Lateral wall osteotomy combined with embedded biodegradable implants for displaced intra-articular calcaneal fractures

Calcaneal fractures are among the most common tarsal fractures, approximately 75% of which are displaced intra-articular calcaneal fractures (DIACFs) [1]. The extensile lateral approach (ELA) has been widely used to treat DIACFs and remains the gold standard procedure for calcaneal fracture surgery owing to its excellent visualization of the subtalar joint, sinus tarsi, and calcaneocuboid joint, and its easy implant placement [2]. Orthopedic surgeons are extremely concerned of the high rate of wound complications, including superficial, deep infection, skin flap necrosis, and wound dehiscence, which have been reported to be as high as 24% [3].

The impaired microvascularization of the posterior lateral skin flap that resulted from the initial or iatrogenic injury was considered the cause of numerous wound-healing complications, because the lateral calcaneal artery (LCA), derived from the posterior peroneal artery, is responsible for blood supply to the posterior lateral area of the foot. To avoid these vexing complications, the microvascularization of the posterior lateral skin flap should be protected. The minimal invasion approach or percutaneous reduction could avoid damaging LCA. However, achieving the ideal reduction and stable fixation of calcaneal fractured fragments is difficult in these procedures, thereby leading to poor clinical outcomes [4, 5]. Moreover, some modifications of ELA were proposed, such as making a curved corner of the incision to decrease the wound complications rates, and several new wound closure techniques were also devised, but failed to avoid injury of LCA [6]. Meanwhile, different metallic implants were designed for minimally invasive approaches or other newly developed approaches. However, secondary surgical procedures for metallic implant removal were also a wound-healing risk. Fixation strength of biodegradable implants was described previously, and its safety and effects at different terms were also confirmed [7‐9].

To reduce wound complications after ELA, we devised a new technique of lateral wall osteotomy combined with embedded biodegradable plate and screws for treating DIACFs. This study aimed to present this new surgical technique and report our preliminary results.

All radiological parameters were significantly improved at the last follow-up, with an increase of 15.58°, 8.38°, and 7.65 mm in Böhler’s angle, Gissane’s angle, and calcaneal height, respectively, and a decrease of 2.51 mm in calcaneal width (p < 0.05) (Table 1).

The mean AOFAS score at the last follow-up was 84.37 ± 9.98 (range, 65–95), with 9, 6, and 4 feet having excellent, good, and fair rates, respectively (Table 2). The excellent and good rates account for 78.95% of all cases. The 4 feet with fair AOFAS score were those of patients with Sander’s type IV fracture. No nonunion, delayed union, or malunion was observed after a mean follow-up period of 34.69 ± 5.22 (range, 28–48) months. All returned to pre-injury work, and none required secondary surgery for implant removal.

Our findings revealed that our novel technique had a low rate of wound-healing complications. To avoid damage to the LCA, a vertical incision was done at the posterior one-third distance between the posterior border of the lateral malleolus and the lateral border of the Achilles tendon. Moreover, the full-thickness lateral flap, containing the lateral wall of calcaneus instead of peeling the lateral skin flap from the lateral wall, circumvented the disturbance of the sural nerve and the angiosome to the lateral skin flap. The LCA with a 6-mm diameter consists of an intricate vessel net surrounding the lateral hind foot and lateral malleolus and provides approximately 14% of blood supply to the skin flap in this area [11]. Several branches of the LCA penetrate the lateral wall of the calcaneus, accounting for approximately 45% of its blood supply [12]. Hence, the disturbance of the LCA caused by either initial or iatrogenic injury will diminish a large portion of blood supply to the lateral skin flap and calcaneus, increasing the likelihood of wound-healing complications and nonunion of the fractured calcaneus. As commonly described, the vertical limb of the incision was situated midway between the posterior edge lateral malleolus and lateral edge of the Achilles tendon, which would inevitably damage the LCA because the vertical incision was located around the course of the lateral calcaneal artery, and the tourniquet was used during the whole procedure [13, 14].

To avoid iatrogenic injury to the LCA, Elsaidy et al. introduced a dangerous triangle, which contained the superficial course of the LCA as the posterior border, and highlighted that the classically described vertical incision would cross this dangerous triangle and disturb the LCA [15]. Kwon et al. also found that a more posterior vertical incision decreased in fourfolds the risk of damaging the LCA compared to the classical ELA [16]. Theoretically, the osteotomy of the calcaneal lateral wall, instead of detaching the lateral soft tissue envelope from the lateral wall of calcaneus, allows tension-free retraction during the operation with the support of lateral wall to avoid injury to the penetrating branches of the lateral calcaneal artery, eliminate edema between the lateral wall of calcaneus and lateral skin flap, and remove the dead space between the lateral skin flap and implants.

In our previous study, the metallic plate and screws were applied to obtain rigid fixation of the fractured calcaneus [17]. Inherent demerits of embedding the metal implants in the osteotomy surface are as follows: removing implants is difficult with this procedure and there would be a residual dead space between the lateral wall and the implants. In an attempt to address these problems, we used biodegradable implants to fix calcaneal fractures. To the best of our knowledge, this is the first report on treating DIACFs with biodegradable implants. Biodegradable implants have been used for years in the treatment of less stressful fractures, such as ankle, mandibular, and pediatric clavicular fractures, with excellent results [18‐20]. The less fixation strength of the biodegradable implant utilized for the fractures of the calcaneus may lead to stability problems of fracture fixation. Thus, weight-bearing activities were not allowed until there was bony union on radiographs. However, in our study, screw breakage occurred in one patient because of early weight-bearing exercises. Biodegradable implants maintain its stiffness for about 18 weeks, which is long enough for fracture union [7]. After 18 weeks, the stress shifts to the calcaneus gradually as the implant degrades slowly, resulting in less stress-shielding as compared to metallic implants and enabling dense bone formation [21]. The clinical result showed that the excellent and good rates of AOFAS score account for 78.95% of all cases (mean score, 84.37 ± 9.98; range, 65–95). In the present series, four Sander’s type IV fractures were included, which may be associated with poor clinical results. No more screw breakage was observed in this case series at the final follow-up. Therefore, we believed that the fixation of biodegradable implants was strong enough, as we were able to prolong the period of weight-bearing-free joint exercises (Fig. 3). According to the findings of this study, the indications of this approach were Sander’s type II and III closed calcaneal fractures. However, this approach is contraindicated in patients with Sander’s type IV fractures, open fractures, severe osteoporosis, diabetes mellitus, and serious injuries.

One superficial infection was observed (5.26%), which was lower than that previously reported [22]. This infected foot in the present study was classified as Sander’s IV type and had no preoperative Doppler examination [23]. Thus, we could not determine whether the superficial infection was caused by preoperative injury to the LCA or iatrogenic damage or was a highly comminuted fracture itself. No calcaneal fracture nonunion or malunion was found in the present study.

The advantages of our developed technique include primary wound-healing tendency, complete visualization of fractured fragments, posterolateral subtalar joint facet and calcaneocuboid joint facet, no requirement for secondary operation for implant removal, and less stress-shielding of the calcaneus, which is beneficial for bony union. Its main disadvantage is that it has less fixation strength of biodegradable implants leading to delayed weight-bearing rehabilitation, which may result in poor clinical outcomes.

Major limitations of the present study include its relatively small patient sample size, and inclusion of two patients with bilateral fractures that made the comparison of both sides impossible, and patients with Sander’s type IV and bilateral calcaneal fractures that may be caused by severe trauma, which may result in poor radiological and clinical outcomes. Furthermore, given that a comparison group treated using classical ELA with metallic implants was absent, we cannot confirm if this new approach is superior to classical ELA for all types of fractures. Moreover, as the fixation strength of biodegradable implants is weaker than metallic implants, according to findings of present study and our experience, our new surgical technique is not fit for Sander’s type IV fractures. A proper prospective randomized controlled clinical study with long-term follow-up and a large sample size is needed to determine the safety and reliability of this surgical technique.

Osteotomy of the lateral wall of calcaneus allows tension-free suturing and avoids damage to penetrating branches of the LCA. Biodegradable implants are easy to reshape and do not require surgical removal. However, they should be limited to Sander’s type II and III fractures only.