Introduction

Bone defects usually originate from high-energy injury, infection, tumor or congenital malformations. Large bone defects cannot heal by themselves, posing a challenge to orthopaedic surgeons [10]. The approach to the preparation of the spacer involves whether the spacer is difficult to remove, damage risk and integrity of the IM. The integrity of the IM affects its osteogenic activity, which is related to the effect of repairing bone defect to a certain extent. Therefore, it is necessary to know whether the outcomes of the two methods differ. However, it rarely is reported in the literature. The purpose of this study was to retrospectively compare the intraoperative and postoperative outcomes of extracorporeal vs. intracorporeal formation of a spacer using the IMT for repairing bone defects.

Materials and methods

Patients

We performed a retrospective review of all patients with a tibial fracture and defects resulting from an open fracture or infection and surgical debridement treated using IMT in our hospital from January 2009 to October 2019. The study was reviewed and approved by the Institutional Review Board of Wuxi No. 9 People’s Hospital (No. WXJY-LY-20010017), and performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. Signed informed consent was obtained from each patient. A total of 80 patients were selected for the present study. Exclusion criteria were: (i) patients who did not receive the second stage of IMT; non-PMMA cement spacer used; (ii) complications from poor stability after the second stage surgery; (iii) the follow-up time after the second stage surgical procedure was less than 12 months; (iv) patients with incomplete follow-up data or poor compliance with treatment. 12 patients (15%) were excluded by these criteria. The remaining 68 patients (85%) met the inclusion criteria and included an intracorporeal group (36 cases) and an extracorporeal group (32 cases) according to the mode of preparation of the spacer.

The average age of patients in the intracorporeal group was 42.08 years (range 13–75 years), and included 22 males and 14 females. There were 8 patients with non-infectious bone defects (comminuted fractures with bone defects), and 28 patients with infectious bone defects (defects with infection). There were 24 patients with segmental bone defects and 12 cases with partial bone defects. 23 patients had an associated injury (tendon, nerve or vascular injury or skin defect). The average length of the bone defects was 5.72 cm (range 2.0–12.0 cm). Bone defect site: 8 cases in the upper segment, 13 cases in the middle segment, and 15 cases in the lower segment of the tibia. Before the IMT, the average times of other surgeries performed was 2.39 per person (range 0–4 surgeries/person) Table 1.

Table 1 Comparison of preoperative data between the two groups
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The average age of patients in the extracorporeal group was 39.78 years (range 15–71 years), and included 19 males and 13 females. There were 9 patients with non-infectious bone defects (comminuted fractures with bone defects), and 23 patients with infectious bone defects. There were 19 patients with segmental bone defects and 13 with partial bone defects. 20 patients had an associated injury. The average length of the bone defects was 5.22 cm (range 2.0–10.0 cm). Bone defect site: 5 cases in the upper segment, 12 cases in the middle segment, and 15 cases in the lower segment of the tibia. Before the IMT, the patients underwent other surgeries with an average of 2.41 times per person (range: 0–4 times/person) Table 1.

Surgical methods

In the first stage, thorough bone and soft tissue debridement were performed, including removal of free bone or sclerotic bone without a blood supply, and the medullary cavity was opened. In cases involving infectious bone defects, internal fixations were removed and the wound was washed with hydrogen peroxide, iodophor, and large amounts of saline several times. Pulse irrigation was used until the flushing fluid became clear. For non-infective bone defects, PMMA and internal or external fixation were used, whereas PMMA loaded with the antibiotics (vancomycin or/and gentamicin) and external fixation were used for infectious bone defects.

In the intracorporeal group, the cement was implanted in a dough phase, then shaped to match the size of the bone defect and wrapped at the ends. At the same time, normal saline was used to wash and cool the heating of the cement until it solidified.

In the extracorporeal group, depending upon the size and shape of the bone defect, cylinder, single or multiple blocks or beads of cement were made during the dough phase, and then were inserted into the bone defect site after natural solidification and cooling to room temperature (Fig. 1). In some cases, the multi-column structure pacer was internally fixed with sutures or a thin layer of cement.

Fig. 1
figure 1

Different shapes of spacer prepared by extracorporeal formation (cylinder, single or multiple blocks, and beads)

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The associated skin defect was repaired with a skin flap or myocutaneous flap. For non-infectious bone defects, internal or external fixation was used during the operation, and prophylactic antibiotic therapy was prescribed for 3–5 days after the operation; for infectious bone defects, external fixation was used during the operation, and sensitive or broad-spectrum antibiotics were used intravenously for about 2 weeks following which oral antibiotics were prescribed until 6 weeks after the surgery. For patients with infectious bone defects, the second stage operation of IMT was not performed until the white blood cells, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were reduced to normal or close to the normal levels without clinical symptoms of infection.

In the second stage, the wound was opened through the original surgical approach, the IM was cut longitudinally, the spacer was removed and autologous cancellous bone was grafted into the IM. If the iliac bone graft was insufficient, it was supplemented with no more than one-third of allogeneic bone or artificial bone. Reliable and stable internal fixation including intramedullary nails or locking plates were used. Antibiotics were used for 3–5 days postoperatively.

Postoperative management

All patients were reexamined every month postoperatively, and every 3 months after bone defect healing. Patients with internal or external fixation began rehabilitation activities 3 days postoperatively and gradually moved adjacent joints. Partial weight-bearing was allowed after callus bridging was confirmed by imaging.

Evaluation

The time interval between the first and second stages, time required to remove the spacer, injury of the IM or the bone ends, bone healing, infection control and functional recovery were recorded. Injury of the IM or the bone ends was defined as an IM defect area of larger than 1 × 1cm2, or an iatrogenic fracture or defects at the end of the bone. Clinical healing was defined as the radiographic presence of bridging bone on 3 of 4 cortices without gross motion or tenderness at the site of the bone defect during a physical examination [11, 12]. In situations where a clear determination could not be made, a CT scan was obtained to confirm union. Nonunion was defined when a minimum of 9 months had elapsed since the fracture or bone defect without visible progressive signs of healing for 3 months. Delayed union was defined as slow healing over 9 months. At the final follow-up, lower limb functional recovery was evaluated using the Johner—Wruhs scoring system [13].

Statistical analysis

Statistical analyses were conducted using the statistical package SPSS version 17.0 (SPSS Inc., Chicago, IL, USA). For comparison between groups, Student’s t-tests for measurement data of in a normal distribution or Mann–Whitney U test for measurement data of non-normal distribution was used for continuous variables. For categorical variables, the chi-square test was used, whereas Fisher’s exact test was used when the expected counts were < 5. In all analyses, statistical significance was determined by a value of P < 0.05.

Result

Preoperative data results

There were no significant differences in age, gender, defect type, length and site, associated injury or times of surgeries between the two groups (P > 0.05).

Perioperative period results

After the first stage, flap necrosis occurred in 2 cases in the intracorporeal group, and 1 case in the extracorporeal group, resulting in the exposure of the spacer, which needed to be repaired with a skin flap again. There was no significant difference in the time interval between the intracorporeal and extracorporeal groups (12.64 ± 4.41vs. 13.22 ± 4.96 weeks,P = 0.611). However, the time required to removal (3.97 ± 2.34 Min) was longer, and the injury of the IM or bone ends ( 28/38) was greater in the intracorporeal group than those (0.56 ± 0.38 min and 1/32) in the extracorporeal group, showing significant difference (P < 0.001, each) Table 2 and Fig. 2.

Fig. 2
figure 2

Comparison of the therapeutic effect between the intracorporeal and extracorporeal groups. a The time interval, time requires to remove the spacer, injury of the IM or the bone ends and infection control were compared. b The healing time, delayed healing, nonunion and functional recovery were compared

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Complications and follow up

All patients were followed up for 12–48 months (average 18.7 months) after the second stage. There were no significant differences in the infection control rate (26/28 vs. 20/23, P = 0.647), nonunion (2/38 vs. 1/32, P = 0.545), delayed union (2/38 vs. 2/32, P = 0.904) and clinical healing time (7.47 ± 2.13vs. 7.50 ± 2.14 mos, P = 0.957) between the intracorporeal and extracorporeal groups. 7 cases with bone nonunion and delayed union were mainly related to higher proportion of cortical bone or artificial bone and relatively poor stability of fixation. At the last follow-up, 12 cases were excellent, 18 cases were good, and 6 cases were fair in the intracorporeal group (the excellent or good rate was 83.33%), and 12 cases were excellent, 14 cases were good, and 6 cases were fair (the excellent or good rate was 81.25%) in the extracorporeal group, showing no significant difference between the two groups (P = 0.822) Table 2. Typical cases are shown in Fig. 3 and Fig. 4.

Table 2 Comparison of outcomes between the two groups
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Fig. 3
figure 3

A 49 years-old male patient with segmental defects of the left tibia treated with IMT. a The cement spacer was prepared by extracorporeal formation. B X-rays showed the defects clinically healed in 7 months

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Fig. 4
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A 47 years-old male patient with segmental defects of the right tibia treated with IMT. a The cement spacer was prepared by intracorporeal formation. b X-rays showed the defects clinically healed in 7 months

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Discussion

Advantages and disadvantages of extracorporeal and intracorporeal formation

This study showed that there were no differences on bone defect repair and infection control. However, there were differences in the time required to removal and the incidence of injury of the IM or bone ends between the two groups.

The classical application of the IMT is intracorporeal formation of a cement spacer. Masquelet and other scholars emphasized that the spacer should wrap 1-2 cm of the ends forming an expanded "collar", in which bone grafting can avoid or significantly reduce the occurrence of bone nonunion [3, 4]; the other advantage of intracorporeal formation is that it can provide additional stability for the bone defect and even restore the stability immediately after surgery. However, there are some disadvantages to intracorporeal formation as well: (1) thermal necrosis of 1–2 mm of the interface bone tissue caused by high heat [3, 4, 10, 2]. The integrity and biological activity of the IM are related to the outcomes of bone defect repair. Defects of the IM lead to weakening of the effects of mechanical wrap** and biological osteogenesis of the IM, and might affect the bone defect repair [13]. However, in the study, the differences were not significant in terms of the healing time and healing rate between the two groups, which may be due to smaller defect size of the IM, followed by a small sample size.

It has been reported that the infection control rate of antibiotic-loaded bone cement for infectious defects is 78—100% [16,17,18,19,

Conclusions

The results show that the formation of a cement spacer by extracorporeal and intracorporeal methods in conjunction with the use of IMT has similar effects on bone defect repair and infection control. However, intracorporeal formation has advantages in terms of additional stability, while extracorporeal formation has advantages in terms of removal. Therefore, different method should be selected according to different situations. We recommended the extracorporeal or the modified extracorporeal formation in most cases.