|Year : 2019 | Volume
| Issue : 1 | Page : 1-3
Acetabular and femoral reconstruction in total hip replacement for adult hip dysplasia: A technical guide for surgeons in our environment
Olukemi Lawani, Michael Okunola, Imoniche Adeoye-Sunday, Charles Ayekoloye
Department of Orthopaedics and Trauma, University College Hospital, Ibadan, Nigeria
|Date of Web Publication
Dr. Olukemi Lawani
Department of Orthopaedics and Trauma, University College Hospital, Ibadan 200212
Source of Support: None, Conflict of Interest: None
Hip dysplasia is abnormal development of the hip joint resulting in joint incongruity and characterised by a shallow acetabulum, inadequate femoral head coverage and femoral and acetabular version abnormalities. Childhood hip dysplasia is uncommon in this environment because of child swaddling practices. Adolescent onset forms are however not uncommon and present in adulthood more frequently than is recognized for total hip arthroplasty. Clinical and radiologic evaluation is key for diagnosis and surgical planning. The pathologic abnormalities on both sides of the hip joint present formidable challenges to total hip arthroplasty which remains the mainstay of treatment for end-stage arthritis secondary to adult hip dysplasia. Posterior approach is preferred in our unit as it provides excellent acetabular exposure and enables assessment of sciatic nerve integrity when addressing leg-length discrepancy common in this condition. Leg lengthening more than 3–4 cm should, however, be avoided with arthroplasty for this condition. We outline technical tips for successful total hip arthroplasty for this condition. This study aims to describe total hip arthroplasty in the setting of adult hip dysplasia. The objectives are to describe the pathologic changes in adult hip dysplasia, the evaluation of these patients and surgical technique.
Keywords: Acetabular defects, acetabular reconstruction, adult hip dysplasia, femoral head autografts, total hip arthroplasty
|How to cite this article:
Lawani O, Okunola M, Adeoye-Sunday I, Ayekoloye C. Acetabular and femoral reconstruction in total hip replacement for adult hip dysplasia: A technical guide for surgeons in our environment. Niger J Orthop Trauma 2019;18:1-3
|How to cite this URL:
Lawani O, Okunola M, Adeoye-Sunday I, Ayekoloye C. Acetabular and femoral reconstruction in total hip replacement for adult hip dysplasia: A technical guide for surgeons in our environment. Niger J Orthop Trauma [serial online] 2019 [cited 2024 Feb 25];18:1-3. Available from: https://www.njotonline.org/text.asp?2019/18/1/1/263518
Adult hip dysplasia is a common cause of hip arthritis in females in many developed countries with comprehensive and well-established hip-screening programs. With increase in the availability of arthroplasty services in the country, there is the increasing recognition that similar cases occur here which are either missed by the current screening programs (missed developmental dysplasia of the hip) or develop hip dysplasia in adolescence (adolescent-onset acetabular dysplasia). Congenital and adolescent- onset hip dysplasia appear to be etiologically different, but share similar pathoanatomic changes. Recognition of these patients is crucial to anticipate their peculiar pathologic problems and to apply the required surgical technique to tackle these successfully.
Pathology of dysplasia involves bony as well as soft-tissue deformities. Dysplastic hips are characterised by distorted and shallow acetabulum, distorted proximal femoral anatomy with increased femoral anteversion correlated with shortening of the abductor lever arm, joint incongruency and subsequently early osteoarthritis. The greater trochanter is located posteriorly. In addition, there may be alteration of the proximal femoral geometry with mediolateral narrowing of the medullary canal.,
Total hip arthroplasty continues to be the main treatment option for symptomatic osteoarthritis secondary to adult hip dysplasia. Patients' age and sex are important as patients present with end-stage disease at a relatively young age often in the 4th and 5th decades and are more often females.
| Evaluation and Surgical Technique
Impingement on function and quality of life should be documented. Medication needs, walking aids and pre-operative function scores should be noted. The patients' expectations with regard to leg- length equality, pain and function must be carefully itemized, understood, and possibilities and trade- offs discussed. Both the objective leg-length measurements and subjective/functional leg-length differences using a 'block' test should be documented.
Careful and fully informed consent must be obtained for the following:
- Higher risk of infection and hemorrhage due to the use of more extensive approaches than for routine hip replacements in normal hips
- Leg-length inequality with leg lengthening beyond 3 cm is fraught with the risk of sciatic nerve palsy
- Increased risk of posterior dislocation postoperatively because of capsular attenuation.
We routinely use the posterior approach with the patient placed in the lateral position with the patient properly supported such that the shoulders and sacrum are in line with all pressure areas padded. A trochanteric slide osteotomy can also be useful for restoring abductor lever arm and soft-tissue tension and may aid with reattachment of the trochanter in a more anatomic lateral position. We routinely identify the sciatic nerve though we do not dissect it free to preserve the vasa nervorum. The capsule and short external rotators are reflected together. Some attenuation of the capsule is usual. Hip dislocation is not usually difficult in dysplastic and low dislocation types. Femoral shortening osteotomy can be employed to reduce tension on the sciatic nerve or aid reduction, when trying to reconstruct a high dislocation to an anatomic hip centre. Femoral shortening osteotomy is generally not required in dysplastic or low dislocation if a low femoral neck cut is carried out.
There are three options for positioning the acetabular component in dysplasia: a high hip centre often with a small cup; an anatomic hip centre with variable uncovering of the acetabular component with the medial wall intact; or with deliberate medialisation by fracturing the medial wall (cotyloplasty) to obtain good coverage. Our preference is to position the acetabular component at the anatomic acetabular centre without violating the medial wall and reconstruct the uncovered acetabulum if necessary, using femoral head autografts. Careful pre-operative templating as well as intraoperative location of the acetabular tear drop intraoperatively determines the floor of the acetabulum. Intraoperatively, the insertion of the hypertrophic ligamentum teres femoris identifies the anatomical acetabulum.
Anatomic cup positioning requires some medialisation of the acetabulum with a small acetabular implant with care taken to preserve the medial acetabular wall. Careful central acetabular perforation using controlled drilling without plunging can also be used to judge the thickness of residual medial acetabular wall. A depth gauge is useful in this regard. A thickness of 3 mm medially is required to support the cup while preventing iatrogenic protrusion after medialisation. Reaming is adjudged adequate when anteroposterior scratch fit is obtained as attempt to ream to superioinferior fit will result in reaming out the anterior and posterior walls. The pre-operative templating and the intraoperative assessment of cup coverage will indicate whether a bulk autograft support is needed as the degree of uncovering can be assessed with the last reamer in the optimal position of abduction and anteversion. The defect, usually anterosuperior, may need grafting if more than 25%–30% of the cup is uncovered or if there is superoinferior instability due to the defect. The corticated acetabular rim defect is freshened using a reamer of appropriate size and multiply drilled to expose some subchondral bone. The bulk femoral head autograft is shaped to fit the defect and provisionally fixed with k-wire into position. This is followed by screw insertion which is tightened to achieve compression. We use two 6.5-mm half-threaded screws. The last reamer is used to ensure that the cup can still be placed after the graft has been secured. Multi-hole cup should be used and primary stability augmented with multiple screw fixation. A lipped liner should be placed with the lip posterior to reduce the risk of posterior dislocation. The material reamed further provides morselised bone graft (flying buttress grafts) which can be packed into cavities and crevices and the junction between bulk graft and pelvic sidewall. Take care to ensure that the anterior part of the graft is not excessively bulky as it can cause impingement in flexion with resulting risk of posterior dislocation. The bulk autograft provides both structural supports for the acetabular cup being inserted at the time in addition to augmenting bone stock for further revision surgeries in these often young patients. Femoral canal preparation can usually be achieved in the usual fashion.
Cemented acetabular fixation with femoral head autograft has shown high failure rates at mid-term follow-up. Our preference is, therefore, uncemented acetabular fixation with or without bulk autograft as it has demonstrated better results at equivalent follow-up.
Careful step-by-step identification of the structures must proceed with deeper dissection because it is not uncommon for vital structures to be seen in non-anatomical locations due to the distortion caused by the dysplasia. The posterior approach, however, has the advantage of providing access for the assessment and protection of the sciatic nerve, particularly when leg-lengthening occurs. It also affords excellent visualisation of the acetabulum.
Acetabular reconstruction using the excised femoral head or shelf graft, in our environment is a useful technique as it provides adequate quantities of autogenous cortical and cancellous bone graft for use. Spangehl et al. found good, moderate-to-long-term results for uncemented acetabular components using bulk femoral head autografts. Revision in one case only was due to acetabular component fracture, and in this case, most of the cup was supported on graft bone. Femoral head grafts provide both support and augmentation of future bone stock for revision purposes. Acetabular bone coverage of 75%–80% is ideal for stability and adequate bone ingrowth. Acetabular cage construct is an option for severe uncontained bone defects <45%. Leg-length equalisation is also easier to achieve with an anatomic hip centre.,,,
The use of a high acetabular centre may be associated with increased failure rates theoretically related to increased load bearing and wear. While a small cup is usually required for a high hip centre, this could result in inferior wear properties. It must be remembered, however, that some persistence of abnormal gait, especially in the early post-operative period, is due to habit, and this may be overcome by dedicated gait training. Hendrich et al. reported excellent results at 11 years of follow-up from cementless acetabular reconstructions using structural grafts. Significant polyethylene wear occurs with cup inclination <45° or placement lateral to tear drop by <25 mm, and aseptic loosening with cup placement <25 mm superior to the acetabular tear drop has been found. Poor coverage also increases the Dislocation rate 6 as does the high hip centre, causing bony impingement on the anterior inferior iliac spine and sacrum.
Femoral stem abnormalities may also occur. They may be subclassified into the 'good', the 'bad' and the 'ugly'. These represent the fairly 'normal' mildly dysplastic femur with normal intramedullary canal, the 'narrow' dysplastic markedly anteverted femur, and the 'deformed', previously osteotomised femur respectively. Abnormal anteversion can be corrected by derotation osteotomies with or without femoral shortening, or proximal modular implant insertion with component derotation. In turn, osteotomies are managed by adequate fixation with avoidance of cement. A proper low neck resection may also assist with correction of abnormal anteversion. The consistent abnormality of acetabular version is a superior and anterior uncoverage. This is also corrected by the position of the bulk femoral head graft in this position.
Faldini et al. reported improvement in Harris hip scores from 56 ± 9 pre-operative to 90 ± 9 at 12 months after cementless total hip arthroplasty in young patients with hip dysplasia. They found excellent long-term results with the use of tapered femoral stems in these patient cohort. Zhen et al. similarly used the same Wagner cone stem in a similar population of patients with comparable results.
Total hip arthroplasty remains the mainstay of treatment for end-stage arthritis secondary to adult hip dysplasia. Posterior approach is preferred in our unit as it provides excellent acetabular exposure and enables assessment of sciatic nerve integrity when addressing leg-length discrepancy common in this condition. Meticulous attention to anatomic detail helps avoid complications.
Femoral head bulk autograft is required for acetabular reconstruction in these young patients to achieve acetabular cup stability and restore bone stock for future revision. Proximal femoral version abnormalities should be addressed with appropriate choice of femoral component.
Satisfactory long-term results can be obtained when the bony and soft-tissue abnormalities are properly addressed.
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Conflicts of interest
There are no conflicts of interest.
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