Table 2). At the final follow‐up, the VAS pain score on the affected side was 1.80 ± 0.91 and the AOFAS score was 90.93 ± 2.90; the FAOS scores were 91.81 ± 3.98 for Pain, 91.79 ± 4.30 for Symptoms, 94.60 ± 4.22 for Activities of Daily Living, 87.25 ± 6.60 for Sport, and 89.84 ± 6.28 for Quality of Life.

TABLE 2.

Treatment of calcaneal fractures with out‐in postures: imaging and functional scores (Means ± SD).

Calcaneus	Preoperative	Postoperative	p	95% CI
Height (mm)	39.35 ± 4.44	50.93 ± 3.18	<0.001	[−13.21, −9.94]
Length (mm)	79.35 ± 2.70	82.23 ± 1.90	<0.001	[−3.62, −2.13]
Width (mm)	45.75 ± 2.87	39.67 ± 1.58	<0.001	[5.07, 7.08]
Böhler's angle (°)	13.13 ± 3.02°	27.95 ± 3.41°	<0.001	[−16.18.−13.47]
Gissane's angle (°)	105.15 ± 8.94°	122.85 ± 5.54°	<0.001	[−20.55, −14.85]
+inward/−outward (°)	7.73 ± 2.26°	3.80 ± 1.80°	<0.001	[3.98, 5.32]

Complication

One patient (2.5%) developed a superficial infection in the incision after surgery. We found that it occurred at a similar rate as in the literature, ¹⁶ which was controlled after anti‐infection and dressing change. Two patients (5%) were treated with nerve‐nourishing drugs because of the numbness, suggesting that intraoperative traction or placement of screws or plates should be cautious, and positive pre‐planning may improve this situation. In another case, one patient presented with peroneal tendon inflammation, which is considered due to plate irritation. ¹⁷ All other patients showed no complications, such as post‐traumatic arthritis and calcaneus deformity.

Discussion

During the follow‐up period, which lasted for an average of >2 year after the surgery, significant improvements were observed in both foot function and pain level for the included patients. Therefore, we believe that this procedure is beneficial for the inversion shortening calcaneal fractures.

Advantages of “out‐in” Position

We use the “out‐in” position suggested by Zheng et al. ¹⁸ for three‐column tibial plateau fractures when choosing an intraoperative position: the injured foot is externally rotated and abducted in the “out” position, which leaves the medial calcaneus free for reduction using the Kirschner wire guide device of the varus shortening fracture. To reduce and fix the articular surface of the calcaneus, the afflicted limb is rotated and adducted into the “in” position. Significant benefits of this posture include the ability to achieve an acceptable limb position intraoperatively, ease of intraoperative operation, and avoidance of switching to the prone position, which compromises the patient's respiratory physiology and raises the risk of surgery. ¹⁹ , ²⁰

Advantages of Guided Distractor

Besch et al. ²¹ reported excellent results using external fixators for calcaneal fractures with severe soft tissue injuries. Rodemund et al. ⁸ reported the use of a spreader in the lateral position, but its limitations include the need to perform it under a specially designed stent. To achieve a good reduction effect and soft tissue protection, we began to use the distractor in the medial foot to correct shortening varus deformity. In contrast to previous manual traction difficulties in maintaining the reset, and sometimes the assistant has to be exposed to the X‐ray, the guided spreader can be directly opposite and maintain the traction of the shortened bone with the help of only two Kirschner wires. While liberating manpower, limited invasion is important for the protection of soft tissue.

Application

This technique can be used for Sanders II‐IV calcaneal varus shortening fractures. The medial shortening and inversion deformity of the heel bone were successfully treated with the guiding spreader application, which also restored the heel bone's length, breadth, and height in the 40 cases of feet studied in this study. At the final follow‐up, VAS pain scores, ankle AOFAS scores, and FAOS scores recovered positively, favoring the improvement of the patient's quality of life and return to work.

The standard surgical method for displaced intra‐articular calcaneal fractures is the L‐shaped extensile lateral approach (ELA) with subsequent ORIF. This approach allows for excellent visualization of the posterior facet. However, up to 37% and 20%, respectively, of serious wound and infection problems have been linked to it. ²² Limited‐incision sinus tarsi approach and percutaneous fixation reducing the necessity for peroneal dissection and its anticipated side effects of irritation and subluxation should result in a lower incidence of wound and infection complications. The risk of permanent subtalar dislocation remains, although Sanders type II fractures have better results in a limited sense and only provide that view of the subtalar joint. ²³

Our study's flexible use of the out‐in posture enabled appropriate exposure of the operative site. The STA/PA technique was used at the same time to lessen soft tissue injury. According to Kim GB's study, phased medial external fixation can restore the normal morphology of the medial wall in response to insufficient repair of inversion shortening of the articular surfaces by minor incisions, although it may take longer time from damage to definitive internal fixation. ²⁴ Guan et al. ²⁵ found that Dwyer or Modified Dwyer osteotomy can repair the varus deformity but cannot address issues with articular facets such as collapse and rotation. The shorter angular deformity can be promptly corrected by the guide spreader. In addition, we discovered that by using the spreader in the “out” position, the medial shortening of the valgus deformity was already corrected, leaving just the articular surface collapse and the restoration of the Böhler's and Gissane's angles to be fixed in the “in” position.

Deficiencies and Prospect

The number of cases included in this clinical study was relatively few, and it was a retrospective study without a control group for a comparative study. Every Sanders type had a few cases included, making it difficult to perform a large data analysis to count the variability between each type. And the follow‐up period is relatively short, with arthritic conditions believed to occur as time increases. It is hoped that a multicenter, large sample size, prospective randomized controlled study of minimally invasive treatment of valgus shortened heel fractures in the “out‐in” position will be conducted in the future.

Conclusions

Minimally invasive treatment of inversion shortening calcaneal fractures in the “out‐in” position can effectively solve the clinical difficulty of inversion shortening deformity displacement, restore the anatomical structure, and realize the minimally invasive treatment. It is a safe and effective method with the advantages of repeatable placement during operation and rapid postoperative recovery.

Author Contributions

HJ‐F and LX‐S designed the study. YL, WJ‐L and HL‐B collected the data. YL, LX‐S and HL‐B wrote the manuscript. HJ‐F revised the manuscript. LX‐S and YL approved the final manuscript for submission.

Conflict of Interest Statement

We declare that we have no competing interests.

Ethics Statement

The present study was approved from Zhongshan Hospital of Traditional Chinese Medicine institutional review board review.