Acetabular reconstruction with femoral head autograft in primary total hip arthroplasty through a direct anterior approach is a reliable option for patients with secondary osteoarthritis due to developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) predisposes to early secondary osteoarthritis of the hip [1]. Despite new born screening programs some cases are missed, treated incorrectly or insufficiently. These patients often develop secondary osteoarthritis needing a total hip arthroplasty (THA) at an average age of 53 years old [2]. Due to the typically anterolateral and superior acetabular deficiencies, an increased femoral antetorsion, decreased intramedullary canal size and either coxa vara or valga THA in a dysplastic hip is technically more challenging [3]. For acetabular reconstruction, different techniques are described ranging from autologous bone reconstruction, metal augments, reinforcement rings to cranial positioning of the acetabulum [4]. The anatomical reconstruction of the center of rotation (COR) in particular by filling the acetabular defect with a femoral head has several advantages. It has been shown that a medialization and distalization of the COR positively affects hip function [5‐7] and has been associated with increased survival of THA [8‐10]. Furthermore, it may possibly decrease the rate of aseptic loosening [11, 12], as differences of as little as 5 mm in superolateral displacement decreases abductor function and relevantly deteriorates the ratio of body weight moment arm to abductor moment arm [12, 13]. In THA with acetabular autologous bone wedge augmentation, the center of rotation can be perfectly placed more medially and distally. The bone stock is increased and revision surgery is potentially facilitated [14, 15]. The possibility of using a smaller acetabular cup simplifies anterior osseous coverage and allows normal anteversion. Last but not least, the femoral head is readily available and cheap as a means for acetabular augmentation.

Augmentation of the deficient acetabulum has been traditionally performed through an anterolateral, lateral or posterolateral approach with encouraging short-, mid- and long-term results [14, 16‐19]. However, the direct anterior approach (DAA) is known for several advantages like the true internervous and intermuscular plane resulting in less muscle damage and quicker early rehabilitation [20], less postoperative pain and pain medication [21‐23], improved early postoperative mobilization, shorter hospital length of stay [23, 24], a greater proportion of patients discharged home vs. a rehabilitation center [25] and improved postoperative as well as early functional outcomes [26‐28].

This study was designed to retrospectively analyze the reliability, the clinical outcome, surgical results, complications with and without implant revision as well as radiographic parameters in all primary THA with acetabular augmentation with a bulk femoral head autograft through a DAA.

This study was approved by our ethical review board (KEK-ZH-2020-02193) and all participants gave written informed consent.

The demographic information is depicted in Table 1.

The aim of this present study was to analyze the reliability, the clinical outcome, surgical results, complications with and without implant revision as well as radiographic parameters in primary THA with acetabular augmentation with a bulk femoral head autograft through a DAA. In our cohort, we were able to successfully perform acetabular augmentation and place an uncemented cup through the DAA in all cases without conversion of the approach. Thus, all the patients could benefit from the advantages of the DAA such as quicker rehabilitation, less postoperative pain, less pain medication and a shorter hospital length of stay as well as increased early functional outcomes [20‐28]. While the muscle damage seen in this subgroup of patients (DDH) is greater than in less complex cases, this muscle damage especially seen in the obturator internus does not affect clinical outcome [36]. In addition to the advantages of the DAA discussed in the introduction, the supine position of the patient allows intraoperative fluoroscopy to verify the acetabular position not only regarding inclination and anteversion but also regarding the medialization and distalization of the COR. An average intended medialization of 18 mm and distalization of 9 mm of the COR was achieved [12, 13], increasing the lever arm and the pretension of the hip abductors, theoretically increasing hip function [6, 7] and potentially increasing longevity of the THA [8‐12, 37]. The autograft was fully integrated after 1 year increasing the bone stock in these young patients potentially facilitating revision surgery. At last follow-up, the screws did not show any signs of loosening. No compromises had to be made regarding the anteversion of the cup (Table 3), despite the naturally shallow acetabulum and anterior wall deficiency typically seen in this patient collective. In our opinion, this is a clear advantage of using an autograft instead of using a larger acetabular cup, which is either implanted with clearly more anteversion or remains partially uncovered potentially leading to iliopsoas impingement [38]. As an alternative metallic foam augments could be used. In our opinion, the benefit of increasing the bone stock using an autograft is obvious and apart from the technical challenge and some fluoroscopy exposure there are no disadvantages. In addition, autografts are substantially cheaper than metallic foam augments.

After a mean follow-up of 35 months (12–137), no acetabular loosening was seen and no other acetabular cup was revised. In our series, we did not see any dislocation after a mean follow-up of 35 months (12–137), albeit a standard 28 mm prosthetic head was used in 28 cases and a DM cup was implanted in one patient due to the advanced age. This is less than the dislocation rate of approximately 3% described in the literature [39]. Achieving press-fit in the reconstructed acetabulum was possible in all cases; however, an additional screw fixation was deemed necessary in two cases.

An additional advantage of femoral head autografts is the increased pelvic bone stock which may facilitate revision surgery in the long term [15]. In the patients with a follow-up of more than 5 years (n = 7), the bone graft did not show radiological signs of resorption and remained fully integrated.

Uncemented acetabular components with femoral autografts for acetabular reconstruction in DDH have shown good short- and long-term results performed through anterolateral, lateral and posterolateral approaches [17‐19, 40, 41].

The results presented in this study with THA performed through a direct anterior approach are comparable to the literature for femoral head autograft augmentation for DDH and acetabular segmental defects through other approaches. Zlatic et al. reported no acetabular loosening and three dislocations (5%) after a mean follow-up of 45 months in 61 patients and showed a full integration of the bone graft in all patients [19]. Yamaguchi et al. reported two (11%) acetabular loosening and no dislocations after a mean follow-up of 3.3 years in 18 hips and attributed the high rate of acetabular loosening to a lateral insertion of the acetabular component; a known risk factor [42]. This rate is higher than our 0% and is most likely explained by the high rate of severe dysplasia in their patient collective comprising of 55% Crowe type IV and possibly the slightly longer mean follow-up [43]. The bone grafts showed full integration in all 18 patients. DeWal et al. [40] reported no acetabular loosening in primary THA with 1 (7.7%) acetabular cup showing a radiolucency in all Charnley zones in a patient collective of 15 patients with a mean follow-up of 7.7 years. All grafts were fully incorporated without evidence of resorption. This study, however, can only be compared to ours to a limited extent as different indications were included, the most frequent indication, however, being DDH in seven cases (46.7%). Spangehl et al. reported 4 (9%) acetabular revisions, whereas only 1 (2%) was due to acetabular loosening and no dislocations in 44 patients after a mean follow-up of 7.5 years. 43 of 44 bone grafts showed no radiographic evidence of resorption [16].

There are limitations to the direct anterior approach in our hands. When a larger extension of the femur is necessary due to a higher degree of dysplasia, it is not possible to palpate the tension of the sciatic nerve through this approach. A femoral shortening osteotomy performed through a lateral subvastus approach would have to be done through a new incision. A distal extension of the direct anterior approach to perform a femoral shortening osteotomy poses a great risk for neurovascular structures supplying the quadriceps muscle [44]. We acknowledge that other authors perform THA for higher grade dysplasia as well with satisfactory results; however, we limit the indication to DDH grade A and B according to Hartofilakidis for the above-mentioned reasons. In higher grade dysplasia, we perform primary THA through a posterior approach to directly control the tension of the sciatic nerve and perform a femoral shortening osteotomy when necessary.

The present study has several limitations, including its retrospective design, relatively small cohort size, heterogeneity of implant models and the short minimal follow-up of 12 months [mean follow-up 35 months (12–137)]. However, there were no patients lost to follow-up and we do not expect any major changes in the results in the next 2–4 years as the acetabular cup was stable and the autograft is fully bony integrated in all patients. Therefore, this series shows a good and true validity and is of informative value. Patients with secondary osteoarthritis due to DDH benefit from the advantages of an anatomic placement of the COR and the DAA collectively.

Acetabular reconstruction with femoral head autograft in primary THA through a direct anterior approach seems to be a reliable option for the treatment of secondary osteoarthritis in patients with DDH Hartofilakidis grade A and B. Prospective cohort studies with a large sample population and a long-term follow-up are necessary to confirm our findings.