Comparison between Total Hip Arthroplasty for Avascular Osteonecrosis of Femoral Head and That for Fixation Failure of Femoral Neck Fracture

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Abstract

INTRODUCTION

Femoral neck fractures are a common injury in orthopedic surgery, and the worldwide increases in life expectancy and combined osteoporosis have led to increasing incidence of femoral neck fracture. In these injuries, old age and concomitant chronic disease result in significant morbidity and mortality [1–3]. Femoral neck fracture occurs in younger patients as a result of high-energy trauma, but it occurs in elderly patients as a result of low-energy trauma. The common treatment of choice for younger patients or non-displaced fracture is osteosynthesis with internal fixation, but that for elderly patients or displaced fracture is arthroplasty [4–6].

Osteosynthesis with internal fixation for femur neck fracture has many advantages, including short operation time, preservation of hip joint, low cost, and low cardiopulmonary complication. However, it can also result in complications including non-union, avascular necrosis (AVN) of femoral head, post-traumatic OA, and malunion. If complications occur, it may be necessary to convert to arthroplasty [7–9]. However, we do not know exactly what makes secondary arthroplasty different compared to primary arthroplasty, and what complications can occur in secondary arthroplasty after fixation failure of femoral neck fracture. As we know, there have also been few reports on this subject published in Korea specifically.

Therefore, we evaluate and compare clinical and radiologic results between primary total hip arthroplasty in patients with AVN of femoral head and secondary total hip arthroplasty with fixation failure of femoral neck fracture. We assumed that secondary total hip arthroplasty after fixation failure of femoral neck fracture would involve more complications than primary total hip arthroplasty.

MATERIALS AND METHODS

From March 2014 to February 2023, we retrospectively evaluated a total of 53 patients that underwent either primary total hip replacement arthroplasty (THRA) with AVN of femoral head (33 cases) or secondary THRA with fixation failure of femoral neck fracture (20 cases), and the minimum follow-up duration was 2 years. There were 16 women and 37 men. The mean ages of participants who underwent primary THRA with AVN and secondary THRA with fixation failure of femoral neck fracture were 56 years old (range, 39–64 years old) and 52 years old (range, 26–59 years old), respectively. The mean follow-up durations of primary THRA with AVN and secondary THRA with fixation failure of femoral neck fracture were 52 months (range, 24–70 months) and 49 months (range, 24–65 months); they were not significantly different (P=0.531 and P=0.426, respectively). All operations were conducted by one senior surgeon, and the Bencox femoral stem (Corentec, Seoul, Korea) was used in the operations. Table 1 summarizes the demographics. This study was conducted with approval from the Institutional Review Board (IRB) of Soonchunhyang University Bucheon Hospital (IRB no., 2020-10-015) informed consent was obtained from all individual participants included in the study.

Table 1

Demographics

1. Clinical and radiologic evaluation

Clinical and radiologic evaluations were performed at 4 weeks, 12 weeks, 6 months, and 1 year postoperatively, and then annually thereafter. Clinical analyses were evaluated using Harris hip score [10], Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [11], and University of California, Los Angeles (UCLA) [12] score. Radiologic evaluations were performed using standardized anteroposterior and lateral radiographs of the affected hips taken at each follow-up visit for stem alignment, stem stability, the appearance of heterotrophic ossification, stress shielding, and any signs of osteolysis or loosening. Stem alignment was classified as valgus, neutral, or varus as per Aldinger et al. [13]. Varus or valgus malalignment of the stem was defined as deviation from the longitudinal femoral axis of >5° [14] (Fig. 1). Stem stability was classified into three types among stable, fibrous stable, or unstable according to the method described by Engh et al. [15]. The appearance of ectopic ossification was graded according to the criteria of Brooker et al. [16]. Osteolysis was defined as focal bone resorption evidenced by a cystic lesion [17]. Cup loosening was defined as the presence of a radiolucent line around the entire circumference, a change in inclination angle of at least 5°, or migration of at least 2 mm [18]. Stem loosening was defined as the appearance of a complete radiolucent line around the femoral stem, progressive axial subsidence of >3 mm, or a varus-valgus shift [19,20]. Stem subsidence was determined by the difference in preoperative and postoperative distances between the top of the greater trochanter and the lower edge of the stem [14].

Fig. 1

Stem alignment was classified as valgus, neutral, or varus. Varus or valgus malalignment of the stem (black line) was defined as deviation from the longitudinal femoral axis (dotted black line) of >5°.

RESULTS

In primary THRA for AVN group, the mean Harris hip score improved from 47.8 points (range, 28–76 points) to 92.1 points (range, 87–95 points) at the final follow-up. The mean WOMAC score and UCLA activity score at final follow-up were 17 points (range, 15–18 points) and 6.4 points (range, 4–7 points), respectively. In secondary total hip arthroplasty for fixation failure of femoral neck fracture group the mean Harris hip score improved from 41.8 points (range, 10–69 points) to 91.3 points (range, 85– 94 points) at the final follow-up. The mean WOMAC score and UCLA activity score at final follow-up were 18 points (range, 16–19 points) and 5.8 points (range, 4–7 points), respectively. It showed no difference between both groups.

In hemodynamic analysis, primary total hip arthroplasty for AVN group showed mean 881 mL (range, 400–1,950 mL) blood loss and 2.1 g/dL preoperative–postoperative (preop–postop) hemoglobin (Hb) difference (range, 1.5–4.0 g/dL). Secondary total hip arthroplasty group showed mean 1,072 mL (range, 480–2,350 mL) blood loss and 3.2 g/dL preop–postop Hb difference (range, 2.0–5.5 g/dL). There was significant difference between two groups (P=0.017 and P=0.034, respectively). But transfusion amount was 430 mL (range, 0–600 mL) in primary THRA for AVN group and 440 mL (range, 0–600 mL) in secondary THRA for fixation failure of femoral neck fracture group. It was no different between two groups (P=0.631). The mean operation time was 70 minutes (range, 55–90 minutes) in primary THRA for AVN group and 91 minutes (range, 75–120 minutes) in secondary THRA for fixation failure of femoral neck fracture group. Primary THRA for AVN group had shorter operation time than secondary THRA for fixation failure of femoral neck fracture group significantly (P=0.035) (Table 2).

Table 2

Comparison of clinical and hemodynamic results

In radiologic evaluation postoperatively, stem alignment in AVN of femoral head group was varus 1.50° (range, 0–7.0°) in AVN of femoral head group and varus 3.50° (range, 0–8.0°) in fixation failure of femoral neck fracture group. The case of varus femoral stem position was one case in AVN of femoral head group and six cases in fixation failure of femoral neck fracture group. It was significant different statistically (P=0.010 and P=0.020, respectively). At final follow-up, all cases in both groups showed stable stem stabilities and no stress shielding, osteolysis, and ectopic ossification. There was no loosening and revision cases (Table 3).

Table 3

Comparison of radiologic results

DISCUSSION

The principal findings of this study are that total hip arthroplasty in patients with fixation failure of femoral neck fracture showed a longer operation time, an increased amount of bleeding, and more varus position in stem alignment than that in patients with AVN of femoral head.

The treatment of femoral neck fracture can classify anatomical reduction and internal fixation and arthroplasty broadly. The common treatment of choice for younger patients or non-displaced fracture is osteosynthesis with internal fixation. Osteosynthesis with internal fixation for femur neck fracture has many advantages, including a short operation time, preservation of hip joint, low cost, and low cardiopulmonary complication. However, it can also result in complications, including non-union, AVN of femoral head, post-traumatic OA, and malunion. Studies have shown that up to 30% of internally fixed fractures will fail, thus requiring salvage THRA. Therefore, the outcome of salvage THRA must be considered in the decision-making process [21]. In our study, the failure of osteosynthesis with femoral neck fracture refers to any complications, including non-union, AVN of femoral head, post-traumatic OA, and malunion, which can be developed after osteosynthesis of femoral neck fracture.

Winemaker et al. [22] compared the short-term outcomes of total hip arthroplasty after complications of open reduction internal fixation for hip fractures and those of unilateral THRA for osteoarthritis. The Harris hip scores at 1 year were 79.3 points in THRA after complications of open reduction internal fixation for hip fractures and 80.9 points in THRA for osteoarthritis. They showed that the functional outcomes of the two procedures were equivalent to each other [22]. Our study showed there was no different between both groups in the clinical evaluation. In primary total hip arthroplasty for the AVN group, the mean Harris hip score, WOMAC, and UCLA at final follow-up were 92.1 points, 17 points, and 6.4 points. In secondary total hip arthroplasty for fixation failure of femoral neck fracture group, the mean Harris hip score, WOMAC, and UCLA at final follow-up were 91.3 points, 18 points, and 5.8 points. These results did not show significant differences between the two groups.

Kim et al. [23] reported the result of secondary total hip arthroplasty after primary internal fixation failure in femoral neck fracture patients and compared the results with that of primary total hip arthroplasty for femoral neck fracture. The group that received secondary total hip arthroplasty had a longer operation time, an increased amount of bleeding, and a longer period to start gait. However, there were no differences in clinical and radiologic results at final follow-up. We compared secondary total hip arthroplasty for fixation failure of femoral neck fracture to primary total hip arthroplasty for AVN of femoral head. Our study has similar results to this study in terms of the finding of a longer operation time and more bleeding. The group of AVN has 874 mL blood loss, 2.0 g/dL preop–postop Hb difference, and an operation time of 73 minutes. Meanwhile, the group of internal fixation failure group has 1,089 mL blood loss and 3.0 g/dL preop–postop Hb difference, and an operation time of 96 minutes. These were statistically significant differences. Because the need for an additional procedure, including removal of internal fixation and anatomical deformity due to malunion, made the surgery difficult, this could have increased both the operation time and amount of bleeding.

Mahmoud et al. [24] performed a systemic review and meta-analysis to compare the outcomes of salvage THRA and primary THA for intracapsular fractures of the femoral neck. That review included 11 studies published between 2004 and 2013. In total, 558 patients were included in the eligible studies. It revealed a significantly higher risk of complications, including deep infection, early dislocation, and periprosthetic fracture in salvage THRA following failed internal fixation of intracapsular fractures of the femoral neck compared to primary THRA for the femoral neck fracture [24]. In our study, there were no complications including deep infection, early dislocation, or periprosthetic fracture. We believe that this difference can be attributed to the fact that we include a small number of cases and a short follow-up period compared to that study.

The patient with varus stem alignment represented one case in the group of primary total hip arthroplasty for AVN. However, the group with secondary total hip arthroplasty for fixation failure of femoral neck fracture comprised four cases (P=0.028). The stem angles in the groups of primary total hip arthroplasty for AVN and secondary total hip arthroplasty for fixation of femur neck fracture were varus 1.7° and varus 3.3°, respectively (P=0.011). This was a statistically significant difference. We believe the reason for this is anatomical variation due to malunion of femoral neck fracture. Malunion of femoral neck fracture typically affects the anatomy of proximal femur to varus and anterior angulation. The second lesion is that sclerotic bone formation around inferior screw interrupts the femoral stem proceeding with the insertion through the femoral canal in a straight manner (Fig. 2). In some cases, sclerotic bone was removed during the operation (Fig. 3).

Fig. 2

Sclerotic bone formation around inferior screw (black arrow) interrupting the femoral stem proceeding through the femoral canal straightly. In some cases, sclerotic bone had to be removed during the operation.

Fig. 3

Removal of sclerotic bone during operation.

There are several limitations to this study that must be noted. First, our study has a small sample size. There were 53 cases in total in our study. Second, the follow-up period was relatively short. We can therefore show more long-term clinical results. Third, this study is a non-randomized retrospective study. It can therefore show selection bias. Fourth, as a radiographic analysis, simple X-ray is used, and CT is not involved; therefore, it cannot show a more exact result. Fifth, the comparison between primary THRA and secondary THRA can be shown to be unequal. Secondary THRA in our study does not refer to revision THRA after primary THRA. It instead refers to primary THRA after the failure of osteosynthesis with femoral neck fracture. Our result can be interpreted to mean that primary THRA with previous operation can have more complications than primary total hip arthroplasty without previous operation, and that it requires more careful preparation than primary THRA without previous operation. Sixth, the additional procedure of screw removal can affect the difference in operation time between the two groups. However, even considering the additional procedure, there is a large difference in operation time between the two groups. As mentioned in the discussion, bleeding and anatomical deformity due to malunion as well as the additional procedure could make the operation difficult. This led to the significant difference in operation time between the two groups.

In conclusion, secondary total hip arthroplasty in patients with fixation failure of femoral neck fracture showed a longer operation time, an increased amount of bleeding, and more varus position in stem alignment than primary total hip arthroplasty in patients with AVN of femoral head. When secondary total hip arthroplasty was conducted in patients with fixation failure of femoral neck fracture, it was necessary to pay more attention to reduce bleeding and infection. If the predicted femoral stem was not inserted due to varus position, removal of the sclerotic bone around the inferior screw was sometimes necessary.

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