Medial wall/arthroscopy/posterior facet (MAP) strategy for displaced intra-articular calcaneal fractures: evaluation of a novel minimally invasive protocol in a retrospective comparative cohort

Abstract

Background

Displaced intra-articular calcaneal fractures (DIACFs) pose substantial challenges due to their complex three-dimensional deformity and the high risk of soft tissue complications. Minimally invasive percutaneous methods and subtalar arthroscopy have emerged to mitigate soft tissue injury, but their limited exposure often hinders reliable reduction of the medial wall. To address these limitations, we developed a novel MAP strategy (Medial wall/Arthroscopy/Posterior facet) that prioritizes a medial-to-lateral sequence to achieve effective and stable reduction.

Methods

This retrospective analysis included 180 cases of unilateral DIACFs treated between 2022 and 2024. Patients were classified into three groups based on the surgical treatment as follows: arthroscopy-assisted percutaneous screw fixation (MAP, 40 cases), percutaneous screw fixation (PF, 49 cases), and open reduction and internal fixation (ORIF, 91 cases). Outcomes were assessed at 12 months postoperatively, including complications, radiographs, and functional scores using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle hindfoot score, visual analog scale (VAS) and Maryland Foot Score.

Results

The MAP group exhibited the longest surgical duration (80.0 [70.0, 90.0] min) but had the shortest hospital stay (5.0 [4.0, 6.0] days). The ORIF group experienced a longer preoperative delay (6.0 [6.0, 7.0] days) and had a significantly higher overall complication rate compared to the MAP and PF groups (31.9% vs. 15.0% and 14.3%, p = 0.027). At the 12-month postoperative follow-up, the MAP group demonstrated significantly greater AOFAS scores (84.50 [78.25, 86.00]) compared to the PF group (80.00 [75.00, 84.00], p = 0.029) and the ORIF group (81.00 [74.00, 86.00], p = 0.021). The VAS pain score in the MAP group (2.00 [1.25, 3.00]) was significantly lower than that in the ORIF group (3.00 [2.00, 3.00], p = 0.009). Regarding radiographic assessments, all three groups demonstrated satisfactory postoperative restoration in Böhler’s angle, calcaneal height, and calcaneal width compared to preoperative baselines, with no significant intergroup differences observed.

Conclusion

In this retrospective cohort study, the MAP strategy was associated with favourable short-term functional outcomes and a low rate of soft-tissue complications in DIACFs.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13018-026-06925-x.

Introduction

Approximately 2% of all fractures are intra-articular calcaneal fractures, and 75% of these are displaced intra-articular calcaneal fractures (DIACFs) [1]. Surgical correction of calcaneal height, width, and length, as well as subtalar joint congruence, is considered the primary treatment [2–5]. Historically, efforts to achieve reliable reduction have focused on lateral approaches. Early in the 20th century, McReynolds and Burdeaux highlighted the importance of the medial wall in calcaneal reduction and proposed a medial approach to directly address medial wall displacement [6]. The extensile lateral approach (ELA) provides broad exposure [7], and meanwhile it is associated with a high incidence of soft tissue complications, including wound edge necrosis and infection [8–10]. In response to the limitations of open techniques, a range of minimally invasive strategies has been developed, including the sinus tarsi approach, percutaneous screw fixation, and arthroscopically assisted procedures [11–18]. Compared with the ELA, these methods are associated with fewer soft tissue complications [19]. Nevertheless, these minimally invasive techniques are constrained by limited exposure of the operative field, which may present a challenge in the reduction of the medial wall and the overall calcaneal morphology. Specifically, conventional percutaneous strategies tend to prioritize correction of the lateral wall or posterior facet first, while neglecting the foundational role of the medial wall in reestablishing the three-dimensional architecture of the calcaneus.

We developed a reduction strategy that emphasizes a medial-to-lateral reduction sequence, termed the MAP method (Medial wall/Arthroscopy/Posterior facet). The medial wall is first reduced percutaneously to establish a stable medial wall, followed by precise arthroscopic reduction of the posterior facet. In this retrospective comparative study, we evaluated the clinical efficacy and safety of the MAP method for displaced intra-articular calcaneal fractures (DIACFs) by analysing operative variables, complication rates, functional recovery, and radiographic outcomes, and we compared these results with those of percutaneous fixation (PF) and the ELA. The purpose of this study was to evaluate the clinical and radiographic outcomes of the MAP method and to compare them with those of PF and ELA in the treatment of DIACFs.

Methods

Patients’ demographic characteristics

This study was designed as a retrospective cohort study. 486 consecutive patients with DIACFs treated at Shanghai Sixth People’s Hospital between January 2022 and July 2024 were enrolled. The choice of surgical technique (MAP, PF, or ORIF) was determined by the treating surgeon based on fracture characteristics, soft-tissue condition, and clinical judgment. And we enrolled participants based on the following inclusion criteria: (1) adults aged > 18 years; (2) had unilateral DIACFs (Sanders type II, III or IV); and (3) managed either with MAP, PF, or ORIF. The exclusion criteria were as follows: (1) open fractures, (2) concurrent fractures in the ipsilateral lower limb, (3) neurovascular injuries, (4) systemic comorbidities including diabetes mellitus and osteoporosis, (5) incomplete follow-up. Each patient received at least 12-month follow-up via telephonic or face-to-face interviews. All functional outcome data analyzed in this study were collected at the 12-month postoperative time point. The main demographic characteristics are presented in Table 1. In total, 180 eligible patients (180 feet) with complete clinical data and follow-up records for at least 12 months were included in this retrospective study (Fig. 1).

Table 1.

Characteristics of patients and calcaneal fractures

Variable	MAP (n = 40)	PF (n = 49)	ORIF (n = 91)	p value
Age (years)	48.6 ± 13.9	52.6 ± 11.4	49.3 ± 11.4	0.152
BMI (kg/m2)	23.9 [22.0, 25.3]	24.5 [22.1, 26.7]	24.5 [22.8, 26.8]	0.383
Sex				0.083
Male	35 (87.5%)	38 (77.6%)	83 (91.2%)
Female	5 (12.5%)	11 (22.4%)	8 (8.8%)
Side				0.361
Right	23 (57.5%)	27 (55.1%)	43 (47.3%)
Left	17 (42.5%)	22 (44.9%)	48 (52.7%)
Sanders classification				0.732
Type II	25 (62.5%)	32 (65.3%)	58 (63.7%)
Type III	13 (32.5%)	16 (32.7%)	26 (28.6%)
Type IV	2 (5.0%)	1 (2.0%)	7 (7.7%)
Essex-Lopresti classification				0.180
Tongue type	24 (60.0%)	20 (40.8%)	48 (52.7%)
Joint-depression type	16 (40.0%)	29 (59.2%)	43 (47.3%)
Time from injury to surgery (days)	2.0 [2.0, 3.0]	3.0 [2.0, 4.0]	6.0 [6.0, 7.0]	< 0.001
Operative time (minutes)	80.0 [70.0, 90.0]	60.0 [45.0, 65.0]	55.0 [45.0, 62.5]	< 0.001
Hospital stay (days)	5.0 [4.0, 6.0]	5.0 [4.0, 6.0]	9.0 [9.0, 10.5]	< 0.001
Frequency of intraoperative fluoroscopy (times)	21.3 [17.0, 24.8]	31.0 [25.5, 37.0]	17.0 [13.0, 21.0]	< 0.001

Data are presented as mean ± SD, median [Q1, Q3], or n (%). Age was compared using one-way ANOVA. BMI, time from injury to surgery, operative time, and hospital stay were compared using the Kruskal-Wallis test. Categorical variables were compared using Fisher’s exact test. Bold characters indicate significant values (p < 0.05). MAP, minimally invasive arthroscopic procedure; PF, percutaneous fixation; ORIF, open reduction and internal fixation; BMI, body mass index; SD, standard deviation

Fig. 1.

Patient selection flow diagram illustrating the screening and inclusion of patients with displaced intra-articular calcaneal fractures (DIACFs) between 2022 and 2024. A total of 180 patients met the inclusion criteria and were included in the final analysis (MAP, n = 40; PF, n = 49; ORIF, n = 91)

Preoperative treatment

For all patients, the injured foot was elevated and temporarily immobilized in a cast. Ice therapy was administered three times daily. Surgery was performed when the soft-tissue conditions permitted surgical intervention.

Surgical procedures

After general anaesthesia, the patient was placed in a prone-lateral position, with the operative extremity draped free and a tourniquet applied to the proximal thigh (Fig. 2). The detailed surgical procedures of the three groups are described in the Supplementary Materials.

Fig. 2.

A typical case from the MAP group: a 35-year-old male with a right joint-depression type calcaneal fracture (Sanders III BC). A. Preoperative X-ray radiographs. B-C. CT images show a Sanders III BC type calcaneal fracture. D. The position of the patient and C-arm to obtain an axial view. E. In axial view, the mal-alignment of the medial wall. F. After bilateral distraction and clamping, the medial wall was reduced and temporarily fixed with a K-wire. G. Subtalar arthroscopy using the sinus tarsi approach. H. Subtalar arthroscopy shows step-off between posterior facet fragments. By inserting a 3.0-mm K-wire from the plantar side, we were able to elevate the posterior fragment and achieve anatomical reduction. I. Loose chondral or osteochondral fragments were removed, and intraoperative fluoroscopy shows good reduction without step-off on the posterior facet. J. Intraoperative image of anatomic reduction of the calcaneus. K, L. Postoperative radiography showed that the length, height, and width of the calcaneus were corrected, and the varus deformity was corrected

MAP technique

First, the medial wall of the calcaneus was reduced percutaneously under axial fluoroscopic guidance using ankle distractors and a percutaneous clamp to restore calcaneal alignment and height. Temporary fixation with K-wires was performed. Second, subtalar arthroscopy was used to visualize the posterior facet, remove loose chondral or osteochondral fragments, and assist reduction of the articular surface. Finally, the posterior facet was reduced and stabilized with percutaneous screws according to the fracture pattern.

Percutaneous fixation (PF)

Reduction of the calcaneal tuberosity and medial wall was achieved using percutaneous distraction and clamp-assisted reduction under fluoroscopic guidance. The posterior facet was subsequently reduced under fluoroscopy, followed by temporary K-wire fixation and definitive percutaneous screw fixation.

Open reduction and internal fixation (ORIF)

After soft-tissue swelling subsided, the fracture was exposed through an extensile lateral approach. The posterior facet and calcaneal morphology were anatomically reduced under direct visualization, and fixation was achieved using a lateral locking plate.

Radiological evaluation

All patients routinely underwent preoperative X-ray and computed tomography (CT) scan for confirmation of fracture type according to the Essex–Lopresti and Sanders classifications [2, 3]. Postoperatively, X-ray and CT scan were performed routinely on each patient to assess the reduction quality. The Böhler angle and the width and height of the calcaneus were measured using X-ray films and CT imaging as described previously [8, 20, 21] (Fig. 3). Radiographic measurements were independently performed by two experienced orthopaedic surgeons who were not involved in the surgical procedures. The observers were blinded to the clinical outcomes and treatment groups during the measurement process. Each parameter was measured independently, and any discrepancies were resolved through discussion until consensus was reached.

Fig. 3.

A typical case from the PF group: a 40-year-old male with a tongue-type Sanders III AB calcaneal fracture. A. Preoperative X-ray radiographs show the tongue-type fracture. B. CT images show a Sanders III AB type calcaneal fracture. C, D. In axial view, after sufficient bilateral distraction, mal-alignment of the medial wall remained. Using the Essex-Lopresti technique, a 3.0-mm K-wire was drilled into the tongue-type fragment under fluoroscopic guidance, and the posterior facet was generally reduced. E. After clamping between the sustentaculum tali fragment and tuberosity, the posterior tuberosity was pushed medially, and satisfactory alignment of the medial wall was obtained. The medial wall was then temporarily fixed with K-wires. F. The Borden's view shows a remaining step-off between posterior facet fragments. G. The die-punch fragment was reduced by using a K-wire inserted from the plantar side, which helped to elevate the minor fragments. After reduction, the posterior facet was fixed with K-wires. H-I. The anatomical reduction after screw fixation. J. Postoperative X-ray showed that the length, height, and width of the calcaneus were corrected, and the varus deformity was corrected. K. Postoperative CT image showed the anatomic reduction of the calcaneus with no step-off left in the posterior facet

Postoperative rehabilitation

All patients followed a standardized postoperative rehabilitation protocol at our institution: unrestricted postoperative active movement without weight-bearing was permitted. On the first postoperative day, patients were guided by a professional rehabilitation team to perform active plantar flexion and dorsiflexion, along with subtalar inversion and eversion exercises. Partial weight-bearing with a walking boot commenced at 8 weeks postoperatively, and normal daily activities were resumed at 10 weeks (Fig. 4). This rehabilitation protocol was generally applied to all patients regardless of the surgical technique used. Because this study was retrospective, strict monitoring of patient compliance with the rehabilitation program was not systematically recorded.

Fig. 4.

A 2.5-month follow-up of a DIACF patient in the MAP group. A. The hindfoot alignment was normal without varus or valgus deformity. B-E. The range of motion of the ankle showed good recovery, indicating good function of the ankle and subtalar joints. F. The range of motion of the subtalar joint showed good recovery

Incidence of complications

Postoperative complications were recorded during follow-up. Superficial infection was defined as infections involving skin and subcutaneous tissue without surgical intervention, whereas deep infection was defined as infection involving fascia and muscle requiring surgical debridement or intravenous antibiotic therapy. Subtalar arthritis was assessed on follow-up radiographs and defined by degenerative changes of the subtalar joint, including joint space narrowing, subchondral sclerosis, or osteophyte formation. Loss of reduction was defined as a postoperative decrease in Böhler angle exceeding 10° compared with the immediate postoperative radiograph. Sural nerve injury was diagnosed clinically based on postoperative sensory disturbance in the sural nerve distribution area.

Assessment of foot function

Postoperative complications and functional recovery were documented during follow-up. Functional scores were collected by dedicated assessors blinded to fracture characteristics and surgical techniques. In this study, the Maryland Foot Score (MFS), the American Orthopaedic Foot and Ankle Society Hind Foot Score (AOFAS) [22], and the Visual Analogue Scale (VAS) [23] were analyzed as co-primary functional outcomes to capture complementary aspects of postoperative recovery. Specifically, MFS was used to assess midfoot-related function, AOFAS to evaluate overall foot and ankle function, and VAS to measure postoperative pain. Assessments were conducted through one-on-one interviews during outpatient visits or via structured telephone interviews using standardized questionnaires.

Statistical analysis

Statistical analysis was conducted using SPSS version 25.0 (IBM Corp., Armonk, NY) and R version 4.3.0. Normality of continuous variables was assessed using the Shapiro-Wilk test. Continuous data are presented as median with the first and third quartiles [Q1, Q3] for non-normally distributed variables or mean ± standard deviation (SD) for normally distributed variables. For normally distributed variables, one-way ANOVA with post-hoc Tukey HSD correction was applied; for non-normally distributed variables, the Kruskal–Wallis H test was used for comparisons among the three groups, followed by Dunn’s test with Bonferroni correction for pairwise comparisons. To account for potential confounding factors, multivariable linear regression analyses were performed for all functional outcomes, adjusting for age, sex, Sanders classification, time from injury to surgery, and BMI. Furthermore, effect size estimates and bootstrap sensitivity analyses (1,000 resamples) were calculated to assess the robustness of the findings. A p value less than 0.05 was considered statistically significant.

Results

Follow-up and baseline characteristics

This retrospective comparative study included 180 patients who underwent three types of surgical procedures: MAP (40 cases, 22.2%), PF (49 cases, 27.2%), and ORIF (91 cases, 50.6%). The demographic analysis revealed no significant differences in the mean age across the groups (MAP: 48.6 ± 13.9 years; PF: 52.6 ± 11.4 years; ORIF: 49.3 ± 11.4 years, p = 0.152). The ORIF group had the highest proportion of male patients (83 males vs. 8 females), followed by the MAP group (35 males vs. 5 females) and the PF group (38 males vs. 11 females). Sanders Type II fractures were the most common fracture pattern, with 25, 32, and 58 cases in the MAP, PF, and ORIF groups, respectively. There were 13, 16, and 26 cases of Type III fractures in the MAP, PF, and ORIF groups, respectively. Type IV fractures were relatively uncommon, with 2, 1, and 7 cases in the MAP, PF, and ORIF groups, respectively. With respect to the Essex–Lopresti classification, in the MAP, PF, and ORIF groups, 24, 20, and 48 cases, respectively, had tongue-type fractures, whereas 16, 29, and 43 cases, respectively, had joint-depression fractures. The median time from injury to surgery in each group was 2.00 [2.00, 3.00], 3.00 [2.00, 4.00], and 6.00 [6.00, 7.00] days in the MAP, PF, and ORIF groups, respectively. This delay was primarily attributed to delayed hospital admission and the necessity of waiting for the recovery of skin conditions to minimize the risk of soft-tissue complications. The MAP group exhibited a significantly longer median surgical time (p < 0.001) of 80.0 [70.0, 90.0] min, in contrast to the PF and ORIF groups (60.0 [45.0, 65.0] and 55.0 [45.0, 65.0] min, respectively). The median length of hospital stay in the MAP and PF groups (both 5.0 [4.0, 6.0]) was considerably shorter than that for the ORIF group, which had a median hospital stay of 9.0 [9.0, 10.5] days (p < 0.001). Moreover, the lowest number of intraoperative fluoroscopy images (p < 0.001) was recorded in the ORIF group (17.0 [13.0, 21.0]), followed by the MAP group (21.3 [17.0, 24.8]) and the PF group (31.0 [25.5, 37.0]) (Table 1).

Complications

The overall complication rates were 15.0% (6/40) in the MAP group, 14.3% (7/49) in the PF group, and 31.9% (29/91) in the ORIF group, with a statistically significant difference among groups (Fisher’s exact test, p = 0.027). The incidences of superficial infection (10 cases, 11.0%) and incision necrosis (6 cases, 6.6%) in the ORIF group were significantly higher than those in the MAP and PF groups (no infections occurred in the minimally invasive treatment groups) (p < 0.001), which underscores the advantages of minimally invasive techniques in reducing wound complications. Among those, infections in 8 cases were alleviated following dressing changes whereas 2 cases subsequently developed sinus tracts. The hardware was removed after fracture healing, and the sinus tracts were eventually closed. None of the patients with postoperative complications required flap reconstruction. The incidence of traumatic arthritis was lower in the MAP group (5%) and the PF group (4.1%), as compared to 6.6% in the ORIF group. The rates of sural nerve injury were similar in the MAP and PF groups (7.5% and 6.1%, respectively) and in the ORIF group (5.5%). Furthermore, reduction loss was noted in 1 case (2.5%) in the MAP group, 2 cases (4.1%) in the PF group, and 2 cases (2.2%) in the ORIF group, potentially linked with early weight-bearing by the patients. These cases were managed conservatively without revision surgery. No cases of calcaneal deformity or non-union were observed in any group (Table 2).

Table 2.

Postoperative complications at 12-month follow-up

Complication	MAP (n = 40)	PF (n = 49)	ORIF (n = 91)	p value
Wound-related complications	0 (0.0%)	0 (0.0%)	16 (17.6%)	< 0.001
Superficial infection	0 (0.0%)	0 (0.0%)	10 (11.0%)
Incision necrosis	0 (0.0%)	0 (0.0%)	6 (6.6%)
Deep infection	0 (0.0%)	0 (0.0%)	0 (0.0%)
Subtalar arthritis	2 (5.0%)	2 (4.1%)	6 (6.6%)
Sural nerve injury	3 (7.5%)	3 (6.1%)	5 (5.5%)
Calcaneal deformity	0 (0.0%)	0 (0.0%)	0 (0.0%)
Loss of reduction	1 (2.5%)	2 (4.1%)	2 (2.2%)
Calcaneal nonunion	0 (0.0%)	0 (0.0%)	0 (0.0%)
Total complications	6 (15.0%)	7 (14.3%)	29 (31.9%)	0.027

Data are presented as n (%). p values were calculated using Fisher’s exact test. Wound-related complications include superficial infection and incision necrosis. Bold characters indicate significant values (p < 0.05). MAP, minimally invasive arthroscopic procedure; PF, percutaneous fixation; ORIF, open reduction and internal fixation

Comparison of clinical outcome and functionality

Most patients had good clinical outcomes and functional recovery (Fig. 4). At the 12-month postoperative follow-up, functional evaluation results revealed a significant difference in the AOFAS score (p = 0.028) among the three groups. The AOFAS score of patients in the MAP group (84.50 [78.25, 86.00]) was significantly greater than that in the PF group (80.00 [75.00, 84.00], p = 0.029) and the ORIF group (81.00 [74.00, 86.00], p = 0.021). The MFS scores for the MAP, PF, and ORIF groups were 81.50 [77.25, 86.75], 82.00 [76.00, 84.00], and 79.00 [73.00, 84.00], respectively, without significant intergroup differences (p = 0.066). VAS pain scores significantly differed among the three groups (p = 0.021). The MAP group experienced significantly lower pain levels (2.00 [1.25, 3.00]) compared to the ORIF group (3.00 [2.00, 3.00], p = 0.009) (Table 3). Comprehensive descriptive statistics (including mean ± SD), covariate-adjusted comparisons, effect size estimates, and bootstrap sensitivity analyses are fully detailed in Supplementary Tables S1–S4. Regarding radiographic evaluations, all three groups demonstrated satisfactory postoperative restoration in Böhler’s angle, calcaneal height, and calcaneal width compared to their preoperative baselines. However, no significant differences were observed among the three groups in any of the postoperative radiographic parameters (Table 4).

Table 3.

Clinical outcomes at 12-month follow-up

Outcome measures	MAP (n = 40)	PF (n = 49)	ORIF (n = 91)	p value	p value MAP vs. PF	p value MAP vs. ORIF	p value PF vs. ORIF
AOFAS	84.50 [78.25, 86.00]	80.00 [75.00, 84.00]	81.00 [74.00, 86.00]	0.028	0.029	0.021	1.000
MFS	81.50 [77.25, 86.75]	82.00 [76.00, 84.00]	79.00 [73.00, 84.00]	0.066	0.377	0.032	0.416
VAS	2.00 [1.25, 3.00]	3.00 [2.00, 3.00]	3.00 [2.00, 3.00]	0.021	0.076	0.009	0.820

Data are presented as median [Q1, Q3]. Overall group comparisons were performed using the Kruskal-Wallis test. Pairwise comparisons were performed using Dunn’s test with Bonferroni correction. For MFS, the overall Kruskal-Wallis test did not reach statistical significance (p = 0.066); pairwise comparisons are presented for reference only. Bold characters indicate significant values (p < 0.05). AOFAS, American Orthopaedic Foot and Ankle Society score; MFS, Maryland Foot Score; VAS, Visual Analogue Scale; MAP, minimally invasive arthroscopic procedure; PF, percutaneous fixation; ORIF, open reduction and internal fixation; Q1, first quartile; Q3, third quartile

Table 4.

Preoperative and postoperative radiographic measurements

Radiographic parameters	MAP (n = 40)	PF (n = 49)	ORIF (n = 91)	p value
Preoperative
Böhler’s angle (°)	14.0 [3.2, 18.2]	17.0 [11.0, 21.0]	15.0 [9.0, 20.0]	0.095
Calcaneal height (mm)	38.0 [33.5, 40.0]	38.0 [35.0, 41.0]	37.0 [34.0, 40.0]	0.223
Calcaneal width (mm)	38.0 [35.0, 42.0]	37.0 [33.0, 40.0]	38.0 [34.0, 41.0]	0.464
Postoperative
Böhler’s angle (°)	31.4 ± 7.9	30.1 ± 7.3	29.3 ± 6.2	0.248
Calcaneal height (mm)	44.5 ± 3.0	43.2 ± 3.6	42.7 ± 3.9	0.042
Calcaneal width (mm)	33.0 [30.0, 36.0]	32.0 [30.0, 35.0]	32.0 [31.0, 35.0]	0.822

Data are presented as median [Q1, Q3] or mean ± SD as appropriate. Non-normally distributed variables (Pre Böhler’s angle, Pre calcaneal height, Pre calcaneal width, Post calcaneal width) were compared using the Kruskal-Wallis test. Normally distributed variables (Post Böhler’s angle, Post calcaneal height) were compared using one-way ANOVA. Bold characters indicate significant values (p < 0.05). MAP, minimally invasive arthroscopic procedure; PF, percutaneous fixation; ORIF, open reduction and internal fixation; Q1, first quartile; Q3, third quartile; SD, standard deviation

Discussion

The ideal treatment for calcaneal fractures remains controversial. Although the ELA is acknowledged as the most commonly used approach for DIACFs, it is associated with a high incidence of wound dehiscence, deep infection, and incision necrosis [24]. Minimally invasive surgeries, including PF and the STA technique, have lower complication rates [10, 25, 26], but potentially increase the risk of inadequate reduction of the medial wall, which results in the medial wall overlap and hindfoot varus deformity. These malreductions can alter gait and foot biomechanics [27, 28]. Therefore, when performing calcaneal fracture surgery, good axial alignment should not be neglected as it is essential in minimally invasive surgery to achieve medial wall correction and smooth posterior facet reduction. In this study, we investigated the clinical outcomes of the MAP strategy, which is a standardized procedure that combines medial wall stabilization, arthroscopic-guided clearance of the subtalar joint, and posterior facet reduction. This combination may facilitate effective reduction and stable fixation while maintaining a low complication profile (while the incidence of sural nerve injury and reduction loss was comparable across the treatment groups). We also observed that postoperative radiographic parameters, including Böhler angle, calcaneal height, and width, showed no significant differences among the three groups. Despite this radiographic similarity, functional outcomes varied between groups. This discrepancy can be attributed to the fact that radiographic measurements primarily assess restoration of bony architecture, but do not adequately reflect subtalar joint congruity or the extent of cartilage injury. Functional recovery following calcaneal fractures is multifactorial, influenced by cartilage damage, postoperative joint stiffness, and rehabilitation quality [29–31], rather than solely by calcaneal volume, posterior facet area, or fracture fragment number [32]. Consequently, comparable radiographic restoration does not guarantee equivalent functional results.

There were several improvements in the MAP strategy. First, we performed the reduction of the medial wall as the first step, followed by the reduction of the lateral column (posterior joint surface). This differs from previous reports in which arthroscope-assisted posterior joint surface restoration was initially performed [12]. Woon et al. demonstrated that the tuberosity and anterior process should not be reduced as a first step because malreduction may impede reduction of the posterior facet [12]. Mobilizing the ‘articular block’ and tuberosity independently further allows the tuberosity fragment to be brought out to length [33]. However, in our study, the reduced medial wall did not impede the reduction of the posterior facet and, conversely, served as a template for the correct reduction of the lateral fragment, which made it much easier to achieve reduction of the posterior joint surface using subtalar arthroscopy. The concept and significance of the reduction of the medial wall in cases of calcaneal fracture were reported in the 1980s [6, 34, 35]. The reduction and solid fixation of the medial wall can avoid the varus or valgus malalignment and are critical for maintaining the calcaneal height. Although some authors have used a medial approach to directly reduce and fix the medial fragment, this necessitates another lateral incision for the reduction of the depressed posterior fracture, which leads to increased incision risks and interference with the medial neurovascular bundle [36]. In our study, while the "M" procedure eliminates the varus or valgus malalignment and restores the height of the calcaneum, it also creates additional space for later reduction of the lateral fragments. In the present study, significant improvements in Böhler angle, calcaneal height, and calcaneal width were observed postoperatively in all groups, suggesting satisfactory restoration of calcaneal anatomy. These findings are generally consistent with previously published studies evaluating surgical treatment of displaced intra-articular calcaneal fractures [37].

Subtalar arthroscopy was reported to be most useful in the reduction of Sanders Type II DIACFs [12, 33, 38, 39]. However, few studies have reported outcomes in Sanders Type III or Type IV DIACFs. This is partly attributable to the difficulty in the restoration of the central collapsed fragment. Though subtalar arthroscopy facilitates direct visualization of the subtalar joint, its narrow field of view can sometimes cause excessive reduction, insufficient reduction, or rotational inward tilt of the posterior articular fragment. By using the correctly restored medial wall as a template and following a medial-to-lateral reduction sequence, anatomic reduction of the posterior facet was more easily achieved and reduced the occurrence of the above-mentioned complications. Therefore, subtalar arthroscopy-assisted percutaneous reduction may be applicable to selected DIACFs. However, fracture-type–specific conclusions cannot be drawn from the present study. The operative duration of the MAP procedure in this study was similar to that reported for other arthroscopy-assisted techniques [38]. In our study, the operative duration was 80.0 (70.0, 90.0) min, which is shorter than that in Woon’s study (95 [60–165] min) [12]. In previous reports, the average operative duration for arthroscopy-assisted DIACFs was 82.6 to 112.9 min [38, 40, 41], which possibly contributed to the good arrangement of surgical procedure. In MAP group, the reduction and evaluation of the medial wall is primarily in axial view (feet in a prone position), and the subsequent arthroscope-assisted reduction of the posterior articular surface is undertaken in the lateral decubitus feet position. Therefore, it reduced the time for fluoroscopy and the need to repeatedly change the feet positions. Moreover, our medial-to-lateral reduction sequence facilitated easier achievement of good alignment of the calcaneal body and anatomic reduction of the posterior facet. Previous clinical studies have also emphasized the importance of proper reduction strategies in calcaneal fracture surgery, particularly the restoration of medial wall alignment and overall calcaneal morphology when performing minimally invasive fixation techniques [42]. Similar surgical principles and favourable clinical outcomes have been reported in other regional clinical experiences [43]. Finally, multiple free cartilage fragments and minor bone fragments in the posterior joint were removed in the MAP group. The occurrence of traumatic arthritis is closely associated with a longer postoperative period [38]. We believe that removing the fragments could reduce the likelihood of subtalar arthritis over time. We also found significantly better AOFAS scores in the MAP group compared to both the PF and ORIF groups, along with significantly lower VAS pain scores compared to the ORIF group. However, the absolute differences were modest. It should be noted that the minimal clinically important difference (MCID) represents the smallest change perceived as beneficial by patients. Previous studies [44, 45] indicate that the MCID for the AOFAS score ranges from 7.9 to 30.2 points, while the MCID for VAS typically ranges between 1.5 and 2.0 points. Therefore, the observed functional differences in our cohort may not fully meet this clinical threshold.

Regarding perioperative safety and complications, both the MAP and PF groups exhibited a significantly reduced length of hospital stay compared to the ORIF group. Additionally, the time from injury to surgery was notably longer in the ORIF group. In routine clinical practice, ORIF is typically delayed until soft-tissue swelling subsides and the “wrinkle sign” appears to minimize wound-related risks. Despite this preoperative precaution, the incidence of soft-tissue complications remained higher in the ORIF group. The literature reports total wound complication rates for the extensile lateral approach (ELA) ranging from 14.3 to 30% [25, 46–48]. Consistent with these historical data, our ORIF cohort experienced superficial infections in 10 cases (11.0%) and incision necrosis in 6 cases (6.6%). In stark contrast, the MAP group had zero soft-tissue complications. Although baseline differences in initial soft-tissue conditions may represent a potential confounding factor, the absence of wound complications in the MAP and PF groups strongly reflects the inherent advantages of minimally invasive approaches with limited soft-tissue dissection. Furthermore, while sural nerve injuries were recorded, most cases presented merely as mild sensory disturbances or numbness along the lateral aspect of the foot. These symptoms gradually improved during follow-up without additional treatment and did not significantly affect the final functional outcomes. In addition, fluoroscopy time in the MAP group was significantly shorter than that in the PF group, which may reduce radiation exposure for both patients and surgical staff. During the follow-up period, two instances of asymptomatic subtalar arthritis were detected in both the MAP and PF groups, which necessitates no additional treatment owing to the lack of symptoms. Remarkably, the rate of sural nerve injuries was similar in the MAP and PF groups (7.5% and 6.1% respectively), yet marginally less in the ORIF (5.5%). Our theory suggests that the observed discrepancy could stem from damage to the sural nerve during the insertion of screws on the posterior side, which underscores the need for meticulous dissection of the underlying subcutaneous tissues behind the peroneal tendons to prevent nerve harm.

This retrospective cohort follow-up study has several limitations. First, this is a single-centre study with a retrospective design, which lacks randomization in patient characteristics. Because treatment allocation was not randomized, potential selection bias cannot be completely excluded. The unequal distribution of cases among treatment groups may affect variance estimation and statistical power. Although the non-parametric methods employed are applicable to unequal group sizes and bootstrap sensitivity analyses confirmed the stability of our findings, this imbalance should be considered when interpreting the results. While multivariable regression analyses were performed to adjust for key potential confounders including age, sex, Sanders classification, time from injury to surgery, and BMI, residual confounding from unmeasured factors cannot be entirely excluded given the retrospective study design. Second, a significant proportion of patients with DIACFs are workers who have been injured in falls, characterized by high mobility and relatively low educational levels, which contributed to a follow-up loss rate of 30–40%. Consequently, the exclusion of these patients due to incomplete follow-up means that potential attrition bias cannot be completely ruled out. Third, preoperative functional scores were not systematically available in this retrospective dataset, which limited the ability to evaluate functional improvement from baseline. In addition, standardized patient-reported outcome measures (PROMs) were not included in the present analysis, and formal interobserver reliability statistics were not calculated. Fourth, the relatively short follow-up duration is insufficient to fully evaluate long-term complications such as post-traumatic subtalar arthritis, which can develop or progress over several years, particularly in comminuted fractures. Our arthritis incidence should be interpreted as early-stage findings, and longer follow-up is needed to assess the durability of functional outcomes and true incidence of late degenerative changes. Future studies might benefit from identifying sensitive biomarkers for osteoarthritis progression [49–51]. Finally, as the primary aim of this study was to compare outcomes among different surgical strategies, fracture-type specific subgroup analysis was not performed. Moreover, the number of Sanders type IV fractures in our cohort was relatively small. Future studies with larger sample sizes will be required to evaluate the effectiveness of the MAP strategy in more comminuted fractures.

Conclusion

In this retrospective cohort study, the MAP strategy was associated with favourable short-term functional outcomes and a low rate of soft-tissue complications in patients with displaced intra-articular calcaneal fractures. However, given the observational study design and the modest magnitude of functional differences, these findings should be interpreted with caution. Further prospective studies are required to confirm the potential role of the MAP strategy in the surgical management of DIACFs.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

Yixuan Chen, Jiachen Wu and Shutao Zhang designed the study. Shutao Zhang and Jiachen Wu collected the data and drafted the statistical analysis plan. Tianyi Wu collected the data. Daoyu Zhu conducted the data analysis. Yixuan Chen and Chang Liu drafted the manuscript with the supervision of Xin Ma, Mingjie Tang and Zhongmin Shi. All other authors reviewed the manuscript and then provided feedback and comments. Before submission, all authors reviewed the manuscript and approved it.

Funding

Science and Technology Commission of Shanghai Municipality (24Y32800100). National Key Research and Development Program of China (2025YFC2423305). Shanghai Municipal Health Commission (ZHYYZXYYD-202502).

Data availability

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

Declarations

Ethics approval and consent to participate

This retrospective cohort study involving human participants was reviewed and approved by the Ethics Committee of Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Approval No. 2024.KY-301(K)). All procedures performed in this study were in accordance with the ethical standards of the institutional research committee and with the Declaration of Helsinki. Written informed consent for participation and for the use of clinical and imaging data for medical research had been obtained from all participants during routine clinical care. The requirement for obtaining additional informed consent for this retrospective study was waived by the Ethics Committee.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.