Short-term results of total hip arthroplasty using a tapered cone stem for patients with previous femoral osteotomy

Kosei Sakamoto; Goro Motomura; Satoshi Hamai; Satoshi Ikemura; Masanori Fujii; Shinya Kawahara; Yusuke Ayabe; Yasuharu Nakashima

doi:10.1016/j.jor.2022.02.021

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30 (); 83-87

doi:

10.1016/j.jor.2022.02.021

Short-term results of total hip arthroplasty using a tapered cone stem for patients with previous femoral osteotomy

Kosei Sakamoto^a, Goro Motomura^a,, Satoshi Hamai^a, Satoshi Ikemura^a, Masanori Fujii^a, Shinya Kawahara^a, Yusuke Ayabe^a, Yasuharu Nakashima^a

a Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu Universit 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan

∗Corresponding author: Goro Motomura. goromoto@ortho.med.kyushu-u.ac.jp

Received: 2021-10-10, Accepted: 2022-2-17, Published: 2022-2-20

Professor P K Surendran Memorial Education Foundation

Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

In total hip arthroplasty (THA) for patients with previous femoral osteotomy, we hypothesized that a tapered cone stem may be an option due to the altered morphology of the proximal femur. The purpose of this study was to assess the short-term results of THA after femoral osteotomy using a tapered cone stem, and to identify issues that require further attention.

Twenty-two hips in 21 consecutive patients who underwent THA after femoral osteotomy using a Wagner Cone tapered cone stem were retrospectively reviewed, with a mean follow-up period of 34.4 (range, 24–50) months. Clinical information was obtained from medical records. On preoperative radiographs, the Dorr type was classified based on the anteroposterior cortical index. On postoperative radiographs, the degree of stem subsidence and the stem location with the highest canal fill ratio were assessed.

The mean Harris hip score significantly improved from 55.2 at baseline to 84.8 at final follow-up. Radiologically, stem subsidence (>3 mm) was observed in seven hips, and it stabilized within 1 year after THA in all cases. In five of seven hips with stem subsidence, the highest postoperative canal fill ratio was observed in the distal third of the stem. The proportions of males and Dorr type A were significantly higher among hips with stem subsidence than among those without. During the follow-up period, no hips showed implant loosening or required revision surgery.

The occurrence of stem subsidence should be noted when using Wagner Cone stems for Dorr type A femurs after femoral osteotomy.

Keywords

Wagner cone

Tapered cone stem

Total hip arthroplasty

Stem subsidence

Previous osteotomy

Dorr classification

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1 Introduction

In total hip arthroplasty (THA) for degenerative joints that have been previously treated with proximal femoral osteotomy, optimal placement of the femoral stem can be technically challenging due to the altered morphology of the proximal femur.^1–4 A recent systemic review demonstrated that the proportion of patients who experienced intraoperative complications during THA after femoral osteotomy ranged from 0% to 17%, and the most common intraoperative complication was femoral fracture.⁴ Although changes in the anatomy of the proximal femur are thought to be the main cause of complications, there is no consensus on what kind of cementless stem should be used for THA after femoral osteotomy.

A tapered cone stem achieves press-fit fixation at the metaphyseal–diaphyseal junction and proximal diaphyseal region.⁵ In addition, there is freedom in controlling version, making it advantageous in complicated cases with altered proximal femoral anatomy.⁵ Several reports demonstrated good results of the tapered cone stem in patients with a small physique or complicated morphology of the proximal femur, including excessive anteversion of the femoral neck,⁶^,⁷ although there have been few reports on the use of this stem in THA after femoral osteotomy.^8–10 Considering the altered anatomy of the proximal femur in this setting, the tapered cone stem may be a viable option.

The purpose of this study was to assess the short-term results of THA after femoral osteotomy using the tapered cone stem, and to identify issues that require further attention.

2 Material and methods

2.1

2.1 Patients

This retrospective review was approved by our institutional review board. Between December 2016 and January 2019, 24 consecutive hips in 23 patients at our institution underwent cementless THA after femoral osteotomy using the Wagner Cone (Zimmer-Biomet, Warsaw, IN, USA) tapered cone stem. Two hips in two patients were excluded due to loss to follow-up within 2 years postoperatively. We therefore retrospectively investigated a total of 22 hips in 21 patients, with a follow-up rate of 91%. The patients included five males and 16 females, with a mean age at THA of 59.6 (range, 40–77) years, a mean follow-up period after THA of 34.4 (range, 24–50) months, and a mean period from osteotomy to THA of 31.8 (range, 11–51) years. One patient received bilateral THA after femoral osteotomy during this period; the hip with longer follow-up was selected in this patient to avoid duplication of the demographic data in statistical analyses. The primary diagnosis was osteonecrosis in nine hips, developmental dysplasia of the hip in eight hips, and benign chondroblastoma within the femoral head in one hip that had been treated with femoral osteotomy after excision of the tumor. The diagnosis of the remaining three hips that had been treated during infancy was unknown. Previous femoral osteotomies consisted of transtrochanteric curved varus osteotomy in nine hips, transtrochanteric rotational osteotomy in six hips, transtrochanteric valgus osteotomy in three hips, and unspecified osteotomies performed during infancy in three hips. THA was performed through the posterolateral approach. Canal reaming was performed manually until noticeable resistance was felt, in accordance with the manufacturer's recommendations. The distal part of the trial stem was then inserted until it was firmly fixed. The stem height was checked after assembly with the proximal part of the trial stem, and if it was lower than planned preoperatively, the reaming size was increased again, and care was taken to avoid proximal fixation. The anteversion was changed by rotating only the proximal part of the trial stem, and care was taken to achieve appropriate anteversion with regard to joint stability. The capsule and short rotator muscles were repaired as much as possible. All surgeries were performed by experienced hip surgeons. Cementless acetabular cups were used in all procedures, including the G7 cup (Zimmer-Biomet) in 15 hips and the Continuum cup (Zimmer-Biomet) in six hips. The head size was 32 mm in 20 hips and 28 mm in one hip. Crosslinked polyethylene was used in all hips, consisting of an elevated liner in 11 hips and a neutral liner in 10 hips. Postoperatively, immediate full weight-bearing with crutches was allowed.

2.2

2.2 Clinical assessments

The Harris hip score (HHS)¹¹ was evaluated preoperatively and at the time of final follow-up. In addition, operation time, intraoperative blood loss, and intraoperative and postoperative complications during the follow-up period were determined from medical records.

2.3

2.3 Radiological assessments

Plain radiographs of the hip were taken using the same technique throughout the study period, with standardized beam positions and radiographic penetration. On preoperative radiographs, the Dorr type (medullary cavity shape) was classified based on the CI (cortical index) using anteroposterior X-ray (AP-CI), which was calculated as the ratio of cortical bone thickness at the point 10 cm distal to the apex to that at the level of the lesser trochanter.¹² The cutoff points of AP-CI between Dorr types A and B and between Dorr types B and C were 0.58 and 0.49, respectively.¹² Seven hips were classified as Dorr type A, seven as type B, and eight as type C. On postoperative radiographs, the degree of stem subsidence and the stem location with the highest canal fill ratio were assessed (Fig. 1).¹³ Subsidence of the femoral stem was defined when the femoral stem progressively sank >3 mm between 1 month after THA and the latest follow-up.¹⁴ The canal fill ratio, defined as the width of the stem divided by the width of the canal,¹³ was measured at three stem levels, including the proximal, middle, and distal thirds, using anteroposterior radiographs taken just after surgery (Fig. 1B). In 19 hips that underwent postoperative computed tomography, stem anteversion was measured with respect to the posterior condylar line of the femur in the axial plane.¹⁵ The determination of each radiological parameter was based on the consensus between two observers (K.S. and G.M.) (see Fig. 2).

(A) The base of the perpendicular line drawn from the top of the greater trochanter on a straight line along the stem is defined as point A, and the most proximal part of the stem is defined as point B. The distance from point A to B was used to assess stem subsidence. (B) The stem was divided into three parts: proximal, medial, and distal thirds. The canal fill ratio of the stem was defined as the width of the stem (Ws) divided by the width of the canal (Wc).

A representative case of stem subsidence. The patient was a 53-year-old male who had undergone transtrochanteric curved varus osteotomy for osteonecrosis of the femoral head. (A) The Dorr type was classified as A based on a preoperative radiograph. (B) A radiograph taken just after surgery. The highest canal fill ratio is observed in the distal third of the stem. (C) A postoperative radiograph taken 6 months after surgery. The total degree of stem subsidence is 8.64 mm.

2.4

2.4 Statistical analysis

Data were organized using descriptive statistics. Baseline characteristics, operative outcome, and radiographic parameters are expressed as mean and standard deviation, and were compared using the Wilcoxon test between groups with or without stem subsidence. Gender, Dorr type (A or non-A), and location with the highest canal ratio (middle third area or other) were compared between two groups using the Fisher exact test. Preoperative and postoperative HHSs were compared using the paired t-test. All statistical analyses were performed using the JMP software program (version 15.0, SAS Institute, Cary, NC, USA), and differences were considered significant when the P value was <0.05.

3 Results

The mean HHS significantly improved from 55.2 to 84.8 at the final follow-up (P < 0.01). The mean operation time was 131 (range, 72–216) minutes and the mean intraoperative blood loss was 197 (maximum 594) mL. The mean stem anteversion was 31.7 (range, 6–50) degrees. Prophylactic cerclage wiring was performed in 12 hips. No intraoperative fracture occurred, while incomplete periprosthetic fracture (Vancouver type B1) was found in one hip 6 days after surgery on routine postoperative imaging, and it was conservatively treated. One hip developed a superficial infection that was treated by wound irrigation. No dislocation occurred throughout the observation period, and no hips showed implant loosening or required revision surgery. Except for one case of incomplete fracture, none of the patients were subjected to strict load restriction.

Radiologically, stem subsidence (>3 mm) was observed in seven hips (31.8%): three after transtrochanteric rotational osteotomy, two after transtrochanteric curved varus osteotomy, one after transtrochanteric valgus osteotomy, and one after osteotomy during infancy. The mean subsidence was 5.7 (range, 3.2–8.6) mm, and in all cases it stabilized within 1 year after THA. The mean subsidence by prior osteotomy was 3.3 (range, 0.6–6.9) mm after transtrochanteric rotational osteotomy, 2.4 (range, 0–8.6) mm after transtrochanteric curved varus osteotomy, and 2.7 (range, 0.4–5.6) mm after transtrochanteric valgus osteotomy. The proportions of males and Dorr type A were significantly higher among hips with stem subsidence than among those without (P = 0.001 and P = 0.005, respectively) (Table 1). On radiographs taken just after surgery, the highest canal fill ratio was observed in the distal third of the stem in five of seven hips with stem subsidence, while it was seen in the middle third of the stem in 13 of 14 hips without stem subsidence (P = 0.005) (Table 1).

Table 1 The results of clinical and radiological assessments.

	Subsidence (＋)Group: 7 Hips	Subsidence (−)Group: 14 Hips	P Value
Gender (n)
Male/Female	5/2	0/14	0.001^a
Age at THA (y)	60.9 ± 7.4	58.5 ± 11.1	0.70
Follow-up duration (months)	34.4 ± 7.5	34.4 ± 9.2	1
Period from osteotomy to THA (y)	23.6 ± 11.9	34.9 ± 11.1	0.093
HHS
Preoperative	49 ± 12.8	58.3 ± 20.4	0.31
Final follow-up	84.1 ± 9.4	85.1 ± 11.6	0.83
Operation time (min)	130 ± 31.5	129 ± 39.8	0.82
Intraoperative Blood loss (ml)	307.9 ± 173.6	150.57 ± 124.7	0.057
Prophylactic cerclage wiring (n)
+/−	2/5	10/4	0.081
Dorr Type (n)
A/non-A	5/2	1/13	0.005^a
Location with the highest canal fill ratio (n)
Middle/proximal and distal	2/5	13/1	0.005^a

a Statistical significance was established at P < 0.05.

4 Discussion

Several past studies discussed the use of different stem designs, either cementless or cemented, for THA after femoral osteotomy. However, there is no consensus on what kind of stem should be used in this setting. This study is the first to report the short-term results of THA after femoral osteotomy using the Wagner Cone tapered cone stem. In the current case series, there were no intraoperative complications and all postoperative complications were comparatively minor, resulting in clinically good outcomes. On the other hand, stem subsidence of greater than 3 mm was confirmed in more than 30% of the cases, although it eventually stabilized, suggesting that the ideal initial fixation at the middle third of the stem was not achieved in these cases.

Previous studies showed that the frequency of stem subsidence after THA using the Wagner Cone stem ranged from 0% to 12.3%.¹⁶^,¹⁷ One possible reason for the relatively high rate of cases with stem subsidence in the current series may be the use of the Wagner Cone stem for Dorr type A femurs. The tapered cone–type stem is supposed to be fixed at its middle third.¹ When used in femurs with narrow medullary cavities, such as those of Dorr type A, it tends to be fixed at the distal portion, causing jamming of the proximal portion and instability, thereby resulting in stem subsidence. Although there was no difference in clinical outcome between cases with and without stem subsidence in the current series, we consider that care should be taken when using Wagner Cone stems for Dorr type A femurs after femoral osteotomy.

In this study, male gender was also shown to be associated with stem subsidence, a relationship that has not previously been established, including in reports on the Wagner Cone stem. Considering that four of five male femurs in the current series were classified as Dorr type A, we speculate that male gender may have been associated with stem subsidence due to its relationship with Dorr type A.

It has been reported that the most common intraoperative complication during THA after femoral osteotomy is femoral fracture.⁴ However, no intraoperative fractures occurred in the current series, in which 12 hips underwent prophylactic cerclage wiring during surgery. Although this study cannot prove the efficacy of prophylactic cerclage wiring, we believe that the results support its use in conjunction with THA after femoral osteotomy.

No studies have directly compared cemented and cementless stems in post-osteotomy cases. Since 2000, 10 studies on THA after femoral osteotomy have been reported (Table 2). Of these, two used cemented stems and the remainder used cementless stems. Although these results are not exactly comparable due to the differences in osteotomy types and observation periods, the results associated with the cemented stems were not always superior.

Table 2 Past studies on THA after femoral osteotomy.

StudyFirst author	Hips (n)	Stem (n)Cemented/cementless	Transtrochanteric osteotomy (n)Varus/valgus/rotational/n.a.^a	Follow-up duration years (range)	Stem loosening (％)	Femoral fracture (％)	Dislocation (％)	Infection (％)
Kawasaki¹⁸ (2005)	15	0/15	0/0/15/0	5.0 (3.4–8.7)	0	0	13	0
Haverkamp¹⁹ (2006)	121	121/0	0/0/0/121	11.9 (2.4–19.6)	15	5.0	0	3
Suzuki²⁰ (2007)	30	0/30	0/30/0/0	6.8 (5–20.5)	0	3.3	0	0
Lee²¹ (2009)	14	0/14	0/0/14/0	4.8 (2–9.6)	0	0	7.1	0
Rijnen²² (2009)	16	16/0	0/0/16/0	6.4 (2.2–12.7)	25	0	12.5	12.5
Merle²³ (2012)	48	0/48	0/0/0/48	16 (10–20)	6.3	4.2	2.1	2.1
Park²⁴ (2014)	18	0/18	0/0/18/0	4.5 (2.3–9.3)	0	0	0	0
Ohishi² (2016)	66	0/66	24/42/0/0	7.3 (1–14)	4.5	6.1	0	0
Utsunomiya³ (2017)	24	0/24	0/0/24/0	9.5 (5–16.3)	0	0	8.3	4.2
Osawa²⁵ (2017)	20	1/19	0/20/0/0	6.8 (1–22)	5	n.r.^b	5	5

a n.a.: not applicable.

b n.r.: not reported.

This retrospective study has several limitations. First, the sample size was small due to the relatively small number of THA cases after femoral osteotomy. We therefore could not perform a multivariate analysis. Further case series are needed to generalize the findings of this study, but considering the limited number of cases of THA after femoral osteotomy, we believe that this information will provide insight into the optimal use of the Wagner Cone in THA after femoral osteotomy. Second, we could not determine the long-term effect of stem subsidence. Further follow-up is needed to determine if subsidence is clinically problematic. Third, because the same surgeon did not perform every operation, the use of prophylactic cerclage wiring was not standardized. A future prospective study is needed to clarify the efficacy of this technique.

5 Conclusion

The occurrence of stem subsidence should be noted when using Wagner Cone stems for Dorr type A femurs after femoral osteotomy.

Funding source

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethics approval

This study was approved by our institutional review board, and informed consent was waived due to the retrospective and anonymous study design.

Authors contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by K.S. and G.M. The first draft of the manuscript was written by K.S. and G.M. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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