Long-Term Results of Total Hip Arthroplasty with Step-Cut Osteotomy in Crowe Type IV Dysplastic Hips

Abstract

Objective

The purpose of this study was to evaluate the long-term results of sub-trochanteric step-cut shortening osteotomy (SSCO) used in the total hip arthroplasty (THA) procedure for treatment of Crowe type IV dysplastic hips.

Materials and Methods

Crowe type IV dysplastic 35 hips of 31 patients were treated with cementless THA. Patients were followed up meanly 9.2 years (range 4–18). SSCO was applied to all hips to reduce the femoral head into the true acetabulum. Autologous bone grafts which were obtained by shortening the femur and cable cerclage wires were used for fixing the osteotomy site. The results were evaluated clinically and radiologically. In clinical evaluation, Harris hip score (HHS) and d'Aubigne hip evaluation criteria were used.

Results

The mean HHS increased from 40.6 to 92.5. Merle d’Aubigne hip evaluation score was increased on average from 1.76 to 5.8 in terms of pain and from 2.9 to 5.5 in terms of range of motion. In 9 hips (25.7%), medialization was achieved by creating a controlled fracture in the acetabulum. The hip rotation center was lowered by an average of 5.7 cm. The average leg lengthening was 3.4 cm. No more than 4 cm lengthening was made. Dislocation did not develop in any of the patients.

Conclusion

It was concluded that the long-term results were found to be successful in the THA with SSCO in Crowe type IV dysplastic hips, since nerve complications were reduced, leg-lengthening was achieved, and a painless and mobile hip joint could be achieved.

Introduction

Although developmental dysplasia of the hip (DDH) has been attempted to be reduced by early diagnosis and treatment methods in recent years, high hip dislocations and associated secondary coxarthrosis, which have not been treated or failed, are frequently encountered today. Unlike primary coxarthrosis, arthroplasty applications at high hip dislocations require treatment of advanced deformities in bone and soft tissue. There is an abnormal rotation center, insufficiency in the abductor muscles, and leg length discrepancies in the associated lower extremity. The femoral head is small and deformed, the femoral neck is more antevert, the trochanter major is located in the posterior and is osteoporotic, and the medulla is flat and narrow at the affected site. On the acetabular side, the acetabular covering is inadequate, the acetabulum is shallow, defective superior and anteriorly, more antevert than normal, and it is osteoporotic, because it carries no or partial load. Soft tissues, especially large nerves and veins, do not follow normal anatomical pathways [1–5]. Accompanying bone and soft-tissue deformities and being relatively young and active are still important problems in terms of prosthetic surgery techniques among these patients [6–8].

Total hip arthroplasty (THA) is the preferred treatment method in patients with coxarthrosis on the ground of DDH. Despite the technical difficulties and complications, today, THA is an application that provides successful results with the development of this technique and technology with such severe dysplastic or high dislocated hips. It is well known that more successful clinical results are obtained by placing the acetabular component in the true acetabulum in these patients [2–5, 8–10]. However, complications such as nerve lesions can be encountered without femoral shortening or lengthening of more than 4 cm. To avoid this, femoral shortening osteotomies are applied to lower the hip in its anatomical location. Femoral shortening osteotomy can be done from one of the intertrochanteric, trochanteric, or sub-trochanteric regions. Subtrochanteric osteotomies can also be performed as transverse, oblique, step-cut, and double-chevron. Although step-cut and double-chevron osteotomies are complex, difficult, and time-consuming methods, there is a strong consensus on their stability [1, 2, 11–18].

The purpose of this study was to evaluate the long-term results of sub-trochanteric step-cut shortening osteotomy (SSCO) used in the total hip arthroplasty procedure for the treatment of Crowe type IV dysplastic hips.

Materials and Methods

This retrospective study was performed after obtaining local ethical committee approval. Medical records of the DDH patients who were treated with cementless arthroplasty between January 1996 and January 2015 were gathered from the hospital’s archive. Inclusion criteria were having a Crowe type 4 hip, being treated with an SSCO, having an adequate follow-up. Patients who were lost to follow up, with a hip of Crowe type 3 or lower, and who had incomplete records were excluded. Cementless THA was applied to 186 patients who developed coxarthrosis based on high hip dislocation between, January 1996 and January 2015. Thirty-five hips (Crowe type 4) of 31 patients (30 females and one male) which shortening was obtained by SSCO of which shortening and adequate follow-up and controls can be made were included.

Preoperative Evaluation Protocol

Conventional radiographs were taken in anteroposterior (AP) and lateral positions for all patients. In the case of uncertainty about the bone stock and size of the acetabulum, computed tomography (CT) was added as additional imaging. The surgical treatment was recommended to patients who did not respond to conservative treatments, wake up with pain at night, have walking difficulties, and cannot perform their daily activities.

For prophylactic purposes, 160 mg gentamicin was started with 2 g of cefazolin sodium and continued for 3 days. The operations were performed by the same surgeon.

Leg length inequality was evaluated radiologically and clinically. On conventional radiography, the lowering amount of the center of the femoral head and the lesser trochanter was measured. To prevent the magnification error, ratio of the measured size of resected femoral head during the operation and measurement on preoperatively taken radiograph was used. Whether the acetabular component was placed in the true acetabulum was examined by measuring the distance of the lower edge of the acetabular component to the line connecting the teardrops in the horizontal plane.

Surgical Technique

Subcutaneous adductor tenotomy was applied to patients with adductor contracture if it was present at the examination performed before the operation. All patients were placed in the lateral decubitus position and operated with a direct lateral Hardinge approach [16]. After a longitudinal lateral incision, the 1/3 anterior gluteus medius fibers and the gluteus minimus muscle were cut and reached to the capsule. The true acetabulum was found by following the structures after opening the capsule. Fibrotic tissues in the capsule and acetabulum were radically resected. In all patients, the acetabular component was placed in the true acetabulum. In cases where the acetabulum is very small, small acetabular components (no 40–46) were used. Care was taken to ensure that the acetabular component coverage was not less than 70%. In cases where 70% coverage could not be obtained, the acetabulum was reamed toward to posterior and medial walls. Medialization (cotyloplasty) was performed by creating a controlled fracture if necessary. Thus, more robust bone stock and the covering were provided. Bone graft was not used in any single patient.

Since in this dislocation type, superior migration of the femoral head is generally above 4 cm all patients underwent a transverse sub-trochanteric osteotomy (Fig. 1a). Proximal metaphyseal part of the femur was prepared by rasping. The proximal femur was placed at the desired angle to the acetabulum and held in that way. The distal part was kept neutral, with the patella facing directly anterior (increased anteversion of proximal femur was corrected in this way) (Fig. 1a). The amount to be shortened was determined by measuring the overlapping amount of both parts. Soft-tissue tension was also taken into consideration in determining the amount of shortening. Since hamstring and quadriceps muscle tension directly affect limb function, care was taken not to stretch them. Then, SSCO was performed as proximal step lying laterally and distal step medially (Fig. 1b). Apart from this, no additional soft-tissue release was made. The bone fragments were removed from the osteotomy site and were placed medially and laterally over the osteotomy site without stripping them from the surrounding soft tissue. After the stepped osteotomy tips were reduced and stabilized with cable (s), the femoral stem was inserted (Fig. 1c). At least three cables were used for fixation, one on the osteotomy line and one on each bone graft.

Fig. 1.

Demonstration of the sub-trochanteric transverse osteotomy and correction of the increased proximal femoral anteversion (a); technique of step-cut osteotomy (b); stabilization of the osteotomy site (c)

Post-operative Rehabilitation and Follow-Up Protocol

All patients were seated on the first postoperative day. After 24 h, the hemovac drain and urinary catheter were removed. Rehabilitation started from the 48th hour. The patients were mobilized with double crutches without allowing load-bearing. Partial load-bearing was started according to the radiological evaluation performed at the end of the sixth week. Patients were allowed full load-bearing after the 10th week. Low-molecular-weight heparin was started 12 h after the operation. It was continued for an average of 20 days. The remaining follow-up was performed on the 1st, 3rd, 6th, and 12th months after the operation. If there was no problem, it was continued as annual checks.

In clinical evaluation, Harris [17] hip score (HHS) and d'Aubigne [18] hip evaluation criteria were used.

Statistical Analysis

Statistical Package for Social Sciences (SPSS) version 17 was used for statistical analysis. After performing the Shapiro–Wilk test for evaluating the normality for preoperative and postoperative HHS and Merle d'Aubigne hip score, it was observed that the data distributed non-normally, so Mann–Whitney U test was used for the comparison. A p value below 0.05 is considered statistically significant.

Results

The operation was performed on left, right, and both hips in 16, 11, and 4 patients, respectively (Figs. 2 and 3). Shortening of the femur was obtained by SSCO in all 35 hips. The mean age of the patients was 42.3 (range, 39–65). The mean follow-up time was 9.2 years (range, 4–18). Three patients had a previous surgery history for DDH (all Salter Osteotomy). The mean operation time was 165 min (range, 125–210 min). The average blood transfusion rate was about 1.8 units. Incomplete fracture occurred in the femur during reaming in 4 patients.

Fig. 2.

Preoperatively taken radiograph of coxarthrosis as a result of bilaterally dislocated (Crowe type 4) hips

Fig. 3.

Healed radiograph of the patient who is shown in Fig. 2

In the clinical evaluation, the mean HHS was found to be 40.6 ± 8.6 (range, 30–62) preoperatively, whereas it was increased to 92.5 ± 6.9 (range, 60–100). There was a statistically significant difference between preoperative and postoperative HSS scores (p < 0.001). The mean absolute results for hip function according to Merle d'Aubigne hip score evaluation (pain and mobility) were determined to be increased to 11.3 ± 0.9 (range, 9–12), whereas it was 4.7 ± 1.4 (range, 2–8) preoperatively (p < 0.001). According to Merle d'Aubigne scores, 27 of the hips were evaluated as very good (77.1%), six were good (17.1%), and two were moderate (5.8%).

The femoral head was placed in the true acetabulum in all patients. None of the patients had peri-acetabular grafts. The hip rotation center was lowered by an average of 5.7 cm. An average of 3.4 cm (range, 2–5) shortening was achieved. In unilateral dislocations, the lower extremity length discrepancy decreased from an average of 43 mm (range, 23–75 mm) preoperatively to 10 mm (range, 0–22 mm) after the surgery. The gained length was 34 mm on average (range, 30–40 mm). There was no significant length difference in bilateral cases. The Trendelenburg gait, which was present in all patients preoperatively, disappeared in 14 patients, decreased in 15 patients, continued moderately in 4 patients, and remained unchanged in 2 patients after the operation. At the last follow-up, it was observed that the Trendelenburg gait did not change in 2 patients and continued mildly in 6 patients.

In nine hips, a controlled fracture was created by reaming the acetabulum medially and posteriorly (cotyloplasty). This area was filled with cancellous grafts which were removed from the femoral head. Approximately 10 weeks later, the grafts were found to be fused to form medial support on X-rays.

One of the patients had osteolysis and non-union in the osteotomy site. In this patient, the fixation was performed by bilateral femoral strut graft + Dall-Miles plate and cable cerclages and screws without touching the prostheses (Figs. 4, 5, 6). Healing was achieved after about 6 weeks. In four patients who developed femoral incomplete fracture, union with cable cerclage fixation was uneventful. No dislocation or osteolysis was observed to require revision surgery at the early or late period.

Fig. 4.

Postoperatively taken radiograph of a patient with sub-trochanteric step-cut osteotomy

Fig. 5.

The autologous grafts were resorbed and the osteotomy site did not heal

Fig. 6.

After opening the osteotomy site, double strut femoral graft and Dall-Miles plate with cable cerclages and screws were used for fixation

Partial nerve palsies developed in four of the patients. Three patients had involvement in the sciatic nerve and one had in the peroneal nerve. All nerve palsies returned spontaneously after 6–12 months. None of the patients had deep vein thrombosis that was evident clinically.

In 22 (71%) patients, there were signs of varying degrees of low back pain; in 9 (29%) patients, sciatica findings were present in addition to low back pain. On conventional radiographs, almost all of them had mild scoliosis and spondylarthrosis in the lumbar region. These patients were the group with unilateral dislocated hip and had an advanced age. In the last controls, only 5 of 22 patients with preoperative low back pain evaluated to be suffering low-level complaints. The signs of sciatica remained in one patient. However, the findings of spondylarthrosis in their radiographs continued as same as in the preoperative period. Dislocation complication was not observed in any of cases. Three examples of patients with long-term follow-up are shown in Fig. 7a–f.

Fig. 7.

a 35 year old female patient. b Post-operative 8th year radiography. c 38 year old female patient. d Post-operative 9th year radiography. e 34 year old female patient. f Post-operative 10th year radiography

Discussion

In high dislocations of the hip on the presence of the DDH, there is a common consensus in the literature about placing the femoral head in the true acetabulum, despite all its difficulties and potential complication risks [1, 2, 11, 17, 19, 20]. Thus, the acetabular component should be well covered by the bone and the hip joint should be protected from intense compressive forces, and finally, the possibility of loosening should be reduced. Important biomechanical advantages should be obtained in terms of the durability of the acetabular cup. By creating sufficient abduction strength, the pelvis is kept in balance; as the shortening of the extremity is eliminated, the Trendelenburg gait decreases or disappears completely, and it contributes greatly to the stability of the prosthesis, especially in cementless applications [1, 3, 13, 17, 21–24].

It was reported that when the acetabular components were placed in the false acetabulum, Trendelenburg gait continues with loosening rates of the acetabular component up to 42%. Linde reported that the rate of loosening in prostheses when placed in the true acetabulum was 13% and 42% when it was placed in the high level [3, 24]. We placed the acetabular component into the true acetabulum, and we did not observe any loosening of the implants in any of our cases.

Patients with Crowe IV-type dislocations have severe soft-tissue contractures. These contracted tissues prevent the femoral head to be placed in the true acetabulum. Forced reductions without shortening can cause lengthening of the leg and finally neurological deficits. Femoral shortening is performed to place the acetabular component to its original location without any complications. Thus, the development of neurological deficit is prevented, and ante version of the proximal femur is regulated by osteotomy and derotation of the proximal femur. Also, abductor mechanism restoration is provided, and leg length discrepancy is eliminated [17].

Performing an osteotomy from the trochanteric region makes the surgery area better visible and facilitates the procedure. However, the distal transfer and fixation of the greater trochanter are inconvenient in many studies, since it is prone to complications [1, 15]. Some studies report good results with trochanteric region osteotomies. Eskelinen et al. [2] followed 56 patients who underwent trochanteric progression osteotomy together with femoral shortening for 12.3 years and reported a survival rate of 98.4%. Hartofilakidis et al. encountered insufficiency in 11 hips during the 6.4-year follow-up of the 84 hips, where the femoral neck was shortened, and the greater trochanter was advanced distally [2]. We did not prefer trochanteric osteotomy, since the trochanteric region is important in terms of cancellous bone stock, there is a little possibility of non-union, and for possible future revision surgery.

In recent years, the general trend has been increasing toward osteotomies of the sub-trochanteric region [1, 2, 5, 8–11, 15, 17, 23–28]. Simple transverse osteotomies made from this region are considered as unstable [20]. However, in some recent publications, it has been reported that with the use of S-ROM type modular femoral stems, no instability has developed in transverse osteotomies, anteversion can be easily adjusted [1, 19, 20, 27], and successful results have been obtained in terms of the stability of oblique osteotomies whether the same type of prosthesis has been used or not [11, 14].

Step-cut and double-chevron osteotomies are more resistant to torsional and axial forces than other osteotomies [15, 16, 24]. The major disadvantages are that techniques are difficult and complex, require a long learning curve, and require a longer time. However, these techniques are among the advantages accepted in many studies that they are resistant to axial and torsional forces, have a high probability of union due to their wide contact surfaces, and prevent failure of the femoral stem by reducing the diameter difference between the proximal and distal parts [11, 15]. In addition to the advantages mentioned above, we preferred the SSCO because of the advantages of making the femur closer to normal, providing better fixation from the metaphyseal region, and removal of that section in some patients with very thin femoral medulla or in patients who had previously undergone Schanz type pelvis support osteotomies.

In cases where the acetabular coverage is inadequate, the femoral head has been placed as a graft in the superolateral portion of the acetabulum for many years. The amount of coverage of the graft on the acetabular component should not exceed 40%. As the rate of coverage of the acetabular component with the graft increases, the rate of loosening of the prosthesis increases [14, 18, 28]. However, studies are reporting that there is no significant relationship between the amount of graft covering and loosening in cemented and cementless acetabular components [18, 22, 29]. Good results have been reported in cementless acetabular components, whether or not grafts are used [13, 14]. We did not use grafts in any of our patients for increasing the acetabular component. Instead, we preferred to use medialization (cotyloplasty) and small cups. In some of our patients, a controlled fracture was created, and adequate coverage of the acetabulum was provided. During the final controls, no patient showed any signs of loosening.

In sub-trochanteric osteotomies, delayed or non-union may occur due to the rotational and axial forces. The rate of instability in the osteotomy area causing complications such as non-union and delayed union has been reported between 8 and 29% [15, 19, 21, 23]. To prevent these complications, the importance of osteotomy type and the design of used femoral stem is increasing. Extra-medullary methods such as strut graft, cable cerclage, and plate fixation have been defined to increase the stabilization of the osteotomy site [11]. Using long prostheses is recommended for stability. Especially the stems that pass the osteotomy site twice as much as the femoral diameter and fit into the narrow canal increase the stability. The stem should serve as an intramedullary nail [15, 17]. In our patients, we fixed the muscle pedicle femoral bone fragments which were removed from the osteotomy line with the help of a cable to the osteotomy area. We also tried to select the femoral stems as wide and longest as possible. Only one of our patients had a non-union in the osteotomy site, which was attributed to a technical error. This complication was solved by opening the non-union site and applying the femoral strut graft and Dall-Miles plate with cables and screws.

In femoral shortening osteotomies, fractures can occur when the femur is reamed. The fracture rate during the femoral stem implantation is reported to be between 5 and 22% [2, 19, 30]. Incomplete fracture occurred in four patients during the perioperative period. All healed with simple cerclage wire fixation. We did not use cerclage wire for prophylactic purposes, as some authors did [19].

Since these patients are relatively young and active, the biggest problem is the mechanical failures that may develop in the prosthesis in the future. These failures either depend on the used cemented implants or the type of prosthesis used. Cemented implants are not recommended for either the acetabular side or the femoral side. Because the true acetabulum is small and the femoral canals are narrow, only a thin and weak layer of cement can be placed. This may break the cement and cause the prosthesis to be loosened. On the other hand, studies have been reported on cement particles entering the osteotomy sites, delaying, or preventing union [1, 12]. We did not use cement in any of our patients, because we had this opinion.

One of the biggest problems in these patients is the type and size of the prosthesis to be used due to the inappropriate anatomical structures. Especially, the narrow and flat femoral canal and the underdevelopment of the true acetabulum also affect the type and size of the implants to be used. During our follow-up period, we had to make revisions in two patients due to polyethylene wear and in one patient due to acetabular loosening. The patients we revised were young and active patients who were actively working.

Clinical improvement after the surgical intervention is very important. In our patients, HHS increased from 40.6 to 92.5 on average. This was statistically significant (p < 0.001). The Merle d'Aubigne hip score, in which especially pain and movement were evaluated, increased from 1.76 to 5.8 in pain, and from 2.9 to 5.5 in range of motion. In both cases, it was found to be statistically significant (p < 0.001). According to the Merle d'Aubigne hip score, good and very good results in 33 hips (94.2%) and moderate results in two hips (5.8%) were interpreted as the clinical success of the method we applied.

This study has some limitations. The first is that it is a retrospective study and there is no control group. The second is that the limited number of included cases and relatively short follow-up. Third, it was not possible to show whether nerve lesions are related to lengthening, and how much lengthening can cause this problem.

In conclusion, during our follow-up period, the survival rate was 93% at the end of 5 years and 89% at the end of 9.2 years. These values were compatible with the literature. Our results demonstrated that SSCO is a reliable method that should be preferred to minimize complications in THA operations based on DDH.

Funding

Not received.

Declarations

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethical Standard Statement

This article does not contain any studies with human or animal subjects performed by the any of the authors.

Informed Consent

For this type of study, informed consent is not required.