Modular stem in total hip arthroplasty for patients with trochanter valgus deformity: surgical technique and case series

doi:10.21203/rs.2.15961/v3

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Modular stem in total hip arthroplasty for patients with trochanter valgus deformity: surgical technique and case series

https://doi.org/10.21203/rs.2.15961/v3

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published 24 Feb, 2020

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Background: Trochanter valgus deformity (TVD) is a rare condition of total hip arthroplasty (THA). The femoral osteotomy might be required to correct the deformity to implant the femoral stem in severe TVD. In this study, we described one unpublished technique of reverse sleeve of S-ROM to get through the complex situation. This study aimed to summarize and evaluate its technical challenges, safety and effectiveness.

Methods : From January 2006 to December 2014, the patients whose sleeves were implanted towards the great trochanter rather than sitting on the calcar, to solve the TVD in THA were enrolled. Their demographics, perioperative and postoperative information were recorded. To explore its indication, we measured and analyzed the ratio of greater trochanter/lesser trochanter (G/L ratio) and trochanter valgus angle (TVA).

Results : Twelve patients (1 male and 11 female, average age 42.30±10.23) who had the complete clinical data were analyzed. The survivorship of femoral prosthesis were 100% with mean follow-up of 6 years. No other complications were found, except for two patients with intraoperative fracture of femur. The Harris hip score (HHS) increased from preoperative 34.31±14.43 to postoperative 84.12±11.33. All patients’ G/L ratio were larger than 1.50.

Conclusions: The reverse sleeve of S-ROM was a reliable method for the patients with severe trochanter valgus deformity, which brought satisfying clinical outcomes in mid-term follow-up.

Orthopedic Surgery

cementless modular stem

reverse sleeve

total hip arthroplasty

trochanter valgus deformity

Trochanter valgus deformity (TVD) is an uncommon type of proximal femoral deformity [1,2]. Before ceramics and highly cross-linked polyethylene being used in orthopedic surgery, total hip arthroplasty (THA) in young patients had a high rate of failure [3]. To delay THA, trochanter valgus osteotomy (TVO) used to be one useful treatment for developmental dysplasia of the hip (DDH) and osteonecrosis of the femoral head (ONFH) [4]. However, when these patients had severe hip arthritis, they have no choice but to receive THA. The significant angled femoral cavity would complicate the femoral preparation and stem implantation [5,6]. THA with concurrent femoral osteotomy is a demanding procedure technically. Lewallen et al reported 32% patients underwent reoperation at 4.6 years after THA and femoral osteotomy [5]. TVO was the leading cause of trochanter valgus deformity, followed by malunion of fracture and congenital factors.

Few studies on THA in patients who had trochanter valgus deformity have been published [1,2]. Iwase et al reported that the failure rate of cementless stem was 22.5% at 4 years after conversion THA and concluded that cemented stems were preferable for THA in patients with previous femoral valgus osteotomy [1]. However, another Japanese surgeon in 2017 reported 100% survivorship of the femoral component and suggested that modular femoral components should be used when undertaking total hip replacement in patients with previous femoral valgus osteotomy [2].

Appropriate choice of femoral prosthesis could simplify surgical procedures and improve clinical results. The S-ROM femoral component (DePuy Orthopaedics, Warsaw, Indiana) is a cementless, modular and cylindrical prosthesis, which was specially designed for proximal femoral deformity [7]. Modularity at the stem-sleeve junction allows the surgeon to decide the anteversion of the femoral stem independent of sleeve, which could best fit and fill the proximal femur.

In this case-series study, we described one special implanting position of sleeve of S-ROM in THA for patients with TVD. The sleeve towards the great trochanter rather than sitting on the calcar, could take advantage of, rather than correct the deformity, which could improve the efficiency and reduce trauma greatly. Although this technique has been discussed in some meetings before, no previous studies ever specially described it. This study aimed to summarize and evaluate its technical challenges, safety and effectiveness.

The study was approved by the institutional review board. From January 2006 to December 2014, fifteen patients who had the sleeve towards the greater trochanter in THA were reviewed in our joint registry system. Three patients who hadn’t have regular follow-up (> 1 years) and complete information were excluded.

The remaining twelve patients had severe hip arthritis and TVD. The S-ROM consists of the sleeve and stem. The sleeve is porouscoated or hydroxyapatite (HA)-coated, and is designed to convert shear and hoop stresses to compressive forces at the sleeve-bone interface. The titanium alloy stem is polished distally; it also has several options of neck length and offset proximally [7]. The sleeve achieves bone ingrowth in the metaphysis and the stem can be freely rotated to accommodate any deformity or asymmetry in the proximal femur [8].

The angle between sleeve’s spout and stem is 30 degree, which is designed to adapt the medial cortex of proximal femur, so the sleeve’s triangle was placed to the lesser trochanter commonly. In this study, we placed the sleeve towards the opposite direction, which means its triangle points to the greater trochanter.

Surgical technique

In clinical practise, we usually used film (before 2014) or the Orthoview software (Version 6.6.1, Materialise, Leuven, Belgium) for preoperative template. According to the plan, we considered to implant the sleeve outward when the modular stem could not be inserted by the ordinary technique without corrective osteotomy simultaneously. All surgeries were performed by two senior surgeons through posterolateral approach.

After dislocating femoral head, femoral neck osteotomy was performed along with the intertrochanteric crest (Figure 1.A).
The accurate entry can obtain the proper stem alignment and decrease the incidence of periprosthetic fracture. According to the preoperative template, the site of entry was recognized (Figure 1.B). Then the smallest reamer was used to find the medullary cavity with or without the aid of intraoperative fluoroscopy (Figure 1.C). Then the distal reamer size was increased sequentially until it touched the cortical bone. The depth of reaming was appropriate when its mark aligned with the tip of greater trochanter. More attention should be paid to the orientation of reamer to avoid the protrusion.
According to the size of distal reamer, the proximal reamer was used to prepare the proximal femur (Figure 1.D). When the medial cortex of femur is unable to support the sleeve, we placed the sleeve towards the greater trochanter. Because there was no specific tools, the surgeon used the reamer to prepare the calcar and handled the spout manually (Figure 1.E). The medial cortical bone should be resurfaced to prevent impingement (Figure 1.F). In order to avoid subsidence of sleeve and stem, we adopted the larger sleeve as far as possible (Figure 1.GH).
The stem was adjusted in proper anteversion. When the hip stability and leg length were satisfying, the real prosthesis were implanted. (Figure 1.IJKL).
For the patients who had residual plate and screw, fractures of the greater trochanter should be watched out. In some cases, wires were pre-bundled around the trochanter and removed after reduction.

Postoperative follow-up and evaluation.

The patients were followed up at 4 and 12 months after surgery, and then checked every 2-3 year.

We analyzed the perioperative and postoperative complications, Harris hip score (HHS) and radiographic results in the last follow-up. Complications were defined as neurovascular impairment, dislocation, aseptic loosening, periprosthetic femoral fractures, periprosthetic joint infection and re-operation for any reasons.

Postoperative radiographic evaluation: migration of the femoral component was assessed by

measuring the vertical distance from the lower edge of the stem to the tip of the greater trochanter, and the angle between the axis of stem and femur. Femoral subsidence of >4mm, swing in the stem alignment of >2°, or a complete radiolucent line was considered to indicate stem loosening [9-11]. The fixation of the proximal sleeve was classified into bone ingrown, fibrous stable, or unstable, according to the classification system of Engh [12]. Spot welding was defined as bone densification and trabecular streaming between the cortex and the implant [13] The angle of varus stem was showed as positive and the valgus stem was showed as negative. The methods of measuring the G/L ratio and trochanter valgus angle (TVA) was showed (Figure 2).

Statistical analysis

Statistical analysis was performed using SPSS 21.0 statistical software (Inc, Chicago, US). All data were quantitative expressed as x ± s (maximum and minimum, median, interquartile range). The test level value p is taken as 0.05 on both sides. The intraclass correlation coefficient (ICC) was used to determine variations in different measurements. The radiologic measurement was performed by two independent observers (KXP and YMZ). Each observer made the measurements again after 2 weeks without knowing the first values. The intra-observer and inter-observer agreements were found to have nearly perfect reliability for all of the measurements (ICC >0.81).

Twelve patients (11 female and 1 male) were enrolled in this study. Their basic information was showed (Table 1). The primary diagnoses of these patients were DDH (9, 75%), ankylosing spondylitis (1, 8.3%), ONFH (1, 8.3%) and proximal femoral fractures (1, 8.3%). The causes for TVO were osteotomy (10, 83.33%), suppurative joint sequela (1, 8.3%), malunion of fracture (1, 8.3%).

All patients obtained the neutral alignment of femoral stem (<3°). There were no neurovascular impairment, dislocation, aseptic loosening, periprosthetic femoral fractures, periprosthetic joint infection or reoperation for any reasons until the last follow-up.

One patient had a small split near the lesser trochanter and was treated with a cerclage wire. Another patient had fracture in the bottom of the greater trochanter when we removed the previous plate. Frozen cortical strut allograft and titanium cable were used to immobilize the trochanter. The fractures in the two patients were healed within postoperative 4 months.

All 12 hips demonstrated stable bone ingrowth. No stems were found to have stable fibrous ingrowth or unstable status on the radiograph. Spot welding around the inferior border of the metaphyseal sleeve was observed in 10 hips (83.33%).

The G/L ratios in 12 patient were 2.58±0.95 and all of these were larger than 1.50 (Table 2)

The typical cases were showed (Figure 3-8).

Various hip preservation surgeries used to be performed for the young patients with hip dysplasia or ONFH [2,14-16]. When these patients developed arthritis, the residual deformity would bring more challenge to the following THA [17]. The surgical strategy of THA varies along with the severity and position of deformity [18]. As one uncommon type of femoral deformity, the severe valgus deformity of trochanter is critical for the prosthetic morphology and surgical technique.

The concurrent arthroplasty with femoral osteotomy was a technically demanding procedure and had the high risk of complications [1,5]. Some surgeons suggested that customized prosthesis may provide one effective solution for severe femoral deformity [19-21]. However, its demanding technology and economic cost limited its wide application.

According to the design of S-ROM, the angle between sleeve and femoral stem can be adjusted freely, but the angle is seldom beyond 90 degree in clinical practise. The opposite direction of sleeve (180 degree) described in this study have never been reported in previous study.

In this study, no aseptic loosening or revision of femoral stem were found in the case series with a mean follow up of 6 years. All patients obtained the significant increase of HHS. The significant improvement of function and less complication indicated the safety and effectiveness of the technique in patients who had severe TVD. The high revision rate of complex osteotomy or cemented THA were avoided. In the meanwhile, the sleeve decrease the risk of subsidence, which cannot be ignored in the fully-coated cylindrical stem and cone [22-23]. The cone has the advantages including easier bone preparation, less bone loss in the trochanteric area and less stress shielding. It should be considered when an osteotomy is not planned, because the anti-rotation stability would be weaken by the osteotomy [23-24].

Although the method have has yielded satisfying clinical results, we should still be aware of its technical flaws and cautions. Firstly, it can’t get through all valgus deformities of the greater trochanter, and some patients with severe deformity still need osteotomy to facilitate the offset and straighten the medullary cavity. Secondly, since the valgus greater trochanter is not corrected, the increased joint offset would increase the risk of greater trochanteric bursitis. Two patients reported lateral thigh pain after surgery, which was probably related to the bursitis. Thirdly, the manual work of implanting sleeve and malformed medullary cavity increased the risk of proximal femoral fractures. In this study, 2 patients had the intra-operative fracture, although we bundled the wires around the trochanter before implanting. Burs or other certain tools should be standing by for bone preparation. Fourthly, the leg length might be influenced by the residual deformity. While the equal leg length could be achieved by the proper neck length and femoral head.

The clear indication of this special sleeve-implanting method was also important. The medial support and the lateral cover are two essential aspects of the technique, once the medial cortex of proximal femur is destroyed, the opportunity for implanting sleeve towards to the great trochanter is lost. We can make basic predictions though measuring the G/L ratio and TVA. Both the differences of G/L ratio and TVA between two groups were significant, which indicated that their anatomy of proximal femur were characteristic. The G/L ratio can be seen one good indicator for the technique, when it was larger than 1.50.

Nowadays, an angular osteotomy on the proximal femur is not suggested in hip preservation surgeries for the consideration of added difficulties for potential future THA. But this specific deformity is still occasionally seen in this region in conversion THA for DDH, which accounts for significant challenge. Although we introduced one alternative for the angular osteotomy, it is necessary to remind the surgeons who are still performing angular osteotomy on proximal femurs of its potentially serious consequences.

This study has several limitations. Firstly, given that hip arthritis combining with trochanter valgus deformity were relative rare (12 cases in 9 years), the suitable control cases could hardly be found to conduct the case-control study. No comparison to other prostheses or other surgical methods would inevitably affect the persuasiveness of the study on technical notes. Secondly, because it was a retrospective case-series study, we had no need of the prospective ethics approval. In the future, multicenter randomized controlled trial will be performed to further evaluate its safety and effectiveness. Thirdly, the study was conducted over a long period of time, and changes in surgical personnel and related technical details might affect the final evaluation. Fourthly, the heterogeneity of the study population including various primary etiologies, which also influenced the persuasiveness of the study to some extent.

The reverse sleeve of S-ROM was a reliable method for the patients with severe trochanter valgus deformity, which brought satisfying clinical outcomes in mid-term follow-up.

Ttrochanter valgus deformity: TVD; Total hip arthroplasty: THA; Greater trochanter/lesser trochanter: G/L ratio; Developmental dysplasia of hip: DDH; Osteonecrosis of the femoral head: ONFH; Hydroxyapatite: HA; Harris hip score: HHS; Trochanter valgus angle: TVA; Transtrochanteric valgus osteotomy: TVO; Greater trochanter to the femoral axis: GF₁; Lessor trochanter to the femoral axis: GF₂; Interclass correlation coefficient: ICC.

Ethics approval and consent to participate: The medical ethics committee of Chinese PLA General Hospital approved the study. All procedures were conducted in compliance with the guidelines of the Declaration of Helsinki. The patients were informed consent that their clinical images and medical records for scientific report.
Consent for publication: We have obtained the written consent for publication.
•Availability of data and material: All data generated or analyzed during this study are included in this published article.
•Competing interests：The authors declare that they have no competing interests.
•Funding: None.
Authors’ Contributions: Xiangpeng Kong and Wei Chai contributed equally to this work and were co-first authors. They have made substantial contributions to: (1) the conception and design of the study,acquisition of data, or analysis and interpretation of data, (2) drafting the article or revising it critically for important intellectual content. Yan Wang and Yonggang Zhou: primarily responsible for oversight of the research project, including all data acquisition and analysis, and manuscript preparation and approval. Yan Wang and Yonggang Zhou contributed equally to this work and were co-corresponding authors. Jiying Chen helped revised the discussion. Minzhi Yang helped statistical analysis. Alvin Ong: helped revised the discussion and polished the manuscript. All authors have read and approved the final submitted manuscript.
Acknowledgement: Not applicable.

1.Iwase T,Hasegawa Y,Iwasada S et al. Total hip arthroplasty after failed intertrochanteric valgus osteotomy for advanced osteoarthrosis.[J] .Clin. Orthop. Relat. Res., 1999, undefined: 175-81.

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Table 1. The basic information of patients.

Patients

Data

Gender (male:female)

1:11

Age (years)

BMI (kg/m2)

Follow up (years)

Preoperative Harris score

Postoperative Harris score

42.30±10.23 (30-66, 45, 15)

22.99±2.34 (19.10-30.10, 24.10, 7.88)

5.96±3.29 (2-13, 7, 7)

34.31±14.43 (17-62, 32, 19)

84.12±11.33 (67-98, 88, 21)

All data were quantitative expressed as x ± s (maximum and minimum, median, interquartile range).

Table 2. The comparison of G/L ratio and TVA in two groups.

Patients

Data

G/L ratio

TVA (°)

2.58±0.95 (1.50-4.43, 2.60, 2.11)

144.50±9.66 (128-156, 142, 20)

All data were quantitative expressed as x ± s (maximum and minimum, median, interquartile range).

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published 24 Feb, 2020

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Editorial decision: Minor revision
11 Feb, 2020
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09 Feb, 2020
Submission checks completed at journal
08 Feb, 2020
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Modular stem in total hip arthroplasty for patients with trochanter valgus deformity: surgical technique and case series

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