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 . The surgical strategy of THA varies along with the severity and position of deformity . 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, it was retrospective and had no control group. No comparison to other prostheses or other surgical methods would inevitably affect the persuasiveness of the study on technical notes. Secondly, because hip arthritis combining with trochanter valgus deformity were relative rare, the sample size was small. In the future, larger sample size and longer follow-up 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.